US3527163A - Silk screen master - Google Patents

Description

I United States Patent [1113,527,163

[72] Inventor Lloyd F. Bean 2,898,279 8/1959 Metcalfe et a1. 101/128.3UX Rochester, New York 2,949,848 8/1960 Mott 101/1283 [21] AppLNo. 634,268 2,860,576 11/1958 Short..... 101/1283 [22] Filed April 27, 1967 3,226,227 12/1965 Wolff 96/364 [45] Patented Sept' 1970 Primar Eraminer-Ed arS Burr [73] Assignee Xerox Corporation y g Rocheser, New Ynrk Attorney James J. Ralabate a corporation of New York [54] SILK SCREEN MASTER 6 Claims, 11 Drawing Figs.

[52] US. Cl 101/1284, 101/129,101/127,96/36.4,117/35.5 [51] lnt.Cl B41c 1/14 [50] Field ofSearch 101/114, 127,1282,128.3,128.4,1Z9;96/36.4;117/35.5, 17.5, 21; 118/620, 624

[56.] References Cited UNITED STATES PATENTS 3,097,594 7/1963 Bankhead [OI/128.4

ABSTRACT: The subject matter of this application pertains to a method of preparing a stencil master utilizing xerographic techniques. A xerographic toner image is transferred to the surface of a screen substrate the interstitial spaces of which have been filled with a resinous filler material. The filler and toner material are selected such that each is soluble in a different solvent. Following fusing of the toner image to the screen the resinous tiller material is selectively removed to produce a stencil master. The image sense of the screen may be reversed by applying a second material which will fill the pores of the screen in the non-image areas and then subsequently removing the toner image with a solvent which will not effect the second filler resin.

Patented ,Sept. 8, 1970 3,527,163

Sheet 1 of 2 3 2 I D IXQXUXOXOXOX XXXIXOXOk'XI I O F/GZ/ FIG. 3

1X xr-gg INVENTOR. $1.1m) F. BEAN ATTORNEYS Patented Sept. 8,1970 3,527,163

Sheet 2- of 2 INVENTOR. LLGYD F. BE

BY 15M ATTORNEYS SILK SCREEN MASTER BACKGROUND OF THE INVENTION This invention relates to a duplicating system, and more specifically, to a stencil duplicating system.

At the present time various techniques are utilized for producing stencils or stencil duplicating systems. One such technique involves the cutting of a wax impregnated, porous, tissue paper. The cut stencil permits passage of aqueous ink directly from a reservoir of ink to the final copy through the cut openings. Similar processes have been envoked whereby a silk screen is prepared having a design attached thereto either by manually applying a pattern thereto or by photographically controlled gelatin layers. The masked screen is then used to control the flow of ink, paint, varnish or the like from an applicator to the paper or other final support.

More particularly, the photographic processes used create a reproduction of the original in a tacky powder form. The softened powder image is pressed against a coated donor sheet and upon separation the powdered image removes portions of the coating from the coated donor sheet which correspond to the original copy. The remaining coating on the donor sheet is then transferred to a tissue or silk screen base and the base carrying the coating may be used as the master in the stencil duplicating or the silk screen duplicating process. Although this process eliminates the disadvantages encountered during the manual preparations mentioned above, such as typing, drawing, cutting and the like, the photographic system is encumbered by other inherent problems such as the requirement of long exposure times, multiple transfers and especially prepared intermediate transfer sheets and, in addition, the process is limited as to the sense of the final image that can be reproduced. In addition, stencils may be prepared by photochemical techniques, however, they too have certain disadvantages, generally requiring the use of high contrast photographic positives during stencil preparation, in conjunction with contact exposure.

It is, therefore, an object of this invention to provide a sten' cil duplicating system which will overcome the above noted disadvantages.

It is a further object of this invention to provide a novel method of preparing a stencil duplicating master.

It is still a further object of this invention to provide a means of using a novel stencil duplicating master.

Yet, still a further object of this invention is to provide a novel technique of preparing a stencil, silk screen master through the use ofxerography.

Another object ofthis invention is to provide a means for preparing a stencil master by a system whereby the original may be reproduced in either a positivetopositive or a positive-to-negative mode.

