# US 5,705,234 A · Method for manufacturing magnetic hard disk

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- Number: US 5,705,234 A
- Document ID: US5705234A
- Status: Granted
- Kind: A
- Application number: 08/779,630
- Filed: 1997-01-07
- Granted: 1998-01-06
- Earliest claimed: 1996-08-26
- Assignees: Nihon Micro Coating Co., Ltd.
- Inventors: Motokazu Yamamoto; Noriko Nakamura
- Web page: https://patentgrep.com/patent/US5705234A

## CPC

- G11B 5/8404: {manufacturing base layers}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

An object of the present invention is to provide a method for manufacturing a magnetic hard disk wherein a magnetic material layer adhered on a surface of a substrate of the magnetic hard disk has a flat surface. A method for manufacturing a magnetic hard disk comprising steps of: structurally transforming a surface of an amorphous Ni--P alloy film layer formed a substrate (10) of the magnetic hard disk; and adhering a magnetic material layer on the surface of a substrate (10), wherein the step of structurally transforming the a-Ni--P alloy film layer is a step of heating only a desired portion of the surface of the substrate (10) by an electric discharge to generate Ni and crystallized compounds of Ni and P only at the desired portion (T) of the surface thereof. The electric discharge in the step of structurally transforming the a-Ni--P alloy film layer is carried out by applying a discharge potential between at least one electric discharger (11) and a metallic table (12) as an electrode which carries the substrate (10) thereon, the electric discharger (11) being positioned in opposite to the surface of the substrate (10).

## Claims

### Claim 1

A method for manufacturing a magnetic hard disk comprising steps of:
(1) structurally transforming a surface of a film layer made of an amorphous Ni--P alloy and formed a surface of a substrate of said magnetic hard disk, wherein said step of structurally transforming said surface of said film layer is a step of heating only a desired portion of said surface of said substrate by an electric discharge to generate Ni and crystallized compounds of Ni and P only at said desired portion of said surface; and
(2) adhering a magnetic material layer on said surface of said substrate.

### Claim 2 (depends on 1)

A method of claim 1 wherein said electric discharge in said step of structurally transforming said surface of said film layer is carried out by applying a discharge potential between at least one electric discharger and a metallic table as an electrode which carries said substrate thereon, said electric discharger being positioned opposite to said surface of said substrate.

### Claim 3 (depends on 2)

A method of claim 2 wherein said discharge potential in said step of structurally transforming said surface of said film layer is created by D.C. voltage, A.C. voltage or a superposed voltage of D.C. voltage and A.C. voltage.