JP5854473B2 - Solar cell encapsulant and solar cell module - Google Patents

Description

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

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

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

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

  On the other hand, the resin composition for solar cell sealing materials which consists of an ethylene-alpha-olefin copolymer, an organic peroxide, and a silane coupling agent is proposed (for example, refer patent document 1). . This resin composition for solar cell encapsulant is said to be excellent in heat resistance, transparency, flexibility and adhesion to a glass substrate.

International Publication No. 2010/114028 Pamphlet

  However, according to the study by the present inventors, a solar cell encapsulant mainly composed of an ethylene / α-olefin copolymer as described in Patent Document 1 has good extrusion moldability and transparency. However, it has been clarified that there may be a problem that the solar cell element and the wiring are shifted when the solar cell module is formed. In addition, it has become clear that the solar cell encapsulating material protrudes during laminating, which may cause a problem that soils the laminating apparatus and the oven.

  Then, this invention makes it a subject to provide the solar cell sealing material excellent in the yield at the time of solar cell module manufacture.

  The inventors of the present invention have made extensive studies on the factors that cause the above-described problems when manufacturing a solar cell module. As a result, the inventors have found that the above-described problems can be suppressed by appropriately adjusting the complex viscosity of the solar cell sealing material, and have completed the present invention.

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

[1]
A solar cell encapsulant comprising an ethylene / α-olefin copolymer and an organic peroxide,
According to ASTM D1238, the MFR of the ethylene / α-olefin copolymer is 10 to 50 g / 10 min as measured under conditions of 190 ° C. and 2.16 kg load,
The minimum viscosity of the complex viscosity (η *) of the solar cell encapsulant in the measurement of the solid viscoelasticity in a measurement temperature range of 25 to 180 ° C., a frequency of 0.016 Hz, a heating rate of 3 ° C./min, and a shear mode is 2. The solar cell sealing material which exists in the range of 0 * 10 < ³ > Pa * s-3.0 * 10 < ⁴ > Pa * s.

[2]
The solar cell encapsulating material according to [1], wherein the ethylene / α-olefin copolymer satisfies the following requirements a1) to a3).
a1) The content rate of the structural unit derived from ethylene is 80-90 mol%, and the content rate of the structural unit derived from a C3-C20 alpha olefin is 10-20 mol%.
a2) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a3) Shore A hardness measured according to ASTM D2240 is 60-85.

[3]
The solar cell encapsulating material according to [1] or [2], wherein the temperature of the minimum viscosity is 100 to 120 ° C.

[4]
Furthermore, the solar cell sealing material according to any one of [1] to [3], further including silica powder.

[5]
The solar cell encapsulating material according to [4], wherein the silica powder is hydrophilic silica.

[6]
The solar cell sealing material according to [4] or [5], wherein the silica powder has a specific surface area measured by a BET method of 50 to 500 m ² / g.

[7]
The solar cell encapsulant according to any one of [4] to [6], wherein the silica powder is non-porous silica.

[8]
[4] to [7], wherein the content of the silica powder in the solar cell encapsulant is 1.0 to 15.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material as described in any one.

[9]
The solar cell sealing material according to any one of the above [1] to [8], wherein the total light transmittance of the solar cell sealing material in a wavelength region of 350 to 800 nm is 85% or more.

[10]
The organic peroxide has a 1 minute half-life temperature of 100 to 170 ° C.,
[1] to [9], wherein the content of the organic peroxide in the solar cell encapsulant is 0.1 to 3 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material as described in any one.

[11]
Further comprising a silane coupling agent,
[1] to [10], wherein the content of the silane coupling agent in the solar cell encapsulant is 0.1 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material as described in any one.

[12]
Further comprising a hindered phenol stabilizer,
[1] The content of the hindered phenol stabilizer in the solar cell encapsulant is 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. ] The solar cell sealing material as described in any one of [11].

[13]
Further comprising a hindered amine light stabilizer,
[1] The content of the hindered amine light stabilizer in the solar cell encapsulant is 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. Thru | or [12] The solar cell sealing material as described in any one.

[14]
Further comprising a phosphorus stabilizer,
The content of the phosphorus stabilizer in the solar cell sealing material is 0.005 to 0.5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. [13] The solar cell sealing material according to any one of the above.

[15]
Further comprising a UV absorber,
[1] to [14], wherein the content of the ultraviolet absorber in the solar cell encapsulant is 0.005 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material as described in any one.

[16]
Further comprising a crosslinking aid,
[1] to [15], wherein the content of the crosslinking aid in the solar cell encapsulant is 0.05 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material as described in any one.

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

[18]
The solar cell sealing according to [17], obtained by melt-kneading a resin composition containing the ethylene / α-olefin copolymer and the organic peroxide and then extruding the resin composition into a sheet shape. Wood.

