JP2011171321A - Solar-cell sealing material and solar-cell module using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar-cell sealing material that facilitates module manufacturing and is excellent in transparency, adhesion properties, film strength and toughness, processing characteristics, insulation properties, and non-corrosiveness while having improved heat resistance and proper melt viscosity. <P>SOLUTION: The solar-cell sealing material includes a resin composition containing a polyvinyl acetal resin (A), a plasticizer (B), and an amorphous polymer (C). The mass ratio between the polyvinyl acetal resin (A) and the amorphous polymer (C) in the resin composition is 70:30-35:65. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell sealing material in a solar cell module, and a solar cell module using the same.

  Hydropower, wind power and solar power generation, which can reduce carbon dioxide and improve other environmental problems by using inexhaustible natural energy, are attracting attention. Among these, solar power generation has seen remarkable improvements in the performance of solar cell modules, such as power generation efficiency, but the price has been reduced, and the national and local governments have promoted the introduction of residential solar power generation systems. In recent years, the spread has progressed.

  Since the solar cell unit is extremely fragile, as disclosed in, for example, Japanese Patent Laid-Open No. 58-23870 (Patent Document 1) or Japanese Patent Laid-Open No. 6-177712 (Patent Document 2), as a sealing material Often crosslinkable systems based on ethylene-vinyl acetate copolymers (hereinafter sometimes abbreviated as EVA) or curable casting resins are used. When these fillers are not cured, they can be adjusted to a low viscosity so as to surround the solar cell unit without containing bubbles. In addition, after the crosslinking reaction with the curing agent or the crosslinking agent, an adhesive layer that exhibits a certain level or more of mechanical strength is obtained. A problem of a solar cell module using EVA is corrosion of metal components by acetic acid generated by hydrolysis or thermal decomposition of EVA.

  Further, as described in JP-A-2006-013505 (Patent Document 3) and the like, a film based on polyvinyl butyral (hereinafter sometimes abbreviated as PVB) which is a thermoplastic resin is also used as a filler. used. PVB has the advantage that there are few acetic acid units which cause an acid component, and it is hard to cause the corrosion of a metal component compared with EVA. Moreover, since it is a thermoplastic resin, its viscosity at the flow start temperature is high, and there is little fear that the resin flows from the glass end portion and stains the apparatus and the glass surface. Also, from the viewpoint of mechanical properties, a film made of PVB resin has excellent adhesion to glass and penetration resistance of the film itself, so it is suitable for automotive windshields and architectural safety laminated glass. Can be used as an interlayer film.

It is known that PVB resin having such excellent mechanical properties also lacks heat resistance. In general, it has been found that when the glass transition temperature Tg or higher is reached, the film softens, and in particular, sufficient performance cannot be exhibited in the vicinity of 100 ° C. In the PVB resin system, high temperature properties can be imparted by reducing the amount of plasticizer, increasing the degree of polymerization of the resin, and introducing a crosslinked structure in order to impart heat resistance, but increase in melt viscosity, gelation during production Because of the problems, it is expected that it is not an effective means. The above-mentioned EVA-based sealing materials have also been studied. Cross-linking by electron beam irradiation (Patent Document 4), combined use of organic peroxide, silane coupling agent, etc. (Patent Document 5), crystalline polyolefin composite Giving mechanical properties according to (Patent Document 6) has been studied. However, in the combined use of electron beam crosslinking, organic peroxides, and silane coupling agents, it is difficult to control the reaction (temperature, time, and amount added), so it takes time and effort to manufacture, which is a factor that increases manufacturing costs. It was supposed to be one. Crystalline polyolefin composite system is not an effective means because by combining the crystalline component with the amorphous matrix, the transparency is deteriorated and the total light transmittance which is important for the solar cell sealing material is deteriorated. .

JP 58-23870 A Japanese Patent Laid-Open No. 6-177412 JP 2006-013505 A JP 2001-119047 A JP 2001-144313 A JP 2001-332750 A

  The object of the present invention relates to the development of mechanical properties particularly at high temperatures, and other physical properties required as a solar cell encapsulant are transparency (total light transmittance), adhesiveness, low water absorption, strength. It provides a film excellent in toughness, processing characteristics, insulating properties, non-corrosive properties, and melt viscosity.

  The present invention has been made to solve the above problems. Said subject is solar cell sealing material which consists of a resin composition containing polyvinyl acetal resin (A), a plasticizer (B), and an amorphous polymer (C), Comprising: Polyvinyl acetal resin in this resin composition The problem is solved by providing a solar cell encapsulant characterized in that the mass ratio of (A) to amorphous polymer (C) is 70:30 to 35:65.

  In said case, it is preferable that the glass transition temperature (Tgc) of an amorphous polymer (C) is 5 degreeC or more higher than the glass transition temperature (Tga) of a polyvinyl acetal resin (A). Here, the glass transition temperature is a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm, with a sine frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It is a peak temperature (Tα) of loss tangent (tan δ) of main dispersion when dynamic viscoelasticity measurement is performed.

  In a laminated glass in which a 0.7 mm thick test piece is sandwiched between two 1.3 mm thick glasses, the total light transmittance according to JIS K7105 is preferably 80% or more.

