US3427180A - Pressure-sensitive record system and compositions - Google Patents

Description

Feb. 1969 P. s. PHILLIPS, JR 3,427,180

PRESSURE-SENSITIVE RECORD SYSTEM AND COMPOSITIONS Filed March 31, 1965 INVENTOR PAUL S. PHILLIPS, JR.

HIS ATTOR EYS 3,427,180 PRESSURE-SENSITIVE RECORD SYSTEM AND COMPOSITIONS Paul S. Phillips, .lr., Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Mar. 31, 1965, Ser. No. 444,274 US. Cl. 117 -36.2 27 Claims Int. Cl. B41m /16, 5/22 ABSTRACT OF THE DISCLOSURE .This invention relates to pressure-sensitive record systems in which a mark is produced according to the pattern of pressure by the chemical reaction of mark-forming components and in particular wherein the mark-forming components comprise a primary chromogenic component, a polymeric material reacting with said chromogenic component, a liquid solvent medium in which the primary chromogenic component and the material are This invention relates to improvements in pressuresensitive record systems, and to materials utilized therewith. More particularly, it relates to improved systems employing a combination of materials including two types of chromogenic components, one of which, hereinafter called a primary chromogenic material, reacts with a third ingredient to form a mark or color during the application of pressure to the record system, and the second of which, hereinafter termed a secondary chromogenic material, forms a color only upon exposure to light.

Recently there has been developed a novel pressuresensitive record system having at least two sheets of supporting material. This system, disclosed in a co-pending United States patent application of Robert E. Miller and Paul S. Phillips, Jr., Ser. No. 392,404, filed Aug. 27, 1964, now abandoned, obviates many of the difficulties experienced with prior pressure-sensitive mark-forming systems. However, even the improved system of the copending application still retains the problem of stability of the print or color upon exposure of the pressure-formed print to light; for example, daylight. In other words, the print formed by the reaction of the mark-forming components tend to fade when exposed to light, such as sunlight, fluorescent lighting, etc.

It is, therefore, an object of the present invention to improve the pressure-sensitive record system disclosed in the aforementioned co-pending United States patent application.

Another obpect of the invention is to provide a pressure-sensitive record system in which the intensity of the print formed by the application of pressure to the system is maintained at a level easily readable by a sensing organ (e.g., the eye) upon exposure of the print to light.

Still another object of the invention is to provide a novel mark-forming composition having a combination of chromogenic components which, as when incorporated into a record system sensitive to marking pressures, main- 3,427,180 Patented Feb. 11, 1969 tains the readability of the formed print when it is exposed to light, even when one of the chromogenic materials fails, as by fading.

Still a further object of the invention is to provide a transfer sheet for use in the aforementioned pressuresensitive record system comprising supporting base or sheet material having disposed thereon and/or therein the above-mentioned mark-forming composition which maintains its reflective intensity by the action of light to which it is exposed.

These and other objects of the invention will become apparent from the following detailed description and from the drawing.

Broadly speaking, this invention comprises combina tions of materials and the pressure-sensitive record systems into which they can be incorporated, either as a single composition or separately. These materials, which can be disposed on and/or within the supporting sheet or base material of the record systems is contiguous juxtaposition to each other, comprise a first or primary chromogenic component, a polymeric material reactive therewith when both are in solution to form a mark, a liquid solvent medium in which the primary chromogenic component and the polymeric material are soluble, a pressure-rupturable material which isolates the liquid solvent medium from at least either the primary chromogenic components or the polymeric material, and a secondary chromogenic component, which does not react with the primary chromogenie material, the polymeric material, or the liquid solvent, but which upon exposure to light forms a mark itself. When the materials are disposed on and/or within the supporting sheet material, the application of markforming pressure causes a breach in the pressure-rupturable material, whereupon the formerly isolated liquid solvent, released according to the pressure pattern, dissolves both the primary chromogenic component and the polymeric material, thereby bringing them into contact while each is in solution to permit a primary mark-forming reaction, which results in a distinctive mark. The liquid solvent medium also acts as a fluid carrier for the secondary chromogenic material, which can be either dispersed or dissolved in the liquid medium to distribute it throughout the same pattern as the mark produced by the primary mark-forming components.

It has been discovered that the utilization of a specific group of secondary chromogenic materials consisting of l0-pivalyl-3,7-bis (dimethylamino) phenothiazine (N- pivalyl leuco methylene blue), l0-(a,a-dimethylbutyryl)- 3,7-lbis (dimethylamino) phenothiazine (2,2 dimethylbutyryl leuco methylene blue), and 10-(p-anisoyl)-3,7- bis(dimethylamino) phenothiazine (p-anisoyl leuco methylene blue) in the aforedescribed pressure-sensitive mark-forming system maintains the intensity of the print at an easily readable level when the print is exposed to light. Thus the same light that causes fading of the mark formed by the reaction of the primary chromogenic material and the polymeric material induces an oxidation type of reaction in the secondary chromogenic material, henceforth called a secondary mark-forming reaction, to develop a mark in the exact area of fading which compensates substantially for the fading of the prior formed mark.

