JP2000015670A - Disc substrate molding die, molding apparatus and molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage to a contact surface of a stamper and a signal surface mirror member due to sliding between a stamper and a signal surface mirror member, and to greatly improve the life of the stamper. Provided are a substrate molding die, a molding device, and a molding method. SOLUTION: One of two mold cores 11, 12 arranged to be openable and closable opposite to each other, and one of mirror members 13, 14 provided on mutually opposite sides of each mold core. 13 and a stamper 16 attached to the mold 13.
By at least the stamper and the other mirror member,
A disk substrate molding die for forming a disk substrate molding cavity 17;
A molybdenum disulfide film 20 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk substrate molding die and a molding apparatus for injection-molding a disk substrate, the surface of a disk made of a resin such as an optical disk having irregularities indicating information. And a molding method.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a disk substrate such as an optical disk, for example, required characteristics of the disk substrate include mechanical characteristics such as dimensions, warpage, and roundness, optical characteristics such as birefringence, and the like. Injection molding, in which the molten resin is injected into a mold including a stamper at high pressure and then cured, taking into account the transfer characteristics of pits and grooves and the defect characteristics such as foreign matter, scratches and molding defects. The law has been adopted.
Such an injection molding method is performed using, for example, an injection molding apparatus as shown in FIG.

[0003] In FIG. 3, an injection molding apparatus 1 comprises two mold cores, ie, a mold core 2 and a mold core 3, which are openable and closable from the left and right in the figure.
3, a flat signal surface mirror member 4 and a reading surface mirror member 5 provided on mutually facing surfaces;
And a stamper 6 whose outer peripheral edge is in contact with the surface of the signal surface mirror member 4 by a stamper retainer 6a.
And a resin injection hole 8a penetrating near the center of the mold core 2 for injecting a molten resin into a cavity 7 formed by the concave portion 5a formed in the reading surface mirror member 5 and the stamper 6. It includes a spool 8 and a punch portion 9 provided near the center of the mold core 3.

The mold cores 2 and 3 are relatively moved by a pressing device of a molding device (not shown),
At a predetermined pressure, they are closed close to each other or opened apart from each other.

According to the injection molding apparatus 1 having such a configuration, the cavities 7 formed by the reading surface mirror member 5 and the spool 6 are closed by closing the mold cores 2 and 3 first. After the punch 9 is moved, the molten resin is injected into the cavity 7 through the resin injection hole 8a of the spool 8 at a predetermined pressure. As a result, the molten resin fills the cavity 7 and is molded in accordance with the shape of the cavity 7 and the stamper 6
The pits and grooves of the stamper 6 are transferred by being formed in accordance with the uneven shape formed on the surface of the stamper 6.

After the molten resin in the cavity 7 is hardened to form a resin molded product, the punch 9 moves to form a center hole in the disk substrate, which is the resin molded product in the cavity 7. You. Thereafter, the mold cores 2 and 3 are opened, and the resin molded product is protruded from the inside of the cavity 7 by an ejector (not shown) or the like, and is released.

[0007]

The contact surface between the stamper 6 and the signal surface mirror member 4 is as shown in FIG. In the figure, the contact surface 4a of the signal surface mirror member 4 is mirror-finished and smooth. On the other hand, the back surface 6a of the stamper 6 is generally set to have a surface roughness of 0.2 to 1.0S. Here, the stamper 6 rapidly expands due to the heat of the molten resin injected from the spool 8, and transfers the heat through the vertex of the roughness of the back surface 6 a contacting the contact surface 4 a of the signal surface mirror member 4. By being transmitted to the plane mirror member 4, it is cooled and contracts. Therefore, the stamper 6 repeats expansion and contraction in each molding cycle in a high temperature state due to the molten resin, and also under a high pressure due to the injection pressure and the mold clamping pressure.

At this time, the stamper 6 is provided with the signal surface mirror member 4.
Is not mechanically fastened to the signal surface mirror member 4 during the expansion and contraction. As a result, the entire back surface 6a of the stamper 6 becomes rough due to damage or wear. Therefore, the stamper 6 and the signal surface mirror member 4
The contact state with the stamper 6 becomes uneven, and the cooling of the stamper 6 and the disk substrate, which is a resin molded product, becomes uneven. Therefore, there is a problem that the disk substrate has a problem related to quality such as abnormal polarization.

