JP6106945B2 - Manufacturing method of sealing material sheet for solar cell module - Google Patents

Description

  The present invention relates to a method for producing a sealing material sheet for a polyethylene-based solar cell module, and more particularly to a sealing material sheet that has been subjected to crosslinking treatment with ionizing radiation such as an electron beam.

  Conventionally, as a sealing material for a solar cell module, a combination of an ethylene-vinyl acetate copolymer resin (EVA) and a crosslinking agent typified by an organic peroxide has been used. In recent years, polyethylene resins have been studied in place of EVA taking advantage of excellent water vapor barrier properties.

  In this regard, in the following Patent Document 1, a composition obtained by adding a coupling agent such as an organic silane compound to EVA or polyethylene resin is irradiated with ionizing radiation to be crosslinked, thereby obtaining a predetermined gel fraction. A technique for improving creep resistance and adhesion without using an organic peroxide is disclosed.

  Patent Document 2 below discloses a technique for improving heat resistance, adhesion and the like by heating and crosslinking a composition obtained by adding a silane coupling agent and an organic peroxide to a polyethylene resin. ing.

JP 2009-249556 A JP 2012-25946 A

  However, like the sealing material sheet described in Patent Document 1, the sealing material sheet obtained by simply irradiating the polyethylene resin with ionizing radiation improves the heat resistance, but improves the transparency. I can't. Transparency greatly affects power generation efficiency. In particular, in the case of polyethylene resin, the haze value is higher than EVA and the transparency is inferior. For this reason, the polyethylene-type sealing material sheet | seat which is excellent also in transparency while irradiating ionizing radiation and improving heat resistance was calculated | required.

  On the other hand, when a silane coupling agent and an organic peroxide are used in combination in the production of a sealing material sheet having a polyethylene resin as a base resin, as in the sealing material sheet described in Patent Document 2, a sealing material composition is obtained. At the time of melt molding, there is a problem in that unnecessary gels are generated in the polyethylene resin during film formation, which hinders optical properties and lowers productivity. In addition, FIG. 3 is an enlarged photograph in which a 90 × 120 mm range of the pre-sealing material sheet of Comparative Example 2 which will be described in detail in the examples described later is taken with a camera, and a gel is shown in the arrow g portion in the figure. You can see what is happening.

  The present invention has been made in order to solve the above problems, and its purpose is to improve the heat resistance by irradiating with ionizing radiation, and at the same time, a polyethylene-based sealing material sheet having excellent transparency and adhesion. Is to provide stable.

  The inventors of the present invention intentionally include a small amount of a crosslinking agent that is an organic peroxide that is considered unnecessary when irradiating with ionizing radiation, thereby improving heat resistance by ionizing radiation and maintaining transparency. It became possible, and it discovered that the said subject could be solved by limiting the silane coupling agent added for the improvement of adhesiveness to a vinyl-type silane coupling agent, and came to complete this invention. . More specifically, the present invention provides the following.

(1) Sheet forming step of obtaining a pre-encapsulant sheet by melt-molding an encapsulant composition containing low-density polyethylene having a density of 0.900 g / cm ³ or less, a silane coupling agent, and a crosslinking agent And a crosslinking step of crosslinking the preliminary sealing material sheet by irradiation with ionizing radiation, wherein the silane coupling agent is a vinyl-based silane coupling agent. Manufacturing method of sealing material sheet.

  (2) The sealing material sheet for a solar cell module according to (1), wherein the content of the silane coupling agent in the sealing material composition is 0.01% by mass or more and 1.0% by mass or less. Manufacturing method.

  (3) The sealing material for solar cell modules according to (1) or (2), wherein the content of the crosslinking agent in the sealing material composition is 0.005% by mass or more and 1.0% by mass or less. Sheet manufacturing method.

  (4) The method for producing a sealing material sheet according to any one of (1) to (3), wherein the gel fraction of the pre-sealing material sheet after the melt molding is 0%.

  (5) The manufacturing method of the sealing material sheet in any one of (1) to (4) whose gel fraction of the sealing material sheet after the said crosslinking process is 0%.

  (6) The manufacturing method of the sealing material sheet for solar cell modules in any one of (1) to (5) whose haze value in the thickness of 600 micrometers of the sealing material sheet after the said crosslinking process is 4% or less .

(7) Ionizing radiation is applied to a pre-sealing material sheet obtained by molding a sealing material composition containing a low-density polyethylene having a density of 0.900 g / cm ³ or less and a vinyl-based silane coupling agent into a sheet shape. Irradiated, sealing material sheet for solar cell module,
The vinyl-based silane coupling agent content in the encapsulant sheet is 0.01% by mass or more and 1.0% by mass or less, and the gel fraction of the encapsulant sheet after the crosslinking treatment is 0%. And the haze value in thickness 600 micrometers is 4% or less, The sealing material sheet characterized by the above-mentioned.

