JP2006104008A - Method of manufacturing mold for molding optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a mold for molding an optical element capable of improving the durability of the mold. <P>SOLUTION: In manufacturing a mold for molding an optical element using a hard carbon film as a mold release layer and an amorphous silicon carbide film as an intermediate layer, direct current pulse bias is applied to the mold when the hard carbon film and the amorphous silicon carbide film are formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a method of manufacturing an optical element molding die used when manufacturing an optical element made of glass such as a lens or a prism by press molding a glass material.

  The technology for manufacturing lenses by press-molding glass materials without the need for a polishing process eliminates the complicated processes required in conventional manufacturing, making it possible to manufacture lenses easily and inexpensively. In addition, prisms and other optical elements made of glass have come to be used.

  Properties required for such a mold material used for press molding of a glass optical element include excellent hardness, heat resistance, releasability, and mirror finish. Conventionally, many proposals have been made for this type of mold material, such as metals, ceramics, and materials coated with them.

  As some examples, JP-A-49-51112 (Patent Document 1) discloses 13Cr martensite steel, and JP-A-52-45613 (Patent Document 2) describes SiC and Si3. N4 is disclosed in Japanese Patent Application Laid-Open No. 60-246230 (Patent Document 3). A material obtained by coating a cemented carbide with a noble metal is disclosed in Japanese Patent Application Laid-Open No. Sho 61-183134 (Patent Document 4) and Japanese Patent Application Laid-Open No. Sho 61. JP-A-281030 (Patent Document 5) and JP-A-1-301864 (Patent Document 6) disclose a diamond thin film or a diamond-like carbon film in JP-A 64-83529 (Patent Document 7), respectively. Has proposed a material coated with a hard carbon film.

Japanese Patent Publication No. 2-31012 (Patent Document 8) proposes forming a carbon film of 5 to 500 nm on either the lens or the mold. Further, according to Japanese Patent Application Laid-Open No. 6-72728 (Patent Document 9) filed by the present inventors, an intermediate formed on the surface of carbon and a mold base material or a base material using a carbon ion beam of high ion energy. There is described a method for producing a mold that does not cause peeling of a film and generation of cracks by forming a mixing layer comprising at least one element constituting the layer.
JP-A-49-51112 JP 52-45613 A JP 60-246230 A JP-A-61-183134 JP-A 61-281030 JP-A-1-301864 JP-A-64-83529 Japanese Patent Publication No. 2-31012 JP-A-6-72728

  However, 13 martensitic steel is easy to oxidize, and further has the disadvantage that Fe diffuses into the glass at high temperature and the glass is colored. SiC and Si3 N4 are generally considered difficult to oxidize, but oxidation occurs at a high temperature, and SiO2 is formed on the surface, resulting in glass fusion. A material coated with a noble metal is less likely to cause fusion, but has a drawback that it is very soft and is easily scratched and easily deformed.

  In general, a mold using a diamond-like carbon film, an aC: H film, or a hard carbon film has a good mold releasability between the mold and glass and hardly causes fusion with the glass. The adhesion is generally low, and if the molding operation is repeated several hundred times or more, the film may be partially peeled off, resulting in insufficient molding performance in the molded product. was there. Further, the diamond thin film has high hardness and excellent thermal stability. However, the diamond thin film has a mold as compared with an amorphous carbon film such as the diamond-like carbon film, aC: H film, and hard carbon film. The releasability between glass and glass was poor, and further improvement in releasability was desired.

  JP-A-1-301864 proposes that a carbon source gas concentration is set to 3% or more to form a film made of diamond crystal, graphite crystal, or amorphous carbon to have a maximum surface roughness of 20 nm or less. However, the presence of graphite crystals in the film causes deterioration of hardness and oxidation resistance, and causes deterioration of mold durability.

  In addition, the carbon film obtained by the forming method (vacuum vapor deposition method) used in the examples of JP-B-2-31012 generally has a weak adhesion between the film and the substrate, and the film is formed during molding. There may be a problem in durability such as peeling.

  In addition, the method of forming an optical element molding mold material by ion implantation of carbon ions described in JP-A-6-72728 can increase the adhesion between the film and the mold base material. Since a high voltage needs to be applied, there is a drawback that the manufacturing apparatus tends to be very expensive. In addition, since a highly directional ion beam is used, a hard carbon film having a uniform film thickness is formed on the molding surface of a lens mold material having a small curvature or a diffractive optical element mold material having a stepped step. There was a drawback that it was not possible.

