Glass for magnetic recording medium substrate or for glass spacer for magnetic recording and reproducing
A glass, which is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording and reproducing apparatus, is an amorphous oxide glass. 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 Na 2 O content is 0 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 Na 2 O content is 0 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 is equal to or less than 10 mol %;
a B 2 O 3 content ranges from 0 mol % to 4 mol %;
a CaO content is 0 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.
3. 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 %.
4. 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 %.
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 2 ,
wherein a total content of BaO and SrO ranges from 0 mol % to 2 mol %.
7. The glass according to claim 3 ,
wherein a total content of BaO and SrO ranges from 0 mol % to 2 mol %.
8. The glass according to claim 4 ,
wherein a total content of BaO and SrO ranges from 0 mol % to 2 mol %.
9. 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.
10. 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.
11. The glass according to claim 3 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
12. The glass according to claim 4 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
13. The glass according to claim 5 ,
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 6 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
15. The glass according to claim 7 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
16. The glass according to claim 8 ,
wherein an average linear expansion coefficient at 100° C. to 300° C. ranges from 40×10 −7 to 70×10 −7 /° C.
17. The glass according to claim 1 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.
18. The glass according to claim 3 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.
19. The glass according to claim 5 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.
20. The glass according to claim 7 ,
wherein a CaO content ranges from 0 mol % to 18 mol %.