JP2002326231A - Mold for optical element, optical element and master mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for an optical element excellent in cutting properties capable of enhancing dimensional accuracy, capable of forming the shape of a desired optical surface of dimensional reference surface by transfer and capable of also forming a fine shape, the optical element formed using the mold and a master mold for molding the same. SOLUTION: A second mold 10' is formed by applying cutting processing to a first mold 10, which is formed by molding an amorphous alloy MG having a supercooling liquid region to form an optical molding surface 10a to the first mold 10. Since the optical molding surface 10a of the second mold 10' is used for molding the optical surface or dimensional reference surface of a lens, the properties to be cut of the amorphous alloy is extremely good and, therefore, the molding surface of the mold corresponding to the optical surface or dimensional reference surface of the lens can be accurately finished and the life of a tool can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a mold for an optical element,
The present invention relates to an optical element and a master mold, and more particularly to a mold for an optical element in which a desired optical surface can be easily formed and dimensional accuracy is improved, an optical element molded thereby, and a master mold for molding the same.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a mold for an optical element of a plastic optical element, a blank (primary product) is made of, for example, steel or stainless steel, and a blank is formed on the blank. By chemical plating called electrolytic nickel plating, an amorphous alloy of nickel and phosphorus is plated to a thickness of about 100 μm, and this plated layer is cut with a diamond tool by an ultra-precision processing machine to produce a highly accurate optical surface. I was getting it.

[0003]

According to the prior art method, since the component shape is basically created by machining, the component accuracy can be easily increased to near the motion accuracy of the processing machine, but the manufacturing process is not improved. Machine processing and chemical processing are mixed and complicated and it takes a long delivery time. It is necessary to prepare blanks (primary processed products) in consideration of the thickness of the plating layer. The plating process is not always stable. The compositional deviation of the composition and the degree of contamination may cause the adhesion strength of the plating layer to vary, or pinhole-shaped defects called pits to occur, and the optical molding surface corresponding to the optical surface of the optical element in the thickness of the plating layer Because it has to be created,
When the optical molding surface is reworked, the plating thickness may not be sufficient and processing may not be possible due to lack of margin, and in general, repetitive use is not possible, and the mold cost is high.

In addition, when the optical molding surface is machined in a large amount, the shape of the optical molding surface which has been finely cut and finished varies depending on the state of the cutting edge of the tool, the machining condition, and the change of the machining environment temperature. This variation in optical molding surface processing generally causes an optical surface shape error of about 100 nm, and an error of about 50 nm remains even when processing very carefully,
This was the processing accuracy limit.

In recent years, an optical system for efficiently correcting chromatic aberration by providing a diffraction groove on an optical surface has been put to practical use in the field of optical information recording and has been produced in large quantities. As the optical material, plastic or glass is used, but a crystal material such as ZnSe is used in an infrared optical system or the like.
An efficient method when mass producing such an optical element is molding, but at this time, a technique for efficiently manufacturing an optical molding surface having a fine diffraction groove of a molding die with high accuracy and efficiency,
It is extremely important.

For example, when a fine pattern having an optical function such as a diffraction groove is created on an optical molding surface by diamond cutting, the sharpness of the cutting edge affects the accuracy of the diffraction groove shape and is transferred as an optical surface. It is known that it sometimes has a large effect on diffraction efficiency, as described in Japanese Patent Application Laid-Open No. 2001-195768.

Therefore, the size of the cutting edge must be made sufficiently small in order not to lower the diffraction efficiency of the diffraction zone.
Therefore, the cutting resistance concentrates on the small cutting edge portion, so that the cutting amount must be reduced, and the number of processing times increases until the entire optical molding surface is uniformly cut and removed. Also,
In order to prevent the surface roughness of the optical molding surface from deteriorating due to small cutter marks, the tool feed speed must be reduced.
The optical molding surface processing time per time also becomes longer. As a result, the cutting length is increased, so that the wear of the tool edge is increased, and the tool is frequently changed. In other words, when machining an optically molded surface with a fine shape by conventional diamond cutting, the life of the tool becomes extremely short, and the carbon in the diamond diffuses to the blank by cutting, thereby extending the life of the tool. It is to be further shortened. In addition, since the time required to process one optical molding surface also increases, the processing efficiency is greatly reduced, the productivity of the mold is reduced, and the cost is rapidly increased. Therefore, especially in the case of finishing an optical molding surface having a fine shape on the surface by diamond cutting, a simple and short delivery time mold manufacturing method is desired.

In addition, in recent years, it has been attempted to add a new optical function to an optical element by providing a fine structure several times smaller than the wavelength and smaller than the wavelength on the optical surface. For example, a diffraction groove is formed on the surface of a molded lens having an aspherical optical surface, and a normal light-condensing function due to refraction and a positive dispersion generated as a side effect at that time are used. A single-lens optical element having an achromatic function that cannot be achieved by refraction alone has been put to practical use as a DVD / CD compatible optical disk pickup objective lens. This utilizes the diffraction effect of a diffraction groove having a size several tens of times the wavelength of light transmitted through an optical element, and the region that handles the diffraction effect of a structure sufficiently larger than the wavelength is called a scalar region. Have been.

On the other hand, conical projections are densely formed on the surface of the optical surface at minute intervals of a fraction of the wavelength of light transmitted through the optical element, thereby exhibiting a light reflection suppressing function. I know I can do that. That is, by forming projections at minute intervals, the refractive index change at the air interface when a light wave enters the optical element is instantaneously changed from 1 to the medium refractive index as in a conventional optical element. Instead, it can be changed gradually, thereby suppressing the reflection of light. The surface on which such projections are formed is a fine structure called a so-called moth eye, and since the structures finer than the wavelength of light are arranged at a shorter period than the wavelength, the individual structures are no longer diffracted. Instead, it functions as an average refractive index for a light wave, and a region having such an action is generally called an equivalent refractive index region. Regarding such an equivalent refractive index region, for example, IEICE Transactions C Vol. J83-CN
o. 3pp. 173-181 described in March 2000.

