US3650741A

US3650741A - Silver complex diffusion transfer process

Info

Publication number: US3650741A
Application number: US715551A
Authority: US
Inventors: Camille A Vandeputte; Paul Desire Van Pee
Original assignee: Agfa Gevaert NV
Current assignee: Agfa Gevaert NV
Priority date: 1968-03-25
Filing date: 1968-03-25
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21

Abstract

An improved silver complex diffusion transfer copy image is obtained when for purposes of better sensitivity and/or continuous-tone reproduction, a silver bromide or silver bromoiodide emulsion is utilized as the light-sensitive emulsion from which diffusion transfer takes place, by forming the diffusion transfer image in the presence of a quaternary phosphonium salt wherein three of the quaternary substituents are aryl groups and the fourth is an alkyl group. Known diffusion transfer additives, especially the tetrazoline-5 thiones and certain water soluble amines are preferably used together with the phosphonium salt.

Description

United States Patent Vandeputte et a].

[ 1 Mar. 21, 1972 [541 SILVER COMPLEX DIFFUSION TRANSFER PROCESS [72] Inventors: Camille A. Vandeputte, Mortsel; Paul Desire Van Pee, Ede'gem, both of Belgium [52] US. Cl. ..96/29 R, 96/52, 96/58, 96/66 R [51] Int. Cl ..G03c 5/54 [58] Field of Search ..96/29, 52,58, 66R

[56] References Cited UNITED STATES PATENTS 2,238,632 4/1941 Dersch et al.... 96/109 2,271,622 2/1942 Carroll et al.... .96/104 3,017,270 1/1962 Tregillus et a1. 96/58 X 3,161,506 12/1964 Becker ..96/3 3,314,789 4/1967 White et a1 ..96/52 X 3,431,108 3/1969 Willems et a1. ..96/52 X FOREIGN PATENTS OR APPLICATIONS 1,042,477 9/ 1966 Great Britain ..96/29 1,052,022 12/1966 Great Britain ..96/29 1,054,253 l/1967 Great Britain ..96/29 OTHER PUBLICATIONS Bylemans, Image Transfer Process," Progress in Photography, Vol. III, pps. 24- 37 1958.

Primary Examiner-William D. Martin Assistant Examiner-Harry J. Gwinnell Attorney-William J. Daniel [57] ABSTRACT An improved silver complex diffusion transfer copy image is obtained when for purposes of better sensitivity and/or continuous-tone reproduction, a silver bromide or silver bromoiodide emulsion is utilized as the light-sensitive emulsion from which diffusion transfer takes place, by forming the diffusion transfer image in the presence of a quaternary phosphonium salt wherein three of the quaternary substituents are aryl groups and the fourth is an alkyl group. Known diffusion transfer additives, especially the tetrazoline-S thiones and certain water soluble amines are preferably used together with the phosphonium salt.

16 Claims, No Drawings SILVER COMPLEX DIFFUSION TRANSFER PROCESS The present invention relates to a method of producing images according to the silver complex diffusion transfer process.

The principle of the silver complex diffusion transfer process is generally known and comprises the image-wise exposure and development of a light-sensitive silver halide emulsion layer, the complexation of undeveloped silver halide in the unexposed areas of the emulsion layer and the diffusion of the complexed silver halide thus formed to a layer or surface where a substance or substances are present that promote conversion of the said complexed silver halide to form a visible image.

In carrying out the silver complex diffusion transfer process mostly silver chloride emulsions are used in that mostly the reproduction of a line original on an image-receiving material having a paper support is intended and no camera sensitivity is required. However, when a high sensitivity is required and/r continuous-tone reproductions have to be made and/or a copy has to be produced on a usual transparent hydrophobic film support, silver bromide or silver bromo-iodide emulsions are used.

The substances normally applied for improving the image tone when silver chloride emulsion layers are used are not sufficiently effective when silver bromide or silver bromo-iodide type emulsions are used.

It is an object of the present invention to provide compounds that in a silver complex diffusion transfer process wherein a silver bromide or a silver bromo-iodide emulsion is used, considerably improve the image tone of the diffusion transfer image produced and have some further advantageous effects detailedly described hereinafter.

