JP2009149474A - Molding die and method for manufacturing the die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press-molding die having excellent releasability and durability. <P>SOLUTION: The press-molding die is characterized by having a carbon nanotube layer made of a plurality of carbon nanotubes mounted vertically, which is formed on the surface of a die material at least the surface of which is formed by SiC. In this case, it is more preferable that the die material is SiC and the plurality of carbon nanotubes are grown almost vertically to the SiC surface. When the length of the plurality of carbon nanotubes is 0.1-10 μm, desirable releasability is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molding die used for press molding, and relates to a die having extremely good releasability. In particular, the present invention relates to a press mold used for press molding a lens made of glass, plastic, ceramics, or the like.

  Conventionally, a molded object such as a glass lens has been formed by press molding. At this time, the surface condition such as the surface roughness of the mold used at the time of press molding is directly transferred to the surface of the molded lens. Therefore, for example, when a metal mold is used, it cannot be used as a lens as it is molded, and finishing polishing is necessary. Also, so-called releasability was not good.

  Therefore, Patent Document 1 discloses a glass lens molding method in which the molding die is made of glassy carbon so that it can be used as a lens as molded. According to the present invention, it is possible to obtain the performance as a lens while being molded. Moreover, it has good releasability. However, since glassy carbon is a brittle material and has a low impact strength, there is a problem that cracks and the like are generated during use as a mold and the durability is poor.

In order to solve this problem, if the ceramic mold surface is coated with glassy carbon or pyrolytic carbon, and processed into the precision and shape required for the surface of the object to be molded, for example, the lens surface, Since a lens finishing process is not required and a ceramic porous body is used as a base material, the ceramic porous body has higher strength than glassy carbon, and thus has been invented to improve durability (Patent Document 2). . Further, since the glassy carbon is coated after the base material is processed into a lens shape, processing time can be saved, and the base material is a ceramic porous body, so that the base material can be easily processed.
However, the problem remains that the glassy carbon or pyrolytic carbon peels off during use and the releasability is lowered, and the molding material such as a lens material and the mold are fixed after pressing.

JP 47-11277 A JP 2004-345899 A Japanese Patent No. 3183845

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a molding die that has a good releasability from a molded body and is excellent in durability.

  As a result of intensive studies to solve the above problems, the present inventor has found that it is effective to form a carbon nanotube layer on the surface of the mold material, and has completed the present invention. That is, according to the present invention, by forming the carbon nanotube layer on the mold surface, it is possible to provide a mold having extremely high releasability and excellent durability. The present invention has the following features.

(1) The molding die according to the present invention is characterized in that a carbon nanotube layer in which a plurality of carbon nanotubes are erected is formed at least on the surface of a mold material whose surface is formed of SiC. And
(2) In the molding die described in (1) above, the mold material is formed of SiC.
(3) The molding die according to (1) or (2) is characterized in that the plurality of carbon nanotubes grow substantially perpendicular to the surface of the molding die.
(4) In the molding die according to any one of (1) to (3), a length of the plurality of carbon nanotubes is 0.1 μm to 10 μm.
(5) In the molding die according to (4), the length of the plurality of carbon nanotubes is 1 μm to 3 μm.
(6) In the molding die according to any one of (1) to (5), the surface of the mold material is porous.
(7) In the molding die according to (6), the porosity of the porous portion on the surface of the mold material is 30 to 50%.

(8) A method for producing a molding die according to the present invention comprises a step of sublimating silicon at least on a surface of a die material by heating a die material having a surface made of SiC, and forming a plurality of carbons on the surface of the die material. A carbon nanotube layer in which the nanotubes are erected is formed.
(9) In the method for manufacturing a molding die according to (8), the mold material is formed of SiC.
(10) In the method for manufacturing a molding die according to (8) or (9), at least a surface of the mold material is porous.

According to the present invention, it is possible to provide a molding die excellent in durability and releasability. In particular, the molding die of the present invention in which a SiC porous body is used as a base material and the surface of the base material is covered with a carbon nanotube layer exhibits extremely superior durability compared to a conventional press mold.

The molding die according to the present invention is not limited to a metal die, and may be a ceramic die. That is, the molding die according to the present invention is characterized in that at least the surface is made of ceramics made of SiC, and the surface is covered with a layer made of carbon nanotubes. If the surface of the carbon nanotube is processed into the precision and shape required for the object to be molded, for example, the surface of the lens, the finishing process of the lens after molding is unnecessary, and the releasability is extremely good. Since ceramic is used for the base material, the strength of the ceramic is higher than that of glassy carbon, so the durability is improved. In addition, since the mold base material is processed into the shape of an object to be molded such as a lens and then the carbon nanotubes are covered, the processing time can be saved.
The molding die according to the present invention is very effective for a molding method of pressing an individual. Further, even in the molding method of solidifying the liquid, when the wettability between the liquid as the molding object and the carbon nanotube is poor, the excellent releasability can be exhibited as in the case of an individual. Therefore, it is not limited to press molding, and is preferably used for extrusion molding, blow molding, casting molding, injection molding, and the like.

The carbon nanotubes having high adhesion strength can be produced by the following method (hereinafter also referred to as sublimation method) as described in Patent Document 3.
That is, heating may be performed at a temperature at which the SiC surface of the mold material is decomposed and silicon atoms are lost under vacuum. When SiC is heated under vacuum, for example, when the degree of vacuum is 10 ⁻⁷ torr, 1
At 400 ° C., SiC decomposes and silicon atoms are lost. At this time, since the silicon atoms are lost in order from the surface of the SiC crystal, the surface of the SiC crystal is first changed to a silicon atom-deficient layer (carbon layer), and this Si removal layer (carbon layer) gradually becomes the original SiC crystal. Increase the thickness to penetrate inside. When this layer is observed with a microscope, it is known that the carbon nanotube is a layer formed vertically from the SiC surface. The length of the generated carbon nanotube is usually about several μm.