The sensitivity of the secondary chromogenic materials to light-induced mark formation is a characteristic personal to each individual chromogenic material. Generally, the sensitivity should be sufiicient to produce a mark which permits continued manifestation of the mark should the original mark formed by the reaction of the primary chromogenic material and the polymeric material fade considerably or completely. Preferably, there should be utilized a substantially balanced system in which the intensity of the printed mark, as measured by the sensing organ or other sensing means, remains approximately constant. That is, as the original mark fades upon its exposure to light, the intensity of the mark formed by the secondary mark-forming reaction manifestly increases at about the same rate at which the original mark fades. Such a balanced system can be obtained by predetermining the rate of fade and the rate of development of the respective marks among eligible chromogenic materials and selecting from them the system appropriate to the expected environment of use.

The secondary chromogenic mark-forming materials are preferably colorless, though low-intensity hues can be utilized, prior to their exposure to light, and are capable of color change to form an intense, distinctive, easily readable mark upon reactive exposure to light. Usually, a single compound is utilized, although in some instances, particularly when the aforedescribed substantially balanced systems are employed, combinations 'of two or more secondary chromogenic compounds can be used advantageously for their individual response to light or for their color. The secondary chromogenic materials can be insoluble in the liquid solvent used to dissolve the primary chromogenic material and the polymeric material, or, as in the usual case, they also can be dissolved in the same solvent. Of course, a second solvent utilized specifically to dissolve one of the secondary chromogenic materials also can be present.

The primary chromogenic mark-forming component generally reacts with the polymeric material through acidic groups to produce a colored material, The prirnary chromogenic component in its unreacted state is preferably colorless, though low-intensity hues can be tolerated, and is capable of color change to a strong distinctive color upon reactive contact with the polymeric material. While various reactive combinations of primary chromogenic material and polymeric material from colorproducing systems can be used, preferably the chromogenic material is a base and the complementary polymeric material is acidic; i.e., where the color or change in color is brought about -by the acidic action of the polymer constituent on the primary chromogenic material. These color-forming systems will hereafter be described and illustrated by reference to said base and acid components.

Examples of suitable basic primary materials having chromogenic groups are diaryl phthalides; leucauramines; acyl auramines; nap-unsaturated aryl ketones; basic mono azo dyes; Rhodamine B Lactams such as N(p-nitrophenyl) Rhodamine B Lactams; polyaryl carbinols; and 8'- methoxy benzoindolinospiropyrans, which may be identified as (8-rnethoxy BIPS). Illustrative compounds of each group are diaryl phthalides:-3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (Crystal Violet Lactone, hereinafter referred to as CVL) and 3,3-bis (p-di methylaminophenyl) phthalide (Malachite Green Lactone, hereinafter referred to as MGL); leucauramines:- the N- halophenyl derivatives of leucauramine disclosed in United States Patent No. 2,828,341, issued to Clyde S. Adams, Marjorie J. Cormack, and Mary Lou Frazier on Mar. 25, 1958; and the N-alkylhalophenyl derivatives of leucauramine disclosed in United States Patent No. 2,828,342, issued to Clyde S. Adams and Marjorie J. Cormack on Mar. 25, 1958, said patents being incorporated by reference herein, particularly N-(2,5-dichlorophenyl) leucauramine; acyl auramines: N-benzoyl auramine; and N-acetyl auramine; c p-unsaturated aryl ketones: dianisylidene acetone; dibenzylidene acetone; and anisylidene acetone; basic mono azo dyes: p-dimethylamino-azobenzene-o-carboxylic acid (Methyl Red); 4- amiuoazobenzene (Oil Yelloy AAB); and 4-phenylazo-1- naphthylamine; Rhodamine B Lactams: N(p-nitrophenyl) Rhodamine B Lactam (hereinafter referred to as RBL); polyaryl carbinols: bis(p-dimethyl-aminophenyl) methanol, called Michlers Hydrol; Crystal Violet Carbinol; and Malachite Green Carbinol; 8-methoxy BIPS: 8'- methoxy 'benzoindolinospiropyran; 4,7,8-trimethoxy ben- 'zoindolino'spiropyran; and 6-chloro, 8-methoxy.benzoindolinospiropyran; and p-dirnethylaminostyryl quinoline.

In the primary base-acid color system, as stated above, the polymeric mark-forming component(s) chosen must be acidic relativeto the basic primary chromogenic compound and reactive -with the primary chromogenic material to effect distinctive color formation or color change. Moreover, the polymeric mark-forming component(s) shouldhave a common solubility with the primary chromog'enic material in at least one liquid solvent.

It should be understood that in a signal system there can be utilized one or more primary chromogenic materials on the one hand and one or more polymeric markforming components on the other hand. Thus, for example, several primary chromogenic materials may be used with the same or different polymeric materials, and.

vice versa.

As mentioned above, the solvent is maintained in physical isolation in minute droplets until such time as it is released by application of pressure. This may be accomplished by any of several known techniques, but preferably isolation is maintained -by individual encapsulation of the solvent droplets in a microcapsule according to the procedures described, for example, in United States Patents Nos. 2,712,507, issued to Barrett K. Green on July 5, 1955; 2,730,457, issued to Barrett K. Green and Lowell Schleicher on Jan. 10,1956; 2,800,457, issued to Barrett K. Green and Lowell Schleicher on July 23, 1957, and 2,800,458, issued to Barrett K. Green on July 23, 1957, reissued as Reissue Patent No. 24,899 on Nov. 29, 1960. The microscopic capsules, when disposed in pro fusion within and/or on a support sheet in contiguous juxtaposition, are rupturable by pressure, such as the pressures normally attending writing and printing operations.

