Pressure-sensitive record material

June 27, 1972

R. E. MILLER ETAL

3,672,935

PRESSURE-SENSITIVE record material

Original Filed Aug. 27, 1954

Sheets-Sheet 1

FIG.I

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RECEIVING SURFACE OF UNDERSHEET COATED WITH POLYMER

BASE-SHEET OF RECORD MATERIAL COATED ON REAR WITH MINUTE PRESSURE- RUPTURABLE CAPSULES CONTAINING LIQUID SOLUTION OF CHROMOGENIC MATERIAL DEVELOPABLE ON CONTACT WITH POLYMER TO COLORED FORM

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INVENTORS ROBERT E. MILLER PAUL S. PHILLIPS, JR/

THEIR ATTORNEYS.

June 27, 1972

R. E. MILLER ETAL 3,672,935

PRESSURE-SENSITIVE RECORD MATERIAL

Original Filed Aug. 27, 1964

Sheets-Sheet 2

LEGEND FIG.2 • CHROMOGENIC MATERIAL SOLID PARTICLES + POLYMERIC REACTANT PARTICLES O LIQUID SOLVENT (ISOLATED)

Q CHROMOGENIC MATERIAL REACTANT DISSOLVED IN LIQUID SOLVENT (ISOLATED) © POLYMERIC REACTANT DISSOLVED IN LIQUID SOLVENT(ISOLATED)

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||l|| POLYMERIC CONTINUOUS COATING

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INVENTORS ROBERT E.MILLER PAUL S. PHILLIPS, JR

THEIR ATTORNEYS

June 27, 1972 r. e. miller etal 3,672,935

PRESSURE-SENSITIVE RECORD MATERIAL Original Filed Aug. 27, 1964 3 Sheets-Sheet 3

FIG.2 (CONTINUED)

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INVENTORS ROBERT E. MILLER PAUL S. PHILLIPS, JR·

THEIR ATTORNEYS.

United States Patent Office

3,672,935

Patented June 27, 1972

3,672,935

PRESSURE-SENSITIVE RECORD MATERIAL Robert E. Miller and Paul S. Phillips, Jr., Dayton, Ohio, assignors to National Cash Register Company, Dayton, Ohio

Continuation of application Ser. No. 744,601, June 17, 1968, which is a continuation of application Ser. No. 392,404, Aug. 27, 1964. This application June 9, 1970, Ser. No. 44,805

Int. Cl. B41m 5/22

U.S. Cl. 117—36.8 9 Claims

ABSTRACT OF THE DISCLOSURE

A pressure-sensitive record unit comprising support sheet material having mark-forming components and a pressure-releasable liquid solvent for said mark-forming components arranged in contiguous juxtaposition on said sheet material, at least one of the mark-forming components being maintained in isolation from the other markforming component(s) prior to release of the solvent, and said mark-forming components comprising at least one chromogenic material and at least one phenol-aldehyde polymeric material soluble in the liquid solvent and reactive with the chromogenic material to produce a mark.

This is a continuous application for that filed by the same applicants on June 17, 1968, under the provisions of the Commissioner’s Order for Filing Streamlined Continuation Applications appearing in volume 824 O.G., page 1, which was given the Ser. No. 744,601 and a filing date of June 17, 1968, and which in tum was a continuation of original application Ser. No. 392,404, filed Aug. 27, 1964, now abandoned.

This invention relates to an improved pressure-sensitive record material. More particularly, this invention relates to a novel mark-forming system wherein mark-forming components are brought, upon selective release of minute droplets of an isolated common solvent for said components, into mark-forming contact by solution in the released portion of said common solvent, and wherein one of the mark-forming components is a polymer present in the pristine mark-forming record material prior to the application of pressure.

In the past, there have been provided pressure-sensitive mark-forming units and systems which comprised a chromogenic component, generally present as a solute in a liquid solvent which is the core or nucleus material of a pressure-rupturable microcapsule, and an insoluble solid mark-forming component distributed in particulate form on a supporting sheet material, both components being arranged in proximate relation to each other, so that, upon the application of marking pressure to a capsule, the capsule ruptures and releases the liquid-carried chromogenic component, and the consequent contact of the mark-forming components produces a mark or color in those regions where pressure is brought to bear. In the most practiced form, the prior units and systems had a micro-encapsulated solution of chormogenic material, such as crystal violet lactone, distributed as isolated liquid droplets on the under side of a supporting sheet, and a solid particulate material (namely, attapulgite clay) topcoated on an adjacent sheet. Upon rupture of a capsule, the solution of chromogenic material migrated to and was absorbed by the nearby attapulgite particles to produce a mark according to the rupture pattern. In other prior systems, the capsules and the attapulgite were arranged on a single sheet.

