JP2555149B2 - Optical disc substrate and its molding die - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disc substrate and a molding die for the same, and particularly to an optical disc substrate having an excellent information pit shape, and a preferable molding method for the same. The present invention relates to a molding die.

[Conventional technology]

A conventional molding die for molding an optical disk substrate,
The outline of the optical disk substrate molded by this will be described.

FIG. 11 is a cross-sectional view showing a conventional optical disc substrate molding die.

In FIG. 11, reference numeral 1 is an optical disc substrate molding die (hereinafter referred to as a molding die).
A stamper 2 for transferring information to a plastic to be an optical disc substrate is attached to the movable mirror block 4 by an inner peripheral stamper holder 5 and an outer peripheral stamper holder 6. Then, the transparent resin heated and melted by an injection molding machine (not shown in the figure) passes through the sprue portion 7 of the molding die 1, is cast into the cavity 3 provided with the stamper 2, and is provided on the stamper 2. The information thus transferred is transferred and solidified by cooling. The replica that has opened on the movable side and remains on the movable side (this becomes the optical disc substrate) is taken out from the molding die 1 by the ejector pin 8. In order to improve the transferability of the information pits of the stamper 2, the stamper attached to the movable side mirror block 4 follows the contraction of the resin during cooling and is pressed against the movable side mirror block side by air pressure. It was

As a technique related to this type, for example, Japanese Patent Laid-Open No. 61-11211 is known.

[Problems to be Solved by the Invention]

In the above-mentioned conventional technology, although the transferability until the molten resin is cast into the cavity and solidified is good, the transferability in the mold releasing process of the replica is not taken into consideration, and the information pit shape is There is a problem that the optical disc substrate which is deformed and has an excellent pit shape cannot be obtained.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an optical disc substrate having an excellent information pit shape and a molding die used directly for this molding.

[Means for solving the problem]

The above-mentioned object can be achieved by configuring the information transfer surface having the information pits of the stamper to be uniformly released from the replica at the same time when the mold is opened in the releasing process.

That is, the configuration of the optical disc substrate of the present invention is an optical disc substrate having an information surface having an information pad formed in an information storage area and a mirror surface on the back side of the information surface. A mirror surface with a concave portion or a convex portion is formed in the area opposite to the area excluding the area, or the disk outer peripheral surface is a conical surface outer peripheral surface having a smaller diameter on the information surface side than on the mirror surface side. It is the one.

Further, the optical disk substrate molding die of the present invention is provided with a stamper formed with information pits in the information storage area of the information transfer surface, and the movable die and the fixed die are closed. By casting molten resin into the cavity formed by transferring the information pits of the stamper to this resin, the optical disk substrate molding die capable of molding the optical disk substrate, the stamper A movable mirror having a mirror surface attached to a fixed type through a fixed mirror block having a mirror surface on the side abutting with and having a concave or convex portion formed in a region facing the region excluding the information storage region of the stamper. The block is attached to the movable type so that the mirror surface and the information transfer surface of the stamper face each other, and the cavity is connected to the information transfer surface of the stamper. The movable mirror block is formed by the mirror surface of the movable mirror block and the movable mold, or the movable mirror block having a mirror surface is moved so that the mirror surface and the information transfer surface of the stamper face each other. It is attached to a mold, and the cavity forming surface of this movable mold has a smaller diameter on the fixed mold side than on the movable mold side. The conical surface is formed, and the cavity is formed by the information transfer surface of the stamper, the mirror surface of the movable mirror block, and the movable cavity forming surface.

[Action]

The operation of the present invention will be described in comparison with that of a conventional molding die.

FIG. 12 is a sectional view showing the movable mold side after the optical disc substrate molding die according to FIG. 11 is opened, and FIG.
It is an expanded sectional view showing the important section in a figure.

