WO2015182282A1 - Polyester film for solar cell back sheets - Google Patents

Polyester film for solar cell back sheets Download PDF

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Publication number
WO2015182282A1
WO2015182282A1 PCT/JP2015/061851 JP2015061851W WO2015182282A1 WO 2015182282 A1 WO2015182282 A1 WO 2015182282A1 JP 2015061851 W JP2015061851 W JP 2015061851W WO 2015182282 A1 WO2015182282 A1 WO 2015182282A1
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WIPO (PCT)
Prior art keywords
polyester film
layer
stretching
film
polyester
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PCT/JP2015/061851
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French (fr)
Japanese (ja)
Inventor
仲辻健太郎
長谷川正大
Original Assignee
東レ株式会社
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Publication date
Application filed by 東レ株式会社 filed Critical 東レ株式会社
Priority to KR1020167030816A priority Critical patent/KR20170012216A/en
Priority to CN201580026449.8A priority patent/CN106463558B/en
Priority to JP2015521176A priority patent/JPWO2015182282A1/en
Publication of WO2015182282A1 publication Critical patent/WO2015182282A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
    • C08G63/16—Dicarboxylic acids and dihydroxy compounds
    • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
    • C08G63/199—Acids or hydroxy compounds containing cycloaliphatic rings
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/048—Encapsulation of modules
    • H01L31/0481—Encapsulation of modules characterised by the composition of the encapsulation material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/048—Encapsulation of modules
    • H01L31/049—Protective back sheets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention relates to a polyester film for a solar battery back sheet, which has little reduction in film thickness even when used outdoors for a long period of time, and has little reduction in wet heat resistance, weather resistance, and electrical insulation.
  • Polyester films are used for magnetic recording media, for electrical insulation, for solar cells, for capacitors, for packaging, and for various industries by utilizing excellent mechanical properties, thermal properties, electrical properties, surface properties, and heat resistance. It is used for various applications such as materials for use.
  • a power generation element is sealed with a transparent sealing material such as ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVA), a transparent substrate such as glass, and a solar cell back sheet.
  • EVA ethylene-vinyl acetate copolymer
  • a resin sheet is bonded together.
  • Sunlight is introduced into the solar cell through the transparent substrate.
  • Sunlight introduced into the solar cell is absorbed by the power generation element, and the absorbed light energy is converted into electrical energy.
  • the converted electric energy is taken out by a lead wire connected to the power generation element and used for various electric devices.
  • the solar cell backsheet is used for the purpose of protecting the power generation element of the solar cell from external influences such as rain.
  • the polyester film is used as a solar battery back sheet or as one member constituting the back sheet because of its excellent characteristics.
  • the polyester film for solar cell backsheets Since solar cells are placed outdoors for a long period of time, the polyester film for solar cell backsheets is required to have little deterioration in mechanical properties (moisture and heat resistance) when placed in a high temperature and high humidity for a long period of time. Further, the solar cell is installed under direct sunlight. Therefore, the polyester film for a solar battery back sheet is required to have little deterioration in mechanical properties (weather resistance) when placed for a long time under ultraviolet irradiation. Moreover, the characteristic (electrical insulation) which electrically insulates a power generation element and external air is also calculated
  • Patent Documents 1 to 4 Various studies have been made so far to solve the above problems.
  • polyester films obtained by the methods of Patent Documents 1 to 4 are excellent in moisture and heat resistance, weather resistance, and electrical insulation, but when used outdoors for a long period of time, film loss occurs, moisture and heat resistance, weather resistance, There was a problem that the electrical insulation was greatly reduced.
  • the problem of the present invention is that even when used outdoors for a long period of time, there is little decrease in the thickness of the film (hereinafter, this characteristic may be referred to as film resistance), and it is used outdoors for a long period of time.
  • Another object of the present invention is to provide a polyester film in which there is little decrease in wet heat resistance, weather resistance, and electrical insulation (hereinafter, this characteristic may be referred to as durability).
  • P1 layer A solar cell having a polyester layer satisfying the following (1) to (3) (referred to as P1 layer) on at least one surface layer and having an elongation retention of 40% or more after a durability test Polyester film for back sheet.
  • the thickness of the P1 layer is 30 ⁇ m or more and 250 ⁇ m or less.
  • the surface roughness (Ra) of the P1 layer is greater than 0.10 ⁇ m and 0.50 ⁇ m or less.
  • the amount of decrease in the thickness of the P1 layer after the durability test is 15 ⁇ m or less.
  • the polyester resin composition constituting the P1 layer contains rutile type titanium oxide, and the content of the rutile type titanium oxide is 14 to 20% by weight based on the whole polyester resin composition constituting the P1 layer.
  • the polyester resin composition constituting the P1 layer contains a polyester resin composition mainly composed of 1,4-cyclohexylenedimethylene terephthalate unit (hereinafter referred to as CHT unit), and the CHT unit.
  • the solar cell bag according to any one of (a) to (d), wherein the content of the polyester resin composition containing as a main component is 14 to 20% by weight based on the entire polyester resin composition constituting the P1 layer Polyester film for sheet.
  • the polyester resin constituting the polyester film has an intrinsic viscosity of 0.6 to 1.0 dl / g and a terminal carboxyl group content of 5 to 20 equivalents / t.
  • the polyester film for solar cell backsheet of description The polyester film for solar cell backsheet of description.
  • (G) The method for producing a polyester film for solar cell backsheet according to any one of (a) to (f), which satisfies the following (4) to (6).
  • the temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
  • the time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
  • the stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 ⁇ m, and the stretching roll;
  • the nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  • (G) The method for producing a polyester film for a solar cell backsheet according to any one of (a) to (f), which satisfies the following (4) to (10): (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film. (5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer. (6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds. (7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C.
  • the uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film.
  • the step of obtaining. (9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
  • the stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 ⁇ m, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  • Ko A solar battery back sheet using the polyester film for a solar battery back sheet according to any one of (a) to (f).
  • Sa A solar battery using the solar battery back sheet described in (ko).
  • the present invention it is possible to provide a polyester film for a solar battery back sheet that is excellent in film resistance and durability. Since the polyester film for solar cell backsheet of the present invention is excellent in film resistance and durability, the solar cell comprising the solar cell backsheet comprising the polyester film for solar cell backsheet of the present invention has long-term performance. Can be maintained, and the service life can be extended.
  • the polyester film of the present invention has a P1 layer on at least one surface layer. Having a P1 layer on at least one surface layer may be a single-layer polyester film composed of only the P1 layer, and may be a P1 layer / P2 layer, a P1 layer / P2 layer / P1 layer, a P1 layer / P2 layer / P3 layer.
  • a laminated polyester film such as
  • the P1 layer of the present invention needs to have a thickness of 30 ⁇ m or more and 250 ⁇ m or less.
  • the thickness of the P1 layer is less than 30 ⁇ m, even the P1 layer of the present invention, which has excellent film resistance, is used under conditions where it is exposed to wind, rain, dust, sand dust, dead leaves, etc. for a long time under ultraviolet irradiation. As a result, sufficient mechanical properties cannot be maintained.
  • the thickness of the P1 layer is less than 30 ⁇ m, the electric insulation is insufficient, and dielectric breakdown may occur when used under a high voltage, which is not preferable as a polyester film for a solar battery backsheet.
  • the thickness of the P1 layer is greater than 250 ⁇ m, the processability is poor, and it becomes difficult to make the surface of the P1 layer have a surface shape excellent in film resistance and durability.
  • the polyester film of the present invention is used as a polyester film for a solar battery back sheet, the overall thickness of the solar battery cell may become too thick, which may not be preferable.
  • the P1 layer of the present invention needs to have a surface roughness (Ra) of more than 0.10 ⁇ m and 0.50 ⁇ m or less.
  • Ra surface roughness
  • the surface roughness (Ra) of the P1 layer When the surface roughness (Ra) of the P1 layer is in the above range, the water repellent property when the film surface gets wet is improved. Therefore, even after the polyester film is exposed to rain and wind, the time during which water is present on the film surface can be shortened, and degradation due to hydrolysis on the film surface can be suppressed. Moreover, it becomes possible to reflect an ultraviolet-ray on the film surface by making the surface roughness (Ra) of P1 layer into said range. As a result, it is considered that the ultraviolet rays entering the film can be reduced, and the deterioration of the resin constituting the film can be suppressed.
  • the film resistance of the film can be divided into two stages: film resistance at the initial stage and film resistance at the medium to long term. By setting the surface roughness of the P1 layer in the above range, it is possible to significantly improve the initial stage film resistance.
  • the surface roughness (Ra) of the P1 layer is 0.10 ⁇ m or less, since the deterioration of the resin constituting the film due to the reflection of ultraviolet rays cannot be suppressed, the film reduction rate of the film due to wind and rain and dust increases. Moreover, when the surface roughness (Ra) of the P1 layer is larger than 0.50 ⁇ m, the film surface is poorly repelled when wet, so that deterioration on the film surface cannot be suppressed, resulting in film loss. Increases speed.
  • the surface roughness (Ra) of the P1 layer is more preferably 0.20 ⁇ m or more and 0.40 ⁇ m or less.
  • the polyester film having the surface roughness (Ra) of the P1 layer in the above range can be obtained by the production method described later, the type of resin, and the amount added.
  • the film thickness is reduced little by little. Since film reduction proceeds from the surface of the film, the surface roughness of the film changes with time. Therefore, even if the surface roughness (Ra) of the P1 layer is a film in the above range, the surface roughness changes when used outdoors in the middle and long term, so that high film resistance is maintained. It is not possible.
  • the film resistance at the medium to long-term stage can be improved by adding a resin and additives described later to the polyester resin composition constituting the film.
  • the P1 layer of the present invention is required to have a thickness reduction amount of 15 ⁇ m or less after the durability test described below.
  • ⁇ Durability test> (I) Using a xenon lamp (manufactured by Suga Test Instruments, SC750) under the conditions of a temperature of 65 ° C. and a relative humidity of 50% RH, the surface on the P1 layer side of the polyester film is 102 at an irradiance of 180 W / m 2 . Irradiate for (t-1) minutes. (Ii) After (i), while continuing irradiation with a xenon lamp, a water shower at 16 ° C. ⁇ 5 ° C.
  • Durability test is an accelerated test that assumes the usage of solar cells that are used outdoors for a long period of time under conditions of exposure to wind and rain, dust, sand dust, dead leaves, and the like.
  • the polyester film is deteriorated by being irradiated with ultraviolet rays by a xenon lamp or being subjected to high temperature and high humidity conditions. And since the deteriorated polyester film flows out by a water shower, a reduction in film thickness (film reduction) occurs. Even if it is a polyester film excellent in wet heat resistance, weather resistance, and electrical insulation, if this film reduction is large, its performance will deteriorate during long-term use outdoors.
  • the amount of decrease in the thickness of the P1 layer is more preferably 12 ⁇ m or less. Although it is preferable that the amount of decrease in the film thickness is small, it is difficult to make the thickness less than 0.1 ⁇ m, and it is particularly preferable that the thickness is 0.1 ⁇ m or more and 10 ⁇ m or less.
  • the polyester film of the present invention needs to have an elongation retention after the durability test of 40% or more. If the elongation retention after the durability test is less than 40%, it indicates that the film surface is cracked, and hydrolysis is promoted by accumulation of water in the crack generated on the film surface. It has a fatal effect on the subsequent film properties.
  • the elongation retention after the durability test is more preferably 60% or more.
  • the polyester film of the present invention preferably has a partial discharge voltage maintenance ratio of 90% or more after the durability test.
  • a partial discharge voltage maintenance ratio of 90% or more is preferable as an insulating material used in an environment that is exposed to the outdoors for a long period of time because it can maintain a state of high electrical insulation even outdoors for a long period of time. More preferably, it is 95% or more.
  • the partial discharge voltage (namely, partial discharge voltage before a weather resistance test) of the polyester film of this invention is 1000V or more.
  • the P1 layer of the present invention is mainly composed of a polyester resin.
  • the main constituent component of the polyester resin means that the polyester resin is contained in an amount exceeding 50% by mass with respect to the resin constituting the P1 layer.
  • Specific examples of the polyester resin constituting the P1 layer include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polylactic acid.
  • the polyester resin used in the present invention includes 1) polycondensation of dicarboxylic acid or an ester-forming derivative thereof (hereinafter collectively referred to as “dicarboxylic acid component”) and a diol component, and 2) carboxylic acid or carboxylic acid in one molecule. It can be obtained by a polycondensation of an acid derivative and a compound having a hydroxyl group, and 1) 2).
  • the polymerization of the polyester resin can be performed by a conventional method.
  • dicarboxylic acid component malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid
  • Aliphatic dicarboxylic acids such as ethylmalonic acid
  • alicyclic dicarboxylic acids such as adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4
  • dicarboxyl obtained by condensing oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids, at least one carboxy terminus of the dicarboxylic acid component described above.
  • oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids, at least one carboxy terminus of the dicarboxylic acid component described above.
  • oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids, at least one carboxy terminus of the dicarboxylic acid component described above.
  • Compounds can also be used.
  • the diol component includes aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. , Cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) fluorene, etc. Aromatic diols are typical examples. Moreover, these may be used independently or may be used in multiple types as needed. In addition, a dihydroxy compound formed by condensing a diol with at least one hydroxy terminal of the diol component described above can also be used.
  • aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-but
  • examples of the compound having a carboxylic acid or a carboxylic acid derivative and a hydroxyl group in one molecule include oxyacids such as l-lactide, d-lactide and hydroxybenzoic acid, and derivatives thereof, oligomers of oxyacids, dicarboxylic acids Examples thereof include those obtained by condensing an oxyacid with one carboxyl group of the acid.
  • the dicarboxylic acid component and the diol component constituting the polyester resin may be copolymerized by selecting one from the above, or may be copolymerized by selecting a plurality of each.
  • the polyester resin constituting the P1 layer may be a single type or a blend of two or more types of polyester resins. From the viewpoint of mechanical strength and processability, it is preferable to use polyethylene terephthalate (PET) as the main constituent.
  • PET polyethylene terephthalate
  • the resin constituting the P1 layer of the present invention has a polyester resin as the main constituent as described above, but has an intrinsic viscosity of 0.60 dl / g or more and 1.00 dl / g or less, and a terminal carboxyl group amount of 20 equivalents / It is preferable that the heat resistance is not more than tons because heat resistance, moldability, and durability are good. Intrinsic viscosity is preferably 0.65 dl / g or more and 0.80 dl / g or less because moisture and heat resistance, film moldability, and durability are further improved.
  • the resin that constitutes the P1 layer is a solar cell bag that is extremely excellent in durability, moist heat resistance, and moldability by having PET as the main constituent and the intrinsic viscosity and the amount of terminal carboxyl groups satisfy the above ranges. It can be set as the polyester film for sheets.
  • the number average molecular weight of the polyester resin constituting the P1 layer is preferably 8000 to 40000, more preferably 9000 to 30000, and still more preferably 10,000 to 20000.
  • the number average molecular weight of the polyester resin constituting the P1 layer is a gel permeation chromatography method by separating the P1 layer from the polyester film for solar battery backsheet of the present invention and dissolving it in hexafluoroisopronol (HEIP).
  • HEIP hexafluoroisopronol
  • PET-5R polyethylene terephthalate
  • dimethyl terephthalate having a known molecular weight as standard samples from values measured by (GPC method) and detected by a differential refractometer.
  • GPC method polyethylene terephthalate
  • the number average molecular weight of the polyester resin constituting the P1 layer is less than 8000, it is not preferable because the long-term durability of the sheet such as moisture and heat resistance may be deteriorated.
  • it exceeds 40,000 even if the polymerization is difficult or the polymerization can be performed, it may be difficult to extrude the resin with an extruder and film formation may be difficult.
  • the P1 layer is preferably uniaxially or biaxially oriented.
  • characteristics such as moist heat resistance and heat resistance can be improved by orientation crystallization.
  • the polyester resin composition constituting the P1 layer of the present invention contains titanium oxide particles, and the content thereof is 14% by mass or more and 20% by mass or less with respect to the entire polyester resin composition constituting the P1 layer. Preferably there is. This makes it possible to obtain the effect of reducing deterioration due to ultraviolet irradiation over a long period of time by utilizing the ultraviolet absorption ability and light reflectivity of the titanium oxide particles. Can be improved.
  • the effect of improving the film resistance at the initial stage is particularly large when the surface roughness of the P1 layer is 0.20 ⁇ m to 0.40 ⁇ m.
  • a method of melt-kneading the polyester resin and the particles using a vent type twin-screw kneading extruder or a tandem type extruder is preferably used.
  • a high-concentration master pellet having a particle content larger than the amount of particles contained in the polyester resin constituting the P1 layer is prepared, mixed with the polyester resin and diluted to obtain a desired particle content P1 layer. It is preferable to produce it from the viewpoint of heat and humidity resistance.
  • the P1 layer of the present invention may include a heat-resistant stabilizer, an oxidation-resistant stabilizer, an ultraviolet absorber, and an ultraviolet-ray stabilizer as long as the effects of the present invention are not impaired.
  • Agents, organic / inorganic lubricants, organic / inorganic fine particles, fillers, nucleating agents, dyes, dispersants, coupling agents, and the like, and bubbles may be blended.
  • an ultraviolet absorber is selected as the additive, the ultraviolet resistance of the film of the present invention can be further improved.
  • anti-static agents are added to improve electrical insulation, or organic or inorganic fine particles or bubbles are included to express light reflectivity, or a color material to be colored is added to create a design. Can also be given.
  • the polyester resin composition constituting the P1 layer of the present invention contains a polyester resin mainly composed of 1,4-cyclohexylenedimethylene terephthalate unit (hereinafter also referred to as CHT unit), and the content thereof is It is preferable that it is 14 mass% or more and 20 mass% or less with respect to the whole polyester resin composition which comprises P1 layer.
  • CHT unit 1,4-cyclohexylenedimethylene terephthalate unit
  • the effect of improving the film resistance at the initial stage is particularly large when the surface roughness of the P1 layer is 0.20 ⁇ m to 0.40 ⁇ m.
  • the polyester that has deteriorated by ultraviolet rays is contained in the resin constituting the polyester film by containing a resin having a CHT unit, which has a large viscosity characteristic, as a constituent component. It is estimated that the speed of flowing out is reduced.
  • the content of the CHT unit is less than 14% by mass, the above effect may not be sufficiently obtained.
  • it is more than 20% by mass the film forming property may be deteriorated.
  • content of the polyester resin which makes the main component the CHT unit with respect to the whole polyester resin composition which comprises a polyester film shall be the addition amount with respect to the whole polyester resin composition which comprises a polyester film.
  • the polyester film of the present invention is preferably a laminated polyester film composed of at least two layers having a base material layer (P2 layer) in addition to the P1 layer.
  • P2 layer a base material layer
  • P1 layer may be distribute
  • the P2 layer and the P1 layer it is desirable to co-press the P2 layer and the P1 layer to obtain a polyester film for a solar battery backsheet.
  • curling may occur at the time of bonding, or deterioration may proceed from the adhesive used for bonding.
  • the P2 layer is mainly composed of a polyester resin composition as in the P1 layer. If the composition is the same as that of the P1 layer, the film can be formed (coextruded) at the same time as the P1 layer, and the adhesion to the P1 layer can be improved.