  Moreover, in said solar cell sealing material, ratio (E '@ 25 degreeC / E' @) of the storage elastic modulus (E '@ 25 degreeC) in 25 degreeC and the storage elastic modulus (E' @ 100 degreeC) in 100 degreeC 100 ° C.) is preferably 75 or less. Here, the storage elastic modulus was measured using a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm under conditions of a sine frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It is a value when dynamic viscoelasticity measurement is performed.

  Said solar cell sealing material WHEREIN: It is also preferable that the said amorphous polymer (C) is a polymer obtained by superposing | polymerizing the monomer containing an alkyl (meth) acrylate.

  This invention also includes the solar cell module containing said solar cell sealing material and a photovoltaic cell.

  The solar cell encapsulant of the present invention exhibits low transparency while exhibiting transparency (total light transmittance), adhesiveness, film strength and toughness, and non-corrosive properties that have been required as conventional solar cell encapsulants. It is an unprecedented solar cell encapsulant that is a sealing material that exhibits water absorption and mechanical properties in a high-temperature region, and that has a good melt viscosity, making it easy to produce a module.

  The solar cell sealing material of this invention consists of a resin composition containing a polyvinyl acetal resin (A), a plasticizer (B), and an amorphous polymer (C).

  The polyvinyl acetal resin (A) used in the present invention is a resin obtained by acetalizing polyvinyl alcohol with aldehydes, and is produced by a known method.

  Polyvinyl alcohol used as a raw material for the polyvinyl acetal resin (A) can be obtained, for example, by polymerizing a vinyl ester monomer and saponifying the obtained polymer.

  Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, and palmitic acid. Examples thereof include vinyl, vinyl stearate, vinyl oleate, vinyl benzoate and the like, and vinyl acetate is particularly preferable.

  Moreover, when polymerizing the said vinyl ester-type monomer, it can also be copolymerized with another monomer in the range which does not impair the main point of this invention. Examples of other monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid or a salt thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, Acrylic esters such as n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc .; methacrylic acid and salts thereof; methyl methacrylate, methacrylic acid Methacrylic acid esters such as ethyl, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Kind; Acry Amide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine or its salt or its quaternary salt, N-methylolacrylamide and its Acrylamide derivatives such as derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine or salts thereof or quaternary salts thereof, N-methylolmethacrylamide or Methacrylamide derivatives such as derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n -Vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride, fluorine Vinylidene halides such as vinylidene chloride; allyl compounds such as allyl acetate and allyl chloride; maleic acid, salts thereof, esters thereof and anhydrides thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like. These monomer units are usually used in a proportion of less than 20 mol%, more preferably less than 10 mol%, relative to the vinyl ester monomer.

As a method for polymerizing the vinyl ester monomer, a conventionally known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be applied. As the polymerization initiator, an azo initiator, a peroxide initiator, a redox initiator, or the like is appropriately selected according to the polymerization method. At this time, the reaction may be performed in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid, or other chain transfer agent.

  As the saponification reaction, a conventionally known alcoholysis or hydrolysis using an alkali catalyst or an acid catalyst can be applied. Among them, a saponification reaction using a caustic soda catalyst with methanol as a solvent is simple and most preferable.

  There is no restriction | limiting in particular as aldehyde used for acetalization of said polyvinyl alcohol, Preferably a C1-C12 aldehyde compound is mentioned. Examples of such aldehyde compounds include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde, benzaldehyde and the like. Among these, a C1-C6 saturated alkyl aldehyde compound is more preferable, and a C1-C4 saturated alkyl aldehyde compound is more preferable. Specifically, butyraldehyde and acetaldehyde are preferable from the viewpoint of the mechanical properties of the film when used for a solar cell encapsulant. Moreover, aldehydes may use a single thing and may use 2 or more types together. Further, a small amount of polyfunctional aldehydes or aldehydes having other functional groups may be used in a range of 20% by mass or less of the total aldehydes.

  Although there is no restriction | limiting in particular as a manufacturing method of polyvinyl acetal resin (A), For example, the method of making an aldehyde compound react on acidic conditions in a polyvinyl alcohol solution is mentioned.

  Although there is no restriction | limiting in particular in the solvent for manufacturing a polyvinyl acetal resin (A), When manufacturing in large quantities industrially, it is preferable to use water, Polyvinyl alcohol is beforehand used before reaction at high temperature, for example, 90 It is preferable to dissolve sufficiently at a temperature of at least ° C. Moreover, 5-40 mass% is preferable, as for the density | concentration of the polyvinyl alcohol in aqueous solution, 5-20 mass% is more preferable, and 8-15 mass% is further more preferable. If the concentration of the polyvinyl alcohol is too low, the productivity may be deteriorated. On the other hand, if the concentration is too high, stirring during the reaction becomes difficult, or gelation due to intermolecular hydrogen bonding of the polyvinyl alcohol occurs, causing a reaction. There is a risk of unevenness.

