US3111407A - Methods for making record materials - Google Patents

Description

Nov. 19, 1963 R., M. LINDQUIST ETAL METHODS FOR MAKING RECORD MATERIALS Filed Feb. 26, 1960 F I e. 3

T 6 S SM R OW LR EM TA NH 0 @2 R ATTORNEYS site States Patent ()fiice ddllfih? Patented Nov. 19, l9d3 METHGBS non MzZiEGNG REQGRD MATEREALS Robert l' /i. lldinuquist, Los Gates, and Zoiia Reyes, lvienio Paris, Calii, assiguors, by mesue assignments, to into;-

national Business Machines Corporation, New York,

FLY, a corporation oi New Yo;-

Filed Feb. 26, 1%9, Ser. No. 111,237 4 Qlaims. (El. %27) This invention relates generally to record materials, and more particularly to such materials responsive to application of light and pressure.

The use of or anic compounds as lightsensitive media for photographic processes is Well Wu, and is perhaps best exemplified by the diazo process. This process is based on the photochemical changes eiected in various diazonium salts upon exposure to light, and which affect their capacity to form dyes. In general, dyes are formed when the diazonium compounds, or diazotized amines, couple with phenols or aromatic amines in alkaline medium. Upon exposure to light, the diazonium compounds undergo decomposition and are rendered incapable of coupling and dye formation. Several types of copying papers employing this principle have been used heretofore. In one process, use is made of diazo-anhydrides and a coupler in a neutral medium. Papers of this type are developed by contact with ammonia fumes. In another process, paper coated With the diazo compound is developed by immersion in an alkaline solution containin a coupler.

While copying papers of this type have been successfully used for years, they are su ect to the drawbaca in that an external application of a developing fluid (gaseous or liquid) is required.

It is generally accepted that a record material, such as a copying paper, would find a good market if it could be printed and developed dry, Without the use of externally applied chemical solutions or gases. A material of this sort which could be processed by purely mechanical steps is particularly to be desired. In general, it is an object of the present invention to provide an improved record material which can be printed and developed solely by application of light and pressure.

Another object of the invention is to provide a record material of this character adapted to record either an riginal li ht or pressure image, a copy image, or both.

Another object is to provide a material of this charac ter which is extremely stable; and in Which reactive ingredients are protected from the environment.

A further object is to provide methods for making the improved record materials, and for their use.

ther objects and advantages of the present invention will appear from the following description and from the drawings in which:

FiG RE 1 is a cross sectional detail illustrating a record material embodying the invention;

FIGURES 2 to 4 are like views showing various modifications of the invention; and

FlGURE 5 is a like view, illustrating a particular application of the invention.

The present invention is predicated upon our discovery that particular types of liquid containing microcapsules olier a convenient means of preparing dry, light-andpressure sensitive coatings of dissolved dyes, inks or reactive chemical solutions so that the solutions are isolated and protectcdfrom the surrounding environment. More specifically, it is predicated upon discovery that microcapsules formed of polymerized material, by virtue of their ability to successfully retain aqueous and other polar solutions, make it possible to provide a record or copy material of this type employing the diazo process.

As noted above, this process requires (1) a diazonium compound, (2) a coupler, and (3) a material to adjust the pH so that the coupling or reaction of the first two components to form an azo dye can occur in an alkaline medium.

in accordance with the present invention, We separate at least one of the three components of the diazo process by isolating a solution of such a component in a profuse number of microcapsules. When these microcapsules are incorporated With the other dye forming components in a record material, an improved light-and-pressure sensitive material is obtained. It is pressure responsive in that pressure ruptures the microcapsules to free the missing component (or components) so that marking occurs. It is light sensitive in that exposure decomposes the diazonium compound so that it becomes incapable of coupling and dye formation. Light and pressure modulation of the record material can therefore be obtained in several Ways, for example, by exposure to light followed by a uniform pressure to develop the image; or the use of selected pressure to print the image followed by a light exposure to destroy the residual diazo compound and thus iix the image. As will appear, many variations and applications of this dual characteristic of light and pressure sensitivity are possible, all falling within the scope of the present invention.

The record materials of the present invention are made by the deposit of the pressure-rupturable polymeric microcapsules on a suitable substrate or base sheet material such as paper, plastic, cloth, glass, etc, along with a coating reactive with the es psulated solution to form the azo dye. In one embodiment the microcapsules are applied to the substrate in the form of a coating containing the microcapsules. In another embodiment the microcapsul s are applied as a thin film-like layer separately from the coating, which may lie above or beneath the microcapsules on the surface of the substrate. As an lternative, a manifold may be prepared by assembling a number of coated substrates in such fashion that the encapsulated component is brought into contact with the remaining components carried by an adjoining substrate.

