| 摘要 |
PURPOSE:To detect the degradation of a recorded layer caused by reloading as early as possible and to avoid the worst that information are lost by providing a part, for which durability to the repetition of recording and erasing is weaker than the other part, in one part of each prescribed information unit. CONSTITUTION:Between an address part 11 and a data part 12 of a sector 1, an indicator signal recording part 13 is provided and width between lands 21 and 22 of the indicator signal recording part 13 is made narrow. Then, the indicator signal recording part 13 is formed so that a recording mark S of an indicator signal can cover a boundary between the land 21 or 22 and a group 3. As a result, a step is provided for the recording mark and in comparison with the flat mark of the other address part and data part, damage caused by thermal shock is received more easily. Thus, since the degradation of the recorded layer caused by the reloading can be detected as early as possible, the state that the information are lost can be prevented in advance. |
