JP2012214788A - Solar cell sealing material sheet and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material sheet for solar cells effective for suppressing troubles of cell breakage in a lamination step of a solar cell production process and a residue of bubbles in the sealing material.SOLUTION: The solar cell sealing material sheet contains an ethylene vinyl acetate copolymer composition as a resin composition constituting the surface part, and has separate protrusions A having a height of 60-300 μm at a density of 40-2,300 protrusions/cm, wherein the ratio of the protrusion height T to the base length of the separate protrusion is 0.05-0.80.

Description

  The present invention relates to a sealing material sheet for solar cells. In particular, the present invention relates to a solar cell sealing material sheet and a solar cell module using the same, which can suppress problems such as cell cracking during lamination in a solar cell manufacturing process and bubbles in the sealing material.

In recent years, solar cells that directly convert sunlight into electrical energy have attracted attention in terms of effective use of resources and prevention of environmental pollution. Generally, a solar cell has a configuration in which solar cells are sealed (protected) by a sealing material sheet inserted between a light-receiving surface protective material represented by a glass substrate and a back surface protective material called a back sheet. Is adopted.
For example, in the case of a crystalline silicon solar cell that is the mainstream as a solar cell module, a glass substrate, an encapsulant sheet made of an ethylene vinyl acetate copolymer (hereinafter, the ethylene vinyl acetate copolymer may be referred to as EVA), solar A battery cell (silicon power generation element), an encapsulant sheet made of EVA, and a back sheet are laminated in this order, and the laminate is heated under vacuum by a vacuum laminator, whereby the encapsulant sheet is heated and melted to be crosslinked and cured. Thus, a solar cell module bonded without bubbles is manufactured.

  In the manufacturing process of such a solar cell module, when a temperature spot in the vacuum laminator (a temperature locally decreases at the end of the laminator, etc.) occurs, the heating of the EVA sealing material becomes insufficient, The solar cell may be broken by the local pressing force of the encapsulant on the solar cell, which is one factor that reduces the manufacturing efficiency of the module.

  EVA is a material that easily adheres, and when close contact with local cells occurs during vacuum lamination, there is a problem that air remaining between the encapsulant sheet and the solar cells becomes bubbles, which is Similarly, it contributes to a reduction in module manufacturing efficiency. The following studies have been made on the above trouble. For example, the embossing process is performed on the encapsulant sheet to form irregularities, the cell cushioning is improved by improving the cushioning property of the sheet, and the remaining air is degassed by the grooves formed in the sheet, and air bubbles This is a technique for improving troubles (see, for example, Patent Documents 1 and 2). However, with these technologies, defects such as cell cracks and bubbles in the sealing material can be suppressed at a certain level, but because the height of the unevenness is shallow and insufficient deaeration in the direction perpendicular to the groove, It has been difficult to completely prevent the above-mentioned trouble without reaching an essential suppression.

  Furthermore, in recent years, in order to suppress defects such as cracking of the cells and bubbles in the sealing material, an independent convex portion having a height of 0.05 to 0.5 mm is provided on the surface of the sealing material sheet. The sealing material sheet which has is proposed (for example, refer patent document 3). However, this technique has a problem of causing cell cracking during vacuum lamination.

  On the other hand, in the manufacturing process of the solar cell module, there is a technology that reduces the heat shrinkage rate of the encapsulant sheet and eliminates the cracking of the solar cell and the displacement of the cell due to the shrinkage of the encapsulant sheet during vacuum lamination. (See, for example, Patent Documents 4 and 5). However, in these techniques, since the heat shrinkage rate cannot be sufficiently reduced, cracking and misalignment of the solar battery cells cannot be essentially improved. However, in Patent Document 5, the sealing material is made of polyethylene and a high melting point. Therefore, there is a problem that it takes time to heat the encapsulant sheet and the production efficiency is lowered.

JP 2000-183388 A (Claim 3) JP-A-2006-134970 (Claims 1 and 2) JP 2010-232231 (Claim 1, paragraph 0036, FIG. 1) Japanese Patent Laying-Open No. 2010-100032 (paragraph 0076, Table 1) JP 2007-245555 (paragraphs 0045 and 0095)

  The objective of this invention is providing the sealing material sheet for solar cells which can suppress simultaneously the malfunction of the crack of the cell at the time of the lamination in the manufacturing process of a solar cell, and the residual of the bubble in a sealing material.

In order to solve the above problems, the present invention has the following configuration. That is,
(1) the resin composition constituting the surface portion consists of ethylene-vinyl acetate copolymer composition, wherein the surface portion comprises 40 to 2,300 pieces / cm ² independent high protrusions 60～300Myuemu, and, The solar cell encapsulant sheet, wherein the ratio (T / D) of the height (T) and the base length (D) of the independent protrusions is 0.15 to 0.80.
(2) When the solar cell encapsulating sheet is left on a hot water surface at 80 ° C. for 1 minute, the solar cell encapsulating of (1), wherein the heat shrinkage in the sheet flow direction of the encapsulant sheet is 30% or less Stop sheet.
(3) The solar cell encapsulant sheet according to (1) or (2), wherein the shape of the independent protrusion is hemispherical and / or quadrangular pyramid.
(4) When the surface of the solar cell encapsulant sheet having the protrusions is compressed 100 μm in the thickness direction of the encapsulant sheet, the sheet has a repulsive stress of 70 kPa or less (1) to (3) The solar cell sealing material sheet of any of these.
(5) The solar cell encapsulant sheet according to any one of (1) to (4), wherein the surface having the projections of the solar cell encapsulant sheet further has a projection of 1 to 15 μm in height.
(5) The light receiving surface protective material, the back surface protective material, and the light receiving surface protective material and the back surface protective material are disposed between the solar cell sealing material sheets according to any one of (1) to (5). A solar cell module comprising a layer in which cells are sealed.
It is.

  ADVANTAGE OF THE INVENTION According to this invention, the sealing material sheet for solar cells which can suppress simultaneously the malfunction of the crack of the cell at the time of the lamination in the manufacturing process of a solar cell, and the bubble remaining in a sealing material can be provided.

FIG. 1 is a diagram for explaining a method of measuring the height of a protrusion of a solar cell sealing material sheet having a protrusion formed on one side. FIG. 2 is a diagram for explaining a method of measuring the height of the protrusion of the solar cell encapsulant sheet having protrusions formed on both sides. FIG. 3 is a diagram illustrating the length D of the bottom side of the protrusion.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the resin composition constituting the sealing material sheet of the present invention, it is preferable that at least the resin composition constituting the surface portion on the side where the protrusions are formed satisfy the composition of the resin composition described below. Of course, it is more preferable that all the resin compositions constituting the sheet satisfy the composition of the resin composition described below.

  The resin composition constituting the encapsulant sheet employs an ethylene vinyl acetate copolymer composition from the viewpoint of transparency that is important as a solar cell encapsulant and adhesiveness with solar cells. From the viewpoint of transparency, the composition contains 90% by mass or more of an ethylene vinyl acetate copolymer (hereinafter referred to as EVA), and, if necessary, other polyolefin resins, organic peroxides, A crosslinking aid, a silane coupling agent, a light stabilizer, an ultraviolet absorber, an antioxidant and the like may be included.

  Note that EVA is a copolymer synthesized from ethylene and vinyl acetate, but the EVA used in the present invention preferably has a vinyl acetate (VA) content of 20 to 35 mass%. If the vinyl acetate (VA) content is greater than 35% by mass, the water vapor transmission rate may increase, and the moisture permeability required as a sealing material for solar cells may not be ensured. Moreover, since vinyl acetate (VA) content rate is less than 20 mass%, since resin is too hard, the crack of a cell may generate | occur | produce at the time of the lamination in the manufacturing process of a solar cell.

  The encapsulant sheet has independent protrusions having a height of 60 to 300 μm on the surface. By having independent protrusions with a height of 60 μm or more on the surface of the encapsulant sheet, the air remaining between the encapsulant sheet and the solar cells is multi-directional during vacuum lamination when manufacturing a solar cell module. It is possible to efficiently remove the bubbles and suppress the generation of bubbles. Furthermore, it is possible to disperse the pressing force of the encapsulant sheet to the solar battery cells and suppress the occurrence of cell cracking. If the shape of the surface of the sealing material sheet is not an independent protrusion but a continuous groove shape, deaeration in a direction perpendicular to the groove becomes insufficient, and the remaining air becomes bubbles. Further, when the height of the protrusion is 300 μm or less, the concentration of the load on the top of the protrusion during vacuum lamination is suppressed, and the solar battery cell can be prevented from cracking. Here, the “independent protrusion” refers to a protrusion having a bottom length D, which will be described later, in the range of 70 to 6000 μm when attention is paid to the bottom surface of the protrusion.

In addition, the independent protrusions are sandwiched between flat plates, applied with a pressure of 50 kPa in the thickness direction and compressed to deform the protrusions, and when the area where the tops of the protrusions contact the flat plate expands, It is preferable that a gap of 20 to 800 μm is ensured between the two regions derived from the protrusions to be formed.
When the height (T) of the protrusion is less than 60 μm, it is difficult to effectively suppress the above-described bubbles and cell cracks.

  The independent protrusion has a ratio (T / D) of the protrusion height (T) to the protrusion base length (D) of 0.05 to 0.80. Preferably it is 0.15-0.80. When the T / D ratio is less than 0.05, the cushioning property of the sealing material sheet becomes insufficient. When the T / D ratio exceeds 0.80, a concentrated load on the top of the protrusion occurs and cell cracking occurs. The height T of the protrusion is measured as follows. First, the case where there is a protrusion on one side will be described. The surface of the encapsulant sheet having the protrusions is referred to as A surface, and the surface having no protrusion is referred to as B surface. As shown in FIG. 1, the distance from the apex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion having no protrusion on the A surface to the B surface is Tmin. The difference between Tmax and Tmin is the height T of the protrusion. Next, the case where both have projections will be described. One side of the encapsulant sheet is referred to as A side and the other side is referred to as B side. As shown in FIG. 2, the distance from the apex of the projection on the A surface to the portion without the projection on the B surface is TAmax, the distance from the apex of the projection on the B surface to the portion without the projection on the A surface is TBmax, The distance from the portion having no protrusion to the portion having no protrusion on the B surface is defined as Tmin. The difference between TAmax and Tmin is the height TA of the projection on the A surface, and the difference between TBmax and Tmin is the height TB of the projection on the B surface. The length of the bottom of the projection is the outer diameter D of the projection shown in FIG. When the shape of the bottom surface of the protrusion is a polygon such as a triangle or a hexagon or an ellipse, the length of the bottom of the protrusion is the diameter of the smallest perfect circle including the shape of the bottom surface. The above Tmax, Tmin, and D can be measured by observing the sheet with a stereomicroscope.

  Desirable protrusion height T is 60 to 300 μm as described above. When the height T of the protrusion is 60 μm, the length of the base D of the protrusion is 75 to 1200 μm, preferably 75 to 400 μm. When the height T of the protrusion is 300 μm, the length of the base D of the protrusion is 375 to 6000 μm, preferably 375 to 2000 μm.

The number of independent protrusions is in the range of 40 to 2300 per 1 cm ² area on one side of the sheet. Preferably 40 to 1100. If the number of independent protrusions is less than 40 / cm ² , cell cracks or bubbles may occur. If it exceeds 2300 pieces / cm ² , the T / D ratio increases, and cell cracking may occur due to the concentrated load on the top of the protrusion.

  The encapsulant sheet preferably has a heat shrinkage rate of 30% or less, more preferably 25% or less, when left in warm water at 80 ° C. for 1 minute. Here, “Leave in warm water” means that if the specific gravity of the encapsulant sheet is small and the encapsulant sheet floats on the surface of the hot water, the encapsulant sheet can be pressed from above and submerged in the warm water. Instead, leave it in its floating state. On the other hand, when the specific gravity of the encapsulant sheet is large and the encapsulant sheet sinks in warm water, the encapsulant sheet is not allowed to be supported from below but is left in its submerged state. The “sheet flow direction” is a direction in which the process sheet flows in the manufacturing process of the sealing material sheet. In a general vacuum laminating process in the manufacture of a solar cell module, vacuuming is performed without applying pressure to the sealing material sheet until the sealing material sheet is sufficiently melted, and the sealing material sheet is melted and removed. Do care. At this time, since the encapsulant sheet is exposed to a no-load state at a high temperature of about 80 ° C., the encapsulant sheet contracts, and as a result, cell cracks and displacement occur. As a result of investigations by the inventors focusing on cell cracks and misalignment, when the process sheet is left for 1 minute in a no-load state that reproduces the inside of the vacuum laminator, the heat shrinkage rate in the sheet flow direction is 30. It was found that the cell cracking can be further suppressed if it is at most%. The state where the inside of the vacuum laminator is reproduced is a state where the process sheet is left in 80 ° warm water. The heat shrinkage rate in the direction orthogonal to the flow direction of the sheet is not particularly limited because it is minute compared to the flow direction, but is preferably 5% or less.

  The shape of the independent protrusion is preferably a hemispherical shape, a pyramid shape such as a triangular pyramid, a quadrangular pyramid, a hexagonal pyramid, or a cone, or a trapezoidal shape with a flat top portion thereof. Moreover, the state in which these protrusion shapes are mixed may be used. Among these, a hemispherical shape and / or a quadrangular pyramid shape are preferable. Here, “hemispherical and quadrangular pyramid” means a surface shape in which hemispherical protrusions and quadrangular pyramidal protrusions are mixed. A hemispherical shape is preferable in that a concentrated load on the solar battery cell is difficult to be applied and the load can be uniformly dispersed when the pressure is applied to the solar battery cell. Further, a quadrangular pyramid shape is also preferable in that unevenness of reflected light hardly occurs and the surface quality is excellent. And since both hemispherical and quadrangular pyramid features can be obtained, a shape in which a hemispherical shape and a quadrangular pyramid shape are mixed is also preferable. When the hemispherical shape and the quadrangular pyramid shape are mixed, the ratio of each may be arbitrarily determined according to which feature is to be obtained. Particularly preferably, all are hemispherical patterns.

