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:
Jul. 27, 1999
Filed:
Aug. 07, 1997
Mikio Yoshida, Miyagi, JP;
Masaki Takenouchi, Miyagi, JP;
Sony Corporation, Tokyo, JP;
Abstract
An optical disc having a functional film, formed by a thin metal plate, and a protective film, formed on a transparent substrate, is disclosed. The protective film satisfies a condition d.gtoreq.2d.sub.0, where d is a maximum film thickness at an outer periphery of the protective film and d.sub.0 is a mean film thickness at a flat portion on a data area. A magneto-optical disc having a functional film which is a metal thin film having magneto-optical effects is also disclosed, wherein the protective film satisfies a condition that a difference L.sub.1 between a maximum film thickness d at the outer periphery of the protective film and a mean film thickness d.sub.0 at a flat portion of the data area is 40 .mu.m or less and the protective film has a curved surface having a radius of curvature R.sub.1 .gtoreq.12.48 mm at the outer periphery of the protective film. The present invention provides an optical disc having superior recording properties and a sufficient corrosion resistance even when the disc is provided with a highly corrosive thin metal film, such as a rare earth-transition metal amorphous thin film.