JP2008197216A - Antireflection coating and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an antireflection coating on which a convex part having excellent scratch resistance at the tip thereof is formed, and to provide the antireflection coating having excellent scratch resistance at the tip of the convex part formed on the surface thereof. <P>SOLUTION: The method for producing the antireflection coating 30 having the convex part 32 on the surface thereof includes: a step (i) of supplying a liquid resin material having a viscosity of 1 to 1×10<SP>5</SP>Pa-s onto the surface of a mold on the surface of which a concave part corresponding to the convex part 32 is formed; a step (ii) of solidifying the supplied liquid resin material to form the antireflection coating 30; a step (iii) of separating the antireflection coating 30 from the mold; and a step (iv) of, if necessary, further solidifying the solidified resin material. The antireflection coating 30 obtained by this producing method satisfies 0<r<R (wherein r is the curvature radius of the tip of the convex part 32; and R is a half of the maximum width of the convex part). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antireflection film and a manufacturing method thereof.

  In recent years, materials having a fine concavo-convex structure with a period equal to or less than the wavelength of visible light on the surface exhibit functionality such as an antireflection function and a Lotus effect, and thus have been attracting attention for their usefulness. In particular, a fine concavo-convex structure called a Moth-Eye structure in which approximately conical convex portions are arranged can be an effective antireflection means by continuously increasing from the refractive index of air to the refractive index of the material. It has been known.

  As a method for forming a fine concavo-convex structure on the material surface, there are a method of directly processing the surface of the material and a method using a mold having an inverted structure corresponding to the fine concavo-convex structure. From the viewpoint of productivity and economy, the latter The method is excellent. As a method for forming an inverted structure in a mold, an electron beam drawing method, a laser beam interference method, and the like are known. However, the manufacturing cost of the mold by these methods is very high, resulting in a large cost added to the material having a fine concavo-convex structure on the surface.

  In recent years, anodized porous alumina has attracted attention as a mold that can be easily produced (for example, Patent Document 1). A technique for accurately forming a fine concavo-convex structure using this anodized porous alumina has steadily advanced.

In general, when the surface has a fine concavo-convex structure, it is known that the mechanical strength is low and the scratch resistance is insufficient. For example, the cross-sectional shape of the convex portion is 0.3 <h / h ^* <0.9 (where h is the actual height of the convex portion, and h ^* is the bottom of both side surfaces of the convex portion in the cross-section of the convex portion. Is a height up to the point where the tangent line t at the part in contact with the surface intersects.) (Patent Document 2).
However, Patent Document 2 describes only the result of the simulation, and does not mention a method of manufacturing a convex portion that actually satisfies the above formula.

A method for manufacturing an optical element in which the shape of the concave portion of the mold does not match the shape of the convex portion formed using this mold is disclosed (Patent Document 3). However, the invention described in Patent Document 3 only describes the injection molding conditions for making the depth of the concave portion of the mold 1.5 to 10 times the height of the convex portion to be formed. The method for forming a conical convex portion having excellent scratch resistance at the tip is not mentioned.
JP 2005-156695 A JP 2005-173457 A JP 2006-133722 A

  Accordingly, an object of the present invention is to provide a method capable of producing an antireflection film having a convex portion having excellent scratch resistance at the tip portion, and an antireflection film having excellent scratch resistance at the tip portion of the convex portion formed on the surface. Is to provide.

The method for producing an antireflection film of the present invention is a method for producing an antireflection film having a convex portion formed on a surface thereof, (i) on the surface of a mold having a concave portion corresponding to the convex portion formed on the surface, A step of contacting a liquid resin material having a viscosity of 1 to 1 × 10 ⁴ Pa · s, (ii) a step of forming the antireflection film by making the resin material solid or semi-solid, and (iii) And a step of separating the antireflection film and the mold.

The antireflection film of the present invention is an antireflection film obtained by the production method of the antireflection film of the present invention and having a convex portion formed on the surface, and the curvature radius r of the tip portion of the convex portion is as follows: The expression (1) is satisfied.
0 <r <R (1).
However, R is half of the maximum width of the convex portion.

According to the method for producing an antireflection film of the present invention, it is possible to produce an antireflection film in which a convex portion having excellent scratch resistance at the tip portion is formed.
The antireflection film of the present invention is excellent in scratch resistance at the tip of the convex portion formed on the surface.

