JP2002003226A - Die for molding optical element and its producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die for an optical element, which enables the shape of an optical element with a polyhedral body and a free curved face, which cannot be realized by any conventional grinding work, to repeatedly be press-formed and also to precisely be transferred regardless of a glass species or a molding condition; to provide a producing method for the die; to provide a free-curved-face, polyhedral-body optical element. SOLUTION: The optical element molding die has a transfer-face for forming an optical element on a part of a base material. The producing method for the die comprises a transfer process wherein a transfer is conducted onto the surface of a transfer-material by using a matrix cut and processed into a shape inverse to that of the transfer-face after the transfer-material is formed on the base material, a process wherein the transfer-material is cured, an etching process wherein the transfer-material and the base material are subjected to dry etching and the transfer-shape is engraved on the base material, a process wherein an intermediate layer and a surface layer are formed on the surface of the base material etched. The optical element molding die obtained by the above producing method is provided and the free-curved-face, polyhedral-body optical element is also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for manufacturing an optical element made of glass such as a lens or a prism with high precision by press-molding a glass material, and a method for manufacturing the same.

[0002]

2. Description of the Related Art The technology of manufacturing a lens by press molding a glass material without the need for a polishing step eliminates the complicated steps required in conventional manufacturing, and allows the lens to be manufactured easily and inexpensively. In recent years, it has been used in the manufacture of optical elements made of not only lenses but also prisms and other glasses.

[0003] The properties required of a mold used for press molding of such a glass optical element include excellent hardness, oxidation resistance, heat resistance, mold release properties and mirror workability. Can be Heretofore, many proposals have been made as a mold material of this kind, such as metal, ceramics, and a material obtained by coating them. If some examples, 13Cr martensitic steels in JP-A-49-51112 is, Japanese Patent Publication No. Sho 52-45613 is SiC and Si ₃ N _4, Sho 59-121126 JP Has Ti
A mixed material of C and a metal is disclosed in Japanese Patent Application Laid-Open No. 60-246230.
Also, JP-A-61-183134 and JP-A-61-2
JP-A-81030 and JP-A-1-301864 disclose a material coated with a diamond thin film or a diamond-like carbon film, and JP-A-64-83529 discloses a material coated with a hard carbon film.

However, in the conventional mold material, the hardness,
A product satisfying all of oxidation resistance, heat resistance, mold release property and mirror workability has not been obtained.

[0005] For example, 13 martensitic steel has the drawback that it is easily oxidized and that Fe diffuses into the glass at a high temperature to color the glass.

Further, SiC, Si ₃ N ₄ , TiC, diamond thin film, diamond-like carbon film and hard carbon film are
Although the hardness of the material is very high and the mechanical strength is excellent, the workability is inferior and it is difficult to process the material into a highly accurate mold shape. Furthermore, in SiC, Si ₃ N ₄ and TiC,
Oxidation occurs at high temperatures, causing glass fusing.

In a mold in which a noble metal thin film, a diamond thin film, a diamond-like carbon film, or a hard carbon film is coated on a cemented carbide base material, it is possible to use a diamond grindstone as a means for processing the cemented carbide. Although it is general, it has a drawback that it cannot be processed into a spherical surface or a free-form surface with a small curvature. The free-form surface here means
This is a surface including a non-axisymmetric aspheric surface.

As a measure for improvement, a cutting layer which can be easily machined on a cemented carbide base material is disclosed in
No. 23230, an electroless Ni-P plating film, and JP-A-7-41326, a ternary alloy containing P (P-N
i, Co, Fe-Si, Ti, Cu, Zr, Nb, M
o, Ru, Ph, Pd, Hf, Ta, W, Re, Os,
A method is disclosed in which Ir) is sputter-deposited, the cut layer is cut with a necessary diamond tool to form a transfer surface, and a noble metal-based alloy thin film is sputter-deposited on the cut layer. ing.

However, the electroless Ni-P plating film and the ternary alloy sputtered film do not have sufficient adhesion, and the molding conditions and glass types, especially high-melting glass, are repeatedly cut during press molding. There are disadvantages in that a crack occurs in the processed layer and the base material and the cut layer are separated.

As a mold for transferring a fine shape such as a diffraction grating, Japanese Patent Application Laid-Open No. 6-279036 discloses a method in which Si or SiO ₂ is processed into a desired shape by photolithography and dry etching instead of a cutting layer. Japanese Patent Application Laid-Open No. 10-337734 discloses that a base material is processed into a desired shape by photolithography and dry etching using a resist, but has a drawback that the type of glass and the shape are limited. ing.

