JP2008168488A - Reflection-proof electroconductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent reflection-proof electroconductive film which uses a polyester film as a base film and has high rate of light beam permeability and excellent reflection proofness while featuring dimensional stability, especially the usefulness as a solar cell base film. <P>SOLUTION: This reflection-proof electroconductive film comprises a biaxially oriented polyester film, a reflection-proof layer formed on the biaxially oriented polyester film and a transparent electroconductive layer formed on the reflection-proof layer. In addition, the reflection-proof layer contains a metallic compound and has a refractive index and a thickness which can meet the conditions of the following formulae (1) and (2): (1) 105-40.0×N≤d≤180-40.0×N, (2) 1.75≤N≤2.0 (in the formulae (1) and (2), N is the refractive index of the reflection-proof layer and d is the thickness (nm) of the reflection-proof layer). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antireflection conductive film.

Polyester films have been conventionally used for various applications, and in recent years, they have also been used as members for solar cells.
Solar cells include a rigid type using glass as a substrate material and a flexible type using a film as a substrate material. Recently, a flexible type solar cell has been widely used as an auxiliary power source for mobile communication devices such as watches, mobile phones, and mobile terminals.

Japanese Patent Laid-Open No. 1-198081 JP-A-2-260577 Japanese Patent Publication No. 6-5782 JP 2005-216504 A JP 2005-158727 A Japanese Patent Laid-Open No. 2003-3272 JP-A-6-318728 Japanese Patent Laid-Open No. 2003-257509 Japanese Patent Laid-Open No. 2001-077396 JP 2005-244073 A

In order to improve the power generation efficiency of the solar cell, it is necessary to take a sufficient amount of light incident on the photoelectric conversion element, so it is important to reduce the reflectance.
The present invention provides a transparent antireflection conductive film having a high light transmittance and excellent antireflection properties while using a polyester film as a base film and having dimensional stability, in particular, a solar cell base. It is an object of the present invention to provide an antireflection conductive film useful as a film.

That is, the present invention comprises a biaxially stretched polyester film, an antireflection layer provided thereon, and a transparent conductive layer provided on the antireflection layer. The antireflection conductive film is characterized in that the refractive index and the thickness satisfy the conditions of the following formulas (1) and (2).
105-40.0 × N ≦ d ≦ 180-40.0 × N (1)
1.75 ≦ N ≦ 2.0 (2)
(In the formula, N is the refractive index of the antireflection layer, and d is the thickness (nm) of the antireflection layer.)
Moreover, this invention is said antireflection electroconductive film used as a member of a solar cell.

  According to the present invention, a polyester film is used as a base film, and a transparent antireflection conductive film having high light transmittance and excellent antireflection properties while providing dimensional stability is provided. An antireflection conductive film useful as a base film can be provided.

[polyester]
In the present invention, a biaxially stretched polyester film is used as the base film that supports the conductive layer. The polyester constituting the biaxially stretched polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

  Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate. The polyester may be a homopolymer or a copolymer obtained by copolymerizing the third component, but a homopolymer is preferred. Among these polyesters, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable because of a good balance between mechanical properties and optical properties. Polyethylene-2,6-naphthalate is particularly preferable because it has a high mechanical strength, a low thermal shrinkage rate, and a small amount of oligomer generated during heating.

  As the polyethylene terephthalate, those having an ethylene terephthalate unit of preferably 90 mol% or more, more preferably 95 mol% or more, particularly preferably 97 mol% or more are preferably used. As polyethylene-2,6-naphthalate, it is preferable to use those having polyethylene-2,6-naphthalate units of preferably 90 mol% or more, more preferably 95 mol% or more, particularly preferably 97 mol% or more.

  The intrinsic viscosity of the polyester is preferably 0.40 dl / g or more, more preferably 0.40 to 0.90 dl / g. If the intrinsic viscosity is less than 0.40 dl / g, process cutting may occur frequently, which is not preferable. If it exceeds 0.90 dl / g, melt extrusion becomes difficult because of high melt viscosity, and the polymerization time is long and uneconomical. There is not preferable.