  In this specification, (meth) acrylate means an acrylate or a methacrylate.

<Method for producing antireflection film>
The method for producing an antireflection film of the present invention is a method for producing an antireflection film having a convex portion formed on the surface, and includes the following steps.
(I) A step of bringing a liquid resin material having a viscosity of 1 to 1 × 10 ⁵ Pa · s into contact with the surface of the mold in which concave portions corresponding to the convex portions are formed on the surface.
(Ii) The step of forming the resin material into a solid state and forming the antireflection film.
(Iii) A step of separating the antireflection film and the mold.
In the present invention, if necessary, the method may further include (iv) a step of making the resin material solid after the step (iii).

(I) Process:
(mold)
As the mold, a mold having fine recesses on the surface can be used, and so-called anodized porous alumina in which pores (recesses) are formed in an aluminum oxide film (alumite) is preferable.

Anodized porous alumina can be produced, for example, through the following steps (a) to (e).
(A) A step of forming an oxide film by anodizing aluminum in an electrolytic solution under a constant voltage.
(B) A step of removing the oxide film and forming pore generation points for anodic oxidation.
(C) A step of anodizing aluminum again in an electrolytic solution to form an oxide film having pores at the pore generation points.
(D) A step of enlarging the diameter of the pores.
(E) A step of repeatedly performing the steps (c) and (d).

(A) Process:
The purity of aluminum is preferably 90% or more, more preferably 99% or more, and particularly preferably 99.5% or more. When the purity of aluminum is low, when anodized, an uneven structure having a size to scatter visible light may be formed due to segregation of impurities, or the regularity of pores obtained by anodization may be lowered.

Examples of the electrolytic solution include an acidic electrolytic solution and an alkaline electrolytic solution, and an acidic electrolytic solution is preferable.
Examples of the acidic electrolyte include sulfuric acid, oxalic acid, phosphoric acid, and a mixture thereof.

When using oxalic acid as electrolyte:
The concentration of oxalic acid is preferably 0.7 M or less. When the concentration of oxalic acid exceeds 0.7M, the current value becomes too high, and the surface of the oxide film may become rough.
When the voltage is 30-60 V, anodized porous alumina having highly regular pores with a period of 100 nm can be obtained. Regardless of whether the formation voltage is higher or lower than this range, the regularity tends to decrease, and the period may be longer than the wavelength of visible light.
The temperature of the electrolytic solution is preferably 60 ° C. or lower, and more preferably 45 ° C. or lower. When the temperature of the electrolytic solution exceeds 60 ° C., a so-called “burn” phenomenon occurs, and the pores may be broken, or the surface may melt and the regularity of the pores may be disturbed.

When using sulfuric acid as the electrolyte:
The concentration of sulfuric acid is preferably 0.7M or less. If the concentration of sulfuric acid exceeds 0.7M, the current value may become too high to maintain a constant voltage.
When the voltage is 25 to 30 V, anodized porous alumina having highly regular pores with a period of 63 nm can be obtained. Regardless of whether the formation voltage is higher or lower than this range, the regularity tends to decrease, and the period may be longer than the wavelength of visible light.
The temperature of the electrolytic solution is preferably 30 ° C. or lower, and more preferably 20 ° C. or lower. When the temperature of the electrolytic solution exceeds 30 ° C., a so-called “burn” phenomenon occurs, and the pores may be broken, or the surface may melt and the regularity of the pores may be disturbed.

The diameter control of the pores may be performed according to a conventional method. For example, the diameter of the pores increases as the anodic oxidation is performed at a higher voltage. When an acidic electrolyte is used, the pore diameter increases in the order of sulfuric acid, oxalic acid, and phosphoric acid.
The period of the pores is preferably 20 to 500 nm. If the period of the pores is less than 20 nm, it is difficult to control anodization, and pores having a period according to the purpose cannot be obtained. If the period of the pores exceeds 500 nm, the voltage exceeds the withstand voltage of the electrolyte, and pores cannot be formed. The period of the pore is a distance from the center of the pore to the center of the pore adjacent to the pore.

  The thickness of the oxide film is preferably 10 μm or less, more preferably 1 to 5 μm, and particularly preferably 1 to 3 μm when observed with a field emission scanning electron microscope. When the thickness of the oxide film exceeds 10 μm, the crystal grain boundaries of aluminum can be visually confirmed, and even the irregularities of the crystal grain boundaries may be transferred to the antireflection film surface.