According to such a fine structure of the equivalent refractive index region, a large antireflection effect can be obtained at the same time while reducing the angle dependence and wavelength dependence of the antireflection effect as compared with the conventional antireflection coating. Also, since the optical surface and the fine structure can be created simultaneously by molding, the lens function and the anti-reflection function can be obtained at the same time. It is considered to have a great merit and is attracting attention. Furthermore, by arranging such a fine structure in the equivalent refractive index region so as to have directionality with respect to the optical surface, it is possible to impart strong optical anisotropy to the optical surface. The birefringent optical element thus manufactured can be obtained by molding, and a new optical function can be added in combination with a refractive optical element or a reflective optical element.
The optical anisotropy in this case is called structural birefringence.

[0011] Between the scalar region and the equivalent refractive index region, there is a resonance region where the diffraction efficiency changes abruptly due to a slight difference in the incident conditions. For example, as the diffraction groove width is reduced, the diffraction efficiency sharply decreases at several times the wavelength,
Also, a phenomenon (anomaly) of increasing occurs. By adjusting such a diffraction groove width, as a guided mode resonance grating filter that reflects only a specific wavelength,
An effect equivalent to that of a normal interference filter can be realized with less angle dependence.

When an optical element is to be formed using a scalar region, an equivalent refractive index region, or a resonance region, it is necessary to form fine projections (or depressions) on the optical surface. In order to mass-produce an optical element having such fine projections (or depressions), it can be generally said that molding is performed using plastic as a material. It is necessary to provide an optical molding surface having a depression (or projection) corresponding to the depression in the mold.

However, with respect to the projections (or depressions) in the equivalent refraction region and the resonance region as described above, projections (or depressions) must be formed at intervals of several tens to several hundreds of nanometers. However, it is extremely difficult to perform mechanical processing including, and at present, practical dies have not been manufactured. In addition, there is a problem that the conventional mold is difficult to reuse.

The present invention has been made in view of the above-mentioned problems of the prior art, and based on a completely different idea from the prior art, has excellent machinability, can improve dimensional accuracy, and has a desired optical surface. It is an object of the present invention to provide a mold for an optical element capable of transferring and forming the shape of the above. Another object of the present invention is to provide a mold for an optical element capable of transferring and forming a fine shape, an optical element formed using the same, and a master mold for molding the optical element.

[0015]

A mold for an optical element according to claim 1 is a mold for an optical element for molding an optical element, wherein an amorphous alloy having a supercooled liquid region is molded. The surface used to mold the optical surface or the dimensional reference surface of the optical element with respect to the first mold formed by
Since it was formed by performing a shaving process, the machinability of the amorphous alloy was extremely good, so that the optical molding surface or molding dimensional standard of the mold corresponding to the optical surface or dimensional standard surface of the optical element was used. The surface can be finished with high accuracy, and the service life of the tool can be extended.
The dimension reference surface refers to a surface serving as a reference for positioning when the optical element is mounted on another member, such as a peripheral surface of a flange portion of the optical element.

Here, an amorphous alloy having a supercooled liquid region (also referred to as an amorphous alloy) will be described. An amorphous alloy having a supercooled liquid region is also called a metallic glass, and is an amorphous alloy that becomes a supercooled liquid when heated. This is because, while ordinary metals have a polycrystalline composition, the structure is amorphous, the composition is microscopically uniform, the mechanical strength and chemical resistance at room temperature are excellent, and the glass transition point is When heated to around +50 to 200 ° C. (this is referred to as a supercooled liquid region), the material is softened and press-forming can be performed.

Conventionally, a technique for forming a molding die for metallic glass by this hot press molding has been disclosed in Japanese Patent Laid-Open No. 10-2.
No. 17257, and an optical element having a ridge line is described in JP-A-9-286627. Also. Japan Society of Mechanical Engineers Vol.65, No.633, 346-35
2 "Study on precision and fine processing of metallic glass" describes an example in which metallic glass is press-molded to create a molding die part having an optical molding surface. In this example, the shape accuracy of the transfer optical surface (optical molding surface) by press molding is 5
00 nm and the surface roughness is 90 nm.

Here, the present inventor pays attention to the amorphous structure of metallic glass, and newly finds that a high-precision optical mirror surface can be easily obtained by directly performing ultra-precision cutting with a diamond tool on metallic glass. Was. The reason for this is that this material is amorphous and has no crystal grain boundaries, so the machinability is uniform regardless of the location, and the crystallization energy is increased to maintain the amorphous state, and the composition is polycrystalline. Therefore, it was found that the diffusion wear of the diamond during the cutting process was small and the life of the cutting edge of the tool could be maintained long. The same can be said for a grinding process using a diamond tool or the like.

In particular, in the example to which the present invention is applied, an optical surface of an optical element is not created by only the conventional hot press molding, but first, a metallic glass is formed into a near net shape, that is, a finished shape by hot press molding. After manufacturing a close blank (first mold), the surface corresponding to the optical surface of the optical element and other mating surfaces is cut by diamond cutting with an ultra-precision processing machine to finish the second mold. That is.

When molding by such a method, the parting line may be formed by using a split mold so that the parting line remains on the optical molding surface of the molded optical element mold. Is also good. This is because it can be easily deleted by post-processing such as cutting. In addition, after forming a reference surface on the first mold formed by hot press molding or the like, the surface is attached to a processing machine such that the eccentricity is minimized based on this surface, and the surface corresponding to the optical surface (optical molding) Surface) with an ultra-precision processing machine, it is possible to easily create a highly accurate optical molded surface with little eccentricity. According to this method, the dimensional accuracy of the first mold may be formed so as to be larger than the final finished dimension by about 5 to 10 μm, and the machining allowance in the post-processing becomes about 1/10 or less of the conventional one. Therefore, it can be said that the optical element mold according to the present invention can be mass-produced extremely efficiently.

In addition, the mold for an optical element of the present invention basically does not need to perform chemical plating as in the conventional mold, and it is also necessary to consider the plating thickness in determining the blank size. Since there is no blank, the blank manufacturing process up to the optical molding surface processing is extremely simplified, and the delivery time can be reduced to 1/4 or less of the conventional one. Furthermore, the optical molding surface can be re-cut many times, and even when it becomes unnecessary, a mold material of another shape can be obtained by hot press molding, so that the material life becomes semi-permanent.

On the other hand, when the present invention is viewed from another angle, the following may be considered. The present inventor has pointed out that metallic glass is fundamentally different from molding of plastics and the like because it is a metal material, the heat conductivity is very high, the whole solidifies instantaneously, the cooling shrinkage is small, and regardless of the molding part Because it occurs proportionally and has low reactivity with the mold, it is possible to optimize the molding pressure and molding time and transfer it with the same or higher precision as the optical surface obtained by plastic molding with high reproducibility. I thought I could do it.

