JP2000207788A - Mold release method of optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold release method of an optical disk substrate that can avoid an adverse influence due to nonuniform air blow without adding any special mechanism to a die and a molding machine to be used. SOLUTION: In a method for releasing an optical disk substrate that is formed through a filling process for filling the cavity of a die with fused resin, and a cooling process for cooling the filled resin, a mechanical mold release process for mechanically releasing the optical disk substrate where the molding has been completed from the die is optimally combined with an air blow mold release process using air blow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for releasing an optical disk substrate, and more particularly, to a technology for molding a DVD or an optical disk having a larger capacity.

[0002]

2. Description of the Related Art Various types of optical disks, such as a CD system and an MO system, have been used in various types for reading only, additional recording, and rewriting. Meanwhile, 1
It has become necessary to mount a larger amount of information on a single optical disc.
Efforts are being made for a new optical disk having information of a large capacity equal to or larger than VD. What is required for an optical disk substrate by increasing the capacity of such optical disks is to make the substrate thickness thinner (for example, the DVD-based substrate thickness is 1.2 mm compared to the conventional CD / MO-based optical disk substrate thickness of 1.2 mm). 0.6 mm), and to more precisely transfer a pit row or a guide groove for tracking a pickup on the substrate, which means information. Substrates used for such optical discs are molded and produced by injection molding or injection compression molding using a resin mainly composed of polycarbonate in view of production efficiency and cost.

In each of the above-mentioned methods of molding an optical disk substrate, a mold is closed or a cavity is filled with a molten resin material. Then, at a temperature at which the resin can be taken out of the mold, the required resin is cooled and solidified in the mold to form a predetermined substrate shape. Note that, in the above-described cavity, a stamper in which information necessary for the optical disc is engraved as a pit row or a guide groove is set, and during the process of filling the above-described molten resin into the cavity and solidifying it, The necessary information engraved on the stamper is transferred onto the optical disk substrate to be molded.

[0004] After the cooling step in the mold is completed, the optical disc substrate molded in the mold is taken out of the mold and transferred to the next step after molding.

In order to take out the molded optical disk substrate from the mold after the completion of the cooling step, first, at an appropriate timing before and after the completion of the cooling step, the optical disk substrate is formed on the inner periphery of each of the fixed / movable molds. A mold release air blow blows out from the air slit, and the optical disk substrate is released from the mold using the air pressure. In particular, at the start of the mold opening operation (movable retreat operation) after the completion of the cooling step, the substrate must be completely released from the fixed mold. Then, in the mold opening step after the cooling step, the optical disk substrate is supported by the movable mold and retreats to the mold retreat limit according to the movable mold retreating operation (mold opening operation). Subsequently, the optical disk substrate supported by the movable mold and retracted to the mold retreat limit is mechanically released from the ejector mechanism formed on the inner periphery of the movable mold at the retreat limit position by the protrusion of the ejector mechanism and the movable mold described above. It is completely released from the movable mold by the air blow blown from the inner periphery. Then, the optical disk substrate completely released from both the fixed / movable type is
It is taken out of the mold by the substrate take-out port bot and transferred to the next process after molding.

As described above, the method of releasing the molded optical disk substrate from the mold includes a releasing method using air blow blown from the inner peripheral portions of both the fixed and movable dies, and an ejector of the inner peripheral portion of the movable die. Conventionally, a method of combining a mechanical release method by a mechanism protruding operation has been adopted.

However, since the thickness of the optical disk substrate has been reduced for the purpose of increasing the capacity, it is difficult to directly apply the conventional method of releasing the optical disk substrate, particularly the release method using air blow. It became clear.

The cause of the above-mentioned difficulties is, first of all, that the blowing of the air blow for releasing is not completely uniform. Air for mold release is blown out (circularly) from a slit (usually about 10 to 20 μm in width) formed in an annular shape on the inner periphery of the mold. In addition, this blowout is designed to blow out evenly in the circumferential direction from the viewpoint of design. However, in practice, there are portions that blow out well and portions where air is not blown out much.

The unevenness of the release air is caused by the fact that the slit having a constant width in the circumferential direction at the air outlet is actually a problem in the processing accuracy and assembling accuracy of the components. There is a part where the width is widened and a part where the width is narrowed. The partial width of the slit width is caused by the difficulty in the partial blowing of the release air.

