JPH06124482A - Optical recording medium - Google Patents

Abstract

PURPOSE:To eliminate a substrate undulation and to enhance the mechanical strength and the accuracy of the optical recording medium by a method wherein, when disk- shaped substrates are molded, ring-shaped protrusions which protrude from recording layers are molded integrally at inner circumferential edge parts and outer circumferential edge parts of the substrates and the protrusions are faced with each other and bonded. CONSTITUTION:Ring-shaped protrusions which protrude from faces of recording layers 12, 12' are molded integrally at inner circumferential edge parts 13, 13' and outer circumferential edge parts 14, 14' of resin substrates 11, 11', a gap 17 is formed, an air sandwich structure is formed, and a ring-shaped spacer is not required. Consequently, when the substrates are pasted, they are not displaced, and the dynamic balance of the substrates becomes good. In addition, since the inner and outer circumferential edge parts 13, 14 of the substrates are thick and are formed to be continuously ring- shaped, a substrate undulation is not caused when the substrates are pasted. In addition, although the outermost parts at the substrates are quenched inside a mold when the substrates are injection-molded, a strain is relaxed when they are quenched because recessed parts 15, 16 are formed in the substrates, and the strain does not reach the inner circumferential part. Consequently, the mechanical characteristic of the title recording medium is made good.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium. More specifically, the present invention relates to a disc-shaped optical recording medium in which a recording layer is provided on the surface of a synthetic resin disc-shaped substrate, and the recording layers are opposed to each other with a predetermined gap therebetween and integrated.

[0002]

2. Description of the Related Art In recent years, an optical recording medium has attracted attention as a memory medium having a large storage capacity and capable of reading and writing data at high speed. Optical recording media are roughly classified into a read-only type (compact disc, CD-ROM), a recording / reproducing type (write-once type), a recording / reproducing / erasing / rewritable type (rewritable type), and the like.

A typical structure of such an optical recording medium is as follows.
It is roughly classified into a single-sided recording type, a double-sided recording type, an air sandwich structure type, and a double-sided recording type. Among them, in the air sandwich structure type optical recording medium, as shown in FIG. 4, resin substrates 41 having a recording layer 42 on one surface are disposed with a predetermined gap 44 with the recording layer 42 inside. The annular spacers 43 are made to face each other and along the inner peripheral edge and the outer peripheral edge.
A resin-made ring-shaped space holding member is interposed, and the resin-made substrate 41 is bonded or fused to be integrated.

[0004]

However, in such an optical recording medium of the air sandwich structure, since the substrate and the spacer are separate bodies, the spacer is apt to be displaced particularly at the inner peripheral edge portion at the time of bonding or fusing. As a result, a displacement occurs between the two substrates, which is inconvenient in that the dynamic balance is lost when the disc is rotated. In addition, there are problems that the bonding process is complicated and it is difficult to bond them uniformly.

[0005]

Means for Solving the Problems As a result of intensive investigations by the present inventors to solve the problems of the optical recording medium of the air sandwich structure type, as a result, the inner peripheral edge portion of the substrate and The present invention has been completed by finding that the above-mentioned problems can be solved by integrally forming an annular protrusion along with the substrate along the outer peripheral edge and joining the annular protrusions to each other by abutting them.

That is, the gist of the present invention is to provide an optical recording medium obtained by bonding a disc-shaped substrate having a recording layer on its surface so that the recording layer side faces the inside and a predetermined gap is maintained. An optical recording medium, characterized in that annular projections protruding from the recording layer are integrally formed along the inner peripheral edge portion and the outer peripheral edge portion of the substrate at the time of molding, and the annular projections are opposed to each other and are joined together. Exist in.

The present invention will be described in more detail below.
FIG. 1 shows an example of an embodiment of an optical recording medium of the present invention, in which recording layers 12, 12 'are provided on disk-shaped substrates 11, 11' obtained by injection molding of synthetic resin. With the layer side inside, facing through the gap,
Inner peripheral edges 13, 13 'and outer peripheral edges 14, 14' of the substrate
Are bonded and integrated by bonding or fusion.

The inner peripheral edges 13 and 13 'and the outer peripheral edge 1 of the substrate
The annular projections 4 and 14 'are formed integrally with the substrates so as to project from the surfaces of the recording layers 12 and 12' of the substrates. As a result, the voids 17 are formed, and an air sandwich structure type optical recording medium is obtained. According to the present invention, it is not necessary to bond the substrate and the separate annular spacer to each other as in the prior art. Therefore, when the substrates are bonded, the displacement between the substrate and the spacer and the displacement between the two substrates do not occur, so that the dynamics at the time of rotating the disk are eliminated. Good balance.

Further, in the present invention, the inner peripheral edge portion 13 of the substrate is
Since the outer peripheral edge portion 14 is thick and has a continuous annular shape, the waviness of the substrates at the time of laminating the substrates is eliminated and a disk having effective mechanical characteristics can be obtained. Inner peripheral edge 13 of substrate
It is preferable that the joint area in the outer peripheral edge portion 14 is large. Further, it is preferable that the outer portion from the recording area is as wide as possible.

Further, recesses 15 and 16 are formed adjacent to the joint portion at the inner peripheral edge portion or the outer peripheral edge portion of the substrate. By providing such recesses, the substrates 11, 1
Inner peripheral edge portion 13 or outer peripheral edge portion 14 when 1'is bonded
If the adhesive or the like is squeezed out, the recesses 15 and 16
Can be accumulated in the recording medium, and the inconvenience that the adhesive reaches the recording area is reduced.