  Polyester can be obtained by a conventionally known method. For example, it can be obtained by a method of directly obtaining a low-polymerization degree polyester by reaction of dicarboxylic acid and glycol. Alternatively, it can be obtained by a method in which a lower alkyl ester of dicarboxylic acid and glycol are reacted with each other using a transesterification catalyst, and then a polymerization reaction is performed in the presence of a polymerization reaction catalyst. As the transesterification reaction catalyst, conventionally known compounds such as sodium, potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, and cobalt can be used. Examples of the polymerization reaction catalyst include those conventionally known, for example, antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds represented by germanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate, or a portion thereof. Titanium compounds such as hydrolysates, titanyl ammonium oxalate, potassium titanyl oxalate, and titanium trisacetylacetonate can be used. When polymerization is performed via a transesterification reaction, a phosphorus compound such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, or normal phosphoric acid is usually added for the purpose of deactivating the transesterification catalyst before the polymerization reaction. However, the content in the polyester as the phosphorus element is preferably 20 to 100 ppm from the viewpoint of thermal stability. The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization under heating under reduced pressure or in an inert gas stream such as nitrogen.

[Biaxially stretched polyester film]
The biaxially stretched polyester film used as the base film in the present invention preferably has an in-plane refractive index of 1.63 to 1.78. An average in-plane refractive index of less than 1.63 is not preferable because the polymer is not sufficiently oriented and sufficient thermal dimensional stability cannot be obtained. On the other hand, if it exceeds 1.78, sufficient toughness of the film cannot be obtained and handling becomes difficult, which is not preferable.

  In the biaxially stretched polyester film of the present invention, the absolute value of the difference in thermal shrinkage between the longitudinal direction and the width direction of the film when treated at 200 ° C. for 10 minutes is preferably 0.8% or less, more preferably 0.8. 5% or less, particularly preferably 0.3% or less. If the absolute value of the difference in heat shrinkage ratio exceeds 0.8%, it is not preferable because the dimensional change occurs in the heating process for battery preparation, the adhesiveness with the photoelectric conversion layer, etc. deteriorates and stable photovoltaic power generation performance cannot be obtained. .

  In addition, the thermal shrinkage in the longitudinal direction of the film when the biaxially stretched polyester film in the present invention is treated at 200 ° C. for 10 minutes is preferably smaller in order to improve the adhesion with the layer placed on the film, Preferably it is 0-0.5%, More preferably, it is 0-0.3%.

  The biaxially stretched polyester film of the present invention preferably has a light transmittance at a wavelength of 370 nm of 3% or less, and a light transmittance at 400 nm of preferably 70% or more. The light transmittance is a numerical value measured using a spectrophotometer MPC3100 manufactured by Shimadzu Corporation. This light transmittance can be obtained by using a polyester containing a monomer that absorbs ultraviolet rays, such as 2,6-naphthalenedicarboxylic acid, or by incorporating an ultraviolet absorber in the polyester.

  When an ultraviolet absorber is used, examples of the ultraviolet absorber include 2,2′-p-phenylenebis (3,1-benzoxazin-4-one) and 2,2′-p-phenylenebis (6-methyl-). 3,1-benzoxazin-4-one), 2,2′-p-phenylenebis (6-chloro-3,1-benzoxazin-4-one), 2,2 ′-(4,4′-diphenylene) And cyclic imino ester compounds such as bis (3,1-benzoxazin-4-one) and 2,2 ′-(2,6-naphthylene) bis (3,1-benzoxazin-4-one). it can.

  The thickness of the polyester film in the present invention is preferably 10 to 500 μm, more preferably 20 to 400 μm, and particularly preferably 50 to 300 μm, from the viewpoint of achieving both mechanical strength and productivity.

