JP4560001B2 - Solar cell sealing film and solar cell using the sealing film - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a solar cell sealing film comprising an ethylene-vinyl acetate copolymer as a main component and a solar cell using the sealing film, and particularly to a solar cell sealing film and a solar cell excellent in productivity. .

  In recent years, solar cells that directly convert sunlight into electric energy have attracted attention and are being developed from the viewpoint of effective use of resources and prevention of environmental pollution.

  As shown in FIG. 1, a solar cell generally has an EVA (ethylene-vinyl acetate copolymer) film sealed between a glass substrate 1 as a front surface side transparent protective member and a back surface side protective member (back cover) 2. It is set as the structure which sealed the cells 4 for solar cells, such as a silicon power generation element, by the stop films 3A and 3B. In the following, the sealing film disposed on the light receiving surface side with respect to the cell is referred to as “front surface side sealing film”, and the sealing film disposed on the rear side of the cell is referred to as “back surface side sealing film”.

  In such a solar cell, the glass substrate 1, the front side sealing EVA film 3A, the silicon power generation element 4, the back side sealing EVA film 3B and the back cover 2 are laminated in this order, heated and pressurized, and EVA It is manufactured by cross-linking and curing and integrating.

  In the solar cell, it is strongly desired from the viewpoint of improving power generation efficiency that light incident on the solar cell can be taken into the solar cell as efficiently as possible. Therefore, it is desirable that the sealing EVA film has transparency as high as possible, does not absorb or reflect incident sunlight, and transmits most of sunlight. Furthermore, when a solar cell is used for a long period of time, the EVA film for sealing turns yellow due to fading, etc. due to the influence of light, heat, etc., and the phenomenon that the transmittance of sunlight is reduced is observed. A sealing EVA film having excellent properties is required, and further improvement of these characteristics is desired.

  Even when the EVA film for sealing, which is relatively excellent in transparency, light resistance, and heat resistance as described above, is used in the process of sealing the silicon power generation element in the transparent substrate when manufacturing a solar cell (module). If a long time is required, it becomes a problem from the viewpoint of productivity. In general, the sealing EVA film having the improved characteristics often requires a relatively long time in the sealing step. That is, the glass substrate 1, the front side sealing EVA film 3A, the silicon power generation element 4, the back side sealing EVA film 3B, and the back cover 2 are laminated in this order, and heated and pressurized to crosslink and cure the EVA film. In the process of bonding and integrating, it takes several tens of minutes to cross-link and cure the EVA film, which is considered to be a major cause of the long time required for manufacturing the solar cell.

  In general, as an organic oxide (cross-linking agent) used for cross-linking, an EVA film can be formed in a shorter time by using a highly reactive material having a low half-life temperature or by increasing the amount of organic oxide. It can be crosslinked and cured. However, when organic oxides with a low half-life temperature (eg, alkyl peroxyesters, peroxyketals) are used, or when the amount of organic oxide is increased, blistering occurs due to long-term use of the EVA film after crosslinking. There is a problem that it is easy to do.

  On the other hand, it is also known to use a crosslinking aid for improving transparency and various mechanical properties. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-206921) discloses ethylene / vinyl acetate / triallyl having high transparency by using triallyl isocyanurate as a crosslinking aid in an ethylene / vinyl acetate copolymer. It is described that a transparent film of isocyanurate terpolymer (EVAT) can be obtained.

Japanese Patent Laid-Open No. 2001-206921

  When triallyl isocyanurate is used as the crosslinking aid, the crosslinking density is improved, but the crosslinking rate is not sufficiently increased. In order to increase the crosslinking rate, as described above, it is necessary to use an organic oxide having a low half-life temperature, or to increase the amount of the organic oxide. In this case, the crosslinking time is shortened, There is a problem that swelling (foaming) is likely to occur during molding or after long-term use.

  The inventors of the present invention have made extensive studies in order to suppress the occurrence of swelling while maintaining a high crosslinking density and to shorten the crosslinking time, and have reached the present invention.

  Accordingly, an object of the present invention is to provide a sealing film for a solar cell that is excellent in productivity and has a good appearance with no blistering.

  Another object of the present invention is to provide a solar cell sealing film that is excellent in productivity, excellent in appearance, and excellent in durability with no occurrence of swelling or the like over time.

  Furthermore, an object of the present invention is to provide a solar cell having excellent productivity and good appearance using the solar cell sealing film.

  Still another object of the present invention is to provide a solar cell that is excellent in productivity using the solar cell sealing film, has a good appearance, and has excellent durability.

  The inventors of the present invention have both good characteristics and excellent productivity, while maintaining the characteristic that a good appearance can be maintained for a long time by suppressing the occurrence of swelling, and also shortening the crosslinking time. In order to obtain the sealing film for solar cells, it has been intensively studied. According to the study by the present inventors, it is possible to shorten the crosslinking time by selecting and increasing the type of organic oxide (such as half-life temperature), but it is possible to stably suppress the occurrence of swelling. It was difficult. Therefore, we investigated the possibility of materials other than organic oxides, and found that by using two specific combinations of crosslinking aids, it was possible to simultaneously suppress the occurrence of swelling and improve the crosslinking rate. It was.

［但し、Ｒ ¹ がメチル基を表し、Ｒ ² がエチレン基を表し、そしてＲ ³ がｔ−ブチル基を表す。］で表されるジアルキルパーオキサイドを含み、
該架橋助剤として、トリアリルイソシアヌレート及びトリメチロールプロパントリ（メタ）アクリレートを含み、
トリアリルイソシアヌレート及びトリメチロールプロパントリ（メタ）アクリレートの合計配合量が、エチレン／酢酸ビニル共重合体に対して１〜２．５質量％の範囲であり、且つ
トリアリルイソシアヌレート及びトリメチロールプロパントリ（メタ）アクリレートの配合比が、質量で６５：３５〜８５：１５の範囲にあることを特徴とする太陽電池用封止膜により達成することができる。 Therefore, the purpose is
In a sealing film for solar cells containing an ethylene / vinyl acetate copolymer, an organic peroxide and a crosslinking aid,
As the organic peroxide, the following formula I:

[However, R ¹ represents a methyl group, R ² represents an ethylene group, and R ³ represents a t-butyl group. A dialkyl peroxide represented by
As the crosslinking aid, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate,
The total amount of triallyl isocyanurate and trimethylolpropane tri (meth) acrylate is in the range of 1 to 2.5% by mass with respect to the ethylene / vinyl acetate copolymer, and triallyl isocyanurate and trimethylolpropane. The compounding ratio of tri (meth) acrylate can be achieved by a sealing film for solar cells, characterized in that it is in a range of 65:35 to 85:15 by mass.

  The preferable aspect of the sealing film for solar cells of this invention is listed below.

( 1 ) Triallyl isocyanurate is contained in an amount of 0.5 to 2.0 % by mass based on the ethylene / vinyl acetate copolymer.

( 2 ) Trimethylolpropane tri (meth) acrylate is contained in an amount of 0.1 to 0.5 % by mass with respect to the ethylene / vinyl acetate copolymer.

(3 ) As an organic peroxide,
Formula II below:

[However, R ⁴ represents a t-butyl group, and R ⁵ represents a 2-ethylhexyl group . ]
The peroxyester represented by these is included.

( 4 ) The peroxyester and dialkyl peroxide are used in combination, and the mass ratio of the peroxyester to the dialkyl peroxide (peroxyester / dialkyl peroxide) is in the range of 1/99 to 9/91. It is preferable to use it.

( 5 ) The organic peroxide is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the ethylene / vinyl acetate copolymer.

( 6 ) 1.0-10 mass parts of crosslinking adjuvant (compound which has a radically polymerizable group) is contained with respect to 100 mass parts of ethylene / vinyl acetate copolymers.

( 7 ) Further, a dihydroxydimethoxybenzophenone ultraviolet absorber is included. In the system of the composition of the sealing film of the present invention, the yellowing prevention effect is particularly excellent.

( 8 ) Furthermore, a silane coupling agent is included. Adhesion is improved and heat resistance and the like are improved.

( 9 ) The vinyl acetate unit of the ethylene / vinyl acetate copolymer is in the range of 10 to 36% by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.

  Moreover, the preferable crosslinking temperature of the sealing film of this invention is 135-180 degreeC (further 140-180 degreeC, especially 155-180 degreeC). The crosslinking time is generally 5 to 30 minutes (especially 5 to 15 minutes).

The present invention also provides
In a solar cell in which a solar cell is sealed using a sealing film between a front surface side transparent protective member and a back surface side protective member, the solar cell is interposed between the solar cell and the back surface side protective member. There is also a solar cell characterized by being integrated by crosslinking using the solar cell sealing film as a sealing film.

  The sealing film for solar cells of the present invention comprises an ethylene / vinyl acetate copolymer (EVA), an organic peroxide and a crosslinking aid as main components, and triallyl isocyanurate and trimethylolpropane tris as the crosslinking aid. (Meth) acrylate is used in combination. Thereby, the crosslinking time of EVA is greatly shortened, and the occurrence of swelling during and after the crosslinking is hardly observed.

  In addition, the occurrence of blistering and the like when used for a long time is remarkably suppressed, and a good appearance can be maintained for a long time. Therefore, the solar cell sealing film of the present invention has high productivity, excellent appearance, and excellent earth properties.

  Therefore, the solar cell having such a solar cell sealing film also has high productivity, good appearance, and improved durability.

  The solar cell sealing film of the present invention is mainly composed of an ethylene / vinyl acetate copolymer (EVA), an organic peroxide (crosslinking agent), and a crosslinking aid. In the present invention, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are contained as the crosslinking aid (generally, the total amount is 0.1 to 10 with respect to the ethylene / vinyl acetate copolymer). mass%). As a result, it is possible to increase the crosslinking speed while suppressing the occurrence of swelling and maintaining a good appearance. In particular, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are generally mixed in a mass ratio of 10:90 to 90:10, preferably 60:40 to 90:10, in particular 65:35 to 85:15 ( By using it in triallyl isocyanurate: trimethylolpropane trimethacrylate), it is possible to achieve the suppression of bulge generation and the improvement of the crosslinking rate in a very high dimension.

  Therefore, the solar cell sealing film of the present invention has a high EVA crosslinking rate, and the occurrence of blistering during and after crosslinking is remarkably suppressed, resulting in excellent productivity, good appearance, and improved durability. It has.

  The solar cell sealing film of the present invention can be easily produced, for example, by depositing the EVA resin composition having the above-described structure according to a conventional method.

  The thickness of the resulting solar cell sealing film of the present invention is generally in the range of 50 μm to 2 mm.

  Next, the EVA resin composition of the present invention will be described.

  As the organic resin used in the EVA resin composition of the present invention, an ethylene / vinyl acetate copolymer (EVA) is used. Furthermore, polyvinyl acetal resins (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB), and vinyl chloride resins can be used as secondary agents. In that case, PVB is particularly preferable.

  The EVA has a vinyl acetate content of generally 10 to 40% by mass, preferably 10 to 36% by mass, particularly 10 to 33% by mass, and more preferably 20 to 30% by mass. When this vinyl acetate content exceeds 40 masses, the viscosity of the resin is lowered, and it tends to flow out from between the glass substrate and the back cover during sealing, which is not preferable. Furthermore, the tackiness increases and handling becomes difficult. When the vinyl acetate content is less than 10 mass, the workability is lowered and the resulting film becomes too hard, so the deaeration performance is lowered, and the cells are easily damaged during the production of the solar cell.

  EVA used in the present invention preferably has a melt flow rate of 0.7 to 40 g / 10 min, particularly 1.5 to 10 g / 10 min.

  The EVA resin composition used in the present invention contains an organic peroxide (crosslinking agent) in order to improve durability and weather resistance, whereby a crosslinked structure is obtained.

［但し、Ｒ ¹ がメチル基を表し、Ｒ ² がエチレン基を表し、そしてＲ ³ がｔ−ブチル基を表す。］で表されるジアルキルパーオキサイド、即ち２，５−ジメチル−２，５−ビス（ｔ−ブチルパーオキシ）ヘキサンを含んでいる。本発明の架橋助剤の組合せを、この式Ｉのジアルキルパーオキサイドを使用した条件で使用した場合に、効果的であり、フクレの抑制と生産性の向上を特に高次元で実現することができる。 As the above organic peroxide (crosslinking agent), an organic peroxide that generates radicals at 100 ° C. or higher is generally used. The thing whose temperature is 70 degreeC or more is preferable. Examples of such an organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 3-di-t-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl- 2,5-bis (t-butylperoxy) hexane; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α′-bis (t-butylperoxide) Oxyisopropyl) benzene; n-butyl-4,4-bis (t-butylperoxy) butane; t-butylperoxy-2-ethylhexyl monocarbonate; 2,2-bis (t-butylperoxy) butane; , 1-bis (t-butylperoxy) cyclohexane; 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylper Alkoxy benzoate; benzoyl peroxide and the like can be used.
In the present invention, as the organic peroxide, the following formula I:

[However, R ¹ represents a methyl group, R ² represents an ethylene group, and R ³ represents a t-butyl group. In other words, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane is included. When the combination of the crosslinking aids of the present invention is used under the conditions using the dialkyl peroxide of the formula I, it is effective, and the suppression of swelling and the improvement of productivity can be realized at a particularly high level. .

  The organic peroxide (in total amount) is generally used in a range of generally 5 parts by mass or less, preferably 0.1 to 5 parts by mass, especially 0.2 to 3 parts by mass with respect to 100 parts by mass of EVA.

Or as an organic oxide,
Formula II below:

[However, R ⁴ represents a t-butyl group and R ⁵ represents a 2-ethylhexyl group. ]
It is also preferable to use a peroxy ester represented by the formula: t-butyl peroxy-2-ethylhexyl monocarbonate.

The use of the peroxy ester le is preferable particularly in view of the crosslinking rate.

It is also preferred to use both a dialkyl peroxide of formula I and a peroxy ester of formula II, the mass ratio of peroxy ester to dialkyl peroxide (peroxy ester / dialkyl peroxide) being from 1/99 to 9/91. It is preferable to be in the range.

The dialkyl peroxides of the above formula I generally have a high half-life temperature and are less likely to cause swelling, but require a relatively long time for EVA crosslinking. Formula II above the peroxy ester le, since generally half-life temperature is low although EVA crosslinking time is reduced, blistering tends to occur. By using the combination of specific crosslinking aids of the present invention, swelling can be suppressed and the crosslinking time can be shortened. Any of the above organic oxides may be used. Two types are particularly preferred. When using one kind, the dialkyl peroxide of the said formula I is preferable.

  It has also been found that such characteristics tend to be easily obtained by short-time crosslinking at high temperatures. The preferred crosslinking temperature is 135 to 180 ° C, 140 to 180 ° C, particularly 155 to 180 ° C. The crosslinking time (the total of the degassing time and press time described later) is generally 5 to 30 minutes (particularly 5 to 15 minutes).

  In the present invention, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are used as a crosslinking aid (a compound having a radical polymerizable group as a functional group) in order to improve the crosslinking rate while preventing swelling. Contains. The crosslinking aid is generally added to the EVA resin in order to improve the gel fraction of EVA and improve the durability, but in the present invention, it is used for improving the crosslinking rate. Is groundbreaking.

In the present invention, the use of triallyl isocyanurate and trimethylolpropane tri (meth) acrylate at a specific blending ratio is particularly effective in suppressing the occurrence of swelling and shortening the crosslinking time. In the present invention, distribution Gohi of triallyl isocyanurate and trimethylolpropane tri (meth) acrylate, 65 mass: 35 to 85: a: (trimethylol propane tri (meth) acrylate triallyl isocyanurate) 15.

The amount of the triallyl isocyanurate is preferably 0.1 to 10 mass% of the ethylene / vinyl acetate copolymer, rather more preferably from 0.5 to 5% by weight, especially 0.5 to 2.0 % By mass . The amount of trimethylolpropane tri (meth) acrylate is preferably from 0.01 to 4 wt% of the ethylene / vinyl acetate copolymer, rather more preferably from 0.1 to 2% by weight, in particular 0.1 It is -0.5 mass% . In the present invention, the total amount of triallyl isocyanurate and trimethylolpropane tri (meth) acrylate used is in the range of 1 to 2.5% by mass relative to the ethylene / vinyl acetate copolymer.

  Crosslinking aids other than those described above may also be used in secondary amounts. Examples of such a crosslinking assistant include trifunctional allyl compounds such as triallyl cyanurate, bifunctional allyl compounds such as diallyl phthalate, diallyl fumarate and diallyl malate, polyhydric alcohols and (meta And monofunctional or bifunctional (meth) acrylate compounds such as (meth) acrylic esters (eg, NK esters) which are esters with acrylic acid. Although the above bifunctional (meth) acrylate compound can be used in combination with triallyl isocyanurate and trimethylolpropane tri (meth) acrylate, it is preferable to use a trifunctional compound in combination.

Moreover, a silane coupling agent can be added to EVA resin as a sealing film of a solar cell for the purpose of improving the adhesive force with a power generating element. Known silane coupling agents used for this purpose are, for example, γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxy. Propyltrimethoxysilane; β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be mentioned. These silane coupling agents are used in an amount of 5 parts by mass or less, preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of EVA. Hydroquinone; hydroquinone monomethyl ether; p for the purpose of improving the stability of EVA. -Benzoquinone; methylhydroquinone and the like can be added, and these are generally used at 5 parts by mass or less based on 100 parts by weight of the EVA resin.

  In the present invention, a colorant, an ultraviolet absorber, an antiaging agent, a discoloration preventing agent and the like can be further added as necessary. Examples of the colorant include inorganic pigments such as metal oxides and metal powders, and organic pigments such as azo-based, phthalocyanine-based, additive-based, acidic or basic dye-based lakes. Examples of ultraviolet absorbers include monohydroxyalkoxybenzophenones such as 2-hydroxy-4-octyloxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone; 2,2-dihydroxy-4,4-dimethoxybenzophenone and the like There are dihydroxyalkoxybenzophenone series; benzotriazole series such as 2- (2′-hydroxy-5-methylphenyl) benzotriazole; phenyl salsylate; hindered phenol series such as pt-butylphenyl salsylate. Examples of the light stabilizer include hindered amines such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, and anti-aging agents such as amines; phenols; bisphenyls.

  In the present invention, in order to prevent yellowing, it is preferable to use the dihydroxydimethoxybenzophenone ultraviolet absorber. 2,2-dihydroxy-4,4-dimethoxybenzophenone is particularly preferable.

  The ultraviolet absorbers and the like are generally used in the range of 0.01 to 3 parts by mass with respect to 100 parts by mass of the ethylene / vinyl acetate copolymer.

  The sealing film for solar cells of the present invention can be produced according to a conventional method by forming the EVA resin composition of the present invention by heating and rolling by, for example, extrusion molding or calendering. The heating temperature is preferably a temperature at which the crosslinking agent does not react or hardly reacts. For example, 40-80 degreeC is preferable.

In order to manufacture a solar cell using the solar cell sealing film of the present invention, the glass substrate 1, the EVA film 3A, the silicon power generation element 4, the EVA film 3B and the back cover 2 are laminated as shown in FIG. The back side EVA film 3B is laminated using the sealing film of the present invention, and the front side EVA film 3A is laminated using the sealing film of the present invention, and the laminate is laminated with a vacuum laminator according to a conventional method. Pressurizing pressure at a temperature of 135 to 180 ° C. (further 140 to 180 ° C., particularly 155 to 180 ° C.), a deaeration time of 2 to 15 minutes, a press pressure of 0.1 to 1.5 kg / cm ² , and a press time of 8 to 45 minutes. The EVA films 3A and 3B can be cross-linked during the heating and pressurization to form a sealing film excellent in light resistance, heat resistance and weather resistance.

  The glass substrate 1 used in the present invention is usually silicate glass. The glass plate thickness is generally 0.1 to 10 mm, preferably 0.3 to 5 mm. The glass substrate is generally chemically or thermally strengthened.

  The back guard 2 used in the present invention is generally a plastic film (eg, polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE)), but a fluorinated polyethylene film is preferable in consideration of heat resistance.

  The following examples further illustrate the present invention.

[Example 1]
[EVA resin composition formulation 1 (parts by mass)]
EVA resin: 100
(Vinyl acetate content 26 wt%, melt flow rate 4 g / 10 min)
Crosslinker 1: 1.5
(2,5-dimethyl-2,5-bis (t-butylperoxy) hexane)
Crosslinking aid 1 (triallyl isocyanurate): 1.0
Crosslinking aid 2 (trimethylolpropane trimethacrylate): 0.5
Additive 1 (hindered amine light stabilizer) 0.1
[Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate]
Additive 2 (UV absorber): 0.03
(2,2-dihydroxy-4,4-dimethoxybenzophenone)
An EVA film was formed by extrusion molding at 80 ° C. using the EVA resin composition having the above composition. The film thickness was 600 μm.

  Using the obtained EVA film as the front side sealing EVA film 3A and the back side sealing EVA film 3B, as shown in FIG. 1, from a glass plate 1 having a thickness of 3 mm and a fluorinated polyethylene film having a thickness of 38 μm. A solar battery cell 4 was sealed between the back cover 2 and the solar battery. In addition, sealing was performed by thermocompression bonding under a vacuum laminator under conditions of a temperature of about 140 to 175 ° C., a degassing time of 3 minutes, and a pressing time of 10 minutes to crosslink EVA.

[Comparative Example 1]
In the EVA resin composition formulation 1, a solar cell was produced in the same manner as in Example 1 except that only the crosslinking aid 1 (1.0 part by mass) was used and the crosslinking aid 2 was not used.

[Reference Example 1]
In the EVA resin composition formulation 1, a solar cell was produced in the same manner as in Example 1 except that the amount of the crosslinking aid 2 was changed from 0.5 parts by mass to 1.0 part by mass.

[Example 2]
In the EVA resin composition formulation 1, a solar cell was produced in the same manner as in Example 1 except that the amount of the crosslinking agent 1 used was changed from 1.5 parts by mass to 1.9 parts by mass.

[Comparative Example 2]
In Example 2, a solar cell was produced in the same manner as in Example 2 except that only the crosslinking aid 1 (1.0 part by mass) was used and the crosslinking aid 2 was not used.

[Reference Example 2]
In Example 2, a solar cell was produced in the same manner as in Example 2 except that the amount of the crosslinking aid 2 was changed from 0.5 parts by mass to 1.0 part by mass.

[Example 3]
In EVA resin composition formulation 1, except that the amount of crosslinking agent 1 used was changed from 1.5 parts by weight to 2.1 parts by weight, and the amount of crosslinking aid 1 used was changed from 1.0 parts by weight to 2.0 parts by weight. A solar cell was manufactured in the same manner as in Example 1.

[Comparative Example 3]
In Example 3, a solar cell was produced in the same manner as in Example 3 except that only the crosslinking aid 1 (2.0 parts by mass) was used and the crosslinking aid 2 was not used.

[Reference Example 3]
In Example 3, the usage amount of the crosslinking aid 1 was changed from 2.0 parts by mass to 1.0 part by mass, and the usage amount of the crosslinking aid 2 was changed from 0.5 parts by mass to 1.0 part by mass. A solar cell was manufactured in the same manner as in Example 3.

[Example 4]
[EVA resin composition blend 2 (parts by mass)]
EVA resin: 100
(Vinyl acetate content 26 wt%, melt flow rate 4 g / 10 min)
Crosslinker 1: 1.3
(2,5-dimethyl-2,5-bis (t-butylperoxy) hexane)
Cross-linking agent 2: 0.1
(T-Butylperoxy-2-ethylhexyl monocarbonate)
Crosslinking aid 1 (triallyl isocyanurate): 2.0
Crosslinking aid 2 (trimethylolpropane trimethacrylate): 0.5
Additive 1 (hindered amine light stabilizer) 0.1
[Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate]
Additive 2 (UV absorber): 0.03
(2,2-dihydroxy-4,4-dimethoxybenzophenone)
An EVA film was formed by extrusion molding at 80 ° C. using the EVA resin composition having the above composition. The film thickness was 600 μm.

  Using the obtained EVA film as the front side sealing EVA film 3A and the back side sealing EVA film 3B, as shown in FIG. 1, from a glass plate 1 having a thickness of 3 mm and a fluorinated polyethylene film having a thickness of 38 μm. A solar battery cell 4 was sealed between the back cover 2 and the solar battery. In addition, sealing was performed by thermocompression bonding under a vacuum laminator under conditions of a temperature of about 140 to 175 ° C., a degassing time of 3 minutes, and a pressing time of 10 minutes to crosslink EVA.

<Evaluation of solar cell sealing film>
(1) 50% cross-linking torque (kgf / cm)
Resin compositions similar to those in the above Examples, Comparative Examples and Reference Examples were similarly formed on a glass plate having a release layer, and then the sheet was peeled off. The obtained sheet was set at 150 ° C., and the torque was measured by reading the value for 15 minutes with a cure torque meter (type IV; manufactured by JSR Corporation). The intermediate value between the maximum torque value and the minimum value was 50% cross-linking.
(2) 50% cross-linking time (minutes)
The same resin compositions as those in the above Examples, Comparative Examples and Reference Examples were formed in the same manner on a glass plate having a release layer, and then the sheet was peeled off. The obtained sheet was set at 150 ° C., and its torque was measured by reading the value for 15 minutes with a cure torque meter (type IV; manufactured by JSR Corporation), and required 50% for crosslinking. The time was determined as 50% crosslink arrival time.
(3) Foam
The obtained solar cell was allowed to stand for 800 hours in an environment of a temperature of 85 ° C. and a relative humidity of 85%, and the appearance (inflation, foaming) after the standing was visually observed and evaluated as follows.
◯: No swelling or foaming is observed Δ: Slight swelling or foaming is observed ×: Swelling or foaming is observed Tables 1 and 2 show the results.

  As is clear from the above results, when two specific types of crosslinking aids of the present invention are used, crosslinking is possible in a short time compared to the sealing film of the comparative example using only one type, and There is no occurrence of blisters.

It is sectional drawing which shows a common solar cell.

Explanation of symbols

1 Glass substrate 2 Back cover 3A, 3B EVA film 4 Silicon power generation element

Claims (10)

In a sealing film for solar cells containing an ethylene / vinyl acetate copolymer, an organic peroxide and a crosslinking aid,
As the organic peroxide,
Formula I below:

[However, R ¹ represents a methyl group, R ² represents an ethylene group, and R ³ represents a t-butyl group. A dialkyl peroxide represented by
As the crosslinking aid, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are included,
The total amount of triallyl isocyanurate and trimethylolpropane tri (meth) acrylate is in the range of 1 to 2.5% by mass with respect to the ethylene / vinyl acetate copolymer, and triallyl isocyanurate and trimethylolpropane. The sealing film for solar cells, wherein the mixing ratio of tri (meth) acrylate is in the range of 65:35 to 85:15 by mass.   The sealing film for solar cells of Claim 1 which contains 0.5-2.0 mass% of triallyl isocyanurate with respect to an ethylene / vinyl acetate copolymer.   The sealing film for solar cells of Claim 1 or 2 which contains 0.1-0.5 mass% of trimethylol propane tri (meth) acrylate with respect to an ethylene / vinyl acetate copolymer. As organic peroxide,
Formula II below:

[However, R ⁴ represents a t-butyl group and R ⁵ represents a 2-ethylhexyl group. ]
The solar cell sealing film of any one of Claims 1-3 containing peroxyester represented by these. The sealing for solar cells according to any one of claims 1 to 4 , wherein the organic peroxide is contained in an amount of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene / vinyl acetate copolymer. film. The crosslinking aid, in a total amount of ethylene / sealing a solar cell according to any one of claims 1 to 5, vinyl acetate copolymer with respect to 100 parts by weight and contains 0.1 to 10 parts by weight Stop film. Furthermore, the sealing film for solar cells of any one of Claims 1-6 containing a dihydroxy dimethoxy benzophenone series ultraviolet absorber. The solar cell sealing film according to any one of claims 1 to 7 further comprising a silane coupling agent. The vinyl acetate unit of an ethylene / vinyl acetate copolymer exists in the range of 10-36 mass% with respect to 100 mass parts of ethylene vinyl acetate copolymers, For solar cells of any one of Claims 1-8 . Sealing film. In a solar cell formed by sealing a solar cell through a sealing film between a front surface side transparent protective member and a back surface side protective member,
Solar cell, wherein the sealing film is a solar cell sealing film according to any one of claims 1-9.

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