Patent ID: 7580340

Claim:
An optical recording medium comprising a plurality of information layers on a substrate, at least one of the information layers other than a farthest one of the information layer from a light-incident surface on which a laser beam is incident being translucent and including a recording layer formed of a phase change material, wherein at least one of width and length of a recording mark after high-temperature storage is 0.9 times or more at least one of width and length of a recording mark before high-temperature storage, the recording mark before high-temperatures storage is formed in the recording layer before a high-temperature storage, in the high-temperature storage, a storage temperature t is in a range from 60° C. to 90° C. and a storage time is at least 50−(4/3)(t−60) hours, the recording mark after high-temperature storage is formed in the recording layer after the high-temperature storage and has the same bit length as the recording mark before high-temperature storage.