(B) Process:
The regularity of the pores can be improved by once removing the oxide film and using this as the pore generation point for anodization (for example, Masuda, Applied Physics, vol. 69, No. 5, p 558 (2000). )).
Examples of the method for removing the oxide film include a method in which aluminum is not dissolved but is dissolved in a solution that selectively dissolves alumina and removed. Examples of such a solution include a chromic acid / phosphoric acid mixed solution.

(C) Process:
As shown in FIG. 1, when the aluminum 12 from which the oxide film has been removed is anodized again, an oxide film 16 having cylindrical pores (recesses 14) is formed.
Anodization may be performed under the same conditions as in step (a). Deeper pores can be obtained as the anodic oxidation time is lengthened.

(D) Process:
As shown in FIG. 1, a process of expanding the diameter of the pore (recessed portion 14) (hereinafter referred to as a pore diameter expanding process) is performed. The pore diameter expansion treatment is a treatment for expanding the diameter of the pores obtained by anodic oxidation by immersing in a solution dissolving alumina. Examples of such a solution include a phosphoric acid aqueous solution of about 5% by mass.
The longer the pore diameter expansion processing time, the larger the pore diameter.

(E) Process:
As shown in FIG. 1, when the anodic oxidation in the step (c) and the pore diameter enlargement process in the step (d) are repeated, pores having a shape in which the diameter continuously decreases in the depth direction from the opening (recess 14). ) Anodized porous alumina (mold 10) is obtained.
By repeating the anodic oxidation and the pore diameter enlargement process under the same conditions, substantially conical pores (recesses 14) as shown in FIG. 2 are formed. By changing the anodizing time and the pore diameter expansion processing time, a reverse bell-shaped pore (recessed portion 14) as shown in FIG. 3 and a sharp-shaped pore (recessed portion 14) as shown in FIG. 4 are formed. it can.
The total number of repetitions is preferably 3 times or more, and more preferably 5 times or more. If the number of repetitions is 2 times or less, the diameter of the pores decreases discontinuously, so that the antireflection film manufactured using a mold having such pores is inferior in the reflectance reduction effect.

The surface of the antireflection film manufactured using a mold having pores (concave portions) as shown in FIGS. 2 to 4 has a so-called Moth-Eye structure, which is an effective antireflection means.
The depth of the pores is preferably 50 nm or more, and more preferably 100 nm or more. When the depth of the pores is 50 nm or more, the reflectance of the obtained antireflection film is sufficiently low.
The aspect ratio (depth / cycle) of the pores is preferably 0.5 or more, and more preferably 1 or more. When the aspect ratio is 0.5 or more, the reflectance of the obtained antireflection film is sufficiently low, and the incident angle dependency is also small.
The opening diameter of the pores is preferably 10 to 500 nm, and more preferably 20 to 300 nm. If the opening diameter of the pore is 10 nm or more, the production of the mold can be arbitrarily controlled. If the opening diameter of the pores is 500 nm or less, it is easy to adjust the viscosity of the liquid resin material so that the liquid resin material is not completely filled into the pores.

The surface of the mold may be treated with a release agent so as to facilitate separation from the antireflection film. Examples of the treatment method include a method of coating a silicone polymer or a fluorine polymer, a method of depositing a fluorine compound, a method of coating a fluorine silane coupling agent or a fluorine silicone silane coupling agent, and the like.
Examples of the shape of the mold include a flat plate shape, a columnar shape, and a cylindrical shape. Examples of the columnar or cylindrical mold include a mold made of columnar or cylindrical aluminum, or a mold having an aluminum layer on the surface of a columnar or cylindrical support.

(Liquid resin material)
Examples of the liquid resin material include a curable resin composition or a thermoplastic resin in a molten state.

  Examples of the curable resin composition include a mixture of a component that causes a photocuring reaction, an electron beam curing reaction, or a thermosetting reaction, and a component that accelerates these reactions. For example, the curable resin composition includes a polymerizable compound and a polymerization initiator. A mixture is mentioned.

  Examples of the polymerizable compound include an esterified product A obtained from 1 mol of a polyhydric alcohol and 2 mol or more of (meth) acrylic acid or a derivative thereof; a polyhydric alcohol and a polyvalent carboxylic acid or an anhydride thereof. And esterified product B obtained from (meth) acrylic acid or a derivative thereof.

