JP2004345910A - Mold for shaping optical element, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of a film on a mold surface and to prevent the coarsening of the mold surface even when a glass material is used as a mold base material. <P>SOLUTION: A method for manufacturing a mold for shaping an optical element comprises forming a hard carbon film 16 on the shaping surface of the mold base material 12 having the shaping surface for shaping the optical element on its surface and formed from glass containing SiO<SB>2</SB>. The method for manufacturing the mold includes a first thin film forming process for forming a first thin film 13 made of SiO<SB>2</SB>on the shaping surface, a second thin film forming process for forming a second thin film 14 made of SiO<SB>x</SB>(0<x<2) on the first thin film 13, a third thin film forming process for forming a third thin film 15 made of Si on the second thin film 14, and a fourth thin film forming process for forming a hard carbon film 16 on the third thin film 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mold for molding an optical element, which is mainly used for producing an optical element made of glass such as a lens or a prism by press molding a glass material, and a method for producing the same.
[0002]
[Prior art]
The technology of manufacturing a lens by press molding of a glass material without the need for a glass polishing step has eliminated the complicated steps required in conventional manufacturing, making it possible to manufacture lenses easily and inexpensively. In addition to lenses, prisms and other optical elements made of glass have come to be used.
[0003]
Properties required for such a mold used for press molding of a glass optical element include excellent hardness, heat resistance, mold release properties, mirror workability, and the like. Conventionally, many proposals have been made for this type of mold material, such as metals, ceramics, and materials coated with them.
[0004]
To mention some examples, JP-A-49-51112 (Patent Document 1) discloses 13Cr martensitic steel, and JP-A-52-45613 (Patent Document 2) discloses SiC and Si. ₃ N ₄ is, in JP-60-246230 (Patent Document 3), coated material noble metals cemented carbide, also, JP 61-183134 (Patent Document 4), JP JP-A-61-281030 (Patent Document 5) and JP-A-1-301864 (Patent Document 6) respectively disclose a diamond thin film or a diamond-like carbon film in JP-A-64-83529 (Patent Document 7). ) Proposes a material coated with a hard carbon film.
[0005]
Further, Japanese Patent Publication No. 2-31012 (Patent Document 8) proposes forming a carbon film of 5 to 500 nm on one of a lens and a mold. Furthermore, according to Japanese Patent Application Laid-Open No. 6-72728 (Patent Document 9), which has already been filed by the applicant of the present application, carbon and a mold base material or a surface of the base material are formed by using a carbon ion beam of high ion energy. It describes a method for producing a mold in which peeling and cracking of a film hardly occur by forming a mixing layer comprising at least one or more elements constituting an intermediate layer.
[0006]
Next, Japanese Patent Application Laid-Open No. 62-186816 (Patent Document 10) discloses that a conventional cemented carbide mainly composed of WC (tungsten carbide) can be processed by grinding and polishing as a material of a mold base material. In addition, there is described a production method of obtaining an optical element molding die by transferring a molding die by pressing a molding die material made of glass with a molding master while hot. As an improvement thereof, Japanese Patent Application Laid-Open No. 2-102136 (Patent Document 11) discloses a molding die body made of glass which is hot-pressed and a joined body made of a metal or ceramics having heat resistance. An optical element molding die integrally formed is described.
[0007]
[Patent Document 1]
JP-A-49-51112 [Patent Document 2]
JP-A-52-45613 [Patent Document 3]
JP-A-60-246230 [Patent Document 4]
JP-A-61-183134 [Patent Document 5]
JP-A-61-281030 [Patent Document 6]
JP-A-1-301864 [Patent Document 7]
JP-A-64-83529 [Patent Document 8]
Japanese Patent Publication No. 2-31012 [Patent Document 9]
JP-A-6-72728 [Patent Document 10]
JP-A-62-186816 [Patent Document 11]
JP-A-2-102136.
[0008]
[Problems to be solved by the invention]
However, 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 the glass and is unlikely to cause fusion with the glass. Adhesion is generally low, especially when the mold base material is glass, if the molding operation is repeated several tens of times or more, the film is partially peeled off, and sufficient molding performance may not be obtained. There was a problem in durability.