  The encapsulant sheet of the present invention preferably further has fine protrusions having a height of 1 to 15 μm on the surface having independent protrusions. By having the minute protrusions, the slipperiness of the sheet is improved and the handling becomes easy. In addition, light is scattered by the minute protrusions, and the whiteness of the sheet is improved, so that it is easy to inspect adhered foreign matter and the like.

  Such minute protrusions can be achieved by the preferred manufacturing method of the present invention in which embossing is performed after the annealing step described later. In the conventional method of performing annealing by heating after embossing, large protrusions with a height of several tens of μm may remain on the sheet even after the heat treatment, but they are as small as several μm in height. The protrusion disappears with the heat treatment.

  In addition, the height of the minute protrusion is a numerical value measured as follows. In accordance with JIS B0601 (2001), the surface of the sheet is photographed at a magnification of 400 using a well-known laser microscope such as a laser microscope VK-X100 manufactured by Keyence Corporation. In the roughness curve of the obtained image, the Rz value when the cutoff value is 0.080 mm is defined as the height of the minute protrusion.

  Next, the raw material used for the sealing material sheet of this invention is demonstrated.

The EVA melt flow rate is preferably within a range of 12 to 40 g / 10 min at 190 ° C. By using EVA with a melt flow rate of 12 g / 10 min or more at 190 ° C., the flow of the composition is promoted by heating during vacuum lamination, and local loads are dispersed to suppress cell cracking and efficiency. Thus, the air between the sheet and the cell can be removed. Moreover, the melt outflow from the module edge part of the sealing material sheet | seat at the time of vacuum lamination can be suppressed by making a melt flow rate into 40 g / 10min or less. It is also possible to use a mixture of EVA having different melt flow rates. In this case, what is necessary is just to mix and use so that the melt flow rate after mixing may be 12-40 g / 10min.
The EVA melt flow rate used in the sealing material sheet of the present invention conforms to JIS K7210 (1999) “Plastic-thermoplastic plastic melt mass flow rate (MFR) and melt volume flow rate (MVR) test methods”. And measured under test conditions of a temperature of 190 ° C. and a load of 2.16 kg.

  The EVA composition used for the sealing material sheet of the present invention preferably contains an organic peroxide. Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates radicals. The organic peroxide may be selected in consideration of the temperature at the time of producing the sealing material sheet, the heating / bonding temperature at the time of producing the solar cell module, the storage stability of the crosslinking agent itself, and the like. In particular, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred. Examples of such organic peroxides include 1,1-di (t-hexylperoxy) cyclohexane, n-butyl 4,4-di- (t-butylperoxy) valerate, 2,5-dimethyl- 2,5-di (t-butylperoxy) hexane, di-t-butyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 Disuccinic acid peroxide, di (4-t-butylcyclohexyl) peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexa Noate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, di (4-t-butylcyclohexyl) Syl) peroxydicarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxy- 2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxyacetate, t-butylperoxyisononanoate, t-amylperoxy-2-ethylhexanoate, t-amylperoxy Normal octoate, t-amylperoxyoxynononanoate, t-amylperoxy-2-ethylhexyl carbonate, di-t-amylperoxide, 1,1-di (t-butylperoxy) cyclohexane, ethyl 3,3 -Di (t-butylperoxy) butyrate, 1,1-di (t-amyl) Peroxy) cyclohexane and the like. These organic peroxides may be used in combination of two or more. The content of these organic peroxides is 0.1 to 5 parts by mass, preferably 0.1 to 3 parts by mass, particularly preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the EVA resin. Preferably there is. If the content of the organic peroxide is less than 0.1 parts by mass, the EVA resin may not be crosslinked. Even if the content exceeds 5 parts by mass, the content effect is low, and undecomposed organic peroxide may remain in the encapsulant sheet, which may cause deterioration over time.

  The EVA composition used for the encapsulant sheet of the present invention may further contain a crosslinking aid, a silane coupling agent, a light stabilizer, an ultraviolet absorber, an antioxidant, and the like.

  The crosslinking aid is a polyfunctional monomer having a plurality of unsaturated bonds in the molecule, and reacts with the active radical compound generated by the decomposition of the organic peroxide to uniformly and efficiently cross-link EVA. Used. Examples of these crosslinking aids include triallyl isocyanurate, triallyl cyanurate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tris [(meth) acryloyloxyethyl] isocyanurate, Dimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, dipentaerystol penta (meth) acrylate, dipentaerystol hexa (meth) acrylate, divinylbenzene, etc. Can be mentioned. These crosslinking aids may be used alone or in combination of two or more. In the present invention, “(meth) acrylate” means “acrylate or methacrylate”.

  Among these crosslinking aids, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are particularly preferable. Content of these crosslinking adjuvants is 0-5 mass parts with respect to EVA 100 mass parts, Preferably it is 0.1-3 mass parts, More preferably, it is the range of 0.3-3 mass parts. Even if the content exceeds 5 parts by mass, the effect is only slightly improved, which causes a cost increase.

  The silane coupling agent is used to improve the adhesion between the encapsulant sheet and various members such as a solar battery cell, a back sheet, and glass. Content of a silane coupling agent is the range of 0.05-2 mass parts with respect to 100 mass parts of ethylene vinyl acetate copolymer resin. If the amount is less than 0.05 parts by mass, there is no content effect, and even if the content exceeds 2 parts by mass, the effect of improving adhesiveness is small, which is meaningless. Although it does not specifically limit as a silane coupling agent, For example, at least 1 sort (s) chosen from methacryloxy group, acryloxy group, epoxy group, mercapto group, ureido group, isocyanate group, amino group, hydroxyl group Examples include alkoxysilane compounds having a functional group. Specific examples thereof include alkoxysilane compounds containing a methacryloxy group such as γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and γ-methacryloxypropyltrimethoxysilane. , Acryloxy group-containing alkoxysilane compounds such as γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyl Epoxy group-containing alkoxysilane compounds such as trimethoxysilane, mercapto group-containing alkoxysilane compounds such as γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane Ureido group-containing alkoxysilane compounds such as γ-ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, γ- (2-ureidoethyl) aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ- Isocyanatopropyltrimethoxysilane, γ-isocyanatopropylmethyldimethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, γ-isocyanatopropylethyldimethoxysilane, γ-isocyanatopropylethyldiethoxysilane, γ-isocyanatopropyl Isocyanato group-containing alkoxysilane compounds such as trichlorosilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ Amino group-containing alkoxysilane compounds such as aminopropyltrimethoxysilane, .gamma.-hydroxypropyl trimethoxysilane, a hydroxyl group-containing alkoxysilane compounds such as .gamma.-hydroxypropyl triethoxysilane and the like. Among these, from the viewpoint of compatibility with the ethylene vinyl acetate copolymer resin, a methacryloxy group-containing alkoxysilane compound is preferable, and γ-methacryloxypropyltrimethoxysilane is more preferable.