Japanese Patent Application Laid-Open No. 8-43605 discloses an optical element for directly processing a fine shape such as a diffraction grating.
Processing to a desired shape by replica and dry etching, and Japanese Patent Application Laid-Open No. 9-243812 discloses cutting a resist and then processing to a desired shape by dry etching, but the shape is limited. And has the disadvantage of low productivity.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem and provide an optical element having a polyhedral free-form surface which cannot be realized by conventional grinding.
An object of the present invention is to provide an optical element molding die capable of transferring a shape precisely even if press molding is repeatedly performed regardless of molding conditions and glass types of glass, a manufacturing method thereof, and a free-form polyhedral optical element.

Another object of the present invention is that when mass-producing optical elements, a large number of molds having the same shape are required. In particular, in the case of polyhedral molding, in the case of a split mold in which a plurality of molds are combined, variations among the molds are reduced. To provide a method for manufacturing a mold for optical element molding, which can quickly and inexpensively produce an integrated mold having the same shape in such a case since it takes a lot of time to adjust a mold combination. It is in.

[0014]

According to the present invention, there is provided a molding die having a transfer surface for molding an optical element on a part of a base material, wherein a transfer material is formed on the base material and then transferred. Using a matrix cut into an inverted shape corresponding to the surface, a transfer step of transferring to the surface of the transfer material, a step of curing the transfer material, and a step of curing the transfer material and the base material Provided is a method for manufacturing an optical element molding die, comprising: an etching step of engraving a transfer shape on the base material by performing dry etching; and a step of forming an intermediate layer and a surface layer on the etched base material surface. Is done.

Further, according to the present invention, there is provided an optical element molding die manufactured by the above method for manufacturing an optical element molding die.

Further, according to the present invention, there is provided a free-form surface polyhedral optical element molded using the optical element molding die manufactured by the above-described method for manufacturing an optical element molding die.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, there is provided a molding die having a transfer surface for molding an optical element on a part of a base material,
After forming the transfer material on the base material, using a mother die cut into an inverted shape corresponding to the transfer surface, a transfer step of transferring to the surface of the transfer material, and curing the transfer material Performing a dry etching on the transfer material and the base material, engraving the transfer shape on the base material, and forming an intermediate layer and a surface layer on the etched base material surface. And

Further, it is preferable to obtain a mold having a desired shape by cutting the master having been cut into an inverted shape corresponding to the transfer surface into a shape in which the surface change due to etching has been corrected in advance. . Further, according to the required performance of the optical element, a step of uniformly polishing and rolling the base material surface after the etching step is provided.

[0019] The mother die cut into an inverted shape corresponding to the transfer surface is made of a metal such as copper, aluminum and phosphor bronze which can be easily processed with a diamond tool. It is preferable in terms of. In addition, since the master mold only molds a transfer material such as a resin before curing, it does not need the hardness and heat resistance of a super hard metal, and only needs to consider the machinability.

As the base material, a cemented carbide mainly composed of tungsten carbide (WC) in terms of high-temperature hardness, and quartz which is easy to adjust the etching rate with the transfer material are preferable. As the transfer material, a photocurable resin, a thermosetting resin, or a thermoplastic resin, which has the same transferability as the base material and the etching rate, is preferable. As the intermediate layer, metal carbides, nitrides, and carbonitrides are preferable in terms of adhesion to the surface layer. As the surface layer, a hard carbon film and a noble metal based alloy film are preferable in terms of releasability from glass.

Further, for example, Si, Cr, Ti and T are formed on the base material so that the transfer material and the etching rate are equal.
It is preferable to form a transfer material after forming an etching adjustment layer made of a metal such as a and an oxide of the metal, from the viewpoint of the mirror surface of the base material surface.

Further, if necessary, after the transfer step, the surface of the transfer material can be softened to smooth the surface on which the feed trace of the cutting of the matrix has been transferred.

It is preferable to form the transfer material after the base material is processed to an approximate shape by electric discharge machining, grinding, or the like, from the viewpoint of improving the transferability accuracy.

When the matrix has a free-form surface shape, it is preferable that the matrix be cut and then uniformly polished.

Further, even if the mold for performing polyhedral molding has a shape in which adjacent surfaces themselves interfere with each other and the integrated mold cannot be cut, a desired shape can be obtained by combining the mother dies which are cut and uniformly polished one by one. A mold for molding a polyhedral mother optical element with good reproducibility can be obtained.

