WO2007027619A2 - Surface relief holographic film - Google Patents

Surface relief holographic film Download PDF

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Publication number
WO2007027619A2
WO2007027619A2 PCT/US2006/033551 US2006033551W WO2007027619A2 WO 2007027619 A2 WO2007027619 A2 WO 2007027619A2 US 2006033551 W US2006033551 W US 2006033551W WO 2007027619 A2 WO2007027619 A2 WO 2007027619A2
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WO
WIPO (PCT)
Prior art keywords
layer
embossed
film
holographic film
substrate
Prior art date
Application number
PCT/US2006/033551
Other languages
French (fr)
Other versions
WO2007027619A3 (en
Inventor
Anne Herrmann
Original Assignee
General Binding Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Binding Corporation filed Critical General Binding Corporation
Publication of WO2007027619A2 publication Critical patent/WO2007027619A2/en
Publication of WO2007027619A3 publication Critical patent/WO2007027619A3/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H1/0252—Laminate comprising a hologram layer
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F3/00—Labels, tag tickets, or similar identification or indication means; Seals; Postage or like stamps
    • G09F3/02—Forms or constructions
    • G09F3/0291—Labels or tickets undergoing a change under particular conditions, e.g. heat, radiation, passage of time
    • G09F3/0292—Labels or tickets undergoing a change under particular conditions, e.g. heat, radiation, passage of time tamper indicating labels
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H1/024—Hologram nature or properties
    • G03H1/0244—Surface relief holograms
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/02—Details of features involved during the holographic process; Replication of holograms without interference recording
    • G03H1/0276—Replicating a master hologram without interference recording
    • G03H1/028—Replicating a master hologram without interference recording by embossing
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2250/00—Laminate comprising a hologram layer
    • G03H2250/36—Conform enhancement layer
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2250/00—Laminate comprising a hologram layer
    • G03H2250/40—Printed information overlapped with the hologram

Definitions

  • the invention pertains to holographic films, and more specifically to translucent holographic films.
  • Holographic laminating films generally are well known in the art. They are frequently used for decorative purposes such as packaging or label stocks, or security purposes on objects such as credit cards, passports, driver licenses, etc.
  • these types of holographic laminating films are reflection-type holograms and comprise a substrate layer that is embossed to form a relief hologram on the substrate.
  • the substrate layer is coated with an adhesive, such as a pressure sensitive or thermal adhesive, to permit the substrate to attach to an object.
  • these types of holographic films are frequently coated with a metalized layer that provides a silver metallic appearance to the film. Holographic films having this type of metallic layer are useful for security and certain other applications, but, due to the metalized layer, they do not permit a user to view an image displayed below such holographic films.
  • Translucent holographic laminating films i.e., holograms without an opaque metalized layer such as aluminum
  • These types of films permit the viewing of both the holographic effects of the film and any image displayed on the object below the hologram.
  • Many of these films utilize a pressure sensitive adhesive.
  • Pressure sensitive laminating films are useful when the object or a part of the lamination film is sensitive to heat.
  • pressure sensitive films tend to be rather expensive as they generally require a release liner which is disposed of during the lamination process.
  • both the substrate and the adhesive layers are relatively thick, increasing the cost of these films.
  • the lamination process is generally slow with pressure sensitive films, ranging from 3 to 10 feet per minute in many cases. Thermal films are advantageous for numerous reasons.
  • thermal films consist of commodity resins that can be as much as 75% less expensive than pressure sensitive systems, and thinner substrates and thinner adhesive layers can be used. Further, thermal films do not require a release liner, inasmuch as the adhesive is not tacky at room temperatures. As a result, thermal films on the whole are typically less expensive than pressure sensitive films. Additionally, thermal films allow faster lamination processing, ranging from 5 to 150 or more feet per minute. Thus, thermal laminating films in general offer increased productivity at a reduced price as compared to pressure sensitive laminating films.
  • Translucent holographic laminating films utilizing thermal adhesives are also known in the art. These films are typically constructed of materials that tend to be relatively expensive and have relatively strong mechanical strengths that make them undesirable for snapping. Snapping is a form of sheet separation using an edge of perforations and acceleration to tear each sheet away from the next during lamination. When the mechanical strength is undesirably strong, it can lead to stretching of the material and raggedly torn edges, which can inhibit the ability to cleanly palletize sheets of the film.
  • a further difficulty with current laminating films is that partial delaminations frequently occur between the adhesive layer and the layer adjacent to the adhesive (such as the substrate or the high refractive index coating, hereinafter HRI coating).
  • This delamination may manifest itself in a variety of problems commonly known to those in the lamination industry (such as, "popping" along a score line or hinge, edge lifting along a cut edge, or voids below the holographic image).
  • problems commonly known to those in the lamination industry (such as, "popping" along a score line or hinge, edge lifting along a cut edge, or voids below the holographic image).
  • These failures are a result of a separation between the adhesive, which typically has an affinity to paper and inks, and the adjacent layer.
  • This is particularly problematic when the adhesive is disposed adjacent to an HRI coating, which is typically strongly bonded to the substrate layer, because there is often very little affinity between the thermal adhesive and the HRI coating.
  • HRI coating high refractive index coating
  • the invention provides an improved translucent holographic thermal laminating film that is suitable for use on books or other similar structures. [0009] The invention further provides a film that combines low cost and improved processability, both during manufacture and lamination.
  • the invention further provides a translucent holographic thermal laminating film having moisture absorption characteristics to avoid curling.
  • the invention further provides a translucent holographic thermal laminating film with sufficient adhesion between the layers of the improved translucent thermal laminating film to resist delamination during cutting, scoring, folding, bookbinding or similar operations.
  • the improved translucent holographic thermal laminating film may comprise a substrate layer that provides strength and support for the film.
  • the substrate is embossed with a plurality of ridges in a pattern that produces a holographic effect when viewed by an observer.
  • the substrate could be homogeneous or it could comprise a substrate with an added coating to form an alternate embossable layer.
  • the substrate is coated with a thermal adhesive to enable the translucent holographic film to be adhered to another object. Additional layers may be applied to the film, such as, for example, a coating layer composed of a material having a high refractive index that enhances the holographic effect and provides additional optical durability to the film, and an adhesion promoter between the thermal adhesive and an adjacent layer.
  • the invention provides a translucent holographic film including an adhesive layer and an embossed layer.
