PROCESS OF PREPARING A REDUCED DISPERSITY TABULAR GRAIN EMULSION

摘要

PROCESS OF PREPARING A REDUCED DISPERSITY TABULAR GRAIN EMULSION A process is disclosed of preparing a photographic emulsion containing tabular silver halide grains exhibiting a reduced degree of total grain dispersity. After forming a population of silver halide grain nuclei containing parallel twin planes, a portion of the silver halide grain nuclei are ripened out. The silver halide grain nuclei containing parallel twin planes remaining are then grown to form tabular silver halide grains. The total grain dispersity of the emulsion is reduced by incorporating bromide ion in the dispersing medium prior to forming the silver halide grain nuclei and, at the time parallel twin planes are formed in the silver halide grain nuclei, a grain dispersity reducing concentration of a polyalkylene oxide block copolymer surfactant is present comprised of two terminal lipophilic alkylene oxide block units linked by a hydrophilic alkylene oxide block unit accounting for at least 4 percent of the molecular weight of the copolymer.