TW201037840A - Polyester film for solar cell, backsheet of solar cell using the same and solar cell - Google Patents

Abstract

The present invention provides a polyester film for solar cell having excellent heat resistance and hydrolysis resistance, and a solar cell using the same has high durability. The present invention provides a polyester film for solar cell, wherein the concentration of carboxyl end group is less than 13eq/ton and the temperature of endothermic peak value of less than 220 DEG C is measured by a differential scanning calorimeter (DSC).

Description

[Technical Field] The present invention relates to a polyester film for a solar cell excellent in heat resistance and hydrolysis resistance, a solar cell backsheet using the same, and a solar cell using the same. In recent years, solar power generation, which is a clean energy source of semi-permanent and pollution-free next-generation energy, has attracted attention, and solar cells are rapidly gaining popularity. As the film system of the solar battery back sheet, for example, a polyethylene-based resin and a polyester-based resin sheet, and a fluorine-based film can be used (see Patent Documents 1 to 3). Most of the solar cells are installed outside the house, and in this case, durability (weather resistance, heat resistance, and UV (UV) resistance) to the natural environment is highly demanded. PRIOR ART DOCUMENT Patent Document Patent Document 1: Japanese Patent Laid-Open No. Hei 11-26 1 08 5A. Patent Document 2: Japanese Laid-Open Patent Publication No. Hei 11-186575.专利 Patent Document 3: Japanese Patent Laid-Open No. 2006-270025. SUMMARY OF THE INVENTION However, even in the films described in Patent Documents 1 to 3, heat resistance and hydrolysis resistance are insufficient, which hinders long-term use of solar cells outside the house. Accordingly, the present invention has been made to solve such problems, and it is desired to provide a polyester film for a solar cell which has both heat resistance and hydrolysis resistance, a solar battery back sheet and a solar battery using the same. In other words, the present invention is a solar cell having a carboxyl end group concentration of 13 eq/t 〇 n or less, 201037840 and having a small endothermic peak temperature Tmeta ( ° C ) of 220 ° C or less according to differential scanning calorimetry (DSC). Use a polyester film, a solar cell backsheet using it, and a solar cell. According to the present invention, a polyester film for a solar cell having both heat resistance and hydrolysis resistance, a solar battery back sheet using the same, and a solar battery can be provided. Further, by using this, the solar cell backsheet can achieve better durability and thinner than conventional ones, so that the durability and thickness of the solar cell can be improved. [Embodiment] The film of the present invention must be a polyester film. Preferably, the polyester film of the present invention is prepared from an ester component of a polyester component in an amount of 90 mol% or more of an ethylene component, and has heat resistance and mechanical properties, but may be used as another copolymerization component. A copolymer of a dicarboxylic acid or an ester-forming form inducer and a diol is used. The copolymerizable dicarboxylic acid component can be exemplified by isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6 naphthalene dicarboxylic acid, 4,4'- Diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylindole dicarboxylic acid, and the like. Further, examples of the alicyclic dicarboxylic acid component which can be copolymerized include 1,4-cyclohexanedicarboxylic acid. Further, examples of the diol component include ethylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, and 1, 6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol An aliphatic, alicyclic or aromatic diol such as 2,2-bis(4'β-hydroxyethoxyphenyl)propane. These components may be used alone or in combination of two or more. The melting point of the polyester to be used is preferably 250 ° C or more in which heat resistance is preferable, and the productivity is preferably in the case of 201037840 3 00 t or less. As long as it is within this range, other components may be copolymerized and mixed. Further, various additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, inorganic particles, organic particles and the like may be added to the polyester. In particular, inorganic particles or organic particles can effectively impart smoothness to the surface of the film to improve the usability of the film. The polyester can be produced according to a conventional polyester production method. In other words, a dialkyl ester can be used as the acid component, and after the transesterification reaction with the diol component, the reaction product is heated under reduced pressure, and the remaining diol component is removed and polycondensed. production. Further, a dicarboxylic acid can also be used as an acid component, and it can be produced by a conventional direct polymerization method. As the reaction catalyst, a titanium compound, a lithium compound, a calcium compound, a magnesium compound, a ruthenium compound, a ruthenium compound or the like can be used. The polyester thus obtained, by solid phase polymerization, can further increase the degree of polymerization and lower the concentration of the carboxyl end group. The solid phase polymerization can be carried out in a dryer of 200 to 250 ° C under a reduced pressure atmosphere of ltorr or under a nitrogen gas stream. In the present invention, in order to satisfy the hydrolysis resistance, the inherent viscosity of the polyester film is preferably in the range of 0.6 to 1.2 dl/g. More preferably, it is in the range of 0.65 to 0.8 dl/g, and most preferably in the range of 0.7 to 0.8 dl/g. In order to improve the hydrolysis resistance, although it is preferable to increase the intrinsic viscosity, when the intrinsic viscosity exceeds 1.2 dl/g, it is necessary to lengthen the solid phase polymerization time in the production of the polyester resin, so that the cost is remarkably increased, which is not preferable. Further, in the case of less than 0.6 dl/g, heat resistance and hydrolysis resistance are remarkably lowered due to a low degree of polymerization, which is not a preferable choice. The polymerization conditions at the time of production of the polyester resin can be adjusted so that the intrinsic viscosity of 201037840 is maintained within the above preferred range. In the present invention, in order to enhance the hydrolysis resistance, the carboxyl group end group concentration of the polyester film must be in the range of 13 eq (equivalent) / ton or less. It is preferably 1 2 eq/ton or less, more preferably 8 eq/ton or less, and most preferably 5 eq/ton or less. Although the lower limit is not particularly limited, the theoretical lower limit is Oeq/ton ° such that the carboxyl terminal group concentration is within the above preferred range. With regard to the polyester resin as a raw material, it is preferred to use a polycondensation having a small carboxyl terminal group concentration. Ester resin. The purpose of reducing the concentration of the carboxyl end group in the polyester resin can be achieved by lengthening the solid phase polymerization time in the production of the polyester resin. Further, in order to make the carboxyl terminal group concentration within the above preferred range, a terminal blocking agent can also be used in a preferred embodiment. The blocking agent may, for example, be a carbodiimide compound, an oxazoline compound, an epoxy compound, a carbonate compound or the like. The effect of adding together with the polyester resin at the time of film formation is high. It is preferred to use a carbodiimide compound compound, and it is preferably contained in an amount of from 0.3 to 5% by weight based on the total amount of the polyester film. Of course, solid phase polymerization and blocking agents can also be used at the same time. Θ The film of the present invention satisfies sufficient hydrolysis resistance, and the micro endothermic peak temperature Tmeta (°C) obtained by differential scanning calorimetry (DSC) must be in the range of 220 ° C or less. It is preferably 205 ° C or lower, more preferably 195 ° C or lower. Although the lower limit is not particularly limited, the heat shrinkage rate is remarkably improved when the temperature is less than 150 ° C, and therefore it is preferably 150 ° C or more. More preferably at 160 ° C or above. The temperature of the heat treatment at the time of film formation can be changed so that the temperature of the minute endothermic peak 在 is within the above preferred range. Although the film thickness at the time of film formation differs from the film forming speed, the heat treatment temperature is preferably 22 (TC or less, 201037840), and the film forming method and heat treatment step of the film of the present invention will be described later. Most of the manufacturing steps are thermal contact steps. When the heat shrinkage rate of the polyester film for solar cells is too large, in the manufacturing process of the solar cell, the polyester film or the solar cell back sheet of the solar cell may shrink, possibly causing the sun. The entire battery unit is thus twisted to cause cracks. In view of the above, the film of the present invention preferably has a small heat shrinkage rate. Specifically, the long side direction (MD) of the film and its transverse direction (TD) (sometimes referred to as width) The heat shrinkage rate at 150 ° C for 30 minutes is preferably 〇 6 % or less, more preferably 0.4% ^ or less, more preferably 0.2% or less. Further, the heat shrinkage rate is preferably -0.5%. Further, in the present invention, in order to improve hydrolysis resistance, it is preferred to lower the heat treatment temperature, and as a result, the heat shrinkage ratio may be increased. Therefore, in order to achieve a heat shrinkage ratio within the above preferred range, it is preferred to use the latter. (1) or (2) One of the methods (of course, the methods (1) and (2) can also be used at the same time). Method (1): In the heat treatment step, while the film is heat-treated, the MD direction and the TD direction of the film are respectively contracted by 0. 5 to 10% of the method 〇 Method (2): A method of performing heat treatment on an off-line basis using a film (for example, a furnace, etc.) for the film to be formed into a film. In the method, the heating temperature is preferably 150 to 220 °. C, and the heating time is preferably between 10 and 60 seconds. The film of the present invention preferably has a plane alignment coefficient of 0.130 or more, preferably 0.165 or more, more preferably 0.168 or more, still more preferably 0.170 or more, and most Preferably, it is 0. 1 74 or more, and the hydrolysis resistance is further improved. The plane alignment coefficient referred to in the present invention is obtained by using an Abbe refractometer according to the following formula (A^201037840).

