JPH05210877A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent a scratch or a wear caused by the sliding of a magnetic head and to improve the durability of a magneto-optical recording medium. CONSTITUTION:A recording part 2 is formed on a transparent base board 1, and the recording part 2 is covered to form a protective film. At this time, the protective film is constituted by laminating a current protective film 3 consisting of an ultraviolet curing resin and a wear resistant protective film 4 obtained from a coating film of an ultraviolet curing resin added with silicon dioxide particles. As the silicon dioxide particles, particles having 0.5-2.0mum average grain diameter are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium used in a magneto-optical recording system for recording while sliding a magnetic head on the magneto-optical recording medium.

[0002]

2. Description of the Related Art In a magneto-optical recording method, a magnetic thin film is partially heated above a Curie point or a temperature compensation point to eliminate the coercive force of this portion and magnetize in the direction of a recording magnetic field applied from the outside. The basic principle is to reverse the direction of
It is being put to practical use in an optical file system, an external storage device of a computer, a recording device of audio and video information, and the like. As a magneto-optical recording medium used in this magneto-optical recording system, a recording magnetic layer having a large magneto-optical effect and having an easy axis of magnetization in the direction perpendicular to the film surface on one main surface of a transparent substrate made of polycarbonate or the like. A recording unit is formed by laminating (for example, a rare earth-transition metal alloy amorphous thin film), a reflection layer, and a dielectric layer, and a signal is read by irradiating a laser beam from the transparent substrate side. Are known.

[0003]

By the way, the magneto-optical recording system is roughly classified into an optical modulation system and a magnetic field modulation system, and since they can be overwritten, expectations for the magnetic field modulation system are increasing. .. The above magnetic field modulation method is
The information signal is written in the magnetic thin film by reversing the applied magnetic field at high speed, and the magnetic field is normally applied by a magnetic head having magnetic field generating means. At present, an electromagnetic actuator is used as a magnetic head for applying such a high-speed reversal magnetic field, but it is used while sliding on a magneto-optical recording medium at the time of recording due to cost requirements. A so-called sliding type magnetic head has been studied.

When recording is performed with this sliding type magnetic head, since the magnetic head and the magneto-optical disk are used in a state of being completely in contact with each other, scratches and abrasions of the recording magnetic layer due to sliding are problematic. Become. Therefore, it is necessary to provide a wear resistant protective film for the purpose of protecting the recording magnetic layer. Conventionally, an ultraviolet curable resin has been used as the wear resistant protective film. This ultraviolet curable resin is characterized in that it is easily applied to a polycarbonate substrate, has good adhesion, has low moisture permeability, and is harder than the polycarbonate substrate. As described above, although the ultraviolet curable resin has very excellent characteristics, it is considered as a material for the wear-resistant protective film used in the magneto-optical recording medium premised on the use of the sliding magnetic head. If it does, the hardness of the film itself is insufficient. For this reason, the abrasion-resistant protective film may be damaged by sliding of the magnetic head, and as a result, the recording magnetic layer may be damaged.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and it is an object of the present invention to provide a magneto-optical recording medium capable of ensuring sufficient durability even when a magnetic head is slid. To aim.

[0006]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, contain spherical silicon dioxide particles in an ultraviolet curable resin used as a material for an abrasion resistant protective film. It was found that the hardness of the obtained coating film is improved by doing so, and the present invention has been completed. That is,
The magneto-optical recording medium of the present invention comprises a recording magnetic layer formed on a transparent substrate and a wear-resistant protective film laminated on the surface opposite to the transparent substrate. Contains silicon dioxide particles having an average particle diameter of 0.5 to 2.0 μm.

[0007]

When recording is performed while the magnetic head slides on the magneto-optical recording medium, an increase in error rate due to wear and damage of the magneto-optical recording medium poses a problem. By forming the wear-resistant protective film on the sliding surface of the magnetic head, the above-mentioned wear and damage can be prevented. At this time, the wear-resistant protective film has an average particle size of 0.
By including the silicon dioxide particles of 5 to 2.0 μm, the hardness of the wear-resistant protective film is increased, and even better durability is secured.

