GB517424A - Improvements in and relating to multilayer colour photographic processes - Google Patents

Abstract

517,424. Colour photography. KODAK, Ltd. and JELLEY, E. E. July 25, 1938, No. 22044. [Class 98 (ii)] In the reversal processing of multi-layer colour photographic elements, the latent images are first developed to silver, the residual silver halide in all layers is rendered non-sensitive and the layers are then selectively re-sensitized to light, exposed and colour developed. The multi-layer material may have three differently sensitized layers inseparably coated on one side of the support. in the order non-sensitized, green sensitized and red sensitized. After exposure it is developed to produce negative silver images and then subjected to a permanganate reversal bath as described in Specification 440,032. This treatment desensitizes the layers. After rinsing in very dilute ammonia, the top layer of the material is resensitized in a 75 per cent. glycerol solution containing 2 per cent. of sodium bisulphite. It is then exposed to white light, the two bottom layers cleared in the dark with an aqueous sodium bisulphite solution, and the top image colour developed, e.g., to yellow. After removal of the developed silver from the top layer, the second layer is then resensitized, exposed and colour developed, e.g., to magenta. The material is finally treated with sodium bisulphite, fully exposed, and colour developed, e.g., to blue green.' The silver is then removed. In a modification all the layers are developed to silver which is removed by a permanganate reversal bath. The desensitized layers are all resensitized by a bisulphite clearing bath and the top two layers are desensitized with pinakryptol yellow or tetramethyl benzidine in glycerol - water - alcohol solution and the bottom layer is exposed and developed to blue-green. The film is resensitized with aqueous bisulphite solution, and dried, and the top layer is desensitized. The film is exposed to white light and the middle layer developed to magenta. After resensitization with bisulphite, the film is exposed, the top layer developed to yellow, and all silver is removed. False colour records may be processed in this manner. Specifications 427,518, 454,498, 454,499, 475,784, 475,786, and 507,841 also. are referred to.