WO2021192860A1 - Solar cell sealing material sheet and method for producing same - Google Patents

Abstract

The present invention provides: a solar cell sealing material sheet which is mainly composed of a polyolefin resin, and which enables a solar cell module that uses this solar cell sealing material sheet to be effectively suppressed in the formation of air bubbles or bulges at high temperatures; and a method for producing this solar cell sealing material sheet. The above are achieved by means of a method for producing a solar cell sealing material sheet, said method comprising: a step wherein crosslinkable resin pellets are produced by impregnating pellets, which are mainly composed of a polyolefin resin, with a crosslinking agent and a crosslinking assistant; a step wherein the crosslinkable resin pellets are fed into a cylinder through a supply port of an extrusion molding machine, and a resin composition containing the polyolefin resin, the crosslinking agent and the crosslinking assistant is melted and kneaded in the cylinder; and a step wherein the resin composition is extrusion molded into a sheet through a die of the extrusion molding machine. With respect to this method for producing a solar cell sealing material sheet, the crosslinking agent contains a compound that has two or more alkylperoxy groups represented by formula (1) in the structure; and the crosslinking assistant contains triallyl isocyanurate. (1): R1-OO- (In the formula, R1 represents an alkyl group having from 1 to 6 carbon atoms.)

Description

Solar cell encapsulant sheet and its manufacturing method

The present invention relates to a solar cell encapsulant sheet and a method for producing the same, and more specifically, to a solar cell encapsulant sheet and a method for producing the same, which maintains performance even at high temperatures and is excellent in productivity.

As global environmental problems and energy problems are becoming more serious, solar cells are attracting attention as a clean and non-depleting energy generation means. When the solar cell is used outdoors such as on the roof of a building, it is generally used in the form of a solar cell module.

The solar cell module is a solar cell element sealed with a solar cell encapsulant sheet and integrated with a protective sheet for the solar cell module as needed. For example, in order to obtain a crystalline solar cell module, first, a protective sheet for the solar cell module (transparent protective member on the surface side) / solar cell encapsulant sheet / crystalline solar cell element / solar cell encapsulant sheet / solar cell The protective sheets for modules (protective members on the back surface side) are laminated in this order to form a laminated body. Then, the obtained laminate is pressurized and heated to be integrated. After that, the solar cell module can be manufactured by cross-linking and curing the solar cell encapsulant.

As a material for the solar cell encapsulant sheet, a polyolefin resin such as an ethylene / α-olefin copolymer is preferably used from the viewpoint of transparency, insulation, flexibility, cost and the like.
A solar cell module using a solar cell encapsulant sheet containing a polyolefin resin as a main component may generate bubbles or swell when exposed to a high temperature, and the performance and appearance of the solar cell module. From the viewpoint of durability and the like, a solution has been sought.

Further, in the solar cell encapsulant sheet containing a polyolefin resin as a main component, additives such as a cross-linking agent and a cross-linking aid may segregate in the sheet, and the polyolefin resin may be impregnated in advance. May take a considerable amount of time, and solving these problems has become a technical issue. In order to solve this problem, in the step of melt-kneading the resin composition containing the polyolefin resin and the above additive in the extrusion molding machine, an injection nozzle provided between the supply port of the extrusion molding machine and the tip of the screw is provided. Therefore, it has been proposed to further add an additive (see, for example, Patent Document 1 and the like).
However, the provision of such direct-injection equipment is a factor of cost increase, and a polyolefin-based solar cell that can be manufactured in a relatively short time using a standard extrusion molding machine in which no direct-injection equipment is provided. A sealing material sheet has been sought.

International Publication No. 2013/161273 A1 Pamphlet

In view of the above requirements, the present invention is a solar cell encapsulant sheet containing a polyolefin resin as a main component, and can effectively suppress the generation and swelling of bubbles at a high temperature of a solar cell module using the sheet. An object of the present invention is to provide a capable solar cell encapsulant sheet and a method for producing the same.
Further, the present invention further aims to improve productivity, such as enabling production in a relatively short time using a standard extrusion molding machine.

As a result of diligent studies, the present inventor has found that the above problems can be solved by using a cross-linking agent having a specific chemical structure in combination with a specific cross-linking aid, and has completed the present invention. rice field.

That is, the first invention of the present application is
[1]
A step of producing a crosslinkable resin pellet by impregnating a pellet containing a polyolefin resin as a main component with a crosslinking agent and a crosslinking aid.
A step of putting the crosslinkable resin pellet into a cylinder from a supply port of an extrusion molding machine and melt-kneading the resin composition containing the polyolefin resin, the crosslinking agent, and the crosslinking aid in the cylinder.
A step of extruding the resin composition into a sheet from the die of the extrusion molding machine, and
It is a manufacturing method of a solar cell encapsulant sheet having
The cross-linking agent contains two or more compounds having an alkyl peroxy group represented by the following formula (1) in the structure, and R ^1- OO- (1).
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.),
The present production method, wherein the cross-linking aid comprises triallyl isocyanurate.

Hereinafter, [2] to [6] are each one of the preferred embodiments of the first invention of the present application.
[2]
The production method according to [1], wherein the time for performing the step of producing the crosslinkable resin pellet is 100 minutes or less.
[3]
The production according to [1] or [2], wherein the amount of the compound having 2 or more alkyl peroxy groups in the structure is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. Method.
[4]
A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or bonded via two or more carbon atoms. The production method according to any one of [1] to [3].
[5]
The production method according to any one of [1] to [4], wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate.
[6]
The production method according to any one of [1] to [5], wherein a solar cell encapsulant sheet having a gel fraction of 40% or more after encapsulation of the solar cell is produced.

That is, the second invention of the present application is
[7]
Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.), And a crosslinkable resin composition for a solar cell encapsulant, which comprises triallyl isocyanurate.

Hereinafter, [8] to [10] are each one of the preferred embodiments of the second invention of the present application.
[8]
The crosslinkable resin composition according to [7], wherein the compounding amount of the compound having two or more alkyl peroxy groups is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin.
[9]
A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or bonded via two or more carbon atoms. The crosslinkable resin composition according to [7] or [8].
[10]
The crosslinkable resin composition according to any one of [7] to [9], wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate.

That is, the third invention of the present application is
[11]
Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.), And a solar cell encapsulant sheet containing triallyl isocyanurate.
Regarding.

Hereinafter, [12] to [16] are each one of the preferred embodiments of the third invention of the present application.
[12]
The solar cell encapsulant sheet according to [11], wherein the compounding amount of the compound having two or more alkyl peroxy groups is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin.
[13]
A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or are bonded via two or more carbon atoms. The solar cell encapsulant sheet according to [11] or [12].
[14]
The solar cell encapsulant sheet according to any one of [11] to [13], wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate.
[15]
A solar cell module having a crosslinked cured product of the solar cell encapsulant sheet according to any one of [11] to [14].
[16]
A step of sealing a solar cell with the solar cell encapsulant sheet according to any one of [11] to [14], and a step of cross-linking and curing the solar cell encapsulant sheet.
A method for manufacturing a solar cell module.

According to the present invention, there is provided a high-quality polyolefin-based solar cell encapsulant sheet that can effectively suppress problems such as bubble generation and swelling even when used in a solar cell module at a high temperature. Further, since the solar cell encapsulant sheet of the present invention can be produced in a relatively short time using a standard extrusion molding machine, it has high practical value such as excellent cost and productivity.