The particular component(s) chosen as the wall material of the microcapsule, in addition to being pressurerupturable, must be incompatible with the contents of the capsule and all of the mark-forming components, in the sense that the wall material retains its integrity under normal storage conditions until such time as the contents are released by the application of marking pressure.

For use in record materials, the capsule size generally should not exceed 50 microns; however, the preferable upper limit is 15 microns and most preferably from 5 to 10 microns.

Any polymeric material having the aforementioned characteristics can be used herein. To illustrate, broadly, reference is hereinafter made to certain basic-type primary chromogens as one of the primary mark-forming components, and certain phenol-aldehyde and phenolacetylene polymers, maleic acid-rosin resins, partially or wholly hydrolyzed styrene-maleic anhydride copolymers and ethylene-maleic anhydride copolymers, carboxy polymethylene (Carbopol 934), and wholly or partially hydrolyzed vinyl methyl ether-maleic anhydride copolymer are specified as typical of the reactive acidic polymeric materials.

Among the phenol-aldehyde polymers found useful are members of the type commonly referred to as novolacs, which are characterized by solubility in common organic solvents and which are, in the absence of cross-linking agents, permanently fusible. Another group of useful phenol polymeric materials are alkylphenol-acetylene resins, likewise soluble in common organic solvents and possessing permanent fusibility in the absence of being treated by cross-linking materials. Generally, the phenolic polymer material is characterized by its solubility in organic solvents and relative insolubility in aqueous media, and by the presence of free hydroxyl groups and the absence of groups, such as methylol, which tend to promote infusibility or cross-linking of the polymer.

Resoles, if they are still soluble, can be used, though subject to change in properties upon aging.

A laboratory method useful in the selection of suitable phenolic resins is a determination of the infra-red absorption pattern. It has been found that phenolic resins shown an absorption in the 32003500 cm. region (which is indicative of the free hydroxyl groups) and not having an absorption in the 16001700 cm.- region are suitable. The latter absorption region is indicative of the desensitization of the hydroxyl groups and consequently makes such groups unavailable for reaction with the chromogenic materials.

The preparation of the phenolic-formaldehyde poly meric materials suitable for practicing this invention is described in Industrial and Engineering Chemistry, volume 43, pages 134 to 141, January 1951, and a particular polymer thereof is described in Example 1 of United States Patent No. 2,052,093, issued to Herbert Honel on Aug. 25, 1936. The preparation of the phenol-acetylene polymers is described in Industrial and Engineering Chemistry, volume 41, pages 73 to 77, January 1949.

The preparation of the maleic anhydride copolymers is described in the literature, such as, for example, one of the maleic anhydride-vinyl copolymers, as disclosed in the publication Vinyl and Related Polymers, by Calvin E. Schildknecht, second printing, published April 1959 by John Wiley & Sons, Incorporated. See pages 65 to 68 (styrene-maleic anhydride copolymer), 628 to 630 (vinyl methyl ether-maleic anhydride copolymer), and 530 to 531 (ethylene-maleic anhydride copolymer).

The polymer material can have film-forming properties, with the consequent attainment of high resolution of recorded data that attends the use of a continuous film.

Generally, the polymeric material can be present in the form of a film or finely-divided particles prior to the mark-forming reaction. However, as is preferable, the presence of the polymer in film form provides several advantages; namely, that the zone of marking has a protective film surrounding it, which substantially diminishes removal of the mark by abrasive action. Additionally, in the case of the preferred material-namely, the phenolic polymersthe water-insolubility of the polymer precludes decoloration by atmospheric moisture attack.

Where the polymeric material is disposed originally on the support sheet member as a continuous film, it provides large surface area of reactive material in a form that is readily soluble. Additionally, the presence of the polymer in film form provides for greater ease of adaptability to existing application apparatus, such as, for example, a printing ink applicator. Finally, as compared with prior-art systems, the polymer, because of its great affinity for the substrate, substantially reduces the socalled picking problem associated with coatings of particulate materials such as attapulgite.

The liquid solvent chosen must be capable of dissolving the primary chromogenic material and the polymeric material. In the majority of cases, it also dissolves at least a portion of the secondary chromogenic material. The solvent can be volatile or non-volatile, and a single or multiple component solvent may be used which is wholly or partially volatile. Examples of volatile solvents useful with the aforedescribed components are toluene, petroleum distillate, perchloroethylene, and xylene. Examples of non-volatile solvents are high-boiling-point petroleum fractions and chlorinated diphenyls.

Generally, the solvent chosen should be capable of dissolving at least 1%, on a weight basis, of the primary chromogenic material, preferably in excess of 2%, and a corresponding amount of polymeric material to form an efficient reaction. However, in the preferred system, the solvent should be capable of dissolving an excess of the polymeric material, so as to provide every opportunity for utilization of the primary chromogenic material and thus to assure the maximum coloration at a reaction site.

A further criterion of the solvent is that it must not interfere with the mark-forming reaction of either the primary or the secondary chromogenic component. In some instances, the presence of the solvent may interfere with the markforming reaction of the primary chromogenic material or diminish the intensity of the mark, in which case the solvent chosen should be sufficiently vaporizable to assure its removal from the reaction site after having, through solution, brought the primary markforming components into intimate admixture and contact, so that the mark-forming reaction proceeds.

