Patent GB-1234532-A (GB)
IPC: G03C8/00
Filed: 1969-05-22
Abstract: 1,234,532. Photographic silver halide elements and dye-diffusion transfer processes. POLAROID CORP. May 22, 1969 [May 23, 1968], No.26262/69. Headings G2A and G2C. A photographic film unit which may be processed by passage through the nip of a pair of rollers 35 is of the form shown in the Fig: and comprises a photo-sensitive element 13 comprising a composite structure containing layers secured in superposed fixed relationship and comprising, in sequence, a first dimensionally stable support layer 14 which is preferably opaque (see below), a photo-sensitive silver halide emulsion layer 16, 19 or 22, having associated therewith a compound providing, as a function of development of the associated silver halide emulsion, an imagewise distribution of a dye imageproviding material (preferably a dye-developer) which is soluble and diffusible, in alkali, at a first pH, an alkaline solution permeable polymeric layer 24 dyeable by the dye image-providing material, a transparent alkaline solution permeable polymeric acid layer 26, containing sufficent acidifying groups to effect reduction of an alkaline processing composition having a first pH to a second pH at which the dye image-providing material is substantially insoluble and non- diffusible, a second dimensionally stable support layer 27, transparent to incident actinic radiation; and a rupturable container (11 with 11a separately retaining first 12 and second 12a aqueous processing compositions, the first composition 12 containing dispersed therein an opacifying agent and the second composition 12a containing dispersed therein a reflecting agent, fixedly positioned and extending transverse a leading edge of the photosensitive element to effect unidirectional discharge of the first and second compositions, in order, layer-wise, intermediate the emulsion layer (e.g. 22) and the dyeable polymeric layer (24) next adjacent thereto, the first and second compositions, taken together, possessing the first pH and the opacifying and reflecting agents, taken together, present in a quantity sufficient, upon distribution, to mask the compound associated with the emulsion layer and to prevent exposure of the emulsion layer during processing in the presence of radiation actinic thereto and incident on the second support layer 27. The unit may include an alkaline solution permeable polymeric sheet 36 extending intermediate the dyeable polymeric layer 24 and the photosensitive silver halide emulsion layer (e.g. 22) next adjacent thereto, and in which the rupturable container is mounted to effect unidirectional discharge of the first composition 12 intermediate the polymeric sheet 36 and the photo-sensitive silver halide emulsion layer next adjacent thereto (e.g. 22) and of the second composition 12a intermediate the polymeric sheet 36 and the dyeable polymeric layer 24 next adjacent thereto. The reflecting agent is preferably titanium dioxide and the opacifying agent is preferably carbon black. The light-sensitive part of the unit and the imagereceiving part are superposed as stated above and are not separated after transfer of the dyedeveloper to give a positive dye image. The image is viewed as a positive through the second dimensionally stable layer 27 and generally the emulsion is also exposed through this layer, in which event all the layers intermediate the emulsion(s) and the dimensionally stable transparent layer 27 must be transparent. In this case, the first dimensionally stable layer 14 is preferably opaque. This layer 14 may be transparent and the silver halide layer(s) may be exposed through this layer, in which event the film unit preferably also includes an opaque sheet fixedly positioned, for example, to an edge of the film unit and is capable of being folded over the first dimensionally stable layer 14 to be superposed on and coextensive with this.