JP2013187472A - Cover sheet for solar batteries and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover sheet for solar batteries to realize a solar battery module which is hard to have poor appearance in a laminate sheet even if a hot spot phenomenon occurs.SOLUTION: The cover sheet for solar batteries comprises: a laminate sheet having an A layer which satisfies the condition (a) and a B layer which satisfies the condition (b) provided that the ratio [A/A+B] of the thickness of the A layer to the total thickness of the A layer and B layer is 40% or larger; and a sealant whose outgassing quantity measured at 150°C is 1×10g/cmor less. The condition (a) is that the linear expansion coefficient is 5×10/°C or smaller in both the lengthwise direction (MD) and the crosswise direction (TD), and the storage elastic modulus measured at 150°C with a vibration frequency of 10 Hz is 1×10Pa or larger. The condition (b) is that the linear expansion coefficient is 5×10/°C or larger in at least one of the lengthwise direction (MD) and the crosswise direction (TD), and the storage elastic modulus measured at 150°C with a vibration frequency of 10 Hz is 1×10Pa or larger.

Description

  The present invention relates to a solar cell cover sheet and a solar cell module.

  In recent years, with increasing awareness of environmental issues such as global warming, expectations are increasing especially for photovoltaic power generation in terms of its cleanliness and non-polluting properties. The solar cell constitutes the central part of a photovoltaic power generation system that directly converts sunlight energy into electricity. In general, a plurality of solar cell elements (cells) are wired in series and in parallel as the structure, and various packaging is performed to protect the cells, thereby forming a unit. The unit built in this package is called a solar cell module, and the surface exposed to sunlight is generally covered with a transparent base material (glass / translucent solar cell sheet; front sheet) as the upper protective material, and the back surface is protected underneath. The material is protected by a back sheet including a weather resistant film as a material, and the gap is filled with a sealing material (sealing resin layer) made of a thermoplastic (for example, ethylene-vinyl acetate copolymer).

The hot spot phenomenon is a problem when using solar cells. The hot spot phenomenon is a phenomenon in which a reverse bias is applied to a cell that is shaded due to adhesion of fallen leaves or the like (a hot spot cell), and the resistance increases to cause a temperature rise (for example, non-patented). Reference 1). Due to this phenomenon, the appearance of defects such as cell breakage and undulation or swelling of the back sheet is generated.
On the other hand, Patent Document 1 proposes a technique for forming a bypass circuit for the purpose of providing a solar cell module that reduces the temperature when the hot spot phenomenon occurs and leveles the temperature distribution. Yes. Patent Document 2 proposes a technique for dispersing a nucleating agent in a filler (sealing material) resin for the purpose of suppressing the cloudiness of the sealing material due to the hot spot phenomenon.
On the other hand, in Patent Document 3, for the purpose of reducing the risk of appearance defects such as swelling of the backsheet while maintaining heat resistance, the gas generated at a predetermined temperature is suppressed to a specific amount and the gel fraction is specified. A resin sealing sheet (sealing material) in an amount has been proposed.

JP 2010-34353 A JP 2006-245503 A JP 2010-226048 A

Japanese Industrial Standards JIS C8990, “Requirements for Confirmation of Design Qualification and Type Approval for Crystalline Solar Cell (PV) Modules Installed on the Ground”

  However, although the technique described in Patent Document 1 can reduce the area of the overheated cell, the situation where there is still a portion exposed to a high temperature of about 150 ° C. or more cannot be solved. Moreover, in patent document 2, although the proposal for suppressing the cloudiness of the sealing material by a hot spot is made | formed, suppression of the external appearance defect of a backsheet is not eliminated. In this regard, Patent Document 3 discloses a sealing material for reducing the risk of appearance defects such as swelling of the backsheet, but its production requires electron beam crosslinking that requires large energy. There was a problem that the process was complicated.

  The subject of this invention is providing the solar cell cover sheet for implement | achieving the solar cell module which an external appearance defect does not produce easily even if a hot spot phenomenon arises.

The present inventors have observed that the hot spot phenomenon is not that the entire solar cell is overheated, but only a limited area near a specific cell is overheated and develops a temperature difference from its surroundings. did. As a result of intensive studies to solve the above problems, the stress generated from the backsheet becomes a factor of undulation, that is, the overheated portion in the backsheet is deformed by the linear expansion behavior (length). It has been found that a difference in deformation amount is produced between the peripheral portion and the back sheet undulate due to the stress generated from the relationship between the difference in deformation amount and the storage elastic modulus. .
Since solar cells are used outdoors, it is common that a laminated sheet for solar cells has a weather resistant film regardless of whether it is a back sheet or a front sheet. However, most of the weather resistant films have a large linear expansion coefficient and storage elastic modulus, and are liable to cause appearance defects such as swelling and undulation of the laminated sheet during the hot spot phenomenon. Therefore, the A layer having a small linear expansion coefficient and the B layer composed of a layer having a large linear expansion coefficient and a storage elastic modulus like a weather resistant film, and the A layer with respect to the total thickness of the A layer and the B layer It has been found that by using a laminated sheet having a thickness ratio [A / A + B] of a specific ratio or more, it is possible to realize a solar cell cover sheet having weather resistance and suppressed appearance defects. In addition to this, it has been found that outgas generated from the sealing material causes blistering and deteriorates the waving.

  That is, the present invention controls the deformation behavior of the laminated sheet from the viewpoint of the linear expansion coefficient and storage elastic modulus, which determine the stress generated from the weather resistant film, among various factors of appearance defects, and the outgas amount is It has been found that by combining with a sealing material that is within the regulations, it greatly contributes to suppression of appearance defects such as swelling and undulation of the laminated sheet.

  Moreover, according to the cover sheet for solar cells having the combination of the laminated sheet and the sealing material specified in the present invention, it is possible to realize a solar cell module that is less likely to cause poor appearance on the back sheet even when a hot spot phenomenon occurs. it can. The present invention has been completed based on such findings.

That is, the present invention relates to the following [1] to [9].
[1] A layer satisfying the following condition (a) and a B layer satisfying the following condition (b), and the thickness ratio of the A layer to the total thickness of the A layer and the B layer [A / A + B] is 40% A solar cell cover sheet comprising: the laminated sheet as described above; and a sealing material having an outgas amount of 1 × 10 ⁻⁵ g / cm ² or less measured at 150 ° C.
Condition (a): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 × 10 with a linear expansion coefficient of 5 × 10 ⁻⁵ / ° C. or less in both the machine direction (MD) and the transverse direction (TD). ⁸ Pa or more.
Condition (b): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 when the linear expansion coefficient in at least one of the machine direction (MD) or the transverse direction (TD) is greater than 5 × 10 ⁻⁵ / ° C. × 10 ⁶ Pa or more.
[2] The cover sheet for a solar cell according to [1], wherein the layer A is made of biaxially stretched polyethylene terephthalate and / or biaxially stretched polyethylene naphthalate.
[3] One or more selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer. The solar cell cover sheet according to the above [1] or [2], comprising the fluorine resin.
[4] The solar cell cover sheet according to any one of [1] to [3], wherein the sealing material includes a polyethylene-based resin composition.
[5] The ethylene-based resin composition satisfies 99 to 50% by mass of an ethylene-α-olefin random copolymer (I) that satisfies the following condition (i) and ethylene that satisfies the following condition (ii): The cover sheet for solar cells according to the above [4], which is a resin composition (III) containing 1 to 50% by mass of an α-olefin block copolymer (II).
(I) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(Ii) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.
[6] The solar cell cover sheet according to any one of [1] to [5], which is used as a solar cell backsheet.
[7] A solar cell module having the solar cell cover sheet according to any one of [1] to [6].
[8] The solar cell module according to [7], including a solar cell made of a single crystal silicon compound or a polycrystalline silicon compound.
[9] The solar cell module according to the above [7] or [8], which has a front member made of a translucent member.

  The solar cell module produced using the solar cell cover sheet of the present invention is less prone to appearance defects such as swelling and undulation in the laminated sheet even when a hot spot phenomenon occurs. In addition, according to the present invention, it is not necessary to perform electron beam cross-linking that requires a large amount of energy, and it is not necessary to form a complicated circuit when designing a solar cell. Can be prevented.

The cover sheet for solar cells of the present invention includes a laminated sheet having at least two layers and a sealing material. The laminated sheet functions as a back sheet and / or a front sheet for solar cells.
[Laminated sheet]
In the present invention, the two layers constituting the laminated sheet are specifically an A layer that satisfies the following condition (a) and a B layer that satisfies the following condition (b).
Condition (a): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 × 10 with a linear expansion coefficient of 5 × 10 ⁻⁵ / ° C. or less in both the machine direction (MD) and the transverse direction (TD). ⁸ Pa or more.
Condition (b): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 when the linear expansion coefficient in at least one of the machine direction (MD) or the transverse direction (TD) is greater than 5 × 10 ⁻⁵ / ° C. × 10 ⁶ Pa or more.

In the present invention, the thickness ratio [A / A + B] of the A layer to the total thickness of the A layer and the B layer in the laminated sheet is 40% or more, preferably 50% or more, more preferably 60% or more. According to this, it is possible to suppress the swelling and undulation phenomenon of the laminated sheet. The upper limit is not particularly limited, but is preferably 95% or less, more preferably 90% or less, and still more preferably 80% or less. According to this, it is possible to express the weather resistance of the B layer.
When the laminate sheet includes a plurality of layers A and / or B, the thickness of the A layer is the thickness of all the A layers that satisfy the above-described condition (a), and the thickness of the B layer is , The thickness of all the B layers satisfying the above-mentioned condition (b).
The thickness of the laminated sheet is not particularly limited, but is preferably 50 μm or more, more preferably 100 μm or more, still more preferably 150 μm or more, and preferably 500 μm or less, more preferably 450 μm or less, and further Preferably, it may be 400 μm or less.

