Patent GB-1451420-A (GB)
Title: Diffusion-transfer colour photographic silver halide film unit
IPC: G03C8/44
Filed: 1974-05-16
Abstract: 1451420 Diffusion transfer colour photograhic silver halide film unit FUJI PHOTO FILM CO Ltd 16 May 1974 [16 May 1973] 21922/74 Headings G2C and G2X A photographic film unit comprises (1) a lightsensitive element comprising a transparent support bearing in order at least one light-sensitive silver halide emulsion layer having associated therewith a dye image-forming material which, upon development, forms an imagewise distribution of a diffusible dye image-forming material and a processing composition permeable light-intercepting layer containing a light absorbent, (2) an image-receiving element comprising a transparent support bearing a transparent, processing composition permeable image-receiving layer, (3) a pressure -rupturable container containing an alkaline processing composition and capable on rupture of spreading the composition between the surfaces of elements (1) and (2) furthest from their supports, and (4) a light-reflecting substance, which when the opposite surfaces to their respective supports of each of elements (1) and (2) are in contact, is either coated in advance as a film or introduced therebetween simultaneously with the spreading of the processing composition, and the film unit is adapted to be processed, after imagewise exposure in a camera through the transparent support of element (1), by a pressure-applying means which rupture container (3) when the opposite surfaces to their respective supports of each of elements (1) and (2) are in contact, the light absorbent and the light-reflecting substance being present in sufficient amount to together shield the at least one silver halide emulsion layer from ambient light from the side further from the support of (1) during development and  for the light-reflecting substance to mask the lightintercepting layer and to form a white background for the dye transfer image. The light-intercepting layer may contain as light absorbent carbon black of various types, black colloidal silver, a mixture of magenta, yellow and cyan dyes or a nigrosine dye (see Preparations A-F and Examples 2, 3 and 5). The light-reflecting substance (4) may be TiO 2  (e.g. nitile) in the rupturable container (3) (see Examples 1-5) or in the rupturable container (3) and as a layer on element (2) (see Example 6). Many types of dye image-forming material are disclosed such as coupler developers (Examples 1 and 3) and diffusible couplers (Examples 3-6). Element (1) in Examples 3, 5 and 6 bears a backing layer comprising gelatine containing stearic acid amide and (2-hydroxy-4-t-butylphenyl)-benzotriazole. Element (1) in Example 3 comprises chemically fogged silver bromoiodide emulsions adjacent the blue-, green- and red-sensitive negative silver bromoiodide emulsions. In Examples 4 and 5 the exposed and processed element (1) is separated from the film unit, the light-intercepting layer is removed and the element is subjected to alkaline processing, bleaching and fixing to give a permanent colour negative original for making ordinary colour prints. The composition may be placed in rupturable container (3) in an atmosphere of gaseous dichlorodifluoromethane (see Example 3). The image-receiving element (2) can be delaminated after spreading the processing composition. A layer containing the light-reflecting substance in the processing composition may adhere to the imagereceiving element (2) when it is delaminated. The film unit may further include a light-intercepting element capable of covering the surface of the support (1) and thereby protecting the light-  sensitive emulsion layer(s) from ambient light during processing. The light-intercepting element may be a polyethylene terephthalate light-intercepting sheet 100Á thick and containing 5 wt. per cent carbon black (see Example 2) or a 70Á thick cellulose acetate film containing 3 wt. per cent carbon black (see Example 3). The film unit may comprise a light-sensitive element 1 bearing a light-intercepting layer 60 supported in a camera by pressure plate 100 and connected to leader paper 5 at its leading edge, image-receiving element 2 and light-intercepting element 3 connected respectively to leader papers 6 and 7 each at the leading edge and rupturable container 4.