JPS6168748A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the performance of recording and reproduction and shelf life by forming a reflecting layer of two metallic layers, of which the metallic layer on the side further from a magnetic recording layer is made to have the larger tendency to ionization than the other metallic layer and is made to permit the formation of a passive film. CONSTITUTION:The material for the reflecting layer 3' further from the magnetic recording layer 2 is selected from the metals which have the higher tendency to ionization than the material of the other reflecting layer 3 and form the passive film when oxidized. Cr is more particularly preferable for said material. The corrosion of the layer 2 is prevented in addition to the effect intrinsic to the reflecting layer by the above-mentioned constitution of the layers 3, 3'. Since the layer 3 is protected against corrosion by the layer 3', the material for the layer 3 can be selected by placing emphasis on the reflecting power of recording light and reproducing light. The material is thus effective not only for the improvement in the corrosion resistance but also in the improvement of the recording and reproducing efficiency. The performance of the recording and reproducing and the shelf life are thus improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to erasable and rewritable high-density memory,
The present invention relates to magneto-optical recording media in the form of disks, cards, and sheets that are recorded by heating with light irradiation and can be read using magneto-optical effects such as the magnetic Kerr effect and the Faraday effect.

[Conventional technology]

Conventionally, as magneto-optical recording media, Mini, Mn (
: Polycrystalline thin film such as u old, GdCo, GdFe, T
bFe, [1yFe.

GdTbFe, ↑b lower Fe, GdFeCo, T
Amorphous thin film such as bFeCo, GdTbCo, Gd
Single crystal S films such as Fe garnet are known.

Among these thin films, the film-forming efficiency when manufacturing large-area thin films at temperatures near room temperature, the writing efficiency for writing signals with small photothermal energy, and the reading efficiency for reading written signals with a good SIN ratio are important. Considering these factors, the amorphous PJIli is recently considered to be excellent for use in photothermal magnetic recording media.

Furthermore, in order to improve writing efficiency and reading efficiency, a configuration has been proposed in which the amorphous thin film is made ultra-thin to the extent that light can pass therethrough, and a reflective layer is provided thereon.

[Problem that the invention seeks to solve]

However, the above-mentioned amorphous magnetic thin film generally has poor corrosion resistance, and has the disadvantage that it corrodes in a humid atmosphere, resulting in deterioration of magnetic properties, and has a problem in long-term storage as a recording medium. Furthermore, in the configuration in which the reflective layer is provided, the amorphous magnetic thin film is very thin and is even more susceptible to corrosion.

The metal material for the reflective layer must have a sufficiently high reflectance for the light used for recording and reproduction, and it is difficult to achieve both corrosion resistance and moisture resistance. The purpose is to solve the problems and provide a magneto-optical recording medium with high corrosion resistance.

[Means for solving problems]

The magneto-optical recording medium of the present invention has an FIi magnetic recording layer on a substrate, and further has a reflective layer on the magnetic recording layer, wherein the reflective layer is a two-layer metal layer. The magnetic recording layer is characterized in that the metal disposed on the side far from the magnetic recording layer is a metal that has a greater ionization tendency than the other metal layer, and is also made of a metal that can form a passive film.

[Preferred mode for carrying out the invention]

Hereinafter, the magneto-optical recording medium of the present invention will be explained in more detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing one embodiment of the magneto-optical recording medium of the present invention.

Reference numeral 1 represents a substrate, and conventionally known materials such as glass, acrylic resin, polycarbonate, polyethylene, and polyimide can be used.

2 is a magnetic recording layer, and from the purpose of the present invention, an amorphous magnetic f
It is preferable to form the MnB i film.

It may be a thin film having a conventionally known magneto-optic effect, such as a polycrystalline thin film such as MnCuB1.

In particular, in order to obtain good recording efficiency and reproduction efficiency, Gd,
An amorphous magnetic thin film consisting of one or more metal elements among rare earth metals such as Tb and Dy and one or more metal elements among transition metals such as Fe, Go, and Ni is desirable, for example, GdCa. , TbFe, GdTbFe, Tb
DyFe.

Amorphous thin films such as TbFeCo and GdTbFeC:o can be used.

The magnetic recording layer 2 is formed by a vacuum evaporation method, a sputtering method, or the like.

