JP5621436B2 - Mold, manufacturing method thereof, element and optical element - Google Patents

Description

  The present invention relates to an element having a fine concavo-convex structure, a mold suitable for molding an optical element, a manufacturing method thereof, and an element and an optical element obtained by the mold.

  In a light-transmitting optical element, it is common to perform an antireflection treatment on the surface of the optical element in order to reduce the light transmittance and prevent the occurrence of ghosts and flares. Examples of the antireflection treatment include an antireflection structure that provides an antireflection effect by forming fine irregularities on the surface of the optical element with a period smaller than the wavelength of incident light. Antireflection structures have attracted attention in recent years because they have antireflection properties superior to antireflection films.

  Examples of the method for forming the antireflection structure include a method in which anodized porous alumina having a reverse pattern of the antireflection structure is used as a transfer die (molding die). Anodized porous alumina is generally pores with a period of several tens to several hundreds of nanometers on a surface of a mold base made of high-purity aluminum (pure aluminum) in an acidic electrolyte. A layer of a porous structure of aluminum oxide (alumina) having a two-dimensionally arranged structure is formed. By transferring this porous structure to an optical element made of resin, glass or the like, an antireflection structure can be obtained.

  High-purity aluminum is suitable for the formation of anodized porous alumina because it has few impurities and hardly causes defects during anodization. For example, Japanese Laid-Open Patent Publication No. 2005-156695 (Patent Document 1) and Japanese Laid-Open Patent Publication No. 2007-086283 (Patent Document 2) disclose a method for forming fine irregularities by anodizing a high-purity aluminum substrate. Yes. However, since high-purity aluminum has low hardness and is easily deformed, its strength is not sufficient for use in injection molding of optical elements and molds such as glass molds.

In JP 2006-053220 A (Patent Document 3), a high-purity aluminum film is formed on a glass substrate, and in JP 2003-043203 A (Patent Document 4), an anodizing treatment is performed. Yes. However, since glass substrates and Si substrates are highly brittle and do not have the strength to withstand pressure, impact, rapid temperature changes, etc., they are not suitable for use in optical element molding dies by injection molding.

JP 2005-156695 A JP 2007-086283 A JP 2006-053220 A JP 2003-043203 A

  Accordingly, an object of the present invention is to provide a molding die having porous alumina having a plurality of pores on the molding surface and sufficient hardness and mechanical strength, and a method for producing the same.

  Another object of the present invention is to provide an element and an optical element obtained by the molding die.

  As a result of earnest research in view of the above problems, the present inventors formed an aluminum film containing aluminum at a higher ratio than the above ratio on the molding surface of the mold base containing the valve metal or its alloy at a predetermined ratio, By performing the anodizing treatment, the mold material does not dissolve during the anodizing treatment, and the molding surface is formed with porous alumina having a plurality of pores and sufficient hardness and mechanical strength. It was discovered that a mold for use was obtained, and the present invention was conceived.

That is, the optical element and the manufacturing method thereof according to the present invention have the following characteristics.
(1) Forming an aluminum film made of high-purity aluminum having a content ratio of 99% or more on the molding surface of a mold base material containing a valve metal or an alloy of the valve metal at a ratio of 50% or more and less than 99% , A method for producing a mold, characterized in that porous alumina having a plurality of pores is formed on an aluminum film by anodic oxidation.
( 2 ) The method for producing a mold according to ( 1 ), wherein the purity of the high-purity aluminum is 99.9% or more.
( 3 ) The method for producing a mold according to (1) or (2 ) above, wherein the valve metal is aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth or antimony. Mold manufacturing method.
( 4 ) The mold manufacturing method as described in ( 3 ) above, wherein the valve metal is aluminum.
( 5 ) The method for producing a mold according to the above (1) or (2) , wherein the mold base is ultraduralumin.
( 6 ) A mold manufactured by the method according to any one of (1) to ( 5 ) above.
( 7 ) The mold according to ( 6 ), wherein the mold is for injection molding.
( 8 ) In the mold according to ( 7 ), the plurality of pores are formed with a two-dimensional period equal to or less than a wavelength of light used for an element molded by the mold, and are reflected by the element. A mold characterized in that a prevention structure can be provided.
( 9 ) An element formed by the mold according to any one of ( 6 ) to ( 8 ).
( 10 ) An optical element molded by the mold according to any one of ( 6 ) to ( 8 ).

