WO2013186992A1

WO2013186992A1 - Solar cell sealing material and solar cell module

Info

Publication number: WO2013186992A1
Application number: PCT/JP2013/003214
Authority: WO
Inventors: 成伸池永; 文人竹内; 伊藤　智章
Original assignee: 三井化学東セロ株式会社
Priority date: 2012-06-14
Filing date: 2013-05-21
Publication date: 2013-12-19
Also published as: CN104334631B; CN104334631A; TW201402665A; JP5922232B2; TWI586724B; JPWO2013186992A1

Abstract

This solar cell sealing material contains, as essential components, an ethylene/α-olefin copolymer, an organic peroxide and an acid acceptor. It is preferable that the acid acceptor is composed of at least one substance that is selected from the group consisting of magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetraoxide, calcium hydroxide, aluminum hydroxide, iron (II) hydroxide, calcium carbonate, and hydrotalcite compounds and/or fired products thereof.

Description

Solar cell encapsulant and solar cell module

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

As solar environment and energy problems become more serious, solar cells are attracting attention as a means of generating energy that is clean and free from depletion. When a solar cell is used outdoors such as a roof portion of a building, it is generally used in the form of a solar cell module.

The above solar cell module is generally manufactured by the following procedure. First, a crystalline solar cell element (hereinafter, referred to as a power generation element or a cell) formed of polycrystalline silicon, single crystal silicon, or the like, or amorphous silicon or crystalline silicon is placed on a substrate such as glass. A thin-film solar cell element obtained by forming a very thin film of μm is manufactured.
Next, in order to obtain a crystalline solar cell module, a solar cell module protective sheet (surface side transparent protective member) / solar cell encapsulant / crystalline solar cell element / solar cell encapsulant / protection for solar cell module The sheets (back side protective member) are laminated in this order.
On the other hand, in order to obtain a thin film solar cell module, the thin film solar cell element / solar cell sealing material / solar cell module protective sheet (back surface side protective member) are laminated in this order. Then, a solar cell module is manufactured by utilizing the lamination method etc. which vacuum-suck these and heat-press them. The solar cell module manufactured in this way has weather resistance and is suitable for outdoor use such as a roof portion of a building.

As a solar cell encapsulant, an ethylene / vinyl acetate copolymer (EVA) film is widely used because it is excellent in transparency, flexibility, adhesion, and the like (for example, Patent Documents 1 to 4). reference). However, when the EVA composition is used as a constituent material of the solar cell sealing material, there is a concern that components such as acetic acid gas generated by the decomposition of EVA may affect the solar cell element.

On the other hand, a resin composition for a solar cell encapsulant comprising an ethylene / α-olefin copolymer, an organic peroxide, and a silane coupling agent has been proposed (see, for example, Patent Document 5). . This resin composition for solar cell encapsulant is said to be excellent in heat resistance, transparency, flexibility and adhesion to a glass substrate.

JP 2008-115344 A JP 2008-118073 A JP 2012-15346 A JP2012-19179A International Publication No. 2010/114028 Pamphlet

However, according to the study by the present inventors, the resin composition for solar cell encapsulant described in Patent Document 5 has adhesion to a glass substrate, but adhesion to the metal electrode and solder of the solar cell. It has been found that sex is insufficient. Furthermore, it has been found that the adhesiveness of the resin composition for solar cell encapsulant described in Patent Document 5 decreases under constant temperature and humidity.

Therefore, an object of the present invention is to provide a solar cell encapsulant that has excellent adhesion to metal electrodes and solder and can maintain the adhesion for a long period of time even under constant temperature and humidity.

The inventors of the present invention have made extensive studies on the adhesiveness of the solar cell sealing material to metal electrodes and solder. As a result, by further including an acid acceptor in a solar cell encapsulant containing an ethylene / α-olefin copolymer and an organic peroxide, it has excellent adhesion to metal electrodes and solder, and It has been found that a solar cell encapsulant that can maintain adhesiveness for a long period of time even under constant temperature and humidity is obtained, and the present invention has been completed.

That is, according to the present invention, the following solar cell sealing material and solar cell module are provided.

[1]
A solar cell encapsulant comprising an ethylene / α-olefin copolymer, an organic peroxide, and an acid acceptor.

[2]
The acid acceptor is magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetroxide, calcium hydroxide, aluminum hydroxide, iron hydroxide (II), calcium carbonate, and a hydrotalcite compound and / or a fired product thereof. The solar cell encapsulating material according to the above [1], comprising at least one selected from the group consisting of:

[3]
[1] or [1], wherein the content of the acid acceptor in the solar cell encapsulant is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to [2].

[4]
The solar cell encapsulant according to any one of [1] to [3], wherein the ethylene / α-olefin copolymer satisfies the following requirements a1) to a4).
a1) The content of structural units derived from ethylene is 80 to 90 mol%, and the content of structural units derived from α-olefins having 3 to 20 carbon atoms is 10 to 20 mol%.
a2) Based on ASTM D1238, MFR measured under the conditions of 190 ° C. and 2.16 kg load is 10 to 50 g / 10 min.
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.

[5]
The solar cell according to [4], wherein the MFR of the ethylene / α-olefin copolymer measured in accordance with ASTM D1238 and measured at 190 ° C. and a load of 2.16 kg is 10 to 27 g / 10 min. Sealing material.

[6]
The solar cell encapsulating material according to any one of [1] to [5], wherein a median diameter in a volume-based particle size distribution determined by a laser diffraction / scattering particle size distribution measurement method of the acid acceptor is 1.0 μm or less.

[7]
The solar cell encapsulant according to any one of [1] to [6], wherein the acid acceptor is a hydrotalcite compound represented by the following general formula (A) and / or a fired product thereof.
M ²⁺ _1-a · M ³⁺ _a (OH) ₂ · An ⁿ⁻ _{a / n} · mH ₂ O (A)
(0.2 ≦ a ≦ 0.35, 0 ≦ m ≦ 5, M ²⁺ : Mg ²⁺ , Zn ²⁺ , Ni ²⁺ , Ca ²⁺ , at least one divalent metal ion, M ³⁺ : Al ³⁺ , Fe ^At least one trivalent metal ion selected from ³⁺ , An: an n-valent anion)

[8]
The solar cell encapsulant according to [7], wherein the hydrotalcite compound has an average plate surface diameter of 0.02 to 0.9 μm.

[9]
The organic peroxide has a 1 minute half-life temperature of 100 to 170 ° C.,
[1] to [8], wherein the content of the organic peroxide in the solar cell encapsulant is 0.1 to 3 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material in any one.

[10]
Further comprising a silane coupling agent,
[1] to [9], wherein the content of the silane coupling agent in the solar cell encapsulant is 0.1 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material in any one.

[11]
Further comprising a hindered phenol stabilizer,
[1] The content of the hindered phenol stabilizer in the solar cell encapsulant is 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material in any one of [10].

[12]
Further comprising a hindered amine light stabilizer,
[1] The content of the hindered amine light stabilizer in the solar cell encapsulant is 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. Thru | or [11] The solar cell sealing material in any one.

[13]
Further comprising a phosphorus stabilizer,
The content of the phosphorus stabilizer in the solar cell encapsulant is 0.005 to 0.5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. [12] The solar cell encapsulant according to any one of the above.

[14]
Further comprising a UV absorber,
[1] to [13] above, wherein the content of the ultraviolet absorber in the solar cell encapsulant is 0.005 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material in any one.

[15]
Further comprising a crosslinking aid,
[1] to [14], wherein the content of the crosslinking aid in the solar cell encapsulant is 0.05 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material in any one.

[16]
Any of the above [1] to [15] obtained by melt kneading the ethylene / α-olefin copolymer, the organic peroxide, and the acid acceptor and then extruding the sheet into a sheet. The solar cell sealing material according to.

[17]
The solar cell encapsulating material according to any one of [1] to [16], which is in a sheet form.

[18]
A surface-side transparent protective member;
A back side protection member;
A solar cell element;
The solar cell element formed by crosslinking the solar cell sealing material according to any one of [1] to [17] is sealed between the front surface side transparent protective member and the back surface side protective member. A sealing layer;
Solar cell module with

According to the present invention, it is possible to provide a solar cell encapsulant that is excellent in adhesion to metal electrodes and solder, and that can maintain adhesion for a long period of time even under constant temperature and humidity.

Further, according to the present invention, by using such a solar cell encapsulant, in addition to the above characteristics being excellent, the encapsulant may be deformed even when the temperature rises during use of the solar cell module. Trouble can be avoided. And the solar cell module excellent in economical efficiency, such as cost, can be provided, without impairing the external appearance of a solar cell.

The above-described object and other objects, features, and advantages will be further clarified by a preferred embodiment described below and the following drawings attached thereto.

It is sectional drawing which shows typically one Embodiment of the solar cell module of this invention. It is a top view which shows typically the example of 1 structure of the light-receiving surface and back surface of a solar cell element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate. Further, “˜” represents the following from the above unless otherwise specified.

1. Solar Cell Encapsulant The solar cell encapsulant of the present invention contains an ethylene / α-olefin copolymer, an organic peroxide, and an acid acceptor as essential components. According to the present invention, a solar cell encapsulant containing an ethylene / α-olefin copolymer and an organic peroxide further contains an acid acceptor, thereby providing excellent adhesion to metal electrodes and solder. And the solar cell sealing material which can maintain adhesiveness for a long period of time also under constant temperature and humidity can be obtained. The reason why such an effect is obtained is not necessarily clear, but is presumed as follows.

First, a solar cell module is generally obtained by joining a solar cell element and a metal electrode with solder.
Here, in order to improve the solder wettability of the joint between the metal electrode and the solar cell element and the joint between the metal electrodes, usually, a rosin-based flux or a water-soluble flux is applied to the surface of the metal electrode. . The fatty acid contained in the flux component generates an acid by moisture that has permeated into the solar cell sealing material under constant temperature and humidity at 85 ° C. and 85% rh, for example.

According to the study by the inventors, the acid generated from the flux component cuts the bond between the silane coupling agent and the metal electrode in the solar cell encapsulant, resulting in a decrease in adhesion. It became clear that.
Since the solar cell sealing material of the present invention contains an acid acceptor, the generated acid can be captured by the acid acceptor. As a result, it is considered that the breakage of the bond between the silane coupling agent and the metal electrode due to the acid can be suppressed. For the above reasons, it is speculated that the solar cell encapsulant of the present invention can maintain the adhesion for a long period of time even under constant temperature and humidity while improving the adhesion to the metal wiring and the solder.

In addition, in the solar cell encapsulating materials described in Patent Documents 1 to 4, an acid acceptor is also added. This acid acceptor captures acetic acid generated from an ethylene / vinyl acetate copolymer (EVA). Has been added to. Therefore, the technical significance is different from that of the acid acceptor of the present invention.

(Ethylene / α-olefin copolymer)
The solar cell encapsulant of the present embodiment is one of the preferred embodiments that includes the following ethylene / α-olefin copolymer.

The ethylene / α-olefin copolymer used for the solar cell encapsulant of the present embodiment is obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. As the α-olefin, α-olefins having 3 to 20 carbon atoms can be used singly 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 used in the solar cell encapsulant of the present embodiment may be a copolymer comprising 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.

The ethylene / α-olefin copolymer used for the solar cell encapsulant of this embodiment is an aromatic vinyl compound such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o, p- Styrenes such as dimethyl styrene, methoxy styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl benzyl acetate, hydroxystyrene, p-chlorostyrene, divinylbenzene; 3-phenylpropylene, 4-phenylpropylene, α-methylstyrene, carbon Cyclic olefins having a number of 3 to 20, such as cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, etc. may be used in combination.

The ethylene / α-olefin copolymer of the present embodiment preferably further satisfies 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%. It is particularly preferably 82 to 87 mol%. The content of the structural unit derived from the 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 to 20 mol%, further preferably 12 to 18 mol%, particularly preferably 13 to 18 mol%.

When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is 10 mol% or more, high transparency can be obtained. 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 the 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 the gel-like foreign matter is not present on the sheet of the solar cell encapsulant. 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 20 mol% or less, the crystallization speed of the ethylene / α-olefin copolymer becomes appropriate, so that it was extruded from an extruder. Since the sheet is not sticky, it 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 occurs in the sheet, blocking can be prevented, and the sheet feeding property is improved. In addition, a decrease in heat resistance can be prevented.

(Requirement a2)
According to ASTM D1238, the melt flow rate (MFR) of an ethylene / α-olefin copolymer measured at 190 ° C. under a load of 2.16 kg is usually 0.1 to 50 g / 10 min, preferably Is 2 to 50 g / 10 min, more preferably 10 to 50 g / 10 min, still more preferably 10 to 40 g / 10 min, particularly preferably 12 to 27 g / 10 min, and most preferably 15 to 25 g / 10 min. Minutes. The MFR of the ethylene / α-olefin copolymer can be adjusted by adjusting the polymerization temperature, the polymerization pressure, the molar ratio of the ethylene and α-olefin monomer concentrations and the hydrogen concentration in the polymerization system, which will be described later. Can be adjusted.

(Calendar molding)
When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, a sheet can be produced by calendar molding. When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, the fluidity of the resin composition containing the ethylene / α-olefin copolymer is low, so that the sheet protrudes when the sheet is laminated with the solar cell element. This is preferable in that the laminating apparatus can be prevented from being soiled by the molten resin.