  • the polyester resin constituting the P2 layer of the present invention has an intrinsic viscosity of 0.50 dl / g or more and 0.80 dl / g or less, and a terminal carboxyl group amount of 5 eq / ton or more and 40 eq / ton or less, It is preferable because the film forming property and workability can be improved. It is preferable that the intrinsic viscosity is 0.55 dl / g or more and 0.75 dl / g or less and the terminal carboxyl group amount is 10 equivalents / ton or more and 35 equivalents / ton or less because the heat and humidity resistance becomes better.
  • the polyester resin composition constituting the P2 layer has good film forming properties and workability when the content of titanium oxide particles is 14% by mass or less with respect to the entire polyester resin composition constituting the P2 layer. This is preferable. More preferably, it is 1 mass% or more and 14 mass% or less.
  • the polyester resin composition constituting the P2 layer contains 1% by mass or more and 20% by weight or less of a polyester resin having a CHT unit as a main constituent component. It is preferable to use the above-described resin as the polyester resin composition that constitutes the P2 layer, because the adhesion with the P1 layer can be improved during film formation.
  • the thickness of the P2 layer is 30 ⁇ m or more and 250 ⁇ m or less because the film forming property and workability are improved.
  • the polyester film of the present invention preferably has a total film thickness of 50 ⁇ m or more and 1000 ⁇ m or less.
  • the total thickness of the film is 250 ⁇ m or more, the partial discharge voltage becomes high (electrical insulation becomes good), which is preferable. More preferably, it is 300 micrometers or more, More preferably, it is 350 micrometers or more. On the other hand, if it exceeds 500 ⁇ m, the film forming property and workability may be inferior.
  • the polyester film for solar battery backsheet of the present invention is excellent in durability and film resistance. Therefore, the solar cell on which the polyester film for solar cell backsheet of the present invention is mounted can be a solar cell whose output does not decrease even when placed outdoors for a long period of time.
  • the polyester film for solar battery backsheet of the present invention can be obtained by, for example, the production methods described in (i), (b) and (b) below.
  • (Ii) A method for producing a polyester film for a solar battery back sheet that satisfies the following (4) to (6).
  • (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
  • the temperature of the cooling drum is from Tg-70 ° C. to Tg-30 ° C. of the polyester resin constituting the P1 layer.
  • the time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
  • (B) A method for producing a polyester film for a solar battery back sheet that satisfies the following (4), (7) to (10).
  • (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
  • (7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film.
  • Including. The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C.
  • the stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 ⁇ m, and the stretching roll;
  • the nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  • (Ha) A method for producing a polyester film for a solar battery backsheet that satisfies the following (4) to (10).
  • (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
  • the temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
  • the time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
  • the uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film.
  • the step of obtaining. (9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
  • the stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 ⁇ m, and the stretching roll;
  • the nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  • the polyester film of the present invention preferably includes a step of obtaining a non-oriented polyester film by melt-kneading the polyester resin composition constituting the P1 layer with an extruder and then extruding and cooling and solidifying on a cooling drum.
  • the polyester film of the present invention is a laminated polyester film containing a P2 layer in addition to the P1 layer, the raw materials of the P1 layer and the P2 layer are heated and melted in two extruders, merged, and cooled from the die. It is preferable to include a process (melt casting method, co-pressing method) of extruding onto a cast drum to obtain an unoriented laminated polyester film.
  • the temperature of the cooling drum is preferably a glass transition temperature (hereinafter referred to as Tg) of the polyester resin constituting the P1 layer of ⁇ 70 ° C. or higher and Tg ⁇ 30 ° C. or lower.
  • Tg glass transition temperature
  • the surface roughness can be easily increased from 0.1 ⁇ m to 0.5 ⁇ m.
  • the temperature of the cooling drum is preferably Tg ⁇ 60 ° C. or higher and Tg ⁇ 35 ° C. or lower, particularly preferably Tg ⁇ 55 ° C. or higher and Tg ⁇ 40 ° C. or lower, of the polyester resin constituting the P1 layer.
  • the time of contact with the cooling drum is preferably 20 seconds or more and 120 seconds or less.
  • the time of contact with the cooling drum is preferably 20 seconds or longer and 60 seconds or shorter, and particularly preferably 25 seconds or longer and 45 seconds or shorter.
  • the polymer When the time is shorter than 20 seconds, the polymer is rapidly cooled, so that thermal crystallization is greatly generated, and variation in thermal crystallization is increased, so that the surface roughness of the film is in the range of 0.1 to 0.5 ⁇ m. It may be difficult to do, or the film may be broken after stretching in the longitudinal direction.
  • the polyester film of the present invention can be obtained by subjecting the unstretched polyester film to a conventionally known stretching and heat treatment.
  • the polyester film of the present invention was prepared by melt-kneading the polyester resin composition constituting the P1 layer with an extruder, and then extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
  • To (10) are obtained by a production method including a stretching step and a heat treatment step.
  • the uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C.
  • the stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 ⁇ m, and the stretching roll;
  • the nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  • the stretching in the longitudinal direction is performed using a stretching roll and a stretching nip roll, and the heating in the stretching process is preferably performed by a heated stretching roll.
  • the surface roughness Ra of the drawing roll is 0.5 to 1.5 ⁇ m and the nip pressure between the drawing roll and the drawing nip roll is 0.4 to 1.0 MPa, film breakage or the like may occur.
  • the surface roughness of the P1 layer can be easily made larger than 0.10 ⁇ m and 0.50 ⁇ m or less with good suppression and high productivity.
  • productivity is maintained well. As it is, it is preferable because the durability and film resistance of the resulting polyester film can be improved.
  • the film obtained in the step (7) is guided to a tenter while holding both ends of the film with clips, and is perpendicular to the longitudinal direction in an atmosphere heated to a temperature of 70 to 150 ° C.
  • the film is preferably stretched 3 to 4 times in the direction (width direction).
  • the area ratio obtained by multiplying the draw ratios in the longitudinal direction and the width direction is 9 to 15 times, the durability and film resistance of the resulting polyester film can be improved while maintaining good productivity.
  • step (8) When the biaxially oriented polyester film obtained in step (8) is heat treated at 205-240 ° C. and includes a step of relaxing 0-10% in the width direction, the surface shape formed in the P1 layer is maintained as it is. Easy to do.
  • the polyester film of the present invention is excellent in film resistance and durability, it can be preferably used for solar battery backsheets.
  • the polyester film of this invention is a laminated polyester film which consists of P1 layer and P2 layer, it is preferable to use P1 layer in the aspect used as the outermost layer (code
  • the solar cell including the solar cell back sheet using the polyester film of the present invention can maintain its performance over a long period of time and can prolong its useful life.
  • Terminal carboxyl group amount was measured by the following method according to the method of Malice. (Document M. J. Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)). 2 g of a measurement sample (polyester resin (raw material) or polyester film) was dissolved in 50 mL of o-cresol / chloroform (weight ratio 7/3) at a temperature of 80 ° C., and titrated with a 0.05 N KOH / methanol solution to obtain a terminal carboxyl. The base concentration was measured and indicated as equivalent / polyester 1t.
  • the indicator at the time of titration used phenol red, and the place where it changed from yellowish green to light red was set as the end point of titration. If there is insoluble matter such as inorganic particles in the solution in which the measurement sample is dissolved, the solution is filtered to measure the weight of the insoluble matter, and the value obtained by subtracting the weight of the insoluble matter from the measurement sample weight The following correction was made.
  • the surface roughness (Ra) of the polyester film was measured under the following conditions according to JIS-B0601 (1994) using a high-definition fine shape measuring instrument of the stylus method.
  • Measuring device 3D fine shape measuring instrument (model ET-4000A manufactured by Kosaka Laboratory)
  • Analysis equipment 3D surface roughness analysis system (Model TDA-31, manufactured by Kosaka Laboratory)
  • Stylus Tip radius 0.5 ⁇ m R, Diameter 2 ⁇ m, Diamond needle pressure: 100 ⁇ N
  • Measurement direction / calculation method The film longitudinal direction and the film width direction are each measured 10 times. The average value of the 20 measurements is defined as the surface roughness.
  • Titanium oxide content Using an ICP emission analyzer (manufactured by Perkin Elmer: OPTIMA 4300 DV), the amount of titanium element contained in the film is determined by the following method, and the titanium oxide content is obtained from the obtained titanium element amount. The amount was converted.
  • the polyester film is a laminated polyester film
  • the surface of the laminated polyester film is shaved, a measurement sample is taken from each layer, and the titanium oxide contained in each layer The amount was determined.
  • the collected sample is weighed in a platinum crucible, sulfuric acid is added, and carbonization is performed using a hot plate and a burner.
  • ashing is performed by heating at 550 ° C. for 2 hours in an electric furnace.
  • a mixed flux of sodium carbonate and boric acid is added to the resulting incinerated product, and the mixture is heated with a burner for melting treatment. After standing to cool, diluted nitric acid and hydrogen peroxide solution are added and dissolved. The sample solution is introduced into an ICP emission analyzer, and the titanium element is quantified.
  • the wet heat resistance was determined as follows.
  • A When the breaking elongation after the wet heat test is 20% or more and less than 40% of the breaking elongation before the wet heat test: B
  • C When the breaking elongation after the wet heat test is 10% or more and less than 20% of the breaking elongation before the wet heat test: C
  • D The wet heat resistance is good in A to C, and A is the best among them.
  • Partial Discharge Voltage Based on the following measurement method, partial discharge was measured with the P1 layer facing up to evaluate electrical insulation. Conformity standard: IEC60664 / A2: 2002 4.1.2.4 Partial discharge tester: KPD2050, manufactured by Kikusui Electronics Corporation Maximum applied voltage: 1.6 kV Maximum applied voltage time: 5 seconds Start voltage Charge threshold: 1.0 pC Vanishing voltage charge threshold: 1.0 pC Test time: 22.0 sec Measurement pattern: trapezoid (8) Characteristics after durability test Durability test is performed under the following conditions in accordance with JISK 7350-2 (2008). Thereafter, each characteristic was measured.
  • the thickness ( ⁇ m) of the P1 layer after the durability test was determined as the amount of decrease in the thickness ( ⁇ m) of the P1 layer after the durability test.
  • Glass transition temperature (Tg) of the polyester resin constituting the P1 layer In accordance with JIS K7121 (1999), the differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. and the disk session “SSC / 5200” for data analysis were used as follows. Perform the measurement.
  • the resin constituting the P1 layer is shaved from the polyester film using a microtome and used as a measurement sample.
  • 5 mg of the obtained measurement sample was weighed in a sample pan, heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. To do.
  • the temperature was increased again from 25 ° C. to 300 ° C. at a rate of temperature increase of 20 ° C./minute, and a 2ndRUN differential scanning calorimetry chart (the vertical axis represents thermal energy and the horizontal axis represents temperature) Get.
  • a straight line that is equidistant from the extended straight line of each base line in the vertical axis direction and a curve of the step change portion of the glass transition are The glass transition temperature (Tg) (° C.) is determined from the intersecting point. When two or more stepwise changes in glass transition are observed, the glass transition temperature is obtained for each, and the average of these temperatures is taken as the glass transition temperature (Tg) (° C.) of the sample.
  • (10) Film-forming property The film-forming property was determined as follows according to the frequency of film breakage during film formation. Film breaks once / day or more: A Film breaks once / 12 hours or more and less than 1 day: B Film breaks once / 5 hours or more and less than 12 hours: C Film tear once less than 5 hours: D As for the film forming property, A is good and becomes worse in the order of BCD.
  • An ethylene vinyl acetate copolymer resin sheet, a solar cell, and a light-transmitting glass plate are laminated on the side of the solar cell backsheet laminated with the gas barrier film, and are integrated by heating and compressing in the lamination process.
  • a solar cell module is taken out and supplied to the panel loading step of the solar cell panel line.
  • the primer coating step the primer is coated on the adhesive surface with the aluminum frame. Subsequently, the primer is left for about 1 minute as the drying time of the primer in the drying process, and then is carried out from the carry-out process to the frame line side. On the other hand, on the frame line side, an assembled aluminum frame will be introduced.
  • the aluminum frame has a projecting piece for supporting the light receiving surface of the solar cell module on which the solar cells are arranged and the surface side to be installed on the back, and can be provided over the entire periphery of the end of the solar cell module, And it has the structure which made the light-receiving surface side of the solar cell module the open state.
  • the solar cell module coated with the primer is transported, and the aluminum frame and the solar cell module coated with the primer in the panel bonding step are placed (solar cell panel bonding step).
  • a molding is attached as necessary to produce a solar cell panel.
  • the back side of the panel is constituted by a solar cell back sheet, and the P1 layer is located on the outermost layer of the solar cell back sheet.
  • PET raw material A A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Next, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours, and then subjected to solid phase polymerization at 220 ° C. and a vacuum degree of 0.3 Torr for 9 hours to have a melting point of 255 ° C. and an intrinsic viscosity of 0.80 dl / g. A PET raw material A having a terminal carboxyl group amount of 10 equivalents / ton and a Tg of 80 ° C. was obtained.
  • PET raw material B> A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Subsequently, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours to obtain a PET raw material B having a melting point of 255 ° C., an intrinsic viscosity of 0.65 dl / g, a terminal carboxyl group amount of 25 equivalents / ton, and a Tg of 80 ° C.
  • PET raw material C PET-A base titanium oxide / CHT master
  • PET raw material A PET-A base titanium oxide / CHT master
  • rutile-type titanium oxide particles having an average particle diameter of 210 nm, and 1,4-cyclohexylenedimethylene terephthalate were mixed at a ratio of 5% by weight, 50% by weight, and 45% by weight, respectively.
  • the mixture was melt-kneaded in a vented 290 ° C. extruder to prepare a PET-A base titanium oxide master (PET raw material C).
  • PET raw material C PET raw material C using anatase type titanium oxide instead of rutile type titanium oxide was used.
  • PET-A base titanium oxide master A PET-A base titanium oxide master (PET raw material D) was melt-kneaded in an extruder at 290 ° C. in which 100 parts by weight of the PET raw material A obtained above and 100 parts by weight of rutile titanium oxide particles having an average particle diameter of 210 nm were vented. was made.
  • PET-A base CHT master A PET-A base CHT master (PET raw material E) was prepared by melt-kneading in a 290 ° C. extruder vented with 100 parts by weight of the PET raw material A obtained above and 100 parts by weight of 1,4-cyclohexylenedimethylene terephthalate. did.
  • PET raw materials A to E vacuum-dried at 180 ° C. for 2 hours are in the proportions shown in the table (the values in the table are the proportions of each raw material relative to the whole raw material when the weight of the whole raw material is 100% by weight)
  • the mixture was melt kneaded in an extruder at 280 ° C. and introduced into a T die die.
  • Example 1 was discharged in a single layer, and otherwise, the raw materials were separately melt-kneaded by two extruders, introduced into the T die die from the two extruders via feed blocks, and P1 / A laminated sheet of P2 is obtained. At this time, the screw rotational speeds of the two extruders were adjusted so that the stacking ratio of P1 / P2 was 4/1.
  • the sheet was melt-extruded into a sheet form from a T-die die and adhered and cooled and solidified by an electrostatic application method on a cooling drum maintained at a surface temperature of 18 ° C. to obtain an unstretched polyester film.
  • the rotation speed of the cooling drum is adjusted so that the time of contact with the cooling drum (residence time) is 30 seconds.
  • the both ends of the obtained uniaxially stretched polyester film are guided to a preheating zone at a temperature of 80 ° C. in a tenter while holding both ends with a clip, and then in a heating zone maintained continuously at 90 ° C. in a direction perpendicular to the longitudinal direction (width direction) ) Was stretched 3.5 times. Subsequently, heat treatment was performed at 215 ° C. for 20 seconds in the heat treatment zone in the tenter, and further, relaxation treatment was performed in the 7% width direction at 215 ° C. Then, it was gradually cooled gradually to obtain a polyester film having a total thickness of 250 ⁇ m.
  • Example 15 to 18 A polyester film was obtained in the same manner as in Example 2 except that the discharge speed and the drum speed were changed and the residence time in the drum was changed to 15, 20, 120.125 seconds, respectively. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 19 A polyester film was obtained in the same manner as in Example 2 except that the temperature of the drum was changed to 10 ° C. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 20 A polyester film was obtained in the same manner as in Example 2 except that the surface roughness of the drawing roll during uniaxial drawing and the drawing nip pressure were changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 23 A polyester film was obtained in the same manner as in Example 2 except that the heat treatment temperature was changed to 240 ° C. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 24 A polyester film was obtained in the same manner as in Example 2 except that the relaxation rate after biaxial stretching was changed to 3% and 10%. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 26 A polyester film was obtained in the same manner as in Example 2 except that the heat treatment temperature after biaxial stretching was 200 ° C. and the relaxation rate was changed to 15%. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Example 27 A polyester film was obtained in the same manner as in Example 2 except that the thickness of the film was changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • Comparative Examples 1 to 6, 9, 10 A polyester film was obtained in the same manner as in Example 2 except that the drum temperature, residence time, roll surface roughness during longitudinal stretching, and stretching nip pressure were set as shown in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table. In any of Comparative Examples 1 to 6, 9, and 10, the thickness reduction amount of the film in the durability test was large, and the characteristics were greatly deteriorated by the durability test.
  • Example 7 A polyester film was obtained in the same manner as in Example 2 except that the titanium oxide was not contained in the polyester film. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table. If titanium oxide was not added, the elongation retention after the durability test was greatly inferior.
  • Example 8 A polyester film was obtained in the same manner as in Example 2 except that the thickness of the film was changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
  • the polyester film of the present invention is excellent in film resistance and durability, it can be suitably used as a polyester film for a solar battery backsheet.
  • the solar cell provided with the solar cell backsheet comprising the polyester film for solar cell backsheet of the present invention can maintain its performance over a long period of time, and can extend the service life.
  • Back sheet 2 Sealing material 3: Power generation element 4: Transparent substrate 5: Surface on the sealing material 2 side of the solar cell backsheet 6: Surface on the opposite side of the sealing material 2 of the solar cell backsheet

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Abstract

A polyester film for solar cell back sheets, which comprises a polyester layer (hereinafter referred to as "a P1 layer") that satisfies the requirements (1)-(3) described below at least as one surface layer. (1) The P1 layer has a thickness of from 30 μm to 250 μm (inclusive). (2) The P1 layer has a surface roughness (Ra) of more than 0.10 μm but 0.50 μm or less. (3) The reduction of the thickness of the P1 layer after an endurance test is 15 μm or less, and elongation retention after an endurance test is 40% or more. Provided is a polyester film which is small in the reduction of the film thickness and is suppressed in decrease of wet heat resistance, weather resistance and electrical insulation even if used outdoors for a long period of time.

Description

太陽電池バックシート用ポリエステルフィルムPolyester film for solar battery backsheet
　本発明は、長期間屋外で使用しても、フィルムの厚みの減少が少なく、かつ、耐湿熱性、耐候性、電気絶縁性の低下の少ない太陽電池バックシート用ポリエステルフィルムに関する。 The present invention relates to a polyester film for a solar battery back sheet, which has little reduction in film thickness even when used outdoors for a long period of time, and has little reduction in wet heat resistance, weather resistance, and electrical insulation.
　ポリエステルフィルムは、優れた機械特性、熱特性、電気特性、表面特性、および耐熱性などの性質を利用して、磁気記録媒体用、電気絶縁用、太陽電池用、コンデンサー用、包装用および各種工業用材料など種々の用途に用いられている。 Polyester films are used for magnetic recording media, for electrical insulation, for solar cells, for capacitors, for packaging, and for various industries by utilizing excellent mechanical properties, thermal properties, electrical properties, surface properties, and heat resistance. It is used for various applications such as materials for use.
