US3219445A - Photographic processes - Google Patents

Description

Nov. 23, 1965 J. E. LU VALLE ETAL 3,219,445

PHOTOGRAPHIC PROCESSES Filed April 9, 1962 PHOTOGRAPH IC SHEET SUPPORT B!NDER FREE PARTICULATE DEVELOPED PHOTOSENSITVE SILVER IMAGE SILVER HALIDE LAYER Z wE S ION ENHANCING EEQQ SUPPORT INVENTORS JAMES E. LUVALLE GERSHON M. GOLDBERG IGNATIUS E THEO U BY A TORNEYS United States Patent 3,219,445 PHOTOGRAPHIC PROCESSES James E. Ln Valle, Stony Brook, N.Y., and Gershon M.

Goldberg, Arlington, and ignatius E. Theodorou, Watertown, Mass, assignors, by mesne assignments, to Technical Operations, Incorporated, a corporation of Delaware Filed Apr. 9, 1962, Ser. No. 186,190 13 Claims. (Cl. 96-47) This invention relates to photography, and more particularly, to novel photographic transfer processes.

A number of photographic transfer processes are known and currently in use. Among the more important of such is the diffusion transfer process in which photosensitive sheet material bearing a silver halide emulsion is exposed to form a latent image. The image is developed with a processing composition, for example, an aqueous solution of a silver halide developer, a silver halide solvent, and an alkali. During development, the emulsion surface is maintained in superposed relationship with an imagereceiving surface or transfer sheet for a predetermined processing period. During this period, the exposed silver halide of the photosensitive material is reduced to silver, and the unreduced silver halide forms a watersoluble, complex silver salt which diffuses through the processing composition to the transfer sheet where, upon being reduced to silver, it forms a visible image.

In yet another process, similar to the diffusion transfer process, an exposed photosensitive sheet material is treated to form dye silver salts. The fully exposed areas of the treated photosensitive material are hardened in an activator but the unexposed areas are dyed to form the salts and do not harden. Hence, upon superposing the developed photosensitive sheet material with a transfer sheet, a dye silver salt is transferred to the latter to form a visible image.

An additional known transfer process is an electrostatic process, now known as xerography, which is based upon creation of an electrostatic image upon a photoconductive plate formed, for instance, of selenium. The plate is first given a uniform electrostatic charge and is then exposed to an optical image which destroys the charge selectively according to the intensity of the image portions. A powder, charged oppositely to the plate, is then dusted on the latter and is electrostatically bound wherever the appropriate charge is present. The powder image thus formed may be transferred to a receiving sheet, such as paper, as by pressure, and fixed to the surface of the latter, as by heating.

This latter process being based upon electrostatic phenomena, is not concerned with photosensitive silver salts, nor the transfer of silver images. The other transfer processes are based upon the photosensitivity of silver halides. But, both of these latter transfer processes require intermediate chemical processing to effect image transfer; in none is developed silver transferred directly. In the diffusion transfer process, the processing fluid itself acts as a medium for transferring silver complexes, and usually a special receiving sheet having silver precipitating nuclei is required to precipitate silver from the complex silver salts at the receiving sheet. On the other hand, the dye silver process requires the formation of special dye silver complex before transfer can be effected, and the transferred image is constituted of these dye complexes rather than simple silver.

Accordingly, a principal object of the present invention is to provide novel methods for producing photographic records. Particularly, the methods of the invention involve coherent images formed of developed silver particles on a substrate of silver halide and the mechanical transfer of such images from the substrate to a transfer material, thereby forming an essentially silver halide-free image upon the latter, while leaving the substrate substantially silver-free. The mechanical transfer is achieved through preferential adhesion of the developed silver images with the transfer material. Other objects of the present invention are to provide a transfer process of the type described wherein is employed a photosensitive sheet material formed as a binder-free, particulate silver halide stratum on an appropriate base material; to provide a transfer process of the type described wherein the silver halide stratum has been sensitized to provide either a direct positive or a negative; to provide a transfer process of the type described in which exposed silver halide is developable by either wet or dry processing compositions; and to provide a transfer process of the type described in which a developer composition is carried by a receiving sheet to which the developed silver image is transferable by adhesion.

