High-density multi-layer recording medium and an apparatus for writing to or reading from such a recording medium

摘要

In one embodiment, the recording medium includes a light incident surface and an opposite surface of the light incident surface, a substrate having a transparent layer, and a first recording layer located close to the light incident surface. A second recording layer is located between the first recording layer and the opposite surface. The minimum thickness from the light incident surface to the first recording layer and the maximum thickness from the light incident surface to the second recording layer depend on a refractive index of the transparent layer, and the minimum and maximum thickness have larger values in case that the refractive index of the transparent layer is 1.7 than the refractive index of the transparent layer is 1.6. Furthermore a distance between the first and second recording layers is a value of more than 18.5 mum.