JPH07282480A - Magneto-optical disk and magneto-optical recording method using the same - Google Patents

Abstract

PURPOSE:To prevent damage and wear by a magnetic head by composing the sliding protective film of a magneto-optical disk which executes recording while sliding the magnetic head of a mixture composed of a UV curing resin and a lubricity imparting agent. CONSTITUTION:A magnetic thin film having perpendicular magnetic anisotropy is used as a magneto-optical recording layer. For example, amorphous alloy thin films of rare-earth transition metals, such as DyFeCo, TbFeCo, GdFeCo and NaFeCo, and artificial laminated films of noble metals/transition metals such as Pt/Co are used. Dielectric layers consisting of oxides and nitrides, such as SiO2, Al2O3, Ta2O3 and Si3N4, and mixtures composed thereof, and composite compds. such as Al-Ta-0 are usually preferably formed above and below the magneto-optical recording layer. In such a case, the recording is executed while the magnetic head is slid relative to the disk surface and, therefore, the durability and lubricity are assured by providing the surface of the magneto-optical recording layer with the sliding protective film directly or via the dielectric layer and reflection layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk and a magneto-optical recording method using the same, which is used in a magneto-optical recording system for recording while sliding a magnetic head on the magneto-optical disk. Regarding the disc.

[0002]

2. Description of the Related Art As a conventional magneto-optical disk, there is a magneto-optical disk formed of a protective film made of resin on a magneto-optical recording magnetic layer made of TbFeCo or the like provided on a substrate directly or via another layer. In recent magneto-optical recording, a magnetic field modulation method capable of overwriting information, that is, laser light is continuously or intermittently irradiated onto the magneto-optical recording layer,
Attention has been paid to a method in which the direction of the magnetic field is modulated by an external magnetic field applying unit to record at least a portion irradiated with laser light.

The magnetic field is usually applied by a magnetic field head having a magnetic field generating means. At present, a magnetic head applying such a high-speed reversal magnetic field can generate only a weak magnetic field. Therefore, it is necessary to bring the magnetic head as close as possible to the magneto-optical recording magnetic layer. From such a demand, a so-called sliding type magnetic head has been proposed which is used while sliding on a magneto-optical disk during recording.

This sliding type magnetic head is used for a music recording magneto-optical disk having a diameter of 64 mm and a diameter of 120 mm. However, when recording is performed with this sliding type magnetic head, the rotating magneto-optical disk and the magnetic head come into contact with each other, so that if the recording magnetic layer is exposed, the recording magnetic layer is damaged by the magnetic head. However, there is a problem that the recorded information is destroyed.

Therefore, a protective film is provided for the purpose of protecting the recording magnetic layer. However, since the conventional protective film is inferior in lubricity, the absolute value of the frictional force applied to the disk increases and the fluctuation of the frictional force also increases. Then, the rotation of the disc becomes unstable, which may cause a recording error or a tracking error.

Further, the surface hardness required for the protective film becomes high, and if the hardness becomes insufficient, it will be worn or damaged.

[0007]

SUMMARY OF THE INVENTION The present invention was devised in view of these problems, and ensures sufficient durability and good lubricity even when the magnetic head is slid. It is an object of the present invention to provide an optical magneto-optical disc.

[0008]

According to the present invention, a magneto-optical recording layer is provided on a substrate, and a sliding protective film made of a curable resin is provided on the substrate directly or through another layer. A magneto-optical disk for recording while sliding the
The magneto-optical disk is characterized in that the sliding protection film comprises a mixture of an ultraviolet curable resin and a lubricity imparting agent.

Further, according to the present invention, the magneto-optical disk is used, and the recording light or the reproducing light is irradiated from the substrate side while the magnetic head is slid on the sliding protection layer to apply the modulation magnetic field. It is a recording method. Needless to say, the performance required of the sliding protection film is appropriate hardness and surface lubricity because the magnetic head slides on the protection film.

As the lubricity-imparting agent, a commonly used silicon compound, polydimethylsiloxane, for example, polydimethylsiloxane (L manufactured by Nippon Unicar Co., Ltd.)
-45), polydimethylsiloxane / polyether block copolymer (PS072 manufactured by Chisso Corporation, L-7001 manufactured by Nippon Unicar Co., Ltd.), alkyl group-modified polydimethylsiloxane (KF41 manufactured by Shin-Etsu Silicone Co., Ltd.)
2) or a fluorine-based compound (Sumitomo 3M Co., Ltd., Florard FC-430).

