US2702244A

US2702244A - Photographic processes for producing prints by transfer

Info

Publication number: US2702244A
Application number: US301085A
Authority: US
Inventors: Edwin H Land
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1952-07-16
Filing date: 1952-07-16
Publication date: 1955-02-15
Anticipated expiration: 1972-02-15
Also published as: FR1088205A; DE959516C; BE521429A; NL87015C; GB739018A

Description

Feb. 15, 1955 E. H. LAND 2,702,244

PHOTOGRAPHIC PROCESSES FOR PRODUCING PRINTS BY TRANSFER Filed July 16, 1952 Supporjl' lOa Pho'fosensfiive Pho'fosensiiive lo Elemen+ lOb Emulsion Processing Silver Precipilcd'ing ComposH'ion Layer l6 l2 LPrini' Receiving Suppor+ IZca Elemeni' FIG. I

lNVENTOR BY Zowx/M ATTORNEYS United States Patent f PHOTOGRAPHIC PROCESSES FOR PRODUCING PRINTS BY TRANSFER Edwin H. Land, Cambridge, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Application July 16, 1952, Serial No. 301,085

7 Claims. (Cl. 9588) This invention relates to photographic products, compositions and processes, and more particularly to transfer processes which involve the development of a latent image in a silver halide emulsion and the transfer of components from said emulsion to another layer to effect the formation of a print of said latent image in said other layer, and to products and compositions useful in the performance of said processes.

It has been proposed to carry out transfer processes with a photosensitive element comprising a silver halide emulsion layer by distributing a processing composition in a thin layer over said element. This distribution of the processing liquid is preferably accomplished by spreading the liquid between the said photosensitive element and another element, the latter element preferably serving as a print-receiving element for a positive transfer print. However, the layerwise distribution may also be effected by doctoring, roll-coating or otherwise applying the processing composition directly to the surface of the photosensitive element or by distributing the processing liquid on or in the surface portion of another element which is thereafter brought into face-to-face engagement with the said photosensitive element. Processes of this type are characterized by the fact that the processing composition which is distributed layerwise constitutes the sole source of liquid for the processing operation and, when spread between the photosensitive element and another element, is essentially confined between the outer surfaces of said elements throughout the processing. The processing composition contains a developing agent or dissolves such an agent upon application to the photosensitive element, and, in order to render the developing agent operative to perform its developing function, the processing composition has a pH preferably in excess of 11.

The processing of a silver halide emulsion by means of a single layerwise application of a liquid processing composition and without recourse to the conventional liquid baths is obviously of great advantage, especially if the single processing operation will give a finished positive print that requires no subsequent liquid treatment. However, because the reagents in this type of processing are essentially confined to the sheet materials involved in the processing and cannot be washed out as they are when conventional baths are used, a highly alkaline environment is produced in the photosensitive and print-receiving elements, and this environment for most types of prints, if permitted to exist, tends to introduce several sources of instability which adversely afiect the pictorial quality of the print with time. The occurrences of these phenomena are reduced markedly if the alkalinity of the print-receiving element can be effectively diminished within a relatively short time after the formation of the transfer print therein.

It is an object of the present invention to provide an improved process for forming prints, by transfer, in the foregoing manner wherein a developing composition of relatively high alkalinity may be used during the print formation but which gives a finished transfer print whose ultimate alkalinity is low enough to substantially eliminate the possibility of the aforementioned print instabilities. This object is achieved by providing the processing composition with a volatile alkali capable of maintaining the alkalinity of the processing composition at the desired high level during the development of the latent image and the formation of the transfer print but which evaporates after the print-receiving element containing the posi- ICC tive print is stripped from the photosensitive element, thereby providing a sufficiently neutral environment within the transfer print to essentially avoid the instabilities which arise from the higher alkalinity. This process is especially effective when carried out with processing compositions which are contained, until just prior to use, in hermetically sealed containers, for example, of the general type illustrated and described in my Patent No. 2,543,181.

It is another object of the present invention to provide a novel photographic product comprising a single-use, disposable container carrying a highly alkaline processing composition, the product being capable of maintaining the a kalinity of said composition at a predetermined value for prolonged periods prior to use, the alkalinity of said composition diminishing, however, after it is dispensed and freely exposed to the atmosphere.

