JPH0469829A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To improve signal quality and reliablity by forming a spacer layer of a specified structure. CONSTITUTION:On a PC substrate, there are formed a SiO2 film as the first thin film layer by sputtering to 300 - 1000Angstrom thickness, ZnSe film as the second thin film layer by sputtering to 100 - 600Angstrom , and further SiN or AlN film as the third thin film layer to 200 - 800Angstrom thickness. A TbFeCo film is formed as the recording film by sputtering with using an alloy target, and then a SiN film is again formed as a protective film. The refractive index of the SiO2 film is specified to 1.40 - 1.55. Thereby, the signal quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a medium configuration of a magneto-optical disk.

[Prior art] Using a polycarbonate (hereinafter abbreviated as PC) substrate,
In magneto-optical disks whose recording film is an amorphous rare earth-transition metal film, SiN is used between the PC board and the recording film.
,Aj! A nitride film such as N is formed (this layer is referred to as a spacer layer).

The reason why nitride films are used is that the refractive index of these materials is 2.
It is large compared to oxides such as SiO2 at the front and back, and can optically enhance the Kerr effect. It also blocks moisture and oxygen that reach the recording film through the PC board and cause corrosion of the recording film. This is because it is stable and does not decompose or react with the recording film or PC board, so it has favorable characteristics in terms of optical performance and reliability.

However, in recent years, there has been a desire to further improve the performance of magneto-optical disks, and one method for achieving this is to use a material with a higher refractive index than the conventional nitride as a material for the spacer layer. For example, ZnS, ZnSe, or chalcogen glass has a large refractive index of 2.3 or more, so if these are used in place of a nitride film, the C/H will increase by roughly 1 to 3 dB compared to a nitride film. can get.

[Problems to be Solved by the Invention] However, ZnS, ZnSe, or chalcogen glass has poor chemical stability, and therefore has a problem of poor reliability under high temperature and high humidity conditions.

The present invention was made in view of these conventional circumstances, and takes advantage of the high reliability of nitride films and the high refractive index of zns, znSe, or chalcogen glass.
It is an object of the present invention to provide a magneto-optical disk having a spacer layer that is highly reliable and optically excellent.

[Means for Solving the Problems] The present invention provides a magneto-optical disk in which the substrate is a polycarbonate substrate having pregrooves and the recording film is a rare earth-transition metal based amorphous thin film. This is a magneto-optical disk characterized in that thin films consisting of the following three layers are successively deposited.

■A film is formed on the substrate to a thickness of 300 to 1000 A, and S
The first thin film layer is made of a composite oxide mainly composed of i 02 or SiO2 and has a refractive index of 1.40 to 1.55.

(2) A second thin film layer formed on the first thin film layer to a thickness of 100 to 600 mm and made of ZnS, Zn5e or chalcogen glass.

■A film is formed on the second thin film layer to a thickness of 200 to 800 layers, and is made of SiN or AI! A third thin film layer made of N.

[Effect 1 In the present invention, the first thin film layer made of a composite oxide mainly composed of 5i02 or 3102 has a refractive index almost equal to that of the substrate, and can be optically considered to be included in the substrate. . This first thin film layer has greater mechanical strength than a chalcogen compound, and not only reinforces this, but also provides strong adhesion to the substrate. The thickness of the film is 300 to 100 mm. If the film thickness is less than 300 Å, the strength will be insufficient, which is undesirable, and if it is thicker than 1000 Å, it will be vulnerable to sudden changes in temperature and humidity.
Limited to: It is also chemically stable against PC boards and chalcogen compounds, and has high reliability over time.

On the other hand, since the portion in contact with the rare earth-transition metal recording film is a nitride film, which is the third thin film layer, the reliability of the recording film is extremely high. Furthermore, the second thin film layer, chalcogen compounds and nitride film, forms a so-called optical multilayer film, and can be designed to behave as if it were a single film with a high refractive index, allowing signal Quality can be improved.

The thickness of the chalcogen compound layer and the nitride film layer is limited by this condition.

[Example] Next, embodiments of the present invention will be described in detail.

500 people formed a 3i02 film containing 20 mol % of ZnO2 on a PC substrate by sputtering. Next, Zn5e was added to 5
It was formed by a 00 person sputtering method. Furthermore, 300 SiN
Formed a person. The recording film was a TbFeC0 film formed by 800 people by sputtering using an alloy target. 800 layers of SiN were again formed as a protective film. zn-containing SiO2
The refractive index of the film was 1.55.

As a comparative example, a disk with a single spacer layer of 800 SiN was also fabricated.

The signal quality of the disc of this example and the disc of the comparative example is
Recording was performed at a linear velocity of 11.3 m/s and a frequency of 7.5 MHz for comparison. In this example, C/849 dB was obtained, and in the comparative example, C/N 46 dB was obtained. 3d
It was confirmed that there is an improvement effect of B.

In this embodiment, an example using a recording film consisting of a single recording layer has been described, but the present invention is not limited to this. When the recording film is, for example, a two-layer film combining GdFeCO and TbFe, Al-IHA T b Fe
This effect can also be obtained in the case of a so-called overridable exchange coupling film made of Co/Gd Fe Co/Gd T b FeCo, etc., and the signal quality can be improved.

[Effects of the Invention] As explained above, the magneto-optical disk according to the present invention has the following advantages:
By having the spacer layer in a predetermined configuration, signal quality is improved and reliability is excellent.

Claims (1)

[Claims] (1) In a magneto-optical disk in which the substrate is a polycarbonate substrate with pregrooves and the recording film is a rare earth-transition metal-based amorphous thin film, between the substrate and the recording film, a thin film consisting of the following three layers is sequentially formed. A magneto-optical disk characterized in that a film is formed. [1] A film is formed on the substrate to a thickness of 300 to 1000 Å,
The first thin film layer is made of SiO_2 or a composite oxide mainly composed of SiO_2 and has a refractive index of 1.40 to 1.55. [2] A second thin film layer formed on the first thin film layer to a thickness of 100 to 600 Å and made of ZnS, ZnSe, or chalcogen glass. [3] A third thin film layer formed on the second thin film layer to a thickness of 200 to 800 Å and made of SiN or AlN.