Still other objects of the present invention are to provide novel processing sheets, novel receiving sheets, and novel coating compositions for protecting silver images, all adapted for use with the transfer process described. Yet other objects of the present invention are to provide novel transfer processes by which a single image or a plurality of successive images, either negative or positive in type, can be obtained from a single latent image by mechanical transfer of developed silver through adhesion.

Other objects of the present invention will in part be obvious and will in part appear hereafter. The invention, accordingly, comprises the method and compositions respectively comprising the steps and procedures, and combination of elements, which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in connection with the accompanying drawing in which is shown an exemplary embodiment of the invention.

The methods of the present invention preferably employ a photographic element such as photosensitive sheet material comprising a binder-free, particulate stratum of silver halide mounted upon an appropriate base material as shown in the drawing; particularly a silver halide deposited upon the base sheet in the form of an evaporated film as by vacuum deposition techniques. Among appropri ate base materials are baryta paper (paper coated with, for example, barium sulphate in gelatin): vitreous materials such as glass', cellulose esters, e.g., cellulose acetate, cellulose butyrate, cellulose propionate; synthetic polymeric resins such as Mylar (polyethylene terephthalate), polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer; and other polyesters, polyarnides and the like.

This base material may be transparent to radiation actinic to the silver halide, or opaque depending upon the desired form of the image to be obtained and the method of exposure to be used. The silver halide is in the form of a light-sensitive silver salt such as silver bromide, silver iodobromide, and others. Examples of photographic media of this type are disclosed in copending US. application, Serial No. 840,973 filed September 18, 1-959, now abandoned; US. Patent No. 1,970,496 issued July 19, 1960 to H. Mansfeld.

Media of this type have some pronounced advantages over gelatin emulsion films in that they are free from limitations imposed by the gelatin binder. In standard photographic emulsions, the silver halide is usually imbedded in a gelatin matrix. This limits the speed of the development process because the developer reagent generally must diffuse through the binder before it can react with the halide grains. Processing of ordinary emulsion film also involves fixation of the developed image by chemical removal of the undeveloped silver halide. Additionally, in developed emulsions, oxidation products are bound in the gelatin in the areas where development has taken place; this creates a loss in acutance. The separation of the halide grains and any subsequent developed silver by the emulsion adversely affects resolution. In the present invention, however, because there is no binder, diffusion by the developer reagent is no factor, and no extra reagent is necessary to provide gelatin saturation. In addition, the images produced by the present invention in some instances do not necessarily require fixation to remain substantially permanent with respect to actinic radiation. The lack of binder, of course, provides superior resolution and acutance in that developed silver grains may be contiguous and no organic oxidation can occur. Unlike a developed silver image in a gelatin matrix, the images formed in the preferred photographic media are formed of binder-free silver, and this permits the separation of the silver from the silver halide to be effected mechanically by adhesion rather than chemically.

Photosensitive sheet material of the type described may be exposed to actinic radiation to form a developable latent image in the silver halide stratum, as by contact printing, direct exposure to an optically formed image, by reflex printing, or the like. The latent image thus formed is developable by an alkaline silver halide developing solution containing a silver halide developing agent, with or without a silver halide solvent depending upon the variation of the process desired. Silver halide developing solutions such as Eastman Kodaks D-19 comprising an aqueous solution of p-methylaminophenol, sodium sulphite, hydroquinine, sodium carbonate and potassium bromide may be used. If it is desired to retard the speed of development, in view of the binder-free nature of the photosensitive stratum, it is preferred to dilute the D-19 by forming a solution of 70% thereof with 30% of a 5% gelatin solution. Another developing solution adapted for use in the present invention and preferred as a surface developer comprises:

p-Methylaminophenol Hydroquinone Sodium sulfite g 26.0 Sodium carbonate g 26.0 Potassium bromide g 0.67 Gelatin g 1.67 Water to make l 1 Other developing solutions may be used, typically, solutions containing developing agents such as hydroquinone derivatives, 1 phenyl-3 pyrazolidone, phenylhydrazine, phenylhydroxalamine and many others. Such developing solutions may be directly flushed onto the exposed silver halide stratum as in a bath, or may be sprayed on as a fine mist, or may be used by being absorbed in a carrier such as a sponge, blotter or the like, which is then applied to the silver halide stratum to release the developing agent.