One class of alkalizing agents comprehended by the present invention are the amines whose one normal solution has a pH in excess of 10 and which are relatively volatile, having a boiling point of the order of C. or less. Examples of suitable amines are ammonia, diethylamine, triethylamine, diisopropylamine, allylamine and ethylamine. These are preferably used alone but may be used in mixture with less volatile and more conventional alkalis such as the alkali metal hydroxides. Although aliphatic amines having boiling points of the order above noted are preferred, it is evident that amines in general will be substantially more volatile and therefore more useful in this respect than conventional alkalis such as sodium hydroxide whose boiling point is of the order of 1400 C. Moreover, it is known that certain amines are capable of forming more volatile compounds, such as carbonates, when exposed to air and the usefulness of such amines will depend on the volatility of these reaction products.

The reduction in alkalinity of the print-receiving layer which results from the use of the volatile alkalizing components may be supplemented when the latter are used in mixture with the less volatile alkalis by the use of special acidifying agents of the general type disclosed in my Patent No. 2,584,030, issued January 29, 1952, for Light Sensitive Silver Halide Photographic Product for image Transfer and Process Utilizing the Same and in my copendmg application Serial No. 37,252, filed July 6, 1948, tor Photographic Product and Process, now Patent No. 2,635,048.

These and other obiects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product 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.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein: Figure l is a diagrammatic, enlarged, sectional view illustrating the association of elements during one stage of the performance of one form of the novel transfer process of the invention, the thicknesses of the various materials being exaggerated and not necessarily in correct relative proportion; and

Fig. 2 is a perspective view, with parts broken away, of one form of print-receiving element capable of carrying out the said process in conjunction with a photosensitive element, said print-receiving element having hermetically sealed containers mounted thereon for holding the novel processing composition.

The present invention comprehends improved processes, products and compositions of the type whereby a positive print may be obtained in a single step by suitably treating a silver halide emulsion containing a latent image with a uniformly applied layer of processing liquid. Preferably, the processing composition is in a viscous condition and is spread in a liquid film 14 (Fig. 1) between the photosensitive element 10 and a print-receiving element 12. The photosensitive element, as shown, comprises a support a and a silver halide emulsion 10b and the print-receiving element is preferably of a type suitable for receiving silver transfer prints and comprises a support 12a upon which is mounted a silver precipitating layer 16. In this form of the process, the liquid composition develops the latent image in the emulsion and forms a soluble silver complex with undeveloped silver halide. This soluble silver complex is at least in part transported in the direction of print-receiving element 12 and the silver thereof is largely precipitated in the silver precipitating layer 16 to form a positive image in silver.

It has been proposed to use in the silver precipitating layer certain compounds and elements whose presence during the transfer process has a desirable efiect on the amount and character of the silver precipitated dur1ng image formation. For this purpose, such materials as, for example, metallic sulfides and selenides, thiooxalates and thioacetamides have been disclosed in my copending applications Serial No. 727,385, filed February 8, 194 for Photographic Product and Process, Serial No. 7,795, filed February 12, 1948 for Photographic Process, now Patent No. 2,647,056, and Serial No. 164,908, filed May 29, 1950 for Photographic Silver Halide Transfer Product and Process. Other precipitating agents have been proposed, such as the colloidal metals and specifically colloidal silver. It is also desirable, as disclosed in the said copending applications, to provide, as the vehicle for the silver precipitating agents in layer 16, a macroscopically continuous film that consists of submacroscopic conglomerations of minute particles of a suitable water-insoluble, inorganic, preferably siliceous, material, such, for example, as silica gel. The use of such a vehicle for the precipitating agents tends to aggregate the silver that is precipitated into its most effective form for print making.

As noted hereinabove, the processing composition is preferably viscous and has dispersed therein, usually in solution, a sufficient amount of solid film-forming thickening agent for imparting thereto its desired viscosity. By suitably selecting the film-forming thickening agent and treating the surfaces of the print-receiving element and/ or the photosensitive element, it becomes possible to strip the essentially solid film, which is the residue of the processing composition, with either of said elements. In general, this residual film will adhere to the print-receiving element. However, there have been disclosed in my aforementioned copending application, Serial No. 7,795, various types of processing compositions and methods of treating the surfaces of the print-receiving element and/or the photosensitive element so that said residual film adheres to the photosensitive element as the latter is stripped from the print-receiving element.

It is also possible to dispense with the silver precipitating layer 16 as such and to provide suitable silver precipitating agents in the processing composition so that the silver is essentially precipitated in said composition. This may be accomplished, for example, in the manner disclosed in my copending application, Serial No. 88,832, filed April 21, 1949, for Photographic Transfer Processes and Products and Compositions for the Practice of Said Processes, now Patent No. 2,662,822. In the latter type of transfer process, it is preferable that the residual film, obtained from the processing composition and in which the transfer print is formed, adhere to support 120 as the latter is stripped from the photosensitive element 10.

To provide the desired control of the alkalinity of the print-receiving element, subsequent to the formation thereon of the transfer print, in accordance with the present invention, there is included as the alkali in the processing agent 14 a compound from the class consisting of the relatively volatile amines whose one normal solution has a pH in excess of 10 and whose boiling point is less than approximately 175 C. The amine is preferably water soluble. However, relatively Water-insoluble amines can be used if the processing composition has as at least a part of its solvent a material which dissolves said amine. Examples of satisfactory amines are ammonia, diethylamine, triethylamine, diisopropylamine, allylamine and ethylamine.

Referring again to Fig. 1, liquid layer 14 may be obtained by spreading the processing composition, for example, in a manner disclosed in my said copending application Serial No. 7,795. Preferably, the processing composition contains, in addition to the alkali, the silver halide developer and the material for forming the soluble silver complex with the undeveloped silver halide, i. e., a silver halide fixer. These materials are preferably in aqueous solution. It is to be understood, however, that the silver halide developer and/ or the silver halide fixer may be, in part or wholly, added to the processing composition as or after it is spread between

elements

10 and 12, said reagents being so located in or adjacent the surface of one or both of said elements as to be dissolved by or otherwise interacted with the liquid composition when the latter contacts said surface.

The liquid processing composition may be provided for spreading as a layer 14 between

elements

10 and 12 by being discharged from an elongated rupturable container 20 which, as shown in Fig. 2, has a length at least equal to the transverse dimension of the area of photosensitive element 10 to which the liquid processing agent is to be applied. Individual containers may be manually or mechanically fed between the print-receiving and the photosensitive elements by mechanism of the type shown in my Patents Nos. 2,435,718 and 2,543,180. One or more containers 20 may also be attached to one of

elements

10 or 12 and, in Fig. 2, two such containers are shown secured to the print-receiving surface of element 12, being spaced apart, lengthwise of said element, a distance equal at least to the length of a single frame of the photosensitive element 10. Said

elements

10 and 12 may be connected together so that they can be superposed with the container so positioned that it can release its contents in a film therebetween. The container 20 is preferably inexpensive and disposable and so constructed as to be capable of retaining the liquid processing agent or composition therein for relatively long periods of time without vapor loss or oxidation. One example of a suitable container of this type is formed from a single multilayer sheet of material comprising three laminae. The inner lamina, which provides the inner surface of the container, is formed of a material which is chemically inert to the reagents in the processing agent and which is impervious to the liquid of the agent. One material suitable for this purpose is polyethylene. The intermediate lamina is preferably impervious to the vapor of the processing agent and is formed, for example, of a metallic foil such as lead, aluminum or silver foil. The outer or backing lamina is formed of a strong, deformable, relatively inexpensive sheet material such as a kraft paper.

The container 20 is preferably formed by taking the single sheet of three-ply material and folding the same medially at 22, and thereafter securing the end marginal portions 24 and the longitudinal portions 26 of the two foldedfaces to one another, providing a central space or cavity 28 for containing the processing liquid. The seal provided at the longitudinal portions 26 is preferably weaker than the end seals, providing a liquid-discharging lip which substantially parallels the long dimension of the container.

To fill the container it is possible to adhere together the opposite longitudinally extending marginal portions 26 and one of the end marginal portions 24, the container beiilg1 filled through the other end, which is thereafter sea e Photosensitive element 10 may be any of the commercially available photosensitive silver halide films, the term films being understood to include paper-backed emulsions. The products of the present invention are particularly useful in improving the results obtained when the transfer process is carried out with one of the highspeed photosensitive silver halide emulsions such as the emulsion of the relatively high-speed orthochromatic films, e. g., Eastman Kodak Verichrome film, having an A. S. A. speed rating of 0200 and an A. S. A. exposure index rating in the daylight of 50, and the extremely high-speed panchromatic emulsions, e. g., Eastman Kodak Super XX Pan having an A. S. A. speed rating of 0400 and an A. S. A. exposure index rating in the daylight of 100, and Ansco Triple S Pan.