(Extrusion molding)
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.
When the MFR is 50 g / 10 min or less, the molecular weight increases, 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 “stiffness”, 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 molding 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 Can be obtained.
In the case where the resin composition is not subjected to crosslinking treatment in the solar cell module laminating step, which will be described later, since the influence of decomposition of the organic peroxide is small in the melt extrusion step, the MFR is 0.1 g / 10 min or more and 10 g / 10. A sheet can also be obtained by extrusion molding using a resin composition of less than 5 minutes, preferably 0.5 g / 10 minutes or more and less than 8.5 g / 10 minutes. When the organic peroxide content of the resin composition is 0.15 parts by weight or less, a resin composition having an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min is used. It is also possible to produce a sheet by extrusion molding at a molding temperature of 170 to 250 ° C. while performing a 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 with 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 . More preferably, it is 0.866 to 0.880 g / cm ³ , and particularly preferably 0.867 to 0.880 g / 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 0.884 g / cm ³ or less, the crystallinity is lowered and the transparency can be enhanced. Furthermore, extrusion molding at low temperature becomes easy, and for example, extrusion molding can be performed at 130 ° C. or lower. For this reason, even if an organic peroxide is kneaded into the ethylene / α-olefin copolymer, the cross-linking reaction in the extruder is prevented from progressing, and the generation of gel-like foreign matters on the solar cell encapsulant sheet is suppressed. In addition, deterioration of the appearance of the sheet can be suppressed. Moreover, since it is highly flexible, it is possible to prevent the occurrence of cell cracks and thin film electrode cracks, which are solar cell elements, when the solar cell module is laminated.

On the other hand, when the density of the ethylene / α-olefin copolymer is 0.865 g / cm ³ or more, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the sheet extruded from the extruder is sticky. It is difficult, peeling with a cooling roll becomes easy, and the sheet | seat of a solar cell sealing material can be obtained easily. 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 can fully bridge | crosslink, a heat resistant fall can be suppressed.

(Requirement a4)
The Shore A hardness of the ethylene / α-olefin copolymer, measured in accordance with ASTM D2240, is preferably 60 to 85, more preferably 62 to 83, even more preferably 62 to 80, particularly Preferably, it is 65-80. The Shore A hardness of the ethylene / α-olefin copolymer can be adjusted by controlling the content 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 a high density has a high Shore A hardness. On the other hand, an ethylene / α-olefin copolymer having a low content of ethylene units and a low density has a low Shore A hardness.

When the Shore A hardness is 60 or more, the ethylene / α-olefin copolymer is less sticky and blocking can be suppressed. Moreover, when processing a solar cell sealing material into a sheet form, the drawing | feeding-out property of a sheet | seat can also be improved and the fall of heat resistance can also be suppressed.

On the other hand, when the Shore A hardness is 85 or less, the crystallinity is lowered and the transparency can be increased. Furthermore, since it is highly flexible, it is possible to prevent cracking of cells that are solar cell elements and chipping of thin film electrodes during laminate molding of the solar cell module.

Furthermore, it is a preferable aspect that the solar cell encapsulant of the present embodiment further satisfies the following requirements.

(Melting peak)
The melting peak of the ethylene / α-olefin copolymer based on differential scanning calorimetry (DSC) is preferably in the range of 30 to 90 ° C., more preferably in the range of 33 to 90 ° C., It is particularly preferable that it exists in the range of ˜88 ° C. When the melting peak is 90 ° C. or lower, the degree of crystallinity is lowered, and the flexibility of the obtained solar cell encapsulant is increased. Therefore, when the solar cell module is laminated, cell cracks and thin film electrode cracks are observed. Occurrence can be prevented. On the other hand, when the melting peak is 30 ° C. or higher, the flexibility of the resin composition can be appropriately increased, and thus a solar cell encapsulant sheet can be easily obtained by extrusion molding. Further, blocking due to stickiness of the sheet can be prevented, and deterioration of the sheet feeding property can be suppressed.

(Volume resistivity)
The solar cell encapsulant of this embodiment has a volume specific resistance of 1.0 × 10 ¹³ to 1.0 × 10 ¹⁸ Ω · cm measured at a temperature of 100 ° C. and an applied voltage of 500 V in accordance with JIS K6911. It is preferable. A solar cell encapsulant having a large volume resistivity tends to have a characteristic of suppressing the occurrence of the PID phenomenon. Furthermore, in the time zone in which sunlight is irradiated, the module temperature of a conventional solar cell module may be, for example, 70 ° C. or higher. Therefore, from the viewpoint of long-term reliability, conventionally reported normal temperature (23 ° C.) The volume resistivity under a high temperature condition is demanded from the volume resistivity at 1 and the volume resistivity at a temperature of 100 ° C. is important.

The volume specific resistance (hereinafter also simply referred to as “volume specific resistance”) measured at a temperature of 100 ° C. and an applied voltage of 500 V in accordance with JIS K6911 is more preferably 1.0 × 10 ¹⁴ to 1.0 × 10. ¹⁸ Ω · cm, more preferably 5.0 × 10 ¹⁴ to 1.0 × 10 ¹⁸ Ω · cm, and particularly preferably 1.0 × 10 ¹⁵ to 1.0 × 10 ¹⁸ Ω · cm. When the volume resistivity is 1.0 × 10 ¹³ Ω · cm or more, the occurrence of a PID phenomenon in a short period of about 1 day can be suppressed in a constant temperature and humidity test at 85 ° C. and 85% rh. When the volume resistivity is 1.0 × 10 ¹⁸ Ω · cm or less, static electricity is less likely to be generated on the sheet, so that adsorption of dust can be prevented and dust is mixed into the solar cell module to generate power. It is possible to suppress a decrease in efficiency and long-term reliability.
In addition, it is desirable that the volume resistivity is 5.0 × 10 ¹⁴ Ω · cm or more because the PID phenomenon tends to be further prolonged in the constant temperature and humidity test at 85 ° C. and 85% rh.
The volume resistivity is measured after being molded into a sealing material sheet and then processed into a cross-linked and flat sheet by a vacuum laminator, a hot press, a cross-linking furnace, or the like. Moreover, the sheet | seat in a module laminated body measures by removing another layer.

(Aluminum element content)
The content (residue amount) of aluminum element (hereinafter also referred to as “Al”) contained in the ethylene / α-olefin copolymer is preferably 10 to 500 ppm, more preferably 20 to 400 ppm, and still more preferably 20 ~ 300 ppm. The Al content depends on the concentration of the organoaluminum oxy compound or organoaluminum compound added in the polymerization process of the ethylene / α-olefin copolymer.

When the Al content is 10 ppm or more, the organoaluminum oxy compound or organoaluminum compound added in the polymerization process of the ethylene / α-olefin copolymer can be added at a concentration that allows the activity of the metallocene compound to be sufficiently expressed. Therefore, it is unnecessary to add a compound that reacts with the metallocene compound to form an ion pair. When the compound that forms the ion pair is added, the compound that forms the ion pair may remain in the ethylene / α-olefin copolymer, thereby causing a decrease in electrical characteristics (for example, 100 ° C. or the like). However, this phenomenon can be prevented. In addition, in order to reduce the Al content, a deashing treatment with an acid or alkali is required, and the acid or alkali remaining in the resulting ethylene / α-olefin copolymer tends to cause corrosion of the electrode. However, since the cost of the ethylene / α-olefin copolymer is increased due to the deashing treatment, such a deashing treatment becomes unnecessary.

Further, when the Al content is 500 ppm or less, the progress of the crosslinking reaction in the extruder can be prevented, so that a gel-like foreign matter is generated on the sheet of the solar cell sealing material and the appearance of the sheet is prevented from deteriorating. be able to.
As a method for controlling the aluminum element contained in the ethylene / α-olefin copolymer as described above, for example, (II-1) Organoaluminum described in the method for producing an ethylene / α-olefin copolymer described later is used. By adjusting the concentration in the production process of the oxy compound and (II-2) organoaluminum compound or the polymerization activity of the metallocene compound in the production conditions of the ethylene / α-olefin copolymer, the ethylene / α-olefin copolymer It is possible to control the aluminum element contained in.

(Method for producing ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer can be produced using a Ziegler compound, a vanadium compound, a metallocene compound or the like as a catalyst. Among them, it is preferable to produce using 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.

As a polymerization reaction using a metallocene compound, for example, the following modes can be mentioned as preferred examples.

A conventionally known metallocene compound, (II) (II-1) an organoaluminum oxy compound, (II-2) a compound that reacts with the metallocene compound (I) to form an ion pair, and (II-3) an organoaluminum In the presence of an olefin polymerization catalyst comprising at least one compound selected from the group consisting of compounds (also referred to as a co-catalyst), one or more monomers selected from ethylene and α-olefin are supplied.

Examples of (II-1) an organoaluminum oxy compound, (II-2) a compound that reacts with the metallocene compound (I) to form an ion pair, and (II-3) an organoaluminum compound include, for example, The metallocene compounds described in Japanese Patent No. 077261, Japanese Patent Application Laid-Open No. 2008-231265, Japanese Patent Application Laid-Open No. 2005-314680, and the like can be used. However, you may use the metallocene compound of a structure different from the metallocene compound described in these patent documents. These compounds may be put into the polymerization atmosphere individually or in advance in contact with each other. Further, for example, it may be used by being supported on a particulate inorganic oxide support described in JP-A-2005-314680.
Preferably, (II-2) the ethylene / α-olefin having excellent electrical characteristics is produced by substantially using the compound (II-2) that reacts with the metallocene compound (I) to form an ion pair. A copolymer can be obtained.

The ethylene / α-olefin copolymer can be polymerized 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. When an ethylene / α-olefin copolymer is produced by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms using the metallocene compound as described above, the metallocene compound (I) The amount used is usually 10 ⁻⁹ to 10 ⁻¹ mol, preferably 10 ⁻⁸ to 10 ⁻² mol per liter of volume.

In compound (II-1), the molar ratio [(II-1) / M] of compound (II-1) to all transition metal atoms (M) in compound (I) is usually 1 to 10,000, preferably The amount used is 10 to 5,000. The compound (II-2) has a molar ratio [(II-2) / M] to the total transition metal (M) in the compound (I) of usually 0.5 to 50, preferably 1 to 20. Used in various amounts. Compound (II-3) is generally used in an amount of 0 to 5 mmol, preferably about 0 to 2 mmol, per liter of polymerization volume.

In the solution polymerization method, by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of the metallocene compound as described above, the comonomer content is high, the composition distribution is narrow, and the molecular weight distribution is narrow. An ethylene / α-olefin copolymer can be produced efficiently. Here, the charged molar ratio of ethylene to the α-olefin having 3 to 20 carbon atoms is usually ethylene: α-olefin = 10: 90 to 99.9: 0.1, preferably ethylene: α-olefin = 30:70 to 99.9: 0.1, more preferably ethylene: α-olefin = 50: 50 to 99.9: 0.1.

The “solution polymerization method” is a general term for a method of performing polymerization in a state where a polymer is dissolved in an inert hydrocarbon solvent described later. The polymerization temperature in the solution polymerization method is usually 0 to 200 ° C., preferably 20 to 190 ° C., more preferably 40 to 180 ° C. In the solution polymerization method, when the polymerization temperature is less than 0 ° C., the polymerization activity is extremely lowered and it is difficult to remove the heat of polymerization, which is not practical in terms of productivity. On the other hand, when the polymerization temperature exceeds 200 ° C., the polymerization activity is extremely lowered, so that it is not practical in terms of productivity.

The polymerization pressure is usually from normal pressure to 10 MPa gauge pressure, preferably from normal pressure to 8 MPa gauge pressure. Copolymerization can be carried out in any of batch, semi-continuous and continuous methods. The reaction time (average residence time when the copolymerization reaction is carried out in a continuous manner) varies depending on conditions such as the catalyst concentration and polymerization temperature, and can be selected as appropriate, but is usually 1 minute to 3 hours, Preferably, it is 10 minutes to 2.5 hours. Furthermore, the polymerization can be carried out in two or more stages having different reaction conditions. The molecular weight of the obtained ethylene / α-olefin copolymer can also be adjusted by changing the hydrogen concentration or polymerization temperature in the polymerization system. Furthermore, it can also adjust with the quantity of the compound (II) to be used. When hydrogen is added, the amount is suitably about 0.001 to 5,000 NL per kg of the ethylene / α-olefin copolymer to be produced. In addition, the vinyl group and vinylidene group present at the molecular ends of the obtained ethylene / α-olefin copolymer can be adjusted by increasing the polymerization temperature and decreasing the amount of hydrogenation as much as possible.

The solvent used in the solution polymerization method is usually an inert hydrocarbon solvent, preferably a saturated hydrocarbon having a boiling point of 50 ° C. to 200 ° C. under normal pressure. Specific examples include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane, dodecane, and kerosene; and alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane. Aromatic hydrocarbons such as benzene, toluene and xylene, and halogenated hydrocarbons such as ethylene chloride, chlorobenzene and dichloromethane are also included in the category of “inert hydrocarbon solvents” and their use is not limited. .

As described above, in the solution polymerization method, a modified methyl such as MMAO that dissolves in an aliphatic hydrocarbon or an alicyclic hydrocarbon as well as an organoaluminum oxy compound that dissolves in an aromatic hydrocarbon that has been widely used conventionally. Aluminoxane can be used. As a result, if aliphatic hydrocarbons or alicyclic hydrocarbons are used as the solvent for solution polymerization, there is a possibility that aromatic hydrocarbons are mixed in the polymerization system or in the ethylene / α-olefin copolymer produced. It becomes possible to eliminate almost completely. That is, the solution polymerization method has characteristics that it can reduce the environmental burden and can minimize the influence on human health. In order to suppress variations in physical property values, the ethylene / α-olefin copolymer obtained by the polymerization reaction and other components added as desired are melted by any method, and kneaded, granulated, etc. Preferably it is applied.

(Organic peroxide)
The solar cell sealing material of this embodiment contains an organic peroxide. The organic peroxide is used as a radical initiator for graft modification of a silane coupling agent and an ethylene / α-olefin copolymer, and also for the laminate molding of an ethylene / α-olefin copolymer solar cell module. It is used as a radical initiator in the crosslinking reaction. By graft-modifying a silane coupling agent to the ethylene / α-olefin copolymer, a solar cell module having good adhesion to the front surface side transparent protective member, the back surface side protective member, the cell, and the electrode can be obtained. Further, by crosslinking the ethylene / α-olefin copolymer, a solar cell module excellent in heat resistance and adhesiveness can be obtained.