  The appearance of the laminated sheet may be appropriately selected depending on the type and part of the solar cell to be applied. However, when used on the light receiving surface side (front sheet), it is preferable to have transparency. Further, when used on the back side of the light receiving surface (back sheet), it preferably has a concealing property, and preferably contains a white pigment, a black pigment, or the like in one or more layers. It is also preferable to apply pigment ink or the like.

[A layer]
The layer A constituting the laminated sheet in the present invention has a linear expansion coefficient of 5 × 10 ⁻⁵ / ° C. or less in both the machine direction (MD) and the transverse direction (TD), and is measured at 150 ° C. and a vibration frequency of 10 Hz. The storage elastic modulus is 1 × 10 ⁸ Pa or more (condition (a)).

(Linear expansion coefficient of layer A)
The linear expansion coefficient of the layer A is 5 × 10 ⁻⁵ / ° C. or less in the ^machine direction (MD) and the transverse direction (TD), preferably 4 × 10 ⁻⁵ / ° C. or less, more preferably 3 × 10. ^-5 / ℃ or less.
The linear expansion coefficient is preferably as small as possible in the vertical direction (MD) and the horizontal direction (TD). For example, if the difference in linear expansion coefficient between the longitudinal direction (MD) and the lateral direction (TD) of the film is large, problems such as warping may occur when the film is placed in a high temperature environment.
In addition, the linear expansion coefficient in this invention is the heat | fever of the range of 20-70 degreeC at the time of making it heat up at the rate of 5 degree-C / min from room temperature using the thermal-stress-strain measuring apparatus, fixing with load 0.1g. It is a value calculated from the temperature dependence of expansion.

(Storage elastic modulus of layer A)
It is important that the storage elastic modulus of the A layer measured at 150 ° C. and the vibration frequency of 10 Hz is 1 × 10 ⁸ Pa or more, preferably 5 × 10 ⁸ Pa or more, and more preferably 1 × 10 ⁹ Pa. That's it. The upper limit is not particularly limited, but is preferably 1 × 10 ¹⁰ Pa or less, more preferably 5 × 10 ⁹ Pa or less.
In the present invention, the storage elastic modulus is a value at 150 ° C. measured at a predetermined temperature at a rate of temperature increase of 3 ° C./min at a vibration frequency of 10 Hz strain 0.1% using a viscoelasticity measuring device. It is obtained with.

The material constituting the A layer is not limited as long as it satisfies the linear expansion coefficient and the storage elastic modulus. From the viewpoint of industrial availability, biaxially stretched polyethylene terephthalate (BOPET) and / or Or biaxially stretched polyethylene naphthalate (BOPEN) is preferred.
The above-mentioned BOPET and BOPEN are manufactured by a known manufacturing method. The stretching conditions, heat setting conditions, and the like are not particularly limited, but in order to reduce the linear expansion coefficient, the stretching ratio in the machine direction (MD) and / or the transverse direction (TD) is preferably 2 times or more. Moreover, it is preferable that extending | stretching temperature is the range of Tg (glass transition temperature) + 10-50 degreeC. In order to increase the storage elastic modulus, it is preferable to carry out a predetermined heat setting at a temperature not lower than Tg and lower than Tm (melting point) following the stretching.

[B layer]
The layer B constituting the laminated sheet in the present invention has a linear expansion coefficient of at least one of the machine direction (MD) or the transverse direction (TD) greater than 5 × 10 ⁻⁵ / ° C., 150 ° C., and a vibration frequency of 10 Hz. The measured storage elastic modulus is 1 × 10 ⁶ Pa or more (condition (b)).

The linear expansion coefficient of the B layer is greater than 5 × 10 ⁻⁵ / ° C. in at least one of the machine direction (MD) or the transverse direction (TD), and the upper limit is not particularly limited, but preferably 2 × 10 ⁻⁴ / ° C. More preferably, it is 1 × 10 ⁻⁴ / ° C.
The linear expansion coefficient of the B layer is preferably greater than 5 × 10 ⁻⁵ / ° C. in both the machine direction (MD) and the transverse direction (TD).
The linear expansion coefficient of the B layer is a value calculated by the same method as the linear expansion coefficient of the A layer as described above.
A smaller linear expansion coefficient is preferable because a dimensional change when the solar cell module is overheated is small, that is, a generated stress is also small, so that appearance defects are less likely to occur. In order to reduce the linear expansion coefficient, a method of stretching as mentioned above can be mentioned, but it is preferable to use an unstretched film from the viewpoint of industrial availability.

The storage elastic modulus of the B layer measured at 150 ° C. and the vibration frequency of 10 Hz is 1 × 10 ⁶ Pa or more, and the upper limit is not particularly limited, but is preferably 1 × 10 ⁸ Pa, more preferably 1 × 10 ^{8 7} Pa.
A smaller storage elastic modulus is preferable because a stress generated when the solar cell module is overheated is small, so that appearance defects are less likely to occur. On the other hand, a larger storage elastic modulus is preferable because it can exhibit take-out stability during extrusion molding, heat resistance, and mechanical strength.

The material constituting the B layer is not limited as long as the linear expansion coefficient and the storage elastic modulus are satisfied, and a polyethylene resin, a polypropylene resin, a cyclic polyolefin resin, a polystyrene resin, a polyvinyl chloride resin, Known resin materials such as acrylic resins, fluorine resins, polycarbonate resins, polyethylene terephthalate resins, polyethylene naphthalate resins, polyphenylene ether resins, polyphenylene sulfide resins can be used.
In addition, since B layer is a layer contained in the lamination sheet which comprises the cover sheet for solar cells, it is preferable that it is a film which has a weather resistance. Therefore, a film composed of an acrylic resin, a fluorine resin, a polycarbonate resin, a polyethylene terephthalate resin, a polyethylene naphthalate resin, a polyphenylene ether resin, a polyphenylene sulfide resin, etc., known as a weather resistant film. Preferably used. In particular, a fluororesin is preferably used from the viewpoint of weather resistance stability (weather resistance) when used in an outdoor environment.
Examples of fluororesins include polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-tetrafluoro. Propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), poly-3-fluoroethylene chloride (PCTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), etc. It can be preferably used. Among these, polyvinyl fluoride, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, or tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer is industrially easily available, heat resistance, and weather resistance. It is particularly preferably used because it is excellent in moisture resistance and transparency, and also has antifouling properties and flame retardancy.

[Other layers]
In the present invention, in addition to the A layer and the B layer, an easy adhesion layer, a gas barrier layer, a hard coat layer, a colored layer, and the like may be further provided.

[Easily adhesive layer]
The easy-adhesion layer may be any material that can be softened or melted by heat (about 120 to 170 ° C.) when a solar cell module to be described later can be melted and fused with the sealing material. From the viewpoint of easy availability, polyolefin resins are preferably used.
For example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear (linear) low-density polyethylene are used as polyethylene resins, and polypropylene homopolymers and polypropylene copolymers are modified as polypropylene resins. As polyolefin resin, EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene-vinyl alcohol copolymer), E-MMA (ethylene-methyl methacrylate copolymer), E-EAA (ethylene-ethyl acrylate copolymer) Polymer), E-GMA (ethylene-glycidyl methacrylate copolymer), ionomer resin (ionic crosslinkable ethylene-methacrylic acid copolymer, ionic crosslinkable ethylene-acrylic acid copolymer), silane crosslinkable polyolefin, and Maleic anhydride graft copolymer One or a film or sheet of resin comprising more resins of the body or the like can be used.
The easy-adhesion layer is selected from a material having a melt flow rate (MFR) (JIS K7210, temperature: 190 ° C., load: 21.18 N) of about 2 to 50 g / 10 min from the viewpoint of extrusion productivity and the like. . Further, the storage elastic modulus at 150 ° C. is sufficiently smaller than the above-described A layer and B layer, and the generated stress is small, so that it hardly contributes to the appearance defect phenomenon.

[Layer structure of laminated sheet]
In the present invention, the layer structure of the laminated sheet is not particularly limited, but from the viewpoint of weather resistance, adhesion to the sealing material, and the like, the easy adhesion layer / A layer / B layer and B layer / A are sequentially formed from the sealing material surface. A layer configuration such as layer / B layer can be exemplified.

[Production method of laminated sheet]
The laminated sheet in the present invention can be obtained by lamination, and the method for laminating is not particularly limited. As a method of laminating, for example, after forming the A layer and the B layer separately, a method of laminating by a thermal lamination method, a dry lamination method, etc. A method of laminating the film on the sheet by an extrusion lamination method, an extrusion coating method, a calender coating method, a solution coating method or the like, a method of co-extrusion of the A layer and the B layer, and the like can be selected. In the present invention, a dry lamination method is preferably used from the viewpoint of productivity and the like.

In the above, the thermal lamination method, the dry lamination method, the extrusion lamination method, the extrusion coating method, the calendar coating method, the solution coating method, and the coextrusion method are all known lamination methods, but will be briefly described below.
In either case, the lamination surface of each layer can be subjected to an easy adhesion treatment such as an anchor coat as necessary.
The thermal lamination method is a method in which the A layer and the B layer, which are formed in advance in a film shape, are stacked and heat-bonded by heating and pressing with a heating roll or the like.
In the dry lamination method, a two-component curable polyurethane adhesive is applied to the laminated surface of the A layer (or B layer) that has been formed into a film in advance, and the solvent component is removed by hot air drying, etc. before curing. In the state of tack (adhesiveness), layer B (or layer A) is laminated and pressure-bonded on it, usually rolled up into a roll, stored at room temperature or a relatively low heating temperature, and adhered over time This is a method of curing and bonding the agent.