An additional object of this invention is to provide a method of preparing a stencil master utilizing a single transfer process.

Yet, still an additional object of this invention is to provide a means of preparing a stencil, silk screen master without requiring long exposure times and especially prepared intermediate substrates.

SUMMARY OF THE INVENTION The foregoing objects and others are accomplished in accordance with the present invention, generally speaking, by transferring the powder particles utilized to develop an electrostatic latent image of the original copy to the surface of a silk screen support which has been precoated with a resinous filler material so as to fill the interstices of the screen. The resulting resinous toner image is fused to the surface ofthe impregnated screen. The resinous filler and powder toner materials are selected such that each has a different solubility property. Following fusing of the toner image to the impregnated screen, the latter support is selectively treated with a solvent which will dissolve and thus effectively remove the resinous filler material while not affecting the toner image, thereby opening the interstitial spaces of the screen in those areas not protected by the toner image to produce the stencil master. The image sense of the screen may be reversed by applying a second resinous filler material to the resulting stencil, thereby refilling the spaces in the now non-image areas and then removing the toner image with a selective solvent which will not attack the second resin filler. Utilizing either approach, it is thus possible to reproduce a copy of the original in either a positive-to-negative or positive-to-positive mode.

BRIEF DESCRIPTION OF DRAWINGS The invention is further illustrated in the following drawings wherein:

FIG. 1 is a side sectional view of the resin impregnated silk screen support of the present invention;

FIG. 2 is a side sectional view of the silk screen support of FIG. I with a toner image on the surface thereof;

FIG. 3 is a side sectional view of the silk screen support of FIG. 2 following fusing ofthe toner image and removal of the resinous filler;

FIG. 4 represents a frontal view of the stencil of FIG. 3;

FIG. 5 represents the application ofink to the stencil master of FIG. 3;

FIG. 6 illustrates the printing of the silk screen master of FIG. 5;

FIG. 7 represents the further process of refilling the interstices ofthe imaged silk screen master of FIG. 3:

FIG. 8 illustrates the reverse master of FIG. 3;

FIG. 9 illustrates a frontal view of the stencil master of FIG.

FIG. 10 illustrates the application of ink to the master of FIG. 8', and

FIG. 11 illustrates the printing of the stencil master of FIG.

DETAILED DESCRIPTION OF DRAWINGS Referring now to FIG. I, there is seen a silk screen support generally designated 1 consisting of a mesh screen 2 impregnated with a resinous filler material 3, such as Staybelite, a thermoplastic ester resin made from hydrogenated wood rosin. For purposes of the present illustration, utilizing the procedures disclosed in US. Pat. No. 2,297,691, an electrostatic latent image of the original copy is reproduced and developed and the resulting resinous toner particles transferred to the surface of the silk screen support as is illustrated in FIG. 2. The toner particles 5 are then fixed to the surface of the silk screen support 1. Any suitable fixing technique may be employed such as the application of heat or by subjecting the imaged silk screen to a solvent vapor system in which the toner particles are rendered tacky. Following the development of the powder image on the surface of the silk screen support, the resinous filler material 3 is dissolved out of the interstices of the silk screen 2 so as to produce a silk screen stencil master as is illustrated in FIG. 3. The fused toner particles 5 serve as a mask in those areas where present. FIG. 4 represents a frontal view of the imaged silk screen master of FIG. 3.

FIGS. 5 and 6 represent the utilization of the stencil of the present invention. In FIG. 5 the silk screen master is placed in contact with copy sheet 7 and an ink applicator 8 drawn across the surface of the stencil. The ink 9 is forced through the screen 2 in the areas void of the toner particles and prints an image on the surface of the copy sheet 7 as is illustrated upon the separation of the silk screen master from the copy sheet in FIG. 6.

FIG. 7 illustrates the further process of the present invention whereby following the preparation ofa silk screen master of FIG. 3 the voided interstitial spaces ofthe screen are again filled with a resinous material 11, such as gelatin, so as to once again occlude the pores of the screen. Following the application of the second resinous composition, the toner image is selectively removed with a solvent, the latter being effective to remove only the resinous toner particles without disturbing the resinous filler material. The resulting silk screen stencil which is represented in FIG. 8 will now print a duplicate of the original copy. FIG. 9 represents a frontal view of the positiveto-positive stencil master shown in FIG. 8.