The organic peroxides preferably used are particularly those that can graft-modify a silane coupling agent on the ethylene / α-olefin copolymer or crosslink the ethylene / α-olefin copolymer. Although not limited, the one minute half-life temperature of the organic peroxide is preferably 100 to 170 ° C. in view of the balance between productivity in extrusion sheet molding and the crosslinking rate at the time of laminate molding of the solar cell module. When the half-life temperature of the organic peroxide is 100 ° C. or higher, gels are less likely to occur in the solar cell encapsulating sheet obtained from the resin composition during extrusion sheet molding, and thus the increase in the torque of the extruder is suppressed. Sheet forming can be facilitated. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the surface of a sheet | seat with the gel thing which generate | occur | produced in the extruder, the fall of an external appearance can be prevented. Moreover, since the generation | occurrence | production of the crack inside a sheet | seat can be prevented when a voltage is applied, the fall of a dielectric breakdown voltage can be prevented. Furthermore, it is possible to prevent a decrease in moisture permeability. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the sheet | seat surface, the adhesiveness with a surface side transparent protection member, a cell, an electrode, and a back surface side protection member becomes favorable at the time of the lamination process of a solar cell module, and adhesiveness also improves. If the extrusion temperature of extrusion sheet molding is lowered to 90 ° C. or lower, molding is possible, but productivity is greatly reduced. When the one-minute half-life temperature of the organic peroxide is 170 ° C. or lower, it is possible to suppress a decrease in the crosslinking rate when the solar cell module is laminated, and thus it is possible to prevent a decrease in the productivity of the solar cell module. Moreover, the heat resistance of a solar cell sealing material and the fall of adhesiveness can also be prevented.

Known organic peroxides can be used. Preferred examples of the organic peroxide having a 1 minute half-life temperature in the range of 100 to 170 ° C. include dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate Dibenzoyl peroxide, 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-amylperoxy) cyclohexane, t-amylperoxyisononanoate, t-amylperoxynormal Octoate, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di ( -Butylperoxy) cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-amyl-peroxy Examples include benzoate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, 2,2-di (t-butylperoxy) butane, t-butyl peroxybenzoate, and the like. Preferably, dilauroyl peroxide, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxybenzoate, etc. Is mentioned. The said organic peroxide may be used individually by 1 type, and may mix and use 2 or more types.

The content of the organic peroxide in the solar cell encapsulant is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the aforementioned ethylene / α-olefin copolymer. It is more preferably 2 to 3.0 parts by weight, and particularly preferably 0.2 to 2.5 parts by weight.

When the content of the organic peroxide is 0.1 parts by weight or more, the deterioration of the crosslinking characteristics such as the crosslinking degree and crosslinking rate of the solar cell encapsulant is suppressed, and the ethylene copolymer of the silane coupling agent It is possible to improve the graft reaction to the main chain and suppress the decrease in heat resistance and adhesiveness.
When the organic peroxide content is 3.0 parts by weight or less, the solar cell encapsulating sheet obtained from the resin composition at the time of extrusion sheet molding does not generate gel, and the torque of the extruder can be suppressed. Becomes easy. Since the sheet does not generate a gel in the extruder, the surface of the sheet is not uneven and the appearance is good. In addition, since there is no gel, cracks due to the gel in the sheet do not occur even when a voltage is applied, so that the dielectric breakdown resistance is good. Moreover, moisture permeability is also favorable. Furthermore, since there is no unevenness | corrugation on the sheet | seat surface, the adhesiveness with a surface side transparent protection member, a cell, an electrode, and a back surface side protection member is favorable at the time of the lamination process of a solar cell module.

(Acid acceptor)
The solar cell sealing material of this embodiment contains an acid acceptor. By including an acid acceptor, the adhesion to metal wiring and solder can be improved, and the adhesion can be maintained for a long time even under constant temperature and humidity.

The content of the acid acceptor in the solar cell encapsulant of the present embodiment is preferably 0.1 to 3.0 parts by weight, more preferably 100 parts by weight of the ethylene / α-olefin copolymer. Is 0.1 to 2.8 parts by weight, particularly preferably 0.2 to 2.5 parts by weight, and most preferably 0.2 to 1.0 parts by weight.
When the content of the acid acceptor is equal to or higher than the lower limit, sufficient acid acceptability by the acid acceptor can be obtained. The transparency of a solar cell sealing material can be maintained as content of an acid acceptor is below the said upper limit, and the balance of acid accepting performance and transparency is favorable.

For example, in the case of producing a high concentration blended resin composition for solar cell encapsulant such as a masterbatch, it is preferable to use 5 to 50 parts by weight. Producing a solar cell encapsulant using a masterbatch is preferable from the standpoint of acid acceptor dispersion and handling.
The median diameter of the acid acceptor contained in the solar cell encapsulant of the present embodiment in the volume-based particle size distribution by the laser diffraction / scattering particle size distribution measurement method is preferably 0.1 to 1.0 μm, more preferably 0. .1 to 0.9 μm, particularly preferably 0.1 to 0.5 μm.
It is desirable that the solar cell encapsulant has high transparency in order to allow a large amount of incident light to enter the solar cell, and it is particularly required to have high transparency when placed on the light receiving surface side. It is done. Therefore, in order to improve the high transparency of the solar cell sealing material to ensure high power generation performance over the long term from the beginning of power generation, and to obtain high acid receiving performance by the acid acceptor, the light receiving surface side solar cell sealing It is particularly effective to make the median diameter of the acid acceptor contained in the material within the above-mentioned range.

By making the median diameter of the acid acceptor not more than the above upper limit value, it has a high light receiving product, so that high acid accepting performance by the acid acceptor can be obtained, and the acid acceptor is highly dispersed to seal the solar cell. High transparency of the material can be ensured. In addition, by setting the median diameter of the acid acceptor to be equal to or greater than the lower limit, aggregation of the acid acceptor is suppressed, and the acid acceptor is highly dispersed in the light receiving surface side solar cell sealing material. it can.
In the present embodiment, the median diameter of the acid acceptor can be measured using, for example, a laser diffraction particle size distribution analyzer.

In the present embodiment, the composition of the acid acceptor contained in the light-receiving surface side solar cell encapsulant is not particularly limited as long as it has a function of absorbing and / or neutralizing an acid.

As the acid acceptor of the present embodiment, a metal oxide, a metal hydroxide, a metal carbonate or a composite metal hydroxide is used, and can be appropriately selected according to the amount of acid generated and the application. Specific examples of the acid acceptor include magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, barium carbonate, calcium carbonate, calcium borate, zinc stearate, calcium phthalate, Periodic table Group 2 metal oxides such as calcium phosphate, zinc oxide, calcium silicate, magnesium silicate, magnesium borate, magnesium metaborate, calcium metaborate, barium metaborate, hydroxide, carbonate, carvone Acid salts, silicates, borates, phosphites, metaborate, etc .; tin oxide, basic tin carbonate, tin stearate, basic tin phosphite, basic tin sulfite, trilead tetraoxide, silicon oxide, stearin Group 14 metal oxides such as silicon acid, basic carbonate, basic carboxylate, base Phosphites, and basic sulfite salt; zinc oxide, aluminum oxide, aluminum hydroxide, iron hydroxide (II); composite metal hydroxide such as hydrotalcite compounds; aluminum hydroxide gel compound; and the like. These may be used individually by 1 type, and may mix and use 2 or more types. Among these, magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetroxide, calcium hydroxide, aluminum hydroxide, iron hydroxide (II), calcium carbonate, hydrotalcite compound and / or a fired product thereof are preferable. A hydrotalcite compound and / or a fired product thereof is more preferable.

In the present embodiment, the hydrotalcite compound and the fired product thereof are compounds in a layered form having interlayer ion exchange properties and neutralization reactivity with acids. And when used in solar cell modules, water that has entered the solar cell encapsulant and acid generated from the flux are taken in between layers, and the neutralization of the solar cell encapsulant and power generation elements is prevented by neutralization. (Hereinafter also referred to as an acid / water scavenging effect). The acid / water trapping effect is determined by the charge density of ions entering the interlayer, and anions having a higher valence and a smaller ionic radius are more likely to be trapped between the layers.

In addition to hydrotalcite compounds, metal oxides, metal hydroxides, metal carbonates, and the like are known as compounds having the acid / water scavenging effect, but many of these compounds have a high refractive index. Therefore, when added to an ethylene / α-olefin copolymer, the difference in refractive index from that of the ethylene / α-olefin copolymer becomes large, causing light scattering and reflection to become opaque, resulting in a decrease in conversion efficiency. The hydrotalcite compound in the present embodiment can improve transparency and increase the efficiency of the acid / water capturing effect, and can further suppress the decrease in adhesion and the conversion efficiency with the protective member over time.

In the present embodiment, it is preferable to use general natural hydrotalcite or synthesized hydrotalcite as the hydrotalcite compound.

In this embodiment, the fired hydrotalcite compound can be produced by firing the hydrotalcite compound. This fired product exhibits a higher acid / water scavenging effect than the hydrotalcite compound. In addition, the baked product captures acid and water, thereby changing the chemical composition, lowering the refractive index, and reducing the difference in refractive index from the ethylene / α-olefin copolymer, thereby improving the transparency over time. There is a tendency.

The hydrotalcite compound used in the present embodiment is preferably a hydrotalcite compound represented by the following general formula (A).
M ²⁺ _1-a · M ³⁺ _a (OH) ₂ · An ⁿ⁻ _{a / n} · mH ₂ O (A)
(0.2 ≦ a ≦ 0.35, 0 ≦ m ≦ 5, M ²⁺ : Mg ²⁺ , Zn ²⁺ , Ni ²⁺ , Ca ^2+, etc., at least one divalent metal ion, M ³⁺ : Al ³⁺ , (At least one trivalent metal ion selected from Fe ³⁺ , An: n-valent anion)

In the general formula (A), the M ³⁺ content ratio a is preferably 0.2 to 0.35. If it is 0.2 or more, it is easy to produce a hydrotalcite compound, and if it is 0.35 or less, the difference in refractive index from the ethylene / α-olefin copolymer is small and the transparency is better. A battery sealing material is obtained. Further, as M ³⁺ , Al ³⁺ is more preferable. The moisture content m is preferably 0 ≦ m ≦ 5, more preferably 0 ≦ m ≦ 1. The type of the anion An ^n- is not particularly limited, and examples thereof include a hydroxide ion, a carbonate ion, a silicate ion, an organic carboxylate ion, an organic sulfonate ion, and an organic phosphate ion. The index a in the general formula (A) can be obtained by dissolving the layered composite metal compound with an acid and analyzing it with a “plasma emission spectroscopic analyzer SPS4000 (manufactured by Seiko Denshi Kogyo)”.

The hydrotalcite compound represented by formula (A) preferably has an average plate surface diameter of 0.02 to 0.9 μm. From the viewpoint of dispersibility and transparency, 0.02 to 0.65 μm is more preferable. If it is not more than the above upper limit, the transparency when blended with the ethylene / α-olefin copolymer can be further improved. Industrial productivity of a hydrotalcite compound can be improved as it is more than the above-mentioned lower limit.
In addition, the plate | board surface diameter of a hydrotalcite compound is a number average value which calculated | required the area circle equivalent diameter of the hydrotalcite compound by observing with a scanning electron microscope.

The refractive index of the hydrotalcite compound represented by the general formula (A) is preferably 1.48 to 1.6. From the viewpoint of transparency due to a difference in refractive index from the ethylene / α-olefin copolymer, 1.48 to 1.55 is more preferable. Industrial productivity of a hydrotalcite compound can be improved as it is more than the above-mentioned lower limit. On the other hand, when it is not more than the above upper limit, the transparency and the sustainability of the acid / water trapping effect when blended with the ethylene / α-olefin copolymer can be further improved. The refractive index can be measured based on JIS-K0062. For example, it can be measured by Becke method using “Abbe refractometer: 3T (manufactured by Atago Co., Ltd.)” at 23 ° C. using α-bromonaphthalene and DMF as a solvent.

The fired product preferably has an average plate surface diameter of 0.02 to 0.9 μm. From the viewpoint of dispersibility and transparency, 0.02 to 0.65 μm is more preferable. When the amount is not more than the above upper limit, the acid scavenging ability when blended with the ethylene / α-olefin copolymer is good. Industrial production of a hydrotalcite compound is possible as it is more than the said lower limit.
The refractive index of the fired product is preferably 1.58 to 1.72. When it is 1.58 or more, firing becomes sufficient, crystal defects are hardly generated, and deterioration of the solar cell sealing material can be suppressed. Further, when it is 1.72 or less, the transparency when blended with the ethylene / α-olefin copolymer can be further improved.

The hydrotalcite compound represented by formula (A) and the fired product thereof preferably have an acetic acid adsorption amount of 0.1 to 0.8 μmol / g. When the amount is 0.1 μmol or more, the acid scavenging ability is sufficiently exhibited. On the other hand, when it is 0.8 μmol or less, the catalytic activity of the filler can be suppressed, and the hydrolysis of the resin can be suppressed. The amount of acetic acid adsorbed was 1 g of the above layered composite metal compound, 30 ml of an ethylene glycol monomethyl ether solution of 0.02 mol / L acetic acid was added and ultrasonically washed for 1 hour and a half, adsorbed on the layered composite metal compound, and centrifuged. The supernatant obtained by the above can be obtained with a 0.1 N potassium hydroxide solution by a back titration method by potentiometric titration.

Hydrotalcite compound and its calcined product is preferably has a BET specific surface area of ^{1 ~ 200m 2 / g, 1} ~ 160m 2 / g is more preferable. When it is at least the above lower limit, chemical bonding with other additives such as UVA hardly occurs, and the influence on other additives can be suppressed. When the amount is not more than the above upper limit, the basicity of the hydrotalcite compound can be suppressed, and deterioration of the ethylene / α-olefin copolymer can be suppressed.

