US3589900A - Photosoluble layer processing in silver halide solvent solution in presence of reducing agents - Google Patents

Abstract

SILVER HALIDE CRYSTALS OF PHOTOSOLUBLE SILVER HALIDE LAYERS, E.G., OF THE TYPE DEFINED IN BLAKE 3,155,507, NOV. 3, 1964, ARE PREFERENTIALLY REMOVED IN EXPOSED AREAS TO FORM A POSITIVE SILVER HALIDE IMAGE BY A SILVER HALIDE SOLVENT SOLUTION IN THE PRESENCE OF SMALL AMOUNTS OF A SILVER HALIDE REDUCING AGENT AND A DMAX MAINTAINING AGENT. THE PHOTOGRAPHIC SPEED IS INCREASED.

Description

United. States Patent a 589 900 PHOTOSOLUBLE LAYER i RocEssING IN SILVER HALIDE soLvENT soLUTIoN IN PRESENCE OF REDUCING AGENTS Ralph Kingsley Blake, Westfield, N.J., assignor to E. I. du

Pont de N emours and Company, Wilmington, Del. No Drawing. Filed Nov. 22, 1967, Ser. No. 684,924

Int. Cl. G03c 5/30 U.S. CI. 96-64 I 14 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for forming images from photosoluble silver halide layers, e.g., of the type defined in Blake 3,155,507. The invention is an improvement on silver halide photosolubilization processes of said patent characterized by the presence of a small amount of a silver halide reducing agent and a Dmax maintaining agent during dissolution (by treatment with a silver halide solvent) of exposed silver halide crystals and on new dissolution developers therefor. The reducing agent increases the photographic speed by increasing the rate of dissolution of exposed versus, unexposed silver halide crystals, particularly the rate of dissolution of slightly exposed crystals.

Description of the prior art Photosolubilization image-forming processes and photosoluble layers and elements useful in the basic process are described in U.S. Patents 3,155,507 and 3,155,514 to 3,155,519 inclusive, Nov. 3, 1964; Blake 3,284,206, Nov. 8, 1966, and in assignees U.S. patent applications Blake and Fan, Ser. No. 403,660 filed Oct. 13, 1964, U.S.P. 3,368,899, Feb. 13, 1968; Fan, Ser. Nos. 403,631 and 403,632 filed Oct. 13, 1964, U.S. Patents 3,407,068 and 3,407,067, respectively, Oct. 22, 1968; and Hunt Ser. No. 388,919 filed Aug. 11, 1964, U.S.P. 3,418,124, Dec. 24, 1968. In these applications and patents there are described simple and useful layers and processes for obtaining a positive silver halide image in a single processing step. Intensification of the image, e.g., by reduction to a black metallic silver image, constitutes an additional optional step.

The use of silver halide solvents with photographic silver halide developing agents is Well known in the field of monobath processing. However, these baths operate by reducing the exposed silver halide grains to metallic silver while removing the unexposed grains by dissolution as soluble ions which diffuse into the bath. These compositions must reduce an exposed grain to visible silver before substantial dissolution occurs. According to the present invention, reducing agents such as silver halide developing agents are used to initiate imagewise silver halide dissolution and any substantial reduction of silver halide to visible silver is intolerable.

SUMMARY OF THE INVENTION This invention pertains to an improvement in a photosolubilization process of forming a direct-positive silver halide image which comprises:

Patented- June 29, 1971 iCe (a) Forming a direct positive latent image by imagewise exposing a photosoluble emulsion layer containing silver halide crystals treated with sufiicient organic compound whose silver salt is less soluble in water than silver chloride to make said crystals relatively less soluble in a silver halide solvent prior to exposure,

(b) Developing said direct positive latent image in a solution of silver halide solvent in the presence of a silver halide reducing agent and a Dmax maintaining agent so that dissolution of exposed silver halide in said solvent is substantially greater than the reduction by said reducing agent. Suitable Dmax maintaining agents are listed and classified in assignees applications Blake U.S. Ser. Nos. 648,229, (U.S.P. 3,493,373, Feb. 3, 1970) 648,250, U.S. Pat. 3,495,982, Feb. 17, 1970, and Strange Ser. No. 653,590 filed June 23, 1967, U.S. Pat. 3,495,983,

Feb. 17, 1970; including 1,2-dichloroethane.

