JPH07169225A - Optical disk - Google Patents

Abstract

PURPOSE:To improve the adhesive property of a hub to an optical disk and to prevent the generation of dust at the time of repeatedly attaching and detaching a drive by forming the inner circumferential part of the hub with an opaque resin excellent in wear resistance and the outer circumferential part with a transparent resin. CONSTITUTION:Transparent polycarbonate is injected into a mold for molding a hub in which the magnetic plate 2 of the hub has been set to form the outer circumferential part 3 of the hub. The magnetic plate 2 with the molded outer circumferential part 3 is fitted to a mold and polycarbonate mixed with 10% polytetrafluoroethylene resin as a resin having such a low coefft. of friction as <=0.4 is injection-molded to form the inner circumferential part 4. Optical disks each made of molded polycarbonate are placed opposite to each other with the recording films inward and they are stuck together with a hot-melt adhesive to obtain a both side type optical disk. A UV-curing adhesive is applied to the hub bonding region of this disk at the inner circumference and the bonding face 5 of the hub is aligned and bonded by curing the adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk having a hub for a magnet clamp attached to the center thereof.

[0002]

2. Description of the Related Art Conventionally, an optical disk such as a magneto-optical disk has been known as a recording medium for various information signals. As this type of optical disc, there is known an optical disc having a recording layer formed on the surface of a disk-shaped substrate made of a transparent synthetic resin.

On the other hand, since such an optical disk is mounted on a drive device and is recorded and reproduced while rotating, it is necessary to securely clamp the disk during the recording and reproduction. A magnet clamp hub is usually attached to this optical disk in order to facilitate clamping to a drive device. A magnet clamp is a magnetic material (having a property of adsorbing to a magnet) around a spindle insertion hole provided in the center of an optical disc.
This is a system in which an annular body made of is attached, and the annular magnetic body is attracted by a magnet provided in the drive device to fix the optical disk.

As an optical disk equipped with the above-mentioned magnet clamp hub, a resin ring is integrally formed on the disk body at the peripheral portion of a magnetic metal body provided at the center of the disk body, and ultrasonic welding is performed on the disk body. It is known that a hub having a mounting portion is attached by ultrasonic welding.

[0005]

The optical disk hub described above has a problem in that the mold structure thereof is complicated because the mounting portion of the ultrasonic welding portion is integrally formed. What has the property is required.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, in which a hub integrally formed with a resin holding a metal magnetic material on an optical disk substrate is provided with an ultraviolet curable resin. As a result of conducting intensive studies to improve the adhesiveness by using a hub having a simple structure, the adhesiveness can be improved by forming a specific hub structure, and the above problems can be solved. Find out that
The present invention has been completed.

That is, the gist of the present invention is an optical disc in which a hub for a magnet clamp is attached to the center of a disc-shaped optical disc, the hub being an annular magnetic body and a synthetic resin holding the magnetic body. And the circumferential portion of the hub is made of an opaque synthetic resin having a friction coefficient of 0.4 or less,
Further, the outer peripheral portion of the hub is made of a light-transmitting synthetic resin,
The hub resides in an optical disc characterized in that the hub is adhered to the optical disc at a resin portion of the outer peripheral portion through an ultraviolet curable resin.

In the present invention, as the thermoplastic resin used for integrally molding the outer peripheral portion of the annular magnetic body with a resin, a resin having excellent adhesiveness to the optical disk substrate is used, such as polycarbonate and polymethylmethacrylate. ,
A light-transmitting (transparent) resin such as ABS resin may be used.
Particularly when the disk substrate is made of polycarbonate resin, it is preferable to use transparent polycarbonate resin for the outer peripheral portion of the hub.

Further, the inner peripheral portion of the hub is made of a resin having abrasion resistance and lubricity due to repeated attachment / detachment to / from the drive device, for example, polyacetal resin, fluorine resin, ultra-high molecular weight polyethylene, etc. in an amount of 0.5 to 40% by weight. A thermoplastic resin such as a polycarbonate resin containing about a certain amount is used. The same thermoplastic resin as that used for the outer peripheral portion of the hub is used as the thermoplastic resin. Examples of the fluorine-based resin include polytetrafluoroethylene and polychlorotrifluoroethylene. In particular, a composition obtained by mixing both a fluororesin and an ultrahigh molecular weight polyethylene in a total amount of 0.5 to 40% by weight with a polycarbonate resin is preferably used. An opaque resin is used for the inner peripheral portion of the hub.

