GB535410A - Improvements in the production of multicolour pictures - Google Patents

Abstract

535,410. Colour photography. GASPAR, B. Jan. 12, 1939, No. 1050. [Class 98 (ii)] Multicolour images are produced on exposed light-sensitive material having superposed on a support at least three gelatin layers, two or which contain different colour component silver images and the third of which is an intermediate layer containing uniformly exposed silver halide, by colouring the images with the same destructible dye, treating the material with a tanning solution which tans the gelatin in presence of metallic silver, converting the dye image in the surface layer into a dye image of different colour, and removing the silver from all three layers. In an example, multilayer material comprises a top bluesensitive layer, an intermediate layer containing a yellow filter dye and finely divided exposed silver halide, a green-sensitized middle layer, a second intermediate layer containing infra-red-sensitized silver halide, which may contain a red dye, and a rear red-sensitized layer. The red and green sensitized layers may be interchanged. After exposure, the film is developed, dyed blue-green if the rear layer was red-sensitized or magenta if the rear layer was green-sensitized, exposed to infra-red light, developed in a tanning developer, fixed, and immersed in 3 per cent. sodium hydrosulphite solution to destroy the dye in the front two layers, which are then re-dyed magenta or blue-green. The material is then treated in a dye-destruction solution. The dye in the rear layer may be more readily bleachable than the dye in the front two layers or the rear layer may contain a dye-destruction catalyst, such as 3 : 3<SP>1</SP>-carbonyl-bis-2-hydroxy- 3-aminophenazine. The silver is bleached with a bleach-hardening solution, and the film is fixed and dried. The dye in the top layer is destroyed with a 3 per cent. sodium hydrosulphite solution and the relief image therein is dye-toned with Chrysophenine G. In another example the order of the emulsion layers is reversed, but the intermediate layers are the same, and exposure is effected through the support, which contains or is provided with a layer containing an infra-red absorbing substance. In printing material a paper support may be used. Two-layer material having an intermediate infra-red sensitive layer is exposed with the exclusion of infra-red light, developed with a colour developer, exposed to infra-red light, and developed in a tanning developer. The dye in the surface layer is decolorized with an acid solution, the film is illuminated by white light, and the film redeveloped with a colour developer. Silver and silver halide are removed with Farmer's reducer. Printing on to similar material with similar treatment gives a two-colour positive. Specification 505,099 is referred to.