JPH03219475A - Optical disk - Google Patents

Abstract

PURPOSE:To reduce residual stress generated in a disk substrate and to reduce retardation by performing the injection molding of a hub with synthetic resin with the same coefficient of thermal expansion as that of the disk substrate. CONSTITUTION:An optical disk 2 is mainly comprised of the disk substrate 6 having a recording layer on the plane on one side and the hub 7 fixed at the inside of the substrate. The hub 7 is formed with the synthetic resin with almost the same coefficient of thermal expansion as that of the substrate 6. A collar part 11 to stick on the substrate 6 is provided protrusively at the outer peripheral part of the hub 7, and a magnetic plate 12 is injection-molded in the center part of the upper plane. Thereby, it is possible to reduce the residual stress generated in the substrate 6 even when peripheral speed is varied, therefore, the optical disk generating few retardation can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in M Industry] The present invention relates to an optical disc, and particularly to an optical disc having a structure in which a hub is joined to the center of a disc substrate.

[Prior Art] Conventional optical discs consist of a transparent disc substrate that has a recording layer with minute irregularities such as pre-groups and pre-pits formed on one side, and an adhesive bonded to the outer surface of the disc substrate on which the recording layer is not formed. It mainly consists of a hub fixed with an agent, and an inner spacer and an outer spacer for bonding two disk substrates with the recording layer inside each other with a predetermined gap.

The hub is made of a metal magnetic plate such as a magnetic stainless steel plate, and has a flange formed on the outer periphery of the hub for adhesion to the disk substrate.

This hub made of a magnetic plate is arranged to face a magnet provided on the drive shaft of the optical disk device. A peripheral wall portion is integrally provided at the center of the hub by bending, and a hole into which the tip of the drive shaft is inserted is formed inside the peripheral wall portion.

[Problems to be Solved by the Invention] However, in this conventional device, the disk substrate is made of a synthetic resin such as polycarbonate, the hub is made of a metal such as a stainless steel plate, and the 1iIff members are joined together by adhesive. Ru.

Therefore, due to the difference in coefficient of thermal expansion between the two, residual stress is generated in the disk substrate, which has the disadvantage of increasing retardation.

Next, an optical disk cartridge according to an embodiment of the present invention will be explained with reference to the drawings.

1 and 2 are a plan view and a front view of an optical disk cartridge according to an embodiment with the shutter opened.

The optical disk cartridge according to this embodiment mainly includes a cartridge case 1 consisting of an upper case and a lower case, a recording disk 2, and a shutter 3.

The cartridge case 1 is made of polycarbonate, for example.
It is molded from synthetic resin such as ABS resin, a mixture of polycarbonate and ABS resin, and polypropylene.As shown in Fig. 1, approximately in the center of the cartridge case 1 is an elongated hole with a drive shaft insertion opening. A hesytocess opening 4 is formed. Furthermore, as shown in the figure, a substantially rectangular sliding recess 5 that is slightly stepped down from the top surface of the cartridge case 1 is provided in a substantially left half region including the head access opening 4 .

As shown in FIG. 3, the optical disc 2 is single-sided.An object of the present invention is to eliminate the drawbacks of the prior art, reduce the residual stress generated in the disc substrate, and produce a high-quality optical disc with low retardation. Our goal is to provide the following.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the present invention provides an optical disc equipped with a disc substrate made of a transparent synthetic resin and having a recording layer on one side, which has the same coefficient of thermal expansion as the disc substrate. A flange is provided on the outer periphery of the hub injection-molded with synthetic resin, and this flange is integrally joined to the inner periphery of the recording shoulder side of the disk substrate.

[Function] As mentioned above, the hub of the present invention has almost the same coefficient of thermal expansion as the disk substrate, so even if the ambient temperature changes, the residual stress generated in the disk substrate can be reduced, thereby reducing retardation. A small and highly reliable optical disc can be provided.

[Example 1] A transparent disc-shaped substrate 6 having a recording layer (not shown) formed with fine irregularities such as pre-groups and pre-pits, and a hub fixed to the inner circumferential side of the substrate 6 with adhesive. 7
It is mainly composed of an inner circumferential spacer 9 and an outer circumferential spacer 10 for bonding two substrates 6 with the recording layer inside, with a predetermined gap 8 between them.

The hub 7 is made of synthetic resin having approximately the same coefficient of thermal expansion as the substrate 6. In this embodiment, both the substrate 6 and the hub 7 have thermal expansion coefficients of 8x10-5 cm/cm.
/''C polycarbonate is used.A collar portion 11 for adhering to the substrate 6 is provided protruding from the outer periphery of the hub 7, and a magnetic plate 12 is injection molded at the center of the upper surface.

One surface of the magnetic plate 12 is exposed from the hub 7 so as to face a magnet provided on the drive shaft of the recording/reproducing device. A peripheral wall portion 13 is integrally provided at the center of the magnetic plate 12 by bending, and an insertion hole 14 into which the tip of the active shaft is inserted is formed inside the peripheral wall portion 13. As shown in FIG. 7, the tip 15 of the shoulder wall 13 is bent slightly outward in the radial direction so that the edge of the tip 15 does not come into direct contact with the curved surface of the drive shaft. This serves to prevent the magnetic plate 12 from being pulled out. Further, one or more tongue pieces 16 (three pieces in this embodiment) are vertically provided on the outer circumference of the magnetic plate 12 along the circumferential direction, and as shown in FIG. It is embedded in the hub 7 and functions to prevent the magnetic plate 2 from being removed. As shown in FIGS. 4 and 5, a plurality of (three in this embodiment) positioning holes 17 are formed in the magnetic plate 12, and when the magnetic plate 12 is injection molded onto the hub 7, a molding die is used. A positioning pin protruding from the hub 7 is inserted into the hole 17 and molded, and the magnetic plate 12 is embedded at a predetermined position in the hub 7 as described later.

