JPS63129541A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To suppress an increase in double refraction at the time of an environmental temp. and humidity change and to obtain a recording charateristic having high reliability by mounting an annular center fitting having notches to least at one point on the inner periphery of a disk substrate. CONSTITUTION:The annular center fitting 2 having the notches 3 at least at one point are mounted on the inner periphery of the substrate to constitute an optical information recording medium such as the optical disk substrate 1 to be magnetically clamped for an optical information recording reproducing device. The notches 3 are preferably so provided that the fitting 2 is divided by the same. The mere formation of the notches (not to the complete division) 3 is equally well. The result is better as the number of the notches 3 to be provided is larger. The fitting 2 may be directly mounted to the inner peripheral part of the substrate 1 or may be mounted via an intermediate ring 4 onto the inner peripheral part of the substrate 1. The generation of the stain arising from the temp. and humidity change by a material difference between the fitting 2 and the substrate 1 is suppressed by providing the notches 3 to the fitting 2 in the above-mentioned manner, by which the increase in the double refractions of the substrate 1 is decreased.

Description

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

(Conventional technology) In recent years, the amount of information stored in offices and homes has been increasing dramatically. An information recording carrier and an information recording/reproducing device are desired.

Conventionally, contact magnetic recording systems have been mainly used to record and reproduce information, but recently optical disk devices that record and reproduce information in a non-contact manner using laser light have been developed and are being put into practical use.

Up to now, two types of clamping methods for optical discs suitable for information recording and reproducing devices have been proposed: a mechanical chuck method and a magnetic clamp method, but the magnetic clamp method is advantageous for the following reasons. .

That is, the structure of an optical disk is roughly divided into three types: a single-plate structure, an air sandwich structure, and a full-surface contact structure, and the thickness of the information recording carrier differs depending on each structure. Single-disc structures are used in read-only CDs and CD-ROMs, and the thickness is standardized, so there is no problem. In the case of , the structure also differs depending on the information recording format, that is, a case involving a physical change in shape such as opening or void formation, and a case without a change in physical shape such as magneto-optical or phase change. The former has an air sandwich structure, and the latter mainly has a full-surface contact structure, so the thickness is not uniform.

Ninth, while the mechanical method has the drawback that it is not compatible with the mounting and removal of optical discs in recording and reproducing devices, the magnetic clamp method does not have this drawback.

By the way, in the magnetic clamp method, it is necessary to fix center metal fittings for attaching the optical disc to the information recording/reproducing apparatus to both sides of the disc substrate.

As shown in Figures 3a and 3b, the basic structure of a conventional optical information recording medium using a magnetic crank system is composed of a flat ring-shaped center fitting 6 made of plastic and having one side. .

(Problem to be Solved by the Invention) However, in this structure, the center metal fitting 6 is ring-shaped and is continuously restrained along the inner circumference t-360° of the disk substrate l. , since the disk substrate l is not easily deformed in the radial direction, the photoelastic constant C of the center fitting 6 and the dip is large (C
= 6.8 Regarding magneto-optical disks that utilize the Kerr effect, there is a problem in that this influence is large.

An object of the present invention is to solve such problems, to provide an information recording medium that suppresses the increase in birefringence when the temperature and humidity of the environment changes, and has excellent reliability in terms of recording characteristics.

(Means for Solving the Problems) The structure of the present invention is characterized in that a ring-shaped center fitting having at least one notch is mounted on the inner periphery of the disk substrate.

It is preferable that the sill-shaped center fitting is divided by the cut edge, but it is possible to reduce birefringence even if the ring-shaped center fitting is not completely divided. It is.

The more cuts there are, the more effective it is in reducing birefringence, but when the ring-shaped center metal fitting is divided by cuts in the radial direction, the number of fan-shaped parts created by the cuts also increases.
Since the manufacturing cost also increases, it is preferable that the ring-shaped center metal fitting is divided into 2 to 6 fan-shaped pieces by cuts in the radial direction.

The center metal fitting may be attached directly to the inner circumference of the disk substrate with adhesive, or it may be attached to the inner circumference of the disk substrate through an intermediate ring that acts as a buffer layer to reduce the strain applied to the disk substrate. It may be set.

