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Publication numberUS3906123 A
Publication typeGrant
Publication dateSep 16, 1975
Filing dateApr 23, 1973
Priority dateApr 23, 1973
Also published asCA1015162A1, DE2417297A1
Publication numberUS 3906123 A, US 3906123A, US-A-3906123, US3906123 A, US3906123A
InventorsGolden Ronald R, Vincent David N
Original AssigneeChampion Int Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Self-contained pressure-sensitive system
US 3906123 A
Abstract
A self-contained, pressure-sensitive record system is provided which comprises a support having a coating of microscopic, pressure-rupturable microcapsules on the surface of the support, which microcapsules contain a substantially colorless color-reactant material. A continuous, non-permeable, water-insoluble, pressure-rupturable polymeric barrier layer is provided over the microcapsular coating and a third layer in the form of an adsorbent, electron-acceptor material is provided over the barrier layer. Under the application of localized pressure, the polymeric barrier layer and the walls of the microcapsules are ruptured thereby permitting contact between the color-reactant material and the adsorbent, electron-acceptor material which react to provide a distinctive colored mark.
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Vincent et al.

United States Patent [191 Sept 16, 1975 SYSTEM SELF-CONTAINED PRESSURE-SENSITIVE [73] Assignee: Champion International Corporation, New York, NY.

[22] Filed: Apr. 23, 1973 [21] Appl. No: 353,810

[52] US. Cl. 427/145; 427/150; 428/411 [51] Int. Cl. B41M 5/00 [58] Field of Search 117/369, 36.2, 36.8

[56] References Cited UNITED STATES PATENTS 2,929,736 3/1960 Miller et a1. 117/369 3,036,924 5/1962 Newman ll7/36.2 X

3,287,154 11/1966 Haas 117/369 3,418,250 12/1968 Vassilliades.... ll7/36 2 X 3,418,656 12/1968 Vassilliades.... 252/316 3,740,761 6/1973 Fechter 346/135 Primary ExaminerThomas J. Herbert, Jr. Attorney, Agent, or FirmRoylance, Abrams, Berdo & Kaul 57 ABSTRACT A self-contained, pressure-sensitive record system is provided which comprises a support having a coating of microscopic, pressure-rupturable microcapsules on the surface of the support, which microcapsules contain a substantially colorless color-reactant material. A continuous, non-permeable, water-insoluble, pressurerupturable polymeric barrier layer is provided over the microcapsular coating and a third layer in the form of an adsorbent, electron-acceptor material is provided over the barrier layer. Under the application of localized pressure, the polymeric barrier layer and the walls of the microcapsules are ruptured thereby permitting contact between the color-reactant material and the adsorbent, electron-acceptor material which react to provide a distinctive colored mark.

22 Claims, No Drawings SELF-CONTAINED PRESSURE-SENSITIVE SYSTEM This invention relates to a pressure-sensitive record system. More particularly, this invention relates to a self-contained pressure-sensitive record system wherein premature contact between color-reactive components is prevented even under severe conditions of heat and humidity.

Pressure-sensitive marking systems are well-known which involve localized contact between a chromogenic compound, such as crystal violet lactone and benzoyl leuco methylene blue, and a color-developing substance, such as an acid-treated clay, to produce a colored marking on paper or the like. Generally, such systems involve the encapsulation of a substantially colorless chromogenic substance that is dissolved in minute oil droplets, and thus provided within the walls of pressure-rupturable microcapsules. Such systems are generally of the two types; the transfer copy system and the self-contained or autogenous system. In the transfer copy system, the microcapsules containing the colorless chromogenic substance are coated onto a substrate which is superimposed onto the receiving sheet, which is coated with an electron-accepting material, for example, of the Lewis acid type, such as acidtreated clay. Upon application of localized pressure to the top side of the microcapsule-coated sheet, the walls of the microcapsules, which are on the underside of the sheet, are ruptured and the colorless, chromogenic substance is released for reaction with the acidic coreactant to provide a distinctive mark. Typical transfer copy systems are described in US. Pat. Nos. 3,418,656 and 3,418,250 to A. E. Vassiliades. In the self-contained system, the colorless chromogenic material and the acidic co-reactant are present on the same substrate, and thus when the capsule walls are ruptured, there is no physical movement of either of the mark-forming components from one sheet to another, but rather, the colored mark is produced on the surface of the sheet where the capsules are coated.

