PROCESSES FOR THE PREPARATION OF SILVER HALIDE EMULSIONS OF CONTROLLED GRAIN SIZE DISTRIBUTION, EMULSIONS PRODUCED THEREBY AND PHOTOGRAPHIC ELEMENTS

摘要

PROCESSES FOR THE PREPARATION OFSILVER HALIDE EMULSIONS OF CONTROLLED GRAIN SIZEDISTRIBUTION, EMULSIONS PRODUCED THEREBY,AND PHOTOGRAPHIC ELEMENTSAbstract of the DisclosureA process is disclosed of producing photo-graphically useful radiation sensitive silver halideemulsions the grains of which are of a predeterminedsize distribution, including selection of maximum andminimum grain diameters find selection of the distri-bution of grains of maximum, minimum, and interveningdiameters. This is achieved by modifying a doublejet precipitation to introduce during the run stablesilver halide grains capable of acting as host grainsfor the deposition of additional silver and halideions. The degree to which the host grains initiallyintroduced are grown determines the maximum graindiameter of the emulsion. The minimum diameter ofthe grains in the emulsion produced can be determinedby the diameter of the stable silver halide grainsintroduced at the end of the run. The rate at whichthe stable host grains are introduced during the runcontrols the distribution of intervening grain sizes.The silver halide emulsion produced invarious forms can be comprised of silver halidegrains differing in diameter such that (a) therelative frequency of grain size occurrences isrelatively invariant over much of the range of grainsizes present; (b) the maximum relative frequency ofgrain sizes occurs near the minimum grain diameter ofthe emulsion; (c) the maximum relative frequency ofgrain sizes occurs near the maximum grain diameter;or (d) maximum relative frequencies of grain sizesoccur near both the maximum and minimum grain sizes.