JP4835818B2 - Optical element molding mold and optical element molding mold manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a molding die for optical element molding dies.as well asThe present invention relates to a method for manufacturing an optical element molding die.
[0002]
[Prior art]
As a method of manufacturing a mold for an optical element of a plastic optical element that has been generally performed conventionally, for example, a blank (primary processed product) is made of steel, stainless steel, etc., and an electroless nickel plating is formed thereon. An amorphous nickel-phosphorus alloy was coated to a thickness of about 100 μm by chemical plating, and this plated layer was cut with a diamond tool by an ultra-precision machine to obtain a highly accurate optical surface.
[0003]
[Problems to be solved by the invention]
According to such a conventional technique, the part shape is basically created by machining, so that the part accuracy can be easily increased to near the motion accuracy of the processing machine, but the manufacturing process is complicated and complicated. It is necessary to produce a blank (primary processed product) in consideration of the thickness of the plating layer, and the plating process is not necessarily stable. Optical molding because the adhesion strength of the layer varies, pinhole-like defects called pits occur, and the optical molding surface corresponding to the optical surface of the optical element must be created within the thickness of the plating layer. When reworking the surface, etc., there are cases where the plating thickness has no margin and it may be impossible to process, and generally it cannot be used repeatedly and the mold cost is high, etc. It has occurred.
[0004]
Further, when the optical molding surface is machined in large quantities, 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, machining conditions, changes in the machining environment temperature, and the like. This optical molding surface processing variation generally generates an optical surface shape error of about 100 nm, and even when processed very carefully, an error of about 50 nm remains, which is the limit of processing accuracy.
[0005]
In recent years, an optical system that efficiently corrects chromatic aberration by providing a diffraction groove on an optical surface has been put into practical use in the optical information recording field and produced in large quantities. As the optical material, plastic or glass is used, but in an infrared optical system or the like, a crystal material such as ZnSe is also used. An efficient method for mass production of such optical elements is molding. At this time, a technique for efficiently producing an optical molding surface having fine diffraction grooves of a molding die with high accuracy is extremely important. It is important.
[0006]
For example, when creating a fine pattern having an optical function such as a diffraction groove on an optical molding surface by diamond cutting, the sharpness of the blade edge affects the accuracy of the diffraction groove shape, and the diffraction efficiency when it is transferred as an optical surface. It is known that it has a great influence on the image quality as described in JP-A-2001-195769.
[0007]
Therefore, in order not to reduce the diffraction efficiency of the diffraction ring zone, the size of the blade edge must be made sufficiently small. Therefore, the cutting resistance is concentrated on the small blade edge part, so the cutting amount must be reduced, and the optical The number of machining operations increases until the entire molding surface is uniformly cut and removed. Further, in order to prevent the surface roughness of the optical molding surface from being deteriorated due to a small cutter mark, the tool feed speed must be slowed down, and the processing time for one optical molding surface is increased. As a result, since the cutting length increases, the wear of the tool edge increases, and the tool is frequently changed. In other words, when processing an optical molding surface having a fine shape by conventional diamond cutting, the tool life is extremely shortened, and the carbon in the diamond is diffused into the blank by cutting, thereby increasing the tool life. Further shortening is required. In addition, since the time for processing 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, in particular, when finishing an optical molding surface having a fine shape on the surface by diamond cutting, a simple and short delivery method for producing a mold is desired.
[0008]
In addition, in recent years, an attempt has been made to add a new optical function to an optical element by applying a fine structure on the optical surface from several times the wavelength to a smaller size. For example, a diffraction groove is formed on the surface of a molded lens having an aspheric optical surface, and the normal dispersion function due to refraction and the positive dispersion that occurs as a side effect at that time are used, and the negative dispersion with large diffraction by the diffraction groove is used. A single lens optical element having an achromatic function that is essentially impossible by refraction alone has been put to practical use as a DVD / CD compatible pickup objective lens for an optical disk. This utilizes the diffractive action of a diffraction groove having a size several tens of times the wavelength of light transmitted through the optical element, and the region that handles the diffractive action by a structure sufficiently larger than the wavelength is called a scalar region. It is.
[0009]
On the other hand, the light reflection suppression function can be exhibited by forming the conical projections densely on the surface of the optical surface at a minute interval of a fraction of the wavelength of the light transmitted through the optical element. Is known. That is, by forming protrusions at fine 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 the conventional optical element. Instead, it can be changed gently so that reflection of light can be suppressed. The surface on which such protrusions are formed has a fine structure called a so-called “eyes”, and individual structures are no longer diffracted by arranging structures finer than the wavelength of light with a period shorter than the wavelength. The region that acts as an average refractive index with respect to the light wave is generally called an equivalent refractive index region. Regarding such an equivalent refractive index region, see, for example, IEICE Transactions C Vol. J83-C No. 3pp. 173-181, described in March 2000.
[0010]
According to such a fine structure of the equivalent refractive index region, it is possible to obtain a large antireflection effect at the same time while reducing the angle dependency and wavelength dependency of the antireflection effect as compared with the conventional antireflection coating, Since the optical surface and microstructure can be created simultaneously by molding, the lens function and anti-reflection function can be obtained at the same time. It is considered to be big and attracts attention. Furthermore, if such a fine structure of the equivalent refractive index region is arranged so as to have directionality with respect to the optical surface, it is possible to give the optical surface strong optical anisotropy. Thus, the birefringent optical element that has been 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 above-described scalar region and equivalent refractive index region, there is a resonance region in which the diffraction efficiency changes rapidly due to a slight difference in incident conditions. For example, when the width of the diffraction groove is narrowed, a phenomenon (anomaly) occurs in which the diffraction efficiency rapidly decreases and increases by several times the wavelength. By adjusting the diffraction groove width as described above, an effect equivalent to that of a normal interference filter can be realized with less angular dependency as a waveguide mode resonance grating filter that reflects only a specific wavelength.
