JP2012089597A - Back sheet for solar cell and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet for a solar cell excellent in weather resistance.SOLUTION: A white pigment-containing layer is provided on a rear side of a liquid crystalline polyester layer to form a back sheet for a solar cell. The liquid crystalline polyester layer includes a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2) and a repeating unit represented by the following formula (3). And it is preferable that the content of a repeating unit containing a 2,6-naphtylene group be 40 mol% or more based on the total amount of all of the repeating units. -O-Ar-CO...(1) -CO-Ar-CO-...(2) -O-Ar-O-...(3) (In the formulae, Arrepresents a 2,6-naphtylene group, a 1,4-phenylene group or a 4,4'-biphenylylene group. Arand Areach independently represent a 2,6-naphtylene group, a 1,4-phenylene group, a 1,3-phenylene group or a 4,4'-biphenylylene group.)

Description

  The present invention relates to a solar cell backsheet having a liquid crystal polyester layer. Moreover, this invention relates to the solar cell module which uses this solar cell backsheet.

  A solar cell module usually has a structure in which a surface protection sheet is disposed on the front side (light receiving surface side) of a solar cell element, and a back sheet is disposed on the back side (surface side opposite to the light receiving surface). An example is shown in FIG. In this example, the solar cell element 3 is sealed with a front-side sealing layer 2 and a back-side sealing layer 4, the surface protection sheet 1 is disposed on the outer side (front side) of the front-side sealing layer 2, and the back side A back sheet 5 is disposed outside (back side) of the sealing layer 4. Further, the peripheral portions of the surface protection sheet 1 and the back sheet 5 are fixed by a frame 6.

  Patent Documents 1 and 2 disclose that a liquid crystal polyester film is used for the back sheet because of its excellent water vapor barrier property. Patent Document 2 also discloses that a resin film is laminated on the inner side (front side) of a liquid crystal polyester film, and this laminated film is used as a back sheet.

Japanese Patent Laid-Open No. 2002-64213 JP 2006-324478 A

  As disclosed in Patent Document 1 and Patent Document 2, a solar cell backsheet having a conventional liquid crystal polyester layer is not necessarily sufficient in weather resistance, for example, when receiving light irradiation from the back side for a long time by reflected light, Warping may come off or tear. Then, the objective of this invention is providing the solar cell backsheet which has a liquid-crystal polyester layer and is excellent in a weather resistance.

  In order to achieve the above object, the present invention provides a solar cell backsheet disposed on the back side of a solar cell element, wherein the white pigment-containing layer is provided on the back side of the liquid crystal polyester layer. I will provide a.

  Moreover, this invention also provides the solar cell module by which a surface protection sheet is arrange | positioned at the front side of a solar cell element, and the said solar cell backsheet is arrange | positioned at the back side of the said solar cell element.

  The solar cell backsheet of the present invention is excellent in weather resistance.

It is sectional drawing which shows the example of a solar cell module typically. It is sectional drawing which shows the example of the solar cell backsheet of this invention typically.

  As shown in FIG. 2, the solar cell backsheet of the present invention is provided with a white pigment-containing layer 56 on the back side of the liquid crystal polyester layer 53. As shown in FIG. 1, the back side of the solar cell element 3 is provided. Is to be arranged.

  The liquid crystal polyester constituting the liquid crystal polyester layer 53 is a liquid crystal polyester that exhibits liquid crystallinity in a molten state, and is preferably melted at a temperature of 450 ° C. or lower. The liquid crystal polyester may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide. The liquid crystal polyester is preferably a wholly aromatic liquid crystal polyester using only an aromatic compound as a raw material monomer.

  A typical example of the liquid crystal polyester is polymerization (polycondensation) of an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, and at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. At least one compound selected from the group consisting of aromatic dicarboxylic acids and aromatic diols, aromatic hydroxyamines and aromatic diamines, And those obtained by polymerizing a polyester such as polyethylene terephthalate and an aromatic hydroxycarboxylic acid. Here, the aromatic hydroxycarboxylic acid, the aromatic dicarboxylic acid, the aromatic diol, the aromatic hydroxyamine, and the aromatic diamine are each independently replaced with a part or all of the polymerizable derivative. Also good.