The manufacturing method of a hydrotalcite compound is demonstrated.
At least one metal salt aqueous solution of magnesium salt aqueous solution, zinc salt aqueous solution, nickel salt aqueous solution, calcium salt aqueous solution, alkaline aqueous solution containing anion, and aluminum salt aqueous solution are mixed, and the pH is in the range of 8-14. After making into a solution, the mixed solution can be obtained by aging in the temperature range of 80 to 100 ° C.
The pH during the ripening reaction is preferably 10 to 14, more preferably 11 to 14. When the pH is at least the above lower limit, a hydrotalcite compound having a small plate surface diameter and an appropriate thickness can be obtained.
When the aging temperature is in the range of 80 ° C. to 100 ° C., it is possible to obtain a hydrotalcite compound having an appropriate plate surface diameter. A more preferable aging temperature is 85 to 100 ° C.

The aging time for the ripening reaction of the hydrotalcite compound is not particularly limited, but is, for example, about 2 to 24 hours. When it is 2 hours or longer, a layered composite metal compound having a small plate surface diameter and an appropriate thickness can be obtained. If it is 24 hours or less, aging is economical.
The alkaline aqueous solution containing the anion is preferably a mixed alkaline aqueous solution of an aqueous solution containing an anion and an aqueous alkali hydroxide solution.

As an aqueous solution containing an anion, aqueous solutions such as sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, organic carboxylate, organic sulfonate, and organic phosphate are preferable.
As the alkali hydroxide aqueous solution, sodium hydroxide, potassium hydroxide, ammonia, urea aqueous solution and the like are preferable.

As the metal salt aqueous solution in the present embodiment, a metal sulfate aqueous solution, a metal chloride aqueous solution, a metal nitrate aqueous solution, or the like can be used, and a magnesium chloride aqueous solution is preferable. Further, a slurry of metal oxide powder or metal hydroxide powder may be substituted.

As the aluminum salt aqueous solution in this embodiment, an aluminum sulfate aqueous solution, an aluminum chloride aqueous solution, an aluminum nitrate aqueous solution, or the like can be used, and an aluminum sulfate aqueous solution or an aluminum chloride aqueous solution is preferable. A slurry of aluminum oxide powder or aluminum hydroxide powder may be substituted.

The mixing order of an aqueous alkali solution containing an anion, an aqueous magnesium salt solution, an aqueous zinc salt solution, an aqueous nickel salt solution, an aqueous calcium salt solution, and an aqueous aluminum salt solution is not particularly limited, Each aqueous solution or slurry may be mixed simultaneously. Preferably, an aqueous solution or slurry in which at least one metal salt aqueous solution of magnesium salt aqueous solution, zinc salt aqueous solution, nickel salt aqueous solution, calcium salt aqueous solution and aluminum salt aqueous solution are mixed is added to the alkaline aqueous solution containing anions. .

Moreover, when adding each aqueous solution, you may carry out either when adding this aqueous solution at once, or when dripping continuously.
The pH of the hydrotalcite compound represented by the general formula (A) is preferably 8.0 to 10.0. When the pH is 8.0 or more, the neutralization efficiency with the acid is good. When the pH is 10.0 or less, deterioration of the ethylene / α-olefin copolymer due to metal elution can be suppressed. The pH of the hydrotalcite compound can be measured by the following method. First, 5 g of a sample is weighed into a 300 ml Erlenmeyer flask, 100 ml of boiled pure water is added and heated to keep the boiled state for about 5 minutes. Next, it is stoppered, allowed to cool to room temperature, water corresponding to the weight reduction is added, stoppered again, shaken for 1 minute, and allowed to stand for 5 minutes. Thereafter, the pH of the obtained supernatant is measured according to JIS Z8802-7, and the obtained value can be used as the pH of the hydrotalcite metal compound.

In the production of the fired product, the hydrotalcite compound is preferably fired at 200 to 800 ° C., more preferably 250 to 700 ° C. The firing time may be adjusted according to the firing temperature and is not particularly limited, but is preferably 1 to 24 hours, and more preferably 1 to 10 hours. The atmosphere during firing may be either an oxidizing atmosphere or a non-oxidizing atmosphere, but it is preferable not to use a gas having a strong reducing action such as hydrogen.

(Silane coupling agent)
It is preferable that the solar cell sealing material of this embodiment further contains a silane coupling agent. The content of the silane coupling agent in the solar cell encapsulant of this embodiment is preferably 0.1 to 5 parts by weight, more preferably 100 parts by weight of the ethylene / α-olefin copolymer. The amount is 0.1 to 4 parts by weight, and particularly preferably 0.1 to 3 parts by weight.

If the content of the silane coupling agent is 0.1 parts by weight or more, the adhesion is improved. On the other hand, when the content of the silane coupling agent is 5% or less, the amount of the organic peroxide added for grafting the silane coupling agent to the ethylene / α-olefin copolymer when laminating the solar cell module is reduced. Can be suppressed. For this reason, since gelatinization at the time of obtaining a solar cell sealing material by making into a sheet form with an extruder can be suppressed and the torque of an extruder can be suppressed as a result, shaping | molding of an extrusion sheet becomes easy. Since no gel material is generated in the extruder, the surface of the sheet is not uneven and the appearance of the sheet is good. In addition, since there is no gel, cracks due to the gel in the sheet do not occur even when a voltage is applied, so that the dielectric breakdown resistance is good. Moreover, moisture permeability is also favorable.

In addition, the silane coupling agent itself undergoes a condensation reaction and exists as white streaks in the solar cell encapsulant, which may deteriorate the appearance of the product. However, if the silane coupling agent is 5 wt. Occurrence can also be suppressed.

A conventionally well-known silane coupling agent can be used, and there is no restriction in particular. Specifically, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltri Methoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N- (1,3- Dimethyl-butylidene) propyla N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3- Methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane and the like can be used. Preferably, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyl with good adhesion Examples include triethoxysilane, 3-acryloxypropyltrimethoxysilane, and vinyltriethoxysilane.

(Hindered amine light stabilizer)
The solar cell encapsulant of this embodiment preferably further contains a hindered amine light stabilizer. By containing a hindered amine light stabilizer, radical species harmful to the ethylene / α-olefin copolymer can be captured and generation of new radicals can be suppressed.

Examples of hindered amine light stabilizers 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 }] And the like, hindered piperidine compounds, and the like can be used.
Moreover, the low molecular weight hindered amine light stabilizer of the following general formula (1) can also be used.

In the general formula (1), R ₁ and R ₂ represent hydrogen, an alkyl group, or the like. R ₁ and R ₂ may be the same or different. R ₁ and R ₂ are preferably hydrogen or a methyl group. R ₃ represents hydrogen, an alkyl group, an alkenyl group, or the like. R ₃ is preferably hydrogen or a methyl group.

Specific examples of the hindered amine light stabilizer represented by the general formula (1) include 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1,2,2. , 6,6-pentamethylpiperidine, 4-acryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1-propyl-2,2,6,6-tetramethylpiperidine 4-acryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2, 6,6-pentamethylpiperidine, 4-methacryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyl Oxy-1-butyl-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-1-propyl-2,2, Examples include 6,6-tetramethylpiperidine.
Moreover, the high molecular weight hindered amine light stabilizer represented by the following formula can also be used. The high molecular weight hindered amine light stabilizer means one having a molecular weight of 1000 to 5000.

The content of the hindered amine light stabilizer in the solar cell encapsulant of this embodiment is preferably 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer described above. More preferably 0.01 to 1.6 parts by weight, particularly preferably 0.05 to 1.6 parts by weight. When the content of the hindered amine light stabilizer is 0.01 parts by weight or more, the weather resistance and heat resistance are good. When the content of the hindered amine light stabilizer is 2.0 parts by weight or less, extinction of radicals generated by the organic peroxide can be suppressed, and adhesiveness, heat resistance, and crosslinking characteristics are good.

(Hindered phenol stabilizer)
It is preferable that the solar cell sealing material of this embodiment further contains a hindered phenol-based stabilizer. By containing a hindered phenol stabilizer, radical species harmful to the ethylene / α-olefin copolymer can be captured in the presence of oxygen, generation of new radicals can be suppressed, and oxidative degradation can be prevented.
As the hindered phenol stabilizer, a conventionally known compound can be used. For example, 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenylbutane, 4,4 ′ -Butylidenebis (3-methyl-6-t-butylphenol), 2,2-thiobis (4-methyl-6-t-butylphenol), 7-octadecyl-3- (4'-hydroxy-3 ', 5'-di -T-butylphenyl) propionate, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate methane, pentaerythritol-tetrakis [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxypheny) L) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis (n-octylthio) -6- (4 -Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 2,2-thio- Diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy) -hydrocinna Amido, 2,4-bis [(octylthio) methyl] -o-cresol, 3,5-di-t-butyl-4-hydroxybenzyl-phosphonate-diethyl ester, tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid ester, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4-8,10-tetraoxaspiro [5.5] Undecane can be mentioned, among others, pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionic acid ester is preferred.

The content of the hindered phenol stabilizer in the solar cell encapsulant of this embodiment is preferably 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. More preferred is 0.01 to 0.1 part by weight, and particularly preferred is 0.01 to 0.06 part by weight. When the content of the hindered phenol stabilizer is 0.005 parts by weight or more, the heat resistance is good, and for example, in a heat aging test at a high temperature of 120 ° C. or more, yellowing of the solar cell sealing material can be suppressed. There is a tendency. When the content of the hindered phenol stabilizer is 0.1 parts by weight or less, the crosslinking property of the solar cell encapsulant is good, and the heat resistance and adhesiveness are good.

In addition, under constant temperature and humidity, when used in combination with a basic hindered amine light stabilizer, the hydroxyl group of the hindered phenol stabilizer forms a salt, forming a conjugated bisquinone methide compound that is quinonated and dimerized, and is sealed with solar cells. Although it tends to cause yellowing of the material, when the hindered phenol-based stabilizer is 0.1 parts by weight or less, the yellowing of the solar cell sealing material can be suppressed.

(Phosphorus stabilizer)
It is preferable that the solar cell sealing material of this embodiment further contains a phosphorus-based stabilizer. When the phosphorus stabilizer is contained, decomposition of the organic peroxide during extrusion molding can be suppressed, and a sheet having a good appearance can be obtained. When a hindered amine light stabilizer and a hindered phenol stabilizer are included, the generated radicals can be extinguished and a sheet with a good appearance can be produced, but the stabilizer is consumed in the sheet extrusion process, Long-term reliability such as heat resistance and weather resistance tends to decrease.

As the phosphorus stabilizer, a conventionally known compound can be used, for example, 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, and bis (2,4 -Di-tert-butylphenyl) pentaerythritol diphosphite. Of these, tris (2,4-di-tert-butylphenyl) phosphite is preferable.

The content of the phosphorus stabilizer in the solar cell encapsulant of the present embodiment is preferably 0.005 to 0.5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer, and more The amount is preferably 0.01 to 0.5 parts by weight, particularly preferably 0.02 to 0.2 parts by weight. When the content of the phosphorus stabilizer is 0.005 parts by weight or more, decomposition of the organic peroxide during extrusion molding can be suppressed, and a sheet having a good appearance can be obtained. Moreover, heat resistance is favorable, and it exists in the tendency which can suppress yellowing of a solar cell sealing material, for example in the heat-resistant aging test in 120 degreeC or more high temperature. When the content of the phosphorus stabilizer is 0.5 parts by weight or less, the crosslinking property of the solar cell encapsulant is good, and the heat resistance and adhesiveness are good. In addition, there is no influence of acid generated by the decomposition of the phosphorus stabilizer, and metal corrosion does not occur.
In addition, there is a stabilizer having a phosphite structure and a hindered phenol structure in the same molecule, but in a composition containing a large amount of organic peroxide like the solar cell sealing material of this embodiment. Has insufficient performance to suppress the decomposition of the organic peroxide during extrusion molding, and tends to produce a gel and a sheet having a good appearance.

(UV absorber)
It is preferable that the solar cell sealing material of this embodiment further contains an ultraviolet absorber.
The content of the ultraviolet absorber in the solar cell encapsulant of this embodiment is preferably 0.005 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. It is preferable for the content of the ultraviolet absorber to be in the above-mentioned range since the balance between weather resistance stability and crosslinking properties is excellent.

Specific examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy. Benzophenone series such as -4-carboxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy- Benzotriazoles such as 5-methylphenyl) benzotriazole; salicylic acid esters such as phenyl salicylate and p-octylphenyl salicylate are used.

(Other additives)
In the resin composition constituting the solar cell encapsulant of the present embodiment, various components other than the components detailed above can be appropriately contained within a range not impairing the object of the present invention. Examples include various polyolefins other than ethylene / α-olefin copolymers, styrene-based, ethylene-based block copolymers, and propylene-based polymers. The content of various components in the solar cell encapsulant is preferably 0.0001 to 50 parts by weight, more preferably 0.001 to 40 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. Parts by weight. Various resins other than polyolefin, and / or various rubbers, plasticizers, fillers, pigments, dyes, antistatic agents, antibacterial agents, antifungal agents, flame retardants, crosslinking aids, hindered phenol stabilizers and phosphorus One or more additives selected from other heat stabilizers other than system stabilizers, dispersants and the like can be appropriately contained.

Other heat stabilizers other than hindered phenol stabilizers and phosphorus stabilizers include 3-hydroxy-5,7-di-tert-butyl-furan-2-one, o-xylene, and the like. Lactone heat-resistant stabilizers such as reaction products, dimyristylthiodipropionate, dilaurylthiodipropionate, distearylthiodipropionate, ditridecylthiodipropionate, pentaerythritol-tetrakis- (β-lauryl- Thiopropionate), 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptomethylbenzimidazole, 4,4′-thiobis (6-t-butyl) -3-methylphenol), 2,6-di-t-butyl-4 And the like amine heat stabilizer; (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) sulfur-based heat stabilizers such as phenol.

In particular, when a crosslinking aid is contained, the content of the crosslinking aid in the solar cell encapsulant of this embodiment is preferably 0.05 with respect to 100 parts by weight of the ethylene / α-olefin copolymer. -5 parts by weight, more preferably 0.1-3 parts by weight. It is preferable for the content of the crosslinking aid to be in the above-mentioned range since an appropriate crosslinked structure can be obtained, and heat resistance, mechanical properties and adhesiveness can be improved.

As the crosslinking aid, conventionally known ones generally used for olefinic resins can be used. Such a crosslinking aid is a compound having two or more double bonds in the molecule. Specifically, monoacrylates such as t-butyl acrylate, lauryl acrylate, cetyl acrylate, stearyl acrylate, 2-methoxyethyl acrylate, ethyl carbitol acrylate, methoxytripropylene glycol acrylate; t-butyl methacrylate, lauryl methacrylate, cetyl methacrylate Monomethacrylates such as stearyl methacrylate, methoxyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate; 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate , Diethylene glycol diacrylate, tetraethylene glycol diacrylate Diacrylates such as polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate; 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, Dimethacrylates such as neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate; triacrylates such as trimethylolpropane triacrylate, tetramethylolmethane triacrylate, pentaerythritol triacrylate Trimethylolpropane trimethacrylate, Trimethacrylates such as limethylolethane trimethacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; divinyl aromatic compounds such as divinylbenzene and di-i-propenylbenzene; triallyl cyanurate and triallyl isocyanurate A diallyl compound such as diallyl phthalate; a triallyl compound; an oxime such as p-quinonedioxime, p, p′-dibenzoylquinonedioxime; and a maleimide such as phenylmaleimide.
Among these crosslinking aids, more preferred are triacrylates such as diacrylate, dimethacrylate, divinyl aromatic compound, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, pentaerythritol triacrylate; trimethylolpropane trimethacrylate , Trimethacrylates such as trimethylolethane trimethacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; cyanurates such as triallyl cyanurate and triallyl isocyanurate; diallyl compounds such as diallyl phthalate; triallyl compounds; p -Oximes such as quinonedioxime, p, p'-dibenzoylquinonedioxime; phenylmaleimi And maleimides. Further, among these, triallyl isocyanurate is particularly preferable, and the balance between the generation of bubbles and the crosslinking property of the solar cell sealing material after lamination is most excellent.

The solar cell encapsulant of this embodiment has an organic peroxide content of 0.1 to 3 parts by weight with respect to 100 parts by weight of the above-mentioned ethylene / α-olefin copolymer, and is a hindered phenol-based material. The stabilizer content is 0.005 to 0.1 parts by weight, the hindered amine light stabilizer content is 0.01 to 2.0 parts by weight, and the phosphorus stabilizer content is 0.005. It is a preferred embodiment that the resin composition is in an amount of ˜0.5 parts by weight.

Furthermore, the solar cell encapsulant of this embodiment has an organic peroxide content of 0.2 to 2.5 parts by weight with respect to 100 parts by weight of the above-mentioned ethylene / α-olefin copolymer, The hindered phenol stabilizer content is 0.01 to 0.06 parts by weight, the hindered amine light stabilizer content is 0.05 to 1.6 parts by weight, and the phosphorus stabilizer content is It is a particularly preferred embodiment that the resin composition comprises 0.02 to 0.2 parts by weight.

The solar cell encapsulant of the present embodiment is excellent in adhesion to metal wiring and solder and long-term reliability under constant temperature and humidity while maintaining transparency, and further has a surface side transparent protective member and a back side protective member , Balance with various solar cell members such as thin film electrodes, aluminum, solar cell elements, balance of heat resistance, extrusion moldability and crosslinking characteristics, flexibility, appearance, weather resistance, volume resistivity, electrical insulation, moisture permeability Excellent balance between electrode corrosivity and process stability. For this reason, it is used suitably as a solar cell sealing material of a conventionally well-known solar cell module. As a method for producing the solar cell encapsulant of the present embodiment, a commonly used method can be used, but it is preferably produced by melt blending with a kneader, a Banbury mixer, an extruder or the like. In particular, the production with an extruder capable of continuous production is preferred.

It is one of the preferred embodiments that the solar cell encapsulant has a sheet shape as a whole. Moreover, the solar cell sealing material combined with the other layer which has at least one sheet | seat which consists of the above-mentioned solar cell sealing material can also be used suitably. The thickness of the solar cell encapsulant layer is usually 0.01 to 2 mm, preferably 0.05 to 1.5 mm, more preferably 0.1 to 1.2 mm, still more preferably 0.2 to 1 mm, particularly preferably. Is 0.3 to 0.9 mm, most preferably 0.3 to 0.8 mm. When the thickness is within this range, damage to the surface side transparent 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.

Although there is no restriction | limiting in particular in the shaping | molding method of a solar cell sealing material sheet | seat, Well-known various shaping | molding methods (Cast shaping | molding, extrusion sheet shaping | molding, inflation shaping | molding, injection molding, compression molding, calendar shaping | molding, etc.) are employable.
Among these, the following method is the most preferred embodiment. First, ethylene / α-olefin copolymer, organic peroxide, acid acceptor (may be master batch), silane coupling agent, hindered amine light stabilizer, hindered phenol as required One or more additives selected from system stabilizers, phosphorus stabilizers, ultraviolet absorbers, crosslinking aids, and other additives, for example, blending manually in a bag such as a plastic bag, Blend using a stirring mixer such as a Henschel mixer, tumbler or super mixer. Next, the obtained resin composition is put into a hopper of an extrusion sheet molding machine, and extrusion sheet molding is performed while melt-kneading to obtain a sheet-shaped solar cell encapsulant.

In addition, when the pelletized resin composition is once pelletized with the compounded resin composition and further formed into a sheet by extrusion molding or press molding, generally an aqueous layer is passed through or an underwater cutter type extrusion is performed. The strand is cooled using a machine and cut to obtain pellets. Therefore, since moisture adheres, deterioration of additives, particularly silane coupling agents, occurs, for example, when a sheet is formed again with an extruder, the condensation reaction between silane coupling agents proceeds, and the adhesiveness tends to decrease. Therefore, it is not preferable.
Additives other than ethylene / α-olefin copolymers and organic peroxides and silane coupling agents (stabilizers such as hindered phenol stabilizers, phosphorus stabilizers, hindered amine light stabilizers, UV absorbers, etc.) ) Is pre-mastered using an extruder, blended with an organic peroxide or silane coupling agent, and then sheeted again with an extruder or the like, a hindered phenol stabilizer and phosphorus stabilizer Stabilizers such as hindered amine light stabilizers and UV absorbers are not preferred because they are twice passed through an extruder, and the stabilizers deteriorate and long-term reliability such as weather resistance and heat resistance tends to decrease.

As the extrusion temperature range, the extrusion temperature is 100 to 130 ° C. When the extrusion temperature is 100 ° C. or higher, the productivity of the solar cell encapsulant can be improved. When the extrusion temperature is 130 ° C. or lower, gelation hardly occurs when the resin composition is formed into a sheet with an extruder to obtain a solar cell sealing material. Therefore, an increase in the torque of the extruder can be prevented and sheet forming can be facilitated. Moreover, since it becomes difficult for unevenness | corrugation to generate | occur | produce on the surface of a sheet | seat, the fall of an external appearance can be prevented. Moreover, since generation | occurrence | production of the crack inside a sheet | seat can be suppressed when a voltage is applied, the fall of a dielectric breakdown voltage can be prevented. Furthermore, a decrease in moisture permeability can also be suppressed. In addition, since unevenness on the sheet surface is less likely to occur, adhesion to the surface side transparent protective member, cells, electrodes, and back surface side protective member is improved when laminating the solar cell module, thereby improving adhesion. it can.

Further, when the MFR of the ethylene / α-olefin copolymer is less than 10 g / 10 minutes, for example, a sheet or film having a desired thickness is produced by rolling the molten resin with a heated metal roll (calender roll). Using a calendar molding machine, ethylene / α-olefin copolymer, silane coupling agent, organic peroxide, UV absorber, light stabilizer, heat stabilizer, and other additives used as required It is also possible to obtain a sheet-shaped solar cell encapsulant by calendar molding while performing melt kneading.
As the calendar molding machine, various known calendar molding machines can be used, and a mixing roll, a three-calendar roll, and a four-calendar roll can be used. As the four calender rolls, I type, S type, inverted L type, Z type, oblique Z type, etc. can be used. Moreover, it is also preferable to heat the ethylene-based resin composition to an appropriate temperature before it is applied to the calender roll. For example, it is one of preferred embodiments to install a Banbury mixer, a kneader, an extruder, or the like. Regarding the temperature range for calendering, the roll temperature is usually preferably 40 to 100 ° C.

Further, the surface of the solar cell encapsulant sheet (or layer) may be embossed. By decorating the sheet surface of the solar cell encapsulant by embossing, blocking between the encapsulant sheets or between the encapsulant sheet and other sheets can be prevented. Furthermore, since the embossing reduces the storage elastic modulus of the solar cell encapsulant (solar cell encapsulant sheet), it becomes a cushion for the solar cell element when laminating the solar cell encapsulant sheet and the solar cell element. Thus, damage to the solar cell element can be prevented.

Porosity P expressed as a percentage V _H / V _A × 100 of the total volume V _H of the recesses per unit area of the solar cell encapsulant sheet and the apparent volume _VA of the solar cell encapsulant sheet (%) Is preferably 10 to 50%, more preferably 10 to 40%, and still more preferably 15 to 40%. The apparent volume _VA of the solar cell encapsulant sheet is obtained by multiplying the unit area by the maximum thickness of the solar cell encapsulant. When the porosity P is 10% or more, the elastic modulus of the solar cell encapsulating material can be sufficiently lowered, so that sufficient cushioning properties can be obtained. Therefore, in the module manufacturing process, when laminating (pressing process) in two steps, the crystalline solar cell prevents the cracking of the silicon cell and the solder that fixes the silicon cell and the electrode, and the thin film solar cell Then, the crack of a silver electrode can be prevented. That is, when the porosity of the solar cell encapsulant is 10% or more, even if pressure is locally applied to the solar cell encapsulant, the convex portion to which pressure is applied is deformed so as to be crushed. To do. For this reason, even when a large pressure is locally applied to the silicon cell, for example, during the lamination process, the silicon cell can be prevented from being broken. Moreover, since the passage of air can be ensured as the porosity of the solar cell encapsulant is 10% or more, it can be well deaerated during lamination. For this reason, it is possible to prevent the appearance of the solar cell module from deteriorating due to air remaining, or the corrosion of the electrode due to the remaining moisture in the air during long-term use. Furthermore, since the space | gap which arises in the resin composition which flowed at the time of a lamination decreases, it can prevent that it protrudes outside each adherend of a solar cell module, and contaminates a laminator.

On the other hand, when the porosity P is 80% or less, air can be satisfactorily degassed at the time of pressurization of the laminating process, so that air can be prevented from remaining in the solar cell module. For this reason, deterioration of the external appearance of the solar cell module is prevented, and corrosion of the electrode does not occur due to residual moisture in the air during long-term use. Moreover, since air can be satisfactorily degassed at the time of pressurization during laminating, the adhesion area between the solar cell sealing material and the adherend increases, and sufficient adhesion strength can be obtained.

The porosity P can be obtained by the following calculation. The apparent volume V _A (mm ³ ) of the embossed solar cell encapsulant is the maximum thickness t _max (mm) of the solar cell encapsulant and the unit area (for example, 1 m ² = 1000 mm × 1000 mm = 10). ⁶ mm ² ), and is calculated as the following formula (12).
V _A (mm ³ ) = t _max (mm) × 10 ⁶ (mm ² ) (12)
On the other hand, the actual volume V ₀ (mm ³ ) of the solar cell encapsulant of this unit area is based on the specific gravity ρ (g / mm ³ ) and unit area (1 m ² ) of the resin constituting the solar cell encapsulant. It is calculated by applying the actual weight W (g) of the solar cell encapsulant to the following equation (13).
V ₀ (mm ³ ) = W / ρ (13)
The total volume V _H (mm ³ ) of the recesses per unit area of the solar cell encapsulant is expressed as “Actual volume V _A of solar cell encapsulant” from “Actual volume V _A ” as shown in the following formula (14). It is calculated by subtracting the volume “V ₀ ”.
V _H (mm ³ ) = V _A −V ₀ = V _A − (W / ρ) (14)
Therefore, the porosity (%) can be obtained as follows.
Porosity P (%) = (V _H / V _A ) × 100
= ((V _A- (W / ρ)) / V _A ) × 100
= (1-W / (ρ · V _A )) × 100
= (1-W / (ρ · t _max · 10 ⁶ )) × 100

The porosity P (%) can be obtained by the above calculation formula, but it can also be obtained by taking an image of a cross section or an embossed surface of an actual solar cell encapsulant and performing image processing. it can.

The depth of the recess formed by embossing is preferably 20 to 95% of the maximum thickness of the solar cell encapsulant, more preferably 50 to 95%, and 65 to 95%. More preferred. The percentage of the depth D of the recess with respect to the maximum thickness t _{max of the} sheet may be referred to as the “depth ratio” of the recess.

The depth of the embossed concave portion indicates a height difference D between the topmost portion of the convex portion and the deepest portion of the concave portion of the uneven surface of the solar cell sealing material by the embossing. In addition, the maximum thickness t _max of the solar cell encapsulant is, when embossed on one surface of the solar cell encapsulant, the solar cell encapsulant from the top of the convex portion on one surface to the other surface (solar cell When the embossing is applied to both surfaces of the solar cell encapsulant, the distance from the top of the convex portion on one surface to the maximum of the convex portion on the other surface is shown. The distance (in the solar cell encapsulant thickness direction) to the top is shown.

