JP2014204091A - Sealing material for solar cell and solar cell module manufactured using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for solar cell which facilitates formation of a solar cell module of good appearance because it has sufficient heat resistance, and exhibits excellent flexibility when laminating, and to provide a solar cell module manufactured by using the same.SOLUTION: A sealing material for solar cell composed of a resin composition containing at least a polyethylene-based resin (A), and a polyethylene-based resin (B) having a density higher than that of the polyethylene-based resin (A) satisfies the following conditions (1)-(3). (1) The crystal melting calorie measured at a heating rate of 10°C/min in the differential scanning calorimetry is 110 J/g or less, (2) The crystal melting calorie at 120°C or more measured at a heating rate of 10°C/min in the differential scanning calorimetry is 3.0-50 J/g, and (3) The flow starting temperature under a load of 1 kgf/cmis 160°C or less.

Description

  The present invention relates to a solar cell encapsulant and a solar cell module produced using the same, and more specifically, a solar cell encapsulant excellent in heat resistance and flexibility during lamination, and using the same. The present invention relates to a solar cell module with good appearance after lamination.

  In recent years, as awareness of environmental issues such as global warming has increased, solar power generation, in particular, has high expectations in terms of cleanliness and non-pollution. 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 incorporated in this package is called a solar cell module, and the surface that is generally exposed to sunlight is covered with a transparent substrate (glass or resin sheet, hereinafter referred to as a front sheet) as an upper protective material, A back surface sealing sheet (hereinafter referred to as a back surface) is filled with a sealing material (sealing resin layer) made of thermoplastic plastic (for example, ethylene-vinyl acetate copolymer or polyethylene polymer), and the back surface is a lower protective material. It may be written as a sheet).

  In addition, the sealing material has flexibility and impact resistance for protecting the solar cell element, heat resistance when the solar cell module generates heat, water vapor barrier property, flexibility, and sunlight is efficiently applied to the solar cell element. Transparency (total light transmittance, etc.), durability, dimensional stability, etc. are mainly required. Furthermore, since the sealing material is generally used after being laminated, its process suitability and appearance after lamination are also important.

  As a main material of the sealing material, an ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVA) is widely used. However, when used over a long period of time, the circuit corrosion of solar cells due to acetic acid generated due to the high moisture permeability of EVA, hydrolysis, etc., and the concern thereof, as well as with peripheral members caused by crosslinking agents, crosslinking aids, acetic acid, etc. Interfacial peeling, damage to the vacuum laminator due to outgassing, etc. are major problems.

  Polyolefin-based solar cell encapsulating materials that do not use an EVA sheet are attracting attention for the problems of EVA as described above. For example, Patent Document 1 discloses that a solar cell filler composition contains an ethylene-α-olefin copolymer polymerized using a single site catalyst and a crosslinking agent.

  Patent Document 2 discloses a solar cell module filler characterized by using a crosslinking agent and a specific crosslinking aid for polyethylene having a specific density and MFR. Specifically, heat resistance is imparted by weak crosslinking during film formation of the filler.

  Patent Document 3 discloses a solar cell encapsulant made of a resin composition containing two types of polyethylene resins having different densities.

JP 2000-91611 A JP 2012-99585 A JP 2011-37883 A

  Generally, in order to obtain heat resistance with a polyethylene resin, it is desirable to increase the density. However, when the density is increased, the flexibility is lowered.

  On the other hand, as disclosed in Patent Documents 1 and 2, it is known to impart heat resistance to a low-density polyethylene resin by adding a crosslinking agent or a crosslinking aid. However, the interfacial peeling and outgassing from the peripheral members caused by the crosslinking agent and the crosslinking aid are not improved. In addition, since crosslinking proceeds during molding, sufficient flexibility cannot be obtained when the module is laminated, and the mobility of the encapsulant is reduced. For example, glass / encapsulant / solar cell element / encapsulant / In the case of the back sheet configuration, it was considered that the back sheet surface could be uneven because the steps such as the wiring and between the cells could not be filled sufficiently. That is, a sealing material that satisfies both heat resistance and flexibility during lamination has not been obtained.

  In Patent Document 3, the density of the polyethylene-based resin is defined within a predetermined range. Furthermore, it is described that it is desirable that the difference in density between the two types of polyethylene resin is small. In general polyethylene-based resins, a resin having a low density is excellent in flexibility but inferior in heat resistance, and a resin having a high density is excellent in heat resistance but inferior in flexibility. That is, it is difficult to achieve both heat resistance and flexibility at a high level with this blending design, and a new solar cell encapsulant that solves these problems has been desired.

  An object of the present invention is to provide a solar cell encapsulant that has both sufficient heat resistance and flexibility at the time of lamination, and that can be easily formed into a solar cell module with good appearance, and a solar cell manufactured using the same. To provide a module.

  As a result of intensive studies, the present inventors have used a resin composition containing two types of polyethylene resins having different densities, and set the thermal characteristics and flow characteristics within a predetermined range, thereby encapsulating solar cells. The present invention has been completed by finding a blended design that has various required characteristics required for materials and solar cell modules using the same, and that is particularly compatible with heat resistance and flexibility at the time of lamination, which are likely to be anti-twisting characteristics.

The present invention relates to the following [1] to [12].
[1] A solar cell encapsulant comprising at least a polyethylene resin (A) and a resin composition containing a polyethylene resin (B) having a higher density than the polyethylene resin (A), A sealing material for solar cells, wherein the stopper material satisfies the following conditions (1) to (3).
(1) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 110 J / g or less. (2) 120 ° C. or higher measured at a heating rate of 10 ° C./min in differential scanning calorimetry. The heat of crystal fusion is 2.0 J / g or more and 50 J / g or less. (3) The flow start temperature at a load of 1 kgf / cm ² is 160 ° C. or less. [2] Measured according to JIS K7210 of the sealing material. The sealing material for solar cells according to [1] above, wherein the MFR at a temperature of 190 ° C. and a load of 2.16 kg is 1 g / 10 min or more and 20 g / 10 min or less.
[3] The above [1] or [2], wherein the sealing material has a crystal melting peak temperature of 100 ° C. or higher and 150 ° C. or lower measured at a heating rate of 10 ° C./min in differential scanning calorimetry. The sealing material for solar cells as described in.
[4] The sealing material has two or more crystal melting peak temperatures (Tm) measured at a heating rate of 10 ° C./min in differential scanning calorimetry, and the difference in crystal melting peak temperatures is 5 to 60 ° C. The solar cell encapsulant according to any one of [1] to [3], wherein the encapsulant is for solar cells.
[5] The density of the polyethylene resin (A) is 0.865 to 0.910 g / cm ³ , and the density of the polyethylene resin (B) is 0.910 to 0.965 g / cm ^3. The sealing material for solar cells according to any one of [1] to [4], which is characterized in that
[6] The difference between [1] to [5], wherein the difference between the density of the polyethylene resin (A) and the density of the polyethylene resin (B) is 0.01 g / cm ³ or more. The sealing material for solar cells of any one of Claims 1.
[7] The mixing mass ratio (% by mass) of the polyethylene resin (A) and the polyethylene resin (B) contained in the resin composition is 50:50 or more and 92: 8 or less. The sealing material for solar cells according to any one of [1] to [6].
[8] The above [1] to [7], wherein the sealing material has a water vapor transmission rate of 3 g / m ² · day or less per 500 μm thickness measured at 40 ° C. and 90% RH. ] The sealing material for solar cells of any one of these.
[9] The solar cell according to any one of [1] to [8], wherein the sealing material is 70% by mass or more of xylene-soluble matter measured by ASTM 2765-95. Sealing material.
[10] The solar cell encapsulant according to any one of [1] to [9], wherein the encapsulant further contains a silane-modified ethylene polymer.
[11] The solar cell sealing material according to any one of [1] to [10], wherein the sealing material is a back surface side sealing material.
[12] A solar cell module produced using the solar cell encapsulant according to any one of [1] to [11].

