US3113866A

US3113866A - Photographic processes and compositions useful therein

Info

Publication number: US3113866A
Application number: US635501A
Authority: US
Inventors: Edwin H Land
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1957-01-22
Filing date: 1957-01-22
Publication date: 1963-12-10
Anticipated expiration: 1980-12-10
Also published as: BE551270A; GB837972A; US3249433A; FR1162197A

Description

Dec. 10, 1963 E. H. LAND 3,113,866

PHOTOGRAPHIC PROCESSES AND COMPOSITIONS USEFUL THEREIN Filed Jan. 22, 1957 2 Sheets-Sheet 1 Exl'ernal Phase Conlaining Aqueous Silver Halide Developer and Solvenl' Emulsion {Inlernal Phase Conlaininq Liquid 12 for lmpar'l'inq Viscosil'y Supporl Silver Halide Sl'ru'lum Confalninq Lulenl' Image Silver Precipil'al'ing S'l'rul'urn 2O----" Supporl' S'lrlpping and Drying FIG.

Silver Precipil'a'l'inq Sl'rul'um Conl'uining Visible Prin'l Exl'ernul Phase Conl'aining Coupling Developer Phol'osensilive Sl'rulum Con'lalninq Ferric or Dlazo Mcrl'eriul FIG. 2

v INVENTOR. BYWW 'mwm AT TOR NEYS Dec. 10, 1963 E. H. LAND 3,113,866

PHOTOGRAPl-IIOPROCESSES AND COMPOSITIONS USEFUL THEREIN Filed Jan. 22, 1957 2 Sheets-Sheet 2 Infernal Phase Conlaininq Organic Liquid Soluflon of Plasfic Shipping and Drying Plusfic Prolcci'iv: Cooling for Silver Prinl FIG. 3

Plusfic Prol'cclive Coqfinq for Prin'l v Formed from Ferric or Diuzo Mcl'erial FIG. 4

Ex'l'crnul Phase Con'lqining Aqueous Silver Halide Developer and Solvcn'l Foam Gas for Imparfing [In'l'crnul Phase Conl'oining Viscosi'ly IN V TOR.

@NMW M M AT TO R N E YS United States Patent 3,113,2966 PHGTOGRAPHEC PRQCESSES AND CUR 11 G51- TlONS USEFUL THEREHJ Edwin H. Land, Cambridge, Mass, assignor to lolaroid Corporation, Cambridge, Mass, a corporation of Delaware Filed Jan. 22, 1957, Ser. No. 6355591 17 (Ilalms. (til. 96-56) The present invention relates to photography and, more particularly, to the application of fluid photographic compositions in thin layers to photographic sheets.

The present application is a continuation-impart of applications Serial Nos. 299,358, filed luly 17, 1952; 500,073; filed April 8, 1955; and 346,014, filed March 31, 1953.

A variety of photographic processes may be performed by applying fluid compositions in thin layers to photographic sheets. For example, a print may be formed from a latent image when such a composition, containing a silver halide developer and a silver halide solvent, is spread between a silver halide stratum and a silver-recept-ive stratum in order to reduce exposed silver halide to silver, to form a complex silver salt from unreduced silver halide and to precipitate silver from the complex silver salt onto the silver-receptive stratum. Furthermore, a print formed in the foregoing Way may be Washed and protected when such a composition, containing water and a dispersed plastic, is applied thereto. These two exemplary processes are preferred embodiments of the wide variety of photographic processes herein contemplate The present invention contemplates such a composition which is characterized by dispersed liquid droplets or gaseous bubbles in order to effect a plurality of photographic functions by components which are physically isolated from each other in a novel Way. The liquid droplets provide, in the strict chemical-physical sense, an emulsion, i.e., a dispersion having an external phase and an internal phase, both of which are liquid. The gaseous bubbles provide, in the strict chemicahphysioal sense, a foam or a froth, i.e., a dispe sion having a liquid external phase and a gaseous internal phase. The term external phase is synonymous with such terms as dispersion medium" and dispersion phase. The term internal phase is synonymous with such terms as dispersed medium and dispersed phase. Here, as in the case of emulsions and foams in general, stable heterogeneous equilibrium between the external phase and the internal phase ordinarily requires the presence of one of the variety of materials known as emulsifying agents or foaming agents.

Emulsions and foams of the present invention have been found advantageous for various reasons. In the case of print-forming compositions of the foregoing type: since interference by the internal phase with the mobility of agents in the external phase is small, interference with the agents activity is minimized; the dispersion retains a constant viscosity; the dispersion possesses a low thermal coefficient of viscosity, i.e., retains substantially a predetermined viscosity throughout a wide temperature range; the wetting characteristics of the external phase are substantially unaffected by the internal phase; and the dispersion possesses W coefiicient of plasticity, i.e., flows immediately in response to applied forces. In the case of wash- Wee ing and protecting compositions of the foregoing type, the washing component, which preferably is aqueous, and the protecting component, which preferably is organic, can be thoroughly mixed although they are very incompatible, the organic protecting component being hydrophobic for the purpose of providing a Water-impervious coatin Accordingly, the primary objects of the present invention are: to provide photographic processes in which emulsions or foams are applied in thin layers to photographic strata, the emulsions and foams being of the type comprising a fluid external phase that performs a first photographic function and a fluid internal phase that performs a second photographic function, the external phase and the internal phase being initially isolated from each other; to provide photographic processes in which such emulsions and foams are applied in thin layers to silverrcceptive strata of the type employed in silver transfen reversal processes; and to provide compositions useful in the foregoing processes.

