JP2001198963A - Mold for molding substrate, injection molding machine, and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold capable of manufacturing a thin substrate in high throughput, an injection molding machine, and an injection molding method. SOLUTION: First and second cooling circuits 6, 7 for cooling a molten resin are respectively formed in a fixed mold 1 and a movable mold 2 so as to be spaced apart from a cavity 5 by different distances. At the time of filling with the molten resin, a cooling medium controlled to the glass transition temperature of the molten resin or higher is supplied to the first cooling circuit 6. A cooling medium having lower temperature is supplied to the second cooling circuit 7. After the filling with the resin, the cooling medium supplied to the first cooling circuit 6 is made to be the same as that supplied to the second cooling circuit 7. By this constitution, the temperature in the cavity can be easily cooled to enhance productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding an optical disk substrate, an injection molding machine having the same, and an injection molding method, and more particularly to a mold suitable for molding a thin optical disk substrate. And an injection molding machine and an injection molding method.

[0002]

2. Description of the Related Art With the advent of the multimedia age, optical recording media such as optical disks have been widely used as recording media suitable for recording and reproducing audio and image information. As a substrate of an optical disk, a transparent resin substrate obtained by injection molding or injection compression molding of a material such as a polycarbonate resin, a polymethyl methacrylate resin, and an amorphous polyolefin resin is often used.

In recent years, as the amount of information has increased, it has been demanded to further increase the storage capacity of optical discs, and DVDs (digital versatile discs) have attracted attention as one of the optical discs having realized a large storage capacity. DVD
Has a structure in which two thin disk substrates having a thickness approximately half that of a disk substrate used in a CD-ROM are attached to each other.

As a method of manufacturing such a thin disk substrate, for example, Japanese Patent Application Laid-Open No. Hei 8-66945 discloses that the melting temperature of a resin material and the temperature of a mold are considerably higher than those in the case of manufacturing a substrate for a CD or CD-ROM. A method of setting a higher value is disclosed. However, in the molding method in which the melting temperature of the resin material and the mold temperature are set to be higher, the temperature of the optical disc substrate is simultaneously increased when the optical disc substrate is removed from the mold, so that the substrate is cooled to about room temperature. During this, the substrate is warped or distorted.

[0005]

As a method for solving this problem, for example, Japanese Unexamined Patent Publication No. Hei 8-156059 discloses a method for increasing the temperature of a cavity when a molten resin is injected into a mold. Set the temperature high so as not to impair the fluidity of the molten resin, and after the injection of the molten resin into the mold is completed, lower the temperature inside the cavity,
A method for reducing warpage and distortion of an optical disk substrate is disclosed.

However, the mold used in this method has a structure as shown in FIG. 4, and the entire mold 10 'must be heated and cooled only by the cooling circuit 9. For this reason, it is extremely difficult to raise and lower the temperature in the cavity 5 in a short time, and there has been a problem that the time required for molding the optical disk substrate becomes longer. That is,
Although the warpage and distortion of the substrate are reduced, the productivity is deteriorated, and thus it is extremely unsuitable as a practical method.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce warpage and distortion of a thin optical disk substrate.
An object of the present invention is to provide a disk substrate molding die, an injection molding machine, and an optical disk substrate molding method capable of reducing the occurrence of birefringence and improving the productivity.

[0008]

According to a first aspect of the present invention, there is provided a fixed mold and a movable mold, and molten resin is provided in a cavity defined between the fixed mold and the movable mold. In the mold for molding a substrate to be filled, the fixed mold and the movable mold each include first and second cooling circuits for cooling the molten resin therein, and the first and second cooling circuits are provided. ,
A substrate molding die is provided, which is formed at a position separated by a different distance from the cavity.

The mold according to the present invention comprises a two-system cooling circuit comprising a first mold and a second cooling circuit for cooling the molten resin injected into the cavity into the fixed mold and the movable mold. And the first and second cooling circuits are arranged inside the fixed mold and the movable mold so that the shortest distances from the cavity are different from each other. The first cooling circuit and the second cooling circuit
The cooling circuits can be supplied with cooling media at different temperatures. For example, the first cooling circuit is arranged on the side closer to the cavity, the second cooling circuit is arranged at a position farther from the cavity, and a cooling medium of a predetermined temperature is continuously supplied to the second cooling circuit to keep the outside of the mold. While maintaining the predetermined temperature, a cooling medium whose temperature is controlled is supplied to the first cooling circuit. As a result, the temperature of the cavity can be efficiently controlled, and the productivity of the substrate is significantly improved.