　近年、半永久的で無公害の次世代のエネルギー源としてクリーンエネルギーである太陽電池が急速に普及しつつある。太陽電池は、発電素子をエチレン－酢酸ビニル共重合体（以降ＥＶＡと称することがある）などの透明な封止材により封止したものに、ガラスなどの透明基板と、太陽電池バックシートと呼ばれる樹脂シートを貼り合わせて構成される。太陽光は透明基板を通じて太陽電池内に導入される。太陽電池内に導入された太陽光は、発電素子にて、吸収され、吸収された光エネルギーは、電気エネルギーに変換される。変換された電気エネルギーは発電素子に接続したリード線にて取り出されて、各種電気機器に使用される。ここで、太陽電池バックシートは、太陽電池の発電素子を、雨などの外的影響から保護する目的で用いられる。ポリエステルフィルムはその優れた特性から太陽電池バックシートとして、あるいはバックシートを構成する一部材として用いられている。 In recent years, solar cells, which are clean energy, are rapidly spreading as a next-generation energy source that is semi-permanent and non-polluting. In a solar cell, a power generation element is sealed with a transparent sealing material such as ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVA), a transparent substrate such as glass, and a solar cell back sheet. A resin sheet is bonded together. Sunlight is introduced into the solar cell through the transparent substrate. Sunlight introduced into the solar cell is absorbed by the power generation element, and the absorbed light energy is converted into electrical energy. The converted electric energy is taken out by a lead wire connected to the power generation element and used for various electric devices. Here, the solar cell backsheet is used for the purpose of protecting the power generation element of the solar cell from external influences such as rain. The polyester film is used as a solar battery back sheet or as one member constituting the back sheet because of its excellent characteristics.
　太陽電池は、長期間屋外に置かれることから、太陽電池バックシート用ポリエステルフィルムには、高温多湿下に長期間置かれた時に機械特性の低下が少ないこと（耐湿熱性）が求められる。また、太陽電池は、太陽光の直射下に設置される。そのため、太陽電池バックシート用ポリエステルフィルムには、紫外線照射下に長期間置かれた時に機械特性の低下が少ないこと（耐候性）が求められる。また、太陽電池バックシート用ポリエステルフィルムには、発電素子と外気を電気的に絶縁する特性（電気絶縁性）も求められる。上記の課題を解決すべく、これまでに種々の検討がなされている（特許文献１～４）。 Since solar cells are placed outdoors for a long period of time, the polyester film for solar cell backsheets is required to have little deterioration in mechanical properties (moisture and heat resistance) when placed in a high temperature and high humidity for a long period of time. Further, the solar cell is installed under direct sunlight. Therefore, the polyester film for a solar battery back sheet is required to have little deterioration in mechanical properties (weather resistance) when placed for a long time under ultraviolet irradiation. Moreover, the characteristic (electrical insulation) which electrically insulates a power generation element and external air is also calculated | required by the polyester film for solar cell backsheets. Various studies have been made so far to solve the above problems (Patent Documents 1 to 4).
特開２０１３－５１３９５号公報JP 2013-51395 A 特開２０１１－１４２１２８号公報JP 2011-142128 A 国際公開第２０１２／８４８８号パンフレットInternational Publication No. 2012/8488 Pamphlet 特開２０１２－２０４７９７号公報JP 2012-204797 A
　上記特許文献１～４の方法では、耐湿熱性、耐候性、電気絶縁性に優れたポリエステルフィルムを得ることができる。しかしながら、太陽電池は、屋外に置かれるため、太陽電池バックシートの表面は、風雨、砂埃や砂塵、枯葉など様々なものに曝される。長期間屋外において、風雨、砂埃や砂塵、枯葉などに曝されると、太陽電池バックシートに用いられるポリエステルフィルムの表面は少しずつ摩耗し、フィルム厚みが減少（膜減が発生）する。上記特許文献１～４の方法で得られるポリエステルフィルムは、確かに、耐湿熱性、耐候性、電気絶縁性に優れるが、屋外で長期間使用すると、膜減が発生し、耐湿熱性、耐候性、電気絶縁性が、大きく低下してしまうという問題があった。 According to the methods described in Patent Documents 1 to 4, a polyester film having excellent heat and moisture resistance, weather resistance, and electrical insulation can be obtained. However, since the solar cell is placed outdoors, the surface of the solar cell back sheet is exposed to various things such as wind and rain, dust, sand dust, and dead leaves. When exposed to wind and rain, sand dust, sand dust, dead leaves, etc. outdoors for a long period of time, the surface of the polyester film used for the solar battery backsheet is gradually worn down, and the film thickness decreases (film loss occurs). The polyester films obtained by the methods of Patent Documents 1 to 4 are excellent in moisture and heat resistance, weather resistance, and electrical insulation, but when used outdoors for a long period of time, film loss occurs, moisture and heat resistance, weather resistance, There was a problem that the electrical insulation was greatly reduced.
　そこで、本発明の課題は、長期間屋外で使用しても、フィルムの厚みの減少が少なく（以降、この特性を耐膜減性と称する場合がある）、また、長期間屋外で使用しても、耐湿熱性、耐候性、電気絶縁性の低下が少ない（以降、この特性を耐久性と称する場合がある）ポリエステルフィルムを提供することを目的とする。 Therefore, the problem of the present invention is that even when used outdoors for a long period of time, there is little decrease in the thickness of the film (hereinafter, this characteristic may be referred to as film resistance), and it is used outdoors for a long period of time. Another object of the present invention is to provide a polyester film in which there is little decrease in wet heat resistance, weather resistance, and electrical insulation (hereinafter, this characteristic may be referred to as durability).
　本発明はかかる課題を解決するために、次のような手段を採用するものである。すなわち、
（ア）下記（１）～（３）を満たすポリエステル層（該層をＰ１層と称する）を少なくとも一方の表層に有し、耐久性試験後の伸度保持率が４０％以上である太陽電池バックシート用ポリエステルフィルム。
（１）Ｐ１層の厚みが３０μｍ以上２５０μｍ以下であること。
（２）Ｐ１層の表面粗さ（Ｒａ）が０．１０μｍより大きく０．５０μｍ以下であること。
（３）耐久性試験後のＰ１層の厚みの減少量が１５μｍ以下であること。
＜耐久性試験＞
（ｉ）　温度６５℃、相対湿度５０％ＲＨの条件下で、キセノンランプ（スガ試験機製、ＳＣ７５０）を用いて、ポリエステルフィルムのＰ１層側の面を、放射照度１８０Ｗ／ｍ２にて、１０２分間（ｔ－１）照射する。
（ｉｉ）　（ｉ）の後、キセノンランプの照射を続けながら、１６℃±５℃の水シャワーをＰ１層面に２．１Ｌ±０．１ｍＬ／分の量で１８分間（ｔ－２）かける。
なお、（ｔ－１）＋（ｔ－２）＝１２０分となるようにする。
（ｉｉｉ）　（ｉ）（ｉｉ）を１５００回繰り返す。
（イ）少なくとも２層からなる積層ポリエステルフィルムである（ア）に記載の太陽電池バックシート用ポリエステルフィルム。
（ウ）耐久性試験後の部分放電電圧維持率が９０％以上である（ア）または（イ）に記載の太陽電池バックシート用フィルム。
（エ）Ｐ１層を構成するポリエステル樹脂組成物が、ルチル型酸化チタンを含有しており、ルチル型酸化チタンの含有量がＰ１層を構成するポリエステル樹脂組成物全体に対して１４～２０重量％である(ア)～（ウ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルム。
（オ）Ｐ１層を構成するポリエステル樹脂組成物が、１，４－シクロヘキシレンジメチレンテレフタレートユニット（以下、ＣＨＴユニットと称する）を主たる構成成分とするポリエステル樹脂組成物を含有しており、ＣＨＴユニットを主たる構成成分とするポリエステル樹脂組成物の含有量がＰ１層を構成するポリエステル樹脂組成物全体に対して１４～２０重量％である（ア）～（エ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルム。
（カ）ポリエステルフィルムを構成するポリエステル樹脂の固有粘度が０．６～１．０ｄｌ／ｇであり、末端カルボキシル基量が５～２０当量／ｔである(ア)～（オ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルム。
（キ）下記（４）～（６）を満たす、（ア）～（カ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上Ｔｇ－３０℃以下であること。
（６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。
（ク）下記（４）、（７）～（１０）を満たす、（ア）～（カ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
（８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
（９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
（１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。
（ケ）下記（４）～（１０）を満たす、（ア）～（カ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上Ｔｇ－３０℃以下であること。
（６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。
（７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
（８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
（９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
（１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。
（コ）（ア）～（カ）のいずれかに記載の太陽電池バックシート用ポリエステルフィルムを用いた太陽電池バックシート。
（サ）（コ）に記載の太陽電池バックシートを使用した太陽電池。 The present invention employs the following means in order to solve such problems. That is,
(A) A solar cell having a polyester layer satisfying the following (1) to (3) (referred to as P1 layer) on at least one surface layer and having an elongation retention of 40% or more after a durability test Polyester film for back sheet.
(1) The thickness of the P1 layer is 30 μm or more and 250 μm or less.
(2) The surface roughness (Ra) of the P1 layer is greater than 0.10 μm and 0.50 μm or less.
(3) The amount of decrease in the thickness of the P1 layer after the durability test is 15 μm or less.
<Durability test>
(I) Using a xenon lamp (manufactured by Suga Test Instruments, SC750) under the conditions of a temperature of 65 ° C. and a relative humidity of 50% RH, the surface on the P1 layer side of the polyester film is 102 at an irradiance of 180 W / m 2 . Irradiate for (t-1) minutes.
(Ii) After (i), while continuing irradiation with a xenon lamp, a water shower at 16 ° C. ± 5 ° C. is applied to the P1 layer surface at an amount of 2.1 L ± 0.1 mL / min for 18 minutes (t−2).
Note that (t-1) + (t-2) = 120 minutes.
(Iii) Repeat (i) and (ii) 1500 times.
(A) The polyester film for solar cell backsheet according to (A), which is a laminated polyester film comprising at least two layers.
(C) The film for solar cell backsheet according to (a) or (b), wherein the partial discharge voltage maintenance ratio after the durability test is 90% or more.
(D) The polyester resin composition constituting the P1 layer contains rutile type titanium oxide, and the content of the rutile type titanium oxide is 14 to 20% by weight based on the whole polyester resin composition constituting the P1 layer. The polyester film for solar cell backsheet according to any one of (a) to (c).
(E) The polyester resin composition constituting the P1 layer contains a polyester resin composition mainly composed of 1,4-cyclohexylenedimethylene terephthalate unit (hereinafter referred to as CHT unit), and the CHT unit. The solar cell bag according to any one of (a) to (d), wherein the content of the polyester resin composition containing as a main component is 14 to 20% by weight based on the entire polyester resin composition constituting the P1 layer Polyester film for sheet.
(F) The polyester resin constituting the polyester film has an intrinsic viscosity of 0.6 to 1.0 dl / g and a terminal carboxyl group content of 5 to 20 equivalents / t. The polyester film for solar cell backsheet of description.
(G) The method for producing a polyester film for solar cell backsheet according to any one of (a) to (f), which satisfies the following (4) to (6).
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
(6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
(H) The method for producing a polyester film for solar cell backsheet according to any one of (a) to (f), which satisfies the following (4) and (7) to (10).
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
(8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
(9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
(10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
(G) The method for producing a polyester film for a solar cell backsheet according to any one of (a) to (f), which satisfies the following (4) to (10):
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
(6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
(7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
(8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
(9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
(10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
(Ko) A solar battery back sheet using the polyester film for a solar battery back sheet according to any one of (a) to (f).
(Sa) A solar battery using the solar battery back sheet described in (ko).
　本発明によれば、耐膜減性、耐久性に優れる太陽電池バックシート用ポリエステルフィルムを提供することが出来る。本発明の太陽電池バックシート用ポリエステルフィルムは、耐膜減性、耐久性に優れるため、本発明の太陽電池バックシート用ポリエステルフィルムからなる太陽電池バックシートを備えた太陽電池は、長期にわたりその性能を維持することができ、耐用年数を長くすることができる。 According to the present invention, it is possible to provide a polyester film for a solar battery back sheet that is excellent in film resistance and durability. Since the polyester film for solar cell backsheet of the present invention is excellent in film resistance and durability, the solar cell comprising the solar cell backsheet comprising the polyester film for solar cell backsheet of the present invention has long-term performance. Can be maintained, and the service life can be extended.
本発明の太陽電池裏面保護用シートを用いた太陽電池の構成の一例を模式的に示す断面図である。It is sectional drawing which shows typically an example of a structure of the solar cell using the solar cell back surface protection sheet of this invention.
　本発明のポリエステルフィルムは、Ｐ１層を少なくとも一方の表層に有する。Ｐ１層を少なくとも一方の表層に有するとは、Ｐ１層のみからなる単層ポリエステルフィルムであっても良く、Ｐ１層／Ｐ２層やＰ１層／Ｐ２層／Ｐ１層やＰ１層／Ｐ２層／Ｐ３層のような積層ポリエステルフィルムであっても良い。 The polyester film of the present invention has a P1 layer on at least one surface layer. Having a P1 layer on at least one surface layer may be a single-layer polyester film composed of only the P1 layer, and may be a P1 layer / P2 layer, a P1 layer / P2 layer / P1 layer, a P1 layer / P2 layer / P3 layer. A laminated polyester film such as
　本発明のＰ１層は、厚みが３０μｍ以上２５０μｍ以下であることが必要である。Ｐ１層の厚みが３０μｍ未満であると、耐膜減性に優れる本発明のＰ１層であっても、紫外線照射下、長期間、風雨、砂埃や砂塵、枯葉などに曝される状況下で使用すると、機械特性を十分に保持することができない。また、Ｐ１層の厚みが３０μｍ未満であると電気絶縁性が不足し、高電圧下で使用した際に絶縁破壊を起こすことがあり、太陽電池バックシート用ポリエステルフィルムとして好ましくない。一方、Ｐ１層の厚みが２５０μｍより厚いと加工適性が悪く、Ｐ１層の表面を耐膜減性、耐久性に優れた表面形状とすることが困難となる。また、本発明のポリエステルフィルムを太陽電池バックシート用ポリエステルフィルムとして用いた場合に、太陽電池セルの全体厚みが厚くなり過ぎることがあり、好ましくない場合がある。 The P1 layer of the present invention needs to have a thickness of 30 μm or more and 250 μm or less. When the thickness of the P1 layer is less than 30 μm, even the P1 layer of the present invention, which has excellent film resistance, is used under conditions where it is exposed to wind, rain, dust, sand dust, dead leaves, etc. for a long time under ultraviolet irradiation. As a result, sufficient mechanical properties cannot be maintained. Moreover, when the thickness of the P1 layer is less than 30 μm, the electric insulation is insufficient, and dielectric breakdown may occur when used under a high voltage, which is not preferable as a polyester film for a solar battery backsheet. On the other hand, if the thickness of the P1 layer is greater than 250 μm, the processability is poor, and it becomes difficult to make the surface of the P1 layer have a surface shape excellent in film resistance and durability. Moreover, when the polyester film of the present invention is used as a polyester film for a solar battery back sheet, the overall thickness of the solar battery cell may become too thick, which may not be preferable.
　本発明のＰ１層は、表面粗さ（Ｒａ）が０．１０μｍより大きく０．５０μｍ以下であることが必要である。Ｐ１層の表面粗さを上記の範囲とすることによって、耐膜減性を良好にすることができる。この効果が得られるメカニズムは、いかなる理論に拘泥するものでもないが、発明者らは以下のように推定している。 The P1 layer of the present invention needs to have a surface roughness (Ra) of more than 0.10 μm and 0.50 μm or less. By setting the surface roughness of the P1 layer in the above range, the film resistance can be improved. The mechanism by which this effect is obtained is not limited to any theory, but the inventors presume as follows.
　Ｐ１層の表面粗さ（Ｒａ）を上記の範囲とすることで、フィルム表面が水に濡れた場合の水弾き性が良好となる。そのため、ポリエステルフィルムが雨風にさらされた後でも、フィルム表面に水が存在する時間を短くすることが可能となり、フィルム表面において加水分解による劣化を抑制することが可能となる。また、Ｐ１層の表面粗さ（Ｒａ）を上記の範囲とすることで、フィルム表面で紫外線を反射させることが可能となる。その結果、フィルム内部に侵入する紫外線を減らし、フィルムを構成する樹脂の劣化を抑制することが可能となるものと考えている。なお、フィルムの耐膜減性は、初期段階での耐膜減性と、中長期段階での耐膜減性の２つの段階に分けることができる。Ｐ１層の表面粗さを上記の範囲にすることにより、初期段階の耐膜減性を格段に向上させることが可能となる。 When the surface roughness (Ra) of the P1 layer is in the above range, the water repellent property when the film surface gets wet is improved. Therefore, even after the polyester film is exposed to rain and wind, the time during which water is present on the film surface can be shortened, and degradation due to hydrolysis on the film surface can be suppressed. Moreover, it becomes possible to reflect an ultraviolet-ray on the film surface by making the surface roughness (Ra) of P1 layer into said range. As a result, it is considered that the ultraviolet rays entering the film can be reduced, and the deterioration of the resin constituting the film can be suppressed. The film resistance of the film can be divided into two stages: film resistance at the initial stage and film resistance at the medium to long term. By setting the surface roughness of the P1 layer in the above range, it is possible to significantly improve the initial stage film resistance.
　Ｐ１層の表面粗さ（Ｒａ）が０．１０μｍ以下であると、紫外線を反射させることによるフィルムを構成する樹脂の劣化を抑制できないため、風雨、砂埃によるフィルムの膜減り速度が大きくなる。また、Ｐ１層の表面粗さ（Ｒａ）が０．５０μｍより大きいと、水に濡れたときのフィルム表面の水の弾きが悪いため、フィルム表面での劣化を抑制することができず、膜減り速度が大きくなる。Ｐ１層の表面粗さ（Ｒａ）は、０．２０μｍ以上０．４０μｍ以下であることがより好ましい。Ｐ１層の表面粗さ（Ｒａ）を上記の範囲としたポリエステルフィルムは、後述する製造方法や樹脂の種類、添加量により得ることができる。 When the surface roughness (Ra) of the P1 layer is 0.10 μm or less, since the deterioration of the resin constituting the film due to the reflection of ultraviolet rays cannot be suppressed, the film reduction rate of the film due to wind and rain and dust increases. Moreover, when the surface roughness (Ra) of the P1 layer is larger than 0.50 μm, the film surface is poorly repelled when wet, so that deterioration on the film surface cannot be suppressed, resulting in film loss. Increases speed. The surface roughness (Ra) of the P1 layer is more preferably 0.20 μm or more and 0.40 μm or less. The polyester film having the surface roughness (Ra) of the P1 layer in the above range can be obtained by the production method described later, the type of resin, and the amount added.
