JP2012138490A - Polyester film for solar cell back surface protective material, and member for solar cell back surface protective material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a solar cell back surface protective material, excellent in hydrolysis resistance and good in wet-heat-resistant adhesion between a polyester film and a fluoropolymer.SOLUTION: A polyester film for a solar cell back surface protective material includes a coating layer obtained by coating a coating agent on one surface of a polyester film having a content of a terminal carboxyl group of 26 equivalents/ton or less and an intrinsic viscosity (IV) of 0.65 dl/g or more, the coating agent containing an acrylic resin, an epoxy compound and an oxazoline compound. A member for a solar cell back surface protective material includes a layer comprising a fluoropolymer on a coating layer of the polyester film for a solar cell back surface protective material.

Description

  TECHNICAL FIELD The present invention relates to a polyester film for solar cell back surface protective material and a member for solar cell back surface protective material. Specifically, at least one surface has excellent hydrolysis resistance with a fluoropolymer having good weather resistance. And a polyester film for a solar cell back surface protective material and a member for a solar cell back surface protective material, which have good hydrolysis resistance of the polyester film itself.

  In recent years, photovoltaic power generation has attracted a great deal of attention as an energy source that is clean and useful for preventing global warming, and has already begun to spread considerably. As a representative example of the solar power generation, a solar cell using a semiconductor such as single crystal silicon, polycrystalline silicon, amorphous silicon, and the like can be given. A solar cell is a practical application of the principle that current can be taken out when sunlight hits a semiconductor.

  The solar cell is composed of glass / sealing material (mainly EVA) / semiconductor / sealing material (mainly EVA) / back surface protective material. This solar cell is installed in unused places such as deserts and wasteland, roofs of houses or large buildings, etc., all of which are exposed to the sun. Therefore, the solar cell is required to have weather resistance against sunlight also on the back surface protective material. In addition, since it is usually installed in a humid environment, moisture and heat resistance is also required.

  About the back surface sealing material which comprises a solar cell, patent document 1 describes the invention regarding the solar cell back surface protection material which provided the fluoropolymer layer on the single side | surface on the polyester film. Since the solar cell back surface protective material according to the present invention has a fluoropolymer, it has resistance to sunlight. However, when the solar cell back surface protective material according to the present invention is used in a high-temperature and high-humidity region, the hydrolysis resistance of the polyester film and the wet heat-resistant adhesion between the polyester film and the fluoropolymer are not considered.

Special table 2010-519742 gazette

  The present invention has been made in view of the above circumstances, and the problem to be solved is to provide a polyester film for a solar cell back surface protective material that has good hydrolysis resistance and good wet heat resistance between the polyester film and the fluoropolymer. It is to be.

  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 an acrylic resin, an epoxy compound, and an oxazoline compound are provided on one side of a polyester film having a terminal carboxyl group amount of 26 equivalents / ton or less and an intrinsic viscosity (IV) of 0.65 dl / g or more. A polyester film for a solar cell back surface protective material, characterized by having a coating layer obtained by coating a coating agent containing, and a layer made of a fluoropolymer on the coating layer of the film It exists in the member for solar cell back surface protection materials.

  ADVANTAGE OF THE INVENTION According to this invention, it has the outstanding hydrolysis resistance, and also can provide the polyester film for solar cell back surface protection materials which has the heat-and-moisture resistant adhesiveness between a polyester film and a fluoropolymer. Moreover, by using the polyester film for solar cell back surface protective material of the present invention, a member for solar cell back surface protective material having good hydrolysis resistance, moisture and heat resistance adhesion, and weather resistance can be provided.

