| 摘要 |
PURPOSE:To eliminate troubles with moisture absorptive substance by a method in which a conductive material obtained from mixing pure carbon black with a thermoplastic resin is molded into a disc-shaped molding having an unevenness corresponding to signals of information and then the surface of the molding is subjected to a water-washing treatment. CONSTITUTION:A conductive carbon black is washed with water or a weak acid and dried to obtain a purified carbon black, and the carbon black is mixed with a thermoplastic resin to obtain a conductive material. The conductive material is molded into a disc-shaped molding having a swirled or concentrical unevenness corresponding to signals of information. The surface of the molding is washed with water to form a disc-shaped recording medium. Water-soluble ash present in the carbon black is removed out as much as possible by water or weak acid washing and the remaining water-soluble ash on the disc surface after molding of the disc is washed away by water washing. The conductive carbon black, after being washed with water of weak acid, is mixed with a thermoplastic resin and then the surface of the molding is washed with water, so that defects originated from the ash content can be reduced. |