  (8) A sealing material sheet for a multilayer solar cell module having at least an outer layer that is disposed in the outermost layer and constitutes an adhesion reinforcing layer, and another inner layer, wherein the sealing material composition is A multilayer pre-sealing sheet formed by an extrusion method is irradiated with ionizing radiation, and the content of the vinyl-based silane coupling agent in the outer layer is 0.1% by mass or more and 1.0% by mass or less. Yes, the vinyl-based silane coupling agent content in the inner layer is 0.01% by mass or more and 1.0% by mass or less, and the gel fraction of the multilayer encapsulant sheet after the crosslinking treatment is 0% And having a haze value of 4% or less at a thickness of 600 μm, a multilayer encapsulant sheet.

  (9) The multilayer encapsulant sheet according to (8), wherein the thickness of the outer layer is 10% to 20% of the total thickness of the encapsulant sheet.

  (10) The sealing material sheet according to any one of (7) to (9) and a transparent front substrate made of glass, wherein the sealing material sheet and the transparent front substrate are in close contact with each other. A stacked solar cell module.

  ADVANTAGE OF THE INVENTION According to this invention, while irradiating ionizing radiation and improving heat resistance, the polyethylene type sealing material sheet which is excellent also in transparency and adhesiveness simultaneously can be provided.

It is sectional drawing which shows typically an example of the laminated constitution of the solar cell module which is one Embodiment of this invention. In the enlarged photograph which shows a mode that the gel has not generate | occur | produced in the preliminary sealing material sheet (90 * 120 mm range) at the time of the extrusion molding in the manufacturing process of the sealing material sheet (Example 1) which is one Embodiment of this invention. is there. It is an enlarged photograph which shows a mode that the gel has generate | occur | produced in the preliminary sealing material sheet (range of 90x120 mm) at the time of the extrusion molding in the manufacturing process of the general sealing material sheet (comparative example 2) made into the comparative example. .

  Hereinafter, the encapsulant composition according to the present invention (hereinafter also simply referred to as “encapsulant composition”), the encapsulant sheet for the solar cell module of the present invention (hereinafter also simply referred to as “encapsulant sheet”). ) And a solar cell module using this encapsulant sheet.

<Encapsulant composition>
The encapsulant composition used in the present invention contains low density polyethylene having a density of 0.900 g / cm ³ or less, a vinyl-based silane coupling agent, and a crosslinking agent as essential components. Hereinafter, after describing the essential components, other resins and other components will be described.

[Low density polyethylene]
In the present invention, low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less, preferably linear low density polyethylene (LLDPE) is used. Linear low density polyethylene is a copolymer of ethylene and α- olefin, in the present invention, within the scope thereof density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ within the following ranges , more preferably from 0.870 g / cm ³ or more 0.885 g / cm ³ or less. If the density is within the range of 0.900 g / cm ³ or less, good flexibility and transparency can be imparted while maintaining sheet processability.

  In the present invention, it is preferable to use a metallocene linear low density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and a softness | flexibility can be provided with respect to a sealing material. As a result of the flexibility, the adhesion between the sealing material and the substrate, such as the adhesion between the sealing material and the transparent front substrate and the adhesion between the sealing material and the back surface protective sheet, is increased.

  In addition, metallocene linear low density polyethylene has a narrow crystallinity distribution and a uniform crystal size, so that not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the sealing material which consists of a sealing material composition of this invention is arrange | positioned between a transparent front substrate and a solar cell element, power generation efficiency hardly falls.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material can be given good flexibility and good strength. As a result, the adhesion between the sealing material and the substrate is further increased.

  The melt mass flow rate (MFR) of the low density polyethylene is MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS-K6922-2 (in the present specification, the measurement value under this measurement condition is hereinafter referred to as MFR). It is preferably 0.5 g / 10 min or more and 40 g / 10 min or less, and more preferably 2 g / 10 min or more and 40 g / 10 min or less. The encapsulant sheet of the present invention is a crosslinked encapsulant sheet that undergoes a crosslinking treatment by irradiation with ionizing radiation after melt formation of the encapsulant composition. For this reason, even if the MFR of the low density polyethylene used as a base is high, the fluidity at the time of modularization can be suppressed by the crosslinking treatment after film formation. For this reason, even if it is high MFR like the said range, it can be used conveniently.

