US3687662A

US3687662A - Silver diffusion transfer process having hydroxylamine,cyclic imide and a pyrazolidinone

Info

Publication number: US3687662A
Application number: US80186A
Authority: US
Inventors: Jozef Frans Willems; Robrecht Julius Thiers; Roger Alois Spriet
Original assignee: Agfa Gevaert NV
Current assignee: Agfa Gevaert NV
Priority date: 1969-10-27
Filing date: 1970-10-12
Publication date: 1972-08-29
Anticipated expiration: 1989-08-29
Also published as: CA935015A; JPS492611B1; BE757147A; DE2049699A1; GB1320330A; FR2072163A5; NL7014995A

Abstract

A SILVER COMPLEX DIFFUSION TRANSFER PROCESS IS DESCRIBED UTILIZING A HYDROXYLAMINE DEVELOPING AGENT, A CYCLIC IMIDE SILVER COMPLEXING AGENT, AND A PYRAZOLIDINONE HAVING THE FORMULA:

2-R1,3-R4,4-R2,4-R3,5-(O=)PYRAZOLIDINE

WHEREIN:

R1 STANDS FOR ARYL INCLUDING SUBSTITUTED ARYL, EACH OF R2 AND R3 (THE SAME OR DIFFERENT) STANDS FOR HYDROGEN, AND ALKYL GROUP, AN ARALKYL GROUP, OR AN ARYL GROUP, AND R4 STANDS FOR HYDROGEN, ALKYL, ALKOXY, ARALKOXY OR ARYLOXY.

BETTER QUALITY TRANSFER IMAGES AT SUBSTANTIALLY LOWER ILLUMINATION LEVELS ARE REALIZED.

Description

United States Patent 3,687,662 SILVER DIFFUSION TRANSFER PROCESS HAV- ING HYDROXYLAMINE, CYCLIC IlVHDE AND A PYRAZOLIDINONE Jozef Frans Willems, Wilrijk, Robrecht Julius Thiers, Brasschaat, and Roger Alois Spriet, Edegem, Belgium, assignors to Gevaert-Agfa N.V., Mortsel, Belgium No Drawing. Filed Oct. 12, 1970, Ser. No. 80,186 Claims priority, application Great Britain, Oct. 27, 1969, 52,572/69 Int. Cl. G03c 5/54 US. CI. 96-29 6 Claims ABSTRACT OF THE DISCLOSURE A silver complex diffusion transfer process is described utilizing a hydroxylamine developing agent, a cyclic imide silver complexing agent, and a pyrazolidinone having the formula:

R stands for aryl including substituted aryl,

each of R and R (the same or different) stands for hydrogen, an alkyl group, an aralkyl group, or an aryl group, and

R stands for hydrogen, alkyl, alkoxy, aralkoxy or aryloxy.

Better quality transfer images at substantially lower illumination levels are realized.

The present invention relates to the formation of silver images by the silver complex diffusion transfer process.

Processes for forming silver images by the steps of imagewise exposure and development of a photosensitive silver halide element, the formation of a diffusible complex of unexposed silver halide in the unexposed areas of the said photosensitive element and the transfer by diffusion of said complex to an element, in superposed relationship with the photosensitive element, where the silver of said complex is precipitated or reduced to form a visible image, are now well known.

The element to which the silver complex is transferred is often referred to as the image-receiving element and generally comprises agents, known as development nuclei, that promote the precipitation of the silver of said silver complex.

According to a typical embodiment of the silver complex diffusion transfer process suitable for in-camera processing a composite material of unitary structure is used which comprises a photosensitive element, an imagereceiving element and a viscous processing fluid contained in a pod or container. After image-wise exposure of the photosensitive element, which comprises a silver halide emulsion layer, the superposed elements i.e. the photosensitive element and the image-receiving element are guided between a pair of pressure rollers whereby the viscous processing liquid is spread as a uniform layer between the photo-sensitive element and the image-receiving element.

