Patent GB-837813-A (GB)
Title: Method of correcting copy material
IPC: G03F1/54
Filed: 1956-07-19
Abstract: In the method of reproducing copy material by photographic means, errors in the copy material are corrected by covering them with a photographically non-detectable correction coating composition comprising a polymeric resin binder capable of forming a flexible film and containing at least one polar group per monomeric unit, an organic solvent, and an opaque pigment in an amount of from 50% to 85% by volume of the binder and pigment; drying the coating composition; imprinting corrections on said composition; and photographing said corrected copy material to produce a negative from which may be produced a duplicate of said corrected copy material on which neither the covered errors nor the coating composition are discernible.  Suitable binders include methyl acrylate-methyl methacrylate copolymers, shellac, vinyl chloride-vinyl acetate copolymers, cellulose acetate and styrene-butadiene copolymers; plasticizers may be included. Suitable pigments include titanium dioxide, zinc sulphide, zinc oxide, basic lead carbonate or sulphate; extenders such as barium sulphate, calcium carbonate, talc, clay or mica may be included. Coloured pigments are used if the base material is coloured. Specified solvents are benzene, toluene and carbon tetrachloride, with or without the addition of isopropyl ether.  In examples, compositions comprise (1) methyl acrylate-methyl methacrylate copolymer, titanium dioxide, toluene and isopropyl ether; (2) an alkyd resin, a modified rosin ester, titanium dioxide, toluene and ethyl acetate, to which is added, after grinding, a solution of nitrocellulose in ethyl acetate; (3) shellac, titanium dioxide and methyl alcohol; (4) vinyl chloride-vinyl acetate copolymer, titanium dioxide and methyl ethyl ketone; (5) cellulose acetate, plasticizers, titanium dioxide and methyl ethyl ketone; and (6) butadiene-styrene copolymer, chlorinated biphenyl, titanium dioxide and benzene.ALSO:A coating composition for use in a photographic reproduction process comprises a polymeric resin binder capable of forming a flexible film and containing at least one polar group per monomeric unit, an organic solvent, and an opaque pigment in an amount of from 50 to 85% by volume of the binder and pigment. Suitable binders include methyl acrylate-methyl methacrylate copolymers, shellac, vinyl chloridevinyl acetate copolymers, cellulose acetate and styrene-butadiene copolymers; plasticizers may be included.  Suitable pigments include titanium dioxide, zinc sulphide, zinc oxide, basic lead carbonate or sulphate; extenders such as barium sulphate, calcium carbonate, talc, clay or mica may be included.  Specified solvents are benzene, toluene and carbon tetrachloride, with or without the addition of isopropyl ether.  In examples, compositions comprise: (1) methyl acrylate-methyl methacrylate copolymer, titanium dioxide, toluene and isopropyl ether; (2) an alkyd resin, a modified rosin ester, titanium dioxide, toluene and ethyl acetate, to which is added, after grinding, a solution of nitrocellulose in ethyl acetate; (3) shellac, titanium dioxide and methyl alcohol; (4) vinyl chloride-vinyl acetate copolymer, titanium dioxide and methyl ethyl ketone; (5) cellulose acetate, plasticizers, titanium dioxide and methyl ethyl ketone; and (6) butadiene-styrene copolymer, chlorinated biphenyl, titanium dioxide and benzene.