While the aforementioned prior units and systems represented a substantial advance over their predecessors, experience has shown that exposure of the record material to ambient conditions oftentimes resulted in a desensitization of the attapulgite particles, believed to be caused by the take-up of atmospheric substances at the reactive sites 5 present at the surface of the clay particles, and consequent loss or diminution of its potential for reaction with the chromogenic material.

The present invention provides a pressure-sensitive mark-forming system which is an improvement over the 10 atmospheric-sensitive prior systems and which offers additional advantages, characterized hereafter. Broadly stated, the novel mark-forming system of this invention comprises disposing on and/or within sheet support material the unreacted mark-forming components (at least 15 one of which is a polymeric material) and a liquid solvent in which each of the mark-forming components is soluble, said liquid solvent being present in such form that it is maintained isolated by a pressure-rupturable barrier from at least one of the mark-forming components until the ap20 plication of pressure causes a breach in the barrier according to the pressure pattern, whereupon the liquid solvent is released according to the presure pattern and the markforming components thereby are brought into reactive contact, producing a distinctive mark.

The mark-forming components generally comprise a chromogenic material and a polymeric material reactive with the chromogenic material to produce a distinctive mark (through acidic groups). The chromogenic material in unreacted state preferably should be colorless, though 30 light tones may be tolerated, and capable of color change to a strong distinctive color upon reactive contact with the polymeric material mark-forming component. While combinations of chromogenic material and polymeric material from any of the known color-producing systems may 35 be used, the invention has particular utility in regard to the color-forming system wherein 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 con40 stituent on the chromogenic material. The invention will hereafter be described and illustrated by reference to said base-acid system.

Examples of suitable basic materials having chromogenic groups are diaryl phthalides; leucauramines; acyl 45 auramines; α,/3-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' methoxy BIPS). Illustrative compounds of each 50 group are diaryl phthalides: 3,3-bis(p-dimethylaminophenyl)-6-dimethylamiiiophthalide (Crystal Violet Lactone, hereinafter refered to as CVL) and 3,3-bis(4-dimethylaminophenyl) phthalide (Malachite Green Lactone, hereinafter referred to as MGL); leucauramines; the N-halo55 phenyl derivatives of leucauramine disclosed in U.S. Pat.

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 U.S. Pat. No. 2,828,342, issued to Clyde S. Adams and 60 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; a,^-unsaturated aryl ketones: dianisylidene acetone; dibenzylidene acetone; 65 and anisylidene acetone; basic mono azo dyes: p-dimethylaminoazobenzene-o-carboxylic acid (Methyl Red); 4aminoazobenzene (Oil Yellow AAB); and 4-phenylazo-l naphthylamine; Rhodamine B Lactams: N-(p-nitrophenyl) Rhodamine B Lactam (hereinafter referred to as 70 RBL); polyaryl carbinols: bis(p-dimethylaminophenyl) methanol, called Michler’s Hydrol; Crystal Violet carbinol; and Malachite Green carbinol; 8'-methoxy BIPS;

3,672 ..3

8’ - methoxybenzoindolinospiropyran; 4,7,8'-trimethoxybenzoindoliiiospiropyran; and 6' - chloro, 8'-methoxybenzoindolinospiropyran; and p-dimethylaminostyryl quinoline.

In the base-acid color system, as stated above, the poly- 5 meric mark-forming component (s) chosen must be acidic relative to the basic chromogenic compound and reactive with the chromogenic material to effect distinctive color formation or color change. Moreover, the polymeric mark-forming component(s) should have a common solu- 10 bility with the chromogenic material in at least one liquid solvent.

It should be understood that the scope of the invention includes in a single system the utilization of one or more chromogenic materials on one hand and one or j₅more polymeric mark-forming components on the other hand. Thus, for example, several chromogenic materials rriay be, used with the same or different polymeric materials and vice versa.

As mentioned above, the solvent is maintained in 20 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 25 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; 30 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 within and/or on a support sheet as a profusion in contiguous juxtaposition, are rupturable by pressure, such as the 35 pressures normally attending writing and printing operations.

The particular material(s) chosen as the wall material of the microcapsule, in addition to being pressure-rupturable, must be incompatible with the contents of the &lt;0 capsule and the mark-forming components, in the sense that the wall material retains its integrity under normal storage conditions until such time as it is 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 is useful in this invention. To illustrate ₅θ the broad concept, reference is hereafter made to certain basic-type chromogens as one of the mark-forming components, and certain phenol-aldehyde and phenolacetylene polymers, maleic acid-rosin resins, partially or wholly hydrolyzed styrene-maleic anhydride copolymers _ggand 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. 60

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 _6gphenol 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 useful in practicing this invention is γθ . characterized 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, and by their solubility in organic solvents and relative insolubility in aqueous media. . 75 ,935 ..... -4

Resoles, if they are still soluble, may 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 showing an absorption in the 3200-3500 cm.^-1 region (which is indicative of the free hydroxyl groups) and not having an absorption in the 1600-1700 cm.^-1 region are suitable. The latter absorption region is indicative of the de-sensitization of the hydroxyl groups and consequently makes such groups unavailable for reaction with the chromogenic materials.

