05/307893

09/02/1975

11/20/1972

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Eastman Kodak Company (Rochester, NY)

430/505

430/570, 430/936

G03C7/30; G03C1/76; G03C1/06

96/3,74,95

Torchin, Norman G.

Brammer J. P.

Chipaloski M. R.

I claim

1. An unexposed photographic element comprising a support having thereon at least two image dye-providing layer units, each containing a silver halide emulsion having associated therewith a color coupler, wherein one of said image dye-providing layer units contains a coarse-grain silver halide emulsion which has a mean grain size which is at least 50 percent greater than the mean grain size of said silver halide emulsion in said other image dye-providing layer unit, said photographic element containing a black-and-white silver halide developing agent associated with the image dye-providing layer unit containing said coarse-grain silver halide emulsion.

2. A photographic element according to claim 1 wherein said color coupler of said image dye-providing layer unit containing said coarse-grain silver halide emulsion is a yellow image dye-producing color coupler.

3. A photographic element according to claim 1 wherein said image dye-providing layer unit contains said black-and-white developing agent in a concentration of from about 0.1 to about 200 mg./ft.².

4. A photographic element according to claim 1 wherein said black-and-white developing agent is a 3-pyrazolidone silver halide developing agent.

5. A photographic element according to claim 1 wherein said coarse-grain silver halide emulsion has a mean grain size of at least 0.8 micron.

6. A photographic element according to claim 1 wherein said image dye-providing layer units are separated by an interlayer.

7. A photographic element according to claim 1 wherein said color coupler of said image dye-providing layer unit containing said coarse-grain emulsion in a yellow image dye-providing color coupler and said element contains two additional image dye-providing layer units which each contain a silver halide emulsion having a main grain size which is less than half the mean grain size of said coarse-grain silver halide emulsion and a cyan image dye-providing color coupler or a magenta image dye-providing color coupler.

8. A photographic element according to claim 1 wherein at least one of said image dye-providing layer units contains less than 30 mg./ft.² of silver halide based on silver coverage.

9. A photographic element according to claim 1 wherein said image dye-providing layer unit which contains the smaller means-grain-size silver halide emulsion also contains said color coupler in a stoichiometric excess based on silver halide.

10. A photographic element according to claim 9 wherein said image dye-providing layer unit contains said color coupler in at least a 40 percent stoichiometric excess based on silver halide.

11. An unexposed multicolor photographic element comprising a support having thereon an image dye-providing layer unit containing a fine-grain silver halide emulsion and a color coupler in a stoichiometric excess based on said silver halide and an image dye-providing layer unit containing a coarse-grain silver halide emulsion having a mean grain size at least 50 percent larger than said fine-grain silver halide emulsion, a color coupler, and a black-and-white silver halide developing agent.

12. A photographic element according to claim 1 wherein the color coupler of said image dye-providing layer unit containing said fine-grain emulsion is a cyan or magenta image dye-providing layer unit and said color coupler of said image dye-providing layer unit containing said coarse-grain emulsion is a yellow image dye-providing coupler.

13. An unexposed photographic element comprising a support and at least one image dye-providing layer thereon containing a silver halide emulsion having a mean grain size of at least 0.8 micron, a color coupler, and a black-and-white silver halide developing agent at a concentration of about 0.1 to 200 mg./ft.².

14. A photographic element according to claim 13 wherein said black-and-white silver halide developing agent is a 3-pyrazolidone.

15. A photographic element according to claim 13 wherein said color coupler is present in at least a 40 percent stoichiometric excess based on silver in said layer unit.

16. An unexposed photographic element comprising a support having thereon 1) an image dye-providing layer unit containing a blue-sensitive silver halide emulsion having a mean grain size of at least 0.8 micron and having associated therewith a yellow image dye-forming coupler and from 0.1 to 200 mg./ft.² of a black-and-white silver halide developing agent, 2) an image dye-providing layer unit containing a green-sensitive silver halide emulsion having associated therewith a magenta image dye-forming color coupler and 3) an image dye-providing layer unit containing a red-sensitive silver halide having associated therewith a cyan image dye-forming color coupler.

17. A photographic element according to claim 16 wherein said cyan and magenta image dye-forming color coplers are present in said image dye-providing layer units in at least a 40 percent stoichiometric excess based on silver.

18. A photographic element according to claim 17 wherein said image dye-providing layer units containing said green-sensitive silver halide emulsion and said red-sensitive silver halide emulsion each contain less than 30 mg./ft.² of silver halide based on silver.

19. A photographic element according to claim 16 wherein said blue-sensitive silver halide emulsion has a mean grain size which is at least 50 percent greater than the mean grain size of said green- or red-sensitive silver halide emulsions.

20. A photographic element according to claim 16 wherein said black-and-white developing agent is a 3-pyrazolidone.

21. A photographic element according to claim 16 wherein said image dye-providing layer units which contain said red- and green-sensitive silver halide emulsions are substantially free of black-and-white silver halide developing agent.

22. A photographic element according to claim 16 wherein said black-and-white developing agent is a 4,4-diethyl-3-pyrazolidone or a 4-alkyl-4-hydroxy-3-pyrazolidone.

23. A photographic element according to claim 16 wherein said support has thereon the image dye-providing layers in sequence with the image dye-providing layer containing the yellow dye-forming coupler nearer said support.

