JP2014156553A - Polyester film, back sheet for solar cell module, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film having excellent adhesion and moist heat resistance in addition to hydrolysis resistance.SOLUTION: The polyester film of the present invention comprises polyester and terminal-sealing agent. The average percentage content of the terminal-sealing agent is 0.1-10 mass% relative to the polyester. The in-plane variation of the percentage content of the terminal-sealing agent is 2-20%.

Description

  The present invention relates to a polyester film, a back sheet for a solar cell module, and a solar cell module.

  Generally, a solar cell module is formed by laminating glass or a front sheet / transparent filling material (sealing material) / solar cell element / sealing material / back sheet (BS) in this order from the light-receiving surface side on which sunlight enters. It has a structure. Specifically, the solar cell element is generally embedded in a resin (sealing material) such as EVA (ethylene-vinyl acetate copolymer), and further has a structure in which a solar cell protective sheet is attached thereon. Is done. The solar cell protective sheet, particularly the back sheet (BS) for the solar cell module, which is the outermost layer, is expected to be placed in an environment where it is exposed to outdoor wind and rain or direct sunlight for a long period of time. Therefore, excellent weather resistance (wet heat resistance and heat resistance) is required.

  Conventionally, a polyester film, particularly a polyethylene terephthalate (hereinafter referred to as PET) film has been used as a back sheet for a solar cell module. Polyester films have excellent heat resistance, mechanical properties, chemical resistance, and the like, and are therefore industrially used in many products. However, since these films have poor hydrolysis resistance, the molecular weight decreases due to hydrolysis, and embrittlement progresses, resulting in a decrease in mechanical properties. For this reason, practical strength could not be maintained over a long period of time as a back sheet for solar cells.

In order to solve such a problem, it has been proposed to add an end-capping agent to a polyester film to improve hydrolysis resistance (for example, Patent Documents 1 to 5). In patent document 1, the polycarbodiimide compound is employ | adopted as terminal blocker, and in patent documents 2 and 3, the cyclic carbodiimide compound is employ | adopted as terminal blocker. These carbodiimide compounds react with the terminal carboxyl group of the polyester and function to suppress the hydrolysis of the polyester.
Moreover, in patent document 4 and 5, the ketene imine compound is employ | adopted as terminal blocker. Similarly to the carbodiimide compound, the ketene imine compound is known to react with the terminal carboxyl group of the polyester to suppress the hydrolysis of the polyester.

JP 2011-222580 A International Publication No. 2011-072111 Pamphlet International publication 2011/093478 pamphlet JP-A-10-130482 US Pat. No. 3,692,745

  However, in the polyester film containing the terminal blocking agent as described above, the hydrolysis resistance is improved, but when another member is laminated on the polyester film, the adhesion with the other member is deteriorated. This has been clarified by the study of the present inventors. In particular, in a harsh environment of high temperature and high humidity, there is a problem because the deterioration of adhesion becomes remarkable.

  Further, it is clear from the study by the present inventors that the polyester film containing the end-capping agent does not have sufficient heat and moisture resistance and cannot sufficiently maintain the strength of the polyester film in a high humidity environment. It became. For this reason, the improvement was calculated | required so that it might have the more excellent heat-and-moisture resistance.

  Therefore, in order to solve the problems of the prior art, the present inventors have proceeded with investigations for the purpose of providing a polyester film having excellent adhesion and wet heat resistance in addition to hydrolysis resistance. .

  As a result of intensive studies to solve the above problems, the present inventors set the average content of the end-capping agent contained in the polyester film within a predetermined range, and the aspect of the content of the end-capping agent It has been found that by adjusting the internal variation to 2 to 20%, in addition to hydrolysis resistance, adhesion and moist heat resistance can be improved, and the present invention has been completed.

Furthermore, the present inventors have found that by using a ketene imine compound having a specific structure as an end-capping agent, it is possible to improve manufacturing suitability such as suppressing gas volatilization in a film forming process.
Specifically, the present invention has the following configuration.

（一般式（１）中、Ｒ₁およびＲ₂は、それぞれ独立にアルキル基、アリール基、アルコキシ基、アルコキシカルボニル基、アミノカルボニル基、アリールオキシ基、アシル基またはアリールオキシカルボニル基を表し、Ｒ₃はアルキル基またはアリール基を表す。）
［５］前記末端封止剤は、下記一般式（２）で表されるケテンイミン化合物であることを特徴とする［１］または［２］に記載のポリエステルフィルム。

（一般式（２）中、Ｒ₁はアルキル基、アリール基、アルコキシ基、アルコキシカルボニル基、アミノカルボニル基、アリールオキシ基、アシル基またはアリールオキシカルボニル基を表す。Ｒ₂は置換基としてＬ₁を有するアルキル基、アリール基、アルコキシ基、アルコキシカルボニル基、アミノカルボニル基、アリールオキシ基、アシル基またはアリールオキシカルボニル基を表す。Ｒ₃はアルキル基またはアリール基を表す。ｎは１から４の整数を表し、Ｌ₁はｎ価の連結基を表す。）
［６］前記一般式（２）における、ｎが３または４であることを特徴とする［５］に記載のポリエステルフィルム。
［７］前記末端封止剤が、下記一般式（３）で表されるケテンイミン化合物であることを特徴とする［１］または［２］に記載のポリエステルフィルム。

（一般式（３）中、Ｒ₁およびＲ₅はアルキル基、アリール基、アルコキシ基、アルコキシカルボニル基、アミノカルボニル基、アリールオキシ基、アシル基またはアリールオキシカルボニル基を表す。Ｒ₂およびＲ₄は置換基としてＬ₂を有するアルキル基、アリール基、アルコキシ基、アルコキシカルボニル基、アミノカルボニル基、アリールオキシ基、アシル基またはアリールオキシカルボニル基を表す。Ｒ₃およびＲ₆はアルキル基またはアリール基を表す。Ｌ₂は単結合または二価の連結基を表す。）
［８］前記ケテンイミン化合物のケテンイミンを構成する窒素原子と該窒素原子に結合している置換基を除く部分の分子量が３２０以上であることを特徴する［４］〜［７］のいずれかに記載のポリエステルフィルム。
［９］リン元素の含有率が３０〜６００ｐｐｍとなるようにリン化合物をさらに含み、
前記リン元素の含有率の面内変動が２〜２０％であることを特徴とする［１］〜［８］のいずれかに記載のポリエステルフィルム。
［１０］前記リン元素の平均含有率をＹａｖｅ、面内標準偏差をσｙとしたとき、０．５≦（σｙ／Ｙａｖｅ）×１００≦５であることを特徴とする［９］に記載のポリエステルフィルム。
［１１］微粒子をさらに含み、前記微粒子の含有率は、前記ポリエステルに対し０．５〜１０質量％であることを特徴とする［１］〜［１０］のいずれかに記載のポリエステルフィルム。
［１２］ボイドをさらに含み、前記ボイドの含有率は、前記ポリエステルの断面積に対して５〜５０％であることを特徴とする［１］〜［１１］のいずれかに記載のポリエステルフィルム。
［１３］ポリエステルと末端封止剤を含む第１の組成物と、ポリエステルを含み、前記第１の組成物と末端封止剤の含有率が異なる第２の組成物の混合物を作製する工程と、
前記混合物を溶融して製膜する工程を有し、
前記混合物を作製する工程では、前記第１の組成物と前記第２の組成物を不均一に混合することを特徴とするポリエステルフィルムの製造方法。
［１４］前記混合物を作製する工程は、前記第１の組成物と前記第２の組成物を混練押出し機に投入する工程を含み、前記投入する工程では、前記第１の組成物の投入量を変動させることを特徴とする［１３］に記載のポリエステルフィルムの製造方法。
［１５］［１３］または［１４］に記載の方法により製造したポリエステルフィルム。
［１６］［１］〜［１２］および［１５］のいずれかに記載のポリエステルフィルムを用いた太陽電池用バックシート。
［１７］［１６］に記載の太陽電池量バックシートを用いた太陽電池用モジュール。 [1] A polyester film containing polyester and an end-capping agent,
The average content of the terminal blocker is 0.1 to 10% by mass with respect to the polyester, and the in-plane variation of the content of the terminal blocker is 2 to 20%. Polyester film.
[2] As described in [1], when the average content of the end-capping agent is Xave and the in-plane standard deviation is σx, 0.5 ≦ (σx / Xave) × 100 ≦ 5 Polyester film.
[3] The polyester film according to [1] or [2], wherein the terminal blocking agent is a chain carbodiimide compound, a cyclic carbodiimide compound, or a ketene imine compound.
[4] The polyester film according to [1] or [2], wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (1).

(In the general formula (1), R ₁ and R ₂ each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group; ₃ represents an alkyl group or an aryl group.)
[5] The polyester film according to [1] or [2], wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (2).

(In the general formula (2), R ₁ represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group. R ₂ represents L ₁ as a substituent. Represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group, wherein R ₃ represents an alkyl group or an aryl group, and n is 1 to 4. Represents an integer, and L ₁ represents an n-valent linking group.)
[6] The polyester film as described in [5], wherein in the general formula (2), n is 3 or 4.
[7] The polyester film as described in [1] or [2], wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (3).

(In the general formula (3), R ₁ and R ₅ represent an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. R ₂ and R ₄ Represents an alkyl group having L ₂ as a substituent, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group, wherein R ₃ and R ₆ are an alkyl group or an aryl group. L ₂ represents a single bond or a divalent linking group.)
[8] The molecular weight of the portion other than the nitrogen atom constituting the ketene imine of the ketene imine compound and the substituent bonded to the nitrogen atom is 320 or more, [4] to [7] Polyester film.
[9] A phosphorus compound is further included so that the phosphorus element content is 30 to 600 ppm,
The polyester film according to any one of [1] to [8], wherein an in-plane variation of the phosphorus element content is 2 to 20%.
[10] The polyester according to [9], wherein 0.5 ≦ (σy / Yave) × 100 ≦ 5 when the average content of the phosphorus element is Yave and the in-plane standard deviation is σy. the film.
[11] The polyester film according to any one of [1] to [10], further including fine particles, wherein the content of the fine particles is 0.5 to 10% by mass with respect to the polyester.
[12] The polyester film according to any one of [1] to [11], further including voids, wherein the void content is 5 to 50% with respect to the cross-sectional area of the polyester.
[13] A step of producing a mixture of a first composition containing polyester and an end-capping agent, and a second composition comprising polyester and having a different content of the first composition and the end-capping agent; ,
A step of melting the mixture to form a film;
In the step of producing the mixture, the first composition and the second composition are mixed non-uniformly.
[14] The step of preparing the mixture includes a step of charging the first composition and the second composition into a kneading extruder, and in the charging step, an input amount of the first composition [13] The method for producing a polyester film as described in [13].
[15] A polyester film produced by the method according to [13] or [14].
[16] A solar cell backsheet using the polyester film according to any one of [1] to [12] and [15].
[17] A solar cell module using the solar cell backsheet according to [16].

  According to the present invention, the average content of the end-capping agent contained in the polyester film is within a predetermined range, and the content of the end-capping agent is allowed to have in-plane variation within the predetermined range. Adhesion with other members laminated on the substrate can be improved. The polyester film of the present invention can exhibit high adhesion even in a high temperature and high humidity environment.

Moreover, according to this invention, the heat-and-moisture resistance of a polyester film can be improved and the intensity | strength of a polyester film can fully be maintained in a high humidity environment.
Thus, since the polyester film of the present invention has excellent adhesion and wet heat resistance in addition to hydrolysis resistance, it is preferably used as a back sheet for a solar cell module.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Polyester film)
The polyester film of this invention contains polyester and terminal blocker. The average content of the end capping agent is 0.1 to 10% by mass, and the in-plane variation of the content of the end capping agent is 2 to 20%. Here, the in-plane means a region including a surface extending in both the longitudinal direction and the width direction of the polyester film surface, and the in-plane variation is when the polyester film is equally divided in both the longitudinal direction and the width direction. The difference between the maximum value and the minimum value of the content of the end-capping agent per unit area measured in the divided unit region is expressed as a percentage divided by the average value.

  The polyester film of the present invention gives in-plane variation to the content of the end-capping agent. That is, the content of the end-capping agent varies along the surface of the polyester film (in the surface direction). Thus, the adhesiveness of a polyester film and another member can be improved because the content rate of terminal blocker has distribution within a surface. Furthermore, when the content of the end-capping agent has a distribution in the plane, the heat and moisture resistance of the polyester film can be improved.

The following mechanism is conceivable as a mechanism for improving adhesion and moist heat resistance by controlling the in-plane variation of the content of the end-capping agent to 2 to 20%.
Usually, when a polyester film containing an end-capping agent is stored in a moist heat environment, the compound itself constituting the end-capping agent or a decomposition product thereof is deposited on the film surface, resulting in poor adhesion. At this time, if a region having a small content of the end-capping agent is present in the film plane, the compound constituting the end-capping agent itself or the decomposition product thereof is reduced in that region. That is, in the polyester film of the present invention, the compound itself that constitutes the end-capping agent, and a portion where the precipitation of the decomposition product is large and a portion where the precipitation is small are generated. be able to. Thus, it is thought that the adhesiveness as the whole film can be improved by producing the location where adhesiveness is locally high.
Moreover, in the part with a large content rate of terminal sealing agent, heat-and-moisture resistance increases and film strength can be strengthened. Thereby, it can suppress that a film breaks or a crack generate | occur | produces and can suppress adhesion failure. On the other hand, in a portion where the content of the terminal sealing agent is small, the heat and moisture resistance and the film strength are lowered. However, by providing in-plane variation in the content of the end-capping agent, the portion with a large amount of the end-capping agent can complement the small portion and improve the heat and moisture resistance. Thus, it is thought that the location where the content rate of terminal blocker is high and the location where it is low complement each other's function, and are improving the adhesiveness and heat-and-moisture resistance.

  Moreover, since the terminal blocker functions to lower the glass transition temperature (Tg) of the polyester, it promotes thermal shrinkage when the polyester film is stored in a humid heat environment. At this time, if the content of the end-capping agent is large, the heat shrinkage occurs uniformly and greatly, so that the difference from the heat shrinkage with other members that are in close contact with each other increases, resulting in poor adhesion due to shear between the members. . On the other hand, in the part where the content rate of the terminal sealing agent is small, the thermal shrinkage is small, and the adhesion failure due to the shear between the members is suppressed. Since the polyester film of the present invention has an in-plane variation in the content of the end-capping agent, there are locations where the thermal shrinkage is large and locations where the thermal shrinkage is small. In such a polyester film, even if there is a portion with large heat shrinkage, if there is a small portion, the shrinkage is stopped there, and it is considered that adhesion failure due to shearing between members is suppressed.

  In order to obtain the effect of improving the adhesion and heat-and-moisture resistance, the in-plane variation of the content of the end-capping agent in the polyester film of the present invention needs to be 2 to 20%. The in-plane variation of the content of the end-capping agent may be 2% or more, preferably 4% or more, and more preferably 6% or more. Further, the in-plane variation of the content of the terminal blocking agent may be 20% or less, preferably 15% or less, and more preferably 10% or less. By setting the in-plane variation of the content of the terminal sealing agent within the above range, the adhesion between the polyester film and other members (for example, sealing agent (EVA), adhesive, functional coating layer, etc.) is improved. Can be increased. Furthermore, the moisture and heat resistance of the polyester film can be increased, and the strength of the film can be enhanced. In addition, the above effects cannot fully be acquired as the in-plane fluctuation | variation of the content rate of terminal blocker is less than the said lower limit. On the other hand, if the in-plane variation of the content of the end-capping agent exceeds the above upper limit value, there is a portion where the heat shrinkage is extremely large, and this portion may promote distortion and cause poor adhesion.

The in-plane variation F (%) of the end-capping agent contained in the polyester film of the present invention can be expressed by the following relational expression.
F (%) = (Xmax−Xmin) / Xave × 100
Here, Xmax is the maximum value of the content of the end-capping agent per unit region (unit area) of the polyester film, and Xmin is the content of the end-capping agent per unit region (unit area) of the polyester film. It is the minimum value, and Xave is the average value of the content of the end-capping agent contained in all unit regions of the polyester film.
Here, the unit region refers to one region formed by being divided when the polyester film is equally divided in both the longitudinal direction and the width direction. For example, if the film has a longitudinal direction of less than 3 m, the central 2/3 region in the longitudinal direction is divided into 10 equal parts in the longitudinal direction, and the central 2/3 region in the width direction is equally divided into 10 parts in the width direction. By dividing the film into 100, 100 unit areas can be obtained. The content of the end-capping agent per unit area contained in one unit region is measured, and the difference between the maximum value and the minimum value is divided by the average value and expressed as a percentage. It can be.
Further, if the film has a longitudinal direction of 3 m or more, an arbitrary point in the longitudinal direction is set as the central point, and 5 points each from the central point in the upstream direction and the downstream direction in the longitudinal direction, a total of 10 points in the longitudinal direction. The film may be equally divided, and the film is divided into 100 by dividing the center 2/3 region in the width direction into 10 equal parts in the width direction, and 100 unit regions may be obtained.