In the present invention, the temperature of the cooling medium supplied to the first cooling circuit located near the cavity is preferably equal to or higher than the glass transition temperature of the resin used. By setting the temperature to be equal to or higher than the glass transition point, it is possible to improve the fluidity of the molten resin filled in the cavity and to suppress the occurrence of warpage and birefringence of the molded substrate. Also,
The temperature of the cooling medium supplied to the second cooling circuit is preferably lower than the temperature of the cooling medium supplied to the first cooling circuit, and may be set to, for example, about 100 ° C to 120 ° C.

[0011] In the mold of the present invention, the first cooling circuit includes:
The second cooling circuit is preferably arranged such that the shortest distance from the cavity surface is 10 mm or less, and the second cooling circuit is preferably arranged such that the shortest distance from the cavity surface is 20 mm or less.

Further, in the mold of the present invention, a heat insulating layer may be formed between the first cooling circuit and the second cooling circuit. Such a heat insulating layer can be constituted by using a ceramic material such as alumina and zirconia.

In the present invention, both the fixed mold and the movable mold can be formed to have two layers in the mold opening / closing direction using two kinds of materials having different thermal conductivity. The mold part in which the first cooling circuit is formed is made of a material having high thermal conductivity such as a cemented carbide (a sintered alloy of tungsten and carbon), and the second cooling circuit is formed. The mold part can be made of a material having a lower thermal conductivity than the material constituting the first cooling circuit, for example, alloy steel. By configuring the mold portion in which the first cooling circuit is formed by using a material having high thermal conductivity, the time required for raising and lowering the temperature of the mold can be further shortened, so that productivity is improved. Further improve.

According to a second aspect of the present invention, there is provided an injection molding machine for molding a substrate, comprising a fixed mold and a movable mold, wherein an injection molding machine is provided in a cavity defined by the fixed mold and the movable mold. A mold filled with a molten resin, wherein first and second cooling circuits for adjusting mold temperature are formed inside each of the fixed mold and the movable mold, and the first and second cooling circuits are formed. A mold in which a second cooling circuit is formed at a different distance from the cavity; and a cooling medium supply device for supplying a temperature-controlled cooling medium to the first and second cooling circuits, respectively. An injection molding machine is provided.

[0015] The injection molding machine of the present invention includes a mold in which first and second cooling circuits for adjusting the mold temperature are formed in a fixed mold and a movable mold. In this mold, the first and second cooling circuits are sequentially formed at different distances from the cavity in a direction away from the cavity defined by the fixed mold and the movable mold. The cooling medium supply device is, for example,
A first cooler capable of supplying a cooling medium having a temperature on the order of or higher than the glass transition temperature of the molten resin, and supplying a cooling medium having a lower temperature than the cooling medium of the first cooler. It can be configured by using two types of coolers, ie, a second cooler capable of performing the above.

The injection molding machine of the present invention may further include a switching device for switching the supply of the cooling medium to the first and second cooling circuits. Thereby, when the molten resin is injected into the mold, the supply of the cooling medium is switched by the switching device so as to supply the cooling medium to the first cooling circuit from the first cooler,
The cooling medium from the second cooler can be supplied to the second cooling circuit. After completion of the filling of the molten resin, the switching device switches the cooling medium supplied to the first cooling circuit to the cooling medium from the second cooling machine. Thereby, the molten resin filled in the mold is cooled at a temperature lower than the glass point transfer temperature, and a molded substrate having a desired outer shape is manufactured. Further, since the mold is provided with two cooling circuits, the temperature rise / fall cycle is shortened as compared with the conventional case, and the productivity is improved.

In the injection molding machine of the present invention, the cooling medium supply device supplies refrigerants having different temperatures.
It is also possible to use more than one type of cooler. At the time of injection molding, the cooling medium from these coolers can be appropriately selected by the switching device and supplied to the first and second cooling circuits.

