JP2009260274A - Transparent member for solar cell, and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent member for a solar cell low in reflectivity, and small in wavelength dependency of the reflectivity; and a solar cell suppressing reflection of entering light, and small in light reception loss. <P>SOLUTION: This transparent member 10 for a solar cell has a minute uneven structure on a front surface. In the transparent member 10 for a solar cell, the minute uneven structure is formed by transferring a minute uneven structure on a surface of anodized alumina. In this solar cell, the transparent member 10 for a solar cell is arranged so that the surface on the side with the uneven structure formed thereon becomes a light entering side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solar cell transparent member and a solar cell.

In the solar cell, an antireflection treatment is applied to the surface on the light incident side so that incident light is reflected on the surface and no light reception loss occurs. As a solar cell, the following are disclosed, for example.
A solar cell in which a light-receiving surface side of a solar cell element is protected with glass, and a low-reflection coating layer is provided on the surface of the glass (Patent Document 1).
A dye-sensitized solar cell in which an antireflection film formed by alternately laminating a low refractive index transparent inorganic thin film and a high refractive index transparent inorganic thin film is formed on the surface of a glass substrate on the light receiving surface side (Patent Document 2).

  However, the low-reflective coating layer and the antireflection film have a problem that the reflectance is not sufficiently low, and the reflectance is dependent on the wavelength, so that it is effective only for light of a certain wavelength. .

JP 2003-152202 A International Publication No. 2004/017452 Pamphlet

  The present invention provides a transparent member for a solar cell having a low reflectance and a low wavelength dependency of the reflectance, and a solar cell in which reflection of incident light is suppressed and light receiving loss is small.

The transparent member for solar cell of the present invention is a transparent member for solar cell having a fine uneven structure on the surface, and the fine uneven structure is formed by transferring the fine uneven structure on the surface of anodized alumina. It is characterized by being.
It is preferable that the fine concavo-convex structure has a plurality of convex portions, and an average period between the convex portions is 400 nm or less.
The solar cell of the present invention is characterized in that the solar cell transparent member of the present invention is arranged such that the surface on which the fine concavo-convex structure is formed is the light incident side.

The transparent member for solar cell of the present invention has a low reflectance, and the wavelength dependency of the reflectance is small.
In the solar cell of the present invention, the reflection of incident light is suppressed, and the light receiving loss is small.

It is sectional drawing which shows an example of the transparent member for solar cells of this invention. It is a block diagram which shows an example of the manufacturing apparatus of the antireflection film used for the transparent member for solar cells of this invention. It is sectional drawing which shows the manufacturing process of the mold which has an anodized alumina on the surface. It is sectional drawing which shows an example of the solar cell of this invention. It is sectional drawing which shows the other example of the solar cell of this invention. It is sectional drawing which shows the other example of the solar cell of this invention. It is a figure which shows the layer structure of the simulation model of the transparent member for solar cells.

  In the present specification, “(meth) acrylate” means acrylate or methacrylate. “Active energy rays” means visible rays, ultraviolet rays, electron beams, plasma, heat rays (infrared rays, etc.) and the like. “Transparent” means transmitting at least light having a wavelength of 400 to 1170 nm.

<Transparent member for solar cell>
FIG. 1 is a cross-sectional view showing an example of the transparent member for solar cell of the present invention. The solar cell transparent member 10 includes a member main body 12 and an antireflection film 16 attached to the member main body 12 via an adhesive layer 14 and having a fine uneven structure (not shown) on the surface.

(Member body)
The member main body 12 is a member that can transmit light. Examples of the material of the member main body 12 include glass, acrylic resin, polycarbonate, styrene resin, polyester, cellulose resin (such as triacetyl cellulose), polyolefin, and alicyclic polyolefin.

  The shape of the member main body 12 is not limited to a plate shape as in the illustrated example, and may be a wedge shape having a triangular cross section in which the other surface is inclined with respect to the surface of one (light incident side). The lens may have a concave or convex surface or both surfaces. When the shape of the member main body 12 is a prism shape or a lens shape, a condensing function can be imparted to the solar cell transparent member 10, and the light receiving efficiency of the solar cell can be improved. Further, the member main body 12 may be provided with a light guide function as employed in a known light guide plate. When the member main body 12 has a light guide function, the light receiving efficiency of the solar cell can be further improved.

(Adhesive layer)
Examples of the adhesive for the adhesive layer 14 include known transparent adhesives, pressure-sensitive adhesives, double-sided adhesive tapes, and pressure-sensitive adhesive tapes.

(Antireflection film)
The antireflection film 16 includes a transparent substrate 18 and a cured resin film 20 having a fine uneven structure (not shown) formed on the surface of the transparent substrate 18.
The transparent substrate 18 is a film or sheet that can transmit light. Examples of the material for the transparent substrate 18 include acrylic resins, polycarbonate resins, styrene resins, polyester resins, cellulose resins (such as triacetyl cellulose), polyolefin resins, and alicyclic polyolefin resins. .

The cured resin film 20 is, for example, a film made of a cured product of an active energy ray curable resin composition described later, and has a fine uneven structure on the surface.
The fine concavo-convex structure is formed by transferring the fine concavo-convex structure on the surface of anodized alumina, and has a plurality of convex portions made of a cured product of the active energy ray-curable resin composition.

  As the fine concavo-convex structure, a so-called moth-eye structure in which a plurality of protrusions (convex portions) having a substantially conical shape or a pyramid shape are arranged is preferable. It is known that the moth-eye structure in which the distance between the protrusions is less than or equal to the wavelength of visible light can be an effective anti-reflection measure by continuously increasing the refractive index from the refractive index of air to the refractive index of the material. ing.

  The average period between the convex portions is preferably not more than the wavelength of visible light, that is, not more than 400 nm. When the convex portions are formed using an anodized alumina mold, the average period between the convex portions is about 100 nm, and therefore, 200 nm or less is more preferable, and 150 nm or less is particularly preferable.

