Glass for magnetic recording medium substrate, magnetic recording medium substrate, magnetic recording medium, glass spacer for magnetic recording and reproducing apparatus, and magnetic recording and reproducing apparatus
Provided is a glass for a magnetic recording medium substrate, which is an amorphous oxide glass, in which an SiO 2 content ranges from 56 mol % to 80 mol %, an Li 2 O content ranges from 1 mol % to 10 mol %, a B 2 O 3 content ranges from 0 mol % to 4 mol %, a total content of MgO and CaO (MgO+CaO) ranges from 9 mol % to 40 mol %, and the oxide glass has a specific gravity of 2.75 g/cm 3 or less, a glass transition temperature of 650° C. or higher, and a Young's modulus of 90 GPa or more.
1. A glass,
which is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording and reproducing apparatus,
which is an amorphous oxide glass,
wherein an SiO 2 content ranges from 56 mol % to 80 mol %;
an Li 2 O content ranges from 1 mol % to 10 mol %;
a B 2 O 3 content ranges from 0 mol % to 4 mol %;
a MgO content is less than 14 mol %;
a total content of MgO and CaO (MgO+CaO) ranges from 9 mol % to 40 mol %; and
the oxide glass has a specific gravity of 2.75 g/cm 3 or less, a glass transition temperature of 650° C. or higher, and a Young's modulus of 90 GPa or more.
2. A glass,
which is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording and reproducing apparatus,
which is an amorphous oxide glass,
wherein an SiO 2 content ranges from 56 mol % to 80 mol %;
an Li 2 O content ranges from 1 mol % to 10 mol %;
a B 2 O 3 content ranges from 0 mol % to 4 mol %;
a MgO content is less than 14 mol %;
a total content of MgO and CaO (MgO+CaO) ranges from 9 mol % to 40 mol %;
a mole ratio of a total content of SiO 2 and ZrO 2 relative to an Al 2 O 3 content ((SiO 2 +ZrO 2 )/Al 2 O 3 ) ranges from 2 to 13; and
the oxide glass has a glass transition temperature of 650° C. or higher, and a Young's modulus of 90 GPa or more.
3. The glass according to claim 1 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
4. The glass according to claim 1 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.
5. The glass according to claim 1 ,
wherein a total content of BaO and SrO ranges from 0 mol % to 2 mol %.
6. The glass according to claim 1 ,
wherein a total content of Li 2 O, Na 2 O, and K 2 O (Li 2 O+Na 2 O+K 2 O) ranges from 2.5 mol % to 10 mol %.
7. The glass according to claim 1 ,
wherein a total content of SnO 2 and CeO 2 (SnO 2 +CeO 2 ) ranges from 0.05 mol % to 2 mol %.
8. A magnetic recording medium substrate, which is comprised of the glass according to claim 1 .
9. A magnetic recording medium comprising a magnetic recording layer on the magnetic recording medium substrate according to claim 8 .
10. A magnetic recording and reproducing apparatus, comprising the magnetic recording medium according to claim 9 .
11. The glass according to claim 1 ,
wherein the MgO content is equal to or less than 13.81 mol %.
12. The glass according to claim 2 ,
wherein the MgO content is equal to or less than 13.81 mol %.
13. The glass according to claim 2 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
14. The glass according to claim 2 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.
15. The glass according to claim 2 ,
wherein a total content of BaO and SrO ranges from 0 mol % to 2 mol %.
16. The glass according to claim 2 ,
wherein a total content of Li 2 O, Na 2 O, and K 2 O (Li 2 O+Na 2 O+K 2 O) ranges from 2.5 mol % to 10 mol %.
17. The glass according to claim 2 ,
wherein a total content of SnO 2 and CeO 2 (SnO 2 +CeO 2 ) ranges from 0.05 mol % to 2 mol %.
18. A magnetic recording medium substrate, which is comprised of the glass according to claim 2 .
19. A magnetic recording medium comprising a magnetic recording layer on the magnetic recording medium substrate according to claim 18 .
20. A magnetic recording and reproducing apparatus, comprising the magnetic recording medium according to claim 19 .