US3820997A - Method of color development processing for forming stable photographic images - Google Patents

Abstract

In a color development process for forming stable photographic images by color-developing and bleach-fixing a silver halide color photographic material containing one or more couplers, the improvement which further comprises processing the material with an oxidizing solution containing 0.3 - 3 g/liter of a ferricyanide complex salt. Preferably this processing is followed by processing in a solution containing a reducing compound. The solutions used are also set out in detail.

Description

United States Patent 1 1 Shirasu et al.

METHOD OF COLOR DEVELOPMENT PROCESSING FOR FORMING STABLE PHOTOGRAPHIC IMAGES lnventors: Kazuo Shirasu; Tadao Hatano; Isao Shimamura; Mitsuo Ozawa; Haruhiko Iwano, all of Kanagawa, Japan Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed: Oct. 12, 1972 Appl. No.2 297,163

Assignee:

Foreign Application Priority Data Oct. 15, 1971 Japan 46-81379 US. Cl 96/56, 96/22, 96/60 R,

96/60 BF, 96/61 R Int. Cl. G03c 7/00, G03c 5/32, G03c 5/38 Field of Search 96/22, 61, 60, 56

References Cited UNITED STATES PATENTS 12/1948 Knott et al 96/22 Primary Examiner-J. Travis Brown Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT In a color development process for forming stable photographic images by color-developing and bleachfixing a silver halide color photographic material containing one or more couplers, the improvement which further comprises processing the material with an oxidizing solution containing 0.3 31' g/liter of a ferricyanide complex salt.

Preferably this processing is followed by processing in a solution containing a reducing compound. The solutions used are also set out in detail.

19 Claims, No Drawings METHOD OF COLOR DEVELOPMENT PROCESSING FOR FORMING STABLE PHOTOGRAIHIC IMAGES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of color development for forming stable photographic images and, more particularly, to an improved method of color photographic processing whereby stable images capable of being stored for a long period of time can be obtained with a lowered amount of harmful materials which pollute the environment, and to the composition of the processing solution used therefor.

2. Description of the Prior Art in general, the development processing of a .color photographic material includes the step of development with a color developer, bleaching wherein the developed silver is oxidized, and fixing wherein silver salt produced by the oxidation is dissolved to be removed from the photographic material.

In some cases, a bleach-fixing step is included wherein bleaching and fixing are conducted at the same time. The bleaching solution and the bleach-fixing solution contain an oxidizing agent for oxidizing the developed silver. Typical examples of such oxidizing agents include red prussiate, potassium dichromate, ethylenediaminetetraacetic acid-iron (ill) complex salt, copper (ll) compounds, etc. Of these, red prussiate is particularly strong in its silver salt-bleaching ability and, since it is easily available atlow price and can be stored for long periods, it has been widely used.

However, red prussiate has a defect, i.e., its main component, ferricyanide ion, is decomposed by photolysis to form the cyanide ion, and discharge of the processing waste liquor is harmful to the environment.

Although a bleach-fixing solution wherein an aminopolycarboxylic acid-iron (Ill) complex salt is used as the oxidizing agent does not contain such a compound harmful to the environment, it has the defect that the color density of the image obtained is not sufficient due to insufficient oxidizing ability.

Different classes of coupler groups are used in photographic color materials, e.g., Z-equivalent couplers, which are so called because 1 mol of dye is formed by the reduction of 2 mols of silver halide. To this group belong the phenol-type or naphthol-type couplers wherein the p-position with respect to an OH group i.e., the coupling position, is substituted with an atom or atoms other than H, and those of the pyrazolone-type or benzoylacetanilide-type containing an active methylene group wherein one of the hydrogen atoms attached to the active methylene carbon is substituted by another atom or atoms. Since these couplers rarely remain in the non-colored structure upon coupling, the density of the image is rarely insufficient even when the aforesaid bleach-fixing solutions are used.

However, in the case of the 4-equivalent couplers, which are more generally used, i.e., couplers wherein the carbon atom at the 4-position of the aforesaid phenol-type or naphthol-type coupler or hydrogen atom attached to the active methylene carbon of pypyrazolone-type, benzoylacetanilide-type or pivaloylacetanilide-type coupler is not substituted, a non-colored leuco-type structure is initially formed by the coupling reaction with the oxidation product of a p phenylenediamine'type developing agent, and then the completed dye is formed by a second oxidation. 4 Mols of silver halide must be reduced in order to produce 1 mol of such a dye. A strong bleaching agent such as red prussiate can color the color light-sensitive material where a 4-equivalent coupler is used to an almost sufficient extent. However, in the case of the aforesaid bleach-fixing solutions, their oxidizing ability is not usually sufficient and, in many cases, they lack the ability to complete the oxidation of the leuco dye though developed silver is oxidized. Thus, in the lightsensitive material wherein a 4-equivalent coupler is used,-the color density is often low.

One solution to these problems involving 4- equivalent couplers is to sufficiently bleach the silver in a bleach-fixing solution containing a fixing agent using an aminopolycarboxylic acid-irontlll) complex salt as an oxidizing agent, and then process with a red prussiate solution to oxidize the remaing leuco-type noncolored dye (see US. Pat. No. 3,189,452).

In this case, though sufficient color density can be obtained, the environment-polluting factor is encountered. Further, another defect occurs, i.e., the color image thus processed with a red prussiate solution, particularly the magenta color image, has poor lightfastness.

To summarize the above descriptions, of the practical mathods of processing color light-sensitive materials, methods providing sufficient color density deteriorate the light-fastness of the magenta color image and produce an environment-polluting agent, while methods favorable to light-fastness which prevent environmental pollution cannot provide sufficient color density. Thus, an effective method satisfying the two conditions recited was not available to the art.

For example, a photographic material suitable for being processed with a bleach-fixing solution containing ethylene-diaminetetraacetic acid-iron(lll) complex salt is limited to color photographic materials prepared by selecting a color former capable of providing a practical level of color density even when processed with such an oxidizing agent, and thus the possible range of selection of the color former is narrow.