(A) Plane alignment coefficient = (nMD + nTD ) / 2-nZD In the above formula (A), nMD represents the refractive index of the long side direction (MD) of the film, nTD represents the transverse direction (TD) of the film, nZD Represents the refractive index in the thickness direction of the film. By increasing the stretching ratio at the time of film formation, it is achieved that the plane alignment coefficient of the film is maintained within the aforementioned range. Preferably, the longitudinal direction (MD) of the film and the transverse direction (TD) of the film are adjusted to 2.5 to 6.0 times, and in order to make the plane alignment coefficient of the film reach 0.165 or more, the MD and TD directions are respectively extended. It is preferred to adjust to 3.0 to 5.0 times. Further, although the upper limit of the plane alignment coefficient of the film is not particularly limited, if the stretching ratio is continuously increased in order to increase the plane alignment coefficient, the film stability is deteriorated, so from the viewpoint of productivity, it is preferably 0.200. Hereinafter, it is more preferably 0.185 or less. With respect to the film of the present invention, the micro endothermic peak temperature Tmeta (°C) obtained by differential scanning calorimetry (DSC) and the plane alignment coefficient B2 of the film preferably satisfy the following formula (B). (B) B2^ 0.0 0 0 8 6 X Tmeta-0.0 0 2 8 6 ° When formula (B) is satisfied, hydrolysis resistance can be improved (average elongation after 72 hours at 125 ° C and 100% humidity) Degree retention rate, etc.). In the present invention, it is preferred to add a degradation compound which inhibits hydrolysis to the film. It is preferred to contain a special phosphorus compound. Therefore, in the present invention, the amount of phosphorus atoms in the polyester film is preferably 200 ppm or more as measured by fluorescent X-ray. More preferably, it is 300 ppm or more and more preferably 400 ppm or more. As the phosphorus compound, preferably one or more phosphorus compounds selected from the group consisting of phosphoric acid, phosphorous acid, acid, phosphonic acid, methyl ester, ethyl ester, phenyl group, half ester, and other inducers may be used. Preferably, the invention may specifically be a methyl ester, an ethyl ester or a phenyl group of phosphoric acid, phosphorous acid or phosphonic acid. Further, the method of containing the phosphorus compound is preferably carried out by adding a phosphorus compound while producing a polyester raw material substrate. When used as a solar cell backsheet, it is preferable to be less susceptible to deterioration by sunlight. Therefore, a UV (ultraviolet) absorber and a substance that reflects UV characteristics can be added to the film. Further, in a preferred embodiment, the average reflectance of the wavelength of 400 to 700 nm is 80% or more on at least one of the film surfaces. More preferably, it is 85% or more, and the best is more than 90%. By making the average reflectance of the wavelength of 400 to 700 nm 80% or more, the solar cell using the film of the present invention in the case of direct sunlight irradiation is less likely to cause deterioration of the film. The method of making the average reflectance of the wavelength of 400 to 700 nm by 80% or more is a method of allowing the film to contain inorganic particles, or a method of generating a void in the polyester film by adding a polyester and a non-compatible resin. Suitable inorganic particles for the former are: wet and dry cerium oxide, colloidal cerium oxide, calcium carbonate, aluminosilicate, calcium phosphate, aluminum oxide, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide. (zinc white), cerium oxide, cerium oxide, zirconium oxide, tin oxide, antimony oxide, magnesium oxide, barium carbonate, zinc carbonate, lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, Mica titanium, talc, clay, kaolin, lithium fluoride, calcium fluoride, and the like, but preferably, particularly, titanium oxide or barium sulfate. The content of the inorganic particles is preferably 5 to 55% by weight, preferably 5 to 5% by weight, based on the entire polyester film. When the content is less than the above range, a film having a deteriorated reflectance is formed. Conversely, when the content of 201037840 is more than the above range, the film is likely to be broken when it is stretched, and productivity is lowered. In the case where productivity is important, the film of the present invention preferably has two or more layers of polyester. In the case of having two or more polyester layers, in any of the polyester layers, the inorganic particles are preferably 5 to 5% by weight (relative to the polyester layer). More preferably, it is contained in an amount of 5 to 35% by weight. Although the inorganic particle content of the other polyester layer is not particularly limited, the smaller the content, the more the productivity can be improved. Further, as the non-compatible resin of the polyester used in the latter method, Ο is preferably used: a polyolefin resin such as polyethylene, polypropylene, polybutene or polypentene, a polystyrene resin, or a polypropylene resin. , polycarbonate resin, polyacrylonitrile resin, polyphenylene sulfide resin and fluorine resin. These non-compatible resins may be a homopolymer or a copolymer, or two or more kinds of incompatible resins may be used in combination. Among them, a polyolefin resin such as polypropylene having a small surface tension and polypentene is preferable, and polypentene is preferable. The difference in surface tension between the polypentene and the polyester is relatively large and has a high melting point, and is characterized in that the effect of forming voids per unit addition amount is preferable, and is a particularly suitable non-compatible resin. In the case of containing a non-phase-soluble resin, the amount is preferably from 5 to 20% by weight, preferably from 0.5 to 10% by weight, based on the total amount of the polyester film. When the content is less than the above range, a film having a deteriorated reflectance is formed. Conversely, when the content is more than the above range, since the density of the entire film is lowered, the film is liable to be broken when it is stretched. Will reduce productivity. In order to further improve the hydrolysis resistance, the present invention preferably has at least two or more polyester layers. Preferably, the layer is laminated with a layer excellent in hydrolysis resistance and a layer having a wavelength of 400 to 700 nm and an average reflectance of 80% or more, and the foregoing structure is advantageous from the viewpoint of characteristics and cost of -10-201037840. It is preferable that the polyester film for a battery has an average elongation retention ratio of 50% or more after being left for 48 hours at 125 ° C and a humidity of 100%. It is preferably 55% or more, more preferably 60% or more, most preferably 65% or more, and particularly preferably 70% or more. When the average elongation retention ratio is less than 50%, the mechanical strength in long-term use is lowered, and as a result, when a solar cell having the same as the backing plate is used, if any externally applied surface is applied to the solar cell (for example, When the solar cell is hit by a falling stone or the like, it may cause the backing plate to break, etc., which is not a preferable choice. In the polyester film for a solar cell of the present invention, by maintaining the average elongation retention ratio of 50% or more, the durability of the mechanical strength of the back sheet during long-term use can be improved. The polyester film for a solar cell of the present invention preferably has an average elongation retention ratio of at most 1% by weight after being left for 72 hours at 125 ° C and a humidity of 100%. The above average elongation retention test after 72 hours of storage at 125 ° C and a humidity of 1% was more severe than the average elongation retention test after 48 hours of the test. Therefore, in the case of applications such as solar cell use 0 that require long-term durability, the average elongation retention rate after 72 hours can be used as an evaluation index. The average elongation retention after 72 hours is preferably 20% or more, more preferably 30% or more, most preferably 40% or more, and particularly preferably 50% or more. When the average elongation retention rate after 72 hours is less than 1%, the film strength for the solar cell will significantly reduce the internal mechanical strength during long-term use. Therefore, if any external impact is applied to the solar cell (for example, if the solar cell is hit by a falling stone), the back plate may be broken -11-201037840, etc., which is not a preferred choice. Moreover, the solar cell back sheet containing one or more polyester films for solar cells of the present invention preferably has an average elongation retention ratio of 50% or more after being left for 48 hours at 125 ° C and a humidity of 100%. . The average elongation retention ratio obtained by the above method is preferably 55% or more, preferably 60% or more, more preferably 65% or more, and most preferably 70% or more. In order to maintain the average elongation retention ratio within the above preferred range, the ratio of the thickness of the polyester film for a solar cell of the present invention to the overall thickness of the back sheet is preferably between 5 and 100%. In other words, in order to further increase the average elongation retention ratio, it is preferred that the thickness of the polyester film for a solar cell of the present invention should be more thick. Hereinafter, a specific production method (one embodiment) of the polyester film of the present invention will be described. First, the polyethylene terephthalate (PET) resin is dried in a nitrogen atmosphere or a vacuum atmosphere as needed. Next, the dried polyester resin is supplied to a single-screw or twin-screw extruder, melt-extruded, and discharged into a sheet shape on a cooling cylinder by a T-die to obtain an unstretched sheet. Ο Next, after the unstretched film is extended in the longitudinal direction, it is extended in the width direction, or after extending in the width direction, and then extended in the longitudinal direction (sequential biaxial stretching method) The extension is performed by extending the longitudinal direction and the width direction of the film at the same time (simultaneous biaxial stretching method). After the extension, heat treatment of the film is performed. The heat treatment can be carried out by any conventional method known in the art such as a tenter, a heating furnace or a heating roll. Although the heat treatment is generally carried out at a temperature lower than the melting point of the polyester, the present invention -12-201037840 is such that Tmeta (°C) is at most 220 ° C, so that the heat treatment temperature is preferably 22 〇t or less. It is preferably at most 2 1 ° C, more preferably below 200 ° C, and most preferably below 1 90 ° C. The lower limit of the heat treatment temperature is not particularly limited, but the heat shrinkage rate is remarkably improved at less than 150 ° C, so it is preferably at least 150 ° C, more preferably at least 160 ° C. Next, the film may be heat-treated while being relaxed in the longitudinal direction and/or the width direction. Next, the film of the present invention can be obtained by crimping the film subjected to the above heat treatment. ^ Further, a plurality of heat treatment steps may be performed, but in this case, the heat treatment temperature of the highest temperature heat treatment step is preferably 22 (TC or less, preferably 2 10 ° C or lower, more preferably 200 ° C or lower). (Optimum below 190 °C) [Evaluation method of characteristics] (1) Intrinsic viscosity The film was dissolved in o-chlorophenol, and the viscosity of the solution was measured at 25 ° C, and the intrinsic viscosity was obtained according to the following formula.

