JPS6168750A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce the cost and time for production by providing protective layers consisting of an org. resin between the respective recording layers and adhesive layers of a photomagnetic recording medium of a lamination type. CONSTITUTION:Substrates 1, 1' are formed of, for example, glass, acrylic resin, etc., antireflecting layers 2, 2' of SiO, etc. and the recording layers 3, 3' of a thin amorphous film, respectively. The protective layers 4, 4' can be uniformly coated on the layers 3, 3', etc. by a coating method. Materials which can be cured by solvent evaporation, heating, etc. such as acryl, urethane resin and silicone rubber are used for said layers. If the protective layers of the org. resin are provided to the recording medium made of such lamination construction, the corrosion resistant performance is practically the same as compared with the protective layers of the inorg. type but the cost and time for production are considerably reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is used in erasable and rewritable high-density memory, which records data by heating by light irradiation, and which produces magneto-optical effects such as the magnetic Kerr effect and the Faraday effect. It relates to disks, cards, and sheet-like magneto-optical recording media that can be used and read out.

[Conventional technology]

Conventionally, as a magneto-optical recording medium device, MnB1. MnCu
Polycrystalline t'1lllQ such as B1, GdCo, Gd
Fe, TbFe, DyFe.

GdTbFe, TbDlFe, GdFeGo, T
bFeC:o, amorphous thin film such as GdTbCo, T
Single crystal thin films such as bFeO3 are known.

Among these thin films, there are various issues such as film formability when manufacturing large-area thin films at temperatures near room temperature, writing efficiency for writing signals with small photothermal energy, and readout of written signals with a good S/N ratio. Considering read efficiency,
In the near future, the amorphous thin film is considered to be excellent as a magneto-optical recording medium. In particular, GdTbFe has a large Kerr rotation angle and a single Curie point of around 150° C., making it optimal as a magneto-optical recording medium.

A magneto-optical recording medium made of such an amorphous thin film is known, in which two recording media having a recording layer on a substrate and a substrate are bonded together using an adhesive layer so that the recording layers face each other, and recording and reproduction can be performed on both sides. There is.

However, amorphous magnetic materials generally used in magnetic recording media such as photothermal magnetic recording media such as GdTbFe have a drawback of poor corrosion resistance. That is,
When exposed to air or water vapor, its magnetic properties deteriorate, and eventually it becomes completely oxidized and becomes transparent.

Also in the laminated magneto-optical recording medium of No. 1111,
Air and moisture permeate through the adhesive layer used for bonding, and air bubbles and moisture contained in the adhesive layer often deteriorate the magnetic properties of the recording layer. In addition, the recording layer was sometimes corroded by the atmosphere and moisture before it was bonded together.

In order to eliminate such drawbacks, it has been conventionally known that a protective layer of a transparent material, for example 5i, is used between the adhesive layer and each recording layer.
02. It has been proposed to provide an inorganic protective layer such as SiO.

[Problem that the invention seeks to solve]

However, protective layers of inorganic materials such as Sin and SiO□ must be formed using vacuum equipment such as evaporation or sputtering, and the film formation also takes time, resulting in huge equipment investment and personnel costs. This has caused an increase in the cost of recording media.

The present invention has been made to solve the above problems, and provides a magneto-optical recording medium having an optimal protective layer on a laminated structure that can be formed at low cost, in a short time, and with simple operations. The purpose is to

[Means for solving problems]

The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which two recording media each having at least a recording layer on a substrate are bonded together via an adhesive layer so that the recording layers face each other. It is characterized in that a protective layer made of an organic resin is provided between the recording layer and the adhesive layer.

[Preferred mode for carrying out the invention]

The protective layer of the magneto-optical recording medium of the present invention is made of an organic resin. The protective layer may be provided directly on each recording layer of the two recording media to be bonded together, or if another layer is provided on the recording layer, it may be provided on this layer.

This protective layer can be uniformly applied onto the recording layer, etc. by a coating method such as spray, coater, printing, spinner, or dipping, and can be cured by solvent volatilization, heating, two-part heating, U, V, irradiation, etc. Any acrylic, epoxy, or urethane type is fine.

Silicone-based, polyamide-based, polyester-based resin, silicate-based rubber, etc. are used. In particular, hot-melt resins immediately dissipate heat when applied onto a recording layer after being heated and melted, solidify due to rapid temperature drop, and form a retaining IJ layer in a short period of time, making them excellent in terms of workability. Also, the cost is low.

The thickness of the protective layer varies depending on its material, the thickness of the recording layer, etc., but is usually about 3,000 to 100 mm.

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

1 and L' are a substrate, and 2 and 2' are antireflection layers, which are used to prevent reflection of recording light and reproduction light and to effectively utilize the energy of these lights.

3 is a recording layer. Substrate 1.1; antireflection layer 2, 2'
, M layers 3 and 3' can be made of conventionally known materials.For example, the substrates l and 1' can be made of glass, acrylic resin, polycarbonate, etc.; the antireflection layer 2 and 2' can be made of
5i02 * Si3N4 * TiO□, etc.; For the purpose of the present invention, the recording layers 3 and 3' are formed of amorphous magnetic thin films, but they are formed of thin II films having a conventionally known magneto-optical effect.
I, for example MnB1. It may also be a polycrystalline thin film such as Mr+CuB1.

