JP2007084385A - Manufacturing method of molding die for optical element and molding die for optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding die for an optical element which has high productivity, hardly causes peeling, is excellent in cutting properties, and can improve dimensional accuracy. <P>SOLUTION: The manufacturing method of a molding die for an optical element is characterized in that it comprises forming an amorphous alloy layer on a base body by an aerosol deposition method, and thereafter forming and creating an optical surface transcript plane by diamond cutting or heating press molding the amorphous alloy layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical element molding die and an optical element molding die.

  In recent years, according to a conventional method for producing a mold for molding plastic optical elements, a blank (primary work product) is made of, for example, steel or stainless steel, and then electroless nickel is formed thereon. By chemical plating called plating, an amorphous nickel-phosphorus alloy is deposited to a thickness of about 100 μm, and this plated layer is cut with a diamond tool by an ultra-precision processing machine to form the optical surface of the optical element. In order to obtain a highly accurate optical surface transfer surface.

  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 machining process and the chemical plating process are mixed. It is complicated and takes delivery time, it is necessary to prepare a blank (primary processed product) in consideration of the thickness of the plating layer, the plating process is not necessarily stable, and it depends on the blank composition and the degree of dirt Rework the optical surface transfer surface because the adhesion strength of the plating layer varies, pinhole-like defects called pits occur, and the optical surface transfer surface must be created within the thickness of the plating layer. In some cases, there was a problem that the plating thickness could not be processed because it could not be processed.

  Furthermore, according to the prior art, it is necessary to perform a large amount of diamond cutting on the optical surface transfer surface. In such a case, the cutting is affected by the state of the cutting edge of the tool, processing conditions, changes in the processing environment temperature, etc. There was also a problem that the shape of the processed and finished optical surface transfer surface varied slightly. This variation in the processing of the optical surface transfer surface is due to the poor machinability of the material. Generally, an optical surface shape error of about 100 nm occurs, and even when processed very carefully, it is about 50 nm. Although a shape error remains, this is a processing accuracy limit when a large amount of the optical surface transfer surface having the same shape is created.

  As means for improving electroless nickel plating, a technique is disclosed in which an amorphous alloy having a supercooled liquid region is attached to a substrate and a mold for optical element molding is manufactured by diamond cutting or the like (see Patent Document 1). ). According to this technology, an amorphous alloy film can be formed at a film forming speed of about 20 μm / h at the maximum, so that the mold can be delivered at a much faster delivery time than the processing time of several weeks required for electroless nickel plating. Manufacture is now possible.

  Here, an amorphous alloy having a supercooled liquid region (so-called amorphous alloy) will be described. In recent years, an amorphous alloy material called a metallic glass, which becomes a supercooled liquid when heated, has attracted attention. This is because the normal metal has a polycrystalline structure, but the structure is amorphous, so the composition is microscopically uniform, excellent in mechanical strength and room temperature chemical resistance, has a glass transition point, and is a supercooled liquid. When it is heated to a range from a glass transition point to a crystallization temperature (usually around glass transition point + 200 ° C.), it softens into a glassy state, so that it has a characteristic not found in ordinary metals. Also in cutting, it is known that a highly accurate mirror surface can be easily obtained particularly when ultra-precision cutting is performed with a diamond tool. The reason for this is that this material is amorphous and has no grain boundaries, so that machinability is uniform regardless of location, and in order to maintain the amorphous state, the crystallization energy is increased to increase the composition. Since it is made of a crystal, it is considered that there is little diffusion wear of diamond during the cutting process, and the tool edge life of the tool can be kept long.

  As described above, an optical element molding die using a metallic glass thin film can be manufactured with higher efficiency than the prior art, but there is some room for improvement in the deposition rate of the thin film. A sputtering method is used to manufacture the thin film, but the apparatus is expensive because high vacuum is used, and the film formation time including vacuuming requires about one day. In addition, Patent Document 1 describes PVD processing, ion plating, vapor deposition, and CVD processing other than sputtering, but any of these methods has similar problems. Another problem is peeling of the metallic glass film. An optical element molding die needs to have a film thickness of about 100 μm. When such a thick film is formed, the adhesion between the substrate and the metallic glass film can be improved by means such as reverse sputtering. In some cases, peeling occurred due to internal stress of the metal glass film itself.

