JP5286643B2 - Solar cell back surface protection sheet and solar cell module using the same - Google Patents

Description

  The present invention relates to a solar cell back surface protection sheet having various characteristics such as heat resistance, weather resistance, and moisture resistance that can withstand a harsh natural environment over a long period of time, and a solar cell module using the same.

  In recent years, various efforts have been made in various fields in order to suppress the emission of carbon dioxide while interest in various fields regarding the global warming problem has increased. The increase in the consumption of fossil fuels causes an increase in atmospheric carbon dioxide, and the greenhouse effect increases the temperature of the earth, which has a significant impact on the global environment such as climate change.

  Therefore, various attempts have been made to suppress the increase in fossil fuel consumption and to replace fossil fuels that do not emit carbon dioxide, but there are expectations for solar power generation as a clean energy source. Is growing. A solar cell used for photovoltaic power generation constitutes the heart of a photovoltaic power generation system that directly converts sunlight energy into electricity, and is made of a semiconductor. As its structure, a single solar cell element is not used as it is, and generally several to several tens of solar cell elements are wired in series and in parallel, and over a long period (about 20 years). In order to protect the device, various packaging is performed and unitized.

  The unit built in this package is called a solar cell module. Generally, the surface exposed to sunlight is covered with glass, the gap is filled with a filler made of a thermoplastic resin, and the back surface is made of a heat-resistant, weather-resistant plastic material or the like. The structure is protected by a white sheet. The reason for using the white sheet is to reflect light and increase the power generation effect.

  Since these solar cell modules are used outdoors, sufficient durability and weather resistance are required in the materials used and their configurations. In particular, the back surface protection sheet is required to be white and have a weather resistance and a low water vapor transmission rate. This is because if the filler in the unit is peeled off or discolored due to the permeation of moisture or the wiring is corroded, the module output itself is adversely affected.

  Conventionally, as this back surface protection sheet for solar cells, there are many back surface protection sheets having a laminated structure in which an aluminum foil is sandwiched between white polyvinyl fluoride film (PVF) [manufactured by DuPont, trade name: Tedlar (registered trademark)]. It was used. However, this polyvinyl fluoride film has low mechanical strength and is softened by the heat of 140-150 ° C. hot press applied during the production of the solar cell module, and the protrusions of the solar cell element electrode part penetrate the filler layer. Furthermore, by penetrating the inner surface of the polyvinyl fluoride film constituting the back surface protection sheet and contacting the aluminum foil in the back surface protection sheet, the solar cell element and the aluminum foil are short-circuited, and the battery performance is adversely affected. At the same time, there are drawbacks and the cost is high, which is one of the obstacles in reducing the cost of solar cell modules. In order to improve these problems, a solar cell back surface protective sheet in which a white polyethylene terephthalate film (PET) having heat resistance and weather resistance is laminated as an alternative to a polyvinyl fluoride film has been proposed (for example, Patent Document 1, (See Patent Document 2).

However, the white polyethylene terephthalate film (PET) used in the above-mentioned proposed solar cell back surface protection sheet uses a film in which a white pigment such as titanium oxide is kneaded, and has hydrolysis resistance. There were disadvantages such as poor, dielectric breakdown strength and partial discharge voltage, and poor electrical insulation.

  As a countermeasure, the intrinsic viscosity is 0.6 (dl / g) or more on one vapor deposition thin film layer surface or both surfaces of the vapor deposition film obtained by laminating a vapor deposition thin film layer of aluminum oxide or silicon oxide on one surface of the base film, and a ring shape. A solar cell back surface protection sheet comprising a laminate of a white multilayer polyethylene terephthalate having a trimer content of 0.5% by weight or less and a white multilayer polyethylene terephthalate having a foamed resin layer in the middle has been proposed ( For example, see Patent Document 3.)

Prior art documents are shown below.
JP 2002-134770 A JP 2002-134771 A JP 2005-11923 A

  The countermeasure proposal is to use a biaxially stretched polyethylene terephthalate film with improved hydrolysis resistance by specifying the amount of cyclic oligomer from the aspects of hydrolysis resistance and weather resistance of polyethylene terephthalate resin, In this case, a heat fixing process such as annealing is separately required for the problem of sheet shrinkage in the module process due to a large heat shrinkage rate.

  The present invention is intended to solve such problems of the prior art, and is excellent in environmental resistance such as hydrolysis resistance and weather resistance, has good electrical insulation and dimensional stability, and can be made into a large module. It is an object of the present invention to provide an inexpensive solar cell back surface protective sheet that can be applied to the heat fixing step such as annealing, and a solar cell module using the same.

The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 of the present invention is a first base film (1) which is an unstretched film made of polytrimethylene terephthalate resin. And any one surface of the second base film (5) composed of a vapor deposition film provided with a vapor deposition thin film layer (3) of an inorganic oxide on one surface of the support film (4), and the support film It is a back surface protection sheet for solar cells, comprising a laminate in which a thermally crosslinkable primer layer is provided between the deposited thin film layers .

The invention according to claim 2 of the present invention is the solar cell back surface protective sheet according to claim 1, wherein the first base film (1) made of the polytrimethylene terephthalate resin has a thermal shrinkage ratio of 1.2 in MD. %, And a TD is 1.2% or less.

The invention according to claim 3 of the present invention is the solar cell back surface protection sheet according to claim 1 or 2 , wherein the first base film (1) is a white film. It is a sheet.

The invention according to claim 4 of the present invention is the solar cell back surface protective sheet according to any one of claims 1 to 3 , wherein the inorganic oxide is either aluminum oxide or silicon oxide. It is the back surface protection sheet for solar cells.

The invention according to claim 5 of the present invention is the back protective sheet for solar cell according to any one of claims 1 to 4 , wherein the first base film (1) and the second base film (5 ) And a third base film (7) made of the first base film (1) or another base film, which are sequentially laminated. It is.

