JPH01269259A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve characteristics and to reduce cost by using broad materials by providing a 1st layer having tensile stress and the 2nd layer having compressive stress to the magneto-optical medium constituted by laminating and forming plural films on a substrate. CONSTITUTION:The magnetic recording layer 2 consisting of TbFeCo is formed on the substrate 1 consisting of a polycarbonate resin. An Si2N4 film 3 is formed as the 1st layer having the tensile stress on the magnetic recording layer 2 and further, a UV curing resin layer 4 is formed as the 2nd layer having the compressive stress thereon. The camber of the substrate 1 is thus decreased and the use of the Si2N4 film 3 as the protective film of the magnetic recording layer 2 is enabled. The characteristics are, therefore, improved and the cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium, and more specifically to an improvement in its multilayer structure.

[Prior art]

Magneto-optical recording media are formed with a multilayer structure including dielectric layers or metal layers in order to protect the magnetic recording layer and improve its characteristics. For example, Japanese Patent Publication No. 60-131659 discloses a magnetic recording layer provided with a SiJm protective layer in order to prevent oxidative deterioration;
Japanese Patent No. 58 discloses a structure in which a Si+Na layer is provided as a radiation layer of a magnetic recording layer heated by laser light to improve the characteristics of the magnetic recording layer.

Furthermore, since the Kerr effect of magneto-optical recording media is generally small, it is possible to increase the Kerr effect by creating a multilayer structure, for example, as described in "Journal of the Japan Society of Applied Magnetics J Vol.

9.11h2.1985, page 105.

As described above, magneto-optical recording media have conventionally often had a multilayer structure.

[Problem to be solved by the invention]

However, when the magneto-optical recording medium has a multilayer structure,
Warpage may occur in the magneto-optical recording medium due to internal stress in each layer. Generally, in magneto-optical recording media, it is necessary to keep the angle of warpage to 5 mrad or less in view of the performance requirements of the optical head. This makes it difficult to control the conditions for forming a multilayer film, and there is also the problem that materials with large internal stress cannot be used.

The present invention was made in view of the above circumstances, and by combining a layer with tensile stress and a layer with compressive stress, it is possible to suppress the occurrence of warping due to the internal stress of each multilayer film, and to improve material selection. It is an object of the present invention to provide a magneto-optical recording medium that can expand the width of the recording medium, improve its characteristics, and reduce its cost.

[Means to solve the problem]

A magneto-optical recording medium according to the present invention is a magneto-optical recording medium in which a plurality of films are layered on a substrate, and includes a first layer having tensile stress and a second layer having compressive stress. Features.

[Effect]

The first layer having tensile stress formed on the substrate tends to cause the substrate to warp from the film surface side to the substrate side. On the other hand, due to the second layer having compressive stress, the substrate tends to warp from the substrate side to the film surface side.

Therefore, the first and second layers bring the substrate into equilibrium and reduce warping.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing examples thereof.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the magneto-optical recording medium according to the present invention, where l is a substrate made of a transparent resin such as polycarbonate resin or acrylic resin;
A magnetic recording layer 2 made of TbFeCoTi, a Si3N4 film 3 serving as a protective layer, and an ultraviolet curing resin layer 4 serving as an overcoat layer are laminated thereon in this order.

Furthermore, Figures 2 to 5 are diagrams showing two types of magneto-optical recording media used to confirm the effects of this example, and Figure 2 is a magneto-optical recording medium in which materials having tensile stress are laminated. FIG. 3 is a schematic perspective view showing a warped state of the magneto-optical recording medium shown in FIG. The cross-sectional view, FIG. 5, is a schematic perspective view showing a warped state of the magneto-optical recording medium shown in FIG. 4.

The magneto-optical recording medium shown in FIG. 2 shows the case where the ultraviolet curable resin layer 4 of the example is not laminated, and a T film is placed on a polycarbonate resin substrate 1 with a thickness of 1.2 mm and a diameter of 120 mm.
A magnetic recording layer 2 of bPeCo with a thickness of 900 mm and a film 3 with a thickness of tJ of 800 mm were formed.

Although the Si3N4 film 3 has a great protective effect on the magnetic recording layer 2,
Because the internal stress is large, the board is likely to warp. In particular, when plastic is used for the substrate, the strength of the substrate is weak, so warping becomes noticeable. In this case, as shown in FIG. 3, the magneto-optical recording medium is warped in the shape of a bowl with the substrate 1 as the inner wall due to the tensile stress of the 5i) N4 film 3, and a maximum warp angle of 10 mrad was measured at the periphery. Ta.

The magneto-optical recording medium shown in FIG. 4 shows the case where the 5iJ4 film 3 of the example is not laminated, and has a thickness of 1.2 mm and a diameter of 12 mm.
TbFeCo on substrate 1 made of polycarbonate resin
A magnetic recording layer 2 with a thickness of 900 mm and an ultraviolet curing resin layer 4 with a thickness of 10 μm were formed.

Since compressive stress acts on the base Fi1 in the ultraviolet curing resin layer 4, the magneto-optical recording medium is warped in a bowl shape with the substrate 1 as the outer wall, as shown in FIG.
The warpage angle of ad was measured.

As is clear from the above (the 543N4 film 3 and the ultraviolet curing resin layer 4 cause the substrate l to warp in the opposite direction,
It was found that the shapes were also approximately the same. Therefore, in the magneto-optical recording medium of the present invention, both are combined and laminated, making it possible to suppress the warp angle to a maximum of 5 mrad or less.

In this way, in this example, the 5iJn film 3 was used as the first layer having tensile stress, and the ultraviolet curing resin N4 was used as the second layer having compressive stress, so it was possible to reduce the warpage of the substrate 1. 5iJn, which is highly effective, can now be used as a protective film for the magnetic recording layer 2.

Although the 5iJ4 film and the ultraviolet curing resin layer were combined in this example, the present invention is not limited to this, and can be widely applied as long as layers having tensile stress and compressive stress are combined. Needless to say.

〔effect〕

As detailed above, according to the magneto-optical recording medium of the present invention, warping due to internal stress of each layer of the multilayer film can be reduced by combining a layer with compressive stress and a layer with tensile stress, and a wide range of materials can be used. It is possible to create a magneto-optical recording medium with a multilayer structure by using the present invention, and the same effect can be achieved by making it possible to improve the characteristics and reduce the cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a magneto-optical recording medium according to the present invention, FIG. 2 is a schematic cross-sectional view showing a magneto-optical recording medium laminated with materials having tensile stress, and FIG. FIG. 2 is a schematic perspective view showing the state of warpage of the magneto-optical recording medium, FIG. 4 is a schematic cross-sectional view showing the magneto-optical recording medium laminated with materials having compressive stress, and FIG. FIG. 3 is a schematic perspective view showing a warped state of the magnetic recording medium shown in FIG. l...Substrate 2...Magnetic recording layer 3...SiJ,
Membrane 4...Ultraviolet curable resin layer patent Applicant: Sanyo Electric Co., Ltd. Agent Patent attorney: Noboru Kono Answer 1. Prison calculation 2. Book 3. Illustration 5.

Claims (1)

[Claims] 1. A magneto-optical recording medium in which a plurality of films are layered on a substrate, characterized by comprising a first layer having tensile stress and a second layer having compressive stress. magneto-optical recording medium.