The preparation of the phenolic-formaldehyde polymeric' 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, U.S. Pat. No. 2,052,093, issued to Herbert Honel on Aug. 25, 1936, and the preparation of the phehol-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 &amp; 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 liquid solvent chosen must be capable of dissolving the mark-forming components. The solvent may 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 basic chromogen-acidic polymer markforming 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 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 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. In some instances, the presence of the solvent may interfere with the mark-forming reaction 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 mark-forming components into intimate admixture, so that the mark-forming contact proceeds.

Inasmuch as the mark-forming reaction requires an intimate mixture of the components to be brought about through solution of said components, one or more of the 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 mark-forming reaction be maintained undissolved by a droplet until the droplet is released by application of pressure.

In the usual case, the mark-forming components are so chosen as to produce a mark upon application of pressure at room temperature (20 to 25 degrees centigrade). However, the present invention includes a system 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.

The support member on Which the components of the system are disposed may comprise a single or dual sheet

3,672,935 arrangement of the various components which are identified by characters translatable according to the legend accompanying them. These views show the disposition of the mark-forming components in symbol form to illustrate some constructions of record material coming within the scope of the invention. Other constructions coming within the principle of the invention are possible, some being set forth in the examples to follow.

FIG. 1 generally shown a two-sheet unit in perspective in which the under side of the over-sheet is supplied on the surface, or near it, with a profusion of minute pressure-rupturable microcapsules each containing a liquid droplet. The droplets are released on rupture of the capsules in data-representing configuration in printing or writing operations, as shown in FIG. la. The liquid of the released droplets is transferred in the pattern of the data configuration to the top of the under-sheet, which is supplied with a material co-reactant with the received liquid to produce a distinctively-colored mark corresponding to the configuration of the pressure pattern. In the drawing, the surface of the under-sheet is marked with symbols (see legend, FIG. 2) indicating a polymeric reactant film material (a novolac type of phenolic polymer material having an acid-reacting OH group, for instance), and the capsules on the rear of the over-sheet are marked with symbols indicating a contained liquid solution of chromogenic material (CVL or MGL, for instance). However, if desired, the capsules may contain the polymeric material in liquid solution, and the top surface of the undersheet may be supplied with the chromogenic material in particulate form. A representative number of architectural arrangements of the several components with respect to support material are shown in FIG. 2, views I to XV.

As noted generally above, these capsules may be applied to a support sheet 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 may have binder material added, if considered necessary. Paper coated with capsules of microscopic size and containing printing fluid, and the method of making them, are shown in U.S. Pat. No. 2,712,507, which issued July 5, 1955, on the application of Barrett K. Green, and which has been mentioned before.

In the instance where the mark-forming components are interspersed throughout a single support sheet material (so-called self-contained unit), the following techniques or procedures have been found useful:

In FIG. 2, views VZ&gt; through Nd, where either the liquid solvent or one or more of the mark-forming components are disposed on the surface of the support member, and wherein the remaining components of the system are disposed within the support member, this architecture may be achieved by supplying in the furnish the component to be interspersed in the support sheet, then having the furnish pass onto the Fourdrinier wire. After the formed sheet is dried, the remaining necessary component or components may be coated thereon. In FIG. 2, views VII, IX, and XIII, the various components are coated individually or simultaneously onto the support member. In FIG. 2, views VHI, X, XI, and XV, the several components are interspersed within the support sheet according to the technique outlined above for views Nb through Nd.

The slurry of capsules may 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 distance depending on the freeness of the pulp and the water content of the web at the point of application.

The capsules may be placed directly in the paper pulp furnish before it is applied to the paper machine screen, and thus appear throughout the thickness of a sheet (see FIG. 2, views VHI, X, XI, XII, and XV).

As the liquid content of these capsules of views VIII and XI, for instance, must make contact with the dry assembly. In the case where all components are disposed on a single sheet, the record material is referred to as a “self-contained” system. Where there must be a migration of the solvent, with or without mark-forming component, from one sheet to another, the record material is re- 5 ferred to as a “transfer” system. (Such a system may also be referred to as a “couplet” system, in that at least two sheets are required and each sheet includes a component, cr components, essential to the mark-forming reaction.) Where a copious amount of the colored reaction product 10 in liquid form is produced on a surface of one sheet, it may produce a mark by transfer to a second sheet as a colored mark.

