Title:
磁気ディスク用ガラス基板、磁気ディスク
Document Type and Number:
Japanese Patent JP5703430
Kind Code:
B2
Abstract:
A magnetic-disk glass substrate has a circular hole at a center, and includes a pair of main surfaces and a side wall surface orthogonal to the main surfaces. A roundness of the circular hole is 1.5 μm or less. A difference between a maximum value and a minimum value of radii of three inscribed circles that are respectively derived from outlines in the circumferential direction at three positions spaced apart by 200 μm in a substrate thickness direction on the side wall surface of the circular hole is 3.5 μm or less.
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Inventors:
Tamaki Masanori
Takahashi Takeyoshi
Ueda Masaaki
Takahashi Takeyoshi
Ueda Masaaki
Application Number:
JP2014561653A
Publication Date:
April 22, 2015
Filing Date:
February 24, 2014
Export Citation:
Assignee:
HOYA CORPORATION
International Classes:
G11B5/73
Domestic Patent References:
| JP2008226376A | 2008-09-25 | |||
| JP2012113802A | 2012-06-14 | |||
| JP2013028512A | 2013-02-07 | |||
| JP2008310842A | 2008-12-25 | |||
| JP2011198428A | 2011-10-06 | |||
| JP5126401B1 | 2013-01-23 |
Foreign References:
| WO2010041537A1 | 2010-04-15 |
Attorney, Agent or Firm:
Global IP Tokyo Patent Business Corporation