  Examples of polymerizable derivatives of a compound having a carboxyl group such as an aromatic hydroxycarboxylic acid and an aromatic dicarboxylic acid include those obtained by converting a carboxyl group into an alkoxycarbonyl group or an aryloxycarbonyl group, and a carboxyl group as a haloformyl. And those obtained by converting a carboxyl group into an acyloxycarbonyl group. Examples of polymerizable derivatives of hydroxyl group-containing compounds such as aromatic hydroxycarboxylic acids, aromatic diols and aromatic hydroxyamines include those obtained by acylating a hydroxyl group and converting it to an acyloxyl group. . Examples of the polymerizable derivative of a compound having an amino group such as aromatic hydroxyamine and aromatic diamine include those obtained by acylating an amino group and converting it to an acylamino group.

  As the liquid crystalline polyester, since it has excellent water vapor barrier properties, a repeating unit represented by the following formula (1) (hereinafter sometimes referred to as repeating unit (1)) and a repeating unit represented by the following formula (2): Those having a repeating unit (hereinafter sometimes referred to as repeating unit (2)) and a repeating unit represented by the following formula (3) (hereinafter sometimes referred to as repeating unit (3)) are preferably used.

—O—Ar ¹ —CO— (1)
—CO—Ar ² —CO— (2)
—O—Ar ³ —O— (3)

(Ar ¹ represents a 2,6-naphthylene group, a 1,4-phenylene group or a 4,4′-biphenylylene group. Ar ² and Ar ³ are each independently a 2,6-naphthylene group, 1,4 -Represents a phenylene group, a 1,3-phenylene group or a 4,4'-biphenylylene group, wherein the hydrogen atom in the group represented by Ar ¹ , Ar ² or Ar ³ is independently a halogen atom or a carbon number (It may be substituted with an alkyl group of 1 to 10 or an aryl group of 6 to 20 carbon atoms.)

As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group, An n-octyl group and n-decyl group are mentioned, The carbon number is 1-10 normally. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms is usually 6 to 20. . When the hydrogen atom is substituted with these groups, the number is usually 2 or less for each group represented by Ar ¹ , Ar ² or Ar ³ , and preferably 1 It is as follows.

The repeating unit (1) is a repeating unit derived from a predetermined aromatic hydroxycarboxylic acid. As the repeating unit (1), Ar ¹ is preferably a 2,6-naphthylene group, that is, a repeating unit derived from 6-hydroxy-2-naphthoic acid is preferable.

The repeating unit (2) is a repeating unit derived from a predetermined aromatic dicarboxylic acid. As the repeating unit (2), Ar ² is a 2,6-naphthylene group, that is, a repeating unit derived from 2,6-naphthalenedicarboxylic acid, and Ar ² is a 1,4-phenylene group, Repeating units derived from terephthalic acid are preferred.

The repeating unit (3) is a repeating unit derived from a predetermined aromatic diol. As the repeating unit (3), Ar ³ is a 1,4-phenylene group, that is, a repeating unit derived from hydroquinone, and Ar ³ is a 4,4′-biphenylylene group, that is, 4,4′-. Repeating units derived from dihydroxybiphenyl are preferred.

Content of repeating unit containing 2,6-naphthylene group in the liquid crystalline polyester, that is, repeating unit (1) in which Ar ¹ is a 2,6-naphthylene group, repeating in which Ar ² is a 2,6-naphthylene group The total content of the unit (2) and the repeating unit (3) in which Ar ³ is a 2,6-naphthylene group is the total amount of all repeating units (the mass of each repeating unit constituting the liquid crystalline polyester is It is preferable that it is 40 mol% or more with respect to the substance amount equivalent amount (mole) of each repeating unit by dividing by the formula amount (the value obtained by adding them). Thereby, water vapor | steam barrier property can be improved. The content of the 2,6-naphthylene group is more preferably 50 mol% or more, further preferably 60 mol% or more, and particularly preferably 70 mol% or more.

  In the liquid crystalline polyester, the content of the repeating unit (1) is preferably 30 to 80 mol%, more preferably 40 to 70 mol%, and further preferably 45 to 65, based on the total amount of all repeating units. The content of the repeating unit (2) is preferably 10 to 35 mol%, more preferably 15 to 30 mol%, still more preferably 17.5 to 27, based on the total amount of all repeating units. The content of the repeating unit (3) is preferably 10 to 35 mol%, more preferably 15 to 30 mol%, still more preferably 17.5, based on the total amount of all repeating units. ˜27.5 mol%. The liquid crystal polyester having such a predetermined repeating unit composition has an excellent balance between heat resistance and moldability. In addition, it is preferable that content of a repeating unit (2) and content of a repeating unit (3) are substantially equal. Further, the liquid crystalline polyester may have repeating units other than the repeating units (1) to (3) as necessary, but the content thereof is usually 10 with respect to the total amount of all repeating units. The mol% or less, preferably 5 mol% or less.

