JP2012052004A - Method of manufacturing sealing material for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for a solar cell module, in which the heat shrinkage when vacuum heat laminating is small.SOLUTION: A sealing material composition includes: based on 100 pts.mass of an ethylene-vinyl acetate copolymer resin in which the vinyl acetate content is at least 28 mass% and at most 33 mass%, at least 0.5 pt.mass and at most 1.0 pt.mass of a crosslinking agent; and at least 0.5 pt.mass and at most 1.0 pt.mass of a crosslinking auxiliary. A method of manufacturing the sealing material for a solar cell module includes: molding the sealing material composition; and then annealing the sealing material composition at least at 120°C and at most 140°C for at least 0.5 minutes and at most 10 minutes. In the sealing material for a solar cell module obtained by the method, since the thermal shrinkage is at most 10% and the heat shrinkage when vacuum heat laminating is small, the crack of a solar cell can be inhibited.

Description

  The present invention relates to a method for producing a solar cell module encapsulant, and more particularly to a method for producing a solar cell module encapsulant having a small thermal shrinkage during vacuum heating lamination in a modularization process.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed and proposed. In general, a solar cell module has a configuration in which a transparent front substrate, a solar cell element, and a back surface protection sheet are laminated via a sealing material (filler).

  As a sealing material for a solar cell module, a configuration mainly containing EVA (ethylene-vinyl acetate copolymer) from the viewpoint of transparency and fluidity and containing a crosslinking agent and a crosslinking aid is known (patent). Reference 1). In this case, the above composition is formed uncrosslinked and crosslinked by heating during modularization.

  However, since EVA has a significant thermal shrinkage at the time of crosslinking, there is a problem that the solar cell element breaks during vacuum heating lamination due to this shrinkage stress. In particular, in recent years, the thickness of solar cell elements tends to be as thin as 0.2 mm or less, and this thermal shrinkage is a more significant problem than ever before.

  In order to prevent EVA thermal shrinkage, it is known that annealing treatment for stress relaxation is effective. For example, in Patent Document 1 below, heat shrinkage is performed by performing an annealing treatment for about 1 minute to 2 minutes at a temperature higher by about 20 ° C. to 25 ° C. than the softening point immediately after EVA deposition and before the softening point is reached. It is disclosed that the rate can be reduced.

JP 2000-84996 A

  The EVA sealing material of Patent Document 1 corresponds to a fast cure sealing material that omits the curing process after the thermal lamination process at the time of manufacturing the solar cell module, that is, when an organic peroxide having a lower decomposition temperature is selected. However, since the annealing temperature is low with respect to the increase in the thermal shrinkage due to the decrease in the resin temperature during extrusion, the improvement in the thermal shrinkage becomes insufficient. In addition, since a large amount of a crosslinking agent or a crosslinking aid is blended, when the temperature is raised, crosslinking proceeds, and the flexibility as a sealing material is reduced, resulting in a decrease in sealing performance (fillability). There is.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a sealing material for a solar cell module that can maintain thermal flexibility while suppressing thermal shrinkage in an EVA sealing material. It is in.

  The present inventors pay attention to the relationship between the amount of the crosslinking agent and the crosslinking aid and the annealing conditions, and conventionally, the amount of the crosslinking agent and the crosslinking aid is reduced, and the annealing treatment is further performed at a high temperature for a short time. As a result, the inventors have found that the above problems can be solved, and have completed the present invention. More specifically, the present invention provides the following.

  (1) 0.5 to 1.0 parts by mass of a crosslinking agent and 0.5 to 1.0 parts by mass of a crosslinking aid with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer resin. A method for producing a sealing material for a solar cell module, in which an annealing treatment is performed at 120 ° C. to 140 ° C. for 0.5 minutes to 10 minutes after molding an encapsulant composition.

  (2) Thermal shrinkage, which is the shrinkage ratio of the side length of the test piece before and after heating, after placing a test piece of a 100 mm × 100 mm sealing material film on a talc plate heated to 100 ° C. and allowing it to stand for 10 minutes The manufacturing method of the sealing material for solar cell modules as described in (1) whose is 10% or less.

  (3) The manufacturing method of the sealing material for solar cell modules as described in (1) or (2) whose vinyl acetate content of the said ethylene-vinyl acetate copolymer resin is 28 mass% or more and 33% mass or less.

