US3730755A - Pressure-sensitive record materials - Google Patents

Abstract

A CHROMOGENIC MATERIAL OF NORMALLY COLORLESS FORM IS DISCLOSED, HAVING THE STRUCTURAL FORMULA:

6''-((R4)2-N-),4''-R,3''-R1,2''-R2,3-(O=),R3-SPIRO(PHTHALAN-

1,9''-XANTHENE)

WHEREIN ON OF R, R1, R2, AND R3 REPRESENTS A NITRO- OR AMINO-RADICAL AND THE REMAINING OTHER OF R, R1, R2, AND R3 COMPRISE HYDROGEN, HALOGEN, PHENYL AND ALKYL RADICALS AND R4 REPRESENTS ALKYL RADICALS HAVING LESS THAN FIVE CARBONS, SAID MATERIAL ASSUMING A COLORED FORM UPON REACTIVE CONTACT WITH A LEWIS ACID MOLECULE. EXAMPLES INCLUDE 6''DIETHYLAMINO - 2'' -NITROFLUORAN, 6''-DIETHYLAMINO-2''-METHYL4'' - NITROFLUORAN, 2'' - CHLORO-6''-DIETHYLAMINO 3''-METHYL-5NITROFLUORAN, AND 6 - AMINO-2''-CHLORO-6''-DIETHYLAMINO-3''METHYLFLUORAN.

Description

May 1, 1973 CHAO'HAN LIN 3,730,755

PRESSURE-SENSITIVE RECORD MATERIALS Original Filed Jan. 21, 1969 BASE-SHEET OF RECORD MATERIAL COATED ON THE REAR WITH MINUTE PRESSURERUPTURABL E CAPSULES CONTAINING LIQUID SOLUTION OF CHROMOGENIC MATERIAL DEVELOPABLE ON CONTACT WITH AN ELECTRON- ACCEPTING MATERIAL .OF THE LEWIS- ACID TYPE TO COLORED FORM RECEIVING SURFACE OF UNDERSHEET COATED WITH AN ELECTRON-ACCEPTING MATERIAL OF THE LEWIS- ACID TYPE United States Patent 3,730,755 PRESSURE-SENSITIVE RECORD MATERIALS Chao-Han Lin, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio Original application Jan. 21, 1969, Ser. No. 792,279, new Patent No. 3,624,107. Divided and this application Jan. 11, 1971, Ser. No. 105,687

Int. Cl. B41m 5/16; C07d 5/00 US. Cl. 11736.2 16 Claims ABSTRACT OF THE DISCLOSURE A chromogenic material of normally colorless form is disclosed, having the structural formula:

BACKGROUND OF THE INVENTION This is a division of Pat. No. 3,624,107 issued Nov. 20, 1971.

This invention pertains to novel chromogenic compounds for use in pressure sensitive record material and to an improved mark-forming manifold system incorporating these novel chromogenic compounds. More specifically, this invention pertains to nitroand amino-substituted dialkylamino fiuorans which have the form of substantially colorless, i.e. white, or slightly colored solids, or approach being colorless when in dilute liquid solution, but which may be converted to dark-colored forms upon reactive contact with appropriate acidic material. As used in markforming systems, marking in desired areas on support webs or sheets may be accomplished by eifecting localized reactive contact between the novel chromogenic material and the acidic material on or in such a web or sheet, such material being brought thereto by transfer, or originally there, in situ-the desired reactive contact forming relatively intensely-colored materials in the intended image areas.

Pressure-sensitive, mark-forming systems of the prior art include that disclosed in, now abandoned, application for Letters Pat. No. 392,404, filed Aug. 27, 1934, now abandoned, in the names of Robert E. Miller and Paul S.

Phillips, Jr. The above-mentioned patent application provides a marking system of disposing on and/or within sheet support material, mutually .reactant but unreacted mark-forming components (at least one component 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 an application of pressure causes a breach or rupture of the barrier in the area delineated by the pressure pattern. The mark-forming components thereby are brought into reactive contact, producing a distinctive mark.

It is an object of this invention to provide new and improved substances having chromogenic properties which may be incorporated in a web or coated onto the surface of a web or coated onto the surface of a web to provide a novel manifolding unit, and which, moreover, are useful in carrying out improved methods of marking involving reactive contact with a color-activating material to yield dark-colored reaction products in areas where marking is desired.

