IL44046A - Process and inhibitor removing bath for direct positive color photographic development - Google Patents

Abstract

1451422 Photographic dye formation inhibitor removing bath MINNESOTA MINING & MFG CO 21 Jan 1974 [22 Jan 1973 28 Dec 1973] 02786/74 Heading G2C A photographic bath comprises (A) a colour accelerating agent (i.e. materials which accelerate colour dye formation in the development of photographic silver halide reversal films) at at least 0.05 moles/litre, (B) a contrast control agent (i.e. materials which control the gradation of the intensity of dye images in colour photographic silver halide processing) at at least 4 x 10<SP>-3</SP> moles/litre and (C) a buffering agent to provide a pH within the bath of 11-13, the bath containing less than 0.05 moles/litre phosphate and less than one half the molar concentration of colour developer required for full colour development i.e. to generate an optical density of 3À0. The bath may contain no colour developer. Component (A) may be ethylene diamine or (3-phenylethyl amine. Component (B) may be citrazinic acid or potassium iodide or bromide. Component (C) may be trisodium phosphate. The bath may also contain (D) a colour reversal agent (i.e. a nucleating or fogging agent) at at least 1À6 x 10<SP>-</SP><SP>3</SP> moles/litre e.g. a borohydride, amine-complexed borane or hydrazine. A colour photographic reversal development process comprises (1) treating a colour photographic element having a hydrophilic colloid silver halide layer bearing a latent image with a bath comprising in aqueous solution of pH 8À5-14 (a) at least 0À02 moles/litre photographic colour developing agent capable, upon oxidation, of reacting with a colour coupler to form a dye and having a polarographic half-wave potential at pH 11À0 of -159 to -305 mV, (b) at least one black and white developing agent having a polarographic half-wave potential at pH 10À0 of -10 to -187 mV and (c) a water-soluble, dye formation inhibitor at at least 0À10 moles/litre present in sufficient quantity so that all dye formation of a silver halide photographic element is restrained in the bath after the element has been exposed to light, the mole ratio of (c) to (a) being a least 0À97, to develop solely a negative black and white silver image therein, (2) fogging and (3) treating with a bath as defined in the previous paragraph to reduce the inhibiting effect of (c). Fogging (2) may be effected by colour reversal agent (d) in bath (3). Specification 1403408 is referred to. [GB1451422A]

Description

Process and inhibitor removing ba h for direct positive color photographic development MINNESOTA WIJSIJSO AND MANUFACTUBING COMPANY A widely used process for reversal color development of silver halide photographic films emplo^^ a succession of baths through which exposed photographic films must be passed. For example, a first bath may include a black and white developing agent which reduces silver halide in latent image areas of a film to silver, forming negative silver image therein. Thereafter the film may be uniformly exposed to light to form fog centers in undeveloped areas of the film, and then treated with a color developer solution in which a color developing agent reduces silver halide in the fogged areas to silver, and is itself oxidized. The oxidation product of the developer reacts with one or more color couplers which may be distributed throughout various layers of the film to form dyes therein. The silver images may then be bleached from the film, and unreacted silver halide may be removed therefrom by "fixing" to thus provide positive, colored images. To avoid cross-contamination of the various processing baths, a number of intermediate wash baths are commonly employed. Further, a "stop" bath is ordinarily utilized to halt black and white development immediately after treatment of the film in the black and white developer bath.

As will be evident from the above description, the process described employs many steps and utilizes many different processing baths. In addition, the shelf-life of these prepared solutions are poor. Further, the above procedure must be very carefully regulated in order to provide satisfactory photographic color repro- 44046/2 ductions. Moreover, the time which is required to full,^ process an exposed roll of color film (a major cost factor) is inordinately long. A faster, more efficient, less-detailed color reversal development process is hence much to be desired.

A novel color reversal process for the rapid access positive color development of silver _lide photographic elements which eliminates some of these steps and greatly reduces the complete development time was disclosed in U.S. Patent Specification No. 3,883,354.

The process disclosed therein develops color photographic elements through the use of a monobath developing solution. A single developing solution which comprises a combination of at least one color developing, agent, at least one black and white developing agent, each having given electromotive potentials, and a dye-formation inhibitor. Upon oxidation of the color developing agent by the silver halide of the emulsion, the dye formation inhibitor prevents the formation of a color image by combining or associating with the oxidized color developer. To form the color positive image, the inhibiting effect on the oxidized color developer must be reduced sufficiently to allow development of a dye image or be rec moved. In the instance where the oxidized color developer is inhibited from coupling with dye couplers in the emulsion because of the formation of salts with the oxidized developer (as by the addition of a sufficient concentration of sulfite ions to the bath), the inhibiting moiety should be removed as by washing the element with water. All of this is disclosed in the above-mentioned U.S. Patent Specification, the entire disclosures of which are incorporated herein.

The essential characteristics of the color reversal process and developing monobath of U.S.

Patent Specification No. 3,883,354 are as follows : Monobath — an aqueous solution containing at least one photographic color developing agent in a total color developing agent concentration of at least about 0.02 moles/liter capable, upon oxidation thereof, of reacting with a photographic color coupler to form a dye; at least one black and white color developing agent having a polarographic half-wave potential at pH 10.0 of from about -10 millivolts to about -187 millivolts; and a water-soluble, dye-formation inhibitor in sufficient quantity to restrain substantially all dye formation in a silver halide photographic element and in an absolute concentration of at least about 0.10 moles/liter, the molar ratio of inhibitor to color developer being at least about 0.97· Process — (1) immersing a silver halide, color photographic element having a latent image therein Into the monobath solution of the invention to imbibe said silver halide element (the emulsion layer thereof containing the silver halide) with said 44046/2 monobath solution to develop solely a negative black and white silver image ^ therein; (2) thereafter fogging said silver halide layer to render said layer developable in non-imaged areas; (3) treating said silver halide layer to reduce the inhibiting effect of said dye formation l^nhib-itor without intermediate removal of said imbibed solution; and ( ) allowing development therein of a positive color image in the presence of a color coupler.

It has been found in the practice of the above-mentioned color reversal process that although sharp prints with viewable color densities and contrasts are formed when the monobath devi loped elements are washed, as with water, it is desirable to enhance the densities and tones produced by such processing.

This invention relates to a treatment bath, and more specifically to a wash bath, which when used as the wash bath in the process of U.S. Patent Specification No. 3,883,354 after immersion of the element into the monobath developing solution, significantly enhances the densities and tones ^of the final color image.

