JPH10208312A - Method for molding optical disk substrate, and metal mold for molding, as well as molding device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the variation in characteristics between substrates, by setting the pressure applied on a cavity small at the time of starting clamping of metal mold and increasing the pressure applied on the cavity right after the annihilation of the influence on a hydraulic system. SOLUTION: The internal pressure of a resin reservoir part begins to rise first right after the start of packing by the packing pressure of packing a molten resin 8 into the cavity and exhibits the max. pressure at the time of completion of an injection stage. The internal pressure is sharply dropped by the volume expanding operation of the resin reservoir inducing the retreat of an ejector pin 7 to a retreat position. The excessively packed excess resin, however, flows into the resin reservoir and packs the resin reservoir. As a result, the internal pressure rises again and exhibits a second peak. If gate cutting is executed by advancing a cutting punch 6 at the point of this time, the press kept applied on the cavity 4 thereafter presses the resin in the cavity 4 to constitute the optical disk substrate and acts only to mold the resin to the prescribed shape. The overpacking of the resin conversely into the resin reservoir does not arise any more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method, a molding die and a molding apparatus for an optical disk substrate used for an optical disk such as a read-only type, a write-once type, and a rewritable type. The present invention relates to a method for molding an optical disk substrate, a molding die, and a molding apparatus capable of molding a thinner substrate such as the above.

[0002]

2. Description of the Related Art Until now, CDs (Compact Discs)
Various types of optical disks, such as an optical system and an MO (magneto-optical disk) system, have been used in a form corresponding to each use of read-only, write-once, and rewrite. Substrates used for these optical disks are molded and produced by injection molding or injection compression molding using a resin mainly composed of polycarbonate from the viewpoint of production efficiency and cost. on the other hand,
It has become necessary to mount a larger amount of information on one optical disc, and a new optical disc such as a DVD is being worked on. One approach to increasing the capacity of these optical discs on an optical disc substrate is to reduce the thickness of the substrate (for example, the substrate thickness of a DVD-based optical disc is 0 mm compared to the conventional 1.2 mm CD- or MO-based optical disc substrate thickness). .6 mm). It is another object of the present invention to more precisely transfer a pit row indicating information or a guide groove (track) for tracking a pickup onto a substrate.

As an example of a method for molding an optical disk substrate, a molding die including a fixed mold and a movable mold is used, and a mold is clamped between the fixed mold and the movable mold. An annular flat stamper is mounted in the cavity formed by the above method, and a molten optical resin is injected into the cavity to form a flat optical disk substrate on which the pits, guide grooves and the like of the stamper are transferred. However, in the case of a large-capacity optical disk such as a DVD, the thickness of the cavity of the molding die is also reduced because the substrate thickness of the optical disk substrate is reduced, and the substrate is formed by filling the cavity with a molten resin. At that time, the filling of the molten resin itself became difficult. For this reason, it is difficult not only to accurately transfer the pit rows and guide grooves with higher density onto the optical disc substrate, but also to realize small birefringence and good mechanical properties required for the characteristics of the optical disc substrate. It turned out to be.

In order to improve the transferability by improving the filling property of filling the cavity with the resin, the set temperatures of the mold temperature and the resin temperature may be set higher. However, with this method, there is a limit on the material properties of the material used, such as decomposition of the resin used or carbonization caused by setting a high resin temperature setting. The cooling of the formed resin does not proceed sufficiently, so that the mechanical characteristics of the molded optical disk substrate deteriorate, and the characteristics of the birefringence also deteriorate due to the mold temperature being set too high.

[0005] In order to solve the problem caused by poor filling by setting the temperature higher, it is necessary to set the cooling time after filling the molten resin into the cavity of the mold. Should be set longer. By setting this cooling time appropriately long, the mechanical properties and birefringence of the molded optical disk substrate can be improved,
Prolonging the cooling time lengthens the molding cycle, which not only reduces the productivity, but also lowers the actual temperature of the cavity, which causes a problem that the filling and transfer properties of the molten resin are reduced. In other words, as described above, for an optical disc substrate that is required to transfer thinner pit rows and guide grooves with a smaller thickness, appropriate properties such as transferability as well as mechanical properties and birefringence are obtained. It is becoming clear that it is very difficult to make the optical disk substrate have the required characteristics, that is, to satisfy the entire characteristics required for the optical disk substrate. In addition, an article relating to the technology and the problem centered on the molding process of the DVD substrate is published in “Electronic Materials, June 1996, pp. 42-45”.

