GB960783A - A photographic reversal process - Google Patents

Abstract

960,783. Photographic-silver dye-bleach processes. CIBA Ltd. Aug. 24, 1962 [Sept. 6, 1961], No.32690/62. Heading G2C. A process for producing a reversal colour image by the silver dye bleaching process in a single- or multi-layer material containing at least one silver halide emulsion and at least one dye which is sensitive to oxidation, fast to diffusion and can be bleached by the silver dye bleaching process by the steps of exposure, primary development, removal of primarily developed silver in an oxidation bath, secondary development, dye bleaching and removal of residual silver is characterized in that the oxidation bath contains sulphuric acid and a compound of hexavalent chromium and that removal of the primarily developed silver therein is carried out in the presence of an organic base or a salt thereof. Such base or salt may be incorporated in the emulsion or in any bath up to and, preferably, including the oxidation bath. Preferred bases are quaternary nitrogen bases and guaradine derivatives. Specified bases and salts are:- ethylenediamine, benztriazole, diphenyl-4: 4<SP>1</SP>-dibiguanide hydrochloride or acetate, dicyandiamide, betanaphthylbiguanide acetate, ethyl pyridinium bromide, tetra-n-butyl ammonium bromide,benzyl trimethyl ammonium chloride, 1: 2-dimethyl quinolinium methylsulphate, 3-methyl-2-methylmercapto benzthiazolium methylsulphate, 1-(4<SP>1</SP>-nitrobenzyl)- pyridinium chloride, methyl quinolinium methylsulphate, 2: 3-dimethyl benzthiazolium methylsulphate, 1: 2-dimethyl pyridinium methylsulphate, N: N<SP>1</SP>-trimethylene-bis-pyridinium-di-bromide or -p-toluenesulphonate, alpha: betadi-piperidinoethane dihydrobromide and N: N<SP>1</SP>-ethylene-N: N<SP>1</SP>- dimethyl-di-(piperidinium-p-toluenesulphonate). The oxidation bath may also contain a surfaceactive agent, preferably a fluorinated carboxylic acid or salt.