JPH01223643A - Recording medium for optical disk - Google Patents

Abstract

PURPOSE:To prevent the microcracks which are generated on the inside circumference of the central hole of a glass substrate by coating the inside circumferential end face of said hole with an org. resin and cutting the org. resin-coated part to match the concentricity of the guide groove and central hole of an optical disk. CONSTITUTION:Org. resin coating materials of a thermoplastic resin, thermosetting resin, etc., are used as the org. resin material in contact with the inside circumferential end face of the glass substrate 1. The org. resin film 2 coats the part where a taper cone central shaft and the central hole 11 of the disk come into contact with each other. The org. resin coating coated on the inside circumferential end face is cut in order to match the concentricity if the concentricity of the guide groove and the central hole is not matched after the org. resin coating. While the preferred thickness of the film 2 is usually about 20-50mum, the film thicker than said value needs be formed in order to assure the allowance for cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc recording medium that simplifies central processing of a glass disc substrate.

[Prior art]

First, a mechanism for mounting an optical disc recording medium into a normal reproduction, recording, and erasing device (hereinafter referred to as the device) will be explained.

FIG. 3 is a schematic cross-sectional view of the device rotation mechanism when the optical disc recording medium 1 is mounted. When disc 1 is installed,
Disk 1 is pressed by clamper 8 and spring 6
Tapered cone central axis (hereinafter referred to as central axis) supported by 3
is pushed down by the disk 1 to center the disk 1, and the disk 1 is clamped by the clamping surface 7 and the clamp 8. With this mechanism, the center hole 11 of the disk
Even if the diameters of the discs are slightly different, it is possible to always mount the disc 1 without wobbling.

Conventionally, in an optical disk recording medium using a glass disk substrate (hereinafter referred to as a glass substrate), a hub 9 made of plastic or metal is fitted into the inner periphery of the center hole of the disk 1, as shown in FIG. By adhering the hub 10 to the surface of the disk 1 as shown in Figure 5, (a) when the disk is repeatedly attached and detached for a long period of time, the taper cone central axis 3
This prevents the inner circumferential end surface of the glass substrate center hole 11 from repeatedly colliding with the inner circumferential end surface of the glass substrate center hole, causing microcracks to occur on the inner circumferential end surface of the glass substrate center hole, thereby preventing the glass from being damaged and the central shaft from being worn out. In addition, by aligning the hub with the center axis of the guide groove when bonding the hub to the disk, or by reprocessing the inner circumference of the hub after bonding, the optical guide groove (hereinafter referred to as guide groove) of the optical disk recording medium can be adjusted. By aligning the center of (b) with the center hole of the disk, when the disk (b) is rotated, the guide groove is prevented from swinging significantly and making it difficult to follow the light beam.

(Problem to be Solved by the Invention) However, in these conventional techniques, a separate member called a hub is used in the center hole to prevent (a), and a guide groove is used when bonding the hub to the disk to prevent (b). There was a problem in that the inner peripheral part of the hub had to be reworked after alignment with the central axis of the hub or after gluing.

This invention is an attempt to eliminate the above-mentioned drawbacks by improving the central hole portion of an optical disc recording medium.

[Means for Solving the Problem] According to the present invention, in an optical disc recording medium using a glass substrate having a center hole, the inner peripheral end surface of the center hole of the glass substrate is coated with an organic resin, and the inner peripheral end surface of the glass substrate is coated with an organic resin. An organic resin coating film is formed.

The organic resin material in contact with the inner circumferential end surface of the glass substrate may be either a thermoplastic resin or a thermosetting resin, such as a solvent drying effect type, a -liquid moisture absorption curing type, a two-liquid room temperature curing type,
Various organic resin coating agents such as heat curing type and electron beam curing type can be used.

As a coating method, an organic resin coating may be formed on the inner peripheral end surface of the glass substrate by, for example, applying a coating liquid to the inner peripheral end surface with a brush or dispenser while rotating the disk. The organic resin coating only needs to cover the area where the tapered cone center shaft 3 and the center hole 11 of the disk come into contact, and even if it covers only the edge portion of one side of the inner periphery of the disk, it may cover the edge portions of both sides. It may be covered. In a double-sided recording type disk medium, it is preferable to coat the edges of both sides. In addition, in order to improve the adhesion between the organic resin coating and glass, silane coupling agents, etc. are added to the organic resin, and inorganic powders, so-called fillers, are added to the organic resin to improve the toughness and abrasion resistance of the organic resin. It is also possible to add.

