JPH09315827A - Molding die for optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die provided with necessary properties for the molding die and hardly deteriorated in the properties even in the increase of molding cycle by applying successively two specific carbonaceous thin films on the surface of a die base material in a molding die for a glass molding of an optical device. SOLUTION: This molding die 10 for the glass molding is composed of the base material 11, the diamond like carbon thin film layer 12 laminated and formed on the molding surface 11a of the base material 11 and the carbon thin film layer 13 laminated and formed on the diamond like carbon thin film layer 12. The base material 11 is preferably silicon carbide. The diamond like carbon thin film layer 12, for example, can be formed by CVD method. The carbon thin film layer 13, for example, can be formed by a sputtering method using carbon as a target material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mold for an optical glass element used in a glass molding method.

[0002]

2. Description of the Related Art Optical glass elements, for example, aspherical glass lenses, are difficult to mass-produce by polishing, so molding has been attempted. In the glass molding method, the optical glass material (preform) is heated as it is or after being preheated, and then it is heated and pressed between the press molding surfaces of a pair of molding dies that are being heated to soften the shape of the molding surface into a preform. It is a method of transferring and molding.

The mold used in this glass molding method is
It is required to have heat resistance, chemical stability against optical glass, high hardness at high temperature, surface accuracy, and oxidation resistance, as well as excellent mold releasability and durability to withstand repeated use. In order to meet such demands, many proposals for the mold have been made and put into practical use. As materials excellent in chemical stability and oxidation resistance for optical glass, precious metals such as platinum and gold, diamond thin films, carbon films, etc. are known, and a molding die in which these are coated on the molding surface of the base material It is used. As the base material, cemented carbide,
It is general to use cermet, zirconia, alumina, silicon carbide or the like to maintain the strength of the molding die.

However, in the conventional molding die, as the number of press moldings of the optical glass element increases, the thin film coated on the press molding surface is slightly deformed, and the optical characteristics of the obtained optical glass element change. Therefore, there is a problem that the number of times of use is small. Further, as the number of times of press molding is increased, the releasability is deteriorated and the molded element adheres to the mold. Furthermore, the conventional molds are difficult to regenerate, and once the usage limit was reached, all had to be replaced.

[0005]

The object of the present invention is to provide properties required for a mold for an optical glass element, namely, heat resistance, chemical stability against optical glass, high hardness at high temperature, surface accuracy, oxidation resistance, and mold release. It is an object of the present invention to obtain a mold having properties and the like, and these properties are not deteriorated even if the number of times of press molding is increased. Another object of the present invention is to obtain a mold for an optical glass element that can be reproduced relatively easily when the usage limit is reached.

[0006]

SUMMARY OF THE INVENTION The present invention has been completed as a result of research on a material of a thin film to be laminated on a molding surface of a base material,
A feature is that a diamond-like carbon thin film layer and a carbon thin film layer are sequentially formed on the molding surface of the base material. The base material is preferably composed of silicon carbide. The diamond-like carbon thin film layer is specifically formed by CVD.
The carbon thin film layer can be formed by a sputtering method.

[0007]

1 is a schematic view of a glass mold 10 according to the present invention. This glass mold 10 is composed of a base material 11 and a diamond-like carbon (DIAMOND) laminated on the forming surface 11a of the base material 11.
LIKE CARBON) thin film (DLC thin film) 12 and this DL
Hard carbon thin film 1 further laminated on C thin film 12
It consists of 3. The molding surface 11a has a surface roughness R _max = 0.02 μ, which is obtained by cutting the base material 11 into a desired shape with an ultra-precision lathe and then using, for example, a diamond paste abrasive.
Polish to m or less.

The base material 11 can be composed of silicon carbide, cemented carbide, cermet, zirconia, or alumina, with silicon carbide being preferred. Silicon carbide has the advantages of high altitude and excellent oxidation resistance even at high temperatures.

