WO2012090674A1 - Surface material for solar battery, coating material for solar battery, and solar battery module - Google Patents

Abstract

Provided is a surface material for a solar battery, which has excellent adhesion to a filler, can maintain the adhesion for a long period, and does not affect the power generation efficiency of the solar battery. Also provided are a coating material formed by overlaying the surface material and the filler, and a solar battery module using the coating material. An UV absorber including cerium oxide is contained in a fluororesin film the surface of which is treated by means of glow discharge treatment.

Description

Surface material for solar cell, coating material for solar cell, and solar cell module

The present invention relates to a solar cell surface material, a solar cell coating material, and a solar cell module.

Fluororesin, especially ethylene-tetrafluoroethylene copolymer (ETFE), has been noted for its weather resistance and is used as a surface material instead of glass in flexible solar cells. The ETFE film used as the surface material of the solar cell is made of a material such as an ethylene-vinyl acetate copolymer (EVA), a modified polyethylene, or polybutyl vinyl (PVB) that serves as a filler for enclosing the solar cell. The film is heat laminated at 135 to 160 ° C. without using an adhesive.
However, a fluororesin film such as an ETFE film does not have sufficient adhesion to a filler such as EVA as it is.

For the purpose of improving the adhesion between the fluororesin film and other members, a surface modification technique for discharging the fluororesin is known.
For example, Patent Document 1 describes that a fluorine resin attached to a transparent electrode of a solar cell is subjected to corona discharge treatment and oxygen atoms and nitrogen atoms are introduced into the surface of the fluorine resin. Patent Document 2 describes that a fluororesin is subjected to a discharge treatment in an atmosphere containing methane gas and carbon dioxide in a rare gas. Patent Document 3 describes that a fluororesin is subjected to a discharge treatment in an atmosphere containing a polymerizable unsaturated compound gas and carbon dioxide in an inert gas. Patent Document 4 describes that a fluororesin is subjected to a discharge treatment in an inert gas atmosphere containing an organic compound having a functional group.
However, in these discharge treatments, it has been difficult to sufficiently improve the adhesion of the fluororesin to EVA or the like. Even if the adhesion immediately after the treatment was improved, the adhesion could not be maintained for a long time.

As a cause that it is difficult to maintain the adhesion between the fluororesin film and EVA or the like for a long period of time, deterioration of EVA or the like due to ultraviolet rays transmitted through the fluororesin film is known. In order to prevent the deterioration of EVA or the like due to ultraviolet rays, a method using an ultraviolet absorber has been proposed.
For example, Patent Document 5 describes that a high-molecular ultraviolet absorber having a molecular weight of 300 or more is added to a fluororesin film. This high molecular weight UV absorber is inferior in heat resistance and cannot withstand the temperature (200 ° C. or more) at the time of molding the fluororesin. Therefore, in this document, after forming a fluororesin as a film, the fluororesin film is immersed in an organic solvent in which a high-molecular UV absorber is dissolved, and the UV absorber is vaporized by a dyeing method in which the UV absorber is contained. A method is described in which a high-molecular ultraviolet absorber is added to the fluororesin film by a thermal diffusion method in which the fluororesin film is exposed and impregnated with the ultraviolet absorber.

Patent Document 6 describes an invention in which an ultraviolet absorber is added to a surface coating material composed of a laminate of a fluororesin film and EVA, and in the examples, it is described that an ultraviolet absorber is added to EVA. Has been. In Patent Document 6, examples of the ultraviolet absorber include inorganic ultraviolet absorbers such as titanium oxide, zinc oxide and tin oxide, and high molecular weight ultraviolet absorbers.
Patent Document 7 describes that a fluorine resin laminated with EVA contains titanium oxide particles for the purpose of preventing EVA deterioration and surface contamination.

Japanese Unexamined Patent Application Publication No. 2004-055570 Japanese Unexamined Patent Publication No. 05-043721 Japanese Unexamined Patent Publication No. 10-273546 Japanese Unexamined Patent Publication No. 05-092530 Japanese Patent No. 2756082 Japanese Patent No. 3135477 Japanese Unexamined Patent Publication No. 10-30030

However, even if a polymer ultraviolet absorber is added to the fluororesin film as in Patent Document 5, it is unlikely that the ultraviolet absorption performance can be maintained for over 10 years. This is because it is considered that the ultraviolet absorbent is volatilized from the fluororesin because the fluororesin and the hydrocarbon-based material such as the ultraviolet absorbent are poorly compatible. In particular, since the surface temperature of the solar cell is 70 ° C. or higher in summer, it is considered that it is more likely to volatilize. Therefore, the effect of maintaining the adhesion with EVA for a long time cannot be expected.
On the other hand, if a UV absorber is added to EVA inside the fluororesin film as in Patent Document 6, even if a high molecular weight UV absorber is used, volatilization is suppressed and UV absorption is achieved. The performance can be maintained to some extent. However, as a result of investigation by the present inventors, it has been found that the method of adding an ultraviolet absorber to EVA cannot maintain the adhesion between the fluororesin film and EVA for a long period regardless of the type of the ultraviolet absorber. .
Further, as in Patent Document 7, when titanium oxide particles are contained in a fluororesin laminated with EVA, the photocatalytic action of titanium oxide causes the fluororesin film to discolor and light transmittance is reduced, and mechanical strength is reduced. Problems occur.

The present invention has been made in view of the above problems, and although it is excellent in weather resistance, as it is, it is composed of a fluororesin film having poor adhesion to a filler such as EVA, but the filler and It is an object of the present invention to provide a surface material for a solar cell that is excellent in the adhesion of the solar cell, can maintain the adhesion for a long period of time, and does not adversely affect the power generation efficiency of the solar cell.
In addition, for solar cells that can be used stably for a long period of time without adversely affecting the power generation efficiency of the solar cell by laminating the filler and the surface material for solar cell that can maintain the adhesion with the filler for a long period of time It is an object to provide a covering material.
Another object of the present invention is to provide a solar cell module that has excellent durability and does not impair power generation efficiency by having a solar cell coating material that can be used stably for a long period of time.