  As esterified product A, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate , Trimethylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerin tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate , Tripentaerythritol hexa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, and the like.

Examples of the esterified product B include polycarboxylic acids such as malonic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, fumaric acid, itaconic acid and maleic anhydride, or anhydrides thereof, trimethylolethane, trimethylolpropane, Examples thereof include esterified products obtained by combinations selected arbitrarily from polyhydric alcohols such as glycerin and pentaerythritol, and (meth) acrylic acid or derivatives thereof.
A polymeric compound may be used individually by 1 type, and may use 2 or more types together.

  When utilizing a photocuring reaction, examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl, benzophenone, p-methoxybenzophenone, 2,2-diethoxy. Acetophenone, α, α-dimethoxy-α-phenylacetophenone, methylphenylglyoxylate, ethylphenylglyoxylate, 4,4′-bis (dimethylamino) benzophenone, 2-hydroxy-2-methyl-1-phenylpropane- Carbonyl compounds such as 1-one; sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, benzoic acid Diethoxy phosphine oxide, and the like. These may be used alone or in combination of two or more.

  When using an electron beam curing reaction, examples of the polymerization initiator include benzophenone, 4,4-bis (diethylamino) benzophenone, 2,4,6-trimethylbenzophenone, methyl orthobenzoylbenzoate, 4-phenylbenzophenone, t- Thioxanthone such as butylanthraquinone, 2-ethylanthraquinone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone; diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl Dimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholy Acetophenone such as phenyl) -butanone; benzoin ether such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl)- Acylphosphine oxides such as 2,4,4-trimethylpentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; methylbenzoylformate, 1,7-bisacridinylheptane, 9-phenyl Examples include acridine. These may be used alone or in combination of two or more.

  When a thermosetting reaction is used, examples of the thermal polymerization initiator include methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxy octoate, organic peroxides such as t-butylperoxybenzoate and lauroyl peroxide; azo compounds such as azobisisobutyronitrile; N, N-dimethylaniline, N, N-dimethyl-p- Examples thereof include a redox polymerization initiator combined with an amine such as toluidine.

  As for the quantity of a polymerization initiator, 0.01-10 mass parts is preferable with respect to 100 mass parts of polymeric compounds. If the amount of the polymerization initiator is less than 0.01 parts by mass, sufficient curing of the curable resin composition cannot be realized. If the amount of the polymerization initiator exceeds 10 parts by mass, the molecular weight of the resin decreases, the strength of the resin becomes insufficient, or a problem of coloring the antireflection film after curing occurs due to a residue of the polymerization initiator, etc. Or

The curable resin composition may contain a non-reactive polymer and an active energy ray sol-gel reactive composition as necessary.
Non-reactive polymers include acrylic resins, styrene resins, polyurethane resins, cellulose resins, polyvinyl butyral resins, polyester resins, thermoplastic elastomers, and the like.
Examples of the active energy ray sol-gel reactive composition include alkoxysilane compounds and alkylsilicate compounds.

As an alkoxysilane compound, the compound of following formula (2) is mentioned.
R _x Si (OR ′) _y (2).
However, R and R ′ each represent an alkyl group having 1 to 10 carbon atoms, and x and y represent integers satisfying the relationship of x + y = 4.

  Examples of the alkoxysilane compound include tetramethoxysilane, tetra-iso-propoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltriethoxysilane, Examples include methyltripropoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, trimethylmethoxysilane, trimethylpropoxysilane, and trimethylbutoxysilane.

Examples of the alkyl silicate compound include compounds of the following formula (3).
R ¹ O (Si (OR ³ ) (OR ⁴ ) O) _z R ² (3).
However, R < ¹ > -R < ⁴ > represents a C1-C5 alkyl group, respectively, and z represents the integer of 3-20.

  Examples of the alkyl silicate compound include methyl silicate, ethyl silicate, isopropyl silicate, n-propyl silicate, n-butyl silicate, n-pentyl silicate, acetyl silicate and the like.

  The curable resin composition may further contain various additives such as a thickener, a leveling agent, an ultraviolet absorber, a light stabilizer, a heat stabilizer, a solvent, and an inorganic filler as necessary.