The organic compound is present in the treated crys tals referred to in paragraph (a) above in amounts as definedin Blake 3,155,507 or 3,284,206, Nov. 8, 1966, that is present in such amount, in terms of the ratio of its weight to the surface area of said silver halide crystals, that when admixed in such ratio with an aqueous silver chlorobromide (70/30 mole percent) gelatin dispersion containing 10 g. of gelatin per mole of Ag and .57 mg. of Ag per ml., and said silver chlorobromide dispersion is treated with 10%, by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver and mg. of sodium thiosulfate), at least three times the amount of silver chlorobromide remains undissolved as compared with a similar dispersion successively treated with 5%, by weight, aqueous sodium hypochlorite and 10%, by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver, 25 mg. of sodium hypochlorite and 100 mg. of sodium thiosulfate), after vigorous agitation of both dispersions for 30 seconds at 25C.

As disclosed above, the step (b) is carried out in the presence of a Dmax maintaining agent including those disclosed in Blake U.S. Pats. 3,493,373 and 3,495,982, and Strange U.S. Pat. 3,495,983. These Dmax maintainers are organic compounds such as o-phenylphenol and the organic compound may be present either in the photosoluble element being processed or in the dissolution developer solution (i.e., the solution of silver halide solvent).

The invention also pertains to an aqueous solution for treating an exposed photosoluble element to form a positive silver halide image, i.e., a reducing dissolution developer solution comprising:

Water-soluble thiosulfate salt-2O to 300 g.

Water-soluble sulfite salt0 to 100 g.

Silver halide developing agent0.1 to 3.0 g. I Dmax maintaining organic compound0.01 to 50.0 g. Alkali to bring solution pH Within the range-7.0 to 11.5 Water to make 1 liter.

Preferred developing agents are the 3-pyra zolidone compounds of U.S. 2,289,367, July 14, .1942, especially l-phenyl-3-pyrazolidone and said compound with a methyl group substituted in the -4 and/or -5 position. Metol is also a preferred developing agent. Suitable Dmax maintaining compounds and concentrations for their use are those prescribed in U.S. patents 3,493,373, 3,495,982 and 3,495,983, a particularly useful compound being o-phenylphenol at a concentration of 0.25 to 1.5 g. per liter. The soluble thiosulfate and sulfite salts are preferably alkali metal (e.g., Na or K) or ammonium salts.

The other silver halide reducing agents can be substituted for the developing agent of the table given above in the same, or substantially the same, amounts. The

pH will vary with the concentration and particular developer or Dmax maintainer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the process of the invention, a photosoluble silver halide layer as disclosed and defined in U.S. 3,159,507, preferably a layer of a silver chloride emulsion insolubilized with 2-mercapto-4-phenylthiazole (referred to hereinafter as MPT) or a related mercaptan as disclosed in said patent. The element may advantageously have a photographic spectral sensitizing dye associated with its silver halide crystals as disclosed in assignees copending application of Blake, U.S. Ser. No. 390,460, filed Aug. 18, 1964, U.S. Pat. 3,384,485, May 21, 1968. The photosoluble layer is exposed, image wise, to actinic radiation and then treated in an aqueous bath comprising 0.1 to 2 moles per liter of a thiosulfate (e.g., sodium thiosulfate) silver halide solvent and a reducing agent such as l-phenyl-3-pyrazolidone. Preferably, the reducing agent is a conventional photographic silver halide developing agent or mixture of such developing agents. Also, in accordance with the invention, a Dmax maintaining compound is present in Dmax maintaining amounts during the treatment in said aqueous bath, i.e., either present in the bath itself or in the photosoluble element. The time and temperature of treatment in the aqueous bath are obviously dependent variables but at a temperature of 70 F. the time should be about 30 sec. to 5 min. This treatment removes silver halide from the exposed areas at a much fater rate than from the unexposed areas, leaving a positive silver halide image. A useful positive image can be produced, particularly for viewing by projection, by this single treatment, although a washing step is generally used. For most purposes, it is desirable to intensify the silver halide image, usually by treating with photographic silver halide developer solution to reduce the image to one of black metallic silver. Other methods of intensifying the silver halide image, e.g., by toning, color developing, etc., are disclosed in U.S. 3,155,507.

Any of the various photosoluble silver halide elements defined in the U.S. patents and Blake and Fan applications listed above can be used in the process of this invention. These, of course, may be modified as discribed in the patents and applications by variations in the silver halide, the binder (if present), the organic compounds for insolubilization of silver halide (whose utility can be established by the simple tests defined therein for determination of useful compounds), the adjuvants generally employed in silver halide systems, the supports, and the relative concentrations of components.