Nsp/C=[r(]+Κ[η]2 · C 〇 where nsp=(solution viscosity/solvent viscosity)-1, C system 100ml Solvent polymer weight contained in the solvent (this measurement is lg/ 10 〇ml), K system Huggins constant (0.3 43). Also, the solution viscosity and solvent viscosity were measured using an Ostwald viscometer. (2) The carboxyl end group concentration will be 〇.5g of film. It is dissolved in hydrazine-cresol and measured by potentiometric titration using potassium hydroxide to determine the concentration of the carboxyl end group. (3) The micro endothermic peak is obtained by differential scanning calorimetry (DSC)-13- 201037840値temperature τ meta ( °c ) The micro endothermic peak temperature Tmeta (°C ) is based on JIS K7122-1987 (refer to the JIS Handbook 1999 edition) using the differential scanning calorimetry equipment manufactured by Seiko Instruments. The DSC-RDC220 automatically controls the device'' and analyzes the data using the Discs Discs "SSC/5200". The 5mg film is measured in a vortex at a temperature increase rate of 20 °C / min from 25 °C is raised to 300. (: and measured. With the differential scanning calorimetry obtained In the table, the micro endothermic peak temperature before the peak of the crystal dissolution is Tmeta (°c). If it is difficult to observe the micro endothermic peak, the data analysis unit enlarges the peak and the peak, and then reads the peak. The method of reading the micro endothermic chart is described, but it can be performed by the following method. First, draw a straight line of 135 °c and 155 °c値 to obtain the area on the heat absorbing side of the graph curve. C with 160 ° C, 145 ° C and 165 ° C, 150 ° C and 17 (TC, 155 ° C and 175 ° C, 160 ° C and 180 ° C, 165 ° C and 185 ° C, 170 ° C with 190°C, 175°C and ❹195°C, 180°C and 200°C, 185°C and 205°C, 190°C and 210°C, 195°C and 215°C, 200°C and 220 The area of 17 °C, such as °C, 205 °C and 225 °C, 210 °C and 230 °C, 215 °C and 235 °C, 220 °C and 240 °C. The heat absorption of the tiny peaks is usually 〇· 2 to 5.0 J/g, so only 0.2 J/g or more and 5. (U/g or less) is used as valid data. Among the total of 18 area data, the temperature data area of the largest area of the effective data is in the temperature field. Endothermic The peak temperature as Zhi Zhi Tmeta (° C). In the absence of valid data, there is no Tmeta ( °C ). The chart is shown in Figure 1. -14- 201037840 (4) Heat shrinkage rate According to JIS-C23 1 8 (2007), a sample having a width of 10 mm and a mark gap of about 100 mm was heat-treated at a temperature of 150 ° C and a load of 0.5 g for 30 minutes. The heat shrinkage rate measuring device (AMM-1 No. 1) manufactured by TECHNO NEEDS COMPANY LTD. was used and the mark gap before and after the heat treatment was measured, and the heat shrinkage rate was calculated according to the following formula. Heat shrinkage rate (%) = {(L0-L) / L0} χΙΟΟ L0 : Marking gap before heat treatment ^ L : Marking gap after heat treatment (5) Plane alignment coefficient using ABBE manufactured by ATAGO The shell type refractometer type 4T uses a sodium gas lamp as a light source to measure the refractive index of the film.

(A) Plane alignment coefficient = (nMD + nTD ) / 2-nZD In the above formula (A), nMD represents the refractive index of the long side direction (MD) of the film, nTD represents the transverse direction (TD) of the film, nZD Represents the refractive index in the thickness direction of the film. 〇 (6) Measurement of phosphorus atom content by fluorescent X-ray measurement The content of phosphorus atoms was measured by a fluorescent X-ray method (ZSXIOOe, manufactured by Rigaku Corporation). (7) The average reflectance at a wavelength of 400 to 700 nm is attached to an integrating sphere accessory (ISR2200 manufactured by Shimadzu Corporation) in a spectrophotometer (Shimadzu Corporation UV245 0), with barium sulfate as a standard plate and relative reflection at 100% standard plate. The rate is measured as a measure. In the wavelengths of 400 to 700 nm, the relative reflectance per wavelength of 0.5 nm is measured, and the average 値 of the relative reflectances of the -15-201037840 is taken as the average reflectance. (8) The elongation retention after 48 hours of standing at 125 ° C and 100% humidity is measured according to AS TM-D 8 8 2-97 (refer to the 1 999 ASTM Annual Standard Index Manual ( ANNUAL BOOK OF ASTM STANDARDS)), the sample x was cut into a size of 1 cm x 20 cm, and the elongation at break (initial) at the time of stretching was measured at a jig pitch of 5 cm and a tensile speed of 300 mm/min. Further, the measurement was performed for 5 samples, and the obtained average value of 〇 was taken as the elongation at break (initial) A0. Next, the sample was cut into a size of 1 cm x 20 cm, and subjected to a highly accelerated life test apparatus EHS-221MD manufactured by ESPEC CORP., and subjected to treatment at a temperature of 125 ° C and a humidity of 100% for 48 hours, and then referred to ASTM-D882-97C. The tensile elongation of the sample after treatment in the 1999 ASTM Annual Standard Index Manual was measured for elongation at break (after treatment) at a clamp pitch of 5 cm and a tensile speed of 300 mm/min. Further, five samples were measured for the average enthalpy obtained as the elongation at break (after treatment) A 1 . Using the obtained elongation at breaks A0 and A1, the elongation retention ratio was calculated according to the following formula (1). The elongation retention ratio (%) = A1/A 〇 x 100 ( 1 ) Further, the average elongation retention ratio is calculated according to the following formula (2). Average elongation retention rate (%) = (MD direction elongation retention rate + TD direction elongation retention rate) / 2 ( 2 ) In addition, even using the high accelerated life test equipment of Hirayama Manufacturing Co., Ltd.-16- 201037840 (HAST Equipment) PC -30 4R8D is measured in the same number as ESP-221MD, which is used in ESPEC CORP.'s highly accelerated life testing equipment. Therefore, it can also be used in the high-acceleration life testing equipment (HAST equipment) PC-304R8D of Hirayama Works. measuring. (9) Measurement of elongation at break after standing for 72 hours at 125 ° C and humidity of 100% The measurement of elongation at break is based on ASTM-D882-97 (refer to the 1999 ASTM Annual Standard Index Manual). The lcmx20cm is large and small, and the elongation at break (initial) at the time of stretching is measured at a jig pitch of 5 cm and a tensile speed of 300 mm/min. Further, measurements were made for 5 samples, and the obtained average enthalpy was taken as the elongation at break (initial) A2. Next, the sample was cut into a size of 1 cm x 20 cm, and the sample was processed using a high accelerated life test apparatus (HAST equipment) PC-304R8D manufactured by Hirayama Seisakusho Co., Ltd. under the conditions of 125 ° C and a humidity of 100% for 72 hours. The elongation at break is based on ASTM-D 882-97 (1 999 ) -97 (refer to the 1 999 edition of the ASTM Annual Standard Index Manual).

