JPH0416254Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an optical information recording disk, and more particularly to an optical information recording disk having a so-called air sandwich structure in which a hollow portion faces a signal recording layer on the inner surface of a substrate.

BACKGROUND ART Conventionally, in optical information recording disks, information such as address information and guide track information is recorded as a large number of pits, etc., which are microscopic holes.
It is important to protect the layer in which the pits are formed, that is, the signal recording layer. For this reason, there is an optical information recording disk in which a pair of transparent circular substrates each carrying a signal recording layer on at least one side are arranged facing each other with the surface having the signal recording tank inside, and a space is formed between them.

Such optical information recording disks, e.g.
To record information on a DRAW (Direct Read After Write) disk, a laser beam is irradiated perpendicularly to the substrate surface, passes through the substrate, and focuses on the recording layer that is in close contact with the substrate.The recording layer is partially evaporated and pits are formed. This is done by forming a Information is reproduced by irradiating the recording layer with a laser beam having a power that does not change the recording layer in the same manner as during recording and reading the presence or absence of pits.

FIG. 1 shows a cross-sectional perspective view of an example of a DRAW disk cut in the diametrical direction. Circular substrates 1 and 5 are annular members, and a recording layer 2 is supported on the substrate 1 via an inner circumferential spacer 3 and an outer circumferential spacer 4.
are separated and glued so that they enter the hollow part. Further, a recording layer may also be formed on the substrate 5 to form a double-sided disk. The substrates 1 and 5 are made of transparent resin such as PMMA resin or polycarbonate resin by injection molding or the like. The annular groove 6 is formed in the substrate during injection molding. This is formed, for example, in order to use a mold to which a stamper is attached during injection molding in order to provide a guide track for guiding a laser beam.

An example of a mold for a stamper mounting portion of a substrate injection molding apparatus in such an injection molding method is shown in a schematic partial cross-sectional view in FIG. The stamper 7 is a disk having a center hole. The stamper 7 is fixed at its center hole with an inner periphery pressing member 8, and at its outer periphery by an outer periphery pressing member 9 on a stamper base mold 10. The molten resin normally flows from a spool 11 vertically above the center of the stamper surface through an annular slit formed by the upper mold 12 and the stamper base mold 10, and then the molten resin flows into the cavity 13 where the substrate is to be formed. It flows from the center toward the outer periphery as shown by the arrow. Thereafter, the resin filled in the void is solidified to form a circular substrate.

The injection molding method is a method that is highly suitable for mass production because it can simultaneously mold the substrate and transfer information such as pits. Further, a filling method in which the resin flows radially from the center of the substrate-shaped void 13 to be molded is ideal because there is no confluence of the resin and no weld line occurs. In addition, in order to increase productivity, the mold 10
Alternatively, a mechanism for making a center hole in the molded substrate and releasing the mold is required at the center of the stamper 7, and the stamper 7 needs to be provided with a center hole. Therefore, in order to fix the stamper 7 to the mold, not only the stamper outer periphery pressing member 9 but also the inner periphery pressing member 8 is required.

Therefore, an annular groove 6 that is concentric with the substrate and complementary to the presser claw portion 14 of the inner peripheral presser member 8 is formed in the molded substrate.

In the substrate formed in this manner, the presser claw portion 14 that fixes the inner circumferential edge of the stamper during molding protrudes into the gap 13, which acts as a barrier to the resin flowing from the center, and prevents the concentric annular groove 6 of the substrate after molding. Stress strain tends to remain on the inside in the radial direction. Such residual strain eases over time, but tends to cause deformation of the substrate.

FIG. 3 shows the deformation of the cut surface of a PMMA resin injection molded substrate cut into eight equal parts in the radial direction and immersed in hot water at a temperature of 90° C. for 3 hours. Compared to the desired shape of the substrate shown by the broken line, the portion of the substrate outside the groove 6 is hardly deformed, but the portion of the substrate inside the groove 6 is slightly bent.
This is because the resin flow on the main surface on the groove 6 side is blocked by the groove and the injection pressure is strong, resulting in high stress strain, but on the main surface without grooves, the compressed resin flows and stress strain increases. This is because the main surface on the lower groove side contracts more.

When assembling a substrate with such residual stress into an optical information recording disk of the form shown in Fig. 1, since the spacer 3, that is, the annular member is bonded inside the groove 6, the portion of the substrate inside the groove 6 may be deformed. This causes deformation of the portion of the substrate outside the groove that carries the recording layer. If the deformation of the substrate portion supporting the recording layer is too large, the laser beam may exceed the focusing range, making it impossible to record or reproduce information, and the emitted laser beam may not return, making it difficult to reproduce information.

Summary of the invention The purpose of the invention is to provide a highly reliable optical information recording disk with less warpage of the substrate.