The processing of silver halide color photographic materials generally used at present encounters the problems described above, and it would be extremely valuable to overcome these problems, i.e., to achieve the following three points: (1) to provide a photographic material wherein 4- or Z- equivalent couplers can be used with sufficient color density without limiting the selection range of the couplers; (2) to control the concentration of the total cyanide in the waste liquor discharged from the processing machine so as not i to exceed values prescribed by law; and (3) to obtain a color image which is not discolored or faded by heat, light or humidity during storage after processing.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a novel method of color development processing satisfying the above-described three conditions.

Another object of the invention is to provide a method of color photographic processing of high quality, which always provides a definite color density regardless of small changes in the daily processing conditions.

A further object of the invention is to provide a stable oxidative coloring method wherein the processing solution deteriorates little even in continuous development processing by an automatic developing machine.

Still a further object of the invention is to provide an excellent color photographic processing method causing no color stain on the white support of the color photograph.

Yet a further object of the invention is to provide a method of color development processing which provides a safe working environment avoiding using strongly oxidative processing solutions or irritating solutions.

As the result of searching for a color photographic processing method which satisfies the abovementioned objects, the inventors discovered the method hereinafter described.

The processing method of the present invention comprises forming a color image or uncolored leuco-type dye and developed silver by developing an exposed silver halide color photographic material containing a coupler or couplers with a color developer containing an aromatic primary amine developer agent, subsequently processing the material with a bleach-fixing solution containing an oxidizing agent, e.g., an iron(III) complex salt such as aminopolycarboxylic acidiron(lll) or a cobalt(III) complex salt such as polyamite-cobalt(l) or cobalt nitrate(lll) or quinone, or a mixture thereof, to thereby remove the developed silver and nonreacted silver halide from the emulsion, and further processing the material with an oxidizing solution containing 0.3 3 g/liter of a ferricyanide complex salt to thereby oxidize and color substantially all of the remaining non-colored leuco-type compound, and then preferably processing with a final solution containing one or more reducing agents.

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in greater detail. That is, as described before, in many cases in color photographic materials subjected to color development and the above-described bleachfixing, sufficient color density is not obtained. If the resulting color photographic material is then processed with an oxidizing solution containing 30 g of red prussiate per 1 liter of the solution as described in U.S. Pat. No. 3,189,452, sufficient color density can be provided. However, at the same time, since this oxidizing solution contains ferricyanide ions harmful to the environment at high concentrations, the used solution cannot be discharged as it is. Thus, troublesome aftertreatment of the waste solution must be conducted.

In addition, when processing with such a red prussiate solution is conducted there is observed the phenomenon of reduction in the light-fastness of the formed color image, and from this viewpoint too, aftertreatment of the material with the red prussiate solution after bleach-fixing as in the above U.S. Pat. is dis advantageous to the light-fastness of the color image.

As the red prussiate concentration is reduced, though the color density is not reduced until the concentration is reduced to some degree, the reduction in color density occurs when the red prussiate concentration becomes smaller than a certain value.

The inventors have discovered that there exists a range of red prussiate concentration wherein the color density is not reduced and the problem of environmental pollution is almost removed. This range of concentration varies depending upon the coupler contained in the photographic material, but it ranges approximately from 0.3 to 3 g/liter.

Since a bleach-fixing solution containing aminopolycarboxylic acid-iron(III) complex salt is capable of bleaching and removing the developed silver with sufficient speed, but it insufficient to oxidize the noncolored leuco-type compound remaining in the emulsion film to thereby form a dye, it can be expected that the oxidation potential necessary to provide enough coloring is higher than that required to bleach the developed silver. From the fact that an aqueous solution containing 3 g/liter of red prussiate cannot be practically used as a bleaching solution due to its extremely weak ability to bleach developed silver, or the fact that even a latent image formed by low illuminance exposure cannot be bleached with this solution within the processing period given, it has so far been believed that a red prussiate solution of such low concentration cannot contribute to intensify the color of the color image at all since the solution lacks the ability to bleach even developed silver.

However, surprizingly enough, it has been found that even at concentrations as low as are used in this invention, such a solution still has the power to intensify color.

In comparison with the concentration of a ferricyanide complex salt solution conventionally employed, the above-described concentration is smaller by more than one order of magnitude. Therefore, the discovery of the fact that oxidation to a dye can take place at a concentration at which bleaching is impossible is one of the features of the present invention.

Another advantage of a red prussiate solution of such low concentration is that the degree of reduction in light-fastness of the color image thus processed is considerably improved as compared with that in the method of the aforesaid U.S. Pat.

However, the inventors have found that the lightfastness of the color image can further be improved by immersing the photographic material in a reducing solution after processing with the red prussiate solution. In addition, it has also been found that, while there is the defect that stain isformed in the blank portions of the print processed with a oxidizing solution after bleach-fixing when stored at high temperature, this stain formation can effectively be prevented by processing with the above-described reducing solution.

Therefore, as described before, by bleach-fixing a color photographic material subjected to color development, processing the material with an oxidative solution, and then processing with an aqueous solution containing a reducing agent, sufficient color density can be obtained with a low amount of environmental pollutants in the waste processing solutions, and color photographic processing is made possible whereby high lightfastness of the color image can be obtained and the formation of stain on the image due to high temperature and humidity is prevented.

The bleach-fixing solutions used in the present invention are well known in the art, for example, bleach fixing solutions as are disclosed in German Pat. No. 866,605, British Pat. No. 991,412, U.S. Pat. No. 3,293,036 and U.S. Pat. No. 3,582,322 are representative of the types which may be used in the present invention. Specific examples of the oxidizing agents are:

aminopolycarboxylic acid-iron(lll) complex salts such as iron(lll) chelate compounds with ethylene sliamisemtst ea a id, fi mim-lzp s assl tetraacetic acid, propylenediaminetetraacetic acid, aminotriacetic acid, cyclohexane-l ,3- diaminotetraacetic acid, aminodiacetic acid, N- hydroxyethyl-ethylenediamine-triacetic acid, nitrilotriacetic acid, and the like.

There may also be used a cobalt(lll) complex salt such as tetraminecarbonatocobalt(lll) nitrate, quinone, and simple water-soluble iron salts such as ferric chloride.

As the silver halide-dissolving agent present together with such oxidizing agents, there can be illustrated thiosulfates, thiocyanates, thioureas, thioglycol, watersoluble organic diols containing sulfur and oxygen in the molecule (e.g., 3,6-dithia-1,8-octanediol), and the like.

