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. 22, 2014
Filed:
Sep. 29, 2009
Shinji Eda, Shinjuku-ku, JP;
Hideki Isono, Shinjuku-ku, JP;
Takashi Maeda, Shinjuku-ku, JP;
Hiroshi Tsuchiya, Shinjuku-ku, JP;
Yoshinori Marumo, Shinjuku-ku, JP;
Shinji Eda, Shinjuku-ku, JP;
Hideki Isono, Shinjuku-ku, JP;
Takashi Maeda, Shinjuku-ku, JP;
Hiroshi Tsuchiya, Shinjuku-ku, JP;
Yoshinori Marumo, Shinjuku-ku, JP;
Hoya Corporation, Tokyo, JP;
Abstract
Provided are a magnetic disk substrate and a method of manufacturing the same, wherein the magnetic disk substrate has very few defects present on its surface with an arithmetic mean roughness (Ra) at a level in the vicinity of 0.1 nm and thus is suitable as a substrate for a magnetic disk with high recording density. The magnetic disk glass substrate is such that the arithmetic mean roughness (Ra) of the main surface of the glass substrate measured using an atomic force microscope with a resolution of 256×256 pixels in a 2 μm×2 μm square is 0.12 nm or less and the number of defects detected to have a size of 0.1 μm to 0.6 μm in plan view and a depth of 0.5 nm to 2 nm is less than 10 per 24 cm, wherein the defects are each detected using a shift in wavelength between incident light and reflected light upon irradiating and scanning helium neon laser light with a wavelength of 632 nm on the main surface of the glass substrate.