  In the present invention, the polyester film as a base material has excellent hydrolysis resistance even in a high temperature and high humidity environment. At the same time, the coating layer for improving adhesion to the fluoropolymer is also resistant to hydrolysis. It is based on the technical idea that it will have hydrolysis resistance as an easy-adhesion film for fluoropolymers for the first time. If either the polyester film of the substrate or the coating layer provided on it is inferior in hydrolysis resistance, the hydrolysis resistance of the easily adhesive polyester film has a strong effect on whichever one is inferior. Will be inadequate. Therefore, in order to make a polyester film excellent in hydrolysis resistance as an easily adhesive polyester film, it is an indispensable element that both the base film and the coating layer are excellent in hydrolysis resistance. Based on this technical idea, the polyester film as the base material of the present invention and the coating layer will be roughly divided and explained in order.

  The polyester film used as the base material of the present invention is required to have a terminal carboxyl group amount of 26 equivalent / ton or less and an intrinsic viscosity (IV) of 0.65 dl / g or more.

  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 base material of the present invention, a metal compound polymerization catalyst such as antimony, titanium, germanium and the like, which are usually used in 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 It is good to set it as the range of -40 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 is detected by analysis using a fluorescent X-ray analyzer described later.

  The catalyst of the polyester raw material used in the polyester film of the present invention is preferably titanium from the viewpoint of transparency. 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 there is a tendency for oligomers to be easily formed as a by-product in the process of melt-extrusion of the polyester. May have poor adhesion. Further, when no titanium element is contained, the productivity at the time of production of the polyester raw material tends to be inferior, and the polyester raw material reaching the target degree of polymerization may not be obtained.

  The polyester film used as the base material of the present invention may contain a color pigment as long as the hydrolysis resistance is not impaired. There is no limitation as long as the color matches the color of the roof. As this colored pigment, known inorganic pigments, organic pigments, and the like can be used.

  Examples of inorganic pigments that can be used include white pigments such as titanium dioxide and barium sulfate, red pigments such as bengara, molybdenum red, and cadmium red; Blue pigments such as cobalt blue and cerulean blue, green pigments such as chromium oxide, pyridian, emerald green, cobalt green, yellow pigments such as yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, purple such as manganese violet and mineral violet Examples thereof include black pigments such as pigments and 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 normally selected from the range of 0.01-10 micrometers, Preferably it is 0.02-5 micrometers. 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.

In addition to the color pigment added to the polyester film, a white pigment can be added in combination for the purpose of adjusting the color tone. Examples of the white pigment include titanium dioxide, zinc oxide, zinc sulfide, and barium sulfate. The average particle diameter of the white pigment can be selected in the range of usually 0.01 to 10 μm, preferably 0.02 to 5 μm. The color tone of the film after toning is preferably close to the color tone (brightness) of the solar cell by adjusting the addition amount so that the lightness (L ^* ) is 40% or less, further 30% or less. . Furthermore, in the polyester film of the present invention, in addition to the above-described colored pigment and white pigment, particles may be blended mainly for the purpose of imparting 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 thereof include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, silicon oxide, and kaolin. And particles such as aluminum oxide. 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%.

  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. Also, 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 at the point which makes a base amount low.

  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 triazines, benzophenones, and benzoxazinones. Among these, benzoxazinone ultraviolet absorbers and the like are 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 needs to be 26 equivalents / ton or less, preferably 24 equivalents, when the amount of terminal carboxyl groups of the entire film (part excluding the coating layer) is measured by the measurement method described later. / 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.

  The polyester film of the present invention is required to have an intrinsic viscosity (IV) of 0.65 dl / g or more, preferably 0.68 dl / g or more, based on the measurement method described later. It is. When the intrinsic viscosity of the polyester film is 0.65 dl / g or more, a film having good long-term durability and hydrolysis resistance can be obtained. On the other hand, although there is no upper limit of the intrinsic viscosity of the polyester film, it is about 0.90 dl / g from the viewpoint of the efficiency of the polycondensation reaction and the prevention of pressure increase in the melt extrusion process.

  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. When a twin screw extruder is used. For example, a method of providing a vent port and maintaining a reduced pressure of 40 hectopascals or less, preferably 30 hectopascals or less, and more preferably 20 hectopascals or less can be employed. 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.