[0012]
By the way, 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 protrusions (or depressions) on the optical surface. In order to mass-produce optical elements having such fine protrusions (or depressions), it can be said that it is generally suitable to perform molding using plastic as a raw material. It is necessary to provide the mold with an optical molding surface having a depression (or protrusion) corresponding to the depression.
[0013]
However, with respect to the protrusions (or depressions) in the equivalent refractive region and the resonance region as described above, protrusions (or depressions) must be formed at intervals of several tens to several hundreds of nanometers. It is extremely difficult to machine. In addition, the conventional mold has a problem that it is difficult to reuse.
[0014]
  The present invention has been made in view of the problems of the prior art, and based on a completely different idea from the conventional one, it is excellent in machinability, can improve dimensional accuracy, and has a desired optical molding surface shape. It is an object of the present invention to provide a molding die for an optical element molding die that can transfer and form a film. The present invention also provides,lightIt is an object of the present invention to provide a method for manufacturing a chemical element mold.
[0015]
[Means for Solving the Problems]
The molding die for an optical element molding die according to claim 1 is a molding die for an optical element molding die for molding an optical element molding die, and an amorphous alloy having a supercooled liquid region Therefore, a more accurate optical element molding die can be molded, and a more accurate optical element can be molded using the mold.
[0016]
An optical element for molding an optical element molding die formed by molding a first amorphous alloy having a supercooled liquid region. A molding die for a molding die, which is formed by using a second amorphous alloy having a supercooled liquid region and having a glass transition point higher than that of the first amorphous alloy. Therefore, a more accurate optical element molding die can be molded, and a more accurate optical element can be molded using the mold. More specifically, since the machinability and workability of the second amorphous alloy are extremely good, the mother optical surface and the mother dimension reference surface of the molding die for the optical element molding die are set. The optical element can be finished with high accuracy corresponding to the optical surface or dimension reference surface of the optical element, and the tool life can be extended. The dimension reference surface is a surface that serves as a positioning reference when the optical element is attached to another member, such as the flange peripheral surface of the optical element.
[0017]
Here, an amorphous alloy (also referred to as an amorphous alloy) having a supercooled liquid region 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 a normal metal has a polycrystalline composition, but because the structure is amorphous, the composition is microscopically uniform, excellent in mechanical strength and room temperature chemical resistance, has a glass transition point, and has a glass transition point. Since it softens when heated to around +50 to 200 ° C. (this is referred to as a supercooled liquid region), it has a feature not found in ordinary metals.
[0018]
Conventionally, a technique for creating a molding die of metal glass by this hot press molding is described in Japanese Patent Laid-Open No. 10-217257, and an optical element having a ridge line is described in Japanese Patent Laid-Open No. 9-286627. Also. In the Japan Society of Mechanical Engineers, Vol. 65, No. 633, 346-352, “Study on Precision / Fine Processing of Metallic Glass”, an example in which a metallic mold part having an optical molding surface is formed by press-molding metallic glass is described. In this example, the shape accuracy of the transfer optical surface (optical molding surface) by press molding is 500 nm, and the surface roughness is 90 nm.
[0019]
Here, the present inventor paid attention to the amorphous structure of the metal glass, and found that a high-precision optical mirror surface can be easily obtained when the metal glass is directly subjected to ultraprecision cutting with a diamond tool. The reason 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 keep the amorphous state, and the composition is polycrystalline. Therefore, it was found that there was little diffusion wear of diamond during the cutting process and that the tool edge life could be kept long. The same is true for grinding using a diamond tool or the like.
[0020]
In particular, in the example to which the present invention is applied, the optical surface of the optical element or the optical molding surface of the optical element molding die is not created only by the conventional hot press molding, but the metallic glass is first heated by press molding. After manufacturing a shape, that is, a blank very close to the finished shape, for example, in an optical element molding die, optical element molding for molding the optical surface of an optical element by diamond cutting with an ultra-precision machine A surface corresponding to the optical molding surface of the mold (referred to as a mother optical surface), a surface corresponding to the other fitting surface, and the like are cut to finish a molding die for an optical element molding die.
[0021]
When molding by such a method, a parting line may be molded using a split mold so as to remain on the molded mother optical surface, or a draft may be provided. This is because it can be easily deleted by post-processing such as cutting. In addition, after creating a reference surface for the optical element molding die formed by hot press molding, etc., it is attached to a processing machine so that the eccentricity is minimized with this surface as a reference. If the corresponding mother optical surface is diamond-cut with an ultra-precision machine, a highly accurate mother optical surface with less eccentricity can be easily created. According to this method, the dimensional accuracy of the molding die for optical element molding dies should be molded to be about 5 to 10 μm larger than the final finished dimension, and the machining allowance by post-processing is about 1/10 or less of the conventional one. Become. Therefore, it can be said that the optical element molding die according to the present invention can be manufactured in large quantities with extremely high accuracy.
[0022]
Further, the molding die for optical element molding die of the present invention basically does not need to be subjected to chemical plating treatment as in the conventional die, and the plating thickness needs to be considered in determining the blank size. Therefore, the blank manufacturing process up to the mother optical surface processing becomes extremely simple, and the delivery time can be reduced to 1/4 or less of the conventional delivery time. Further, the mother optical surface can be recut any number of times, and even when it becomes unnecessary, a mold material having a different shape can be formed by hot press molding, so that the material life is semi-permanent.
[0023]
On the other hand, when the present invention is viewed from a different angle, the following may be considered. The present inventor found that metallic glass is fundamentally different from molding of plastics, etc., because it is a metallic material, its thermal conductivity is extremely high, and the whole solidifies instantaneously, cooling shrinkage is small, and it does not depend on the molding site. Proportionally generated and low reactivity with the mold, etc., but by optimizing the molding pressure and molding time, it is equivalent to the optical molding surface obtained by plastic molding or with high reproducibility with high reproducibility I thought I could transfer it.