In addition, in order to properly track signals when recording or repeating signals, it is necessary to ensure that the centers of the substrate 6 and the hub 7 are aligned and bonded together. Therefore, in the present invention, an annular groove 20 is formed near the root of the flap 11, and even if a protrusion 21 is formed, it is accommodated in the groove 20 and the substrate 6 and the collar 11 are bonded together. We ensure that Further, this groove 2o is formed by an adhesive 2 for bonding the substrate 6 and the collar portion 11.
It also helps to accommodate the surplus of 2.

The optical disc according to this embodiment is of a ventilated air sandwich type. In FIG. 3, the outer circumferential spacer 10 is coated with adhesive continuously in the circumferential direction on both the upper and lower surfaces and is bonded to the upper and lower substrates 6, respectively, so that no air permeability is provided.

On the other hand, the adhesive 22 is applied to the inner circumferential spacer 11 as shown by dotted hatching in FIG. A portion 23 that is not covered is formed.

Further, as shown in FIG. 3, a gap 24 is formed between the upper and lower hubs 7 at opposing portions. Therefore, this optical disc is
As shown in FIGS. 5 and 6, a plurality of (in this embodiment, three A connecting portion 19 is formed between the adjacent chucking pawl insertion windows 18.
is provided. The tongue piece 16 is designed to be buried at the connecting portion 19 so as to make the length of the tongue piece 16 as long as possible. The positioning hole 17 positions the magnetic plate 12 within the mold so that the tongue piece 16 is positioned at the center of the connecting portion 19 without shifting.

As shown in FIGS. 4 and 9, an annular groove 20 is formed on the upper surface near the base of the collar 11. When molding the substrate 6, protrusions 21 are formed on the inner periphery of the substrate 6, as shown in FIG. may be formed. When attempting to bond the substrate 6 with the protrusion 21 to the flange 11 in this way, there is a risk that the adhesive surface of the substrate 6 will rise above the upper surface of the flange 11 by the height of the protrusion 21, resulting in incomplete adhesion. .

The gap 8 is configured to communicate with the outside air. In addition, in FIG. 3, 25 indicates the recording area of the substrate 6. Further, in the same figure, reference numeral 27 denotes a stepped portion formed so that the inner peripheral portion of the disk substrate 6 is thinned, and the flange portion 11 of the hub 7 is adhered to this stepped portion 27.

The outer surface of the substrate 6 of this optical disc (especially the recording area 25
In order to prevent the optical disc 2 from coming into contact with the inner surface of the cartridge case 1, the outer periphery of the quick-acting shaft insertion opening 4a on the inner surface of the cartridge case 1 is designed to prevent A protrusion 2G is formed to suppress sticking.

FIG. 12 shows another embodiment of the present invention, which differs from the previous embodiment in that two disk substrates 6 are bonded to each other with an adhesive layer 28 made of, for example, ultraviolet curing resin.

FIG. 13 is a diagram showing still another embodiment of the present invention. In this embodiment, unlike the above-mentioned optical disc, the optical disc is constructed of a single plate.

[Effects of the Invention] As mentioned above, the hub of the present invention has almost the same coefficient of thermal expansion as the disk substrate, so even if the surrounding temperature changes, the residual stress generated in the disk substrate can be reduced. A highly reliable optical disc with low retardation can be provided.

[Brief explanation of drawings]

The drawings are all for explaining the present invention in detail, and FIGS. 1 and 2 are a plan view and a front view of an optical disk cartridge according to an embodiment with the shutter opened, and FIG. 4, 5, and 6 are a plan view, a sectional view, and a bottom view of the hub; FIG. 7 is an enlarged sectional view of the central portion of the hub; FIGS. 8 and 9 10 is an enlarged sectional view of the vicinity of the inner circumferential spacer; FIG. 11 is an enlarged sectional view of the vicinity of the drive shaft insertion opening of the cartridge case; FIGS. 12 and 13. 52 is a half-mounted sectional view of an optical disc according to another embodiment of the present invention;
6... Board, 7... Hub, 11...
...Brim portion, 12...Magnetic plate, 16...
Tongue piece, 17... Positioning hole, 18... Chucking claw insertion window, 2o... Annular groove, 28
...adhesive layer. @Figure 4 Figure 5 14・ Figure 9 Figure 10 Figure 1 Figure 1 Figure 710- Figure 12 Figure 13

Claims (5)

[Claims] (1) In an optical disc equipped with a disc substrate made of a transparent synthetic resin having a recording layer on one side, a flange is provided on the outer periphery of a hub injection-molded with a synthetic resin having the same coefficient of thermal expansion as the disc substrate, An optical disc characterized in that the flange portion is integrally joined to the inner peripheral portion of the disc substrate on the recording layer side. (2) The optical disc according to claim (1), wherein the hub is made of the same material as the disc substrate. (3) In claim (1), the two optical disks are arranged so that their recording layers face inward and face each other, and a predetermined gap is formed between both recording layers. An optical disc characterized in that an inner spacer and an outer spacer are provided between the optical discs, and the two optical discs are bonded via the inner spacer and the outer spacer. (4) According to claim (1), the two optical disks are arranged so that their recording layers face inward and face each other, and an adhesive layer is interposed between both recording layers. optical disk. (5) The optical disc according to claim (1), wherein a stepped portion is formed so that the inner peripheral portion of the disk substrate is thin, and the flange portion of the hub is joined to the stepped portion.