Patent GB-684592-A (GB)
Title: Improvements in or relating to photography
IPC: G03C8/34
Filed: 1947-01-29
Abstract: 684,592. Photographic processing products and self-processing films. STEVENS, A. H. (International Polaroid Corporation). Jan. 29, 1947, No. 2761/47. Class 98 (ii). The product comprises a container with processing agent therein and includes a wall member of material impervious to the processing agent for preventing release thereof during normal handling of the product, the wall member being rupturable to permit release of the processing agent on application of mechanical stress to the container when this is in contact with sheet material. The container may be sheet-like, and may include a porous sheet material such as blotter paper having the processing agent in the pores, or a sheet material having recesses containing the agent; preferably the contaner is of flat elongated shape and is made of deformable material which releases the agent along a predetermined edge of the container on application of pressure. The container may be mounted on sheet material which may have a photo-sensitive area or an image receiving layer or both, and in the latter case the assembly constitutes a self-processing film for direct production of a positive picture, whereby as described and claimed in Specification 684,641, exposure may be effected, the container ruptured to spread processing agent between the exposed area and the receiving layer, to develop the image of the former and, by transfer and reduction of non-exposed photo-sensitive material, to produce the positive in the latter. In a modification the container may be of brittle material such as glass and the processing agent may be a gas such as ammonia for processing a photo-sensitive material of diazonium type. For silver halide photography the container, is contained processing agent, and other layers, are of materials as described in Specification 658,740. In the embodiment of the invention shown in Fig. 3 a self-processing photographic film has a transparent base 32, preferably a plastic material such as a cellulose ester or a polymer of nylon type, a layer 34 of clear gelatin, polyvinyl alcohol or other transparent material, a photosensitive layer 36 such as a silver halide gelatin emulsion, the liquid-containing assembly 38 comprising a sheet 40 as of blotter paper containing a predetermined quantity of at least the solvent, e.g. water for the liquid reagent, a frangible liquid-retaining wall or membrane 42 as of polystyrene, a porous layer 48 for example as of the same material as sheet 40 and which may contain in solid form one or more compounds for solution in the liquid reagent to be dissolved as the liquid passes through layer 48, a film 44 of water-vapour impervious material such as paraffin or polyethylene and an outer coating 46 for the base 32, all of the layers being laminated together. The liquid reagent may provide a developer such as hydroquinone and a compound such as sodium thiosulphate which forms a soluble complex with silver halide. On exposure as in a camera and squeezing together of the layers, as more particularly described and claimed in Specification 684,641, the membrane 42 is fractured to cause the reagent to permeate layer 36, when development takes place in the exposed areas 50, and at the unexposed areas 52 the silver halide is transported to form the positive silver areas 54 in layer 34, after which the upper portion of the laminate containing a positive picture may be removed, as shown. As examples of innumerable modifications and alternatives, Fig. 13 shows a container 100 in flat form mounted within a transparent film base 106, phoso-sensitive emulsion 108 and image-receiving layer 102; and Fig. 14 shows the container 100 as part of unitary structure and positioned to spread its contained reagent between a photo-sensitive layer 112 and an image-receiving area 120 provided with framing means 124 and indentations 130a in member 130 to absorb surplus reagent. Specification, 684,594 also is referred to.