[0009]
Further, the method described in Patent Document 9 is a preferable method as compared with other methods of manufacturing a mold for molding an optical element. However, since carbon ions having high ion energy are used, the surface of the mold material may be roughened. . This is not a major problem for general-purpose optical elements.However, in the case of high-performance lenses or when a large number of these optical elements are used, the transmittance of the lens may decrease or halo may occur. is there.
[0010]
The problems of the adhesion of the film and the roughness of the surface of the mold material are remarkable especially when the mold base material is a glass material. The use of a glass material as a mold base material is very useful for cost reduction, such as low material costs and easy processing. However, since carbon-containing ions are involved in the formation of a carbon film, in the case of an insulating material such as a glass material, the effect of ion bombardment cannot be obtained, so that the adhesion between the film and the mold base material decreases. In addition, there have been problems that the mold base material is charged up, abnormal discharge occurs, and the surface is roughened.
[0011]
Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to improve the durability of a film on a mold surface and prevent the roughness of the mold surface even when a glass material is used as a mold base material. Is to be able to do it.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, a method for manufacturing an optical element molding die according to the present invention is provided with a molding surface for molding an optical element on a surface and formed from glass containing SiO _2. Forming a first thin film made of SiO _{2 on} said molding surface by forming a hard carbon film on said molding surface of said mold base material. Forming a second thin film formed of SiOx (0 <x <2) on the first thin film; and forming Si on the second thin film. A third thin film forming step of forming a third thin film; and a fourth thin film forming step of forming the hard carbon film on the third thin film.
[0013]
Further, in the method of manufacturing an optical element molding die according to the present invention, in the second thin film forming step, the second thin film moves from the first thin film to the third thin film in a thickness direction thereof. , Wherein the second thin film is formed such that the value of x gradually decreases from 2 to 0.
[0014]
Further, in the method of manufacturing an optical element molding die according to the present invention, in the first to third thin film forming steps, the first to third thin films are formed by a sputtering method.
[0015]
Further, in the method of manufacturing an optical element molding die according to the present invention, in the fourth thin film forming step, the hard carbon film is formed by an ion beam evaporation method or an ion plating method.
[0016]
Further, the mold for molding an optical element according to the present invention has a molding surface for molding an optical element on the surface and forms a hard carbon film on the molding surface of a mold base material formed of glass containing SiO _2. An optical element molding die, comprising: a first thin film made of SiO ₂ formed on the molding surface; and SiOx (0 <x <2) formed on the first thin film. A second thin film made of Si, a third thin film made of Si formed on the second thin film, and the hard carbon film formed on the third thin film. It is characterized by.
[0017]
Further, in the optical element molding die according to the present invention, the value of x gradually decreases from 2 to 0 as the second thin film moves from the first thin film to the third thin film in the thickness direction. It is characterized by a composition that decreases toward the end.
[0018]
Further, in the optical element molding die according to the present invention, the first to third thin films are formed by a sputtering method.
[0019]
Further, in the optical element molding die according to the present invention, the hard carbon film is formed by an ion beam evaporation method or an ion plating method.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a schematic sectional view of an embodiment of the optical element molding die of the present invention.
[0022]
In FIG. 1, reference numeral 11 denotes a cemented carbide base having WC (tungsten carbide) as a main component, and reference numeral 12 denotes a molding die having a transfer surface shape made of glass containing SiO ₂ which is hot pressed. The molding die 12 is joined to the cemented carbide base 11 and is integrally formed. In FIG. 1, a lens mold having a free-form surface having three concave surfaces is shown. However, the present invention is not limited to the shape, and a concave-convex lens mold, an aspheric lens mold, The present invention can be applied to a mold having another shape such as a mold for molding a cylindrical lens.
[0023]
The mold base material whose transfer surface is made of glass containing SiO ₂ used in the present embodiment is formed by pressing a master mold made of a cemented carbide material or the like to form a large number of mold base materials with a high cycle time. This is a mold base material made of a glass material that can be used.Because the machining time can be greatly reduced compared to the mold machining by grinding and polishing, the cost of machining and the lead time of mold machining can be reduced. Achieved.