3 and 3' are reflective layers, and during recording, the recording light that has passed through the magnetic recording layer 2 is irradiated onto the magnetic recording layer 2 again by the reflective layers 3 and 3', so that the energy of the recording light is effective. Available for During reproduction, part of the reproduction light is reflected by the magnetic recording layer 2, and part of the reproduction light is transmitted through the magnetic recording layer 2 and reflected by the reflective layers 3 and 3'.The former reflected light has the Kerr effect. Since the latter reflected light is subject to the Faraday effect, the reproduction efficiency can be increased by detecting both of the reflected lights.

The material for the reflective layer 3 is selected from metals that have sufficient reflectance at the wavelength of light used and have a relatively small tendency to ionize. Particularly preferred are Cu, Au, Aipt, etc., while the material for the first reflective layer 3' is selected from corrosion-resistant metals that have a greater ionization tendency than the material for the reflective layer 3 and form a passive film when oxidized. . Preferred materials include Or, Ti, jV! , Ta, etc. In particular, Or is preferable because it forms a strong passive film when oxidized.

The reflective layers 3 and 3' are formed using the above-mentioned materials by vacuum deposition, sputtering, or other methods.

By having the reflective layers 3 and 3' configured as described above, in addition to the original function of the reflective layer described above, the recording layer 2
It also has the function of preventing corrosion. That is, the reflective layer 3'
Even if the adhesive layer 4 provided thereon absorbs moisture, the reflective layer 3' forms a passive film, so oxygen, moisture, etc. do not pass through the layer 3'.

Corrosion of the magnetic recording layer 2 is prevented. In addition, even if there are glass balls in the first reflective layer 3', the reflective layer 3 is not easily corroded for the following reasons.In general, metals with a large ionization tendency are easily oxidized, and metals with a different ionization tendency are are adjacent, oxygen at the adjacent interface,
This is because when moisture penetrates, corrosion progresses first on metal surfaces with a high ionization tendency, and as a result, the progress of corrosion on metal surfaces with a low ionization tendency is suppressed.

As described above, the reflective layer 3 is protected from corrosion by the reflective layer 3', so the material for the layer 3 is selected based on its ability to reflect recording and reproducing light without worrying about corrosion resistance. It's a monkey. Therefore, the magneto-optical recording medium of the present invention is effective not only in improving corrosion resistance but also in improving recording efficiency and reproduction efficiency.

The total thickness of the reflective layers 3 and 3' is approximately the same as the thickness of a single conventional reflective layer.

The adhesive layer 4 is bonded to a substrate (not shown) for mechanical protection of the magneto-optical recording medium, or is bonded to another recording medium (not shown) so that recording and reproduction can be performed on both sides. This is a layer for

In addition, in order to further improve the corrosion resistance and durability of the magneto-optical recording medium, SiO, 5
Although protective layers such as i02, Sl, Nm, and Aiq03 are not provided, other layers may be provided at certain positions for various purposes.

In addition, as shown in FIG. 2, the magnetic recording layer #i layer 2 and the reflective layer 3
A dielectric layer 5 of SiO, 5iiN*, etc. is placed between the
It may be provided by a method such as deposition or sputtering. By doing this, a part of the reproduction light transmitted through the magnetic recording layer 2 is multiple-reflected between this dielectric material and the reflective layers 3 and 3', and this light and the reproduction light reflected by the magnetic recording layer 2 are combined. By simultaneously detecting a part of the data, it is also possible to improve the regeneration efficiency.

Further, the magneto-optical recording medium of the present invention may be provided with guide grooves as shown in FIG. 3 for accurate recording and reproduction. This is done by providing guide grooves on the substrate 1 by injection molding or the like.
It can be formed by uniformly coating various layers on this substrate 1. In Fig. 3, 6 is SiO, SiO□
, Si3N, , Affi, 03 and the like.

〔Effect of the invention〕

As explained above, both the recording and reproducing performance and the shelf life can be improved by a simple improvement in which the reflective layer is made up of two metal layers with different ionization tendencies.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 A magneto-optical recording medium having the configuration shown in FIG. 2 was prepared.