  • the embossed layer includes an embossed side defining ridges having peaks pointing toward the adhesive layer.
  • the invention further provides processes for manufacturing a translucent holographic thermal laminating film.
  • the invention provides a method of manufacturing a translucent holographic film including providing an embossed layer having an embossed side and a non-embossed side, and applying an adhesive layer onto the embossed side of the embossed layer, hi one aspect, applying the adhesive layer onto the embossed side of the embossed layer includes applying a high refractive index coating to the embossed side and then applying the adhesive layer onto the high refractive index coating.
  • providing an embossed layer includes applying a high refractive index coating to a material that will form the embossed layer, and then embossing the coated material to form the embossed layer.
  • FIG. 1 is a fragmentary sectional view showing a first embodiment of a translucent holographic film in accordance with teachings of the invention
  • FIG. 2 is a fragmentary sectional view showing a second embodiment of a translucent holographic film in accordance with teachings of the invention
  • FIG. 3 is a fragmentary sectional view showing a third embodiment of a translucent holographic film in accordance with teachings of the invention.
  • FIG. 4 is a fragmentary sectional view showing a fourth embodiment of a translucent holographic film in accordance with teachings of the invention.
  • FIG. 5 is fragmentary sectional view showing a fifth embodiment of a translucent holographic film in accordance with teachings of the invention.
  • FIG. 6 is a simplified diagram showing a process for making a translucent holographic film in accordance with teachings of the invention.
  • FIG. 7 is another simplified diagram showing a process for making a translucent holographic film in accordance with teachings of the invention.
  • FIG. 8 is a simplified diagram showing a process for applying a thermal adhesive to a translucent holographic film in accordance with teachings of the invention.
  • the holographic film of the present invention has a structure that permits the film to display a hologram and attach to another object, such as a book cover.
  • the holographic film is translucent such that when the holographic film is disposed on the surface of an object, any image or color displayed on the surface of the object is at least partially visible through the holographic film.
  • a book cover may have an image printed on the cover.
  • the translucent holographic film may be disposed over this book cover, and both the image printed on the cover and the hologram above the image are visible. Therefore, both the hologram and the surface of the object are simultaneously visible to a viewer.
  • the film is embossed with any suitable pattern in the form of a texture or a plurality of ridges to create any suitable holographic effect when viewing the film.
  • the holographic film may be attached to any suitable object, including, but not limited to books.
  • the holographic film may comprise an adhesive layer formed by any suitable adhesive.
  • the adhesive layer of the holographic film is disposed adjacent to a surface of the target object.
  • a thermal (hot melt) adhesive is utilized, heat is applied to the holographic film to activate the adhesive, and bind the holographic film to the object.
  • the holographic film 100 comprises a substrate material 110 that provides strength to the holographic film 100.
  • the substrate has a first surface 112 and a second surface 114.
  • ridges 116 are embossed directly onto the first surface 112 of the substrate 110.
  • An adhesive layer 120 is disposed on the second surface 114 of the substrate 110.
  • the embossed first surface 112 of the substrate 110 is exposed to the viewer, with the peaks 118 of the ridges 116 pointing away from the adhesive layer 120 and from the object to which the holographic film 100 is adhered.
  • the adhesive layer 120 is adjacent the non-embossed second surface 114 of the substrate 110.
  • the film may be treated with an adhesion promoter. Sufficient adhesion between the layers of the film is important to prevent delamination during cutting, scoring, folding, bookbinding or similar operations.
  • the surface of the layer of film to which the adhesive is attached may have a surface treatment to promote adhesion.
  • the second surface 114 of the substrate 110 may include a surface treatment 150 between the substrate 110 and the adhesive layer 120 to strengthen the adherence between these layers.
  • the surface treatment may be any suitable process or material that enhances the adhesion between the adhesive layer and an adjacent layer including, but not limited to, a surface treatment such as corona, UV, ozone, plasma, flame treatment, the use of a primer, or any combination thereof.
  • FIG. 2 another embodiment of a translucent holographic film 200 is shown. Similar to the previous embodiment, this embodiment has a substrate layer 210 and an adhesive layer 220 disposed on the second surface 214 of the substrate 210. Furthermore, this embodiment may include a surface treatment 250 disposed between the substrate layer 210 and the adhesive layer 220. This embodiment additionally includes a coating layer 230 that is disposed on the embossed first surface 212 of the substrate 210 to enhance the holographic effect and/or provide protection for the embossed first surface 212 of the substrate 210. For example, the coating layer 230 maybe disposed between the substrate and the viewer of the holographic film 200. Thus, the substrate 210 is not directly exposed to external elements, but is shielded by the coating layer 230.
  • the coating layer 230 is preferably a translucent material having a high refractive index relative to the embossed layer.
  • the high refractive index coating may have, for example, a refractive index differential greater than 0.2.
  • An example of a suitable high refractive index coating material includes, but is not limited to, zinc sulfide (ZnS).
  • FIG. 3 another embodiment of a translucent holographic film 300 is shown. Similar to previous embodiments, this embodiment has a substrate layer 310 and an adhesive layer 320 disposed on the second surface 314 of the substrate 310. Furthermore, this embodiment may include a surface treatment 350 disposed between the substrate layer 310 and the adhesive layer 320. In this embodiment, the substrate 310 is not embossed, and an additional layer 340 is disposed on the first surface 312 of the substrate 310.
  • the additional layer 340 may be composed of a material that may generally provide a more durable/wear resistant structure compared to the substrate 310 of certain embodiments and/or may generally be more conducive to hologram formation than the material used for the substrate 310 of certain embodiments.
  • the additional layer 340 maybe composed, for example, of a low melting thermoplastic, an acrylic, or a radiation-curable thermosetting resin.
  • the peaks 348 of the ridges 346 on the additional layer 340 point away from the adhesive layer 320, the substrate 310, and the object to which the holographic film 300 is adhered, and the substrate 310 is disposed between the additional layer 340 and the adhesive 320.
  • the adhesive layer 320 is not adjacent the embossed surface (of the additional layer 340 in FIG. 3).
  • the films 100, 200, and 300 of the invention utilize substrate materials not previously used in holographic films.
  • the substrate materials 110, 210, and 310 may be constructed of a material that has sufficient moisture absorption properties to substantially avoid curling problems inherent in other translucent holographic films when adhered to certain objects (such as book covers, papers, etc.). Basically, the substrate material 110, 210, 310 will have a similar moisture absorption rate as the material of the underlying object (e.g., paper) such that little or no absorption rate differential is present, therefore minimizing or eliminating curl.
