JPH03164437A - Optical element forming die - Google Patents

Abstract

PURPOSE:To develop the optical element forming die having excellent characteristics by forming an Al-N thin film on the forming surface of the die made of SiC, etc., by PVD, CVD, etc., and heating the die to high temp. in an oxidizing atmosphere to oxidize the Al-N thin film into an alpha-Al2O3 film. CONSTITUTION:The curved surface 1a of an optical element forming die base material 1 made of SiC, WC, Si3N4, etc., is specularly finished, and an Al-N thin film 2 is formed on the surface by PVD, CVD, etc. The material is heated to a high temp. of >=1000 deg.C in an oxidizing atmosphere such as air to form an oxide film 4 of alpha-Al2O3 on the surface of the thin film 2. The product is used as the forming die, and optical glass is heated and pressed to produce an optical element. An optical element forming die free of the burning of glass, without the film 4 being released and withstanding long use is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for forming an optical element. [Prior Art] Generally, it is widely practiced to shape optical glass using a hot press to obtain a desired optical element. When using such hot press means, the mold for forming the optical element is subjected to large thermal shock and pressure from the optical glass heated to a high temperature. In order to manufacture optical elements at low cost, the molding material must be able to withstand repeated training over a long period of time. Conventionally, it has been known that the outermost surface of a mold for molding an optical element is made of Altos, taking note of the fact that aluminum oxide (AN!03) is a thermally stable substance.
g4 For example, in Japanese Patent Application Laid-open No. 123630/1983, A l
t. 0. A mold for forming an optical element is disclosed using sapphire, which is a single crystal. In addition, in Japanese Patent Publication No. 10407/1987, titanium carbide (T
iC), titanium nitride (TiN), titanium carbonitride (TiN)
A vapor-deposited coating layer of A f gos is formed through a vapor-deposited intermediate layer of CN). [Invention tries to solve! ! However, when using sapphire to form a mold for molding optical elements, it is extremely difficult to manufacture the sapphire itself.
That is, Af. It takes a long time to grow a single crystal, making it expensive and difficult to stabilize the quality. In addition, processing a zOs single crystal into a desired curved surface with a small roughness requires cutting while ignoring the orientation of the crystal, which tends to cause minute cracks and chips, resulting in poor reproducibility. There is a problem with this.

In this regard, 14L, after forming the mowing coating layer of ^p,01 through the above-mentioned stem-coating intermediate layer, a thin film (vapor-deposited coating layer) was applied after processing the mold base material, which is easy to process, into a desired curved surface. C. :、However, it is possible to keep a stable product at a relatively low price,、、Ap. Even with molds for molding optical elements that have a vapor-deposited coating layer of When hot pressing optical glass with a narrow temperature range, it is necessary to heat the mold to a very high gk and apply a large amount of pressure to deform the glass. Ti(:+TiNTiCN) was changed due to oxidation, and a separation of 1% occurred between the traced intermediate layer and the lining 3 layer.Naturally, T+C.T+ of the deposited intermediate layer
~, DingiCN has a working temperature of 500'C.
It is a substance that has good oxidation resistance to a certain extent. However, when the temperature exceeds 500'C, monooxidation proceeds rapidly and Tie. and T: *Od7: Oxidizes. Therefore, when the mold is exposed to high temperatures during molding, the oxidation of the vapor-deposited intermediate layer progresses, and the
The connection between the two is severed, and as a result, E11-ri resides there.

-・Ko, A.P. F03 is a substance that forms various crystal forms depending on a certain temperature, and the specific surface area changes depending on the crystal form. Here, the higher the temperature, the smaller the specific surface area (the smaller the interatomic distance), and at about 1200℃, α
It becomes minimum when it reaches 1.03 (α-wa! ZOX) of the type. σ−Aj'! ,0. is the distance A between two types of atoms
1-0 is I. The crystallinity is 89 (3 pieces) and 1.93 (3 pieces), which is superior to the γ-type AE20r having a Subinel structure with lattice defects.

