JPH0825434A - Molding method for board of disk - Google Patents

Abstract

PURPOSE:To obtain a board for an optical disk in which molds releasing unevenness, a pit deviation and the occurrence of a double transfer can be controlled for a long time at the time of molding the board by starting to diffuse the air for releasing a mold mounted with a stamper from the opposite side mold at specific timing. CONSTITUTION:In order to mount a stamper 14 having pre-format information in the cavity of molds, to introduce molten resin into the cavity and to then open the mold 10 to remove a board for a disk in which the pre-format information is transferred, diffusing of mold release air is started from the mold 11 side mounted with the stamper 14 for 0.2sec after molds opening is started immediately after the molds opening is started. Diffusing of the mold release air is started from the mold 10 of the opposite side to the mold 11 mounted with the stamper 14 after 0.1-0.7sec after the air diffusing.

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 an optical disk substrate, and more particularly to a method for molding an optical disk substrate which prevents pit displacement, double transfer and the like during substrate molding.

[0002]

2. Description of the Related Art In recent years, an optical recording medium has attracted attention as a large-capacity, high-speed memory medium. As the optical recording medium, a read-only type optical disc (CD, CD-ROM, etc.), a recording / playback type optical disc (write-once type), recording, reproducing, erasing,
A rewritable optical disc (rewritable type) and the like are known. A resin substrate (polycarbonate resin, acrylic resin, etc.) is generally used as the substrate of these optical recording media.

These disk substrates are usually manufactured by injection molding or injection compression molding from the viewpoint of productivity. In this method, an annular flat stamper having preformat information is mounted in a cavity formed in a mold clamped state between a fixed mold and a movable mold, and a molten resin material is introduced into the cavity. Is a method of molding a disk substrate on which preformat information such as stamper signals (pits) and laser guide grooves are transferred.

[0004]

However, in the conventional optical disk substrate, there is a problem that the pit shift of the preformat information of the stamper and the double transfer of the pit occur during the injection molding. These pit gaps and 2
Double transfer causes an ID error in an optical disc (write-once type, rewritable type). Also, in the case of an optical disc of the zone recording format, when changing the zone,
Since pit shift and double transfer occur in the recording area, there is a problem of causing a burst error.

The inventors of the present invention have made diligent studies on such problems at the time of molding the substrate. As a result, uneven mold release, pit shift, and double transfer cause the mold release of the substrate from the stamper for transferring pits and guide grooves. Was found to be due to the non-uniformity. As a method of improving the releasability of this substrate, (1) control of the pit depth and pit shape of the stamper (2) selection of the type and amount of release agent added to the resin (3) release of the substrate to the mold Although blowing air control of mold air (Japanese Patent Laid-Open No. 6-8018) and the like are known, none of them is a satisfactory method. In particular, at the beginning of molding, there is no mold release unevenness or pit shift, that is, the mold release property of the substrate is good, and the mold release property of the substrate gradually deteriorates as the number of molding times increases. It has been found that release unevenness and pit shift often occur. An object of the present invention is to provide a method for molding a substrate for an optical disk, which can remarkably control mold release unevenness, pit shift, and double transfer generation during substrate molding over a long period of time.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to attach a stamper having preformat information in a cavity of a mold, introduce molten resin into the cavity, and then open the mold to perform preformatting. When taking out the disk substrate to which information was transferred, release air is started from the side of the mold to which the stamper is attached from the same time as the mold opening starts until 0.2 seconds after the mold opening starts. Then, 0.1 to 0.7 seconds after the air is blown, the releasing air is started to be blown from the mold opposite to the mold to which the stamper is attached. .

The disk substrate molding method of the present invention will be described in detail below. FIG. 1 is a partial sectional view showing an example of a molding apparatus for carrying out the substrate molding method of the present invention.
The mold 10 includes a movable mold 11 and a fixed mold 12,
A stamper 14 for transferring and forming pits and laser guide grooves on the surface of the substrate is fixed to the movable mold 11.
The stamper 14 is usually made of a thin plate such as nickel and is fixed to the mold surface (usually the movable mold surface).
The back surface side of 4 may be sucked by the suction hole 13 provided in the mold 11 to be closely attached and fixed.

An outer peripheral holder 16 is provided on the outer peripheral portion of the stamper 14 and an inner peripheral holder 15 is provided on the inner peripheral portion thereof. The holders 15 and 16 are not in contact with the front surface side and the peripheral end surface of the stamper 14 and are not in contact with each other. Keep on. Between the surface side of the stamper 14 and the holders 15 and 16 is usually 5 to 50 μ.
A gap of some degree is formed. If the surfaces of the stamper 14 are held in contact with each other by the holders 15 and 16 without forming this gap, the stamper 14 is distorted and the pit shift is likely to occur.

On the other hand, the fixed die 12 is mounted on a fixed platen, and a sprue portion 18, that is, a sprue portion 18 is provided at the center. At the center of this sprue portion 18 is a resin inflow passage 18
a is formed, and one end 18b of the a is formed of the molds 11 and 12
It opens in the cavity 19 formed in between and the other end is connected to the injection nozzle (not shown). Movable mold 11
And the fixed mold 12 are temperature control channels 22a to 22
f, 23a to 23f are provided, and the temperature of the inner side (hereinafter referred to as the inner peripheral portion) and the temperature of the outer side (hereinafter referred to as the outer peripheral portion) of each mold 11 and 12 is adjusted by this channel. A cooling medium passage 24 is formed in the sprue portion 18 so as to surround the central resin inflow passage 18a.