When the above-mentioned resin having abrasion resistance and lubricity is blended with the thermoplastic resin, the blending ratio is 60-60 thermoplastic resin.
Resin with abrasion resistance and lubricity of 40% to 9.5%
It is in the range of 0.5 wt%. When the proportion of the resin having abrasion resistance and slipperiness is more than 40 wt%, the flexibility of the molded product increases, the deformation tends to occur, and the abrasion tends to occur, which is not preferable.

The wear coefficient was obtained by performing a thrust friction wear test using a Suzuki type friction wear tester (manufactured by Toyo Baldwin Co., Ltd.). As a mating material, carbon steel for machine structure (45C) was used, and it was performed in a non-lubricated state. The sliding speed was 30 (m / min) and the surface pressure was 5 (kg / cm ² ). The test was conducted under each condition, and the friction coefficient after continuous operation for 1 hour was measured.

In mixing the above resins, a thermoplastic resin and a resin having abrasion resistance and lubricity are dry blended, or a general kneader such as a Banbury mixer, a Henschel mixer, a mixing roll, an extruder, etc. Are melt-kneaded by, and the kneaded material is extruded and pelletized by cutting or the like, or pulverized to have a predetermined particle size to obtain a molding material.

The molding is carried out by injection molding using a normal injection molding machine while keeping the mold temperature and injection pressure constant. A magnetic body is mounted in the mold, and the outer peripheral portion is injection-molded with the above-mentioned thermoplastic resin to obtain an outer peripheral portion molded body. Then
The optical disk hub having an inner peripheral portion and an outer peripheral portion can be obtained by mounting the outer peripheral molded body on a mold of a molding machine and injection-molding a resin having abrasion resistance and lubricity of the inner peripheral portion. Further, when a so-called two-color molding machine (double mold) having two cylinders and capable of continuously molding the inner peripheral portion and the outer peripheral portion in one cycle is used, an optical disk hub can be obtained with high productivity. .

The outer peripheral portion (portion made of transparent resin) of the thus-obtained optical disk hub is attached to the optical disk substrate by adhesion via an ultraviolet curable resin. At the time of this bonding, alignment is very important, and after aligning so that the inclination and eccentricity of the substrate are minimized,
It is necessary to bond.

Examples of the ultraviolet curable resin include acrylic resins, epoxy resins and urethane resins, and acrylic ultraviolet curable resins are particularly preferably used. The acrylic ultraviolet curable resin may contain a polymerizable oligomer, a monomer, a photopolymerizable initiator and a sensitizer. As the polymerizable oligomer, an oligomer containing a functional group such as an acrylic ester, a methacrylic ester double bond, an acryloyl group, and a methacryloyl group is used, and the main chain structure of the base oligomer is a polyester type, a polyether type,
Examples thereof include urethane type, epoxy type, acrylic type, polythiol type, and polyimide type. Specifically, polymerizable oligomers such as polyester acrylate, polyether acrylate, polyurethane acrylate, epoxy acrylate, and polybutadiene acrylate are preferably used. Benzoin ethers as photopolymerization initiators,
Examples thereof include benzophenones and acetophenones.

In the present invention, the above ultraviolet curable resin paint, for example, a paint containing a polymerizable oligomer, a monomer, a photopolymerization initiator and a sensitizer, and optionally a solvent, is applied to the hub adhesion region of the optical disk substrate. After that, the hub is aligned, and ultraviolet rays are irradiated from obliquely above the hub to cause a polymerization reaction to form a cured resin. The above-mentioned cured resin can be applied by a known method such as spin coating, dipping, spray coating, or gravure coating on the surface of the optical disc substrate. This curable resin can be applied to the entire outer surface of the optical disk substrate to serve as both the protective coating agent and the hub adhesive. The viscosity of the cured resin is usually 1
It is in the range of 10 cps.

In the present invention, as described above, since the inner peripheral portion of the optical disk hub is formed of the opaque resin and the outer peripheral portion is formed of the transparent resin independently, the flatness of the adhesive portion of the optical disk hub is improved. 100 μm or less, preferably 60 μm
The thickness of the adhesive can be significantly reduced in the adhesive portion, and the adhesiveness (adhesive strength) with the optical disk substrate can be significantly improved.

[0018]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A hub 1 having the shape shown in FIG. 1 was produced. A commercially available transparent polycarbonate (Panlite manufactured by Teijin Chemicals Ltd.) was injected into the molding die of the hub on which the magnetic plate 2 of the hub is set to form the outer peripheral portion 3 of the hub. The injection conditions are as follows. Cylinder temperature 2 using an injection molding machine with 1 ounce injection capacity
60 ℃, mold temperature 55 ℃, maximum injection pressure 450kg / c
The outer peripheral portion 3 was molded under the conditions of m ² and a molding cycle of 35 seconds.

Next, to form the inner peripheral portion 4, a polycarbonate having a small friction coefficient mixed with 10% of tetrafluoroethylene resin (Mitsubishi Kasei, NOVAREX)
7025M10) was injection molded. Friction coefficient is 0.18
Met. The magnetic plate 2 having the outer peripheral portion 3 molded was mounted on the mold, and the inner peripheral portion 4 was injection-molded. Bonding surface 5 of the obtained hub
The warp was 50 μ toward the outer peripheral side in the radial direction. Separately molded outer diameter 130 mm, inner diameter 15 mm,
A polycarbonate optical disk having a thickness of 1.2 mm was adhered to the inside of the recording film with a hot melt adhesive to obtain a double-sided optical disk.

An ultraviolet-curing type adhesive is applied to the hub bonding area on the inner circumference of the thus obtained double-sided type optical disk, and the bonding surface 5 (surface of the outer peripheral portion 3) of the hub obtained above is aligned. Then, it was irradiated with ultraviolet rays to cause a polymerization reaction to be cured and adhered. A disk having a high mechanical strength with an adhesive strength of 50 kg / cm ² or higher was obtained without unevenness of the adhesive on the hub adhesive surface produced in this way. Also, the appearance after loading 20,000 times on the recording / reproducing drive device did not change, the hub inner diameter dimensional change was 0.002, and wear resistance was good.

Example 2 The mold was changed to obtain the mold for the hub 1 having the structure shown in FIG.
Injection molding was carried out in the same manner as in Example 1 to obtain the hub 1 shown in FIG.
However, the resin forming the inner peripheral part is made of polycarbonate with tetrafluoroethylene 5% and ultra high molecular weight polyethylene 5
% Mixed resin was used. The friction coefficient of the molded product of this resin was 0.19. The adhesive surface 5 (surface of the outer peripheral portion 3) of the obtained hub 1 slightly warped toward the outer peripheral side in the radial direction, but the warp was 10 μ. The optical disc used was one in which a recording film was formed on a polycarbonate resin substrate having an inner diameter of 15 mm, an outer diameter of 86 mm, and a thickness of 1.2 mm. The bonding surface 5 of the obtained hub 1 was bonded via an ultraviolet curable resin. The unevenness of the adhesive on the adhesion surface 5 of the hub produced in this way gave an adhesive strength of 50 kg / cm ² or more without inclusion of air bubbles. The appearance after loading 20,000 times in the recording / reproducing drive device did not change, the hub inner diameter dimensional change was 0.003, and wear resistance was good.

Comparative Example Using commercially available polycarbonate (Panlite manufactured by Teijin Chemicals Ltd.) (resin used for forming the outer peripheral portion in Example 1), the inner peripheral portion and the outer peripheral portion as shown in FIG. 3 were used. The hub 1 having the resin portion 6 integrated with the above was formed under the same molding conditions as in Example 1. The warp on the adhesive surface of the obtained hub was 130 μ in the radial direction.
The obtained hub was adhered to an optical disc in the same manner as in Example 1. Bubbles were mixed in the hub bonding surface when prepared in this way, and the bonding strength was 20 kg / cm ² . Further, after the loading test was performed 20000 times on the recording / reproducing drive device, friction powder was generated, the dimensional change of the hub inner diameter was 0.015, and the wear resistance was insufficient.

[0024]

The hub of the present invention has an inner peripheral portion made of an opaque resin having excellent wear resistance and an outer peripheral portion made of a transparent resin.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an example of a hub used for an optical disc of the present invention.

FIG. 2 is a vertical cross-sectional view of an example of a hub used in the optical disc of the present invention.

FIG. 3 is a vertical sectional view of an example of a conventional hub.

[Explanation of symbols]

 1 hub 2 magnetic plate 3 outer peripheral part of hub 4 inner peripheral part of hub 5 adhesive surface

Claims (1)

[Claims] 1. An optical disc comprising a disc-shaped optical disc and a hub for magnet clamp attached to the center of the disc, wherein the hub comprises an annular magnetic body and a synthetic resin holding the magnetic body. The inner peripheral portion of the hub is made of an opaque synthetic resin having a friction coefficient of 0.4 or less, and the outer peripheral portion of the hub is made of a light transmissive synthetic resin.
An optical disc, wherein the resin portion of the outer peripheral portion is adhered via an ultraviolet curable resin.