However, when forming a thin film on A by PVD such as sputtering or ion plating, the operating temperature (substrate temperature) is as low as 600°C, so the specific surface area is comparatively low. The target becomes too large. Therefore, the molecules constituting the glass were easily adsorbed to the AlzozR film, and the large pressure generated at high mold temperatures caused condensation and seizure of the glass.

On the other hand, when forming an A N zOx thin film by CVD, P
Compared to VD, the substrate temperature is about 1000'C higher, so the specific surface area can be made smaller, but the hydrogen (H2) used as the carrier gas is A7! It remains in the ZOS thin film. Therefore, since the optical glass to be formed absorbs hO, it becomes Al. 0, I on the surface of the thin film
This resulted in hydrogen bonding with 1, which caused the glass to seize when high mold temperatures and large pressures were applied.

The present invention has been made in view of these conventional problems, and is inexpensive and has stable quality, and is capable of molding various optical glasses, especially optical glasses with a high softening point and a narrow temperature range with low viscosity. It is an object of the present invention to provide a mold for molding an optical element that does not cause burning of the glass or separation of the film even when the glass is heated.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides that at least the outermost layer of the molding surface contains aluminum (CA j'!) and nitrogen (N) in a certain amount {from A material By heating the base mold for an optical element mold in an oxidizing atmosphere, α-A/. 0, and used it as a mold for optical elements.

[Function] In the optical element precept type of the present invention having such a configuration,
α-A 1 . 0, the Q surface layer consists of fl#. Formed by heating -M to very high temperatures (e.g. over 1000°C), -N has very good oxidation resistance and is not oxidized at all at temperatures around 600°C. It is from. Further, since the outermost layer α-AI<zos was formed by thermally oxidizing the i-N layer, there is no clear interface between the two.

Therefore, distortions such as thermal stress are less likely to occur.
α-＾1! The tOs layer has great peeling resistance. Furthermore, since α-A1.03 has the smallest specific surface area as described above, molecules constituting the glass are difficult to adsorb. Even if the AN-N layer contains carrier gas 118 as an impurity, it gasifies during the thermal oxidation process, and H is not present in the α-Al zo3 layer. Therefore, even in a usage environment where the mold temperature is high and a large pressure is applied, seizure of the glass is extremely unlikely to occur.

〔Example〕

(First Example) As shown in Fig. 2, a cylindrical silicon carbide (
SiC) was used as the mold base material 1, one end surface of this mold base material 1 was mirror-finished into a spherical surface with a radius of curvature of 45 m, and the mold base surface 1 was
It was set as a. Then, an Al--N thin film 2 was formed on the basic surface 1a by the sputtering method to form the basic surface 1a. The sputtering conditions were as follows: ^l alone was used as the target, ^r gas was introduced to I X 1 0-' Torr, and then N! Introducing gas to a total pressure of 5X 10-'Torr, input power of 500W, and substrate temperature of
The film thickness was set to 1μ. Next, the base mold 3 of the mold for molding an optical element obtained in this way was heated in the atmosphere at a heating rate of 100° C./hr to 120° C.
The mold was heated to 0°C, maintained at 1200°C for 2 hours, and then allowed to cool naturally to form a mold for forming an optical element. As shown in FIG. 1, this mold for molding an optical element is heated in the oxidizing atmosphere to form the ^IN thin film 2.
The outermost layer of is α-^l-O, layer 4. When the optical element of this example was analyzed in the depth direction by ESCA (photoelectron spectroscopy), the results shown in Figure 3 were obtained. Furthermore, the etch rate is 40.
Person/sin. In Figure 3, the horizontal axis shows the etching time (
sin), and the atomic ratio (at 1%) is plotted on the vertical axis. In Fig. 3, the solid line 5 indicates oxygen (0), and the solid line 6 indicates Al
, and the solid line 7 indicates carbon (C). As can be seen from Figure 3, it was confirmed that the top 500 people were completely oxidized. Furthermore, when the optical element of this example was subjected to XvA diffraction, the results shown in FIG. 4 were obtained. As can be seen from Figure 4, α-Affixe
We were able to confirm a peak indicating the safety of s. In addition, when BaSFO8, which is an optical glass with a high softening point and low viscosity and a narrow temperature range, was molded using the mold for molding an optical element of this example, no burning of the glass or film peeling occurred. , we were able to obtain a lifespan of over 10,000 shots.
(Second Example) A cylindrical tungsten carbide (WC) with a diameter of IO 1 was used as a mold base material, and one end surface of this mold base material was mirror-finished into a spherical surface with a radius of curvature of 100-, and was used as a molding base surface. . And W.C.
Since the temperature at which oxidation begins is low, the entire surface of the mold base material is coated with AIN using the ion beam bank ring method.
IM was formed. The conditions were such that an AIN sintered body was targeted, N2 gas was introduced to IXlO-'Torr, the acceleration voltage was 1 kV, and the film thickness was 2 .mu.-. Next, the base mold for the optical element mold thus obtained was heated to 1000'C in the air at a heating rate of 100°C/hr, and heated for 10 hours while maintaining the temperature at 1000°C. After that, it was naturally cooled and used as a mold for molding optical elements. The thus obtained optical element mold of this example was analyzed by ESCA and X-ray diffraction, and it was found that the first
As in the example, α1A j! is applied to the outermost layer. We were able to confirm that zOs was under strict supervision.