In the conventional molding die, when the mold is opened, the replica 9 serving as the optical disc substrate is attached to the movable die side, on which the stamper 2 is attached, by the adhesion of the information surface and the adhesion of the outer peripheral surface of the disc. It remains together with this stamper 2. Next, after the mold is completely opened, the replica 9 is taken out upward by the ejector pin 8. That is,
First, the mirror surface (the upper surface in FIG. 13) of the replica 9 is released from the fixed mold side, and the information surface (the lower surface having the information pit 9a in FIG. 13) is released later.
Therefore, from the first opening of the mold until the information surface is released from the mold, the mirror surface of the replica 9 is exposed to the outside air, the temperature of the entire replica decreases, and thermal contraction occurs. In the case of CD-RAM optical system disk substrate molding, the mold temperature is usually 100 ℃ ~ 130
C., and when using a polycarbonate resin, there is a temperature drop of about 10.degree. C. before the information surface is released from the mold. Therefore, thermal contraction of about 40 μm occurs on the outer peripheral surface of the φ130 disk. The replica 9 that has undergone this heat contraction is displaced toward the center, and the convex portion 2a of the stamper 2 (that is, the information pit)
And slip. Then, the pressing force acts from the convex portion 2a to the information pit 9a of the replica 9 (the information pit on which the convex portion 2a is transferred), and the information pit 9a is deformed, thereby damaging the shape of the transferred information pit. there were. In addition, stamper 2
The dimensions of the convex portion 2a are about 0.5 μm in width and about 0.2 μm in height.

On the other hand, according to the configuration of the present invention, the information transfer surface of the stamper and the information surface of the replica are uniformly released at the same time when the mold opening is started, so that the problems caused by the heat shrinkage described above are completely eliminated. Therefore, an optical disc substrate having an excellent information pit shape can be obtained.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

 First, the optical disc substrate will be described.

FIG. 1 is a perspective view (partially cut away view) showing an embodiment of the optical disk substrate of the present invention, and FIG. 2 is an enlarged cross-sectional view of an essential part in FIG.

The optical disk substrate 21 has an information surface 20 in which information pits 20a are formed in the information storage area 22, and a mirror surface on the back surface of the information storage area 22, and the mirror surface serves as the information storage area 22 of the information surface 20. In the area opposite to the removed area 23, a mirror surface 19 having a circumferential undercut concave portion 18 is formed, and the outer peripheral surface of the disk is a mirror surface 19 on the information surface 20 side.
The outer peripheral surface 17 of the disk is a conical surface having a smaller diameter than the side.

In the optical disc substrate 21 configured in this way, the shape of the information pit 20a is transferred extremely accurately (the reason for accurate transfer will be described in detail in the embodiment of the molding die). Can be memorized exactly,
There is an effect that the reading performance of the information pit 20a is excellent.

In this embodiment, the undercut-shaped concave portion 18 is formed in a circular shape, but in addition to this, an undercut-shaped convex portion, an undercut round hole, or the like is formed in the region. May be.

Further, in the present embodiment, the undercut-shaped concave portion 18 is formed on the mirror surface and the outer peripheral surface of the disk is formed into the conical surface shape, but even if either one is carried out, substantially the same effect can be obtained. .

Next, the structure of the molding die for the optical disc substrate and its operation will be described.

In this embodiment, the stamper is attached to the fixed mold side and the replica is left on the movable mold side.

FIGS. 3 to 6 show one embodiment (for molding of the optical disc substrate according to FIG. 1) of the optical disc substrate molding die of the present invention, and FIG. 3 is a sectional view when the mold is closed. 4 and 5 are enlarged cross-sectional views showing the details of the mold release state at the time of mold opening, FIG. 5 is a cross-sectional view showing the movable mold side after mold opening, and FIG. 6 is a molded product. It is sectional drawing of a replica.

The outline of this molding die will be described with reference to the drawings. This molding die is equipped with a stamper 2 (details will be described later) formed by forming information pits 2a in an information storage area of an information transfer surface 2b.
Molding the optical disc substrate 21 by casting molten resin into a cavity 3 (described later in detail) formed by closing the fixed die 12 and the fixed die 12 and transferring the information pits 2a of the stamper 2 to this resin. The stamper 2 is attached to the fixed mold 12 via a fixed-side mirror block 14 having a mirror surface 14a on the side contacting the stamper 2.
A movable side mirror block 4 having a mirror surface 4a having an undercut-shaped convex portion 16 formed in an area opposite to the area excluding the information storage area of the stamper 2 (the reason for forming the convex portion 16 in the area will be described later). The mirror surface 4a and the information transfer surface 2b of the stamper 2 are attached to the movable mold 13 and the cavity forming surface 13a is attached to the movable mold 13 on the fixed mold side rather than on the movable mold side. The cavity 13 is formed into a conical surface having a small diameter, and the cavity 13 is formed on the information transfer surface of the stamper 2.
2b, the mirror surface 4a of the movable side mirror block 4 and the cavity forming surface 13a of the movable mold 13 are optical disc substrate molding dies.