, In the preferred case, where microcapsules are employed, they may be present in the support material either 15 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 the polymeric 20 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 25 composition is disposed as a film on the support material and dried, the capsules are held therein subject to rupture to release the liquid contained. This latter technique, relying on the incompatibility of the microcapsule and the dispersing medium of the film-forming mark-forming 30 component, allows for a method of preparing a sensitive record coating with the capsules interspered 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 mark-forming components, insoluble 35 therein, and disperse in said medium the insoluble microcapsules, with the result that all components of the markforming system may be disposed on or within the support sheet in the one operation. Obviously, the several components may be applied individually. 40

The arrangement and the physical state of the components of the mark-forming system in relation to support material will be further discused hereafter, and specific arrangements are shown in the drawings.

The respective amounts of the several components will _4gvary, depending primarily upon the nature of the materials and the architecture of the record material unit. Suitable amounts include, in the case of the chromogenic material, 0.03 to 0.075 pound per ream (a ream in this application meaning five hundred sheets of 25 x 38 _ggpaper, totalling 3,300 square feet), the preferred amount being 0.05 pound per ream; in the case of the solvent, 1 to 3 pounds per ream; and in the case of the polymer, Vi to 3 pounds per ream. One half pound per ream of 3300 sq. ft. is equivalent to 0.45 pound per 3000 sq. ft. ream. _ggIn all instances, the upper limit is primarily a matter of economic consideration.

Of the drawings:

FIG. 1 is a highly diagrammatic representation of a “couplet” system with adjacent faces of the sheets sensi- ₆₀tized with mark-forming components, the bottom surface of the overlying sheet having a coating of pressure-rupturable capsules containing a solution of the basic chromogenic component, and the acidic component being a phenolic polymeric material coating on the upper sur- _egface of the lower sheet, there to make a colored mark as by the use of a stylus, a type character, or other pressurewriting means applied to the “couplet.”

FIG. la is a highly diagrammatic cross-section of a portion of a transfer system being subjected to a stylus γθ impression.

FIG. 2 is a representation, in a series of highly diagrammatic sections through a self-contained record sheet unit (views V-XIII) or a “couplet” unit of two paper sheets (views I-IV, XIV, and XV), showing the physical 75

3,672,935 polymeric material component of the record unit of this type, the quantity of capsules, the quantity of retained liquid, and the availability of the liquid to make contact with the dry particles are details that must be tailored to the desired construction and performance standards desired. The same criteria must be met wherever the liquid is situated or whatever it contains.

The presence of droplets of isolated liquid is of the essence of the invention, which does not reside solely in the isolation of them in capsules, as the liquid droplets may be retained as a discontinuous emulsion droplet phase in a continuous film of pressure-rupturable material. Such film-holding of droplets that are released by writing or printing pressures is a well-known expedient, disclosed in U.S. Pat. No. 2,299,694 and in U.S. Pat. No. 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 polymeric film material which is applied to a record sheet and dried. Wherever reference is made to the isolation of liquid droplets 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 they may be treated as particles for incorporation into the paper-machine furnish. Thus, where the views of FIG. 2 show circles as the droplets on or in a support sheet, it means not only capsule structures but films which hold a multitude of droplets for local release in an area subject to pressure.

View Ια of FIG. 2 shows the relative relation of markforming components disposed in a two-sheet unit, wherein the sheet that receives the droplets has buried in it solid particles of both components, which, being water-insoluble, may be incorporated in a paper sheet as it is being made. The isolated solvent is applied to the under side of the over-sheet as droplets in sufficient amount to penetrate among the paper fibers of the under-sheet to mutually dissolve the particulate color-forming components disposed there.

To make a dispersion of water-insoluble particulate polymeric material, a solution thereof in an evaporable solvent is introduced into twice as much water and agitated while the evaporable solvent is blown off by an air blast. This leaves an aqueous colloidal dispersion slurry of the polymeric material, which may be applied to the paper so as to leave a surface residue, or the slurry may be applied to paper at the size-press station of a paper-making ma* chine by roller. In another method of making a polymersensitized sheet, the water-insoluble polymer is ground to the desired particle size in a ball mill with water, preferably with a dispersing agent, such as a small quantity of sodium silicate. If a binder material of hydrophilic properties is ground with the phenolic material, the binder itself may act as a dispersant. If desired, an amount of binder material of up to 40%, by weight, of the employed amount of the polymeric material may be added to the ball-milled slurry of materials, such binder materials being of the paper-coating binder class including gum arabic, casein, hydroxyethylcellulose, and latex (such as styrenebutadiene copolymer). If desired, oil adsorbents in the form of fuller’s earths may be added to the polymeric materal particles to assist in retaining, in situ, the liquid droplets to be transferred to it in data-representing configuation, for the purpose of preventing “bleeding” of the print.

Another way of applying the chromogenic or polymeric material individually to a single sheet of paper is by immersing a sheet of paper in a 1% to 10% solution of the material in an evaporable solvent. Obviously, this must be done alone for each reactant because, if the other reactant material were present, it would result in a premature coloration over the sheet area. A dried sheet with one component then may be coated with a solution of the other component, the solvent of which is a non-solvent to the already-supplied component.

The polymeric material may be dissolved in ink composition vehicles to form a printing “ink” of colorless character and, thus, may be used to spot-print a proposed record sheet unit sensitized for recording in a reactionproduced color in those areas by application of a solution of the chromogenic material.

In the case of phenolic polymer, a printing ink may be made of up to 75%, by weight, of the phenolic polymeric material in a petroleum solvent to a viscosity suitable for printing purposes.

In all the views, which in themselves constitute specific construction examples without naming specific color reactants, it is to be understood, the showing is in 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 efficiency, and other factors, all of which are things that may be worked out empirically by one familiar with the art, and which do not determine the principle of the invention, which, in part, involves means for enabling the bringing into solution, by marking pressure, of two normally solid components in a common liquid solvent component held isolated as liquid droplets, preferably in marking-pressurerupturable capsules having film walls, or else held isolated in a continuous marking-pressure-rupturable film as a discontinuous phase.

In the arrangement of material components of a multiple-sheet unit which requires one or more components to be on the back of an overlying sheet such as that shown in FIG. 2, views I to IV, if the co-reactant material were supplied on the otherwise uncoated back surface of the under-sheet, it could serve as the middle sheet of a stack of three or more sheets to furnish another rendition of the recorded data. Thus, if in FIG. 2, view I, the undersheet were coated on its back surface with solvent-containing capsules, it could transfer the released solvent for action with the top surface of a second under-sheet, and so on. In this respect, the action between the back of the middle sheet and the sensitizing material of the second under-sheet, it could serve as the middle sheet of a stack of an intentionally-made difference in the selection of components materials, or an intentionally-made difference in the physical arrangement of the components between the back of the second sheet and the top of the third sheet according to the various species of the invention shown in the drawings and disclosed in the specification.

The invention is further illustrated in the following examples:

EXAMPLE I

This, the preferred, example pertains to that form of the invention termed the “transfer” or “couplet” system, wherein a basic chromogenic material is dissolved in a solvent, said solvent and dissolved chromogenic material being microencapsulated and disposed oh a support sheet, and wherein an acidic polymeric material is disposed on a second support sheet placed in contigous juxtaposition to the sheet supporting the capsules.

Preparation of sheet having the chromogenic material

In this example as made, the chromogenic material was CVL, and the solvent comprised two parts by weight of chlorinated diphenyl (Aroclor 1242) and one part by weight of petroleum solvent having a boiling range of

3,672,935

390 to 496 degrees Fahrenheit (Shell Dispersol). A 3% solution of CVL was then microencapsulated in the following manner:

(a) Emulsification: Into a Waring Blendor were weighed 53 grams of 1%, by weight, solution of poly- 5 vinylmethylether maleic anhydride copolymer in water, 30 grams of water, and 113.7 grams of 11% aqueous gelatin sol. With the blendor running at slow speed, 200 grams of the CVL solution (internal phase) was added, and the blendor was operated until the particle size of the dis- 10 persed internal phase was about 5 microns or less.

(b) Coacervation: 75.8 grams of 11% aqueous gum arabic sol was slowly added, with stirring, to the internalphase-gelatin-sol emulsion (a). After thorough stirring, the contents of the blendor was passed into a vessel and 15 diluted by the addition of 600 grams of water at a temperature of 55 degrees centigrade. The pH was then adjusted to about 9.0 by the addition of sodium hydroxide. The pH was lowered at the rate of 0.1 pH unit per minute by the addition of 14% aqueous acetic acid until a pH of 20 4.6 was reached, to thereby cause a liquid coacervate wall to separate and deposit about the dispersed internal phase.

(c) Hardening: After the encapsulation was completed, the system was chilled to 10 degrees centigrade to gel the coacervate walls, and 6.5 milliliters of 25% glutaralde- 25 hyde solution was added and allowed to stir for ninety minutes. The capsules so produced were then coated on a support sheet (transfer sheet) to yield a dried coating of 4 pounds per ream of 500 sheets 25 by 38 inches.