  Next, the preferable manufacturing method of the biaxially stretched polyester film in this invention is demonstrated. The glass transition temperature is abbreviated as Tg. First, polyester is melt-extruded into a film shape, cooled and solidified with a casting drum to form an unstretched film, and this unstretched film is once or twice or more in the longitudinal direction at Tg to (Tg + 60) ° C. The film is stretched to 6 times, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C., and further heat-treated at 160 to 255 ° C. for 1 to 60 seconds as necessary. Can be obtained. In order to reduce the difference between the heat shrinkage rates in the longitudinal direction and the width direction of the biaxially stretched polyester film and to further reduce the heat shrinkage in the longitudinal direction, for example, in the heat treatment step disclosed in JP-A-57-57628, It is possible to use a method of shrinking in the direction or a method of relaxing heat treatment in a suspended state as disclosed in JP-A-1-275031.

[Antireflection layer]
In the antireflection conductive film of the present invention, the antireflection layer is provided on the polyester film. That is, the antireflection layer is provided between the polyester film and the transparent conductive layer. In the antireflection conductive film of the present invention, it is necessary that the refractive index and thickness of the antireflection layer satisfy the conditions of the following formulas (1) and (2).
105-40.0 × N ≦ d ≦ 180-40.0 × N (1)
1.75 ≦ N ≦ 2.0 (2)
(In the formula, N is the refractive index of the antireflection layer, and d is the thickness (nm) of the antireflection layer.)

  When the refractive index N is less than 1.75, the reflection between the antireflection layer and the film is not sufficiently suppressed, and when the refractive index N exceeds 2.0, the reflection between the antireflection layer and the transparent conductive layer is sufficient. The target low reflectance is not achieved without being suppressed. The refractive index N is preferably 1.78 to 1.95.

The thickness d of the antireflection layer needs to be in the range represented by the above formula (1). In this range, in order to reduce the reflectance at the absorption wavelength of the target solar cell, the reflection between the antireflection layer-atmosphere and the reflection between the antireflection layer-film interfere and cancel each other. Thus, an antireflection function can be obtained. If the thickness d is outside the range defined by the formula (1), the reflectance is not sufficiently lowered due to light interference.
The number of antireflection layers is preferably 3 or less from the viewpoint of economy and productivity. More preferably, it consists of one layer.

  In the present invention, the antireflection layer contains a metal compound. As metal compounds, zinc oxide, zinc sulfide, titanium oxide, zirconium oxide, tungsten oxide, iron oxide, copper oxide calcium oxide, aluminum oxide, silicon oxide, barium titanate, barium oxide, magnesium oxide, magnesium fluoride, titanic acid Examples include strontium, indium oxide, and alloys thereof. One kind of metal compound may be used, or a plurality of combinations may be used for adjusting the refractive index.

  In the present invention, the antireflection layer preferably comprises 10% by weight or more, more preferably 20% by weight or more of a metal compound. If the content of the metal compound in the antireflection layer is less than 10% by weight, the necessary refractive index cannot be obtained, which is not preferable.

  The antireflection layer contains a metal compound as described above, but may further contain a polymer component, an additive, or the like. In particular, when an antireflection layer is provided by coating, when a polymer component is used, a good coating film, that is, an antireflection layer can be obtained rather than acting as a binder.

Examples of the polymer component include polyester resin, acrylic resin, urethane acrylic resin, urethane resin, silicon acrylic resin, melamine resin, polysiloxane resin, polymethacrylic resin and polystyrene resin, polyimide resin, UV curable resin, epoxy resin, and these Cross-linked products can be mentioned. These resins can be used alone or as a mixture of two or more.
The polymer component may be used in the form of a solution or in the form of fine particles, or may be applied and reacted on the film in the form of a precursor.

  Examples of the additive include an oxazoline group-containing compound and a surfactant. These may be used in combination. By using together, the adhesiveness of an antireflection layer and a base film becomes high, and it is preferable.

  As a method of providing an antireflection layer on a polyester film, and a method of laminating a plurality of layers in some cases, for example, a dry coating method such as a vacuum deposition method, a sputtering method, a CVD method, an ion plating method, etc. can be used. A wet coating method such as a gravure method, a reverse method, or a die method can be used.

  Prior to the formation of the antireflection layer, the polyester film may be subjected to pretreatment such as corona discharge treatment, plasma treatment, sputter etching treatment, electron beam irradiation treatment, ultraviolet ray irradiation treatment, primer treatment, and easy adhesion treatment.