On the other hand, when looking at the unevenness of the release air blowing from the optical disk substrate to be released, the optical disk substrate receives a non-uniform force in the circumferential direction from the release air during the release. Means

At this time, since the rigidity of the optical disk substrate which has been reduced in thickness due to the increase in capacity is reduced due to the reduction in thickness, the optical disk substrate is unevenly separated when subjected to uneven force by the release air. It will be deformed. In particular, there is a strong tendency for a write-once or rewritable large-capacity optical disk substrate which is required to have higher transferability and is formed with a high mold temperature.

The above-mentioned non-uniform mold release / deformation at the time of mold release not only results in a change in the overall shape of the final optical disk substrate, but also causes the pit or groove shape transferred onto the substrate to become uneven. It also causes deformation at the minute shape level such as deformation due to uniform release operation, and adversely affects final media (signal) characteristics.

FIG. 2 shows the circumferential profile (undulation / distortion shape) of the inner peripheral portion of the optical disk substrate which has been released by the release air, where there are strong and weak blowout portions, and FIG. Clouds 31 each having a visually impaired appearance of the optical disk substrate due to uneven release of the optical disk substrate due to release air that blows in a non-uniform manner. In the cloud 31, which is a defective appearance portion shown in the inner peripheral portion of the optical disk substrate in FIG. 3, the pits / grooves transferred onto the substrate are deformed due to uneven release of the substrate. I have.

However, the non-uniformity of the release air, which causes the shape deformation at the minute level such as the entire optical disk substrate and the pits / grooves, is extremely small in the processing accuracy and the assembling accuracy of the components constituting the mold. (Micron order) level, and it is practically impossible to completely solve this.

On the other hand, in order to avoid the adverse effects of air blow that cannot avoid non-uniformity, if a mold release method using only a mechanical mold release method is adopted instead of a mold release method by air blow, molding It became clear that it was impossible to release the substrate from the mold itself.

By the way, when the thickness of the optical disk substrate is reduced to increase the capacity, the operation itself of filling the cavity with the molten resin becomes difficult.

Usually, when a product (molded product) is molded by injection molding, the molten resin filled in the cavity is
Cooling / solidification starts immediately after filling into the cavity, and the filled resin shrinks accordingly. Therefore, in order to obtain a molded product having a desired shape by compensating for the shrinkage of the filling resin, after the molten resin is injected and filled in the cavity, a process of supplementing (additionally) filling the shrinkage of the resin (pressure holding step) ), Followed by a cooling step and removal of the molded product.

However, in the case of molding a thinned optical disk substrate, the cooling of the resin proceeds rapidly as the thickness of the substrate (cavity) becomes thinner, so that the (supplementary) filling operation becomes more difficult, and an allowable range during the cooling process is reduced. It has a shape that is liable to cause shrinkage (sink) of the filled resin.

From the viewpoint of the above-described phenomenon in which the resin filled in the cavity shrinks, the mold substrate is released from the mold, and the resin filled in the cavity is closely adhered to the cavity inner wall, and the shape of the optical disk substrate is reduced. When the resin starts to shrink as it is cooled, the force of adhering to the inner wall of the cavity also decreases. That is, the optical disk substrate formed by cooling and shrinking is in a state where it is easily released.

However, the ease with which the optical disc substrate is released from the mold due to the progress of cooling and shrinkage of the filling resin is not uniform over the entire surface of the molded optical disc substrate.
The reason is that immediately after the molten resin is filled into the cavity, the temperature and pressure inside the resin are not uniform but have a certain distribution, and the subsequent cooling progress is not uniform. This is because they do not proceed.

That is, a problem in the release operation of a thinned optical disk substrate is that a substrate having a non-uniform release characteristic distribution is released using release air that is blown out unevenly. The problem is that the optical disk substrate to be released has the property of being easily deformed both macroscopically and microscopically when subjected to uneven force, which makes the problem even more difficult. I have.

As a conventional method for releasing the optical disk substrate by solving the above-mentioned problem, for example, Japanese Patent Publication No. 6-717
In Japanese Patent Publication No. 49, “Disc peeling method in disc molding”, the adhesion between the molding substrate and the mirror surface on the side opposite to the stamper set in the cavity is increased by air suction, and the adhesion between the molding substrate and the mirror surface is increased. Then, a method is employed in which the molded substrate is completely released from the stamper, and then the molded substrate is released from the mirror surface. The method of releasing an optical disk substrate according to this conventional method is to prevent a large amount of transfer of pits or grooves caused by the molded substrate being released from the stamper once (or partially) and then coming into contact again, This is an effective release method for controlling the warpage shape (radial deformation).