It is another object of this invention to provide compounds, based upon the nitroand amino-substituted dialkylamino fluorans disclosed herein which are substantially colorless, or slightly colored, in dilute solution or not, offering a new and improved variety of chromogenic characteristics, and yielding novel, relatively dark-colored, substances upon contact with color-activating materials.

It is a further object of this invention to provide new and improved, normally substantially colorless, chrome genic substances yielding Lewis acid-reacted color products which exhibit improved color stability on exposure to light and improved reproduction capabilities when copied by xerographic or diazo processes.

It is a further object of this invention to provide new and improved, normally substantially colorless, chromogenic substances yielding colored reaction products when placed in reactive contact with certain selected Lewis acid materials.

It is a further object of this invention to provide a new and improved mark-forming system which comprises disposing, within a web or upon the surface of a web or sheet-support-material, unreacted chromogenic material in a location suitable for subsequent reactive contact with an acidic material to produce relatively dark-colored reaction products, thus providing means for making marks of desirable color intensity and hue. I

In accordance with one feature of this invention, there is provided a novel, substantially colorless or slightly colored, chromogenic compound having the structural formula:

wherein one of R, R R and R represents a nitroor amino-radical and the remaining others of R, R R and R comprise hydrogen, halogen, phenyl, and alkyl radicals and R represents alkyl radicals having less than five carbon atoms. Examples of these novel compounds include 6 diethylamino 2'-nitrofiuoran having the structural formula:

2' amino 6-diethylamino-3'-methylfluoran having the structural formula:

6'-diethylamino-2-methyl-4'-nitrofluoran having the structural formula:

6-amino-2'-chloro-'6-diethylamino-3-methylfluoran having the structural formula:

CzHa

/N -C CH3 (32115 i 0 I NHz In accordance with another feature of this invention, a new composition of matter is disclosed which comprises a dark-colored product of chemical reaction having a resonant chemical structure and produced by contact of a color-activating material with one of the above-mentioned chromogenic compounds. The color-developing or activating material is an acidic substance useful for converting the chromogenic compounds to colored forms.

The method of marking of this invention, i.e., the method of developing a dark-colored material from substantially colorless or slightly colored chromogenic compounds, comprises providing a chromogenic compound selected from among the above-mentioned compounds and bringing such chromogenic compounds into reactive contact with an acidic color-activating substance, in areas where marking is desired, to produce a dark-colored form of the chromogenic compound by the action thereon of said acidic substance.

Acidic materials employed in this invention can be any compound within the definition of a Lewis acid, i.e., any G FQUQ a p qrt Prsfsrab yq aq rl s organic p y rs such as phenolic polymers are employed as the acidic material. The novel chromogenic materials exhibit the advantage of improved color stability when they are reacted with such phenolic polymers. Solution formation of solid particles of the polymeric material in a solvent system with the substantially colorless chromogenic compounds permits penetration of the dark-colored reaction product into a porous support sheet, e.g., paper, so that the colored form of the chromogenic material is absorbed into the body of the sheet and is not merely on the surface of the sheet. The absorption feature provides protection against the erasure of recorded data by attrition of the surface of a record sheet made in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic representation of a two-sheet unit manifold, in perspective. The bottom surface of the overlying sheet is supplied on the surface or near th'e surface with a multiplicity of minute pressure-rupturable microcapsules containing a solution of the novel, substantially colorless, chromogenic component. An acidic comopnent, such as an acid clay or a phenolic polymeric material lies within the lower web or undersheet or upon the upper surface of the lower web or undersheet. A colored mark is made by the use of a stylus, a type character, or other pressure-exerting means applied to the two-sheet unit manifold.

The encapsulated solution is released on the event of rupture of the capsules in writing operations, as is shown in FIG. 2. FIG. 2 is a sectioned view of the two-sheet unit manifold of FIG. 1. The elements are not to scale and are so-shown in order to more effectively depict their interrelation. The released solution is transferred from the overlying or base-sheet to the receiving surface of the underlying sheet in conformance with the pressure pattern of the writing operation. The drawing shows that the top of the underlying sheet is coated or impregnated with a material reactant with the chromogenic material, e.g., an acid clay or an acidic phenolic polymer material; and that capsules are present on the overlying or basesheet which capsules contain a liquid solution of chromogenic material. In another embodment of the record material, however, the capsules can contain the polymeric phenolic material in liquid solution and the receiving surface of the underlying sheet can be supplied with the chromogenic material. The improvement in the system resides in the chromogenic material, which chromogenic material is the novel substance of the instant invention.