It is a schematic diagram which shows an example of the manufacturing method of the 1st invention of this application. It is a schematic diagram which shows the manufacturing method of the prior art. It is a schematic diagram explaining the evaluation method of high temperature durability in one Example of this invention.

Hereinafter, modes for carrying out the present invention will be described.
The first invention of the present application is
A step of producing a crosslinkable resin pellet by impregnating a pellet containing a polyolefin resin as a main component with a crosslinking agent and a crosslinking aid.
A step of putting the crosslinkable resin pellet into a cylinder from a supply port of an extrusion molding machine and melt-kneading the resin composition containing the polyolefin resin, the crosslinking agent, and the crosslinking aid in the cylinder.
A step of extruding the resin composition into a sheet from the die of the extrusion molding machine, and
It is a manufacturing method of a solar cell encapsulant sheet having
The cross-linking agent contains two or more compounds having an alkyl peroxy group represented by the following formula (1) in the structure, and R ^1- OO- (1).
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.),
The above-mentioned production method, wherein the cross-linking aid contains triallyl isocyanurate.
That is, in the first invention of the present application, a solar cell encapsulant sheet is produced by using at least a polyolefin resin, a cross-linking agent containing a specific component, and a cross-linking aid containing a specific component. In the first invention of the present application, components other than the above-mentioned polyolefin resin, cross-linking agent, and cross-linking aid, for example, other additives can be used as optional components.
Hereinafter, each material used in the production method of the first invention of the present application will be described in detail.

Polyolefin-based resin The polyolefin-based resin used in the first invention of the present application may be a polymer having a structural unit derived from an olefin having 2 or more carbon atoms, and is not particularly limited, but as a preferable example thereof. , Low density ethylene resin, medium density ethylene resin, ultra low density ethylene resin, propylene (co) polymer, 1-butene (co) polymer, 4-methylpentene-1 (co) polymer, ethylene α-olefin copolymer, ethylene / cyclic olefin copolymer, ethylene / α-olefin / cyclic olefin copolymer, ethylene / α-olefin / non-conjugated polyene copolymer, ethylene / α-olefin / conjugated polyene copolymer Examples thereof include coalescence, ethylene / aromatic vinyl copolymer, ethylene / α-olefin / aromatic vinyl copolymer and the like.
These polyolefin-based resins may be used alone or in combination of two or more.

Polyolefin-based resins may or may not have structural units derived from vinyl acetate, but polyolefin-based resins that do not substantially have structural units derived from vinyl acetate are cross-linking agents and cross-linking aids. Since uniform impregnation of the agent has been relatively difficult in the past, applying the first invention of the present application to a polyolefin-based resin having substantially no structural unit derived from vinyl acetate has a particularly high technical value. Have.

Among the above-mentioned various polyolefin resins, an ethylene / α-olefin copolymer having a structural unit derived from ethylene and an α-olefin having 3 to 20 carbon atoms is required to have transparency and adhesiveness as a solar cell encapsulant. It is preferable because it has an excellent balance of various properties such as flexibility, heat resistance, appearance, cross-linking property, electrical property and extrusion moldability.

The melt flow rate (MFR) of the polyolefin resin used in the first invention of the present application is usually 0.1 g / 10 minutes or more and 50 g /, which is measured under the conditions of 190 ° C. and 2.16 kg load according to ASTM D1238. It is 10 minutes or less, preferably 2 g / 10 minutes or more and 40 g / 10 minutes or less, more preferably 2 g / 10 minutes or more and 30 g / 10 minutes or less, and further preferably 5 g / 10 minutes or more and 10 g / 10 minutes or less. Is. The MFR of the polyolefin resin can be adjusted by adjusting the polymerization temperature and the polymerization pressure at the time of the polymerization reaction, and the molar ratio of the monomer concentration such as ethylene and the hydrogen concentration in the polymerization system.

When the MFR is 0.1 g / 10 minutes or more and less than 10 g / 10 minutes, the sheet can be easily manufactured by calendar molding. When the MFR is 0.1 g / 10 minutes or more and less than 10 g / 10 minutes, the fluidity of the resin composition containing the ethylene / α-olefin copolymer is low, so that the melt that protrudes when laminating the sheet and the battery element It is preferable in that it can effectively prevent the laminating apparatus from being contaminated by the resin.

Further, when the MFR is 2 g / 10 minutes or more, preferably the MFR is 4 g / 10 minutes or more, and more preferably the MFR is 10 g / 10 minutes or more, the fluidity of the resin composition containing the ethylene / α-olefin copolymer Can be improved, and the productivity at the time of sheet extrusion molding can be improved.

Further, if unevenness is generated on the surface of the sheet, the adhesion between the sheet and the transparent protective member on the front surface side, the cell, the electrode, and the protective member on the back surface side deteriorates during the laminating process of the solar cell module, and the adhesion becomes insufficient, but MFR When the amount is 50 g / 10 minutes or less, the molecular weight becomes large, it becomes easy to form a sheet having a uniform thickness, and these problems can be suppressed more effectively. In addition, since adhesion of chill rolls and the like to the roll surface can be effectively suppressed, the need for a peeling step and the like is low, which can contribute to productivity improvement and cost reduction. Further, since the resin composition has a so-called "stiffness", a thick sheet having a thickness of 0.1 mm or more can be molded more easily. In addition, since the cross-linking characteristics of the solar cell module during laminating molding are improved, it is possible to sufficiently cross-link the solar cell module and more effectively suppress the decrease in heat resistance.
When the MFR is 27 g / 10 minutes or less, the drawdown during sheet molding can be effectively suppressed, a wide sheet can be molded, and the cross-linking characteristics and heat resistance are further improved, which is a particularly good solar cell. A sealing material sheet can be obtained.

The polyolefin resin used in the first invention of the present application preferably has a density measured in accordance with ASTM D1505 in the range of ^{0.865 to 0.884 g / cm 3.} The density of the polyolefin resin can be adjusted by the content ratio of the ethylene-derived constituent units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a polyolefin-based resin having a high density can be obtained. On the other hand, when the content ratio of the ethylene-derived structural unit is lowered, the crystallinity is lowered, and a polyolefin-based resin having a low density can be obtained.

When the density of the polyolefin resin is 0.884 g / cm ³ or less, the crystallinity is low and the transparency can be high. Further, extrusion molding at a low temperature becomes easy, and extrusion molding can be performed at, for example, 130 ° C. or lower. Therefore, even if the organic peroxide is kneaded into the polyolefin resin, it is possible to prevent the cross-linking reaction from proceeding in the extruder. Further, since the flexibility is high, it is possible to more effectively prevent the generation of cracks in the cells of the solar cell element and chipping of the thin film electrodes during the laminating molding of the solar cell module.

On the other hand, when the density of the polyolefin resin is 0.865 g / cm ³ or more, the crystallization rate of the polyolefin resin can be increased, so that the sheet extruded from the extruder is less sticky and peeled off by the first cooling roll. It becomes easy and the solar cell encapsulant sheet can be obtained with high productivity. In addition, since stickiness is less likely to occur on the sheet, it is possible to suppress the occurrence of blocking and improve the payability of the sheet. In addition, since it is sufficiently crosslinked, it is possible to effectively suppress a decrease in heat resistance.

