JPH02108257A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve preservable stability by setting the open time of hot melt resin layers provided between an adhesive agent layer and org. protective layers shorter than the open time of the adhesive agent layer. CONSTITUTION:Two sheets of the magneto-optical recording media 6 and 6' of veneers having the magneto-optical recording layers 9, 9' which consist of the laminated films of the recording layers 2, 2' and the thin films of dielectric protective layers 3, 4, 3, 4 disposed above and below the recording layers 2, 2' respectively so as to crimp these layers are well as the org. protective layers 5, 5' provided to cover the magneto-optical recording layers 9, 9' on substrates 1, 1' are stuck to each other via the adhesive agent layer 10 in such a manner that the substrate 1, 1' are positioned on the outermost surface and the org. protective layers 5, 5' are positioned on the innermost surface. The hot-melt resin layers 7, 7' are provided between the org. protective layers 5, 5' and the adhesive agent layer 10, by which the magneto-optical recording medium 8 of a both-face recording type is formed. The adhesive agent layer 10 is a hot- melt adhesive agent and the open time thereof is set longer than the open time of the hot-melt resin layers 7, 7'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magneto-optical recording medium, and more particularly to a laminated double-sided recording type magneto-optical recording medium with improved storage stability.

[Prior art and its problems] In recent years, magneto-optical recording media have been put into practical use as magneto-optical disks that can be written and read using laser light, such as large-capacity data files.

Magneto-optical recording media are generally used in two ways: a single medium in which a magneto-optical recording layer consisting of a thin film of a recording layer or a protective layer formed by a film-forming method such as sputtering is provided on a transparent substrate; 2 of the veneers with the adhesive layer facing outwards.
It is sometimes used in the form of a double-sided recording type in which sheets are pasted together. The latter double-sided recording type has a large recording capacity and is therefore widely used.

A problem with this double-sided recording type magneto-optical recording medium is that the recording layer is often corroded by air or moisture entering through the adhesive layer or by air bubbles contained in the adhesive layer. In order to solve this problem, a method of providing a protective layer made of an organic resin between the adhesive layer and the magneto-optical recording layer is disclosed in, for example, Japanese Patent Laid-Open No. 61-68750. In particular, it has been proposed to use ultraviolet curing resins and hot melt resins as organic resins. It has also been proposed to use epoxy resin or hot melt type resin for the adhesive layer.

As the protective layer for the organic substance mentioned above, ultraviolet curable resins are excellent because they do not require heating during production, can be cured quickly, and have good air and moisture barrier properties. As disclosed in Japanese Patent No. 58-6!536, hot melt resin is the most suitable for the adhesive layer in terms of mass productivity and the like.

However, a double-sided recording type optical recording medium uses an ultraviolet curable resin as an organic protective layer and a hot-melt resin as an adhesive layer to bond two single-plate magneto-optical recording media on the organic protective layer side. For example, when a magnetic recording medium is left at 80° C. and 90% RH as an accelerated test for storage stability over time, the plastic flow of the hot melt resin layer is significantly reduced to about 100%.
After 0 hours of standing time, the adhesive layer, which was supposed to be uniformly coated on the organic protective layer, began to show unevenness, and the mechanical properties, such as surface runout and surface runout acceleration, decreased significantly. This has raised concerns about the storage stability of magneto-optical recording media.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of the prior art, and is a method of laminating two single-plate magneto-optical recording media with particularly improved storage stability. The object of the present invention is to provide a double-sided recording type magneto-optical recording medium.

[Means for Solving the Problems] The object of the present invention is to provide two media having a magneto-optical recording layer and an organic protective layer on a substrate, with the substrate as the outermost surface, and the organic protective layer as the innermost surface. In a double-sided recording type magneto-optical recording medium that is bonded together via an adhesive layer, there is a hot melt resin layer between the adhesive layer and the organic protective layer, and the open time of the hot melt resin layer is longer than the adhesive layer. This is achieved by a magneto-optical recording medium characterized by a shorter open time than the open time of the agent layer.