[Transparent conductive layer]
As the transparent conductive layer, for example, a conductive metal oxide or a carbon material can be used.
Examples of the conductive metal oxide include gallium-doped zinc oxide, aluminum-doped zinc oxide, germanium-doped zinc oxide, boron-doped zinc oxide, titanium-doped zinc oxide, fluorine-doped tin oxide, indium-tin composite oxide (ITO), An indium-zinc composite oxide (IZO) or a metal thin film (eg, platinum, gold, silver, copper, aluminum) can be used.

  The transparent conductive layer may be a single layer, a laminate of two or more layers, or a composite structure. The transparent conductive layer is preferably made of ITO or IZO. In this case, high light transmittance and low resistance can be obtained.

  The surface resistance of the transparent conductive layer is preferably 100Ω / □ or less, more preferably 40Ω / □ or less. If it exceeds 100Ω / □, the resistance in the battery becomes too large and the photovoltaic power generation efficiency decreases, which is not preferable.

  The thickness of the transparent conductive layer is preferably 100 to 500 nm. If the thickness is less than 100 nm, the surface resistance value cannot be lowered sufficiently, which is not preferable. If the thickness exceeds 500 nm, the light transmittance is lowered and the transparent conductive layer is easily broken.

  The transparent conductive layer can be formed using, for example, a dry coating method such as a vacuum deposition method, a sputtering method, a CVD method, an ion plating method, or a coating method, such as a gravure method, a reverse method, or the like. A wet coating method such as a method or a die method can be used.

[Easily adhesive layer]
The antireflection conductive film of the present invention is preferably used as a member for solar cells. An easy adhesion layer may be laminated for the purpose of improving the handleability in the manufacturing process, for example, the handleability in continuous production using a roll of film, and for the purpose of improving the adhesion to other members. .

  When providing the easily bonding layer in this case, the thickness becomes like this. Preferably it is 1-200 nm, More preferably, it is 10-150 nm. When the thickness of the easy-adhesion layer is less than 1 nm, the effect of improving the adhesion is poor, and when it exceeds 200 nm, the easy-adhesion layer tends to cause cohesive failure and the adhesion may be lowered.

  As the constituent material of the easy-adhesion layer, a material exhibiting excellent adhesion to both the polyester film and the conductive layer, photoelectric conversion element, and the like laminated thereon may be used. For example, a polyester resin, an acrylic resin, a urethane acrylic resin, a silicon acrylic resin, a melamine resin, and a polysiloxane resin can be exemplified. These resins may be used alone or as a mixture of two or more.

Next, the present invention will be described in more detail with reference to examples.
In addition, each characteristic value in an example was measured with the following method. “Parts” represents parts by weight.
(1) Intrinsic viscosity Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 35 ° C.

(2) Film thickness Using a micrometer (K-402B type manufactured by Anritsu Co., Ltd.), measurements were made at 10 cm intervals in the continuous film forming direction and in the width direction of the film, and the film thicknesses at 300 locations were measured in total. The average value of the film thicknesses of the obtained 300 locations was calculated and used as the film thickness.

(3) Heat shrinkage rate The film was held in an oven set at 200 ° C. for 10 minutes in an unstrained state, and the dimensional change before and after each heat treatment in the film longitudinal direction (MD) and width direction (TD) Was calculated by the following equation as the heat shrinkage rate, and the heat shrinkage rate in the longitudinal direction (MD) and the width direction (TD) was obtained. However, L ₀ is the distance between the gauge marks before heat treatment, L is漂点distance after heat treatment.
Thermal shrinkage% = ((L ₀ −L) / L ₀ ) × 100

(4) Thickness of antireflection layer A small piece of film is embedded in an epoxy resin (Refotech Co., Ltd. Epomount) and sliced to 50 nm thickness together with the embedded resin using Microtome 2050 manufactured by Reichert-Jung. The film was observed with a transmission electron microscope (LEM-2000) at an acceleration voltage of 100 KV and a magnification of 100,000, and the thickness of the coating layer was measured.

