JPH0536131A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium excellent in durability when repeating recording and/or reproducing by containing a particle having 1300-3000kg/mm<2> Vickers hardness in a protective layer opposed to a magnetic head. CONSTITUTION:In the magneto-optical recording medium having the magneto- optical recording layer 3 between the substrate 1 and the protective layer 6, the particle having 1300-3000kg/mm<2> Vickers hardness is contained in the protective layer 3. Av. particle diameter of the particle in the protective layer is 1-3mum, content of the particle in the protective layer is 5-50wt.%, and when content of the particle is preferably 10-30wt.%, statical friction coefficient is in the region of 0.01-0.3kg/mm<2> and mechanical strength of the protective layer is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of recording, reproducing and erasing with a light beam, and more particularly to an overwritable magneto-optical recording medium by a magnetic field modulation method.

[0002]

2. Description of the Related Art In recent years, a magneto-optical recording medium has attracted attention as an erasable and rewritable optical recording medium.

An overwritable magneto-optical recording medium or a magneto-optical recording / reproducing apparatus capable of overwriting without erasing old information prior to rewriting information is disclosed in, for example, JP-A-51-107121. JP-A-63-217
548, JP-A-59-215008, JP-B-60-
It is described in Japanese Patent No. 48806.

Here, in order to overwrite the magneto-optical recording medium, a magnetic coil and a core are arranged on the magnetic head slider, and the magnetic coil and the core are arranged so as to face the protective layer of the rotating magneto-optical recording medium. The magnetic head slider is levitated above the magneto-optical recording medium by the air flow generated between the two. Therefore, the magnetic head slider does not come into direct contact with the magneto-optical recording medium due to the action of the air flow at a predetermined number of rotations of the magneto-optical recording medium. It is not wear-damaged during the process.

However, at the beginning or the end of driving of the magneto-optical recording medium, the magnetic head slider loses its levitation force due to the decrease in the relative rotational speed, and the magnetic head slider comes into direct sliding contact with the magnetic recording medium. The magnetic head may be worn or damaged, or the recording medium side may be worn and damage the magneto-optical recording layer.The worn protective layer material adheres to the magnetic head and accumulates between the magnetic head and the protective layer. Then, both of them are attracted (sticking), which makes it impossible to drive the magnetic head slider and the magneto-optical recording medium. Then, for example, in Japanese Patent Laid-Open No. 64-64148,
There is disclosed a magneto-optical disk in which a filler such as alumina is mixed in a slide-resistant protective film on the magnetic head side to improve its mechanical strength.

However, it is still insufficient to prevent wear and scratches on the protective film when the magnetic head and the protective film slide, and there is a problem of lack of long-term reliability.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is a magneto-optical device which prevents abrasion of the protective layer and damage to the protective layer when the magnetic head and the protective film slide. It is intended to provide a recording medium.

[0008]

The magneto-optical recording medium of the present invention has a magneto-optical recording layer between a substrate and a protective layer, and the Vickers hardness in the protective layer is 1300 to 3000 Kg / mm.
It is characterized by containing particles of ² .

That is, according to the present invention, the Vickers hardness of 1300 to 3000 kg / m in the protective layer facing the magnetic head.
By including particles having a hardness of m ² , the protective layer can retain strength to the extent that it is not scratched or abraded even when contacted with a magnetic head, and durability during repeated recording and / or reproduction. It is possible to obtain an excellent magneto-optical recording medium.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a magneto-optical recording medium according to the present invention. In FIG. 1, 1 is a substrate, 3 is a magneto-optical recording layer, 2 and 4 are dielectric layers which are protective layers for the magneto-optical recording layer 3, 5 is a reflective layer, 6 is a protective layer, 7 is a magnetic head slider, 8 Is a laser beam.

As the protective layer 6 of the present invention, a resin layer containing particles having a Vickers hardness of 1300 to 3000 Kg / mm ² is used. The Vickers hardness of the particles in the protective layer is 1300 to 3000 Kg / mm.
² , preferably in the range of 1500 to 2000 kg / mm ² , scratches and abrasion on the protective layer can be prevented when the magnetic head slider and the protective layer slide, and conversely, the magnetic head slider when sliding. It does not cause wear or damage.

The particles used in the present invention are, for example, SiC, mullite (3Al ₂ O ₃ .2SiO ₂ ), A
particles such as l ₂ O ₃ having a Vickers hardness of 1300 to 3
000 Kg / mm ² , preferably 1500-2000 K
Those in the range of g / mm ² can be appropriately selected and used. Specifically, in the case of Al ₂ O ₃ , Sumitomo Chemical Co., Ltd.
AKP-10 (Vickers hardness 1600Kg / m
m ² ) and AKP-1.3 (Vickers hardness 1750 Kg
/ Mm ² ) and the like can be preferably used, and in the case of SiC, Sumitomo Cement Co., Ltd. B grade (Vickers hardness 1950 Kg / mm ² ) and the like can be preferably used.

