Silver halide dispersions prodn. - by pptn. in medium contg. silver salt and soluble salt, and growing the grains whilst reducing the vol. of the dispersion

摘要

In a process for the pptn. of Ag halides, a dispersion of photosensitive Ag halide is made by reacting an Ag salt with one or more metallic halides in soln. to form Ag halide grains and soluble salts in the presence of a dispersion medium. The grains are grown in a reactor contg. the grains and the dispersion medium, the vol. of the dispersion being reduced during the growth phase by sepg. part of the dispersion medium whilst retaining the grains of Ag halide in the residual dispersion. The dispersion medium pref. contains a hydrophilic colloidal peptising agent. The process avoids the tendency for continuous formation of Ag halide grains during the growth phase of the pptn. (renucleation); reduces crystalline imperfections in the Ag halide grains; reduces the formation of fog by redn. in the Ag halide grains; and gives Ag halide grains with more reproducible sensitivity.