One of the difficulties encountered with selfcontained copy systems is that the color-reactive materials prematurely come in contact under the effects of humidity and heat encountered in storage. In addition, such premature reaction can occur when the copy system is being manufactured. In the manufacture of such systems the capsule coating and the adsorbent clay coating may be each coated onto the paper substrate or alternatively, the capsules and the clay may be coated onto the paper web in a single step. Regardless of the manner in which the coatings are applied, they must be dried under relatively high temperature conditions, which may result in a premature reaction caused by a permeation of the microcapsular shell by the colorreactant material.

It has now been found that premature contact between the color-reactant components of a selfcontained system can be prevented even under severe conditions of heat and humidity by providing a pressure-sensitive record material comprising a support bearing a first coating .of microscopic, pressurerupturable capsules on the surface thereof, said microcapsules containing a substantially colorless colorreactant material, a second coating comprising a continuous, non-permeable, pressure-rupturable, waterinsoluble polymeric barrier layer on the surface of the pressure-rupturable microcapsules, and a third coating comprising an adsorbent, electron-acceptor material coated over the barrier layer. Surprisingly, it was found that the employment of a thin, pressure-rupturable, water-insoluble, polymeric barrier layer or film between the capsule coating and the electron-acceptor material, serves to prevent premature reaction between the col-' or-reactants until the desired localized pressure is applied, without interfering with the color-forming reaction where the localized pressure is applied. At such time, both the capsule wall and the pressure-rupturable barrier layer are ruptured to permit reaction and thus color formation between the color-reactant materials.

Barrier coatings have been suggested for selfcontained record systems in the past. Thus, for example, US. Pat. No. 2,929,736 to Miller et al .disclosed a self-contained record system having a polyvinyl methyl ether barrier layer disposed between particles of a solid co-reactant and microcapsules. However, the barrier layer described in such patent is not pressurerupturable at ambient temperatures, but requires temperatures of at least 50C. in order to cause a failure of the insulating film.

As previously indicated, the barrier layer which separates the microcapsules from the electron-accepting material, which is preferably an acidified clay, must be a continuous, non-permeable, water-insoluble, pressure-rupturable, polymeric layer. The expression pressure-rupturable as employed herein is intended to mean that the barrier layer will rupture under localized pressure even at ambient conditions, e.g., 2025C. Suitable polymeric materials for use as the barrier layer or film include, for example, polyhydroxyl polymers, such as polyvinyl alcohol, methycellulose, starch, hydroxyethylcellulose, and the like. Likewise, proteins, such as gelatin, and natural gums, such as guar gum, may be employed. In order to render such materials water-insoluble, a cross-linking agent, such as an aldehyde, e.g. formaldehyde, glyoxal, glutaraldehyde; borax (sodium borate Na B O -H O); boric acid; a partially condensed formaldehyde condensation product, e.g., urea-formaldehyde, melamineformaldehyde, or the like may be employed.

Suitable barrier layers may also be formed from partially condensed, water-soluble, formaldehyde condensation products without the need for additional crosslinking agents in order to render the barrier layer water-insoluble. Thus, reaction products of formaladehyde with carbamides, such as urea; triazines, such as melamine; amino and amido compounds, such as aniline, p-toluenesulfonamide, ethyleneurea and guanadine may be employed in the formation of a barrier layer. Under the influence of heat, such resins change irreversibly from a fusible and/or soluble material into an infusible and insoluble material.

The formation of such partially condensed formaldehyde condensation products is well-known, and they may be easily prepared according to conventional practices. For example, a melamine-formaldehyde partial condensate or syrup may be prepared by refluxing grams of melamine in 184 milliliters of a 37 percent by weight aqueous solution of formaldehyde and neutralized to a pH of 8 with sodium carbonate. A mole ratio of formaldehyde to melamine may be, for example, 2.5 to 1, and the reaction may be continued from about 1 to about 1 /2 hours at a temperature between 92 and 96C. or until one volume of the condensate becomes turbid when'diluted with 2 to volumes of water. A substituted condensation product may be produced by adding a small amount of methanol, e. g. 6 to percent by weight, to the condensate.

