JP2875089B2 - Protective film for magneto-optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a magneto-optical disk such as a microminiature magneto-optical disk.

[0002]

2. Description of the Related Art A magneto-optical disk is known as one of so-called writable optical disks capable of writing, erasing and reading information using a light beam.

In this magneto-optical disk 1, a magneto-optical recording layer 2 made of a perpendicular magnetization film is provided on a transparent substrate 2 as shown in FIG.
A reflective film 4 made of a thin film is laminated, and the reflective film 5
A protective film 5 made of, for example, an ultraviolet curing resin is formed thereon.

[0004] As a recording method of a magneto-optical disk, a magnetic field modulation method and the like are known. In the magneto-optical recording of the magnetic field modulation system, an optical pickup for irradiating a laser beam on the substrate 2 side with a magneto-optical disk in between is provided with a magnetic field generating means for moving in synchronization with the laser spot on the protective film 5, ie, a magnetic head. Then, the direction of the magnetic field is changed by changing the direction of the current flowing through the magnetic head.

[0005] The magneto-optical disk is rotated at a predetermined rotational speed about the center of the disk.

When a magnetic field corresponding to the recording signal is formed near the laser spot, the portion to be rewritten on the magneto-optical disk is heated to a temperature higher than the Curie temperature by the laser spot and demagnetized, and then moves from the laser spot to the Curie. When the temperature drops below the temperature, recording is performed by magnetizing the magnetic field in the above-described magnetic field direction.

The conventional magneto-optical disk 1 is a non-contact medium, so that the magnetic head is arranged at a necessary and sufficient distance from the protective film 5 of the magneto-optical disk 1.

The ultraviolet curable resin constituting the protective film 5 of the magneto-optical disk 1 does not generally have lubricity.

[0009]

On the other hand, the present applicant has previously proposed an ultra-small magneto-optical disk device for recording by bringing a magnetic head into contact with a magneto-optical disk. In this case, it is necessary to prevent the magnetic disk from scratching the disk surface even when the magnetic head slides.

Therefore, in order to impart lubricity to the protective film of the magneto-optical disk, a method of adding (internally adding) or bonding a lubricant such as silicon, a higher fatty acid, a metal salt thereof, or a higher alcohol has been adopted. However, it has been difficult to sufficiently reduce the coefficient of friction of the protective film even by adding a lubricant such as silicon. In such cases,
As a side effect of adding or binding a lubricant,
There was a problem that the function as a stable protective film for a magneto-optical disk was deteriorated, such as a decrease in adhesion due to bleeding of the lubricant on the surface of the protective film or an interface with the reflective film, and a decrease in slipperiness after aging. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to reduce the coefficient of friction of the surface of a protective film without deteriorating the function as a stable protective film for a magneto-optical disk. To provide a protective film for a magneto-optical disk.

[0012]

The present invention provides a resin comprising an oligomer and a reactive diluent represented by the following general formula:

Embedded image The product contains a PO (propylene oxide) / EO (ethylene oxide) modified silicone compound represented by the formula: In this case, the PO / EO-modified silicone compound is added in an amount of 0.03% by weight to 5% by weight based on the resin component.
It is also effective to include them.

As the oligomer, for example, urethane acrylate, epoxy acrylate and polyester acrylate oligomers are used. As the reactive diluent, for example, HDDA (hexanediol diacrylate) is used.

[0014]

In the present invention having such a constitution, since the PO / EO-modified silicone-based compound is contained as a lubricant in the resin comprising the oligomer and the reactive diluent, the friction coefficient on the surface of the protective film is reduced. . In this case, the friction coefficient hardly increases even when aging occurs, and the lubricant does not bleed on the surface of the protective film.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Example 1 50 parts by weight of urethane acrylate (trade name: UV7700B, manufactured by Nippon Synthetic Chemical Co., Ltd.) as a base of an overcoat agent, 50 parts by weight of HDDA (hexanediol diacrylate) as a diluent, and start of acetophenone-based photopolymerization 5 parts by weight of an agent (Darocure 1173, manufactured by Merck) and a lubricant represented by the following general formula

Embedded image 0.1 parts by weight of a PO (propylene oxide) / EO (ethylene oxide) modified silicone compound (trade name: SM11, manufactured by Matsumoto Yushi Co., Ltd.) was mixed with a stabilizer and the like to prepare an ultraviolet-curable overcoat agent. Then, the overcoating agent was coated with aluminum to a thickness of 100
Using a coil bar No. 12 on the vapor-deposited surface of a μm PET (polyethylene terephthalate) film,
It was applied so as to have a thickness of 5 μm. Thereafter, the applied surface was irradiated with ultraviolet light at an integrated light amount of 0.5 j / cm ² to cure the overcoat agent, thereby obtaining a test piece. The ultraviolet irradiation was performed using a metal halide lamp, and the height of the lamp was set to 10 cm.

Then, a surface property measuring device (trade name: HEIDO)
N14D), the coefficient of friction of the surface of the protective film was measured. In addition, the head of this surface property measuring device was made of sapphire and had a radius of curvature of 1 mm, and the load applied during the measurement was 100 g. The sliding speed is 500mm / m
in. Further, at a temperature of 85 ° C. for 100 hours, 9
After aging to 5%, the friction coefficient was measured by the same method. On the other hand, whether or not bleeding occurred in the protective film was inspected by touch. Table 1 shows the results.

