Glass substrate for magnetic recording medium, magnetic recording medium, and method of manufacturing the same

• US 6,548,139 B2
• Filed: 02/14/2002
• Issued: 04/15/2003
• Est. Priority Date: 08/19/1998
• Status: Expired due to Term

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Matsuda, Syoji, Sakai, Hiroyuki, Ono, Katsutoshi
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US10/074,002
• Publication Number:
  US 20020142191A1
• Time in Patent Office: 425 Days
• Field of Search: 428/141, 428/65.3, 428/426, 428/432, 428/694.ST, 428/694.SG, 428/900, 360/135
• US Class Current: 428/848.2
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C03C 15/00 Surface treatment of glass, not in the form of fibres or filaments, by etching etching or surface-brightening compositions, in general C09K13/00
• CPC Class Codes: C03C 15/02 for making a smooth surface
• CPC Class Codes: C03C 19/00 Surface treatment of glass, not in the form of fibres or filaments, by mechanical means sand-blasting, grinding, or polishing glass B24
• CPC Class Codes: C03C 2204/08 Glass having a rough surface
• CPC Class Codes: G11B 5/8404 manufacturing base layers
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]

Abstract

In a glass substrate for use in a magnetic recording medium, a surface roughness of at least a principal surface of the glass substrate is measured by the use of the interatomic force microscope (AFM), Ra falls within the range between 0.2 and 2.5 nm, Rmax falls within the range between 3 and 25 nm, and Rmax/Ra falls within the range between 3 and 35.

Claims

1. A glass substrate which is for use in a magnetic recording medium and which has surface roughness Ra and Rmax, where Ra is representative of a center-line mean roughness, Rmax is defined as a maximum height representative of a difference between a highest point and a lowest point wherein:

a surface roughness of at least a principal surface of the glass substrate is measured by the use of the interatomic force microscope (AFM),

Ra falls within the range between 0.2 and 2.5 nm,

Rmax falls within the range between 3 and 25 nm, and

Rmax/Ra falls within the range between 3 and 35; and

wherein;

a surface parallel to a virtual principal surface is defined as a contour surface when it is assumed that the principal surface of said glass substrate is completely flattened,

when roughness formed on the principal surface are cut by the use of the contour surface, a percentage rate of a total area of the principal surface for sum of areas of the cut cross sectional surface is defined as a bearing ratio,

the contour surface having the bearing ratio of 50% is defined as a referential surface,

each distance from the referential surface to each contour surface having each bearing ratio is specified as a bearing height,

the bearing height of the contour surface having the bearing ratio of 2.5% is defined as B.H. (2.5) while the bearing height of the contour surface having the bearing ratio of 5.0% is defined as B.H. (5.0), and

B.H. (2.5)/Rmax falls within the range between 0.1 and 0.5 or B.H. (5.0)/Rmax falls within the range between 0.1 and 0.45.

2. A glass substrate as claimed in claim 1, wherein:

the surface roughness of at least the principal surface is measured by the use of the interatomic force microscope (AFM),

Rmax falls within the range between 5 and 25 nm, and

B.H. (2.5)/Rmax falls within the range between 0.1 and 0.5 or B.H. (5.0)/Rmax falls within the range between 0.1 and 0.45.

3. A glass substrate as claimed in claim 2, wherein:

said glass substrate contains at least alkali metal oxide and alkali earth oxide, and

the content of the alkali earth oxide is not exceeding 3 mol %.

4. A glass substrate as claimed in claim 3, wherein:

said glass substrate is used for a magnetic disk which has a glide height having 1.2 μ

inch or less.

5. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 4.

6. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 3.

7. A glass substrate as claimed in claim 2, wherein:

said glass substrate is used for a magnetic disk which has a glide height having 1.2 μ

inch or less.

8. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 7.

9. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 2.

10. A glass substrate as claimed in claim 1, wherein:

said glass substrate contains at least alkali metal oxide and alkali earth oxide, and

the content of the alkali earth oxide is not exceeding 3 mol %.

11. A glass substrate as claimed in claim 10, wherein:

said glass substrate is used for a magnetic disk which has a glide height having 1.2 μ

inch or less.

12. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 11.

13. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 10.

14. A glass substrate as claimed in claim 1, wherein:

said glass substrate is used for a magnetic disk which has a glide height having 1.2 μ

inch or less.

15. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 14.

16. A magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate claimed in claim 1.