JPH11269479A - Production of molded article using metal mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the interval between disassembly and maintenance works of a metal mold and to decrease equipment troubles by applying, to the sliding section of the mold, a grease which comprises a perfluoropolyether as the base oil and a polymer powder consisting of carbon and fluorine atoms only as the thickener. SOLUTION: The thickener is pref. a tetrafluoroethylene resin and pref. has a particle size of 0.5-10 μm. Since the clearance at the sliding section of a metal mold used in molding substrates for optical recording media is very small, i.e., about 10 μm, a thickener having a particle size larger than 10 μm resists sliding. The particle size smaller than 0.5 μm reduces the thickening effect. In applying the grease to the sliding section of a metal mold, it is applied pref. in the min. necessary amt. in order to decrease the amt. of a gas released at high temps. A practically suitable method for applying the grease is that the grease attached on a finger is smeared to the sliding section and then is lightly wiped off with gauze or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a molded article. More specifically, the present invention relates to a method of using a specific grease in a mold having a sliding portion for removing a molded product,
In particular, the present invention relates to a method of manufacturing a molded article applied to a mold for molding a substrate of an optical recording medium requiring precision molding.

[0002]

2. Description of the Related Art In recent years, DVD-RA has been used as an optical storage medium.
Various media such as M, MO, and phase change disks are used, and are manufactured by injection molding a thin substrate molded product using a mold.

A mold used for manufacturing such a substrate usually has a sliding portion called an ejector, an ejector pin, or a floating punch for taking out a molded product. These materials are steel, stainless steel, etc.
The contact surface is worn because it slides every shot.

As a method for preventing this, Ti
A method of providing a thin film layer of N or the like and hardening the surface has been put to practical use. However, even in this method, when tens of thousands to hundreds of thousands of shots are formed, sliding may be difficult due to abrasion or may stop. Also, even if malfunction does not occur, abrasion powder is generated, goes out of the mold and adheres to the molded product, for example,
In the case of an optical disk substrate, problems such as a worse error rate occur. Therefore, it is necessary to periodically disassemble and disassemble the mold and perform surface polishing or TiN processing, which is a major problem in terms of stable molding and maintenance of the mold.

[0005] Even in a mold, grease may be used for the tie bar portion. The grease usually used is a semi-solid, solid lubricant composed of a base oil and a thickener at room temperature. As the oil, synthetic oils such as mineral oil and diester oil,
As the thickener, fatty acid metal soaps such as Li, Ca, and Na, and organic and inorganic compounds such as benton and fine silica are used.

When such a grease is used for the above-mentioned sliding portion, the time until the malfunction occurs becomes longer, but not completely.
There is a problem that an abrasion powder or the like is generated, and the error rate of the optical disc is deteriorated.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of manufacturing a molded article using a mold using a grease using a grease which can increase the interval for disassembling and maintaining the mold and has no equipment trouble. Is to provide. Particularly, in a mold used for molding a substrate of an optical recording medium, the clearance between a sliding portion such as an ejector and an ejector pin and a contact portion thereof has become extremely small as the required characteristics of the medium have become strict. . In particular, in a mold for molding a substrate of a DVD-RAM, an ASMO, and a 90 mm 1.3 GB phase change disk having a thickness of about 0.6 mm, these clearances are 10 μm because it is necessary to increase the fluidity of the resin.
m, and its importance is increasing.

[0008]

According to the present invention, a grease comprising a polymer powder comprising perfluoropolyether as a base oil and a thickener comprising only C and F atoms is used for a sliding portion of a mold. It is intended to provide a method of manufacturing a molded article characterized by performing the following.

Further, the present invention provides a method for producing a molded article, characterized in that the thickener is tetrafluoroethylene and the particle size is 0.5 to 10 μm. It is.

[0010] The present invention also provides a method for producing a molded article of a mold, characterized in that such grease is used in at least one of an ejector, an ejector pin and a stamper inner retainer mounting portion of a mold. is there.

Further, the present invention is characterized in that such a molded article is a substrate of an optical recording medium, particularly a substrate having a thickness of 0.63 mm or less, and the grease is used for a sliding portion of the mold. An object of the present invention is to provide a method for manufacturing a molded article.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method in which a base oil is a perfluoropolyether, and a thickener is a grease made of a polymer powder consisting of only C and F atoms. A method of manufacturing a molded article.