In another aspect, this invention relates to a process for rapid access positive color development of silver halide photographic elements.

In a further aspect, this invention relates to wash bath compositions which will remove dye formation inhibiting effects present within silver halide photo- graphic elements as a result of immersion in the developer monobath and partial development (without the subseque^ washing step) according to the process of U.S. Patent Specification No. 3,883,354 (hereinafter the Molenda proces By use of the term partial development, the fact that the s image has been developed while the dye image has been prevented is emphasized. i Summary of the Invention After an exposed color photographic element has been Immersed in the monobath of the Molenda process, there is substantially no colored dye present in the resultant image due to the effect of the dye formation inhibitor. In order to achieve a satisfactory color image, this inhibiting effect must be removed in the subsequent wash bath. In many instances, water alone is sufficient to remove much of the inhibiting effect, however, the final images may not be as good as those obtainable through other processes, without further treatment .

It has been found that many different enhancing functions may be included into this inhibitor removing bath so that the final color image is at least comparable to those re-sultant from other processing techniques.

It has further been found that these functions may be combined into one bath without adverse interreaction between the components and without greatly extending the total processing time for the Molenda process.

It has been found that if, at a minimum, four washing environment characteristics or processing functions are provided in wash baths following development in the Molenda monobath, color images of very high quality θΆτ ' be produced. These functions which must be provided are: 1. color accelerating, 2. color reversal [nucleating or fogging], 3. contrast control, and 4. a pH control agent (buffering within a particular pH range).

It should be noted that light may be used for the color reversal and that the inhibitor removing bath providing functions necessary for effective inhibitor removal may actually be more than one bath if desired. After immersion in the Molenda monobath these fou functions or only 1, 3* and 4 following a light reversal step may be provided by the use of specific classes of compounds in a wash bath. The compounds which provide these functions are those compounds known in the art as : (1) color accelerati g agents, (2) color reversal agents, (3) contrast control agents, and (4) buffering or pH control agents. It is an obvious consideration in the selection of components for this bath that the individual components should also be selected for mutual compatibility.

Color accelerating agents are those materials known in the photographic art which speed up color dye formation in the development of photographic reversal films. Examples of such are ethylene diamine and β-phenyl ethyl amine. Further examples may be found in Mason, Photographic Processing Chemistry, Focal Press p 259 ff.

Color reversal agents, also known in the art as nucleating agents or fogging agents, cause sites with developmental sensitivity to form on silver hallde grains In the photographic emulsions. These sites activate 4-the grain so that It may be developed Into an Image by reduction to metallic silver, as by p_-phenylene diamine developers. Fogging agents are discussed, for example, In 0. P. Duf in, Photographic Emulsion Chemistry, Focal Press, pp 202-3, and 22 (1966); and P. Glafkides, Photographic Chemistry, Vol. II, Foundation Press, pp 626-7 (I960).

Contrast control agents are those materials which control the gradation of the intensity of dye images in color photographic processing. The dye density gradient in a photographically developed emulsion can be reduced by using less silver halide or by reducing the size of the silver halide grains. To achieve the desired gradient by these methods, however, requires either the use of Insufficient silver halide to generate acceptable images in the first Instance, or the sacrifice of sensitivity in the emulsion with small grain sizes. U. S. Patents N03. 3,520,690; 2,7^2,832, and 2,689,793 disclose numerous compounds known in the art as contrast control agents. Specific examples of contrast control agents are potassium bromide or citrazinic acid.

The buffering agent should maintain a pH in the Inhibitor removing bath of from at least about pH 11.0 to about pH 13.0. The preferred pH range for these buffering agents would be from about 11.7 to 12.5.

When the pH control or buffering agent contains the phosphate ion, it has been found that only limited concentrations thereof are tolerable. When the concen- tration of the phosphate ion excedes .05 moles/liter, an undesirable green cast develops in the image. There^ fore, when phosphate ion is used in the inhibitor removing bath of the present invention, it should be in a concentration of less than 0.05 moles/liter.

The amounts of the four agents which must be in the inhibitor wash bath to effect the desired results depends to some degree upon the active strength of the particular compound selected to provide that function. The minimum amounts, based on a few selected and preferred compounds for the agents (e.g., ethylene diamine, hydrazine, sodium borohydride, potassium bromide) are as follows: 1. color accelerating agent in sufficient quantity to enable the developed color photographic element to have a minimum Drnax of 1.5. This is approximately a minimum amount of 0.05 moles/liter. 2. color reversing agent in sufficient quantity to render a color photographic element developable in non-imaged areas (non-photosensitized areas, or silver halide grains not having developable latent image). This is approximately a minimum amount of 1.6 x 10""^ moles/liter. 3. contrast control agent in sufficient quantity to yield a contrast ( γ ) in a color photographic element of 2.4 or less. Preferably a gamma range of 0.9- 2.1» is desired. This is a minimum of about 4 x 10*"^ moles liter After development of the colored, positive Image, the ordinary process steps normally used in finishing the picture should be used here. That is, after the bara to remove the inhibiting effect, there should be an acid stop bath, then bleach bath, fix bath (or bleach/fix bath), wash, and stabill2ing bath. Hardeners may be added to any or all of the stop, bleach, fix or bleach/fix baths, or a prehardening bath may be .used prior to development in the monobath. The compositions of such baths are well known in the art and need not be discussed here.

Between the development bath and the bath to remove the inhibitor a quick wash step has been found desirable to remove the solution retained on the surface of the photographic element so as to prevent contamination of the latter bath. This wash is not of sufficient length or intensity as to reduce the inhibiting effect, but is only used to remove the solution held by surface tension on the photographic element. Of course if one is using water as the inhibitor removing second bath such a quick wash would be unnecessary.

Certain other known photographic addenda may be added to the inhibitor removing bath. Stabilizers or antioxidants such as sulfite and ascorbic acid may be added. However, when the inhibitor removing bath is to remove a sulfite inhibitor from the photographic emulsion being processed, it is desirable to keep the concentration of sulfite in the bath at minimum levels. - 8a - Other addenda such as color developing agent may be added to the Inhibitor removing bath. In small^ quantities, such color developer may enhance the dye Image or cause no change in image quality. Again, how-ever, only limited amounts of color developer are tolerable in the inhibitor removing bath. It has been found that when the concentration of color developer in the bath excedes one-half the molar concentration necessary for full color development (i.e., to generate an optical density of 3.0), the quality of the image is significantly reduced. It is therefore desirable to have in the inhibitor removing bath no more than one-half the molar concentration of color developer necessary to produce full color development.

The invention will be further illustrated by the following Examples.

PREPARATION A A commercially available photographic film coated with red, green and blue sensitive layers of silver hallde (Ektochrome X) was exposed through a wedge (continuous, logarithmic density) in a sensitometer . The exposed film was then Immersed in a developing monobath comprised of: Water 850 ml.

Sodium sulfite 48.0 g.

Sodium hexametaphosphate 2.0 g. 2-methyl-4 ( -eth l-N-B-hydroxy- ethyl)amino aniline sulfate salt 28.0 g.

Hydroqulnone 6.0 g.

Sodium thiocyanate 0.5 g.

Potassium bromide 2.0 g.

Potassium iodide .01 g.

Sodium carbonate 30.0 g.

Water to 1000 Sodium hydroxide to a pH of 10.2 (about 4.0 g.) for 3-5 minutes at 73°Ρ· These color photographic elements as yet had no developed color image due to the action of the dye formation inhibitor.

Film strips partially developed in the above developing bath composition were used as the film strips in those following examples where inhibitor removing baths are illustrated. The term "partially developed" as used in the context of this invention refers to the fact that the silver image has been developed, but the color dye image has not been developed because of the dye formation inhibiting effect of the development baths of the olenda process.

EXAMPLE I A partially developed film strip (according to Preparation A) was placed in a bath of water for 5 seconds to remove droplets of the monobath from the surface of the film. The film was then immersed in an inhibitor-removing bath (without a color accelerating agent) made of: Formulation I Water 2850 ml.

Sodium borohydride (color reversal agent) .150 g.

Hydrazine (color reversal agent) .075 ml.

Potassium bromide (contrast control agent) 3·0 g.

Na3P01| · 12 H20 (buffering agent) 12.0 g.

Na2S03 .3 g.

KI solution (1 g/1) 30 ml.

Water to 3000 ml.

The pH was adjusted to 12.29 by adding sodium hydroxide solution. The film was then immersed in a stop bath solution of: Glacial acetic acid 12.0 ml.

Sodium acetate 6.3 g.

Water to 1000 ml. for 1 minute; thence into a bleach bath of: Water 800 ml.

Potassium ferricyanide 112.0 g.

Potassium bromide 24.0 g.

Disodium hydrogen phosphate 12.0 g.

Sodium thiocyanate 12.5 g.

Sodium dihydrogen phosphate 12.5 g.

Water to 1000 ml. for 2.5 minutes. At this time, the dye image is visible. Removal of the silver halide occurs when the film is fixed in a solution of: Water 800 ml.

Ammonium thiosulfate (60% aqueous solution) 120 g.

Sodium metabisulfite 20.0 g.

Water to 1000 ml.

Washing twice with water removes residual thiosulfate, so that the film dries to a clear state .

Densitometry of the film shows : Dmin. Contrast Dmax.

To blue light .35 • 5 2.1 To green light .35 • 5 1.2 To red light .20 .5 1.2 EXAMPLE II The above developing process was repeated. The bath contained, in addition to the components listed above in Formula I, 12.5 ml/1 of ethylene diamine (a color accelerating agent). The bath gave densitometry results as follows: Dmin. Contrast Dmax.

To blue light .28 1.65 3.40 To green light • 35 1.A5 2.85 To red light .20 1.35 2.85 As can be seen from the densitometric : data of this example, the color accelerating agent in combination with the other three essential agents of the wash bath yields much more satisfactory color densities than does a wash bath containing only the three agents (reversing agent, buffering agent, and contrast control agent).

EXAMPLE III An inhibitor removing bath of the following composition was made to investigate the effects of pH variance on the sensitometric qualities of the developed Images .

Water 2850 ml.

Na3P04 12 g.

KI solution (1 g/1) 30 ml.

KBr 3.0 g.

Na2S03 0.3 g.

Ethylene diamine 37 ml.

Water to 3000 ml.

The bath was split into four portions. In the first and second, 18 mg. hydrazine and 37 mg. borohydride were added. The third and fourth portions contained 6 mg. t-butylamine borane. The first and third portions were adjusted to a pH of 11.0, and the second and fourth portions adjusted to a pH of 12.3> all pH control accomplished by the addition of a sodium hydroxide solution.

The film was processed as described earlier, using each of the inhibitor removing bath portions, and the following sensitometric results were obtained: Portion 1 fog contrast Dmax blue .12 .5 1.96 green .36 .5 1.86 red .28 .5 1.60 Portion 2 fog contrast Dmax blue .28 1.65 3.40 green .35 1.45 2.85 red .20 1.35 1.85 Portion 3 fog contrast Dmax blue .10 .6 1.62 green .36 .6 1.38 red .26 .6 1.34 Portion 4 contrast Dmax blue .18 1.65 2.6 green .40 1.50 2.6 red .34 1.65 3-3 The data shows the significant effect of pH levels upon the quality of the images produced by this method of developing color images.

EXAMPLE IV The effect of contrast control agents was examined by making three inhibitor removing wash baths follows : Water 1 1.

Sodium borohydride 50 rag.

Hydrazine 25 mg.

Sodium sulfite .1 g Na^O^ H20 4.0 g Ethylene diamine 12.0 g.

NaOH to pH 12.2 In the first bath 0.05 g. of K Br was added, in the second 1.0 g. of K Br and in the third 2.0 g. of K Br.

The density results were: K Br K Br K Br 05 1.0 2.0 Dmin To blue light • 30 • 30 .17 To green light • 24 .28 .25 To red light • 18 .36 .32 Mean Contrast To blue light 1. 65 1.56 1.65 To green light 2. 20 2.00 1.85 To red light 1. 82 1.81 1.68 Dmax To blue light 3. 25 3.68 3.04 To green light 3. 67 3.54 3.04 To red light 3. 60 3.45 3.14 The sensitometric data clearly show that de-sirable contrast and Dmax are dependent upon the use of contrast control agents in the inhibitor removing bath.

Water 925 ml.

Calgon (sodium hexametaphosphate) 2.0 g 4-N,N-diethylamino-o-toluidine 6.0 g Potassium sulfite 48.0 g Phenidone .3 g Hydroquinone 6.0 g Potassium bromide 2.0 g Potassium iodide .01 g.