(4) A module forming step of laminating the solar cell module sealing material according to any one of (1) to (3) by vacuum heating lamination,
The manufacturing method of the solar cell module whose vacuum heating lamination temperature in the said modularization process is 140 to 160 degreeC, and whose vacuum heating lamination time is 10 minutes or more and 30 minutes or less.

  (5) The method for producing a solar cell module according to (4), wherein the gel fraction after the vacuum heating lamination is 70% or more and 99% or less.

(6) 0.5 to 1.0 parts by mass of a crosslinking agent with respect to 100 parts by mass of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 28 to 33% by mass; 0.5 to 1.0 parts by mass of a crosslinking aid,
The side of the test piece before and after heating after placing a test piece of 100 mm × 100 mm sealing material film on a talc plate heated to 100 ° C. with a gel fraction of 0% or more and 3% or less. The sealing material for solar cell modules whose heat shrinkage rate which is a shrinkage ratio of length is 10% or less.

  (7) The solar cell module sealing material according to (6), wherein the gel fraction after the crosslinking treatment at 140 ° C. to 160 ° C. for 10 minutes to 30 minutes is 70% to 99%.

  According to the sealing material for solar cell modules and the manufacturing method thereof of the present invention, it is possible to provide an EVA sealing material for solar cell modules which can maintain flexibility while suppressing thermal shrinkage.

It is a graph which shows the measurement result of the dynamic viscoelasticity (tan-delta) in an Example. It is a graph which shows the result of having measured the relationship between the vacuum heating lamination time in an Example (no annealing process) and a gel fraction. It is a graph which shows the result of having measured the relationship between the vacuum heating lamination time in an Example (with annealing process) and a gel fraction. It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

<Encapsulant composition>
The encapsulant composition used in the present invention is 0.5 parts by mass or more and 1.0 part by mass or less of a crosslinking agent with respect to 100 parts by mass of ethylene-vinyl acetate copolymer resin (EVA), and 0.5 And 1 to 1.0 parts by mass of a crosslinking aid. Hereinafter, after explaining these essential components, other resins and other components will be explained.

[EVA]
Although EVA can use a conventionally well-known thing, it is not specifically limited, It is a gel content after the vacuum heating lamination process of a solar cell preparation process that a vinyl acetate content (VA content) is 28 mass% or more and 33% mass or less. It is preferable from the viewpoint of obtaining heat resistance of 100 ° C. or higher and 150 ° C. or lower with a high degree of crosslinking of 70% or more.

  The melt mass flow rate (MFR) of the EVA resin is preferably 1 g / 10 min or more and 40 g / 10 min or less, more preferably 15 g / 10 min or more and 40 g / 10 min or less at 190 ° C. in JIS K7210 method. The Vicat softening point of JIS K7206 is preferably in the range of 30 ° C to 40 ° C. When the MFR and softening point are within the above ranges, the resin is excellent in the property of being melted by heating, uniformly fluidized with the additive, and deformed to a constant shape until cooling.

[Crosslinking agent]
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 may be mentioned dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst. These may be used alone or in combination of two or more. Specifically, the fast cure method in the vacuum heating lamination process of solar cell production (the sealing material is highly crosslinked only by vacuum heating lamination, and is allowed to stand at about 150 to 160 ° C. for 30 minutes to 1 hour to post-crosslink the sealing material. T-Butylperoxy-2-ethylhexyl carbonate (TBEC) is preferably used from the viewpoint of application to a method of omitting the curing step.

  The 10-hour half-life temperature of the crosslinking agent is preferably an organic peroxide of 100 ° C. to 120 ° C. from the upper limit of the resin temperature at which the crosslinking reaction does not start in the extruder.

  The content of the cross-linking agent is preferably 0.5 parts by mass to 1.0 part by mass with respect to 100 parts by mass of EVA. If it is less than 0.5 parts by mass, the heat resistance at high temperatures is inferior due to insufficient crosslinking, and the crosslinking time becomes long and cannot be fast cured. Fast cure means that a post-crosslinking step is not required in the modularization step described later. When the amount exceeds 1.0 part by mass, crosslinking is promoted by an annealing treatment described later, and the flexibility of the sealing material is lowered, which is not preferable.

[Crosslinking aid]
In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group is preferable, and a functional group of the polyfunctional monomer is preferably an allyl group, a (meth) acrylate group, or a vinyl group. This promotes an appropriate crosslinking reaction.

