Patent GB-810863-A (GB)
Title: Improvements in or relating to heat sensitive copying sheets
Inventor: CLARK BRYCE L
IPC: B41M5/36
Filed: 1955-06-20
Abstract: 810,863. Heat-sensitive copying material. MINNESOTA MINING & MANUFACTURING CO. June 20, 1955, No. 17839/55. Drawings to Specification. Class 98(2) Heat-sensitive copying material for use in the copying of documents according to the method described in Specification 673,244 comprises a base of low-heat conductivity and a heat-sensitive coating comprising light dispersing particles of a transparent stable fusible organic solid melting without appreciable volatilization or decomposition between 60 and 115‹C. distributed throughout a thin stratum of a transparent film-forming binder which is infusible within the said range, the organic solid and the binder being mutually compatible and having substantially the same refractive index and the organic solid in liquid form having good wetting properties towards the binder so as to render the layer transparent in the places where it is heated. A protective layer may be applied over the heat-sensitive layer. The support may be transparent or opaque and may be coloured or coated with a coloured layer before the heat-sensitive layer is applied. Alternatively colouring matter may be incorported in the heat-sensitive layer or in the protective layer. The material may be exposed by the "back-printing" method, i.e. the heat-sensitive sheet is placed against the back of the document to be copied and the printed face of the document is irradiated, in which case the support of the heat-sensitive material may be opaque, coloured or coated with a coloured layer. In the "front-printing" method the radiation passes first through the heat-sensitive sheet and then to the printed face of the document to be copied, and the reproduction is viewed from the side of the sheet from which it was irradiated, the support and any coloured protective layer being transparent. In the examples the heat-sensitive layer comprises cadmium stearate, lead caprylate, lead laurate and/or palmitate dispersed in latex rubber, hydrogenated fatty oil wax ("Cornelowax'') or hydrogenated castor oil wax ("Opalwax") dispersed in a mixture of nitrocellulose and/or ethyl cellulose, waxy polyethylene glycol dispersed in nitro cellulose, glycerol monostearate in cellulose acetate, lead myristate in nitrocellulose, 2;4-di-nitro phenetole in polyvinyl alcohol, and "Cornelowax" in polyvinyl butyral, polyvinyl acetate, rubber hydrochloride, methyl methacrylate polymer or chlorinated rubber. A small quantity of plasticizer such as dioctyl phthalate may be included. Other fusible materials specified are laurane, cerotene, ceryl alcohol, coumarin, dicyclohexyl phthalate, dimethyl - 4 - nitro phthalate, dimethyl - iso - phthalate, diphenyl phthalate, diphenyl, N-ethylp - toluene sulphonamide, nonacosane, o - and p - toluene sulphonamides, o - cresyl - p - toluene sulphonate, octadecanol - 1 and stearamide. The support may be paper (which may be treated), glassine, vinyl film, films of terephthalic acid - ethylene glycol resin and cellulose film. In the examples a paper base is given a black undercoat of nigrosine dye or carbon black in crepe rubber, or a blue undercoat of ultramarine blue or toluidine toner in cellulose acetate before the heat-sensitive layer is applied. A protective layer of cellulose acetate may be applied over the heat sensitive layer. In other examples glassine is coated with a heat-sensitive layer and a coloured protective layer of "Diane blue" in ethyl cellulose then applied. Alternatively the "Diane blue" pigment is added to the heat-sensitive composition. In place of Diane blue for the overcoat, phthalocyanine blue, triphenylmethane basic dye, dibenzarthrone, or isodibenzarthrone may be used. Alternatively an infra-red transmitting dye may be used in a red cellulose base.