US20110278770A1 - Mold, mold manufacturing method and method for manufacturing anti-reflection film using the mold - Google Patents

Mold, mold manufacturing method and method for manufacturing anti-reflection film using the mold Download PDF

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Publication number
US20110278770A1
US20110278770A1 US13/138,256 US201013138256A US2011278770A1 US 20110278770 A1 US20110278770 A1 US 20110278770A1 US 201013138256 A US201013138256 A US 201013138256A US 2011278770 A1 US2011278770 A1 US 2011278770A1
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Prior art keywords
mold
film
conductive layer
alumina layer
recessed portions
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English (en)
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Akinobu Isurugi
Kiyoshi Minoura
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Sharp Corp
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Assigned to SHARP KABUSHIKI KAISHA reassignment SHARP KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ISURUGI, AKINOBU, MINOURA, KIYOSHI
Publication of US20110278770A1 publication Critical patent/US20110278770A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3828—Moulds made of at least two different materials having different thermal conductivities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/42—Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
    • B29C33/424—Moulding surfaces provided with means for marking or patterning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/56—Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
    • B29C33/60—Releasing, lubricating or separating agents
    • B29C33/62—Releasing, lubricating or separating agents based on polymers or oligomers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/045—Anodisation of aluminium or alloys based thereon for forming AAO templates
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/12—Anodising more than once, e.g. in different baths
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/24—Chemical after-treatment
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G02B1/118—Anti-reflection coatings having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures

Definitions

  • the present invention relates to a mold, a method of fabricating a mold, and a method of fabricating an antireflection film using the mold.
  • the “mold” includes molds that are for use in various processing methods (stamping and casting), and is sometimes referred to as a stamper.
  • the mold can also be used for printing (including nanoimprinting).
  • Display devices for use in TVs, cell phones, etc., and optical elements, such as camera lenses, etc. usually adopt an antireflection technique in order to reduce the surface reflection and increase the amount of light transmitted therethrough. This is because, when light is transmitted through the interface between media of different refractive indices, e.g., when light is incident on the interface between air and glass, the amount of transmitted light decreases due to, for example, Fresnel reflection, thus deteriorating the visibility.
  • the two-dimensional size of a raised portion of an uneven pattern which performs an antireflection function is not less than 10 nm and less than 500 nm.
  • This method utilizes the principles of a so-called motheye structure.
  • the refractive index for light that is incident on the substrate is continuously changed along the depth direction of the recessed portions or raised portions, from the refractive index of a medium on which the light is incident to the refractive index of the substrate, whereby reflection of a wavelength band that is subject to antireflection is prevented.
  • the motheye structure is advantageous in that it is capable of performing an antireflection function with small incident angle dependence over a wide wavelength band, as well as that it is applicable to a number of materials, and that an uneven pattern can be directly formed in a substrate. As such, a high-performance antireflection film (or antireflection surface) can be provided at a low cost.
  • Patent Documents 2 to 4 As the method of forming a motheye structure, using an anodized porous alumina layer which is obtained by means of anodization of aluminum has been receiving attention (Patent Documents 2 to 4).
  • anodized porous alumina layer which is obtained by means of anodization of aluminum is briefly described.
  • a method of forming a porous structure by means of anodization has been receiving attention as a simple method for making nanometer-scale micropores (very small recessed portions) in the shape of a circular column in a regular arrangement.
  • An aluminum base is immersed in an acidic electrolytic solution of sulfuric acid, oxalic acid, phosphoric acid, or the like, or an alkaline electrolytic solution, and this is used as an anode in application of a voltage, which causes oxidation and dissolution.
  • the oxidation and the dissolution concurrently advance over a surface of the aluminum base to form an oxide film which has micropores over its surface.
  • micropores which are in the shape of a circular column, are oriented vertical to the oxide film and exhibit a self-organized regularity under certain conditions (voltage, electrolyte type, temperature, etc.).
  • this anodized porous alumina layer is expected to be applied to a wide variety of functional materials.
  • a porous alumina layer prepared under specific conditions includes cells in the shape of a generally regular hexagon which are in a closest packed two-dimensional arrangement when seen in a direction perpendicular to the film surface. Each of the cells has a micropore at its center. The arrangement of the micropores is periodic. The cells are formed as a result of local dissolution and growth of a coating. The dissolution and growth of the coating concurrently advance at the bottom of the micropores which is referred to as a barrier layer. As known, the size of the cells, i.e., the interval between adjacent micropores (the distance between the centers), is approximately twice the thickness of the barrier layer, and is approximately proportional to the voltage that is applied during the anodization.
  • micropores depends on the type, concentration, temperature, etc., of the electrolytic solution but is, usually, about 1 ⁇ 3 of the size of the cells (the length of the longest diagonal of the cell when seen in a direction vertical to the film surface).
  • Such micropores of the porous alumina may constitute an arrangement which has a high regularity (periodicity) under specific conditions, an arrangement with a regularity degraded to some extent depending on the conditions, or an irregular (non-periodic) arrangement.
  • Patent Document 2 discloses a method of producing an antireflection film (antireflection surface) with the use of a stamper which has an anodized porous alumina film over its surface.
  • Patent Document 3 discloses the technique of forming tapered recesses with continuously changing pore diameters by repeating anodization of aluminum and a pore diameter increasing process.
  • Patent Document 4 discloses in Patent Document 4 the technique of forming an antireflection film with the use of an alumina layer in which very small recessed portions have stepped lateral surfaces.
  • Patent Documents 1, 2, and 4 by providing an uneven structure (macro structure) which is greater than a motheye structure (micro structure) in addition to the motheye structure, the antireflection film (antireflection surface) can be provided with an antiglare function.
  • the two-dimensional size of a raised portion of the uneven structure which is capable of performing the antiglare function is not less than 1 ⁇ m and less than 100 ⁇ m.
  • Utilizing such an anodized porous aluminum film can facilitate the fabrication of a mold which is used for formation of a motheye structure over a surface (hereinafter, “motheye mold”).
  • motheye mold a mold which is used for formation of a motheye structure over a surface
  • the structure of the surface of a motheye mold which is capable of forming a motheye structure is herein referred to as “inverted motheye structure”.
  • Non-patent Document 1 discloses a method of fabricating a mold for nanoimprinting which has light transmissivity.
  • the light-transmitting mold is obtained by forming an anodized porous alumina film which has a predetermined structure on one of the surfaces of an aluminum plate and then thoroughly anodizing the remaining aluminum from the rear surface of the aluminum plate.
  • a regular pattern of a UV-curable resin which is formed on a silicon substrate using the light-transmitting mold is disclosed.
  • the UV-curable resin can advantageously be irradiated with light through the mold.
  • Non-patent Document 1 the entire mold structure of the light-transmitting mold disclosed in Non-patent Document 1 is formed by an anodized porous alumina film, and both surfaces of the film have micropores. This leads to a problem that the mold is easily broken. Increasing the thickness of the mold in order to obtain sufficient mechanical strength leads to a problem that anodizing the entirety of the aluminum plate is difficult.
  • Non-patent Document 1 an electrode is attached to an edge of an aluminum plate that is to be processed into a mold. Therefore, in fabrication of a large-surface mold, it is difficult to anodize the entirety of the aluminum plate. Since aluminum does not have light transmissivity, an intended light-transmitting mold cannot be obtained.
  • Non-patent Document 1 includes the step of anodizing an aluminum plate from both sides and is therefore not applicable to an aluminum film formed on a base.
  • the present invention was conceived for the purpose of solving the above problems.
  • Major objects of the present invention includes providing a method of fabricating a large-surface motheye mold which is capable of transmitting ultraviolet light and providing a motheye mold which is fabricated according to the fabrication method.
  • a mold of the present invention includes: a base; a conductive layer provided on the base; and an anodized film provided on the conductive layer, the anodized film having an inverted motheye structure in its surface, the inverted motheye structure having a plurality of recessed portions whose two-dimensional size viewed in a direction normal to the surface is not less than 10 nm and less than 500 nm, wherein the base, the conductive layer, and the anodized film are capable of transmitting ultraviolet light.
  • the conductive layer is formed by a titanium film whose thickness is not more than 100 nm.
  • the thickness of the titanium film is preferably not less than 1 nm.
  • the mold further includes a mold release layer provided on the anodized film.
  • the mold release layer may be, for example, a water-repellent resin layer.
  • the anodized film has minute pores on a side of the plurality of recessed portions which is closer to the conductive layer, the minute pores being smaller than the plurality of recessed portions.
  • the anodized film includes a porous alumina layer which has the inverted motheye structure in its surface and an alumina layer which does not have a minute pore (sometimes referred to as “barrier layer”), the alumina layer being provided on a side of the porous alumina layer which is closer to the conductive layer.
  • a porous alumina layer which has the inverted motheye structure in its surface and an alumina layer which does not have a minute pore (sometimes referred to as “barrier layer”), the alumina layer being provided on a side of the porous alumina layer which is closer to the conductive layer.
  • a thickness of the alumina layer which does not have a minute pore is not less than 100 nm.
  • the thickness of the alumina layer which does not have a minute pore is preferably not more than 400 nm.
  • a mold fabrication method of the present invention is a method of fabricating a mold that has an inverted motheye structure in its surface, the inverted motheye structure having a plurality of recessed portions whose two-dimensional size viewed in a direction normal to the surface is not less than 10 nm and less than 500 nm, the method including the steps of: (a) providing a base which is capable of transmitting ultraviolet light; (b) forming on the base a conductive layer which is capable of transmitting ultraviolet light; (c) depositing an aluminum film on the conductive layer; and (d) anodizing an entirety of the aluminum film, the step (d) including (d1) anodizing the aluminum film to form a porous alumina layer which has a plurality of very small recessed portions, (d2) after step (d1), bringing the porous alumina layer into contact with an etchant, thereby enlarging the plurality of very small recessed portions of the porous alumina layer, and (d3) after step (d2),
  • step (d) includes, after step (d3), further performing step (d2) and step (d3).
  • step (d) further includes (da) forming the inverted motheye structure in a surface of the porous alumina layer through steps (d1) to (d3), and (db1) after step (da), further anodizing the aluminum film to form minute pores on a side of the porous alumina layer which is closer to the conductive layer, the minute pores being smaller than the plurality of recessed portions.
  • the fabrication method further includes (db2) after step (db1), anodizing the aluminum film to form an alumina layer which does not have the minute pores on a side of the porous alumina layer which is closer to the conductive layer.
  • step (db2) is performed in an electrolytic solution whose pH is more than 4.0 and not more than 7.0.
  • the electrolytic solution used in step (db2) is an aqueous solution which contains at least one of acids or salts selected from a group consisting of tartaric acid, ammonium tartrate, potassium sodium tartrate, boric acid, ammonium borate, ammonium oxalate, ammonium citrate, maleic acid, malonic acid, phthalic acid, and citric acid.
  • step (db2) is performed in an acidic aqueous solution with a concentration of not more than 0.1 mol/L.
  • a low-concentration acidic aqueous solution which has a sufficiently small aluminum oxide solubility may be used.
  • a phosphoric acid aqueous solution with a concentration of not more than 0.1 mol/L may be used.
  • An antireflection film fabrication method of the present invention includes the steps of: providing any of the above-described molds and a work; and irradiating a UV-curable resin provided between the mold and a surface of the work with ultraviolet light supplied through the mold, thereby curing the UV-curable resin.
  • a method of fabricating a large-surface motheye mold which is capable of transmitting ultraviolet light is provided.
  • a novel motheye mold which is capable of transmitting ultraviolet light can be provided.
  • a method of fabricating an antireflection film with the use of the above mold is provided.
  • the present invention is advantageous in that a large-surface motheye mold can be fabricated and is, however, as a matter of course, applicable to fabrication of a small-surface motheye mold.
  • FIGS. 1 ( a ) and ( b ) are schematic diagrams for illustrating disadvantages of a conventional anodization step.
  • FIGS. 2 ( a ) and ( b ) are schematic diagrams of cross sections of a motheye mold obtained according to a conventional anodization method and SEM images of the cross sections.
  • ( a ) shows a cross-sectional structure of a portion 90 A in which an aluminum film was completely anodized.
  • ( b ) shows a cross-sectional structure of a portion 90 B in which part of the aluminum film was remaining.
  • FIG. 3 A graph showing the transmission spectrum of the portion 90 A of the motheye mold shown in FIG. 2( a ).
  • FIG. 4 ( a ) to ( c ) are schematic diagrams for illustrating a method of fabricating a motheye mold according to an embodiment of the present invention.
  • FIG. 5 ( a ) to ( c ) are SEM images of a cross section of the motheye mold, which demonstrate that a barrier layer is formed by anodization in a neutral solution.
  • FIG. 6 A graph showing the relationship between the thickness of the barrier layer formed by anodization in an ammonium tartrate solution and the applied voltage.
  • FIG. 7 A graph showing the transmission spectrum of a motheye mold fabricated according to a fabrication method of an embodiment of the present invention.
  • FIG. 8 A schematic cross-sectional view for illustrating the step of forming an antireflection film with the use of a motheye mold 100 A.
  • FIG. 9 A schematic cross-sectional view for illustrating the step of forming an antireflection film with the use of a motheye mold 100 B.
  • FIG. 10 ( a ) is a schematic diagram showing a cross-sectional structure of a polarizer.
  • ( b ) is a schematic diagram showing a cross-sectional structure of a polarizer on which an antireflection film is formed according to an antireflection film fabrication method of an embodiment of the present invention.
  • samples 10 As the base which is capable of transmitting ultraviolet light, two glass substrates 10 b of different sizes, a 5 cm square piece and a 10 cm square piece, were provided. On the glass substrates 10 b , a 1.0 ⁇ m thick aluminum film 10 a was deposited by sputtering. The resultant pieces are referred to as “samples 10 ”.
  • the anodization step was performed with the samples 10 , including a 5 cm square piece and a 10 cm square piece, being immersed in an electrolytic solution 26 in a container 24 as shown in FIGS. 1( a ) and 1 ( b ), respectively.
  • the 5 cm square piece sample 10 was held standing by a plastic jig such that a diagonal direction of the sample 10 was identical with the vertical direction as shown in FIG. 1( a ).
  • the 10 cm square piece sample 10 was held standing by a plastic jig such that a pair of opposite sides of the sample 10 were identical with the vertical direction as shown in FIG. 1( b ).
  • an electrode 22 a that was in contact with the aluminum film 10 a was coupled to the positive electrode of an external DC power supply 22 D via a lead wire.
  • the negative electrode used in the anodization step was a platinum-plated tantalum plate 20 which had approximately the same size as either sample 10 .
  • An electrode 22 c that was in contact with the tantalum plate 20 was coupled to the negative electrode of the external DC power supply 22 D via another lead wire.
  • the electrolytic solution 26 used herein was a 0.6 mass % oxalic aqueous solution at 5° C.
  • the anodization was performed with an applied voltage at 90 V for 25 seconds. Thereafter, the sample was immersed in a 10 mass % phosphoric acid aqueous solution at 30° C.
  • the aluminum film 10 a can be completely anodized near the electrode 22 a , but however, the anodized aluminum (alumina) does not have electrical conductivity, so that a portion which is distant from the electrode 22 a by about 7 cm or more is electrically disconnected from the external DC power supply 22 D. In this portion, the anodization does not advance, so that the aluminum film remains. Note that the same result was obtained from another sample which only underwent the anodization step.
  • FIG. 2( a ) a portion in which the aluminum film 10 a was completely anodized (transparent portion 90 A) is cross-sectionally shown in FIG. 2( a ), and another portion in which part of the aluminum film 10 a was remaining (non-transparent portion 90 B) is cross-sectionally shown in FIG. 2( b ).
  • transparent portion 90 A a portion in which the aluminum film 10 a was completely anodized
  • non-transparent portion 90 B is cross-sectionally shown in FIG. 2( b ).
  • FIGS. 2( a ) and 2 ( b ) a schematic cross-sectional diagram and a SEM image of the cross section are shown together.
  • the aluminum film 10 a was completely anodized so that a porous alumina layer 12 a having a plurality of very small recessed portions 12 p abutted on the glass substrate 10 b .
  • the very small recessed portions 12 p of the mold have a two-dimensional size of not less than 10 nm and less than 500 nm when viewed in a direction normal to the surface and that the distance between adjacent ones of the recessed portions is not less than 30 nm and less than 600 nm (see Patent Documents 1, 2 and 4).
  • the recessed portions 12 p of the porous alumina layer 12 a formed herein have such dimensions that, for example, the diameter of the opening is 100 nm to 200 nm, the depth is 900 nm to 1 ⁇ m, and the distance between adjacent ones of the recessed portions 12 p is 150 nm to 250 nm.
  • the aluminum film 10 a ′ was remaining between the porous alumina layer 12 a and the glass substrate 10 b .
  • the aluminum film 10 a ′ was remaining in the non-transparent portion.
  • a conductive layer 11 is provided over the glass substrate 10 b as shown in FIG. 4( a ).
  • the conductive layer 11 used herein is capable of transmitting at least 10% of ultraviolet light (365 nm) supplied for the purpose of curing a UV-curable resin.
  • the transmittance of a mold finally obtained is preferably not less than 10%, more preferably not less than 40%.
  • the conductive layer 11 a 20 nm thick titanium film was used.
  • the titanium film was formed by sputtering.
  • the thickness of the titanium film may be not less than 1 nm and not more than 100 nm. If the thickness of the titanium film is less than 1 nm, uniform conductivity may not be ensured. If the thickness of the titanium film exceeds 100 nm, the transmittance may be less than 10%.
  • the material for the conductive layer 11 is preferably titanium.
  • Other possible examples include an ITO film and an IZO film which are known as transparent conductive films, although these are less preferable in terms of etching durability.
  • a molybdenum film and a tungsten film are superior to the ITO film and the IZO film in terms of etching durability but may undergo formation of pits in the surface by etching. Thus, titanium is most preferable.
  • anodization and etching were alternately repeated. Specifically, the anodization was performed for 25 seconds with the applied voltage at 80 V using a 0.6 mass % oxalic aqueous solution at 5° C. Thereafter, the etching was performed by immersing the resultant structure in a 10 mass % phosphoric acid aqueous solution at 30° C. for 25 minutes. This etching was to enlarge very small recessed portions formed in the porous alumina layer in the preceding anodization step.
  • the above-described anodization step and etching step are alternately performed, for example, each step performed twice, whereby a porous alumina layer 12 a which has very small recessed portions 12 p , i.e., which has an inverted motheye structure in its surface, is formed as shown in FIG. 4( a ).
  • the aluminum film 10 a ′ may be remaining.
  • the resultant structure including the remaining aluminum film 10 a ′, was then anodized using a 0.6 mass % oxalic aqueous solution at 5° C. with the applied voltage at 80 V till the entire mold became transparent.
  • a mold 100 A was obtained, the cross-sectional structure of which is schematically shown in FIG. 4( b ).
  • minute pores 12 s that are smaller than the plurality of recessed portions 12 p are formed at a side of the porous alumina layer 12 a which is closer to the conductive layer 11 as shown in FIG. 4( b ).
  • the two-dimensional size of the recessed portions 12 p is not less than 10 nm and less than 500 nm, and the distance between adjacent ones of the recessed portions 12 p is not less than 30 nm and less than 600 nm.
  • the mold 100 A shown in FIG. 4( b ) includes the glass substrate 10 b , the conductive layer (titanium film) 11 provided on the glass substrate 10 b , and the anodized film (porous alumina layer) 12 a provided on the conductive layer 11 , but does not have a remaining aluminum film between the conductive layer 11 and the porous alumina layer 12 a .
  • the cross-sectional structure of the porous alumina layer 12 a of the mold 100 A looks as if a plurality of pencils (with pointed tips) were arranged.
  • a mold release layer 14 of a water-repellent resin e.g., fluorine resin
  • fluorine resin is an amorphous fluorine resin (AF grade: AF1600) manufactured by DU PONT-MITSUI FLUOROCHEMICALS COMPANY, LTD.
  • the mold release layer 14 may be formed by applying the fluorine resin by spin coating, for example.
  • the minute pores 12 s of the porous alumina, layer 12 a of the mold 100 A can be filled up according to the method described below.
  • the mold 100 A is anodized in a neutral electrolytic solution (pH being more than 3.0 but less than 8.0), whereby the minute pores 12 s can be filled up. Therefore, as a result of anodization in the above-described electrolytic solution, an alumina layer 12 b that does not have the minute pores 12 s , which is also referred to as “barrier layer”, can be formed on a side of the porous alumina layer 12 a which is closer to the conductive layer 11 as shown in FIG. 4( c ).
  • the pH of the neutral electrolytic solution is preferably more than 4.0 and not more than 7.0.
  • the electrolytic solution is preferably an aqueous solution which contains at least one of acids or salts selected from a group consisting of tartaric acid, ammonium tartrate, potassium sodium tartrate, boric acid, ammonium borate, ammonium oxalate, ammonium citrate, maleic acid, malonic acid, phthalic acid, and citric acid.
  • acids or salts selected from a group consisting of tartaric acid, ammonium tartrate, potassium sodium tartrate, boric acid, ammonium borate, ammonium oxalate, ammonium citrate, maleic acid, malonic acid, phthalic acid, and citric acid.
  • the above electrolytic solution may be replaced by an acidic aqueous solution with a concentration of not more than 0.1 mol/L (liter), which has a sufficiently small aluminum oxide solubility.
  • an acidic aqueous solution with a concentration of not more than 0.1 mol/L (liter) which has a sufficiently small aluminum oxide solubility.
  • a phosphoric acid aqueous solution with a concentration of not more than 0.1 mol/L may be used.
  • FIGS. 5( a ) to 5 ( c ) illustrate the process of filling up the minute pores 12 s by performing anodization with the use of, for example, ammonium tartrate (concentration: 0.1 mol/L, pH 6.5, solution temperature: 23.2° C.) as the neutral electrolytic solution.
  • FIGS. 5( a ) to 5 ( c ) are SEM images of a cross section of a motheye mold, which demonstrate that the barrier layer 12 b ( FIG. 4( c )) is formed by anodization in the neutral solution.
  • An anodized film (having the minute pores 12 s shown in FIG. 4( b )) which was obtained by alternately performing the anodization step and the etching step, each step performed four times, to form a motheye structure and further performing anodization (under the same conditions as those established in the anodization step for formation of the motheye structure) till the entire mold became transparent as described above was anodized for 180 seconds with the applied voltage at 100 V with the use of the above-described neutral electrolytic solution, whereby part of the minute pores was filled so that a 96.5 nm thick barrier layer was formed as shown in FIG. 5( a ). Then, the anodized film shown in FIG.
  • the thickness of the barrier layer obtained by anodization with the use of the neutral electrolytic solution depends on the applied voltage. As for the neutral electrolytic solution, the result shown in FIG. 6 was obtained.
  • the depth of the recessed portions 12 p of the porous alumina layer 12 a which constitute the motheye structure is preferably not less than 150 nm and not more than 500 nm.
  • the thickness of the barrier layer 12 b is preferably more than 0 nm and not more than 400 nm.
  • the thickness of the initial aluminum film 10 a is preferably about 500 nm. From the viewpoint of limiting the thickness of the barrier layer 12 b to the above condition, the thickness of the initial aluminum film 10 a is preferably not more than 900 ⁇ m.
  • FIG. 7 shows the transmission spectrum of a mold 100 B.
  • the mold 100 B has a transmittance of about 60% over the ultraviolet range around 365 nm and the entire visible light wavelength range.
  • the mold 100 A a similar transmission spectrum was obtained.
  • the transmittance of the mold 100 E is higher than that of the motheye mold portion 90 A ( FIG. 2( a )). The reason for this result is not yet confirmed.
  • the mold 100 A or 100 B is prepared as shown in FIG. 8 or FIG. 9 .
  • a UV-curable resin 32 provided between the surface of a work 42 and the mold 100 A or 100 B is irradiated with ultraviolet light (UV) supplied through the mold 100 A or 100 B, whereby the UV-curable resin 32 is cured.
  • the UV-curable resin 32 may be applied to the surface of the work 42 or, alternatively, may be applied to the mold surface of the mold 100 A or 100 B (a surface which has the motheye structure).
  • an acrylic resin for example, may be used.
  • an antireflection film can readily be formed on, for example, the surface of a conventional polarizer.
  • a polarizer 50 shown in FIG. 10( a ) includes a polarizing layer 52 a which is made of PVA and protector layers 52 b and 52 c between which the polarizing layer 52 a is interposed.
  • the protector layers 52 c and 52 b are made of, for example, COP (cycloolefin polymer) or TAC.
  • COP cycloolefin polymer
  • TAC TAC
  • ultraviolet light cannot be supplied from the polarizer 50 side.
  • ultraviolet light can be supplied through the mold. Therefore, an antireflection film 62 which has a motheye structure can be formed on the polarizer 50 as shown in FIG. 10( b ).
  • the present invention is widely applicable to formation of an antireflection film.
  • the antireflection film is applicable to various uses of which antireflection is demanded, typically to optical elements for use in display devices or the like.

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CN103014808B (zh) * 2012-12-14 2015-07-29 中国计量学院 用酒石酸阳极氧化制备铝合金阳极氧化膜的方法
CN103112130B (zh) * 2013-02-28 2014-01-01 佛山市科尔技术发展有限公司 一种塑胶模具及其生产方法
CN106062257B (zh) * 2014-02-28 2018-01-23 夏普株式会社 模具的再利用方法
US11335831B2 (en) * 2017-03-29 2022-05-17 Sharp Kabushiki Kaisha Optical device case and optical device
JP6605553B2 (ja) * 2017-09-11 2019-11-13 シャープ株式会社 電子放出素子およびその製造方法ならびに電子素子の製造方法

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CN102301040A (zh) 2011-12-28

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