[0024]
Further, the mold body may be entirely made of glass. However, in terms of mechanical strength and machining of screws and the like, an integrated type of glass and cemented carbide is desirable.
[0025]
13 is a SiO ₂ layer, 14 is a SiOx (0 <x <2) layer, 15 is a Si layer, and these layers are sequentially laminated by sputtering, CVD, ion plating or the like.
[0026]
FIG. 2 is a schematic sectional view of a sputtering film forming apparatus for forming the SiO ₂ layer 13, the SiOx (0 <x <2) layer 14, and the Si layer 15. These forming methods are:
(1) The mold base material 22 is set in the vacuum chamber 21, and the mold base material 22 is rotated on the target 24 by the rotation shaft 23. The temperature is detected by the thermocouple 25, the temperature is heated to 300 ° C. by the heater 26 such as a halogen lamp, and the ultimate degree of vacuum in the chamber is exhausted to 1 × 10 ⁻⁵ Pa or less.
(2) An argon gas and an oxygen gas are introduced, the mold base material 22 is rotated, a high frequency is applied to the Si metal target 24, the raw material is turned into plasma, and the SiO ₂ layer 13 is formed to have a thickness of 0.01 to 1 μm.
(3) The argon gas is constantly or gradually increased, the oxygen gas is gradually decreased, the mold base material 22 is rotated, a high frequency is applied to the Si metal target 24, the raw material is turned into plasma, and the SiOx (0 < x <2) The layer (graded layer) 14 is formed in a thickness of 0.01 to 1 μm.
(4) The oxygen gas is stopped, only the argon gas is introduced, the mold base material 22 is rotated, high frequency is applied to the Si metal target 24, the raw material is turned into plasma, and the Si layer 15 is formed to have a thickness of 0.01 to 1 μm.
[0027]
Thus obtained, an SiO ₂ layer, SiOx (0 <x <2 ) layer (graded layer) stack of Si layer on the glass containing SiO _2, since the SiO ₂ layer 13 are laminated The adhesion at the interface between the glass 12 and the SiO ₂ layer 13 increases, and the SiO x (0 <x <2) layer (graded layer) 14 increases the adhesion between the SiO ₂ layer 13 and the Si layer 15. Further, when the hard carbon film 16 is formed, the Si layer 15 has a higher adhesion because the SiC layer is formed on the surface of the Si layer 15.
[0028]
Note that, in the above, the case where the sputtering method is used as the film forming method has been described. However, a known CVD or ion plating method can be used, and the film forming apparatus is not limited to the above film forming apparatus.
[0029]
16 is a hard carbon film. A hard carbon film is basically called an diamond-like carbon film because it is basically amorphous, has high hardness, and has high transparency in an infrared region. Since this hard carbon film is amorphous, it has a very smooth surface, and by being formed on the surface of the mold base material, it has the same or higher surface smoothness as that of the mold base material. Smoothness can be obtained.
[0030]
The hard carbon film usually does not have any crystallinity. However, when a minute region (nm order) is observed in detail by an electron microscope or the like, a fine crystalline diamond or graphite having a size of about several nm is obtained. May be observed. The amount of these crystallites is also very difficult to estimate, but is likely to be at most a few percent of the total volume.
[0031]
The “hard carbon film” referred to in the present embodiment is a carbon film containing only a carbon crystal phase (diamond, graphite) of a negligible amount or less. For forming the hard carbon film, a method called an ion beam evaporation method or an ion plating method is used. The above-described film forming method is to form a carbon source gas, and a diluting gas such as hydrogen, oxygen, chlorine, fluorine, and a rare gas into a hot filament or a high frequency, and further, by applying a magnetic field or the like, to form a plasma, and from this plasma, In this method, ions are accelerated and extracted by using an electric field, and the ions are irradiated onto a mold base material to form a hard carbon film on the molding surface.
[0032]
In the method for forming a hard carbon film of the present embodiment, various carbon-containing gases and liquid organic compounds can be vaporized and used as the carbon source. Examples of the liquid organic compound include 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. As the carbon-containing gas, hydrocarbon gas such as methane, ethane, ethylene, and acetylene, carbon monoxide, and halogenated carbon can be used.