[0024]
Therefore, as an optical element molding die having fine protrusions (or depressions) on the optical surface, it is molded and transferred from a master made of some amorphous alloy (molding die for optical element molding die). If an optical element molding die made of a crystalline alloy is obtained, it is possible to easily obtain a large amount of molds having a higher shape accuracy than an optical element such as plastic which is the final molded product. In order to form an optical element molding die having such a high-precision optical molding surface, a high-precision optical element molding die is prepared in advance by forming a molding die for an optical element molding die having a corresponding shape. The mold can be easily obtained by molding. Such a mold for an optical element molding die is obtained by applying a resist to the mother optical surface corresponding to the optical surface of the optical element by spin coating, exposing a fine pattern with an electron beam or a laser beam, and then developing the resist. Can be obtained by shaping a fine pattern on the optical surface.
[0025]
In other words, the molding die for optical element molding die according to the present invention is a method for forming an optical molding surface of an optical element molding die having a fine shape having three times or more compared with the processing time of a conventional optical molding surface. It can be easily molded from a net-shaped blank, and post-processing is not required, and processing efficiency can be greatly improved. However, the scope of the present invention does not depend on a fine optical pattern. Moreover, it does not depend on the diamond tool shape used or cutting conditions.
[0026]
However, the glass transition point of the second amorphous alloy that is the material of the molding die for the optical element molding die is lower than the glass transition point of the first amorphous alloy that is the material of the optical element molding die. For example, the molding die for optical element molding dies may be melted and deformed during hot press molding. Therefore, in order to prevent this, the glass transition point of the second amorphous alloy is set higher than the glass transition point of the first amorphous alloy.
[0027]
As long as the above conditions are satisfied, the types of the first and second amorphous alloys that can be used in the optical element molding die and the optical element molding die of the present invention are not limited. Although known metallic glasses such as Pd-based, Mg-based, Ti-based, Fe-based, and Zr-based materials can be used, an amorphous alloy material having a supercooled liquid region is necessary for the present invention. These compositions and types are not limited. However, as an optical element molding die material for plastic optical elements, since the resin temperature is close to 300 ° C., Pd-based, Ti-based, Fe-based, etc. are advantageous because of their high glass transition point, but more preferable. Is advantageous in that the Pd system is hardly oxidized in the air and can be heated and formed in a large bulk shape. Furthermore, although Pd (palladium) is a noble metal and expensive, it can be reused by being cast and reused if the metal glass mold of the present invention is no longer needed. When combined with a low value, the mold cost over a long period of time can be reduced even if a metallic glass containing Pd is used.
[0028]
An optical element for molding an optical element molding die formed by molding a first amorphous alloy having a supercooled liquid region. A molding die for a molding die, which has a supercooled liquid region and has a glass transition point higher than that of the first amorphous alloy by 50 ° C. or more (preferably 100 ° C. or more). Therefore, the optical element molding die is also used when the optical element molding die is formed by hot press molding the first amorphous alloy. A stable mold shape can be maintained even when used repeatedly without causing deformation of the molding die.
[0029]
5. The molding die for an optical element molding die according to claim 4, wherein the optical molding surface of the optical element molding die (a surface for molding the optical surface of the optical element) or a molding dimension reference surface (a dimension reference surface of the optical element). The surface to be molded is formed and transferred by hot press molding, so that the optical molding surface and the molding dimension reference surface can be accurately formed.
[0030]
Since the molding die for optical element molding die according to claim 5 is formed with the corresponding depression or projection so that the projection or depression is transferred and formed on the optical molding surface of the optical element molding die. The desired depression or protrusion can be formed without post-processing the optical molding surface.
[0031]
The molding die for an optical element molding die according to claim 6 is equivalent in that the protrusions or depressions of the optical element molding die are transferred to the optical surface of the optical element molded by the optical element molding die. Since the fine structure of the refractive index region is formed, the light transmittance of the optical element can be further increased. In addition, it is preferable that the space | interval of the said protrusion or a hollow is below the wavelength of the light which permeate | transmits the optical surface of the said optical element.
[0032]
The molding die for an optical element molding die according to claim 7, wherein a projection or a depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die and reflected. Since the fine structure generating the prevention effect is formed, the light transmittance of the optical element can be further increased. In addition, it is preferable that the space | interval of the said protrusion or a hollow is below the wavelength of the light which permeate | transmits the optical surface of the said optical element.
[0033]
A molding die for an optical element molding die according to claim 8, wherein a projection or a depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die. Since a fine structure that generates birefringence is formed, for example, the light transmittance of the optical element can be changed with respect to the vibration direction of light. In addition, it is preferable that the space | interval of the said protrusion or a hollow is below the wavelength of the light which permeate | transmits the optical surface of the said optical element.
[0034]
The molding die for an optical element molding die according to claim 9, wherein a projection or a depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die, so that resonance occurs. Since the fine structure of the region is formed, for example, the degree of aberration of the optical element can be changed to exhibit different functions.
[0035]
The molding die for an optical element molding die according to claim 10, wherein the projection or depression of the optical element molding die is transferred to the optical surface of the optical element molded by the optical element molding die, Since the optical element has a function of adjusting a change in aberration due to a change in wavelength of a light source that emits light to the optical element, the optical function of the optical element can be enhanced.
[0036]
12. The molding die for an optical element molding die according to claim 11, wherein the protrusion or depression of the optical element molding die is transferred to the optical surface of the optical element molded by the optical element molding die, and the temperature is increased. Since it has a function of adjusting the aberration change due to the change, the optical function of the optical element can be enhanced.
[0037]
13. The molding die for an optical element molding die according to claim 12, wherein a projection or a depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die and is diffracted. Since an annular zone (annular diffractive surface) is formed, it is no longer necessary to cut the optical molding surface in order to form a diffractive annular zone. Can be reduced in labor and cost.
[0038]
In the molding die for an optical element molding die according to claim 13, the mother optical surface (the surface on which the optical molding surface of the optical element molding die is molded) is created by cutting. Can be extended.