  It is more preferable that the EVA composition used for the sealing material sheet of the present invention further contains an ultraviolet absorber. The UV absorber absorbs harmful UV rays in the irradiated light and converts them into innocuous heat energy within the molecule, preventing the active species that initiate photodegradation in the polymer from being excited. . Known ultraviolet absorbers can be used. For example, benzophenone series, benzotriazole series, triazine series, salicylic acid series, cyanoacrylate series, etc. can be used. One of these may be used, or two or more may be used in combination.

  Examples of the benzophenone ultraviolet absorber include 2,2′-dihydroxy-4,4′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-4,4′-di (2-hydroxyethyl) benzophenone, 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (2-hydroxy) Ethyl) benzophenone, 2,2′-dihydroxy-3,3′-di (hydroxymethyl) -5,5′-dimethoxybenzophenone, 2,2′-dihydroxy-3,3′-di (2-hydroxyethyl)- 5,5′-dimethoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone and the like can be mentioned.

  Examples of the benzotriazole ultraviolet absorber include 2- [2′-hydroxy-5 ′-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-hydroxyethyl). ) Phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-methyl-5'- (Hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-methyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy- 3′-methyl-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3 -T-butyl-5 '-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(2-hydroxyethyl) phenyl] -2H-benzo Triazole, 2- [2′-hydroxy-3′-t-butyl-5 ′-(2-hydroxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-3′-t -Butyl-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5'-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-t-octyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy 3′-t-octyl-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole or the like, or 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (hydroxymethyl) ) Phenol], 2,2'-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2'-methylenebis [6- (5-chloro-2H- Benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-methylenebis [6- (5-bromo-2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol], 2, 2'-methylenebis [6- (5-chloro-2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol], 2,2'-methylenebis [6- (5-bromo-2H-benzotriazoly- 2-yl) -4- (3-hydroxypropyl) phenol], 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 2,2 ′ -Methylenebis [6- (5-chloro-2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 2,2'-methylenebis [6- (5-bromo-2H-benzotriazoly-2- Yl) -4- (4-hydroxybutyl) phenol], 3,3- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydro Ci-4- (2-hydroxyethyl) phenyl]} propane, 2,2- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydroxy-4- (2-hydroxyethyl) ) Phenyl]} butane, 2,2′-oxybis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-bis [6- (2H-benzotriazolyl) 2-yl) -4- (2-hydroxyethyl) phenol] sulfide, 2,2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfoxide, 2, 2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfone, 2,2′-bis [6- (2H-benzotriazo 2-yl) -4- (2-hydroxyethyl) phenol] amine.

  Examples of the triazine-based ultraviolet absorber include 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-diphenyl-s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4, 6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy -4- (2-hydroxyethyl) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4, 6-diphenyl-s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2 -Hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl]- 4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-bis (2-hydroxy-4-methylphenyl) -s- Triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- ( 2-hydroxyethoxy) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxyl) (Lopyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2 -Hydroxy-4-methylphenyl) -s-triazine, 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol and the like.

  Examples of the salicylic acid-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and the like.

  Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate, ethyl-2-cyano-3,3'-diphenyl acrylate, and the like.

  Of these ultraviolet absorbers, benzophenone-based ultraviolet absorbers are most preferable from the viewpoints of the ultraviolet absorption effect and coloring of the ultraviolet absorber itself.

  Said ultraviolet absorber is used in 0.05-3 mass parts with respect to 100 mass parts of EVA, More preferably, it is used in 0.05-2.0 mass parts.

  It is preferable that the EVA composition used for the sealing material sheet of the present invention further contains a light stabilizer. The light stabilizer traps radical species that are harmful to the polymer and prevents the generation of new radicals. As the light stabilizer, a hindered amine light stabilizer is preferably used.

  As a hindered amine light stabilizer, bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane produced by reaction with decanedioic acid 70% by mass of a product and 30% by mass of polypropylene, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxy Phenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidylsebacate mixture, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl)- , 2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, 2,2,6, A mixture of 6-tetramethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl A mixture of -4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate, poly [{6- (1,1,3,3-tetra Methylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6- Tramethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, N, N ′, N ″, N ″ ′-tetrakis -(4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1, A mixture of 10-diamine, dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, dibutylamine, 1,3,5-triazine, N, N′— Polycondensates of bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine, etc. All I can get lost. The above-mentioned hindered amine light stabilizers may be used alone or in combination of two or more.

  Among these, a mixture of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, and methyl-4 It is preferable to use piperidyl sebacate and bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate. Moreover, it is preferable to use a melting point of 60 ° C. or higher.

  The content of the light stabilizer is preferably 0.05 to 3.0 parts by mass, more preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of EVA.

  In addition, an antioxidant, a flame retardant, a flame retardant aid, a plasticizer, a lubricant, a colorant, and the like may be contained as necessary within the range not inhibiting the effects of the present invention.

The sealing material sheet of the present invention is an index for evaluating the cushioning property of the sealing material sheet for suppressing cell cracking of the solar battery, when the surface having the protrusion of the sealing material sheet is compressed by 100 μm in the thickness direction. Adopt the repulsive stress of the sheet. As a result of intensive studies on the relationship between the cell cracking property of the solar battery and the cushioning property of the sealing material sheet, it was found that the repulsive stress at which cell cracking is suppressed is preferably 70 kPa or less. The above repulsive stress is a sealing material sheet using a compression test apparatus having a resolution of 5 μm or less as a compression displacement and 100 Pa or less as a compression load, and a flat pressure terminal at a pressure rate of 0.02 mm / s. It is obtained by measuring the repulsive stress (kPa) of the sheet when the surface having the protrusions is pressed 100 μm in the thickness direction.
When the repulsive stress of the encapsulant sheet is 70 kPa or less, the solar cell can be prevented from cracking by laminating the surface having the protrusion so as to be in contact with the solar cell and performing vacuum lamination. In addition, although the shape of the surface on the opposite side to the surface which has the processus | protrusion of a sealing material sheet is not specifically limited, From points, such as adhesion prevention of the sealing material sheet at the time of solar cell module manufacture, about 2-10 micrometers in height. It is preferable to have a minute protrusion.

