JPH08276479A - Molding of disk substrate - Google Patents

Abstract

PURPOSE: To obtain a good double refractive index and to shorten a molding cycle time in molding a disk substrate enhanced in mechanical characteristics. CONSTITUTION: The movable mold and fixed mold of a mold for a disk substrate are respectively attached to the movable plate and fixed plate of a molding machine and, when the movable mold is moved toward the fixed mold so as to leave a predetermined distance of 0-0.5mm by mold clamping operation moving the movable plate through a mold clamping cylinder, injection filling is started and, at the time of the completion of mold clamping, the oil pressure applied to the mold clamping side of the mold clamping cylinder is adjusted to hold mold clamping force to the predetermined value corresponding to about 10-40% of rated mold clamping force. After the completion of the injection process, mold clamping oil pressure is raised to perform not only the control of mold clamping force of one stage or a plurality of stages but also a molten resin cooling process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a disc substrate having an improved structure, and more particularly to a disc substrate having an improved quality, particularly for producing an optical disc stably and with good moldability. The present invention relates to a method for molding a disc substrate.

[0002]

2. Description of the Related Art Conventionally, there are two methods for molding a disk, an injection molding method and an injection compression molding method. In one injection molding method, the movable platen is moved to open and close the mold with the fixed plate, and the molten resin material is melted into the product cavity while the mold is clamped with a larger force. After injection and filling, the resin material is solidified after a predetermined cooling time, the mold is opened, and the molded product is taken out.

In this injection molding method, a mold clamping force is required so that the mold does not open even when the mold is filled with the resin material. When molding the disk substrate, for example,
A disk substrate with a diameter of 120 mm requires a clamping force of 40 tons or more, and a disk substrate with a diameter of 300 mm has a clamping force of 200 tons.
Mold clamping force of ton or more is required. Further, in order to produce a better product, for example, after completion of the mold closing operation, after increasing the pressure and maintaining the mold clamping holding pressure, injection filling, injection holding pressure, and cooling are performed. It is designed to perform a series of molding cycles. Further, the mold clamping holding pressure is controlled by increasing and decreasing the first mold clamping pressure, the second mold clamping pressure, and the multi-stage (3 to n times) mold clamping pressure by setting a plurality of timers.

In such a conventional injection molding method,
When manufacturing a thin product such as a CD disc, the molding conditions are narrow, and the large mold clamping pressure is applied during injection as described above. It is difficult to reduce the birefringence, there are large variations in the quality of the products, and the yield is low.

Further, a method of injecting with a high injection pressure has been adopted in order to fill the resin into the narrow cavity, but the pressure distribution of the molten resin cannot be made uniform and the molded disk substrate In many cases, pressure fringes are formed on the peripheral portion, and the quality of the product due to the pressure difference varies between the inner peripheral side and the outer peripheral side, and in particular, the birefringence of the product is ± 100 nm or more. For this reason, a method of increasing the fluidity of the resin and injecting it by increasing the mold temperature and the resin temperature has been adopted. However, since the mold temperature is close to the heat deformation temperature of the resin, the product is twisted. It deforms and cannot function as a disc.

As described above, in the molding of the disc substrate, as an important item, it is required to improve the mechanical properties such as transfer, birefringence, warpage and flatness, but it is thin like the disc substrate and has a large projected area. In large molding, it is difficult to satisfy all of these characteristics. Moreover, the applicability of the disk substrate will be expanded in the future, the specification value will be strict, and the current 1.2 mm thickness will be further thinned in the future. In the current situation where the use of two sheets of 0.6 mm thickness bonded together is being considered, in the conventional molding method, products that meet the required specifications should be manufactured by normal injection molding. Is limited.

In the other injection compression molding method, in consideration of shrinkage due to cooling and solidification of the resin material, the mold is opened for a predetermined compression stroke,
Inject and fill the resin material in the product cavity, then
By reducing the birefringence due to the residual stress, the mold is pressed to compress the resin material.

However, in this case, a device for opening the mold by the compression stroke is required, the price of the molding machine becomes expensive, and the cycle time of the molded product becomes long due to its operating time, and the production efficiency is accordingly increased. There is a problem in that

For this reason, in the injection compression molding machine described in Japanese Patent Publication No. 3-12530, the resin material is injected and filled in the cavity with the mold closed by the first hydraulic cylinder. At the time when the injection pressure of the resin material acts on the movable plate, the push-back means including the second hydraulic cylinder for pushing back the movable plate is actuated, and the mold opening force by the injection pressure and the push-back of the push-back means are pushed back. By the action of the force, the movable plate is pushed back in the direction of separating from the fixed plate against the mold closing force of the first hydraulic cylinder, the mold is opened by a predetermined distance, and the volume of the product cavity is increased. At the same time, the product cavity is further filled with a resin material.