The photosensitive element and the image-receiving element are maintained in superposed relation for a determined period, usually of the order of 10 to 120 seconds, during which the exposed silver halide is developed, the

3,687,662 Patented Aug. 29, 1972 undeveloped silver halide is converted into a water-soluble complex silver salt and the said complex is transferred through the layer of processing liquid to the silver precipitating layer of the image-receiving element where it is converted into a visible print. At the end of this contact period the photosensitive element is separated by stripping from the image-receiving element. Elements suitable for use in this silver complex diffusion transfer process are described in detail e.g. in United States patent specification 2,543,181 of Edwin H. Land, issued Feb. 27, 1951.

A wide variety of silver halide developing agents and silver halide complexing agents, are known for use in such diffusion transfer processes.

As silver halide developing agents it has been proposed amongst others in United States patent specification 2,857,276 of Edwin H. Land and Helen 1. Tracy, issued Oct. 21, 1958 to use hydroxylamine and derivatives thereof, of which the oxidation products leave no residual stain in the positive silver image obtained. Hydroxylamine itself is less suitable because it gives rise to fog but the N,N-dialkylhydroxylamines such as N,N-diethylhydroxylamine and the heterocyclic N-hydroxylamines such as N-hydroxymorpholine, N-hydroxypiperidine and N-hydroxypyrrolidine disclosed in the above United States patent specification are particularly suitable. Other hydroxylamine derivatives that have been proposed for use as silver halide developing agents and of which the development activity is higher than that of the N,N-dialkylhydroxylamines include for example aminoalkyl hydroxylamines, more especially N,N dialkylhydroxylamines having in at least one of the N-alkyl groups an intralinear amino nitrogen atom, either cyclic or acyclic, examples of which can be found in United States patent specification 3,287,125 of Milton Green, Adnan A. Sayigh and Henri Ulrich, issued Nov. 22, 1966, alkoxy hydroxylamines, more especially, N,N-dialkyl hydroxylamines of which at least one of the N-alkyl groups is substituted by alkoxy or alkoxy-alkoxy, examples of which can be found in United States patent specification 3,293,034 of Milton Green, Adnan A. Sayigh and Henri Ulrich, issued Dec. 20, 1966 and sulphone hydroxylamines, more especially N,N-dialkyl hydroxylamines having in at least one of the N-alkyl groups an intralinear sulphonyl (SO group, examples of which can be found in United States patent specification 3,287,124 of Milton Green, Adnan A. Sayigh and Henri Ulrich.

Particularly suitable silver halide complexing agents are the cyclic imides disclosed in United States patent specification 2,857,276 mentioned above, especially barbituric acid, uracil and urazole including the derivatives thereof.

It has now been found that when using, in a process for the production of silver images according to the silver complex diffusion transfer process, carried out in the presence of a cyclic imide as silver halide complexing agent and a hydroxylamine derivative as silver halide developing agent, a photosensitive element comprising a silver halide emulsion layer and a compound corresponding to the following general formula:

R stands for aryl such as phenyl, a-naphthyl and B-naphthyl including substituted aryl e.g. substituted by alkyl such as methyl, aralkyl such as benzyl, alkoxy such as methoxy, amino, dialkylamino, halogen such as bromine and chlorine, acetamido, hydroxyalkyl and hydrox'y;

each of R and R (the same or different) stands for hydrogen, and alkyl group such as methyl, ethyl and butyl, an aralkyl group such as benzyl or an aryl group such as phenyl, and

R stands for hydrogen, alkyl preferably comprising at most 4 C-atoms, alkoxy preferably comprising at most 4 C-atoms, aralkoxy or aryloxy,

transfer images of improved quality are obtained.

The use of compounds corresponding to the above general formula in a silver complex diffusion transfer process wherein use is made of a cyclic imide and a hydroxylamine derivative, is effective to give better quality transfer images at substantially lower illumination levels than are necessary in the absence of said compounds.

Moreover, in the presence of said compounds the images obtained generally have greater maximum density than when no such compounds are used.

Therefore, in accordance with the present invention, there is provided a process of forming silver transfer images which comprises the steps of exposing a photosensitive element containing a silver halide emulsion layer and a compound corresponding to the above general formula, developing the exposed photosensitive silver halide emulsion layer and forminga soluble silver complex of unexposed silver halide by treating the said photosensitive silver halide emulsion layer with an alkaline processing liquid in the presence of a hydroxylamine derivative and a. cyclic imide, transferring said soluble silver complex by diffusion to the silver receptive layer of an imagereceiving element in superposed relationship with said silver halide emulsion, forming at said silver receptive layer an image incorporating silver from said silver complex, and separating said image-receiving element from said photosensitive element.