An especially preferred pressure-rupturable, poly alcohol is a fully hydrolyzed medium or high molecular weight form of polyvinyl alcohol. Thus, a medium or high molecular weight polyvinyl alcohol which has been'hydrolyzed to an extent of 97 to 100 percent by weight is preferable, although polyvinyl alcohol having a lower degree of hydrolysis and/or lower molecular weight can be used, if desired.

After the microcapsular coating is dried, the barrier coating is applied thereover. The microcapsules for use in the present invention may be any suitable pressurerupturable microcapsules that are made by a physical or chemical process. Suitable microcapsules and their preparation include those described in U.S. Pat. Nos. 3,418,656 and 3,418,250 to A. E. Vassiliades, the disclosures of which are hereby incorporated by reference. However, preferred microcapsules are those produc'ed by admixing:

A. a water-immiscible, oily material containing an oil-soluble, non-polymeric cross-linking agent selected from the group consisting of a polyfunctional isocyanate and anorthoester of a Group IV element; and V B. an aqueous solution of an hydroxyl groupcontaining polymeric emulsifying agent.

The oily material and the aqueous solution are admixed under conditions to form an oil-in-water emulsion wherein the oily material is dispersed in the form of microscopic emulsion droplets in an aqueous, continuous phase. The cross-linking agent thereby reacts with the polymeric emulsifying agent in order to form a solid, cross-linked capsule wall around .each of the oil droplets.

The reaction of the cross-linking agent with the polymeric emulsifying agent may be conducted at any temperature between ambient temperature and 100C. for between about 1 and about 24 hours. The ratioof polymeric emulsifying agent to cross-linking agent is at least 1 part by weight of emulsifying agent per part of crosslinking agent, e.g. between 1 and about 100 parts by weight, preferably between about 4 and about parts by weight of emulsifying agent per part of cross-linking agent. The oil-soluble polyfunctional isocyanates include, for example, 4,4 '-diphenylmethane diisocyanate, toluene diisocyanate,' hexamethylene diisocyanate, triphenylmethane triisocyanate, mixtures of such isocyanates, and adducts of such isocyanates with polyhydric alcohols, such as trimethylolpropane.

Suitable hydroxyl group-containing polymers include polyvinyl alcohol, methylcellulose, starch, and the like, described above as being suitable for the barrier layer.

Suitable orthoesters of Group IV elements which may be employed as cross-linking agents include the aliphatic and aromatic orthoesters of Group IVA and IVB elements, preferably the lower alkyl and aryl orthoesters of Group IV elements, such astetraethyl orthosilicate, tetrapropyl orthosilicate, tetraphenyl orthosilicate, tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, tetraphenyl titanate, tetraethylgermanate, tetrapropyl orthocarbonate, and the like.

The microcapsules employed in the system of the present invention may be any suitable size, e.g., 0.1 to several hundred microns. However, the preferred caps'ule size is between about 3 and about 10 microns, with between about 4 and about 8 microns being especially preferred.

The electron-accepting adsorbent coating is the top coat and forms a continuous layer over the dried barrier layer. This layer may comprise any of the wellknown acidic, solid particulate materials including bentonite, kaolin, acidic clays, talc, aluminum silicate, calcium citrate, metal oxides, metal chlorides or the like. Such materials are well-known in the art.

The most common substrate for employing in selfcontained systems is paper and, this is the preferred substrate for use in the present invention. However, the microcapsules may be coated on other substrates such as plastic and fabric or textile webs. When the web material or substrate has a high degree of porosity, it may be precoated with a material that will reduce seepage of the microcapsular coating through the web. Thus, the web material may be impregnated with polyvinyl alcohol, styrene-butadiene latex or any other suitable material.