As a method of forming an optical disk substrate by solving the above-mentioned problems, a temperature setting relating to a molding condition setting such as a mold temperature setting and a resin temperature setting must be balanced with a material property, a mechanical property and a birefringence to be used. A molding method that sets the highest possible temperature after balancing, reduces the pressure applied to the cavity when filling the cavity with molten resin, and applies a large pressure to the cavity (filled resin inside) after completion of filling. It is common practice to employ

Here, the above-mentioned molding method will be specifically described with reference to FIG. 3. For example, when an optical disk substrate is molded by an injection molding method, as shown in FIG. Movable mold 11 and fixed mold 1
2 without completely closing it, open sprue 1
4, the molten resin 15 is filled into the cavity 13. After the filling is completed, the movable mold 11 and the fixed mold 12 of the mold 10 are completely closed as shown in FIG. Apply tightening force. As a result, the internal pressure of the filling resin in the cavity is increased, the adhesion to the stamper is increased, and the transferability of the pit rows and guide grooves is improved. In addition, variations in internal pressure are reduced, and variations in characteristics between molded substrates are also reduced. In the case of the injection compression molding method, first, the mold is closed and a mold clamping force is applied, while the compressive force is hardly applied, and the molten resin is filled with the cavity thickness expanded by a predetermined compression allowance. This is a method in which a compressive force is applied to the cavity after the completion of filling, and the same effect as described above can be obtained.
JP-A-8-17078 discloses a method of molding an optical disc substrate by the above-described injection molding method, and describes a setting range of a mold opening amount when introducing a molten resin into a cavity. I have.

In the molding method described above, while the cavity is being filled with the molten resin, the thickness of the cavity is increased, so that the flow resistance of the resin is reduced and the filling property is improved. Therefore, the amount of strain generated inside the resin during filling is also reduced, so that the stress strain remaining in the molded optical disk substrate is reduced, and the birefringence and mechanical properties are improved.
In addition, since the filling is performed in a more fluid state, the transferability of the pit rows and the guide grooves is also improved. Further, by applying a large pressure to the cavity after completion of filling, the internal pressure of the resin in the cavity increases. Then, due to the high internal pressure of the resin after the rise, the resin in the cavity strongly adheres to the stamper set in the cavity,
The pit rows and guide grooves are precisely transferred onto the molded substrate. At the same time, the variation in the internal pressure of the resin generated at the time of filling is also made uniform and eliminated by this operation.

[0009]

As described above, the molding method utilizing the control of changing the pressure applied to the cavity before and after filling the molten resin is an effective method for obtaining a thin and high quality optical disk substrate. . However, this method still has many problems.

If the operation of increasing the pressure applied to the cavity in the above-described method is performed while the resin in the cavity maintains fluidity, a greater effect can be obtained for improving the transferability and making the internal pressure of the resin uniform. . As the resin filled in the cavity begins to cool immediately after entering the cavity and loses its fluidity, the earlier the operation of increasing the pressure applied to the cavity, the higher the internal pressure of the resin Can obtain more effects. However, if the timing of increasing the pressure applied to the cavity is too early, pressure will be applied during the process of filling the molten resin into the cavity, and a large resistance will be applied to the resin flowing in the cavity. As a result, the characteristics of the optical disc substrate including the transferability are deteriorated. Therefore, it can be said that the most effective operation is to increase the pressure applied to the cavity at the same time when the filling of the molten resin into the cavity is completed.