Referring again to FIG. 1, comprising an overlying or base-sheet having the chromogenic material within or upon the sheet; it is possible to incorporate the chromo genic material in a solid, crystalline state in a binder material so that the chromogenic material may be transferred from the overlying sheet, upon the application of pressure, to deposit some of the chromogenic material on the receiving surface of the undersheet, which receiving surface carries a color-activating polymeric material. Preferably, the chromogenic substance is dissolved in an appropriate solvent and minute droplets of the solution of the chromogenic material are encapsulated in minute, rupturable, capsules. It is apparent that many other arrangements are possible, including different configurations and relationships of the solvent and all of the mark-forming materials with respect to their encapsulation and location on the supporting underlying or overlying sheets or wets can be envisioned. Such arrangements are thoroughly described in the aforementioned abandoned application Ser. No. 392,404 in the names of Miller et al. and need not be repeated herein.

SUMMARY OF THE INVENTION It is noted that the polymeric mark-forming components should have a common solubility with the novel chromogenic material in at least one liquid solvent when the acid-reacting material is a pheno ic or o her acidic organic polymer. It is also noted that in a single system several chromogenic materials may be used with the same or different polymeric materials. Several polymeric materials can be reactively contacted with a single chromogenic compound or with a mixture of chromogenic compounds.

As mentioned above, the solvent: can be maintained in physical isolation in minute droplets until such time as it is released by application of pressure. This may be accomplished by several known techniques, but, preferably, isolation is maintained by encapsulation of individual droplets of the solvent in a microcapsule according to the procedures described, for example, in US. Pat. No. 2,712, 507, issued July 5, 1955, on the application of Barrett K. Green; 2,730,457, issued Jan. 10, 1956, on the application of Barrett K. Green and Lowell Schleicher; 2,800,457, issued July 23, 1957, on the application of Barrett K. Green and Lowell Schleicher; 2,809,458, issued July 23, 1957, on the application of Barrett K. Green, reissued as Reissue Pat. No. 24,899 on Nov. 29, 1960; and 3,041,289, issued June 26, 1932, on the application of Bernard Katchan and Robert E. Miller. The microscopic capsules, when disposed within or upon a supporting web as a multiplicity in contigous juxtaposition, are rupturable by pressure, such as normal marking pressure found, for example, in writing or typing operations.

The material or materials chosen as the wall material for the droplet-contaianing microcapsules, in addition to being pressure rupturable, must be inert or unreactive with respect to the intended contents of the capsules and other mark-froming components so that the capsule wall material will remain intact under normal storage conditions until such time as it is released by an application of marking pressure. Preferred examples of eligible capsule wall materials include gelatin, gem arabic and many others thoroughly described in the aforementioned patents.

For most uses in record material, the capsule size should not exceed about 50 microns in diameter. Preferably, the capsules should be smaller than about microns in diameter.

The acidic organic polymeric material useful for developing the color of novel chromogenic compounds in this invention include phenolic polymers, phenol acetylene polymers, maleic acid-rosin resins, partially or wholly hydrolyzed styrene-maleic anhydride copolymers and ethylene-maleic anhydride copolymers, carboxy polymethylene and wholly or partially hydrolyzed vinylmethylether-maleic anhydride copolymer and mixtures thereof.

More specifically, phenolic polymers found useful include alkyl-pehnol acetylene resins, which are soluble in common organic solvents and possess permanent fusibility in the absence of being treated by cross-linking materials. Anoth'er specific group of useful phenolic polymers are members of the type commonly referred to as novolacs (a type of phenolformaldehyde polymeric material) which are characterized by solubility in common organic solvents and which are, in the absence of cross-linking agents, permanently fusible. Resol resins, if they are still soluble, may be used, though they are subject to change in properties upon aging. Generally, phenolic polymer material found useful in practicing this invention is characterized by the presence of hydroxyl groups and by the absence of groups such as methylol, which tend to promote infusibility or cores-linking of the polymer, and, further, by being soluble in organic solvents and relatively insoluble in aqueous media. Again, it should be remembered that mixtures of these organic polymers and other acidic materials can be employed.