[0039]
15. The molding die for optical element molding die according to claim 14, wherein the protrusions or depressions are formed by applying a resist on a mother optical surface, exposing by electron beam drawing and performing development processing. It is characterized by.
[0040]
For example, the present inventor has devised a method for creating a fine surface shape such as a diffractive optical element on the mother optical surface of a molding die for optical element molding dies. For example, a resist is directly applied to a thickness of 0.1 to 3 μm by spin coating on the mother optical surface of a molding die for an optical element molding die molded into an aspheric shape. After drawing and developing directly with an electron beam or laser beam, a fine optical pattern of the resist is formed on the mother optical surface, and then fine etching such as protrusions or depressions corresponding to the diffraction grooves on the mother optical surface by dry etching To obtain a molding die for optical element molding dies.
[0041]
As described above, metallic glass is basically a material that is amorphous and has a uniform overall structure and no crystal grain boundaries, and therefore has no single composition direction at any part. In other words, in dry etching, etching does not proceed selectively in the crystal orientation as in, for example, single crystal silicon, and etching proceeds uniformly according to conditions. Therefore, when a fine optical pattern is formed on the surface of the amorphous alloy with the resist thickness, and the resist surface is irradiated with ions or ionized gas components accelerated from one direction, the irradiation direction is almost proportional to the thickness. Etching progresses. Since an amorphous alloy is a conductor, an electric field can be easily formed when the charged particles are accelerated by the electron beam exposure or ion etching and hit the surface. The process of applying is unnecessary and good.
[0042]
Etching with charged particles has already been put to practical use as a tool for sharply processing the tip of diamond and the like, and the device ionizes rare gas etc. to ionize it, accelerates it by applying an electric field and hits it. Because of the simple structure, it is not necessary 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 exposure / development processing is not particularly limited. Optical element with a high-precision microstructure by dry etching by irradiating charged particles onto the mother optical surface of a molding die for optical element molding molds using an amorphous alloy. Obtaining a mold for a molding die is also within the scope of the present invention.
[0043]
Here, the exposure / development processing of the optical element molding die 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 protrusions) on the mother optical surface of the optical element molding die.
[0044]
That is, on the mother optical surface such as an aspherical surface in the molding die for optical element molding die, the photoresist is applied in the same manner by spin coating method, and a fine pattern is exposed by an electron beam or a laser beam and then developed. Thus, a fine pattern such as a depression (or protrusion) on the mother optical surface is formed.
[0045]
According to this method, in addition to the above-described fine dents (or protrusions), a fine shape including an asymmetrical or non-axisymmetric pattern or shape, which is extremely difficult to create by normal machining, can be obtained. It is possible to create the optical surface with high accuracy by controlling the exposure beam.
[0046]
Although the thickness of the photoresist is usually about 1 μm, the photoresist can be thickened by re-coating after coating and drying and post-baking to solidify sufficiently. In the exposure method, by adjusting the exposure amount (dose amount) such as electron beam or laser beam, the negative type resist is more solidified in the negative type resist and remains during development, while the positive type is developed in reverse. Since it elutes in the liquid, the development progresses depending on the exposure amount, and the three-dimensional fine shape of the resist can be created.
[0047]
Since the resist is a resin, its strength and adhesion are insufficient for use as the mother optical surface of the mold as it is, and its practicality is poor. Therefore, it is necessary to transfer the fine shape on the mother optical surface by this resist to the mold material as a master by some method. Conventionally, electroforming has been used as one of the methods. For example, when manufacturing a stamper mold by transferring a pit pattern of an optical disk, the surface of an optical recording pattern called a pit created on a glass substrate by a resist is made conductive by flash plating such as copper. Thereafter, an electric field is applied in the electrolytic solution to deposit and deposit metallic nickel, thereby copying the fine shape.
[0048]
However, as can be easily imagined from the generation method of electroforming, the phenomenon that the electric field density increases and the plating proceeds further as it deposits and protrudes, so the electric field distribution in the plating solution constantly fluctuates microscopically. Therefore, the thickness of electroforming does not increase uniformly. For this reason, a very large stress is generated in the electroforming, so that the fine shape of the surface can be accurately transferred, but the planar shape of the substrate is usually warped at the stage of peeling from the master due to the stress. When the whole is flat like the optical disk substrate described above, the thickness of the electroforming is made very thin to 0.1 mm or less, and the back surface is thinly polished after peeling from the master to ensure flatness, etc. By performing a post-process and attaching it so as to follow the planar portion of the mold, the planar shape is maintained in the mold.
[0049]
On the other hand, when the substrate shape is a highly accurate three-dimensional shape such as an aspherical mother optical surface, such a conventional method cannot be used, and the mother optical surface is instantly peeled off from the master after electroforming. There is a problem that the shape is distorted. Although depending on the state of electroforming, when electroforming is performed to a thickness of several millimeters, it is necessary to consider deformation of the mother optical surface due to distortion by about 10 μm. In the world, the shape accuracy of an optical surface having a fine shape is required to be at least 100 nm or less, and for high-accuracy applications, 50 nm or less is required. Therefore, a higher-precision mother optical surface is transferred by electroforming from a resist. It is difficult to obtain a mold. Therefore, a mother optical surface having a fine shape formed of a resist on its surface can be copied even if it is transferred by electroforming, but the shape of the mother optical surface is distorted and difficult to use.
[0050]
Therefore, in the present invention, first, a molding die for an optical element molding die of a near net shape having a mother optical surface accurately matched with, for example, an aspherical shape of the optical surface of the optical element, After applying a resist to the mother optical 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 to form, for example, a fine depression (or protrusion). I try to do it. The above processing is an example of development / exposure processing, but is not limited thereto. Examples of dry etching include chemical etching by gas etching, physical etching such as ion etching, and plasma etching, and an etching technique that combines them. In addition, there is a technique that positively utilizes the etching anisotropy of the substrate material to create a fine shape.
