GB759157A - Improvements in or relating to the production of written matter - Google Patents

Abstract

759,157. Printing processes. CARIBONUM, Ltd. June 22, 1954 [July 21, 1953], No. 20257/53. Class 100 (2). [Also in Group VIII] Sheet material suitable for receiving and displaying written or typewritten matter comprises paper on which is applied an opaque coating which masks the colour of a contrasting colouring material, the coating being adapted to be rendered transparent by the application of an oily substance of approximately the same refractive index caused by the action of writing or typing to allow the colour of the colouring matter to appear. The paper may be coloured or may be white or tinted with colour applied by printing or coating. The oily substance may be contained in a typewriter ribbon. Where a plurality of sheets are used each may be written or typed on simultaneously by having the oily substance as a coating on the back of each sheet so that at the points where pressure is exerted the oily substance on each sheet will be transferred to the opaque coating of the next sheet. Alternatively, the oily substance may be coated on to the coloured front surface of the paper below the opaque coating, and the oil may be in the form of minute discrete particles bound with glue and emulsified in a solution of glue in water, or may be separated from the opaque coating by a protective coating, which may be a water-soluble cellulose derivative such as methyl cellulose. The oily substance may be an oil, wax, petroleum jelly, a mixture of more than one of the above, or a plasticizer such as tricresyl phosphate or dimethyl phthalate. The opaque coating may be a suspension of calcium carbonate in a water solution of sodium alginate. The coloured coating may be an ink formed by an aniline dye such as nigrosine insoluble in water dissolved in a spirit, or an ink containing pigments such as carbon black and a binder such as shellac soap, or a suspension of carbon black in a solution of ethyl cellulose. The colouring matter may be prepared from mineral colours, e.g. dark brown earths such as the darker ochres, chrome green, bronze blue, or suitable lake colours such as the very light-fast tungsten lakes of methyl violet or other triphenylmethane or related dyes. Alternatively, the calcium carbonate may be mixed in 10 per cent or less of the colour to be developed, and the mixture suspended in a solution of sodium alginate and coated directly on to white or coloured paper, giving a grey or pastel shade which contrasts with the colour where the calcium carbonate is rendered transparent.