Thus, as a molding die for an optical element having fine projections (or depressions) on the optical surface, a mold for such an amorphous alloy optical element can be obtained by molding and transferring from a master. For example, it is possible to easily obtain a large number of molds having higher shape accuracy than optical elements such as plastics, which are final molded products. By removing the parting line and the like generated during molding from the first mold having the optical molding surface with high precision formed in this way, it is possible to obtain a mold for optical element with high precision. You can do it. The master required to mold the optical element mold, after applying a resist on the surface corresponding to the optical surface of the optical element by spin coating, etc., and after exposing a fine pattern with an electron beam or laser beam, It can be obtained by shaping a fine pattern on the optical surface by development.

That is, the optical element mold of the present invention has a near net shape even in the processing of an optical molded surface having a fine shape, which requires three times or more time as compared with the conventional optical molded surface. Can be easily manufactured, and the number of times the optical molding surface is cut can be greatly reduced to improve the processing efficiency.
However, the scope of the present invention is not limited to a mold for an optical element in which a fine optical pattern (an optical molding surface having a fine shape) is formed. Also, it does not depend on the diamond tool shape or cutting conditions used. Further, another aspect of the present invention is that the first alloy obtained by molding based on the knowledge newly discovered by the inventor that an amorphous alloy which is a metallic glass can obtain a high-precision optical surface by diamond cutting. A high-precision mold for an optical element, in which a second mold is formed by forming an optical molding surface by diamond cutting or creating a dimensional reference surface for the mold described above, is included in the category.

There is no limitation on the type of amorphous alloy that can be used in the optical element mold of the present invention. Pd-based, Mg-based, T
Known metallic glasses such as i-based, Fe-based, and Zr-based can be used. However, an amorphous alloy material having a supercooled liquid region is a necessary condition for the present invention. The type does not matter. However, as a mold material for molding a plastic optical element, Pd-based, Ti-based, and Fe-based materials are advantageous because the resin temperature is close to 300 ° C. and have a high glass transition point. The system is advantageous in that the system can be heated and pressed in the air with little oxidation, and that a large bulk shape can be obtained. In this case, Pd (palladium) is a noble metal and is expensive, but since a metal glass forming die manufactured by the method of the present invention can be crushed and reused if it is unnecessary, processing labor cost is short and the processing labor cost is low. Taken together, long-term mold costs can be lower than conventional molds.

According to a second aspect of the present invention, in the mold for an optical element, the first mold is formed by heating and softening the amorphous alloy having the supercooled liquid region and press-molding the amorphous alloy. Even if the shape is complicated, a near net shape very close to it can be easily formed.

In the mold for an optical element according to the third aspect, if the machining of the surface is a machining, the machining can be performed with high accuracy.

In the optical element mold according to the fourth aspect, if the processing for cutting the surface is grinding processing, accurate processing can be performed.

In the mold for an optical element according to the fifth aspect, when the surface is cut by using a diamond tool, high-precision processing can be performed and the life of the diamond tool can be greatly extended. And the manufacturing cost can be reduced.

The mold for an optical element according to the present invention is a mold for an optical element for molding an optical element, and is formed by molding an amorphous alloy having a supercooled liquid region. The optical molding surface used for molding the optical surface or the dimensional reference surface of the optical element is formed on the first mold by performing exposure and development processing. Depressions (or projections) can be formed on the surface by the above-described processing, and thereby forming multi-functional optical elements by forming fine projections (or depressions) on the optical surface of the molded optical element. be able to. Here, the optical molding surface including both the projections and the depressions is of course within the scope of the present invention.

Further, the present inventor has devised a method of directly forming an optical surface having a fine shape such as a diffractive optical element on an optical molding surface of a mold. As an example, a resist is directly applied to a thickness of 0.1 to 3 μm on an optical molding surface of a first mold formed into an aspherical shape or the like by spin coating or the like, and an electron beam or a laser is applied thereto. After drawing and developing directly with a beam etc., forming a fine optical pattern of resist on the optical surface, dry etching forms fine shapes such as protrusions or dents corresponding to the diffraction grooves of the diffraction ring zone on the optical molding surface. It is formed to obtain a mold for an optical element.

As described above, metallic glass is basically
Since the material is amorphous and has no crystal grain boundaries as a whole, the material has no single composition directionality at any part. That is, in dry etching, etching does not proceed selectively in the crystal orientation as in, for example, single crystal silicon, but etching proceeds uniformly according to conditions. Therefore, when a fine optical pattern is formed on the surface of the amorphous alloy with the thickness of the resist and ions and ionized gas components are irradiated from one direction to the resist surface, the irradiation direction is almost proportional to the thickness. Etching proceeds. Since amorphous alloys are conductors, an electric field can be easily formed when charged particles are accelerated by electron beam exposure or ion etching to strike the surface. Is unnecessary, and the condition is good.

Further, such etching with charged particles has already been put into practical use as an application for sharply processing the tip of diamond or the like, and the apparatus is also capable of ionizing a rare gas or the like to ionize it and apply an electric field to accelerate it. Because of the very simple structure of hitting, there is no need to develop special equipment to realize the present invention. In the present invention, the type of charged particles used for dry etching as an example of the exposure and development processing is not particularly limited. On the optical molding surface of the optical element mold using an amorphous alloy, the fine shape formed of the resist is dry-etched by irradiating the charged particles with charged particles to obtain a highly accurate microstructure optical element mold. This is also within the scope of the present invention.

The method of directly applying a resist to the amorphous alloy serving as the first mold and performing dry etching is effective when the required number of molds is not large. On the other hand, a method of transferring an optical pattern of a fine shape formed on a master mold by hot press molding to obtain a mold of an amorphous alloy is effective when a large number of molds are required.

Here, the first type of exposure and development processing will be described more specifically. As a method of forming a semiconductor element or the like, a method of applying a photoresist (also referred to as a resist) to a silicon wafer and irradiating a laser beam to draw a predetermined pattern is known. By utilizing this, it is conceivable to form fine depressions (or projections) in the first mold.