Further, when the average content of the end-capping agent contained in the entire polyester film is Xave and the in-plane standard deviation is σx, it is preferable that 0.5 ≦ (σx / Xave) × 100 ≦ 5, It is more preferable that 1 ≦ (σx / Xave) × 100 ≦ 3. A value obtained by dividing the standard deviation by the average value is called a coefficient of variation (relative standard deviation), and represents the degree of variation of the end-capping agent present in the polyester film. Here, the in-plane standard deviation means the standard deviation of the content of the end-capping agent measured in the divided unit area when the polyester film is equally divided in both the longitudinal direction and the width direction.
In the polyester film of the present invention, by setting the coefficient of variation (relative standard deviation) within the above range, a desired distribution can be imparted to the content of the end-capping agent present in the polyester film, and the adhesiveness In addition, the heat and humidity resistance can be effectively increased.

  As a method for controlling the variation in the content of the end-capping agent, (1) a step of melt-mixing the polyester added with the end-capping agent and the polyester not added is provided. (2) A step of melting and mixing the polyester with and without the end-capping agent is provided, and the viscosity is varied by making the difference in the molecular weight of each polyester. The method of performing etc. is mentioned.

  Although the thickness of the polyester film of this invention changes with uses, when using as a member of the solar cell module backsheet, it is preferable that it is 25-300 micrometers, and it is more preferable that it is 120-300 micrometers. By setting the thickness to the above lower limit or higher, sufficient mechanical strength can be obtained, and by setting the thickness to the upper limit or lower, a merit in cost can be obtained.

  The polyester film of the present invention is preferably stretched, more preferably biaxially stretched, and plane biaxially stretched is particularly preferable as compared with stretching such as tubular, and sequential biaxial stretching. It is particularly preferred that

(polyester)
The polyester film of the present invention contains polyester. The kind in particular of polyester is not restrict | limited, A well-known thing can be used as polyester.

  The polyester is preferably a saturated polyester. Thus, by using a saturated polyester, a polyester film that is superior in terms of mechanical strength as compared with a film using an unsaturated polyester can be obtained. Examples of the polyester include a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

  Specific examples of the linear saturated polyester include polyethylene terephthalate (PET), polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate, of which polyethylene terephthalate ( PET) or polyethylene-2,6-naphthalate (PEN) is particularly preferable from the viewpoint of the balance between mechanical properties and cost, and polyethylene terephthalate is more particularly preferable.

  The polyester may be a homopolymer or a copolymer. Further, polyester may be blended with a small amount of other types of resin, such as polyimide. Further, as the polyester, a crystalline polyester capable of forming anisotropy when melted may be used.

  From the viewpoint of heat resistance and viscosity, the molecular weight of the polyester is preferably 5000 to 30000, more preferably 8000 to 26000, and particularly preferably 12,000 to 24,000. As the weight average molecular weight of the polyester, a value in terms of polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent can be used.

  The polyester can be obtained by reacting a dicarboxylic acid or an ester-forming derivative thereof with a low molecular weight aliphatic diol or a high molecular weight diol. Examples of the dicarboxylic acid or its ester-forming derivative include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, paraphenylene dicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, dimethyl orthophthalate, dimethyl naphthalene dicarboxylate, and paraphenylene. And dimethyl dicarboxylate. These may be used alone or in combination of two or more.

  Examples of the low molecular weight aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,5-pentane. Examples include diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and the like. These may be used alone or in combination of two or more. Examples of the high molecular weight diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol and the like. These may be used alone or in combination of two or more.

  Examples of the crystalline polyester composed of the above components include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, butanediol terephthalate polytetramethylene glycol copolymer, and the like. . These may be used alone or in combination of two or more. Particularly preferred among the aromatic polyesters described herein are those using terephthalic acid and naphthalenedicarboxylic acid as main components as dicarboxylic acids, and those having ethylene glycol and cyclohexanedimethanol as main components as diols. Preferred are polyethylene terephthalate, polyethylene naphthalate, and polycyclohexanedimethylene terephthalate, and more preferred are polyethylene terephthalate and polyethylene naphthalate.

  Polyester can be synthesized by a known method. For example, polyester can be synthesized by a known polycondensation method or ring-opening polymerization method, and any of transesterification and direct polymerization can be applied.

  When the polyester used in the present invention is a polymer or copolymer obtained by a condensation reaction mainly comprising an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, An aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof can be produced by an esterification reaction or an ester exchange reaction and then a polycondensation reaction. Moreover, the carboxylic acid value and intrinsic viscosity of the polyester can be controlled by selecting the raw material and reaction conditions. In order to effectively advance the esterification reaction or transesterification reaction and polycondensation reaction, it is preferable to add a polymerization catalyst during these reactions.

  As a polymerization catalyst for polymerizing polyester, Sb-based, Ge-based, and Ti-based compounds are preferably used from the viewpoint of suppressing the carboxyl group content to a predetermined range or less, and Ti-based compounds are particularly preferable. In the case of using a Ti-based compound, an embodiment in which polymerization is performed by using the Ti-based compound as a catalyst in a range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm is preferable. When the proportion of the Ti-based compound is within the above range, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the polymer substrate can be kept low.

  Examples of the synthesis of polyester using a Ti compound include Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3997756, Japanese Patent No. 3996226, Japanese Patent No. 3997866, Japanese Patent No. 39968671, The methods described in Japanese Patent No. 40000867, Japanese Patent No. 4053837, Japanese Patent No. 4127119, Japanese Patent No. 4134710, Japanese Patent No. 4159154, Japanese Patent No. 4269704, Japanese Patent No. 431538, and the like can be applied.

  The polyester is preferably solid-phase polymerized after polymerization. Thereby, a preferable carboxylic acid value can be achieved. Solid-phase polymerization may be a continuous method (a method in which a tower is filled with a resin, which is slowly heated for a predetermined time and then sent out), or a batch method (a resin is charged into a container). , A method of heating for a predetermined time). Specifically, solid-phase polymerization is described in Japanese Patent No. 2621563, Japanese Patent No. 3121876, Japanese Patent No. 3136774, Japanese Patent No. 3603585, Japanese Patent No. 3616522, Japanese Patent No. 3617340, Japanese Patent No. 3680523, Japanese Patent No. 3717392, Japanese Patent No. 4167159, etc. The method can be applied.

  The temperature of the solid phase polymerization is preferably 170 to 240 ° C, more preferably 180 to 230 ° C, and further preferably 190 to 220 ° C. The solid phase polymerization time is preferably 5 to 100 hours, more preferably 10 to 75 hours, and further preferably 15 to 50 hours. The solid phase polymerization is preferably performed in a vacuum or in a nitrogen atmosphere.

  The terminal carboxyl group content in the polyester (the carboxylic acid value of the polyester, hereinafter also referred to as AV) is preferably 25 eq / ton or less, more preferably 20 eq / ton or less, and particularly preferably 16 eq / ton or less with respect to the polyester. More preferably, it is 15 eq / ton or less. Further, AV is preferably 1 eq / ton or more, and more preferably 2 eq / ton or more. The term “terminal carboxyl group content (AV)” as used herein refers to the average terminal carboxyl group content (AV) of the entire polyester film. By making AV of a polyester film in the said range, hydrolysis of polyester can be suppressed and embrittlement can be prevented. Moreover, by making AV of a polyester film into the said range, the molecular weight of polyester can be made into an appropriate range, and it can prevent that a viscosity increases more than necessary.

  AV in the polyester can be adjusted by polymerization catalyst species, polymerization time, and film forming conditions (film forming temperature and time). AV is H.264. A. Pohl, Anal. Chem. 26 (1954) 2145, and can be measured by a titration method. Specifically, the polyester is dissolved in benzyl alcohol at 205 ° C., a phenol red indicator is added, and titrated with a solution of sodium hydroxide in water / methanol / benzyl alcohol to determine the carboxylic acid value (eq / ton) can be calculated.

The intrinsic viscosity (IV) of the polyester of the present invention is preferably 0.65 to 0.95 dl / g, more preferably 0.68 to 0.90 dl / g, and particularly preferably 0.70 to 0.85 dl / g. preferable. By making the intrinsic viscosity of the polyester within the above range, the film forming property can be improved and the film thickness uniformity can be improved.
The intrinsic viscosity (IV) of the polyester is the intrinsic viscosity of the polyester in which all the polyesters are mixed when there are two or more kinds of polyesters used in film formation (such as when the recovered polyesters of JP2011-256337A are used). It is preferable that the viscosity satisfies the above range.
The intrinsic viscosity (IV) of the polyester was obtained by dissolving the polyester in orthochlorophenol and obtaining the intrinsic viscosity from the following formula from the solution viscosity measured at 25 ° C.
ηsp / C = [η] + K [η] ² · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the dissolved polymer weight per 100 ml of solvent (in this measurement, 1 g / 100 ml), and K is the Huggins constant (0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

  In the present invention, in order to have in-plane variation in the content of the end-capping agent contained in the polyester film, a step of melting and mixing the polyester with and without the end-capping agent is provided, and each polyester molecular weight It is good also as making a difference in a viscosity by making a difference in. For example, when these two polyesters are mixed, non-uniform mixing is performed by increasing the IV of the polyester to which the end-capping agent is added and lowering the IV of the polyester without the end-capping agent. Can do. Thereby, in-plane fluctuation | variation can be given to the content rate of terminal blocker in a polyester film.

(End sealant)
The polyester film of the present invention contains a terminal sealing agent. The end-capping agent is preferably a chain carbodiimide compound, a cyclic carbodiimide compound or a ketene imine compound, and particularly preferably a ketene imine compound. The chain carbodiimide compound, the cyclic carbodiimide compound, or the ketene imine compound may be used alone or in combination.

  The terminal sealing agent should just be contained 0.1-10 mass% with respect to polyester, it is preferable that 0.1-4 mass% is contained, and 0.1-2 mass% is contained. More preferably. By making the content rate of a cyclic carbodiimide compound in the said range, the adhesiveness of a polyester film and another member can be improved. Moreover, the heat-and-moisture resistance of a polyester film can be improved. In addition, when a carbodiimide compound and a ketene imine compound are used together, it is preferable that the sum total of the content rate of two types of compounds exists in the said range.

  The polyester film of the present invention does not refuse to contain a compound other than the end-capping agent unless it is contrary to the spirit of the present invention. It is preferable that 70% or more by weight of the organic compound other than the polyester contained in the polyester film of the present invention is an end-capping agent as described later, more preferably 80% or more, and particularly 90% or more. preferable.

<Carbodiimide compound>
Examples of the carbodiimide compound include compounds having one or more carbodiimide groups in the molecule (including a chain polycarbodiimide compound). Specifically, as the monocarbodiimide compound, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, Examples include diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, N, N′-di-2,6-diisopropylphenylcarbodiimide. As the polycarbodiimide compound, those having a degree of polymerization of usually 2 or more, preferably 4 or more and an upper limit of usually 40 or less, preferably 30 or less, are used, U.S. Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Pat. Org. Chem. 28, p2069-2075 (1963), and Chemical Review 1981, 81, No. 4, p. And those produced by the method described in 619-621 and the like.

  Examples of the organic diisocyanate that is a raw material for producing the polycarbodiimide compound include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures thereof. Specifically, 1,5-naphthalene diisocyanate, 4 , 4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4 A mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate And 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate, etc. .

  Specific examples of industrially available polycarbodiimides include carbodilite HMV-8CA (manufactured by Nisshinbo), carbodilite LA-1 (manufactured by Nisshinbo), Starbazole P (manufactured by Rhein Chemie), starbactol P100 (manufactured by Rhein Chemie), and starbactol P400. (Product made by Rhein Chemie), Stabilizer 9000 (made by Rashihi Chemi), etc. are illustrated. The carbodiimide compound can be used alone, but a plurality of compounds can also be mixed and used.

<Cyclic carbodiimide compound>
The polyester film of the present invention contains a cyclic carbodiimide compound. A cyclic carbodiimide compound containing one carbodiimide group in the ring skeleton and having in the molecule at least one cyclic structure in which the first nitrogen and the second nitrogen are bonded by a bonding group functions as a cyclic sealant.
A cyclic carbodiimide compound can be prepared by the method described in International Publication 2011/093478 pamphlet.

  The cyclic carbodiimide compound used in the present invention has a cyclic structure. The cyclic carbodiimide compound may have a plurality of cyclic structures. The cyclic structure has one carbodiimide group (—N═C═N—), and the first nitrogen and the second nitrogen are bonded by a bonding group. One cyclic structure has only one carbodiimide group. For example, when there are a plurality of cyclic structures in the molecule, such as a spiro ring, one cyclic structure bonded to a spiro atom is included in each cyclic structure. As long as it has a carbodiimide group, the compound may have a plurality of carbodiimide groups. The number of atoms in the cyclic structure is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15.

  Here, the number of atoms in the ring structure means the number of atoms that directly constitute the ring structure, and is, for example, 8 for an 8-membered ring and 50 for a 50-membered ring. This is because if the number of atoms in the cyclic structure is smaller than 8, the stability of the cyclic carbodiimide compound is lowered, and it may be difficult to store and use. From the viewpoint of reactivity, there is no particular restriction on the upper limit of the number of ring members, but cyclic carbodiimide compounds having more than 50 atoms are difficult to synthesize, and the cost may increase significantly. From this viewpoint, the number of atoms in the cyclic structure is preferably 10-30, more preferably 10-20, and particularly preferably 10-15.

As the cyclic carbodiimide compound, it is preferable to use a cyclic carbodiimide compound represented by the following general formula (O-1) or general formula (O-2).
Hereinafter, the preferable structure of the cyclic carbodiimide compound of this invention is demonstrated in order of the following general formula (O-1) and general formula (O-2).

First, the cyclic carbodiimide compound represented by the general formula (O-1) will be described.

In general formula (O-1), R ¹ and R ⁵ each independently represents an alkyl group, an aryl group, or an alkoxy group. R ^{2 to} R ⁴ and R ^{6 to} R ⁸ each independently represent a hydrogen atom, an alkyl group, an aryl group, or an alkoxy group. R ^{1 to} R ⁸ may be bonded to each other to form a ring. X ¹ and X ² each independently represents a single bond, —O—, —CO—, —S—, —SO ₂ —, —NH— or —CH ₂ —. L ¹ represents a divalent linking group.

In the general formula (O-1), R ¹ and R ⁵ each independently represents an alkyl group, an aryl group or an alkoxy group, preferably an alkyl group or an aryl group, or a secondary or tertiary alkyl group or Representing an aryl group is more preferred from the viewpoint of suppressing the reaction between the isocyanate end linked to the terminal of the polyester and the hydroxyl terminal of the polyester and suppressing the thickening, and particularly preferably a secondary alkyl group.

The alkyl group represented by R ¹ and R ⁵ is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms, and an alkyl group having 2 to 6 carbon atoms. It is particularly preferred. The alkyl group represented by R ¹ and R ⁵ may be linear, branched or cyclic, but is branched or cyclic, and isocyanate and polyester linked to the end of the polyester. It is preferable from the viewpoint of suppressing the reaction at the hydroxyl terminal and suppressing thickening. The alkyl group represented by R ¹ and R ⁵ is preferably a secondary or tertiary alkyl group, and more preferably a secondary alkyl group. The alkyl groups represented by R ¹ and R ⁵ are methyl, ethyl, n-propyl, sec-propyl, iso-propyl, n-butyl, tert-butyl, sec-butyl, iso-butyl. Group, n-pentyl group, sec-pentyl group, iso-pentyl group, n-hexyl group, sec-hexyl group, iso-hexyl group, cyclohexyl group, etc., among them, iso-propyl group, tert group -Butyl group, iso-butyl group, iso-pentyl group, iso-hexyl group and cyclohexyl group are preferable, iso-propyl group, cyclohexyl group and tert-butyl group are more preferable, and iso-propyl group and cyclohexyl group are particularly preferable. .
The alkyl group represented by R ¹ and R ⁵ may further have a substituent, and the substituent is not particularly limited. However, the alkyl group represented by R ¹ and R ⁵ preferably has no further substituent from the viewpoint of reactivity with carboxylic acid.

The aryl group represented by R ¹ and R ⁵ is preferably an aryl group having 6 to 20 carbon atoms, more preferably an aryl group having 6 to 12 carbon atoms, and an aryl group having 6 carbon atoms. Particularly preferred. The aryl group represented by R ¹ and R ⁵ may be an aryl group formed by condensing R ¹ and R ² or condensing R ⁵ and R ^6, but R ¹ and R ⁵ are each represented by R ² It is preferable that the ring is not condensed with R ⁶ . Examples of the aryl group represented by R ¹ and R ⁵ include a phenyl group and a naphthyl group, and among them, a phenyl group is more preferable.
The aryl group represented by R ¹ and R ⁵ may further have a substituent, and the substituent is not particularly limited. However, the aryl group represented by R ¹ and R ⁵ preferably has no further substituent from the viewpoint of reactivity with carboxylic acid.

The alkoxy group represented by R ¹ and R ⁵ is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and an alkoxy group having 2 to 6 carbon atoms. It is particularly preferred. The alkoxy group represented by R ¹ and R ⁵ may be linear, branched or cyclic, but is branched or cyclic, and isocyanate and polyester linked to the end of the polyester. It is preferable from the viewpoint of suppressing the reaction at the hydroxyl terminal and suppressing thickening. Preferred examples of alkoxy groups R ¹ and R ⁵ represent, the may include groups terminated -O- is linked alkyl group represented by R ¹ and R ^5, the same preferable ranges R ¹ and R ⁵ It is a group in which —O— is linked to the terminal of a preferred alkyl group.
The alkoxy group represented by R ¹ and R ⁵ may further have a substituent, and the substituent is not particularly limited. However, the alkoxy group represented by R ¹ and R ⁵ preferably has no further substituent from the viewpoint of reactivity with carboxylic acid.

R ¹ and R ⁵ may be the same or different, but are preferably the same from the viewpoint of cost.