  • the substrate may be constructed of a material that does not deform when raised to temperatures necessary to activate a thermal adhesive.
  • Such a substrate is polyamide (e.g., nylon).
  • Other advantageous substrate materials contemplated by the present invention are materials that are relatively inexpensive and have mechanical strengths suitable for clean sheet separation using an edge perforation, such as polypropylene (including bi-axially oriented polypropylene or BOPP).
  • FIG. 4 another embodiment of a translucent holographic film 400 is shown. Similar to previous embodiments, this embodiment comprises a substrate layer 410, an adhesive layer 420, and a coating layer 430.
  • the construction illustrated in FIG. 4 has a significant constructional improvement over conventional constructions, hi this embodiment, the substrate 410 is embossed with a plurality of ridges 416 to form the hologram, and the coating layer 430 is disposed against the embossed second surface 414 of the substrate 410.
  • the adhesive layer 420 is disposed against the coating layer 430 and conforms to the ridges 416 embossed into the holographic film 400.
  • the adhesive layer 420 is applied to the embossed side (of the substrate 410 and the coating layer 430 in FIG. 4) ⁇
  • This embodiment may include a surface treatment ⁇ 450 disposed between the coating layer 430 and the adhesive layer 420.
  • the adhesive 420 is disposed against the object and the unembossed first surface 412 of the substrate 410 is exposed to the viewer with the peaks 418 of the ridges 416 directed away from the viewer, toward the adhesive layer 420, and toward the object to which the film 400 is applied. Therefore, the hologram is viewed through the substrate 410.
  • the hologram formed on the holographic film 400 is relatively durable and wear resistant because the embossed second surface 414 is not directly exposed to external elements, but is instead shielded between the substrate 412 and the object adhered to the holographic film 400.
  • the handling of the holographic film 400 over time can allow foreign substances (such as finger oils, lotions, or other liquids, etc.) to accumulate between the ridges 416 and/or direct contact can cause the peaks 418 of the ridges 416 to deform, which can substantially and undesirably affect the quality of the hologram.
  • this type of damage may alter how the light is refracted/reflected by the image resulting in the diminishment of the brightness and clarity of the hologram.
  • Protecting the embossed second surface 414 within the film 400 circumvents these hologram quality issues.
  • FIG. 5 another embodiment of a translucent holographic film 500 is shown. Similar to previous embodiments, this embodiment comprises a substrate layer 510, an adhesive layer 520, a coating layer 530, and an additional layer 540. Similar to the embodiment shown in FIG. 4, this embodiment also includes the improved construction in which the embossed surface is protected from the surrounding environment. In this embodiment, the first surface 512 of the substrate 510 is exposed to the viewer. The additional layer 540 is disposed on the second surface of the substrate 514 and is embossed with a plurality of ridges 546 to create the holographic image. The coating layer 530 is disposed adjacent to the ridges 546 of the additional layer 540. Finally, the adhesive 520 is disposed on the coating layer 530.
  • This embodiment may include a surface treatment 550 disposed between the coating layer 530 and the adhesive layer 520.
  • the adhesive layer 520 is applied to the embossed side (of the additional layer 540 and the coating layer 530 in FIG. 5).
  • improved wear resistance and durability of the hologram is obtained because the peaks 548 of the ridges 546 are directed toward the adhesive layer 520 and toward the object to which the holographic film 500 is adhered and thus, not directly exposed to external elements that can damage the embossed surface.
  • the exposed surfaces 412 and 512 are generally smooth, and do not include the exposed peaks and valleys of the embodiments shown in FIGS. 1-3, the exposed surfaces 412 and 512 are also well-suited to receive overprinting if desired, hi other words, portions of the surfaces 412 and 512 could be printed upon to further add to the aesthetic qualities of the films 400 and 500.
  • the substrates 410 and 510 could be chosen from a material conducive to receiving print (e.g., inks), or could be treated with a primer or other suitable surface treatment to facilitate receiving print.
  • the high refractive index (HRI) coating is particularly useful with the embodiments shown in FIGS. 4 and 5 where the adhesive layer fills in the valleys present in the embossed surface.
  • the HRI coating is thin enough to enable transparency and generally mimics the topography of the underlying embossment.
  • the use of the HRI coating allows the holographic image to retain its brightness and clarity even if the valleys of the embossment are filled in, provided that there is a sufficient difference in the refractive index of the HRI coating and the substance in contact with it.
  • the HRI layer serves to brighten the appearance of the holographic image.
  • the translucent holographic film may be manufactured by any suitable process.
  • "soft" or “hard” embossing techniques may be utilized to form the hologram surface by embossing a desired pattern of ridges into the film.
  • FIG. 6 a flow diagram representing "soft" embossing processes is shown, hi step 600, the substrate is provided for embossing.
  • the substrate may be embossed directly using a heated roll having a desired texture in step 602.
  • an additional layer comprising a low melting thermoplastic or radiation-curable thermosetting resin may be embossed to form the hologram.
  • the low melting thermoplastic layer may be applied to the substrate via extrusion in step 606, and then the low melting thermoplastic layer may be embossed with a heated roll having a desired texture in step 608.
  • the resin may be applied to the substrate by a gravure process in step 610.
  • the resin may be embossed by subjecting the resin layer against a roll having a desired texture and UV curing the holographic pattern into the resin in step 612.
  • an HRI coating layer may be applied to the embossed surface in step 614.
  • the HRI coating may be applied by a vacuum metalizing (such as for applying ZnS) or sputtering (such as TiO x ) process.
  • a so-called "hard” embossing technique may be used to form the hologram surface.
  • a substrate is provided in step 700.
  • a surface treatment may be applied to a surface of the substrate.
  • the surface treatment strengthens the adherence between the substrate and an adjacent layer.
  • the surface treatment may be any suitable surface treatment including, but not limited to, corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof.
  • a low melting thermoplastic layer may be applied to the substrate via extrusion, or in step 706, a radiation-curable thermosetting resin may be applied to the substrate by a gravure process.
  • An HRI coating may then be applied to the low melting thermoplastic layer or the radiation-curable thermosetting resin layer in step 708.
  • a hologram pattern may then be embossed into the HRI coating and either the low melting thermoplastic layer or the radiation-curable thermosetting resin by applying pressure to emboss the film.
