Patent GB-500611-A (GB)
Title: Improvements in and relating to materials for colour photography and the processing thereof
IPC: G03C7/26
Filed: 1937-05-10
Abstract: 500,611. Colour photography. KODAK, Ltd. May 10, 1937, No. 34979/38. Convention date, May 9, 1936. Divided out of 500,826. [Class 98 (ii)] Colour photographic material has coated on a single support one emulsion layer containing a mixture of two silver halide emulsions respectively sensitized for the red and green regions of the spectrum and a second emulsion layer consisting of not specially sensitized silver halide, and a decolourable yellow filter is provided between the two emulsion layers. The two emulsion layers may be on the same side of the support with either uppermost, or they may be on opposite sides of the support. The red and the green sensitized emulsions may be separately pulverized or emulsified in non- mixing solvents such as tetrahydronaphthalene or xylene, and may be re-emulsified after weak tanning in gelatine or collodion or other colloids permeable to the developer. One or both emulsions may be collodion emulsions. One emulsion may be pulverized and emulsified in the other emulsion. Re-emulsification may be effected in collodion and a layer of gelatine, dextrine or gum-arabic superimposed on the emulsion layer. Particles of silver halide collodion emulsion may be re-emulsitied in gelatine solution or silver halide gelatine emulsion. Mixed silver chloride and silver bromide emulsions, one yellow-green sensitized and the other red sensitized, may be employed. The homogeneous emulsion may be of silver chloride if the layers are on opposite sides of the support. After ordinary development and removal of developed silver, the red-sensitive grains are exposed to red light and colour developed blue-green, the yellow-green sensitive grains exposed to yellow light and colour developed purple, and the blue-sensitive emulsion is exposed to blue or white light and colour developed yellow. If the yellow filter resists development, the homogeneous layer may be exposed to blue light and developed yellow, the silver removed or converted, and the grains exposed and developed separately. If a mixture of silver chloride and silver bromide grains is used, of if grains of one kind are dispersed in an emulsion of the other kind, the residual silver bromide of the blue-sensitive emulsion is exposed and developed yellow, and after exposure or pre-treatment with thiourea or other fogging agent the silver chloride grains are selectively colour developed, and finally the silver bromide grains are colour developed. The mixed grain layer may be selectively developed before the blue-sensitive emulsion. A blue-sensitive silver chloride emulsion may be on the same side of the support as the mixed grain-layer and the redsensitive grains may contain a developerresistant infra-red sensitizer. After ordinary development and exposure to red and infrared light through the support the red-sensitive grains are developed blue-green, all residual silver halide is made developable by thiourea or other fogging agent, the silver chloride is developed yellow, the silver bromide of the other grains is developed purple, and all silver removed. A mixture of yellow-green and red sensitive silver bromide grains may bo coated on a viscose film impregnated with blue and blue-green sensitive silver halide and previously coated with a water-impermeable layer such as celluloid, the substance known under the Registered Trade Mark " Zapon " or cellone lacquer. The viscose film may be impregnated with silver bromide and a mixture of yellowgreen sensitive silver chloride grains and redsensitive silver bromide gelatine grains coated on the film or a yellow-green sensitized silver chloride emulsion containing red-sensitive silver bromide grains in suspension. The grains may be hardened and developed under conditions limiting swelling of the gelatine. The silver halide of the blue-sensitive emulsion may be converted to a coloured complex compound or a coloured mercaptide. The materials may be coloured processed after development, fixing and bleaching. Specifications 500,716 501,000, 501,001, and 501,002 are referred to. The Specification as open to inspection under Sect. 91 comprises also the use of a yellowdyed rear emulsion. A viscose film impregnated with silver bromide has a sticky layer of silver halide emulsion applied thereto and a yellowgreen sensitive silver chloride emulsion is applied on this sticky layer. This subjectmatter does not appear in the Specification as accepted.