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the sealing material for solar cells which satisfy | fills various required characteristics simultaneously, such as the heat resistance of a sealing material, the softness | flexibility at the time of a lamination, and the back sheet surface appearance of a module. Since it is a polyethylene-based solar cell sealing material that does not contain a crosslinking agent or crosslinking aid, there is no concern about the corrosion of peripheral members and the durability is excellent. Further, since the sealing material can be designed with a relatively inexpensive material, it is excellent in economic efficiency.

It is a figure which shows the calculation method of crystal melting calorie | heat amount (DELTA) Hm (> 120 degreeC) of 120 degreeC or more. It is a figure which shows the solar cell module used when heat resistance (120 degreeC) is evaluated.

The present invention is described in detail below.
The solar cell encapsulant of the present invention comprises at least a polyethylene resin (A) and a resin composition containing a polyethylene resin (B) having a higher density than the polyethylene resin (A), and the following ( It satisfies the conditions 1) to (3).
(1) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 110 J / g or less. (2) 120 ° C. or higher measured at a heating rate of 10 ° C./min in differential scanning calorimetry. The heat of crystal fusion is 2.0 J / g or more and 50 J / g or less. (3) The flow start temperature at a load of 1 kgf / cm ² is 160 ° C. or less.

[Polyethylene resin (A)]
Although it does not specifically limit as a kind of polyethylene-type resin (A) used for this invention, For example, an ultra-low density polyethylene, a low density polyethylene, a linear low density polyethylene (ethylene-alpha-olefin copolymer) And medium density polyethylene. Specifically, a polyethylene resin having a density of 0.865 to 0.910 g / cm ³ is preferable in order to impart excellent transparency and low temperature flexibility of the sealing material, and in particular, the density is 0.870 to 0. A linear low density polyethylene (ethylene-α-olefin copolymer) of 900 g / cm ³ is preferred. Among the ethylene-α-olefin copolymers used in the present invention, an ethylene-α-olefin random copolymer is more preferable from the viewpoint of low crystallinity and excellent light transmittance and flexibility. These may be used alone or in a combination of two or more.

  The ethylene-α-olefin copolymer used in the present invention is a copolymer of ethylene and α-olefin. Here, the type of α-olefin copolymerized with ethylene is not particularly limited, but usually an α-olefin having 3 to 20 carbon atoms is preferably used. For example, propylene, 1-butene 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 3-methyl-butene-1, 4-methyl-pentene-1, and the like. In the present invention, a copolymer having 1-octene or 1-hexene as a copolymerization component as an α-olefin is preferable from the viewpoint of industrial availability and economy. As the α-olefin copolymerized with ethylene, only one type may be used alone, or two or more types may be used in combination at any ratio.

  Further, the content of the α-olefin copolymerized with ethylene is not particularly limited, but is usually 2 mol% or more and 40 mol% or less, preferably 3 mol% or more with respect to the whole monomer used for copolymerization. It is 30 mol% or less, More preferably, it is 5 mol% or more and 25 mol% or less. If the content of the α-olefin copolymerized with ethylene is within the above range, it is preferable because transparency (for example, total light transmittance) is improved by reducing the crystallinity due to the copolymerization component. Moreover, if the content of the α-olefin copolymerized with ethylene is within the above range, it is preferable to produce pellets by mixing all the materials because blocking of raw material pellets is suppressed. In addition, the kind and content of the α-olefin copolymerized with ethylene can be analyzed by a well-known method, for example, a nuclear magnetic resonance (NMR) measuring device or other instrumental analyzer.

The ethylene-α-olefin copolymer used in the present invention may contain monomer units based on monomers other than α-olefin. Examples of the monomer include cyclic olefins, vinyl aromatic compounds (such as styrene), polyene compounds, and the like. The content of the monomer unit is preferably 20 mol% or less, more preferably 15 mol% or less, assuming that all monomer units in the ethylene-α-olefin copolymer are 100 mol%. is there.
Further, the steric structure, branching, branching degree distribution, molecular weight distribution and copolymerization form (random, block, etc.) of the ethylene-α-olefin copolymer are not particularly limited, but have, for example, long chain branching. The copolymer generally has good mechanical properties, and has an advantage that the melt tension (melt tension) at the time of molding the sheet is increased and the calendar moldability is improved.

  The MFR (JIS K7210: temperature 190 ° C., load 21.18 N) of the polyethylene resin (A) used in the present invention is not particularly limited, but is preferably 1 g / 10 min to 20 g / 10 min. More preferably, it is 2 g / 10 min or more and 10 g / 10 min or less.

  The manufacturing method of the polyethylene-type resin (A) used for this invention is not specifically limited, The well-known polymerization method using the well-known ethylene polymerization catalyst is employable. Known polymerization methods include, for example, a slurry polymerization method, a solution polymerization method, a gas polymerization method 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 phase polymerization method and a bulk polymerization method using a radical initiator. In the present invention, a polymerization method using a single site catalyst capable of polymerizing a raw material having a low molecular weight and a narrow molecular weight distribution from the viewpoint of easy granulation after pelletization and prevention of blocking of raw material pellets, etc. It is preferable to use it to produce a polyethylene resin.

The crystal melting peak temperature of the polyethylene resin (A) used in the present invention is not particularly limited, but is preferably less than 100 ° C. If it is this range, the outstanding transparency and low temperature flexibility of a sealing material will be easy to be ensured. In the present invention, a crystal melting peak temperature is not expressed, that is, an amorphous polymer can be applied. However, in consideration of blocking of raw material pellets, the crystal melting peak temperature is 50 ° C. or more and less than 100 ° C. It is more preferable that the temperature is 60 ° C. or higher and lower than 100 ° C.
The crystal melting heat amount of the polyethylene resin (A) used in the present invention is not particularly limited, but is usually 0 to 100 J / g, preferably 5 to 80 J / g, more preferably 10 -65 J / g. Within such a range, the flexibility and transparency (total light transmittance) of the sealing material for solar cell of the present invention are secured, which is preferable.
The crystal melting peak temperature and the crystal melting heat amount can be measured at a heating rate of 10 ° C./min according to JIS K7121 using a differential scanning calorimeter.

Although the flow start temperature of the polyethylene-type resin (A) used for this invention is not specifically limited, Usually, it is 160 degrees C or less, Preferably, it is 150 degrees C or less. The lower limit of the flow start temperature is not particularly limited, but is usually about 70 ° C. When the flow start temperature is within this range, it is preferable because a solar cell module having a good appearance after lamination is easily secured when the solar cell module is manufactured.
In addition, a flow start temperature can be measured by the method as described in the Example mentioned later.

[Polyethylene resin (B)]
The polyethylene resin (B) used in the present invention is not particularly limited. Since the polyethylene resin (A) preferably used in the present invention is low density polyethylene, the polyethylene resin (A) alone may be inferior in heat resistance of the sealing material. Therefore, it is important that the density of the polyethylene resin (B) is larger than the density of the polyethylene resin (A). Thereby, heat resistance can be maintained, maintaining the softness | flexibility of the sealing material of this invention. The density of the polyethylene resin (B) is preferably 0.910~0.965g / cm ^3, more preferably 0.910~0.940g / cm ^3, 0.910~0.925g More preferably, it is / cm ³ .
Further, the difference between the density of the polyethylene resin (B) and the density of the polyethylene resin (A) (hereinafter sometimes referred to as a density difference) is preferably 0.01 g / cm ³ or more. More preferably, it is 0.02 g / cm ³ or more. If the difference in density is in the above range, both heat resistance and flexibility are easily achieved. Although the upper limit of the difference in density is not particularly limited, it is about 0.05 g / cm ³ from the viewpoint of close crystallinity between the polyethylene resin (A) and the polyethylene resin (B). Yes, preferably 0.04 g / cm ³ . If the difference in density is too large, the transparency of the sealing material may be inferior.

  Examples of the type of polyethylene resin (B) used in the present invention include low density polyethylene, linear low density polyethylene (ethylene-α-olefin copolymer), medium density polyethylene, and high density polyethylene. From the viewpoint of easily achieving both flexibility and heat resistance, linear low density polyethylene (ethylene-α-olefin copolymer) is preferable, and ethylene-α-olefin random copolymer is more preferable.

