WRITE-ONCE TYPE OPTICAL RECORDING MEDIUM AND ITS RECORDING AND REPRODUCING METHOD AND OPTICAL RECORDING AND REPRODUCING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a write-once type optical recording medium capable of performing stable recording of high density using a laser having a numerical aperture (NA) of ≥0.6 and <0.7 and to provide a recording and reproducing method and an optical recording and reproducing apparatus for the write-once type optical recording medium.

SOLUTION: The write-once type optical recording medium has first and second substrates and at least a reflection layer, a dielectric layer and a recording layer between the first and the second substrates in this order. Recording and reproduction are performed by irradiation with a laser beam from the second substrate side by using the laser having a numerical aperture (NA) of ≥0.6 and <0.7, the first and the second substrates have 0.5 to 0.7 mm thickness and the recording layer contains either of bismuth and a bismuth oxide.

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