WO1999028791A1

WO1999028791A1 - Multilayer imaging medium comprising polypropylene, method of imaging said medium, and image-bearing medium

Info

Publication number: WO1999028791A1
Application number: PCT/US1997/021844
Authority: WO
Inventors: David T. Ou-Yang
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1997-12-02
Filing date: 1997-12-02
Publication date: 1999-06-10
Also published as: JP2003522983A; WO1999028791A8; EP1125169A1

Abstract

Multiple-layer imaging media comprising: a backing layer of polypropylene, an intermediate layer which may, for example, comprise an ethylene-α-olefin polymer, and a receptor layer. The imaging media are particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature or with dry toner. Methods of imaging media and imaged media are provided.

Description

MULTILAYER IMAGING MEDIUM COMPRISING POLYPROPYLENE, METHOD OF IMAGING SAID MEDIUM, AND IMAGE-BEARING

MEDIUM

Field of the Invention

The present invention relates to an imaging medium. More particularly, the imaging medium of the present invention is a multilayer composite comprising a backing layer comprising a propylene homopolymer and/or a propylene copolymer; an intermediate layer which may, for example, comprise an ethylene-α-olefin polymer; and an imageable receptor layer; that is, a surface capable of being imaged.

The present invention is particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature or with dry toner. The present invention also provides methods of imaging such a medium and such an imaged medium.

Background of the Invention

In certain cases it is desirable that a film be electrophotographically printable. Methods and apparatuses for electrophotographic printing are known. Electrophotographic printing generally includes imparting an image on a final receptor by forming a latent image on selectively charged areas of a photoconducter such as a charged drum, depositing a charged toner onto the charged areas of the photoconductor to thereby develop an image on the photoconductor, and transferring the developed toner from the charged drum under heat and/or pressure onto the final receptor. An optional transfer member can be located between the photoconductor and the final receptor. Examples of electrophotographic apparatuses and methods are disclosed in U.S. Patent Nos. 5,276,492; 5,380,611; and 5,410,392. The '492 and '392 patents both disclose that a preferred toner is a liquid toner comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which solvate in the carrier liquid at elevated temperatures. Examples of such liquid toners are disclosed in U.S. Patent No. 4,794,651. The '492 patent and the '392 patent both disclose that the toner image can be transferred to a receiving substrate such as paper ('492 patent: column 7, lines 19-20; '392 patent: column 4, lines 57- 58). While having their own utility, paper substrates are not desired for all applications and uses. The '611 patent discloses that the toner image can be transferred to a receiving substrate such as a transparency, without disclosing any particular composition of a transparency (column 4, lines 17).

It is also known that certain polymeric and ionomeric compositions are suitable for use with some printing methods and apparatuses. For example, flexographic printing on films made from SURLYN brand ionomeric resin, available from E.I. du Pont de Nemours & Company, Wilmington, DE has been suggested. See Brooks & Pirog. Processing of Surlyn® Ionomer Resins by Blown and Cast

Film Processes, p. 18, Du Pont Company, Plastics Department, Polyolefins Division, Technical Services Laboratory. U.S. Patent No. 5,196,246 discloses a wall decorating system that, in one embodiment, includes a SURLYN blend film that can be printed by etching, embossing, flexographic printing, silk screening, or gravure processes (column 14, lines 16-19).

Conventional printing processes include flexographic, gravure, and screen printing. These processes require a long time to make printing patterns, such as printing plates or gravure cylinders. Furthermore, the printing equipment needed for such processes is rather expensive. Such printing processes are not practical for short run print-on-demand type printing.

Polypropylene films are widely used in the printing industry especially in the areas of labels and packaging. Desirable features of polypropylene include its low cost, compoundability, and ease of processing.

Short run, print-on-demand type printing is becoming increasingly popular. Printers capable of providing such short run print-on-demand printing include those developed by Indigo Ltd. and those developed by Xeikon N. V. The Indigo printers can employ electrophotographic liquid toner whereas the Xeikon printers employ dry toner.

Commercially available polypropylene films which are untreated cannot be printed with an Indigo printer. A special solvent based polyamide coating (such as that available from Indigo Ltd. under the name Topaz) is usually required in order to yield acceptable printing with the Indigo printer. However, the image printed over such a coating typically exhibits poor Taber abrasion resistance (i.e., below 6).

Commercially available Topaz coated polypropylene films can be readily printed with a Xeikon printer. However, the resultant images demonstrate inadequate Taber abrasion resistance (i.e. below 6).

Ou-Yang et al., U.S. Patent Application Serial No. 08/615,010 and PCT International Publication No. WO US97/02506 describe a polymeric imaging medium comprising a receptor layer and an optional backing layer particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature, methods of imaging such a medium, and such an imaged medium. In one preferred embodiment, the receptor layer comprises a polymer of ethylene, n-butylacrylate, and methacrylic acid. In another preferred embodiment, the receptor layer comprises a blend of 60 to 90 percent by weight of a polymer comprising ethylene, n-butylacrylate, and methacrylic acid and about 10 to 40 percent by weight of a neutralized ethylene-methacrylic acid copolymer. Backing materials dislcosed include but are not limited to polyester, polyimide, polyvinylchloride (PVC), polycarbonate, and polypropylene. The receptor layer can be joined to the backing layer by a number of techniques. Suitable joining means include pressure sensitive adhesives, heat activated adhesives, sonic welding, and the like.

Copending U.S. Application Serial No. 08/846398, Ou-Yang, entitled "IMAGING MEDIUM COMPRISING POLYCARBONATE, METHOD OF MAKING, METHOD OF IMAGING, AND IMAGE-BEARING MEDIUM," discloses a polymeric imaging medium comprising a receptor layer and a polycarbonate backing layer particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature or with dry toner, making the imaging medium in the substantial absence of ultraviolet light radiation, method of imaging, and such an imaged medium which contains ultraviolet light stabilizers.

Copending U.S. Application Serial No. 08/847136, Ou-Yang, entitled "IMAGING MEDIUM COMPRISING POLYVINYL CHLORIDE, METHOD OF IMAGING SAID MEDIUM, AND IMAGE-BEARING MEDIUM," discloses a polymeric imaging medium comprising a receptor layer and a polyvinyl chloride backing layer particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature or with dry toner, methods of imaging such a medium, and such an imaged medium. Various packaging films are known which include ethylene-α-olefin polymers in a heat sealable layer. These films are primarily used in packaging applications that require sealing of a film to itself. Many of these materials have relatively broad composition distributions and low alpha-olefin content (less than or equal to 9 percent), and high density (greater than or equal to 0.910 gm/cm³). Furthermore, many of them do not adhere well to polypropylene. New ethylene-α-olefin polymers having a narrow composition distribution, however, have been developed. Examples of these are described in U.S. Patent No. 5,206,075 (Hodgson, Jr. et al., April 27, 1993) and International Publication No. WO 93/03093 (Meka et al., February 18, 1993). Although these materials display significant improvements over previous ethylene-α- olefin polymers, they are not universally useful for all packaging applications, particularly those that require sealing of a film to polypropylene.

PCT International Publication No. WO 95/23697 (Ou-Yang, published September 8, 1995) discloses a multiple layer composite film comprising: a layer of polymeric material that is capable of absorbing ultraviolet radiation and contains one or more polar functional groups and a layer of heat sealable material containing an ethylene -alpha -olefin polymer. The multiple-layer composite film is described as being capable of forming a strong bond with a polypropylene substrate, and capable of being cleanly separated from the polypropylene substrate when removal therefrom is desired. According to the reference the multiple-layer film composite can be used as a lidding film or sealing film for containers made of polymers comprising a significant percentage of propylene monomeric units.

U.S. Patent No. 5,346,764 discloses a resin laminate composed of a heat- sealable layer (A) containing a random copolymer obtainable by copolymerizing ethylene with an alpha-olefin having from 4 to 10 carbon atoms, having a density ranging from 0.900 to 0.920 g/cm³, a melt index ranging from 5 to 50 grams per 10 minutes (190°C), and a film thickness ranging from 2 to 15 micrometers, and a polyolefinic resin layer (B) having a tensile modulus of 4,000 kg/cm² or higher and a melting point higher than that of the heat-sealable layer (A), in which the heat- sealable layer (A) is laminated on the polyolefinic resin layer (B). According to the reference the resin laminate has an excellent heat sealability and is particularly suitable for packing liquid, powdery or granular matters such as various food, beverages, chemicals, and the like. A number of films are disclosed, including polypropylene.

SUMMARY OF THE INVENTION

What is desired is an imaging medium comprising a backing comprising propylene homopolymer and/or propylene copolymer (which is optionally modified by rubber) that can readily be printed by short run electrophotographic methods and apparatuses to produce high quality images and that is strong, durable, and abrasion-resistant.

I have discovered such an imaging medium. The present invention provides multilayer composite imaging media comprising a backing layer comprising a propylene homopolymer and/or propylene copolymer, a layer of intermediate material, and a receptor layer. The imaging media of the present invention are particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature. The imaging media of the present invention are also particularly useful in electrophotographic printing processes employing dry toner (such as dry powder toner). The present invention also provides methods of imaging such imaging media, and such an imaged media.

One advantage of the present invention is that all three layers, i.e., the receptor layer, the intermediate layer, and the backing layer can be coextruded together to form a composite film.

A first embodiment of the imaging medium of the invention is an imaging medium comprising:

(a) a backing layer comprising a backing polymer(s) wherein each backing polymer is independently formed from monomers comprising propylene; and wherein the melting point of the backing layer is not less than about 120°C; (b) an intermediate layer selected from the group consisting of ethylene- alpha-olefin polymer having a total alpha-olefin content of about 10 to about 30 weight %, a density of less than about 0.910 g/cm³, and a polydispersity of less than about 3.5; ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent, acid modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; acid and anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent; and less than or equal to about 45 weight percent; and mixtures thereof; and

(c) a receptor layer, wherein the receptor layer comprises a receptor layer polymer(s), wherein each receptor layer polymer independently is formed from monomers comprising (i) ethylene, (ii) monomer(s) selected from the group consisting of vinyl acetate, vinyl acrylate, vinyl carboxylic acids and mixtures thereof, and (iii) optionally an anhydride(s), wherein the receptor layer has a melt index of at least about 2.5 grams/10 minutes; and wherein the intermediate layer is bonded between said backing layer and said receptor layer; and and wherein at least one of the following of (i) and (ii) is true:

(i) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a liquid toner is at least about 6;

(ii) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a dry thermoplastic toner is at least about 6; and wherein at least one of the following of (I) and (II) is true:

(I) the intermediate layer and the receptor layer are not the same chemically when the intermediate layer is selected from the group consisting of: ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; acid modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 and less than or equal to about 45 weight percent; anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 and less than or equal to about 45 weight percent; acid and anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent; and less than or equal to about 45 weight percent; and mixtures thereof;

(H) the imaging medium is made in the substantial absence of ultraviolet light radiation. Preferably with respect to the imaging medium of the invention at least one of the following of (i) and (ii) is true:

(i) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a liquid toner is at least about 7; (ii) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a dry thermoplastic toner is at least about 7.

More preferably with respect to the imaging medium of the invention at least one of the following of (i) and (ii) is true:

(i) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a liquid toner is at least about 8; (ii) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a dry thermoplastic toner is at least about 8.

The imaging medium optionally can be made in the substantial absence of ultraviolet radiation and thus can include ultraviolet light stabilizers such as inhibitors and/or absorbers wherein the media can readily be printed by short run electrophotographic methods and apparatuses to produce high quality images and that is strong, durable, and abrasion-resistant.

The receptor layer utilized surprisingly demonstrates good adhesion to the intermediate layer and the intermediate layer to the backing layer in the substantial absence of ultraviolet ("UV") light radiation application. By discovering such a method and medium, components such as UV stabilizers can be included and not rendered useless by the manner of making the medium. Printing of such media results in imaged media which has highly desirable properties including resistance to fading on exposure to UV radiation due to the present discovery.

An imaging medium or imaged medium can be analyzed to determine whether it has experienced ultraviolet light degradation. This can be accomplished via electron spectroscopy for chemical analysis (ESCA). The following references discuss analysis for ultraviolet light degradation: Polymer Degradation, T. Kelen,

Chapter 7 (1983); Ultraviolet Light Induced Reactions in Polymers, by S. S. Labana, American Chemical Society Symposium Series #25, (1976); and Polymer Degradation and Stability, Vol. 2, p 203, (1980); all incorporated in their entirety herein by reference.

The imaging media and imaged media of the invention can be made in a manner such that they are free or substantially free of ultraviolet light degradation effects as determined by ESCA.

Preferably the intermediate layer comprises an ethylene-α-olefin polymer containing a total α-olefin content of about 10-30% and having a density of less than about 0.910 g/cm³ and a polydispersity of less than about 3.5. The present invention provides a method comprising a step of using the imaging medium of the present invention in an electrophotographic printing process.

An image may be formed from a dry thermoplastic toner or from a composition comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature.

The present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium wherein the toner employed is a liquid toner. The method comprises the steps of: a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature; b) heating the developed image to a temperature at least as high as the second temperature to thereby form a single phase of the thermoplastic particles and liquid carrier; and c) thereafter transferring the developed image to the receptor layer of the imaging medium of the invention at a temperature of about 120 to about 165°C. The present invention also provides a method of transferring an electrophotographically developed image from a photoconductor to an imaging medium, comprising the steps of: a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of thermoplastic dry toner particles wherein the toner particles are solid at a first temperature, but which soften or melt at or above a second temperature; b) transferring the developed image onto a receptor layer of an imaging medium of the present invention; c) heating and optionally applying pressure to the developed image such that it reaches a temperature at least as high as the second temperature to soften or melt the toner particles to form a final fixed image.

The present invention also provides an imaged article. The imaged article comprises a receptor layer having an imaging surface (also referred to as an "imageable surface"), that is, a surface capable of being imaged, and an image on the imaging surface, the image typically comprising a substantially continuous layer. In one embodiment the layer of the image comprises the thermoplastic and a liquid carrier that is not a solvent for the particles at a first temperature and which is a solvent for the particles at or above a second temperature, the layer having been deposited onto the imaging surface while in substantially a single phase with a liquid carrier. The resultant image is at least 95% free, preferably at least 98% free, more preferably at least 99% free and most preferably 100% free of solvent. In another embodiment the layer of the image is formed from dry toner particles.