Referring to the drawing, FIGURE 1 represents a substrate it? on Which a coating 12 containing uniformly dispersed microcapsules 14 has been deposited. As previously explained, the microcapsules contain an aqueous or other polar solution of one or more dye forming compoents, Whereas the coating contains the remaining components necessary to form an azo dye. By way of illustration, the coating 12 may comprise intermixed coupler and material to adjust pH, and the microcapsules 1d diazonium salt. Alternatively the microcapsules 14 may contain a solution to adjust pH (or such solution intermixed with the coupler) whereas the coating 12 may contain the additional dye forming ingredients. It Will be understood that the coating 12 and microcapsules 14 are most conveniently deposited on the substrate 19 in a single operation, for example, by flooding of the surface, although such processing is not essential.

FIGURE 2 illustrates a modified record material in Which the microcapsules 24 are first deposited on the substrate 20, as an underlayer following which the coating 22 is deposited as a surface layer. The dye forming components can be separated as before, that is, the microcapsules 2-4 may contain either a diazonium salt, a coupler, or a mixture of coupler and solution to adjust pH, and the surface coating 22 addit onal dye ingredients as necessary to react with the isolated content of the microcapsules.

The record material of FIGURE '3 is similar to that of FIGURE 2 except that the coating layer 32 is deposited first with the microcapsules 34 being adhered to this coating as the surface layer. As will appear, various techniques have been developed to deposit the microcapsules in successive cooperative layers upon a substrate, for example, by a series of successive spray drying operations.

FIGURE 4 illustrates a further modification in which a number of separate coated substrates are assembled into a manifold record material. As illustrated the microcapsules 44 are deposited on one side of a base sheet it), and a coating containing the remaining dye-forming components deposited on the reverse side of the sheet, as at 42. Upper and lower sheets 45 and 48 are similarly prepared except that exterior surfaces need not be coated. A manifold can be prepared by assembling the sheets 45 and 48 so that the encapsulated component (in the microcapsules 44) is brought into contact with the remaining components dispersed in the containing layers 42.

Marking of the record materials just described is accomplished by crushing or breaking the microcapsules to release the isolated dye forming component. Such marl;- ing may result from localized pressure or impact, for example, the scratch of a stylus or the stroke of a typewriter key. When the record material has previously been exposed to a light image, marking may be in response to uniform pressure applied over the entire surface of the record material, as in calendering operation. The color reaction, in either case, is of the well known coupling type to form an azo dye, the fundamental reaction being expressed as follows:

where RN X represents a diazonium salt (X- an acid radical), and RN=NR'OH represents the dye. In this reaction, coupling is believed to occur through the agency of the diazonium ion. Coupling is obtained in an a kaline medium with aromatic amines and with phenols, occurring in the para position of the ring. thro derivatives may also result if the para position is occupied. If a very active d-iazon-ium compound is used, coupling may be obtained by modified couplers (e.g., phenolic ether and compounds containing activated methylene groups). Coupling occurs quite rapidly upon application of pressure to the record material to release the isolated component, and produces a mark of distinctive color.

Referring again to FIGURE 1, application of pressure in the region 50 will bring about a dye-forming or coupling reaction due to rupture of the microcapsules 14 to release the encapsulated component (or components). Marking can likewise be accomplished in each of the other modifications (FIGURES 2 to 4), by a similar application of pressure to break or crush the microcapsules. Due to the light sensitivity of the diazonium salt component, it is also possible to prevent marking at a particular point of pressure application, by means of a prior exposure to light. Thus, in FIGURE 5, the region 52 represents an area which has been previously exposed to light, whereas the arrows 59 signify the application of pressure over the entire surface of the recorded material. In the regions 56 marking will occur as before due to rupture of the miorocapsules 34 to permit coupling reaction between the separated components of the microcapsules and the coating 32. However in the region 52, no marking will occur due to the prior decomposition of the diazonium salt component, which renders the intermixed components incapable of coupling to form a dye.

