JPH05163027A - Mold for molding optical glass element and its production - Google Patents

Abstract

PURPOSE:To form a glass-releasing film having excellent adhesivity to a mold for forming an optical glass element, releasability from glass and oxidation resistance. CONSTITUTION:A glass-releasing film is formed by evaporating B and one or more materials selected from the nitride, carbide or oxide of Al, Si, C and the transition metal of group 4a, 5a or 6a of the periodic table and elemental Ni, Fe, Co and C by ion sputtering simultaneously with ion bombardment with one or more kinds of ions selected from nitrogen ion, nitrogen-containing ion and inert gas ion. The adhesiveness of the releasing layer to the mold is improved by forming a mixing layer between the releasing film and a base layer of the substrate mirror-polished to a surface roughness Ra of <=100nm. The crystal structure of boron nitride constituting the main component of the thin film can be made to be 'zincblende structure' or 'wurtzite structure' by selecting the film-forming condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for manufacturing a glass optical element by press molding and a manufacturing method thereof.

[0002]

2. Description of the Related Art Recently, a method of manufacturing a glass optical element such as a lens or a prism by press-molding a glass material which has been softened by heating has been rapidly developed.
The release film with the glass formed on the molding surface of the molding die used in this press molding prevents fusion of the glass softened at high temperature to the molding die and protects the molding die processed with high precision. have. Therefore, the release film is required to have film properties such as adhesiveness with a molding die, releasability from glass, oxidation resistance, smoothness, and high hardness.

In response to these requirements, many proposals have been made so far to apply various coatings to a molding die made of metal, ceramics or the like. For example, Japanese Patent Publication No.
No. 59863 discloses that boron (B) is vapor-deposited from a boron evaporation source on the surface of a substrate placed in a vacuum reaction chamber.
It is disclosed that a film of cBN or hBN is formed on the surface of the substrate by irradiating with continuous N ₂ ions.
Further, Japanese Patent Publication No. 3-61617 proposes an optical element molding die in which a surface of a ceramic substrate is coated with silicon carbide (SiC) and a nitride such as boron nitride is coated thereon. There is. Japanese Patent Publication No. 3-61615 proposes to apply a thin film in which cBN and aBN are mixed to an optical element molding die. As another example, JP-A-2-243523 proposes an optical element molding die in which an intermediate layer made of carbide or nitride is formed on the surface of a substrate, and a diamond film is coated on the intermediate layer. There is.

[0004]

These releasing films are suitable for press molding of lead-free glass materials such as BK7.
Has obtained molding durability of 000 times or more. However, SF
In press molding of a glass material containing lead such as No. 6, lead in the glass component is reduced by the carbon of the diamond film, a minute amount is deposited on the surface of the molded glass optical element, and the surface becomes clouded, resulting in surface roughness. Will be reduced. Further, the deposited lead causes countless scratches on the surface of the release film, which significantly deteriorates the durability of the release film.

Further, among the film characteristics required as a mold release film, such as adhesion to a mold, mold release property to glass, oxidation resistance, smoothness, high hardness, etc., a conventional mold release film has good adhesion. The problem of the property has not been solved, and when the heat cycle is repeated, the film peels off due to the stress due to the difference in thermal expansion, and the durability as a release film of the molding die is deteriorated.

When a thin film in which cBN and aBN are mixed is coated as the release film, it becomes possible to remove the residual strain inside the thin film and alleviate the difference in the coefficient of thermal expansion.
Improvement of heat shock property can be expected. However, aBN
In the case of B / N = 1, it is difficult to obtain B / N = 1 and the composition is likely to be rich in metallic boron, so that the oxidation resistance is poor. Therefore, the aBN portion is oxidized during glass forming, and the surface roughness of the forming surface is reduced.

[0007]

[Means for Solving the Problems] A substrate, an underlayer formed on the surface of a molding surface of the substrate and made of the same material as the substrate, a mixed layer formed on the substrate, and a boron nitride as a release film on the outermost surface. Is contained in at least 30% by volume and the balance is Al, S
i, at least one selected from nitrides, carbides and oxides of transition metals of groups 4a, 5a and 6a of the Periodic Table of Elements and Ni, Fe, Co and a thin film composed of 70% by volume or less did. This release film is formed by depositing a material of the same material as that of the substrate on the surface of the substrate to be formed, vapor-depositing the surface of the substrate to a mirror finish, and then B, Al, Si, C, 4a of the periodic table of elements, While depositing at least one kind of nitrides, carbides and oxides of group 5a and 6a transition metals and Ni, Fe, Co and C, at the same time, nitrogen ions, nitrogen-containing substance ions, and inert gas ions are formed. It was obtained by irradiating at least one kind of ions from among the above to form a mixed layer at the interface with the mirror-finished surface, and forming the release film via the mixed layer.

In this film forming method, a mixing layer by dynamic ion mixing is formed on the interface between the molding surface and the release film by controlling the mixing ratio of the ion gas to be irradiated and the acceleration voltage, and the release film is attached. Improved strength.

