JPS639049A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obviate the generation of cracks in a recording layer and the generation of exfoliation between respective layers by using specific silicon oxide to form an under coat layer in contact with a substrate. CONSTITUTION:The under coat layer 2c consisting of SiO1+x (where 0<x<1) is formed on the substrate 1a consisting of plastic (e.g.; polycarbonate). The under coat layer 2b consisting of a ZnS film, etc., the recording layer 3 consisting of a GdTbFe film or the like, a spacer layer 4, a reflective layer 5 and a protective layer 6 are successively laminated on the layer 2c. A substrate 1b for protection is stuck by an adhesive agent 7 on the surface of the layer 6. The recording medium with which cracks and exfoliation are hardly generated is thereby obtd. and the environmental resistance of the recording medium for which the plastic substrate in particular is used is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical recording medium capable of recording and reproducing information using a light beam, and particularly relates to a magneto-optical recording medium having a magneto-optical recording layer. be.

(Prior Art) Conventionally, optical recording media used in optical discs include thin films of rare earth-transition metal alloys, thin films of continuous oxides such as chalcogen compounds that utilize phase transition from amorphous to crystalline, Heat mode recording media, thermoplastic recording media, etc. are known. For example, as a magneto-optical recording medium formed of a rare earth-aB gold metal alloy thin film, MnB1.
Polycrystalline thin films such as MnCuB1, GdCo, GdFe
, TbFe, DyFe, GdTbFe, TbDy
Amorphous thin films such as Fe, GdFeCo, TbFeCo, and GdTbCo, and single crystal thin films such as Gd1G are known.

Among these thin films, the film forming performance when producing a large-area thin film at a temperature near room temperature, the writing efficiency for writing signals with small photothermal energy, and the S
Considering readout efficiency etc. to read out with good /N ratio,
Recently, planar amorphous thin films are considered to be excellent for use in magneto-optical recording media. In particular, (+dTbFe), which has a Curie temperature of about 150 to 200°C, and GdTbFe, which has a large Kerr rotation angle and excellent reproduction performance (:o (Japanese Unexamined Patent Publication No. 1986-196639)), are used for magneto-optical recording media. I am a connoisseur.

However, in general, amorphous magnetic materials used in magneto-optical recording media, such as the above-mentioned GdTbFe, have a drawback of poor corrosion resistance. In other words, when it comes into contact with air or water vapor, its magnetic properties deteriorate, and eventually it becomes completely oxidized, becomes transparent, and loses its magnetic properties.

In order to eliminate such defects, for example, SiO
Magneto-optical recording media have been proposed that are provided with various functional layers such as undercoat layers and protective layers made of transparent materials such as , Si3N4, and 2nS. Among these substances, ZnS
Because of its excellent corrosion resistance, it is widely used as an undercoat layer or protective layer of the above-mentioned magneto-optical recording media. however,
Since ZnS lacks adhesion to hygroscopic substrates such as plastic, magneto-optical recording media using such substrates are prone to cracks in the magneto-optical recording layer and peeling between layers. there were. In particular, under the environmental conditions adopted as a durability evaluation method for such magneto-optical recording media, for example, under high temperature and high humidity conditions such as a temperature of 45°C and a relative humidity of 95%, racks and peeling may occur as described above. Problems were inevitable.

In order to solve this problem, multiple undercoat layers are used, such as providing an undercoat layer made of SiO, which has excellent adhesion to the substrate, on the substrate, and then providing an undercoat layer made of ZnS on top of it. Attempts have also been made to improve durability by changing the layer structure.

FIG. 2 shows an example of such a conventional magneto-optical recording medium.

This magneto-optical recording medium has Si on the writing side substrate la.
An undercoat layer 2a made of O is provided, and an undercoat layer 2b made of ZnS is further provided thereon to form a multilayer undercoat layer. On top of this, a magneto-optical recording layer 3, a spacer layer 4, and a reflective layer are formed. 5,
After sequentially laminating the protective layer 6 and the adhesive layer 7, the protective substrate 1b
It is formed by adhesion.

However, even with this, under more severe environmental conditions, such as a temperature of 60°C and a relative humidity of 90%, problems with racking and peeling as described above occur, and magneto-optical recording with improved environmental resistance Media is desired.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above points, and an object of the present invention is to provide a magneto-optical recording medium that has better environmental resistance than conventional magneto-optical recording media. be.

[Means for solving problems]

The above objects of the present invention are achieved by the present invention as follows.

In a magneto-optical recording medium comprising a substrate and an undercoat layer in contact with the substrate, and having at least a magneto-optical recording layer and a protective layer on the underlayer, the undercoat layer in contact with the substrate is S.
A magneto-optical recording medium characterized by comprising in, or w (where O<x<1).

[Function] The magneto-optical recording medium of the present invention has 5I014X (where 0<
x < 1, preferably 0.4 < Furthermore, even under severe conditions such as a temperature of 60° C. and a relative humidity of 90%, the above-mentioned problems such as cracking and peeling do not occur, and it has extremely excellent environmental resistance.

Although it is not necessarily clear why such an effect can be noticed, it is presumed to be due to the following reasons. 5i(
1 and 5i02 are conventionally used as an undercoat layer or a protective layer, but SiO has the disadvantage that although it has excellent adhesion to the substrate, it lacks denseness and is inferior in antioxidation function. On the other hand, although 5i02 is denser than SiO and has an excellent anti-oxidation function, it has the disadvantage of poor adhesion to the substrate.

This is thought to be because the dangling bonds of Si, which are thought to improve the adhesion with the substrate in the thin groove, are saturated in the latter. However, the presence of such dangling bonds acts as a negative factor in terms of compactness, and is thought to reduce the moisture permeation prevention function of SiO. However, in the present invention, since the undercoat layer is composed of a composition ratio between SiO and 5i02, the excellent properties of both are fully exhibited, and it is thought that the environmental resistance of the magneto-optical recording medium is improved. It will be done.

The above Sin. Formation of an undercoat layer having a composition of
2 vacuum evaporation in an atmosphere, or SiO and 5i02
It is preferable to simultaneously evaporate or sputter them using these as starting materials.

An example of the magneto-optical recording medium of the present invention having such an undercoat layer is shown in FIG.

In FIG. 1, what is indicated by the reference numeral 20 is a substrate 1.
5iO1*x provided adjacent to a (however, 0<x<1
) is the undercoat layer. The magneto-optical recording medium of this example is
Except for providing such an undercoat layer 2C, the structure is the same as that of the conventional magneto-optical recording medium illustrated in FIG. 3 is a magneto-optical recording layer, 4 is a spacer layer, and 5 is a layer.
6 is a reflective layer, 6 is a protective layer, 7 is an adhesive layer, and lb is a protective substrate.

〔Example〕

In order to explain the present invention more specifically, Examples of the present invention are shown below.

Example 1 The magneto-optical recording medium illustrated in FIG. 1 was produced as follows.

A plastic plate made of polycarbonate with a thickness of 1.2 mm is used as the substrate 1a, and a plate with a thickness of about 1300 mm is placed on the substrate Ia.
An undercoat layer 2c made of human Sin or I (O<x<1) was formed by vacuum evaporation.

The undercoat layer 2c is formed by placing the substrate 1 in a vacuum chamber of a well-known film forming apparatus capable of performing both vapor deposition and sputtering.
After inserting the IXI
This was done by evaporating SiO as a starting material at a pressure of Q'4 Torr. At this time, when the film was formed by controlling the deposition rate so that the refractive index of the undercoat layer 2c was 1.55±0.022, 5lO
An undercoat layer 2c having a composition of I*x (x=0.8) was obtained.

Next, while maintaining the vacuum in the vacuum chamber, an undercoat layer 2b made of ZnS having a thickness of approximately 300 was formed by sputtering on the undercoat layer 2c.

Next, in the same manner as above, without breaking the vacuum in the vacuum chamber, a magneto-optical recording layer 3 made of GdTbFe with a thickness of approximately 150 mm was formed on the undercoat layer 2b by high frequency sputtering.

Hereinafter, by sputtering similar to the above without breaking the vacuum, ZnS with a thickness of 300 and S with a thickness of approximately 1100 were prepared.
A spacer layer 4 made of iO, a reflective layer 5 made of At about 800 thick, and a protective layer 6 made of SiO about 2800 thick were successively formed.

After that, the substrate 1a on which each of the above layers was formed was taken out from the vacuum chamber, and a hot melt adhesive was used as the adhesive layer 7.
A magneto-optical recording medium was completed by bonding it to a protective plastic substrate 1b.

The magneto-optical recording medium thus obtained was kept in a constant temperature and humidity chamber at a temperature of 60°C and a relative humidity of 90% and subjected to an environmental resistance test for 1000 hours.
No particular changes in appearance were observed even after the passage of time, and no cracks or peeling of the film occurred, indicating that it has unprecedented environmental resistance.

Example 2 02 for undercoat layer 2c film formation was 2 x 10'4 each.
Torr and 8 x to STorr, but in the same manner as in Example 1, the undercoat layer 2c was 5101+X
(However, x = 0.85) and Sin, □ (However,
Magneto-optical recording media each having a composition of x=0.7) were obtained.

When these magneto-optical recording media were subjected to the same environmental resistance test as in Example 1, no cracks or peeling of the film were observed in any case even after 1000 hours as in Example 1, indicating that they had excellent environmental resistance. It had a sexual nature.

Comparative Example The starting materials were SiO and 5i02, respectively, and Si
A magneto-optical recording medium having the conventional structure illustrated in FIG. 2 and having an undercoat layer 2a made of O and 5i02 was obtained.

When these magneto-optical recording media were subjected to the same environmental resistance test as in Example 1, it was found that the one with the undercoat layer 2a made of SiO was tested after 300 hours, and the one with the undercoat layer 2a made of SiO□ was tested after 400 hours. Membrane peeling and cracking occurred after passage.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a magneto-optical recording medium with significantly improved environmental resistance compared to the conventional one. In particular, it is possible to improve the environmental resistance of a magneto-optical recording medium using a plastic substrate, which otherwise has low environmental resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of the magneto-optical recording medium of the present invention;
FIG. 2 is a schematic cross-sectional view of an example of a conventional magneto-optical recording medium. 18%lb--Substrate 2a, 2b, 2c--Undercoat layer 3--Magneto-optical recording layer 4--Spacer layer 5--Reflection layer 6--Protective layer 7--Adhesive layer

Claims (1)

[Claims] (1) A magneto-optical recording medium comprising a substrate and an undercoat layer in contact with the substrate, and having at least a magneto-optical recording layer and a protective layer on the underlayer, wherein the undercoat layer in contact with the substrate A magneto-optical recording medium comprising SiO_1_+_x (0<x<1).