Patent GB-475786-A (GB)
Title: Improvements in and relating to colour photography
IPC: G03C7/28
Filed: 1936-02-21
Abstract: 475,786. Colour photography. KODAK, Ltd., and CROWTHER, R. E. (Eastman Kodak Co.) Feb. 21, 1936, No. 5227. [Class 98 (ii)] Three-colour records of subtractive type in correct colours are produced by processing a photographic element having three gelatinosilver halide layers inseparably coated on a support and containing red, green, and blue component colour records, one only of the layers being processed to the colour complementary to the colour of which the image in the layer is a record, printing the resulting images onto similar material, and processing the records in this material each to the same colour as the record in the layer of the first material having a similar sensitivity. Alternatively, the original records are each processed to a colour not complementary to the sensitivity of the layer, and printed onto similar material and each of the resulting records is processed to the same colour as the record in the layer of the first material having a similar sensitivity, the resulting records being printed onto similar material and processed in a similar manner. For example, Fig. 1 shows an object consisting of coloured areas and Figs. 2-4 show the records formed by exposing a material comprising a blue sensitive uncoloured layer, a green sensitive layer coloured minus blue, and a red sensitive layer coloured minus green. After exposure, the upper layer is coloured minus red in the non-image parts, e.g. by dyetoning, imbibition, or colour development and the colour destroyed in the presence of the silver image in the other two layers (Fig. 2). The resulting record is printed on similar material and the process repeated producing a second record (Fig. 3) in incorrect colours. This is again printed on similar material and processed as before resulting in a record (Fig. 4) in correct colours. Figs. 13 and 14 show the process applied to material comprising a blue sensitive, a green sensitive, and a red sensitive layer, all of which are initially uncoloured and, during processing, are coloured respectively minus red, minus green and minus blue (Fig. 13). The resulting record is printed on similar material processed in a similar manner and a correct colour record results (Fig. 14). Sensitive material suitable for the process and for that described in Specification 475,784 consists of an upper blue sensitive uncoloured layer, and two lower layers sensitized respectively for red and green, the layer next to the upper layer being coloured yellow and the bottom layer minus red or minus green. In the case of initially coloured layers, the known dye destruction process may be used. Uncoloured layers may be coloured by the processes described in Specifications 440,032, 440,089, and 447,092 by uniform colouring of the layer followed by dye destruction at the image parts, by differentially hardening the layer and dyeing the unhardened parts, or by the introduction of a leuco base which is oxidized to colour with sodium perborate and the colour bleached at the image parts with alkaline stannous chloride. In some cases, a dye of one colour, e.g. minus green can be converted to another colour, e.g. minus red, for example, by employing a dye with a free amino group, diazotizing, and coupling with a suitable phenol. For instance, the magenta dye formed by coupling diazotized 2 4-dinitroaniline or 2- bromo-4-nitroaniline with m-phenylenediamine, m-cresidine or m-anisidine may be diazotized by treatment with hydrochloric and nitrous acid solution and coupled with 1-amino-8- naphthol to form a blue-green dye. Where one of the layers is coloured with Niagara blue G it may be converted into a blue-green dye by treatment with pyridine. The layers may be sensitized to red and green with the sensitizing dyes described in Specifications 378,885 and 385,267. A panchromatic layer dyed black may be arranged below the sensitive layers. Specifications 441,325, 444,198, and 468,560 also are referred to.