In this molding method, it is not necessary to open the mold prior to the injection of the resin material, and the resin material can be injected immediately after the mold is closed by the first hydraulic cylinder. Since the mold is clamped after the resin has been filled by opening the specified compression stroke, the cycle time that is substantially the same as that of injection compression molding is required. Since it is necessary to provide the second hydraulic cylinder and the pair of separating devices on the side, it is not possible to satisfy the manufacturing of the disk substrate molded in a unit cycle of about 5 to 6 seconds.

Further, Japanese Patent Publication No. 19774/1990 discloses that
A resin material is injected into the product cavity by the injection primary pressure that causes a mold opening force that is slightly larger than the mold clamping force to act on the movable mold, and the amount of resin required to form the target disk substrate is adjusted to the product cavity. When the resin is injected into the mold, the injection pressure is switched to the injection secondary pressure, where the mold opening force that acts on the movable mold becomes smaller than the mold clamping force. In addition to filling the cavity, the gas in the product cavity pushed out by the filling is discharged from the gap between the inner surface of the stamper pressing member and the stepped rising wall of the fixed mold. There is proposed an injection molding method for a disk substrate, which is characterized by the following.

[0012]

However, the conventional molding method is a method of controlling the mold clamping pressure by increasing the mold clamping pressure to a certain pressure after the completion of the mold closing and controlling the mold clamping pressure. In molding, the method is to increase or decrease the mold clamping pressure while applying the injection holding pressure after injection filling, so that it is affected by the pressure fluctuation and the control accuracy of the pressure control valve of the hydraulic circuit.

Further, in the invention according to the above publication,
It is necessary to precisely control the pressure control, and it may be difficult to adjust the pressure balance between the injection primary pressure and the secondary pressure as the mold opening force and the mold clamping force.

Therefore, in such a molding method, it is difficult to control the injection pressure, and in molding a substrate as thin as a disc having a plate thickness of 0.6 mm, in order to keep the birefringence within the specified value, the mold temperature is set to that of the resin. It is necessary to set the temperature near the heat distortion temperature (120 ° C. or higher for polycarbonate resin) and to take a long cooling time. However, even in this case, the birefringence of the finished molded product is limited to the range of 60 to 80 nm by double pass, and the tilt of the product (small warp of the laser light incident / reflected portion of the substrate) etc. The mechanical characteristics of swell well beyond the standard value. Further, in disk molding, the standards for high-density disks are becoming more stringent in the future.

In view of the above circumstances, an object of the present invention is to provide a method for molding a disk substrate which can obtain good birefringence without maintaining the temperatures of the resin and the mold at high temperatures. Another object of the present invention is to provide a method for manufacturing a disk substrate having a shortened molding cycle time and improved mechanical properties.

[0016]

In order to achieve the above-mentioned object, a method of molding a disk substrate according to a first aspect of the present invention is such that a movable plate and a fixed plate of a molding machine have a movable mold for a disk substrate mold. And the fixed mold are respectively attached, and the movable mold is moved to a predetermined distance of 0 to 0.5 mm with respect to the fixed mold by a mold closing operation of moving the movable plate through a mold clamping cylinder. At this time, the injection of the molten resin filled in the cavity of the disk substrate mold is started from the nozzle of the injection device, and it is detected that the movable mold is in contact with the fixed mold, and the mold clamping is performed. The hydraulic pressure supplied to the mold clamping side of the cylinder is adjusted so that the mold clamping force is maintained at a predetermined value corresponding to approximately 10 to 40% of the rated mold clamping force. Increase the hydraulic pressure supplied to the mold clamping side to 1
It is characterized in that the mold clamping pressure control is performed in multiple stages or a plurality of stages, and the step of cooling the molten resin in the cavity is performed.

According to the second aspect of the present invention, the mold clamping device in which the booster ram is added to the mold clamping cylinder is used to limit the mold clamping force by the booster ram alone to the lower limit, and further the adjusting hydraulic pressure supplied to the mold clamping cylinder is used. The upper limit of the added mold clamping force is set to a value corresponding to approximately 40% of the rated mold clamping force, and the predetermined mold clamping force within the set range is maintained.