In the bleachfixing solution other general additives for bleach-fixing solutions may be incorporated, such as pH-buffering salts, antiswelling salts, or sulfite or like stabilizers. The silver halide dissolving agent is preferably present in an amount of from about to about 150 g/liter of solution. Such bleach-fixing solutions are known not only from the specifications of German Pat. No. 866,605, British Pat. No. 1,014,396 and German Pat. No. 966,410, but also from the color development method used by the main photographic companies in Europe and described in The British Journal of Photography (1960), at pages 122, 123 and 126.

In the oxidizing solution of the invention a second oxidizing agent may also be added such as persulfuric acid or salts thereof, in addition to the ferricyanide complex salt (e.g., potassium or sodium salt). The second oxidizing agent is unable to provide sufficient color density when used independently. However, by a synergistic effect, when an aqueous solution containing a ferricyanide complex salt and persulfuric acid or a salt thereof is used, sufficient color can be provided by the presence of persulfuric acid or the salt thereof even when the concentration of ferricyanide complex salt is at a low degree where sufficient color cannot be obtained by the independent use of the ferricyanide complex salt. Therefore, even when the concentration of ferricyanide complex salt is lowered to the range where environmental pollution is safely avoided, the color density remains at a satisfactory level. That is, the co-existence of a ferricyanide complex salt and persulfuric acid or a salt thereof synergistically increases the capability to oxidize and color a leuco-type non-colored dye.

The same effect as for persulfuric acid is obtained with hypochlorous acid, chlorous acid, chloric acid or the alkali metal salts thereof, hydrogen peroxide, or iodine. Compatible mixtures of such materials may, of course, be used.

Further, when an alkali halide such as potassium bromide, sodium bromide, potassium iodide or sodium iodide, and/or an ammonium halide such as ammonium bromide or ammonium iodide, is added in an amount of 0.1 100 g per liter of oxidizing solution, singly or preferably in combination with the above compounds such as the persulfate, better color images can be obtained.

As the persulfate to be used in the oxidizing solution of the invention, the sodium salt, ammonium salt or like salts are preferred. The amount thereof is about 1 to about 20 g per liter, with the optimum amount being about 4 to about 10 g per liter, though the value will vary depending upon the kind and the amount of the coupler in the light-sensitive material processed.

As the ferricyanide complex salt to be used in such a combination, there is used a water-soluble salt comprising ferricyanide ion and a monovalent metal cation, such as potassium ferricyanide or sodium ferricyanide. The concentration thereof in the solution is dependant upon the kind and the amount of the coupler in the light-sensitive material and the thickness of the film. The range (of the concentration of ferricyanide complex salt) satisfying the aforesaid various factors is from about 0.3 to about 3.0 g per liter and, particularly favorably, about 0.5 to l g per liter.

In the case of using chlorous acid or a salt thereof in place of persulfuric acid, the amount thereof added is from about 8 to about 50 g per liter and, in the case of using hypochlorous acid or a salt thereof, from about 10 to about 100 ml/liter of a concentrated aqueous solution of sodium hypochlorite or potassium hypochlorite is used and, in the case of iodine from about 0.2 to about 3 g per liter of iodine is used.

When hydrogen peroxide is used, it is preferably used in an amount of from 10 to 100 ml/liter of oxidizing solution percent aqueous hydrogen peroxide solution).

lodine is preferably used together with potassium iodide.

In this oxidizing solution there may further be incorporated acids, bases or salts for the purpose of adjust ing the pH and providing a buffering property, e.g., so dium carbonate, sodium bicarbonate, borax, boric acid, sodium phosphate, potassium hydrogen phthalate, sodium acetate, acetic acid, etc.

in addition, the pH of the oxidizing solution may be varied over a wide range, the pH being adjusted to a value most favorable considering the relationship with the steps before and after the bath in the processing steps. ln general, the solution is used at a pH of from about 3 to about 10, but the pH value is not overly important.

If necessary, other additives may be incorporated into the oxidizing solution. For example, hardeners such as aluminum sulfate and potash alum, fluorescent brightening agent (e.g., such as described in U.S. Pat. No. 2,632,701), surface active agents such as polyoxyethylene nonylphenyl ether, antiseptic or antifungal agents such as benzoic acid or salts thereof, trichlorophenol, etc. may be incorporated therein.

The final bath of the present invention contains a reducing agent in an amount just sufficient to prevent the formation of color stain in the color image by oxidation during storage for a long period of time. This solution at the same time improves the light-fastness of the ma genta color image.

in the conventional processing of color photographic material, in some cases a solution bath, called a stabilizing bath, is provided as a final bath. Some conventional final baths have the effect of improving the waterdraining property by including a surface active agent, control the pH inside the image-forming layer by including a pl-l-buffering agent, stabilize the image by adding formalin, or enhance the whiteness of the tin ished print by adding a brightening agent. In the final bath of the present invention, the conventional final bath is further provided with a reducing composition.

The reducing agent to be used can be found among,

(wherein R and R represent alkyl, hydroxyalkyl, aryl or allyl, or R and R may be connected with each other to form a 5 or 6 membered heterocyclic ring, R represents alkyl, hydroxyalkyl or allyl when R, and R do not form a heterocyclic ring, or represents hydrogen, alkyl or hydroxyalkyl when R, and R form a heterocyclic ring, and X represents 0, S or NH),

R -SO M (wherein R represents aryl or substituted aryl, and M represents a monovalent metal),

(wherein R R and R represent lower alkyl such as methyl, ethyl, etc.; hydrogen, hydroxyl; lower alkoxy such as methoxy, ethoxy, etc.; carboxyl; sulfo or halogen, provided that R R and R are not hydrogen at the same time or two or more of R R and R are not hydroxyl groups at the same time, and when one of R R and R is hydrogen, halogen, carboxyl or sulfo, the other two are not lower alkyl groups),

HONR R, (wherein R and R represent lower alkyl such as methyl or ethyl; or lower alkoxyalkyl such as methoxy or ethoxy; this compound may be in the form of a salt such as a hydrochloride, sulfate, etc.), and

hydroxypolycarboxylic acid or a salt thereof with a monovalent metal.

As specific examples of the reducing agent used in the method of this invention, there are, for example, the following compounds.