In addition, using the optical element molding mold of this example, S
When KII was used, no glass burning or film peeling occurred, and the product had a lifespan of more than 10,000 shots. (Third Example) A cylindrical silicon nitride (SiJ4) with a diameter of 15 l was used as a mold base material, and one end surface of this mold base material was mirror-finished to a spherical surface with a radius of curvature of 30 degrees, and was used as a molding base surface. ．． Then, a ffi-Nl film was formed on the molded base surface by CVD.The CVD conditions were such that the substrate temperature was 1000°C and the film thickness was 2μ. Next, the base surface of the optical element molding mold obtained in this way was heated to 120 °C in the atmosphere at a heating rate of 100 °C/hr.
It was heated to 0°C and heated for 5 hours while maintaining the temperature at 1200''C. When the thus obtained optical element mold of this example was analyzed by ESCA and X-ray diffraction, it was found that it was the same as that of the first example. Similarly, it was confirmed that a large amount of light was generated at the very beginning.

In addition, when LLF6, which is an optical glass with a high softening point and a narrow temperature range with one lower viscosity, was formed using the mold for molding an optical element of this example, it was found that the glass λ burn-in and film peeling M
14゛No outbreak at all, +0000 Shigonoto -L no F
If you want to get it, it's good.

(Effects of the Invention) As described above, according to the mold for molding an optical element of the present invention, at least the outermost layer of the molding surface is made of a material mainly containing Af! and N. 1',! in an oxidizing atmosphere for 2t.L children to form α-i.0, on the outermost layer of 111, which is cheaper than using a single crystal J-fire. , stable quality can be obtained, and when used for molding, glass baking 7.1 hardening film 1
ノ1 No separation δ This long period z. : Can be used across the board. especially,
Even when an optical glass with a high softening point or a narrow temperature range with one lower viscosity is to be molded, it can be used for a long period of time without burning or peeling of the glass.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a mold for forming an optical element according to the present invention, and FIG. 2 shows a basic mold of a mold for forming an optical element according to the first embodiment of the present invention. In the vertical cross-sectional view, the third space shows the ES of the shape surface of the optical element shape mold of the first embodiment of the present invention.
Graph showing the results of CA, the fourth threshold is the first threshold of the present invention.
It is a graph which shows the X-ray diffraction result about the molding surface of the optical element mold of an Example. 1... Mold base material 2... Ap. -N membrane 3...Basic type 4...α-A l. 0, layer patent Debetsujin Olympus Optical Co., Ltd. Fig. 1 Fig. 2 Fig. 3 Fig. 7 Etching time (min) Fig. 4 5000 2θ (degree)

Claims (1)

[Claims] (1) At least the outermost layer of the molding surface is made of a material mainly composed of aluminum and nitrogen. By heating the base mold of an optical element molding die in an oxidizing atmosphere, the outermost layer is oxidized with α-type. A mold for molding an optical element characterized by being made of aluminum.