  • FIG. 7 also illustrates the technique in which the HRI coating can be applied directly to the substrate, and then the coated substrate can be embossed (sequence of steps 700, then step 708, and then step 710).
  • FIG. 8 discloses a process for applying a thermal adhesive to the holographic film.
  • a film with a hologram embossed thereon is provided.
  • the film may, for example, be provided following one of the processes shown in FIG. 6 or FIG. 7.
  • one or more techniques or materials may be applied to the film to improve adhesion and resist delamination between the thermal adhesive and the surface of the film layer to which the thermal adhesive is applied.
  • a surface treatment may be applied to the surface that will be receiving the thermal adhesive.
  • the surface treatment may be any suitable surface treatment including, but not limited to, corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof.
  • the surface treatment may include corona treating a surface as in step 804.
  • the surface may then be coated with a primer as in step 806.
  • the primer may be any suitable primer including, but not limited to, an aqueous-based primer with a medium crosslink density.
  • Such a primer may be applied, for example, utilizing a gravure coating station.
  • the primer may then be dried and/or cured. This may be accomplished by applying heat at a temperature below the melting point of the layer of the film having the lowest melting point.
  • the thermal adhesive may be applied to the film in step 810.
  • the thermal adhesive may be applied via extrusion through a die. It may be desirable to extrude the adhesive in an ozone-rich environment. Furthermore, it may be preferable to extrude the adhesive such that the adhesive layer is relatively thin (for example, between approximately 0.003 to 0.0005 inches thick). If desired, the adhesive may then receive a corona treatment in step 812. If the film is provided on a roll, then the film may then be rewound onto the roll. Through this process, the adhesion between the adhesive layer and an adjacent layer of the film is enhanced.
  • the substrate 410, 510 of films 400 and 500 may be constructed of a material that has sufficient moisture absorption properties to substantially avoid curling problems inherent in other translucent holographic films when adhered to certain objects (such as book covers, papers, etc.).
  • the substrate may be constructed of a material that does not deform when raised to temperatures necessary to activate a thermal adhesive.
  • An example of such a substrate is polyamide (e.g., nylon).
  • materials that are relatively inexpensive and have mechanical strengths suitable for clean sheet separation using an edge perforation such as polypropylene (including bi-axially oriented polypropylene or BOPP).
  • the substrates 410 and 510 may, however, be constructed of any suitable material.
  • polyethylene terephthalate including bi-axially oriented polyethylene terephthalate or BOPET
  • PVC polyvinyl chloride
  • PMMA polymethyl methacrylate
  • the adhesive layer may comprise any suitable adhesive.
  • suitable thermal adhesives include, but are not limited to, ethylene/vinyl acetate (EVA), polyester resins, polyethylene resins, ethylene/isobutyl acrylate copolymer resins, polyvinyl acetate and vinyl acetate copolymer resins, and polypropylene resins.
  • the coating layer may comprise a material having a high refractive index (HRI) including, but not limited to, zinc sulfide (ZnS), titanium dioxide (TiO 2 ), and dialuminum trioxide (Al 2 O 3 ).
  • HRI high refractive index
  • ZnS zinc sulfide
  • TiO 2 titanium dioxide
  • Al 2 O 3 dialuminum trioxide
  • any suitable material may be used.
  • Alternate materials that may be used include, but are not limited to, SiO and TiO.
  • ZnS is preferred of these coatings as it can be applied using established metallizing equipment, and can be applied at faster speeds than other materials, thus it lends to sufficient productivity with minimal investment in alternate equipment, hi some embodiments, the HRI coating can be pierced or otherwise broken or interrupted to further facilitate bonding with the adhesive layer.
  • the additional layer described above may be made of any suitable material, including low melting thermoplastics or radiation-curable thermosetting resins including but not limited to urethane acrylate, epoxy acrylate, polyester acrylate, or polyether acrylate, or thermoplastic resins, including but not limited to acrylics, polystyrene, or polyvinylchloride.
  • the surface treatment may be any suitable surface treatment for enhancing the adherence between adjacent layers of the holographic film and may be applied between any suitable adjacent layers of the film.
  • suitable surface treatments include, but are not limited to,- corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof.
  • the translucent holographic film may be adhered to any suitable object including, but not limited to, books, papers, packaging materials, paper-based boards, etc.

Abstract

The invention provides a translucent holographic film that is suitable for use on books or other similar structures. The translucent holographic film may comprise a substrate that provides strength and support for the film. In certain embodiments, the substrate is embossed to form a relief hologram. The substrate may be coated with a thermal adhesive to enable the translucent holographic film to be adhered to another object. Additional layers may be applied to the film, such as, for example, a coating layer composed of a material having a high refractive index. This coating layer can enhance the holographic effect and provide additional durability to the film, hi addition, certain embodiments may include additional layers that provide increased durability and/or other desirable qualities to the film. A method of making a translucent holographic film is also provided.

Description

HOLOGRAPHIC FILM
RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent Application No. 60/712,934 filed August 31, 2005, the entire content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention pertains to holographic films, and more specifically to translucent holographic films.
BACKGROUND OF THE INVENTION
[0003] Holographic laminating films generally are well known in the art. They are frequently used for decorative purposes such as packaging or label stocks, or security purposes on objects such as credit cards, passports, driver licenses, etc. Typically, these types of holographic laminating films are reflection-type holograms and comprise a substrate layer that is embossed to form a relief hologram on the substrate. The substrate layer is coated with an adhesive, such as a pressure sensitive or thermal adhesive, to permit the substrate to attach to an object. Additionally, these types of holographic films are frequently coated with a metalized layer that provides a silver metallic appearance to the film. Holographic films having this type of metallic layer are useful for security and certain other applications, but, due to the metalized layer, they do not permit a user to view an image displayed below such holographic films.
[0004] Translucent holographic laminating films (i.e., holograms without an opaque metalized layer such as aluminum) are known in the art. These types of films permit the viewing of both the holographic effects of the film and any image displayed on the object below the hologram. Many of these films utilize a pressure sensitive adhesive. Pressure sensitive laminating films are useful when the object or a part of the lamination film is sensitive to heat. However, pressure sensitive films tend to be rather expensive as they generally require a release liner which is disposed of during the lamination process. Additionally, both the substrate and the adhesive layers are relatively thick, increasing the cost of these films. Further, the lamination process is generally slow with pressure sensitive films, ranging from 3 to 10 feet per minute in many cases. Thermal films are advantageous for numerous reasons. For example, thermal films consist of commodity resins that can be as much as 75% less expensive than pressure sensitive systems, and thinner substrates and thinner adhesive layers can be used. Further, thermal films do not require a release liner, inasmuch as the adhesive is not tacky at room temperatures. As a result, thermal films on the whole are typically less expensive than pressure sensitive films. Additionally, thermal films allow faster lamination processing, ranging from 5 to 150 or more feet per minute. Thus, thermal laminating films in general offer increased productivity at a reduced price as compared to pressure sensitive laminating films.