Sodium thiocyanate .5 g.

Sodium carbonate 30.0 g. φ Water to 1 1.

Sodium hydroxide to pH of 10.2 The exposed film was immersed in this bath for 3· 5 minutes at 73°F. It was washed for five seconds and then immersed in an inhibitor removing bath consisting of: 4< Water 1 1.

Sodium borohydride 50 mg.

Hydrazine 25 mg.

Ethylene diamine 12.0 g.

Potassium bromide 1.0 g.

Sodium sulfite .1 g.

Na3P0lj 12 H20 ^.0 g.

NaOH to pH of 12.2 The stop, bleach, fix, and wash steps were repeated as in previous examples.

Densitometry readings were : Dmin. Dmax.

To blue light .56 3-26 To green light .65 . 8 To red light Λ5 2.70 EXAMPLE V Another developing bath according to U. S. patent specification No. 3,883,354 was used to partially develop Ektochrome X, exposed as in Preparation A. This developing bath consisted of: Water 925 ml.

Sodlum/hexametaphosphate 2.0 g. 2-methyl-4 (N-ethyl-N-3-hydroxy ethyl) amino aniline sulfate salt 22.0 g.

Potaasium sulfite 48.0 g.

Phenidone .30 g.

Hydroquinone 5·0 g.

Potassium bromide 2.0 g.

Potassium iodide .01 g.

Sodium thiocyanate .5 g.

Sodium carbonate 30.0 g.

Water to 1 1.

Sodium hydroxide to pH 10.2 The exposed film was immersed in the monobath at 73°P. for 3-5 minutes. After a five-second wash in tap water, the inhibitor removing wash bath described in the previous instance was used to completely develop the color in the film. Following the stop, bleach, fix and wash operation, densitometry was: Dmin. Dmax.

To blue light .24 3-20 To green light .28 2.65 To red light .30 2.50 The same monobath was used to partially develop similarly exposed film, but the ethylene diamine concentration was reduced to 5 gm/1 in the inhibitor removing wash bath. Densitometry readings were lower in the Dmax.

Dmin. Dmax.

A To blue light .23 2.70 To green light • 34 2.15 To red light • 34 2.10 Note in this comparison that the reduced concentration of color developer in the Molenda developer bath and of ethylene diamine in the inhibitor removing wash bath lowers the Dmax to an undesirable level.

The sensitometric parameters, contrast, and Dmax, have been indicated throughout the specification as primarily dependent upon the contrast control agent and the color accelerating agent respectively, as is correct in this developing procedure. Any significant variation in the other components (pH control agent, and reversing agent) will also secondarily affect these parameters, but as previously stated, the primary effects on those particular parameters are caused by the contrast control agent and color accelerating agent once the pH range is established and the color reversal is effected. ■» 31 y n 2 £717 » s 3 - -- » - » » T > 5 roceso nd inhibitor removing bo.th for direct positive color photographic development U¾W/iA iiJ ItK.; AtvlJ li vMiiTVOiUJaKtt Cli JrVNY A widely used process for reversal color development of silver halide photographic films employ a succession of baths through which exposed photographic films must be passed. For example, a first bath may include a black and white developing agent which reduces silver halide in latent image areas of a film to silver, forming negative silver image therein. Thereafter the film may be uniformly exposed to light to form fog centers in undeveloped areas of the film, and then treated with a color developer solution in which a color developing agent reduces silver halide in,, the fogged areas to silver, and is itself oxidized. The oxidation product of the developer reacts with one or more color couplers which may be distributed throughout various layers of the film to form dyes therein. The silver images may then be bleached from the film, and unreacted silver halide may be removed therefrom by "fixing" to thus provide positive, colored images. To avoid cross-contamination of the various processing baths, a number of intermediate wash baths are commonly employed. Further, a "stop" bath is ordinarily utilized to halt black and white development immediately after treatment of the film in the black and white developer bath.

As will be evident from the above description, the process described employs many steps and utilizes many different processing baths . In addition, the shelf-life of these prepared solutions are poor. Further, the above procedure must be very carefully regulated in order to provide satisfactory photographic color repro- 44046/2 ' ductions. Moreover, the time which is required to full^ process an exposed roll of color film (a major cost factor) is inordinately long. A faster, more efficient, less-detailed color reversal development process is hence much to be desired.

A novel color reversal process for the rapid access positive color development of silver _lide photographic elements which eliminates some of these steps and greatly reduces the complete development time was disclosed in D.S. Patent Specification No. 3,883,354.

The process disclosed therein develops color photographic elements through the use of a monobath developing solution. A single developing solution v/hich comprises a combination of at least one color developinr agent, at least one black and white developing agent, each having given electromotive potentials, and a dye-formation inhibitor. Upon oxidation of the color developing agent by the silver halide of the emulsion, the dye formation inhibitor prevents the formation of a color image by combining or associating with the oxidized color developer. To form the color positive image, the inhibiting effect on the oxidized color developer must be reduced sufficiently to allow development of a dye image or be re<-inoved. In the Instance where the oxidized color developer is inhibited from coupling with dye couplers in the emulsion because of the formation of salts with the oxidized developer (as by the addition of a sufficient concentration of sulfite ions to the bath) , the inhibiting moiety should be removed as by washing the element with water. All of this is disclosed in the t above-mentioned U.S. Patent Specification, the entire disclosures of which are incorporated herein.

The essential characteristics of the color reversal process and developing monobath of U.S.

Patent Specification No. 3,883,354 are as follows : Monobath — an aqueous solution containing at least one photographic color developing agent in a total color developing agent concentration of at least about 0.02 moles/liter capable, upon oxidation thereof, of reacting with a photographic color coupler to form a dye; at least one black and white color developing agent having a polarographic half-wave potential at pH 10.0 of from about -10 millivolts to about -187 millivolts; and a water-soluble, dye-formation inhibitor in sufficient quantity to restrain substantially all dye formation in a silver halide photographic element and in an absolute concentration of at least about 0.10 moles/liter, the molar ratio of inhibitor to color developer being at least about 0.97.

Process — (1) immersing a silver halide, color photographic element having a latent image therein into the monobath solution of the invention to imbibe said silver halide element (the emulsion layer thereof containing the silver halide) with said 44046/2 monobath solution to develop solely a negative black and white silver image therein; (2) thereafter fogging said silver halide layer to render said layer developable in non-imaged areas; (3) treating said silver halide layer to reduce the inhibiting effect of said dye formation i^hi itor without intermediate removal of said imbibed solution; and (Ί) allowing development therein of a positive color image in the presence of a color coupler.

