JPS61252122A - Method and device for regulating temperature of mold for manufacturing disc base plate - Google Patents

Abstract

PURPOSE:To obtain a molding condition including no residual strain and prominent in transferring property by a method wherein the flow of cooling medium is switched to a main flow path and a branch flow path in synchronizing with a molding cycle. CONSTITUTION:The temperature-regulating device for the mold for manufacturing the disc plate, which is attached to an injection molding machine, is provided with the branch flow path, consisting of a branch pipeline 18 branched from a switching valve 17 and a non-return valve 19, in the main flow path of the cooling medium. When mold clamping forming a cavity 5 is finished and, immediately before biginning the injection, the switching valve 17 is operated by a signal from the injection molding machine, the flow path of the cooling medium is switched from the main flow path to the branch flow path, circulation to the fluid-passing holes 6, 7 of the molds 3, 4 is stopped and the stopping condition is maintained until resin material 16 is injected into the cavity 5 and the internal pressure of the resin material is increased sufficiently. Accordingly, the cooling speed of the resin material 16 in the cavity 5 is slowed down and the solidification of the skin layer is delayed, whereby the transferring property may be improved, and the remaining strain may be reduced and birefringence may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold temperature control method and a mold temperature control device for manufacturing disk substrates such as optical disks and magneto-optical disks.

(Prior Art) Video discs, compact discs, write-once or erasable optical discs, and magneto-optical discs are manufactured using injection molding or injection compression molding, and various developments related to this are in progress. It is being

Molding of disk substrates is thin-wall precision molding, and it is important to improve the precision of the mold, develop resin materials, and develop molding conditions such as mold temperature, cylinder temperature, injection pressure and speed. This has become a major issue.

There are many requirements for an optical disc substrate, among them the orientation of molecular chains during molding, which causes increased birefringence, and low residual strain, and the transferability of signal bits or guide grooves for tracking. Being good is important. These items include the development of resin materials with a small photoelastic coefficient and good fluidity when melted, and improvements in molding conditions, such as improving the fluidity of resin materials, improving transferability, and lowering birefringence. (1) Increase the cylinder temperature, (2) Increase the mold temperature, (3) Reduce the injection pressure as much as possible, (4)
) Improvements can be made such as increasing the injection speed as much as possible. However, each of the above conditions (1) to (4) has its limitations. For example, in (1) there is a problem of thermal deterioration of the resin material, and in (2) the cooling time is extended and the molding cycle is Problems that impede shortening.

Term (3) improves birefringence but reduces transferability, and Term (4) tends to overfill and requires control, making it difficult to find a complete solution. (Plastic Age Mar, 1984 p.
103-p, 106) - Furthermore, regarding conventional mold temperature control systems that determine the temperature of the mold, attention has been focused only on increasing the cooling capacity of the resin injected into the mold.

A cross-sectional view of a conventional disc substrate manufacturing mold installed in an injection molding machine and a mold temperature control device will be explained with reference to FIG. In the figure, a cavity 5 is formed on the mating surfaces of molds 3 and 4 attached to a fixed die plate 1 and a movable die plate 2, respectively, of an injection molding machine, around which a cooling medium for cooling the resin is circulated. Fluid passage hole 6
and 7 are provided. Although not shown in the figure, a stamper is attached inside the cavity 5 described above. The cooling medium for resin cooling undergoes heat exchange in the mold temperature control device 8 to reach a predetermined temperature, and is then passed through the outgoing pipes 9 and 1 for supply.
0 to the molds 3 and 4, passes through the fluid passage holes 6 and 7, and returns to the mold temperature control device 8 via return piping 11 and 12 for reflux.

Heater 1 wrapped around the outer circumference of injection cylinder 13 of an injection molding machine
4 and the frictional heat between the screw 15 and the inner wall of the cylinder 13, the resin material 16 is melted into the injection cylinder 1.
It is supplied to the cavity 5 from the nozzle No. 2.

The conventional mold temperature control device 8 supplies a cooling medium set at a constant temperature to the mold in order to remove the amount of heat from the resin material 16 injected into the cavity 5 .