[19]
A surface-side transparent protective member;
A back side protection member;
A solar cell element;
The solar cell element formed by crosslinking the solar cell encapsulant according to any one of [1] to [18] is sealed between the front surface side transparent protective member and the back surface side protective member. A sealing layer to stop;
Solar cell module with

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell sealing material excellent in the yield at the time of solar cell module manufacture can be provided.

  Further, according to the present invention, by using such a solar cell encapsulant, the balance of various characteristics of the solar cell encapsulant is excellent, and even if the temperature rises during use of the solar cell module, the sealing is performed. It is possible to avoid troubles such as deformation of the stop material. And the solar cell module excellent in economical efficiency, such as cost, can be provided, without impairing the external appearance of a solar cell.

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

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

1. About solar cell sealing material The solar cell sealing material of this embodiment contains the ethylene-alpha-olefin copolymer and the organic peroxide as an essential component.

The solar cell encapsulant of the present embodiment has a measurement temperature range of 25 to 180 ° C., a frequency of 0.016 Hz, a temperature increase rate of 3 ° C./min, and a complex viscosity (η *) in solid viscoelasticity measurement in shear mode. The minimum viscosity is 2.0 × 10 ³ Pa · s or more, preferably 3.0 × 10 ³ Pa · s or more, and more preferably 3.5 × 10 ³ Pa · s or more.
In addition, the solar cell encapsulant of this embodiment has a complex viscosity (η *) in a measurement of a solid viscoelasticity in a shear mode with a measurement temperature range of 25 to 180 ° C., a frequency of 0.016 Hz, a heating rate of 3 ° C./min. The minimum viscosity is 3.0 × 10 ⁴ Pa · s or less, preferably 2.5 × 10 ⁴ Pa · s or less.

  In general, the complex viscosity of the solar cell encapsulant decreases with increasing temperature. And complex viscosity rises rapidly from a certain temperature. This sudden increase in the complex viscosity is caused by the decomposition of the organic peroxide contained in the solar cell encapsulant, thereby initiating a crosslinking reaction of the solar cell encapsulant. Therefore, the minimum viscosity of the complex viscosity is a viscosity at a certain temperature before the complex viscosity suddenly increases, and means the complex viscosity at the start of the crosslinking reaction.

According to the study by the present inventors, a conventional solar cell encapsulant mainly composed of an ethylene / α-olefin copolymer has a low complex viscosity at the start of the crosslinking reaction, and thus a solar cell module is produced. It has become clear that sometimes solar cell elements and wirings are misaligned, and that the solar cell encapsulating material protrudes during laminating, resulting in a problem of soiling the laminating apparatus and oven.
Therefore, the present inventors have intensively studied to eliminate the above-mentioned problems that occur when manufacturing solar cell modules. As a result, it was found that by adjusting the minimum viscosity of the complex viscosity (η *) to a specific range, a solar cell encapsulant excellent in yield at the time of manufacturing a solar cell module can be obtained. It came to be completed.

The solar cell encapsulant of the present embodiment has a problem that the solar cell element and the wiring are displaced when the solar cell module is created, because the minimum viscosity of the complex viscosity (η *) is equal to or higher than the lower limit. It can suppress that the solar cell sealing material protrudes at the time of a lamination process, and the malfunction which soils a lamination apparatus and oven also arises.
Moreover, when the minimum viscosity of complex viscosity ((eta) *) is below the said upper limit, the solar cell sealing material with a favorable external appearance can be obtained in extrusion molding.

  Therefore, according to the present invention, when the minimum viscosity of the complex viscosity (η *) is within the above range, a solar cell encapsulant excellent in yield at the time of manufacturing a solar cell module can be obtained.

The solar cell encapsulant of this embodiment has a measurement temperature range of 25 to 180 ° C., a frequency of 0.016 Hz, a heating rate of 3 ° C./min, and a minimum complex viscosity (η *) in solid viscoelasticity measurement in shear mode. It is preferable that the temperature in viscosity is 100 to 120 ° C.
When the temperature at the minimum viscosity is 100 ° C. or higher, a sheet excellent in extrusion moldability and having a better sheet appearance can be obtained. When the temperature at the minimum viscosity is 120 ° C. or lower, crosslinking in the laminating process can be performed at an early stage, and the displacement of the solar cell element or electrode can be further suppressed. Furthermore, dirt on the laminating apparatus and the oven can be further suppressed.
In addition, the solid viscoelasticity measurement in the shear mode was performed by creating a press sheet having a thickness of 0.5 mm and applying a frequency of 0.016 Hz from 25 ° C. (room temperature) to 180 ° C. using ReoPress (manufactured by HAAKE). It can be measured at a rate of temperature increase of 3 ° C./min. The temperature at the minimum viscosity can be read from the measurement profile.