An embodiment of the imaged medium of the invention is an imaged medium comprising:

(a) the imaging medium of the invention;

(b) an image on a surface of the receptor layer of the imaging medium which surface is not bonded to the intermediate layer, wherein the image is formed from a composition comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature.

Another embodiment of the imaged medium of the invention is an imaged medium comprising:

(a) the imaging medium of the invention;

(b) an image on a surface of the receptor layer of the imaging medium, which surface is not bonded to the intermediate layer (i.e. the surface opposite the surface bonded to the intermediate layer), wherein the image is formed from a dry thermoplastic toner.

Definitions

Certain terms are used in the description and the claims that, while for the most part are well known, some additional information is provided. It should be understood that the term "electrophotographic printing" refers to printing processes in which an image is imparted on a receptor by forming a latent image on selectively charged areas of a photoconducter such as a charged drum, depositing a charged toner onto the charged areas of the photoconductor to thereby develop an image on the photoconductor, and transferring the developed toner from the charged drum under heat and/or pressure onto an imaging medium. An optional transfer member can be located between the charged drum and the imaging medium. Examples of electrophotographic printing apparatuses are well known in the art and include, but are not limited to, the OMNIUS and E-1000 electrophotographic printers, available from Indigo, Ltd. of Rehovot, Israel; the DCP-1 printer available from Xeikon N. V. of Mortsel, Belgium; and the LANIER 6345 copier available from Lanier Worldwide, Inc. of Atlanta, Georgia.

The term "in the substantial absence of ultraviolet light radiation" as used herein means that an artificial source of ultraviolet light radiation such as a UV generating lamp is not present. Very minor amounts of ultraviolet light radiation may be present due to standard room lighting (such as fluorescent or incandescent lighting) or natural lighting. However, these amounts are insubstantial and would be less than about 10^"1 watts/inch (4x10^"4 watts/cm). Thus, bondings, etc. occurring in natural or standard room lighting would thus be considered to be in the substantial absence of ultraviolet light radiation.

All parts, percentages, ratios, etc. herein are by weight unless indicated otherwise.

Brief Description of the Drawings

Figure la is a cross-sectional view of a first embodiment of an imaging medium according to the present invention;

Figure lb is a cross-sectional view of a second embodiment of an imaging medium according to the present invention;

Figure 2 is a partial schematic view of an electrophotographic imaging apparatus for use with the present invention; and

Figure 3 is part of a simplified typical phase diagram for a preferred toner for use with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides imaging media comprising a particular receptor layer, an intermediate layer, and a backing layer comprising a homopolymer and/or copolymer of propylene monomer. The imaging media of the present invention are particularly useful in electrophotographic printing processes with liquid toners comprising thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature. The imaging media is also useful in electrophotographic printing processes with dry toner. The present invention also provides methods of imaging such imaging media, and such an imaged media.

The present invention provides multiple-layer, i.e., multilayer, composite films comprising a backing layer comprising propylene homopolymer and/or copolymer (which is preferably sequentially or simultaneously biaxially oriented), a layer of intermediate material , and an imageable receptor layer thereover. The strength of the bond between the backing layer and the intermediate layer is preferably at least about 32 ounces/inch (358 g/cm) as determined by a T-peel Adhesion Test described later herein. Thus, the films of the present invention eliminate the need for a tie layer or interdispersed anchor to bond the intermediate layer to the backing layer. Thus the intermediate layer functions as an anchor to bond the receptor layer to the backing. In this way, additional solvents, adhesives, and various other surface preparation techniques, such as corona discharge, are not needed to tie the two layers together. The strength of the bond between the receptor layer and the intermediate layer is also preferably at least about 32 ounces/inch (358 g/cm) as determined by a T-peel Adhesion Test described later herein

Advantageously and preferably, the backing layer is directly adhered to the intermediate layer. Thus, preferred films of the present invention are free of a tie layer between the backing layer and the intermediate layer

IMAGING MEDIUM

Referring now to Figure la, there is illustrated a first prefened embodiment of imaging medium 40. This embodiment includes receptor layer 42 bonded (such as by adhesion, for example) to polypropylene backing layer 50 via an intermediate layer 43. Both the receptor layer 42 and the backing layer 50 should preferably be able to form a strong bond, i.e., at least about 32 ounces/inch (358 g/cm) as measured via the T-Peel Adhesion Test (described later herein) with the intermediate layer.

Receptor layer 42 includes first major surface, or image surface 44, and second major surface, or back surface 46. Backing layer 50 includes first major surface 52 bonded via the intermediate layer 43 to the second surface 46 of the receptor layer. Backing layer also includes second major surface 54 opposite the first major surface 52. Optional layer of adhesive 20 may be provided on the second major surface 54 of the backing layer. When the adhesive layer is a pressure sensitive adhesive, then it is preferable to provide release liner 22 as is well known in the art. Direct printed image 18 has been printed on imaging surface 44 as is discussed in detail below. The receptor layer 42 preferably comprises receptor layer polymer(s) obtained by polymerizing ethylene with one or more monomers selected from the group consisting of vinyl acetate, esters of alkyl acrylic acid, esters of alkacrylic acid, vinyl acrylic acid, vinyl alkyl acrylic acid, and/or their anhydride derivatives, and mixtures thereof.

Referring now to Figure lb, there is illustrated a second preferred embodiment of imaging medium 80. This embodiment includes receptor layer 42 bonded to backing layer 50 via an intermediate layer 43. Receptor layer 42 includes first major surface, or image surface 44, and second major surface, or back surface 46. Backing layer 50 includes first major surface 52 joined via the intermediate layer 43 to the second surface 46 of the receptor layer. Backing layer also includes second major surface 54 opposite the first major surface 52. Optional layer of adhesive 20 may be provided on the first major surface 44 of the receptor layer 42 over reverse printed image 18. When the adhesive layer is a pressure sensitive adhesive, then it is preferable to provide release liner 22 thereover. Reverse printed image 18 has been printed on imaging surface 44. The backing layer 50 and the intermediate layer 43 should be translucent, transparent or a combination thereof and the receptor layer 42 should be translucent, transparent or a combination thereof to allow viewing of the image therethrough. Most preferably, the backing layer 50, the intermediate layer 43, and receptor layer 42 are transparent. Alternatively, the imaged medium of the invention may further comprise a layer of adhesive coated over the image and the surface of the receptor layer not bonded to the intermediate layer, wherein the receptor layer, the intermediate layer and the backing layer are selected such that the image can be viewed therethrough. For example, the receptor layer, the intermediate layer and the backing layer may each independently be transparent, translucent, or a combination thereof.

Ultraviolet Light Stabilizers

A variety of ultraviolet light stabilizers may optionally be used according to the present invention especially for imaging media which it is desired to be reverse imaged. These may be included in the receptor layer, the intermediate layer, and/or the backing layer. One class of such components are ultraviolet light absorbers. These materials typically function by absorbing harmful ultraviolet radiation and dissipating it as heat energy. Examples of such materials include but are not limited to those selected from the group consisting of benzotriazoles (such as Tinuvin 328 and Tinuvin 900, available from Ciba-Geigy Corporation, New York), benzophenones (such as Sandover 3041 available from Clariant Corporation,

Charlotte, North Carolina), and oxalanilides (such as Sandover VSU, available from Clariant Corporation) and triazines such as that available as Cyagard UV-1164 from Cytec Industries Inc., New Jersey.

Another class of such components are ultraviolet light inhibitors. These materials typically trap free radicals with subsequent regeneration of active stabilizer moieties, energy transfer, and peroxide decomposition. Examples of such materials include but are not limited to those selected from the group consisting of hindered amines (such as Tinuvin 292 and Tinuvin 144, both from Ciba-Geigy Corporation). If ultraviolet light stabilizer is included in the receptor layer, preferably both ultraviolet light absorber and ultraviolet light inhibitor are present at a weight ratio of ultraviolet light absorber to ultraviolet light inhibitor of about 1 :3 to about 3:1, more preferably about 1.5:2.5 to about 2.5:1.5.

The receptor layer may further comprise about 0 to about 3 percent by weight of a component (typically about 0.05 to about 3 percent, more typically about 0.1 to about 3 percent, if included) selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof, based on the total weight of the receptor layer, more preferably about 0.3 to about 1.5 percent by weight and most preferably about 0.5 to about 1 percent by weight.

Attachment of Receptor Layer and Intermediate Layer to the Backing

The receptor layer 42, can be bonded (or otherwise attached) such as by adhesion, for example, to the intermediate layer 43 by a number of techniques.

Suitable joining means include, for example, pressure sensitive adhesives and heat activated adhesives. In one preferred embodiment of imaging medium 40, the receptor layer 42, and the intermediate layer 43 are co-extruded on to the backing layer 50 to form a multilayer composite structure. In another preferred embodiment the materials from which receptor layer 42, intermediate layer 43, and backing layer 50 are formed are coextruded together to form a multilayer composite structure. The material of the receptor layer 42 and intermediate layer 43 are coated onto the backing layer 50 in a molten state by a conventional extrusion process. The temperature of the material of the receptor layer (or one of the individual layers of a receptor layer), when in the extruder, typically ranges from about 250°F (121°C) to about 560°F (293°C). The temperature of the material of the receptor layer 42 and intermediate layer 43 as it exits the extruder is typically from about 350°F (177°C) to about 560°F (293°C). After the material is extruded onto the backing layer, the thus-formed composite structure can be allowed to cool to typically ambient temperature.

Backing Layer

The backing layer comprises propylene homopolymer and/or a copolymer of propylene and one or more other olefins such as ethlylene, butene, pentene, hexene, etc.

Preferably the olefins have at least two carbon atoms, more preferably 2 or 4 carbon atoms, and most preferably two carbon atoms.. The backing material may optionally be modified with rubber. The backing layer may, for example, be casted. The backing layer may optionally be biaxially oriented (sequentially or simultaneously, for example). Simultaneously biaxially oriented polypropylene is commercially available from 4P Folie,

Forchheim, Germany with a manufacturer stated stretch ratio of 7: 1 in the machine direction and 7: 1 in the transverse (i.e. cross machine) direction.

The polymer for the backing layer (and the backing layer itself) is preferably chosen such that its melting or softening point is at least about 50°F (28°C) higher than that of the receptor layer. Preferably the melting point of the backing layer is not less than about 140°C.

Polypropylene backing layer materials useful in the present invention preferably have a melt flow rate (MFR) of at least about 2.5 grams/10 minutes, preferably ranging from about 3.0 to about 45 grams/10 minutes. Melt flow rate is determined by following the procedures set forth in ASTM Standard "D- 1238", " Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer", incorporated by reference herein, at 230°C; 2.16 kg.

Useful materials for the backing layer must withstand the temperatures involved in the printing process. That is, the most preferred polymeric materials for the backing layer do not melt or deteriorate significantly at temperatures up to about 320°F (160°C).

The backing layer can also include additives of a type and in an amount that do not substantially detrimentally impact its strength. For example, it can include: slip or antiblock agents such as silica or fatty acids (preferably in an amount no greater than about 1%); antifogging agents such as silicates (preferably in an amount no greater than about 1%); antioxidants or uv-stabilizers such as butylated hydroxy toluene anitioxidant

(preferably in an amount no greater than about 1%); pigments such as titanium dioxide, zinc oxide, iron oxide, or carbon black (preferably in an amount no greater than about 5%); and fillers such as calcium carbonate (preferably in an amount no greater than about 30%). The total amount of additives in the backing layer generally should not exceed about 40% of the total weight of the composition, i.e., unsaturated polymer and additives.

The choice of backing layer thickness is determined by the intended use of the multiple-layer composite imaging medium. The thickness of the backing layer is preferably from about 0.0025 to 0.25 mm (0.1 to 10 mils), and more preferably about 0.013 to 0.13 mm (0.5 to 5 mils). When an opaque backing is desired it preferably has an optical density of 2.5 +/- 10% as measured on a MacBeth TD927 densitometer, available from Macbeth of Newburgh, NY.

Intermediate Layer In the broadest sense, the ethylene vinyl acetate containing polymer of the intermediate layer has a melt point index of at least 2.5 grams/ 10 minutes and a vinyl acetate content greater than about 9% and less than or equal to about 45% by weight, preferably from about 12 to 35 % by weight. In another embodiment, the polymer further comprises acrylic or methacrylic acid in an amount of at least about 0.1 % by weight but less than or equal to about 6.0 %, preferably at least about 1% by weight. The polymer may further comprise a small amount of an anhydride, preferably less than about 3.0 % , more preferably less than about 2.0% by weight. In one preferred embodiment, the intermediate layer comprises an ethylene vinyl acetate ("EVA") copolymer. Preferably, the EVA has a vinyl acetate content of at least about 10% by weight, preferably about 12 to 35% by weight. One example of a preferred EVA copolymer is EL VAX 3175 commercially available from E.I. du Pont de Nemours & Company, Wilmington, DE ("du Pont") and has a melt index of approximately 6.0 grams/ 10 minutes and a vinyl acetate content of about 28%. If the intermediate layer comprises an EVA modified with acid, for example methacrylic acid, it preferably comprises at least 1.0% acid. One example of such a terpolymer is EL VAX 4260 commercially available from du Pont which has a melt index of approximately 6.0 grams/ 10 minutes, a vinyl acetate content of approximately 28%, and a methacrylic acid content of approximately 1.0%. If the receptor comprises an EVA modified with anhydride, it preferably comprises at least 0.1% anhydride, such as maleic anhydride. One example of such a terpolymer is "MODIC E-300-K" available commercially from Mitsubishi Petroleum Co., Ltd. of Japan.

In another embodiment the intermediate layer comprises an ethylene-α-olefin polymer. The polymers are preferably single site polymers as defined below. The ethylene-α- olefin polymer is chosen such that the intermediate layer does not delaminate from the backing layer and such that it forms a strong bond to the receptor layer.

The T-peel Adhesion of the receptor layer to the intermediate layer is preferably at least 32 ounces/inch (358 g/cm), more preferably at least about 48 ounces/inch (537 g/cm), and most preferably at least about 60 ounces inch (671 g/cm) according to the T-Peel Adhesion Test described later herein.

