Magnetic-disk substrate and magnetic disk

Patent metadata

Field	Value
Publication number	US-11587585-B2
Application number	US-202117364730-A
Country	US
Kind code	B2
Filing date	Jun 30, 2021
Priority date	Aug 29, 2012
Publication date	Feb 21, 2023
Grant date	Feb 21, 2023

Abstract

A magnetic-disk substrate has an average value of squares of inclinations that is 0.0025 or less, and a frequency at which squares of inclinations are 0.004 or more is 15% or less, in a case where samples of inclinations on a main surface are obtained at intervals of 10 nm. The main surface is configured to receive at least a magnetic recording layer thereon. The magnetic-disk substrate includes an outer circumferential end portion and an inner circumferential end portion, and the outer circumferential end portion and the inner circumferential end portion have chamfered portions.

First claim

What is claimed is:

1. A magnetic-disk substrate in which an average value of squares of inclinations is 0.0025 or less and a frequency at which squares of inclinations are 0.004 or more is 15% or less, in a case where samples of inclinations on a main surface are obtained at intervals of 10 nm,
the main surface is configured to receive at least a magnetic recording layer thereon,
the magnetic-disk substrate includes an outer circumferential end portion and an inner circumferential end portion, and
the magnetic-disk substrate is configured to constitute a magnetic disk of a perpendicular magnetic recording system.

2. The magnetic-disk substrate according to claim 1 ,
wherein the frequency at which squares of inclinations are 0.004 or more is 10% or less.

3. The magnetic-disk substrate according to claim 1 ,
wherein an arithmetic average roughness of the main surface is 0.15 nm or less.

4. The magnetic-disk substrate according to claim 1 , wherein
an RMS (Rq) value that is calculated as a roughness in a wavelength bandwidth of 100 μm to 500 μm on the main surface is 0.5 nm or less.

5. The magnetic-disk substrate according to claim 1 ,
wherein the magnetic-disk substrate is configured as a substrate of a magnetic disk for energy-assisted magnetic recording.

6. The magnetic-disk substrate according to claim 1 ,
wherein the magnetic-disk substrate is made of glass.

7. The magnetic-disk substrate according to claim 6 ,
wherein the glass has a glass-transition temperature of 650° C. or more.

8. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 1 .

9. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 2 .

10. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 3 .

11. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 4 .

12. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 5 .

13. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 6 .

14. A magnetic disk having at least the magnetic recording layer formed on the main surface of the magnetic-disk substrate according to claim 7 .

15. The magnetic disk according to claim 8 ,
wherein the magnetic disk has a linear recording density of at least 2000 kbpi.

16. The magnetic disk according to claim 8 ,
wherein the magnetic disk further includes a soft magnetic layer formed on the main surface of the magnetic-disk substrate, and
the soft magnetic layer has a thickness of 30 nm or less.

17. The magnetic disk according to claim 9 ,
wherein the magnetic disk further includes a soft magnetic layer formed on the main surface of the magnetic-disk substrate, and
the soft magnetic layer has a thickness of 30 nm or less.

18. The magnetic disk according to claim 10 ,
wherein the magnetic disk further includes a soft magnetic layer formed on the main surface of the magnetic-disk substrate, and
the soft magnetic layer has a thickness of 30 nm or less.

19. The magnetic disk according to claim 11 ,
wherein the magnetic disk further includes a soft magnetic layer formed on the main surface of the magnetic-disk substrate, and
the soft magnetic layer has a thickness of 30 nm or less.

20. The magnetic disk according to claim 12 ,
wherein the magnetic disk further includes a soft magnetic layer formed on the main surface of the magnetic-disk substrate, and
the soft magnetic layer has a thickness of 30 nm or less.

Assignees

• Itaya Masanobu
• Osakabe Kinobu
• Takizawa Toshio
• Hoya Corp
• Hoya Glass Disk Vietnam Ii Ltd

Inventors

• Itaya Masanobu
• Osakabe Kinobu
• Takizawa Toshio

Classifications

• G11B5/82 Primary

  Disk carriers · CPC title

• G11B5/73921

  Glass or ceramic substrates · CPC title

• G11B5/667

  including a soft magnetic layer · CPC title