In the general formula (O-1), R ^{2 to} R ⁴ and R ^{6 to} R ⁸ each independently represent a hydrogen atom, an alkyl group, an aryl group or an alkoxy group, and a hydrogen atom, an alkyl having 1 to 20 carbon atoms. Group, preferably an alkoxy group having 1 to 20 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and particularly preferably a hydrogen atom.
The alkyl group, aryl group or alkoxy group represented by R ^{2 to} R ⁴ and R ^{6 to} R ⁸ may further have a substituent, and the substituent is not particularly limited.
In the cyclic carbodiimide compound of the present invention, it is preferable that R ² and R ⁶ are both hydrogen atoms in the general formula (O-1) from the viewpoint of easily introducing bulky substituents into R ¹ and R ⁵ . Here, WO2010 / 072111 exemplifies a compound in which an alkyl group or an aryl group is substituted at a site corresponding to R ² and R ⁶ in the general formula (O-1) (meta position with respect to the carbodiimide group). However, these compounds cannot suppress the reaction between the isocyanate linked to the terminal of the polyester and the hydroxyl terminal of the polyester, and in the general formula (O-1), the sites corresponding to R ² and R ⁶ It is difficult to introduce a substituent at (ortho position with respect to the carbodiimide group).

In the general formula (O-1), R ^{1 to} R ⁸ may be bonded to each other to form a ring. The ring formed at this time is not particularly limited, but is preferably an aromatic ring. For example, two or more of R ^{1 to} R ⁴ may be bonded to each other to form a condensed ring, and an arylene group or heteroarylene group having 10 or more carbon atoms is formed together with the benzene ring substituted by R ^{1 to} R ^4. May be. Examples of the arylene group having 10 or more carbon atoms formed at this time include aromatic groups having 10 to 15 carbon atoms such as naphthalenediyl group.
Similarly, for example, two or more of R ^{5 to} R ⁸ may be bonded to each other to form a condensed ring, and an arylene group or heteroarylene having 10 or more carbon atoms together with a benzene ring substituted by R ^{5 to} R ^8. A preferred range at that time is the same as the preferred range when an arylene group or heteroarylene group having 10 or more carbon atoms is formed together with the benzene ring substituted by R ^{1 to} R ⁴ .
However, in the cyclic carbodiimide compound of the present invention, in the general formula (O-1), R ^{1 to} R ⁸ are preferably not bonded to each other to form a ring.

In the general formula (O-1), X ¹ and X ² are each independently selected from a single bond, —O—, —CO—, —S—, —SO ₂ —, —NH—, and —CH ₂ —. At least one selected from the group consisting of —O—, —CO—, —S—, —SO ₂ — and —NH—, among which —O— and —S— are easy to synthesize. From the viewpoint of

In the general formula (O-1), L ¹ represents a divalent linking group, which may contain a heteroatom and a substituent, respectively, a divalent aliphatic group having 1 to 20 carbon atoms, a divalent It is preferably an alicyclic group having 3 to 20 carbon atoms, a divalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and preferably a divalent aliphatic group having 1 to 20 carbon atoms. More preferred.

Examples of the divalent aliphatic group represented by L ¹ include an alkylene group having 1 to 20 carbon atoms. Examples of the alkylene group having 1 to 20 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. More preferred are a methylene group, an ethylene group and a propylene group, and an ethylene group is particularly preferred. These aliphatic groups may be substituted. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

Examples of the divalent alicyclic group represented by L ¹ include a cycloalkylene group having 3 to 20 carbon atoms. Examples of the cycloalkylene group having 3 to 20 carbon atoms include cyclopropylene group, cyclobutylene group, cyclopentylene group, cyclohexylene group, cycloheptylene group, cyclooctylene group, cyclononylene group, cyclodecylene group, cyclododecylene group, and cyclohexadecylene. Group and the like. These alicyclic groups may be substituted. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

Examples of the divalent aromatic group represented by L ¹ include an arylene group having 5 to 15 carbon atoms, which includes a hetero atom and may have a heterocyclic structure. Examples of the arylene group having 5 to 15 carbon atoms include a phenylene group and a naphthalenediyl group. These aromatic groups may be substituted. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

In the general formula (O-1), the number of atoms in the cyclic structure containing a carbodiimide group is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15. .
Here, the number of atoms in the cyclic structure containing a carbodiimide group means the number of atoms that directly constitute the cyclic structure containing a carbodiimide group. It is. This is because if the number of atoms in the cyclic structure is smaller than 8, the stability of the cyclic carbodiimide compound is lowered, and it may be difficult to store and use. From the viewpoint of reactivity, there is no particular restriction on the upper limit of the number of ring members, but cyclic carbodiimide compounds having more than 50 atoms are difficult to synthesize, and the cost may increase significantly. From this viewpoint, in the general formula (O-1), the number of atoms in the cyclic structure is preferably 10 to 30, more preferably 10 to 20, and particularly preferably 10 to 15.

Next, the cyclic carbodiimide compound represented by the general formula (O-2) will be described.

In general formula (O-2), R ¹¹ , R ¹⁵ , R ²¹ and R ²⁵ each independently represents an alkyl group, an aryl group or an alkoxy group. R ^{12 to} R ¹⁴ , R ^{16 to} R ¹⁸ , R ^{22 to} R ²⁴ and R ^{26 to} R ²⁸ each independently represent a hydrogen atom, an alkyl group, an aryl group or an alkoxy group. R ^{11 to} R ²⁸ may combine with each other to form a ring. X ¹¹ , X ¹² , X ²¹ and X ²² each independently represent a single bond, —O—, —CO—, —S—, —SO ₂ —, —NH— or —CH ₂ —. L ² represents a tetravalent linking group.

In the general formula (O-2), the preferred ranges of R ¹¹ , R ¹⁵ , R ²¹ and R ²⁵ are the same as the preferred ranges of R ¹ and R ^{5 in} the general formula (O-1).
In the aryl group represented by R ¹¹ , R ¹⁵ , R ²¹ and R ²⁵ , R ¹¹ and R ¹² are condensed, R ¹⁵ and R ¹⁶ are condensed, R ²¹ and R ²² are condensed, or R ²⁵ and R ²⁶ are condensed. Although it may be an aryl group formed, it is preferable that R ¹¹ , R ¹⁵ , R ²¹ and R ²⁵ do not form a ring by condensing with R ¹² , R ¹⁶ , R ²² and R ²⁶ , respectively.
R ¹¹ , R ¹⁵ , R ²¹ and R ²⁵ may be the same or different, but are preferably the same from the viewpoint of cost.

In the general formula (O-2), a preferable range of R ^{12 to} R ¹⁴ , R ^{16 to} R ¹⁸ , R ^{22 to} R ²⁴ and R ^{26 to} R ²⁸ is R ² in the general formula (O-1). to R are the same as the preferred ranges of ⁴ and R ⁶ to R ^8.
Among ^{R 12 ~R 14, R 16 ~R} 18, R 22 ~R 24 and R ²⁶ to R ^28, can R ^12, R ^16, R ²² and R ²⁶ are both hydrogen atoms, R ^11, R ¹⁵ , R ²¹ and R ²⁵ are preferable from the viewpoint of easy introduction of bulky substituents.

  Thus, by introducing a bulky group such as an alkyl group, an aryl group or an alkoxy group in the vicinity of the carbodiimide group, an isocyanate group and a terminal hydroxyl group of the polyester produced after the reaction of the carbodiimide group and the terminal carboxylic acid of the polyester. Can be suppressed. As a result, high molecular weight of the polyester can be suppressed, and generation of chips due to the increase in the viscosity of the polyester as described above can be suppressed.

In the general formula (O-2), R ^{11 to} R ²⁸ may be bonded to each other to form a ring, and a preferable ring range is the above general formula (O-1), in which R ^{1 to} R ⁸ are each other. This is the same as the range of the ring formed by bonding.

In the general formula (O-2), preferred ranges of X ¹¹ , X ¹² , X ²¹ and X ²² are the same as the preferred ranges of X ¹ and X ^{2 in} the general formula (O-1).

In the general formula (O-2), L ² represents a tetravalent linking group, each of which may contain a heteroatom and a substituent, a tetravalent C 1-20 aliphatic group, a tetravalent A alicyclic group having 3 to 20 carbon atoms, a tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof is preferable, and a tetravalent aliphatic group having 1 to 20 carbon atoms is preferable. More preferred.

Examples of the tetravalent aliphatic group represented by L ² include an alkanetetrayl group having 1 to 20 carbon atoms. As an alkanetetrayl group having 1 to 20 carbon atoms, methanetetrayl group, ethanetetrayl group, propanetetrayl group, butanetetrayl group, pentanetetrayl group, hexanetetrayl group, heptanetetrayl group, octanetetrayl Group, nonanetetrayl group, decanetetrayl group, dodecanetetrayl group, hexadecanetetrayl group and the like, methanetetrayl group, ethanetetrayl group, propanetetrayl group are more preferable, and ethanetetrayl group is particularly preferable preferable. These aliphatic groups may contain a substituent. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

Examples of the tetravalent alicyclic group represented by L ² include a cycloalkanetetrayl group having 3 to 20 carbon atoms as the alicyclic group. As a cycloalkanetetrayl group having 3 to 20 carbon atoms, a cyclopropanetetrayl group, a cyclobutanetetrayl group, a cyclopentanetetrayl group, a cyclohexanetetrayl group, a cycloheptanetetrayl group, a cyclooctanetetrayl group, a cyclononanetetrayl group Yl group, cyclodecanetetrayl group, cyclododecanetetrayl group, cyclohexadecanetetrayl group and the like. These alicyclic groups may contain a substituent. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an arylene group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

Examples of the tetravalent aromatic group represented by L ² include an arenetetrayl group having 5 to 15 carbon atoms which may include a hetero atom and have a heterocyclic structure. Examples of the C5-C15 arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may be substituted. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

In the general formula (O-2), two cyclic structures containing a carbodiimide group are included via L ² which is a tetravalent linking group.
The preferred range of the number of atoms in the cyclic structure containing each carbodiimide group in the general formula (O-2) is the preferred range of the number of atoms in the cyclic structure containing the carbodiimide group in the general formula (O-1). It is the same.

The cyclic carbodiimide compound of the present invention is an aromatic carbodiimide having no ring structure in which the first nitrogen and the second nitrogen of two or more carbodiimide groups are bonded by a linking group in the molecule. The carbodiimide compound is monocyclic and is preferably represented by the general formula (O-1) from the viewpoint of being hard to thicken.
However, from the viewpoint of suppressing volatilization and suppressing generation of isocyanate gas during production, the cyclic carbodiimide compound of the present invention preferably has a plurality of cyclic structures and is represented by the general formula (O-2). .

It is preferable for the cyclic carbodiimide compound used in the present invention to have a molecular weight of 400 or more because volatility is small and generation of isocyanate gas during production can be suppressed. Further, the upper limit of the molecular weight of the cyclic carbodiimide compound is not particularly limited as long as the effects of the present invention are not impaired, but 1500 or less is preferable from the viewpoint of reactivity with carboxylic acid.
As for the molecular weight of the cyclic carbodiimide compound used for this invention, it is more preferable that it is 500-1200.

Specific examples of the cyclic carbodiimide compound represented by the general formula (O-1) or the general formula (O-2), that is, specific examples of the cyclic carbodiimide compound of the present invention include the following compounds. It is done. However, the present invention is not limited to the following specific examples.

The cyclic carbodiimide compound of the present invention is a compound having at least one structure (carbodiimide group) represented by -N = C = N- adjacent to the aromatic ring. For example, in the presence of a suitable catalyst, The organic isocyanate can be heated and produced by a decarboxylation reaction. The cyclic carbodiimide compound of the present invention can be synthesized with reference to the method described in JP2011-256337A.
In synthesizing the cyclic carbodiimide compound of the present invention, there is no particular limitation as a method for introducing a specific bulky substituent into the ortho position of the arylene group adjacent to the first nitrogen and the second nitrogen of the carbodiimide group. By nitrating alkylbenzene by the method, nitrobenzene substituted with an alkyl group can be synthesized, and based on this, cyclic carbodiimide can be synthesized by the method described in WO2011 / 158958.

<Ketene imine compound>
The polyester film of the present invention preferably contains a ketene imine compound. The ketene imine compound may be used alone or in combination with the cyclic carbodiimide compound.
As the ketene imine compound, a ketene imine compound represented by the following general formula (1) is preferably used. Hereinafter, the ketene imine compound represented by the following general formula (1) will be described.

Here, in general formula (1), R ₁ and R ₂ each independently represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group. , R ₃ represents an alkyl group or an aryl group.

The molecular weight of the portion excluding the nitrogen atom of the ketene imine compound and the substituent bonded to the nitrogen atom is preferably 320 or more. That is, in the general formula (1), the molecular weight of the R ₁ —C (═C) —R ₂ group is preferably 320 or more. The molecular weight of the portion excluding the nitrogen atom of the ketene imine compound and the substituent bonded to the nitrogen atom is preferably 320 or more, more preferably 500 to 1500, and even more preferably 600 to 1000. . Thus, the adhesiveness of a polyester film and an easily bonding layer can be improved by making the molecular weight of the part except a nitrogen atom and the substituent couple | bonded with this nitrogen atom into the said range. This is because the portion excluding the nitrogen atom and the substituent bonded to the nitrogen atom has a molecular weight within a certain range, so that the polyester terminal having a certain bulkiness diffuses into the easy-adhesion layer and exhibits the anchoring effect. Because.

The alkyl group represented by R ₁ and R ₂ is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. The alkyl group represented by R ₁ and R ₂ may be linear, branched or cyclic. Examples of the alkyl group represented by R ₁ and R ₂ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, sec-butyl group, iso-butyl group, n- A pentyl group, a sec-pentyl group, an iso-pentyl group, an n-hexyl group, a sec-hexyl group, an iso-hexyl group, a cyclohexyl group, and the like can be given. Of these, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an iso-butyl group, and a cyclohexyl group are more preferable.
The alkyl group represented by R ₁ and R ₂ may further have a substituent. Unless the reactivity of a ketene imine group and a carboxyl group is lowered, the substituent is not particularly limited, and the above substituents can be exemplified similarly. In addition, carbon number of the alkyl group which R < ₁ > and R < ₂ > represent shows carbon number which does not contain a substituent.

The aryl group represented by R ₁ and R ₂ is preferably an aryl group having 6 to 20 carbon atoms, and more preferably an aryl group having 6 to 12 carbon atoms. Examples of the aryl group represented by R ₁ and R ₂ include a phenyl group and a naphthyl group, and among them, a phenyl group is particularly preferable.
The aryl group includes a heteroaryl group. The heteroaryl group refers to a group in which at least one of the ring-constituting atoms of a 5-membered, 6-membered or 7-membered ring exhibiting aromaticity or a condensed ring thereof is substituted with a heteroatom. Examples of heteroaryl groups include imidazolyl, pyridyl, quinolyl, furyl, thienyl, benzoxazolyl, indolyl, benzimidazolyl, benzthiazolyl, carbazolyl, and azepinyl groups. . The hetero atom contained in the heteroaryl group is preferably an oxygen atom, a sulfur atom, or a nitrogen atom, and particularly preferably an oxygen atom or a nitrogen atom.
The aryl group or heteroaryl group represented by R ₁ and R ₂ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. The carbon number of the aryl group or heteroaryl group represented by R ₁ and R ₂ is the number of carbons not including a substituent.

The alkoxy group represented by R ₁ and R ₂ is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and an alkoxy group having 2 to 6 carbon atoms. It is particularly preferred that The alkoxy group represented by R ₁ and R ₂ may be linear, branched or cyclic. Preferable examples of the alkoxy group represented by R ₁ and R ₂ include a group in which —O— is linked to the terminal of the alkyl group represented by R ₁ and R ₂ . The alkoxy group represented by R ₁ and R ₂ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. In addition, carbon number of the alkoxy group which R < ₁ > and R < ₂ > represent shows carbon number which does not contain a substituent.

The alkoxycarbonyl group represented by R ₁ and R ₂ is preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, more preferably an alkoxycarbonyl group having 2 to 12 carbon atoms, and 2 to 6 carbon atoms. Particularly preferred is an alkoxycarbonyl group. Examples of the alkoxy moiety of the alkoxycarbonyl group represented by R ₁ and R ₂ include the examples of the alkoxy group described above.

The aminocarbonyl group represented by R ₁ and R ₂ is preferably an alkylaminocarbonyl group having 1 to 20 carbon atoms and an arylaminocarbonyl group having 6 to 20 carbon atoms. Preferable examples of the alkylamino part of the alkylaminocarbonyl group include a group in which —NH— is linked to the terminal of the alkyl group represented by R ₁ and R ₂ . The alkylaminocarbonyl group represented by R ₁ and R ₂ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered.
Preferable examples of the arylamino moiety of the arylaminocarbonyl group having 6 to 20 carbon atoms include a group in which —NH— is linked to the terminal of the aryl group represented by R ₁ and R ₂ . The arylaminocarbonyl group represented by R ₁ and R ₂ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. In addition, carbon number of the alkylaminocarbonyl group which R < ₁ > and R < ₂ > represent shows carbon number which does not contain a substituent.

The aryloxy group represented by R ₁ and R ₂ is preferably an aryloxy group having 6 to 20 carbon atoms, and more preferably an aryloxy group having 6 to 12 carbon atoms. Examples of the aryl moiety of the aryloxy group represented by R ₁ and R ₂ include the examples of the aryl group described above.

