JP2006117455A - Optical element forming die and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems such that adhesion between a film and a die base material lowers as ion bombardment effects can not be attained or surface roughness arises due to abnormal discharge caused by charge-up of the die base material, in case that the die base material is of an insulative material such as glass. <P>SOLUTION: In a hybrid die and its manufacturing method, the constitution is made by laminating an SiO<SB>X</SB>C<SB>Y</SB>(0<X<2, 0<Y<1) layer, an SiC layer and a hard carbon film in this order from the surface of glass. By virtue of this, adhesive force between the hard carbon film and the hybrid die base material can be improved. <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 of glass materials without the need for a glass 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.

If some examples, the JP-A-49-51112, 13Cr martensite steel, the JP-A-52-45613, the SiC and Si ₃ N _4, JP 60- No. 246230 discloses a material obtained by coating a cemented carbide with a noble metal, and Japanese Patent Laid-Open Nos. 61-183134, 61-281030, and 1-301864 disclose diamonds, respectively. JP-A-64-83529 proposes a material in which a thin film or a diamond-like carbon film is coated with a hard carbon film.

  Japanese Patent Publication No. 2-31012 proposes forming a carbon film of 5 to 500 nm on either the lens or the mold. Furthermore, according to Japanese Patent Application Laid-Open No. 6-72728 filed by the present inventors, an intermediate layer formed on carbon and the mold base material or the base material surface is configured using a carbon ion beam with high ion energy. A method is described in which a mold that does not cause peeling of a film and generation of cracks by forming a mixing layer made of at least one kind of element is described.

Next, in JP-A-1-33022, as a material of a mold base material, not only a conventional carbide containing WC as a main component is processed by grinding and polishing, but also a molding mold material made of glass is used. A manufacturing method is described in which an optical element molding die is obtained by transferring a molding mother die by pressing with a molding die while hot. Further, as an improvement, Japanese Patent Laid-Open No. 2-102136 discloses an optical element in which a molding die body made of glass press-molded hot and a joined body made of heat-resistant metal or ceramics are integrally formed. A mold is described.
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 JP-A-1-33022 Japanese Patent Laid-Open No. 2-102136

  However, in general, a mold using a diamond-like carbon film, an aC: H film, or a hard carbon film has good mold releasability between the mold and glass and hardly causes fusion with the glass. In general, when the mold base material is glass, when the molding operation is repeated several tens of times or more, the film is partially peeled off and sufficient molding performance is obtained in the molded product. There was a problem in durability, such as being unable to.

  In addition, the method described in JP-A-6-72728 is a preferable method compared to other methods for manufacturing a mold for optical element molding. However, since carbon ions having high ion energy are used, the surface of the mold material is roughened. May occur. This is not a big problem for general-purpose optical elements, but 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.

  The above-mentioned problem of film adhesion and roughness of the mold material surface are particularly noticeable when the mold base material is a glass material. The use of a glass material as the mold base material is very useful for reducing costs, such as low material costs and easy processing. However, since carbon-containing ions are involved in the formation of the carbon film, in the case of an insulating material such as a glass material, the effect of ion bombardment cannot be obtained, so the adhesion between the film and the mold base material is reduced. However, there is a problem in that the mold base material is charged up, abnormal discharge occurs, and the surface becomes rough.

In order to solve these problems, in the present invention, a molding die having a transfer surface made of glass for forming an optical element on a part of a base material, and a hard carbon on a transfer surface made of glass containing SiO _2. In the method for producing an optical element molding die for forming a film, a SiO _X C _Y (0 <X <2, 0 <Y <1) layer, a SiC layer, and a hard carbon film are sequentially laminated from the glass surface. And

Furthermore, it is possible to make the SiO _X C _Y layer a gradient layer in which the value of X gradually decreases from 2 to 0 and the value of Y gradually increases from 0 to 1 in the surface side direction. It is desirable in terms of film adhesion.

In addition, it is desirable that the SiO _X C _Y (0 <X <2, 0 <Y <1) layer and the SiC layer are formed by sputtering or ion plating in terms of film thickness and X and Y controllability.

  The hard carbon film is preferably formed by ion beam deposition or ion plating.

  According to the present invention, it becomes possible to form a hard carbon film formed as a release layer on a mold base material made of a glass material with good adhesion to the mold material and with a better surface roughness, thereby forming an optical element. Mold materials can be provided at a significant cost reduction.