Examples of compounds corresponding to the above general formula that were found to be particularly suitable for use according to the present invention are:

( 1 1- (p-tolyl) -4,4-dimethyl--methoxy-3 -pyrazolidinone (2) l- (p-tolyl) -4,4-dimethyl-S-ethoxy-3 -pyrazolidinone (3) 1- (p-tolyl) -4,4-dimethyl-5-n-propoxy-3 -pyrazolidinone (4) 1- (p-tolyl)-4,4-dimethyl-S-isopropoxy-Il-pyrazo lidinone (5 1- (p-tolyl) -4,4-dimethyl-5-n-butoxy-3-pyrazolidinone (6) 1-(p-tolyl)-4,4-dimethyl-5-benzyloXy-3-pyrazolidinone (7) 1-phenyl-4,4dimethy1-5-methoxy-3-pyrazolidinone (8 1-phenyl-4,4-dimethyl-5-ethoxy-3 -pyrazlolidinone 9 1-phenyl-4,4-dimethyl-5 -n-propoxy-3-pyrazolidinone (10) 1-pheny1-4,4-dimethyl-5 -isopropox'y-3-pyrazolidinone (11 1-phenyl-4,4-dimethyl-5-benzyloxy-3-pyrazolidinone 12) 1-phenyl-4,4-dimethyl-5phenoXy-3-pyrazolidinone l3 1-phenyl-3-pyrazo1idinone (14) 1-phenyl-4-methyl-3-pyrazolidinone (15) 1-phenyl-5-methyl-3-pyrazolidinone (16) 1-phenyl-4-diliydr0Xymethyl-3 -pyrazolidinone 17) 1-phenyl-4,4-dimethyl-3-pyraz01idinone (1 8 1-p-chlorophenyl-4-methyl-4-ethy1-3-pyrazolidinone 19) 1-p-acetamidophenyl-4,4-diethyl-3 -pyrazolidinone (20) 1-p}8-hydroxyethylphenyl4,4-dimethyl-3-pyrazolidinone (2 l 1 -p-hydroxyphenyl-4,4-dimethyl-3 -p'yrazolidinone (22 1-p-methoxyphenyl-4,4-diethyl-3 -pyrazolidinone (23) 1-p-tolyl-4,4-dimethyl-3 pyrazolidinone These compounds can be prepared as known in the 4 art e.g. as described in United States patent specifications 2,772,282 of Charles F. H. Allen and John R. Byers, issued Nov. 27, 1956 and 3,330,839 of Jozef Frans Willems, Albert Lucien Foot and Raymond Albert Roosen, issued July 11, 1967.

In a process for preparing silver transfer images according to the present invention wherein compounds corresponding to the above general formula are used, the said compounds are present in the photosensitive element. These compounds may be located in the silver halide emulsion layer of said element or in a layer in waterpermeable relationship with said emulsion layer. They may be used in amounts varying between very wide limits, preferably, they are used in amounts comprised between 30 mg. and 15 g. per mole silver halide.

The silver halide emulsions utilized in preparing photosensitive elements used in the present dilfusion transfer system can be any of the conventional negative-type emulsions. Typical suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, silver chlorobrornide, silver chloroboromoiodide, etc. These silver halide emulsions can contain spectral sensitizers, speed-increasing addenda, hardeners, coating aids, antifoggants, plasticizers and the like conventional emulsion addenda.

