JP2003073134A - Method for forming optical element and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an optical element enabling to form an optical glass element with high precision having good optical performances in a short tact by a direct press method of optical glass. SOLUTION: The method for forming an optical element by pressing a glassy material with a mold under heating comprises using a mold 1 on the surface of which a coating film 2 of hydrogenated amorphous carbon is formed which contains one or more metals selected from the group consisting of iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), platinum (Pt), tungsten (W), and tantalum (Ta).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing an optical glass element, and more particularly to a method and a mold for molding an optical glass element which does not require a polishing step after press molding.

[0002]

2. Description of the Related Art In recent years, optical glass lenses have tended to be aspherical in order to achieve both simplification of the lens structure of optical equipment and weight reduction of the lens portion at the same time. In order to manufacture this aspherical lens, the direct press molding method is regarded as promising because the optical polishing method, which is a conventional optical lens manufacturing method, is inferior in workability and mass productivity.

The direct press molding method is a method in which a lump of optical glass is heated on an aspherical mold which has been finished to a desired surface quality and surface accuracy in advance, or a lump of glass which is preheated. Is press-molded, and an optical lens is manufactured after the press-molding without requiring further polishing or polishing steps.

However, in the above-mentioned method for producing an optical glass lens, the precision must be so high as not to impair the image forming quality of the obtained lens after press molding. Particularly in the case of an aspherical lens, it is required to be able to be molded with high accuracy. Further, in consideration of mass productivity, it is required that the mold and the glass are easily released at a high temperature and that the production can be performed with a short tact.

Therefore, as the mold material, there is little chemical action on the glass at high temperature, the glass press surface of the mold is not easily damaged by scratches, the fracture resistance by thermal shock is high, and the glass is It is necessary to have low adhesion.

A mold material satisfying the above-mentioned conditions necessary for a press-molding mold for an optical glass element to some extent,
In Japanese Patent Publication No. 4-16415 and Japanese Patent Publication No. 4-81530, a thin film containing iridium-rhenium or iridium-osmium or iridium-rhenium-osmium alloy as a main component is formed on a cemented carbide or a heat-resistant material. Coated molds have been proposed. Further, Japanese Patent Publication No. 6-88803 proposes a mold coated with a thin film containing an iridium-rhenium compound containing 20 to 50 wt% of carbon as a main component.

[0007]

However, the above-mentioned conventional mold material (Japanese Patent Publication No. 4-16415, Japanese Patent Publication No. 4415).
-81530) does not satisfy all the above conditions. For example, the above-mentioned mold material has little chemical action on glass at high temperatures, is less susceptible to damage such as scratches on the glass press surface, and has high resistance to destruction by thermal shock, but the major drawback is that it adheres well to glass. Due to the high force, even if you try to take out the glass element molded from the mold at a relatively high temperature in order to shorten the production tact, the lens firmly adheres to the mold and you can not take it out Alternatively, the film coated on the mold may peel off and stick to the molded product.

Further, in Japanese Patent Publication No. 6-88803, it is stated that Ir-Re-C (20 to 50 wt%) exhibits high oxidation resistance, heat resistance and alkali resistance, and has low wettability with glass. However, the amount of C is atom
% Is 79 to 94 atom%, and usually Re, I
The solid solubility of C in r is not so high (for example, "Revised 3rd Edition Metallurgical Handbook, The Japan Institute of Metals, Maruzen Co., Ltd. P
855 "), this compound cannot be an interstitial solid solution. On the other hand, since there is no data that iridium carbide and rhenium carbide exist stably, it cannot be considered as an interstitial compound. In this composition, carbon is much larger (4 to 16 times) than the metal components (Ir, Re), and cannot be an interstitial compound (a compound in which carbon enters between the lattices of metals). Therefore, even if the substance of this composition could be coated on the mold, the substance cannot be stable, and it is unsuitable as a mold material that decomposes only by heating the mold. Seem.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is to enable a high-accuracy optical glass element to be molded with good optical performance with a short tact time by a direct pressing method of optical glass. To provide a molding method and a molding die of an optical element for achieving the above.