  On the other hand, in recent years, an aerosol deposition method (hereinafter also referred to as AD method) has been developed as a new thick film forming technique, and the production of thick films such as ceramics such as piezoelectric materials and phosphors by the present inventor has been studied (patents). References 2 and 3). In this method, ceramic fine particles are agitated and mixed with gas in an aerosol chamber to form an aerosol, transported to the film formation chamber by a gas flow due to a pressure difference with the film formation chamber, accelerated through a slit-shaped nozzle, and applied to the substrate. The ceramic thick film is produced on the substrate by spraying. This film forming method can form a thick ceramic film at a high speed at a relatively low temperature.

Thick film formation other than ceramics has also been attempted, and recently, a technique for forming a metallic glass film by the AD method has been disclosed (see Patent Document 4). However, the Co and Fe-based metallic glasses disclosed therein are only examples of applications as magnetic materials, and are not preferable as mold materials for optical element molding from the viewpoint of oxidation resistance and heat resistance. It is.
JP 2003-154529 A Japanese Patent Laid-Open No. 2-16379 Japanese Patent Laid-Open No. 2005-91200 JP 2005-60805 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical element molding die that has high productivity, is less likely to be peeled off, has excellent machinability, and can improve dimensional accuracy. There is to do.

  The above object of the present invention can be achieved by the following constitution.

  (1) An optical element molding die, wherein an amorphous alloy layer is formed on a substrate by an aerosol deposition method, and then the amorphous alloy layer is formed by diamond cutting or heat press molding to form an optical surface transfer surface. Manufacturing method.

  (2) An optical element molding die manufactured by the method for manufacturing an optical element molding die described in (1) above.

  (3) The optical element molding die as described in (2) above, wherein the amorphous alloy of the amorphous alloy layer contains 20 to 80 mol% of Pd element.

  According to the present invention, it is possible to provide an optical element molding die that has high productivity, is unlikely to be peeled off, has excellent machinability, and can improve dimensional accuracy.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  Embodiments of the present invention will be described.

  First, the manufacturing process of the optical element molding die will be described. A base is formed from a stainless steel material or the like. Since the base material may be a generally used mold material such as steel or stainless steel, the supply is stable and the price is low. The base as a blank has an approximate shape of the mold by forming a recess corresponding to the optical surface (for example, aspherical surface) of the optical element and a peripheral surface around it at one end. An amorphous alloy having a supercooled liquid region (hereinafter, also simply referred to as an amorphous alloy) is attached to the recess and the peripheral surface, and further to the peripheral surface of the end portion of the substrate as follows. The shape accuracy of the indentation, the peripheral surface, and the peripheral surface of the edge of the substrate depends on the film thickness of the amorphous alloy applied to the surface, but if an amorphous alloy of about 100 μm is formed, the accuracy of about 10-20 μm If so, the blanking process itself can be performed in several tens of minutes using an NC lathe.

(Metal glass film formation by AD method)
When manufactured using alloy fine particles having an average particle size of 2 μm or less, it is preferable because an amorphous alloy member made of an amorphous alloy thick film having good surface smoothness can be manufactured. Preferably, the alloy fine particles have an average particle diameter of 0.1 to 2 μm.

  Amorphous alloy fine particles according to the present invention are amorphous alloy powders produced by water atomization method or gas atomization method, amorphous alloy fine particles obtained by pulverizing or classifying these powders, amorphous alloy fine particles obtained by pulverizing and classifying amorphous ribbons produced by liquid quenching method. These are amorphous alloy fine particles obtained by hydrogenating an amorphous alloy and finely divided, and amorphous alloy fine particles produced using DC plasma or high frequency plasma.

In the present invention, it is preferable to use metallic glass containing palladium. Examples of the palladium-based amorphous alloy include Pd ₄₀ Cu ₃₀ Ni ₁₀ P ₂₀ , Pd ₇₆ Cu ₆ Si ₁₈ , Pd ₆₁ Pt ₁₅ Cu ₆ Si ₁₈ , and the content of palladium is at least 20 mol% or more. Otherwise, other constituent atoms are easily oxidized or crystallized, and hot press molding in the air becomes difficult. On the other hand, when the content of palladium is 80 mol% or more, generally, the glass transition point does not exist and an amorphous alloy is not formed. Therefore, it is preferable that the amorphous alloy material has a palladium content of 20 mol% or more and 80 mol% or less. In addition to palladium, which is the most abundant atom, it is preferable to contain at least 3 mol% of copper, nickel, aluminum, silicon, phosphorus, or boron in order to obtain an amorphous amorphous alloy.

  The film forming chamber is evacuated by a vacuum pump or the like, and the degree of vacuum in the chamber is adjusted as necessary. In the present invention, the degree of vacuum is preferably 0.1 to 1000 Pa.