The invention according to claim 6 of the present invention is a solar cell module comprising the solar cell back surface protective sheet according to any one of claims 1 to 5 .

The back surface protection sheet for solar cells according to the present invention includes a first base film of an unstretched film made of polytrimethylene terephthalate resin, and a deposited film provided with a deposited thin film layer of aluminum oxide or silicon oxide on one side of a support film. Because it is made of a laminate in which either side of the second base film is laminated, it has excellent gas barrier properties, especially water vapor barrier properties, and environmental resistance such as hydrolysis resistance and weather resistance Is excellent. Further, the polytrimethylene terephthalate thermal shrinkage of the first base film made of resin MD 1.2% or less, because TD is 1.2% or less, and good dimensional stability. Further, by sequentially laminating the first base film, any one surface of the second base film, and a third base film made of the first base film or another base film. High electrical insulation and good adhesion to the filler can be obtained. Furthermore, since the first base film is a white film, the power generation efficiency is high and the performance is high. By unitizing with such a back surface protection sheet for solar cells, stable quality can be obtained that the wiring is not bent and the battery is not displaced, and the heat setting step such as annealing can be omitted. A large-sized solar cell module can be obtained at low cost.

  An embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a side sectional view showing one embodiment of the layer structure of the back surface protective sheet for solar cells according to the present invention, and FIG. 2 shows another embodiment of the layer structure of the back surface protective sheet for solar cells according to the present invention. FIG. 3 is a side sectional view showing a solar cell module using the solar cell back surface protection sheet according to the present invention, and FIG. 4 is a solar cell back surface protection according to the present invention. It is a sectional side view which shows the other Example of the solar cell module using a sheet | seat.

  As shown in FIG. 1, the layer structure of the solar cell back surface protective sheet (A) showing one embodiment according to the present invention is an unstretched film first base film (1) made of polytrimethylene terephthalate resin and The adhesive film (2) is attached to the vapor-deposited thin film layer (3) surface of the second substrate film (5) comprising a vapor-deposited thin film layer (3) made of aluminum oxide or silicon oxide on one side of the support film (4). 2).

  Moreover, as shown in FIG. 2, the layer structure of the back surface protection sheet for solar cells (B) which shows the other Example which concerns on this invention is said 1st base film (1) and said 2nd base film. (5) In the layer structure which laminated | stacked the support body film (4) surface and the 3rd base film (7) which consists of said 1st base film (1) sequentially through the adhesive layer (2, 6). is there.

The polytrimethylene terephthalate resin (PTT) is a kind of thermoplastic polyester resin having the same crystallinity as polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT), and is an engineering plastic. Produced from propanediol.

  The PTT has the following excellent features. In terms of physical properties, for example, (1) since it has good weather resistance, it can be used without painting outdoors. (2) Excellent hydrolysis resistance. (3) Since it is difficult to absorb water, it has excellent dimensional and strength stability. (4) Excellent chemical resistance and contamination resistance. (5) The non-reinforced product is excellent in bending resistance and surface impact resistance. (6) Excellent electrical characteristics such as electrical insulation.

  In terms of formability, the mold appearance is excellent due to excellent mold transferability and low glass float while being highly rigid, eliminating the conventional painting process and reducing the film thickness, resulting in significant cost reductions. Is possible. Moreover, even a normal glass fiber reinforced grade has the same or better performance than the conventional sled improved grade of PBT or nylon. Furthermore, in secondary workability, it is excellent in adhesiveness with an epoxy adhesive or a coating material.

The polytrimethylene terephthalate resin (PTT) having the above characteristics is melt-extruded by a T-die method, closely adhered to a metal drum, and cooled to prepare an unstretched film. Alternatively, it is melt-extruded by an inflation method and air-cooled to obtain an unstretched film. At that time, the first base film (1) made of the polytrimethylene terephthalate resin has a thermal shrinkage of MD of 1.2% or less and TD of 1.2% or less, whereby dimensional stability is obtained. . Therefore, the conventional heat-fixing process of stretched film can be omitted, so that it is not limited to film forming equipment, and it is possible to manufacture a back protection sheet for solar cells with excellent dimensional stability at a very low cost. It becomes.

  The first base film (1) of the unstretched film made of the polytrimethylene terephthalate resin (PTT) may be transparent, but a white film that reflects light is used in consideration of the power generation efficiency of the solar cell element. preferable. This white film is produced by kneading white pigments such as titanium oxide, silica, alumina, calcium carbonate, and barium sulfate at a ratio of 5 to 20 parts by weight with respect to 100 parts by weight of the polytrimethylene terephthalate resin (PTT). And melt extrusion by a T-die method or an inflation method. It is preferable that the thickness is arbitrarily selected within the range of 20 to 200 μm. More preferably, it is the range of 30-50 micrometers. A foamed layer may be provided for whitening.

  Depending on the color, the white pigment and carbon black may be used in combination. For amorphous type solar cells, a black film kneaded with carbon black may be used.

  The first base film (1) of the unstretched film made of the polytrimethylene terephthalate resin may be blended with a flame retardant, an antioxidant, an ultraviolet absorber, an antistatic agent, etc. as necessary. .

  Next, the 2nd base film (5) which is a barrier layer which consists of a vapor deposition film which provided the vapor deposition thin film layer (3) of aluminum oxide or silicon oxide on the single side | surface of a support body film (4) is demonstrated in detail.

  The support film (4) is not particularly limited, but a single film and various laminated films can be used in consideration of processability and the like.

For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN)
), Polyesters such as polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT), polyolefins such as polypropylene (PP) and polystyrene (PS), polyamides (PA) such as nylon-6 and nylon-66, polycarbonate (PC) ), Polyacrylonitrile (PAN), polyimide (PI) and the like.