  It is also important to obtain a polyester film having a terminal carboxyl group amount in a specific range by forming a film using a polyester material having a low terminal carboxyl group amount and a high intrinsic viscosity. Specifically, the total amount of terminal carboxyl groups of the raw material polyester is preferably 20 equivalents / ton, more preferably 15 equivalents / ton or less. Conventionally known methods such as a method of increasing the polymerization efficiency, a method of increasing the polymerization rate, a method of suppressing the decomposition rate, and a combination of melt polymerization and solid phase polymerization are used as a method for reducing the amount of terminal carboxyl groups of the raw material polyester. Can be adopted. For example, it is carried out by a method for shortening the polymerization time, a method for increasing the amount of polymerization catalyst, a method using a highly active polymerization catalyst, a method for lowering the polymerization temperature, or the like. In the case of using solid phase polymerization in combination, it may be formed into a chip after melt polymerization, and solid phase polymerization may be performed in a temperature range of 180 to 240 ° C. in an inert air stream such as nitrogen under heating or reduced pressure. The intrinsic viscosity is preferably 0.70 dl / g or more, more preferably 0.80 dl / g. In film production, the amount of terminal carboxyl groups increases when a regenerated raw material that has undergone a melting step is added. Therefore, in the present invention, it is preferable not to add such a regenerated raw material. preferable.

  The polyester film 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 170 ppm when the entire film is measured. More preferably, it is in the range of 0 to 140 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, and the like.

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.

  The fluoropolymer layer on the polyester film is, for example, a fluoropolymer containing a fluoropolymer having an alkyl vinyl ether (VE) or a reactive OH functional group and a crosslinking agent selected from the group consisting of organic titanate / silane / isocyanate / melamine. It is provided by applying a liquid containing a polymer on a polyester film. In order to improve the wet heat resistance with the fluoropolymer layer, it is necessary to provide a coating layer (primer layer) on the polyester film. Next, formation of the coating layer which comprises the polyester film in this invention is demonstrated.

  As for the coating layer, it may be provided by in-line coating, which treats the film surface during the stretching process of the polyester film, or may be applied off-system on the film once manufactured, and may employ both offline coating. You may use together. In-line coating is preferably used in that it can be applied at the same time as film formation, and thus can be manufactured at low cost, and the thickness of the coating layer can be changed by the draw ratio.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  In the present invention, it is an essential requirement to have a coating layer formed by coating a coating liquid containing an acrylic resin, an epoxy compound and an oxazoline compound on at least one side of a polyester film.

  As a result of various investigations, it has been found that the adhesion to the fluoropolymer layer is improved by forming a coating layer using one kind of a crosslinking agent such as an acrylic resin and an epoxy compound or an oxazoline compound. As a result of further investigation, it was found that the coating layer made of an acrylic resin, an epoxy compound, and an oxazoline compound exhibits very good adhesion.

  The acrylic resin used in the present invention is a polymer comprising a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing vinyl monomers such as (meth) acrylimide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, Various vinyl esters such as vinyl acetate and vinyl propionate; γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, “Silaplane FM-07” (methacryloyl silicon macromer) manufactured by Chisso Corporation Various silicon-containing polymerizable monomers; phosphorus-containing vinyl monomers; vinyl chloride, biliden chloride, vinyl fluoride, vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafur Various vinyl halides such as Russia propylene; various conjugated dienes such as butadiene and the like.

  In order to improve the adhesion with the fluoropolymer layer, it is also possible to use an acrylic resin containing a functional group such as a hydroxyl group, an amino group, or an amide group.

  In forming the coating layer in the film of the present invention, the coating layer of the coating layer is strengthened, has sufficient adhesion with the fluoropolymer layer, and as a crosslinking agent to improve the heat and moisture resistance after forming these layers. Epoxy compounds and oxazoline compounds are used.

