Nucleating agents for crystallized glasses, crystallized glasses, magnetic discs substrate and magnetic discs

• US 6,372,319 B1
• Filed: 09/08/1999
• Issued: 04/16/2002
• Est. Priority Date: 09/10/1998
• Status: Expired due to Fees

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Yasui, Itaru, Abe, Masahiro, Yamada, Yusuke
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US09/392,130
• Time in Patent Office: 951 Days
• Field of Search: 428/694.SG, 428/694.ST, 428/426, 428/141, 428/65.3, 501/4, 501/7
• US Class Current: 428/846.2
• CPC Class Codes: C03C 10/0027 containing SiO2, Al2O3, Li2O as main constituents
• CPC Class Codes: G11B 5/73921 Glass or ceramic substrates
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]

Abstract

A nucleating agent for producing a crystallized glass, which nucleating agent is to make fine particles at least in the cristobalite phase when added into the crystallized glass containing at least the cristobalite phase, and includes one or more kinds of metallic compounds selected from the group consisting of molybdenum compounds and tantalum compounds.

Claims

1. An Li₂O—

Al₂O₃—

SiO₂ based crystallized glass comprising lithium disilicate, Li₂O-2SiO₂, as a main crystalline phase, a cristobalite phase as a sub-crystalline phase, and at least one metallic oxide selected from the group consisting of molybdenum oxide and tantalum oxide in a total amount of 0.5 to 7.0% by weight, wherein when a diffraction intensity I of the lithium disilicate phase, L2S, is taken as 100, measured by an X-ray diffraction method, a diffraction intensity I of the cristobalite phase, CR1, is not less than 20 and not more than 70.

2. The crystallized glass set forth in claim 1, which contains 0.5 to 5% by weight of molybdenum oxide, substantially free from tantalum oxide.

3. The crystallized glass set forth in claim 1, which contains 0.5 to 7% by weight of tantalum oxide, substantially free from molybdenum oxide.

4. The crystallized glass set forth in claim 1, which contains molybdenum oxide and tantalum oxide in a total amount of 0.5 to 6.0 wt %.

5. The crystallized glass set forth in claim 1, which contains 72 to 82% by weight of SiO₂, 8 to 12% by weight of Li₂O, 3 to 8% by weight of Al₂O₃, 1 to 3% by weight of P₂O₅ and 0.5 to 6% by weight of ZrO₂.

6. The crystallized glass set forth in claim 5, which contains 75 to 80% by weight of SiO₂, 9 to 11% by weight of Li₂O, 4 to 6% by weight of Al₂O₃, 1.5 to 2.5% by weight of P₂O₅, 1 to 4% by weight of ZrO₂, 1 to 4% by weight of K₂O, and 0.2 to 0.5% by weight of Sb₂O₃% by weight.

7. The crystallized glass set forth in claim 1, which contains 0.5 to 5% by weight of TiO₂.

8. The crystallized glass set forth in claim 1, which has a coefficient of thermal expansions in a range of 25°

C. to 100°

C. being not less than 80×

10<sup>−

7</sup>/K and not more than 120×

10<sup>−

7</sup>/K.

9. A magnetic disc substrate made of the crystallized glass set forth in claim 1, which has a surface with a center line average height (Ra) of not more than 10 Å

.

10. A magnetic disc comprising the magnetic disc substrate set forth in claim 9, an under film formed on the surface of the substrate, and a magnetic metallic layer formed on the under film.

11. An Li₂O—

Al₂O₃—

SiO₂ based crystallized glass comprising lithium disilicate, Li₂O-2SiO₂, as a main crystalline phase, a cristobalite phase as a sub-crystalline phase, 72 to 82% by weight of SiO₂, 8 to 12% by weight of Li₂O, 3 to 8% by weight of Al₂O₃, 1to 3% by weight of P₂O₅, 0.5 to 6% by weight of ZrO₂, and at least one metallic oxide selected from the group consisting of molybdenum oxide and tantalum oxide in a total amount of 0.5 to 7.0% by weight.

12. The crystallized glass set forth in claim 11, wherein when a diffraction intensity I of the lithium disilicate phase, L2S, is taken as 100, as measured by an X-ray diffraction method, a diffraction intensity I of the cristobalite phase, CR1, is not less than 20 and not more than 70.

13. The crystallized glass set forth in claim 11, which contains 0.5 to 5% by weight of molybdenum oxide, substantially free from tantalum oxide.

14. The crystallized glass set forth in claim 12, which contains 0.5 to 5% by weight of molybdenum oxide, substantially free from tantalum oxide.

15. The crystallized glass set forth in claim 11, which contains 0.5 to 7% by weight of tantalum oxide, substantially free from molybdenum oxide.

16. The crystallized glass set forth in claim 12, which contains 0.5 to 7% by weight of tantalum oxide, substantially free from molybdenum oxide.