  In addition, the method of producing a hard carbon film by applying a direct current pulse bias to a substrate described in JP-A-2000-143221 is a hard carbon with a uniform film thickness on the molding surface compared to other production methods. Although a film can be formed and a hard carbon film can be formed with good adhesion to the mold material, further uniform film thickness and improved adhesion to the mold material are desired.

  Furthermore, the method of forming a diamond-like carbon film after forming an intermediate layer composed of an amorphous mixture of silicon and carbon as an intermediate layer described in JP-A-5-1224825 is compared with other manufacturing methods. A hard carbon film can be formed with good adhesion to the mold material, but further improvement in adhesion with the mold material is desired.

  For this reason, in the present invention, in the method of manufacturing an optical element molding die material that forms a hard carbon film at least on the outermost surface layer, a source gas containing at least carbon and silicon is ionized by an ionization source, and negative in the die base material. After forming an amorphous silicon carbide film by applying a DC pulse bias, a source gas containing at least carbon is ionized by an ionization source, and a negative DC bias is applied to the mold base material to form a hard carbon film. The purpose is to form.

  According to the present invention, in the method for manufacturing an optical element molding die material that forms a hard carbon film at least on the outermost surface layer, a source gas containing at least carbon and silicon is ionized by an ionization source, and the mold base material is negative. After forming an amorphous silicon carbide film by applying a DC pulse bias, a source gas containing at least carbon is ionized by an ionization source, and a negative DC bias is applied to the mold base material to form a hard carbon film. By forming the optical element molding die, it is possible to provide a hard carbon film formed as a release layer with good adhesion to the die material and having a uniform film thickness regardless of the shape.

(Function)
Next, the action of the present invention will be described below together with the knowledge obtained in making the present invention. In view of the problems of conventional optical element molding molds, the present inventor has a method of forming a hard carbon film formed as a release layer with good adhesion to a mold material, and in various shapes with a uniform film thickness. As a result of continuing detailed experiments, it was discovered.

  In other words, in a method for manufacturing an optical element molding die that forms a hard carbon film at least on the outermost surface layer, a source gas containing at least carbon and silicon is ionized by an ionization source, and a negative DC pulse bias is applied to the die base material. After forming an amorphous silicon carbide film by applying, ionizing a source gas containing at least carbon with an ionization source and applying a negative DC bias to the mold base material to form a hard carbon film Thus, it is possible to form a hard carbon film evenly in a complicated shape with good adhesion to the mold material.

  A hard carbon film mainly composed of an amorphous material formed by a conventional manufacturing method is superior to other ceramics and metal thin films in terms of adhesion to glass, and thus has excellent releasability. The film has weak adhesion, and the film may be peeled off while the glass is being formed. This is presumably because the hard carbon film generally has a large film stress inside and easily peels off due to heat or force during molding.

  A method for forming a diamond-like carbon film after forming an intermediate layer made of an amorphous mixture of silicon and carbon (amorphous silicon carbide film) as an intermediate layer described in Japanese Patent Application Laid-Open No. 5-124825. Compared to other manufacturing methods, a hard carbon film can be formed with good adhesion to the mold material. However, the method of forming an amorphous silicon carbide film is called a bias-applied plasma CVD method. Since this method is applied, there is a limit to the adhesion of the film, and depending on the conditions of use, delamination may occur between the mold material and the amorphous silicon carbide film or between the amorphous silicon carbide film and the hard carbon film. was there.

  On the other hand, according to the manufacturing method of the present invention, since the pulse bias is applied, the plasma density on the surface of the mold material is increased, and the effect of mixing carbon atoms and silicon atoms with the atoms of the mold material is improved. The adhesion between the crystalline silicon carbide film and the mold material is greatly improved. Furthermore, by applying a pulse bias on this to form a hard carbon film, the effect of mixing atoms occurs between the amorphous silicon carbide film and the hard carbon film, forming a hard carbon film with good adhesion. I can do it.