The average period between the convex portions is preferably 25 nm or more from the viewpoint of easy formation of the convex portions. Further, the average period between the convex portions is preferably 80 nm or more, more preferably 130 nm or more, and particularly preferably 150 nm or more, from the viewpoint that the effect of capturing light at a high incident angle by light diffraction can be expected. Since the light incident on the solar cell varies greatly depending on the time and season, the solar cell transparent member 10 that can also be expected to capture light at a high incident angle by light diffraction is a solar cell protective plate, a transparent electrode transparent substrate. Especially useful as such.
The average period between the convex portions is obtained by measuring 50 intervals between adjacent convex portions (distance from the center of the convex portion to the center of the adjacent convex portion) by electron microscope observation, and averaging these values. .

100-500 nm is preferable and, as for the height of a convex part, 150-400 nm is more preferable. When the height of the convex portion is 100 nm or more, the reflectance is sufficiently low and the wavelength dependence of the reflectance is small. If the height of a convex part is 500 nm or less, the scratch resistance of a convex part will become favorable.
The height of the convex portion is obtained by measuring the height of 50 convex portions by electron microscope observation and averaging these values.

  The aspect ratio of the convex portion (height of the convex portion / average period between the convex portions) is preferably 1 to 5, more preferably 1.2 to 4, particularly preferably 1.5 to 3, and most preferably 2-3. preferable. When the aspect ratio of the convex portion is 1 or more, the reflectance is sufficiently low. When the aspect ratio of the convex portion is 5 or less, the scratch resistance of the convex portion is good.

  The shape of the convex part is a shape in which the convex sectional area in the direction perpendicular to the height direction continuously increases in the depth direction from the outermost surface, that is, the sectional shape in the height direction of the convex part is a triangle, trapezoid, A shape such as a bell shape is preferred.

  The difference between the refractive index of the cured resin film 20 and the refractive index of the transparent substrate 18 is preferably 0.2 or less, more preferably 0.1 or less, and particularly preferably 0.05 or less. When the refractive index difference is 0.2 or less, reflection at the interface between the cured resin film 20 and the transparent substrate 18 is suppressed.

  When the surface has a fine concavo-convex structure, if the surface is made of a hydrophobic material, super water repellency can be obtained by the lotus effect, and if the surface is made of a hydrophilic material, super hydrophilicity can be obtained. It is known that

  When the material of the cured resin film 20 is hydrophobic, the water contact angle on the surface of the fine concavo-convex structure is preferably 90 ° or more, more preferably 100 ° or more, and particularly preferably 110 ° or more. If the water contact angle is 90 ° or more, water stains are less likely to adhere, so that sufficient antifouling properties are exhibited. Moreover, since water does not adhere easily, anti-icing can be expected.

  When the material of the cured resin film 20 is hydrophilic, the water contact angle on the surface of the fine concavo-convex structure is preferably 25 ° or less, more preferably 23 ° or less, and particularly preferably 21 ° or less. If the water contact angle is 25 ° or less, the dirt attached to the surface is washed away with water, and oil dirt is less likely to adhere, so that sufficient antifouling properties are exhibited. The water contact angle is preferably 3 ° or more from the viewpoint of suppressing the deformation of the fine concavo-convex structure due to water absorption of the cured resin film 20 and the accompanying increase in reflectance.

<Method for producing transparent member for solar cell>
The solar cell transparent member 10 is manufactured by adhering the member main body 12 and the antireflection film 16 via the adhesive layer 14.

The antireflection film 16 is manufactured as follows using, for example, a manufacturing apparatus shown in FIG.
An active energy ray-curable resin composition from a tank 24 between a roll-shaped mold 22 having a fine concavo-convex structure (not shown) on the surface and a strip-shaped transparent base material 18 that moves along the surface of the roll-shaped mold 22. Supply things.

  The transparent base material 18 and the active energy ray-curable resin composition are nipped between the roll-shaped mold 22 and the nip roll 28 whose nip pressure is adjusted by the pneumatic cylinder 26, and the active energy ray-curable resin composition is Further, it is uniformly distributed between the transparent substrate 18 and the roll-shaped mold 22, and at the same time, is filled in the concave portions of the fine concavo-convex structure of the roll-shaped mold 22.

From the active energy ray irradiation device 30 installed below the roll-shaped mold 22 in a state where the active energy ray-curable resin composition is sandwiched between the roll-shaped mold 22 and the transparent substrate 18, the transparent substrate 18, the active energy ray-curable resin composition is irradiated with active energy rays to cure the active energy ray-curable resin composition, whereby the cured resin film 20 to which the fine uneven structure on the surface of the roll-shaped mold 22 is transferred. Form.
The antireflection film 16 is obtained by peeling the transparent substrate 18 having the cured resin film 20 formed on the surface by the peeling roll 32.

The active energy ray irradiation device 30 is preferably a high-pressure mercury lamp, a metal halide lamp, or the like. In this case, the amount of light irradiation energy is preferably 100 to 10,000 mJ / cm ² .

(Roll mold)
The roll-shaped mold 22 is a mold having anodized alumina on the surface. The roll mold can increase the area of the antireflection film and is easy to produce.

  Anodized alumina is a porous oxide film (alumite) of aluminum and has a plurality of pores (concave portions) on the surface.

A mold having an anodized alumina on the surface can be produced, for example, through the following steps (a) to (e).
(A) A step of forming an oxide film by anodizing roll-shaped 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 the roll-shaped aluminum again in the 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:
As shown in FIG. 3, when the aluminum 34 is anodized, an oxide film 38 having pores 36 is formed.
The purity of aluminum is preferably 99% or more, more preferably 99.5% or more, and particularly preferably 99.8% 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 oxalic acid and sulfuric acid.

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 formation voltage is 30 to 60 V, anodized 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.
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 formation voltage is 25 to 30 V, anodized alumina having highly regular pores with a period of 63 nm can be obtained. The regularity tends to decrease whether the formation voltage is higher or lower than this range.
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.

