PURPOSE: To manufacture a seamless image retaining drum fit for high-speed recording by forming an insulating layer based on a resin obtd. by the polycondensation of a monomer having a phenoxaphosphine ring and bisphenols on a photoconductive layer.

CONSTITUTION: An insulating layer based on a resin obtd. by the polycondensation of dicarboxylic acid of formula II or its deriv. having a phenoxaphosphine ring represented by formula I (where T is H, alkyl, aryl or the like) and bisphenols is directly formed on a photoconductive layer on an electrically conductive substrate. A sealing layer of ethylene-actylic acid copolymer resin or epoxy acrylate photosetting coating or other insulating layer may be formed on the photoconductive layer. For example, a soln. of P-contg. polyester in chloroform is applied and dried at 80°C for 10min to form the above-mentioned insulating layer. This layer is insoluble in ordinary solvents and has moisture resistance, a low coefft. of friction, high cleanability and high endurance. In addition, it is formed at a seamless state in case of a cylindrical drum photoreceptor, so it is fit for high-speed copy.