[0023]

However, in this conventional release method, an air blow blown from a slit formed in the inner periphery of the mold is used as a main driving force for releasing the molded substrate from the mirror surface and the stamper. ing. And
As described above, since the air blow blows in a non-uniform manner in the circumferential direction, the release of the molded substrate also proceeds non-uniformly, and as shown in FIG. In the direction (tangential direction) and the shape of the pits and grooves transferred onto the molded substrate. In addition, these deformations may cause unstable tracking of a drive that reads information on an optical disk or newly writes information on an optical disk, or causes an error in information that is read or written.

The present invention has been made to solve these problems, and a mold and a mold used in a method of releasing an optical disk substrate from being forced to use an air blow which is inevitable to blow out unevenly. It is an object of the present invention to provide a method of releasing an optical disk substrate, which can avoid an adverse effect of an air billow that performs uneven blowing without adding a special mechanism to the machine.

[0025]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a molding process which includes a filling step of filling a molten resin into a cavity of a mold and a cooling step of cooling the filled resin. An optical disk substrate releasing method for releasing the molded optical disk substrate from the mold, a mechanical releasing step of mechanically releasing the molded optical disk substrate from the die, and an air blow release using an air blow. The feature is that it is optimally combined with the mold process. Therefore,
It is possible to avoid the adverse effects of air blowing that causes non-uniform blowing without adding a special mechanism to a mold and a molding machine to be used.

The air blow release process is started after the operation of the mechanical release process starts, so that the mechanical release process triggers the release of the optical disk substrate, and the uneven blowing method. The adverse effects of air blowing can be avoided.

Further, since the air blow releasing step is not performed during the cooling step, a part near the air outlet is released in the cavity during the cooling step before the mold opening operation by performing the air blowing operation during the cooling step. It is possible to prevent the mold from being unevenly released from the entire optical disk substrate, and to cause a characteristic failure caused by the release.

Further, by controlling the mold clamping force for controlling the close contact between the resin filled in the cavity of the mold and the cavity during the cooling step, the optical disk substrate is appropriately released from the cavity. be able to.

Further, after a mold clamping force having a predetermined maximum value is applied for a predetermined first time, a predetermined second time (0.1 to 0.1) is applied.
By performing control to reduce the mold clamping force to a predetermined value over 0.2 seconds), it is possible to provide an appropriate mold clamping force control method for assisting uniform release of the optical disc substrate.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An optical disk substrate is released from a mold through a filling step of filling a molten resin into a cavity of a mold and a cooling step of cooling the filled resin. In the mold method, a mechanical release step of mechanically releasing the optical disk substrate from which the molding has been completed from the mold and an air blow release step using air blow are optimally combined.

[0031]

An embodiment of the present invention will be described below with reference to the drawings. The method of forming an optical disk substrate according to the present invention will be described according to the procedure. First, in the case of the injection molding method, the mold is closed and a mold clamping force is generated at an extremely low pressure setting, that is, the molten resin is filled into the cavity while a weak force is applied to the cavity. And
Performing an operation to raise the mold clamping force to a predetermined pressure at an appropriate timing before and after the filling process is switched from the injection process to the pressure holding process to the molten resin to generate a high pressure inside the resin filled in the cavity, This pressure is used to improve the substrate characteristics mainly of the transferability of the substrate. In addition, in the case of the injection compression molding method, first, the mold is closed and the 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, A similar effect is obtained by applying a large compressive force to this cavity after filling is complete.

At this time, if a large clamping force (or compressive force) is continuously applied for a long time (for example, until the completion of the cooling step as shown in FIG. 1B), the mechanical properties of the molded substrate are adversely affected. On the other hand, if the magnitude of the large mold clamping force is not sufficient or the time for applying the force is too short, the necessary information engraved on the stamper cannot be sufficiently transferred onto the molded substrate.

Accordingly, in the present invention, as shown in FIG. 1A, a large mold clamping force (or compressive force) is applied with a necessary and sufficient minimum and for a necessary and sufficient minimum time. Later, control was performed to reduce the mold clamping force (or compression force) applied to the resin in the cavity.

