JPH10324529A - Glass forming die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass forming die without the protective film being released even if glass is repeatedly formed, excellent in durability and suitable to produce an optical lens by a reheat-press process by treating the die in a nitrogen atmosphere and decreasing the nitrogen atom concn. continuously from the die surface toward the inside. SOLUTION: Silicon carbide and sintered hard alloy are optimum as the base material of the die. The die is allowed to stand in the nitrogen atmosphere at 0.7×10<5> -4×10<5> Pa and 1,200-1,800 deg.C for 1-10 hr and heat-treated or treated with the nitrogen plasma of 100-500 W at room temp. to 500 deg.C for 1-5 hr. By such treatment, a part of the outermost surface is converted mainly to silicon nitride when the base material is made of silicon carbide and converted to tungsten nitride when the base material is formed with sintered hard alloy. Consequently, a die capable of being easily released even from glass is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a glass molding die,
More specifically, the present invention relates to a glass molding die suitable for manufacturing an optical lens by a reheat press method.

[0002]

2. Description of the Related Art Various types of glass molding dies have been proposed, and it is customary to provide a protective film on the surface of each of the dies in order to improve the releasability and extend the life of the dies. Have been done. As the material of the protective film, a material that is chemically stable under a high-temperature molding environment and does not react with glass is used. As such, boron nitride (B
N), hard carbon, diamond-like carbon (DL
C) and the like are said to be effective.

[0003] For example, Japanese Patent Publication No. 3-61617 discloses that a part or the whole of a substrate made of ceramic is made of Si.
C, and a mold for forming an optical element formed by further coating a nitride thereon;... BN... In Japanese Patent Publication No. 4-61816, "... forming a hard carbon film on a substrate material ..."
The substrate material is a silicon carbide sintered body ... ".

When a protective film is formed on the surface of a mold base material,
In order to enhance the adhesion between the above-mentioned protective film such as boron nitride, hard carbon, diamond-like carbon and the base material, appropriate measures have been taken in forming the protective films.

In Japanese Patent Publication No. 3-61617, a boron nitride film is formed by a chemical vapor deposition method (CVD method) or a laser vapor deposition method via a silicon carbide (SiC) film. Tokuhei 4
In Japanese Patent Application No. 61816, although a general sputtering method is used, sputtering is performed with argon at a substrate temperature of 250 to 450 ° C. It is also described that a silicon carbide film is interposed.

[0006]

However, each of the techniques disclosed above employs a configuration in which a protective film is provided on the surface of a mold of a base material. In such a configuration, when the glass molding is repeated, the protective film is fused to the glass and peels off, resulting in a problem that the durability is poor. In addition, when the various manufacturing conditions are limited as described above, not only does the production of the mold become complicated, but also the production cost increases.

[0007] The present invention is not limited to the conventional method in which a protective film is separately formed on the mold surface of a mold base material, but is modified by modifying the surface of the mold base material itself, so that the conventional glass molding can be performed. It is an object of the present invention to provide a glass molding die having excellent durability without causing such a problem of peeling of a protective film.

[0008]

That is, the present invention relates to a glass forming mold obtained by treating in a nitrogen atmosphere. As a base material of a glass molding die capable of being treated according to the present invention, silicon carbide (SiC), cemented carbide (WC-C
o, WC-TiC-Co, and other alloys prepared by blending a transition element series carbide and an iron group metal and then sintering), hard carbon (C), alumina (Al ₂ O ₃ ), titanium (TiO3), stainless steel (SUS304, etc.), and the like, which are most suitable for silicon carbide and cemented carbide.

In the present invention, the above-described glass molding die base material is treated in a nitrogen atmosphere. Pressure ^{0.7 × 10 5 Pa~4 × 10 5} Pa in the processing, for example nitrogen, is preferably 0.
8 × 10 ⁵ Pa to 2 × 10 ⁵ Pa, and a temperature of 1200 to 1
The heat treatment may be performed by leaving the substrate at 800 ° C., preferably 1400 to 1600 ° C. for 1 to 10 hours, or 100 to 500 at a nitrogen pressure of 0.5 to 10 Pa.
The nitrogen plasma treatment of W is performed at room temperature to 500 ° C. for about 1 to 5 hours.

When the treatment is performed in a nitrogen atmosphere as described above, for example, when the base material of the mold is silicon carbide, a part of the outermost surface layer is mainly converted to silicon nitride. When the mold base material is a cemented carbide, part of the outermost surface layer has been converted to tungsten nitride. In any case, the base material itself is continuously denatured and degraded by treating in a nitrogen atmosphere.
It does not exist in the form of the conventional protective film, so that the phenomenon that the protective film is peeled off from the base material does not occur unlike the conventional case, and a glass molding die having excellent durability can be obtained. Needless to say, since the surface layer portion of the surface is made of silicon nitride or tungsten nitride, it has excellent releasability from glass.

The glass molding die of the present invention obtained as described above is suitably used for glass molding, for example, for producing an optical lens, and a good optical lens can be easily produced by repeating reheat pressing.

[0012]

EXAMPLE A mold made of silicon carbide as a base material was subjected to a 300 W nitrogen plasma treatment for 1800 minutes under a nitrogen pressure of 2 Pa.

As a comparative example, a metal mold provided with a silicon nitride film having a thickness of 3000 ° as a protective film by magnetron sputtering was prepared.

These dies were analyzed in the depth direction by Auger analysis. The mold of the present invention is 30
Nitrogen concentration is about 41 atom on the mold surface up to around 00Å
The structure is such that the carbon concentration continuously decreases toward the inside from c%, and the carbon concentration continuously increases toward the inside from 21 atomic% on the mold surface, and the portion deeper than that is the silicon carbide (SiC) structure of the base material. The component was the main component. FIG. 1 shows the results of surface analysis of the mold of the present invention.

On the other hand, the mold of the comparative example is about 280 from the surface.
Up to a depth of 0 ° is composed of silicon nitride (SiN) components, and after passing through a mixed region of nitrogen, silicon and carbon atoms at a depth of about 200 °, is composed of components of silicon carbide (SiC) as a base material. Was.

Glass molding was performed using the molds of the present invention and the comparative examples. Using a lanthanum silica borate glass (transition point: 623 ° C.) as a glass material, molding was repeated by a reheat press method, and the durability of the mold was examined.
Molding temperature is 670 ° C and pressure is 50k under nitrogen atmosphere.
g / cm ² and a pressurization time of 30 seconds, and the press molding was repeated. Table 1 shows the results.

[0017]

[Table 1]

As can be seen from Table 1, the mold of the present invention
Even after the molding of 5,000 shots was repeated, there was almost no change and it was good. However, in the mold of the comparative example, the silicon nitride film was peeled off from the base material at 816 shots, and fusion with glass occurred.

From the above, it was confirmed that the mold of the present invention had good releasability from glass, did not easily fuse with glass, and had excellent durability.

[0020]

The glass molding die of the present invention is excellent in mold releasability and durability.

[Brief description of the drawings]

FIG. 1 is a graph showing Auger analysis results of the surface of a glass molding die base material of the present invention.

Claims (3)

[Claims] 1. A glass forming mold obtained by treating in a nitrogen atmosphere. 2. The glass molding die according to claim 1, wherein the nitrogen atom concentration continuously decreases from the surface of the die toward the inside. 3. The glass forming mold according to claim 1, wherein the base material of the mold is silicon carbide or a cemented carbide.