An example of the double-sided recording type magneto-optical recording medium of the present invention is shown in FIG. A recording layer 2.2 on the substrate 1.1 and the recording layer 2
．． 2-Thin films of dielectric protection N3.4.34- arranged above and below so as to sandwich each other cover the magneto-optical recording layer 9.9 made of a laminated film and the magneto-optical recording layer 9.9-. Two single-plate magneto-optical recording media 6 and 6- having organic protection N5.5- provided as above are mounted on the substrate 1.
The organic protective layer 5.5- is positioned at the outermost surface and the organic protective layer 5.5- is positioned at the innermost surface, and the organic protective layer 5.5- and the adhesive layer are bonded together via an adhesive layer 10. A hot-melt resin layer 7.7- is provided between the two sides of the double-sided recording type magneto-optical recording medium 8.

In the magneto-optical recording medium 8 of the present invention, the adhesive N10 is usually a hot melt adhesive, and its open time is longer than the open time of the hot melt resin layer 7.7- in contact with it. long.

As described above, in the magneto-optical recording medium of the present invention, the adhesive F! 10 and the organic protective layer 5.5-, the hot melt resin layer 7.7- is provided, and the adhesive N
The hot melt resin N7.7 with an open time of 10
- By making the magneto-optical recording medium 8 of the present invention longer than the open time of the present invention, no abnormality occurs in the adhesive layer 10 even if the magneto-optical recording medium 8 of the present invention is left under high temperature and high humidity for a long time for an acceleration test over time. When a conventional magneto-optical recording medium was left under the conditions described above, the adhesive layer, which was supposed to be uniformly coated on the organic protection N5.5-, became uneven. As a result, mechanical properties such as surface runout and surface runout acceleration do not deteriorate significantly. Therefore, in the magneto-optical recording medium of the present invention, there is little risk that the mechanical properties will deteriorate during storage or use.

Open time as used in the present invention refers to the time during which hot melt adhesive can be applied to objects to be bonded and then bonded together. (Published by Japan Society, May 1985), pages 14 to 18.

In other words, it is the heat retention time that allows bonding to some extent at high temperatures. Therefore, the open time does not represent the inherent properties of the hot melt adhesive, but is a value determined by the coating and bonding work conditions, such as the coating temperature, the temperature of the object to be bonded, the coating amount, and the bonding speed. In the present invention, when the adhesive layer and the hot melt resin layer are compared under the same coating and bonding working conditions, the open time of the hot melt resin layer is longer than the open time of the adhesive layer. It is characterized by its short length.

The difference between the open time of the adhesive layer and the open time of the hot melt resin layer is such that the former is 10 times larger than the latter.
It is desirable that it be at least twice as large.

By establishing the above-mentioned relationship between the adhesive layer and the hot-melt resin layer during their open time, hot-melt resin can be formed between the conventional adhesive layer and the organic protective layer as in the magneto-optical recording medium of the present invention. It has become possible to provide a magneto-optical recording medium that prevents plastic flow of the adhesive layer over storage time and has no deterioration in mechanical properties compared to a case where a resin layer is not provided.

Although many aspects of the factors contributing to this effect of the present invention are not clear, it is likely that the hot melt resin layer functions to moderate temperature changes in the viscoelastic properties of the adhesive layer.

Examples of the hot melt adhesive used in the adhesive layer of the present invention include 5EBS resin, SBS resin, and SIS resin.

On the other hand, examples of hot melt resins used for the hot melt resin layer include EVA resins, acrylic resins, polyamide resins, and the like.

As the organic protective layer of the present invention, an ultraviolet curable resin is preferable because it does not require heating during production, can be cured quickly, and has good air and moisture barrier properties.
Examples include acrylic resin, urethane acrylate resin, and epoxy acrylate resin.

The adhesive layer and the hot melt resin layer are both 1
It is melted at a high temperature of 00° C. or higher and coated with a roll coater to a thickness of about 10 μm, and then pressed together to bond two single-plate magneto-optical recording media together.