 The details are as follows.

First, the undercut convex portion of the movable side mirror block 4
The formation positions of 16 will be described with reference to FIGS.

In order to read information from the optical disc substrate 21, laser light is incident from the mirror surface 19 side of the optical disc substrate 21,
The information pit 20a is irradiated, but at this time, the undercut concave portion 18 should not be in the optical path of the laser light. That is, the undercut-shaped concave portion 18 has the information surface 20.
Must be in a region opposite to the region 23 excluding the information storage region 22 of FIG. In order to make this possible, in the present embodiment, the circumferential undercut-shaped convex portions 16 are formed in the area facing the area excluding the information storage area of the stamper 2, that is, in the block inner peripheral portion and the block outer peripheral portion. Is formed.

Further, the conical slope of the cavity forming surface 13a of the movable die 13 for determining the disk outer peripheral surface 17 of the optical disk substrate 21 is 0.5 degree.

The stamper 2 is attached to the fixed die 12 by an inner peripheral stamper holder 5 and an outer peripheral stamper holder 6.

With this structure, the molten resin is cast into the cavity 3 through the sprue portion 7 and solidified. When the mold is opened, the solidified replica 15 has an undercut convex portion 16 of the movable side mirror block 4 and a cavity forming surface 13 of the movable mold 13.
Due to the adhesive force of a, as shown in detail in FIG. 4, the mold is released so as to remain on the movable mold 13 side. This replica 15
It is taken out from the movable side mirror block 4 by the ejector pin 8 and the state shown in FIG. 6 is obtained. And the sprue portion 15a
The optical disk substrate shown in FIG.
21 is obtained.

According to the embodiment described above, the replica 15 is opened when the mold is opened.
Since the stamper 2 and the stamper 2 are released at the same time on the entire surface, the information pit shape is not deformed due to heat contraction of the replica as in the conventional case, and the transferability until it is cast and solidified, and the transferability in the releasing process However, there is an effect that the optical disk substrate 21 having an excellent information pit shape is obtained very well.

The dimensions of the undercut-shaped convex portion 16 and the slope of the cavity forming surface 13a in this embodiment are examples, and the dimensions of the undercut-shaped convex portion 16 are, for example, a width of 0.2 to 3 mm and a height of 0.1 to 1.2 mm. In the range, the size of the optical disk substrate,
An appropriate size may be selected depending on the thickness and molding conditions.

7 to 9 show various changes in the shape of the concave portion (or convex portion) formed in the movable mirror block in the optical disc substrate molding die according to FIG. 3 and the gradient of the movable cavity forming surface. It is sectional drawing which shows the example of the replica shape | molded using what.

A replica 15A according to FIG. 7 has a circular undercut convex portion 18A formed on a mirror surface 19A thereof. The replica 15A has an advantage that dust or the like does not collect on the mirror surface 19A and is less likely to get dirty. Further, the movable side mirror block (not shown) used for molding this can be easily manufactured because the circumferential undercut groove is formed in the mirror surface, and the maintenance is also easy. There is an advantage.

The replica 15B according to FIG. 8 is formed by forming four round-hole-shaped recessed portions 18B, each having four undercuts, four each on the orthogonal diameter of the mirror surface 19B. In addition, the movable side mirror block used for molding
Eight round pins are planted at positions facing 18B.

The replica 15C according to FIG. 9 has a convex portion 18C without undercut (having a size slightly larger than that of the convex portion 18A in FIG. 7) formed on the mirror surface 19C of the replica 15C. It has a cylindrical shape (no gradient).
A recess may be formed instead of the protrusion 18C.

Similarly to the replica 15 shown in FIG. 6, the replica shown in FIGS. 7 to 9 is such that the replica and the stamper 2 are released at the same time when the mold is opened.

Finally, an embodiment of the molding die will be described in which the stamper is attached to the movable die side and the replica is left on the fixed die side.

FIG. 10 is an enlarged sectional view of an essential part showing details of another embodiment of the optical disc substrate molding die of the present invention (released state at the time of mold opening).

In FIG. 10, those given the same numbers as in FIG. 4 are the same parts. And the cavities are stamper 2
Information transfer surface 2b and fixed side mirror block 14A mirror surface 1
4b and the cavity forming surface 12a of the fixed die 12A.

The molding operation by the molding die configured as described above is similar to that of the molding die according to FIG. 4, and when the mold is opened, the replica 15 and the stamper 2 are released at the same time, and the same effect is obtained. is there.