(5) Light transmittance Using a spectrophotometer MPC3100 manufactured by Shimadzu Corporation, light transmittance at a wavelength of 300 nm to 800 nm was measured in increments of 2 nm. For evaluation of the amount of light transmission, a light transmittance of 550 nm and an average light transmittance of 400 to 800 nm were used.

(6) Refractive Index of Antireflection Layer Using a laser refractometer prism coupler, model 2010, manufactured by Metricon, measurement was performed using a wavelength of 633 nm. As the refractive index of the antireflection layer, the measured value of the dried product of the coating liquid for the antireflection layer was used.

(7) Average in-plane refractive index of film Measurement was performed using a laser refractometer prism coupler, model 2010, manufactured by Metricon, using a wavelength of 633 nm. The average of the in-plane refractive index of the film is an average value of the in-plane refractive index in the MD direction and the in-plane refractive index in the TD direction of the film.

[Example 1]
<Creation of film polymer>
Using 100 parts of dimethyl naphthalene-2,6-dicarboxylate and 60 parts of ethylene glycol as a transesterification catalyst, 0.03 part of manganese acetate tetrahydrate, and gradually increasing the temperature from 150 ° C. to 238 ° C. for 120 minutes A transesterification reaction was performed. On the way, when the reaction temperature reached 170 ° C., 0.024 part of antimony trioxide was added, and after the transesterification reaction, trimethyl phosphate (135 ° C. in ethylene glycol, 0.11 to 0.16 MPa for 5 hours) was added. The solution heat-treated under pressure: 0.023 parts in terms of trimethyl phosphate was added. Thereafter, the reaction product is transferred to a polymerization reactor, heated to 290 ° C., subjected to a polycondensation reaction under a high vacuum of 27 Pa or less, and substantially contains particles having an intrinsic viscosity of 0.62 dl / g. No polyethylene-2,6-naphthalenedicarboxylate was obtained.

<Coating liquid for easy adhesion layer>
66 parts of dimethyl 2,6-naphthalenedicarboxylate, 47 parts of dimethyl isophthalate, 8 parts of dimethyl 5-sodium sulfoisophthalate, 54 parts of ethylene glycol and 62 parts of diethylene glycol were charged into the reactor, and 0.05 parts of tetrabutoxy titanium Was added and heated under a nitrogen atmosphere while controlling the temperature at 230 ° C., and the produced methanol was distilled off to conduct a transesterification reaction. Subsequently, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction to obtain a polyester. 25 parts of this polyester was dissolved in 75 parts of tetrahydrofuran, and 75 parts of water was dropped into the resulting solution under high-speed stirring at 10,000 rpm to obtain a milky white dispersion. Then, this dispersion was subjected to a reduced pressure of 20 mmHg. Distillation was performed, and tetrahydrofuran was distilled off to obtain an aqueous dispersion of polyester having a solid content of 25% by weight.

  Next, 3 parts of sodium lauryl sulfonate as a surfactant and 181 parts of ion-exchanged water are charged into a four-necked flask and the temperature is raised to 60 ° C. in a nitrogen stream, and then 0.5% ammonium persulfate is used as a polymerization initiator. Part, 0.2 part of sodium hydrogen nitrite was added, and further 30.1 parts of methyl methacrylate, 21.9 parts of 2-isopropenyl-2-oxazoline, polyethylene oxide (n = 10) methacrylic acid 39 A mixture of .4 parts and 8.6 parts of acrylamide was added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70.degree. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an acrylic aqueous dispersion having a solid content of 35% by weight.

On the other hand, 0.2% by weight of silica filler (average particle size: 100 nm) (trade name Snowtex ZL manufactured by Nissan Chemical Co., Ltd.), polyoxyethylene (n = 7) lauryl ether (Sanyo Chemical Co., Ltd.) as a wetting agent An aqueous solution to which 0.3% by weight of Naroactee N-70 (trade name) was added was prepared.
8 parts by weight of the polyester aqueous dispersion, 7 parts by weight of the acrylic water dispersion, and 85 parts by weight of the aqueous solution were mixed to prepare an easy-adhesion layer coating solution.

