GB461006A - Production of coloured photographic pictures - Google Patents

Abstract

461,006. Colour photography. GROVES, W. W. (I. G. Farbenindustrie Akt.-Ges.) July 5, 1935, No. 19269. Drawings to Specification. [Class 98 (ii)] In a process of the kind in which multicolour pictures are produced by direct exposure in a camera or by copying, on multilayer material comprising silver halide emulsion layers separated by one or more colour filter layers stable to the developing and fixing baths, and in which the partial colour records are developed, fixed, bleached to silver halide, and then converted into dyestuff images, one or some of the developed, fixed and bleached silver images are again exposed separately to monochromatic light in such wise that the filter or filters confine the light action to the particular halide layer to be exposed, and are not removed until the exposed silver halide images have been converted into colour images. In an example, a support is coated successively with a red-sensitive layer, red filter, green-sensitive layer, yellow filter, and blue-sensitive layer. The red filter may contain the aluminium lake of the dyestuff from diazotized naphthylamine and 2-oxy-naphthalene-3 : 6-disulphonic acid ; and the yellow filter Fuller's yellow. After exposure, developing, fixing, and bleaching the images to silver halide, the image in the front layer is exposed to blue light and developed to yellow as with 1-para-chlorophenyl-3-methyl- 4-amino-5-pyrazolone; the image in the rear layer is exposed through the support to blue light and developed to blue-green as with dimethyl-para-phenylenediamine and trichlornaphthol ; the filter layers, which have in the previous steps served to prevent the blue light from reaching the image in the middle layer, are decolourized as with sodium hydrosulphite ; the silver is removed from the front and rear images; the middle silver halide image is coloured red by chemical or dye-toning or by exposure and colour development as with thioindoxyl; and the silver image is removed from the middle layer. A modified process is described in which the red-sensitive layer is on the back of the film, and the red filter layer is dispensed with.