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. 09, 2013
Filed:
Sep. 12, 2007
Katsuyuki Iwata, Shinjuku-ku, JP;
Hideki Isono, Shinjuku-ku, JP;
Kenichiro Terada, Shinjuku-ku, JP;
Hoya Corporation, Tokyo, JP;
Abstract
The present invention provides a method for producing a glass substrate for a magnetic disk in which the occurrence of micro-waviness on the glass substrate is prevented in a cooling step after a chemically strengthening step so that the glass substrate has a significantly smooth principal surface, and provides a method for producing a magnetic disk in which head crash, thermal asperity failures, and the like are prevented, the flying height of a magnetic head can be decreased, and high-density recording is enabled. In a method for producing a glass substrate for a magnetic disk including a chemically strengthening step in which a glass substrate is immersed in a heated chemically strengthening salt solution prepared by dissolving a chemically strengthening salt under heating, and metal ions in the glass substrate are ion-exchanged with metal ions in the chemically strengthening salt, wherein the chemically strengthening step is carried out using a chemically strengthening salt solution in which the dissolved chemically strengthening salt does not solidify until the temperature decreases to a temperature that provides hardness at which the surface shape of the glass substrate is not deformed by a force applied to the glass substrate when the chemically strengthening salt having adhered onto the glass substrate solidifies.