(B) Process:
As shown in FIG. 3, the regularity of the pores can be improved by once removing the oxide film 38 and using it as the pore generation point 40 for anodic oxidation.

  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 the oxide film and removed. Examples of such a solution include a chromic acid / phosphoric acid mixed solution.

(C) Process:
As shown in FIG. 3, when the aluminum 34 from which the oxide film has been removed is anodized again, an oxide film 38 having cylindrical pores 36 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. 3, a process of expanding the diameter of the pores 36 (hereinafter referred to as a pore diameter expansion 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 the oxide film. 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. 3, when the anodic oxidation in the step (c) and the pore diameter expansion process in the step (d) are repeated, the pores 36 have a shape in which the diameter continuously decreases in the depth direction from the opening. An anodized alumina is formed, and a mold (roll mold 22) having an anodized alumina on the surface is obtained.
The total number of repetitions is preferably 3 times or more, and more preferably 5 times or more. When the number of repetitions is 2 times or less, the diameter of the pores decreases discontinuously. Therefore, the effect of reducing the reflectance of the cured resin film 20 produced using anodized alumina having such pores is insufficient. is there.

  The surface of the anodized alumina may be treated with a release agent so that separation from the cured resin film 20 is easy. Examples of the treatment method include a method of coating a silicone resin or a fluorine-containing polymer, a method of depositing a fluorine-containing compound, a method of coating a fluorine-containing silane coupling agent or a fluorine-containing silicone-based silane coupling agent, and the like.

Examples of the shape of the pore 36 include a substantially conical shape, a pyramid shape, a cylindrical shape, and the like, and a cross-sectional area of the pore in a direction perpendicular to the depth direction, such as a cone shape and a pyramid shape, is a depth from the outermost surface. A shape that continuously decreases in the direction is preferred.
The average period between the pores 36 is not more than the wavelength of visible light, that is, not more than 400 nm. The average period between the pores 36 is preferably 25 nm or more.

The depth of the pores 36 is preferably 100 to 500 nm, and more preferably 150 to 400 nm.
The aspect ratio of the pores 36 (depth of pores / average period between pores) is preferably 1 to 5, more preferably 1.2 to 4, and particularly preferably 1.5 to 3.
The surface of the cured resin film 20 formed by transferring the pores 36 as shown in FIG. 3 has a so-called moth-eye structure.

(Active energy ray-curable resin composition)
The active energy ray-curable resin composition contains a polymerizable compound and a polymerization initiator.
Examples of the polymerizable compound include monomers, oligomers, and reactive polymers having a radical polymerizable bond and / or a cationic polymerizable bond in the molecule.
The active energy ray-curable resin composition may contain a non-reactive polymer and an active energy ray sol-gel reactive composition.

Examples of the monomer having a radical polymerizable bond include a monofunctional monomer and a polyfunctional monomer.
Monofunctional monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, t- Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, alkyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, Phenoxyethyl (meth) acrylate, isobornyl (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, allyl (meth) acrylate, 2-hydroxyethyl ( )) (Meth) acrylate derivatives such as acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate; (meth) acrylic acid, (meth) acrylonitrile; styrene, α -Styrene derivatives such as methylstyrene; (meth) acrylamide derivatives such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and the like. These may be used alone or in combination of two or more.

  Polyfunctional monomers include ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, isocyanuric acid ethylene oxide modified di (meth) acrylate, triethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate , Neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, polybutylene glycol di (Meth) acrylate, 2,2-bis (4- (meth) acryloxypolyethoxyphenyl) propane, 2,2-bis (4- (meth) acryloxyethoxyphenyl) propane, 2,2-bis (4- (3- ( Ta) acryloxy-2-hydroxypropoxy) phenyl) propane, 1,2-bis (3- (meth) acryloxy-2-hydroxypropoxy) ethane, 1,4-bis (3- (meth) acryloxy-2-hydroxypropoxy) ) Butane, dimethylol tricyclodecane di (meth) acrylate, ethylene oxide adduct di (meth) acrylate of bisphenol A, propylene oxide adduct di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) hydroxypivalate Bifunctional monomers such as acrylate, divinylbenzene, and methylenebisacrylamide; pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide Functional tri (meth) acrylate, trimethylolpropane propylene oxide modified triacrylate, trimethylolpropane ethylene oxide modified triacrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate and other trifunctional monomers; succinic acid / trimethylolethane / acrylic acid 4 or more functional monomers such as dipentaerystol hexa (meth) acrylate, dipentaerystol penta (meth) acrylate, ditrimethylolpropane tetraacrylate, tetramethylolmethanetetra (meth) acrylate; bifunctional or more Urethane acrylates, bifunctional or higher functional polyester acrylates, and the like. These may be used alone or in combination of two or more.

  Examples of the monomer having a cationic polymerizable bond include monomers having an epoxy group, an oxetanyl group, an oxazolyl group, a vinyloxy group, and the like, and a monomer having an epoxy group is particularly preferable.

  Examples of the oligomer or reactive polymer include unsaturated polyesters such as a condensate of unsaturated dicarboxylic acid and polyhydric alcohol; polyester (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, epoxy (meth) Examples thereof include acrylates, urethane (meth) acrylates, cationic polymerization type epoxy compounds, homopolymers of the above-described monomers having a radical polymerizable bond in the side chain, and copolymerized polymers.

Examples of non-reactive polymers include acrylic resins, styrene resins, polyurethanes, cellulose resins, polyvinyl butyral, polyesters, thermoplastic elastomers, and the like.
Examples of the active energy ray sol-gel reactive composition include alkoxysilane compounds and alkyl silicate compounds.

As an alkoxysilane compound, the compound of following formula (1) is mentioned.
R ¹ _x Si (OR ² ) _y (1)
^However, R 1, ^{R 1} each represent an alkyl group having 1 to 10 carbon atoms, x, y represents an integer satisfying the relation of x + y = 4.