[0005] Translucent holographic laminating films utilizing thermal adhesives are also known in the art. These films are typically constructed of materials that tend to be relatively expensive and have relatively strong mechanical strengths that make them undesirable for snapping. Snapping is a form of sheet separation using an edge of perforations and acceleration to tear each sheet away from the next during lamination. When the mechanical strength is undesirably strong, it can lead to stretching of the material and raggedly torn edges, which can inhibit the ability to cleanly palletize sheets of the film.
[0006] Another problem with currently used substrates in holographic laminating films when utilized in certain applications is the film substrate's inability to absorb moisture, hi certain applications, such as when laminating a single side of apaper sheet or when applying the substrate to book covers, curling of the laminated object can result. Curling results when the laminating film and the paper (or other underlying surface) have significantly different moisture absorption characteristics. When the paper expands to a much greater extent than the film, then the laminated object begins to curl. This is both aesthetically and functionally undesirable. Thus, there is a need for transparent thermal laminating films utilizing substrates that reduce the finished cost of the film and/or avoid moisture induced curling of laminated objects.
[0007] , A further difficulty with current laminating films is that partial delaminations frequently occur between the adhesive layer and the layer adjacent to the adhesive (such as the substrate or the high refractive index coating, hereinafter HRI coating). This delamination may manifest itself in a variety of problems commonly known to those in the lamination industry (such as, "popping" along a score line or hinge, edge lifting along a cut edge, or voids below the holographic image). These failures are a result of a separation between the adhesive, which typically has an affinity to paper and inks, and the adjacent layer. This is particularly problematic when the adhesive is disposed adjacent to an HRI coating, which is typically strongly bonded to the substrate layer, because there is often very little affinity between the thermal adhesive and the HRI coating. Thus, there is a need for a translucent holographic film that resists delamination between layers of the film.
BRIEF SUMMARY OF THE INVENTION
[0008] The invention provides an improved translucent holographic thermal laminating film that is suitable for use on books or other similar structures. [0009] The invention further provides a film that combines low cost and improved processability, both during manufacture and lamination.
[0010] The invention further provides a translucent holographic thermal laminating film having moisture absorption characteristics to avoid curling.
[0011] The invention further provides a translucent holographic thermal laminating film with sufficient adhesion between the layers of the improved translucent thermal laminating film to resist delamination during cutting, scoring, folding, bookbinding or similar operations.
[0012] The improved translucent holographic thermal laminating film may comprise a substrate layer that provides strength and support for the film. In certain embodiments, the substrate is embossed with a plurality of ridges in a pattern that produces a holographic effect when viewed by an observer. The substrate could be homogeneous or it could comprise a substrate with an added coating to form an alternate embossable layer. The substrate is coated with a thermal adhesive to enable the translucent holographic film to be adhered to another object. Additional layers may be applied to the film, such as, for example, a coating layer composed of a material having a high refractive index that enhances the holographic effect and provides additional optical durability to the film, and an adhesion promoter between the thermal adhesive and an adjacent layer.
[0013] More specifically, the invention provides a translucent holographic film including an adhesive layer and an embossed layer. The embossed layer includes an embossed side defining ridges having peaks pointing toward the adhesive layer.
[0014] The invention further provides processes for manufacturing a translucent holographic thermal laminating film. In one embodiment the invention provides a method of manufacturing a translucent holographic film including providing an embossed layer having an embossed side and a non-embossed side, and applying an adhesive layer onto the embossed side of the embossed layer, hi one aspect, applying the adhesive layer onto the embossed side of the embossed layer includes applying a high refractive index coating to the embossed side and then applying the adhesive layer onto the high refractive index coating. In another aspect, providing an embossed layer includes applying a high refractive index coating to a material that will form the embossed layer, and then embossing the coated material to form the embossed layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a fragmentary sectional view showing a first embodiment of a translucent holographic film in accordance with teachings of the invention;
[0016] FIG. 2 is a fragmentary sectional view showing a second embodiment of a translucent holographic film in accordance with teachings of the invention;
[0017] FIG. 3 is a fragmentary sectional view showing a third embodiment of a translucent holographic film in accordance with teachings of the invention;
[0018] FIG. 4 is a fragmentary sectional view showing a fourth embodiment of a translucent holographic film in accordance with teachings of the invention;
[0019] FIG. 5 is fragmentary sectional view showing a fifth embodiment of a translucent holographic film in accordance with teachings of the invention;
[0020] FIG. 6 is a simplified diagram showing a process for making a translucent holographic film in accordance with teachings of the invention;
[0021] FIG. 7 is another simplified diagram showing a process for making a translucent holographic film in accordance with teachings of the invention; and
[0022] FIG. 8 is a simplified diagram showing a process for applying a thermal adhesive to a translucent holographic film in accordance with teachings of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The holographic film of the present invention has a structure that permits the film to display a hologram and attach to another object, such as a book cover. The holographic film is translucent such that when the holographic film is disposed on the surface of an object, any image or color displayed on the surface of the object is at least partially visible through the holographic film. For example, a book cover may have an image printed on the cover. The translucent holographic film may be disposed over this book cover, and both the image printed on the cover and the hologram above the image are visible. Therefore, both the hologram and the surface of the object are simultaneously visible to a viewer. To create the hologram, the film is embossed with any suitable pattern in the form of a texture or a plurality of ridges to create any suitable holographic effect when viewing the film. Moreover, the holographic film may be attached to any suitable object, including, but not limited to books.
[0024] In order to attach the holographic film to an object, the holographic film may comprise an adhesive layer formed by any suitable adhesive. In use, the adhesive layer of the holographic film is disposed adjacent to a surface of the target object. When a thermal (hot melt) adhesive is utilized, heat is applied to the holographic film to activate the adhesive, and bind the holographic film to the object.