This invention relates to photographic elements and processes for developing image records in said photographic elements. In one aspect, this invention relates to photographic elements comprising an image dye-providing layer unit which comprises a light-sensitive silver halide, a stoichiometric excess of a color coupler based on effective silver and a black-and-white silver halide developing agent. In another aspect, this invention relates to multicolor photographic elements which comprise one image dye-providing layer unit, preferably a yellow dye image-providing layer unit, which comprises a silver halide emulsion, which preferably has an effective sensitivity to blue light, a color coupler and a black-and-white silver halide developing agent.

The use of developing agents incorporated in a photographic element, along with silver halide emulsions, whereby development can proceed by activation with an alkaline solution is well-known in the art, for example, as disclosed in U.S. Pat. Nos. 2,315,966 issued April 3, 1943; 2,592,368 issued April 8, 1952; 2,716,059 issued Aug. 23, 1955; 2,751,300 issued June 19, 1956; 3,276,871 issued Oct. 4, 1966; 3,278,307 issued Oct. 11, 1966; 3,287,129 issued Nov. 22, 1960; 3,291,609 issued Dec. 13, 1966; and 3,342,599 issued Sept. 19, 1967.

The incorporation of black-and-white developing agents as auxiliary developers in image transfer systems utilizing preformed dyes is known in the art, for example, as disclosed in U.S. Pat. No. 3,192,044. In certain color systems such as reversal systems, incorporated black-and-white developers have been used to carry out the first development step followed by light or chemical fogging of the remainder of the undeveloped silver halide and then carrying out color development in the presence of a color developer such as an aromatic primary amino silver halide developing agent and a color coupler to form dye images. In those reversal systems where the black-and-white developing agent is incorporated in the element, it is generally associated with all emulsion layers to provide contact during the first development step and all silver halide emulsion layers are generally of substantially the same means grain size. It is also known in the art to use small amounts of black-and-white developing agents in color-developing compositions to act as competing developers and the like.

Several color photographic systems used commercially are known in the prior art to utilize photographic elements containing image dye-providing layer units which contain light-sensitive silver halide emulsions having associated therewith a color coupler. Generally, the image dye is formed by reaction of an aromatic primary amino developing agent with silver halide to oxidize the aromatic compound which, in turn, reacts with the color coupler to produce an image dye. The amount of dye formed is, thus, directly dependent on the amount of color-developing agent oxidized by the exposed silver halide. Therefore, black-and-white developers used in a color-coupler system would be at the expense of dye formation if used to develop silver in the areas where dye formation is essential. Thus, excess stoichiometric quantities of developable silver halide would be necessary to obtain the same dye formation if black-and-white developers were used in this type of color system.

I have now found that improved color photographic elements can be made which generally comprise an image dye-providing layer unit containing a silver halide emulsion, a color coupler and a black-and-white silver halide developing agent, preferably in sufficient quantity to reduce at least 5 percent and more preferably at least 10 percent of the silver halide to silver.

In one embodiment, the photographic elements of this invention comprise one image dye-providing layer unit which contains a coarse-grain silver halide emulsion, a color coupler in a stoichiometric excess based on silver halide in said layer unit, and at least one image dye-providing layer unit which contains a black-and-white silver halide developing agent.

In a highly preferred embodiment, multicolor photographic elements can be made in accordance with this invention wherein one image dye-providing layer, and preferably only one of the image dye-providing layer units, comprises a silver halide emulsion, color coupler and sufficient black-and-white developer to develop at least 5 percent of said silver halide. Preferably, the multicolor element is a subtractive color element comprising cyan, magnenta and yellow image dye-providing layer units and the yellow image dye-providing layer unit is the only unit which contains sufficient black-and-white silver halide developing agent to develop at least 5 percent of said silver halide.

In another embodiment, photographic elements are prepared according to this invention which comprise at least two image dye-providing layer units which contain silver halide emulsions and color coupler, said silver halide emulsion of at least one dye-providing layer unit having a mean grain size which is 0.5 micron greater or 50 percent greater than the mean grain size of the silver halide emulsion of another of said image dye-providing layer units, wherein said image dye-providing layer unit containing the silver halide emulsion of larger mean grain size has associated therewith a black-and-white silver halide developing agent.

In the drawing, FIG. 1 shows a schematic diagram of one preferred photographic element according to this invention. The yellow image dye-providing layer unit is preferably a coarse-grain silver halide emulsion and a black-and-white silver halide developing agent is present in said layer unit, while the magenta and cyan image dye-providing layer units contain fine-grain, spectrally sensitized silver halide emulsions and do not contain an incorporated silver halide developing agent.

FIG. 2 shows the sensitometric evaluation of the dyes produced with a photographic element according to Example 1, wherein the yellow image dye-providing layer unit contains a black-and-white developing agent, and

FIG. 3 is a sensitometric evaluation of a control element without the incorporated black-and-white incorporated developer. Further details are given in Example 1.

The photographic elements of this invention comprise a support having thereon at least one image dye-providing layer unit comprising a color coupler and a silver halide emulsion and at least one layer containing a black-and-white silver halide developing agent.

Preferably the image dye-providing layer unit of said element comprises a stoichiometric excess of color coupler based on effective or developable silver halide. Moreover, where the silver halide of the image dye-providing layer unit is a coarse-grain silver halide emulsion, the black-and-white silver halide developing agent is preferably contained in said unit in a manner where it preferentially will start development of the coarse-grain silver halide of said layer unit before starting development of any adjacent layer units.