(Problems to be Solved by the Invention) In the conventional mold temperature control device, attention is paid to improving the heat exchange ability. It has become possible to remove heat from the mold as quickly as possible, shortening the time it takes to open the mold. However, in the case of molding a disk substrate, in order to improve the above-mentioned birefringence and the transferability of signal pits or guide grooves, it is necessary to Conventionally, it is better not to take heat away from the resin material 16.

Since the mold temperature is set to about 10 to 40 degrees Celsius lower than the thermal deformation temperature of the resin material 16, the skin layer of the resin material 16 that is injected into the cavity 5 and comes into contact with its surface will solidify immediately. , as the transferability decreases,
There was a problem in that if pressure was applied during solidification, residual strain would occur and birefringence would worsen.

The present invention solves the above-mentioned problems, and aims to provide a mold temperature control method and a mold temperature control device that do not leave residual strain and provide molding conditions with good transferability.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a mold temperature control device that controls the cooling medium in the mold when manufacturing a disk substrate by injection molding or injection compression molding. In addition to the main flow path through which the cooling medium flows through the fluid passage holes, a branch flow path that does not pass through the fluid passage holes is provided, and the flow of the cooling medium is switched between the main flow path and the branch flow path in synchronization with the molding cycle. The aim is to create a mold temperature control method that allows for better mold temperature control.

(Function) In the mold temperature control method and mold temperature control device for manufacturing disk substrates of the present invention, before the resin material enters the mold cavity from the nozzle of the injection cylinder, the cooling medium is added to the fluid in the mold. The flow path of the cooling medium is switched from the main flow path passing through the passage hole to the branch flow path, and the flow of the cooling medium inside the fluid passage hole is stopped to temporarily stop taking away the heat from the filled resin material, and the inside of the mold cavity is stopped. By slowing down the cooling rate of the resin material to improve transferability, and applying pressure before assimilation progresses, the residual strain generated in the skin layer of the disk substrate is reduced and birefringence is improved. .

(Example) Embodiments of the present invention will be explained with reference to FIGS. 1 to 3.

Figure 1 shows a cross-sectional view of a mold for manufacturing disk substrates attached to an injection molding machine, and a mold temperature control device according to the present invention. Valve 1
A branch flow path consisting of a branch pipe 18 and a check valve 19 branching off from 7 is provided. Note that the injection molding machine, the molds 3 and 4 attached thereto, and the mold temperature control device 8 are the same as those shown in FIG. 4, so a description thereof will be omitted.

FIG. 2 is a cooling medium flow path switching diagram showing a switching process in which the cooling medium flows through the main flow path and the branch flow paths when manufacturing a disk substrate by injection molding. The injection molding cycle includes mold clamping in which the movable die table i pull 2 is driven toward the fixed die table 1 and the molds 4 and 3 are brought together to form a cavity 5, injection in which the cavity 5 is filled with molten resin material 16, and The mold temperature controller 8 circulates the cooling medium through the fluid passage holes 6 and 7 of the molds 3 and 4 to remove heat from the resin material 6 in the cavity 5, and the molded disk substrate is transferred to the mold 3. The process consists of four steps: opening the mold and taking it out from step 4.

In the mold temperature control method according to the present invention, immediately before mold clamping ends and injection begins, that is, the 1-hour T period is set by a timer, and immediately before that period ends, the switching valve 17 is activated by a signal from the injection molding machine, and the cooling medium is teeth.

The flow path is switched from the main flow path to a branch flow path, the circulation to the fluid passage holes 6 and 7 of the molds 3 and 4 is stopped, and the resin material 16 is injected into the cavity S, filling is completed and the resin internal pressure is reduced. It will remain stopped until it has climbed sufficiently. By stopping this circulation, the temperature of the resin material 16 in the cavity 5 decreases at a slower cooling rate than in the conventional temperature control method.
Solidification of the skin layer is delayed and transferability is improved, residual strain is reduced and birefringence is improved.