According to the present invention these objects are accomplished by carrying out the diffusion transfer process in the presence of a well defined type of phosphonium salts. Thus the present invention relates to a method of producing images according to the silver complex diffusion transfer process wherein the light-sensitive emulsion layer is a silver bromide or silver bromo-iodide emulsion layer, said process being characterized by the fact that it is carried out in the presence of a phosphonium salt corresponding to the following formula:

wherein:

each of R R and R represents an aryl group, e.g., phenyl, chlorophenyl, bromophenyl, alkoxphenyl, tolyl, naphthyl, biphenylyl R represents an alkyl group, e.g., methyl, cyanomethyl, carboxymethyl and esters thereof, ethyl, hydroxyethyl, heptyl, benzyl, chlorobenzyl, bromobenzyl, nitrobenzyl, and

X represents an acid radical.

The acid radical preferably is chloride, bromide, iodide, perchlorate, thiocyanate, benzenesulphonate, p-toluene sulphonate, or an alkyl sulphate e.g., methylsulphate or ethylsulphate.

Examples of specific compounds according to the above formula that have proved to be especially suitable for carrying out the method of the present invention are methyltriphenylphosphonium chloride, methyltriphenylphosphonium methylsulphate, ethyltriphenylphosphonium iodide, (cyanomethyl)-triphenylphosphonium bromide, (carboxymethyl)-triphenylphosphonium chloride ethyl ester, benzyltriphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium isothiocyanate, (2,5- dichlorobenzyl)-triphenylphosphonium chloride, (pnitrobenzyl)-triphenylphosphonium bromide, n-heptyltriphenylphosphonium bromide, (2-hydroxyethyl)-triphenylphosphonium chloride, (2-hydroxyethyl)-tri-ptolylphosphonium chloride, methyl-trinaphthylphosphonium methylsulphate, ethyl-tri(p-chlorophenyl)-phosphonium ethylsulphate, ethyl-tri(biphenylyl)-phosphonium sulphate. 7

Two or more phosphonium salts may be used together. The phosphonium salts are preferably dissolved in a minor amount of a suitable water-miscible organic solvent, e.g., a lower alcohol or the methyl ether of ethylene glycol, whereupon this solution is added to the coating composition of the layer in which the phosphonium salt has to be incorporated or to a processing liquid applied in carrying out the diffusion transfer image formation. t

The phosphonium salts for use in carrying out the method of the present invention favorably influence the tone of the diffusion transfer image produced in that they shift this tone to a warm black or bluish black tone. Besides, the phosphonium salts influence the gradation of continuous-tone diffusion transfer images: the sensitometric curve shows a steeper gradation in its toe. Finally, it has been observed that the phosphonium salts increase or decrease the maximum density of the diffusion transfer image dependent on the concentration in which they are applied.

In carrying out the method of the present invention the phosphonium salts may be incorporated into the photographic material(s) used, i.e., in the light-sensitive material, and/or in the image-receiving material, or occasionally in the multilayer material comprising both the light-sensitive silver bromide or silver bromo-iodide emulsion layer and the imagereceiving layer. In the material(s) used the phosphonium salt has to be present in (a) layer(s) in effective contact with the image-receiving layer and/or in the image-receiving layer itself. By the wording effective contact is meant that at least an effective part of the phosphonium salt by diffusion reaches the image-receiving layer in due time, i.e., at the stage of the diffusion transfer image formation.

Generally, however, the phosphonium salts have proved to be the most effective when used in the processing liquid for carrying out the diffusion transfer image formation, i.e., an aqueous alkaline liquid that may contain developing sub stances. The phosphonium salts can also be incorporated into another processing liquid applied in the production of the diffusion transfer image, e.g., in a separate aqueous liquid mostly containing development nuclei. Of course the phosphonium salts can also be present simultaneously in a processing liquid and in at least one of the materials used.

In the materials used the phosphonium salt mostly is applied in a concentration of 10 to 400 mg. per sq.m. of material, and in a processing liquid in a concentration of 10 to 500 mg. per liter.

The present invention also relates to photographic materials and processing liquids as described above and containing a phosphonium salt according to the above formula.

