JP3164967B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk, and more particularly, to an optical disk having a substrate fixing region at a central portion.

[0002]

2. Description of the Related Art FIGS. 3 to 5 show a conventional example. This figure 3
The conventional optical disc shown in FIGS. 5 to 5 has a molded substrate 52 having signal irregularities on the surface in the order of submicrons and a concave portion 52A formed by a stamper holding jig, and an information recording surface side of the molded substrate 52. Recording layer 54 applied to
And a protective layer 56 applied on the recording layer 54. Reference numeral 58 denotes a support member for supporting the molded substrate 52.

Here, the concave portion 52A on the molded substrate 52 will be described. Generally, when a substrate for an optical disk is molded by injection molding, a stamper having submicron-order signal irregularities in a cavity for forming the substrate is provided. Inserted. In this case, a stamper holding jig is used to hold the stamper in the mold. On the other hand, since a part of the stamper holding jig has a structure protruding from the surface of the stamper, a concave portion 52 </ b> A is formed on the surface of the molded substrate 52. That is, the concave portion 52A is formed by a stamper holding jig and is well known to those skilled in the art. The concave portion 52A is formed inside the recording layer 54 as is apparent from FIG.

[0004]

As described above, the molded substrate 52 has a concave portion 52A which can be called a jig groove on its surface.
(Formed clearly inside the recording layer 54 from FIG. 3), the strength is reduced as a whole, and the state is easily warped.

FIG. 5 shows an example in which the "warp" of the optical disk generated in FIG. 3 is enlarged. In this case, if the film layer itself forming the recording layer 54 has a property of hardening and expansion, the warp of this optical disk appears more strongly. On the other hand, when the film layer forming the recording layer 54 has the property of curing and shrinking, the warp of the optical disc is reversed. In any case, there is a disadvantage that the optical disk is likely to be warped after assembly due to the influence of the concave portion 52A. When the optical disk is warped, not only the readout accuracy is reduced, but also a head crash is caused, and the reliability of the entire device is impaired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disk capable of improving the disadvantages of the prior art and effectively suppressing the warpage of an optical disk after assembling, and thereby improving the reading accuracy of a magneto-optical head. Its purpose is to provide.

[0007]

According to the present invention, there is provided a molded substrate having signal irregularities on the surface in sub-micron units and having a concave portion caused by a stamper holding jig, and applying the molded substrate to an information recording surface side of the molded substrate. In an optical disc having a recorded recording layer and a protective layer applied on the recording layer, the protective layer is composed of a first protective layer and a second protective layer. Then, the first protective layer is laminated on the recording layer described above,
The second protective layer is laminated on the entire surface of the molded substrate except for the central portion of the molded substrate. This aims to achieve the above-mentioned object. That is,
The protective layer of No. 2 is filled in the concave portion, and the concave portion is further
Will cover.

[0008]

In the case of the first aspect, when the concave portion 2A of the molded substrate 2 is warped to a convex state as shown in FIG. 5, the internal stress of the recording layer 4 acts to expand, that is, expand. In addition, it functions so as to extend the surface of the above-mentioned molded substrate 2 over the entire surface. On the other hand, since the curing shrinkable resin is used as the second protective layer 6B, the action opposite to the action of the internal stress of the recording layer 4 described above, that is, the surface of the molded substrate 2 is entirely covered. Functions to contract.

Therefore, the action of the recording layer 4 (the action of expanding the surface over the entire surface) and the second action
(The effect of shrinking the surface over the entire surface) of the protective layer 6B is canceled, and the warpage of the molded substrate 2 is suppressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

In FIGS. 1 and 2, reference numeral 2 denotes a molded substrate. The molded substrate 2 has signal irregularities on the order of submicron on the surface, as in the first embodiment described above.
Further, a concave portion 2A formed by a stamper holding jig is provided. The recording layer 4 is applied to the information recording surface side of the molded substrate 2. Then, a protective layer 6 is provided on the recording layer 4.

[0012] The central portion of the molded substrate 2, mounting holes 2B for fixing the molded substrate 2 is provided.
The molded substrate 2 is fixed to and supported by the support member at the mounting hole 2B. Here, as shown in FIG.
It is formed in a region above and surrounded by the recording layer 4 (a region between the mounting hole 2B and the recording layer 4).

The protective layer 6 is composed of a first protective layer 6A and a second protective layer 6B. The first protective layer 6A is laminated on the recording layer 4 described above. The second protective layer 6B is laminated on the entire surface of the molded substrate 2 except for the central portion of the molded substrate 2 described above. For this reason, the concave portion 2A on the molded substrate 2 is in a state of being buried by the second protective layer 6B.

In the present embodiment, the second protective layer 6B is made of a cured shrinkable resin having a property of shrinking with curing, but has a property of expanding with curing as described later. It may be composed of a curable resin.

[0015] Next, the operation of the above embodiment.

As shown in FIG. 5, the molded substrate 2 has a recess 52A.
When the side (corresponding to the concave portion 2A in FIG. 1) warps to a convex state, the internal stress of the recording layer 4 acts to expand, that is, expands. It works to spread the surface. On the other hand, as the second protective layer 6B is made of a hardening / shrinkable resin, the action opposite to the action of the internal stress of the recording layer 4 described above, that is, over the entire surface of the molded substrate 2 It functions to shrink the surface.

[0017] Therefore, with respect to the molded substrate 2, (effect of expanding the surface over the entire surface) the action of the recording layer 4 and the second
(The effect of shrinking the surface over the entire surface) of the protective layer 6B is canceled, and the warpage of the molded substrate 2 is suppressed.

[0018] Here, in the above embodiment, the case has been described where the molded substrate 2 by the action of the recording layer 4 is warped in a convex state as shown in FIG. 5, the molding substrate 2 is warped in a direction opposite to the FIG. 5 In this case, as the second protective layer 6B, a cured expandable resin having a property of expanding with curing is used.
By doing so, the contracting action of the recording layer 4 is offset by the expanding action of the second protective layer 6B, and the warpage of the molded substrate 2 is suppressed.

[0019]

Since the present invention is constructed and functions as described above, according to this, since the internal stress of the recording layer is offset by the action of the protective layer, the occurrence of warpage of the optical disk after assembly is particularly effective. Therefore, when the optical disk device is equipped with the optical disk device, the reading accuracy of the magneto-optical head can be maintained with high accuracy over time, and the occurrence of head crash can be reduced. An excellent optical disk that has never existed before can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged partial cross-sectional view showing a part of a protective layer portion disclosed in FIG.

FIG. 3 is a sectional view showing a conventional example.

FIG. 4 is an enlarged partial cross-sectional view showing a part of the protective layer portion disclosed in FIG.

FIG. 5 is an explanatory diagram in which warpage of the optical disc in FIG. 3 is emphasized;

[Explanation of symbols]

 Reference Signs List 2 molded substrate 2A recess 4 recording layer 6 protective layer 6A first protective layer 6B second protective layer

Claims (1)

(57) [Claims] 1. A molded substrate having signal irregularities in submicron units on its surface and a concave portion formed by a stamper holding jig, a recording layer applied to the information recording surface side of the molded substrate, An optical disc comprising a protective layer applied on a recording layer, wherein the protective layer is a first protective layer laminated on the recording layer and a second protective layer formed on the first protective layer. From the protective layer
And the second protective layer covers the surface of the first protective layer.
There, and said stacked on the molded substrate to cover the recess while being filled in the recess, for forming the substrate of the recording layer side is deformed to a convex shape, the second protective layer An optical disc comprising a cured shrinkable resin having a property of shrinking with curing.