  Specific crosslinking aids include triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate and other polyallyl compounds, 4-hydroxybutyl acrylate glycidyl ether and two epoxy groups Examples thereof include epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, triallyl isocyanurate (TAIC) can be preferably used because it has a relatively slow reaction rate and a low shrinkage rate due to the reaction.

  Trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1, Poly (meth) acryloxy compounds such as 9-nonanediol diacrylate, glycidyl methacrylate containing a double bond and an epoxy group, and the like are not preferable because of a high reaction rate.

  The content of the crosslinking aid is preferably included in the range of 0.5 parts by mass to 1.0 part by mass with respect to 100 parts by mass of EVA. If it is less than 0.5 parts by mass, the heat resistance at high temperatures is inferior due to insufficient crosslinking, and the crosslinking time becomes long and cannot be fast cured. When the amount exceeds 1.0 part by mass, crosslinking is promoted by an annealing treatment described later, and the flexibility of the sealing material is lowered, which is not preferable.

[Radical absorbent]
In the present invention, the gel fraction may be further finely adjusted by adjusting the degree of cross-linking by using the above-mentioned cross-linking agent serving as a radical polymerization initiator in combination with the radical absorbent for quenching it. Examples of such radical absorbers 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. It is preferable that the usage-amount of a radical absorber is contained in 0.01 to 3 mass% in a composition, More preferably, it is the range of 0.05 mass part-2.0 mass parts. If it exists in this range, a crosslinking reaction can be suppressed moderately.

[Other ingredients]
The sealing material composition can further contain other components. For example, a weather resistance masterbatch for imparting weather resistance to the encapsulant prepared from the encapsulant composition for solar cell modules of the present invention, various fillers, light stabilizers, ultraviolet absorbers, heat stabilizers, etc. These components are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001 to 5 mass% in the solar cell module encapsulant composition. By including these additives, it is possible to impart a long-term stable mechanical strength, an effect of preventing yellowing, cracking, and the like to the encapsulant composition for solar cell modules.

  The weather-resistant masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer, the above-mentioned antioxidant, etc. in a resin such as EVA, and this is used as a sealing material composition for a solar cell module. By adding to, favorable weather resistance can be imparted to the solar cell module sealing material. 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 EVA used in the present invention, or 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 encapsulant composition include adhesion improvers such as silane coupling agents, nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants, and the like. Can be mentioned.

  Next, an example of the solar cell module sealing material of the present invention and a solar cell module using the same will be described with reference to the drawings. FIG. 3 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present 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 solar cell module sealing material (hereinafter also simply referred to as “sealing material sheet”) for at least one of the front sealing material layer 3 and the back sealing material layer 5. .

<Sealant for solar cell module>
The encapsulant sheet of the present invention is obtained, for example, by subjecting the above encapsulant composition to a forming (film formation) process by a conventionally known T-die method or the like, followed by annealing treatment, and has a thickness of 300. To 650 μm sheet or film. In addition, the sheet form in this invention means the film form, and there is no difference in both. Examples of the molding temperature are 90 ° C. to 120 ° C.

  The encapsulant sheet formed into a sheet is not necessarily a single layer. In order to improve adhesion between the encapsulant sheet and the encapsulated members such as the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6, the encapsulant for the solar cell module of the present invention is formed at the interface. The composition should just be arrange | positioned. By allowing the encapsulant composition of the present invention to be present near the interface, the encapsulant sheet of the present invention can be produced at a lower cost.

  As a method for causing the sealing material composition of the present invention to be present in the vicinity of the interface, for example, the structure of the sealing material sheet has three or more layers, that is, two outermost layers and the outermost layer. Examples thereof include a method comprising a multilayer film having at least a sandwiched core layer. In order to produce a sealing material sheet made of a multilayer film as described above, for example, a conventionally known T-die multilayer coextrusion method can be used.