The chromogenic material which is encapsulated for subsequent reaction with the acidic clay or the like may be any of the conventional color-reactant materials including the colorless or substantially colorless dye intermediates commonly referred to as leuco dyes, such as, for example, crystal violet lactone [3,3-bis(p-dimethylaminophenol)6-dimethylamino phthalide benzoyl leuco methylene blue and the like. The dye intermediates are colorless or substantially colorless in an alkaline medium and react to form a distinctive color when placed in contact with an acidic medium such as an acid-treated clay.

Thepressure-sensitive record system of the present invention may be prepared in various ways. According to one aspect of the invention, the substrate, e.g., paper, is initially coated with an aqueous dispersion of microcapsules containing the color-reactant material dispersed in oily droplets. The aqueous dispersion of microcapsules can contain a binding agent, such as gelatin, gum arabic, methycellulose, starch, polyvinyl alcohol or the like in order to aid in securing the capsules to the substrate. Next, the microcapsular coating is itself coated by a barrier coating solution, such as one of the'barrier materials mentioned previously. The preferred barrier coating is-polyvinyl alcohol which may be applied, for example, by means of a dilute, aqueous solution, such as between about 0.5 and about 10 percent, preferably between about 1 and about 3 percent polyvinyl alcohol in water. According to an especially preferred embodiment of the present invention, the aqueous barrier solution contains a small amount, for example, between about 0.005 and about 0.1, preferably between about 0.01 and about 0.03 percent of a surface active agent, such as anionic compounds, such as fatty acid salts, salts of higher alcohol sulfates, alkylbenzene sulfonates, --alkylnaphthalene sulfonates, or salts of poly( oxyethylene)sulfates; nonionic compounds, such as polypropylene oxide-polyethylene oxide block copolyrners, poly(oxyethylene)a lkyl ethers, poly(oxyethylene) alkylphenol ethers, sorbitol fatty acid esters, poly(oxyethylene)sorbitol fatty acid esters, poly(oxyethyleneyalkyl esters or fatty acid monoglycerides; and cationic-compounds such as,

quaternary ammonium salts with" long-{chain alkyl group(s) or pyridinium salts. Preferred surfactants are sodium lauryl sulfate or polypropylene oxidepolyethylene oxide block copolymers. The surfactant is employed in this manner for the purpose of insuring that the capsule coating is completely wetted by the barrier coating solution so as to provide a continuous, rather than a discontinuous barrier film.

lln order to eliminate the water solubility of the poly meric barrier coating, a suitable cross-linking agent such as those previously mentioned, including glyoxal, water-soluble urea-formaldehyde, melamineformaldehyde or the like may be included in the aqueous solution of the polymeric barrier coating, such as polyvinyl alcohol. However, cross-linking agents may be omitted when such materials including the watersoluble urea-formaldehyde and melamineformaldehyde resins are employed, since such materials form highly cross-linked polymeric matrices upon dehydration.

According to a preferred aspect of the invention, a cross-linkin g agent may be included in the clay coating. However, such cross-linking agent must be one capable of providing substantially instantaneous waterinsolubilization of the barrier polymer. A preferred cross-linking agent for this purpose is sodium borate which, when applied to a polyvinyl alcohol barrier coating, for example, immediately gels the polymer thereby rendering it water-insoluble. Thus, a preferred acid-reactive coating comprises a mixture of acidic clay, zinc oxide, a dispersant such as tetrasodium pyrophosphate, a latex binder, borax, ammonia and water.

According to still another aspect of the present invention, the polymeric barrier layer may be provided by treating the microcapsular coating containing a suitable, polymeric binding agent with a cross-linking agent which serves to cross-link the binder. Thus, for example, if a polyvinyl alcohol, starch or the like polyhydroxy polymeric binding agent is incorporated in the microcapsular dispersion prior to coating, a crosslinking agent, such as formaldehyde, glyoxal, sodium borate, glutaraldehyde, urea-formaldehyde, melamineformaldehyde, or the like may be applied to the microcapsular coating and thus cross-link and render wateninsoluble the polymeric binding agent. This prevents contact of the acid-reactive material with its coreactant when it is coated onto the microcapsular coating.

when the barrier layer is to be formed from a crosslinked binding agent, suitable amounts of binder include, between about and about 40 parts, preferably between about and about parts of polymeric binder per 100 parts by weight of microencapsulated oil.