A laboratory method useful in the selection of suitable phenolic resins is the determination of the infrared absorption pattern. It has been found that phenolic resins which undergo absorption in the 3200-3500 cm. region (which is indicative of hydroxyl groups) on the resin molecules and which do not absorb in the 1600- 1700 cm." region are eligible. This latter absorption region is indicative of desensitization of hydroxyl groups which desensitization renders such groups unavailable for reaction with the chromogenic materials.

The preparation of some organic polymeric materials useful for practicing this invention has been described in Industrial and Engineering Chemistry, vol. 43, pp. 134 to 141, January 1951, and a particular polymer thereof is described in Example I of US. Pat. No. 2,052,093, issued to Herbert Hiinel on Aug. 25, 1936. The preparation of the phenol-acetylene polymers has been described in Industrial and Engineering Chemistry, vol. 41, pp. 73 to 77, January 1949. The preparation of maleic anhydride copolymers is described in the literature, such as, for example, one of the maleic anhydride vinyl copolymers, as disclosed in Vinyl and Related Polymers, by Calvin E. Schildknecht, second printing, published April 1959, by John Wiley & Sons, Incorporated: See pp. 65 to 68 (styrene-maleic anhydride copolymer), 530 to 531 (ethylene-maleic anhydride copolymer) and 628 to 630 (vinylmethylether-maleic anhydride copolymer).

When the acidic material used as a mark-forming component in the present invention is one of the aforementioned organic polymers, the liquid solvent chosen must be capable of dissolving it. The solvent may be volatile or nonvolatile, and a singleor multiple-component solvent may be used which is wholly or partially volatile. Examples of volatile solvents useful in practicing the present invention includes toluene, petroleum distillate, perchloroethylene, and xylene. Examples of nonvolatile solvents include high-boiling-point petroleum fractions and chlorinated biphenyls. Generally, the solvent chosen should be capable of dissolving at least about 0.3 percent, by weight, of the chromogenic material, and at least about 3 to 5 percent, by Weight, of the acidic polymeric material to yield an effective 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 maximum coloration at the reaction site.

A further criterion for selection of the solvent is that the solvent must not interfere with the mark-forming reaction. In some instances, the presence of the solvent may be found to interfere with the mark-forming reaction or diminlsh the intensity of the mark, in which instances the solvent chosen should be sufliciently volatile to assure its removal from the reaction site soon after having brought the mark-forming components into reactive contact so that the mark-forming reaction can proceed.

Since the mark-forming reaction requires that an intlmate mixture of the components be brought about through solution of said components, one or more of the mark-forming components can be dissolved in solvent droplets isolated by encapsulation, the only requirement being that at least one of the components essential to the mark-forming reaction be maintained isolated until the mark-forming reaction is desired.

In the usual case, the mark-forming components are so chosen as to produce a mark upon application of pressure to a coated system of sheets at room temperature (20 to 25 degrees Centigrade). However, the present invention also includes a system wherein the solvent component is not liquid at temperatures near room temperature but 18 liquid and in condition for forming solutions only at elevated temperature.

The support sheet member on which components of the system are disposed may comprise a single or a dual sheet assembly. In the case where all components are disposed on a single sheet, the record material is referred to as a self-contained or autogenous system. Where there must be a migration of solvent, with or without the markforming component, from one sheet to another, the record material is referred to as a transfer system. (Such as system may also be referred to as a two-fold system, in that at least two sheets are required and such sheet 7 includes a component, or components, essential to the mark-forming reaction.) Where an adequate amount of the colored reaction product is produced in liquid or dissolved form on a surface of one sheet, a colored mark can be recorded on a second sheet by transfer of the colored reaction product.