It may be helpful in understanding this invention to note that, while the incorporation of black-and-white developers in color photographic elements was at the expense of dye formation per unit of silver, high dye yields can be obtained in the present elements since dye formation can proceed catalytically. Thus, the black-and-white developers can be used in systems containing high stoichiometric ratios of coupler to silver or where the element contains both coarse-grain and fine-grain emulsions to form catalytic silver at a high rate without subsequent loss of image dye.

The term "black-and-white silver halide developing agent" as used herein generally refers to silver halide developing agents other than the color silver halide developing agents which enter into coupling reactions with color couplers to form image dyes, i.e., such as the aromatic primary amino silver halide developing agents. The black-and-white developing agents were previously known in the art for reducing silver halide to silver to produce an imagewise distribution of visible silver, and are to be distinguished from the color-developing agents which form image dye by a secondary reaction.

The black-and-white developers may be incorporated in the photographic elements of this invention by methods disclosed in the prior art and may be dispersed in separate colloid layers or dispersed directly in the silver halide emulsion. Generally, the balck-and-white silver halide developers are present in an image dye-forming layer unit in a concentration of from about 0.1 to 200 mg./ft. ² and preferably from 0.5 to 100 mg./ft. ² depending, of course, on the concentration of the silver halide in the image dye-providing layer unit.

Useful black-and-white developing agents which can be incorporated in the photographic elements of this invention include those black-and-white developers disclosed in U.S. Pat. Nos. 2,315,966 by Knott issued April 6, 1943; 2,592,368 by Yackel issued April 8, 1952; 2,685,510 by Yackel issued Aug. 3, 1954, 2,716,059 by Yutzy et al. issued Aug, 23, 1955, 2,751,300 by James et al. issued June 19, 1956; 3,146,104 by Yackel et al. issued Aug. 25, 1964; 3,180,731 by Roman et al. issued April 27, 1965; 3,276,871 by Abbott issued Oct. 4, 1966; 3,278,307 by Stewart et al. issued Oct. 11, 1966; 3,287,129 by Rees et al. issued Nov. 22, 1966; 3,291,609 by Porter et al. issued Dec. 13, 1966; and 3,301,678 by Humphlett et al. issued Jan. 31, 1967.

In one preferred embodiment, the black-and-white developers are 3-pyrazolidone silver halide developing agents. Useful developers of this type generally have the formula: ##EQU1## in which R ¹ , R ² , R ³ , R ⁴ and R ⁵ can each be a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms or an aryl group preferably of the benzene or naphthalene series and including substituted aryl groups, and R ² , R ³ , R ⁴ and R ⁵ can each additionally be an hydroxy group or an hydroxyalkyl group containing from 1 to 4 carbon atoms. Typical useful 3-pyrazolidone silver halide developing agents include:

1-phenyl-3-pyrazolidone,

1-p-tolyl-3-pyrazolidone,

5-phenyl13-pyrazolidone,

5-methyl-3-pyrazolidone,

1-p-chlorophenyl-3-pyrazolidone,

1-phenyl-5-phenyl-3-pyrazolidone,

1-m-tolyl-3-pyrazolidone,

1-phenyl-5-methyl-3-phyrazolidone,

1-p-tolyl-5-phenyl-3-pyrazolidone,

1-p-methoxyphenyl-3-pyrazolidone,

1-acetamidophenyl-3-pyrazolidone,

1-phenyl-2-acetyl-4,4-dimethyl-3-pyrazolidone,

1-phenyl-4,4-dimethyl-3-pyrazolidone,

1-m-aminophenyl-4-methyl-4-propyl-3-pyrazolidone,

1-o-chlorophenyl-4-methyl-4-ethyl-3-pyrazolidone,

1-m-acetamidophenyl-4,4-diethyl-3-pyrazolidone,

1-(p-β-hydroxyethylphenyl)-4,4-dimethyl-3-phrazolidone,

1-p-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone,

1-p-methoxyphenyl-4,4-diethyl-3-pyrazolidone,

1-p-tolyl-4,4-dimethyl-3-pyrazolidone,

1-(7-hydroxy-2-naphtyl)-4-methyl14-n-propyl-3-pyrazolido ne,

1-p-diphenyl-4,4-dimethyl-3-pyrazolidone,

1-p-β-hydroxyethylphenyl)-3-pyrazolidone,

1-o-tolyl-3-pyrazolidone,

1-o-tolyl-4,4-dimethyl-3-pyrazolidone,

1-phenyl14-methyl-3-pyrazolidone,

4-hydroxy-4-methyl-1-phenyl-3-pyrazolidone, and

4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone.

In one preferred embodiment, the 4,4-dialkyl-3-pyrazolidone or 4-alkyl-4-hydroxy-3-phyrazolidone compounds are especially useful to obtain fast development.

Other useful black-and-white developing agents include hydroquinone, catechol, pyrogallol, N-methyl-p-aminophemol, p-β-hydroxyethylaminophenol, p-β-aminoethylaminophenol, N-methyl-N-(β-sulfoamidoethyl)-p-aminophenol, ascorbic acid and p-hydroxphenylglycine.

In certain preferred embodiments, reductones can be used such as morpholino hexose reductone, 2,6-dimethyl morpholino hexose reductone, piperidino hexose reductone, piperidino hexose reductone monoacetate, 4-methyl piperidino hexose reductone, pyrrolidino hexose reductone, dimethylamino hexose reductone, N-methylbenzylamino hexose reductone, and the like.

The photographic elements of this invention can be processed to provide image records by several procedures.

