Patent GB-1313354-A (GB)
Title: Photographic products and diffusion transfer processes
IPC: G03C8/52
Filed: 1970-10-07
Abstract: 1313354 Photographic colour diffusion transfer process POLAROID CORP 7 Oct 1970 [7 Oct 1969 20 Oct 1969 (2)] 47727/70 Heading G2C A composite colour print comprising a positive colour image over a negative image and separated therefrom by a light opacifying layer that permits the positive image to be viewed as a positive reflection print is formed by development of an exposed film unit comprising, in order, in superposed fixed relationship, a first support, an exposed silver halide emulsion layer having associated therewith a compound, e.g. a dyedeveloper, providing, as a function of development of the associated emulsion layer, a dye imageforming material which is soluble and diffusible in aqueous alkaline processing composition, a polymeric layer dyeable by the dye image forming material and a transparent second support, thereby forming an imagewise distribution of mobile dye image-forming material at least a portion of which is transferred by diffusion to the dyeable polymeric layer and forms a dye image therein, in which process the light opacifying layer is present before development or formed during development and in which process a polymeric layer impermeable to the dye imageforming material is formed between the dyeable polymeric layer and the silver halide layer after substantial image formation. The aqueous alkaline processing composition may be retained in a rupturable container. The first support may be transparent and the opacifying agent may be present between the dyeable polymeric layer and the photo-sensitive silver halide emulsion layer next adjacent thereto. The first support may alternatively be opaque and the opacifying agent may be in the processing composition. The opacifying agent may be titanium dioxide. The film unit may contain a polymeric acid layer between the first support and the silver halide emulsion layer or between the second support and the dyeable polymeric layer. The means for forming the dye image-forming material impermeable polymeric layer may comprise a polymeric film-forming material contained in the processing composition, the material forming a film on spreading of the processing composition which film is permeable to dye imageforming material at alkaline pH but is impermeable after diffusion transfer at a lower pH. Alternatively the polymeric layer may be present in the material, the layer being permeable to dye image-forming material at alkaline pH, but impermeable at a lower pH. In another embodiment the means for forming a dye image-forming material polymeric layer may comprise (i) a polymeric thickening agent in the processing composition and a diffusible cross-linking agent therefor in a layer of the material or (ii) a layer, between the dyeable polymeric layer and the silver halide emulsion layer next adjacent thereto, of a dye image-forming material permeable polymeric layer which is capable of being crosslinked to form the desired impermeable layer, and a diffusible cross-linking agent in a layer of the material or in the processing composition. The cross-linkable polymeric layer may be of polyvinyl alcohol and the cross-linking agent boric acid. In a further embodiment the dye image-forming material impermeable polymeric layer may comprise a dispersion in the processing composition of an insoluble polymeric material which, upon loss of processing composition solvent, coalesces at ambient temperature to form the impermeable layer. The polymeric dispersion may comprise a carboxylated styrene/butadiene copolymer.