In addition, the ethylene / α-olefin copolymer contained in the solar cell encapsulant of the present embodiment is a melt flow rate (MFR) measured under conditions of 190 ° C. and 2.16 kg load in accordance with ASTM D1238. Is 10 g / 10 min or more, preferably 13 g / 10 min or more, more preferably 14 g / 10 min or more.
In addition, the ethylene / α-olefin copolymer contained in the solar cell encapsulant of the present embodiment is a melt flow rate (MFR) measured under conditions of 190 ° C. and 2.16 kg load in accordance with ASTM D1238. Is 50 g / 10 min or less, preferably 40 g / 10 min or less, more preferably 35 g / 10 min or less, particularly preferably 27 g / 10 min or less, and most preferably 25 g / 10 min or less. It is.
The MFR of the ethylene / α-olefin copolymer is adjusted by adjusting the polymerization temperature, the polymerization pressure, the molar ratio of the ethylene and α-olefin monomer concentration and the hydrogen concentration in the polymerization system, which will be described later. Can be adjusted.

  When the MFR is 10 g / 10 min or more, the fluidity of the resin composition containing the ethylene / α-olefin copolymer is improved, and the productivity at the time of sheet extrusion molding can be improved. Moreover, since the scorch property of a resin composition falls, gelatinization can be suppressed. When gelation is suppressed, the torque of the extruder is reduced, and sheet molding can be facilitated. Moreover, since generation | occurrence | production of a gel thing can be suppressed in an extruder after a sheet | seat is obtained, generation | occurrence | production of the unevenness | corrugation in the surface of a sheet | seat can be suppressed, and the fall of an external appearance can be suppressed.

  In addition, if there is a gel material inside the sheet, cracks will occur around the gel material when voltage is applied, and the dielectric breakdown voltage will decrease, but by reducing the MFR to 10 g / 10 min or more, the dielectric breakdown voltage will decrease. Can be suppressed. Further, if there is a gel material inside the sheet, moisture permeation easily occurs at the gel material interface. However, by reducing the MFR to 10 g / 10 min or more, a decrease in moisture permeability can be suppressed.

  Moreover, when unevenness | corrugation generate | occur | produces on the sheet | seat surface, adhesiveness with a surface side transparent protective member, a cell, an electrode, and a back surface side protective member will deteriorate at the time of a lamination process of a solar cell module, and adhesion | attachment becomes inadequate, but MFR is 50g. When it is set to / 10 minutes or less, the molecular weight is increased, and therefore, adhesion to a roll surface such as a chill roll can be suppressed. Furthermore, since it becomes a resin composition with “koshi”, a thick sheet of 0.1 mm or more can be easily formed. Moreover, since the crosslinking characteristic at the time of laminate molding of the solar cell module is improved, it is possible to sufficiently crosslink and suppress a decrease in heat resistance. If the MFR is 27 g / 10 min or less, the drawdown during sheet forming can be further suppressed, so that a wide sheet can be formed, the cross-linking characteristics and heat resistance are further improved, and the best solar cell sealing A material sheet can be obtained.

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

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

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

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

  The ethylene / α-olefin copolymer of the present embodiment preferably further satisfies the following requirements a1 to a3.

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

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is 10 mol% or more, high transparency is obtained. Further, extrusion molding at a low temperature can be easily performed, and for example, extrusion molding at 130 ° C. or lower is possible. For this reason, even when the organic peroxide is kneaded into the ethylene / α-olefin copolymer, it is possible to suppress the progress of the crosslinking reaction in the extruder, and gel-like foreign matters are present on the sheet of the solar cell sealing material. Occurrence and deterioration of the appearance of the sheet can be prevented. Moreover, since moderate softness | flexibility is acquired, generation | occurrence | production of the crack of a solar cell element, the crack of a thin film electrode, etc. can be prevented at the time of lamination molding of a solar cell module.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is 20 mol% or less, the crystallization speed of the ethylene / α-olefin copolymer becomes appropriate, and thus the ethylene / α-olefin copolymer was extruded from an extruder. The sheet is not sticky, can be easily peeled off by a cooling roll, and a sheet-like solar cell sealing material can be obtained efficiently. Further, since no stickiness is generated on the sheet, blocking can be prevented, and the sheet feeding property is good. In addition, a decrease in heat resistance can be prevented.

(Requirement a2)
The density of the ethylene / α-olefin copolymer measured according to ASTM D1505 is preferably 0.865 to 0.884 g / cm ³ , more preferably 0.866 to 0.883 g / cm ³ . , more preferably from 0.866~0.880g / cm ^3, particularly preferably 0.867~0.880g / cm ^3. The density of the ethylene / α-olefin copolymer can be adjusted by a balance between the content ratio of ethylene units and the content ratio of α-olefin units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a high-density ethylene / α-olefin copolymer can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and an ethylene / α-olefin copolymer having a low density can be obtained.

When the density of the ethylene / α-olefin copolymer is 0.884 g / cm ³ or less, the crystallinity is lowered and the transparency can be increased. Furthermore, extrusion molding at low temperature becomes easy, and for example, extrusion molding can be performed at 130 ° C. or lower. For this reason, even if an organic peroxide is kneaded into the ethylene / α-olefin copolymer, the cross-linking reaction in the extruder is prevented from progressing, and the generation of gel-like foreign matters on the sheet of the solar cell encapsulant is suppressed. In addition, deterioration of the appearance of the sheet can be suppressed. Moreover, since it is highly flexible, it is possible to prevent the occurrence of cell cracks and thin film electrode cracks, which are solar cell elements, when the solar cell module is laminated.