  Examples of the thermoplastic resin in a molten state include polyester resin (polyethylene terephthalate, polybutylene terephthalate, etc.), polymethacrylate resin, polycarbonate resin, vinyl chloride resin, ABS resin, styrene resin, etc. heated to the melting temperature or higher. It is done.

The viscosity of the liquid resin material is 1 Pa · s to 1 × 10 ⁴ Pa · s, and preferably 1 Pa · s to 5 × 10 ³ Pa · s. If the viscosity of the liquid resin material is less than 1 Pa · s, the penetration of the resin material into the concave portion of the mold cannot be controlled, so that the resin material is completely filled into the concave portion of the mold. As a result, it is not possible to obtain an antireflection film having a convex portion in which the radius of curvature r of the tip satisfies the formula (1). When the viscosity of the liquid resin material exceeds 1 × 10 ⁴ Pa · s, the fluidity of the liquid resin material becomes low and a stable film cannot be formed.

The viscosity of the liquid resin can be measured by a general rheometer or the like, and the measured viscosity includes, for example, a complex viscosity.
Examples of methods for adjusting the viscosity of the liquid resin material include a method of changing the mixing ratio of components, a method of using a thickener or a solvent, and a method of changing the temperature. Thus, the shape of the front-end | tip part of a convex part can be changed by adjusting a viscosity.

Examples of the method of bringing the liquid resin material into contact with the surface of the mold include the following method (I) or (II).
(I) A method of applying a liquid resin material 20 to the surface of the mold 10 as shown in FIG. After applying the liquid resin material 20 to the surface of the mold 10, the coating film of the liquid resin material 20 may be covered with the resin base material 24.
(II) A method of pressing the mold 10 against the coating film of the liquid resin material 20 after applying the liquid resin material 20 on the resin substrate 24 as shown in FIG.

Examples of the coating method include a roller coating method, a bar coating method, and an air knife coating method.
Examples of the resin base material 24 include polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polymethacrylate resins, polycarbonate resins, vinyl chloride resins, ABS resins, styrene resins, and the like.

(Ii) Process:
As a method of making the liquid resin material solid or semi-solid, when the resin material is a photocurable resin composition, a method of irradiating light, when the resin material is an electron beam curable resin composition, Examples include a method of irradiating an electron beam, a method of heating when the resin material is a thermosetting resin composition, and a method of cooling when the resin material is a thermoplastic resin in a molten state.

(Iii) Process:
When the liquid resin material is brought into a solid state in contact with the resin base material, the antireflection film is separated from the mold together with the resin base material. The resin base material separated from the bold together with the antireflection film may be used as a part of the antireflection member together with the antireflection film.

(Iv) Process:
As a method for making a liquid resin material into a solid state, the same operation as in (ii) is performed. However, when the resin material is a photocurable resin composition, a method of irradiating light, and the resin material is an electron. In the case of a linear curable resin composition, a method of irradiating with an electron beam, a heating method in the case where the resin material is a thermosetting resin composition, a cooling in the case of a thermoplastic resin in which the resin material is in a molten state Methods and the like.

<Antireflection film>
FIG. 7 is a cross-sectional view showing an example of the antireflection film of the present invention. The antireflection film 30 is a film having a plurality of convex portions 32 formed on the surface. A resin base material 24 may be provided on the back surface of the antireflection film 30.

In the antireflection film obtained by the production method of the present invention, the radius of curvature r of the tip of the convex portion satisfies the following formula (1), and preferably satisfies the following formula (1-1).
0 <r <R (1).
20 nm ≦ r <R (1-1).
However, R is half of the maximum width of the convex portion.

That is, the shape of the convex portion is an intermediate shape between the shape shown in FIG. 8 (the tip radius of curvature is 0) and the shape shown in FIG. 9 (the tip radius of curvature is R). Become.
When the curvature radius r of the tip portion is 0, the tip portion is sharpened, so that it is very weak against abrasion. When the radius of curvature r of the tip is greater than or equal to R, the tip becomes flat, so the refractive index changes abruptly at the interface between the antireflection film and air, and the antireflection effect by the Moth-Eye structure is weakened. End up.

The radius of curvature r can be obtained by observation with an atomic force microscope, observation with an electron microscope, or the like. For example, it can be obtained by observing the cross section of the convex portion with an electron microscope and approximating the tip portion with an arc from the obtained cross-sectional view.
The maximum width of the convex portion is the maximum value of the width in the direction crossing the convex portion when the cross section of the convex portion is observed, and is usually the width of the bottom portion of the convex portion. For example, when the convex portion has a substantially conical shape, half R of the maximum width of the convex portion is the radius of the bottom surface of the cone.