<Annealing treatment of sealing material>
The sealing material sheet of the present invention is obtained by annealing the sealing material composition after molding. Here, the annealing conditions are 120 ° C. or more and 140 ° C. or less and a high temperature short time treatment of 0.5 minutes or more and 10 minutes or less, and more preferably, the treatment time is 1 minute or more and 2 minutes or less. If the annealing temperature is less than 120 ° C, the heat shrinkage rate will not be less than 10%, which is not preferable. If the annealing temperature exceeds 140 ° C, the flexibility is lost and the fluidity is lowered, and the shape followability to the cell (solar cell element). Is not preferable because of worsening. Also, if the annealing time is less than 0.5 minutes, the thermal shrinkage rate will not be 10% or less, which is not preferable, and if it exceeds 10 minutes, it will be hardened although the degree of crosslinking is low.

  The gel fraction after the annealing treatment is preferably 3% or less, more preferably 0%.

  As described above, the present invention is characterized in that both the low thermal shrinkage rate and the flexibility are achieved by the combination of the above-described sealing material composition and the high temperature short time annealing treatment. This will be described with reference to FIG. 1 (Test Example 1) and FIG. 2 (Test Example 2) of Examples described later.

  As shown in FIG. 1, the encapsulant composition used in the present invention is greatly different in the behavior of tan δ in the low temperature part by reducing the amounts of the crosslinking agent and the crosslinking aid. Specifically, in the vicinity of 150 ° C., which is a vacuum heating lamination temperature in the modularization process, tan δ is similarly reduced by sufficient crosslinking. There is no significant change in behavior in this region. On the other hand, in the vicinity of 90 ° C. to 140 ° C., which is lower than the crosslinking temperature, the encapsulant composition used in the present invention has a larger tan δ, that is, has a softer property. It can be seen that in Comparative Example 1 in which the amount of the auxiliary agent is large, tan δ is small and hard. That is, since the present invention has flexibility in the vicinity of 90 ° C. to 140 ° C. when the temperature rises in the modularization process, the sealing performance is excellent. Of course, the heat shrinkage rate can be reduced by reducing the amount of the crosslinking agent and the crosslinking aid.

  Next, considering from the viewpoint of the relationship between the vacuum heating laminating time at 150 ° C. and the gel fraction according to FIG. 2, the encapsulant composition used in the present invention has a more rapid rise in gel fraction than the comparative example. The gel fraction is zero until the vacuum heating lamination time is around 8 minutes. On the other hand, in the comparative example, the gel fraction gradually increases from around 4 minutes in the vacuum heating lamination time. From this fact, it can be understood that when the annealing process is performed at a high temperature for a short time in the comparative example, the crosslinking proceeds, the flexibility is lowered, and the sealing performance in the modularization process is deteriorated.

  That is, in the present invention, a low heat shrinkage rate is enabled by reducing the amount of the crosslinking agent and the crosslinking aid, and the crosslinking is delayed by obtaining a time-gel fraction profile as shown in FIG. This enables high-temperature and short-time annealing treatment, and in addition to a low thermal shrinkage rate, to obtain a very well-balanced EVA sealing material sheet having flexibility at low temperatures and crosslinkability (heat resistance) at high temperatures. Is a successful one.

  The heat shrinkage rate at the stage of the encapsulant sheet is as follows: a test piece side before and after heating after placing a test piece of 100 mm × 100 mm encapsulant film on a talc plate heated to 100 ° C. It is 10% or less, preferably 5% or less, measured as the shrinkage ratio of the side length. When the shrinkage rate differs depending on the MD / CD direction (longitudinal direction and lateral direction) on the side of the test piece, the value with the larger shrinkage rate is adopted.

<Solar cell module>
As shown in FIG. 4, in the modularization process, the solar cell module 1 includes, for example, 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 members can be laminated one after another and integrated by vacuum suction or the like, and then the above-mentioned members can be manufactured by thermocompression forming as an integrally formed body by a molding method such as a vacuum heating lamination method.

  Moreover, the solar cell module 1 is formed on the front side and the back side of the solar cell element 4 by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. The back sealing material layer 5 is melt-laminated, the solar cell element 4 is sanded with the front sealing material layer 3 and the back sealing material layer 5, and then the transparent front substrate 2 and the back protection sheet 6 are sequentially laminated, Then, they may be manufactured by a method in which these are integrated by vacuum suction or the like and heat-pressed.

