Patent ID: 7564769

Claim:
A phase-change optical storage medium comprising: a substrate; and a recording layer, to be recorded on which is at least one recorded mark representing information to be recorded by irradiating a recording light beam onto the recording layer in accordance with a recording pulse pattern of recording pulses rising from an erasing power and formed between a recording power larger than the erasing power and a bottom power smaller than the erasing power and of erasing pulses rising from the bottom power to the erasing power, wherein expressions (1) and (2): 1.00<( R 1/ R 0)<1.15 (1) 1.05<( R 9/ R 0)<1.20 (2) are satisfied for the recording layer, in which R 0 is a reflectivity exhibited by an un-recorded section of the recording layer, on which no data has ever been recorded, when irradiated with a reproducing light beam, R 1 is a reflectivity exhibited by the un-recorded section when irradiated with the reproducing light beam, after irradiated once with the recording light beam in accordance with the recording pulse pattern, and R 9 is a reflectivity exhibited by the un-recorded section when irradiated with the reproducing light beam, after irradiated nine times with the recording light beam in accordance with the recording pulse pattern.