  As an epoxy compound, the compound containing an epoxy group in a molecule | numerator, its prepolymer, and hardened | cured material are mentioned, for example. Examples include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, and polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. is there. Examples of the polyepoxy compound include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylol. Examples of the propane polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether Ether, polypropylene glycol diglycidyl ether, Ritetramethylene glycol diglycidyl ether and monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N ′,-tetraglycidyl-m. -Xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

  An oxazoline compound is a compound having an oxazoline group in the molecule. In particular, a polymer containing an oxazoline group is preferable, and it can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  It is also possible to contain particles in the coating layer in order to improve the slipperiness and blocking of the coating layer. Examples of the particles used include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles.

  Furthermore, as long as it does not impair the gist of the present invention, the coating layer has an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, foaming as necessary. Agents, dyes and the like may be contained.

  In the present invention, the content of the acrylic resin in the coating layer is usually 20 to 90% by weight, preferably 25 to 85% by weight, and more preferably 30 to 80% by weight. When the amount is less than 20% by weight, the adhesion may not be sufficient due to the small amount of the acrylic resin component, and when it exceeds 90% by weight, the coating layer becomes brittle due to the small amount of the crosslinking agent component, and the adhesion is not sufficient. In some cases, the heat and humidity resistance may not be sufficient.

  In this invention, the quantity of the compound derived from the epoxy compound and oxazoline compound which occupies in a coating layer is 10-80 weight% normally, Preferably it is 15-75 weight%, More preferably, it is 20-70 weight%. When the amount is less than 10% by weight, the coating layer becomes brittle and may not sufficiently withstand moisture and heat. When the amount exceeds 80% by weight, the adhesion may not be sufficient. Moreover, it is preferable that at least one of an epoxy compound and an oxazoline compound exceeds 5 weight%. When both are 5 wt% or less, the adhesion to the fluoropolymer layer may not be stable when exposed to high temperature and high humidity conditions for a long time.

In the polyester film of the present invention, a coating layer can also be provided on the surface opposite to the surface on which the coating layer is provided. For example, an ethylene-vinyl acetate copolymer resin (hereinafter sometimes abbreviated as EVA) or a polyvinyl acetal resin (hereinafter sometimes abbreviated as PVB) that is generally used as a solar cell encapsulant. It is possible to improve the moisture and heat resistance of the sealing material resin.
As a component of the coating layer formed on the opposite surface, it is preferable to contain a polyurethane having at least one of a polycarbonate skeleton or a polyether skeleton, and a crosslinking agent.
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.

  The polycarbonate polyol used for the polyurethane of the coating layer formed on the opposite surface can be obtained, for example, by reaction of diphenyl carbonate, dialkyl carbonate, ethylene carbonate or phosgene with a diol. 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 good in terms of improving adhesiveness, and has good 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.

  The polyether polyol used for the polyurethane of the coating layer formed on the opposite surface is polyoxyethylene polyol (polyethylene glycol, etc.), polyoxypropylene polyol (polypropylene glycol, etc.), polyoxytetramethylene polyol (polytetramethylene ether glycol) Etc.), copolymer polyether polyols (block copolymers and random copolymers such as polyoxyethylene glycol and polyoxypropylene glycol), and the like. 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.

  Examples of the polyisocyanate used for the polyurethane of the coating layer formed on the opposite surface include known polyisocyanates such as aliphatic, alicyclic, and aromatic.

  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.

  The polyurethane having at least one of the polycarbonate structure or the polyether structure used for the coating layer formed on the opposite surface may be one using an organic solvent as a medium, but preferably one containing water as a medium. is there. 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 for introducing an ionic group into the urethane resin in the coating layer formed on the opposite surface, various methods can be taken in each stage of the polymerization reaction. 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 above-mentioned polyurethane, the coating layer formed on the opposite surface has a crosslinking agent for imparting heat resistance, heat-resistant adhesiveness, moisture resistance, and blocking resistance to the coating layer formed on the opposite surface. Need to be used together. 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, for example, under the trade name of Carbolite (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 formed on the opposite surface, the total of the polyurethane and the crosslinking agent component described above is preferably present in an amount of 50% by weight or more, and more preferably 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 formed on the opposite surface and to impart slipperiness, it is possible to add fine particles to the coating layer formed on the opposite surface. 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, the coating layer formed on the opposite surface can contain components other than those described above as 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 formed on the opposite surface is preferably coated on the polyester film as a coating solution mainly containing water. The polyester film to be applied may be biaxially stretched in advance, but it is preferable to use a so-called in-line coating method in which the polyester film is stretched in at least one direction after being applied 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 adverse effects of are likely to occur.

