Patent GB-553963-A (GB)
Title: Colour photography and kinematography
IPC: G03C7/20
Filed: 1941-12-05
Abstract: 553,963. Colour photography. TULL, A. G. Dec. 5, 1941, No. 15706. [Class 98 (ii)] Exposed bi-pack material comprising two supports, one of which carries two superimposed silver halide emulsion layers and the other a single emulsion layer is processed by separating the supports, producing chemically toned images simultaneously in the two layers carried by the first support and producing a third colour image in the single emulsion layer on the other support, either from the residual silver halide or from developed silver, e.g. by colour development, chemical toning, dye toning, the silver diazotate process, a process relying on the formation of a relief image in differentially hardened gelatine either of the layer itself or in a separately applied colloid layer, or the dye destruction process. In reversal, the silver may be removed at a final stage with Farmer's Reducer, or preliminarily with acid dichromate. The single-layer element may comprise a transparent support carrying a blue-sensitive emulsion layer, and the two-layer element an opaque or transparent support carrying a lower green-sensitive layer and an upper red-sensitive layer. A decolourizable yellow filter layer may be coated either on the bluesensitive or the red-sensitive layer, or a separate yellow filter may be disposed between the two elements. The material is exposed through the support of the blue-sensitive layer. The latent images are developed in a developer containing a silver salt solvent, e.g. NH 3  or KCNS. The residual silver halide in the two-layer element is converted to a silver ferrocyanide complex by treatment in a solution containing thiourea and potassium ferrocyanide, and the two images simultaneously chemically toned to Prussian Blue and uranium ferrocyanide images as described in Specification 540,971. The uranium ferrocyanide image may be converted into a dyetoned image as described in Specification 540,979. The residual silver halide in the single-layer element may be re-exposed and colour developed, or may be treated in a solution containing thiourea and potassium chromate and then in a lead nitrate-nitric acid solution to give a yellow lead chromate image. Alternatively, the residual halide may be treated with a solution containing thiourea and potassium ferrocyanide and then in a solution containing lead nitrate, nitric acid, and potassium bromide, and finally in a potassium chromate solution. The residual halide may also be toned to lead vanadate. Alternatively, the developed silver may be removed with acid dichromate, a complex silver ferrocyanide image formed, and the element then treated successively in aqueous thiourea (possibly containing potassium bromide) and in Tartrazine solution to give a yellow dye-toned image. Thiourea may also be added to the dye-bath. The precipitated dye may be insolubilized by treatment with barium chloride, a quaternary ammonium dye-fixing compound, or a basic dye, e.g. Acronol Yellow, and the silver salt may then be fixed out with hypo. The two components may be joined by an adhesive, left separate for printing, or brought together in registry for kinematographic projection or printing, registration being ensured by the sprocket holes. The two components may be used for printing successively or simultaneously on to the same or different material, and the material according to the invention may be used for printing from an original on different material. The emulsion layers may be separated from the supports by stripping layers and may be stripped after processing and transferred in register to a new support. Only one support may carry a stripping layer, and the emulsion layer or layers carried thereby transferred in register to the layer or layers carried by the other support. The front element may have between the support and the emulsion, a transparent layer capable of being rendered opaque white during processing, as described in Specification 540,976, to provide a reflective rear layer. Specifications 541,355, 547,722, 553,952 and 553,961 also are referred to.