JPH0337843A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To lessen the deformation of a substrate by moisture absorption even under severe high-temp. and high-humidity environmental conditions by sticking polypropylene (PP) films coated with polyvinylidene chloride onto one or both surfaces of the recording medium. CONSTITUTION:A magneto-optical recording layer is formed on the guide surface of a transparent plastic substrate 1 and further, an adhesive layer 3 in common use as a protective layer is formed thereon. The PP films 4 coated with the polyvinylidene chloride are stuck onto one or both surfaces thereof. The films are so stuck that the polyvinylidene chloride side comes into contact with the layer 3 and the PP side exists on the outside surface. The magneto-optical recording medium having excellent durability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording medium that can be recorded, reproduced and erased using laser light. More specifically, the present invention relates to a magneto-optical recording medium that exhibits excellent durability under high-temperature, high-humidity conditions in which the substrate absorbs little water and the recording layer exhibits little oxidative deterioration.

(Prior art) Conventionally, there is a magneto-optical recording medium used in erasable and rewritable high-density memory that is recorded by heating with light irradiation and that can be read using magnetic effects such as the magnetic Kerr effect and Faraday effect. .

In particular, Gd, Tb, and Fe are used in the recording film of the magneto-optical recording medium.

The amorphous thin film made of Co has excellent film-forming properties when producing a large-area thin film at temperatures near room temperature, writing efficiency for writing signals and small optical energy, and high efficiency for writing written signals with S It is optimal as a magneto-optical recording medium because it has a readout efficiency for good /N ratio, a large Kerr rotation angle, and a Curie point of around 1500C.

However, magneto-optical recording layers made of Gd, Tb, Fe, Co, etc. generally have a drawback of poor corrosion resistance. That is, when it comes into contact with air or water vapor, it is oxidized and its magnetic properties deteriorate, and eventually it becomes completely oxidized and becomes transparent. This phenomenon is further accelerated under high temperature and high humidity conditions.

Conventionally, SiO was used to prevent oxidation of the recording film.

A method of sealing the recording film with a protective layer of inorganic materials such as 5i02, Si3N4, Al2O3, etc. has been proposed and implemented, but a sufficient oxidation prevention effect cannot be obtained under high-temperature conditions. Cr, Ti
.

A method of sealing with a double anti-oxidation film has been proposed, such as coating a protective film in a vacuum system with a metal such as Au, Hf, A1, etc. by vapor deposition or spatter.

Even then, a sufficient antioxidant effect cannot be obtained, so the recording layer or the entire medium is further coated with moisture-proofing halogenated organic resin, ultraviolet curable acrylate resin, thermosetting epoxy resin, or photomelt resin. A method has been proposed. For example, a method of coating polyvinylidene chloride on the surface of a plastic substrate opposite to the recording layer in order to prevent moisture absorption or oxygen permeation (Japanese Patent Application Laid-Open No. 61-8564)
6) can be mentioned.

(Problem to be solved by the invention) By the way, it is well known that polyvinylidene chloride has the best gas barrier properties against oxygen and water vapor, and it is usually dissolved in tetrahydrofuran or dissolved in water. 3. When applied to a plastic substrate such as polycarbonate while stirring, tetrahydrofuran dissolves the polycarbonate and the smoothness of the substrate surface is lost.
If the temperature is too high, solvent cracks will occur on the substrate surface, which is undesirable. In addition, when using an emulsion type, repellency occurs when spin-coating, making it impossible to uniformly coat the substrate surface.

Previously, the present inventors proposed applying a polyvinylidene chloride film, but this film has high elasticity and
The bonded surfaces had minute wrinkles, which caused signal errors.

An object of the present invention is to solve the above-mentioned problems and provide a magneto-optical recording medium with excellent durability, with less deformation due to moisture absorption of the substrate and less oxidative deterioration of the recording layer even under harsher high temperature and high temperature environmental conditions. That is.

(Means for Solving the Problems) The magneto-optical recording medium of the present invention has the following features:1. 2. A magneto-optical recording medium consisting of a transparent plastic substrate and a magneto-optical recording layer provided on the substrate, in which a polypropylene film coated with polyvinylidene chloride is bonded to one or both sides of the medium. In a magneto-optical recording medium, two pieces of a magneto-optical recording medium each consisting of a transparent plastic substrate and a magneto-optical recording layer provided on the substrate are placed facing each other with the recording layer facing inside and bonded together with an adhesive. This is a magneto-optical recording medium made by laminating a polypropylene film coated with polyvinylidene chloride on one or both sides of the medium.

Examples of the plastic substrate include substrates using acrylic resin, polycarbonate resin, polyolefin resin, epoxy resin, and the like. For the magneto-optical recording layer, an inorganic dielectric material such as SjO, 5i0 is used as an anti-oxidation underlayer.
2, Si3N4, Al2O3, etc., on top of which there is a thin alloy film of Gd, Tb, Fe, Co, etc. as a magneto-optical recording edge, and on top of this there is an inorganic dielectric film similar to the above. Incidentally, a reflective layer such as A1, Au, etc. may be further formed on this. Furthermore, an organic protective coating layer such as a photo-curing layer resin, hot-melt resin, epoxy resin, UV-curing resin, etc. is provided on this 3, and as an adhesive, 9, photo-melt resin, epoxy resin, UV-curing resin, etc. 1. (Function and implementation) The magneto-optical recording medium of the present invention is described below based on FIGS. 1 and 2 in Example 1. It is a transparent plastinox disk substrate, with a diameter of 130 mm.
Inner diameter 15mm, N 1. ．． The recording area is 2 mm, and the concentric or spiral guide groove has a groove width of 0.8 pm.
It was mass-produced by injection molding with dimensions of groove depth 5ooA and groove pitch 1.6 pm.

On the guide groove side of the substrate 1, a 1,000-layer Si02 layer and a 4-layer Si3N layer were formed by magnetron sputtering.

Gd, Tb, Fe, Co magnetic recording layer 1000
A. A magneto-optical recording layer 2 was provided by sequentially laminating 800 Si3N4 layers and 500 A1 reflective layers. This was used as a sample for film lamination of the present invention. Furthermore, on top of that, a protective layer/adhesive layer 3 is made of ultraviolet curing resin (SD-17
, Dainippon Ink Co., Ltd.) using a spin coater to a film thickness of 2.
It was applied so that the amount was 0 pm.

Next, a polypropylene film 4 coated with polyvinylidene chloride of the present invention (trade name: KO
P-200 (Daicel stock vinylidene chloride thickness 5pm, polypropylene thickness 50pm) were bonded together. When the bonded films had no bubbles or wrinkles, the polyvinylidene chloride side was brought into contact with the adhesive layer 3, and the polypropylene side was made to be the outer surface.

In order to cure the adhesive layer 3, ultraviolet rays were irradiated from the top of the bonded polypropylene film. Irradiation conditions are high pressure mercury lamp 80mm, distance 5cm, conveyance speed 3m/min.
Met.

In the same manner, the film of the present invention was also laminated onto the substrate on the opposite side from the recording layer 2. Further, the film of the present invention was similarly bonded to both sides of a double-sided magneto-optical recording medium. Next, as Example 2, the same film of the present invention as in Example 1 was bonded to both outer surfaces of a magneto-optical disk for double-sided reading.

For comparison, Comparative Example 1 for veneer single-sided readout and Comparative Example 2 for laminated double-sided readout samples were prepared, in which the film of the present invention was not attached.

These samples were incubated at 60'C and 90% relative humidity for 12 hours.

Table 1 shows the results of a cycle test in which one cycle was 12 hours at -20°C. As can be clearly seen from Table 1, in the comparative example, lifting of the recording layer due to water absorption by the substrate and deformation of the substrate (warping, surface runout) was noted after 20 cycles, but no abnormalities were observed in this example. figure,
It was found to have excellent durability.

(Effect of the invention) One side of a magneto-optical recording medium using a transparent plastic substrate,
Alternatively, the magneto-optical recording medium of the present invention, which has a polypropylene film coated with polyvinylidene chloride on both sides, will not deform due to moisture absorption of the substrate even if it is left for a long time under harsher environmental conditions of high temperature and high to low humidity. , surface runout), there is no lifting of the recording layer (blister) due to moisture absorption of the substrate, and there is little oxidation deterioration of the recording layer, improving long-term reliability.
This has the effect of improving quality.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a magneto-optical single disk of the present invention,
FIG. 2 is a cross-sectional view of the magneto-optical double-sided reading disk of the present invention. (Explanation of symbols) 1, ......-Plastic substrate 2, ...
... Magneto-optical recording layer 3, ...
Protective layer/adhesive layer 4... Film layer Figure 1

Claims (2)

[Claims] (1) A magneto-optical recording medium consisting of a transparent plastic substrate and a magneto-optical recording layer provided on the substrate, characterized in that a polypropylene film coated with polyvinylidene chloride is bonded to one or both sides of the medium. Magneto-optical recording medium. (2) Magneto-optical recording in which two magneto-optical recording media consisting of a transparent plastic substrate and a magneto-optical recording layer provided on this substrate are placed facing each other with the recording layer on the inside and bonded together via an adhesive. 1. A magneto-optical recording medium comprising a polypropylene film coated with polyvinylidene chloride attached to one or both sides of the medium.