Magnetic-disk glass substrate, magnetic-disk glass substrate intermediate, and method for manufacturing magnetic-disk glass substrate
A magnetic-disk glass substrate containing an alkaline earth metal component as a glass composition includes an edge surface that is a mirror surface, and has a roughness percentage of 40% or more when a bearing ratio of a roughness cross-sectional area is 50% in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the edge surface obtained after the edge surface is etched by 2.5 μm is measured.
1. A magnetic-disk glass substrate containing an alkaline earth metal component as a glass composition, the magnetic-disk glass substrate comprising:
an edge surface that is a mirror surface,
the edge surface including a surface having a roughness percentage of 40% or more and 68% or less when a bearing ratio of a roughness cross-sectional area is 50% in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the edge surface obtained after the edge surface is etched by 2.5 μm is measured.
2. The magnetic-disk glass substrate according to claim 1 , wherein
the roughness percentage is 50% or more.
3. The magnetic-disk glass substrate according to claim 1 , wherein
the roughness percentage is 60% or less.
4. The magnetic-disk glass substrate according to claim 1 , wherein
an arithmetic average surface roughness of the mirror surface is 0.015 μm or less.
5. The magnetic-disk glass substrate according to claim 1 , wherein
a glass transition point of the glass composition that constitutes the magnetic-disk glass substrate is 700° C. or more.
6. The magnetic-disk glass substrate according to claim 1 , wherein
the glass composition that constitutes the magnetic-disk glass substrate is alkali-free glass.
7. The magnetic-disk glass substrate according to claim 1 , wherein
the glass substrate is a magnetic-disk glass substrate that is to be mounted in a hard disk drive together with a magnetic head provided with a DFH (dynamic flying height) function.
8. The magnetic-disk glass substrate according to claim 1 , wherein
the glass substrate is a glass substrate that is to be used as a magnetic disk for an energy-assisted magnetic recording method.
9. A magnetic disk, wherein
a surface of the magnetic-disk glass substrate according to claim 1 has at least a magnetic film.
10. A glass substrate intermediate containing an alkaline earth metal component as a glass composition and serving as a blank for a magnetic-disk glass substrate, the glass substrate intermediate comprising:
an edge surface that is a mirror surface,
the edge surface including a surface having a roughness percentage of 40% or more and 68% or less when a bearing ratio of a roughness cross-sectional area is 50% in a bearing ratio curve of roughness cross-sectional areas obtained when a surface roughness of the edge surface obtained after the edge surface is etched by 2.5 μm is measured.
11. The glass substrate intermediate according to claim 10 , wherein
the roughness percentage is 50% or more.
12. The glass substrate intermediate according to claim 10 , wherein
the roughness percentage is 60% or less.
13. The glass substrate intermediate according to claim 10 , wherein
the glass composition that constitutes the glass substrate intermediate is alkali-free glass.
14. A method for manufacturing a magnetic-disk glass substrate, the method comprising:
performing at least polishing processing on a main surface of the glass substrate intermediate according to claim 10 .
15. The magnetic-disk glass substrate according to claim 1 , wherein
an arithmetic average roughness Ra of a main surface of the magnetic-disk glass substrate is 0.15 nm or less.
16. The magnetic-disk glass substrate according to claim 1 , wherein
a glass transition point of the glass composition that constitutes the magnetic-disk glass substrate is 600° C. or more.
17. The glass substrate intermediate according to claim 10 , wherein
an arithmetic average surface roughness of the mirror surface is 0.015 μm or less.
18. The glass substrate intermediate according to claim 10 , wherein
a glass transition point of the glass composition that constitutes the glass substrate intermediate is 600° C. or more.
19. The glass substrate intermediate according to claim 10 , wherein
a glass transition point of the glass composition that constitutes the glass substrate intermediate is 700° C. or more.