[0010]

[Means for Solving the Problems]
In order to achieve the object, a method of molding an optical element according to the present invention is a method of molding an optical element by pressing a glass material with a mold under heating, and iridium (Ir), rhenium ( Re), osmium (Os), palladium (Pd), rhodium (R
h), ruthenium (Ru), gold (Au), platinum (P
t), tungsten (W), tantalum (Ta), the glass material is press-molded using a mold having a coating film of amorphous hydrogenated carbon containing at least one metal selected from the above. .

Further, in the optical element molding method according to the present invention, the content of the metal in the coating film is set to 0.1 to 50 atom%.

In the method for molding an optical element according to the present invention, a cutting layer made of cemented carbide containing tungsten carbide (WC) as a main component or free-cutting ceramics is formed as a material for the mold body. It is characterized by using a cemented carbide having a surface or silicon nitride containing boron nitride.

Further, in the optical element molding method according to the present invention, at least one intermediate layer is provided between the mold body and the coating film.

In the method of molding an optical element according to the present invention, the intermediate layer is formed of aluminum (Al), boron (B), chromium (Cr), hafnium (Hf), niobium (Nb), tantalum (Ta). , Titanium (Ti), vanadium (V), zirconium (Zr) 1
It is characterized in that it is formed from one or more kinds of metal or metal nitride, metal carbide, metal boride or metal carbonitride.

Further, in the optical element molding die according to the present invention, a glass material is pressed under heating to mold the optical element. In the optical element molding die, iridium (Ir), Rhenium (R
e), one or more metals selected from osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), platinum (Pt), tungsten (W), tantalum (Ta). It is characterized in that a coating film of amorphous hydrogenated carbon containing is formed.

The optical element molding die according to the present invention is characterized in that the content ratio of the metal in the coating film is 0.1 to 50 atom%.

In the mold for the optical element according to the present invention, a cutting layer made of cemented carbide containing tungsten carbide (WC) as a main component or free-cutting ceramics is used as the material of the main body of the mold. It is characterized by using a cemented carbide having a molding surface or silicon nitride containing boron nitride.

Further, in the mold for the optical element according to the present invention, at least one or more intermediate layers are provided between the main body of the mold and the coating film.

In the optical element molding die according to the present invention, the intermediate layer is formed of aluminum (Al), boron (B), chromium (Cr), hafnium (Hf), niobium (Nb), tantalum (Ta). , Titanium (Ti), vanadium (V), zirconium (Zr), or one or more kinds of metal, metal nitride, metal carbide, metal boride, or metal carbonitride.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below.

First, the outline of the embodiment will be described.

In the present embodiment, a material having heat resistance and excellent workability is used as a base material of a press-molding die, and this is processed into a pressing die having an optical glass element shape to be formed, and further, a uniform shape is formed thereon. Iridium (Ir), rhenium (R
e), one or more metals selected from osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), platinum (Pt), tungsten (W), tantalum (Ta). An optical glass element in which a glass to be molded in an inert gas atmosphere or under vacuum is heated to a softening temperature or higher and pressure-molded by using a pair of molds having a coating film of amorphous hydrogenated carbon containing To get

In the above structure, a material having heat resistance and excellent workability is used as the base material of the press-molding die, so that the performance required for the base material is sufficient. Further, amorphous hydrogenated carbon is Although the moldability is very good, the abrasion resistance is somewhat difficult, so the amorphous hydrogenated carbon that wears the places where the film is easily rubbed at several thousand shots contains a metal component that greatly increases the hardness. The hardness of the surface is increased, and the thin film coated on the base material has improved scratch resistance more than ever.

Further, since the film of this embodiment is basically amorphous hydrogenated carbon, its adhesion to glass is remarkably low, and the releasability of the molded product is remarkably good. Therefore, it is excellent in oxidation resistance, which is important in the optical glass element molding method, is inert to glass, is excellent in mechanical strength so that the shape accuracy is not broken when pressed, and is excellent in workability and precision processing. It completely satisfies the requirement that it should be easy and that it should be possible to produce it with a shorter tact.

