Write once read many type optical disc

Abstract

A write once read many type optical disc comprises a light transmissive substrate having a tracking groove formed therein, a light absorbing layer disposed on a surface of the substrate on which the tracking groove is formed, and a light reflection layer disposed on the light absorbing layer, wherein an RMI value defined by the following formula is not lower than 0.22: RMI value=(I.sub.l -I.sub.g)I.sub.o, wherein I.sub.l denotes an electric potential at a land portion, I.sub.g denotes an electric potential at a groove portion, and I.sub.o denotes an electric potential at a mirror surface portion. When the write once read many type optical disc is caused to have a structure as described above, there may be provided the write once read many type optical disc having a good playability, i.e., the optical disc wherein the TE level may be provided assuredly on the basis of a value obtained from one beam.

Dependencies are inferred from the claim text.