The filling process in injection molding (or injection compression molding) can be divided into two stages, an injection process and a pressure-holding process. For the molding of a thin optical disk substrate, which is a problem in this case, most of the filling process is performed. The operation for increasing the pressure applied to the cavity for obtaining the most advantageous effect described above is considered to be completed during the injection process, as shown in FIG. It can be said that it is sufficient to synchronize with the timing of shifting from the process to the pressure holding process. However, most of the optical disk substrate molding is performed using a molding apparatus using hydraulic pressure as a drive source. When the above operation is viewed from the viewpoint of the operation of such a molding apparatus, the valve of the hydraulic system controlling the injection operation of the apparatus is closed and at the same time the valve of the hydraulic system controlling the pressure holding operation is opened, and the cavity is opened. The operation of increasing the pressure of the hydraulic system that controls the pressure applied to the hydraulic system is performed. In the operation of the molding apparatus described above, the operation of closing the valve of the hydraulic system that controls the injection operation generates vibration called “water hammer” (a phenomenon that occurs when the flow of fluid is suddenly stopped by a valve or the like). ), And propagates into the hydraulic fluid. Since all hydraulic systems of the molding apparatus are pressurized by the same motor, all systems are always connected somewhere. Therefore, the water hammer vibration generated in the injection operation system is also transmitted to the hydraulic system for controlling the pressure applied to the cavity, and as shown in FIG. 4, the control for increasing the mold clamping pressure applied to the cavity becomes unstable.

As described above, the pressure applied to the cavity plays a significant role in improving the characteristics of the optical disk substrate to be formed. Because this pressure rise control is performed unstable,
The characteristics of the optical disk substrate to be formed also become unstable, causing a problem that the characteristic variation between the formed substrates becomes large. Also, the water hammer phenomenon itself is an inevitable phenomenon caused by the opening and closing operation of a valve in a fluid,
As long as a device driven by hydraulic pressure is used, this phenomenon cannot be completely avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and achieves the maximum effect by controlling the pressure applied to the cavity before and after filling with the molten resin, and at the same time produces the driving hydraulic system of the molding apparatus. It is an object of the present invention to provide a method of forming an optical disk substrate that can avoid deterioration of substrate characteristics and variation in characteristics between substrates caused by a water hammer phenomenon. It is another object of the present invention to provide a mold for molding an optical disk substrate having a structure for performing molding by the method for molding an optical disk substrate, and further to operate a configuration given to the molding die. An object of the present invention is to provide a molding device having a possible configuration and to simplify the structure of a mold to be used.

[0014]

As a means for solving the above-mentioned problems, according to the first aspect of the present invention, there is provided a molding apparatus which performs operation and control of filling of a molten resin and clamping of a mold by using hydraulic pressure as a driving source. In the method of molding an optical disc substrate in which the pressure applied to the cavity to be filled with the resin is controlled in multiple stages, the pressure applied to the cavity is set small at the start of the mold clamping, and the filling control system of the molding device is It is characterized by performing control to increase the pressure applied to the cavity immediately after the effect on the hydraulic system due to switching from injection control to holding pressure control disappears, thereby controlling the pressure applied to the cavity in multiple stages. Of the substrate characteristics caused by the water hammer phenomenon that occurs in the drive hydraulic system of the molding equipment It is possible to avoid variations in characteristics between.

According to a second aspect of the present invention, in the method of forming an optical disk substrate according to the first aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. This makes it possible to obtain more effects associated with an increase in the internal pressure of the resin filled in the cavity.

According to a third aspect of the present invention, in a molding die for an optical disk substrate for molding an optical disk substrate according to the molding method of the second aspect, the projecting operation of the formed sprue portion on the central axis of the die is performed. The ejector pin to be performed is characterized by having a structure capable of retreating an appropriate amount from the normal setting position as well as the normal setting position and the protruding operation position after molding when filling the cavity with the molten resin, and thereby, in the cavity, It is possible to obtain a mold used to obtain more effects associated with an increase in the internal pressure of the filled resin.

According to a fourth aspect of the present invention, there is provided an optical disk substrate molding apparatus for molding an optical disk substrate in accordance with the molding method according to the second aspect using the molding die according to the third aspect, wherein the ejector pins are operated. However, it is characterized in that the ejector pin has a configuration capable of operating not only the normal setting position and the protruding operation position but also to a position retracted by an appropriate amount from the normal setting position, and thereby, A molding apparatus having a configuration capable of operating the configuration given to the mold can be provided, and the structure of the mold to be used can be simplified.

