Patent GB-853478-A (GB)
Title: Colour photographic processes and products therefor
IPC: C10L1/233
Filed: 1957-01-25
Abstract: 853,478. Colour photographic products and processes. INTERNATIONAL POLAROID CORPORATION. Jan. 25, 1957. [Feb. 13, 1956], No. 2736/57. Drawings to Specification. Class 98(2) The product comprises a plurality of superposed differentially sensitive silver halide emulsion layers on a common support, each layer being associated with a colour-providing substance capable, on processing of the emulsions, of being solubilised in unexposed areas and adapted to be transferred to a superposed image-receiving layer to form a positive colour image in the latter, and the process comprises exposing the product and then such processing with image transfer. The image-receiving layer and also liquid processing composition, which may be in a rupturable container, may form part of the product, the whole then constituting a self developing colour element. The emulsion layers may be processed simultaneously or, by controlled diffusion of the processing liquid, successively, an upper layer or layers being affected before the lower; and after completion of processing and image transfer the receiving layer having the positive colour image may be separated. Preferred colour-providing substances are dye-developers and the desired imagewise distribution thereof in diffusible form in the emulsion layers results from immobilisation in the negative areas by oxidation in developing the latent silver images, but numerous other ways of producing a similar distribution in diffusible form are indicated, thus it is stated that such may result from coupling between oxidised colour developer and a colour coupler with reaction of uncoupled coupler with a stabilised diazonium salt or with an oxidising agent; or from use of coupling dyes, or complete dyes which are immobilised by tanning, or use of leuco dye developers, or selfcoupling developers. Layer-wise processing may be effected with aid of slowly permeable barrier layers, or variations of pH during development as by use of two containers, or by use of colour-providing substances in particle form for slow release by the processing composition. The products are illustrated in six figures (not shown), all of which are concerned with dye developers in strata or particle form or in layers adjacent to the sensitive layers, except that Fig. 5 has a cyan dye for use with tanning developer, magenta coupling dye, and dye developer only for the yellow, and three of which figures illustrate the processing liquid container. Three examples to illustrate the techniques employed rather than to obtain accurate colour reproduction are concerned with multilayer materials having green sensitive silver halide layers containing particles of, or else adjacent'to layers of, yellow dye developers and similarly positioned red sensitive layers with cyan dye developers, and these are exposed and treated with a pyrazolidone developer while adjacent to image receiving layers, to give yellow, cyan and green positive images in the latter. Specifications 684,591, 684.592, 706,921, 732,420, 804,971, 804,972, 804,976, 811,579 and 853,480 are referred to.