In Example VII below, no Dmax maintainer was present in the solutions. The 2-mercapto-4,5-diphenyloxazole was in substantial excess of optimum amount, namely the minimum amount at which maximum image density occurs after processing. When present in greater amounts, the excess solubilizing compounds acts as a Dmax maintainer and cooperates with the reducing agent.

Various auxiliary layers may also be present, such as abrasion overcoatings, subbing layers, and antihalation undercoats or backing layers. The elements may include multilayer as well as monolayer structures. The various layers, including the support, may include inert ingredients, e.g., pigments, organic polymer latices, and matting agents. As disclosed in U.S. 3,155,507, the silver halide may be insolubilized by treatment with an appropriate organic compound either during emulsion manufacture or by treatment of the coated element With a solution of the organic compound.

The reducing, dissolution developer may contain various adjuvants such as shown below in the working examples. The only essential components for this invention are water, a silver halide solvent, and one or more silver halide reducing agents. Even if already present in the photosoluble element, a Dmax maintaining organic compound is a particularly useful additive to the reducing dissolution developer. Numerous useful silver halide solvents are disclosed in U.S. 3,155,507 but in the present application only the use of preferred silver halide solvents which contain the thiosulfate anion are described in the examples.

The invention will be further illustrated by but is not intended to be limited to the following Examples.

EXAMPLE I A light sensitive gelatino-silver chloride coagulum, made by precipitation and coagulation washing in the manner taught in Moede, U.S. Pat. 2,772,165, was redispersed in an aqueous gelatin solution so as to achieve a gelatin to silver chloride weight ratio of 0.79. The resulting emulsion was digested at F. for 20 minutes in the presence of 0.80 g. of 2-mercapto-4-phenylthiazole (MPT) and 0.025 g. of the merocyanine spectral sensitizing dye of Example I of U.S. 2,342,546, Feb. 22, 1944, per mole of silver chloride. Normal emulsion adjuvants were added, including gelatin hardening agents and coating aids, and the emulsion was coated on a vinylidene chloride copolymer subbed polyester (base prepared as described in Example IV of Alles, U.S. Pat. 2,779,684 (and to which a gelatin sub-layer had been subsequently applied). The coating weight was 46 mg./dm. calculated as metallic silver.

A sample of the dried photosoluble film was exposed through a stepwedge for 2 seconds at 20 inches distance from a high intensity, tungsten filament, incandescent lamp (General Electric Reflector Photoflood lamp, No. PH/RFL 2). The exposed film, serving as a control, was precessed for 3 minutes at 68 F. in the following silver halide solvent solution:

Sodium thiosulfate, anhyd.-32 g. Sodium sulfite, anhyd.10 g. Solution of (n=5 or less) In distilled water, specific gravity 1.0138 ml.

1-(l-naphthyD-Z-thiourea, 2% by wt. solution in 2-butoxyethanol2.4 ml.

H O to 1 liter.

Sodium hydroxide to pH of 11.0.

Another sample of the photosoluble film, given the same exposure, was tested in a similar silver halide solvent solution except for the addition of 0.8 g. per liter of the reducing agent, p-aminodiethylaniline hydrochloride.

The films were washed one minute in tap water and given an overall exposure to white light from a suitable lamp. Then the images were intensified by treatment for 1 minute in a photographic silver halide developer of the following composition, which had been diluted 1:1 with water before use:

Water-J50 ml. p-Methylaminophenol sulfate3 g. Na SO (anhyd.)45 g. Hydroquinone12 g.

Water to make 1 liter.

The films were then washed in water for 1 minute, dried in air, and the optical densities of thevarious exposure steps were read in a densitometer. The film processed in the dissolution developer containing the reducing agent showed a two-fold increase in effective speed over the control containing no reducing agent. Thus the processing improvement of this invention which permits a twofold increase in elfective speed would permit the formation of a good image at only one-half the exposure level otherwise required.

EXAMPLE II Strips of the photosoluble film prepared and exposed as in Example I were processed for 3 minutes at 68 F. in the following dissolution developer solutions:

Solution A B Sodium thiosultate, anhyd., g 32 32 Sodium sulfite, anhyd, g 10 10 o-Phenylphenol, 5% by wt. solution in 1 N N aOH, ml 10 10 Hydroquinone, g 0. 8 H2O, liter 1 1 Further processing, including intensification, as in Example I gave positive silver images with the strip processed in Solution B exhibiting about 40% higher effective speed than the control strip processed in Solution A.

