JP2007129204A - Film for sealing rear surface of solar cell, and solar cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polybutylene terephthalate film which is excellent in a reflectance, a thermal resistance, a steam barrier nature, a hydrolysis-proof nature, a weatherproof nature, an insulating nature, a workability, and an extrusion nature; and is excellent for sealing a rear surface of a solar cell, and the solar cell using the film. <P>SOLUTION: A film for sealing the rear face of the solar cell consists of the polybuthylene terephthalate film containing titanium oxide manufactured by a chlorine method or a lamination of the polybuthylene terephthalate film, wherein furthermore the titanium oxide is desirably a rutile-type. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell back surface sealing film made of a polybutylene terephthalate film and a solar cell using the same.

  In recent years, solar cells have attracted attention as a next-generation energy source, and development is progressing from the construction field to electrical and electronic parts. The solar cell back surface sealing film used for some of the battery components is also strongly required to have durability (hydrolysis resistance and weather resistance) against the natural environment. Furthermore, the improvement of the solar light conversion efficiency of a battery is also requested | required and the high reflectance of the back surface sealing film of a solar cell is requested | required. There is also a demand for lightness, strength, and battery processability.

  As a structure of the solar cell, a high light transmissive material / ethylene-vinyl acetate copolymer (hereinafter EVA) / solar cell module / EVA / back surface sealing film is generally known. EVA is a filling resin layer of the solar cell module.

  Moreover, as a solar cell back surface sealing film, it is known to use a polyethylene-type resin, a polyester-type resin sheet, or a fluorine-type film for patent document 1, patent document 2, etc., for example.

However, these conventional film base materials have the following problems.
Polyethylene terephthalate resins have limited use in this field due to poor hydrolysis resistance. Moreover, although the white colored polyethylene terephthalate has improved reflection efficiency, it has poor hydrolyzability. Furthermore, in order to satisfy these demands, it is difficult to produce a film by coextrusion because biaxial stretching is indispensable for producing a laminate in order to produce a highly functional film as in Patent Document 3. In addition, since a stretching process is required, it is disadvantageous in terms of cost and work efficiency.

  In addition, the fluorine-based film is excellent in adhesion to EVA, but has a drawback that the film has poor gas barrier properties (particularly, water vapor barrier properties) and the film is weak. Therefore, such a film has been used by laminating a metal foil such as aluminum in order to improve the barrier property and provide the strength of the back surface sealing film layer. However, this is contrary to the purpose of this field where weight reduction is required, and it is disadvantageous in terms of cost.

  Moreover, although the thing using a polyethylene sheet is comparatively cheap, there existed difficulty in the heat resistance when exposed to high temperature (100-120 degreeC).

Moreover, although the back surface protection sheet for solar cells which uses a PBT film like patent document 4 is proposed, a reflectance, a weather resistance, and hydrolysis resistance were not enough.
JP-A-11-261085 JP-A-11-186575 JP 2002-026354 A JP 2001-119051 A

  The present invention provides a solar cell back surface sealing film comprising a polybutylene terephthalate film having excellent mechanical properties and heat resistance, and a solar cell using the same, from the background of such conventional technology. is there.

  As a result of intensive studies to solve the problems of the prior art, the present inventors adopt the following means.