According to a third aspect of the present invention, there is provided an injection molding method for manufacturing an optical disk substrate by injecting and filling a molten resin into a cavity defined by a movable mold and a fixed mold. A mold including a mold and a movable mold, wherein the fixed mold and the movable mold are formed with first and second cooling circuits for adjusting mold temperature, and Filling the cavity with molten resin while supplying cooling media having different temperatures to the first and second cooling circuits by using a mold in which the second cooling circuit is sequentially formed at different distances in a direction away from the cavity. In addition, there is provided an injection molding method characterized in that after filling the molten resin, the temperatures of the cooling media supplied to the first and second cooling circuits are made equal.

In the injection molding method of the present invention, a mold having a structure as shown in FIG. 1 is used as a mold for injection molding a substrate. First and second cooling circuits 6, 7 for adjusting the mold temperature are both formed in the fixed mold 1 and the movable mold 2, and the first and second cooling circuits 6, 7 are fixed. It is formed at different distances from the cavity 5 defined by the mold 1 and the movable mold 2. When the molten resin is injected and filled into the mold, a high-temperature cooling medium is supplied to the first cooling circuit 6 located closer to the cavity 5 and the second cooling circuit located farther from the cavity 5 is supplied. The circuit 7 is supplied with a low temperature cooling medium. in this way,
By flowing a high-temperature cooling medium through the first cooling circuit 6, the temperature of the cavity 5 can be increased at the time of injection filling, so that the flowability of the molten resin into the cavity is improved, and the warpage and distortion of the substrate are improved. Can be prevented from occurring.

On the other hand, after the injection and filling, the cooling medium supplied to the first cooling circuit 6 is made the same as the cooling medium supplied to the second cooling circuit 7, for example, to lower the temperature of the cavity 5. Thus, the molten resin filled in the cavity 5 is cooled in the cavity 5 and a resin substrate is formed. At this time, since the temperature of the mold portion forming the periphery of the first cooling circuit 6 is maintained at a constant temperature by the second cooling circuit 7, the temperature is supplied to the first cooling circuit 6 and to the second cooling circuit 7. By supplying the same cooling medium as the cooling medium, the entire mold can be cooled in a short time.

In the present invention, the temperature of the cooling medium supplied to the second cooling circuit is desirably lower than the glass transition temperature of the molten resin, and is a temperature sufficient to cool the molten resin filled in the cavity. I just need.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. The embodiments described below are merely preferred examples of the present invention, and do not limit the present invention.

[0023]

1 and 3 show a preferred embodiment of a disk molding die according to the present invention and an injection molding machine having the same. In FIG. 3, the injection molding machine 100 mainly includes a mold 1
0, a cooling medium supply device 11 for supplying a cooling medium to the first cooling circuit 6 and the second cooling circuit 7 provided in the mold 10, and two systems of the first and second cooling circuits 6 and 7. A switching device for switching a cooling medium to be supplied to the cooling circuit. The cooling medium supply device 11 includes two systems of a first cooler 13 and a second cooler 14. 1st cooling machine 1
3 is adjusted so that the temperature of the cooling medium is equal to or higher than the glass transition point temperature of the molten resin, and the second cooler 14 has a temperature of 100 ° C., which is lower than that of the first cooler 13.
The temperature is adjusted to be in the range of ° C to 120 ° C. The first cooling device 13 is connected to the first cooling circuit 6 through the switching device 12 and the piping.
It is connected to the. The second cooler 14 is connected to the second cooler 7 via a pipe, and is also connected to the first cooling circuit 7 via a switching device 12.

As shown in FIG. 1, the mold 10 includes a fixed mold 1, a movable mold 2, a stamper 3 having an information signal as a concavo-convex pattern, a spool bush 4 as an injection port for molten resin, and cooling of two systems. It comprises a first cooling circuit 6 and a second cooling circuit 7 as circuits. The cavity 5 is defined by clamping the fixed mold 1 and the movable mold 2.
The first cooling circuit 6 has a minimum distance L1 of 6 from the cavity.
The fixed mold and the movable mold are respectively formed at positions within the range of 10 mm to 10 mm. The second cooling circuit 7 is formed in each of the fixed mold and the movable mold at a position where the shortest distance L2 from the cavity is 16 mm to 20 mm or less.
A heat insulating layer 8 is formed between the first cooling circuit 6 and the second cooling circuit 7. As a material of the heat insulating layer 8, a ceramic material such as alumina or zirconia can be used.

