KINITSUOOKISANO HAROGENKAGINYUNYUKAEKINO SEIHO

摘要

1469480 Silver halide emulsions CIBAGEIGY AG 15 July 1975 [7 Aug 1974] 34769/74 Heading G2C In the production of a silver halide emulsion comprising uniformly sized crystals of twinned octahedral type by mixing an aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium halide in an aqueous dispersing medium containing a protective colloid e.g. gelatin, the initially formed silver halide nuclei are ripened in the presence of a silver halide solvent by Ostwald ripening to produce twinned octahedral seed crystals which are grown without substantial further Ostwald ripening or nucleation by the further addition of aqueous silver and halide solutions at a rate within a range which is determined experimentally at the beginning of and at a plurality of times during the crystal growth. The pBr is maintained above 0À15, preferably between 1À0 and 1À3 during the crystal growth. The required conditions during crystal growth may be controlled by controlling (a) rate of addition of solutions, (b) temperature, (c) concentration of silver halide solvent, or (d) pAg. The temperature may be 45-55‹C and the pAg below 10À1 during crystal growth. The preferred rate of addition is 90 per cent of the maximum rate possible without renucleation. The solutions may be added at stepwise or continuously increasing rates. An increased amount of silver may be added at each successive crystal growth stage.