　Ｐ１層の表面粗さ（Ｒａ）が上記の範囲のポリエステルフィルムであっても、中長期間にわたって屋外で使用されると、少しずつではあるが、膜減りが進行する。膜減りはフィルムの表面から進行するため、フィルムの表面粗さは時間の経過とともに変化する。そのため、Ｐ１層の表面粗さ（Ｒａ）が上記の範囲のフィルムであっても、中長期間屋外で使用されると、表面粗さは変化しているため、高い耐膜減性を維持することはできない。中長期段階での耐膜減性は、フィルムを構成するポリエステル樹脂組成物に、後述する樹脂や添加剤を含有させることで向上させることが出来る。 Even if the surface roughness (Ra) of the P1 layer is in the above range, when it is used outdoors over a medium to long period, the film thickness is reduced little by little. Since film reduction proceeds from the surface of the film, the surface roughness of the film changes with time. Therefore, even if the surface roughness (Ra) of the P1 layer is a film in the above range, the surface roughness changes when used outdoors in the middle and long term, so that high film resistance is maintained. It is not possible. The film resistance at the medium to long-term stage can be improved by adding a resin and additives described later to the polyester resin composition constituting the film.
　本発明のＰ１層は、下に記載の耐久性試験後のＰ１層の厚みの減少量が１５μｍ以下であることが必要である。
＜耐久性試験＞
（ｉ）　温度６５℃、相対湿度５０％ＲＨの条件下で、キセノンランプ（スガ試験機製、ＳＣ７５０）を用いて、ポリエステルフィルムのＰ１層側の面を、放射照度１８０Ｗ／ｍ２にて、１０２分間（ｔ－１）照射する。
（ｉｉ）　（ｉ）の後、キセノンランプの照射を続けながら、１６℃±５℃の水シャワーをＰ１層面に２．１Ｌ±０．１ｍＬ／分の量で１８分間（ｔ－２）かける。
なお、（ｔ－１）＋（ｔ－２）＝１２０分となるようにする。
（ｉｉｉ）　（ｉ）（ｉｉ）を１５００回繰り返す。 The P1 layer of the present invention is required to have a thickness reduction amount of 15 μm or less after the durability test described below.
<Durability test>
(I) Using a xenon lamp (manufactured by Suga Test Instruments, SC750) under the conditions of a temperature of 65 ° C. and a relative humidity of 50% RH, the surface on the P1 layer side of the polyester film is 102 at an irradiance of 180 W / m 2 . Irradiate for (t-1) minutes.
(Ii) After (i), while continuing irradiation with a xenon lamp, a water shower at 16 ° C. ± 5 ° C. is applied to the P1 layer surface at an amount of 2.1 L ± 0.1 mL / min for 18 minutes (t−2).
Note that (t-1) + (t-2) = 120 minutes.
(Iii) Repeat (i) and (ii) 1500 times.
　耐久性試験は、長期間、屋外で風雨、砂埃や砂塵、枯葉などに曝される状況下で使用されるという太陽電池の使用態様を想定した加速試験である。耐久性試験において、ポリエステルフィルムは、キセノンランプによる紫外線の照射や高温高湿条件下に置かれることによって劣化してゆく。そして、劣化したポリエステルフィルムは、水シャワーによって流出するため、膜厚の減少（膜減り）が発生する。耐湿熱性、耐候性、電気絶縁性に優れたポリエステルフィルムであっても、この膜減りが大きいと、屋外で長期間使用するうちに、その性能は低下してしまう。耐久性試験によるＰ１層の膜厚の減少量が１５μｍを超えると、屋外で長期間使用するうちに耐湿熱性、耐候性、電気絶縁性が大きく低下し、また、フィルムの表面が劣化したポリエステルで覆われるため外観が悪くなる。さらに、フィルム表面の劣化により発生したフィルム表面の厚み斑や割れによりフィルム内部に水がさらに浸食し加水分解を加速させるため、加速度的にフィルム特性を低下させてしまう。Ｐ１層の膜厚の減少量は、より好ましくは１２μｍ以下であることが好ましい。膜厚の減少量は少ないことが好ましい態様であるが、０．１μｍ未満とすることは困難であり、０．１μｍ以上１０μｍ以下であることが特に好ましい。 Durability test is an accelerated test that assumes the usage of solar cells that are used outdoors for a long period of time under conditions of exposure to wind and rain, dust, sand dust, dead leaves, and the like. In the durability test, the polyester film is deteriorated by being irradiated with ultraviolet rays by a xenon lamp or being subjected to high temperature and high humidity conditions. And since the deteriorated polyester film flows out by a water shower, a reduction in film thickness (film reduction) occurs. Even if it is a polyester film excellent in wet heat resistance, weather resistance, and electrical insulation, if this film reduction is large, its performance will deteriorate during long-term use outdoors. When the amount of decrease in the thickness of the P1 layer by the durability test exceeds 15 μm, the moisture and heat resistance, weather resistance, and electrical insulation are greatly reduced during long-term outdoor use, and the film surface is deteriorated. Appearance deteriorates because it is covered. Furthermore, since water is further eroded inside the film due to thickness irregularities and cracks generated by the deterioration of the film surface and the hydrolysis is accelerated, the film characteristics are accelerated. The amount of decrease in the thickness of the P1 layer is more preferably 12 μm or less. Although it is preferable that the amount of decrease in the film thickness is small, it is difficult to make the thickness less than 0.1 μm, and it is particularly preferable that the thickness is 0.1 μm or more and 10 μm or less.
　本発明のポリエステルフィルムは、耐久性試験後の伸度保持率が４０％以上であることが必要である。耐久性試験後の伸度保持率が４０％未満であると、フィルム表面に割れが発生していることを表し、フィルム表面に発生した割れの中に水がたまることにより加水分解が促進され、その後のフィルム特性に致命的な影響を与える。耐久性試験後の伸度保持率は、６０％以上であるとより好ましい。 The polyester film of the present invention needs to have an elongation retention after the durability test of 40% or more. If the elongation retention after the durability test is less than 40%, it indicates that the film surface is cracked, and hydrolysis is promoted by accumulation of water in the crack generated on the film surface. It has a fatal effect on the subsequent film properties. The elongation retention after the durability test is more preferably 60% or more.
　本発明のポリエステルフィルムは、耐久性試験後の部分放電電圧維持率が、９０％以上であることが好ましい。部分放電電圧維持率は、以下の式から求められる。
部分放電電圧維持率（％）＝（耐久性試験後の部分放電電圧（Ｖ））／（耐久性試験前の部分放電電圧（Ｖ））×１００
部分放電電圧維持率が、９０％以上であると、長期間屋外においても電気絶縁性が高い状態を維持できるため、長期間屋外にさらされる環境で用いられる絶縁材料として好ましい。より好ましくは、９５％以上である。また、本発明のポリエステルフィルムは、部分放電電圧（すなわち耐候性試験前の部分放電電圧）が、１０００Ｖ以上であることが好ましい。 The polyester film of the present invention preferably has a partial discharge voltage maintenance ratio of 90% or more after the durability test. The partial discharge voltage maintenance ratio is obtained from the following equation.
Partial discharge voltage maintenance ratio (%) = (Partial discharge voltage after durability test (V)) / (Partial discharge voltage before durability test (V)) × 100
A partial discharge voltage maintenance ratio of 90% or more is preferable as an insulating material used in an environment that is exposed to the outdoors for a long period of time because it can maintain a state of high electrical insulation even outdoors for a long period of time. More preferably, it is 95% or more. Moreover, it is preferable that the partial discharge voltage (namely, partial discharge voltage before a weather resistance test) of the polyester film of this invention is 1000V or more.
　本発明のＰ１層は、ポリエステル樹脂を主たる構成成分とする。ここで、ポリエステル樹脂を主たる構成成分とするとは、該Ｐ１層を構成する樹脂に対してポリエステル樹脂が５０質量％を超えて含有されていることをいう。Ｐ１層を構成するポリエステル樹脂としては、具体的にはポリエチレンテレフタレート、ポリエチレン－２、６－ナフタレート、ポリプロピレンテレフタレート、ポリブチレンテレフタレート、ポリ乳酸などが挙げられる。また、本発明に用いられるポリエステル樹脂は、１）ジカルボン酸もしくはそのエステル形成性誘導体（以下、「ジカルボン酸成分」と総称する）とジオール成分の重縮合、２）一分子内にカルボン酸もしくはカルボン酸誘導体と水酸基を有する化合物の重縮合、および１）２）の組み合わせにより得ることができる。また、ポリエステル樹脂の重合は常法により行うことができる。 The P1 layer of the present invention is mainly composed of a polyester resin. Here, the main constituent component of the polyester resin means that the polyester resin is contained in an amount exceeding 50% by mass with respect to the resin constituting the P1 layer. Specific examples of the polyester resin constituting the P1 layer include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polylactic acid. The polyester resin used in the present invention includes 1) polycondensation of dicarboxylic acid or an ester-forming derivative thereof (hereinafter collectively referred to as “dicarboxylic acid component”) and a diol component, and 2) carboxylic acid or carboxylic acid in one molecule. It can be obtained by a polycondensation of an acid derivative and a compound having a hydroxyl group, and 1) 2). The polymerization of the polyester resin can be performed by a conventional method.
　１）において、ジカルボン酸成分としては、マロン酸、コハク酸、グルタル酸、アジピン酸、スベリン酸、セバシン酸、ドデカンジオン酸、ダイマー酸、エイコサンジオン酸、ピメリン酸、アゼライン酸、メチルマロン酸、エチルマロン酸等の脂肪族ジカルボン酸類、アダマンタンジカルボン酸、ノルボルネンジカルボン酸、シクロヘキサンジカルボン酸、デカリンジカルボン酸などの脂環族ジカルボン酸、テレフタル酸、イソフタル酸、フタル酸、１，４－ナフタレンジカルボン酸、１，５－ナフタレンジカルボン酸、２，６－ナフタレンジカルボン酸、１，８－ナフタレンジカルボン酸、４，４’－ジフェニルジカルボン酸、４，４’－ジフェニルエーテルジカルボン酸、４，４’－ジフェニルスルホンジカルボン酸、５－ナトリウムスルホイソフタル酸、フェニルエンダンジカルボン酸、アントラセンジカルボン酸、フェナントレンジカルボン酸、９，９’－ビス（４－カルボキシフェニル）フルオレン酸などの芳香族ジカルボン酸、もしくはそのエステル誘導体などが代表例としてあげられる。また、これらは単独で用いても、複数種類用いても構わない。 In 1), as the dicarboxylic acid component, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, Aliphatic dicarboxylic acids such as ethylmalonic acid, alicyclic dicarboxylic acids such as adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid Acid, 5-sodium Ruhoisofutaru acid, phenyl ene boys carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) aromatic dicarboxylic acids such as fluorene acid, or the like its ester derivatives and the like as a typical example. These may be used alone or in combination.
　また、上述のジカルボン酸成分の少なくとも一方のカルボキシ末端に、ｌ-ラクチド、ｄ－ラクチド、ヒドロキシ安息香酸などのオキシ酸類およびその誘導体や該オキシ酸類が複数個連なったもの等を縮合させたジカルボキシ化合物も用いることができる。 In addition, dicarboxyl obtained by condensing oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids, at least one carboxy terminus of the dicarboxylic acid component described above. Compounds can also be used.
　次に、ジオール成分としては、エチレングリコール、１，２－プロパンジオール、１，３－プロパンジオール、１，４－ブタンジオール、１，２－ブタンジオール、１，３－ブタンジオールなどの脂肪族ジオール、シクロヘキサンジメタノール、スピログリコール、イソソルビドなどの脂環式ジオール、ビスフェノールＡ、１，３－ベンゼンジメタノール，１，４－ベンセンジメタノール、９，９’－ビス（４－ヒドロキシフェニル）フルオレンなどの芳香族ジオールが代表例としてあげられる。また、これらは単独で用いても、必要に応じて、複数種類用いても構わない。また、上述のジオール成分の少なくとも一方のヒドロキシ末端にジオール類を縮合させて形成されるジヒドロキシ化合物も用いることができる。 Next, the diol component includes aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. , Cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) fluorene, etc. Aromatic diols are typical examples. Moreover, these may be used independently or may be used in multiple types as needed. In addition, a dihydroxy compound formed by condensing a diol with at least one hydroxy terminal of the diol component described above can also be used.
　２）において、一分子内にカルボン酸もしくはカルボン酸誘導体と水酸基を有する化合物の例としては、ｌ-ラクチド、ｄ－ラクチド、ヒドロキシ安息香酸などのオキシ酸、およびその誘導体、オキシ酸類のオリゴマー、ジカルボン酸の一方のカルボキシル基にオキシ酸が縮合したもの等があげられる。 In 2), examples of the compound having a carboxylic acid or a carboxylic acid derivative and a hydroxyl group in one molecule include oxyacids such as l-lactide, d-lactide and hydroxybenzoic acid, and derivatives thereof, oligomers of oxyacids, dicarboxylic acids Examples thereof include those obtained by condensing an oxyacid with one carboxyl group of the acid.
　ポリエステル樹脂を構成するジカルボン酸成分およびジオール成分は、上述した中から１種類ずつを選択して共重合させても良いし、それぞれ複数種を選択して共重合させても良い。 The dicarboxylic acid component and the diol component constituting the polyester resin may be copolymerized by selecting one from the above, or may be copolymerized by selecting a plurality of each.
　また、Ｐ１層を構成するポリエステル樹脂は、単一種でも良いし、２種以上のポリエステル樹脂をブレンドしたものでも良い。機械強度、加工性の観点からは、ポリエチレンテレフタレート（ＰＥＴ）を主たる構成成分とすることが好ましい。 The polyester resin constituting the P1 layer may be a single type or a blend of two or more types of polyester resins. From the viewpoint of mechanical strength and processability, it is preferable to use polyethylene terephthalate (PET) as the main constituent.
　本発明のＰ１層を構成する樹脂は、前述のとおりポリエステル樹脂を主たる構成成分とするが、固有粘度は０．６０ｄｌ／ｇ以上１．００ｄｌ／ｇ以下であり、末端カルボキシル基量は２０当量／トン以下であることが、耐湿熱性、成形性、耐久性が良好となるため好ましい。固有粘度は０．６５ｄｌ／ｇ以上０．８０ｄｌ／ｇ以下であると、耐湿熱性、フィルム成形性、耐久性がより良好となるため好ましい。固有粘度ＩＶが上記範囲を満たしており、かつ、末端カルボキシル基量が２０当量／トン以下であると、耐湿熱性がより良好となるため、好ましい。よって、Ｐ１層を構成する樹脂は、ＰＥＴを主たる構成成分とし、かつ、固有粘度と末端カルボキシル基量が上記範囲を満たすことによって、耐久性、耐湿熱性、成形性に非常に優れた太陽電池バックシート用ポリエステルフィルムとすることが出来る。 The resin constituting the P1 layer of the present invention has a polyester resin as the main constituent as described above, but has an intrinsic viscosity of 0.60 dl / g or more and 1.00 dl / g or less, and a terminal carboxyl group amount of 20 equivalents / It is preferable that the heat resistance is not more than tons because heat resistance, moldability, and durability are good. Intrinsic viscosity is preferably 0.65 dl / g or more and 0.80 dl / g or less because moisture and heat resistance, film moldability, and durability are further improved. It is preferable that the intrinsic viscosity IV satisfies the above range and the terminal carboxyl group amount is 20 equivalents / ton or less because the heat and humidity resistance becomes better. Therefore, the resin that constitutes the P1 layer is a solar cell bag that is extremely excellent in durability, moist heat resistance, and moldability by having PET as the main constituent and the intrinsic viscosity and the amount of terminal carboxyl groups satisfy the above ranges. It can be set as the polyester film for sheets.
　本発明の太陽電池バックシート用ポリエステルフィルムにおいて、Ｐ１層を構成するポリエステル樹脂の数平均分子量は８０００～４００００が好ましく、より好ましくは数平均分子量が９０００～３００００、更に好ましくは１００００～２００００である。ここでいうＰ１層を構成するポリエステル樹脂の数平均分子量とは、本発明の太陽電池バックシート用ポリエステルフィルムからＰ１層を分離し、ヘキサフルオロイソプロノール（ＨＥＩＰ）に溶解させ、ゲル浸透クロマトグラフ法(ＧＰＣ法)で測定、示差屈折率計で検出した値から、標準試料として分子量既知のポリエチレンテレフタレート（ＰＥＴ－５Ｒ：Ｍｗ５５８００）とジメチルテレフタレートを用いて得られた値である。Ｐ１層を構成するポリエステル樹脂の数平均分子量が８０００に満たない場合、耐湿熱性や耐熱性などのシートの長期耐久性が落ちる可能性があるため好ましくない。また、４００００を超えると、重合が困難であるか重合できたとしても押出機による樹脂の押出が困難となり、製膜が困難となる場合がある。また、本発明の太陽電池バックシート用ポリエステルフィルムにおいて、Ｐ１層は一軸、もしくは二軸に配向していることが好ましい。Ｐ１層が、一軸、もしくは二軸に配向していると、配向結晶化により耐湿熱性や耐熱性などの特性を向上させることができる。 In the polyester film for solar battery backsheet of the present invention, the number average molecular weight of the polyester resin constituting the P1 layer is preferably 8000 to 40000, more preferably 9000 to 30000, and still more preferably 10,000 to 20000. Here, the number average molecular weight of the polyester resin constituting the P1 layer is a gel permeation chromatography method by separating the P1 layer from the polyester film for solar battery backsheet of the present invention and dissolving it in hexafluoroisopronol (HEIP). It is a value obtained by using polyethylene terephthalate (PET-5R: Mw 55800) and dimethyl terephthalate having a known molecular weight as standard samples from values measured by (GPC method) and detected by a differential refractometer. When the number average molecular weight of the polyester resin constituting the P1 layer is less than 8000, it is not preferable because the long-term durability of the sheet such as moisture and heat resistance may be deteriorated. On the other hand, if it exceeds 40,000, even if the polymerization is difficult or the polymerization can be performed, it may be difficult to extrude the resin with an extruder and film formation may be difficult. In the polyester film for solar battery backsheet of the present invention, the P1 layer is preferably uniaxially or biaxially oriented. When the P1 layer is uniaxially or biaxially oriented, characteristics such as moist heat resistance and heat resistance can be improved by orientation crystallization.
　本発明のＰ１層を構成するポリエステル樹脂組成物は、酸化チタン粒子を含有しており、その含有量が、Ｐ１層を構成するポリエステル樹脂組成物全体に対して１４質量％以上２０質量％以下であることが好ましい。これによって酸化チタン粒子による紫外線吸収能と光反射性を活かして、長期に亘って紫外線の照射による劣化を低減するという効果を得ることができるため、初期段階および中長期段階での耐膜減性を向上させることができる。初期段階での耐膜減性向上効果は、Ｐ１層の表面粗さが０．２０μｍ～０．４０μｍのときに特に大きく得られる。この効果がどのようなメカニズムに由来するのか明らかではないが、酸化チタンを一定量含有し、Ｐ１層の表面粗さを特定の範囲にすると、Ｐ１層の表面で紫外線が効果的に反射するため、紫外線がポリエステルフィルムの内部にまで到達せず、ポリエステルの劣化を抑制することができているものと推定している。また、本発明のＰ１層を構成するポリエステル樹脂組成物に上記の範囲で酸化チタン粒子を含有させると、本発明のフィルムを搭載した太陽電池の発電効率を高めることができる。酸化チタン粒子の含有量が１４質量％未満では、上記の効果が十分に得られない場合がある。２０質量％より多いと製膜性が悪くなる場合がある。また、他の層と共押し、積層する際に密着性が悪くなる場合がある。また、酸化チタンは、優れた耐紫外線性と光反射性の両立という観点で、ルチル型酸化チタンを用いるのがより好ましい。 The polyester resin composition constituting the P1 layer of the present invention contains titanium oxide particles, and the content thereof is 14% by mass or more and 20% by mass or less with respect to the entire polyester resin composition constituting the P1 layer. Preferably there is. This makes it possible to obtain the effect of reducing deterioration due to ultraviolet irradiation over a long period of time by utilizing the ultraviolet absorption ability and light reflectivity of the titanium oxide particles. Can be improved. The effect of improving the film resistance at the initial stage is particularly large when the surface roughness of the P1 layer is 0.20 μm to 0.40 μm. It is not clear what kind of mechanism this effect is derived from, but when a certain amount of titanium oxide is contained and the surface roughness of the P1 layer is in a specific range, ultraviolet rays are effectively reflected on the surface of the P1 layer. It is presumed that the ultraviolet rays do not reach the inside of the polyester film and the deterioration of the polyester can be suppressed. Further, when the polyester resin composition constituting the P1 layer of the present invention contains titanium oxide particles in the above range, the power generation efficiency of the solar cell equipped with the film of the present invention can be increased. If the content of titanium oxide particles is less than 14% by mass, the above effect may not be sufficiently obtained. When it is more than 20% by mass, the film forming property may be deteriorated. In addition, adhesion may deteriorate when co-pushing and laminating with other layers. Moreover, it is more preferable to use rutile type titanium oxide from the viewpoint of achieving both excellent ultraviolet resistance and light reflectivity.