  It is known that the valve metal is formed with an oxide layer by anodizing treatment, whereas the metal other than the valve metal is not formed with an oxide film and the metal is dissolved. According to the present invention, an aluminum film containing aluminum at a higher ratio than the above ratio is formed on the molding surface of a mold base material containing a valve metal or an alloy thereof at a predetermined ratio, and anodization is performed. In addition, since an oxide layer is formed on the mold surface simultaneously with the aluminum film on the molding surface during the anodizing treatment, the mold material does not dissolve, and the formed oxide layer is the same as the aluminum film on the molding surface. Since it has a certain electrical resistance, it can prevent excessive current from flowing through the mold, and the aluminum film on the molding surface can be stably anodized, so that the molding surface has a plurality of pores. A molding die having a desired porous alumina and sufficient hardness and mechanical strength can be obtained.

It is sectional drawing which shows the optical element by one Example of this invention. It is a figure which shows the manufacturing method of a metal mold | die. It is a figure which shows an anodizing apparatus. It is a figure which shows the manufacturing method of the optical element by one Example of this invention. It is a figure which shows the manufacturing method of the optical element by another Example of this invention.

[1] Mold As shown in FIG. 1, the mold 1 of the present invention has an aluminum film 20 formed on the molding surface of a mold base 10, and a plurality of aluminum films 20 formed by anodization. The porous alumina 21 having the pores is formed. The plurality of pores of the porous alumina 21 have a cylindrical structure having a substantially uniform diameter in the depth direction.

The aluminum film 20 is preferably made of high purity aluminum. By using high-purity aluminum as the material of the aluminum film 20, it is possible to form a highly accurate fine concavo-convex shape without defects. The purity of the high purity aluminum Ri der least 99%, preferably at least 99.9% and more accurate mold for lens surface fine irregularities is required.

  The mold base 10 is made of a valve metal or an alloy containing an alloy thereof (hereinafter referred to as a valve metal alloy) at a ratio lower than the aluminum content of the aluminum film 20. The mold base 10 has mechanical strength and workability that can be used as a mold, and, like the aluminum film 20, an oxide layer is formed on the surface by anodization, so that no dissolution reaction occurs. In order to prevent an excessive current from being supplied to the aluminum film, a stable anodic oxidation treatment of the aluminum film becomes possible. Specific examples of valve metals are aluminum (Al), tantalum (Ta), niobium (Nb), titanium (Ti), hafnium (Hf), zirconium (Zr), zinc (Zn), tungsten (W), bismuth (Bi). And antimony (Sb).

  When the mold base 10 is made of an aluminum (Al) alloy, examples of the metal to be added include Si, Fe, Cu, Mn, Mg, Cr, Zn, Zr, Ti, V, Ni, and Ga. When the mold base 10 is made of a tantalum (Ta) alloy, examples of the metal to be added include Nb, Fe, Ti, W, Si, Ni, etc., and the mold base 10 is made of a niobium (Nb) alloy. In this case, Zr, Al, Sn, Ge, Ga and the like are listed as the added metal. When the mold base 10 is made of a titanium (Ti) alloy, the added metal is Al, V, Si, Fe, Mo, Sn, Zr, Nb, Cr, Mn, and the like are listed. When the mold base 10 is made of a hafnium (Hf) alloy, examples of the added metal include Sn, Fe, Zr, Cr, and Nb. When the mold base 10 is made of a zirconium (Zr) based alloy, examples of the metal to be added include Fe, Cu, Al, Mg, Sn, Cr, Ni, etc., and the mold base 10 is zinc (Zn). Added when made of alloy Examples of the genus include Al, Cu, Mg, Fe, Sn, and Pb. When the mold base 10 is made of a tungsten (W) alloy, Ni, Cu, Fe, Mo, or the like can be given as an added metal. When the mold base 10 is made of a bismuth (Bi) alloy, examples of the added metal include Cd, Sn, Pb, In, and Sb, and the mold base 10 is made of an antimony (Sb) alloy. In this case, Pb, Sn, etc. can be mentioned as added metals. The substances to be added to the mold base 10 are not limited to those described above, and various substances can be added as long as the characteristics of the mold base 10 used in the present invention are not impaired.