In a preferred case, where microcapsules are employed, they can be present in the sheet support material either disposed therethroughout or as a coating thereon, or both. The capsules can be applied to the sheet material as a dispersion in the liquid vehicle in which they were manufactured, or, if desired, they can be separated from the vehicle and thereafter dispersed in a solution of the acidreacting polymeric component (for instance, 30 grams of water and 53 grams of a 1 percent, by Weight, aqueous solution of polyvinylmethylether-maleic anhydride) to form a sheet-coating composition in which, because of the inertness of the solution and the capsules, both components 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 release of the contained liquid by rupture of the capsule walls. The latter technique, relying on the inertness of the microcapsule and the dispersing medium of the filmforming mark-forming polymeric component, provides a method for preparing a sensitive record material coating having the capsules interspersed directly in a dry film of the polymeric material as the film is laid down from solution. A further alternative is to disperse one or more mark-forming components, and the chromogenic-material-containing microscapsules in a liquid medium not a solvent for either the mark-forming components or the 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. Of course, the several components may be applied individually. The capsules can also be coated onto a sheet as a dispersion in a solution of polymeric material which is not necessarily reactive with the capsule-contained solution of chromogenic materials.

The respective amounts of the several components can be varied according to the nature of the materials and the architecture of the record material unit desired or required. Suitable lower amounts include, in the case of the chromogenic material, about 0.005 to 0.075 pound per ream (a ream in this application meaning five hundred (500) sheets of 25" x 38" paper, totalling 3,300 square feet); in the case of the solvent, about 1 to 3 pounds per ream; and in the case of the polymer, about 0.5 pound per ream. In all instances, the upper limit is primarily a matter of economic consideration.

The slurry of capsules can be applied to a wet web of paper, for example, as it exists on the screen of a Fourdrinier paper machine, so as to penetrate 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 can be placed directly in or on a paper or support sheet. Not only capsule structures, but continuous films which contain a multitude of microscopic, unencapsulated, droplets for local release in an area subjected to pressure can be utilized. (See, for example, U.S. Pat. No. 2,299,694 which was issued Oct. 20, 1942, on the application of Barrett K. Green.)

With respect to the acidic organic polymeric component, a solution thereof in an evaporable solvent can be introduced into an amount of water and the resulting mixture can be agitated while the evaporable solvent is blown off by an air blast. This operation leaves as aqueous colloidal dispersion slurry of the polymeric material, which may be applied to finished paper so as to leave a surface residue or the slurry may be applied to a Wet web of paper or at the size-press station of a paper making machine. In another method for making a polymersensitized sheet, the water-insoluble polymer can be ground to a desired or required 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 polymeric material, the binder itself may act as a dispersant. If desired, an amount of binder material of up to 40 percent, by weight, of the amount of polymeric material can be added to the ball-milled slurry of materials-such binder materials being of the paper coating binder class, including, for example, gum arabic, casein, hydroxyethylcellulose, and latexes (such as styrene-butadiene copolymer). If desired, oil absorbents in the form of fullers earths may be combined with the polymeric material particles to assist in retaining, in situ, the liquid droplets of chromogenic material solution to be transferred to it in data-representing configuration, for the purpose of preventing bleeding of the print.

Another method for applying the chromogenic or polymeric material individually to a single sheet of paper is by immersing a sheet of paper in 1-10 percent, by weight, solution of the material is an evaporable solvent. Of course, this operation must be conducted individually for each reactant, because if the other reactant material were present, contact of the reactants would result in a premature coloration over the sheet area. A dried sheet with one component can then be coated with a solution of another component, the solvent of which is a nonsolvent to the already-supplied component.

The polymeric material can also 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. reaction-produced color in those spot-printed 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 percent, by Weight, of the phenolic polymeric material in a petroleum-based solventthe ink being built to a viscosity suitable for printing purposes. The relative amounts of reactive, mark-forming, components to be used in practice of this invention, are those most convenient and economical amounts consistent with adequate, desired or required visibility of the recorded data. The resolution of the recorded data is dependent on, among other things particle or capsule size, distribution and amount of particles or capsules, liquid solvent migration, chemical reaction efficiency, and other factors, all of which can be optimized empirically by one skilled in the art. Such factors do not determine the primicple of the present invention, which invention, in part, relates to means for enabling the bringing into solution contact, by marking pressure, two normally solid, chemically reactive, components dissolved in a common liquid solvent component held isolated as liquid droplets. The isolated liquid droplets are preferably in marking-pressure-rupturable capsules having polymeric-film Walls, or are isolated, as a discontinuous phase, in a continuous marking-pressure-rupturable film.