Preparation of sheet having the polymeric material

The polymeric material was prepared in the following manner:

170 grams (1 mole) of paraphenylphenol, 65 grams of 35 37% aqueous formaldehyde, 10 cubic centimeters of concentrated hydrochloric acid (37% ), 1 gram of oxalic acid dihydrate, and 40 cubic centimeters of water were added to a resin kettle and refluxed at the boiling point of the water for eight to twelve hours, after which the reaction 40 mass was allowed 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 mass was poured into a stainless steel tray and allowed to cool. A second support ⁴⁵sheet (receiving sheet) was impregnated with the polymer by being dipped into a 4% xylene solution of the resin and dried.

Upon bringing the capsule-coated surface of the associated support sheets into contiguous relation to the poly- ⁵⁰meric-impregnated sheet and applying a pressure stroke to the uncoated side of the sheet containing the microcapsules, a vivid blue mark was produced on the polymerbearing support sheet.

EXAMPLE la

In distinction to Example I, the present example illustrates the invention wherein the polymer is present on the receiving sheet in particulate form and as a coating on ₆q the surface of the support sheet, as opposed to the impregnation, resulting from the dipping step, set out in Example I. The preparation of the microcapsules, the solution of the chromogenic material, and the coating of the capsules on the transfer sheet were the same as in Example I; like- _cgwise, the preparation of the polymer. The receiving sheet was coated with the polymeric material in the following manner:

grams of the polymer of Example I, 1.5 grams of gum arabic, and 43.5 grams of water were ball-milled for γθ approximately eighty hours to a particle size of under five microns. The resulting aqueous dispersion was then coated onto one side of a receiving sheet. Upon contacting the sheet surfaces as in Example I and applying pressure, a vivid blue mark was produced on the receiving sheet. 75

EXAMPLE lb

This example illustrates the invention wherein the polymeric material is present in particulate form in the support sheet but is substantially evenly distributed throughout the body of the sheet.

The preparation of the microcapsules, the solution of chromogenic material, and the coating on a transfer sheet was carried out as in Example I; likewise, the preparation of the polymer. The polymer was incorporated in the receiving sheet in the following manner:

The dispersion of Example la, having had added thereto a sufficient quantity of a pulp dispersion to produce a five-to-one ratio of pulp to polymer solids, and then having been diluted to a final solids content of 0.5%, was subsequently passed onto a Fourdrinier wire in order to form a sheet. The sheet so formed was placed in contact with the capsule side of the microcapsule-coated sheet, and, upon application of pressure, a blue mark was formed on the polymer-bearing sheet.

EXAMPLE II

The following example illustrates the invention wherein the polymer is the p-cyclohexyl phenol-formaldehyde condensation product.

CVL was the chromogenic material used, and the preparation of the CVL solution and its microencapsulation were the same as in Example I. Likewise, the support sheet was coated with the microcapsules as in Example I.

The polymer was prepared as follows:

176 grams of p-cyclohexyl phenol, 65 grams of 37% aqueous solution of formaldehyde, 10 cubic centimeters of concentrated hydrochloric acid (37%), and 40 cubic centimeters of water were added to a resin kettle and refluxed at the boiling point of the water for eight to twelve hours, after which the reaction mass was allowed to cool, and the water layer was decanted. The resin mass was then distilled under reduced pressure (bench aspirator) until the flask temperature reached 120 to 130 degrees centigrade. Following the vacuum distillation, the resin mass was poured onto a stainless steel tray and allowed to cool.

A receiving sheet was treated as in Example I with a solution of said polymer, and, after bringing the surfaces of the support sheets into contiguous juxtaposition relation and applying pressure thereto, a blue mark was formed on the polymer-bearing sheet.

EXAMPLE Ila

The transfer sheet was prepared as in Example I.

The polymer used was the p-tertiary-amylphenol-formaldehyde condensation product. Said polymer was prepared according to the method of Example II, using one mole of the p-tertiary-amyl phenol compound to .8 mole of formaldehyde.

A receiving sheet was prepared according to the method described in Example I, using the phenol-formaldehyde polymer of this example. Application of pressure to the untreated side of the transfer sheet produced a blue mark on the receiving sheet.

EXAMPLE lib

The transfer sheet was prepared as in Example I.

The polymer used was the p-nonyl-phenol-formaldehyde condensation product. Said polymer was prepared according to the method of Example II, using one mole of the p-nonyl-phenol compound and .8 mole of formaldehyde.

The receiving sheet was prepared as in Example I, using the p-nonyl-phenol-formaldehyde polymer. Application of pressure as in Example Ila produced a blue mark on the receiving sheet.

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1ί

EXAMPLE III

- This example illustrates the invention wherein a phenolacetylene polymer condensation product was used.

CVL was the chromogenic material used.

The preparation of the CVL solution and its microencapsulation were the same as in Example I; likewise, the transfer sheet bearing said microcapsules was prepared according to Example I.