[0051]
The molding die for an optical element molding die according to claim 15 is formed by applying a resist to the mother optical surface, exposing the mother optical surface by a resist, and performing development processing by exposure with laser light drawing. It is characterized by.
[0052]
The molding die for an optical element molding die according to claim 16 is characterized in that the projection or the depression is formed by a dry etching process after the development of the resist.
[0053]
The molding die for an optical element molding die according to claim 17 is characterized in that a mother optical surface of the molding die for an optical element molding die is created by gas deposition using a focused ion beam. . Gas deposition using a focused ion beam will be described later with reference to an embodiment.
[0054]
19. The molding die for an optical element molding die according to claim 18, wherein the second amorphous alloy used in the molding die for the optical element molding die is formed by press molding the optical element molding die. When the hardness is maintained at Hv 300 or higher, the shape can be maintained even after repeated use.
[0055]
The molding die for an optical element molding die according to claim 19, wherein the second amorphous alloy used in the molding die for the optical element molding die has a hardness of Hv 700 or less at room temperature. It is preferable because of excellent machinability.
[0056]
21. The molding die for optical element molding die according to claim 20, wherein nickel, hafnium, or palladium is contained in the composition of the second amorphous alloy in a proportion of 30 mol% to 50 mol%. It is suitable as a material for a molding die for a molding die.
[0057]
The molding die for optical element molding die according to claim 21, wherein the composition of the second amorphous alloy contains at least 3 mol% of copper, zirconia, copper, aluminum, or phosphorus. Then, it is suitable as a material for a molding die for optical element molding dies.
[0083]
  Claim22The method for manufacturing an optical element molding die described in 1 is a method for manufacturing an optical element molding mold for molding an optical element formed by molding a first amorphous alloy having a supercooled liquid region. An optical element molding die formed by using a second amorphous alloy having a supercooled liquid region and having a glass transition point higher than that of the first amorphous alloy. Since the optical element molding die is manufactured by hot press molding the first amorphous alloy with the molding die, a more accurate optical element molding die can be molded, and more A highly accurate optical element can be molded.
[0084]
The diffraction ring zone used in this specification refers to a relief formed as a substantially concentric ring zone around the optical axis on the optical surface of an optical element (for example, a lens), and collects light flux by diffraction. A diffractive surface that has light or divergence. For example, when the cross section is viewed on a plane including the optical axis, each annular zone is known to have a sawtooth shape, but such a shape is included. The diffraction zone is also referred to as a diffraction groove here.
[0085]
When the present invention is applied, the shape of each fine structure, the arrangement period, and the like, such as the arrangement of protrusions (or depressions), are not relevant. Whatever the fine structure, if it is made for the purpose of adding a new function to the optical element, the molding die is included in the scope of the present invention. Further, the function to be newly added is not limited to the function for reducing aberration. The case where the aberration is intentionally increased according to the characteristics of the optical system is also included in the scope of the present invention as long as it is performed for the purpose of finally bringing it closer to the ideal aberration.
[0086]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a process of manufacturing a molding die for an optical element molding die for molding an optical element molding die. First, as shown in FIG. 1A, a column 105 is attached to a master mold 101 on which a mother aspheric surface 101a corresponding to an aspheric surface of a lens which is an example of an optical element is formed, and a cylindrical shape is formed using a bolt 103. The blank mold 102 is assembled. Further, as shown in FIG. 1B, the master mold 101 and the blank mold 102 are preheated by the heater H, and the amorphous alloy MG heated and softened between the supercooled liquid regions is rapidly solidified. Is inserted into the blank mold 102, and is pressurized by the plunger 106. At this time, the air in the blank mold 102 flows out to the outside through an air vent (a groove 102a formed on the end face of the blank mold 102). Since the amorphous alloy MG is flexible like the molten resin, even if it is slightly pressurized, it is deformed so as to match the inner shape of the blank mold 102. It is deformed to match the shape of the spherical surface 101a. That is, the mother optical surface (1a described later) corresponding to the mother aspherical surface 101a of the master mold 101 is formed in an aspherical shape. By softening and molding the amorphous alloy MG, it is possible to suppress the wear of the master mold 104 composed of the master mold material 101 and the blank mold 102 and extend its life.
[0087]
Further, as shown in FIG. 1 (c), the master mold 104 and the plunger 106 are integrally submerged in a container 107 filled with cooling water, thereby rapidly cooling the amorphous alloy MG. Such cooling may be natural cooling. Thereafter, the master die 104 and the plunger 106 taken out from the container 107 are separated, and the solidified amorphous alloy MG is taken out, whereby the optical element molding die 1 is formed. At this time, the mother optical surface 1a (FIG. 2) of the molding die 1 for optical element molding dies is only the mother aspherical surface, and no depressions or protrusions are formed. In the finishing process of the outer peripheral surface of the flange of the amorphous alloy after forming, after adjusting the tilt on the tilt reference surface of the master mold 101, the mother optical surface 1a is rotated and adjusted based on the amount of eccentricity. The removal of the eccentricity of the mother optical surface 1a can be performed by machining.
[0088]
FIG. 2 is a diagram illustrating a processing step of a mother optical surface of a molding die for optical element molding dies. First, as shown in FIG. 2 (a), a resist R is applied to the mother optical surface 1a while rotating the molding die 1 for optical element molding dies around the optical axis by a driver (not shown) (spin coating). ). The resist R is coated on the upper surface of the master mold 1 including the mother optical surface 1a with an equal film thickness.
[0089]
Further, the mother optical surface 1a coated with the resist R is irradiated with an electron beam LB by an exposure machine (not shown) to form a fine pattern by exposure. Subsequently, as shown in FIG. 2B, the optical element molding die 1 is immersed in a solution, and the resist R is removed on the mother optical surface 1a 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.