When Q was 5 cm and the drawing speed was 300 mm/min, the elongation at break (after treatment) was measured. Further, measurements were made for 5 samples, and the average enthalpy obtained was taken as the elongation at break (after treatment) A3. Using the obtained elongation at breaks A2 and A3, the elongation retention ratio was calculated according to the following formula (3). The elongation retention ratio (%) = Α 3 / Α 2 χ 100 (3) Further, the average elongation retention ratio is calculated according to the following formula (4). Average elongation retention ratio (%) = (MD direction elongation retention rate + TD side -17 - 201037840 extension elongation retention rate) / 2 (4) EXAMPLES Hereinafter, the related embodiments of the present invention will be exemplified, but The invention is not limited to the embodiments. Example 1 (raw material PET-1) For a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.08 parts by weight of calcium acetate and 0.03 parts by weight of antimony trioxide were added, and The temperature is raised by a conventional method to carry out a transesterification reaction. Next, 0.16 part by weight of lithium acetate and 0.11 part by weight of trimethyl phosphate were added to the transesterification reaction product, followed by displacement in a polymerization reactor. Next, the reaction was carried out under reduced pressure to a temperature of 1 mmHg for the reaction under heating, and the polymerization was carried out at 290 ° C by a conventional method to obtain a polyester having an intrinsic viscosity [η] of 0.52 (polyethylene terephthalate). Glycol ester). The polyester was cut into a cube of 2 mm x 4 mm x 4 mm, and subjected to heat treatment at 23 ° C for 20 hours under a reduced pressure of 5 5 mmHg using a rotary vacuum polymerization apparatus to obtain an intrinsic viscosity [η] 〇 · 79. A carboxylic acid having a carboxyl end group concentration of 10,5 eq/ton. The raw material PET-1 obtained above was dried under reduced pressure at a temperature of 180 ° C and a vacuum of 0.5 mmHg for 2 hours, and supplied to a heated extruder at 295 ° C to filter out foreign matter with a 50 μm filter. After that, import it into the T-die cover. Next, in the crucible mold cover, a molten single-layer sheet is extruded into a sheet, and the molten single-layer sheet is solidified by contact cooling on a storage cylinder having a surface temperature of 20 ° C by means of pinning. Obtained a non--18 - 201037840 extended monolayer film. Next, the unstretched single-layer film was preheated by a heating roll group having a temperature of 85 ° C, and then extended by a heating roll group having a temperature of 90 ° C in the longitudinal direction (MD) at a stretching ratio of 3.3 times. The uniaxially stretched film (uniaxial alignment film) was obtained by cooling with a roll group of a temperature of 25 °C. The two ends of the obtained uniaxially stretched film are clamped by a jig and guided to a preheating zone at a tenter temperature of 95 ° C, and then the heating zone at a temperature of 105 ° C continuously for the vertical direction of the long side direction ( TD) is extended at a magnification ratio of 3.6 times. Then, the process is continued, and the heat treatment zone in the tenter is heat-treated at a heat treatment temperature of 185 ° C (first heat treatment temperature) for 20 seconds, and further, at a temperature of 180 ° C and a relaxation rate of 3% in the width direction. (TD) performs relaxation treatment. Next, after uniformly cooling to 25 ° C, it was rolled up to obtain a film having a thickness of 125 μm. The evaluation results are shown in Table 1. The hydrolysis resistance of the film was evaluated as good. Further, the solar battery back sheet can be manufactured in the following manner. First, the film of the present invention having a thickness of 125 μm as described above was used as the first layer. Next, as the adhesion layer, 90 parts by weight of "TAKELAC: TM" O-A310C manufactured by Mitsui Takeda Chemical Co., Ltd. and "ΑΚΕΝΑΤΕTM" Α3 (manufactured by Mitsui Takeda Chemical Co., Ltd.) were applied to the surface of the first layer, followed by the adhesion layer. A deposited layer of BarrialoxTM "HGTS" (aluminum-deposited PET film manufactured by Toray Film Processing Co., Ltd.) having a thickness of 12 μm was used as the second layer and bonded to the opposite side of the first layer. Next, the same adhesion layer as the above-mentioned adhesion layer was applied to the second layer, and a biaxial alignment polyester film "Lumirr〇rTM" Ε20 (manufactured by Toray Film Processing Co., Ltd.) having a thickness of 50 μm was bonded to each other. On the adhesion layer, a backing plate having a total thickness of 1 87 μm was formed. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as -19-201037840. Examples 2 to 4 Film formation was carried out in the same manner as in Example 1 except for the film formation conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The 0 hydrolysis resistance of the back sheet was evaluated as good. Example 5 (raw material PET-2) The same method as the raw material PET-1 was carried out except that a rotary vacuum polymerization apparatus was used, which was subjected to a heat treatment at 230 ° C for 40 hours under a reduced pressure of 5 mmHg. A polyester (polyethylene terephthalate) having an intrinsic viscosity [η] of 0.82 and a carboxyl end group concentration of 8.5 eq/t〇n was obtained. A film was formed in the same manner as in the practice of Example Q except that the above-mentioned raw material PET-2 was used as a raw material to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Examples 6 to 8 Film formation was carried out in the same manner as in Example 5 except for the film formation conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. -20- 201037840 Then, using the obtained polyester film, a back sheet was produced in the same manner as in the example " The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 9 (raw material PET-3) Stabax〇i@pi〇〇0 (polycarbodiene) manufactured by Rhein Chemie C〇rporation was added in an amount of 1 part by weight relative to 90 parts by weight of the raw material pet-1'. Imine) is mixed. The mixture is a raw material PET_^, except that 90 parts by weight of the raw material pet-1 is mixed with 1 part by weight of the raw material PET-3 (corresponding to 1 part by weight of the polycarbodiimide) as a raw material, and Film formation was carried out in the same manner as in Example 1 to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The water resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrazine hydrolysis resistance of this back sheet was evaluated as good. Example 1 0 to 1 2 Film formation was carried out in the same manner as in Example 9 except for the film formation conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, a back sheet was produced in the same manner as in Example 1 using the obtained polyester film'. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 1 3 to 1 4 - 21 to 201037840 A film was formed in the same manner as in Example 6 except for the film forming conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 1 5 ^ (raw material PET-4) 〇 In addition to the addition amount of trimethyl phosphate to 0.13 parts by weight, and using a rotary vacuum polymerization apparatus, it was carried out at 230 ° C under a reduced pressure of mm 5 mmHg. A polyester (polyethylene terephthalate) having an intrinsic viscosity [η] of 0.82 and a carboxyl end group concentration of 8.5 eq/t〇I1 was obtained in the same manner as the raw material petu except for the heat treatment for 40 hours. A film was formed in the same manner as in Example 13 except that the aforementioned PET-4 was used as a raw material to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good, and then a back sheet was produced in the same manner as in Example 1 using the obtained polyester film. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 1 6 (raw material PET-5) In addition to changing the amount of trimethyl phosphate added to 0.25 parts by weight, and using a rotary vacuum polymerization apparatus, 40 hours at 23 ° C under a reduced pressure of 0.5 mmHg. In addition to the heat treatment, and in the same manner as the raw material pEjd-22-201037840, a polyester (polyethylene terephthalate) having an intrinsic viscosity [η] of 0.82 and a carboxyl end group concentration of 8 to 5 eq/toii was obtained. A film was formed in the same manner as in Example 13 except that the aforementioned PET-5 was used as a raw material to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 1 7 The raw material PET-5 was dried under reduced pressure for 2 hours under the conditions of a temperature of 180 ° C and a vacuum of 0.5 mmHg, and supplied to a heated extruder at 295 ° C, and the foreign matter was filtered out with a 50 μm filter. After that, import it into the T-die cover. Next, in the crucible mold cover, a molten single-layer sheet is extruded into a sheet, and the molten single-layer sheet is solidified by contact printing on a storage cylinder having a surface temperature of 20 ° C to obtain unstretched Single layer film. Next, the unstretched single-layer film is preheated by a heating roll group having a temperature of 85 ° C, and then extended by a heating roll group having a temperature of 90 ° C for a longitudinal direction (MD) at a stretching ratio of 3.3 times. The roll group at a temperature of 25 ° C was cooled to obtain a uniaxially stretched film. The two ends of the obtained uniaxially stretched film are clamped by a jig and guided to a preheating zone at a tenter temperature of 95 ° C, and then, at a temperature of 1 〇 5 ° C, the heating zone is continuously oriented for the long side direction. The vertical direction (TD) is extended at a stretching ratio of 4.0 times. Then, the process was continued, and the heat treatment in the tenter was performed at a heat treatment temperature of 205 1 (first heat treatment temperature) for 20 seconds. Then, at a temperature of 18 (TC environment, the relaxation treatment is performed at a relaxation rate of 3% in the width direction of -23-201037840 degrees (TD), and the longitudinal direction (MD) is reduced by the clamp interval of the tenter. The relaxation rate of 1.5% was relaxed. Secondly, after uniformly cooling to 25 ° C, the polyester film was obtained by rolling up. The evaluation results are shown in the table. The hydrolysis resistance of the film was evaluated as good. The obtained polyester film was formed into a back sheet in the same manner as in Example 1. The evaluation results of the back sheet are shown in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 1 8 Except for the long side direction (MD) Film formation was carried out in the same manner as in Example 17 except that the tenter interval of the tenter was reduced by a relaxation rate of 2.0%. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the back sheet are shown in the table. The hydrolysis resistance was evaluated as good. Example 1 9 Using an extruder (a) The composite film forming apparatus of the extruder (b) is based on 5 parts by weight of an average particle diameter of 0.2 μm of titanium oxide (surface untreated, rutile type), and 0.15 part by weight of a fluorescent whitening agent "ΟΒ-1" ( The ratio of the raw material PET-5 manufactured by Eastman Kodak Company and 94.85 parts by weight is mixed, and dried under reduced pressure for 2 hours under the conditions of a temperature of 180 ° C and a vacuum of 5 5 mmHg. To the extruder (the side of the crucible, after melt extrusion at 280 ° C), the foreign matter was filtered out with a 50 μm filter, and then introduced into a composite lid of a crucible mold. -24- 201037840 Further, the raw material PET-5 was subjected to temperature. The mixture was dried under reduced pressure at 180 ° C under a vacuum of 5 mmHg for 2 hours, and supplied to the side of the heated extruder (a) at 29 5 ° C, and the foreign matter was filtered off with a 50 μm filter. And introduced into the composite cover of the Τ-type mold. Secondly, in the composite cover of the 模具-type mold, after the polymer from the extruder (a) and the polymer from the extruder (b) are layered and merged, Co-extruding flaky molten laminate sheets. However, controlling the extrusion of two extruders The aforementioned compounding ratio of the output: the extruder (a) layer / [extruder (a) layer + extruder (b) layer] should be 12%. Secondly, extruded into a T-die cover The flaky molten laminated sheet was solidified by contact cooling on a holding cylinder having a surface temperature of 20 ° C to obtain an unextended laminated film. Then, the unstretched film was subjected to a temperature of 85 t. After the preheating of the heating roller group, the heating roller group having a temperature of 90 ° C in the longitudinal direction (MD) is extended at a stretching ratio of 3.5 times, and then cooled by a roller group having a temperature of 25 ° C to obtain a uniaxial stretching. membrane. The two ends of the obtained uniaxially stretched film are clamped by a jig and guided to a preheating zone at a tenter temperature of 95 ° C, and then, at a temperature of 1 〇 5 ° C, the heating zone is continuously oriented for the long side direction. The vertical direction (TD) is extended at a stretching ratio of 4.0 times. Next, the step was continued, and heat treatment was carried out for 20 seconds at a heat treatment temperature (first heat treatment temperature) of 2 〇 5 ° C in the heat treatment zone in the tenter. Then, at a temperature of 180 ° C, the relaxation treatment is performed in the width direction (TD) at a relaxation rate of 3%, and the long-side direction (MD) is reduced by 1.5% due to the reduction of the clamp interval of the tenter. Relaxation. Next, after uniformly cooling to 25 ° C, the polyester film having a thickness of -25 to 201037840 125 μm can be obtained by rolling up. The (a) layer thickness of the obtained film was a layer thickness of ιιομιη. The evaluation results of the obtained film showed that the hydrolysis resistance of the film was evaluated as good. Further, the solar battery back sheet can be manufactured in the following manner. First, the two-layer laminated film obtained as described above was applied as an adhesive layer to 90 parts by weight of "TAKELACTM" - Α2 Tian Chemical Co., Ltd. and "ΑΚΕΝΑΤΕ·TM" A3 (manufactured by Mitsui Division) to the surface of (b) layer. , with a thickness of 12 μm, "HGTS" (the deposited layer of alumina deposited by Toray Film Processing Co., Ltd. as the second layer thereon, and bonded to the first layer and then coated on the second layer with the aforementioned adhesion A biaxially oriented polyester film (manufactured by Lumi rror Film Co., Ltd.) having the same thickness of 50 μm was bonded to the back sheet having a thickness of 187 μm on the adhesive layer. The evaluation results are shown in Table 1. The solution was evaluated as Further, since the (a) layer is located at the outermost layer, the UV resistance is good. 实施 Example 2 0 In addition to changing the average particle diameter 〇2 μιη titanium oxide (surface not stone type) to 30 parts by weight, the fluorescent whitening The amount of the agent "manufactured by 〇Β 4 达 达) was changed to 0.15 parts by weight and the ratio of the raw material pETd was mixed, and the mixture was dried under reduced pressure for 2 hours under a vacuum of 18 Torr, and then supplied to the outside of the extrusion. Again with the embodiment 19 The same method was used to form a film. The evaluation results of the obtained film are shown in the table. The 1 5 μιη - (b) is in the table. The first layer. 丨10 (Mitsui Takeda Chemical Co., Ltd. BarrialoxTM [PET Film) Opposite side. Adhesive layer, and don't "E20 (East, to make the water-resistant position of the total backboard, due to treatment, gold red j (Eastmanke 5 changed to 69.85 degrees 0.5mmHg out of the machine (a) side The hydrolysis resistance of the polyester film was evaluated as good as -26-201037840. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the back sheet are shown in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 2 1 (raw material PET-6) In addition to using a rotary vacuum polymerization apparatus, heat treatment was performed at 230 r for 5 hours under a reduced pressure of 0.5 mmHg. Further, a polyester (polyethylene terephthalate) having an intrinsic viscosity [η] of 0.65 and a carboxyl terminal group concentration of 18 eq/ton was obtained in the same manner as in the raw material Ο PET-1. 10 parts by weight of the raw material PET-6 added 10 parts by weight of Stain Chemical manufactured by Sta Baxol P100 (polycarbodiimide) for mixing. The mixture is the raw material PET-7. In addition to 90 parts by weight of raw material PET-6 and 10 parts by weight of raw material Q PET·7 (equivalent to 1 part by weight) The carbodiimide was mixed and used as a raw material, and film formation was carried out in the same manner as in Example 6 to obtain a polyacetate film. The evaluation results of the obtained film are shown in the table. Evaluation of hydrolysis resistance of the film For the good. Then, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 22 (raw material PET-8) -27- 201037840 In addition to the use of a rotary vacuum polymerization apparatus, in a reduced pressure environment of 55 mmHg, 'heat treatment at 270 ° C for 1 〇 0 hours, and The same procedure as the raw material PET-1 was carried out to obtain a polyester having an intrinsic viscosity [η] 2 and a carboxyl end group concentration of 8.0 eq/ton. A film was formed in the same manner as in Example 6 except that the above-mentioned raw material PET-8 was used as a raw material to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, using the obtained polyester film, a back sheet was produced in the same manner as in Example 1. The evaluation results of the backboard are listed in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 2 3 A film having a thickness of 1 2 5 μm was obtained in the same manner as in Example 6. The results of the evaluation are listed in the table. Further, the solar battery back sheet can be manufactured in the following manner. A film having a thickness of 125 μm obtained as described above was used as the first layer. Next, as the adhesion layer, 90 parts by weight of "TAKELACTM" - Α 310 (manufactured by Mitsui Takeda Chemical Co., Ltd.) and "ΑΚΕΝΑΤΕTM" A3 (manufactured by Mitsui Takeda Chemical Co., Ltd.) were applied to the surface of the first layer to a thickness of 12 μm BarrialoxTM. A deposited layer of HGTS (aluminum-deposited PET film manufactured by Toray Film Processing Co., Ltd.) is used as the second layer on the adhesive layer, and is bonded to the opposite side of the first layer, and then coated on the second layer with the aforementioned adhesion. The same adhesion layer was used, and a biaxially oriented polyester film "Lumirr〇rTM" S10 (manufactured by Toray Film Processing Co., Ltd.) having a thickness of 250 μm was bonded to the adhesion layer as a third layer. Next, the same adhesion layer as the above-mentioned adhesion layer -28-201037840 was applied to the third layer, and a biaxial alignment polyester film "LumirrorTM" Ε2〇 (manufactured by Toray Film Processing Co., Ltd.) having a thickness of 50 μm was attached to each other. On the adhesive layer, a back sheet having a total thickness of 43 μm was produced. The evaluation results of the back sheet are shown in the table. The hydrolysis resistance of the back sheet was evaluated as good. Example 24 A polyester film was obtained in the same manner as in Example 6 except that a polyester film having a thickness of 50 μm was used. The evaluation results of the film are shown in the table. Further, the solar battery back sheet can be manufactured in the following manner. A film having a thickness of 50 μm obtained as described above was used as the first layer. Next, as the adhesion layer, 90 parts by weight of "TAKELACTM"-A3 10 (manufactured by Mitsui Takeda Chemical Co., Ltd.) and "ΑΚΕΝ ATETM" A3 (manufactured by Mitsui Takeda Chemical Co., Ltd.) were applied to the first layer to a thickness of 12 μm BarrialoxTM. a deposited layer of "HGTS" (aluminum-deposited PET film manufactured by Toray Film Processing Co., Ltd.) as a second layer on the adhesive layer, and bonded to the opposite side of the first layer, and then coated on the second layer with the foregoing The adhesive layer having the same adhesion layer and a biaxially oriented polyester film having a thickness of 250 μm were bonded to each other on the adhesive layer as a third layer. The same adhesion layer as the above-mentioned adhesion layer was applied to the third layer, and a biaxially oriented polyester film "LumirrorTM" 20 (manufactured by Toray Film Processing Co., Ltd.) having a thickness of 188 μm was adhered to the adhesion layer. The back sheet having a total thickness of 500 μm was shown in Table 1. The hydrolysis resistance of the back sheet was evaluated as good. Examples 25 to 42 In addition to the film forming conditions listed in the table, Example 5 is the same -2 The method of 9-201037840 was carried out to obtain a polyester film. The evaluation results of the obtained film are shown in the table. The hydrolysis resistance of the film was evaluated as good. Next, the obtained polyester film was used and implemented. The back sheet was prepared in the same manner as in Example 1. The evaluation results of the back sheet are shown in the table. The hydrolysis resistance of the back sheet was evaluated as good. Comparative Example 1 (raw material PET-9) 100 parts by weight of terephthalic acid 0.08 parts by weight of calcium acetate and 0.03 parts by weight of antimony trioxide were added to a mixture of dimethyl formate and 60 parts by weight of ethylene glycol, and the mixture was heated and subjected to a transesterification reaction by a conventional method. Secondly, the transesterification was carried out. 0.16 parts by weight of lithium acetate and 0.11 part by weight of trimethyl phosphate were added to the reaction product, and then transferred to a polymerization reactor. Then, under a reduced pressure of 1 mmHg for slowly depressurizing the reaction under heating, Polymerization was carried out at 290 ° C according to the conventional method to obtain a polyester having an intrinsic viscosity [η] of 0.52. The polyester was cut into cubes each having a side length of 2 mm x 4 mm x 4 mm, and a rotary vacuum polymerization apparatus was used in a reduced pressure environment of .5 mmHg. The mixture was heat-treated at 203 ° C for 8 hours to obtain a polyester having an intrinsic viscosity [η] of 0.74 and a carboxyl end group concentration of 13 eq/ton. In addition to using the above-mentioned raw material PET-9 as a raw material, A film having a thickness of 125 μm was obtained in the same manner as in Example 1. The evaluation of the film revealed that the hydrolysis resistance was poor. Further, a back sheet having a thickness of 187 μm was produced in the same manner as in Example 1. The evaluation results are shown in the table. In the evaluation of the back sheet, it was found that the hydrolysis resistance was poor. -30- 201037840 Comparative Example 2 'In addition to the film forming conditions listed in the table, film formation was carried out in the same manner as in Comparative Example 1 to obtain a polymer. Ester film. The evaluation results of the obtained film are shown in the table, and in particular, the result of poor hydrolysis resistance appeared. Further, a back sheet was also produced in the same manner as in Example 1 to obtain a back sheet having a thickness of 187 μm. The results of the evaluation are listed in the table. In particular, the result of poor hydrolysis resistance has appeared. Comparative Example 3 A film was formed in the same