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Title:
GLASS SUBSTRATE FOR MAGNETIC RECORDING MEDIUM AND METHOD FOR MANUFACTURING MAGNETIC RECORDING MEDIUM
Document Type and Number:
WIPO Patent Application WO/2018/008161
Kind Code:
A1
Abstract:
Provided is a glass substrate for a magnetic recording medium, wherein the glass substrate has a glass strain point Ts of 585°C or more, the maximum value of retardation measured by radiating light having a wavelength of 543 nm in a vertical direction relative to the main surface is 4 nm or less at a location 0.2 mm radially outward from the inner peripheral end and at a location 0.2 mm radially inward from the outer peripheral end while the difference between the maximum and minimum retardation values thereat is 1.2 nm or less, and the depth λ of elements introduced via chemical strengthening is 3-9 µm at all portions 0.5 mm or more radially outward from the inner peripheral end and 0.5 mm or more radially inward from the outer peripheral end.

Inventors:
KUROIWA Yutaka (Limited 5-1, Marunouchi 1-chome, Chiyoda-k, Tokyo 05, 〒1008405, JP)
NAKASHIMA Tetsuya (Limited 5-1, Marunouchi 1-chome, Chiyoda-k, Tokyo 05, 〒1008405, JP)
AKIYAMA Jun (Limited 5-1, Marunouchi 1-chome, Chiyoda-k, Tokyo 05, 〒1008405, JP)
Application Number:
JP2016/072519
Publication Date:
January 11, 2018
Filing Date:
August 01, 2016
Export Citation:
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Assignee:
ASAHI GLASS COMPANY, LIMITED (5-1 Marunouchi 1-chome, Chiyoda-ku Tokyo, 05, 〒1008405, JP)
International Classes:
G11B5/73; C03C3/083; C03C3/085; C03C3/087; C03C21/00; G11B5/82; G11B5/84
Attorney, Agent or Firm:
EIKOH PATENT FIRM, P.C. (Toranomon East Bldg. 10F, 7-13 Nishi-Shimbashi 1-chome, Minato-k, Tokyo 03, 〒1050003, JP)
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