The T-peel Adhesion of the backing to the intermediate layer is preferably at least 32 ounces/inch (358 g/cm), more preferably at least about 48 ounces/inch (537 g/cm), and most preferably at least about 60 ounces inch (671 g/cm) according to the T- Peel Adhesion Test described later herein. For desired adhesion, the total α-olefin content of the ethylene-α-olefin polymer is about 10-30%. Preferably, the ethylene-α-olefin polymers are prepared from olefins having at least 4 carbon atoms, more preferably 4-20 carbon atoms, and most preferably 4-12 carbon atoms. Examples include but are not limited to those selected from the group consisting of butene, pentene, hexene, heptene, octane, and mixtures thereof. Particularly preferred α-olefins are 1 -butene, 1-octene, and 1 -hexene. Of these, 1- butene is the most preferred. The ethylene-α-olefin polymers can include one or more types of α-olefin comonomers. For example, combinations of ethylene and one type of α-olefin monomer, or copolymers of three monomers, such as a terpolymer of ethylene and two types of α-olefin monomers. The material used in the intermediate layer can also include mixtures of different ethylene-α-olefin polymers. Useful ethylene-α-olefin polymers are characterized as having a low degree of crystallinity such that the polymers readily flow in the molten state and such that the composite film formed will be flat. Preferably, the density is less than about 0.910 g/cm³, more preferably less than about 0.900 g/cm³, and most preferably about 0.850 g/cm³ to about 0.900 g/cm³ (as determined by ASTM Test Method D 792-91, Method A, 1991).

Useful ethylene-α-olefin polymers are also characterized as having a relatively narrow molecular weight distribution and/or a relatively small number of carbons in the short side-chain branches of the otherwise linear ethylene polymer. Preferably, useful ethylene-α-olefin polymers have a polydispersity, i.e., a molecular weight distribution (MyJMn), of less than about 3.5, more preferably less than about 3.0, and greater than about 1.5. Most preferably, the ethylene-α-olefin polymers used in the intermediate layers of the imaging media of the present invention have a polydispersity within a range of about 2.0-3.0.

The composition distribution of useful ethylene-α-olefin polymers is preferably less than about 40 total carbons in the short chain branches (which result from the addition of the α-olefin monomers) per 1000 carbons in the polymer, and more preferably within a range of about 5-35 per 1000. Alternatively, the composition distribution of useful ethylene-α-olefin polymers can be reported as the composition distribution breadth index (CDBI). Preferably the CDBI is at least about 50%, and more preferably at least about 70%. The CDBI is the weight percent of the polymer molecules having a comonomer content within 50% of the median molar comonomer content. Either way of reporting, the composition distribution can be determined by Temperature Rising Elution Fractionation as described by Wild et al., J. Poly. Sci.. Poly. Phys. Ed.. 20, 441 (1982), which is incorporated herein by reference.

The ethylene-α-olefin polymers should also have an essentially single melting point characteristic with a peak melting point (T_m) of no greater than about 100°C , as determined by Differential Scanning Calorimetry (DSC). Preferably the DSC peak T_m is about 50°C to about 100°C. "Essentially single melting point" as used herein means that at least about 80% by weight of the material corresponds to a single T_m peak. The melt index (MI) of useful ethylene-α-olefin polymers for the films of the present invention is greater than about 1.0 gram/10 minutes, preferably about 2.5-100 grams/10 minutes, as determined by ASTM Test Method D1238-90B, Method A, 1990.

Ethylene-α-olefin polymers that meet all the requirements of the polymers used in the intermediate layers of the imaging media of the present invention include those prepared using single-site catalysts, i.e., catalysts that permit olefins such as ethylene and α-olefin to react only at single sites on the catalyst molecules. Suitable such ethylene-α- olefin polymers are described in U.S. Patent No. 5,206,075 (Hodgson, Jr. et al., April 27, 1993) and International Publication No. WO 93/03093 (Meka et al., February 18, 1993), the disclosures of which are incorporated herein by reference. They are commercially available from Exxon Chemical Company, Houston, TX, under the tradename EXACT or from Dow Chemical, Midland, MI, under the tradenames

AFFINITY and ENGAGE. These ethylene-α-olefin polymers are referred to herein as "single site" polymers.

These "single site" polymers are distinguished from ethylene-α-olefin polymers made using Ziegler Natta catalysts, which have multiple active sites, in that the single site polymers typically have narrower molecular weight distributions and more desirable α-olefin short-chain branching distributions. As indicated herein, however, not all single site ethylene-olefin polymers are suitable for use in the intermediate layers of the imaging media of the present invention. For example, those having an α-olefin content of 9.0% or less do not adhere well to polypropylene. Also, those having an α-olefin content of greater than about 30% are generally too tacky to handle in the process. In preferred embodiments of the imaging medium of the present invention, the intermediate layer 43 contains a blend of an ethylene-α-olefin polymer and a compatible elastomeric polymer, e.g., rubber, having a low degree of crystallinity and tack. As used herein, the term "compatible" means that the elastomeric polymer does not bloom from the composition. Preferably, the compatible elastomeric polymer has a glass transition temperature (Tg) of less than about 0°C, and a molecular weight (Staudinger) of greater than about 10,000, more preferably about 11,000-99,000. Suitable such elastomeric polymers include polyisobutylene and ethylene propylene rubber. The preferred elastomeric polymer is polyisobutylene. Preferably this blend includes at least about 10%, more preferably about 10% to about 40%, and most preferably about 10% to about 30% elastomeric polymer, e.g., polyisobutylene, based on total weight of the blend. If it is greater than about 40% by weight, the composition, i.e., blend, is too tacky, and does not flow well.

The ethylene-α-olefin elastomeric polymer blend can be prepared by blending the rubber using a twin screw extruder designed for rubber, such as is available from the

Bonnot Co., Creen, OH, with the ethylene-α-olefin polymer. The molten polymeric blend is then extruded as a rod form into a water bath. The solid blend can then be pelletized using a standard chopper.

The intermediate layer can also contain small amounts of other materials, such as the additives described above for the backing layer, so long as these materials do not adversely affect the function of the polymers. The total amount of additives in the intermediate layer generally should not exceed about 40% of the total weight of the composition.

The thickness of intermediate layer is not necessarily critical, but it preferably ranges from about 0.3 mil (0.008 mm) to about 10.0 mils (0.254 mm), more preferably from about 0.7 mil (0.018 cm) to about 1.5 mils (0.04 mm). The choice of thickness is determined by intended use of the imaging medium.

Receptor Layer Receptor layer materials useful in the present invention preferably have a melt index (MI) of at least about 2.5 grams/ 10 minutes, preferably ranging from about 3.0 to about 45 grams/10 minutes. Melt index is determined by following the procedures set forth in ASTM Standard "D-1238", "Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer", incorporated by reference herein, at 190°C; 2.16 kg. The thickness of the receptor layer is not necessarily critical, but it is preferably from about 0.008 to about 0.25 mm (about 0.3 to about 10 mils), more preferably from about 0.013 to about 0.13 mm (about 0.5 to about 5 mils). The desired thickness is determined by the intended use of the film and desired characteristics of the imaging medium affecting handling and cutting. To produce the receptor layer used according to this invention, pellets or powder of resin along with optional resins or additives, as obtained from the manufacturer, are mixed together, melted, and extruded to form a film. The film can be extruded onto the intermediate layer as described in detail later herein. Alternatively the aforementioned layers can be coextruded. Alternatively, all three layers (receptor, intermediate, and backing) may be coextruded.

Preferably the polymer(s) making up the receptor layer (i.e. the receptor layer polymer(s)) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 75 to about 99 percent by weight ethylene and about 1 to about 25 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 52 to about 85 percent by weight ethylene and about 15 to about 48 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 60 to about 90 percent by weight ethylene and about 10 to about 40 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 37 to about 89 percent by weight ethylene, about 1 to about 15 weight percent vinyl carboxylic acid, and about 10 to about 48 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 45 to about 89 percent by weight ethylene, about 1 to about 15 weight percent vinyl carboxylic acid, and about 10 to about 40 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 37 to about 89.9 percent by weight ethylene, about 0.1 to about 15 weight percent anhydride, and about 10 to about 48 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 45 to about 94.9 percent by weight ethylene, about 0.1 to about 15 weight percent anhydride, and about 5 to about 40 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof. More preferably the receptor layer polymer(s) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 80 to about 98 percent by weight ethylene and about 2 to about 20 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 60 to about 85 percent by weight ethylene and about 15 to about 40 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 70 to about 90 percent by weight ethylene and about 10 to about 30 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 48 to about 84 percent by weight ethylene, about 1 to about 12 weight percent vinyl carboxylic acid, and about 15 to about 40 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 52 to about 89 percent by weight ethylene, about 1 to about 12 weight percent vinyl carboxylic acid, and about 10 to about 30 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 42 to about 84.9 percent by weight ethylene, about 0.1 to about 12 weight percent anhydride, and about 15 to about 40 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 52 to about 89.9 percent by weight ethylene, about 0.1 to about 12 weight percent anhydride, and about 10 to about 30 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof.

Most preferably the receptor layer polymer(s) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 85 to about 96 percent by weight ethylene and about 4 to about 15 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 65 to about 82 percent by weight ethylene and about 18 to about 35 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 75 to about 85 percent by weight ethylene and about 15 to about 25 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 55 to about 81 percent by weight ethylene, about 1 to about 10 weight percent vinyl carboxylic acid, and about 18 to about 35 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 65 to about 83 percent by weight ethylene, about 2 to about 10 weight percent vinyl carboxylic acid, and about 15 to about 25 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 55 to about 81.5 percent by weight ethylene, about 0.5 to about 10 weight percent anhydride, and about 18 to about 35 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 65 to about 84 percent by weight ethylene, about 1 to about 10 weight percent anhydride, and about 15 to about 25 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof.

Optionally, the polymer(s) which make up the receptor layer may be modified by the incorporation of anhydrides (e.g., maleic anhydride) or vinyl carboxylic acid (e.g., methacrylic acid, acrylic acid, etc., mixtures thereof) or mixtures thereof, etc., into the polymer. For example, the previously mentioned polymer may be neutralized with a metal cation thereby forming an ionomer, having a neutralized acid content of from about 2 to about 6% by weight and an acid content of no more than about 15% by weight based upon the total weight of the polymer(s). The ionomer may comprise, for example, a neutralized ethylene-co- methacrylic acid ionomer. For example, the polymer(s) may comprise methacrylic acid in an amount of at least about 1% by weight based upon the total weight of the polymer(s). As another example, the polymer(s) may comprise an anhydride in an amount of at least about 0.1% by weight based upon the total weight of the polymer(s). As another example, the polymer(s) may comprise methacrylic acid in an amount of at least about 2% by weight based upon the total weight of the polymer(s). As another example, the polymer(s) may comprise the polymerization product of a composition comprising ethylene and an acid selected from the group consisting of methacrylic acid and acrylic acid, having a melt index of at least about 2.5 grams/10 minutes and an acid content of from about 2 to about 20% by weight based upon the total weight of the polymer(s). Optionally, those receptor layer polymer(s) modified with acid may be partially neutralized by the addition of a metal cation, thus forming ionomers. Alternatively, blends of receptor layer polymer(s) may be formed and used by mixing together two or more of the above polymers. Additionally, one or more of these receptor layer polymers or blends may be further blended with low density (0.910 g/cc) (or below) polyethylene

(LDPE) or linear low density polyethylene (LLDPE). LLDPE's are commonly made by low pressure polymerization carried out at pressures in the range of about 7 to 20 bar in the gas phase in a fluid bed reactor or in the liquid phase. In low pressure polymerization, ethylene units polymerize in a linear fashion, whereby short branches or side chains can be built into the structure at intervals by copolymerizing with small amounts of α-olefins such as propylene, butene, octene, or hexene. The density of the LDPE or LLDPE polymer is controlled by the frequency of the side chains.

In one preferred embodiment, the receptor layer polymer(s) comprises an ethylene vinyl acetate ("EVA") copolymer. (It may, for example, comprise two monomers, three monomers, etc.). Typically the EVA(s) has a vinyl acetate ("VA") content of at least about 15% by weight, preferably about 15% to about 40% by weight, and more preferably about 18% to about 35% by weight based upon the total weight of the polymer(s) and a melt index of at least about 2.5 grams/ 10 minutes. One example of a preferred EVA copolymer is EL VAX 3175 commercially available from E.I. du Pont de Nemours & Company, Wilmington,

DE ("du Pont") and has a melt index of approximately 6.0 grams/10 minutes and a vinyl acetate content of about 28%. If the receptor layer comprises an EVA modified with acid, for example methacrylic acid, it typically comprises at least about 1 percent by weight acid, preferably about 1 to about 12% by weight acid. As a specific example, the receptor layer polymer(s) may be formed from monomers comprising ethylene, vinyl acetate, and methacrylic acid, the receptor layer polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes, wherein the vinyl acetate content is about 15 to about 40 percent by weight and the acid content is about 1 to about 12 percent by weight based upon the total weight of the receptor layer polymer(s). One example of such a terpolymer is EL VAX 4260 commercially available from du Pont which has a melt index of approximately 6.0 grams/ 10 minutes, a vinyl acetate content of approximately 28%, and a methacrylic acid content of approximately 1.0%. If the receptor layer polymer comprises an EVA modified with anhydride, it preferably comprises at least about 0.1% anhydride, such as maleic anhydride. One example of such a terpolymer is

"MODIC E-300-K" available commercially from Mitsubishi Petroleum Co., Ltd. of Japan. Polymers having a vinyl acetate content below about 15% by weight tend to have poor printability characteristics; and polymers having a vinyl acetate content above about 35% by weight tend to be sticky and less practical to use in the extrusion and printing processes.