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

(Requirement a3)
The Shore A hardness of the ethylene / α-olefin copolymer, measured according to ASTM D2240, is preferably 60 to 85, more preferably 62 to 83, still more preferably 62 to 80, and particularly Preferably it is 65-80. The Shore A hardness of the ethylene / α-olefin copolymer can be adjusted by controlling the content ratio and density of the ethylene units in the ethylene / α-olefin copolymer within the above-mentioned numerical range. That is, an ethylene / α-olefin copolymer having a high ethylene unit content and high density has a high Shore A hardness. On the other hand, an ethylene / α-olefin copolymer having a low ethylene unit content and a low density has a low Shore A hardness.

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

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

  Furthermore, the solar cell sealing material of this embodiment is also a preferable aspect that further satisfies the following requirements.

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

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

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

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

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

Polymerization of the ethylene / α-olefin copolymer can be carried out by any of the conventionally known gas phase polymerization methods and liquid phase polymerization methods such as slurry polymerization methods and solution polymerization methods. Preferably, it is carried out by a liquid phase polymerization method such as a solution polymerization method. When the ethylene / α-olefin copolymer is produced by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms using the metallocene compound as described above, the metallocene compound of (I) It is used in an amount of usually 10 ⁻⁹ to 10 ⁻¹ mol, preferably 10 ⁻⁸ to 10 ⁻² mol per liter of volume.

  In the compound (II-1), the molar ratio [(II-1) / M] of the compound (II-1) and all transition metal atoms (M) in the compound (I) is usually 1 to 10,000, preferably It is used in such an amount that it becomes 10-5000. In the compound (II-2), the molar ratio [(II-2) / M] of the compound (II-2) and the total transition metal (M) in the compound (I) is usually 0.5 to 50, Preferably it is used in such an amount as to be 1-20. Compound (II-3) is generally used in an amount of 0 to 5 mmol, preferably about 0 to 2 mmol, per liter of polymerization volume.

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

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

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

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

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

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

  The organic peroxides preferably used are particularly those that can graft-modify a silane coupling agent on the ethylene / α-olefin copolymer or crosslink the ethylene / α-olefin copolymer. Although not limited, it is preferable that the 1-minute half-life temperature of an organic peroxide is 100-170 degreeC from the balance of the productivity in extrusion sheet | seat shaping | molding, and the crosslinking rate at the time of the lamination shaping | molding of a solar cell module. When the half-life temperature of the organic peroxide is 100 ° C. or higher, gels are less likely to occur in the solar cell encapsulating sheet obtained from the resin composition during extrusion sheet molding, and thus the increase in the torque of the extruder is suppressed. Sheet forming can be facilitated. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the surface of a sheet | seat with the gel thing which generate | occur | produced in the extruder, the fall of an external appearance can be prevented. Moreover, since the generation | occurrence | production of the crack inside a sheet | seat can be prevented when a voltage is applied, the fall of a dielectric breakdown voltage can be prevented. Furthermore, it is possible to prevent a decrease in moisture permeability. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the sheet | seat surface, the adhesiveness with a surface side transparent protection member, a cell, an electrode, and a back surface side protection member becomes favorable at the time of the lamination process of a solar cell module, and adhesiveness also improves. If the extrusion temperature of extrusion sheet molding is lowered to 90 ° C. or lower, molding is possible, but productivity is greatly reduced. When the one-minute half-life temperature of the organic peroxide is 170 ° C. or lower, it is possible to suppress a decrease in the crosslinking rate when the solar cell module is laminated, and thus it is possible to prevent a decrease in the productivity of the solar cell module. Moreover, the heat resistance of a solar cell sealing material and the fall of adhesiveness can also be prevented.

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

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

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

(Silica powder)
It is preferable that the solar cell sealing material of this embodiment further contains silica powder. Since most of the chemical components of silica powder are SiO ₂ and a crosslinking reaction occurs via a silane coupling agent, it is assumed that the crosslinking characteristics of the solar cell encapsulant are improved. The silica powder is preferably amorphous synthetic silica. Among these, amorphous synthetic silica having a uniform particle size of the primary aggregate (aggregate) and the secondary aggregate (agglomerate) is preferable. As the amorphous synthetic silica, any of dry silica obtained as a by-product when producing a combustion method, metal silicon, ferrosilicon, or other silicon alloys, a precipitation method, a gel method, or a wet silica by a sol-gel method may be used. Furthermore, any of hydrophilic silica and hydrophobic silica may be used, but hydrophilic silica is preferred because it is excellent in improving the crosslinking property.

