JPH0578145A - Fusing preventing coating film - Google Patents

Abstract

PURPOSE:To improve facial properties of high, precision and durability by forming two layers of a protecting film of preventing a metal from diffusing from a mold and a coating film of a nonoxidizable compound on a molding mold. CONSTITUTION:A material consisting essentially of tungsten carbide, etc., is alloyed by using a metal such as cobalt as a binder to give a hard metal alloy 1 having high facial precision. Then, the allay 1 is pressed into a dented shape to prepare a mold, which is abraded to give a mirror surface. Then a thin film of tantalum is formed on the mirror surface by sputtering method, etc., to make a diffusion protecting film 2 of preventing cobalt in the alloy 1 from diffusing. Then thin films of h-BN and C-BN are alternately produced on the film 2 by deposition method and an nonoxidizable compound film 3 is developed to yield a mold of molding glass having a fusing preventing coating film of suppressing fusing to glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-fusion coating formed on a press-molding die for mass-producing glass optical components by press molding.

[0002]

2. Description of the Related Art For press-molding high-precision glass optical parts, the mold material is stable even at high temperatures and has excellent surface accuracy.
A mold having excellent oxidation resistance is required, and a mold having a base material made of cemented carbide and a noble metal coating used as a fusion preventing coating is used.

[0003]

However, in order to obtain an optical component with high precision or complicated shape, tungsten carbide, titanium nitride, titanium carbide,
A cemented carbide is used which is mainly composed of alumina and the like, and is alloyed with cobalt and nickel as a binder.

When such a cemented carbide is repeatedly used as a press die at high temperature, cobalt or nickel of the die material is diffused into the anti-fusing coating to form an oxide coating on the die surface and fuse with glass. Therefore, an accurate optical component cannot be obtained. Further, if the film thickness of the protective film is increased in order to prevent metal diffusion of the mold material, the shape processed into the cemented carbide will be broken, and an optical component having a complicated shape cannot be obtained.

The present invention solves the above-mentioned problems by forming a protective film for preventing metal diffusion from a mold material and forming a non-oxidized compound thin film for preventing fusion with glass, thereby achieving high precision glass by press molding. It is to provide a molding die that enables obtaining an optical component.

[0006]

In order to solve the above problems, according to the present invention, on a cemented carbide die on which a metal such as cobalt or nickel is alloyed as a binder,
It is composed of two layers of a protective film for preventing metal diffusion from metal and a non-oxidized compound thin film for preventing fusion with glass.

As the cemented carbide, a material containing tungsten carbide, titanium nitride, titanium carbide, alumina or the like as a main component, and alloyed with a metal such as cobalt or nickel as a binder to improve surface accuracy is used. To do.

The protective film for preventing metal diffusion from the die material is preferably tantalum or rhenium having a high melting point and oxidation resistance in order to prevent precipitation of cobalt or nickel due to high heat.

As the non-oxidized compound thin film for preventing fusion with glass, a mixed thin film of C-BN and h-BN which does not generate phase separation or intermetallic compound at high temperature is preferable.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to a sectional view of a press molding die shown in FIG.

Using a cemented carbide 1 having a diameter of 25 mm and a thickness of 10 mm and containing tungsten carbide as a main component and cobalt as a binder, a mold having a concave pressing surface with a radius of curvature of 50 mm was prepared. Then, it was mirror-polished using diamond abrasive grains. Next, in order to prevent the diffusion of cobalt in the cemented carbide, tantalum is formed on the mirror surface by sputtering to have a thickness of 0.1 μm to form the diffusion protection film 2. Further, in order to prevent fusion with glass, a thin film of h-BN or C-BN is alternately produced by a vapor deposition method to obtain a h-BN of 1.2 μm,
A mixed thin film of C-BN was formed as the non-oxidized composite film 3.

As a comparative sample, a platinum-iridium alloy coating, which has been conventionally used as a non-oxidizing alloy coating for preventing fusion with glass, was sputtered on the mirror surface of cemented carbide with the same shape as the above. It was formed into a mold with a thickness of 1.1 micrometers by the method.

With these molds, 600 ° C. in a nitrogen atmosphere
The press molding process was carried out at various degrees to examine the change in surface properties.

The results of press-forming for 200 hours are as follows. The mold of the present invention has no change, whereas the mold for comparison starts clouding due to the precipitation of cobalt oxide after 80 hours, and after 110 hours, the mirror surface becomes cloudy and the surface roughness is After 145 hours, cobalt oxide was further deposited and fused with glass,
Molding of glass became impossible.

In the mold of the present invention, the diffusion preventive protective film is formed between the cemented carbide and the non-oxidized compound thin film to prevent precipitation of cobalt contained in the cemented carbide with a high melting point and oxidation resistance. It is suppressed by tantalum, which has a property to prevent its diffusion into the non-oxidized compound thin film.

The conventional diffusion preventive protective film has a thickness of 5 to 20.
Although it was formed to have a thickness of 1 μm, it can function as a diffusion prevention protective film with a thickness of 1 to 2 μm by being composed of two layers of a diffusion prevention protective film and a non-oxidized compound thin film as in the present invention. To do.

A platinum alloy coating is conventionally used as the glass fusion preventing coating, but the coating hardness is Hv90.
From 0 to 1200, small scratches were observed during the press molding process, which deteriorated the quality of the optical component with excellent accuracy, and left a problem in the durability of the molding die. On the other hand, the mixed coating of C-BN and h-BN according to the present invention has Hv 2500 to 3000 due to the cubic crystal structure of C-BN, has high abrasion resistance, and greatly contributes to the prevention of scratches. In the 200-hour molding process, 20 minutes after the start of molding
In the surface roughness measurement after the lapse of 0 hours, the surface roughness Rmax of 10 nm immediately after the start of molding was compared with the Rma even after 200 hours.
A good result of x21 nm was obtained. In addition, for preventing fusion with glass, the mixed coating of C-BN and h-BN has an excellent lubricity due to the hexagonal crystal structure of h-BN, and the release of the molded product after press molding is performed. Was also very good.

As described above, by forming two layers of a diffusion preventing protective film and a non-oxidized compound thin film on a cemented carbide in which a metal is alloyed as a binder, an optical component with excellent precision is pressed. It became possible to obtain it by molding.

[0019]

EFFECTS OF THE INVENTION According to the present invention, a cemented carbide having an excellent surface property and containing a metal binder can be used as a mold for glass molding, and it is possible to obtain a highly accurate optical component as compared with the conventional one. It has the effect of significantly extending the durability of the glass molding die.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a press molding die showing a two-layer structure of a diffusion prevention protective film and a non-oxidized compound thin film according to an embodiment of the present invention.

[Explanation of symbols]

 1 Cemented Carbide 2 Diffusion Prevention Protective Film 3 Non-Oxidized Compound Thin Film

Claims (1)

[Claims] 1. A protective film formed on a glass molding die, which comprises two layers of a protective film for preventing metal diffusion from the die and a non-oxidized compound thin film for preventing fusion with glass. An anti-fusion coating to be used.