Title:
A manufacturing method of a disc-like glass substrate, a glass substrate for magnetic disks, and a glass substrate for magnetic disks, a magnetic disk
Document Type and Number:
Japanese Patent JP5912002
Kind Code:
B2
Abstract:
A disk-shaped glass substrate for a magnetic-disk glass substrate includes an outer circumference having a roundness of 1.3 μm or less. A first reference circle is obtained with a least squares method from a first outline corresponding to a shape of a lap around the outer circumference. A second reference circle is obtained with a least squares method from a second outline obtained by performing low-pass filtering using a period in which the number of peaks per lap is 150 as a cut-off value on the first outline. A ratio of the second peak count value defined by the number of peaks of the second outline that project outward in a radial direction from the second reference circle to the first peak count value defined by the number of peaks of the first outline that project outward in a radial direction from the first reference circle is 0.2 or less.
Inventors:
Ryuichi Kashima
Application Number:
JP2015524129A
Publication Date:
April 27, 2016
Filing Date:
June 27, 2014
Export Citation:
Assignee:
HOYA CORPORATION
International Classes:
G11B5/73; C03C19/00; G11B5/82; G11B5/84
Domestic Patent References:
| JP2013093091A | 2013-05-16 | |||
| JP2004079009A | 2004-03-11 | |||
| JP2013093091A | 2013-05-16 | |||
| JP2004079009A | 2004-03-11 |
Foreign References:
| WO2009081565A1 | 2009-07-02 | |||
| WO2009081565A1 | 2009-07-02 |
Attorney, Agent or Firm:
Global IP Tokyo Patent Business Corporation
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