First, the grease used in the present invention will be described. Grease consists of a semi-solid or solid lubricant composed of a base oil, which is a liquid lubricant, and a thickener.
The base oil used in the present invention has thermal stability, chemical stability,
It is necessary to be a perfluoropolyether because of low outgassing at high temperatures. This has the structure of the following formula (1).

[0014]

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On the other hand, the thickener used in the present invention is a polymer powder consisting of C and F atoms.
A tetrafluoroethylene resin (PTFE, the following formula (2)) and a tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP, the following formula (3)) can be used. Among them, PTFE has a higher heat resistance temperature than FEP and is preferably used.

[0016]

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[0017]

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The thickener has a particle size of 0.5 to 0.5.
It needs to be 10 μm. More preferably,
0.5 to 4 μm. Since the clearance of the sliding portion of the mold used for molding the optical recording medium substrate is as small as about 10 μm, if the particle size is too large, the sliding resistance is adversely affected.
If it is too small, not only is it difficult to produce a powder, but also the thickening effect decreases.

Next, a method of manufacturing an optical recording medium substrate using a mold coated with the above-mentioned grease according to the present invention will be described.

FIG. 1 is a schematic view showing an example of an inner peripheral portion of a mold for molding a substrate of an optical recording medium when a stamper is provided on a fixed side. In the figure, A is a fixed side that is in contact with the heating cylinder, and B is a movable side that is opened when removing a molded product. In this example, the inner stamper retainer (1) for fixing the inner periphery of the stamper is provided on the movable side, and is in contact with the fixed bush (2) and the fixed side main body (4). The inner stamper presser does not move during molding,
When the stamper is attached or detached, it slides. (3) is a sprue bush, (9) is a sprue portion cavity, and (5) is a substrate portion cavity.

On the other hand, on the movable side, an ejector (6) for projecting a substrate, a cutter (7) for punching out a central portion, and an ejector pin (8) for projecting a sprue are arranged as shown in FIG. It slides between each other and between the mold body (10). The sliding parts of these parts are often provided with a TiN layer in order to improve the wear resistance of the surface.

Next, a method of providing the grease of the present invention on a sliding portion of a mold will be described. Even if the grease of the present invention emits a small amount of gas at a high temperature, it is not zero, and it is preferable to keep the applied amount to a minimum. In particular,
For example, a method in which grease is applied to a finger and rubbed on a sliding portion, and then lightly wiped with gauze, ben cotton, or the like is preferably used. The application may be provided on both sides of the sliding portion or on only one side.

The mold of the present invention is a mold for molding not only the mold for molding a substrate of an optical recording medium described above but also all molded articles including household goods and industrial products.

However, especially in the formation of a substrate for an optical recording medium,
In order to satisfy strict requirements such as transferability and birefringence, each mold component is also required to have high dimensional accuracy and narrow clearance between sliding parts. As a result, the friction and wear of the sliding portion have become more important. In particular, 0.
This point becomes very important in a mold for molding a 6 mm substrate.

The optical recording medium referred to in the present invention is a recording medium on which information is recorded, reproduced, and / or erased by light such as a laser beam. There are a video disk, a recordable optical disk, a rewritable magneto-optical disk, and a phase change disk. Among these discs, various ones have been proposed, and they are particularly preferably used in DVD-RAM, ASMO, 90 mm 1.3 GB phase change discs using a substrate with a thickness of 0.6 mm.

[0026]

EXAMPLES The effects of the present invention will be described below with reference to examples.

Example 1 An injection molding machine (model name: MO40D3H) manufactured by Nissei Plastic Industry Co., Ltd.
A mold for a VD-2.6 GB substrate (substrate thickness: about 0.6 mm) was attached. This mold was disassembled in advance, and the (1) / (4) interface, (1) / (2) interface, (10) /
Grease Z-300 manufactured by Japan Vacuum Co., Ltd. was provided on the (6) interface, (6) / (7) interface, and (7) / (8) interface.