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

Examples of the alkyl silicate compound include a compound of the following formula (2).
R ³ O [Si (OR ⁵ ) (OR ⁶ ) O] _z R ⁴ (2)
However, R < ³ > -R < ⁶ > 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.

  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, benzoyl Examples include diethoxyphosphine oxide. 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 utilizing a thermosetting reaction, 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, 0.1-10 mass parts is preferable with respect to 100 mass parts of polymeric compounds. When the amount of the polymerization initiator is less than 0.1 parts by mass, the polymerization is difficult to proceed. When the amount of the polymerization initiator exceeds 10 parts by mass, the cured film may be colored or the mechanical strength may be lowered.

  The active energy ray-curable resin composition may contain an antistatic agent, a release agent, an additive such as a fluorine compound for improving the antifouling property, fine particles, and a small amount of a solvent, if necessary.

(Hydrophobic material)
In order to make the water contact angle of the surface of the fine concavo-convex structure of the cured resin film 20 90 ° or more, a fluorine-containing compound or a silicone compound is used as an active energy ray-curable resin composition capable of forming a hydrophobic material. It is preferable to use the composition containing.

Fluorine-containing compounds:
As the fluorine-containing compound, a compound having a fluoroalkyl group represented by the following formula (3) is preferable.
_{- (CF 2) n -X ···} (3).
However, X represents a fluorine atom or a hydrogen atom, n represents an integer greater than or equal to 1, 1-20 are preferable, 3-10 are more preferable, and 4-8 are especially preferable.

  Examples of the fluorine-containing compound include a fluorine-containing monomer, a fluorine-containing silane coupling agent, a fluorine-containing surfactant, and a fluorine-containing polymer.

Examples of the fluorine-containing monomer include a fluoroalkyl group-substituted vinyl monomer and a fluoroalkyl group-substituted ring-opening polymerizable monomer.
Examples of the fluoroalkyl group-substituted vinyl monomer include fluoroalkyl group-substituted (meth) acrylates, fluoroalkyl group-substituted (meth) acrylamides, fluoroalkyl group-substituted vinyl ethers, and fluoroalkyl group-substituted styrenes.

  Examples of the fluoroalkyl group-substituted ring-opening polymerizable monomer include fluoroalkyl group-substituted epoxy compounds, fluoroalkyl group-substituted oxetane compounds, and fluoroalkyl group-substituted oxazoline compounds.

As the fluorine-containing monomer, a fluoroalkyl group-substituted (meth) acrylate is preferable, and a compound of the following formula (4) is particularly preferable.
^{_{CH 2 = C (R 7)}} C (O) O- (CH 2) m - (CF 2) p -X ··· (4).
However, R ⁷ represents a hydrogen atom or a methyl group, X represents a hydrogen atom or a fluorine atom, m represents an integer of 1 to 6, preferably 1 to 3, more preferably 1 or 2, p Represents an integer of 1 to 20, preferably 3 to 10, and more preferably 4 to 8.

As the fluorine-containing silane coupling agent, a fluoroalkyl group-substituted silane coupling agent is preferable, and a compound of the following formula (5) is particularly preferable.
(R ^f ) _a R ⁸ _b SiY _c (5).

R ^f represents a C1-C20 fluorine-substituted alkyl group which may contain one or more ether bonds or ester bonds. Examples of R ^f include 3,3,3-trifluoropropyl group, tridecafluoro-1,1,2,2-tetrahydrooctyl group, 3-trifluoromethoxypropyl group, and 3-trifluoroacetoxypropyl group. It is done.

R ⁸ represents an alkyl group having 1 to 10 carbon atoms. Examples of R ⁸ include a methyl group, an ethyl group, and a cyclohexyl group.

Y represents a hydroxyl group or a hydrolyzable group.
Examples of the hydrolyzable group include an alkoxy group, a halogen atom, R ⁹ C (O) O (wherein R ⁹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms) and the like.
Examples of the alkoxy group include methoxy group, ethoxy group, propyloxy group, i-propyloxy group, butoxy group, i-butoxy group, t-butoxy group, pentyloxy group, hexyloxy group, cyclohexyloxy group, heptyloxy group, Examples include octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, 3,7-dimethyloctyloxy group, lauryloxy group, and the like.
Examples of the halogen atom include Cl, Br, I and the like.
Examples of R ⁹ C (O) O include CH ₃ C (O) O, C ₂ H ₅ C (O) O, and the like.

  a, b, and c are integers satisfying a + b + c = 4 and satisfying a ≧ 1, c ≧ 1, and preferably a = 1, b = 0, and c = 3.

  Fluorine-containing silane coupling agents include 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriacetoxysilane, dimethyl-3,3,3-trifluoropropylmethoxysilane, Examples include decafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane.

  Examples of the fluorine-containing surfactant include a fluoroalkyl group-containing anionic surfactant and a fluoroalkyl group-containing cationic surfactant.

Examples of the fluoroalkyl group-containing anionic surfactant include a fluoroalkylcarboxylic acid having 2 to 10 carbon atoms or a metal salt thereof, disodium perfluorooctanesulfonyl glutamate, 3- [omega-fluoroalkyl (C ₆ -C ₁₁ ) oxy. ] -1-alkyl _(C 3 _{~C 4)} sulfonate, sodium 3- [omega - fluoroalkanoyl _{(C 6 ~C} 8) -N- ethylamino] -1-sodium sulfonic acid, fluoroalkyl _{(C 11} ~ C ₂₀ ) carboxylic acid or a metal salt thereof, perfluoroalkyl carboxylic acid (C _{7 to} C ₁₃ ) or a metal salt thereof, perfluoroalkyl (C _{4 to} C ₁₂ ) sulfonic acid or a metal salt thereof, perfluorooctane sulfonic acid diethanolamine N-propyl-N- (2-hydroxy Chill) perfluorooctane sulfonamide, perfluoroalkyl _(C 6 _{-C 10)} sulfonamide propyl trimethyl ammonium salts, perfluoroalkyl _{(C 6} -C 10)-N-ethylsulfonyl glycine salts, monoperfluoroalkyl _{(C 6} -C ₁₆₎ ethyl phosphoric acid ester, and the like.