[0090]
Thereafter, as shown in FIG. 2C, the upper surface of the optical element molding die 1 from which the resist R has been partially removed is placed in an atmosphere of an ion shower IS (accelerated argon ions or the like). Exposure (dry etching) is performed, and the surface of the optical element molding die 1 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, the surface of the processed mother optical surface 1a ′ of the optical element molding die 1 is left by leaving the thick circular resist R at the time of exposure. In addition, a large number of small cylindrical protrusions are formed.
[0091]
The optical element molding die 1 thus formed is fixed with a bolt 3 so as to close one end of a cylindrical blank die 2 to form a master die 4. (FIG. 2D). Grooves 2a are formed on the end surface of the blank mold 2 so that an air vent is formed between the blank mold 2 and the optical element molding mold 1. The processing of the optical element molding die 1 does not require a large-scale facility and can reduce the manufacturing cost. If there is one, the optical element molding die can be formed as described later. Since it can be manufactured in large quantities, further cost reduction can be expected.
[0092]
FIG. 3 is a diagram showing a manufacturing process of the optical element molding die. First, as shown in FIG. 3A, the support column 5 is attached to the master mold 4 manufactured in the process shown in FIG. Furthermore, as shown in FIG. 3B, the master mold 4 is preheated by the heater H, and the amorphous alloy MG ′ heated and softened between the supercooled liquid regions is suppressed from rapid solidification. Then, it is inserted into the blank mold 2 and pressurized with the plunger 6. At this time, the air in the blank mold 2 flows out through the air vent (groove 2a). At this time, the glass transition point of the amorphous alloy MG (second amorphous alloy) that is the material of the molding die 1 for the optical element molding die is the amorphous alloy MG ′ to be molded (first The glass transition point of the amorphous alloy) is preferably 50 ° C. or higher (more preferably 100 ° C.) or higher, so that the molding die 1 for optical element molding dies may be deformed by heat during molding. Absent.
[0093]
Since the amorphous alloy MG ′ is flexible like the melted resin, it deforms to match the inner shape of the blank mold 2 even with a slight pressure, and the optical element molding die It deform | transforms so that it may correspond with the shape of the mother optical surface 1a 'of the molding die 1 for an object. That is, a recess corresponding to the cylinder is formed on the optical molding surface (10a to be described later) of the optical element molding die corresponding to the mother optical surface 1a 'of the molding die 1 for optical element molding die. . By softening and molding the amorphous alloy MG ', it is possible to suppress the wear of the master mold 4 and extend its life.
[0094]
Further, as shown in FIG. 3C, the master mold 4 and the plunger 6 are integrally submerged in a container 7 filled with cooling water, thereby rapidly cooling the amorphous alloy MG '. Such cooling may be natural cooling. Thereafter, the master die 4 and the plunger 6 taken out from the container 7 are separated, and the solidified amorphous alloy MG ′ is taken out, thereby forming the optical element molding die 10 (FIG. 4).
[0095]
In the above description, an example in which the molding die 1 for optical element molding dies is formed of an amorphous alloy is exemplified. However, if the blank die 2 is similarly made of an amorphous alloy, it is advantageous for cost reduction. . FIG. 4 is a cross-sectional view showing a mold for forming a lens which is one of optical elements. The optical element molding die 10 formed from the amorphous alloy MG ′ as described above and the optical element molding die 11 formed in the same manner are arranged so that the optical molding surfaces 10a and 11a face each other. Then, the lens is inserted into the die set molds 13 and 14, the molten plastic material PL is injected between the optical element molding molds 10 and 11, and further cooled, whereby a lens having a desired shape can be obtained.
[0096]
As an example of the amorphous alloys MG and MG ′, a metal glass having the following composition can be used.
Pd₄₀Ni₁₀Cu₃₀P₂₀
Zr₅₅Cu₃₀Al₁₀Ni₅
Pd₅₃Cu₂₈Ni₁₀P₉
Pd₇₆Cu₁₇Si₇
[0097]
FIG. 5 is a partial cross-sectional perspective view showing an enlarged optical surface of a lens formed by such an optical element molding die. FIG. 5A shows a configuration in which a large number of fine cylinders C are formed in a matrix on the optical surface of the lens as an example of a plurality of protrusions (example of fine structure of equivalent refractive index region). For example, when such a lens is used as an objective lens of a DVD recording / reproducing optical pickup device, the light transmitted through the lens is in the vicinity of 650 nm. Therefore, when the interval Δ between the minute cylinders C is set to 160 nm, the light incident on the objective lens is hardly reflected, and a lens with extremely high light transmittance can be provided.
[0098]
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 an example of a plurality of protrusions, and the same remarkable effect as in FIG. Have. As this space | interval (DELTA), since scattering is reduced as it is 0.1-0.2 micrometer or less, it is preferable. In FIG. 5C, a large number of fins F (example of fine structure of structural birefringence) spaced apart by a distance Δ are formed on the optical surface of the lens as an example 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). A lens having such a configuration has a so-called polarization effect in which light having a vibration surface is transmitted in a direction along the fin F, but light in a direction intersecting the fin F is not transmitted. In FIG. 5D, a diffraction ring zone D is formed as an example of a plurality of continuous protrusions on the optical surface of the lens. Regarding the diffraction zone D, for example, Japanese Patent Laid-Open No. 2001-195769 describes in detail chromatic aberration correction and temperature correction, which are effects according to the shape thereof, and thus the following description is omitted. 5A to 5C show an example in which these protrusions are provided on a flat surface for the sake of simplicity, but the bottom surface thereof is a curved surface having an appropriate curvature such as a spherical surface or an aspherical surface. It may be provided on the curved surface.
[0099]
In the above-described embodiment, the processing of the mother optical surface 1a of the optical element molding die 1 is performed using an electron beam. However, the present invention is not limited to this, and a laser beam or a diamond is used. Machining such as cutting can be performed. Further, in the following example, processing is performed by gas deposition using a focused ion beam.
[0100]
FIG. 6 is a diagram schematically showing a main part of a focused ion beam apparatus that can be used for processing the mother optical surface 1a of the molding die 1 for optical element molding die.
