Information recording medium, information recording apparatus, information recording method, information playback apparatus, information playback method, recording program recording medium, and playback program recording medium

摘要

An optical disk from which information is played back when the optical disk is irradiated with a playback light beam which does not pass through a photochromic layer before its transparency is changed by irradiation with a recording light beam, but passes through the photochromic layer after its transparency is changed, including: the photochromic layer which is initialized with initialization light and also maintains a change in its transparency caused by irradiation with a recording light beam after end of the irradiation; and a fluorescent layer for emitting, as detection light, light of a frequency different from the frequency of the playback light beam when the fluorescent layer is irradiated with the playback light beam, wherein the photochromic layer and the fluorescent layer are formed in order in the direction in which the recording light beam and the playback light beam are irradiated.