In the color system of this invention the acidic markforming material reacts with the novel chromogenic material to effect distinctive color formation or color change. In a multi-sheet system in which an acidic organic polymer is empolyed, it may be desirable to include other materials to supplement the polymer reactants. For example, kaolin can be added to improve the transfer of the liquid and/or the dissolved materials between the sheets. In addition, other materials such as bentonite, attapulgite, talc, feldspar, halloysite, magnesium trisilicate, silica gel, pyrophyllite, zinc sulfate, calcium sulfate, calcium citrate, calcium phosphate, calcium fluoride, barium sulfate and tannic acid can be included.

Various methods known to the prior art and others disclosed in the aforementioned abandoned application Ser. No. 392,404 in the names of Miller, et al. and in U.S. Pat. No. 3,455,721, issued July 15, 1969, on the application of Phillips, et al, can be employed in compositions useful for coating mark-forming materials into supporting sheets. An example of the compositions which can be coated onto the receiving surface of an underlying sheet of a multi-sheet to react with a capsule coating on the underside of an overlying sheet is as follows:

Coating composition: Percent by weight Phenolic polymer mixture 17 Paper coating kaolin (white) 57 Calcium carbonate 12 Styrene butadiene latex 4 Ethylated starch M 8 Gum arabic 2 Having disclosed, generally, the novel chromogenic materials of this invention and preferred methods for utilizing the novel chromogenic materials, in combination with other materials, as reactive components in mark-forming record material: examples will now be disclosed wherein preparation of several of the novel chromogenic materials is described.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1 Preparation of 6-diethylamino-2-nitrofluoran A reaction mixture of 3.1 grams of 2-carboxy-4'-diethylamino 2 hydroxybenzophenone, 1.4 grams of pnitrophenol, and 30 milliliters of 90 percent, by weight, sulfuric acid was heated for one hour in a bath maintained at 145-154 degrees centigrade. The reaction mixture was poured onto 300 grams of ice and made alkaline, by addition of dilute ammonium hydroxide, to a pH above 8. The chilled, alkaline, system was extracted three times with 100 milliliter-volumes of benzene to remove the product of reaction; and then the benzene extract was washed 3 times with 100 milliliter-volumes of percent, by weight, aqueous sodium hydroxide solution followed by repeated washes with distilled water until the wash water was no longer alkaline. The water-washed benzene extract was then evaporated to dryness to obtain about 1.2 grams of crude reaction product. The crude product was chromatographically purified over activated alumina and then recrystallized from benzene-petroleum ether. It exhibited a melting point of 192-193 degrees centigrade. A benzene solution of the purified product imparted an orange color to paper coated with a mixture of kaolin and phenolic polymer.

'EXAMPLE 2 Preparation of 2'-amine-6'-diethylaminofluoran A suspension was prepared by adding 0.4 gram of 6'- diethylamino 2 nitrofluoran, the product of Example 1, above, to a reducing solution comprising 1.0 gram of stannous chloride dihydrate, 4.5 milliliters of hydrochloric acid (having a specific gravity of about 1.15), and

i 1.5 milliliters of water. The suspension was warmed and agitated until a solution was formed. The solution was cooled to about room temperature, was diluted with about 40 milliliters of water and the pH was adjusted to about 12 using a 10 percent, by weight, aqueous solution of sodium hydroxide in order to precipitate the reaction product. The precipitate was extracted by two 50-milliliter volumes of benzene and the benzene extract was washed repeatedly with distilled water until the wash water was no longer alkaline. The Water-washed benzene extract was concentrated to about 6-7 milliliters. On standing, the reaction product separated from solution, was removed by filtration, and was washed with 2-3 milliliters of benzene. The product of this example weighed 0.21 gram and exhibited a melting point of 213-215 degrees centigrade. A benzene solution of the product impaired a purple color to paper coated with a mixture of kaolin and phenolic polymer.