The disk substrate molding method of the present invention is carried out by such a mold 10. That is, the mold 1
At 0, the movable mold 11 is closed by the fixed mold 12, and molten resin such as polycarbonate is injected from the injection nozzle into the cavity 19 through the resin inflow path 18a of the sprue portion 18. The movable mold 11 is pressurized at a high pressure before, during, or immediately after the injection process of the molten resin into the cavity 19.

The pressure applied to the movable mold 11, that is, the mold clamping pressure, is usually 100 to 600 kgf / c in terms of disk surface pressure.
m ² , preferably in the range of 200 to 500 kgf / cm ² . Due to this mold clamping pressure, the molten resin in the cavity 19 is press-molded into a disk having a desired plate thickness, and preformat information such as pits or grooves of the stamper 14 is transferred. After press molding, the mold clamping pressure is maintained as it is or is changed with time. After that, the molded disk substrate is taken out from the molds 11 and 12.

In the present invention, when the disk substrate is released from the movable side mold 11 and the fixed side mold 12, after a molten resin is injected and filled into the cavity between the molds, a fixed cooling time is required. After placing, the mold starts to open and the release air is blown out within a predetermined time. That is, the blow-off of the release air 30 is started from the side of the stamper-attached mold (the movable mold 11 side) at the same time after the start of the mold opening and within 0.2 seconds after the start of the mold opening. Then, 0.1 to 0.7 seconds (after the start of blowing air), the release air 40 is started to be blown from the die side (fixed side die 12) opposite to the stamper mounting side.

Specifically, as shown in FIG. 2, the mold opening signal 2 from the molding machine 1 is sent to the arithmetic unit 3. Also, the molding machine 1
The mold release airs 30 'and 40' are measured for their respective flow rates through the flow rate sensor 4, and the signal 5 of the flow rate sensor 4 is sent to the arithmetic unit 3 in the same manner as the mold opening signal 2. The arithmetic unit 3 obtains the difference between the mold opening start time and the blowing air start time of the release air 30, 40 based on the respective input signals.

That is, the mold opening start time is set to 0 seconds, the delays of the blow-off start times of the release airs 30 and 40 are obtained, and the values of the time delays are predetermined target values which are input to the arithmetic unit 3 in advance. Based on the comparison result, the set value 6 of the blowing start time of the release airs 30 and 40 is changed, and the release airs 30 and 4 at the time of molding the next substrate.
The balloon start time of 0 is adjusted so as to reach a predetermined target value. As the target value of the release start time of the release air, the release start time of the release air was variously changed at the time of molding the substrate, and a state without release unevenness or pit deviation was obtained by trial and error. It is a thing.

[0015]

EXAMPLES Examples will be shown below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 An apparatus schematically shown in FIG. 1 was used. The stamper 14 was adsorbed and fixed to the movable mold side by the suction hole 13. Holder 1
The gap between 5, 16 and the stamper surface was 20 μm. The inner side surface of the outer peripheral holder 16 was perpendicular to the stamper mounting surface. The polycarbonate molten resin material was injected into the cavity at a mold temperature of 110 ° C. The mold clamping pressure is kept at 300 kg / cm ² as the disc surface pressure, then returned to normal pressure and 0.1 seconds after the mold opening is started, air is supplied between the stamper 14 on the movable mold 11 side and the disc substrate. did. Furthermore, 0.6 after the start of this air supply
After a second, air was supplied between the fixed mold 12 and the disk substrate to separate them. Obtained diameter 1
The disc substrate having a diameter of 30 mm and a plate thickness of 1.2 mm had good transferability of the grooves and pits of the stamper, and no mold release unevenness or pit shift was observed.

Comparative Example 1 In the example, molding was performed continuously for 5000 shots without adjusting the air supply timing, and the air blowing start time between the fixed mold 12 and the disk substrate showed that the mold releasability was high. Due to the change, it was simultaneously blown out 0.2 seconds after the mold opening was started. The transferability of the grooves and pits of the stamper of the obtained disk substrate was poor, and uneven mold release and pit shift were generated.

Example 2 In Example 1, as shown in FIG. 2, the blowing time of the release air was adjusted to be the same as in Example 1, and as a result, the number of moldings was 10,000 shots. Also, the same results as in Example 1 were obtained.

Comparative Example 2 In Example 1, 1 minute before starting the mold opening, AA was supplied from the fixed mold 12 side, and 0.5 seconds after that, the movable mold 1 was started.
The same operation was performed except that air was supplied from the side 1 to perform the mold opening operation of the mold. The obtained disk substrate had considerable mold release unevenness and pit shift.

Comparative Example 3 In Example 1, the fixed mold 12 was used 0.2 seconds after the start of mold opening.
Air is supplied from the side, then 1 second later, the movable mold 1
The same procedure was performed except that air was supplied from the side 1 to perform the mold opening operation. The obtained disk substrate had slight mold release unevenness and pit deviation.

[0020]

According to the method of the present invention, it is possible to obtain a disk substrate in which the tracking grooves and pits, which are preformat information, are transferred well.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an example of an apparatus used in the method of the present invention.

FIG. 2 is an explanatory diagram of an example of a flow when the method of the present invention is carried out.

[Explanation of symbols] 10 mold 11 movable mold 12 fixed mold 14 stamper 15 inner peripheral holder 16 outer peripheral holder 30 release air 40 release air

Claims (1)

[Claims] 1. A stamper having preformat information is mounted in a cavity of a mold, a molten resin is introduced into the cavity, the mold is opened, and a disk substrate to which the preformat information is transferred is taken out. At the same time, from the start of opening the mold to 0.2 seconds after the start of opening the mold, air for releasing the mold is started from the side of the mold to which the stamper is attached, and after the air is blown, the air for release is released.
A method for forming a disk substrate, characterized in that after 1 to 0.7 seconds, a mold air on the side opposite to the mold to which the stamper is attached starts blowing air for release.