Inasmuch as the primary mark-forming reaction requires an intimate mixture of the primary chromogenic material and the polymeric material to be brought about through their solution, one or more of these mark-forming components may be dissolved in the isolated solvent droplets, the only requirement being that at least one of the components essential to the primary mark-forming reaction be maintained undissolved by the droplets until they are released by application of pressure.

In the usual case, the primary mark-forming components are so chosen'as to produce a mark upon application of the pressure at room temperature (20 to 25 degrees centigrade). However, there also can be employed systems in which the solvent component is not liquid at temperatures around room temperature but is liquid and in condition for forming solutions only at elevated temperatures.

In the preferred case, where microcapsules are employed, they may be present in the support sheet or base material either disposed therethroughout or as a coating thereon, or both. The capsules may be applied to the sheet material while still dispersed in the liquid vehicle in which they were manufactured, or, if desired, separated and the separated capsules thereafter dispersed in a solution of, for example, the polymeric component (for instance, 30 grams of water and 53 grams of a 1% aqueous solution of polyvinyl methyl ether maleic anhydride) to form a coating composition in which, because of incompatibility of the solution and the capsules, both retain their identity and physical integrity. When this composition is disposed as a film on the support material and dried, the capsules are held therein subject to rupture to release the liquid which they contain. This latter technique, relying on the incompatibility of the microcapsule and the dispersing medium of the film-forming polymeric mark-forming component, allows for a method of preparing a sensitive record coating with the capsules interspersed directly in a dry film of the polymeric material as it is laid down from the solution. A further alternative is to disperse in a liquid medium one or more primary mark-forming components, insoluble therein, and disperse in said medium the insoluble microcapsules, with the result that all components of the mark-forming system may be disposed on or within the support sheet in the one operation. Obviously, the several components may be applied individually.

The application of the secondary chormogenic material(s) to the supporting base material can be accomplished by dispersing them in finely-divided form or in solution, along with the microcapsules, in the solution of the polymeric component or in the liquid medium, as described above. The secondary chromogenic component(s) can also be dispersed or dissolved in the liquid solvent contained within the microcapsules. Thus a single composition comprising all the ingredients can be produced by encapsulating a solvent solution of one primary mark-forming component and the secondary chormogenic material(s), mixing the capsules with a solution or a dispersion of the other primary mark-forming component, and coating the resultant composition on the supporting base material. As above mentioned, the several components can also be applied to the supporting base material individually.

The respective amounts of the several components will vary, depending primarily upon the nature of the materials and the architecture of the record material unit. Suitable amounts include, in the case of the secondary chromogenic material, about .01 to about 0.20 pound per ream (a ream in this application means five hundred sheets of 25" x 38" paper, totalling 3,300 square feet), the preferred amount being about .03 and .05 pound per ream; in the case of the primary chromogenic material, about .03 to about .075 pound per rea m, the preferred amount being about .05 pound per ream; in the case of the solvent, about 1 to 3 pounds per ream; and in the case of the polymeric material, about /2 to 3 pounds per ream. In all instances, the upper limit is primarily a matter of economic consideration.

The arrangement and the physical state of the components of the mark-forming system in relation to support material will be further discussed hereinafter, a specific arrangement being illustrated in the drawing.

In the drawing, only the supporting sheet material, the capsules, and the polymeric material are shown. The arrangement of the primary and secondary chromogenic materials and the solvent, as well as various exemplary modifications of the positions of the aforementioned components, will be discussed in the following explana tion of the drawing.

FIGURE 1 is a diagrammatic perspective view of a preferred embodiment of a pressure-sensitive record system, showing a supporting sheet and a receiving sheet 12 having their adjacent faces coated with pressurerupturable capsules 11 and a polymeric material 13, such as phenolic polymer, respectively.

FIGURE 2 is a diagrammatic cross-sectional view taken on line 22 of FIGURE 1, showing the results of the application of pressure to the system by a pencil 14, or any stylus, type character, or other pressure-inducing means, producing marks 15 and 16 on the transfer and receiving sheets 10 and 12, respectively.

In the embodiment of FIGURES 1 and 2, the capsules contain a liquid solvent in which are dissolved a basic primary chromogenic component and a secondary chromogenic component. Although the latter component is usually dissolved in the same solvent as the former, this is not essential. For example, the secondary chromogenic material can be dissolved in a second solvent or in some instances merely dispersed in the solution of the primary chromogenic material. As the pencil is pressed over the surface of the top or transfer sheet of supporting material, the pressure exerted upon the sheet is transmitted to the capsules, thereby rupturing those which lie in the pattern produced by the pencil. The solution of the primary and secondary chromogenic components is then released and transferred to the bottom, or receiving, sheet, where the solvent then dissolves the polymeric material; for example, a phenolic polymer, which reacts with the dissolved primary chromogenic material to produce a mark corresponding to the configuration of the pattern formed by the pencil.

Although only a two-sheet record system is illustrated, the marking-forming components can be employed in multiple-sheet systems having three or more sheets, it only being necessary to coat the upper and lower surfaces of each contiguous sheet with the components required to produce a mark. For example, as illustrated in the drawing, the lower surface of the sheet 12 can be coated with capsules, and the upper surface of a third sheet (not shown) can be coated with a film of polymeric material. When pressure is applied to the top surface of the sheet 10, a mark is formed on the upper surface of the third sheet in the same manner as the mark produced on the upper surface of the sheet 12.