Furthermore, in molding a disk substrate of an optical disk, a molding cycle time can be shortened by employing a high-speed operation molding machine and a high-speed ejector in order to reduce manufacturing costs. However, as a result of the shortening of the molding cycle time, the back surface of the stamper is severely damaged due to sliding between the stamper and the signal surface mirror member, and the life of the stamper is shortened. For this reason, the replacement cycle of the stamper and the mirror member is shortened, and frequent replacement is required. Accordingly, the incidental time other than the substantial molding is increased, and the operation time is reduced. There is a problem that the improvement in performance is hindered.

For this reason, it is necessary to provide lubrication to the contact surface between the stamper 6 and the signal surface mirror member 4. For example, Japanese Unexamined Patent Publication No. 3-266616 discloses that the contact surface between the stamper and the mirror has a viscous surface. It is disclosed that a thin film having a certain characteristic is formed. However, in the case of molding a disk substrate for an optical disk, the temperature of the injection molten resin is 300 ° C.
In an environment where the mold temperature also exceeds 70 ° C., it is substantially difficult to obtain a viscous thin film that can stably maintain lubricity. Further, in order to ensure effective lubricity, it is necessary to form a considerable amount of thin film, and the thin film is scattered to the stamper 6, which is not practical.

In view of the above, the present invention reduces damage to the contact surfaces of the stamper and the signal surface mirror member due to sliding between the stamper and the signal surface mirror member, and greatly improves the life of the stamper. It is an object of the present invention to provide a disk substrate molding die, a molding apparatus and a molding method.

[0012]

SUMMARY OF THE INVENTION According to the present invention, there is provided, in accordance with the present invention, two mold cores which are opposed to each other and which are openable and closable, and are provided on opposite sides of each mold core. A stamper attached to one of the mirror members, and in a state where the mold cores are closed to each other,
By at least the stamper and the other mirror member,
A disk substrate molding die in which a disk substrate molding cavity is formed, wherein a molybdenum disulfide film is formed on at least one of the mutually facing contact surfaces of the one mirror member and the stamper. This is achieved by a disk substrate molding die.

Further, according to the present invention, the above object is achieved by providing two mold cores which are openably and closably opposed to each other, and a mirror member provided on each of the opposite sides of each mold core. , A stamper attached to one of the mirror members,
Injection means for injecting a molten resin at a predetermined pressure into at least a cavity formed by the stamper and the other mirror member in a state where the mold cores are closed to each other, wherein the one mirror member and the stamper This is achieved by an injection molding apparatus for a disk substrate, in which a molybdenum disulfide film is formed on at least one of the contact surfaces facing each other.

Further, according to the present invention, the above object is achieved by providing one of the mirror members provided on opposite sides of two mold cores which are openably and closably opposed to each other. With the stamper attached, the mold resin is injected at a predetermined pressure into at least the cavity formed by the stamper and the other mirror member while the mold cores are closed to each other, and the molten resin in the cavity is After cooling and curing, a resin molded product is taken out, wherein the injection molding method of a disk substrate, wherein at least one of the opposing contact surfaces of the one mirror member and the stamper has a molybdenum disulfide film. Is formed,
This is also achieved by a method of injection molding a disk substrate.

According to the above arrangement, at least one of the contact surfaces between the stamper forming the cavity for forming the disk substrate and one of the mirror members is preferably provided with a disulfide having a thickness of 0.1 to 5 μm. A molybdenum film is formed by, for example, a sputtering method. Therefore, when the stamper repeatedly expands and contracts due to the molding cycle time, even if the stamper slides on the mirror member, the molybdenum disulfide film is interposed between the stamper and the mirror member, Damage due to sliding of the stamper and the mirror member can be reduced based on the solid lubrication action of the molybdenum disulfide film itself.

