JPH07156218A - Mold for optical disk substrate and molding method - Google Patents

Abstract

PURPOSE:To obtain a gate cutting mechanism with a structure having no interferences between parts, which functions stably for a long time and does not produce flash. CONSTITUTION:With advance to the center of a board thickness, a diameter becomes smaller stepwise. In addition, a diameter at a position of a sprue bush 1 equivalent to the surface of a cavity is set to be larger than the largest diameter of the sprue bush 1 protruding in the cavity. An annular film gate 4 is formed by the end face of the sprue bush 1 and an end face of a punch rod 2. A resin material is injected and an optical disk substrate 5 is molded. Thereafter, the punch rod 2 proceeds for punching the gate 4 and the optical disk substrate having a specific center hole is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for an optical disk substrate and a molding method, and more specifically, a molding die for an information recording medium for recording / reproducing information or only reproducing information by optical means. And a molding method.

[0002]

2. Description of the Related Art A substrate of an information storage medium for recording / reproducing or only reproducing information by optical means is usually manufactured by injection molding. Then, in the injection molding, a sprue bush, which is generally slidably fitted in a through hole of a fixed mold formed concentrically with the substrate molding cavity in the axial direction, is disposed at its tip end portion. The cavity is placed near the center in the thickness direction of the cavity, while the cutting edge of the punch rod is supported by the movable die coaxially with the sprue bush and slidably in the axial direction. In the cavity, the tip end of the sprue bush is arranged so as to be opposed to the sprue bush with a predetermined gap therebetween, and the sprue bushing is formed after the substrate is molded by injecting an injection resin material into the cavity. A molding die having a structure in which a central hole of the substrate is punched out by pushing the substrate to the side is used.

As a known document which describes a conventional molding die for an optical disk substrate, for example, Japanese Patent Laid-Open No. 54-16 is available.
There is a 2754 publication. This publication discloses a casting mold formed between a movable mold and a fixed mold to enable automatic cutting of a runner during a molding process, and an injection gate which communicates with the casting mold into the casting mold. And a slidably provided gate means, and a movement drive means for moving the gate means to cut the runner. Further, the one disclosed in Japanese Patent Laid-Open No. 59-229327 is a free-supporting type in which all the molds are aligned on the mold mounting plate by a small circumferential taper in the central portion, and the molten resin is heated in the cavity. At the initial stage of filling, the outer peripheral portion of the mold body can freely expand and contract. Each of the above publications has a means for cutting the gate portion without opening the mold.

Japanese Utility Model Publication No. 5-13537 relates to a disk replica molding die for molding a disk replica such as an optical disk or a magnetic disk, which penetrates the fixed mold into which a sprue bush is fitted. An opening peripheral portion of the hole on the cavity side is a protruding surface parallel to the cavity surface connected to the cavity surface on the fixed mold side with a smoothly changing connection surface, and the sprue is formed during injection of the resin material. The tip surface of the bush is flush with the protruding surface.

5 to 7 are views for explaining a conventional molding die for an optical disk substrate, in which 11 is a sprue bush, 12 is a punch rod, 13 is a fixed bush, and 14 is a bush.
Is a gate portion (film gate), 15 is a substrate, and 16 is an opening edge. A state above the center line is a state where the resin material is being injected, and a state below the center line is a state where the gate portion 14 has been cut after the injection. After the resin material that has passed through the film gate 14 is filled in the cavity to form the substrate 15, the punch rod 12 advances, cuts the gate portion 14 from the substrate 15 (molded product), and as a result, information having a central hole is formed. A storage medium substrate is obtained. The problem with this means is that when the film gate 14 is cut, the inner surface of the central hole of the substrate 15 and the cut surface of the film gate 14 rub against each other, and the punch rod 12 and the rotating bush 1 are used.
Due to the clearance relationship with No. 3, there was a burr at the opening edge of the central hole, which impairs the quality of the substrate as a molded product.

FIG. 6 shows a configuration made to solve this point. The difference from FIG. 5 is that the edge portion of the central hole of the fixed bush 13 is projected to the cavity side, and the substrate having this configuration has a shape in which the opening edge of the central hole is one step lower than the original substrate surface. A schematic sectional view of the substrate is shown in FIG. As is clear from FIG. 7, even if burrs are generated on the opening edge 16, it does not affect the substrate surface. Compact discs (CDs) currently on the market
Is a molded substrate made of a mold having almost the configuration shown in FIG.