  In addition, since a sealing material sheet is uncrosslinked at the time of shaping | molding as mentioned above, it bridge | crosslinks in this modularization process. In this case, the vacuum heating laminating time in the modularization step is a predetermined temperature, for example, the vacuum heating laminating time temperature is 140 ° C. to 160 ° C., and the vacuum heating laminating time is within 10 to 30 minutes, The rate can be reached and crosslinking can be completed. In addition, since it may damage a cell when it exceeds 160 degreeC, it is unpreferable. That is, the sealing material sheet of the present invention can be fast-cured in a separate process and does not require a crosslinking treatment.

  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 that are members other than the front surface sealing material layer 3 and the back surface 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 | seat of this invention is applicable not only to a single crystal type but to all other solar cell modules.

  In the solar cell module of the present invention thus obtained, the gel fraction after crosslinking of the encapsulant sheet is 70% or more and 99% or less, preferably 80% or more and 99% or less. In addition, as shown in FIG.2 and FIG.3 of the Example mentioned later, the gel fraction in this invention is 150 degreeC x 30 minutes by the method of an Example, when there is no designation | designated in temperature and time especially. It means the gel fraction after the crosslinking treatment. In addition, the above “completion of crosslinking” means a time point when the gel fraction reaches a steady state (saturate) after increasing.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
<Manufacture of sealing material for solar cell module>
The following materials were mixed and melted as a composition having the composition shown in Table 1, and formed into a film having a thickness of 400 μm by a conventional T-die method to obtain an uncrosslinked sealing material. The film forming temperature was 95 ° C. An annealing treatment is not performed.
EVA-1: vinyl acetate content 33%, manufactured by Mitsui DuPont Polychemical, trade name EVAFLEX / EV150R grade EVA-2: vinyl acetate content 28%, manufactured by Mitsui DuPont Polychemical, trade name EVAFLEX / EV250R grade

Cross-linking agent (TBEC): t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi, trade name Luperox TBEC)
Crosslinking agent (101): 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi Corporation, trade name Luperox 101)
Crosslinking aid A (TMPT): trimethylolpropane trimethacrylate (manufactured by Sartomer, trade name SR350)
Crosslinking aid B (TAIC): triallyl isocyanurate (Sartomer, trade name SR533)
Silane coupling agent (SC agent): manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM503
UV absorber (UV agent): Chemipro Kasei Co., Ltd., trade name KEMISORB12)
Antioxidant A: BASF Corporation, trade name Irganox 1076
Antioxidant B: Product name Irganox 1330, manufactured by BASF
Antioxidant C: Product name Irganox 1010 manufactured by BASF
Antioxidant D: manufactured by BASF, trade name Irgafos 168
Hindered amine light stabilizer (HALS): manufactured by BASF, Tinuvin 770

<Test Example 1>
For Example 1 and Comparative Example 1, the change in dynamic viscoelasticity (tan δ) was measured. The result is shown in FIG. In addition, the measurement was performed using the apparatus Anton Paar, Physica MCR301, under the measurement conditions of swing angle γ = 5% and angular frequency ω = 11 / s.

<Test Example 2>
For Examples 1 and 2 and Comparative Example 2, the change in gel fraction (%) when the vacuum heating lamination time was changed at a vacuum heating lamination temperature of 150 ° C. was measured. The results are shown in FIGS. FIG. 2 shows no annealing treatment, and FIG. 3 shows the result of measuring the gel fraction after annealing at 120 ° C. for 1 minute.

The gel fraction was measured under the following conditions. The gel fraction measurement sample was a 50 μm-thick PET film (100 mm × 100 mm) subjected to a mold release treatment and a sealing material (50 mm × 50 mm × thickness of about 0). .4 to 0.5 mm) was sandwiched and laminated for a predetermined temperature and time using a vacuum heating laminator.
Gel fraction (%): 0.1 g of the sealing material after cross-linking was put into a resin mesh, extracted with 60 ° C. toluene for 4 hours, then taken out together with the resin mesh, weighed after drying treatment, and the weight was compared before and after extraction. The mass% of insoluble matter was measured and used as the gel fraction.
Thermal contraction rate (%): The shrinkage ratio of the side length of the test piece before and after heating after placing a test piece of 100 mm × 100 mm on a talc plate heated to 100 ° C. and leaving it to stand for 10 minutes. The heat shrinkage rate was used.