BET specific surface area of the silica powder of the present embodiment is preferably 50 to 500 m ² / g, more preferably 70~500m ² / g, and particularly preferably a 80~400m ² / g.
When the BET specific surface area of the silica powder is 50 m ² / g or more, the apparent particle size of the primary aggregate or primary particle of the silica powder can be suppressed, and thus the transparency of the obtained solar cell sealing material is further improved. be able to. Moreover, since the adsorption | suction of the organic peroxide and silane coupling agent in a silica powder can be suppressed as the BET specific surface area of a silica powder is 500 m < ² > / g or less, the bridge | crosslinking characteristic of a solar cell sealing material falls. Can be suppressed. Further, when the BET specific surface area of the silica powder is 500 m ² / g or less, the silica powder can be synthesized.

As content of the silica powder in a solar cell sealing material, it is preferable that it is 1.0-15.0 weight part with respect to 100 weight part of the above-mentioned ethylene alpha-olefin copolymer, 2.0 It is more preferably ˜15.0 parts by weight, and particularly preferably 3.0 to 10.0 parts by weight.
When the content of the silica powder is 1.0 part by weight or more, the crosslinking characteristics of the solar cell sealing material are further improved. In addition, when the content of the silica powder is 15.0 parts by weight or less, the crosslinking characteristics are further improved, and a solar cell encapsulant that is more excellent in transparency can be obtained.

The silica powder of this embodiment is preferably nonporous silica. Since the adsorption of the organic peroxide and the silane coupling agent into the silica powder can be further suppressed when it is non-porous silica, it is possible to further suppress the deterioration of the crosslinking characteristics of the solar cell sealing material.
Moreover, since the apparent particle diameter of the primary aggregate or primary particle of a silica powder can be suppressed as it is a non-porous silica, the transparency of the solar cell sealing material obtained can be improved further.

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

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

  In addition, the silane coupling agent itself undergoes a condensation reaction and exists as white streaks in the solar cell sealing material, which may deteriorate the appearance of the product. However, when the silane coupling agent is 5 parts by weight or less, the white streaks Can also be suppressed.

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

(Hindered amine light stabilizer)
It is preferable that the solar cell sealing material of this embodiment further contains a hindered amine light stabilizer. By including a hindered amine light stabilizer, radicals harmful to the ethylene / α-olefin copolymer can be captured, and generation of new radicals can be suppressed.

Examples of hindered amine light stabilizers include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3. , 5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino }] And the like, hindered piperidine compounds, and the like can be used.
Moreover, the low molecular weight hindered amine light stabilizer of the following general formula (1) can also be used.

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

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

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

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

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

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

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

  As the phosphorus stabilizer, a conventionally known compound can be used, for example, tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diylbisphosphonite, and bis (2,4 -Di-tert-butylphenyl) pentaerythritol diphosphite and the like. Among these, tris (2,4-di-tert-butylphenyl) phosphite is preferable.

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

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

  Specific examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy- Benzophenones such as 4-carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy-5 -Methylphenyl) benzotriazol-based compounds such as benzotriazole; salicylic acid ester-based compounds such as phenylsalicylate and p-octylphenylsalicylate are used.

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

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

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

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

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

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

  The solar cell encapsulant of this embodiment is excellent in yield at the time of manufacturing a solar cell module while maintaining extrudability and transparency, and further, a front surface side transparent protective member, a back surface side protective member, a thin film electrode, aluminum, solar Excellent balance of adhesion to various solar cell members such as battery elements, heat resistance, flexibility, appearance, weather resistance, volume resistivity, electrical insulation, moisture permeability, electrode corrosion, and process stability. For this reason, it is used suitably as a solar cell sealing material of a conventionally well-known solar cell module. As a method for producing the solar cell encapsulant of this embodiment, a commonly used method can be used, but it is preferably produced by melt blending with a kneader, a Banbury mixer, an extruder, or the like. In particular, the production with an extruder capable of continuous production is preferred.

  The solar cell encapsulant is also one of preferred embodiments in which the overall shape is a sheet. Moreover, the solar cell sealing material combined with the other layer which has at least one sheet | seat which consists of the above-mentioned solar cell sealing material can also be used suitably. The thickness of the solar cell encapsulant layer is usually 0.01 to 2 mm, preferably 0.05 to 1.5 mm, more preferably 0.1 to 1.2 mm, still more preferably 0.2 to 1 mm, particularly preferably. Is 0.3 to 0.9 mm, most preferably 0.3 to 0.8 mm. When the thickness is within this range, damage to the surface side transparent protective member, solar cell element, thin film electrode, etc. in the laminating step can be suppressed, and a high amount of photovoltaic power can be obtained by ensuring sufficient light transmittance. be able to. Furthermore, it is preferable because the solar cell module can be laminated at a low temperature.

  In the solar cell encapsulant of the present embodiment, the total light transmittance of the solar cell encapsulant in the wavelength region of 350 to 800 nm is preferably 85% or more, more preferably 88% or more, 90% or more is particularly preferable. When the total light transmittance is equal to or higher than the lower limit, the obtained solar cell module can obtain a higher amount of photovoltaic power generation.

