Substrate for magnetic disk and magnetic disk
A substrate for a magnetic disk has a disk shape. 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 ).
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,
regarding a Young's modulus E and the thickness T of the substrate, a value of E·T 3 is 3 to 18 (GPa·mm 3 ), and
a material of the substrate has a Q-value of 1500 or less under conditions of 3000 Hz and room temperature.
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. 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.
5. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 4 is provided with at least a magnetic film.
6. 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.
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 magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 1 is provided with at least a magnetic film.
9. A hard disk drive comprising:
the magnetic disk according to claim 8 .
10. The substrate for a magnetic disk according to claim 1 , wherein
the substrate is a non-magnetic metal substrate, and
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.
11. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 10 is provided with at least a magnetic film.
12. 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,
regarding a Young's modulus E and the thickness T of the substrate, a value of E·T 3 is 3 to 18 (GPa·mm 3 ), and
a material of the substrate has a ρ·(1−v) 2 ·Q/E value of less than 25 (g/cm 3 /GPa), where ρ represents a density (g/cm 3 ) of the material at room temperature, Q represents a Q-value of the material under conditions of 3000 Hz and room temperature, E represents a Young's modulus (GPa) of the material at room temperature, and v represents a Poisson's ratio of the material at 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 magnetic disk according to claim 13 .
15. The substrate for a magnetic disk according to claim 12 , 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.
16. A magnetic disk,
wherein a surface of the substrate for a magnetic disk according to claim 15 is provided with at least a magnetic film.
17. The substrate for a magnetic disk according to claim 12 , 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 12 , wherein
the substrate is a non-magnetic metal substrate, and
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.