In a highly preferred embodiment, the photographic elements can be processed to provide an image record by the procedures described in my copending application, U.S. Ser. No. 189,289, entitled "Image-Forming Process and Compositions" filed Oct. 14, 1971, now abandoned and incorporated herein by reference. In one embodiment of this process, the imagewise-exposed element is contacted with a photographic color-developing agent and an oxidizing agent, such as a cobalt (III) metal complex having a coordination number of 6, until the desired dye density is obtained. The cobalt metal complex is apparently reduced to cobalt (II) in the presence of silver, which appears to act as a catalyst, and the color developer is oxidized whereby it can react with the color coupler in each respective layer unit to form the desired image dye. The formation of oxidized developer can continue as long as there is a sufficient supply of the metal complex and color developer in the presence of the silver catalyst.

In another highly preferred process, a photographic element in accordance with this invention is processed as disclosed by Travis, U.S. Ser. No. 256,071 entitled "Process for Developing Photographic Elements", filed on May 23, 1972, now U.S. Pat. No. 3,765,891 this process the photographic element in accordance with this invention which has been imagewise-exposed is developed to convert the developable silver halide into metallic silver and form image dye. With negative emulsions, the exposed areas will be developable, whereas with direct-positive emulsions or reversal emulsions the unexposed areas will be developed. The photographic element containing undeveloped silver halide and an imagewise distribution of metallic silver is then contacted with a suitable metal complex, such as a cobalt (III) complex having a coordination number of 6, in the presence of a color-developing agent which is preferably imbibed into the element during the color-development step and carried into the bath containing the cobalt metal complex. Preferably, the photographic element is treated with a liquid bath containing the suitable metal complex and which also contains a silver halide development restrainer, thus allowing this step to proceed in roomlight. by using this process one can observe the dye formation and stop dye formation at the desired dye density.

In still another embodiment, the elements of this invention can be processed by using a physical developing agent such as described in Dipple et al., U.S. Pat. No. 2,750,292 issued June 12, 1956. By treating imagewise-exposed elements of this invention with a solution containing only the color-developing agent and the physical developing agent, rather than the solution described by Dipple et al., it is possible to obtain a multicolor image record.

In still another embodiment, the elements of this invention can be developed by using a variation of the process described in Weber, U.S. Pat. No. 2,173,739. The elements of this invention which have been imagewise-exposed can be developed, bleached partially with a solution as described in Weber, such as a potassium ferricyanide bleach, redeveloped in color developer to intensify the image, etc., until the desired dye density is obtained. Peroxy treatments such as used in British Pat. No. 1,268,126 could also be adapted in a manner similar to the next above process for use in development of a multicolor element according to this invention.

In still another embodiment, the elements of this invention can be designed for use in and can be processed by the color negative or color reversal processes referred to in U.S. Pat. Nos. 3,046,129 by Graham issued July 24, 1962; 3,547,640 by Beckett, and 2,944,900.

The silver halide emulsions used in accordance with this invention can comprise, for example, silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide crystals or mixtures thereof. They may be coarse- or fine-grain emulsions prepared by any of the well-known techniques, e.g., single-jet emulsions such as those described in Trivelli and Smith, The Photographic Journal, Vol. LXXIX, May, 1939 (pp. 330-338), double-jet emulsions such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions such as those described in U.S. Pat. No. 2,222,264 by Nietz et al. issued Nov. 19, 1940; 3,320,069 by Illingsworth issued May 16, 1967; and 3,271,157 by McBride issued Sept. 6, 1966. Surface-image emulsions may be used or internal-image emulsions may be used such as those described in U.S. Pat. Nos. 2,592,250 by Davey et al. issued May 8, 1952; 3,206,313 by Porter et al. issued Sept. 14, 1965; 3,367,778 by Berriman issued Feb. 6, 1968, and 3,447,927 by Bacon et al. issued June 3, 1969. If desired, mixtures of surface- and internal-image emulsions may be used as described in Luckey et al, U.S. Pat. No. 2,996,382 issued Aug. 15, 1961. The emulsions may be regular-grain emulsions such as the type described in Klein and Moisar, J. Phot. Sci., Vol. 12, No. 5, Sept,/Oct., 1964, pp. 242-251. Negative-type emulsions may be used or direct-positive emulsions may be used such as those described in U.S. Pat. Nos. 2,184,013 by Leermakers issued Dec. 19, 1939; 2,541,472 by Kendal et al. issued Feb. 13, 1951; 3,367,778 by Berriman issued Feb. 6, 1968; 3,501,307 by Illingsworth issued March 17, 1970; 2,563,785 by Ives issued Aug. 7, 1951; 2,456,953 by Knott et al. issued Dec. 21, 1948; and 2,861,885 by Land issued Nov. 25, 1958; British Pat. No. 723,019 by Schouwenaars issued Feb. 2, 1955, and French Pat. No. 1,520,821 by Illingsworth issued March 4, 1968. Preferably, the emulsions are negative, developing-out-type, silver halide emulsions.