  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.

  The polyester film of the present invention contains an alkyl vinyl ether (VE) or a fluoropolymer having a reactive OH functional group and a crosslinking agent selected from the group consisting of organic titanate, silane, isocyanate, and melamine on the coating layer. By applying the liquid to be applied onto the polyester film, the fluoropolymer layer can be provided.

Fluoropolymers that can be used in a fluoropolymer liquid formulation include, but are not limited to, Lumiflon (registered trademark: Asahi Glass Co., Ltd.) and Zeffle (registered trademark: Daikin Co., Ltd.). Absent.
Lumiflon (R) is an amorphous fluoropolymer of chlorotrifluoroethylene (CTFE) with several specific alkyl vinyl ethers (VE).
Zeffle® is a solution-type copolymer of tetrafluoroethylene and a hydrocarbon with reactive OH functionality, formulated for use as a main agent in high performance paints and coatings.

  Optional pigments and fillers that can be included in the fluoropolymer layer include titanium dioxide, carbon black, perylene pigments, dyes, dyes, mica, polyamide powder, boron nitride, zinc oxide, aluminum oxide, silica, UV absorption Including, but not limited to, agents, corrosion inhibitors, and desiccants. One preferred pigment is Ti-Pure® R-105 (DuPont), which is titanium dioxide. One preferred hydrophobically modified silica is Cab-o-sil TS720 (Cabot). Pigments, UV absorbers, and corrosion inhibitors function to impart opacity and weather resistance. Orgasol® Ultrafine is a preferred polyamide powder (Arkema Inc) and can be included to reduce gloss. Carbon black, pigments, and dyes can be included to change the color of the backsheet. Mica can be included to impart flame retardancy. Boron nitride, aluminum nitride, and / or aluminum oxide can be included to improve thermal conductivity. Cloisite (registered trademark) Nanoclaims (Southern Cray Products), 3M (registered trademark) Glass Bubbles, and a desiccant are preferably included in order to improve moisture barrier properties. Silica and / or boron nitride can be included to improve dielectric properties. Silica can also be included to reduce gloss and impart flame retardancy.

  Organic solvents that can be used to form the fluoropolymer solution include methyl ethyl ketone (MEK), acetone, methyl isobutyl ketone (MIBK), toluene, xylene, methanol, isopropanol, ethanol, heptane, ethyl acetate, isopropyl acetate, n -Includes but is not limited to butyl acetate, n-butyl alcohol, or mixtures thereof. Preferred solvents include xylene, cyclohexanone, and methyl ethyl ketone (MEK). A suitable solvent is one whose boiling point is sufficiently low that all components dissolve and minimize or eliminate residual solvent in the coating.

  In order to prevent brittle fracture of the fluoropolymer layer, it is preferable to use a crosslinking agent in the fluoropolymer solution. Preferred crosslinkers include, but are not limited to, DuPont Tyzor® organic titanate, silane, isocyanate, and melamine. In order to ensure weather resistance, aliphatic isocyanates are preferable because the solar cell back surface protective material is generally intended for outdoor use for 30 years or more.

  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) Amount of terminal carboxyl groups (equivalent / ton)
The amount of terminal carboxyl groups was measured by a so-called titration method. That is, polyester was dissolved in benzyl alcohol, phenol red indicator was added, and titrated with a water / methanol / benzyl alcohol solution of sodium hydroxide. 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.