A typical example of a liquid crystal polyester having high heat resistance and high melt tension is a repeating unit (1) in which Ar ¹ is a 2,6-naphthylene group, that is, 6-hydroxy-2-hydroxy, based on the total amount of all repeating units. The repeating unit derived from naphthoic acid is preferably 40 to 74.8 mol%, more preferably 40 to 64.5 mol%, still more preferably 50 to 58 mol%, and Ar ² is a 2,6-naphthylene group. The repeating unit (2), that is, a repeating unit derived from 2,6-naphthalenedicarboxylic acid, is preferably 12.5 to 30 mol%, more preferably 17.5 to 30 mol%, still more preferably 20 to 25 a mole%, repeating units Ar ² is 1,4-phenylene group (2), i.e., repeating units derived from terephthalic acid, preferably 0.2 to 15 mol%, more preferably 0. 12 mol%, more preferably has 2 to 10 mol%, the repeating units Ar ³ is 1,4-phenylene group (3), i.e., a repeating unit derived from hydroquinone, preferably 12.5 to 30 mol %, More preferably 17.5 to 30 mol%, still more preferably 20 to 25 mol%, and the content of the repeating unit (2) in which Ar ² is a 2,6-naphthylene group is such that Ar ² is The total content of the repeating unit (2) which is a 2,6-naphthylene group and the repeating unit (2) wherein Ar ² is a 1,4-phenylene group is preferably 0.5 mol times or more, more preferably It is 0.6 mol times or more.

  The liquid crystalline polyester is preferably produced by melt polymerization of monomers and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, liquid crystalline polyester with high heat resistance and high melt tension can be manufactured with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, , N, N-dimethylaminopyridine, N-methylimidazole, and the like, and nitrogen-containing heterocyclic compounds are preferably used.

  The liquid crystal polyester has a flow initiation temperature of preferably 280 ° C. or higher, more preferably 290 ° C. or higher, further preferably 295 ° C. or higher, and usually 380 ° C. or lower, preferably 350 ° C. or lower. As the flow start temperature is higher, the heat resistance and melt tension are more likely to be improved. However, if the flow start temperature is too high, a high temperature is required for melting, and thermal deterioration tends to occur during molding.

The flow start temperature is also called flow temperature or flow temperature, and is 4 ° C / min under a load of 9.8 MPa (100 kg / cm ² ) using a capillary rheometer having a nozzle having an inner diameter of 1 mm and a length of 10 mm. This is a temperature at which the melt viscosity shows 4800 Pa · s (48,000 poise) when the heated melt of liquid crystal polyester is extruded from the nozzle at a temperature rising rate, and is a measure of the molecular weight of the liquid crystal polyester (Naoyuki Koide) Ed., “Liquid Crystal Polymer—Synthesis / Molding / Application—”, CMC, June 5, 1987, p. 95).

  The liquid crystal polyester may be blended with other components as necessary to form a composition. Examples of other components include fillers, thermoplastic resins other than liquid crystal polyesters, and additives. The ratio of the liquid crystal polyester in the entire composition is preferably 80% by mass or more, and more preferably 90% by mass or more.

  Examples of fillers include glass fibers such as milled glass fibers and chopped glass fibers, potassium titanate whiskers, alumina whiskers, aluminum borate whiskers, silicon carbide whiskers, silicon nitride whiskers, and other metal or non-metallic whiskers. , Glass beads, hollow glass spheres, glass powder, mica, talc, clay, silica, alumina, potassium titanate, wollastonite, calcium carbonate (heavy, light, colloidal, etc.), magnesium carbonate, basic magnesium carbonate, sodium sulfate , Calcium sulfate, barium sulfate, calcium sulfite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium silicate, silica sand, quartz, quartz, titanium oxide, zinc oxide, iron oxide graphite, molybdenum, asbestos, silica alumina Fiber , Alumina fibers, gypsum fibers, carbon fibers, carbon black, white carbon, diatomaceous earth, bentonite, sericite, Shirasu and graphite are mentioned, it is also possible to use two or more of them, if necessary. Among these, glass fiber, mica, talc and carbon fiber are preferably used.