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

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

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

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

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

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

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

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

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

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

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

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

  The solar cell encapsulant sheet may be composed of only a layer made of the solar cell encapsulant of the present embodiment, or a layer other than the layer containing the solar cell encapsulant (hereinafter “other layers”). May also be included). Examples of other layers include a hard coat layer, an adhesive layer, an antireflection layer, a gas barrier layer, and an antifouling layer for protecting the front or back surface, if classified for purposes. If classified by material, layer made of UV curable resin, layer made of thermosetting resin, layer made of polyolefin resin, layer made of carboxylic acid modified polyolefin resin, layer made of fluorine-containing resin, cyclic olefin (co) Examples thereof include a layer made of a polymer and a layer made of an inorganic compound.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  In the step (i), it is preferable to dispose the surface on which the uneven shape (embossed shape) of the solar cell sealing material is formed on the solar cell element side.

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

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

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

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

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

The solar cell encapsulant of the present embodiment is obtained by, for example, collecting 1 g of the encapsulant sheet sample from the solar cell module and calculating the gel fraction of the solar cell encapsulant sheet laminated under the above crosslinking conditions. Soxhlet extraction with toluene is performed for 10 hours, filtered through a 30 mesh stainless steel mesh, the mesh is dried under reduced pressure at 110 ° C. for 8 hours, and the method of calculating from the residual amount on the mesh is used, the gel fraction is It is in the range of 50 to 95%, preferably 50 to 90%, more preferably 60 to 90%, and most preferably 65 to 90%.
When the gel fraction is 50% or more, the heat resistance of the solar cell encapsulant becomes good, a constant temperature and humidity test at 85 ° C. × 85% RH, a high strength xenon irradiation test at a black panel temperature of 83 ° C., − Adhesiveness in a heat cycle test and a heat resistance test at 40 ° C. to 90 ° C. is improved. When the gel fraction is 95% or less, a solar cell sealing material having high flexibility is obtained, and temperature followability in a heat cycle test at −40 ° C. to 90 ° C. is improved, thereby preventing occurrence of peeling. be able to.

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

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

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

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

[density]
The density of the ethylene / α-olefin copolymer was measured according to ASTM D1505.

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

[BET specific surface area]
Measurement was performed by a gas phase adsorption method in which a gas molecule (nitrogen molecule) having a known occupation area was adsorbed on the surface of the silica powder, and the specific surface area was determined from the amount of adsorption of the gas molecule. As a measuring instrument, Shibata Science Opportunity Industries Co., Ltd. (SA1100) was used.

[Solid viscoelasticity in shear mode]
A press sheet sample having a thickness of 0.5 mm is subjected to a temperature increase rate of 0.016 Hz from 25 ° C. (room temperature) to 180 ° C. at a temperature increase rate of 3 ° C./min. Measured with The plate was a 20 mmφ portable parallel plate, and the strain was controlled at 0.01. The minimum complex viscosity and the temperature at the minimum complex viscosity were read from the measurement profile.

[Total light transmittance]
A white plate glass having no absorption region within a wavelength range of 350 to 800 nm is used, and an embossed sheet sample cut into a white plate glass size is composed of a white plate glass / embossed sheet sample / white plate glass, and a vacuum laminator (manufactured by NPC, LM -110X160S), placed on a hot plate adjusted to 150 ° C., decompressed for 3 minutes, heated for 15 minutes, and then crosslinked in an oven at 150 ° C. for 30 minutes to produce a laminate. Using the obtained laminate, a spectrophotometer (trade name “U-3010”) manufactured by Hitachi, Ltd., with an integrating sphere of φ150 mm attached, in the wavelength range of 350 to 800 nm in the laminate. The total light transmittance of the sheet sample was measured. Then, the total light transmittance (Tvis) of visible light was calculated by multiplying the measurement result by the standard light D65 and the standard luminous efficiency V (λ).

[Electrode displacement test]
The obtained embossed sheet sample was cut into the same white glass glass size (12.5 × 7.5 cm) as above, and three aluminum sheets each having a width of 1 cm, a length of 5 cm and a thickness of 0.2 mm were arranged in the long side direction. Are placed in a sheet sample, white glass / embossed sheet sample / aluminum sheet / embossed sheet sample / PET film, and prepared in a vacuum laminator (NPC, LM-110X160S), and the temperature is adjusted to 150 ° C. After being placed on a plate and decompressed for 3 minutes and heated for 15 minutes, it was crosslinked in an oven at 150 ° C. for 30 minutes to produce a laminate.
The deviation of the left and right aluminum sheets relative to the three central aluminum sheets in the obtained laminate was evaluated as follows. The evaluation is an average value of left and right deviations in five samples.
○: There is no deviation of the aluminum sheet Δ: The deviation of the aluminum sheet is 2 mm or less ×: The deviation of the aluminum sheet is over 2 mm

[Dirt of laminating equipment]
In the process of preparing the sample for measuring the total light transmittance, the stain on the glass-polytetrafluoroethylene (PTFE) sheet containing the glass mesh sandwiching the laminate was visually observed at the stage of lamination with the laminating apparatus.
○: No dirt △: There is a little dirt on the PTFE sheet with the lower glass mesh ×: The sealing material hangs on the PTFE sheet with the lower glass mesh, and there is a large dirt on the PTFE sheet with the glass mesh

[Oven dirt]
In the process of producing the sample for measuring the total light transmittance, the stain on the wire mesh of the oven on which the laminate was placed was visually observed at the stage where the laminated sample was crosslinked in the oven.
○: No dirt △: There is a little dirt on the wire mesh.