[0033]
FIG. 3 is a schematic diagram showing a film forming apparatus for forming a hard carbon film that can be used in the present embodiment. 31 is a vacuum chamber, 32 is an ion source, which is connected to a valve, a gas flow regulator, a pressure regulator, and a gas cylinder (not shown), and can ionize a carbon-containing gas using a heated filament and an electric field. . Reference numeral 33 denotes a power supply for applying a bias to the substrate holder. 34 schematically shows an ion beam, and 35 is a mold. A gas exhaust port 36 is connected to a valve, a turbo-molecular pump, and a rotary pump (all not shown). Reference numeral 37 denotes a substrate holder which can fix a mold member. It should be noted that the film forming apparatus used in the present invention is not limited to the above apparatus at all.
[0034]
In the embodiment of the present invention, the SiO ₂ layer 13, the SiO x (0 <x <2) layer (graded layer) 14, the Si layer 15, and the hard carbon film 16 are formed using different apparatuses. This is to make the explanation easy to understand, and it is usually desirable to form a film with a film forming apparatus having a sputtering source and an ion source in the same chamber in terms of adhesion and contamination. However, the effects of the present invention are not impaired even if the films are formed by separate film forming apparatuses.
[0035]
Next, specific examples will be described.
[0036]
(Example 1)
FIG. 1 is a schematic sectional view of an optical element molding die according to an embodiment of the present invention.
[0037]
First, a transfer surface shape made of borosilicate glass (glass transition point = 540 ° C., softening point = 730 ° C.) 12 as a glass containing SiO ₂ is placed on a cemented carbide base 11 mainly composed of WC (tungsten carbide). Is press-formed hot. The general press molding process is the following steps (1) to (4).
Step (1): A cemented carbide base 11 mainly composed of WC and a glass 12 containing SiO ₂ are heated by a heat source.
Step (2): The glass 12 containing SiO ₂ in the matrix is pressed against the cemented carbide base 11 mainly composed of WC, and the glass 12 containing SiO ₂ is melted into the cemented carbide base 11 mainly composed of WC. To wear.
Step (3): The optical function surface of the matrix is transferred to the glass 12 containing SiO ₂ .
Step (4): Cool to separate the matrix and the glass 12 containing SiO ₂ .
[0038]
Next, after thoroughly cleaning the mold base material, the sputtering device shown in FIG. 2 was used to form an SiO ₂ layer 13 of 30 nm, a SiOx (0 <x <2) layer 14 of 30 nm, The layer 15 is formed to have a thickness of 30 nm. At the time of film formation, an argon gas and an oxygen gas, which are not shown in the drawing, are introduced through a mass flow while controlling them as shown in the schematic flow rate diagram shown in FIG. The flow rate depends on the size of the chamber and the capacity of the exhaust system. The thickness of each layer varies depending on the optical element shape, glass material, and molding conditions.
[0039]
Next, the mold base material is set in the film forming apparatus shown in FIG. 3, and the hard carbon film 16 is formed using an ion source. The film formation conditions were as follows: gas flow rate: acetylene: 20 ml / min, hydrogen: 10 ml / min, substrate temperature: no heating, pressure: 4 × 10 ⁻¹ Pa. Further, a DC bias was applied to the mold base material using the bias power supply 33, and the voltage was set to -2.5 kV. This film formed a hard carbon film of about 100 nm. When the average surface roughness (Ra) of this hard carbon film was measured, it was 1.6 nm.
[0040]
Next, 1,000 shots of an optical lens were formed using this optical element molding die.
[0041]
The molding glass was a phosphate glass (Tg: 370 ° C.), and the molding was performed under a nitrogen atmosphere at a pressing temperature of 420 ° C. During molding, the mold releasability between the mold and the molded optical element was good. Further, when the surface of the mold after molding was observed with a scanning electron microscope, no peeling of the film, no generation of cracks, and no fusion of the glass were observed, indicating that the mold had good surface properties. Also, the molded glass lens did not show any cracks in the glass, and had good surface roughness.