[0101]
In the focused ion beam apparatus of FIG. 6, when an acceleration voltage is applied to the emitter 111a of the gallium liquid metal ion source 111 and a negative high voltage is applied to the electrode 111b, ions are emitted from the emitter 111a, and the electrodes 111b and 111c are configured. Focused by a focusing lens. The focused ion beam b includes a condenser lens 112 for collimating the beam, a blanker 113 for turning on / off the beam irradiation, an aligner 114 for adjusting the beam position with respect to the aperture 115, an aperture 115 for determining a beam opening angle, An aligner 116 for passing the beam through the center of the objective lens 117, an objective lens 117 for focusing the beam on the surface of the substrate in a spot shape, and the beam on the surface of the substrate (molding die 1 for optical element molding die). Are sequentially passed through a deflection scanning unit 118 that deflects the beam by an electric field or a magnetic field so as to be scanned by, and irradiated onto the mother optical surface 1a of the molding die 1 for the optical element molding die that is mounted and fixed on the XY stage 121. The
[0102]
Further, the gas discharge unit 119 blows deposition gas from the nozzle 119a toward the mother optical surface 1a. Further, secondary electrons emitted from the mother optical surface 1 a by irradiation of the focused ion beam are detected by the secondary electron detector 120. The XY stage 121 is slightly moved in the XY direction by the driving units 121a and 121b, and the relative position between the irradiation point of the focused ion beam and the mother optical surface 1a is controlled by the control of the driving units 121a and 121b of the XY stage control unit 122. Fine adjustment is possible. The above-described portions 111 to 122 of the focused ion beam apparatus of FIG. 6 are controlled by the control device 123 as a whole.
[0103]
When a gas is blown onto the mother optical surface 1a from the nozzle 119a of the gas discharge section 119 while irradiating the focused ion beam with the focused ion beam device of FIG. 6, the atmosphere in the vicinity of the surface of the mother optical surface 1a formed by this blowing gas. Collides with the focused ion beam. By depositing molecules / atoms generated by this collision on the surface of the mother optical surface 1a, deposition can be performed on the surface, and a desired pattern shape can be formed by this deposition.
[0104]
As ions used in the focused ion beam, argon or the like is used in addition to gallium, but an element having a larger atomic weight has a higher energy density and is suitable for processing. In addition, since it is desirable for ions to be liquid at room temperature, it is usually preferable to use gallium as the ion generating element. Further, in order to perform deposition at high speed efficiently, it is desirable that the gas decomposition efficiency is high. Therefore, it is better to use gallium having high kinetic energy for acceleration ions when accelerated. Therefore, the ion beam becomes a positive charged particle, but the positive or negative of the charge of the ion beam is not related to the essence of the present invention.
[0105]
6 can control the scanning range (field) of the focused ion beam by an electric field or a magnetic field, but this scanning range is usually very narrow, 5 μm square to 20 μm square. A wide mother optical surface can be formed by relatively changing the position of the irradiation point of the focused optical beam 1a and the focused ion beam on the stage 121. That is, when the size of the mother optical surface pattern to be formed exceeds the scanning range of the focused ion beam, the mother optical surface 1a is moved while moving the mother optical surface 1a by the XY stage 121 and connected to the mother optical surface, A wider mother optical surface can be formed.
[0106]
As described above, it is preferable to move the mother optical surface 1a with the XY stage 121 for the connection irradiation because the base is generally much smaller and lighter than the focused ion beam device (accelerator). In addition, since the connecting accuracy of the scanning pattern is very important for obtaining a desired optical surface shape and optical characteristics, the XY stage 121 is a biaxial actuator that is practically used in, for example, an existing electron beam drawing apparatus. Since the fine movement stage is a device intended for the same continuous exposure, it can be used as it is.
[0107]
Further, when the shape of the substrate is a three-dimensional shape such as a spherical surface other than a flat surface or an aspherical surface, the surface of the base material is always located near the focal point of the focused ion beam in order to form the mother optical surface of the present invention. Therefore, the fine movement stage is preferably XYZ three-axis driving or rotation driving for each axis. In this case, since the beam opening angle of the focused ion beam is about 2 to 3 degrees, depending on the desired optical surface accuracy, the depth of focus can be set to about 5 μm, and the focused ion beam optical axis direction of the fine movement stage It is not necessary to set the positioning accuracy of the high resolution and high accuracy. When forming a mother optical surface on a deep spherical or aspherical base, the surface inclination angle of the portion irradiated with the focused ion beam may be as large as 50 to 70 degrees. In such a case, if the fine movement stage is controlled so that the surface inclination angle with respect to the optical axis of the focused ion beam approaches 0 degrees (vertical) by rotating the workpiece, the deposition condition becomes substantially uniform on the substrate. The film thickness can be easily controlled. However, since the surface tilt angle of the substrate is not inherently related to the amount of deposition medium generated by decomposition by the focused ion beam and its sputtering energy, the above method is not easily affected by the surface tilt angle of the substrate, By correcting a slight irradiation time in accordance with the surface inclination angle, the mother optical surface shape can be formed with a desired film thickness with high accuracy.
[0108]
In addition, as shown in FIG. 7, the diameter of the focal spot s of the focused ion beam is usually about 20 nm, but the gas decomposed by the irradiation of the focused ion beam diffuses or the scattering direction varies, so the beam is formed in a line shape. A protrusion occurs on one side of the pattern deposited during scanning, and the protrusion amount t is about several tens to several hundreds of nm as shown by the broken line in FIG. Since this protrusion is extremely reproducible for each scan, when the optical surface pattern is formed, the protrusion amount is estimated in advance, and the scan pattern is offset to the side where the film thickness becomes thicker than the scan line. The desired optical pattern shape can be obtained with high accuracy.
[0109]
The amount of protrusion described above varies depending on the type of gas and the deposition conditions, and is generally small when the deposition rate is small and large when it is large. Therefore, the offset amount for correcting the amount is determined according to the amount of protrusion. It ’s fine. In such an embodiment, this offset amount is approximately in the range from 50 nm to 500 nm due to restrictions on practical deposition conditions.
