JP2655936B2 - Release method of substrate for optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for molding an optical recording medium substrate, and more particularly to a method for releasing an optical recording medium substrate from a mold (stamper).

[Conventional technology]

Conventionally, CD (compact disc), video disc,
Injection molding, 2P, and the like are generally used as a method for molding a substrate of an optical disk such as a DRAW disk or a magneto-optical disk that optically records and reproduces information.

When molding a substrate using an injection molding method, particularly in the case of an optical disc having small pits or guide grooves, the mold release resistance between the molded substrate and the stamper is increased, so that the molding material such as aromatic polycarbonate is used. It is a common practice to add a type of surfactant called a mold release agent to the mold to promote mold release.

However, it is difficult to completely remove the release agent from the molded substrate obtained by internally adding the release agent to the molding material, which may cause trouble in the subsequent optical recording film formation process. It is pointed out that the storage characteristics of the optical disk are adversely affected. Therefore, development of a cleaning process that can remove a release agent from a molded substrate as much as possible has been an important issue.

[Problems to be solved by the invention]

As described above, although the effect of the release agent is excellent in terms of improving the release between the substrate and the stamper, considering the post-process and the stability of the product, the amount of the release agent should be reduced as much as possible or the added release agent It is necessary to set up a cleaning process that removes as much as possible, but without the release agent, it is difficult to release the mold, resulting in reduced production efficiency and roughening of the substrate surface. On the other hand,
Complete removal was difficult and the effects of the remaining release agent were unavoidable.

The present invention has been made in view of the above-mentioned state of the art, and provides a method of effectively releasing a substrate from a mold by using a novel release agent.

[Means for solving the problem]

The present invention is characterized in that the release agent is not added internally to the molding material, but is introduced into the mold in a gas state during the injection molding and release steps. That is, as a first embodiment, in a step of molding a substrate for an optical recording medium in a mold by injection molding and releasing the substrate from the mold, a release agent is injected into the mold in a gaseous state before injection molding. The method for releasing a substrate described above, and as a second aspect, also in the step of injection molding and release, performing injection molding in the presence of a gaseous release agent. A method of releasing the substrate.

According to this method, even when the amount of the release agent used is small, an excellent release effect can be exhibited, and at the same time, the amount impregnated in the substrate can be reduced. The process is simpler and the time can be shortened.

First, in the present invention, the target optical recording medium substrate is a substrate for various optical disks or optical cards for optically recording and reproducing information, and is formed in a mold by injection molding. . Generally, the mold comprises a movable half having a stamper and a fixed half, and after injection molding of the substrate, the movable half is opened to release the substrate from the mold. In addition, the mold release is usually carried out both by the action of gas pressure by blowing compressed air and by the action of mechanical operation. The compressed air is blown from both the movable side and the fixed side. The present invention can be applied to a commonly used stamper.

In such an injection molding / release process, in the present invention, a release agent is introduced into a mold in a gaseous state. The timing of introduction is immediately before injection molding as the first mode. That is, after the release, before the start of the next injection molding, an air flow containing the release agent is introduced into the mold, and the effect is exhibited by forming a release layer of several molecular layers on the surface of the stamper. Things. In this embodiment, the gas containing the release agent may be introduced into the mold through a release air blowing passage (either fixed side or movable side) provided in the mold, or separately. A dedicated pipe may be provided and introduced. The concentration of the release agent in the gas may be about 10 to 500 mg /, and may be appropriately set according to the amount of the gas introduced into the mold for one molding. The pressure and flow rate of the introduced gas are not essential, but are preferably about ² to 7 kg / cm ² from the viewpoint of efficient and uniform formation of the release agent molecule layer. Thus, a release agent molecule layer can be effectively formed on the surface of the stamper before the resin for injection molding is introduced into the mold. The release agent molecule layer is usually a few molecular layers, but if it is too thin, the release effect of the release agent cannot be obtained, and if it is too thick, it becomes uneven or impregnated into the molded product more than necessary. . When the mold release agent is contained in the mold release air, the mold release agent is contained in the movable mold release air, so that the molded substrate is released from the mold mold at the same time as the mold release from the mold mold. Several molecular layers of the release agent can be coated, eliminating the need for a separate step of introducing the release agent. However, in this case, the release agent-containing air hits the surface of the substrate after release, and the release agent slightly adheres, but this can be easily removed by the cleaning process.

Next, in another embodiment of the present invention, injection molding is performed in the presence of a gaseous release agent. In this case, the release agent-containing air is introduced at the same time as or immediately before molding, so that the release agent is present in a gaseous state in the mold at the time of molding. Thus, when the resin is injected, the release agent molecules enter the interface between the stamper and the resin, so that substantially the same effect as described above can be obtained. The concentration of the release agent present in the mold during molding is
The dose may be about 10 to 500 mg /.

As the release agent that can be used in the present invention,
Any other known release agents such as butyl stearate, amyl stearate, butyl palmitate, butyl myristate, and the like can be used.

