GB775197A - Colour photographic process - Google Patents

Abstract

775,197. Colour photographic processes. IMPERIAL CHEMICAL INDUSTRIES, Ltd. Sept. 30, 1955 [Oct. 8, 1954], No. 29040/54. Class 98(2) A colour photographic process comprises the development with a colour developer in the presence of a colour coupler of an exposed photographic material carrying a gelatino silver halide emulsion which has been formed by reacting, in the presence of gelatin and a rhodium salt an aqueous solution of a soluble silver salt with an aqueous solution of soluble halide. The rhodium salt increases the contrast obtained (usually with a reduction in speed), and about 0.001 molecular proportion of rhodium salt per 100 molecular proportions of soluble silver salt may be used. The colour coupler may be incorporated in the developing solution or may be incorporated in the emulsion layer or in resin particles which are dispersed in the emulsion layer. The material may be used in printing: In Example 1, an emulsion is prepared by mixing aqueous solutions containing (a) potassium chloride, potassium bromide, gelatin and rhodium trichloride and (b) silver nitrate, and subsequently treating in the normal manner. The chlorobromide emulsion obtained is sensitized with bis - (3 - ethyl - 5 - phenylbenoxazole) - 9 - ethyltrimethincyanine ethosulphate and the magenta coupler 1 - # -- octadecylsuccinamido - 4 - omega - cyanoacetobenzene is incorporated. The exposed material is colour developed using 2 - amino - 5 - diethylaminotoluene hydrochloride as colour developing agent and is compared as regards speed and contrast with a similar emulsion not prepared in the presence of rhodium trichloride. Similar comparisons are drawn in Examples 2 and 3 with emulsions containing the yellow coupler 3 - (p - anisoylacetamino) - 4 - (N - methyl: N - octadecylamino) - benzoic acid and the cyan coupler 1 - hydroxy - 4 - sulpho - 2 - naphthoyloctadecylamide respectively. In example 4, a similar comparison is drawn for silver iodobromide emulsions prepared with or without rhodium trichloride and containing the magenta coupler 1 - # -octadecenylsuccinamido - 4 - omega - cyanoacetobenzene.