GB1336361A - Photographic silver halide products and diffusion transfer processes - Google Patents

Abstract

1336361 Photographic diffusion transfer film unit POLAROID CORP 15 Jan 1971 [19 Jan 1970] 2124/71 Heading G2C A photographic film unit, for forming by diffusion transfer a composite print in which a positive image is formed over a negative image the composite print being viewable without separation of the two images as a positive reflection print, comprises a photo-sensitive laminate comprising a support, a photo-sensitive silver halide emulsion layer, a polymeric image-receiving layer and, between the silver halide emulsion and image-receiving layer, a layer comprising a dispersion of reflecting inorganic pigment having a first mean particle size, which layer transmits incident actinic radiation to expose the photosensitive silver halide emulsion layer and which dispersion upon contact with alkaline processing composition provides a dispersion of the pigment having a second, larger, mean particle size such that the dispersion is effective to mask imageforming material in the silver halide emulsion layer. The pigment may be titanium dioxide. The first particle size may be less than 0À2 microns and the second particle size greater than 0À2 microns. The support may be opaque and the image-receiving layer may be distant from the opaque support and a transparent cover sheet may cover the image-receiving layer or maybe connected to the opaque support and be capable of covering the image-receiving layer. Alternatively the support may be transparent, the silver halide layer may be distant from the transparent support and a second sheet may cover the silver halide layer or may be connected to the transparent support and be capable of covering the silver halide layer. The film unit may contain a rupturable container that contains alkaline processing composition positioned to discharge the composition between the laminate and the second sheet. The processing composition may contain an opacifying agent. Each silver halide emulsion layer may have associated therewith a compound providing a dye image forming material e. g. a dye-developer. The film unit may contain an acidic layer. The film units and processes of Specification 1326035 are disclaimed. Film units and processes in which the present invention is usable are described and claimed in Specification 1336362.