The polyolefin resin used in the first invention of the present application has a shore A hardness of preferably 60 to 85, more preferably 62 to 83, still more preferably 62 to 80, as measured in accordance with ASTM D2240. , Particularly preferably 65-80. The Shore A hardness of the polyolefin resin can be adjusted by controlling the content ratio and density of ethylene units of the polyolefin resin within the above numerical range. That is, a polyolefin-based resin having a high content ratio of ethylene units and a high density has a high shore A hardness. On the other hand, a polyolefin-based resin having a low ethylene unit content and a low density has a low shore A hardness. The Shore A hardness is measured after 15 seconds or more have passed after the test piece sheet is loaded.

When the Shore A hardness is 60 or more, the polyolefin resin is less likely to become sticky and blocking can be suppressed. Further, when the solar cell encapsulant is processed into a sheet shape, the feeding property of the sheet can be improved, and the decrease in heat resistance can be suppressed.

On the other hand, when the Shore A hardness is 85 or less, the crystallinity is low and the transparency can be high. Further, since the flexibility is high, it is possible to prevent cracking of the cell, which is a solar cell element, and chipping of the thin film electrode during laminating molding of the solar cell module.

Ethylene / α-olefin copolymer The ethylene / α-olefin copolymer preferably used as a polyolefin resin has a structural unit derived from ethylene and a structural unit derived from α-olefin having 3 to 20 carbon atoms. Is preferable. Such an ethylene / α-olefin copolymer can be obtained, for example, by copolymerizing ethylene with an α-olefin having 3 to 20 carbon atoms. As the α-olefin, usually one type of α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more types. Of these, α-olefins having 10 or less carbon atoms are preferable, and α-olefins having 3 to 8 carbon atoms are particularly preferable.

Specific examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, and 4-methyl-1-. Examples thereof include penten, 1-octene, 1-decene, 1-dodecene and the like. Of these, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferable because of their availability. The ethylene / α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferable from the viewpoint of flexibility.

The proportion of the structural unit derived from the α-olefin having 3 to 20 carbon atoms (hereinafter, also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer used in the present embodiment is 10 to 20 mol%. Is preferable.
When the ratio of the α-olefin unit is 10 mol% or more, it is easy to obtain a sheet having high transparency. Further, extrusion molding at a low temperature can be easily performed, and for example, extrusion molding at 130 ° C. or lower is possible.
Therefore, even when the ethylene / α-olefin copolymer is impregnated with the cross-linking agent, it is possible to suppress the progress of the cross-linking reaction in the extruder. Further, since appropriate flexibility can be obtained, it is possible to effectively prevent cracking of the solar cell element and chipping of the thin film electrode during laminating molding of the solar cell module.

When the content ratio of the α-olefin unit is 20 mol% or less, the crystallization rate of the ethylene / α-olefin copolymer becomes appropriate, so that the sheet extruded from the extruder is not sticky and is used in the first cooling roll. The peeling is easy, and a sheet-shaped solar cell encapsulant can be obtained more efficiently. Further, since the sheet does not become sticky, blocking can be effectively prevented, and the sheet can be unwound well. In addition, it is possible to effectively prevent a decrease in heat resistance.

It is particularly preferable that the ethylene / α-olefin copolymer used in the present embodiment satisfies the following requirements a1 to a4.
a1) The content ratio of the structural unit derived from ethylene is 80 to 90 mol%, and the content ratio of the structural unit derived from α-olefin having 3 to 20 carbon atoms is 10 to 20 mol%.
a2) According to ASTM D1238, the MFR measured under the conditions of 190 ° C. and 2.16 kg load is 2 to 40 g / 10 minutes.
a3) The density measured according to ASTM D1505 is 0.865 to 0.884 g / cm ³ .
a4) Shore A hardness measured according to ASTM D2240 is 60-85.

Cross-linking agent The cross-linking agent used in the first invention of the present application is a compound having two or more alkyl peroxy groups represented by the following formula (1) in its structure (hereinafter, also referred to as "specific peroxide"). include.
R ¹ -OO- (1)
In the above formula (1), R ¹ represents an alkyl group having 1 to 6 carbon atoms.
By using the specific peroxide as at least a part of the cross-linking agent, the solar cell encapsulant sheet obtained by the production method of the first invention of the present application can effectively suppress the generation and swelling of bubbles at high temperature. .. In addition, since this cross-linking agent has excellent permeability to polyolefin-based resins, it is possible to manufacture a solar cell encapsulant sheet having good performance in a relatively short time using a standard extrusion molding machine, which improves productivity. It also contributes to cost reduction.

By cross-linking the polyolefin resin, a solar cell module having excellent heat resistance and adhesiveness can be obtained. When a silane coupling material is used, the polyolefin resin is graft-modified with the silane coupling agent by using a cross-linking agent together, so that the front surface side transparent protective member, the back surface side protective member, and the cell are used. , A solar cell encapsulant sheet having good adhesiveness to other members such as electrodes can be obtained.
The amount of the cross-linking agent used is not particularly limited and can be appropriately set according to various performances required for the solar cell encapsulant sheet and various conditions of the manufacturing process, but with a specific cross-linking aid described later. In the combination, it is preferable to use an amount such that the gel fraction after sealing the solar cell is 40% or more.
More specifically, from the viewpoint of sufficient cross-linking, it is preferable that the specific peroxide is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. The amount of the specific peroxide used is more preferably 0.4 to 3.0 parts by mass and particularly preferably 0.4 to 1.5 parts by mass with respect to 100 parts by mass of the polyolefin resin. ..
When the content of the cross-linking agent is not more than the above lower limit value, the deterioration of the cross-linking property of the sealing sheet is suppressed, the graft reaction of the silane coupling agent to the main chain of the cross-linking resin described later is improved, and the heat resistance is improved. , The decrease in adhesiveness can be suppressed. Further, when the content of the cross-linking agent is not more than the above upper limit value, the amount of decomposition products of the cross-linking agent generated is further reduced, and it is possible to more reliably suppress the generation of bubbles in the sealing sheet. ..

R ¹ -OO- (1)
Among the alkyl peroxy groups represented by the formula (1) of 2 or more possessed by the specific peroxide, R ¹ is an alkyl group having 1 to 6 carbon atoms, and there are no other restrictions, but the carbon atoms are 3 to 3 to 6. It is preferably an alkyl group of 6.
R ¹ may be linear or branched, but it is preferably a bulky group from the viewpoint of stability of the specific peroxide, and therefore it is often preferable that it is branched. .. A particularly preferred example is the t-butyl group.

The specific peroxide may have two or more alkylperoxy groups represented by the following formula (1), and there are no other restrictions on the chemical structure, but two or more alkylperoxy groups. However, it is preferable to have a structure in which the same carbon atom is bonded or is bonded via two or more carbon atoms.

The carbon atom in a specific peroxide in which two or more alkylperoxy groups are bonded to the same carbon atom is not particularly limited, but a cycloalkane having 1 to 18 carbon atoms, a chain alkane, or an ester can be used. It is preferably one of the constituent carbon atoms. Suitable examples of such specific peroxides are 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t-butylperoxy) butane, n-butyl-4,4-di. (T-Butylperoxy) Valerate, etc. can be mentioned.