In the extrusion lamination method, the B layer (or A layer) is melt-extruded into a film shape with a T-die or the like on the laminated surface of the A layer (or B layer) formed in advance in a film shape, and cooled with a chill roll. It is a method of laminating.
In the extrusion coating method, an anchor coat (a kind of primer coat) is applied to the laminated surface of the A layer (or B layer) as necessary, and the B layer (or A layer) is formed into a film with a T die or the like. While being melt extrusion coated, the film is cooled and pressure-bonded with a chill roll and laminated.
In the calender coating method, for example, the material constituting the B layer (or A layer) is heated with a calender to be formed into a film, and at the same time, this is overlaid on the laminated surface of the A layer (or B layer) and pressed. It is a method of cooling and laminating.
The solution coating method uses an organic solvent such as acetone, ethyl acetate, isopropyl alcohol, or an aqueous solvent as a material constituting the B layer (or A layer) on the laminated surface of the A layer (or B layer) formed in a film shape in advance. In this method, a solution dissolved or dispersed in is applied, the solvent component is removed by hot air drying or the like, and the layers are laminated.
The co-extrusion method is a method in which the materials constituting the A layer and the B layer are joined together in a molten state by a feed block or a multi-manifold die, melt-extruded into a film shape by a T die, etc., and cooled and stacked by a chill roll. is there. In some cases, an adhesive layer may be interposed between the A layer and the B layer.

  By adopting the production method as described above, the wide and long A layer and B layer can be continuously laminated, so that the laminated sheet in the present invention can be produced with high productivity.

[Encapsulant]
When outgas is generated from the sealing material, the back sheet of the solar cell module is swollen and the quality and appearance of the solar cell module are deteriorated. Therefore, it is important for the sealing material used in the present invention that the amount of outgas measured at 150 ° C. is 1 × 10 ⁻⁵ g / cm ² or less, preferably 5 × 10 ⁻⁶ g / cm ² or less. More preferably, it is 1 × 10 ⁻⁶ g / cm ² or less.

As long as the outgas amount is suppressed within the above range, the material constituting the sealing material is not limited, but from the viewpoint of suppressing the outgas amount, a material that does not contain a crosslinking agent, in particular, does not include a crosslinking agent. It is preferable to use a material comprising a polyolefin resin composition.
Conventionally, many sealing materials which mix | blended the crosslinking agent with the ethylene-vinyl acetate copolymer are used, and it is thought that outgas resulting from a crosslinking agent generate | occur | produces in such a sealing material.
This cross-linking agent is used to give a cross-linked structure for the purpose of improving heat resistance, increasing mechanical strength, and the like, generating radicals particularly at 100 ° C. or higher, and having a decomposition temperature of 70 ° C. or higher at a half-life of 10 hours. Certain organic peroxides are often used as crosslinking agents.

  Examples of such a crosslinking agent include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; 3-di-t. -Butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α'-bis (t-butylperoxyisopropyl) ) Benzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane; , 1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylperoxybenzoate; benzoyl peroxide, etc. The

In the production of the solar cell module, the members are integrated by high-temperature vacuum lamination, so that the crosslinking agent may be decomposed in this high-temperature process. Further, even after modularization or during use as a product, it may be exposed to high temperatures due to the occurrence of a hot spot phenomenon, etc., which is considered to be caused by decomposition of the crosslinking agent and generation of carbon dioxide gas or the like. This causes swelling of the laminated sheet. Therefore, in order to suppress the amount of outgas, it is preferable to use a sealing material that does not use a crosslinking agent.
Among these, from the viewpoint of industrial availability, flexibility, heat resistance, transparency and the like, which will be described later, a resin composition mainly composed of a polyolefin resin (including a modified polyolefin resin) that does not contain a crosslinking agent. A sealing material is preferred.
Specific (modified) polyolefin-based resins are exemplified below, but these resins may be used alone or in admixture of two or more. Further, the sealing material may be a single layer or a laminate of two or more layers as long as the outgas amount is suppressed within the above range.

<Polyolefin resin>
The type of the polyolefin resin is not particularly limited, but is preferably at least one resin selected from the group consisting of a polyethylene resin, a polypropylene resin, and a cyclic olefin resin.

(Polyethylene resin)
The type of the polyethylene-based resin is not particularly limited, and specifically, ultra-low density polyethylene, low density polyethylene, linear low density polyethylene (ethylene-α-olefin copolymer), medium density polyethylene, High density polyethylene, ultra high density polyethylene, etc. are mentioned. Among these, linear low density polyethylene (ethylene-α-olefin copolymer) has low crystallinity and excellent transparency and flexibility, so that it inhibits the power generation characteristics of the solar cell element and causes excessive stress to the solar cell element. In addition, it is preferable because it is difficult to cause problems such as damage.

  The ethylene-α-olefin copolymer may be a random copolymer or a block copolymer. Although it does not specifically limit as a kind of alpha olefin copolymerized with ethylene, Usually, a C3-C20 alpha olefin is used suitably. Examples of the α-olefin copolymerized with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 3-methyl-butene. -1,4-methyl-pentene-1 and the like. In the present invention, propylene, 1-butene, 1-hexene, and 1-octene are preferably used as the α-olefin copolymerized with ethylene from the viewpoints of industrial availability, various characteristics, economy, and the like. It is done. The α-olefin copolymerized with ethylene may be used alone or in combination of two or more.

  Further, the content of the α-olefin copolymerized with ethylene is not particularly limited, but is usually 2 mol% or more, preferably 3 mol% or more, more preferably 5 mol% or more, and usually It is 40 mol% or less, preferably 30 mol% or less, more preferably 25 mol% or less. Within this range, transparency is improved by reducing crystallinity due to the copolymerization component, and problems such as blocking of raw material pellets are less likely to occur. In addition, the kind and content of the α-olefin copolymerized with ethylene can be qualitatively and quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring apparatus or other instrumental analyzer.

  The method for producing the polyethylene resin is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst can be employed. For example, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization using a multi-site catalyst typified by a Ziegler-Natta type catalyst, or a single-site catalyst typified by a metallocene catalyst or a post-metallocene catalyst. Examples thereof include a bulk polymerization method using a radical initiator and the like. The ethylene-α-olefin copolymer used as the sealing material is preferably a relatively soft resin, and has a low molecular weight component from the viewpoint of ease of granulation after polymerization and prevention of blocking of raw material pellets. A polymerization method using a single site catalyst capable of polymerizing a raw material having a small molecular weight distribution is suitable.

  Specific examples of the polyethylene resin used in the present invention include trade names “Hizex”, “Neozex”, “Ultzex”, and Nippon Polyethylene Co., Ltd. manufactured by Prime Polymer Co., Ltd. Product names “Kernel”, “Novatec HD”, “Novatech LD”, “Novatech LL”, product names “Engage”, “Affinity” manufactured by Dow Chemical Co., Ltd. ) ”“ Infuse ”, trade names“ TAFMER A ”,“ TAFMER P ”manufactured by Mitsui Chemicals, Inc., and the like.

Here, when a polyethylene resin is used, from the viewpoints of flexibility, transparency, and heat resistance, the ethylene-α-olefin random copolymer (I) that satisfies the following condition (i) and the following condition (ii): It is preferable to use a resin composition (III) containing an ethylene-α-olefin block copolymer (II) that satisfies the following.
(I) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(Ii) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.

The ethylene-α-olefin random copolymer (I) preferably has a heat of crystal melting measured at a heating rate of 10 ° C./min in the condition (i) differential scanning calorimetry, preferably 0 to 70 J / g, more preferably 5 to 70 J / g, more preferably 10 to 65 J / g. If it is in this range, since the softness | flexibility of a sealing material, transparency (total light transmittance), etc. are ensured, it is preferable. Moreover, if the amount of heat of crystal fusion is 5 J / g or more, it is more preferable because problems such as blocking of raw material pellets hardly occur. Here, as reference values for the heat of crystal fusion, general-purpose high-density polyethylene (HDPE) is about 170 to 220 J / g, and low-density polyethylene resin (LDPE) and linear low-density polyethylene (LLDPE) are 100 to 160 J. / G or so.
The heat of crystal melting can be measured at a heating rate of 10 ° C./min according to JIS K7122 using a differential scanning calorimeter.

In addition, the crystal melting peak temperature of the ethylene-α-olefin random copolymer (I) is not particularly limited, but is usually less than 100 ° C. and often 30 to 90 ° C. Here, as reference values for the crystal melting peak temperature, general-purpose high-density polyethylene (HDPE) is about 130 to 145 ° C., and low-density polyethylene resin (LDPE) and linear low-density polyethylene (LLDPE) are 100 to 125. It is about ℃. That is, the ethylene-α-olefin random copolymer (I) is distinguished from the ethylene-α-olefin block copolymer (II).
The crystal melting peak temperature can be measured at a heating rate of 10 ° C./min according to JIS K7121 using a differential scanning calorimeter.

  Specific examples of the ethylene-α-olefin random copolymer (I) include trade names “Engage”, “Affinity” manufactured by Dow Chemical Co., Ltd., and Mitsui Chemicals Co., Ltd. Examples include the product names “TAFMER A”, “TAFMER P”, “TAFMER H”, and the product name “Kernel” manufactured by Nippon Polyethylene Co., Ltd. it can.