  As for the thickness of a sealing material sheet, 50-1500 micrometers is preferable. More preferably, it is 100-1000 micrometers, Most preferably, it is 200-800 micrometers. If it is less than 50 μm, the cushioning property of the solar cell encapsulant sheet may be poor, or a problem may occur from the viewpoint of workability. On the other hand, if the thickness exceeds 1500 μm, a decrease in productivity and a decrease in adhesion may be a problem. In addition, the thickness of a sealing material sheet is the distance from the vertex of a processus | protrusion to the surface on the opposite side to the surface which has a processus | protrusion, when the processus | protrusion is formed only in the single side | surface of the encapsulant sheet. When protrusions are formed on both surfaces of the encapsulant sheet, the distance is from the top of the protrusion on one surface to the top of the protrusion on the opposite surface.

  Thus, in order to accurately form independent protrusions on the surface of the encapsulant sheet, or to suppress the heat shrinkage rate of the encapsulant sheet within a specific range, the encapsulant sheet is produced by a production method described later. It is preferable to do.

  Hereinafter, the preferable manufacturing method for obtaining the sealing material sheet of this invention is demonstrated.

(Sheet casting process)
The film forming process is a process in which a raw material resin and an additive are uniformly mixed, formed into a sheet shape, and cooled to obtain a process sheet.

  In the sheet film-forming process, an extruder that melts and kneads the raw resin and additives at high temperature, a die that extrudes the kneaded molten resin into a sheet, and the extruded high-temperature process sheet is cooled and solidified to form a solid sheet A polishing roller is provided.

  As the extruder, it is preferable to use a twin-screw extruder rather than a single-screw extruder from the viewpoints of productivity, kneadability of resin and additive, and the like.

  The raw material resin and additive to be charged into the extruder may be mixed in advance using a mixer or a blender, or may be charged individually. Alternatively, side feed may be performed from the middle of the extruder, or a liquid may be added using an injection pump or the like.

  The temperature at which the resin and additive are kneaded depends on the type and viscosity of the resin used, but is generally in the range of 10 ° C. or more higher than the melting point of the resin and 50 ° C. or less higher than the melting point. In the present invention, the melting point is an endothermic peak value temperature when the temperature is raised at 10 ° C./min in differential scanning calorimetry (DSC). In the case of an EVA sheet generally used as a solar cell encapsulant sheet, since it often contains an organic peroxide as a cross-linking agent, it should be noted that it is kneaded without being decomposed as much as possible. There is a need. Therefore, as the resin temperature, for example, in the case of EVA having a melting point of about 70 ° C., the resin temperature at the die outlet is preferably around 90 to 130 ° C., more preferably in the range of 100 to 120 ° C. . Below 90 ° C, the kneadability becomes insufficient, and the uniform dispersibility of the additive may decrease, and the appearance of the sheet may deteriorate. When the temperature exceeds 130 ° C, the organic peroxide decomposes. The quality of the encapsulant sheet may not be stable and the continuous productivity may be poor.

  In addition, the method for forming the process sheet may be the above-described extruder, or a known method such as molding with a calendar roller may be used.

  The molten resin obtained by melting the raw material resin and the additive in an extruder or the like and being mixed together is extruded into a sheet shape using a die. As such a die, a T die or a circular die can be used. Since a flat die has a wide shape in accordance with the sheet width to be extruded, it becomes a T shape when attached to an extruder, and is collectively called a T die. In addition, since the residence time and flow velocity differ in the die width direction in the T die, problems such as uneven thickness and uneven thickness in the width direction are likely to occur. In order to solve this, it is also possible to use a cylindrical circular die. The circular die is a cylindrical die for extruding a resin into a cylindrical shape and cutting it into a sheet shape, and the physical properties in the width direction of the sheet are likely to be relatively uniform.

  Moreover, when using T-die, a process sheet can also be made into a laminated structure by coextrusion methods, such as a feed block system and a multi-die system, extruding a different resin composition using a some extruder. By setting it as such a laminated structure, a function required as a sealing material sheet can be isolate | separated for every layer, and cost can be reduced by adjusting the amount of additives.

  The process sheet extruded using a die is formed into a sheet shape by a polishing roller. A polishing roller is a process sheet conveying apparatus comprised of a plurality of rollers for simultaneously pressing and pressing a molten resin between a pair of rollers to form the sheet thickness and surface properties. Each configured roller includes a mechanism that is adjusted to a temperature suitable for cooling and shaping of the molten resin, and a mechanism that can adjust the gap between the rollers and the pressure applied. Moreover, it is preferable to prevent sticking of a process sheet | seat by flowing temperature control water, such as chiller water, as needed, and to improve a moldability, and it is preferable to adjust temperature to about 0-30 degreeC.

(Annealing process)
Next, the annealing process will be described.

  The purpose of the annealing process is to remove the residual distortion of the process sheet formed in the film forming process and reduce the heat shrinkage of the sheet. In the annealing process, a method of passing a process sheet on a plurality of conveying rollers while heating with a heater installed in a furnace can be mentioned.

  The heater for heating the sheet is not particularly limited as long as it can heat the process sheet, and a known heater such as a ceramic heater, a stainless steel heater, or a sheath heater can be used.

  Since the conveyance roller for conveying a process sheet conveys the heated process sheet, it is required that it is excellent in releasability. For this reason, fluorocarbon resins such as polytetrafluoroethylene, perfluoroethylene propene copolymer, and perfluoroalkoxyalkane are coated on metal rollers that have uneven surfaces by embossing or thermal spraying of compounds such as metals and metal oxides. You may use what was used, or what wound the paper or film etc. which carried out the releasable coating process around the surface of the metal roller. These methods for imparting releasability are not particularly limited, and conventionally known methods can be used. The degree of releasability of these rollers is preferably a material having a peel strength of 5 N / mm or less with respect to the cellophane tape manufactured by Nichiban Co., Ltd. according to the method defined in JIS Z0237 (2009). In addition, it is preferable to control the speed of the conveying roller in the furnace individually in accordance with the shrinkage of the sheet in order to efficiently remove the heat shrinkage.

  The surface temperature of the sheet in the annealing treatment step is preferably heated until the maximum temperature of at least one surface of the sheet reaches a temperature equal to or higher than the melting point of the resin composition constituting the surface portion. The surface on the heated side is embossed in the embossing process which is the next process. Here, the “resin composition constituting this surface portion” is a resin composition constituting the process sheet when the process sheet is a single-layer sheet, and the process sheet is a laminate in which a plurality of layers are laminated. In the case of a sheet, it is a resin composition constituting a layer on the surface on the heated side. Even if an annealing process is performed in which the maximum temperature is only a temperature lower than the melting point of the resin composition, the effect of reducing the heat shrinkage rate is insufficient, or a long-time process is required. The maximum surface temperature is within the temperature range of (melting point of the resin composition constituting the heated surface portion + 5 ° C.) to (melting point of the resin composition constituting the heated surface portion + 35 ° C.). preferable. If the temperature during the annealing process becomes too high, the process sheet may adhere to the transport roller, the flatness may deteriorate, or wrinkles may occur in the next process (c) due to these reasons. For example, in the case of a process sheet using EVA resin having a melting point of 71 ° C., it is preferable that the maximum temperature reached in the annealing process is in the range of 76 to 106 ° C. If the temperature is lower than 75 ° C, the effect of the annealing treatment cannot be obtained sufficiently, and it becomes necessary to lengthen the annealing furnace unnecessarily. If the temperature exceeds 105 ° C, the process sheet tends to stick to the conveyance roller, and the flatness is lowered and wrinkles are reduced. Cause.