EXAMPLE III Example II was essentially repeated except that the hydroquinone of Solution B was replaced with 0.8 g. of p-methylaminophenol sulfate. Processing in the presence of this reducing agent caused a four-fold increase in eifective speed over that of the control containing no reducing agent.

EXAMPLE IV Example II was essentially repeated except that the hydroquinone of Solution B was replaced with 1 ml. of a 10% by weight solution of sodium borohydride (NaBH in 1 N NaOH. The final solution had pH 10.0. The NaBH reducing agent caused a two-fold increase in elfective speed over that of the control containing no reducing agent.

EXAMPLE V Strips of the photosoluble film prepared and exposed as in Example I were processed for 3 minutes at 68 F.

1 Complex formed by mixing 35 g. FeSO 7H 0, 92 g. K C Oi. H20 and H20 to total volume of 500 ml.

Further processing, including intensification, as in Example I gave positive silver images with the strip processed in Solution B exhibiting about twice the effective speed of the strip processed in Solution A.

EXAMPLE VI A large grain silver bromide photosoluble emulsion free of sensitizing dye and containing 0.63 g. of the insolubilizer, 2-mercapto-4,S-diphenylimidazole, per mole of silver bromide was coated on the film base of Example I to yield a photosolube fillm having a coating Weight of 57 mg./dm. of silver bromide. Two strips of the film were exposed as in Example I except that the time of exposure was 8 seconds. One of the strips, serving as a control, was processed for 3 minutes in the following dissolution developer which contained no reducing agent:

H O-500 ml.

NaOH crystals-1.2 g.

Na SO anhyd.-10 g.

o-phenylphenol, by wt. solution in 1 :N NaOH Glacial acetic acid1.3 g.

H O to 1 liter.

pH adjusted with glacial acetic acid to 8.8.

The other exposed film sample was processed 3 minutes in the dissolution developer solution just disclosed to which had been added, per liter of solution, the reducing agents:

l-phenyl-3-pyrazolidon 0.5 Ascorbic acid I 2.5

Further processing, including intensification as in Example I, gave positive silver images. The strip processed in the dissolution developer containing the two reducing agents had a considerably higher contrast than the control strip with similar speeds at lower exposure levels but with effective speeds at higher exposure levels being about four times that of the control.

EXAMPLE VII A film was prepared as in Example VI except that the silver bromide was insolubilized with 0.63 g. of 2-mercapto-4,5-diphenyloxazole per mole of silver bromide. Strips of the film were exposed as in Example VI and processed 3 minutes in the following developer solutions. The 0.63 g. was in substantial excess of the amount for optimum insolubilization, the excess functioning as a Dmax maintainer.

Solution N a2Sz03, anhyd, g N azSOa, anhyd, g l-phenyl-3-pyraz0lidone, Ascorbic acid, g

20, liter pH Further processing as in Example I gave positive sil'ver images with the strip processed in Solution B (containing the reducing agents) exhibiting about twice the effective speed of the control strip processed in Solution A.

EXAMPLE VIII Ascorbic acid10 g. 1-phenyl-3-pyrazolidone1 g. N212CO320* g.

H O to 1 liter.

Both films were exposed and processed as in Example I, using Solution A of that Example (the control solution containing no reducing agents) as the dissolution developer. The film containing reducing agents in the emulsion had about 140% higher effective speed than the control.

EXAMPLE IX A support as described in Example I was coated with a thin subbing layer from a 5% by weight aqueous gelatin solution. Another support was coated similarly except that ml. of the ascorbic acid/1-phenyl-3-pyrazolidone solution of Example VIII were added per liter of the 5% gelatin solution. Both of the coated supports were then overcoated with the photosoluble silver chloride emulsion of Example I and processed as in Example I using Control Solution A (except that the solution pH was 10.0). By comparing the images formed in the two elements it was obvious that the element having reducing agents in the gelatin layer exhibited greatly increased eifective speed at lower exposure levels with smaller increases in elfective speed at higher exposure levels. Thus the reducing agents caused an increase in image contrast.