The transfer process of the present invention is accomplished by placing the silver image of a developed photographic sheet of the preferred type in superposed relation with an appropriate transfer element or receiving sheet to create adhesion between the latter and the image as shown in the drawing. The term adhesion as used herein applies to the tendency of matter to cling to other matter through the interaction of strong molecular forces established by molecules that come into relatively intimate contact with one another. The term adhesion is intended to include adhesion of any nature, whether brought about because of the plasticity of a surface, the smoothness of a material, or the use of adhesives such as gums and glues or the like. Adhesion between the silver image and the superposed receiving sheet can be efiected merely by pressure and the selection of an appropriate transfer element which exhibits selective adhesion with respect to the silver, i.e., where adhesion forces are created between the receiving sheet and the silver which are greater than the adhesion forces between the silver and the silver halide. Such a receiving sheet also preferably exhibits substantially less adhesion with respect to the silver halide than the base material upon which the silver halide has been deposited, thereby insuring that the silver halide will not transfer. Where the base material of the photographic sheet would normally exhibit inherently poor adhesion with respect to silver halide deposited thereon, an adhesion enhancing layer or bonding layer of adhesive material may be deposited upon the receiving sheet to form a substrate for silver halide deposition thereon.

Because the forces of adhesion increase inversely as a function of distance, it is desirable to have the receiving sheet brought into very close contact with the silver image intended to be transferred thereto. The smoothness, i.e. the freedom from surface irregularities of the receiving sheet can contribute in this respect. Thus glass, polymeric materials such as polyethylene terephthalate, polyvinyl acetate, and the like, capable of being calendered, cast or ground into smooth sheets, are appropriate in this respect. Additionally, the adhesion characteristics of the receiving sheet may be enhanced, in some instances, by selecting a material for the receiving sheet which is capable of being softened slightly by the application thereto of heat. For instance, a sheet coated to provide a softenable surface can be prepared by coating a suitable sheet support with a gelatin-urea mixture, polyvinyl alcohol or the like. This softening, by changing the plasticity of the receiving sheet, allows the latter to deform minutely with respect to the silver grains of the image, and thus adapt its surface to conform to the shape of the silver grains, thereby increasing the adhesion between the surface of the sheet and the contacting surface of the grains.