The arrangement of the primary color-producing components can be modified in any manner so long as at least of of the components is isolated from the solvent. For example, the primary chromogenic material in particulate form can be coated on the upper surface of the receiving sheet 12, and the polymeric material can be dissolved in the solvent contained within the capsules 11. Examples of other modifications include the arranging of both the polymeric material in either a coating or particulate form,

and the particulate primary chromogenic material on the upper surface of the receiving sheet and the solventcontaining capsules either on the under side of the transfer sheet or on the upper surface of the receiving sheet along with the primary mark-forming components. Of course, each of the aforedescribed primary mark-forming components and capsules can be located throughout the thickness of the sheets of supporting material rather than, or in addition to, being coated on the surface(s) so long as there is a sufficient quantity to provide a clear and distinct mark.

Whereas the primary mark-forming components must be in contact in solution to form a color, the secondary chromogenic material, whether dissolved or not, need only be exposed to light to produce its mark. Consequently, the arrangement of the latter within the record system is necessarily more limited. Obviously the secondary chromogenic material cannot be located on any surface of the receiving sheet, which is exposed to a light source, since the entire sheet would be colored by the ensuing reaction, leaving no distinctive pattern. Conversely, it usually is located on a surface of the transfer sheet which is not exposed to light. Surface is here meant to include the thickness of the sheet to a depth to which the remaining thickness of the sheet will protect the secondary chromogenic material from premature development when the other surface is exposed to light. Whatever the final arrangement of the secondary chromogenic material, caution must be exercised to prevent its exposure to strong light prior to the usage of the transfer sheet for recording purposes. Although inclusion of this material in the capsules affords some protection from premature coloration, neither the surface of the sheets on which it is located nor the back of such sheets, unless they are sufficiently opaque to prevent passage of substantially all light therethrough, should be exposed to bright light for any length of time.

The secondary chromogenic material is usually arranged in the form of finely-divided discrete particles coated directly on the transfer sheet or, preferably, dispersed in finely-divided form or dissolved in the liquid contained within the capsules positioned thereon. Thus, the secondary chromogenic material can be distributed throughout the liquid, either as a finely-divided dispersion or as a solution, either prior to or following release of the liquid from the capsules. In either case, the essential feature is the distribution of this material throughout the liquid, which acts as a carrier to transfer it to the receiving sheet in the configuration of the pattern produced by the pressure-rupture of the capsules.

All of the components can be arranged on a single transfer sheet as long as sufiicient amounts of solvent are disposed on the bottom surface of or within the thickness of the sheet to effect the transfer to a receiving sheet of an adequate amount of primary and secondary colorforming materials to maintain the mark produced on the receiving sheet at an easily readable level after its exposure to light in the atmosphere.

The capsules can be applied to the base supporting material in any convenient manner known to the prior art. They can be coated onto the sheets from an aqueous slurry in which they were made, with an amount of aqueous vehicle material added or removed to give the slurry proper coating consistency. The slurry can have binder material added, if necessary. The slurry of capsules can be applied to a wet web of paper as it exists on the screen of a Fourdrinier paper machine, so as to sink into the paper web a controlled distance. The capsules also can be placed directly in the paper pulp furnish before it is applied to the paper machine screen, and thus appear throughout the thickness of the sheet.

The remaining components which are not contained within the capsules can be coated on and/ or interspersed throughout the supporting sheets. This also can be accomplished by a variety of methods known to the prior art.

For example, the component(s) to be interspersed throughout the sheet can be dispersed (or dissolved) in the furnish, which then is passed onto the Fourdrinier wire. While the sheet is in its wet state, or after it is dried, the remaining component(s) can be coated individually or simultaneously onto the support sheet from an aqueous dispersion or a solution, with subsequent removal of the vehicle, in any known manner. Of course, care must be exercised during the making of the record units to prevent contact of the primary chromogenic component and the polymeric material While both are dissolved. Details of a number of these methods are clearly described in the aforementioned co-pending United States patent application of Robert E. Miller et a1., and, since they form no part of the inventive concept of this application, they will not be repeated herein. The methods disclosed as useful for adding the primary-mark-forming components (e.g., the primary chromogenic material and the polymeric material) to the supporting sheets can also be employed for the application of the secondary chromogenic material; e.g., the N-pivalyl leuco methylene blue, to the supporting members, again care being exercised to dispose the secondary chromogenic material only on one surface of the transfer sheet.

The quantities of the aforementioned components which can be added to the supporting material are dependent upon the arrangement of the components and can be tailored to the construction and performance standards desired for each specific record system. Such considerations as the quantity of capsules required to provide sufficient liquid content to make contact with the other components of the system, the position of the components, e.g., on the surface and/or throughout the support sheet, etc., vary with the individual requirements of use of each record system and can be predetermined by one skilled in the art.

The liquid solvent contained in the aforedescribed capsules also can be isolated from at least one of the primary mark-forming components by other means such as the liquid droplets of a discontinuous emulsion phase in a continuous film of pressure-rupturable material, which, in essence, forms a continuous wall separating the individual droplets. Such film-holding of droplets that are released by writing or printing pressure is a well-known expedient, disclosed in United States Patents Nos. 2,299, 694 and 2,374,862, issued to Barrett K. Green on Oct. 20, 1942, and May 1, 1945, respectively, and are made by dispersing the oil droplets in a solution of polymetric film material which is applied to a record sheet and dried. Wherever reference is made to the isolation of liquid solvent in this application, it includes this continuous film structure as a full equivalent of capsules, except that the liquid is more impermeably retained in the capsules, and the latter can be treated as particles for incorporation into the paper-machine furnish. Thus, the circles shown in the figures represent not only capsule structure but films which hold a multitude of droplets for local release in an area subject to pressure.