　ここでＰ１層を構成するポリエステル樹脂に前記の粒子を含有させる方法としては、ポリエステル樹脂と粒子をベント式二軸混練押出機やタンデム型押出機を用いて、溶融混練する方法が好ましく用いられる。ここで、ポリエステル樹脂に粒子を含有させる際にポリエステル樹脂が熱負荷を受けると、ポリエステル樹脂は少なからず劣化する。そのため、Ｐ１層を構成するポリエステル樹脂に含まれる粒子量よりも粒子含有量が多い高濃度マスターペレットを作製し、それをポリエステル樹脂と混合して希釈し、所望の粒子含有量としたＰ１層を作製するのが、耐湿熱性の観点から好ましい。 Here, as a method of incorporating the particles into the polyester resin constituting the P1 layer, a method of melt-kneading the polyester resin and the particles using a vent type twin-screw kneading extruder or a tandem type extruder is preferably used. Here, when the polyester resin is subjected to a thermal load when the polyester resin contains particles, the polyester resin deteriorates not a little. Therefore, a high-concentration master pellet having a particle content larger than the amount of particles contained in the polyester resin constituting the P1 layer is prepared, mixed with the polyester resin and diluted to obtain a desired particle content P1 layer. It is preferable to produce it from the viewpoint of heat and humidity resistance.
　本発明のＰ１層には、前記の酸化チタン粒子やカーボン粒子以外にも、本発明の効果が損なわれない範囲で必要に応じて、耐熱安定剤、耐酸化安定剤、紫外線吸収剤、紫外線安定剤、有機系／無機系の易滑剤、有機系／無機系の微粒子、充填剤、核剤、染料、分散剤、カップリング剤等の添加剤や、気泡が配合されていてもよい。例えば、添加剤として紫外線吸収剤を選択した場合には、本発明のフィルムの耐紫外線性をより高めることが可能となる。また、帯電防止剤などを添加して電気絶縁性を向上させたり、有機系／無機系の微粒子や気泡を含有して光反射性を発現させたり、着色したい色の材料を添加して意匠性を付与することもできる。 In addition to the titanium oxide particles and carbon particles described above, the P1 layer of the present invention may include a heat-resistant stabilizer, an oxidation-resistant stabilizer, an ultraviolet absorber, and an ultraviolet-ray stabilizer as long as the effects of the present invention are not impaired. Agents, organic / inorganic lubricants, organic / inorganic fine particles, fillers, nucleating agents, dyes, dispersants, coupling agents, and the like, and bubbles may be blended. For example, when an ultraviolet absorber is selected as the additive, the ultraviolet resistance of the film of the present invention can be further improved. In addition, anti-static agents are added to improve electrical insulation, or organic or inorganic fine particles or bubbles are included to express light reflectivity, or a color material to be colored is added to create a design. Can also be given.
　本発明のＰ１層を構成するポリエステル樹脂組成物は、１，４－シクロヘキシレンジメチレンテレフタレートユニット（以下、ＣＨＴユニットとも称する）を主たる構成成分とするポリエステル樹脂を含有しており、その含有量が、Ｐ１層を構成するポリエステル樹脂組成物全体に対して１４質量％以上２０質量％以下であることが好ましい。これによって耐湿熱性を付与するとともに、初期段階および中長期段階での耐膜減性を向上させるという効果を得ることができる。初期段階での耐膜減性向上効果は、Ｐ１層の表面粗さが０．２０μｍ～０．４０μｍのときに特に大きく得られる。この効果がどのようなメカニズムに由来するのか明らかではないが、粘度特性が大きくことなるＣＨＴユニットを構成成分とする樹脂をポリエステルフィルムを構成する樹脂中に含むことにより、紫外線によって劣化したポリエステルが系外に流出する速度を低減しているのではないかと推定している。ＣＨＴユニットの含有量が１４質量％未満では、上記の効果が十分に得られない場合がある。２０質量％より多いと製膜性が悪くなる場合がある。なお、本発明において、ポリエステルフィルムを構成するポリエステル樹脂組成物全体に対するＣＨＴユニットを主たる構成成分とするポリエステル樹脂の含有量は、ポリエステルフィルムを構成するポリエステル樹脂組成物全体に対する添加量とする。 The polyester resin composition constituting the P1 layer of the present invention contains a polyester resin mainly composed of 1,4-cyclohexylenedimethylene terephthalate unit (hereinafter also referred to as CHT unit), and the content thereof is It is preferable that it is 14 mass% or more and 20 mass% or less with respect to the whole polyester resin composition which comprises P1 layer. As a result, the heat and moisture resistance can be imparted, and the effect of improving the film resistance at the initial stage and the medium to long-term stage can be obtained. The effect of improving the film resistance at the initial stage is particularly large when the surface roughness of the P1 layer is 0.20 μm to 0.40 μm. It is not clear what kind of mechanism this effect is derived from, but the polyester that has deteriorated by ultraviolet rays is contained in the resin constituting the polyester film by containing a resin having a CHT unit, which has a large viscosity characteristic, as a constituent component. It is estimated that the speed of flowing out is reduced. When the content of the CHT unit is less than 14% by mass, the above effect may not be sufficiently obtained. When it is more than 20% by mass, the film forming property may be deteriorated. In addition, in this invention, content of the polyester resin which makes the main component the CHT unit with respect to the whole polyester resin composition which comprises a polyester film shall be the addition amount with respect to the whole polyester resin composition which comprises a polyester film.
　耐湿熱性、耐久性を向上させるために、Ｐ１層を構成するポリエステル樹脂の固有粘度を高くすると、Ｐ１層単膜のポリエステルフィルムを製膜しようとすると、製膜性、加工性が悪くなる場合がある。そのため、本発明のポリエステルフィルムは、Ｐ１層の他に基材層（Ｐ２層）を有する少なくとも２層からなる積層ポリエステルフィルムであることが好ましい。なお、２層以上からなる本発明のポリエステルフィルムを太陽電池バックシートに用いる際には、Ｐ１層を太陽電池バックシートの表層（風雨に曝される側）に配するように用いる。本発明ではＰ２層とＰ１層を共押しして太陽電池バックシート用ポリエステルフィルムとすることが望ましい。貼り合わせ法により製造すると、張り合わせ時にカールが発生したり、貼り合わせに用いる接着剤から劣化が進行することがある。 If the intrinsic viscosity of the polyester resin constituting the P1 layer is increased in order to improve the heat and moisture resistance and durability, the film formability and workability may deteriorate when attempting to form a polyester film of a single P1 layer film. is there. Therefore, the polyester film of the present invention is preferably a laminated polyester film composed of at least two layers having a base material layer (P2 layer) in addition to the P1 layer. In addition, when using the polyester film of this invention which consists of two or more layers for a solar cell backsheet, it uses so that P1 layer may be distribute | arranged to the surface layer (side exposed to a wind and rain) of a solar cell backsheet. In the present invention, it is desirable to co-press the P2 layer and the P1 layer to obtain a polyester film for a solar battery backsheet. When manufactured by the bonding method, curling may occur at the time of bonding, or deterioration may proceed from the adhesive used for bonding.
　Ｐ２層は、Ｐ１層と同様ポリエステル樹脂組成物を主たる構成成分とする。Ｐ１層と同じ組成であればＰ１層と同時に製膜（共押出）することが出来、Ｐ１層との密着性も良好となる。 The P2 layer is mainly composed of a polyester resin composition as in the P1 layer. If the composition is the same as that of the P1 layer, the film can be formed (coextruded) at the same time as the P1 layer, and the adhesion to the P1 layer can be improved.
　本発明のＰ２層を構成するポリエステル樹脂は、固有粘度は０．５０ｄｌ／ｇ以上０．８０ｄｌ／ｇ以下であり、末端カルボキシル基量は５当量／トン以上４０当量／トン以下であることが、製膜性、加工性を良好にできるため好ましい。固有粘度は０．５５ｄｌ／ｇ以上０．７５ｄｌ／ｇ以下、末端カルボキシル基量は１０当量／トン以上３５当量／トン以下であると、耐湿熱性がより良好となるため好ましい。 The polyester resin constituting the P2 layer of the present invention has an intrinsic viscosity of 0.50 dl / g or more and 0.80 dl / g or less, and a terminal carboxyl group amount of 5 eq / ton or more and 40 eq / ton or less, It is preferable because the film forming property and workability can be improved. It is preferable that the intrinsic viscosity is 0.55 dl / g or more and 0.75 dl / g or less and the terminal carboxyl group amount is 10 equivalents / ton or more and 35 equivalents / ton or less because the heat and humidity resistance becomes better.
　また、Ｐ２層を構成するポリエステル樹脂組成物は、酸化チタン粒子の含有量が、Ｐ２層を構成するポリエステル樹脂組成物全体に対して１４質量％以下であると、製膜性、加工性が良好となるため好ましい。より好ましくは１質量％以上１４質量％以下である。 The polyester resin composition constituting the P2 layer has good film forming properties and workability when the content of titanium oxide particles is 14% by mass or less with respect to the entire polyester resin composition constituting the P2 layer. This is preferable. More preferably, it is 1 mass% or more and 14 mass% or less.
　また、Ｐ２層を構成するポリエステル樹脂組成物は、ＣＨＴユニットを主たる構成成分とするポリエステル樹脂を１質量％以上２０重量％以下で含有させることが望ましい。Ｐ２層を構成するポリエステル樹脂組成物を上記の樹脂とすることで、製膜時にＰ１層との密着力を良好にすることができるため、好ましい。 Further, it is desirable that the polyester resin composition constituting the P2 layer contains 1% by mass or more and 20% by weight or less of a polyester resin having a CHT unit as a main constituent component. It is preferable to use the above-described resin as the polyester resin composition that constitutes the P2 layer, because the adhesion with the P1 layer can be improved during film formation.
　また、Ｐ２層の厚みは、３０μｍ以上２５０μｍ以下であると、製膜性、加工性が良好となるため好ましい。 Further, it is preferable that the thickness of the P2 layer is 30 μm or more and 250 μm or less because the film forming property and workability are improved.
　本発明のポリエステルフィルムは、フィルム総厚みが５０μｍ以上１０００μｍ以下であることが好ましい。フィルムの総厚みが２５０μｍ以上であると、部分放電電圧が高くなる（電気絶縁性が良好となる）ため好ましい。より好ましくは３００μｍ以上である、さらに好ましくは３５０μｍ以上である。一方、５００μｍを超えると製膜性、加工性に劣る場合がある。 The polyester film of the present invention preferably has a total film thickness of 50 μm or more and 1000 μm or less. When the total thickness of the film is 250 μm or more, the partial discharge voltage becomes high (electrical insulation becomes good), which is preferable. More preferably, it is 300 micrometers or more, More preferably, it is 350 micrometers or more. On the other hand, if it exceeds 500 μm, the film forming property and workability may be inferior.
　本発明の太陽電池バックシート用ポリエステルフィルムは、以上の通り、耐久性、耐膜減性に優れる。そのため、本発明の太陽電池バックシート用ポリエステルフィルムを搭載した太陽電池は、長期間屋外に置いても出力が低下しない太陽電池とすることができる。 As described above, the polyester film for solar battery backsheet of the present invention is excellent in durability and film resistance. Therefore, the solar cell on which the polyester film for solar cell backsheet of the present invention is mounted can be a solar cell whose output does not decrease even when placed outdoors for a long period of time.
　本発明の太陽電池バックシート用ポリエステルフィルムは、例えば、以下（い）、（ろ）、（は）に記載された製造方法により得ることができる。 The polyester film for solar battery backsheet of the present invention can be obtained by, for example, the production methods described in (i), (b) and (b) below.
　（い）下記（４）～（６）を満たす太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上～Ｔｇ－３０℃であること。
（６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。 (Ii) A method for producing a polyester film for a solar battery back sheet that satisfies the following (4) to (6).
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(5) The temperature of the cooling drum is from Tg-70 ° C. to Tg-30 ° C. of the polyester resin constituting the P1 layer.
(6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
　（ろ）下記（４）、（７）～（１０）を満たす太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
（８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
（９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
（１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。 (B) A method for producing a polyester film for a solar battery back sheet that satisfies the following (4), (7) to (10).
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
(8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
(9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
(10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
　（は）下記（４）～（１０）を満たす太陽電池バックシート用ポリエステルフィルムの製造方法。
（４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
（５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上Ｔｇ－３０℃以下であること。
（６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。
（７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
（８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
（９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
（１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。 (Ha) A method for producing a polyester film for a solar battery backsheet that satisfies the following (4) to (10).
(4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
(5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
(6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
(7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
(8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
(9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
(10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
　まず、（い）に係る方法について説明する。 First, the method related to (i) will be described.
　本発明のポリエステルフィルムは、Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むことが好ましい。本発明のポリエステルフィルムが、Ｐ１層の他にＰ２層を含む積層ポリエステルフィルムである場合は、Ｐ１層、Ｐ２層それぞれの原料を２台の押出機内で加熱溶融し、合流させて口金から冷却したキャストドラム上に押し出して未配向積層ポリエステルフィルムを得る工程（溶融キャスト法、共押し法）を含むことが好ましい。 The polyester film of the present invention preferably includes a step of obtaining a non-oriented polyester film by melt-kneading the polyester resin composition constituting the P1 layer with an extruder and then extruding and cooling and solidifying on a cooling drum. When the polyester film of the present invention is a laminated polyester film containing a P2 layer in addition to the P1 layer, the raw materials of the P1 layer and the P2 layer are heated and melted in two extruders, merged, and cooled from the die. It is preferable to include a process (melt casting method, co-pressing method) of extruding onto a cast drum to obtain an unoriented laminated polyester film.
　前記、冷却ドラムの温度は、Ｐ１層を構成するポリエステル樹脂のガラス転移温度（以降Ｔｇと称する）－７０℃以上Ｔｇ－３０℃以下であることが好ましい。冷却ドラムの温度を上記の範囲とすることで、未配向ポリエステルフィルムを構成するポリエステル樹脂の熱結晶化度を適当な範囲に維持したまま長手方向の延伸へと進むことが可能となり、Ｐ１層の表面粗さを容易に０．１μｍより大きく０．５μｍ以下とすることが出来る。冷却ドラムの温度をＰ１層を構成するポリエステル樹脂のＴｇ－７０℃より低くすると、ポリマーの冷却が急激となるため、熱結晶化が大きく発生し、また、熱結晶化のバラつきが大きくなるため、フィルムの表面粗さを０．１～０．５μｍの範囲にすることが困難となったり、長手方向の延伸以降でフィルム破れを起こしてしまう場合がある。冷却ドラムの温度は、Ｐ１層を構成するポリエステル樹脂のＴｇ－６０℃以上Ｔｇ－３５℃以下であることが好ましく、Ｔｇ－５５℃以上Ｔｇ－４０℃以下であることが特に好ましい。 The temperature of the cooling drum is preferably a glass transition temperature (hereinafter referred to as Tg) of the polyester resin constituting the P1 layer of −70 ° C. or higher and Tg−30 ° C. or lower. By setting the temperature of the cooling drum in the above range, it is possible to proceed to stretching in the longitudinal direction while maintaining the thermal crystallization degree of the polyester resin constituting the unoriented polyester film in an appropriate range, and the P1 layer The surface roughness can be easily increased from 0.1 μm to 0.5 μm. When the temperature of the cooling drum is lower than Tg-70 ° C. of the polyester resin constituting the P1 layer, the polymer is rapidly cooled, so that thermal crystallization occurs greatly, and the variation in thermal crystallization increases. It may be difficult to make the surface roughness of the film in the range of 0.1 to 0.5 μm, or the film may be broken after stretching in the longitudinal direction. The temperature of the cooling drum is preferably Tg−60 ° C. or higher and Tg−35 ° C. or lower, particularly preferably Tg−55 ° C. or higher and Tg−40 ° C. or lower, of the polyester resin constituting the P1 layer.
　また、前記、冷却ドラムに接触している時間（滞留時間）は、２０秒以上１２０秒以下であることが好ましい。冷却ドラムに接触している時間を上記の範囲とすることで、十分に吐出したポリマーを冷却することが可能となり、ポリエステルフィルム中の熱結晶化度のバラつきを少なくしたまま長手方向の延伸へと進むことが可能となり、Ｐ１層の表面粗さのバラつきを少なくし、且つＰ１層の表面粗さを容易に０．１０μｍより大きく０．５０μｍ以下とすることができる。冷却ドラムに接触している時間（滞留時間）は、２０秒以上６０秒以下であることが好ましく、２５秒以上４５秒以下であることが特に好ましい。２０秒より短いとポリマーの冷却が急激となるため、熱結晶化が大きく発生し、また、熱結晶化のバラつきが大きくなるため、フィルムの表面粗さを０．１～０．５μｍの範囲にすることが困難となったり、長手方向の延伸以降でフィルム破れを起こしてしまう場合がある。 In addition, the time of contact with the cooling drum (residence time) is preferably 20 seconds or more and 120 seconds or less. By making the time in contact with the cooling drum within the above range, it becomes possible to cool the polymer that has been sufficiently discharged, and stretching in the longitudinal direction while reducing variations in the thermal crystallinity in the polyester film. It is possible to proceed, the variation in the surface roughness of the P1 layer can be reduced, and the surface roughness of the P1 layer can be easily made larger than 0.10 μm and 0.50 μm or less. The time of contact with the cooling drum (residence time) is preferably 20 seconds or longer and 60 seconds or shorter, and particularly preferably 25 seconds or longer and 45 seconds or shorter. When the time is shorter than 20 seconds, the polymer is rapidly cooled, so that thermal crystallization is greatly generated, and variation in thermal crystallization is increased, so that the surface roughness of the film is in the range of 0.1 to 0.5 μm. It may be difficult to do, or the film may be broken after stretching in the longitudinal direction.
　上記未延伸ポリエステルフィルムを、その後、従来公知の延伸、熱処理を行うことにより、本発明のポリエステルフィルムを得ることができる。 The polyester film of the present invention can be obtained by subjecting the unstretched polyester film to a conventionally known stretching and heat treatment.
　次に、（ろ）に係る方法について説明する。 Next, the method related to (b) will be described.