it is essential that the microcapsular coating be the coating adjacent the surface of the substrate followed by the barrier layer and the acidic adsorbent layer in that order. It has been found that when the order is reversed and the acidic clay adsorbent layer is adjacent the substrate with the microcapsular layer as the top coat, rupture of the capsules results in a transfer of the bulk of the released dye-containing oil in an upward direction rather than down into the clay, thereby reducing the intensity of the image.- 4

Any suitable thickness of barrier layer maybe employed, for example, between about 0.05 and about 1, preferably between about 0.1 and about 0.5 pounds of dry polymeric barrier material, e.g., polyvinyl alcohol, may be employed per ream of substrate, e.g., paper (as used herein, the term ream represents 3,300 square feet). Thus, a suitable pressure-sensitive copy system will involve, for example, the employment of a capsule coating at a coat weight of between about 2 and about 7, preferably between about 4 and about 5 pounds per ream, with a barrier coating utilized at a coat weight of between about 0.05 and about 1, preferably between about 0.1 and about 0.5 pounds per ream. Similarly, the adsorbent co-reactant layer may be varied in concentration over fairly broad range. Suitably, this coating may be in the range of between about 2 and about 8, preferably between about 4.5 and about 5.5 pounds per ream. The various coatings may be applied to the substrate in any conventional manner including, for example, by means of an air knife or roller coater.

Accordingly, the present three-layered pressuresensitive system provides a means for preventing premature contact between the colorless dye precursor and the acidic adsorbent material, and under the application of localized pressure by means of a stylus or the like, the solid particles of the acid-reactant coating are pushed through the pressure-sensitive barrier coating and the capsule walls to release the oily solution of the basic chromogenic material for reaction with the acidic clay particles.

The invention will be further illustrated by the following examples. The percentages are by weight unless otherwise specified.

EXAMPLE 1 One hundred grams of an alkylated, partially hydrogenated naphthalene oil, containing 2.1 percent by Weight crystal violet lactone, 1.8 percent by weight benzoyl leuco methylene blue and 5 grams of the 3 to 1 molar reaction product of toluene diisocyanate with trimethylolpropane, are emulsified in 400 grams of a 5 percent aqueous solution of a high molecular weight, about 88 percent hydrolyzed, polyvinyl alcohol (commercially available, for example as Covol 9740 from Corn Products Company, Elvanol 50-52 from duPont or Gelvatol 20-90 from Monsanto) employing a Waring blender. Emulsification is continued until an average particle size of about 6 microns in diameter is obtained.

The emulsion is then heated while under mild agitation at a temperature of about C. for about 2 hours.

The resulting microcapsular suspension is cooled and 4 grams of a percent by weight aqueous solution of a melamine-formaldehyde condensation product, and 25 grams of a 5 percent by weight aqueous solution of carboxymethylcellulose binding agent are added. The dispersion is then coated onto a paper substrate and dried.

The capsule-coated surface of the paper substrate is then coated with a 5 percent solution of sodium borate using a Mayer rod and is then dried in a forced-air over at a temperature of C.

Next, an acid-reactive coating comprising a mixture of acidic clay, zinc oxide, ammonia, a tetrasodium pyrophosphate dispersant, a latex binder and water is applied to the dried microcapsular coating at a coat weight of about 4 pounds per ream and dried in a forced-air oven at 80C.

The resulting coated sheet is substantially white in color. The application of localized pressure to the sheet results in an instantaneous blue image of high intensity. This sheet has excellent storage stability.

EXAIVIPLE 2 The procedure of Example 1 is repeated with the exception that the step of providing the microcapsular coating with a percent sodium borate solution overcoat is omitted.

The resulting sheet is strongly blue thereby indicating that a successful self-contained system is not provided without the formation of a barrier layer that was formed by the cross-linking of the carboxymethylcellulose and excess polyvinyl alcohol binding agents with the sodium borate.

EXAMPLE 3 The procedure of Example 1 is repeated with the exception that a 5 percent solution of glyoxal is substituted for the sodium borate of that Example. The resulting coating is nearly white and provides a strongly blue image when localized pressure is applied.