[0025] Referring to FIG. 1, a simplified diagram of an embodiment of a translucent holographic film 100 in accordance with teachings of the invention is shown. The holographic film 100 comprises a substrate material 110 that provides strength to the holographic film 100. The substrate has a first surface 112 and a second surface 114. In this embodiment, ridges 116 are embossed directly onto the first surface 112 of the substrate 110. An adhesive layer 120 is disposed on the second surface 114 of the substrate 110. When this embodiment is attached to an object, the embossed first surface 112 of the substrate 110 is exposed to the viewer, with the peaks 118 of the ridges 116 pointing away from the adhesive layer 120 and from the object to which the holographic film 100 is adhered. In other words, the adhesive layer 120 is adjacent the non-embossed second surface 114 of the substrate 110.
[0026] In order to maintain sufficient adhesion between the thermal adhesive and-the surface of the layer of the film to which the thermal adhesive is adhered, the film may be treated with an adhesion promoter. Sufficient adhesion between the layers of the film is important to prevent delamination during cutting, scoring, folding, bookbinding or similar operations. In accordance with teachings of the invention, the surface of the layer of film to which the adhesive is attached may have a surface treatment to promote adhesion. For example, as shown in FIG. 1, the second surface 114 of the substrate 110 may include a surface treatment 150 between the substrate 110 and the adhesive layer 120 to strengthen the adherence between these layers. The surface treatment may be any suitable process or material that enhances the adhesion between the adhesive layer and an adjacent layer including, but not limited to, a surface treatment such as corona, UV, ozone, plasma, flame treatment, the use of a primer, or any combination thereof.
[0027] hi certain embodiments, it may be desirable to add a material to the substrate to enhance the holographic effect and/or provide protection to the surface embossed with the hologram. For example, referring to FIG. 2, another embodiment of a translucent holographic film 200 is shown. Similar to the previous embodiment, this embodiment has a substrate layer 210 and an adhesive layer 220 disposed on the second surface 214 of the substrate 210. Furthermore, this embodiment may include a surface treatment 250 disposed between the substrate layer 210 and the adhesive layer 220. This embodiment additionally includes a coating layer 230 that is disposed on the embossed first surface 212 of the substrate 210 to enhance the holographic effect and/or provide protection for the embossed first surface 212 of the substrate 210. For example, the coating layer 230 maybe disposed between the substrate and the viewer of the holographic film 200. Thus, the substrate 210 is not directly exposed to external elements, but is shielded by the coating layer 230.
[0028] The coating layer 230 is preferably a translucent material having a high refractive index relative to the embossed layer. The high refractive index coating may have, for example, a refractive index differential greater than 0.2. An example of a suitable high refractive index coating material includes, but is not limited to, zinc sulfide (ZnS). When this embodiment is adhered to an object, the adhesive 220 is disposed adjacent the object with the peaks 218 of the ridges 216 pointing away from the adhesive 220 and from the object to which the holographic film 200 is adhered. Again, the adhesive layer 220 is adjacent the non-embossed second surface 214 of the substrate 210.
[0029] Turning to FIG. 3, another embodiment of a translucent holographic film 300 is shown. Similar to previous embodiments, this embodiment has a substrate layer 310 and an adhesive layer 320 disposed on the second surface 314 of the substrate 310. Furthermore, this embodiment may include a surface treatment 350 disposed between the substrate layer 310 and the adhesive layer 320. In this embodiment, the substrate 310 is not embossed, and an additional layer 340 is disposed on the first surface 312 of the substrate 310. The additional layer 340 may be composed of a material that may generally provide a more durable/wear resistant structure compared to the substrate 310 of certain embodiments and/or may generally be more conducive to hologram formation than the material used for the substrate 310 of certain embodiments. The additional layer 340 maybe composed, for example, of a low melting thermoplastic, an acrylic, or a radiation-curable thermosetting resin. When this embodiment is adhered to an object, the peaks 348 of the ridges 346 on the additional layer 340 point away from the adhesive layer 320, the substrate 310, and the object to which the holographic film 300 is adhered, and the substrate 310 is disposed between the additional layer 340 and the adhesive 320. Again, the adhesive layer 320 is not adjacent the embossed surface (of the additional layer 340 in FIG. 3).
[0030] While the holographic film constructions illustrated in FIGS. 1-3 are conventional, the films 100, 200, and 300 of the invention utilize substrate materials not previously used in holographic films. The substrate materials 110, 210, and 310 may be constructed of a material that has sufficient moisture absorption properties to substantially avoid curling problems inherent in other translucent holographic films when adhered to certain objects (such as book covers, papers, etc.). Basically, the substrate material 110, 210, 310 will have a similar moisture absorption rate as the material of the underlying object (e.g., paper) such that little or no absorption rate differential is present, therefore minimizing or eliminating curl. Furthermore, the substrate may be constructed of a material that does not deform when raised to temperatures necessary to activate a thermal adhesive. An example of such a substrate is polyamide (e.g., nylon). Other advantageous substrate materials contemplated by the present invention are materials that are relatively inexpensive and have mechanical strengths suitable for clean sheet separation using an edge perforation, such as polypropylene (including bi-axially oriented polypropylene or BOPP).
[0031] Turning to FIG. 4, another embodiment of a translucent holographic film 400 is shown. Similar to previous embodiments, this embodiment comprises a substrate layer 410, an adhesive layer 420, and a coating layer 430. However, the construction illustrated in FIG. 4 has a significant constructional improvement over conventional constructions, hi this embodiment, the substrate 410 is embossed with a plurality of ridges 416 to form the hologram, and the coating layer 430 is disposed against the embossed second surface 414 of the substrate 410. The adhesive layer 420 is disposed against the coating layer 430 and conforms to the ridges 416 embossed into the holographic film 400. In other words, the adhesive layer 420 is applied to the embossed side (of the substrate 410 and the coating layer 430 in FIG. 4)~ This embodiment may include a surface treatment~450 disposed between the coating layer 430 and the adhesive layer 420. When this embodiment is attached to an object, the adhesive 420 is disposed against the object and the unembossed first surface 412 of the substrate 410 is exposed to the viewer with the peaks 418 of the ridges 416 directed away from the viewer, toward the adhesive layer 420, and toward the object to which the film 400 is applied. Therefore, the hologram is viewed through the substrate 410.