  In addition, in the sealing material composition using a polyethylene resin as a base resin, it is widely known that a sealing material sheet is provided with necessary and sufficient adhesion by further containing a silane-modified polyethylene resin. (Described in Japanese Patent Laid-Open No. 2003-46105). However, the sealing material sheet of the present invention seals sufficient adhesion equal to or higher than that of the conventional sealing material sheet by a combination of addition of a vinyl-based silane coupling agent and crosslinking by ionizing radiation. The material sheet can be provided. Therefore, it is not necessary to add a silane-modified polyethylene resin, which is generally expensive in the market, and the manufacturing cost can be greatly reduced.

The content of the polyethylene resin having a density of 0.900 g / cm ³ or less contained in the encapsulant composition is preferably 10% by mass or more and 99% by mass or less, more preferably 50% by mass or more in the composition. It is 99 mass% or less, More preferably, it is 90 mass% or more and 99 mass% or less. That is, other resins may be included as long as the effects of the present invention are not impaired. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later.

[Silane coupling agent]
In the manufacturing method of the sealing material sheet which performs the crosslinking process by irradiation of ionizing radiation, it is preferable to add a silane coupling agent for improving adhesion to the sealing material composition. This is because when the ionizing radiation is irradiated in a large amount, the enlargement ratio can be suppressed, but the adhesion component on the surface of the sealing material sheet may be damaged and the adhesion may be lowered, but the low molecular weight silane coupling agent It is presumed that the adhesion can be ensured by the seepage effect. However, as described above, generally, when a large amount of a silane coupling agent is added, there is a problem that the film formability is lowered due to a reaction with a crosslinking agent in the sealing material composition. Therefore, in the present invention, this problem has been solved by limiting the silane coupling agent added as an adhesion improver to a vinyl silane coupling agent having relatively low radical reactivity.

  Here, the silane coupling agent refers to a silane compound having a functional group that binds to an organic material and an inorganic material in the molecule, and is represented by a general formula R—Si (OR ′) 3 ( R is an organic functional group, and R ′ is a methyl group or an ethyl group). The vinyl silane coupling agent is a silane coupling agent having a vinyl group as an organic functional group. As such a vinyl-based silane coupling agent, a known silane coupling agent can be suitably used. For example, there are “KBM1003” and “KBE1003” (both manufactured by “Shin-Etsu Silicone Co., Ltd.”), which are easily available from the market.

  The content of the vinyl-based silane coupling agent is 0.01% by mass or more and 1.0% by mass or less, preferably 0.02% by mass or more and 1.0% by mass or less in the sealing material composition. . Adhesiveness to the member which comprises a solar cell module is not improved to the preferable range as it is less than 0.01 mass%. On the other hand, if it exceeds 1.0% by mass, the film-forming property is deteriorated due to the generation of gel even if it is a vinyl silane coupling agent, and the silane coupling agent is agglomerated and solidified over time. So-called bleed-out, which powders on the surface, may occur, which is not preferable.

  Vinyl groups are relatively low in radical reactivity compared to other organic functional groups such as acryloxy groups and methacryloxy groups, and unnecessary gels during film formation are added when the amount necessary to improve adhesion is added. The occurrence of is very unlikely. In the production of a sealing material sheet using a crosslinking agent such as an organic peroxide, the film forming property is improved by limiting the silane coupling agent to be added for improving adhesion to a vinyl silane coupling agent. This makes it possible to improve the glass adhesion while maintaining a very good state, and this is a novel point of the present invention.

[Crosslinking agent]
Conventionally, it has been considered that a crosslinking agent such as an organic peroxide is unnecessary when performing a crosslinking treatment by irradiation with ionizing radiation, unlike the case of a thermal crosslinking treatment. However, the encapsulant composition used in the present invention contains a small amount of a crosslinking agent while performing a crosslinking treatment by irradiation with ionizing radiation. This improves the transparency of the encapsulant sheet as compared to the case where no crosslinking agent is added. The action of the cross-linking agent in the cross-linking treatment by irradiation with ionizing radiation is not clear, but since ionizing radiation has strong energy, cross-linking proceeds, but the crystals that cause HAZE do not loosen and do not participate in cross-linking unless the temperature exceeds a certain temperature. It is estimated that this is because it remains. As described above, the addition of the crosslinking agent has a novel feature of the present invention in that the heat resistance is improved by the irradiation of ionizing radiation and the transparency can be maintained.

  A well-known thing can be used for a crosslinking agent, It does not specifically limit, For example, a well-known radical polymerization initiator can be used. Examples of radical polymerization initiators include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl Cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3, etc. Dialkyl peroxides; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide; t-butyl peroxyacetate, t-butyl pero Ci-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2 , 5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate Oxyesters; organic peroxides such as methyl peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, or azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile), dibutyltin Diacetate, dibutyltin dilaurate It can be mentioned dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst.