EXAMPLE 4 The procedure of Example 1 is repeated with the exception that a 3 percent solution of a water-soluble melamine-formaldehyde resin (commercially available as Virset 654-4 from the Virginia Chemical Company) is substituted for the sodium borate of the Example.

Once again, a substantially white coating results which produces a strongly blue image upon the application of localized pressure.

EXAMPLE 5 A clay slurry is prepared containing 100 parts of a clay, parts by weight of zinc oxide, 12 parts by weight of a 28 percent aqueous solution of ammonia, 1 part by weight of sodium hexametaphosphate (commercially available as Calgon T) and 40 parts by weight of a 50 percent styrene-butadiene latex (commercially available as Dow 620).

In addition, 5 parts by weight of sodium borate are dissolved in 95 parts by weight of the clay slurry, and this coating is applied to a dried microcapsular coating of the type described in Example 1. The sodium borate-clay slurry is applied with a Mayer rod at a coat 'weight of 4.5 pounds per ream and is dried in a forcedair oven at 80C.

The sodium borate in the clay coating instantaneously gels the polyvinyl alcohol binding agent in the microcapsular coating, thereby preventing intermixture of the dye materials with the acid-treated clay. The resulting record material is white in color and the application of pressure produces a strong blue mark.

EXAMPLE 6 A batch of the microcapsules described in Example 1 is coated onto a paper substrate using a Dixon coater to provide a coat weight of 5.5 pounds per ream. Next, a second coating comprising 1 pound of a fully hydrolyzed, medium molecular weight polyvinyl alcohol (commercially available as Vinol 125 from Airco) in 99 pounds of water and 30 grams of a 30 percent by weight solution of aqueous sodium lauryl sulfate is coated over the capsule layer at a coat weight of 0.1 pound per ream. Next, a third coating comprising a clay slurry having a composition of the clay slurry described in Example 5 including the 5 parts of sodium borate is applied over the barrier coat at a coat weight of 5.7 pounds per ream. All three of the coatings are applied with an air doctor.

The resulting self-contained record material is white and remains white even after heating for 3 hours at C. Application of pressure produces a strong blue image.

EXAMPLE 7 The microcapsular dispersion of Example 1 is coated onto a paper substrate at a coat weight of 4.4 pounds per ream. Next, a second coating comprising an aqueous solution of 2 pounds of polyvinyl alcohol, 98.5 pounds of water, and 30 grams of a 30 percent solution of aqueous sodium lauryl sulfate are applied over the capsule coating at a coat weight of 0.17 pounds per ream.

A clay coating identical to that of Example 5 including the sodium borate is then applied over the barrier coat at a coat weight of 0.7 pounds per ream. Finally, an 11 percent aqueous solution of melamineformaldehyde resin is applied to the paper substrate on the side opposite the capsule coating side at a coat weight of 0.44 pounds per ream to control curl.

The resulting self-developing record material is white and remains white even after heating for 3 hours at 100C. or after standing for 3 months under ambient conditions. Application of a localized pressure produees a strong blue image at the points of contact.

This invention has been described in considerable detail with particular reference to preferred embodiments, that it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described in the appended claims.

What is claimed is:

1. Pressure-sensitive record material comprising a support carrying, in order,

a first layer comprising microscopic pressurerupturable capsules on the surface of said support, said capsules containing a substantially colorless, color-reactant material:

a second layer adjacent said first layer comprising a continuous, non-permeable, pressure-rupturable, water-insoluble, polymeric barrier layer, said barrier layer being rupturable under localized pressures at an ambient temperature in the range of 2025C.

a third layer adjacent said second layer comprising an adsorbent, electron-acceptor material;

said color-reactant material and said electron-acceptor material being capable of reacting to form a distinctive color upon contact.

2. Record material recording to claim 1 wherein said electron-acceptor material is an acidic clay.

3. Record material according to claim 1 wherein said barrier layer comprises a polyhydroxy polymer.

4. Record material according to claim 3 wherein said polyhydroxy polymer is polyvinyl alcohol, methyl cellulose or starch.

5. Record material according to claim 4 wherein the capsule walls of said microcapsules are cross-linked polyvinyl alcohol and said barrier layer is polyvinyl alcohol.