The use of the positive-to-positive stencil is demonstrated in FIGS. 10 and 11 wherein an ink applicator 12 is drawn across the surface of the stencil master of FIG. 8, thereby forcing ink 13 down through the interstitial spaces of the screen, in those areas void of the resinous fiber, to be deposited on the copy sheet 14. Upon removal of the silk screen stencil as in FIG. 11 the resulting printed image 13a is represented on the copy sheet 14.

The application of the process of the present invention hinges on the use of specific materials which have different solubility properties. The resinous filler material initially used in the system must have a solubility different from that ofthe resinous toner particles utilized as the masking material. Similarly, the resinous material utilized with that aspect of the invention which reverses the image sense of the screen must also have a solubility property different from that of the resinous toner material. With this in mind, any suitable resinous material may be used as the filler in order to carry out the process of the present invention. Typical resinous materials include: Staybelite, a thermoplastic resin prepared from hydrogenated wood rosin and commercially available from Hercules Powder Co.; Piccotex and Piccolastic resins, thermoplastic polystyrene resins commercially available from the Pennsylvania Industrial Chemical Corporation; Piccopale resins, thermoplastic hydrocarbon resins produced by the polymerization of unsaturates derived from the deep cracking of petroleum, also available from the Pennsylvania Industrial Chemical Corporation; Piccolite, a hydrocarbon thermoplastic terpene resin, also commercially available from the Pennsylvania Industrial Chemical Corporation. When utilized, these filler resins may be used in conjunction with chlorinated solvents, long chain alcohols, and mineral oil among others. Other resinous filler materials may be utilized such as gelatin, polyvinyl alcohol, methyl cellulose, carboxy methyl cellulose, hydroxy ethyl cellulose, carboxyethylhydroxyethyl cellulose and the like. These resinous materials may be removed utilizing water based solvents.

Various xerographic developer materials have been found to work' well in the present invention. Such materials are available under the tradename Xerox and are sold as developer" or toner" by Xerox Corporation of Rochester, New York. Typical resinous materials utilized comprise polystyrene copolymers and phenol formaldehyde resins, the latter commercially available from Rohm and Haas Co. Other suitable developer compositions are described in U.S. Pat. Nos. 3,079,342; 2,788,288; 2,659,670; 2,618,552; 2,618,551 and Reissue U.S. Pat. No. 25,136. Other developers and toners generally known in the art have also been found to work well with this invention. Aromatic solvents such as naphtha, acetone and toluene have been found to successfully selectively remove the toner mask without effecting the particular resinous filler being used.

The resinous toner particles used during the course of the present invention generally range in size from about 7 to about 14 microns. However, the size of the particles have not been found to be critical and, therefore, the process of the present invention is not limited to this particular size range. The screen utilized is of conventional silk screen material such as stainless steel, nylon and Orlon. The mesh of the screen utilized generally ranges from about 65 to about 380 with a range of from about 310 to 340 producing optimum results. The resulting toner or powder image will generally be from about l-3 mils thick.

When vapor tackification is used to fix the toner image, the particular tackifying vapor will depend upon the nature of the image material or powder and the particular filler resin. Various solvent vapors which may be used are, for example, trichloroethylene; carbon tetrachloride; various chloromatic solvents; aromatic and aliphatic hydrocarbons such as benzene, toluene; oxygenated solvents such as ethanol,

acetone, ethyl acetate; and other alcohols, ketones. esters, and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS To further define the specifics of the present invention the following examples are intended to illustrate and not limit the particulars of the present system. The parts and percentages are by weight unless otherwise indicated. The examples are also intended to illustrate various preferred embodiments of the present invention.