The structure of a specific peroxide in which two or more alkyl peroxy groups are bonded via two or more carbon atoms and having the two or more carbon atoms is not limited, but is preferably an alkylene group. The alkylene group in this case is not particularly limited, but is preferably a linear or branched alkylene group having 1 to 18 carbon atoms. Further, instead of the alkylene group, a structure in which a part of the structure of the alkylene group is substituted with a structure containing an aromatic ring or a triple bond may be used.
Suitable examples of such specific peroxides are 2,5-dimethyl2,5-di (t-butylperoxy) hexane, 2,5-dimethyl2.5-di (t-butylperoxy) hexyne. -3, etc. can be mentioned.

The 1-minute half-life temperature of the specific peroxide is preferably 140 to 200 ° C. from the viewpoint of the balance between the productivity in the extrusion sheet molding and the cross-linking speed at the time of laminating the solar cell module.
When the one-minute half-life temperature of the specific peroxide is 140 ° C. or higher, it is possible to effectively suppress the progress of the cross-linking reaction of the solar cell encapsulant during extrusion sheet molding. When the one-minute half-life temperature of the organic peroxide is 200 ° C. or less, the cross-linking speed at the time of laminating the solar cell module becomes sufficient, so that the productivity of the solar cell module can be improved. can. In addition, it becomes easy to secure the heat resistance and adhesiveness of the solar cell encapsulant.

These specific peroxides may be used alone or in combination of two or more. Further, only the specific peroxide may be used as the cross-linking agent, or the specific peroxide may be used in combination with another cross-linking agent. When the specific peroxide is used in combination with another cross-linking agent, the ratio of the specific peroxide in the total cross-linking agent is preferably 80% by mass or more, and particularly preferably 90% by mass or more. The type of other cross-linking agent is not particularly limited, but a peroxide that does not correspond to a specific peroxide is preferable.

Cross-linking aid In the first invention of the present application, in order to promote the cross-linking reaction and increase the degree of cross-linking of the polyolefin-based resin, the pellet containing the polyolefin-based resin as a main component is impregnated with the cross-linking aid.
The cross-linking aid used in the first invention of the present application contains triallyl isocyanurate. Triallyl isocyanurate can sufficiently cross-link a polyolefin resin in a relatively small amount in combination with a cross-linking agent containing a specific peroxide, so that productivity and quality of the produced solar cell encapsulant sheet can be obtained. Can be compatible at a high level.
In the present invention, only triallyl isocyanurate may be used as a cross-linking aid, or triallyl isocyanurate may be used in combination with another cross-linking aid. When triallyl isocyanurate is used in combination with other cross-linking aids, the proportion of triallyl isocyanurate in the total cross-linking aid is preferably 50% by mass or more, particularly preferably 80% by mass or more. ..
The type of the other cross-linking aid is not particularly limited, but a conventionally used compound having two or more double bonds in the molecule can be preferably used. It is more preferable that the compound has three or more double bonds in the molecule.

The amount of triallyl isocyanurate used can be appropriately set according to various performances required for the solar cell encapsulant sheet and various conditions of the manufacturing process, but in combination with a specific cross-linking agent, the solar cell seal is used. It is preferable to use an amount such that the gel fraction after stopping is 40% or more. More specifically, it is more preferably 0.1 to 1.0 parts by mass, and particularly preferably 0.1 to 0.4 parts by mass with respect to 100 parts by mass of the polyolefin resin.
By setting the amount of triallyl isocyanurate to be within the above range, impregnation can be performed relatively easily and in a short time. As a result, a solar cell encapsulant having an appropriate crosslinked structure as well as excellent productivity can be obtained, and the heat resistance, mechanical properties, and adhesiveness of the solar cell encapsulant can be improved. ..

Other Additives In the method for producing a solar cell encapsulant sheet of the first invention of the present invention, in addition to the above-mentioned cross-linking agent and cross-linking aid, various other additives are appropriately used as long as the object of the present invention is not impaired. can do. For example, silane coupling materials, UV absorbers, light stabilizers, antioxidants, various resins other than polyolefin resins, various rubbers, plasticizers, fillers, pigments, dyes, antioxidants, antistatic agents, antibacterial agents. One or more additives selected from agents, antifungal agents, flame retardants, light diffusers, discoloration inhibitors, dispersants and the like can be appropriately added.

The use of a silane coupling agent is useful for improving the adhesiveness to substrates, protective sheets, solar cell elements, and the like. For example, a compound having a hydrolyzable group such as an alkoxy group as well as an amino group or an epoxy group can be mentioned. Specifically, vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tris (β-methoxyethoxysilane), γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane. Etc. can be used. Preferred examples thereof include γ-glycidoxypropylmethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriethoxysilane, which have good adhesiveness. These silane coupling agents may be used alone or in combination of two or more.

The amount of the silane coupling agent added varies depending on the type of the silane coupling agent, but is preferably 0.1 to 4 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the polyolefin resin. Is more preferable. When it is at least the above lower limit value, the adhesiveness of the solar cell encapsulant sheet is excellent. Further, when it is not more than the above upper limit value, the balance between the cost and the performance of the solar cell encapsulant sheet is excellent.

Examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4-carboxybenzophenone, Benzophenones such as 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy-5-methylphenyl) benzo Benzophenorizoles such as triazole; salicylate esters such as phenylsulfate and p-octylphenylsulfylate can be mentioned as preferred examples. These ultraviolet absorbers may be used alone or in combination of two or more.

The amount of the ultraviolet absorber added varies depending on the type of the ultraviolet absorber, but is preferably 0.005 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. When the amount of the ultraviolet absorber added is within the above range, the effect of improving the weather resistance stability is sufficiently ensured, and the transparency of the solar cell encapsulant, the front side transparent protective member, the back surface side protective member, and the cell , It is preferable because it can prevent deterioration of adhesiveness with electrodes and aluminum.

Examples of the photostabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate and 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 amine type compounds, hindered piperidine type compounds and the like are preferably used. These light stabilizers may be used alone or in combination of two or more.

The amount of the light stabilizer added varies depending on the type of the light stabilizer, but is preferably 0.005 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. When the amount of the light stabilizer added is within the above range, the effect of improving the weather resistance stability is sufficiently ensured, and the transparency of the solar cell encapsulant, the front side transparent protective member, the back surface side protective member, It is preferable because it can prevent a decrease in adhesiveness to cells, electrodes, and aluminum.

Specific examples of the heat-resistant stabilizer include tris (2,4-di-tert-butylphenyl) phosphite and bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester. Hypophosphate, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diylbisphosphonite, and bis (2,4-di-tert-butylphenyl) Phenyl heat stabilizers such as pentaerythritol diphosphite; lactone heat stabilizers such as reaction products of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene; 3,3', 3 ", 5,5', 5" -hexa-tert-butyl-a, a', a "-(methylene-2,4,6-triyl) tri-p-cresol, 1,3 , 5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-) Hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Phenyl-based heat-resistant stabilizers such as propionate; sulfur-based heat-resistant stabilizers; amine-based heat-resistant stabilizers can be mentioned as preferable examples. Among these, phosphite-type heat-resistant stabilizers and hindered phenol-type heat-resistant agents can be mentioned. Stabilizers are preferable. These heat-resistant stabilizers may be used alone or in combination of two or more.

The amount of the heat-resistant stabilizer added varies depending on the type of the heat-resistant stabilizer, but is preferably 0.005 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. When the amount of the heat-resistant stabilizer added is within the above range, the effects of improving resistance to high temperature and humidity, heat cycle resistance and heat-resistant stability are sufficiently ensured, and the transparency of the solar cell encapsulant is increased. It is possible to prevent deterioration of the adhesiveness with the front surface side transparent protective member, the back surface side protective member, the cell, the electrode, and aluminum.