Generally, each of the color-providing layer units of the photographic elements contains a light-sensitive silver salt which is preferably a silver halide. In one preferred embodiment, at least two of the color-providing layer units each comprise a silver salt at a concentration of up to 30 mg. of silver/ft. ² . Generally, these layer units will be the red- and green-sensitive silver halide-containing layer units. However, while the developable silver halide is preferably present at concentrations based on silver of less than 30 mg./ft. ² , it is possible to coat blended emulsions at higher coverages within this embodiment, as long as no more than 30 mg./ft. ² of silver develops; for example, such emulsions may contain silver halide grains which are relatively light-insensitive or may contain development restrainers, such as with development inhibitor-releasing couplers, and still provide a photographic element which is advantageously used in the various processes as described herein to produce improved image records. In some instances, emulsions containing relatively light-insensitive grains or development inhibitors are desirable to enable one to obtain more uniform coating coverage with less precise coating equipment, as well as for other reasons. Thus, highly preferred photographic elements of this invention contain at least two color-providing layer units, each containing a silver halide emulsion, defined in terms of "effective coverage" and developability as one which, when it is fully exposed and processed for about 1 minute at 100°F. in Developer A as follows:

Color Developer A ______________________________________ benzyl alcohol 10 ml. K ₂ SO ₃ 2 g. KBr 0.4 g. hydroxylamine sulfate 2 g. 4-amino-N-ethyl-N-(2-methoxyethyl)-m- 5 g. toluidine di-paratoluenesulfonate K ₂ CO ₃ 30 g. ethylenediamine tetraacetic acid-sodium salt 5 g. water to 1 liter pH 10.1 at 24° C. ______________________________________ will provide less than 30 mg. of metallic silver/ft. ² and preferably less than 15 mg./ft. ² . It is understood that the term "effective silver" refers to that amount of silver which is developed in this test and that ratios of coupler to silver are based on "effective silver" which is produced by this type of development when so specified herein. In most instances, the quantity of effective silver as silver halide in the undeveloped, unexposed photographic element will be quite similar to quantity of total silver present as silver halide. The fully exposed layer containing silver halide emulsion is one which is exposed to Dmax as is well-known in the art, for example, by exposure to a 500-watt, 3000°K lamp for about 10 seconds (total exposure at the film plane =11.3 × 10 ⁴ ergs./cm. ² ).

In certain embodiments, the emulsions of at least one image dye-providing layer unit comprise a coarse-grain silver halide generally having a mean grain size at least 0.8 micron and preferably at least 1.0 micron. Grain sizes can be measured by methods commonly used in the art for this purpose. A typical procedure is set forth by Loveland, "Methods of Particle-Size Analysis", ASTM Symposium on Light Microscopy, 1953, pp. 94-122, or in chapter 2 of The Theory of the Photographic Process, Mees and James, 3rd Ed. (1966), published by MacMillan Co. The grain size can be measured using the projected areas of the grains or approximate diameter. When the grains are substantially uniform in shape, the size distribution can be expressed quite accurately as either diameter or projected area. The size-frequency relationship can be determined as disclosed in an article by Trivelli and Smith entitled "Empirical Relations between Sensitometric and Size Frequency in Photographic Emulsion Series", The Photographic Journal, Vol. LXXIX, 1949, pp. 330-338.

The light-sensitive silver salts are generally coated in the color-providing layer units in the same layer with the photographic color coupler. However, they can be coated in separate adjacent layers as long as the coupler is effectively associated with the respective silver halide emulsion layer to provide for immediate dye-providing reactions to take place before substantial color-developer oxidation reaction products diffuse into adjacent color-providing layer units.

As used herein, the terms "photographic color coupler" and "image dye-providing color coupler" include and compound which reacts (or couples) with the oxidation products of primary aromatic amino developing agent on photographic development to form an image dye, and are nondiffusible in a hydrophilic colloid binder (e.g., gelatin) useful for photographic silver halide, and also those couplers which provide useful image dyes when reacted with oxidized primary aromatic amino developing agents such as by a coupler-release mechanism. The couplers can form diffusible or nondiffusible dyes. Typical preferred color couplers include phenolic, 5-pyrazolone and open-chain ketomethylene couplers. Specific cyan, magenta and yellow color couplers which can be employed in the practice of this invention are described in Graham et al., U.S. Pat. No. 3,046,129 issued Jan. 24, 1962, column 15, line 45, through column 18, line 51, which disclosure is incorporated herein by reference. Such color couplers can be dispersed in any convenient manner, such as by using the solvents and the techniques described in U.S. Pat. Nos. 2,322,027 by Jelley et al. issued June 15, 1943, or 2,801,171 by Fierke et al. issued July 30, 1957. When coupler solvents are employed, the most useful weight ratios of color coupler to coupler solvent range from about 1:3 to 1:0.1. The useful couplers include Fischer-type incorporated couplers such as those described in Fischer, U.S. Pat. No. 1,055,155 issued Mar. 4, 1913, and particularly nondiffusible Fischer-type couplers containing branched carbon chains, e.g., those referred to in the references cited in Frohlich et al., U.S. Pat. No. 2,376,679 issued May 22, 1945, column 2, lines 50-60. Particularly useful in the practice of this invention are the nondiffusible color couplers which form nondiffusible dyes.

In certain preferred embodiments, the incorporated couplers in the layer units of this invention are water-insoluble color couplers which are incorporated in a coupler solvent which is preferably a moderately polar solvent. Typical useful solvents include tri-o-cresyl phosphate, di-n-butyl phthalate, diethyl lauramide, 2,4-diarylphenol, liquid dye stabilizers as described in an article entitled "Improved Photographic Dye Image Stabilizer-Solvent", Product Licensing Index,Vol. 83, pp. 26-29, March 1971, and the like. The elements containing coupler solvents appear also to aid in imbibing color developer in those processes where it is carried from a developer bath into an amplifier bath.

The term "nondiffusible" used herein as applied to couplers and products derived from couplers has the meaning commonly applied to the term in color photography and denotes materials which for all practical purposes do not migrate or wander through photographic hydrophilic colloid layers, such as gelatin, particularly during processing in aqueous alkaline solutions. The same meaning is attached to the term "immobile". The terms "diffusible " and "mobile" have the converse meaning.

