| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical disk compliant with specification of both a conventional optical disk such as a BD, HD, DVD and the like and a next-generation high-density optical disk of a near-field light recording system and the like. <P>SOLUTION: An information recording medium includes a first information recording layer and a second information recording layer, to/from which information is recorded or reproduced using a laser beam. The first information recording layer is formed at a laser beam entrance surface, and is configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a first numerical aperture NA1 and a laser beam of a first wavelength λ1. The second information recording layer is formed so as to have a distance to the laser beam entrance surface of 0.05 to 1.2 mm and is configured so that information can be recorded thereupon and/or reproduced therefrom using a second objective lens having a second numerical aperture NA2 and a laser beam of a second wavelength λ2. When a diffraction limit δ2, determined by the numerical aperture NA2 and the second wavelength λ2, is defined as δ2=0.61×λ2/NA2, a track pitch Tp1 of a track formed on the first information recording layer is Tp1<δ2. <P>COPYRIGHT: (C)2008,JPO&INPIT |