In another preferred embodiment, the receptor layer polymer comprises an ethylene/vinyl acrylate copolymer, the vinyl acrylate comprising, for example, vinyl alkyl acrylates such as vinyl methyl acrylate, vinyl ethyl acrylate, vinyl propyl acrylate, vinyl n-butyl acrylate, vinyl n-pentyl acrylate, vinyl n-hexyl acrylate, and other acrylates such as vinyl alkacrylates such as vinyl methacrylate, vinyl ethacrylate, vinyl propacrylate, vinyl butacrylate, vinyl pentacrylate, vinyl hexacrylate, and mixtures thereof. In a preferred embodiment the receptor layer polymer comprises a polymer of ethylene acrylate, having a melt index of at least about 2.5 grams/ 10 minutes and an acrylate content of from about 10 to about 30% by weight, based upon the total weight of the receptor layer polymer(s). If the receptor layer polymer(s) comprises an ethylene/vinyl acrylate terpolymer having acid, for example methacrylic acid incorporated therein, it comprises at least about 1% acid, preferably about 1 to about 12 percent by weight acid, based upon the total weight of the receptor layer polymer(s). As a specific example, the receptor polymer(s) may be formed from monomers comprising ethylene, vinyl acrylate, and methacrylic acid, the receptor layer polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes, wherein the vinyl acrylate content is about 10 to about 30 percent by weight and the acid content is about 1 to about 12 percent by weight based upon the total weight of the receptor layer polymer(s). One example of such a terpolymer is "BYNEL CXA 2002" from du Pont, a terpolymer comprising ethylene, n-butylacrylate, and methacrylic acid having a melt index of approximately 10.0 grams/ 10 minutes, a methacrylic acid content of about 10%, and an n-butylacrylate content of about 10%, based upon the total weight of the receptor layer polymer(s). If the receptor layer polymer(s) comprises an ethylene vinyl acrylate anhydride terpolymer, it preferably comprises at least about 0.1% anhydride, such as maleic anhydride, based upon the total weight of the receptor layer polymer(s). The acrylate content is preferably about 10 to about 30%, based upon the total weight of the receptor layer polymer(s).

In another prefened embodiment, the receptor layer polymer comprises an ethylene/acid copolymer, the acid preferably comprising methacrylic acid or other vinyl carboxylic acid in an amount of about 2 to 20% by weight based upon the total weight of the copolymer and a melt index of at least about 2.5 grams/10 minutes. Polymers having a lower acid content may not have sufficient abrasion resistance. Polymers having a higher acid content may damage processing equipment over extended periods of time. An example of such an ethylene/acid copolymer is NUCREL 1207 available from du Pont, having a melt index of about 7.0 g/10 minutes and a methacrylic acid content of about 12.0%. In another prefened embodiment, the receptor layer polymer(s) comprises an ethylene acid copolymer that has been partially neutralized with a metal cation, thereby forming an ionomer. The salt content is preferably be greater than about 1% by weight, and preferably ranges from about 2 to about 6% by weight, with preferably no more than 15% leftover acid. Preferred examples of ionomers include copolymers of ethylene with acrylic acid or methacrylic acid, neutralized with a metal cation such as zinc, sodium, potassium, or magnesium. Particularly preferred ionomeric polymers are copolymers of ethylene with methacrylic acid. E.I. Du Pont de Nemours Co. produces a line of neutralized ethylene-co-methacrylic acid ionomeric polymers under the trade designation "SURLYN" that are acceptable for the present use, provided that the selected resin has the requisite melt index. A particularly preferred ionomeric resin is commercially available under the trade designation "SURLYN 1705", which has a melt index of 5.5 grams/ 10 minutes which is neutralized with zinc cation, is about 3% acid neutralized, and has about 12% acid content .

In one preferred embodiment, the receptor layer polymer component of the receptor layer 42 comprises a blend of any one of the above receptor layer polymers in an amount of about 60 to about 90% with any other of the receptor layer polymers in an amount of about 10 to about 40% based upon the total weight of the receptor layer polymer component. In yet another preferred embodiment, the receptor layer comprises a blend of any one of the above receptor layer polymers with up to about 40% LDPE or LLDPE.

A specific example of a receptor layer polymer blend is a blend of one receptor layer polymer and another receptor layer polymer, wherein the one receptor layer polymer comprises a polymer of ethylene, n-butylacrylate, and methacrylic acid having a melt index of at least about 2.5 grams/ 10 minutes; and wherein the other receptor layer polymer comprises a neutralized ethylene-co- methacrylic acid ionomer. The receptor layer polymer(s) component of the receptor layer preferably comprises a blend of the one receptor layer polymer in an amount from about 60 to about 90% by weight and the other receptor layer polymer in an amount from about 10 to about 30% by weight, based upon the total weight of the receptor layer polymer(s) component.

Method of Making Multilayer Composite Imaging Medium of the Invention The intermediate layer can be bonded to the backing layer by a number of techniques. In a preferred manner, the material of the receptor layer and the intermediate layer are applied to the backing layer by means of extrusion to form a composite structure. The material of the backing layer is provided as a film of polymeric material. The material of the receptor layer and the intermediate layer are coated onto the supporting polymer film in a molten state by a conventional extrusion process. The temperature of the material of the intermediate layer, when in the extruder, typically ranges from about 250°F (138°C) to about 560°F (293°C). A typical process temperature profile for a three-zone extruder is 250°F (121 °C ) (Zone 1), 350°F (177°C) (Zone 2), 450°F (221°C) (Zone 3), 450°F (221°C) (die). The temperature of the material of the intermediate layer, as it exits the extruder, typically ranges from about

350°F (177°C) to about 560°F (293°C) A more economical way is to co-extrude the backing layer (propylene hompolymer and/or copolymer), intermediate layer, and the receptor layer together and simultaneously or sequentially orient them in both the machine direction and transverse direction. Preferably the imaging medium is capable under the "PRINT QUALITY TEST' described later herein of displaying a value of "FAIR/GOOD' OR "GOOD", preferably "GOOD" when the receptor layer is printed on a described above.

Adhesives Adhesives useful in the preparation of an adhesive coated imaging medium according to the present invention include both pressure sensitive and non-pressure sensitive adhesives such as hot melt and curable adhesives (such as ultraviolet light curable adhesives, for example). Adhesive may be used, for example, between a backing layer and a release liner (See Fig. la) Pressure sensitive adhesives are normally tacky at room temperature and can be adhered to a surface by application of, at most, light finger pressure, while non-pressure sensitive adhesives include solvent or heat activated adhesive systems. Pressure sensitive adhesives are a preferred class of adhesives for use in the present invention. Examples of adhesives useful in the invention include those based on general compositions of polyacrylate; polyvinyl ether; diene-containing rubber such as natural rubber, polyisoprene, and polyisobutylene; polychloroprene; butyl rubber; butadiene-acrylonitrile polymer; thermoplastic elastomer; block copolymers such as styrene-isoprene and styrene- isoprene-styrene block copolymers, ethylene-propylene-diene polymers, and styrene-butadiene polymer; poly-alpha-olefin; amorphous polyolefin; silicone; ethylene-containing copolymer such as ethylene vinyl acetate, ethylacrylate, and ethyl methacrylate; polyurethane; polyamide; epoxy; polyvinylpynolidone and vinylpyrrolidone copolymers; polyesters; and mixtures of the above. Additionally, the adhesives can contain additives such as tackifiers, plasticizers, fillers, antioxidants, stabilizers, pigments, diffusing particles, curatives, and solvents.

A general description of useful pressure sensitive adhesives may be found in Encyclopedia of Polymer Science and Engineering. Vol. 13. Wiley-Interscience

Publishers (New York, 1988). Additional description of useful pressure sensitive adhesives may be found in Encyclopedia of Polymer Science and Technology. Vol. 1, Interscience Publishers (New York, 1964).

Other pressure sensitive adhesives useful in the invention are described in the patent literature. Examples of these patents include Re 24,906 (Ulrich), U.S.

Patent No. 3,389,827 (Abere et al.), at Col. 4-Col. 5, U.S. Patent No. 4,080,348 (Korpman), U.S. Patent No. 4,136,071 (Korpman), U.S. Patent No. 4,181,752 (Martens et al.), U.S. Patent No. 4,792,584 (Shiraki et al.), U.S. Patent No. 4,883,179 (Young et al.), and U.S. Patent No. 4,952,650 (Young et al.). Commercially available adhesives are also useful in the invention. Examples include those adhesives available from 3M Company, St. Paul, MN; H.B. Fuller Company, St. Paul, MN; Century Adhesives Corporation, Columbus, OH; National Starch and Chemical Corporation, Bridgewater, NJ; Rohm and Haas Company, Philadelphia, PA; and Air Products and Chemicals, Inc., Allentown, PA. In one embodiment the imaged medium further comprises a layer of adhesive coated over a surface of the backing layer not bonded to the intermediate layer and a release liner attached to a surface of the adhesive layer opposite the backing layer.

In another embodiment the imaged medium further comprises a layer of adhesive coated over the image and the surface of the receptor layer not bonded to the intermediate layer, and wherein the intermediate layer, the receptor layer and the backing layer are selected such that the image can be viewed therethrough.

TONERS

Liquid Toners Liquid toners typically comprise pigments, binder, carrier solvent, dispersing agents, and charge additives. Preferably, the toner comprises thermoplastic toner particles in a liquid carrier that is not a solvent for the particles at a first temperature and that is a solvent for the particles at a second temperature, especially those disclosed in U.S. Patent No. 5,192,638, "Toner for Use in Compositions for Developing Latent Electrostatic Images, Method of Making the Same, and Liquid

Composition Using the Improved Toner" (Landa et al.), the entire disclosure of which is incorporated herein by reference. Landa et al. '638 discloses a liquid composition for developing latent electrostatic images comprising toner particles associated with a pigment dispersed in a nonpolar liquid. The toner particles are formed with a plurality of fibers or tendrils from a thermoplastic polymer and carry a charge of a polarity opposite to the polarity of the latent electrostatic image. The polymer is insoluble or insolvatable in the dispersant liquid at room temperature. The toner particles are formed by plasticizing the polymer and pigment at elevated temperature and then either permitting a sponge to foπn and wet-grinding pieces of the sponge or diluting the plasticized polymer-pigment while cooling and constantly stirring to prevent the forming of a sponge while cooling. When cool, the diluted composition will have a concentration of toner particles formed with a plurality of fibers.

These fibers are formed from a thermoplastic polymer and are such that they may interdigitate, intertwine, or interlink physically in an image developed with a developing liquid through which has been dispersed the toner particles of the instant invention. The result is an image on the photoconductor having good sharpness, line acuity-that is, edge acuity-and a high degree of resolution. The developed image on the photoconductor has good compressive strength, so that it may be transferred from the surface on which it is developed to the imaging medium without squash. The intertwining of the toner particle permits building a thicker image and still obtaining sharpness. The thickness can be controlled by varying the charge potential on the photoconductor, by varying the development time, by varying the toner-particle concentration, by varying the conductivity of the toner particles, by varying the charge characteristics of the toner particles, by varying the particle size, or by varying the surface chemistry of the particles. Any or a combination of these methods may be used.

In addition to being thermoplastic and being able to form fibers as above defined, the polymer used in the particles of Landa et al. '683 preferably has the following characteristics: it is able to disperse a pigment (if a pigment is desired); it is insoluble in the dispersant liquid at temperatures below 40°C, so that it will not dissolve or solvate in storage; it is able to solvate at temperatures above 50°C; it is able to be ground to form particles between 0.1 micron and 5 microns in diameter; it is able to form a particle of less than 10 microns; it is able to fuse at temperatures in excess of 70°C; by solvation, the polymers forming the toner particles will become swollen or gelatinous. This indicates the formation of complexes by the combination of the molecules of the polymer with the molecules of the dispersant liquid.

Landa et al. '683 discloses three methods of forming toner particles having the desired fibrous morphology. The first method briefly includes dispersing or dissolving pigment particles in a plasticized polymer at temperatures between 65°C and 100°C. The plasticized material when cooled has the form of a sponge. The sponge is then broken into smaller pieces and ground. Another method includes dissolving one or more polymers in a nonpolar dispersant, together with particles of a pigment such as carbon black or the like. The solution is allowed to cool slowly while stirring, which is an essential step in this method of forming the fiber-bearing toner particles. As the solution cools, precipitation occurs, and the precipitated particles will be found to have fibers extending therefrom. A third method is to heat a polymer above its melting point and disperse a pigment through it. In this method, fibers are formed by pulling the pigmented thermoplastic polymer apart without first forming a sponge. The fibrous toner particles, formed by any of the foregoing methods, are dispersed in a nonpolar carrier liquid, together with a charge director known to the art, to form a developing composition.

Landa et al. '683 discloses a toner particle formed with a plurality of fibers- that is to say, one with such morphology. Such a toner particle enables forming a developing composition for developing latent electrostatic images by dispersing the toner particles in small amounts in a nonpolar liquid such as an ISOPAR. The weight of the toner particle may be as low as 0.2 percent by weight of the weight of the dispersant liquid. The toner particle is pigmented and formed of a polymeric resin. A charge director is added to the composition in small amounts, which may be as low as one-tenth percent by weight of the weight of the toner particles in the developing composition. The charge director may be selected to impart either a positive or a negative charge to the toner particles, depending on the charge of the latent image. Those in the art will understand that the charge on the toner particles is generally opposite in polarity to that carried by the latent electrostatic image. In Landa et al. '683, the nonpolar dispersant liquids are, preferably, branched-chain aliphatic hydrocarbons-more particularly, ISOPAR-G, ISOPAR-H,

ISOPAR-K, ISOPAR-L, and ISOPAR-M. These ISOPARs are narrow cuts of isoparaffinic hydrocarbon fractions with extremely high levels of purity. For example, the boiling range of ISOPAR-G is between 156°C. and 176°C. ISOPAR-L has a mid-boiling point of approximately 194°C. ISOPAR-M has a flash point of 77°C and an auto-ignition temperature of 338°C. They are all manufactured by the Exxon Corporation. Light mineral oils, such as MARCOL 52 or MARCOL 62, manufactured by the Humble Oil and Refining Company, may be used. These are higher boiling aliphatic hydrocarbon liquids.