The photographic elements of this invention, as defined above, comprise a support having thereon image dye-providing layer units. A multicolor photographic element comprises at least two of said image dye-providing layer units which each records light primarily in different regions of the light spectrum. The layer unit comprises a light-sensitive silver salt, which is generally spectrally sensitized to a specific region of the light spectrum, and has associated therewith a photographic color coupler. In certain preferred embodiments, the color-providing layer units are continuous layers which are effectively isolated from other layer units by barrier layers, spacer layers, layers containing scavengers for oxidized developer and the like to prevent any substantial color contamination between the image dye-providing layer units. In other embodiments, the layer units are discontinuous layers comprising mixed packets which are effectively isolated from each other, as disclosed in Godowsky, U.S. Pat. No. 2,698,794 issued Jan. 4, 1954. The effective isolation of the layer units is known in the art and is utilized to prevent contamination in many commercial color products.

In certain preferred embodiments, photographic elements of this invention comprise a support having thereon at least one image dye-producing layer unit containing a light-sensitive silver salt, preferably silver halide, having associated therewith a stoichiometric excess of coupler. The equivalency of color couplers is known in the art, for example, a 4-equivalent coupler requires 4 moles of oxidized color developer, which in turn requires development of 4 moles of silver, to produce 1 mole of dye. Thus, for the stoichiometric reaction with silver halide, 1-equivalent weight of this coupler will be 0.25 mole. In accordance with this embodiment, the color image-providing unit can comprise at least a 40 percent excess of the equivalent weight of image dye-providing color coupler required to react on a stoichiometric basis with the developable silver and preferably a 70 percent excess of said coupler. In one highly preferred embodiment, at least a 110 percent excess of the coupler is present in said dye image-providing layers based on silver. Preferably, the coupler-to-silver ratio is based on effective silver as defined herein. The ratio can also be defined as an equivalent excess with a coupler-to-silver ratio of at least 1.4:1, and preferably at least 1.7:1 (i.e., 2:1 being a 100 percent excess). In certain preferred embodiments, the photographic color couplers are employed in the image dye-providing layer units at a concentration of at least three times, such as from three to 20 times, the weight of the silver in the silver halide emulsion. Weight ratios of coupler-to-silver coverage which are particularly useful are from 4 to 15 parts by weight coupler to 1 part by weight silver. Advantageously, the coupler is present in an amount sufficient to give a density of at least 1.7 and preferably at least 2.0. Preferably, the difference between the maximum density and the minimum density (which can comprise unbleached silver) is at least 0.6 and preferably at least 1.0.

It is realized that the density of the dye may vary with the developing agent combined with the respective coupler, and accordingly the quantity of coupler can be adjusted to provide the desired density. Preferably, each layer unit contains at least 1 ×10 ^{- 5} moles/ft. ² of color coupler.

Advantageously, the photographic color couplers utilized are selected so that they will give a good neutral dye image. Preferably, the cyan dye formed has its major visible light absorption between about 600 and 700 nm., the magenta dye has its major absorption between about 500 and 600 nm., and the yellow dye has its major absorption between about 400 and 500 nm.

The photographic elements of this invention are particularly useful in the processes of the type disclosed in my copending application, Ser. No. 189,289, entitled "Image-Forming Processes and Compositions", filed Oct. 14, 1971 now abandoned and incorporated herein by reference. Generally, in processes of this type, a redox reaction between an oxidizing agent and a reducing agent is utilized to produce a change in light value. This change in light value can come about directly by a change in the light value of either the oxidizing agent or reducing agent. Alternatively, the redox reaction can result in one or more reaction products which can react with each other or with another component, such as a reactive species, to produce a change in light value. In another variation, the reactivity of the reactive species can be reduced imagewise by one of the reaction products of the redox reaction.

The redox reaction which takes place when the elements are processed by this procedure occurs at a catalytic surface. The catalyst is metallic silver which, of course, can be produced by development of silver halide which contains a latent image. The catalyst appears to promote redox reaction in true catalystic fashion. The amount of redox reaction products is not limited by the amount of catalytic present, since the catalyzed redox reaction of this invention does not proceed on a stoichiometric basis with respect to the catalyst.