[0032] hi this embodiment, the hologram formed on the holographic film 400 is relatively durable and wear resistant because the embossed second surface 414 is not directly exposed to external elements, but is instead shielded between the substrate 412 and the object adhered to the holographic film 400. As an example, in embodiments wherein the ridges 416 are exposed to the viewer, the handling of the holographic film 400 over time can allow foreign substances (such as finger oils, lotions, or other liquids, etc.) to accumulate between the ridges 416 and/or direct contact can cause the peaks 418 of the ridges 416 to deform, which can substantially and undesirably affect the quality of the hologram. For example, this type of damage may alter how the light is refracted/reflected by the image resulting in the diminishment of the brightness and clarity of the hologram. Protecting the embossed second surface 414 within the film 400 circumvents these hologram quality issues.
[0033] Turning to FIG. 5, another embodiment of a translucent holographic film 500 is shown. Similar to previous embodiments, this embodiment comprises a substrate layer 510, an adhesive layer 520, a coating layer 530, and an additional layer 540. Similar to the embodiment shown in FIG. 4, this embodiment also includes the improved construction in which the embossed surface is protected from the surrounding environment. In this embodiment, the first surface 512 of the substrate 510 is exposed to the viewer. The additional layer 540 is disposed on the second surface of the substrate 514 and is embossed with a plurality of ridges 546 to create the holographic image. The coating layer 530 is disposed adjacent to the ridges 546 of the additional layer 540. Finally, the adhesive 520 is disposed on the coating layer 530. This embodiment may include a surface treatment 550 disposed between the coating layer 530 and the adhesive layer 520. Again, the adhesive layer 520 is applied to the embossed side (of the additional layer 540 and the coating layer 530 in FIG. 5). As in the previous embodiment, improved wear resistance and durability of the hologram is obtained because the peaks 548 of the ridges 546 are directed toward the adhesive layer 520 and toward the object to which the holographic film 500 is adhered and thus, not directly exposed to external elements that can damage the embossed surface.
[0034] Because the exposed surfaces 412 and 512 are generally smooth, and do not include the exposed peaks and valleys of the embodiments shown in FIGS. 1-3, the exposed surfaces 412 and 512 are also well-suited to receive overprinting if desired, hi other words, portions of the surfaces 412 and 512 could be printed upon to further add to the aesthetic qualities of the films 400 and 500. The substrates 410 and 510 could be chosen from a material conducive to receiving print (e.g., inks), or could be treated with a primer or other suitable surface treatment to facilitate receiving print.
[0035] The high refractive index (HRI) coating is particularly useful with the embodiments shown in FIGS. 4 and 5 where the adhesive layer fills in the valleys present in the embossed surface. The HRI coating is thin enough to enable transparency and generally mimics the topography of the underlying embossment. The use of the HRI coating allows the holographic image to retain its brightness and clarity even if the valleys of the embossment are filled in, provided that there is a sufficient difference in the refractive index of the HRI coating and the substance in contact with it. In addition, the HRI layer serves to brighten the appearance of the holographic image.
[0036] The translucent holographic film may be manufactured by any suitable process. For example, "soft" or "hard" embossing techniques may be utilized to form the hologram surface by embossing a desired pattern of ridges into the film. Referring to FIG. 6, a flow diagram representing "soft" embossing processes is shown, hi step 600, the substrate is provided for embossing. The substrate may be embossed directly using a heated roll having a desired texture in step 602. Alternately, as explained above, in certain embodiments the substrate is not embossed directly, but instead, an additional layer comprising a low melting thermoplastic or radiation-curable thermosetting resin may be embossed to form the hologram. The low melting thermoplastic layer may be applied to the substrate via extrusion in step 606, and then the low melting thermoplastic layer may be embossed with a heated roll having a desired texture in step 608. Alternately, if a radiation-curable thermosetting resin is utilized, then the resin may be applied to the substrate by a gravure process in step 610. The resin may be embossed by subjecting the resin layer against a roll having a desired texture and UV curing the holographic pattern into the resin in step 612.
[0037] After the substrate, low melting thermoplastic layer, or the radiation-curable thermosetting resin are embossed, an HRI coating layer may be applied to the embossed surface in step 614. By way of example and not limitation, the HRI coating may be applied by a vacuum metalizing (such as for applying ZnS) or sputtering (such as TiOx) process.
[0038] Turning to FIG. 7, a so-called "hard" embossing technique may be used to form the hologram surface. A substrate is provided in step 700. In step 702, a surface treatment may be applied to a surface of the substrate. The surface treatment strengthens the adherence between the substrate and an adjacent layer. The surface treatment may be any suitable surface treatment including, but not limited to, corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof. In step 704, a low melting thermoplastic layer may be applied to the substrate via extrusion, or in step 706, a radiation-curable thermosetting resin may be applied to the substrate by a gravure process. An HRI coating may then be applied to the low melting thermoplastic layer or the radiation-curable thermosetting resin layer in step 708. Turning to step 710, a hologram pattern may then be embossed into the HRI coating and either the low melting thermoplastic layer or the radiation-curable thermosetting resin by applying pressure to emboss the film. FIG. 7 also illustrates the technique in which the HRI coating can be applied directly to the substrate, and then the coated substrate can be embossed (sequence of steps 700, then step 708, and then step 710).
[0039] FIG. 8 discloses a process for applying a thermal adhesive to the holographic film. In step 800, a film with a hologram embossed thereon is provided. The film may, for example, be provided following one of the processes shown in FIG. 6 or FIG. 7. In accordance with teachings of the invention, one or more techniques or materials may be applied to the film to improve adhesion and resist delamination between the thermal adhesive and the surface of the film layer to which the thermal adhesive is applied. As shown in step 802, a surface treatment may be applied to the surface that will be receiving the thermal adhesive. The surface treatment may be any suitable surface treatment including, but not limited to, corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof. [0040] By way of example and not limitation, the surface treatment may include corona treating a surface as in step 804. The surface may then be coated with a primer as in step 806. The primer may be any suitable primer including, but not limited to, an aqueous-based primer with a medium crosslink density. Such a primer may be applied, for example, utilizing a gravure coating station. In step 808, the primer may then be dried and/or cured. This may be accomplished by applying heat at a temperature below the melting point of the layer of the film having the lowest melting point.
[0041] Once the surface treatment(s) have been applied, the thermal adhesive may be applied to the film in step 810. The thermal adhesive may be applied via extrusion through a die. It may be desirable to extrude the adhesive in an ozone-rich environment. Furthermore, it may be preferable to extrude the adhesive such that the adhesive layer is relatively thin (for example, between approximately 0.003 to 0.0005 inches thick). If desired, the adhesive may then receive a corona treatment in step 812. If the film is provided on a roll, then the film may then be rewound onto the roll. Through this process, the adhesion between the adhesive layer and an adjacent layer of the film is enhanced.