  The block structure of the ethylene-α-olefin block copolymer (II) is not particularly limited as long as the above-mentioned condition (ii) is satisfied, but balance of flexibility, heat resistance, transparency, etc. is achieved. Multi-block structure containing two or more, preferably three or more segments or blocks having different comonomer contents, crystallinity, density, crystal melting peak temperature (melting point Tm), or glass transition temperature (Tg) It is preferable that Specific examples include a completely symmetric block, an asymmetric block, and a tapered block structure (a structure in which the ratio of the block structure gradually increases in the main chain). The structure and production method of the copolymer having a multi-block structure are disclosed in detail in International Publication No. 2005/090425, International Publication No. 2005/090426, International Publication No. 2005/090427, etc. Can be adopted.

Hereinafter, the ethylene-α-olefin block copolymer having the multi-block structure will be described in detail.
The ethylene-α-olefin block copolymer having a multiblock structure can be suitably used in the present invention, and an ethylene-octene multiblock copolymer having 1-octene as a copolymerization component as an α-olefin is preferable. As the block copolymer, an almost non-crystalline soft segment copolymerized with a large amount of octene component (about 15 to 20 mol%) with respect to ethylene and a small amount of octene component with respect to ethylene (about 2 mol%). Less) a multiblock copolymer in which two or more highly crystalline hard segments each having a copolymerized crystal melting peak temperature of 110 to 145 ° C. are present. By controlling the chain length and ratio of these soft segments and hard segments, both flexibility and heat resistance can be achieved.
As a specific example of the copolymer having the multi-block structure, trade name “Infuse” manufactured by Dow Chemical Co., Ltd. may be mentioned.

  The ethylene-α-olefin block copolymer (II) has a crystal melting peak temperature measured at a heating rate of 10 ° C./min in the condition (ii) differential scanning calorimetry and is 100 ° C. or more, and a heat of crystal melting. Preferably satisfies 5 to 70 J / g. The crystal melting peak temperature of the ethylene-α-olefin block copolymer (II) is more preferably 105 ° C or higher, still more preferably 110 ° C or higher, and the upper limit is usually 145 ° C. Further, the heat of crystal fusion is more preferably 10 to 60 J / g, still more preferably 15 to 55 J / g. The method for measuring the crystal melting peak temperature and the crystal melting heat amount is as described above.

  Generally, a solar cell module is heated to about 85 to 90 ° C. due to heat generated during power generation or radiant heat of sunlight, etc. If the crystal melting peak temperature is 100 ° C. or higher, the heat resistance of the encapsulant should be ensured. On the other hand, an upper limit temperature of 145 ° C. is preferable because it can be sealed without excessively high temperature in the sealing step of the solar cell element. Further, it is preferable that the amount of heat of crystal melting is within the above range because the sealing material has flexibility and transparency (total light transmittance) and the like, and troubles such as blocking of the raw material pellet hardly occur.

  Here, when using resin composition (III) containing these copolymer (I) and copolymer (II), it is used for each of copolymer (I) and copolymer (II). The type of α-olefin may be the same or different, but in the present invention, the same one improves the compatibility when mixed and the transparency of the sealing material. That is, it is preferable because the photoelectric conversion efficiency of the solar cell is improved.

  Next, the contents of the ethylene-α-olefin random copolymer (I) and the ethylene-α-olefin block copolymer (II) in the resin composition (III) are flexibility, heat resistance, transparency, etc. Are preferably 50 to 99% by mass and 1 to 50% by mass, more preferably 60 to 98% by mass and 2 to 40% by mass, and still more preferably, respectively. They are 70-97 mass% and 3-30 mass%. Further, the mixing (containing) mass ratio of the ethylene-α-olefin random copolymer (I) and the ethylene-α-olefin block copolymer (II) is not particularly limited, but preferably (I) / (II) = 99-50 / 1-50, more preferably 98-60 / 2-40, more preferably 97-70 / 3-30, more preferably 97-80 / 3-20, Preferably, it is 97-90 / 3-10. However, the total of (I) and (II) is 100 parts by mass. Here, it is preferable if the mixed (containing) mass ratio is within the above range because a sealing material excellent in balance of flexibility, heat resistance, transparency and the like can be easily obtained.

(Polypropylene resin)
The type of the polypropylene resin is not particularly limited, and specific examples include a propylene homopolymer, a propylene copolymer, a reactor type polypropylene thermoplastic elastomer, and a mixture thereof. .
As a copolymer of propylene, a random copolymer (random polypropylene) of propylene and ethylene or other α-olefin, a block copolymer (block polypropylene), a block copolymer or a graft copolymer containing a rubber component Etc. The other α-olefin copolymerizable with propylene is preferably one having 4 to 12 carbon atoms, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4 -Methyl-1-pentene, 1-decene, etc. are mentioned, The 1 type (s) or 2 or more types of mixture is used.

  Further, the content of the α-olefin copolymerized with propylene is not particularly limited, but is usually 2 mol% or more, preferably 3 mol% or more, more preferably 5 mol% or more, and usually It is 40 mol% or less, preferably 30 mol% or less, more preferably 25 mol% or less. Within this range, transparency is improved by reducing crystallinity due to the copolymerization component, and problems such as blocking of raw material pellets are less likely to occur. In addition, the kind and content of the α-olefin copolymerized with propylene can be qualitatively and quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

  The method for producing the polypropylene resin is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst can be employed. For example, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas phase polymerization using a multi-site catalyst typified by a Ziegler-Natta type catalyst, or a single-site catalyst typified by a metallocene catalyst or a post-metallocene catalyst. Examples thereof include a bulk polymerization method using a radical initiator and the like. The propylene-α-olefin copolymer used as the sealing material is preferably a relatively soft resin, and has a low molecular weight component from the viewpoint of ease of granulation after pelletization and prevention of blocking of raw material pellets. A polymerization method using a single site catalyst capable of polymerizing a raw material having a small molecular weight distribution is suitable.

  Specific examples of the polypropylene resin used in the present invention include trade names “NOVATEC-PP”, “WINTECH”, and product names of Prime Polymer Co., Ltd., manufactured by Nippon Polypro Co., Ltd. Examples thereof include “PRIME-POLYPRO”, “PRIME-TPO”, and trade name “NORBREN” manufactured by Sumitomo Chemical Co., Ltd.

(Cyclic olefin resin)
The type of the cyclic olefin-based resin is not particularly limited, and specifically, a cyclic olefin polymer obtained by ring-opening polymerization of one or more cyclic olefins, a hydride thereof, and a linear chain. Examples thereof include block copolymers of α-olefins and cyclic olefins, and random copolymers of linear α-olefins and cyclic olefins.

  The type of cyclic olefin constituting the cyclic olefin-based resin is not particularly limited, but bicyclohept-2-ene (2-norbornene) and derivatives thereof such as norbornene, 6-methylnorbornene, and 6-ethylnorbornene. 6-n-butylnorbornene, 5-propylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, 5-benzylnorbornene, tetracyclo-3-dodecene and derivatives thereof For example, 8-methyltetracyclo-3-dodecene, 8-ethyltetracyclo-3-dodecene, 8-hexyltetracyclo-3-dodecene, 10-dimethyltetracyclo-3-dodecene, 5,10-dimethyltetra Cyclo-3-dodecene, etc. It is exemplified. In the present invention, norbornene, tetracyclododecene, and the like are preferably used from the viewpoints of industrial availability, various characteristics, economy, and the like.

  Although it does not specifically limit as a kind of linear alpha olefin copolymerized with the said cyclic olefin, Usually, a C2-C20 linear alpha olefin is used suitably. Examples of the linear α-olefin copolymerized with the cyclic olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene. Etc. are exemplified. In the present invention, ethylene is preferably used as the linear α-olefin copolymerized with the cyclic olefin from the viewpoints of industrial availability, various characteristics, economy and the like. The linear α-olefin copolymerized with the cyclic olefin may be used alone or in combination of two or more.

  Further, the content of the cyclic olefin copolymerized with the linear α-olefin is not particularly limited, but is usually 5 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more. And, it is usually 70 mol% or less, preferably 60 mol% or less, more preferably 50 mol% or less. When the content of the cyclic olefin is increased, the heat resistance, the barrier property and the transparency can be improved, and when the content is decreased, the flexibility is improved, which is preferable. If the content of the cyclic olefin is within this range, it is preferable because the crystallinity is reduced by the copolymerization component so that transparency is exhibited and problems such as blocking of raw material pellets are not likely to occur. In addition, the kind and content of the cyclic olefin copolymerized with the linear α-olefin can be qualitatively and quantitatively analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

  The cyclic olefin resins used in the present invention are, for example, JP-A-60-168708, JP-A-612012016, JP-A-61-115912, JP-A-61-115916, Manufactured according to known methods described in JP-A-61-271308, JP-A-61-272216, JP-A-62-252406, JP-A-62-2252407, etc. Can do.

  Specific examples of the cyclic olefin resin used in the present invention include trade name “APEL” manufactured by Mitsui Chemicals, Inc., trade name “TOPAS” manufactured by Topas Advanced Polymers, Japan, Examples include trade names “ZEONOR” and “ZEONEX” manufactured by ZEON Corporation.

<Modified polyolefin resin>
The type of the modified polyolefin resin is not particularly limited, but EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene-vinyl alcohol copolymer), E-MMA (ethylene-methyl methacrylate copolymer). Coalescence), E-EAA (ethylene-ethyl acrylate copolymer), E-GMA (ethylene-glycidyl methacrylate copolymer), ionomer resin (ionic crosslinkable ethylene-methacrylic acid copolymer, ion crosslinkable ethylene-acrylic) An acid copolymer), a silane crosslinkable polyolefin, and a maleic anhydride graft copolymer are preferable.