The microcapsules employed in the record materials of the present invention consist of an aqueous or other polar solvent solution of one or more of the components for dye formation as a core, and a polymerized material, encapsulating such solution and forming an outer protective shell. Any suitable hydrophobic polymer having desired characteristics for encapsulation purposes may be employed. Preferred polymers are those which possess excellent chemical and water resistance and dimensional stability, which are heat stable, and which retain suitable flexibility and toughness upon variation in temperature. Examples of suitable polymers include those ba ed on cellulose, such as ethyl cellulose, cellulose nitrate, cellulose acetate-butyrate and other mixed and higher esters of cellulose. Polystyrene and polystryene copolymers (hydrophobic) can also be satisfactorily employed, likewise vinyl acetate-vinyl chloride copolymers, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polybutene, polyisobutylene, and natural and synthetic rubbers, polyvinyl fluoride, polyesters such as styrenated polyesters, resins such as alkyd resins and blends of these polymers and resins. Ethyl cellulose is particularly satisfactory because of its extensive compatibility, its stability to light, and its resistance to heat and chemical action by acids and bases.

The formation of the solution filled rnicrocapsules, and the depositing of a profusion of such microcapsules on a sheet of base material, can be accomplished in a number or": different ways. One suitable procedure is disclosed in the copending Reyes application Serial No. 11,341, filed February 25, 1969. This procedure involves the dispersing of a polar solution of a component for dye formation in a continuous phase solution of a polymer followed by the addition of a nonsolvent for the polymer to cause its precipitation about colloidal droplets of this solution to produce microcapsules. Also disclosed is the step of coating with the microcapsules by spray drying onto a substrate. Another suitable procedure is disclosed in copending Hull and Marshall application, Serial No. 39,150, filed lune 27, 1960. The procedure of this application involves a freeze hardening technique by which the solution filled polymeric microcapsules can be readily insolubilized and separated from the continuous phase liquid for deposit on the substrate. A further procedure, disclosed in copending Reyes application, Serial No. 11,286, filed February 26, E1960, involves a solvent hardening technique whereby a gradual insolubilization of the polymer (by successive washing with solvent-uonsolvent mixtures decreasing in the amount of solvent), is obtained. The last two procedures produce a profusion of isolated microcapsules in the form of a fine powder, which is dry to the touch, although the powder may actually comprise as much as of aqueous or other dye-containing solution. This powder may be applied to the substrate separately, or as part of a diazo coating, by any one of a number of well known techniques.

The following examples are illustrative of the practice of the invention:

Example 1 The following solution is prepared, in parts by weight:

1.0 of borax 1.4 of trisodium phosphate 25.0 of polyethylene glycol 460 72.6 of water The solution is emulsified in 400 parts of 5% ethyl cellulose in xylene-carbon tetrachloride (1:1 by weight). A finely divided solidified castor oil derivative (Thixcin R,) is used as emulsifying agent in the proportion of 1% on the weight of the aqueous solution. The emulsion is diluted with carbon tetrachloride to 2 /2 with respect to ethyl cellulose. Upon slowly adding petroleum ether (65- C.) with stirring, ethyl cellulose is gradually precipitated, trapping and encapsulating the droplets of the aqueous solution. The microcapsule suspension obtained is cooled to 15 C. with simultaneous agitation, and allowed to settle. The equilibrium liquid is decanted and the wet capsules suspended in a -1:2 mixture (-by volume) of carbon tetrachloride and petroleum ether (65-110 C.). The resulting suspension is sprayed on paper or film along with a current of Warm air (3080 C.) to form a coating.

A De Vil'bis fog-type spray gun with No. 30 nozzle, and operated at 40 to 50 p.s.i., can be used for these coatings. When the coatings are deposited on plain paper, they can be used to print by pressure on (e.g., develop) diazo papers which contain both components of the azo dye, the diazonium salt and the coupler in one layer. Such use would be similar to that described in connection with FIGURE 4. When the coatings are made by spraying the capsule suspension directly on a diazo paper, which contains the diazonium salt and the coupler in one layer, a self-developing diazo paper results, as in FIGURE 3.

Example 2 Powder-like capsules are also obtained by spray drying Inicrocapsule suspensions, obtained as in Example 1, in a Nerco-Niro Spray Dryer (portable model). The resulting powder-like microcapsules can be dispersed in -a coating medium, containing the other two components of the diazo process, and coated in a single operation to give a self-developing diazo paper of the type illustrated in FIG- URE 1. In a specific instance, a dispersion of the microcapsules in 4% polyisobutylene is mixed with an emulsion of a solution of the other two components (the diazonium salt and the coupler) in the same polymer, and coated on plain paper to give the self-developing diazo paper containing all components in one layer, as in FIGURE 1.