  Although it does not specifically limit as a kind of alpha olefin copolymerized with ethylene, Usually, a C3-C20 alpha olefin is used suitably, for example, propylene, 1-butene, 1- Examples include pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 3-methyl-butene-1, 4-methyl-pentene-1. In the present invention, a copolymer having 1-butene and 1-hexene as a copolymerization component as an α-olefin is preferable from the viewpoint of industrial availability and economy. As the α-olefin copolymerized with ethylene, only one type may be used alone, or two or more types may be used in combination at any ratio.

  Further, the content of the α-olefin copolymerized with ethylene is not particularly limited. When the total monomer units in the ethylene-α-olefin copolymer is 100 mol%, it is usually 15 mol. % Or less, more preferably 10 mol or less. If it is in this range, it is preferable because both the flexibility and heat resistance are easily secured by the copolymerization component. 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 ethylene-α-olefin copolymer may contain monomer units based on monomers other than α-olefin. Examples of the monomer include cyclic olefins, vinyl aromatic compounds (such as styrene), polyene compounds, and the like. The content of the monomer units is 20 mol% or less, preferably 15 mol% or less, based on 100 mol% of all monomer units in the ethylene-α-olefin copolymer.

  The MFR (JIS K7210: temperature 190 ° C., load 21.18 N) of the polyethylene resin (B) used in the present invention is not particularly limited, but is preferably 1 g / 10 min to 20 g / 10 min. More preferably, it is 2 g / 10 min or more and 10 g / 10 min or less.

  Moreover, the polyethylene-type resin (B) used for this invention can be manufactured using the manufacturing method similar to the polyethylene-type resin (A) mentioned above.

The crystal melting peak temperature of the polyethylene resin (B) used in the present invention is preferably 100 ° C. or higher and 140 ° C. or lower, and 110 ° C. or higher and 130 ° C. or lower in order to satisfy the condition (2) described later. It is more preferable. If it is this range, it will be easy to ensure both the softness | flexibility and heat resistance of a sealing material.
The crystal melting heat amount of the polyethylene resin (B) used in the present invention is not particularly limited, but is usually 0 to 200 J / g, preferably 30 to 160 J / g, more preferably 90. ~ 150 J / g. Further, the heat of crystal melting of the polyethylene resin (B) at 120 ° C. or higher (hereinafter sometimes referred to as ΔHm (≧ 120 ° C.)) is 4 J / g or more and 100 J in order to satisfy the condition (1) described later. / G or less, more preferably 6 J / g or more and 50 J / g or less. Within this range, the heat resistance of the solar cell encapsulant of the present invention is secured, which is preferable.

The method for measuring the crystal melting peak temperature is as described above. Further, the heat of crystal melting (ΔHm) and the heat of crystal melting of 120 ° C. or higher (ΔHm (≧ 120 ° C.)) are measured using a differential scanning calorimeter at a heating rate of 10 ° C./min according to JIS K7121. be able to.
Here, the heat of crystal melting ΔHm (≧ 120 ° C.) of 120 ° C. or higher is the portion of the melting peak area measured at a heating rate of 10 ° C./min in differential scanning calorimetry (the thermometer shown in FIG. 1). It is calculated from the hatched part in the gram.

  The flow starting temperature of the polyethylene resin (B) used in the present invention is not particularly limited, but is usually 180 ° C. or lower, preferably 160 ° C. or lower, more preferably 150 ° C. or lower. It is. The lower limit of the flow start temperature is not particularly limited, but is usually about 70 ° C. When the flow start temperature is within this range, it is preferable because a solar cell module having a good appearance after lamination is easily secured when the solar cell module is manufactured.

[Resin composition]
The resin composition which comprises the sealing material of this invention contains the polyethylene-type resin (A) and polyethylene-type resin (B) which were mentioned above at least. Further, the resin composition, the polyethylene resin density of 0.865~0.910g / cm ³ (A), a polyethylene resin density of 0.910~0.965g / cm ³ (B) It is preferable to contain.
Although the kind of polyethylene-type resin (A) and polyethylene-type resin (B) contained in a resin composition is not specifically limited, Each may use only 1 type, It uses combining multiple types. Also good.
Here, the mixing (containing) mass ratio (mass%) of the polyethylene resin (A): the polyethylene resin (B) is preferably 50:50 or more and 92: 8 or less, more preferably 60:40 or more and 90. : 10 or less. However, the total of the polyethylene resin (A) and the polyethylene resin (B) is 100 parts by mass. Here, it is preferable that the mixing (containing) mass ratio is in the above range because a sealing material excellent in balance of heat resistance, water vapor barrier properties, low temperature characteristics, and the like can be easily obtained.
The total content of the polyethylene resin (A) and the polyethylene resin (B) contained in the resin composition is not particularly limited, but is 50% by mass or more in 100% by mass of the resin composition. It is preferably 65% by mass or more, and more preferably 80% by mass or more.
Moreover, when making the resin composition which comprises the sealing material of the laminated structure mentioned later contain the polyethylene-type resin (A) and the polyethylene-type resin (B) mentioned above, a polyethylene-type resin (A) and a polyethylene-type resin ( Although it is not necessary for B) to be contained in the same layer, both resins are preferably contained in the same layer. Moreover, it is more preferable that at least the polyethylene-based resin (A) is contained in the resin composition constituting each layer of the laminated sealing material.
When the resin composition contains a plurality of polyethylene resins, although not particularly limited, a polyethylene resin having a density of 0.910 g / cm ³ or more is regarded as a polyethylene resin (B), A polyethylene resin having a density of less than 0.910 g / cm ³ is considered as the polyethylene resin (A).

  In addition, from the viewpoints of ease of regenerative addition at the time of manufacturing the sealing material and improvement in economics such as yield, the polyethylene resin (A) and the polyethylene resin (B) contained in the resin composition Are both ethylene-α-olefin random copolymers.

[Other resins]
If the sealing material of this invention can satisfy conditions (1)-(3) mentioned later, various physical properties (a softness | flexibility, heat resistance, transparency, adhesiveness, etc.), a moldability, economical efficiency, etc. will be improved further. For purposes, resins other than those described above can be included. Examples of resins other than those described above include modified polyolefin resins, tackifier resins, various elastomers (olefin-based, styrene-based, etc.) and the like.

(Modified polyolefin resin)
The type of the modified polyolefin resin is not particularly limited. For example, silane-modified polyolefin, acid-modified polyolefin, ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), ethylene- Methyl methacrylate copolymer (E-MMA), ethylene-ethyl acrylate copolymer (E-EAA), ethylene-glycidyl methacrylate copolymer (E-GMA), ionomer resin (ionic crosslinkable ethylene-methacrylic acid copolymer) It is preferably at least one resin selected from the group consisting of a polymer and an ionically crosslinkable ethylene-acrylic acid copolymer. Especially, in order to improve the adhesiveness to glass or a solar cell element, it is preferable to add silane modified polyolefin. In the case of a sealing material having a laminated structure to be described later, the silane-modified resin polyolefin is preferably contained in a layer serving as a front and back layer.

  Further, the content of various monomers for modifying the modified polyolefin resin is not particularly limited, but is usually 0.5 mol% or more and 40 mol% or less, preferably 1 mol% or more and 30 mol% or less. More preferably, it is 2 mol% or more and 25 mol% or less. If the content of various monomers is within the above range, it is preferable because the transparency of the encapsulant is improved by reducing the crystallinity. In addition, when the content of various monomers is within the above range, it is preferable that all the materials are mixed to produce pellets because blocking of raw material pellets is difficult to occur. In addition, the kind and content of various monomers which modify | denature modified polyolefin resin can be analyzed with a well-known method, for example, an NMR measuring apparatus, and another instrumental analyzer.

  The content of these modified polyolefin resins is not particularly limited, but is preferably 50% by mass or less, and 30% by mass or less, in 100% by mass of the resin composition constituting the sealing material. It is more preferable. When the content of the modified polyolefin resin is within the above range, various physical properties (flexibility, heat resistance, transparency, adhesiveness, etc.), moldability, etc. of the sealing material can be appropriately adjusted.