The acyl group represented by R ₁ and R ₂ is preferably an acyl group having 2 to 20 carbon atoms, more preferably an acyl group having 2 to 12 carbon atoms, and an acyl group having 2 to 6 carbon atoms. It is particularly preferred that The acyl group represented by R ₁ and R ₂ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered. In addition, carbon number of the acyl group which R < ₁ > and R < ₂ > represent shows carbon number which does not contain a substituent.

Aryloxycarbonyl group represented by R ₁ and R ₂ is preferably an aryloxycarbonyl group having 7 to 20 carbon atoms, more preferably R ₁ and be an aryloxycarbonyl group having 7 to 12 carbon atoms Examples of the aryl moiety of the aryloxycarbonyl group represented by R ₂ include the examples of the aryl group described above.

R ₃ represents an alkyl group or an aryl group. The alkyl group is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. The alkyl group represented by R ₃ may be linear, branched or cyclic. Examples of the alkyl group represented by R ₃ include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a tert-butyl group, a sec-butyl group, an iso-butyl group, an n-pentyl group, A sec-pentyl group, an iso-pentyl group, an n-hexyl group, a sec-hexyl group, an iso-hexyl group, a cyclohexyl group, and the like can be given. Of these, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, and a cyclohexyl group are more preferable.
The alkyl group represented by R ₃ may further have a substituent. Unless the reactivity of a ketene imine group and a carboxyl group is lowered, the substituent is not particularly limited, and the above substituents can be exemplified similarly.
The aryl group is preferably an aryl group having 6 to 20 carbon atoms, and more preferably an aryl group having 6 to 12 carbon atoms. Examples of the aryl group represented by R ₃ include a phenyl group and a naphthyl group, and among them, a phenyl group is particularly preferable.

The aryl group includes a heteroaryl group. The heteroaryl group refers to a group in which at least one of the ring-constituting atoms of a 5-membered, 6-membered or 7-membered ring exhibiting aromaticity or a condensed ring thereof is substituted with a heteroatom. Examples of heteroaryl groups include imidazolyl, pyridyl, quinolyl, furyl, thienyl, benzoxazolyl, indolyl, benzimidazolyl, benzthiazolyl, carbazolyl, and azepinyl groups. . The hetero atom contained in the heteroaryl group is preferably an oxygen atom, a sulfur atom, or a nitrogen atom, and particularly preferably an oxygen atom or a nitrogen atom.
The aryl group or heteroaryl group represented by R ₃ may further have a substituent, and the substituent is not particularly limited as long as the reactivity between the ketene imine group and the carboxyl group is not lowered.

In addition, General formula (1) may contain the repeating unit. In this case, at least one of R _{1 and} R ₃ is a repeating unit, and this repeating unit preferably contains a ketene imine moiety.

  Moreover, as a ketene imine compound, it is preferable to use the ketene imine compound represented by following General formula (2). Hereinafter, the ketene imine compound represented by the following general formula (2) will be described.

Here, in the general formula (2), R ₁ represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. R ₂ represents an alkyl group having L ₁ as a substituent, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. R ₃ represents an alkyl group or an aryl group. n represents an integer of 1 to 4, and L ₁ represents an n-valent linking group. The molecular weight of the (R ₁ —C (═C) —R ₂ —) nL ₁ group is preferably 320 or more.

In general formula (2), R ₁ is the same as that in general formula (1), and the preferred range is also the same.

In general formula (2), R ₂ is an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group having L ₁ which is an n-valent linking group. Represents. The alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group has the same meaning as that in formula (1), and the preferred range is also the same.

In general formula (2), R ₃ is the same as that in general formula (1), and the preferred range is also the same.

L ₁ represents an n-valent linking group, where n represents an integer of 1 to 4. Especially, it is preferable that n is 2-4.
Specific examples of the divalent linking group include, for example, —NR ₈ — (R ₈ represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent, A hydrogen atom is preferred), —SO ₂ —, —CO—, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, an alkynylene group, a substituted or unsubstituted phenylene group, substituted or unsubstituted Examples thereof include a substituted biphenylene group, a substituted or unsubstituted naphthylene group, -O-, -S- and -SO-, and a group obtained by combining two or more thereof.
Specific examples of the trivalent linking group include a group obtained by removing one hydrogen atom from those having a substituent among the linking groups mentioned as examples of the divalent linking group.
Specific examples of the tetravalent linking group include, for example, a group obtained by removing two hydrogen atoms from those having a substituent among the linking groups mentioned as examples of the divalent linking group.

  In the present invention, by setting n to 2 to 4, a compound having two or more ketene imine moieties in one molecule can be obtained, and a more excellent end-capping effect can be exhibited. Further, by using a compound having two or more ketene imine moieties in one molecule, the molecular weight per ketene imine group can be lowered, and the ketene imine compound and the terminal carboxyl group of the polyester can be reacted efficiently. Furthermore, it can suppress that a ketene imine compound and a ketene compound volatilize by having two or more ketene imine parts in 1 molecule.

In general formula (2), n is more preferably 3 or 4. By setting n to 3 or 4, a compound having 3 or 4 ketene imine moieties in one molecule can be obtained, and a more excellent end-capping effect can be exhibited. Also, by placing the n 3 or 4, even when the molar molecular weight of the substituents R ₁ or R ₂ in the general formula (2) in the small, it is possible to suppress the volatilization of keteneimines compound.

  As the ketene imine compound, a ketene imine compound represented by the following general formula (3) is preferably used. Hereinafter, the ketene imine compound represented by the following general formula (3) will be described.

In the general formula (3), R ₁ and R ₅ represent an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. R ₂ and R _{4 each} represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group having L ₂ as a substituent. R ₃ and R ₆ represent an alkyl group or an aryl group. L ₂ represents a single bond or a divalent linking group. _{R 1 -C (= C) -R} 2 -L 2 -R 4 -C (= C) molecular weight of -R ₅ groups is preferably 320 or more.

In general formula (3), R ₁ is the same as that in general formula (1), and the preferred range is also the same. R ₅ is the same as R ₁ in the general formula (1), and the preferred range is also the same.

In general formula (3), R ₂ is the same as that in general formula (2), and the preferred range is also the same. R ₄ is the same as R ₂ in the general formula (2), and the preferred range is also the same.

In general formula (3), R ₃ is the same as that in general formula (1), and the preferred range is also the same. R ₆ is the same as R ₃ in the general formula (1), and the preferred range is also the same.

In General Formula (3), L ₂ represents a single bond or a divalent linking group. Specific examples of the divalent linking group include the linking groups exemplified for L ₁ in formula (2).

  In the present invention, the molecular weight of the portion excluding the nitrogen atom of the ketene imine compound and the substituent bonded to the nitrogen atom is preferably 320 or more. The molecular weight of the portion excluding the nitrogen atom of the ketene imine compound and the substituent bonded to the nitrogen atom may be 320 or more, preferably 400 or more, and more preferably 500 or more. The molar molecular weight of the ketene imine compound relative to the number of ketene imine moieties in one molecule (mole molecular weight / number of ketene imine moieties) is preferably 1000 or less, more preferably 500 or less, and preferably 400 or less. Further preferred. In the present invention, by controlling the molecular weight of the substituent on the ketene imine carbon of the ketene imine compound and the molar molecular weight of the ketene imine compound relative to the number of ketene imine moieties within the above range, the volatilization of the ketene imine compound itself is suppressed, and the terminal carboxyl group of the polyester Volatilization of the ketene compound that occurs when sealing is suppressed, and the terminal carboxyl group of the polyester can be sealed with a low addition amount of ketene imine compound.

  The ketene imine compound of the present invention is a compound having at least one ketene imine group. Am. Chem. Soc. , 1953, 75 (3), pp 657-660 and the like.

  Although the preferable specific example of General formula (1) is shown below, this invention is not limited to this.

As shown in the exemplary compound, in the present invention, the ketene imine compound is more preferably trifunctional or tetrafunctional. Thereby, the terminal sealing effect can be improved more and volatilization of a ketene imine compound and a ketene compound can be suppressed effectively.
Also, if having a cyclic structure keteneimines portion as a ring skeleton as exemplified compound (6), R ₁ and R ₃ form a cyclic structure linked, R ₃ is alkylene or arylene group ring skeleton Become. In this case, R ₁ has a linking group containing a ketene imine moiety.
Illustrative compound (10) represents a repeating unit having a repeating number n, and n represents an integer of 3 or more. The left end shown in exemplary compound (10) is a hydrogen atom, and the right end is a phenyl group.

(Phosphorus compound)
The polyester film of the present invention preferably contains a phosphorus compound. The phosphorus compound is preferably included so that the phosphorus element content is 30 to 600 ppm. That is, in this invention, in addition to the said terminal blocker, a phosphorus compound can be added in polyester.
As the phosphorus compound, it is preferable to use one or more phosphorus compounds selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, methyl esters, ethyl esters, phenyl esters, half esters and other derivatives thereof. In the present invention, phosphoric acid, phosphorous acid, phosphonic acid methyl ester, ethyl ester, and phenyl ester are particularly preferable.

  In the present invention, the content of the phosphorus element in the polyester when measured by fluorescent X-ray is preferably 30 ppm or more, more preferably 40 ppm or more, and further preferably 50 ppm or more. The phosphorus element content is preferably 600 ppm or less, more preferably 500 ppm or less, and even more preferably 400 ppm or less. By making the content rate of the phosphorus element content within the above range, it is possible to suppress the decomposition of the polyester or the end-capping agent. Thereby, the adhesiveness and heat-and-moisture resistance of a polyester film can be improved.

  The in-plane variation of the content of phosphorus element contained in the polyester film of the present invention is preferably 2 to 20%. The in-plane variation of the phosphorus element content is preferably 2% or more, more preferably 4% or more, and even more preferably 6% or more. The in-plane variation of the phosphorus element content is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. By increasing the in-plane variation of the phosphorus element content within the above range, the adhesion between the polyester film and other members (for example, sealant (EVA), adhesive, functional coating layer, etc.) is increased. Can do. Furthermore, the moisture and heat resistance of the polyester film can be increased, and the strength of the film can be enhanced. In addition, about the mechanism which adhesiveness and heat-and-moisture resistance improve by controlling the in-plane fluctuation | variation of the content rate of a phosphorus element in the said range, the in-plane fluctuation | variation of the content rate of terminal blocker as mentioned above was provided. It can be considered that the mechanism is similar to the case.

The in-plane variation f (%) of the phosphorus element content can be expressed by the following relational expression.
f (%) = (Ymax−Ymin) / Yave × 100
Here, Ymax is the maximum value of the content of phosphorus element per unit area of the polyester film, Ymin is the minimum value of the content of phosphorus element per unit area of the polyester film, and Yave is the entire polyester film. It is the average value of the content rate of the contained phosphorus element.

Further, when the average content of phosphorus element contained in the entire polyester film is Pave and the in-plane standard deviation is σy, 0.5 ≦ (σy / Yave) × 100 ≦ 5 is preferable, and 1 ≦ It is more preferable that (σy / Yave) × 100 ≦ 3. A value obtained by dividing the standard deviation by the average value is called a coefficient of variation (relative standard deviation) and represents the degree of variation of the phosphorus element present in the polyester film. Here, the in-plane standard deviation means the standard deviation of the content of phosphorus element measured in the divided unit area when the polyester film is equally divided in both the longitudinal direction and the width direction. As for the method of equally dividing the polyester film in both the longitudinal direction and the width direction, the same method as that used when calculating the in-plane variation of the terminal sealing agent can be used.
In the polyester film of the present invention, by setting the coefficient of variation (relative standard deviation) within the above range, a desired distribution can be imparted to the phosphorus element content present in the polyester film, and adhesion and moisture resistance can be increased. Thermal property can be effectively increased.

(Fine particles (pigments))
The polyester film of the present invention may further contain fine particles. The fine particles used in the present invention are preferably inorganic fine particles, and more preferably pigments.

Examples of the pigment include inorganic pigments such as titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, ultramarine blue, bitumen, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. It is done. Among these pigments, a white pigment is preferable from the viewpoint of constituting a colored layer as a reflective layer that reflects incident sunlight. As the white pigment, for example, titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and the like are preferable.
When these pigments are contained in the polyester film of the present invention, the adhesion between the polyester film and other members can be improved. The mechanism is that voids (cavities) are formed around the pigments in the film, where the end-capping agent, phosphorus compounds, and decomposition products accumulated during the film formation process and storage in a humid heat environment accumulate. This is thought to be due to the suppression of precipitation.

  The content of fine particles is preferably 0.5 to 10.0% by mass, more preferably 1.0 to 8.0% by mass, and particularly preferably 1.0 to 6.0% by mass. By making the content rate of the fine particles within the above range, the adhesion can be more effectively improved.

(Void)
The polyester film of the present invention may further contain a void. The formation method of the void is not particularly limited. For example, the void is formed by allowing the polyester resin to contain inorganic fine particles, resin (incompatible resin) or inert gas having low affinity, and stretching the polyester resin. can do. Among these, it is preferable to form a void by mixing an incompatible resin with a polyester resin and stretching the extruded raw material.

  Examples of incompatible resins include polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, polystyrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, and fluorine resins. Among these, polyolefin resins having a low critical surface tension are preferable. Polyolefin resins incompatible with polyester include crystalline polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, and bicyclo [2,2,1] hept. 2-ene, 6-methylbicyclo [2,2,1] hept-2-ene, 5,6-dimethylbicyclo [2,2,1] hept-2-ene, 1-methylbicyclo [2,2, 1] hept-2-ene, 6-ethylbicyclo [2,2,1] hept-2-ene, 6-n-butylbicyclo [2,2,1] hept-2-ene, 6-i-butylbicyclo [2,2,1] hept-2-ene, 7-methylbicyclo [2,2,1] hept-2-ene, tricyclo [4,3,0,12.5] -3-decene, 2-me Ru-tricyclo [4,3,0,12.5] -3-decene, 5-methyl-tricyclo [4,3,0,12.5] -3-decene, tricyclo [4,4,0,12. 5] -3-decene, amorphous cyclic olefin resin such as 10-methyl-tricyclo [4,4,0,12.5] -3-decene, and ethylene and the cyclic olefin exemplified above were copolymerized Resins are preferably used. These may be a homopolymer or a copolymer, and two or more resins may be used in combination. In particular, a resin having a large difference in critical surface tension from polyester and being difficult to be deformed by heat treatment after stretching is preferred, and among them, a copolymer of polymethylpentene, ethylene and the amorphous cyclic olefin exemplified above is particularly preferred.

  The glass transition temperature of the cyclic olefin copolymer resin is preferably 120 to 230 ° C, more preferably 160 to 220 ° C. When the glass transition temperature of the cyclic olefin copolymer resin is less than 120 ° C., the cyclic olefin copolymer resin is plastically deformed when the film is stretched, which is not preferable. When the glass transition temperature of the cyclic olefin copolymer resin exceeds 230 ° C., the dispersion of the cyclic olefin copolymer resin is caused when the polyester resin and the cyclic olefin copolymer resin are melt-kneaded using an extruder or the like and discharged into a sheet shape. It becomes insufficient. If the glass transition temperature of the cyclic olefin copolymer resin is lower than the heat setting temperature in the tenter, void collapse occurs due to plastic deformation. The glass transition temperature of the cyclic olefin copolymer resin can be adjusted by changing the copolymerization ratio.

In addition, in this invention, it is preferable that the average long diameter L of the void formed is 2-40 micrometers, it is more preferable that it is 10-35 micrometers, and it is further more preferable that it is 15-30 micrometers.
The aspect value of the void is preferably within a certain range. The average aspect ratio of voids is preferably 4 to 20, more preferably 5 to 17, and still more preferably 6 to 15. The aspect ratio is L when the average minor axis of the void in the thickness direction orthogonal to the major axis direction of the void is r (μm) and the average major axis of the void in the major axis direction of the void is L (μm). / R ratio. That is, the aspect ratio refers to a value obtained by cutting a cross section of a film and observing a void, and dividing the major axis of the void by the minor axis. In the present invention, by setting the average major axis L of the void within the above range and the aspect value of the void within the above range, the strength of the film can be increased and the durability can be increased.

  Thus, the adhesiveness of a polyester film and another member can be improved by making a polyester film of this invention contain a void. The mechanism is that when voids are formed in the film, the heat and moisture resistance of the adhesion is improved, but the ketene imine compound, phosphorus compound and decomposition products generated in the film formation process are accumulated in the cavity, and the precipitation on the surface is suppressed. It is thought that it is to be done.

  The average void content is preferably 5.0 to 50.0%, more preferably 10.0 to 45.0%, and particularly preferably 20.0 to 40.0%. . Here, the content rate of a void can be represented by the occupation area with respect to the cross-sectional area of a polyester film. For example, in the present invention, the void content may be the ratio of the ratio of the void area to the cross-sectional area in the longitudinal direction and the average ratio of the void area to the cross-sectional area in the width direction. For example, for the void content, the measurement range is set so that 20 to 30 voids are included in the image of the cross section of the polyester film, and the area of all the voids is measured. It can be calculated by dividing by the total area. By calculating this for each of the cross sections parallel to the longitudinal direction and the width direction, and determining the average value thereof, the void content can be calculated. The void content (%) can be calculated as 100 × S / R, where S is the area of the void in the cross-sectional area and R is the total area of the cross-sectional area. By setting the void content within the above range, the adhesion can be more effectively improved.