Other objects of the present invention are: to provide, as a novel photographic composition, an emulsion or foam of the type comprising a relativel fluid external phase including an aqueous solution of at least a photographic agent and a fluid internal phase for rendering the composition relatively viscous; and to provide a novel photographic process in which a photographic composition of the foregoing type is applied, in a thin layer, to a photo graphic sheet.

Further objects of the present invention are: to provide an emulsion, particularly useful in photography, which comprises an internal phase containing an aqueous solution of a first functional agent and an external phase containing an organic solution of a second functional agent; to provide a process for washing and protecting a photographic silver image by applying thereto an emulsion, which includes an aqueous internal phase and an external phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material, in order to wash residual processing agents from the image and to form an emulsion layer, and by drying the emulsion layer in order to fonrn a substantially water-impermeable protective coating for the image; to provide a process of the foregoing type in which the emulsion is applied by sWabb-ing the image with an absorbent applicator; to provide a process of the foregoing type in which the emulsion employed contains, in solution, in its internal phase, a protective agent which becomes dispersed throughout the protective coating which is fonmed when the emulsion dries; to provide a stabilizing composition for photographic silver images which cornprises an emulsion including an internal phase containing an aqueous solution of a protective agent and an external phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material; to provide a photographic product comprising a photographic silver image and a protective coating therefor composed of a hydrophobic organic plastic material in which is dispersed a protective agent; and to provide aprocessing composition and a photographic product of the foregoing types where in the protective agent is a salt which provides cations for capturing the sulfide unions of atmospheric sulfur compounds that have penetrated the coating in order to prevent their adversely afiecting the image.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the composition possessing the features, properties and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

Generally, the external phase of an emulsion or foam useful in a print-forming process of the present invention includes a relatively mobile aqueous solution of a photographic agent. This agent may be a developing agent for processing a photosensitive material that has been photoexposed or that is about to be photoexposed or may be a photosensitizing agent or a photosensitive material that is to be spread immediately before photoexposure is effected. Examples of suitable developing agents are silver reducers that difierentiate between exposed and unexposed photosensitive silver salts to form visible silver particles, couplers that differentiate between exposed and unexposed ferric salts to form visible reduction products, and couplersthat differentiate between exposed and unexposed diazonium compounds to form visible dyes. Where the photosensitive material to be processed is a silver salt, a silver complexing agent, as well as a silver reducer, may be incorporated in the external phase of the emulsion to effect silver transfer as well as silver reduction. Examples of suitable photosensitizing materials are optical sensitizers and hypersensitizers. Examples of suitable photosensitive materials are photosensitive heavy metal salts, including silver salts and ferric salts, and diazoniurn compounds.

Generally, the internal phase of the emulsion or foam includes a liquid such as an emulsifiable oil or gas, preferably inert, such as nitrogen substantially insoluble in the external phase for imparting a relatively high viscosity to the emulsion and, where desired, for performing additional functions. For example, where the dispersion is an emulsion, if the internal phase is nonvolatile or fixed, as compared with water, it dries slowly enough to prevent the emulsion from bonding together the contiguous sheets between which it has been spread even if they are not stripped apart for some time. On the other hand, if the internal phase is relatively volatile, it may be associated with a relatively volatile external phase to form an emulsion which leaves no harmful residue on drying. Furthermore, the internal phase may serve as a vehicle for a dissolved polymer which, after the external phase has produced a print, forms a protective coating.

Spreading of the emulsion or foam preferably is accomplished between a pair of sheets, the adjacent surfaces of one or both of which may be intended to participate in one or more photographic reactions. The sheets may be opaque so that photoexposure can occur only before spreading, and viewing only after stripping. Or one or both of the sheets may be transparent so that photoexposure may occur after spreading, and viewing without stripping. The internal phase for best results is contained in a quantity sufficient to impart to the emulsion or foam a viscosity of from 100 to 200,000 centipoises at a temperature of 20 C. This viscosity, which is high relative to that of the external phase itself, makes it possible to spread the emulsion uniformly and assures that it completely covers any area on which it is spread.

For a fuller understanding of the nature and objects of the invention, reference should be had to the followring detailed description taken in connection with the ac companying drawings wherein:

FIGURE 1 illustrates, in successive distorted sectional views, photographic materials being processed in accordance with the present invention and their product;

FIG. 2 illustrates, in distorted section, other photographic materials being processed in accordance with the present invention;

PEG. 3 illustrates, in successive distorted sectional views, further photographic materials being processed in accordance with the present invention and their product;

FIG. 4 illustrates, in distorted section, another product of a process performed in accordance with the present invention; and

FIG. 5 illustrates, in distorted section, still other photographic materials being processed in accordance with the present invention.