Other transfer materials or receiving sheets exhibiting preferential adhesion for a developed silver image on a binder-free silver halide layer may also be employed. For instance, a sheet formed of a pressure-sensitive adhesive or having an adhesion enhancing coating thereof may be employed as shown in the drawing. Typical pressure-sensitive, adhesive-coated tapes or sheets are commercially available from Minnesota Mining and Manufacturing Company under the trade name of Scotch brand tapes, and from other manufacturers. The use of tapes of this type are described and claimed in the copending application of Lu Valle, Goldberg and Pack, filed on the same day as this application and assigned to the same assignee. A typical tape of this type can be formed of a flexible support such as cellophane, polystyrene, polyvinyl acetate, cellulose acetate, polyethylene glycol terephthalic acid film or the like, coated with an adhesive comprising an elastomer such as a natural rubber latex, a tackifier such as a coumarone-indene resin, and a filler such as zinc oxide, titanium dioxide or aluminum hydrate, with a stabilizer or antioxidant such as 2,6 ditertiary butyl-p-cresol if desired. A specific adhesive useful in the present invention and requiring no tackifier is one containing metal salts of esters of maleic anhydride-styrene copolymers. In the class of pressure-sensitive tapes can be included an appropriate support material of the type described coated with an adhesion enhancing layer of Eastman Kodak Companys 910 adhesive, which is polymerized by pressure to form a non-tacky surface. The use of this latter material as a transfer or receiving sheet allows the latter to be placed in superposition with the developed surface silver image on a binder-free halide layer, and when pressure is applied thereto substantially normal to the surface of a silver image, adhesion is effected between the receiving sheet and the silver while, at the same time, the adhesive polymerizes. Thus a silver image is transferred to the receiving sheet and fixed thereto simultaneously. Other receiving sheets can be made which will adhere and lift surface silver images, which receiving sheets are readily processed to fix the image. For example, a mixture of gelatin and sufiicient sorbitol to render the gelatin tacky can be coated on a sheet of subbed polyethylene terephthalate, polystyrene or the like. This provides a tacky coat which will readily adhere with a surface silver image and remove same from a binder-free layer of silver halide. After the image has been affixed thereto, this receiving sheet may be washed in water or alcohol to remove the sorbitol, thereby fixing the image in a substantially non-tacky matrix of gelatin. A similar sheet may be prepared with a coating of water-softenable silicate such as potassium silicate or the like; the transferred image to this type of sheet may be fixed by heat dehydration which transforms the silicate matrix into insoluble silicon oxides which are relatively permanent and non-tacky.

Following superposition which allows the silver image on the developed photosensitive sheet material to adhere to a receiving sheet, the latter is mechanically separated or stripped from the developed photosensitive sheet material. Thus a receiving sheet is obtained bearing an image comprising the large bulk of the developed silver in substantially silver halide-free form, while leaving the developed photosensitive sheet material substantially silver-free as shown in the drawing. Where the original photosensitive sheet material was developed to form a negative image, the silver transferred to the receiving sheet, of course, forms a negative image, leaving a positive image on the photosensitive sheet material in the form of undeveloped silver halide. This image can be brought out by fogging or other processing which substantially changes all of the residual silver halide to free silver, thereby creating a positive silver image on the original base material. For instance, the original silver halide can be re-exposed to light generally and then developed in a standard developer; or the silver halide can merely be flushed for suflicient time with a developer to cause fogging. Other methods are also known. Where the original photosensitive sheet material has been pretreated or sensitized to provide solarization upon development, processing of a developable latent image in such material will result in the formation of a direct silver positive. This latter, when transferred by adhesion to a receiving sheet, of course, forms a direct positive print on the transfer element.

Photosensitive sheet materials which comprise a binderfree, particulate layer of light sensitive silver halide are readily adapted for sensitization procedures which will provide solarization upon development of latent images formed therein. For instance, sensitization of such sheet materials may be accomplished by vacuum deposition thereon of a variety of substances in substantially elemental form, e.g. gold, selenium, tellurium, silver, sulphur, and many others, in a concentration of approximately 10 to 10 atoms of sensitizing material per square centimeter of the surface of the silver halide layer. The technique for accomplishing such solarization and the products achieved thereby are disclosed in detail in copending US. application, Serial No. 68,986, filed November 14, 1960, now abandoned, by Lu Valle et a1.

It is also possible, through the process of the present invention, to obtain a plurality of successive images from a single exposure of the preferred photosensitive sheet material having a binder-free, silver halide stratum. As has been described previously, after a latent image is formed in such a stratum, and the image is developed with a surface developer to form a silver image, application of a receiving sheet which will adhere to the image virtually completely removes the developed image from the surface of the stratum. If proper precaution is taken to prevent the residual silver halide stratum from being further exposed, redevelopment with a surface developer will again bring out another silver surface image on the stratum, which image, on subsequent transfer, yields a second permanent copy on another receiving sheet. If the silver halide layer is thick enough and the latent image extends therethrough, the process can be repeated several times to form a series of approximately identical images, each of which is transferable by adhesion. It has been found that a silver bromide layer in a binder-free form which is approximately one micron thick will yield as many as seven images in this manner.

