GB540444A - Improvements in colour photography and materials therefor - Google Patents

Abstract

540,444. Colour photography and sensitive material therefor. KODAK, Ltd. (Eastman Kodak, Co.). Jan. 11, 1940, No. 622. [Class 98 (ii)] Material suitable for making subtractive prints comprises a support, as of paper, glass, synthetic resin, a cellulose ester, or a metal such as aluminium, carrying a mixed grain emulsion layer consisting of grains sensitive only to blue, grains sensitized also for green, and grains sensitized also for red, the inherent blue speed of the firstmentioned grains being at least 10 times that of the green and red sensitized grains, preferably 20 times and even as much as 50 times. Alternatively, the support may carry one mixed grain emulsion layer containing fast grains sensitive only to blue and slow grains sensitized also for green or red, and another emulsion layer, e.g. on the opposite side, containing slow grains sensitized also for the third colour. The material either carries also a de-colourisable filter layer as of tartrazine, or is exposed through a separate such filter layer, which is so chosen that it passes light of a colour to which the printing speed of the grains sensitive only to blue is substantially the same as that of the silver halide grains sensitized to green and red, and at the same time reduces the effective speed to blue light of the slow grains :almost to zero, so that they record susbstantially no blue light. The emulsions are of silver bromide, or preferably silver bromo-iodide. The blue-recording emulsion may be of the kind used for motion-picture negative or press film. The other emulsions may be of the kind used for positive films or enlarging papers; one may be sensitized for red with an 8-alkyl or 8-phenyl-3, 4, 31, 41 dibenzthiacarbocyanine dye, and another sensitized for green with a thia- or selena-21- cyanine dye or a 3, 4-benzthia-2<SP>1</SP>-cyanine dye. Colour couplers, e.g. those having a methylene group or phenolic hydroxyl group reactive in the coupling process, may be incorporated in the emulsions, but are preferably in three separate developing solutions, which may contain as colour forming developing agent a primary aromatic annine such as diethyl-p-phenylene diamine. The images may also be processed by image-wise oxidation of leuco dyes, e.g. as described in Specifications 521,746, 521,833, 521,834 and 521,888. The procedure described in Specifications 540,451 and 540,464 may be adopted to minimize wandering of the sensitizing dyes. Specifications 468,560, 478,933, 500,611, 516,536, 524,552 and 532,098 and Specification 37402/38 (as open to inspection under Sect. 91) also are referred to.