The optical information recording disk of the present invention includes a pair of circular resin substrates, at least one of which has concentric annular grooves formed by injection molding, and at least one of which has a signal recording layer; An optical information recording disk comprising an inner circumferential annular member and an outer circumferential annular member provided at the inner circumferential and outer circumferential positions of a substrate, respectively, so as to be coupled at intervals with the inner circumferential annular member having an annular groove. It is characterized by being provided on the outside in the radial direction.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 4 is a cross-sectional perspective view showing the first embodiment of the present invention. In the figure, a substrate 1 is a circular substrate 20 cm in diameter made by injection molding PMMA resin using a mold equipped with a stamper. A recording layer 2 on which information can be additionally recorded using a laser beam is formed on the substrate 1. Spacers 3 and 4 are made by casting PMMA resin. The inner spacer 3 is provided outside the annular groove 6 of the substrates 1 and 5 and inside the recording layer 2 of the substrate 1. These inner and outer spacers 3 and 4 are bonded to the substrates 1 and 5 with an ultraviolet curing adhesive. These spacers are
This is an annular member made of PMMA resin cast into an annular shape.

FIG. 5 is a cross-sectional perspective view showing a second embodiment of the present invention. FIG. 5 shows the second embodiment and the first embodiment shown in FIG. 4.
The structure is the same as that of the embodiment except for the inner spacer. The first inner circumferential spacer 15 in FIG. 5 is an annular member formed by casting PMMA resin into an annular shape, and the second inner circumferential spacer 16 is an annular member formed by processing a plate material of nitrile butadiene rubber (NBR) into an annular shape. The substrate and the spacers are bonded together using an ultraviolet curing adhesive as in the first embodiment.

Second Embodiment In both of the second embodiments, the substrate portion near the center hole is configured to be deformable.

FIG. 6 is a graph showing the magnitude of deformation when the conventional disk and the disk of this embodiment were left in an environment of 60° C. and 90% RH. The samples were a conventional disk and a disk according to this embodiment, both of which had a diameter of 2 cm and were constructed in the same manner except for the inner peripheral spacer. The amount of displacement of each sample is the value of warpage at the outermost periphery with the back surface of the groove portion of the substrate as a reference. In FIG. 6, curves A and △ are disks of the first embodiment, curves B and □
The curve C and ◯ indicate the displacement amount of the second embodiment disk, and the curve C and ◯ indicate the displacement amount of the conventional disk, respectively.

As shown in the graph, the displacement amount reaches its maximum value on the 3rd to 4th day for both the conventional example and the disks of the first and second embodiments, but in the conventional example, the displacement remains large and remains fixed. I won't go back. This is because the substrate is deformed inside the groove, but in the conventional example, due to the difference in the magnitude of deformation between the pair of substrates, the deformation is large on one side. However, if the magnitude of deformation happens to be the same for a pair of substrates, the amount of deformation will be small.

In the first embodiment, the amount of displacement becomes almost 0 after 12 days or more. In the first embodiment, the deformation of the substrate inside the groove does not affect the deformation of the substrate outside the groove, so the deformation becomes zero by leaving the substrate in the environmental test for a long time.

In the second embodiment, it becomes stable at about 0.3 mm. In the second embodiment, the NBR spacer inside the groove absorbs deformation, so the warpage of the disk is smaller than that of the conventional example.

The optical information recording disk of this embodiment is configured to concentrate deformation on the inside of the annular groove of the substrate in the radial direction, so that the contact portion between the drive unit that rotates the disk and the disk is located outside of the groove. In this case, the influence of deformation of the inner peripheral portion of the substrate is reduced.

Furthermore, even if one of the pair of substrates has an annular groove as described above, deformation in the vicinity of the center hole of the substrate is inevitable, so at least one of the substrates is formed by injection molding to use a grooved substrate. The present invention can be applied to optical information recording disks.

Effects of the Invention As described above, according to the present invention, the influence of deformation near the center hole during manufacturing of the substrate of an optical information recording disk does not affect the signal recording/reproducing portion of the disk. Furthermore, even when used in harsh environments, it is possible to avoid deformation of the entire disk due to deformation in the vicinity of the center hole, making it possible to reproduce information stably.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional perspective view of a conventional optical information recording disk, FIG. 2 is a partially sectional view of a substrate molding die implementing the present invention, and FIG. 3 is a schematic sectional view showing deformation of the substrate. 4 and 5 are partial cross-sectional views of the optical information recording disk according to this example, and FIG. 6 shows the amount of deformation of the optical information recording disk over time during an environmental test. This is a graph. Explanation of symbols of main parts, 1 and 5...Circular resin substrate, 2...Information recording layer, 3...Inner spacer,
4... Outer periphery spacer, 6... Annular groove, 7... Stamper, 8... Stamper inner periphery holding member, 9... Stamper outer periphery holding member, 10... Stamper base mold, 11... Spool, 12... Upper mold, 13
... Board shape gap, 14 ... Inner peripheral presser claw part, 1
5...First inner circumference spacer, 16...Second inner circumference spacer.

Claims (1)

[Claims for Utility Model Registration] (1) A pair of circular resin substrates, at least one of which has concentric annular grooves formed by injection molding, and at least one of which has a signal recording layer; An optical information recording disk comprising an inner circumference and an outer circumference annular member provided at the inner circumference and outer circumference positions of the substrate, respectively, for bonding the layers at intervals with the layers inside, the inner circumference annular member An optical information recording disk characterized in that: is provided on the radially outer side of the annular groove. (2) A utility model according to claim 1, characterized in that an annular flexible member made of a material having greater flexibility than the inner circumferential annular member is provided inside the annular groove in the radial direction. Optical information recording disk. (3) The optical information recording disk according to claim 1 or 2 of the utility model registration claim, which is in contact with a holding member of an optical information recording disk drive device on the radially outer side of the annular groove. .