In the silver halide emulsion layer or in a layer in water-permeable relationship with the said emulsion layer, the photosensitive silver halide elements of use in the present diffusion transfer system may further comprise as compounds having a favourable effect on the maximum density of the image formed and/or on the speed of the photosensitive element diamine or polyamine compounds and morpholine derivatives, typical examples of which are the compounds represented by the following formulae:

CH3 CH OH-CH3 CHg-CHz-OH Hg? H (llHz CH2 1120 CHZ 112C CH2 As previously noted, processing occurs with an alkaline processing liquid in the presence of a cyclic imide and a hydroxylamine derivative. The cyclic imide and the hydroxylamine derivative are preferably present in the processing liquid itself although it is also possible to incorporate them in the photo-sensitive or image-receiving element. For instance, the hydroxylamine derivatives can be incorporated in the said elements in the form of acid salts thereof e.g. in hydrochloride or hydrobromide form. When the developing and/or silver complexing agents are incorporated in the photosensitive and/or image-receiving element, the development of the exposed silver halide and the formation of the silver complex of unexposed silver halide is activated when the alkaline processing solution is spread as a thin layer between the photosensitive element and the image-receiving element.

Particularly useful cyclic imides are barbituric acid, uracli and urazole as well as derivatives thereof, examples of which can be found in United States patent specification 2,857,276 mentioned above. Among the hydroxylamine derivatives that are particularly suitable, mention may be made of the heterocyclic N-hydroxylamines such as N-hydroxymorpholine, N-hydroxy piperidine and N-hydroxypyrrolidine, the primary and secondary N-lower alkyl hydroxylamines such as N,N-diethylhydroxylamine, the alkoxy-substituted derivatives thereof such as N,N-di- (2-ethoxyethyl)hydroxylamine and N-ethyl-N-(Z-ethoxyethyl)hydroxylamine, the sulphone-hydroxylamines such as N-methyl-N-Z-ethylsulphonylethyl hydroxylamine and bis 2 (methylhydroxylamino)ethyl sulphone and the aminoalkyl hydroxylamines such as N-methyl-N-Z-dimethylaminoethyl-hydroxylamine. Further examples of such hydroxylamine derivatives can be found in the United States patent specifications referred to above.

The processing fluid comprises bases imparting to the fluid the required alkalinity. As examples of such bases mention may be made of alkali-metal hydroxides, e.g. sodium and potassium hydroxide, sodium carbonate, borax, sodium metaborate, trisodiumphosphate, etc.

As is known, the processing fluid employed in these dilfusion transfer processes is relatively viscous, of the order of 1000 to 200,000 centipoises at (3., so as to be easily controlled when spread. In order to obtain the desired viscosity, the liquid contains a thickening agent, preferably a water-soluble film-forming material such as water-soluble plastic so that when the liquid is removed from the processing layer by absorption and/or evaporation there remains a solid plastic film. The film-forming plastic may be any of the high-molecular weight polymers which are stable to alkali and which are soluble in aqueous alkaline solutions, e.g. hydroxyethylcellulose, starch or gum, polyvinylalcohol, the sodium salts of polymethacrylic acid and polyacrylic acid, sodium alginate, sodium carboxymethyl cellulose. As is known in the art, stripping of the silver halide element from the image-receiving element may separate the solidified layer of processing composition from the image-receiving element or may permit the layer of processing composition to remain in contact with the image-receiving element so that the solidified layer provides a protective coating over the image obtained.

The liquid may further contain, or dissolve in its travel to the photosensitive element, other compounds which are desired in the treatment of the photosensitive layer and in the production of the positive image in the image-receiving layer.

The viscous processing fluid of use in the process according to the present invention is preferably confined within a hermetically sealed container or pod which is positioned between the photosensitive element and the image-receiving element and which is ruptured and releases its contents upon advancing the photosensitive element and imagereceptive element between a pair of pressure-rollers. Such a container is impervious to the processing liquid and to the vapour of said liquid, and may be formed of a multilayer composite material comprising as inner layer in contact with the liquid, a material which is impervious to the liquid, as intermediate layer a substance which is impervious to the vapour of said liquid and as outer layer a material merely serving as a backing or support. In its preferred form, the container is formed of a multilayer material whose inner layer is formed of a plastic such as polyvinyl acetal, e.g. polyvinyl butyral, polymeric esters such as cellulose acetate, cellulose acetate butyrate, polyvinyl acetate, polyvinyl chloride, etc., said layer being backed by a metal foil, e.g. a lead foil or leadtin foil which is impervious to the vapours of said solution. The containers may be strengthened by a more rapid backing material such as kraft paper or a plastic such as polyvinyl acetate and polyvinyl chloride. More details as to the construction of such a rupturable container can be found amonst others in United States patent specification 2,634,- 886 of Edwin H. Land, issued Apr. 14, 1953.