(2) Intrinsic viscosity (IV)
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 to determine the intrinsic viscosity (IV) [dl / g]. 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) Quantification of catalyst-derived elements The amount of elements in the film was determined under the conditions shown in Table 1 below using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation). 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.

(4) Film elongation hydrolysis resistance The film was treated for 72 hours in an atmosphere of 120 ° C.-100% RH using a personal pressure cooker PC-242HS-E manufactured by Hirayama Seisakusho. Next, after adjusting the temperature and humidity for 24 hours in an atmosphere of 23 ° C. and 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 30-60% ×: Retention rate is less than 30%

(5) Moisture and heat resistant adhesive strength with fluoropolymer layer <Solution adjustment method>
Lumiflon (registered trademark) is of LF200 grade obtained as a 60% solution (200 g) of xylene from Asahi Glass Co., Ltd. The pigment used in this example is Ti-Pure (R) R-105 (76.2 g) obtained from DuPont. The cross-linking agent is Desmodur® N3300 (21.4 g) obtained from Bayer. The pigment was mixed with the Lumiflon® solution using a high shear mixer and the solvent and crosslinker were added.

<Application to polyester>
The solution was applied to a polyester film. In addition, when there was a primer layer, it apply | coated on the surface with a primer. The liquid formulation was transferred from the pan to the film with an applicator roll and weighed with a Meyer rod to obtain the desired coating weight. The coating was applied to a polyester film. The coating is applied at a coating weight of 10 to 120 g / m ² , preferably 30 to 90 g / m ² , more preferably 30 to 45 g / m ² .

<Heat and heat resistant adhesive strength>
The sample in which the fluoropolymer layer was formed was processed for 48 hours in an atmosphere of 120 ° C.-100% RH using a personal pressure cooker PC-242HS-E manufactured by Hirayama Seisakusho. Next, the temperature and humidity were controlled for 24 hours in an atmosphere of 23 ° C. and 50% RH. A cross cut (100 squares of 1 mm ² ) is applied to the film, and an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) is applied to the film, and a peeling angle of 180 degrees is applied. After peeling off suddenly, the peeled surface was observed. The evaluation results are as follows.
○: Peeling area is less than 20% Δ: Peeling area is 20% or more and less than 50% ×: Peeling area is 50% or more

Next, the polyester raw material used in the following examples will be described.
<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 Continuous transfer to a third stage polycondensation tank set at 280 ° C. and an absolute pressure of 0.3 kPa so that the intrinsic viscosity of the resulting polyester resin is 0.65 (dl / g) In each polycondensation 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 12 (equivalent / t).

<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 was performed by continuously supplying to the solid phase polycondensation apparatus and adjusting the residence time so that the intrinsic viscosity of the resulting polyester resin was 0.75 (dl / g) at 215 ° C. in a nitrogen atmosphere. To obtain a polyester raw material (2). The amount of terminal carboxyl groups was 8 (equivalent / t).

<Method for producing polyester raw material (3)>
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 1.5% 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 (3). The intrinsic viscosity was 0.60 dl / g, and the amount of terminal carboxyl groups was 21 equivalent / t.

<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 0.06 wt%, 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 0.55 dl / g due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. Subsequently, the obtained polyester chip was subjected to solid phase polymerization at 220 ° C. under vacuum to obtain a polyester raw material (4). The intrinsic viscosity was 0.75 dl / g, and the amount of terminal carboxyl groups was 25 equivalents / t.

<Method for producing polyester raw material (5)>
In the production method of the polyester raw material (4), a polyester is produced in the same manner except that an amount of 40 g / resin t as a titanium atom per 1 t of the polyester resin from which tetra-n-butyl titanate is obtained is added. A raw material (5) was produced. The intrinsic viscosity was 0.71 dl / g and the amount of terminal carboxyl groups was 27 equivalents / t.

<Method for producing polyester raw material (6)>
In the production method of the polyester raw material (1), when the esterification reaction product is polymerized, the polyester raw material (6) is used under the same conditions as the polyester raw material (1) except that tetra-n-butyl titanate is not added. ) Polymerized. The obtained polyester chip had an intrinsic viscosity of 0.49 dl / g and was a raw material that was severely brittle and unsuitable for forming a polyester film.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Acrylic resin: (I) Aqueous dispersion of acrylic resin polymerized with the following composition 2-hydroxyethylmethyl methacrylate / methyl methacrylate / t-butyl methacrylate / acrylic acid = 10/57/30/3 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)
Polyester resin: (II) A water dispersion of a polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1 4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)
Epoxy compound: (III) Denacol EX-521 (manufactured by Nagase ChemteX), which is polyglycerol polyglycidyl ether
・ Oxazoline compounds: (IV)
Acrylic polymer Epocros WS-500 having an oxazoline group and a polyalkylene oxide chain (manufactured by Nippon Shokubai, type containing about 38% by weight of 1-methoxy-2-propanol solvent)

(Example of coating solution)
A coating solution was prepared as shown in Table 2 below.

Example 1:
A polyester obtained by mixing the polyester raw material (2) and the polyester raw material (3) in a ratio of 96: 4 is used as a raw material, melt-extruded at 290 ° C. by one twin-screw extruder with a vent, and using an electrostatic application adhesion method. An unstretched single-layer sheet was obtained by rapid cooling and solidification on a casting drum set at a surface temperature of 40 ° C. 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 solution 1 shown in Table 2 was applied to the surface of the machined film and led to a tenter. A polyester film with a thickness of 125 μm that is 3.8 times stretched at 120 ° C. in the direction, heat-treated at 221 ° C., then relaxed 2% in the lateral direction, and the coating amount (after drying) is 0.03 g / m ² Got. When various adhesiveness was evaluated regarding the obtained polyester film, in any evaluation, it was favorable. The properties of this film are shown in Table 3 below.

Examples 2-4:
In Example 1, a film was obtained in the same manner as in Example 1 except that the polyester raw material in the mixture was changed to the polyester mixing ratio shown in Table 3. The properties and evaluation results of the obtained film are shown in Table 3 below.

Comparative Examples 1-6:
In Example 1, a film was obtained in the same manner as in Example 1 except that the polyester raw material or coating solution in the mixture was changed as shown in Table 4 below. Table 4 shows the properties and evaluation results of the obtained film.

Comparative Example 7:
A polyester obtained by mixing the polyester raw material (2) and the polyester raw material (3) in a ratio of 96: 4 is used as a raw material, melt-extruded at 290 ° C. by one twin-screw extruder with a vent, and using an electrostatic application adhesion method. An unstretched single-layer sheet was obtained by rapid cooling and solidification on a casting drum set at a surface temperature of 40 ° C. 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, then led to a tenter, stretched 3.8 times at 120 ° C. in the transverse direction, and heat-treated at 221 ° C. Later, it relaxed by 2% in the lateral direction. Thereafter, the obtained film was subjected to corona treatment. The thickness of the obtained film was 125 μm. Table 4 shows the properties and evaluation results of the obtained film.

Reference example 1:
An attempt was made to form a polyester film using the polyester raw material (6), but the film was so brittle that the shape of the film could not be maintained.

  The film of this invention can be utilized suitably as a polyester film for solar cell back surface protection materials. Moreover, it can become a member for solar cell back surface protection materials by coat | covering a fluoropolymer. The industrial significance of the present invention is high.

Claims (2)

A coating agent containing an acrylic resin, an epoxy compound, and an oxazoline compound is applied to one side of a polyester film having a terminal carboxyl group amount of 26 equivalents / ton or less and an intrinsic viscosity (IV) of 0.65 dl / g or more. The polyester film for solar cell back surface protection materials characterized by having the coating layer obtained by this. A member for protecting a back surface of a solar cell, comprising a layer made of a fluoropolymer on the coating layer of the film according to claim 1.