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

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

(Synthesis Example 3)
Bis (p-tolyl) methylene (cyclopentadienyl) (1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10 as the main catalyst A hexane solution of octahydrodibenz (b, h) -fluorenyl) zirconium dichloride is 0.003 mmol / hr, a toluene solution of methylaluminoxane as a cocatalyst is 3.0 mmol / hr, and a hexane solution of triisobutylaluminum is 0. Each was supplied at a rate of 6 mmol / hr; ethylene was supplied at a rate of 4.3 kg / hr; 1-octene was supplied at a rate of 6.4 kg / hr instead of 1-butene; 1-octene And dehydrated and purified normal so that the total of dehydrated and purified normal hexane used as a polymerization solvent and polymerization solvent is 20 L / hr. An ethylene / α-olefin copolymer was obtained in the same manner as in Synthesis Example 1, except that xylene was continuously supplied; hydrogen was supplied at a rate of 60 NL / hr; and the polymerization temperature was 130 ° C. It was. The yield was 4.3 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 4)
An ethylene / α-olefin copolymer was obtained in the same manner as in Synthesis Example 1 except that hydrogen was supplied at a rate of 4 NL / hr. The yield was 2.1 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 5)
An ethylene / α-olefin copolymer was obtained in the same manner as in Synthesis Example 1 except that hydrogen was supplied at a rate of 6 NL / hr. The yield was 2.1 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 6)
An ethylene / α-olefin copolymer was obtained in the same manner as in Synthesis Example 2 except that hydrogen was supplied at a rate of 90 NL / hr. The yield was 1.2 kg / hr. The physical properties are shown in Table 1.

(Synthesis Example 7)
Bis (p-tolyl) methylene (cyclopentadienyl) (1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10 as the main catalyst -Octahydrodibenz (b, h) -fluorenyl) zirconium dichloride in hexane solution at 0.004 mmol / hr, methylaluminoxane in toluene solution at 4.0 mmol / hr, and hydrogen at a rate of 70 NL / hr In the same manner as in Synthesis Example 3, an ethylene / α-olefin copolymer was obtained. The yield was 5.0 kg / hr. The physical properties are shown in Table 1.

(3) Production of solar cell encapsulant (sheet) (Example 1)
1.0 part by weight of t-butylperoxy-2-ethylhexyl carbonate having a 1-minute half-life temperature of 166 ° C. as an organic peroxide, based on 100 parts by weight of the ethylene / α-olefin copolymer of Synthesis Example 1, silica 2 parts by weight of hydrophilic fumed silica having a BET specific surface area of 380 m ² / g as powder 1, 0.5 parts by weight of 3-methacryloxypropyltrimethoxysilane as a silane coupling agent, and triallyl isocyanurate as a crosslinking aid 1.2 parts by weight, 0.4 part by weight of 2-hydroxy-4-normal-octyloxybenzophenone as an ultraviolet absorber, and bis (2,2,6,6-tetramethyl-4-piperidyl as a hindered amine light stabilizer ) 0.2 parts by weight of sebacate, octadecyl-3- (3,5-di) as a hindered phenol stabilizer -Tert-butyl-4-hydroxyphenyl) propionate 0.05 parts by weight and tris (2,4-di-tert-butylphenyl) phosphite 0.1 parts by weight as a phosphorus stabilizer were blended.
The obtained blend was kneaded at 100 ° C. and 30 rpm for 5 minutes using a small kneading apparatus (laboplast mill 4C150-01, manufactured by Toyo Seiki Seisakusho) with an internal volume of 60 cc. The kneaded sample was heated at 100 ° C. for 3 minutes and pressed at 10 MPaG for 2 minutes, and then cooled and pressed at 10 MPaG to obtain a press sheet having a thickness of 0.5 mm. Using the obtained press sheet, solid viscoelasticity measurement was performed in shear mode. The measurement results are shown in Table 2.

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

(Examples 2 to 7)
A press sheet and an embossed sheet (solar cell sealing material sheet) were obtained in the same manner as in Example 1 except that the composition shown in Table 2 was used. The void ratios of the obtained embossed sheets were all 28%. Table 2 shows various evaluation results of the obtained embossed sheet.