　本発明のポリエステルフィルムは、Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得た後、下記の（７）～（１０）を満たす延伸工程、熱処理工程を含む製造方法により得られる。
（７）未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
（８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
（９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
（１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。 The polyester film of the present invention was prepared by melt-kneading the polyester resin composition constituting the P1 layer with an extruder, and then extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film. ) To (10) are obtained by a production method including a stretching step and a heat treatment step.
(7) A step of stretching an unoriented polyester film in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film.
(8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
(9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
(10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
　長手方向の延伸は、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、延伸工程における加熱が、加熱された延伸ロールによって実施されるものであることが好ましい。また、延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであると、膜破れなどの発生を抑制し、生産性良く、Ｐ１層の表面粗さを容易に０．１０μｍより大きく０．５０μｍ以下とすることができる。特に、延伸ロールの表面粗さＲａが０．７～１．２μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．５～０．８ＭＰａであると、生産性を良好に維持したまま、得られるポリエステルフィルムの耐久性、耐膜減性を良好にできるため好ましい。 The stretching in the longitudinal direction is performed using a stretching roll and a stretching nip roll, and the heating in the stretching process is preferably performed by a heated stretching roll. In addition, when the surface roughness Ra of the drawing roll is 0.5 to 1.5 μm and the nip pressure between the drawing roll and the drawing nip roll is 0.4 to 1.0 MPa, film breakage or the like may occur. The surface roughness of the P1 layer can be easily made larger than 0.10 μm and 0.50 μm or less with good suppression and high productivity. In particular, when the surface roughness Ra of the drawing roll is 0.7 to 1.2 μm and the nip pressure between the drawing roll and the drawing nip roll is 0.5 to 0.8 MPa, productivity is maintained well. As it is, it is preferable because the durability and film resistance of the resulting polyester film can be improved.
　幅方向の延伸は、（７）の工程で得られたフィルムを、フィルムの両端をクリップで把持しながらテンターに導き、７０～１５０℃の温度に加熱された雰囲気中で、長手方向に直角な方向（幅方向）に３～４倍に延伸することが好ましい。長手方向、幅方向の延伸温度、延伸倍率を上記の範囲とすることにより、膜破れなどの発生を抑制し、生産性良く、Ｐ１層の表面粗さを０．１μｍより大きく０．５０μｍ以下とすることができる。中でも、長手方向と幅方向の延伸倍率をかけ合わせた面積倍率を９～１５倍とすると、生産性を良好に維持したまま、得られるポリエステルフィルムの耐久性、耐膜減性を良好にできるため好ましい。また、（７）と（８）の工程の間に、２０～５０℃の温度のロール群で冷却する工程を含むと生産性を良好にできるため好ましい。 In the stretching in the width direction, the film obtained in the step (7) is guided to a tenter while holding both ends of the film with clips, and is perpendicular to the longitudinal direction in an atmosphere heated to a temperature of 70 to 150 ° C. The film is preferably stretched 3 to 4 times in the direction (width direction). By adjusting the stretching temperature and stretching ratio in the longitudinal direction and the width direction within the above ranges, the occurrence of film breakage or the like is suppressed, the productivity is high, and the surface roughness of the P1 layer is greater than 0.1 μm and 0.50 μm or less. can do. In particular, if the area ratio obtained by multiplying the draw ratios in the longitudinal direction and the width direction is 9 to 15 times, the durability and film resistance of the resulting polyester film can be improved while maintaining good productivity. preferable. In addition, it is preferable to include a step of cooling with a roll group having a temperature of 20 to 50 ° C. between the steps (7) and (8) because productivity can be improved.
　（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むと、Ｐ１層に形成された表面形状をそのまま維持することが容易となる。 When the biaxially oriented polyester film obtained in step (8) is heat treated at 205-240 ° C. and includes a step of relaxing 0-10% in the width direction, the surface shape formed in the P1 layer is maintained as it is. Easy to do.
　次に、（は）に係る方法ついて説明する。 Next, the method related to (ha) will be described.
　（は）に係る方法は、（い）を満たす方法で未延伸ポリエステルフィルムを得た後、（ろ）を満たす方法で延伸、熱処理を行うものである。（は）を満たす製造方法は、安定的に、かつ、生産性良く、本発明のポリエステルフィルムを得ることができるため好ましい。 In the method according to (ha), after an unstretched polyester film is obtained by a method satisfying (ii), stretching and heat treatment are performed by a method satisfying (ro). A production method satisfying () is preferable because the polyester film of the present invention can be obtained stably and with good productivity.
　本発明のポリエステルフィルムは、耐膜減性、耐久性に優れるため、太陽電池バックシート用途に好ましく用いることができる。なお、本発明のポリエステルフィルムが、Ｐ１層、Ｐ２層からなる積層ポリエステルフィルムである場合は、Ｐ１層を太陽電池バックシートの最外層（図１の符号６側）となる態様で用いることが好ましい。 Since the polyester film of the present invention is excellent in film resistance and durability, it can be preferably used for solar battery backsheets. In addition, when the polyester film of this invention is a laminated polyester film which consists of P1 layer and P2 layer, it is preferable to use P1 layer in the aspect used as the outermost layer (code | symbol 6 side of FIG. 1) of a solar cell backsheet. .
　また、本発明のポリエステルフィルムを用いた太陽電池バックシートを含む太陽電池は、長期にわたりその性能を維持することができ、耐用年数を長くすることができる。 Moreover, the solar cell including the solar cell back sheet using the polyester film of the present invention can maintain its performance over a long period of time and can prolong its useful life.
　〔特性の測定方法および評価方法〕
　（１）固有粘度
　オルトクロロフェノール１００ｍｌに、測定試料（ポリエステル樹脂（原料）又はポリエステルフィルム）を溶解させ（溶液濃度Ｃ（測定試料重量／溶液体積）＝１．２ｇ／１００ｍｌ）、その溶液の２５℃での粘度をオストワルド粘度計を用いて測定した。また、同様に溶媒の粘度を測定した。得られた溶液粘度、溶媒粘度を用いて、下記式（Ｉ）により、［η］を算出し、得られた値をもって固有粘度（ＩＶ）とした。
ηｓｐ／Ｃ＝［η］＋Ｋ［η］２・Ｃ　・・・（Ｉ）
（ここで、ηｓｐ＝（溶液粘度／溶媒粘度）―１、Ｋはハギンス定数（０．３４３とする）である。）
なお、測定試料を溶解させた溶液に無機粒子などの不溶物がある場合は、以下の方法を用いて測定を行った。
ｉ）オルトクロロフェノール１００ｍＬに測定試料を溶解させ、溶液濃度が１．２ｇ／１００ｍＬよりも濃い溶液を作成する。ここで、オルトクロロフェノールに供した測定試料の重量を測定試料重量とする。
ｉｉ）次に、不溶物を含む溶液を濾過し、不溶物の重量測定と、濾過後の濾液の体積測定を行う。
ｉｉｉ）濾過後の濾液にオルトクロロフェノールを追加して、（測定試料重量（ｇ）－不溶物の重量（ｇ））／（濾過後の濾液の体積（ｍＬ）＋追加したオルトクロロフェノールの体積（ｍＬ））が、１．２ｇ／１００ｍＬとなるように調整する。
（例えば、測定試料重量２．０ｇ／溶液体積１００ｍＬの濃厚溶液を作成したときに、該溶液を濾過したときの不溶物の重量が０．２ｇ、濾過後の濾液の体積が９９ｍＬであった場合は、オルトクロロフェノールを５１ｍＬ追加する調整を実施する。（（２．０ｇ－０．２ｇ）／（９９ｍＬ＋５１ｍＬ）＝１．２ｇ／１００ｍＬ））
ｉｖ）ｉｉｉ）で得られた溶液を用いて、２５℃での粘度をオストワルド粘度計を用いて測定し、得られた溶液粘度、溶媒粘度を用いて、上記式（Ｃ）により、［η］を算出し、得られた値をもって固有粘度（ＩＶ）とする。 [Measurement method and evaluation method of characteristics]
(1) Intrinsic viscosity In 100 ml of orthochlorophenol, a measurement sample (polyester resin (raw material) or polyester film) is dissolved (solution concentration C (measurement sample weight / solution volume) = 1.2 g / 100 ml). The viscosity at 0 ° C. was measured using an Ostwald viscometer. Similarly, the viscosity of the solvent was measured. [Η] was calculated according to the following formula (I) using the obtained solution viscosity and solvent viscosity, and the obtained value was defined as intrinsic viscosity (IV).
ηsp / C = [η] + K [η] 2 · C (I)
(Where ηsp = (solution viscosity / solvent viscosity) −1, K is the Huggins constant (assuming 0.343))
In addition, when there existed insoluble matters, such as inorganic particles, in the solution in which the measurement sample was dissolved, the measurement was performed using the following method.
i) A measurement sample is dissolved in 100 mL of orthochlorophenol to prepare a solution having a solution concentration higher than 1.2 g / 100 mL. Here, let the weight of the measurement sample used for orthochlorophenol be a measurement sample weight.
ii) Next, the solution containing the insoluble matter is filtered, and the weight of the insoluble matter and the volume of the filtrate after filtration are measured.
iii) Orthochlorophenol was added to the filtrate after filtration, and (measured sample weight (g) −insoluble matter weight (g)) / (volume of filtrate after filtration (mL) + volume of orthochlorophenol added) (ML)) is adjusted to 1.2 g / 100 mL.
(For example, when a concentrated solution having a measurement sample weight of 2.0 g / solution volume of 100 mL was prepared, the weight of insoluble matter when the solution was filtered was 0.2 g, and the filtrate volume after filtration was 99 mL Adjusts by adding 51 mL of orthochlorophenol ((2.0 g-0.2 g) / (99 mL + 51 mL) = 1.2 g / 100 mL))
iv) Using the solution obtained in iii), the viscosity at 25 ° C. is measured using an Ostwald viscometer, and the obtained solution viscosity and solvent viscosity are used to calculate [η] according to the above formula (C). And the obtained value is taken as the intrinsic viscosity (IV).
　（２）末端カルボキシル基量
　末端カルボキシル基量については、Ｍａｕｌｉｃｅの方法に準じて、以下の方法にて測定した。（文献Ｍ．Ｊ． Ｍａｕｌｉｃｅ， Ｆ． Ｈｕｉｚｉｎｇａ，  Ａｎａｌ．Ｃｈｉｍ．Ａｃｔａ，２２  ３６３（１９６０））
測定試料（ポリエステル樹脂（原料）またはポリエステルフィルム）２ｇをｏ－クレゾール／クロロホルム（重量比７／３）５０ｍＬに温度８０℃にて溶解し、０．０５ＮのＫＯＨ／メタノール溶液によって滴定し、末端カルボキシル基濃度を測定し、当量／ポリエステル１ｔの値で示した。なお、滴定時の指示薬はフェノールレッドを用いて、黄緑色から淡紅色に変化したところを滴定の終点とした。なお、測定試料を溶解させた溶液に無機粒子などの不溶物がある場合は、溶液を濾過して不溶物の重量測定を行い、不溶物の重量を測定試料重量から差し引いた値を測定試料重量とする補正を実施した。 (2) Terminal carboxyl group amount The terminal carboxyl group amount was measured by the following method according to the method of Malice. (Document M. J. Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)).
2 g of a measurement sample (polyester resin (raw material) or polyester film) was dissolved in 50 mL of o-cresol / chloroform (weight ratio 7/3) at a temperature of 80 ° C., and titrated with a 0.05 N KOH / methanol solution to obtain a terminal carboxyl. The base concentration was measured and indicated as equivalent / polyester 1t. In addition, the indicator at the time of titration used phenol red, and the place where it changed from yellowish green to light red was set as the end point of titration. If there is insoluble matter such as inorganic particles in the solution in which the measurement sample is dissolved, the solution is filtered to measure the weight of the insoluble matter, and the value obtained by subtracting the weight of the insoluble matter from the measurement sample weight The following correction was made.
　（３）Ｐ１層、Ｐ２層の厚み
　ミクロトームを用いて、ポリエステルフィルムの表面に対して垂直方向に切削した小片を作成し、その断面を電界放射走査型電子顕微鏡ＪＳＭ－６７００Ｆ（日本電子（株）製）を用いて１０００～５０００倍に拡大観察して撮影した。その断面写真よりＰ１層、Ｐ２層の厚みを拡大倍率から逆算して求めた。なお、サンプル数はｎ＝１０にて実施し、その平均値とした。 (3) Thickness of P1 layer and P2 layer Using a microtome, a small piece cut in a direction perpendicular to the surface of the polyester film was prepared, and the cross section was taken as a field emission scanning electron microscope JSM-6700F (JEOL Ltd.) ) And magnified to 1000 to 5000 times. The thicknesses of the P1 layer and the P2 layer were calculated from the cross-sectional photographs by reverse calculation from the magnification. Note that the number of samples was n = 10, and the average value was used.
　（４）表面粗さ（Ｒａ）
触針法の高精細微細形状測定器を用いてＪＩＳ－Ｂ０６０１（１９９４年）に準拠して、下記条件にてポリエステルフィルムの表面粗さ（Ｒａ）を測定した。
測定装置：３次元微細形状測定器(小坂研究所製　型式ＥＴ－４０００Ａ)
解析機器：３次元表面粗さ解析システム（小坂研究所製　型式ＴＤＡ－３１）
触針:先端半径０．５μｍＲ、径２μｍ、ダイヤモンド製
針圧：１００μＮ
測定方向・算出法:フィルム長手方向、フィルム幅方向を各々１０回測定する。その２０回の測定の平均値を表面粗さとする。 (4) Surface roughness (Ra)
The surface roughness (Ra) of the polyester film was measured under the following conditions according to JIS-B0601 (1994) using a high-definition fine shape measuring instrument of the stylus method.
Measuring device: 3D fine shape measuring instrument (model ET-4000A manufactured by Kosaka Laboratory)
Analysis equipment: 3D surface roughness analysis system (Model TDA-31, manufactured by Kosaka Laboratory)
Stylus: Tip radius 0.5 μm R, Diameter 2 μm, Diamond needle pressure: 100 μN
Measurement direction / calculation method: The film longitudinal direction and the film width direction are each measured 10 times. The average value of the 20 measurements is defined as the surface roughness.
　（５）酸化チタン含有量
　ＩＣＰ発光分析装置（パーキンエルマー社製：ＯＰＴＩＭＡ ４３００ ＤＶ）を用いて、以下の方法によって、フィルムに含まれるチタン元素量を求め、得られたチタン元素量から酸化チタン含有量を換算した。なお、ポリエステルフィルムが積層ポリエステルフィルムである場合、（３）の方法でフィルム各層の厚みを確認した後、積層ポリエステルフィルムの表面を削り、各層から測定サンプルを採取し、各層に含有する酸化チタン含有量を求めた。
ｉ）採取したサンプルを白金るつぼに秤取り、硫酸を添加し、ホットプレートとバーナーを用いて炭化処理を行う。
ｉｉ）さらに電気炉にて５５０℃、２時間加熱を行い、灰化処理を行う。
ｉｉｉ）得られた灰化物に炭酸ナトリウム－ほう酸の混合融剤を加え、バーナーで加熱して融解処理を行い、放冷後、希硝酸と過酸化水素水を添加して、溶解させたものを試料溶液として、ＩＣＰ発光分析装置に導入し、チタン元素の定量を行う。 (5) Titanium oxide content Using an ICP emission analyzer (manufactured by Perkin Elmer: OPTIMA 4300 DV), the amount of titanium element contained in the film is determined by the following method, and the titanium oxide content is obtained from the obtained titanium element amount. The amount was converted. In addition, when the polyester film is a laminated polyester film, after confirming the thickness of each layer of the film by the method (3), the surface of the laminated polyester film is shaved, a measurement sample is taken from each layer, and the titanium oxide contained in each layer The amount was determined.
i) The collected sample is weighed in a platinum crucible, sulfuric acid is added, and carbonization is performed using a hot plate and a burner.
ii) Further, ashing is performed by heating at 550 ° C. for 2 hours in an electric furnace.
iii) A mixed flux of sodium carbonate and boric acid is added to the resulting incinerated product, and the mixture is heated with a burner for melting treatment. After standing to cool, diluted nitric acid and hydrogen peroxide solution are added and dissolved. The sample solution is introduced into an ICP emission analyzer, and the titanium element is quantified.
　（６）耐湿熱性
　ポリエステルフィルムを測定片の形状１０ｍｍ×２００ｍｍに切り出した後、高度加速寿命試験装置プレッシャークッカー（エスペック（株）製）にて、温度１２５℃、相対湿度１００％ＲＨの条件下にて４８時間処理を行い、その後、ＡＳＴＭ－Ｄ８８２（１９９７）に基づいて破断伸度を測定した。なお、測定はチャック間５０ｍｍ、引っ張り速度３００ｍｍ／ｍｉｎ、測定回数ｎ＝５とし、また、シートの長手方向、幅方向のそれぞれについて測定した後、その平均値を湿熱試験後の破断伸度とした。得られた湿熱試験後の破断伸度から、耐湿熱性を以下のように判定した。
湿熱試験後の破断伸度が湿熱試験前の破断伸度の４０％以上の場合：Ａ
湿熱試験後の破断伸度が湿熱試験前の破断伸度の２０％以上４０％未満の場合：Ｂ
湿熱試験後の破断伸度が湿熱試験前の破断伸度の１０％以上２０％未満の場合：Ｃ
湿熱試験後の破断伸度が湿熱試験前の破断伸度の１０％未満の場合：Ｄ
　耐湿熱性はＡ～Ｃが良好であり、その中でもＡが最も優れている。 (6) Heat-and-moisture resistance After cutting the polyester film into a measurement piece shape of 10 mm × 200 mm, it was subjected to the conditions of a temperature of 125 ° C. and a relative humidity of 100% RH with a highly accelerated life tester pressure cooker (manufactured by Espec Corp.). For 48 hours, and then the elongation at break was measured based on ASTM-D882 (1997). Note that the measurement was performed between the chuck 50 mm, the pulling speed 300 mm / min, the number of measurements n = 5, and after measuring for each of the longitudinal direction and the width direction of the sheet, the average value was defined as the breaking elongation after the wet heat test. . From the elongation at break after the obtained wet heat test, the wet heat resistance was determined as follows.
When the breaking elongation after the wet heat test is 40% or more of the breaking elongation before the wet heat test: A
When the breaking elongation after the wet heat test is 20% or more and less than 40% of the breaking elongation before the wet heat test: B
When the breaking elongation after the wet heat test is 10% or more and less than 20% of the breaking elongation before the wet heat test: C
When the breaking elongation after the wet heat test is less than 10% of the breaking elongation before the wet heat test: D
The wet heat resistance is good in A to C, and A is the best among them.
　（７）部分放電電圧
　下記の測定法に基づき、Ｐ１層を上にして部分放電を測定して電気絶縁性を評価した。
準拠規格：ＩＥＣ６０６６４/Ａ２:２００２　４．１．２．４
部分放電試験機：菊水電子工業社製、ＫＰＤ２０５０
最大印加電圧：１．６ｋＶ
最大印加電圧時間：５秒
開始電圧電荷しきい値：１.０ｐＣ
消滅電圧電荷しきい値：１．０ｐＣ
試験時間：２２．０ｓｅｃ
測定パターン：台形
　（８）耐久性試験後の特性
　ＪＩＳＫ７３５０－２(２００８年）に準じて、以下の条件にて、耐久性試験を実施する。その後、各特性を測定した。
＜耐久性試験＞
（ｉ）　温度６５℃、相対湿度５０％ＲＨの条件下で、キセノンランプ（スガ試験機製、ＳＣ７５０）を用いて、ポリエステルフィルムのＰ１層側の面を、放射照度１８０Ｗ／ｍ２にて、１０２分間（ｔ－１）照射する。
（ｉｉ）　（ｉ）の後、キセノンランプの照射を続けながら、１６℃±５℃の水シャワーをＰ１層面に２．１Ｌ±０．１ｍＬ／分の量で１８分間（ｔ－２）かける。
なお、（ｔ－１）＋（ｔ－２）＝１２０分となるようにする。
（ｉｉｉ）　（ｉ）（ｉｉ）を１５００回繰り返す。 (7) Partial Discharge Voltage Based on the following measurement method, partial discharge was measured with the P1 layer facing up to evaluate electrical insulation.