  The amount of the crosslinking agent added to the encapsulant composition of the present invention is preferably 0.005% by mass or more and 1.0% by mass or less, and 0.01% by mass or more and 0% by mass in the encapsulant composition. More preferably, it is 0.5 mass% or less, and it is still more preferable that it is 0.02 mass% or more and less than 0.1 mass%. By making the addition amount of the crosslinking agent to the sealing material composition within this range, in addition to heat resistance and adhesion, a sealing material sheet that is particularly excellent in transparency can be obtained. In this case, if the content of the crosslinking agent is less than 0.005% by mass, the effect of improving the transparency is insufficient, and if it exceeds 1.0% by mass, the load during extrusion increases, As a result of gel generation, the film-forming property is lowered and the transparency is also lowered. In addition, although the sealing material sheet of the present invention can be obtained by performing a crosslinking treatment by irradiation with ionizing radiation, in this case, the addition amount of the crosslinking material is different from the conventional thermal crosslinking, Even if the addition amount of the crosslinking material is less than 0.5% by mass, sufficient heat resistance can be obtained. Thereby, the risk of the productivity fall by the gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced, and manufacturing cost can also be reduced by reducing the usage-amount of a crosslinking agent.

  In general, a conventional uncrosslinked sealing material sheet is required to be subjected to all crosslinking treatments in a modularization process. For this reason, the half-life temperature of the crosslinking agent used for such thermal crosslinking treatment is limited to the heating temperature and heating time conditions in the modularization process, and the one-minute half-life temperature is generally less than 185 ° C. It was limited. However, when manufacturing the sealing material sheet of this invention, a crosslinking agent can be selected without receiving said restrictions. In general, the upper limit temperature of the crosslinking agent is about 230 ° C. from the viewpoint of resin oxidative degradation, but in the production of the sealing material sheet of the present invention, the half-life temperature for 1 minute is 185 ° C. or more within this range. The cross-linking agent can be freely selected. In addition, by expanding the selection range in this way, there is an advantage that the temperature at which molding can be performed without cross-linking is improved and the productivity is improved.

[Crosslinking aid]
It is preferable that the sealing material composition of the present invention substantially does not use a crosslinking aid. Here, the crosslinking assistant is, for example, a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer, and specifically, triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fuma. Polyallyl compounds such as rate and diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6 -Poly (meth) acryloxy compounds such as hexanediol diacrylate and 1,9-nonanediol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycol Epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and the like containing two or more diyl ethers and epoxy groups Can be mentioned. In the present invention, “substantially not using a crosslinking aid” means that an amount that does not show a crosslinking effect is included in the scope of the present invention even if it is contained as an impurity. For example, it is less than 0.01% by mass in the composition.

[Radical absorbent]
In the present invention, the gel fraction can be further finely adjusted by adjusting the degree of crosslinking by using the above-mentioned crosslinking agent in combination with the radical absorbent that quenches the crosslinking agent. Examples of such radical absorbents include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. The amount of the radical absorbent used is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2.0% by mass or less in the encapsulant composition. . Within this range, the gel fraction can be adjusted by appropriately suppressing the crosslinking reaction.

[Other ingredients]
The sealing material composition may further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to a sealing material produced from the sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and a heat stabilizer are exemplified. Is done. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001% by mass or more and 5% by mass or less in the sealing material composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant composition.

  A weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thus, good weather resistance can be imparted to the encapsulant. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used for the weatherproof masterbatch may be the low density polyethylene used in the present invention, or the other resins described above. These light stabilizers, ultraviolet absorbers, heat stabilizers and antioxidants can be used alone or in combination of two or more.

  In addition to the above, other components used in the sealing material composition of the present invention include adhesion improvers, nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants, and the like. it can.

<Sealing material sheet>
The sealing material sheet of the present invention obtains a preliminary sealing material sheet by a sheeting process in which the above-described sealing material composition is melt-molded at a temperature exceeding its melting point, and then undergoes a crosslinking process by ionizing radiation, It becomes a sheet-like or film-like sealing material sheet for the solar cell module of the present invention. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  The encapsulant sheet may be a monolayer sheet or film form of the encapsulant composition of the present invention, or the encapsulant sheet comprising the encapsulant composition of the present invention. It is good also as a multilayer sealing material sheet formed by co-extruding the sealing material sheet | seat of a different composition containing. A single-layer encapsulant sheet is preferable because both sides of the encapsulant sheet have a high adhesion to glass and can be used in various layer configurations.