Examples of the fluoroalkyl group-containing cationic surfactant include aliphatic quaternary compounds such as fluoroalkyl group-containing aliphatic primary, secondary or tertiary amine acids, and perfluoroalkyl (C ₆ -C ₁₀ ) sulfonamidopropyltrimethylammonium salts. Examples thereof include ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

  Fluorine-containing polymers include polymers of fluoroalkyl group-containing monomers, copolymers of fluoroalkyl group-containing monomers and poly (oxyalkylene) group-containing monomers, and copolymers of fluoroalkyl group-containing monomers and crosslinking reactive group-containing monomers. A polymer etc. are mentioned. The fluorine-containing polymer may be a copolymer with another copolymerizable monomer.

As the fluorine-containing polymer, a copolymer of a fluoroalkyl group-containing monomer and a poly (oxyalkylene) group-containing monomer is preferable.
As the poly (oxyalkylene) group, a group represented by the following formula (6) is preferable.
− (OR ¹⁰ ) _q − (6)
^{However, R 10} represents an alkylene group having 2 to 4 carbon atoms, q represents an integer of 2 or more. Examples of R ¹⁰ include —CH ₂ CH ₂ —, —CH ₂ CH ₂ CH ₂ —, —CH (CH ₃ ) CH ₂ —, —CH (CH ₃ ) CH (CH ₃ ) —, and the like.

The poly (oxyalkylene) group may be composed of the same oxyalkylene unit (OR ¹⁰ ), or may be composed of two or more oxyalkylene units (OR ¹⁰ ). The arrangement of two or more oxyalkylene units (OR ¹⁰ ) may be a block or random.

Silicone compounds:
Examples of the silicone compound include (meth) acrylic acid-modified silicone, silicone resin, silicone silane coupling agent and the like.
Examples of the (meth) acrylic acid-modified silicone include silicone (di) (meth) acrylate.

(Hydrophilic material)
In order to set the water contact angle on the surface of the fine uneven structure of the cured resin film 20 to 25 ° or less, the composition containing the following polymerizable compound as an active energy ray-curable resin composition capable of forming a hydrophilic material It is preferable to use a product.
10 to 50% by mass of a tetrafunctional or higher polyfunctional (meth) acrylate,
30-80% by weight of bifunctional or higher hydrophilic (meth) acrylate,
A polymerizable compound comprising a total of 100% by mass of 0 to 20% by mass of a monofunctional monomer.

As tetrafunctional or higher polyfunctional (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, dipentaerythritol hydroxypenta (meth) acrylate, di Pentaerythritol hexa (meth) acrylate, succinic acid / trimethylolethane / acrylic acid molar mixture 1: 2: 4 condensation reaction mixture, urethane acrylates (manufactured by Daicel-Cytec: EBECRYL220, EBECRYL1290K, EBECRYL1290K, EBECRYL5129, EBECRYL8210, EBECRYL 8301, KRM 8200), polyether acrylates (manufactured by Daicel-Cytec: EBEC) YL81), modified epoxy acrylates (manufactured by Daicel-Cytec: EBECRYL3416), polyester acrylates (manufactured by Daicel-Cytech: EBECRYL450, EBECRYL657, EBECRYL800, EBECRYL810, EBECRYL8111, EBECRYL81L, EBECRYL81L It is done. These may be used alone or in combination of two or more.
The polyfunctional (meth) acrylate having 4 or more functional groups is more preferably a polyfunctional (meth) acrylate having 5 or more functional groups.

  The proportion of the tetrafunctional or higher polyfunctional (meth) acrylate is preferably 10 to 50% by mass, more preferably 20 to 50% by mass, and particularly preferably 30 to 50% by mass from the viewpoint of water resistance and chemical resistance. If the ratio of the tetrafunctional or higher polyfunctional (meth) acrylate is 10% by mass or more, the elastic modulus is increased and the scratch resistance is improved. If the ratio of the tetrafunctional or higher polyfunctional (meth) acrylate is 50% by mass or less, small cracks are hardly formed on the surface, and the appearance is hardly deteriorated.

Long-chain polyethylene such as Aronix M-240, Aronix M260 (manufactured by Toagosei Co., Ltd.), NK ester AT-20E, NK ester ATM-35E (manufactured by Shin-Nakamura Chemical Co., Ltd.) Examples thereof include polyfunctional acrylates having glycol and polyethylene glycol dimethacrylate. These may be used alone or in combination of two or more.
In the polyethylene glycol dimethacrylate, the total of the average repeating units of the polyethylene glycol chain present in one molecule is preferably 6 to 40, more preferably 9 to 30, and particularly preferably 12 to 20. If the average repeating unit of the polyethylene glycol chain is 6 or more, the hydrophilicity is sufficient and the antifouling property is improved. When the average repeating unit of the polyethylene glycol chain is 40 or less, the compatibility with a polyfunctional (meth) acrylate having 4 or more functionalities is improved, and the active energy ray-curable resin composition is hardly separated.

  30-80 mass% is preferable and, as for the ratio of bifunctional or more hydrophilic (meth) acrylate, 40-70 mass% is more preferable. When the ratio of the bifunctional or higher hydrophilic (meth) acrylate is 30% by mass or more, the hydrophilicity is sufficient and the antifouling property is improved. When the proportion of the bifunctional or higher hydrophilic (meth) acrylate is 80% by mass or less, the elastic modulus is increased and the scratch resistance is improved.

As the monofunctional monomer, a hydrophilic monofunctional monomer is preferable.
Examples of the hydrophilic monofunctional monomer include monofunctional (meth) acrylate having a polyethylene glycol chain in the ester group such as M-20G, M-90G, M-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.), hydroxyalkyl (meth) acrylate, etc. And cationic monomers such as monofunctional (meth) acrylates having a hydroxyl group in the ester group, monofunctional acrylamides, methacrylamidopropyltrimethylammonium methyl sulfate, and methacryloyloxyethyltrimethylammonium methyl sulfate.
Moreover, as a monofunctional monomer, you may use viscosity modifiers, such as acryloyl morpholine and vinyl pyrrolidone, adhesive improvement agents, such as acryloyl isocyanate which improves the adhesiveness to a member, etc.

  The proportion of the monofunctional monomer is preferably 0 to 20% by mass, and more preferably 5 to 15% by mass. By using a monofunctional monomer, the adhesion between the member and the cured resin is improved. When the proportion of the monofunctional monomer is 20% by mass or less, antifouling property or scratch resistance is sufficient without a shortage of tetrafunctional or higher polyfunctional (meth) acrylate or bifunctional or higher hydrophilic (meth) acrylate. Expressed in

  The monofunctional monomer may be blended in the active energy ray-curable resin composition in an amount of 0 to 35 parts by mass as a polymer having a low polymerization degree obtained by (co) polymerizing one type or two or more types. As a polymer having a low degree of polymerization, 40/60 of monofunctional (meth) acrylates having a polyethylene glycol chain in an ester group such as M-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.) and methacrylamide propyltrimethylammonium methyl sulfate. Copolymer oligomer (MRC Unitech Co., Ltd., MG polymer) and the like can be mentioned.

  In the transparent member 10 for solar cells described above, the surface has a fine uneven structure, and the fine uneven structure is formed by transferring the fine uneven structure on the surface of anodized alumina. The reflectance at the surface is low and the wavelength dependence of the reflectance is small.

  In addition, the solar cell transparent member of the present invention is not limited to the solar cell transparent member 10 in the illustrated example. For example, in the solar cell transparent member 10, the fine concavo-convex structure is formed on the surface of the cured resin film 20 of the antireflection film 16, but on the surface of the transparent substrate 18 without providing the cured resin film 20. It may be formed directly, or may be formed directly on the surface of the member main body 12 without sticking the antireflection film 16. However, the cured resin film 20 of the antireflection film 16 from the point that the fine uneven structure can be efficiently formed using the roll-shaped mold 22 and the antireflection film 16 can be reattached when the fine uneven structure is damaged. It is preferable that a fine concavo-convex structure is formed on the surface.

<Solar cell>
In the solar cell of the present invention, the transparent member for solar cell of the present invention is arranged such that the surface on the side where the fine uneven structure is formed is the light incident side.
As the solar cell, a pn junction type, a dye-sensitized type, and the like are known, but the solar cell of the present invention may be any type of solar cell.

(Pn junction type)
FIG. 4 is a cross-sectional view showing an example of the solar cell of the present invention. The solar cell 50 includes a plurality of solar cell elements 54 connected via an interconnector 52; and the surface on the light receiving surface side of the solar cell element 54 on which the fine concavo-convex structure is formed is the light incident side. The solar cell transparent member 10 disposed on the solar cell element 54; the second member 56 disposed on the side opposite to the light receiving surface of the solar cell element 54; and the solar cell transparent member 10 and the second member 56 are bonded together. At the same time, it has a transparent resin layer 58 for fixing the solar cell element 54 therebetween.

The solar cell element 54 is a pn junction solar cell element having a structure in which a p-type semiconductor and an n-type semiconductor are joined. Examples of the pn junction solar cell element include silicon-based, inorganic compound-based, and organic compound-based devices.
Examples of the material of the second member 56 include glass, acrylic resin, polycarbonate, styrene resin, polyester, cellulose resin (such as triacetyl cellulose), polyolefin, and alicyclic polyolefin.
Examples of the material of the transparent resin layer 58 include polyvinyl butyral and ethylene-vinyl acetate copolymer.

(Dye-sensitized type)
FIG. 5 is a cross-sectional view showing another example of the solar cell of the present invention. The solar cell 60 includes a solar cell transparent member 10 disposed such that the surface on which the fine uneven structure is formed becomes the light incident side; and the fine uneven structure of the solar cell transparent member 10 is formed. A first transparent electrode 62 formed on the surface opposite to the first side; a metal oxide comprising a metal oxide semiconductor 66 formed on the surface of the first transparent electrode 62 and adsorbing the spectral sensitizing dye 64 A second semiconductor member disposed opposite to the metal oxide semiconductor film; and a second member formed on a surface of the second member facing the metal oxide semiconductor film. Two transparent electrodes 72; a counter electrode 74 formed on the surface of the second transparent electrode 72; and an electrolyte 76 sealed between the metal oxide semiconductor film 68 and the counter electrode 74.

Examples of the first transparent electrode 62 and the second transparent electrode 72 include a conductive metal oxide thin film. Examples of the conductive metal oxide include indium oxide (ITO) doped with tin.
Examples of the spectral sensitizing dye 64 include metal complexes (such as metal phthalocyanines) and organic dyes (such as cyanine dyes).
Examples of the metal oxide semiconductor 66 include titanium oxide.
Examples of the material of the second member 70 include glass, acrylic resin, polycarbonate, styrene resin, polyester, cellulose resin (such as triacetyl cellulose), polyolefin, and alicyclic polyolefin.
Examples of the counter electrode 74 include a platinum electrode.
As the electrolyte ^76, _I ^- / I ₃ - include redox electrolyte such systems.

(Prism type)
FIG. 6 is a cross-sectional view showing another example of the solar cell of the present invention. The solar cell 80 is attached to the incident-side surface of the prism-shaped member main body 12 having a triangular cross section whose other surface is inclined with respect to the incident-side surface via an adhesive layer (not shown). The solar cell transparent member 10 composed of the antireflection film 16 and the reflective layer 82 provided on the other surface of the member body 12; the sunlight incident on the member body 12 through the antireflection film 16 is the member The solar power generation cell 84 is provided on the end surface of the member main body 12 which is condensed while being reflected in the main body 12.

