GB501001A - Process for colour photography - Google Patents

Abstract

501,001. Colour photography; photographic developing processes. KODAK, Ltd. May 10, 1937, No. 26470/38. Convention date, May 9, 1936. Divided out of 500,826. [Class 98 (ii)] Process of producing colour-developed reversed images in a three-layer photographic element, whose upper layer is not specially colour sensitized and which contains a colour sensitizer in the middle layer which is resistant to the action of photographic developing baths and of mild silver-oxidizing baths and a yellow filter dyestuff in the upper layer or between the upper layer and the middle layer, consists in developing the first latent images to silver, then removing the silver without destruction of the yellow filter dyestuff, then exposing the reversed silver halide image in the middle layer only by means of light of a colour to which it is selectively sensitized from either side, and colour developing it, then exposing the reversed silver halide image in the upper layer by means of blue light from the top, and colour developing it, and finally exposing and colour developing the reversed silver halide image in the lower layer. The middle layer may be sensitive to red and orange by using for sensitizer 4 : 4<1>-dichloro-2 : 2<1> : 8- triethylthiacarbocyainine chloride as described in Specification 501,003. The residual silver halide may be converted in one or more layers to silver chloride in a fine state of subdivision as described in Specification 501,003. In order 'to avoid the effect of local under-exposure in the lower layers all the layers are first saturated with developing agent in high concentration and are then treated with weak alkali to effect development. Alternatively a concentrated developing solution is allowed to diffuse into all the layers at as low a temperature as it is possible to employ without alteration in composition of the solution and the development process started or accelerated by warming the layers to room temperature or above. Specificatiens 427,518, 427,620, 454,498, 454,499, 454,622, and 501,002 also are referred to.