10 EXAMPLE 3 Preparation of 6'-diethylamino-3-methyl-2- nitrofluoran A reaction mixture of 14.1 grams of 2-carboxy-4- diethylamino 2' hydroxybenzophenone, 6.9 grams of 3-methyl 4 nitrophenol and 180 milliliters of percent, by weight, sulfuric acid were heated for two hours in a bath maintained at 124-128 degrees centigrade. The reaction mixture was poured onto 700 grams of ice and made alkaline by addition of concentrated ammonium hydroxide to a pH of about 9. The reaction product precipitated and was removed by filtration. The thusremoved reaction product was washed twice by suspending it in 500-milliliter portions of water, stirring the suspension for one-half hour and filtering. The resulting, waterwashed, crude product of reaction was black in color and Weighed about 17.7 grams. The crude product was repeatedly extracted using small volumes of warmed ethyl acetate until a new volume of extract imparted only a faint color to paper coated with a mixture of kaolin and phenolic polymer. The ethyl acetate extract solution was concentrated, by evaporation, to a volume of about 150 milliliters. Cooling of the concentrated solution caused precipitation and about 13.4 grams of the precipitate was isolated and purified as in previous examples. The purified product was pale yellow and had a melting point of 266-268 degrees. A benzene solution of the purified product imparted an orange color to paper coated with a mixture of kaolin and phenolic polymer.

EXAMPLE 4 Preparation of 2-amino-6'-diethylamino- 3 -methylfiuoran A suspension was prepared by adding 8.6 grams of 6'-diethylamino3'-methyl-2'-nitrofiuoran, the product of Example 3, above to a reducing solution comprising 2.5 grams of stannous chloride dihydrate, milliliters of hydrochloric acid (having a specific gravity of about 1.15), 34 milliliters of water and 70' milliliters of ethanol. The system was warmed, cooled, diluted, and the pH was adjusted to about 12, all according to the procedure of Example 2. The suspension was extracted several times by benzene and the extract was washed with aqueous sodium hydroxide solution and water. The washed extract was concentrated by evaporation and, on standing, the reaction product separated from solution, was removed by filtration, and was purified by recrystallization from benzene. The purified product exhibited a double melting point, i.e., on heating, it melted at about 140 degrees centigrade, resolidified and melted again at about 183-185 degrees centigrade. A benzene solution of the product imparted a purple color to paper coated with a mixture of kaolin and phenolic polymer.

EXAMPLE 5 Preparation of 6'-diethylamino-2-methyl-4-nitrofiuoran This example was conducted according to the procedure of Example 1 except that 4-methyl-2-nitrophenol was substituted for the p-nitrophenol therein. A benzene solution of the reaction product imparted a reddishorange color to paper coated with a mixture of kaolin and phenolic polymer EXAMPLE 6 Preparation of 4-arnino-3-diethylarnino- 2'-methylfiuoran 6'-diethylamino-2'-methyl-4'-nitrofluoran from Example 5, above, was reduced with stannous chloride according to the procedure of Example 2, above. The reaction product exhibited a double melting point, i.e., on heating, it melted at degrees centigrade, resolidified, and melted again at about 230 degrees centigrade. A benzene solution of the product imparted an orange color to paper coated with a mixture of kaolin and phenolic polymer.

1 1 EXAMPLE 7 Preparation of 2'-chloro-6 '-diethylamino-3-methyl (or 6)-nitrofluoran Five grams of m-diethylaminophenol, 5.8 grams of 4- nitrophthalic anhydride, and 100 milliliters of benzene were refluxed together for about three hours. The mixture was, cooled and extracted twice with 100 millilitervolumes of 5 percent, by weight, aqueous sodium carbonate solution. Dilute, aqueous, hydrochloric acid was added, dropwise, to the sodium carbonate-extract solution to precipitate the reaction product. The precipitate thrown down between pH 6 and pH 2 was collected for use as an intermediate to the desired product of this example. Said intermediate is 2-carboxy-4'-diethylamino- 2-hydroXy-4(or 5)-nitrobenzophenone and 4.3 grams of it were obtained. The intermediate was condensed with 4-chloro-3-methylphenol in 80 percent, by weight, sulfuric acid at 95-105 degrees centigrade, for about 3 hours and the reaction product was isolated by the technique described in Example 1, above. A benzene solution of the product imparted a red color to paper coated with a mixture of kaolin and phenolic polymer.

EXAMPLE 8 Preparation of 5 (or 6)-amino-3'-chloro-6'-diethylamino-3-methylfiuoran 2'-chloro-6'-diethylamino 3'-methyl-5 (or 6)-nitrofiuoran from Example 7, above, was reduced with stannous chloride according to the procedure of Example 3, above. A benzene solution of the reaction product imparted a red color to paper coated with a mixture of kaolin and phenolic polymer.