The period of the convex part is preferably not more than the wavelength of visible light (380 to 780 nm), and more preferably 20 to 500 nm which is the same as the period of the concave part of the mold. The period of a convex part is the distance from the center of a convex part to the center of the convex part adjacent to this.
The height of the convex part is preferably 50 nm or more, and more preferably 100 nm or more. When the height of the convex portion is 50 nm or more, the reflectance of the antireflection film is sufficiently low.
The aspect ratio (height / cycle) of the convex part is preferably 0.5 or more, and more preferably 1.0 or more. When the aspect ratio is 0.5 or more, the reflectance of the antireflection film is sufficiently low and the incident angle dependency is also small.

The haze of the antireflection film is preferably 3% or less, more preferably 1% or less, and particularly preferably 0.5% or less. When the haze exceeds 3%, for example, when used in an image display device, the sharpness of the image is lowered.
The antireflection film may have an antiglare function that scatters external light. An anti-glare function can be imparted by providing a convex portion in the present invention having a period equal to or less than the wavelength of visible light on a fine concavo-convex structure having a period equal to or greater than the wavelength of visible light.

The antireflection film of the present invention is, for example, an image display device (liquid crystal display device, plasma display panel, electroluminescence display, cathode tube display device, etc.), lens, show window, antireflection film such as glasses, and antireflection film. It is used as an antireflection sheet.
When used in an image display device, an antireflection film may be applied on the outermost surface, or an antireflection film may be formed directly on the material forming the outermost surface, and the antireflection film is formed on the front plate of the image display device. A film may be provided.

In the manufacturing method of the antireflection film of the present invention described above, since the liquid resin material having a viscosity of 1 to 1 × 10 ⁴ Pa · s is used, the convex portion having excellent scratch resistance at the tip portion is formed. The formed antireflection film can be manufactured. That is, since the liquid resin material having a viscosity of 1 to 1 × 10 ⁴ Pa · s is not completely filled in the concave portion of the mold, the curvature radius r of the tip portion of the convex portion to be formed exceeds 0. It will be. A convex portion having a radius of curvature r of the tip portion exceeding 0 exhibits strength against abrasion.
Moreover, since the shape of the convex portion can be changed by changing the viscosity of the liquid resin material, several types of antireflection films can be manufactured with one mold, and the enormous cost for manufacturing the mold can be suppressed.

Examples of the present invention are shown below. However, the present invention is not limited to these.
Various measurements and evaluations in the examples were performed according to the following methods.

(Thickness of oxide film, pore shape)
Part of the mold is shaved, platinum is deposited on the cross section for 1 minute, and the cross section is observed under a condition of an acceleration voltage of 3.00 kV using a field emission scanning electron microscope (JSM-7400F, manufactured by JEOL Ltd.). The thickness of the oxide film, the period of the pores, the opening diameter of the pores, and the depth of the pores were measured. Each measurement was performed for 5 points, and the average value was obtained.

(Convex shape)
Platinum is deposited on the fracture surface of the anti-reflection film for 5 minutes, and the cross section is observed in the same manner as the mold. It was measured. Each measurement was performed for 5 points, and the average value was obtained.

(viscosity)
The viscosity of the curable resin composition is such that the sample is sandwiched between 25 mm parallel plates using a rheometer (manufactured by TA Instruments Inc., ARES), and the temperature is 30 ° C. to 120 ° C. at a distance of 1 mm between the plates. The complex viscosity was measured at an angular frequency of 10 rad / sec.

(Reflectance)
For the reflectance of the antireflection film, a spectrophotometer (manufactured by Hitachi High-Technologies Corporation: U-4100) was attached with a 5 ° regular reflection accessory device, and the reflectance in the visible region (380 to 780 nm) was measured. By the way, the measurement was performed after the operation of spraying black spray on the back surface for the purpose of suppressing the reflection on the back surface of the sample.

(Abrasion resistance)
An abrasion test was performed using a spectacles wipe (trade name: Toraysee, manufactured by Toray Industries, Inc.). The conditions were a load of 2000 g / 20 mmφ and 300 reciprocations. The sample after the test was visually observed and evaluated according to the following criteria.
A: No scar is seen.
○: Scars can be confirmed when staring.
Δ: Several scars can be confirmed.
X: 10 or more scars can be confirmed.