Further, since the molybdenum disulfide film complements the surface roughness of the stamper, the substantial contact area between the stamper and the mirror member is greatly increased. For this reason, the heat conduction from the stamper to the mirror member is improved, and the cooling efficiency of the stamper is improved, so that the molding cycle time of the disk substrate can be further reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows a main part of an embodiment of a disk substrate injection molding apparatus provided with a molding die to which the present invention is applied. In FIG. 1, an injection molding apparatus 10 includes two mold cores, that is, a mold core 11 and a mold core 12, which are arranged to be openable and closable from right and left in the figure. The signal surface mirror member 13 and the reading surface mirror member 14 provided on the surface to be fixed and the mirror surface 13a of the signal surface mirror member 13 which is mounted on the mirror surface 13a of the signal surface A resin injection hole that penetrates the vicinity of the center of the mold core 11 for injecting molten resin into a cavity 17 formed by the stamper 16 that is in contact with the recess 14 a formed in the reading surface mirror member 14 and the stamper 16. It includes a spool 18 provided with 18 a and a punch portion 19 provided near the center of the mold core 12.

The mold cores 11 and 12 are relatively moved by a pressurizing device of a molding device (not shown) so that they are closed close to each other at a predetermined pressure or open apart from each other. ing.

The signal surface mirror member 13 is a mold core 1
1 and has a mirror-finished mirror surface 13 a facing the reading surface mirror member 14. The reading surface mirror member 14 is attached to the mold core 12 and has a concave portion 14a forming the cavity 17, and the bottom surface of the concave portion 14a is a mirror-finished mirror surface. The stamper retainer 15 is formed in an annular shape, surrounds the outer peripheral edge of the stamper 16 from the outside, and has a mirror surface 13 a of the signal surface mirror member 13.
To be brought into contact with.

When the disk substrate to be injection-molded is, for example, a compact disk (CD), the stamper 16 is a so-called father stamper in which pits and grooves that become CD signals are formed in a convex shape on the surface thereof. That is, for example, a flat disk-shaped nickel master having a thickness of about 0.3 mm. The cavity 17 is formed so as to have the shape of the disk substrate to be formed.

The spool 18 has a resin injection hole 18.
Through a, for example, a molten resin such as polycarbonate,
The light is injected into a cavity 17 formed by the reading surface mirror member 14 and the stamper 16 in the closed mold cores 11 and 12.

The punch portion 19 is movably supported with respect to the mold core 12, and is moved right and left in the figure by drive means (not shown) to cure the resin injected into the cavity 17. After that, it protrudes toward the resin molded product in the cavity 17 to form a center hole of the disk substrate which is the resin molded product.

Further, in the injection molding apparatus 10, the mirror surface 13a of the signal surface mirror member 13 and the stamper 1
6, a molybdenum disulfide film 20 is formed.

Here, the molybdenum disulfide film 20 is
Since it is extremely difficult to use a bulk material and use of a powder is unsuitable for maintaining cleanliness, various thin films such as a sputtering method such as an RF sputtering method and a reactive sputtering method are used. It is formed by a forming method. When the molybdenum disulfide film is formed on the back surface of the stamper 16 by the sputtering method, for example, it is performed as follows.

That is, a sputtering device having a planetary rotation mechanism and an RF magnetron cathode is used as a sputtering device, and molybdenum disulfide having a purity of 2N (99%) or more is used as a target material. Then, the stamper 16 is appropriately masked using the back surface 16a as a film forming surface, and is set on a planetary rotation mechanism of a sputtering apparatus. Ar gas flow rate 200sccm, gas pressure 5mTorr, electric power 1.5k
Under the film forming conditions of W, a film forming speed of the molybdenum disulfide film of 5 nm / min was obtained.

The disk substrate injection molding apparatus 10 according to the present embodiment is configured as described above, and the disk substrate is injection-molded as follows. First, when the mold cores 11 and 12 are closed, the cavity 1 formed by the reading surface mirror member 14 and the spool 16 is formed.
7 is sealed. After the punch 19 is moved, the molten resin is injected into the cavity 17 through the resin injection hole 18a of the spool 18 at a predetermined pressure. Thereby, the molten resin is filled in the cavity 17,
While being molded according to the shape of this cavity 17,
The pits and grooves of the stamper 16 are transferred by being formed in accordance with the uneven shape formed on the surface of the stamper 16.

Then, after the molten resin in the cavity 17 is hardened to form the resin molded product 21, the punch portion 19 is moved, and the center hole is formed with respect to the disk substrate as the resin molded product in the cavity 17. Is formed. Thereafter, the mold cores 11 and 12 are opened, and the disk substrate 21 is opened.
Is protruded from the cavity 17 by an ejector (not shown) or the like, and is released.

