| 摘要 |
PURPOSE:To obtain a highly reliable discoid recording medium free from swelling due to impurity on the surface by applying preliminarily stabilizing processing to conductive carbon black which is added to resin. CONSTITUTION:Conductive carbon black is heat treated in the atmosphere of inert gas of 550-850 deg.C. Then, it is heat treated in the current of 300-850 deg.C that contains carbon dioxide gas and water vapor. The carbon black is cooled and washed with weak hydrochloric acid and water and dried. Then, a conductive material is prepared by mixing the refined carbon black with thermoplastic resin. This is shaped and a discoid recording medium that forms pits 3 that correspond to information signals swirlingly or concentrically at specified intervals is formed. Carbon black is added suitably to the resin in the proportion that makes the volume specific resistance of formed product desirably <=100OMEGA. cm, and desirable quantity of added carbon black is 10-40pts.wt. to 100pts.wt. of the disk forming resin. |