Next, as the resin containing the above-mentioned particles, a photocurable resin or a thermosetting resin can be used.
An ultraviolet curable acrylic resin, an epoxy resin, a polyene polyol resin, a thermosetting phenol resin, an epoxy resin, an acrylic resin or a polyester resin can be used.

Further, the coefficient of static friction of the surface of the protective layer facing the magnetic head slider of the present invention is 0.01 to 0.3.
Kg / mm ^2, particularly preferably a 0.1~0.2Kg / mm ^2. That is, by setting the coefficient of static friction within the above range, the phenomenon of sticking (sticking) between the magnetic head slider and the magneto-optical recording medium is prevented, and it becomes impossible to drive the magnetic head slider and the magneto-optical recording medium. Can be prevented.

The particles contained in the protective layer of the present invention have an average particle diameter of 1 to 3 μm and a compounding amount of 5 to 50% by weight, preferably 10 to 30% by weight.
In this case, the coefficient of static friction can be within the above range and the mechanical strength of the protective layer can be improved.

The thickness of the protective layer of the present invention is set to 2 to 30 μm, particularly 5 to 10 μm. This makes it possible to prevent peeling due to shrinkage during curing of the protective layer.

Next, a method of manufacturing the magneto-optical recording medium of the present invention will be described.

First, the dielectric layer 2 is formed on the substrate 1 by vapor deposition or sputtering. The substrate 1 is not particularly limited and, for example, a substrate made of glass, polycarbonate resin, acrylic resin, polystyrene resin, or polyolefin resin is used.

A preformat such as a tracking group or prepit may be formed on the surface of these substrates.

Then, the magneto-optical recording layer 3, the dielectric layer 4 and the reflective layer 5 are formed on the dielectric layer 2 by vapor deposition or sputtering in the same manner as the dielectric layer 2.

The magneto-optical recording layer is not particularly limited,
For example, GdTb, TbFe, GdTbFe, TbFeC
o, GdTbFeCo, TbFeCoCr, GdTeF
Examples thereof include amorphous and perpendicular magnetic recording layers such as eCr, and laminated films of these.

The dielectric layer preferably has a function of mechanically and chemically protecting the magneto-optical recording layer, and examples thereof include SiO ₂ , SiO and Si ₃ N ₄ . Further, examples of the reflective layer include Al, Ag and Au.

Next, the protective film 5 is formed by dispersing a predetermined amount of the particles having the Vickers hardness of 1300 to 3000 Kg / mm ² in the monomer and / or prepolymer of the thermosetting resin or the ultraviolet curing resin described above. The magneto-optical recording medium of the present invention is manufactured by coating the composition with a coater, roll coater, spin coater, yagravure coater or the like and then heating or irradiating the resin to cure the resin layer.

[0025]

EXAMPLES Next, the present invention will be described more specifically according to examples.

(Example 1) Thickness 1.2 mm, inner diameter 15 m
m, outer diameter 86 mm, radius 0.5 μm on one surface, track grooves of pitch 1.6 μm are concentrically formed on a disc substrate made of a polycarbonate resin, R22 to R
Si ₃ N ₄ as a dielectric layer with a thickness of 110
The film is formed to 0Å, and then Gd-Fe-Co is formed as a magnetic recording layer
-Cr amorphous film and Tb-Fe-Co-Cr amorphous film are combined to 300 Å, and then Si ₃ N ₄ is formed thereon as a dielectric layer to a thickness of 300 Å and further to a reflective layer. A as 5
l was deposited to a thickness of 600Å. The film formation was performed by the sputtering method.

Next, Al ₂ O ₃ (trade name: AKP-10, Sumitomo Chemical Co., Ltd.) having an average particle size of 1.0 μm and a Vickers hardness of 1600 Kg / mm ² in the ultraviolet curable resin composition.
20 w% dispersed in a UV lamp (irradiated surface of 233 mW / irradiated surface) on the reflective layer 5 and the inner and outer peripheral portions of the substrate by a spin coating method so as to directly contact the substrate.
cm ² and wavelength 365 nm) for 7 seconds to cure the resin and obtain a resin protective layer.

As the ultraviolet curable resin composition,
The following composition was used.

[0029] Epoxy acrylate 20 wt% Dimethylolpropane diacrylate 65 wt% Trimethylolpropane triacrylate 10 wt% Irgacure 184 5 wt%

Next, the static friction coefficient of the protective layer of the magneto-optical disk thus obtained was measured by using a friction stiction tester (FST series; manufactured by Minebea Co., Ltd.), and the measuring method and conditions were determined by ANSI X3B7 / 87. The result of measurement according to the method of measuring the friction coefficient between the magnetic head and the disk was 0.15.

