US 3637757 A
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CHAO-HAN LIN 3,637,757
DIETHYLAMINO FLUORARN Jan. 25, 1972 Filed Jan. 21, 1969 COATED ON THE REAR WITH MINUTE PRESSURE-RUPTURABLE 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 FIG 2 INVENTOR CHAO-HAN LIN B EWQXL HIS AGENT United States Patent flice 3,637,757 Patented Jan. 25, 1972 3,637,757 DIETHYLAMINO FLUORANS Chao-Han Lin, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio Filed Jan. 21, 1969, Ser. No. 792,325 Illt. C1. C07(] 21/00 U.S. Cl. 260-6433 3 Claims ABSTRACT OF THE DISCLOSURE- A chromogenic material of normally colorless form is disclosed, having a structural formula:
BACKGROUND OF THE INVENTION This invention pertains to chromogenic compounds for use in pressure sensitive record material and to an improved mark-forming manifold system incorporating these chromogenic compounds. More specifically, this invention pertains to acyl-, ether-, and ester-substituted dialkylamino fiuorans which have the form of substantially colorless, i.e., White, or slightly colored solids, or approach being colorless when in liquid solution, but which may be converted to dark-colored forms upon reactive contact with appropriate acidic material. As used in mark-forming systems, marking in desired areas on support webs or sheets may be accomplished by effecting 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 darkcolored materials in the intended image areas.
Pressure-sensitive, mark-forming systems of the prior art include that disclosed in application for Letters Patent No. 392,404 (now abandoned), filed Aug. 27, 1964, 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 markforming components (at least one component of which is a polymeric material) and a liquid solvent in which each of the mark-forming components is solublesaid liquid solvent being present in such form that 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 to provide a manifolding unit, and which are, moreover, 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 acyl-, ether-, and ester-substituted dialkylamino fluorans disclosed herein which are substantially colorless, or slightly colored offering a new and improved variety of chromogenic characteristics, and yielding novel dark-colored substances upon contact with color-activating materials.
It is a further object of this invention to provide a new and improved, normally substantially colorless, chromogenic 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, chromogenie 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 dark-colored reaction products, thus providing means for making marks of desirable color intensity and hue.
In accordance with one feature of this invention, there is provided a substantially colorless or slightly colored, chromogenic compound having the structural formula:
6 diethylamino 2-formylfiuoran having the structural formula:
2'-carbomethoxy-6-diethylaminofiuoran having the structural formula:
2' benzoyl-6'-diethylamino-4'-methylfluoran having the structural formula:
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 r 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 compound 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. 40
Acidic materials employed in this invention can be any compound within the definition of a Lewis acid, i.e. any electron acceptor. Preferably, acidic organic polymers such as phenolic polymers are employed as the acidic material. The novel chromogenic materials exhibit the ad vantage 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 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 the surface With a multiplicity of minute pressure-rupturable microcapsules containing a solution of the novel, substantially colorless, chromogenic component. An acidic component, 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 twosheet 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 base-sheet which capsules contain a liquid solution of chromogenic material. In another embodiment 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 substance of the instant invention.
Referring again to FIG. 1, comprising an overlying or base-sheet having the chromogenic material located within or upon the sheet; it is possible to incorporate the chromogenic 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 webs can be envisioned. Such arrangements are thoroughly described in the aforementioned application Ser. No. 392,404 (now abandoned) 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 chromogenic material in at least one liquid solvent when the acidreacting material is a phenolic or other 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 25, 1957 on the application of Barrett K. Green and Lowell Schleicher; 2,800,458, issued July 23, 1957 on the application of Barrett K. Green and Lowell Schleicher; 2,800,458, issued July 23, 1957 on the application of Barret K. Green, reissued as Reissue Pat. No. 24,899 on Nov. 29, 1960; and 3,041,289, issued June 26, 1962 on the application of Bernard Katchen and Robert E. Miller. The microscopic capsules, when disposed within or upon a supporting web as a multiplicity in contiguous juxtaposition, are rupturable by pressure, such as normal marking pressure found, for example, in writing or typing operations. I
The material or materials chosen as the wall material for the droplet-containing microcapsules, in addition to being pressure rupturable, must be inert or unreactive with respect to the intended contents of the capsules and the other mark-forming 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, gum 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 15 microns in diameter.
The acidic organic polymeric material useful for developrng the color of novel chromogenic compounds in this lnvention 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 vinylmethylethermalerc anhydride copolymer and mixtures thereof.
