Acylacetamide type couplers represented by benzoylacetanilide and pivaloylacetanilide couplers have been commonly used as yellow couplers for the formation of color photographic images. The former type of couplers normally exhibit a high activity on coupling with the oxidation product of an aromatic primary amine developing agent upon development, and the yellow dyes produced therefrom exhibit a slightly greater molecular extinction coefficient than that produced from the Latter type of couplers. Thus, the former type of couplers are used mainly for color photographic material for picture taking, which require a high sensitivity. On the other hand, the latter type of couplers have superior spectral absorption characteristics and the fastness of the yellow dyes produced therefrom is better than the former type of couplers. Thus, the latter couplers are used mainly for color papers and color reversal systems.
Couplers having a high coupling reactivity which produce dyes having a high molecular extinction coefficient can provide a high sensitivity, a high gradation and a high color density, giving a high so-called color developability. The term "yellow image with excellent spectral absorption characteristics" as used herein means a "yellow image with a low absorption density on the long wavelength side and hence little undesirable absorption in the green light range".
It has thus been desired to develop a yellow coupler which can form a dye with a high molecular extinction coefficient that gives a high color density, excellent spectral absorption characteristics and an excellent colored image fastness.
With reference to N,N-substituted malondiamide type yellow couplers of the present invention, French Patent 1,558,452 describes so-called o-release type yellow couplers containing a release group at the coupling active position via an oxygen atom, most of which are diffusable.
Further, European Patent Disclosure No. 447,920A describes partial yellow couplers as exemplary compounds.
Moreover, of the N,N'-substituted malondiamide type couplers, functional couplers are disclosed as couplers which release a development-inhibiting compound in JP-A-52-69624, JP-A-52-82424, JP-A-57-151944, and JP-A-2-250053 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") , and the above cited European Patent Disclosure No. 447,920A. However , JP-A-52-82424 and JP-A-57-151944 do not disclose specific examples of such compounds, and JP-A-52-69624 contains no description of specific examples of effects achieved.
Of the couplers disclosed in these patents, some provide improvements in color developability, colored image fastness and color reproducibility. However, most of them still leave much to be desired. Further, the development-inhibiting compound-releasing type couplers leave much to be desired in image quality improvement effect.
On the other hand, the use of paraphenylenediamine, particularly N,N-dialkyl-substituted paraphenylenediamine compounds has often been proposed as color developing agents to be incorporated in color developers. For example, with reference to the modification of alkyl group substituted in the N-position, an N-hydroxyalkyl group is described in U.S. Pat. No. 2,108,243, British Patent 807,899, and European Patent 410,450A2, an N-sulfonamidoalkyl group is described in U.S. Pat. Nos. 2,193,015, 2,552,240, and 2,566,271, an N-carbamoylalkyl group is described in U.S. Pat. No. 2,374,337, and JP-A-3-246542 and JP-A-3-246543, an N-sulfamoyl group is described in U.S. Pat. No. 2,193,015, an N-acylaminoalkyl group is described in U.S. Pat. Nos. 2,552,242, and 2,592,363, an N-quaternary ammonium alkyl group is described in British Patent 539,937, a nucleated N-alkyl group containing a phosphorus atom as a substituent on the alkyl group is described in British Patent 539,395, an N-acylalkyl group is described in U.S. Pat. No. 2,374,337, an N-alkoxyalkyl group is described in U.S. Pat. No. 2,603,656, JP-A-47-11534, and JP-A-47-11535, and JP-B-54-16860, JP-B-58-14670, and JP-B-58-23618 (the term "JP-B" as used herein means an "examined Japanese patent publication") , an N-sulfoalkyl group is described in British Patent 811,679, and an N-aralkyl group is described in U.S. Pat. No. 2,716,132. Further, with reference to the modification of the substituent for the benzene nucleus, a nucleated alkoxy group is described in U.S. Pat. Nos. 2,304,953, 2,548,574, 2,552,240, and 2,592,364, a nucleated acylaminosulfonamide group is described in U.S. Pat. Nos. 2,350,109, and 2,449,919, a nucleated acylaminoalkyl sulfonamidoalkyl group is described in U.S. Pat. Nos. 2,552,241, 2,556,271, and 2,592,364, a nucleated amino group is described in U.S. Pat. Nos. 2,570,116, 2,575,027, and 2,652,331, and a nucleated thiosulfonic group is described in British Patent 872,683. Moreover, with reference to the use of analogous paraphenylenediamine compounds as color developing agents, tetrahydroquinoline and dihydroindole compounds are described in U.S. Pat. Nos. 2,196,739, and 2,566,259, N-(p-aminophenyl)hexamethyleneimine compounds are described in U.S. Pat. No. 2,612,500, and 9-aminojulolidine compounds are described in U.S. Pat. No. 2,707,681.
However, none of these color developing agents have been found to meet all requirements such as development activity, stability, image quality, e.g., fastness, graininess, sharpness and spectral absorption characteristics of color images formed on a color photographic light-sensitive material with these color developing agents, and stable color development.
European Patent Disclosure No. 410,450 describes some of color developing agents of the present invention. However, the above cited European patent can be applied to a silver halide color photographic material comprising a silver halide emulsion substantially free of silver iodide and containing 80 mol % or more of silver chloride but has no description of application to a silver halide emulsion with a high silver bromide or silver iodide content. Thus, the effects of these color developing agents on such a silver halide emulsion cannot be predicted from the above cited European patent. Further, the effects of N,N-substituted malondiamide type couplers cannot be fully predicted from the above cited European patent. Moreover, JP-A-4-11255 discloses some of color developing agents of the present invention but has no description of improvements in image quality by the use of N,N-substituted malondiamide type couplers. Thus, the effects of N,N-substituted malondiamide type couplers cannot be predicted from the above cited Japanese patent application disclosures.
As previously described, it has been desired to provide a stable color development process which provides further improvements in color developability, dye fastness and image quality when N,N-substituted malondiamide type yellow couplers are used and a further enhancement of the image quality improving effect when these N,N-substituted malondiamide type yellow couplers are development inhibitor-releasing type couplers.