In carrying out the method of the present invention it is often advantageous to use together with the phosphonium salt at least one other compound whose favorable effect on the tone of the diffusion transfer image is known. As especially suitable compounds of that kind may be mentioned tetrazoline-S-thiones, e.g., l-phenyl-2-tetrazoline-5-thione, and certain water-soluble amines. The effective amines include the primary aliphatic amines containing an unbranched carbon chain of from four to six carbon atoms, i.e., amines of the n-butylto hexylamine series. Other amines which are effective are the a, w-alkylene diarnines containing from three to 12 carbon atoms in the alkylene chain, linking the amino groups, as in the series from a, m-propylene-diamine to a, wdodecylene-diamine. Also, one of the amino groups of the diamine may be replaced by a hydroxyl group as in the alkanolamines. In addition, benzylamine and especially cyclohexylamine are most useful in carrying out the method of the invention. The tetrazoline-S-thiones as well as the amines referred to above further darken the tone of the diffusion transfer image.

The tetrazolihe-S-thiones are preferably incorporated into the light-sensitive material, but can also be added to the processing liquid, to the image-receiving material and, if a ethylmultilayer material is used, to this material. If incorporated into the silver halide emulsion layer, the tetrazoline-S-thione moreover exerts a stabilizing effect on the light sensitive material. In the latter material the tetrazoline-S-thione generally is present in a concentration up to 5 mg. per sq.m.

Preferably, the amines are not incorporated into the material(s) but in a processing liquid, especially in the alkaline processing liquid for carrying out the diffusion transfer image formation mostly in a concentration of from 0.2 to g. per liter.

According to a preferred embodiment both a tetrazoline-S- thione and a suitable amine are used together with the phosphonium salt, the tetrazoline-S-thione mostly being incorporated into the silver halide emulsion layer, and the amine and the phosphonium salt in the alkaline processing liquid,

The method of the present invention may be carried out very advantageously with a so-called multilayer material comprising both a light-sensitive silver bromide or silver bromoiodide emulsion layer and an image-receiving layer containing a substance or substances (further on called development nuclei or shortly nuclei) for promoting the conversion of complexed silver halide so as to form a visible image, or to which such nuclei are added during processing. The light-sensitive silver halide emulsion layer preferably is situated on top of the image-receiving layer as described in German Pat. specification No. 1,032,091, filed Apr. 18, 1957, by Kodak in the UK. Pat. specifications No, 746,948, filed Oct. 22, 1952, by Kodak and No. 1,006,292, filed Apr. 30, 1962, by Gevaert Photo- Producten N.V., but it can also be comprised between the support and the nuclei-containing layer as is known from the U.K. Pat. specifications No. 746,186, filed May 1, 1953, by Kodak and No. 758,627, filed Dec. 6, 1954, by Agfa. On top of the silver halide emulsion layer the nuclei can be supplied at the processing stage in that they are present in the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation as described, e.g., in U.K. Pat. specifications No. 1,001,558, filed Apr. 13, 1962, and No. 1,052,022, filed Aug. 2, 1963, both by Gevaert Photo-Producten N.V., or in another processing liquid to be applied before the wetting stage with the alkaline processing liquid as is known, e.g., from the published Dutch Pat. application No. 68,00432, filed Jan. 1 l, 1968, by Gevaert-Agfa N.V. It is also within the scope of the present invention to incorporate the phosphonium salt and/or some other substances, e.g., a tetrazoline-S-thione and/or an amine (both types of compounds already referred to above), into another processing liquid than the alkaline processing liquid for carrying out the diffusion transfer image formation, e.g., in a separate processing liquid supplying development nucleiv For the embodiment according to which the diffusion transfer image is produced on top of the silver halide emulsion layer, the diffusion transfer image may be physically transferred to a receiving material, as it is the case according to the method of U.K. Pat. specifications NO. 746,186, filed May 1, 1953, by Kodak No. 758,627, filed Dec. 6,1954, by Agfa, No. 1,001,558, filed Apr. 13,1962, and No. 1,052,022, filed Aug. 2, 1963, both by Gevaert Photo-Producten N.V. referred to above. For more particulars on the specific embodiments according to which the diffusion transfer image is produced on top of the silver halide emulsion layer, reference is made to the patent specifications cited above.

