| 摘要 |
PURPOSE:To prevent warpage or distortion in a substrate from being generated and to maintain a satisfactory recording characteristic for a long period by forming an air hole at a large number of island shape joined parts with a certain interval. CONSTITUTION:A recording medium is formed by joining a resin film 12 on a disk shape resin substrate 11, and a hole part 13 is provided in the center of the film 12, and a joined area 14 at a ring shape inner peripheral side and a joined area 15 at an outer peripheral side are joined at an area corresponding to a non-recording area on the substrate 11. A large number of joint is formed on the area 14 with almost the same interval. The substrate 11 is provided with the hole part 17 in its center, and is provided with the non-recording area 18 at the inner peripheral side and the non-recording area 19 at the outer peripheral side on the outside of the limb of the hole part 17 and the inside of the outer limb part, respectively, and a recording layer 20 is formed between the areas 18 and 19. On the film 12, each joined area is formed on each non- recording area by an ultrasonic welding method, and also, the air hole 21 is formed between the joined parts 16. |