FIG. 1 illustrates a processing emulsion 10 spread between the superposed surfaces of a photosensitive sheet 12 and a print-receptive sheet 14. Photosensitive sheet 12 includes a support 16 and a silver halide stratum 18. Print-receptive sheet 14 includes a support 20 and a silver precipitating stratum 22. Processing emulsion 10 includes an external phase containing an alkaline aqueous solution of a silver halide developer and a silver halide solvent, and an internal phase containing a hydrophobic organic polymer. The internal phase is magnitied for clarity in relation to the thickness of the layer of emulsion. Silver halide stratum 18 may be photoexposed either before or after processing emulsion 10 is spread. Once stratum 18 is photoexposed and emulsion is spread, the external phase of emulsion 10 re duces silver halide to silver in stratum 18 and reacts with unreduced silver halide to form a complex silver salt which diffuses through the layer of emulsion to stratum 22 where it is reduced to silver to form a positive print. Thereafter, sheet 12, together with the layer of emulsion in, is stripped from sheet 14 to render the positive print available for use. Alternatively, as disclosed in copending application Serial N0. 466,889, filed on November 4, 1954, now U.S. Patent No. 2,861,885, in the name of Edwin H. Land, where the covering power of silver in stratum 22 is much greater than the covering power of silver in stratum 18, the composite print, which includes both the negative of stratum 1'8 and the positive of stratum Z2, is useful without stripping. In the latter case, the layer of emulsion 10 is dried to form a firm bond between the sheets.

Preferably, stratum 18 contains a photosensitive silver halide emulsion in which one or more of the silver halides, e.g., silver chloride, silver bromide and silver iodide, are dispersed in a suitable colloid material such as gelatin, casein, collodion, a cellulose ester, a polyvinyl alcohol, or a linear polyamide. Examples of specific formulations of conventional emulsions of the foregoing type are described in T. T. Baker, Photographic Emulsion Technique, American Photographic Publishing Company, Boston, 1948, Chapter IV.

Preferably silver precipitating stratum 22 is thin relative to silver halide stratum l8 and provides one of the vigorous silver precipitating environments described in Patents Nos. 2,698,237 and 2,698,245, issued to Edwin H. Land on December 28, 1954. Such an environment includes silver precipitating nuclei such as the metal sulfides and selenides, the colloidal noble metals, or organic thio compounds dispersed in a macroscopically continuous vehicle comprising minute, preferably colloidal, particles of a water-soluble, inorganic, preferably siliceous, material such as silica aerogel. The positive print is formed in this stratum from fine silver particles concentrated primarily at its surface. Only a minute amount of silver in this condition is necessary for image formation because of its extremely high covering power.

Supports

16 and 20 are composed of a paper at least one surface of which has been sized with a suitable material such as hardened gelatin or baryta in plastic. Alternatively, the supports are composed of a plastic mate rial which may be transparent, for example cellulose nitrate, or an organic cellulose ester such as cellulose acetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate or cellulose acetate butyrate. The interface between support 16 and stratum 18 in the latter case, in order to assure good adhesion, is treated, for example, with a mixture of gelatin and cellulose nitrate.

Developers of one type suitable for dissolution in the external phase of emulsion are benzene derivatives having at least two hydroxyl and/or amino groups substituted in ortho or para position on the benzene nucleus. Examples of such developers are hydroquinone, amidol, metol, glycin, p-aminophenol and pyrogallol. Developers of another type suitable for dissolution in the external phase are hydroxylamines, in particular primary and secondary aliphatic and aromatic N-substituted or fl-hydroxylamines which are soluble in aqueous alkali. Examples of such developers are hydroxylamine, N-methyl hydroxylamine, N-ethyl hydroxylamine, and others described in application Serial No. 470,802, filed November 23, 1954, in the name of Land et al., now US. Patent No. 2,857,276. Examples of silver halide solvents useful as solutes in the external phase of processing emulsion 10 are conventional fixing agents such as sodium thiosulfate, sodium thiocyanate, ammonium thiosulfate, ammonia and others described in the aforementioned Patent No. 2,543,181, and associations of cyclic imides and nitrogenous bases such as associations of barbiturates or uracils and ammonia or amines, and other associations described in application Serial No. 378,684, filed September 4, 1953, in the name of Land et al., now US. Patent No. 2,857,274.

Examples of organic liquids suitable for the internal phase of emulsion 10 are oils and the like including straight chain saturated hydrocarbons such as n-octane, branch chain saturated hydrocarbons such as isooctane, cyclic hydrocarbons such as cyclooctane, pe roleums such as kerosene, aliphatic ethers such as di-n-butyl ether, aromatic ethers such as diphenyl ether, alkyl halides such as n-butyl bromide, halogen carbon compounds such as carbon tetrachloride, high boiling amines such as n-hexyl amine, and aromatic hydrocarbons such as toluene, xylene, cumene, cyrnene, and naphthalene.

Examples of emulsifying agents for maintaining the external and internal phases of processing emulsion 10 in heterogeneous equilibrium are: lyophilic alkali-inert carbon compounds including long chain carbon corn pounds with polar groups such as sodium, potassium and ammonium salts of the higher fatty acids; synthetic detergents such as the higher paraifln chain sulfates, sulfonates, sulfonic acids, quaternary ammonium and pyridinium salts; and hydrophilic amorphous materials such as gums including gum arabic, proteins including gelatin and polymers including carboxymethyl cellulose.