The phenol used for the preparation of the phenolacetylene resin was para-tertiary-butyl phenol, and the preparation of the resin was according to the procedure butline on page 73 of the publication “Industrial and Engineering Chemistry,” 1949, where the particular phenol is disclosed as being reacted with acetylene at elevated temperature and pressure.

A 4% solution of the para-tertiary-butyl phenol-acetylene resin in benzene was prepared, and a receiving sheet was impregnated therewith by being dipped into the solution. Upon the application of pressure on the support sheets held in contact position, a blue mark was formed on the polymer-bearing sheet.

EXAMPLE Illa

As an alternative to the impregnation procedure of Example III, a support sheet was coated on one side with an aqueous dispersion of said para-tertiary-butyl phenol-acetylene resin. The dispersion was prepared as follows:

grams of resin, 3.5 grams of gum arabic, and 50 grams of water were ball-milled for eighty-four hours, and the dispersion was coated on a sheet and dried. The polymer-coated sheet, upon contact with the transfer sheet having the microencapsulated chromogenic material, produced a colored mark upon application of marking pressure to the transfer sheet.

In Examples IV to VIII which follow, different chromogenic material was used in conjunction with p-phenyl phenol-formaldehyde polymer. In all cases, the polymer and the receiving sheet were prepared according to the procedure of Example I.

EXAMPLE IV

8'-methoxy BIPS was the chromogenic material, the solution being made by dissolving 4 grams of the BIPS compound in 100 cubic centimeters of chlorinated diphenyl (Aroclor 1242).

The BIPS solution was encapsulated in the following manner:

(a) Emulsification: Into a Waring Blendor were placed 80 cubic centimeters of the BIPS solution, 80 cubic centimeters of 11% aqueous gelatin sol, and 80 cubic centimeters of 11% aqueous gum arabic sol; the pH was adjusted to 6-6.5; and the blendor was operated until the BIPS internal phase droplet size was 5 microns or less, to thereby emulsify the BIPS solution in the gelatin-gumarabic sols.

(b) Coacervation: The emulsion of step (a) was transferred to a beaker, and, with constant stirring, the emulsion was diluted by the addition of water to make one liter. The pH of the mass was then slowly lowered by the addition of 10% acetic acid until the visual test of cloudiness, as outline in Green and Schleicher United States Patent No. 2,800,458, issued July 23, 1957, indicated that coacervation was complete.

(c) Hardening step: The mass was then chilled to 10 degrees centigrade and allowed to stand for one hour at this temperature. Subsequently, 5 cubic centimeters of 25% glutaraldehyde solution was added, and the entire mass was stirred overnight before use.

The capsules so produced were then coated on a transfer sheet according to the technique of Example I. Upon application of pressure to contiguously-disposed transfer and receiving sheets, a brown mark was produced.

EXAMPLE V

All components were the same as in Example IV except' that the chromogenic material was N-benzoyl auramine, which material was dissolved in 2/1 ratio by volume of chlorinated diphenyl (Aroclor 1242) and petroleum distillate, boiling range 316 to 358 degrees Fahrenheit (Shell 360), to give a 1% N-benzoyl auramine solution. The record unit system containing N-benzoyl auramine as the chromogenic material gave a green-blue mark upon application of pressure.

EXAMPLE VI

All materials and procedures were the same as in Example IV except that the chromogenic material· was pdiphenyl aminostyrylquinoline. Two grams of the chromogenic material was dissolved in a sufficient amount of equal parts by volume of chlorinated diphenyl and petroleum distillate (boiling range 316 to 358 degrees Fahrenheit) to yield a 2% solution. A record unit using the chromogenic material in this example yielded a red-brown mark upon the application of pressure in the usual manner.

EXAMPLE VII

All materials and procedures were the same as in Example IV except that the chromogenic material was a 3% , by weight, solution of N-(2,5-dichloro phenyl) leucauramine in a 2/1 weight ratio mixture Of chlorinated diphenyl in petroleum distillate (boiling range 385 to 496 degrees Fahrenheit) Again, a record unit containing the indicated chromogenic material produced a blue mark upon application of pressure in the usual manner.

EXAMPLE VIII

The materials and procedures of this example were the same as in Example IV except that the chromogenic material was 3% of Michler’s Hydrol in 2/1 weight ratio mixture of chlorinated diphenyl and petroleum distillate (boiling range 385 to 496 degrees Fahrenheit).

EXAMPLE IX

Five grams of a partially-hydrolyzed ethylene-maleic anhydride copolymer (Monsanto DX-843-81), 1.5 grams Ethocel (Hercules Powder Company, Ethyl Cellulose, Type N 14, 14.1% Ethoxyl), and 44.25 grams of carbon tetrachloride were admixed to give a dispersion of the copolymer in the carbon tetrachloride. Styrene-maleic anhydried copolymer, vinylmethylether-maleic anhydride copolymer, and carboxy polymethylene are useful substitutes for the ethylene-maleic anhydried copolymer but are not as reactive.