NH-CH:

CHaCH1OH NHCH2CH2=CH2 CHzCHaOH Niiz noooom 23 HO-QOH t-CHn 24 OH H 2H:

2s amen-H01 27 HCnNHOH-H2SO4 28 (crHeJzNoH 29 (CHaOC2H5)2NOH C(OH)CO0H omcoorr a1 omomooon mornooorr a2 motion CHCOOH as omoooa mooofl COOH as CHaCSNH:

36.... ..N s,o

A process for preparing the group of compounds to which reducing agents 5 l3 belong is described in German Pat. OLS No. 1,547,876.

The above-described compounds may also be used in the form of monovalent metal salt such as a alkali metal salt, e.g., a sodium salt or potassium salt, or ammonium salt, or may form isomeric structures.

The above description is only illustrative of the reducing compounds for use in the method of this invention, and reducing compounds other than those recited, such as sugars, may also be used.

The concentration of the reducing agent-containing solution can be varied depending upon various processing conditions, and a concentration is satisfactory which maintains the interior of the image-forming layer processed in a more reduced state than in the case of conducting washing with water. Accordingly, there is no limit on the concentration of the reducing agent in order to achieve the objects of the invention. The agents are preferably used in an amount (or concentration) which is as small as possible solely for economic reasons. Considering this point alone, the amount of the reducing agent used is generally less than g per liter. For practical ease of operator measurement, usually more than about 0.1 g liter of the reducing agent I will be present.

surface active agents such as polyoxyethylene nonyl phenyl ether wherein the polymerization degree of the oxyethylene chain is about 6 14, polyoxyethylene methylphenyl ether alkylsulfates wherein the polymerization degree of the oxyethylene chain is about 6 l0, and sodium dodecylbenzenesulfonate can be incorporated therein.

In addition, known fluorescent brightening agents or bluing agents may also be incorporated therein. In some cases, a small amount of formaldehyde or acetaldehyde is also added. Short-chain alcohols such as methanol and ethanol may also be added in order to aid dissolution. In some cases, the inorganic hardening salts such as potash alum, aluminum sulfate or zirconium sulfate, or ionic strength-increasing additives such as sodium sulfate are added to the final bath. Additives as are described in British Pat. No. 1,001,446 and US. Pat. No. 2,647,057 can also be used in the present invention.

The color photographic material is processed in the final bath, and then dried as it is or after a short-water washing.

The color developer used in the present invention is in accordance with those that generally used by the prior art, i.e., an aqueous alkaline solution of an aromatic primary amine color developing agent which preferably contains benzyl alcohol. As the color developing agent there can be used, for example, any of the known aromatic primary amine color developing agents broadly described as phenylene diamine derivatives such as N-diethyl-p-phenylenediamine sulfate, 4- amino-N-ethyl-N-beta-hydroxyethylaniline sulfate, 3- methyl-4-amino-N-ethyl-beta-methanesulfoamidoethylaniline sesquisulfate monohydrate, 3-methyl-4- amino-N-ethyl-N-beta-hydroxyethylaniline sulfate, 3- methyl-4-amino-N,N-diethylaniline sulfate, etc. Known developer additives such as alkali metal sulfites, carbonates, bicarbonates, bromides, iodides, antifogging carried out, and, if necessary, processing with a reduc ing solution and/or with an image-stabilizing solution, for example, as disclosed in US. Pat. No. 3,140,177.

In the above description, the fundamental order of the processing steps has been described and, needless to say, known supplementary baths such as washing baths, stopping baths, hardening baths, after-baths, aldehyde-neutralizing baths, etc. can be used between the above-described steps, depending upon the color photographic material to be processed, in a manner known to the art. Needless to say, in applying the invention to reversal color development, black-and-white development is conducted prior to the color develop ment. Standard art recognized techniques are used for the black and white development.

For the reasons as described above, the color photographic material to which the present invention is applied shows a large effect particularly when it contains I it'iest ofibr more 4-equivalent couplers in the emulwherein R represents a substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group, or substituted or unsubstituted heterocyclic group, and R represents an alkyl, carbamyl, amino or amido group.

As specific examples of such materials there are l-psec-amylphenyl-3-n-amyl-S-pyrazolone, 2-cyanoacetyl- -(p-sec-amylbenzoylamino)-coumarone, 2- cyanoacetylcoumarone-S-(N-n-amyl-p-tamylsulfoanilide), 2-cyanoacetylcoumarone-S-sulfo-N- n-butyl-anilide, l-p-laurylphenyl-3-methyl-5 pyrazolone, l-beta-naphthyl-3-amyl-5-pyrazolone, 1-p nitrophenyl-3-n-amyl-5-pyrazolone, l-phenyl-3- acetylamino-5pyrazolone, l-phenyl-3-n-valeriamino- 5-pyrazolone, l-phenyl-3-chloroacetylamino-5- pyrazolone, l-phenyl-3-(m-aminobenzoyl)amino-5- pyrazolone, l-p-phenoxyphenyl-3-( p-t amyloxybenzoyl)amino-S-pyrazolone, l-( 2 ',4 ',6 trichlorophenyl)-3-benzamido-5-pyrazolone, l-(2',4-dichlorophenyl)-3-[3"-(2"', 4"'-di-t-amylphenoxy-acetamido)-benzamido]-5- pyrazolone, l-(2,4-dimethyl-6-chlorophenyl)-3-[3"- (2 ',4 '-di-t-amylphenoxy-acetamido)benzamido1-5- pyrazolone, and the like. in addition, the 4-equivalent couplers described in British Pat. No. 1,142,553 or U.S. Pat. No. 3,337,344 are also representative materials.

As examples of benzoylacetanilideor pivaloylacetanilide-type 4-equivalent couplers providing yellow dyes, there can be illustrated the yellow couplers described in British Patent No. 1,] 13,038 or U.S. Pat. No. 3,337,344, and the following compounds: or- {3-[0z-(m-pentadecylphenoxy)butylamido1benzoyl} -2-chloro-acetanilide, a- {3-[a-(2,4-di-t-amylphenoxy)butylarnido]benzoyl} -2-methoxy-acetanilide, a- 3-[a(2,4-di-t-amylphenoxy)acetamidolbenzoyl} -2-chloroacetanilide, 2-cl1loro-3'-[a-(2,4-di-tamylphenoxy)-butylamido]benzoyl-acetanilide, a- {3-[a-(2,4-di-t-amylphenoxy)acetamido]benzoyl) benzoylacetanilide, and a-pivalyl-Z,5-dichloro-4-N'- (n-octadecyl)-N-methylsulfamyl acetanilide.