  In the case of a multilayer encapsulant sheet, for example, the encapsulant sheet is composed of two layers, one is a core layer, and the encapsulant sheet made of the encapsulant composition of the present invention is adhered to only the other layer. You may arrange | position as a reinforcement layer, and you may arrange | position an adhesion reinforcement | strengthening layer for the outer layer laminated | stacked on at least one outermost layer as a structure of 3 layers or more on both sides of a core layer. By using at least one of the outer layers as an adhesion reinforcing layer made of the sealing material composition of the present invention, the adhesion reinforcing layer comes into contact with the glass substrate, so that the adhesion between the glass interface and the sealing material sheet is sufficient. Rise. Although the component contained in a core layer is not specifically limited, The above-mentioned silane copolymer, other resin, and another component can be contained preferably. Specifically, the vinyl-based silane coupling agent content in the outer layer is 0.1% by mass or more and 1.0% by mass or less, and the vinyl-based silane coupling agent in the inner layer is a layer other than the core layer and other outer layers. The silane coupling agent content is preferably 0.01% by mass or more and 1.0% by mass or less. By making the composition of each layer as such, the sealing material sheet can be provided with preferable adhesion derived from the adhesion of the outer layer and stable moldability derived from the small shrinkage rate of the inner layer, and The amount of the silane component used in the entire encapsulant sheet can be saved and the manufacturing cost can be reduced. In addition, even if it is not a multilayer sheet formed by coextrusion of each layer, for example, by a separate means, the concentration of a specific component such as increasing the concentration of the silane coupling agent near the lamination surface and decreasing it inside, It is within the scope of the present invention to satisfy the above configuration by changing within the encapsulant sheet.

  The thickness of the sealing material sheet is preferably 100 μm or more and 800 μm or less. If it is less than 100 μm, the impact cannot be sufficiently mitigated, and if it exceeds 800 μm, no further effect can be obtained, which is uneconomical.

  In addition, about the case where a sealing material sheet is a multilayer sheet | seat, it is preferable that the thickness of each outer layer is 10 to 20% of the thickness of the whole sealing material sheet. By making the ratio of the thickness of each layer in such a range, it is possible to give a preferable adhesion to the encapsulant sheet, and to save the production cost by saving the amount of the silane component used in the entire encapsulant sheet. Can be lowered.

  The haze value of the sealing material sheet of the present invention is 4% or less, preferably 3.9% or less, at a thickness of 600 μm. As described above, in the present invention, the sealing agent composition used in the production process for performing the crosslinking treatment with ionizing radiation is intentionally added with a crosslinking agent which has been made unnecessary conventionally, and thereby the crosslinking with ionizing radiation. In the case of performing the treatment, both the heat resistance and the transparency of the encapsulant sheet are improved.

  Moreover, about the glass adhesiveness of a polyethylene-type sealing material sheet, when passing through the bridge | crosslinking process by ionizing radiation, it may fall to an unpreferable value as a sealing material sheet for solar cell modules. However, in the sealing material sheet of the present invention, the glass adhesiveness of the sealing material sheet is practically preferable, that is, at least glass by adding a vinyl-based silane coupling agent to the sealing material composition. It is characterized in that it can be maintained at 29 N / 15 mm or more in terms of adhesion strength. In addition, in this specification, glass adhesion strength means the adhesion strength with respect to the glass of the sealing material for solar cell modules measured by the method as described in the following Example.

[Method for producing sealing material sheet]
(Sheet making process)
The melt molding of the sealing material composition is carried out by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. When the encapsulant sheet is a multi-layer encapsulant sheet, a multi-layer encapsulant sheet can be obtained by a method in which each layer is co-extruded and molded.

  The sealing material sheet of the present invention is limited in that the silane coupling agent added to improve the adhesion is limited to the vinyl-based silane coupling agent, thereby suppressing the generation of unnecessary gel in this melt formation stage. It has a characteristic.

  The lower limit of the molding temperature at the time of the above melt molding may be a temperature exceeding the melting point of the encapsulant composition, and the upper limit is that the cross-linking during film formation depends on the 1-minute half-life temperature of the cross-linking agent used. The temperature is not particularly limited as long as the temperature does not proceed excessively, and is within those ranges. In the manufacturing method of the sealing material sheet of the present invention, as described above, since a crosslinking agent having a half-life temperature higher than that of the conventional one can be used, by setting the molding temperature to be higher than the conventional one, It is possible to reduce the load applied to the extruder or the like and increase the productivity of the sealing material sheet.

  Moreover, it is preferable that the gel fraction in the state of this pre-sealing material sheet is 0%. At this stage, crosslinking may not be started at all, or preliminary crosslinking with heat and a crosslinking agent may proceed in a limited manner as long as the film formability does not deteriorate.