Further, in this embodiment, a material having heat resistance and broken in workability is used as a base material of a press molding die, and this is processed into a pressing die having an optical glass element shape to be formed, Iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd),
Rhodium (Rh), Ruthenium (Ru), Gold (Au),
Platinum (Pt), Tungsten (W), Tantalum (Ta)
Provided is a mold for molding an optical glass element, which has a coating film of amorphous hydrogenated carbon containing at least one metal selected from the above at least on its surface.

In the above structure, a material having heat resistance and excellent workability is used as the base material of the press-molding die, so that the performance required for the base material is sufficient. Although the moldability is very good, the abrasion resistance is somewhat difficult, so the amorphous hydrogenated carbon that wears the places where the film is easily rubbed at several thousand shots contains a metal component that greatly increases the hardness. The hardness of the surface is increased, and the thin film coated on the base material has improved scratch resistance more than ever.

Further, since the film of this embodiment is basically amorphous hydrogenated carbon, its adhesion to glass is extremely low, and the releasability of the molded product from the mold is extremely good. Therefore, it is necessary for optical glass element molding dies, has excellent oxidation resistance, is inert to glass, has excellent mechanical strength that does not lose shape accuracy when pressed, and has excellent workability and precision processing. It completely meets the conditions that it must be easy to produce and can be produced with a shorter tact.

In the present embodiment, the metal contained in the metal-containing amorphous hydrogenated carbon is iridium (I
r), rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (R
u), gold (Au), platinum (Pt), tungsten (W), tantalum (Ta), and the content thereof is 0.
It is 1 to 50 atom%.

If the content of the metal is less than 0.1 atom%, the effect of increasing the hardness of the mold is not sufficient and 50 at
If it is more than om%, the adhesion with glass increases and the releasability deteriorates, so it is necessary to lower the release temperature, which leads to a large increase in tact, and in some cases, the molded product is subject to thermal stress. It becomes unsuitable as a mold material because it will crack at. Therefore, the preferable metal content range is 0.1.
It becomes ~ 50 atom%. Iridium (Ir), rhenium (Re), osmium (Os), palladium (P
d), rhodium (Rh), ruthenium (Ru), gold (A
u), platinum (Pt), tungsten (W), and tantalum (Ta) are selected as one or more of these elements when they have low reactivity with glass and when they are contained in amorphous hydrogenated carbon. This is because it has the effect of increasing the hardness. In general, the solubility of these metals in carbon is at most several atom%, so that they cannot stably exist as a normal metal interstitial interstitial solid solution. In metal-containing amorphous hydrogenated carbon,
Since it consists of nanometer-sized metal particles cross-linked to a C: H matrix, the metal is not dissolved in carbon, so solubility does not need to be taken into consideration and the metal can exist stably.

Further, the type of metal to be contained is defined as one or more, because when a plurality of metals are contained, the surface energy of the mold is lowered due to the mixing enthalpy effect due to the addition of these elements, and This is because the moldability may be improved.

Further, in this embodiment, as a press-molding die base material, a cemented carbide having tungsten carbide (WC) as a main component, or a cemented carbide having a cutting layer made of free-cutting ceramics on the molding surface. An alloy or silicon nitride containing boron nitride is used.

In the above-mentioned structure, the cemented carbide is not only capable of electric discharge machining, but also in the case of performing general grinding, it is better than conventional silicon carbide or silicon nitride used as a mold for glass lens molding. The feature is that it is possible to easily and highly accurately process the die shape. Further, since free-machining ceramics and boron nitride-containing silicon nitride have sufficient strength and hardness and can be cut, precision processing can be easily performed. Furthermore, no special equipment is required for processing. Processing time is short. Therefore, the die cost can be made very low. Furthermore, it becomes possible to fabricate a surface that can only be created by cutting. In addition, compared with the method of forming a plating layer and cutting the layer, this base material has excellent heat resistance, so it can also be used for forming high melting point glass,
It does not peel off unlike plating.

Further, in the present embodiment, at least one intermediate layer is provided between the metal-containing amorphous hydrogenated carbon film and the base material.