That is,
(1) A solar cell back surface sealing film comprising a polybutylene terephthalate film containing titanium oxide produced by a chlorine method or a laminate of polybutylene terephthalate films.
(2) The solar cell back surface sealing film according to (1), wherein the titanium oxide is a rutile type.
(3) The solar cell back surface sealing film according to (1) or (2), wherein the titanium oxide average particle diameter is 0.10 to 0.24 μm.
(4) The solar cell back surface sealing film according to any one of (1) to (3), wherein the titanium oxide contains two types of surface treatment agents, alumina hydrate and silicic acid hydrate.
(5) The film for sealing a back surface of a solar cell according to any one of (1) to (4), further comprising one or more epoxy compounds of glycidyl ester or glycidyl ether.
(6) The solar cell back surface sealing film according to any one of (1) to (5), further containing a benzotriazole-based compound or a benzophenone-based compound.
(7) A polybutylene terephthalate film layer containing the titanium oxide according to any one of (1) to (4), a polybutylene terephthalate film layer containing a benzotriazole compound or a benzophenone compound, a glycidyl ester or a glycidyl ether. A solar cell back surface sealing film in which any two or more of polybutylene terephthalate film layers containing one or more epoxy compounds are laminated.
(8) The manufacturing method of the film for solar cell backside sealing in any one of (1)-(7) by coextruding a film.
(9) A solar cell comprising the solar cell back surface sealing film according to any one of (1) to (7).
Is provided.

  The solar cell back surface sealing film of the present invention is a film excellent in reflectance, heat resistance, water vapor barrier properties, hydrolysis resistance, weather resistance, insulation properties, workability, and extrudability, and these properties are balanced. A good solar cell can be used.

  The present invention is described in detail below.

  The solar cell referred to in the present invention refers to a system that converts sunlight into electricity and stores the electricity, and preferably includes a high light transmissive material, a solar cell module, a filling resin layer, and a back surface sealing film as shown in FIG. Specifically, some are incorporated in the roof of a house, others are used for electrical and electronic parts, and some have flexible properties.

  Here, the high light-transmitting material is a material that efficiently allows sunlight to enter and protects the internal solar cell module. Preferably, glass, high light-transmitting plastic, a film, or the like is used. The solar cell module converts sunlight into electricity and stores it, and is the heart of the solar cell. The module is made of a semiconductor such as silicon, cadmium-tellurium, or germanium-arsenic. Currently widely used are single crystal, polycrystalline silicon, amorphous silicon, and the like. The filled resin layer is used for the purpose of fixing and protecting the solar cell module in the solar cell and for electrical insulation, and among them, ethylene vinyl acetate resin is preferably used in terms of performance and price.

  And the solar cell back surface sealing film of the present invention is an important role of protecting the solar cell module on the back side of the solar cell, and the film can block the entry of water vapor and ultraviolet rays from the outside which the solar cell module dislikes. Such is preferably used. In addition, by reflecting sunlight leaking from the upper part of the battery, the reflected light is also converted, and the conversion efficiency is improved.

  In the present invention, a polybutylene terephthalate film is used as the solar cell back surface sealing film. The polybutylene terephthalate referred to here is a polymer obtained by an ordinary polymerization method such as a polycondensation reaction mainly comprising terephthalic acid or an ester-forming derivative thereof and 1,4-butanediol or an ester-forming derivative thereof. In addition, other copolymer components may be included in a range that does not impair the characteristics, for example, about 20% by weight or less. Preferred examples of these (co) polymers include polybutylene terephthalate, polybutylene (terephthalate / isophthalate), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene ( Terephthalate / naphthalate), poly (butylene / ethylene) terephthalate, and the like. These may be used alone or in combination. Among them, in the present invention, a polybutylene terephthalate resin composition containing polybutylene terephthalate as a main component is preferably used.

  The polybutylene terephthalate resin composition of the present invention includes a reinforcing material, a filler, an antioxidant, a stabilizer, an ultraviolet absorber, a colorant, a mold release agent, a flame retardant, etc., as long as the effects of the present invention are not impaired. Conventional additives and small amounts of other polymers can be added.

  Examples of the reinforcing material and filler include glass fiber, carbon fiber, asbestos fiber, rock wool, calcium carbonate, silica sand, bentonite, kaolin, clay, wollastonite, barium sulfate, glass beads, mica, and silica.

  Examples of antioxidants include 2,6-di-t-butyl-4-methylphenol, tetrakis (methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) methane, tris Phenol compounds such as (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, sulfur such as dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate And phosphorous compounds such as trisnonylphenyl phosphite and distearyl pentaerythritol diphosphite.