<Creation of polyester film>
The polyethylene-2,6-naphthalene dicarboxylate pellets previously prepared as a polymer for film were dried at 170 ° C. for 6 hours, then supplied to an extruder hopper, melted at a melting temperature of 305 ° C., and an average opening of 17 μm. It filtered with the stainless steel fine wire filter, extruded on the rotating cooling drum with a surface temperature of 60 degreeC through the slit-shaped die of 3 mm, and rapidly cooled, and the unstretched film was obtained. The unstretched film thus obtained was preheated at 120 ° C., and further heated by an IR heater at 850 ° C. from above 15 mm between low-speed and high-speed rolls and stretched 3.2 times in the longitudinal direction. The easy-adhesion layer was formed by coating the easy-adhesion coating solution on one side of the film after the longitudinal stretching with a roll coater so that the thickness of the coating film was 100 nm.

Then, it supplied to the tenter and extended | stretched 3.3 times in the horizontal direction at 140 degreeC. The obtained biaxially stretched film was heat-fixed at a temperature of 244 ° C. for 5 seconds to obtain a biaxially stretched polyester film having an intrinsic viscosity of 0.58 dl / g and a film thickness of 125 μm. When the biaxially stretched polyester film was treated at 200 ° C. for 10 minutes, the thermal shrinkage in the longitudinal direction was 0.58%, the thermal shrinkage in the width direction was 0.12%, and the difference between the thermal shrinkage in the longitudinal and width directions Was 0.46%.
The minimum reflectance on the biaxially stretched polyester film thus obtained was 718 nm, and the light transmittance at 550 nm was 89.6%.

<Installation of antireflection layer>
A coating solution comprising 35.3 g of a titanium oxide sol containing 1.7 wt% of a titanium oxide component (manufactured by PTAsol, Yoshikawa General Development Co., Ltd.), 0.014 g of a surfactant (manufactured by Phageentent 250 Neos) and 4.7 g of ethanol was prepared. This coating solution was applied onto a polyester film with a bar coater and dried. The antireflection layer thus prepared had a thickness of 84 nm and a refractive index of 1.87.

<Installation of transparent conductive layer>
A transparent conductive layer made of IZO having a thickness of 260 nm was formed by a direct current magnetron sputtering method using an IZO target mainly made of indium oxide and added with 10% by weight of zinc oxide. Formation of the transparent conductive layer by sputtering is performed by evacuating the chamber to 5 × 10 ⁻⁴ Pa before plasma discharge, introducing argon and oxygen into the chamber to a pressure of 0.3 Pa, and applying 2 W to the IZO target. Electric power was applied at a power density of / cm ² . The oxygen partial pressure was 3.7 mPa. The surface resistance value of the transparent conductive layer was 15Ω / □.
The antireflection conductive film thus obtained had a light transmittance of 550 nm of 80.9% and an average light transmittance of 400 to 800 nm of 78.6%.

[Example 2]
An antireflection conductive film was obtained in the same manner as in Example 1 except that the thickness of the antireflection layer was set to 99 nm in the installation of the antireflection layer. The obtained antireflection conductive film had a light transmittance of 550 nm of 82.0% and an average light transmittance of 400 to 800 nm of 79.0%.

[Comparative Example 1]
A conductive film was obtained in the same manner as in Example 1 except that no antireflection layer was provided. The obtained conductive film had a light transmittance of 550 nm of 80.5% and an average light transmittance of 400 to 800 nm of 77.4%.

  The antireflection conductive film of the present invention can be suitably used as a solar cell member.

Claims (2)

A biaxially stretched polyester film and an antireflection layer provided thereon, and a transparent conductive layer provided on the antireflection layer, the antireflection layer containing a metal compound and having a refractive index and a thickness of the antireflection layer An antireflection conductive film characterized by satisfying the conditions of the following formulas (1) and (2).
105-40.0 × N ≦ d ≦ 180-40.0 × N (1)
1.75 ≦ N ≦ 2.0 (2)
(In the formula, N is the refractive index of the antireflection layer, and d is the thickness (nm) of the antireflection layer.)   The antireflection conductive film according to claim 1, which is used as a member of a solar cell.