A glass substrate with a thickness of 1.1 mm was used as the substrate (2), and an amorphous alloy thin film of GdTbFeCa having a thickness of 150 mm was formed thereon as the magnetic recording layer 2 using a sputtering device. Subsequently, a silicon nitride film having a thickness of 38 QQA (7) was formed as the dielectric layer 5 thereon by sputtering using a Si target in the same apparatus and using gases in the proportions of Ar and N2. Thereafter, this was taken out from the Subashi taring apparatus, placed in a vacuum evaporation apparatus, and then Cu was deposited to a thickness of 100 OA as a reflective layer 3, and Cr was vacuum-deposited to a thickness of 3000 Å. Next second reflective layer 3
A magneto-optical recording medium was prepared by adhering it to a plate glass using a silicone adhesive.

III) of this magneto-optical recording medium! In order to examine the corrosivity, it was left for 1000 hours at 85° C. and 85% RH.

As a result, there was no change in appearance, and the decrease in coercive force was within 10% of the initial value.

Example 2 Ti with a layer thickness of 2 QOOA was used instead of Cr as the reflective layer 3'.
A magneto-optical recording medium was prepared in exactly the same manner as in Example 1 except for the above, and was left for 1000 hours at 85° C. and 85% RH. As a result, there was no change in appearance, and the decrease in coercive force was within 10% of the initial value.

Comparative Example 1 A magneto-optical recording medium was prepared in exactly the same manner as in Example 1 except that the reflective layer was a single layer of Cu film with a layer thickness of 3000 mm, and was heated under the conditions of 85° C. and 585% RH. 10
It was left for 00 hours. As a result, pinhole-like corrosion occurred partially and the coercive force decreased by 30% of its initial value.

Comparing Example 1.2 and Comparative Example, #1 according to the present invention
It is clear that the corrosivity is improved.

Example 3 First, a protective layer 6 of silicon nitride was applied using a sputtering device to a disk-shaped substrate 1 made of PMMA on which a tracking guide groove was formed.
After that, 200 amorphous magnetic alloy thin films similar to those in Example 1 were formed, and 3 silicon nitride 11Q was formed as the dielectric layer 3. Cu was deposited to a thickness of 100 mm as the reflective layer 3 in a vacuum evaporation device.
Cr was vacuum-deposited to a thickness of 300A as the reflective layer 3'. In this way, two magneto-optical recording media are formed,
The reflective layers 3' were bonded to each other using a silicone adhesive.

The magneto-optical recording medium was evaluated using a recording and reproducing device. Rotation speed 180Orpm, recording laser power 7mW, reproduction laser power 211IllI, wavelength 830nm, 4M
The Hz CAM ratio was 46 cents.

This recording medium was heated at 45°C and 195% RH.
After being left for 0 hours, recording and reproduction was performed again, and the G/N was 44 mm. There was no noticeable change in appearance.

Comparative Example 2 Cull one reflective layer to a layer thickness of 4000 in Example 3
A magneto-optical Q-coupled body was prepared and evaluated in exactly the same manner as in Example 3 except that only one I2 layer was used.

The initial CAM was 46tII, but at 45℃, 95%
IIIH.

After 1000 hours, the value dropped to 3448, and discoloration that appeared to be corrosion was observed in appearance.

Comparative Example 3 A magneto-optical recording medium was prepared and evaluated in exactly the same manner as in Example 3, except that one reflective layer was a single Cr film with a thickness of +oooA.

The early CAM was too low to be of practical use, at 36 (Lll).

Even when comparing Example 3 and Comparative Examples 2.3, it is clear that the present invention has high corrosion resistance and good magnetic properties.

[Brief explanation of drawings]

1 to 3 are schematic cross-sectional views showing examples of the magneto-optical recording medium of the present invention. 6 1: Xi plate, 2: Ra air recording layer. 3.3': reflective layer, 4: adhesive layer, 5: dielectric layer, 6: protective layer.

Claims (1)

[Scope of Claims] 1) A magneto-optical recording medium having a magnetic recording layer on a substrate and further having a reflective layer on the magnetic recording layer, wherein the reflective layer is composed of two metal layers, A magneto-optical recording medium characterized in that the metal layer disposed on the side far from the magnetic recording layer is made of a metal that has a greater ionization tendency than the other metal layer and is also made of a metal that can form a passive film. 2) The magneto-optical recording medium according to claim 1, wherein the magnetic recording layer comprises one or more metal elements selected from transition metals and one or more metal elements selected from rare earth metals. 3) The metal layer disposed on the side far from the magnetic recording layer is C
A magneto-optical recording medium according to claim 1, comprising r.