manner as in Example 1 except for the film forming conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are shown in the table. In particular, the result of poor hydrolysis resistance has appeared. Further, a back sheet was also produced in the same manner as in Example 1 to obtain a thickness of 187 μm @@back sheet. The results of the evaluation are shown in Table 1 » especially the results of poor hydrolysis resistance. Comparative Example 4 A film was formed in the same manner as in Example 9 except for the film forming conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are listed in the table. In particular, the result of poor hydrolysis resistance has appeared. Further, a back sheet was also produced in the same manner as in Example 1 to obtain a thickness of 187 μm @@back sheet. The evaluation results are shown in Table 1. In particular, the result of poor hydrolysis resistance has appeared. Comparative Example 5 A film was formed in the same manner as in Example 5 except for the film forming conditions listed in the table to obtain a polyester film. The evaluation results of the obtained film are listed in the table -31 - 201037840 1 8 7 μ m. In particular, a result of poor hydrolysis resistance was observed. Further, a back sheet was produced by the method of Example 1 to obtain a thick back sheet. The evaluation results are shown in the table. In particular, there is a result of resistance to water.

〇-32- 201037840 Ο ο Example 7 1 Raw material ΡΕΤ-2 C0 CO CD CO ο CM m in CN T- r— r— LO 〇CN| d Ο 00 »— 〇> r—CO Two inches CO Τ Ο Not satisfied I τ 00 ΙΟ Ι Ω CD 卜 CO T - Example 6 Raw material ΡΕΤ-2 C0 00 to CO to o CN heap u> CJ r*~ T~ r- oo CM 卜 d Ο 00 7~ inch cs) LO Τ— 0. Ί 64 Not satisfied 〇C0 ο CO CO CO 00 r^ CO T—1 Example 5 Raw material ΡΕΤ-2 C0 CO &lt;D CO in OD 1—in OJ t— 1— o 00 1—bd ο ω 寸 CO CO inch CD 1«-» 6 satisfies j CSJ tn 00 CO &gt; —· σ &gt; Γ- ω T—Example 4 Raw material ΡΕΤ-1 C0 CO CD CO tn CM CM Purple LH OJ T— CO r -* 220 卜 a ο C0 τ — 00 r — CM r — 0. 1 64 Not satisfied 00 eg r— LO &lt; N CO ω 卜 r — Example 3 Raw material ΡΕΤ-1 C0 &lt;0 CO CO 〇T — CN m in CM r— CO v— LO o CM r- o ο 00 r— 〇CV4 inch r—inch&lt;D τ- Ο Meet 00 OJ 〇LO LO Γ-· GO r—寅Example 2 Raw materialΡΕΤ -1 CO C0 CO CO tn om U&gt; CM r— CO r— 〇〇CM 卜 d ο 00 τ*~ in &lt;Ν CD T—inch to τ α Not satisfied C0 LO 〇 00 CO p-1 Example 1 Raw material ΡΕΤ-1 Γ0 C0 Φ CO in CO t— 璀ΙΛ CsJ T~~ CO r— 〇00 1— 〇ο 00 LO Γ ΟΟ I 0. 1 64| Cn CN o CO 〇CO 00 . 00 τ — Raw material J MD stretching ratio (1) TD stretching ratio (I) I First processing temperature rc) j MD thief _ degree _) Residue end group concentration (eq/ton) Tiny Inhalation temperature · Tmeatfc) I Intrinsic viscosity (dl / g) α. &amp; m If MD Q 1- 1 Plane alignment coefficient B2 (-) I (B) formula for the average reflectance of the 1 wavelength of 400 ~ 700nm (%) 镰72 • After hours Y-I# II 1| Welcome m H-,s 1 m 13⁄4 | Total thickness of sheet (&quot;m) I Sun I 醤fine 150°C30 Heat shrinkage rate (%) feS s ? 蟀 K·审 p|| s si lif -ero- 201037840 Ο ο Example 14 | Raw material PET-2 Ο inch· tr&gt; ID o CJ m in &lt;N r — t — T— oo CM Ο ο ω τ — to 04 &lt; D τ — Ι Ω Τ Ο satisfy 1 C0 CM Γ - CO o CNi CS( σ > r- ω τ - Example 13 Raw material PET-2 in η o 2 0.5 Destruction LO CM T~* T— 〇〇CM rs d ο ω in CM CO r— Bu ω r~ Ο Not satisfied 〇co LO 00 C〇ο Oi 卜 00 τ— Example 12 lL θ ω I® CO CO CD CO in CM CM m LO CSJ T*~ in 〇CSJ CM οο 〇00 τ- CJ) Τ'&quot; 09 二廿CD τ— ο Not satisfied 00 (N ID ID oi ο CO Γ ΟΟ r—Example 11 Product CO CO &lt;D CO 〇CM 璀ω CN r— in 20 5 ο ο 00 τ — r— CM LO Τ·&quot; Inch CD r- d Not satisfied Ο CO to 00 to ο ω 00 r—Example 10 cl ^ W 0μ ϊΐ CO 00 (D 00 in 〇CM m LO 〇jr—in 200 〇 〇 ο 00 τη» &lt;〇CN τ—inch CD Τ Ο Not satisfied 00 CM 〇05 σ&gt; co σ&gt; 00 r*&quot; Example 9 - hi Μ α &lt; idiot 00 CO &lt; D CO in c〇r - 璀 LO OJ r - 10 O co r - 卜d ο ω τ—CO 00 00 CO 寸 CO d satisfies 1—CO ID OU) co &lt;Si r^ 00 τ— |Example 8 Raw material PET-2 00 CQ CD CO LD CJ CM Destroy LO CM r— t— o CM CM ο ο C0 r— 卜τ-* r~ r—inch CD r— d Not satisfied CD CM 00 in CM ο &lt;D 00 r—Material MD extension ratio TD extension ratio (1) ! 〇 〇 c) ! MD system brewing! Facial _) Xiang Ji * S ^ ® i degree (called / ton) micro Lai dirty brew TmeatfC) I Laerdal (dl/g&gt; Deng X-ray measurement of the disc atomic setting (ppm) Q 2 TD | plane alignment coefficient is called) (B) formula of the average reflectance of the wavelength of 400~700nm (%) placed 48 Xiaolin After 72 hours of placement, hang II <ίΓ _降's pm 53⁄4 s« 驷滔1 total thickness of sheet (&quot;m) 1 150t30 heat shrinkage rate (%) «sg _ H铢p S is si X gt lif inch £ · 201037840 Ο 〇 Example 21 1 ! ai hQ-UJ tor-Q- ^ h- Gong 4Q IgCD CO CO φ CO L〇o CM destroy in CM 〇〇 2 CM &lt;0 6 Ο 00 r - inch CSi Ι Ω 1—inch CD 7~ d Fine J 0D CM in to 00 r— CD CO &gt;r—Example 20 (Refer to the specification) U) CO ο 寸 LO 〇CM L〇S &lt;N 1-2 τ- 200 : | 0. 67| Ο r—· inch (D d CM d 0. 1 67 does not satisfy I 00 1-05 CO EQIH; • se 卜 Γ 0 00 00 r—Example 19 (Refer to the manual &gt; LO CO ο ID o CM L〇3 CM r— r— 〇〇CM 03 CD 〇ο τ—inch CD d 〇 ( (D Τ Ο not satisfied CsJO CO CQ sleep compensation ^-N CO inch CO 00 τ - Example 18 Raw material PET-5 i〇CO ο inch·iO o CnJ LO CM t— τ-~ 200 6 ο r—inch d OJ d Bu (D y - 〇 not satisfied 〇) CN CN O) 00 inch σ> 00 T~~ Example 17 Raw material PET-5 to CO ο LO o C\J You in CM T—two 200 b d Ο inch CD 6 CM d 卜 CD r - d not satisfied o CO r - cn 卜 inch CD 卜 € 0 - Example 16 raw material PET-5 ΙΛ 03 ο Ι Ω o CNi m LO CvJ r~ 200 卜 d Ο r - inch CM CM CD 卜 to r—d not satisfied 00 CNJ 〇O) 00 94 00 r~ |Example 15 Raw material ΡΕΤ·4 lO CO ο Ι Ι o CM 壊LD Csl r— τ— τ— 200ί 1 d Ο τ~· CM CM CM (D II Bu CD r - d not satisfied τ - CO 00 00 Bu CN σ &gt; Γ ΟΟ T*~ Raw materials | MD stretching ratio (1) 丄 im im ; 〇! H | 1st processing brewing. c) MOmmm 麒 degree ((4) ; carboxy 录 degree (eq/ton) ! 1 —__________ 1 Micro endothermic temperature TmeaCC) Solidity (dl/g) im MD TD Plane alignment coefficient B2(-) (B) The average reflectance (%) of the formula for the filling wavelength of 400~700nm is placed at 48 / j. If £ 18 O uij sg S| gl IS total thickness of the sheet (&quot;m) | 1 醤 150 150TC30 thermal shrinkage rate ( %) 倾·ε? ? ^ κ:» p|| « Sft X gt lif m 201037840 ο ο Example 28 1 Raw material ΡΕΤ-2 〇CO CNi CO 〇CO T— m in CNJ r— T~~ r— ir&gt卜d 〇00 04 a CO * CN ΙΟ ΙΟ Ο Meet l t 00 τ- 00 03 CM in 00 00 Example 27 Raw material ΡΕΤ-2 LO inch to to ID T- 薬in CM t-*· r- R- O to 卜do €0 T-· o (D 00 in h' 〇τ- Ο Meet 00 CN m σ&gt; CO LD 卜 卜 GO r- 丨Example 26 Raw material ΡΕΤ-2 . CO CO o inch iO To r~ 〇 i〇CM T- r~ r- o ΙΩ 卜 do 00 1- CO ui inch U) N r~ d Satisfy ο CO ο 0) CO 寸 CO 0) CO r-* Example 25 Raw material ΡΕΤ- 2 · 00 00 CM in ΙΏ T- m in CM T~ T-~ r- o LO y- r-. do 00 T~ inch CM CM CO τ- Ο Meet 00 csl ο 00 o &lt; N inch CO Bu CO r- 〇o LO Example 24 Raw material ΡΕΤ-2 CO CO CO CO in o 04 Destruction o ID 1~ oo CM Bu 00 T-inch CM in y-inch iD τ- Ο Not satisfied 04 CM ο 00 卜 〇 l Example 23 Raw material ΡΕΤ-2 CO CO &lt;£&gt; CO to o OJ Destroy to CM T- 二 200 卜do 00 r—· 寸 寸 寸&lt;£&gt; r·· Ο '00 00 00 00 inch is not satisfied (D 卜CO inch|Example 22 ΡΕΤ-8' CO CO CO CO o o CNJ m LD (N r- r- 〇o OJ OJ r- o 00 r- inch cs LO Inch (Ο r- d not satisfied 〇CO 〇σ> σσ> r- 00 Raw material I MD stretching ratio (1) | TD stretching ratio (1) | 1st processing temperature (t) 1 MD loose surface 1 degree (&quot ;m) Qian Ke Na degree (eq/t〇n) Micro heat absorption temperature TmesitfC) Intrinsic viscosity (dl/g) Atomic volume (ppm) measured by fluorescent X-ray MD QH Plane alignment coefficient B2(-) ( B) The average reflectance (%) of the formula for the charging wavelength of 400~700nm 丨 Placed for 48 hours and placed for 72 hours after II s « one #· e° fib sl 鹆 运 β β m read; mi: m 150°G30 points MSI rate (%) ig| p|| 111 朦北¢#1 鹤趣:劫_9ε — 201037840 〇o |Example 35 I Raw material ΡΕΤ-2 ' inch to 〇CM m IX) CM 1—r—to o CM Ο 〇CO r—inch CO 1—CO CD 〇> r~ 6 Meet 00 CvJ r~ CO 00 C \( in CO Γ 实施 Example 34 Raw material ΡΕΤ-2 CM meter' ο 谷ο r- eg m ω CM r*- r- -t— 2 05 卜d 〇CD