Element 12 may be formed by applying to a suitable support 12a, for example, of baryta paper, a coating of a suspension or sol of the silica containing the silver precipitating agent. This sol is permitted to dry and provides layer 16. The suspension of silica may be obtained by dispersing the silica, for example, in water, and then adding the silver precipitating agent either directly or by introducing into the sol salts whose reaction product is the precipitating agent. The sol may also be applied to the sheet without the silver precipitating agent, and the sheet with the layer of silica thereon may then be dipped in a solution or mixture of the silver precipitating agent to deposit the latter in said layer.

As noted hereinabove, it is possible to use the novel volatile alkali of the present invention in processing compositions which also contain other more conventional alkalizing agents, such as sodium or potassium hydroxide. In the preferred form of the invention, the relatively highly alkaline amines constitute the predominant alkalizing agents in the processing composition, i. e., they directly impart more than roughly two-thirds of the alkalinity of the composition. It is possible, however, to use lesser molar quantities of these materials in mixture with the other less volatile alkalis, in which case a somewhat lesser reduction in the alkalinity of the print-receiving element is obtained subsequent to print formation as a result of the evaporation of the volatile alkalizing agent, and it becomes desirable to supplement the acidification of the print-receiving element by the use of suitable acidifying materials of the type disclosed in my above noted Patent No. 2,584,030 and application Serial No. 37,252.

Examples of the novel processes of the invention for forming positive transfer prints in silver are given below, but it is to be expressly understood that these examples are merely illustrative and that the invention is not limited to the materials or proportions set out therein.

Example 1 A processing composition is prepared by mixing to gether the following ingredients:

Water 350 A print-receiving element 12 is formed by immersing the baryta-coated surface of a sheet of baryta paper in a mixture comprising:

Silica aerogel (Santocel C) grams 300 1% solution of sodium sulfide cc 2800 Cadmium acetate grams 30 Lead acetat (10.... 1 Zinc nitrate do 30 Water cc 100 for approximately ten seconds. As the sheet is withdrawn from the mixture, the excess of the mixture is removed from the surface or the sheet by a bufier roll or squeegee. The sheet is then dried and washed in water to remove a substantial portion of the soluble salts thereof, leaving thereon a layer 16 of silica aerogel containing predominantly metallic sulfides.

The processing composition is spread in a layer of approximately .002.003 inch in thickness between the treated baryta surface of element 12 and the photosensitive silver halide emulsion b of photosensitive element 10. Emulsion 10b is a relatively high speed orthochromatic emulsion like the emulsion of Eastman Kodak Verichrome film and has been exposed to predetermined subject matter so that it contains a latent image of this subject matter, and support 10a for said emulsion is a white paper. The lamination formed by the spreading of the processing agent in a layer 14 between

elements

10 and 12 is kept intact for approximately one-half to one and one-half minutes, preferably one minute, and at the end of this time, element 12 is stripped from element 10. Element 12, when so stripped, carries a positive print in silver of the subject matter of the latent image of emulsion 10b. In this form of the process, the film of sodium carboxymethyl cellulose contained in the layer 14 of the processing composition adheres to the surface of element 12 and solidifies to form a film thereon.

So much of the amine as is contained in unexhausted form in the print-receiving element, either in the surface portions of element 12 or in the residue of layer 14, be-

gins to evaporate shortly after the stripping of said printreceiving element from the photosensitive element so that there is soon produced a sufiicient diminution in the alkalinity of the print-receiving element to prevent the creation of the stains and other sources of instability.

Other materials may be substituted for those used in the foregoing process and the proportions may be varied to an appreciable extent. For example, the film-forming material in the processing agent which imparts the desired viscosity to the latter may be any of the high molecular weight polymers which are stable to alkalis and which are soluble in aqueous alkaline solutions. For example, such other plastics as hydroxyethyl cellulose, carboxymethyl-hydroxyethyl cellulose, polyvinyl alcohol and the sodium salts of polymethacrylic acid and polyacrylic acid may be used. It is desirable that the plastic be contained in the agent in sufiicient quantities to impart to the composition a viscosity in excess of 1000 centipoises at a temperature of approximately 24 C. Preferably the viscosities of the processing agent are of the order of 1000 to 200,000 centipoises.