It is to be understood that in the figures the showing is in an exaggerated form, as the record materials in their manufactured form are hardly distinguishable from ordinary coated-paper printing stock, the normal coloration being that of the base sheet stock, and the sensitizing materials as to particle size, when particles are involved, being small enough to escape observation, but close enough to each other to afford a good recording surface or background surface against which the record can be visually sensed. The relative amounts of components to be used are the most convenient and economical amounts consistent with proper visibility of the recorded data. The resolution of the recorded data is, among other things, dependent on particle size, distribution and amount of particles, liquid solvent migration, chemical reaction efiiciency, and other factors, all of which are things that may be worked out empirically by one familiar with the art.

EXAMPLE 1 A solution of a primary chromogenic material, Crystal Violet Lactone (CVL), and a second chromogenic material, N-pivalyl leucomethylene blue (PLMB), was encapsulated using the following procedure:

Into 100 cc. of a solvent comprising a 1:1 ratio by volume of chlorinated diphenyl (Aroclor 1242) and a petroleum hydrocarbon solvent consisting of 57.6% paraffins, 35.2% naphthenes, and 7.2% aromatics and having a boiling range of 316 to 358 degrees Fahrenheit (Shell 360), there were dissolved 2 grams of CVL and 1 gram of PLMB. Into a Waring Blendor there were placed cc. of the CVL-and-PLMB solution and an aqueous sol of 10 grams of gelatin in grams of water at 50 to 55 degrees centigrade. The blendor was operated until droplets of the solution having a diameter of 5 microns or less were emulsified in the gelatin sol. An aqueous sol of 10 grams of gum arabic in 90 grams of water was then added to the emulsion, the pH was adjusted to 66.5, and under constant stirring sufficient water was added to produce a total volume of one liter. The pH was then lowered slowly by the addition of a 10% acetic acid solution until the visual test of cloudiness, as outlined in United States Patent No. 2,800,458, issued July 23, 1957, to Barrett K. Green and Lowell Schleicher, indicated that coacervation was complete.

The resulting mass was then chilled to 10 degrees centigrade or lower and allowed to stand for one hour at this temperature. Subsequently, .5 milliliter of a 25% glutaraldehyde solution was added, and the entire mass was stirred overnight.

A second solution of the primary chromogenic material, CVL, was encapsulated, without there being present any secondary chromogenic material, in the following manner:

Into a Waring Blendor were placed 189 milliliters of an internal phase comprising a solution of 1 /2%, by weight, of the total solution, of CVL dissolved in a 2-to-1 ratio, by volume, of chlorinated diphenyl (Aroclor 1242) and a petroleum solvent comprising 48.6% parafiins and 51.4% naphthenes and having a boiling range of 390 to 496 degrees Fahrenheit (known commercially as Magna- Flux Oil or Shell Dispersol) and 136 grams of an 11% aqueous gelatin sol having a pH of about 6.5 The blendor was operated until there was formed an emulsion in which the droplets of the internal phase were about 5 microns and under in diameter. To the emulsion were added 91 grams of an 11% aqueous gum arabic sol, 12 grams of a 5% aqueous solution of a vinylmethy'lether-maleic anhydrlde copolymer, and 725.5 grams of water. The pH of the mixture was raised to about 10 by the addition of a 10% aqueous solution of sodium hydroxide. Under constant stirring, the pH of the diluted emulsion was slowly lowered to an end-point of 4.8 by the addition of 13.5 milliliters of a 14% aqueous actic acid solution to complete the coacervation.

The resulting batch of capsules was chilled to 10 degrees Centigrade or lower, followed by the addition of 7.5 milliliters of glutaraldehyde.

The resulting batches of capsules and supernatant liquid were then coated on one surface of separate supporting sheets of material and dried to yield a capsule-containing coating of a quantity equal to about 4 /2 pounds per ream of 500 sheets 25 by 38 inches.

An acidic polymeric material was prepared by the following procedure:

grams (1 mole) of paraphenylphenol, 65 grams of 37% aqueous formaldehyde, 10 cc. of concentrated hydrochloric acid (37%), 1 gram of oxalic acid dihydrate, and 40 cc. of water were added to a resin kettle and refiuxed at the boiling point of the water for eight to twelve hours, after which the reaction mass was allowed 1 1 to cool, and the water layer was decanted. The resin mass then was distilled under reduced pressure (bench aspirator) until the flask temperature reached 120 to 130 degrees centigrade. Following the vacuum distillation, the resin batch was poured into a stainless steel tray and allowed to cool.

A sheet of supporting material was impregnated with the polymer by being dipped into a 4% xylene solution of the polymer and dried.

Upon bringing the respective capsule-coated surfaces of the supporting sheets into contiguous relation with supporting sheet "impregnated with the acidic material and applying a pressure stroke to the uncoated side of the sheets carrying the capsules, marks were produced on the polymer-impregnated sheets.