Conformity standard: IEC60664 / A2: 2002 4.1.2.4
Partial discharge tester: KPD2050, manufactured by Kikusui Electronics Corporation
Maximum applied voltage: 1.6 kV
Maximum applied voltage time: 5 seconds Start voltage Charge threshold: 1.0 pC
Vanishing voltage charge threshold: 1.0 pC
Test time: 22.0 sec
Measurement pattern: trapezoid (8) Characteristics after durability test Durability test is performed under the following conditions in accordance with JISK 7350-2 (2008). Thereafter, each characteristic was measured.
<Durability test>
(I) Using a xenon lamp (manufactured by Suga Test Instruments, SC750) under the conditions of a temperature of 65 ° C. and a relative humidity of 50% RH, the surface on the P1 layer side of the polyester film is 102 at an irradiance of 180 W / m 2 . Irradiate for (t-1) minutes.
(Ii) After (i), while continuing irradiation with a xenon lamp, a water shower at 16 ° C. ± 5 ° C. is applied to the P1 layer surface at an amount of 2.1 L ± 0.1 mL / min for 18 minutes (t−2).
Note that (t-1) + (t-2) = 120 minutes.
(Iii) Repeat (i) and (ii) 1500 times.
　（８－１）耐久性試験後のＰ１層の厚みの減少量
　耐久性試験後のＰ１層の厚みを、（３）に方法にて測定した後、耐久性試験前のＰ１層の厚み（μｍ）－耐久性試験後のＰ１層の厚み（μｍ）を、耐久性試験後のＰ１層の厚みの減少量（μｍ）として求めた。 (8-1) Amount of decrease in the thickness of the P1 layer after the durability test After the thickness of the P1 layer after the durability test was measured by the method in (3), the thickness of the P1 layer before the durability test (μm The thickness (μm) of the P1 layer after the durability test was determined as the amount of decrease in the thickness (μm) of the P1 layer after the durability test.
　（８－２）耐久性試験後の伸度保持率
　耐久性試験前と後の破断伸度をＡＳＴＭ－Ｄ８８２（１９９７）に基づいて測定した。なお、測定はチャック間５０ｍｍ、引っ張り速度３００ｍｍ／ｍｉｎ、測定回数ｎ＝５とし、また、シートの長手方向、幅方向のそれぞれについて測定した後、その平均値をそれぞれの破断伸度とした。耐久性試験後の破断伸度（％）／耐久性試験前の破断伸度（％）×１００を、耐久性試験後の伸度保持率（％）として求め、以下により評価した。
耐久性試験後の伸度保持率が６０％以上の場合：Ａ
耐久性試験後の伸度保持率が４０％以上６０％未満の場合：Ｂ
耐久性試験後の伸度保持率が２０％以上４０％未満の場合：Ｃ
耐久性試験後の伸度保持率が２０％未満の場合：Ｄ
　評価Ａ～Ｂが良好である。 (8-2) Elongation retention after durability test The elongation at break before and after the durability test was measured based on ASTM-D882 (1997). In addition, the measurement was performed between the chucks of 50 mm, the pulling speed of 300 mm / min, and the number of times of measurement n = 5. The elongation at break (%) after the durability test / the elongation at break (%) before the durability test × 100 was determined as the elongation retention (%) after the durability test, and was evaluated as follows.
When the elongation retention after the durability test is 60% or more: A
When the elongation retention after the durability test is 40% or more and less than 60%: B
When the elongation retention after the durability test is 20% or more and less than 40%: C
When the elongation retention after the durability test is less than 20%: D
Evaluations A to B are good.
　（８－３）耐久性試験後の部分放電電圧維持率
　耐久性試験後の部分放電電圧を、（７）に方法にて測定した後、耐久性試験後の部分放電電圧（Ｖ）／耐久性試験前の部分放電電圧（Ｖ）×１００を、耐久性試験後の部分放電電圧維持率（％）として求めた。 (8-3) Partial discharge voltage maintenance ratio after durability test After measuring the partial discharge voltage after the durability test by the method in (7), the partial discharge voltage (V) after the durability test / durability The partial discharge voltage (V) × 100 before the test was determined as the partial discharge voltage maintenance ratio (%) after the durability test.
　（９）Ｐ１層を構成するポリエステル樹脂のガラス転移温度（Ｔｇ）
　ＪＩＳ　Ｋ７１２１（１９９９）に準じて、セイコー電子工業（株）製示差走査熱量測定装置”ロボットＤＳＣ－ＲＤＣ２２０”を、データ解析にはディスクセッション”ＳＳＣ／５２００”を用いて、下記の要領にて、測定を実施する。 (9) Glass transition temperature (Tg) of the polyester resin constituting the P1 layer
In accordance with JIS K7121 (1999), the differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. and the disk session “SSC / 5200” for data analysis were used as follows. Perform the measurement.
　ポリエステルフィルムからミクロトームを用いてＰ１層を構成する樹脂を削りだし、測定試料に供する。得られた測定試料５ｍｇをサンプルパンに秤量し、２５℃から３００℃まで２０℃／分の昇温速度で加熱し（１ｓｔＲＵＮ）、その状態で５分間保持し、次いで２５℃以下となるよう急冷する。直ちに引き続いて、再度２５℃から２０℃／分の昇温速度で３００℃まで昇温を行って測定を行い、２ｎｄＲＵＮの示差走査熱量測定チャート（縦軸を熱エネルギー、横軸を温度とする）を得る。当該２ｎｄＲＵＮの示差走査熱量測定チャートにおいて、ガラス転移の階段状の変化部分において、各ベースラインの延長した直線から縦軸方向に等距離にある直線とガラス転移の階段状の変化部分の曲線とが交わる点からガラス転移温度（Ｔｇ）（℃）を求める。２以上のガラス転移の階段状の変化部分が観測される場合は、それぞれについて、ガラス転移温度を求め、それらの温度を平均した値を試料のガラス転移温度（Ｔｇ）（℃）とする。 The resin constituting the P1 layer is shaved from the polyester film using a microtome and used as a measurement sample. 5 mg of the obtained measurement sample was weighed in a sample pan, heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. To do. Immediately thereafter, the temperature was increased again from 25 ° C. to 300 ° C. at a rate of temperature increase of 20 ° C./minute, and a 2ndRUN differential scanning calorimetry chart (the vertical axis represents thermal energy and the horizontal axis represents temperature) Get. In the 2ndRUN differential scanning calorimetry chart, in the step change portion of the glass transition, a straight line that is equidistant from the extended straight line of each base line in the vertical axis direction and a curve of the step change portion of the glass transition are The glass transition temperature (Tg) (° C.) is determined from the intersecting point. When two or more stepwise changes in glass transition are observed, the glass transition temperature is obtained for each, and the average of these temperatures is taken as the glass transition temperature (Tg) (° C.) of the sample.
　（１０）製膜性
　製膜性は、製膜する際のフィルム破れの頻度で、以下の通り判定した。
フィルム破れが１回／１日以上：Ａ
フィルム破れが１回／１２時間以上１日未満：Ｂ
フィルム破れが１回／５時間以上１２時間未満：Ｃ
フィルム破れが１回／５時間未満：Ｄ
製膜性はＡが良好であり、ＢＣＤの順に悪くなっていく。 (10) Film-forming property The film-forming property was determined as follows according to the frequency of film breakage during film formation.
Film breaks once / day or more: A
Film breaks once / 12 hours or more and less than 1 day: B
Film breaks once / 5 hours or more and less than 12 hours: C
Film tear once less than 5 hours: D
As for the film forming property, A is good and becomes worse in the order of BCD.
　（１１）太陽電池パネルの出力維持特性
　ポリエステルフィルムのＰ１層（表面粗さ（Ｒａ）が０．１０μｍより大きく０．５０μｍ以下であるフィルム面）の反対側のフィルム表面に、ポリエステル接着剤主剤ＬＸ７０３ＶＬとポリイソシアネート硬化剤ＫＲ９０（いずれも大日本インキ化学工業（株）製）を重量比で１５：１に混合した接着剤（乾燥重量４ｇ／ｍ２）を、塗布した。ついで、これと、ガスバリアフィルムであるアルミナ透明蒸着フィルム（東レフィルム加工（株）製バリアロックス（登録商標）、１２μｍ厚）とをドライラミネートし、太陽電池用バックシートを作成した。太陽電池用バックシートのガスバリアフィルムをラミネートした側の上にエチレン酢酸ビニル共重合樹脂シ－ト、太陽電池セル、および光透過性ガラス板を積層し、ラミネ－ト工程で加熱圧縮することによって一体化し、太陽電池モジュ－ルを形成する。さらに、太陽電池モジュールを取り出し、太陽電池パネル用ラインのパネル投入工程に供給し、プライマー塗布工程において、アルミフレームとの接着面にプライマーを塗布する。続いて乾燥工程にてプライマーの乾燥時間として約１分間放置した後、搬出工程からフレーム用ライン側に搬出される。一方フレーム用ライン側では、組み立て済のアルミフレームを投入する。アルミフレームは太陽電池セルを配置した太陽電池モジュールの受光面と背設する面側を支持するための突片を有するとともに、前記太陽電池モジュールの端部全周に亙って設け得る形状で、かつ太陽電池モジュールの受光面側を開放状態とした構造を有する。続いて、プライマー塗布済の太陽電池モジュールを搬送し、パネル貼り合わせ工程にてプライマーを塗布したアルミフレームと太陽電池モジュールを載置する（太陽電池パネル接着工程）。最後に必要に応じてモール取り付け工程において、モールを取り付け太陽電池パネルを作製する。以上の工程で得られた太陽電池パネルは、パネルの裏側が太陽電池バックシートで構成されており、該太陽電池バックシートの最表層にはＰ１層が位置するものである。作製した太陽電池パネルの裏面に破れやヒビ割れがないことを確認し、太陽電池パネルを温度８５℃、相対湿度８５％ＲＨの条件下にて３０００時間処理を行い、裏面の外観と出力低下（ＪＩＳ－Ｃ８９１３（１９９８））を下記で評価した。 (11) Output maintenance characteristics of solar cell panel Polyester adhesive main agent LX703VL on the film surface opposite to the P1 layer of polyester film (film surface with surface roughness (Ra) greater than 0.10 μm and 0.50 μm or less) And a polyisocyanate curing agent KR90 (both manufactured by Dainippon Ink & Chemicals, Inc.) in a weight ratio of 15: 1 were applied (dry weight 4 g / m 2 ). Next, this was dry-laminated with an alumina transparent vapor-deposited film (Barrier Rocks (registered trademark) manufactured by Toray Film Processing Co., Ltd., 12 μm thick) as a gas barrier film to prepare a back sheet for solar cells. An ethylene vinyl acetate copolymer resin sheet, a solar cell, and a light-transmitting glass plate are laminated on the side of the solar cell backsheet laminated with the gas barrier film, and are integrated by heating and compressing in the lamination process. To form a solar cell module. Further, the solar cell module is taken out and supplied to the panel loading step of the solar cell panel line. In the primer coating step, the primer is coated on the adhesive surface with the aluminum frame. Subsequently, the primer is left for about 1 minute as the drying time of the primer in the drying process, and then is carried out from the carry-out process to the frame line side. On the other hand, on the frame line side, an assembled aluminum frame will be introduced. The aluminum frame has a projecting piece for supporting the light receiving surface of the solar cell module on which the solar cells are arranged and the surface side to be installed on the back, and can be provided over the entire periphery of the end of the solar cell module, And it has the structure which made the light-receiving surface side of the solar cell module the open state. Subsequently, the solar cell module coated with the primer is transported, and the aluminum frame and the solar cell module coated with the primer in the panel bonding step are placed (solar cell panel bonding step). Finally, in the molding attaching process, a molding is attached as necessary to produce a solar cell panel. In the solar cell panel obtained by the above steps, the back side of the panel is constituted by a solar cell back sheet, and the P1 layer is located on the outermost layer of the solar cell back sheet. After confirming that the back surface of the produced solar cell panel was not torn or cracked, the solar cell panel was treated for 3000 hours under conditions of a temperature of 85 ° C. and a relative humidity of 85% RH, and the appearance and output of the back surface were reduced ( JIS-C8913 (1998)) was evaluated as follows.
　破れ、ヒビ割れがなく出力が低下しない（出力の低下量が、初期出力量に対して１０％未満）；Ａ
　破れ、ヒビ割れが若干見られ、一部出力が低下をする（出力の低下量が、初期出力量に対して１０％以上３０％未満）；Ｂ
　破れ、ヒビ割れが見られ、出力が大きく低下（出力の低下量が、初期出力量に対して３０％以上５０％未満）；Ｃ
　破れ、ヒビ割れが大きく、出力がほとんどしない（出力の低下量が、初期出力量に対して５０％以上８０％未満）；Ｄ
　破れ、ヒビ割れがひどく、出力しない（出力の低下量が、初期出力量に対して８０％以上）；Ｅ
　Ａ～Ｃが良好であり、その中でもＡが最も優れている。 No tearing, cracking, and output does not decrease (output decrease is less than 10% of initial output); A
Tearing, some cracks are seen, and some output decreases (output decrease is 10% or more and less than 30% with respect to initial output); B
Torn, cracked, and greatly reduced output (output reduction is 30% or more and less than 50% of initial output); C
Tearing, large cracks, almost no output (output reduction is 50% or more and less than 80% of initial output); D
Tearing, cracking severe, no output (output decrease is more than 80% of initial output); E
A to C are good, and among them, A is the best.
　以下、本発明について実施例を挙げて説明するが、本発明は必ずしもこれらに限定されるものではない。 Hereinafter, the present invention will be described with reference to examples, but the present invention is not necessarily limited thereto.
　（ポリエステル系樹脂原料）
　＜ＰＥＴ原料Ａ＞
ジカルボン酸成分としてテレフタル酸１００質量部、ジオール成分としてエチレングリコール１００質量部を用い、触媒として酢酸マグネシウム、三酸化アンチモン、亜リン酸を用いて重縮合反応を行った。次いで、得られたポリエチレンテレフタレートを１６０℃で６時間乾燥、結晶化させたのち、２２０℃、真空度０．３Ｔｏｒｒ、９時間の固相重合を行い、融点２５５℃、固有粘度０．８０ｄｌ／ｇ、末端カルボキシル基量１０当量／トン、Ｔｇ８０℃のＰＥＴ原料Ａを得た。 (Polyester resin raw material)
<PET raw material A>
A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Next, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours, and then subjected to solid phase polymerization at 220 ° C. and a vacuum degree of 0.3 Torr for 9 hours to have a melting point of 255 ° C. and an intrinsic viscosity of 0.80 dl / g. A PET raw material A having a terminal carboxyl group amount of 10 equivalents / ton and a Tg of 80 ° C. was obtained.
　＜ＰＥＴ原料Ｂ＞
　ジカルボン酸成分としてテレフタル酸１００質量部、ジオール成分としてエチレングリコール１００質量部を用い、触媒として酢酸マグネシウム、三酸化アンチモン、亜リン酸を用いて重縮合反応を行った。次いで、得られたポリエチレンテレフタレートを１６０℃で６時間乾燥、結晶化させ、融点２５５℃、固有粘度０．６５ｄｌ／ｇ、末端カルボキシル基量２５当量／トン、Ｔｇ８０℃のＰＥＴ原料Ｂを得た。 <PET raw material B>
A polycondensation reaction was performed using 100 parts by mass of terephthalic acid as the dicarboxylic acid component, 100 parts by mass of ethylene glycol as the diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. Subsequently, the obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours to obtain a PET raw material B having a melting point of 255 ° C., an intrinsic viscosity of 0.65 dl / g, a terminal carboxyl group amount of 25 equivalents / ton, and a Tg of 80 ° C.
　＜ＰＥＴ原料Ｃ（ＰＥＴ－Ａベース酸化チタン／ＣＨＴマスター）＞
　上記によって得られたＰＥＴ原料Ａと、平均粒子径２１０ｎｍのルチル型酸化チタン粒子と、１，４－シクロヘキシレンジメチレンテレフタレートをそれぞれ５重量％、５０重量％、４５重量％の比率で混ぜ合わせ、ベントした２９０℃の押出機内で溶融混練し、ＰＥＴ－Ａベース酸化チタンマスター（ＰＥＴ原料Ｃ）を作製した。但し、実施例６には、ルチル型酸化チタンではなく、アナターゼ型酸化チタンを用いたＰＥＴ原料Ｃを用いた。 <PET raw material C (PET-A base titanium oxide / CHT master)>
The PET raw material A obtained above, rutile-type titanium oxide particles having an average particle diameter of 210 nm, and 1,4-cyclohexylenedimethylene terephthalate were mixed at a ratio of 5% by weight, 50% by weight, and 45% by weight, respectively. The mixture was melt-kneaded in a vented 290 ° C. extruder to prepare a PET-A base titanium oxide master (PET raw material C). However, in Example 6, PET raw material C using anatase type titanium oxide instead of rutile type titanium oxide was used.
　＜ＰＥＴ原料Ｄ（ＰＥＴ－Ａベース酸化チタンマスター）＞
　上記によって得られたＰＥＴ原料Ａ１００重量部と、平均粒子径２１０ｎｍのルチル型酸化チタン粒子１００重量部をベントした２９０℃の押出機内で溶融混練し、ＰＥＴ－Ａベース酸化チタンマスター（ＰＥＴ原料Ｄ）を作製した。 <PET raw material D (PET-A base titanium oxide master)>
A PET-A base titanium oxide master (PET raw material D) was melt-kneaded in an extruder at 290 ° C. in which 100 parts by weight of the PET raw material A obtained above and 100 parts by weight of rutile titanium oxide particles having an average particle diameter of 210 nm were vented. Was made.
　＜ＰＥＴ原料Ｅ（ＰＥＴ－ＡベースＣＨＴマスター）＞
　上記によって得られたＰＥＴ原料Ａ１００重量部と、１，４－シクロヘキシレンジメチレンテレフタレート１００重量部をベントした２９０℃の押出機内で溶融混練し、ＰＥＴ－ＡベースＣＨＴマスター（ＰＥＴ原料Ｅ）を作製した。 <PET raw material E (PET-A base CHT master)>
A PET-A base CHT master (PET raw material E) was prepared by melt-kneading in a 290 ° C. extruder vented with 100 parts by weight of the PET raw material A obtained above and 100 parts by weight of 1,4-cyclohexylenedimethylene terephthalate. did.
　（実施例１～１４）
　１８０℃で２時間真空乾燥したＰＥＴ原料Ａ～Ｅを、表に記載の割合（表中の値は、原料全体の重量を１００重量％としたとき、原料全体に対して各原料がしめる割合である）で調合し２８０℃の押出機内で溶融混練し、Ｔダイ口金に導入した。 (Examples 1 to 14)
PET raw materials A to E vacuum-dried at 180 ° C. for 2 hours are in the proportions shown in the table (the values in the table are the proportions of each raw material relative to the whole raw material when the weight of the whole raw material is 100% by weight) The mixture was melt kneaded in an extruder at 280 ° C. and introduced into a T die die.
　このとき実施例１は単層で吐出し、それ以外は、原料を２台の押出機でそれぞれ別に溶融混練し、２台の押出機からフィードブロックを介してＴダイ口金に導入してＰ１／Ｐ２の積層シートを得る。またこの際、Ｐ１／Ｐ２の積層比が４／１となるように２台の押出機のスクリュー回転数を調整した。 At this time, Example 1 was discharged in a single layer, and otherwise, the raw materials were separately melt-kneaded by two extruders, introduced into the T die die from the two extruders via feed blocks, and P1 / A laminated sheet of P2 is obtained. At this time, the screw rotational speeds of the two extruders were adjusted so that the stacking ratio of P1 / P2 was 4/1.
　次いで、Ｔダイ口金よりシート状に溶融押出して表面温度１８℃に保たれた冷却ドラム上に静電印加法で密着冷却固化させて、未延伸ポリエステルフィルムを得た。この時、冷却ドラムに接触している時間（滞留時間）が３０秒間となるように冷却ドラムの回転速度を調整しておく。 Subsequently, the sheet was melt-extruded into a sheet form from a T-die die and adhered and cooled and solidified by an electrostatic application method on a cooling drum maintained at a surface temperature of 18 ° C. to obtain an unstretched polyester film. At this time, the rotation speed of the cooling drum is adjusted so that the time of contact with the cooling drum (residence time) is 30 seconds.
　続いて、該未延伸ポリエステルフィルムを８０℃の温度に加熱したロール群で予熱した後、８８℃の温度に加熱したロールと２５℃の温度に調整したロール間で３倍の速度差をつけることで長手方向（縦方向）に３倍に延伸した後、２５℃の温度のロール群で冷却して一軸延伸ポリエステルフィルムを得た。この時、表面粗さ１．０μｍの延伸ロールと延伸ニップロールを用い、ニップ圧を０．５ＭＰａにて実施した。 Subsequently, after preheating the unstretched polyester film with a group of rolls heated to a temperature of 80 ° C., a three-fold speed difference is created between the roll heated to a temperature of 88 ° C. and the roll adjusted to a temperature of 25 ° C. Then, the film was stretched 3 times in the longitudinal direction (longitudinal direction) and then cooled with a roll group having a temperature of 25 ° C. to obtain a uniaxially stretched polyester film. At this time, using a stretching roll having a surface roughness of 1.0 μm and a stretching nip roll, the nip pressure was 0.5 MPa.
　得られた一軸延伸ポリエステルフィルムの両端をクリップで把持しながらテンター内の８０℃の温度の予熱ゾーンに導き、引き続き連続的に９０℃に保たれた加熱ゾーンで長手方向に直角な方向（幅方向）に３．５倍に延伸した。さらに引き続いて、テンター内の熱処理ゾーンで２１５℃で２０秒間の熱処理を施し、さらに２１５℃で７％幅方向に弛緩処理を行った。次いで均一に徐冷を行い、全体厚みが２５０μｍのポリエステルフィルムを得た。 The both ends of the obtained uniaxially stretched polyester film are guided to a preheating zone at a temperature of 80 ° C. in a tenter while holding both ends with a clip, and then in a heating zone maintained continuously at 90 ° C. in a direction perpendicular to the longitudinal direction (width direction) ) Was stretched 3.5 times. Subsequently, heat treatment was performed at 215 ° C. for 20 seconds in the heat treatment zone in the tenter, and further, relaxation treatment was performed in the 7% width direction at 215 ° C. Then, it was gradually cooled gradually to obtain a polyester film having a total thickness of 250 μm.
　得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例１５～１８）
　吐出速度、ドラム速度を変更してドラムでの滞留時間をそれぞれ、１５、２０、１２０．１２５秒に変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Examples 15 to 18)
A polyester film was obtained in the same manner as in Example 2 except that the discharge speed and the drum speed were changed and the residence time in the drum was changed to 15, 20, 120.125 seconds, respectively. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例１９）
　ドラムの温度を１０℃に変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Example 19)
A polyester film was obtained in the same manner as in Example 2 except that the temperature of the drum was changed to 10 ° C. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例２０、２１、２２）
　１軸延伸時の延伸ロールの表面粗さ、延伸ニップ圧をそれぞれ表に記載した通りに変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Examples 20, 21, and 22)
A polyester film was obtained in the same manner as in Example 2 except that the surface roughness of the drawing roll during uniaxial drawing and the drawing nip pressure were changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例２３）
　熱処理温度を２４０℃に変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Example 23)
A polyester film was obtained in the same manner as in Example 2 except that the heat treatment temperature was changed to 240 ° C. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例２４、２５）
　２軸延伸後の緩和率を３％、１０％に変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Examples 24 and 25)
A polyester film was obtained in the same manner as in Example 2 except that the relaxation rate after biaxial stretching was changed to 3% and 10%. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例２６）
　２軸延伸後の熱処理温度を２００℃にし、緩和率を１５％に変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Example 26)
A polyester film was obtained in the same manner as in Example 2 except that the heat treatment temperature after biaxial stretching was 200 ° C. and the relaxation rate was changed to 15%. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（実施例２７～２９）
　フィルムの厚みを表に記載のとおりに変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Examples 27 to 29)
A polyester film was obtained in the same manner as in Example 2 except that the thickness of the film was changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
　（比較例１～６、９、１０）
ドラムの温度、滞留時間、長手方向延伸時のロール表面粗さ、延伸ニップ圧を表の条件にした以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。比較例１～６、９、１０のいずれフィルムも耐久性試験でのフィルムの厚み減少量が大きく、また、耐久性試験によって特性の劣化が大きかった。 (Comparative Examples 1 to 6, 9, 10)
A polyester film was obtained in the same manner as in Example 2 except that the drum temperature, residence time, roll surface roughness during longitudinal stretching, and stretching nip pressure were set as shown in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table. In any of Comparative Examples 1 to 6, 9, and 10, the thickness reduction amount of the film in the durability test was large, and the characteristics were greatly deteriorated by the durability test.
　（比較例７）
　ポリエステルフィルム中に酸化チタンを含有しないようにした以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。酸化チタンを入れないと耐久性試験後の伸度保持率が大きく劣る結果となった。 (Comparative Example 7)
A polyester film was obtained in the same manner as in Example 2 except that the titanium oxide was not contained in the polyester film. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table. If titanium oxide was not added, the elongation retention after the durability test was greatly inferior.
　（比較例８）
　フィルムの厚みを表に記載のとおりに変更した以外は実施例２と同様の方法でポリエステルフィルムを得た。得られたポリエステルフィルムについて、特性を評価した結果、表に記載したとおりとなった。 (Comparative Example 8)
A polyester film was obtained in the same manner as in Example 2 except that the thickness of the film was changed as described in the table. As a result of evaluating the characteristics of the obtained polyester film, it was as described in the table.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
本発明のポリエステルフィルムは、耐膜減性、耐久性に優れるため、太陽電池バックシート用ポリエステルフィルムとして好適に使用することができる。本発明の太陽電池バックシート用ポリエステルフィルムからなる太陽電池バックシートを備えた太陽電池は、長期にわたりその性能を維持することができ、耐用年数を長くすることができる。 Since the polyester film of the present invention is excellent in film resistance and durability, it can be suitably used as a polyester film for a solar battery backsheet. The solar cell provided with the solar cell backsheet comprising the polyester film for solar cell backsheet of the present invention can maintain its performance over a long period of time, and can extend the service life.
１：バックシート
２：封止材
３：発電素子
４：透明基板
５：太陽電池バックシートの封止材２側の面
６：太陽電池バックシートの封止材２と反対側の面 1: Back sheet 2: Sealing material 3: Power generation element 4: Transparent substrate 5: Surface on the sealing material 2 side of the solar cell backsheet 6: Surface on the opposite side of the sealing material 2 of the solar cell backsheet

Claims (11)

  1. 下記（１）～（３）を満たすポリエステル層（該層をＰ１層と称する）を少なくとも一方の表層に有し、耐久性試験後の伸度保持率が４０％以上である太陽電池バックシート用ポリエステルフィルム。
    （１）Ｐ１層の厚みが３０μｍ以上２５０μｍ以下であること。
    （２）Ｐ１層の表面粗さ（Ｒａ）が０．１０μｍより大きく０．５０μｍ以下であること。
    （３）耐久性試験後のＰ１層の厚みの減少量が１５μｍ以下であること。
    ＜耐久性試験＞
    （ｉ）　温度６５℃、相対湿度５０％ＲＨの条件下で、キセノンランプ（スガ試験機製、ＳＣ７５０）を用いて、ポリエステルフィルムのＰ１層側の面を、放射照度１８０Ｗ／ｍ２にて、１０２分間（ｔ－１）照射する。
    （ｉｉ）　（ｉ）の後、キセノンランプの照射を続けながら、１６℃±５℃の水シャワーをＰ１層面に２．１Ｌ±０．１ｍＬ／分の量で１８分間（ｔ－２）かける。
    なお、（ｔ－１）＋（ｔ－２）＝１２０分となるようにする。
    （ｉｉｉ）　（ｉ）（ｉｉ）を１５００回繰り返す。     For a solar battery backsheet having a polyester layer satisfying the following (1) to (3) (this layer is referred to as a P1 layer) on at least one surface layer and having an elongation retention of 40% or more after a durability test Polyester film.
    (1) The thickness of the P1 layer is 30 μm or more and 250 μm or less.
    (2) The surface roughness (Ra) of the P1 layer is greater than 0.10 μm and 0.50 μm or less.
    (3) The amount of decrease in the thickness of the P1 layer after the durability test is 15 μm or less.
    <Durability test>
    (I) Using a xenon lamp (manufactured by Suga Test Instruments, SC750) under the conditions of a temperature of 65 ° C. and a relative humidity of 50% RH, the surface on the P1 layer side of the polyester film is 102 at an irradiance of 180 W / m 2 . Irradiate for (t-1) minutes.
    (Ii) After (i), while continuing irradiation with a xenon lamp, a water shower at 16 ° C. ± 5 ° C. is applied to the P1 layer surface at an amount of 2.1 L ± 0.1 mL / min for 18 minutes (t−2).
    Note that (t-1) + (t-2) = 120 minutes.
    (Iii) Repeat (i) and (ii) 1500 times.
  2. 少なくとも２層からなる積層ポリエステルフィルムである請求項１に記載の太陽電池バックシート用ポリエステルフィルム。 The polyester film for solar cell backsheet according to claim 1, which is a laminated polyester film comprising at least two layers.
  3. 耐久性試験後の部分放電電圧維持率が９０％以上である請求項１に記載の太陽電池バックシート用フィルム。 The film for solar cell backsheet of Claim 1 whose partial discharge voltage maintenance factor after a durability test is 90% or more.
  4. Ｐ１層を構成するポリエステル樹脂組成物が、ルチル型酸化チタンを含有しており、ルチル型酸化チタンの含有量がＰ１層を構成するポリエステル樹脂組成物全体に対して１４～２０重量％である請求項１に記載の太陽電池バックシート用ポリエステルフィルム。 The polyester resin composition constituting the P1 layer contains rutile type titanium oxide, and the content of the rutile type titanium oxide is 14 to 20% by weight based on the whole polyester resin composition constituting the P1 layer. Item 12. A polyester film for solar cell backsheet according to Item 1.
  5. Ｐ１層を構成するポリエステル樹脂組成物が、１，４－シクロヘキシレンジメチレンテレフタレートユニット（以下、ＣＨＴユニットと称する）を主たる構成成分とするポリエステル樹脂組成物を含有しており、ＣＨＴユニットを主たる構成成分とするポリエステル樹脂組成物の含有量がＰ１層を構成するポリエステル樹脂組成物全体に対して１４～２０重量％である請求項１に記載の太陽電池バックシート用ポリエステルフィルム。 The polyester resin composition constituting the P1 layer contains a polyester resin composition mainly comprising a 1,4-cyclohexylenedimethylene terephthalate unit (hereinafter referred to as CHT unit), and the CHT unit is mainly constituted. The polyester film for solar battery backsheet according to claim 1, wherein the content of the polyester resin composition as a component is 14 to 20% by weight based on the entire polyester resin composition constituting the P1 layer.
  6. ポリエステルフィルムを構成するポリエステル樹脂の固有粘度が０．６～１．０ｄｌ／ｇであり、末端カルボキシル基量が５～２０当量／ｔである請求項１に記載の太陽電池バックシート用ポリエステルフィルム。 The polyester film for a solar battery back sheet according to claim 1, wherein the polyester resin constituting the polyester film has an intrinsic viscosity of 0.6 to 1.0 dl / g and a terminal carboxyl group content of 5 to 20 equivalent / t.
  7. 下記（４）～（６）を満たす、請求項１に記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
    （４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
    （５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上Ｔｇ－３０℃以下であること。
    （６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。     The method for producing a polyester film for a solar battery back sheet according to claim 1, wherein the following (4) to (6) are satisfied.
    (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
    (5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
    (6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
  8. 下記（４）、（７）～（１０）を満たす、請求項１に記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
    （４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
    （７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
    （８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
    （９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
    （１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。     The method for producing a polyester film for a solar battery backsheet according to claim 1, wherein the following (4) and (7) to (10) are satisfied.
    (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
    (7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
    (8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
    (9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
    (10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  9. 下記（４）～（１０）を満たす、請求項１に記載の太陽電池バックシート用ポリエステルフィルムの製造方法。
    （４）Ｐ１層を構成するポリエステル樹脂組成物を押出機で溶融混練した後、押出しし、冷却ドラム上にて冷却固化して未配向ポリエステルフィルムを得る工程を含むこと。
    （５）前記、冷却ドラムの温度がＰ１層を構成するポリエステル樹脂のＴｇ－７０℃以上Ｔｇ－３０℃以下であること。
    （６）前記、冷却ドラムに接触している時間（滞留時間）が２０秒以上１２０秒以下であること。
    （７）（４）により得られた未配向ポリエステルフィルムを、長手方向に、延伸温度７０～１２０℃、延伸倍率２．０～４．０倍で延伸して、一軸配向ポリエステルフィルムを得る工程を含むこと。
    （８）（７）の工程で得られた一軸配向ポリエステルフィルムを、幅方向に、延伸温度７０～１５０℃、延伸倍率３．０～４．０倍で延伸して、二軸配向ポリエステルフィルムを得る工程を含むこと。
    （９）（８）の工程で得られた二軸配向ポリエステルフィルムを、２０５～２４０℃で熱処理しながら、幅方向に０～１０％弛緩する工程を含むこと。
    （１０）前記（７）における延伸が、延伸ロールおよび延伸ニップロールを用いて実施されるものであり、前記延伸ロールの表面粗さＲａが０．５～１．５μｍであって、延伸ロールと、延伸ニップロールの間のニップ圧が０．４～１．０ＭＰａであること。     The method for producing a polyester film for a solar battery backsheet according to claim 1, wherein the following (4) to (10) are satisfied.
    (4) A step of melt-kneading the polyester resin composition constituting the P1 layer with an extruder and extruding and cooling and solidifying on a cooling drum to obtain an unoriented polyester film.
    (5) The temperature of the cooling drum is between Tg-70 ° C. and Tg-30 ° C. of the polyester resin constituting the P1 layer.
    (6) The time (residence time) in contact with the cooling drum is 20 seconds to 120 seconds.
    (7) A step of stretching the unoriented polyester film obtained in (4) in the longitudinal direction at a stretching temperature of 70 to 120 ° C. and a stretching ratio of 2.0 to 4.0 times to obtain a uniaxially oriented polyester film. Including.
    (8) The uniaxially oriented polyester film obtained in the step (7) is stretched in the width direction at a stretching temperature of 70 to 150 ° C. and a stretching ratio of 3.0 to 4.0 times to obtain a biaxially oriented polyester film. Including the step of obtaining.
    (9) A step of relaxing the biaxially oriented polyester film obtained in the step (8) by 0 to 10% in the width direction while being heat-treated at 205 to 240 ° C.
    (10) The stretching in (7) is performed using a stretching roll and a stretching nip roll, and the surface roughness Ra of the stretching roll is 0.5 to 1.5 μm, and the stretching roll; The nip pressure between the stretching nip rolls is 0.4 to 1.0 MPa.
  10. 請求項１に記載の太陽電池バックシート用ポリエステルフィルムを用いた太陽電池バックシート。 The solar cell backsheet using the polyester film for solar cell backsheets of Claim 1.
  11. 請求項１０に記載の太陽電池バックシートを使用した太陽電池。
          The solar cell using the solar cell backsheet of Claim 10.
PCT/JP2015/061851 2014-05-28 2015-04-17 Polyester film for solar cell back sheets WO2015182282A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017157831A (en) * 2016-02-29 2017-09-07 東レ株式会社 Solar battery backside protection sheet
KR20180006146A (en) * 2016-07-08 2018-01-17 코오롱인더스트리 주식회사 White film and manufacturing method thereof
KR20180033732A (en) * 2016-09-26 2018-04-04 코오롱인더스트리 주식회사 Backsheet for pv module and manufacturing method thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012018971A (en) * 2010-07-06 2012-01-26 Teijin Dupont Films Japan Ltd Polyester film for solar battery backside protective film
WO2013051403A1 (en) * 2011-10-05 2013-04-11 東レフィルム加工株式会社 Back-protective sheet for solar cell module and solar cell module using same
WO2013153978A1 (en) * 2012-04-13 2013-10-17 富士フイルム株式会社 Polyester film, backsheet for solar cell module, and solar cell module

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5471451B2 (en) 2010-01-05 2014-04-16 東洋紡株式会社 Easy-adhesive white polyester film for solar cells
US8912427B2 (en) 2010-07-14 2014-12-16 Toyobo Co., Ltd. Polyester film for sealing backside of solar cell
JP5613093B2 (en) 2011-03-28 2014-10-22 富士フイルム株式会社 Film, solar cell backsheet, and film production method
JP5352703B2 (en) 2011-08-03 2013-11-27 東洋インキＳｃホールディングス株式会社 Solar cell back surface protection sheet and solar cell module

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012018971A (en) * 2010-07-06 2012-01-26 Teijin Dupont Films Japan Ltd Polyester film for solar battery backside protective film
WO2013051403A1 (en) * 2011-10-05 2013-04-11 東レフィルム加工株式会社 Back-protective sheet for solar cell module and solar cell module using same
WO2013153978A1 (en) * 2012-04-13 2013-10-17 富士フイルム株式会社 Polyester film, backsheet for solar cell module, and solar cell module

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017157831A (en) * 2016-02-29 2017-09-07 東レ株式会社 Solar battery backside protection sheet
KR20180006146A (en) * 2016-07-08 2018-01-17 코오롱인더스트리 주식회사 White film and manufacturing method thereof
KR102584924B1 (en) 2016-07-08 2023-10-04 코오롱인더스트리 주식회사 White film and manufacturing method thereof
KR20180033732A (en) * 2016-09-26 2018-04-04 코오롱인더스트리 주식회사 Backsheet for pv module and manufacturing method thereof
KR102544688B1 (en) 2016-09-26 2023-06-15 코오롱인더스트리 주식회사 Backsheet for pv module and manufacturing method thereof

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