Further, the crystal structure of boron nitride can be made into a "sphalerite" or "wurtzite type" by controlling the mixing ratio of the irradiation ions and the acceleration voltage.

[0010]

This release film has a Knoop hardness of 3000 to 500.
The boron nitride film has a high hardness of 0 kg / mm ² , and has a molding durability of 3000 times or more. The decomposition temperature of boron nitride is 2300 ° C, and it has heat resistance such that it can be used at 1200 ° C even in an oxidizing atmosphere. Further, it has a feature that it does not react with a glass material containing lead such as SF6. In addition, AlN, Al ₂ O ₃ , Si ₃ N ₄ , SiC,
TiC, TiN, ZrC, ZrN, Cr ₂ C, Cr ₂ O
_{Since 3} , WC and the like are hard compounds, when they are contained in the film, they become a high hardness film, which makes it difficult for scratches to be formed during press molding and improves durability.

This release film does not chemically react with lead in press molding of an optical material containing lead such as SF6, so that precipitated lead is not generated and an optical glass containing lead which could not be conventionally formed. Enables press molding.

[0012]

EXAMPLES Examples of the present invention will be described below. Experimental Example 1 As shown in FIG. 1, a substrate 1 of a glass optical element molding die is set in a reaction chamber 2 and evacuated by a vacuum pump 7, and then heated by a heater 3 to 400 ° C. to 800 ° C.
An organic compound gas 4 of Al, Si, and 4a, 5a, 6a transition metals of the periodic table of elements is introduced into the reaction chamber 2. Then, the ultraviolet laser 6 is mirrored from outside the furnace, and the laser introduction window 1
The surface of the substrate 1 is irradiated via 0. Laser introduction window 1
A laser introduction window protective gas 5 is flown in 0, and the exhaust gas at the time of evacuation is processed by the exhaust gas processing equipment 8.
By the above photo MOCVD reaction, a dense and flat film can be formed.

As the substrate 1 of the glass optical element molding die, S is used.
Using iC (silicon carbide), a SiC film having a thickness of several 100 μm was vapor-deposited as an underlayer on the molding surface by the CVD method.
Next, the surface of the SiC film was mirror-finished so that Ra = 1 nm or less. This substrate 1 was placed in the optical MOCVD apparatus of FIG. 1 and heated to 550 ° C., and the raw material gas was introduced into the reaction chamber 2 according to the conditions of Table 1 to form a film.

At the same time, an ultraviolet laser 6 is applied to the surface of the substrate.
By irradiating with, the CVD reaction was caused efficiently to form a smooth and dense film. As shown in Table 1, the film formation was performed by changing the transportation conditions of the source gas. Crystal structure, composition,
Table 1 shows the results of measuring the Knoop hardness and the number of times of durability (the number of times of press molding of an optical material containing lead such as SF6). B
When the content of N was 30% by volume or more, molding durability performance of 3000 times or more was obtained.

[0015]

[Table 1]

Experimental Example 2 As shown in FIG. 2, the substrate 11 was placed in the reaction chamber shown in FIG. Metallic boron was set on the target (1) 12 and the reaction chamber was evacuated to 10 ^-6 Torr or less. While depositing metallic boron at a deposition rate of about 1 nm / min by Ar ion beam sputtering, at the same time, 40 keV of mixed gas ions of Ar / N ₂ = 0.3 from the ion source 20 for ion irradiation.
The mixed layer between the surface of the mold and the release film was changed in thickness by irradiating with an accelerating voltage of 2 and changing the mixing time as shown in Table 2. Subsequently, Ar / N ₂ = 0.
While irradiating the ions of the mixed gas of 3 at an acceleration voltage of 10 keV, the deposition rate was controlled so that the B / N composition ratio was about 1, and a boron nitride film was formed to a thickness of about 300 nm.

With the above ion beam sputtering deposition apparatus, it is possible to obtain a release film firmly adhered to the surface of the substrate. In this vapor deposition method, a mixed layer can be formed at the interface between the molding surface and the release film by controlling the vapor deposition rate and the acceleration voltage of the ion irradiation, and the adhesion strength of the release film can be improved. In addition, by controlling the mixing ratio and the accelerating voltage of the ion gas to be irradiated, it is possible to generate the "sphalerite-type boron nitride" or "wurtzite-type boron nitride" that is an ultra-high pressure phase and an ultra-hard material. ..

Table 2 shows the results of examining the relationship between the mixing treatment time and the Knoop hardness at this time. The increase in hardness due to the mixing treatment is considered to be due to the increase in the adhesiveness of the release film.

Further, the influence of the type of substrate and the surface roughness of its surface was investigated. The film forming conditions of boron nitride were the same as those of Experiment No. 4 in Table 2. At this time, the surface roughness and Knoop hardness,
Table 3 shows the results of examining the relationship with the durability count (the number of press moldings of the optical material containing lead such as SF6). When Ra is about 100 nm or less, a good mixing effect can be obtained, and a film having good releasability can be obtained.