[Production Example 1]
(A) Process:
Anodization was carried out for 0.5 hour under conditions of a voltage of 40 V and a temperature of 16 ° C. using 0.5 M oxalic acid as the electrolyte, and an aluminum plate having a thickness of 0.5 mm as the cathode and the anode, respectively. The thickness of the obtained oxide film was 2.8 μm.
(B) Process:
The anode on which the oxide film was formed was immersed in 6% by mass phosphoric acid / 1.8% by mass chromic acid mixed acid at 70 ° C. to remove the oxide film.

(C) Process:
After the anode was washed with pure water, anodization was performed for 30 seconds using 0.3 M oxalic acid as an electrolyte under conditions of a voltage of 40 V and a temperature of 16 ° C.
(D) Process:
The anode was immersed in 5% by mass phosphoric acid at 32 ° C. for 8 minutes to carry out pore size expansion treatment.

(E) Process:
The steps (c) and (d) were repeated five times in total to obtain anodized porous alumina having a pore period of 100 nm, a pore opening diameter of 80 nm, and a pore depth of 250 nm.
The anodized porous alumina was treated with a silane coupling agent (manufactured by Shin-Etsu Silicone Co., Ltd., KP-801M) to perform a fluorination treatment on the oxide film surface.

[Production Example 2]
(A) Process:
Anodization was performed for 0.5 hour under the conditions of a voltage of 120 V and a temperature of 1 ° C. using 0.5 M oxalic acid as the electrolyte, and an aluminum plate having a thickness of 0.5 mm as the cathode and the anode, respectively. If a voltage of 120V is suddenly applied, so-called “burning” occurs, and it is necessary to gradually increase the voltage from a constant voltage of about 40V. The thickness of the obtained oxide film was 2.7 μm.
(B) Process:
The anode on which the oxide film was formed was immersed in 6% by mass phosphoric acid / 1.8% by mass chromic acid mixed acid at 70 ° C. to remove the oxide film.

(C) Process:
After the anode was washed with pure water, anodization was performed for 30 seconds under conditions of a voltage of 80 V and a temperature of 1 ° C. using 4% by mass phosphoric acid as an electrolytic solution.
(D) Process:
The anode was immersed in 5% by mass phosphoric acid at 32 ° C. for 8 minutes to carry out pore size expansion treatment.

(E) Process:
The steps (c) and (d) were repeated 5 times in total to obtain anodized porous alumina having a pore period of 280 nm, a pore opening diameter of 260 nm, and a pore depth of 250 nm.
The anodized porous alumina was treated with a silane coupling agent (manufactured by Shin-Etsu Silicone Co., Ltd., KP-801M) to perform a fluorination treatment on the oxide film surface.

[Preparation Example 1]
30 parts by mass of hexamethylene diisocyanate,
30 parts by mass of polycaprolactone diol (Daicel Chemical Industries, Plaxel 205),
A curable resin composition A was prepared by mixing 40 parts by mass of hydroxyethyl acrylate and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone (Ciba Specialty Chemicals, Irgacure 184).

[Example 1]
(I) Process:
A curable resin composition A (viscosity 2.7 × 10 ³ Pa · s) was applied to the surface of the anodized porous alumina obtained in Production Example 1 and covered with a polyethylene terephthalate film.
(Ii) Process:
Using a UV irradiation machine (high pressure mercury lamp, integrated light amount 3600 mJ / cm ² , peak illuminance 180 mW / cm ² ), the coating film of the curable resin composition A is irradiated with UV rays to cure the curable resin composition A. The antireflection film was formed.

(Iii) Process:
The antireflection film and the mold were separated to obtain an antireflection film having convex portions formed on the surface. The period of the convex part was 100 nm, the height of the convex part was 200 nm, the width of the bottom part of the convex part was 80 nm, and the curvature radius of the tip part of the convex part was 20 nm. The reflectance of the antireflection film is 0.6% or less in the whole range of 380 to 780 nm, and application as an antireflection film with little wavelength dependency can be expected. Further, the evaluation of scratch resistance was ◯.