  Further, the content of various monomers for modifying the modified polyolefin resin is not particularly limited, but is usually 0.5 mol% or more, preferably 1 mol% or more, more preferably 2 mol% or more. And it is usually 40 mol% or less, preferably 30 mol% or less, more preferably 25 mol% or less. Within this range, transparency is improved by reducing crystallinity due to the copolymerization component, and problems such as blocking of raw material pellets are less likely to occur. The types and contents of various monomers that modify the modified polyolefin resin can be qualitatively and quantitatively analyzed by a known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

  The production method of the modified polyolefin resin used in the present invention is not particularly limited, and a known olefin polymerization catalyst is used except for the ionomer resin, silane crosslinkable polyolefin, and maleic anhydride graft copolymer shown below. Known polymerization methods such as slurry polymerization method, solution polymerization method, bulk polymerization method, gas phase polymerization method using multi-site catalyst typified by Ziegler-Natta type catalyst and single-site catalyst typified by metallocene catalyst, etc. Moreover, the block polymerization method using a radical initiator, etc. are mentioned.

  The ionomer resin contains at least a part of an unsaturated carboxylic acid component of a copolymer comprising ethylene, an unsaturated carboxylic acid, and other unsaturated compounds as optional components, at least one of a metal ion and an organic amine. It can be obtained by summing. The ionomer resin can also be obtained by saponifying at least a part of an unsaturated carboxylic acid ester component of a copolymer comprising ethylene, an unsaturated carboxylic acid ester, and other unsaturated compounds as optional components. .

  The silane crosslinkable polyolefin can be obtained by melt-mixing a polyolefin-based resin, a silane coupling agent described later, and a radical generator at a high temperature and graft polymerization.

  The maleic anhydride graft copolymer can be obtained by melt-mixing a polyolefin resin, maleic anhydride, and a radical generator at a high temperature and graft polymerization.

  Specific examples of the modified polyolefin resin used in the present invention include EVA (ethylene-vinyl acetate copolymer), trade name “Novatech EVA (NOVATECH-EVA)” manufactured by Nippon Polyethylene Co., Ltd., Mitsui DuPont. The product name “EVAFLEX” manufactured by Polychemical Co., Ltd., “NUC” series manufactured by Nihon Unicar Co., Ltd., and EVOH (ethylene-vinyl alcohol copolymer) products manufactured by Nippon Synthetic Chemical Co., Ltd. The name “SOARNOL”, the product name “EVAL” manufactured by Kuraray Co., Ltd., and E-MMA (ethylene-methyl methacrylate copolymer) are trade names “ACRIFT” manufactured by Sumitomo Chemical Co., Ltd. ACRYFT) ”and E-EAA (ethylene-ethyl acrylate copolymer) as Nippon Polyethylene Trade name “REX PEARL EEA” manufactured by Co., Ltd., E-GMA (ethylene-glycidyl methacrylate copolymer) as trade name “BONDAST” manufactured by Sumitomo Chemical Co., Ltd., and ionomer Is a product name “HIMILAN” manufactured by Mitsui DuPont Polychemical Co., Ltd., and as a silane crosslinkable polyolefin, a product name “LINKLON” manufactured by Mitsubishi Chemical Corporation, maleic anhydride graft copolymer. Examples thereof include “Admer” manufactured by Mitsui Chemicals, Inc.

  The melt flow rate (MFR) of the (modified) polyolefin resin is not particularly limited. For example, in the case of a polyethylene resin, MFR (JIS K7210, temperature: 190 ° C., load: 21.18 N) is Preferably it is 0.5 g / 10 min or more, more preferably 2 g / 10 min or more, still more preferably 3 g / 10 min or more, and preferably 100 g / 10 min or less, more preferably 50 g / 10 min or less, still more preferably 30 g / 10 min. The following are used. Here, the MFR may be selected in consideration of molding processability at the time of molding the sheet, adhesiveness at the time of sealing the solar cell element (cell), wraparound condition, and the like. For example, when calendering a sheet, the MFR is preferably relatively low, specifically 0.5 g / 10 min or more and 5 g / 10 min or less from the handling property when the sheet is peeled off from the forming roll. In the case of extrusion molding using a T die, MFR is preferably 2 g / 10 min, more preferably 3 g / 10 min or more, and preferably 50 g / min from the viewpoint of reducing the extrusion load and improving the extrusion rate. What is used is 10 min or less, more preferably 30 g / 10 min or less. Furthermore, from the viewpoint of adhesion and ease of wraparound when sealing a solar cell element (cell), the MFR is preferably 2 g / 10 min, more preferably 3 g / 10 min or more, and preferably 50 g / What is used is 10 min or less, more preferably 30 g / 10 min or less.

  The purpose of the sealing material used in the present invention is to further improve the physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), molding processability, economy, etc., without departing from the spirit of the present invention. Resins other than those described above can be mixed. Examples of the resin include various elastomers (olefin-based, styrene-based, etc.), resins modified with polar groups such as carboxyl groups, amino groups, imide groups, hydroxyl groups, epoxy groups, oxazoline groups, thiol groups, silanol groups, and the like. Examples include tackifying resins.

  Examples of the tackifying resin include petroleum resins, terpene resins, coumarone-indene resins, rosin resins, and hydrogenated derivatives thereof. Specifically, the petroleum resin includes cyclopentadiene or an alicyclic petroleum resin derived from a dimer thereof and an aromatic petroleum resin derived from a C9 component, and the terpene resin includes a terpene resin derived from β-pinene and a terpene resin. The phenol resin is, for example, coumarone-indene copolymer or coumarone-indene-styrene copolymer as coumarone-indene resin, and rosin resins include rosin resins such as gum rosin and wood rosin, glycerin, An esterified rosin resin modified with pentaerythritol or the like can be exemplified. The tackifying resin can be obtained with various softening temperatures mainly depending on the molecular weight, but the compatibility, bleed over time and color tone when mixed with the polyolefin resin and modified polyolefin resin component described above. From the viewpoint of heat stability and the like, the hydrogenated derivatives of alicyclic petroleum resins having a softening temperature of preferably 100 or more, more preferably 120 ° C. or more, and preferably 150 ° C. or less, more preferably 140 ° C. or less preferable. When a resin other than the polyolefin-based resin described above is mixed, the content is preferably 20% by mass or less, and more preferably 10% by mass or less, with respect to 100% by mass of the resin composition constituting the sealing material layer in the present invention.

  Moreover, various additives can be added to the sealing material used in the present invention as necessary. Examples of the additive include a silane coupling agent, an antioxidant, an ultraviolet absorber, a weathering stabilizer, a light diffusing agent, a nucleating agent, a pigment (for example, a white pigment), a flame retardant, and a discoloration preventing agent. . In the present invention, it is preferable that at least one additive selected from a silane coupling agent, an antioxidant, an ultraviolet absorber, and a weathering stabilizer is added for reasons described later.

[Silane coupling agent]
Silane coupling agents are useful for improving adhesion to protective materials for sealing materials (glass, resin front sheets, back sheets, etc.) and solar cell elements, such as vinyl groups, Examples thereof include compounds having a hydrolyzable group such as an alkoxy group together with an unsaturated group such as an acryloxy group and a methacryloxy group, an amino group, and an epoxy group. Specific examples of the silane coupling agent include N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and γ-aminopropyltriethoxy. Examples include silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like. In the present invention, γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane are preferably used because of good adhesiveness and little discoloration such as yellowing. The addition amount of the silane coupling agent is to suppress an increase in resin pressure at the time of extrusion molding and generation of foreign matters such as gel and fish eye, and to suppress defects such as bleed out from a molded product. The amount is preferably 5% by mass or less and more preferably 3% by mass or less with respect to 100% by mass of the resin composition constituting the sealing material layer in the present invention. Moreover, in order to express adhesiveness, it is preferable that it is 0.1 mass% or more, and it is more preferable that it is 0.2 mass% or more.
In addition, similar to the silane coupling agent, a coupling agent such as an organic titanate compound can also be used effectively.

[Antioxidant]
As the antioxidant, various commercially available products can be applied, and various types such as phenol, sulfur, phosphite and the like such as monophenol, bisphenol and polymer phenol can be exemplified.

Examples of the monophenol antioxidant include 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl-3- And (3,5-di-tert-butyl-4-hydroxyphenyl) propionate.
Examples of the bisphenol antioxidant include 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-6-tert-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidene-bis- (3-methyl-6-tert-butylphenol), 3,9-bis [{1,1 -Dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl} 2,4,9,10-tetraoxaspiro] 5,5-undecane, etc. Can do.

  Polymeric phenolic antioxidants include 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-tert-butyl-4-bidoxybenzyl) benzene, tetrakis- {methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate} Methane, bis {(3,3′-bis-4′-hydroxy-3′-tert-butylphenyl) butyric acid} glycol ester, 1,3,5-tris (3 ′, 5′-di-tert -Butyl-4'-hydroxybenzyl) -s-triazine-2,4,6- (1H, 3H, 5H) trione, tocopherol (vitamin E) and the like.

  Examples of sulfur-based antioxidants include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  Phosphite antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) phos Phyto, cyclic neopentanetetrayl bis (octadecyl phosphite), tris (mono and / or dinonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite 9,10-dihydro-9-oxa-10-phosphaphenalene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa -10-phosphaphenanthrene-10 Oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, cyclic neopentane Examples thereof include tetrayl bis (2,6-di-tert-butylphenyl) phosphite, 2,2-methylene bis (4,6-tert-butylphenyl) octyl phosphite, and the like.