Impregnation Step In the method for producing a solar cell encapsulant sheet of the first invention of the present application, in one step, a crosslinkable resin pellet is formed by impregnating a pellet containing a polyolefin resin as a main component with a crosslinking agent and a crosslinking aid. To make.
Here, the shape and size of the pellets are not particularly limited, and the shapes and sizes conventionally used in the art may be appropriately adopted, but the average particle size of the pellets is in the range of 0.2 to 10 mm. It is preferable to have. When the average particle size of the pellets is within the above range, it is preferable because the balance between the stirring property of the pellets mainly composed of the polyolefin resin described later and the impregnation time of the additive into the pellets is excellent.

Having a polyolefin-based resin as a main component means that the polyolefin-based resin is a component having the maximum amount among the constituent components of the pellet. The polyolefin-based resin preferably constitutes 90% by mass or more of the pellets, and particularly preferably 99% by mass or more.
The method for producing pellets containing a polyolefin resin as a main component is not particularly limited, but for example, the polyolefin resin is melt-kneaded by a uniaxial or biaxial extrusion molding machine and extruded into a strand or a sheet, and a pelletizer is used. , A method obtained by cutting into pellets so as to have a predetermined particle size and the like. The pellet may contain additives other than the above-mentioned cross-linking agent and cross-linking aid as appropriate as long as the object of the present invention is not impaired.

Including in the immersion step, the pellets composed mainly of polyolefin resin, may be separately including immersion a crosslinking agent and crosslinking aid, uniform both in production efficiency and crosslinking agent and a crosslinking aid from the viewpoint of containing immersion, a crosslinking agent and a crosslinking aid were mixed, it is preferred to impregnate them.
Triallyl isocyanurate, which is used as at least a part of the cross-linking agent, has a melting point near room temperature, and many of the specific peroxides used as at least a part of the cross-linking agent are liquid or highly concentrated at room temperature. Since it is supplied in the form of a hydrocarbon solution of, it is often possible to mix a cross-linking agent and a cross-linking aid to form a liquid, and the liquid is prepared in advance in this way, and this is mainly composed of a polyolefin resin. it is preferable to containing immersed into pellets. When the cross-linking agent and / or the cross-linking aid is a solid, a diluting solvent may be appropriately added in order to improve the solubility or dispersibility of the solid component.
The liquid for including immersion, the additives other than crosslinking agent and crosslinking aid in advance may be added. When the additive other than the cross-linking agent and the cross-linking aid is a solid, a diluting solvent may be appropriately added in order to improve the solubility or dispersibility of such a solid additive.

At this time, the method for dissolving or dispersing the solid component and the solid additive is not particularly limited. , And / or other additives are added, and solid cross-linking agents, cross-linking aids and / or other additives are added thereto and mixed by stirring to obtain a cross-linking agent, a cross-linking aid, and a desired one. Can prepare a liquid containing other additives.

The temperature for stirring and mixing is not particularly limited, but may be room temperature or may be heated to about 30 to 50 ° C. in order to improve stirring efficiency. When it is at least the above lower limit value, the dissolution or dispersion rate of the solid additive can be improved, so that the productivity of the solar cell encapsulant sheet can be improved. Further, when it is not more than the above upper limit value, deterioration of the additive can be suppressed.
The time for stirring and mixing is not particularly limited, but it is preferable to carry out until the solid components are visually and uniformly dissolved or dispersed.
Here, as the components that are liquid at room temperature, many of the cross-linking agents, cross-linking aids, silane coupling agents, and the like are liquid at room temperature. On the other hand, many ultraviolet absorbers, heat-resistant stabilizers, light stabilizers and the like are solid at room temperature.

The following method can be exemplified as a specific method for impregnating pellets containing a polyolefin resin as a main component with a cross-linking agent and a cross-linking aid.
First, pellets containing a polyolefin-based resin as a main component and a liquid containing a cross-linking agent and a cross-linking aid are supplied to, for example, a stirring mixer such as a Henschel mixer, a tumbler mixer, a super mixer, or a rotary mixer.
Next, the stirring mixer is stirred to bring the pellet mainly composed of a polyolefin resin into contact with the liquid, and the pellet is impregnated with the liquid to prepare a crosslinkable resin pellet. It is preferable to supply the whole amount of the pellets containing the polyolefin resin as the main component before rotating the stirring mixer. On the other hand, the liquid containing the cross-linking agent and the cross-linking aid may be supplied in its entirety before the stirring mixer is rotated, or may be supplied in divided amounts. From the viewpoint of more uniformly impregnating the pellets, it is preferable to supply the pellets in a divided manner in a stirring mixer. From the viewpoint of shortening the production time, it is preferable to supply the entire amount.
The motor power value of the stirring mixer at the time of stirring and mixing and the motor integrated power value of the stirring mixer at the time of stirring and mixing can be determined according to the impregnation speed and the processing amount of the cross-linking agent, the cross-linking aid, etc. It is a matter.

The temperature of the pellets when the pellets containing the polyolefin resin as the main component are impregnated with the cross-linking agent and the cross-linking aid is not particularly limited, and may be room temperature, or may be added to about 30 to 50 ° C. to increase the impregnation rate. It doesn't matter if you warm it. When it is at least the above lower limit value, the impregnation rate of the solution containing the additive into the pellets can be improved, so that the productivity of the solar cell encapsulant sheet can be improved. Further, when it is not more than the above upper limit value, deterioration of the cross-linking agent, the cross-linking aid and the like can be further suppressed. Further, it is possible to further suppress the fusion of pellets and the fusion of pellets to the stirring mixer. Here, the temperature of the pellet refers to the surface temperature of the pellet.

The time for impregnating the pellet containing the polyolefin resin as the main component with the cross-linking agent and the cross-linking aid, that is, the time for carrying out the step of preparing the cross-linkable pellet is preferably short from the viewpoint of productivity, and therefore is 100 minutes or less. Is preferable, and 60 minutes or less is particularly preferable. Since the present application In the first invention, a high free immersion of the polyolefin resin crosslinking agent and a crosslinking aid into pellets mainly, also in this embodiment, to reduce the time required for impregnation, increase productivity can do. Further, this makes it possible to further suppress the deactivation of the cross-linking agent, the cross-linking aid, other additives and the like.
In this embodiment, whether or not the pellets have been impregnated with the cross-linking agent and the cross-linking aid can be confirmed by the motor power value of the stirring mixer. When the impregnation is completed, the moistness of the pellets disappears, so that the power value of the motor rises sharply.

According to the method for producing a solar cell encapsulant sheet in the present embodiment, the cross-linking agent, the cross-linking aid, etc. are deteriorated by impregnating the pellet containing the polyolefin resin as the main component with the cross-linking agent, the cross-linking aid, etc. in advance. It is possible to uniformly distribute the cross-linking agent, the cross-linking aid, and the like inside the pellet while suppressing the above. Therefore, it is possible to stably obtain a solar cell encapsulant sheet in which the cross-linking agent, the cross-linking aid and the like are uniformly dispersed in the sheet.
The combination of specific crosslinking agent and a specific crosslinking aid used in the present first invention is excellent in containing immersion resistance, since a relatively short time can be uniformly contains immersion into pellets composed mainly of polyolefin resin The production method of the first invention of the present application can produce a high-quality solar cell encapsulant sheet with high productivity.