This release film has a Knoop hardness of 3000 to 50.
It is a high-hardness boron nitride film of 00 kg / mm ₂ , and has a molding durability of 3000 times or more.

[0021]

[Table 2]

[0022]

[Table 3]

Experimental Example 3 Using the same apparatus as in Experimental Example 2, two kinds of targets as shown in Table 5 were selected from the 10 kinds of targets for ion beam sputtering shown in Table 4, and the ion irradiation conditions were changed. By changing it, a composite film of boron nitride and a metal oxide, a metal nitride, or a metal carbide was formed. Crystalline phase in the film,
Table 5 shows the results of evaluation of the BN content, the Knoop hardness, and the number of times of durability.

This release film has a Knoop hardness of 4000 to 50.
It is a high-hardness boron nitride film of 00 kg / mm ² , and has a molding durability of 4000 times or more.

The hardness and durability were improved as compared with Experimental Example 1, because AlN, Al ₂ O ₃ mixed in the boron nitride film,
Si ₃ N ₄ , SiC, TiC, TiN, ZrC, Zr
N, Cr ₂ C, Cr ₂ O ₃ , WC, etc. are hard compounds, so when they are contained in the film, they become a high hardness film, which makes it difficult for scratches to be formed during press molding and improves durability. is there.

[0026]

[Table 4]

[0027]

[Table 5]

Experimental Example 4 Using the same apparatus as in Experimental Example 2, the target (1) shown in FIG.
Metallic boron was set in No. 12, the conditions of mixed gas ions for ion irradiation were changed as shown in Table 6, and the crystal phase generated in the film was evaluated by X-ray diffraction and Raman spectroscopy.

Ar / N ₂ = 30%, He / Ne = 30%
When the acceleration voltage is 2 and 20 KeV, cBN and wBN
A crystalline phase of wurtzite BN was confirmed. From this, it was found that the BN films obtained in Experimental Examples 2 and 3 had a mixed crystal phase of cBN and wBN.

[0030]

[Table 6]

[0031]

As described above, according to the present invention, it is possible to form a mixed layer having a function of improving the adhesion by optimizing the gas mixing ratio, the ion acceleration voltage and the mixing time under the film forming conditions shown in the examples. It is possible to obtain a glass release film of a glass optical element molding die containing boron nitride as a main component, which is produced under optimum conditions and has excellent adhesion to the molding die substrate.

This release film is a composite thin film of boron nitride and a metal oxide, a metal nitride, or a metal carbide, and it can be seen that it has excellent press durability as shown in the examples. Further, the release film of the glass optical element molding die made of boron nitride containing this metal does not chemically react with lead in press molding of an optical material containing lead such as SF6, so that precipitated lead is not generated. In addition, it enables the press molding of optical glass containing lead, which could not be molded conventionally.

[Brief description of drawings]

FIG. 1 is a schematic view of a film forming apparatus by an optical MOCVD method in an example of the present invention.

FIG. 2 is a schematic diagram of a film forming apparatus by an ion beam sputtering method in an example of the present invention.

[Explanation of symbols]

 1, 11 Substrate 2 Reaction chamber 3 Heating heater 4 Raw material gas 5 Laser introduction window protection gas 6 Ultraviolet laser 7 Vacuum pump 8 Exhaust gas treatment facility 9 Mirror 10 Laser introduction window 12 Target (1) 13 Target (2) 14 Target (3) 15 target (4) 16 ion source for ion beam sputtering 1 17 ion source for ion beam sputtering 2 18 ion source for ion beam sputtering 3 19 ion source for ion beam sputtering 4 20 ion source for ion irradiation

Claims (3)

[Claims] 1. A substrate, an underlayer formed on the surface of the molding surface of the substrate and made of the same material as the substrate, a mixed layer formed on the substrate, and at least 30 boron nitride as a release film on the outermost surface.
At least one selected from the group consisting of Al, Si, nitrides, carbides and oxides of transition metals of groups 4a, 5a and 6a of the periodic table of the elements and Ni, Fe and Co in the balance 70% by volume or more A glass optical element molding die, comprising a thin film composed of less than or equal to volume%. 2. B and Al, Si, C, 4 of the Periodic Table of the Elements
a, 5a, and 6a transition metal nitrides, carbides, oxides, and at least one of Ni, Fe, Co, and C are vapor-deposited, and at the same time, nitrogen ions, nitrogen-containing ions, and inert gas ions At least one kind of ion irradiation is performed to form a mixed layer at an interface with the surface of the underlayer that is mirror-finished, and the release film according to claim 1 is formed on the re-surface through the mixed layer. A method for manufacturing a glass optical element molding die. 3. The glass optical element molding die according to claim 1, wherein the boron nitride has a “zincblende type” or “wurtzite type” crystal structure.