Method of manufacturing substrate for magnetic disk, apparatus for manufacturing substrate for magnetic disk, and method of manufacturing magnetic disk

• US 7,175,511 B2
• Filed: 07/09/2004
• Issued: 02/13/2007
• Est. Priority Date: 07/15/2003
• Status: Expired due to Fees

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Ueda, Masaaki, Kashima, Ryuichi
• Primary Examiner(s): Wilson; Lee D.
• Assistant Examiner(s): Ojini; Anthony
• Application Number:
  US10/542,803
• Publication Number:
  US 20060148386A1
• Time in Patent Office: 949 Days
• Field of Search: 451/11, 451/41, 451/21, 451/37, 451/42, 451 53- 55, 451/60, 451/63, 451/259, 451285-290, 451/283, 451/364, 451/384, 451/397, 451/402, 252/62.52, 51307-309
• US Class Current: 451/63
• CPC Class Codes: G11B 5/8404 manufacturing base layers

Abstract

A magnetic polishing method capable of easily and satisfactorily polishing the inner peripheral end face of a circular hole (1) at the center part of a disk substrate (2) even if the diameter of the circular hole is reduced. By this method, a large quantity of disk substrates with stable quality can be supplied, thermal asperity trouble and head crush can be prevented from occurring on a magnetic disk, and the density of the information recording surface of the magnetic disk can be increased. In the method for polishing the inner peripheral end face of the circular hole (1) at the center part of the disk substrate (2), a magnetic field is formed on the inner peripheral side of the circular hole (1), abrasive materials (4) including magnetic particles and abrasive grains are held by the magnetic field in the circular hole, and the magnetic field is moved to the inner peripheral end face of the circular hole (1) to move the abrasive materials (4) to the inner peripheral end face of the circular hole (1) for polishing the inner peripheral end face of the circular hole (1).

Claims

1. A method of manufacturing a substrate for a magnetic disk, having a step of polishing at least an end face on an inner peripheral side of a circular hole of a nonmagnetic disk substrate having the circular hole at a center portion thereof, wherein:

the end face on the inner peripheral side of the circular hole is polished by magnetic abrasive finishing in which a magnetic field is formed at least on the inner peripheral side of the circular hole, an abrasive material containing magnetic particles and abrasive particles is held in the circular hole by the magnetic field and, by moving the magnetic field with respect to the end face on the inner peripheral side of the circular hole, the abrasive material is moved with respect to the end face on the inner peripheral side of the circular hole to thereby polish the end face on the inner peripheral side of the circular hole.

2. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the abrasive material in which the magnetic particles and the abrasive particles are integrated with each other is used in the magnetic abrasive finishing.

3. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the magnetic particles contained in the abrasive material are ferrite-based magnetic particles.

4. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the abrasive particles contained in the abrasive material are cerium oxide abrasive particles, colloidal silica abrasive particles, alumina abrasive particles, or diamond abrasive particles.

5. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the abrasive material is formed into a slurry by adding a liquid so as to use the abrasive particles as free abrasive particles.

6. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the magnetic abrasive finishing is performed by disposing a magnet in the circular hole and using a magnetic field formed by the magnet.

7. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the magnetic abrasive finishing is performed by disposing a magnet on an outer peripheral side of the nonmagnetic disk substrate and using a magnetic field formed by the magnet.

8. A method of manufacturing a substrate for a magnetic disk according to claim 6, wherein:

a rare earth-based permanent magnet or an electromagnet is used as the magnet.

9. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

the nonmagnetic disk substrate is a glass disk substrate.

10. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

a plurality of nonmagnetic disk substrates are concentrically placed in layers and end faces on the inner peripheral side of circular holes of the nonmagnetic disk substrates are simultaneously polished.

11. A method of manufacturing a substrate for a magnetic disk according to claim 1, wherein:

a chamfered face provided at an end face portion on the inner peripheral side of the nonmagnetic disk substrate is polished by the magnetic abrasive finishing.

12. A method of manufacturing a magnetic disk, wherein:

at least a magnetic layer is formed on a main surface portion of the substrate for the magnetic disk manufactured by a method of manufacturing a substrate for a magnetic disk according to claim 1.

13. An apparatus for manufacturing a substrate for a magnetic disk, comprising:

retaining means for retaining a nonmagnetic disk substrate having a circular hole at a center portion thereof,

magnetic field forming means for forming a magnetic field at least on an inner peripheral side of the circular hole of the nonmagnetic disk substrate, and

magnetic field rotation means for rotating the magnetic field with respect to an end face on the inner peripheral side of the circular hole,

wherein an abrasive material containing magnetic particles and abrasive particles is held in the circular hole at the center portion of the nonmagnetic disk substrate by the magnetic field formed by the magnetic field forming means and, by rotating the magnetic field with respect to the end face on the inner peripheral side of the circular hole by the magnetic field rotation means, the abrasive material is rotated with respect to the end face on the inner peripheral side of the circular hole to thereby polish the end face on the inner peripheral side of the circular hole.

14. An apparatus for manufacturing a substrate for a magnetic disk according to claim 13, wherein:

at least part of the retaining means is made of an insulating material.