Further, in the structure of claim 3, at the time of injection filling, the screw in the heating cylinder of the injection device is
It is characterized by advancing to the movable limit and eliminating the cushion amount of the molten resin and injecting a fixed amount of the molten resin.

[0019]

According to the present invention, immediately before the completion of the mold closing operation in which the mold clamping force has not been applied yet, or when the mold closing is completed, that is, the predetermined opening amount of the mold reaches the predetermined value of 0 to 0.5 mm. At this time, the injection process is started and the cavity is filled with the molten resin.

As a result, the mold clamping force is not acting at the start of the injection, and further, based on the signal detected that the movable mold has come into contact with the fixed mold during the operation of the subsequent injection process. The mold clamping force is maintained at a predetermined value that corresponds to approximately 10 to 40% of the rated mold clamping force, and is further increased to a predetermined mold clamping pressure after the injection process is completed.

As a result, at the time of injection filling, a uniform pressure distribution is applied to the molten resin in the cavity, so that the resulting product has good birefringence. In this case, the fluidity of the molten resin in the cavity is not suppressed by the extremely low mold clamping pressure, there is no need to increase the mold temperature and the resin temperature, and the product has a thickness of 0.6 mm. Also, the internal strain of the product is relieved.

Further, during injection filling, the mold clamping force has a predetermined value corresponding to approximately 10 to 40% of the rated mold clamping force. Therefore, the mold clamping force and the injection pressure balance to the movable limit. Since it is possible to move the resin forward, and the amount of resin cushion is eliminated, the injection amount filled in the cavity is reliably measured, so that the opening amount of the mold can be stabilized.

[0023]

EXAMPLES Before explaining examples of the molding method of the present invention,
The structure of a conventional disk mold using this molding method and a molding machine for mounting the mold will be briefly described with reference to FIGS. 1 to 3.

As shown in FIG. 1, a disc mold for producing an optical disc such as a video disc and a compact disc has a predetermined stamper inside a product cavity 3 formed by a movable mold 1 and a fixed mold 2. 4 are arranged, and the inner peripheral edge and the outer peripheral edge of the stamper 4 are fixed by the stamper pressing rings 5 and 6, respectively. Further, spiral pits or concentric pits are formed on the surface 4a of the stamper in order to transfer the recorded information data to the disc.

Also, the stamper 4 into the cavity 3 is
Is usually attached to the inner periphery of a doughnut-shaped stamper by means of an appropriate fixing means.
Is fixed to the outer peripheral edge portion by a stamper pressing ring 6 as shown in FIG.
When a predetermined resin material is filled in the cavity between the mirror surface plate 7 of the fixed mold 2 and the stamper surface 4a, a gas releasing portion 8 for discharging the gas in the cavity pushed out to the outside is provided. The presser foot angle α is about 7 ° and the presser foot is formed with a predetermined gap.

In the mold used in the molding method of the present invention, it is preferable that the angle α of the stamper pressing ring of the stamper pressing ring provided on the outer peripheral edge of the stamper be used as a measure for degassing when the molten resin is filled in the cavity. 1) refer to the conventional 7
The device has been devised to change from ° to 3.5 °, which makes it possible to suppress the occurrence of burrs.

FIG. 2 is a basic mechanical view of a mold clamping device and a heating cylinder in a conventional molding machine used for carrying out this method, and FIG. 3 is a sectional view showing the structure of another mold clamping device. is there.

In FIG. 2, the mold clamping device of the injection molding machine is
A fixed platen 10 is attached to the front end of the tie bar 9, a mold clamping cylinder 11 is fixed to the rear end of the tie bar, and a movable platen that slides on the tie bar by a mold clamping ram 12 of the mold clamping cylinder 11 driven by hydraulic pressure. The movable mold 1 is attached to the movable platen 13, and the fixed mold 2 is attached to the fixed platen 10.

A servo valve 41 is provided in a pipe line connecting the hydraulic pressure source 40 and the port 14a of the mold clamping cylinder to supply the mold clamping hydraulic pressure to the mold clamping device. This servo valve 41 is driven by feedback control by a closed loop, and compares the hydraulic pressure set value set in the mold clamping force setting device 42 with the feedback signal of the pressure detector 43 that detects the hydraulic pressure of the mold clamping cylinder 11. The circuit configuration is provided in which the difference signal is compared by the device 44, the PID calculation is performed by the amplifier 45, the current signal is converted into the current signal, and the current signal is output.