[Example 2]
(I) Process:
The curable resin composition A was applied to the surface of the anodized porous alumina obtained in Production Example 1 and covered with a polyethylene terephthalate film.
(Ii) Process:
Using a UV irradiation machine (high pressure mercury lamp, integrated light quantity 600 mJ / cm ² , peak illuminance 180 mW / cm ² ), the coating film of the curable resin composition A is irradiated with UV light to cure the curable resin composition A. The antireflection film was formed.

(Iii) Process:
The antireflection film and the mold were separated to obtain an antireflection film having convex portions formed on the surface.
(Iv) Process:
Using an ultraviolet irradiation machine (high pressure mercury lamp, integrated light amount 3600 mJ / cm ² , peak illuminance 180 mW / cm ² ), the antireflection film is irradiated with ultraviolet rays to cure the curable resin composition A, and the antireflection film is applied. Formed. The period of the convex part was 100 nm, the height of the convex part was 240 nm, the width of the bottom part of the convex part was 80 nm, and the radius of curvature of the tip part of the convex part was 20 nm. The reflectance of the antireflection film is 0.6% or less in the whole range of 380 to 780 nm, and application as an antireflection film with little wavelength dependency can be expected. Further, the evaluation of scratch resistance was ◯.

Example 3
An antireflection film was obtained in the same manner as in Example 1 except that the anodized porous alumina obtained in Production Example 2 was used. The period of the convex part was 280 nm, the height of the convex part was 200 nm, the width of the bottom part of the convex part was 260 nm, and the radius of curvature of the tip part of the convex part was 60 nm. The reflectance of the antireflection film is 0.6% or less in the whole range of 380 to 780 nm, and application as an antireflection film with little wavelength dependency can be expected. Further, the evaluation of scratch resistance was ◎.

Example 4
(Ii) An antireflection film was obtained in the same manner as in Example 1 except that the step was held at 70 ° C. for 5 minutes before the step. The viscosity of the curable resin composition at 70 ° C. was 2.4 Pa · s. The period of the convex part was 100 nm, the height of the convex part was 220 nm, the width of the bottom part of the convex part was 80 nm, and the radius of curvature of the tip part of the convex part was 10 nm. The reflectance of the antireflection film is 0.6% or less in the whole range of 380 to 780 nm, and application as an antireflection film with little wavelength dependency can be expected. Further, the evaluation of scratch resistance was ◯.

  Since the antireflection film produced by the production method of the present invention is excellent in scratch resistance, the applicable range is wider than that of the conventional antireflection film. In addition to the antireflection film, it has a fine concavo-convex structure, such as optical articles such as optical waveguides, relief holograms, lenses, and polarization separation elements, cell culture sheets, superhydrophobic films, superhydrophilic films, etc. Can be expected.

It is sectional drawing which shows a part of manufacturing process of an anodized porous alumina. It is sectional drawing which shows an example of the shape of the pore of an anodized porous alumina. It is sectional drawing which shows the other example of the shape of the pore of an anodized porous alumina. It is sectional drawing which shows the other example of the shape of the pore of an anodized porous alumina. It is sectional drawing which shows an example of the anti-reflective film of this invention. It is sectional drawing which shows an example of the manufacturing method of the antireflection film of this invention. It is sectional drawing which shows the other example of the manufacturing method of the antireflection film of this invention. It is sectional drawing which shows an example of the convex part whose curvature radius of a front-end | tip part is 0. It is sectional drawing which shows an example of the convex part whose curvature radius of a front-end | tip part is R.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mold 14 Concave part 20 Liquid resin material 30 Antireflection film 32 Convex part

Claims (3)

A method for producing an antireflection film having convex portions formed on the surface,
(I) a step of bringing a liquid resin material having a viscosity of 1 to 1 × 10 ⁴ Pa · s into contact with the surface of the mold in which concave portions corresponding to the convex portions are formed on the surface;
(Ii) making the resin material solid or semi-solid, and forming the antireflection film;
(Iii) A method for producing an antireflection film, comprising the step of separating the antireflection film and the mold.   Furthermore, the manufacturing method of the anti-reflective film of Claim 1 which has the process of making the said resin material into a solid state after the process of (iv) said (iii). An antireflection film obtained by the method for producing an antireflection film according to claim 1 and having a convex portion formed on a surface thereof,
An antireflection film in which the radius of curvature r of the tip of the convex portion satisfies the following formula (1).
0 <r <R (1).
However, R is half of the maximum width of the convex portion.

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