[0110]
【The invention's effect】
According to the present invention, a molding die for an optical element molding die that is excellent in machinability, can improve dimensional accuracy, and can transfer and form the shape of a desired optical molding surface, based on a completely different concept from the conventional one. Can be provided. In addition, according to the present invention, it is possible to provide an optical element molding die molded by the optical element molding die, an optical element formed using the same, and a method of manufacturing the optical element molding die. it can. In addition, high-precision optical elements can be mass-produced at a very low cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a manufacturing process of a molding die for an optical element molding die according to the present embodiment.
FIG. 2 is a diagram showing a processing step of a mother optical surface of a molding die for optical element molding dies.
FIG. 3 is a diagram showing a manufacturing process of the optical element molding die of the present embodiment.
FIG. 4 is a cross-sectional view showing a mold for forming a lens which is an optical element.
FIG. 5 is an enlarged partial cross-sectional perspective view showing an optical surface of a lens formed by a mold for optical elements.
FIG. 6 is a diagram schematically showing a main part of a focused ion beam apparatus that can be used for processing a mother optical surface of a molding die for optical element molding dies.
7 schematically shows the protrusion amount t on one side of the pattern deposited when the beam is scanned in a line with respect to the diameter of the focal spot s of the focused ion beam on the substrate in the ion beam apparatus of FIG. FIG.
[Explanation of symbols]
1 Mold for optical element mold
2 Blank type
4 Master type
5 props
6 Plunger
7 containers
10, 11 Optical element molding die
101 Master mold material
102 Blank type
104 Master type
105 prop
106 Plunger
107 containers

Claims (22)

  An optical element forming mold for forming an optical element forming mold, wherein the optical element forming mold is formed by using an amorphous alloy having a supercooled liquid region. Mold for molding.   An optical element molding die for molding an optical element molding die formed by molding a first amorphous alloy having a supercooled liquid region, the supercooled liquid region having a supercooled liquid region. And a molding die for an optical element molding die, which is formed using a second amorphous alloy having a glass transition point higher than that of the first amorphous alloy. .   An optical element molding die for molding an optical element molding die formed by molding a first amorphous alloy having a supercooled liquid region, the supercooled liquid region having a supercooled liquid region. And an optical element molding die formed using a second amorphous alloy having a glass transition point higher by 50 ° C. than the glass transition point of the first amorphous alloy. Mold for molding.   4. The optical element molding die according to claim 1, wherein an optical molding surface or a molding dimension reference surface of the optical element molding die is formed and transferred by hot press molding. Molding mold.   5. The optical element according to claim 1, wherein a corresponding depression or protrusion is formed so that the protrusion or depression is transferred and formed on the optical molding surface of the optical element molding die. Mold for molds.   The protrusion or recess of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die to form a fine structure of an equivalent refractive index region. 5. A molding die for optical element molding die according to 5.   The protrusion or recess of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die to form a fine structure that generates an antireflection effect. Item 7. A molding die for an optical element molding die according to Item 5 or 6.   The protrusion or recess of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die to form a microstructure that generates structural birefringence. Item 8. A molding die for optical element molding dies according to any one of Items 5 to 7.   6. The projection or the depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die to form a fine structure of a resonance region. The molding die for optical element molding dies in any one of 8.   The protrusion or depression of the optical element molding die is transferred to the optical surface of the optical element molded by the optical element molding die, and the aberration changes due to the wavelength change of the light source that irradiates the optical element with light. 6. The molding die for optical element molding die according to claim 5, which has a function of adjusting the above.   The projection or recess of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die, and has a function of adjusting an aberration change due to a temperature change. Item 11. A molding die for an optical element molding die according to Item 5 or 10.   The projection or depression of the optical element molding die is transferred to an optical surface of an optical element molded by the optical element molding die to form a diffraction ring zone. The molding die for optical element molding dies of description.   The molding die for an optical element molding die according to any one of claims 1 to 12, wherein a mother optical surface of the molding die for optical element molding die is created by cutting.   The projection or recess of the optical element molding die is formed by applying a resist on a mother optical surface, exposing by electron beam drawing, and performing development processing. The molding die for optical element molding dies in any one of 5-12.   The projection or depression of the molding die for optical element molding dies is formed by applying a resist on a mother optical surface, exposing by laser beam drawing, and performing development processing. The molding die for optical element molding dies in any one of 5-12.   16. The molding die for an optical element molding die according to claim 14, wherein the protrusion or the depression of the molding die for optical element molding is formed by a dry etching process after the development of the resist.   13. The optical element molding die according to claim 1, wherein a mother optical surface of the molding die for the optical element molding die is created by gas deposition using a focused ion beam. Molding mold.   The second amorphous alloy used in the molding die for optical element molding dies maintains a hardness of Hv300 or more when the optical element molding die is press-molded. The molding die for optical element molding dies in any one of -17.   19. The molding die for optical element molding die according to claim 18, wherein the second amorphous alloy used in the molding die for optical element molding die has a hardness of Hv 700 or less at room temperature. Type.   The optical element molding metal according to any one of claims 1 to 19, wherein the composition of the second amorphous alloy contains nickel, hafnium, or palladium in a proportion of 30 mol% to 50 mol%. Mold for mold.   The composition of the second amorphous alloy contains any one of copper, zirconia, copper, aluminum and phosphorus in a proportion of at least 3 mol% or more. Mold for optical element molding dies.   A method for manufacturing an optical element molding die for molding an optical element formed by molding a first amorphous alloy having a supercooled liquid region, comprising a supercooled liquid region, The first amorphous alloy is formed by a molding die for optical element molding die formed by using a second amorphous alloy having a glass transition point higher than that of the first amorphous alloy. A method for producing an optical element molding die, comprising producing an optical element molding die by hot press molding.

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