According to a fifth aspect of the present invention, in the method for molding an optical disk substrate according to the second aspect, the control for increasing the volume of the resin pool at the center of the cavity is performed in accordance with the operation of increasing the pressure applied to the cavity. In addition, the volume of the resin reservoir to be increased by the control is set to 5% to 10% of the cavity volume reduction amount due to the operation of increasing the pressure applied to the cavity. The size can be provided, and the effect accompanying the increase in the internal pressure of the resin filled in the cavity can be maximized.

According to a sixth aspect of the present invention, in the optical disk substrate molding method according to the second aspect, the control for increasing the volume of the resin pool at the center of the cavity is performed in accordance with the operation of increasing the pressure applied to the cavity. In addition, the operation of increasing the volume of the resin reservoir is characterized in that it is performed immediately after the pressure applied to the cavity reaches the set value, whereby it is possible to provide appropriate settings for the above control, and the cavity is filled. It is possible to maximize the effect of increasing the internal pressure of the resin.

According to a seventh aspect of the present invention, in the method for molding an optical disk substrate according to the second aspect, the control for increasing the volume of the resin pool at the center of the cavity is performed in accordance with the operation of increasing the pressure applied to the cavity. In addition, molding is performed by setting the temperature of the mirror surface of the mold that constitutes the cavity such that the temperature becomes higher as the position is closer to the center of the cavity. A method for maintaining the fluidity of the resin filled in the resin can be provided, and it is possible to obtain more effects by the above control.

According to an eighth aspect of the present invention, in the method of molding an optical disk substrate according to the seventh aspect, the chiller temperature control of the cut punch, which is a main portion forming a resin reservoir, is punched out by punching an inner hole of the optical disk substrate, and the mirror surface temperature is set. It is characterized in that it is set to the same temperature as the preset temperature, thereby providing a method of maintaining the fluidity of the resin filled around the resin reservoir in the center of the cavity, and adjusting to the operation of increasing the pressure applied to the cavity. As a result, it is possible to obtain more effects by controlling to increase the volume of the resin pool at the center of the cavity.

According to a ninth aspect of the present invention, in the method for molding an optical disk substrate according to the second aspect, the control for increasing the volume of the resin pool at the center of the cavity is performed in accordance with the operation of increasing the pressure applied to the cavity. The feature is that the gate cut operation is performed immediately after the pressure inside the resin pool shows the second maximum value, thereby providing an appropriate setting to increase the capacity of the resin pool and filling the cavity. It is possible to maximize the effect of the increased internal pressure of the resin.

According to a tenth aspect of the present invention, the molding die of the third aspect and the molding apparatus of the fourth aspect are used, and the molding method of the first, second, fifth, sixth, seventh, eighth or ninth aspect is used. In the optical disk substrate molding method for molding an optical disk substrate, the pressure applied to the cavity, the operation control of the cut punch and the ejector pin are controlled by the pressure detected value of the corresponding hydraulic system of the molding device for applying pressure to the cavity and the internal pressure in the resin reservoir. It is characterized in that it is performed in accordance with the detected value, whereby it is possible to optimally control the operation of pressing the cavity, the cut punch and the ejector pin.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for forming an optical disk substrate according to the present invention, a molding die and a molding apparatus used for molding the optical disk substrate will be described below in detail with reference to the drawings.

The method of forming an optical disk substrate according to the present invention will be described in accordance with the procedure. The following procedure describes the operation in the case of molding an optical disc substrate by an injection molding method using a molding device that uses a hydraulic pressure as a driving source, using a molding die including a fixed mold and a movable mold. However, as described in the section on the related art, the same configuration and operation can be easily performed even when molding is performed by the injection compression molding method.

