Multilayer optical disk and method of initializing the same

Abstract

Initialization nonuniformity due to interference of light which occurs during an initialization process is reduced without causing degradation in the characteristic of signals recorded/reproduced on/from respective recording layers. A multilayer optical disk comprising at least a first information recording layer and a second information recording layer formed, on a substrate, into a multilayer structure with an intermediate layer disposed therebetween is illuminated with initializing light from the side of the first information recording layer to initialize the first information recording layer formed of a phase-change material serving as a recording material. The illumination with the initializing light is performed such that the numerical aperture NA of an objective lens used for illumination with the illuminating light, the longitudinal length L of the beam size of the initializing light, the thickness D of the intermediate layer, and the ratio R1 of the amount of light striking the first information recording layer after passing through the first information recording layer and being reflected by the second information recording layer to the amount of light incident on the first information recording layer satisfy the following relation for a wavelength &lgr;i of the initializing light: L×R1 ≦25[1−exp(−0.0004× ×D )].