In the present invention, phenol-based and phosphite-based antioxidants are preferably used from the effects of antioxidants, thermal stability, economics, etc., and the combination of both is used as an antioxidant for the added amount. Since an effect can be heightened, it is still more preferable.
The addition amount of the antioxidant is usually 0.1% by mass or more, preferably 0.2% by mass or more, and 1% by mass with respect to 100% by mass of the resin composition constituting the sealing material layer in the present invention. % Or less, preferably 0.5% by mass or less.

[Ultraviolet absorber]
As the ultraviolet absorber, various commercially available products can be applied, and various types such as benzophenone-based, benzotriazole-based, triazine-based, and salicylic acid ester-based types can be exemplified.

  Examples of the benzophenone-based UV absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-n. -Dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2 , 4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, etc. Door can be.

The benzotriazole-based ultraviolet absorber is a hydroxyphenyl-substituted benzotriazole compound, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole, 2- (2-methyl-4-hydroxy Phenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- ( 2-hydroxy-3,5-di-tert-butylpheny ) Can be exemplified benzotriazole.
Examples of the triazine ultraviolet absorber include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- (4 , 6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol and the like.
Examples of the salicylic acid ester group include phenyl salicylate and p-octylphenyl salicylate.

  The addition amount of the ultraviolet absorber is usually 0.01% by mass or more, preferably 0.05% by mass or more with respect to 100% by mass of the resin composition constituting the sealing material layer in the present invention, and 2. It is preferable to add in the range of 0% by mass or less, preferably 0.5% by mass or less.

[Anti-stabilizer]
A hindered amine light stabilizer is suitably used as a weather stabilizer that imparts weather resistance in addition to the above ultraviolet absorber. A hindered amine light stabilizer does not absorb ultraviolet rays like an ultraviolet absorber, but exhibits a remarkable synergistic effect when used together with an ultraviolet absorber. In addition to hindered amines, there are those that function as light stabilizers, but they are often colored and are not preferred for the encapsulant layer in the present invention.

Examples of hindered amine light stabilizers include dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, 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}], N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2, 6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl) separate, 2- (3 , 5-Di-tert-4-H And droxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl).
The addition amount of the hindered amine light stabilizer is usually 0.01% by mass or more, preferably 0.05% by mass or more, with respect to 100% by mass of the resin composition constituting the sealing material layer in the present invention. 0.5% by mass or less, preferably 0.3% by mass or less.

  The above-mentioned antioxidant, ultraviolet absorber and anti-wrinkle stabilizer generally tend to cause yellowing as the addition amount increases. Therefore, it is preferable that only the minimum necessary amount is added, and no addition is also preferable. It is.

[Flexibility]
The flexibility of the sealing material used in the present invention may be appropriately adjusted in consideration of the shape, thickness, installation location, etc. of the applied solar cell. For example, the vibration frequency in dynamic viscoelasticity measurement is 10 Hz, temperature The storage elastic modulus (E ′) at 20 ° C. is preferably 1 to 2000 MPa. From the viewpoint of protection of the solar cell element, the storage elastic modulus (E ′) is preferably lower. However, handling properties when the above-described sealing material is collected in a sheet shape or the like, and blocking of sheet surfaces from each other are prevented. In consideration, it is more preferably 3 to 1000 MPa, further preferably 5 to 500 MPa, and particularly preferably 10 to 100 MPa. The storage elastic modulus (E ′) is obtained by measuring at a predetermined temperature at a vibration frequency of 10 Hz using a viscoelasticity measuring device and obtaining a value at a temperature of 20 ° C.

[Heat-resistant]
The heat resistance of the encapsulant used in the present invention is influenced by various properties (crystal melting peak temperature, crystal melting heat, MFR, molecular weight, etc.) of the resin constituting the encapsulant, and in particular, ethylene-α- When the olefin block copolymer (II) is contained, the crystal melting peak temperature has a strong influence. Generally, a solar cell module is heated to about 85 to 90 ° C. due to heat generated during power generation or radiant heat of sunlight, etc. If the crystal melting peak temperature is 100 ° C. or higher, the heat resistance of the encapsulant should be ensured. Is preferable. The evaluation of the heat resistance is, for example, a sheet-like seal having a thickness of 0.5 mm between a white plate glass (size: 75 mm length, 25 mm width) and a 5 mm thickness aluminum plate (size: length 120 mm, width 60 mm). A sample obtained by laminating a stop material and laminating and pressing at 150 ° C. for 15 minutes using a vacuum press machine is installed at an inclination of 60 ° in a 100 ° C. constant temperature bath, and after 500 hours have elapsed. By observing the state, it is possible to evaluate the superiority or inferiority by ◯ when the glass did not deviate from the initial reference position, and x when the glass deviated from the initial reference position or when the sheet melted.

[transparency]
The total light transmittance of the sealing material used in the present invention is not so much when applied to a type of solar cell to be applied, for example, an amorphous thin film type silicon type or a portion that does not block sunlight reaching a solar electronic element. Although it may not be emphasized, it is preferably 85% or more, more preferably 87% or more, and more preferably 90% or more in consideration of the photoelectric conversion efficiency of the solar cell and handling properties when overlapping various members. More preferably.

[Method of forming a sealing material]
Next, a method for forming a sealing material will be described. The thickness of the sealing material is not particularly limited, but is usually 30 μm or more, preferably 50 μm or more, more preferably 100 μm or more, and about 1000 μm (1 mm) or less, preferably 700 μm or less, more preferably 500 μm. The following is sufficient.
As a film forming method, a known method such as a single-screw extruder, a multi-screw extruder, a Banbury mixer, a kneader or the like may be used, and an extrusion casting method using a T die, a calendar method, or the like may be employed. Although not particularly limited, in the present invention, an extrusion casting method using a T die is preferably used from the viewpoints of handleability and productivity. The molding temperature in the extrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film-forming properties of the resin composition to be used, but is generally 80 ° C or higher, preferably 100 ° C or higher, more preferably 120 ° C or higher, More preferably, it is 140 ° C. or higher, and is generally 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. or lower, still more preferably 180 ° C. or lower. When a silane coupling agent or the like is added, a crosslinking reaction It is preferable to lower the molding temperature in order to suppress an increase in resin pressure and an increase in fish eyes accompanying the above. Various additives such as silane coupling agents, antioxidants, UV absorbers, and weathering stabilizers may be dry blended with the resin in advance and then supplied to the hopper. It may be supplied after producing or a master batch in which only the additive is previously concentrated in the resin may be produced and supplied. Also, if necessary, embossing and various irregularities for the purpose of preventing blocking between sheets when the sheet is used as a scroll and improving the ease of air removal and handling in the sealing process of solar cell elements. (Cone, pyramid shape, hemispherical shape, etc.) may be processed. Furthermore, when forming a sheet, for the purpose of improving the handleability at the time of forming the sheet, another base film (such as stretched polyester film (OPET) or stretched polypropylene film (OPP)) and extrusion lamination It may be laminated by a method such as a sand laminating method.

<Solar cell cover sheet>
Since the cover sheet for solar cells of the present invention includes the laminated sheet and the sealing material, appearance defects such as swelling and undulation are unlikely to occur in the laminated sheet even if a hot spot phenomenon occurs. In addition, it is not necessary to perform electron beam cross-linking that requires a large amount of energy, and it is not necessary to form a complicated circuit when designing a solar cell, so that appearance defects can be prevented without placing an economic burden.

[Method for producing cover sheet for solar cell]
The cover sheet for solar cells of the present invention can be obtained by laminating the laminated sheet and the sealing material. This may be performed by stacking and integrating the laminated sheet and the sealing material, which are manufactured in advance in a sheet shape, when the solar cell module described later is manufactured. The laminated sheet and the sealing material may be laminated by a known method such as thermal lamination. Moreover, you may laminate | stack on the said laminated sheet manufactured previously, melt-extruding the said sealing material.

The cover sheet for a solar cell of the present invention is not particularly limited as long as the laminated sheet and the sealing material are each laminated one or more layers, but the sealing material is usually a solar cell element. It is preferable that the laminated sheet is present in the outermost layer that is in close contact, and the laminated sheet is present in the outermost layer on the opposite side.
For example, 2 types and 2 layers such as laminated sheet / sealing material, 3 types and 3 layers such as laminated sheet / adhesive layer / sealing material, 2 types, 4 layers such as laminated sheet / sealing material / laminated sheet / sealing material A structure etc. are mentioned preferably.

Although the total thickness of a cover sheet is not specifically limited, Preferably it is the range of 80-1500 micrometers, More preferably, it is the range of 250-900 micrometers.
The thickness ratio of the laminated sheet / sealing material is preferably in the range of 1/10 to 1/1, more preferably in the range of 1/5 to 1/2.

  Regarding the adhesiveness between the laminated sheet and the sealing material in the solar cell cover sheet of the present invention, the peel peel strength between two layers measured according to JIS K6854 is preferably 10 N / cm width or more, and 20 N / It is particularly preferable that the width is not less than cm width.

  The cover sheet for a solar cell of the present invention can be suitably used as a front sheet (upper protective material) and / or a back sheet (lower protective material) of a solar cell module.