Oxidants preferred in the practice of this process are the metal complexes, such as a transition metal complex, e.g., a Group VIII metal complex, or a complex of a metal of Series 4 of the periodic table appearing on pp. 54 and 55 of Lange's Handbook of Chemistry, 8th Edition, published by Handbook Publisher, Inc., Sandusky, Ohio, 1952. Such complexes feature a molecule having a metallic atom or ion. This metallic atom or ion is surrounded by a group of atoms, ions or other molecules which are generically referred to as liquids. The metallic atom or ion in the center of these complexes is a Lewis acid; the ligands are Lewis bases. Werner complexes are well-known examples of such complexes. The useful metal salts are typically capable of existing in at least two valent states. In a preferred aspect of the invention, the metal complexes are those referred to by American chemists as "inert" and by European chemists as "robust". Particularly useful are complexes of a metal ion with a ligand which, when a test sample thereof is dissolved at 0.1 molar concentration at 20°C. in an inert solvent solution also containing 0.1 molar concentrationn of a tagged ligand of the same species which is uncoordinated, exhibits essentially no exchange of uncoordinated and coordinated ligands for at least 1 minute, or more. This test is advantageously conducted under the pH conditions which will be utilzed in the practice of the invention. In silver halide photography, this generally will be a pH of over about 8. Many metal complexes useful in this invention show essentially no exchange of uncoordinated and coordinated ligands for several days. The definition of "inert" metal complexes and the method of measuring ligand exchange using radioactive isotopes to tag ligands are well-knownn in the art; see, for example, Taube, Chem. Rev., Vol. 50, p. 69 (1952), and Basolo and Pearson, Mechanisms of Inorganic Reactions, a Study of Metal Complexes and Solutions, 2nd Edition, 1967, published by John Wiley and Sons, p. 141. Further details on measurement of ligand exchange appear in articles by Adamson et al., J. Am. Chem. Soc., Vol., 73, p. 4789 (1951). The inert metal complexes should be contrasted with labile complexes which, when tested by the method described above, have a reaction half-life generally less than 1 minute. Metal chelates are a special type of metal complex in which the same ligand (or molecule) is attached to the central metal ion at two or more different points. The metal chelates generally exhibit somewhat slower ligand exchange than nonchelated complexes. Labile-type chelates may have a half-life of several seconds, or perhaps slightly longer. Generally, the oxidizing agents employed are not reduced to a zero valent metal during the redox reaction.

Preferred metal complexes in accordance with this process have coordination numbers of 6 and are known as octahedral complexes. Cobalt complexes are especially useful in the practice of this invention. Most square planar complexes (which have a coordination number of 4) are rather labile, although some Group VIII metal square planar complexes, particularly platinum and palladium square planar complexes, exhibit inertness to rapid ligand exchange.

A wide variety of ligands can be used with a metal ion to form suitable metal complexes. Nearly all Lewis bases (i.e., substances having an unshared pair of electrons) can be ligands in metal complexes. Some typical useful ligands include the halides, e.g., chloride, bromide, fluoride, nitrite, water, amino, etc., as well as such common ligands as those referred to on p. 44 of Basolo el al., supra. The lability of a complex is influenced by the nature of the ligands selected in forming said complex.

Particularly useful cobalt complexes have a coordination number of 6 and have a ligand selected from the group consisting of ethylenediamine(en), diethylenetriamine(dien), triethylenetetraamine(trien), ammine(NH ₃ ), nitrate, nitrite, azide, chloride, thiocyanate, isothiocyanate, water, carbonate, and propylenediamine(tn). The preferred cobalt complexes comprise 1) at least 2 ethylenediamine ligands or 2) at least 5 ammine ligands or 3) 1 triethylenetriaamine ligand. Especially useful are the cobalt hexammine salts (e.g., the chloride, bromide, sulfite, sulfate, perchlorate, nitrite and acetate salts). Some other specific highly useful cobalt complexes include those having one of the following formulas: [Co(NH ₃ ) ₅ H ₂ O]X; [Co(NH ₃ ) ₅ CO ₃ ] X; [Co(NH ₃ ) ₅ Cl]X; [Co(NH ₃ ) ₄ CO ₃ ]X; [Co(en) ₃ ]X; cis-[Co(en) ₂ (N ₃ ) ₂ ]X; trans-[Co(en) ₂ Cl(NCS)]X; trans-[Co(en) ₂ (N ₃ ) ₂ ]X; cis-[Co(en) ₂ (NH ₃ )N ₃ ]X; cis-[Co(en) ₂ Cl ₂ ]X; trans-[Co(en) ₂ Cl ₂ ]X; [Co(en) ₂ (SCN) ₂ ]X; [Co(en) ₂ (NCS) ₂ ]X; [Co(tn) ₃ ]X; [Co(tn) ₂ (en)]X; and [Co(tn)(en) ₂ ]X; wherein X represents one or more anions determined by the charge neutralization rule. Complexes containing oxidized noble metals or ferromagnetic metals, such as complexes of Cr ^III , Fe ^III , Rh ^III , Pt ^IV , Pd ^IV and Ir ^III , which have reactivities similar to the complexes listed above, could be used in the practice of this invention. The redox equilibra published in Stability Constants of Metal-Ion Complexes, Sillen and Martell, published by The Chemical Society, Burlington House, London, England (1964), indicate that other complexes have reactivities generally similar to the cobalt complexes mentioned above.

With many complexes, such as cobalt hexammine, the anions selected can substantially effect the reducibility of the complex. The following ions are listed in the order of those which give increasing stability to cobalt hexammine complexes: bromide, chloride, nitrite, perchlorate, acetate, carbonate, sulfite, and sulfate. Other ions will also effect the reducibility of the complex. These ions should, therefore, be chosen to provide complexes exhibiting the desired degree of reducibility. Some other useful anions include chloride, nitrate, thiocyanate, dithionate and hydroxide. Neutral complexes such as [Co(dien)(SCN) ₂ OH], are useful, but positively charged complexes are generally preferred.

Numerous reducing agents can be utilized in carrying out the same process. The reducing agents utilized herein undergo redox reaction with the oxidizing agent at a catalytic surface. In certain aspects, the reducing agent used in this process is an aromatic primary amine color-developing agent such as p-aminophenols or p-phenylenediamines. Color-developing agents which can be used include 3-acetamido-4-amino-N,N-diethylaniline, 4-amino-N-ethyl-N-β-hydroxyethylaniline sulfate, N,N-diethyl-p-phenylenediamine, 2-amino-5-diethylaminotoluene, N-ethyl-N-β-methanesulfonamidoethyl-3-methyl-4-aminoaniline , 4-amino-N-ethyl-3-methyl-N-9β-sulfoetyl)aniline, and the like. See Bent et al., JACS, Vol. 73, pp. 3100-3125 (1951), and Mees and James, The Theory of the Photographic Process, 3rd Edition, 1966, published by MacMillan Co., New York, pp. 278-311, for further typical, useful developing agents.