  The aerosolized raw material particles can be deposited on the substrate by preferably colliding with a carrier gas having a flow rate of 100 to 400 m / sec. The particles colliding with the carrier gas are bonded to each other by impact of the collision to form a film.

  In the production method of the present invention, nitrogen gas is preferable as the carrier gas for accelerating and ejecting the alloy particles. A rare gas such as He is not preferable because discharge is likely to occur at the time of particle collision and defects may be introduced into the film. When a defect is introduced, the transparency of the film deteriorates, and light converted from radiation cannot be extracted, resulting in a deterioration in detection efficiency.

  In the production method of the present invention, the temperature of the substrate on which the alloy particles collide is preferably maintained at −100 ° C. or higher and 200 ° C. or lower. When the substrate temperature is heated to 300 ° C. or higher, the film crystallizes and loses its properties as a metallic glass, so that characteristics such as machinability and press formability are lost.

  The film formation rate obtained by this method is preferably in the range of 1 to 50 μm / min, and can be adjusted by optimizing control factors such as the degree of vacuum, aerosol density, and flow rate.

(Mold processing)
Subsequently, the surface of the amorphous alloy is transferred to a desired optical surface transfer surface (corresponding to the indentation of the substrate) by performing diamond cutting, hot press molding, or a combination thereof on the amorphous alloy film. Finish. Diamond cutting uses a single crystal diamond tool and cuts one by one with an ultra-precise lathe, etc., so it undergoes basically the same processing steps as the conventional mold manufacturing method using electroless nickel plating. In comparison, the optical surface transfer surface is rapidly and densely formed by the AD method, and since there is no chemical plating treatment, there are no defects such as pinholes and the process delivery time is fast, and the machinability is very good, so tool wear is reduced. It can be said that it is a more excellent feature that the shape creation by cutting is easy.

  In addition, the AD method of the present invention is characterized by extremely high adhesion to the substrate as compared with PVD and CVD film forming methods including sputtering.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
<< Production of optical element molding die of the present invention (aerosol deposition method) >>
PdCuSi alloy was arc melted in a mixed gas of hydrogen gas and Ar gas, and the generated fine particles were collected. The average particle size of the alloy fine particles was 50 nm. As a result of the composition analysis, the composition (mol% ratio) of the alloy fine particles was Pd ₇₆ Cu ₆ Si ₁₈ . As a result of X-ray diffraction, the alloy fine particles showed a halo pattern peculiar to amorphous, and were confirmed to be amorphous alloy fine particles. As a result of observation with a transmission electron microscope, almost no crystal lattice was observed, and it was confirmed that the amorphous phase occupied most of the fine particles.

Next, the amorphous alloy fine particles were agitated and mixed with N ₂ gas in an aerosol-generating chamber to be aerosolized, and were transported to the film-forming chamber by a gas flow caused by a pressure difference with the film-forming chamber to produce an alloy member. The film formation rate was 10 μm / min.

  The time required to obtain a 100 μm film was 1 hour including setup and vacuuming.

  An optical surface transfer surface was formed on the produced member by diamond cutting, and an optical element molding die was manufactured.

  When 100 optical elements thus manufactured were used to perform optical element molding, all molds could be molded 50,000 times.

<Production of comparative optical element molding die (sputter deposition method)>
An amorphous alloy target was prepared, and a film was formed by sputtering using the amorphous alloy fine particles. Further, an optical surface transfer surface was formed by diamond cutting to produce an optical element molding die. The sputter deposition rate was 20 μm / h. The time required to obtain a 100 μm film was 12 hours including setup and vacuuming.

  When the optical element was molded using 100 molds manufactured in this manner, 97 molds could be molded a specified number of times (50,000 times). The remaining three molds could not be molded because the metal glass layer peeled off at the prescribed number of times of 50%, 67% and 96%.

  Comparing the results of the above <Preparation of optical element molding die of the present invention (aerosol deposition method)> and << Preparation of comparative optical element molding die (sputter deposition method) >> In the case of the above, a method for producing an optical element molding die and an optical element molding die capable of producing high productivity, being difficult to cause peeling, excellent in machinability, and improving dimensional accuracy are provided. Obviously it can be done.

Claims (3)

A method of manufacturing an optical element molding die, comprising forming an amorphous alloy layer on a substrate by an aerosol deposition method and then forming the optical surface transfer surface by diamond cutting or hot press molding of the amorphous alloy layer . An optical element molding die produced by the method for producing an optical element molding die according to claim 1. The optical element molding die according to claim 2, wherein the amorphous alloy of the amorphous alloy layer contains 20 to 80 mol% of Pd element.