Patent GB-541298-A (GB)
Title: Improvements in methods of producing colour photographs employing colour correction and colour photographic materials therefor
IPC: G03C7/18
Filed: 1940-02-15
Abstract: 541,298. Colour photography KODAK, Ltd. (Eastman Kodak Co.). Feb. 15, 1940, No. 844. [Class 98 (ii)] Colour photographic sensitive material has inseparably coated on a support, on one side of a yellow filter layer, a sensitive silver salt emulsion for recording the blue component image, and on the other side of the yellow filter layer two sensitive silver salt emulsions each sensitized respectively to different spectral regions between green and infra-red and not specially colour sensitized silver salt emulsion layer. The auxiliary emulsion may have a lower sensitivity than the other emulsions, for example not more than one-fifth, preferably one-twentieth, of that of the bluesensitive emulsion, and is preferably more contrasty for example of a gradation double that of the blue-sensitive layer. The auxiliary emulsion is preferably a fire-grain emulsion thinly coated. and may consist of silver chloride or contain at least 75 per cent of silver chloride. The other emulsions preferably consist of silver bromide or iodo-bromide, and the red-and-green-sensitive emulsion may be mixed as in Specification 500,611. Colour couplers may be incorporated in any of the emulsions. In printing material, one of the emulsions may be infra-red sensitive. The auxiliary layer. If the green-sensitizing dye does yellow filter layer and the support, but is preferably directly under the filter layer. No image is recorded in the auxiliary layer or exposure, but the latent images in the other emulsion layers may be developed to silver and the residual silver halide images successively exposed and colour developed. All silver is removed in a bath not dissolving silver halide, such as an acid solution of potassium dichromate containing sodium sulphate or a cupric chloride solution (followed by ammonia or ammonium sulphite) or the bath given in Specification 516,514. The yellow filter layer may comprise colloidal silver or a yellow dye destroyed by oxidation. On exposure to white light through the support, development, and fixing, a black-and-white negative image corresponding to the undesired blue absorption in the blue-green and magenta images is produced in the auxiliary layer. If the green-sensitizing dye does not fully resist the processing baths, the redsensitive layer may be coated between the greensensitive and filter layers. By varying the position of the auxiliary layer different forms of colour correction may be obtained. The auxiliary layer may also be used to form a positive black key image by treatment by the reversal process after exposure. A coloured correcting or additional image may also be produced in the auxiliary layers. The emulsions may be processed separately or simultaneously by colour production or colour suppression for example by colour development or image-wise oxidation of leuco dyes. False-colour processing may be employed. Specifications 468,560, 475,784, 475,786, 478,933, 500,611, 507,841, 516,514, 516,816, 521,833, 521,834, 521,888, 524,154, 524,554, 524,555; 537,256 and 516,536, 521,746 and 37402/38, all as open to inspection under Sect. 91 are referred to.