  The thermal shrinkage rates after annealing of Examples 1 and 2 were 5% and 5%, respectively, and the thermal shrinkage rates after annealing of Comparative Examples 1 and 2 were 5% and 5%, respectively. Considering this result together with FIG. 3, it can be seen from FIG. 3 that, in Comparative Example 1 having a composition containing more crosslinking agent and crosslinking aid than the present invention, crosslinking proceeds by annealing treatment, resulting in a vacuum heating lamination time of 8 It can be seen that the gel fraction is increased to around 50% in minutes, and the curing has already progressed and the flexibility is poor. On the other hand, in Examples 1 and 2, the gel fraction was 0% at a vacuum heating lamination time of 8 minutes, the thermal shrinkage ratio was lowered by annealing at a high temperature for a short time, and excellent flexibility after annealing. I understand.

<Test Example 3>
Except having changed the crosslinking agent, the crosslinking assistant, the kind and the amount as shown in Table 2, the sealing agents of Examples 3 and 4 and Comparative Examples 3 to 6 were obtained in the same manner as in Example 1. About these, the thermal contraction rate and dynamic viscoelasticity (DMA) after 120 degreeC x 10-minute annealing treatment were measured. In addition, these uncrosslinked sealing materials were treated with a vacuum heating laminator at 155 ° C. for 10 minutes to perform crosslinking (corresponding to vacuum heating lamination in a modularization process), and each of Examples and Comparative Examples was sealed after crosslinking. I got the material. The results are summarized in Table 2. In the table, DMA change XX is evaluated when tan δ does not change from 80 ° C. to 110 ° C., and X when change occurs.

  From Table 2, in Comparative Example 3 in which the crosslinking agent and the crosslinking aid are less than within the scope of the present invention, the gel fraction after annealing is as low as 0% and the DMA change is small, so the flexibility after annealing is maintained. However, the gel fraction after vacuum heating lamination is as low as 40% and is inferior in heat resistance. Further, in Comparative Example 4 in which the crosslinking agent and the crosslinking aid are larger than the range of the present invention, the gel fraction after vacuum heating lamination is as high as 95% and excellent in heat resistance, but the gel fraction after annealing is 10%. And the tan δ of the DMA is large, so that the flexibility after the annealing treatment is inferior.

  In Test Examples 5 and 6 using TMPT as a crosslinking aid, the gel fraction after annealing was high at 4 to 8% because of the high crosslinking rate, and the tan δ of DMA was large and the flexibility after annealing was high. Inferior.

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 (7)

  0.5 parts by mass or more and 1.0 parts by mass or less of a crosslinking agent, and 0.5 parts by mass or more and 1.0 parts by mass or less of a crosslinking aid, relative to 100 parts by mass of the ethylene-vinyl acetate copolymer resin The manufacturing method of the sealing material for solar cell modules which performs the annealing process for 0.5 to 10 minutes at 120 to 140 degreeC after shaping | molding the sealing material composition containing this.   After placing a test piece of 100 mm × 100 mm sealing material film on a talc plate heated to 100 ° C. and leaving it to stand for 10 minutes, the thermal shrinkage rate, which is the shrinkage ratio of the side length of the test piece before and after heating, is 10%. The manufacturing method of the sealing material for solar cell modules of Claim 1 which is the following.   The manufacturing method of the sealing material for solar cell modules of Claim 1 or 2 whose vinyl acetate content of the said ethylene-vinyl acetate copolymer resin is 28 mass% or more and 33% mass or less. A modularization step of laminating the solar cell module sealing material according to any one of claims 1 to 3 by vacuum heating lamination,
The manufacturing method of the solar cell module whose vacuum heating lamination temperature in the said modularization process is 140 to 160 degreeC, and whose vacuum heating lamination time is 10 minutes or more and 30 minutes or less.   The method for producing a solar cell module according to claim 4, wherein the gel fraction after the vacuum heating lamination is 70% or more and 99% or less. With respect to 100 parts by mass of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 28% by mass to 33% by mass, Containing not less than 1.0 part and not more than 1.0 part by mass of a crosslinking aid,
The side of the test piece before and after heating after placing a test piece of 100 mm × 100 mm sealing material film on a talc plate heated to 100 ° C. with a gel fraction of 0% or more and 3% or less. The sealing material for solar cell modules whose heat shrinkage rate which is a shrinkage ratio of length is 10% or less.   The encapsulant for a solar cell module according to claim 6, wherein the gel fraction after the crosslinking treatment at from 140 ° C to 160 ° C for from 10 minutes to 30 minutes is from 70% to 99%.

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