If the concentricity of the organic resin-coated diameter guide groove and the center hole do not match, the organic resin coating coated on the inner circumferential end surface of the center hole is cut in order to match the concentricity.

As a cutting method, for example, the disc is held on a rotary table, the disc is rotated, and the guide groove is observed using a microscope.
After moving and adjusting the position of the disc until the guide groove no longer swings, use a cutting tool to cut the coated organic resin film while rotating the disc, or similarly using a grinding wheel instead of the cutting tool. The concentricity of the guide groove and the disk center hole may be matched by cutting the coated organic resin coating. In addition, if a quick-curing organic resin such as an ultraviolet curable resin is used as a coating agent, the rotational application of the resin to the disk and the subsequent cutting of the inner diameter to align the concentricity with the optical guide groove can be performed continuously on the same rotary table. You can also do that.

The thickness of the organic resin coating is preferably 3 to 200 μs when the guide groove and the center hole of the glass substrate have good concentricity and no cutting work is required for adjustment, and usually about 20 to 50 μs.
When cutting is performed due to poor concentricity, it is necessary to form a thicker coating to ensure a cutting margin, so this can be determined depending on the degree of misalignment.

〔Example〕

Example 1 A playback optical disc recording medium using a glass disc substrate manufactured by a conventional method was rotated on a rotating table (the disc was held horizontally outside the effective recording area, and the disc rotation center was set relative to the outer peripheral edge of the disc). 50r
After applying the coating solution to the inner circumferential end surface of the center hole of the glass substrate using a brush applied with heat-curing type (epoxy polyamide) coating solution while rotating at 100°C, heat curing was performed at 100°C for 2 hours. An organic resin film was formed as shown in the cross-sectional view of the optical disc recording medium.

Example 2 An optical disc recording medium was set on a rotary table (a lathe equipped with a jig that held the disc on its outer edge and had a centering mechanism), and an ultraviolet curing resin (acrylic polyurethane) was applied to the disc for 10 minutes. It was applied to the center hole using a dispenser while rotating at .degree. rpm, and then cured with ultraviolet light while continuing the same rotation. Next, while rotating the disk, observe the guide groove using a microscope etc., move and adjust the disk position until the guide groove no longer swings, then increase the rotation speed to 2000 rpm, cut the organic resin coating with a cutting tool, and cut the guide groove and center hole. The concentricity was matched. The inner peripheral end surface of this center hole was chamfered as shown in the enlarged view of FIG.

〔Effect of the invention〕

As explained above, by coating the circumferential end surface of the center hole of a glass substrate for optical disks with an organic resin coating, it is possible to prevent the center axis of the device from coming into direct contact with the inner circumference of the center hole without using a conventional hub. Therefore, it is possible to easily prevent wear of the center shaft and generation of microcracks on the inner periphery of the center hole of the glass substrate. Furthermore, by cutting the organic resin coating, the concentricity between the center of the guide groove and the center hole can be easily adjusted.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the optical disc recording medium obtained in Example 1, Fig. 2 is a partially enlarged view of the inner peripheral end surface of the center hole of the optical disc recording medium obtained in Example 2, and Fig. 3 is a cross-sectional view of the optical disc recording medium obtained in Example 2. A schematic cross-sectional view of the state in which the recording, reproducing, and erasing device is mounted on the rotation mechanism, and FIGS. 4 and 5 are examples of conventional optical disc recording media, and are optical disc recording media with a hub glued to the inner circumference or bottom surface. FIG. 1 is an optical disk recording medium, 3 is a tapered cone center ring of the device, 4 is a turntable, 5 is a motor, 6 is a spring, 7 is a clamp surface, 8 is a clamper, 9, IO is a hub, and 11 is a center hole. Patent applicant Canon Co., Ltd.

Claims (2)

[Claims] (1) An optical disc recording medium using a glass substrate having a center hole, in which the inner peripheral end surface of the center hole of the glass substrate is coated with an organic resin. (2) A method for manufacturing an optical disc recording medium, which comprises cutting the organic resin coating of the optical disc recording medium according to claim 1 to match the concentricity of the guide groove and the center hole of the optical disc.