  Furthermore, by applying a pulse bias, it becomes possible to form a uniform plasma along the shape of the mold material, and the amorphous silicon carbide film and the hard carbon film are even on the complex shape mold material. It can be formed with a film thickness. When a biased plasma CVD method described in Japanese Patent Application Laid-Open No. 5-124825 is used and an amorphous silicon carbide film is formed on a complex shaped mold material, a thick part and a thin part may be formed. is there. In the thin part of the amorphous silicon carbide film, the effect as an intermediate layer is reduced, and peeling is likely to occur between the amorphous silicon carbide film and the mold material. By forming the amorphous silicon carbide film and the hard carbon film with such a uniform film thickness, there is an effect that an amorphous silicon carbide film can be formed on the mold material with good adhesion.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Here, the typical cross section of the optical element molding die of the present invention is shown in FIG. In the figure, 11 is a mold base material having a hard carbon film 13 on the molding surface. Although FIG. 1 shows a convex lens molding die, the present invention is not limited to a convex lens molding die, but may be a concave lens molding die, an aspheric lens molding die, a cylindrical lens molding die, or the like. Can also be used.

  In the present invention, the hard carbon film is basically amorphous, has a high hardness, and is highly transparent in the infrared region, and is also called a diamond-like carbon film. Since this hard carbon film is amorphous, it has a very smooth surface. By forming the hard carbon film on the surface of the mold base material, it is the same as or more than the smoothness of the surface of the mold base material. Smoothness can be obtained.

  In addition, a hard carbon film usually does not have any crystallinity. However, when a minute region (on the order of nm) is observed in detail with an electron microscope or the like, a microcrystalline diamond or graphite having a size of several nanometers is obtained. May be observed. The amount of these microcrystals is also very difficult to estimate, but seems to be no more than a few percent of the total volume. That is, the “hard carbon film” is an amorphous carbon film containing only a carbon crystal phase (diamond, graphite) in an amount that is almost negligible. For forming the hard carbon film, a method called an ion beam vapor deposition method or an ion plating method is used. The film forming method is a method of converting a carbon source gas and a dilution gas such as hydrogen, oxygen, chlorine, fluorine, and a rare gas into a plasma by applying a hot filament or a high frequency, and further applying an electric field or a magnetic field. In this method, ions are accelerated and extracted from the plasma using an electric field, and the ions are irradiated onto a mold base material to form a hard carbon film on the molding surface.

  In the present invention, the hard carbon film is formed on an amorphous silicon carbide film as an intermediate layer. Amorphous silicon carbide film has high hardness and excellent chemical stability, so it is optimal as an intermediate layer. In addition, when a sintered body such as a super hard material is used as a mold base material, the smoothness of the surface may not be sufficiently improved due to particle dropping or pores. It is effective in improving the smoothness of the film. On the other hand, the crystalline silicon carbide film is inferior in surface smoothness, and the surface smoothness required for optical element molding dies may not be obtained. Further, the optimum thickness of the amorphous silicon carbide film is generally 0.05 μm or more, preferably 0.1 μm or more. The amorphous silicon carbide film of the present invention is performed by applying a negative DC pulse bias to the mold material. The negative DC pulse bias voltage varies depending on the mold material and shape, but is applied at about 0.5 to 20 kV. The negative DC pulse bias to be applied may be a constant value at the time of film formation, but may be high immediately after the start of film formation and may be low at the end of film formation. This is to increase the adhesion between the mold base and the amorphous silicon carbide film by applying a high negative DC pulse bias immediately after the start of film formation. For example, a negative pulse bias of 5 kV or more and 20 kV or less is applied. When applied, carbon and silicon-containing ions are implanted into the mold base material, and the adhesion between the amorphous silicon carbide film and the mold base material is improved. Further, the reason for applying a low negative DC pulse bias at the end of film formation is to increase the smoothness of the amorphous silicon carbide film, for example, by applying a negative pulse bias of 1 kV or more and 4 kV or less. An amorphous silicon carbide film having high smoothness can be obtained. As a specific example, immediately after the start of film formation, the bias voltage is set to 7 kV, and thereafter, the voltage is gradually decreased to 5 kV, 3 kV, and 1 kV, and film formation is completed. be able to.

  Further, the optimum conditions for the repetition frequency and duty ratio of the DC pulse voltage vary depending on conditions such as the applied voltage and the film thickness to be deposited, but typically, the repetition frequency is 500 to 20 kHz and the duty ratio is 2 to 40%. To do.

  The ionization of the gas containing carbon and silicon is performed with an ion source. The ion source decomposes and ionizes the carbon-containing gas by applying an electric field or a magnetic field to the heated filament or applying a high frequency. An amorphous silicon carbide film can be formed on the surface of the mold material by drawing ions containing carbon and silicon formed by the ion source in the vicinity of the mold material with a negative DC pulse bias.