EXAMPLE X Strips of a film as described in Example I were exposed as in that example for 10 seconds at a distance of 2 feet but at a reduced lamp voltage of 40 volts. Dissolution and reducing dissolution developers A, B, C and D were prepared as follows:

Solution I II III IV H20, ml 800 800 800 800 p-Methylaminophenol sulfate, g 3 3 0 N azSO 50 50 0 Hydroquinone, g 0 9 0 KzC s, g 50 50 0 KBr,g 4.5 4.5 0 Nazszoa, g 0 O 127 Water, mL, to 1 ,000 1,000 1,000

Dissolution and reducing dissolution developers A B O D Solution, m1.:

I 0 150 0 0 II- 0 0 150 0 III- 0 0 0 150 IV- 150 150 150 150 Water, ml- 150 0 0 0 1,2-dichloroethanoL ml 3 3 3 3 1 Dispersed in solution with vigorous agitation for minute.

Strips of the exposed film were processed for 2 minutes at 68 F. in the above dissolution developers, A, B, C and D. The film strips were then washed, flashed to white light, intensified by treatment for 1 minute at 68 F. in Solution III of this example, and evaluated in a manner similar to that described in Example I. The control strips treated in Solutions A and B (dissolution developers) were relatively very slow so that, at the exposure level used, positive images were barely indicated. Strips processed in Solutions C and D (reducing dissolution developers) had effective speds which were many times higher than the controls. Processing in Solution C (p methylaminophenol sulfate as the only reducing agent) resulted in lower maximum densities but also better cleanout (lower minimum densities) relative to processing in Solution D which contained hydroquinone as a second reducing agent.

EXAMPLE XI step wedge and a Wratten No. 79 filter for 10 seconds at a distance of 76 cm. from a 500-watt tungsten filament lamp. The exposed strips were processed for 5 minutes at 68 F. in the following reducing dissolution developer solutions:

Solution A B O D E F G H I J 1 H2O, ml 500 500 500 500 500 500 500 500 500 500 NazSzOa, g 32 32 32 32 32 0 0 0 O 0 KzSzOa, g. 0 0 0 0 0 32 32 0 0 0 NH4SzO4, 0 0 0 0 O 0 0 32 32 32 NaOH crystals, g 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1-phenyl-3-pyrazolidone,g .5 0.5 0 0 0.5 0.5 0.5 0.5 0.5 0.5 1-phenyl-4methyl-3- pyrazolidone, g 0 0 0. 5 O. 5 0 O 0 0 0 0 NazS0 anhyd., g 10 10 10 1O 0 10 0 l0 0 1O Ascorbic acid, g 2.5 0 0 2.5 2.5 2.5 2.5 2.5 2.5 0 o-Phenylphenol, 5%

by wt. solution in 1 N NaOII, ml--- 10 10 10 10 10 10 10 10 10 10 Glacial acetic acid, g 1. 3 1. 3 1. 3 1. 3 1. 3 1. 3 1. 3 1. 3 1. 3 1. 3 H2O, liter 1 1 1 1 1 l 1 1 l 1 pH Ad usted to 8.8-8.9 for all solutions 1 With solutions .1, pHs of 7.0 and 7.5 were found practical with slight speed losses.

The film strips were then washed, flashed to white light, intensified, washed, dried and evaluated as in Example I. All of the solutions contained the preferred reducing agent, l-phenyl-3-pyrazolidone, or its 4-methyl derivative. The 4-methyl derivative gave comparable results except for a very slight loss in eflFective speed. Ascorbic acid, as an auxiliary reducing agent, gave an increase in effective speed but at the expense of an increase in stain. Potassium and ammonium thiosulfates, as silver halide solvents, gave results comparable to those obtained with sodium thiosulfate, with the use of ammonium thiosulfate appearing to offer a means of obtaining a lower contrast image. Sodium sulfite provides slight advantages with certain formulations but has no major effeet on the processing results. Another film strip which received the same exposure gave almost no detectable image when processed in a dissolution developer containing no reducing agents.

EXAMPLE XII Exposed strips of film as described in Example XI were treated at 68 F. for various times varying between 1 and 5 minutes in the reducing dissolution developing solutions below, all of which contained 1-phenyl-3-pyrazolidone as the silver halide reducing agent. The more reactive solutions, e.g., those having a higher pH and having higher concentrations of the silver halide reducing agent and the silver halide solvent, required shorter times of development. Good, positive silver halide images were obtained at the optimum processing times in each of these solutions. The images were intensified after dissolution development as described in Example XI.