In the above structure, by providing the intermediate layer, the adhesion between the outermost surface layer of the mold and the mold base material is better than that without the intermediate layer, and the surface of the mold is peeled off even under severe molding conditions. Disappears. Also, if it is necessary to peel off the mold surface for maintenance for some reason (for example, when foreign matter is mixed into the mold and the surface of the mold is scratched), it is sufficient to maintain only the intermediate layer. This eliminates the need for re-polishing and grinding of the die base material, greatly reducing maintenance costs.

In this embodiment, the intermediate layer is made of aluminum (Al), boron (B), chromium (Cr),
Hafnium (Hf), Niobium (Nb), Tantalum (T
a), titanium (Ti), vanadium (V), zirconium (Zr), and one or more kinds of metal, metal nitride, metal carbide, metal boride, or metal carbonitride.

In the above structure, the above-mentioned metal group, metal nitride, metal carbide, metal boride or metal carbonitride has the property of increasing the adhesion between the mold base material and the outermost surface layer, and It has sufficient strength, hardness, oxidation resistance, etc. and is optimal as an intermediate layer.

The present embodiment can obtain a mold satisfying all the above-mentioned necessary conditions which cannot be realized by the conventional mold material by the above-mentioned constitution, and by using this mold, the optical glass element is directly pressed. Then, it becomes possible to mold.

An embodiment of the method for manufacturing an optical element of the present invention will be specifically described below with reference to the drawings.

Using a columnar cemented carbide having a diameter of 16 mm, a pair of optical glass lens press-molding main bodies consisting of upper and lower molds having a concave pressing surface with a radius of curvature of 10 mm were processed.

The press surface of these mold bodies was mirror-polished using 0.1 μm diamond abrasive grains. Next, on this mirror surface, using an RF reactor, PVD method and CVD
By combining the methods, a coating film of metal-containing amorphous hydrogenated carbon shown in FIG. 4 was formed to prepare a mold for glass pressing. A side sectional view of this mold is shown in FIG.
In FIG. 1, 1 is a mold body, and 2 is a coating film.

More specifically, after depressurizing the chamber to 10 ^-4 Pa, a bias voltage of 0 to 100 V was applied to the mold, and an argon plasma (32 sccm) with a bias voltage of -2 kV was used to sputter a metal target to be contained. However, a small amount of ethylene gas (C ₂ H ₂ ) (0 to
A ratio of 15%: Ar, the metal content is changed by changing this ratio). The metal-containing amorphous hydrogenated carbon coating film shown in FIG. 4 was formed by introducing into a vacuum chamber.

Next, an optical element was molded using the mold shown in FIG. 4 obtained as described above.

The glass is borosilicate glass SK12 (n
d = 1.58313, yd = 59.4, transition point Tg = 5
50 ° C., yield point At = 588 ° C., see FIG. 5 for composition) and lanthanum-based glass LaK12 (nd = 1.67790,
υd = 55.3, transition point Tg = 554 ° C., yield point At =
It was processed into a ball lens by using 596 ° C. and the composition (see FIG. 6).

FIG. 2 is a schematic view of the apparatus used for the molding test. In FIG. 2, 24 is a chamber, 25 is an upper shaft, 26 is a lower shaft, 27 is a block containing a heater (heater block), 28 is a heater block, and 29 is a heater block.
Is an upper mold, 30 is a lower mold, 31 is glass, and 32 is a hydraulic cylinder.

After the chamber 24 is evacuated by a vacuum pump (not shown), N ₂ gas is introduced and the chamber 2
After the N ₂ atmosphere 4, the heater block 27,2
The upper mold 29 and the lower mold 30 are heated by 8 and the temperature corresponding to the viscosity of the glass to be molded is 10 ⁻⁹ d · Pa · s (SK1
2: 630 ° C., LaK 12: 615 ° C.), the hydraulic cylinder 32 pulls up the upper shaft 25 to lower the lower mold 3
A molding material (ball lens) was placed on No. 0 by an auto hand (not shown). After keeping the mold temperature as it is for 1 minute, the upper shaft 25 is lowered by the hydraulic cylinder 32,
The ball lens was pressed by the upper mold 29 and the lower mold 30 with a force of 3,000 N for 3 minutes. Thereafter, cooling is performed at 70 ° C./minute, and when the temperature of the upper and lower molds reaches 540 ° C., the upper mold 29 is raised and the molded product 3 on the lower mold 30 is moved by an unillustrated auto hand.
1 is taken out, and then a molded product 3 is manufactured by a replacement device (not shown).
1 was taken out from the chamber 24. The upper and lower molds were heated again, and the above operation was repeated to perform 5,000 shot molding. The results are shown in Fig. 4.