In the method for forming an amorphous silicon carbide film of the present invention, an organic silicon compound or a mixture of a carbon compound and a silicon compound can be used as a raw material. As the organosilicon compound, methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, tetraethoxysilane, hexamethyldisiloxane, or the like can be used. As the carbon compound, various carbon-containing gases and liquid organic compounds can be vaporized and used. As the liquid organic compound, alcohols such as methanol and ethanol, ketones such as acetone, aromatic hydrocarbons such as benzene, ethers such as dimethyl ether, and organic acids such as formic acid and acetic acid can be used. As the carbon-containing gas, hydrocarbon gas such as methane, ethane, ethylene, acetylene, carbon monoxide, or carbon halide can be used.
As the silicon compound, silane, disilane, silicon tetrafluoride, or the like can be used.

  The hard carbon film of the present invention is formed by applying a negative DC pulse bias to the mold material. The negative DC pulse bias voltage varies depending on the mold material and shape, but is applied at about 0.5 to 20 kV. The negative DC pulse bias to be applied may be a constant value at the time of film formation, but may be high immediately after the start of film formation and may be low at the end of film formation. This is to increase the adhesion between the mold base material and the hard carbon film by applying a high negative DC pulse bias immediately after the start of film formation. For example, by applying a negative pulse bias of 8 kV or more and 20 kV or less. Carbon-containing ions are implanted into the mold base material to improve the adhesion between the hard carbon film and the mold base material. Moreover, the reason for applying a low negative DC pulse bias at the end of film formation is to increase the smoothness of the hard carbon film. For example, by applying a negative pulse bias of 1 kV or more and 4 kV or less, high smoothness is achieved. A hard carbon film can be obtained. As a specific example, immediately after the start of film formation, the bias voltage is set to 10 kV, and then the voltage is gradually decreased to 7.5 kV, 5 kV, and 2.5 kV to complete the film formation. It can be performed.

  Further, the optimum conditions for the repetition frequency and duty ratio of the DC pulse voltage vary depending on conditions such as the applied voltage and the film thickness to be deposited, but typically, the repetition frequency is 500 to 20 kHz and the duty ratio is 2 to 40%. To do.

  The ionization of the carbon-containing gas is performed with an ion source. The ion source decomposes and ionizes the carbon-containing gas by applying an electric field or a magnetic field to the heated filament or applying a high frequency. A hard carbon film can be formed on the surface of the mold material by drawing carbon-containing ions formed by the ion source in the vicinity of the mold material with a negative DC pulse bias.

  In the method for forming a hard carbon film of the present invention, various carbon-containing gases and liquid organic compounds can be vaporized and used as the carbon source. As the liquid organic compound, alcohols such as methanol and ethanol, ketones such as acetone, aromatic hydrocarbons such as benzene, ethers such as dimethyl ether, and organic acids such as formic acid and acetic acid can be used. As the carbon-containing gas, hydrocarbon gas such as methane, ethane, ethylene, acetylene, carbon monoxide, or carbon halide can be used.

  The mold base material used in the present invention includes oxide ceramics such as alumina / zirconia, carbide / nitride ceramics such as silicon carbide / silicon nitride / titanium carbide / titanium nitride / tungsten carbide, and WC super Hard alloys, metals such as molybdenum, tungsten, and tantalum can be used. The shape of the mold base (base) can be arbitrarily determined depending on the shape of the molding apparatus and the molded lens. For example, when molding a lens, the molding surface is curved to match the curvature of the lens diameter. The amorphous silicon carbide film and the hard carbon film are formed on the curved surface.

  FIG. 3 is a schematic view showing a film forming apparatus for forming an amorphous silicon carbide film and a hard carbon film used in the present invention. Reference numeral 30 denotes a vacuum chamber, and 31 denotes a gas exhaust port, to which a valve, a turbo molecular pump, and a rotary pump (all not shown) are connected. An ion source 32 can ionize the source gas using a heated filament, an electric field, and a magnetic field. In addition, a valve, a gas flow regulator, a pressure regulator, a gas cylinder, and a liquid vaporizer (not shown) are connected to the 32 ion source. 33 schematically shows an ion beam. Reference numeral 34 denotes a mold material. Although the figure shows a convex mold material, the mold material of the present invention is not limited to this. Reference numeral 35 denotes a base holder that can fix the mold material and adjust the film forming temperature of the mold material by using a cooling mechanism or a heating mechanism (not shown). Reference numeral 36 denotes a DC pulse bias power source, which can apply a DC pulse bias to the mold material and the substrate holder.

