Patent GB-1168645-A (GB)
Title: Reproduction of Images from Printed Surfaces.
IPC: B41M5/025
Filed: 1966-10-19
Abstract: 1,168,645. Printing processes. CHAMPION PAPER CO. Ltd. 19 Oct., 1966 [20 Oct., 1965; 4 Aug., 1966], No. 46844/66. Heading B6C. In a process of making copies from a printed sheet having image areas which differ in sorbtivity for moisture from the non-image areas, a porous film is formed on a surface of an impermeable copy sheet, the film is moistened and then is held in contact with the printed sheet to permit the moisture to be differentially sorbed by the printed sheet as between the image and non-image areas. The printed sheet preferably includes cellulosic fibres and the printing of the image areas forms a barrier to the migration of moisture from the copy sheet. The moistening liquid may be water or an organic compound and the porous film on the copy sheet may initially be opaque but capable of having its optical properties changed in the presence of a liquid such that on removal of the copy sheet from the printed sheet the former bears a permanent visible image. The porous film may be formed either by subjecting the copy sheet surface to a reagent capable of forming pores in the surface and thereafter removing the reagent from the surface or by coating the surface with a porous film-forming substance. The copy sheet may be of glass, polyethylene, cellulose acetate, polystyrene, polypropylene, whilst the porous film material is selected from the group consisting of cellulose acetate, cellulose nitrate, vinyl chloride, ethylene maleic anhydride copolymer, polyvinyl acetate, cellulose acetate butyrate, copolymer of polyvinyl acetate and crotonic acid and other vinyl polymer polycarboxylates and cellulosic compounds. The copy sheet, which may be held against the printed sheet for 2 seconds, may be subjected after separation to a developer which combines with the moisture in the surface of the film to produce a visible image. The film may contain a developer reactant which is moistened by the transferred moistener. The copy sheet, after separation, is subjected to a developer which reacts with the reactant to produce an image. The developer may be a vapour of a substance which reacts with the reactant to produce or change a colour. The film may be moistened with water and after separation from the printed sheet the copy sheet is subjected to a liquid mixture of an inert carrier and two substances which react with each other only in the presence of water, the two substances permeating the copy sheet and reacting with each other in the areas of greater moisture content. After separation from the printed sheet the copy sheet may be pressed against a final sheet to form a visible image thereon. The latter may carry a film whose optical properties are capable of being changed by the moistening substance. This film may comprise a layer of dye which is soluble in the moistener and a permeable skin covering the dye. The copy sheet film may be pressed, after separation from the printed sheet, against a final sheet to differentially adhere the copy sheet to the final sheet as between the relatively moist and relatively dry areas of the copy sheet film. After separation, at least a portion of the copy sheet film is transferred to the areas of adhesion on the final sheet. Alternatively, if the final sheet is provided with a separable coating, at least a portion of this coating adheres to the copy sheet film after separation.