The silver halide emulsion layer and/or the imagereceiving layer may be coated on opaque or transparent supports. In this way it is possible to expose the photosensitive element from either side as desired and it is possible to form either reflection prints or transparencies.

The image-receiving layer of the image-receiving ele ment preferably comprises agents promoting precipitation of the silver from the transferred silver complex. Examples of such agents, called development nuclei or shortly nuclei, are well known and include sulphides, selenides, polysulphides, polyselenides, thioureas, thioacetamides, mercaptans, stannous halides, heavy metals or their salts and fogged silver halide. Sulphides of heavy metals such as of antimony, bismuth, cadmium, cobalt, lead, nickel and silver are also suited. Lead sulphide and Zinc sulphide as well as the complex salts thereof are especially effective either in themselves or mixed with thioacetamide, dithiobiuret and dithio-oxamide. Among the heavy metals silver, gold, platinum, palladium and mercury are to be mentioned, preferably in colloidal form.

The development nuclei are generally associated with a granular, inorganic, water-insoluble, substantially chemically inert substance such as silica as vehicle for the said nuclei whereby aggregation of the precipitated silver is promoted.

In at least one layer of the image-receiving element other substances may also be incorporated which play a part in the formation of the diffusion transfer image e.g. black-toning agents, anti-yellowing agents, optical bleaching agents, softening agents, etc.

The image-receiving elements may be constructed as described in United States patent specification 2,823,112

of Edwin H. Land, issued Feb. ll, 1958. According to this United States patent specification the print-reciving element is so constructed that the viscous processing fluid separates therefrom and leaves no droplets or film of developing composition on the print-receiving layer. The image-receiving layer is thin, holding a mass of water so small that there is no tactual wetness. Moreover, by making the print-receiving layer so thin the tendency to curl is also avoided. Consequently, when peeled from the photosensitive element, which carries the viscous processing layer, the image-receiving element appears to be a dry sheet.

According to this United States patent specification a layer, which is substantially impervious to the processing liquid and which may be the liquid-impervious surface of a supporting sheet which is entirely formed of liquidimpervious material is provided between the silver precipitating layer in which the positive is formed, and the remainder of the image-receiving element. Further, the image-receiving layer is provided with a surface from which the viscous film of processing fluid may be readily stripped. Thus, according to said United States patent specification the outer surface of the image-receiving element contacting the layer of processing composition is so constituted as to have a lesser adhesion for the solid residue of the liquid processing composition than does the photosensitive element. As a result, the photosensitive element, when stripped from the image-receiving element, carries with it the residue of the processing composition. Further, between the image-receiving layer and the stripping layer an abrasion resistant coating may be provided.

According to this United States patent specification stripping of the silver halide element from the imagereceiving element separates the layer of processing solution from the image-receiving element. However, as noted hereinbefore in order to provide the image-receiving element with a protective coating, it is also possible that upon stripping the layer of processing solution remains in contact with the said image-receiving element. Such stripping techniques are taught in 'United States patent specification 2,647,056 of Edwin H. Land, issued July 28, 1953.

The following examples illustrate the present invention. In these examples the values given for the speed are relative values, measured at density 0.5.

EXAMPLE 1 A photosensitive element was prepared comprising on a paper support a silver bromoiodide emulsion layer containing per kg. an amount of silver halide corresponding to 60 g. of silver nitrate and a compound as listed in the table below in the amount given.

After exposure, the photosensitive element and an image-receiving element, which comprises a silver receptive layer containing development nuclei dispersed in a matrix of colloidal silica coated on a water-impervious support according to the practice described in United States patent specification 2,823,122 of Edwin H. Land, issued Feb. 11, 1958, were advanced in superposed relationship between a pair of pressure-applying rollers to 9 spread between them in a thin layer a processing composition comprising per litre:

sodium carboxymethyl cellulose40 g. sodium hydroxide35 g.

