Dye forming couplers are developed as intermediates of information recording materials such as silver halide photographic light-sensitive materials, color forming reagent compositions, filters, paints and inks or dyes for printing. Especially, in the field of silver halide photographic light-sensitive material, it is well known that an aromatic primary amine color developing agent when oxidized with an oxidizing agent of an exposed silver halide reacts with a coupler to give indophenol, indaniline, indamine, azomethine, phenoxazine, phenazine or a like dye, to thereby form a color image. In such a photographic system, a subtractive color photographic process is employed, where color images are formed with yellow, magenta and cyan dyes.
For forming yellow color images, acylacetanilide or benzoylacetanilide couplers are employed. For forming magenta color images, 5-pyrazolone, cyanoacetophenone, imidazolone, pyrazolobenzimidazole or pyrazolotriazole couplers are employed. For forming cyan color images, phenol or naphthol couplers are employed.
Almost all the magenta couplers which have hitherto been studied are 5-pyrazolone compounds. However, as the dyes to be derived from the couplers have some unfavorable absorption in the vicinity of 430 nm, they extremely lower the color reproducibility of the couplers.
In order to overcome this problem, pyrazolobenzimidazole skeletons disclosed in British Patent 1,047,612, indazolone skeletons disclosed in U.S. Pat. No. 3,770,447, and pyrazolotriazole skeletons disclosed in U.S. Pat. No. 3,725,067 and British Patents 1,252,418 and 1,334,515, have been proposed. Among them, the dyes to be derived from the pyrazolotriazole couplers are almost free from the unfavorable absorption in the vicinity of 430 nml, and therefore, they are favorable to the color reproducibility.
However, these couplers have other problems. For example the process of producing the couplers requires many reaction steps or the yield of the couplers by the process is poor. Additionally, they have further problems in that the coupling reaction activity in the reaction between the couplers and developing agents is low and the dyes formed from the couplers by the coupling reaction have a poor light-fastness.
On the other hand, the phenol or naphthol couplers which have heretofore been employed as the cyan coupler give dyes which have some unfavorable absorption in the region of a green color and therefore have a problem that the couplers extremely lower the color reproducibility.
In order to overcome the problem, 2,4-diphenylimidazole couplers described in European Patent 249,453 has been proposed. The dyes formed from the couplers are almost free from the unfavorable absorption in the region of a green color and therefore are favorable to the color reproducibility of the couplers.
However, the couplers have some problems that the coupling activity thereof is low and the dyes formed therefrom have an extremely poor fastness to heat and light.