JPH0432039A - information recording medium - Google Patents

Abstract

PURPOSE:To prevent the occurrence of flaws by uniformly providing a film harder than the material of a substrate on the substrate surface from the outside end part up to the part brought into contact with a rotating stage of a recording and reproducing device. CONSTITUTION:A film 11 harder than the substrate material is uniformly provided on the surface of a substrate 1 from the outside end part up to the part brought into contact with the rotating stage of the recording and reproducing device. Substrates 1 are stuck to each other with an adhesive 7, and a chucking hub 8 is provided in the center part of the substrate. The hard film 11 is provided over a part from the clamping area, which is provided on the outside of a hub outer end 9 and on the inside of a group innermost periphery 10, to the substrate terminal. Thus, flaws due to repeated attachment and detachment of disks are prevented to extend the life.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical information recording medium.

[Prior Art] Optical discs have the advantage of being non-contact with the pickup used for recording and reproducing, and are resistant to scratches. However, during long-term use, scratches may occur due to wiping off dirt on the surface. In particular, polycarbonate resin has low hardness and is easily scratched. Therefore, JP-A-61-'139961.59-1826
No. 52 proposes providing a coating with an ultraviolet curing resin.

On the other hand, when the disk is actually used, there is a contact portion between the rotary stage and the substrate for holding the substrate. When the media is used for a long period of time, this contact area (hereinafter referred to as the clamping area) is also damaged due to the attachment and detachment of the media, causing problems such as generation of dust and worsening of tilt.

Therefore, a coating harder than the substrate material is provided up to this clamping area.

However, on the side opposite to the recording surface of the injection molded substrate, a convex portion usually occurs at the joint between the outer part and the inner part of the mold (FIG. 2). The above-mentioned film is generally formed by a spin code method, but the presence of these convex portions causes uneven coating, which seriously impedes recording and reproducing.

[Problems to be Solved by the Invention] In view of these circumstances, the present invention aims to provide an optical disc that prevents scratches caused by disc attachment and detachment and has a long life.

[Means for Solving the Problems] As a result of intensive studies to solve the above-mentioned problems, the inventor of the present invention has developed a method of uniformly covering the disk edge with a hardened protective film to the contact area with the rotary stage of a recording/reproducing device. We have found that this is effective, leading to the present invention.

That is, the present invention provides a recording medium in which information is recorded and reproduced by irradiation with a high-energy beam such as a laser, in which a film harder than the substrate material is formed on the surface of the substrate, starting from the outer edge of the substrate.
This is an information recording medium that is uniformly provided even on the part that comes into contact with the rotary stage of a recording/reproducing device.

FIG. 1 shows an example of the information recording medium of the present invention.

The substrate 1 includes a dielectric layer 2, a magnetic layer 3, a dielectric layer 4, a reflective layer 5,
A protective layer 6 is provided, and the two substrates are bonded together using an adhesive 7. A hub 8 for chucking is provided at the center of the board. The clamping area is provided outside the hub outer end 9 and inside the innermost group circumference 10. A hardened film 11 is provided to cover the area from this clamping area to the end of the substrate.

As the material for the film, an ultraviolet curing resin is used, and an acrylate resin such as an acrylic monomer, urethane-modified acrylate, epoxy-modified acrylate, or polyol-modified acrylate, or a photo-curable epoxy is used.

Furthermore, in order to impart conductivity, fillers such as 5n02 and In2O3 may be dispersed, or surfactants and conductive resin materials may be mixed.

The required hardness is preferably H or higher in terms of hardness.

A spin code method is used to form the film.

At this time, it is important to form a film evenly and uniformly.

In the conventional molding die, as shown in FIG. 2, the stander facing surface is an outer member 13 for molding the outside of the disk substrate.
and an inner member 14 for molding the inside of the disk substrate, and there is a gap between these members, into which resin flows during molding and a convex portion 12 is formed on the molded substrate. That will happen.

This inner member is a part that becomes a relief when punching the center hole of the disk after molding, and it is difficult to eliminate it in principle.

Adjust the position of the convex part so that it does not affect the spin code! (inner side than the clamp area), but this is practically impossible because the inner member becomes smaller and there is a problem with mechanical strength.

The presence of these convex portions causes coating unevenness when forming a film by the above-described spin code method. In particular, if the height h of the convex portion exceeds 20 .mu.cm, radial streaks will appear during spin coding, which will interfere with recording and reproduction.

In the present invention, in order to form a uniform film, the height h of the convex portion is set to 15μ or less, which does not have a substantial adverse effect, as shown in FIG. has been established. That is, the inner member 14 on the surface facing the stamper is assembled lower than the outer member 13 (farther from the stamper), and the height difference 18 is 1 to 30.
μ mark is preferred. Note that 1B represents a group and 17 represents a gate groove. By configuring the mold in this manner, the resin during molding can be prevented from entering the corner portions shown in FIG. 3, and the convexity at the gap portions can be made smaller than in the conventional example. If the level difference is less than 1 μl, the effect of reducing the convex portion cannot be obtained, and if it is more than 30 μl, coating unevenness will occur due to the level difference. Further, if the outer portion is lowered, a step will be created which will hinder coating, which is not preferable.

The present invention is applicable not only to magneto-optical recording media but also to WORM, phase change media, CDs, CD-ROMs, etc.

[Example code] Example The height of the protrusion on the opposite side to the group side was set to 5μ.

On a polycarbonate resin substrate, a 5iNz layer of 1000 layers, a TbDyFeCo layer of 200 layers, and a SiN layer were formed as recording layers.
After forming 500 x 800 x SA layers, a 4 μm layer of ultraviolet curable acrylic resin (SD-301: manufactured by Dainippon Ink) was formed to obtain a veneer media. On the opposite side of the recording layer of this medium, an ultraviolet curable resin (EX-801, manufactured by Dainippon Ink) was applied to the outer end from a position of radius 13+n+n to obtain a cured layer. The two media thus obtained were bonded together by a hot melt method, and then a hub was attached to form a double-sided media.

The surface hardness was 2H. The media thus obtained was tested 20,000 times to be inserted into and removed from the drive, but no scratches were found in the clamp area.

Comparative Example 1 A radius of 251 mm was applied to the veneer media obtained in the same manner as in the example.
An ultraviolet curing resin was applied from the m11 position to obtain a cured film. Furthermore, a hub was attached in the same manner as in the example.

The media obtained in this way was tested for installation and removal into the drive.
After doing this 10,000 times, scratches appeared on the clamp area, and the
Several pieces of dust with a size of 0μ■ were observed.

Comparative Example 2 A veneer media obtained in the same manner as in Example except that the height of the convex portion on the opposite side to the group surface was 20 μm was coated with UV curing resin from a position with a radius of 13 cm. Streaks occurred.

[Effects of the Invention] As explained above, the information recording medium of the present invention can prevent scratches due to repeated attachment and detachment of the disk by providing a hardened film even in the clamp area, and can extend its life. did it.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the information recording medium of the present invention, FIG. 2 is a diagram illustrating a conventional mold for molding a disk substrate, and FIG.
The figure is a diagram illustrating a mold for forming a disk substrate for a recording medium according to the present invention.

Claims (1)

[Claims] In recording media where information is recorded and reproduced by irradiation with high-energy beams such as lasers, a film that is harder than the substrate material is uniformly coated on the surface of the substrate from the outer edge of the substrate to the part that contacts the rotating stage of the recording and reproducing device. An information recording medium characterized by: