JPH02195543A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a magneto-optical recording medium and to obtain stable magnetic characteristics for a long period by incorporating at least one element from Cr, Mn, V, Zr, Mo, Ta, W and Hf by 0.3-10 atomic% into the metal component of the magneto-optical disk having a protective metal film or a reflecting metal film. CONSTITUTION:At least one element from Cr, Mn, V, Zr, Mo, Ta, W and Hf is incorporated by 0.3-10 atomic% into the metal component such as Al, Bi and Pb used for the protective metal film or the reflecting metal film. Addition of the metal produces an passivated film formed on the surface of the metal film to prevent corrosive material such as oxygen from intruding into the metal film itself, and consequently prevent from intruding into the magneto-optical recording film. Thus, the obtd. medium has stable magnetic characteristics for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical disk, particularly a magneto-optical disk having a novel protective metal film or reflective metal film.

[Conventional technology]

Magneto-optical disks, in which information is recorded, reproduced, and erased by irradiating a light beam onto a magneto-optical recording medium layer, can record rewritable information at high density, so they are expected to find wide use in a variety of fields. ing.

Conventionally, the structure of this type of magneto-optical disk is to protect the magneto-optical recording medium described below as a first layer on a transparent substrate made of a transparent polymer material such as glass, polycarbonate, acrylic, or epoxy. The light reflected by the magneto-optical recording medium film in the information reading light is internally multiple reflected (interfered) to increase the apparent Kerr concavity angle of the readout reflected light and improve the reproduction C7N ratio (enhancement effect). ), AIN,, dielectric film such as TaO, SiO, SiN, Tb-Fe system, Tb- as the second layer.
A magneto-optical recording medium film made of Fe-Co type film or the like having a film thickness thicker than 350 mm, a metal film such as Al or triSpb which protects the magneto-optical recording medium as 3N, and a transparent substrate. , the first layer is a dielectric film that protects the magneto-optical recording medium described later; the second layer is a magneto-optical recording medium film having a thickness of 350 Å or less; and the third layer is a magneto-optical recording medium that protects the magneto-optical recording medium and this film. The information readout light that has passed through is subjected to multiple reflections (interference) between this film and the metal film described later, increasing the apparent Faraday rotation angle of the readout reflected light and improving the reproduction C/N ratio (enhancement effect). ) A dielectric film and a metal film formed as the fourth layer are known as the most promising ones from the viewpoint of providing a magneto-optical disk that is sufficiently suitable for practical use.

However, in the magneto-optical disk with the above structure,
There were problems with corrosion resistance and, ultimately, with dropout of recorded information.

[Problem to be solved by the invention]

The purpose of the present invention is to solve this problem, improve the corrosion resistance of a magneto-optical recording medium, and stabilize its magnetic properties over a long period of time, thereby providing a magneto-optical disk that is fully worthy of practical use. be.

[Means to solve the problem]

The present invention achieves the above object by including Cr, Mn, ■, Zr, Mo,
M of one or more of Ta, W and Hf is 0.3 to 1
This is a magneto-optical disk characterized in that it contains 0 atomic percent.

[For production]

In the present invention, Cr is added to a known metal such as Af, Bi, or Pb as a protective metal film or a reflective metal film.
, Mn, V, Zr, Mo, Ta, W and I
It is necessary to contain 0.3 to 10 atom % of one or more types of M among ff. By adding M, a magneto-optical disk with significantly improved corrosion resistance can be obtained. This removes corrosive substances such as oxygen from the known discs.
While easily oxidizable elements are captured in the metal film as oxides and prevented from penetrating into the magneto-optical recording medium film, in the present invention, the passive film formed on the surface of the metal film by the addition of M This is presumed to be due to the fact that the metal film does not penetrate into the metal film itself, and furthermore, does not penetrate into the magneto-optical recording medium film. This M
Even if the amount of is less than 0.3 at% or exceeds 10 at%,
Corrosion resistance is not improved sufficiently. This metal film is preferably formed to have a thickness of 200 Å or more.

If the film thickness is less than 200 mm, non-uniformity of the film due to pinholes and the like will increase, and even the addition of M will not have a sufficient effect of protecting the magneto-optical recording medium film.