The above control is performed immediately after the injection and filling, so that a high pressure is generated inside the material resin which is still in a soft state, and the effect of improving the substrate characteristics mainly of the transfer property is obtained. Immediately after, it aims to reduce this internal pressure. When the internal pressure of the resin is reduced in such a way, the material resin is still in a state of maintaining fluidity to some extent at this time. Since it is possible to move a relatively large distance (compared with the control in which the pressure is reduced by the pressure), the internal stress can be more reliably alleviated. When the internal stress is reduced, the internal pressure is reduced, and at the same time, the unevenness of the internal distribution of the pressure, which was uneven under the high internal pressure state, is also reduced. The magnitude of the distortion and the non-uniformity of the distortion remaining in the optical disk substrate in the product state can also be reduced. As a result, the transferability and mechanical characteristics of the obtained optical disk substrate are improved, and at the same time, the size of the birefringence and the internal variation can be reduced.

From the viewpoint of the above-mentioned state of the internal pressure of the resin material in terms of the adhesion between the molding substrate and the cavity or the releasability of the molding substrate from the cavity, the above-described mold clamping force (or compressive force). Control to reduce the magnitude of the adhesion between the molded substrate and the cavity and at the same time to reduce the non-uniformity of the distribution of the adhesion, or to increase the releasability of the molded substrate and reduce the non-uniformity of the release property Control. This has a very great effect in that the mechanical operation performed after the completion of the cooling step and the release operation of the formed substrate performed by the blowing operation of the air blow are uniformly advanced.

By the way, when controlling the mold clamping force (or compression force) according to the present invention, immediately after applying a large mold clamping force (or compression force), the internal pressure of the filling resin in the cavity is alleviated. For this purpose, the mold clamping force (or compressive force) is reduced to a small value. At this time, if the mold clamp force (compressive force) is reduced too rapidly to reduce the internal pressure, the internal pressure of the material resin decreases sharply. That is, molding defects such as uneven mold release and "sinking" due to a sharp decrease in the adhesive force between the molded substrate and the cavity occur.

Therefore, in the present invention, in order to appropriately relax the internal pressure of the material resin in the cavity and obtain an optical disk substrate having only good characteristics, as shown in FIG. It has been clarified that it is necessary to control the mold clamping force (compression force) to be small for a certain period of time after applying the clamping force (or compression force) for an optimum time. Further, it has been clarified that it is most appropriate to set the time required for the control to lower the mold clamping force (or the compression force) to between 0.1 and 0.2 seconds. The reason why there is a width in the above setting range is that the optimal required time for stress relaxation is set by setting a large clamping force (or compressive force) (size / time) and reducing the mold after a small reduction. This is because the setting depends on the setting of the tightening force (or the compression force) and the setting of other molding conditions such as the setting of the mold temperature.

After the control of the mold clamping force (or the compression force) according to the present invention, the adhesion between the cavity and the molding substrate (the resin filled in the cavity) becomes small. Therefore, at this time (during the cooling step before the start of the mold opening operation), if the blowing of the air blow for releasing is started, the portion near the slit for blowing the air and where the blowing of the air is strong (as described above). (It is virtually impossible to blow the mold release air completely evenly in this way), while the mold release of the molded substrate is started, but since the mold is still closed, most of the molded substrate is in the cavity. And keep close contact. That is, if the blowing of the air blow is started during the cooling step before the mold opening operation starts, the release unevenness of the molded substrate corresponding to the blow-out unevenness of the release air occurs, and the optical disc characteristics deteriorate.

Therefore, in the present invention, the releasing operation from the cavity of the optical disk substrate by the blowing operation of the releasing air is not performed during the cooling step. In addition, it is practically impossible to make the release air blow out uniformly. Therefore, if air blow is used as the main method of releasing the release air blow from the cavity, uneven release of the molded substrate will occur. 2. To avoid the deformation of the mold and the shape of the optical disc substrate caused by it, especially in the circumferential direction (tangential direction) as shown in FIG. 2, and the deformation of the pits and grooves transferred onto the molded substrate. Can not.