Using an opacimeter which measures the refiectance of surfaces over a narrow band of wave lengths which peak simultaneously 'with the wavelengths of light to which thehuman eye is most sensitive, the optical density (O.D.) of the marks produced above was determined and recorded in the following table:

OPTICAL DENSITY" PLMB+CVL on Phenolic Resin Phenolic Resin South Window Exposure Daylight Fluorescent Exposure *Optical Density (O.D.)=negative log I/Io where I=reflectance of the mark produced on the receiving sheet by the pressure applied to the tilanifer sheet. Io=refiectance of the background area of the receiving S 88 These optical density tests, which measure the intensity of the marks produced on the sheets and, therefore, indicate the ease of readability of the marks, show that while the development of the mark produced by the secondary chromogenic material (PLMB) does not compensate entirely for the fading of the mark produced by the reaction of the primary chromogenic material (CVL) and the the acidic polymeric material, the combination of the two yields a considerable improvement in the readability of the marks. For example, after exposure in a south window for twenty-two days, the combination of ingredients mark produced a fivefold improvement over the mark formed solely of the reaction product of the primary chromogenic material (CVL) and the acidic polymeric material.

EXAMPLE 2 Compositions of a primary chromogenic material, Crystal Violet Lactone (CVL), and each of the following secondary chromogenic materials, N-pivalyl leucomethylene blue (PLMB), 2,2 dimethylbutyryl leucomethylene blue (DLMB), and p-anisoyl leuco methylene blue (ALMB), were encapsulated by the following method:

Into a Waring Blendor were placed 189 milliliters of an internal phase comprising a solution of 1 /2%, by weight, of the total solution of the secondary chromogenic material and l /z%, by weight, of the total solution of CVL dissolved in a 2-to-1 ratio by volume of chlorinated diphenyl (Aroclor 1242) and MagnaFlux Oil (Shell Dispersol), and 136 grams of an 11% aqueous gelatin sol having a pH of about 6.5. The same ingredients and procedures employed in the preparation of the CVL-containing capsules of Example 1 were utilized during the emulsification, the coacervation, and the hardening steps to complete the encapsulation of the aforementioned compositions.

A l /2%, by weight, CVL solution was encapsulated using the same materials and procedures. Only the secondary chromogenic material was removed.

To 200 grams of a 20%, by weight, emulsion of each of the resulting batches of capsules and supernatant liquid, there were added, under constant stirring, 20 grams of a 20% aqueous starch solution, 4 grams of talc, 12 grams of floc, and 37 grams of water. These compositions were then coated on one surface of separate supporting sheets of material and dried to yield a coating of a quantity equal to about 4% pounds per ream of material.

An acidic polymeric material was prepared by the procedure described in Example 1. The resulting polymer was dried, and 5 grams of the dry polymer was ball-milled with 1% grams of gum'arabic and 43 /2 grams of water,

and coated on one surface of additional sheetsof suppork ing material.

Following the procedure described in Example 1, the support sheets were brought into contiguous relation, and marks were produced on the sheets containing the polymer material. Using an opacirneter, the optical density of the marks was determined and recorded in the following table:

OPTICAL DENSITY CVL on CVL Plus CVL Plus CVL Plus Time (Days) Phenolic PLMB on DLMB on ALMB on Resin Pnenolie Phenolic Phenolic Resin Resin Resin Room Exposure Daylight Fluorescent Exposure As in Example 1, the optical density tests emphasize that the addition of any one of the secondary chromogenie materials to the primary chromogenic material (CVL) improves considerably the readability of the mark produced on the sheet coated with the polymeric material.

As will be apparent to those skilled in the art, various other modifications can be carried out from the above disclosure without departing from the spirit and scope of the invention embodied within the claims,

What is claimed is:

1. A transfer sheet for use in a pressure-sensitive record system having at least said transfer sheet and a receiving sheet, comprising:

(a) supporting base material,

(b) primary mark-forming components comprising at least one primary chromogenic material and at least one polymeric material reactive with the primary chromogenic material to produce a mark when both are in solution,

(c) a liquid solvent for said primary mark-forming components,

((1) pressure-rupturable means for isolating said solvent from at least one of said primary mark-forming components prior to release of the solvent from said means, and

(e) a secondary chromogenic material, which upon exposure to light forms a mark, selected from the group consisting of N-pivalyl leucomethylene blue, 2,2-dimethylbutyryl leucomethylene blue, and panisoyl leucomethylene blue, and mixtures thereof; each of said primary mark-forming components, said solvent, said pressure-rupturable solvent-isolating means, and said secondary chromogenic material being supported by said base material, said secondary chromogenic material being located only on one surface of said transfer sheet, and said each arranged in contiguous juxtaposition to each other, whereby upon rupture of said solvent-isolating means, the liquid solvent is released therefrom, said primary mark-forming components are brought into reactive contact by the released solvent, said secondary chromogenic material is distributed throughout said solvent, and the said primary mark-forming componets and secondary chromogenic material are transferred to the receiving sheet by the solvent.

2. The transfer sheet of claim 1 in which said pressurerupturable means are microcapsules, said microcapsules containing said solvent.

3. The transfer sheet of claim 2 in which said secondary chromogenic material is N-pivalyl leumomethylene blue.

4. The transfer sheet of claim 2 in which said secondary chromogenic material is 2,2 dimethylbutyryl leucomethylene blue.