Where it is desirable to protect the transferred silver image from mechanical damage, oxidation or the like, the silver image on the receiving sheet may be readily coated. Where, for instance, the support material of the receiving sheet is a polyethylene terephthalate based film, it is especially desirable to coat the developed image unless the latter has already been fixed by one of the methods heretofore disclosed. Among the coating solutions which may be used is one containing a polymeric resin such as a terpolymer of vinyl acetate, vinyl chloride and maleic acetate (commercially available as Derex 3098 from Dewey & Almy Co.) mixed with acetic acid, acetone and ethyl acetate solvent. Other known coating compositions can also be employed.

The invention, and various aspects thereof, is illustrated in more detail in the following specific examples:

Example 1 A latent image was recorded by exposure to light of a binder-free, particulate layer of AgBr on baryta paper. The image was developed by immersion of photographic material in an Elon-hydroquin-one-type developer and washed. A flat glass plate was coated with a layer of fluid sodium silicate, and the developed silver image was superposed with the silicate layer to form a sandwich. Pressure was applied to the latter to insure intimate contact through the surfaces of the entire silver image and the silicate layer. While under pressure, the sandwich was subject to heating at 25 C. for 1 hour to dehydrate the silicate layer. Following drying, the sandwich was immersed in warm water to soak and separate the paper backing. The paper was then peeled from the glass leaving the silver image embedded in the dehydrated silicate layer and the silver image Washed with a very dilute solution of acetic acid to remove any gelatin left from the baryta paper substrate.

Example 2 A very thin (less than 0.1 binder-free, particulate "layer of silver iodobromide Was formed by vacuum deposition on a sheet of polyethylene glycol terephthalate film and exposed to form a negative latent image thereon. The latent image was reduced to silver with a Dl9 type of developer solution and air dried. A sheet of cellophane coated with a pressure-sensitive adhesive (Scotch brand tape) was superposed under pressure with the silver image to form a sandwich and then stripped from the sandwich. The silver image, in coherent form, was essentially completely transferred to the cellophane sheet.

Example 3 A binder-free particulate layer of silver bromide was vacuum deposited upon a sheet support of polyethylene terephthalate and sensitized by substantially uniform deposit of a layer of elemental gold particles by vacuum deposition on the silver bromide layer in a concentration of gold of between 10 to 10 atoms per square centimeter of AgBr layer surface as taught in the aforesaid application of Lu Valle. The sensitized silver bromide layer Was then exposed to form a latent image which was developed by spray processing to form a surface silver image which was a direct positive. A receiving sheet was prepared by coating a glass sheet with a urea-gelatine mixture in 1 to 2 /2 proportion, and allowing the coating to dry overnight. The coated surface of the receiving sheet was placed in superposed relation with the surface of the silver image under pressure and the glass heated to 120 C. to soften the gelatin-urea mixture. After 1 minute, upon stripping the polyethylene terephthalate sheet from the glass and cooling, it was found that a coherent silver image had been transferred as a positive image to the glass support.

Example 4 A binder-free, photosensitive layer was formed as in Example 2 and exposed to form a negative latent image. The latent image was reduced to silver using a developer of the Elon-hyd-roquinone type substantially free from silver halide solvent. The image was transferred as in Example 2 leaving the polyethylene glycol terephthalate film with .substantially silver-free and silver halide-free areas. The residual silver halide on its support was redeveloped by immersion in D-19 developer solution for a time sufficient to reduce all of the residual silver halide to silver. The resulting positive silver image was then superposed with another receiving sheet coated with pressure-sensitive adhesive, and pressure was applied to provide intimate contact between the latter image and the latter receiving sheet. Upon stripping the halide support from the receiving sheet, it was found that the positive coherent silver image had been almost completely transferred to the receiving sheet.