The solar power generation cell 84 may be a pn junction type or a dye sensitized type.
Examples of the reflective layer 82 include a metal thin film and a metal vapor deposition film.

  In the solar cell of the present invention described above, the transparent member for solar cell of the present invention is arranged so that the surface on which the fine concavo-convex structure is formed is the light incident side. The reflection of light is suppressed, and the loss of light reception is small.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. The incident angle in the present embodiment is an angle when the direction orthogonal to the surface of the cured resin film is 0 °.

(Pores of anodized alumina)
A part of the anodized alumina is shaved, platinum is vapor-deposited on the cross section for 1 minute, and the cross section is subjected to an acceleration voltage of 3.00 kV using a field emission scanning electron microscope (JSM-7400F, manufactured by JEOL Ltd.). Observed and measured pore spacing and pore depth. Each measurement was performed for 50 points, and the average value was obtained.

(Convex part of cured resin film)
Platinum was vapor-deposited on the fracture surface of the cured resin film for 10 minutes, and the cross-section was observed in the same manner as the anodized alumina, and the interval between the convex portions and the height of the convex portions were measured. Each measurement was performed for 50 points, and the average value was obtained.

(Weighted average reflectance)
About the transparent member for solar cells coated with matte black after roughening the surface of the transparent member for solar cells where the fine uneven structure is not formed, a spectrophotometer (manufactured by Hitachi, Ltd., U-4000) The relative reflectance of the surface of the cured resin film was measured in the range of an incident angle of 5 ° and a wavelength of 380 to 780 nm, and calculated according to JIS R3106.

(Water contact angle)
Using a contact angle measuring device (manufactured by Kruss, DSA10-Mk2), 1.6 μL of water was dropped on the surface of the fine concavo-convex structure of the cured resin film, and after 10 seconds of dropping, the water contact angle was 1 second apart. 10 points were measured, and the average value was obtained. Furthermore, the same operation was performed 3 times by changing the position where water was dropped, and the average value of 4 times in total was further averaged.

(Wavelength dependence of reflectance)
About the transparent member for solar cells coated with matte black after roughening the surface of the transparent member for solar cells where the fine uneven structure is not formed, a spectrophotometer (manufactured by Hitachi, Ltd., U-4000) The relative reflectance of the surface of the cured resin film was measured at an incident angle of 5 °, wavelengths of 450, 550, 650, and 750 nm.

(Incident angle dependence of weighted average reflectance)
About the transparent member for solar cells coated with matte black after roughening the surface of the transparent member for solar cells where the fine uneven structure is not formed, a spectrophotometer (manufactured by Hitachi, Ltd., U-4000) The weighted average reflectance of the surface of the cured resin film was measured according to JIS R3106 at an incident angle of 20, 30, 40, 50, and 60 °.

(Power generation improvement rate)
The improvement rate of the power generation amount of the solar cell in which the antireflection film was attached to the transparent substrate on the incident side was determined with respect to the power generation amount of the solar cell in which the antireflection film was not attached to the incident side transparent substrate. The measurement conditions for the amount of power generation were the conditions when the solar cell was installed at a 20 ° inclination at a 20 ° inclination when the summer was clear in Tokyo.

[Manufacture of roll-shaped mold a]
A roll made of aluminum having a purity of 99.99% was electropolished in a perchloric acid / ethanol mixed solution (1/4 volume ratio).
(A) Process:
The roll was anodized in a 0.5 M oxalic acid aqueous solution for 6 hours under the conditions of a direct current of 40 V and a temperature of 16 ° C.
(B) Process:
The roll on which the oxide film was formed was immersed in a 6% by mass phosphoric acid / 1.8% by mass chromic acid mixed aqueous solution for 6 hours to remove the oxide film.

(C) Process:
The roll was anodized in a 0.3 M oxalic acid aqueous solution for 30 seconds under the conditions of a direct current of 40 V and a temperature of 16 ° C.
(D) Process:
The roll on which the oxide film was formed was immersed in 5 mass% phosphoric acid at 32 ° C. for 8 minutes to carry out pore diameter expansion treatment.

(E) Process:
The step (c) and the step (d) are repeated a total of 5 times to obtain a roll-shaped mold a having anodized alumina having substantially conical pores with an average period of 100 nm and a depth of 240 nm formed on the surface. It was.
The roll-shaped mold a was immersed in a 0.1% by weight diluted solution of OPTOOL DSX (manufactured by Daikin Chemicals Sales Co., Ltd.) and air-dried overnight to subject the oxide film surface to a fluorination treatment.

[Manufacture of roll-shaped mold b]
Anodization having substantially conical pores having an average period of 100 nm and a depth of 180 nm in the same manner as in the production of the roll mold a, except that the anodic oxidation time in step (c) was changed to 25 seconds. A roll mold b having alumina formed on the surface was obtained.
The roll-shaped mold b was immersed in a 0.1% by weight diluted solution of OPTOOL DSX (manufactured by Daikin Chemicals Sales Co., Ltd.) and air-dried overnight to subject the oxide film surface to fluorination treatment.

[Preparation of active energy ray-curable resin composition]
Each component was mixed in the ratio shown in Table 1 and Table 2, and active energy ray-curable resin compositions A and B were prepared.

Abbreviations in the table are as follows.
DPHA: dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., Aronix M400),
M260: polyethylene glycol diacrylate n = 13-14 (Toagosei Co., Ltd., Aronix M260),
HEA: 2-hydroxyethyl acrylate,
Ir184: 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals).

Abbreviations in the table are as follows.
TAS: trimethylolethane, acrylic acid, succinic anhydride condensed ester,
C6DA: 1,6-hexanediol diacrylate,
X-22-1602: radical polymerizable silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd.)
Ir184: 1-hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals).

