Patent GB-687768-A (GB)
Title: Indophenazines as catalysts in dye bleach baths for color photography
IPC: G03C7/28
Filed: 1951-07-16
Abstract: 687,768. Colour photography. GENERAL ANILINE & FILM CORPORATION. July 16, 1951 [July 22, 1950], No. 16817/51. Class 98 (ii). A coloured image is produced in a photographic emulsion layer containing a silver image and a bleachable azo dye by treatment with an aqueous solution of a water-soluble mineral or organic acid and an accelerating amount of an indophenazine of one of the general formulµ wherein R represents monocyclic aryl and Z and Z<SP>1</SP> each represents the atoms necessary to complete a benzene, naphthalene, or anthracene ring or ring-system. The acid used may be hydrochloric, hydrobromic, hydroiodic, sulphuric, sulphamic, or phosphoric acid, with or without the presence of ammonium chloride or an alkali halide such as sodium or potassium bromide or iodide or sodium chloride. The use of a weaker acid such as acetic, propionic, tartaric, citric, boric, or an aryl sulphonic acid, with increase of the amount of accelerator, permits the imagewise destruction of an azo dye in the presence of an azomethine dye image to permit of the production of a masking azo dye image in a multilayer film which has been processed by colour development. The pH of the dye-destruction bath may be from 2 to 4. Accelerators specified are indophenazine, 2-, 3-, and 9-methyl-indophenazine, 9: 10-, 8: 9-, and 1 : 2 - benzo - indophenazine, 2 - and 3 - ethoxy-indophenazine, 3-chloro-2-methylindophenazine, 2: 3-dimethoxyindophenazine, 9-methoxyindophenazine, 8: 9- and 9: 10-naphthoindophenazine, 2: 3 - diphenyl - 1 - pyrrolo - [2: 3-b-]-quinoxaline, and 3-phenyl-2-tolyl-1- pyrrolo-[2:3-b]-quinoxaline. In example 1, an exposed, developed, and fixed red-sensitive silver halide emulsion containing Direct Sky Blue is treated in an aqueous bath containing KI, HCI, and indophenazine to produce a dye image. In example 2, the emulsion is greensensitive and contains Fast Acid Magenta, and the bath contains 2-methylindophenazine. In example 3, the emulsion is blue-sensitive and contains diphenylbiguanide hydrochloride and Dianil Yellow, and the bath contains 2-ethoxyindophenazine. In example 4, the emulsion is green-sensitive and contains diphenylbiguanide hydrochloride and Cotton Red, and the bath consists of an aqueous solution of KI, glacial acetic acid, and 9: 10-benzoindophenazine. In example 5, a film is successively coated with a red-sensitive emulsion containing 1-hydroxy- 4 - sulpho - N - stearyl - 2 - naphthamide as colour coupler and Brilliant Purpurine IOB and diphenylbiguanide hydrochloride, with a green-sensitive emulsion containing 1-(4<SP>1</SP>-phenoxyphenyl-31-sulphonic acid)-stearyl-arnino-5- pyrazolone as colour coupler and Benzo Fast Yellow and diphenylbiguanide hydrochloride, with a yellow filter layer, and a blue-sensitive silver halide emulsion layer containing 5-(4<SP>1</SP>- stearylaminobenzoylacetamino) - terephthalic acid as colour coupler. After exposure and colour development in an aqueous solution of sodium hexametaphosphate, sodium bisulphite, 4 - diethylaminoaniline, sodium carbonate, hydroxylamine hydrochloride, and KBr, the excess developer is washed out, and the film is treated in an aqueous solution of KI, acetic acid, and indophenazine to provide positive yellow and reddish or orange masking images in the green- and red-sensitive layers. The remaining silver is removed by bleaching in a ferricyanide or copper chloride or bromide bath followed by fixing. In example 6, the procedure is similar, but Orange TA is incorporated in the red-sensitive layer and Light Fast Yellow in the green-sensitive layer.