Example 5 A photographic element was prepared by coating a polyethylene terephthalate sheet to a thickness of approximately 1 with a binder-free particulate layer of AgBr, and exposed to provide a latent image extending well through the thickness of the layer. The layer was spray developed with a silver halide solvent-free developer solu tion to provide a surface silver image. The latter was superposed with a gelatin-urea coated surface (7 parts to 3) of a very smooth baryta paper and subjected for 5 seconds to pressure of about pounds per square inch in the area including the contacted silver image. The baryta paper was stripped with silver image adhering thereto and the photographic element again spray processed to develop another surface silver image from the latent image. This silver image was transferred by adhesion to a pressure-sensitive adhesive surface of a second receiving sheet much as described in Example 2. The process was repeated to provide several separate images on individual receiving sheets.

To provide both adhesion and fixing, the receiving sheet may also be coated with a polymerizable substance incorporating a monomer which is polymerized during the development process as shown in the following example:

Example 6 A suitable support material is coated first with a mixture of 8% gelatin 50 g., calcium acrylate 4 g., calcium acetate 0.5 g., and 0.2 g. polyvinyl pyrrolidone and dried. The dried sheet is dipped into a solution of 2.5% p-aminophenol with pH adjusted to 10 with CaO just prior to use. On contact of the wet coated surface of the sheet with the latent image, the latter develops and polymerization of the acrylate occurs at the development sites. When the receiving sheet is then stripped after 5-10 minutes from the silver halide layer, it contains the developed silver image in a matrix of a substantially permanent polymer both the image and polymer having adhered to the receiving sheet.

It should be noted that in the use of this latter type of receiving sheet, development and transfer are accomplished with the use of a single receiving sheet which incorporates the developer.

Since certain changes may be made in the aforementioned process and products, without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic transfer process comprising the steps of: forming, by exposure, a developable latent image in a binder-free, particulate stratum of silver halide mounted on a base material; developing said latent image to form a silver image on the surface of said stratum; placing a receiving element and said silver image in such initimate contact with one another as to effect adhesion therebetween; separating said element with substantially all of said silver image adhering thereto-in substantially silver halide-free form from the undeveloped residual silver stratum on said base material; and reducing said residual silver halide stratum to silver so as to form a second image which is the reverse of the first mentioned silver image.

2. A photographic transfer process comprising the steps of: forming, by exposure, a latent image in a thin layer of binder-free, particulate silver halide mounted on a base material; said latent image being normally developable into a negative image; developing said latent image to form a negative silver image extending substantially through the thickness of said layer; placing a receiving element and said negative silver image in such intimate contact with one another that substantially all of said negative silver image is adhered to said element in preference to adhesion to both said base material and the undeveloped silver halide; removing substantially all of said negative silver image in substantially silver halide-free form by separating said receiving element from the undeveloped silver halide residue on said base material, leaving the latter with substantially silver and silver halide-free areas; and reducing said silver halide residue to silver to form a positive image upon said base material.

3. A photographic transfer process comprising the steps of: forming by exposure a developable latent image in a binder-free, particulate stratum of silver halide mounted on a support sheet; developing said latent image to form a silver image on the surface of said stratum; bringing said silver image into intimate contact with a layer of hydrated silicate on a receiving sheet, maintaining said image in said contact while heating said layer to dehydrate said silicate, and separating said receiving sheet with said silver image embedded in the dehydrated silicate from said support sheet.

4. A photographic transfer process comprising the steps of: forming by exposure a developable latent image in a binder-free particulate stratum of silver halide on a support sheet; superposing said stratum of said support sheet with a surface layer on a receiving sheet, said surface layer comprising a substance wetted with a developer solution and polymerizable during development of said latent image, maintaining said stratum and said layer in superposition for a time sufiicient to develop said latent image into a silver image and polymerize said substance at the development sites, and separating said receiving sheet with the silver image thereon imbedded in the polymer from the support sheet.

5. A photographic transfer process comprising the steps of forming by exposure a developable latent image in a binder-free particulate stratum of silver halide on a sup port sheet, developing said latent image to form a silver image on the surface of said stratum, superposing said silver image with a surface layer of a receiving sheet, said surface layer including a pressure-polymerizable substance, applying pressure to the superposed sheets to polymerize said substance, and separating said support sheet from said receiving sheet with the silver image adhered to the polymerized layer on the latter.

