Sony Corporation

Manabu Iwai

Atsushi Takeuchi

Hiroshi Nakayama

Masayoshi Kanno

Masataka Shinoda

Sohmei Endoh

Jun Shimizu

Tomiji Tanaka

Yoshihito Fukushima

Katsuhiko Ohtomo

Takeshi Gouko

Yuko Nakamura

In an optical recording medium having a writable area in which grooves are formed along recording tracks and a read-only area in which pits are formed along the recording tracks, sufficient levels of signals required for data write and read can be assured even with the track pitch reduced for a higher recording density. Assuming that the refractive index of a medium provided extending from a light-incident surface to a surface in which the grooves and pits are formed is n and the wavelength of a light used for data write and read is &lgr;, the grooves and pits has a width within a range of &lgr;/7.5 n to &lgr;/6. On the assumption that the width of each of the grooves formed in the writable area is Wg and the pitch between the recording tracks in the writable area is Tp , Wg/Tp is within a range of 18.4% to 31.1%. When it is assumed that the width of each of the pitches formed in the read-only area is Wp and the pitch between the recording tracks in the read-only area is Tp , Wp/Tp is within a range of 35.7% to 44.3%.

Optical recording medium capable of assuring sufficient levels of signals required for reading/writing data, and stamper for manufacture of the same

A magneto-optical recording medium from which data is read by using a Kerr effect and which is capable of preventing signal imbalance caused from change in birefringence even in a system in which the amplitude of a reproduced signal is small and the spatial frequency of a shortest record signal train of the magneto-optical recording medium is 1.1&times;NA/&lgr;(line/m) or higher. The photoelastic coefficient of a substrate of the magneto-optical recording medium is 50&times;10,cm,/dyne or smaller. The vertical birefringence of the substrate is 250&times;10,or smaller, the coefficient of water absorption of the same is 0.2 wt % or lower and the thermal coefficient of expansion of the same is 6.5&times;10,cm/cm&middot;&deg; C. or lower.

Magneto-optical recording medium

Growing community of inventors

Miyagi, Japan

Manabu Iwai