First, the mold is clamped in a state where the cavity is slightly opened without completely closing the movable mold of the mold (with extremely weak mold clamping force) with respect to the fixed mold. Fill the cavity. After a very short time after the filling step of the molten resin is switched from the injection step to the pressure-holding step, the operation of raising the mold clamping force to a predetermined pressure is performed to increase the internal pressure of the resin filled in the cavity. Utilization is used to improve substrate characteristics mainly in transferability from a stamper to a substrate. Here, FIG. 1 shows the timing of switching the set value of the mold clamping force and the detected value of the mold clamping pressure when switching from the injection process to the pressure holding process in the optical disk substrate molding method according to the present invention. As described above, the timing of increasing the mold clamping force is slightly delayed from the moment when the injection process is switched to the pressure-holding process. As a result, as shown in FIG. Since the mold clamping pressure can be increased without being adversely affected, the deterioration of the substrate characteristics and the variation in characteristics between the substrates can be avoided, and the effect of improving the substrate characteristics by increasing the pressure of the filling resin in the cavity is obtained. be able to. The setting of the time to delay the mold clamping force described above varies depending on the type of the molding machine and the injection condition setting,
It is approximately 0.02 sec to 0.04 sec. In addition, if the control to increase the mold clamping force is performed after confirming the decrease in the influence of the water hammer with the pressure value detected by the hydraulic system that performs the mold clamping force control, the above-described operation is performed more reliably.
The effect can be obtained.

In the above-described operation, the reason that the cavity is very slightly opened during the injection step is to improve air bleeding from the cavity during the filling step and to reduce the cavity volume during the filling step to the filling amount. On the other hand, by slightly increasing the amount, the flow resistance of the molten resin to be filled is reduced while suppressing the rise in the resin pressure during the filling step. By this operation, the filling property of the molten resin into the cavity is improved, and the characteristics of the molded substrate including transferability are improved.

The effect of improving the filling property described above increases as the opening amount of opening the cavity during filling increases. However, if the opening amount is too large, burrs are generated at the outer peripheral end of the optical disk substrate, another problem is caused such as overfilling due to excessive improvement in filling property, and the plate thickness becomes too thick. On the other hand, regarding the overfilling, when considering the pressurizing process for the cavity performed after the filling step, if the cavity is overfilled with the resin, the internal pressure of the filled resin increases due to the pressurizing process and the property improving effect obtained thereby. Becomes larger.

Accordingly, in the present invention, the volume of the resin pool provided at the center of the cavity of the mold is adjusted in accordance with the operation of filling the cavity of the mold with the molten resin slightly excessively and increasing the pressure applied to the cavity. Control to increase was performed. By this control operation, the effect of increasing the internal pressure of the resin filled in the cavity can be obtained more, and at the same time, the excess resin that is overfilled can be absorbed in the resin pool to keep the thickness of the molded substrate within an appropriate range. Can be.

FIG. 2 shows an outline of the configuration and operation of a molding die portion of the optical disk substrate molding apparatus according to the present invention. As shown in FIG. 2, the molding die 1 of the molding apparatus includes a movable die 2 and a fixed die 3, and a molten resin 8 flows into the cavity 4 at the center of the fixed die 3. The movable mold 2 provided with a sprue 5 for performing a cutting operation and having a stamper (not shown) fixed thereto has a cut punch 6 at the center of the movable mold 2 for performing an operation of punching an inner hole of the optical disk substrate. An ejector pin 7 is provided on the central axis O inside the cut punch 6 to eject the resin from the sprue 5 after molding and opening the optical disk substrate. The opening and closing operations of the movable mold 2 and the fixed mold 3 are performed by a drive system (not shown) using the hydraulic pressure of the molding apparatus as a drive source.

The resin pool in the cavity 4 of the optical disk substrate molding die 1 is provided in the movable die 2, and usually has an inner peripheral portion at the tip of the cut punch 6 and a central axis inside the cut punch 6. Ejector pin 7 placed on O
Are formed as resin pools.
In general, the ejector pin 7 can be operated only between two positions: a normal position and a protruding position where the resin of the sprue 5 is protruded.
A structure capable of operating the ejector pin 7 from the normal position shown in FIG. 2 (A) to the position shown in FIG. 2 (B) to a third set position for increasing the volume of the resin pool is also provided. Thereby, the above-described control is enabled.