  Among these various films, in the case of the support film (4), a biaxially stretched polyethylene terephthalate film (OPET) arbitrarily stretched in the biaxial direction is used in terms of strength, processability, cost, and the like. Is preferred.

  Next, as the inorganic oxide forming the vapor deposition thin film layer (3), it is basically possible to use a metal oxide, for example, aluminum, silicon, magnesium, calcium, potassium, tin, Examples thereof include oxides such as sodium, boron, titanium, lead, zirconium, yttrium, and mixtures thereof.

  In general, aluminum oxide, silicon oxide, or the like is preferably used from the viewpoint of transparency, physical properties, productivity, and the like.

  As a method for forming such an inorganic oxide vapor-deposited thin film layer (3), a vacuum vapor deposition method, a sputtering method, or the like can be used. However, in consideration of productivity, production cost, etc., the vacuum vapor deposition method is preferable. .

  The vacuum deposition method is roughly classified into three types according to the form of the body to be vapor-deposited. 1) Batch method: vapor deposition method of molded product, 2) take-up type semi-continuous method: roll film (web) After unwinding, vapor deposition, and winding in a vacuum system, return to the air system again and take out the vapor deposition product. 3) Unwinder (unwinding device) for roll film (web) ) And a rewinder (winding device) are arranged in the atmospheric system, and a vapor deposition drum and an evaporation source are arranged in a vacuum system to deposit an evaporating substance on a roll film (web). This is a method called “air method”.

  When evaporating a vaporized material on a roll film (web), a take-up semi-continuous method is particularly widespread. Describe the structure.

  First, the constituent elements are a roll film (web), an evaporation source, an evaporation substance, a vapor deposition drum, a vacuum system, an unwinder (unwinding device), a rewinder (winding device), a guide roll, and the like.

  Next, the outline of the work process will be described. First, as a preparation, the door of the vacuum deposition apparatus is opened, the roll film (web) is set on the unwinder (unwinding apparatus), and it is arranged between the unwinder and the deposition drum. The roll-shaped film (web) travels to the vapor deposition drum through the guide roll, and the rewinder (winding device) passes through the guide roll arranged between the rewinder (winding device). Winding up and preparation for vapor deposition of the evaporated substance on the roll film (web) are completed.

  Next, the door of the vacuum vapor deposition apparatus is closed, and the vacuum vapor deposition chamber divided by the vacuum suction constant pressure chamber and the partition wall in the vacuum vapor deposition apparatus is set to a predetermined vacuum environment by a vacuum pump, and an unwinder (unwinding apparatus) The roll-shaped film (web) is fed out from the above-mentioned roll and the roll-shaped film (web) traveled through the guide roll is heated and evaporated from an evaporation source disposed at the lower part of the vapor deposition drum. The film is deposited on a film (web).

  Since the vapor deposition drum is cooled, the evaporated film is recrystallized and fixed to the roll film (web), and the roll film (web) deposited via the guide roll on the rewinder side is attached to the rewinder. It is wound up.

  The internal structure of the vacuum deposition apparatus is divided into a vacuum suction constant pressure chamber and a vacuum deposition chamber by a partition, and the vacuum suction constant pressure chamber is an unwinder, a guide roll, a tension control device, a speed control device, a position control device, and a deposition drum. A rewinder or the like is arranged.

The vacuum vapor deposition chamber is provided with a part of a vapor deposition drum, an evaporation source, its heating device, and the like, and the vacuum suction constant pressure chamber has a degree of vacuum by means of a vacuum pump attached around the vacuum vapor deposition device body. 1 × 10 ⁰ MPa about, the vacuum deposition chamber provided via the partition wall is set to a degree 1 × 10 ^-2 MPa (SI units).

  Since the chamber is divided into two partitions, impurities (dust) such as gas generated from the roll-shaped film (web) in the vacuum suction constant pressure chamber have a bad influence on the deposition in the vacuum deposition chamber. Few.

  Conversely, the radiant heat from the evaporation source disposed in the vacuum vapor deposition chamber has little influence on the vacuum suction constant pressure chamber, so that the influence on the roll film (web) is small.

  The vacuum deposition method is also a heating method: 1) indirect resistance method, 2) direct resistance heating method (wire feed method), 3) high frequency induction heating method, 4) electron beam method (EB method for short) There are four methods, but when the evaporated substance uses an insulating metal oxide such as aluminum oxide or silicon oxide, the electron beam method with good energy conversion efficiency is optimal.

  The winding-type electron beam vacuum deposition method is a method in which an evaporating substance such as aluminum oxide or silicon oxide is directly irradiated with an electron beam, and the surface of the evaporating substance is scanned to heat the evaporating substance surface. In this method, energy is converted at a portion where the beam hits to evaporate the evaporated substance.

  Although the thickness of this vapor deposition thin film layer (3) is suitably selected by the kind and structure of the inorganic oxide used, it is preferable to exist in the range of 5-300 nm. If the film thickness of the deposited thin film layer is less than 5 nm, a uniform film cannot be provided. Therefore, sufficient oxygen gas barrier property and water vapor barrier property cannot be obtained. It is not preferable because cracks and peeling easily occur in the deposited thin film layer (3) due to external factors such as.

In addition, a thermally crosslinkable primer coat layer (not shown) is provided between the support film (4) made of the biaxially stretched polyethylene terephthalate film (OPET) and the deposited thin film layer (3), and the support film (4) and using the second base material film (5) with improved adhesion between the deposited thin film layer (3).