According to the preferred embodiment, according to which the image-receiving layer is situated between the silver halide emulsion layer and the support of the multilayer material the silver halide emulsion layer mostly is removed after the diffusion transfer image has been produced. In carrying out the method of the present invention this support preferably is a transparent hydrophobic synthetic film support such as a support of a cellulose ester, e.g., cellulose triacetate, or of a polyester, e.g., polyethylene terephthalate. The diffusion transfer copy obtained on such transparent support is very suited to be used as an intermediate in all sorts of reproduction techniques.

1n the case the support of the multilayer material is a transparent support and the negative image produced in the outer silver halide emulsion layer is sufficiently screened from the eye on examining the diffusion transfer image produced in the underlying image-receiving layer through the support, as is the case according to the UK. Pat. specification No. 746,948, filed Oct. 22, 1952, by Kodak referred to above, the silver halide emulsion layer is not removed after the diffusion transfer image has been produced.

Of course, the way in which the method of the present invention is carried out may be the most usual one, viz with the use of a separate light-sensitive material comprising a lightsensitive silver bromide or silver bromo-iodide emulsion layer, and a separate image-receiving material comprising development nuclei, incorporated therein at the preparation stage, which is the most conventional embodiment, or applied at the processing stage by means or the aqueous alkaline processing liquid, or by a preliminary treatment with a liquid composition containing development nuclei. The development nuclei may also be contained in a pod and at the processing stage will be spread over the layer wherein or whereon the diffusion transfer image will be produced.

Summarizing one can say that the method of the present in vention always comprises the steps of image-wise exposing a light-sensitive silver bromide or silver bromo-iodide emulsion layer, wetting the light-sensitive layer with an aqueous alkaline processing liquid in the presence of a developing substance whereby an image is developed in the exposed areas of the light-sensitive layer, and keeping the light-sensitive layer, in the presence of a complexing agent for silver halide, in effective contact with an image-receiving layer containing development nuclei, whereby complexed silver halide diffuses from the unexposed and undeveloped areas of the light-sensitive layer to the receiving layer where a diffusion transfer image is formed. By the wording effective contact" is understood such a contact that the diffusion of complexed silver halide can take place.

More particulars on the general composition of the materials used, the various ingredients to be incorporated therein, the techniques for the production of the diffusion transfer image, suitable apparatus for carrying out the various processing steps and further general data concerning the image formation according to the silver complex diffusion process can be found in the patent specifications referred to above and hereinafter and in Progress in Photography" Vol. I, 1940-1950, pages 76-77 and vol. 11, 1951-1954, pages 1567; vol. 111, 1955-1958, pages 24-36 and the patent literature cited therein.

As essential ingredients in the diffusion transfer process may be mentioned developing substances, preferably hydroquinone and a 3-pyrazolidinone developing compound, e.g., l-phenyl-3-pyrazolidinone and/or 1-phenyl-4-methyl -3- pyrazolidinone, a complexing agent for silver halide and an alkaline substance. Further ingredients often applied are preservatives for developing substances, stabilizers, anti-yellowing agents, toning agents and anti-silver sludge agents, hardeners including latent hardening agents, softening agents, coating aids, etc.

With respect to the developing substances it has to be mentioned that sometimes they are omitted at least partially from the aqueous alkaline processing liquid and that they are incorporated into the material(s) used, whereby the alkaline processing liquid can be restricted to a mere aqueous alkaline liquid, which is substantially free from any developing substance. Such a processing liquid is called an activator. For more particulars on this matter reference is made to UK. Pat specifications No. 1,012,476, filed Dec. 18, 1961, No. 1,042,477, filed June 17, 1963, No. 1,054,253, filed Aug, 6, 1963, No. 1,057,273, filed Feb. 3, 1964, all by Gevaert Photoproducten N.V., and Nos. 1,086,510, 1,093,177, both filed Dec. 16, 1964, by Gevaert-Agfa NV.

The following examples illustrate the method and the materials according to the present invention.

Example 1 A suspension of the following composition was prepared:

water 950 ccs. gelatin 30 g. sodium alginate g. 01% aqueous suspension of colloidal silver sulphide 5 ccs. aqueous solution of formaldehyde 2 ccs.

sodium salt of oleyl methyl tauride 1 cc.

From this suspension an image-receiving layer was coated onto a subbed transparent film support in such a way that the weight of the dried layer amounted to 2.5 g./sq.m. The transparent film support was a biaxially stretched polyethylene terephthalate sheet of 120 g./sq.m. and the subbing layer consisted of a polyethylene isophthalate layer applied to the sup-,

port and a mixed gelatin cellulose nitrate layer on top thereof.