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 cemented carbide containing WC as a main component, 12 is a molding die having a transfer surface shape made of glass containing SiO ₂ that has been hot-pressed, and is bonded to the cemented carbide comprising 11. And are integrally configured. FIG. 1 shows a free-form lens molding die having three concave surfaces. However, the present invention is not limited to the shape, and the concave-convex lens molding die and the aspherical lens molding die. It can also be used for cylindrical lens molding dies.

A mold base material made of glass containing SiO ₂ as a transfer surface used in the present invention is to perform press molding with a master mold made of a super hard material and 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 processed, and the machining time can be significantly shortened compared to mold machining by grinding and polishing, thus reducing the cost of machining and shortening the lead time of mold machining. .

  The mold base material may be made entirely of glass. However, an integrated type of glass and cemented carbide is desirable in terms of mechanical strength and machining such as screws.

Reference numeral 13 denotes a SiO _X C _Y (0 <X <2, 0 <Y <1) layer, and reference numeral 14 denotes a SiC layer that is sequentially laminated by sputtering, CVD, ion plating, or the like.

FIG. 2 is a schematic cross-sectional view of a sputter deposition apparatus for forming the SiO _X C _Y (0 <X <2, 0 <Y <1) layer 13 and the SiC layer 14. These forming methods are:
(1) The mold base material 22 is installed in the vacuum chamber 21, and the mold base material 22 rotates on the target 24 by the rotation shaft 23. The temperature is detected by a thermocouple 25, heated to 300 ° C. by a heater 26 such as a halogen lamp, and the ultimate vacuum in the chamber is evacuated to 1 × 10 ⁻⁵ Pa or less.

(2) Argon gas is increased constant or (gradually), oxygen gas is decreased (gradually), the mold base material 22 is rotated, a high frequency is applied to the Si metal target 24, and the raw material is turned into plasma. A SiO _X C _Y (0 <X <2, 0 <Y <1) layer (gradient layer) 13 is formed to 0.01 to 1 μm.

  (3) Oxygen gas is stopped, only argon gas is introduced, the mold base material 22 is rotated, a high frequency is applied to the SiC target 24, the raw material is turned into plasma, and the SiC layer 14 is formed to 0.01 to 1 μm.

The laminate of the SiO _X C _Y (0 <X <2, 0 <Y <1) layer and the SiC layer obtained in this way is formed on a glass containing SiO ₂ with SiO _X C _Y (0 <X <2, 0 <Y <1) Since the layer 13 is laminated, the adhesion between the glass and the SiC layer 14 is increased. Furthermore, since the SiC layer 14 has good adhesion to the hard carbon film 15, the adhesion between the mold and the hard carbon film is improved. The SiO _X C _Y (0 <X <2, 0 <Y <1) layer and the SiC layer are preferably amorphous from the viewpoint of the surface roughness of the film. If it is in the desired range, the crystal component may be partially included.

  In addition, although the sputtering method has been described as the film forming method, known CVD and ion plating methods are also possible, and the film forming apparatus is not limited to the above film forming apparatus.

  Reference numeral 15 denotes a hard carbon film. The hard carbon film is basically amorphous, has high hardness, and high transparency in the infrared region, and is therefore 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.

  Note that the “hard carbon film” in the present invention is a 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 above film forming method converts a carbon source gas and a diluting gas such as hydrogen, oxygen, chlorine, fluorine, or a rare gas into a plasma by applying a hot filament or a high frequency, and further a magnetic field. This is a method of accelerating and extracting ions using an electric field and irradiating the ions on a mold base material to form a hard carbon film on the molding surface.

  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.

  FIG. 3 is a schematic view showing a film forming apparatus for forming a hard carbon film that can be used in the present invention. A vacuum chamber 31 and an ion source 32 are connected to a valve (not shown), a gas flow regulator, a pressure regulator, and a gas cylinder, and can ionize a carbon-containing gas using a heated filament and an electric field. . Reference numeral 33 denotes a power source for applying a bias to the substrate holder. 34 schematically shows an ion beam, and 35 is a mold material. Reference numeral 36 denotes a gas exhaust port to which a valve, a turbo molecular pump, and a rotary pump (not shown) are connected. Reference numeral 37 denotes a base material holder which can fix the mold material. In addition, the film-forming apparatus used by this invention is not limited to the said apparatus at all.

  For example, a suitable film forming method of the hard carbon film of the present invention is performed by applying a negative DC pulse bias to the mold material. When a bias is applied in a pulsed manner, the density of plasma on the surface of the mold material increases, a mixing layer is formed at the interface between the hard carbon film and the SiC layer, and the adhesion between the hard carbon film and the SiC film is greatly improved. 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.

In the embodiment of the present invention, the SiO _X C _Y (0 <X <2, 0 <Y <1) layer, the SiC layer, and the hard carbon film are formed using different apparatuses. This is for the sake of easy understanding. Usually, the SiO _X C _Y (0 <X <2, 0 <Y <1) layer, the SiC layer, and the hard carbon film are put into the atmosphere during the film formation by the same film forming apparatus. It is desirable in terms of adhesion and contamination that the film is continuously formed without being exposed. In this case, a film forming apparatus having a sputtering source and an ion source in the same chamber is used, or the SiO _X C _Y (0 <X <2, 0 <Y <1) layer and the SiC layer are formed in the same manner as the hard carbon film formation. There is a method such as forming by an appropriate ion plating method. When forming an SiO _X C _Y (0 <X <2, 0 <Y <1) layer by an ion plating method, an organic silicon compound or a mixture of carbon compound and silicon compound as a raw material with oxygen or an oxygen compound, etc. Can be used. When the SiC layer is formed by an ion plating method, 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. As the oxygen compound, oxygen gas, carbon monoxide, carbon dioxide, nitrogen oxide, or the like can be used. As a film forming method, these source gases are converted into plasma by applying a hot filament or a high frequency, and further an electric field, a magnetic field, etc., and ions are accelerated and extracted from the plasma using an electric field. Ions are irradiated onto the mold base material to form a SiO _X C _Y (0 <X <2, 0 <Y <1) layer and a SiC layer on the molding surface.

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

Example 1
FIG. 1 is a schematic cross-sectional view of an optical element molding die according to the present invention.

First, the cemented carbide 11 mainly composed of WC is pressed with heat having a transfer surface shape made of borosilicate glass (glass transition point = 540 ° C., softening point = 730 ° C.) 12 as glass containing SiO _2. Mold. A general press molding process includes the following steps 1 to 4.

Step 1: WC cemented carbide 11 mainly composed of a glass 12 containing SiO ₂ is heated by a heat source.

Step 2: The glass containing 12 SiO ₂ as a matrix is pressed against a cemented carbide containing 11 WC as a main component, and the glass 12 containing SiO ₂ is fused to the cemented carbide 11 containing WC as a main component.

Step 3: The optical function surface of the master mold is transferred to the glass 12 containing SiO ₂ .

Step 4: Cool and separate the matrix and the glass 12 containing SiO ₂ .

Next, after thoroughly cleaning this mold base material, a SiO _X C _Y (0 <X <2, 0 <Y <1) layer of 50 nm is formed on the optical element molding surface side using the sputtering apparatus shown in FIG. The SiC layer was formed in 50 nm increments by controlling from the argon gas and oxygen gas inlets through the mass flow not shown in the figure as shown in the schematic diagram of the flow rate shown in FIG. The flow rate depends on the size of the chamber and the capacity of the exhaust system. Moreover, the film thickness of each layer changes with optical element shapes, glass materials, and molding conditions.

Next, the mold base material is set in the ion plating film forming apparatus shown in FIG. 3, and the hard carbon film 15 is formed using an ion source. The film forming conditions were such that the gas flow rate was acetylene: 20 ml / min, hydrogen: 10 ml / min, the substrate temperature was not heated, and the pressure was 4 × 10 ⁻¹ Pa. Further, a DC bias was applied to the mold base using a 33 bias power source, and the voltage was set to -2.5 kV. By this film formation, a hard carbon film of about 100 nm was formed. When the average surface roughness (Ra) of this hard carbon film was measured, it was 1.6 nm.

  Next, 1000 shots of the optical lens were molded using the mold for molding an optical element.

  The molding glass was phosphoric acid glass (Tg: 370 ° C.), and the molding conditions were a nitrogen atmosphere and a press temperature of 420 ° 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.

(Examples 2 to 4)
In Example 1, a step of forming a SiO _X C _Y (0 <X <2, 0 <Y <1) layer by 40 nm and a SiC layer by 50 nm on the optical element molding surface side using a sputtering apparatus, By controlling the flow rate as shown in the schematic diagrams of FIGS. 5 to 7, the SiO _X C _Y (0 <X <2, 0 <Y <1) layer is directed to the surface side, and the value of X gradually increases from 2 to 0. The mold for optical element molding was produced in the same manner except that the gradient layer was gradually reduced and the Y value gradually increased.

