Patent GB-577812-A (GB)
Title: Improvements in and relating to the production and processing of photographic materials
IPC: G03C7/32
Filed: 1943-09-27
Abstract: 577,812. Photographic emulsions. KODAK, Ltd. (Eastman Kodak Co., and Peterson, W. D.). Sept. 27, 1943, No. 12382/45. Divided out of 577,804. [Class 98 (ii)] A photographic emulsion is produced by forming a light-sensitive silver salt in a colloid carrier and then introducing into the colloid carrier a cadmium salt, more insoluble than the light-sensitive silver salt, of a coupling component having a heterocylic nucleus not containing a coupling function but containing an imino group or a mercapto group which is next to or next but one to a nitrogen atom in the nucleus having an unshared pair of electrons or is next to a thiocarbonyl or carbonyl group in the nucleus. Colour photographic material may have two or more such emulsions coated on one or more supports', e.g. three differentially colour sensitized emulsions coated in superimposed layers on the same side of a single support. The colloid carrier may be gelatine, a cellulose ester, or a synthetic resin. Coupling components specified are : 6-benzoylacetaminoindazole, 6 - (o - hydroxybenzoylamino) - indazole, indazole-5-malonamide, 6- (alpha -hydroxy -#-naph. thoylamino) - indazole, 5 - benzoylacetamino - benzimidazole, 6- (21-cyanacetylnaphthalene- 61- sulphonamido) - indazole, 5 - (4<1> - benzoylacet - aminobenzenesulphonamido) - 2 - azole, 2 - mer - capto - 6 - (1<1> - naphthol - 5<1> - sulphonamido) - benz - thiazole, 2 - mercapto 5 - (2<1> - cyanacetyl - coumaronyl - 5<1> - sulphonamido) - benzimidazole, and 2 - mercapto - 5 - acetylacetaminobenzimid - azole. The silver salt may be silver chloride, bromide, ferricyanide, orthophosphate, arsenate, oxalate, cyanate or citrate. An aqueous caustic soda solution of 5-(4<1>-benzoylacetaminobenzene sulphonamido) - 2 - mercaptobenzimidazole may be added to a solution made by simultaneously adding aqueous trisodium phosphate and cadmium chloride solutions to aqueous gelatin solution, and adding the dispersion obtained to a gelatino silver halide emulsion. In producing multilayer material, the emulsions may be coated in superimposition on a support with a yellow filter layer containing colloidal silver in gelatine or the metallic salt of a dye as in Specification 524,500 in gelatine (e.g. a layer prepared by adding to a fine-grain silver chloride emulsion an aqueous solution of sodium p-sulphophenylazothiobarbiturate) between the green- and blue-sensitive emulsions. A colour developer containing p - aminodiethylaniline hydrochloride is described. The material may first be developed in a black - and - white developer and the residual silver halide colour developed. The developed material may be treated in an acetic acid stop bath, and ferri- ,cyanide and hypo baths applied to remove silver, remaining silver halide and unused coupler. The coupling components are resistant to diffusion. When the cadmium is removed from the couplers with alkaline cyanide or alkaline hypo solutions, the unreacted coupler is readily removed. The coupling components exert a fog-inhibiting action in black-and-white and colour developers. The final dye images may be mordanted with alum or silver nitrate. The support may be cellulose nitrate or acetate, glass, synthetic resin, paper or pigmented cellulose ester. Specifications 503,752, 524,557 and 577,804 also are referred to.