The emulsion may be carried by a container which, when deformed by opposed compressional forces, is capable of releasing its contents through a rupturable mouth. Such a container, as disclosed in the aforementioned U.S. Letters Patent No. 2,543,181, is constructed from a blank of three-ply sheet material having a single fold. The outer ply, serving as a backing or support, is composed of a thin, relatively inexpensive, tough material, preferably a paper such as kraft paper. The intermediate ply is composed of a substantially vapor-, liquid-impervious material, for example a metal foil such as silver or lead. The inner ply is composed of a suitable thermoplastic or thermosetting plastic material, for example, a polyvinyl acetal such as polyvinyl butyral or polyvinyl formal, which protects the container contents from contamination. A composition comprising by weight approximately 60% to 70% polyvinyl butyral, approximately to 23% of nitrocellulose and approximately 5% dibutyl sebacate is particularly satisfactory. At opposite end portions of each container, the two folds of the inner ply are sealed to each other as by the application of heat and pressure. Those sections of the two folds defining the mouth are bonded together by a strip of adhesive which is so constituted that the adhesive forces between the strip and the inner ply are less than the cohesive forces between end portions of the inner ply that are sealed together. A

satisfactory strip may be composed, for example, of ethyl cellulose or a mixture of ethyl cellulose and paraflin, the mixture including at least by weight of ethyl cellulose. Since the bonding forces between those sections defining the month are less than the bonding forces between the other sections of the container, the application of opposed compressional forces to the container causes discharge of its contents through its mouth.

Example I In a specific example of the foregoing process, silver halide stratum 3.8 is a moderately high speed gelatino iodobromide emulsion, silver-receptive stratum 22 is 1 to 8 microns thick and contains lead sulfide dispersed in a siliceous vehicle, and processing emulsion 10 is formulated by dissolving the following materials:

G. Sodium sulfite 78.0 Sodium hydroxide 54.6 Sodium thiosulfate 14.5 Hydroquinone 52.0

in the external phase of: Mineral oil in water emulsion sold by Squibb under the trade name Mineral Oil Emulsion 1860.0

Another print was produced as in Example I with an emulsion of the following formulation:

Water g 1860.0 Turpentine cc 100.0 Sodium carboxymethyl cellulose g 50.0 Sodium sulfite g 78.0 Sodium hydroxide g 54.6 Sodium thiosulfate g 14.5 Hydroquinone g 52.0

It is to be understood that processing emulsion 10 need not effect silver transfer reversal but rather may merely develop the latent image in silver halide stratum 13. In this case, sheet 14 is not provided with a silver precipitating stratum 22. and serves merely to confine the emulsion during spreading and, where desired, to separate it from stratum 18 during stripping.

KG. 2 illustrates a processing emulsion 24 spread upon the face of a print-receptive sheet 26 with the aid of an auxiliary sheet 23 that serves merely to confine the emulsion during spreading and to separate it from sheet 26 during stripping. The internal phase is magnified for clarity in relation to the thickness of the layer of emulsion. Sheet 26 includes a support 30 and a print-receptive stratum 32. Emulsion 24, like emulsion 10, comprises an organic liquid in water. Support 30 and support 28 are composed of materials mentioned above in connection with

supports

16 and 20.

in one form, print-receptive stratum 32 contains, as a photosensitive material, a ferric salt or a diazonium compound, and processing emulsion 24 contains, as a solute in its external phase, a coupler that appropriately differentiates between exposed and unexposed ferric salt to form a visible reduction product or between. exposed and unexposed diazonium compound to form a visible dye.

Suitable photosensitive ferric salts, for example, are ferric chloride, and ferric salts of organic acids such as ferric oxalate, ferric tartrate and ferric citrate. Suitable couplers for such ferric salts, for example, are potassium ferricyanide, potassium ferrocyanide, the tannins, B- naphthaquinone sulfonic acid, and silver, platinum and palladium salts. Examples of specific formulations of conventional ferric and ferrous photosensitive and processing materials are described in Baker, supra, pages 268- 275.

Suitable diazonium compounds, for example, are prepared by treating aromatic amines with nitrous acid at low temperatures. Suitable couplers for such diazonium compounds are phenols, naphthols and amino compounds that combine with exposed or unexposed diazoninm compounds to form visibly distinguishable azo dyes. Examples of specific formulations of conventional diazonium photosensitive and processing materials are given in Baker, supra, pages 277-278, in L. P. Clerc, Photography, Theory and Practice, Pitman, New York, 1937, page 444, and in J. S. Friedman, History of Color Photography, American Publishing Company, Boston, 1944, pages 487-493.

In another form, print-receptive stratum 32 is merely a vehicle for the reception of a photosensitive material from emulsion 24. Such an emulsion is useful, for example, where it is desired to form a photosensitive stratum immediately before it is photoexposed. Here the emulsion contains, as a solute in its external phase, a ferric salt or a diazonium compound of the types referred to above. Here, print-receptive stratum 32 is composed of a suitable colloid material adapted to imbibe the external phase of emulsion 10. Or the print-receptive stratum may be omitted if support So is composed of a paper, the surface of which is adapted to absorb the external phase of the emulsion.