The above description is illustrative of the 4- equivalent couplers contained in the photographic material to which the invention can be applied but, needless to say, the invention is not limited to the aboveillustrated couplers.

Since these couplers form dyes via a comparatively stable leuco-type structure which is different from the 2-equivalent couplers, in many cases the couplers do not form a sufficient color in a bleach-fixing bath. However, by subjecting these couplers to the processing step of the present invention. even these couplers can form sufficient color and, in addition. the problem of discharging harmful material is markedly improved.

The effects of the present invention will be explained more concretely below by reference to the following non-limitative Examples. method of the invention may of course be effectively applied to photographic materials comprising Z-equivalent couplers. V q i g The technical features of the invention can be summarized by the following 3 elements:

1. the discovery of the concentration range of red prussiate, wherein the concentration is reduced to such an extent that the problem of environmental pollution can be solved and yet the color density can be maintained,

2. the discovery that the combination with bleachfixing is possible, though the bleaching of the silver is impossible in this concentration range, and

3. the discovery that the reducing final bath is effective against the formation of stain during storage at high temperature which occurs when the bleachfixing and the oxidizing bath are combined with each other.

The method of the invention can be applied to the processing of any general silver halide color photo graphic materials such as color negative films, color papers, color positive films, color reversal films for slides, color reversal films for movies, color reversal films for TV, etc. Therefore, there are essentially no restrictions on the type of silver halide, type of protective colloid or the type of additives to be added to the silver halide mul on...

The effect of the invention is particularly large when the method of the invention is employed in developing of films for general amateurs or in the developing of movie films in large amounts, since the large scale of development in such places is particularly liable to cause envionrmental pollution due to waste liquor from the development processing.

The effects of the present invention will be explained more concretely below by reference to the following non-limitative Examples.

EXAMPLE 1 Color papers were prepared by applying onto a baryta paper a silver bromide emulsion containing a yellow coupler emulsion dispersion, a silver chlorobromide emulsion containing a magenta coupler emulsion dispersion (silver chloride content: mol percent), a silver chlorobromide emulsion containing a cyan coupler emulsion dispersion (silver chloride content: 70 mol percent), and a gelatin layer containing an ultraviolet absorbing agent. Each coupler emulsion used was prepared by dispersing each coupler in a mixture of dibutyl phthalate and tricresyl phosphate and dispersing the resulting mixture in a gelatin solution as an o/w emulsion using as the dispersing emulsifier sorbitan monolaurate, Turkey red oil and sodium dodecylbenzenesulfonate. The couplers used were l-(2',4,6'- trichlorophenyl)-3-[3-(2,4-di-tamylphenoxyacetamido)benzamido]-5-pyrazolone, l- (hydroxy)-4-chloro-2-n-dodecylnaphthamide, and a-(Z-methylbenzoyl)-acet-(2-chloro5-dodecoxycarbonyl)anilide. The ultraviolet absorbing agent described in Japanese Patent Publication No. 9586/70 was employed. The sodium salt of 2,4-dichIoro-6- hydroxy-l,3,5-triazine was added to each emulsion.

The composition of each layer is further described in the following Table:

The processing solution used had the 13 14 Layer Coupler Emulsion Coupler! Coupler/ (Solvent Coupler Gelatin Solvent Gelatin)/ (wt/7a) (weight (weight Emulsit'ying ratio) ratio) Agent Red Cyan AgBr 100% III III lOO/l Green Magenta AgBr 30% do. do. do.

AgCl 70% a Blue Yellow AgBr 30% do. do. do.

AgCl 70% UV (UV Agent) do. do.

(UV Agent/ (Solvent UV Solvent) Agent Gelatin)/ Processing l Time Developing step Temperature (C) (min.)

Color development Stopping Washing Bleaching Washing Hardening Washing Stabilizing bath Drying N-bts-INNMNO following compositions.

Color developer:

Benzyl alcohol Diethylene glycol Sodium hydroxide Sodium sulfite Potassium bromide Sodium chloride Borax Hydroxylamine sulfate Ethylenediaminetetraacetic acid 4-Arnino-3-methyl-N-ethyl-N-(bctasullonamidoethyl)aniline sesquisulfate monohydratc Water to make the total Stopping solution Sodium thiosulfate Ammonium thiosulfate (70%) Sodium acetate 5 Acetic acid Potash alum Water to make the total I Bleaching solution:

Red prussiate Potassium bromide 5 (Boraxt l H O) Boric acid 7 water to make the total 1 Hardening solution:

Sodium thiosullate Sodium sulfite Sodium carbonate (monohydrate) Sodium bicarbonate Water to make the total 1 Stabilizing solution (I):

Formalin (37% aqueous solution) :auoomoa 3 Boric acid 5 Sodium metaborate (4 H 0) 3 Potash alum Water to make the total l Enema: 3 q

Emulsit'ying Agent When the color papers were continuously processed using a small developing machine, the total cyanide concentration in the waste water at the drain of the developing machine was as high as 25 ppm even when the overflow of the bleaching solution was collected separately from the draining system.

However, the standard color paper samples did have satisfactory color density as shown in the table below.

Then, further processings were conducted as follows: processing ll where the bleaching step and the hardening step in processing l were changed to a bleach-fixing step and an immersion in an oxidizing bath, respectively; processing Ill where the bleaching and oxidizing bath were conducted similarly to processing ll, and further the stabilizing solution of processing I was changed to stabilizing bath lll. Processing ll is also a comparative example, while processing III is an example of the invention.

Bleach-fixing solution (Processings l1 and I'll):

Stabilizing solution (Processing lll):

Sodium citrate.(2 H O) Boric acid Sodium metaborate.(4 H 0) Potash alum Formalin (37% aqueous solution) Water to make the total liter When exposed color papers as described for processing 1 were processed by a small automatic developing machine, the cyanide concentration in the waste water at the draining outlet of the machine was less than the legally prescribed value in processings II and III as follows:

Processing ll Processing III 0.8 ppm 0.8 ppm The waste water was analyzed when the photographic materials processed by the solution could no ionger possess the photographic properties shown in the Examples.