In one highly preferred embodiment, aromatic primary amino color-developing agents which provide good results in this process are 4-amino-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-β-(methanesulfonamido)ethylanili ne sulfate hydrate, 4-amino-3-methyl-N-ethyl-N-β-hydroxyethylaniline sulfate, 4-amino-3-dimethylamino-N,N-diethylaniline sulfate hdyrate, 4-amino-3-methoxy-N-ethyl-N-β-hydroxyethylaniline hydrochloride, 4-amino-3-β-(methanesulfonamido)ethyl-N,N-diethylaniline dihydrochloride and 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfonate.

The invention can be further illustrated by the following examples.

EXAMPLE 1

A multilayer photographic element is prepared by coating the following layers in order with the ingredient being listed in mg./ft. ² :

1. paper support;

2. layer containing blue-sensitive silver halide emulsion (1.2 microns mean grain size) at 16 mg./ft. ² based on silver, gelatin at 122, the yellow image dye-providing coupler α-pivalyl-4-(4-benzyloxyphenylsulfonyl)phenoxy-2-chloro-5-[ Γ-( 2,4-di-tert-amylphenoxy)butyramido]acetanilide at 60, coupler solvent di-n-butyl phthalate at 15, and 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone at 2;

3. layer combining gelatin at 100 and the scavenger for oxidized developer di-tert-octyl hydroquinone at 5;

4. layer containing a green-sensitive silver halide emulsion (0.3 micron mean grain size) at 10 mg./ft. ² based on silver, gelatin at 132, the magenta image dye-providing color coupler 1(2,4,6-trichlorophenyl)-3-5-[α-(3-tert-butyl-4-hydroxyphen oxy)tetra decanamido]-2-chloroaniliano-5-pyrazolone at 25, and the coupler solvent tri-cresyl phosphate at 12.5;

5. layer containing gelatin at 160 and di-tert-octyl hydroquinone at 4.5;

6. layer containing a red-sensitive silver halide emulsion (0.3 micron mean grain size) at 6 mg./ft. ² based on silver, gelatin at 90, the cyan dye image-providing coupler 2-[α-(2,4-di-tert-amylphenoxy)butyramido]-4,6-dichloro-5-me thylpheno l at 35, and di-n-butyl phthalate at 17.5;

7. layer containing gelatin at 100.

The phototgraphic element is exposed through a graduated-density test object and processed in the following sequence: color-develop 0.5 min. (40° C.) amplify 1.5 min. (40° C.) bleach-fix 1 min. (40° C.) wash 1.5 min. (26° C.) dry

The processing baths have the following composition:

Color Developer ______________________________________ benzyl alcohol 15 ml. K ₂ SO ₃ 4 g. KBr 0.4 g. hydroxylamine sulfate 2 g. 4-amino-N-ethyl-N-(2-methoxyethyl)-m- 7.5 g. toluidine di-paratoluenesulfonate K ₂ CO ₃ 30 g. diaminopropanol tetraacetic acid 5 g. water to 1 liter; pH 10.1 Amplifier benzyl alcohol .5 ml. [Co(NH ₃ )6]Cl ₃ 10 g. KBr 2 g. K ₂ CO ₃ 7.5 g. K ₂ SO ₃ 2.0 g. diaminopropanol tetraacetic acid 10.0 g. water to 1 liter; pH 10.1 Bleach-Fix diaminopropanol tetraacetic acid 3 g. acetic acid 20 ml. 60% (NH ₄ ) ₂ S ₂ O ₃ 150 ml. Na ₂ SO ₃ 15 g. [Co(NH ₃ )6]Cl ₃ 3 g. water to 1 liter; pH 4.5 ______________________________________

The processed sample is sensitometrically evaluated by recording the H and D curves of the developed yellow, magenta and cyan dye images. The curves are illustrated in FIG. 2.

The process is repeated with a control sample where 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone has been omitted from the blue-sensitive, silver halide emulsion layer. The H and D curves for the processed sample are shown in FIG. 3.

A comparison between the two sets of H and D curves shows the beneficial effect of the incorporated developing agent on the development of the yellow dye image in the initially blue-sensitive, silver halide emulsion layer.

Yellow contrast is increased due to increased developability of the coarse-grained emulsion. There is a very small speed increase in the other two layers, but no significant change in curve shape. Only the yellow dye image is improved substantially.

EXAMPLE 2

Results similar to those described in Example 1 are produced with separate coatings wherein the blue-sensitive, silver halide emulsion layer contains 1) 2 mg./ft. ² of 1-phenyl-4,4-dimethyl-3-pyrazolidone, 2) 10 mg./ft. ² of 1-phenyl-4,4-dimethyl-3-pyrazolidone, 3) 10 mg./ft. ² of 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone, and 4) 50 mg./ft. ² of piperidino hexose reductone.

EXAMPLE 3

A prolongation of the development time in the procedure described in Example 1 for the control sample from 30 seconds to 1 minute provides an increase in yellow-dye density. It appears that the development time in the color developer must be doubled for this element which does not contain incorporated black-and-white developer in order to achieve a substantial match of the yellow-dye image H and D curve with the cyan and magenta H and D curves.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention. pg,26