[0007]

However, the problem remains in the conventional mold. That is, even if the shape is such that burrs are avoided, the occurrence of burrs must be suppressed as much as possible, and as a result, the punch rod must be partially fitted into the fixed bush. As long as the gate is cut by fitting, the clearance between the fitting hole of the fixed bush and the punch rod has an influence, and burr may occur or contact (caulking) at the fitting part of both may occur depending on the dimensional relationship between the two. Furthermore, it becomes a factor that deteriorates the substrate quality.

The present invention has been made in view of the above circumstances, and has a structure in which there is no interference between parts, functions stably for a long period of time, and forms an optical disk substrate having a gate cutting mechanism that does not cause burrs. It is intended to provide a mold and a molding method.

[0009]

In order to achieve the above-mentioned object, the present invention is (1) slidable to a fixed mold side in a cavity formed between a fixed mold and a movable mold. By injecting a resin material through the inner hole of the sprue bush arranged in the mold, an optical disk substrate on which the relief pattern of the stamper arranged in the movable mold is transferred is molded, while it is slidable on the movable mold side. As the punch rods are advanced, the center hole of the optical disk substrate is punched out, the optical disk substrate is released from the movable mold by an eject sleeve, and the resin in the punched part of the central hole is moved by an eject pin. In a molding die for an optical disk substrate which is separated from the die, an annular ring formed by the punch rod and the sprue bush both protruding into the cavity. The punch rod has a film gate and is cut without partially inserting the punch rod into the fixed mold side when cutting from the optical disk substrate. Furthermore, (2) in the sprue bush, the outer diameter of the punch rod is a cavity. The diameter becomes smaller from the surface toward the gate forming surface, and (3) the outer diameter of the gate forming surface of the punch rod that forms the annular film gate facing the sprue bush is the gate of the sprue bush. The outer diameter of the forming surface is almost the same, or (4) in the method of forming an optical disk substrate using the optical disk substrate forming die described in (1), the sprue bush and the punch rod forming the film gate are formed. Relative temperature difference of 10
Molding while maintaining the temperature below ℃, (5) In the method for molding an optical disk substrate using the optical disk substrate molding die described in (1) above, the pressure for advancing to the opposite side of the punch rod is sprue. The pressure is higher than the pressure for advancing to the opposite side of the bush, and further, (6) in the optical disc substrate forming method using the optical disc substrate forming die described in (1), the punch rod starts advancing to the opposite side. The sprue bush starts to retreat to the side opposite the cavity at a predetermined time interval from the
(7) It is characterized in that it has a detecting means for detecting the temperature of the sprue bush and the punch rod, and a temperature adjusting means for keeping the temperature difference between the detected temperature data of less than 10 ° C.

[0010]

When the annular film gate formed by the punch rod and the sprue bush both protruding into the cavity is cut from the optical disk substrate, the punch rod is cut without being partially inserted into the fixed mold side. Further, since the outer diameter of the gate forming surface of the punch rod that forms the annular film gate facing the sprue bush is substantially the same as the outer diameter of the gate forming surface of the sprue bush, the gate portion is conventionally separated. Since the cutting is performed by a method completely different from the cutting by the fitting method, it is possible to prevent the occurrence of burrs. Even if burrs occur, they do not affect the surface of the substrate, and as a result, when mounting the substrate on the optical disc manufacturing apparatus or the recording / reproducing apparatus, there is no trouble or problem such as catching. Further, even if the punch rod advances toward the opposite side, there is no interfering component, so contact (stripping) between components cannot occur. Further, in the sprue bush, the outer diameter thereof becomes smaller from the cavity surface toward the gate forming surface, so by providing an appropriate gap between the gate separating portion and the sliding surface of the sprue bush, Stable continuous molding is possible without being affected by the gate separation residue or the resin residue when the resin material is injected.