  In addition, it is preferable to make the addition rate of the incompatible resin with respect to polyester into the range of 3-30 mass% with respect to the total amount of polyester, and 5-12 mass% is especially preferable. By setting the addition ratio of the incompatible resin within the above range, it is possible to form a void that can sufficiently trap the end-capping agent, the phosphorus compound, and the decomposition product thereof, and the strength of the film and the strength of the waist. Can have.

(Production method of polyester film)
The manufacturing method of the polyester film of this invention includes the process of mixing and mixing two types of compositions from which the content rate of terminal blocker differs. In the step of mixing two kinds of compositions having different content ratios of the end capping agents, the two kinds of compositions are mixed unevenly. In addition, the manufacturing method of the polyester film of this invention further includes the process of melt | dissolving and film-forming the heterogeneous mixture obtained in this way.
Below, each process of the manufacturing method of a polyester film is demonstrated in detail.

<Making polyester>
Polyester can be obtained by polycondensation of diol and dicarboxylic acid. Polyester can be produced by an existing method. For example, the method described in paragraph [0079] of JP2012-179919A can be referred to.

<Preparation of composition (masterbatch)>
The end capping agent can be added to the polyester by using a known method, but it is preferable to use a master batch method (MB method) in which the polyester and the end capping agent are mixed in advance by an extruder. . In the master batch method, the mixture is made into a pellet-like composition (master batch).
In the masterbatch method, a polyester resin and ketene imine compound that have not been dried in advance can be put into an extruder, and a method of preparing a masterbatch while degassing moisture and air can be adopted. It is preferable to employ a method of producing a masterbatch using the polyester resin prepared. Thereby, hydrolysis of polyester can be suppressed. Further, in this case, there are a method of extruding while degassing, a method of extruding without deaeration with a sufficiently dried polyester resin, and the like.

In the present invention, it is preferable to prepare at least two types of compositions (master batches) having different end sealant contents. Two types of compositions (masterbatch) are, for example, a composition in which a terminal blocker is added to polyester (first composition) and a composition in which no terminal blocker is added (second composition). ) Can be obtained. In addition, although the terminal blocker may be contained also in the 2nd composition, it is preferable to contain so that it may differ greatly from the density | concentration of the terminal blocker contained in the 1st composition. Thus, in-plane fluctuation | variation can be provided about the content rate of terminal blocker by producing two types of compositions from which the density | concentration of terminal blocker differs.
In addition, ρ2 / ρ1 is 0.0 to 0.95, where ρ1 is the content of the end capping agent in the first composition and ρ2 is the content of the end capping agent in the second composition. Is preferable, 0.0 to 0.80 is more preferable, and 0.0 to 0.70 is more preferable.

  The concentration of the end-capping agent added to the composition is preferably higher than the concentration finally contained in the polyester film. For example, the concentration of the end-capping agent contained in the first composition is preferably 1.5 to 20 times the use concentration in the film, more preferably 2 to 15 times, and even more preferably 3 to 10 times. is there. The reason why the additive concentration is set higher than the target concentration is that the target concentration is obtained by diluting with the second composition in the next film forming step.

  Moreover, you may produce two types of compositions which changed intrinsic viscosity (IV value) by changing the polymerization conditions etc. of polyester. As described above, the first composition and the second composition are prepared using polyesters having different IV values, and the in-plane variation can be imparted with respect to the content of the end-capping agent by kneading the first composition and the second composition. .

  It is preferable that a phosphorus compound is added to the first composition or the second composition. In addition, it is preferable to contain so that the density | concentration in a composition may also differ about a phosphorus compound. That is, the phosphorus compound is preferably added to either the first composition or the second composition. Thus, in-plane fluctuation | variation can be provided about the content rate of a phosphorus compound by producing two types of compositions from which the density | concentration of a phosphorus compound differs.

  It is preferable that a pigment or an incompatible resin is added to the first composition and / or the second composition. The pigment or incompatible resin may be added to either the first composition or the second composition, or may be added to both.

<Film formation>
The first composition and the second composition are fed into a hopper of a kneading extruder by a feeder. As the kneading extruder, various kneaders such as a single screw extruder, a twin screw extruder, a Banbury mixer, and a Brabender can be used. Among these, it is preferable to use a twin screw extruder.

The first composition and the second composition are mixed in a kneading extruder to form a mixture. Here, it is preferable to mix the first composition and the second composition non-uniformly. That is, in the mixture of the first composition and the second composition, the first composition and the second composition exist with a distribution. The non-uniform presence means that there is a difference in the abundance ratio between the first composition and the second composition existing per unit volume (1 cm ³ ). Specifically, when the volume of the first composition present in the unit volume (1 cm ³ ) is P and the volume of the second composition present in the unit volume (1 cm ³ ) is Q, | PQ |> 0.1.

In the present invention, it is preferable to change the input amount of the first composition or the second composition at the time of input to the kneading extruder. When charging into the kneading extruder, the input amount of either the first composition or the second composition may be varied, but the first composition containing the end-capping agent It is preferable to change the input amount. The variation rate of the input amount of the first composition is preferably 2.0 to 25 wt%, more preferably 4.0 to 25.0 wt%, and even more preferably 6.0 to 20.0 wt%. Here, the fluctuation rate of the input amount refers to a difference between the maximum value and the minimum value of the input amount of the first composition within a specified time (1 minute) divided by an average value and expressed as a percentage.
In this way, the amount in the polyester can be varied by varying the amounts of the two types of compositions having different end capping agent concentrations. The same method can be used for the method of imparting in-plane variation of the phosphorus compound.

Next, the resin obtained by kneading the first composition and the second composition is heated and melted so that the maximum temperature of the resin temperature becomes 300 ° C. The molten resin is then extruded through a die onto a chill roll. The molten resin is solidified on a cooling roll, and the film thus obtained becomes a cast film (unstretched original fabric). The molten resin is preferably passed through a melt pipe, a gear pump, and a filter. It is also preferable to provide a static mixer in the melt pipe to promote mixing of the resin and the additive.
In order to suppress the decomposition of the end-capping agent, the extrusion as described above is preferably performed in a vacuum exhaust or an inert gas atmosphere.

<Extension process>
The (unstretched) film formed by the film forming step can be subjected to a stretching treatment in the stretching step. Stretching is preferably performed in at least one of the machine direction (MD) and the transverse direction (TD), and it is more preferable to perform both MD and TD stretching in order to balance the physical properties of the film. Such bi-directional stretching may be performed sequentially in the vertical and horizontal directions, or may be performed simultaneously. In the stretching step, the film that has been cooled and solidified with a cooling roll (unstretched) is preferably stretched in one or two directions, and more preferably stretched in two directions. Stretching in two directions (biaxial stretching) includes stretching in the longitudinal direction (MD: Machine Direction) (hereinafter also referred to as “longitudinal stretching”) and stretching in the width direction (TD: Transverse Direction) (hereinafter referred to as “lateral stretching”). It is also preferred that The longitudinal stretching and lateral stretching may each be performed once, or may be performed a plurality of times, and may be simultaneously performed longitudinally and laterally.

A preferable draw ratio is 280% to 500%, more preferably 300% to 480%, and further preferably 320% to 460% on at least one side. In the case of biaxial stretching, the film may be stretched uniformly in the vertical and horizontal directions, but it is more preferable to stretch one of the stretch ratios more than the other and unevenly stretch. Either vertical (MD) or horizontal (TD) may be increased. The draw ratio here is determined using the following equation.
Stretch ratio (%) = 100 × {(Length after stretching) / (Length before stretching)

  In the stretching step, the film can be subjected to heat treatment or thermal relaxation treatment before or after the stretching treatment, preferably after the stretching treatment. By performing heat treatment or thermal relaxation treatment, microcrystals can be generated, and mechanical properties and durability can be improved.

[Back sheet for solar cell module]
The polyester film of the present invention can also be used as a laminated film in which a coating layer such as an easy adhesion layer is provided thereon. The polyester film and laminated film of the present invention are used for various applications, but are preferably used as a back sheet for a solar cell module (protective sheet for a solar cell module). Since the polyester film of the present invention has excellent adhesion and moisture and heat resistance, when used in a back sheet for a solar cell module, the solar cell module can be protected over a long period of time, and the power generation efficiency of the solar cell module Will not be damaged. Moreover, since the polyester film of this invention is suppressed from yellowing, the design property of a solar cell module is not impaired.

  A back sheet for a solar cell module can be formed by laminating the following functional layer on the polyester film of the present invention. When laminating functional layers, it is preferable to provide an easy-adhesion layer in between. In addition, before laminating | stacking a functional layer, it is preferable to surface-treat the surface of a polyester film, for example, a flame treatment, a corona treatment, a plasma treatment, an ultraviolet treatment etc. can be given.

<Reflective layer (colored layer)>
In the back sheet of the present invention, it is preferable to provide a light reflection layer on the inner side surface (side to be bonded to the sealing material). By providing the reflective layer, it is possible to reflect the light that has passed through the solar cell and reaches the back sheet out of the sunlight incident on the solar cell module, and return it to the solar cell. Thereby, power generation efficiency can be improved.
Further, the reflective layer preferably has an adhesive strength of 10 N / cm or more, more preferably 20 N / cm or more, with respect to the sealing material.

(binder)
First, the binder for the reflective layer will be described. As the binder for the reflective layer of the present invention, acrylic, polyester, polyurethane, and polyolefin polymers can be used. Of these, polyolefin polymers are preferred.

Specifically, the polyolefin polymer used in the present invention is preferably one of the following.
-Copolymer consisting of ethylene or polypropylene and acrylic monomer or methacrylic monomer-Copolymer consisting of ethylene or polypropylene and carboxylic acid (including anhydride)-Ethylene or polypropylene, acrylic monomer or methacrylic monomer, and carboxylic acid (anhydrous) (Including products)

Specific examples of the acrylic monomer or methacrylic monomer constituting the polyolefin-based polymer include methyl methacrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate and the like.
Examples of the carboxylic acid constituting the polyolefin polymer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride and the like.
These may be used alone or in combination of a plurality of types.
The total of ethylene or polypropylene in the polyolefin-based polymer is preferably 80 to 98 mol%, more preferably 85 to 95 mol%. Further, the acrylic monomer or methacrylic monomer is preferably in the range of 0 to 20 mol%, more preferably 3 to 10 mol% in total. Furthermore, the total amount of carboxylic acid is preferably 0 to 15 mol%, more preferably 1 to 10 mol%. By setting the monomer composition within this range, both good adhesion and durability can be achieved.

The molecular weight of the polyolefin-based polymer used in the present invention is preferably about 2000 to 200000. The polyolefin-based polymer may have a linear structure or a branched structure.
By using the polyolefin-based polymer described above as the binder of the reflective layer, it becomes possible to particularly improve the adhesiveness between the reflective layer and the support, and keep the decrease in adhesiveness small even after a long period of time. It becomes possible.

The polyolefin polymer of the present invention is preferably in the form of an aqueous polymer dispersion (so-called latex). The preferable particle size of the latex of the silicone-based composite polymer is about 50 to 2000 nm, and the preferable concentration is about 15 to 50% by mass.
The polyolefin polymer of the present invention may be prepared by an emulsification method or an emulsification dispersion method for producing an aqueous polymer dispersion, the former being preferred. For a specific method, for example, the method described in Japanese Patent No. 3699935 can be referred to.
The polyolefin polymer of the present invention preferably has a water-affinity functional group such as a carboxyl group or a hydroxyl group when the aqueous polymer is in the form of latex. When the silicone-based composite polymer of the present invention has a carboxyl group, the carboxyl group may be neutralized with sodium, ammonium, amine or the like.
In addition, when used in the form of latex, an emulsion stabilizer such as a surfactant (eg, anionic or nonionic surfactant) or a polymer (eg: polyvinyl alcohol) may be added to improve the stability. Good. Further, if necessary, a pH adjuster (eg, ammonia, triethylamine, sodium hydrogen carbonate, etc.), preservative (eg: 1,3,5-hexahydro- (2-hydroxyethyl) -s-triazine, 2- (4 -Thiazolyl) benzimidazole, etc.), thickeners (eg, sodium polyacrylate, methylcellulose, etc.), film-forming aids (eg, butyl carbitol acetate, etc.), etc. Good.

  Some polyolefin-based binders that can be used in the present invention are commercially available. Specific examples of commercially available products include Bondine HX-8210, HX-8290, TL-8030, LX-4110 (manufactured by Sumitomo Chemical Co., Ltd.), Arrow Base SA-1200, SB-1010, SE-1013N, and SE1200. (Unitika Ltd.)

(Crosslinking agent)
The reflective layer of the present invention preferably contains an epoxy-based, isocyanate-based, oxazoline-based, carbodiimide-based or the like crosslinking agent in order to further improve the adhesion with the sealing material.
Of these cross-linking agents, carbodiimide cross-linking agents and oxazoline cross-linking agents are particularly preferable from the viewpoint of ensuring adhesion after wet heat aging. The carbodiimide crosslinking agent used in the present invention is a compound having one or more carbodiimide groups in the molecule.

The carbodiimide-based crosslinking agent can be obtained, for example, by a de-CO ₂ reaction of isocyanate.
Isocyanates include methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate, octadecyl isocyanate, phenyl isocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethyl. Examples include xylylene diisocyanate.
For the above reaction, known methods such as 1-ethyl-3-methyl-3-phospholene oxide, 1-phenyl-3-methyl-3-phospholene oxide, 1-phenyl-3-methyl-2-phospholene oxide, etc. A catalyst may be used.

  In addition, the carbodiimide-based crosslinking agent of the present invention may have a polyalkylene structure in the molecule and be water-soluble.

Specific examples of the carbodiimide-based crosslinking agent include N, N′-dicyclohexylcarbodiimide, N, N′-diisopropylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N- [3- ( Dimethylamino) propyl] -N′-ethylcarbodiimide, N- [3- (dimethylamino) propyl] -N′-propylcarbodiimide, N-tert-butyl-N′-ethylcarbodiimide and the like.
Moreover, as a commercial item marketed, Carbodilite V-02-L2 (Nisshinbo Co., Ltd. product) etc. are mentioned.

The oxazoline-based crosslinking agent used in the present invention is a compound having two or more oxazoline groups in the molecule. Specifically, the oxazoline-based crosslinking agent is obtained from the following oxazoline group-containing compounds or compounds capable of reacting with them.
Specific examples of the oxazoline group-containing compound 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, 2,2'-bis- (2-oxazoline), 2,2'-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline) ), 2,2′-hexamethylene-bis- (2-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (4 4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m Compounds containing oxazoline group-containing compounds such as -phenylene-bis- (4,4'-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide Can be mentioned.

  Specific examples of oxazoline group-containing compounds or compounds capable of reacting with them include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, (meta ) -2-ethylhexyl acrylate, methoxypolyethylene glycol (meth) acrylate, lauryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, monoesterified product of (meth) acrylic acid and polyethylene glycol, ( Examples include meth) acrylic acid-2-aminoethyl and salts thereof, (meth) acrylic acid and salts thereof; acrylonitrile, methyl vinyl ether, and the like.

The oxazoline-based crosslinking agent used in the present invention may be a low molecular compound or a (co) polymer of these compounds.
Further, as commercially available products, Epocross WS-700, Epocross WS-500 Epocross K-2020E (both manufactured by Nippon Shokubai Co., Ltd.) and the like can be used.

  When using an oxazoline-based crosslinking agent, it is preferable to use a catalyst such as an onium salt in combination. Specific examples of the onium salt catalyst include benzyltriethylammonium chloride, diammonium hydrogen phosphate, and boron tetrafluoride diphenylmethylsulfonium. These catalysts are preferably added in an amount of 0.5 to 5% by mass relative to the crosslinking agent. When the added amount is less than 0.5% by mass, a sufficient crosslinking accelerating effect may not be obtained. When the added amount exceeds 5% by mass, the pot life of the coating solution may be shortened or coloring may occur. There is.

  As content of a crosslinking agent, 5 mass%-40 mass% are preferable with respect to the binder which comprises a reflection layer, and 8 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect is obtained while maintaining the strength and adhesiveness of the polymer layer. When the content is 40% by mass or less, the pot life of the coating solution is kept longer. Can do.

(Pigments and reflectance)
It is preferable to add a white pigment to the reflective layer of the present invention for the purpose of increasing the reflectance.
Preferred examples of the white pigment include titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, and talc. Of these, titanium oxide is particularly preferable from the viewpoints of whiteness, reflectance, and durability. Titanium oxide has three types of crystal systems of rutile, anatase, and brookite, but those having a rutile crystal structure are preferred because of their high refractive index, whiteness, and low photocatalytic activity.

The titanium oxide used in the present invention is preferably subjected to a surface treatment in order to control dispersibility and photocatalytic activity. The surface treatment method is not particularly limited, and a known surface treatment method using aluminum oxide (Al ₂ O ₃ ), dioxide (SiO ₂ ), an alkanolamine compound, a silicon compound, or the like can be used. In addition, the preferable average particle diameter of a pigment is about 0.15-0.45 micrometer. By setting the particle size within this range, a high reflectance can be obtained.

  The white pigment of the present invention may use a dispersant in order to improve the dispersibility in the coating solution. As a preferable example of the dispersant, for example, when the solvent of the coating solution is water, polyvinyl alcohol can be exemplified. In this case, it is preferable to use in a dispersed state using a known disperser.

The coating amount of the white pigment in the reflective layer is preferably 3 to 10 g / m ² , more preferably 4 to 8 g / m ² . By making the coating amount of the white pigment in the range of 3 to 10 g / m ² , it becomes possible to achieve both necessary reflectance and adhesiveness.
The white pigment is preferably added in such an amount that the reflectance of the reflective layer of the present invention is 65% or more, more preferably 70% or more when the wavelength is 550 nm. Improvement in power generation efficiency can be achieved by setting the reflectance to 65% or more.

