GB521550A - Improvements in and relating to colour forming developers and processes of colour development - Google Patents

Abstract

521,550. Colour photography. GEVAERT PHOTO-PRODUCTEN N. V., and MERCKX, P. L. J. R. Oct. 20, 1938, No. 30328, [Class 98 (ii)] A colour former for colour development is a derivative of general formula A-CO-CH 2 -CONXX 1 , where A is methyl substituted or not and X and X' are aromatic nuclei substituted or not. An example is acetoacetodiphenylamine. The colour former may be in the silver salt emulsion or in the developer. The developing agent may be a mono-, di- or tri-amino aryl compounds, including aromatic o- and p-diamines such as pphenylenediamine, diethyl-p-phenylenediamine, dimethyl-p-phenylenedianine, monoethyl-pphenylenediamine and 3 - amino - 6 - dimethyl - amino-toluene and including aminophenols and aminocresols and their halogen derivatives and aminonaphthols. Two colour developing formulae are given. The developed silver may be removed by a bath comprising potassium ferricyanide and sodium thiosulphate. The colour former may be added to the emulsion before or after coating, for example by absorption on the silver salts. The colour developed images may be produced on plates, films or papers having one or more emulsion layers on one or both sides of the support and employing gelatine or other substance as the emulsion binder. The colour formers may be added to the developing bath without previous solution or may be added in solution in acetone or in alcohols such as methanol.