Substrate for magnetic disk and magnetic disk
A disk-shaped substrate for a magnetic disk has a diameter D of 85 mm or more and a thickness T of 0.6 mm or less, and a material of the substrate has a Young's modulus E of 90 GPa or more.
1. A substrate for a magnetic disk having a disk shape,
wherein the substrate has a diameter D of 85 mm or more and a thickness T of 0.6 mm or less,
when an impact is applied to the substrate under conditions of 70 (G) and 2 (msec) in a normal direction of main surfaces of the substrate in a state in which an inner circumferential end portion of the substrate is fixed, the maximum amplitude of vibration in a thickness direction of an outer circumferential end portion of the substrate is 0.25 mm or less,
the substrate is a non-magnetic metal substrate, and
regarding the Young's modulus E and the thickness T of the substrate, a value of E·T 3 is 3 to 18 (GPa·mm 3 ).
2. The substrate for a magnetic disk according to claim 1 , wherein the diameter D is 90 mm or more.
3. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 2 is provided with at least a magnetic film.
4. A hard disk drive comprising:
the substrate for a magnetic disk according to claim 3 .
5. The substrate for a magnetic disk according to claim 1 , wherein the substrate has a Vickers hardness Hv of 650 (kgf/mm 2 ) or more, or a Knoop hardness Hk of 600 (kgf/mm 2 ) or more.
6. The substrate for a magnetic disk according to claim 1 ,
wherein a chamfered face is formed on at least an outer circumferential end face of the substrate, and
a width W 1 of the chamfered face in a radial direction of the substrate is 120 μm or less.
7. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 6 is provided with at least a magnetic film.
8. A hard disk drive comprising:
the substrate for a magnetic disk according to claim 7 .
9. The substrate for a magnetic disk according to claim 1 , wherein a ratio of a value obtained by multiplying, by 2, a width W 2 of the chamfered face in a thickness direction of the substrate to the thickness T, namely (2·W 2 )/T is 0.4 or less.
10. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 9 is provided with at least a magnetic film.
11. A hard disk drive comprising:
the substrate for a magnetic disk according to claim 10 .
12. The substrate for a magnetic disk according to claim 1 , wherein a material of the substrate has a Q-value of 1500 or less under conditions of 3000 Hz and room temperature.
13. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 12 is provided with at least a magnetic film.
14. A hard disk drive comprising:
the substrate for a magnetic disk according to claim 13 .
15. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 1 is provided with at least a magnetic film.
16. A hard disk drive comprising:
the substrate for a magnetic disk according to claim 15 .
17. The substrate for a magnetic disk according to claim 1 , wherein
a material of the substrate has a Young's modulus E of 90 GPa or more.
18. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 17 is provided with at least a magnetic film.
19. The substrate for a magnetic disk according to claim 1 , wherein
the non-magnetic metal substrate is an aluminum alloy substrate that has a surface with which an alloy film including Ni and P is provided.
20. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 19 is provided with at least a magnetic film.