JPH07182711A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a protective film which completely shuts off a magnetic layer and an external world, has good affinity to the magnetic layer and a synthetic resin substrate and is effective by providing the surface of a substrate with a protective layer contg. a Ta oxide, then providing the surface thereof with the magnetic layer. CONSTITUTION:An amorphous magnetic alloy of rare earths and transition metals, such as DyFeCo, and a polycrystalline perpendicularly magnetized film, such as MnBi, are used on the substrate consisting of glass or acrylic resin. a Ta oxide is formed as the protective film between the substrate and the magneto-optical active layer. The multi component oxide protective layer has excellent transparency and refractive index and is, therefore, disposed on a light incident side. There is a need for disposing the protective layer between the substrate and the magnetic layer as well in the case of the synthetic resin substrate. The protective film is formed by sputtering a Ta metal target in O2 and inert gas. The gaseous pressure is set as low as about 4m Torr. Next, the surface is bombarded by high-energy particles (K.E of 1 to 100eV) to reform the boundary state between the Ta oxide and the magnetic layer, etc. The magneto-optical recording medium having excellent corrosion resistance, recording sensitivity quality and productivity is obtd. by this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magneto-optical medium suitable for magneto-optical recording.

[0002]

2. Description of the Related Art Among the optical memory devices, an erasable type memory capable of additional recording and erasing is in a stage where the magneto-optical recording system is the most practical.
As a magneto-optical recording medium, rare earth and transition metal thin films are the most excellent from the viewpoint of comprehensive characteristics, but there is a drawback that they are lacking in corrosion resistance as a fatal defect.

That is, many defects such as a decrease in coercive force which is a necessary condition for high density recording due to corrosion, a decrease in Kerr rotation angle which is a necessary condition for a high S / N ratio, and an increase in error rate are exposed. Becomes

Conventionally, two methods have been taken as countermeasures. That is, (i) an additive is added to the magnetic layer to improve the corrosion resistance. (Ii) A protective film is formed to improve corrosion resistance. The present invention focuses on the method of using the protective film among the above two methods.

[0005]

The protective film on the substrate side is desired to have a high light transmittance (low absorption coefficient) and a high refractive index in order to improve the signal quality, and to further improve the recording sensitivity. A material having low thermal conductivity is a preferable material. As a protective film, SiO ₂ or the like is known, but it has a very low refractive index (1.4 to 1.5) and does not meet the above conditions.

Next, an oxygen-deficient Si oxide such as SiO is considered. This is because if the oxygen content is too large compared to a certain Si: O ratio, the magnetic layer reacts with the SiO layer to deteriorate the magneto-optical characteristics. However, if it is too small, there is a defect that the adhesiveness with the resin substrate decreases. Further, as a protective film other than the above-mentioned oxide-based one, a nitride film such as AlN and Si ₃ N ₄ is a material that does not contain oxygen, and therefore, the magnetic layer is less likely to be oxidized, so that a good protective property is obtained. It has been revealed that it has. However, the nitride has a very high thermal conductivity, and the heat release during the laser irradiation to the recording medium is large, so that the adhesion to the resin substrate is poor, and therefore the peeling under high temperature and high humidity is a problem.

Further, the magneto-optical medium has a structure in which a synthetic resin, glass or the like is used as a substrate and a magnetic layer is provided on the substrate. Especially when the substrate is made of a synthetic resin such as polycarbonate resin or acrylic resin, Contained in the substrate,
Deterioration of the magnetic layer due to a small amount of permeating air and moisture becomes a problem, so the protective layer has affinity with the magnetic layer and substrate, does not permeate moisture and air, and itself deteriorates due to moisture and air. It is required to be something that cannot be done.

The present invention has the following problems.
Completely shields the magnetic layer from the outside world, has low interfacial reactivity with the magnetic layer, has excellent affinity with the magnetic layer and synthetic resin substrates such as polycarbonate, and does not deteriorate itself by moisture or air. It is intended to provide a protective film having a low thermal conductivity and a large refractive index, and capable of efficiently forming a film.

[0009]

DISCLOSURE OF THE INVENTION As a result of studying the chemical stability, low thermal conductivity and high refractive index of Ta oxide, the present inventors have found that a protective film formed by a specific method is a magnetic layer. The present invention has been accomplished by finding that a stable protective film with less reaction with is obtained.

That is, the gist of the present invention is to provide a method of manufacturing a magneto-optical medium comprising a magneto-optical active layer (magnetic layer) provided on a substrate, wherein a protective layer containing a tantalum oxide is provided on the substrate. A method for producing a magneto-optical recording medium is characterized in that a target is formed by reactive sputtering in which oxygen and an inert gas are sputtered, and then a magnetic layer is provided.

The present invention will be described in detail below. First, examples of the substrate used in the present invention include glass, plastic such as acrylic resin and polycarbonate resin, and metal such as aluminum. The thickness of the substrate is 1
It is generally about 2 mm.