In the above-described configuration, for example, the ejector pin 7 is connected to an air cylinder that can be positioned in three stages and is located on the central axis O of the movable mold 2 of the molding mold 1. This can be achieved by: The mechanism for causing the ejector pin 7 to perform the three-stage position control may use not only the air drive described above but also other systems such as hydraulic pressure. It is also possible to provide a mechanism for operating the ejector pin 7 in the molding apparatus, and in such a case, it is possible to simplify the structure of the mold used.

Further, the molding device and the metal mold used for the operation of retracting the ejector pin 7 to the retracted position in accordance with the operation of increasing the pressure applied to the cavity 4 to increase the volume of the resin pool at the center of the cavity are described. Although it depends on the mold structure and the filling conditions including the filling amount, the mold opening amount during the filling step, that is, the cavity volume that is excessively larger than the predetermined substrate volume, and the cavity volume that is increased when the mold cavity is pressed are increased. By associating the volume ratio of the resin pool with the results of the evaluation of the substrate characteristics of the molded optical disk substrate, it is possible to set the volume for increasing the resin pool to 5 to 10% of the cavity volume reduction caused by the operation of increasing the pressure applied to the cavity. The characteristics (transferability, birefringence, mechanical properties) required for the molded optical disc substrate are most balanced It was found to be in good condition.

In addition, the ejector pin 7 is retracted to the retracted position in accordance with the above-described operation of increasing the pressure applied to the cavity 4, and the control for increasing the volume of the resin pool at the center of the cavity is performed. If the pressure is increased, the internal pressure of the cavity is reduced, and the effect of the intended increase in the resin pressure in the cavity cannot be obtained.
The operation control of the ejector pin 7 is performed after confirming that the detected pressure value of the hydraulic system for pressurizing the pressure reaches the set pressure.

In the present invention, the molten resin 8 is slightly overfilled in the cavity 4 of the molding die 1 and the internal pressure of the filled resin is increased, and then the excess resin is absorbed into the resin pool. I have. For this purpose, it is necessary that the resin in the cavity, particularly the resin in the inner peripheral portion of the cavity and around the resin pool, has sufficient fluidity. Therefore, in the present invention, the temperature control setting of the inner peripheral portion of the cavity is set higher, and the chiller temperature control setting of the cut punch 6, which is usually set several tens degrees lower than the cavity temperature setting, is the same as the cavity temperature control setting. Temperature setting.

In the above-described process, the internal pressure of the resin reservoir initially starts rising immediately after the filling is started due to the filling pressure for filling the molten resin 8 into the cavity, and indicates the maximum pressure when the injection process is completed. And the ejector pin 7
The internal pressure suddenly decreases due to the operation of expanding the volume of the resin pool that retracts the resin to the retracted position. However, as described above, the internal pressure rises again due to the excess resin that has been excessively filled flowing into the resin pool and being filled. Indicates a peak. At the time of the second pressure peak, it is indicated that the resin was completely filled in the resin pool after the volume was increased. At this point, if the cut punch 6 was advanced to perform the gate cut, then the cavity was formed. The pressure that is continuously applied acts only to press the resin in the cavity serving as the optical disk substrate to have a predetermined shape, and also prevents the resin pool portion from being overfilled with the resin.

If the control operation performed in accordance with the pressure detection value of the corresponding hydraulic system of the molding apparatus for applying pressure to the cavity and the internal pressure detection value in the resin reservoir is performed over the entire operation described above, the present invention intends. It is possible to form an optical disk substrate that can reliably obtain the effect.

[0038]

As described above, according to the first aspect of the present invention, a molding apparatus for performing operation and control of filling of a molten resin and clamping of a mold using hydraulic pressure as a driving source is used, and the resin is filled. In the optical disk substrate molding method in which the pressure applied to the cavity is controlled in multiple stages, the pressure applied to the cavity is set small at the start of mold clamping, and the filling control system of the molding device switches from injection control to pressure holding control. The control to increase the pressure applied to the cavity immediately after the influence on the hydraulic system due to this disappears, so that the effect of controlling the pressure applied to the cavity in multiple stages is maximized, and at the same time it occurs in the drive hydraulic system of the molding device It is possible to avoid deterioration of substrate characteristics and variation in characteristics between substrates caused by the water hammer phenomenon.