  The film forming apparatus used in the present invention is not limited to the above apparatus, but in the present invention, after forming an amorphous silicon carbide film as in the above apparatus, it is not exposed to the atmosphere. It is desirable that the hard carbon film can be continuously formed in the same film forming apparatus. This is because when an amorphous silicon carbide film is formed and exposed to the atmosphere, oxygen and moisture are adsorbed on the surface, and even if a hard carbon film is formed thereon, an amorphous silicon carbide film and a hard carbon film are formed. This is because a large amount of oxygen atoms remain at the interface, thereby reducing the adhesion of the hard carbon film.

  The above-described present invention has been conventionally used for peeling off hard carbon films, such as large-diameter glass lenses, thin glass lenses, glass lenses with a large thickness ratio, and diffractive optical elements having a stepped shape. Molding a lens that has a problem with the durability of the mold has the effect of greatly improving the mold durability.

  Next, the present invention will be described in detail based on examples.

  1 and 2 show one embodiment of an optical element molding die according to the present invention. 1 shows a state before press molding of the optical element, and FIG. 2 shows a state after molding of the optical element. Here, reference numeral 11 is a mold base material, 12 is a glass material, 13 is a release film made of the hard carbon film of the present invention, and reference numeral 21 in FIG. 2 is an optical element. As shown in FIG. 1, an optical element 21 such as a lens is formed by press-molding a glass material 12 placed between molds.

  Next, the optical element molding die of the present invention will be described in detail. As a mold base material, a binderless WC-based cemented carbide sintered body (manufactured by Fujidais Co., Ltd., trade name J-05) was processed into a predetermined shape and then polished so that Ra = 1.8 nm.

Next, this mold base material is thoroughly cleaned and then placed in the film forming apparatus shown in FIG. 3 to first form an amorphous silicon carbide film. The mold was heated to 300 ° C. using the substrate heating mechanism of the substrate holder, introduced as a raw material gas at a flow rate of tetraethoxysilane: 20 ml / min, and the pressure was adjusted to 2 × 10 ⁻¹ Pa. The source gas is decomposed and ionized by applying a heated filament, an electric field and a magnetic field with an ion source, and a substrate bias is applied to the mold base material using a DC pulse bias power source of 36 so that the surface of the mold material is amorphous. A silicon carbide film was formed. The DC pulse bias was -2.5 kV, the repetition frequency was 2 kHz, and the duty ratio was 10%. An amorphous silicon carbide film having a thickness of about 100 nm was formed by film formation for 10 minutes.

Subsequently, a hard carbon film is formed. The gas flow rates were toluene: 20 ml / min, hydrogen: 10 ml / min, the mold material temperature was 300 ° C., and the pressure was 3 × 10 ⁻¹ Pa. The source gas was decomposed and ionized with an ion source, and a direct current pulse bias was applied to the mold base material to form a hard carbon film. The DC pulse bias was -4 kV, the repetition frequency was 2 kHz, and the duty ratio was 10%. A hard carbon film having a thickness of about 300 nm was formed in 30 minutes.

  Next, an optical lens was molded using this mold for molding an optical element.

  The molded glass is crown optical glass SK12 (softening point Sp = 672 ° C., transition point Tg = 550 ° C.), diameter radius: φ30 mm, central part: 2.2 mm thickness, outermost circumference: 1.5 mm thickness The ultra-thin convex meniscus lens is molded. The molding conditions were a nitrogen temperature and a press temperature of 620 ° C. During molding, the mold release property between the mold and the molded optical element was good. Further, when the mold surface after molding was observed with a scanning electron microscope, film peeling, generation of cracks, and glass fusion were not observed, and the mold surface property was good. The molded glass lens also had good surface roughness with no glass breakage.

As a mold base material, a WC cemented carbide was processed into a predetermined shape, and then the molding surface was mirror-polished to Rmax = 0.04 μm. Next, this mold base material was thoroughly washed and then placed in the film forming apparatus shown in FIG. 3, and an amorphous silicon carbide film was first formed as an intermediate layer. The film forming conditions were as follows: mold material temperature: 200 ° C., source gas: trimethylsilane: 25 ml / min, and pressure: 3 × 10 ⁻¹ Pa. The source gas was decomposed and ionized with an ion source, and a substrate bias was applied to the mold base material using a DC pulse power source. In the DC pulse bias, the voltage was changed to -6 kV, -3.5 kV, and -1 kV every 10 minutes from the start of film formation. The repetition frequency was 2 kHz and the duty ratio was 10%. An amorphous silicon carbide film having a thickness of about 200 nm was formed in 30 minutes.