[0011]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a mold for an optical disk substrate according to the present invention, which is a block diagram of the center part of the mold. In the figure, 1 is a sprue bush, 2 is a punch rod, 3 is a fixed bush, 4 is a gate portion (film gate), and 5 is an optical disk substrate. In the conventional example shown in FIG. 5 and FIG. 6, the sprue bush 11 is uniform.
In FIG. 1, the diameter of the tip portion of the is gradually changed to a smaller diameter toward the center of the plate thickness. In addition, the diameter of the portion of the sprue bush 1 corresponding to the surface of the cavity is larger than the maximum diameter of the portion of the sprue bush 1 protruding into the cavity. The ring-shaped film gate 4 is formed by the end surface of the sprue bush 1 and the end surface of the punch rod 2. A resin material is injected in the state of FIG. 1 to mold the optical disk substrate 5. After that, the punch rod 2 advances to punch out the gate portion 4, and an optical disk substrate having a predetermined center hole is completed.

FIG. 2 is a view showing an initial state in which the punch rod is advanced to punch out the gate portion in FIG.
Reference numerals in the figure are the same as those in FIG. The stamping process of the present invention begins with compressing the thickness of the film gate portion 4. The other end (the left end in the figure) of the punch rod 2 is directly connected to a hydraulic cylinder (not shown),
The driving force of the cylinder advances the sprue bush 1 side. At this time, the other end (the right end in the drawing) of the sprue bush 1 is in contact with the injection nozzle (not shown) of the injection molding machine at a certain pressure.

When the punch rod 2 advances in the pressure of the hydraulic cylinder, the resin in the film gate portion 4 is removed or compressed by the pressure. When the exclusion or compression of the gate portion 4 with respect to the resin reaches the limit, the punch rod 2
Pressure acts on the sprue bush 1 via the resin. At this time, there is a relation of P ₁ > P ₂ between the pressure P _{1 of the} hydraulic cylinder and the injection nozzle touch pressure P _2, and the punch rod 2 transmitted through the residual resin in the gate portion 4
As a result, the pressure acts as a pressure for retracting the sprue bush 1, and finally the gate portion 4 is moved to the optical disk substrate 5
Will be separated from.

FIG. 3 is a diagram showing the final state in FIG. 1, and the reference numerals in the figure are the same as those in FIG. This is a state after the center hole has been completely punched out in accordance with the above-mentioned process.
The punching of the center hole according to the present invention is not a cutting that depends on the clearance between the outer diameter of the punch rod 2 and the inner diameter of the fixed bush 3, and therefore burrs and contact between parts as in the past may occur. Absent.

However, in the present invention, in order to ideally separate the gate portion 4 and the molded substrate 5, the gate portion 4 is ideally thinned (compressed) between the punch rod 2 and the sprue bush 1. The temperature difference between the two is controlled. Although not shown in FIGS. 1 to 3, the sprue bush 1 and the punch rod 2 are provided with temperature sensors, and further, a controller for controlling the temperature difference between the sprue bush 1 and the punch rod 2 to less than 10 ° C. is provided. There is. By virtue of its function, the outer diameters of the two maintain a good dimensional relationship, and as a result, the gate portion 4 is ideally thinned (compressed), and burr generation is effectively suppressed.

In this embodiment, the gate thickness at the time of injecting the resin material is 0.4 mm, and the advance pressure of the punch rod is 120 k.
gf / cm ² , touch pressure of injection nozzle is 100 kgf
When it was molded at a rate of / cm ² , a good molded substrate without burrs was obtained, and naturally, no contact between the parts occurred. Further, in the present embodiment, the final separation of the gate portion 4 is performed by the balance of the pressure applied to the punch rod 2 and the sprue bush 1, but in addition to this, the advancement of the punch rod 2 and the sprue bush 1 are performed. Similar results are obtained with a time difference between forced retreat.

FIG. 4 is a view showing another embodiment of the optical disk substrate molding die according to the present invention, and the reference numerals in the drawing are the same as those in FIG. The sprue bush 1 shown in FIG. 4 also has a structure in which the portion projecting into the cavity gradually decreases in diameter toward the plate thickness center. However, the portion corresponding to the cavity surface has the same diameter as the maximum diameter portion of the cavity protruding portion. Even with this configuration, the above effect was obtained, but when continuous molding was performed, separation scraps of the gate portion 4 were accumulated on the sliding surface between the sprue bush 1 and the fixed bush 3, and the sliding movement of the sprue bush 1 gradually. I can prevent exercise. This induces adhesion of defects to the molded product, which eventually makes continuous molding impossible.