Embossing may be performed on one side of the solar cell encapsulant or on both sides. When increasing the depth of the embossed recess, it is preferably formed only on one side of the solar cell encapsulant. When embossing is performed only on one side of the solar cell encapsulant, the maximum thickness t _max of the solar cell encapsulant is 0.01 mm to 2 mm, preferably 0.05 to 1 mm, more preferably 0.1 to 1 mm, more preferably 0.15 to 1 mm, more preferably 0.2 to 1 mm, further preferably 0.2 to 0.9 mm, and particularly preferably 0.3 to 1 mm. 0.9 mm, most preferably 0.3 to 0.8 mm. When the maximum thickness t _max of the solar cell encapsulant is within this range, damage to the surface side transparent protective member, solar cell element, thin film electrode, etc. in the laminating step can be suppressed, and the solar cell module laminate can be performed even at a relatively low temperature. It is preferable because it can be molded. Moreover, the solar cell sealing material can ensure sufficient light transmittance, and the solar cell module using the solar cell encapsulant has a high photovoltaic power generation amount.

Further, the sheet can be used as a solar cell encapsulant in a single wafer form cut to fit the solar cell module size or a roll form that can be cut to fit the size just before producing the solar cell module. . The sheet-like solar cell encapsulant (solar cell encapsulant sheet) which is a preferred embodiment of the present invention only needs to have at least one layer made of the solar cell encapsulant. Therefore, the number of layers made of the solar cell encapsulant of this embodiment may be one layer or two or more layers. From the viewpoint of simplifying the structure and reducing costs, and from the viewpoint of effectively utilizing light by minimizing interfacial reflection between layers, it is preferable to be further increased.

The solar cell encapsulant sheet may be composed of only a layer made of the solar cell encapsulant of the present embodiment, or a layer other than the layer containing the solar cell encapsulant (hereinafter “other layers”). May also be included). Examples of other layers include a hard coat layer, an adhesive layer, an antireflection layer, a gas barrier layer, and an antifouling layer for protecting the front or back surface, if classified for purposes. 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.

The positional relationship between the layer made of the solar cell encapsulant of this embodiment and the other layers is not particularly limited, and a preferable layer configuration is appropriately selected in relation to the object of the present invention. That is, the other layer may be provided between layers made of two or more solar cell encapsulants, or may be provided in the outermost layer of the solar cell encapsulant sheet, or in other locations. It may be provided. In addition, other layers may be provided only on one side of the layer made of the solar cell sealing material, or other layers may be provided on both sides. There is no restriction | limiting in particular in the number of layers of another layer, Arbitrary number of other layers can be provided and it is not necessary to provide another layer.

From the viewpoint of simplifying the structure and reducing costs, and from the viewpoint of effectively utilizing light by minimizing interface reflection, the other layers are not provided, and only the layer made of the solar cell encapsulant of the present embodiment is used. What is necessary is just to produce a battery sealing material sheet. However, if there are other layers necessary or useful in relation to the purpose, such other layers may be provided as appropriate.

In the case of providing other layers, there are no particular restrictions on the method of laminating the layer made of the solar cell encapsulant of this embodiment and the other layers, but there are no limitations on cast molding machines, extrusion sheet molding machines, inflation molding machines, injections. A method of obtaining a laminate by co-extrusion using a known melt extruder such as a molding machine, or a method of obtaining a laminate by melting or heating and laminating the other layer on one previously formed layer is preferred.

In addition, suitable adhesives (for example, maleic anhydride-modified polyolefin resin (trade name “Admer (registered trademark)” manufactured by Mitsui Chemicals, Inc., product name “Modic (registered trademark)” manufactured by Mitsubishi Chemical Corporation, etc.)), unsaturated Including low (non) crystalline soft polymers such as polyolefins, ethylene / acrylic acid ester / maleic anhydride terpolymers (trade name “Bondaine (registered trademark)” manufactured by Sumika DF Chemical Co., Ltd.), etc. An acrylic adhesive, an ethylene / vinyl acetate copolymer, or an adhesive resin composition containing these) may be laminated by a dry laminating method or a heat laminating method. As the adhesive, those having a heat resistance of about 120 to 150 ° C. are preferably used, and a polyester-based or polyurethane-based adhesive is exemplified as a suitable one. Moreover, in order to improve the adhesiveness of both layers, for example, a silane coupling treatment, a titanium coupling treatment, a corona treatment, a plasma treatment, or the like may be used.

2. About solar cell module A solar cell module is a crystalline solar cell in which, for example, a solar cell element usually formed of polycrystalline silicon or the like is sandwiched between solar cell sealing material sheets, and both front and back surfaces are covered with a protective sheet. Module. That is, a typical solar cell module includes a solar cell module protective sheet (front surface side transparent protective member) / solar cell encapsulant / solar cell element / solar cell encapsulant / solar cell module protective sheet (back side protection). Member).
However, the solar cell module which is one of the preferred embodiments of the present invention is not limited to the above-described configuration, and a part of each of the above layers is appropriately omitted or the above-described range within a range not impairing the object of the present invention. Other layers can be provided as appropriate. Examples of the layer other than the above include an adhesive layer, a shock absorbing layer, a coating layer, an antireflection layer, a back surface rereflection layer, and a light diffusion layer. These layers are not particularly limited, but can be provided at appropriate positions in consideration of the purpose and characteristics of each layer.

(Crystalline silicon solar cell module)
FIG. 1 is a cross-sectional view schematically showing one embodiment of the solar cell module of the present invention. In FIG. 1, an example of the configuration of a crystalline silicon solar cell module 20 is shown. As shown in FIG. 1, the solar cell module 20 includes a plurality of crystalline silicon-based solar cell elements 22 electrically connected by an interconnector 29, a pair of front surface side transparent protective members 24 and a back surface thereof. A side protection member 26 is provided, and a sealing layer 28 is filled between these protection members and the plurality of solar cell elements 22. The sealing layer 28 is obtained by bonding the solar cell sealing material of the present embodiment and then thermocompression bonding, and is in contact with the electrodes formed on the light receiving surface and the back surface of the solar cell element 22. The electrode is a current collecting member formed on each of the light receiving surface and the back surface of the solar cell element 22 and includes a power collecting wire, a tabbed bus, a back electrode layer, and the like which will be described later.

FIG. 2 is a plan view schematically showing one configuration example of the light receiving surface and the back surface of the solar cell element. In FIG. 2, an example of the configuration of the light receiving surface 22A and the back surface 22B of the solar cell element 22 is shown. As shown in FIG. 2 (A), the light receiving surface 22A of the solar cell element 22 collects a large number of linearly-collected current lines 32, charges from the current collector lines 32, and interconnector 29 (FIG. 1). ) And a bus bar with a tab (bus bar) 34 A connected thereto. Further, as shown in FIG. 2B, a conductive layer (back electrode) 36 is formed on the entire back surface 22B of the solar cell element 22, and charges are collected from the conductive layer 36 on the back surface 22B. A tabbed bus bar (bus bar) 34B connected to the connector 29 (FIG. 1) is formed. The line width of the collector line 32 is, for example, about 0.1 mm, the line width of the tabbed bus 34A is, for example, about 2 to 3 mm, and the line width of the tabbed bus 34B is, for example, about 5 to 7 mm. is there. The thickness of the current collector 32, the tabbed bus 34A and the tabbed bus 34B is, for example, about 20 to 50 μm.

The current collector 32, the tabbed bus 34A, and the tabbed bus 34B preferably contain a highly conductive metal. Examples of such highly conductive metals include gold, silver, copper, and the like. From the viewpoint of high conductivity and high corrosion resistance, silver, silver compounds, alloys containing silver, and the like are preferable. The conductive layer 36 contains not only a highly conductive metal but also a highly light reflective component, for example, aluminum from the viewpoint of improving the photoelectric conversion efficiency of the solar cell element by reflecting light received by the light receiving surface. It is preferable. The current collector 32, the tabbed bus 34 A, the tabbed bus 34 B, and the conductive layer 36 are formed by applying a conductive material paint containing the above highly conductive metal to the light receiving surface 22 A or the back surface 22 B of the solar cell element 22, for example, a screen. It is formed by applying to a coating thickness of 50 μm by printing, drying, and baking at, for example, 600 to 700 ° C. as necessary.

Since the surface side transparent protective member 24 is disposed on the light receiving surface side, it needs to be transparent. Examples of the surface side transparent protective member 24 include a transparent glass plate and a transparent resin film. On the other hand, the back surface side protection member 26 does not need to be transparent, and the material is not particularly limited. Examples of the back surface side protection member 26 include a glass substrate and a plastic film, but a glass substrate is preferably used from the viewpoint of durability and transparency.

The solar cell module 20 can be obtained by any manufacturing method. The solar cell module 20 is a process of obtaining a laminated body in which, for example, the back surface side protective member 26, the solar cell sealing material, the plurality of solar cell elements 22, the solar cell sealing material, and the front surface side transparent protective member 24 are stacked in this order. A step of pressurizing and laminating the laminate with a laminator or the like, and simultaneously heating as necessary; after the step, the laminate is further subjected to a heat treatment as necessary to obtain the step of curing the sealing material; be able to.
The solar cell element 22 is usually provided with a collecting electrode for taking out the generated electricity. Examples of current collecting electrodes include bus bar electrodes, finger electrodes, and the like. In general, the collector electrode has a structure in which the collector electrode is disposed on both the front and back surfaces of the solar cell element. However, if the collector electrode is disposed on the light receiving surface, the collector electrode blocks light and power generation efficiency is reduced. Problems can arise.

Further, in order to improve the power generation efficiency, a back contact type solar cell element that does not require a collector electrode on the light receiving surface can be used. In one aspect of the back contact solar cell element, p-doped regions and n-doped regions are alternately provided on the back surface side provided on the opposite side of the light receiving surface of the solar cell element. In another aspect of the back contact solar cell element, a p / n junction is formed on a substrate provided with a through hole (through hole), and the surface (light-receiving surface) side of the through hole inner wall and the through hole peripheral portion on the back surface side is formed. A doped layer is formed, and the current on the light receiving surface is taken out on the back side.

Generally, in the solar cell system, the above-mentioned solar cell modules are connected in series from several units to several dozen units, 50V to 500V even in a small scale for residential use, and 600 to 1000V in a large scale called mega solar. Is operated. An aluminum frame or the like is used for the outer frame of the solar cell module for the purpose of maintaining strength, and the aluminum frame is often grounded (grounded) from the viewpoint of safety. As a result, when the solar cell generates power, a voltage difference due to power generation occurs between the surface-side transparent protective member surface having a lower electrical resistance than the sealing material and the solar cell element.
As a result, the solar cell encapsulant that is sealed between the power generation cell and the surface-side transparent protective member or the aluminum frame is required to have good electrical characteristics such as high electrical insulation and high resistance.

(Thin film silicon (amorphous silicon) solar cell module)
The thin-film silicon-based solar cell module has (1) a surface-side transparent protective member (glass substrate) / thin-film solar cell element / sealing layer / back-side protective member stacked in this order; (2) a surface-side transparent protective member / Sealing layer / thin film solar cell element / sealing layer / back surface side protective member may be laminated in this order. The front surface side transparent protective member, the back surface side protective member, and the sealing layer are the same as those in the above-mentioned “crystalline silicon solar cell module”.

The thin film solar cell element in the aspect of (1) includes, for example, transparent electrode layer / pin type silicon layer / back electrode layer in this order. Examples of the transparent electrode layer include semiconductor oxides such as In ₂ O ₃ , SnO ₂ , ZnO, Cd ₂ SnO ₄ , ITO (In ₂ O ₃ with Sn added). The back electrode layer includes, for example, a silver thin film layer. Each layer is formed by a plasma CVD (chemical vapor deposition) method or a sputtering method. A sealing layer is arrange | positioned so that a back surface electrode layer (for example, silver thin film layer) may be contact | connected. Since the transparent electrode layer is formed on the front surface side transparent protective member, the sealing layer is often not disposed between the front surface side transparent protective member and the transparent electrode layer.

The thin-film solar cell element in the aspect (2) includes, for example, a transparent electrode layer / pin type silicon layer / metal foil, or a metal thin film layer (for example, a silver thin film layer) disposed on a heat-resistant polymer film. In order. Examples of the metal foil include stainless steel foil. Examples of the heat resistant polymer film include a polyimide film. The transparent electrode layer and the pin type silicon layer are formed by the CVD method or the sputtering method as described above. That is, the pin-type silicon layer is formed on a metal foil or a metal thin film layer disposed on a heat-resistant polymer film; and the transparent electrode layer is formed on a pin-type silicon layer. Moreover, the metal thin film layer arrange | positioned on a heat resistant polymer film can also be formed by CVD method or a sputtering method.

In this case, the sealing layer is disposed between the transparent electrode layer and the front surface side transparent protective member; and between the metal foil or the heat resistant polymer film and the back surface side protective member. Thus, the sealing layer obtained from a solar cell sealing material is in contact with electrodes, such as a current collection line of a solar cell element, a bus bar with a tab, and a conductive layer. In addition, the thin-film solar cell element in the aspect (2) has a silicon layer that is thinner than a crystalline silicon-based solar cell element. Hard to do. For this reason, the softness | flexibility of the solar cell sealing material used for a thin film solar cell module may be lower than what is used for a crystalline silicon type solar cell module. On the other hand, since the electrode of the thin film solar cell element is a metal thin film layer as described above, when it is deteriorated by corrosion, the power generation efficiency may be significantly reduced.

