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. 30, 1993
Filed:
Dec. 23, 1991
Akihiro Wada, Inagi, JP;
Rin-ichi Kakuta, Tokyo, JP;
Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, JP;
Abstract
A novel optical element substrate which comprises a random copolymer comprising, in specific weight proportions, a methyl methacrylate unit, an aromatic vinyl compound unit, an unsaturated aliphatic acid unit and a hexagonal acid anhydride unit of the formula ##STR1## The substrate has excellent heat resistance, thermal stability, transparency, resistance to scratching and metal layer corrosion preventive properties and exhibits advantageously low double refraction and warpage. The novel substrate can be advantageously employed as a substrate for an optical element such as an optical disc, e.g. a digital audio disc, a video disc and a disc capable of being directly read after recording, a mirror, a lens and the like.