If the disk substrate is attached to the inner circumference of the disk substrate via the intermediate ring, the disk substrate and the intermediate ring may be joined by adhesive or directly fused together using ultrasonic waves, high frequency waves, etc. Examples include things that are difficult to understand. Furthermore, the center metal fitting and the intermediate ring may be joined by adhesive, or the center metal fitting and the intermediate ring may be simultaneously manufactured by insert molding. When manufacturing by insert molding, it is necessary to provide a bar to prevent separation of the intermediate ring and center metal fitting.

The material of the center metal fitting is SUS 4031 SUS 416, which has excellent corrosion resistance and is also magnetic. SUS
430°N1 or the like is suitable.

Examples of adhesives include reactive adhesives such as resorcinol cyanoacrylate, epoxy, and urethane;
A. Synthetic rubber, polyester, polyamide hot melt adhesives and general purpose resins such as polyethylene, polypropylene, polycarbonate, polymethyl methacrylate, polyester, polyamide, etc. can be used.

To bond using hot-melt adhesives and general-purpose resins, you can use them in a heated and molten state, or apply ultrasonic waves or high-frequency waves as a heat source to melt the resin that has been filled in advance. Compared to methods using reactive adhesives, bonding and curing can be completed in a shorter time, which is extremely advantageous in terms of process.

A suitable material for the intermediate ring is a polymeric material having a coefficient of linear hygroscopic expansion and linear expansion comparable to that of the disk substrate, or a polymeric material having an elastic constant equal to or less than the value of the material of the disk substrate.

(Example) Example 1 As shown in Figures 1a and 1b, the inner diameter is 15 m and the outer diameter is 3 m.
A ring made of 5US403 with a thickness of 2u1 and a thickness of 0.3lIa is divided into four equal parts by a radial cut 3.The center metal fitting 2 has an outer diameter of 32mm, an inner diameter of 4w5, and is made of PC resin with a disk board on the outside of the inner circumference on one side. A ring 4 is fitted into the center hole of the disk substrate 1 for easy installation on the disk substrate 1, and a ninth recording material 7 is made of PC and records information on one or both sides. The center metal fitting 2 is bonded to the recessed part of the intermediate ring 4 with an epoxy adhesive, and the intermediate ring 4 is bonded to the outside of the inner circumference of the disk substrate l with an epoxy adhesive. It is.

The birefringence of the disk substrate l of Example 1 at a position with a radius of 30s+a was measured and was zsnm (double pass). This was carried out in an environment of 60℃ and 901RH (relative humidity).
After humidifying for 20 hours, the birefringence was measured again at 32 nm (double pass).

The birefringence was measured at a radius of 30 m on the disk substrate of an optical information recording medium that was exactly the same as in Example 1, except that the center metal fitting had a ring shape without a cut, and the result was 2.8 nm.
(double pass). This is t-60℃, so%RH
After humidifying for 120 hours in an environment of (relative humidity), the birefringence was measured again and it was found to be aonm (double pass). It can be seen that the increase in birefringence due to changes in temperature and humidity is small.Example 2 As shown in Figs. Metal fittings 2
The center metal fitting 2 is made of a PC and is composed of a recording sensitive material 7t for recording information on one or both sides of the disc substrate l, which is pasted together with an adhesive layer 8. It is directly joined to the outside of the inner periphery.

(Effects of the Invention) According to the present invention, since the center metal fitting has a cut, the restraint of the disk substrate by the center metal fitting is reduced compared to the conventional one without a cut, and the number of disk substrates can be reduced. Therefore, it has become possible to reduce the increase in birefringence of the disk substrate caused by distortion compared to conventional optical information recording disks.

[Brief explanation of the drawing]

FIG. 1a is a plan view of one embodiment of the present invention, and FIG. 1b is a plan view of an embodiment of the present invention.
Fig. 2a is a plan view of another embodiment; Fig. 2b is a sectional view taken along line 0B-B in Fig. 2a; Fig. 3a is a cross-sectional view of a conventional optical information recording medium. Plan view, Figure 3b is the third
It is a sectional view taken along the line CC in figure a. l: Disc board, 2 = center metal fitting (with cut),
3: Cut, 4: Intermediate ring, 5: Protrusion, 6: Center metal fitting (no cut), 7: Recording sensitive material, 8: Adhesive layer Patent applicant Asahi Kasei Industries, Ltd. Figure 10 Figure 1b A- Fig. 20 Fig. 2b Fig. B-8 @ side view

Claims (1)

[Claims] An optical information recording medium magnetically clamped to an optical information recording/reproducing device, characterized in that a ring-shaped center fitting with at least one cut is attached to the inner periphery of a disk substrate. recoding media