Magnetic-disk glass substrate and magnetic disk

Patent metadata

Field	Value
Publication number	US-2017194025-A1
Application number	US-201715467492-A
Country	US
Kind code	A1
Filing date	Mar 23, 2017
Priority date	Sep 28, 2012
Publication date	Jul 6, 2017
Grant date	—

Abstract

A magnetic-disk glass substrate according to the present invention is a doughnut-shaped magnetic-disk glass substrate having a circular hole provided in the center, a pair of main surfaces, and an outer circumferential end surface and an inner circumferential end surface each including a side wall surface and a chamfered surface that is formed between each main surface and the side wall surface. A measurement point is provided on the outer circumferential end surface every 30 degrees in the circumferential direction with reference to a center of the glass substrate, and when a curvature radius of a shape of a portion between the side wall surface and the chamfered surface is determined at each measurement point, the difference in the curvature radius between neighboring measurement points is 0.01 mm or less.

First claim

What is claimed is:

1 . A magnetic-disk substrate for use as a magnetic disk, the magnetic-disk substrate comprising:
a pair of main surfaces, an arithmetic mean roughness for wavelength components of 10 to 50 nm of a surface of the main surfaces being 0.15 nm or less when an area of 1 μm square is divided into sections of 512 by 512 and each section is measured using an atomic force microscope, there is no texture in a circumferential direction on the main surfaces, and micro-waviness (Rq) for a wavelength band of 100 to 500 μm in the surface of the main surfaces is 0.5 nm or less.

2 . A magnetic-disk substrate for use as a magnetic disk, the magnetic-disk substrate comprising:
a pair of main surfaces, an arithmetic mean roughness for wavelength components of 10 to 30 nm of a surface of the main surfaces being 0.12 nm or less when an area of 1 μm square is divided into sections of 512 by 512 and each section is measured using an atomic force microscope, there is no texture in a circumferential direction on the main surfaces, and micro-waviness (Rq) for a wavelength band of 100 to 500 μm in the surface of the main surfaces is 0.5 nm or less.

3 . A magnetic-disk substrate for use as a magnetic disk, the magnetic-disk substrate comprising:
a pair of main surfaces, an arithmetic mean roughness of a surface of the main surfaces when an area of 1 μm square is divided into sections of 512 by 512 and each section is measured using an atomic force microscope being 0.15 nm or less when a wavelength band is not specified, the arithmetic mean roughness of the surface of the main surfaces when wavelength components of 10 to 20 nm are extracted being 0.10 nm or less, there is no texture in a circumferential direction on the main surfaces, and micro-waviness (Rq) for a wavelength band of 100 to 500 μm in the surface of the main surfaces is 0.5 nm or less.

4 . The magnetic-disk substrate according to claim 1 , wherein
in addition to the arithmetic mean roughness for wavelength components of 10 to 50 nm of the surface of the main surfaces being 0.15 nm or less, the arithmetic mean roughness of the surface of the main surfaces is 0.15 nm or less when a wavelength band is not specified.

5 . The magnetic-disk substrate according to claim 2 , wherein
in addition to the arithmetic mean roughness for wavelength components of 10 to 30 nm of the surface of the main surfaces being 0.12 nm or less, the arithmetic mean roughness of the surface of the main surfaces is 0.15 nm or less when a wavelength band is not specified.

6 . The magnetic-disk substrate according to claim 1 , configured for use as a magnetic disk for energy-assisted magnetic recording.

7 . The magnetic-disk substrate according to claim 1 , configured for use as a magnetic disk which has a linear recording density of at least 2000 kbpi.

8 . The magnetic disk according to claim 1 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

9 . The magnetic disk according to claim 6 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

10 . The magnetic disk according to claim 7 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

11 . The magnetic-disk substrate according to claim 2 , configured for use as a magnetic disk for energy-assisted magnetic recording.

12 . The magnetic-disk substrate according to claim 2 , configured for use as a magnetic disk which has a linear recording density of at least 2000 kbpi.

13 . The magnetic disk according to claim 2 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

14 . The magnetic disk according to claim 11 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

15 . The magnetic disk according to claim 12 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

16 . The magnetic-disk substrate according to claim 3 , configured for use as a magnetic disk for energy-assisted magnetic recording.

17 . The magnetic-disk substrate according to claim 3 , configured for use as a magnetic disk which has a linear recording density of at least 2000 kbpi.

18 . The magnetic disk according to claim 3 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

19 . The magnetic disk according to claim 16 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

20 . The magnetic disk according to claim 17 , further comprising
at least a magnetic layer formed on the surface of at least one of the main surfaces of the magnetic-disk substrate.

Assignees

• Hoya Corp

Inventors

• Itaya Masanobu
• Osakabe Kinobu

Classifications

• G11B5/739

  Magnetic recording media substrates · CPC title

• C23C14/35

  by application of a magnetic field, e.g. magnetron sputtering {(C23C14/3457 takes precedence)} · CPC title

• G11B5/7315 Primary

  Physics · mapped topic

• G11B5/73921 Primary

  Glass or ceramic substrates · CPC title