  Here, the gel fraction (%) means that 0.1 g of a sealing material sheet is put in a resin mesh, extracted with 60 ° C. toluene for 4 hours, taken out together with the resin mesh, weighed after drying, and mass before and after extraction. Comparison is made to measure the mass% of the remaining insoluble matter, and this is used as the gel fraction.

(Crosslinking process)
A solar cell module in which a cross-linking process for performing a cross-linking process by ionizing radiation is performed on the preliminary encapsulating material sheet after the sheet forming process, and the sealing material is integrated with other members after the sheet forming process is completed. Before the integration process starts. By this crosslinking step, by optimizing the gel fraction of the encapsulant sheet within a predetermined range, it is possible to obtain an encapsulant sheet having higher adhesion and heat resistance.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited, and may be set as appropriate so that the gel fraction is 20% or less, preferably 0% as a total treatment result. Specifically, it can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. The acceleration voltage in electron beam irradiation is determined by the thickness of the sheet that is the object to be irradiated, and the thicker the sheet, the larger the acceleration voltage is required. For example, a 0.5 mm-thick sheet is irradiated with 100 kV or more, preferably 200 kV or more. If the acceleration voltage is lower than this, the crosslinking is not sufficiently performed. The irradiation dose is in the range of 5 kGy to 1000 kGy, preferably 5 kGy to 300 kGy. When the irradiation dose is less than 5 kGy, sufficient crosslinking is not performed, and when it exceeds 1000 kGy, there is a concern about deformation or coloring of the sheet due to generated heat. In addition, you may irradiate ionizing radiation from both sides. Irradiation may be in an air atmosphere or a nitrogen atmosphere. Further, this crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line.

<Solar cell module>
FIG. 1: is sectional drawing which shows an example of the layer structure about the solar cell module using the sealing material sheet of this invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 are sequentially laminated from the incident light receiving surface side. ing. The solar cell module 1 of the present invention uses the above-described sealing material sheet for at least one of the front sealing material layer 3 and the back sealing material layer 5, and preferably for at least the front sealing material layer 3.

[Method for manufacturing solar cell module]
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method.

  In the solar cell module 1, the incidental and limited crosslinking reaction of the encapsulant sheet may be further advanced during the above-described thermocompression molding.

  By using such a sealing material sheet of the present invention, the flow of the sealing material sheet in the vacuum heating laminate can be suppressed. In addition, since there is no need for a crosslinking step by a modularization step or a subsequent heating step, the degree of freedom of the vacuum heating lamination conditions in the modularization step is increased as much as it is not necessary to consider the crosslinking conditions. This shortens the time required for production and greatly improves productivity. In particular, the problem of the polyethylene-based encapsulant sheet having a slower crosslinking rate than that of EVA can be solved, and the modularization time can be greatly shortened.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4 and the back surface protection sheet 6 which are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. In addition, the sealing material sheet of this invention is applicable not only to a single crystal type but to all other solar cell modules.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

  In order to measure and evaluate the glass adhesion strength, 150 ° C. vertical shear test, heat shrinkage rate, gel fraction, haze value (JIS K7136) and film forming suitability of the sealing material sheet of the present invention, The sealing material sheet of an Example, a comparative example, and a reference example was manufactured.