The content of the valve metal in the mold base 10, workability is high, as a strength as a mold, 50% or more and less than 99% der is, less than 75% or more 99% Is preferable, and it is more preferable that it is 85% or more and less than 99%. If the valve metal content is less than 50%, the formation of an oxide layer on the surface by anodization is not sufficient, and if the valve metal content is 99% or more, sufficient mechanical strength can be used as a mold. And processability is not obtained.

  It is preferable to use an alloy containing aluminum or an aluminum alloy (hereinafter referred to as an aluminum-based metal) at a lower ratio than the aluminum film 20 as the mold base 10. While high-purity aluminum is a very soft material, aluminum-based metals can be made stronger and harder, and can be used as a mold material for molding optical elements such as lenses, and anodized. Since an oxide layer is formed on the surface by the treatment, no dissolution reaction occurs.

  Aluminum metal used for mold base 10 is Al-Zn-Mg-Cu-based A7075 alloy (extra super duralumin), Al-Zn-Mg-based A7N01 alloy and A7003 alloy, etc. 7000 series aluminum alloys (JIS standard) Further, 2000 series aluminum alloys such as Al-Cu series A2024 (super duralumin) and 5000 series aluminum alloys such as Al-Mg series A5052 are preferable because of their high strength. Other examples of the mold base 10 include Ti-Al-V-based 6-4 alloy (JIS 60 class), Ti-V-Cr-Al-Sn-based 15-3-3- Titanium alloys such as 3 alloys, Zn-Al-Cu-Mg-Fe zinc alloy (Zamark alloy) as zinc metal, W-Ni-Cu W-Ni-Fe tungsten alloy as tungsten metal, etc. Is mentioned.

  The mold 1 can be used for various molding methods such as glass molding and injection molding, but is preferably for injection molding.

  The plurality of pores of the porous alumina 21 are preferably arranged with a period equal to or less than the wavelength of light used for the element formed by the mold 1. Thereby, it is possible to impart an antireflection function to the fine concavo-convex structure transferred to the element by the mold 1 and to avoid the occurrence of light scattering.

[2] Mold manufacturing method As shown in FIG. 2 (a), a high-purity aluminum film is formed on the surface of a mold base 10 having a substantially inverted shape of the surface of a desired element by vacuum deposition or sputtering. Form 20.

  As shown in FIG. 3, the mold base 10 on which the aluminum film 20 is formed is set on the anode, immersed in an acidic electrolyte, and an anodizing treatment is performed by applying a voltage, thereby FIG. A porous alumina 21 having a two-dimensional periodic pore structure shown in FIG. Examples of the electrolyte used for the anodizing treatment include oxalic acid, sulfuric acid, and phosphoric acid.

  The pore depth, width, and period of porous alumina 21 correlate with manufacturing conditions such as applied voltage, current, treatment time, acid type, concentration, temperature, surface area of aluminum to be treated, etc. To do. Therefore, by adjusting these manufacturing conditions, the depth, width and period of the pores of the porous alumina 21 can be controlled. For example, when the voltage applied at the time of anodization is increased, the period is increased, and when the treatment time for anodization is increased, the depth of the pores is increased.

  Since the pore diameter of the porous alumina at the stage where the anodizing treatment is completed is small for transferring the antireflection structure, a treatment for expanding the pore diameter of the porous alumina 21 may be performed. For example, the pore diameter can be increased by immersing in an acid such as phosphoric acid. The pore diameter may be adjusted by adjusting the processing conditions such as the acid type, concentration, temperature, immersion time, etc., and the structure obtained by the transfer has desired optical characteristics. For example, if the immersion time in the acid is increased, the pore diameter can be increased.

  Porous alumina may be formed by once forming porous alumina by anodizing treatment, immersing it in a stripping solution such as a mixed acid of chromic acid and phosphoric acid to peel the porous alumina, and then performing anodizing treatment again. By performing such pretreatment, the surface state of the porous alumina 21 and the periodicity of the pores can be adjusted.

[3] Element A fine uneven structure is formed on the surface of the element 2 using the mold 1 of the present invention. Specifically, as shown in FIG. 4, the element 2 is brought into contact with the mold 1 and pressed while being heated to a temperature at which the element 2 is softened, thereby transferring the pore structure of the porous alumina 21 to the element 2. And methods (thermal transfer method, hot embossing method, thermal imprinting method, etc.). As another transfer method, a molten resin is injected into the mold 1 and cured to form the element 2 and simultaneously transfer the pore structure to the surface (injection molding method). A method of injecting a highly fluid resin such as a thermosetting resin or a photo-curing resin and curing it by heating or light irradiation to form a device 2 and simultaneously transfer the pore structure to the surface (casting method) The mold 1 and the element 2 are brought into contact with each other, a thermosetting resin having high fluidity is inserted into the gap and cured by heating, or a photocurable resin is inserted and cured by light irradiation. And a method of transferring the pore structure to the surface (in particular, a method using an ultraviolet curable resin is referred to as a UV imprint method). In order to improve the releasability between the mold 1 and the element 2, a mold release agent made of a fluorine-based material or the like may be applied to the surface of the mold 1.

  The obtained element 2 has a fine uneven structure on the surface. The fine concavo-convex structure may be provided on both surfaces of the element 2. The fine concavo-convex structure of the element 2 has a plurality of columnar convex portions, and these are preferably arranged at a two-dimensional period equal to or less than the wavelength of light to be used. Thereby, it functions as an antireflection film having an intermediate refractive index between the refractive index of the incident medium and the refractive index of the element 2. By controlling the period, height and thickness of the cylindrical convex part, the effective refractive index and optical thickness of the structure can be controlled, so there is a degree of freedom compared to conventional antireflection films, Good antireflection characteristics can be obtained regardless of the type of incident medium and substrate.

  The fine concavo-convex structure is not limited to a cylindrical shape, and may have a structure such as a cone, a truncated cone, a prism, or a pyramid as long as it has an antireflection effect. A structure in which the effective refractive index of the structure gradually changes from the incident medium to the element may be formed by devising the pore shape of the porous alumina and sharpening the shape obtained by the transfer. .

  The element 2 is not particularly limited, but is preferably an optical element. As shown in FIG. 5, a fine concavo-convex structure may be provided on both surfaces of the optical element 2 using molds 1 a and 1 b each having a substantially inverted shape of each surface of the optical element 2. Thereby, a favorable antireflection characteristic can be imparted to the optical element 2.

  Although the period of the cylindrical convex part of the metal mold | die 1 can be suitably adjusted with the material of the element 2, and the wavelength of incident light, it is preferable that it is smaller than the wavelength to be used. It is preferable that the period of the cylindrical convex portion is 50 to 1000 nm. The height and thickness of the cylindrical convex portion can be appropriately adjusted depending on the material of the element 2 and the wavelength of incident light. Since the effective refractive index and optical thickness of the structure can be controlled by controlling the period, height, and thickness of the cylindrical convex portion, there is a degree of freedom compared to the antireflection film, and the incident medium In addition, good antireflection properties can be obtained regardless of the type of substrate. The structure of the columnar convex portion is not limited to that shown in FIGS. 4 and 5 and may have a structure such as a cone, a truncated cone, a prism, or a pyramid as long as it has an antireflection effect.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Using a mold base 10 of 25 mm x 25 mm x 15 mm made of extra super duralumin [YH75 (manufactured by White Bronze Co., Ltd.)], grinding one surface of the mold base 10 of 25 mm x 25 mm -An optical mirror surface was formed by polishing. A high-purity aluminum film 20 having a purity of 99.99% was formed on the optical mirror surface of the mold base 10 by vacuum deposition to a thickness of about 1 μm. The mold base 10 was immersed in a 0.3 M oxalic acid electrolyte at 17 ° C., and a voltage of 60 V was applied to the anode for 2 minutes to form porous alumina on the surface of the mold base 10. This mold substrate 10 was immersed in a stripping solution of a mixed acid of chromic acid and phosphoric acid to strip the porous alumina. The treatment was again performed under the same conditions for 30 seconds to form porous alumina 21 on the surface of the mold base 10 and immersed in 5 wt% phosphoric acid at 30 ° C. for 30 minutes to perform pore diameter expansion treatment. The mold base 10 thus obtained was washed with pure water and then dried to produce the mold 1.

  The appearance of the molding surface of the mold 1 after the anodizing treatment was not particularly defective. As a result of SEM observation, a good fine concavo-convex structure having a two-dimensional period of about 150 nm was formed. The element molded using the mold 1 of Example 1 had a desired shape and accuracy, and problems such as unevenness and scattering were not observed.

Example 2
A mold base 10 of 25 mm × 25 mm × 15 mm made of 6-4 titanium alloy [titanium GRADE5 (made by White Copper Co., Ltd.) was used. Mold 1 was produced.

  As in Example 1, the appearance of the molding surface of the mold 1 after the anodizing treatment was not particularly defective, and as a result of SEM observation, it was confirmed that a fine fine concavo-convex structure having a two-dimensional period of about 150 nm was formed. . In addition, the element molded using the mold 1 of Example 2 had a desired shape and accuracy, and problems such as unevenness and scattering were not observed.

Comparative Example 1
Mold 1 as in Example 1 except that a mold base 10 of 25 mm × 25 mm × 15 mm made of high-purity aluminum with a purity of 99.99% is used and no high-purity aluminum film 20 is vacuum deposited. Was made. The appearance of the mold 1 was as good as in Example 1. However, since high-purity aluminum has low strength, it is firmly fixed to assemble the mold into a molding apparatus, or a large force or pressure is applied during molding. As a result, the mold shape is deformed, and as a result of molding using the mold 1 of Comparative Example 1, an element having a desired precision shape could not be produced.

Comparative Example 2
A mold 1 was produced in the same manner as in Example 1 except that the high-purity aluminum film 20 was not vacuum-deposited. As a result of observation by SEM, fine irregularities having a period of about 150 nm were formed, but defects of several hundred nm to several μm were locally generated. In addition, in the element molded using the mold 1 of Comparative Example 2, generation of scattering derived from defect transfer of the mold was observed.

Comparative Example 3
A mold 1 was produced in the same manner as in Example 1 except that quartz glass was used as the material of the mold base 10. The appearance of the mold 1 was as good as in Example 1. However, the quartz glass is brittle and has low strength, so that the mold cannot be firmly assembled in the molding apparatus. Since pressure could not be applied, the element molded using the mold 1 of Comparative Example 3 could not obtain the desired shape and accuracy.

Comparative Example 4
A mold 1 was produced in the same manner as in Example 1 except that stainless steel [HPM38 (manufactured by Hitachi Metals Tool Steel Co., Ltd.)] was used as the material of the mold base 10. Dispersion of stainless steel occurs at the time of anodizing treatment, and unevenness of processing seems to be caused by the stable anodizing treatment of the aluminum film on the molding surface of the mold 1 after the anodizing treatment due to the influence of the dissolution reaction Was confirmed. As a result of SEM observation, the desired fine uneven structure was not obtained, and the shape was non-uniform.

1 ... Mold
10 ... Mold base
20 ... Aluminum film
21 ... Porous alumina 2 ... Element

Claims (10)

An aluminum film made of high-purity aluminum having a content rate of 99% or more is formed on the molding surface of the mold base material containing the valve metal or the valve metal alloy at a ratio of 50% or more and less than 99%. A method for producing a mold, comprising forming porous alumina having a plurality of pores by anodization. 2. The mold manufacturing method according to claim 1 , wherein the purity of the high-purity aluminum is 99.9% or more. 3. The method of manufacturing a mold according to claim 1, wherein the valve metal is aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth or antimony. . 4. The mold manufacturing method according to claim 3, wherein the valve metal is aluminum. 3. The method for manufacturing a mold according to claim 1, wherein the mold base is ultraduralumin. The metal mold | die manufactured by the method in any one of Claims 1-5 . 7. The mold according to claim 6 , wherein the mold is for injection molding. 8. The mold according to claim 7 , wherein the plurality of pores are formed with a two-dimensional period equal to or less than a wavelength of light used for an element molded by the mold, thereby providing the element with an antireflection structure. A mold that can be made. The element shape | molded by the metal mold | die in any one of Claims 6-8 . The optical element shape | molded by the metal mold | die in any one of Claims 6-8 .

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