In a further form, print-receptive stratum 32 contains a photosensitive silver salt, for example one or more of the silver halides, and emulsion 2'4 contains, as a solute in its external phase, a silver salt hypersensitizer or optical sensitizer. For example, Where the photosensitive matetrial is a conventional gelatino silver halide dispersion, the external phase, in one form, contains an optical sensitizer such as a dye in extremely weak concentration. Suitable dyes include derivatives of fiuorescein such as erythrosine and eosin, and various cyanines such as thiazole, thiazoline, pyridine, benzoxazole, benzoselenazole, 3,3-dimethyl indolenine, n-aphtho (2,1) thiazole and naphtho (1,2) thiazole. Further examples of specific formulations of conventional optical sensitizing compositions suitable for use in an emulsion of the foregoing type are described in Baker, supra, Chapter IV.

Also, where the photosensitive material is a conventional gelatino silver halide dispersion, the external phase, in one form, contains a hypersensitizing composition. Such a hypersensitizing composition, for example, includes any one of ammonia, a thiourea such as palmityl thiourea or styrene fumaryl allyl thiourea, allyl isocyanate, thiazole, quinolene and pyridine. Further examples of specific formulations of conventional hypersensitizing compositions suitable for such use are more fully described in Baker, supra, Chapter XV.

Alternatively, print-receptive stratum 32 is composed of a material capable, after being treated with a suitable dichromate solution, of becoming differentially insolubilized or canned when pho-toexposed. The various regions of such a differentially insoluble coating are capable of forming a visible print by ditferentially absorbing a suitable color material. Here, print-receptive stratum 32, for example, is a hydrophilic colloid material such as gelatin, glue or gum 'anabic and emulsion 24 contains,

as a solute, in its external phase, a dichromate such as chrome alum, potassium dichromate or ammonium dichromate. Examples of specific formulations of conventional dichromate materials suitable for such use are described in Clerc, supra, pages 434437 and page 419, Section 645.

As already noted, the internal phase of an emulsion of the present invention may perform functions in addition to determining overall viscosity.

For example, the internal phase, if volatile, after the emulsion is spread and dried, leaves no residue on the silver, ferric and diazo prints formed in the abovedescribed processes. Such an internal phase preferably is at least as volatile as water. An internal phase of this type, however, is particularly important in the production of silver transfer-reversal images in accordance with the process described in connection with FIG. 1. Thus, where the silver halide devloper and silver halide solvent of the external phase and the organic liquid of the internal phase are for the most part volatile, they leave no permanently harmful residue on the resulting print. For this purpose, suitable silver halide developers are low molecular weight hydroxyl-amines, suitable solvents are associations of cyclic imides and low molecular weight amines, and suitable organic liquids are low molecular weight aliphatic and aromatic hydrocarbons and alcohols. Here, all constituents of the emulsion are volatile with the exception of the cyclic imides which we rendered harmless upon evaporation of their associated amines.

Alternatively, the internal phase of the emulsion of the present invention, if nonvolatile or fixed by comparison with water, functions to permit the sheets to be stripped apart after remaining in superposition for a period during which ordinarily they would have become laminated together. In the process of 'FIG. 1, for example, ordinarily

sheets

12 and 14 are stripped apart approximately 1 minute after emulsion ft is spread between them. Where the concentrations in stratum 18 and developer and solvent in emulsion '10 are limited, it is possible to obtain prints of high quality in stratum 22 although

sheets

12 and 14 remain in superposition for prolonged periods of time. As has been indicated, where the covering power of the silver precipitated in stratum 22 is considerably greater than the covering power of silver reduccd in stratum 18, the two strata may be kept in contact so that their positive and negative together serve as a useful composite print. Under certain circumstances, however, it is desirable to strip the two strata apart after they have been superposed for a prolonged period. In the absence of an organic liquid internal phase having slow drying or nondrying characteristics, the aqueous solution of the external phase permeates into sheets 12 and 1d and upon drying bonds them together. Although the external phase may volatilize, the internal phase, if slow drying or nondrying, remains as a stripping layer between the sheets to permit their separation at the end of periods greatly in excess of one minute. Where, for example, the internal phase contains a high boiling hydrocarbon such as kerosene, sepanation may occur for example in excess of a half hour after spreading.

The internal phase, in another form, is illustrated in FIG. 3 in connection with photosensitive and printcreceptive sheets of the type shown in FIG. 1. The internal phase is magnified for clarity in relation to the thickness of the layer of emulsion. Here, the emulsion,

' designated by '34, includes an external phase of the type described in connection with FIG. 1 and an internal phase containing an organic liquid solution of a polymer. After the emulsion is spread and the external phase performs its silver developing and dissolving functions, the polymer forms a protective coating 36 for the print formed in the silver-receptive stratum. Of course, the polymer dissolved in the internal phase of such an emulsion is designed to form a protective coating 38, as shown in FIG. 4, for a print formed in a photosensitive stratum containing ferric or diazo materials as shown in FIG. 2.