That is, the photoresist is applied to the optically formed surface such as the aspherical surface of the first mold by the spin coating method or the like, and the fine pattern is exposed by the electron beam or the laser beam, and then the optical pattern is developed by the development. It forms a fine pattern such as a depression (or projection) on the surface.

According to this method, in addition to the above-mentioned fine depressions (or projections), fine shapes including asymmetric and non-axisymmetric patterns and shapes, which are extremely difficult to create by ordinary machining. Can be created on the optical molding surface with high precision by controlling the exposure beam.

Although the thickness of the photoresist is usually about 1 μm, the thickness of the photoresist can be increased by post-baking after application and drying to sufficiently solidify and then re-application. The exposure method adjusts the exposure amount (dose amount) of the electron beam or laser beam, so that the area where the exposure amount is large in the negative resist is more solidified and remains during development, and in the case of the positive type, it is developed in reverse. Since it is eluted in the solution, the progress of the development varies depending on the amount of exposure, whereby a three-dimensional fine shape of the resist can be created.

Since the resist is a resin, if it is used as it is as a molding transfer surface of a mold, the strength and adhesiveness are insufficient and the practicality is poor. Therefore, it is necessary to transfer the fine shape on the optical surface of the resist to a mold material by some method as a master. Conventionally, electroforming has been used as one of the methods. For example, when a stamper mold is manufactured by transferring the pit pattern of an optical disk, the surface of an optical recording pattern called a pit created on a glass substrate by resist is made conductive by flash plating with copper or the like. Then, an electric field is applied in the electrolytic solution to deposit and deposit metallic nickel, thereby capturing a fine shape.

However, as can be easily imagined from the production method of electroforming, the phenomenon that the electric field density increases and the plating proceeds further as the electrode is deposited and protrudes,
For this reason, the electric field distribution in the plating solution constantly changes microscopically, and the thickness of electroforming does not always increase uniformly. Therefore, a very large stress is generated in the electroforming, so that the fine shape of the surface can be transferred with high accuracy. However, the planar shape of the substrate usually warps when it is separated from the master by the stress. When the whole is a flat shape as in the optical disk substrate described above, the thickness of the electroforming is made extremely thin to 0.1 mm or less, and the back surface is polished thinly after peeling from the master to secure the flatness. By performing a post-process and mounting so as to follow the plane part of the mold, the plane shape is maintained in the mold.

On the other hand, in the case where the substrate shape is a highly accurate three-dimensional shape such as an aspherical optical molded surface, such a conventional method cannot be used. There is a problem that the optical molding surface shape is distorted. Although it depends on the state of electroforming, when electroforming is performed to a thickness of several mm, it is necessary to consider about 10 μm of deformation of the optical molding surface due to distortion. In the world, the shape precision of an optical molding surface having a fine shape is required to be at least 100 nm or less, and for high-precision applications, it is required to be 50 nm or less.
Therefore, it is not possible to obtain a mold from a resist by transferring such a highly accurate optical molding surface by electroforming. Therefore,
The optically molded surface having a fine shape formed by a conventional resist on the surface can be transferred to a fine shape even when transferred by electroforming, but the shape of the optically molded surface cannot be used because it is distorted.

Therefore, in the present invention, first, the optical surface of the optical element is provided with, for example, an optical molding surface precisely matched to, for example, an aspherical surface, and a surface (molding dimension reference surface) to be fitted to the dimension reference surface. Molding the first mold of the near net shape
Further, after applying a resist to the optical molding surface by a spin coating method, a predetermined pattern is formed by an electron beam or a laser beam, and then dry etching is performed, for example, fine depressions (or projections) are formed. I am trying to be. The above processing is an example of the development / exposure processing, but is not limited thereto. As dry etching,
There are chemical etching by gas etching, physical etching such as ion etching and plasma etching, and an etching technique in which these are combined. There is also a technique for positively utilizing the etching anisotropy of a substrate material for creating a fine shape.

An optical element mold according to a seventh aspect is an optical element mold for molding an optical element, which is formed by molding an amorphous alloy having a supercooled liquid region. The first mold is formed by subjecting a surface used for molding an optical surface or a dimension reference surface of an optical element to a shaving process and performing an exposure and development process. With the mold for an optical element of the present invention, it is possible to form an optical molding surface or the like with a higher precision or a desired pattern. In addition, for example, the first
In the mold, when the optical molding surface corresponding to the optical surface of the optical element is not formed with high accuracy, the finishing is performed by cutting the optical molding surface as a predetermined surface by cutting or the like. Also, in the first mold, when an optical molding surface corresponding to the optical surface of the optical element is formed with high precision, the optical molding surface as a predetermined surface is further exposed and developed (or cut). Forming fine projections by performing (working) is also included in the scope of the present invention. The same can be said for the mold surface corresponding to the dimension reference surface.

The mold for an optical element according to claim 8, wherein the first mold is formed by heating and softening the amorphous alloy having the supercooled liquid region and press-molding the amorphous alloy. Even if the shape is complicated, a near net shape very close to it can be easily formed.

In the optical element mold according to the ninth aspect, if the processing for cutting the surface is a cutting processing, the processing can be performed with high accuracy.

In the mold for an optical element according to the tenth aspect, when the processing for cutting the surface is a grinding processing, the processing can be performed with high accuracy.

In the mold for an optical element according to the eleventh aspect, when the surface is cut using a diamond tool,
High-precision machining can be performed, the life of the diamond tool can be greatly extended, and the manufacturing cost can be reduced.

According to a twelfth aspect of the present invention, there is provided a mold for an optical element, wherein a plurality of projections or depressions are formed by transfer on the optical surface of the optical element. Can be transferred and molded onto the optical surface, so that a multifunctional optical element can be obtained.

According to a thirteenth aspect of the present invention, there is provided a mold for an optical element, wherein the projections or depressions on the optical surface of the optical element form a fine structure in an equivalent refractive index region. Can be further enhanced. In addition, it is preferable that the interval between the protrusions or depressions is equal to or less than the wavelength of light transmitted through the optical surface of the optical element.

According to a fourteenth aspect of the present invention, there is provided a mold for an optical element, wherein the projections or dents on the optical surface of the optical element form a fine structure that produces an antireflection effect. The rate can be further increased. In addition, it is preferable that the interval between the protrusions or depressions is equal to or less than the wavelength of light transmitted through the optical surface of the optical element.