The antireflection layers 2 and 2'; the recording layers 3 and 3' can be formed using the above-mentioned materials by vacuum evaporation, sputtering, electron beam evaporation, or the like.

4.4' is the protective layer of the organic resin described above.

5 is an adhesive layer, and the material is not particularly limited, but it is preferably a material that has good adhesion to the protective layer 4 and is easy to work with;
Acrylic, silicone, epoxy, urethane, and other adhesives can be used.

Note that the antireflection layer 2.2' may be omitted depending on the recording efficiency and reproduction efficiency, or other layers may be coated at predetermined positions for various purposes.

〔Effect of the invention〕

The magneto-optical recording medium of the present invention, in which a protective layer of an organic resin is provided on a recording medium with a laminated structure, has almost no difference in #corrosion performance compared to a conventional one in which a protective layer of an inorganic material is provided. Moreover, it has become possible to significantly reduce manufacturing costs (and manufacturing time).

〔Example〕

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

Example 1 A donut-shaped substrate 1°1' made of acrylic resin is coated with Si to a thickness of 500 mm as an antireflection layer 2.2', respectively.
After vacuum evaporation of O, the thickness was +20OA as recording layers 3 and 3'.
(7) GdTbFeC:a was laminated on the antireflection layer 2.2' by sputtering method, and then the protective layer 4.4' was formed using an acrylic ultraviolet curable resin (For Honto'-300 Myojo Churchill ■). was applied onto the recording layer 3.3' to a thickness of 10 mm using a spin code method, and irradiated with a high-pressure mercury lamp for 1 minute under the condition of LOW/crn' toward the north of the disk surface to cure the acrylic resin. The protective layers 4 and 4' of these two recording media were bonded together using an epoxy adhesive to produce a magneto-optical recording medium having a bonded structure according to the present invention.

When this magneto-optical recording medium was left at 45° C. and 95% relative humidity for 1,000 hours, the coercive force decreased by 10% from the initial value.

Comparative Example 1 As protective layer 4.4', S i 0 to thickness 3,000
A magneto-optical recording medium was prepared in the same manner as in Example 1 except that 11Q was formed by vacuum evaporation, and when it was left at 45°C and 95% relative humidity for 1,000 hours, the coercive force was the initial value. This was a 9% decrease.

As is clear from a comparison between Example 1 and Comparative Example 1, the present invention in which an organic resin layer is provided as a protective layer has a high protective effect because the film thickness can be increased through a simple process. It is possible to obtain a material that has almost no change in coercive force over time and has the same level of corrosion resistance as that provided as a layer. Furthermore, as mentioned above, the formation of an acrylic protective layer can be performed in a very short time, and compared to the conventional thin film formation of inorganic materials in a vacuum, it is possible to form a thick film at a very low cost. As a whole, we were able to provide a magneto-optical recording medium that was extremely low in cost.

Example 2 After forming antireflection layers 2 and 2' and recording layers 3 and 3' on substrates 1 and 1' in the same manner as in Example 1, EVA-based hot melt adhesive (Hot melt 092 A.C.I. Japan Limited) was melted at 120℃,
The protective layers 4 and 4' were formed by coating with a hot melt coater to a thickness of 20 μs. This protective layer, 1, 4'
Synthetic rubber hot melted at 120°C, A
A melt adhesive (Hot melt PS-15x manufactured by ICI Japan Ltd.) was applied. This 2
The protective layers 4 and 4' of the two recording media are adhesively pressed together.

When a magneto-optical recording medium with a laminated structure of the present invention was laminated and left for 1,000 hours at 45°C and 95% relative humidity, the coercive force decreased by 8% from the initial value. .

Comparative Example 2 A magneto-optical recording medium was produced in the same manner as in Example 2, except that a SiO film with a thickness of 4,000 mm was formed by vacuum evaporation as the protective layers 4 and 4', and the medium was heated at 45° C. and relative humidity. When left for 1,000 hours under 85% conditions, the coercive force decreased by 8% from the initial value.

As is clear from comparing Example 2 and Comparative Example 2, even when a hot melt adhesive is used as a protective layer, the performance is comparable to that of a conventional inorganic protective layer. Since almost no resin curing time was required, the magneto-optical recording medium could be produced in a shorter time than in Example 1.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the magneto-optical recording medium of the present invention. 1, 1': Board 2, 2’: Antireflection layer 3, 3’: Recording layer 4, 4' 2 protection) 7 5: Adhesive layer

Claims (1)

[Claims] In a magneto-optical recording medium in which two recording media each having at least a recording layer on a substrate are stacked such that the recording layers face each other with an adhesive layer interposed therebetween, the relationship between each recording layer and the adhesive layer is A magneto-optical recording medium characterized by having a protective layer made of an organic resin therebetween.