The DLC thin film 12 is excellent in mechanical strength, thermal conductivity, electrical insulation, light transmission, chemical resistance and adhesion,
It has this name because it has physical properties close to diamond, such as a low coefficient of friction. The DLC thin film 12 is formed by, for example, an ion beam method or plasma CVD (CHEMICAL VAPOR DEPOSIT).
ION) method.

The carbon thin film 13 is similar to the DLC thin film 12 in mechanical strength, thermal conductivity, electrical insulation, light transmission,
It has excellent properties such as excellent chemical resistance and adhesiveness and a low friction coefficient, but has a lower film hardness than the DLC thin film 12. One of the features of the present invention is that the surface of the hard DLC thin film 12 is covered with a carbon thin film 13 which is softer than the surface of the DLC thin film 12. For example, in the configuration in which the DLC thin film 12 directly contacts the optical glass element, the DLC thin film 1
When the surface of 2 is scratched, it adversely affects the molded glass element and is difficult to repair. On the other hand, when the carbon thin film 13 is present on the surface of the DLC thin film 12, the carbon thin film 13 acts to protect the DLC thin film 12, and even if the carbon thin film 13 is scratched,
Only the carbon thin film 13 can be peeled off by polishing. Therefore, there is an advantage that the DLC thin film 12 is left as it is, only the carbon thin film 13 is removed by polishing, and then the film is formed again, so that the film can be reused many times. The carbon thin film 13 can be formed by, for example, a sputtering method using carbon as a target material.

[Example] The molding surface 11a of the base material 11 made of silicon carbide was ground into a desired shape by an ultra-precision lathe, and then a diamond paste abrasive was used to obtain a surface roughness R _max.
= 0.02 μm or less. On the molding surface 11a of the base material 11, ultra-hard diamond-like carbon (D
LC) is formed by the CVD method and the thickness of D is 0.4 μm.
The LC thin film 12 was formed. A hard carbon film was further formed on the DLC thin film 12 by a sputtering method to form a carbon thin film 13 having a thickness of 0.6 μm.

Using the pair of glass mold dies 10 thus prepared, as shown in FIG. 2, an optical glass element material (preform; product name: F-2, Ohara Optics) is provided between the molding surfaces 11a. (Made of glass) 20 was sandwiched and pressed under heat in a non-oxidizing gas atmosphere.

This press molding was repeated 500 times, but the releasability between the preform 20 and the molding surface 11a (carbon thin film layer 13) was always good and no deterioration was observed. Further, a high-precision optical glass element could be molded with good reproducibility without causing scratches or slight deformation on the surface of the molding surface. After the number of times of molding exceeded 1,000, the carbon thin film 13 was deteriorated, and the shape of the optical glass element to be molded began to be changed. Therefore, only the carbon thin film 13 was cerium oxide (CeO). ) A carbon thin film 13 was formed on the DLC thin film 12 again by a sputtering method after peeling (removing) using an abrasive. As a result, a glass mold 10 similar to a new one
Was obtained and could be subjected to molding again.

[0014]

According to the present invention, it is possible to obtain a mold having the properties required for a mold for an optical glass element, and the properties of which do not deteriorate even if the number of times of press molding is increased. Further, the mold of the present invention, when the use limit is reached,
Recycling is possible by removing only the carbon thin film layer and forming the film again.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a mold for an optical glass element according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a molding state of the molding die of FIG.

[Explanation of symbols]

 10 Mold for Glass Mold 11 Base Material 12 DLC Thin Film 13 Carbon Thin Film 20 Preform (Optical Glass Element Material)

Claims (4)

[Claims] 1. A molding die for use in a glass molding method for press-molding an optical glass element under heating, comprising: a base material having a molding surface; a diamond-like carbon thin film layer formed on the molding surface of the base material; A carbon thin film layer formed on a diamond-like carbon thin film layer;
A mold for an optical glass element, comprising: 2. The molding die for an optical glass element according to claim 1, wherein the base material is made of silicon carbide. 3. The mold for an optical glass element according to claim 1, wherein the diamond-like carbon thin film layer is formed by a CVD method. 4. The molding die for an optical glass element according to claim 1, wherein the carbon thin film layer is formed by a sputtering method.