The polymers used in Landa et al. '683 are thermoplastic, and the preferred polymers are known as EL VAX II, manufactured by du Pont, including resin numbers 5550; 5610; 5640; 5650T; 5720; and 5950. The original EL VAX resins (EVA) were the ethylene vinyl acetate copolymers. The new family of EL VAX resins, designated EL VAX II are ethylene copolymers combining carboxylic acid functionality, high molecular weight, and thermal stability. The preferred ethylene copolymer resins of Landa et al. '683 are the EL VAX II 5720 and 5610. Other polymers which are usable are the original EL VAX copolymers and polybutyl terephthalate. Still other useful polymers made by Union Carbide are the DQDA 6479 Natural 7 and DQDA 6832 Natural 7. These are ethylene vinyl acetate resins. Other useful polymers are NUCREL ethylene acrylic acid copolymers available from du Pont. Landa et al. '683 also discloses that another useful class of polymers in making the particles are those manufactured by du Pont and sold under the trademark ELVACITE. These are methacrylate resins, such as polybutyl methacrylate (Grade 2044), polyethyl methacrylate (Grade 2028), and polymethyl methacrylate (Grade 2041). If desired, a minor amount of carnauba wax may be added to the composition. However, this tends to produce bleed-through and an oil fringe on the copy and is not preferred. Furthermore, if a hard polymer such as 5650T is used, a minor amount of hydroxy-ethyl cellulose may be added. This is not preferred.

The polymers of Landa et al. '683 are normally pigmented so as to render the latent image visible, though this need not be done in some applications. The pigment may be present in the amount of 10 percent to 35 percent by weight in respect of the weight of the polymer, if the pigment be Cabot Mogul L (black pigment). If the pigment is a dye, it may be present in an amount of between 3 percent and 25 percent by weight in respect of the weight of the polymer. If no dye is used-as, for example, in making a toner for developing a latent image for a printing plate-an amount of silica such as CABOSIL may be added to make the grinding easier. Examples of pigments are Monastral Blue G (C.I. Pigment Blue 15 C.I. No. 74160), Toluidine Red Y (C.I. Pigment Red 3), Quindo Magenta (Pigment Red 122), Indo Brilliant Scarlet Toner (Pigment Red 123, C.I. No. 71145), Toluidine Red B (C.I. Pigment Red 3), Watchung Red B (C.I. Pigment Red 48),

Permanent Rubine F6B13-1731 (Pigment Red 184), Hansa Yellow (Pigment Yellow 98), Dalamar Yellow (Pigment Yellow 74, C.I. No. 11741), Toluidine Yellow G (C.I. Pigment Yellow 1), Monastral Blue B (C.I. Pigment Blue 15), Monastral Green B (C.I. Pigment Green 7), Pigment Scarlet (C.I. Pigment Red 60), Auric Brown (C.I. Pigment Brown 6), Monastral Green G (Pigment Green 7), Carbon Black, and Stirling NS N 774 (Pigment Black 7, C.I. No. 77266).

Landa et al '683 also discloses that a finely ground ferromagnetic material may be used as a pigment. About 40 percent to about 80 percent by weight of Mapico Black is preferred, with about 65 percent Mapico Black being optimum, other suitable materials such as metals including iron, cobalt, nickel, various magnetic oxides including Fe₂O₃, Fe O₄, and other magnetic oxides; certain ferrites such as zinc, cadmium, barium, manganese; chromium dioxide; various of the permalloys and other alloys such as cobalt-phosphorus, cobalt-nickel, and the like; or mixtures of any of these may be used.

Landa et al. '683 theorizes that, in dispersion, all of the toner particles have the same polarity of charge. When the particles approach each other, they are repelled, owing to the fact that each possesses a charge of the same polarity. When the latent electrostatic image is developed, the toner particles are impelled to go to the latent electrostatic image, which has a higher potential and a charge of opposite polarity. This forces the toner particles to associate with each other and to mat or interdigitate. The fact that the toner particles in the developed image are matted enables a more complete transfer from the photoconductor to be made to the carrier sheet. The matting also prevents spreading of the edges of the image and thus preserves its acuity. The small diameter of the toner particles ensures good resolution, along with the other results outlined above. It is known that to impart a negative charge to the particles, such charge directors as magnesium petronate, magnesium sulfonate, calcium petronate, calcium sulfonate, barium petronate, barium sulfonate, or the like, may be used. The negatively charged particles are used to develop images carrying a positive charge, as is the case with a selenium-based photoconductor. With a cadmium-based photoconductor, the latent image carries a negative charge and the toner particles must therefore be positively charged. A positive charge can be imparted to the toner particles with a charge director such as aluminum stearate. The amount of charge director added depends on the composition used and can be determined empirically by adding various amounts to samples of the developing liquid. The invention can be practiced using a variety of toner types but is especially useful for toners comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which solvate carrier liquid at elevated temperatures. This is a characteristic of the toner of Example 1 of U.S. Pat. No. 4,794,651, previously incorporated by reference. Part of a simplified phase diagram of a typical toner of this type is shown in Figure 3. This diagram represents the states of the polymer portion of the toner particles and the carrier liquid. The pigment in the particles generally takes little part in the process, and references herein to "single phase" and to "solvation" refer to the state of the polymer part of the toner particles^' together with the carrier liquid. In a preferred embodiment, the toner is prepared by mixing 10 parts of EL VAX II 5950 ethylene vinyl acetate copolymer (from E. I. du Pont) and 5 parts by weight of ISOPAR L (Exxon) diluent which is not a solvent for the EL VAX II 5950 at room temperature. The mixing is performed at low speed in a jacketed double planetary mixer connected to an oil heating unit for one hour, the heating unit being set at 130°C. A mixture of 2.5 parts by weight of Mogul L carbon black (Cabot) and 5 parts by weight of ISOPAR L is then added to the mix in the double planetary mixer and the resultant mixture is further mixed for one hour at high speed. 20 parts by weight of ISOPAR L pre-heated to 110°C are added to the mixer and mixing is continued at high speed for one hour. The heating unit is disconnected and mixing is continued until the temperature of the mixture drops to 40°C. 100 g of the resulting material is mixed with 120 g of ISOPAR L and the mixture is milled for 19 hours in an attritor to obtain a dispersion of particles. The material is dispersed in ISOPAR L to a solids content of 1.5% by weight. The prefened liquid developer prepared comprises toner particles which are formed with a plurality of fibrous extensions or tendrils as described above. The prefened toner is characterized in that when the concentration of toner particles is increased above

20%, the viscosity of the material increases greatly, apparently in approximately an exponential manner. A charge director, prepared in accordance with the Example of U.S. Patent No. 5,047,306, "Humidity Tolerant Charge Director Compositions" (Almog), the entire disclosure of which is incorporated herein by reference, is preferably added to the dispersion in an amount equal to about 3% of the weight of the solids in the developer. Examples of preferred thermoplastic toner particles are selected from the group consisting of ethylene vinyl acrylate copolymers, ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ionomers of ethylene acrylic acid copolymers, and mixtures thereof.

A specific example of a preferred toner for use with the present invention is commercially known as ELECTROINK for E-PRINT 1000 ethylene vinyl acetate based toner manufactured by Indigo Ltd. of Rehovot, Israel.

Dry Toners

Dry thermoplastic toners are also useful according to this present invention. Examples of useful dry thermoplastic toners include but are not limited to those selected from the group consisting of polyester toners (such as those available from Xeikon N. V.). It is theorized that other dry thermoplastic toners would be useful according to the present invention such as styrene/acrylate copolymer available from Lanier Worldwide, Inc.

IMAGING METHODS AND APPARATUS

In electrophotographic processes, an electrostatic image may be produced by providing a photoconductive layer, such as on a rotating drum, with a uniform electrostatic charge and thereafter selectively discharging the electrostatic charge by exposing it to a modulated beam of radiant energy. It will be understood that other methods may be employed to form an electrostatic image, such, for example, as providing a carrier with a dielectric surface and transferring a preformed electrostatic charge to the surface. The charge may be formed from an anay of styluses. A latent image is thus formed on the charged drum. Charged toner is deposited on the charged areas of the drum, and the toner is then transfened under heat and/or pressure to the imaging medium 40. Images may be printed on imaging medium 40 using direct image printing or reverse image printing. Preferably, the toner can be transfened in an intermediate step to a transfer member between the charged drum and the imaging medium.

While the present invention can be advantageously used with many known electrophotographic methods and apparatuses, a particularly preferred apparatus and method is disclosed in U.S. Patent No. 5,276,492, "Imaging Method and Apparatus" (Landa et al.), the entire disclosure of which is incorporated herein by reference.

In a preferred embodiment of the invention, a liquid toner image is transfened from an image forming surface to an intermediate transfer member for subsequent transfer to a final substrate. The liquid toner image includes a liquid portion including carrier liquid and a solids portion including pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and the polymer portion of which forms substantially a single phase with canier liquid at elevated temperatures. The prefened imaging method generally includes the steps of concentrating the liquid toner image to a given nonvolatile solids percentage by compacting the solids portion thereof and removing carrier liquid therefrom; transferring the liquid toner image to an intermediate transfer member; heating the liquid toner image on the intermediate transfer member to a temperature at least as high as that at which the polymer portion of the toner particles and the carrier liquid form substantially a single phase at the given solids percentage; and transferring the heated liquid toner image to a final substrate.

Liquid toner images are developed by varying the density of pigmented solids in a developer material on a latent image bearing surface in accordance with an imaged pattern. The variations in density are produced by the corresponding pattern of electric fields extending outward from the latent image bearing surface. The fields are produced by the different latent image and background voltages on the latent image bearing surface and a voltage on a developer plate or roller. In general, developed liquid toner images comprise carrier liquid and toner particles and are not homogeneous. To improve transfer of a developed image from the latent image bearing surface to a substrate, it is most desirable to ensure that, before transfer, the pigmented solids adjacent background regions are substantially removed and that the density of pigmented solids in the developed image is increased, thereby compacting or rigidizing the developed image. Compacting or rigidizing of the developed image increases the image viscosity and enhances the ability of the image to maintain its integrity under the stresses encountered during image transfer It is also desirable that excess liquid be removed from the latent image bearing surface before transfer. Many methods are known to remove the carrier liquid and pigmented solids in the region beyond the outer edge of the image and thus leave relatively clean areas above the background. The technique of removing carrier liquid is known generally as metering. Known methods include employing a reverse roller spaced about 50 microns from the latent image bearing surface, an air knife, and corona discharge. It is also known to effect image transfer from a photoreceptor onto a substrate backed by a charged roller. Unless the image is rigidized before it reaches the nip of the photoreceptor and the roller, image squash and flow may occur.

Figure 2 illustrates a preferred electrophotographic imaging apparatus 100 for use with the present invention. The apparatus is described for liquid developer systems with negatively charged toner particles, and negatively charged photoconductors, i.e., systems operating in the reversal mode. For other combinations of toner particle and photoconductor polarity, the values and polarities of the voltages are changed, in accordance with the principles of the invention. As in conventional electrophotographic systems, the apparatus 100 of

Figure 2 typically comprises a drum 110 arranged for rotation about an axle 112 in a direction generally indicated by arrow 114. Drum 110 is formed with a cylindrical photoconductor surface 116.

A corona discharge device 118 is operative to generally uniformly charge photoconductor surface 116 with a negative charge. Continued rotation of drum

110 brings charged photoconductor surface 116 into image receiving relationship with an exposure unit including a lens 120, which focuses an image onto charged photoconductor surface 116, selectively discharging the photoconductor surface, thus producing an electrostatic latent image thereon. The latent image comprises image areas at a given range of potentials and background areas at a different potential. The image may be laser generated as in printing from a computer or it may be the image of an original as in a copier.

Continued rotation of drum 110 brings charged photoconductor surface 116, bearing the electrostatic latent image, into a development unit 122, which is operative to apply liquid developer, comprising a solids portion including pigmented toner particles and a liquid portion including carrier liquid, to develop the electrostatic latent image. The developed image includes image areas having pigmented toner particles thereon and background areas. Development unit 122 may be a single color developer of any conventional type, or may be a plurality of single color developers for the production of full color images as is known in the art. Alternatively, full color images may be produced by changing the liquid toner in the development unit when the color to be printed is changed. Alternatively, highlight color development may be employed, as is known in the art.

In accordance with a preferred embodiment of the invention, following application of toner thereto, photoconductor surface 116 passes a typically charged rotating roller 126, preferably rotating in a direction indicated by an arrow 128.

Typically, the spatial separation of the roller 126 from the photoconductor surface 116 is about 50 microns. Roller 126 thus acts as a metering roller as is known in the art, reducing the amount of carrier liquid on the background areas and reducing the amount of liquid overlaying the image. Preferably the potential on roller 126 is intermediate that of the latent image areas and of the background areas on the photoconductor surface. Typical approximate voltages are: roller 126: 500 V, background area: 1000 V and latent image areas: 150 V. The liquid toner image which passes roller 126 should be relatively free of pigmented particles except in the region of the latent image. Downstream of roller 126 there is preferably provided a rigidizing roller

130. Rigidizing roller 130 is preferably formed of resilient polymeric material, such as polyurethane which may have only its natural conductivity or which may be filled with carbon black to increase its conductivity. According to one embodiment of the invention, roller 130 is urged against photoconductor surface 116 as by a spring mounting (not shown). The surface of roller 130 typically moves in the same direction and with the same velocity as the photoconductor surface to remove liquid from the image.

Preferably, the biased squeegee described in U.S. Patent No. 4,286,039, "Method and Apparatus for Removing Excess Developing Liquid From Photoconductive Surfaces" (Landa et al.), the entire disclosure of which is incorporated herein by reference, is used as the roller 130. Roller 130 is biased to a potential of at least several hundred and up to several thousand Volts with respect to the potential of the developed image on photoconductor surface 116, so that it repels the charged pigmented particles and causes them to more closely approach the image areas of photoconductor surface 116, thus compacting and rigidizing the image.

In a preferred embodiment of the invention, rigidizing roller 130 comprises an aluminum core having a 20 mm diameter, coated with a 4 mm thick carbon-filled polyurethane coating having a Shore A hardness of about 30-35, and a volume resistivity of about 10⁸ ohm-cm. Preferably roller 130 is urged against photoconductor surface 116 with a pressure of about 40-70 grams per linear cm of contact, which extends along the length of the drum. The core of rigidizing roller 130 is energized to between about 1800 and 2800 volts, to provide a voltage difference of preferably between about 1600 and 2700 volts between the core and the photoconductor surface in the image areas. Voltage differences of as low as 600 volts are also useful.

After rigidization under these conditions and for the preferred toner, the solids percentage in the image portion is believed to be as high as 35% or more, when carrier liquid absorbed as plasticizer is considered as part of the solids portion. It is preferable to have an image with at least 25-30% solids, after rigidizing. When the solids percentage is calculated on a non-volatile solids basis, the solids percentage is preferably above 20% and is usually less than 30%. Values of 25% have been found to be especially useful. At these concentrations the material has a paste like consistency.

Alternatively, the carbon filled polyurethane can be replaced by unfilled polyurethane with a volume resistivity of about 3 x 10¹⁰, and the voltage is adjusted to give proper rigidizing.

Downstream of rigidizing roller 130 there is preferably provided a plurality of light emitting diodes (LEDs) 129 to discharge the photoconductor surface, and equalize the potential between image and background areas. For process color systems, where yellow, magenta and cyan toners are used, both red and green LEDs are provided to discharge the areas of the photoconductor behind the developed image as well as the background areas.

Downstream of LEDs 129 there is provided an intermediate transfer member 140, which rotates in a direction opposite to that of photoconductor surface 116, as shown by arrow 141. The intermediate transfer member is operative for receiving the toner image from the photoconductor surface and for subsequently transferring the toner image to the imaging medium 40.

Various types of intermediate transfer members are known and are described, for example, in U.S. Patent No. 4,684,238, "Intermediate Transfer Apparatus" (Till et al.) and U.S. Patent No. 5,028,964, "Imaging System With Rigidizer And Intermediate Transfer Member" (Landa et al.) the entire disclosures of both of which are incorporated herein by reference.

In general, intermediate transfer member 140 is urged against photoconductor surface 116. One of the effects of the rigidization described above is to prevent substantial squash or other distortion of the image caused by the pressure resulting from the urging. The rigidization effect is especially pronounced due to the sharp increase of viscosity with concentration for the preferred toner.

Transfer of the image to intermediate transfer member is preferably aided by providing electrical bias to the intermediate transfer member 140 to attract the charged toner thereto, although other methods known in the art may be employed. Subsequent transfer of the image to imaging surface 44 of receptor layer 42, respectively, on the imaging medium is preferably aided by heat and pressure, with pressure applied by a backing roller 143, although other methods known in the art may be employed.

Following transfer of the toner image to the intermediate transfer member, photoconductor surface 116 is engaged by a cleaning roller 150, which typically rotates in a direction indicated by an arrow 152, such that its surface moves in a direction opposite to the movement of adjacent photoconductor surface 116 which it operatively engages. Cleaning roller 150 is operative to scrub and clean surface 116. A cleaning material, such as toner, may be supplied to the cleaning roller 150, via a conduit 154. A wiper blade 156 completes the cleaning of the photoconductor surface. Any residual charge left on photoconductor surface 116 is removed by flooding the photoconductor surface with light from a lamp 158.

In a multi-color system, subsequent to completion of the cycle for one color, the cycle is sequentially repeated for other colors which are sequentially transfened from photoconductor surface 116 to intermediate transfer member 140. The single color images may be sequentially transfened to the imaging medium 40 in alignment, or may alternatively be overlaid on the intermediate transfer member 140 and transferred as a group to the imaging medium.

Details of the construction of the surface layers of preferred intermediate transfer members are shown in U.S. Patent No. 5,089,856, "Image Transfer Apparatus Incorporating An Integral Heater" (Landa et al.), the entire disclosure of which is incorporated herein by reference. Generally, the image is heated on intermediate transfer member 140 in order to facilitate its transfer to imaging medium 40. This heating is preferably to a temperature above a threshold temperature of substantial solvation of the carrier liquid in the toner particles. As seen in Figure 3, when the image is heated, the state of the image, i.e. of the polymer portion of the toner particles and the carrier liquid, depends on several factors, mainly on the temperature of the intermediate transfer member and on the concentration of toner particles. Thus, if the percentage of toner particles is "A" and the intermediate transfer member temperature is " Y" the liquid image separates into two phases, one phase being substantially a liquid polymer/carrier-liquid phase and the other phase consisting mainly of canier liquid. On the other hand, if the percentage of toner particles is "B" at the same temperature, then substantially only one phase, a liquid polymer/carrier-liquid phase will be present. It is believed to be preferable that separate liquid polymer/carrier-liquid and liquid phases do not form to any substantial degree, as will be the case for example if the concentration is "C". This type of phase separation is believed to be undesirable on the intermediate transfer member 140. It is believed that an absence of substantial phase separation of this type in the image on the intermediate transfer member results in improved image quality, including an improvement in line uniformity.

It is understood that heating the image on the intermediate transfer member 140 is not meant to completely dry the image, although some evaporation of carrier liquid may result. Rather, the image on the intermediate transfer member remains a viscous liquid until its transfer to the final substrate.

Other methods of concentrating the image than those just described, i.e., compacting the solids portion thereof and removing liquid therefrom, can be utilized provided they concentrate the image to the extent required. These methods include the use of separate solids portion compactors and liquid removal means, such as those described in U.S. Patent No. 5,028,964, previously incorporated herein by reference. Alternatively the apparatus may utilize a solids portion compactor followed by an intermediate transfer member urged against the photoconductor to remove liquid from the image. As a further alternative, the commutated intermediate transfer member described in the '964 patent may be used to provide both solids portion compacting and liquid removal, just prior to transfer to the intermediate transfer member. Furthermore the concentrating step may take place on the intermediate transfer member after transfer of the liquid toner image thereto and before heating the image.

The receptor layers of the present invention provide a superior bond to the toners described herein when applied by electrophotographic printing methods just described. This is believed to result from the chemical compatibility between the toner's carrier resin and the receptor layer. Without desiring to be bound by any particular theory, it is presently believed that the thermoplastic toners described herein have a solubility parameter that is a close match to that of the receptor layer. This indicates a chemical compatibility between the receptor layer and the toner polymer resulting in a strong bond between the toner and the receptor layer.

The imaging media of the present invention are particularly durable and abrasion resistant in addition to being readily printable by the short run methods described herein.

The method of the present invention employing a dry toner can, for example, employ a copy machine such as Hewlett Packard Laser Jet copy machine available from Hewlett Packard or a Lanier 6540 copier available from Lanier Worldwide, Inc.

Uses

The imaging media of the present invention are well suited for use as labels, tags, tickets, signs, data cards, name plates, and packaging films (such as self sealing packaging films, for example), for example, although the uses of the imaging media of the present invention are not thereby limited.

Properties

The imaging medium of the present invention has a T-Peel adhesion value of the intermediate layer to the receptor layer and of the intermediate layer to the backing layer preferably at least about 32 oz/in (358 g/cm), more preferably at least about 48 oz/in (537 g/cm), and most preferably at least about 60 oz/in (671 g/cm).

The imaged medium of the present invention typically has a print quality value of at least about fair, preferably at least about fair/good, and most preferably at least about good, when printed by either or both the Xeikon and Indigo printing methods such as those described later herein.

The imaged medium of the present invention typically has a Taber abrasion resistance value of at least about 6 (most typically at least 6), preferably at least about 7, and most preferably at least 8 when printed by either or both the Xeikon and Indigo printing methods such as those described later herein (as well as other electrophotographic printing methods). The above described properties can, for example, be measured on an image which is produced by a four-color process (yellow, magenta, cyan, black). Such a four-color process was used according to the test methods and examples below.

TEST METHODS

The following test methods are utilized herein.

Taber Abrasion Resistance Test

The following abrasion test was used herein. A modified version of ASTM Test method Designation: D 4060-81 , Standard Test Method for ABRASION

RESISTANCE OF ORGANIC COATINGS BY THE TABER ABRASER, was used (pp. 918-920 of the 1982 ANNUAL BOOK OF ASTM STANDARDS, Part 27, ASTM, Philadelphia, Pennsylvania, U.S.A.) incorporated by reference herein. The following machine was used: a Taber Abraser Model 503 (Standard Abrasion Tester) by Teledyne Taber, Tonawanda, New York. The apparatus used was such that the abrasive wheels used according to 5.2 were resilient calibrated wheels No. CS-10. With respect to 6.1, the specimens were 4 in. (108 mm) square with rounded corners and with a V* in. (6.3 mm) hole centrally located on each panel. With respect to 7.1 the load on the wheels was adjusted to 250 g. With respect to 7.3 the suction regulator was set to approximately 100% on the dial. According to

9.4 the specified number of cycles was 100. Sections 8, 10, 11, and 12 of the test were not employed.

A limitation is included in certain claims that an image formed by a liquid toner and/or an image formed by a dry thermoplastic toner on the receptor layer must have a certain Taber abrasion resistance value. In order to test compliance with this requirement, one would provide an image on an imaging medium receptor layer with the Indigo printer and liquid toner as discussed in the Print Quality Testin order to test an image formed from a liquid toner. In order to test an image formed from a dry toner, one would use the Xeikon printer and dry thermoplastic toner discussed in the Print Quality Test in order to provide an image formed from a dry toner. Images thus provided could be tested for Taber abrasion resistance. (Although it is desirable that the imaging medium of the invention having an image provided on its surface according to any of the methods and toners described herein have an acceptable Taber abrasion resistance value, this test method provides a convenient, consistent means of making such a determination.)

T-Peel Adhesion Test T-peel adhesion of heat sealed samples was measured using two samples, each 4-5 inches (10.2-12.7 cm) down-web by 6 inches (15.2 cm) cross-web, cut from an imaging medium comprising a backing layer, an intermediate layer, and a receptor layer. The two cut samples were placed receptor layer to receptor layer and put in a heat sealer (Model No. 12 AS, from Sentinel Machinery Packaging Industries, Montclair, NJ) set at 250°F (121°C) with a pressure of 40 p.s.i. (2815 g/cm^) and a dwell time of 1 second. The resultant heat sealed sample was removed from the heat sealer and stored at about 73°F (22.8°C)/50% relative humidity for about 24 hours. Three strips, each 2.5 cm wide and 10.2 cm long, were cut from the heat sealed sample perpendicular to and across the sealed area to form a test sample of about 1 inch (2.54 cm) square with unsealed leaders on each edge. One leader of the test sample was clamped in the upper jaw of an INSTRON Tensile Tester (Model No. 1123) and the other leader was clamped in the lower jaw of the tensile tester. The test sample was separated at a rate of 12 inches (30.48 cm)/minute.

180° Peel Test

Sealability of the multiple-layer composite film to a substrate comprising a propylene polymer was determined by means of a 180° Peel Test. The procedure is as follows: (1) from a roll of multiple-layer composite film, samples 1 inch (2.54 cm) wide by 4 inches (10.16 cm) long were cut; (2) a sheet of polypropylene approximately 5 inches (12.7 cm) by 4 inches (10.16 cm) was cut from a web; (3) three samples of composite film were placed on the polypropylene sheet (surfaces to be sealed should be clean and dry) and sealed via the heat sealable layer using a

Sentinel heat sealer under the following sealing conditions: desired temperature ~ 410°F (210°C) (for the samples of Table 1A), b) 40 lbs/in² (2815 g/cm²), 1.0 second dwell time with the composite film located next to the upper sealer jaw and the polypropylene sheet located next to the lower sealer jaw; (4) when the seals had cooled, the polypropylene sheet was cut into three sections taking care not to cut into the composite film; (5) all sealed samples were conditioned at room temperature for 24 hours after sealing before the Instron 180° Peel Test was performed; (6) the peel strength was tested at room temperature (i.e., 20-30°C) by placing a portion of the composite film in the upper jaw of an Instron 180° peel testing apparatus and a portion of the polypropylene sheet in the lower jaw of the Instron apparatus (the Instron apparatus was set at 100 ounces (2838 g) scale with crosshead speed of about 12 inches (30.48 cm) per minute and chart speed of about 5 inches (12.7 cm) per minute and jaw separation at 3 inches (7.62 cm); (7) the entire seal was then pulled and the jaws pulled away from each other at a speed of about 12 inches (30.48 cm) per minute and the maximum force in ounces/inch necessary to separate the bond recorded.

Print Quality Test

Printing on the imaging medium was performed by either the Indigo press or the Xeikon press. The Indigo press utilized was a Scorpion model press available from Indigo. The Xeikon press utilized was a DCP-1 model press available from Xeikon. When the Indigo press was utilized, the imaging medium was web fed into the press at 200 steps using a blanket set up temperature of 140°C. The liquid toner used with the Indigo press was an ethylene vinyl acetate based toner known as ELECTROINK for E-PRINT 1000 manufactured by Indigo Ltd. of Rehovot, Israel.

When the Xeikon press was utilized, the imaging medium was also web fed by using radiation heat to fuse the powder toner of the image at approximately 400°F (204.4°C). The dry powder toner used with the Xeikon press was a polyester toner available from Xeikon under the name Xeikon toner. The print quality was assessed visually by holding the printed film at normal reading distance (about 12 inches [30.5 cm]) from the naked eye. "No Printing" indicates that no portion of an image was transferred from the blanket to the receptor; "Poor" indicates that less than about 50% of the image was transferred; "Fair" indicates that 50-80% of the image was transferred; "Fair/Good" indicates that greater than 80% but less than 95% of the image was transfened; and "Good" indicates that at least about 95% of the images was transferred.

With respect to all the tests herein, any of the above indicated inks can be substituted by other products provided as newer or replacement versions of the specific inks listed herein.

The invention will be further described by reference to the following detailed examples. These examples are offered to further illustrate the various specific and prefened embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present invention. All parts, percentages, ratios, etc. in the examples and elsewhere throughout are by weight unless indicated otherwise.

EXAMPLES 1-33

Imaging media comprising a polypropylene backing layer, an intermediate layer and a receptor layer were prepared. All grades of polypropylene listed in TABLE I were obtained from Union Carbide. The three materials identified in TABLE I were independently used as the intermediate layer between the backing layer and the receptor layer. The receptor layer used in all the examples was 80%

BYNEL CXA 2002 (acid modified ethylene acrylate; MI of about 10.0 g/10 min.; available from duPont) :20% SURLYN 1705 (neutralized ethylene-co-methacrylic acid ionomeric polymer; about 3% acid neutralized with zinc cation; melt index of about 5.5 g/10 min.; about 12% acid content; available from duPont). The materials for each imaging medium in TABLE I were melted and extruded using three extruders, each independently containing the respective polypropylene, the material of the intermediate layer and the receptor layer polymers respectively. The temperature profile of each extruder was: zone 1 = 250°F (121°C); zone 2 = 350°F (177°C); zone 3 = 450°F (221°C). The die temperature was 450°F (221°C). The overall thickness of the final three layer composite was about 4 mils (0.1 mm) with the backing layer being about 1.5 mils (0.04 mm), the intermediate layer being about 1.0 mil (0.03 mm) and the receptor layer being about 1.5 mils (0.04 mm).

Samples of each example in TABLE I were prepared and the adhesion measured as described in the T-Peel Adhesion Test (i.e., at 250°F (121°C)) . Additional samples of each example in TABLE I were prepared and adhesion measured as described in the T-Peel Adhesion Test, except that the heat sealer temperature was set at 280°F (138°C) instead of 250°F (121°C). The results reported are the average of three independent determinations. The results are in oz/in and in parentheses in g/cm. The T-Peel Adhesion values reported in TABLE I reflect the bond strength between the backing layer and the intermediate layer and show the particularly good adhesion obtained between particular polypropylene backings and particular materials comprising the intermediate layer.

TABLE I

MFR = Melt Flow Rate.

2

Tm = Melt temperature. ³ CXA-11E573 = BYNEL CXA-11E573; acid modified EVA with MI of about 6.9 g/10 min., density of 0.923 g/cc and melt temperature of 95°C; available from duPont.

E = Ethylene. B = Butene. EPR = Ethylene propylene rubber.

⁷ CXA 1123 = BYNEL CXA 1123; acrylic acid modified EVA with MI of about 6.6 g/10 min.; available from duPont.

⁸ EXACT 3027 = Ethylene/butene copolymer; MI of about 3.5 g/10 min.; density of 0.900 g/cc; available from Exxon. To measure the 180 degree peel adhesion between the intermediate layer and the backing layer, eight constructions were prepared. TABLE I A shows the 180 degree peel adhesion for eight constructions. The backing layer for all the constructions was Himont USA, Wilmington, Delaware, PF-101 (polypropylene homopolymer), melt flow rate=2.0.

To prepare each construction, the material of the intermediate layer identified in TABLE IA was melted and extruded onto the ethylene vinyl acetate side of SP-135 film (0.3 mil [0.008mm] thick ethylene vinylacetate film laminated to 0.56 mil [0.01mm] polyester; commercially available from Minnesota Mining and Manufacturing Company (3M Company) under the trademark SCOTCHPAK™). The temperature profile of the extruder was: zone 1 = 250°F (121°C); zone 2 = 350°F (177°C); zone 3 = 450°F (221°C). The die temperature was 450°F (221°C). The overall thickness of the two layer composite was 2.4 mils (0.06 mm) with the thickness of the intermediate layer being 1.5 mils (0.038 mm).

Using the procedure of the 180° Peel Test, each two-layer composite construction was sealed to the Himont PF-101 backing and the peel adhesion determined. The data in Table IA below demonstrate the 180° peel adhesion between the intermediate layer and the polypropylene backing layer (Himont PF-101).

TABLE IA

Run Weight %

No. Vinyl Acetate

Intermediate 180 Degree Melt Index Wt. %

Layer Peel Adhesion Methacrylic Acid

7 Surlyn 1605⁷ 0.5 ... 28 Na ion modified

8 Surlyn 1705^s 1.0 ... 5.5 Zn ion modified

1 e _*thyl tene methacrylic acid copolymer available from DuPont

2 ethylene vinylacetate copolymer available from DuPont ethylene vinylacetate copolymer available from DuPont ethylene vinylacetate copolymer available from DuPont ethylene vinylacetate copolymer available from DuPont ethylene vinylacetate copolymer modified with methacrylic acid available from DuPont ethylene methacrylic acid copolymer neutralized with sodium ion available from DuPont ethylene methacrylic acid copolymer neutralized with zinc ion available from DuPont

To measure the bond strength between the intermediate layer and the receptor layer, imaging media comprising a backing layer, an intermediate layer and a receptor layer were prepared. For all the Run Nos., the three materials identified in TABLE II were independently extrusion laminated onto the ethylene vinyl acetate side of SP-135. For each Run No., the receptor layer utilized was the BYNEL:SURLYN portion of a 2-layer composite, Y-3984 (1.64 mil [0.04 mm]

80% BYNEL CXA 2002:20% SURLYN 1705 on a 0.92 mil [0.02 mm] film of PET), available from 3M Company under the trademark 3M Y-3984.

For each Run No. in TABLE II, the material of the intermediate layer was melted and extruded at a thickness of 1.0 mil (0.03 mm) onto the EVA film side of the SP-135. The temperature profile of the extruder was: zone 1 = 250°F (121°C); zone 2 = 350°F (177°C); zone 3 = 450°F (221°C). The die temperature was 450°F (221°C).

Strips of Y-3984 were cut as described in the T-Peel Adhesion Test and heat sealed to the intermediate layer that had been extruded onto the SP-135. The BYNEL:SURLYN portion of Y-3984 was placed adjacent the intermediate layer and the conditions for sealing were as described in the T-Peel Adhesion Test.

Adhesion between the receptor layer and the intermediate layer was measured for each Run No. in TABLE II. Samples of each example in TABLE II were prepared and the adhesion measured as described in the T-Peel Adhesion Test (i.e., at 250°F (121°Q). Additional samples of each example in TABLE II were prepared and adhesion measured as described in the T-Peel Adhesion Test, except that the heat sealer temperature was set at 280°FC (138°C) instead of 250°F (121°C). The results reported are the average of three independent determinations. The results are in oz/in and in parentheses in g/cm. The T-Peel Adhesion values reported in TABLE II reflect the bond strength between the intermediate layer and the receptor layer and show the excellent adhesion obtained between a particular material comprising the receptor layer and three different materials comprising the intermediate layer.

TABLE π

EXACT 4011 = Ethylene butene copolymer; about 20-25% butene; MI of about 2.2 g/10 min. and density of 0.885 g/cc; available from Exxon.

EXAMPLES 34-35 AND COMPARATIVE EXAMPLES 36-37

Imaging media comprising a polypropylene backing layer, an intermediate layer and a receptor layer of the invention were prepared in Examples 34 and 35.

For Example 34, the resin for the polypropylene backing layer was FINA 3374X (MFR of 3; available from Fina Oil and Chemical Company, Dallas, TX). The polypropylene was extruded using an extruder temperature profile of: zone 1 = 250°F (121°C); zone 2 = 350°F (177°C); zone 3 = 450°F (221°C). The die temperature was 450°F (221°C). The polypropylene backing was sequentially biaxially oriented in the machine direction at a ratio of 5 : 1 and then in the transverse direction at a ratio of 7.5: 1, resulting in a backing layer that was 1.4 mil (0.04 mm) thick. For example 35 the polypropylene backing layer was a simultaneously biaxially oriented polypropylene from 4P Folie, Forchheim, Germany with a manufacturer stated stretch ratio of 7:1 in the machine direction and 7:1 in the transverse (i.e., cross machine) direction.

The material identified as the intermediate layer in Run No. 3 in TABLE II and the material identified as the receptor layer in Examples 1-33 were independently melted and coextruded onto the polypropylene backing layer with the intermediate layer being extruded on the polypropylene backing layer and the receptor layer being extruded on the intermediate layer. The extruder temperature profile and the die temperature utilized for both the intermediate layer and the receptor layer were that detailed for the polypropylene backing layer. The thickness of the intermediate layer was 0.5 mil (0.01 mm) and the thickness of the receptor layer was 1.5 mils (0.04 mm).

Comparative Examples 36 and 37 were two different image media identified in TABLE III and available from Mobil Chemical Company under the tradename DIGLLYTE.

The samples of Examples 34-35 and Comparative Examples 36-37 were direct image printed using the Indigo press. Two imaged samples of each example were evaluated to determine the image quality using the Print Quality Test. Taber abrasion resistance (TAR) was measured on the imaged samples using the Taber Abrasion Resistance Test. The print quality assessment and the TAR values in TABLE III show that both the examples of the invention and the DIGLLYTE exhibited Good print quality, but that the composite image media of the invention had far superior Taber abrasion resistant properties.

TABLE m

Samples comprising various receptor layers was imaged with both the Indigo press and the Xeikon press and the print quality assessed using the Print Quality Test. Taber abrasion resistance was measured on imaged samples using the Taber Abrasion Resistance Test.

The data in TABLE IV show that Runs 1-13 all demonstrate Fair-Good or Good print quality with an Indigo and/or Xeikon printing process. Taber abrasion resistance was good for all samples evaluated. For Runs 1-13 the side of the receptor layer which was not printed was adhered to a polycarbonate layer. However, this would have no effect on the printability or Taber Abrasion Resistance of the receptor layer.

TABLE IV

* Taber Abrasion Resistance.

¹ EVA copolymer with VA content of about 18% and MI of about 8.0 g/10 min.; available from duPont.

² EVA copolymer with VA content of about 28% and MI of about 6.0 g/10 min.; available from duPont.

³ EVA copolymer with VA content of about 28% and MI of about 150 g/10 min.; available from duPont.

⁴ Ethylene methyl acrylate with methyl acrylate content of about 20%; MI of about 6.0 g/10 min.; available from Chevron Chemical Company, Orange, TX.

⁵ Ethylene methyl acrylate with methyl acrylate content of about 20%; MI of about 3.5 g/10 min.; contains slip agent; available from Chevron Chemical Company, Orange, TX.

⁶ Acrylic acid modified EVA with MI of about 6.6 g/10 min.; available from duPont.

⁷ Methacrylic acid modified EVA with MI of about 7.9 g/10 min.; available from duPont.

⁸ Anhydride modified ethylene acrylate; MI of about 6.5 g/10 min.; available from duPont.

⁹ Acid modified ethylene acrylate; MI of about 10.0 g/10 min.; available from duPont. ¹⁰ EVA copolymer with VA content of about 28% and MI of about 3.0 g/10 min.; available from duPont.

¹¹ EVA copolymer with VA content of about 28% and MI of about 6.0 g/10 min.; available from duPont.

The complete disclosure of all patents, patent documents, and publications cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one of skill in the art will be included within the invention defined by the claims.

Claims

What Is Claimed Is:

1. An imaging medium comprising :

(a) a backing layer comprising a backing polymer(s) wherein each backing polymer is independently formed from monomers comprising propylene; and wherein the melting point of the backing layer is not less than about 120┬░C;

(b) an intermediate layer selected from the group consisting of ethylene- alpha-olefin polymer having a total alpha-olefin content of about 10 to about 30 weight %, a density of less than about 0.910 g/cm³, and a polydispersity of less than about 3.5; ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent, acid modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; acid and anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent; and less than or equal to about 45 weight percent; and mixtures thereof; and

(c) a receptor layer, wherein the receptor layer comprises a receptor layer polymer(s), wherein each receptor layer polymer independently is formed from monomers comprising (i) ethylene, (ii) monomer(s) selected from the group consisting of vinyl acetate, vinyl acrylate, vinyl carboxylic acids and mixtures thereof, and (iii) optionally an anhydride(s), wherein the receptor layer has a melt index of at least about 2.5 grams/10 minutes; and wherein the intermediate layer is bonded between said backing layer and said receptor layer; and and wherein at least one of the following of (i) and (ii) is true: (i) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a liquid toner is at least about 6; (ii) the Taber abrasion resistance test value for an image electrophotographically formed on the receptor layer with a dry thermoplastic toner is at least about 6; and wherein at least one of the following of (I) and (II) is true: (I) the intermediate layer and the receptor layer are not the same chemically when the intermediate layer is selected from the group consisting of: ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent and less than or equal to about 45 weight percent; acid modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 and less than or equal to about 45 weight percent; anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 and less than or equal to about 45 weight percent; acid and anhydride modified ethylene vinyl acetate having a vinyl acetate content of greater than about 9 weight percent; and less than or equal to about 45 weight percent; and mixtures thereof; (H) the imaging medium is made in the substantial absence of ultraviolet light radiation.

2. The imaging medium of claim 1 which is capable under the PRINT QUALITY TEST of displaying a value of "FAIR/GOOD" or "GOOD."

3. The imaging medium of claim 1 which is capable under the PRINT QUALITY TEST of displaying a value of "GOOD."

4. The imaging medium of claim 1 wherein the composition of the imaging medium is selected such that the T-peel adhesion of the intermediate layer to the backing layer is at least about 537 g/cm, at a heat seal temperature of about 121┬░C, a pressure of about 2815 g/cm^ and a dwell time of about 1 second.

5. The imaging medium of claim 1 wherein the composition of the imaging medium is selected such that the T-peel adhesion of the intermediate layer to the backing layer is at least about 671 g/cm, at a heat seal temperature of about 121┬░C, a pressure of about 2815 g/cm^ and a dwell time of about 1 second.

6. The imagaging medium of claim 1 wherein the intermediate layer comprises an ethylene-╬▒-olefin polymer containing a total ╬▒-olefin content of about 10-30% and having a density of less than about 0.910 g/cm³ and a polydispersity of less than about 3.5

7. The imaging medium of claim 1 wherein the ethylene-╬▒-olefin polymer is a single site polymer and wherein the ╬▒-olefin monomer is selected from the group consisting of butene, pentene, hexene, heptene, octene, and mixtures thereof.

8. The imaging medium of claim 1 wherein the backing layer is selected from the group consisting of simultaneously biaxially oriented polypropylene and sequentially biaxially oriented polypropylene.

9. The imaging medium of claim 1 wherein the backing layer is simultaneously biaxially oriented polypropylene.

10. The imaging medium of claim 1 wherein the melting point of the backing layer is not less than about 140┬░C.

11. The imaging medium of claim 1 wherein the ethylene-╬▒-olefin polymer has a composition distribution breadth index of at least about 70%.

12. The imaging medium of claim 1 wherein the ethylene-╬▒-olefin copolymer has a density of less than about 0.900 g/cm³, a melting point of no greater than about 100┬░C, and a melt index of greater than about 1.0 gram/ 10 minutes.

13. The imaging medium of claim 1 wherein the intermediate layer comprises ethylene-╬▒-olefin copolymer and further comprises polyisobutylene.