6. A photographic transfer process comprising the steps of forming by exposure a developable latent image in a binder-free particulate stratum of silver halide on a support sheet; developing said latent image to form a silver image on the surface of said stratum, superposing said silver image with a surface layer of a receiving sheet, said surface layer including a polymerizable substance, polymerizing said substance while said image and layer are in superposed relation and separating said support sheet from said receiving sheet with the silver image adhered to the polymerized layer on the latter.

7. In a process of forming a record image by means of a recording element having a stratum of vapor deposited silver halide microcrystals adhered directly to a substrate base and cohered directly with each other, by selectively reducing a portion of said silver halide to silver along the surface of said stratum to delineate a first record image, the improvement comprising the additional steps of selectively separating the silver and the residual silver halide portions from each other by physically removing one portion from said element, and reducing said residual silver halide to silver to form a second record image which is a reversal of said first record image.

8. In a process as set forth in claim 7, said selective separation being effected by contacting the surface of said stratum delineating said first record image with a layer of material having a greater adhesion than said element for said first record image silver and a lesser adhesion than said element for said residual silver halide, and separating said layer from said element with said first record image silver adhered thereto.

9. In a process as set forth in claim 8, said stratum of silver halide microcrystals having a thickness of a fraction of a micron.

10. In a process as set forth in claim 9, said thickness being about 0.1 micron.

11.. In a process as set forth in claim 7, said stratum of silver halide microcrystals having a thickness of a fraction of a micron.

12. In a process as set forth in claim 7, said stratum of silver halide microcrystals having a thickness of about 0.1 micron.

13. In a process of forming a record image by means of a recording element having a stratum of vapor deposited binder-free photosensitive silver halide microcrystals essentially continuous in phase and substantially covering a recording surface area, by selectively reducing a portion of said silver halide to silver along the surface of said stratum to delineate a first record image, the improvement comprising the additional steps of selectively separating the silver and the residual silver halide portions from each other by physically removing one portion from said element, and reducing said residual silver halide to silver to form a second record image Which is a reversal of said first record image.

References Cited by the Examiner UNITED STATES PATENTS 1,970,496 8/1934 De Boer et al. 96-94 2,596,754 5/ 19.52 Yackel 96-28 2,830,900 4/1958 'Land et al 9650 2,835,575 5/1958 Cowden et al. 96-28 2,956,877 10/1960 Land at al 9629 FOREIGN PATENTS 802,041 9/ 1958 Great Britain.

NORMAN G. TORCHIN, Primary Examiner,

Claims (1)

1. A PHOTOGRAPHIC TRANSFER PROCESS COMPRISING THE STEPS OF: FORMING, BY EXPOSURE, A DEVELOPABLE LATENT IMAGE IN A BINDER-FREE, PARTICULATE STRATUM OF SILVER HALIDE MOUNTED ON A BASE MATERIAL; DEVELOPING SAID LATENT IMAGE TO FORM A SILVER IMAGE ON THE SURFACE OF SAID STRATUM; PLACING A RECEIVING ELEMENT AND SAID SILVER IMAGE IN SUCH INTIMATE CONTACT WITH ONE ANOTHER AS TO EFFECT ADHESION THEREBETWEEN; SEPARATING SAID ELEMENT WITH SUBSTANTIALLY ALL OF SAID SILVER IMAGE ADHERING THERETO IN SUBSTANTIALLY SILVER HALIDE-FREE FORM FROM THE UNDEVELOPED RESIDUAL SILVER STRATUM ON SAID BASE MATERIAL; AND REDUCING SAID RESIDUAL SILVER HALIDE STRATUM TO SILVER SO AS TO FORM A SECOND IMAGE WHICH IS THE REVERSE OF THE FIRST MENTIONED SILVER IMAGE.

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