It has been found in the practice of the above-mentioned color reversal process that although sharp prints with viewable color densities and contrasts are formed when the monobath devf loped elements are washed, as with water, it is desirable to enhance the densities and tones produced by such processing.

This invention relates to a treatment bath, and more specifically to a wash bath, which when used as the wash bath in the process of U.S. Patent Specification No. 3,883,354 after immersion of the element into the monobath developing solution, significantly enhances the densities and tones Of the final color image.

In another aspect, this invention relates to a process for rapid access positive color development of silver halide photographic elements.

In a further aspect, this invention relates to wash bath compositions which will remove dye formation Inhibiting effects present within silver halide photo- graphic elements as a result of immersion in the developer monobath and partial development (without the subseque washing step) according to the process of U.S. Patent Specification No. 3,883,354 (hereinafter the Molenda process) . By use of the term partial development, the fact that the silv image has been developed while the dye image has been prevented is emphasized.

Summary of the Invention After an exposed color photographic element has been immersed in the monobath of the Molenda process, there is substantially no colored dye present in the resultant image due to the effect of the dye formation inhibitor. In order to achieve a satisfactory color image, this inhibiting effect must be removed in the subsequent wash bath. In many instances, water alone is sufficient to remove much of the inhibiting effect, however, the final images may not be as good as those obtainable through other processes, without further treatment .

It has been found that many different enhancing functions may be included into this inhibitor removing bath so that the final color image is at least comparable to those resultant from other processing techniques.

It has further been found that these functions may be combined into one bath without adverse interreactlon between the components and without greatly extending the total processing time for the Molenda process.

It has been found that If, at a minimum, four washing environment characteristics or processing functions are provided in wash baths following development in the Molenda monobath, color images of very high quality car be produced.. These functions which must be provided are: 1. color accelerating, 2. color reversal [nucleating or fogging], 3» contrast control, and ij. a pll control agent (buffering within a particular pH range).

It should be noted that light may be used for the color reversal and that the inhibitor removing bath providing functions necessary for effective inhibitor removal may actually be more than one bath if desired. After immersion in the Molenda monobath these four functions or only 1, 3> and *J following a light reversal step may be provided by the use of specific classes of compounds in a wash bath. The compounds which provide these functions are those compounds known in the art as: (1) color accelerating agents, (2) color reversal agents, (3) contrast control agents, and ( ) buffering or pH control agents. It Is an obvious consideration in the selection of components for this bath that the individual components should also be selected for mutual compatibility.

Color accelerating agents are those materials known in the photographic art which speed up color dye formation in the development of photographic reversal films. Examples of such are ethylene diamine and 0-phenyl ethyl amine. Further examples may be found in Mason, Photographic Processing Chemistry, Focal Press p 259 ff.

Color reversal agents, also known in the art as nucleating agents or fogging agents, cause sites with developmental sensitivity to form on silver hallde grains in the photographic emulsions. These sites activate the grain ao that it raay be developed into an image by reduction to metallic silver, as by p_-phenylene diamine developers. Fogging agent* are discussed, for example, In G. F. Duffin, Photographic Emulsion Chemistry, Focal Press, 202- 3 , and 224 ( 1966 ) ; and P. Glafkidea, Fhotogrephic Chemistry, Vol. II, Foundation Press, pp 626 - 7 ( i 960 ) .

Contrast control agents are those materials which control the gradation of the Intensity of dye Images in color photographic processing. The dye density gradient in a photographically developed emulsion can be reduced by using less silver hallde or by reducing the ΓΛΖΘ of the silver halide grains. To achieve the desired gradient by these methods, however, requires either the us e of insufficient silver halide to generate acceptable ima es in the first Instance, or the sacrifice of sens-it vlty in the emulsion with small grain sizes. U. S. Patents Nos. 3 , 520 , 690 ; 2 , 7^ 2 , 832 , and 2 , 689 , 793 disclose numerous compounds known in the art as contrast control age ts. Specific examples of contrast control agents r potasnium bromide or citrazinic acid.

The buffering agent should maintain a pH in the inhibitor removing bath of from at least about pH 11. 0 to about pH 13. 0. The preferred pH range for these buffering agents would be from about 11 . 7 to 12 . 5 .

When the pH control or buffering agent contains the phosphate ion, It has been found that only limited concentrations thereof are tolerable. When the eoncen- - 7 - tration of the phosphate ion excedes .05 moles/liter, an undesirable green cast develops in the image. There fore, when phosphate ion is used in the inhibitor remov- ing bath of the present invention, it should be in a concentration of less than 0.05 moles/liter.

The amounts of the four agents which must be In the inhibitor wash bath to effect the desired results depends to some degree upon the active strength of the particular compound selected to provide that function. The minimum amounts, based on a few selected and preferred compounds for the agents (e.g., ethylene diamine, hydrazine, sodium borohydrlde, potassium bromide) are as follows : 1. color accelerating agent in sufficient quantity to enable the developed color photographic element to have a minimum Dmax of 1.5. This is approximately a minimum amount of 0.05 moles/liter. 2. color reversing agent in sufficient quantity to render a color photographic element developable in non-imaged areas (non-photosensitized areas, or silver halide grains not having developable latent image). This Is approximately a minimum amount of 1.6 x 10~^ moles/liter 3. contrast control agent in sufficient quantity to yield a contrast ( γ ) in a color photop^raphic element of 2.H or less. Preferably a gamma range of 0.9- 2 A is desired. This is a minimum of about l x 10~3 moles/liter.

After development of the colored, poaltlve Image, the ordinary process steps normally used in finishln the picture should be used here. That is, after the batn to remove the inhibiting effect, there should be an acid Btop bath, then bleach bath, fix bath (or bleach/fix bath), wash, and stabilizing bath. Hardeners may be added to any or all of the stop, bleach, fix or bleach/fix baths, or a prehardening bath may be used prior to development in the monobath. The compositions of such baths are well known in the art and need not be discussed here.

Between the development bath and the bath to remove the inhibitor a quick wash step has been found desirable to remove the solution retained on the surface of the photographic element so as to prevent contamination of the latter bath- This wash is not of sufficient length or intensity as to reduce the Inhibiting effect, but is only used to remove the solution held by surface tension on the photographic element. Of course if one Is using water as the inhibitor removing second bath such a quick wash would be unnecessary.

