| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a phase change type optical information recording medium which facilitates the management of the lower limit of reflectivity by constituting the information recording medium in such a manner that the reflectivity in a recorded state is higher than the reflectivity in an unrecorded state, i.e. the reflectivity is made higher and the reflectivity in an unrecorded portion is made lowest by accumulation of recording and which has good reproduction interchangeability simply by regulating the reflectivity in the unrecorded state or simply by checking the reflectivity above a standard, makes a stable reproduction signal obtainable and permits the condition of recording/reproducing with high accuracy. <P>SOLUTION: The optical information recording medium has at least a phase change recording layer on a substrate having concentrical circle or spiral guide grooves and performs recording and/or writing of information by causing a phase change in the recording layer by irradiation with a semiconductor laser beam. When the reflectivity Rb in the unrecorded portion of the guide groove section and the reflectivity Ra(m) at the time of performing overwrite recording (direct overwriting, DOW) m times (m is a natural number) are compared, Ra(m)/Rb≥1. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