On the other hand, the color densities* in processing l1 and 111 were sufficient and as high as in processing 1 (as shown in the following table) in spite of the bleachfixing processing. density in all examples was measured by a Densitometer manufactured by Fuji Photo Film Co., Ltd.

EXAMPLE 2 Color papers as described in Example 1 were exposed as in Example 1 and were continuously developed with the use of a small color paper developing ma- V In the above Table, R, G and B represent the reflection density values measured with the use of light passed through a red filter, a green filter, and a blue filter, respectively.

The whiteness of the blank portion of the color paper in processing [11 in accordance with the invention is obviously whiter than that in the conventional method (processing 1) as shown by the reflection density values.

Then, each of the developed samples was set in a fading resistance testing machine provided with a xenon light source wherein it was irradiated for 50 hours at an illumination of 100,000 lux. In processing I, the ratio of density reduction at the portion whose green filter light density before irradiation had been 1.0 reached 35 percent, whereas in processing 11, the reduction ratio was only 12 percent and in processing 111 in accordance with the invention the reduction ratio was 8%. Thus, the light-fastness is excellent in processings 11 and 111 and, above all, in processing 111.

Then, each of the developed samples was left for 1 week at 50C under a relative humidity of 70 percent to test stability to long-period storage. As a result, it was demonstrated that, as shown in the following Table, the density at the blank portion was seriously deteriorated in the case of processing 11 (particularly the blue filter light density) and the material had no commercial capability, whereas the density at the blank portion was stable (substantially unaltered) in processing 111 in accordance with the invention.

Stain at unexposed portions R G B Processing 1 (Comparative example) 016 0.24 0.28 Processing 11 do. 0.10 0.18 0.52 Processing 111 (The invention) 0.08 0.10 0.10

As is apparent from the above description, it is only processing 111 that is satisfactory in all points of color density, image light-fastness, stain formation during storage, and total cyanide concentration in the processing waste liquor.

Processing 1 is inferior in every point other than the first, and processing 11 has the fatal defect of forming stain during storage, though some improvement is achieved over processing 1.

chine. The papers were processed in thefollowing color developer for 6 minutes, then in the following stop-fixing bath for 2 minutes, washed for 2 minutes, and processed in the following bleach-fixing solution for 4 minutes.

Color developer solution:

Calgon (Trade name of the water softeln processing 1V washing was conducted for 2 minutes after bleach-fixing and the sample was then directly dried by a ferrotype machine. In processing V the sample was immersed for 1 minute in an oxidizing solution having the following composition after bleachfixing, and then washed for 3 minutes and dried. In processing V] the sample was immersed for 1 minute in the oxidizing solution described below after bleach-fixing, washed for 2 minutes and further immersed in the stabilizing bath described below. The samples obtained by each processing were compared with each other in the same manner as in Example 1, each sample having been subjected to identical exposure conditions.

The results obtained are shown in the table below, wherein the materials subjected to processings V and V1 (where the oxidizing solution was used) showed sufficient color density.

Oxidizing solution: (in processings V and V1) Red prussiate Potassium persulfate Each sample was then subjected to an one-day incubation test in dry air at a temperature of 80C. Processing V was seriously inferior, and only processing VI in accordance with the invention wasmexcellent in both color density and storage stability.

Change in density of unexposed portions left for one day at 50C (measured as in Example I) a G s Processing IV (Comparative 0.01 0.02

example) Processing V (Comparative 0.02 0.05 0.23

example) Processing Vl (Example) 0 0.01 0.02

Additionally, the total cyanide concentration in the discharged water was less than 1 ppm.

EXAM LE 3 The following experiment was conducted using a color negative photographic light-sensitive material prepared by coating on a cellulose triacetate film base a red-sensitive silver halide bromoiodide emulsion (Agl content: 7 mol percent) in which l-hydroxy-4-chloro- 2-n-dodecylnaphthamide had been emulsified as a cyan coupler, a green-sensitive silver bromoiodide emulsion in which l-(2,4', 6'-trichlorophenyl )-3-[ 3 2",4' "-di-t-amylphenoxyacetamido)benzamido]--pyrazolone had been emulsitied as a magenta coupler, and a blue-sensitive silver bromoiodide emulsion in which a-(2-methylbenzoyl)- acet-(2'-chloro-5'-dodecoxycarbonyl)-anilide had been emulsified as a yellow coupler.

The materials were used in amounts as shown in Example 1 and were otherwise the same except that all AgX emulsions were replaced by an AgBr 93 percent Agl 7 percent emulsion.

In the emulsification of each coupler, dibutyl phthalate and tricresyl phosphate were used as solvents for the coupler, sorbitan monolaurate and sodium dodecylbenzenesulfonate as emulsifiers and sodium 1- (e-nonylphenoxytrioxyethylene)butane-4-sulfonate and sucrose laurate were added as coating aids.

The resulting film sample was divided into two portions one being processed according to a conventional development processing method (processing VII) and the other being processed according to the method of the present invention(processing VIII).

Steps of processing VII (Comparative example):

Color development 24C Stopping bath do. Hardening bath do.

ashing do. Bleaching bath do. Washing do. Fixing bath do. Washing do. Drying 12 min. {i do. 4 do. 4 do. 6 do. 4 do. 8 do. 8 do.

Steps of processing VIII (Present invention): The steps after bleaching in processing VII were ssw siefel sus.

Bleach-fixing Washing oxidizing solution Washing Stabilizing solution Drying Stopping solution:

Sodium acetate Glacial acetic acid Water to make the total Hardening bath:

Sodium hexametaphosphate Borax'5 H 0 Formalin (37%) Water to make the total Bleaching bath (processing VII):

Red prussiate Potassium bromide Borax'5 H O Boric acid Disodium ethylenediaminetetraacetate Water to make the total Fixing bath (processing Vlll):

Sodium hexametaphosphatc Sodium sullitc Sodium thiosult'atc Acetic acid Water to make the total do. do.

Bleach-fixing solution (processing Vlll):

Ferric sulfate Disodium cthylenediaminetctraacetate'(2 H O) Sodium carbonate monohydrate Boric acid Sodium sulfite Aqueous solution of ammonium thiosulfate The pH was adjusted to 5.5. and

water was added to make the total amount 1 liter.

