Patent ID: 7359310

Claim:
An optical recording medium comprising a support substrate and a plurality of information recording layers, at least one information recording layer other than an information recording layer farthest from a light incidence plane through which a laser beam is projected being constituted so as to be irreversibly changed when the laser beam is projected thereonto and comprising a first dielectric film, a second dielectric film and a recording layer disposed between the first dielectric film and the second dielectric film and a thickness of at least one of the first dielectric film and the second dielectric film being determined so as to be equal to or larger than D 21 and equal to or smaller than D 22 , where D 21 is smaller than D 2 , D 22 is larger than D 2 , D 2 is a second smallest thickness among a plurality of thicknesses at which the dependency X of light transmittance of the at least one information recording layer other than the information recording layer farthest from the light incidence plane on the wavelength of a laser beam locally becomes minimal, and D 21 and D 22 are determined in such a manner that the dependency X of light transmittance of the information recording layer other than the information recording layer farthest from the light incidence plane on the wavelength of a laser beam is smaller than 1.2·X 2 when at least one of the first dielectric film and the second dielectric film has a thickness of D 21 to D 22 , where X 2 is the wavelength dependency corresponding to the second smallest thickness D 2 .