According to a fifteenth aspect of the present invention, since the projections or depressions on the optical surface of the optical element form a fine structure that generates structural birefringence, for example,
The light transmittance of the optical element can be changed with respect to the light vibration direction. In addition, the interval between the protrusions or depressions is
The wavelength is preferably equal to or less than the wavelength of light transmitted through the optical surface of the optical element.

In the mold for an optical element according to the present invention, since the projections or depressions on the optical surface of the optical element form a fine structure in a resonance region, for example, the degree of aberration of the optical element can be reduced. It can be varied to perform different functions.

According to a seventeenth aspect of the present invention, there is provided a mold for an optical element, wherein a protrusion or a depression on an optical surface of the optical element has a function of adjusting an aberration change due to a wavelength change of a light source that irradiates the optical element with light. Therefore, the function of the optical element can be further enhanced.

According to the optical element mold of the present invention, the projections or depressions on the optical surface of the optical element have a function of adjusting the aberration change due to the temperature change, so that the function of the optical element can be further enhanced. Can be.

In the mold for an optical element according to the nineteenth aspect, since the projections or depressions on the optical surface of the optical element are diffraction zones (ring-shaped diffraction surfaces), for example, at the stage of the first mold. By forming an optical molding surface corresponding to the diffraction zone of the optical element,
Conventionally, the cutting process used to form the diffraction ring zone becomes unnecessary, and the labor and cost for the processing can be reduced.

According to a twentieth aspect of the present invention, the amorphous alloy having the supercooled liquid region has a hardness Hv at room temperature.
It is preferably 300 or more.

The mold for an optical element according to claim 21, wherein the amorphous alloy having the supercooled liquid region has a hardness Hv at room temperature.
Preferably it is 700 or less.

Usually, the hardness of the mold material is required to be high enough to satisfy the durability in actual use, such as abrasion and scratches caused by sliding with the die set mold and cleaning of the optical molding surface. Therefore, Hv300 or more is necessary. But,
If the hardness is too high, the burden on the tool during diamond cutting of the optical molding surface increases, shortening the tool life and creating a highly accurate optical molding surface shape becomes difficult.
It is preferably at most 00. The hardness of an amorphous alloy that is a metallic glass is generally Hv500 to 600 at room temperature, which is almost equal to that of conventional electroless nickel plating.
The tensile strength is about twice as high as that of the conventional blank steel material, the mechanical strength is satisfactory, and it can be said that the die material is stronger than the conventional one. Furthermore, because of its high chemical resistance, it is stable against a small amount of corrosive gas generated during molding of a plastic optical element, and it is possible to prevent the optical surface of the optical element from fogging during molding.

In the mold for an optical element according to the present invention, when palladium is contained in the composition of the amorphous alloy having the supercooled liquid region, oxidation of the mold for the optical element can be prevented.

According to a twenty-third aspect of the present invention, there is provided a mold for an optical element, wherein the composition of the amorphous alloy having a supercooled liquid region contains palladium in a proportion of 30 mol% or more and 50 mol% or less. A suitable amorphous alloy can be obtained.

The mold for an optical element according to claim 24, wherein the composition of the amorphous alloy having the supercooled liquid region contains at least 3 mol% of copper, nickel, phosphorus, zirconia or aluminum. Therefore, an amorphous alloy suitable for a mold for an optical element can be obtained.

The optical element mold according to claim 25 is formed by using the optical element mold according to any one of claims 1 to 24, so that a highly accurate or multifunctional optical element can be manufactured. It can be obtained at low cost.

Since the optical element according to the twenty-sixth aspect is made of a plastic material, for example, a fine shape of an optical molding surface can be transferred with high accuracy.

Since the optical element according to the twenty-seventh aspect is made of a glass material, for example, a fine shape of an optical molding surface can be transferred with high accuracy.

When the optical element according to claim 28 is a lens, an aspherical optical surface or the like which is difficult to mass-produce by machining can be easily and inexpensively formed by transfer.

A master mold according to a twenty-ninth aspect is the mold for an optical element according to any one of the first to twenty-fourth aspects, wherein the master mold is used for molding the first mold.

The master mold according to claim 30 is 500
If the material is formed of a material having a hardness of 300 or more in Hv at 300C, a heated and softened amorphous alloy can be formed.

The master mold according to claim 31 is preferably made of quartz because it has the characteristics described in claim 30 and is excellent in chemical stability.

The master mold according to claim 32 is preferably made of single-crystal silicon because it has the characteristics described in claim 30 and is excellent in chemical stability.

In the master mold according to the present invention, if the material of the master mold contains tungsten carbide, it can be formed by powder metallurgy and can be formed by heating and softening an amorphous alloy.

The diffraction ring zone used in the present specification means that a relief formed as a substantially concentric ring zone centered on the optical axis is provided on the optical surface of an optical element (for example, a lens) and diffracted by diffraction. A diffraction surface having the function of condensing or diverging a light beam. For example, looking at the cross section of a plane including the optical axis, each annular zone is known to have a saw-tooth-like shape, but includes such a shape. The diffraction ring zone is also referred to herein as a diffraction groove.

In applying the present invention, the shape and arrangement period of individual microstructures, such as the arrangement of protrusions (or depressions), do not matter. Regardless of the fine structure, if it is created for the purpose of adding a new function to an optical element, its molding die (optical element die) is included in the scope of the present invention. Further, the function to be newly added is not limited to a function for reducing aberration. The case where the aberration is intentionally increased in accordance with the characteristics of the optical system is included in the scope of the present invention as long as the aberration is finally brought close to the ideal aberration.

[0073]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a process of manufacturing a mold for an optical element. First, as shown in FIG. 1A, a support 5 is provided on a master mold 1 having a mother aspherical surface 1a corresponding to an aspherical surface of a lens which is an example of an optical element.
And a cylindrical blank mold 2 is assembled using bolts 3. Further, as shown in FIG. 1 (b), the master mold material 1 and the blank mold 2 are preheated by the heater H, and the amorphous alloy MG heated and softened between the supercooled liquid regions is rapidly solidified. And pressurized by the plunger 6. At this time, the air in the blank mold 2 flows out through the air vent (the groove 2a formed in the end face of the blank mold 2). Since the amorphous alloy MG has the same flexibility as the molten resin, it is deformed to match the inner shape of the blank mold 2 even with a slight pressurization. Deforms to match the shape of the spherical surface 1a. That is, an optical transfer surface corresponding to the base aspherical surface 1a of the master mold 1 (1.
0a) is formed in an aspherical shape. The master mold 4 is formed by softening and molding the amorphous alloy MG.
(Master mold material 1 and blank mold 2)
Its life can be extended.