The magneto-optical recording layer provided on this substrate is, for example, DyFeCo, TbFeCo, TbC.
Amorphous magnetic alloys of rare earths such as o and transition metals, and Mn
A polycrystalline perpendicular magnetization film such as Bi or MnCuBi is used. It is particularly effective when used for a rare earth alloy magnetic film.

In the present invention, tantalum oxide is formed as a protective film between the substrate and the magneto-optical active layer.
When the magneto-optical medium according to the present invention is used as a magneto-optical recording medium, it is desirable to arrange the compound oxide protective layer on the recording / reproducing light incident side for use because it has excellent transparency and refractive index. In many cases, the recording / reproducing light is incident from the substrate side, so that the protective film of the present invention is often deposited on the substrate.

When a synthetic resin such as polycarbonate is used as the substrate, moisture or air may enter from the substrate side, so that the protective layer of the present invention must be provided between the substrate and the magnetic layer. Only the Ta oxide layer is provided between the substrate and the magnetic layer,
Alternatively, this layer and a layer for improving adhesion are inserted between the Ta oxide layer and the substrate. However, this adhesive layer is preferably 300 Å or less.

The protective layer of the present invention is used on one surface of the magnetic layer,
It is also possible to use another protective layer on the other side, in which case B
Nitride such as N, Si ₃ N ₄ , TiN, ZrN, NbN, TaN, or TiC, NbC, TaC, Mo ₂
Carbides such as C, TaSi ₂ , CrSi ₂ , CoS
A silicide such as i ₂ , VSi ₂ , TiSi ₂ , Ta _4.5 Si, or SiO ₂ or SiO may be used as the protective layer. Of course, the protective layer of the present invention may be used on the other surface.

The protective film is produced by reactive sputtering in which a Ta metal target is sputtered in oxygen and an inert gas. This method is suitable for high speed film formation.
Unless the tantalum oxide of the present invention is densely formed, oxygen in the tantalum oxide reacts with the magnetic layer and deteriorates the characteristics, so that it is necessary to form a dense film. This is also effective for obtaining a film having a high refractive index.

The sputtering method is suitable for this purpose. When the present tantalum oxide film is formed by the sputtering method, it is preferable that the sputtering gas pressure be as low as possible within the range in which the film is transparent and the film stress does not become extremely high. A preferable gas pressure is about 4 mtorr or less.

Next, high energy particles (1 to 100 eV) are used for the purpose of modifying the state of the interface between the tantalum oxide and the magnetic layer.
The kinetic energy of) impacts the surface. This method may be any method as long as high-energy particles are obtained,
A normal sputtering apparatus is equipped with a plasma etching processing mechanism, and by this means, plasma is applied to the substrate side to bombard a thin film made of Ar gas.
The typical etching time is 0.1 to 1 W / cm ² and about 1 to 20 minutes.

[0019]

【Example】

Example 1, Comparative Example 1 A Ta metal target of 5 ″ φ was attached to a cathode in a vacuum chamber, a polycarbonate substrate was attached, and 9.0 × 10 ⁻¹ t
After exhausting to orr, Ar gas and appropriate amount of oxygen gas are 30SC
CM was introduced and the vacuum chamber was set to 1.0 mtorr. High frequency power (13.56MHz) 500W after pre-sputtering
Was applied to sputter. The distance between the electrodes was 16 cm, and the substrate rotation speed was 90 rpm. 10 Ta ₂ O ₅ film on the substrate
00Å formed. Next, a high-frequency power of 50 W was applied to the substrate side at an Ar flow rate of 18 SCCM and an Ar gas pressure of 3.0 mtorr to etch the surface of the Ta ₂ O ₅ film for 5 minutes.

Next, a TbFeCo layer was formed to a thickness of 800 Å, and a protective layer made of Ta ₂ O ₅ was formed to a thickness of 1000 Å under the same conditions as described above. As a comparative example, a magneto-optical medium having an aluminum oxide protective layer formed under the same conditions was produced. The obtained medium was excellent in carrier-to-noise ratio (C / N) and recording sensitivity. The results are shown in Table 1.

[0021]

[Table 1] Measurement method: Differential detection

[0022]

[Table 2] Recording conditions r = 45 mm, 600 rpm hit length 5.0 μm The laser power that minimizes the secondary distortion was defined as the recording sensitivity. Reproduction condition r = 45 mm, 1800 rpm, laser power 2.4 mW

[0023]

According to the present invention, a magneto-optical medium excellent in corrosion resistance and recording sensitivity signal quality and easy to produce can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Watanabe 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd. (72) Inventor Masao Komatsu 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd.

Claims (2)

[Claims] 1. A method of manufacturing a magneto-optical recording medium comprising a magnetic layer provided on a substrate, wherein a protective layer containing a tantalum oxide is sputtered on a substrate using a tantalum metal target in oxygen and an inert gas. A method for manufacturing a magneto-optical recording medium, which comprises forming by reactive sputtering and then providing a magnetic layer. 2. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein the surface of the protective layer containing the tantalum oxide in contact with the magnetic layer is subjected to plasma etching before forming the magnetic layer.