Although these compounds (hereinafter sometimes referred to as non-reactive lubricants) do not react with the resin during the curing reaction for forming a protective film, they are sufficient under ordinary use conditions. It is possible to achieve the desired performance. When it is used for a long period of time, the non-reactive lubricant is gradually wiped off from the surface of the protective film.

Then, the friction coefficient of the surface of the sliding protection film becomes high, and a very large force is applied to the sliding magnetic head, which may cause scratches. Such a phenomenon is caused by a reactive functional group or a polymerizable group, preferably (meth)
This can be solved by using a lubricity-imparting agent having an acrylic group, an amino group, an epoxy group, a carboxyl group or a hydroxyl group in the molecule, preferably a polydimethylsiloxane type, alone or in combination.

Of these, polydimethylsiloxane having a methacryl group or an amino group in the molecule is particularly preferable. Such a reactive functional group- or polymerizable group-containing lubricity imparting agent (hereinafter sometimes referred to as reactive lubricant) is
Since it reacts with the resin during UV irradiation for the protective film formation reaction, unlike one non-reactive lubricant, it will not be wiped off during long-term use. It is possible to maintain good surface slipperiness over time.

The present invention will be described in detail below. In the present invention, the substrate is not particularly limited, and a resin substrate such as a polycarbonate resin, an acrylic resin, or a polyolefin resin, a glass substrate or the like can be usually used. The substrate generally has a thickness of 0.5 to 1.5 mm.

A magnetic thin film having perpendicular magnetic anisotropy is used as the magneto-optical recording layer. For example, DyFeCo,
Rare earth-transition metal alloy amorphous thin films such as TbFeCo, GdFeCo and NdFeCo, precious metals such as Pt / Co /
A transition metal artificial laminated film or the like is used. The thickness of the magneto-optical recording layer is preferably about 5 to 50 nm.

The upper and lower portions of the magneto-optical recording layer are usually made of Si.
It is preferable to provide a dielectric layer made of an oxide such as O ₂ , Al ₂ O ₃ , Ta ₂ O ₃ , or Si ₃ N ₄ , a nitride thereof, a mixture thereof, a composite compound such as Al—Ta—O, or the like. . The dielectric layer is intended for a moisture permeation preventing effect, an optical interference effect, a heat insulating effect and the like.

Furthermore, it is preferable to provide a reflective layer on the dielectric layer for sensitivity adjustment and signal level adjustment. A for the reflective layer
1 alloy or the like is preferable. Each of these layers is preferably formed by a sputtering method, a vapor deposition method, or the like. In the magneto-optical disk of the present invention, since recording is performed while the magnetic head is slid on the disk surface, a slide protection film is provided directly on the magneto-optical recording layer or via a dielectric layer and a reflective layer. ,
It ensures durability and lubricity.

It has been found that this sliding protection film is preferably obtained by curing a mixture of a resin and a lubricity-imparting agent. Among them, it is cheaper to use an ultraviolet curable resin as the resin. From the viewpoint of high productivity, other resins, for example,
It is preferable as compared with a thermosetting resin or the like. The sliding protection film is preferably obtained by applying a resin, which is a mixture of an ultraviolet curable resin and a lubricity imparting agent, onto a magneto-optical disk by a spin coating method or the like, and then irradiating it with ultraviolet rays to cure it.

The thickness of the sliding protection film is preferably in the range of 1 to 50 μm. If the film thickness is less than 1 μm, the durability becomes insufficient. When it exceeds 50 μm, cracks are likely to occur in the recording magnetic layer or the dielectric layer and warp of the disk tends to be large due to shrinkage during curing of the resin. The UV curable resin may be any UV curable resin that is generally used, but it should not contain a component that adversely affects the magneto-optical recording layer.

It is also preferable that the storage stability is excellent. As such an ultraviolet curable resin, a mixture of a 1- to 2-functional (meth) acrylate having a viscosity of 100 cps or less at 25 ° C., a bifunctional or higher (meth) acrylate having a viscosity of 100 cps or more under the same conditions, and a photopolymerization initiator is preferably used. To be done. Furthermore, as an optional component, an antistatic agent,
A leveling agent, a silane coupling agent, etc. can also be added.

Specific examples of the mono- and bifunctional (meth) acrylates having a viscosity of 100 cps or less include tetrahydrofurfuryl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 1,6-hexanediol diacrylate and neo. Pentyl glycol diacrylate etc. can be mentioned. Examples of the bifunctional or higher (meth) acrylate having a viscosity of 100 cps or more include polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and the like.