[0042]
(Example 2)
In Example 1, a gas flow rate was used in the step of forming a 30 nm SiO ₂ layer 13, a 30 nm SiOx (0 <x <2) layer 14, and a 30 nm Si layer 15 on the optical element molding surface side using a sputtering apparatus. Is controlled as shown in the schematic diagram of the flow rate shown in FIG. 5 so that the SiOx (0 <x <2) layer 14 is turned to the surface side direction, and the SiOx (0 <x <2) layer A molding for optical element molding was produced in the same manner except that the molding was performed.
[0043]
Next, 1500 shots of an optical lens were formed using this optical element molding die.
[0044]
The molding glass was a phosphate glass (Tg: 370 ° C.), and the molding was performed under a nitrogen atmosphere at a pressing temperature of 420 ° C. During molding, the mold releasability between the mold and the molded optical element was good. Further, when the surface of the mold after molding was observed with a scanning electron microscope, no peeling of the film, no generation of cracks, and no fusion of the glass were observed, indicating that the mold had good surface properties. Also, the molded glass lens did not show any cracks in the glass, and had good surface roughness.
[0045]
(Example 3)
In Example 1, a gas flow rate was used in the step of forming a 30 nm SiO ₂ layer 13, a 30 nm SiOx (0 <x <2) layer 14, and a 30 nm Si layer 15 on the optical element molding surface side using a sputtering apparatus. Is controlled as shown in the schematic diagram of the flow rate shown in FIG. 6 so that the SiOx (0 <x <2) layer 14 is moved toward the surface side, and the gradient layer where the value of x gradually decreases from 2 to 0 is formed. A molding for optical element molding was produced in the same manner except that the molding was performed.
[0046]
Next, 2000 shots of an optical lens were formed using this optical element molding die.
[0047]
The molding glass was a phosphate glass (Tg: 370 ° C.), and the molding was performed under a nitrogen atmosphere at a pressing temperature of 420 ° C. During molding, the mold releasability between the mold and the molded optical element was good. Further, when the surface of the mold after molding was observed with a scanning electron microscope, no peeling of the film, no generation of cracks, and no fusion of the glass were observed, indicating that the mold had good surface properties. Also, the molded glass lens did not show any cracks in the glass, and had good surface roughness.
[0048]
(Example 4)
In Example 1, a gas flow rate was used in the step of forming a 30 nm SiO ₂ layer 13, a 30 nm SiOx (0 <x <2) layer 14, and a 30 nm Si layer 15 on the optical element molding surface side using a sputtering apparatus. Is controlled as shown in the schematic diagram of the flow rate shown in FIG. 7 so that the SiOx (0 <x <2) layer 14 is moved in the direction toward the surface side so that the value of x gradually decreases from 2 to 0. A molding for optical element molding was produced in the same manner except that the molding was performed.
[0049]
Next, 2000 shots of an optical lens were formed using this optical element molding die.
[0050]
The molding glass was a phosphate glass (Tg: 370 ° C.), and the molding was performed under a nitrogen atmosphere at a pressing temperature of 420 ° C. During molding, the mold releasability between the mold and the molded optical element was good. Further, when the surface of the mold after molding was observed with a scanning electron microscope, no peeling of the film, no generation of cracks, and no fusion of the glass were observed, indicating that the mold had good surface properties. Also, the molded glass lens did not show any cracks in the glass, and had good surface roughness.
[0051]
(Example 5)
In the first embodiment, a gas flow rate was used in the step of forming a 30 nm SiO ₂ layer 13, a 30 nm SiOx (0 <x <2) layer 14, and a 30 nm Si layer 15 on the optical element molding surface side using a sputtering apparatus. Is controlled as shown in the schematic diagram of the flow rate shown in FIG. 8 so that the SiOx (0 <x <2) layer 14 is moved toward the surface side, and the gradient layer where the value of x gradually decreases from 2 to 0 is formed. A molding for optical element molding was produced in the same manner except that the molding was performed.
[0052]
Next, 2000 shots of an optical lens were formed using this optical element molding die.