Examples of the heat-crosslinkable primer coat layer include, for example, a general formula M (OR) n (wherein M: a metal element such as Si, Zr, Ti, Al, or an alkyl group such as R: CH ₃ , C ₂ H _5). , N: oxidation number of metal element) or a hydrolyzate of the metal alkoxide, or a general formula, R′Si (OR) ₃ (R ′: alkyl group, vinyl group, epoxy group, glycid A composite of at least one of a trifunctional organosilane represented by R: an alkyl group or the like or a hydrolyzate of the organosilane with a polyol compound and an isocyanate compound can also be used. .

Or a trifunctional organosilane represented by a general formula, R′Si (OR) ₃ (wherein R ′: amino group, isocyanate group, sulfoxide group, etc., R: alkyl group, etc.), a polyol compound, and an isocyanate. It may be composed of a compound with a compound.

Next, the metal alkoxide has a general formula, M (OR) n (wherein M: a metal element such as Si, Zr, Ti, Al, R: an alkyl group such as CH ₃ or C ₂ H ₅ , n: For example, an alkoxysilane compound, a zirconium alkoxide compound, a titanium alkoxide compound, or the like can be used.

Specifically, tetramethoxysilane [Si (O—CH ₃ ) ₄ ], tetraethoxysilane [Si (O—C ₂ H ₅ ) ₄ ], tetraisopropoxysilane [Si (O—iso—C ₃ H _{7). 4} ], tetrabutoxysilane [Si (O—C ₄ H ₉ ) ₄ ], dimethyldimethoxysilane [(H ₃ C) ₂ Si (O—CH ₃ ) ₂ ], trimethoxymethylsilane [H ₃ CSi (O -CH _{3) 3],} dimethyldiethoxysilane _{[(H 3 C) 2 Si} (O-C 2 H 5) 2] alkoxysilane compounds such as tetramethoxysilane zirconium _{[Zr (O-CH 3)} 4], tetra Ethoxyzirconium [Zr (O—C ₂ H ₅ ) ₄ ], tetraisopropoxyzirconium [Zr (O-iso-C ₃ H ₇ ) ₄ ], tetrabutoxyzirconium [Zr (O—C ₄ H ₉ ) ₄ ] and the like Zirconi Arm alkoxide compounds, tetramethoxysilane titanium _{[Ti (O-CH 3)} 4], tetraethoxysilane titanium _{[Ti (O-C 2 H} 5) 4], tetraisopropoxy titanium [Ti (O-iso-C 3 H 7) ₄ ] and titanium alkoxide compounds such as tetrabutoxytitanium [Ti (O—C ₄ H ₉ ) ₄ ].

In addition, the metal alkoxide has a general formula, M (OR) n (wherein M: a metal element such as Si, Zr, Ti, Al, R: an alkyl group such as CH ₃ or C ₂ H ₅ , n: a metal It may be a hydrolyzate of a compound represented by the oxidation number of the element.

Next, the trifunctional organosilane has a general formula R′Si (OR) ₃ (wherein R ′: alkyl group, vinyl group, epoxy group, glycidoxypropyl group, R: alkyl group, etc.) ), And examples thereof include ethyltrimethoxysilane, vinyltrimethoxysilane, glycidoxypropyltrimethoxysilane, glycidoxytrimethoxysilane, and epoxycyclohexylethyltrimethoxysilane. These compounds may be used alone or in a mixture of two or more. Further, hydrolysis of a compound represented by the above general formula, R′Si (OR) ₃ (wherein R ′: alkyl group, vinyl group, epoxy group, glycidoxypropyl group, R: alkyl group, etc.) It may be a thing.

Further, the trifunctional organosilane is a compound represented by the general formula, R′Si (OR) ₃ (wherein R ′: amino group, isocyanate group, sulfoxide group, etc., R: alkyl group, etc.). For example, γ-amino-propyltrimethoxysilane, γ-amino-propyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, and the like can be mentioned. It may be used in a mixture of two or more. Further, it may be a hydrolyzate of a compound represented by the above general formula, R′Si (OR) ₃ (wherein R ′: amino group, isocyanate group, sulfoxide group, etc., R: alkyl group, etc.). .

  Next, a polyester polyol or an acrylic polyol can be used as the polyol compound constituting the thermally crosslinkable primer coat layer.

The polyester polyol is terephthalic acid, isophthalic acid, phthalic acid, methylphthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, succinic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexa Acid raw materials for hydrophthalic acid and reactive derivatives thereof, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-hexanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, neopentyl Terminals of polyester resins obtained by known production methods from alcohol raw materials such as glycol, bishydroxyethyl terephthalate, trimethylol methane, trimethylol propane, glycerin and pentaerythritol Those having 2 or more hydroxyl groups (hydroxyl groups), are those which react with the isocyanate groups of the isocyanate compound added later.

  Next, the acrylic polyol has a hydroxyl group at the terminal out of a polymer compound obtained by polymerizing an acrylic acid derivative monomer or a polymer compound obtained by copolymerization with an acrylic acid derivative monomer and other monomers. It is made to react with the isocyanate group of the isocyanate compound added later.

  Among them, an acrylic polyol obtained by polymerizing an acrylic acid derivative monomer such as ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, or hydroxybutyl methacrylate alone, or an acrylic polyol copolymerized by adding other monomers such as styrene is preferably used. .

  In consideration of reactivity with an isocyanate compound, the hydroxyl value is preferably between 5 and 200 (KOHmg / g).

  Next, the blending ratio of the polyol compound and the trifunctional organosilane is preferably in the range of 1/1 to 100/1 by weight ratio, more preferably in the range of 2/1 to 50/1. It is.

  The dissolving and diluting solvent is not particularly limited as long as it can be dissolved and diluted. For example, esters such as ethyl acetate and butyl acetate, alcohols such as methanol, ethanol and isopropyl alcohol, and ketones such as methyl ethyl ketone. In addition, aromatic hydrocarbons such as toluene and xylene can be used alone or arbitrarily blended.

