JPS62102449A - Manufacture of optical magnetic disk - Google Patents

Abstract

PURPOSE:To delete an unnecessary magnetic domain on a disk and to improve the quality of a signal by degaussing an overall disk after a recording layer is formed on a substrate. CONSTITUTION:When a photomagnetic recording layer 2 is formed on the substrate 1 having a pregroup, writing a bit 4 generates a medium noise due to the existence of a small magnetic domain 3 if no processing is made. Accordingly a 10KOe magnetic field is applied to the overall disk to degauss. Thus the unnecessary magnetic domain 3 on the disk surface is eliminated to improve the quality of a signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical disk, and more particularly to a method of manufacturing a medium with excellent signal quality.

[Conventional technology]

In conventional magneto-optical recording media, the recording layer is formed by vapor deposition or sputtering, and then subjected to magnetic treatment.

However, as shown in FIG. 1, the magneto-optical recording layer 2 formed on the one pregroup substrate 1 is asdepo.

(as formed), a small magnetic domain 3 existed, and when bit 4 was written on top of this, the medium noise was large.

There is also a method of demagnetizing only the inside of the pre-group using a laser beam, but this method has not been able to sufficiently reduce noise.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate unnecessary magnetic domains by demagnetizing the magneto-optical disk before using it, and to achieve a high C.
/H disc.

[Effect]

By demagnetizing the entire surface of the magneto-optical disk, a disk with a high C/N can be obtained.

There are two methods for demagnetizing the entire disk: one is to demagnetize the entire disk at once, and the other is to demagnetize the entire disk by rotating and moving the disk while partially demagnetizing it.

[Example] The procedure for producing an optical disk medium is shown below. A PMMA substrate with spiral pre-groups is mounted in a vacuum evaporator. The diameter of this board is 20cy.

The thickness is 1. It is z10+. After evacuating the inside of the evaporator and making the vacuum level 6×10”Pa, electron beam evaporation was performed to deposit n and F.
e8゜Co,. was codeposited. Board rotation speed 10100
TbFe to a thickness of 100 nm at rp'rb deposition rate 0.3 nm/s, 'l'eco deposition rate 0, dnm/s.
A Co film was deposited.

The medium thus produced is taken out and written with a laser.

The writing laser power is 4mW, the disk rotation speed is 900rpm, and the recording frequency is
The 1.0MHz bias magnetic field is 40
It is 00e.

(1) First, for disks that are not demagnetized at all, C/N4
It was 0dB.

(2) When DC erase was performed using only laser light, the C/N was improved by about 4 dB to 44 dB. but,
The C/N value is insufficient. A laser cannot erase magnetic domains between groups.

(3) Next, when writing was performed after demagnetizing the entire disk by applying a magnetic field of 10 KOe, the noise level decreased to a sufficient value of C/N 50 dn.

By applying the method of the present invention to demagnetize the disk by applying a magnetic field, the magnetic domains that existed from the time of vapor deposition are removed, resulting in a reduction in noise.

〔Effect of the invention〕

According to the present invention, unnecessary magnetic domains existing on the disk surface can be erased, and signal quality can be improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of magnetic domains on a magneto-optical recording disk. 1; Substrate having pregroup, 2: Magneto-optical recording film, 3
: Magnetic domain existing during film formation, 4: Bit.

Claims (1)

[Claims] 1. A method for manufacturing a magneto-optical disk, which comprises forming a recording layer on a substrate and then demagnetizing the entire magneto-optical disk.