As another solar cell module, there is a solar cell module using silicon as a solar cell element. Solar cell modules using silicon for solar cell elements include hybrid type (HIT type) solar cell modules in which crystalline silicon and amorphous silicon are laminated, and multi-junction type (tandem type) solar cells in which silicon layers having different absorption wavelength ranges are laminated. A battery module, a back contact solar cell module in which p-doped regions and n-doped regions are alternately provided on the back side provided on the opposite side of the light-receiving surface of the solar cell element, innumerable spherical silicon particles (diameter of about 1 mm) and Examples include a spherical silicon solar cell module combined with a concave mirror (also serving as an electrode) having a diameter of 2 to 3 mm for increasing the light collecting ability. Further, in a solar cell module using silicon as a solar cell element, the role of an amorphous silicon type p-type window layer having a conventional pin junction structure is induced by “field effect” from “insulated transparent electrode”. A field effect solar cell module having a structure replaced with an “inversion layer” is also included. Also, a GaAs solar cell module using single crystal GaAs for the solar cell element; I-III called chalcopyrite system made of Cu, In, Ga, Al, Se, S, etc., instead of silicon as the solar cell element -CIS or CIGS (chalcopyrite) solar cell module using a group VI compound; CdTe-CdS solar cell using a Cd compound thin film as a solar cell element, Cu ₂ ZnSnS ₄ (CZTS) solar cell module, etc. It is done. The solar cell encapsulant of this embodiment can be used as a solar cell encapsulant for all these solar cell modules.

In particular, the sealing material layer laminated under the photovoltaic element constituting the solar cell module has an adhesive property with the sealing material layer / electrode / back surface protection layer laminated on the photovoltaic element. It is necessary to have. Moreover, in order to maintain the smoothness of the back surface of the solar cell element as a photovoltaic element, it is necessary to have thermoplasticity. Furthermore, in order to protect the solar cell element as a photovoltaic element, it is necessary to be excellent in scratch resistance, shock absorption and the like.

The sealing material layer preferably has heat resistance. In particular, when manufacturing solar cell modules, sealing is performed by heating such as in the lamination method in which vacuum suction is applied and thermocompression bonding, or by the action of heat such as sunlight in long-term use of solar cell modules, etc. It is desirable that the resin composition constituting the material layer does not change in quality or deteriorate or decompose. If the additives contained in the resin composition are eluted or decomposed products are generated, they act on the electromotive force surface (element surface) of the solar cell element, deteriorating its function and performance. It will end up. Therefore, heat resistance is indispensable as a characteristic of the sealing material layer of the solar cell module.
Furthermore, the sealing material layer is preferably excellent in moisture resistance. In this case, moisture permeation from the back side of the solar cell module can be prevented, and corrosion and deterioration of the photovoltaic element of the solar cell module can be prevented.

Unlike the filler layer laminated on the photovoltaic element, the sealing material layer does not necessarily need to have transparency. The solar cell encapsulant of the present embodiment has the above-described characteristics, and the solar cell encapsulant on the back surface side of the crystalline solar cell module and the solar cell encapsulant of the thin-film solar cell module vulnerable to moisture penetration Can be suitably used.

The solar cell module of the present embodiment may appropriately include any member as long as the object of the present invention is not impaired. Typically, an adhesive layer, a shock absorbing layer, a coating layer, an antireflection layer, a back surface rereflection layer, a light diffusion layer, and the like can be provided, but not limited thereto. There are no particular limitations on the positions where these layers are provided, and the layers can be provided at appropriate positions in consideration of the purpose of providing such layers and the characteristics of such layers.

(Surface-side transparent protective member for solar cell module)
The surface side transparent protective member for the solar cell module used in the solar cell module is not particularly limited, but because it is located on the outermost layer of the solar cell module, including weather resistance, water repellency, contamination resistance, mechanical strength, It is preferable to have a performance for ensuring long-term reliability in outdoor exposure of the solar cell module. Moreover, in order to utilize sunlight effectively, it is preferable that it is a highly transparent sheet | seat with a small optical loss.

Examples of the material for the surface side transparent protective member for solar cell modules include resin films and glass substrates made of polyester resin, fluororesin, acrylic resin, cyclic olefin (co) polymer, ethylene-vinyl acetate copolymer, and the like. . The resin film is preferably a polyester resin excellent in transparency, strength, cost and the like, particularly a polyethylene terephthalate resin, a fluorine resin having good weather resistance, and the like. Examples of fluororesins include tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (PTFE), and tetrafluoroethylene. -There are propylene hexafluoride copolymer (FEP) and polytrifluoroethylene chloride (PCTFE). Polyvinylidene fluoride resin is excellent from the viewpoint of weather resistance, but tetrafluoroethylene-ethylene copolymer is excellent from the viewpoint of both weather resistance and mechanical strength. In addition, it is desirable to perform corona treatment and plasma treatment on the surface-side transparent protective member in order to improve adhesion with materials constituting other layers such as a sealing material layer. It is also possible to use a sheet that has been subjected to stretching treatment for improving mechanical strength, for example, a biaxially stretched polypropylene sheet.

When a glass substrate is used as the surface side transparent protective member for a solar cell module, the glass substrate preferably has a total light transmittance of light having a wavelength of 350 to 1400 nm of 80% or more, more preferably 90% or more. . As such a glass substrate, it is common to use white plate glass with little absorption in the infrared region, but even blue plate glass has little influence on the output characteristics of the solar cell module as long as the thickness is 3 mm or less. . Further, tempered glass can be obtained by heat treatment to increase the mechanical strength of the glass substrate, but float plate glass without heat treatment may be used. Further, an antireflection coating may be provided on the light receiving surface side of the glass substrate in order to suppress reflection.

(Back side protection member for solar cell module)
The solar cell module back surface side protective member used for the solar cell module is not particularly limited, but is located on the outermost surface layer of the solar cell module, so that the weather resistance, mechanical strength, etc. are similar to the above surface side transparent protective member. Are required. Therefore, you may comprise the back surface side protection member for solar cell modules with the material similar to a surface side transparent protection member. That is, the above-mentioned various materials used as the front surface side transparent protective member can also be used as the back surface side protective member. In particular, a polyester resin and glass can be preferably used. Moreover, since the back surface side protection member does not presuppose passage of sunlight, the transparency calculated | required by the surface side transparent protection member is not necessarily requested | required. Therefore, a reinforcing plate may be attached to increase the mechanical strength of the solar cell module or to prevent distortion and warpage due to temperature change. As the reinforcing plate, for example, a steel plate, a plastic plate, an FRP (glass fiber reinforced plastic) plate or the like can be preferably used.

Furthermore, the solar cell sealing material of this embodiment may be integrated with the back surface side protective member for the solar cell module. By integrating the solar cell encapsulant and the back side protection member for the solar cell module, the process of cutting the solar cell encapsulant and the back side protection member for the solar cell module into a module size at the time of module assembly can be shortened. Moreover, the process of laying up the solar cell encapsulant and the back side protection member for the solar cell module can be shortened or omitted by making the process of laying up with an integrated sheet. . The method for laminating the solar cell sealing material and the solar cell module back surface protection member in the case of integrating the solar cell sealing material and the solar cell module back surface side protection member is not particularly limited. The lamination method includes a method of obtaining a laminate by co-extrusion using a known melt extruder such as a cast molding machine, an extrusion sheet molding machine, an inflation molding machine, an injection molding machine, or the like; A method of obtaining a laminate by melting or heat laminating the other layer is preferred.

In addition, suitable adhesives (for example, maleic anhydride-modified polyolefin resin (trade name “Admer (registered trademark)” manufactured by Mitsui Chemicals, Inc., product name “Modic (registered trademark)” manufactured by Mitsubishi Chemical Corporation, etc.)), unsaturated Including low (non) crystalline soft polymers such as polyolefins, ethylene / acrylic acid ester / maleic anhydride terpolymers (trade name “Bondaine (registered trademark)” manufactured by Sumika DF Chemical Co., Ltd.), etc. An acrylic adhesive, an ethylene / vinyl acetate copolymer, or an adhesive resin composition containing these) may be laminated by a dry laminating method or a heat laminating method.

The adhesive preferably has a heat resistance of about 120 to 150 ° C., and specifically, a polyester-based or polyurethane-based adhesive is preferable. In order to improve the adhesion between the two layers, at least one of the layers may be subjected to, for example, a silane coupling treatment, a titanium coupling treatment, a corona treatment, or a plasma treatment.

(Solar cell element)
The solar cell element used for the solar cell module is not particularly limited as long as it can generate power using the photovoltaic effect of the semiconductor. Solar cell elements include, for example, silicon (single crystal, polycrystal, amorphous) solar cells, compound semiconductor (III-III, II-VI, etc.) solar cells, wet solar cells, organic A semiconductor solar cell or the like can be used. Among these, a polycrystalline silicon solar cell is preferable from the viewpoint of balance between power generation performance and cost.

Both silicon solar cell elements and compound semiconductor solar cell elements have excellent characteristics as solar cell elements, but are known to be easily damaged by external stress and impact. Since the solar cell sealing material of this embodiment is excellent in flexibility, it has a great effect of absorbing stress, impact, etc. on the solar cell element and preventing damage to the solar cell element. Therefore, in the solar cell module of this embodiment, it is desirable that the layer made of the solar cell sealing material of this embodiment is directly joined to the solar cell element. In addition, when the solar cell encapsulant has thermoplasticity, the solar cell element can be taken out relatively easily even after the solar cell module is once produced. Yes. Since the resin composition constituting the solar cell encapsulant of the present embodiment has thermoplasticity, the solar cell encapsulant as a whole has thermoplasticity, which is also preferable from the viewpoint of recyclability.

(Metal electrode)
Although the structure and material of the metal electrode used for a solar cell module are not specifically limited, In a specific example, it has a laminated structure of a transparent conductive film and a metal film. The transparent conductive film is made of SnO ₂ , ITO, ZnO or the like. The metal film is made of at least one metal selected from silver, gold, copper, tin, aluminum, cadmium, zinc, mercury, chromium, molybdenum, tungsten, nickel, vanadium, and the like. These metal films may be used alone or as a composite alloy. The transparent conductive film and the metal film are formed by a method such as CVD, sputtering, or vapor deposition.

A solar cell element and a metal electrode are joined by the following method, for example. First, a well-known rosin flux, a water-soluble flux of IPA (isopropyl alcohol) or an aqueous solution of water is applied to the surface of the metal electrode. Next, the surface of the metal electrode is coated with solder through a solder melt which is dried with a heater or hot air and melted in a solder melting tank. Then, it reheats and a solar cell element and a metal electrode or metal electrodes are joined.
In recent years, a method of directly applying a flux and solder or solder to the joining portion and joining the solar cell element and the metal electrode or metal electrodes is also taken.

(Method for manufacturing solar cell module)
The manufacturing method of the solar cell module of the present embodiment includes (i) a surface-side transparent protective member, a solar cell sealing material of the present embodiment, a solar cell element (cell), and a solar cell sealing material of the present embodiment. And a step of laminating the back-side protection member in this order to form a laminate, and (ii) a step of pressurizing and heating the obtained laminate to integrate them.

In step (i), it is preferable that the surface on which the uneven shape (embossed shape) of the solar cell encapsulant is formed is disposed on the solar cell element side.

In step (ii), the laminate obtained in step (i) is integrated (sealed) by heating and pressing using a vacuum laminator or a hot press according to a conventional method. In sealing, since the solar cell sealing material of this embodiment has high cushioning properties, damage to the solar cell element can be prevented. Moreover, since the deaeration property is good, there is no air entrainment, and a high-quality product can be manufactured with a high yield.

When the solar cell module is manufactured, the ethylene / α-olefin resin composition constituting the solar cell encapsulant is crosslinked and cured. This crosslinking step may be performed simultaneously with step (ii) or after step (ii).

When the cross-linking step is performed after step (ii), vacuum and heating is performed for 3 to 6 minutes at a temperature of 125 to 160 ° C. and a vacuum pressure of 10 Torr or less in step (ii); The above laminate is integrated for about one minute. The crosslinking step performed after step (ii) can be performed by a general method. For example, a tunnel-type continuous crosslinking furnace may be used, or a shelf-type batch-type crosslinking furnace may be used. . The crosslinking conditions are usually 130 to 155 ° C. and about 20 to 60 minutes.

On the other hand, when the crosslinking step is performed simultaneously with the step (ii), the crosslinking step is performed in the step (ii) except that the heating temperature in the step (ii) is 145 to 170 ° C. and the pressurization time at atmospheric pressure is 6 to 30 minutes. This can be done in the same way as after ii). The solar cell encapsulant of this embodiment has excellent cross-linking properties by containing a specific organic peroxide, and does not need to go through a two-step bonding process in step (ii), and at a high temperature. It can be completed in a short time, the cross-linking step performed after step (ii) may be omitted, and the module productivity can be significantly improved.

In any case, the solar cell module of this embodiment is manufactured at a temperature at which the crosslinking agent is not substantially decomposed and the solar cell sealing material of this embodiment melts. The solar cell encapsulant is temporarily adhered to the substrate, and then the temperature is raised to sufficiently bond and crosslink the encapsulant. What is necessary is just to select the additive prescription which can satisfy various conditions, for example, what is necessary is just to select the kind and impregnation amount, such as the said crosslinking agent and the said crosslinking adjuvant.

The crosslinking is preferably carried out to such an extent that the gel fraction of the crosslinked ethylene / α-olefin copolymer is 50 to 95%. The gel fraction is more preferably 50 to 90%, still more preferably 60 to 90%, and most preferably 65 to 90%. The gel fraction can be calculated by the following method. For example, 1 g of a sample of the encapsulant sheet is taken from the solar cell module and subjected to Soxhlet extraction with boiling toluene for 10 hours. The extract is filtered through a stainless mesh of 30 mesh, and the mesh is dried under reduced pressure at 110 ° C. for 8 hours. The weight of the residue remaining on the mesh is measured, and the ratio (%) of the weight of the residue remaining on the mesh to the sample amount (1 g) before the treatment is defined as the gel fraction.
When the gel fraction is equal to or higher than the lower limit, the heat resistance of the solar cell encapsulant is improved. For example, a constant temperature and humidity test at 85 ° C. × 85% RH, high intensity xenon irradiation at a black panel temperature of 83 ° C. It is possible to suppress a decrease in adhesion in a test, a heat cycle test at -40 ° C to 90 ° C, and a heat resistance test. On the other hand, when the gel fraction is not more than the above upper limit value, it becomes a highly flexible solar cell encapsulant, and the temperature followability in the heat cycle test at −40 ° C. to 90 ° C. is improved. Can be prevented.