<Solar cell module>
Using the cover sheet for solar cells of the present invention, for example, by fixing the upper part of the solar cell element with the cover sheet of the present invention and fixing the lower part of the solar cell element with the sealing material and the back sheet as the lower protective material A solar cell module can be produced. Moreover, the upper part of the solar cell element can be fixed with a transparent base material (front sheet) and a sealing material as an upper protective material, and the lower part of the solar cell element can be fixed with the cover sheet of the present invention. A solar cell module can also be produced using the cover sheet of the present invention for both the upper part and the lower part of the element. Examples of such solar cell modules include various types.

  In addition, in the solar cell module of the present invention, when the sealing material is used in two or more parts, the cover sheet of the present invention may be used in all parts, or the sealing material made of a different resin composition May be used. In the case where the sealing material is used for a portion requiring light transmittance, the sealing material must be transparent. However, when the sealing material is used as a lower protective material, the sealing material may not be transparent.

As a specific example, in order from the sunlight receiving side, the solar cell cover sheet of the present invention (in this case, the sealing material is disposed on the solar cell element side), the solar cell element, the sealing material, A back sheet is laminated, and a junction box (a terminal box for connecting wiring for taking out electricity generated from the solar cell element) is adhered to the lower surface of the back sheet. The solar cell elements are connected by wiring in order to conduct the generated current to the outside. The wiring is taken out to the outside through a through-hole provided in the sealing material and the back sheet, and is connected to the junction box.
The back sheet is a single layer or multilayer sheet such as metal or various thermoplastic resin films, for example, metals such as tin, aluminum, stainless steel, inorganic materials such as glass, polyester, inorganic vapor deposition polyester, fluororesin, Mention may be made of a single-layer or multilayer sheet of polyolefin or the like.

  Since the solar cell module deteriorates when moisture enters the inside, when attaching accessories such as a junction box, ensure sufficient sealing so that outside air does not enter the inside of the solar cell module. Although it is necessary, according to the cover sheet for solar cells of the present invention, since it can be bonded only by heat treatment, it is possible to easily and reliably prevent the intrusion of outside air.

As another specific example, a transparent substrate, a sealing material, a solar cell element, a solar cell cover sheet (in this case, a sealing material is disposed on the back side of the solar cell element in order from the sunlight receiving side) Furthermore, a junction box (a terminal box for connecting wiring for taking out electricity generated from the solar cell element) is bonded to the lower surface of the solar cell cover sheet of the present invention. The solar cell elements are connected by wiring in order to conduct the generated current to the outside. The wiring is taken out through a through-hole provided in the solar cell cover sheet of the present invention and connected to the junction box.
Examples of the transparent substrate include glass or single layer or multilayer sheets of acrylic resin, polycarbonate, polyester, fluororesin and the like. In the case of plastic, for the purpose of imparting gas barrier properties, an inorganic thin film is formed in the same manner as the gas barrier layer constituting the laminated sheet for solar cells, or heat resistance, weather resistance, mechanical strength, chargeability, For the purpose of improving dimensional stability, etc., crosslinking agents, antioxidants, light stabilizers, UV absorbers, antistatic agents, reinforcing fibers, flame retardants, preservatives, etc. are added, and various sheets are added to this. Can be stacked. The thickness of the transparent substrate can be appropriately set in view of strength, gas barrier properties, durability, and the like.

  Examples of the solar cell element include a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, various compound semiconductor types, a dye sensitized type, and an organic thin film type.

  Although it does not specifically limit as a manufacturing method of the solar cell module at the time of using the cover sheet for solar cells of this invention, For example, the cover sheet for solar cells of this invention, a solar cell element, a sealing material, and a back sheet in this order. A step of laminating and aligning, a step of vacuum-sucking them and thermocompression bonding them, and a step of trimming the resin or the like constituting the protruding sealing material to a predetermined dimension. Moreover, when the laminated sheet and the sealing material are laminated in advance, the cover sheet for a solar cell of the present invention can be used to easily perform the lamination, alignment process, trimming process, and the like in the above process. be able to.

  The solar cell module produced using the solar cell cover sheet of the present invention is a small solar cell represented by a mobile device, a large solar cell installed on a roof or a roof, depending on the type and module shape of the applied solar cell. The battery can be applied to various uses regardless of whether it is indoors or outdoors.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the various measured value and evaluation about the cover sheet and solar cell module which are displayed in this specification were performed as follows. Here, the flow direction of the sheet from the extruder is called the vertical direction, and the orthogonal direction is called the horizontal direction.

(1) Linear expansion coefficient Using a thermal stress strain measuring device manufactured by SII NanoTechnology Co., Ltd., trade name “TMA / SS6100”, each sheet (10 mm length, 3 mm width) before being laminated is loaded. From the temperature dependence of thermal expansion in the range of 20 to 70 ° C. when fixed at 0.1 g and heated from room temperature at a rate of 5 ° C./min, the linear expansion coefficient in the machine direction (MD) (1 / ° C. )
Similarly, the linear expansion coefficient (1 / ° C.) in the transverse direction (TD) was determined using each sheet (length 3 mm, width 10 mm) before being formed into a laminated sheet.

(2) Storage elastic modulus measurement Each sheet (4 mm long, 60 mm wide) before being made into a laminated sheet using a viscoelasticity measuring device manufactured by IT Measurement Co., Ltd., trade name “Viscoelastic Spectrometer DVA-200” Was measured from −150 ° C. to 200 ° C. in the transverse direction at a vibration frequency of 10 Hz, a strain of 0.1%, a heating rate of 3 ° C./min, and a gap between chucks of 25 mm, and the storage elastic modulus at 150 ° C. (E ') (Pa) was determined.

(3) Outgas amount measurement A sheet of sealing material (2 mm long, 2 mm wide) is used at 150 ° C. for 10 minutes using a heat desorption device manufactured by Nippon Analytical Industries, Ltd., trade name “P & T Autosampler JTD-505III”. Heated and generated outgas was transferred to a mass spectrometer manufactured by Shimadzu Corporation, trade name “Gas Chromatograph GC-17A” using He gas as a carrier gas. The amount of outgas at g (g / cm ² ) was determined.

(4) Appearance evaluation On tempered glass (length 150 mm, width 150 mm, thickness 3.2 mm), sealing material, film heater (made by Sakaguchi Electric Heat Co., Ltd., trade name Samicon polyimide heater, length 100 mm, width 100 mm , 0.2 mm thick), a sealing material, and a laminated sheet were laminated in this order, and a sample that was laminated and pressed at 150 ° C. for 10 minutes using a vacuum press was prepared.
Subsequently, it heated to 150 degreeC by supplying with electricity to a heater, the state after progress for 5 hours was observed, and the following references | standards evaluated.
(◎) No waviness or swelling occurs in the laminated sheet.
(◯) Mild undulation is generated in the laminated sheet.
(X) The corrugated sheet is greatly waved or swollen.

Example 1
[Laminated sheet]
Biaxially stretched polyethylene terephthalate (manufactured by Teijin DuPont Co., Ltd., trade name “Tetra”, thickness 250 μm, coefficient of linear expansion (MD: 2 × 10 ⁻⁵ / ° C., TD: 1 × 10 ⁻⁵ / ° C.) at 150 ° C. The measured storage modulus 6 × 10 ⁸ Pa) was used as the A layer, polyvinylidene fluoride (manufactured by Arkema Co., Ltd., trade name “Kyner”, thickness 38 μm, coefficient of linear expansion (MD: 9 × 10 ⁻⁵ / ° C., TD: 7 × 10 ⁻⁵ / ° C.), storage elastic modulus 9 × 10 ⁷ Pa) measured at 150 ° C. is defined as B layer, and a urethane-based adhesive is used, and the layer configuration is B layer / A layer / B layer. The laminated sheet was obtained by bonding.
[Encapsulant]
As ethylene-α-olefin random copolymer (I), ethylene-octene random copolymer (manufactured by Dow Chemical Co., Ltd., trade name: engage 8200, octene content: 10.1 mol% (31 mass%) , MFR: 5, Tm: 65 ° C., ΔHm: 53 J / g) (hereinafter abbreviated as I-1) 95 parts by mass and ethylene-α-olefin block copolymer (B) as ethylene-octene block copolymer Polymer (manufactured by Dow Chemical Co., Ltd., trade name: Infuse 9100, octene content: 12.8 mol% (37% by mass), MFR: 1, Tm: 119 ° C., ΔHm: 38 J / g) (below The resin composition (III) mixed with 5 parts by mass (abbreviated as II-1) is melt-kneaded at a set temperature of 200 ° C. using a 40 mmφ single screw extruder equipped with a T die, and cast at 20 ° C. A sheet-like sealing material (hereinafter abbreviated as PO) having a thickness of 500 μm was obtained (outgas amount 2 × 10 ⁻⁶ g / cm ² measured at 150 ° C.).
Table 1 shows the results of evaluation using the laminated sheet and the sealing material.

Example 2
[Laminated sheet]
In Example 1, the A layer was changed to 100 μm, and the layer constitution was A layer / B layer / other layers (adhesive layer: low density polyethylene, melting point 104 ° C., storage temperature measured at 150 ° C. 5 × 10 ³ A laminated sheet was obtained in the same manner as in Example 1 except that the thickness was changed to be Pa and thickness 120 μm.
Table 1 shows the results of evaluation using the above laminated sheet and the same sealing material as in Example 1.

Example 3
[Laminated sheet]
In Example 1, a laminated sheet was obtained in the same manner as in Example 1 except that the A layer was changed to 100 μm.
Table 1 shows the results of evaluation using the above laminated sheet and the same sealing material as in Example 1.

