Many kinds of silver halide color photographic materials and methods of forming color images are commercially available at the present time. Various improvements and inventions thereon have been made depending on the end use. It is generally required that silver halide emulsions employed in these photographic light-sensitive materials have high sensitivity. Therefore, silver iodobromide, silver chloroiodobromide, and silver chlorobromide each being mainly composed of silver bromide, are used as the silver halide in the emulsions at present. Further, various kinds of development accelerators have been investigated in order to increase the color forming property and to shorten the processing time in color development during processing of color photographic light-sensitive materials. Particularly, benzyl alcohol is widely employed at present.
Recently, however, reduction of development processing time, simplification of the processing system and operation, and achievement of low environmental pollution have been highly required in addition to high sensitivity.
This is because reduction of the period to finish, simplification of laboratory work, improvement in productivity and miniaturization, and simple operation of the processing system for small scale laboratories which are designated so-called mini-labos, etc., are desired. With respect to these requirements of rapid processing, simplification of the processing system, and achievement of low environmental pollution, benzyl alcohol which is used in the color developing solution causes severe problems.
Since benzyl alcohol has a low water solubility, it is necessary to use a solvent such as diethylene glycol, etc., in order to assist in dissolution of the benzyl alcohol. These compounds including benzyl alcohol exhibit large values of BOD (biological oxygen demand) and COD (chemical oxygen demand) which indicate a large load for prevention from environmental pollution. Therefore, it is desirable to eliminate these compounds in view of the preservation of good surroundings. Also, it takes much time to dissolve benzyl alcohol in a developing solution even when the above-described solvent is employed and, thus, it is desired to eliminate benzyl alcohol for the purpose of simplification of work for the preparation of the developing solution. However, to simply eliminate benzyl alcohol results in a severe lag of color development which is contrary to the needs of rapid processing in the market. Thus, it has been desired to develop a means which is a substitute for the use of benzyl alcohol.
Silver halides mainly composed of silver bromide which have been mostly employed hitherto are theoretically disadvantageous for the purpose of rapid processing since bromine ions which are released from the silver halides when they are developed have a development inhibiting function. From the standpoint of rapid processing, it is preferred to employ silver halides mainly composed of silver chloride. However, it is known that silver halide emulsions mainly composed of silver chloride have some disadvantages in that they are apt to fog while they have a high development speed; they are poor in preservation stability; and that they have low sensitivity.
Because of their disadvantages described above, it is difficult for silver halides mainly composed of silver chloride to materialize their excellent developability in methods of forming images having relatively high sensitivity.
Accordingly, many attempts have been made in order to overcome these disadvantages. For instance, in order to increase sensitivity, silver chlorobromide emulsions having a high silver chloride content which contain silver chlorobromide grains having a stratiform structure are known. These silver chlorobromide emulsions are described in detail, for example, in Japanese Patent Application (OPI) Nos. 95736/83, 108533/83, 222844/85, and 222845/85 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). Further, a method for increasing sensitivity by means of doping metal ions in inner portions of grains is described in Japanese Patent Application (OPI) No. 135832/80. Fog also occurs during sensitization of grains formed. Methods for restraining such a fog are described in Japanese Patent Application (OPI) Nos. 125612/83 and 47940/86.
Although various attempts for increasing sensitivity and restraining the formation of fog with respect to silver halides mainly composed of silver chloride have been made while maintaining their excellent developability, they are still insufficient and, thus, a further improvement has been desired.
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