Other developing agents may be used, for example one of the following: p-aminophenol hydrochloride; bromohydroquinone; chlorohydroquinone; diaminophenol hydrochloride; toluhydroquinone; monomethyl-p-aminophenol sulfate; a mixture consisting by weight of onehalf hydroquinone and one-half p-hydroxyphenylaminoacetic acid; and a mixture consisting by weight of onefourth hydroquinone and three-fourths p-hydroxyphenylaminoacetic acid.

To form the soluble silver complex, such other complex-forming substances as sodium thiocyanate, ammonium thiocyanate and ammonia may be employed.

Support 12a of element 12 may consist of gelatin, cellophane, polwinyl alcohol, sodium alginate, and cellulose ethers such as methyl cellulose and their derivatives such as hydroxyethyl cellulose.

An example of a processing composition whose only alkalizing agent is an amine is the following:

Example 3 The concentration of the sodium hydroxide in the processmg composition of Example 1 may be increased so that there are equivalent quantities of the sodium hydroxide and the amine in the composition, in which case the stabilizing effect of volatile amine is supplemented by coating on the print-receiving element 12 of Example 1 a supplemental stabilizing composition comprising 4.6% by weight of gum arabic and 10% by weight of dimethyl oxalate, thus forming on the silica aerogel layer 16 of said element a thin coating of gum arabic containing dimethyl oxalate. To provide the gum arabic, the commercially available Arabol may be used. This is a water solution of gum arabic, whose solid content varies between 57% and 61% and which has a viscosity varying between 1500 and 5000 centipoises.

Another form of print-receiving element 12 especially useful when the stabilizing effect of the volatile amine is to be supplemented is one that is formed in exactly the same manner as the print-receiving element of Example 1, except that the washing operation which washes out the excess soluble salts is omitted so that the latter are available for stabilizing the positive print.

Example 4 The residual film of carboxymethyl cellulose may be stripped with the photosensitive element instead of the print-receiving element by providing on the surface of the print-receiving element a stripping layer. This is accomplished by roll-coating on the processed print-receiving element of Fig. 1 against a smooth surface such, for example, as the polished surface of a metal drum, a 5% aqueous solution of polyvinyl alcohol in a layer whose thickness is of the order of .001 inch. An equivalent amount by weight of hydroxyethyl cellulose or polymethacrylic acid maylbe substituted for the polyvinyl alcohol of this examp e.

Another example of a processing composition whose only alkalizing agent is an amine is the following:

Chlorobenzotriazole do .4

It is believed to be evident that the practical utilization of volatile amines as photographic reagents depends, at least in part, upon the provision of suitable means for preventing the volatilization of these reagents prior to their application to the photosensitive emulsion. In this respect, the container means 20 which keeps the processing agent hermetically sealed and prevents the loss of the amine by volatilization cooperates in a novel manner with the processing agents of the invention to give a useful and practical photographic product.

It has already been noted that some of the reagents of the processing compositions hereinabove described may be contained in or on the sheet materials which are treated with the liquid composition so as to be dissolved by the composition as the latter is disposed from its container 20 and applied to said sheet materials. In this connection, the contents of the container may comprise essentially an aqueous solvent, a film-forming thickening agent and the volatile amine, the other reagents of the processing composition being contained in solid form in or on the surfaces of the elements and 12 which are to be processed by the composition.

As noted hereinabove, the silver precipitations agents which aid in the reduction and precipitation of the metallic silver of the positive print may be contained in the developer composition. One example of a composition which can be usefully employed in this manner to thereby avoid the need for a special silver precipitation layer upon the print-receiving element is the following:

This composition is spread, as in Example 1, between a photosensitive emulsion of the Verichrome type and the baryta-coated surface of a plain baryta sheet. At the end of approximately a minute, the baryta sheet is stripped from the emulsion and carries with it the solid residue of the spread composition. The silver precipitate which produces the positive is formed largely in this residual film and gives a positive print of good quality, high resolving power and excellent stability.