Melt-kneading step Next, the crosslinkable resin pellets obtained in the kneading step are put into a cylinder from a supply port of an extrusion molding machine, and the polyolefin resin, the cross-linking agent, and the cross-linking aid are introduced in the cylinder. The resin composition containing the above is melt-kneaded.
The process is schematically shown in FIG. Reference numeral 100 in FIG. 1 is an extrusion molding machine.
Examples of the extruder 100 in the present embodiment include various known twin-screw extruders and single-screw extruders. As the extrusion molding machine, a twin-screw extrusion molding machine is preferable because it has excellent kneading performance.

As shown in FIG. 1, in the extrusion molding machine 100, for example, a supply port 101 capable of charging the crosslinkable resin pellets obtained in the kneading step into the cylinder 103 is arranged in the uppermost stream portion, and a screw 105 is arranged in the cylinder 103. A die 109 such as a T die or a ring die is provided at the most downstream tip portion.
First, the crosslinkable resin pellets are charged into the cylinder 103 from the supply port 101. Next, the crosslinkable resin pellets charged into the cylinder 103 are heated and melted by a heater arranged outside the cylinder 103, and melt-kneaded by a rotating screw 105.

In the prior art, since the free immersion of the polyolefin resin crosslinking agent and crosslinking aid is not necessarily sufficient, as shown in FIG. 2, during the period from the supply port 101 to the tip of the screw 105, cross An injection nozzle 107 capable of injecting the agent and / or the cross-linking aid was provided. The cross-linking agent and / or the cross-linking aid was supplied from the container 201 to the injection nozzle 107 by using the supply pump 203, for example.
The injection nozzle 107 is not provided in a standard extrusion molding machine, and the provision of the injection nozzle 107 causes a significant increase in cost. In addition, installing the container 201, the supply pump 203, and the piping thereof also causes an increase in cost.
Present in the first invention, is excellent in containing immersion of the polyolefin resin crosslinking agent and a crosslinking aid, without the need for the injection nozzle 107 or the like, carrying out the kneading step using a standard extruder This is possible and can greatly contribute to the reduction of production costs.

Extrusion molding process In the first invention of the present application, a resin composition containing a polyolefin resin, a cross-linking agent, and a cross-linking aid obtained in the melt-kneading step is extruded into a sheet from a die of an extrusion molding machine.
In the extrusion molding step of the embodiment shown in FIG. 1, the resin composition is extruded into a sheet from the die 109 of the extrusion molding machine 100 as shown below.

While the resin composition is melt-kneaded from the supply port 101, it is extruded into a sheet from a die 109 such as a T die attached to the tip of the extrusion molding machine 100 to obtain a solar cell encapsulant sheet.
The extrusion temperature is not particularly limited, but it is preferable that the cross-linking agent used is melt-kneaded at a temperature lower than the one-hour half-life temperature and extruded into a sheet. By doing so, the deactivation of the cross-linking agent can be suppressed.
Specifically, the extrusion temperature (cylinder temperature) is preferably 70 to 130 ° C. By setting the extrusion temperature to the above lower limit value or more, the productivity of the solar cell encapsulant can be improved. Further, by setting the extrusion temperature to the above upper limit value or less, deterioration of the additive can be suppressed. In addition, gelation of the solar cell encapsulant can be suppressed.

As described above, in the method for manufacturing the solar cell encapsulant sheet in the present embodiment, the additive passes through the extrusion molding machine 100 only once. Therefore, it is possible to suppress deactivation of various additives due to heating in the extruder 100 and frictional heat with the screw blades, and it is possible to stably produce a high-quality solar cell encapsulant sheet. ..

In addition, in order to improve the degassing property, the surface of the sheet may be embossed after being extruded into a sheet shape.
The method of embossing the surface of the sheet is not particularly limited, but the sheet extruded from the T-die is divided into an embossed roll having an embossed pattern on the surface and a rubber roll arranged to face the embossed roll. A method of embossing the surface of the sheet while supplying the material between the two and pressing the embossing roll against the molten sheet can be mentioned. The obtained sheet may be heated again to be melted and embossed.

It is preferable from the viewpoint of productivity that the solar cell encapsulant sheet extruded from the T-die or the like is cooled and solidified with a cooling roll while maintaining a uniform thickness, and then wound up by the winder 205. The line speed at this time is preferably high in consideration of productivity, for example, preferably 0.5 m / min or more, and more preferably 1 m / min or more.
In the present embodiment, the obtained solar cell encapsulant sheet is in a single-wafer type cut according to the size of the solar cell module, or in a roll type that can be cut according to the size immediately before manufacturing the solar cell module. Can be used.

Crosslinkable resin composition The second invention of the present application is
Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.), And a crosslinkable resin composition for a solar cell encapsulant containing triallyl isocyanurate.

The crosslinkable resin composition of the second invention of the present application contains a compound having two or more alkyl peroxy groups represented by the formula (1) in a structure that functions as a crosslinking agent, and triallyl isocyanurate that functions as a crosslinking aid. in combination, in polyolefin resin with, uniform, and were free immersion in an amount sufficient to make a good crosslinking, a high quality crosslinkable resin composition, the solar cell encapsulant applications It can be preferably used. The solar cell module formed by using the crosslinkable resin composition of the second invention of the present application effectively suppresses problems such as generation of bubbles and swelling even when used at a high temperature.
Further, the crosslinkable resin composition of the second invention of the present application contains a compound having two or more alkyl peroxy groups represented by the formula (1) in a structure that functions as a crosslinking agent, and a triallyl that functions as a crosslinking aid. the combination of isocyanurate, since it is easy to uniformly and sufficiently Ryo含immersion in the polyolefin-based resin, excellent in productivity, by using an extruder which is usually used one relatively short period of time in the manufacturing can.

The polyolefin resin constituting the crosslinkable resin composition of the second invention of the present application, the compound having two or more alkyl peroxy groups represented by the formula (1) in the structure, the details of triallyl isocyanurate, and the details thereof. The preferred embodiment is similar to that described above with respect to the first invention of the present application.
The crosslinkable resin composition of the second invention of the present application contains a polyolefin resin, a compound having two or more alkyl peroxy groups represented by the formula (1) in its structure, and components other than triallyl isocyanurate. Also, the details and preferred forms of these components are similar to those described above with respect to the first invention of the present application.
The preferred composition of the crosslinkable resin composition of the second invention of the present application, that is, a polyolefin resin, a compound having two or more alkylperoxy groups represented by the formula (1) in the structure, and triallyl isocyanurate, and desired. The preferable usage ratio of the other components used in the above is also the same as that described above with respect to the first invention of the present application.

The method for producing the crosslinkable resin composition of the second invention of the present application is not particularly limited, but it is preferably produced by the production method of the first invention of the present application, and up to the melt-kneading step of the first invention of the present application. It is also preferable that it is manufactured in.
The shape of the crosslinkable resin composition of the second invention of the present application is not particularly limited, but it is preferably in the form of pellets or sheets. In the case of a sheet, the crosslinkable resin composition of the second invention of the present application may at the same time correspond to the solar cell encapsulant sheet of the third invention of the present application.

Solar cell encapsulant sheet The third invention of the present application is
Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms), and a solar cell encapsulant sheet containing triallyl isocyanurate.