  However, since an aqueous solution such as hydrochloric acid or acetic acid is sometimes used to hydrolyze the trifunctional organosilane, a solvent in which isopropyl alcohol or the like and a polar solvent, ethyl acetate, are arbitrarily mixed is used as a co-solvent. More preferably.

Further, a reaction catalyst may be added in order to accelerate the reaction when the trifunctional organosilane is blended. The catalyst to be added is a tin compound such as tin chloride (SnCl ₂ , SnCl ₄ ), tin oxychloride (SnOHCl, Sn (OH) ₂ Cl ₂ ), tin alkoxide from the viewpoint of reactivity and polymerization stability. Is preferred. These catalysts may be added directly at the time of compounding, or may be added after being dissolved in a solvent such as methanol. If the addition amount is too small or too large, the catalytic effect cannot be obtained, and therefore the molar ratio is preferably within a range of 1/10 to 1/10000 with respect to the trifunctional organosilane, more preferably 1 More preferably within the range of / 100 to 1/2000.

  Next, the isocyanate compound is added in order to improve the adhesion to the base film or the deposited thin film layer by a urethane bond formed by reacting with a polyester polyol or an acrylic polyol. Acts as

As such isocyanate compounds, monomers such as aromatic tolylene diisocyanate, diphenylmethane diisocyanate, aliphatic xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and polymers and derivatives thereof are used. Are used alone or as a mixture.

  The blending ratio of the polyol compound and the isocyanate compound is not particularly limited, but if the isocyanate compound is too small, curing may be poor, and if it is too much, blocking or the like occurs and there is a problem in processing. . Therefore, the mixing ratio of the polyol compound and the isocyanate compound is preferably 50 times or less of the isocyanate group derived from the isocyanate compound than the hydroxyl group derived from the polyol compound. Particularly preferred is a case where an isocyanate group and a hydroxyl group are mixed in an equal amount, and a known method can be used as the mixing method.

  Next, as a method of preparing a primer solution for forming the heat-crosslinkable primer coat layer, a composite mixed solution in which trifunctional organosilane, a polyol compound and an isocyanate compound are mixed at an arbitrary mixing ratio is prepared. It is formed by coating on a substrate film.

  As a method of making the composite mixed solution, a method of mixing a trifunctional organosilane and a polyol compound, adding a solvent and a diluent, diluting to an arbitrary concentration, and then mixing with an isocyanate compound to make a composite mixed solution, Alternatively, a method in which a trifunctional organosilane is mixed in a solvent in advance and then a polyol compound is mixed and then diluted to an arbitrary concentration by adding a solvent and a diluent, and then an isocyanate compound is added to make a composite mixed solution. and so on.

  Various additives such as tertiary amines, imidazole derivatives, carboxylic acid metal chlorides, quaternary ammonium salts, quaternary phosphonium salts, and other accelerators, phenols, sulfurs, and phosphites It is also possible to add antioxidants, leveling agents, flow preparation agents, catalysts, crosslinking reaction accelerators, fillers and the like as necessary.

  Next, the thickness of the thermally crosslinkable primer coat layer is not particularly limited as long as a uniform coating film can be formed, but the dry film thickness is preferably in the range of 5 to 300 nm. If the thickness is 5 nm or less, a uniform coating cannot be formed, and stable adhesion cannot be obtained. If the thickness is 300 nm or more, physical properties are reached, which is not economical.

  Next, as a method of forming the heat-crosslinkable primer coat layer, for example, a known gravure roll coating method, reverse roll coating method, bar coating method, dropping method or the like can be used.

  In order to further improve the adhesion, the surface of the support film (4) is pretreated by a known method such as corona discharge treatment, glow discharge treatment, low temperature plasma treatment, flame treatment, chemical treatment, or solvent treatment. May be performed. In addition, various known additives and stabilizers such as antistatic agents, ultraviolet absorbers, plasticizers, and lubricants can be used on the front and back surfaces of the support film (4).

  Next, in order to further enhance the gas barrier property of the second base film (5), a gas barrier coating layer (not shown) is laminated on the inorganic oxide vapor-deposited thin film layer (3). I do not care. As the gas barrier coating layer, for example, a material comprising at least one of a water-soluble polymer and (a) one or more metal alkoxides and hydrolysates thereof or (b) tin chloride is used. Can do.

The gas barrier coating layer is provided on the vapor deposition thin film layer (3) in order to prevent various secondary damages in the subsequent steps of the vapor deposition thin film layer (3) and to provide higher gas barrier properties. The main component is an aqueous solution or a water / alcohol mixed solution containing at least one of a water-soluble polymer and (a) one or more metal alkoxides and hydrolysates thereof, or (b) tin chloride. A coating agent to be applied is applied onto the deposited thin film layer (3) to form a gas barrier coating layer.

  For example, a solution in which a water-soluble polymer and tin chloride are dissolved in an aqueous (aqueous solution or water / alcohol mixed solution) solvent, or a solution in which a metal alkoxide is directly or previously hydrolyzed and mixed. Is deposited on the vapor-deposited thin film layer (3) and dried by heating.

  Examples of the water-soluble polymer include polyvinyl alcohol (PVA), polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate.

  In particular, polyvinyl alcohol (PVA) is preferable because of its excellent gas barrier properties. The polyvinyl alcohol (PVA) here is generally obtained by saponifying polyvinyl acetate.

  Examples of the polyvinyl alcohol (PVA) include, for example, fully saponified polyvinyl alcohol (PVA) in which only several percent of acetic acid groups remain from so-called partially saponified polyvinyl alcohol (PVA) in which several tens percent of acetic acid groups remain. There is no particular limitation.

  The tin chloride is stannous chloride, stannic chloride, or a mixture thereof, and anhydrides and hydrates of these tin chlorides can also be used.

  Next, as the metal alkoxide, tetraethoxysilane, triisopropoxyaluminum and the like that are relatively stable in an aqueous solvent after hydrolysis are preferable.

  Furthermore, known additives such as isocyanate compounds, silane coupling agents, or dispersants, stabilizers, viscosity modifiers, colorants and the like are added to the coating agent as necessary, as long as the gas barrier properties are not impaired. Can be added.

  As the isocyanate compound added to the coating agent, those having two or more isocyanate groups in the molecule are preferable.

  Examples of such isocyanate compounds include monomers such as tolylene diisocyanate, triphenylmethane triisocyanate, and tetramethylxylene diisocyanate, and polymers and derivatives thereof.

  The gas barrier coating layer is formed on the deposited thin film layer (3) by applying a known method such as a gravure coating method, reverse roll coating method, air knife coating method, etc., followed by heating and drying.

  In this case, the thickness of the gas barrier coating layer is preferably in the range of 0.01 to 50 μm after drying. When the thickness after drying is 0.01 μm or less, sufficient gas barrier properties cannot be obtained, and when it is 50 μm or more, the coating film is liable to crack and adversely affects the gas barrier.

As mentioned above, the 2nd base film (5) which is a barrier layer which comprises the back surface protection sheet for solar cells which concerns on this invention is the support body film layer (4) / primer layer (not shown) / You may use the vapor deposition film which consists of a layer structure of the vapor deposition thin film layer (3) / gas barrier film layer (not shown) of an inorganic oxide.

  Next, the first base film (1) and the second base film (5) shown in FIG. 1, or the first base film (1) and the second base film (5) shown in FIG. Examples of the method of sequentially laminating the third base material film (7) include, for example, a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, and a sandwich / extrusion lamination method using an extrusion lamination method. These methods can be used as appropriate.

  First, the dry lamination method is a method of laminating one film and the other film through an adhesive layer (2, 6) made of an adhesive. The dry lamination method includes a coating unit, a drying device, and a nip roller unit. It consists of a section and an unwinding, winding and tension control system.

  The coating portion generally employs a gravure roll coating method or a reverse roll coating method.

  The adhesive used for the dry lamination method requires that the adhesive strength deteriorates after long-term outdoor use, does not cause delamination, and the adhesive does not yellow due to solar heat or the like. Polyacrylic, polyester, epoxy, polyvinyl acetate, cellulose, and other laminating adhesives can be used.

  As the lamination adhesive, a solvent-type adhesive or a solvent-free adhesive is used. However, when a solvent-free adhesive is used, a drying apparatus is unnecessary, and in particular, a non-solvent dry lamination method and I'm calling.

  The hot melt lamination method is performed by using an adhesive layer made of hot melt adhesive blended with heat-melted ethylene-vinyl acetate copolymer (EVA), wax, tackifier, plasticizer, filler, etc. In this method, the film and the other film are immediately laminated.

  In the extrusion lamination method, a thermoplastic resin such as a low density polyethylene resin (LDPE) is heated, melted in a cylinder called a cylinder, extruded by applying pressure with a screw, and a T die at the tip of the cylinder. This is a method of extruding the thermoplastic resin dissolved in the form of a curtain from a thin slit to form a film and then directly laminating it on the substrate film.

  Using such an extrusion lamination method, a sandwich that laminates one film and the other film using a thermoplastic resin such as low density polyethylene resin (LDPE) or polypropylene resin (PP) as an adhesive. • The extrusion lamination method can also be used.

FIG. 3 shows a solar cell module (C) unitized using the solar cell back surface protective sheet (A) according to the present invention described above. The solar cell module (C) includes an upper transparent material (13), a filler (10, 12), a cell (11) composed of a solar cell element (11a) and a wiring (11b), a back surface protection sheet for solar cells ( A) It is formed of a frame (14). The back protective sheet for solar cell (A) is a filler (10) on the second base film (5) side of the barrier layer.
Use on the side.

  In addition, as shown in FIG. 2, the first base film (1) or other base is further provided on the second base film (5) in order to enhance electrical insulation and adhesion to the filler (10). A solar cell module (D) as shown in FIG. 4 may be used by using a solar cell back surface protective sheet (B) on which a third base film (7) made of a material film is laminated.

  The upper transparent material (13) has good light transmittance, excellent weather resistance over a long period of time (about 20 years), little decrease in light transmittance, dust and the like are difficult to adhere, scratches It is necessary to have various functions such as being difficult to stick and having a very low water vapor transmission rate, and glass, acrylic resin, polycarbonate resin, silicone resin, fluorine resin, and the like can be used.

  The fillers (10, 12) have high sunlight transmittance, no change in physical properties such as reduction in light transmittance due to long-term outdoor standing, etc., high insulation resistance, and corrode other materials. And has various functions such as no cracking of the resin due to a sudden change in outside air conditions, interfacial peeling, etc., and ethylene-vinyl acetate copolymer (EVA), polyvinyl butyral resin, silicone resin Vinyl chloride resin, polyurethane resin, etc. can be used.

  For the frame (14), an aluminum mold is generally used.

  An example of the manufacturing method of the solar cell module (C, D) will be described below. A cell (11) composed of solar cell elements (11a) wired in advance (11b) is composed of two fillers (10, 12) After sandwiching between the sheets, the upper transparent material (13) is placed on one filler (12) sheet, and the solar cell back surface protection sheet (A) is placed on the opposite filler (10) sheet. , B) so that the surface of the first base film (1) is on the outside, and then the whole is preheated under reduced pressure from both sides, and then hot-pressed to form the back protective sheet for solar cells (A, B) Are fused and integrated, and the ends are fixed with aluminum frames (14, 14) to produce solar cell modules (C, D).

  Hereinafter, specific examples of the solar cell back surface protective sheet (A, B) and the solar cell module (C, D) using the solar cell back protective sheet (A, B) according to the present invention will be described in more detail, but the present invention is limited thereto. It is not a thing.

<Example 1>
As shown in FIG. 1, a biaxially stretched polyethylene terephthalate film having a thickness of 12 μm was used as the support film (4), and a 50 nm-thick aluminum oxide thin film layer (3 A second base film (5) made of a vapor deposition film laminated with a) was prepared. Subsequently, a first layer comprising a vapor-deposited thin film layer (3) surface of the second base film (5) and an unstretched transparent polytrimethylene terephthalate film (PTT) having a thickness of 50 μm previously formed by a T-die method. a base film (1), solid content 30% by weight of Takeda Chemical Industries, Ltd. polyurethane adhesive (main agent TAKELAC A515 / curing agent Takenate A50 = 10/1 solution) coating amount 5 g / m ² (dry Through the adhesive layer (2) formed by application and drying in the state), lamination was performed with a dry laminating machine to produce a back protective sheet for solar cells (A) according to the present invention.

Next, as shown in FIG. 3, a standard-cure type ethylene-vinyl acetate copolymer having a thickness of 600 μm is formed from a polycrystalline silicone cell (11) composed of solar cell elements (11a) previously wired (11b). After sandwiching between two filler (10, 12) sheets made of coalescence (EVA), the upper transparent material (13) made of a tempered glass plate is placed on one filler (12) sheet, and the opposite The solar cell back surface protective sheet (A) is placed on the side filler (10) sheet so that the first base film (1) surface is on the outside, and preheated at 40 ° C. for 5 minutes. Later, vacuuming was performed at 150 ° C. from both sides (0.5 atm) for 5 minutes × holding for 5 minutes, and then the back protection sheet for solar cells (A) that had been subjected to the crosslinking reaction by holding at 150 ° C. for 30 minutes was melted. The solar cell module (C) was manufactured by attaching and integrating and fixing the ends with aluminum frames (14, 14).

<Example 2>
In Example 1, except that a polytrimethylene terephthalate film (PTT) kneaded with an unstretched white pigment having a thickness of 50 μm formed by the T-die method was used as the first base film (1). It carried out similarly to Example 1, and manufactured the solar cell back surface protection sheet (A) and solar cell module (C) using the same of this invention.

<Example 3>
In Example 1, the same procedure as in Example 1 was used, except that an unstretched 75 μm thick foamed polytrimethylene terephthalate film (PTT) formed by the T-die method was used as the first base film (1). The solar cell back surface protection sheet (A) and the solar cell module (C) using the same were manufactured.

<Example 4>
As shown in FIG. 2, a biaxially stretched polyethylene terephthalate film having a thickness of 12 μm was used as the support film (4), and a 50 nm-thick aluminum oxide thin film layer (3 A second base film (5) made of a vapor deposition film laminated with a) was prepared. Subsequently, a first film comprising the surface of the support film (4) of the second base film (5) and an unstretched transparent polytrimethylene terephthalate film (PTT) having a thickness of 50 μm previously formed by the T-die method. a base film (1), solid content 30% by weight of Takeda Chemical Industries, Ltd. polyurethane adhesive (main agent TAKELAC A515 / curing agent Takenate A50 = 10/1 solution) coating amount 5 g / m ² (dry After being laminated with a dry laminating machine via an adhesive layer (2) that is applied and dried in a state), a white pigment is further kneaded and a 50 μm thick polybutylene terephthalate (PBT) film is formed. Three base film (7) made of Takeda Pharmaceutical Co., Ltd. polyurethane adhesive having a solid content of 30% by weight (main agent Takelac A515 / curing agent Takenate A50 = 10/1 The back surface protection sheet (B) for solar cells was manufactured by sequentially laminating the solution) through an adhesive layer (6) formed by applying and drying the solution at a coating amount of 5 g / m ² (dry state).

  Next, as shown in FIG. 4, a standard cure type ethylene-vinyl acetate copolymer having a thickness of 600 μm is formed by using a polycrystalline silicon cell (11) composed of a solar cell element (11a) previously wired (11b). After sandwiching between two filler (10, 12) sheets made of coalescence (EVA), the upper transparent material (13) made of a tempered glass plate is placed on one filler (12) sheet, and the opposite The solar cell back surface protective sheet (B) is placed on the side filler (10) sheet so that the first base film (1) surface is on the outside, and preheated at 40 ° C. for 5 minutes. Later, vacuuming was performed at 150 ° C. from both sides (0.5 atm) for 5 minutes × holding for 5 minutes, and then the back protection sheet for solar cells (A) that had been subjected to the crosslinking reaction by holding at 150 ° C. for 30 minutes was melted. The solar cell module (D) was manufactured by attaching and integrating and fixing the ends with aluminum frames (14, 14).

<Example 5>
In Example 1, as the first substrate film (1), an unstretched 100 μm-thick coextruded polytrimethylene terephthalate film (PTT) formed by the T-die method (transparent PTT / white pigment kneaded PTT / transparent Except having used PTT), it carried out similarly to Example 1, and manufactured the solar cell back surface protection sheet (A) and solar cell module (C) using the same of this invention.

<Example 6>
In Example 1, the same procedure as in Example 1 was used except that an unstretched 50 μm thick transparent polytrimethylene terephthalate film (PTT) formed by the inflation method was used as the first base film (1). The back surface protection sheet (A) for solar cells of this invention and the solar cell module (C) using the same were manufactured.

<Example 7>
In Example 1, except that a polytrimethylene terephthalate film (PTT) kneaded with an unstretched 50 μm thick white pigment formed by an inflation method was used as the first base film (1). The solar cell back surface protection sheet (A) of the present invention and a solar cell module (C) using the same were produced in the same manner as in Example 1.

    Below, the comparative example of this invention is demonstrated.

<Comparative Example 1>
In Example 1, as a 1st base film (1), except having used the 50-micrometer-thick white polyethylene terephthalate film (PET) formed into the biaxial stretching by the T-die method, it is the same as that of Example 1. The back surface protection sheet (A) for solar cells of this invention and the solar cell module (C) using the same were manufactured.

<Comparative example 2>
In Example 1, as a 1st base film (1), except having used the 50-micrometer-thick heat-resistant polyethylene terephthalate film (PET) formed into the biaxial stretching by the T-die method, it is the same as that of Example 1. The back surface protection sheet (A) for solar cells of this invention and the solar cell module (C) using the same were manufactured.

<Comparative Example 3>
In Example 1, Example 1 was used except that a heat-resistant polyethylene terephthalate film (PET) annealed to a thickness of 50 μm formed biaxially stretched by the T-die method was used as the first base film (1). The solar cell back surface protection sheet (A) of the present invention and a solar cell module (C) using the same were produced in the same manner as described above.

<Comparative example 4>
In Example 4, as the first substrate film (1), an unstretched 38 μm-thick polyvinyl fluoride film (PVF) (Du Pont Co., Ltd., trade name: Tedlar) formed by the T-die method was used. The back surface for a solar cell of the present invention is the same as in Example 4 except that the same third substrate film (7) as the first substrate film (1) is laminated as the second substrate film (5). A protective sheet (B) and a solar cell module (D) using the same were produced.

<Comparative Example 5>
In Example 1, except that an unstretched 12 μm-thick polyethylene terephthalate film (PET) formed by the T-die method without the vapor-deposited thin film layer (3) was used as the second base film (5). It carried out similarly to Example 1, and manufactured the solar cell back surface protection sheet (A) and solar cell module (C) using the same of this invention.

<Evaluation>
Using the solar cell back surface protection sheet and solar cell module produced in Examples 1 to 7 and Comparative Examples 1 to 5, the thermal shrinkage rate (%), hydrolysis resistance, and solar cell output retention rate (%) It measured with the following measuring methods. The results are shown in Table 1.
(1) Thermal contraction rate (%)
Measure the dimensions of the back protective sheet for solar cells with a mark in advance. Then, it hold | maintained for 30 minutes in the atmosphere of 150 degreeC, and measured the shrinkage rate by measuring the dimension of MD (flow direction) and TD (width direction) after a heating.
(2) Hydrolysis resistance The back surface protection sheet for solar cells is stored under high temperature and high humidity of 85 ° C x 85% RH x 1000 hours, the tensile strength and elongation are measured, and the initial breaking elongation is 100%. The retention rate was compared.

○: Retention ratio 70% or more, Δ: Retention ratio 50 to 70% or more, X: Retention ratio 50% or less.
(3) Solar cell output retention rate (%)
After the solar cell module was subjected to an accelerated test for 1000 hours in an environment of 85 ° C. × 85% RH, the retention rate (%) with respect to the initial output was measured by a method based on JIS C-8913.

Table 1 shows the heat shrinkage rate (%), hydrolysis resistance, and solar cell output retention rate using the solar cell back surface protection sheet and solar cell module prepared in Examples 1 to 7 and Comparative Examples 1 to 5. It is the table | surface which showed the measurement result of (%).

  Comparative Example 1 is that the back surface protective sheet for solar cell and the solar cell module of Examples 1 to 7 from Table 1 are comprehensively judged in terms of heat shrinkage rate (%), hydrolysis resistance, and solar cell output retention rate (%). Excellent compared to ~ 5.

It is a sectional side view which shows one Example of the laminated constitution of the back surface protection sheet for solar cells which concerns on this invention. It is a sectional side view which shows the other Example of the layer structure of the back surface protection sheet for solar cells which concerns on this invention. It is a sectional side view which shows one Example of the solar cell module using the back surface protection sheet for solar cells which concerns on this invention. It is a sectional side view which shows the other Example of the solar cell module using the back surface protection sheet for solar cells which concerns on this invention.

Explanation of symbols

A ... Back surface protection sheet for solar cell B ... Back surface protection sheet for solar cell C ... Solar cell module D ... Solar cell module 1 ... First base film 2 ... Adhesive layer 3 ... Deposition thin film layer 4 ... Support film 5 ... Second substrate film 6 ... Adhesive layer 7 ... Third substrate film 10 ... Filler 11 ... Cell 11a .... Solar cell element 11b ... Wiring 12 ... Filler 13 ... Upper transparent material 14 ... Frame

Claims (6)

  One side of the first base film, which is an unstretched film made of polytrimethylene terephthalate resin, and the second base film made of a vapor-deposited film having an inorganic oxide vapor-deposited thin film layer on one side of the support film The back surface protection sheet for solar cells characterized by comprising the laminated body which laminated | stacked by providing the heat-crosslinkable primer layer between the said support body film and the said vapor deposition thin film layer. 2. The solar cell back surface protection according to claim 1, wherein the first base film made of the polytrimethylene terephthalate resin has a thermal shrinkage ratio of MD of 1.2% or less and TD of 1.2% or less. Sheet.   The said 1st base film is a white film, The back surface protection sheet for solar cells of Claim 1 or 2 characterized by the above-mentioned.   The back protective sheet for a solar cell according to any one of claims 1 to 3, wherein the inorganic oxide is either aluminum oxide or silicon oxide.   The first base film, any one surface of the second base film, and a third base film made of the first base film or another base film are sequentially laminated. The back surface protection sheet for solar cells according to any one of claims 1 to 4.   A solar cell module comprising the solar cell back surface protective sheet according to any one of claims 1 to 5.