6. Record material according to claim 5 wherein said capsule walls of said microcapsules comprise polyvinyl alcohol cross-linked by a polyfunctional isocyanate.

7. Record material according to claim 1 wherein said microcapsules have walls comprising cross-linked polyvinyl alcohol and said barrier layer is a formaldehyde condensation product.

8. Record material according to claim 7 wherein said barrier layer is melamine-formaldehyde.

9. A method for the production of a pressuresensitive record system which comprises, providng a substrate, applying a first coating composition to the surface of said substrate, said first coating composition comprising a dispersion of microscopic capsules, each capsule containing a colorless, color-reactant material, applying a second coating composition over said first coating, said second coating composition comprising an aqueous solution of a polymeric material, said polymeric material being capable of providing a continuous non-permeable pressure-rupturable, water-insoluble barrier layer, and applying a third coating composition over said second coating comprising an aqueous dispersion of an adsorbent, electron-acceptor material, said color-reactant material and said electron-acceptor material being capable of reacting to form a distinctive colored mark upon contact, said barrier layer being rupturable under localized pressures at an ambient temperature in the range of 2025C.

10. The method of claim 9 wherein said second coating composition contains a surface active agent, said surface active agent promoting the complete wetting of said capsule coating by said second coating.

1 l. The method of claim 9 wherein said second coating composition comprises a polyhydroxy polymer.

12. The method of claim 11 wherein said polyhydroxy polymer is polyvinyl alcohol, methylcellulose or starch.

13. The method of claim 12 wherein said second coating composition additionally contains a crosslinking agent for rendering the polymeric material contained therein water-insoluble.

14. The method of claim 9 wherein said third coating composition additionally contains a cross-linking agent for rapidly rendering the polymeric material contained in said second coating composition water-insoluble.

15. The method of claim 14 wherein said crosslinking agent is sodium borate.

16. A method for the production of a pressuresensitive record system, which comprises providing a substrate, applying a first coating composition to said substrate, said first coating composition comprising an aqueous dispersion of microscopic capsules containing a colorless, color-reactant material, said dispersion also including a polymeric binding agent, said binding agent being capable of forming a continuous, non-permeable pressure-rupturable, water-insoluble polymeric barrier layer over said pressure-rupturable microcapsules, applying a second coating composition comprising an aqueous solution of a cross-linking agent to said first coating in order to cross-link said polymeric binder and form a pressure-rupturable, water-insoluble polymeric barrier layer, and applying a third coating composition comprising an adsorbent, electron-acceptor material over said second coating, said color-reactant material and said electron-acceptor material being capable of reacting to form a distinctive color upon contact.

17. The method of claim 16 wherein said polymeric binding agent is a polyhydroxy polymer.

18. The method of claim 17 wherein said polyhydroxy polymer is polyvinyl alcohol, methylcellulose or starch.

19. The method of claim 17 wherein said polymeric binder is polyvinyl alcohol and said cross-linking agent is sodium borate.

20. A method for the production of a pressuresensitive record system which comprises, providing a substrate, coating the surface of said substrate with a composition comprising an aqueous dispersion of microscopic capsules containing a substantially colorless, color-forming material, said dispersion also including a polymeric binding agent, said binding agent being capable of forming a continuous, non-permeable, pressure-rupturable, water-insoluble, polymeric barrier layer over said pressure-rupturable microcapsules, applying a second coating composition containing an adsorbent, electron-acceptor material and a cross-linking agent for rapidly rendering said polymeric binding agent water-insoluble, over said microcapsules, said polymeric binding agent and said cross-linking agent reacting to form a continuous, non-permeable, pressure-rupturable, water-insoluble, polymeric barrier layer over said microcapsules, said barrier layer being rupturable under localized pressures at an ambient temperature in the range of 2025C., said colorfomiing material and said electron-acceptor material being capable of forming a distinctive color upon contact.

21. The method of claim 20, wherein said polymeric linking agent is sodium borate.

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Classifications
U.S. Classification503/214, 427/150, 503/226
International ClassificationB41M5/132
Cooperative ClassificationB41M5/132
European ClassificationB41M5/132