  The catalyst for reacting an aldehyde with an aqueous polyvinyl alcohol solution is not particularly limited, and any of organic acids and inorganic acids can be used. For example, acetic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, hydrochloric acid, carbonic acid can be used. Etc. Of these, inorganic acids are preferred, and hydrochloric acid, sulfuric acid and nitric acid are particularly preferred because sufficient reaction rates can be obtained and washing after the reaction is easy. The concentration of the acid used in the reaction depends on the type of acid used, but in the case of hydrochloric acid, sulfuric acid and nitric acid, 0.01 to 5 mol / L is preferable, and 0.1 to 2 mol / L is more preferable. If the acid concentration is too low, the reaction rate becomes slow, and it may take time to obtain the desired degree of acetalization and physical properties of the polyvinyl acetal resin. On the other hand, if the acid concentration is too high, it becomes difficult to control the reaction, and dimers and trimers of aldehydes are likely to be generated.

  Examples of procedures for reacting aldehydes with an aqueous polyvinyl alcohol solution include known methods. For example, a method of adding an aldehyde after adding the above catalyst to an aqueous polyvinyl alcohol solution, an acid after adding the aldehyde first. Examples include a method of adding a catalyst. Moreover, the method of adding the aldehyde or acid catalyst to be added collectively or sequentially, or adding in a divided manner, or adding a mixed solution of an aqueous polyvinyl alcohol solution and an aldehyde or an acid catalyst to an acid catalyst or a solution containing an aldehyde, and the like are also included.

  Although there is no restriction | limiting in particular as reaction temperature, 0-80 degreeC is preferable. In order to obtain a porous polyvinyl acetal resin that can be easily washed after the reaction, the reaction is carried out at a relatively low temperature of 0 to 40 ° C., preferably 5 to 20 ° C. until the polyvinyl acetal particles are precipitated during the reaction. preferable. Thereafter, in order to drive the reaction, it is preferable to increase the reaction temperature.

  The particles of the polyvinyl acetal resin (A) obtained by these reactions are preferably porous in order to efficiently remove remaining acids and aldehydes. The porous polyvinyl acetal resin (A) can be obtained by adjusting the viscosity of the reaction solution, the stirring speed, the shape of the stirring blade, the shape of the reaction vessel, the reaction temperature, the reaction speed, the catalyst and the method of adding aldehydes. For example, when the reaction temperature is too high, the polyvinyl acetal resin is fused and hardly becomes porous.

  The polyvinyl acetal resin (A) thus obtained preferably has a degree of acetalization of 35 to 95 mol%, more preferably 40 to 90 mol%. If the degree of acetalization is less than 35 mol%, the transparency may be deteriorated or the flexibility may be insufficient. Conversely, if the degree of acetalization exceeds 95 mol%, the passability of the production process is deteriorated. There is a risk of cost increase.

  As for the polyvinyl acetal resin used for this invention, it is preferable that the quantity of the vinyl alcohol unit measured based on prescription | regulation of JISK6728: 1977 is 5-34 mol%, 7-32 mol% is more preferable, 10-30 More preferred is mol%. When the amount of the vinyl alcohol unit is increased, the hygroscopicity is increased, and in the solar cell module described later, there is a possibility that metal corrosion due to absorbed water, deterioration of insulation, and peeling of the polyvinyl acetal resin from the base material may occur. . On the other hand, when the amount of vinyl alcohol units decreases, problems such as a decrease in mechanical strength and poor adhesion to the substrate may occur.

  In the polyvinyl acetal resin used in the present invention, the amount of vinyl ester units measured based on JIS K6728: 1977 is preferably 10 mol% or less, more preferably 9 mol% or less, and more preferably 8 mol% or less. Further preferred. When the vinyl ester unit is a vinyl acetate unit in particular, if the amount exceeds 10 mol%, acetic acid, which is a corrosive substance, is generated due to decomposition by heat and hydrolysis by moisture. It tends to be easily colored by generation.

  The amount of chloride ion, sulfate ion and nitrate ion derived from the acetalization catalyst contained in the polyvinyl acetal resin (A) used in the present invention is preferably 100 ppm or less, more preferably 50 ppm or less, and 20 ppm or less. Is more preferable. Since these strong acid ions cause corrosion of metal components used in solar cell modules and the like to be described later, a smaller amount is preferable.

  There is no restriction | limiting in particular as a plasticizer (B) used by this invention, For example, di (2-butoxyethyl) adipate (DBEA), di (2-butoxyethyl) sebacate (DBES), azelaic acid di ( 2-butoxyethyl), di (2-butoxyethyl) glutarate, di (2-butoxyethoxyethyl) adipate (DBEEA), di (2-butoxyethoxyethyl) sebacate (DBEES), di (2-azeoxyethyl) (2- Butoxyethoxyethyl), di (2-butoxyethoxyethyl) glutarate, di (2-hexoxyethyl) adipate, di (2-hexoxyethyl) sebacate, azeladi (2-hexoxyethyl), di (2-hexoxyethyl) glutarate, Di (2-hexoxyethoxyethyl) adipate, di (2-hexoxye) sebacate Xylethyl), di (2-hexoxyethoxyethyl) azelate, di (2-hexoxyethoxyethyl) glutarate, di (2-butoxyethyl) phthalate, di (2-butoxyethoxyethyl) phthalate, triethylene Examples include glycol di (2-ethylhexanoate) (3GO), tetraethylene glycol di (2-ethylhexanoate) (4GO), and diisononyl 1,2-cyclohexanedicarboxylate (DINCH). Among these, it is preferable to use a high-boiling plasticizer in consideration of the high-temperature laminating process. Examples of the high-boiling plasticizer include triethylene glycol di (2-ethylhexanoate) (3GO), tetraethylene glycol di (2-ethylhexanoate) (4GO), and di (2-butoxyethoxy) adipate. Ethyl) (DBEEA), di (2-butoxyethoxyethyl) sebacate (DBEES), diisononyl 1,2-cyclohexanedicarboxylate (DINCH), and the like. The added amount is preferably 3 to 85 parts by mass, and more preferably 5 to 80 parts by mass with respect to 100 parts by mass of the total amount of the polyvinyl acetal resin (A) and the amorphous polymer (C) described later. Two or more plasticizers may be used in combination.

  The compounding quantity in the resin composition of the amorphous polymer (C) used by this invention is a mass ratio with a polyvinyl acetal resin (A), (A) :( C) = 70: 30-35: It is necessary to be in the range of 65, preferably in the range of 65:35 to 40:60. When the compounding quantity of an amorphous polymer (C) is less than the said range, the physical property at the high temperature of the solar cell sealing material obtained and the inhibitory effect of water absorption are insufficient. Moreover, when the compounding quantity of an amorphous polymer (C) exceeds the said range, the compounding quantity of polyvinyl acetal resin (A) becomes relatively small, and the toughness and impact resistance of the solar cell sealing material obtained are reduced. Run short.

  The amorphous polymer (C) used in the present invention preferably has a glass transition temperature (Tgc) of 5 ° C. or more higher than the glass transition temperature (Tga) of the polyvinyl acetal resin (A), and is 7 ° C. or more higher. It is more preferable. When the glass transition temperature is lower than the above range, high-temperature mechanical properties and heat resistance are insufficient, and the effects of the present invention tend to be insufficient. Here, the glass transition temperature is a condition of a sinusoidal frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a rate of temperature increase of 3 ° C./min using a test piece of length 20 mm × width 3 mm × thickness 0.7 mm. Is the peak temperature (Tα) of the loss tangent (tan δ) of the main dispersion when the dynamic viscoelasticity measurement is performed.

  The amorphous polymer (C) used in the present invention has an average degree of polymerization of preferably 100 or more, more preferably 200 to 5000, and still more preferably 200 to 4000 from the viewpoint of strength characteristics and meltability.

  For applications that require more transparency, it is important that the amorphous polymer (C) to be blended has a refractive index close to that of the polyvinyl acetal resin (A) serving as a matrix. For example, the amorphous polymer (C) to be blended can be core-shell type fine particles, the outer layer can be an amorphous polymer, and the refractive index can be controlled by the components of the inner layer, thereby expressing higher transparency.

  The amorphous polymer (C) is preferably a polymer obtained by polymerizing a monomer containing an alkyl (meth) acrylate. Here, examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, and n-butyl methacrylate. These alkyl methacrylates may be used alone or in combination of two or more. Of these, alkyl methacrylates having 1 to 4 carbon atoms in the alkyl group are preferred, and methyl methacrylate is particularly preferred from the viewpoint of physical properties and cost. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, and phenyl acrylate. These alkyl acrylates may be used alone or in combination of two or more. Of these, alkyl acrylates having 1 to 8 carbon atoms in the alkyl group are preferred.

  Examples of the other monomer used in the amorphous polymer (C) include an ethylenically unsaturated monomer copolymerizable with an alkyl (meth) acrylate. Examples of such ethylenically unsaturated monomers include diene compounds such as 1,3-butadiene and isoprene; styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, and styrene nucleus-substituted with halogen. Vinyl aromatic compounds such as 1-vinylnaphthalene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene and 4-dodecylstyrene; ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid Examples include acid, acrylamide, methacrylamide, maleic anhydride, maleic imide, monomethyl maleate, dimethyl maleate and the like. These ethylenically unsaturated monomers may be used alone or in combination of two or more.

  The amorphous polymer (C) obtained from the above monomer may be any of a homopolymer, a random copolymer, a block copolymer, and a graft polymer.

  Antioxidants, ultraviolet absorbers, adhesion improvers, antiblocking agents, pigments, dyes, functional inorganic compounds and the like are added to the solar cell encapsulant of the present invention as necessary.

  Examples of the antioxidant to be used include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants are preferable, alkyl-substituted phenolic antioxidants. Agents are particularly preferred.

  Examples of phenolic antioxidants include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl. Acrylate compounds such as -6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate; 2,6-di-t-butyl-4-methylphenol, 2,6 -Di-t-butyl-4-ethylphenol, octadecyl-3- (3,5-) di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis (4-methyl-6- t-butylphenol), 4,4'-butylidene-bis (4-methyl-6-t-butylphenol), 4,4'-butylidene-bis (6-t-butyl-m-cresol), 4,4 -Thiobis (3-methyl-6-tert-butylphenol), bis (3-cyclohexyl-2-hydroxy-5-methylphenyl) methane, 3,9-bis (2- (3- (3-tert-butyl-4) -Hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, 1,1,3-tris (2-methyl- 4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene- 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate) methane, triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5- Alkyl substituted phenolic compounds such as (tilphenyl) propionate); 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4 -Hydroxy-3,5-dimethylanilino) -2,4-bis-octylthio-1,3,5-triazine, 6- (4-hydroxy-3-methyl-5-t-butylanilino) -2,4- Contains triazine groups such as bis-octylthio-1,3,5-triazine, 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyanilino) -1,3,5-triazine A phenol type compound etc. are mentioned.

  Examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, and tris (2-t-butyl). -4-methylphenyl) phosphite, tris (cyclohexylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, 9,10-dihydro-9-oxa-10- Phosphaphenanthrene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy -9,10-dihydro-9-oxa-10-phosphine Monophosphite compounds such as phenanthrene; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecylphosphite), 4,4′-isopropylidene-bis (phenyl-di) -Alkyl (C12-C15) phosphite), 4,4'-isopropylidene-bis (diphenylmonoalkyl (C12-C15) phosphite), 1,1,3-tris (2-methyl-4-di-tri) And diphosphite compounds such as decylphosphite-5-tert-butylphenyl) butane and tetrakis (2,4-di-tert-butylphenyl) -4,4′-biphenylene phosphite. Of these, monophosphite compounds are preferred.

  Examples of the sulfur-based antioxidant include dilauryl 3,3′-thiodipropionate, distearyl 3,3′-thiodipropionate, lauryl stearyl 3,3′-thiodipropionate, pentaerythritol-tetrakis- (Β-lauryl-thiopropionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like.

  These antioxidants can be used alone or in combination of two or more. The compounding quantity of antioxidant is 0.001-5 mass parts with respect to 100 mass parts of polyvinyl acetal resin (A), Preferably it is the range of 0.01-1 mass part.

  Although there is no restriction | limiting in particular in the timing which adds these antioxidants, It is preferable to manufacture a solar cell sealing material by extrusion molding at least in presence of antioxidant. Moreover, in order to obtain the solar cell sealing material of this invention, it is more preferable to add antioxidant also in the case of manufacture of the polyvinyl acetal resin (A) used as a raw material. Furthermore, it is preferable that an antioxidant is also added to the plasticizer (B) as a raw material.

  Examples of ultraviolet absorbers include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α′dimethylbenzyl) phenyl] -2H-benzotriazole, 2 -(3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3 5-di-t-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2 ′ -Hydroxy-5′-t-octylphenyl) benzotriazole-based UV absorbers such as benzotriazole; 2,2,6,6-tetramethyl-4-piperi Dibenzoate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2- (3,5-di- t-butyl-4-hydroxybenzyl) -2-n-butylmalonate, 4- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) -1- (2- (3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl) -2,2,6,6-tetramethylpiperidine and other hindered amine UV absorbers; 2,4-di-t- And benzoate ultraviolet absorbers such as butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate.The addition amount of these ultraviolet absorbers is preferably 10 to 50,000 ppm, more preferably 100 to 10,000 ppm, based on the mass with respect to the polyvinyl acetal resin (A). These ultraviolet absorbers can be used in combination of two or more.

  As the adhesion improver, for example, those disclosed in WO03 / 033583A1 can be used, and the addition of an alkali metal salt and / or alkaline earth metal salt of an organic acid is preferably used, particularly potassium acetate and / or Or magnesium acetate is preferable. The addition amount is preferably 1 to 10000 ppm, more preferably 5 to 1000 ppm, and still more preferably 10 to 300 ppm based on the mass with respect to the polyvinyl acetal resin (A). The optimum addition amount of the adhesion improver varies depending on the additive used and also depends on the location where the resulting module is used, but the adhesion of the resulting film to glass is determined by the Pummel Test (WO03). In general, it is preferable to adjust to 3 to 10, and particularly 3 to 6 when high penetration resistance is required, and 7 to 10 when high glass scattering prevention is required. It is preferable to adjust. When high glass scattering prevention property is required, it is also a useful method not to add an adhesion improver.

  Examples of the functional inorganic compound include a light reflecting material, a light absorbing material, a thermal conductivity improving material, an electrical property improving material, a gas barrier property improving material, a mechanical property improving material and the like.

  There are no particular restrictions on the method of adding these additives to produce the solar cell encapsulant, and any known method can be used, but a method of producing the solar cell encapsulant using an extruder is preferably used. . The resin temperature during extrusion is preferably 150 to 250 ° C, more preferably 180 to 230 ° C. If the resin temperature is too high, the polyvinyl acetal resin (A) may be decomposed to increase the content of volatile substances. On the other hand, if the temperature is too low, the content of volatile substances increases. In order to efficiently remove the volatile substance, it is preferable to remove the volatile substance from the vent port of the extruder by reducing the pressure.

  The solar cell encapsulant of the present invention is preferably provided with irregularities on the surface in order to enhance the deaeration property in the laminating process. As a method for providing the unevenness, a conventionally known method can be used. Examples thereof include a method for providing a melt fracture structure by adjusting extrusion conditions, a method for imparting an embossed structure to the extruded film, and the like.

  Although there is no restriction | limiting in particular in the thickness of the solar cell sealing material of this invention, 0.38 mm-2.28 mm are preferable. If the thickness is less than 0.38 mm, the space around the solar cell or the functional unit may not be sufficiently filled. If the thickness is more than 2.28 mm, the cost of the film itself is high, and the cycle time of the laminating process is high. May be longer.

  The solar cell sealing material of the present invention thus obtained has a total light transmittance of 80 according to JIS K7105 in a laminated glass in which a 0.7 mm thick test piece is sandwiched between two 1.3 mm thick glasses. % Or more is preferable, and 85% or more is more preferable. When the total light transmittance is less than 80%, the conversion efficiency of the solar cell is deteriorated, which may be unsuitable for the solar cell sealing material.

  Moreover, the solar cell encapsulant of the present invention has a ratio (E ′ @ 25 ° C./E ′) of the storage elastic modulus at 25 ° C. (E ′ @ 25 ° C.) and the storage elastic modulus at 100 ° C. (E ′ @ 100 ° C.). @ 100 ° C) is preferably 75 or less, more preferably 60 or less. When the ratio exceeds 75, the mechanical properties of the sealing material at a high temperature are remarkably lowered, and the function as a solar cell sealing material is not achieved. There is a fear. Here, the storage elastic modulus was measured using a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm under conditions of a sine frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It is a value when dynamic viscoelasticity measurement is performed.

  The solar cell module of the present invention is manufactured by a known method, and the solar cell sealing material of the present invention is used as a sealing material together with solar cells.

  The type of the solar battery cell used in the solar battery module is not particularly limited, and examples include a crystal type cell and a thin film type cell, and examples of the crystal type cell include single crystal silicon and polycrystalline silicon. Examples of the thin film cell include a thin film silicon type such as amorphous silicon and a laminate of the same and a polycrystalline thin film, a compound semiconductor type using CIS, CIGS, CdTe, GaAs, etc., and an organic solar cell type. .

  In the case of a crystal type cell, the solar cell encapsulant is inserted between a transparent substrate such as glass and the crystal type cell, and / or between the crystal type cell and the back glass or back sheet, laminated, and solar. A battery module is formed. In addition, in the case of a so-called super straight type of a thin film type, it is inserted between a surface transparent substrate on which solar cells are mounted and a back glass or a back sheet. In the case of a substrate type, it is inserted between a surface transparent substrate and a substrate on which solar cells are mounted. The solar cell encapsulant of the present invention can also be used as an adhesive layer for laminating with a transparent substrate, a back sheet, other reinforcing substrates, and the like for these laminates.

As the transparent conductive film in the solar cell module of the present invention, ITO (indium doped tin oxide), ATO (antimony doped tin oxide), FTO (fluorine doped tin oxide), tin oxide (SnO ₂ ), zinc oxide (ZnO), etc. Is mentioned. These films can be produced by using various known film forming methods.

  Although there is no restriction | limiting in particular as glass used for the solar cell module of this invention, Float glass, tempered glass, meshed glass, organic glass, etc. can be used. Although there is no restriction | limiting in particular in the thickness of glass, 1-10 mm is preferable and 2-6 mm is more preferable.

  The backsheet used for the solar cell module of the present invention is not particularly limited, but preferably used is one having excellent weather resistance and low moisture permeability, a polyester film, a fluorine resin film, a laminate thereof, And what laminated | stacked the inorganic compound on them etc. can be used.

  In addition, the solar cell module of the present invention can be combined with known frames, junction boxes, sealing agents, mounting jigs and mounts, antireflection films, various facilities utilizing solar heat, rain gutter structures, and the like.

As a laminating method for obtaining the solar cell module of the present invention, a known method can be adopted. For example, a method using a vacuum laminator device, a method using a vacuum bag, a method using a vacuum ring, or a nip roll is used. Methods and the like. In addition, a method of adding to the autoclave process after provisional pressure bonding can be additionally performed.

  When using a vacuum laminator apparatus, it laminates at the temperature of 100-200 degreeC, especially 130-160 degreeC under the pressure reduction of 1-30000 Pa, for example using the well-known apparatus used for manufacture of a solar cell. A method using a vacuum bag or a vacuum ring is described, for example, in EP12356683B1, for example, laminated at 130-145 ° C. under a reduced pressure of about 20000 Pa.

  In the case of using a nip roll, for example, there is a method in which after the first temporary press-bonding at a temperature equal to or lower than the flow start temperature of the resin composition, the temporary press-bond is performed under a condition close to the flow start temperature. Specifically, for example, after heating to 30 to 70 ° C. with an infrared heater or the like, degassing with a roll, and further heating to 50 to 120 ° C., followed by pressure bonding with a roll and bonding or temporary bonding may be mentioned.

  The autoclave process that is additionally performed after the temporary pressure bonding is performed, for example, at a temperature of 130 to 145 ° C. for about 2 hours under a pressure of about 1 to 1.5 MPa, depending on the thickness and configuration of the solar cell module.

  The solar cell module of the present invention can be used as a member of a window, wall, roof, sunroom, soundproof wall, show window, balcony, handrail wall, or as a partition glass member of a conference room, etc. You can also

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In the following examples, “%” and “part” mean “% by mass” and “part by mass”, respectively, unless otherwise specified.

[Production Example 1]
A 2 m ³ reactor equipped with a stirrer was charged with 1700 kg of a 7.5 mass% aqueous solution of PVA (polymerization degree 1700, saponification degree 99 mol%) and 74.6 kg of butyraldehyde, and the whole was cooled to 14 ° C. To this, 160.1 L of hydrochloric acid having a concentration of 20% by mass was added, and butyralization of PVA was started. After 10 minutes from the end of the addition, the temperature was started to rise, the temperature was raised to 65 ° C. over 90 minutes, and the reaction was further performed for 120 minutes. Then, after cooling to room temperature and depositing the resin, the resin was washed 10 times with 10 times the amount of ion-exchanged water with respect to the resin. Thereafter, it was sufficiently neutralized using a 0.3 mass% sodium hydroxide solution, further washed 10 times with 10 times the amount of ion-exchanged water, dehydrated, and dried to obtain a PVB resin (PVB-1). Obtained.
The degree of acetalization of the obtained PVB-1 was 70 mol%, the vinyl alcohol unit amount was 29.1 mol%, and the vinyl acetate unit amount was 0.9 mol%. The chloride ion concentration was 50 ppm.

  The obtained PVB-1 was hot-pressed at 140 ° C. for 5 minutes to obtain a test piece having a length of 20 mm × width of 3 mm × thickness of 0.7 mm. Using a rheological FT Rheospectrer DVE-V4, the test piece was subjected to dynamic viscoelasticity measurement at a sinusoidal frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It was 92 degreeC when the peak temperature (Tga) of the tangent (tan-delta) was calculated | required. The results are shown in Table 1.

[Production Example 2]
In Production Example 1, PVB resin (PVB-2) was obtained in the same manner as in Production Example 1 except that the amount of butyraldehyde was changed to 85.3 kg. The degree of acetalization of PVB-2 was 78 mol%, the amount of vinyl alcohol units was 21.1 mol%, and the amount of vinyl acetate units was 0.9 mol%. The chloride ion concentration was 50 ppm.
When the peak temperature of the loss tangent (tan δ) of the main dispersion was determined in the same manner as in Production Example 1, it was 88 ° C. The results are shown in Table 1.

  As the amorphous polymer (C), PMMA-1 (polymethyl methacrylate, “Parapet” EH manufactured by Kuraray Co., Ltd.) and PMMA-2 (polymethyl methacrylate, “Parapet” HR-L manufactured by Kuraray Co., Ltd.) were used. PMMA-1 was hot-pressed at 140 ° C. for 5 minutes to obtain a test piece having a length of 20 mm × width of 3 mm × thickness of 0.7 mm. Using a rheological FT Rheospectrer DVE-V4, the test piece was subjected to dynamic viscoelasticity measurement at a sinusoidal frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It was 135 degreeC when the peak temperature (Tgc) of the tangent (tan-delta) was calculated | required. The peak temperature (Tgc) of the loss tangent (tan δ) of the main dispersion was similarly determined for PMMA-2 and found to be 141 ° C. The results are shown in Table 1.

  PVB-1: 40 parts by mass, triethylene glycol-di (2-ethylhexanoate) (3GO) as plasticizer: 27.5 parts by mass, PMMA-1: 32.5 parts by mass, manufactured by Toyo Seiki Co., Ltd. Was used and melt-kneaded at a resin temperature of 200 ° C. and a rotation speed of 100 rpm to obtain a resin composition. Using the obtained resin composition, hot pressing was performed at 140 ° C. for 5 minutes to produce a solar cell sealing material having a length of 200 mm × width of 200 mm × thickness of 0.7 mm (F-1). Using this test piece, the total light transmittance, stress at 50% strain and breaking strain, heat resistance, water absorption, creep characteristics, and MFR120 were evaluated by the following methods. The results are shown in Table 2.

[Stress at 50% strain and fracture strain]
Using an autograph AG-5000B manufactured by Shimadzu Corporation, a No. 2 dumbbell (thickness 0.7 mm) described in JIS K7113 was measured at a tensile speed of 5 mm / min according to JIS K7162.

[Heat-resistant]
Using a rheology FT Rheospectrer DVE-V4, a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm, having a sine frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature rising rate of 3 ° C./min Under the measurement conditions, the storage elastic modulus E ′ was measured. The ratio of the storage elastic modulus at 25 ° C. (E ′ @ 25 ° C.) to the storage elastic modulus at 100 ° C. (E ′ @ 100 ° C.) (E ′ @ 25 ° C./E′@100° C.) (Temperature dependence of film strength).

[Water absorption rate]
Using a test piece having a length of 50 mm, a width of 50 mm, and a thickness of 0.7 mm, which was previously vacuum-dried at 25 ° C. for 1 week and completely removed of water, 23 ° C., 80% RH (desiccator humidity control) and The water absorption rate of the film was measured under conditions of 23 ° C. and water immersion.

[Creep characteristics]
A sample was placed in an oven set at 110 ° C using a test piece of length 30mm x width 10mm x thickness 0.7mm that had been previously vacuum-dried at 25 ° C for 1 week and completely removed water. With a load of 3.14 g applied, the elongation (mm) of the sample after 17 minutes was measured.

[MFR120]
According to DIN 53735, the amount of resin eluted in 10 minutes was measured under the condition of applying a 10 kg load at 120 ° C.

[Total light transmittance]
A sheet having a length of 200 mm, a width of 200 mm, and a thickness of 0.7 mm was sandwiched between two sheets of 1.3 mm thick glass, and then held at 140 ° C. for 90 minutes under reduced pressure to prepare a laminated glass sample. This sample was measured according to JIS K 7105 using a Nippon Denshoku Industries Co., Ltd. haze meter NDH5000 type, and the total light transmittance TL was calculated.