Oxidizing solution (processing VIII):

Sodium nitrate Red prussiatc Potassium persuliate Disodlum hydrogen phosphate l2 H,O Sodium hydrogen phosphate Water to make the total Stabilizing solution (processing Vlll):

Boric acid Borax Sodium thiosulfutc Formalln (37% aqueous solution) Sodium bcnzoate Sodium tctraphosphatc Water to make the total NMNAQ When each processing was continuously conducted by means of a small automatic developing machine, the total cyanide concentrations in the waste water discharged from the machine from the washing step were portion, light-fastness of the color image, and total cyanide concentration in the processing waste water. The whiteness after storage for 1 week at 50C and at 70 percent RH was as follows.

as follows: 5

. R o B Processing VII (Comparative example) [5 ppm Processing viii (Example) 0.7 do. 008 09 10 The fi procesed accprdmg to elther Processing Thus, it can be seen that the effects of the present in- VH or provided Satisfactory results m photovention are further more im roved than in the processgraphic properties such as color density and fog denin m p sity. There was also no large difference therebetween g in the change in density when stored at high temperal 5 E l 5 ture, though in processing VIII the change in density Xamp e was a little smaller. The following stabilizing baths were formed and the When the light-fastness of the image was measured in exact procedure of Example 4 followed except for subthe same manner as in Example 1, the density reducstituting one of stabilizing boths A K for the stabiliztion ratio of the magenta color image was as follows, ing both of Example 4. All units are in grams unless processing VIII being superior to processing VII. otherw se indicated.

A B c o E F o H i J K Formalin (37% aqueous 3 g 4 g 3 g 3 g 3 g 3 g 3 g 3 g 3 g 3 g 4 g solution) Boric acid 5 5 5 5 5 5 5 5 5 5 5 Sodium metaborate 3 3 3 3 3 3 3 3 3 3 3 Potash alum l5 l5 l5 l5 l5 l5 l5 l5 l5 l5 15 Sodium tetrapolyl l l l l l l l l l phosphate Sodium citrate 8 8 8 8 8 Thiourea peroxide 1 Hydroxylamine sulfate 2 Ethylenethiourea 1 2 Thioacetamide I 2 N-Ethylthiourea Sodium toluenesul- 2 phinate t-Butylhydroquinone l Urea 2 In all of the processings wherein the above-described Ratio of reduction in Green density stabilizing baths were used, approximately the same re- Z; sults as in processing III of Example were obtained.

While the invention has been described in detail and In contrast, when the Stabilizing bath in processing with reference to specific embodiments thereof, it w1ll VIII was omitted, stain increased in the incubation test be apparent to P sklned m the an a vfmous at high temperature (80C, dry i d h such changes and modificat on can be made therein without cessing had no practicality (with blue density, the dendeparms m the P and Scope thereofsity at the unexposed portion increased by 0.2, whereas what Clalmed g o g Processmg of the mvemlon, Increased only by 1. In a color development process for forming stable photographic images by color-developing with a developer containing a non-colored leuco d e com ound Example 4 l P P "I E l l d f 55 and bleach-fixing in the absence of ferricyanide comh 9 28 P f Q l aPlf b i b plex salt, a silver halide color photographic material C angmg t e composltlon O t e Sta 1 at to containing one or more couplers, the improvement which comprises further processing the material with an oxidizing solution containing 0.3 3 g/liter of a ferriswbmzing bath: cyanide complex salt to thereby oxidize and color sub- Formalin 37% aqueous solution) 3 ml stantially all the non-colored leuco dye compound. Sodium citrate (dihydrate) 8 g 50 i; acid b g g 2. The process as claimed in claim 1, wherein said oxggfigffjf g idizing solution further contains persulfuric acid, chlo- Sodium thiosulfate l g rous acid, chloric acid or an alkali metal salt thereof. Water to make the total 1 liter N The results obtained were the same as in processing III with respect to color density, whiteness of the blank 3. The process as claimed in claim I wherein said oxidizing solution further contains an alkali metal halide or an ammonium halide.

4. The process of claim 2 wherein said oxidizing solution further contains an alkali metal halide or an ammonium halide.

5. The process of claim 1 wherein the oxidizing solution is at a pH of from about 3 to about 10.

6. in a color development process for forming stable photographic images, which comprises colordeveloping with a developer containing a non-colored leuco dye compound and bleach-fixing in the absence of a ferricyanide complex salt, a silver halide color photographic material containing one or more couplers, the improvement comprising then processing the material with an oxidizing solution containing 0.3 3g/liter of a ferricyanide complex salt to thereby oxidize and color substantially all the non-colored leuco dye compound and then processing with a solution of a reducing compound.

7. The process of claim 6 where the reducing compound has an oxidation potential not greater than 100 mV based on a saturated calomel electrode.

8. The process of claim 6 wherein the solution of reducing compound contains less than 15 g of reducing compound per liter of solution.

9. A method as described in claim 6, wherein said reducing agent is selected from the following compounds:

(wherein M represents a monovalent metal or ammonium group),

2. M 8 0 (wherein M is as defined above),

3. M 80 (wherein M is as defined above),

4. R-SO -R, (wherein R and R represent NH NHR or NR R R and R being lower alkyl), 5.

(wherein R, and R represent alkyl, hydroxyalkyl, aryl (wherein R R and R represent lower alkyl, H, OH, OCH;,, OC H COOH, halogen or -SO H, provided that two or more of R R and R do not represent OH at the same time, or

that R,,, R and R do not represent H at the same time, and that, when one of R R and R represents H, COOH, halogen or -SO H, the remaining two of R R or R do not represent aly 8. HONR R (wherein R and R represent H, lower alkyl or lower alkoxyalkyl, or a salt thereof),

9. polycarboxylic acids or salts thereof with monovalent metal, and

10. thioacetamide.

10. In a color development processing for forming stable photographic images which comprises (1 developing a silver halide color photographic material containing one or more couplers with a developer containing an aromatic primary amine developing agent to form color image, a non-colored leuco dye compound and developed silver, (2) processing with a bleachfixing solution in the absence of a ferricyanide complex salt to remove developed silver and residual silver salt, the improvement comprising then: (3) processing with an oxidizing processing solution containing 0.3 3 g/liter of a ferricyanide complex salt to thereby oxidize and color substantially all the noncolored leuco dye compound, and then (4) processing with a solution of a reducing compound.