Examples of the wide variety of hydrophobic organic solvents to be employed in this form of the invention are: aromatic hydrocarbons such as xylene, cume-ne, cymene, ethyl and diethyl benzene and aromatic aliphatic hydrocarbon mixtures such as those obtained from petroleum fractionation. Preferably, Ithese hydrophobic organic solvents have boiling points ranging from to 200 C.

by reason of which they are, in general, quick drying but not so volatile as to preclude their convenient storage for prolonged periods. Examples of the wide variety of hydrophobic plastic materials to be employed in this form of the invention are phenol formaldehydes such as those sold by Rohrn & Haas under the trade name Amberol, maleic rosins such as those sold by Rohm & Haas under the trade name Amberlac, polystyrenes such as those sold by Dow under the name PS3, paraffin wax, ethyl celluloses such as those sold by Hercules under the trade name Ethocel, hydrogenated rosin esters such as those sold by Hercules under the trade name Staybelite, coumarone indene resins such as those sold by Neville under the trade name Nevindene," polymerized rosin esters such as those sold by Hercules under the trade name Poly-Pale and acrylic resins such as those sold by Rohm & Haas under the trade name Acryloid.

FIG. illustrates a processing foam 4e spread between the superposed surfaces of a photosensitive sheet 12 and a print-receptive sheet 14. Photosensitive sheet 12 and print-receptive sheet 14, as in PEG. 1, include a silver halide stratum l3 and a silver precipitating stratum 22, respectively. Processing foam 4d: includes an external phase containing, as does the external phase of FIG. 1, an alkaline aqueous solution of a silver halide developer and a silver halide solvent, and an internal phase containing nitrogen or another gas or mixture of gases substantially insoluble in the external phase. The internal phase is magnified for clarity in relation to the thickness of the layer of foam.

Examples of foaming agents for maintaining the external and internal phases of processing foam '4'? in heterogeneous equilibrium are: fatty acids and fatty acid derivatives such as oleic acid and sodium oleate; saponins such as saponin; and hydrophilic amorphous materials such as gums including gum arabic, and proteins including gelatin.

A photographic silver transfer-reversal print of the type above described ordinarily retains at least traces of the photographic reagents with which it has been processed and the continued presence of which may adversely affect its stability. For example, many oxidized developers tend to oxidize silver and thus to cause the shadows of the image to fade. Or, silver may be oxidized by traces of such processing agents as sodium thiosulfate. Also, silver may be oxidized by such agents as hydrogen sulfide often present in the atmosphere. Furthermore, traces of unexhaustcd developer, if oxidized by atmospheric oxygen, color the highlights of the image.

Generally, an emulsion useful in a Washing and protecting process of the present invention comprises an aqueous internal phase and an external phase containing a hydrophobic organic liquid solution of a dissolved hydrophobic plastic material. The internal phase unexpectedly has been found to be capable of washing residual processing reagents from a silver transfer-reversal image of the foregoing type. The hydrophobic plastic material, preferably, is so constituted as to form, when the emulsion is dried, a protective coating of the following character: impermeable to water; unaffected by fingerprints; stable throughout a wide temperature range; substantially unaffected by solar radiation; optically clear; and nontacky. Additionally, in accordance with the present invention, the protective coating preferably contains an agent capable of protecting the image by reacting with atmospheric oxidizing agents which have penetrated the protective coating before they reach the image. It has been found that such an agent, if dissolved in the aqueous internal phase, becomes dispersed in the protective coating which is formed when the emulsion dries. Both the emulsion and the protective coating above described are, in general, extremely stable.

Preferably, the emulsion is applied to one face of the image by means of an absorbent applicator, composed,

for example, of flannel, cotton batting or cellulose sponge, which is charged with the emulsion. When the face of the image is swabbed with such an applicator, residual reagents in the image are dissolved in the aqueous in ternal phase and, for the most part, transferred into the applicator and the image becomes coated with a thin layer of the emulsion. A smooth layer may be obtained by moving the applicator in contact with the image first irregularly and then rectilinearly. The emulsion layer then is dried to form a protective coating of the above described character.

The laminated product of this process comprises, in sequence, a suitable support, a photographic silver image and a protective coating which, preferably, includes a dispersed protective agent. The process and composition of the present invention are particularly applicable to thin photographic silver images of the type described in the application of Edwin H. Land, Serial No. 302,746, filed August 5, 1952 for Method of Improving the Stabilization of Finished Photographic Prints by Applying a Liquid Composition Thereto (now Patent No. 2,719,791, issued October 4, r955).

Examples of the wide variety of hydrophobic organic solvents to be employed in accordance with the present invention are aromatic hydrocarbons, such as xylene, cumene, cymene, ethyl and diethyl benzene, and aromatic-aliphatic hydrocarbon mixtures such as those obtained from petroleum fractionation. Preferably, these hydrophobic organic solvents have boiling points ranging from to 200 C. by reason of which they are, in general, quick drying but not so volatile as to preclude their convenient storage for prolonged periods.

Examples of the wide variety of hydrophobic plastic materials to be employed in accordance with the present invention are phenol formaldehydes such as those sold by Rohm & Haas under the trade name Amberol, maleic rosins such as those sold by Rohm & Haas under the trade name Am-berlac, polystyrenes such as those sold by Dow under the trade name PS3, parafin wax, ethyl celluloses such as those sold by Hercules under the trade name Ethocel, hydrogenated rosin esters such as those sold by Hercules under the trade name Staybelite, coumarone indene resins such as those sold by Neville under the trade name Nevindene, polymerized rosin esters such as those sold by Hercules under the trade name Poly-Pale, and acrylic resins such as those sold by Rohm & Haas under the trade name Acryloid.

