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Title:
GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, METHOD FOR PRODUCING GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, AND INFORMATION RECORDING MEDIUM
Document Type and Number:
WIPO Patent Application WO/2011/096310
Kind Code:
A1
Abstract:
In order to provide a glass substrate that is for an information recording medium and that is both provided with a chemically strengthened layer through chemical strengthening treatment and has a sufficiently small TIR in the circumferential direction, disclosed is a disc-shaped glass substrate, which has a chemically strengthened layer on the surface that forms a recording layer, and of which the portion aside from the chemically strengthened layer comprises a glass composition that is, by mass, 55-75% SiO2, 5-18% Al2O3, 1-10% Li2O, 3-15% Na2O, 0.1-5% K2O—the total of Li2O+Na2O+K2O being 10-25%—0.1-5% MgO, 0.1-5% CaO, and 0-8% ZrO2, the mass ratio of (MgO+CaO) to (Li2O+Na2O+K2O) being in the range of 0.10 ≤ (MgO+CaO) / (Li2O+Na2O+K2O) ≤ 0.80, wherein, considering the radius of the outer perimeter to be r­1, the TIR of one circumference in the circumferential direction after grinding by means of a grinding step is no more than 1 μm at the position of the surface that is 0.75r1 from the center.

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Inventors:
KAJITA HIROSHI (JP)
KAWAI HIDEKI (JP)
Application Number:
PCT/JP2011/051431
Publication Date:
August 11, 2011
Filing Date:
January 26, 2011
Export Citation:
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Assignee:
KONICA MINOLTA OPTO INC (JP)
KAJITA HIROSHI (JP)
KAWAI HIDEKI (JP)
International Classes:
G11B5/73; C03C3/087; C03C3/095; C03C3/097; C03C21/00; G11B5/84
Domestic Patent References:
WO2008062662A12008-05-29
Foreign References:
JP2001236634A2001-08-31
JP2008169061A2008-07-24
JP2009099239A2009-05-07
JPH07134823A1995-05-23
JPH08124153A1996-05-17
JP2000302482A2000-10-31
JPH07174400A1995-07-14
JP2000076652A2000-03-14
JPH0729170A1995-01-31
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