[0042] As described above with respect to films 100, 200, and 300, the substrate 410, 510 of films 400 and 500 may be constructed of a material that has sufficient moisture absorption properties to substantially avoid curling problems inherent in other translucent holographic films when adhered to certain objects (such as book covers, papers, etc.). Furthermore, the substrate may be constructed of a material that does not deform when raised to temperatures necessary to activate a thermal adhesive. An example of such a substrate is polyamide (e.g., nylon). Also advantageous are materials that are relatively inexpensive and have mechanical strengths suitable for clean sheet separation using an edge perforation, such as polypropylene (including bi-axially oriented polypropylene or BOPP). The substrates 410 and 510 may, however, be constructed of any suitable material. Additional examples of such materials include, but are not limited to, polyethylene terephthalate (including bi-axially oriented polyethylene terephthalate or BOPET), polyvinyl chloride (PVC), polyethylene, polystyrene, polycarbonate, acetate, and polymethyl methacrylate (PMMA).
[0043] The adhesive layer may comprise any suitable adhesive. Examples of suitable thermal adhesives include, but are not limited to, ethylene/vinyl acetate (EVA), polyester resins, polyethylene resins, ethylene/isobutyl acrylate copolymer resins, polyvinyl acetate and vinyl acetate copolymer resins, and polypropylene resins.
[0044] As described above, the coating layer may comprise a material having a high refractive index (HRI) including, but not limited to, zinc sulfide (ZnS), titanium dioxide (TiO2), and dialuminum trioxide (Al2O3). One of ordinary skill in the art, however, would appreciate that any suitable material may be used. Alternate materials that may be used include, but are not limited to, SiO and TiO. ZnS is preferred of these coatings as it can be applied using established metallizing equipment, and can be applied at faster speeds than other materials, thus it lends to sufficient productivity with minimal investment in alternate equipment, hi some embodiments, the HRI coating can be pierced or otherwise broken or interrupted to further facilitate bonding with the adhesive layer.
[0045] The additional layer described above may be made of any suitable material, including low melting thermoplastics or radiation-curable thermosetting resins including but not limited to urethane acrylate, epoxy acrylate, polyester acrylate, or polyether acrylate, or thermoplastic resins, including but not limited to acrylics, polystyrene, or polyvinylchloride.
[0046] The surface treatment may be any suitable surface treatment for enhancing the adherence between adjacent layers of the holographic film and may be applied between any suitable adjacent layers of the film. Examples of suitable surface treatments include, but are not limited to,- corona, UV, ozone, plasma, flame treatment, the use of a primer, or a combination thereof.
[0047] As indicated above, the translucent holographic film may be adhered to any suitable object including, but not limited to, books, papers, packaging materials, paper-based boards, etc.
[0048] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
[0049] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

WHAT IS CLAIMED IS:
1. A translucent holographic film comprising: an adhesive layer; and an embossed layer, the embossed layer including an embossed side defining ridges having peaks pointing toward the adhesive layer.
2. The translucent holographic film of claim 1, wherein the embossed layer includes a substrate layer of the film.
3. The translucent holographic film of claim 2, wherein the substrate layer is a polyamide.
4. The translucent holographic film of claim 2, wherein the substrate layer is an oriented polypropylene.
5. The translucent holographic film of claim 1, wherein the embossed layer includes a substrate layer and an additional layer coupled to the substrate layer.
6. The translucent holographic film of claim 5, wherein the additional layer is a low melting thermoplastic.
7. The translucent holographic film of claim 5, wherein the additional layer is a radiation-curable thermosetting resin.
8. The translucent holographic film of claim 5, wherein the additional layer is an acrylic.
9. The translucent holographic film of claim 5, wherein the additional layer is between the substrate layer and the adhesive layer.
10. The translucent holographic film of claim 9, wherein the additional layer is embossed and wherein the substrate layer defines a generally smooth surface opposite the additional layer,
11. The translucent holographic film of claim 5, wherein the substrate layer is a polyamide.
12. The translucent holographic film of claim 5, wherein the substrate layer is an oriented polypropylene.
13. The translucent holographic film of claim 1 , further comprising a high refractive index coating between the embossed layer and the adhesive layer.
14. The translucent holographic film of claim 13, further comprising a surface treatment between the high refractive index coating and the adhesive layer to facilitate adhesion of the adhesive layer to the high refractive index coating.
15. The translucent holographic film of claim 1, wherein the embossed layer includes a generally smooth, non-embossed surface opposite the adhesive layer.
16. The translucent holographic film of claim 1, wherein the adhesive layer includes a thermally-activated adhesive.
17. A method of manufacturing a translucent holographic film, the method comprising: providing an embossed layer having an embossed side and a non-embossed side; and applying an adhesive layer to the embossed side of the embossed layer.
18. The method of claim 17, wherein applying the adhesive layer to the embossed side of the embossed layer includes applying a high refractive index coating to the embossed side and then applying the adhesive layer to the high refractive index coating.
19. The method of claim 18, further comprising applying a surface treatment between the high refractive index coating and the adhesive layer to facilitate adhesion of the adhesive layer to the high refractive index coating.
20. The method of claim 17, wherein providing an embossed layer includes applying a high refractive index coating to a material that will form the embossed layer, and then embossing the coated material to form the embossed layer.
21. The method of claim 20, further comprising applying a surface treatment between the high refractive index coating of the embossed layer and the adhesive layer to facilitate adhesion of the adhesive layer to the high refractive index coating.
22. The method of claim 17, wherein providing an embossed layer includes providing a substrate layer and an additional layer different from the substrate layer coupled to the substrate layer, the additional layer being embossed.
23. A translucent holographic film comprising: a polyamide substrate layer; and an adhesive layer coupled with the substrate layer, the film constructed to display a hologram.
24. The translucent holographic film of claim 23 in combination with an object to which the film is adhered, the polyamide substrate layer having a substantially similar moisture absorption rate as the object to substantially minimize curling of the object when the film is adhered thereto.
25. A translucent holographic film comprising: an oriented polypropylene substrate layer; and an adhesive layer coupled with the substrate layer, the film constructed to display a hologram.
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