  The production method of the modified polyolefin resin is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst other than the silane-modified polyolefin, acid-modified polyolefin, and ionomer resin described below, for example, Ziegler-Natta Slurry polymerization method, solution polymerization method, gas phase polymerization method, etc. using multi-site catalyst typified by type catalyst and single-site catalyst typified by metallocene catalyst, and bulk polymerization method using radical initiator, etc. Can be mentioned.

  The silane-modified polyolefin is not limited, but can be obtained, for example, by melt-mixing a polyolefin-based resin, a silane coupling agent and a radical generator described later at high temperature, and graft polymerization.

  The acid-modified polyolefin is not limited, but can be obtained, for example, by melt-mixing a polyolefin-based resin, maleic anhydride and a radical generator at high temperature and graft polymerization.

  The ionomer resin is, for example, at least one of a metal ion or an organic amine at least part of an unsaturated carboxylic acid component of a copolymer comprising ethylene, an unsaturated carboxylic acid, and another unsaturated compound as an optional component. It can obtain by neutralizing with. The ionomer resin can also be obtained, for example, by saponifying at least a part of an unsaturated carboxylic acid ester component of a copolymer comprising ethylene, an unsaturated carboxylic acid ester, and an optional other unsaturated compound. Can do.

  As a specific example of the modified polyolefin resin used in the present invention, as a silane-modified polyolefin, a trade name “LINKLON” manufactured by Mitsubishi Chemical Corporation, and as an acid-modified polyolefin, a product manufactured by Mitsui Chemicals, Inc. The product name “ADMER” and EVA include the product name “NOVATECH-EVA” manufactured by Nippon Polyethylene Co., Ltd., and the product name “EVAFLEX” manufactured by Mitsui DuPont Polychemical Co., Ltd. "NUC" series manufactured by Nihon Unicar Co., Ltd., and EVOH, the product name "SOARNOL" manufactured by Nippon Synthetic Chemical Co., Ltd., the product name "EVAL" manufactured by Kuraray Co., Ltd., As E-MMA, trade names “ACRYFT” manufactured by Sumitomo Chemical Co., Ltd., E-MMA As AA, trade name “REXPEARL EEA” manufactured by Nippon Polyethylene Co., Ltd., as E-GMA, trade name “BONDFAST” manufactured by Sumitomo Chemical Co., Ltd., as ionomer, Mitsui A trade name “HIMILAN” manufactured by DuPont Polychemical Co., Ltd. can be exemplified.

(Tackifying resin)
Examples of tackifying resins include petroleum resins, terpene resins, coumarone-indene resins, rosin resins, and hydrogenated derivatives thereof. Specifically, examples of the petroleum resin include an alicyclic petroleum resin from cyclopentadiene or a dimer thereof and an aromatic petroleum resin from the C9 component, and examples of the terpene resin include β-pinene. Terpene resins and terpene-phenol resins, and as coumarone-indene resins, for example, coumarone-indene copolymers and coumarone-indene-styrene copolymers can be exemplified, and as rosin resins, for example, Examples thereof include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin or pentaerythritol. In addition, tackifying resins having various softening temperatures mainly depending on the molecular weight can be obtained. Therefore, it is particularly preferable to use a hydrogenated derivative of an alicyclic petroleum resin having a softening temperature of preferably 100 ° C. to 150 ° C., more preferably 120 ° C. to 140 ° C. Moreover, it is preferable that it is 20 mass% or less in 100 mass% of resin compositions which comprise a sealing material, and, as for content of tackifying resin, it is more preferable that it is 10 mass% or less.

(Various elastomers)
Various elastomers are not particularly limited, and examples thereof include styrene-based elastomers, polyester-based elastomers, and polyamide-based elastomers. Of these, styrene-based elastomers are preferred from the viewpoint of transparency and hydrolysis resistance. Examples of the styrenic elastomer include SEBS (Styrene-Ethylene-Butylene-Styrene), SEBC (Styrene-Ethylene-Butylene-Crystalline Block Copolymer), HSBR (hydrogenated styrene butadiene rubber), and the like. The styrene content is not particularly limited, but is preferably 20 mol% or less from the viewpoint of weather resistance. Further, the content of various elastomers is preferably 20% by mass or less, and more preferably 10% by mass or less, in 100% by mass of the resin composition constituting the sealing material.

[Additive]
If the sealing material of this invention can ensure the conditions (1)-(3) mentioned later, various additives can be added as needed. 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.

In the present invention, it is not necessary to add a crosslinking agent or a crosslinking aid to the resin composition, but it does not exclude the addition. For example, when high heat resistance is required, As long as the increase in the resin pressure and the generation of foreign substances such as gels and fish eyes can be suppressed, a crosslinking agent and / or a crosslinking aid can be blended.
In the present invention, the encapsulant is preferably an encapsulant that does not substantially crosslink. Here, “substantially not crosslinked” means that the xylene solubles measured by ASTM 2765-95 is usually 70% by mass or more, preferably 85% by mass or more, more preferably 95% by mass or more.

(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, acryloxy groups, Examples thereof include compounds having a hydrolyzable group such as an alkoxy group together with an unsaturated group such as a methacryloxy group, an amino group, an epoxy group and the like. 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. These silane coupling agents can be used alone or in combination of two or more.
The addition amount of this silane coupling agent is about 0.1-5 mass parts normally with respect to 100 mass parts of resin compositions which comprise a sealing material, Preferably it is 0.2-3 mass parts. In addition, similar to the silane coupling agent, a coupling agent such as an organic titanate compound can also be used effectively.

(Antioxidant)
The antioxidant is not particularly limited, and various commercially available products can be applied. Examples of the antioxidant include various types such as phenol, sulfur, phosphite, such as monophenol, bisphenol, and high-molecular phenol.

  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) and 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 and the like. Can be mentioned.

  Examples of the polymeric phenolic antioxidant 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 the sulfur-based antioxidant include dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiopropionate.

  Examples of the phosphite antioxidant include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl). ) Phosphite, cyclic neopentanetetraylbis (octadecyl phosphite), tris (mono and / or dinonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, diisodecylpentaerythritol di Phosphite, 9,10-dihydro-9-oxa-10-phosphaphenalene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9 -Oxa-10-phosphaphenance -10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite, Examples thereof include cyclic neopentanetetraylbis (2,6-di-tert-butylphenyl) phosphite, 2,2-methylenebis (4,6-tert-butylphenyl) octyl phosphite.

  In the present invention, phenolic and phosphite antioxidants are preferably used from the viewpoints of the effect of the antioxidant, thermal stability, economy, etc., and the combination of both is used to prevent oxidation with respect to the added amount. Since the effect as an agent can be improved, it is further more preferable.

  The addition amount of the antioxidant is not limited, but is usually 0.1 parts by mass or more and 1 part by mass or less, preferably 0 with respect to 100 parts by mass of the resin composition constituting the sealing material. .2 parts by mass or more and 0.5 parts by mass or less.

(UV 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 materials 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.

  Examples of the benzotriazole ultraviolet absorber include hydroxyphenyl-substituted benzotriazole compounds such as 2- (2-hydroxy-5-methylphenyl) benzotriazole and 2- (2-hydroxy-5-tert-butyl). Phenyl) benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole, 2- (2-methyl-4) -Hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-amylphenyl) benzotriazole, 2 -(2-hydroxy-3,5-di-tert And butyl phenyl) 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- And (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol.

  Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.

  The addition amount of the ultraviolet absorber is not limited, but is usually 0.01 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the resin composition constituting the sealing material, preferably 0.05 parts by mass or more and 0.5 parts by mass or less.

(Weather resistance stabilizer)
A hindered amine light stabilizer is suitably used as a weather stabilizer that imparts weather resistance in addition to the above ultraviolet absorber. The hindered amine light stabilizer does not absorb ultraviolet rays like the ultraviolet absorber, but has a remarkable synergistic effect when used in combination with the ultraviolet absorber.

  Examples of the hindered amine light stabilizer 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-diter 4-hydroxybenzyl) -2-n-butyl malonic acid bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like.

  The addition amount of the hindered amine light stabilizer is not limited, but is usually 0.01 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the resin composition constituting the sealing material. The amount is preferably 0.05 parts by mass or more and 0.3 parts by mass or less.