The solar cell encapsulant sheet of the third invention of the present application contains a compound having two or more alkyl peroxy groups represented by the formula (1) in a structure that functions as a cross-linking agent, and triallyl isothia that functions as a cross-linking aid. combination with isocyanurate is present in the polyolefin resin, uniformly, and was free immersion in an amount sufficient to make a good crosslinking, a high-quality solar cell encapsulant sheets, sealing the solar cell element It can be suitably used to stop and form a solar cell module.
The solar cell module formed by using the solar cell encapsulant sheet of the third invention of the present application effectively suppresses problems such as generation of bubbles and swelling even when used at a high temperature.
Further, the solar cell encapsulant sheet of the third invention of the present application contains a compound having two or more alkyl peroxy groups represented by the formula (1) in a structure that functions as a cross-linking agent, and a tri that functions as a cross-linking aid. a combination of triallyl isocyanurate, since it is easy to uniformly and sufficiently Ryo含immersion in the polyolefin-based resin, excellent in productivity, by using an extruder which is usually used one relatively short time Can be manufactured.

The polyolefin resin constituting the solar cell encapsulant sheet of the third invention of the present application, the compound having two or more alkyl peroxy groups represented by the formula (1) in the structure, and the details of triallyl isocyanurate, and The preferred form is the same as that described above with respect to the first invention of the present application.
The solar cell encapsulant sheet of the third invention of the present application contains a polyolefin resin, a compound having two or more alkyl peroxy groups represented by the formula (1) in the structure, and a component other than triallyl isocyanurate. The details and preferred forms of these components may be the same as those described above with respect to the first invention of the present application.
The preferred composition of the solar cell encapsulant sheet of the third invention of the present application, that is, a polyolefin resin, a compound having two or more alkyl peroxy groups represented by the formula (1) in the structure, and triallyl isocyanurate, and The preferred ratio of other components used as desired is also the same as that described above with respect to the first invention of the present application.

The method for producing the solar cell encapsulant sheet of the third invention of the present application is not particularly limited, but it is preferably produced by the production method of the first invention of the present application.
The solar cell encapsulant sheet of the third invention of the present application preferably comprises the crosslinkable resin composition of the second invention of the present application, or contains the crosslinkable resin composition of the second invention of the present application.

The thickness of the solar cell encapsulant sheet of the third invention of the present application is not particularly limited, but is usually 0.01 to 2 mm, preferably 0.1 to 1.2 mm, and more preferably 0.2 to 0.9 mm. .. When the thickness is within this range, damage to the glass, the solar cell element, the thin film electrode, etc. in the laminating step can be suppressed, and a high amount of photovoltaic power generation can be obtained by ensuring sufficient light transmittance. Furthermore, it is preferable because the solar cell module can be laminated and molded at a relatively low temperature.

As a method for manufacturing a solar cell module using the solar cell encapsulant sheet of the third invention of the present application, for example, the following is preferable.
A laminated body in which a solar cell is sandwiched is formed by a solar cell encapsulant sheet, and the laminated body is heated at 140 ° C. or higher and 200 ° C. or lower for 3 to 30 minutes while being 0.4 atm or more and 1 atm or less. A sealing step is carried out in which pressure is applied to the laminate with the press pressure of the above to integrate the laminate.

In the sealing step, the polyolefin resin constituting the solar cell sealing material sheet is crosslinked and cured. That is, in the solar cell module manufactured in the above step, the solar cell encapsulant sheet is a cross-linked cured product, and the degree of cross-linking is different from that of the solar cell encapsulant sheet before the above step, and the cross-linking agent. , All or part of the cross-linking aid is consumed.
The degree of cross-linking can be evaluated by the gel fraction, and more specifically, it can be evaluated by, for example, the method described in Examples of the present application.
The gel fraction is preferably 40% by mass or more, more preferably 45% by mass or more, and particularly preferably 50% by mass or more with respect to the mass of the solar cell encapsulant sheet.

The laminate includes, for example, a front surface side transparent protective member (eg, a glass plate), a first solar cell encapsulant sheet, a solar cell, a second solar cell encapsulant sheet, and a back surface side protective member ( Example: A back sheet in which various films are laminated) may be laminated in this order. Details of the configurations of the front surface side transparent protective member, the solar cell, and the back surface side protective member are widely known to those skilled in the art.

The solar cell module manufactured by using the solar cell encapsulant sheet of the third invention of the present application can be manufactured at low cost and high productivity while effectively suppressing problems such as air bubbles and swelling at high temperature. Since it can be used, it can be used in a wide range of applications. For example, it can be applied to various applications regardless of indoors or outdoors, such as small solar cells typified by mobile devices and large solar cells installed on roofs and roofs.

Hereinafter, the present invention will be specifically described with reference to Examples / Comparative Examples. The present invention is not limited to the following examples in any sense.

In the following Examples / Comparative Examples, each characteristic was evaluated by the following method.
(1) Impregnation time In a glass bottle, 1 kg of polyolefin resin and a predetermined amount of a liquid additive mixture containing a cross-linking agent, a cross-linking aid and other additives prepared by the method shown below are placed. A plate mix mill (PMM-20, manufactured by NS Koken Co., Ltd.) was used in an oven heated to 45 ° C. (PHH-401, manufactured by Espec Co., Ltd.) to rotate the glass bottle at about 170 rpm for impregnation.
The glass bottle was taken out from the oven at regular intervals and the state of the resin was observed. When it was confirmed that the surface of the resin and the wall surface of the bottle were not wet, it was judged that the impregnation was completed, and the time required until then was defined as the impregnation time.
(2) Gel fraction A sealing material sheet having a thickness of 400 μm × 100 mm square is sandwiched between two PET films having a thickness of 50 μm × 220 mm square, and this is placed on a glass plate having a thickness of 3.2 mm × 250 mm square to form a laminator. Using (LM-110 x 160, manufactured by NPC Co., Ltd.), the encapsulant sheet is first held at 160 ° C. in a vacuum for 3 minutes and then heated and pressurized at a pressure of about 1 atm for a predetermined time. Was crosslinked and cured.
Approximately 1 g of a sample was weighed from the cross-linked and cured encapsulant described above, and the weight thereof was weighed with an accuracy of four digits (this was designated as the initial weight A).
The sample was placed in a heat-resistant bottle together with 100 ml of xylene, held in an oven heated to 110 ° C. for 12 hours or more, filtered through a 30-mesh metal filter, and the sample remaining on the filter was transferred to a metal petri dish. The sample after filtration on a metal petri dish was dried at 110 ° C. for 8 hours or more, and the weight of the sample after removing xylene was weighed (this was defined as the weight B after drying).
From the initial weight A and the weight after drying B, the gel fraction (%) was calculated according to the following formula.
Gel fraction (%) = (weight after drying B (g) / initial weight A (g)) x 100
(3) High temperature durability As shown in FIG. 3, a glass plate 31 having a thickness of 3.2 mm × 75 mm × 120 mm, a sealing material sheet 32 having a thickness of 400 μm × 75 mm × 120 mm, and an aluminum plate 33 having a thickness of 300 μm × 50 mm square (sun). Cell stop tape 35 (adhesive tape cut to width 9 mm x length 25 mm), and back sheet 34 with thickness 100 μm x 75 mm x 120 mm (manufactured by MA Packaging Co., Ltd., model name:) Using PPN75S), the glass plate 31 / sealing material sheet 32 / aluminum plate 33 / cell stopper tape 35 / sealing agent sheet 32 / back sheet 34 are laminated in this order, and the laminator (LM-110 × 160, N Co., Ltd.) A pseudo solar cell module sample was prepared by first holding the sample in a vacuum at 160 ° C. for 3 minutes at 160 ° C. and then performing a heating and pressurizing treatment at a pressure of about 1 atm for a predetermined time. The cell stopper tape 35 was arranged so as to fix the four corners of the aluminum plate 33.
After cooling the sample to room temperature, the sample was held in an oven (PHH-401, manufactured by ESPEC CORPORATION) heated to 180 ° C. for 30 minutes and then taken out, and the presence or absence of swelling of the back sheet 34 was visually determined.