Certain other known photographic addenda may b added to the inhibitor removing bath. Stabilizers or antioxidants such as sulfite and ascorbic acid may be added. However, when the inhibitor removing bath is to remove a sulfite inhibitor from the photographic emulsion being processed, it is desirable to keep the concentration of sulfite in the bath at minimum levels. - 8a Other addenda such as color developing agent may be added to the inhibitor removing bath. In small quantities, such color developer may enhance the dye image or cause no change in image quality. Again, how-ever, only limited amounts of color developer are tolerable in the inhibitor removing bath. It has been found that when the! concentration of color developer in the bath excedes one-half the molar concentration necessary for full color development (i.e., to generate an optical density of 3.0), the quality of the image is signi icantly reduced. It is therefore desirable to have in the inhibitor removing bath no more than one-half the molar concentration of color developer necessary to produce full color development.

The invention will be further Illustrated by the following Examples.

PREPARATION A A commercially available photographic film coated with red, green and blue sensitive layers of silver halide (Ektochrome X) was exposed through a wedge (continuous, logarithmic density) in a sensitometer . The exposed film was then immersed in a developing monobath comprised of: Water 850 ml.

Sodium sulfite JJ8.0 g.

Sodium hexametaphosphate 2.0 g. meth 1-4 (N-ethyl-N- ^-hydroxy ethyl )amino aniline sulfate 28.0 g.

Hydroquinone 6.0 g.

Sodium thiocyanate 0.5 ε· Potassium bromide 2.0 g.

Potassium iodide .01 g.

Sodium carbonate 30.0 g.

Water to 1000 Sodium hydroxide to a pH of 10.2 (about 4.0 g. ) for 3.5 minutes at 73°F. These color photographic elements as yet had no developed color image due to the action of the dye formation inhibitor.

Film strips partially developed in the above developing bath composition were used as the film strips in those following examples where inhibitor removing baths are illustrated. The term "partially developed" as used in the context of this invention refers to the fact that the silver image has been developed, but the color dye image has not been developed because of the dye formation inhibiting effect of the development baths of the olenda process.

EXAMPLE I A partially developed film strip (according to Preparation A) was placed in a bath of water for 5 seconds to remove droplets of the monobath from the surface of the film. The film was then immersed in an inhibitor-removing bath (without a color accelerating agent) made of: Formulation I Water 2850 ml.

Sodium borohydride (color reversal agent) .150 g.

Hydrazine (color reversal agent) .075 ml.

Potassium bromide (contrast control agent) 3.0 g.

Na3POl · 12 H20 (buffering agent) 12.0 g.

Na2S03 .3 g.

KI solution (1 g/1) 30 ml.

Water to 3000 ml.

The pH was adjusted to 12.29 by adding sodium hydroxide solution. The film was then immersed in a stop bath solution of: Glacial acetic acid 12.0 ml.

Sodium acetate 6.3 g.

Water to 1000 ml. for 1 minute; thence into a bleach bath of: Water 800 ml.

Potassium ferricyanide 112.0 g.

Potassium bromide 2*1.0 g.

Disodlum hydrogen phosphate 12.0 g.

Sodium thiocyanate 12.5 g.

Sodium dlhydrogen phosphate 12.5 g.

Water to 1000 ml. for 2.5 minutes. At this time, the dye image is visible. Removal of the silver halide occurs when the film is fixed in a solution of: Water 800 ml.

Ammonium thiosulfate (60% aqueous solution) 120 g.

Sodium metabisul fite 20.0 g.

Water to 1000 ml.

Washing twice with water removes residual thlosulfate, so that the film dries to a clear state.

Densitometry of the film shows : Dmin. Contrast Dmax.

To blue light 35 To green light 35 To red light 20 EXAMPLE II The above developing process was repeated. The bath contained, in addition to the components listed above in Formula I, 12.5 ml/1 of ethylene diamine (a color accelerating agent). The bath gave densitometry results as follows: Dmin. Contrast Dmax.

To blue light .28 1.65 3.^0 To green light .35 1.45 2.85 To red light .20 1.35 2.85 As can be seen from the densitometric data of this example, the color accelerating agent in com' bination with the other three essential agents of the wash bath yields much more satisfactory color densities than does a wash bath containing only the three agents (reversing agent, buffering agent, and contrast control agent ) .

EXAMPLE III An inhibitor removirg bath of the following - - composition was made to investigate the effects of pH variance on the sensitometric qualities of the developeA images.

Water 2850 ml. a3P04 I 12 g.

KI solution (l g/1) 30 ml.

KBr 3.0 g.

Na2S03 0.3 g.

Ethylene diamine 37 ml.

Water to 3000 ml.

The bath was split into four portions. In the first and second, 18 mg. hydrazine and 37 mg. borohydrlde were added. The third and fourth portions contained 6 mg t-butylamine borane. The first and third portions were adjusted to a pH of 11.0, and the second and fourth portions adjusted to a pil of 12.3» all pH control accomplished by the addition of a sodium hydroxide solution.

The film was processed as described earlier, using each of the inhibitor removing bath portions, and the following sensitometric results were obtained: Portion 1 fog contrast Dmax blue „12 .5 I.96 green ,,36 «5 1.86 red .28 .5 I.60 Portion 2 f°S. contrast Dmax blue .28 1.65 3.10 green .35 1.45 2.85 red .20 1-35 1.85 1 Portion 3 fog contrast Dmax blue .10 1 .6 1.62 green .36 -6 1.38 Portion 4 fog contrast Dmax blue .18 1.65 2.6 green .10 1.50 2.6 red .3^ 1.65 3.3 The data shows the significant effect of pH levels upon the quality of the images produced by this method of developing color images.

EXAMPLE IV The effect of contrast control agents was examined by making three inhibitor removing wash baths follows : Water Sodium borohydride Hydrazine Sodium sulfite Na POjj H20 Ethylene diamine 12 . 0 g.

NaOH to pH 12 . 2 In the first bath 0. 05 g. of K Br was added, in the second 1. 0 g. of K Br and in the third 2 . 0 g. of K Br.

The density results were : i K Br K Br K Br . 05 1.0 2. 0 Dmin To blue light • 30 • 30 • 17 To green light ! .24 . 28 • 25 To red light . 18 . 36 32 Mean Contrast To blue light 1.65 1. 56 1. 65 To green light 2.20 2.00 1. 85 To red light 1.82 1. 81 1. 68 Dmax To blue light 3. 25 3.68 3. 04 To green light 3.67 3.51* 3. 04 To red light 3- 60 3.15 3. 14 The sensitometric data clearly show that de-sirable contrast and Dmax are dependent upon the use of contrast control agents in the inhibitor removing bath.