[0008]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results. The magneto-optical disk of this embodiment is
As shown in FIG. 1, a recording portion 2 is formed on one main surface 1 a of a substrate 1, an ultraviolet curable resin layer 3 is formed so as to cover the surface of the recording portion 2, and further on the ultraviolet curable resin layer 3. The abrasion-resistant protective film 4 is laminated. The substrate 1 is a disk-shaped transparent substrate having a thickness of several mm (for example, 1.2 mm), and its material is acrylic resin,
In addition to plastic materials such as polycarbonate resin, polyolefin resin, and epoxy resin, glass or the like can be used. On the surface of the substrate 1 on the side where the recording section 2 is provided, a guide groove, an address code pit, or the like having a depth of about ¼ of the wavelength of the laser beam used during reproduction is usually used. Both are not shown).

The recording section 2 has a multi-layer structure in which a recording magnetic layer 6, dielectric layers 5 and 7, and a reflection film 8 are laminated, and usually the first dielectric layer 5 is formed on a substrate 1. Is formed, and the recording magnetic layer 6, the second dielectric layer 7, and the reflective film 8 are laminated in this order on the first dielectric layer 5. Of these, oxides and nitrides can be used as the first dielectric layer 5 and the second dielectric layer 7, and oxygen in the dielectric layers 5 and 7 is used as the recording magnetic layer 6. Nitride is more preferable because it may adversely affect the above. Silicon nitride, aluminum nitride, or the like is preferable as a substance that does not allow oxygen and moisture to pass therethrough and allows the used laser beam to pass therethrough sufficiently. The recording magnetic layer 6 is an amorphous magnetic thin film having an easy magnetization direction in a direction perpendicular to the film surface, which is excellent in magneto-optical characteristics and has a large coercive force at room temperature. It is desirable to have a Curie point near 200 ° C. Recording materials that meet such conditions include rare earth-transition metal alloy amorphous thin films and the like.
A FeCo-based amorphous thin film is suitable. This recording magnetic layer 6
An additive element such as Cr may be added to the alloy for the purpose of improving the corrosion resistance.

The reflective film 8 is preferably composed of a film having a high reflectance that reflects 70% or more of the laser light at the boundary with the second dielectric layer 7, and a non-magnetic metal vapor deposition film is suitable. .. Further, the reflective film 8 is preferably a thermally good conductor, and aluminum is suitable in view of availability and film formation. Each of these layers is formed by a so-called vapor phase plating technique such as vapor deposition or sputtering.
At this time, the film thickness of each layer can be set arbitrarily, but is usually set to several hundreds to several thousands Å. It is preferable that these film thicknesses are determined taking into consideration not only the optical properties of each layer alone, but also the effect of combination. This is because, for example, when the film thickness of the recording magnetic layer 6 is thinner than the wavelength of the laser light, the laser light causes multiple interference with the light transmitted through the recording magnetic layer 6 and reflected at each layer boundary, and the combination of the film thicknesses This is because the effective optical and magneto-optical characteristics of the recording magnetic layer 6 greatly change. The ultraviolet curable resin layer 3 is provided for the purpose of flattening and protecting the surface of the recording portion 2, but it may not be provided depending on the material and film thickness of the abrasion resistant protective film 4 described later. The UV curable resin layer 3 is usually obtained from a coating film of acrylic UV curable resin or the like and has a film thickness of 3 to
The thickness is preferably about 5 μm.

The above is the basic structure of the opto-optical disk. In the magneto-optical recording medium of the present invention, magnetic field modulation recording is performed while the magnetic head slides on the disk surface.
A wear resistant protective film 4 is provided directly on the ultraviolet curable resin layer 3 or on the recording portion 2 so as to suppress wear due to sliding and ensure the running performance of the magnetic head. Less than,
The abrasion resistant protective film 4 will be described. The wear-resistant protective film 4 contains spherical silicon dioxide particles.
The average particle diameter of the silicon dioxide particles is 0.5 to 2.0 μm, more preferably 0.7 to 1.5 μm. When the average particle diameter is larger than the above range, the surface of the film becomes rough when cured. On the contrary, if the average particle size is smaller than the above range, sufficient hardness cannot be secured. Thus, by including silicon dioxide particles in the wear-resistant protective film 4, the hardness of the wear-resistant protective film 4 increases, and the wear-resistant protective film 4 is scratched by the sliding of the magnetic head. Wear can be suppressed, and eventually damage to the recording magnetic layer 6 can be prevented. As the abrasion-resistant protective film 4, a usual protective film material can be used, for example, an ultraviolet curable resin (trade name SD-17) or the like is used.