The operation of the present invention will be described with reference to FIG.

Reference numeral 1 of (a1) denotes an optical element molding base material having three transfer surfaces of a free-form surface and processed into an approximate shape. As the base material, a cemented carbide mainly composed of tungsten carbide (WC) in terms of high-temperature hardness, and quartz whose etching rate with the transfer material is easy to adjust in terms of the mirror surface of the transfer surface are applied. Electric discharge machining is used for machining to an approximate shape. Furthermore, a metal such as Si, Cr, Ti, and Ta, or an oxidation of the metal, such that the etching rate is equal to that of the transfer material on a base material processed into an approximate shape on both sides of high-temperature hardness and mirror finish. The etching adjustment layer made of a material can be formed by a known film forming method such as sputtering or CVD.

Reference numerals 21, 22, and 23 in (a2) denote base dies each having a reverse shape corresponding to the free-form surface transfer surface. The matrix is preferably made of a metal such as copper, aluminum or phosphor bronze, which can be easily processed with a diamond tool, in terms of diamond tool wear. This is because it is not necessary to transfer the mold at a high temperature, so that it is not necessary to use a hard metal or the like which is difficult to cut. In addition, it is necessary to remove the feed trace due to the cutting by uniform polishing if necessary for the required optical performance. As the inverse shape of the transfer surface, the cutting process is performed in such a manner that the surface change due to the etching is corrected in advance, so that the etching condition can be easily adjusted. In the present invention, the shape of the transfer surface is not limited to a free-form surface, but may be applied to a combination of a spherical surface, an aspherical surface, a diffraction grating, and the like. Further, in order to improve the releasability of the surface of the matrix, it is possible to form a release film such as a metal thin film or perform a release treatment on the surfaces of the molds 21, 22, and 23 by a known method. it can.

(B) and (c) are transfer steps. A transfer material 3 in a soft state is formed on a base material 1,
Is pressed against the transfer material, the transfer material is cured, and the master is separated. When an ultraviolet curable resin, which is a photocurable resin, is used as the transfer material, the transfer material is cured by irradiating ultraviolet light. When a thermosetting material is used as the transfer material, the transfer material is cured by heating, and when a thermoplastic material is used, the transfer material is softened by heating, and the matrix 2 is heated.
Transfer the surface shape pressing 1, 22, and 23.

Then, from this state, an anisotropic dry etching is performed on the transfer material 3 and the base material 1, and an etching step of engraving the three free-form surfaces of the surface of the transfer material 3 on the base material 1. Is performed, an optical element molding die having three desired free-form surface shapes is obtained as shown in FIG.

In general, physical etching is easier to control than chemical etching, and if the control of the etching rate ratio is the same for the same starting shape, the same desired shape can always be obtained. Excellent reproducibility. Therefore, the etching process is preferably a known physical etching such as ECR, RIE, and low-pressure high-density plasma. In the anisotropic etching in the etching step, if the etching rate ratio between the transfer material and the base material is made equal, the shape formed on the surface of the transfer material can be jointly engraved as it is on the base mold. As means for equalizing the etching rate ratio between the transfer material and the base material, curing conditions of the transfer material are controlled, and rare gas (such as Ar), carbon fluoride gas (such as CF ₄ ), chlorine gas (such as Cl _{2) are used.} Etc.) or by optimizing the combination and flow rate of an etching gas such as an oxygen gas (O ₂ ). Also, depending on the required performance of the optical element, after the etching process, the surface of the base material can be removed by removing fine irregularities by uniform polishing and rolling, thereby increasing the specularity particularly when the mold base material is a cemented carbide. it can.

In the above steps, if the desired shape of the mold base material 1 is obtained, in order to increase the moldability of the glass mold, an intermediate layer is formed on the mold base material as an intermediate layer having an adhesive property with the surface layer. To form a metal carbide, nitride or carbonitride, and as a surface layer on the intermediate layer, a hard carbon film or a noble metal-based alloy film is formed on the surface in terms of mold releasability from glass. An element molding die can be manufactured.

As described above, according to the method of manufacturing an optical element molding die of the present invention, an optical element having a polyhedral free-form surface, which cannot be realized by conventional grinding, can be formed under molding conditions and glass types. In spite of this, it has become possible to provide a mold whose shape is precisely transferred even if press molding is performed repeatedly. In addition, by repeating the above-described steps, it becomes possible to provide an integrated mold having the same shape quickly and inexpensively, eliminating the variation between molds in the case of the split mold, and eliminating the need for enormous adjustment time for mold combinations. Become.