By the operation of the servo valve 41, a mold clamping operation is performed, and hydraulic pressure from a hydraulic pressure supply device (not shown) is supplied to the port 14b of the mold clamping cylinder 11,
The mold clamping ram 12 is retracted to perform the mold opening operation of the mold.

On the other hand, in the injection device, the screw 16 is arranged in the heating cylinder 15, and a predetermined amount of resin is supplied to the screw front end portion 16a side while kneading the molten resin to retract the screw 16 and fix the fixed mold. The molten resin is injected and filled into the cavity of the mold through the nozzle 17 that is abutted against the front surface of the sprue bush.

Another mold clamping device shown in FIG. 3 is a mold clamping device in which a mold clamping cylinder 20 is provided with a booster ram 21, and the mold clamping ram 2 connected to the movable platen 13 is connected to the mold clamping cylinder 20.
2 is slidably arranged and the booster ram 21
One end side of the booster ram 21 is inserted into the center hole of the mold clamping ram 22 and the other end side is protruded from the rear part of the mold clamping cylinder 20, so that the rear end part of the booster ram 21 is separated from the hydraulic pressure supplied into the mold clamping cylinder. The hydraulic pressure is supplied from the port 23 to press the mold clamping ram 22, and the movable platen 13 is closed at high speed.

Also in this booster ram type mold clamping device, feedback control by the above-mentioned servo valve 41 is performed. That is, port 2 of booster ram 21
3 is connected to a pipeline connected to a hydraulic pressure source 24, a rear port 25 of the mold clamping ram 22 in the mold clamping cylinder 20 communicates with a tank via a check valve 26, and the pipeline from the hydraulic power source 24 is connected to the mold. A servo valve 41 is arranged in a pipe line connecting the mold clamping port 27 of the clamping cylinder 20, and the servo valve 41 detects the hydraulic pressure set value from the mold clamping force setting device 42 and the mold clamping cylinder hydraulic pressure of the port 27. The signal from the comparator 43 is compared, and the difference signal is controlled in a closed loop by a current signal obtained through an amplifier 45 which performs a PID operation.

Although the mold clamping device as described above is used in this embodiment, other types such as a side cylinder type mold clamping device, a pressure boosting cylinder type mold clamping device and the like can be used. . Further, an optimum product is obtained by performing feedback control by a servo valve for controlling the mold clamping device, but a conventional electromagnetic relief valve can also be used.

Next, using the above-mentioned mold and molding machine,
The molding method of the present invention will be described. FIG. 4 is an operational procedure step diagram for explaining a process of a method for molding a disk substrate according to an embodiment of the present invention.

The molding of the disk substrate is carried out by the first step of the present invention in which the movable mold 1 and the fixed mold 2 of the mold for the disk substrate are mounted at predetermined positions on the movable platen 13 and the fixed platen 10 of the injection molding machine, respectively. It starts with some preparatory work.

In this preparatory work, when the mold is closed and brought into close contact, the limit switch or the position detection means described later is used to adjust the mold closing position for determining the mold closing operation completion position and the like. In order to preheat the molten resin in the heating cylinder 15 to a set temperature and maintain the mold at a predetermined mold temperature, the temperature and pressure of the operation panel and the temperature of the mold temperature controller are set. Includes management.

After such a preparatory work, FIG. 4 and FIG.
As shown in, the mold closing operation and the injection filling, which are the second and third steps of the present invention, are performed. That is, in the second step, the hydraulic pressure is supplied to the mold clamping cylinder 11 to move the movable platen 13 in the direction of approaching the fixed platen 10 to advance the mold closing operation for combining the movable mold 1 and the fixed mold 2. Immediately before the completion of the mold closing low speed following the mold closing high speed, or the mold closing operation position where the mold clamping force is not yet exerted when the mold closing is completed, that is, the movable mold is set to 0 to 0.5 mm in advance with respect to the fixed mold. Move it to the specified distance. Then, in the third step, an injection step of injecting and filling a fixed amount of molten resin from the nozzle 17 of the injection device into the cavity of the disk substrate mold by the screw 16 in the heating cylinder is started.

Therefore, in the second step, when the mold closing operation completion position is set to 0, the predetermined scale position immediately before that is 0 to 0.5 mm, and the opening amount of the mold is 0 to 0.
This corresponds to the range of 0.5 mm. And
As shown in FIG. 2, the scale position is detected by the sensor 30, and the detection signal is sent to the control device of the molding machine through the amplifier as the position setting comparison device 31. This facilitates the position control of the opening amount of the mold. In the embodiment of the present invention, the scale position is
A position of 0.15 mm to 0.2 mm is desirable.

Such position detecting means is, for example, a magnetic length measuring device (trade name: Sony Magnescale) including the above-described sensor 30, amplifier 31, and scale 32,
Alternatively, an encoder, potentiometer, or the like can be used.

Here, the start of injection filling in the third step occurs when the movable mold moves to the fixed mold to the above-mentioned predetermined distance (scale position),
As in the present embodiment, it is possible to perform injection during the mold closing operation, or to operate when the mold closing operation is completed. Furthermore, the injection and filling of the molten resin may be performed after the completion of the time measurement of the injection start timer that measures the time from the time when the movable mold and the fixed mold contact each other.

In particular, what is important in the present invention is to start the injection filling at the time when the regular mold clamping force does not act. During the injection process, the mold clamping force is approximately 10 to 4 of the rated mold clamping force.
That is, it is in the state of the fourth step, which is a predetermined value corresponding to 0%. The lower limit (10%) and the upper limit (40%) in the defined numerical range each include an error of ± several%.

This mold clamping force is approximately 10 to 40% of the rated mold clamping force.
The reason why molding is possible is that the average resin pressure in the mold cavity is 100 to 200k in conventional injection compression molding.
While this mold clamping force was set so that the mold was opened at g / cm ² , in the present invention, the mold clamping force was kept low and the average resin pressure in the mold cavity was 100 kg / cm ² or less. This is because injection is possible.

In the fourth step, the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder is adjusted to maintain the mold clamping force at a predetermined value corresponding to approximately 10 to 40% of the rated mold clamping force. The method will be described below.

When a hydraulic pressure of 140 kg / cm ² is applied to the mold clamping cylinder of the molding machine used in the method of the present invention,
The rated mold clamping force is 25 tons when calculated. Therefore, in a molding machine with a rated mold clamping force of 25 tons, 40% of the rated mold clamping force is 10 tons, and the supplied hydraulic pressure in this case is 1 ton.
40 × 0.4 = 56 kg / cm ² . Also, 10%
In order to set the mold clamping force of, the mold clamping force is 2.5 tons, and the supply hydraulic pressure in this case is 140 × 0.1 = 14 kg /
It becomes cm ² . In this way, by simply adjusting the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder, the mold clamping force is maintained at a predetermined value within a setting range corresponding to approximately 10 to 40% of the rated mold clamping force. can do.

In the fourth step, as shown in FIG. 4, the first timer operates when the movable mold comes into contact with the fixed mold, that is, when the mold closing is completed. When the mold closing is completed, the control valve of the supply hydraulic circuit is activated based on the signal that the position detecting means detects that the movable mold is in contact with the fixed mold. And after a lapse of a predetermined time determined by the influence of the oil temperature, the mold clamping force is approximately 10 to 40% of the rated mold clamping force via the mold clamping cylinder.
A predetermined state corresponding to Then, the mold clamping force is maintained while the first timer is timing, and the process of injection filling and injection holding pressure of the molten resin in the third step is completed within the operation time of the first timer.

Further, in the present embodiment, after the injection filling is started, the mold clamping force is set to a predetermined state corresponding to approximately 10 to 40% of the rated mold clamping force. When the mold and the fixed mold contact each other, that is, when the mold closing is completed, an injection start timer (not shown) is activated to keep the mold clamping pressure at a predetermined value for a predetermined set time (for example, 0.1 seconds). It is also possible to wait until the value reaches the set value of, and then perform the injection filling after the completion of the timing of this timer.

In this case, as shown in FIG. 3, the mold clamping ram 2
In the mold clamping device having the type 2 and the booster ram 21, the hydraulic pressure supplied to the main mold clamping cylinder 20 is supplied from the servo valve 41, and the maximum supplied hydraulic pressure is supplied to the booster ram 21. In this embodiment, when the cylinder area of the hydraulic pressure applied to the booster ram 21 is approximately 10% or less of the cylinder area of the hydraulic pressure applied to the mold clamping ram 22 and the hydraulic pressure of 140 kg / cm ² is applied to the booster ram, about 2. The mold clamping force is 27 tons, and the servo valve 4
If the hydraulic pressure of 48 kg / cm ² is applied to the mold clamping cylinder 20 by 1, the total mold clamping force of the booster ram 21 and the mold clamping ram 22 can be set to 10 tons, and the booster ram 21 and the mold clamping ram 22 can be combined. Hydraulic pressure supply to one or both,
That is, the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder can be adjusted to set the mold clamping force in a range corresponding to approximately 10 to 40%.

While the mold is being closed by the booster ram 21 shown in FIG. 3, the working oil from the tank is sucked into the mold clamping cylinder 20 from the port 25 via the check valve 26. When the mold closing operation is completed, the hydraulic oil to the mold clamping cylinder 20 is supplied from the mold clamping port 27 via the servo valve 41 and controlled by the closed loop feedback control system.

In this way, according to the present invention, it is possible to maintain the mold clamping force at a low pressure within the range corresponding to approximately 10 to 40% of the rated mold clamping force by adjusting the supplied hydraulic pressure until the end of the injection process.

The fourth step described above ends when the first timer times out, and the next fifth step is started. That is, after the first timer has timed, the second timer operates to start the pressure increasing step, and the mold clamping hydraulic pressure is increased to perform the first mold clamping. In addition, a cooling process that starts after the end of the injection process including the injection holding pressure process that is completed at the same time as or before the operation of the second timer is started.

Further, preferably, during each timing of the third to nth timers following the timing operation of the second timer, the mold clamping force control of one step or a plurality of steps is performed, and the molten resin in the cavity is cooled. It is designed to carry out the process. By this cooling step, the information on the stamper surface 4a (see FIG. 1) exposed on one side of the cavity is transferred to the resin material to be solidified to mold the disk substrate.

In this embodiment, the screw 16 in the heating cylinder at the time of injection filling is mechanically movable, that is, the screw tip portion 16a projects into the nozzle inner end portion 17a (see FIG. 2) with a minute gap. It moves forward until it loses the cushion amount of the molten resin by being applied. For this reason, if a larger amount of resin is injected into the cavity of the mold, the mold will open more, and the amount of opening will be adjusted by the injection stroke. Here, the opening amount of the injection-filled mold is 0.5 mm or less, preferably 0.15 to 0.
A certain amount of molten resin is injected so that the length becomes 2 mm.

Next, the cooling step for solidifying the resin is as follows.
The process is started when the injection filling is completed, and the mold clamping process is started after the completion of the timing of the first timer. Usually, about 0.2 seconds after injection filling, the mold clamping process is started simultaneously with the cooling process. In the mold clamping process, the mold clamping pressure is initially increased, and the first mold clamping pressure is maintained during the set time of the second timer. Next, at the set time of the third timer, the set pressure is made lower than the first mold clamping pressure, and the second mold clamping operation is performed. Further, the fourth to n-th timers can be used to continue the multi-stage third to n-th mold clamping operations.

In this embodiment, as shown in FIG. 5, the first mold clamping hydraulic pressure is 110 kg / cm ² , and the second mold clamping hydraulic pressure is
It is set to 60 kg / cm ² and is a two-stage mold clamping operation. The mold clamping pressure is 140 kg / cm ² and the mold clamping force is 25 tons. Also, the set time of the timer is 0.3 seconds for the first timer, 1.6 seconds for the second timer, and 1.0 for the third timer.
Seconds.

Further, when the die position reaches 0.2 mm, the injection is started and the mold clamping force at the time of injection is about 10 and the injection speed of the injection device for injecting the molten resin under the condition that the mold clamping force is about 10%. And the injection pressure is shown at the bottom of FIG.
The injection speed is 4 steps and the injection pressure is 3 steps. The injection velocities V ₁ , V ₂ and V _{3 at the} injection primary pressure P ₁ are
It is set to be the maximum speed (maximum speed at 99%),
V ₄ is set to 14% of this maximum speed, and is further set to 13% of the maximum speed for injection holding pressures P ₂ and P ₃ .