According to a second aspect of the present invention, in the method of molding an optical disk substrate according to the first aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. Therefore, it is possible to obtain more effects associated with an increase in the internal pressure of the resin (over) filled in the cavity and to obtain an optical disk substrate having a predetermined shape.

According to a third aspect of the present invention, there is provided a mold for molding an optical disk substrate for molding an optical disk substrate according to the method of molding an optical disk substrate according to the second aspect of the present invention, wherein the molded sprue portion is located on the central axis of the mold. Since the ejector pin that performs the ejecting operation of the resin has a structure that is capable of retreating an appropriate amount from the normal setting position as well as the normal setting position when the molten resin is filled in the cavity and the ejecting operation position after molding, the resin filled in the cavity is Can be obtained with more effects obtained by increasing the internal pressure.

According to a fourth aspect of the present invention, an ejector pin is operated in an optical disk substrate molding apparatus for molding an optical disk substrate using the molding die according to the third aspect according to the molding method according to the second aspect. Since the component part has a structure capable of operating the ejector pin not only at the normal setting position and the protruding operation position but also at a position retracted by an appropriate amount from the normal setting position, the ejector pin is provided to the molding die. A molding apparatus having a configuration capable of operating the configuration can be provided, and the structure of a mold to be used can be simplified.

According to a fifth aspect of the present invention, in the method of molding an optical disk substrate according to the second aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. At this time, since the volume of the resin pool to be increased by the control is set to 5 to 10% of the cavity volume reduction amount due to the operation of increasing the pressure applied to the cavity, an appropriate size can be set for the volume of the resin pool, The effect associated with the rise in the internal pressure of the resin filled in the cavity can be maximized.

According to a sixth aspect of the present invention, in the method of molding an optical disk substrate according to the second aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. At this time, the operation of increasing the volume of the resin reservoir is performed immediately after the pressure applied to the cavity reaches the set value, so that the above control can be appropriately set, and the inside of the resin filled in the cavity can be set. The effect associated with the pressure rise can be maximized.

According to a seventh aspect of the present invention, in the optical disk substrate molding method according to the second aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. At this time, molding is performed so that the temperature of the mold mirror surface constituting the cavity is set so that the temperature becomes higher as the position is closer to the center of the cavity, so that the resin filled around the resin pool at the center of the cavity is formed. Fluidity can be maintained, and more effects obtained by the above control can be obtained.

According to an eighth aspect of the present invention, in the optical disk substrate molding method according to the seventh aspect, the chiller temperature control of the cut punch, which is a main portion forming the resin reservoir, is punched out by punching an inner hole of the optical disk substrate. Since the temperature setting is the same as the set temperature, the fluidity of the resin filled around the resin pool in the center of the cavity can be maintained, and the pressure in the center of the cavity can be adjusted to increase the pressure applied to the cavity. More effects can be obtained by controlling the volume of the resin pool to be larger.

According to a ninth aspect of the present invention, in the method of molding an optical disk substrate according to the second aspect, control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. At this time, since the gate cut operation is performed immediately after the pressure inside the resin pool shows the second maximum value, it is possible to perform an appropriate setting to increase the capacity of the resin pool, and the inside of the resin filled in the cavity can be set. The effect associated with the pressure rise can be maximized.

According to a tenth aspect of the present invention, the molding die described in the third aspect and the molding device described in the fourth aspect are used, and the molding die described in the first, second, fifth, sixth, seventh, eighth or ninth aspects is used. In the optical disk substrate molding method for molding an optical disk substrate in accordance with the molding method, the pressure applied to the cavity, the operation control of the cut punch and the ejector pin are controlled by the pressure detection value of the corresponding hydraulic system of the molding device for applying pressure to the cavity and the resin pool. , The pressure on the cavity and the operation control of the cut punch and the ejector pin can be optimally performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a switching timing of a set value of a mold clamping force and a detected value of a mold clamping pressure when switching from an injection process to a pressure holding process in an optical disk substrate molding method according to the present invention.