[0034]

The present invention will be described below in more detail with reference to specific examples.

(Example 1) 1 of (a1) in FIG. 1 is a cemented carbide mainly composed of tungsten carbide (WC) which has three transfer surfaces of a free-form surface and is formed into an approximate shape by electric discharge machining. Is a base material for optical element molding. (A2) in FIG.
Reference numerals 21, 22 and 23 denote oxygen-free copper matrices which are individually cut and even polished into diamond tools in a shape in which surface changes due to etching have been corrected in advance so as to individually correspond to the free-form surface transfer surface. .

FIGS. 1B and 1C show a transfer step. A transfer material 3 made of a thermosetting resin, which is in a soft state, is formed on a base material 1, and a matrix in which 21, 22, and 23 are integrated is pressed against the transfer material, and the transfer material is cured by heating. Is separated.

Next, in this state, anisotropic dry etching is performed on the transfer material 3 and the base material 1, and the three free-form surfaces of the transfer material 3 are etched on the base material 1. The process was performed, and as shown in (d), an optical element mold having the desired three free-form surface shapes was obtained. For this dry etching, a reactive etching apparatus was used, and Ar gas and CF ₄ gas were used as etching gases.
The gas flow ratio was Ar / CF ₄ = 3/1 and the pressure was 0.5 Pa.

Next, the etched surface is uniformly polished.

FIG. 2 is a schematic sectional view of the optical element molding die of the present invention.

A TiN intermediate layer 42 having a thickness of 1 μm was formed on the uniformly polished surface of the mold base material 41 by reactive sputtering using a Ti target and a nitrogen gas as an introduction gas.
m.

Next, a surface layer 43 of a hard carbon film having a thickness of 100 nm is formed on the intermediate layer 42 by an ion beam evaporation method.

By repeating the same steps as those described above, three molds having the same shape are manufactured. The same process is repeated for the mold on the opposite side to produce four molds of the same shape.

When four sets of these molds were used to form a polyhedral free-form prism glass (borosilicate glass) using a continuous molding machine, good molds were obtained even after 3000 shots of each mold. Also, no deterioration of the transfer surface was observed. Also, there was no variation in the shape between the molds of the molded product.

(Example 2) In Example 1, the optical element molding die base material 1 was made of quartz and the transfer material 3 was made of an ultraviolet curable resin. The method of curing the transfer material was such that ultraviolet light was transmitted through the quartz base material. An optical element molding die was manufactured in the same manner as in Example 1 except that the curing and transfer steps were performed.

When four sets of these molds were used to form a polyhedral free-form prism glass using a continuous molding machine (borosilicate glass), good molds were obtained even after 3000 shots of each mold. Also, no deterioration of the transfer surface was observed. Also, there was no variation in the shape between the molds of the molded product.

(Embodiment 3) In the embodiment 1, the transfer material 3
Is a thermoplastic resin, and the method of curing this transfer material is as follows. The transfer material is heated while pressing the matrix onto the transfer material in a solid state, the shape is transferred in a softened state, and then the heating state is stopped and deformed. An optical element molding die was manufactured in the same manner as in Example 1 except that the state was fixed.

When four sets of these molds were used to form a polyhedral free-form surface prism glass (borosilicate glass) using a continuous molding machine, good molds were obtained even after 3000 shots of each mold. Also, no deterioration of the transfer surface was observed. Also, there was no variation in the shape between the molds of the molded product.

(Example 4) In Example 1, the intermediate layer 4
2 except that a carbide, nitride or carbonitride of titanium, tantalum, chromium, or silicon shown in Table 1 was formed instead of forming the TiN film of Example 2. Manufactured. The glass moldability of this mold was measured and found to be the same as in Example 1.

[0049]

[Table 1]

(Example 5) In Example 1, the surface layer 4
Instead of forming the hard carbon film of No. 3, P shown in Table 2
Optical element molding was performed in the same manner as in Example 1, except that a binary alloy of t, Pd, Ir, Rh, Os, Ru, Re, Au, W, and Ta was formed to a thickness of 0.5 μm. A mold was manufactured. The glass moldability of this mold was measured and found to be the same as in Example 1.

[0051]

[Table 2]

In the embodiments of the present invention, the components were changed in the intermediate layer and the surface layer.
It goes without saying that a similar effect can be obtained.

(Example 6) In Example 1, the intermediate layer 4
2 is formed by heating and evaporating metal Ti with an electron gun and performing ion plating in nitrogen plasma.
Except for forming iN, a mold for molding an optical element was manufactured in the same manner as in Example 1.