  Next, 1500 shots of the optical lens were molded using these optical element molding molds.

  The molding glass was phosphoric acid glass (Tg: 370 ° C.), and the molding conditions were a nitrogen atmosphere and a press temperature of 420 ° C. During molding, all of the molds had good releasability between the mold and the molded optical element. In addition, when the mold surface after molding was observed with a scanning electron microscope, none of the molds had film peeling, generation of cracks, or glass fusion, and good mold surface properties. It was. The molded glass lens also had good surface roughness with no glass breakage.

(Comparative example)
In Example 1, a SiO _X C _Y (0 <X <2, 0 <Y <1) layer and a SiC layer were not formed on the optical element molding surface side by using a sputtering apparatus, and a Si layer was formed to a thickness of 50 nm. An optical element molding die was produced in the same manner except that.

  Next, an optical lens was molded in the same manner as in Example 1 using this mold for molding an optical element, but a lot of fine hard carbon film 16 was peeled off in 100 shots.

(Example 5)
A mold base material produced by the same method as in Example 1 was placed in the film forming apparatus shown in FIG.

First, a SiO _X C _Y (0 <X <2, 0 <Y <1) layer and a SiC layer are formed. The mold material is heated to 300 ° C. using the substrate heating mechanism of the substrate holder, and the SiO _X C _Y (0 <X <2, 0 <Y <1) layer is formed to 30 nm and the SiC layer to 60 nm each. Tetraethoxysilane and oxygen gas were controlled by controlling the flow rate as shown in the schematic diagram of FIG. 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, so that SiO _X C _Y ( A 0 <X <2, 0 <Y <1) layer and a SiC layer were formed. The DC pulse bias was -2.5 kV, the repetition frequency was 2 kHz, and the duty ratio was 10%.

  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.

Schematic diagram of optical element mold Schematic diagram of sputtering equipment Schematic diagram of ion plating deposition equipment Schematic diagram of gas flow rate during film formation Schematic diagram of gas flow rate during film formation Schematic diagram of gas flow rate during film formation Schematic diagram of gas flow rate during film formation Schematic diagram of gas flow rate during film formation

Explanation of symbols

11 Cemented carbide containing WC as main component 12 Mold for molding having a transfer surface shape made of glass containing SiO ₂ pressed by hot molding 13 SiO _X C _Y (0 <X <2, 0 <Y <1 ) Layer 14 SiC layer 15 Hard carbon film 21 Vacuum chamber 22 Mold base material 23 Rotating shaft 24 Target 25 Thermocouple 26 Heater 31 Vacuum chamber 32 Ion source 33 Bias power source 34 Ion beam schematically shown 35 Mold material 36 Gas exhaust Mouth 37 Base holder

Claims (6)

A molding die having a transfer surface made of glass for molding an optical element on a part of a base material,
In the method of manufacturing an optical element molding die for forming a hard carbon film on a transfer surface made of glass containing SiO ₂ , a SiO _X C _Y (0 <X <2, 0 <Y <1) layer, SiC, A method for producing an optical element molding die, comprising sequentially laminating a layer and a hard carbon film. The SiO _X C _Y layer is an inclined layer in which the value of X gradually decreases from 2 to 0 and the value of Y gradually increases from 0 to 1 in the surface side direction. A method for producing an optical element molding die according to 1. 3. The method for producing an optical element molding die according to claim 1 or 2, wherein a SiO _X C _Y (0 <X <2, 0 <Y <1) layer and a SiC layer are formed by sputtering. 3. The method for producing an optical element molding die according to claim 1, wherein a SiO _X C _Y (0 <X <2, 0 <Y <1) layer and a SiC layer are formed by an ion plating method.   2. The method for producing an optical element molding die according to claim 1, wherein the hard carbon film is formed by an ion beam deposition method or an ion plating method. A molding die having a transfer surface made of glass for molding an optical element on a part of a base material,
In an optical element molding die for forming a hard carbon film on a transfer surface made of glass containing SiO ₂ , the SiO _X C _Y (0 <X <2, 0 <Y <1) layer, SiC layer, hard A mold for optical element molding, wherein carbon films are sequentially laminated.

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