  Said silane coupling agent, antioxidant, ultraviolet absorber and weathering stabilizer may be used alone or in combination of two or more.

[Sealant for solar cell]
The sealing material for solar cells of the present invention (hereinafter sometimes abbreviated as sealing material) includes the resin composition described above.
In order to obtain a solar cell encapsulant that can easily form a solar cell module having good heat resistance, flexibility during lamination, and good appearance, the encapsulant needs to satisfy the following conditions (1) to (3). .
(1) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 110 J / g or less. (2) 120 ° C. or higher measured at a heating rate of 10 ° C./min in differential scanning calorimetry. The heat of crystal fusion is 2.0 J / g or more and 50 J / g or less. (3) The flow start temperature at a load of 1 kgf / cm ² is 160 ° C. or less.

(Condition (1): Heat of crystal melting (ΔHm)
Here, ΔHm measured at a heating rate of 10 ° C./min in the condition (1) differential scanning calorimetry is 110 J / g or less, preferably 100 J / g or less, more preferably 90 J / g or less. Within this range, since the crystallinity of the sealing resin can be suppressed to a certain level or less, volume shrinkage due to crystallization can be suppressed to a certain level or less. The lower limit of the heat of crystal fusion is not particularly limited, but is usually 20 J / g or more. This suppresses wiring streaks on the backsheet surface caused by the difference in volumetric shrinkage due to the difference in thickness of the sealing material that occurs when the sealing material fills the steps due to cells and wiring during lamination. As a result, it is possible to easily obtain a module having a good appearance. Moreover, by making the amount of heat of crystal melting within the above range, it is easy to balance the heat resistance, flexibility, transparency (total light transmittance) and the like of the solar cell sealing material of the present invention.
The ΔHm can be adjusted depending on the type and content of the resin contained in the resin composition constituting the sealing material.

(Condition (2): heat of crystal melting at 120 ° C. or higher (ΔHm (≧ 120 ° C.))
Here, ΔHm (≧ 120 ° C.) measured at a heating rate of 10 ° C./min in the condition (2) differential scanning calorimetry is 2.0 J / g or more and 50 J / g or less, more preferably 3.0 J / g. g to 20 J / g. If it is in this range, it is preferable because the heat resistance, transparency, productivity, etc. of the obtained sealing material are easily secured. If ΔHm (≧ 120 ° C.) is too low, the heat resistance of the sealing material may not be secured, and if ΔHm (≧ 120 ° C.) is too high, the transparency and productivity may be greatly reduced. is there.
Here, ΔHm (≧ 120 ° C.) is calculated from a melting peak area of 120 ° C. or more. A method of calculating ΔHm (≧ 120 ° C.) will be described with reference to FIG.
FIG. 1 shows a method for calculating ΔHm (≧ 120 ° C.) (FIG. 1 (a): melting peak temperature> 120 ° C .; FIG. 1 (b): melting peak temperature = 120 ° C .; FIG. 1 (c): Melting peak temperature <120 ° C.). ΔHm (≧ 120 ° C.) is calculated from the hatched portion in the thermogram shown in FIG.
The ΔHm (≧ 120 ° C.) can be adjusted by the type and content of the resin contained in the resin composition constituting the sealing material.

(Condition (3): Flow start temperature)
Here, the flow start temperature under condition (3) load 1 kgf / cm ² is 160 ° C. or lower, preferably 150 ° C. or lower, more preferably 140 ° C. or lower. The lower limit of the flow start temperature is not particularly limited, but is usually about 70 ° C. If the flow start temperature of the sealing material of this invention exists in this range, since the solar cell module with a favorable external appearance after a lamination can be ensured when producing a solar cell module, it is preferable.
The said flow start temperature can be adjusted with the kind and content of resin contained in the resin composition which comprises a sealing material.

Moreover, it is desirable that the solar cell encapsulant of the present invention further satisfies the following physical properties.
(MFR)
The MFR (JIS K7210: temperature 190 ° C., load 21.18 N) of the sealing material of the present invention is not particularly limited, but is preferably 1 g / 10 min to 20 g / 10 min, more preferably 2 g / min. It is 10 min or more and 10 g / 10 min or less. If it is in this range, the productivity at the time of shape | molding a sealing material, the adhesiveness at the time of sealing a solar cell element (cell), heat resistance, etc. can be ensured. If the MFR is too large, the heat resistance may be inferior. On the other hand, if the MFR is too small, problems such as productivity and laminate suitability (bubbles and cell cracks) tend to occur.

(Crystal melting peak temperature above 100 ° C)
The sealing material of the present invention preferably has a crystal melting peak temperature of 100 ° C. or higher measured at a heating rate of 10 ° C./min in differential scanning calorimetry, and has a crystal melting peak temperature (Tm) of 110 ° C. or higher. It is more preferable. The upper limit of the crystal melting peak temperature (Tm) is not particularly limited, but is preferably 150 ° C. or lower, more preferably 140 ° C. or lower, since a temperature that can be sufficiently melted at a general laminate setting temperature is preferable. Preferably it is 130 degrees C or less.
In the sealing material of the present invention, the crystal melting peak temperature (Tm) measured at a heating rate of 10 ° C./min in the differential scanning calorimetry is considered in consideration of heat resistance and transparency or transparency, economy, and the like. It has 2 or more and it is preferable that the difference of crystal melting peak temperature is 5-60 degreeC, and it is more preferable that it is 10-40 degreeC. Incidentally, the “difference in crystal melting peak temperature” refers to the highest crystal melting peak temperature (Tm) and the lowest crystal melting peak temperature (Tm) among the many crystal melting peak temperatures (Tm) of the sealing material. Is the difference. If it is this range, it will be easy to balance with the various physical properties of an above-mentioned sealing material.

(Water vapor transmission rate (WVTR))
The WVTR at a thickness of 500 μm of the encapsulant of the present invention is not particularly limited, but preferably 3 g / m in order to suppress problems such as adverse effects on the solar cell elements and electrodes, deterioration, and reduction in power generation efficiency. ² · day or less, more preferably 2.5 g / m ² · day or less, and still more preferably 2.0 g / m ² · day or less. The lower limit is not particularly limited, but is usually 0.1 g / m ² · day or more, and preferably 1.0 g / m ² · day or more from the viewpoint of flexibility of the sealing material.
The water vapor transmission rate can be measured by the method described in Examples described later.

[Method for producing sealing material for solar cell]
Next, the manufacturing method of the sealing material of this invention is demonstrated.
The shape of the sealing material is not limited, but is preferably a sheet from the viewpoint of handleability.

  Further, the encapsulant of the present invention is a single layer or a laminated structure, but in order to achieve the properties required for the encapsulant in a balanced manner, a laminated structure comprising a plurality of layers having different composition contents and composition ratios is preferable. . In the case of a laminated structure, the layer structure is not particularly limited. For example, a two-type two-layer structure including (I) layer and (II) layer, or (I) layer / (II) layer / (I) A two-type three-layer structure in which layers are stacked in order.

As a method for forming a sheet-like sealing material, a known method, for example, an extrusion casting method using a T-die, a calendar having a melt mixing facility such as a single screw extruder, a multi-screw extruder, a Banbury mixer, a kneader, etc. In the present invention, a co-extrusion method using a plurality of extruders is preferably used from the viewpoints of handleability, productivity, and the like. The molding temperature in the co-extrusion 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 130 to 300 ° C, preferably 150 to 250 ° C.
The thickness of the sheet-like sealing material is not particularly limited, but is usually 0.03 mm or more, preferably 0.05 mm or more, more preferably 0.1 mm or more, and usually 1 mm or less, preferably 0. 0.7 mm or less, more preferably 0.5 mm or less.

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 making, or a master batch in which only the additive is previously concentrated in the resin may be made and supplied. In addition, on the surface and / or the back surface of the sealing material obtained in the form of a sheet, if necessary, the sheet can be used as a scroll to prevent blocking between sheets, and in the laminating process of the solar cell element, air handling properties and air Embossing and various unevenness (cone, pyramid shape, hemispherical shape, etc.) processing may be performed for the purpose of improving ease of punching.
In addition, various surface treatments such as corona treatment, plasma treatment and primer treatment can be performed on the surface for the purpose of improving adhesion to various adherends. Here, as a standard of the surface treatment amount, the wet index is preferably 50 mN / m or more, and more preferably 52 mN / m or more. The upper limit of the wetting index is generally about 70 mN / m.