Preferably, the protective agents to be employed in accordance with the present invention are water-soluble salts which are capable of providing cations for capturing the sulfide ions of atom spher-ic sulfur compounds. These salts preferably are composed of: cations such as zinc, cadmium, cerium(ous), cobalt(ous), iron, lead, nickel, manganese, thorium and tin; and anions such as acetate, sulfate, nitrate, borate, chloride, formate, citrate and thionate. Since these salts, in small quantity, are substantially colorless and form substantially colorless sulfides, they and their sulfides do not affect the optical clarity of the protective coating.

The viscosity of the emulsion preferably ranges from 50 to 200 centipoises. This viscosity has been found to permit the emulsion to be controlled readily and yet to be spread easily.

The following nonlimiting examples further illustrate the present invention:

Example H] 0.4 liter of an aqueous 25% solution by weight of cadmium acetate was mixed with 1 liter of a solution prepared by dissolving 500 grams of Rhom & Haas Amberlac D96 in 1 liter of xylene. A stable emulsion was formed by passing the mixture through a Gaulin homogenizer.

Example IV 0.3 liter of an aqueous 20% solution by weight of zinc sulfate was mixed with 1 liter of a solution prepared by dissolving 400 grams of Rhom & Haas Amberol 800 in 1 liter of cymene. A stable emulsion was formed by passing the mixture through a Gaulin homogenizer.

Thus the present invention specifically provides: a novel technique for controlling the spreading of photographic compositions at the same time, if desired, for performing one or more additional functions: and a novel technique for removing residual processing reagents from photographic silver images and providing them with clear prot ctive coatings.

The term emulsion is herein employed in ti e strict sense in reference to a dispersion having an external phase and an internal phase both of which are liquid.

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

What is claimed is:

l. A photographic process for washing and protecting a photographic silver image having therein a residue of the water-soluble processing agents by which it was formed, said process comprising the steps (1) of applying to said image an emulsion, including a discontinuous liquid phase and a continuous liquid phase, said discontinuous phase being aqueous, said continuous phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material, in order to wash said residue from said image into said discontinuous phase and to form an emulsion layer on said image, and (2) of drying said emulsion layer in order to form a substantially water-impermeable protective coating for said image.

2. A photographic process for washing and protecting a photographic silver image having therein a residue of the Water-soluble processing agent by which it was was formed, said process comprising the steps (1) of swabbing said image with an absorbent applicator charged with an emulsion including a discontinuous liquid phase and a continuous liquid phase, said discontinuous phase being aqueous, said continuous phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material, in order to wash said residue from said image into said discontinuous phase and to form an emulsion layer on said image, and (2) of drying said emulsion layer in order to form a substantially water-int ermeable protective coating for said image.

3. A photographic process for washing and protecting a photographic silver image having therein a residue of the water-soluble processing agent by which it was formed, said processing agents including at least one or" the silver halide developers and solvents, said process comprising the steps (1) of applying to said image an emulsion, including a discontinuous liquid phase containing an aqueous solution of a protective water-soluble salt possessing cations reactive with the sulfide ions of atmospheric sulfur compounds and a continuous liquid phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material, in order to wash said residue from the image into said discontinuous phase and to form an emulsion layer on said image, and (2) of drying said emulsion lay-er in order to form a substantially water-impermeable protective coating for said image.

4. The process of claim 3 wherein said hydrophobic organic liquid has a boiling point ranging from 140 to 206 C. and is selected from the group consisting of aromatic hydrocarbons and aromatic-aliphatic hydrocarbon mixtures, and wherein said hydrophobic plastic material is a maleic rosin.

5. A laminated photographic product comprising, in sequence, a support, a photographic silver image and a protective coating having dispersed therein a protective agent, said protective coating containing a maleic rosin, said protective agent being a water-soluble salt composed of (l) a cation selected from the group consisting of cadmium, cerous, cobaltous, iron, lead, nickel, mangaese, thorium and tin, and (2) an anion selected from the group consisting of acetate sulfate, nitrate, borate, chloride, formate, citrate and thionate.

6. A laminated photographic product comprising, in sequence, a support, a photographic silver image and a protective coating having dispersed therein a protective Water soluble salt, said protective coating containing a maleic rosin, said salt possessing cations reactive with sulfide ions to prevent such sulfide ions from adversely ailecting said image.

7. A photographic process for washing and protecting a photographic silver image having therein a residue of the water-soluble processing agents by which it was formed, said process comprising the steps (1) of applying to said image an emulsion including a discontinuous liquid phase and a continuous liquid phase, said discontinuous phase containing an aqueous solution of a protective agent selected from the class consisting of Watersolubie salts possessing cations reactive with the sulfide ions of atmospheric sulfur compounds, in order to wash said residue from said image and to form an emulsion layer thereupon, said continuous phase containing the hydrophobic liquid organic solution of a hydrophobic plastic material, and (2) of drying said emulsion layer, in order to form a substantially water-impermeable protective coating for said image.

8. The process of claim 7 wherein said hydrophobic organic liquid has a boiling point ranging from 140 to 200 C. and is selected from the group consisting of aromatic hydrocarbons and aromatic aliphatic hydrocarbon mixtures.

