The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 06, 2001
Filed:
Feb. 03, 2000
Yoshihito Fukushima, Miyagi, JP;
Jun Shimizu, Miyagi, JP;
Takeshi Gouko, Miyagi, JP;
Atsushi Takeuchi, Miyagi, JP;
Yuko Nakamura, Miyagi, JP;
Manabu Iwai, Miyagi, JP;
Sony Corporation, Tokyo, JP;
Abstract
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×NA/&lgr;(line/m) or higher. The photoelastic coefficient of a substrate of the magneto-optical recording medium is 50×10,cm,/dyne or smaller. The vertical birefringence of the substrate is 250×10,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 6.5×10,cm/cm·° C. or lower.