GB427516A - Improvements in colour photography - Google Patents

Abstract

427,516. Colour photography. KODAK, Ltd., Kodak House, Kingsway, London.- (Assignees of Mannes, L. D., and Godowsky, L. ; Kodak Park, Rochester, New York, U.S.A.) Sept. 21, 1933, No. 18932/34. Convention date, Sept. 21, 1932. Divided out of 427,472. [Class 98 (ii)] Relates to the colour processing of multilayer photographic elements by colour development with a developer containing a colour former as described in Specification 376,838, and consists in a method of processing an element having a plurality of superimposed layers containing different colour sensation silver salt records, e.g. latent or bleached images-on the same side of a single support, which includes colour developing all the silver salt records to one colour, fixing if necessary, and then bleaching all but the bottom layer; the bleached layer is colour developed to a different colour. In an example, a film comprising a support carrying a thin layer of emulsion sensitized to red with naphthocyanol superimposed on a thin layer sensitized to green with erythrosin, after exposure in the manner described in Specification 427,472, is developed in a non-hardening developer, fixed, bleached in a dilute ferricyanide bath, exposed and re-developed in a minus-green colour developer comprising diethyl - p.phenylene - diamine with bromthioindoxyl, fixed if development is not carried to completion, and dried. The upper layer is selectively bleached by a chromic acid-bromide bath the action of which is arrested, before it affects the bottom layer, by time control and the use of a stop bath. A thin layer of clear gelatine is provided between the two emulsion layers to assist control. The stop bath consists of ammonia, with or without sulphite and methanol. The bleached upper layer is then exposed and developed with a minus-red colour developer comprising diethyl-p.phenylene - diamine with di- or tri-chlor-alphanaphthol after which the film is washed, the silver is removed with Farmer's reducer, and the film washed and dried. In an alternative method, the exposed film is directly colour-developed to the minus green. A master positive may be obtained from a negative film, thus processed, by contact printing and similar processing ; alternatively the film may be subjected to ordinary reversal treatment after exposure and then colour processed. Additive red plus green light is advantageous for copying. The colour sensitizing of the layers and their order may be changed ; and the intervening gelatine layer may contain a screening dye ; also the film may be processed to different colours, e.g. blue or blue-green and yellow or orange yellow. The application of the invention to the three-colour printing material set forth in Specifications 427,517 and 427,519 is also described. The invention may be applied to motion picture films or to still pictures on plates or films. Specifications 327,714, 333,902, [both in Class 2 (ii)], 356,308, [Group IV], 427,518 and 427,520 also are referred to.