  The heating time of the process sheet, that is, the time for the process sheet to stay in the annealing furnace is preferably in the range of 22 to 55 seconds. The residence time in the annealing furnace is equal to the heating time for the process sheet cooled by the polishing roller to reach the temperature range of 75 to 105 ° C. where the surface temperature of the process sheet is effective for the annealing treatment, and the above temperature. It is the total of the annealing time for reducing the heat shrinkage after reaching. When the heating time is less than 22 seconds, the removal of the heat shrinkage becomes insufficient, and even if heating is performed for more than 55 seconds, the effect is saturated and the furnace length is merely unnecessarily long. The lower limit of the heating time is preferably 22 seconds or more, and more preferably 25 seconds or more. The upper limit of the heating time is preferably shorter as long as the heat shrinkage can be sufficiently removed, preferably 45 seconds or shorter, and more preferably 40 seconds or shorter.

(Embossing process)
Next, the embossing process will be described.

  The embossing process is a process of heating the process sheet, embossing the process sheet in a high temperature state, and providing independent protrusions having a height of 60 to 300 μm on the process sheet surface. It is preferable to have an embossing roller for imparting protrusions to the process sheet, an opposing roller, and a cooling roller. The method of heating the process sheet is not limited, but it is preferable to introduce the annealed sheet into the embossing process at a high temperature for the purpose of using the heat of the annealing process.

  The embossing roller uses a concave sculpture pattern in order to provide an independent protrusion having a height of 60 to 300 μm on the surface of the process sheet. As the concave engraving pattern, a hemispherical shape, a pyramid shape such as a triangular pyramid, a quadrangular pyramid, a hexagonal pyramid, or a cone, or a trapezoidal shape having a flat top portion thereof can be adopted. Moreover, the pattern in which these shapes were mixed may be sufficient. Among these, a hemispherical shape and / or a quadrangular pyramid shape are preferable. Here, “hemispherical and quadrangular pyramid” means sculpture with a pattern in which hemispherical and quadrangular pyramid are mixed. When the sealing sheet is pressed against the solar battery cell, it is preferably a hemispherical shape that is less likely to be subjected to concentrated weighting and that can uniformly disperse the weight. Further, a quadrangular pyramid shape is preferable in that unevenness of reflected light of the encapsulant sheet hardly occurs and the surface quality is excellent. And since both hemispherical and quadrangular pyramid features can be produced, a pattern in which hemispherical and quadrangular pyramid shapes are mixed is also preferable. When the hemispherical shape and the quadrangular pyramid shape are mixed, the ratio of each may be arbitrarily determined according to which feature is to be obtained. Particularly preferably, all are hemispherical patterns.

The depth of these engraving patterns is preferably in the range of 60 to 350 μm in order to provide protrusions having a height of 60 to 300 μm on the surface of the process sheet. The depth of the engraving pattern on the embossing roller refers to the distance from the center of the embossing roller to the surface of the embossing roller (the part not engraved) and the recess of the engraving pattern (the valley part) from the center of the embossing roller. Indicates the difference from the distance to the deepest part. The depth of this sculpture pattern is indicated by the maximum height Pz (μm) measured using a surface roughness measuring instrument in accordance with JIS B0601 (2001).
The surface of the embossing roller is preferably further provided with a minute recess having a depth of 1 to 20 μm. By embossing with an embossing roller provided with minute depressions, minute projections are formed on the surface of the sheet. As a result, the slipperiness of the sheet is improved and handling is facilitated, and light is scattered by minute projections, and the whiteness of the sheet is improved, so that it is easy to inspect adhered foreign matters and the like. Such a minute depression can be easily formed by carrying out a known blasting process after engraving a pattern on the embossing roller surface. The depth of the minute depression can be adjusted by the particle size at the time of blasting and the pressure condition.

  As the roller facing the embossing roller, in order to improve the transferability of the embossed pattern, a roller obtained by wrapping rubber around a metal roll is used. The type of rubber is not particularly limited, such as silicon rubber, nitrile rubber, chloroprene rubber, etc., but the type A hardness in accordance with JIS K 6253 (2006) is preferably in the range of 65 to 85 °. If the angle is less than 65 ° or exceeds 85 °, the transferability of the embossed pattern is deteriorated. Among these rubbers, silicon rubber is most preferable because it is necessary to have a sheet that easily adheres at high temperatures and good releasability.

In the embossing process, the temperature of the heated surface of the process sheet supplied to the embossing roller is set to (melting point of the resin composition constituting this surface−10 ° C.) to (melting point of the resin composition constituting this surface + 20 ° C.). It is preferable to be within the temperature range. When it is less than (the melting point of the resin composition−10 ° C.), the embossed shape transferability is lowered. If it exceeds (the melting point of the resin composition + 20 ° C.), the temperature of the process sheet in the annealing process becomes too high, and wrinkles and the like are likely to occur in the annealing process. For example, when the surface layer is made of EVA resin having a melting point of 71 ° C., the surface temperature during embossing is in the range of 61 to 91 ° C. Further, the pressing pressure to the embossing roller is linear The pressure is preferably in the range of 150 to 500 N / cm, more preferably in the range of 200 to 450 N / cm. If the linear pressure is less than 150 N / cm, the transferability of the embossed pattern is reduced, and even if it exceeds 500 N / cm, the equipment becomes large and the life of the opposing rubber roller is reduced. In addition, the linear pressure said by this invention is what remove | divided the pressing load of the roller by the surface length of the roller.

  Furthermore, in embossing, in order to improve the transferability of the embossed pattern, it is one of preferred embodiments that the embossing roller holds the sheet. It is preferable that the hugging angle to the embossing roller is in the range of 30 to 270 °. In order to give deep and clear embossing, it is preferable that the hugging angle is 30 ° or more. The hugging angle can be simply calculated from the ratio between the arc length of the portion where the sheet is in contact with the embossing roller and the circumference of the embossing roller. For example, when the hugging angle is 90 °, it means that the sheet is in contact with a portion corresponding to ¼ of the circumference of the embossing roller.

  It is preferable that the surface temperature of the embossing roller is not more than (the melting point of the resin composition constituting the surface portion on the side to which the embossed shape is transferred −20 ° C.). When the temperature of the embossing roller is high, the releasability of the sheet is deteriorated, and when the process sheet is wound around the roller or the process sheet is peeled off from the embossing roller, a new distortion is generated.

  The process sheet released from the embossing roller cools the process sheet by a cooling roll, and quickly reduces the surface temperature to near room temperature.