In the following table are listed the results obtained with freshly prepared photosensitive element and with photosensitive element stored for 5 days at 49 C. and relative humidity as compared with the results obtained under identical circumstances with silver halide uracil g. 5 material (comparison material) comprising in the emulsion N,N-di(2-ethoxyethyl)-hydroxylamine40 ml. layer no Compound 8.

TABLE Fresh material Stored material Speed. Speed 'fl EN!!- Dmiu. Gamma percent Dmnx. Dmin. Gamma Percent Comparison material l. 18 0. O1 0. 86 100 1.01 0. 03 0. 8O Material comprising C0mpound8 1.32 0.03 1.20 104 1.00 0.01 0.79 104 After a contact period of 36 seconds, the emulsion to- EXAMPLE 4 gether with the layer of processing liquid was stripped 20 A photosensitive element was prepared comprising on a from the image-receiving element to uncover the positive a er sup ort a silver bromoiodide emulsion layer con- 0 p p o a print. taining per kg. an amount of silver halide corresponding to In the following table are listed the results obtained with 60 g. of silver nitrate and 1-phenyl-3-pyrazolidinone in freshly prepared photosensitive elements and with photothe amount as listed in the table below. sensitive elements that were stored for 5 days at 57 C. After exposure, the photosensitive element and an and 34% relative humidity. image-receiving element, which comprises a silver recep- TABLE Fresh materials Stored materials Compound added per Speed, Speed, kg. of emulsion Dm Dmin Gamma perc n max Dmi... Gamma percent; None 1. 53 0. 05 1. 53 1.48 0. 0 1 1. 37 117 1 g. of Compound 2 1.67 0. 05 1. 91 103 1. 55 0.01 1. 75 185 0.1 g of Compound 2 1.59 0. 05 1. 59 132 1. 61 0. 05 1. 57 1 g. of Compound 3. 1. 68 0. 05 1.91 172 1. 65 0.03 1. 49 164 1 g. of Compound 4--- 1. 71 0. 05 1. 00 184 1. 09 0. 04 1. 75 172 1 g. 01 Compound 0 1. 00 0. 05 1. 03 181 1. 07 0. 04 1. 70 175 0.1 g. of Compound 6 1.58 0. 05 1.65 122 1.62 0. 04 1. 55 117 1 g. of Compound 7. 1. e9 0. 05 2.01 172 1. 67 0. 05 1. 71 152 1 g. of Compound 0- 1.68 0.05 1.65 153 1.65 0. 05 1.80 1 g. of Compound 11 1. 65 0.05 1.83 153 1. 01 0. 04 1. 00 122 EXAMPLE 2 tive layer containing development nuclei dispersed in a Example 1 was repeated with the difference that storing matex of 9 slhca coaied on WatFr'nnPervmus now took Place for 5 days at and 15% relative support according to the practice described in US. patent humidity specification 2,823,122 mentioned above, were advanced The results obtained are listed in the table below. 45 m superposed relatlonshlp between a pan of pressure'ap TABLE Fresh materials Stored materials Compound added per Speed, Speed kg. of emulsion Dmax. Dmin. Gamma percent Da D Ga percent None- 1. 54 0.06 1. 40 100 1. 60 0 04 1 40 71 2 g. of Compound 8 1. 09 0. 05 2. 03 1. 52 0. 03 1. 15 117 EXAMPLE 3 plying rollers to spread between them in a thin layer a To 1 kg. of a silver bromoiodide emulsion having a sil- Processmg Composmon compnsmg Per lure: ver halide content corresponding to 60 g. of silver nitrate 60 Sodium cafboXymfithyl e11l110Se40 gand comprising 50 mg. of N-benzoylmethyl-morpholine fl ggdmxlde-35 raci g. h drochloride 2 of com ound 8 was added. u

y g p N,N-di(2-ethoxyethyl)-hydroxylamine40 ml.

