Glass for magnetic recording medium substrate or for glass spacer to be used in magnetic recording/reproducing device, magnetic recording medium substrate, magnetic recording medium, glass spacer to be used in magnetic recording/reproducing device, and magnetic recording/reproducing device
Provided is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing device, the glass being an amorphous glass that contains at least Li 2 O, in which a total content of Na 2 O and K 2 O is 0 mol % or more and 6.0 mol % or less, a B 2 O 3 content is 0 mol % or more and 10.0 mol % or less, and a CaO content is 0 mol % or more and 1.0 mol % or less.
1 . A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing device, the glass being an amorphous glass,
wherein a Li 2 O content is 2.5 mol % or more and 6.0 mol % or less,
a total content of Na 2 O and K 2 O is 0 mol %,
a B 2 O 3 content is 0 mol % or more and 1.0 mol % or less,
a CaO content is 0 mol % or more and 0.1 mol % or less,
a MgO content is 19.2 mol % or more and 23.0 mol % or less,
a TiO 2 content is 0 mol %,
a SiO 2 content is more than 56.0 mol % and 65.0 mol % or less,
an Al 2 O 3 content is more than 13.0 mol % and 15.0 mol % or less,
a Y 2 O 3 content is 0 mol %,
an average linear expansion coefficient within a temperature range of 100° C. to 300° C. of the glass is 38.4×10 −7 /° C. or more and 52.5×10 −7 /° C. or less,
a glass transition temperature Tg of the glass is 697° C. or more and 745° C. or less,
a Young's modulus of the glass is 95.9 GPa or more and 100.1 GPa or less, and
a specific elastic modulus of the glass is 38.2 MNm/kg or more and 38.8 MNm/kg or less.
2 . The glass according to claim 1 ,
wherein the B 2 O 3 content is 0.1 mol % or more and 0.5 mol % or less.
3 . A magnetic recording medium substrate made of the glass according to claim 2 .
4 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 3 ; and
a magnetic recording layer.
5 . A magnetic recording/reproducing device comprising
the magnetic recording medium according to claim 4 .
6 . The glass according to claim 2 ,
wherein the glass does not contain any alkali metal oxide other than Li 2 O.
7 . A magnetic recording medium substrate made of the glass according to claim 6 .
8 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 7 ; and
a magnetic recording layer.
9 . A magnetic recording/reproducing device comprising the magnetic recording medium according to claim 8 .
10 . The glass according to claim 1 ,
wherein the glass does not contain any alkali metal oxide other than Li 2 O.
11 . A magnetic recording medium substrate made of the glass according to claim 10 .
12 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 11 ; and
a magnetic recording layer.
13 . A magnetic recording/reproducing device comprising
the magnetic recording medium according to claim 12 .
14 . A magnetic recording medium substrate made of the glass according to claim 1 .
15 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 14 ; and
a magnetic recording layer.
16 . A magnetic recording/reproducing device comprising
the magnetic recording medium according to claim 15 .
17 . The glass according to claim 1 ,
wherein the average linear expansion coefficient within the temperature range of 100° C. to 300° C. of the glass is 46.9×10 −7 /° C. or less.
18 . The glass according to claim 1 ,
wherein the average linear expansion coefficient within the temperature range of 100° C. to 300° C. of the glass is 46.5×10 −7 /° C. or less.
19 . The glass according to claim 1 ,
wherein the average linear expansion coefficient within the temperature range of 100° C. to 300° C. of the glass is 46.3×10 −7 /° C. or less.