More specifically, phenolic polymers found useful include alkyl-phenol acetylene resins, which are soluble in common organic solvents and possess permanent fusibihty 1n the absence of being treated by cross-linking materials. Another 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 cross-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 32003 500 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 densensitization 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 Honel 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 cpolymers, as disclosed in Vinyl and Related Polymer, by Calvin E. Schildknecht, second printing, published April 1959, by John Wiley & Sons, Incorporated: See pages 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 include 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 diminish the intensity of the mark, in which instances the solvent chosen should be sufiiciently 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 intimate mixture of the components be brought about through solution of said components, one or more of the markforming components can be dissolved in solvent droplets isolated by encapsulation, the only requirement being that at least one of the components essential to the markforming reaction be maintained isolated until the markforming 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 is liquid and in condition for forming solutions only at elevated temperatures.
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 mark-forming component, from one sheet to another, the record material is referred to as a transfer system. (Such a system may also be referred to as a two-fold system, in that at least two sheets are required and each sheet 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 film-forming 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 markforming components, and the chromogenic-material-containing microcapsules in a liquid medium not a solvent for either the mark-forming component or the microcapsules, with the result that all components of the markforming 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 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, US. Pat. No. 2,299,694 which 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 an aque ous 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 polymer-sensitized 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 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 110 percent, by weight, solution of the material in 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 non-solvent 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 reactionproduced 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 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 principle 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 chromogenic material to effect distinctive color formation or color change. In a multi-sheet system in which an acidic organic polymer is employed, 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 application S.N. 392,404 (now abandoned) in the names of Miller et al, and in US. patent application S.N. 420,193 in the names of Phillips et al. and issued as US. Pat. No. 3,455,721 on July 15, 1969 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:
Percent Coating composition: by weight Phenolic polymer mixture 17 Paper coating kaolin (white) 57 Calcium carbonate l2 Styrene butadiene latex 4 Ethylated starch 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.
9 EXAMPLE 1 Preparation of 2-benzoyloxy-6'-diethylamino fluoran A reaction mixture of 3.1 grams of 2-carboxy-4'-diethylamino-2'-hydroxybenzophenone, 2.0 grams of benzyloxyphenol, and 30 milliliters of 75 percent, by Weight, aqueous sulfuric acid solution was heated for about 1.5 hours at 95-100 degrees centigrade. The reaction mixture was then poured into about 100 milliliters of water and made alkaline to a pH of above about 8 by addition of dilute, aqueous, sodium hydroxide solution. A precipitate was thrown down and that precipitate was extracted with benzene. The benzene extract was washed 3 times with SO-rnilliliter volumes of 10 percent, by weight, aqueous sodium followed by a wash with Water. The Water-Washed benzene extract was evaporated to dryness to obtain 0.45 gram of crude reaction product. The crude product was chromotographically purified over activated alumina. A benzene solution of the purified reaction product imparted a reddish-purple color to paper coated with a mixture of kaolin and phenolic resin.
EXAMPLE 2 Preparation of 2'-formyl-6-diethylaminofluoran A reaction mixture of 3.1 grams of 2-carboxy-4-diethyl-amino-2-hydroxybenzophenone, 1.2 grams of p-hydroxybenzaldehyde, and milliliters of 90 percent, by weight, aqueous sulfuric acid solution was heated for about 1 hour at 140-145 degrees centigrade. The reaction mixture was then poured into about 0 milliliters of water and made alkaline to a pH of above about 8 by addition of dilute, aqueous, ammonium hydroxide solution. The reaction mixture was extracted by 250 milliliters of benzene and the benzene extract was Washed with sodium hydroxide solution and then with water. The reaction product was chromatographically purified over alumina. A benzene solution of the purified reaction product imparted an orange color to paper coated with a mixture of kaolin and phenolic resin.
EXAMPLE 3 Preparation of 2'-carbomethoxy-6-diethylaminofluoran A reaction mixture of 1.6 grams of 2-carboxy-4'-diethylamino 2' hydroxybenzophenone, 0.76 gram of methyl-p-hydroxybenzoate and 20 milliliters of percent, by weight, aqueous sulfuric acid solution was heated for about 5 hours at 98-102 degrees centigrade. The reaction mixture was then poured into water and made alkaline to a pH of above about 8 by addition of dilute, aqueous, ammonium hydroxide. The reaction mixture was extracted by benzene, washed and concentrated by evaporation. The crude product was chromatographically purified over alumina. 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-benzoyl-6-diethylamino-4- methylfluoran A reaction mixture of 0.3 gram of 2-carboxy-4'-diethylamino-2'-hydroxybenzophenone, 0.2 gram of 4-hydroxy- 3-methylbenzo-phenone, and 10 milliliters of '80 percent, by weight, aqueous sulfuric acid solution was heated for about 1 hour at -140 degrees centigrade. Reaction product isolation and purification was conducted as described in the previous examples, above. A benzene solution of the purified reaction product imparted an orange color to paper coated with a mixture of kaolin and phenolic resin.
What is claimed is:
References Cited UNITED STATES PATENTS 3,514,310 5/1970 Kimura et al. 117-362 ALEX MAZEL, Primary Examiner ANNE MARIE T. TIGHE, Assistant Examiner US. Cl. X.R. 117-362, 36.8