(Comparative Example 1)
Except for the formulation shown in Table 2, an embossed sheet (solar cell encapsulant sheet) was obtained in the same manner as in Example 1, but the torque of the extruder became too high, resulting in torque over. Thus, an embossed sheet could not be obtained.

(Comparative Example 2)
A press sheet and an embossed sheet (solar cell sealing material sheet) were obtained in the same manner as in Example 1 except that the composition shown in Table 2 was used. The void ratios of the obtained embossed sheets were all 28%. Table 2 shows various evaluation results of the obtained embossed sheet. However, gel was seen in the obtained embossed sheet.

(Comparative Examples 3-4)
A press sheet and an embossed sheet (solar cell sealing material sheet) were obtained in the same manner as in Example 1 except that the composition shown in Table 2 was used. The void ratios of the obtained embossed sheets were all 28%. Table 2 shows various evaluation results of the obtained embossed sheet.

Here, the following silica powders 1 to 3 in Table 2 were used.
Silica powder 1: hydrophilic fumed silica having a BET specific surface area of 380 m ² / g (AEROSIL 380, manufactured by EVONIK)
Silica powder 2: hydrophilic fumed silica having a BET specific surface area of 90 m ² / g (AEROSIL 90, manufactured by EVONIK)
Silica powder 3: hydrophilic fumed silica having a BET specific surface area of 200 m ² / g (AEROSIL 200, manufactured by EVONIK)

20 Solar cell module 22 Solar cell element 22A Light receiving surface 22B Back surface 24 Front side transparent protective member 26 Back surface side protective member 28 Sealing layer 29 Interconnector 32 Current collector 34A Tabbed bus 34B Tabbed bus 36 Conductive layer

Claims (17)

A solar cell encapsulant comprising an ethylene / α-olefin copolymer satisfying the following requirement a1) , an organic peroxide, and silica powder,
According to ASTM D1238, the MFR of the ethylene / α-olefin copolymer measured at 190 ° C. and a load of 2.16 kg is 10 to 50 g / 10 min.
The minimum viscosity of the complex viscosity (η *) of the solar cell encapsulant in the measurement of the solid viscoelasticity in a measurement temperature range of 25 to 180 ° C., a frequency of 0.016 Hz, a heating rate of 3 ° C./min, and a shear mode is 2. The solar cell sealing material which exists in the range of 0 * 10 < ³ > Pa * s-3.0 * 10 < ⁴ > Pa * s.
a1) The content rate of the structural unit derived from ethylene is 80-90 mol%, and the content rate of the structural unit derived from a C3-C20 alpha olefin is 10-20 mol%. The solar cell encapsulant according to claim 1, wherein the ethylene / α-olefin copolymer further satisfies the following requirements a 2 ) and a3) .
a 2) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a3) Shore A hardness measured according to ASTM D2240 is 60-85.   The solar cell sealing material according to claim 1 or 2, wherein the temperature of the minimum viscosity is 100 to 120 ° C.   The solar cell sealing material according to any one of claims 1 to 3, wherein the silica powder is hydrophilic silica. The solar cell sealing material as described in any one of Claims 1 thru | or 4 whose specific surface area measured by BET method of the said silica powder is 50-500 m < ² > / g.   The solar cell sealing material according to any one of claims 1 to 5, wherein the silica powder is non-porous silica.   The content of the silica powder in the solar cell encapsulant is 1.0 to 15.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to one item.   The solar cell sealing material as described in any one of Claims 1 thru | or 7 whose total light transmittance of the said solar cell sealing material in the wavelength range of 350-800 nm is 85% or more. The organic peroxide has a 1 minute half-life temperature of 100 to 170 ° C .;
The content of the organic peroxide in the solar cell encapsulant is 0.1 to 3 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to one item. Further comprising a silane coupling agent,
The content of the silane coupling agent in the solar cell encapsulant is 0.1 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to one item. Further comprising a hindered phenol stabilizer,
The content of the hindered phenol stabilizer in the solar cell encapsulant is 0.005 to 0.1 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material as described in any one of thru | or 10. Further comprising a hindered amine light stabilizer,
The content of the hindered amine light stabilizer in the solar cell encapsulant is 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. 11. The solar cell sealing material according to any one of 11 above. Further comprising a phosphorus stabilizer,
The content of the phosphorus stabilizer in the solar cell encapsulant is 0.005 to 0.5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material as described in any one. Further comprising a UV absorber,
The content of the ultraviolet absorber in the solar cell encapsulant is 0.005 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to Item. Further comprising a crosslinking aid,
The content of the crosslinking assistant in the solar cell encapsulant is 0.05 to 5 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin copolymer. The solar cell sealing material according to Item.   The solar cell sealing material according to any one of claims 1 to 15, which is in a sheet form. A surface-side transparent protective member;
A back side protection member;
A solar cell element;
It is a bridge | crosslinking body of the solar cell sealing material as described in any one of Claims 1 thru | or 16 , and seals the said solar cell element between the said surface side transparent protection member and the said back surface side protection member. A sealing layer;
Solar cell module with

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