14. The imaging medium of claim 1 wherein the intermediate layer comprises about 10-40% elastomeric polymer and an ethylene-╬▒-olefin polymer.

15. The imaging medium of claim 14 wherein the ethylene-╬▒-olefin polymer has a density of less than about 0.910 g/cm³ and a polydispersity of less than about 3.5.

16. The imaging medium of claim 1 wherein at least one of the following is true: (i) the Taber abrasion resistance test value for an image formed on the receptor layer with a liquid toner is at least about 8;

(ii) the Taber abrasion resistance test value for an image formed on the receptor layer with a dry toner is at least about 8.

17. The imaging medium of claim 1 wherein the T-peel adhesion value of the receptor layer to the intermediate layer is at least about 671 g/cm at a heat seal temperature of about 121┬░C, a pressure of about 2815 g/cm^ and a dwell time of about 1 second.

18. The imaging medium of claim 1 wherein with respect to the receptor layer the receptor layer polymer(s) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 75 to about 99 percent by weight ethylene and about 1 to about 25 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 52 to about 85 percent by weight ethylene and about 15 to about 48 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 60 to about 90 percent by weight ethylene and about 10 to about 40 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 37 to about 89 percent by weight ethylene, about 1 to about 15 weight percent vinyl carboxylic acid, and about 10 to about 48 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 45 to about 89 percent by weight ethylene, about 1 to about 15 weight percent vinyl carboxylic acid, and about 10 to about 40 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 37 to about 89.9 percent by weight ethylene, about 0.1 to about 15 weight percent anhydride, and about 10 to about 48 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 45 to about 94.9 percent by weight ethylene, about 0.1 to about 15 weight percent anhydride, and about 5 to about 40 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof.

19. The imaging medium of claim 1 wherein with respect to the receptor layer the receptor layer polymer(s) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 80 to about 98 percent by weight ethylene and about 2 to about 20 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 60 to about 85 percent by weight ethylene and about 15 to about 40 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 70 to about 90 percent by weight ethylene and about 10 to about 30 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 48 to about

84 percent by weight ethylene, about 1 to about 12 weight percent vinyl carboxylic acid, and about 15 to about 40 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 52 to about 89 percent by weight ethylene, about 1 to about 12 weight percent vinyl carboxylic acid, and about 10 to about 30 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 42 to about 84.9 percent by weight ethylene, about 0.1 to about 12 weight percent anhydride, and about 15 to about 40 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 52 to about 89.9 percent by weight ethylene, about 0.1 to about 12 weight percent anhydride, and about 10 to about 30 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof.

20. The imaging medium of claim 1 wherein with respect to the receptor layer the receptor layer polymer(s) are selected from the group consisting of: ethylene/vinyl carboxylic acid copolymers, each ethylene/vinyl carboxylic acid copolymer independently comprising about 85 to about 96 percent by weight ethylene and about 4 to about 15 weight percent vinyl carboxylic acid, based upon the total weight of the ethylene/vinyl carboxylic acid copolymer; ethylene/vinyl acetate copolymers, each ethylene/vinyl acetate copolymer independently comprising about 65 to about 82 percent by weight ethylene and about 18 to about 35 weight percent vinyl acetate, based upon the total weight of the ethylene/vinyl acetate copolymer; ethylene/vinyl acrylate copolymers, each ethylene/vinyl acrylate copolymer independently comprising about 75 to about 85 percent by weight ethylene and about 15 to about 25 weight percent vinyl acrylate, based upon the total weight of the ethylene/vinyl acrylate copolymer; ethylene/vinyl carboxylic acid/vinyl acetate copolymers, each ethylene/vinyl carboxylic acid/vinyl acetate copolymer independently comprising about 55 to about 81 percent by weight ethylene, about 1 to about 10 weight percent vinyl carboxylic acid, and about 18 to about 35 percent by weight vinyl acetate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acetate copolymer; ethylene/vinyl carboxylic acid/vinyl acrylate copolymers, each ethylene/vinyl carboxylic acid/vinyl acrylate copolymer independently comprising about 65 to about 83 percent by weight ethylene, about 2 to about 10 weight percent vinyl carboxylic acid, and about 15 to about 25 percent by weight vinyl acrylate based upon the total weight of the ethylene/vinyl carboxylic acid/vinyl acrylate copolymer; ethylene/anhydride/vinyl acetate copolymers, each ethylene/anhydride/vinyl acetate copolymer independently comprising about 55 to about 81.5 percent by weight ethylene, about 0.5 to about 10 weight percent anhydride, and about 18 to about 35 percent by weight vinyl acetate based upon the total weight of the ethylene/anhydride/vinyl acetate copolymer; ethylene/anhydride/vinyl acrylate copolymers, each ethylene/anhydride/vinyl acrylate copolymer independently comprising about 65 to about 84 percent by weight ethylene, about 1 to about 10 weight percent anhydride, and about 15 to about 25 percent by weight vinyl acrylate based upon the total weight of the ethylene/anhydride/vinyl acrylate copolymer; and mixtures thereof.

21. The imaging medium of claim 1 wherein the vinyl carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, and mixtures thereof.

22. The imaging medium of claim 1 wherein with respect to the receptor layer the polymer(s) comprise methacrylic acid in an amount of at least about 1% by weight based upon the total weight of the polymer(s).

23. The imaging medium of claim 1 wherein with respect to the receptor layer the polymer(s) comprise an anhydride in an amount of at least about 0.1% by weight based upon the total weight of the polymer(s).

24. The imaging medium of claim 1 wherein with respect to the receptor layer the polymer(s) comprise methacrylic acid in an amount of at least about 2% by weight based upon the total weight of the polymer(s).

25. The imaging medium of claim 1 wherein with respect to the receptor layer the each receptor layer polymer(s) is independently formed from monomers comprising ethylene and acid selected from the group consisting of methacrylic acid and acrylic acid, having a melt index of at least about 2.5 grams/ 10 minutes and an acid content of from about 2 to about 20% by weight based upon the total weight of the receptor layer polymer(s).

26. The imaging medium of claim 1 wherein with respect to the receptor layer each receptor layer polymer is independently formed from monomers comprising ethylene and vinyl acetate, the polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes and a vinyl acetate content of from about 15 to about 40 percent by weight based upon the total weight of the receptor layer polymer(s).

27. The imaging medium of claim 1 wherein with respect to the receptor layer each receptor layer polymer is independently formed from monomers comprising ethylene and vinyl acrylate, the polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes and an acrylate content of from about 10 to about 30 percent by weight based upon the total weight of the receptor layer polymer(s).

28. The imaging medium of claim 1 wherein with respect to the receptor layer each receptor layer polymer is independently formed from monomers comprising ethylene, vinyl acrylate, and methacrylic acid, the polymer(s) having a melt index of at least about 2.5 grams/ 10 minutes, wherein the vinyl acrylate content is about 10 to about 30 percent by weight and the acid content is about 1 to about 12 percent by weight based upon the total weight of the receptor layer polymer(s).

29. The imaging medium of claim 25 wherein the polymerization product has been neutralized with a metal cation thereby forming an ionomer, having a neutralized acid content of from about 2 to about 6% by weight and an acid content of no more than about 15% by weight based upon the total weight of the polymer(s).

30. The imaging medium of claim 29 wherein the ionomer comprises a neutralized ethylene-co-methacrylic acid ionomer.

31. The imaging medium of claim 1 wherein the vinyl acrylate monomer is selected from the group consisting of vinyl alkyl acrylates, vinyl alkacrylates, and mixtures thereof.

32. The imaging medium of claim 1 wherein the vinyl acrylate monomer is selected from the group consisting of vinyl methyl acrylate, vinyl ethyl acrylate, vinyl propyl acrylate, vinyl n-butyl acrylate, vinyl n-pentyl acrylate, vinyl n-hexyl acrylate, vinyl methacrylate, vinyl ethacrylate, vinyl propacrylate, vinyl butacrylate, vinyl pentacrylate, vinyl hexacrylate, and mixtures thereof.

33. The imaging medium of claim 1 wherein with respect to the receptor layer each receptor layer polymer is independently formed from monomers comprising ethylene, vinyl acetate, and methacrylic acid, the polymer(s) having a melt index of at least about 2.5 grams/10 minutes, wherein the vinyl acetate content is about 15 to about 40 percent by weight and the acid content is about 1 to about 12 percent by weight based upon the total weight of the receptor layer polymer(s).

34. The imaging medium of claim 1 wherein the receptor layer has a thickness of about 0.008 mm to about 0.25 mm.

35. The imaging medium of claim 1 wherein the receptor layer has a thickness of about 0.013 mm to about 0.13 mm.

36. A method comprising the step of using the imaging medium of claim 1 in an electrophotographic printing process.

37. The method of claim 36 in which an image is formed from a composition comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature.

38. The method of claim 37 wherein the thermoplastic toner particles are selected from the group consisting of ethylene vinyl acrylate copolymers, ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ionomers of ethylene acrylic acid copolymers, and mixtures thereof.

39. The method of claim 36 which utilizes a dry thermoplastic toner.

40. The method of claim 39 wherein the toner is selected from the group consisting of polyester and styrene acrylate copolymer.

41. A method of transferring an electrophotographically developed image from a photoconductor to an imaging medium, comprising the steps of:

(a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of thermoplastic toner particles in a liquid carrier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature;

(b) heating the developed image to a temperature at least as high as the second temperature to thereby form a single phase of the thermoplastic particles and liquid carrier; and

(c) thereafter transferring the developed image to the receptor layer of an imaging medium at a temperature of about 120 to about 165┬░C; wherein the imaging medium is that of claim 1.

42. The method of claim 41 wherein the thermoplastic toner particles are selected from the group consisting of ethylene vinyl acrylate copolymers, ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ionomers of ethylene acrylic acid copolymers, and mixtures thereof.

43. A method of transferring an electrophotographically developed image from a photoconductor to an imaging medium comprising the steps of:

(a) selectively providing desired portions of a photoconductor with a developed image, the image comprising a plurality of thermoplastic dry toner particles wherein the toner particles are solid at a first temperature, but which soften or melt at or above a second temperature; (b) transferring the developed image onto a receptor layer of an imaging medium, wherein the imaging medium is that of claim 1;

(c) heating and optionally applying pressure to the developed image such that it reaches a temperature at least as high as the second temperature to soften or melt the toner particles to form a final fixed image.

44. The method of claim 43 wherein the toner is selected from the group consisting of polyester and styrene acrylate copolymer.

45. An imaged medium comprising:

(a) the imaging medium of claim 1;

(b) an image on a surface of the receptor layer, which surface is not bonded to the intermediate layer, wherein the image is formed from a composition comprising a plurality of thermoplastic toner particles in a liquid canier at a first temperature, wherein the liquid carrier is not a solvent for the particles at the first temperature and wherein the thermoplastic particles and the liquid carrier form substantially a single phase at or above a second temperature.

46. The imaged medium of claim 45 wherein the thermoplastic toner particles are selected from the group consisting of ethylene vinyl acrylate copolymers, ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ionomers of ethylene acrylic acid copolymers, and mixtures thereof.

47. An imaged medium comprising: (a) the imaging medium of claim 1 ;

(b) an image on a surface of the receptor layer, which surface is not bonded to the intermediate layer, wherein the image is formed from a dry thermoplastic toner.

48. The imaged medium of claim 47 wherein the toner is selected from the group consisting of polyester and styrene acrylate copolymer.

49. The imaged medium of claim 39 which further comprises a layer of adhesive coated over a surface of the backing layer not bonded to the intermediate layer and a release liner attached to a surface of the adhesive layer opposite the backing layer.

50. The imaged medium of claim 45 which further comprises a layer of adhesive coated over the image and the surface of the receptor layer not bonded to the intermediate layer, and wherein the intermediate layer, the receptor layer and the backing layer are selected such that the image can be viewed therethrough.

51. The imaged medium of claim 47 which further comprises a layer of adhesive coated over the image and the surface of the receptor layer not bonded to the intermediate layer, wherein the receptor layer, the intermediate layer, and the backing layer are selected such that the image can be viewed therethrough.

52. The imaging medium of claim 1, wherein the receptor layer further comprises about 0.05 to about 3 percent by weight of an ultraviolet light stabilizer selected from the group consisting of ultraviolet light absorbers, ultraviolet light inhibitors, and mixtures thereof, based upon the total weight of the receptor layer.

53. The imaging medium of claim 52 wherein the ultraviolet light absorbers are selected from the group consisting of benzotriazoles, benzophenones, oxalanilides, triazines, and mixtures thereof, and the ultraviolet light inhibitors are selected from the group consisting of hindered amines.

54. The imaging medium of claim 52 wherein both ultraviolet light absorber and ultraviolet light inhibitor are present in the receptor layer at a weight ratio of ultraviolet light absorber to ultraviolet light inhibitor of about 1 :3 to about 3:1.

55. The imaging medium of claim 52 wherein both ultraviolet light absorber and ultraviolet light inhibitor are present in the receptor layer at a weight ratio of ultraviolet light absorber to ultraviolet light inhibitor of about 1.5:2.5 to about 2.5:1.5.

56. The imaging medium of claim 52 wherein the receptor layer further comprises about 0.1 to about 3 percent by weight of a component selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof, based on the total weight of the receptor layer.

57. The imaging medium of claim 52 wherein the receptor layer further comprises about 0.3 to about 1.5 percent by weight of a component selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof, based on the total weight of the receptor layer.

58. The imaging medium of claim 52 wherein the receptor layer further comprises about 0.5 to about 1 percent by weight of a component selected from the group consisting of ultraviolet light absorber, ultraviolet light inhibitor, and mixtures thereof, based on the total weight of the receptor layer.

59. The imaging medium of claim 1 wherein the composition of the imaging medium is selected such that the T-peel adhesion of the receptor layer to the intermediate layer is at least about 358 g/cm at a heat seal temperature of about

121┬░C, a pressure of about 2815 g/cm² and a dwell time of about 1 second and such that the T-peel adhesion of the intermediate layer to the backing layer is at least about 358 g/cm, at a heat seal temperature of about 121┬░C, a pressure of about 2815 g/cm² and a dwell time of about 1 second.