Further, the injection primary pressure P ₁ and the injection holding pressure P
₂ and P ₃ , the pressure set value is maintained at the maximum state where the set value is the maximum value from the beginning to the end, and the set times are set to 0.16 seconds, 0 seconds, and 0.02 seconds respectively. P
Injection pressure by eliminating the _second injection secondary pressure is to perform a two-stage. The setting conditions are that the resin material is a polycarbonate resin, the mold temperature is 115 degrees, and the mold opening amount of the injection-filled mold is 0.15 mm to 0.2 mm.

With such a structure, the conventional mold clamping hydraulic pressure is controlled by the electromagnetic relief valve having poor repeatability, so that a slight difference in the mold clamping force affects the quality. Uses a servo valve that has a high repeatability in terms of mechanism and controls in a closed loop to obtain a low mold clamping force, so it is possible to obtain a disc molded product of extremely stable quality regardless of the disc thickness. .

This low pressure mold clamping force is about 1 as described above.
The birefringence data (curve A) obtained by molding at a mold clamping force of 2.27 tons, which is 0 ton or less, was very good as compared with the conventional molding method, as shown in FIG. .

FIG. 6 shows that the plate thickness of the disk is 0.6 mm,
6 is a plot of measurement data of birefringence in the present invention and the conventional molding method when the diameter is 120 mm. Curve A is the case of the present invention, and the condition is that the mold temperature is 10
0 to 110 ° C., molding cycle 3.5 seconds, no deformation, and curve B is the case of conventional injection molding under the conditions:
Mold temperature 140 ℃, molding cycle 15.0 seconds, deformation,
Curve C is the case of injection compression molding, and the conditions are mold temperature 1
30 ℃, molding cycle 15.0 seconds, slightly deformed,
Data was obtained.

According to this molding method of the present invention, a good disk molded product was obtained when the movable mold was opened 0.15 mm to 0.2 mm against the injected resin pressure. Further, in the curve A, the birefringence is deviated in the negative direction at both ends, which is
It shows that the resin is sufficiently filled up to the tip in the cavity, which proves that the mechanical properties such as warpage, flatness and strength related to the shape of the disk molded product are excellent. .

FIG. 7 and FIG. 8 show the results of measuring the warpage characteristics by the conventional molding and the molding of this embodiment. In the conventional example of FIG. 7, the mold clamping force during injection is 50%. The warp angle is − at the disk radial position of 20 to 40 mm.
It fluctuates in the range of 1 ° to + 1.5 °. On the other hand, in the present embodiment shown in FIG. 8, the injection start mold clamping force at the time of closely contacting the mold is set to 10%, and its warpage characteristic is almost the same at the disk radial position as in the case of conventional molding. It has been shown that there is no change.

From these results, it is inferred that it is appropriate to set the mold clamping force to approximately 10 to 40% of the rated mold clamping force. The mold clamping force is the packing of the mold clamping ram. Since it also changes depending on the resistance of the mold, it is difficult to quantitatively determine the numerical range of the mold clamping force applied to the actual mold.

In this embodiment, if the mold clamping force is less than 2.27 tons (about 9% of the rated mold clamping force) when only the booster ram acts, the mold opening amount becomes too large. Since it is pressed and crushed by the mold clamping after the injection step, the deviation of the bit transferred by the stamper becomes large and the so-called transferability deteriorates. On the contrary, if the mold clamping force at the time of injection is large, the mold opening amount is small, the effect of compression molding cannot be obtained, and the birefringence becomes large.

The mold closing position is detected by the limit switch, the proximity switch, etc., for starting the injection and for contacting the mold, and for the encoder, potentiometer, magnetic detector, etc., for the start of the injection. It can be configured to include a die contacting part and a die opening / closing speed switching position.

Furthermore, although it was preferable in the embodiment to perform injection without a cushion, conventional molding with a cushion, that is, the injection holding pressure of P ₂ and P ₃ is made as low as possible to switch from filling to injection holding pressure. At the screw position,
It is also possible to provide an unpressed part.

As described above, according to the embodiment of the present invention, when the mold clamping force corresponds to approximately 10 to 40% of the rated mold clamping force,
By injection-filling, and by pushing the screw down to eliminate the cushion amount of the molten resin in the heating cylinder, it is not necessary to control the cushion amount by the pressure control of the injection device, making the injection amount extremely stable. Since it is possible to operate the pressure control valve for lowering the injection holding pressures P ₂ and P ₃ , it is possible to maintain the maximum scale of the pressure setter from the beginning to the end of the injection pressure, and the accuracy of the pressure control valve can be improved. It is possible to highly accurately inject and fill a fixed amount without depending on, and it is possible to deal with it only by changing the injection speed.