5. The transfer sheet of claim 2 in which said secondary chromogenic material is p-anisoyl leucomethylene blue.

6. The transfer sheet of claim 2 in which said microcapsules additionally contain said secondary chromogenic material.

7. The transfer sheet of claim 6 in which said secondary chromogenic material is dissolved in said solvent.

8. The transfer sheet of claim 6 in which said primary chromogenic material is basic and said polymeric material is acidic and one of said basic primary chromogenic material and acidic polymeric material is dissolved in said solvent.

9. A mark-forming com-position capable of being supported by the transfer sheet of a pressure-sensitive record system, comprising:

'(a) primary mark-forming components comprising at least one primary chromogenic material and at least one polymeric material reactive with the primary chromogenic material to produce a mark when both are in solution,

(b) a liquid solvent for said primary mark-forming components,

(c) pressure-rupturable means for isolating said solvent from at least one of said primary mark-forming components prior to release of the solvent from said means, and

(d) a secondary chromogenic material, which upon exposure to light forms a mark, selected from the group consisting of N-pivalyl leucomethylene blue, 2,2-dimethylbutyryl leucomethylene blue, and panisoyl leucomethylene blue, and mixtures thereof.

10. The composition of claim 9 in which said pressurerupturable means are microcapsules, said microcapsules containing said solvent.

11. The composition of claim 10 in which said secondary chromogenic material is N-pivalyl leucomethylene blue.

12. The composition of claim 10 in which said secondary chromogenic material is 2,2-dimet-hylbutyryl leucomethylene blue.

13. The composition of claim 10 in which said secondary chromogenic material is p-anisoyl leucomethylene blue.

14. The comopsition of claim 10 in which said microcapsules additionally contain said secondary chromogenic material.

15. The composition of claim 14 in which said secondary chromogenic material is dissolved in said solvent.

16. The composition of claim 14 in which said primary chromogenic material is basic and said polymeric material is acidic and one of said basic primary chromogenic material and acidic polymeric material is dissolved in said solvent.

17. A pressure-sensitive record system comprising:

(a) at least two sheets of supporting base material including a transfer sheet and a receiving sheet,

(b) primary mark-forming components comprising at least one primary chromogenic material and at least one polymeric material reactive with the primary chromogenic material to produce a mark when both are in solution,

(c) a liquid solvent for said primary mark-forming components,

(d) pressure-rupturable means for isolating said solvent from at least one of said primary mark-forming components prior to release of the solvent from said means, and

(e) a secondary chromogenic material, which upon exposure to light forms a mark, selected from the group consisting of N-pivalyl leucomethylene blue, 2,2- dimethylbutyryl leucomethylene blue, and p-anisoyl leucomethylene blue, and mixtures thereof; each of said primary mark-forming components, said sol vent, said pressure-rupturable solvent-isolating means, and said secondary chromogenic material being supported by said base material, said secondary chromogenic material being located on the surface of said transfer sheet adjacent to said receiving sheet; and said each arranged in contiguous juxtaposition to each other whereby upon rupture of said solventisolating means, the liquid solvent is released therefrom, said primary mark-forming components are brought into reactive contact by the released solvent, said secondary chromogenic material is distributed throughout said solvent, and the said primary markforming components which are not located on the receiving sheet and said secondary chromogenic material are transferred to the receiving sheet by the solvent.

18. The record system of claim 17 in which said pressure-rupturable means are microcapsules, said microcapsules containing said solvent.

19. The record system of claim 18 in which said secondary chromogenic material is N-pivalyl leucomethylene blue.

20. The record system of claim 18 in which said secondary chromogenic material is 2,2-dimethylbutyryl leucomethylene blue.

21. The record system of claim 18 in which said secondary chromogenic material is p-anisoyl leucomethylene blue.

22. The record system of claim 18 in which said microcapsules additionally contain said secondary chromogenic material.

23. The record system of claim 22 in which said secondary chromogenic material is dissolved in said solvent.

24. The record system of claim 22 in which said primary chromogenic material is basic and said polymeric material is acidic and one of said basic primary chromogenie material and acidic polymeric material is dissolved in said solvent.

25. The record system of claim 18 in which at least one of said primary chromogenic material and said polymeric material is supported on said receiving sheet.

26. The record system of claim 25 in which said polymeric material is supported on said receiving sheet.

27. A pressure sensitive record unit comprising sheet material supporting mark-forming components in contiguous juxtaposition but isolated from each other and a pressure releasable liquid solvent for at least one of the materials characterized in that the sheet material supports as mark-forming components, a primary system comprising a primary chromogenic material and a chromogenicmaterial-reactive polymeric material, said primary chromogenic material and polymeric material being both soluble in the solvent, and a secondary light-sensitive chromogenic material which is selected from the group consisting of N-pivalyl leucomethylene blue, 2,2-dimethyl- 1 5 butyryl leucomethylene \blue, and p-anisoyl leucomethylene blue, and mixtures thereof, said secondary chromogenic material being so disposed as to be transferred to a surface of an underlying receiving sheet in a pattern produced by the released liquid.

References Cited UNITED STATES PATENTS 16 Miller et a1 11736.9 Tien 11736.2 Bakan et a1. 11736.8 Brandle et a1 '117-36.2

Hemstoek 117-36.2

Haas 11736.2

MURRAY KATZ, Primary Examiner.

US. Cl. X.R.

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