Patent GB-500794-A (GB)
Title: Method for the production of colour photographs
IPC: G03C1/83
Filed: 1937-05-10
Abstract: 500,794. Colour photography. KODAK, Ltd. May 10, 1937, No. 34980 /38. Convention date, May 9, 1936. Divided out of 500,826. [Class 98 (ii)] A colour photograph is produced from material containing colour component records in three silver halide emulsions on a single support and containing filter colouring mattersdestroyed or rendered readily removable by oxidation by colouring the component records by means of vat dyestuffs and subjecting the filter colouring matters to oxidation. The material may comprise three differentially colour sensitized silver halide emulsion layers on a single support or may comprise two layers, one a not specially colour sensitized silver halide emulsion layer and the other a mixture of twosilver halide emulsions respectively sensitized to the red and green. The three layer material may comprise a top blueviolet sensitive layer, a middle yellow and green sensitive layer, and a bottom red or infra-red sensitive layer, or a top blue-violet sensitive layer, a middle red and orange or infra red sensitive layer, and a bottom yellow and green sensitive layer, or a top red-sensitive layer, a middle yellow-green sensitive layer and a bottom blue-sensitive layer. A yellow filter may be arranged between the blue-sensitive and middle layers or in the blue-sensitive layer. Green or red-orange filters may be arranged between the middle and lower layers or in the middle layer. A colourless or yellow gelatine layer may be arranged between the middle and upper layers. The whole material may be coloured yellow. Strongly swelling gelatine is used for the filter layers. The red or the yellow-green sensitive layer may be on the opposite side of the support to the two other emulsion layers. 4 : 4<1>-Dichloro-2 : 2<1> : 8-triethylthiacarbocyanine very strongly sensitizes to the extreme orange-red and the red, but not to the yellow and the green. The homogeneous blue-sensitive emulsion layer of the two layer material may be coloured yellow or a yellow filter may be arranged between the two emulsion layers, which may be on opposite sides of the support. The material may be developed with leuco vat dyes. The filter dyes may be triphenylmethane dyes, aminohydroxyanthraquinones and their sulphonic acid salts, substantive azo dyes and, their insoluble or non-diffusing salts, fulgides, and isocyanines and other quinoline dyes. They may be destroyed by weakly acidified permanganates, persulphates, bichromates, hydrogen peroxide, hypochlorites or neutral or alkaline potassium ferricyanide. Acidified, alkali nitrite converts dyes with free amino groups to readily washed out diazonium compounds. The filter dyes and the silver may be simultaneously removed. The material may be processed by reversal or by development, fixing and bleaching or may be processed directly. Specifications 376,746, 498,875, and 500,793 are referred to. The Specification as open to inspection under Sect. 91 comprises also the use of the vat dyes flavanthrene, ciba yellow, thioindigo, and highly halogenated indanthrenes and indigoid dyes. This subject-matter does not appear in the Specification as accepted.