In order to achieve the above object, the present invention employs the following configuration.
[1] A solar cell surface material comprising a fluororesin film having a surface subjected to glow discharge treatment and containing an ultraviolet absorber containing cerium oxide.
[2] The solar cell surface material according to [1], wherein the ultraviolet absorber includes cerium oxide particles and a coating layer that covers a surface of the cerium oxide particles, and the coating layer includes silicon oxide.
[3] The solar cell surface material according to [1] or [2], wherein the light transmittance at 400 nm is 80% or more and the light transmittance at 300 nm is 70% or less.
[4] The solar cell surface material according to any one of [1] to [3], wherein the fluororesin includes an ethylene-tetrafluoroethylene-based copolymer.
[5] The solar cell surface material according to any one of [2] to [4], wherein a ratio of silicon oxide in the coating layer is 60% by mass or more.
[6] The surface material for a solar cell according to any one of [2] to [5], wherein the silicon oxide covering the surface of the cerium oxide particles is amorphous silica.
[7] The solar cell according to [6], wherein the average primary particle diameter of the cerium oxide particles of the cerium oxide-amorphous silica composite in which the surface of the cerium oxide particles is coated with amorphous silica is 10 to 250 nm. Surface material.
[8] The solar cell surface material according to any one of [1] to [7], wherein a content ratio of cerium oxide in the surface material is 0.1 to 2% by mass.
[9] The solar cell surface material according to any one of [2] to [8], wherein a surface of the cerium oxide particles or the cerium oxide particles having the coating layer is subjected to a hydrophobic treatment.
[10] A solar cell coating material, wherein the surface material for a solar cell according to any one of [1] to [9] and a filler made of an organic resin are laminated.
[11] The solar cell coating material according to [10], wherein the surface side of the solar cell surface material that has been subjected to the glow discharge treatment is laminated so as to be in contact with the filler.
[12] The solar cell coating material according to [10] or [11], wherein the filler includes an ethylene-vinyl acetate copolymer.
[13] A solar cell having one or more thin-film photoelectric conversion layers is provided inside, and at least one surface side of the solar cell is for the solar cell according to any one of [10] to [12]. A solar cell module which is covered with a covering material.
[14] The solar cell module according to [13], wherein the solar cell has a thin film photoelectric conversion layer of amorphous silicon (a-Si).

The solar cell surface material of the present invention is excellent in adhesiveness with a filler encapsulating solar cells, can maintain the adhesiveness for a long time, and does not adversely affect the power generation efficiency of the solar cell. Moreover, since the covering material for solar cells of the present invention is constituted by laminating the surface material for solar cells and the filler of the present invention, it can be used stably for a long period of time, and the power generation efficiency of the solar cells is adversely affected. Don't give. Moreover, the solar cell module of the present invention has excellent durability and high power generation efficiency by having a solar cell coating material that can be used stably for a long period of time.

It is a schematic sectional drawing which shows one Embodiment of the solar cell module of this invention. It is an example of the relationship between the wavelength of the solar cell module of this invention, and collection efficiency. It is a figure which shows the light transmittance of the surface material for solar cells of Example 1. FIG. It is a figure which shows the light transmittance of the surface material for solar cells of Example 2. FIG. It is a figure which shows the light transmittance of the surface material for solar cells of Example 3. FIG. It is a figure which shows the light transmittance of the surface material for solar cells of the comparative example 1. FIG. It is a figure which shows the light transmittance of the surface material for solar cells of the comparative example 2. FIG.

<Surface material for solar cell>
The surface material for a solar cell of the present invention is made of a fluororesin film whose surface is modified by glow discharge treatment, and contains an ultraviolet absorber containing cerium oxide in a dispersed manner.
In the surface material for a solar cell of the present invention, the ultraviolet absorber preferably has cerium oxide particles and a coating layer that covers the surface of the cerium oxide particles, and the coating layer preferably contains silicon oxide.
The surface material for solar cells of the present invention preferably has a light transmittance of 80% or more at 400 nm and a light transmittance of 70% or less at 300 nm as the surface material itself.

[Fluororesin]
Examples of the fluororesin constituting the surface material for solar cells include ethylene-tetrafluoroethylene copolymer (hereinafter also referred to as “ETFE”), polytrifluoroethylene chloride (PCTFE), ethylene-trifluorochloride. Highly transparent fluororesin such as ethylene copolymer (ECTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), or these A mixture is mentioned.

Among these, a fluororesin mainly composed of ETFE having a ratio of ETFE in the resin component of 80% by mass or more, preferably 90% by mass or more, and particularly preferably 100% by mass is preferable.
ETFE is a copolymer of ethylene (hereinafter referred to as “E”) and tetrafluoroethylene (hereinafter referred to as “TFE”), or a copolymerizable in addition to a repeating unit based on E and TFE. It is a copolymer containing repeating units based on these monomers.

The ratio (molar ratio) between the repeating unit based on TFE and the repeating unit based on E in ETFE is preferably 70/30 to 30/70, more preferably 65/35 to 40/60, and 60/40 to 40/60. Is particularly preferred.
Unless otherwise specified, “to” indicating the numerical range described above is used to mean that the numerical values described before and after it are used as a lower limit value and an upper limit value, and hereinafter “to” Used with meaning.
In addition to the repeating units based on E and TFE, when containing repeating units based on other monomers that are copolymerizable, the content of the repeating units based on other monomers is in the total repeating units of ETFE. On the other hand, it is preferably 0.1 mol% or more, more preferably 0.5 to 30 mol%, particularly preferably 0.5 to 20 mol%. When the content of the repeating unit based on the comonomer of ETFE is within this range, functions such as high solubility, water repellency, oil repellency, and adhesion to the substrate are imparted without impairing the physical properties of ETFE. Is possible.

Examples of other monomers include other fluoroolefins other than TFE, other olefins other than E, and vinyl monomers.
Examples of other fluoroolefins include C2-C3 fluoroolefins such as chlorotrifluoroethylene, hexafluoropropylene, vinylidene fluoride, and vinyl fluoride. Moreover, fluorovinyl monomers, such as (perfluoroalkyl) ethylene, are mentioned.
Examples of other olefins include propylene and isobutylene.
Examples of vinyl monomers include vinyl ether, allyl ether, carboxylic acid vinyl ester, carboxylic acid allyl ester, and the like.

Examples of the vinyl ether include cycloalkyl vinyl ethers such as cyclohexyl vinyl ether; alkyl vinyl ethers such as nonyl vinyl ether, 2-ethylhexyl vinyl ether, hexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, and t-butyl vinyl ether.
Examples of allyl ethers include alkyl allyl ethers such as ethyl allyl ether and hexyl allyl ether.
Examples of the carboxylic acid vinyl ester include vinyl esters of carboxylic acids such as acetic acid, butyric acid, pivalic acid, benzoic acid, and propionic acid. Examples of the carboxylic acid allyl ester include allyl esters of the above carboxylic acids. Alternatively, a vinyl ester of a carboxylic acid having a branched alkyl group may be used. Specific examples include “Beoba-9” and “Beoba-10” (both manufactured by Shell Chemical Co., Ltd.).
The other copolymer monomers may be used alone or in combination of two or more.

Examples of the resin other than ETFE in the fluororesin mainly composed of ETFE include, for example, hexafluoropropylene-tetrafluoroethylene copolymer, perfluoro (alkyl vinyl ether) -tetrafluoroethylene copolymer, and tetrafluoroethylene. -Fluororesin such as hexafluoropropylene-vinylidene fluoride copolymer and chlorotrifluoroethylene-ethylene copolymer. The fluororesin mainly composed of ETFE may contain a resin other than the fluororesin.
The other resins may be used alone or in combination of two or more.

[Discharge treatment]
The surface material for a solar cell of the present invention comprises a fluororesin film whose surface is modified by glow discharge treatment.
As the glow discharge treatment, by polymerizing a polymerizable gas, a plasma polymerization treatment for introducing a polymer containing oxygen atoms and nitrogen atoms and not containing fluorine onto the fluororesin film; Non-polymerizable plasma treatment in which nitrogen atoms are introduced may be mentioned.
In any case, the introduced oxygen atom or nitrogen atom provides adhesion to the filler.

Both the plasma polymerization treatment and the non-polymerization plasma treatment are plasma treatments using glow discharge caused by ionized plasma. Specifically, a high-frequency electromagnetic field composed of a high frequency, a pulse wave, a microwave, or the like is formed between the discharge electrode and the counter electrode in an atmosphere where a predetermined gas exists, and is disposed between the discharge electrode and the counter electrode. Glow discharge treatment is performed on the surface of the fluororesin film.

As an atmosphere in the case of performing non-polymerizable plasma treatment, a nitrogen atmosphere is preferable in terms of running cost. The oxygen concentration in the nitrogen atmosphere is preferably 100 ppm or less, more preferably 90 ppm or less, and further preferably 60 ppm or less. The lower the oxygen concentration, the easier it is to obtain a fluororesin film that can maintain adhesion for a long period of time by surface treatment.
In a nitrogen atmosphere, carbon dioxide gas and / or hydrogen gas may be introduced in addition to nitrogen gas. Carbon dioxide gas serves as an oxygen supply source for introducing oxygen functional groups such as hydroxy groups on the surface of the fluororesin. The hydrogen gas functions as a hydrogen supply source for introducing amino groups on the surface of the fluororesin.
The total introduction amount of carbon dioxide gas and / or hydrogen gas is preferably 10 mol% or less when the total amount of both is 100 mol%. If the total introduction amount of carbon dioxide gas and hydrogen gas is 10 mol% or less with respect to 100 mol% of nitrogen gas, fluorine oligomers and fluorine low molecular weight substances, which are specific actions of nitrogen plasma gas, are introduced from the surface. Easy to get rid of effect.
Helium gas and argon gas can also be turned into plasma and glow discharge is possible, and the above-described discharge effect is easily obtained. However, these gases are expensive.

As an atmosphere in the case of performing the plasma polymerization treatment, a mixed gas atmosphere composed of a polymerizable unsaturated compound gas and a carbon oxide gas is preferable. Further, methane gas and ethane gas classified as saturated hydrocarbons represented by C ₄ H _{2n + 2} are also preferable because plasma polymerization is performed in a mixed gas with a carbon oxide gas.
Examples of the polymerizable unsaturated compound gas include a compound gas having a double bond such as ethylene gas and propylene gas. Examples of the carbon oxide gas include carbon dioxide gas and carbon monoxide gas.
In the saturated hydrocarbon represented by C ₄ H _{2n + 2} , methane and ethane are preferable, and methane is more preferable. When performing plasma polymerization using this saturated hydrocarbon, polymerizable unsaturated compound gas, and carbon oxide gas, these gases are mixed with helium gas or argon gas, but plasma polymerization is performed. It is preferable to carry out. Thereby, it becomes easy to form a polymer polymerization layer having an irregular structure composed of carbon, hydrogen, oxygen, and nitrogen and having a low polymerization degree, and it becomes easy to obtain strong adhesion to the fluoropolymer. On the other hand, if these gases are mixed in nitrogen gas, plasma polymerization can be performed at low cost.

The atmospheric pressure when performing the glow discharge treatment is preferably near atmospheric pressure. That is, 500 to 800 Torr is preferable, and 700 to 780 Torr is more preferable. If the pressure is 500 Torr or more, it is easy to suppress mixing of gases other than the introduced gas into the discharge part. If the pressure is 800 Torr or less, it is easy to suppress the plasma-treated gases from colliding with each other and reducing the surface treatment effect of the film.
The atmosphere temperature during the glow discharge treatment is not particularly limited and is preferably 0 to 60 ° C, more preferably 10 to 40 ° C.

The electric field applied to the discharge electrode and the counter electrode is preferably a pulsed electric field (hereinafter referred to as “pulse electric field”) having a voltage rise time of 10 μsec or less. If the voltage rise time is 10 μsec or less, the discharge state can be prevented from shifting to arc discharge, and the glow discharge treatment can be performed stably. The voltage rise time of the pulse voltage is more preferably 5 μsec or less. As the voltage rise time is shorter, the gas is more easily ionized and becomes plasma, and glow discharge is more likely to occur. However, the voltage rise time is a time during which the voltage change is continuously positive.
The voltage fall time of the applied electric field is preferably as short as the voltage rise time, and the rise time and the fall time are preferably set to the same time. However, the voltage fall time is a time during which the voltage change is continuously negative.
The waveform of the pulse electric field is not particularly limited, and examples thereof include an impulse waveform, a square waveform, and a modulation waveform. Further, when the frequency exceeds 20 kHz, a sine wave is likely to be formed.

The pulse duration in the pulse electric field is preferably 0.5 to 200 μsec, more preferably 1 to 10 μsec. If the pulse duration is 0.5 μsec or more, the discharge becomes more stable. If the pulse duration is 200 μs or less, it is easy to suppress the transition of glow discharge to arc discharge. The pulse duration can be adjusted by the frequency of the electric field pulse. However, the pulse duration is the time during which the pulses are continuous.
For example, if each pulse is an intermittent pulse that is separated, the pulse duration is the same as the pulse width time. When a plurality of pulses are continuous, the pulse duration is the same as the sum of the pulse width times of the series of continuous pulses.

The electric field strength of the applied electric field is preferably 10 to 1,000 kV / cm, more preferably 100 to 300 kV / cm. If the electric field strength is 10 kV / cm or more, the gas is easily turned into plasma by glow discharge. If the electric field strength is 1000 kV / cm or less, it is easy to suppress the occurrence of arc discharge.
The frequency of the pulse voltage is preferably 0.5 to 100 kHz, more preferably 5 to 50 kHz. When the frequency of the pulse voltage is 0.5 kHz or more, the discharge density of the glow discharge is improved and the time required for the surface treatment is shortened. If the frequency of the pulse voltage is 100 kHz or less, the discharge state can be prevented from shifting to arc discharge, and the glow discharge treatment can be performed stably.

The glow discharge treatment using a pulsed electric field is preferably performed a plurality of times with an interval of 0.01 seconds or more.
The discharge density of each glow discharge treatment, that is, the discharge density between each discharge electrode and the counter electrode is preferably 40 to 200 W · min / m ² , and preferably 60 to 180 W · min / m ^2. More preferred. If the discharge density of each glow discharge treatment is 40 W · min / m ² or more, nitrogen functional groups and oxygen functional groups are easily introduced. Further, when the discharge density is less than that, the number of functional groups to be introduced is extremely small. If the discharge density of each glow discharge treatment is 200 W · min / m ² or less, the adhesion obtained by the surface treatment can be easily maintained for a long period of time.
By performing glow discharge treatment using a pulsed electric field, the increase in the temperature of the fluororesin film to be treated is reduced, and the temperature once increased between each discharge treatment is reduced. Therefore, the movement of the oligomer component to the surface layer due to heat is suppressed. In addition, by suppressing the discharge density and the total sum of each glow discharge treatment, the amount of oligomer components generated due to the breakage of the carbon-carbon bond of the fluororesin on the surface layer is reduced. Therefore, the oligomer component is reduced on the surface layer of the fluororesin film, and oxygen atoms and nitrogen atoms are easily introduced into the fluororesin itself, not into the oligomer component having a weak binding force.

A known electrode structure can be freely adopted as the structure of the discharge electrode and the counter electrode used for the glow discharge. For example, a curved electrode or a flat electrode is used as the counter electrode. In order to prevent arc discharge due to electric field concentration, it is preferable to employ a parallel plate type electrode in which the distance between the electrodes is constant. The distance between both electrodes is preferably 0.5 to 10 mm. By setting the thickness to 0.5 mm or more, it is easy to dispose a fluororesin film between both electrodes. Moreover, by setting it as 10 mm or less, it is easy to obtain discharge with stable discharge and high discharge density.
As a material for both electrodes, a single metal such as copper or aluminum, an alloy such as stainless steel or brass, or the like can be used.

In order to prevent the occurrence of arc discharge, it is preferable to coat a solid dielectric on at least one opposing surface side of both electrodes. In order to create a better plasma state, a solid dielectric should be placed on both electrodes.
As the material of the solid dielectric used on the discharge electrode side, it is preferable to use a metal oxide such as silicon dioxide, aluminum oxide, zirconium dioxide, titanium dioxide. Synthetic resins such as polytetrafluoroethylene and polyethylene terephthalate, and glass can also be used.
In particular, it is preferable to use a solid dielectric having a relative dielectric constant of 10 or more (relative dielectric constant in an environment at 25 ° C., the same shall apply hereinafter). Examples of the solid dielectric having a relative dielectric constant of 10 or more include metal oxides such as zirconium dioxide and titanium dioxide, and double oxides such as barium titanate.

Titanium dioxide is known as a ferroelectric, and in the case of a titanium dioxide single composition, the relative dielectric constant differs depending on the crystal structure, and the relative dielectric constant is about 80 for the rutile crystal structure. Further, a dielectric composition having a relative dielectric constant of about 2000 to 18500 is obtained by using a mixed composition of at least one selected from metal oxides such as Ba, Sr, Pb, Ca, Mg, and Zr and titanium dioxide. The body is obtained. That is, the relative dielectric constant can be changed depending on the type and ratio of other oxides to be mixed and the crystallinity.
Titanium dioxide alone has a drastic compositional change in a heating environment, restricts the use environment, and is difficult to handle when formed as a film on an electrode. Therefore, it is preferable to use a mixed composition composed of 5 to 50% by mass of titanium dioxide and 50 to 95% by mass of aluminum oxide with improved thermal stability.

Zirconium dioxide, when used alone, has a relative dielectric constant of about 12 and is advantageous for generating a discharge plasma at a low voltage. Moreover, it is good also as a mixed composition with another metal oxide. The relative dielectric constant can be changed depending on the type and ratio of other oxides to be mixed and the crystallinity.
Zirconium oxide is preferably mixed with yttrium oxide (Y ₂ O ₃ ), calcium carbonate (CaCO ₃ ), magnesium oxide (MgO), or the like because it is stabilized by preventing expansion and contraction due to crystal transformation.
In the case of a mixed composition with other oxides, at least 70% by mass is zirconium oxide, and the proportion of the other oxides is preferably within 30% by mass. For example, a zirconium oxide film to which 4 to 20% by mass of yttrium oxide is added is preferable because the relative dielectric constant is about 8 to 16.

The thickness of the solid dielectric on the discharge electrode side is appropriately determined depending on the thickness of the substrate to be processed and the applied voltage, but is preferably 0.01 to 4 mm. If it is too thick, a high voltage is required to generate plasma discharge. If it is too thin, dielectric breakdown occurs when voltage is applied, and arc discharge occurs.

Since the solid dielectric on the counter electrode side supports the fluororesin film, it is familiar with the fluororesin film and is preferably a soft material. For example, silicon rubber is effective.

[Ultraviolet absorber]
The surface material for a solar cell of the present invention contains an ultraviolet absorber. As a result of studies by the present inventors, it has been found that functional groups containing oxygen atoms and nitrogen atoms, particularly functional groups containing nitrogen atoms, obtained by glow discharge treatment have low resistance to ultraviolet rays. That is, it has been found that the destruction of these functional groups by ultraviolet rays causes a decrease in adhesion over time. Therefore, in order to obtain a coating material in which the surface material and the filler are stably laminated, it is not only necessary to protect the filler from ultraviolet rays, and the functional groups in the discharge-treated fluororesin should also be protected from ultraviolet rays. I found it. Therefore, in the present invention, an ultraviolet absorber is contained in the surface material, not in the filler.

The ultraviolet absorbent in the present invention is characterized by containing cerium oxide. If it is cerium oxide, it does not have a photocatalytic action like titanium oxide, so even if it is contained in the fluororesin film, the fluororesin film is discolored to reduce the light transmittance or reduce the mechanical strength. Does not cause such problems.
Further, as will be apparent from the examples described later, cerium oxide absorbs less light in a wavelength region of 350 nm or more, which has high collection efficiency in power generation by a solar cell. On the other hand, ultraviolet rays on the low wavelength side (especially less than 350 nm) that have a large influence on the functional group have sufficient absorbency. Therefore, the functional group in the discharge-treated fluororesin can be protected from ultraviolet rays without substantially impairing the power generation efficiency.
For example, zinc oxide and the like are also known as ultraviolet absorbers that do not have a photocatalytic action. However, zinc oxide has a large absorption with respect to light of 350 to 360 nm that can obtain a certain degree of collection efficiency in power generation of a solar cell. For this reason, if zinc oxide is used as a UV absorber for a solar cell surface material, sufficient power generation efficiency cannot be obtained.

Cerium oxide is easily dissolved by hydrogen fluoride generated by the decomposition of the fluororesin. Therefore, in order to obtain higher weather resistance, it is preferable to use composite particles in which the surface of the cerium oxide particles is covered with a coating layer for protecting from hydrogen fluoride.
As the coating layer, a coating layer containing silicon oxide is preferable, and a silicon oxide having a silicon oxide ratio of 60% by mass or more, preferably 80% by mass or more, particularly preferably 100% by mass in the coating layer as a main component. A coating layer is preferred.
Examples of other components contained in the coating layer include aluminum oxide remaining on the surface of the coating layer derived from aluminum sulfate (aggregating agent) used during the production of the composite particles.

That is, the composite particle in which the surface of the cerium oxide particle is covered with a coating layer for protecting from hydrogen fluoride is a cerium oxide-silica composite in which the surface of the cerium oxide particle is covered with silicon oxide (ie, silica). Is preferred. In that case, the CeO ₂ : SiO ₂ mass ratio of the cerium oxide-silica composite particles in which the surface of the cerium oxide particles is covered with silica is preferably 30:70 to 80:20, and 40:60 to 70: 30 is more preferable. Here, the mass ratio of the CeO ₂ and SiO ₂ is cerium oxide - a ratio between CeO ₂ and SiO ₂ in the entire particles of the silica complex. When the ratio of silica is increased, the weather resistance is improved. However, if the amount of silica is too large, water adsorbed on the silica also increases, which may cause foaming streaks during film molding.
Moreover, it is preferable that a silicon oxide is an amorphous silica (namely, amorphous silica) which does not have crystallinity. Specific examples of the amorphous silica include amorphous silica obtained by hydrolyzing sodium silicate.
That is, the composite particle in which the surface of the cerium oxide particle is covered with a coating layer for protecting from hydrogen fluoride is preferably a cerium oxide-amorphous silica composite in which the surface of the cerium oxide particle is covered with amorphous silica. .

The particles of the cerium oxide-amorphous silica composite are preferably secondary particles in which a plurality of particles in which primary particles of cerium oxide are coated with amorphous silica are aggregated and the amorphous silica is fused together. The distribution of the secondary particle diameter of the cerium oxide-amorphous silica composite particles measured by a laser diffraction particle size distribution analyzer is preferably 95% by mass or more in the range of 1 to 30 μm. More preferably, it is in the range of 10 μm. The average secondary particle diameter of the cerium oxide-amorphous silica composite particles measured by a laser diffraction particle size distribution analyzer is preferably 2 to 8 μm, and particularly preferably 1 to 5 μm.
In addition, the average particle diameter (average primary particle diameter) measured by SEM (scanning electron microscope) of the cerium oxide particles in the cerium oxide-amorphous silica composite is such that the necessary ultraviolet absorbing ability is obtained and the solar cell In power generation, the thickness is preferably 10 to 250 nm from the viewpoint of obtaining high transparency with respect to light of 400 nm or more, which can obtain a certain degree of high collection efficiency. The average primary particle size here is the particle size of the cerium oxide particles.
As a method for producing particles of a cerium oxide-amorphous silica composite in which the surface of cerium oxide particles is covered with amorphous silica, for example, as described in JP-A-9-118610 and JP-A-3981483 A method in which a silicate solution is dropped into an aqueous dispersion of insoluble cerium compound particles (for example, Ce (OH) ₄ ) while stirring to obtain a silica-coated insoluble cerium compound, followed by drying and further firing. It is done. This production method is a method for completing the reaction in the liquid layer. Therefore, although the particle size after pulverization / firing is distributed in the range of about 0.5 to 10 μm, the particle size of cerium oxide itself is as small as around 220 nm. Very high transparency can be obtained for the above light.

The method for producing particles of the cerium oxide-amorphous silica composite in which the surface of the cerium oxide particles is covered with amorphous silica is not limited to the above method. For example, cerium oxide particles are synthesized, and water glass or ethyl silicate is synthesized therewith. A method of performing silica coating using as a material may be used.
In the production of a cerium oxide-amorphous silica composite in which the surface of cerium oxide is covered with amorphous silica, a flocculant such as aluminum sulfate is used to facilitate filtration of the silica-coated insoluble cerium compound dispersed in water. Can be used. When aluminum sulfate is used as a flocculant, aluminum oxide derived from aluminum ions attached to the surface remains on the surface of the coating layer, but there is no particular problem in performance.

Moreover, it is preferable that the surface of the ultraviolet absorber containing cerium oxide (that is, cerium oxide particles or cerium oxide particles having a coating layer containing silica) is subjected to a hydrophobic treatment. Thereby, the dispersibility in a fluororesin film improves. In addition, in the step of dispersing the ultraviolet absorber containing cerium oxide in the fluororesin, the fluororesin comes into contact with the screw and the cylinder many times, but the shearing at that time can be kept low by hydrophobization, Resin coloring is suppressed. The degree of hydrophobicity is preferably 40 to 75% of the degree of methanol hydrophobicity.
Methanol hydrophobicity is an index indicating the hydrophobicity of particles. The measurement method is as follows. That is, 50 cc of distilled water is put into a 300 cc beaker, and 5 g of particles are added while stirring well. If the particles are evenly dispersed, the particles are very familiar with distilled water and the degree of methanol hydrophobization is 0%. If the particles are not uniformly dispersed, methanol is gradually added dropwise until the particles are uniformly dispersed in the aqueous solution. The methanol hydrophobization degree D (unit:%) is determined by the following formula from the total methanol addition amount M (unit: cc) until it is evenly dispersed.
D = 100M / (M + 50)

The preferred degree of methanol hydrophobicity required differs depending on the type of fluororesin, and in the case of ETFE, it is preferably 40 to 70%. Hexafluoropropylene-tetrafluoroethylene copolymer or perfluoro (alkyl vinyl ether)- In the case of a tetrafluoroethylene copolymer, it is preferably 60 to 75%, and in the case of a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, it is preferably 40 to 70%.

In order to hydrophobize the surface of the ultraviolet absorber containing cerium oxide, it is preferable to treat with a reactive organosilicon compound in which an acid group or a hydrolyzable group is directly bonded to a silicon atom.
Examples of reactive organosilicon compounds include tetraalkoxysilanes such as tetraethoxysilane and tetramethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, and (3,3,3-trifluoropropyl) trimethoxysilane. Examples include silicone oils such as trialkoxysilanes, dimethyl silicone oil, methyl hydrogen silicone oil, and phenylmethyl silicone oil. Of these, isobutyltrimethoxysilane, hexyltrimethoxysilane, dimethyl silicone oil, and phenylmethyl silicone oil are preferable. .

When the ultraviolet absorber containing cerium oxide is a cerium oxide-amorphous silica composite, the required amount of the reactive organosilicon compound used for the hydrophobization treatment is the size of the specific surface area of the cerium oxide-amorphous silica composite. Is proportional to When the amount of the reactive organosilicon compound is small, the cerium oxide-amorphous silica composite particles may turn black or brown when kneaded with the fluororesin. When there are many reactive organosilicon compounds, the aggregate which consists of a reactive organosilicon compound appears as a lump, and the film external appearance may worsen.
When the reactive organosilicon compound is silicone oil, it is appropriate to treat with 1 to 10% by mass of silicone oil with respect to the ultraviolet absorber, and with alkoxysilane such as isobutyltrimethoxysilane. In this case, it is appropriate to treat with 8 to 20% by mass of alkoxysilane with respect to the ultraviolet absorber.

The content of the UV absorber containing cerium oxide in the surface material is determined in consideration of the balance between the UV absorbing ability required from the viewpoint of maintaining adhesion and the transmittance of light having a wavelength that contributes to power generation. The
That is, the transmittance of 300 nm of the surface material is preferably as low as possible from the viewpoint of improving adhesion, and therefore it is necessary to contain a sufficient amount of the ultraviolet absorber. On the other hand, if the content is too large, the absorption characteristic of cerium oxide becomes remarkable, and the transmittance around 400 nm, which particularly affects the power generation efficiency, is lowered.
The ultraviolet absorber containing cerium oxide is preferably contained so that the transmittance at 400 nm of the surface material is 80% or more and the transmittance at 300 nm is 20 to 70%. Further, it is more preferable that the surface material be contained so that the transmittance at 400 nm is 85% or more and the transmittance at 300 nm is 20 to 50%.

If the ultraviolet absorber containing cerium oxide is used, the surface material having the preferable light transmission characteristics can be easily obtained. Specifically, it is preferable to contain an ultraviolet absorber so that the amount of cerium oxide per unit area in the surface material is 0.1 to 2 g / m ² .
Further, although depending on the thickness of the film and the amount of the coating layer, the ratio of the amount of cerium oxide to the whole surface material is preferably in the range of 0.1 to 2% by mass.

[Other ingredients]
In addition to UV absorbers containing cerium oxide, the surface material contains other UV absorbers, pigments, carbon black, carbon fibers, silicon carbide, glass fibers, mica, cross-linking agents, and fillers. May be.
The thickness of the surface material is preferably 10 to 300 μm, more preferably 20 to 250 μm, and particularly preferably 25 to 200 μm. If it exists in this range, the handling of the film at the time of discharge processing will be easy, and the wrinkle by discharge will not generate | occur | produce easily.

<Solar cell coating>
The covering material for solar cells of the present invention is a laminate of the surface material of the present invention and a filler made of an organic resin. The surface material and the filler are laminated so that the surface of the surface material subjected to the discharge treatment is in contact with the filler.
The filler for the solar battery covers at least the unevenness of the internal element having the solar battery cell, and functions as an adhesive between the internal element and the surface material. Therefore, light resistance, adhesiveness, and heat resistance are required. As an organic resin satisfying these requirements, an ethylene copolymer is preferable, and an ethylene-vinyl acetate copolymer (hereinafter referred to as EVA), an ethylene-ethyl acrylate copolymer (EEA), and an ethylene-methyl acrylate ( EMA) and polybutyl vinylal (PVB). Moreover, what mix | blended the crosslinking material with polyethylene (henceforth PE) is also mentioned. The filler in the solar cell of the present invention preferably contains one or more of EVA, EEA, EMA and PVB.
The filler is preferably cross-linked so as to be resistant to high temperature use environments. When the filler is EVA, crosslinking with an organic peroxide is preferred. Usually, such a crosslinking treatment is preferably performed in a state “after hot pressing” in the step of joining the solar battery cell to the solar battery covering material when the solar battery module is manufactured.
Crosslinking may be performed using a crosslinking agent such as isocyanate or melamine.

<Solar cell module>
An embodiment of the solar cell module of the present invention will be described with reference to FIG. In the solar cell module 10 of FIG. 1, a filler 2a and a surface material 3a are sequentially laminated on the light incident side of the solar battery cell 1, and a covering material 4a is constituted by the filler 2a and the surface material 3a. Yes.
Similarly, the filler 2b and the surface material 3b are sequentially laminated on the side opposite to the light incident side of the solar battery cell, and the covering material 4b is configured by the filler 2b and the surface material 3b.
At least one of the surface material 3a and the surface material 3b is the surface material for solar cells of the present invention. That is, at least one of the coating material 4a and the coating material 4b is the solar cell coating material of the present invention.
In particular, it is preferable that the surface material 3a disposed on the light incident side is the surface material for solar cells of the present invention, that is, the coating material 4a is the coating material for solar cells of the present invention.
It is most preferable that both the surface material 3a and the surface material 3b are the solar cell surface material of the present invention, that is, both the coating material 4a and the coating material 4b are the solar cell coating material of the present invention.

Solar cell 1 has one or more thin film photoelectric conversion layers between a pair of conductive layers. In order to increase the power generation efficiency, a cell in which a plurality of thin film photoelectric conversion layers having different wavelength regions from which high collection efficiency is obtained is widely used.
FIG. 2 shows an amorphous silicon-germanium (a-Si) thin film photoelectric conversion layer with high collection efficiency for light on the short wavelength side as a top cell and amorphous silicon-germanium (with high collection efficiency for light on the long wavelength side). The collection efficiency obtained in a cell in which a thin film photoelectric conversion layer of (a-SiGe) is a bottom cell and a laminate of a top cell and a bottom cell is disposed between a pair of conductive layers is shown. As shown in FIG. 2, the overall collection efficiency is a value obtained by combining the collection efficiencies of the top cell and the bottom cell. The collection efficiency at a wavelength of 300 to 400 nm is almost equal to the collection efficiency of the top cell alone.

As shown in the examples described later, from the wavelength of 400 nm to 300 nm, the transmittance curve of the surface material of the present invention decreases very closely with the collection efficiency curve of the amorphous silicon (a-Si) thin film photoelectric conversion layer of FIG. Show the trend. Therefore, the solar cell module of the present invention easily maintains high power generation efficiency particularly when it has a thin film photoelectric conversion layer of amorphous silicon (a-Si). Similarly, in other solar cells that generate power in a wide wavelength range of 350 to 1500 nm, for example, called CIGS, it is easy to maintain high power generation efficiency.
Moreover, since the transmittance | permeability curve of the surface material of this invention has low transmittance | permeability as the ultraviolet-ray of a low wavelength, it can fully protect the functional group in the surface by which the discharge treatment of the surface material was carried out.
Therefore, the solar cell module of the present invention is excellent in both power generation efficiency and durability.

Specific examples of the above embodiment will be described below as examples. The present invention is not limited to the following examples.
In the following description, “%” means “% by mass” unless otherwise specified.

<Creation of surface material>
[Example 1]
Phenylmethyl silicone oil (manufactured by Toray Dow Corning, SH510) was dissolved in 2-propanol (hereinafter referred to as IPA) to prepare 500 g of a 2% IPA solution of phenylmethyl silicone oil. Silica-coated cerium oxide particles (manufactured by Daito Kasei Kogyo Co., Ltd., SC6832. The ratio of CeO ₂ , SiO ₂ and Al ₂ O ₃ in the entire silica-coated cerium oxide particles is as follows. CeO ₂ : 65%, SiO ₂ : 32%, Al ₂ O ₃ : 3%) was added with slow stirring. Thereafter, this liquid was dried under vacuum to obtain 110 g of silica-coated cerium oxide particles whose surface was hydrophobized with phenylmethylsilicone oil.

100 g of the above-mentioned hydrophobized silica-coated cerium oxide particles was added to 1900 g of ETFE resin (manufactured by Asahi Glass Co., Ltd., Full-on ETFE: 88AX), and after stirring well, hydrophobized silica with a biaxial extruder Master batch pellets containing 5% coated cerium oxide particles (2.95% cerium oxide) were prepared. The extrusion conditions were a cylinder temperature of 310 ° C and a head temperature of 320 ° C.
Subsequently, the pellets and ETFE resin pellets containing no silica-coated cerium oxide particles (Asahi Glass Co., Ltd., Fullon ETFE: 88AX) are put in a polypropylene bag at a ratio of 1: 9 and shaken vigorously by hand 10 times. Mixed. This was molded with a T die having a cylinder temperature and a die temperature of 320 ° C. to obtain an ETFE film having a width of 550 mm and a thickness of 50 μm.

Next, the surface of the ETFE film was discharged. As an apparatus, a plasma processing apparatus RD550 manufactured by Sekisui Chemical Co., Ltd. was used. As the discharge electrode, a ceramic dielectric (solid dielectric) layer having a thickness of 1 mm on a carbon steel plate having a length of 100 mm in the transport direction of the ETFE film and a length of 650 mm in the width direction of the ETFE film and a thickness of 20 mm. The one provided with was used. Moreover, as a counter electrode, the roll electrode which coat | covered the silicon rubber of thickness 2mm was used for the metal roll surface with a diameter of 30 cm, and roll temperature was hold | maintained at 15 degreeC with the circulating water. Nitrogen gas with a purity of 99.99% or more was used as the gas introduced from the gas inlet.

The flow rate of nitrogen gas to be introduced was 50 L / min, and the gas was introduced for 2 minutes, and it was confirmed that the oxygen concentration was 100 ppm. Thereafter, while introducing nitrogen gas, the output voltage of the high frequency power source is 450 V, the output current is 5.4 A, the processing power is 2.43 kW, and the ETFE film is transported at 6 m / min, so that the discharge density is 623 W · min / A glow discharge treatment of m ² was performed. The frequency was 40 kHz. Therefore, the waveform of the pulse electric field is close to a sine wave.
The discharge density was calculated by the following formula (1).
(Discharge density) = (I × V) / (v × d) (1)
However, in Formula (1), I is the output current (unit: A) of a high frequency power supply, V is the output voltage (unit: V) of a high frequency power supply, v is the conveyance speed (unit: m / min) of an ETFE film, d Is the treatment width, that is, the length in the width direction of the ETFE film treated by the discharge electrode.

[Example 2]
An ETFE film was obtained in the same manner as in Example 1 except that the mixing ratio of the masterbatch pellets and ETFE resin containing no silica-coated cerium oxide particles (Asahi Glass Co., Ltd., Fullon ETFE: 88AX) was 1: 4. Further, the surface was discharged in the same manner as in Example 1 to obtain the surface material of Example 2.

[Example 3]
An ETFE film was obtained in the same manner as in Example 1 except that the mixing ratio of the masterbatch pellets and the ETFE resin containing no silica-coated cerium oxide particles (Asahi Glass Co., Ltd., Fullon ETFE: 88AX) was 1:19. Further, the surface was discharged in the same manner as in Example 1 to obtain the surface material of Example 3.

[Comparative Example 1]
An ETFE film was obtained in the same manner as in Example 1 except that only the ETFE resin (Asahi Glass Co., Ltd., Full-on ETFE: 88AX) containing no silica-coated cerium oxide particles was used without using the masterbatch pellets. The surface was discharged in the same manner as in Example 1 to obtain the surface material of Comparative Example 1.

[Comparative Example 2]
ETFE resin (manufactured by Asahi Glass Co., Ltd., Full-on ETFE: 88AX), tinuvin 479 (BASF), which is an organic UV absorber, is used as the UV absorber so that the total amount of the resin after compounding becomes 1.5%. And an ETFE film having a width of 550 mm and a thickness of 50 μm was obtained. The surface of the obtained film was discharged in the same manner as in Example 1 to obtain the surface material of Comparative Example 2.

[Example 4]
An ETFE film was molded in the same manner as in Example 1, and the gas composition introduced from the gas inlet was 99 vol% argon, 0.3 vol% carbon dioxide, 0.7 vol% methane, and a gas flow rate of 20 l / Example 1 except that the output voltage of the high-frequency power source was 110 V, the output current was 2.2 A, the processing power was 2.42 W, the transport speed of the ETFE film was 1 m / min, and the discharge density was 372 W · min / m ^2. The surface material of Example 4 was obtained in the same manner as described above.

[Example 5]
An ETFE film was obtained in the same manner as in Example 2, and the surface was discharged in the same manner as in Example 4 to obtain the surface material of Example 5.

[Example 6]
An ETFE film was obtained in the same manner as in Example 3, and the surface was discharged in the same manner as in Example 4 to obtain the surface material of Example 6.

[Comparative Example 3]
An ETFE film was obtained in the same manner as in Comparative Example 1, and the surface was discharged in the same manner as in Example 4 to obtain the surface material of Comparative Example 3.

[Comparative Example 4]
An ETFE film was obtained in the same manner as in Comparative Example 2, and the surface was discharged in the same manner as in Example 4 to obtain the surface material of Comparative Example 4.

<Evaluation>
[Transmissivity curve]
The transmittance curves of the surface materials of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in FIGS.
The transmittance curve was measured using an ultraviolet-visible near-infrared spectrophotometer UV-3600 apparatus manufactured by Shimadzu Corporation.

[Wetting index]
About the surface material of each Example and the comparative example, the wetting index was calculated | required with the wetting test method based on JISK6768. The results are shown in Table 1.

[Initial adhesion to EVA]
Two pieces of the surface materials of Examples 1 to 6 and Comparative Examples 1 to 4 cut to a size of 7 cm × 15 cm were used, and EVA films (made by Bridgestone, 2540) were sandwiched between the respective discharge treated surfaces, Hot pressing was performed at 145 ° C. for 15 minutes and a surface pressure of 1 MPa to obtain a three-layer laminate. The adhesion between the EVA film and one surface material was measured with Tensilon, and the initial adhesion was measured. The conditions were 180 degree peeling and peeling speed: 50 mm / min. The results are shown in Tables 2 and 3.

[Adhesion after weathering test for EVA]
A plurality of three-layer laminates were obtained in the same manner as the evaluation of the initial adhesion strength to EVA described above. This was put into an accelerated weathering test apparatus (Suga tester: Sunshine 300), the black panel temperature was 63 ° C., and after exposure to light irradiation only for 48 minutes, exposure to light irradiation and rainfall for 12 minutes totaled 60 minutes. The cycle was repeated. The adhesion force between EVA and one surface material after repeating the cycle up to 2500 hours, 5000 hours, and 7500 hours was measured in the same manner as the initial adhesion force. The results are shown in Tables 2 and 3.

[Initial adhesion to modified PE]
Two surface materials of Examples 1 to 6 and Comparative Examples 1 to 4 cut to a size of 7 cm × 15 cm were used, and a modified PE film for solar cell fillers (Dainippon) A modified polyethylene sheet (Z68) manufactured by Printing Co., Ltd. was sandwiched and subjected to hot pressing at 145 ° C. for 15 minutes and a surface pressure of 1 MPa to obtain a three-layer laminate. The adhesion between the modified PE and one surface material was measured with Tensilon, and the initial adhesion was measured. The conditions were 180 degree peeling and peeling speed: 50 mm / min. The results are shown in Tables 4 and 5.

[Adhesion after weathering test for modified PE]
A plurality of three-layer laminates were obtained in the same manner as in the evaluation of the initial adhesion strength to the modified PE described above. This was put into an accelerated weathering test apparatus (Suga tester: Sunshine 300), the black panel temperature was 63 ° C., and after exposure to light irradiation only for 48 minutes, exposure to light irradiation and rainfall for 12 minutes totaled 60 minutes. The cycle was repeated. The adhesion between the modified PE and one surface material after repeating the cycle up to 2500 hours, 5000 hours, and 7500 hours was measured in the same manner as the initial adhesion force. The results are shown in Tables 4 and 5.

As shown in FIGS. 3 to 5, the transmittance of the surface material of each example is very close to the collection efficiency curve of the amorphous silicon (a-Si) thin film photoelectric conversion layer of FIG. 2 from the wavelength of 400 nm to 300 nm. Showed a decreasing trend.
On the other hand, the surface material of Comparative Example 2 had a transmittance of about 360 nm or less, which was a characteristic that had to substantially affect the power generation efficiency of the solar cell.
As shown in Tables 2 to 5, in Examples 1 to 6, the adhesion after the weathering test was maintained well compared to any of Comparative Examples 1 to 4.

The surface material for solar cell of the present invention has excellent adhesion to the filler used for the coating material for solar cell, can maintain the adhesion for a long time, and adversely affects the power generation efficiency of the solar cell. Therefore, it is useful for a solar cell coating material and for a solar cell module.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2010-289675 filed on Dec. 27, 2010 are incorporated herein as the disclosure of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2a, 2b ... Filler, 3a, 3b ... Surface material, 4a, 4b ... Covering material,
10 ... Solar cell module

Claims (14)

A surface material for a solar cell comprising a film of a fluororesin having a surface subjected to glow discharge treatment and containing an ultraviolet absorber containing cerium oxide. 2. The solar cell surface material according to claim 1, wherein the ultraviolet absorber has a cerium oxide particle and a coating layer covering a surface of the cerium oxide particle, and the coating layer contains silicon oxide. The solar cell surface material according to claim 1 or 2, wherein the light transmittance at 400 nm is 80% or more and the light transmittance at 300 nm is 70% or less. The solar cell surface material according to any one of claims 1 to 3, wherein the fluororesin contains an ethylene-tetrafluoroethylene copolymer. The surface material for a solar cell according to any one of claims 2 to 4, wherein a ratio of silicon oxide in the coating layer is 60% by mass or more. The solar cell surface material according to any one of claims 2 to 5, wherein the silicon oxide covering the surface of the cerium oxide particles is amorphous silica. The surface material for a solar cell according to claim 6, wherein the average primary particle diameter of the cerium oxide particles of the cerium oxide-amorphous silica composite in which the surface of the cerium oxide particles is coated with amorphous silica is 10 to 250 nm. The solar cell surface material according to any one of claims 1 to 7, wherein a content ratio of cerium oxide in the surface material is 0.1 to 2 mass%. The surface material for a solar cell according to any one of claims 2 to 8, wherein a surface of the cerium oxide particles or the cerium oxide particles having the coating layer is subjected to a hydrophobic treatment. A solar cell coating material, wherein the surface material for a solar cell according to any one of claims 1 to 9 and a filler made of an organic resin are laminated. The solar cell coating material according to claim 10, wherein the solar cell surface material is laminated so that a surface on which the glow discharge treatment is performed is in contact with the filler. The solar cell coating material according to claim 10 or 11, wherein the filler includes an ethylene-vinyl acetate copolymer. A solar battery cell having one or more thin-film photoelectric conversion layers is provided therein, and at least one surface side of the solar battery cell is covered with the coating material for a solar battery according to any one of claims 10 to 12. A solar cell module characterized by comprising: 14. The solar cell module according to claim 13, wherein the solar cell has a thin film photoelectric conversion layer of amorphous silicon (a-Si).

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