Here, at the time of molding, the stamper 16 repeats expansion and contraction in each molding cycle in a high temperature state due to the molten resin and under a high pressure due to the injection pressure and the mold clamping pressure. At this time, the back surface of the stamper 16 slides with respect to the mirror surface 13 a of the signal surface mirror member 13, but the back surface of the stamper 16 and the mirror surface 1
3a, the molybdenum disulfide film 20 is interposed between the stamper 16 and the signal surface mirror member 1 during sliding due to the solid lubrication of the molybdenum disulfide film 20.
3 will be greatly reduced. In this case, 3
Even if the mold temperature exceeds 70 ° C. due to the molten resin exceeding 00 ° C., the molybdenum disulfide film 20 is stable as a solid lubricant even at such a high temperature, and has excellent lubricity. Sliding between the stamper 16 and the signal surface mirror member 13 will be performed more smoothly,
These damages are reduced.

An actually recordable MD (mini-disc)
A 2 μm-thick molybdenum disulfide film was formed on the back surface of the stamper, and the disk substrate was molded. There was no particular problem regarding the mechanical characteristics, optical characteristics, transfer characteristics and defect characteristics of the disk substrate. A normal disk substrate within the standard was obtained. Regarding the polarization anomaly of the molded disk substrate, when the normal, that is, when the molybdenum disulfide film is not formed on the back surface of the stamper, the polarization anomaly occurs in about 150,000 to 200,000 shots. In the case where a molybdenum disulfide film is formed on the back surface of the stamper, no abnormal polarization occurs even when the number of shots is about twice or more, and deterioration of surface roughness and uneven distribution of vertices are observed on the contact surface of the stamper. Did not.

Here, the thickness of the molybdenum disulfide film is determined based on the value of the surface roughness Rmax of the stamper 20.
It is limited by the minimum that can cover this roughness and the maximum that is limited by the thermal conductivity of the intervening carbon material. Normally, the surface roughness Rmax of the back surface of the stamper
Is about 0.2 to 1.0 μm, the lower limit of the thickness of the molybdenum disulfide film is a value that covers the surface roughness and can exhibit lubricating properties, that is, a value of 0.1 μm, which is half of Rmax.
m is considered appropriate.

Here, the experimental results on the film thickness dependence of the molybdenum disulfide film are shown below. First, when the molybdenum disulfide film thickness was 0.1 μm, the life of the stamper was 2.3 times. As a result of observing the surface of the stamper after the experiment, a little wear of the metal was observed. As a result, the molybdenum disulfide film thickness is set to 0.1.
At 1 μm, although metal damage is observed, it can be seen that the life of the stamper has been significantly improved. Next, when the molybdenum disulfide film thickness was 5 μm, the life of the stamper was 2.9 times, and the observation result of the surface of the stamper after the experiment was good. Subsequently, when the molybdenum disulfide film thickness was 7 μm, the life of the stamper was 0.6 times. As a result of observing the surface of the stamper after the experiment, an aggregate of molybdenum disulfide was observed.

As a result, the thickness of the molybdenum disulfide film becomes 7 μm.
If m is exceeded, the molybdenum disulfide film will be broken and carbon aggregates will be generated in a mottled manner, causing abnormal polarization of the disk substrate, shortening the life of the stamper, and reducing the molybdenum disulfide film. The deformation of the stamper due to the stress was increased, and the film was broken at the time of mounting the mold, resulting in that the stamper was not practical. Therefore, the thickness of the molybdenum disulfide film 20 is 0.1
The thickness of the molybdenum disulfide film 20 is preferably set in the range of 0.1 μm to 5 μm in order to effectively extend the life of the stamper.

As described above, according to the above embodiment, the molybdenum disulfide film is formed on at least one of the contact surfaces between the stamper forming the cavity for forming the disk substrate and one of the mirror members. By having
When the stamper repeatedly expands and contracts due to the molding cycle time, even if the stamper slides with respect to the mirror member, the molybdenum disulfide film is interposed between the stamper and the mirror member. Damage due to sliding of the stamper and the mirror member can be reduced based on the solid lubrication action of the film itself.