[Solar cell module]
In the solar cell module, the solar cell element is provided between the upper and lower protective materials. Examples of the solar cell module include various configurations. For example, (i) upper protective material (front sheet) / sealing material used on the front sheet side / solar cell element / sealing material used on the back sheet side / A structure that is sandwiched between both sides of the solar cell element, such as a lower protective material (back sheet), (ii) Upper protective material / sealing material used on the front sheet side / on the inner peripheral surface A structure in which a sealing material and an upper protective material are provided on a solar cell element provided on the inner peripheral surface of the lower protective material, such as a lower protective material provided with a solar cell element in (iii) Sealing material under the solar cell element provided under the inner peripheral surface of the upper protective material, such as an upper protective material provided with the solar cell element under the peripheral surface / a sealing material used on the back sheet side / a lower protective material And those that are configured to provide a lower protective material It can be mentioned. The symbol “/” indicates that layers sandwiching the symbol “/” are stacked adjacent to each other.

(Solar cell element)
Examples of solar cell elements include single crystal silicon type, polycrystalline silicon type, amorphous silicon type, III-V group and II-VI group compound semiconductor types such as gallium-arsenic, copper-indium-selenium, cadmium-tellurium, Examples include a dye sensitizing type and an organic thin film type.

(Upper protective material, lower protective material)
About each member which comprises a solar cell module, although it does not specifically limit, As an upper protective material, it is a single layer or multilayer sheets, such as an inorganic material and various thermoplastic resin films, for example, glass etc. Mention may be made of a single-layer or multilayer protective material made of a thermoplastic resin such as an inorganic material, polyester, inorganic vapor-deposited polyester, fluorine-containing resin or polyolefin. The lower protective material is a single layer or multilayer sheet such as metal, inorganic material and various thermoplastic resin films, for example, metal such as tin, aluminum, stainless steel, inorganic material such as glass, polyester, inorganic vapor deposition polyester, A single layer or multilayer protective material made of a thermoplastic resin such as a fluorine-containing resin or polyolefin may be used. The surface of the upper and / or lower protective material can be subjected to a known surface treatment such as a primer treatment or a corona treatment in order to improve the adhesion to the sealing material or other members.

The solar cell module manufactured using the sealing material of the present invention is the above-described upper protective material (front sheet) / sealing material used on the front sheet side (light-receiving surface side sealing material) / solar cell element / back. An example of a configuration such as a sealing material (back side sealing material) / lower protective material (back sheet) used on the sheet side will be described. In order from the sunlight receiving side, a front sheet, a sealing material used on the front sheet side, a solar cell element, a sealing material used on the back sheet side, and a back sheet are laminated, and further, a junction box ( A terminal box for connecting wiring for taking out electricity generated from the solar cell element to the outside is bonded. 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 backsheet and connected to the junction box.
The sealing material of the present invention may be used as a light-receiving surface side sealing material or a back surface side sealing material, but is particularly preferably used as a back surface side sealing material.

As a manufacturing method of the solar cell module, a known manufacturing method can be applied, and it is not particularly limited, but in general, an upper protective material, a light receiving surface side sealing material, a solar cell element, a back surface side sealing. A step of stacking the material and the lower protective material in this order, and a step of vacuum-sucking them and thermocompression bonding them. Also, batch type manufacturing equipment, roll-to-roll type manufacturing equipment, and the like can be applied.
In the solar cell module of the present invention, an upper protective material, a light-receiving surface side sealing material, a solar cell element, a back surface side sealing material, and a lower protective material are vacuum laminators, preferably 120 to 180 ° C., according to a conventional method. Preferably by heat and pressure bonding at a temperature of 130 to 150 ° C., a degassing time of 2 to 15 minutes, a pressing pressure of 0.5 to 1 atm, preferably 2 to 45 minutes, more preferably 4 to 20 minutes. Can be manufactured.

  The solar cell module manufactured using the sealing material 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, etc., depending on the type and module shape of the applied solar cell. It can be applied to various uses regardless of 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. Various measurements and evaluations described in this specification were performed as follows. Here, the flow direction of the sheet from the extruder is referred to as the longitudinal direction (MD), and the orthogonal direction is referred to as the transverse direction (TD).

[Measurement and evaluation method of resin and sealing material]
Evaluation of the resin and sealing material used in the examples was performed according to (1) to (5).
(1) Crystal melting peak temperature (Tm)
Using a differential scanning calorimeter (manufactured by PerkinElmer Co., Ltd., trade name: Pyris1 DSC), according to JIS K7121, about 10 mg of a sealing material sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. The temperature was raised and held at 200 ° C. for 5 minutes, then 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. The melting peak temperature (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 K7121, about 10 mg of a sealing material sample was heated from −40 ° C. to 200 ° C. at a heating rate of 10 ° C./min. The temperature was raised and held at 200 ° C. for 5 minutes, then 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. (J / g) was determined.

(3) Flow start temperature Using a high flow type flow tester manufactured by Shimadzu Corporation, trade name “Flow Tester CFT-500C”, nozzle (inner diameter 1 mm, length 2 mm), temperature rising rate 3 ° C./min, It measured on the conditions of load 1kgf / cm < ² > (9.8 * 10 < ⁴ > Pa), and calculated | required the flow start temperature (Tfb) of the sealing material.

(4) MFR
Using a melt indexer, MFR (g / 10 min) was measured at 190 ° C. and a load of 21.18 N according to JISK7210.

(5) Water vapor transmission rate (WVTR)
A sealing material sheet obtained by sandwiching an encapsulating material in an ethylenetetrafluoroethylene copolymer film, heat-treating with a small vacuum laminator at 145 ° C. in a vacuum for 5 minutes and pressing for 5 minutes (100 kPa), and then peeling the film ( The thickness was measured under the conditions of 40 ° C. and 90% RH according to JIS K7129.

[Solar cell module evaluation method]
The solar cell module was produced and evaluated according to the following (i) and (ii).
(I) Heat resistance (120 ° C)
Using a small vacuum laminator, one solar cell module was manufactured under the following conditions (see FIG. 2A), and then a heat resistance evaluation test was performed. By placing the solar cell module in a jig (see FIG. 2B) for 100 hours in an oven at 120 ° C., the heat resistance can be reduced from the shifted distance of the cells (see FIG. 2C). Evaluation was made according to the following criteria.
<Solar cell module configuration>
Glass 101 / Sealing material 201 used on the front sheet side (light receiving surface side sealing material) / Cell 301 / Sealing material 401 used on the back sheet side (back side sealing material) / Back sheet 501
Glass 101; Nakajima Glass Industrial Co., Ltd. blue plate transparent heat treated glass, size 180 mm × 180 mm, thickness 3.2 mm
Light-receiving surface side sealing material 201: Sealing material disclosed in each example or comparative example (see Table 1)
-Cell 301: Solar cell manufactured by Q Cells Japan Co., Ltd. Product name Q6LTT3-G2-180 (6 inches), size 155 mm × 155 mm
Back side sealing material 401: Sealing material disclosed in each example or comparative example (see Table 1)
Back sheet 501: manufactured by TAIFLEX (trade name), trade name: Solmate TPE BTNE, total thickness: 280 μm, laminated structure: (sealing material side) EVA / adhesive layer / PET / adhesive layer / PVF (white; containing titanium oxide), Thermal shrinkage (150 ° C. × 30 minutes, MD): 1.1%, Tm (EVA layer): 103 ° C.)
<Lamination conditions>
・ Lamination setting temperature: 145 ℃
-Vacuum drawing time: 5 minutes-Press holding time: 5 minutes-Pressure condition: 1st (30 kPa), 2nd (60 kPa), 3rd (70 kPa)
・ Cooling fan; not used <Heat resistance evaluation criteria>
(◎) Cell displacement distance is less than 0.5 mm (○) Cell displacement distance is 0.5 mm or more and less than 1 mm (×) Cell displacement distance is 1 mm or more