<Manufacture of encapsulant sheet for solar cell module>
[Preliminary sealing material sheet]
The encapsulant composition raw materials described below are mixed in the proportions shown in Table 1, and are used to create the encapsulant sheets for the inner layer and the outer layer of the encapsulant sheets of Examples, Comparative Examples, and Reference Examples, respectively. It was set as the sealing material composition. Each raw material described below was added in the amount (parts by mass) described in Table 1. However, about the silane coupling agent masterbatch, the addition amount was appropriately adjusted so that the content of the silane coupling agent in the sealing material composition became the ratio (mass%) described in Table 1.
Then, each sealing material composition was presealed for inner layer and outer layer at an extrusion temperature of 220 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a film molding machine having a 200-mm width T-die. A stop material sheet was prepared, and the pre-sealing material sheets for the inner layer and the outer layer were laminated to obtain a pre-sealing material sheet for a three-layer solar cell module. All of the pre-sealing material sheets had a thickness of 600 μm, and the outer layer: inner layer: outer layer thickness ratio was 1: 5: 1. In addition, as a sealing material composition raw material, the following raw materials were used.
(Polyethylene resin)
Metallocene-based linear low density polyethylene (M-LLDPE) (described as “M” in Table 1): density 0.880 g / cm ³ , metallocene-based linear low MFR at 190 ° C. of 3.5 g / 10 min Density polyethylene was used as the base resin.
Silane crosslinkable resin (described as “S” in Table 1): Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. Silane co-polymer in which a silane crosslinkable resin composed of 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) is mixed with the base resin with respect to 98 parts by mass Used as a resin containing coalescence. This resin has a density of 0.884 g / cm ³ and an MFR at 190 ° C. of 1.8 g / 10 min.
(Silane coupling agent)
Silane coupling agent master batch 1 (described as “SC1” in Table 1): with respect to 98.5 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. As a vinyl-based silane coupling agent, compound pellets impregnated with 1.5 parts by mass of commercially available “KBM1003” (manufactured by Shin-Etsu Silicone Co., Ltd.) were used as the silane coupling agent master batch 1.
Silane coupling agent masterbatch 2 (described as “SC2” in Table 1): The silane coupling agent is silane, except that the silane coupling agent is a methacryloxy silane coupling agent (“KBM503” manufactured by “Shin-Etsu Silicone Co., Ltd.”). The same compound pellet as the coupling agent master batch 1 was used as the silane coupling agent master batch 2.
Silane coupling agent masterbatch 3 (described as “SC3” in Table 1): The silane coupling agent was an acryloxy silane coupling agent (“KBM5103” manufactured by “Shin-Etsu Silicone Co., Ltd.”). The same compound pellet as the coupling agent master batch 1 was used as the silane coupling agent master batch 3.
Silane coupling agent master batch 4 (described as “SC4” in Table 1): The silane coupling agent was an silane coupling agent (“KBM403” manufactured by Shin-Etsu Silicone Co., Ltd.) The same compound pellet as the coupling agent master batch 1 was used as the silane coupling agent master batch 4.
(Crosslinking agent)
Crosslinking agent master batch (described as “crosslinked MB” in Table 1): 2 parts per 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. Compound pellets impregnated with 0.5 parts by mass of 5-dimethyl-2,5-di (t-butylperoxy) hexane were used as a crosslinking agent master batch.
(Weatherproofing agent)
Weathering agent master batch (as "weather MB" in Table 1): relative density 0.880 g / cm powder 100 parts by weight of pulverized Ziegler straight linear low density polyethylene ^3, benzophenol-based ultraviolet absorber 3. 8 parts by mass, 5 parts by mass of a hindered amine light stabilizer and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized, and used as a weathering agent master batch.

When the gel fraction of the pre-sealing material sheets of Examples 1 and 2 manufactured as described above was measured by the following method, the gel fraction was 0% for any of the pre-sealing material sheets.
Gel fraction (%): 0.1 g of a sealing material sheet is placed in a resin mesh and extracted with toluene at 60 ° C. for 4 hours. The mass% of the minute was measured and used as the gel fraction. The sample for measuring the gel fraction is obtained by sandwiching a sealing material (50 mm × 50 mm × thickness of about 0.4 to 0.5 mm) on a 50 μm-thick PET film (100 mm × 100 mm) subjected to a release treatment. Then, a laminate laminated at a predetermined temperature and time by a thermal laminator was used.

<Evaluation Example 1>
The following test was performed about the film forming aptitude at the time of said extrusion molding of each sealing material sheet (preliminary sealing material sheet) of an Example, a comparative example, and a reference example, and the following evaluation criteria evaluated.
Presence / absence of gel generation: Each sealing material sheet (preliminary sealing material sheet) after extrusion molding was observed with the naked eye, and the presence or absence of gel generation during film formation was observed. 2 is an enlarged photograph showing that no gel is generated in Example 1, and FIG. 3 is an enlarged photograph showing that a gel is generated in Comparative Example 2.
Resin pressure: The resin pressure was also measured by a Dinisco resin pressure sensor (NP400 series). These results were evaluated based on the following evaluation criteria.
(Filming suitability evaluation criteria)
A: No gel was generated at all, and the resin pressure was less than 180 kgf / cm ² .
B: what is the visual difficulty degree of gel occurred, the resin pressure was less than 200 kgf / cm ² at 180 kgf / cm ² or more.
C: Gel is generated to an extent that is clearly visible, and the resin pressure is 200 kgf / cm ² or more.
The evaluation results are shown in Table 2.

[Encapsulant sheet]
About the preliminary sealing material sheet of Examples 1-2 and Comparative Examples 1-2, the crosslinking process by irradiation of ionizing radiation is performed on the bridge | crosslinking conditions of the following and Table 2, and sealing of an Example and a comparative example, respectively. A stop sheet was created. Moreover, about the preliminary sealing material sheet of a reference example, the crosslinking process by irradiation of ionizing radiation was not performed, but the preliminary sealing material sheet after shaping | molding was used as the sealing material sheet of the reference example as it was. In addition, about an Example and a comparative example, about each pre-sealing material sheet | seat (it describes with "irradiation amount 0" in Table 2) which has not performed the crosslinking process by electron beam irradiation, adhesive strength etc. are measured and evaluated similarly. did.
(Crosslinking conditions)
Using an electron beam irradiation apparatus (product name EC250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.), the acceleration voltage was 200 kV, and the irradiation dose was irradiated on both sides with each irradiation amount shown in Table 2. For example, when there are 20 in the table, each surface is irradiated with 20 kGy, a total of 40 kGy.