An optical disk substrate molding method using such a disk substrate molding die will be described with reference to FIG. As the molten resin to be filled in the mold, a polycarbonate resin, a polymethyl methacrylate resin, an amorphous polyolefin resin, or the like can be used. The molten resin is injected into the mold cavity 5 through a spool bush 4 provided in the mold. At this time, the first cooling circuit 6 provided in each of the fixed mold 1 and the movable mold 2 is provided with a second cooling circuit 7 in order to raise the temperature of the cavity and facilitate the flow of the molten resin in the cavity. A cooling medium having a higher temperature is also flowed. It is desirable that the temperature of the cooling medium flowing through the first cooling circuit 6 be set to the same temperature as the glass transition temperature of the molten resin. On the other hand, the temperature of the cooling medium flowing through the second cooling circuit 7 is preferably lower than the glass transition temperature of the molten resin. As the cooling medium, for example, a liquid such as water or oil can be used.

Immediately after the injection of the molten resin into the cavity 5 is completed, in order to increase the cooling efficiency of the molten resin injected into the cavity 5, the timing shown in FIG.
The switching device 12 switches the cooling medium flowing through the first cooling circuit 6 to the cooling medium supplied from the second cooling device 14. At this time, the temperature of the cooling medium flowing through the first cooling circuit 6 does not need to be limited to the same temperature as that of the second cooling circuit 7, and may be set to an arbitrary temperature as long as the temperature is lower than the glass transition temperature of the molten resin. I can do it.

The molten resin filled in the mold is cooled in the mold and released as a molded substrate. Then, as preparation for the next injection, according to the timing shown in FIG.
The switching device 12 switches the cooling medium flowing through the first cooling circuit 6 of the fixed mold 1 and the movable mold 2 to the cooling medium supplied from the first cooler 13. In the second cooling circuit 7, a cooling medium from the second cooler 14, that is, a cooling medium having a temperature lower than the glass transition temperature of the molten resin flows. When the temperature inside the cavity reaches the glass transition temperature by the first cooling circuit 6, the molten resin is injected into the mold 10 again, and the above-described injection molding method of the optical disk substrate is repeated.

As described above, in this embodiment, the high-temperature cooling medium and the low-temperature cooling medium are repeatedly exchanged in the first cooling circuit 6 near the cavity in accordance with the timing of injection of the molten resin into the mold. Thereby, the first cooling circuit 6
The temperature of only the mold members constituting the surroundings is raised and lowered, so that the cooling / heating cycle of the cavity temperature can be accelerated, and an optical disk substrate with reduced warpage, distortion and birefringence can be manufactured with high productivity.

Although the mold for molding an optical disk substrate and the injection molding machine according to the present invention have been specifically described above, the present invention is not limited to these. Although the cooling medium of the same temperature is supplied to the first cooling device, it is also possible to supply the cooling media of different temperatures to the first cooling device on the fixed mold side and the first cooling device on the movable mold side.

[0030]

The mold of the present invention is provided with two systems of cooling circuits comprising a first cooling circuit and a second cooling circuit in order in the direction away from the cavity, and the cooling circuit formed farther from the cavity is provided. While cooling the outside of the mold to a certain temperature, the cooling circuit formed closer to the cavity can raise and lower only the temperature inside the cavity,
A thin substrate with improved substrate warpage, distortion, and birefringence characteristics can be manufactured with high throughput.

According to the injection molding machine of the present invention, the cooling mediums having different temperatures can be supplied to the two cooling circuits formed in the mold, so that the temperature control of the mold becomes extremely easy. The cycle of raising and lowering the temperature of the mold is shortened, and a thin substrate can be formed in a shorter time than before.

In the injection molding method of the present invention, while the mold portion far from the cavity is cooled at a constant temperature, during injection filling, the mold portion near the cavity is kept at a temperature higher than the glass transition temperature of the molten resin. To improve the flow of the molten resin in the cavity, and after filling the resin into the cavity, set the mold part closer to the cavity to the same temperature as the mold part farther from the cavity. Therefore, the warpage, distortion, and birefringence characteristics of the substrate are reduced, and the injection molding time per thin substrate is shortened, thereby improving the productivity.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a substrate molding die according to the present invention.

