Patent GB-626958-A (GB)
Title: Improvements in or relating to photographic processes
Inventor: JOHN DAVID HUGH OAKLEY
IPC: G03C7/30
Filed: 1947-01-01
Abstract: 626,958. Photographic colour developers; colour photography. MAY & BAKER, Ltd., JOHN, D. H. O., and FIELD, G. T. J. Jan. 1, 1947, No. 95. [Class 98 (ii)] A. developer comprises a reaction product of sulphur dioxide and either p-amino-diethylaniline or 2-amino-5-diethylamino-toluene, a source of alkali, and a colour coupler ; and a process of colour photography comprises subjecting a photographic element carrying a light-sensitive layer which contains an image in a developable silver salt to development by means of such sulphur dioxide reaction products in the presence of a colour coupler, which latter may be provided in the light-sensitive layer or an adjacent layer or in the developer, and which will combine with the oxidation products of these developing agents formed during development to form an image in azomethine or quinone-imine dye in situ with the developed silver image. The element may have been subjected to exposure in a camera or through a positive or negative transparency and development may be effected by the reversal process. The sulphur dioxide reaction products may be made by reacting the base with sulphur dioxide in presence of a small quantity of water or of an alcohol ; quantitative details are furnished in the case of the p-amino-diethylaniline product, and their solutions are cleaner and more stable than solutions of the corresponding hydrochlorides and they do not require bisulphites as preservative. Sodium and potassium carbonate, borax or trisodium phosphate may be used as the source of alkali, and numerous colour couplers are specified. Example I describes a photographic element consisting of the layers (a) support, (b) gelatino silver halide emulsion containing 3 : 31- diethyl - 4 - keto - 5 - [a(3<SP>11</SP> - alkyl - 6<SP>11</SP> : 7<SP>11</SP>- tetramethylene - dihydrobenzthiazolylidene -) -#. phenyl etbylidene] - 41 : 51 - diphenyl - thiazolino - thiazolo - cyanine iodide as red sensitising dye and 3-[1<SP>1</SP>-hydroxy-2<SP>1</SP>-naphthoylamino] - 4 - methyl - octadecylaminobenzene sulphonic acid as cyan colour coupler, (c) gelatino-silver halide emulsion containing 3 : 31- diethyl - 5 : 5<SP>1</SP> - diphenyl - 9 - methyl - oxacarbocyanine iodide as green sensitising dye and 1 - [4<SP>1</SP> - phenoxy - 3<SP>1</SP> - sulphophenyl] - 3- heptadecyl - 5 - pyrazolone as magenta colour coupler, (d) gelatino-silver halide emulsion containing 3 - [p - stearoylamino - benzoylacetamino]-isophthalic acid as yellow colour coupler, which element is exposed to a coloured object, developed in a metol-quinol developer, washed, exposed fully to light to render the residual silver halide developable, developed in an aqueous solution of the p-amino-diethylaniline sulphur dioxide compound, potassium carbonate and sodium sulphite, washed and bathed in Farmer's Reducer, to leave a true colour record of the original coloured object. Examples II, III and IV describe developers as above, but containing, respectively, 2 :5 - dichloroacetoacetanilide, 2- cyanacetyl coumarone, and 5 : 8 - dichler - 1 - napthol as colour couplers for producing yellow, magenta and cyan images.