As the dielectric film other than the above metal film, any one having a known composition can be used. Among these dielectric films, it is desirable that the interference film be formed to have a thickness of 200 to 1200 Å, and that the film other than the interference film be formed to have a film thickness of 200 Å or more. The film thickness as an interference film is 2
If it is less than 0.00, the non-uniformity of the film due to pinholes etc. will increase and information dropout will occur due to oxidation of the magneto-optical recording medium layer, and the effect of protecting this medium layer will be insufficient, and the enhancement effect will not be sufficient. Not demonstrated. On the other hand, if the film thickness exceeds 1,200 people, the variation in film thickness increases and the enhancement effect cannot be used effectively. If the thickness of the film other than the interference film is less than 200 mm, non-uniformity of the film due to pinholes etc. will increase and a sufficient effect of protecting the magneto-optical recording medium film will not be obtained.

The film of each layer of the present invention can be formed by high frequency sputtering, direct current sputtering, vacuum evaporation, or the like.

〔Example〕

Examples of the present invention will be described below along with comparative examples.

Example 1 On a grooved transparent substrate of polycarbonate with a thickness of 1.2 mm,
The first layer has a composition of SiO and a film thickness of 900 mm, and then the composition of Tbo, z. Feo, tzcOo, O8,
a second N magneto-optical recording medium film with a film thickness of 300, and
A third layer having a composition of SiO and a film thickness of 250 mm,
4th layer An' with a film thickness of 600 atomic percent W added at 7 atomic %
The films were formed by a high frequency sputtering method, a direct current sputtering method, a high frequency sputtering method, and a direct current sputtering method, respectively.

The magneto-optical disk thus obtained was heated to a temperature of 75°C.
After being exposed to an atmosphere with a relative humidity of 80% for 5.1020 hours and 30 hours, the Kerr rotation angle θk was measured using a semiconductor laser with a wavelength of 830 nm. When the obtained value was expressed as a relative value to 0 for the Kerr rotation angle θ of the magneto-optical disk at an exposure time of 0, it was 1.0 for any exposure time.

Example 2.3 The fourth layer AI film was prepared by adding (1) 6 atomic % of Mo (
Example 2), (Example 3) was tested in the same manner as in Example 1, except that 21W and Mo were added at 3 atomic % each (Example 3). The time value was also 1.0.

Example 4 A first layer with a composition of SiN and a film thickness of 1000 was deposited on a polycarbonate grooved transparent substrate with a thickness of 1.2 mm, and then:
A second layer magneto-optical recording medium film with a composition of Tbo, zoFeo, qtcoo, and oa and a thickness of ■9 1000 mm, and a third layer 1 with a thickness of 1000 mm, to which 7 at% of W was added.
The films were formed by high frequency sputtering, direct current sputtering, and direct current sputtering, respectively.

The thus obtained magneto-optical disk was tested in the same manner as in Example 1. The relative values obtained were 1.0 for all exposure times.

Examples 5 and 6 To the third layer! The test was carried out in the same manner as in Example 4, except that the films were (Example 5) with 3 atomic % of each of IIW and Mo added, and 7 atomic % of 21Mn (Example 6). The relative value obtained was 1.0 for all exposure times in both Examples.

Comparative Examples 1 and 2 (1) Same as Example 1 (Comparative Example 1) except that 0.1 atomic % of W was added to the fourth layer A1 film, and
(2) The test was conducted in the same manner as in Example 4 (Comparative Example 2) except that the fourth layer A1 film was added with 15 atomic % of W.

The relative values obtained are shown in Table 1.

Table 1 [Effects of the Invention] As described above, according to the present invention, it is possible to provide a magneto-optical disk with long-term stable magnetic properties.

Patent applicant: Sumitomo Metal Mining Co., Ltd.

Claims (1)

[Claims] (1) In a magneto-optical disk having a protective metal film or a reflective metal film, the metal contains Cr, Mn, V, Zr.
, Mo, Ta, W and Hf, one or more M is 0.
A magneto-optical disk characterized by containing 3 to 10 at%.