To the image-receiving layer a further layer was applied, starting from the following solution:

hydroxyethyl starch having a substitution degree of0.27

of hydroxyethyl groups 10 g. water I000 ccs. 5% solution of the sodium salt of dioctyl sulfosuccinic acid in water/ethanol 50/50 2 ccs.

This solution was coated in such a say that l I. covered 40 sq.m. of paper support.

After drying an orthochromatic and contrasty silver bromide emulsion with camera sensitivity and per kg. containing 13 g. of silver bromide and 36 g. of gelatin was applied thereto in such a way that the finally obtained emulsion layer contained 2.4 g. of silver bromide per sq.m.

After image-wise exposure the thus prepared multilayer material was processed in an alkaline developing liquid of the following composition trisodium salt of ethylenediamine tetruacetic acid 1.5 g. sodium sulphite 75 g. hydmquinone 20 g. l-phenyl-Lpyrazolidinone l g. potassium bromide 2 g. sodium thiosulphute 20 g. sodium hydroxide l2 g. orthoboric acid 2 g. solution of 0.4 g. of(2-hydroxyethyl)- triphenylphosphonium chloride in 30 ccs. of

munomethyl ether of ethylene glycol l2.57r aqueous solution of saponine 5 ccs. polyelhyleneglycol (moLweight ca 200) 50 mg. water up to I000 ccs.

After some 2 to 3 minutes the multilayer material was brought into rinsing water at room temperature and after some 20 to 30 seconds the silver halide emulsion layer detached as a coherent membrane without mechanical help. A positive transparency having an excellent black image-tone was obtained. This transparency is very suited as an intermediate in diazotype printing of in the production of offset printing plates.

Example 2 The method of Example 1 was repeated with the difference however, that 1-phenyl-2-tetrazoline-5-thione was added to the silver halide emulsion in such an amount that after coating 2 mg. was present per sq.m. of the multilayer material. Besides, the alkaline developing liquid was replaced by the following one:

4071 aqueous solution of potassium hydroxide 75 ccs. 40% aqueous solution of sodium hydroxide l4 ccs. trisodium salt of ethylenediamine tetraacetic acid 3 g. anhydrous sodium sulphite 110 g. anhydrous potassium metabisulphite 7.5 g hydroquinone 40 g. potassium bromide 4 g. l-phenyl-S-pyrazolidinone 2 g. anhydrous sodium thiosulphate 30 g. cyclohexylumine L75 ccs.

solution of 0.4 g. of (Z-hydroxyethyl) triphenylphosphonium chloride in 30 cos. of monomethyl ether of ethylene glycol 12.571 aqueous solution of saponine 5 ccs. sodium salt ofdioctylsulpho-succinic acid 50 mg. water up to 2000 ccs.

A positive transparency having an excellent black image tone was obtained. This transparency is very suited as an intermediate in all kind of reproduction techniques.

Example 3 An image-receiving material was prepared by applying an image-receiving layer as described in Example 1 to a subbed polyethylene terephthalate support as described in that some Example 1.

A light-sensitive material was prepared by applying a silver bromide emulsion layer as described in Example l to a paper support and by coating a hydroxyethyl starch layer as described in Example 1 on top thereof.

After image-wise exposure of the light-sensitive material it was conducted together with the image-receiving material through the alkaline developing liquid described in Example 2. Then the light-sensitive and the image-receiving material were pressed against each other and after some 3 minutes separated again.

The positive diffusion transfer copy thus obtained showed an excellent black image tone, and is very suited as an intermediate transparency in all kind of reproduction techniques.

What we claim is:

1. In a method of producing black and white silver metal images according to the silver complex diffusion transfer process which comprises image-wise exposing a light-sensitive silver halide emulsion layer and treating the light-sensitive layer with an aqueous alkaline processing liquid in the presence of a silver halide developing substance and a silver halide complexing agent while in contact with an imagereceiving layer containing development nuclei, whereby the unexposed and undeveloped silver halide in said emulsion layer after complexing with said complexing agent diffuses to said image-receiving layer and is precipitated thereon by said nuclei as a black and white silver metal image, the improvement which comprises using as light-sensitive silver halide emulsion layer a light-sensitive silver bromide or silver bromoiodide emulsion layer and treating the said layer with the said aqueous alkaline processing liquid in the presence of a phosphonium salt corresponding to the formula:

wherein:

each of R,, R and R is an aryl group,

R is an alkyl group having from one to seven carbon atoms therein, and

X is an acid radical.

