Method of preparing silver halide photographic emulsions
AssigneeMinnesota Mining and Manufacturing Company
InventorsAlberto Vacca, Paolo Barletta
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Abstract
A method is disclosed of preparing washed silver halide photographic emulsions wherein silver halide grain formation is effected in the presence of an acid-coagulable gelatin derivative or a mixture of gelatin and an acid-coagulable gelatin derivative and coagulation of the emulsion occurs in the presence of ionic copolymers of styrene sulfonic acid and maleic acid.
Claims14
A method of preparing a washed silver halide photographic emulsion comprising the steps of forming a dispersion of silver halide grains in the presence of a hydrophilic colloid and removing undesirable by-products of silver halide grain-formation by lowering the pH to bring about coagulation and by washing coagulum formed in dispersing silver halide grains, the method being characterized by the fact that said hydrophilic colloid comprises an acid-coagulable gelatin derivative and said coagulation is effected in the presence of an ionic copolymer comprising monomer units of:
- (a) a water-soluble salt of a styrene sulfonic acid, and
- (b) maleic acid, the molar ratio of (a) to (b) being at least 1:1 up to 9:1.
A method of preparing a washed silver halide photographic emulsion comprising the steps of forming a dispersion of silver halide grains in the presence of a hydrophilic colloid and removing undesirable by-products of silver halide grain-formation by lowering the pH to bring about coagulation and by washing coagulum formed in dispersing silver halide grains, the method being characterized by the fact that said hydrophilic colloid comprises an acid-coagulable gelatin derivative and said coagulation is effected in the presence of an ionic copolymer comprising monomer units of:
- (a) a water-soluble salt of a styrene sulfonic acid, and
- (b) maleic acid, the molar ration of (a) to (b) being at least 1:1 up to 9:1 and said copolymer having ammonium or alkali metal salts of sulfonic acid groups on said copolymer.
Dependencies are inferred from the claim text.