9. The process of claim 3 wherein said hydrophobic plastic material is a maleic rosin.

10. A photographic process for washing and protecting a photographic silver image having therein a residue of the water-soluble processing agents by which it was formed, said process comprising the steps (1) of applying to'said image an emulsion including a discontinuous liquid phase and a continuous liquid phase, said discontinuous phase containing an aqueous solution of a protective agent selected from the class consisting of a water-soluble salt composed of a cation selection from the group consisting of cadmium, cerous, cobaltous, iron, lead, nickel, manganese, thorium and tin, and an anion selected from the group consisting of acetate, sulfate, nitrate, borate, chloride, formate, citrate and thionate, said salt serving to capture the sulfide ions of atmospheric sulfur compounds, in order to wash said residue from said image and to form an emulsion layer thereupon, said continuous phase containing a hydrophobic liquid organic solution of a maleic rosin, and (2) of drying said emulsion layer in order to form a substantially waterimpermeable protective coating for said image.

11. A composition comprising a dispersion including a discontinuous phase containing an aqueous solution of a Water-soluble salt possessing cations reactive with the sulfide ions of atmospheric sulphur compounds, and a continuous phase containing a hydrophobic organic liquid solution of a hydrophobic plastic material.

12. A photographic process comprising the step of spreading a photographic composition comprising an emulsion in a thin layer between a photosensitive stratum containing a photosensitive silver halide salt and a superposed second stratum, said emulsion including a continuous phase containing an aqueous solution of a silver halide optical sensitizing agent, said emulsion further including a discontinuous phase containing a hydrophobic organic liquid, said emulsion having relatively high viscosity and said continuous phase having relatively low viscosity.

13. A photographic process comprising the step of spreading a photographic composition comprising an emulsion in a thin layer between a photosensitive stratum containing a photosensitive silver halide salt and a superposed second stratum, said emulsion including a continuous phase containing an aqueous solution of a silver halide hypersensitizing agent, said emulsion further including a discontinuous phase containing a hydrophobic organic liquid, said emulsion having relatively high viscosity and said continuous phase having relatively low viscosity.

14. A composition comprising a dispersion including a continuous phase containing an aqueous solution of a silver halide optical sensitizer and a discontinuous phase containing a hydrophobic organic liquid which imparts increased viscosity to said composition.

15. The composition of claim 14 wherein a polymer is dissolved in said hydrophobic organic liquid.

16. A composition comprising a dispersion including a continuous phase containing an aqueous solution of a silver halide hypersensitizing agent and a discontinuous phase containing a hydrophobic organic liquid which imparts increased viscosity to said composition.

17. The composition of claim 16 wherein a polymer is dissolved in said hydrophobic organic liquid.

References Cited in the file of this patent UNITED STATES PATENTS 634,137 Hanneke Oct. 3, 1899 2,269,158 Martinez Jan. 6, 1942 2,322,027 Jelley et al. June 15, 1943 2,540,085 Baldsiefen Feb. 6, 1951 2,543,181 Land Feb. 27, 1951 2,754,279 Hall July 10, 1956 2,852,381 Minsk et al. Sept. 16, 1958 2,866,705 Land et al. Dec. 30, 1958 3,030,207 Land Apr. 17, 1962 FOREIGN PATENTS 167,781 Australia June 17, 1954 1,086,655 France Aug. 11, 1954 4,689 Great Britain Jan. 12, 1895 OTHER REFERENCES Clerc: Photographic Theory and Practice, Pitman, New York, 1954, pages 353 and 354.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,113,866 December 10, 1963 Edwin H Land It is hereby certified that error appears in the above numbered patent reqliring correction and that the said Letters Patent should read as corrected below.

Column 9, line 9, before "name" insert trade column 11, lines 38 and 52, for "agent" each occurrence, read agents Signed and sealed this 23rd day of June 1964.

(SEAL) Mtest:

ERNEST W. SWIDER EDWARD J. BRENNER testing Officer Commissioner of Patents

Claims

1. A PHOTOGRAPHIC PROCESS FOR WASHING AND PROTECTING A PHOTOGRAPHIC SILVER IMAGE HAVING THEREIN A RESIDUE OF THE WATER-SOLUBLE PROCESSING AGENTS BY WHICH IT WAS FORMED, SAID PROCESS COMPRISING THE STEPS (1) OF APPLYING TO SAID IMAGE AN EMULSION, INCLUDING A DISCONTINUOUS LIQUID PHASE AND A CONTINUOUS LIQUID PHASE, SAID DISCONTINUOUS PHASE BEING AQUEOUS, SAID CONTINUOUS PHASE CONTAINING A HYDROPHOBIC ORGANIC LIQUID SOLUTION OF A HYDROPHOBIC PLASTIC MATERIAL, IN ORDER TO WASH SAID RESIDUE FROM SAID IMAGE INTO SAID DISCONTINUOUS PHASE AND TO FORM AN EMULSION LAYER ON SAID IMAGE, AND (2) OF DRYING SAID EMULSION LAYER IN ORDER TO FORM A SUBSTANTIALLY WATER-IMPERMEABLE PROTECTIVE COATING FOR SAID IMAGE.