[Production of film]
75 parts by mass of a rubber-containing multistage polymer obtained by polymerizing methyl methacrylate, butyl acrylate, methyl acrylate, 1,3-butadiene and allyl methacrylate, and 25 parts by mass of an acrylic resin (BR80 manufactured by Mitsubishi Rayon Co., Ltd.) The part was melt-extruded in advance and then formed into a 200 μm thick acrylic resin film.

[Example 1]
An antireflection film was produced using the production apparatus shown in FIG.
As the roll mold 22, the roll mold a was used.
The active energy ray curable resin composition A was used as the active energy ray curable resin composition.
As the transparent substrate 18, the acrylic resin film was used.
The active energy ray-curable resin composition A was cured by irradiating the coating film of the active energy ray-curable resin composition A with ultraviolet rays having an integrated light amount of 3200 mJ / cm ² from the transparent substrate 18 side.

About the obtained antireflection film, the average period between convex parts and the height of the convex part were measured. The results are shown in Table 3.
The obtained antireflection film was attached to a glass plate having a thickness of 2 mm via a double-sided adhesive tape (manufactured by Nitto Denko Corporation, CS9621) to obtain a transparent member for solar cell. About the transparent member for solar cells, the weighted average reflectance and the water contact angle were measured. The results are shown in Table 3.

[Example 2]
An antireflection film and a transparent member for solar cell were obtained in the same manner as in Example 1 except that the active energy ray-curable resin composition B was used. About the antireflection film, the average period between convex parts and the height of the convex parts were measured. The results are shown in Table 3. Moreover, about the transparent member for solar cells, the weighted average reflectance and the water contact angle were measured. The results are shown in Table 3. Moreover, the wavelength dependence of the reflectance was measured. The results are shown in Table 4. Moreover, the incident angle dependence of the weighted average reflectance was measured. The results are shown in Table 5.

Example 3
An antireflection film and a transparent member for solar cell were obtained in the same manner as in Example 1 except that the roll mold b was used as the roll mold 22 and the active energy ray-curable resin composition B was used. About the antireflection film, the average period between convex parts and the height of the convex parts were measured. The results are shown in Table 3. Moreover, the wavelength dependence of the reflectance was measured about the transparent member for solar cells. The results are shown in Table 4. Moreover, the incident angle dependence of the weighted average reflectance was measured. The results are shown in Table 5.

As the aspect ratio of the convex portion increases, the wavelength dependence decreases. Further, the reflection was low in a wide wavelength region.
Moreover, when the aspect ratio of the convex portion was increased, low reflection was obtained even at a high incident angle.

Example 4
An antireflection film was obtained in the same manner as in Example 2 except that a polyethylene terephthalate film (thickness: 38 μm) having one surface treated with an adhesive was used as the transparent substrate 18.
The obtained antireflection film was affixed to the transparent substrate on the incident side of the crystalline silicon solar cell sealed with polyvinyl butyral to obtain a solar cell in which a fine uneven structure was arranged on the light incident side. About the solar cell, the improvement rate of the power generation amount with respect to the incident angle was obtained. The results are shown in Table 6.

  The amount of power generation was improved compared to the case without an antireflection film at all incident angles. Moreover, the power generation amount tended to improve greatly as the incident angle increased. The amount of power generation increased by about 7% per day.

Example 5
The antireflection film obtained in Example 4 was attached to the incident-side surface of the member body 12 of the prism type solar cell shown in FIG. 6 to obtain a solar cell in which a fine uneven structure was arranged on the light incident side. . As the solar power generation cell 84, a crystalline silicon solar cell was used. The angle between the surface of the member body 12 on which the antireflection film is provided and the end face on which the solar power generation cell 84 is provided is 76 °, and the angle between the surface on which the reflective layer 82 is provided and the end face on which the solar power generation cell 84 is provided is 90 °. It was. About the solar cell, the improvement rate of the power generation amount with respect to the incident angle was obtained. The results are shown in Table 7.

  The amount of power generation was improved compared to the case without an antireflection film at all incident angles. Moreover, the power generation amount tended to improve greatly as the incident angle increased. About 5% of power generation per day has improved.

Hereinafter, the effect of the present invention was confirmed by simulation.
As a simulation model of the transparent member for solar cell, the layer structure shown in FIG. 7 was used. The simulation model 90 includes, in order from the top, a polymethacrylate layer 92 (thickness: 0.2 mm, refractive index at a wavelength of 900 nm) formed with a spacing of 100 nm so that the plurality of convex portions 19 are arranged in a plane hexagonal lattice. : 1.482, extinction coefficient: 6.49 × 10 ⁻²³ ), polyethylene terephthalate layer 94 (thickness: 0.037 mm, refractive index at 900 nm wavelength: 1.667, extinction coefficient: 1.65 × 10 ^{− 24} ) and the absorption layer 100 (there is no thickness because of the boundary condition).

  As simulation software, “Diffract MOD (Rsoft)” was used, and Maxwell's equations were solved based on the Rigorous Coupled Wave Analysis (RCWA) method.

[Examples 6 to 10]
TW, BW and H in the simulation model of FIG. 7 were set to the values shown in Table 8, and the reflectance for incident light (wavelength: 500 nm, 800 nm, 1000 nm) with an incident angle α of 5 ° was obtained by simulation. The results are shown in Table 8.

  The transparent member for solar cells of the present invention is useful as a protective plate for solar cells, a transparent substrate for transparent electrodes, a light collector, a light guide plate, and the like.

10 Transparent member for solar cell 50 Solar cell 60 Solar cell 80 Solar cell

Claims (3)

A transparent member for solar cells having a fine uneven structure on the surface,
The transparent member for solar cells, wherein the fine uneven structure is formed by transferring the fine uneven structure on the surface of anodized alumina.   The solar cell transparent member according to claim 1, wherein the fine concavo-convex structure has a plurality of convex portions, and an average period between the convex portions is 400 nm or less.   A solar cell in which the transparent member for a solar cell according to claim 1 or 2 is disposed such that a surface on which the fine concavo-convex structure is formed is an incident side of light.

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