  These various additives may have a synergistic effect by combining two or more kinds, and may be used in combination.

  For example, the additive exemplified as the antioxidant may act as a stabilizer or an ultraviolet absorber. Some of those exemplified as stabilizers also have an antioxidant action and an ultraviolet absorption action. That is, the above classification is for convenience and does not limit the action.

Release agents include plant waxes such as carnauba wax and rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as montan wax, petroleum waxes such as paraffin wax and polyethylene wax, castor oil and its Derivatives, fatty acids, and oil-based waxes such as derivatives thereof. Examples of higher fatty acid derivatives include higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and montanic acid, and monohydric or dihydric or higher alcohols. Esters, partial saponification of these higher fatty acid esters partially with metal oxides such as Ca (OH) ₂ , NaOH, Mg (OH) ₂ , Zn (OH) ₂ , LiOH, Al (OH) ₃ Saponification obtained from esterified esters, higher fatty acids and metal oxides or metal hydroxides Products, higher fatty acids and polyhydric alcohol esters, which are condensed with a dicarboxylic acid such as adipic acid as a binder, mono- or diamides obtained from higher fatty acids and monoamines or diamines.

  Among the flame retardants, brominated flame retardants are preferably used for imparting flame retardancy. Specific examples of the brominated flame retardant include halogenated polycarbonate (for example, tetrabromobisphenol A carbonate oligomer), halogenated acrylic resin, halogenated epoxy resin, halogenated phenoxy resin, halogenated polystyrene, tetrabromobisphenol A / ethyl. High molecular weight organic halogen compounds such as ether oligomers and halogenated polyphenylene ethers (eg, polydibromophenylene oxide); Decabromodiphenyl ether, hexabromophenol, tetrabromobisphenol A, epoxidized tetrabromobisphenol A, tetrabromobisphenol A / bis (2,3-dibromopropyl ether), tetrabromobisphenol A bis (allyl ether), tetrabromobisphenol A. Brominated bisphenol A such as 2-hydroxyethyl ether, hexabromobenzene, tetrabromophthalic anhydride, tribromophenol, bis (tribromophenoxy) ethane, bis (pentabromophenoxy) ethane, ethylenebistetrabromophthalimide, bromine And low molecular weight organic halogen compounds such as bis (2,3-dibromopropyl ether) of tetrabromobisphenol S and tetrabromobisphenol S. These organic halogen flame retardants can be used alone. Also, two or more of them may be used in combination. Moreover, phosphorus-based and inorganic flame retardants can also be used.

  As other types of polymers, polycarbonate resin, nylon resin, PPS resin, polytetrafluoroethylene, polyethylene terephthalate resin, ABS resin and the like can be added.

  The film refers to an unstretched film obtained by melting the above polymer, or a film obtained by heat-treating the unstretched film biaxially. Preferably, an unstretched film that exhibits sufficient characteristics from the viewpoint of work efficiency is preferable. Further, the thickness is preferably in the range of 10 to 2000 μm, more preferably 10 to 500 μm, even more preferably in view of the appropriate waist strength, processability, and light weight of the solar cell as a solar cell back surface sealing film. Is 50-300 μm.

The solar cell back surface sealing film of the present invention is one of the following high reflectance, hydrolysis resistance, and weather resistance from the viewpoint of enhancing the conversion efficiency of the solar cell and protecting it from sunlight and water vapor. It is preferable to have at least one, and it is more preferable to have all the properties.
The reflectance here is a light reflectance at a wavelength λ = 550 nm, and when this value is 80% or more, the conversion efficiency of the solar cell becomes very high, which is preferable in practical use. The reflectance can be measured with an ultraviolet near infrared spectrophotometer UV-3150 manufactured by Shimadzu Corporation.