Any known photopolymerization initiator may be used, but a photopolymerization initiator having good storage stability after compounding is preferable. Examples of such compounds include benzophenone, 1-hydroxycyclohexyl phenyl ketone,
Benzoin isopropyl ether and the like can be mentioned. When a reactive lubricant is used as the lubricity-imparting agent, it is not wiped off for long-term use, and therefore the lubricity protective film can maintain good surface slipperiness over a long period of time.

Examples of such reactive lubricants include:
As the polydimethylsiloxane having a (meth) acrylic group in the molecule, methacryl-modified polydimethylsiloxane with one terminal (BX16-192 manufactured by Toray Dow Corning Silicone Co., Ltd.), both terminals of the polydimethylsiloxane are modified with carbinol. Silicone oil (KF6003 manufactured by Shin-Etsu Chemical Co., Ltd.) and methacryloyloxyethyl isocyanate or m-isopropenyl-α,
Modified polydimethylsiloxane obtained by reacting with α'-dimethylisocyanate, polydimethylsiloxane modified with amino groups at both ends (TSL9 manufactured by Toshiba Silicone Co., Ltd.)
Examples of the modified polydimethylsiloxane obtained by reacting 386) with glycidyl (meth) acrylate.

Examples of the polydimethylsiloxane having a mercapto group in the molecule include α, ω-bis (mercaptomethyl) polydimethylsiloxane (TSL9876 manufactured by Toshiba Silicone Co., Ltd.).

[0025]

EXAMPLES The present invention is described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 80 nm of silicon nitride, 26 nm of Tb ₂₂ Fe ₇₀ Co ₈ (numerical values are component ratios, atomic%) and 20 n of silicon nitride were formed on a polycarbonate resin substrate by a sputtering method.
m, an Al alloy film having a thickness of 80 nm are formed in this order, and a curable resin containing a lubricity imparting agent having the following composition is applied thereon by a spin coating method and cured by ultraviolet irradiation to form a sliding protective film. .

The average thickness of the sliding protection film was 7 μm.
As a durability test, temperature 23 ± 2 ℃, relative humidity 50 ± 5
% Environmental condition, Sony magnetic head RF320-
74G is brought into contact with the disc so that the load is 2 gf, and the disc is continuously run at 600 rpm.
During that time, the coefficient of dynamic friction was measured. As a result, the coefficient of dynamic friction was about 0.30 or less, which was almost the same as the initial value up to 3 million times, and then gradually increased to 0.4 times after 5 million times.
It was 3. The surface of the disk was observed after the durability test, but no scratch was found.

[0027]

Table 1 [Composition] <Resin> 1-2 functional (meth) acrylate having a viscosity of 100 cps or less at 25 ° C. Tetrahydrofurfuryl acrylate: 14 parts by weight · Bifunctional or higher (meth) having a viscosity of 100 cps or more at 25 ° C. Acrylate Trimethylolpropane triacrylate: 11 parts by weight Pentaerythritol triacrylate: 19 parts by weight Pentaerythritol tetraacrylate: 26 parts by weight Dipentaerythritol hexaacrylate: 16 parts by weight Photopolymerization initiator 1-hydroxycyclohexyl phenyl ketone 6 parts by weight <Lubricant> Polydimethylsiloxane / ethylene oxide propylene oxide block copolymer (PS manufactured by Chisso Corporation)
072): 8 parts by weight

Example 2 A magneto-optical disk produced in the same manner as in Example 1 was coated with a curable resin containing a lubricity imparting agent having the following composition by the spin coating method as in Example 1, and then exposed to ultraviolet rays. Irradiated and cured. The thickness of the sliding protection film was 6 μm.

A durability test was conducted under the same conditions as in Example 1.
As a result, the dynamic friction coefficient was 0.32 even after sliding 5 million times, which was about the same as the initial value.

[0030]

[Table 2] [Composition] <Resin> 1 to 2 functional (meth) acrylate having a viscosity of 100 cps or less at 25 ° C. Tetrahydrofurfuryl acrylate: 14 parts by weight · Bifunctional or more (meth) having a viscosity of 100 cps or more at 25 ° C. Acrylate Trimethylolpropane triacrylate: 11 parts by weight Pentaerythritol triacrylate: 19 parts by weight Pentaerythritol tetraacrylate: 26 parts by weight Dipentaerythritol hexaacrylate: 16 parts by weight Photoinitiator 1-hydroxycyclohexyl phenyl ketone: 6 parts by weight <Lubricity imparting agent> Polydimethylsiloxane-ethylene oxide propylene oxide block copolymer (PS manufactured by Chisso Corporation)
072): 3 parts by weight Methacyl-modified polydimethylsiloxane at one end (Toray
BX16-19 made by Dow Corning Silicone Co., Ltd.
2): 5 parts by weight

Example 3 A magneto-optical disk manufactured in the same manner as in Example 1 was coated with a curable resin containing a lubricity imparting agent having the following composition by a spin coating method as in Example 1, and then exposed to ultraviolet rays. Irradiated and cured. The average film thickness of the sliding protection film was 6 μm. A durability test was conducted under the same conditions as in Example 1. As a result, the friction coefficient was 0.35 even after sliding 5 million times, which was about the same as the initial value.

