As cyan dye image forming couplers, there have been known phenols and naphthols.
However, a cyan dye image obtained from the phenols or naphthols known in the art has a problem in color reproduction. Thus, it has an unsharp absorption form in a shorter wave length range, further having an unwanted absorption, i.e., asymmetric absorption in a green wavelength region. Accordingly, in a negative film, correction for the asymmetric absorption must be made by means of masking; in a color paper, however, there is no means for the correction so that it deterirates color reproduction.
Furthermore, the dye image obtained from the phenols and naphthols known in the art has still problems in storage stability thereof. Thus, a dye image obtained from a 2-acylaminophenol cyan coupler as disclosed in U.S. Pat. Nos. 2,367,531 and 2,423,730 was found to be inferior in heat fastness. A dye image obtained from a 2,5-diacylaminophenol cyan coupler as disclosed in U.S. Pat. Nos. 2,369,929 and 2,772,162 was inferior in light fastness and a dye image obtained from a 1-hydroxy-2-naphthamide cyan coupler was generally insufficient in light and heat fastness.
A 2,5-diacylaminophenol cyan coupler as disclosed in U.S. Pat. No. 4,122,369 and JP-A 57-155538 (1982) (the term "JP-A" means an "unexamined published Japanese patent application) and 2,5-diacylaminophenol cyan coupler having a hydroxy group within a ballast group, as disclosed in U.S Pat. No. 3,880,661 have not achieved sufficiently satisfactory level in the light and heat fastness and yellow stain occurred during the prolonged storage of the dye image.
For the purpose of solving these problems, there was proposed pyrazoloazole type cyan coupler as disclosed in JP-A 64-554 (1989), 63-250649 (1988) and 63-250650 (1988).
An electron-withdrawing group and a group capable of hydrogen-bonding were introduced into each of these couplers so as to satisfy an absorption wavelength of a dye formed, so that good color reproduction was attained. However, coupling activity did not reach a sufficiently satisfactory level, so that dye forming property and color reproduction could not be satisfied simultaneously.
In view of these conditions, the inventors of the present invention have made studies broadly and succeeded to find out pyrazoloazole type cyan coupler having improved color reproduction and excellent dye forming property.
USPTO Backgrounds
USPTO Backgrounds