Further, as shown in FIG. 1 (c), the master die 4 and the plunger 6 are integrally settled in a container 7 filled with cooling water to rapidly cool the amorphous alloy MG. . Incidentally, such cooling may be natural cooling. Thereafter, the master mold 4 and the plunger 6 taken out of the container 7 are separated, and the solidified amorphous alloy MG is taken out, whereby the first mold 10 (FIG. 2) is formed. still,
In finishing the outer peripheral surface of the flange of the amorphous alloy after forming, the tilt reference surface (10b in FIG.
After the tilt is adjusted in (1), the optical transfer surface 10a is rotated, and the adjustment is performed based on the amount of eccentricity.
The eccentricity of the optical transfer surface 10a can be removed by machining.

FIG. 2 is a view showing a state in which the first die 10 is machined. In FIG. 2, the optical transfer surface 10a is cut with a diamond tool T while rotating the first mold 10 with a driving body (not shown), and the second mold, that is, the optical element mold 10 '(FIG. 3). Is formed. By such a cutting process, for example, a groove corresponding to the diffraction ring zone of the lens as the final product is formed on the optical transfer surface 10a, and the optical molding surface 1a is formed.
0a 'can be obtained. In addition, it is also possible to process a peripheral surface of a flange provided around an optical surface of a lens for removing a parting line, adjusting eccentricity, and the like. Not only cutting using a diamond tool or the like but also grinding using a diamond grindstone may be used.

FIG. 3 is a cross-sectional view showing a mold for molding a lens which is an optical element. The optical element mold 10 ′ formed from the amorphous alloy MG and machined as described above, and the optical element mold 11 formed in the same manner as described above are optically molded surfaces 10 a ′ and 11 a respectively. Are inserted into the die set molds 13 and 14 so as to face each other.
Mold 1 for optical element using molten plastic material PL
By injecting between 0 ′ and 11 and further cooling, a lens having a desired shape can be obtained.

Next, a second embodiment of the present invention will be described. FIG. 4 is a view showing an exposure / development process on the first mold 10 molded from an amorphous alloy. In advance, the first
The optical transfer surface 10a of the mold 10 is assumed to have an aspherical shape accurately transferred from a master mold material in a molding step as shown in FIG. 2 (FIG. 4A).

Subsequently, as shown in FIG. 4B, a resist R is applied to the optical transfer surface 10a while the first mold 10 is rotated around the optical axis by a driver (not shown) (spin coating). . The resist R is coated with the same thickness on the entire upper surface of the first mold 10 including the optical transfer surface 10a.

Further, the optical transfer surface 10a coated with the resist R is irradiated with an electron beam LB by an exposure device (not shown) to form a fine pattern by exposure. Subsequently, as shown in FIG. 4C, the first mold 10 is immersed in a solution, and the resist R is removed on the optical transfer surface 10a according to the fine pattern formed by exposure. Here, since the beam diameter of the electron beam LB is extremely small, the resist R can be removed at intervals of several tens to several hundreds of nanometers.

Thereafter, as shown in FIG. 4D, the upper surface of the first mold 10 from which the resist R has been partially removed is exposed to an atmosphere of an ion shower IS (accelerated argon ions or the like) ( Dry etching), and the surface of the first mold 10 is removed according to the pattern of the resist R. At this time, since the surface of the remaining portion of the resist R is not removed, by removing the resist R in a number of fine circular shapes during exposure, a small surface is formed on the surface of the optical transfer surface 10a of the first mold 10. A second mold, that is, a mold 10 ′ for an optical element, having a large number of cylindrical recesses and an optical molding surface 10 a ′.
Can be formed. Further, by adjusting the exposure amount (dose amount) of the electron beam, it is possible to arbitrarily form a conical depression or a depression corresponding to a saw-toothed annular zone.

Using the optical element mold 10 'thus formed, an optical element (lens) as shown in FIG.
Can be formed. The second mold 10 'formed as shown in FIG. 4 can be further subjected to a cutting process as shown in FIG. 2, or after the cutting process shown in FIG. Exposure and development processing as shown in FIG.

FIG. 5 is a partially sectional perspective view showing an enlarged optical surface of a lens formed by such a mold for an optical element. In FIG. 5A, on the optical surface of the lens,
As an example of the plurality of protrusions, a configuration in which a large number of fine cylinders C are formed in a matrix (an example of a fine structure in an equivalent refractive index region) is provided. For example, when such a lens is used as an objective lens of a DVD recording / reproducing optical pickup device, light transmitted through the lens is near 650 nm. Thus, if the interval Δ between the fine cylinders C is 160 nm, light incident on such an objective lens is hardly reflected, and a lens with extremely high light transmittance can be provided.

In FIG. 5B, a large number of fine triangular pyramids T separated by an interval Δ are formed on the optical surface of the lens as examples of a plurality of projections. It has a great effect. The interval Δ is 0.1 to 0.2 μ
m or less is preferable because scattering is reduced. FIG.
In (c), a large number of fins F (examples of microstructures with structural birefringence) are formed on the optical surface of the lens at intervals of Δ as examples of a plurality of protrusions. The length of the fin F is longer than the wavelength of transmitted light (650 nm or more in the above example). The lens having such a configuration has a so-called polarization effect of transmitting light having a vibrating surface in a direction along the fin F but not transmitting light in a direction intersecting the fin F. In FIG. 5D, a diffraction ring D as an example of a plurality of continuous projections is formed on the optical surface of the lens.
Is formed. Regarding the diffraction ring zone D, for example,
Since the chromatic aberration correction and the temperature correction, which are effects according to the shape, are described in detail in JP-A-2001-195768, the following description is omitted. FIG. 5 (a)
In (c), the projections are shown on a plane for simplicity, but the bottom surface is a curved surface having an appropriate curvature, such as a spherical surface or an aspherical surface, and is provided on the curved surface. It may be.