Example 3 A solution is prepared having the following composition in parts by Weight:

0.8 of phlorogl-ucinol dihydrate 6.0 of sodium acetate trihydrate 6.0 of urea 4.0 of ethylene glycol 0.1 of sodium hydroxide 83.1 of water The solution is emulsified in :1 16 /370 solution of polystyrene in xylene, employing 1.0% of weight of sorbitan sesquioleate (eg. Arlacel C), as an emulsifying agent. The weight ratio of polar solution to polystyrene is 4:1. The emulsion is treated with a petroleum solvent (e.g. solvent A) to precipitate the polymer around the internal phase. The solvent is added very slowly, with agitation, to achieve a gradual precipitation. At the first appearance of graininess in the emulsion, addition of nonsolvent is stopped. The emulsion is now cooled with agitation to 15 C. and the resulting mic-rocapsule dispersion sprayed on paper or film, along with a current of warm air.

The coatings obtained mark Well on a paper containing a diazonium salt or they can be employed in a manifold as in FIGURE 4. The microcapsules can also be isolated as a dry powder by spray drying. A dispersion of these powder-like microcapsules in a coating medium, when coated on a diazonium' paper which contains only the diazonium compound, gives a self-developing diazo paper as in FIGURE 3. When coatings of microcapsu-les, prepared by spraying the capsule suspension on a substrate, are subsequently sprayed with a solution of a diazom'um salt, a self-developing diazo paper of the type illustrated in FIGURE 2 is produced.

Example 4 A polar solution is prepared having the following composition in parts by weight:

1.5 of 4-dimethyl-aminobenzene diazoniurn chloridezinc chloride double salt 1.0 of Zinc chloride 2.0 of citric acid 2.0 of thiourea 93.5 of water This solution is dispersed in a 5% solution of ethyl cellulose in toluene. The ethyl cellulose can comprise -a 48% ethoxyl polymer (e.g. Hercules N-). The Weight ratio of aqueous solution to polymer in the disper sion is 5:1, 1% by weight of sorbitan sesquioleate (Arlacel C), being used as emulsifying agent. Upon the slow addition of petroleum ether (65110 C), the polymer is precipitated about the dispersed aqueous solution to form a profusion of the tiny polymeric microcapsules (0.5 to 5 microns). After stirring and cooling to about 15 C., the microcapsules are separated from the equilibrium liquid by decantation and are hardened by gradual and progressive insolubilization of the ethyl cellulose, by washing with petroleum ether containing decreasing amounts of toluene. The hardened microcapsules are separated from the final wash mixture by filtration and dispersed in a coating medium comprising an emulsion of an alkaline solution of a napthol coupler, and the coating medium applied to paper. Upon drying, the resulting dry paper (which is of the type illustrated in FIGURE 1) can be imprinted by application of a pressure image to rupture of the microcapsules, causing release or" the diazoniurn salt at the point of the pressure application.

Example 5 A polar solution is prepared in parts by weight as follows:

2.0 of p-diazodimethylaniline-zinc chloride double salt 77.0 of ethylene glycol 5.0 of citric acid 14.0 of water 2.0 of nonionic ethofat 60/ 15 (to aid in emulsification) This solution is encapsulated in ethyl cellulose employing the procedure of Example 1, in Weight ratio of 4:1. The microcapsules are separated from the equilibrium liquid by decantation and are suspended in an amount of mineral oil containing petroleum ether (B.P. 65-110 C.) and xylene just sufficient to cover the microcapsules. The ratio of petroleum ether to xylene is 3:2. The xylene and petroleum ether are gradually removed from the suspension by evaporation under reduced pressure (e.-g., 20 of Hg) in a Rinco evaporator. Polymeric microcapsules remain suspended in the mineral oil as tiny aggregates and isolated units. These aggregates and units oan be employed to produce light and pressure sensitive papers, as in either Example 1 or Example 2.

Example 6 A mixture of two parts by weight of 2 /2% sodium silicate in water and 1 part of polyethylene glycol (mol. wt. 400) is emulsified in a 5% solution of ethyl cellulose in a mixture of xylene and carbon tetrachloride (1:1 by weight). A finely divided, solidified castor oil derivative (Thixcin R) is used as emulsifying agent in an amount comprising 1% by weight of the polar solution. The weight ratio of polar solution to polymer is 5:1. The emulsion :is diluted with carbon tetrachloride to 2%% with respect to ethyl cellulose. By slowly adding petroleum ether (65-110 C.), While stirring, the ethyl cellulose is caused to precipitate and encapsulate the sodium silicate solution. Thereafter the microcapsule suspension is gradually cooled to 15 C. and allowed to settle. The equilibrium liquid is decanted and the microcapsules suspended in a quantity of petroleum ether-carbon tetrachloride mixture (2:1 by weight) just sufficient to cover them. An equal volume of mineral oil is now added, with stirring. The volatile solvents are removed gradually by evaporation under reduced pressure (e.-g. 20 mm. of Hg) in a Rinco evaporator.