  The filler may be surface-treated as necessary, and examples of the surface treatment agent include reactivity such as a silane coupling agent, a titanate coupling agent, and a borane coupling agent. Examples include coupling agents and lubricants such as higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, and fluorocarbon surfactants.

  Examples of thermoplastic resins other than liquid crystal polyesters include polycarbonate, polyamide, polysulfone, polyphenylene sulfide, polyphenylene ether, polyether ketone, and polyetherimide resin.

  Examples of additives include mold release improvers such as fluororesins and metal soaps, nucleating agents, antioxidants, stabilizers, plasticizers, lubricants, anti-coloring agents, coloring agents, ultraviolet absorbers, antistatic agents, Examples include lubricants and flame retardants.

  By forming the liquid crystal polyester thus obtained or a composition thereof into a film, a liquid crystal polyester film to be the liquid crystal polyester layer 53 of the solar cell backsheet of the present invention can be obtained. Examples of the film forming method include an extrusion molding method, a press molding method, a solution casting method, and an injection molding method, and the extrusion molding method is preferable. Examples of the extrusion molding method include a T-die method and an inflation method. In the T-die method, uniaxial stretching or biaxial stretching may be performed.

  The draw ratio (draft ratio) of the uniaxially stretched film is usually 1.1 to 40, preferably 10 to 40, and more preferably 15 to 35. The draw ratio in the MD direction (extrusion direction) of the biaxial film is usually 1.2 to 40 times, and the draw ratio in the TD direction (direction perpendicular to the extrusion direction) of the biaxial film is usually 1.2 to 20 times. Is double. The stretch ratio in the MD direction of the inflation film (drawdown ratio = bubble take-off speed / resin discharge speed) is usually 1.5 to 50, preferably 5 to 30, and the stretch ratio of TD of the inflation film (blow ratio = bubble). (Diameter / annular slit diameter) is usually 1.5 to 10, preferably 2 to 5.

  The thickness of the liquid crystal polyester layer 53 is preferably 5 to 100 μm, more preferably 10 to 75 μm, and still more preferably 15 to 75 μm. If it is too thin, the strength will be insufficient, and if it is too thick, the flexibility will be insufficient.

Liquid crystal polyester layer 53 is water vapor transmission rate being measured at a temperature 40 ° C. and a relative humidity of 90%, is preferably, less 0.05g / m ² · 24h or less 0.1g / m ² · 24h It is more preferable.

  The liquid crystal polyester layer 53 may be provided with a water vapor barrier layer 54 on at least one surface thereof. In the example of FIG. 2, the water vapor barrier layer 54 is provided on the back side of the liquid crystal polyester layer 53. However, the water vapor barrier layer 54 may be provided on the front side of the liquid crystal polyester layer 53. It may be provided on the back side.

  Substances constituting the water vapor barrier layer 54 include at least one element selected from the group consisting of aluminum, silicon, titanium, chromium, iron, cobalt, nickel, copper, zinc, silver and gold, oxide, and nitridation. And oxynitrides are preferable, and two or more of them may be used as necessary.

Examples of the method of forming the water vapor barrier layer 54 include PVD methods such as vapor deposition, sputtering, and ion plating, CVD methods such as plasma CVD, thermal CVD, and laser CVD, and sol-gel methods and plating. And wet methods such as coating method and coating method. Further, a foil prepared or obtained separately may be bonded to the liquid crystal polyester film.

  The thickness of the water vapor barrier layer 54 is preferably 5 to 250 nm, more preferably 40 to 100 nm. If it is too thin, the effect of improving the water vapor barrier property will be insufficient, and if it is too thick, the flexibility will be insufficient.

  A white pigment-containing layer 56 is provided on the back side of the liquid crystal polyester layer 53. Thereby, the solar cell backsheet excellent in a weather resistance can be obtained. In the example of FIG. 2, the white pigment-containing layer 56 is provided via the adhesive layer 55, but the white pigment-containing layer 56 may be provided by thermal fusion, for example, without the adhesive layer 55. Good.

