Patent ID: 8243577
Filing Date: 2012-08-14
Classification: G11B

Abstract:
1. A read-only optical information recording medium in which information has been recorded and from which the information is reproduced in response to reproducing light irradiated onto a prepit provided in the optical information recording medium, the optical information recording medium, comprising: a light-transmitting layer or a transparent substrate; an information recording layer; and a substrate; wherein the light-transmitting layer or the transparent substrate, the information recording layer, and the substrate are stacked in this order from a side from which the reproducing light enters, wherein the information recording layer including at least a reproducing film whose complex refractive index at a light source wavelength λ of the reproducing light is changed by heat allows a track pitch satisfied by the relationship: 0.67×(λ/NA)>TP>0.04×(λ/NA), and wherein TP is a track pitch of a recording track formed by a string of prepits provided on the substrate and NA is a numerical aperture of an objective lens for converging the reproducing light onto the optical information recording medium.