When the carbon nanotube layer is formed by the sublimation method, if the mold material is SiC, the carbon nanotube layer can be processed as it is. In the case of other ceramics such as Si ₃ N ₄ , the surface may be coated with a SiC film.
At this time, if the SiC thin film on the outermost surface of the SiC mold material or other ceramic mold material is the (0001) plane or the (111) plane, the carbon nanotubes are likely to grow substantially perpendicular to the SiC plane. It is preferable to grow vertically because the release property is the highest. When SiC grows in other directions, the orientation of the generated carbon nanotubes may not be aligned, but even when grown in any direction (random), the releasability is significantly reduced. There is nothing, and fully satisfactory release properties are exhibited.

In the carbon nanotube produced by the above sublimation method, the Si atom on the surface of the mold material and the carbon atom of the carbon nanotube are formed from Si—C bonds having extremely large binding energy. The adhesion strength is extremely high, which is a feature that is not found in other carbon nanotube formation methods. Therefore, it was found that only carbon nanotubes produced by this production method (sublimation method) can be used for applications that require high wear resistance such as molds.

  The tip of the carbon nanotube formed on the surface of the mold material is in contact with the object to be molded, but the tip of the carbon nanotube is very fine, and therefore follows the fine irregularities on the surface of the object to be molded. The contact between the mold and the object to be molded is extremely high. For this reason, since the contact thermal resistance between the mold and the molded body is extremely small, the molded body is heated uniformly and quickly, so that there is no unevenness of sintering during sintering of the molded body. There is also an advantage that the time required for press molding can be shortened because the heating time is shortened.

  Carbon nanotubes formed on the surface of the mold material are effective in improving releasability as long as the length is 0.1 μm or more. In mold molding technology that heats and sinters the molded body during press molding, the material component of the molded body is melted in the mold due to the difference in thermal expansion coefficient between the mold material and the molded body or sintered body. Although it is worn or destroyed due to this, if a carbon nanotube layer is formed, this layer becomes a so-called cushion layer, so that such a phenomenon does not occur and the releasability is extremely high. If the length of the carbon nanotube is 10 μm, it can be applied to almost any type of molded body and can exhibit the effect. However, if it exceeds 10 μm, the effect is saturated and the dimensional accuracy may be impaired. The most preferable length of the carbon nanotube is 1 to 3 μm.

In addition, if SiC formed on at least the surface of the mold material used as the base material is made porous, the releasability is further improved and the durability is further improved. At that time, the porosity of the porous body is desirably 30 to 50%. This is because if the porosity of the porous portion exceeds 50%, the strength of the ceramic porous body is lowered, and the effect of improving the durability is reduced. Further, in the dense body having a porosity of less than 30%, the effect of making it porous is not remarkable.

As mold materials, SiC and Si ₃ N ₄ ceramic base materials were prepared and processed into upper punch and lower punch shapes as shown in FIG. GC was used as a comparative material.
Carbon nanotubes were formed on the surface of these ceramics under various conditions. For comparison, glassy carbon was coated by 2 to 3 μm. The coated glassy carbon (GC) surface was polished to obtain a press mold having a mirror-shaped molding surface.
A 700 ° C calcined body of ZnS ceramic having the shape shown in FIG.
The molded object) was molded up to 20000 times, and the possible number of moldings and the reason for failure when molding became impossible were investigated.

The results are shown in Table 1.
In Table 1, CNT means carbon nanotube, and GC means glassy carbon.

Ceramic molds (samples No. 1 to 3) that are not subjected to any treatment on the surface have poor releasability,
In one molding, the ZnS component adhered to the mold, and subsequent tests could not be performed.
By forming the carbon nanotubes, the releasability was improved, and the durability was higher than that obtained by coating amorphous carbon (glassy carbon) (sample No. 4).
It was confirmed that the durability was further improved when the surface of the SiC mold was made porous.

It is a figure which shows the shape of the metal mold | die used in the Example. It is a figure which shows the shape of the to-be-molded body produced in the Example.

Claims (10)

A molding die characterized in that a carbon nanotube layer in which a plurality of carbon nanotubes are erected is formed on the surface of a mold material having at least a surface formed of SiC. The mold for molding according to claim 1, wherein the mold material is made of SiC.   The mold for molding according to claim 1 or 2, wherein the plurality of carbon nanotubes are grown substantially perpendicular to the surface of the mold material.   The mold for molding according to any one of claims 1 to 3, wherein a length of the plurality of carbon nanotubes is 0.1 µm to 10 µm.   The mold for molding according to claim 4, wherein a length of the plurality of carbon nanotubes is 1 μm to 3 μm.   The molding die according to any one of claims 1 to 5, wherein a surface of the mold material is porous.   The mold for molding according to claim 6, wherein the porosity of the porous portion on the surface of the mold material is 30 to 50%. A carbon nanotube layer in which a plurality of carbon nanotubes are erected is formed on the surface of the mold material by a step of sublimating silicon by heating in a vacuum at least on the surface of the mold material formed of SiC. A method for manufacturing a molding die. The method for manufacturing a molding die according to claim 8, wherein the mold material is formed of SiC.   The method for producing a molding die according to claim 8 or 9, wherein at least a surface of the molding material is porous.

Images