  The encapsulant sheet processed in this way is adjusted to a desired width for defect inspection and sheet dimensions, and then wound into a roll with a winder or the like, or cut into a cut sheet of a desired length in some cases. And used in the manufacture of solar cell modules. Moreover, the solar cell module of this invention is arrange | positioned between the light-receiving surface protection material, the back surface protection material, and this light-receiving surface protection material and a back surface protection material, and the solar cell was sealed with the sealing material sheet. Layer. Since the sealing material sheet of the present invention disperses the pressing force applied to the solar cells when the materials having the above-mentioned structure are laminated and integrated, the residual stress at the time of molding between the solar cells and the solar cell sealing material Is small, and no bubbles remain in the encapsulant, so that the solar cell module is excellent in durability over a long period of time.

  The measurement method used in this example is shown below. Unless otherwise specified, the number of measurement n was 5, and the average value was adopted.

(1) Pattern depth of embossed roller Based on JIS B0601 (2001), a small surface roughness measuring instrument SJ401 manufactured by Mitutoyo Corporation was used to measure a standard length of 20 mm, a load of 0.75 mN, and a measurement speed of 0.3 mm / s. Under the conditions, the Pz value (μm) measured using a diamond stylus having a cone of 60 ° and a tip curvature radius of 2 μm was defined as the embossing roller pattern depth (μm).

(2) Melt flow rate resin composition of the resin composition constituting the encapsulant sheet was tested in accordance with JIS K7210 (1999) “Plastic-thermoplastic melt mass flow rate (MFR) and melt volume flow rate (MVR)”. According to “Method”, the measurement was performed under the test conditions of a temperature of 190 ° C. and a load of 2.16 kg.

(3) Projection height (T)
The sealing material sheet was cut so as to pass through the top of the protrusions in a direction (width direction) perpendicular to the running direction of the sheet at the time of manufacture (hereinafter abbreviated as MD direction). A cross section in the thickness direction of the cut sealing material sheet was observed over the entire width of the sheet with a stereomicroscope.
When there is a projection on one side of the encapsulant sheet, the side of the encapsulant sheet with the projection is A side, and the side without the projection is B side. As shown in FIG. 1, the distance from the apex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion having no protrusion on the A surface to the B surface is Tmin. Then, the height T of the protrusion was calculated by the formula (i).
T (μm) = Tmax−Tmin (i)
When there are protrusions on both sides of the encapsulant sheet, one side of the encapsulant sheet is A side and the other side is B side. As shown in FIG. 2, the distance from the apex of the projection on the A surface to the portion without the projection on the B surface is TAmax, the distance from the apex of the projection on the B surface to the portion without the projection on the A surface is TBmax, The distance from the portion having no protrusion to the portion having no protrusion on the B surface is defined as Tmin. Then, the height TA of the projection on the A surface was calculated by the equation (ii), and the height TB of the projection on the B surface was calculated by the equation (iii).
TA (μm) = TAmax−Tmin (ii)
TB (μm) = TBmax−Tmin (iii).

(4) Bottom length of protrusion (D)
The surface having the protrusions on the sheet is observed with a stereomicroscope, and the base length (D) is measured. When the shape of the bottom surface of the protrusion is a polygon such as a triangle or a hexagon, or an ellipse, the diameter of the smallest perfect circle including the shape was measured.

(5) Cell cracking property Two plane square test pieces having a side of 180 mm were cut out from the EVA sheet. On the other hand, an interconnector (thickness: 280 μm, width: 2 mm) was soldered to a polycrystalline solar cell (3 bus bars, size: 156 mm square, thickness: 200 μm) to produce a solar cell with an interconnector. Furthermore, a glass plate (size 180 mm square, thickness 3 mm) and a polyester solar battery back sheet (size 180 mm square, thickness 240 μm) were prepared. On the said glass plate, it laminates | stacks in order of a sealing material sheet | seat, a photovoltaic cell, a sealing material sheet | seat, and a back sheet | seat, on the conditions of temperature 145 degreeC, evacuation 30 seconds, press 1 minute, and pressure holding 10 minutes. A solar cell module was manufactured by vacuum lamination. In addition, in the said lamination | stacking, it laminated | stacked so that the surface in which the protrusion of the sealing material sheet | seat was given contacted the photovoltaic cell. The obtained solar cell module was photographed with a solar cell EL image inspection device, a luminescence image was taken, the total crack length (mm) of the cell crack portion was measured, and the above test was repeated three times to obtain the average value of the crack length. Asked.

(6) Number of bubbles The number of bubbles in the solar cell module produced in the above (5) was counted visually. The average value of the number of bubbles in the test three times was determined.

(7) Heat Shrinkage A flat square test piece having a side of 120 mm was cut out from the encapsulant sheet. On this test piece, two parallel straight lines (5 cm) in the TD direction were drawn at a distance of 100 mm at the center in the TD direction during production. And the mark was attached | subjected to the position (each 5 places) which divides each straight line into 6 equal parts.
Next, the test piece was left in warm water heated to 80 ° C. for 60 seconds. When the specific gravity of the encapsulant sheet was small and the encapsulant sheet floated on the surface of the hot water, the encapsulant sheet was left in the floated state. When the specific gravity of the encapsulant sheet was large and the encapsulant sheet sank in warm water, the encapsulant sheet was left as it was. After 60 seconds, the test piece was taken out from the warm water, immersed in room temperature water at 20 ° C. for 10 seconds and cooled, and then moisture on the sheet surface was removed.
The distance A (mm) from each of the five marks attached to one straight line drawn on the test piece to each opposing mark attached to the other straight line was measured with a caliper, and the heat shrinkage rate based on the following formula Was calculated, and the average value of 5 locations was obtained.
Heat shrinkage rate (%) = (100−A) / 100 × 100.

(8) Repulsive stress A flat square test piece having a side of 120 mm was cut out from the encapsulant sheet. Next, using a compression tester KES FB-3 manufactured by Kato Tech Co., Ltd., the EVA sheet was pressurized at a speed of 20 μm / second from the surface having the protrusion of the test piece with a flat pressure terminal having a diameter of 16 mm, and 100 μm was added in the thickness direction. The repulsive stress (kPa) of the sheet when pressed was measured. The above test was repeated three times to obtain the average value of the repulsive stress.

Example 1
EVA (vinyl acetate content: 28% by mass, melt flow rate: 15 g / 10 min (190 ° C.), melting point: 71 ° C.) 100 parts by mass, t-butylperoxy-2-ethylhexyl monocarbonate (1 hour half-life temperature) 119 ° C) 0.7 parts by mass, triallyl isocyanurate 0.3 parts by mass, γ-methacryloxypropyltrimethoxysilane 0.2 parts by mass, 2-hydroxy-4-methoxybenzophenone 0.3 parts by mass, bis ( A resin composition comprising 0.1 part by weight of 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate was supplied to a twin screw extruder set at 80 ° C. and melt-kneaded. The kneaded resin composition was extruded into an EVA sheet from a T die connected to a twin screw extruder and held at 105 ° C. The lip width of the T die was 1300 mm and the lip gap was 0.8 mm.