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 shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic process for forming, by transfer, a positive print of a latent image contained in the silver halide emulsion of a photosensitive element wherein a single application of liquid to said element is efiective to give a finished print of improved stability, which process comprises the steps of bringing an alkaline processing composition into contact with the photosensitive element so as to permeate said emulsion with the liquid of said composition, said composition comprising a relatively volatile aliphatic amine as its alkalizing agent, said amine having a boiling point lower than approximately 175 C., a one normal solution of said amine having a pl-I in excess of 10; providing a print-receiving element in superposed relation with the photosensitive element so that the processing composition is essentially confined to said superposed elements, said processing composition containing, after permeation of said silver halide emulsion, all of the reagents, including a silver halide developer, for developing the latent image in the silver halide emulsion and for forming a positive print of the subject matter of said latent image upon said print-receiving element, said developer being characterized by its propensity for oxidizing in an alkaline environment to form stains; retaining said photosensitive element and said print-receiving element in superposed relationship until the latent image in the silver halide emulsion is developed and a positive print of the subject matter of said latent image is formed in said print-receiving element; and stripping,

said print-receiving element with the positive print thereon from said photosensitive element, thereby permitting the unexhausted volatile amine to evaporate.

2. A photographic process for forming, by transfer, a positive print of a latent image contained in the silver halide emulsion of a photosensitive element wherein a single application of liquid to said element is eifective to give a finished print sufliciently stable to require no subsequent stabilizing treatments for ordinary use, which process comprises the steps of spreading in a layer between the photosensitive element and another element a processing liquid which includes, in solution, a silver halide developer, a silver halide fixer, a film-forming thickening agent and, as its alkalizing agent, a substantially volatile aliphatic amine having a boiling point lower than approximately C., a one normal solution of sa d amine having a pH in excess of 10, said liquid developing a latent image in said emulsion and forming a positive print in silver in a print-receiving stratum provided by one of said elements and said layer of processmg liquid, the developer being characterized by its propensity for oxidizing in an alkaline environment to produce stains; and stripping said elements from one another after the formation of a silver transfer print in said print-receiving stratum, thereby exposing to the atmosphere the surface portion of said print-receiving stratum which contains said volatile amine and permitting the unexhausted amine to volatilize.

3. The process of claim 2 wherein the amine is water soluble.

4. The process of claim 2 wherein the processing liquid, when spread between the said elements, tends to form a solid layer of the thickening agent and said layer of thickening agent provides said print-receiving stratum.

5. The process of claim 2 wherein the processing liquid, when spread between the said elements, tends to form a solid layer of the thickening agent and said layer of thickening agent adheres to the photosensitive element when the latter is stripped from the other element, a surface portion of said other element providing the printreceiving stratum.

6 A photographic process for forming, by transfer, a positive print of a latent image contained in the silver halide emulsion of a photosensitive element wherein a single application of liquid to said element is eifective to give a finished print of improved stability, which process comprises the steps of bringing an alkaline processing composition into contact with the photosensitive element so as to permeate said emulsion with the liquid of said composition, said composition comprising a relatively volatile aliphatic amine from the class consisting of diethylamine, triethylamine, diisopropylamine, allylamine and et hylamine as its alkalizing agent; providing a printreceiving element in superposed relation with the photosensitive element so that the processing composition is essentially confined to said superposed elements, said processing composition containing, after permeation of said silver halide emulsion, all of the reagents, including a silver halide developer, for developing the latent image in the silver halide emulsion and for forming a positive print of the subject matter of said latent image upon said print-receiving element, said developer being characterized by its propensity for oxidizing in an alkaline environment to form stains; retaining said photosensitive element and said print-receiving element in superposed relationship until the latent image in the silver halide emulsion is developed and a positive print of the subject matter of said latent image is formed in said printreceiving element; and stripping said print-receiving element with the positive print thereon from said photosensitive element, thereby permitting the unexhausted volatile amine to evaporate.