(Other additives)
You may add well-known additives, such as surfactant and antiseptic | preservative, to the reflective layer of this invention as needed.
Examples of the surfactant include known surfactants such as anionic and nonionic surfactants. Examples of the anionic surfactant include sodium alkyl sulfate and sodium alkylbenzene sulfonate, and examples of the nonionic surfactant include polyoxyethylene alkyl ether. Also preferred are fluorosurfactants such as sodium perfluoroalkyl sulfate.

If a surfactant is added, the addition amount thereof is preferably from ^{0.1mg / m 2 ~15mg / m 2} , more preferably ^{0.5mg / m 2 ~5mg / m 2} . When the addition amount of the surfactant is 0.1 mg / m ² or more, it is possible to suppress the occurrence of cissing and obtain a favorable layer formation, and when it is 15 mg / m ² or less, the adhesion can be performed satisfactorily. .
Preservatives include imidazoles (eg, 2- (4-thiazolyl) benzimidazole, methyl 2-benzimidazole carbamate, etc.) and thiazoles (1,2 benzisothiazolin-3-one, 5-chloro-2-methyl- Well-known preservatives such as 4-isothiazolin-3-one) can be used.

(Film thickness)
The thickness of the reflective layer of the present invention is preferably 3 to 10 μm, more preferably 4 to 8 μm.
By making the thickness of the reflective layer in the range of 3 to 10 μm, it is possible to achieve both necessary reflectance and adhesiveness.

(Application method)
There is no restriction | limiting in particular in the method of apply | coating the reflective layer of this invention, Well-known coating methods, such as a roll coat method, the bar-coater method slide die method, and the gravure coater method, can be used.
There is no restriction | limiting also in a coating solvent, You may use organic solvent type | system | group solvents like methyl ethyl ketone, toluene, and xylene, or you may use water as a solvent. However, considering that the environmental load is small, application using water as a solvent is particularly preferable. The coating solvent may be used alone or in combination. In particular, in the case of an aqueous coating solvent, a mixed solvent obtained by adding a small amount of a water-miscible organic solvent to water may be used.
Although there is no restriction | limiting in particular also in drying of a reflection layer, It is preferable to dry about 1 to 10 minutes at the temperature of about 120-200 degreeC from a viewpoint of shortening of drying time. When the drying temperature is less than 120 ° C., the drying time becomes long, which is disadvantageous in production. Conversely, if it exceeds 200 ° C., the flatness of the resulting backsheet may be impaired.

<Overcoat layer>
In the back layer of the present invention, an overcoat layer may be provided on the reflective layer for the purpose of improving the adhesion to the sealing material.

(binder)
As the binder for the overcoat layer, those described for the reflective layer can be preferably used.

(Crosslinking agent)
As the type of crosslinking agent for the overcoat layer, those described for the reflective layer can be preferably used.
As content of the crosslinking agent of an overcoat layer, 5 mass%-40 mass% are preferable with respect to the binder which comprises an overcoat layer, and 10 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect is obtained while maintaining the strength and adhesiveness of the polymer layer. When the content is 40% by mass or less, the pot life of the coating solution is kept longer. Can do.

(Other additives)
As the types and addition amounts of other additives in the overcoat layer, those described for the reflective layer can be preferably used.

(Film thickness)
The film thickness of the overcoat layer is preferably 0.1 to 1.0 μm, more preferably 0.2 to 0.8 μm. By setting the thickness of the overcoat layer in the range of 0.1 to 1.0 μm, it is possible to obtain strong adhesiveness with the sealing material.

(Application method)
As the overcoat layer coating method, coating solvent, and drying method, those described in the reflective layer can be preferably used.

<Back layer>
The back sheet of the present invention is provided with a back surface layer for protecting the support on the outer surface (the surface opposite to the solar battery cell).

(binder)
First, the binder for the back layer will be described. As the binder for the back layer, it is preferable to use a silicone-based composite polymer described below from the viewpoint of durability and adhesion to the support. The silicone-based composite polymer of the present invention (hereinafter sometimes referred to as “composite polymer”) has a polymer structure that is copolymerized with a — (Si (R ¹ ) (R ² ) —O) _n — moiety in the molecule. A polymer containing a moiety.

In the portion of “— (Si (R ¹ ) (R ² ) —O) _n —” which is a polysiloxane segment in the composite polymer, R ¹ and R ² may be the same or different and can be covalently bonded to the Si atom. Represents a monovalent organic group. Examples of the “monovalent organic group that can be covalently bonded to the Si atom” represented by R ¹ and R ² include a substituted or unsubstituted alkyl group (eg, methyl group, ethyl group, etc.), substituted or unsubstituted Aryl groups (eg, phenyl group, etc.), substituted or unsubstituted aralkyl groups (eg, benzyl group, phenylethyl etc.), substituted or unsubstituted alkoxy groups (eg: methoxy group, ethoxy group, propoxy group, etc.), Substituted or unsubstituted aryloxy group (eg, phenoxy group), substituted or unsubstituted amino group (eg, amino group, diethylamino group, etc.), mercapto group, amide group, hydrogen atom, halogen atom (eg: chlorine atom) Etc.). Among them, R ¹ and R ² are each independently an unsubstituted or substituted alkyl group having 1 to 4 carbon atoms (particularly a methyl group or an ethyl group), an unsubstituted or substituted phenyl group, a mercapto group, An unsubstituted amino group and an amide group are preferable.

Specific examples of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer include a hydrolysis condensate of dimethyldimethoxysilane, dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane. Hydrolysis condensate, hydrolysis condensate of dimethyldimethoxysilane / vinyltrimethoxysilane, hydrolysis condensate of dimethyldimethoxysilane / 2-hydroxyethyltrimethoxysilane, dimethyldimethoxysilane / 3-glycidoxypropyltriethoxysilane Hydrolysis condensate of dimethyldimethoxysilane / diphenyl / dimethoxysilane γ-methacryloxytrimethoxysilane.

The — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer may have a linear structure or a branched structure. Furthermore, a part of the molecular chain may form a ring.

The ratio of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer is preferably 15 to 85% by mass with respect to the total mass of the composite polymer. A mass% range is particularly preferred. If the ratio of the polysiloxane moiety is less than 15% by mass, the adhesiveness may be poor when exposed to a moist heat environment, and if it exceeds 85% by mass, the liquid may become unstable.

The molecular weight of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer is about 30,000 to 1,000,000 in terms of polystyrene-converted weight average molecular weight, more preferably about 50,000 to 300,000.

The composite polymer ^{- (Si (R 1) (} R 2) -O) n - moiety may be a known synthetic method is not particularly limited to the method of creating (polysiloxane moiety). Specifically, there is a method of adding an acid to an aqueous solution of an alkoxysilane compound such as dimethylmethoxysilane or dimethylethoxysilane, followed by hydrolysis and condensation.
The polymer structure portion copolymerized with the polysiloxane portion is not particularly limited, and an acrylic polymer, a polyurethane polymer, a polyester polymer, a rubber polymer, or the like can be used. Among these, acrylic polymers are particularly preferable from the viewpoint of durability.

Esters of acrylic acid (eg, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, etc.) or methacrylic acid esters (eg: methyl methacrylate, butyl methacrylate, hydroxyethyl acrylate, glycidyl) as monomers constituting the acrylic polymer And polymers composed of methacrylate, dimethylaminoethyl methacrylate and the like. Furthermore, examples of the monomer include carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, styrene, acrylonitrile, vinyl acetate, acrylamide, and divinylbenzene. The acrylic polymer is a polymer obtained by polymerizing one or more of these monomers, and may be a homopolymer or a copolymer.
Specific examples of the acrylic polymer include methyl methacrylate / ethyl acrylate / acrylic acid copolymer, methyl methacrylate / ethyl acrylate / 2-bidroxyethyl methacrylate / methacrylic acid copolymer, methyl methacrylate / butyl acrylate / 2-bidoxy Examples include ethyl methacrylate / methacrylic acid / γ-methacryloxytrimethoxysilane copolymer, methyl methacrylate / ethyl acrylate / glycidyl methacrylate / acrylic acid copolymer, and the like.

As the polyurethane polymer, a polyurethane polymer comprising a polyisocyanate such as toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and a polyol such as diethylene glycol, triethylene glycol, or neopentyl glycol can be preferably used. There is no restriction | limiting in particular in the preparation method of a polyurethane-type polymer, A well-known synthesis method can be used.
Specific examples of the polyurethane polymer include urethane obtained from toluene diisocyanate and diethylene glycol, urethane obtained from toluene diisocyanate and diethylene glycol / neopentyl glycol, and urethane obtained from hexamethylene diisocyanate and diethylene glycol.

As the polyester polymer, a polyester polymer comprising a polycarboxylic acid such as terephthalic acid, isophthalic acid, adipic acid or sulfoisophthalic acid and the polyol described in the polyurethane can be preferably used. There is no restriction | limiting in particular in the production method of a polyester-type polymer, A well-known synthesis method can be used.
Specific examples of polyester polymers include polyesters obtained from terephthalic acid / isophthalic acid and diethylene glycol, polyesters obtained from terephthalic acid / isophthalic acid / sulfoisophthalic acid and diethylene glycol, and obtained from adipic acid / isophthalic acid / sulfoisophthalic acid and diethylene glycol. There are polyester etc.

As the rubber-based polymer, a copolymer of a diene monomer such as butadiene, isoprene or chloroprene and a copolymer of these diene monomer and a monomer such as styrene copolymerizable therewith can be preferably used. There is no restriction | limiting in particular also in the preparation method of a rubber-type polymer, A well-known synthesis method can be used.
Specific examples of the rubber-based polymer include a rubber-based polymer composed of butadiene / styrene / methacrylic acid, a rubber-based polymer composed of butadiene / methyl methacrylate / methacrylic acid, a rubber-based polymer composed of isoprene / methyl methacrylate / methacrylic acid, and chloroprene / acrylonitrile. / There are rubber polymers made of methacrylic acid.

  The polymer constituting the polymer structure portion copolymerized with the polysiloxane portion may be used alone or in combination of two or more. Furthermore, the individual polymers may be homopolymers or copolymers.

  The molecular weight of the polymer structure portion copolymerized with the polysiloxane portion is about 3000 to 1000000 in terms of polystyrene-equivalent weight average molecular weight, and more preferably about 5000 to 300000.

There is no particular limitation on the method of chemically bonding the-(Si (R ¹ ) (R ² ) -O) _n -moiety (polysiloxane moiety) of the present invention and the polymer structure part copolymerized with this part. A method of separately polymerizing a polysiloxane part and a polymer structure part copolymerized with this part, chemically bonding each polymer, a method of polymerizing a polysiloxane part in advance and graft polymerizing it, There is a method of polymerizing and graft polymerizing a polysiloxane portion. The latter two methods are preferable because they are easy to create. For example, as a method for copolymerizing an acrylic polymer with a polysiloxane portion, there is a method in which a polysiloxane portion obtained by copolymerization of γ-methacryloxytrimethylsilane or the like is prepared, and this and an acrylic monomer are radically polymerized. Further, as a method of copolymerizing polysiloxane with an acrylic polymer portion, there is a method of causing hydrolysis and polycondensation by adding an alkoxysilane compound to an aqueous dispersion of an acrylic polymer containing γ-methacryloxytrimethylsilane.

  When the polymer structure portion copolymerized with the polysiloxane portion is an acrylic polymer, a known polymerization method such as emulsion polymerization or bulk polymerization can be used, but ease of synthesis and aqueous polymer dispersion can be obtained. From the viewpoint, emulsion polymerization is particularly preferable. Moreover, there is no restriction | limiting in particular in the polymerization initiator used for graft polymerization, Well-known polymerization initiators, such as potassium persulfate, ammonium persulfate, and azobisisobutyronitrile, can be used.

  By using the above-mentioned silicone-based composite polymer as the binder for the back layer, it becomes possible to make the adhesion between the back layer and the support particularly good, and the decrease in the adhesion can be reduced even after a long period of time. It becomes possible to keep.

The silicone composite polymer of the present invention is preferably in the form of an aqueous polymer dispersion (so-called latex). The preferable particle size of the latex of the silicone composite polymer is about 50 to 500 nm, and the preferable concentration is about 15 to 50% by mass.
The silicone composite polymer of the present invention preferably has a water-affinity functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group or an amide group when the aqueous polymer is in the form of latex. When the silicone-based composite polymer of the present invention has a carboxyl group, the carboxyl group may be neutralized with sodium, ammonium, amine or the like.
In addition, when used in the form of latex, an emulsion stabilizer such as a surfactant (eg, anionic or nonionic surfactant) or a polymer (eg: polyvinyl alcohol) may be added to improve the stability. Good. Further, if necessary, a pH adjuster (eg, ammonia, triethylamine, sodium hydrogen carbonate, etc.), preservative (eg: 1,3,5-hexahydro- (2-hydroxyethyl) -s-triazine, 2- ( 4-thiazolyl) benzimidazole), thickeners (eg: sodium polyacrylate, methylcellulose, etc.), film-forming aids (eg: butyl carbitol acetate, etc.), etc. May be.

  Some silicone-based composite polymers that can be used in the present invention are commercially available. Specific examples of commercially available products include Ceranate WSA 1060, 1070 (manufactured by DIC Corporation), Polydurex H7620, H7630, H7650 (manufactured by Asahi Kasei Chemicals Corporation) and the like.

(Crosslinking agent)
In order to improve the adhesion to the support, it is preferable to add a crosslinking agent to the back layer of the present invention. As the kind of the cross-linking agent, those described for the reflective layer can be used.
As content of a crosslinking agent, 5 mass%-40 mass% are preferable with respect to the binder which comprises a back surface layer, and 10 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect can be obtained while maintaining the adhesion to the support, and when the content is 40% by mass or less, the pot life of the coating solution can be maintained longer. it can.

(UV absorber)
It is preferable to add an ultraviolet absorber to the back layer of the present invention.
Examples of ultraviolet absorbers include, for example, salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, and the like in the case of organic ultraviolet absorbers. . Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, benzotriazole 2- (2'-hydroxy-5) '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 (2H benzotriazol-2-yl) phenol], a cyanoacrylate Ethyl-2-cyano-3,3′-diphenyl acrylate), others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy]- Phenol, hindered amine-based bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetra Examples include methylpiperidine polycondensate, nickel bis (octylphenyl) sulfide, and 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate. It is done.

Examples of inorganic ultraviolet absorbers include metal oxides such as titanium oxide, zinc oxide, and cerium oxide, and carbon-based components such as carbon, fullerene, carbon fiber, and carbon nanotube. Among these, titanium oxide is particularly preferable from the viewpoints of cost and durability.
The amount of the UV absorber added to the back layer varies depending on the type of the UV absorber, but is preferably in the range of 0.2 to 5 g / m ² , more preferably 0.3 to 3 g / m ² .

(Other additives)
A white pigment may be added to the back layer for the purpose of supplementing the reflectance of the reflective layer. Regarding the type of white pigment, the white pigment described in the reflective layer can be preferably used.
The addition amount of the white pigment in the back layer is preferably 0.3 to 10 g / m ² , more preferably 4 to 9 g / m ² . By making the addition amount 0.3 to 10 g / m ² , both good adhesiveness and improved reflectance can be achieved. In addition, when using a titanium oxide as a white pigment, it can serve as a pigment and a ultraviolet absorber. As the types and addition amounts of other additives in the back layer, those described in the reflective layer can be preferably used.

(Film thickness)
The thickness of the reflective layer of the present invention is preferably 3 to 12 μm, more preferably 4 to 8 μm.
By making the thickness of the back surface layer in the range of 3 to 12 μm, both necessary durability and adhesiveness can be achieved.

(Application method)
As the back layer coating method, coating solvent, and drying method, those described in the reflective layer can be preferably used.

<Back side protective layer>
In the back sheet of this invention, you may provide a back surface protective layer on a back surface layer in order to further improve durability.

<Binder>
The binder for the back surface protective layer of the present invention is preferably a fluoropolymer from the viewpoint of durability.
The fluorine-based polymer that can be preferably used in the present invention is a polymer containing a fluorine-containing monomer in the main chain or side chain. The fluorine-containing monomer may be contained in either the main chain or the side chain, but is preferably contained in the main chain from the viewpoint of durability.
Specific examples of the monomer containing fluorine include ethylene tetrafluoride, ethylene trifluoride, vinylidene fluoride, vinyl fluoride, hexafluoropropylene, fluorine-containing alkyl vinyl ether (eg, perfluoroethyl vinyl ether), fluorine-containing ester, etc. (Perfluorobutyl methacrylate and the like).

The fluorine-based polymer in the present invention may be copolymerized with a non-fluorine-containing monomer as necessary. Specific examples of these monomers include ethylene, alkyl vinyl ethers (eg, ethyl vinyl ether, cyclohexyl vinyl ether), and carboxylic acids (eg, acrylic acid, methacrylic acid, hydroxybutyme vinyl ether, etc.).
In the present invention, the proportion of the fluorine-containing monomer in the fluoropolymer is preferably 30% by mass to 98% by mass, more preferably 40% by mass to 80% by mass. When the proportion of the fluorine-containing monomer is less than 30% by mass, the durability may be insufficient, and when it exceeds 98% by mass, the polymerization may become unstable.

