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:
Apr. 22, 2003
Filed:
Aug. 06, 2002
Kazuishi Mitani, Osaka, JP;
Yasuhiro Saito, Osaka, JP;
Koichi Ataka, Osaka, JP;
Akihiro Koyama, Osaka, JP;
Junji Kurachi, Osaka, JP;
Nobuyuki Yamamoto, Osaka, JP;
Yoshihiro Matsuno, Osaka, JP;
Nippon Sheet Glass Co., Ltd., Osaka, JP;
Abstract
A glass substrate for use as an information recording medium has an average surface roughness (Ra) in the range of 0.3 nm≦Ra<3.0 nm and includes surface irregularities shaped and distributed isotropically and arranged substantially in succession. The surface irregularities include 5 to 50,000 convexities having a height of at least 3 nm and no convexities having a height of at least 15 nm within an area of 50 &mgr;m×50 &mgr;m. A porous region produced by an acid treatment process in the glass substrate would be completely removed if excessively etched by an alkaline solution. However, the etching process using the alkaline solution can be stopped at a stage where the pores in the porous region are enlarged by controlling conditions for the acid and alkali treatment processes.