Further, this magneto-optical disk is set to 3000 rp
The magneto-optical recording / reproducing apparatus was adjusted so that the gap between the magnetic head slider and the protective layer of the magneto-optical disk recording / reproducing apparatus was 1.6 μm when rotated at m. A CSS test was performed in which a series of operations of rotating for 2 seconds and then stopping for 3 seconds was repeated. As a result, the magneto-optical disk and the magnetic head slider did not change even after 100,000 times.

Example 2 Instead of Al ₂ O ₃ used in Example 1, an average particle size of 1.3 μm and a Vickers hardness of 1750.
Al ₂ O ₃ having Kg / mm ² (trade name: AKP-1.3
A magneto-optical disk was produced in the same manner as in Example 1 except that 25 wt% of Sumitomo Chemical Co., Ltd. was contained.

When the static friction coefficient of the protective layer of this magneto-optical disk was measured in the same manner as in Example 1, it was 0.1.

Further, a CSS test was conducted in the same manner as in Example 1, and as a result, no abnormality was found in the disk and the magnetic head slider even after 100,000 cycles.

(Example 3) Instead of Al ₂ O ₃ used in Example 1, an average particle size of 1.0 μm and Vickers hardness of 1950K.
A magneto-optical disk was produced in the same manner as in Example 1 except that 20 wt% of SiC (B grade, manufactured by Sumitomo Cement Co., Ltd.) of g / mm ² was contained. The static friction coefficient of this magneto-optical disk was 0.12.

A CSS test was conducted in the same manner as in Example 1, and as a result, no abnormality was found on the disk or magnetic head slider even after 100,000 cycles.

(Comparative Example 1) Instead of Al ₂ O ₃ used in Example 1, an average particle size of 0.6 μm and Vickers hardness of 1000K.
Example 1 except that 20 wt% of g / mm ² of TiO ₂ (trade name: R-870, manufactured by Toho Titanium Co., Ltd.) was contained.
A magneto-optical disk was manufactured in the same manner as in. The static friction coefficient of the protective layer of this magneto-optical disk was 0.35.

Next, a CSS test was conducted in the same manner as in Example 1, and a head crash occurred after 20,000 times.

(Comparative Example 2) Instead of Al ₂ O ₃ used in Example 1, an average particle size of 0.8 μm and Vickers hardness of 700 kg.
/ Mm ² of SiO ₂ (trade name HS-30 Nissan Chemical Co., Ltd.
A magneto-optical disk was manufactured in the same manner as in Example 1 except that 25% by weight) was added. The static friction coefficient of the protective layer of this magneto-optical disk was (0.4).

Then, when the magneto-optical disk was subjected to the CSS test in the same manner as in Example 1, adsorption (sticking) occurred between the protective layer and the magnetic head slider,
It was impossible to drive the disk and the magnetic head slider.

In this example, the average particle size was measured with a light scattering photometer (trade name: Model 6000; manufactured by Toyo Sokki Co., Ltd.).

The Vickers hardness of the particles in the protective layer can be measured by a Shimadzu dynamic ultra-fine hardness meter (trade name: DUH-
200; manufactured by Shimadzu Corporation.

[0043]

As described above, according to the magneto-optical recording medium of the present invention, the mechanical strength of the protective layer can be appropriately reinforced, and the protective layer can be formed when the magneto-optical recording medium and the magnetic head slider slide. It is possible to prevent wear and damage to the magnetic head slider, and it is possible to obtain an overwritable magneto-optical recording medium by a magnetic field modulation method which is excellent in reliability and durability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a magneto-optical recording medium according to the present invention.

[Explanation of symbols]

1 substrate 2, 4 Dielectric layer 3 Magneto-optical recording layer 5 Reflective layer 6 protective layer 7 Magnetic head slider 8 laser beam

Claims (6)

[Claims] 1. A magneto-optical recording medium having a magneto-optical recording layer between a substrate and a protective layer, wherein the protective layer contains particles having a Vickers hardness of 1300 to 3000 kg / mm ^2. Optical recording medium. 2. The magneto-optical recording medium according to claim 1, wherein the surface of the protective layer on the side not facing the magneto-optical recording layer has a coefficient of static friction of 0.01 or more and 0.3 or less. 3. The coefficient of static friction is 0.1 or more and 0.2 or more.
The magneto-optical recording medium according to claim 2, wherein 4. The magneto-optical recording medium according to claim 1, wherein the average particle diameter of the particles is 1 to 3 μm. 5. The protective layer contains 10 to 30 wt% of the particles.
The magneto-optical recording medium according to claim 1, which contains. 6. The magneto-optical recording medium according to claim 1, wherein the particles are at least one of alumina and SiC.