Water 92 ml.

Calgon (sodium hexametaphosphate) 2.0 g. 4-N,N-diethylamino-o-toluidine 6.0 g.

Potassium sulfite 48.0 g.

Phenidone . 3 g.

Hydroquinone 6.0 g.

Potassium bromide 2.0 g.

Potassium iodide .01 g. - 15 - Sodium thiocyanate .5 g.

Sodium carbonate 30.0 g.

Water to 1 1.

Sodium hydroxide to pH of 10.2 The exposed film was immersed in this bath for 3-5 minutes at 73°F. It was washed for five seconds and then Immersed in an inhibitor removing bath consisting of: Water 1 1.

Sodium borohydride 50 mg.

Hydrazine 25 m .

Ethylene diamine 12.0 g.

Potassium bromide 1.0 g.

Sodium sulfite .1 g.

NaOH to pH of 12.2 The stop, bleach, fix, and wash steps were repeated as in previous examples.

Densitometry readings were: Dmin. Dinax.

To blue light .56 3-26 To green light .65 2. 8 To red light .45 2.70 EXAMPLE V Another developing bath according to U. S. patent specification No. 5.883,354 was used to partially develop Ektochrome X, exposed as in Preparation A. This developing bath consisted of: Water 925 ml.

Sodium/hexametaphosphate 2.0 g. 2-methyl-1! (N-ethyl-N-B-hydroxy ethyl)amino aniline sulfate salt 22.0 g.

Potassium sulfite 48.0 g.

Phenidone .30 g.

Hydroquinone 1 5.0 g.

Potassium bromide 2.0 g.

Potassium iodide .01 g.

Sodium thiocyanate .5 g.

Sodium carbonate 30.0 g.

Water to 1 1.

Sodium hydroxide to pH 10.2 The exposed- film was immersed in the monobath at 73°F. for 3-5 minutes. After a five-seccnd wash in tap water, the inhibitor removing wash bath described in the previous instance was used to completely develop the color in the film. Following the stop, bleach, fix and wash operation, densitometry was: Dmin. Dmax .

To blue light To green light To red light The same monobath was used to partially develop similarly exposed film, but the ethylene diamine concentration was reduced to 5 gm/1 in the inhibitor removing wash bath. Densitometry readings were lower in the Dmax.

Dmin. Dmax.

To blue light .23 2.70 To green light .34 2.15 To red light .34 2.10 Note in this comparison that the reduced concentration of color developer in the Molenda developer bath and of ethylene diamine in the inhibitor removing wash bath lowers the Dmax to an undesirable level.

The sensitometric parameters, contrast, and Dmax, have been indicated throughout the specification as primarily dependent upon the contrast control agent and the color accelerating agent respectively, as is correct in this developing procedure. Any significant variation in the other components (pH control agent, and reversing agent) will also secondarily affect these parameters, but as previously stated, the primary effects on those particular parameters are caused by the contrast control agent and color accelerating agent once the pH range is established and the color reversal is effected.

Claims (20)

1. An inhibitor removing bath for effecting color formation in an exposed color photographic element which has already undergone a color reversal which comprises : 1) a color accelerating agent in sufficient quantity to produce a Omax of at least 1.5, 2) a contrast control agent in sufficient quantity to produce a contrast of less than about 2.4, and 3) a pH control agent which will maintain a pH of 11 to 13 in the inhibitor removing bath and further comprising less than 0.05 moles of phosphate and less than one half the molar concentration of color developer sufficient for full color development .

2. An inhibitor removing bath which comprises : 1) a color accelerating agent in sufficient quantity to produce a Dmax of at least 1.5, 2) a color reversal agent in sufficient quantity to render a silver halide photographic element developable in non-imaged areas, 3) a contrast control agent in sufficient quantity to produce a contrast of less than about 2.k, and 4) a pH control agent which will maintain a pH of from about 11 to 13 and further com risin les t

3. The inhibitor removing bath of claim 2 wherein the pH control agent will provide a pH of from about 11.7 to 12.5.

4. The inhibitor removing bath of claim 1 wherein the color accelerating agent is present in at least a concentration of 0.05 moles/liter, the contrast control agent is present in at least a concentration of 0.50 moles/liter, and the pH control agent is present in a concentration of at least about 1.8 x 10"2 moles/liter.

5. The inhibitor removing bath of claim 2 wherein the color accelerating agent is present in at least a concentration of 0.05 moles/liter, the color reversal agent is present in a concentration of at least about 1.6 x 10"^ moles/liter, the contrast control agent is present in at least a concentration of 0.50 moles/liter, and the pH control agent is present in —2 a concentration of at least about 1.8 x 10 moles/liter.

6. The inhibitor removing bath of claim 2 wherein the color accelerating agent comprises ethylene diamine.

7. The inhibitor removing bath of claim 2 wherein the contrast control agent comprises potassium bromide.

8. The inhibitor removing bath of claim 2 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium borohydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodium phosphate.

9. A color photographic color reversal development process which comprises : (A) treating a color photographic element having a hydrophilic colloid silver halide layer bearing a latent image with an aqueous monobath solution which includes at least one photographic color developing agent in a total color developer concentration of at least about 0.02 moles/liter capable, upon oxidation, of reacting with a photographic color coupler to form a dye, a black and white photographic developer including at least one black and white developing agent having a polarographic half-wave potential at pH 10.0 of from about -10 millivolts to about -I87 millivolts, and a water-soluble dye-formation inhibitor in a concentration of at least about 0.10 moles/liter and in molar ratio to the color developing agent of at least about 0.97, thereby to imbibe said silver halide layer with said monobath solution and to develop solely a negative black and white silver image therein; (B) -thereafter fogging said silver halide layer so as to render said layer developable in non-imaged areas; (C) without intermediate removal of said imbibed monobath solution, treating said layer to reduce the inhibiting effect of said dye formation 1 inhibitor in an inhibitor removing bath comprising: 1) a color accelerating agent in sufficient quantity to produce a Dmax of at least 1.5, 2) a contrast control agent in sufficient quantity to produce a contrast of less than about 2.i», and 3) a pH control agent which will provide a pH of from about the inhibitor removing bath further comprising less than 0.05 moles of phosphate and less than one half the molar concentration of color developer sufficient for full color developmen .