r-* &lt;〇CM σ&gt; r— 〇03 Τ 〇 Satisfy 〇CO σ&gt; 卜1C CN CO 00 Bu CO τ— 实ί® Example 33 Raw material ΡΕΤ-2 tn in inch·ID 〇m LO &lt;N r-· T— 2 00 〇 〇 〇 00 Production tn CO &lt;N 00 CO σ&gt; -ρ- Ο satisfying CO CM CM σ&gt; o LO 卜 σ&gt; Γ' 00 -τ~- Example 32 Raw material ΡΕΤ-2 csj 'φ 〇'ti〇〇&lt;N m 10 CM t—1—200 卜〇o 00 1—00 oj 0 01 σ> Τ Τ 满足 meet r*—CO ο Ο) 〇CO LO Oi 卜 CO r- Example 31 Raw material ΡΕΤ-2 in inch ΙΌ inch · 〇CO r— 璀in &lt;NT~- T-LO 卜t-6 〇CO r— 00 in CO in cn cn Ο 满足 Meet CD CM CO σ> T~ lO ω 卜 00 τ~ Example 30 Raw material ΡΕΤ-2 ' 00 CO Ο o CO 1— m ld eg T— T— LO 卜 i — 卜〇 o CO r~ o to 04 inch · Bub τ- Satisfied, 〇CO CM 05 o inch tn CD 00 τ— |Example 29 Raw material ΡΕΤ-2 CO 00 CO CO 〇00 r— m LO 04 T— T— LD 卜 r~ r- d 〇CO T—to inch CD CO in 1 ο Meet CD CNJ 00 00 LO CO CN Oi Bu CO τ - Raw material 1 MD stretching ratio (1) 1 TD stretching ratio (1) | i-th processing temperature re) I MD squirrel 1 Freshness (&quot; m) carboxyl sulphide (eq/tem) micro-sand tasting TmeatCC) solidity (dl/g) amount of heteroatoms measured by fluorescent X-rays &lt;ppm) MD Ll〇_1 plane-direction coefficient Β2(1) 1 (Β Loose-filled | Sft 400~700nm average®^(%) placed after 48 hours and placed for 72 hours after I barefi §«-ft si extract II total thickness of sheet (_ 1 150 ° C 30 minutes heat shrinkage ( %) Bee P Yao · «si lif • Li_ m 201037840 〇〇Example 42 j Raw material PET-2 to οι CD 04 in to r— m ιο (N 1— 〇ιο r— 卜 6 Ο 00 r~ Ο inch CO CO 03 CNJ Τ Ο Not satisfied | G) CM CO LO CM CM to 00 r- Example 41 Raw material PET-2 . ο Ο LO CSJ CM mm CN r- t- r~ 〇CM 〇Ο 00 r— Oi Τ- 00 T~ o cn d not satisfied t- &lt;Τ) CNJ 00 CD 卜卜ω r- real Example 40 Raw material PET-2 〇CO &lt;N CO LO 00 T~~ m LO &lt;N r- T- r-*· 〇CO r- d Ο 〇0 r— Ο CO r~ CM 0. 1 54 Unsatisfied 00 CsJ to Bub σ&gt; Bu CO r~-1 Example 39 Raw material PET-2. α&gt; CM 00 04 1 80 m in Oi 1—in 卜i— 卜d Ο 00 r- 00 〇i 00 T - m Τ Ο not satisfied CO CO r- σ&gt; CM 00 Bu CO r- Example 38 Raw material PET-2 CO &lt;N CO &lt;N o CO r- destroyed in CM 1- T*~ T&quot;· in to r~ 卜ο 〇00 τ—CO inch CD CO CM CO production d not satisfied 03 OJ ΙΛ GO ο CO 00 τ ～~ Example 37 Raw material PET-2 tr> inch · LO in CNJ CM m LO CM T~ T ~ 〇CM Oi 卜d Ο 〇0 r- in CM in CNJ 00 〇&gt; Τ 满足 Meet 00 CM T- ω 00 T— ΙΩ 00 00 00 r- |Example 36 Raw material PET-2 CO Inch CO Inch I 225 Destroy LO CM T- r- o CNJ CNi ο Ο αο τ- t- CM r- CM CO σ> 〇 meet r- CO co CO ir- Oi 00 00 r- raw material 1 MD extension ratio (1) | TD extension Magnification (1) I 1st treatment temperature 〇c> MD squirrel alcoholicity ((4) | 1 M' I 1 l 1 ΜΛ m 1 Dream § Solidity (dl/g> 丨 fluorescent X-ray measurement of the atomic child ( Ppm) MD TD flat brewing coefficient B2(-) | (B) formula for the average reflectance of the 1 wavelength of 400~700nm (%) 幽回卜 A II II § m —* I齑Ρ涂ιη ψ· a鹆 1 1 Η Sc S total thickness of sheet (&quot;m) | Φβ St si w 探 Ms S _ t铢p|| s Si X gt iif — 8ε — m 鲣201037840

o D 比赖 5 1 Raw material PET-2 Ο inch ο inch 1 2 30| m in C\) T- T- T~ to CM CM 〇ο 00 Ί- 00 r- r- r~- 00 05 t-· d Not satisfied 'I 00 CM CO inch t-03 inch 〇 〇 0 τ - Comparative example 4 Η Μ Ah 竑 竑 S13⁄4 Μ ^ CO CO &lt;〇CO 2 30 m ID CM T~~ LO LD Csi 卜d 〇00 R- CO τ~ Ύ-r-- 0. 1 64 Not satisfied 00 CM 46 o CO Inch 00 τ-· Comparative Example 3 Raw material PET-1 CO CO to CO Ο CO Οί m U&gt; CM T- CO Τ' — LO CM f, d Ο 00 τ- CO V- CN i― 0. 1 64 Not satisfied Ο ¢0 (Μ 寸 寸 inch 00 T- Comparative example 2 Raw material PET-9 CO CO &lt;0 CO m CM CM m lO OJ f- to r- 〇CM CM 卜6 Ο 00 ττ- σ) τ- CNJ r- inch to yr- o Not satisfied CO CM CO inch o inch inch CQ T- |Comparative example 1 Raw material PET-9 CO CO &lt;£) CO ΙΟ 00 T- Destroy &lt;N r~ ΙΩ τ~· 〇CO T- 卜d ο 00 Production &lt;〇00 inch CO Ι Ο Satisfy σ&gt; CM LO inch o CD inch 00 τ - Raw materials | MD stretching ratio (1) | TD stretching ratio (1) 1st processing rc) i MD thief ration (/m) _ end group concentration (eq/ton) Micro endothermic temperature Tmeat (1C) 1 Intrinsic viscosity ( Dl/g) g s If MD HP_ 平® B3 to the coefficient B2(-) (B) The average reflectance of the wavelength of 400~700nm (%) SI II 1| 1| total thickness of the sheet ((4)) | 幽潷1 X amount 150t30 Fractional heat shrinkage rate (%) p|| ss® ^ gt lif 雀造造:#! 嫌北你就— 6· m 201037840 Also, the “sheet” in the table means “backboard”. Industrial Applicability The film of the present invention can be suitably used in a solar cell using a back sheet. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an example of differential scanning calorimetry (DSC) measurement results of a micro endothermic peak temperature of a film. [Main component symbol description] 4E 〇 ❹ 〇 -40-

Claims (1)

201037840 VII. Application for patents. 1. A polyester film for solar cells, comprising: carboxyl terminal; 13 eq/ton or less, and according to differential scanning calorimetry (DSC), the micro endothermic peak temperature Tmeta (°C) is Below 220 °C. 2. For the polyester film for solar cells according to item 1 of the patent application, the side direction (MD) and the transverse direction (TD) thereof are 150 ° C and the 30-fold reduction ratio is 0.6% or less. 3. For the solar cell 聚 ^ in the patent application range 1 or 2, the plane alignment coefficient B2 is 0.165 or more. 4. The solar ester film according to any one of claims 1 to 3, wherein the phosphorus atom determined by the fluorescent X-ray measurement is 200 ppm or more. 5. The solar ester film according to any one of claims 1 to 4, wherein the micro endothermic peak temperature Tmeta (°C) is below. 6. The solar oxime ester film according to any one of claims 1 to 5, wherein the at least one surface has a wavelength of from 400 to 700 nm of 80% or more. 7. The solar ester film according to any one of claims 1 to 6, wherein the intrinsic viscosity is in the range of 0.6 to 1.2 dl/g. 8. In the first to seventh items of the patent application scope. Any of the solar ester films in which the carboxyl terminal group concentration is 12 eq/ton or less. 9. The solar ester film of any one of claims 1 to 8, wherein the polyester layer has at least 2 layers. The i-concentration is the heat-collecting ester film of the obtained film for a long period of time, and the battery has a polycondensation amount of the battery 205. . The use of a polyester film for a solar cell according to any one of the first to ninth aspects of the invention, wherein the film is at 125 ° C. The average elongation retention rate after standing for 48 hours under the conditions of 100% humidity was 50% or more. 11. The polyester film for a solar cell according to any one of claims 1 to 10, wherein the average elongation retention after leaving for 72 hours at 125 ° C and 100% humidity is 10%. the above. 12. For the solar cell _ polyester film according to any one of claims 1 to 11, wherein Tmeta ( °C ) and the plane alignment coefficient B2 satisfy the following formula B Formula (B) B2 g 0.00 0 86 xTmeta -0.002 86. The method for producing a polyester film for a solar cell according to any one of claims 1 to 2, further comprising: after extending at least one axis of the unstretched polyester film The heat treatment is performed at a temperature of 220 ° C or lower. A solar battery back sheet comprising at least one polyester film for a solar cell according to any one of claims 1 to 12. Q 15. For the solar cell backsheet of claim 14, the average elongation retention after leaving for 48 hours at 125 ° C and humidity of 1 〇〇% is more than 50%. 16. A solar cell produced by using a solar cell backsheet as recited in claim 14 or claim 15. A method for producing a polyester film for a solar cell, comprising: after extending at least one axis of the unstretched polyester film in a method for producing a polyester film having a carboxyl group-based group concentration of 13 eq/ton or less; The heat treatment is performed at a temperature of 20.5 ° C or lower. The method for producing a polyester film for a solar cell according to claim 17, wherein the polyester film has a carboxyl terminal group concentration of 12 eq/t 〇 n or less. -43-