As a means for introducing the release agent in a gaseous state, an apparatus having the configuration shown in FIG. 1 may be used. That is, the release agent 3
Is placed in a tight container provided with a heating means 2 and the mold release agent 3 is heated, for example, the mold release air 1 is passed therethrough, bubbled, and taken out as air 4 containing the mold release agent. Is introduced into the mold. The gas introduced into the container may be air, release air, or air introduced into a separate mold. The heating temperature is such that a part of the release agent is vaporized, and specifically, may be, for example, about 80 to 150 ° C. The concentration of the release agent in the air can be adjusted by the heating temperature, the air introduction pressure, and the degree of bubbling. The temperature in the mold is preferably equal to or higher than the temperature of the release agent-containing air to be introduced. This is because the gaseous release agent is not condensed.

In order to introduce the release agent-containing air into the mold by using the release air passage, a pipe that switches between the release air and the release agent-containing air with a valve may be used. In the case where is used as it is, the above device may be inserted in the middle.

The means for allowing the release agent to be contained in the air in gaseous form is not limited to the above-described apparatus, but may be implemented by, for example, spraying in a heated atmosphere and then removing large mist.

Next, the molded substrate obtained by the mold release method of the present invention is subjected to a cleaning process, which can be performed based on a known technique. However, since the degree of impregnation of the release agent in the substrate according to the present invention is significantly reduced as compared with that according to the prior art, the cleaning process can be simplified. The simplification of the cleaning process includes shortening the cleaning time,
Although the number of cleaning tanks is reduced, the cleaning process may not be required at all in some cases.

〔Example〕

Molded substrates were obtained in Examples 1 and 2 and Comparative Examples 1 and 2 shown below, and each was evaluated.

Example 1 Using an aromatic polycarbonate resin having a molecular weight of 20,000,
A Ni-type stamper having an address pit and a guide groove was used as a stamper, and an optical disk substrate having a thickness of 1.2 mm and a diameter of 130 mm was injection-molded. At this time, the mold temperature was set to 100 ° C., and the release air (movable-side release air) was butyl stearate (heated to 100 ° C.) as a release agent as shown in FIG.
After passing through a device filled with, the pressure was used at a pressure of 5 kg / cm ² (the release agent concentration in the release air was about 200 mg / cm 2).

Example 2 Molding was performed in the same manner as in Example 1 except that butyl palmitate was used as a release agent.

Comparative Example 1 Using the same resin as the aromatic polycarbonate resin used in Example 1 except that butyl stearate was used as a mold release agent, 0.1% was used.
Substrates were formed in the same manner as in Example 1 except that a resin composition in which a release agent was uniformly added in advance so as to be 5 wt% and a release air containing no release agent gas were used.

Comparative Example 2 A substrate was molded under the same conditions as in Example 1 except that no release agent was used.

When the substrate obtained in each of the above Examples and Comparative Examples was visually inspected to determine the release failure, in Comparative Example 2, many streaky traces of the release failure were observed. In Comparative Example 1, no such release failure was observed.

The obtained substrate was annealed (80 ° C, 20hr.)
After washing under the same washing conditions with pure water and Freon,
A magneto-optical recording film and a protective film were formed in the following configuration.

PC / SiN (500Å) / TbFeCo (500Å) / SiN (500Å) A backing substrate was bonded with a hot melt adhesive to obtain a magneto-optical disk. Keep these discs at 70 ° C, 90
After being stored for 1000 hours in an environment of% RH, the states of the recording films were compared visually and with an optical microscope. As a result, in Comparative Example 1, defects such as pinholes and film blisters occurred, but no other film defects were observed.

As a result, in Examples 1 and 2 based on the present invention, the mold release was good and the washing could be effectively performed, and no adverse effect due to the mold release step was observed.

〔The invention's effect〕

As described above, by adding a step of introducing an air flow containing a release agent into a mold in injection molding of an optical disk, the amount of the release agent remaining in the substrate is reduced, and the optical disk substrate excellent in storage stability is added. Can be obtained. Further, the cleaning process of the release agent can be simplified. In addition, the release agent can be contained in the release air by a simple means, whereby the release agent can be easily introduced into the mold without complicating the substrate manufacturing process at all.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of an apparatus that can be used to contain a release agent gas in release air. 1: Release air 2: Heater 3: Release agent 4: Release air containing release agent gas

Claims (5)

(57) [Claims] In a step of molding a substrate for an optical recording medium in a mold by injection molding and releasing the substrate from the mold using a release agent, the release agent is introduced into the mold in a gaseous state. The method for releasing a substrate, comprising: introducing the substrate; 2. The method according to claim 1, wherein the release agent in a gaseous state is introduced into a mold before injection molding of the substrate. 3. The method according to claim 1, wherein the release agent in a gaseous state is present in a gaseous state in a mold at the time of injection molding of the substrate. 4. The release method according to claim 1, wherein the release agent in the gaseous state is introduced into release air used for release. 5. The concentration of the release agent in the gaseous state is 10 to 500 m.
The release method according to claim 1, wherein g / g is used.