The method was carried out by applying grease to the surface of each mold part with a finger and then gently wiping it with Bencotton (manufactured by Asahi Kasei Corporation). This Z-300 is about 1 ~
Approximately 30% of polytetrafluoroethylene fine particles having a size of 3 μm and perfluoroalkyl polyether. A stamper having a disk diameter of 120 mm and a storage capacity of 2.6 GDVD-RAM was attached to this mold. The resin is a polycarbonate resin (AD55) manufactured by Teijin Chemicals Ltd.
03) was used.

Before molding, the movable side 123 which is the molding temperature
The temperature was set to 128 ° C. and the gold temperature was fixed to 128 ° C., and the degree of cleanness was measured while sliding the ejector and the ejector pin. The cleanness was measured by using a dust counter Model 82-3200 manufactured by Dan Kagaku Co., Ltd. and measuring the number of dust particles of 0.5 μm or more.

As a result, the number of dust particles of 0.5 μm or more is 10
The number of times of sliding was 10, which was good.

The mold temperature is 123 ° C. on the movable side and 12 ° on the fixed side.
8 ° C. The temperature of the cutter and sprue is 60 ° C.
And The injection speed was 200 mm / sec, and the molten resin was filled into the cavities 5 and 9 of the mold. Molding was performed under the condition that the resin temperature was 380 ° C. in the cylinder section. The molding cycle is 8.0 seconds.

This mold was used for 6 months without disassembling the mold and maintaining the sliding portion, but no abnormality occurred in the sliding portion. The measurement of cleanliness was performed in the same manner.
Individual and hardly changed. The total number of molding shots is 1.2 million shots. The replacement of the stamper was performed 32 times. [Examples 2 to 3] In Example 1, powder of a tetrafluoroethylene-hexafluoropropylene copolymer resin (particle diameter 1) was used in place of tetrafluoroethylene as a thickener.
５5 μm) and mixed with perfluoropolyether at a ratio of 30% to produce grease.

This was molded under the same conditions, but for 6 months
No trouble occurred in the sliding portion at the number of integrated shots of 1,000,000 shots. The cleanliness is 18 at the start of use.
The number was 30 pieces after 6 months, which was good.

Comparative Examples 1 and 2 In Example 1, a mold was assembled simply by wiping with acetone without using grease, and molding was performed under the same conditions (Comparative Example 1). The cleanliness at the start of molding was 136. Four days after the start of molding, the ejector stopped moving at 36,000 shots, and the molding was stopped.

The mold was disassembled, polished with Picard (manufactured by Nippon Kirin Kogyo Co., Ltd.), assembled, and re-starred (Comparative Example 2). As a result, the ejector pin stopped working 68,500 shots 7 days later.

Comparative Example 3 In Comparative Example 2, after polishing with Picard, grease "Martinock Grease" manufactured by Nippon Oil Co., Ltd. was applied, and the same molding was performed. This grease uses mineral oil as a base oil and soap as a thickener.

The cleanliness at the start was 213. Also, the molding was stopped when the number of accumulated shots was 187,000.

[0038]

As described above, the present invention is a method for producing a molded article with less dust generated from the mold, a longer interval for disassembling and maintaining the mold, and without any equipment trouble. By using such a method, a stable and good optical recording medium substrate can be manufactured.

[Brief description of the drawings]

FIG. 1 is an example of a schematic view of a central portion of a mold.

[Explanation of symbols]

 1: inner stamper retainer 2: fixed bush 3: sprue bush 4: fixed mold body 5: substrate cavity 6: ejector 7: cutter 8: ejector pin 9: sprue cavity 10: movable mold body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 50:10

Claims (6)

[Claims] 1. A mold wherein a base oil is perfluoropolyether, and a thickener is a grease made of a polymer powder comprising only C and F atoms for a sliding portion of the mold. Manufacturing method of molded article. 2. The method according to claim 1, wherein the thickener is tetrafluoroethylene. 3. The thickener has a particle size of 0.5 to 10 μm.
3. The method according to claim 1, wherein m is m. 4. The method according to claim 1, wherein the grease is used in at least one of an ejector, an ejector pin, and a stamper inner retainer mounting portion of the mold. . 5. The method according to claim 1, wherein the molded product is a substrate of an optical recording medium. 6. The optical recording medium substrate has a thickness of 0.63 mm.
The method according to claim 5, wherein: