JP2017152567A - Solar battery sealing material and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar battery sealing material which is superior in crosslink characteristics, and which enables the suppression of generation of bubbles in crosslinking.SOLUTION: A solar battery sealing material according to the present invention is used to seal a solar battery element. The solar battery sealing material comprises: an ethylene-α-olefin copolymer; a t-amyl peroxybenzoate as a crosslinking agent; and one or more crosslinking assistant agents selected from a group consisting of a divinyl aromatic compound, a cyanurate compound, a diallyl compound, an acrylate compound, a triallyl compound, an oxime compound and a maleimide compound. In the solar battery sealing material, the content of the t-amyl peroxybenzoate is 0.1-2.0 pts.mass relative to 100 pts.mass of the ethylene-α-olefin copolymer. In the solar battery sealing material, the content of the crosslinking assistant agents is 0.1-3.0 pts.mass relative to 100 pts.mass of the ethylene-α-olefin copolymer.SELECTED DRAWING: None

Description

  The present invention relates to a solar cell sealing material and a solar cell module.

  In recent years, photovoltaic power generation has attracted attention as clean energy, and development of solar cell modules for photovoltaic power generation has been promoted. A solar cell module generally has a configuration of a protective glass (front surface side transparent protective member), a light receiving surface side solar cell sealing material, a solar cell element, a back surface side solar cell sealing material, and a back sheet (back surface side protective member). ing. During the production of the solar cell module, the solar cell encapsulant is heated by heating the solar cell encapsulant in a state where the above layers are laminated, thereby sealing the solar cell element. Adhere to the backsheet.

  As a solar cell encapsulant, an ethylene / vinyl acetate copolymer (EVA) sheet has been widely used since it has excellent transparency, flexibility, workability, durability, and the like. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-53298) discloses a sealing film that is made of an EVA composition containing a cross-linking agent and trimellitic acid ester and is excellent in both adhesiveness and film forming property. Yes.

JP 2010-53298 A

With the widespread use of mega solar, the system voltage is increasing for the purpose of reducing transmission loss. Among solar cell modules used in a state where a high voltage is maintained, a PID (abbreviation of Potential Induced Degradation) phenomenon in which the output is greatly reduced and the characteristics deteriorate may occur.
Here, according to the study by the present inventors, by using a solar cell sealing material containing an ethylene / α-olefin copolymer, a solar cell sealing material containing EVA that has been conventionally used as a sealing material. It was clarified that the PID phenomenon is suppressed compared to.
However, according to the study by the present inventors, the ethylene / α-olefin copolymer is inferior in crosslinking property to EVA, so that when the solar cell module is produced, the lamination temperature is high and the lamination time is also long. It became clear that there was a problem of influence on other members due to heat and an increase in manufacturing cost.
Moreover, if the amount of the crosslinking agent is increased, the crosslinking speed can be increased. However, since the amount of gas generated from the decomposition product of the crosslinking agent is increased, there is a problem that bubbles are likely to be generated at the time of manufacturing the solar cell module.

  The present invention has been made in view of the above circumstances, and provides a solar cell encapsulant that has excellent crosslinking characteristics and suppresses the generation of bubbles during crosslinking.

  The present inventors diligently studied to provide a solar cell encapsulant that is excellent in cross-linking properties and that suppresses the generation of bubbles during cross-linking. As a result, it has been found that by selecting t-amyl peroxybenzoate as a crosslinking agent, crosslinking characteristics can be improved while suppressing the generation of bubbles, and the present invention has been achieved.

  That is, according to this invention, the solar cell sealing material and solar cell module which are shown below are provided.

[1]
A solar cell encapsulant used for encapsulating solar cell elements,
An ethylene / α-olefin copolymer;
A cross-linking agent t-amyl peroxybenzoate;
One or more crosslinking aids selected from the group consisting of divinyl aromatic compounds, cyanurate compounds, diallyl compounds, acrylate compounds, triallyl compounds, oxime compounds and maleimide compounds;
Including
The content of the t-amyl peroxybenzoate in the solar cell encapsulant is 0.1 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. ,
The solar cell encapsulant wherein the content of the crosslinking aid in the solar cell encapsulant is 0.1 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. Stop material.
[2]
The solar cell encapsulating material according to [1], wherein the ethylene / α-olefin copolymer satisfies at least one of the following requirements a1) to a4).
a1) The content rate of the structural unit derived from ethylene is 80-90 mol%, and the content rate of the structural unit derived from a C3-C20 alpha olefin is 10-20 mol%.
a2) Based on ASTM D1238, MFR measured on condition of 190 degreeC and a 2.16kg load is 0.1-50 g / 10min.
a3) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a4) The Shore A hardness measured according to ASTM D2240 is 60 to 85.
[3]
Further comprising a silane coupling agent,
The content of the silane coupling agent in the solar cell encapsulant is 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. The solar cell encapsulating material according to [1] or [2].
[4]
Further comprising at least one additive selected from the group consisting of ultraviolet absorbers, light stabilizers, and heat stabilizers,
The content of the additive in the solar cell sealing material is 0.005 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. [3] The solar cell encapsulant according to any one of the above.
[5]
The solar cell encapsulating material according to any one of the above [1] to [4], which is in a sheet form.
[6]
A surface-side transparent protective member;
A back side protection member;
A solar cell element;
It is comprised by the bridge | crosslinking material of the solar cell sealing material as described in any one of said [1] thru | or [5], and the said solar cell element is interposed between the said surface side transparent protective member and the said back surface side protective member. A sealing layer for sealing;
A solar cell module comprising:

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in a crosslinking characteristic, the solar cell sealing material by which the bubble generation at the time of bridge | crosslinking was suppressed is realizable.

It is sectional drawing which showed typically embodiment of the solar cell module of this invention typically.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, “A to B” in the numerical range represents A or more and B or less unless otherwise specified.

1. About solar cell sealing material The solar cell sealing material which concerns on this embodiment is a solar cell sealing material used in order to seal a solar cell element, Comprising: It is an ethylene-alpha-olefin copolymer and a crosslinking agent. A t-amyl peroxybenzoate, and one or more cross-linking aids selected from the group consisting of divinyl aromatic compounds, cyanurate compounds, diallyl compounds, acrylate compounds, triallyl compounds, oxime compounds and maleimide compounds, Including.
And content of the said t-amyl peroxy benzoate in the said solar cell sealing material is 0.1 mass part or more and 2.0 mass parts or less with respect to 100 mass parts of said ethylene-alpha-olefin copolymers. And the content of the crosslinking aid in the solar cell encapsulant is 0.1 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. .

The present inventors diligently studied to provide a solar cell encapsulant that is excellent in cross-linking properties and that suppresses the generation of bubbles during cross-linking. As a result, it has been found that by selecting t-amyl peroxybenzoate as a cross-linking agent, the cross-linking characteristics can be improved while suppressing the generation of bubbles.
That is, the solar cell encapsulant according to the present embodiment is excellent in cross-linking characteristics and can suppress the generation of bubbles during cross-linking.

  Further, the total content of the t-amyl peroxybenzoate and the crosslinking aid in the solar cell encapsulant according to the present embodiment is preferably based on 100 parts by mass of the ethylene / α-olefin copolymer. Is 0.2 to 3.5 parts by mass, more preferably 0.5 to 2.5 parts by mass, and still more preferably 0.8 to 2.0 parts by mass.

  Moreover, the mass ratio of the content of the crosslinking aid to the content of the t-amyl peroxybenzoate in the solar cell encapsulant according to the present embodiment is preferably 0.1 or more and 10.0 or less, More preferably, it is 0.3 or more and 7.5 or less, More preferably, it is 0.5 or more and 5.0 or less.

  Hereinafter, each component which comprises the solar cell sealing material of this embodiment is demonstrated.

<Ethylene / α-olefin copolymer>
The solar cell encapsulant according to this embodiment contains an ethylene / α-olefin copolymer.
The ethylene / α-olefin copolymer is obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. As the α-olefin, usually, an α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more.
Examples of the α-olefin having 3 to 20 carbon atoms include linear or branched α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3, 3 -Dimethyl-1-butene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like can be mentioned. Among these, α-olefins having 10 or less carbon atoms are preferable, and α-olefins having 3 to 8 carbon atoms are particularly preferable. Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferred because of their availability. The ethylene / α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

  Furthermore, the ethylene / α-olefin copolymer may be a copolymer containing ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene. The α-olefin is the same as described above, and examples of the non-conjugated polyene include 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), and dicyclopentadiene (DCPD). These non-conjugated polyenes can be used alone or in combination of two or more.

  Examples of the ethylene / α-olefin copolymer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o, p-dimethylstyrene, methoxystyrene, vinyl benzoic acid, methyl vinylbenzoate, and vinyl. Aromatic vinyl compounds such as benzyl acetate, hydroxystyrene, p-chlorostyrene, divinylbenzene, 3-phenylpropylene, 4-phenylpropylene, α-methylstyrene; cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, etc. Cyclic olefins having 3 to 20 carbon atoms may be used in combination.

  The ethylene / α-olefin copolymer preferably satisfies at least one of the following requirements a1) to a4).

(Requirement a1)
The content ratio of the structural unit derived from ethylene contained in the ethylene / α-olefin copolymer is preferably 80 to 90 mol%, more preferably 80 to 88 mol%, still more preferably 82 to 88 mol%, particularly preferably. Is 82-87 mol%. The content ratio of the structural unit derived from an α-olefin having 3 to 20 carbon atoms (hereinafter also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer is preferably 10 to 20 mol%. More preferably, it is 12-20 mol%, More preferably, it is 12-18 mol%, Most preferably, it is 13-18 mol%.

  High transparency is acquired as the content rate of the alpha-olefin unit contained in an ethylene-alpha-olefin copolymer is more than the said lower limit. Further, extrusion molding at a low temperature can be easily performed, and for example, extrusion molding at 130 ° C. or lower is possible. For this reason, even when an organic peroxide is kneaded into the ethylene / α-olefin copolymer, it is possible to suppress the progress of the crosslinking reaction in the extruder, and gel-like foreign matters are present on the sheet of the solar cell sealing material. Occurrence and deterioration of the appearance of the sheet can be prevented. Moreover, since moderate softness | flexibility is acquired, generation | occurrence | production of the crack of a solar cell element, the crack of a thin film electrode, etc. can be prevented at the time of lamination molding of a solar cell module.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallization speed of the ethylene / α-olefin copolymer becomes appropriate, so that it is extruded from the extruder. The sheet is not sticky and can be easily peeled off by a cooling roll, and a sheet-like sheet of solar cell encapsulant can be obtained efficiently. Further, since no stickiness is generated on the sheet, blocking can be prevented, and the sheet feeding property is good. In addition, a decrease in heat resistance can be prevented.

(Requirement a2)
According to ASTM D1238, the melt flow rate (MFR) of the ethylene / α-olefin copolymer measured at 190 ° C. under a load of 2.16 kg is usually 0.1 g / 10 min or more and 50 g / 10 min or less. It is preferably 1 g / 10 min or more and 40 g / 10 min or less, more preferably 2 g / 10 min or more and 30 g / 10 min or less, and further preferably 5 g / 10 min or more and 10 g / 10 min or less.
The MFR of the ethylene / α-olefin copolymer can be adjusted by adjusting the polymerization temperature during the polymerization reaction, the polymerization pressure, and the molar ratio of the ethylene and α-olefin monomer and hydrogen concentrations in the polymerization system. can do.

  When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, a sheet can be suitably produced by calendar molding. When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, the flowability of the resin composition containing the ethylene / α-olefin copolymer is low, so that the melted out when laminating the sheet and the battery element This is preferable in that the laminating apparatus can be prevented from being soiled by the resin.

Further, when the MFR is 2 g / 10 min or more, preferably the MFR is 10 g / 10 min or more, the fluidity of the resin composition containing the ethylene / α-olefin copolymer is improved, and the productivity at the time of sheet extrusion molding is improved. Can be improved.
Further, when the MFR is 50 g / 10 min or less, the molecular weight is increased, and therefore, adhesion to a roll surface such as a chill roll can be suppressed. Therefore, peeling is unnecessary, and a sheet having a uniform thickness can be formed. Furthermore, since it becomes a resin composition with “koshi”, a thick sheet of 0.1 mm or more can be easily formed. Moreover, since the crosslinking characteristic at the time of laminate molding of the solar cell module is improved, it is possible to sufficiently crosslink and suppress a decrease in heat resistance.
When the MFR is 27 g / 10 min or less, the draw-down during sheet forming can be further suppressed, a wide sheet can be formed, the cross-linking characteristics and heat resistance are further improved, and the best solar cell encapsulant Sheet of can be obtained.

  When the crosslinking treatment of the resin composition is not performed in the laminating step of the solar cell module, the influence of the decomposition of the crosslinking agent is small in the melt extrusion step, so that the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, preferably A sheet can also be obtained by extrusion molding using a resin composition of 0.5 g / 10 min or more and less than 8.5 g / 10 min. When the content of the crosslinking agent in the resin composition is 0.15 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer, the MFR is 0.1 g / 10 min or more and 10 g / A sheet can also be produced by extrusion molding at a molding temperature of 170 to 250 ° C. using a resin composition of less than 10 minutes and performing a silane modification treatment or a fine crosslinking treatment. When the MFR is within this range, it is preferable in that the laminating apparatus can be prevented from being soiled by the molten resin that protrudes when the sheet is laminated on the solar cell element.

(Requirement a3)
The density of the ethylene / α-olefin copolymer measured according to ASTM D1505 is preferably 0.865 to 0.884 g / cm ³ , more preferably 0.866 to 0.883 g / cm ³ , preferably 0.866~0.880g / cm ^3, particularly preferably 0.867~0.880g / cm ^3.
The density of the ethylene / α-olefin copolymer can be adjusted by a balance between the content ratio of ethylene units and the content ratio of α-olefin units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a high-density ethylene / α-olefin copolymer can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and an ethylene / α-olefin copolymer having a low density can be obtained.

When the density of the ethylene / α-olefin copolymer is not more than the above upper limit, the crystallinity becomes more appropriate, and the transparency of the resulting solar cell encapsulant can be further increased. Furthermore, the crosslinkability can be made better. Moreover, it is excellent in a softness | flexibility and it can suppress more that the crack of a solar cell element, the crack of a thin film electrode, etc. generate | occur | produce when laminate-molding.
On the other hand, if the density of the ethylene / α-olefin copolymer is not less than the above lower limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the sheet extruded from the extruder is not sticky and is cooled. Peeling with a roll becomes easy, and a sheet of a solar cell sealing material can be easily obtained. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since it is made to fully bridge | crosslink, the fall of the heat resistance of a solar cell sealing material can be suppressed.

(Requirement a4)
The Shore A hardness of the ethylene / α-olefin copolymer, measured according to ASTM D2240, is preferably 60 to 85, more preferably 62 to 83, still more preferably 62 to 80, and particularly preferably 65 to 85. 80. The Shore A hardness of the ethylene / α-olefin copolymer can be adjusted by controlling the content ratio and density of the ethylene units in the ethylene / α-olefin copolymer within the above-mentioned numerical range. That is, an ethylene / α-olefin copolymer having a high ethylene unit content and high density has a high Shore A hardness. On the other hand, an ethylene / α-olefin copolymer having a low ethylene unit content and a low density has a low Shore A hardness.

When the Shore A hardness is not less than the above lower limit, a sheet that is easily formed into a sheet and has good blocking resistance can be obtained, and heat resistance can also be improved.
On the other hand, when the Shore A hardness is not more than the above upper limit, the transparency and flexibility can be improved and sheet molding can be facilitated.

  The content of the ethylene / α-olefin copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, when the total resin component contained in the solar cell encapsulant is 100% by mass. More preferably, it is 95 mass% or more, and particularly preferably 100 mass%. Thereby, the solar cell sealing material excellent in balance of various characteristics, such as transparency, adhesiveness, heat resistance, a softness | flexibility, an external appearance, a bridge | crosslinking characteristic, an electrical property, and extrusion moldability, can be obtained.

  The content of the resin component is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably when the entire solar cell sealing material is 100% by mass. 90% by mass or more. Thereby, the solar cell sealing material excellent in balance of various characteristics, such as transparency, adhesiveness, heat resistance, a softness | flexibility, an external appearance, a bridge | crosslinking characteristic, an electrical property, and extrusion moldability, can be obtained.

(Method for producing ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer can be produced using, for example, various metallocene compounds shown below as catalysts. As the metallocene compound, for example, the metallocene compounds described in JP-A-2006-077261, JP-A-2008-231265, JP-A-2005-314680 and the like can be used. However, a metallocene compound having a structure different from the metallocene compounds described in these patent documents may be used, or two or more metallocene compounds may be used in combination.

  Polymerization of the ethylene / α-olefin copolymer can be carried out by any of the conventionally known gas phase polymerization methods and liquid phase polymerization methods such as slurry polymerization methods and solution polymerization methods. Preferably, it is carried out by a liquid phase polymerization method such as a solution polymerization method.

<Crosslinking agent>
The solar cell sealing material according to this embodiment contains t-amyl peroxybenzoate which is a cross-linking agent.
In the solar cell encapsulant according to this embodiment, by containing t-amyl peroxybenzoate, the crosslinking rate of the ethylene / α-olefin copolymer is improved, and the gas derived from the organic peroxide at the time of crosslinking It is possible to obtain an excellent effect that the generation of bubbles due to the components is reduced.

The content of t-amyl peroxybenzoate in the solar cell encapsulant according to this embodiment is 0.1 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. Yes, preferably 0.2 parts by weight or more and 1.5 parts by weight or less, more preferably 0.2 parts by weight or more and 1.0 parts by weight or less.
When the content of t-amyl peroxybenzoate is not less than the above lower limit, the crosslinking property of the solar cell encapsulant becomes better, and the heat resistance of the solar cell encapsulant is further improved. Further, the graft reaction of the silane coupling agent to the main chain of the ethylene / α-olefin copolymer is further improved, and the heat resistance and adhesiveness are further improved.
Further, when the content of t-amyl peroxybenzoate is not more than the above upper limit value, the above cross-linking characteristics, heat resistance, and adhesiveness can be further improved, and gelation during sheet molding can be further suppressed, and the sheet A solar cell encapsulant with better appearance can be obtained. Furthermore, the generation amount of the decomposition product of t-amyl peroxybenzoate is further reduced, and generation of bubbles in the solar cell sealing material can be further suppressed.

One or more other organic peroxides can be used as a crosslinking agent together with t-amyl peroxybenzoate. In that case, the total amount of the organic peroxide (that is, the total amount of t-amyl peroxybenzoate and other organic peroxide) is 1.0 part by mass with respect to 100 parts by mass of the ethylene / α-olefin copolymer. The following is preferable.
Considering the productivity of the solar cell module, other organic peroxides preferably have a half-life of 10 hours or less and a decomposition temperature of 105 ° C. or less. From the viewpoint of safety, it is preferable that the maximum storage temperature is 10 ° C. or higher. Examples of such organic peroxides include dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, dibenzoyl peroxide, cyclohexanone peroxide, di-t -Butyl perphthalate, cumene hydroperoxide, t-butyl hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexene, 2,5-dimethyl-2,5-di (t -Butylperoxy) hexane, t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, 1,1-di (t-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amyl) -Oxy) cyclohexane, t-amylperoxyisononanoate, t-amylperoxynormal octoate, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di ( t-butylperoxy) cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxy Acetate, t-butyl peroxyisononanoate, t-butyl peroxybenzoate, 2,2-di (butylperoxy) butane, n-butyl-4,4-di (t-butylperoxy) petitate, methyl ethyl ketone -Oxide, ethyl-3,3-di (t-butylperoxy ) Butyrate, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxide, 1,1,3,3-tetralamethylbutyl hydroperoxide, acetylacetone peroxide, etc. 1 type, or 2 or more types selected from can be used.

  Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylperoxy- It is preferable to use one or more selected from 2-ethylhexyl carbonate and t-butyl peroxybenzoate.

<Crosslinking aid>
The solar cell sealing material according to the present embodiment includes a crosslinking aid from the viewpoint of improving the crosslinkability.
As said crosslinking adjuvant, the 1 type (s) or 2 or more types selected from the group which consists of a divinyl aromatic compound, a cyanurate compound, a diallyl compound, an acrylate compound, a triallyl compound, an oxime compound, and a maleimide compound can be used.

Content of the crosslinking adjuvant in the solar cell sealing material which concerns on this embodiment is 3.0 mass parts or less with respect to 100 mass parts of ethylene-alpha-olefin copolymers, and 2.0 mass parts or less. It is preferable that it is 1.5 mass parts or less.
Moreover, content of the crosslinking adjuvant in the solar cell sealing material which concerns on this embodiment is 0.1 mass part or more with respect to 100 mass parts of ethylene * alpha-olefin copolymers, and 0.3 mass Part or more, preferably 0.5 part by weight or more. Thereby, it can be set as a moderate bridge | crosslinking structure and the heat resistance of a solar cell sealing material, a mechanical physical property, and adhesiveness can be improved.

Examples of the divinyl aromatic compound include divinylbenzene and di-i-propenylbenzene.
Examples of the cyanurate compound include triallyl cyanurate and triallyl isocyanurate.
Examples of diallyl compounds include diallyl phthalate.
Examples of the triallyl compound include pentaerythritol triallyl ether.
Examples of the acrylate compound include diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and tetramethylolmethane. Examples include tetra (meth) acrylate and tetramethylolmethane tetra (meth) acrylate.
Examples of the oxime compound include p-quinone dioxime, pp′-dibenzoylquinone dioxime, and the like.
Examples of the maleimide compound include m-phenylene dimaleimide.

  As the crosslinking aid, a compound having at least three functional crosslinkable unsaturated bonds such as a vinyl group is preferable. Among them, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane tri (meth) acrylate, ditrimethylol. Propane tetra (meth) acrylate is preferred because it has good crosslinkability.

<Silane coupling agent>
The solar cell sealing material according to this embodiment may further contain a silane coupling agent.
Content of the silane coupling agent in the solar cell sealing material which concerns on this embodiment is 0.1 mass part or more and 5 mass parts or less with respect to 100 mass parts of ethylene-alpha-olefin copolymers. Preferably, it is 0.1 to 4 parts by weight, more preferably 0.1 to 3 parts by weight.
When the content of the silane coupling agent is not less than the above lower limit value, the adhesive strength between the solar cell encapsulant and other members can be made better. On the other hand, when the content of the silane coupling agent is not more than the above upper limit value, the balance between cost and performance is good, and deterioration of moisture permeability can be prevented. Moreover, when it uses as a solar cell sealing material, adhesiveness with a surface side transparent protection member, a cell, an electrode, and a back surface side protection member becomes favorable, and adhesiveness also improves. Moreover, it can suppress that a silane coupling agent itself raise | generates a condensation reaction, exists as a white stripe | line in a solar cell sealing material, and a product external appearance deteriorates.

  A conventionally well-known silane coupling agent can be used, and there is no restriction | limiting in particular. Specifically, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxysilane), γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane 1 type, or 2 or more types selected from etc. can be used. Preferably, one kind or two or more kinds selected from γ-glycidoxypropylmethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane and the like having good adhesiveness are used. be able to.

<Ultraviolet absorber, light stabilizer, heat stabilizer>
The solar cell sealing material according to the present embodiment may further contain at least one additive selected from an ultraviolet absorber, a light stabilizer, and a heat resistance stabilizer. The blending amount of these additives is preferably 0.005 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. Furthermore, it is preferable to contain at least two kinds of additives selected from the above three kinds, and it is particularly preferred that all of the above three kinds are contained. When the blending amount of the additive is within the above range, the effect of improving the weather resistance stability and heat stability can be sufficiently secured, and the transparency and the adhesion with the glass plate can be prevented from being lowered. preferable.

  Examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2- Benzophenone ultraviolet absorbers such as carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy- Benzotriazole ultraviolet absorbers such as 5-methylphenyl) benzotriazole and 2- (2-hydroxy-5-t-octylphenyl) benzotriazole; salicylic acid esters such as phenyl salicylate and p-octylphenyl salicylate Select from UV absorbers, etc. One or may be used two or more substances.

  Examples of the light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3. , 5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino }] Or the like selected from hindered amine compounds, hindered piperidine compounds and the like can be used.

  Examples of the heat stabilizer include tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid Tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphos Phosphite-based antioxidants such as phyto; lactone-based antioxidants such as a reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene; 3,3 ′ , 3 ", 5,5 ', 5" -hexa-tert-butyl-a, a', a "-(methylene-2,4,6-triyl) tri-p-cresol, 1,3,5-trimethyl -2, 4, 6 -Tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- Hindered phenolic antioxidants such as (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] 1 type, or 2 or more types selected from an agent, a sulfur-based antioxidant, an amine-based antioxidant, etc. Among these, a phosphite-based antioxidant and a hindered phenol-based antioxidant are preferable. .

<Solar cell encapsulant sheet>
The solar cell encapsulant according to this embodiment is one of the preferred embodiments in which the overall shape is a sheet.
Although the thickness of the solar cell sealing material sheet (sheet-shaped solar cell sealing material) in this embodiment is not specifically limited, 0.01 mm or more and 2 mm or less are preferable, and 0.2 mm or more and 1.2 mm or less are more preferable. When the thickness is within this range, damage to the light-receiving surface side protective member, solar cell element, thin film electrode, etc. in the laminating step can be suppressed, and a high amount of photovoltaic power can be obtained by ensuring sufficient light transmittance. be able to. Furthermore, it is preferable because the solar cell module can be laminated at a low temperature.

  The solar cell encapsulant sheet of the present embodiment may be laminated with other layers as long as the object of the present invention is not impaired. For example, you may have layers, such as a hard-coat layer for surface or back surface protection, an adhesion layer, an antireflection layer, a gas barrier layer, and an antifouling layer. If classified by material, layer made of UV curable resin, layer made of thermosetting resin, layer made of polyolefin resin, layer made of carboxylic acid modified polyolefin resin, layer made of fluorine-containing resin, cyclic olefin (co) Examples thereof include a layer made of a polymer and a layer made of an inorganic compound.

<Method for producing solar cell encapsulant sheet>
Although the manufacturing method of the solar cell sealing material sheet of this embodiment is not particularly limited, various known molding methods (cast molding, extrusion sheet molding, inflation molding, injection molding, compression molding, calendar molding, etc.) should be adopted. Is possible. In particular, extrusion molding and calendar molding are preferable.

Although the manufacturing method of the solar cell sealing material sheet of this embodiment is not specifically limited, For example, the following method is mentioned. First, an ethylene / α-olefin copolymer, a crosslinking agent, a crosslinking aid, and if necessary, a silane coupling agent, an ultraviolet absorber, a light stabilizer, a heat stabilizer, and further necessary. In response to this, other additives are blended manually, for example, in a bag such as a plastic bag, or by using a stirring mixer such as a Henschel mixer, tumbler or super mixer. Next, the obtained resin composition is put into, for example, a hopper of an extrusion sheet molding machine, and the resin composition is extruded into a sheet form from a T-die of the extrusion sheet molding machine while performing melt kneading to obtain a resin sheet.
In addition, a part of additive can also be added in the middle of melt-kneading after throwing into an extrusion sheet molding machine. As the sheet forming method, calendar forming may be employed.
The molding can be performed by a known method using a T-die extruder, a calendar molding machine, an inflation molding machine or the like.

2. About solar cell module The solar cell sealing material which concerns on this embodiment is used in order to seal a solar cell element in a solar cell module.
As a structure of a solar cell module, the structure which laminated | stacked the surface side transparent protective member / light-receiving surface side sealing layer / solar cell element / back surface side sealing layer / back surface side protective member (back sheet | seat) in this order, for example is mentioned. There is no particular limitation.
The crosslinked product of the solar cell encapsulant according to the present embodiment is used for either one or both of the light receiving surface side sealing layer and the back surface side sealing layer.

In FIG. 1, an example of sectional drawing of the solar cell module 10 of this embodiment is shown.
The solar cell module 10 includes a plurality of solar cell elements 13, a pair of light-receiving surface side sealing layers 11 and a back surface side sealing layer 12 that are sealed with the solar cell elements 13 interposed therebetween, and a front surface side transparent protective member 14 and a back surface. A side protection member (back sheet) 15.

(Solar cell element)
Examples of the solar cell element 13 include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and III-V and II-VI compound semiconductors such as gallium-arsenic, copper-indium-selenium, and cadmium-tellurium. Various solar cell elements such as a system can be used.
In the solar cell module 10, the plurality of solar cell elements 13 are electrically connected in series via an interconnector 16 having a conducting wire and a solder joint.

(Front side transparent protective member)
Examples of the surface-side transparent protective member 14 include a glass plate; a resin plate formed of acrylic resin, polycarbonate, polyester, fluorine-containing resin, and the like.

(Back side protection member)
Examples of the back surface side protection member (back sheet) 15 include single or multilayer sheets such as metals and various thermoplastic resin films. Examples thereof include metals such as tin, aluminum, and stainless steel; inorganic materials such as glass; various thermoplastic resin films formed of polyester, inorganic material-deposited polyester, fluorine-containing resin, polyolefin, and the like.
The back surface side protection member 15 may be a single layer or a multilayer.

  The solar cell sealing material according to the present embodiment exhibits good adhesion to the front surface side transparent protective member 14 and the rear surface side protective member 15.

(Method for manufacturing solar cell module)
Although the manufacturing method of the solar cell module 10 which concerns on this embodiment is not specifically limited, For example, the following method is mentioned.
First, a plurality of solar cell elements 13 that are electrically connected using the interconnector 16 are sandwiched between a pair of light-receiving surface side sealing layers 11 and a back surface-side sealing layer 12, and these light-receiving surface side sealing layers 11 and the back surface The side sealing layer 12 is sandwiched between the front surface side transparent protective member 14 and the back surface side protective member 15 to produce a laminate. Next, the laminate is heated to receive the light-receiving surface side sealing layer 11 and the back surface side sealing layer 12, the light receiving surface side sealing layer 11 and the front surface side transparent protective member 14, and the back surface side sealing layer 12 and the back surface side protective member. 15 is bonded.
More specifically, the solar cell sealing material is heated to a temperature at which the crosslinking agent contained in the solar cell sealing material does not substantially decompose and the ethylene / α-olefin copolymer melts, The light receiving surface side sealing layer 11 and the back surface side sealing layer 12, the light receiving surface side sealing layer 11 and the front surface side transparent protective member 14, and the back surface side sealing layer 12 and the back surface side protective member 15 are temporarily bonded. Next, the temperature is raised, sufficient adhesion is performed, and the ethylene / α-olefin copolymer in the sealing layer is further crosslinked. The temperature for adhesion and crosslinking may be any temperature at which a satisfactory crosslinking rate can be obtained and swelling does not occur. For example, the temperature can be in the range of about 100 to 180 ° C.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

<Preparation of solar cell encapsulant sheet>
About the Example and the comparative example, the solar cell sealing material sheet was produced as follows. First, an ethylene / α-olefin copolymer (synthesized according to Synthesis Example 1 of WO2012 / 060086), a crosslinking agent, a crosslinking aid, and a silane coupling agent were blended in the formulation shown in Table 1 to obtain a resin composition. Obtained.
Using a thermo-plastic single screw extruder (screw diameter 20 mmφ, L / D = 28) equipped with a coat hanger type T die (lip shape: 270 × 0.8 mm), a die temperature of 100 ° C. Using the embossing roll as the first cooling roll at a roll temperature of 30 ° C. and a winding speed of 1.0 m / min, the resulting resin composition was formed into a sheet, and an embossed sheet having a thickness of 500 μm (solar cell) A sealing material sheet) was obtained. The porosity of the obtained sheet was 28%.
In addition, the unit of the mixture ratio of each component in Table 1 is a mass part. Moreover, the detail of each component in Table 1 is as follows.

Crosslinking agent 1: t-amyl peroxybenzoate Crosslinking agent 2: t-butylperoxy-2-ethylhexyl carbonate Crosslinking aid: triallyl isocyanurate Silane coupling agent: γ-methacryloxypropyltrimethoxysilane

<Gel fraction of solar cell encapsulant sheet>
The solar cell encapsulant sheet was sandwiched between both sides of the produced solar cell encapsulant sheet with a PET film coated with silica. At this time, the solar cell encapsulant sheet was sandwiched with the silica coating surface of the PET film on the solar cell encapsulant sheet side. Next, the obtained laminate was placed on a 3.2 mmt transparent float glass. The obtained laminate was laminated with a vacuum laminator (NPC: LM-110 × 160-S) at a hot plate temperature of 150 ° C., a vacuum time of 3 minutes, and a pressure holding time of 8 minutes. The PET film was peeled off from the obtained laminate to prepare a crosslinked body of a solar cell sealing material sheet having a thickness of 0.5 mm.
About 1 g of the prepared crosslinked body was weighed (weighing value A (g)), charged in 100 mL of xylene, and allowed to stand in an explosion-proof oven at 110 ° C. for 12 hours. Subsequently, after filtering with a 30 mesh stainless steel mesh, the stainless steel mesh was dried under reduced pressure at 110 ° C. for 8 hours. The residual amount B (g) on the stainless steel mesh was measured, and the gel fraction was calculated using the following formula.
Gel fraction (mass%) = 100 × B / A

<Glass adhesive strength of solar cell encapsulant sheet>
Silica-coated PET film / solar cell sealing material sheet / 3.2 mmt transparent float glass was laminated. At this time, the silica coating surface of the PET film was set to the sealing material side. The obtained laminate was laminated with a vacuum laminator at a hot plate temperature of 150 ° C., a vacuum time of 3 minutes, and a pressure holding time of 10 minutes. The PET film was peeled off from the laminate after heating to prepare a sample for measuring the adhesive strength. The sealing material layer of this adhesive strength measurement sample was cut into a width of 10 mm, and the peel strength from the glass (glass adhesive strength) was measured with an autograph (manufactured by Shimadzu Corporation: AGS-J) 180 ° peel. Measurement was performed at a chuck interval of 80 mm, a peeling speed of 300 mm / min, and 23 ° C., and an average value of five measurements was adopted.

<Appearance evaluation of laminate>
A PET-based backsheet containing silica-deposited PET / solar cell sealing material sheet / 3.2 mmt transparent embossed glass was laminated. The obtained laminate was laminated with a vacuum laminator at a hot plate temperature of 165 ° C., a vacuum time of 4 minutes, and a pressure holding time of 10 minutes. The obtained laminate was visually observed from the glass side to confirm the presence or absence of bubbles. At this time, the evaluation results were classified as follows.
No bubbles: ○
With bubbles: ×

  The above evaluation results are shown in Table 1.

The solar cell encapsulant of the examples had a high gel fraction and excellent crosslinking characteristics, and the generation of bubbles during crosslinking was suppressed. On the other hand, the solar cell encapsulant of Comparative Example 1 had a gel fraction lower than that of the Examples and was inferior in crosslinking characteristics. Further, when the amount of the crosslinking agent 2 is increased in order to improve the crosslinking property as in Comparative Example 2, the crosslinking property of the solar cell encapsulant is improved, but bubbles are generated in the appearance evaluation of the laminate. Oops.
From the above, it was found that the solar cell encapsulant according to the present embodiment is excellent in cross-linking characteristics and suppresses the generation of bubbles during cross-linking.

DESCRIPTION OF SYMBOLS 10 Solar cell module 11 Light-receiving surface side sealing layer 12 Back surface side sealing layer 13 Solar cell element 14 Front surface side transparent protective member 15 Back surface side protective member 16 Interconnector

Claims (6)

A solar cell encapsulant used for encapsulating solar cell elements,
An ethylene / α-olefin copolymer;
A cross-linking agent t-amyl peroxybenzoate;
One or more crosslinking aids selected from the group consisting of divinyl aromatic compounds, cyanurate compounds, diallyl compounds, acrylate compounds, triallyl compounds, oxime compounds and maleimide compounds;
Including
The content of the t-amyl peroxybenzoate in the solar cell encapsulant is 0.1 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. ,
The solar cell encapsulant wherein the content of the crosslinking aid in the solar cell encapsulant is 0.1 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the ethylene / α-olefin copolymer. Stop material. The solar cell sealing material according to claim 1, wherein the ethylene / α-olefin copolymer satisfies at least one of the following requirements a1) to a4).
a1) The content rate of the structural unit derived from ethylene is 80-90 mol%, and the content rate of the structural unit derived from a C3-C20 alpha olefin is 10-20 mol%.
a2) Based on ASTM D1238, MFR measured on condition of 190 degreeC and a 2.16kg load is 0.1-50 g / 10min.
a3) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a4) The Shore A hardness measured according to ASTM D2240 is 60 to 85. Further comprising a silane coupling agent,
Content of the said silane coupling agent in the said solar cell sealing material is 0.1 mass part or more and 5.0 mass parts or less with respect to 100 mass parts of the said ethylene-alpha-olefin copolymer. Item 3. A solar cell encapsulant according to item 1 or 2. Further comprising at least one additive selected from the group consisting of ultraviolet absorbers, light stabilizers, and heat stabilizers,
Content of the said additive in the said solar cell sealing material is 0.005 mass part or more and 5 mass parts or less with respect to 100 mass parts of said ethylene-alpha-olefin copolymers. The solar cell sealing material as described in any one.   The solar cell sealing material according to any one of claims 1 to 4, which is in a sheet form. A surface-side transparent protective member;
A back side protection member;
A solar cell element;
It is comprised by the bridge | crosslinking material of the solar cell sealing material as described in any one of Claims 1 thru | or 5, and seals the said solar cell element between the said surface side transparent protection member and the said back surface side protection member. A sealing layer;
A solar cell module comprising:

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