[0032]

[Table 3] [Composition] <Resin> 1 to 2 functional (meth) acrylate having a viscosity at 25 ° C. of 100 cps or less 2-hydroxypropyl acrylate: 7 parts by weight 1,6-hexanediol diacrylate: 10 parts by weight Bifunctional or higher-functional (meth) acrylate having a viscosity of 100 cps or more at 30 ° C. Trimethylolpropane triacrylate: 16 parts by weight Pentaerythritol triacrylate: 19 parts by weight Dipentaerythritol hexaacrylate: 27 parts by weight Urethane acrylate (Toa Gosei Co., Ltd. M- 121
0): 8 parts by weight Photoinitiator benzoin isopropyl ether: 6 parts by weight <Lubricity imparting agent> Polydimethylsiloxane-polyether block copolymer (Nippon Unicar L7001): 5 parts by weight Both ends of polydimethysiloxane Oil modified with carbinol (KF60 manufactured by Shin-Etsu Silicone Co., Ltd.)
03) and a modified silicone oil obtained by reacting isocyanate ethyl methacrylate: 8 parts by weight

Example 4 On a magneto-optical disk produced in the same manner as in Example 1, a curable resin containing a lubricity-imparting agent having the following composition was applied by a spin coating method, followed by UV curing to form a sliding protective film. Formed. The average thickness of the sliding protection film was 7 μm. A durability test was conducted under the same conditions as in Example 1. The result is 5
The friction coefficient was 0.34 even after sliding, 000,000 times, which was about the same as the initial value.

[0034]

[Table 4] [Composition] <Resin> 1 to 2 functional (meth) acrylate having a viscosity of 100 cps or less at 25 ° C 1,6-hexanediol diacrylate: 13 parts by weight Tetrahydrofurfuryl acrylate: 13 parts by weight · 25 ° C With a viscosity of 100 cps or more (meth) acrylate Trimethylolpropane triacrylate: 15 parts by weight Dipentaerythritol hexaacrylate: 45 parts by weight Photopolymerization initiator: Methyl benzoyl formate 6 parts by weight <Lubricity imparting agent> Amino Modified silicone oil (KF-865 manufactured by Shin-Etsu Silicone Co., Ltd.): 6 parts by weight Mercapto-modified silicone oil (X-22-980 manufactured by Shin-Etsu Silicone Co., Ltd.): 2 parts by weight

Comparative Example 1 On the magneto-optical disk produced in the same manner as in Example 1, the protective film composition described in Example 1 from which only the lubricity-imparting agent was removed was applied by spin coating, and further ultraviolet rays were applied. It was cured to form a slide protection film. The average thickness of the sliding protection film was 7 μm.

When a durability test was conducted under the same conditions as in Example 1, the coefficient of friction showed a large value of 0.90 or more immediately after the start, and scratches were generated on the surface of the protective film after about 1000 times. At that point the study was discontinued.

[0037]

In the magneto-optical disk according to the present invention, the protective film made of the mixture of the ultraviolet curable resin and the lubricity imparting agent is formed, and the sliding characteristics for the sliding magnetic head are remarkably improved. Therefore, damage and abrasion due to the magnetic head are prevented, so that a highly reliable magneto-optical disk can be provided.

Claims (4)

[Claims] 1. A magneto-optical recording layer is provided on a substrate, and a slide protection film made of a curable resin is provided on the substrate directly or through another layer, and recording is performed while sliding a magnetic head. A magneto-optical disk for use in the above, wherein the sliding protection film is made of a mixture of an ultraviolet curable resin and a lubricity imparting agent. 2. The magneto-optical disk according to claim 1, wherein the lubricity imparting agent is polydimethylsiloxane having a reactive functional group or a polymerizable group in the molecule. 3. A reactive functional group or polymerizable group is (meth).
The magneto-optical disk according to claim 2, which is an acrylic group, an amino group, an epoxy group, a carboxyl group or a hydroxyl group. 4. The recording / reproducing light is applied from the substrate side while using the magneto-optical disk according to claim 1 and applying a modulation magnetic field by sliding a magnetic head on the slide protection layer. A magneto-optical recording method characterized by irradiation.