By this procedure, small aggregates of ethyl cellulose microcapsules, suspended in mineral oil, are obtained. These microcapsules are filtered from the oil, washed with petroleum ether (3560 C.) and, alternatively, transferred to an indiiierent dispersion medium {or coating, or

allowed to dry. The powder-like capsules produce a mark When ruptured in contact with a diazo paper, which contains the diazonium salt and the coupler in one layer, as in FIGURE 4.

We claim:

1. In a dry method for forming a smudge-proof relatively permanent image by means of the diazo process, the steps of coating a substrate with a combination of ingredients reactive to form a diazo dye in an alkaline medium, said ingredients including a diazonium salt decomposable upon exposure to light to prevent its entering into the dye-forming reaction, a chemical coupler and a material to adjust pH to render said medium alkaline, at least one and no more than two of said ingredients being normally isolated by containment in aqueous solution in a profusion of hydrophobic rupturable microcapsules; applying pressure to a selected portion of said substrate to rupture the microcapsules contained within that portion to cause admixture of all three of said ingredients in aqueous medium to develop an image; and then exposing at least the portion of said substrate to which pressure has not been applied to light to decompose only the residual diazonium salt and fix said image.

2, The method of claim 1 in which said microcapsules are formed of a hydrophobic polymeric material.

3. In a dry method for forming a smudge-proof relatively permanent image by means of the diazo process, the steps of coating a substrate with a combination of ingredients reactive to form a diazo dye in an alkaline medium, said ingredients including a diazonium salt decomposable upon exposure to light to prevent its entering into the dye-forming reaction, a chemical coupler and a material to adjust pH to render said medium alkaline, at least one and no more than two of said ingredients being normally isolated by containment in aqueous solution in a pro'fiusion of hydrophobic rupturable microcapsules; exposing a selected portion of said substrate to light to decompose the diazonium salt contained within that portion and render it incapable of reacting with said coupler to form a dye; and then applying pressure to the entire surface of said substrate to rupture the microca-psules and develop a fixed image by reaction of the residual diazonium salt with said coupler in an aqueous alkaline medium.

4. The method of claim 2 in which said microcapsules are formed of a hydrophobic polymeric material.

References Cited in the file of this patent UNITED STATES PATENTS 2,299,694 Green Oct. 20, 1942 2,600,996 Land June 17, 1952 2,627,459 Land Feb. 3, 1953 2,634,677 Klimkowski Apr. 14, 1953 2,800,077 Marron July 23, 1957 2,802,735 Land Aug. 13, 1957 2,846,309 Land Aug. 5, 1953 2,939,009 Tien May 31, 1960 3,001,873 Foris Sept. 26, 1961 3,016,308 Macaulay Jan. 9, 1962 FOREIGN PATENTS 215,524 Australia Aug. 8, 957

1,041,980 Germany Oct. 30, 1958

Claims (1)

1. IN A DRY METHOD FOR FORMING A SMUDGE-PROOF RELATIVELY PERMANENT IMAGE BY MEANS OF THE DIAZO PROCESS, THE STEPS OF COATING A SUBSTRATE WITH A COMBINATION OF INGREDIENTS REACTIVE TO FORM A DIAZON DYE IN AN ALKALINE MEDIUM, SAID INGREDIENTS INCLUDING A DIAZONIUM SALT DECOMPOSABLE UPON EXPOSURE TO LIGHT TO PREVENT ITS ENTERING INTO THE DYE-FORMING REACTION, A CHEMICAL COUPLER AND A MATERIAL TO ADJUST PH OT RENDER SAID MEDIUM ALKALINE, AT LEAST ONE AND NO MORE THAN TWO OF SAID INGREDIENTS BEING NORMALLY ISOLATED BY CONTAINMENT IN AQUEOUS SOLUTION IN A PROFUSION OF HYDROPHOBIC RUPTURABLE MICROCAPSULES; APPLYING PRESSURE TO A SELECTED PORTION OF SAID SUBSTRATE TO RUPTURE THE MICROCAPSULSES CONTAINED WITHIN THAT PORTION TO CAUSE ADMIXTURE OF ALL THREE OF SAID INGREDIENTS IN AQUEOUS MEDIUM TO DEVELOP AN IMAGE; AND THEN EXPOSING AT LEAST THE PORTION OF SAID SUBSTRATE TO WHICH PRESSURE HAS BEEN APPLIED TO LIGHT TO DECOMPOSE ONL THE RESIDUAL DIAZONIUM SALT AND FIX SAID IMAGE.

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