In the embodiments described below, the metallic glass is an amorphous alloy having a supercooled liquid region. (Example 1) Ten lens-forming dies having a cylindrical end face having a diameter of 7 mm and a length of 35 mm and having an aspherical optical forming surface formed by a conventional chemical plating were manufactured by a conventional method. After the molding of No. 1, a comparison was made between those subjected to processing and finishing. In the former, after cutting a first mold 50 μm smaller with a normal lathe, electroless nickel plating is applied to 100 μm, and the outer periphery and the optical molding surface are cut to 50 μm by diamond cutting with an ultraprecision lathe to finish to a specified size. I got the mold. The time required at this time was 2 hours for the first mold processing,
It took 20 hours for electroless nickel plating and 10 hours for diamond cutting, for a total of 32 hours. On the other hand, the mold according to the present invention forms a master mold using a general-purpose lathe, heat-softens a metallic glass material Pd ₄₀ Ni ₁₀ Cu ₃₀ P ₂₀ in air and press-molds it to produce a first mold. 10 μm was removed by diamond cutting using the same ultra-precision lathe as above, and finished to a specified size to form a second mold. The time required at this time was 2 hours for master mold production, 1 hour for hot press molding, and 4 hours for diamond cutting, for a total of 7 hours.
It was time. It was found that the processing efficiency of the mold of the present invention was about five times better. The hardness of metallic glass is
Hv576.

(Example 2) As a mold for an optical element having a diameter of 5 mm and having a projection (step) corresponding to a diffraction ring zone, a mold blank having a conventional electroless nickel plating of 100 μm and a Zr ₅₅ Cu ₃₀ Al _An optical molded surface was obtained by cutting with a first mold obtained by subjecting ₁₀ Ni _5- based metallic glass to near net shape molding in a nitrogen atmosphere by an ultraprecision lathe. Diamond tools have a tip radius of 0.5 μm
Using a sword tip byte. The minimum spacing between the projections was 9 μm, and the number of projections was 28. Since the cutting edge is very small and sharp,
In order to prevent breakage due to the cutting load, the cutting conditions for both were a cutting depth of 2 μm and a tool feed rate of 0.1.
mm / min. For this reason, the time required for one cut to obtain an optical molded surface was about 30 minutes in both cases. In the conventional mold, the unevenness of the surface of the optical molding surface is generated by about 20 μm due to the thick electroless nickel plating. Therefore, the shaving amount needs to be about 50 μm as described above. Therefore, the total cutting time for obtaining the optical molded surface required 13 hours. On the other hand, in the first mold of the near net shape of the present invention, since the shape accuracy for obtaining the optical molding surface can be made 10 μm or less, the total cutting time was 4 hours. The processing efficiency of the optical molding surface having the projection corresponding to the diffraction groove was more than three times higher in the mold according to the present invention. The hardness of the metallic glass was Hv560.

(Embodiment 3) Master type which is a quartz bulk
In addition, a 4.5mm diameter non-
A spherical base aspherical surface was created. Aspherical shape is required
Metallic glass Pd ₅₃Cu₂₈Ni₁₀P₉Shrinkage
Expected to 0.3%. Repeat spin coating of resist
And applied to a 3.0 μm thick aspherical base aspherical surface,
Conductor coated with chrome on the surface so that an electric field can be formed
It has become. Minimum pitch 3μm, step height by electron beam
0.8μm, 250 diffraction grooves
While exposing the resist. After developing this, plasma C
VD: 2 mTorr fluorine gas, RF power: 50
Dry etching for 3 hours at 0 W
The groove of the blazed diffraction zone of m is formed into an aspherical base aspherical surface
To obtain a master mold. This master type (master type
Set a cylinder (blank type) for forming the outer periphery on the material
And metallic glass Pd₄₀Ni₁₀Cu₃₀P₂₀The air
Softening in the air, press forming in a room temperature atmosphere and pressing the first mold
Obtained. The molding transferability of the mother aspherical surface is 100 μm or less.
The radius of curvature of the peak of the diffraction ring zone, which is the coming ridge, is
Was 50 nm or less. Also, diffraction wheel
Some parts of the valley of the obi seem to be quartz chips
Optical of metallic glass with an accuracy of less than 50 nm radius of curvature
It was transferred to the molding surface. As described above, the groove
Is very narrow when cutting with a diamond tool.
Poor efficiency and limitations on sharpening the tool edge
The valley shape becomes inaccurate due to the
Even if the diffraction efficiency of the
According to the invention, accurate diffraction that can secure sufficient diffraction efficiency
Mold for optical element having optical molding surface with annular shape
Can be obtained.

(Example 4) Metallic glass Zr ₅₅ Cu ₃₀
Al ₁₀ Ni ₅ was produced in a first mold having a diameter of 5 mm and a length of 35 mm by near net shape molding in a nitrogen atmosphere, and an aspheric optical molded surface was created by diamond cutting with an ultraprecision lathe. Further, a resist having a thickness of 1.2 μm was applied on the optical molding surface by spin coating. The groove pattern of the diffraction ring zone was exposed while adjusting the irradiation amount by a laser beam drawing apparatus. The resist was developed to form projections corresponding to a blazed diffraction ring having a minimum pitch of 5 μm, a step of 0.8 μm, and 130 grooves. to this,
400 V in an Ar atmosphere of 3.0 × 10 ⁻⁴ Torr
The ion beam accelerated to 1 mm from the optical axis direction of the optical molding surface
Irradiation was performed for 5 minutes and dry etching was performed to obtain a second mold.
A step of 1.5 is formed on the optical molding surface of the metal glass optical element mold.
A projection corresponding to a blaze-shaped diffraction ring band of μm was formed.

FIG. 6 shows the metallic glass Pd ₄₀ Ni ₁₀ Cu
The ₃₀ P ₂₀ with diamond cutting to the planar shape is a photomicrograph observed by atomic force microscope (AFM). The cutting conditions are as follows: tool edge R 0.5 mm, spindle rotation speed 900
rpm, the tool feed rate was 0.4 mm / min, and the cutting depth was 2 microns. The theoretical surface roughness under this condition is R
z is 0.05 nm. The surface roughness of the cutting plane is Rtm
It was 3.83 nm and Ra was 0.61 nm, and was a very smooth surface without burrs or irreversible as shown in the figure. Aluminum alloy for diamond cutting cut under almost the same conditions (S3M)
Has a surface roughness of Rtm 4.9. nm, Ra 0.80 nm
And, compared to the Al alloy which is said to have good machinability,
The cut surface of metallic glass was much better.