As the material for the recording layers 2 and 2- constituting the magneto-optical recording layer of the magneto-optical recording medium of the present invention, thin films of various oxides and metal magnetic substances can be used. For example, MnB
i, crystalline materials such as MnAlGe, MnCuB1, G
d IG gate B 15mErGa IC, B ismYb
Single crystal materials such as coGe IG, as well as GdCo,
' GdFe, TbFe.

DyFe, GdFeBi, GdTbFe, GdFeC
It is a thin film using an amorphous material such as TbFeCo, TbFeNi, or the like. Among them, a recording layer mainly composed of rare earth metals or transition metals is most preferable in terms of sensitivity, C/N, etc., and can be used either as a single layer or in the form of alternating layers of thin films made of transition metals and thin films made of rare earth metals. be done.

In order to improve the corrosion resistance of the recording layer of the magneto-optical recording layer, metals such as Cr, Ti, Pt, A1, etc. may be added to either or both of the transition metal thin film and the rare earth metal thin film.

The thickness of the recording layers 2 and 2- is usually 100 to 2000.
It is A.

It is desirable to provide the dielectric protection N3.4.3- and 4- above and below the recording layer of the magneto-optical recording layer to improve durability and magneto-optical properties. The materials used for the dielectric protective layer include AIN and SiO.

S i02 , S iNx , S 1AION, etc. are used, and among them, SiNx and 5iA1ON are preferable. The thickness of this dielectric protective layer is usually 500 to 2000A.
It is.

3. A dielectric protective layer on the substrate side among the dielectric protective layers.
3- has a Kerr enhancement effect on the recording layer.

The substrates 2 and 2- used in the magneto-optical recording medium of the present invention
For the binding material, polycarbonate, polymethyl methacrylate, epoxy, glass, etc. can be used, and among resin substrates, polycarbonate is particularly desirable.

The magneto-optical recording layer 9.9- of the magneto-optical recording medium of the present invention is formed by depositing the recording layer N2.2- and the dielectric protective layer 3 on the substrate 1.1- by a film forming method such as a sputtering method. .4.3-
It is manufactured by forming a thin film of 14-. It is desirable that the oxygen content in the target used when forming these thin films is as low as possible.

In order to improve the sensitivity and C/N of the magneto-optical recording medium of the present invention, it is also effective to provide a reflective layer on the dielectric protective layer 4.4-, which is the uppermost surface of the magneto-optical recording layer. . This reflective layer is usually a thin film of metal with high reflectance, and for example, At, Au, Cu, Pt, Ta, and Ti are used alone or in alloys. AI and Cu are preferred because they have relatively good thermal conductivity. And its thickness is usually 100 to 1000A.

In the magneto-optical recording medium of the present invention, an organic protective layer such as an ultraviolet curable resin is provided by a spin code method or the like so as to cover the entire magneto-optical recording layer. The thickness of this organic protective layer is typically 1 to 100 μm.

The novel features of the present invention will be explained in more detail by the following Examples and Comparative Examples.

[Example] 130φ, 1.2m with guide groove provided by injection molding
A polycarbonate substrate having a thickness of m was placed in a vacuum chamber, and the inside of the vacuum chamber was evacuated to a degree of vacuum of 5×10 Torr or less. Next, Ar gas was introduced into the vacuum chamber until the degree of vacuum in the vacuum chamber reached 5×10, and then an 8-inch Si3N4
A thin film of a dielectric protective layer made of silicon nitride having a thickness of 900 Å was formed on the substrate by sputtering by applying 1 kW of RF power to the target.

Then, 800W of RF power was applied to the 8-inch Tb target and 1°OkW of RF power was applied to the 8-inch FeCo target.
Power was applied to form a thin recording layer film with a thickness of 100 OA on the dielectric protective layer by dual simultaneous sputtering. Further, on this recording layer, a thin film of silicon nitride was formed at 100 OA as a dielectric protection layer under the same film forming conditions as the dielectric protection layer, and a TbF film was formed on the polycarbonate substrate.
A magneto-optical recording layer was formed in which a recording layer made of eCo was sandwiched between upper and lower dielectric protective layers of silicon nitride.