Example 2 Test pieces were prepared in the same manner as in Example 1 except that the amount of the lubricant was changed to 5.0 parts by weight, and the friction coefficient was measured and the presence or absence of bleed was examined. Table 1 shows the results.

Comparative Example 1 A test piece was prepared in the same manner as in Example 1 without adding a lubricant, and the friction coefficient was measured and the presence or absence of bleed was examined. Table 1 shows the results.

Comparative Example 2 Test pieces were prepared in the same manner as in Example 1 except that the amount of the lubricant was changed to 8 parts by weight, and the friction coefficient was measured and the presence or absence of bleed was examined. Table 1 shows the results.

Examples 3 and 4 Bisphenol A type epoxy acrylate (trade name: SP-1509, manufactured by Showa Polymer Co., Ltd.) was added in an amount of 50 parts by weight as a base of the overcoating agent. A test piece was prepared by the method, and the friction coefficient was measured and the presence or absence of bleed was investigated. Table 1 shows the results.

Comparative Examples 3 and 4 A test piece was prepared in the same manner as in Comparative Example 1 or 2 except that 50 parts by weight of the above-mentioned epoxy acrylate was added as a base of the overcoat agent, and the measurement of friction coefficient and bleeding were performed. Was investigated. Table 1 shows the results.

[0022]

[Table 1]

As can be understood from Table 1, in Examples 1 to 4 in which the lubricant having the above-described structure was added, the friction coefficient was significantly reduced as compared with Comparative Examples 1 and 3 in which no lubricant was added. I have. In this case, the effect is high even if the amount of the lubricant added is small. This point will be described later.

On the other hand, the limit of the amount added is about 5 parts by weight. That is, in the case of excessive addition as in Comparative Examples 2 and 4, bleeding occurs on the surface of the protective film, resulting in a decrease in adhesive strength. Further, there is also a problem that the film becomes cloudy due to poor compatibility with the base resin. The urethane acrylate resin has relatively good compatibility with the lubricant, and the film does not lose transparency even when added in an excessive amount. In contrast,
In the case of an epoxy acrylate resin, the compatibility with a lubricant is generally not as good as that of a urethane acrylate resin, and when an excessive amount of the lubricant is added, cloudiness occurs in the protective film. Further, with respect to the coefficient of friction, when an excessive amount of a lubricant is added, the urethane acrylate-based resin maintains a low coefficient of friction, while the epoxy acrylate-based resin increases.

Example 5 Test pieces were prepared in the same manner as in Example 1 except that the amount of the lubricant was changed to 1 part by weight, and the friction coefficient was measured. Table 2 shows the results.

Comparative Examples 5 to 7 EO-modified silicone compounds (Comparative Example 5, trade name SM12, manufactured by Matsumoto Yushi Co., Ltd.) and oleyl phosphate amine salts (Comparative Example 6, trade name MYA524, manufactured by Matsumoto Yushi Co., Ltd.) as lubricants, respectively. Using a POE alkyl laurate having 12 to 14 carbon atoms (Comparative Example 7, trade name MYB1080, manufactured by Matsumoto Yushi Co., Ltd.), a test piece was prepared in the same manner as in Example 1 except for measuring the friction coefficient. went. Table 2 shows the results.

[0027]

[Table 2]

From Table 2, it is understood that when the PO / EO-modified silicone compound is used as a lubricant, the effect of reducing the coefficient of friction is larger than that of other lubricants. In the case of Comparative Example 6 using oleyl phosphate amine salt, the compatibility with urethane acrylate was poor, and a uniform coating film could not be obtained.

FIG. 1 is a graph showing the relationship between the amount of lubricant added, the protective film and the coefficient of friction. As shown in FIG.
If the addition amount of the / EO-modified silicone compound is within 5% by weight, the coefficient of friction is small and the above-mentioned bleed does not occur, so that it is very effective, for example, as a protective film for a microminiature magneto-optical disk. The coefficient of friction of the protective film is desirably 0.1 or less from the viewpoint of durability and driving power.

FIG. 2 is a graph showing the relationship between the amount of the lubricant added and the coefficient of friction in a semilogarithmic manner. From the figure, when urethane acrylate is used as a base, at least PO /
It is understood that when the EO-modified silicone compound is contained in an amount of 0.03% by weight or more, the friction coefficient becomes smaller than 0.1.

[0031]

As described above, in the present invention, the above-mentioned PO / PO
By containing the EO-modified silicone compound,
The coefficient of friction of the surface of the protective film can be greatly reduced, and since this value does not increase even after aging, it is possible to prevent the surface of the protective film from being damaged during sliding. Further, according to the present invention, since no bleeding occurs on the surface or interface of the protective film, it is possible to prevent a decrease in adhesion. Further, the present invention further exerts the above effects by containing the PO / EO-modified silicone compound in an amount of 0.03% by weight to 5% by weight based on the resin component.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of lubricant added and the coefficient of friction.

FIG. 2 is a semilogarithmic graph showing the relationship between the amount of lubricant added and the coefficient of friction.

FIG. 3 is a sectional view of a magneto-optical disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Transparent substrate 3 Magneto-optical recording layer 4 Reflective film 5 Protective film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10 521

Claims (2)

(57) [Claims] A resin comprising an oligomer and a reactive diluent is represented by the following general formula: A protective film for a magneto-optical disk, comprising a PO / EO-modified silicone compound represented by the formula: 2. The protective film for a magneto-optical disk according to claim 1, wherein the PO / EO-modified silicone compound is contained in an amount of 0.03% by weight to 5% by weight based on the resin component.