GB1458020A - Photographic development and bleach fix process - Google Patents

Abstract

1458020 Photographic silver salt development and bleach-fix process EASTMAN KODAK CO 4 Dec 1973 [4 Dec 1972 1 Oct 1973] 56197/73 Heading G2C A photographic material having a support and at least one imagewise exposed photo-sensitive silver salt layer is treated with an alkaline processing solution to form a first, silver, image and to form a second, non-metallic, image, and the silver image is bleached and fixed by treatment with a combination of a trivalent cobalt ion complex oxidizing agent and a silver salt solvent (i.e. compounds and concentration levels of those compounds which, when used in an aqueous solution at 60 C are capable of dissolving more than 10 times the amount by weight of the silver salt than that which can be dissolved in water at 60‹C), in the presence of the alkaline processing solution. Many different types of silver halide solvents are disclosed. The silver salt is preferably silver halide. The non-metallic image may be (i) a dye image e.g. formed by coupling (see Examples 1-6 and 8), or oxidation of a dye in the presence of silver followed by hydrolysis to give a diffusible dye (see Example 7) or when the cobalt complex contains amine ligands the released ammonia can react with an image-forming substance to form e.g. an azo dye by the amine-induced interaction between a diazonium salt and an appropriate coupler, (ii) when the cobalt complex in its reduced form is a crosslinking agent, it can be used to harden imagewise a hydrophilic colloid binder, or (iii) the reduced cobalt complex can react with e.g. 8-hydroxyquinoline or 2, 4-diaminophenol to produce a coloured compound. The invention also comprises a photographic processing solution comprising an alkaline aqueous solution containing a colour developing agent, 0À5- 250g per litre sodium or potassium thiosulphate and 0À2-20g per litre cobaltic hexammine chloride