Then, the silicon dioxide particles are dispersed in the ultraviolet curable resin. The silicon dioxide particles are
It is preferably added in an amount of 10 to 100 parts by weight with respect to 100 parts by weight of the ultraviolet curable resin. As described above, the cured resin film containing silicon dioxide particles is used as the wear-resistant protective film 4
In this case, the method for forming the same is preferably a method by spin coating, for example. That is, by attaching the magneto-optical disk to the motor rotating shaft and supplying the coating material onto the magneto-optical disk while rotating it to form a coating film, a coating film having uniform thickness can be formed. This method not only facilitates the film formation, but also makes the film thickness uniform, and further it is possible to control the surface roughness and film thickness by manipulating the solid content and viscosity of the coating material. The abrasion-resistant protective film 4 does not necessarily have to be a single layer, and can be formed in multiple layers. In any case, the total thickness of the abrasion-resistant protective film 4 and the ultraviolet curable resin layer 3 is 100 μm or less, and in this embodiment, it is 10 to 15 μm.

When recording is performed on the magneto-optical disk having such a structure, as shown in FIG. 2, the optical pickup 11 and the magnetic head 12 are arranged to face each other with the magneto-optical disk 10 interposed therebetween. A magneto-optical recording device is used. In this magneto-optical recording device, recording is performed while sliding the magnetic head 12 on the magneto-optical disk 10. Here, in order to check the durability of the magneto-optical disk (disk radius 30 mm), the magneto-optical disk is slid under a constant load applied by a magnetic head for a floppy disk to form the abrasion-resistant protective film. Depth of the attached scratch is measured by the stylus type step gauge (DEKTAK303
0). The results are shown in Table 1. At this time, the disk rotation speed was 2000 rpm, the number of passes was 100,000, and the linear velocity was 6.3 m / sec. Further, the average particle size of the silicon dioxide particles contained in the wear resistant protective film was changed as shown in Table 1, and the addition amount was 20 with respect to the ultraviolet curable resin (trade name SD-17). It was set to% by weight.

[Table 1]

As shown in Table 1, in the abrasion-resistant protective film containing silicon dioxide particles, scratches due to sliding of the magnetic head were less than those in the ultraviolet-curing resin film containing no silicon dioxide particles. .. When the average particle size of the silicon dioxide particles is changed in the range of 0.7 to 1.5 μm,
The larger the average particle size, the better the result obtained. From this, it was found that by dispersing the silicon dioxide particles in the ultraviolet curable resin film, the abrasion-resistant protective film obtained was less likely to be exhausted and the sliding resistance was remarkably improved. Therefore,
When the hardness of the wear-resistant protective film containing such silicon dioxide particles was evaluated by pencil hardness, the pencil hardness of the ultraviolet-curing resin film containing no silicon dioxide particles was F, whereas the hardness of the silicon dioxide particles was F. The pencil hardness of the abrasion-resistant protective film containing 2H was 2H, which also proved to be excellent in abrasion resistance.

[0015]

As is apparent from the above description, in the magneto-optical recording medium of the present invention, since the abrasion resistant protective film is formed on the existing protective film, the sliding resistance to the magnetic head is remarkably high. Be improved. Therefore, it is possible to provide a magneto-optical recording medium which is less scratched and worn due to the abrasion resistance of the magnetic head and which has excellent durability. Further, the wear-resistant protective film,
Since the film can be formed by the same method as the existing protective film, the magneto-optical recording medium can be manufactured relatively easily without requiring a special step.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a magneto-optical recording medium of the present invention.

FIG. 2 is a schematic diagram for explaining a sliding type magneto-optical recording system to which the magneto-optical recording medium of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Recording part 3 ... UV curable resin layer 4 ... Wear-resistant protective film

Claims (1)

[Claims] 1. A recording magnetic layer is formed on a transparent substrate, and a wear-resistant protective film is laminated on a surface opposite to the transparent substrate, and the wear-resistant protective film has an average particle size. A magneto-optical recording medium containing silicon dioxide particles of 0.5 to 2.0 μm.