When this mold was subjected to glass molding (borosilicate glass) using a continuous molding machine, a good molded product was obtained even after 3000 shot molding, and no deterioration of the transfer surface was observed.

(Example 7) In Example 1, 1 μm of SiO ₂ was sputtered on the base material 1 as an etching adjusting layer by sputtering.
An optical element molding die was manufactured in the same manner as in Example 1 except that the mold was formed with a film thickness of m.

When this mold was subjected to glass molding (borosilicate glass) using a continuous molding machine, a good molded product was obtained even after 3000 shot molding, and no deterioration of the transfer surface was observed.

[0057] In Example 8 Example 7, as the etching control layer has been to produce an optical element molding die with the material and corresponding etching gas to that shown in place of the SiO ₂ in Table 3, SiO ₂ The same effect as described above was obtained.

[0058]

[Table 3]

(Embodiment 9)
An optical element molding die was manufactured in the same manner as in Example 1, except that the materials 1, 22, and 23 were aluminum and phosphor bronze.

When a glass molding (borosilicate glass) of a polyhedral free-form surface prism was performed using a continuous molding machine using four sets of these molds, good molded products were obtained even after 3000 shot molding. Also, no deterioration of the transfer surface was observed. Also, there was no variation in the shape between the molds of the molded product.

[0061]

As described above, according to the method of manufacturing an optical element molding die of the present invention, an optical element having a polyhedral free-form surface, which cannot be realized by conventional grinding, can be formed under molding conditions or glass conditions. Regardless of the glass type, it is possible to provide an optical element molding die whose shape is accurately transferred even if press molding is repeatedly performed. Further, by repeating the above-described steps, it becomes possible to provide a method of manufacturing an optical element molding die capable of manufacturing an integrated mold having the same shape quickly and inexpensively. Huge adjustment time was not needed for the combination.

[Brief description of the drawings]

FIG. 1 is a schematic process drawing of an optical element molding die according to the present invention.

FIG. 2 is a schematic sectional view of an optical element molding die according to the present invention.

[Explanation of symbols]

 1,41 Mold base material 21,22,23 Base mold 3 Transfer material 42 Intermediate layer 43 Surface layer

Claims (11)

[Claims] 1. A molding die having a transfer surface for molding an optical element on a part of a base material, wherein the transfer material is formed on the base material and then has an inverted shape corresponding to the transfer surface. A transfer step of transferring to the surface of the transfer material using a mother die cut into a shape, a step of hardening the transfer material, and performing dry etching on the transfer material and the base material to form a transfer shape. A method for manufacturing an optical element molding die, comprising: an etching step of engraving on the base material; and a step of forming an intermediate layer and a surface layer on the etched base material surface. 2. The method of manufacturing an optical element molding die according to claim 1, wherein the mother die cut into an inverted shape corresponding to the transfer surface is cut into a shape in which a surface change due to etching is corrected in advance. Method. 3. The method for manufacturing an optical element molding die according to claim 1, wherein the base material surface is uniformly polished after the etching step. 4. The optical element molding die according to claim 1, wherein the mother die cut into an inverted shape corresponding to the transfer surface is a metal that can be easily processed with a diamond tool. Production method. 5. The base material is tungsten carbide (WC)
The main material is a cemented carbide or quartz, the transfer material is a photocurable resin, a thermosetting resin or a thermoplastic resin, the intermediate layer is a metal carbide, nitride or carbonitride, and the surface layer Is a hard carbon film or a noble metal alloy film. The method for manufacturing an optical element molding die according to claim 1, wherein 6. A transfer material is formed after forming an etching adjustment layer made of a metal and an oxide of the metal such that the etching rate is equal to that of the transfer material on the base material.
The method for producing an optical element molding die according to any one of the above. 7. The method for manufacturing an optical element molding die according to claim 1, wherein the transfer material is formed after the base material is processed to an approximate shape by electric discharge machining, grinding, or the like. 8. The method for manufacturing an optical element molding die according to claim 1, wherein the matrix is a free-form surface that is uniformly polished after cutting. 9. The method for manufacturing an optical element molding die according to claim 1, wherein a plurality of mother dies are combined so as to obtain a desired shape. 10. An optical element molding die manufactured by the method for manufacturing an optical element molding die according to claim 1. Description: 11. A free-form polyhedral optical element molded using an optical element molding die manufactured by the method for manufacturing an optical element molding die according to claim 1. Description: