JP2014239128A - Polyester film for solar battery backside sealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a solar battery backside protection material which satisfies the requirements for having hydrolysis resistance, reducing the cost in production, and the adhesiveness with sealant.SOLUTION: A polyester film for solar battery backside sealing comprises a recovered polyester. The film has an intrinsic viscosity (IV) of 0.62-0.73 dl/g, and 26 equivalent/t or less of terminal carboxyl groups (AV). In an intensity profile obtained by wide angle X-ray diffraction, the half-value width (w) of a peak observed in a range of 24-30° is 1.17° or larger. The polyester film further comprise a coated layer at least on one side thereof; the coated layer is formed by application of a coating liquid containing polyurethane having at least one of a polycarbonate skeleton and a polyether skeleton, and a crosslinking agent.

Description

  The present invention relates to a polyester film for a solar cell back surface protective material, and more specifically, for a solar cell back surface protective material satisfying hydrolysis resistance, cost reduction during production, and adhesiveness to a sealing material. It relates to a polyester film.

  Photovoltaic power generation that converts light energy into electrical energy using the photoelectric conversion effect is widely performed as a means for obtaining clean energy. And with the improvement of the photoelectric conversion efficiency of a photovoltaic cell, the photovoltaic power generation system has come to be provided also in many private houses. In order to use such a solar power generation system as an actual energy source, a solar cell module having a configuration in which a plurality of solar cells are electrically connected in series is used.

  Since the solar cell module is used for a long time in a high temperature and high humidity environment, the solar cell back surface sealing film is also required to have long-term durability. For example, Patent Document 1 discloses a technique using a fluorine-based film as a solar cell back surface sealing film. In this document, it is possible to reduce the thermal shrinkage of the fluorine-based film in advance by heat-treating the fluorine-based film in advance, and ethylene vinyl acetate (hereinafter sometimes abbreviated as EVA) as a sealing material. It is described that it is effective in preventing deterioration of physical properties such as weather resistance and water resistance and improving yield during vacuum lamination. However, since the fluorine-based film is expensive, there is a problem that the solar cell module is also expensive.

  A polyester film may be used as the solar cell back surface sealing film. It is known that when a polyester film is used in a high-temperature and high-humidity environment, hydrolysis of an ester bond site in a molecular chain occurs and mechanical properties deteriorate. Therefore, various studies have been made to suppress hydrolysis assuming that the polyester film is used outdoors for a long period (for example, 20 years) or in a high humidity environment.

  It is known that the hydrolysis of polyester is faster as the amount of terminal carboxyl groups in the polyester molecular chain is higher. Therefore, Patent Document 2 and Patent Document 3 disclose a technique for improving hydrolysis resistance by adding a compound that reacts with carboxylic acid to reduce the amount of carboxyl group at the end of the molecular chain. Yes. However, these compounds have a high possibility of inducing gelation and generating foreign substances in the melt extrusion process or the material recycling process in the film forming process, and are not preferable in terms of environment and productivity.

  Patent Document 4 describes a technique for improving hydrolysis resistance by increasing the intrinsic viscosity of a film in addition to lowering the terminal carboxyl group of the polyester molecular chain by optimizing the polyester catalyst and polymerization method. Is disclosed. However, since no recovered raw material is contained, it is not preferable in terms of cost. In addition, since the ingenuity on the control of the crystal structure of the polyester molecule has not been made, when the polyester film is exposed to the outdoors for a long period of time, the susceptibility to brittle fracture of the film due to the accelerated crystallization of the polyester, A satisfactory film has not been obtained. Furthermore, what is satisfactory also about adhesiveness with the ethylene-vinyl acetate copolymer resin (henceforth abbreviated as EVA) which is a sealing material used suitably for solar cells is not obtained.

JP 2002-83978 A JP-A-9-227767 JP-A-8-73719 JP 2012-017456 A

  This invention is made | formed in view of the said actual condition, Comprising: The solution subject is a solar cell back surface protection material which satisfy | fills hydrolysis resistance, the cost reduction at the time of production, and adhesiveness with a sealing material. It is to provide a polyester film.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above-mentioned problems can be easily solved by using a polyester film having a specific configuration, and the present invention has been completed.

  That is, the gist of the present invention is that the intrinsic viscosity (IV) is 0.62 dl / g or more and 0.73 dl / g or less, the terminal carboxyl group amount (AV) is 26 equivalents / t or less, and is obtained by wide-angle X-ray diffraction. A polyurethane having a half-value width (w) of a peak observed in a range of 24 ° to 30 ° of the obtained intensity profile of 1.17 ° or more, containing a recovered polyester, and having at least one of a polycarbonate skeleton or a polyether skeleton And a coating film obtained by coating a coating solution containing a crosslinking agent on at least one surface of the film.

  According to the present invention, a solar cell back surface protective material that has excellent hydrolysis resistance even in a high temperature and high humidity environment, the cost is kept low, and satisfies the adhesiveness to the sealing material, according to the present invention. Polyester film can be provided, and its industrial value is high.

  The polyester used as the substrate of the film of the present invention refers to an aromatic polyester obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Among these polyesters, polyethylene terephthalate (PET) is excellent in balance between cost and performance, and in the present invention, a polyethylene terephthalate film can be preferably used as the polyester film.

  As the polyester raw material of the polyester film used as the substrate of the present invention, a metal compound polymerization catalyst such as antimony, titanium, germanium, and aluminum, which is usually used in the polymerization of polyester, can be used. However, if the amount of these catalysts is large, when the polyester for film formation is melted, the decomposition reaction is likely to occur, the terminal carboxyl group concentration becomes high due to the decrease in molecular weight, etc., and the hydrolysis resistance is inferior. Become. On the other hand, when the amount of the polymerization catalyst is too small, the polymerization reaction rate decreases, so that the polymerization time becomes long and the terminal carboxyl group concentration becomes high, resulting in deterioration of hydrolysis resistance. Therefore, in the present invention, antimony is usually 50 to 400 ppm, preferably 100 to 350 ppm, titanium is usually 1 to 20 ppm, preferably 2 to 15 ppm, and germanium is usually 3 to 50 ppm, preferably 5 If it is -40 ppm and aluminum, it is 1-20 ppm normally, Preferably it is 2-15 ppm. These polymerization catalysts can also be used in combination of two or more. The amount of the compound in the polyester film of the present invention can be detected by analysis using a fluorescent X-ray analyzer.

  It is preferable from the viewpoint of polymerization activity that the polymerization catalyst of the polyester raw material used in the polyester film of the present invention is titanium. Further, the titanium element content is preferably 10 ppm or less, more preferably 9 ppm or less, and particularly preferably 8 ppm or less. Although there is no particular lower limit, in practice, about 2 ppm is the lower limit in the current technology. If the content of the titanium compound is too high, the activation of titanium atoms is high, so that oligomers are easily formed as a by-product in the process of melt-extruding the polyester, resulting in poor adhesion to other members when used as a back surface protective material. . In addition, when no titanium element is contained, productivity at the time of production of the polyester raw material is inferior, and a polyester raw material that has reached the target degree of polymerization may not be obtained.

  Examples of the titanium compound used as the polymerization catalyst include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetra Titanium alkoxide such as cyclohexyl titanate, tetraphenyl titanate, tetrabenzyl titanate, titanium oxide obtained by hydrolysis of titanium alkoxide, titanium and silicon or zirconium composite obtained by hydrolysis of a mixture of titanium alkoxide and silicon alkoxide or zirconium alkoxide Oxide, titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanium titanate-aluminum hydroxide mixture, Titanium fluoride, titanium chloride-aluminum chloride mixture, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, titanium acetylacetonate Among them, titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, titanium oxalate, and potassium potassium oxalate are preferable, and tetra-n-butyl titanate is particularly preferable. .

Aluminum and / or a compound thereof may be used for the polycondensation catalyst used when polymerizing the polyester which is the main constituent of the polyester film for solar cells of the present invention. As said aluminum and / or an aluminum compound, a well-known aluminum compound other than metallic aluminum can be used without limitation.

  Specific examples of aluminum compounds include carboxylates such as aluminum formate, aluminum acetate, basic aluminum acetate, aluminum propionate, and aluminum oxalate; inorganic acid salts such as aluminum chloride, aluminum hydroxide, and aluminum hydroxide chloride; Aluminum alkoxides such as aluminum methoxide, aluminum ethoxide, aluminum iso-propoxide, aluminum n-butoxide, aluminum t-butoxide, aluminum chelate compounds such as aluminum acetylacetonate, aluminum acetylacetate, trimethylaluminum, triethylaluminum, etc. Examples thereof include organoaluminum compounds and partial hydrolysates thereof, and aluminum oxide. Of these, carboxylates, inorganic acid salts and chelate compounds are preferred, and among these, aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride and aluminum acetylacetonate are particularly preferred.

  The polyester film used as the base material of the present invention preferably has an amount of phosphorus element detected by analysis using a fluorescent X-ray analyzer described later in the range of 0 to 70 ppm when the entire film is measured. More preferably, it is in the range of 0 to 50 ppm, and may be 0 ppm. The phosphorus element is usually derived from a phosphoric acid compound, and is added as a catalyst component during polyester production. In the present invention, when the phosphorus element amount satisfies the above range, hydrolysis resistance can be imparted to the film. If the amount of phosphorus element is too large, hydrolysis caused by the phosphate compound is promoted, which is not preferable. The hydrolysis resistance of the polyester film is a characteristic relating to the entire film, and in the present invention, the phosphorus content is preferably within the above-mentioned range for the entire polyester constituting the film.

  Examples of phosphoric acid compounds include known ones such as phosphoric acid, phosphorous acid or esters thereof, phosphonic acid compounds, phosphinic acid compounds, phosphonous acid compounds, and phosphinic acid compounds. Phosphoric acid, monomethyl phosphate, dimethyl phosphate, trimethyl phosphate, monoethyl phosphate, diethyl phosphate, triethyl phosphate, ethyl acid phosphate, monopropyl phosphate, dipropyl phosphate, tripropyl phosphate, monobutyl phosphate Fate, dibutyl phosphate, tributyl phosphate, monoamyl phosphate, diamyl phosphate, triamyl phosphate, monohexyl phosphate, dihexyl phosphate, t Hexyl phosphate, 3,5-di -tert- butyl-4-hydroxybenzyl phosphonic acid diethyl and the like.

In the polyester film of the present invention, particles may be blended mainly for the purpose of imparting easy slipperiness. The type of particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples include, for example, silica, magnesium carbonate, barium carbonate, silicon oxide, kaolin, aluminum oxide, calcium carbonate. And particles such as calcium sulfate.
Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755, etc. may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  Moreover, the particle | grains used in order to provide easy lubricity are 0.1-10 micrometers normally with an average particle diameter, and it can select as the addition amount in 0.005-5.0 weight%.

Examples of inorganic pigments that can be used include white pigments such as titanium dioxide, zinc oxide, zinc sulfide, and barium sulfate, red pigments such as Bengala, molybdenum red, and cadmium red, and orange colors such as reddish yellow lead and chromium permillion. Pigments, blue pigments such as ultramarine, bitumen, cobalt blue and cerulean blue, green pigments such as chromium oxide, pyridian, emerald green and cobalt green, yellow pigments such as yellow lead, cadmium yellow, yellow iron oxide and titanium yellow, manganese violet Violet pigments such as mineral violet, and black pigments such as black iron oxide. As the black pigment, carbon black (channel, furnace, acetylene, thermal, etc.), carbon nanotube (single layer, multilayer), aniline black, etc. can also be used.
Examples of organic pigments include condensed azo, phthalocyanine, quinacridone, oxazine, xanthene, isoindolinone, quinophthalone, and anthraquinone.

  Among these, inorganic pigments, carbon black, carbon nanotubes, and the like are often superior to organic pigments in heat resistance during melt molding of polyester and light resistance when used outdoors. In addition, among these, considering that there is almost no influence such as similarity in color tone with solar cells, coloring power and economics of colored pigments, and acceleration of decomposition with respect to polyester, carbon black is the present invention. It is suitable for the polyester film for solar cell back surface protection materials.

  The above-mentioned color pigments may be used alone, but two or more types of color pigments can be used in combination for the purpose of adjusting the color tone. Moreover, although the range of the preferable particle diameter of said color pigment changes with particle types, as an average particle diameter, it is usually 0.01-10 micrometers, Preferably it is selected from the range of the range of 0.02-5 micrometers. good. In particular, with regard to the hiding power of the colored pigment, the hiding power generally increases as the average particle diameter decreases, reaches a maximum at about 1/2 the wavelength of the light, and further decreases as the hiding power rapidly decreases. In view of increasing transparency, it is preferable to use those having an average particle diameter of about 0.05 to 2 μm in order to increase the hiding power.

  The method for adding the above-described color pigment, easy-slipperity-imparting particles and the like to the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at an arbitrary stage for producing the polyester as a raw material, but it may be added preferably after the esterification stage or after the transesterification reaction to proceed the polycondensation reaction. Further, using a twin screw extruder with a vent, a method of kneading a slurry of particles dispersed in ethylene glycol or water and a polyester raw material, or a method of kneading dried particles and a polyester raw material, etc. Is called. Especially in the case of colored pigments and white pigments, it is added to the polyester raw material as a high-concentration masterbatch and used in the form of diluting it when the film is formed. It is preferable in terms of reducing the amount.

  In the polyester film of the present invention, in addition to the above-described color pigments and slipperiness-imparting particles, conventionally known antioxidants, heat stabilizers, lubricants, antistatic agents, fluorescent enhancements, etc., if necessary. Whitening agents, dyes and the like can be added. For the purpose of improving light resistance, an ultraviolet absorber can be contained in the range of 0.01 to 5 parts by weight with respect to the polyester. Examples of the ultraviolet absorber include triazine-based, benzophenone-based, and benzoxazinone-based. Among these, a triazine-based ultraviolet absorber is particularly preferably used. In addition, when the film itself has a laminated structure of three or more layers as described later, a method of adding these ultraviolet absorbers to the intermediate layer can also be preferably used. Of course, these ultraviolet absorbers and additives can be prepared as a high-concentration master batch, and can be diluted and used during film formation.

  In the present invention, two or three or more polyester melt extruders can be used to form a laminated film of two layers or three or more layers by a so-called coextrusion method. As the layer structure, the number of layers was increased to an A / B structure using an A raw material and a B raw material, or an A / B / A structure, and further using a C raw material to an A / B / C structure or higher. It can be set as the film of a structure.

  The polyester film of the present invention has a content of 26 equivalents / ton or less when the terminal carboxyl group amount (AV) of the entire film (the portion excluding the coating layer if there is a coating layer) is measured by the measurement method described later. Necessary, preferably 24 equivalents / ton or less. When the amount of terminal carboxyl groups exceeds 26 equivalents / ton, the hydrolysis resistance of the polyester film is poor. The hydrolysis resistance of the polyester film is a characteristic related to the entire film, and in the present invention, the terminal carboxyl group amount of the entire polyester constituting the film needs to be in the above-described range. On the other hand, in view of the hydrolysis resistance of the present invention, there is no lower limit of the amount of terminal carboxyl groups of the polyester, but usually from the viewpoint of the efficiency of the polycondensation reaction, hydrolysis and thermal decomposition in the melt extrusion step, etc. It is about tons.

  When the intrinsic viscosity (IV) of the whole film (part excluding the coating layer) is measured by the measurement method described later, the polyester film of the present invention needs to be 0.62 dl / g or more, preferably 0. .63 dl / g or more. When the intrinsic viscosity of the polyester film is 0.62 dl / g or more, a polyester film having good long-term durability and hydrolysis resistance can be obtained. On the other hand, the upper limit of the intrinsic viscosity of the polyester film is 0.73 dl / g or less, preferably 0.71 dl / g or less, more preferably 0.68 dl / g or less. By setting the intrinsic viscosity of the polyester film to 0.73 dl / g or less, the load on the extruder is reduced during the production of the polyester film, the discharge rate is improved, and a polyester film with good productivity is provided. be able to.

  Usually, a polyester film is obtained by stretching an amorphous polyester sheet that has been melt-extruded from a die and rapidly cooled and solidified. And at the time of manufacture of a polyester film, the edge part of a polyester sheet becomes thick by the neck-in phenomenon at the time of extrusion, and is used as a biting allowance of a clip. When commercialized, the end of the polyester film is cut and separated as an ear film. Further, when the master roll from which the ear portion is removed is slit to the product size, the excess slit ear is cut and separated.

  The recovered polyester in the present invention is a flake product obtained by pulverizing the cut-separated ear film or slit ear as described above with a pulverizer, and a pellet obtained by drying the flake product and melt-extruding with a single screw extruder. And a pelletized product obtained by melt-extruding an undried flaked product with a vented twin-screw extruder.

  The content of the recovered polyester in the polyester film of the present invention is 15% by weight or more, more preferably 20% by weight or more, further preferably 25% by weight or more, and most preferably 30% by weight or more from the viewpoint of productivity and cost. It is. Although there is no particular upper limit for the content of recovered polyester in the polyester film of the present invention, it is 80% by weight or less, more preferably 70% by weight or less, more preferably 60% by weight or less, most preferably from the viewpoint of hydrolysis resistance. Is 50% by weight or less.

  In addition, from the viewpoint of maintaining hydrolysis resistance, the flakes obtained by pulverizing the cut edge film and slit ears with a pulverizer from the melt-extruded pellets are preferentially used as recovered polyester. Is preferred.

  In the present invention, in order to set the terminal carboxyl group amount and the intrinsic viscosity of the polyester film within a specific range, in the step of melt-extruding the polyester raw material in film production, a) hydrolysis is caused by moisture contained in the polyester chip. Avoiding as much as possible, b) making the residence time of the polyester in the extruder and melt line as short as possible. As a specific example of a), when a single screw extruder is used, the raw material is sufficiently dried in advance so that the water content is 50 ppm) or less, preferably 30 ppm or less, or a twin screw extruder is used. Can employ a method such as providing a vent port and maintaining a reduced pressure of 40 hectopascals or less, preferably 30 hectopascals or less, more preferably 20 hectopascals or less. As a specific example of b), it is preferable that the residence time from when the raw material is charged into the extruder to when the molten sheet starts to be discharged from the die is 20 minutes or less, more preferably 15 minutes or less.

  The vented twin-screw extruder is formed into a polyester film film in that the flakes obtained by crushing the cut-separated ear film and slit ear as described above with a crusher can be directly supplied to the extruder in an undried state. Sometimes it is preferred to use it.

  Hereinafter, although the manufacturing method of the polyester film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  When the polyester film has a single layer configuration, one melt extruder is used. When the polyester film has a multilayer configuration, a necessary number of melt extruders are combined and laminated according to the stacked configuration. Use feedblocks or multi-layer multi-manifold dies. Supply polyester chips dried by a known method to a single-screw extruder, or supply undried polyester chips to a twin-screw extruder having a vent port connected to a vacuum system, so that the temperature is equal to or higher than the melting point of each polymer. Melt by heating. At this time, a known appropriate polymer filter may be passed through in order to remove foreign substances, or a method of reducing the pulsation of the molten polymer using a gear pump can be employed. Next, the molten polymer is extruded from the die, and rapidly cooled and solidified on the rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times in the machine direction (MD) at 70 to 145 ° C. to form a longitudinal uniaxially stretched film, and then in the transverse direction (TD). Stretching is performed 2 to 6 times at 90 to 160 ° C, and heat treatment is performed at 160 to 240 ° C for 1 to 600 seconds. Or you may heat-process on the same conditions, after extending | stretching simultaneously in the range of 5-20 times as an area magnification at 70-160 degreeC in the vertical direction and a horizontal direction using a simultaneous biaxial stretching machine.

  Further, at this time, it is preferable to relax 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  In the biaxially oriented polyester film of the present invention, the half width (w) of the peak observed in the range of 24 ° to 30 ° of the intensity profile obtained by wide-angle X-ray diffraction is 1.17 ° or more, and 1.26. Is preferably at least 1.36 °, more preferably at least 1.36 °, and most preferably at least 1.48 °. When the full width at half maximum (w) is larger than 1.17 °, brittle fracture derived from crystal growth after the wet heat treatment of the polyester film tends to occur, which is not preferable for use.

  In the polyester film of the present invention, an ethylene-vinyl acetate copolymer resin (hereinafter sometimes abbreviated as EVA) or a polyvinyl acetal resin (hereinafter abbreviated as PVB) that is generally used as a solar cell encapsulant. Polypropylene, polyethylene, maleic anhydride group-containing polyolefin, ethylene-butyl acrylate copolymer, ethylene-methacrylate copolymer, ethylene-methacrylic, which serve as a sealant with the above-mentioned sealant It is possible to provide a coating layer (primer) separately from the above-mentioned coating layer, which improves wet heat resistance with a polyolefin resin selected from the group consisting of acid copolymers.

  As a component of the coating layer (primer) that improves adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant, a polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton, and a crosslinking agent are used. It is preferable to contain.

  The polyurethane having a polycarbonate skeleton or a polyether skeleton is obtained by using a compound having a polycarbonate skeleton or a polyether skeleton as a polyol. In addition, you may have a polycarbonate frame | skeleton and a polyether frame | skeleton simultaneously.

  Examples of the polycarbonate polyol used in the polyurethane of the coating layer (primer) that improves adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant include, for example, diphenyl carbonate, dialkyl carbonate, ethylene carbonate, phosgene and diol It can be obtained by reaction with. Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neo Examples include pentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like. Among these, a polycarbonate polyol using 1,6-hexanediol is preferable because it is easily available industrially, is excellent in terms of improving adhesiveness, and is also excellent in hydrolysis resistance.

  The polycarbonate polyol has a polystyrene-equivalent number average molecular weight by gel permeation chromatography (GPC) and is preferably 300 to 5,000.

  Polyether polyols used in polyurethane for coating layers (primers) that improve adhesion to solar cell encapsulant resins or sealant resins for solar cell encapsulants include polyoxyethylene polyols (polyethylene glycol, etc.), polyoxypropylenes Polyols (polypropylene glycol, etc.), polyoxytetramethylene polyols (polytetramethylene ether glycol, etc.), copolymerized polyether polyols (block copolymers such as polyoxyethylene glycol and polyoxypropylene glycol, random copolymers, etc.), etc. Is mentioned. Among these, polyoxytetramethylene glycol is preferable because it is excellent in terms of improving adhesiveness and also has good hydrolysis resistance.

  The polyether polyol has a number average molecular weight in terms of polyethylene glycol determined by gel permeation chromatography (GPC) and is preferably 300 to 5,000.

  The polyurethane using the above-described polycarbonate polyol or polyether polyol has better resistance to hydrolysis than the polyurethane using polyester polyol, which is another general-purpose polyol.

  Each of these polycarbonate polyols or polyether polyols may be used alone or in combination of two or more. As described above, these polycarbonate polyols and polyether polyols can be used in combination.

  The polyisocyanate used for the polyurethane of the coating layer (primer) that improves the adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant includes known aliphatic, alicyclic and aromatic polyisocyanates. Mention may be made of isocyanates.

  Specific examples of the aliphatic polyisocyanate include, for example, tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2-methylpentane- Examples include 1,5-diisocyanate and 3-methylpentane-1,5-diisocyanate.

  Specific examples of the alicyclic polyisocyanate include, for example, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane-4,4′-diisocyanate, hydrogenated biphenyl-4,4′-diisocyanate, 1,4-cyclohexane diisocyanate. , Hydrogenated tolylene diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, 1,4-bis (isocyanatemethyl) cyclohexane, and the like.

  Specific examples of the aromatic polyisocyanate include, for example, tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and the like can be mentioned. These polyisocyanates may be used alone or in combination of two or more.

  Examples of chain extenders include ethylene glycol, propylene glycol, butanediol, diethylene glycol, neopentyl glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, isophoronediamine, 4,4′-diaminodiphenylmethane, 4,4 ′. -Diaminodicyclohexylmethane, water, etc.

  A polyurethane having at least one of a polycarbonate structure or a polyether structure used for a coating layer (primer) that improves adhesion to a solar cell encapsulant resin or a sealant resin for a solar cell encapsulant has an organic solvent as a medium. However, water is preferably used as the medium. In order to disperse or dissolve polyurethane in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into a polyurethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the skeleton of a polyurethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency and adhesiveness of the resulting coating layer.

  As the ionic group to be introduced, examples of the anionic group include a carboxylate group, a sulfonate group, a phosphate group, and a phosphonate group, and examples of the cationic group include quaternary ammonium. For example, carboxylic acid group as an anionic group is exemplified by dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid, trimellitic acid- Ammonium salts such as bis (ethylene glycol) ester, lower amine salts, and the like can be preferably used. Moreover, about the quaternary ammonium of a cationic group, quaternization products, such as N-alkyl dialkanolamines, such as N-methyldiethanolamine and N-ethyldiethanolamine, can be used preferably. Among these ionic groups, when the carboxylate is a base and the counter ion is an organic amine having a boiling point of 150 ° C. or lower such as ammonia or triethylamine, an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent described later Is particularly preferable in that the crosslink density of the coating layer formed on the opposite surface is increased.

  As a method of introducing an ionic group into the urethane resin in the coating layer (primer) that improves the adhesion with the solar cell encapsulant resin or the sealant resin for solar cell encapsulant, in each stage of the polymerization reaction Various methods are possible. For example, at the time of prepolymer synthesis, a resin having an ionic group can be used as a copolymerization component, or a component having an ionic group can be used as one component such as a polyol or a chain extender.

In addition to the polyurethane described above, the coating layer (primer) that improves the adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant is heat resistant, heat resistant adhesive, moisture resistant and blocking resistant. It is necessary to use a crosslinking agent in combination. This cross-linking agent is preferably water-soluble or water-dispersible. Specifically, in addition to melamine compounds, benzoguanamine compounds, urea compounds, acrylamide compounds, which are methylolated or alkoxymethylolated, epoxy compounds It is preferable to contain at least one selected from an isocyanate compound, a carbodiimide compound, an oxazoline compound, a silane coupling agent compound, a titanium coupling agent compound, and the like. Among these cross-linking agents, oxazoline-based compounds or carbodiimide-based compounds, which are themselves polymer cross-linking agents, greatly improve the heat and moisture resistance adhesion of the coating layer formed on the opposite side, preferable. Such an oxazoline-based cross-linking agent is commercially available, for example, under the trade name Epocross (registered trademark) of Nippon Shokubai Co., Ltd., and a carbodiimide-based cross-linking agent is commercially available, for example, under the trade name Carbodilite (registered trademark) of Nisshinbo Chemical Co., Ltd. .
Moreover, the addition amount of these crosslinking agents is 10: 90-90: 10 by the weight ratio with respect to the polyurethane in the coating layer formed in the opposite surface, Preferably it is used in the ratio of 20: 80-80: 20. It is preferable.

  In the coating layer (primer) that improves the adhesion with the solar cell encapsulant resin or the sealant resin for solar cell encapsulant, the total of the polyurethane and the crosslinking agent component described above is 50% by weight) or more. Is preferably present in an amount of 75% by weight or more. In addition to these resin components, other resins can be additionally added. Examples of the resin component that can be additionally added include polyester resins, acrylic resins, polyvinyl resins, and polyester polyurethane resins. However, polyester resins and polyester polyurethane resins are often poor in hydrolysis resistance, and these resins are preferably not added to the coating layer, or even if added, the added amount is preferably less than 10% by weight.

  In addition, in order to prevent blocking of the coating layer (primer) that improves adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant and to impart slipperiness, the solar cell encapsulant resin or the solar cell It is also possible to add fine particles in the coating layer (primer) that improves the adhesion with the sealant resin for battery sealants. As fine particles, for example, inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles can be used. The size of the fine particles is 150 nm or less, preferably 100 nm or less, and the addition amount in the coating layer is preferably selected in the range of 0.5 to 10% by weight.

  In addition, components other than those described above can be included in the coating layer (primer) that improves adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant, if necessary. For example, surfactants, antifoaming agents, coatability improvers, thickeners, antioxidants, antistatic agents, ultraviolet absorbers, foaming agents, dyes, pigments and the like. These additives may be used alone or in combination of two or more.

  As with the fluoropolymer primer layer, the coating layer (primer) that improves the adhesion to the solar cell encapsulant resin or the sealant resin for solar cell encapsulant is mainly applied to the polyester film as a coating solution using water as a medium. It is preferable that it is applied. The applied polyester film may be biaxially stretched in advance, but it is preferable to use a so-called in-line coating method in which the applied polyester film is stretched in at least one direction and further heat-set.

  Any known method can be applied as a method of applying the coating solution to the polyester film as the substrate. Specifically, roll coating method, gravure coating method, micro gravure coating method, reverse coating method, bar coating method, roll brush method, spray coating method, air knife coating method, impregnation method, curtain coating method, die coating method, etc. It can be applied alone or in combination.

The coating layer in the present invention has a coating amount of 0.005 to 1.0 g as a final dry film after being dried and solidified or after being biaxially stretched or heat-set. / M ² , more preferably 0.01 to 0.5 g / m ² . In the coating amount is less than 0.005 g / m ^2, there is a tendency that adhesion becomes insufficient, when it exceeds 1.0 g / m ² is no longer the adhesive is saturated, such as blocking the reverse There is a tendency that the harmful effects of are easily generated.

  Analysis of the components in the coating layer can be performed by surface analysis such as TOF-SIMS.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

When the coating layer is provided on the film of the present invention, the embodiment is as follows. (1) A coating layer / polyester film formed from a coating solution containing a polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton and a crosslinking agent.
(2) A polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton and a coating layer formed from a coating solution containing a crosslinking agent / polyester film / polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton, and a crosslinking The coating layer formed from the coating liquid containing an agent.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to the following examples, unless the meaning is exceeded. In addition, the measurement and evaluation method of various physical properties of a film are shown below.

(1) Terminal carboxyl group content (equivalent / ton)
If it is a polyester chip, grind it. If it is a polyester film, if there is a coating layer on the film, in order to eliminate this effect, wash the coating layer with water using an abrasive cleanser, then rinse thoroughly with ion-exchanged water and dry. A film is taken as a sample. The obtained sample was dried at 140 ° C. for 15 minutes with a hot air dryer and cooled to room temperature in a desiccator. The solution was dissolved at 195 ° C. for 3 minutes while blowing dry nitrogen gas, and then 5 ml of chloroform was gradually added and cooled to room temperature. One to two drops of phenol red indicator were added to this solution, and titrated with 0.1 (N) benzyl alcohol solution of caustic soda while blowing dry nitrogen gas, and when the color changed from yellow to red, the procedure was terminated. . Further, as a blank, the same operation was carried out without a polyester resin sample, and the acid value was calculated by the following formula.
Acid value (equivalent / t) = (A−B) × 0.1 × f / W
[Where A is the amount of benzyl alcohol solution of 0.1N caustic soda required for titration (μl), B is the amount of benzyl alcohol solution of 0.1N caustic soda required for titration with blank (μl) , W is the amount (g) of the polyester resin sample, and f is the titer of the benzyl alcohol solution of 0.1N caustic soda]

The titer (f) of 0.1N caustic soda benzyl alcohol solution was obtained by taking 5 ml of methanol into a test tube, adding 1 to 2 drops of phenol red ethanol solution as an indicator, and 0.1N caustic soda benzyl alcohol. Titrate to the color change point with 0.4 ml of solution, then add 0.2 ml of 0.1N hydrochloric acid aqueous solution of known titer as a standard solution and add it again to the color change point with 0.1N sodium hydroxide in benzyl alcohol. Titration. (The above operation was performed under dry nitrogen gas blowing). The titer (f) was calculated by the following formula.
Titer (f) = titer of 0.1N aqueous hydrochloric acid × amount of collected 0.1N aqueous hydrochloric acid (μl) / titrated amount of benzyl alcohol solution of 0.1N sodium hydroxide (μl).

(2) Intrinsic viscosity [dl / g]
1 g of a measurement sample is precisely weighed and dissolved in a solvent of phenol / tetrachloroethane = 50/50 (parts by weight) to prepare a solution having a concentration c = 0.01 g / cm ³ , and a relative viscosity with the solvent at 30 ° C. η _r was measured and the intrinsic viscosity: IV [dl / g] was determined. If there is a coating layer on the film, in order to eliminate this effect, wash the coating layer with water using a cleanser containing abrasives, rinse thoroughly with ion-exchanged water, and dry, then measure in the same way. went.

(3) Half width (w)
The biaxially oriented polyester film of the present invention has a peak maximum value in the range of 24 ° to 30 ° of the intensity profile obtained from wide-angle X-ray diffraction (CuKα ray λ = 0.154 nm). Here, the peak having the maximum value in the range of 24 ° to 30 ° is a peak due to the (100) plane of the α crystal.

  The full width at half maximum (w) was obtained from the intensity profile having this peak by the Lorentz equation shown in the following equation (B).

In the above formula, y ₀ h baseline, A is the total area (integrated intensity) between the profile and the baseline, x ₀ is the center of the peak, and w is the total width at half the height of the peak.

(4) Determination of catalyst-derived elements Using an X-ray fluorescence analyzer (model “XRF-1500” manufactured by Shimadzu Corporation), the amount of elements in the film under the conditions shown in Table 1 below; It was. In the case of a laminated film, the content of the film as a whole was measured by melting the film, molding it into a disk shape, and measuring it. Also, if the coating layer is provided on the film, in order to eliminate this effect, rinse the coating layer with water using an abrasive cleanser, rinse thoroughly with ion-exchanged water, and then dry. Measurements were made. The detection limit by this method is usually about 1 ppm.

(5) Film elongation hydrolysis resistance Using a personal pressure cooker PC-242HS-E manufactured by Hirayama Seisakusho, the film was treated in an atmosphere of 120 ° C.-100% RH for 60 hours. Next, after adjusting the temperature and humidity for 24 hours at 23 ° C. × 50% RH, the elongation at break in the film forming direction (MD) was measured as the mechanical properties of the film. For the measurement, a universal tester AUTOGRAPH manufactured by Shimadzu Corporation was used, a sample having a width of 15 mm, a chuck interval of 50 mm, and a tensile speed of 200 mm / min. The retention (%) of elongation at break before and after the treatment was calculated by the following formula (1), and judged according to the following criteria.
Breaking elongation retention rate = breaking elongation after treatment ÷ breaking elongation before treatment × 100 (1)
◎: Retention rate is 80% or more ○: Retention rate is less than 60-80% △: Retention rate is less than 20-60% ×: Retention rate is less than 20%

(6) Adhesive strength with EVA Two pieces of a polyester film having a length of 300 mm and a width of 25 mm were cut out so that the longitudinal direction was MD. On the other hand, one piece of EVA film having a length of 50 mm and a width of 25 mm was cut out and stacked so that the EVA film was sandwiched between two polyester film pieces. This was laminated using a heat seal device (TP-701-B manufactured by Tester Sangyo Co., Ltd.). The EVA film used was 485.00 (standard curing type, thickness 0.5 mm) manufactured by Etimex, Germany, and the heat seal conditions were a temperature of 150 ° C. and a pressure of 0.13 MPa for 20 minutes. In order to measure the adhesive strength with EVA, first, a sample having a length of 300 mm and a width of 15 mm is cut out from a polyester film / EVA film laminate piece having a width of 25 mm. The non-laminated end of this 15 mm wide polyester film piece is mounted in a tensile / bending tester (EZGraph manufactured by Shimadzu Corporation). Subsequently, the force (adhesive strength) required to separate the polyester film / EVA film laminate at an angle of 180 ° and a speed of 100 mm / min was measured for 10 samples, and the average values were classified as follows. did.
◎: Adhesive strength is 50 N / 15 mm width or more ○: Adhesive strength is 30 N / 15 mm width to less than 50 N / 15 mm width Δ: Adhesive strength is 10 N / 15 mm width to less than 30 N / 15 mm width ×: Adhesive strength is less than 10 N / 15 mm width

(7) Moisture and heat-resistant adhesive strength with EVA Using a 25 mm wide test piece of polyester film / EVA film laminate prepared in (6) above, in an atmosphere of 120 ° C.-100% RH as in (5) above The wet heat treatment for 36 hours was performed. Next, after adjusting the temperature and humidity at 23 ° C. × 50% RH for 24 hours, a measurement sample having a width of 15 mm is cut out from the sample, and it is necessary to separate the polyester film / EVA film laminate as in (6) above. The average value of the force (adhesive strength) was determined.
From this value and the adhesive strength before the wet heat treatment, the adhesive strength retention was calculated by the following formula and judged according to the following criteria.
Adhesive strength retention rate (%) = (Adhesive strength after wet heat treatment) / (Adhesive strength before wet heat treatment)
A: Retention ratio is 70% or more B: Retention ratio is 50 to less than 70% B: Retention ratio is 20 to less than 50% X: Retention ratio is less than 20%

The example of the polyester raw material which comprises a polyester film is as follows.
<Method for producing polyester raw material (1)>
A slurry is prepared using a continuous polymerization apparatus comprising a slurry preparation tank, a two-stage esterification reaction tank connected in series to the slurry preparation tank, and a three-stage melt polycondensation tank connected in series to the second-stage esterification reaction tank. To the preparation tank, terephthalic acid and ethylene glycol were continuously supplied at 865 parts by weight and 485 parts by weight, respectively, and a 0.3 wt% ethylene glycol solution of ethyl acid phosphate was added to the phosphorus atom per 1 ton of the resulting polyester resin. Was added continuously in such an amount that the content became 0.129 mol / resin t, and a slurry was prepared by stirring and mixing. This slurry was subjected to a first stage esterification reaction tank set at 260 ° C. under a nitrogen atmosphere, a relative pressure of 50 kPa (0.5 kg / cm ² ), and an average residence time of 4 hours, and then at 260 ° C. under a nitrogen atmosphere. Then, the mixture was continuously transferred to a second stage esterification reaction tank set to a relative pressure of 5 kPa (0.05 kg / cm ² ) and an average residence time of 1.5 hours to cause an esterification reaction. At that time, a 0.6 wt% ethylene glycol solution of magnesium acetate tetrahydrate is contained as magnesium atoms per 1 t of the obtained polyester resin through an upper pipe provided in the second stage esterification reaction tank. The amount was continuously added in an amount of 0.165 mol / resin t, and 60 parts by weight of ethylene glycol was continuously added through another upper pipe provided in the second stage esterification reaction tank. .

  Subsequently, when the esterification reaction product obtained above is continuously transferred to the melt polycondensation tank, tetra-n-butyl titanate is added to the esterification reaction product in the transfer pipe with a concentration of titanium atoms. As an ethylene glycol solution with 0.15% by weight and a water concentration of 0.5% by weight, it is continuously added in such an amount that the content as titanium atoms per 1 ton of the obtained polyester resin is 0.084 mol / resin t. However, the first stage melt polycondensation tank set at 270 ° C. and absolute pressure 2.6 kPa, then the second stage melt polycondensation tank set at 278 ° C. and absolute pressure 0.5 kPa, then Each polycondensation is carried out so that the intrinsic viscosity of the resulting polyester resin is 0.65 dl / g by continuously transferring to a third stage polycondensation tank set at 280 ° C. and an absolute pressure of 0.3 kPa. In the tank The polyester raw material (which is melt polycondensed by adjusting the residence time in the polycondensation tank, continuously extracted in the form of a strand from the outlet provided in the bottom of the polycondensation tank, cooled with water, and cut with a cutter into a chip-like granule ( 1) was produced. The amount of terminal carboxyl groups was 14 equivalents / ton.

<Method for producing polyester raw material (2)>
The polyester raw material (1) is used as a starting raw material, and continuously fed into a stirring crystallizer maintained at about 160 ° C. in a nitrogen atmosphere so that the residence time is about 60 minutes. The solid phase polycondensation apparatus was continuously supplied to the solid phase polycondensation apparatus, and the residence time was adjusted so that the intrinsic viscosity of the resulting polyester resin was 0.82 dl / g) at 215 ° C. in a nitrogen atmosphere. A polyester raw material (2) was obtained. The amount of terminal carboxyl groups was 7 equivalents / ton.

<Method for producing polyester raw material (3)>
High-purity terephthalic acid and ethylene glycol were charged into a 2 liter stainless steel autoclave equipped with a stirrer, and an esterification reaction was performed according to a conventional method to obtain an oligomer mixture.
As a polycondensation catalyst for this oligomer mixture, (1) an ethylene glycol solution in which basic aluminum acetate was adjusted to have an aluminum compound content of 20 g / l; and (2) 3,5-di- 200 g of diethyl tert-butyl-4-hydroxybenzylphosphonate was added, and the mixture of an ethylene glycol solution of a phosphorous compound obtained by stirring and refluxing at 185 ° C. for 60 minutes under reflux was mixed with a residual amount of aluminum element of 20 (Ppm, phosphorus element was added so that the remaining amount was 80 ppm.
Next, the mixture was stirred at 250 ° C. for 10 minutes under a nitrogen atmosphere at normal pressure. Thereafter, while raising the temperature to 280 ° C. over 60 minutes, the pressure of the reaction system is gradually lowered to 13.3 Pa (0.1 Torr), and further the intrinsic viscosity of the polyester is 0.55 dl / under 280 ° C. and 13.3 Pa. The polycondensation reaction was performed until g.

  The melt polycondensation reaction product taken out from the reaction vessel was extruded into a strand from a die, cooled and solidified, and cut by a cutter to form a polyester resin chip: polyester chip having an average weight of 24 mg. The intrinsic viscosity of the polyester chip was 0.56 dl / g, and the amount of terminal carboxyl groups was 13 equivalents / ton.

  The polyester chip obtained by the above melt polymerization is subjected to solid phase polymerization at 220 ° C. under a reduced pressure of 0.5 mmHg to obtain a polyester (3) having an intrinsic viscosity of 0.78 dl / g and a terminal carboxyl group amount of 7 equivalents / ton. Obtained.

<Method for producing polyester raw material (4)>
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used as starting materials, and tetra-n-butyl titanate is obtained as a catalyst. The amount of titanium atoms per 1 ton of polyester resin is 5 g / resin t. In the reactor, the reaction start temperature was 150 ° C., and the reaction temperature was gradually increased as methanol was distilled off. After 4 hours, the transesterification reaction was substantially terminated. The reaction mixture was transferred to a polycondensation tank and the average particle size 2. An ethylene glycol slurry of 5 μm silica particles was added so that the content of the particles with respect to the polyester was 3.0% by weight, and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.60 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester raw material (4). The intrinsic viscosity was 0.64 dl / g, and the amount of terminal carboxyl groups was 21 equivalents / ton.

<Method for producing polyester raw material (5)>
In the production method of the polyester raw material (4), the average particle diameter 2. A polyester raw material (except that an ethylene glycol slurry of synthetic calcium carbonate particles having an average particle diameter of 0.8 μm was added so that the content of the particles with respect to the polyester was 1% by weight, instead of the ethylene glycol slurry of 5 μm silica particles. A polyester raw material (5) was obtained using a method similar to the production method of 4). The intrinsic viscosity was 0.62 dl / g, and the amount of terminal carboxyl groups was 23 equivalents / ton.

<Method for producing polyester raw material (6)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.02 part of magnesium acetate tetrahydrate as a catalyst is added to the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.03 part of ethyl acid phosphate to this reaction mixture, it moved to the polycondensation tank, added 0.04 part of antimony trioxide, and performed polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity of the polyester was 0.63 dl / g, and the amount of terminal carboxyl groups of the polymer was 45 equivalents / ton. Using the above polyester chip as a starting material, solid phase polymerization was performed at 220 ° C. under vacuum to obtain a polyester material (6). The intrinsic viscosity of the polyester raw material (6) was 0.85 dl / g, and the amount of terminal carboxyl groups of the polymer was 32 equivalents / ton.

  Examples of compounds constituting the coating layer are as follows.

(Example compounds)
Urethane U1: Polyurethane water dispersion U2: Polyurethane water dispersion U2: Polycarbonate polyol of hexamethylenediol (number) Aqueous dispersion U3: Polyurethane (average counter weight of triethylamine) consisting of dimethylolpropionic acid and hydrogenated diphenylmethane-4,4′-diisocyanate (average molecular weight about 1000): polyester of aromatic polyester and aliphatic diisocyanate DIC Corporation trade name Hydran (registered trademark) AP-40F, which is an aqueous polyurethane dispersion.
Polyester E1: DIC Corporation trade name Finetech (registered trademark) ES-670, which is an aqueous dispersion of an aromatic polyester
Oxazoline X1: Oxazoline-based water-soluble resin cross-linking agent Nippon Shokubai Co., Ltd. Trade name Epocross (registered trademark) WS-500
X2: Carbodiimide water-soluble resin crosslinking agent Nisshinbo Chemical Co., Ltd. Trade name Carbodilite (registered trademark) V-02-L2
X3: Water-soluble epoxy-based cross-linking agent Nagase ChemteX Corporation Brand name Denacol (registered trademark) EX-521
Silica D1: Silica fine particle aqueous dispersion (average particle diameter 60 nm)

(Example of coating solution)
A coating solution for the coating layer was prepared as shown in Table 2.

<Method for producing recovered polyester (1)>
As a raw material for the surface layer, 70% by weight of the polyester raw material (1) and 30% by weight of the polyester raw material (5) are mixed. As a raw material for the intermediate layer, 84% by weight of the polyester raw material (1) and 16% by weight of the polyester raw material (5) After mixing and supplying each to two twin-screw extruders with vents and melt-extruding at 290 ° C., they were cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A stretched sheet was obtained. Next, the film was stretched 2.8 times in the longitudinal direction at 100 ° C., then subjected to a preheating step in a tenter and subjected to a transverse stretching of 5.1 times at 120 ° C., followed by heat treatment at 220 ° C. for 10 seconds, 4% relaxation was applied in the width direction at 180 ° C. to obtain a master roll of a polyester film having a total thickness of 38 μm (layer structure: surface layer 4 μm / intermediate layer 30 μm / surface layer 4 μm and a width of 2000 mm).

  When the master roll was obtained, it became thick due to the neck-in phenomenon from the base, and the end portion of the polyester film used as a clip bite was cut and separated as an ear film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film having a product width of 1200 mm. At the time of this slitting, cutting and separation were performed as the surplus slit ears generated.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. The obtained pulverized product is dried and then supplied to a single-screw extruder, and the polyester obtained by melt extrusion in a 290 ° C. environment and pelletized is designated as recovered polyester (1). The recovered polyester (1) had an intrinsic viscosity of 0.551 dl / g and a terminal carboxyl group content of 43 equivalents / ton.

Example 1:
The polyester raw material (2) and the polyester raw material (4) mixed at a ratio of 96.0: 4.0 are used as the raw material, and discharged by a twin screw extruder with a vent of 90 mm; 450 kg / hr, cylinder temperature An amorphous polyester sheet that was melt extruded at 290 ° C. and flowed out of the die was rapidly cooled and solidified on a casting drum having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method to form an unstretched single layer sheet Obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. The longitudinally stretched sheet gripped by the clips is stretched 3.8 times in the transverse direction at 120 ° C., heat treated at 221 ° C., relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / A master roll of a polyester film having a thickness of 125 μm and a width of 2000 mm having m ² was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. The obtained pulverized product is designated as recovered polyester (2). The recovered polyester (2) had an IV of 0.729 dl / g and an AV of 13 equivalents / ton.

The polyester raw material (2), the polyester raw material (4), and the recovered polyester (2) are mixed in an undried state at a ratio of 76.8: 3.2: 20.0, and the diameter is 90 mm. In a twin-screw extruder equipped with a vent, melt discharge at 450 kg / hr, cylinder temperature; 290 ° C., and rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A stretched single layer sheet was obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C in the transverse direction, heat treated at 221 ° C, relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A1) was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film. It was pulverized by a pulverizer and stored for recovered polyester.

  A slit was made from a position of 400 mm from both ends of the master roll to obtain a polyester film (A1) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear. It was pulverized by a pulverizer and stored for recovered polyester.

Example 2:
The above-mentioned polyester raw material (2), polyester raw material (4), and recovered polyester (1) are mixed in a ratio of 68.0: 4.0: 28.0 as a raw material, and a twin screw extruder with a vent of 90 mm in diameter. Is discharged at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum whose surface temperature is set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched single layer sheet It was. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 221 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A2) having a width of 2000 mm was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from the position of 400 mm from both ends of the master roll to obtain a polyester film (A2) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. The obtained pulverized product is designated as recovered polyester (3). The recovered polyester (3) had an IV of 0.672 dl / g and an AV of 22 equivalents / ton.

Example 3:
A polyester obtained by mixing the polyester raw material (2), the polyester raw material (4), the recovered polyester (1), and the recovered polyester (3) in a ratio of 48.0: 4.0: 28.0: 20.0, Using a twin-screw extruder with a vent of 90 mm in diameter, melt-extruded at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum set to a surface temperature of 40 ° C. using an electrostatic application adhesion method. Thus, an unstretched single layer sheet was obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 221 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A3) having a width of 2000 mm was obtained.

  When obtaining this master roll, it becomes thick due to the neck-in phenomenon from the base, and the end of the polyester film used as a clip bite is cut and separated as an ear film and pulverized with a pulverizer. Stored as recovered polyester.

  A slit was made from the position of 400 mm from both ends of the master roll to obtain a polyester film (A3) having a product width of 1200 mm. At the time of this slitting, the surplus slit ears produced were also pulverized by a pulverizer and stored as recovered polyester.

Example 4:
The above-mentioned polyester raw material (2), polyester raw material (4), and recovered polyester (1) are mixed in a ratio of 56.0: 4.0: 40.0 as a raw material, and a twin screw extruder with a vent of 90 mm in diameter. Is discharged at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum whose surface temperature is set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched single layer sheet It was. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 221 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A4) having a width of 2000 mm was obtained.

  When obtaining this master roll, it becomes thick due to the neck-in phenomenon from the base, and the end of the polyester film used as a clip bite is cut and separated as an ear film and pulverized with a pulverizer. Stored as recovered polyester.

  A slit was made from a position of 400 mm from both ends of the master roll to obtain a polyester film (A4) having a product width of 1200 mm. At the time of this slitting, the surplus slit ears produced were also pulverized by a pulverizer and stored as recovered polyester.

Example 5:
In Example 2, a polyester film (A5) was obtained in the same manner as in Example 2 except that the polyester raw material (3) was used instead of the polyester raw material (2).

Example 6:
The recovered polyester (2), which is a pulverized product, is dried and then supplied to a single screw extruder, and the polyester that has been pelletized after melt extrusion in a 290 ° C. environment is designated as recovered polyester (4). The recovered polyester (4) had an intrinsic viscosity of 0.670 dl / g and a terminal carboxyl group content of 20 equivalents / ton. The above-mentioned polyester raw material (2), polyester raw material (4), and recovered polyester (4) mixed in a ratio of 26.2: 3.8: 70.0 as a raw material, a twin screw extruder with a vent of 90 mm Is discharged at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum whose surface temperature is set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched single layer sheet It was. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 221 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A6) having a width of 2000 mm was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from the position of 400 mm from both ends of the master roll to obtain a polyester film (A6) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

Example 7:
The above-mentioned polyester raw material (2), polyester raw material (4), and recovered polyester (1) are mixed in a ratio of 68.0: 4.0: 28.0 as a raw material, and a twin screw extruder with a vent of 90 mm in diameter. Is discharged at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum whose surface temperature is set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched single layer sheet It was. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 231 ° C., then relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² , thickness 50 μm, A master roll of a polyester film (A7) having a width of 2000 mm was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film (A7) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

Example 8:
The polyester raw material (2) and the polyester raw material (4) mixed at a ratio of 96.0: 4.0 are used as the raw material, and discharged by a twin screw extruder with a vent of 90 mm; 450 kg / hr, cylinder temperature An amorphous polyester sheet that was melt extruded at 290 ° C. and flowed out of the die was rapidly cooled and solidified on a casting drum having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method to form an unstretched single layer sheet Obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. The longitudinally stretched sheet held by the clip is stretched 3.8 times in the transverse direction at 120 ° C., heat treated at 236 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / A master roll of a polyester film having a thickness of 50 μm and a width of 2000 mm having m ² was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. The obtained pulverized product is designated as recovered polyester (5). The recovered polyester (5) had an IV of 0.729 dl / g and an AV of 13 equivalents / ton.

The polyester raw material (2), the polyester raw material (4), and the recovered polyester (5) are mixed in an undried state at a ratio of 76.8: 3.2: 20.0, and the diameter is 90 mm. In a twin-screw extruder equipped with a vent, melt discharge at 450 kg / hr, cylinder temperature; 290 ° C., and rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A stretched single layer sheet was obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. After stretching 3.8 times at 120 ° C. in the transverse direction and heat treatment at 236 ° C., it is relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (A8) was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film. It was pulverized by a pulverizer and stored for recovered polyester.

  A slit was made from the position of 400 mm from both ends of the master roll to obtain a polyester film (A8) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear. It was pulverized by a pulverizer and stored for recovered polyester.

Example 9:
In Example 2, a polyester film (A9) was obtained in the same manner as in Example 2 except that the coating liquid E-2 was used instead of the coating liquid E-1.

Example 10:
In Example 2, a polyester film (A10) was obtained in the same manner as in Example 2 except that the coating liquid E-3 was used instead of the coating liquid E-1.

Example 11:
In Example 2, a polyester film (A11) was obtained in the same manner as in Example 2 except that the coating liquid E-4 was used instead of the coating liquid E-1.

Example 12:
In Example 2, a polyester film (A12) was obtained in the same manner as in Example 2 except that the coating liquid E-7 was used instead of the coating liquid E-1.

Comparative Example 1:
The polyester raw material (2) and the polyester raw material (4) mixed at a ratio of 96.0: 4.0 are used as the raw material, and discharged by a twin screw extruder with a vent of 90 mm; 450 kg / hr, cylinder temperature An amorphous polyester sheet that was melt extruded at 290 ° C. and flowed out of the die was rapidly cooled and solidified on a casting drum having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method to form an unstretched single layer sheet Obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. The longitudinally stretched sheet gripped by the clips is stretched 3.8 times in the transverse direction at 120 ° C., heat treated at 221 ° C., relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / A master roll of a polyester film (B1) having a thickness of 125 μm and a width of 2000 mm having m ² was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as a clip bite | cut_off was cut and separated as an ear | edge part film, and was discarded.

  A slit was made from a position of 400 mm from both ends of the master roll to obtain a polyester film (B1) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear and discarded. The evaluation results of the obtained polyester film are shown in Table 3 below.

Comparative Example 2:
The polyester raw material (2) and the polyester raw material (4) mixed at a ratio of 96.0: 4.0 are used as the raw material, and discharged by a twin screw extruder with a vent of 90 mm; 200 kg / hr, cylinder temperature An amorphous polyester sheet melt-extruded at 280 ° C. and flowed out of the die was rapidly cooled and solidified on a casting drum having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to form an unstretched single-layer sheet Obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. The longitudinally stretched sheet gripped by the clips is stretched 3.8 times in the transverse direction at 120 ° C., heat treated at 221 ° C., relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / A master roll of a polyester film having a thickness of 125 μm and a width of 2000 mm having m ² was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. Let the obtained pulverized material be recovered polyester (6). The recovered polyester (6) had an IV of 0.745 dl / g and an AV of 11 equivalents / ton.

The polyester raw material (2), the polyester raw material (4), and the recovered polyester (6) are mixed in an undried state at a ratio of 76.8: 3.2: 20.0, and the diameter is 90 mm. In a biaxial extruder with a vent, 200 kg / hr, cylinder temperature; 280 ° C., melt-extruded at 280 ° C., and rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A stretched single layer sheet was obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C in the transverse direction, heat treated at 221 ° C, relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (B2) was obtained.

Comparative Example 3:
In Example 2, a polyester film (B3) was obtained in the same manner as in Example 2 except that the polyester raw material (6) was used instead of the polyester raw material (2).

Comparative Example 4:
The polyester raw material (1) and the polyester raw material (4) mixed at a ratio of 96: 4 are used as a raw material, and discharged by a twin screw extruder with a vent of 90 mm; discharge amount: 500 kg / hr, cylinder temperature: 290 ° C. The amorphous polyester sheet that had been melt-extruded and flowed out of the die was rapidly cooled and solidified on a casting drum having a surface temperature set to 40 ° C. by using an electrostatic application adhesion method to obtain an unstretched single-layer sheet. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. The longitudinally stretched sheet gripped by the clips is stretched 3.8 times in the transverse direction at 120 ° C., heat treated at 221 ° C., relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / A master roll of a polyester film having a thickness of 125 μm and a width of 2000 mm having m ² was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of the master roll to obtain a polyester film having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

  The cut-separated ear film and slit ear were pulverized by a pulverizer. The obtained pulverized product is designated as recovered polyester (7). The recovered polyester (7) had an IV of 0.615 dl / g and an AV of 20 equivalents / ton.

The polyester raw material (1), the polyester raw material (4), and the recovered polyester (7) are mixed in an undried state at a ratio of 67.2: 2.8: 30.0, and the diameter is 90 mm. In a twin-screw extruder with a vent of 500 kg / hr, cylinder temperature: 290 ° C., melt-extruded, and rapidly cooled and solidified on a casting drum set at a surface temperature of 40 ° C. using an electrostatic application adhesion method. A stretched single layer sheet was obtained. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C in the transverse direction, heat treated at 221 ° C, relaxed by 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (B4) was obtained.

  When obtaining this master roll, it becomes thick due to the neck-in phenomenon from the base, and the end of the polyester film used as a clip bite is cut and separated as an ear film and pulverized with a pulverizer. Stored as recovered polyester.

  A slit was made from the position of 400 mm from both ends of the master roll to obtain a polyester film (B4) having a product width of 1200 mm. The surplus produced at the time of this slit was cut and separated as slit ears, pulverized by a pulverizer, and stored as recovered polyester.

Comparative Example 5:
The above-mentioned polyester raw material (2), polyester raw material (4), and recovered polyester (1) are mixed in a ratio of 68.0: 4.0: 28.0 as a raw material, and a twin screw extruder with a vent of 90 mm in diameter. Is discharged at a discharge rate of 500 kg / hr, a cylinder temperature of 290 ° C., and rapidly cooled and solidified on a casting drum whose surface temperature is set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched single layer sheet It was. Next, the film was stretched 3.2 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid E-1 shown in Table 2 was applied to the upper surface of the longitudinally stretched film and led to a tenter. Stretched 3.8 times at 120 ° C. in the transverse direction, heat treated at 245 ° C., relaxed 2% in the transverse direction, and the coating amount (after drying) is 0.03 g / m ² . A master roll of a polyester film (B5) having a width of 2000 mm was obtained.

  In addition, when obtaining this master roll, it became thick by the neck-in phenomenon from a nozzle | cap | die, and the edge part of the polyester film used as the clip allowance of a clip was cut-separated as an ear | edge part film.

  A slit was made from a position 400 mm from both ends of this master roll to obtain a polyester film (B5) having a product width of 1200 mm. At the time of this slit, the generated surplus was cut and separated as a slit ear.

Comparative Example 6:
In Example 2, a polyester film (B6) was obtained in the same manner as in Example 2 except that the coating liquid E-5 was used instead of the coating liquid E-1.

Comparative Example 7:
In Example 2, a polyester film (B7) was obtained in the same manner as in Example 2 except that the coating liquid E-6 was used instead of the coating liquid E-1.

Comparative Example 8:
In Example 2, a polyester film (B8) was obtained in the same manner as in Example 2 except that the coating liquid E-8 was used instead of the coating liquid E-1.

Comparative Example 9:
In Example 2, a polyester film (B9) was obtained in the same manner as in Example 2 except that the coating liquid E-9 was used instead of the coating liquid E-1.

Comparative Example 10:
In Example 2, a polyester film (B10) was obtained in the same manner as in Example 2 except that the coating liquid E-10 was used instead of the coating liquid E-1.

  The film of this invention can be utilized suitably as a polyester film for solar cell back surface protection materials.

Claims (2)

The intrinsic viscosity (IV) is 0.62 dl / g or more and 0.73 dl / g or less, the terminal carboxyl group amount (AV) is 26 equivalents / t or less, and the intensity profile obtained by wide-angle X-ray diffraction is 24 ° to Coating having a half-value width (w) of a peak observed in a range of 30 ° of 1.17 ° or more, containing a recovered polyester, and containing a polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton and a crosslinking agent A polyester film for sealing a back surface of a solar cell, comprising a coating layer obtained by coating a liquid on at least one surface of the film. The polyester film for sealing a back surface of a solar cell according to claim 1, wherein the phosphorus element content is 70 ppm or less.