FIG. 2 shows the timing of injection filling a molten resin into a mold;
FIG. 3 is a diagram illustrating a relationship between a temperature of a cooling medium supplied to a first cooling circuit and a temperature in a cavity.

FIG. 3 is a diagram showing a schematic configuration of an injection molding machine according to the present invention.

FIG. 4 is a schematic sectional view of a conventional substrate molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed mold 2 Movable mold 3 Stamper 4 Spool bush 5 Cavity 6 First cooling circuit 7 Second cooling circuit 8 Heat insulation layer 9 Cooling circuit 10 Mold 11 Cooling medium supply device 12 Switching device 13 First cooling machine 14 Second Cooling machine 100 Injection molding machine

Claims (12)

[Claims] A mold for molding a substrate, comprising: a fixed mold and a movable mold, wherein a molten resin is filled in a cavity defined between the fixed mold and the movable mold. And the movable mold are provided with first and second cooling circuits for cooling the molten resin therein, respectively.
And a second cooling circuit formed at a position different from the cavity by a different distance. 2. The substrate molding method according to claim 1, wherein the shortest distance from the first cooling circuit to the cavity is 10 mm or less, and the shortest distance from the second cooling circuit to the cavity is 20 mm or less. Mold. 3. The substrate molding die according to claim 1, wherein the fixed die and the movable die have a heat insulating layer between the first cooling circuit and the second cooling circuit. . 4. The fixed mold and the movable mold, wherein the mold portion where the first cooling circuit is formed and the mold portion where the second cooling circuit is formed are made of materials having different thermal conductivities. The substrate molding die according to any one of claims 1 to 3, which is configured. 5. An injection molding machine for molding a substrate, comprising: a fixed mold and a movable mold, wherein a molten resin is filled in a cavity defined by the fixed mold and the movable mold. In addition, first and second cooling circuits for adjusting the mold temperature are formed inside each of the fixed mold and the movable mold, and the first and second cooling circuits are arranged at different distances from the cavity. An injection molding machine, comprising: a mold formed at a position separated from a cooling medium; and a cooling medium supply device for supplying a temperature-controlled cooling medium to each of the first and second cooling circuits. 6. The injection molding machine according to claim 5, further comprising a switching device for switching supply of a cooling medium to the first and second cooling circuits. 7. The mold according to claim 5, wherein the shortest distance from the first cooling circuit to the cavity is 10 mm or less, and the shortest distance from the second cooling circuit to the cavity is 20 mm or less. 7. The injection molding machine according to 6. 8. The method according to claim 5, wherein the fixed mold and the movable mold include a heat insulating layer between the first cooling circuit and the second cooling circuit. Injection molding machine. 9. A mold part in which the first cooling circuit is formed and a mold part in which the second cooling circuit is formed are made of materials having different thermal conductivity from each other. An injection molding machine according to any one of claims 5 to 8. 10. An injection molding method for manufacturing an optical disk substrate by injecting and filling a molten resin into a cavity defined by a movable mold and a fixed mold, comprising: a fixed mold and a movable mold. First and second cooling circuits for adjusting the mold temperature are respectively formed inside each of the fixed mold and the movable mold,
In addition, the first and second cooling circuits are formed at different distances from the cavity, and the molds are formed at different positions from each other. Injection molding, wherein the temperature of the cooling medium supplied to the first and second cooling circuits is made equal after filling the molten resin. 11. When injecting the molten resin into the cavity, a cooling medium having a temperature equal to or higher than the glass transition point temperature of the molten resin is supplied to the first cooling circuit, and the glass transition point temperature is supplied to the second cooling circuit. 11. A cooling medium having a lower temperature than the first cooling circuit is supplied to the first cooling circuit after the cavity is filled with the molten resin, and then the cooling medium supplied to the second cooling circuit is supplied to the first cooling circuit. 3. The injection molding method according to 1. 12. The injection molding method according to claim 10, wherein the cooling medium is a liquid.