Information recording medium and recording/reproducing method for the same

Abstract

The information recording medium () of the present invention includes: an information layer () including a recording layer () capable of changing its phase containing at least one selected from Ge—Te, Sb—Te and Ge—Sb, and two or more dielectric layers () disposed on the optical beam incident side with respect to the recording layer (); and a transparent layer () disposed on the optical beam incident side with respect to the information layer () adjacent to the information layer, made of a transparent material with respect to the optical beam, and having a refractive index n of 1.75 or more. When two dielectric layers () from the near side to the transparent layer () each are referred to as a dielectric layer b () and a dielectric layer a () from the optical beam incident side among the two or more dielectric layers (), a relationship of the refractive index n of the transparent layer, a refractive index nof the dielectric layer b () and a refractive index nof the dielectric layer a satisfies n<n<n. In the information recording medium () of the present invention, information can be recorded or reproduced by means of an optical system having a numerical aperture (NA)>1 by irradiation with optical beam.