When the injection process is completed, the switching valve 17 is operated in response to a signal from the injection molding machine, and the coolant flow path is switched from the branch flow path to the main flow path. restarting the circulation to the fluid passage holes 6 and 7 of 3 and 4 and removing heat from the resin material I6 in the cavity 5;
When the molding of the disk substrate is completed, the mold 4 is moved back together with the movable die table 2, and the molded product is taken out from the opened molds 3 and 4, completing the injection molding cycle. In general, the injection process takes 0.5 seconds out of the injection molding cycle time for disk substrates.
Since the time is approximately 5 seconds, the cooling process time hardly increases even if the circulation of the cooling medium in the main flow path is stopped during the injection process.

FIG. 3 is a diagram showing cooling medium flow path switching when manufacturing a disk substrate by injection compression molding.

The injection compression molding cycle includes a compression process in which pressure is applied to the filled resin material 16 after the injection process, and consists of five processes: mold clamping, injection, compression, cooling, and mold opening.

The mold temperature control method according to the present invention in the injection compression molding method includes:
The process until the end of the injection process is the same as in the case of the injection molding method shown in Fig. 2, and the circulation of the cooling medium in the molds 3 and 4 is stopped during the injection process, that is, the flow path of the cooling medium is switched to a branched flow path. The time T2 is set by a timer so that the signal pits or guide grooves of the standber (not shown) are sufficiently transferred to the disk substrate during the compression process.

This time T must be determined in advance through experiments. After 54,718 hours have elapsed, the switching valve 17 is activated by a signal from the injection molding machine, and the cooling medium flow path is switched from the branch flow path to the main flow path, and thereafter the same steps as in FIG. 2 are followed.

(Effects of the Invention) According to the mold temperature control method and mold temperature control device for disk substrate manufacturing according to the present invention, during injection molding or injection compression molding of a disk substrate, the fluid passage holes in the mold are A main flow path through which the fluid flows and a branch flow path that does not pass through the fluid passage holes in the mold are provided.

In synchronization with the injection molding cycle or injection compression cycle, the cooling medium can be switched from the main flow path to the branch flow path to flow, allowing the resin to cool before taking away heat from the resin material injected into the mold cavity. By applying internal pressure, it is possible to improve transferability, reduce residual strain, improve birefringence, and obtain a disk substrate of excellent quality.

Such a mold temperature control method and mold temperature control device.

It can also be used to mold substrates for various optical disks and magneto-optical disks.

In addition, in terms of equipment investment, it is only necessary to add a switching valve, a short branch pipe, a check valve, and a switching valve operation signal device to the conventional mold temperature control device, and the molding cycle is also about 0. It only takes 5 seconds longer, so the impact on manufacturing costs is extremely small.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a mold attached to an injection molding machine and a configuration diagram of a mold temperature control device according to the present invention, and Figs. 2 and 3 are the present invention applied to injection molding method and injection compression molding method, respectively. FIG. 4 is a sectional view of a mold attached to an injection molding machine and a configuration diagram of a conventional mold temperature control device. 1... Fixed die table, 2... Movable die table, 3, 4... Mold, 5... Cavity, 6, 7... Fluid passage hole, 8... Mold temperature control device , 9, 10... Outward piping, 11.12... Return piping, 13... Injection cylinder, 14... Heater, 15
... Screw, 16 ... Resin material, 17 ... Switching valve, 18 ... Branch pipe, 19 ... Check valve. Patent applicant: Matsushita Electric Industrial Co., Ltd. Congee 1 Figure 2 Figure 4 Figure 7 fit fat! collar

Claims (2)

[Claims] (1) When injection molding or injection compression molding a disk substrate, in addition to the main flow path of the cooling medium that flows through the fluid passage holes for cooling the resin material provided in the mold, there are branches that do not pass through the fluid passage holes. A mold temperature control method for manufacturing a disk substrate, characterized in that a flow path is provided and a cooling medium is caused to flow by switching between a main flow path and a branch flow path in synchronization with a molding cycle. (2) When injection molding or injection compression molding a disk substrate, there is a main flow path for the cooling medium that flows through the fluid passage hole for cooling the resin material provided in the mold, a switching valve that branches from this, a branch pipe, and a reverse flow path. A mold temperature control device for disk substrate manufacturing, characterized in that a branch flow path consisting of a stop valve is provided, and the switching valve is actuated by a signal line from an injection molding machine to switch between the main flow path and the branch flow path. .