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, and magnetic recording/reproducing apparatus
Provided is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus, in which a mole ratio of the total content of Al 2 O 3 and MgO relative to the total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less, the total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less, the total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less, the Na 2 O content is 0 mol %, and an average linear expansion coefficient of the glass at 100° C. to 300° C. is 68×10 −7 /° C. or less.
1 . A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus,
wherein the glass comprises the following mole ratios: a mole ratio of a total content of Al 2 O 3 and MgO relative to a total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less,
a total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less,
a total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less,
an Na 2 O content is 0 mol %, and
an average linear expansion coefficient of the glass at 100° C. to 300° C. is 57×10 −7 /° C. or less.
2 . The glass according to claim 1 ,
wherein a total content of TiO 2 and ZrO 2 (TiO 2 +ZrO 2 ) is 0.5 mol % or more.
3 . A magnetic recording medium substrate comprised 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 apparatus comprising:
the magnetic recording medium according to claim 4 ; and
a magnetic head.
6 . A magnetic recording medium substrate comprised of the glass according to claim 1 .
7 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 6 ; and
a magnetic recording layer.
8 . A magnetic recording/reproducing apparatus comprising:
the magnetic recording medium according to claim 7 ; and
a magnetic head.
9 . A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus,
wherein the glass comprises the following mole ratios: a mole ratio of a total content of Al 2 O 3 and MgO relative to a total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less,
a total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less,
a total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less,
a ZrO 2 content is 0 mol %, and
an average linear expansion coefficient of the glass at 100° C. to 300° C. is 57×10 −7 /° C. or less.
10 . The glass according to claim 9 ,
wherein an Na 2 O content is 0 mol %.
11 . A magnetic recording medium substrate comprised 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 apparatus comprising:
the magnetic recording medium according to claim 12 ; and
a magnetic head.
14 . A magnetic recording medium substrate comprised of the glass according to claim 9 .
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 apparatus comprising:
the magnetic recording medium according to claim 15 ; and
a magnetic head.