Therefore, in the present invention, as a main method of releasing the molded substrate from the cavity, a mechanical release operation of the optical disk substrate molding die (molding apparatus) is adopted as a main releasing operation method instead of air blow. The release operation by blowing the release air blow is performed in combination with the release operation by the mechanical method described above as a method of assisting the release operation. The mechanical release operation of the optical disk substrate molding die (forming apparatus) includes the following two operations. One is that the cavity forming the outer peripheral shape of the optical disk substrate provided in the movable die supports the outer peripheral portion of the optical disk substrate at the start of the mold opening operation after the completion of the cooling step, and removes the optical disk substrate from the fixed die. Another operation is an operation in which an ejector sleeve provided on the inner peripheral portion of the movable mold protrudes the inner peripheral portion of the optical disk substrate when the mold is opened after the mold opening operation is completed. In addition, although these mechanical release operations are not completely performed uniformly in the circumferential direction, the release operations are performed in a much more uniform state as compared with the release operation by air blow. .

In the present invention, the operation of pulling out the optical disk substrate from the fixed mold by the cavitation at the completion of the cooling step and the start of the mold opening operation as described above and the operation of ejecting the ejector sleeve from the movable mold by the ejector sleeve when the mold is opened. The main release operation is performed. As the release operation to assist these operations, the optical disk substrate is released by appropriately combining the release operations by blowing out the air blow after the mechanical release operation described above is started at each timing. Type manipulation was performed.

Accordingly, the optical disk substrate is released from the mold by a mechanical method that is performed relatively uniformly in the circumferential direction, so that the release unevenness of the optical disk substrate due to the blow-out unevenness of the air blow does not occur. It has become possible to suppress the deformation of the shape of the optical disk substrate in the circumferential direction (tangential direction) and the shape deformation of the pits and grooves transferred onto the molded substrate.

It should be noted that the present invention is not limited to the above embodiment, and various modifications and substitutions can be made within the scope of the claims.

[0044]

As described above, according to the present invention,
Molding is completed in the optical disk substrate release method of releasing the optical disk substrate formed from the mold through a filling step of filling the molten resin into the mold cavity and a cooling step of cooling the filled resin. It is characterized in that the mechanical release step of mechanically releasing the optical disk substrate from the mold and the air blow release step using air blow are optimally combined. Therefore, it is possible to avoid the adverse effects of the air blow that performs the non-uniform blowing method without adding a special mechanism to the mold and the molding machine to be used.

Also, after the mechanical release process starts to operate, the air blow release process is started, which triggers the release of the optical disk substrate by the mechanical release process, and the uneven blowing method. The adverse effects of air blowing can be avoided.

Further, since the air blow releasing step is not performed during the cooling step, a part near the air outlet is released in the cavity during the cooling step before the mold opening operation by performing the air blowing operation during the cooling step. It is possible to prevent the mold from being unevenly released from the entire optical disk substrate, and to cause a characteristic failure caused by the release.

Further, by controlling the mold clamping force for controlling the close contact state between the resin filled in the cavity of the mold and the cavity during the cooling process, the optical disk substrate is appropriately released from the cavity. be able to.

Further, after a mold clamping force at a predetermined maximum value is applied for a predetermined first time, a predetermined second time (0.1 to 0.1) is applied.
By performing control to reduce the mold clamping force to a predetermined value over 0.2 seconds), it is possible to provide an appropriate mold clamping force control method for assisting uniform release of the optical disc substrate.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing time-clamping force relationships between a mold release method and a normal method according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a state of deformation of a conventional optical disc substrate in a circumferential direction.

FIG. 3 is a view showing a state of appearance failure of a conventional optical disk substrate.

[Explanation of symbols]

 31 Cloud

Claims (6)

[Claims] An optical disk substrate releasing method for releasing an optical disk substrate formed from a mold through a filling step of filling a molten resin into a cavity of a mold and a cooling step of cooling the filled resin. The optical disc substrate according to claim 1, wherein a mechanical release step of mechanically releasing the molded optical disc substrate from the mold and an air blow release step using air blow are optimally combined. Release method. 2. The method for releasing an optical disk substrate according to claim 1, wherein the air blow releasing step is started after the mechanical releasing step starts operating. 3. The method for releasing an optical disc substrate according to claim 1, wherein the air blow releasing step is not performed during the cooling step. 4. The method according to claim 1, wherein control of a mold clamping force for controlling a state of close contact between the resin filled in the cavity of the mold and the cavity is performed during the cooling step. The method for releasing an optical disk substrate according to the above. 5. A control for reducing the mold clamping force to a predetermined value over a predetermined second time after applying the mold clamping force at a predetermined maximum value for a predetermined first time. 5. The method for releasing an optical disk substrate according to item 4. 6. The predetermined second time is 0.1 to 0.2.
6. The method for releasing an optical disk substrate according to claim 5, wherein the time is seconds.