Patent GB-880050-A (GB)
Title: Improvements in recording material
IPC: B41M5/124
Filed: 1959-11-19
Abstract: 880,050. Pressure-sensitive copying paper &c. OXFORD PAPER CO. Nov. 19, 1959 [Nov. 26, 1958], No. 39289/59. Class 96. [Also in Group XVI] Pressure-sensitive, heat-resistant recording material includes a base sheet and a normally opaque coating becoming relatively transparent under writing pressure but not under heat up to charring temperature, said coating comprising a matrix of at least one organic resin and a compatible plasticizer for the resin, the plasticizer-resin ratio being between 1: 3 and 5: 1, and a pigment, having a refractive index substantially the same as said matrix, embedded in said matrix, a surface under the coating contrasting to the colour of the pigment. The coating thickness is 0.0015-0.004 inches, and the ratio of pigment-matrix is between 1: 0.4 and 1:1. The refractive index is preferably 1.45-1.55. The coating may be sandwiched between a further black coating and a transparent film. The particle size of the pigment is such that the surface area is 30,000-35,000 square centimetres per gram. The materials of the matrix are chosen so as to resist hardening when heated or oxidized, to be non-volatile, to be non-reactive together, or with the pigment or the base, to be compatible so as to prevent sweating out or crystallization, to bind the pigment effectively, and to have good lubricating properties. The plasticizer may be viscous or low-viscosity liquid or crystalline solid. The coating may be solvent-based, and the solvent toluene. There may also be added small amounts of emulsifying agents (10% of plasticizer), protective colloids as stabilizers, defoamers, water-repellers and pigment dispersing agents. Examples of resins are cellulose nitrate, cellulose acetate, cellulose acetate-butyrate; ethyl cellulose; polyvinyl acetate, benzoate, butyrate, stearate, acetal, formal, butyral, chloride; polyvinylidene chloride; polymethyl acrylate, polyethyl acrylate; polymethacrylate, polymethylmethacrylate; polyacrylonitrile; polystyrene; polyamides; chlorinated rubber; copolymers of: styrene-butadiene, styreneacrylonitrile; vinyl acetate-vinyl chloride, -vinyl benzoate, -crotonic acid, -maleic anhydride, -dimechylmaleate, -diethylmaleate, -vinyl crotonate, -vinyl stearate; vinyl chloridemethyl acrylate, -ethyl acrylate, -butyl acrylate, -vinylidene chloride. Examples of plasticizers are diphenyl phthalate (crystalline); (octyl diphenyl, cresyl phenyl, triphenyl, tricresyl, triethyl) phosphate; (butyl benzyl, di-[N-octyl], dibutyl, dioctyl, dicyclohexyl, diethyl, dimethyl) phthalate; N-cyclohexyl toluene sulphonamide, N-ethyl toluene sulphonamide; (dioctyl, diisodecyl, diisobutyl, butoxyethyl) adipate; dibutyl sebacate, dioctyl sebacate; ethyl phthalyl ethyl glycolate; pine oil derivatives; orthonitrobiphenol; chlorinated paraffin; triethylene glycol ester of hydrogenated rosin, hydrogenated rosin methyl esters; chlorinated polyphenols; castor oil; acetylated castor oil; butyl acetyl ricinoleate; acetyl tributyl citrate; glycerol triacetate. With the above primary plasticizers may be used secondary plasticizers, e.g. partially hydrogenated alkylaryl hydrocarbons, partially hydrogenated mixed terphenyls. Examples of pigments are silica, calcium silicate, magnesium silicate, diatomaceous earth, magnesium carbonate, slaked line and alum, magnesium aluminium silicate. The dispersing agent may be sodium hexametaphosphate. The water-repeller may be a wax emulsion. Examples of emulsifying agents are alkyl-aryl polyether alcohols, sorbitan monopalmitate, sorbitan monopalmitate polyoxyalkylene derivatives. Examples of protective colloid stabilizers are polyvinyl alcohol, starch, casein, hydroxy-ethyl cellulose, polyacrylamide. Examples of defoamer are butyl alcohol, tributyl phosphate.