JPH05298746A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent adherence of dusts to a surface of an optical disk due to charging. CONSTITUTION:A charge preventing film 5 is so formed as to cover at least an entire light incident surface. Accordingly, since the film 5 is formed also on a nonrecording area of a periphery of an inner hole, the film 5 is always, when an optical disk is placed on a turntable 9 of an optical disk apparatus, electrically connected to the turntable 9. Charges stored on the film 5 leak to a spindle of the apparatus through the turntable 9. As a result, adherence of dusts due to charging can be reduced even in environments having low cleanness over a long period without reducing mass productivity of the disks, and the disk having high general purposes can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc for recording, reproducing, erasing information by using light, and more particularly to an optical disc in which dust is prevented from being attached by providing an antistatic film.

[0002]

2. Description of the Related Art In recent years, optical discs have rapidly spread as recording media with high recording density and large recording capacity, and researches to improve practical performance such as overwrite technology, improvement of reliability, and shortening of access time are becoming more and more active. Has been done.

FIG. 2 shows the structure of a conventional optical disc.
The transparent substrate 31 is a doughnut-shaped disc, and as a material for forming the transparent substrate 31, a polycarbonate having excellent productivity and a low moisture absorption rate is often used. Further, on the surface of the transparent substrate 31 opposite to the light incident surface, fine irregularities 31 such as guide grooves are formed.
a is formed.

Further, the recording layer 32 has fine irregularities 31.
A film is formed on a by sputtering or the like, and a protective film 33 covers and protects the recording layer 32. Transparent substrate 31
On the light-incident surface of the device, a moisture permeation preventive layer 34 for shielding invading external moisture, a protective film 35a for protecting the surface of the transparent substrate 31, and a charging for preventing dust and dirt from adhering to the surface by charging. The protection film 35 is provided in this order.

Further, a hub 36 with a flange is fitted in the inner hole formed in the center of the optical disk, and the flange is bonded to the peripheral portion of the inner hole by, for example, an ultraviolet curable urethane resin adhesive 37. Has been done. The center hole of the hub 36 is positioned at the center of the optical disc and is used for centering when the optical disc is mounted in the optical disc device. A magnetic plate 36a is provided around the center hole of the hub 36. The hub 36 is formed of a resin member by an integral molding method.

On the other hand, on the spindle drive shaft 38 of the optical disk device, there is provided a turntable 3 in which a rotary shaft 39a is erected.
9 is joined. A permanent magnet 39b is incorporated around the rotary shaft 39a. Therefore, when the hub 36 is mounted on the rotating shaft 39a and the turntable 39 receives the peripheral edge portion of the inner hole of the transparent substrate 31, the permanent magnet 39b attracts the magnetic plate 36a by magnetic force.

By the way, in the above-mentioned conventional optical disc, dust or dirt adheres to the light incident surface side of the transparent substrate 31,
Sometimes it was difficult to read and write signals.
This problem becomes noticeable in a magneto-optical disk which requires a larger laser power for recording / erasing than for reproducing.
That is, when the light is scattered by the dust adhering to the light incident surface, a recording error or an unerased residue occurs due to insufficient power.

The air fluid and dust in the air collide with the surface of the substrate when the optical disc rotates at high speed, and generate a charge on the surface of the substrate. As a result, dust adheres to the substrate surface. The adhesion of dust increases when the transparent substrate 31 is formed of an insulator such as plastic such as polycarbonate, that is, when the surface resistance thereof is high.

For the purpose of preventing dust adhesion due to such charging, a method of providing the antistatic protective film 35 on the light incident surface side of the transparent substrate 31 has been adopted as described above. As a method of forming such an antistatic protective film, for example, a method of applying a material mixed with fine particles (filler) such as SnO having conductivity (Japanese Patent Laid-Open No. 3-203050 and Japanese Patent Laid-Open No. 2-203050). No. 123534, JP-A-3-176
No. 832) and a method of forming a transparent metal thin film by sputtering or the like (JP-A-61-222042). In particular, the former method is noted in terms of cost, workability, and mass productivity.

The principle of preventing the adhesion of dust by these methods is to coat the surface of an insulating substrate such as plastic with a conductive material so that the charged charges generated by the collision of the material do not remain on the surface of the substrate, To dissipate the whole thing.

[0011]

However, in the above-described conventional antistatic film, when an object that comes into contact with the optical disk, such as a carrying jig or a cassette case, is charged in the forming process, the antistatic film is not charged. In some cases, the charge of (4) migrates to the conductive coating film, and a large amount of charge is accumulated in the coating film, thereby hindering the antistatic effect. In such a case, conventionally, in a series of manufacturing steps, all the transfer jigs, cases and the like are made non-charged substances to prevent the peripheral charges from moving to the coating film. Therefore, the productivity is significantly reduced.

When the optical disk is used for a long period of time or in an environment where the cleanliness is poor, a large amount of electrified charge is generated due to collision of air fluid and dust in the air with the surface of the substrate. A lot of dust and dirt adheres to it.

In addition to the method of providing the antistatic film, a method of selectively forming an antistatic material on the surface contacting with other parts (Japanese Patent Laid-Open No. 3-178047), and further, a conductive cartridge Contact with case (Japanese Patent Laid-Open No. 1-1
4267, JP-A-3-134878) and the like have been adopted, but all of them have poor mass productivity such as poor workability, too long production time, high material cost, etc. Not at all.

The present invention has been made in view of the above problems, and an object thereof is to improve the method of forming an antistatic film on a substrate for a long period of time or under an environment of poor cleanliness. It is an object of the present invention to provide an optical disk in which the antistatic performance does not deteriorate even when the optical disk is used, and to provide an optical disk with good mass productivity without complicating the manufacturing process.

[0015]

In order to solve the above-mentioned problems, an optical disk according to the present invention is at least an optical disk provided with an antistatic film (for example, a UV-curable resin film mixed with tin oxide filler). When the entire light incident surface is covered and the optical disk is mounted on the spindle section (eg, turntable) of the optical disk device,
It is characterized in that an antistatic film electrically connected to the spindle portion is provided.

[0016]

According to the above construction, since the antistatic film is provided so as to cover at least the entire light incident surface of the optical disk, the antistatic film is formed by the spindle when the optical disk is mounted on the spindle portion of the optical disk device. Is electrically connected to the section. Therefore, the charge generated in the antistatic film due to the high-speed rotation of the optical disc leaks to the device side through the spindle portion, so that the charge is not accumulated in the antistatic film.

As a result, the antistatic effect of the antistatic film is maintained for a long period of time, and dust is prevented from adhering to at least the entire light incident surface of the optical disc, so that the reliability of recording, reproducing and erasing on the optical disc is improved. To do.

Furthermore, since the conventional method of forming an antistatic film is applied only to the entire light incident surface, an optical disk having an improved antistatic effect can be manufactured without lowering mass productivity.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will explain one embodiment of the present invention with reference to FIG.

FIG. 1 shows the structure of the optical disk of the present invention. The transparent substrate 1 made of plastic such as polycarbonate is a donut-shaped disk,
The thickness dimensions are, for example, 86 mm, 15 mm, and 1.
It is 2 mm. On the surface of the transparent substrate 1 opposite to the light incident surface, fine irregularities 1a of 3.5-inch standard preformat are formed.

The recording film 2 is formed on the fine irregularities 1a by sputtering or the like. In this embodiment, in order to utilize the enhancement effect, the recording film 2 is made of AlN.
Layer 50 nm, rare earth such as TbFeCo and GbTbFe-
It has a four-layer structure of a transition metal layer, an AlN layer 25 nm, and an Al layer 50 nm.

The recording film 2 is covered with a protective film 3 and is protected so as not to deteriorate due to intrusion of moisture or oxygen in the atmosphere. On the light incident surface of the transparent substrate 1, a moisture permeation preventive film 4, a base film 5a, and an antistatic film 5 are provided in this order. The role of the moisture permeation preventive film 4 is to prevent the warp caused by the moisture penetrating into the transparent substrate 1 because the optical disc of the present embodiment has a 3.5-inch single plate specification. The roles of the base film 5a and the antistatic film 5 are:
Each is to protect the surface of the transparent substrate 1 in order to improve scratch resistance, and to prevent dust and dirt from adhering to the light incident surface of the optical disc due to electrification.

Further, a hub 6 with a flange is fitted in an inner hole having an inner diameter of 15 mm formed in the center of the optical disk, and the flange is formed by, for example, an ultraviolet curable urethane resin adhesive 7 on the periphery of the inner hole. It is glued to the part. The center hole of the hub 6 is positioned at the center of the optical disc and is used for centering when the optical disc is mounted on the optical disc device for recording / reproducing / erasing. A magnetic plate 6a is provided around the center hole of the hub 6. In addition,
The hub 6 is formed of a resin member by an integral molding method.

On the other hand, a turntable 9 on which a rotary shaft 9a is erected is joined to a spindle drive shaft 8 of the optical disk device. The spindle drive shaft 8, the rotary shaft 9a,
The turntable 9 corresponds to the "spindle portion" recited in the claims. When the hub 6 is mounted on the rotating shaft 9a, the turntable 9 contacts the antistatic film 5 around the inner hole of the transparent substrate 1. Therefore, since the spindle unit including the turntable 9 is electrically connected to the antistatic film 5, the charge accumulated in the antistatic film 5 is
It leaks to the optical disk device side through the spindle section.

The permanent magnet 9 is provided around the rotary shaft 9a.
The hub 6 in which b is incorporated and mounted on the turntable 9.
The magnetic plate 36a and the permanent magnet 39b are attracted by a magnetic force.

In forming the protective film 3, an ultraviolet-curable acrylic resin such as SD-301 manufactured by Dainippon Ink and Chemicals Co., Ltd. was applied onto the recording film 2 by a spin coating method. Here, as a coating condition, the rotation number of the spinner is 30
The protective film 3 having a thickness of 10 μm was formed at 00 rpm, a rotation time of 30 seconds, a dispenser pressure of 3.0 kg / cm ² , and a coating time of 4 seconds.

The moisture permeation preventive film 4 is, for example, a metal thin film such as AlN, and is formed on the light incident surface of the transparent substrate 1 opposite to the surface on which the recording film 2 is formed by a sputtering method or the like. If the film thickness of the moisture permeation preventive film 4 is too thick, an interference fringe pattern is generated. Therefore, it is preferable that the film thickness is 5 nm as long as the moisture permeation preventive effect is not hindered.

When forming the base film 5a, SD-301 manufactured by Dainippon Ink and Chemicals Co., Ltd. was applied onto the moisture permeation preventive film 4 by a spin coating method. As the coating conditions at this time,
Spinner speed 3000 rpm, rotation time 30
Seconds, dispenser pressure 3.0 kg / cm ² , application time 4
Seconds

The antistatic film 5 was formed on the base film 5a to a thickness of 5 .mu.m by spin coating using, for example, MOP-50 manufactured by Nippon Shokubai Kasei. The MOP-50
Is an ultraviolet curable resin 4502 made by Mitsubishi Rayon Co., Ltd.
The conductive fine particles (filler) such as nO are mixed in a weight ratio of 3 to 2. As the coating conditions at this time, the rotation number of the spinner is 3000 rpm, and the rotation time is 3
0 second, the pressure of the dispenser was 0.6 kg / cm ² , and the coating time was 4 seconds.

As shown in FIG. 1, the base film 5a and the antistatic film 5 are located near the edge of the inner hole having an inner diameter of 15 mm, specifically, in the range of 15.5 to 16 mm in diameter. The application started. As a result, the antistatic film 5 is formed even in the non-recording area around the inner hole where the recording film 2 is not formed. The turntable 9 of the optical disk device has a diameter of 16 to
Since the disk is received at 21 mm, the antistatic film 5 and the turntable 9 can be electrically contacted.

On the other hand, at the time of forming a substrate by ordinary injection molding, at a position of diameter 34 to 36 mm on the light incident surface side of the transparent substrate 1, the height 10 to 10 due to the clearance of the mold is formed.
24 μm convex portions are formed. Therefore, if the base film 5a and the antistatic film 5 are applied to the inner circumference of this convex portion,
Streaky uneven coating occurs in the radial direction. Therefore, the base film 5a
Before applying this, the convex portion is applied to the SD-30 manufactured by Dainippon Ink
Coated with 1. When coating the above-mentioned convex portion, the rotation speed of the spinner is 60 rpm, and the pressure of the dispenser is 1.0 kg.
/ Cm ² , and the coating time was 2.0 to 4.0 seconds.

A dust adhesion test was performed on the magneto-optical disk manufactured as described above. In the dust adhesion test, the above-mentioned disc was inserted into the optical disc device in an environment where dust was scattered by a fan in a sealed state,
It was rotated at rpm for 30 minutes to observe the adhesion of dust and measure the charging voltage.

As a result of the dust adhesion test, almost no dust adhered to the antistatic film 5, and the charge potential after the test was 0.02 to 0.03 kV. This was almost equal to the measured value of 0.01 to 0.02 kV in the state in which no electrostatic charge was generated. Further, even if the dust test was continued for 5 to 6 hours, there was no change in the dust adhesion and the charging potential.

As a comparative experiment, as described with reference to FIG. 2 in the section "Prior Art", the antistatic film was not applied to the non-recording area around the inner hole, and the antistatic film and the turntable were not applied. When no contact was made, the same dust adhesion was observed and the charging voltage was measured. As a result, a large amount of dust was found to be attached on the antistatic film, and the charging potential was 0.06 kV, which was two to three times that of the optical disc of the present invention.

Thus, from the edge of the inner hole to the outermost circumference,
When the antistatic film 5 is formed on the entire light incident surface of the optical disk, the optical disk is mounted on the optical disk device in a state where the antistatic film 5 is electrically connected to the spindle unit including the turntable 9. Therefore, the antistatic effect of the antistatic film 5 continues for a long time. Further, as compared with the conventional optical disc, since the antistatic agent is only applied from the inner peripheral side by the spin coating method so as to include the non-recording area, the mass productivity of the optical disc production is not deteriorated.

In this embodiment, the 3.5-inch single-disc type optical disc has been described, but other types of discs such as different size and double-sided type may be used.
Further, the manufacturing method of the transparent substrate 1 is not limited to injection molding, and other methods such as compression molding or 2P (photo polymar-ization) method may be used. Further, the antistatic film 5 is applied by a spin coating method other than the above-mentioned conductive filler type, for example, a surfactant type or a conductive resin type, or a transparent metal such as tin oxide or manganese oxide. The thin film may be formed by sputtering or vapor deposition.

Further, in processing the above convex portion,
For example, a method of removing the convex portion by mechanical processing such as polishing can be adopted.

[0038]

As described above, the optical disk according to the present invention covers at least the entire light incident surface and is electrically connected to the spindle section of the optical disk apparatus when the optical disk is mounted on the spindle section. The antistatic film is provided.

Therefore, the charge accumulated in the antistatic film leaks to the optical disk device side through the spindle portion, so that the mass productivity of the optical disk is not deteriorated.
Even in an environment with poor cleanliness, it is possible to reduce dust adhesion due to charging for a long period of time. As a result, the range of applications of the optical disc is expanded, and it is possible to provide an optical disc with high versatility.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of an optical disc according to the present invention.

FIG. 2 is a vertical cross-sectional view showing the configuration of a conventional optical disc.

[Explanation of symbols]

 5 Antistatic film 8 Spindle drive shaft (spindle part) 9 Turntable (spindle part) 9a Rotating shaft (spindle part)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture

Claims (1)

[Claims] 1. An optical disk provided with an antistatic film, which covers at least the entire light incident surface and is electrically connected to the spindle part of the optical disk device when the optical disk is mounted on the spindle part. An optical disk having a protective film.