  Specific examples of the fluoropolymer of the present invention include tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / ethylene / acrylic acid copolymer, hexafluoropropylene / 4 tetrafluoroethylene copolymer, hexafluoride. Purpyrene / tetrafluoroethylene / ethylene copolymer, ethylene trifluoride / perfluoroethyl vinyl ether copolymer, ethylene trifluoride / perfluoroethyl vinyl ether / methacrylic acid copolymer, ethylene trifluoride / ethyl chloride Examples include vinyl ether copolymers, ethylene chloride trifluoride / ethyl vinyl ether / methacrylic acid copolymers, vinylidene fluoride / methyl methacrylate / methacrylic acid copolymers, vinyl fluoride / ethyl acrylate / acrylic acid copolymers, and the like.

  The molecular weight of the fluoropolymer of the present invention is about 2000 to 1000000 in terms of polystyrene-equivalent weight average molecular weight, and more preferably about 3000 to 300000.

The fluoropolymer of the present invention is preferably used in the form of an aqueous polymer dispersion (so-called latex). There are no particular limitations on the method of making the fluoropolymer of the present invention into a latex form, and there are a method of emulsifying a polymer in water, a method of polymerizing in water by emulsion polymerization, and the like.
There is no restriction | limiting in particular in the method of emulsion polymerization, A well-known emulsion polymerization method can be used.
For example, a known polymerization initiator such as potassium persulfate, ammonium persulfate, or azobisisobutyronitrile can be used as the polymerization initiator. Further, known surfactants can be used as emulsifiers, but CF ₃ CF ₂ CF ₂ C (CF ₃ ) ₂ CH ₂ CH ₂ COONH ₄ , CF ₃ CF ₂ CF ₂ C (CF ₃ ) ₂ CH ₂ CH Fluorine surfactants such as ₂ Na, CF ₃ CF ₂ CF ₂ C (CF ₃ ) ₂ CH ₂ CH ₂ NH ₄ are particularly preferred.
Furthermore, when used in the form of latex, an emulsion stabilizer such as a surfactant (eg, anionic or nonionic surfactant) or a polymer (eg, polyvinyl alcohol) may be added to improve the stability. Good. Further, if necessary, a pH adjuster (eg, ammonia, triethylamine, sodium hydrogen carbonate, etc.), preservative (eg: 1,3,5-hexahydro- (2-hydroxyethyl) -s-triazine, 2- ( 4-thiazolyl) benzimidazole), thickeners (eg: sodium polyacrylate, methylcellulose, etc.), film-forming aids (eg: butyl carbitol acetate, etc.), etc. May be.

When the fluoropolymer of the present invention is used in a latex form, the particle size is preferably about 50 to 500 nm, and the solid content concentration is preferably about 15 to 50% by mass.
The fluoropolymer of the present invention preferably has a water-affinity functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group or an amide group when the aqueous polymer is in the form of latex.

  Some fluoropolymers that can be used in the present invention are commercially available. Specific examples of commercially available products include Lumiflon LF200 (manufactured by Asahi Glass Co., Ltd.), Zeffle GK570 (manufactured by Daikin Industries, Ltd.), Obligard SW0011F (manufactured by AGC Co-Tech Co., Ltd.), and the like.

(Crosslinking agent)
In order to improve the adhesion to the support, it is preferable to add a crosslinking agent to the back surface protective layer of the present invention. As the kind of the cross-linking agent, those described for the reflective layer can be used.

  As content of a crosslinking agent, 5 mass%-40 mass% are preferable with respect to the binder which comprises a back surface protective layer, and 10 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect is obtained while maintaining adhesiveness. When the content is 40% by mass or less, the pot life of the coating solution can be maintained longer.

(Slip agent)
You may add a slipping agent to the back surface protective layer of this invention as needed.
Examples of the slip agent include synthetic wax compounds, natural wax compounds, surfactant compounds, inorganic compounds, organic resin compounds, and the like. Among these, from the viewpoint of the surface strength of the polymer layer, a compound selected from synthetic wax compounds, natural wax compounds, and surfactant compounds is preferable.
Examples of the synthetic wax compounds include olefin waxes such as polyethylene wax and polypropylene wax, esters such as stearic acid, oleic acid, erucic acid, lauric acid, behenic acid, palmitic acid, and adipic acid, amides, bisamides, and ketones. , Metal salts and derivatives thereof, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, phosphate esters, hydrogenated castor oil, hydrogenated waxes of hydrogenated castor oil derivatives, and the like.

Examples of the natural wax compounds include plant waxes such as carnauba wax, candelilla wax and wood wax, petroleum waxes such as paraffin wax and microcrystalline wax, mineral waxes such as montan wax, animals such as beeswax and lanolin. And waxes.
Examples of the surfactant compound include a cationic surfactant such as an alkylamine salt, an anionic surfactant such as an alkyl sulfate ester salt, a nonionic surfactant such as polyoxyethylene alkyl ether, and an alkylbetaine. Amphoteric surfactants, fluorosurfactants and the like.

As the slip agent, a commercially available product may be used. Specifically, as a synthetic wax-based slip agent, for example, Chemipearl series (for example, Chemipearl W700, W900, The same W950 etc.), Polylon P-502, Hymicron L-271, Hydrin L-536, etc. by Chukyo Yushi Co., Ltd. are mentioned. Examples of natural wax-based lubricants include Hydrin L-703-35, Cellosol 524, and Cellosol R-586 manufactured by Chukyo Yushi Co., Ltd.
Examples of the surfactant-based slip agent include NIKKOL series (for example, NIKKOL SCS, etc.) manufactured by Nikko Chemicals Co., Ltd., and Emar series (for example, EMAL 40, etc.) manufactured by Kao Corporation.

(Colloidal silica)
You may add colloidal silica to the back surface protective layer of this invention as needed.
The colloidal silica that can be used in the present invention is one in which fine particles mainly composed of silicon oxide are present in a fine particle state using water, unitary alcohols or diols, or a mixture thereof as a dispersion medium.
The colloidal silica particles have an average primary particle size of about several nm to 100 nm. The shape of the colloidal silica particles may be spherical, or may be one in which these are connected in a bead shape. Specific examples of the colloidal silica particles include, for example, Snowtex ST-20, ST-30, ST-40, ST-C, ST-N, ST-20L, ST-O, ST-OL, manufactured by Nissan Chemical Industries, Ltd. ST-S, ST-XS, ST-XL, ST-YL, ST-ZL, ST-OZL, ST-AK, Snowtex-AK series, Snowtex-PS series, Snowtex-UP, etc. .

(Other additives)
As the types and addition amounts of other additives for the back surface protective layer, those described for the reflective layer can be preferably used.

(Film thickness)
The thickness of the back surface protective layer of the present invention is preferably 0.5 to 6 μm, more preferably 1 to 5 μm. If the thickness of the back surface protective layer is less than 0.5, durability may be insufficient, and if it exceeds 6 μm, it is disadvantageous in terms of cost.

(Application method)
As the coating method, coating solvent, and drying method for the back surface protective layer, those described in the reflective layer can be preferably used.

<Heat treatment>
The backsheet of the present invention may be heat treated at any point in the manufacturing process. The heat treatment can be performed at an arbitrary time after, for example, forming any one of the white layer, the overcoat layer, the back surface layer, and the back surface protective layer. However, the most preferable method is performed after all these layers are formed. There is no restriction | limiting in particular about the form which heat-processes, A sheet | seat form or a roll form may be sufficient. The heat treatment temperature is preferably about 30 to 80 ° C., and the time is preferably about 24 to 72 hours.

[Solar cell module]
The solar cell module of the present invention includes the polyester film of the present invention or the back sheet for the solar cell module of the present invention.
The solar cell module of the present invention comprises a solar cell element that converts light energy of sunlight into electric energy, a transparent substrate on which sunlight is incident, and the polyester film (back sheet for solar cell) of the present invention described above. It is arranged and arranged between. Between a board | substrate and a polyester film, it can seal and comprise with resin (what is called sealing agent), such as an ethylene-vinyl acetate copolymer, for example.

  The members other than the solar cell module, the solar cell, and the back sheet are described in detail in, for example, “Photovoltaic power generation system constituent material” (supervised by Eiichi Sugimoto, Kogyo Kenkyukai, published in 2008).

  The transparent substrate only needs to have a light-transmitting property through which sunlight can pass, and can be appropriately selected from base materials that transmit light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

  Examples of solar cell elements include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenide, and II. Various known solar cell elements such as a group VI compound semiconductor can be applied.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Ketene imine compound>
[Synthesis Example 1]
(Synthesis of Exemplified Compound 1)

  2- (4-hydroxyphenyl) -3-methylbutyric acid (29.1 g, 150 mol) and acetic anhydride (375 ml) were charged into a three-necked flask and stirred under reflux for 3 hours. After confirming the completion of the reaction by TLC, excess acetic anhydride was distilled off under reduced pressure. The obtained solid was dissolved in ethyl acetate and subjected to liquid separation washing with 1N aqueous hydrochloric acid. The solvent was distilled off to obtain 31.0 g (yield: 87.5%) of (1-A). The structure was confirmed by NMR.

(1-A) 17.1 g (72.4 mmol), thionyl chloride 21.5 g (181 mmol), and toluene 50 mL were charged into a three-necked flask and stirred at 70 ° C. for 1 hour. After confirming the completion of the reaction by TLC, excess thionyl chloride and the solvent were distilled off under reduced pressure. Subsequently, 50 mL of toluene was added to dissolve the product, and then the mixture was cooled to 5 ° C., and 14.8 g (159 mmol) of aniline and 16.1 g (159 mmol) of triethylamine were slowly added dropwise at the same time, followed by stirring for 2 hours under ice cooling. . After distilling off the solvent under reduced pressure, the residue was dissolved in ethyl acetate and washed with 1N hydrochloric acid. The solvent was distilled off to obtain 16.2 g of (1-B). (Yield 88%)

  (1-B) 16.2 g (52 mmol), sodium methoxide (28% methanol solution) 15.0 g, and methanol 50 mL were charged into a three-necked flask and stirred at room temperature for 2 hours. After confirming the completion of the reaction by TLC, ethyl acetate was added, followed by liquid separation washing with 1N aqueous hydrochloric acid. After the solvent was distilled off under reduced pressure, 12.2 g of (1-C) was obtained by crystallization with a mixed solvent of ethyl acetate / hexane. (Yield 87%)

  (1-C) 10.7 g (40 mmol), potassium carbonate 16.6 g (120 mmol), and DMF 70 mL were charged into a three-necked flask and stirred at 50 ° C. under nitrogen. Then, 4.31 g (20 mmol) of 1,4-dibromobutane was added dropwise, the system temperature was raised to 110 ° C., and the reaction was performed for 24 hours. After the reaction, ethyl acetate was added, and the mixture was washed with 1N hydrochloric acid, then with 1N aqueous sodium hydrogencarbonate and saturated aqueous sodium chloride. After distilling off the solvent under reduced pressure, 8.3 g of (1-D) was obtained by crystallization with a 2-propanol / hexane mixed solvent. (Yield 70%)

(1-D) 6.0 g (10.1 mmol), triphenylphosphine 6.9 g (26.3 mmol) triethylamine 4.08 g (40.5 mmol), carbon tetrachloride 3.12 g (20.2 mmol), chloroform 210 mL. A three-necked flask was charged and stirred at 70 ° C. under nitrogen for 8 hours. The solvent was concentrated under reduced pressure, washed with hexane, and purified by silica gel chromatography to obtain 2.5 g of exemplary compound (1). (Yield: 45%)
¹ H-NMR (DMSO-d6) δ (ppm); 1.2 (12H), 1.8-1.9 (4H), 2.9 (2H), 4.0 (4H), 6.9- 7.0 (4H), 7.1 (4H), 7.2-7.5 (10H)

[Synthesis Example 2]
(Synthesis of Exemplary Compound 4)

Benzophenone 15.1 g (76 mmol), pentaerythritol tetrabromide 6.08 g (16 mmol), potassium carbonate 31.1 g (225 mmol), and DMF 130 ml were charged into a three-necked flask and stirred at 130 ° C. for 10 hours. The solid obtained by evaporating the solvent under reduced pressure was washed once with distilled water and once with ethanol, and crystallized with ethyl acetate to obtain 13.0 g of (4-A) (yield 95%). The structure was confirmed by NMR.

(4-A) 10.9 g (12.7 mmol), aniline 7.08 g (76.2 mmol), DABCO 22.96 g (154.6 mmol), and 390 ml of chlorobenzene were charged into a three-necked flask and stirred at 125 ° C. for 1 hour. Subsequently, 9.9 g (51 mmol) of tetrachlorotitanium was added and stirred for 4 hours. The resulting reaction solution was filtered under reduced pressure and subsequently concentrated, and the obtained solid was washed with ethanol to obtain 13.5 g of (4-B) (yield 92%). The structure was confirmed by NMR.

  (4-B) 10.2 g (8.7 mmol), triethylbenzylammonium chloride 6.0 g, and chloroform 90 ml were charged into a three-necked flask, and 60 g of 50% aqueous sodium hydroxide solution was added all at once with sufficient stirring. Stir at 45 ° C. for 1 hour. 120 ml of pure water and 180 ml of chloroform were added and washed twice with pure water, and the solvent was distilled off under reduced pressure to obtain 12.9 g (8.7 mmol) of (4-C) (yield 100%). The structure was confirmed by NMR.

(4-C) 12.9 g (8.7 mmol), sodium iodide 39 g, and acetone 210 ml were charged into a flask and refluxed at 75 ° C. for 2 hours. The reaction solution was slowly added dropwise to a 3.5% aqueous sodium thiosulfate solution, stirred for 1 hour, and then filtered under reduced pressure to obtain a solid. The obtained solid was purified by column chromatography to obtain 7.2 g (6.0 mmol) of exemplary compound (4) (yield 69%). The structure was confirmed by NMR.
¹ H-NMR (CDCl ₃ ) δ (ppm); 4.32 (8H), 7.05 (8H), 7.20 (20H), 7.36 (20H), 7.45 (8H)

[Keteneimine compound for comparative example]
The following compounds were used as ketene imine-based end capping agents. In addition, the comparative compound 1 (molecular weight 269) and the comparative compound 2 (molecular weight 550) of a ketene imine compound are compounds represented by mono and bis described in Examples of US Pat. No. 3,692,745.

<Carbodiimide compound>
The following compounds were used as carbodiimide compounds.
The following compounds were used as polycarbodiimide. The polycarbodiimide is Stabaxol P400 (manufactured by Rhein Chemie).

  The following compounds were used as cyclic carbodiimide. The cyclic carbodiimide is a compound having a molecular weight of 516 described in Examples of JP 2011-258461 A, and was synthesized with reference to the synthesis method described in Reference Example 2 of JP 2011-258641 A.

<Phosphorus compound>
The following compounds were used as phosphorus compounds.
Trimethyl phosphoric acid: manufactured by Wako Pure Chemical Industries, Ltd., concentration 99% or higher Phosphoric acid: manufactured by Wako Pure Chemical Industries, Ltd., concentration 85% or higher sodium dihydrogen phosphate dihydrate: manufactured by Wako Pure Chemical Industries, Ltd., concentration 98% or more Phenylphosphonic acid: Wako Pure Chemical Industries, Ltd., concentration 95% or more Irganox1022: Ciba Specialty Chemicals

<Polyester resin>
[PET-1]
-Process (A)-
4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed for 90 minutes to form a slurry, which was continuously supplied to the first esterification reactor at a flow rate of 3800 kg / h. Next, an ethylene glycol solution of a citric acid chelate titanium complex ("VERTEC AC-420", manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied to the first esterification reaction tank. While stirring at an internal temperature of 250 ° C., the reaction was carried out with an average residence time of about 4.4 hours to obtain an oligomer. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of element. The acid value of the obtained oligomer was 500 eq / ton.
The obtained oligomer was transferred to a second esterification reaction tank and reacted by stirring at a reaction tank temperature of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 180 eq / ton. The inside of the second esterification reaction tank is partitioned into two zones from the first zone to the second zone. From the second zone, an ethylene glycol solution of magnesium acetate is added, and the amount of Mg added is 75 ppm in terms of element. Was fed continuously.
As a result, an esterification reaction product was obtained.

-Process (B)-
The esterification reaction product obtained in the step (A) was continuously supplied to the first polycondensation reaction tank. Next, polycondensation (ester exchange reaction) is carried out with an average residence time of about 1.8 hours while stirring the esterification reaction product at a reaction temperature of 270 ° C. and a reaction tank pressure of 20 torr (2.67 × 10 ⁻³ MPa). It was.
Next, the obtained reaction product was transferred from the first polycondensation reaction tank to the second double condensation reaction tank. Thereafter, the reaction product was stirred in the second double condensation reaction tank at a reaction tank temperature of 276 ° C. and a reaction tank pressure of 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. (Transesterification reaction).
Subsequently, the reaction product obtained by the transesterification reaction is further transferred from the second double condensation reaction tank to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature is 278 ° C. and the reaction tank pressure is 1. While stirring at 5 torr (2.0 × 10 ⁻⁴ MPa), the reaction (transesterification reaction) was carried out under the condition of a residence time of 1.5 hours. Carboxylic acid value: 25 eq / ton, IV (intrinsic viscosity): 0.60 dl / G reaction product (polyethylene terephthalate (PET)) was obtained.
Thereafter, the inside of the reaction tank was slightly pressurized, the valve at the bottom of the reaction tank was opened, and gut-like PET was discharged into the water tank. A PET gut cooled in a water bath was cut with a cutter to obtain a chip.