[0053]
The molding glass was a phosphate glass (Tg: 370 ° C.), and the molding was performed under a nitrogen atmosphere at a pressing temperature of 420 ° C. During molding, the mold releasability between the mold and the molded optical element was good. Further, when the surface of the mold after molding was observed with a scanning electron microscope, no peeling of the film, no generation of cracks, and no fusion of the glass were observed, indicating that the mold had good surface properties. Also, the molded glass lens did not show any cracks in the glass, and had good surface roughness.
[0054]
(Comparative example)
Example 1 is the same as Example 1, except that the SiO ₂ layer 13 and the SiO x (0 <x <2) layer 14 were not formed on the optical element molding surface side by using a sputtering apparatus, and only the Si layer 15 was formed to a thickness of 30 nm. A mold for molding an optical element was manufactured.
[0055]
Next, an optical lens was formed using this mold for forming an optical element in the same manner as in Example 1. However, a large number of fine hard carbon films 16 were peeled off at 100 shots.
[0056]
As described above, according to the above embodiment, a hard carbon film formed as a release layer is formed on a mold base material made of a glass material with good adhesion to the mold material and with good surface roughness. This makes it possible to manufacture the optical element molding die at extremely low cost.
【The invention's effect】
As described above, according to the present invention, even when a glass material is used as the mold base material, the durability of the film on the mold surface can be improved, and the roughening of the mold surface can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of one embodiment of an optical element molding die of the present invention.
FIG. 2 is a schematic sectional view of a sputtering film forming apparatus for forming a SiO ₂ layer, a SiOx (0 <x <2) layer, and a Si layer.
FIG. 3 is a schematic view showing a film forming apparatus for forming a hard carbon film.
FIG. 4 is a diagram showing a change over time in a gas flow rate during film formation in Example 1.
FIG. 5 is a diagram showing a change over time in a gas flow rate during film formation in Example 2.
FIG. 6 is a diagram showing a change over time in a gas flow rate during film formation in Example 3.
FIG. 7 is a diagram showing a change over time in a gas flow rate during film formation in Example 4.
FIG. 8 is a diagram showing a change over time in a gas flow rate during film formation in Example 5.
[Explanation of symbols]
Reference Signs List 11 cemented carbide base 12 molding die 13 SiO ₂ layer 14 SiOx layer 15 Si layer 16 hard carbon film

Claims (8)

A method for manufacturing an optical element molding die by forming a hard carbon film on the molding surface of a mold base material formed of glass containing SiO ₂ while having a molding surface for molding an optical element on the surface. So,
A first thin film forming step of forming a first thin film made of SiO _{2 on the} molding surface;
Forming a second thin film of SiOx (0 <x <2) on the first thin film;
A third thin film forming step of forming a third thin film made of Si on the second thin film;
A fourth thin film forming step of forming the hard carbon film on the third thin film;
A method for producing an optical element molding die, comprising: In the second thin film forming step, the value of x gradually decreases from 2 to 0 as the second thin film moves from the first thin film to the third thin film in the thickness direction. The method according to claim 1, wherein the second thin film is formed to have a composition. 2. The method according to claim 1, wherein in the first to third thin film forming steps, the first to third thin films are formed by a sputtering method. 3. The method for manufacturing an optical element molding die according to claim 1, wherein in the fourth thin film forming step, the hard carbon film is formed by an ion beam evaporation method or an ion plating method. An optical element molding die having a molding surface for molding an optical element on a surface thereof and a molding surface of a mold base material formed of glass containing SiO ₂ , wherein a hard carbon film is formed on the molding surface,
A first thin film made of SiO ₂ formed on the molding surface;
A second thin film formed of SiOx (0 <x <2) formed on the first thin film;
A third thin film made of Si formed on the second thin film;
The hard carbon film formed on the third thin film,
A mold for molding an optical element, comprising: The composition of the second thin film, wherein the value of x gradually decreases from 2 to 0 as going from the first thin film to the third thin film in the thickness direction. Item 6. An optical element molding die according to Item 5. The optical element molding die according to claim 5, wherein the first to third thin films are formed by a sputtering method. The optical element molding die according to claim 5, wherein the hard carbon film is formed by an ion beam evaporation method or an ion plating method.

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