  A resin composition was obtained in the same manner as in Example 1 except that PVB-2 was used instead of PVB-1, and various physical properties were evaluated by preparing a sealing material for solar cell (F-2). . The results are shown in Table 2.

  A resin composition was obtained in the same manner as in Example 1 except that PMMA-2 was used instead of PMMA-1, and a solar cell encapsulant (F-3) was prepared to evaluate various physical properties. . The results are shown in Table 2.

  A resin composition was obtained in the same manner as in Example 2 except that PMMA-2 was used instead of PMMA-1, and a solar cell encapsulant (F-4) was prepared to evaluate various physical properties. . The results are shown in Table 2.

Comparative Example 1
PVB-1: 72.5 parts by mass, 3GO: 27.5 parts by mass as a plasticizer was used, and a resin composition was obtained in the same manner as in Example 1 except that the amorphous polymer (C) was not used. Furthermore, the sealing material for solar cells (F-5) was produced and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 2
A resin composition was obtained in the same manner as in Comparative Example 1 except that PVB-2 was used instead of PVB-1, and a solar cell encapsulant (F-6) was prepared to evaluate various physical properties. . The results are shown in Table 2.

Comparative Example 3
PVB-1: 60 parts by mass, 3GO: 40 parts by mass as a plasticizer was used, and a resin composition was obtained in the same manner as in Example 1 except that the amorphous polymer (C) was not used. A battery sealing material (F-7) was prepared and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 4
PVB-2: 85 parts by mass, 3GO: 15 parts by mass as a plasticizer, except that the amorphous polymer (C) was not used, a resin composition was obtained in the same manner as in Example 1, and the sun A battery sealing material (F-8) was prepared and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 5
A resin composition was obtained in the same manner as in Example 1 except that PVB-1: 54 parts by mass, 3GO: 27.5 parts by mass, and PMMA-1: 18.5 parts by mass were used as plasticizers. Sealing material (F-9) was prepared and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 6
PVB-1: 10 parts by mass, 3GO: 27.5 parts by mass as a plasticizer, and PMMA-1: 62.5 parts by mass were used in the same manner as in Example 1 to obtain a resin composition. Sealing material (F-10) was prepared and various physical properties were evaluated. The results are shown in Table 2.

Comparative Example 7
A resin composition was obtained in the same manner as in Comparative Example 5 except that PVB-2 was used instead of PVB-1, and a solar cell encapsulant (F-11) was prepared to evaluate various physical properties. . The results are shown in Table 2.

Comparative Example 8
A resin composition was obtained in the same manner as in Comparative Example 6 except that PVB-2 was used instead of PVB-1, and a solar cell encapsulant (F-12) was prepared to evaluate various physical properties. . The results are shown in Table 2.

  The solar cell encapsulant provided by the present invention is a solar cell encapsulant excellent in transparency (total light transmittance), strength, heat resistance, impact resistance, low water absorption, and melt viscosity. The solar cell encapsulant provided by the present invention has excellent heat resistance (change in storage elastic modulus at 25 ° C. to 100 ° C. is suppressed), high total light transmittance, and excellent physical properties. Since it holds, even if a solar cell module rises to a high temperature region, it is possible to avoid troubles in which the sealing material flows or deforms, and the appearance of the solar cell is hardly impaired. Therefore, the solar cell module which has the outstanding performance using the solar cell sealing material of this invention can be provided.

Claims (6)

A solar cell encapsulant comprising a resin composition containing a polyvinyl acetal resin (A), a plasticizer (B) and an amorphous polymer (C), wherein the polyvinyl acetal resin (A) A solar cell encapsulating material, wherein the mass ratio of the crystalline polymer (C) is 70:30 to 35:65. 2. The solar cell seal according to claim 1, wherein a glass transition temperature (Tgc) of the amorphous polymer (C) is 5 ° C. or more higher than a glass transition temperature (Tga) of the polyvinyl acetal resin (A). Stop material.
The glass transition temperature was measured using a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm under the conditions of a sinusoidal frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It is the peak temperature (Tα) of the loss tangent (tan δ) of the main dispersion when measuring elasticity. 2. A laminated glass obtained by sandwiching a test piece having a thickness of 0.7 mm with two pieces of glass having a thickness of 1.3 mm, wherein the total light transmittance according to JIS K7105 is 80% or more. 2. The solar cell encapsulant according to 2. The ratio of the storage elastic modulus at 25 ° C. (E ′ @ 25 ° C.) to the storage elastic modulus at 100 ° C. (E ′ @ 100 ° C.) (E ′ @ 25 ° C./E′@100° C.) is 75 or less. The solar cell sealing material according to any one of claims 1 to 3, wherein
The storage elastic modulus is a dynamic viscosity using a test piece having a length of 20 mm, a width of 3 mm, and a thickness of 0.7 mm under the conditions of a sine frequency of 10 Hz, a measurement temperature of −50 to 200 ° C., and a temperature increase rate of 3 ° C./min. It is a value when the elasticity measurement is performed. The solar cell sealing material according to any one of claims 1 to 4, wherein the amorphous polymer (C) is a polymer obtained by polymerizing a monomer containing an alkyl (meth) acrylate. . The solar cell module containing the solar cell sealing material and solar cell in any one of Claims 1-5.