Comparative Example 1
[Laminated sheet]
In Example 1, a laminated sheet was obtained in the same manner as in Example 1 except that the A layer was changed to 38 μm.
Table 1 shows the results of evaluation using the above laminated sheet and the same sealing material as in Example 1.

Comparative Example 2
Using the same laminated sheet as in Example 1, an ethylene-vinyl acetate copolymer (manufactured by Bridgestone Corporation, trade name EVASKY S11, sealant, outgas amount measured at 150 ° C. 1 × 10 ⁻⁴ g / cm ² ) (Hereinafter abbreviated as EVA), the results of evaluation in the same manner as in Example 1 are shown in Table 1.

  From Table 1, in the evaluation using the solar cell cover sheet prescribed | regulated by this invention, all had few external appearance changes at the time of a heating, and were favorable (Examples 1-3). On the other hand, it can be confirmed that the thickness ratio and outgas amount are inferior in appearance when they are out of the range of the present invention (Comparative Examples 1 and 2). Specifically, in the case where the thickness range of the A layer is out of range (Comparative Example 1), undulation cannot be suppressed, and in the case where the outgas of the sealing material is large (Comparative Example 2), swelling can be suppressed. Can not.

  Moreover, although the sealing material used for the cover sheet for solar cells of this invention is demonstrated in detail below, this invention does not receive a restriction | limiting at all by these.

(1) Crystal melting peak temperature (Tm)
Using a differential scanning calorimeter manufactured by PerkinElmer, Inc., under the trade name “Pyris1 DSC”, according to JIS K7121, about 10 mg of the sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. After holding at 200 ° C. for 5 minutes, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min. Tm) (° C.) was determined.

(2) Heat of crystal melting (ΔHm)
Using a differential scanning calorimeter manufactured by PerkinElmer Co., Ltd., trade name “Pyris1 DSC”, according to JIS K7122, about 10 mg of the sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. After holding at 200 ° C. for 5 minutes, the temperature was lowered to −40 ° C. at a cooling rate of 10 ° C./min, and again from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min (ΔHm ) (J / g).

(3) Flexibility Using a viscoelasticity measuring device manufactured by IT Measurement Co., Ltd., trade name “Viscoelastic Spectrometer DVA-200”, a sample (4 mm long, 60 mm wide) was subjected to vibration frequency 10 Hz, strain 0.1%. The temperature rise rate was 3 ° C./min, and the transverse direction was 25 mm between the chucks, and −150 ° C. to 150 ° C. was measured.

(4) Heat resistance A sheet-like sealing material having a thickness of 0.5 mm between white plate glass having a thickness of 3 mm (size: length 75 mm, width 25 mm) and an aluminum plate having a thickness of 5 mm (size: length 120 mm, width 60 mm). Using a vacuum press machine, prepare a sample that is laminated and pressed at 150 ° C. for 15 minutes, place the sample at an inclination of 60 ° in a 100 ° C. constant temperature bath, and after 500 hours have passed, Observed and evaluated according to the following criteria.
(○) The glass did not deviate from the initial reference position (×) The glass deviated from the initial reference position or the sheet melted

(5) Total light transmittance A sheet-like sealing material having a thickness of 0.5 mm is stacked between two pieces of white plate glass having a thickness of 3 mm (size: length 75 mm, width 25 mm), and 150 ° C. using a vacuum press. Samples that were laminated and pressed under the conditions of 15 minutes were prepared, the total light transmittance was measured according to JIS K7105, the values were described, and the results evaluated according to the following criteria were also shown.
(◎) Total light transmittance is 90% or more (○) Total light transmittance is 85% or more and less than 90% (×) Total light transmittance is less than 85% or clearly cloudy (not measured) )

Reference example 1
[Encapsulant]
Table 2 shows the results of evaluation using the same sealing material as used in Example 1.

Reference example 2
In Reference Example 1, as shown in Table 2, the resin composition constituting the sheet was 80 parts by mass of (I-1) and an ethylene-octene block copolymer (manufactured by Dow Chemical Co., Ltd., trade name: Infuse 9507, Octene content: 16.4 mol% (44 mass%), MFR: 5, Tm: 123 ° C., ΔHm: 21 J / g) (hereinafter abbreviated as II-2) and resin composition with 20 mass parts A sheet having a thickness of 500 μm was obtained in the same manner as in Reference Example 1 except that it was changed to a product (outgas amount 3 × 10 ⁻⁶ g / cm ² measured at 150 ° C.).
Table 2 shows the results of evaluation using the obtained sheet.

Reference example 3
In Reference Example 1, the resin composition constituting the sheet is shown in Table 2, and (I-1) is an ethylene-propylene-hexene ternary random copolymer (manufactured by Nippon Polyethylene Co., Ltd., trade name: Kernel KJ640T). , Propylene content: 7.4 mol% (10 mass%), hexene content: 4.4 mol% (10 mass%), MFR: 30, Tm: 53 ° C., ΔHm: 58 J / g) (hereinafter I A sheet having a thickness of 500 μm was obtained in the same manner as in Reference Example 1 except that it was changed to “-2” (outgas amount 1 × 10 ⁻⁶ g / cm ² measured at 150 ° C.).
Table 2 shows the results of evaluation using the obtained sheet.

Reference example 4
In Reference Example 1, as shown in Table 2, the resin composition constituting the sheet was the same as Reference Example 1 except that (II-1) was changed to 100 parts by mass without using (II-1). Thus, a sheet having a thickness of 500 μm was obtained (outgas amount measured at 150 ° C. 2 × 10 ⁻⁶ g / cm ² ).
Table 2 shows the results of evaluation using the obtained sheet.

Reference Example 5
In Reference Example 1, as shown in Table 2, the resin composition constituting the sheet is an ethylene-octene random copolymer (manufactured by Prime Polymer Co., Ltd.), which is a general-purpose crystalline polyethylene resin. Name: Moretech 0238CN, Octene content: 1 mol% (4 mass%), MFR: 2.1, Tm: 121 ° C., ΔHm: 127 J / g) (hereinafter abbreviated as P-1) In the same manner as in Reference Example 1, a sheet having a thickness of 500 μm was obtained (outgas amount 2 × 10 ⁻⁶ g / cm ² measured at 150 ° C.).
Table 2 shows the results of evaluation using the obtained sheet.

Reference Example 6
In Reference Example 1, as shown in Table 2, the resin composition constituting the sheet was changed to (P-1) 100 parts by mass without using (I-1) and (II-1). In the same manner as in Reference Example 1, a sheet having a thickness of 500 μm was obtained (outgas amount measured at 150 ° C. 5 × 10 ⁻⁶ g / cm ² ).
Table 2 shows the results of evaluation using the obtained sheet.

In the present invention, not only the sealing material (Reference Example 1) used in Example 1, but also the sealing material that is the amount of outgas specified in the present invention, as in Reference Examples 2 to 6, is also solar. It can be used for a battery cover sheet. The cover sheet for a solar cell having the sealing material of the reference examples 1 to 6 and the sheet in which the thickness ratio of the A layer and the B layer is within a specified value suppresses swelling during heating and suppresses undulation. Therefore, the appearance change is small and good.
And the sealing material which consists of the resin composition illustrated as a preferable range by this invention from Table 2 is further excellent in all the softness | flexibility, heat resistance, and transparency (total light transmittance) in addition to said characteristic. (Reference Examples 1 to 3). When such a sealing material is used for a cover sheet for a solar cell, in addition to being able to maintain a good state with little change in appearance during heating, the photoelectric conversion efficiency and handling properties of the solar cell can be improved. Therefore, it is more preferable.

Claims (9)

A layer satisfying the following condition (a) and a B layer satisfying the following condition (b) are included, and the thickness ratio [A / A + B] of the A layer to the total thickness of the A layer and the B layer is 40% or more. A cover sheet for a solar cell, comprising: a laminated sheet; and a sealing material having an outgas amount of 1 × 10 ⁻⁵ g / cm ² or less measured at 150 ° C.
Condition (a): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 × 10 with a linear expansion coefficient of 5 × 10 ⁻⁵ / ° C. or less in both the machine direction (MD) and the transverse direction (TD). ⁸ Pa or more.
Condition (b): Storage modulus measured at 150 ° C. and a vibration frequency of 10 Hz is 1 when the linear expansion coefficient in at least one of the machine direction (MD) or the transverse direction (TD) is greater than 5 × 10 ⁻⁵ / ° C. × 10 ⁶ Pa or more.   The cover sheet for solar cells according to claim 1, wherein the A layer is made of biaxially stretched polyethylene terephthalate and / or biaxially stretched polyethylene naphthalate.   The B layer is one or more fluorine-based compounds selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer. The cover sheet for solar cells according to claim 1 or 2, comprising a resin.   The cover sheet for solar cells according to any one of claims 1 to 3, wherein the sealing material comprises a polyethylene resin composition. 99 to 50% by mass of the ethylene-α-olefin random copolymer (I) satisfying the following condition (i) and the ethylene-α-olefin satisfying the following condition (ii): The cover sheet for solar cells of Claim 4 which is resin composition (III) containing 1-50 mass% of block copolymers (II).
(I) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 0 to 70 J / g.
(Ii) The crystal melting peak temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. or more, and the crystal melting heat amount is 5 to 70 J / g.   The solar cell cover sheet according to any one of claims 1 to 5, which is used as a solar cell backsheet.   The solar cell module which has a cover sheet for solar cells in any one of Claims 1-6.   The solar cell module of Claim 7 which has a photovoltaic cell consisting of a single crystal silicon type compound or a polycrystalline silicon type compound.   The solar cell module of Claim 7 or 8 which has a front member which consists of a translucent member.