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

PROBLEM TO BE SOLVED: To provide an information recording medium, an information reproducing method, and an information recording method thereof, for the purpose of attaining high recording density. SOLUTION: The information recording medium has: a first multilayer medium comprising a first substrate and a plurality of recording layers stacked on the first substrate for recording information; and a second multilayer medium comprising a second substrate and a plurality of recording layers stacked on the second substrate for recording information. The first multilayer medium and the second multilayer medium are laminated with the faces of the recording layer sides inside. The first and the second substrates are made of glass or plastic. The information in the information recording medium is reproduced and the information is recorded in the information recording medium by irradiating the medium with light from each of the faces on which the first and the second substrates are prepared. Recording or reproducing information on or from each of both faces of the substrates of disk becomes possible. COPYRIGHT: (C)2005,JPO&NCIPI