EXAMPLE] A 325 x 325 mesh silk screen is filled by flOWlli;.; u Staybelite resin slurry heated to a temperature of about 65C. across the surface of the screen. The resulting impregnated screen is cooled to room temperature. An electrostatic latent image of the original is developed using conventional xerographic principles and the resulting toner image consisting of a resinous polystyrene copolymer transferred in imagewise configuration to the surface of the impregnated silk screen. The screen is then brought to a temperature of about 300F. so as to fix the toner image to the surface thereof. Following fusing of the toner image, the Staybelite resin is removed from the in terstices of the silk screen by washing the screen in a dilute solution of isopropanol for about one to two minutes. Following removal of the resinous filler material the resulting silk screen stencil is contacted with a copy sheet and ink forced through the pores of the screen by an ink applicator. The resulting print demonstrates the use of the silk screen stencil for printing purposes.

EXAMPLE [I The process of Example I is repeated with the exception that a Piccolastic A50 polystyrene resin is used in place of the Staybelite. The remaining steps of the process are the same.

EXAMPLE III A silk screen stencil produced according to the process of Example I is flow coated with a gelatin solution. Following solidification of the gelatin filler, the screen is immersed in naphtha solvent thereby dissolving away the original polystyrene toner image. This procedure demonstrates the technique of preparing a screen stencil wherein the image sense of the original master is reversed in order to produce a positive-to-positive print. Silk screen printing is then demonstrated by the application ofink by means of an ink applicator.

Although the present examples are specific in terms of conditions and materials used, any of the above listed typical materials may be substituted when suitable in the above examples with similar results. In addition to the steps used to prepare the silk screen stencil of the present invention, other steps or modifications may be used, if desirable. For example, the reversal silk screen master may be produced directly by removal of the toner image immediately thus eliminating the necessity of removing the initial filler resin from the interstices of the screen and thereby reducing the number of steps in the process. In addition, other materials may be incorporated in the resinous filler material, the toner resinous material, the solvents and inks which will enhance, synergize, or otherwise desirably affect the properties of these materials for their present use. For example, the durability and resistance of the masking material on the silk screen stencil may be increased by treatment with a hardening agent.

Iclaim:

1. .A method of preparing a stencil master comprising developing a resinous toner image on the surface of a screen support said support having its interstitial spaces occupied by resinous filler material, entirely removing said filler material with a solvent, refilling the interstitial spaces of said screen support unprotected by said toner image with a second resinous filler material so as to reverse the sense of said stencil master, and removing said toner image to produce said stencil master.

2. The process as defined in claim 1 wherein said second resinous filler comprises gelatin.

3. A method of preparing a silk screen stencil master comprising impregnating the interstitial spaces of a silk screen support with a resinous filler material, developing a resinous toner image mask on the surface of said impregnated silk screen support, fusing said toner image mask in situ, entirely removing said resinous filler, refilling the interstitial spaces of said silk screen support unprotected by said toner image mask with a second resinous filler material so as to reverse the sense of said stencil master, and selectively removing the originally formed toner image mask so as to produce said stencil master.

4. A method of preparing a silk screen stencil comprising impregnating the interstitial spaces of the silk screen support with a hydrogenated rosin ester, developing a powder image on the surface of said support said powder comprising a polystyrene copolymer, treating the surface of said imaged silk screen support with an isopropanol solvent thereby entirely washing the ester resin free from the interstitial spaces of said screen, refilling the voided interstitial spaces of said silk screen support unprotected by said powder image, and selectively removing the originally formed polystyrene powder image so as to form said stencil.

5. The process as defined in claim 4 wherein the step of refilling the voided spaces of said screen protected by said powder image comprises filling said spaces with a gelatin filler and the removing step comprises dissolving away the polystyrene powder image with a toluene solvent.

6. A method of stencil printing comprising:

a. impregnating the interstitial spaces of a silk screen support with a resinous filler material;

b. developing a resinous toner image on the surface of said impregnated silk screen support;

c. fusing said toner image in situ;

d. entirely removing said resinous filler material from said silk screen; refilling the interstitial spaces of said screen, unprotected by said toner image, with a second resinous filler material; f. selectively removing said toner image from said impregnated silk screen to produce said stencil master; g. contacting the surface of said stencil with a copy sheet;

and h. forcing ink through said stencil to form a screened image.

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