Good moldability was obtained with all the molds shown in FIG. 4 (Examples 1 to 15).

On the other hand, when the metal content is less than 0.1 atom% (Comparative Examples 1 to 3), the wear resistance of the mold is poor, the peripheral portion of the mold is consumed at 2,000 shots, and the base metal is It was exposed, and fusion between the mold and glass occurred. Further, the metal content is set to be greater than 50 atom% (Comparative Example 4 to
In 7), the adhesion between the mold and the glass was high, and the lens could not be taken out from the mold at 540 ° C. When the lens was forcibly taken out, the lens was broken. In some cases, the film on the mold surface was stuck to the broken lens.

Further, a stepped die having a shape which cannot be ground and polished as shown in FIG. 3 was processed by cutting with a cemented carbide tool, and then the press surface was finished with extremely high precision by cutting with a diamond bite. The die base material used at this time was not a cemented carbide but a machinable material (for example, BN-containing silicon nitride, free-machining ceramics provided on a cemented carbide base material, etc.).

The same test as above was performed on this mold, but the same result was obtained. This molded product is a kind of diffraction grating and is an example of a so-called fine optical element.

The shapes that cannot be processed by grinding and polishing here include elements having a free-form surface (so-called free-form surface elements), elements having a fine pattern (so-called fine optical elements), various shapes (spherical surface, aspherical surface, etc.). A flat surface (or the like) is combined to form a mold having a complicated shape that cannot be produced by polishing or is bonded, and a shape obtained by combining these shapes.

In this embodiment, the thickness of the metal-containing amorphous hydrogenated carbon film is 300 nm,
Not limited to this film thickness, 50 nm to 2000 nm (2 μm)
It could be used without problems in the range.

Further, in the present embodiment, the examination was conducted without the intermediate layer, but Cr, Ti, AIN, BN and Cr were formed in the intermediate layer.
N, HfN, NbN, TaN, TiN, VN, ZrN,
TiAIN, TiC, TaC, TiCN, TaCN, T
Similar results were obtained using iN / Ti and TiN / AIN / TiN / Ti. Furthermore, in the molds with these intermediate layers, the durability was improved about 5 times.

As described above, according to the above embodiment,
A material that has heat resistance and has poor workability is used as a base material for a press molding die, and this is processed into a pressing die having the shape of an optical glass element to be molded, and further, with a uniform thickness, iridium (Ir) , Rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (R
u), gold (Au), platinum (Pt), tungsten (W), tantalum (Ta), a pair of molds formed with a coating film of amorphous hydrogenated carbon containing one or more metals selected from This is an ideal method for molding a glass optical element because the glass to be molded in an active gas atmosphere or under vacuum is heated above its softening temperature and pressure-molded to obtain an optical glass element.

A material having heat resistance and excellent workability is used as a base material for a press molding die, which is processed into a pressing die having an optical glass element shape to be molded, and a uniform thickness is formed on the die. , Iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd), rhodium (Rh),
By forming a coating film of amorphous hydrogenated carbon containing one or more metals selected from ruthenium (Ru), gold (Au), platinum (Pt), tungsten (W) and tantalum (Ta), An optical glass press-molding die satisfying all the requirements for an optical glass molding die material is obtained, which is extremely effective for mass-producing high-precision optical glass elements in a very short tact time.

The metals contained in the metal-containing amorphous hydrogenated carbon include iridium (Ir), rhenium (Re), osmium (Os), palladium (Pd),
Rhodium (Rh), Ruthenium (Ru), Gold (Au),
Platinum (Pt), Tungsten (W), Tantalum (Ta)
By forming a coating film having a content of 0.1 to 50 atom% with at least one of the above, an optical glass press-molding die satisfying all the above-mentioned necessary conditions as an optical glass molding die material is obtained. It is extremely effective for mass-producing high-precision optical glass elements with a very short tact.

Further, as a press forming die base material, a cemented carbide containing tungsten carbide (WC) as a main component, or a cemented carbide having a cutting layer made of free-cutting ceramics on the forming surface, or boron nitride. Since the contained silicon nitride is used, it is possible to greatly reduce the time and cost required for processing the mold.

Further, by providing the intermediate layer, it becomes possible to further improve the durability of the mold.

As the intermediate layer, aluminum (A
l), boron (B), chromium (Cr), hafnium (H
f), niobium (Nb), tantalum (Ta), titanium (T
i), vanadium (V), zirconium (Zr) at least one metal or metal nitride or metal carbide or metal boride or metal carbonitride to further improve the durability of the mold. Became possible.

[0059]

As described above, according to the present invention, it is possible to form an optical glass element having good optical performance and high accuracy with a short tact by the direct pressing method of optical glass.

[Brief description of drawings]

FIG. 1 is a side sectional view of a molding die according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a press molding device according to an embodiment.

FIG. 3 is a schematic cross-sectional view of a press mold for an optical element.

FIG. 4 is a diagram showing contained metals in a coating film on a surface of a molding die.

FIG. 5 is a diagram showing a composition of borosilicate glass SK12.

FIG. 6 is a diagram showing a composition of lanthanum glass LaK12.

[Explanation of symbols]

Type 1 body 2 Coating film (press surface) 3 Diffraction grating molding die 24 chambers 25 upper shaft 26 Lower shaft 27 heater block 28 heater block 29 Upper mold 30 Lower mold 31 glass 32 hydraulic cylinder

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuhiro Yamamichi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F-term (reference) 2K009 BB06 CC01 DD04 EE00

Claims (10)

[Claims] 1. A method of molding an optical element by pressing a glass material with a mold under heating, wherein iridium (Ir), rhenium (Re),
Osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), platinum (P
t), the glass material is press-molded using a mold having a coating film of amorphous hydrogenated carbon containing one or more metals selected from tungsten (W) and tantalum (Ta). Optical element molding method. 2. The method for molding an optical element according to claim 1, wherein the content of the metal in the coating film is 0.1 to 50 atom%. 3. A material for the body of the mold, a cemented carbide containing tungsten carbide (WC) as a main component, or a cemented carbide having a cutting layer made of free-cutting ceramics on its forming surface, or containing boron nitride. The method for forming an optical element according to claim 1, wherein silicon nitride is used. 4. The method for molding an optical element according to claim 1, wherein at least one intermediate layer is provided between the main body of the mold and the coating film. 5. The intermediate layer is made of aluminum (Al),
Boron (B), chromium (Cr), hafnium (Hf),
Niobium (Nb), tantalum (Ta), titanium (Ti),
The optical element according to claim 4, which is formed of one or more kinds of metal or metal nitride, metal carbide, metal boride or metal carbonitride selected from vanadium (V) and zirconium (Zr). Molding method. 6. A mold of an optical element for molding an optical element by pressing a glass material under heating, wherein iridium (Ir), rhenium (Re),
Osmium (Os), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), platinum (P
t), a mold for an optical element, characterized in that a coating film of amorphous hydrogenated carbon containing at least one metal selected from tungsten (W) and tantalum (Ta) is formed. 7. The mold for an optical element according to claim 6, wherein the content of the metal in the coating film is 0.1 to 50 atom%. 8. The material of the main body of the mold is a cemented carbide containing tungsten carbide (WC) as a main component, or a cemented carbide having a cutting layer made of free-cutting ceramics on its forming surface, or boron nitride. The optical element molding die according to claim 6, wherein the contained silicon nitride is used. 9. The mold for an optical element according to claim 6, wherein at least one intermediate layer is provided between the main body of the mold and the coating film. 10. The aluminum (A
l), boron (B), chromium (Cr), hafnium (H
f), niobium (Nb), tantalum (Ta), titanium (T
10. The material according to claim 9, which is formed from one or more kinds of metal or metal nitride, metal carbide, metal boride or metal carbonitride selected from i), vanadium (V) and zirconium (Zr). Mold for optical elements.