The emulsion was coated on a paper support and dried. Af d l After exposure, the photosensitive element and an im- 65 ter a} Contact pane of 36 h emu gether with the layer of processing liquid was stripped age'recelvmg element as descflbed m Example 1 were from the image-receiving element to uncover the positive advanced in superposed relationship between a pair of print. pressure applying rollers to pread between them the roc- The ICSUltS obtained 8Y6 listed in thfi table bfilOW. essing composition of Example 1. 70 TABLE After a contact period of 36 seconds the emulsion to- Amount of 1-phenyl-8- Speed, u pyrazolidinone added D Dmin. Gamma percent gether with the layer of processing liquid was stripped 57 0 03 1 73 100 from the image-receiving element to uncover the positive 1.72 0.02 1.23 11 57 1.65 0. 03 i. s 1 2 print.

1 1 EXAMPLE 5 Example 3 was repeated with the difference that the emulsion comprises instead of N-benzoylmethyl-morpholine hydrochloride 50 mg. of N-B-hydroxyethyl-ethyh ene diamine and instead of 2 g. of Compound 8, 100 mg. of Compound 8.

The following results were attained:

12 is present in the silver halide emulsion layer of the photosensitive element in an amount comprised between mg. and 15 g. per mole of silver halide.

5. A process according to claim 1, wherein said photosensitive element also comprises a diamine or polyamine compound.

6. A process of forming silver transfer images which comprises imagewise exposing a photosensitive element Fresh material Stored material Speed, Speed,

Material Dmnx. Dmin. Gamma percent Dm ax. Drain. Gamma percent Comprising neither Compound 8 nor diamine 1. 44 0. 04 1. 54 100 1.50 0.03 1. 99 82 Comprising only Compound 8 1. 41 0. 04 1. 53 133 l. 52 0.03 1. 90 87 Comprising CompoundS and the above diamine 1. 39 0. 04 1. 36 130 1. 50 0.03 1. 97 93 We claims 1. In a process of forming silver transfer images which comprises the steps of image-wise exposing a photosensitive element containing a silver halide emulsion layer, developing the exposed silver halide and forming a solu ble silver complex of unexposed silver halide by treating the said silver halide emulsion layer with an alkaline processing liquid in the presence of a hydroxylamine derivative and a cyclic imide, transferring said soluble silver complex by diffusion to an image-receiving element in superposed relationship with said photosensitive element, forming at an imagereceiving layer of said image-receiving element an image incorporating silver from said silver complex, and separating said image-receiving element from said photosensitive element, the improvement wherein the photosensitive element comprises in a silver halide emulsion layer and/or a hydrophilic colloid layer in water-permeable relationship with the said emulsion layer a compound corresponding to the following general formula:

wherein:

R stands for aryl including substituted aryl,

each of R and R (the same or different) stands for hydrogen, an alkyl group, an arallryl group, or an aryl group, and

R stands for hydrogen, alkyl, alkoxy, aralkoxy or aryloxy.

2. A process according to claim 1, wherein R stands for alkoxy, aralkoxy, or aryloxy.

3. A process according to claim 1, wherein said hydroxylamine and said cyclic imide are present in the alkaline processing liquid.

4. A process according to claim 1, wherein the compound corresponding to the general formula of claim 1 comprising a silver halide emulsion layer and containing in said silver halide emulsion layer and/or a hydrophilic colloid layer in water-permeable relationship with said emulsion layer, a compound corresponding to the formula:

R stands for aryl including substituted aryl, each of R and R (the same or difierent) stands for hydrogen, an alkyl group, an aralkyl group, or an aryl group, and R stands for hydrogen, alkyl, alkoxy, aralkoxy or aryl- Y, developing the exposed silver halide and forming a soluble silver complex of unexposed silver halide by treating the silver halide emulsion layer with an alkaline processing liquid in the presence of a hydroxyl amine derivative and a cyclic imide, transferring said soluble silver complex by diffusion to an image receiving element in superposed relationship with said photosensitive element, forming an image receiving layer of said image receiving element an image incorporating silver from said silver complex, and separating said image receiving element from said photosensitive element.

References (Iited UNITED STATES PATENTS 3,330,839 7/1967 Willems et a1 96-66 HD 3,261,685 7/1966 De Haes et al. 9695 3,433,634 3/1969 De Haes et a1. 9629 NORMAN G. TORCHIN, Primary-Examiner J. L. GOODROW, Assistant Examiner US. Cl. X.R. 96-95