Further, the outermost portion of the substrate is rapidly cooled in the mold during the injection molding of the disc-shaped substrate.
By forming 5 and 16, distortion at the time of cooling is relaxed in the recess. Therefore, the cooling distortion does not reach the inner peripheral portion, and an optical recording medium having good mechanical characteristics can be obtained. Next, FIG.
FIG. 7 shows a partially enlarged view of an embodiment of the disc-shaped substrate of the present invention. It suffices that the height 21 of the protruding portion of the annular protrusion has a void amount that forms an ordinary air sandwich structure when the substrates are bonded together, and is generally 0.2 to 0.3 mm, which is 1/2 of the void amount.
The degree is good.

At the time of molding the substrate, guide grooves, address signal pits and the like are transferred from the stamper as will be described later, but the die is provided with a claw portion for pressing the stamper. If the depth 22 of the recess formed by the claws is too small, the claws of the stamper retainer become small, and the strength with which the stamper is pressed during molding is reduced, which is not preferable because the stamper is displaced, and if it is too large, it is difficult to form in the molding. This is not preferable because the flow resistance of the resin becomes large and the resin tends to be insufficiently filled. Usually the depth of the recess is 0.2 to 0.5 m
About m is preferable.

If the recess width 23 is too small, it is not preferable for the same reason as the recess depth 22, and if it is too large, the width of the annular projection is unavoidably reduced, and the area of the bonded portion of the annular projection is reduced, which is preferable. Absent. Normally the recess width is 0.2
About 1.0 mm is preferable. Further, the substrate near the recesses 15 and 16 is likely to have residual stress during molding, and the optical characteristics may have changed.
It is desirable to provide them just before 5 and 16 so as to stably maintain the outermost characteristics of the recording area.

Examples of the synthetic resin used for the disk-shaped substrate of the present invention include polycarbonate resin, acrylic resin, polymethylmethacrylate resin, polystyrene resin, nylon resin and the like. Substrate thickness is usually 1 to
It is about 1.2 mm. An example of a mold for molding the disc-shaped substrate of the optical recording medium shown in FIG. 1 is shown in FIG.

In FIG. 3, the molding apparatus used for injection molding of the substrate includes a movable mold 31 and a fixed mold 32. The movable mold 31 is fixed with a stamper 33 for transferring and forming pits and laser guide grooves, that is, grooves on the surface of the substrate. That is, the stamper 33 is the movable mold 3
The structure is fixed to the movable mold by an inner peripheral stamper retainer 36 and an outer peripheral stamper retainer 37 so as not to float above 1.

The inner peripheral edge portion 34 and the outer peripheral edge portion 35 of the movable mold 31 are provided so that the inner peripheral edge portion 13 and the outer peripheral edge portion 14 of the substrate obtained by molding have a shape protruding from the recording layer portion. There is. Further, in FIG. 3, reference numeral 38 denotes an inner hole cutter for forming a central hole of the substrate, and 39 denotes a resin inflow port. As a method of integrating the substrates together, first, an inorganic or organic substance to be a recording layer is provided on the disk substrate obtained above by sputtering or the like, and then the inner peripheral edge and the outer peripheral edge of the substrate are formed. Are joined by adhesion, fusion, or the like. The bonding method is not particularly limited, but for example, the adhesive is applied to the inner peripheral edge and the outer peripheral edge of the substrate using a known coating device such as a roll coater. Next, the recording layer side of the substrate is placed inside, and the inner peripheral edge portion and the outer peripheral edge portion are made to face each other and are bonded and bonded to each other to integrate them.

[0017]

According to the present invention, since no displacement occurs between the substrates when the substrates are bonded together, the dynamic balance becomes good when the disc is rotated. Further, in the present invention,
Since the inner peripheral edge portion and the outer peripheral edge portion of the substrate are thick, the undulation of the substrate at the time of laminating the substrates is eliminated, and the mechanical properties of the disk are improved. Furthermore, since the optical recording medium according to the present invention is easy to manufacture, it is possible to improve the accuracy and mass-produce it, and to reduce the cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an optical recording medium of the present invention.

FIG. 2 is a partially enlarged view of an embodiment of the disc-shaped substrate of the present invention.

FIG. 3 is a partial cross-sectional view of an embodiment of a disc-shaped substrate injection molding die of the present invention.

FIG. 4 is a sectional view of an optical recording medium according to a conventional example.

[Explanation of symbols]

 11, 11 ', 41 Resin substrate 12, 12', 42 Recording layer 13, 13 'Substrate inner peripheral edge 14, 14' Substrate outer peripheral edge 15, 16 Recessed portion 17,44 Void 21 Annular protrusion protruding portion Height 22 Recessed portion Depth 23 Concave width 24 Stabilizing area 25 Bonding area 26 Recording area 27 Substrate thickness 31 Movable die 32 Fixed die 33 Stamper 34 Inner peripheral edge protrusion 35 Inner peripheral edge protrusion 36 Inner edge Part stamper retainer 37 outer peripheral edge stamper retainer 38 inner hole cutter 39 resin inlet 43 spacer

Claims (1)

[Claims] 1. An optical recording medium obtained by bonding a disc-shaped substrate having a recording layer on its surface so that the recording layer side faces the inside and a predetermined gap is kept between the disc-shaped substrate and the disc-shaped substrate. An optical recording medium, characterized in that annular projections protruding from the recording layer are integrally formed along the peripheral edge portion and the outer peripheral edge portion, and the annular projections are opposed to each other and are bonded to each other.