Examples of the white pigment contained in the white pigment-containing layer 56 include basic lead carbonate (2PbCO ₃ · Pb (OH) ₂ (lead white), etc.), basic lead sulfate (2PbSO ₄ · Pb (OH) ₂ etc.), base Lead silicate (Pb ₂ SiO ₄ · Pb (OH) ₂ etc.), zinc white (ZnO (zinc oxide)), zinc sulfide, lithopone (mixture of zinc sulfide and barium sulfate), antimony trioxide and titanium oxide Preferably, two or more of them may be used as necessary.

  The white pigment-containing layer 56 is preferably provided using a resin film containing a white pigment. As the resin contained in the resin film, that is, the white pigment-containing layer 56, polyester such as polyethylene terephthalate (PET) is preferable. The content of the white pigment in the white pigment-containing layer 56 is preferably 5 to 90% by mass and more preferably 10 to 80% by mass with respect to the total amount of the white pigment-containing layer 56. The thickness of the white pigment-containing layer 56 is preferably 5 to 500 μm, more preferably 10 to 400 μm.

  On the front side of the liquid crystal polyester layer 53, another resin layer, preferably a polyolefin layer 51, may be provided in order to enhance adhesion to the sealing layer 4 or to provide design properties. In the example of FIG. 2, the polyolefin layer 51 is provided via the adhesive layer 52, but the polyolefin layer 51 may be provided by, for example, heat fusion without using the adhesive layer 52.

  The polyolefin constituting the polyolefin layer 51 is preferably polyethylene, more preferably low density polyethylene (LDPE), and still more preferably linear low density polyethylene (LLDPE). The polyolefin layer 51 is preferably provided using a polyolefin film. When the polyolefin layer 51 is provided in order to impart designability, a desired color pigment or dye may be included in the polyolefin film, that is, the polyolefin layer 51. . The thickness of the polyolefin layer 51 is preferably 5 to 200 μm, more preferably 10 to 100 μm.

  The solar cell backsheet of the present invention thus obtained can be in the form of a product called a solar cell backsheet with a sealing layer by providing the sealing layer 4 on the front side. In this case, the front side of the sealing layer 4 is usually protected with a release film, and the release film is peeled off during use (at the time of manufacturing the solar cell module).

  As shown in FIG. 1, the solar cell module using the solar cell backsheet of the present invention has the surface protection sheet 1 disposed on the front side of the solar cell element 3, and the solar cell module of the present invention on the back side of the solar cell element. A battery back sheet 5 is disposed.

  The solar cell element 3 is usually composed of a plurality of solar cells, a conductive wire that connects the solar cells, and a conductive wire that connects the solar cells and the terminal box for power extraction, and the solar cell is a single crystal silicon semiconductor. It may be a polycrystalline silicon semiconductor, an amorphous silicon semiconductor, a compound semiconductor, or an organic semiconductor. As the surface protection sheet 1, a glass plate is preferably used. Moreover, it is preferable that the solar cell element 3 is sealed with a sealing material, and an ethylene-vinyl acetate copolymer (EVA) is preferably used as the sealing material. In the example of FIG. 1, the sealing layers 2 and 4 are provided on the front side and the back side of the solar cell element 3, but when the solar cell element is directly disposed on the back surface of the glass plate, Only the sealing layer 4 on the back side may be provided.

  Since the solar cell module obtained in this way is provided with the back sheet | seat excellent in a weather resistance, it is excellent in the sustainability of a performance.

[Measurement of flow start temperature]
Using a flow tester (“CFT-500 type” manufactured by Shimadzu Corporation), about 2 g of the sample was filled into a capillary rheometer equipped with a die having an inner diameter of 1 mm and a length of 10 mm, and 9.8 MPa (100 kgf / The sample was extruded while melting at a temperature rising rate of 4 ° C./min under a load of cm ² ), and a temperature at which the melt viscosity was 4800 Pa · s (48000 poise) was measured.

[Evaluation of water vapor barrier properties]
In accordance with JIS K7126 (A method: differential pressure method), a gas permeability / moisture permeability measuring device (“GTR-10X” from GTR Tech Co., Ltd.) under conditions of a temperature of 40 ° C. and a relative humidity of 90% The transmittance was measured.

[Evaluation of weather resistance]
Using an accelerated light resistance tester (“Strong Energy Xenon Weather Meter SC700-WN” from Suga Test Instruments Co., Ltd.), the backsheet was irradiated with xenon under the following conditions, and the appearance of the backsheet was visually observed.
Wavelength: Continuous light of 275nm or more (short wavelength side is cut by a filter)
Intensity: 160 W / m ² (Lamp output)
Temperature: 65 ° C (measured with a flat panel thermometer at the same position as the irradiated surface)
Time: 60 hours

Production Example 1
In a reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 103.499 g (5.5 mol) of 6-hydroxy-2-naphthoic acid and 2,378-naphthalenedicarboxylic acid 378 were added. 0.33 g (1.75 mol), 83.07 g (0.5 mol) of terephthalic acid, 272.52 g of hydroquinone (2.475 mol: 0.225 based on the total amount of 2,6-naphthalenedicarboxylic acid and terephthalic acid) Molar excess), 1226.87 g (12 mol) of acetic anhydride, and 0.17 g of 1-methylimidazole as a catalyst, and after replacing the gas in the reactor with nitrogen gas, stirring at room temperature under a nitrogen gas stream To 145 ° C. over 15 minutes and refluxed at 145 ° C. for 1 hour. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 145 ° C. to 310 ° C. over 3 hours and 30 minutes, held at 310 ° C. for 3 hours, then the contents were taken out and cooled to room temperature did. The obtained solid was pulverized to a particle size of about 0.1 to 1 mm with a pulverizer, then heated from room temperature to 250 ° C. over 1 hour in a nitrogen atmosphere, and increased from 250 ° C. to 310 ° C. over 10 hours. Solid state polymerization was performed by warming and holding at 310 ° C. for 5 hours. After solid state polymerization, the mixture was cooled to obtain a powdery liquid crystal polyester. In this liquid crystalline polyester, 55 mol% of the repeating unit (1) in which Ar ¹ is a 2,6-naphthylene group and Ar ² is a 2,6-naphthylene group in terms of the total amount of all repeating units ( 2) 17.5 mol%, Ar ² is a repeating unit (2) having a 1,4-phenylene group, 5 mol%, and Ar ³ is a repeating unit (3) having a 1,4-phenylene group, 22. 5%, and the flow start temperature was 333 ° C.

Production Example 2
In the same reactor as in Production Example 1, 911 g (6.6 mol) of p-hydroxybenzoic acid, 91 g (0.55 mol) of isophthalic acid, 274 g (1.65 mol) of terephthalic acid, 4,4′-dihydroxybiphenyl 409 g (2.2 mol), 1235 g of acetic anhydride (12.1 mol), and 0.17 g of 1-methylimidazole as a catalyst were added, and the gas in the reactor was replaced with nitrogen gas, followed by stirring under a nitrogen gas stream While raising the temperature from room temperature to 150 ° C. over 15 minutes, the mixture was refluxed at 150 ° C. for 1 hour. Then, after adding 1.7 g of 1-methylimidazole, the temperature was raised from 150 ° C. to 320 ° C. over 2 hours and 50 minutes while distilling off by-product acetic acid and unreacted acetic anhydride, and an increase in torque was observed. At that time, the contents were removed and cooled to room temperature. The obtained solid was pulverized to a particle size of about 0.1 to 1 mm with a pulverizer, then heated from room temperature to 250 ° C. over 1 hour in a nitrogen atmosphere, and increased from 250 ° C. to 285 ° C. over 5 hours. Solid state polymerization was performed by warming and holding at 285 ° C. for 3 hours. After solid state polymerization, the mixture was cooled to obtain a powdery liquid crystal polyester. The liquid crystal polyester had a flow initiation temperature of 327 ° C.

Example 1
The liquid crystalline polyester obtained in Production Example 1 was granulated with a twin screw extruder ("PCM-30" by Ikegai Co., Ltd.), pelletized, and then supplied to a single screw extruder (screw diameter 50 mm). It was melted, extruded from a T die (lip length: 300 mm, lip clearance: 1 mm, die temperature: 350 ° C.) and cooled to obtain a liquid crystal polyester film having a thickness of 25 μm. The water vapor permeability of this liquid crystal polyester film was 0.011 g / m ² · 24 h.

  A urethane adhesive (Mitsui Takeda Chemical Co., Ltd .: main agent “Takelac A511” / curing agent “A50”) on one side of a 250 μm thick white PET film (Tolu Co., Ltd. “Lumirror E20”: containing titanium oxide) = 10/1 (mass ratio)) was applied, and the previously obtained liquid crystal polyester film was bonded to obtain a laminated film. Next, a urethane adhesive (same as above) is applied to the liquid crystal polyester film surface of the laminated film, and a laminated film of a 50 μm thick LLDPE film and a 50 μm thick EVA film is bonded on the LLDPE surface side, and a back sheet Got. As a result of evaluating the weather resistance of the obtained back sheet by irradiating xenon from the white PET film side, no shape change such as warping or tearing was observed.

Example 2
A liquid crystal polyester film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the liquid crystal polyester obtained in Production Example 2 was used in place of the liquid crystal polyester obtained in Production Example 1. The water vapor permeability of this liquid crystal polyester film was 0.343 g / m ² · 24 h.

  Using the obtained liquid crystal polyester film, the same operation as in Example 1 was performed to obtain a back sheet. As a result of evaluating the weather resistance of the obtained back sheet by irradiating xenon from the white PET film side, no shape change such as warping or tearing was observed.

Comparative Example 1
A back sheet was obtained in the same manner as in Example 1 except that the white PET film was not used. As a result of evaluating the weather resistance of the obtained backsheet by irradiating xenon from the liquid crystal polyester film side, no tear was observed, but a large warp was observed.

Comparative Example 2
A back sheet was obtained in the same manner as in Example 2 except that the white PET film was not used. As a result of evaluating the weather resistance of the obtained back sheet by irradiating xenon from the liquid crystal polyester film side, a large warp was observed and tearing was also observed.

1 ... Surface protection sheet,
2 ... sealing layer,
3 ... solar cell element,
4 ... sealing layer,
5 ... Backsheet,
6 ... Frame,
51 ... polyolefin layer,
52 ... adhesive layer,
53 ... Liquid crystal polyester layer,
54 ... water vapor barrier layer,
55 ... adhesive layer,
56: White pigment-containing layer.

Claims (9)

  A solar cell backsheet disposed on the back side of a solar cell element, wherein a white pigment-containing layer is provided on the back side of a liquid crystal polyester layer. The liquid crystal polyester layer has a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2), and a repeating unit represented by the following formula (3), The back sheet for a solar cell according to claim 1, wherein the content of the repeating unit containing a 6-naphthylene group is a layer composed of a liquid crystal polyester of 40 mol% or more based on the total amount of all repeating units.
—O—Ar ¹ —CO— (1)
—CO—Ar ² —CO— (2)
—O—Ar ³ —O— (3)
(Ar ¹ represents a 2,6-naphthylene group, a 1,4-phenylene group or a 4,4′-biphenylylene group. Ar ² and Ar ³ are each independently a 2,6-naphthylene group, 1,4 Represents a -phenylene group, a 1,3-phenylene group or a 4,4'-biphenylylene group, wherein the hydrogen atoms in the group represented by Ar ¹ , Ar ² or Ar ³ are each independently a halogen atom or an alkyl group; Alternatively, it may be substituted with an aryl group.) The back sheet for a solar cell according to claim 1 or 2, wherein the liquid crystal polyester layer has a water vapor permeability of 0.1 g / m ² · 24h or less measured at a temperature of 40 ° C and a relative humidity of 90%.   The white pigment-containing layer includes at least one white pigment selected from the group consisting of basic lead carbonate, basic lead sulfate, basic lead silicate, zinc white, zinc sulfide, lithopone, antimony trioxide, and titanium oxide. It is a layer to contain, The solar cell backsheet in any one of Claims 1-3.   The solar cell backsheet according to any one of claims 1 to 4, wherein the white pigment-containing layer is a layer containing polyester.   The solar cell backsheet according to any one of claims 1 to 5, wherein a water vapor barrier layer is provided on at least one surface of the liquid crystal polyester layer.   The water vapor barrier layer is composed of at least one element selected from the group consisting of aluminum, silicon, titanium, chromium, iron, cobalt, nickel, copper, zinc, silver and gold, an oxide of the element, The solar cell backsheet according to claim 6, which is a layer composed of at least one substance selected from the group consisting of a nitride and an oxynitride of the element.   The solar cell backsheet according to any one of claims 1 to 7, wherein a polyolefin layer is provided on the front side of the liquid crystal polyester layer.   The solar cell module by which a surface protection sheet is arrange | positioned at the front side of a solar cell element, and the solar cell backsheet in any one of Claims 1-8 is arrange | positioned at the back side of the said solar cell element.

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