DRUCKEMPFINDLICHES KOPIERMATERIAL

An improved pressure sensitive copying material comprises an electron-accepting colour-developing agent and a soln. of an electron-donating colour-forming agent. The colour-forming agent is capable of forming colour when it is brought into contact with the colour-developing agent in a solvent (1). The solvent (1) comprises (a) 5-50 vol% of a hydrogenated low polymer of propylene (2) and/or butene (3), and (b) 50-95 vol% of a bicyclic aromatic hydrocarbon (4) and/or chlorinated paraffin oil (5). The density of both :(29 and (3) is lower than 3cSt at 40 deg C and their pts. are 150 deg C or higher (at 1 atm) (pref 170 deg ca. Pref. (a) is a hydrogen additive of a lower polymer, an aliphatic hydrocarbon, an alkyl benzene or a paraffin oil, (4) has a b.pt. of 260 deg C or higher (at 1 atm) and a viscosity of 3 cST or higher at 40 deg C. It has at least two condensed aromatic rings, (5) has a density of 3cSt or higher at 40 deg C. The colour developing agent is aromatic carbonic acid, a polymer of an aromatic carbon acid or metal salt, multi-valence metallised carboxy denatured terpenephenol resin or a deriv. of this.