What is claimed is:

1. A pressure sensitive record unit comprising:

(a) support web or sheet material,

(b) mark-forming components and a releasable liquid solvent for said mark-forming components arranged in contiguous juxtaposition and supported by said sheet material,

(0) said mark-forming components comprising at least one chromogenic amterial of the structure:

wherein:

one of R, R R and R represents nitroradicals and the remaining others of R, R R and R represent radicals selected from the group consisting of hydrogen, halogen, phenyl, and alkyl radicals having less than five carbon atoms; and

R represents alkyl radicals having les than five carbon atoms; and

an electron-accepting material of the Lewis acid type reactive with said chromogenic material to produce a mark; which components upon pressure-release of the liquid solvent are brought into reactive contact in the released solvent.

2. The record unit of claim 1 wherein at least one of the mark-forming components is maintained in isolation from the other mark-forming components prior to the release Qt the solvent.

3. The record unit of claim 1 wherein the liquid solvent is present as the nucleus of a microcapsule.

4. The record unit of claim 1 wherein the chromogenic material is dissolved in the liquid solvent prior to pressure release.

5. The record unit of claim 1 wherein the mark-forming components and the liquid solvent are present in a single support sheet.

6. The record unit of claim 1 where the electron-accepting material of the Lewis acid type comprises a clay.

7. The record unit of claim 1 where the electron-accepting material of the Lewis acid type comprises at least one organic polymer.

8. The record unit of claim 1 where the organic polymer is a phenolic polymer.

9. A mark-forming unit, comprising: a first web sheet having on one surface a transfer coating which contains as a finely dispersed phase a plurality of minute, pressure-rupturable capsules containing as an inner phase a solvent vehicle; a second web or sheet having an adherent coating upon its surface or dispersed within said web or sheet, said first and second webs or sheets being maintained disposed together in face-to-face relationship with said respective transfer and adherent coatings contiguity with each other; a first coating constituent in the form of a substantially colorless or slightly colored chromogenic material which includes as a major functional arrangement the molecular structure:

wherein one of R, R R and R represents nitroradicals and the remaining other of R, R R and R represent ardicals selected from the group consisting of hydrogen, halogen, phenyl, and alkyl radicals having less than five carbon atoms; and

R represents alkyl radicals having less than five carbon atoms; and

a second constituent in the form of an electron-accepting material of the Lewis acid type; one of said constituents being dissolved in said solvent liquid vehicle present as the inner phase of the plurality of minute pressure-rupturable capsules in the transfer coating on or within said first web or sheet, and the other of said coating constituents being bonded to said second web in said adherent coating thereon but accessible to other materials coming into contact with portions of the adherent coating, whereby, upon local impact and rupture of said capsules, releasing said liquid vehicle containing one coating constitutent from at least some of the capsules onto said contiguous adherent coating, reactive contact is eifected between said two constituents to produce a dark-colored material by the action of said electron-accepting material of the Lewis acid type upon said chromogenic material to effect color change in said chromogenic compound to said dark-colored material.

10. The mark-forming unit of claim 9 in which the electron-accepting material of the Lewis acid type comprises a clay.

11. The mark-forming unit of claim 9 in which the electron-accepting material of the Lewis acid type o prises an organic polymer.

12. The mark-forming unit of claim 11 in which the organic polymer is a phenolic polymer.

13. A pressure-sensitive record unit comprising:

(a) support web or sheet material,

(b) mark-forming components and a releasable liquid solvent for said mark-forming components arranged in contiguous juxtaposition and supported by said sheet material,

(c) said mark-forming components comprising at at least one chromogenic material of the structure: 1

wherein R is a chloro-radical, R is an ethyl radical,

2 R is a hydrogen radical, R is a methyl radical,

and R is an amino-radical at one of either the 5- or 6-ring position; and

an electron-accepting material of the Lewis acid type reactive with said chromogenic material to produce a mark; which components upon pressure-release of the liquid solvent are brought into reactive contact in the released solvent.

14. The record unit of claim 13 wherein the markforming components and the liquid solvent are present in a single support sheet.

15. The record unit of claim 13 wherein the electronaccepting material of the Lewis acid type comprises at least one organic polymer.

16. The record unit of claim 13 wherein the electronaccepting material of the Lewis acid type comprises a clay.

References Cited UNITED STATES PATENTS 3,501,331 3/1970 Kimura 1l7-36.2

MURRAY KATZ, Primary Examiner US. Cl. X.R.

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