Further, according to the embodiment of the present invention, since the injection filling can be started before the completion of the mold closing operation, the cycle time can be shortened accordingly, and the cooling time of the molding cycle is As is clear from 5, 0.2 seconds + 1.6
Seconds + 1.0 seconds = 2.8 seconds, which is at least 7 seconds in the past to obtain equivalent molded products, which is a reduction.

[0069]

As is apparent from the above description,
According to the disk substrate molding method of the present invention, an ultra-thin disk can obtain good birefringence at a mold temperature considerably lower than the heat distortion temperature of the resin, and the transfer and mechanical characteristics also clear the standard, The variation between shots can also be improved much more than before. Further, regarding the molding cycle, according to the present invention, it becomes possible to start the injection during the mold closing operation, and the cooling time can be shortened due to the action of the low-pressure mold clamping force and the decrease of the resin pressure at the time of injection. Therefore, the entire molding cycle can be further shortened.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a disk mold used in a molding method according to the present invention.

FIG. 2 is a configuration diagram showing a main part of a molding machine for carrying out the molding method of the present invention.

FIG. 3 is a configuration diagram showing a main part of another mold clamping device.

FIG. 4 is an operational process diagram showing a method of molding a disk substrate according to the present invention.

5 is an operation state diagram showing set values of pressure and speed over time of the mold clamping operation and the injection operation in the method of molding a disc substrate according to FIG.

FIG. 6 is a graph chart in which measurement data obtained by the molding method of the present invention and two molding methods of a conventional example are plotted.

FIG. 7 is a diagram showing a warp characteristic by conventional molding.

FIG. 8 is a diagram showing a warp characteristic by molding in an example of the present invention.

[Explanation of symbols]

 1 movable mold 2 fixed mold 3 cavity 10 fixed plate 11,20 mold clamping cylinder 12,22 mold clamping ram 13 movable plate 14a, 14b port 15 heating cylinder 16 screw 17 nozzle 21 booster ram 23, 25, 27 port 24, 40 Hydraulic power source 26 Check valve 30 Sensor 31 Position setting comparison device 32 Scale 41 Servo valve 42 Mold clamping force setter 43 Pressure detector 44 Comparator 45 Amplifier

Claims (4)

[Claims] 1. A movable platen and a fixed platen of a molding machine are respectively mounted with a movable platen mold and a fixed platen mold, and the movable platen is moved through a mold clamping cylinder to perform the mold closing operation. The movable mold is 0 to 0.5 mm relative to the fixed mold
Of the injection device, injection of the molten resin filled in the cavity of the disk substrate mold was started when the nozzle moved to the movable mold, and the movable mold contacted the fixed mold. Is detected and the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder is adjusted to maintain the mold clamping force at a predetermined value corresponding to approximately 10 to 40% of the rated mold clamping force, After the process is completed, the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder is increased to control the mold clamping pressure in one or more stages, and to cool the molten resin in the cavity. A characteristic method of forming a disk substrate. 2. A movable platen and a fixed platen of a molding machine are mounted with a movable platen mold and a fixed platen mold, respectively, and the movable platen is moved by a mold closing operation for moving the movable platen via a booster ram. The mold is 0 to 0.5m relative to the fixed mold
When moving to a predetermined distance of m, injection of the molten resin filled in the cavity of the disk substrate mold is started from the nozzle of the injection device, and the movable mold contacts the fixed mold. It is detected that the mold clamping force by the booster ram alone is set as the lower limit, and the upper limit mold clamping force obtained by adding the adjusting hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder is approximately 40% of the rated mold clamping force. To maintain a predetermined mold clamping force within a set range that is a value equivalent to, and to increase the hydraulic pressure supplied to the mold clamping side of the mold clamping cylinder after the injection process is completed to increase the pressure in one or more stages. A method of molding a disk substrate, characterized in that a tightening pressure control is performed and a step of cooling the molten resin in the cavity is performed. 3. At the time of injection filling, the screw in the heating cylinder in the injection device advances to the movable limit thereof, eliminates the cushion amount of the molten resin, and injects a fixed amount of the molten resin. Item 1. A method for molding a disk substrate according to item 1 or 2. 4. The method of molding a disk substrate according to claim 1, wherein the means for adjusting the hydraulic pressure of the mold clamping cylinder is a servo valve.