10. The color photographic process of claim 9 wherein fogging is effected by a color reversal agent . 11. The color photographic process of claim 10 wherein the color reversal agent is present in said inhibitor removing bath. 12. The process of claim 11 wherein the concentration of the color reversal agent is at least about 1.6 x 10"* moles/liter. 13. The process of claim 9 wherein the color accelerating agent is present in at least a concentration of 0.05 moles/liter, the contrast control agent is of at least about 1.8 x 10 moles/liter. 14. The process of claim 11 wherein the * ^ color accelerating agent is present in at least a concentration of 0.05 moles/liter,- the color reversal agent is present in a concentration of at least about 1.6 x 10~^ moles/liter, the contrast' control agent is present in at least a concentration of 0.50 moles/ liter, and the pH control agent is present in a con-centration of at least about 1.8 x 10 —2 moles/liter. 15. The process of claim 9 wherein the color accelerating agent comprises ethylene diamine. 16. The process of claim 9 wherein the contrast control agent comprises potassium bromide. 17· The process of claim 9 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium boro-hydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodium phosphate. 18. The process of claim 14 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium boro- hydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodium phosphate. •19. -An inhibitor removing bath for effecting color formation in an exposed color photographic element substantially as described herein. 20. A color photographic color reversal development process substantially as described herein, with refernt to the 1. An inhibitor removing bath for effecting color formation in an exposed color photographic element which has already undergone a color reversal which comprises : 1) a color accelerating agent in sufficient quantity to produce a Dmax of at least 1.5. 2) a contrast control agent in sufficient quantity to produce a contrast of less than about 2. , and 3) a pH control agent which will maintain a pH of 11 to 13 in the inhibitor removing bath and further comprising less than 0.05 moles of phosphate and less than one half the molar concentration of color developer sufficient for full color development. 2. An inhibitor removing bath which comprises : 1) a color accelerating agent in sufficient quantity to produce a Dmax of at least 1.5, 2) a color reversal agent in sufficient quantity to render a silver halide photographic element developable in non-imaged areas, 3) a contrast control agent in sufficient quantity to produce a contrast of less than about 2.4, and Ό a pH control agent which will maintain a pH of from about 11 to 13 and further comprising less than 0.05 moles of 3. The inhibitor removing bath of claim 2 wherein the pH control agent will provide a pH of from about llo7 to 12.5. 4. The inhibitor removing bath of claim 1 wherein the color accelerating agent is present in at least a concentration of 0,05 moles/liter, the contrast control agerit is present in at least a concentration of 0.50 moles/liter, and the pH control agent is present in a concentration of at least about 1.8 x 10"2 moles/liter. 5- The inhibitor removing bath of claim 2 wherein the color accelerating agent is present in at least a concentration of 0.05 moles/liter, the color reversal agent is present in a concentration of at least about 1.6 x 10 moles/liter, the contrast control agent is present in at least a concentration of 0.50 moles/liter, and the pH control agent is present in a concentration of at least about 1.8 x 10 moles/liter. 6. The inhibitor removing bath of claim 2 wherein the color accelerating agent comprises ethylene diamine.. 7. The inhibitor removing bath of claim 2 wherein the contrast control agent comprises potassium bromide . 8. The inhibitor removing bath of claim 2 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium borohydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodium phosphate - 9- A colcjr photographic color reversal de- I velopment process which comprises: (A) treating a color photographic element having a hydrophilic colloid silver halide layer bearing a latent image with an aqueous monobath solution which includes at least one photographic color developing agent in a total color developer concentration of at least about 0,02 moles/liter capable, upon oxidation, of reacting with a photographic color coupler to form a dye, a black and white photographic developer including at least one black and white developing agent having a polarographic half-wave potential at pH lOoO of from about -10 millivolts to about -187 millivolts, and a water-soluble dye-formation inhibitor in a concentration of at least about 0.10 moles/liter and in molar ratio to the color developing agent of at least about 0.97, thereby to imbibe said silver halide layer with said monobath solution and to develop solely a negative black and white silver image therein; (B) thereafter fogging said silver halide layer so as to render said layer developable in non-imaged areas; (C) without intermediate removal of said imbibed monobath solution, treating said layer to r ducf? the inhibiting effect of said dye formation inhibitor in an inhibitor removing bath comprising: 1 ) a color accelerating agent in sufficient; quantity to produce a Dmax of at least 1. 5 , 2 ) a contrast control agent in sufficient, quantity to produce ai contrast of less than about 2.Λ, and 3 ) a pH control agent which will provide a pH of from about 11 , 0 to 13 . 0 the inhibitor removing bath further comprising less than 0 . 05 moles of phosphate and less than one half the molar concentration of color developer sufficient for full color development. 10.. The color photographic process of claim y wherein fogging is effected by a color reversal ^ nt .

11. The color photographic process of claim 10 whnrein the color reversal agent is present in raid inhibitor removing bath.

12. . The process of claim 11 wherein the concentration of the color reversal agent is at least about 1 . 6 x 10~3 moles/liter.

13. The process of claim 9 wherein the color accelerating agent 13 present in at least a concentration of 0. 05 moles/liter, the contrast control agent is present in at least a concentration of 0. 50 moles/liter, of at least about 1.8 x 10~ moles/liter.

14. The process of claim 11 wherein the color accelerating agent is present in at least a concentration of 0.05 moles/liter the color reversal agent is present in a concentration of at least about 1.6 x 10"^ moles/liter, the contrast' control agent is present in at least a concentration of 0.50 moles/ liter, and the pH control agent is present in a con- —2 centration of at least about 1.8 x 10 moles/liter.

15. The process of claim 9 wherein the color accelerating agent comprises ethylene diamine.

16. The process of claim 9 wherein the contrast control agent comprises potassium bromide.

17. The process of claim 9 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium boro- hydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodlum phosphate.

18. The process of claim 11 wherein the color accelerating agent comprises ethylene diamine, the color reversal agent comprises at least one of sodium boro- hydride and hydrazine, the contrast control agent comprises potassium bromide, and the buffering agent comprises trisodium phosphate.

19. Λη inhibitor removing bath for effecting color formntion in an exposed color photogra hic element substantially an described herein.

20. Λ color photographic color reversal development process substantially as described herein, with refereiiJ to the