The present invention relates to a silver halide emulsion containing silver halide tabular grains having a high silver chloride content (hereinafter referred to as a high silver chloride tabular grains) and having {111} planes as principal planes. Further, the present invention relates to both a color photographic light-sensitive material and an image formation method, using the emulsion. Particularly, the present invention relates to a monodisperse, high-speed, and hard gradation (high contrast) emulsion that is excellent in grain shape stability; and to both a color photographic light-sensitive material and an image formation method (particularly, an image formation method that utilizes of a high illumination intensity and short time exposure), using the emulsion.
As a method for forming tabular silver halide emulsion grains having {111} major planes, for example, U.S. Pat. Nos. 4,400,463, 5,185,239, and 5,176,991, JP-A-63-213836 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and U.S. Pat. Nos. 5,176,992 and 5,691,128, disclose a method of forming grains in the presence of crystal habit-controlling agents, i.e. amino azaindenes, triaminopyrimidines, hydroxyaminoazines, thioureas, xanthonoides, and pyridinium salts, respectively.
It is well known in the art that high silver chloride grains originally have a characteristic that selectively {100} planes are apt to come out, and consequently the grains that are ordinarily formed are cubic. In the foregoing patents/publications, with utilizing a crystal habit-controlling agent, tabular grains are formed so that originally unstable {111} planes come out on the grain surface. Therefore, the moment desorption of the crystal habit-controlling agent from the grain surface is occurred, high silver chloride {111} tabular grains are redissolved, and {100} planes arise on the grain surface, so that it is difficult to maintain the grain shape. Further, it is difficult to expect to attain high sensitivity by spectral and chemical sensitization, without desorption of the crystal habit-controlling agent from the grains.
U.S. Pat. No. 5,691,128 discloses that the strength of adsorption of a crystal habit-controlling agent is controlled by pH-regulation, and exchange adsorption is made between a sensitizing dye and the crystal habit-controlling agent, thereby achieving compatibility between stabilization of the grain shape and enhancement of sensitivity.
Further, U.S. Pat. No. 5,272,052 discloses that composite grains composed of host grains and epitaxial portions (epitaxies) can be formed by epitaxially growing silver bromide selectively at the apexes (corners) of a grains by means of adsorption of a crystal habit-controlling agent, which is then replaced on the tabular grain surface by exchange adsorption of a photographically useful compound.
However, these epitaxial grains were also insufficient for a practical use, because during or after the spectral and chemical sensitization, these grains momentarily changed the adsorption state of dyes and the grain shapes, when they were in a condition where a crystal habit-controlling agent had been desorbed from the grains. Especially, the halogen composition of the epitaxial portion was unstable.
An object of the present invention is to provide a silver halide emulsion that is excellent in grain shape stability of {111} tabular grains, and that is a monodisperse, high-speed, and high contrast emulsion, and moreover that is able to concurrently improve both high illumination intensity reciprocity law failure and latent-image stability after exposure to light. Further, another object of the present invention is to provide a high-speed, and high contrast color photographic light-sensitive material that is able to concurrently improve both high illumination intensity reciprocity law failure and latent-image stability after exposure to light. Further, another object of the present invention is to provide an image formation method that is able to exert photographic characteristics of the above-described emulsion or light-sensitive material even when they are subjected to a rapid processing by means of a scanning exposure and so on.
Other and further objects, features, and advantages of the invention will appear more fully from the following description, taken in connection with the accompanying drawings.