17. The crystallized glass set forth in claim 11, which contains molybdenum oxide and tantalum oxide in a total amount of 0.5 to 6.0 wt %.

18. The crystallized glass set forth in claim 12, which contains molybdenum oxide and tantalum oxide in a total amount of 0.5 to 6.0 wt %.

19. The crystallized glass set forth in claim 11, further comprising 0.5 to 5 % by weight of TiO₂.

20. The crystallized glass set forth in claim 12, further comprising 0.5 to 5 % by weight of TiO₂.

21. The crystallized glass set forth in claim 11, which has a coefficient of thermal expansion in a range of 25°

C. to 100°

C. being not less than 80×

10<sup>−

7</sup>/K and not more than 120×

10<sup>−

7</sup>/K.

22. The crystallized glass set forth in claim 12, which has a coefficient of thermal expansion in a range of 25°

C. to 100°

C. being not less than 80×

10<sup>−

7</sup>/K and not more than 120×

10<sup>−

7</sup>/K.

23. A magnetic disc substrate made of the crystallized glass set forth in claim 11, which has a surface with a center line average height (Ra) of not more than 10 Å

.

24. A magnetic disc substrate made of the crystallized glass set forth in claim 12, which has a surface with a center line average height (Ra) of not more than 10 Å

.

25. A magnetic disc comprising the magnetic disc substrate set forth in claim 23, an under film formed on the surface of the substrate, and a magnetic metallic layer formed on the under film.

26. A magnetic disc comprising the magnetic disc substrate set forth in claim 24, an under film formed on the surface of the substrate, and a magnetic metallic layer formed on the under film.

27. An Li₂O—

Al₂O₃—

SiO₂ based crystallized glass comprising lithium disilicate, Li₂O-2SiO₂, as a main crystalline phase, a cristobalite phase as a sub-crystalline phase, and 75 to 80% by weight of SiO₂, 9 to 11% by weight of Li₂O, 4 to 6% by weight of Al₂O₃, 1.5 to 2.5% by weight of P₂O₅, 1 to 4% by weight of ZrO₂, 1 to 4% by weight of K₂O, 0.2 to 0.5% by weight of Sb₂O₃%, and at least one metallic oxide selected from the group consisting of molybdenum oxide and tantalum oxide in a total amount of 0.5 to 7.0% by weight.

28. The crystallized glass set forth in claim 27, wherein when a diffraction intensity I of the lithium disilicate phase, L2S, is taken as 100, as measured by an X-ray diffraction method, a diffraction intensity I of the cristobalite phase, CR1, is not less than 20 and not more than 70.

29. The crystallized glass set forth in claim 27, which contains 0.5 to 5% by weight of molybdenum oxide, substantially free from tantalum oxide.

30. The crystallized glass set forth in claim 28, which contains 0.5 to 5% by weight of molybdenum oxide, substantially free from tantalum oxide.

31. The crystallized glass set forth in claim 27, which contains 0.5 to 7% by weight of tantalum oxide, substantially free from molybdenum oxide.

32. The crystallized glass set forth in claim 28, which contains 0.5 to 7% by weight of tantalum oxide, substantially free from molybdenum oxide.

33. The crystallized glass set forth in claim 27, which contains molybdenum oxide and tantalum oxide in a total amount of 0.5 to 6.0 wt %.

34. The crystallized glass set forth in claim 28, which contains molybdenum oxide and tantalum oxide in a total amount of 0.5 to 6.0 wt %.

35. The crystallized glass set forth in claim 27, further comprising 0.5 to 5 % by weight of TiO₂.

36. The crystallized glass set forth in claim 28, further comprising 0.5 to 5 % by weight of TiO₂.

37. The crystallized glass set forth in claim 27, which has a coefficient of thermal expansion in a range of 25°

C. to 100°

C. being not less than 80×

10<sup>−

7</sup>/K and not more than 120×

10<sup>−

7</sup>/K.

38. The crystallized glass set forth in claim 28, which has a coefficient of thermal expansion in a range of 25°

C. to 100°

C. being not less than 80×

10<sup>−

7</sup>/K and not more than 120×

10<sup>−

7</sup>/K.

39. A magnetic disc substrate made of the crystallized glass set forth in claim 27, which has a surface with a center line average height (Ra) of not more than 10 Å

.

40. A magnetic disc substrate made of the crystallized glass set forth in claim 28, which has a surface with a center line average height (Ra) of not more than 10 Å

.

41. A magnetic disc comprising the magnetic disc substrate set forth in claim 39, an under film formed on the surface of the substrate, and a magnetic metallic layer formed on the under film.

42. A magnetic disc comprising the magnetic disc substrate set forth in claim 40, an under film formed on the surface of the substrate, and a magnetic metallic layer formed on the under film.