(Power generation equipment)
The solar cell module of this embodiment is excellent in productivity, power generation efficiency, life, and the like. For this reason, the power generation equipment using such a solar cell module is excellent in cost, power generation efficiency, life and the like, and has a high practical value. The power generation equipment described above is suitable for long-term use, both outdoors and indoors, such as being installed on the roof of a house, used as a mobile power source for outdoor activities such as camping, and used as an auxiliary power source for automobile batteries. .

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(1) Measuring method [content ratio of ethylene unit and α-olefin unit]
A solution obtained by dissolving 0.35 g of a sample in 2.0 ml of hexachlorobutadiene by heating was filtered through a glass filter (G2), 0.5 ml of deuterated benzene was added, and the mixture was charged into an NMR tube having an inner diameter of 10 mm. Using a JNM GX-400 type NMR measuring apparatus manufactured by JEOL Ltd., ¹³ C-NMR measurement was performed at 120 ° C. The number of integration was 8000 times or more. From the obtained ¹³ C-NMR spectrum, the content ratio of ethylene units and the content ratio of α-olefin units in the copolymer were quantified.

[MFR]
Based on ASTM D1238, the MFR of the ethylene / α-olefin copolymer was measured under the conditions of 190 ° C. and 2.16 kg load.

[density]
Based on ASTM D1505, the density of the ethylene / α-olefin copolymer was measured.

[Shore A hardness]
The ethylene / α-olefin copolymer was pressurized at 190 ° C., heated for 4 minutes and at 10 MPa, and then pressure-cooled at 10 MPa to room temperature for 5 minutes to obtain a sheet having a thickness of 3 mm. Using the obtained sheet, the Shore A hardness of the ethylene / α-olefin copolymer was measured according to ASTM D2240.

[Adhesive strength]
Water-soluble flux (NH-120KM, manufactured by Asahi Chemical Research Co., Ltd.) is applied to a transparent glass plate that is a surface-side transparent protective member for solar cells, a sheet sample having a thickness of 500 μm, and a copper plate having a width of 0.5 cm. And dried for 30 minutes in an oven at 120 ° C., and a solder-coated pseudo metal electrode and a PET back sheet containing silica-deposited PET, transparent glass plate / sheet sample / pseudo metal electrode / sheet sample / PET back surface The protective members were laminated in this order, charged in a vacuum laminator (LMPC-110X160S, manufactured by NPC), placed on a hot plate adjusted to 150 ° C., and heated for 3 minutes under reduced pressure for 15 minutes. Thereafter, the sample was crosslinked in an oven at 150 ° C. for 30 minutes to prepare a sample for adhesive strength, which was a laminate of a transparent glass plate / sheet sample / pseudo metal electrode / sheet sample / PET backside protective member.
A sheet sample layer is cut into a width of 0.5 cm along the pseudo metal electrode from the sample for adhesive strength, and the sheet sample / PET back surface protection member is pulled, and the adhesive strength between the sheet sample and the pseudo metal electrode is 180 degrees peel. It was measured. For the measurement, an Instron tensile tester (trade name “Instron 1123”) was used. Measurements were made at 23 ° C. at 180 ° peel with a span interval of 30 mm and a tensile speed of 30 mm / min, and the average value of three measurements was adopted.

[Adhesive strength after constant temperature and humidity (DH) test]
In accordance with JIS C8917, the laminate obtained above was subjected to an accelerated test of the laminate in a constant temperature and humidity chamber “IW241” manufactured by Yamato Scientific Co., Ltd. under conditions of 95 ° C. and 95% humidity. It went for 100 hours.
The resulting accelerated test sample was measured for adhesive strength in the same manner as described above.

[HAZE]
HAZE was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with ASTM D1003.
The sample is sandwiched between white plate glass plates that do not have an absorption region in the wavelength range of 350 to 800 nm, and this is processed under the same conditions as those for preparing the adhesive strength test sample described above. To obtain a laminate.

(2) Synthesis of ethylene / α-olefin copolymer (Synthesis Example 1)
At one supply port of a 50 L internal polymerization vessel equipped with a stirring blade, 8.0 mmol / hr of a toluene solution of methylaluminoxane as a cocatalyst and bis (1,3-dimethylcyclopentadienyl) zirconium as a main catalyst Supply dichlorinated hexane slurry at a rate of 0.025 mmol / hr and triisobutylaluminum hexane at a rate of 0.5 mmol / hr, so that the total amount of dehydrated and purified normal hexane used as the polymerization solvent and polymerization solvent is 20 L / hr. Was fed continuously with dehydrated and purified normal hexane. At the same time, ethylene is continuously supplied to another supply port at a rate of 3 kg / hr, 1-butene at 15 kg / hr, and hydrogen at a rate of 5 NL / hr, a polymerization temperature of 90 ° C., a total pressure of 3 MPaG, and a residence time of 1.0. Continuous solution polymerization was performed under conditions of time. The ethylene / α-olefin copolymer normal hexane / toluene mixed solution produced in the polymerization vessel is continuously discharged through a discharge port provided at the bottom of the polymerization vessel, and the ethylene / α-olefin copolymer solution is discharged. The jacket portion was led to a connecting pipe heated with 3 to 25 kg / cm ² steam so that the normal hexane / toluene mixed solution had a temperature of 150 to 190 ° C.
Immediately before reaching the connecting pipe, a supply port for injecting methanol, which is a catalyst deactivator, is attached. Methanol is injected at a rate of about 0.75 L / hr, and ethylene / α-olefin copolymer is injected. The mixture was merged into a combined normal hexane / toluene mixed solution. The normal hexane / toluene mixed solution of the ethylene / α-olefin copolymer kept at about 190 ° C. in the connection pipe with steam jacket was subjected to pressure provided at the end of the connection pipe so as to maintain about 4.3 MPaG. The liquid was continuously fed to the flash tank by adjusting the opening of the control valve. In the transfer to the flash tank, the solution temperature and the pressure adjustment valve opening are set so that the pressure in the flash tank is about 0.1 MPaG and the temperature of the vapor part in the flash tank is maintained at about 180 ° C. It was broken. Thereafter, the strand was cooled in a water tank through a single screw extruder set at a die temperature of 180 ° C., and the strand was cut with a pellet cutter to obtain an ethylene / α-olefin copolymer as pellets. The yield was 2.2 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 2)
0.012 mmol / hr of a hexane solution of [dimethyl (t-butylamide) (tetramethyl-η5-cyclopentadienyl) silane] titanium dichloride as the main catalyst, triphenylcarbenium (tetrakispentafluorophenyl) as the cocatalyst Other than supplying borate in toluene at 0.05 mmol / hr and triisobutylaluminum in hexane at a rate of 0.4 mmol / hr, 1-butene at 5 kg / hr and hydrogen at a rate of 100 NL / hr In the same manner as in Synthesis Example 1 described above, an ethylene / α-olefin copolymer was obtained. The yield was 1.3 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 3)
Bis (p-tolyl) methylene (cyclopentadienyl) (1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10 as the main catalyst -Octahydrodibenz (b, h) -fluorenyl) zirconium dichloride in hexane solution at 0.003 mmol / hr, methylaluminoxane as a cocatalyst in toluene solution at 3.0 mmol / hr, and triisobutylaluminum in hexane solution at 0. Each was supplied at a rate of 6 mmol / hr; ethylene was supplied at a rate of 4.3 kg / hr; 1-octene was supplied at a rate of 6.4 kg / hr instead of 1-butene; 1-octene And dehydrated and purified normal so that the total of dehydrated and purified normal hexane used as a polymerization solvent and polymerization solvent is 20 L / hr. An ethylene / α-olefin copolymer was obtained in the same manner as in Synthesis Example 1 except that xylene was continuously supplied; hydrogen was supplied at a rate of 40 NL / hr; and the polymerization temperature was 130 ° C. It was. The yield was 4.3 kg / hr. The physical properties are shown in Table 1.

(3) Production of solar cell encapsulant (sheet) (Example 1)
To 100 parts by weight of the ethylene / α-olefin copolymer of Synthesis Example 1, 1.0 part by weight of t-butylperoxy-2-ethylhexyl carbonate having a half-life temperature of 166 ° C. for 1 minute as an organic peroxide was received. 0.1 parts by weight of magnesium hydroxide having a median diameter of 0.1 μm as an acid agent, 0.5 parts by weight of 3-methacryloxypropyltrimethoxysilane as a silane coupling agent, and 1 part of triallyl isocyanurate as a crosslinking aid 2 parts by weight, 0.4 parts by weight of 2-hydroxy-4-normal-octyloxybenzophenone as an ultraviolet absorber, and bis (2,2,6,6-tetramethyl-4-piperidyl) as a hindered amine light stabilizer 0.2 parts by weight of sebacate, octadecyl-3- (3,5-di-tert- 0.05 part by weight of butyl-4-hydroxyphenyl) propionate and 0.1 part by weight of tris (2,4-di-tert-butylphenyl) phosphite were added as a phosphorus stabilizer.

A coat hanger type T die (lip shape: 270 × 0.8 mm) is attached to a single screw extruder (screw diameter: 20 mmφ, L / D = 28) manufactured by Thermo Plastic, and the die temperature is 100 ° C. Molding was performed using an embossing roll as a cooling roll at a roll temperature of 30 ° C. and a winding speed of 1.0 m / min to obtain an embossed sheet (solar cell sealing material sheet) having a maximum thickness of 500 μm. The porosity of the obtained sheet was 28%. Table 2 shows various evaluation results of the obtained sheet.

(Examples 2 to 6)
An embossed sheet (solar cell sealing material sheet) was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 was used. All the void ratios of the obtained sheets were 28%. Table 2 shows various evaluation results of the obtained sheet.

(Comparative Example 1)
An embossed sheet (solar cell sealing material sheet) was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 was used. All the void ratios of the obtained sheets were 28%. Table 2 shows various evaluation results of the obtained sheet.

Here, the following acid acceptors 1 to 3 in Table 2 were used.
Acid acceptor 1: Magnesium hydroxide (median diameter: 0.1 μm, manufactured by Sakai Chemical Co., Ltd., MGZ-3)
Acid acceptor 2: Mg _0.69 Al _0.31 (OH) ₂ (CO ₃ ) _0.15 · 3.5H ₂ O (median diameter: 0.45 μm, manufactured by Sakai Chemical Co., Ltd., STABIACE HT-P)
Acid acceptor 3: Magnesium hydroxide (median diameter: 1.1 μm, manufactured by Kyowa Chemical Co., Kisuma 5B)
The median diameter in the volume-based particle size distribution of the acid acceptor was measured using a laser diffraction particle size distribution measuring device (product name “SALD-2300” manufactured by Shimadzu Corporation).

This application claims priority based on Japanese Patent Application No. 2012-134646 filed on June 14, 2012, the entire disclosure of which is incorporated herein.

Claims

A solar cell encapsulant containing an ethylene / α-olefin copolymer, an organic peroxide, and an acid acceptor.
The acid acceptor is magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetraoxide, calcium hydroxide, aluminum hydroxide, iron hydroxide (II), calcium carbonate, and a hydrotalcite compound and / or a fired product thereof. The solar cell sealing material according to claim 1, comprising at least one selected from the group consisting of:
The content of the acid acceptor in the solar cell encapsulant is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to.
The solar cell encapsulating material according to any one of claims 1 to 3, wherein the ethylene / α-olefin copolymer satisfies the following requirements a1) to a4).
a1) The content of structural units derived from ethylene is 80 to 90 mol%, and the content of structural units derived from α-olefins having 3 to 20 carbon atoms is 10 to 20 mol%.
a2) Based on ASTM D1238, MFR measured under the conditions of 190 ° C. and 2.16 kg load is 10 to 50 g / 10 min.
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.
The solar cell package according to claim 4, wherein the MFR of the ethylene / α-olefin copolymer measured in accordance with ASTM D1238 and under a condition of 190 ° C. and 2.16 kg load is 10 to 27 g / 10 min. Stop material.
The solar cell encapsulant according to any one of claims 1 to 5, wherein a median diameter in a volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measurement method of the acid acceptor is 1.0 µm or less.
The solar cell sealing material according to any one of claims 1 to 6, wherein the acid acceptor is a hydrotalcite compound represented by the following general formula (A) and / or a fired product thereof.
M 2+ 1-a · M 3+ a (OH) 2 · An n− a / n · mH 2 O (A)
(0.2 ≦ a ≦ 0.35, 0 ≦ m ≦ 5, M 2+ : Mg 2+ , Zn 2+ , Ni 2+ , Ca 2+ , at least one divalent metal ion, M 3+ : Al 3+ , Fe At least one trivalent metal ion selected from 3+ , An: an n-valent anion)
The solar cell encapsulant according to claim 7, wherein an average plate surface diameter of the hydrotalcite compound is 0.02 to 0.9 µm.
The organic peroxide has a one-minute half-life temperature of 100 to 170 ° C .;
The content of the organic peroxide in the solar cell encapsulant is 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material as described in any one.
Further comprising a silane coupling agent,
10. The content of the silane coupling agent in the solar cell encapsulant is 0.1 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to Item.
The ethylene / α-olefin copolymer, the organic peroxide, and the acid acceptor are obtained by melt-kneading and then extruding into a sheet shape. The solar cell sealing material as described.
The solar cell encapsulant according to any one of claims 1 to 11, which has a sheet shape.
A surface-side transparent protective member;
A back side protection member;
A solar cell element;
A seal formed by crosslinking the solar cell encapsulant according to any one of claims 1 to 12 and sealing the solar cell element between the front surface side transparent protective member and the rear surface side protective member. Stop layer,
Solar cell module with