In the above embodiment, the present invention is applied to the optical surface of an optical element. However, similarly, the dimensions of the optical element itself, which requires high accuracy, and the optical element are abutted for positioning. The present invention can be applied to a dimension reference plane useful for a reference position or the like at that time.

[0090]

According to the present invention, a mold for an optical element, which is excellent in machinability, can improve dimensional accuracy, and can transfer and form a desired optical surface or dimensional reference surface shape, or transfers a fine shape. A mold for forming an optical element that can be formed, an optical element formed using the same, and a master mold for molding the same can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a mold for an optical element according to a first embodiment.

FIG. 2 is a view showing a state where a first die 10 is machined.

FIG. 3 is a cross-sectional view showing a mold for forming a lens which is an optical element.

FIG. 4 is a view showing a manufacturing process of a mold for an optical element according to a second embodiment.

FIG. 5 is an enlarged partial cross-sectional perspective view showing an optical surface of a lens formed by an optical element mold.

FIG. 6 shows an atomic force microscope (A) in which a metallic glass Pd ₄₀ Ni ₁₀ Cu ₃₀ P ₂₀ is diamond-cut into a planar shape.
14 is a micrograph observed by FM).

[Explanation of symbols]

 Reference Signs List 1 master mold 2 blank mold 4 master mold 5 support 6 plunger 7 container 10 first mold 10 'second mold (optical element mold)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 3/00 G02B 3/00 Z 3/08 3/08 5/18 5/18 // B29L 11:00 B29L 11:00 F term (reference) 2H049 AA03 AA18 AA22 AA40 AA45 AA64 3C045 DA30 4F202 AA49 AG26 AH74 AH75 AJ02 AJ07 CA01 CA11 CB01 CD22 CK12

Claims (33)

[Claims] 1. A mold for an optical element for molding an optical element, comprising: a first mold formed by molding an amorphous alloy having a supercooled liquid region; A mold for an optical element, wherein a surface used for forming an optical surface or a dimension reference surface is formed by shaving. 2. The optical element metal according to claim 1, wherein the first mold is formed by heat-softening and press-molding the amorphous alloy having the supercooled liquid region. Type. 3. The optical element mold according to claim 1, wherein the processing for shaving the surface is a cutting processing. 4. The mold for an optical element according to claim 1, wherein the processing for shaving the surface is a grinding processing. 5. The optical element mold according to claim 3, wherein the processing for shaving the surface is performed using a diamond tool. 6. A mold for an optical element for molding an optical element, wherein a mold for an optical element is formed with respect to a first mold formed by molding an amorphous alloy having a supercooled liquid region. A mold for an optical element, wherein an optical molding surface used for molding an optical surface or a dimension reference surface is formed by performing exposure and development processing. 7. A mold for an optical element for molding an optical element, wherein a mold for an optical element is formed with respect to a first mold formed by molding an amorphous alloy having a supercooled liquid region. A mold for an optical element, wherein a surface used for molding an optical surface or a dimension reference surface is formed by shaving, and exposing and developing. 8. The optical element according to claim 6, wherein the first mold is formed by heat softening and press-molding the amorphous alloy having the supercooled liquid region. Mold. 9. The optical element mold according to claim 6, wherein the processing for shaving the surface is a cutting processing. 10. The optical element mold according to claim 6, wherein the processing for shaving the surface is a grinding processing. 11. The optical element mold according to claim 9, wherein the surface is cut by using a diamond tool. 12. A method according to claim 6, wherein a corresponding depression or projection is formed on the optical surface of said optical element so that a plurality of projections or depressions are transferred and formed.
2. The mold for an optical element according to claim 1. 13. The optical element mold according to claim 12, wherein the projections or depressions on the optical surface of the optical element form a fine structure in an equivalent refractive index region. 14. The optical element mold according to claim 12, wherein the projections or depressions on the optical surface of the optical element form a fine structure that produces an antireflection effect. 15. The optical element mold according to claim 12, wherein the projections or depressions on the optical surface of the optical element form a fine structure that generates structural birefringence. 16. The optical element mold according to claim 12, wherein the projections or depressions on the optical surface of the optical element form a fine structure in a resonance region. 17. The apparatus according to claim 12, wherein the projection or the depression on the optical surface of the optical element has a function of adjusting an aberration change due to a wavelength change of a light source that irradiates the optical element with light. Mold for optical element. 18. The optical element mold according to claim 12, wherein the protrusion or the depression on the optical surface of the optical element has a function of adjusting a change in aberration due to a change in temperature. 19. The optical element mold according to claim 17, wherein the projection or the depression on the optical surface of the optical element is a diffraction ring zone. 20. The optical element mold according to claim 1, wherein the amorphous alloy having the supercooled liquid region has a hardness Hv of 300 or more at room temperature. 21. The optical element mold according to claim 20, wherein the amorphous alloy having the supercooled liquid region has a hardness Hv of 700 or less at room temperature. 22. The optical element mold according to claim 1, wherein the composition of the amorphous alloy having the supercooled liquid region contains palladium. 23. A composition of the amorphous alloy having a supercooled liquid region, wherein palladium is contained in an amount of 30 mol% to 50 mol%.
23. The optical element mold according to claim 22, wherein the mold is contained in the following ratio. 24. The composition of an amorphous alloy having a supercooled liquid region, wherein at least 3 mol% of copper, nickel, phosphorus, zirconia, or aluminum is contained in the composition. 23. The mold for an optical element according to any one of claims to 22. 25. An optical element formed by using the mold for an optical element according to claim 1. Description: 26. The optical element according to claim 25, wherein the optical element is made of a plastic material. 27. The optical element according to claim 25, wherein the optical element is made of a glass material. 28. The optical element according to claim 25, wherein the optical element is a lens. 29. The optical element mold according to claim 1, wherein the mold is used for molding the first mold. 30. The master mold according to claim 29, wherein the master mold is made of a material having a hardness Hv of 300 or more at 500 ° C. 31. The master mold according to claim 30, wherein the material of the master mold is quartz. 32. The master mold according to claim 30, wherein the material of the master mold is single crystal silicon. 33. The master mold according to claim 30, wherein the material of the master mold includes tungsten carbide.