Next, a hard carbon film is formed. The gas flow rates were acetylene: 20 ml / min, hydrogen: 5 ml / min, substrate temperature: 200 ° C., and pressure: 2 × 10 ⁻¹ Pa. The source gas was decomposed and ionized with an ion source, and a substrate bias was applied to the mold base material using a DC pulse power source. In the DC pulse bias, the voltage was changed to −10 kV, −6 kV, and −2 kV every 10 minutes from the start of film formation. The repetition frequency was 2 kHz and the duty ratio was 10%. A hard carbon film having a thickness of about 300 nm was formed in 30 minutes.

  Next, an optical lens was molded using this mold for molding an optical element.

  The molded glass is crown optical glass SK12 (softening point Sp = 672 ° C., transition point Tg = 550 ° C.), diameter radius: φ12 mm, central part: 1.4 mm thickness, outermost circumference: 2.5 mm thickness The concave menis lens is molded. The molding conditions were a nitrogen temperature and a press temperature of 620 ° C. During molding, the mold release property between the mold and the molded optical element was good. Further, when the mold surface after molding was observed with a scanning electron microscope, film peeling, generation of cracks, and fusion of glass were not observed, and the mold surface property was good. The molded glass lens also had no glass breakage, good surface roughness, high transmittance, and no halo was observed.

(Comparative Example 1)
An optical element molding die was prepared in the same manner as in Example 1 except that amorphous silicon, chromium, and titanium nitride were used as the intermediate layer instead of amorphous silicon carbide (all of the intermediate layers were formed by a known sputtering method). When the optical glass was molded, the hard carbon film peeled off as the molding proceeded, and the glass was fused to the mold material.

(Examples 3-5, Comparative Examples 1-2)
An optical element molding die was formed and an optical element was molded in the same manner as in Example 2 except that various bias application conditions were changed. (The film formation time was adjusted so that the film thickness of the amorphous silicon carbide film was about 200 nm and the film thickness of the hard carbon film was about 300 nm.)
The results are shown in Table 1. In Comparative Examples 1 and 2, a DC bias was applied instead of the DC pulse bias.

◎：非常に良好
○：良好
△：実用上可
×：不可
非晶質炭化けい素及び硬質炭素膜の成膜条件で、直流パルスバイアスを印加する本発明の範囲内とすることで、型の成形耐久性は良好となる。

◎: Very good ○: Good △: Practical acceptable ×: Impossible The film forming conditions of the amorphous silicon carbide and the hard carbon film are within the scope of the present invention in which a DC pulse bias is applied. Molding durability is good.

  On the other hand, when only a DC pulse bias is applied (Comparative Example 2), the amount of adhesion between the mold base material and the hard carbon film decreases, peeling of the hard carbon film occurs, and the durability of the mold deteriorates.

  Further, when a DC pulse bias is applied only to the amorphous silicon carbide film (Comparative Example 3), the adhesion amount between the hard carbon film and the amorphous silicon carbide film decreases, and the hard carbon film and the amorphous silicon film are amorphous. Peeling occurs between the quality silicon carbide films, and the molding durability of the mold deteriorates.

  In addition, when a DC pulse bias is applied only to the hard carbon film (Comparative Example 4), the adhesion amount between the amorphous silicon carbide film and the mold base material decreases, and the amorphous silicon carbide film and the mold base material are reduced. Peeling occurs between the materials, and the molding durability of the mold deteriorates

The state before press molding of the optical element. State after optical element molding. 1 is a schematic diagram of a film forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Type | mold base material 12 Glass material 13 Release film | membrane which consists of hard carbon film of this invention 21 Optical element 30 Vacuum chamber 31 Gas exhaust port 32 Ion source 33 What showed ion beam typically 34 Mold material 35 Base | substrate holder 36 DC pulse Bias power supply

Claims (1)

In the method of manufacturing an optical element molding mold material for forming a hard carbon film at least on the outermost surface layer
A source gas containing at least carbon and silicon is ionized by an ionization source, and after forming an amorphous silicon carbide film by applying a negative DC pulse bias to the mold base material, a source gas containing at least carbon is added. A method for producing an optical element molding die, characterized by ionizing with an ionization source and applying a negative DC bias to the die base material to form a hard carbon film.

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