<Evaluation Example 2>
About the sealing material sheet | seat of an Example, a comparative example, and a reference example, it measured and evaluated about glass adhesive strength, heat resistance (150 degreeC vertical shift | offset | difference test), thermal contraction rate, and haze value (JIS K7136). The results are shown in Table 2. Each test condition is as follows.

  Glass adhesion strength: The sealing material sheets of Examples, Comparative Examples, and Reference Examples cut to a width of 15 mm were adhered to glass substrates (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm), respectively. Processed with a vacuum heating laminator at 18 ° C. for 18 minutes to obtain solar cell module evaluation samples for each of the examples and comparative examples. A vertical peel (50 mm / min) test was performed using a Tensilon universal testing machine (RTF-1150-H) to measure the glass adhesion strength.

  Heat resistance test (150 ° C. vertical displacement test): Two sheets of sealing material sheets of Examples, Comparative Examples and Reference Examples cut out to 5 × 7.5 cm on a large-sized glass plate subjected to graining. Then, 5 × 7.5 grain glass was placed on top of it to carry out a crosslinking treatment. Thereafter, the large glass is placed vertically and left at 150 ° C. for 12 hours. The moving distance (mm) of the 5 × 7.5 grain glass after being left was measured and evaluated.

  Thermal shrinkage test: MD direction before and after heating after placing test pieces of 100 mm × 100 mm in the sealing material sheets of Examples, Comparative Examples and Reference Examples on a talc plate heated to 150 ° C. The shrinkage ratio of the side length of the test piece was measured and calculated. The MD direction is a longitudinal direction that is a discharge direction in the sheet forming process.

  Haze (%): Measured in accordance with JISK7136 with Murakami Color Research Laboratory Haze / Transmittance HM150.

  Gel fraction (%): Measured by the same method as above.

  From Table 2, the sealing material sheet of the Example which consists of the sealing material composition containing a vinyl-type silane coupling agent and a crosslinking agent, and performed the crosslinking process by irradiation of ionizing radiation is the sealing for solar cell modules. It can be understood that the sealing sheet is a polyethylene-based sealing material that has preferable adhesion, heat resistance, and transparency, and also has excellent film forming ability.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back sealing material layer 6 Back surface protection sheet

Claims (6)

A sheeting step for obtaining a pre-encapsulant sheet by melt-molding an encapsulant composition containing a low-density polyethylene having a density of 0.900 g / cm ³ or less, a silane coupling agent, and a crosslinking agent;
A crosslinking step of crosslinking the preliminary sealing material sheet by irradiation with ionizing radiation,
The silane coupling agent is a vinyl silane coupling agent,
Content of the said silane coupling agent in the said sealing material composition is 0.01 mass% or more and 1.0 mass% or less, and content of the crosslinking agent in the said sealing material composition is 0.00. The manufacturing method of the sealing material sheet for solar cell modules which is 005 mass% or more and less than 0.1 mass%. The method for producing a sealing material sheet according to claim 1 , wherein the gel fraction of the pre-sealing material sheet after the melt molding is 0%. The method for producing an encapsulant sheet according to claim 1 or 2, wherein the gel fraction of the encapsulant sheet after the crosslinking treatment is 0%. The method for producing a sealing material sheet for a solar cell module according to any one of claims 1 to 3 , wherein a haze value at a thickness of 600 µm of the sealing material sheet after the crosslinking treatment is 4% or less. The preliminary sealing material sheet is formed by molding the sealing material composition into a sheet by a co-extrusion method, and has at least an outer layer disposed in the outermost layer and constituting an adhesion reinforcing layer, and other inner layers. A multilayer encapsulant sheet having
The vinyl-based silane coupling agent content in the outer layer is 0.1% by mass or more and 1.0% by mass or less, and the vinyl-based silane coupling agent content in the inner layer is 0.01% by mass. 1.0% by mass or less,
Wherein a gel fraction of 0% of the sealing material sheet after the crosslinking treatment, and the sun according to any one of claims 1 to 4, wherein the haze value is not more than 4% at a thickness of 600μm The manufacturing method of the sealing material sheet | seat for battery modules. The method for producing a sealing material sheet according to claim 5 , wherein the thickness of each outer layer is 10% or more and 20% or less of the total thickness of the sealing material sheet.