Title:
GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM AND MAGNETIC DISK DEVICE
Document Type and Number:
WIPO Patent Application WO/2014/208259
Kind Code:
A1
Abstract:
A glass substrate for an information recording medium has a rotational center (CP) and is provided with principal surfaces and an outer peripheral end surface. The difference between the maximum and minimum values in a circumferential distribution of amount of offset relative to a reference position as a radius position is 40 nm or less on both the front and rear surfaces, and the difference between the mean of the circumferential distribution of amount of offset on the front side and the mean of the circumferential distribution of the amount of offset on the rear side is 10 nm or less, where R is the radius of the glass substrate (1G), the reference position is a point (R3) on a reference line (BL) that is 0.99R away from the rotational center (CP), and the amount of offset is the distance to the reference position from a point on a principal surface overlapping the reference position when viewed along the direction of extension of a rotational axis (L1) that passes through the rotational center (CP).
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Inventors:
FUKUMOTO NAOYUKI (JP)
Application Number:
PCT/JP2014/064217
Publication Date:
December 31, 2014
Filing Date:
May 29, 2014
Export Citation:
Assignee:
HOYA CORP (JP)
International Classes:
G11B5/73; G11B5/82
Foreign References:
| JP2013051026A | 2013-03-14 | |||
| JP2008310842A | 2008-12-25 | |||
| JP2010073289A | 2010-04-02 | |||
| JP2013080531A | 2013-05-02 |
Attorney, Agent or Firm:
Fukami Patent Office, p. c. (JP)
Patent business corporation Fukami patent firm (JP)
Patent business corporation Fukami patent firm (JP)
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