11. The process of claim 10 where the reducing com pound has an oxidation potential not greater than 100 mV based on a saturated calomel electrode.

12. A method as described in claim 10, wherein said reducing agent is selected from the following compounds:

I. M 8 0 (wherein M represents a monovalent metal or ammonium group),

(wherein M is as defined above),

3. M (wherein M is as defined above),

4. R-SO -R (wherein R and R represent NH NHR or NR R R and R being lower alkyl),

6. R -SO M (wherein R represents aryl or substituted aryl, and M represents a monovalent metal),

(wherein R R and R represent lower alkyl, H, OH, OCH OC H COOl-l, halogen or -SO H, provided that two or more of R R and R do not represent OH at the same time, or that R R and R do not represent H at the same time,

and that, when one of R R and R represents H, COOH, halogen or -SO H. the remaining two of R R or R do not represent alkyl),

8. HONR R, (wherein R and R represent H, lower alkyl or lower alkoxyalkyl, or a salt thereof),

9. polycarboxylic acids or salts thereof with a monovalent metal, and

10. thioacetamide.

13. The process of claim 10 wherein the solution of reducing compound contains less than g of reducing compound per liter of solution.

14. The process of claim 1 where the bleach-fixing solution contains at least one of an iron(l ll) complex salt, a cobalt(Ill) complex salt or quinone.

15. The process of claim 6 where the bleach-fixing solution contains at least one of an iron(lIl) complex salt, a cobalt(lll) complex salt or quinone.

16. The process of claim 10 where the bleach-fixing solution contains at least one of an iron(lll) complex salt, a cobalt(Ill) complex salt or quinone.

17. The process of claim 1 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about 1 to about 300 g/liter of a silver halide fixing agent.

18. The process of claim 6 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about 1 to about 300 g/liter of a silver halide fixing agent.

19. The process of claim 10 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about i to about 300 g/liter of a silver halide fixing agent.

. H M f. .i

Claims (32)

1. 2. The process as claimed in claim 1, wherein said oxidizing solution further contains persulfuric acid, chlorous acid, chloric acid or an alkali metal salt thereof.
2. 2. M2S2O4 (wherein M is as defined above),
3. 2. M2S2O4 (wherein M is as defined above),
4. 3. M2SO3 (wherein M is as defined above),
5. 3. M2SO3 (wherein M is as defined above),
6. 3. The process as claimed in claim 1 wherein said oxidizing solution further contains an alkali metal halide or an ammonium halide.
7. 4. The process of claim 2 wherein said oxidizing solution further contains an alkali metal halide or an ammonium halide.
8. 4. R-SO2-R1 (wherein R and R1 represent NH2, NHR2 or NR2R3, R2 and R3 being lower alkyl), 5.
9. 4. R-SO2-R1 (wherein R and R1 represent NH2, NHR2 or NR2R3, R2 and R3 being lower alkyl), 5.
10. 5. The process of claim 1 wherein the oxidizing solution is at a pH of from about 3 to about 10.
11. 6. In a color development process for forming stable photographic images, which comprises color-developing with a developer containing a non-colored leuco dye compound and bleach-fixing in the absence of a ferricyanide complex salt, a silver halide color photographic material containing one or more couplers, the improvement comprising then processing the material with an oxidizing solution containing 0.3 - 3g/liter of a ferricyanide complex salt to thereby oxidize and color substantially all the non-colorEd leuco dye compound and then processing with a solution of a reducing compound.
12. 6. R7-SO2M (wherein R7 represents aryl or substituted aryl, and M represents a monovalent metal), 7.
13. 6. R7-SO2M (wherein R7 represents aryl or substituted aryl, and M represents a monovalent metal), 7.
14. 7. The process of claim 6 where the reducing compound has an oxidation potential not greater than 100 mV based on a saturated calomel electrode.
15. 8. The process of claim 6 wherein the solution of reducing compound contains less than 15 g of reducing compound per liter of solution.
16. 8. HONR11R12 (wherein R11 and R12 represent H, lower alkyl or lower alkoxyalkyl, or a salt thereof),
17. 8. HONR11R12 (wherein R11 and R12 represent H, lower alkyl or lower alkoxyalkyl, or a salt thereof),
18. 9. polycarboxylic acids or salts thereof with a monovalent metal, and
19. 9. polycarboxylic acids or salts thereof with monovalent metal, and
20. 9. A method as described in claim 6, wherein said reducing agent is selected from the following compounds:
21. 10. thioacetamide.
22. 10. In a color development processing for forming stable photographic images which comprises (1) developing a silver halide color photographic material containing one or more couplers with a developer containing an aromatic primary amine developing agent to form color image, a non-colored leuco dye compound and developed silver, (2) processing with a bleach-fixing solution in the absence of a ferricyanide complex salt to remove developed silver and residual silver salt, the improvement comprising then: (3) processing with an oxidizing processing solution containing 0.3 - 3 g/liter of a ferricyanide complex salt to thereby oxidize and color substantially all the non-colored leuco dye compound, and then (4) processing with a solution of a reducing compound.
23. 10. thioacetamide.
24. 11. The process of claim 10 where the reducing compound has an oxidation potential not greater than 100 mV based on a saturated calomel electrode.
25. 12. A method as described in claim 10, wherein said reducing agent is selected from the following compounds:
26. 13. The process of claim 10 wherein the solution of reducing compound contains less than 15 g of reducing compound per liter of solution.
27. 14. The process of claim 1 where the bleach-fixing solution contains at least one of an iron(III) complex salt, a cobalt(III) complex salt or quinone.
28. 15. The process of claim 6 where the bleach-fixing solution contains at least one of an iron(III) complex salt, a cobalt(III) complex salt or quinone.
29. 16. The process of claim 10 where the bleach-fixing solution contains at least one of an iron(III) complex salt, a cobalt(III) complex salt or quinone.
30. 17. The process of claim 1 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about 1 to about 300 g/liter of a silver halide fixing agent.
31. 18. The process of claim 6 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about 1 to about 300 g/liter of a silver halide fixing agent.
32. 19. The process of claim 10 where the bleach-fixing is with a solution comprising from about 50 to about 300 g/liter of an oxidizing agent and from about 1 to about 300 g/liter of a silver halide fixing agent.