The dispersion was coated onto the surface of a support sheet (receiving sheet). A record unit comprising the said receiving sheet and a transfer sheet coated with microcapsules of benzoyl auramine gave a green-blue mark upon application of pressure.

EXAMPLE X

A record unit comprising the receiving sheet of Example IX and a transfer sheet bearing microcapsules of N-(2,5-dichlorophenyl) leucauramine gave a blue mark upon application of pressure.

EXAMPLE XI

A record unit comprising the receiving sheet of Example IX and a transfer sheet bearing microcapsules of CVL gave a blue mark upon application of pressure.

EXAMPLE XII

A record unit comprising the receiving sheet of Example IX and a transfer sheet bearing microcapsules of Michler’s Hydrol gave a blue mark upon application of pressure.

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EXAMPLE ΧΠΙ

This example depicts a self-contained sheet as shown in FIG. 2, view Va, wherein the several components are disposed on the surface of the support sheet. The chro- _gmogenic material was 3% CVL in chlorinated diphenyl (Aroclor 1221), to provide a chromogenic solution. This solution was encapsulated according to the technique described in Example IV. The polymeric material was paraphenylphenol formaldehyde. _ io

The polymer was made into a dispersion according to Example I.

The dispersions of capsules and polymer as a mixture were then coated upon a support sheet and dried.

Upon application of pressure to the support sheet, a mark was produced on the coated surface according to the pressure pattern.

EXAMPLE XIV

ΟΛ

This example specifies an architecture wherein one or more of the components of the system are interspersed throughout the support member and the remaining components are coated on the surface as depicted in views Vb, Vc, and Vd of FIG. 2. ... ₂₅

If the chromogenic material is in the body of the sheet, it is applied as a part of the aqueous furnish of fiber to the Fourdrinier wire, and the same method is used in introducing the polymeric material into the body of the sheet. CVL was used as the chromogenic material, ₃θ and a paraphenylphenol formaldehyde condensation product was used as the acidic polymer. The top coatings are applied from aqueous dispersions of the particles or capsules in the usual manner. The solvent was chlorinated diphenyl (Aroclor 1242). Upon the application of pressure to the support sheet, a mark was produced according to the pressure pattern.

EXAMPLE XV

This example demonstrates an architecture wherein the several components of the system are interspersed throughout the support sheet (FIG. 2, views X, XI, and XII).

The chromogenic material was CVL, the solvent was chlorinated diphenyl (Aroclor 1221), and the polymeric 45 material was paraphenylphenol formaldehyde condensation product. The polymeric material was encapsulated according to the procedure of Example IV. Upon the application of pressure to the finished sheet, a mark was produced according to the pressure pattern.

The several components were dispersed in water and supplied to the Fourdrinier wire with the “furnish.”

EXAMPLE XVI

This example demonstrates a self-contained unit wherein the several components of the system are coated onto the support member and further wherein the several components are distributed within a continuous film of the polymeric material, as shown in FIG. 2, view VII. The 60 chromogenic material was CVL, which was dissolved in chlorinated diphenyl (Aroclor 1221) and encapsulated according to Example I, with the exception that the capsules were spray-dried to produce a free-flowing powder. The polymeric material was a paraphenylphenol form- 65 aldehyde condensation product. A xylene solution of the polymeric material was prepared, and the dry powdered capsular product was dispersed therein. The dispersion was then coated on the support sheet material and dried. Upon application of pressure to the coated sheet, a mark 70 was produced in accordance with the pressure pattern.

The chosen polymeric material may have film-fonning properties, with the consequent attainment of high resolution of recorded data that attends the use of a continuous film.

Generally, the polymeric material at the marking sites wll be present as a film subsequent to the production of the mark-forming reaction. 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 polymers—the water-insolubility of the polymer will preclude decolorization 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 solution 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 so-called “picking” problem associated with coatings of particulate materials such as attapulgite.

Under some circumstances, it may be desirable to have the chromogenic material present as a mixture of compounds which yield different hues on reaction with the polymeric material, such hues blending to produce a compound visual effect. For instance, a mixture of a compound yielding a blue color and one yielding a red color would visually combine to a dark purple approaching blackness.

It also may be desirable to mix polymeric components for economic reasons or reaction characteristics. Thus a mixture of the phenolic polymers specified may be used with one or more of the chromogenic materials to produce a desired end product.

It becomes apparent that the invention described is not limited in the use of single pairs of reactant compounds, or even in regard to single and double sheet systems, and that one sheet may have data marked thereon in one color and the next underlying sheet may yield 40 the same mark configurations in same or different colors.