7. A photographic process for forming, by transfer, a positive print of a latent image contained in the silver halide emulsion of a photosensitive element wherein a single application of liquid to said element is elfective to give a finished print sufliciently stable to require no subsequent stabilizing treatments for ordinary use, which process comprises the steps of spreading in a layer between the photosensitive element and another element a processing liquid which includes, in solution, a silver halide developer, a silver halide solvent fixer, a filmforming thickening agent and, as its alkalizing agent, a substantially volatile aliphatic amine from the class consisting of diethylamine, triethylamine, diisopropylamine, allylamine and ethylamine, said liquid developing a latent image in said emulsion and forming a positive print in silver in a print-receiving stratum provided by one of said elements and said layer of processing liquid, the developer being characterized by its propensity for oxidizing in an alkaline environment to produce stains; and stripping said elements from one another after the formation of a silver transfer print in said print-receiving stratum, thereby exposing to the atmosphere the surface portion of said print-receiving stratum which contains said volatile amine and permitting the unexhausted amine t0 volatilize.

References Cited in the file of this patent UNITED STATES PATENTS 767,815 Homolka Aug. 16, 1904 2,138,486 Fournes et al. Nov. 29, 1938 2,308,058 Crowley Jan. 12, 1943 2,371,740 Dearing et al. Mar. 20, 1945 2,388,894 Yackel Nov. 13, 1945 2,466,423 Henn Apr. 5, 1949 2,543,181 Land Feb. 27, 1951 FOREIGN PATENTS 201,538 Great Britain Oct. 2, 1924 879,995 France Dec. 10, 1942 OTHER REFERENCES Henney et al.: Handbook of Photography, McGraW- Hill, N. Y., 1939, pages 339-341.

Claims

1. A PHOTOGRAPHIC PROCESS FOR FORMING BY TRANSFER, A POSITIVE PRINT OF A LATEN IMAGE CONTAINED INTHE SILVER HALIDE EMULSION OF A PHOTOSENSITIVE ELEMENT WHEREIN A SINGLE APPLCATION OF LIQUID TO SAID ELEMENT IS EFFECTIVE TO GIVE A FINISHED PRINT OF IMPROVED STABILITY, WHICH PROCEESS COMPRISES THE STEPS OF BRINGING AN ALKALINE PROCESSING COMPOSITION INTO CONTACT WITH THE PHOTSENSITIVE ELEMENT SO AS TO PERMEATE SAID EMULSION WITH THE LIQUID OF SIAD COMPOSITION, SAID COMPOSITION COMPRISING OF RELATIVELY VOLATILE ALIPHATIC AMINE AS ITS ALKALIZING AGENT, SAID AMINE HAVING A BOILING POINT LOWER THAN APPROXIMATELY 175* C., A ONE NORMAL SOLUTION OF SAID AMINE HAIVNG A PH IN EXCESS OF 10: PROVIDING A PRINT-RECEVING ELEMENT IN SUPERPOSED RELATION WITH THE PHOTOSENSITIVE ELEMENT SO THAT THE PROCESSING COMPOSITION IS ESSENTIALLY CONFINED TO SAID SUPERPOSED ELEMENTS, SAID PROCESSING COMPOSITION CONTAINING, AFTER PERMEATION OF SAID SILVER HALIDE EMULSION, ALL OF THE REAGENTS, INCLUDING A SILVER HALIDE DEVELOPER, FOR DEVELOPING THE LATENT IMAGE IN THE SILVER HALIDE EMULSION AND FOR FORMING A POSITIVE PRINT OF THE SUBJECT MATTER OF SAID LATENT IMAGE UPOIN SAID PRINT-RECEIVEING ELEMENT, SAID DEVELOPER BEING CHARACTERIZED BY ITS PROPENSITY FOR OXIDIZING IN AN ALKALINE ENVIRONMENT TO FORM STAINS; RETAINING SAID PHOTSENSITIVE ELEMENT AND SAID PRINT-RECEIVING ELEMENT IN SUPERPOSED RELATIONSHIP UNTIL THE LATENT IMAGE IN THE SILVER HALIDE EMULSION IS DEVELOPED AND A POSITIOVE PRINT OF THE SUBJECT MATTER OF SAID LATENT IMAGE IS FORMED IN SAID PRINT-RECEIVING ELEMENT; AND STRIPPING SAID PRINT-RECEIVING ELEMENT WITH THE POSITIVE PRINT THEREON FROM SAID PHOTOSENSITIVE ELEMENT, THEREBY PERMITTING THE UNEXHAUSTED VOLATILE AMINE TO EVAPORATE.