Optical disk having a high-density recording layer and a low density recording layer

Claim 1

An optical disk in which information which can be optically read is stored, comprising: a first information recording layer positioned at a first location which corresponds to the optical length of the optical pickup of a first information playback player, with the first information recording layer formed in the vicinity of the middle of the thickness direction of the disk for storing high density information; a second information recording layer positioned at a second location which corresponds to the optical length of the optical pickup of a second information playback player, with the second information recording layer formed in the vicinity of one surface of said optical disk for storing information at a lower density than said first information recording layer; and a light incidence surface into which first and second playback laser beams from said first and second information playback player are irradiated for reading the information on said first and second information recording layers respectively, with said light incidence surface being formed at a side of said optical disk opposite said one surface; wherein, the thickness of the disk extending from said light incidence surface to said second information recording layer is substantially equal to the thickness of the optical disk.