Patent ID: 6083678
Filing Date: 2000-07-04
Classification: G03C

Abstract:
Method for preparing a light-sensitive silver halide photographic emulsion comprising performing at least three distinct precipitation steps in an aqueous medium into a reaction vessel, followed by desalting by means of flocculation and washing or by means of ultrafiltration, said emulsion comprising gelatin having a methionine content of at most 800 ppm as a colloidally stabilizing binder and {100} tabular silver halide grains containing at least 50 mole % of silver chloride, wherein at least 60% by number of all grains is provided by said tabular grains, and wherein said tabular grains exhibit an average aspect ratio of at least 2, an average thickness of at most 0.25 .mu.m with a variation coefficient of at most 0.25, and an average equivalent circular crystal diameter of 0.3 .mu.m or more with a variation coefficient of at most 0.20; said three distinct precipitation steps being a nucleation step and two growth steps, said method being further characterized by introducing after ending the said nucleation step one or more crystal dislocation(s) onto nuclei formed in the said nucleation step in order to provide anisotropic growth of the said nuclei into {100} tabular grains, wherein in the said nucleation step from 5 to 15% of the total available amount of silver nitrate is provided and wherein silver ions and halide ions are introduced in order to get cubic nuclei rich in silver chloride having an edge of at most 0.25 .mu.m, wherein introducing said crystal dislocation(s) is performed within a time taking no longer than the time required to perform a first physical ripening step after the nucleation step in order to get a number of dislocation lines of less than 5, in one and the same crystallographic plane, and wherein said physical ripening step between introducing said dislocation(s) and growing the nuclei having said dislocation(s) in a first growth step proceeds within a time interval from 2 to 10 minutes.