〔The invention's effect〕

As described in detail above, according to the present invention, the CD-RAM
In an optical disc substrate such as, the transferability of the information pit shape of the stamper is improved, and it is effective in improving the information pit reading performance.

In short, it is possible to provide an optical disc substrate having an excellent information pit shape and a molding die directly used for this molding.

[Brief description of drawings]

FIG. 1 is a perspective view (partially cut away view) showing an embodiment of an optical disk substrate of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part in FIG. 1, and FIGS. 1 shows an embodiment of an optical disk substrate molding die of the invention (for molding an optical disk substrate according to FIG. 1), FIG. 3 is a sectional view when the mold is closed, and FIG. FIG. 5 is an enlarged sectional view of an essential part showing the details of the mold release state at the time of opening, FIG. 5 is a sectional view showing the movable mold side after mold opening, and FIG. FIG. 9 shows various shapes of the concave portion (or convex portion) formed in the movable side mirror block and the gradient of the cavity forming surface of the movable die in the optical disc substrate molding die according to FIG. FIG. 10 is a cross-sectional view showing an example of a replica formed by molding the optical system disk substrate molding die of the present invention. Enlarged sectional view showing details (release state during mold opening) of Example of FIG. 11, the conventional optical system sectional view showing a disc substrate molding metal mold, FIG. 12,
FIG. 11 is a cross-sectional view showing the movable mold side after opening the optical disk substrate molding die according to FIG. 11, and FIG. 13 is an enlarged cross-sectional view showing the main parts in FIG. 1A …… Optical disc molding die 2 …… Stamper 2b …… Information transfer surface 2a …… Information pit 3 …… Cavity 4,4A …… Movable mirror block 4a, 4b …… Mirror surface 12,12A …… Fixed type 12a …… Cavity forming surface 13 …… Movable type 13a …… Cavity forming surface 14,14A …… Fixed side mirror block 14a, 14b …… Mirror surface 15,15A, 15B, 15C …… Replica 16 …… Undercut -Shaped convex part 17,17C …… Disk outer peripheral surface 18 …… Undercut concave part 18A …… Undercut convex part 18B …… Undercut round hole concave part 18C …… Undercut convex part 19,19A, 19B, 19C …… Mirror surface 20 …… Information surface 20a …… Information pit 21 …… Optical disk substrate 22 …… Information storage area 23 …… Area excluding information storage area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Takasu 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Hitachi, Ltd., Institute of Industrial Science (56) Reference JP-A-1-264820 (JP, A) Flat 1-264822 (JP, A)

Claims (3)

(57) [Claims] 1. An optical disc substrate having one information surface having information pits formed in an information storage area and the other surface being a mirror surface, wherein the mirror surface is an area excluding the information recording area of the information surface. An optical disk substrate having a mirror surface having a concave portion or a convex portion formed in a region facing the optical disc substrate. 2. A stamper formed by forming information pits in an information storage area of an information transfer surface, a molten resin is cast into a cavity formed by closing a movable die and a fixed die, and the resin is filled with the above-mentioned material. An optical disc substrate molding die capable of molding an optical disc substrate by transferring information pits of the stamper, wherein the stamper is placed through a fixed-side mirror block having a mirror surface on the side in contact with the stamper. A movable mirror block having a mirror surface in which a concave portion or a convex portion is formed in an area opposite to the area excluding the information storage area of the stamper, and the mirror surface and the information transfer surface of the stamper face each other. To the movable die so that the cavity is attached to the information transfer surface of the stamper, the mirror surface of the movable side mirror block, and the movable die. An optical disc substrate molding die characterized by being formed by 3. A stamper formed by forming information pits in an information storage area of an information transfer surface, a molten resin is cast into a cavity formed by closing a movable die and a fixed die, and the resin is filled with the above-mentioned resin. A mold capable of transferring an information pit of a stamper to mold an optical disc substrate, wherein the stamper is attached to a movable mold through a movable mirror block having a mirror surface on a side in contact with the stamper. The fixed side mirror block having a mirror surface having a concave portion or a convex portion formed in a region facing the region excluding the information storage region is attached to a fixed mold so that the mirror face and the information transfer surface of the stamper face each other, The optical system device is characterized in that the cavity is formed by an information transfer surface of the stamper, a mirror surface of the fixed-side mirror block, and the fixed mold. Isk substrate molding die.