(Ii) Back sheet surface appearance (wiring lines, leveling)
Using a vacuum laminator (NPC Co., Ltd., trade name: SLM-240 × 460), three solar cell modules were produced under the following conditions. The back sheet surface appearance (wiring lines, leveling) of the module after lamination was evaluated according to the following criteria.
<Solar cell module configuration>
Glass / sealing material used on the front sheet side (light receiving surface side sealing material) / cell / back sheet side sealing material (back side sealing material) / back sheet glass; white plate manufactured by Nakajima Glass Industrial Co., Ltd. Embossed / Solar cell cover glass Product name Solect, size 996mm x 1664mm, thickness 3.2mm
-Light-receiving surface side sealing material: Sealing material disclosed in each example or comparative example (see Table 1)
-Cell: Solar cell manufactured by Q Cells Japan Co., Ltd. Product name Q6LTT3-G2-180 (6 inches, 3 busbar type)
* 60P (6 rows x 10 cells)
Back side sealing material: Sealing material disclosed in each example or comparative example (see Table 1)
Back sheet: manufactured by TAIFLEX (trade name), product name: Solmate TPE BTNE, total thickness: 280 μm, laminated structure: (sealing material side) EVA / adhesive layer / PET / adhesive layer / PVF (white; containing titanium oxide), heat Shrinkage (150 ° C. × 30 minutes, MD): 1.1%, Tm (EVA layer): 103 ° C.)
<Lamination conditions>
・ Lamination setting temperature: 145 ℃
-Vacuum drawing time: 5 minutes-Press holding time: 5 minutes-Pressure condition: 1st (30 kPa), 2nd (60 kPa), 3rd (70 kPa)
・ Cooling fan; not used <Evaluation criteria for wiring lines>
The average state of the appearance between the cells on the backsheet surface of the three solar cell modules was evaluated according to the following criteria.
(◎) Almost no wiring streaks are confirmed, and the appearance is good.
(◯) Although some wiring streaks are seen, they are inconspicuous.
(×) Wiring streaks are clearly visible in a line.
<Leveling evaluation criteria>
The average state of the appearance between the cells on the backsheet surface of the three solar cell modules was evaluated according to the following criteria.
(◎) Almost no dents between cells, and the appearance is good.
(◯) Although a phenomenon in which the cells are slightly recessed is confirmed, it is inconspicuous.
(X) The cell is clearly dented and has a plate-like chocolate appearance.

[Encapsulant]
The material which comprises a sealing material is described below.
(Ethylene polymer)
(X-1); ethylene-octene random copolymer (manufactured by Mitsui Chemicals, trade name: Tafmer H0530S, density: 0.870 g / cm ³ , ethylene / 1-octene = 68/32% by mass (89 / 11 mol%), Tm: 59 ° C., ΔHm = 56 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 0.5 g / 10 min)

(X-2); ethylene-octene random copolymer (manufactured by Dow Chemical Co., Ltd., trade name: affinity EG8100G, density: 0.870 g / cm ³ , ethylene / 1-octene = 68/32% by mass (89 / 11 mol%), Tm = 59 ° C., ΔHm = 53 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 1 g / 10 min)

(X-3); ethylene-octene random copolymer (manufactured by Dow Chemical Co., Ltd., trade name: affinity EG8200G, density: 0.870 g / cm ³ , ethylene / 1-octene = 68/32% by mass (89 / 11 mol%), Tm = 59 ° C., ΔHm = 53 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 5 g / 10 min)

(X-4); ethylene-butene random copolymer (manufactured by Mitsui Chemicals, Inc., trade name: Tafmer A-1085S, density: 0.885 g / cm ³ , ethylene / 1-butene = 82/18% by mass ( 90/10 mol%), Tm: 66 ° C., ΔHm = 61 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 1.2 g / 10 min)

(X-5); ethylene-butene random copolymer (manufactured by Mitsui Chemicals, Inc., trade name: Tafmer A-4085S, density: 0.885 g / cm ³ , ethylene / 1-butene = 82/18% by mass ( 90/10 mol%), Tm: 66 ° C., ΔHm = 61 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 3.6 g / 10 min)

(X-6); ethylene-octene random copolymer (manufactured by Prime Polymer Co., Ltd., trade name: Evolue P SP00108, density: 0.898 g / cm ³ , ethylene / 1-octene = 82/18% by mass (95 / 5 mol%), Tm: 95 ° C., ΔHm = 65 J / g, ΔHm (≧ 120 ° C.) = 0 J / g, MFR: 10 g / 10 min)

(X-7); ethylene-butene random copolymer (manufactured by ExxonMobil Co., Ltd., trade name: LL1002YB, density: 0.918 g / cm ³ , ethylene / 1-butene = 93/7% by mass (96/4 mol) %), Tm = 122 ° C., ΔHm = 131 J / g, ΔHm (≧ 120 ° C.) = 34 J / g, MFR: 2 g / 10 min)

(X-8); ethylene-octene block copolymer (manufactured by Dow Chemical Co., Ltd., trade name: Infuse 9100, density: 0.877 g / cm ³ , ethylene / 1-octene = 65/35% by mass ( 88/12 mol%), Tm: 122 ° C., ΔHm = 45 J / g, ΔHm (≧ 120 ° C.) = 16 J / g, Tm: 122 ° C., MFR: 1 g / 10 min)

(Silane-modified ethylene polymer)
(Q-1); Silane-modified ethylene-octene random copolymer (Mitsubishi Chemical Co., Ltd., trade name: Linkron SL800N, density: 0.868 g / cm ³ , ΔHm = 45 J / g, ΔHm (≧ 120 ° C. ) = 0 / g, Tm: 54 ° C. and 116 ° C., MFR: 1.0 g / 10 min)

(Q-2); Silane-modified ethylene-octene random copolymer (manufactured by Mitsubishi Chemical Corporation, trade name: Linkron XLE815N, density: 0.915 g / cm ³ , ΔHm = 106 J / g, ΔHm (≧ 120 ° C. ) = 22 J / g, Tm: 122 ° C., MFR: 0.5 g / 10 min)

Example 1
(I) As the layer, (X-5) 85 parts by mass and (Q-2) 15 parts by mass of the resin composition mixed, and (II) as the layer, (X-5) 90 parts by mass, And (X-7) the same direction twin screw extruder using the resin composition mixed at a ratio of 10 parts by mass so as to have a layered structure of (I) layer / (II) layer / (I) layer After co-extrusion molding at a resin temperature of 180 to 200 ° C. using a T-die method using a film, the film was quenched with a cast embossing roll at 25 ° C., the total thickness was 0.50 mm, and each layer thickness was (I) / (II ) / (I) = 0.05 mm / 0.40 mm / 0.05 mm. Hereinafter, the sealing material produced in Example 1 is referred to as B-1.
The total light transmittance measured by 2 mm white plate glass / sealing material / 2 mm white plate glass of B-1 was 88%. Other related evaluation results are shown in Table 1.

Example 2
(I) The resin composition mixed at a ratio of 50 parts by mass (X-5), 35 parts by mass (X-7), and 15 parts by mass (Q-2) as the layer, and (X) as the layer (X) -5) A sealing material was obtained in the same manner as in Example 1 (B-1) except that the resin composition was mixed at a ratio of 50 parts by mass and (X-7) 50 parts by mass. It was. Hereinafter, the sealing material produced in Example 2 is referred to as B-2. The related evaluation results are shown in Table 1.

Example 3
(I) Layer (X-4) 85 parts by mass and (Q-2) 15 parts by mass of resin composition mixed, (II) Layer (X-4) 85 parts by mass and (X) -7) Except having changed into the resin composition mixed in the ratio of 15 mass parts, the sealing material was obtained by the method similar to Example 1 (B-1). Hereinafter, the sealing material produced in Example 3 is referred to as B-3. The related evaluation results are shown in Table 1.

Example 4
(I) 85 parts by mass of (X-6) and (Q-2) 15 parts by mass of resin composition mixed as a layer, (II) 85 parts by mass of (X-6) and (X-) as a layer 7) Except having changed into the resin composition mixed in the ratio of 15 mass parts, the sealing material was obtained by the method similar to Example 1 (B-1). Hereinafter, the sealing material produced in Example 4 is referred to as B-4. The related evaluation results are shown in Table 1.