  Regarding hydrolysis resistance, the film was aged in an atmosphere of 85 ° C. and 95% RH for 3000 hours, the elongation at break of the film was measured by ASTM-D61T, and the ratio when the elongation at break without aging was 100%. (Retention ratio) can be used as an index, and in the present invention, it is preferably 50% or more. When the retention is less than 50%, deterioration due to water vapor may occur due to insufficient hydrolysis resistance, which is not preferable as a film for sealing the back surface of a solar cell.

For weather resistance, the film was measured by ASTM-D61T, which was subjected to the following cycle for 5 cycles using an accelerated tester Ice Par UV Tester (manufactured by Iwasaki Electric Co., Ltd.), and the elongation at break before the treatment was 100%. The elongation can be used as an index, and in the present invention, it is preferably 50% or more. When the breaking elongation after the treatment is less than 50%, it is not preferable because the solar cell may not be protected as a solar cell back surface sealing film due to insufficient weather resistance.
1 cycle: UV irradiation for 8 hours in an atmosphere at a temperature of 60 ° C. and a relative humidity of 50%, followed by aging for 4 hours in a condensation state (temperature of 35 ° C. and relative humidity of 100%).

  Further, in the present invention, from the viewpoint of creating a film having both solar light reflection efficiency and weather resistance characteristics, it is one of the preferred embodiments for a laminate of a polybutylene terephthalate film as a back surface sealing film for solar cells. . A laminate of polybutylene terephthalate film is a laminate of the created films, and each created film is laminated via an adhesive layer, or laminated by coextrusion that is extruded and joined simultaneously. It may be a film. In view of production efficiency, a laminated film by coextrusion is preferred.

  The solar cell back surface sealing film of the present invention preferably uses polybutylene terephthalate containing titanium oxide in order to obtain high reflectance. In addition to titanium oxide, silica, alumina, calcium carbonate, barium sulfate, zinc sulfide, or the like can be used as an inorganic filler. Further, it is more effective to use a fluorescent whitening agent such as thiophenediyl.

  Examples of the titanium oxide used in the present invention include those produced by the sulfuric acid method and the chlorine method, but the titanium oxide produced by the chlorine method has fewer impurities as described above than the titanium oxide produced by the sulfuric acid method, Since it is excellent in the point of whiteness and higher light reflection performance can be obtained, what was manufactured by the chlorine method is more preferable for this invention.

  The crystal form of titanium oxide includes a rutile type and an anatase type, and the rutile type is superior in terms of thermal stability and light resistance, and rutile type titanium oxide is more preferable in the present invention. In order to improve the dispersibility with the resin, the titanium oxide is often treated with various surface treatment agents and coated on the surface, and the surface treatment agents include alumina hydrate, silica Acid hydrates, silica, zinc and the like are usually used, and among them, those containing two kinds of alumina hydrate and silicic acid hydrate are preferable in that the dispersibility of titanium oxide is improved. Moreover, it is preferable that the average particle diameter of a titanium oxide is 0.10-0.24 micrometer, More preferably, it is 0.15-0.22 micrometer. If the average particle size is smaller than 0.10 μm, the dispersibility is deteriorated, causing aggregation and not only lowering the light resistance but also lowering the light shielding property, so that the desired high light reflection performance may not be achieved. If the average particle diameter is larger than 0.24 μm, the appearance of the molded product may be poor, or the desired high light reflection performance may not be achieved. Moreover, considering the addition amount which expresses a reflectance, 0.01 to 60 weight% is preferable with respect to the total weight of a resin composition, More preferably, it is 0.5 to 30 weight%. The average particle diameter was magnified 50000 times with a scanning electron microscope, the diameter in the longitudinal direction of 100 particles was measured, and the number average was taken as the average particle diameter.

The film for sealing a back surface of a solar cell used in the present invention includes a polybutylene terephthalate film containing a benzotriazole compound or a benzophenone compound and / or an epoxy compound in order to obtain high hydrolysis resistance and weather resistance. Is preferred.
The benzotriazole compounds or benzophenone compounds used in the present invention are as follows, and include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 2- (2′-hydroxy-5′-t). -Octylphenyl) benzotriazole, benzotriazole compounds such as 2- (2'-hydroxy-5'-butylphenyl) benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-mesoxy-benzophenone, 2- Benzophenone compounds such as hydroxy-4-n-octoxy-benzophenone. The content of the benzotriazole compound or the benzophenone compound is preferably 0.01 to 2% by weight with respect to the total weight of the resin composition in order to improve the weather resistance.

  The epoxy compound used in the present invention is a compound having an epoxy group having an epoxy equivalent of 1000 or less, which is the number of grams of the compound containing 1 gram equivalent of the epoxy group used in the present invention, which has an effect of improving hydrolysis resistance. It is preferable from the point of view, and it may be generally used by being added to a thermoplastic resin. Further preferred are compounds having a glycidyl ester in the molecule, compounds having a glycidyl ether, and compounds having both a glycidyl ester and a glycidyl ether. These epoxy compounds are used alone or in combination of two or more, and in particular, a combination of a compound having a glycidyl ester and a compound having a glycidyl ether or a compound having both a glycidyl ester and a glycidyl ether is preferable.

  Specific epoxy compounds include resorcin diglycidyl ether, sorbitol polyglycidyl ether, diethylene glycol diglycidyl ether, dibromophenyl glycidyl ether, dibromoneopentyl glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diester. Glycidyl ether, polyglycerin polyglycidyl ether, acrylic glycidyl ether, sorbitan polyglycidyl ether, pt-butylphenyl glycidyl ether, phenyl glycidyl ether, bisphenol-A-diglycidyl ether, bisphenol-S-diglycidyl ether, hydroquinone diglycidyl ether Ether, dimer acid diglycidyl ester, o-phthalic acid diglycidyl ester Ter, hexahydrophthalic acid diglycidyl ester, neodecanoic acid glycidyl ester, terephthalic acid diglycidyl ester, soybean oil glycidyl ester, benzoic acid monoglycidyl ester, stearic acid monoglycidyl ester, lauric acid monoglycidyl ester, p-hydroxybenzoic acid Examples include glycidyl ester ether. In order to improve the hydrolysis resistance, the content of the epoxy compound is preferably 0.01 to 2% by weight based on the total weight of the resin composition.

  What is necessary is just to implement by the method generally known about the manufacturing method of the resin composition used for this invention, and does not need to specifically limit. A typical example is a method of melt-kneading at a temperature of 200 to 350 ° C. using a known melt mixer such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll. Each component may be mixed in advance and then melt kneaded. For example, about a small amount additive component which is 1 weight part or less, after kneading | mixing and pelletizing another component by said method etc., it can also add before shaping | molding. In addition, although it is better that the water | moisture content adhering to each component is less and it is desirable to dry beforehand, not all the components need to be dried.

  As a method for producing the polybutylene terephthalate film of the present invention, the polymer is dried as necessary, supplied to a known melt extruder, a sheet is extruded from a slit-shaped die, and the polymer is adhered to a metal drum. The method of cooling and obtaining an unstretched film is mentioned. In the case of biaxial stretching, a biaxially stretched film can be obtained by a known method such as simultaneous biaxial stretching or sequential biaxial stretching. The film obtained by the above method is a solar cell back surface sealing film.

  The method for laminating the solar cell back surface sealing film of the present invention is to supply each polymer to a separate extruder at the time of the above melt extrusion, and to combine both polymers in a molten state with a composite facility provided in the melt flow path. A method of producing the composite unstretched film is common. Although it is possible to stretch and heat-treat this film while it is composited, the number of processes increases and the behavior when each film is stretched is different, so it may not be stretched well. preferable. Further, the laminate can be a laminate of three or more layers by the above method.

  The evaluation method is shown below.

(1) Reflectance The total light reflectance at a wavelength λ = 550 nm was measured with an ultraviolet near infrared spectrophotometer UV-3150 manufactured by Shimadzu Corporation.
○: Reflectance: 50% or more Δ: Reflectance: 30% or more and less than 50% ×: Reflectance: less than 30%

(2) Heat resistance 120 degreeC, the deformation | transformation of the film at the time of processing for 3000 hours was confirmed.
○: Almost no deformation Δ: Slightly deformed X: Remarkably deformed

(3) Water vapor barrier property The water vapor transmission rate was measured according to JIS Z0208-73. The measurement conditions were a temperature of 40 ° C. and a relative humidity of 90%. The unit was g / m2 / 24h / 0.1 mm.
O: Less than 1.0 x: 1.0 or more.

(4) Hydrolysis resistance When the film was aged in an atmosphere of 85 ° C. and relative humidity 95% for 3000 hours, the breaking elongation of the film was measured by ASTM-D61T, and the breaking elongation without aging was 100%. The ratio (retention ratio) was compared, and the determination was made according to the following criteria.
○: Retention rate 50% or more Δ: Retention rate 30% or more and less than 50% × Retention rate less than 30%

(5) Weather resistance Using an accelerated tester ice par UV tester (manufactured by Iwasaki Electric Co., Ltd.), the following cycle was repeated 5 times, and the breaking elongation of the film measured by ASTM-D61T was measured.
1 cycle: UV irradiation for 8 hours in an atmosphere at a temperature of 60 ° C. and a humidity of 50% RH, followed by aging for 4 hours in a condensed state (temperature of 35 ° C., relative humidity of 100%)
○: Tensile rupture elongation of 50% or more Δ ... Tensile rupture elongation of 25% or more and less than 50% x ... Tensile rupture elongation of less than 25%.

(6) Insulation The dielectric breakdown strength was measured according to JIS C2151. The unit was MV / m.
○ ... 20 or more Δ ... 15 or more but less than 20 x ... less than 15.

(7) Workability The tear characteristics were evaluated in order to cut the solar cell back surface sealing film and incorporate it into the solar cell system. The tear strength was based on JIS 2151 and the strength in the MD direction was measured. The unit was N / mm obtained by dividing the tear load by the thickness.
○ ... 40 or more Δ ・ ・ ・ 10 or more and less than 40 × ... less than 10.

(8) Extrudability Extrudability was determined as follows.
○ Multi-layer extrusion is easy by co-extrusion.
X ... Multi-layer extrusion is difficult by co-extrusion, and film production takes time and cost.

  Although the back surface sealing film for solar cells of this invention is demonstrated according to the following specific example below, this invention is not limited to these Examples.

Aa: Toray PBT resin 1200S
A-b-1: Toray PBT resin 1200S / Ishihara Sangyo Co., Ltd. titanium oxide CR63 (average particle size 0.21 μm, rutile titanium oxide produced by the chlorine method, alumina hydrate and silicic acid hydrate Two types were used as treatment agents.)
(Particle diameter 0.21 μm) = 99 wt% / 1 wt%
Ab-2: Toray PBT resin 1200S / Ishihara Sangyo Co., Ltd. titanium oxide CR63 = 80 wt% / 20 wt%
Ac: Toray PBT resin 1200S / Ishihara Sangyo Titanium oxide CR95 (average particle size 0.28 μm, rutile titanium oxide manufactured by the chlorine method, alumina hydrate and silicic acid hydrate) Was used as a treating agent.) = 80 wt% / 20 wt%
Ad: Toray PBT resin 1200S / Ciatech Japan Co., Ltd. Siasorb UV5411 (benzotriazole compound) = 99.5 wt% / 0.5 wt%
Ae: Toray PBT resin 1200S / EVERSORB10 (benzotriphenone compound) manufactured by Eiko Chemical Industries, Taiwan = 99.5 wt% / 0.5 wt%
Af: Toray PBT resin 1200S / Oilized Shell Epoxy Cardura E10 (Neodecanoic acid glycidyl ester) = 99.5 wt% / 0.5 wt%
Ag: Toray PBT resin 1200S / Cytec Japan Co., Ltd. Siasorb UV5411 / Oilized Shell Epoxy Cardura E10 = 99 wt% / 0.5 wt% / 0.5 wt%
Ah: Toray PBT resin 1200S / EVERSORB10 manufactured by Eiko Chemical Industries, Taiwan / Cardura E10 manufactured by Yuka Shell Epoxy Co., Ltd. = 99 wt% / 0.5 wt% / 0.5 wt%
AI: Toray PBT resin 1200S / EVERSORB10 manufactured by Eikoh Chemical Industry Co., Ltd./Clear 819E10P manufactured by Petrochemicals (57% by weight of glycidyl neodecanoate / 43% by weight of bisphenol A diglycidyl ether) = 99% by weight / 0.5% by weight % / 0.5% by weight
AJ: Toray PBT resin 1200S / Ishihara Sangyo Titanium oxide R670 (average particle size 0.21 μm, rutile titanium oxide produced by sulfuric acid method, alumina hydrate and silicate hydrate) Was used as a treating agent.) = 80 wt% / 20 wt%
AK: Toray PBT resin 1200S / Titanium oxide A220 manufactured by Ishihara Sangyo Co., Ltd. (average particle size 0.16 μm, anatase-type titanium oxide manufactured by the sulfuric acid method was used with one kind of alumina hydrate as a treating agent. .) = 80 wt% / 20 wt%.

Ba: Polyethylene terephthalate resin having an intrinsic viscosity of 0.6 Bb: Polyethylene terephthalate resin having an intrinsic viscosity of 0.6 / Titanium oxide CR63 manufactured by Ishihara Sangyo Co., Ltd.
= 80% / 20%
Bc: Polyethylene terephthalate resin having an intrinsic viscosity of 0.6 / Ciasorb UV5411 manufactured by Cytec Japan / Cardura E10 manufactured by Yuka Shell Epoxy = 99 wt% / 0.5 wt% / 0.5 wt%.

C-a: Polyvinyl fluoride tedlar manufactured by DuPont

Da: Examples and comparative examples are described in a polyethylene resin table having a density of 0.923. In addition, the structure of the film in a table | surface shows the lamination | stacking state of a film. When even one of the characteristic items in the table had x, it was judged unsuitable as a film for sealing a back surface for solar cells and rejected. In all cases, Δ or ○ was accepted.

Examples 1 to 12 and Comparative Examples 6 to 7
As shown in Table 1, after the above materials were vacuum-dried at 130 ° C. for 3 hours, the dried chips were supplied to a 150 mm short-shaft extruder and melt-mixed, and then the inside of the fiber sintered stainless metal filter (cut 5 μm) The sheet was passed through, extruded from a T die die into a sheet, and solidified by cooling while applying an electrostatic charge to a cooling drum maintained at 25 ° C. At this time, the extruder temperature was set to 260 ° C. for the supply section, 280 ° C. for the compression section / metering section, and the residence time was 7 minutes.

  Moreover, about Examples 4-12, the resin composition of (1)-(2) or (1)-(3) was coextruded, it was made into the lamination, and this was made into the film for solar cell backside sealing. In the case of a laminated film, (1) was placed on the side in contact with B in FIG. 1 (the back side of the solar cell). All the examples had good characteristics.

Comparative Examples 1-3
The manufacturing method of the film was performed as follows. As shown in Table 2, after the above materials were vacuum dried at 130 ° C. for 3 hours, the dried chips were supplied to a 150 mm short axis extruder and melt mixed, and then the inside of the fiber sintered stainless metal filter (5 μm cut) The sheet was passed through, extruded from a T die die into a sheet, and solidified by cooling while applying an electrostatic charge to a cooling drum maintained at 25 ° C. At this time, the extruder temperature was set to 290 ° C. for the supply section, 310 ° C. for the compression section / metering section, and the residence time was 7 minutes. Next, the cast film was stretched 4.5 times at 135 ° C. in the longitudinal direction by a roll type stretching machine, then introduced into a tenter, transversely stretched 5.3 times at 140 ° C., and then once cooled to 50 ° C. The film was obtained by heat setting at 200 ° C.

In Comparative Example 1, the extrudability was not good, the tear strength was very low, and the processability was poor.
In Comparative Example 2, although the reflectance of the film was improved, this material cannot exhibit its properties unless it is biaxially stretched, so that the extrudability is not good, the tear strength is very low, the workability is poor, and it is rejected. Met.

  Although Comparative Example 3 has improved reflectivity, hydrolysis resistance, and weather resistance, as in Comparative Examples 1 and 2, the properties cannot be expressed unless it is biaxially stretched, and the extrusion is very difficult. The film was not good, the tear strength was very low, the workability was poor, and it was rejected.

Comparative Example 4
The manufacturing method of the film was performed as follows. As shown in Table 2, after being supplied to a 150 mm short axis extruder and melt mixed, it was passed through a fiber sintered stainless steel metal filter (5 μm cut), extruded from a T die die into a sheet, and brought to 25 ° C. The static cooling was applied to the maintained cooling drum and solidified by cooling. At this time, the extruder temperature was set to 290 ° C. for the supply section, 310 ° C. for the compression section / metering section, and the residence time was 7 minutes. As a result, as shown in Table 2, the water vapor barrier property was poor and it was rejected.

Comparative Examples 5-7
The manufacturing method of the film was performed as follows. Cooling drum that was supplied to a 150 mm short shaft extruder, melted and mixed, then passed through a fiber sintered stainless metal filter (5 μm cut), extruded from a T die die into a sheet, and kept at 25 ° C. The solution was solidified by close contact and cooling while applying an electrostatic charge. At this time, the extruder temperature was set to 200 ° C. for the supply section, 220 ° C. for the compression section / metering section, and the residence time was 7 minutes. As a result, as shown in Table 2, Comparative Example 5 was poor in heat resistance, and Comparative Example 6 and Comparative Example 7 were very bad in weather resistance and failed.

It is explanatory drawing which shows an example of a structure of a solar cell.

Claims (9)

  A solar cell back surface sealing film comprising a polybutylene terephthalate film containing titanium oxide produced by a chlorine method or a laminate of polybutylene terephthalate films.   The film for sealing a back surface of a solar cell according to claim 1, wherein the titanium oxide is a rutile type.   The film for sealing a back surface of a solar cell according to claim 1 or 2, wherein the titanium oxide has an average particle size of 0.10 to 0.24 µm.   The film for sealing a back surface of a solar cell according to any one of claims 1 to 3, wherein the titanium oxide contains two types of surface treatment agents, alumina hydrate and silicate hydrate.   Furthermore, the film for solar cell backside sealing in any one of Claims 1-4 containing the 1 type, or 2 or more types of epoxy compound of glycidyl ester or glycidyl ether.   Furthermore, the film for solar cell backside sealing in any one of Claims 1-5 containing the benzotriazole type compound or the benzophenone type compound.   A polybutylene terephthalate film layer containing the titanium oxide according to any one of claims 1 to 4, a polybutylene terephthalate film layer containing a benzotriazole compound or a benzophenone compound, one or two of glycidyl ester or glycidyl ether A solar cell back surface sealing film in which any two or more of polybutylene terephthalate film layers containing at least one epoxy compound are laminated.   The manufacturing method of the film for solar cell backside sealing in any one of Claims 1-7 by co-extrusion of a film.   The solar cell containing the film for solar cell backside sealing in any one of Claims 1-7.

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