JPH0793811A - Optical disk - Google Patents

Abstract

PURPOSE:To provide the optical disk which has a high adhesion property between a protective coat and an optical disk substrate and is not degraded in its performance in spite of long-term use. CONSTITUTION:This optical disk has a resin substrate, a recording film and the protective coat consisting of a resin. The contact surface of the protective coat on the outer periphery of the resin substrate and the resin substrate is provided with a circular groove centering at around the center of the optical disk (the groove has a width 0.2 to 1.0mm and depth 0.5 to 1.0mm and the center line of the circular groove exists preferably in a range of 1 to 5mm from the outer peripheral end of the resin substrate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical disc.

[0002]

2. Description of the Related Art A recording film of a disk-shaped recording medium (hereinafter referred to as an optical disk) for recording information by using a light beam such as a laser beam is generally made of a material which is easily susceptible to oxidation, corrosion, etc. Is protected by. The service life of an optical disk is generally required to be 10 years or longer. In order to prevent the deterioration of the recording film for 10 years or longer, the oxygen permeability and the water permeability of the protective coating agent are not more than a certain value, and It is required that the coat film and the recording film and the optical disk substrate have high adhesion.

[0003]

PROBLEM TO BE SOLVED BY THE INVENTION A protective coating agent for a recording film which has been applied by a spin coating method and then cured by irradiating with an ultraviolet ray, etc. is deteriorated as the optical disk is used for a long time. However, the performance may be deteriorated due to the deterioration of the substrate, the penetration of moisture into the contact interface, and the like, which may cause the deterioration of the recording film. Particularly, when the adhesion between the coating agent and the optical disk substrate is low, oxygen and water may enter from the end surface of the optical disk, and the recording film may be significantly deteriorated.

An object of the present invention is to provide a high adhesion strength between the protective coat and the exposed portion of the optical disc substrate on the outer peripheral portion of the optical disc,
An object of the present invention is to provide an optical disc in which a protective film is not peeled off even when it is used for a long time and a good recording film protection performance is maintained.

[0005]

According to the present invention, the above-mentioned object is an optical disc having a protective coat composed of a resin substrate, a recording film and a resin, and the contact between the protective coat and the resin substrate on the outer periphery of the resin substrate. This is achieved by an optical disc having a circular groove whose center is near the center of the optical disc.

As the above-mentioned circular groove, 0.2 to 1.0
The width of the circular groove is 0.5 mm to 1.0 mm and the center line of the circular groove is 1 to 1 mm from the outer peripheral edge of the resin substrate.
It is preferably in the range of 5 mm.

As the substrate in the present invention, it is possible to use a transparent resin material having excellent transparency such as polyester resin, polyolefin resin, polyamide resin, polycarbonate resin, polymethacrylic resin, or an inorganic material such as glass. . The resin substrate includes a calendering method, an injection molding method, an injection compression molding method, a compression molding method,
What was shape | molded by arbitrary methods, such as a photopolymer (2P) method, can be used. As the protective coating agent, an ultraviolet curable type is generally used, and one having low oxygen permeability and water permeability is desirable. Further, it is desirable that the metal and the resin have high adhesiveness, but according to the present invention, it is possible to combine a coating agent having a low adhesiveness with an optical disk substrate resin. Examples of the coating agent used include acrylate compounds such as epoxy acrylate, urethane acrylate and polyester acrylate. These coating agents can be applied by any method such as spin coating, dipping, and showering.

[0008]

With the circular groove of the present invention, the contact area between the protective coat and the resin substrate increases, so that the adhesion strength increases,
Even when used for a long period of time, good recording film protection performance can be maintained. Also, when the recording film formation area is eccentric to the substrate due to the displacement of the outer peripheral mask during recording film formation, an area with insufficient protective coating is created, and the deterioration of the recording film starts from that area and extends to the inner peripheral area. However, in the present invention, even if eccentricity occurs in the recording film forming area, the recording film is divided by the circular groove, so that the deterioration does not proceed to the inside.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 A transparent circle made of polycarbonate having a width of 0.5 mm, a groove having a width of 0.5 mm, a depth of 0.5 mm, a groove having a radius of 63 mm from the center as a center line, a thickness of 1.2 mm, an inner diameter of 15 mm, and an outer diameter of 130 mm. After molding the substrate, TbFeCo
A magneto-optical recording film in which a film, a SiN film, and the like were laminated was formed, an ultraviolet-curable protective coating agent made of urethane acrylate was applied by a spin coating method, and was irradiated with ultraviolet rays to be cured. Two substrates were laminated with a hot-melt adhesive with the side of the protective coat facing inward, and then a hub was adhered with an ultraviolet curable adhesive to prepare an optical disk. Example 2 An optical disk was produced in the same manner as in Example 1 except that the width of the circular groove was 0.8 mm and the depth was 0.8 mm. Example 3 An optical disk was produced in the same manner as in Example 1 except that a groove having a width of 1.0 mm and a depth of 1.0 mm having a radius of 62 mm as a center line was provided. Example 4 An optical disc was produced in the same manner as in Example 1, except that the width of the circular groove was 0.2 mm and the depth was 0.5 mm.

Comparative Example 1 The same recording film as in Example 1 was formed on a transparent polycarbonate transparent circular substrate (having no circular groove) having a thickness of 1.2 mm, an inner diameter of 15 mm and an outer diameter of 130 mm, which was produced by an injection molding method. Was formed into a film, a urethane acrylate UV-curable protective coating agent was applied by a spin coating method, and was irradiated with UV rays to be cured. Two substrates were laminated with a hot-melt adhesive with the side of the protective coat facing inward, and then a hub was adhered with an ultraviolet curable adhesive to prepare an optical disk.

In the optical disk of each of the above examples, the CNR (Carrier to Noise Ratio) of the outer peripheral portion is used.
The results of measuring o) are shown in Table 1. In addition, the optical disk of each example was tested at a temperature of 80 ° C. and a humidity of 85% R. H. Under the environment of 20
Table 1 also shows the results of measuring the CNR of the outer peripheral portion after standing for 00 hours.

[0012]

[Table 1]

[0013]

According to the present invention, it is possible to provide an optical disk in which the adhesion between the protective coat and the optical disk substrate is high and the performance is not deteriorated even when used for a long time.

Claims (2)

[Claims] 1. An optical disc having a resin substrate, a recording film, and a protective coat made of a resin, wherein a circular groove centered near the center of the optical disc is formed on a contact surface between the protective coat and the resin substrate on the outer periphery of the resin substrate. An optical disc characterized in that. 2. The circular groove has a width in the range of 0.2 to 1.0 mm and a depth in the range of 0.5 to 1.0 mm, and the center line of the circular groove is the outer peripheral edge of the resin substrate. 2. The optical disk according to claim 1, wherein the optical disk is in the range of 1 to 5 mm.