Next, #5D-17 made by Dainippon Ink Co., Ltd., which is an acrylic ultraviolet curable resin, was applied to a thickness of 10 μm using a spin code method on the magneto-optical recording layer, and a high-pressure mercury lamp was used to apply 100 mW/c. The organic protective layer was formed by curing by irradiating ultraviolet rays under the conditions of m.

AC-1 Japan, an EVA-based hot melt resin
A hot melt resin layer was formed by melting #92 manufactured by Co., Ltd. at 120° C. and applying it to a thickness of 20 μm on the organic protective layer using a hot melt roll coater. Furthermore, 5 on top of that
#PS-45 manufactured by AC-I Japan which is EBS resin
0-20 was melted at 120° C. and applied to a thickness of 20 μm using a hot melt roll coater to form an adhesive layer.

Separately, the open time of the hot melt resin layer and the adhesive layer was determined by applying hot melt resin melted at 120°C to a thickness of 20 μm on a polycarbonate substrate.
This was determined by standing at 5° C. and placing another polycarbonate substrate in close contact with the coated surface, and measuring the time until the adhesive ceased to adhere. As a result, it was 5 seconds for the hot melt resin layer, and 10,000 seconds for the adhesive layer.

As described above, a magneto-optical recording layer and an organic protective layer are provided on a polycarbonate substrate, and two single-plate magneto-optical recording media each having a hot melt resin layer and an adhesive layer are bonded together under pressure to form a double-sided recording type. A magneto-optical recording medium was obtained.

This magneto-optical recording medium was left in a constant temperature and humidity chamber set at 80° C. and 90% RH for 1000 hours.

Pit error rate and surface runout acceleration tests were conducted on the magneto-optical recording medium before and after being left unused.

The pit error rate was measured by recording and reproducing at 1800 rpm and a carrier frequency of 3.7 MHz.

The surface runout acceleration test was performed using a mechanical property measuring machine at 180° rpm.

[Comparative Example-1] A double-sided recording type magneto-optical recording medium was produced under the same conditions as in the example except that a hot melt resin layer was not provided.

The characteristics of the obtained magneto-optical recording medium were measured under the same conditions as in the examples.

[Comparative Example 2] A double-sided recording type magneto-optical recording medium was prepared under the same conditions as in the example except that no organic protective layer was provided.

The characteristics of the obtained magneto-optical recording medium were measured under the same conditions as in the examples.

Table 1 Example before standing 2.4 Comparative example-13,0 Comparative example-22,8 [Effect of the invention] As in the present invention, there is no open time between the organic retention II layer and the adhesive layer. By providing a shorter hot melt resin layer than over time, especially after leaving? , 1 22.7 7.5 Before storage 5.2 6.0 5.8 After storage 3.8 3.5 12.0 Two single-plate magneto-optical recording media with no risk of deterioration in mechanical properties are bonded together. A double-sided recording type magneto-optical recording medium can be obtained. In particular, by combining it with an organic protective layer made of an ultraviolet curable resin, a magneto-optical recording medium with excellent storage stability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the magneto-optical recording medium of the present invention. 1.1--Substrate 2.2-Recording layer 3.3-Dielectric protective layer (enhancement effect) 4.4
- Dielectric protective layer 5.5 - Organic protective layer 6.6 - Adhesive layer 7.7 - Hot melt resin layer 8 - Magneto-optical recording medium 9.9 - Magneto-optical recording layer 10 - Adhesive layer

Claims (1)

[Claims] Double-sided magneto-optical recording in which two media having a magneto-optical recording layer and an organic protective layer on a substrate are bonded together via an adhesive layer, with the substrate as the outermost surface and the organic protective layer as the innermost surface. A magneto-optical recording medium, characterized in that the medium includes a hot-melt resin layer between the adhesive layer and the organic protective layer, and the open time of the hot-melt resin layer is shorter than the open time of the adhesive layer. .