H20, ml NazSzOa, anhyd., g K2SO3, anhyd., g 1-phenyl-3-pyrazolidone, g o-l1henylphnol,15% by wt 1 H2O, liter The present invention has the advantages of the basic process of photosolubilization, especially that of a very simple, single step process of obtaining a positive image. The primary advantage of the present invention over the basic process is a very substantial increase in effective photographic speed of the element. Elements which are severely underexposed for use according to the basic process are able to form good positive images by the process of the present invention. It is believed that the apparent increase in light sensitivity of elements processed according to this invention is obtained by using the latent image silver to modulate the photosoluble image. This has led to positive image speeds (photosoluble emulsions processed by reducing dissolution development) approaching the speeds of the same emulsions processed conventionally to give negative silver images. Thus reducing dissolution development has increased photosoluble speed up to two orders of magnitude.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for forming a direct-positive silver halide image in a photosoluble silver halide layer which comprises:

(a) forming a direct-positive latent image by imagewise exposing a photosoluble emulsion layer containing silver halide crystals treated with sufficient organic compound whose silver salt is less soluble in water than silver chloride to make said crystals relatively less soluble in a silver halide solvent prior to exposure, the organic compound being present in such amount, in terms of the ratio of its weight to the surface area of said silver halide crystals that when admixed in such ratio with an aqueous silver chlorobromide (70/30 mole percent) gelatin dispersion containing 10 g. of gelatin per mole of Ag and 0.57 mg. of Ag per ml., and said silver chlorobromide dispersions is treated with 10%, by weight, aqeous sodium thiosulfate so that the resulting mixture contains 0.29 mg. of silver and 100 mg. of sodium thiosulfate, at least three times the amount of silver chlorobromide remains undissolved as compared with a similar dispersion successively treated with by weight, aqueous sodium hypochlorite and by weight, aqueous sodium thiosulfate so that the resulting mixture contains 0.29 mg. of silver, 25 mg. of sodium hypochlorite and 100 mg. of sodium thiosulfate, after vigorous agitation of both dispersions for 30 seconds at 25 C., and

(b) dissolution developing said direct-positive latent image in a solution of a silver halide solvent in the presence of a small amount of a silver halide reducing agent and D maintaining amounts of 0.01 to 50.0 g. per liter of solution of a D maintaining agent devoid of ionizable iodine or oxidizing or reducing groups that are active at the working pH so that dissolution of exposed silver halide in said solvent is substantially greater than the reduction by said reducing agent Without any substantial reduction of silver halide to visible silver.

2. A process according to claim 1 wherein said D maintaining agent is present initially in said layer.

3. A process according to claim 1 wherein said D maintaining agent is present initially in said solution.

4. A process according to claim 3 wherein said agent is 1,2-dichloroethane.

5. A process according to claim 3 wherein said agent is a phenolic compound devoid of ionizable iodine, or oxidizing or reducing groups that are active at the pH.

6. A process according to claim 3 wherein said agent is a phenol having a hydrocarbon substituent in the o-position to the hydroxyl group.

7. A process according to claim 3 wherein said agent is o-phenylphenol.

8. A reducing dissolution developer solution consisting essentially of 10 Water-soluble thiosulfate salt20 to 300 g. Water-soluble sulfite salt0 to g. Silver halide developing agent-0.1 to 3.0 g. D maintaining organic compound-0.01 to 50.0 g. Alkali to bring solution pH within the range-7.0 to 11.5 Water to make 1 liter.

9. A solution according to claim 8 wherein said D- maintaining agent is 1,2-dichloroethane.

10. A solution according to claim 8 wherein said D maintaining agent is a phenolic compound devoid of ionizable iodine, or oxidizing or reducing groups that are active at the working pH.

11. A solution according to claim 8 wherein said D maintaining agent is a phenol having a hydrocarbon group in the o-position to the hydroxyl group.

12. A solution according to claim 8 wherein said DmzaLx maintaining agent is o-phenylphenol.

13. A solution according to claim 8 wherein said developing agent is 1-phenyl-3-pyrazolidone.

14. A developer solution according to claim 8 wherein said developing agent is N-methy1-p-aminophenol.

References Cited UNITED STATES PATENTS 3,495,983 2/1970 Strange 9664 3,493,373 2/1970 Blake 9664 3,495,982 2/ 1970 Blake 9664 WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner US. Cl. X.R. 9694