Accordingly, the life of the stamper and the mirror member is greatly extended, and the time required for replacing the stamper and the mirror member is reduced by about half, so that the productivity of the disk substrate is remarkably improved.

Further, since the molybdenum disulfide film complements the surface roughness of the stamper, the substantial contact area between the stamper and the mirror member is greatly increased. For this reason, the heat conduction from the stamper to the mirror member is improved, and the cooling efficiency of the stamper is improved, so that the molding cycle time of the disk substrate can be further reduced.

In the above-described embodiment, for example, a stamper for a compact disk has been described as the stamper 16, but the present invention is not limited to this, and a disk substrate for various optical disks such as other mini disks and magneto-optical disks may be used. It is clear that the present invention can be applied to the injection molding of the present invention. In the above-described embodiment, the molybdenum disulfide film 20 is formed on the back surface of the stamper 16, but is not limited thereto.
May be formed on the mirror surface 13a of the signal surface mirror member 13, or may be formed on the back surface of the stamper 16 and the mirror surface 1a.
3a. When the molybdenum disulfide film is formed on both the back surface of the stamper 16 and the mirror surface 13a, the upper and lower limits for the molybdenum disulfide film described above are applied to the total thickness of both molybdenum disulfide films. Things.

[0038]

As described above, according to the present invention, the contact surface of the stamper and the signal surface mirror member due to sliding between the stamper and the signal surface mirror member is reduced, and the life of the stamper is greatly increased. Thus, it is possible to provide a disk substrate molding die, a molding apparatus, and a molding method which are improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an apparatus for injection molding a disk substrate provided with a mold according to the present invention.

FIG. 2 is a partially enlarged sectional view showing a main part in the injection molding apparatus of FIG.

FIG. 3 is a schematic sectional view showing an example of a conventional disk substrate injection molding apparatus.

FIG. 4 is a partially enlarged sectional view showing a main part in the injection molding apparatus of FIG. 3;

[Explanation of symbols]

10 ... injection molding apparatus, 11, 12 ... mold core,
13 ... signal surface mirror member, 13a ... mirror surface,
14: reading surface mirror member, 14a: concave portion, 1
5 ... Stamper press, 16 ... Stamper, 17
··· Cavity, 18 ··· Spool, 18a ··· Resin injection hole, 19 ··· Punch portion, 20 ··· Molybdenum disulfide film, 21 ··· Disk substrate.

Claims (6)

[Claims] 1. A stamper attached to one of two mirror cores disposed opposite to each other so as to be openable and closable, and a mirror member provided on each of the opposite sides of each of the die cores. A disk substrate molding die in which a cavity for molding a disk substrate is formed by at least the stamper and the other mirror member in a state where the respective mold cores are closed with each other. A disk substrate molding die, wherein a molybdenum disulfide film is formed on at least one of contact surfaces of a member and a stamper facing each other. 2. The method according to claim 1, wherein the molybdenum disulfide film is formed by a sputtering method.
4. The mold for molding a disk substrate according to item 1. 3. The disk substrate molding die according to claim 1, wherein said molybdenum disulfide film has a thickness of 0.1 to 7 μm. 4. The disk substrate molding die according to claim 3, wherein the molybdenum disulfide film has a thickness of 0.1 to 5 μm. 5. A stamper attached to one of two mirror cores disposed opposite to each other so as to be openable and closable, and a mirror member provided on each of the opposite sides of each die core. And an injection means for injecting a molten resin at a predetermined pressure into at least a cavity formed by the stamper and the other mirror member in a state in which the mold cores are closed with each other. A molybdenum disulfide film is formed on at least one of contact surfaces of the substrate and the stamper facing each other. 6. A stamper is attached to one of the mirror members provided on the side facing each other of the two mold cores arranged to be openable and closable facing each other, so that each mold core is In a closed state, a molten resin is injected at a predetermined pressure into at least a cavity formed by the stamper and the other mirror member, and after the molten resin in the cavity is cooled and hardened, a resin molded product is taken out. The injection molding method of a disk substrate as described above, wherein a molybdenum disulfide film is formed on at least one of the mutually facing contact surfaces of the one mirror member and the stamper. Substrate injection molding method.