(Comparative Example 1)
In 100 parts by mass of pellets of an ethylene / α-olefin copolymer (Toughmer A-4070S, manufactured by Mitsui Chemicals, Inc., MFR: 3.6 g / 10 min (190 ° C.), density: 870 kg / m ^{3) as a polyolefin resin.} On the other hand, 0.6 parts by mass of t-butylpaooxy2-ethylhexyl carbonate (trade name: Luperox TBEC, manufactured by Alchema Yoshitomi Co., Ltd., purity: 97.7%) as a cross-linking agent, and triallyl isocyanurate 0 as a cross-linking aid. 0.8 parts by mass, 0.3 parts by mass of 3methacryloxypropyltrimethoxysilane (trade name: KBM503, Shin-Etsu Chemical Industry Co., Ltd.) as a silane coupling material, 0.1 parts by mass of a light stabilizer, and 0. The impregnation time was examined using an additive mixture containing 02 parts by mass.
The results are shown in Table 1.

(Comparative Example 2)
Except for changing the amount of triallyl isocyanurate used as a cross-linking aid to 0.2 parts by mass, the impregnation time was examined in the same manner as in Comparative Example 1, and a sealing material sheet was prepared with the same formulation. , Gel fraction and swelling at high temperature were evaluated. The results are shown in Table 1.

(Example 1)
As a cross-linking agent, instead of t-butylpaooxy2-ethylhexyl carbonate, 2,5-dimethyl2,5-di (t-butylperoxy) hexane (trade name: Luperox 101, manufactured by Alchema Yoshitomi Co., Ltd.) Purity: 92.7%) Except for the fact that 0.6 parts by mass was used, the impregnation time was examined in the same manner as in Comparative Example 2, and a sealing material sheet was prepared with the same formulation, and the gel fraction and high temperature were obtained. The swelling in was evaluated. The results are shown in Table 1.

(Example 2)
Except that the amount of 2,5-dimethyl2,5-di (t-butylperoxy) hexane used as a cross-linking agent was changed to 0.9 parts by mass, the impregnation time was examined in the same manner as in Example 1. At the same time, a sealing material sheet was prepared with the same formulation, and the gel fraction and swelling at high temperature were evaluated. The results are shown in Table 1.

(Example 3)
As a cross-linking agent, 1,1-di (t-butylperoxy) cyclohexane (trade name: Luperox 331, Alchema Yoshitomi) is used instead of 2,5-dimethyl2,5-di (t-butylperoxy) hexane. Made by Co., Ltd., Purity: 79.6%) Except for the fact that 0.9 parts by mass was used, the impregnation time was examined in the same manner as in Example 2, and a sealing material sheet was prepared with the same formulation to make a gel. The fraction and swelling at high temperature were evaluated. The results are shown in Table 1.

 

 

With reference to Comparative Example 2 and each Example, it can be seen that by satisfying the requirements of the present invention, generation of bubbles and swelling due to the bubbles can be effectively suppressed even when used at a high temperature.
With further reference to Comparative Example 1 and each of the embodiments, by having a requirement of the present invention, that good free immersion of the polyolefin resin additives including crosslinking agent and crosslinking aid is realized Recognize. The good free immersion resistance, no injection nozzle provided until the tip of the screw from the supply port of the extruder, a relatively melt-kneaded in a short time using standard extruder This makes it possible, and can significantly improve the cost and productivity of the solar cell encapsulant sheet.

The solar cell encapsulant sheet of the present invention can effectively suppress problems such as bubble generation and swelling even when used at a high temperature in a solar cell module, and is also excellent in cost and productivity. It has high utility in various fields of industry such as construction, construction, and machinery.

100: Extrusion machine
101: Supply port 103: Cylinder 105: Screw 107: Injection nozzle 109: Die 201: Container 203: Supply pump 31: Glass 32: Encapsulant sheet 33: Aluminum plate 34: Back sheet 35: Cell stop tape

Claims (16)

A step of producing a crosslinkable resin pellet by impregnating a pellet containing a polyolefin resin as a main component with a crosslinking agent and a crosslinking aid.
A step of putting the crosslinkable resin pellet into a cylinder from a supply port of an extrusion molding machine and melt-kneading the resin composition containing the polyolefin resin, the crosslinking agent, and the crosslinking aid in the cylinder.
A step of extruding the resin composition into a sheet from the die of the extrusion molding machine, and
It is a manufacturing method of a solar cell encapsulant sheet having
The cross-linking agent contains two or more compounds having an alkyl peroxy group represented by the following formula (1) in the structure, and R ^1- OO- (1).
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.),
The above-mentioned production method, wherein the cross-linking aid comprises triallyl isocyanurate. The production method according to claim 1, wherein the time for performing the step of producing the crosslinkable resin pellet is 100 minutes or less. The production method according to claim 1 or 2, wherein the amount of the compound having 2 or more alkyl peroxy groups in the structure is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or bonded via two or more carbon atoms. The production method according to any one of claims 1 to 3. The production method according to any one of claims 1 to 4, wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate. The production method according to any one of claims 1 to 5, wherein a solar cell encapsulant sheet having a gel fraction of 40% or more after encapsulation of the solar cell is produced. Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.) And a crosslinkable resin composition for a solar cell encapsulant containing triallyl isocyanurate. The crosslinkable resin composition according to claim 7, wherein the compounding amount of the compound having two or more alkyl peroxy groups is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or bonded via two or more carbon atoms. The crosslinkable resin composition according to claim 7 or 8. The crosslinkable resin composition according to any one of claims 7 to 9, wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate. Polyolefin resin,
A compound having two or more alkylperoxy groups represented by the following formula (1) in its structure.
R ¹ -OO- (1)
(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms.), And a solar cell encapsulant sheet containing triallyl isocyanurate. The solar cell encapsulant sheet according to claim 11, wherein the compounding amount of the compound having two or more alkyl peroxy groups is 0.4 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. A compound having two or more alkyl peroxy groups in the structure has a structure in which two or more alkyl peroxy groups are bonded to the same carbon atom or bonded via two or more carbon atoms. The solar cell encapsulant sheet according to claim 11 or 12. The solar cell encapsulant sheet according to any one of claims 11 to 13, wherein the polyolefin-based resin does not substantially have a structural unit derived from vinyl acetate. A solar cell module having a crosslinked cured product of the solar cell encapsulant sheet according to any one of claims 11 to 14. A step of sealing a solar cell with the solar cell encapsulant sheet according to any one of claims 11 to 14, and a step of cross-linking and curing the solar cell encapsulant sheet.
A method for manufacturing a solar cell module.

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