Patent GB-1355133-A (GB)
Title: Photographic products and diffusion transfer processes
IPC: G03C8/00
Filed: 1971-05-26
Abstract: 1355133 Photographic dye transfer image production POLAROID CORP 26 May 1971 [1 June 1970] 17190/71 Addition to 1313354 Heading G2C A transfer dye image is produced by exposing a film unit comprising a first dimensionally stable layer, a photo-sensitive silver halide emulsion layer having associated therewith a dye image-forming material which is processing composition soluble and diffusible as a function of exposure of the photo-sensitive silver halide emulsion layer to incident actinic radiation, a polymeric layer dyeable by the dye image-forming material, a second dimensionally stable layer transparent to incident actinic radiation, and means securing the layers in fixed relationship, spreading alkaline processing composition between the silver halide and dyeable layers and thereby developing the silver halide emulsion, thereby forming an imagewise distribution of mobile dye image-forming material at least a portion thereof transferring by diffusion to the dyeable layer to form a dye image, and causing reaction between polyvalent metal ion and barrier polymeric material that are in the film unit or in the processing composition to form after substantial image formation in the dyeable layer a layer that improves stability and quality of the image compared to stability and quality in the absence of the reaction between the metal ion and the barrier polymeric material, and maintaining the composite structure intact subsequent to the processing, and in which process the film unit either contains an opaque layer between the silver halide and dyeable layer sufficient to mask the silver halide emulsion layer after development or such a layer is formed during processing. The layer formed on reaction between the barrier polymeric material and the metal ion is preferably impermeable to dye image-forming material, and the barrier polymeric material may be cross-linked by the metal ion. The barrier polymeric material may be present in the film unit as a layer between the silver halide and dyeable layers or in the processing composition. The metal ion may be in a layer in the film unit e.g. the dyeable layer and be diffusible in the presence of the processing composition or in the processing composition. The barrier polymeric material and metal ion may both be in the processing composition as long as they undergo reaction only at a pH different from the pH of the processing composition. The film unit may contain a polymeric acid layer to cause a change in pH in the film unit after substantial dye image formation. The barrier polymeric material may be carboxymethyl cellulose, carboxyhydroxyethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polyvinyl alcohol, or polymethacrylic acid as well as other polymers having free carboxyl, hydroxyl, amino or mercapto groups. The metal ion may be cadmium, calcium, magnesium, zinc, barium, nickel, zirconium, aluminium or chromium, and preferred anions are acetate, nitrate and carbonate. The first dimensionally stable layer may be opaque or may be transparent and an opaque layer may be present between the silver halide and dyeable layers. The processing composition may contain a light reflecting opacity providing material e.g. titanium oxide. The dye image-forming material may be a dye-developer.