The EVA sheet was cooled and solidified by a polishing roll maintained at 20 ° C. The sheet temperature when the EVA sheet was discharged from the T die was 107 ° C. At this time, the sheet width was 1150 mm, the sheet thickness was 450 μm, and the sheet conveyance speed was 10 m / min.
Next, annealing treatment and embossing were continuously performed.

  For the annealing treatment, a ceramic heater with a surface temperature set at 350 ° C. is installed, and a metal roller coated with “Teflon (registered trademark)” on the surface with a diameter of 150 mm is installed at intervals such that the distance between the centers of the rollers is 250 mm. It was performed by passing through an annealing furnace in which a heat insulating material was wrapped around a SUS case. Hot air was blown from the bottom of the furnace entrance and bottom of the exit at a wind speed of 1 m / sec.

In the embossing process, the sheet taken out from the annealing furnace is wrapped with an embossing roller having a pattern depth of 180 μm, a diameter of 460 μm, and 450 hemispherical concave engraving patterns / cm ² , and silicon rubber having a hardness of 75 ° with a thickness of 10 mm. It was carried out by passing between the opposite rollers.
The details of the manufacturing conditions are as follows.
Sheet surface temperature at the annealing furnace entrance: 23 ° C
Hot air temperature: 93 ° C
Maximum temperature of sheet surface in annealing furnace: 90 ° C
Sheet surface temperature at annealing furnace outlet: 90 ° C
Sheet residence time in the annealing furnace: 28 seconds Sheet speed at the outlet of the annealing furnace 15: 9.6 m / min
Sheet surface temperature at the embossing roller entrance: 78 ° C
Embossing roller temperature: 15 ° C
Embossed roller linear pressure: 350 N / cm
Hook angle to emboss roller: 120 °
The heat shrinkage rate, the repulsive stress, the cell cracking property at the time of module production, and the number of bubbles of the obtained encapsulant sheet were evaluated. The results are shown in Table 1. As shown in Table 1, it was a sealing material sheet having a small sheet heat shrinkage ratio and few cell cracks and bubbles during module production.

(Example 2)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 120 μm, a diameter of 460 μm and a hemispherical concave engraving pattern having 450 pieces / cm ² . .
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few cell cracks and bubbles during module production.

(Example 3)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 300 μm, a diameter of 460 μm, and 450 hemispherical concave engraving patterns / cm ² . .
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few cell cracks and bubbles during module production.

Example 4
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 300 μm and a diameter of 330 μm and a hemispherical concave engraving pattern of 980 pieces / cm ² . .
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few cell cracks and bubbles during module production.

(Example 5)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm, an outer diameter of 460 μm, and a concave pyramid-shaped concave sculpture pattern of 840 pieces / cm ^2. Created.
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few bubbles, although some cell cracking during module production occurred.

(Example 6)
A sealing material sheet was prepared in the same manner as in Example 1 except that the annealing was not performed and the sheet surface temperature was heated to 90 ° C. with an infrared heater and embossing was performed.
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet with a small number of bubbles, although the sheet had a large heat shrinkage rate and cell cracks during module production were slightly generated.

(Example 7)
A sealing material sheet was prepared in the same manner as in Example 1 except that the EVA resin was changed to an EVA resin having a melt flow rate of 10 g / 10 min. As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few bubbles, although some cell cracking during module production occurred.

(Example 8)
The embossing roller, the pattern depth 180 [mu] m, except for changing the concave engraved pattern quadrangular pyramid shape 45 / cm ² with embossing rollers with an outer peripheral diameter of 2000μm is a sealing material sheet in the same manner as in Example 1 Created.
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small number of bubbles, although the sheet heat shrinkage rate was small and cell cracking occurred slightly during module production.

(Comparative Example 1)
Except not embossing, the sealing material sheet implemented to the annealing process by the method similar to Example 1 was created, and it used for evaluation.
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet in which the heat shrinkage rate of the sheet was small, but cell cracks and bubbles were generated in large quantities during module production.

(Comparative Example 2)
The embossing roller was sealed in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm and a semicircular groove (groove width of 460 μm) continuous in the roll rotation direction. A stop sheet was created.
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small amount of sheet heat shrinkage and few cell cracks during module production, but many bubbles.

(Comparative Example 3)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 50 μm, a diameter of 460 μm, and a hemispherical concave engraving pattern having 450 pieces / cm ² . .
As shown in Table 1, the obtained encapsulant sheet had a small sheet heat shrinkage rate, but was a encapsulant sheet with many cell cracks and bubbles during module production.

(Comparative Example 4)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm and a diameter of 150 μm and a hemispherical concave engraving pattern of 4500 pieces / cm ² . .
As shown in Table 1, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage ratio and a small number of bubbles, but many cell cracks during module production.

(Comparative Example 5)
A sealing material sheet was prepared in the same manner as in Example 1 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm, a diameter of 3800 μm, and a hemispherical concave engraving pattern of 7 pieces / cm ² . .

As shown in Table 1, the obtained encapsulant sheet had a small sheet heat shrinkage, but was an encapsulant sheet with many cell cracks and many bubbles during module production.

  The encapsulant sheet of the present invention can be suitably used as an encapsulant sheet for solar cells because it can suppress defects such as cell cracks during lamination in the solar cell production process and bubbles in the encapsulant. .

Claims (6)

The resin composition constituting the surface portion consists of ethylene-vinyl acetate copolymer composition, on the surface part has a height 60~300μm independent projections of 40 to 2300 pieces / cm ^2, and the independent A solar cell encapsulant sheet, wherein the ratio (T / D) of the height (T) of the protrusion to the base length (D) is 0.05 to 0.80. 2. The solar cell sealing according to claim 1, wherein when the solar cell sealing sheet is left in warm water at 80 ° C. for 1 minute, the heat shrinkage in the sheet flow direction of the sealing material sheet is 30% or less. Material sheet. The solar cell encapsulant sealing material sheet according to claim 1 or 2, wherein the shape of the independent protrusion is hemispherical and / or quadrangular pyramid. The repulsive stress of a sheet | seat is 70 kPa or less when the surface which has the said protrusion of the said solar cell sealing material sheet is compressed 100 micrometers in the thickness direction of this sealing material sheet. Solar cell encapsulant sheet. The solar cell sealing material sheet in any one of Claims 1-4 with which the surface which has the processus | protrusion of the said solar cell sealing material sheet further has 1-15 micrometers in height protrusion. It arrange | positions between a light-receiving surface protection material, a back surface protection material, this light-receiving surface protection material, and a back surface protection material, and a photovoltaic cell is sealed with the solar cell sealing material sheet in any one of Claims 1-5. A solar cell module composed of a stopped layer.

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