Patent ID: 7315506
Filing Date: 2008-01-01
Classification: G11B

Abstract:
1. An information recording medium on which information is recorded by irradiation of a recording light beam for information recording, and from which said recorded information is played back by irradiation of a playback light beam for information playback which does not pass through a transparency changing layer before its transparency is changed by irradiation of said recording light beam, but passes through the transparency changing layer after its transparency is changed, comprising: said transparency changing layer whose transparency to said playback light beam increases as energy of the recording light beam increases in correspondence with an energy distribution in the direction perpendicular to an optical axis in the recording light beam when said transparency changing layer is irradiated by said recording light beam while said transparency changing layer is irradiated by a control light beam for controlling a change in the transparency of said transparency changing layer, and whose changed transparency to said playback light beam is also maintained after end of the irradiation with said recording light beam; and a light emission layer for emitting, as detection light, light of a frequency different from the frequency of the playback light beam when being irradiated with said playback light beam, wherein said transparency changing layer and said light emission layer are formed in order from the side irradiated with said recording light beam and said playback light beam.