Glass for data storage medium substrate, glass substrate for data storage medium, and magnetic disk
The present invention pertains to a glass for a data storage medium substrate which contains a specific amount of each of SiO 2 , Al 2 O 3 , MgO, CaO, SrO, BaO, Li 2 O, Na 2 O, and K 2 O, in molar percentage based on the oxides, and does not substantially contain B 2 O 3 or ZrO 2 , wherein the sum of the Li 2 O, Na 2 O, and K 2 O contents (R 2 O), the molar ratio of the SiO 2 content to the Al 2 O 3 content (SiO 2 /Al 2 O 3 ), and the molar ratio of the sum of the SiO 2 and Al 2 O 3 contents (SiO 2 +Al 2 O 3 ) to R 2 O[(SiO 2 +Al 2 O 3 )/R 2 O] fall within their specific ranges, formula (1): 90<[SiO 2 ]+2×[Al 2 O 3 ]+0.8×[RO]−0.5×[R 2 O] [in formula (1), RO represents the sum of the MgO, CaO, SrO, and BaO contents] is satisfied, and the glass transition point T g , the alkali resistance, and the acid resistance fall within their specific ranges.
1. A glass comprising, in terms of mole percentage based on oxides:
60% or more of SiO 2 ,
more than 8.5% and less than 13% of Al 2 O 3 ,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 2% of SrO,
0 to 2% of BaO,
0 to 1% of TiO 2 ,
0% or more and less than 4% of Li 2 O,
3 to 12% of Na 2 O,
0% or more and less than 4% of K 2 O,
0% or more and less than 0.01% of B 2 O 3 , and
0% or more and less than 0.01% of ZrO 2 ,
wherein:
a total content (R 2 O) of Li 2 O, Na 2 O and K 2 O is 3 to 12%,
a total content of SiO 2 and Al 2 O 3 is 80.5% or less,
a molar ratio (SiO 2 /Al 2 O 3 ) of the SiO 2 content to the Al 2 O 3 content is higher than 5,
a molar ratio [(SiO 2 +Al 2 O 3 )/R 2 O] of a total content (SiO 2 +Al 2 O 3 ) of SiO 2 and Al 2 O 3 to R 2 O is higher than 9, and
contents of SiO 2 , Al 2 O 3 , RO and R 2 O are such that a value obtained by the Formula (1) is greater than 90:
[SiO 2 ]+2×[Al 2 O 3 ]+0.8×[RO]−0.5×[R 2 O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO.
2. The glass according to claim 1 , comprising 0.1 to 1% of TiO 2 .
3. The glass according to claim 1 , comprising 4 to 12% of CaO.
4. The glass according to claim 1 , comprising 7 to 12% of CaO.
5. The glass according to claim 1 , comprising 0 to 4% of MgO.
6. The glass according to claim 1 , comprising greater than 0% of ZrO 2 .
7. The glass according to claim 1 , wherein a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower.
8. The glass according to claim 1 , wherein the total content of SiO 2 and Al 2 O 3 is 79.0% or less.
9. A glass comprising, in terms of mole percentage based on oxides:
60% or more of SiO 2 ,
more than 6.5% and less than 13% of Al 2 O 3 ,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 2% of SrO,
0 to 2% of BaO,
0 to 1% of TiO 2 ,
0% or more and less than 4% of Li 2 O,
3 to 12% of Na 2 O,
0% or more and less than 4% of K 2 O, and
0% or more and less than 0.01% of B 2 O 3 ,
wherein:
a total content (R 2 O) of Li 2 O, Na 2 O and K 2 O is 3 to 12%,
a total content of SiO 2 and Al 2 O 3 is 80.5% or less,
a molar ratio (SiO 2 /Al 2 O 3 ) of the SiO 2 content to the Al 2 O 3 content is higher than 5,
a molar ratio [(SiO 2 +Al 2 O 3 )/R 2 O] of a total content (SiO 2 +Al 2 O 3 ) of SiO 2 and Al 2 O 3 to R 2 O is higher than 9, and
contents of SiO 2 , Al 2 O 3 , RO and R 2 O are such that a value obtained by the Formula (1) is greater than 90:
[SiO 2 ]+2×[Al 2 O 3 ]+0.8×[RO]−0.5×[R 2 O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO.