FIG. 2 is an explanatory view showing the outline of the configuration and operation of a molding die portion of the optical disk substrate molding apparatus according to the present invention.

FIG. 3 is an explanatory view showing an outline of a configuration and operation of a molding die portion of a conventional optical disk substrate molding apparatus.

FIG. 4 is a diagram showing a switching timing of a mold clamping force set value and a mold clamping pressure detection value when switching from an injection process to a pressure holding process according to a conventional method of molding an optical disc substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding mold 2 Movable mold 3 Fixed mold 4 Cavity 5 Sprue 6 Cut punch 7 Ejector pin 8 Molten resin

Claims (10)

[Claims] 1. An optical disc substrate for controlling the pressure applied to a cavity filled with a resin in a multi-stage using a molding device for performing operation and control of filling of a molten resin and clamping of a mold by using hydraulic pressure as a driving source. In the molding method, the pressure applied to the cavity is set small at the start of mold closing of the mold, and the cavity is controlled immediately after the influence on the hydraulic system due to the switching of the filling control system of the molding device from the injection control to the holding pressure control disappears. A method for forming an optical disk substrate, comprising: performing control to increase pressure applied to a substrate. 2. The optical disk substrate molding method according to claim 1, wherein control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. Substrate molding method. 3. An optical disk substrate molding die for molding an optical disk substrate according to the molding method according to claim 2, wherein an ejector pin on the central axis of the die for ejecting the formed sprue portion comprises: A mold for molding an optical disk substrate, having a structure capable of retreating by an appropriate amount from a normal set position as well as a normal set position and a protruding operation position after molding when filling a cavity with a molten resin. 4. An optical disk substrate molding apparatus for molding an optical disk substrate using the molding die according to claim 3 according to the molding method according to claim 2, wherein the component for operating the ejector pin includes the ejector pin. An optical disk substrate molding apparatus having a structure capable of operating not only a normal set position and a protruding operation position but also to a position retracted by an appropriate amount from the normal set position. 5. The method of molding an optical disk substrate according to claim 2, wherein the control for increasing the volume of the resin pool at the center of the cavity is performed in accordance with the operation of increasing the pressure applied to the cavity. A method for molding an optical disk substrate, wherein the volume of a resin reservoir to be increased is set to 5 to 10% of a cavity volume reduction amount due to an operation of increasing a pressure applied to a cavity. 6. The method of molding an optical disk substrate according to claim 2, wherein the control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. Characterized by performing the operation of increasing the volume of the optical disk immediately after the pressure applied to the cavity reaches the set value. 7. The method of molding an optical disk substrate according to claim 2, wherein the cavity is formed when the volume of the resin pool at the center of the cavity is controlled in accordance with the operation of increasing the pressure applied to the cavity. A method for forming an optical disk substrate, comprising: performing temperature control on a mirror surface of a mold to be formed so that the temperature increases as the position approaches the center of the cavity. 8. A method for molding an optical disk substrate according to claim 7, wherein the temperature of the chiller of the cut punch, which is a main part of the resin reservoir, is cut out by punching out an inner hole of the optical disk substrate and the temperature of the mirror surface is adjusted to the set temperature. A method for forming an optical disk substrate, comprising setting. 9. The method for molding an optical disk substrate according to claim 2, wherein the control is performed to increase the volume of the resin pool at the center of the cavity in accordance with the operation of increasing the pressure applied to the cavity. Pressure is 2
A molding method for an optical disc substrate, wherein a gate cut operation is performed immediately after the second maximum value is shown. 10. The molding die according to claim 3, and claim 4.
The molding apparatus according to claim 1, wherein the molding apparatus is used.
Alternatively, in the method of molding an optical disk substrate according to the molding method described in 9, the pressurization of the cavity, the operation control of the cut punch and the ejector pin are controlled by detecting the pressure of the corresponding hydraulic system of the molding apparatus for applying pressure to the cavity. A method for molding an optical disk substrate, wherein the method is performed in accordance with a value and a detected internal pressure value in a resin reservoir.