The fact that the portion corresponding to the cavity surface of the sprue bush 1 shown in FIG. 1 is made larger in diameter than the maximum diameter of the protruding portion in the cavity is an invention for that problem, and the sprue bush 1 and the fixed bush 3 are provided. The problem was solved by moving the sliding surface of (2) away from the separation position of the gate portion (4).

[0019]

As is apparent from the above description, the present invention has the following effects. (1) In Claims 1, 3, 4, 5, 6, and 7, the cutting of the gate portion is completely different from the cutting by the conventional fitting method, that is, the conventional punch rod and fixed bush have a male-female relationship. Because it is done because it does not exist,
The burr can be prevented from occurring. Even if burrs are generated, the structure of claims 1 and 3 does not affect the surface of the substrate, and as a result, when mounting the substrate on the optical disc manufacturing apparatus or the recording / reproducing apparatus, there is a problem such as a catch.・ No problem occurs. In addition, according to the constitutions of claims 1 and 3,
Even if the punch rod advances to the opposite side, there is no interfering part, so contact (stripping) between parts cannot occur. (2) Further, according to claim 2, by providing an appropriate gap between the gate separating portion and the sliding surface of the sprue bush, the gate separating residue and the resin residue at the time of injecting the resin material are not affected, Stable continuous molding is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an optical disk substrate molding die according to the present invention.

FIG. 2 is a diagram showing an initial state in which a punch rod is advanced to punch out a gate portion in FIG.

FIG. 3 is a diagram showing a final state in FIG.

FIG. 4 is a view showing another embodiment of the optical disk substrate molding die according to the present invention.

FIG. 5 is a configuration diagram of a conventional optical disk substrate molding die.

FIG. 6 is another configuration diagram of a conventional optical disk substrate molding die.

7 is a configuration diagram near the center of the molded substrate in FIG.

[Explanation of symbols]

1 ... Sprue bush, 2 ... Punch rod, 3 ... Fixed bush, 4 ... Gate part (film gate), 5 ... Optical disk substrate.

Claims (6)

[Claims] 1. A resin material is injected into a cavity formed between a fixed mold and a movable mold by injecting a resin material through an inner hole of a sprue bush slidably arranged on the fixed mold side. While molding the optical disk substrate to which the relief pattern of the stamper arranged in the mold is transferred, by the advancement of the punch rod slidably arranged on the movable mold side,
The center hole of the optical disk substrate is punched out to release the optical disk substrate from the movable mold with an eject sleeve, and the resin in the punched part of the central hole is released from the movable mold with an eject pin. In a molding die for an optical disc substrate, the punch rod and the sprue bush both have an annular film gate formed to project into a cavity, and when the punch rod and the sprue bush are cut off from the optical disc substrate, the punch rod is moved to the fixed die side. A molding die for an optical disk substrate, which is characterized by being cut off without being fitted in a part. 2. The molding die for an optical disk substrate according to claim 1, wherein the sprue bush has an outer diameter that decreases from the cavity surface toward the gate formation surface. 3. The outer diameter of the gate forming surface of the punch rod that forms the annular film gate facing the sprue bush is substantially the same as the outer diameter of the gate forming surface of the sprue bush. Item 1. A molding die for an optical disk substrate according to item 1. 4. A method of molding an optical disk substrate using the optical disk substrate molding die according to claim 1, wherein the relative temperature difference between the sprue bush forming the film gate and the punch rod is maintained below 10 ° C. A method of molding an optical disk substrate, comprising: 5. The method of molding an optical disk substrate using the mold for molding an optical disk substrate according to claim 1, wherein the pressure for advancing to the opposite side of the punch rod is higher than the pressure for advancing to the opposite side of the sprue bush. And a method for molding an optical disk substrate. 6. The method for molding an optical disk substrate using the optical disk substrate molding die according to claim 1, wherein the sprue bush is formed at a predetermined time interval from the time when the punch rod starts to advance to the opposite side. A method for molding an optical disk substrate, characterized by starting retreating to the side opposite to the cavity.