2. Method according to claim 1, wherein the acid radical is selected from the group consisting of chloride, bromide, iodide, perchlorate, thiocyanate, benzenesulphonate, ptoluene sulphonate, and alkyl sulphate.

3. Method according to claim 1, wherein the light-sensitive emulsion layer and image-receiving layer form part of a multilayer material in order comprising a support, said imagereceiving layer containing development nuclei and the lightsensitive emulsion layer.

4. The method according to claim 3 wherein said support is a transparent hydrophobic film.

5. Method according to claim 1, wherein the phosphonium salt is present in the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation.

6. Method according to claim 5, wherein the phosphonium salt is present in an amount of 10 to 500 mg. per liter of the aqueous alkaline processing liquid.

7. Method according to claim 5, wherein the phosphonium salt is a (2-hyclroxyethyl)-triphenylphosphonium halide.

8. Method according to claim 7, wherein the light-sensitive emulsion layer comprises l-phenyl-2-tetrazoline-5-thione and the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation contains cyclohexylamine.

9. Method according to claim 1, wherein the diffusion transfer image formation is carried out in the presence of an additional compound, which favorably influences the image tone of the diffusion transfer image.

10. Method according to claim 9, wherein the said compound is a tetrazoline-S-thione.

11. Method according to claim 10, wherein the tetrazoline- S-thione is present in the light-sensitive silver halide emulsion layer.

12. Method according to claim 11, wherein the tetrazoline- 5-thione is l-phenyl-2-tetrazoline-5-thione.

13. Method according to claim 9, wherein the said compound is a water-soluble amine.

14. Method according to claim 13, wherein the water-soluble amine is present in the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation.

15. Method according to claim 14, wherein the water-soluble amine is present in an amount of 0.2 to 10 g. per liter of the aqueous alkaline processing liquid.

16. Method according to claim 14, wherein the water-soluble amine is cyclohexylamine.

Claims

2. Method according to claim 1, wherein the acid radical is selected from the group consisting of chloride, bromide, iodide, perchlorate, thiocyanate, benzenesulphonate, p-toluene sulphonate, and alkyl sulphate.
3. Method according to claim 1, wherein the light-sensitive emulsion layer and image-receiving layer form part of a multilayer material in order comprising a support, said image-receiving layer containing development nuclei and the light-sensitive emulsion layer.
4. The method according to claim 3 wherein said support is a transparent hydrophobic film.
5. Method according to claim 1, wherein the phosphonium salt is present in the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation.
6. Method according to claim 5, wherein the phosphonium salt is present in an amount of 10 to 500 mg. per liter of the aqueous alkaline processing liquid.
7. Method according to claim 5, wherein the phosphonium salt is a (2-hydroxyethyl)-triphenylphosphonium halide.
8. Method according to claim 7, wherein the light-sensitive emulsion layer comprises 1-phenyl-2-tetrazoline-5-thione and the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation contains cyclohexylamine.
9. Method according to claim 1, wherein the diffusion transfer image formation is carried out in the presence of an additional compound, which favorably influences the image tone of the diffusion transfer image.
10. Method according to claim 9, wherein the said compound is a tetrazoline-5-thione.
11. Method according to claim 10, wherein the tetrazoline-5-thione is present in the light-sensitive silver halide emulsion layer.
12. Method according to claim 11, wherein the tetrazoline-5-thione is 1-phenyl-2-tetrazoline-5-thione.
13. Method according to claim 9, wherein the said compound is a water-soluble amine.
14. Method according to claim 13, wherein the water-soluble amine is present in the aqueous alkaline processing liquid for carrying out the diffusion transfer image formation.
15. Method according to claim 14, wherein the water-soluble amine is present in an amount of 0.2 to 10 g. per liter of the aqueous alkaline processing liquid.
16. Method according to claim 14, wherein the water-soluble amine is cyclohexylamine.