10. The glass according to claim 9 , comprising 0.1 to 1% of TiO 2 .
11. The glass according to claim 9 , comprising 4 to 12% of CaO.
12. The glass according to claim 9 , comprising 7 to 12% of CaO.
13. The glass according to claim 9 , comprising 0 to 4% of MgO.
14. The glass according to claim 9 , further comprising 0% or more of ZrO 2 .
15. The glass according to claim 9 , wherein contents of MgO, Al 2 O 3 , CaO, Na 2 O and SiO 2 are such that a value obtained by the Formula (2) is satisfied less than 30:
3×[MgO]+6×[Al 2 O 3 ]−0.4×[CaO]+0.4×[Na 2 O]—[SiO 2 ] Formula (2).
16. The glass according to claim 9 , wherein a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower.
17. The glass according to claim 9 , wherein the total content of SiO 2 and Al 2 O 3 is 79.0% or less.
18. The glass according to claim 9 , having a liquidus temperature T L lower than 1300° C.
19. The glass according to claim 9 , having a density less than 2.55 g/cm 3 .
20. The glass according to claim 9 , having a specific modulus of 31 MNm/kg or higher.
21. The glass according to claim 9 , having a temperature T 2 at which a viscosity η reaches 10 2 poises (dPa·s) of lower than 1770° C.
22. The glass according to claim 9 , having a temperature T 4 at which a viscosity η reaches 10 4 poises (dPa·s) of lower than 1280° C.
23. The glass according to claim 9 , having a thermal expansion coefficient of 10×10 −7 /° C. or higher.
24. The glass according to claim 9 , having a glass transition point T g higher than 680° C.
25. The glass according to claim 9 , having an alkali resistance lower than 2 mg/cm 2 and an acid resistance lower than 0.1 mg/cm 2 .
26. A glass comprising, in terms of mole percentage based on oxides,
60% or more of SiO 2 ,
4% or more and less than 15% of Al 2 O 3 ,
0 to 5% of MgO,
1 to 12% of CaO,
0 to 7% of SrO,
0 to 5% of BaO,
0 to 10% of TiO 2 ,
0% or more and less than 4% of Li 2 O
0% or more and less than 4% of K 2 O,
3% to 12% of Na 2 O,
0% or more and less than 0.01% of B 2 O 3 and
0 to 5% of ZrO 2 ,
wherein:
a total content of SiO 2 and Al 2 O 3 is 80.5% or less,
a molar ratio (MgO/RO) of MgO to a total content (RO) of MgO, CaO, SrO, and BaO is 0.7 or lower, and
contents of SiO 2 , Al 2 O 3 , RO and R 2 O are such that a value obtained by the Formula (1) is 90 or more:
[SiO 2 ]+2×[Al 2 O 3 ]+0.8×[RO]−0.5×[R 2 O] Formula (1),
wherein in the Formula (1), RO represents a total content of MgO, CaO, SrO, and BaO, and R 2 O represents a total content of Li 2 O, Na 2 O and K 2 O.
27. The glass according to claim 26 , wherein, in terms of mole percentage based on oxides, MgO is less than 5% and at least any one of (1) to (3) is satisfied:
(1) greater than 0% and 4% or less of ZrO 2 is contained;
(2) 7% or less of Na 2 O is contained; and
(3) 9% or less of Na 2 O, 11% or less of Al 2 O 3 and 1% or more and 9.5% or less of CaO are contained.
28. The glass according to claim 26 , comprising 0 to 4% of MgO.
29. The glass according to claim 26 , wherein, in terms of mole percentage based on oxides, MgO is 5% and at least one of (4) and (5) is satisfied:
(4) greater than 0% and 4% or less of ZrO 2 is contained; and
(5) 1% or more and 8.5% or less of CaO is contained.
30. The glass according to claim 26 , comprising 4% to 12% of CaO.
31. The glass according to claim 26 , comprising 7% to 12% of CaO.
32. The glass according to claim 26 , wherein the total content of SiO 2 and Al 2 O 3 is 79.0% or less.