| 摘要 |
PURPOSE: To provide a double-sided recording type optical disk medium capable of precisely and stably identifying the surface and the rear surface with a simple method by providing so that an internal diameter of a reflection film in one side optical disk is different from the internal diameter of the reflection film in the other side optical disk. CONSTITUTION: This double-sided recording type optical disk medium 8 is formed by two pieces of single-sided recording type optical disks 6, 6' having a recording surface 2 on one surface by sticking their non-recording surfaces 4 each other. Then, the reflection film 20 in one side optical disk 6 is provided only on a part equivalent to an information recording area 16, and on the contrary, the reflection film 20' of the other side optical disk is provided until the part of a non-information recording area 12 exceeding the information recording area 16. That is, the reflection films 20, 20' of both optical disks are different from each other in the internal diameter. Thus, no mistake so as to stick the optical disks of the same kinds occurs when the double-sided recording type optical disk medium is manufactured, and further, no label for identifying the surface and the rear surface is necessitated, and the productivity is improved. |
