Patent GB-468509-A (GB)
Title: Method of producing multi-colour photographic pictures
IPC: G03C7/24
Filed: 1936-01-06
Abstract: 468,509. Colour photography. GASPAR, B. Jan. 6, 1936, No. 509. Convention date, Jan. 5, 1935. [Class 98 (ii)] In the production of colour kinematograph films, particularly films also bearing sound records, several picture images are photographically produced at different depths in a single or multi-layer material, developed, transformed into dyestuff pictures, and fixed, all the silver is bleached, the silver salt lying at the surface only is converted into silver or into a dark compound, and the residual silver salt is removed by fixing. A film containing a filter dyestuff is printed from both sides and the silver pictures developed either by quickly acting re-agents, the action of which is arrested by stop baths; or by treatment with alkaline developers followed by an acid stop bath. A multilayer material containing dyestuffs or dyestuff-formers may be provided with an additional uncoloured silver bromide emulsion layer without dyestuff-former and either sensitized to spectral ranges to which the other layers are not sensitive, or panchromatic, or sensitized to infra-red. The sound record and a key print are printed in the colourless layer. After the colour pictures have been processed by the dyedestruction method, all the silver is converted to silver bromide by treatment with cupric bromide, the silver bromide in the colourless layer reduced to silver by an alkaline-developer followed by an acetic acid stop bath, and the residual silver halide is removed by fixing. The colourless layer may carry the sound record only. In a modification the portions of the coloured layers underlying the sound track are diffusely exposed with coloured light to which the colourless layer is not sensitive and the dyestuff diffusely destroyed by suitable reagents. In another modification a two-layer film, the lower layer of which is blue-sensitive and the upper green-sensitive with a yellow filter dyestuff, is exposed in the camera as part of a bi-pack, developed and fixed. The silver is transformed with cupric chloride or bromide into silver chloride or bromide, and the silver halide in the upper layer reduced to silver by a concentrated hydroquinone-caustic soda developer, the penetration of which is stopped by hydrochloric acid solution, or by sodium hydrosulphite, which is stopped by potassium permanganate solution. The hydrosulphite treatment may precede the developer treatment. The reagents may be mixed with dextrine or starch and applied by a roller, sponge or swab. The lower picture is coloured with a basic dyestuff or converted into copper thiocyanate, which is then coloured with a basic dyestuff. The superficial picture may be converted into an iron-blue picture or immersed in a solution of leuco-ester and transformed into a dyestuff picture. Intermediate positives, used for producing pictures in the material described in Specifications 408,991, 415,040, and 416,566, may be obtained by the use of filters. Specifications 397,159, 397,192, and 416,660 also are referred to. The Specification as open to inspection under Sect. 91 comprises also a multi-layer material, Fig. 1 (Cancelled) having a greensensitized blue green layer I, coloured with Diamine Pure Blue, and a red- or infra-red sensitized colourless layer IV on one side of the support, and a red-sensitized yellow layer II, coloured with Chrysophenin G, and a blue-sensitive purple layer III, coloured with Diamine Fast Pink G on the other side of the support. Layer IV may also be a blue-sensitive layer containing Tartrazine. The colour component positives are printed by projection or contact with green, red and blue light respectively into layers I, II and III, and a negative of the sound record and a translation in black letters is printed into layer IV with red light. After developing and fixing the dyestuff is destroyed with thiocarbanide and citric acid at the image portions. The silver is converted into silver chloride by treatment with cupric chloride and nitric acid, the sound record and letters are blackened with sodium hydrosulphite, and the film is washed and fixed. This subject-matter does not appear in the Specification as accepted.