Patent ID: 7645499

Claim:
An optical information recording medium comprising a substrate, a plurality of information layers being provided on the substrate, and an optical separating layer being provided between adjacent information layers, in which information is recorded or reproduced by irradiation of a laser beam, wherein when an information layer being provided closest to a laser beam incident side of the plurality of information layers is taken as a first information layer and an optical separating layer being provided in contact with the first information layer is taken as a first optical separating layer, the first information layer comprises a recording layer that can change between two optically different states, a transmittance adjusting layer that adjusts a transmittance of the first information layer, and a low refractive index layer being provided between and in contact with the transmittance adjusting layer and the first optical separating layer, the low refractive index layer being formed on the optical separating layer, and the transmittance adjusting layer being formed on the low refractive index layer, wherein refractive indices with respect to the laser beam of the transmittance adjusting layer and the low refractive index layer are in ranges of 2.0 to 3.0 and 1.4 to 1.6, respectively, and when the refractive index of the low refractive index layer is taken as n 1 , and the refractive index of the first optical separating layer is taken as n 4 , n 1 and n 4 satisfy: | n 1 −n 4|≦0.5.