Comparative Example 1
(I) Layer (X-5) 85 parts by mass and (Q-2) 15 parts by mass of resin composition mixed, (II) layer (X-5) 95 parts by mass, and (X -7) Except having changed into the resin composition mixed in the ratio of 5 mass parts, the sealing material was obtained by the method similar to Example 1 (B-1). Hereinafter, the sealing material produced in Comparative Example 1 is referred to as B-5. The related evaluation results are shown in Table 1.

Comparative Example 2
(I) As the layer, (X-5) 20 parts by mass, (X-7) 65 parts by mass, and (Q-2) 15 parts by mass of the resin composition mixed, and (II) as the layer (X -5) A sealing material was obtained in the same manner as in Example 1 (B-1) except that the resin composition was mixed at a ratio of 20 parts by mass and (X-7) 80 parts by mass. It was. Hereinafter, the sealing material produced in Comparative Example 2 is referred to as B-6. The related evaluation results are shown in Table 1.

Comparative Example 3
(I) As the layer, (X-1) 85 parts by mass and (Q-2) 15 parts by mass of the resin composition mixed, and as the (II) layer, (X-1) 85 parts by mass and (X -7) Except having changed into the resin composition mixed in the ratio of 15 mass parts, the sealing material was obtained by the method similar to Example 1 (B-1). Hereinafter, the sealing material produced in Comparative Example 3 is referred to as B-7. The related evaluation results are shown in Table 1.

Comparative Example 4
(I) As the layer, (X-2) 35 parts by mass, (X-3) 50 parts by mass, and (Q-1) 15 parts by mass of the resin composition mixed, and (II) as the layer (X -2) Same as Example 1 (B-1) except that the resin composition was mixed at a ratio of 45 parts by mass, (X-3) 50 parts by mass, and (X-8) 5 parts by mass. By this method, a sealing material was obtained. Hereinafter, the sealing material produced in Comparative Example 4 is referred to as A-1.
The total light transmittance measured by 2 mm white plate glass / sealing material / 2 mm white plate glass of A-1 was 90%. Other related evaluation results are shown in Table 1.

Example 5
Using A-1 as the light-receiving surface side sealing material and B-1 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance and (ii) backsheet surface appearance Evaluation was performed. The results are shown in Table 2.

Example 6
Using A-1 as the light-receiving surface side sealing material and B-2 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance, (ii) appearance of the back sheet surface appearance Evaluation was performed. The results are shown in Table 2.

Example 7
Using A-1 as the light receiving surface side sealing material and B-3 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance, (ii) appearance of the backsheet surface Evaluation was performed. The results are shown in Table 2.

Example 8
Using A-1 as the light-receiving surface side sealing material and B-4 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance and (ii) backsheet surface appearance Evaluation was performed. The results are shown in Table 2.

Example 9
Using both the light-receiving surface side sealing material and the back surface side sealing material, the solar cell module was prepared by the above-described method, and (i) heat resistance and (ii) the back sheet surface appearance were evaluated. . The results are shown in Table 1.

Comparative Example 5
Using A-1 as the light-receiving surface side sealing material and B-5 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance, (ii) the appearance of the back sheet surface Evaluation was performed. The results are shown in Table 2.

Comparative Example 6
Using A-1 as the light-receiving surface side sealing material and B-6 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance and (ii) the back sheet surface appearance Evaluation was performed. The results are shown in Table 2.

Comparative Example 7
Using A-1 as the light-receiving surface side sealing material and B-7 as the back surface side sealing material, a solar cell module was prepared by the above-described method, and (i) heat resistance and (ii) the back sheet surface appearance Evaluation was performed. The results are shown in Table 2.

Comparative Example 8
A solar cell module was prepared by the above-described method using both the light-receiving surface side sealing material and the back surface side sealing material, and (i) heat resistance and (ii) appearance of the back sheet surface were evaluated. . The results are shown in Table 2.

  Table 1 describes the evaluation results of the sealing materials produced in Examples 1 to 4 and Comparative Examples 1 to 4, and Table 2 shows the sun produced using the produced sealing material. The evaluation result of the battery module is described. From Table 2, when the sealing material satisfying the characteristics defined in the present invention is used as the back side sealing material (Examples 5 to 8), or the sealing material satisfying the characteristics defined in the present invention is sealed on the back side. When used as a sealing material and a light-receiving surface side sealing material (Example 9), it has excellent heat resistance at high temperatures and the backsheet surface appearance (wiring lines, leveling) of the produced solar cell module is good. It can be confirmed that there is. On the other hand, when a sealing material that does not satisfy the characteristics defined in the present invention is used as the back side sealing material, sufficient heat resistance cannot be obtained, or the back sheet surface when producing a solar cell module It can be confirmed that the appearance is poor (Comparative Examples 5 to 8).

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the sealing material for solar cells which satisfy | fills various required characteristics simultaneously, such as the heat resistance of a sealing material, the softness | flexibility at the time of a lamination, and the back sheet surface appearance of a module. Since it is a polyethylene-based solar cell sealing material that does not contain a crosslinking agent or crosslinking aid, there is no concern about the corrosion of peripheral members and the durability is excellent. Further, since the sealing material can be designed with a relatively inexpensive material, it is excellent in economic efficiency.

101 ... Glass (180mm x 180mm)
201: Light-receiving surface side sealing material 301: Cell (155 mm × 155 mm)
401: Back side sealing material 501: Back sheet

Claims (12)

A solar cell encapsulant comprising at least a polyethylene resin (A) and a resin composition comprising a polyethylene resin (B) having a higher density than the polyethylene resin (A), wherein the encapsulant is The sealing material for solar cells characterized by satisfying the following conditions (1) to (3).
(1) The heat of crystal fusion measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 110 J / g or less. (2) 120 ° C. or higher measured at a heating rate of 10 ° C./min in differential scanning calorimetry. The heat of crystal fusion is 2.0 J / g or more and 50 J / g or less. (3) The flow start temperature at a load of 1 kgf / cm ² is 160 ° C. or less.   2. The solar cell according to claim 1, wherein the MFR at a temperature of 190 ° C. and a load of 2.16 kg measured in accordance with JIS K7210 of the sealing material is 1 g / 10 min or more and 20 g / 10 min or less. Sealing material.   3. The solar cell according to claim 1, wherein the sealing material has a crystal melting peak temperature of 100 ° C. or more and 150 ° C. or less measured at a heating rate of 10 ° C./min in differential scanning calorimetry. Sealing material.   The sealing material has two or more crystal melting peak temperatures (Tm) measured at a heating rate of 10 ° C./min in differential scanning calorimetry, and the difference between the crystal melting peak temperatures is 5 to 60 ° C. The solar cell sealing material according to any one of claims 1 to 3. The density of the polyethylene resin (A) is 0.865 to 0.910 g / cm ³ , and the density of the polyethylene resin (B) is 0.910 to 0.965 g / cm ^3. The sealing material for solar cells of any one of Claims 1-4. The difference between the density of the polyethylene resin (A) and the density of the polyethylene resin (B) is 0.01 g / cm ³ or more, 6. Solar cell encapsulant.   2. The mixing mass ratio (% by mass) of the polyethylene resin (A) and the polyethylene resin (B) contained in the resin composition is 50:50 or more and 92: 8 or less. The sealing material for solar cells of any one of -6. 8. The water vapor permeability per 500 μm thickness measured at 40 ° C. and 90% RH of the sealing material is 3 g / m ² · day or less. The sealing material for solar cells as described in.   The solar cell encapsulant according to any one of claims 1 to 8, wherein the encapsulant is 70% by mass or more of xylene solubles measured by ASTM 2765-95.   The solar cell sealing material according to any one of claims 1 to 9, wherein the sealing material further contains a silane-modified ethylene polymer.   The said sealing material is a back surface side sealing material, The sealing material for solar cells of any one of Claims 1-10 characterized by the above-mentioned.   The solar cell module produced using the sealing material for solar cells of any one of Claims 1-11.

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