GB507841A - Process of producing coloured images in multilayer photographic elements - Google Patents

Abstract

507,841. Colour photography. KODAK, Ltd. (Eastman Kodak Co.) Nov. 19, 1937, No. 31911. [Class 98 (ii)] A process of producing colour developed reversed images in a photographic element having three silver halide emulsion layers coated on the same side of a single support, one of the outer layers being not specially colour-sensitized and the other layers being sensitized to the red and green regions of the spectrum respectively, comprises developing negative images in all the layers, exposing and colour developing the positive image in one or both of the outer layers and exposing the middle layer by visible light passed through the colour developed outer layer or layers and colour developing it, and removing the positive and negative silver when all the layers have been exposed and colour developed. In a particular example, the red-sensitive layer is next the support and the green- and blue-sensitive layers are coated thereon, red and yellow filters being provided respectively between the red and blue-green, and the green and blue layers if desired. 'After exposure, the film is developed to black and white by a developer containing potassium thiocyanate, and, after washing, is exposed from the support side to light passed through a red filter. The film is then colour developed to give a blue-green positive image in the lower layer. If the yellow filter layer is still present, the middle layer may be exposed by white light passed through the colour developed layer, but if the filter is absent, the green sensitizer must be resistant to development and this layer exposed by green light passed through the lower layer. The middle layer is then colour developed to magenta, after which the blue sensitive layer is exposed and colour developed, the positive and negative silver being then removed from all layers by a potassium ferricyanide bath. This bath should also remove any filter layer present such as colloidal silver. If the filter layer resists development, then the upper layer may be exposed first with blue light, then the lower layer, and the middle layer exposed last. The green and red sensitive layers may be reversed in order, the green layer being nearest the support. Examples of colour developers containing potassium thiocyanate are given. An antihalation layer of nickel sulphide in gelatine may be coated on one or both sides of the support, and is removable by the potassium ferricyanide bath. Other sequences of exposure are described in the Specification, and the colour couplers may be contained in one or more of the sensitive layers. Specifications 440,032, 447, 748, 458,664, 458,665, and 500,826 are referred to.