-Step (C)-
Furthermore, the obtained PET chip was heat-treated at 210 ° C. for 30 hours under a reduced pressure of 50 Pa using a rotary vacuum polymerization apparatus. Thereafter, nitrogen gas at 25 ° C. was passed through the vacuum polymerization apparatus, and the pellets were cooled to 25 ° C. to obtain a polyester resin (PET-1) having a carboxylic acid value of 18 eq / ton and IV of 0.73 dl / g. .

[PET-2]
In PET-1, a polyester resin (PET) having a carboxylic acid value of 20 eq / ton and IV of 0.68 dl / g was obtained in the same manner as in PET-1, except that the heat treatment time in step (C) was changed to 20 hours. -2) was obtained.

[PET-3]
In PET-1, a polyester resin (PET) having a carboxylic acid value of 15 eq / ton and IV of 0.76 dl / g was obtained in the same manner as in PET-1, except that the heat treatment time in step (C) was changed to 40 hours. -3) was obtained.

[PET-4]
In PET-1, a polyester resin (PET) having a carboxylic acid value of 22 eq / ton and IV of 0.65 dl / g was obtained in the same manner as in PET-1, except that the heat treatment time in step (C) was changed to 18 hours. -3) was obtained.

[MB-1-1]
The obtained PET-1 is charged into a hopper of a biaxial kneading extruder having a diameter of 50 mm with a main feeder, and the polycarbodiimide compound is charged into a sub-feeder, and the content of the polycarbodiimide compound is PET-1. While weighing to 1 wt%, the resin was melted so that the maximum temperature reached 300 ° C., extruded into a gut shape, and discharged into a water tank. The gut of the resin mixture cooled in the water tank was cut with a cutter to obtain MB-1-1.
MB-1-1 had a carboxylic acid value of 8 eq / ton and an IV of 0.75 dl / g.

[MB-1-2]
For MB-1-1, MB-1-2 was prepared in the same manner as MB-1-1 except that the compound to be added was changed to the aforementioned cyclic carbodiimide.
MB-1-2 had a carboxylic acid value of 7 eq / ton and an IV of 0.98 dl / g.

[MB-1-3]
For MB-1-1, MB-1-3 was prepared in the same manner as MB-1-1 except that the compound to be added was changed to the aforementioned exemplary compound (1).
MB-1-3 had a carboxylic acid value of 8 eq / ton and an IV of 0.74 dl / g.

[MB-1-4] to [MB-1-14]
As shown in the table, MB-1-4 to MB-1-14 were prepared in the same manner as MB-1-1 except that the type and amount of the end-capping agent to be added were changed.

[MB-1-15]
About PET-1, the process A was changed into the following process (A) -2, and PET-5 was created.
MB-1-15 had a carboxylic acid value of 7 eq / ton and an IV of 0.75 dl / g.

-Step (A) -2-
4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed for 90 minutes to form a slurry, which was continuously supplied to the first esterification reactor at a flow rate of 3800 kg / h. Next, an ethylene glycol solution of a citric acid chelate titanium complex (“VERTEC AC-420”, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied to the first esterification reaction tank, and the reaction tank While stirring at an internal temperature of 250 ° C., the reaction was carried out with an average residence time of about 4.4 hours to obtain an oligomer. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of element. The acid value of the obtained oligomer was 500 eq / ton.
The obtained oligomer was transferred to a second esterification reaction tank and reacted by stirring at a reaction tank temperature of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 180 eq / ton. The inside of the second esterification reaction tank is divided into three zones from the first zone to the third zone. From the second zone, an ethylene glycol solution of magnesium acetate is added, and the amount of Mg added is 75 ppm in terms of element. Then, from the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the addition amount of P was 65 ppm in terms of element. The ethylene glycol solution of trimethyl phosphate was prepared by adding a 25 ° C. trimethyl phosphate solution to a 25 ° C. ethylene glycol solution and stirring at 25 ° C. for 2 hours (phosphorus compound content in the solution: 3 .8% by mass).
As a result, an esterification reaction product was obtained.

  In addition, the process (B) and the process (C) obtained PET-5 similarly to PET-1.

Subsequently, the obtained PET-5 was introduced into a hopper of a 50 mm diameter biaxial kneading extruder with a main feeder, and the above-described polycarbodiimide (Stabaxol P400) was introduced into a sub-feeder, and the content was PET. While weighing to 2 wt% with respect to −5, the resin was melted so that the maximum temperature reached 300 ° C., extruded into a gut shape, and discharged into a water tank. The gut of the resin mixture cooled in the water tank was cut with a cutter to obtain MB-1-15.
MB-1-15 had a carboxylic acid value of 5 eq / ton and an IV of 0.76 dl / g.

[MB-1-16] to [MB-1-27]
For MB-1-15, MB-1-15 was carried out in the same manner as MB-1-15 except that the type and amount of the end-capping agent to be added and the type and amount of the phosphorus compound were changed as shown in the table. 16 to MB-1-27 were prepared.

[MB-1-28]
For MB-1-18, MB-1-28 was prepared in the same manner as MB-1-15 except that the following pigment was newly added so that the content was 1 wt% with respect to the polyester resin.
MB-1-28 had a carboxylic acid value of 7 eq / ton and an IV of 0.73 dl / g.

Pigment / Titanium dioxide Typec R-780-2
Volume average particle size 0.42μm
100% solids made by Ishihara Sangyo Co., Ltd.

[MB-1-29] to [MB-1-30]
For MB-1-28, MB-1-29 to MB-1-30 were prepared in the same manner as MB-1-28, except that the amount of pigment added was changed as shown in the table.

[MB-2-1]
About PET-1, the process A was changed into the following process (A) -3, and MB-2-1 was created.
MB-2-1 had a carboxylic acid value of 12 eq / ton and an IV of 0.73 dl / g.

-Step (A) -3-
4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed for 90 minutes to form a slurry, which was continuously supplied to the first esterification reactor at a flow rate of 3800 kg / h. Next, an ethylene glycol solution of a citric acid chelate titanium complex (“VERTEC AC-420”, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied to the first esterification reaction tank, and the reaction tank While stirring at an internal temperature of 250 ° C., the reaction was carried out with an average residence time of about 4.4 hours to obtain an oligomer. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of element. The acid value of the obtained oligomer was 500 eq / ton.
The obtained oligomer was transferred to a second esterification reaction tank and reacted by stirring at a reaction tank temperature of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 180 eq / ton. The inside of the second esterification reaction tank is divided into three zones from the first zone to the third zone. From the second zone, an ethylene glycol solution of magnesium acetate is added, and the amount of Mg added is 75 ppm in terms of element. Then, from the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the added amount of P was 90 ppm in terms of element. The ethylene glycol solution of trimethyl phosphate was prepared by adding a 25 ° C. trimethyl phosphate solution to a 25 ° C. ethylene glycol solution and stirring at 25 ° C. for 2 hours (phosphorus compound content in the solution: 3 .8% by mass).
As a result, an esterification reaction product was obtained.

[MB-2-2] to [MB-2-16]
For MB-2-1, MB-2-2 to MB-2-16 were prepared in the same manner as MB-2-1 except that the type of phosphorus compound to be added and the input amount were changed as shown in Table 1. did.

[MB-2-17]
About MB-2-1, MB-2-17 was added in the same manner as MB-2-1 except that the following incompatible resin was newly added so that the content was 10 wt% with respect to the polyester resin. Created.
MB-2-17 had a carboxylic acid value of 15 eq / ton and an IV of 0.71 dl / g.

・ Incompatible resin Polymethylpentene resin TPX manufactured by Mitsui Petrochemical Co., Ltd.
DX-845

[MB-2-18] to [MB-2-19]
For MB-2-17, MB-2-18 to MB-2-19 were prepared in the same manner as MB-2-17, except that the amount of incompatible resin added was changed as shown in Table 1. did.

<Polyester film>
Example 1
-Extrusion molding-
About PET-1 obtained above, the conditions of the extrusion molding process were made into the extrusion molding conditions A, and the polyester film was produced.

-Extrusion conditions A-
About PET-1 obtained above, MB-1-4 was introduced into the hopper of a biaxial kneading extruder having a diameter of 50 mm with the feeder (1), PET-1 was introduced with the feeder (2), and polycarbodiimide. The resin was melted and extruded so that the maximum temperature of the resin temperature reached 300 ° C. At this time, the amount of chips introduced by the feeder (1) was introduced while giving a fluctuation of 12 wt% / min.
The melt (melt) extruded from the biaxial kneading extruder was passed through a gear pump and a filter (pore diameter: 20 μm), and then extruded from a die onto a cooling roll at 20 ° C. to obtain an amorphous sheet. The extruded melt was brought into close contact with the cooling roll using an electrostatic application method.

-Stretching (biaxial stretching process)-
The unstretched film extruded and solidified on the cooling roll was successively biaxially stretched by the following method to obtain a polyester film having a thickness of 250 μm.
<Stretching method>
(A) Longitudinal stretching The unstretched film was passed between two pairs of nip rolls having different peripheral speeds and stretched in the longitudinal direction (conveying direction). The preheating temperature was 90 ° C., the stretching temperature was 90 ° C., the stretching ratio was 3.5 times, and the stretching speed was 3000% / second.
(B) Transverse stretching The longitudinally stretched film was stretched laterally under the following conditions using a tenter.
<Conditions>
Preheating temperature: 100 ° C
Stretching temperature: 110 ° C
Stretch ratio: 4.2 times Stretch speed: 70% / second

-Heat fixation / thermal relaxation-
Then, the stretched film after finishing longitudinal stretching and lateral stretching was heat-set under the following conditions. Further, after heat setting, the tenter width was reduced and heat relaxation was performed under the following conditions.
<Heat setting conditions>
Heat setting temperature: 198 ° C
Heat setting time: 2 seconds <thermal relaxation conditions>
Thermal relaxation temperature: 195 ° C
Thermal relaxation rate: 5%

-Winding-
After heat setting and heat relaxation, both ends of the polyester film were trimmed by 10 cm. Then, after extruding (knurling) with a width of 10 mm at both ends, it was wound up with a tension of 25 kg / m. The width was 1.5 m and the winding length was 2000 m.
The polyester film of Example 1 was produced as described above.

(Examples 2 to 37)
In Example 1, the polyester film of Examples 2-37 was produced similarly to Example 1 except having changed into the conditions as shown in Table 1 the kind of chip | tip input in an extrusion molding process, quantity, and the variation | change_quantity. .

(Comparative Example 1)
A polyester film of Comparative Example 1 was prepared in the same manner as in Example 1 except that the extrusion molding condition was changed to the extrusion molding condition B in Example 1.

-Extrusion condition B-
About PET-1 obtained above, a PET-1 chip was introduced into a hopper of a biaxial kneading extruder having a diameter of 50 mm with a feeder, and melted and extruded so that the maximum resin temperature reached 300 ° C. .
The melt (melt) extruded from the biaxial kneading extruder was passed through a gear pump and a filter (pore diameter: 20 μm), and then extruded from a die onto a cooling roll at 20 ° C. to obtain an amorphous sheet. The extruded melt was brought into close contact with the cooling roll using an electrostatic application method.

(Comparative Example 2 to Comparative Example 4)
In Comparative Example 1, polyester films of Comparative Examples 2 to 4 were produced in the same manner as Comparative Example 1, except that the chip to be charged was changed from PET-1 to MB-1-1-1 to MB-1-3.

(Comparative Examples 5-8)
In Example 1, polyester films of Comparative Examples 5 to 8 were produced in the same manner as in Example 1 except that the type, amount, and variation of the chips to be introduced in the extrusion process were changed to the conditions shown in Table 1. .

  Table 2 shows the compositions of the polyester films of Examples and Comparative Examples obtained as described above.

<Evaluation method of polyester film>
(1) In-plane variation of the amount of the end-capping agent in the film In-plane variation of the amount of the end-capping agent in the film was determined by the method shown in the following steps (1) to (5). .

Process (1)
In step (1), the location of the film to be sampled was set to the following 100 points.
(B) Determine the center point in the width direction of the film. (B) Sampling a total of 10 points at intervals of 10 cm to the left and right from the film center point. (C) Upstream in the longitudinal direction from the film center point. Sampling 10 points in total, 5 points each at 10 cm intervals in the direction and downstream (d) Sampling 10 points in the width direction for each point in (c) above as in (b) above

Process (2)
For the polyester films obtained in Examples and Comparative Examples, 1 g is sampled from an arbitrary location, freeze-ground using a freeze pulverizer (SPEX 6700) so that no foreign matter such as dust is mixed, and then dried to have a diameter. The powder form was 300 μm or less.

Step (3)
About this powdery polyester, the infrared absorption spectrum was obtained by KBr method known as a conventional method using FT-IR FTS7000 by Digilab.
At this time, the absorption intensity of the absorption peak peculiar to polyethylene terephthalate at 1700 to 1750 cm −1 is I _PET , the absorption intensity of the absorption peak peculiar to the carbodiimide compound at 2100 to 2200 cm −1 is I _CI , and ketene imine at 1900 to 2100 cm −1. The absorption intensity of the absorption peak peculiar to the compound was defined as _IKI .
Then, the abundance in the film of the terminal blocking agent in the sampled portion, I _CI / I _PET or was I _KI / I _PET.

Process (4)
In step (1), for the sampled 100 pieces of film, the amount of the end capping agent in the film was determined by the method shown in step (3), and the average value, maximum value, minimum value of 100 points, The standard deviations are Xave, Xmax, Xmin, and σx, respectively.

Process (5)
For Xave, Xmax, Xmin, and σx obtained in step (4), the in-plane variation and distribution of the abundance of the ketene imine compound in the film are determined using the following formula.
In-plane variation = (Xmax−Xmin) / Xave × 100 [%]
Distribution = σx / Xave

(2) In-plane variation of the abundance of the phosphorus compound in the film The in-plane variation of the abundance of the phosphorus compound in the film was determined by the method shown in the following steps a to d.

Step a
About the polyester film obtained by the Example and the comparative example, it sampled from arbitrary places, and it was FP method on the conditions shown below using the fluorescent X-ray-analysis apparatus (Shimadzu Corporation XRF-1500). to determine the elemental phosphorus amount I _P in the film.
(Fluorescence X-ray analysis conditions)
-X-ray tube target: Rh 4.0 kW
・ Voltage: 40kV
・ Current: 95mA
-Spectral crystal: Ge
・ Detector: FPC
・ 2θ: 141.03 deg
・ Measurement time: 40 seconds

Step b
In step a, the location of the film to be sampled was the following 100 points.
(B) Sampling the center of the film in the width direction (b) Sampling 5 points from the center of the film to the left and right every 10 cm, a total of 10 points (c) Every 10 cm from the center of the film in the longitudinal direction Sampling at 10 points (d) Sampling at 10 points in the width direction for each point in (c) above as in (b) above

Process c
In step b, the film pieces of 100 sampled points, by the method shown in step a, determine the abundance I _P in the film of the phosphorus compound, the average value of 100 points, the maximum value, minimum value, standard deviation, respectively Let Yave, Ymax, Ymin, and σy.

Step d
With respect to Yave, Ymax, Ymin, and σy obtained in step c, the in-plane variation and distribution of the abundance of the phosphorus compound in the film are determined using the following formula.
In-plane variation = (Ymax−Ymin) / Yave × 100 [%]
Distribution = σy / Yave

<Manufacturing aptitude evaluation>
(Increased viscosity)
When the increase in viscosity occurs, there arises a problem that the thickness variation of the polyester film becomes large.
The film thickness fluctuation | variation of the biaxial stretching saturated polyester film at the time of forming into a film continuously for 4 hours was evaluated. Among these, rank A is a practically preferable range. The obtained results are shown in Table 1 below.
A: Film thickness variation is within 5% B: Film thickness variation is 5-15%
C: Film thickness variation is greater than 15%

(Gas volatilization)
Sensory evaluation of smoke and odor generated from the die of the twin screw extruder was performed, and volatility was evaluated according to the following criteria. Among these, rank A is a practically preferable range. The obtained results are shown in Table 1 below.
<Standard>
A: No smoke or odor was generated.
B: Smoke was not generated, but odor was generated.
C: Smoke was generated, but no odor was generated.
D: Smoke and smell occurred.

<Evaluation of moisture and heat resistance of polyester film>
The wet heat resistance was evaluated based on the half life of elongation at break.
Break elongation retention half-life The obtained polyester film was subjected to a storage treatment (heat treatment) under conditions of 120C and a relative humidity of 100%, and the elongation after break (shown by the polyester film after storage) %) Was evaluated by measuring the storage time (breaking elongation retention half-life) of 50% with respect to the breaking elongation (%) exhibited by the polyester film before storage.
It shows that the moisture-heat resistance of a polyester film is excellent, so that break elongation retention half-life is long.
Note that the half life of elongation at break is 130 hours or more in practical use, preferably 150 hours or more, and more preferably 170 hours or more.

[Preparation of back sheet]
<Formation of reflective layer>
-Preparation of titanium dioxide dispersion-
Each component shown in the composition of the following titanium dioxide dispersion was mixed, and the mixture was subjected to dispersion treatment for 1 hour by a dynomill type disperser.
(Composition of titanium dioxide dispersion)
Titanium dioxide (white pigment, volume average particle size 0.42 μm) 39.9 parts [Taipeku R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content 100%]
Polyvinyl alcohol: 16.0 parts [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10%]
・ Surfactant [Demol EP, manufactured by Kao Corporation, solid content: 25%] ・ ・ ・ 0.5 part ・ Distilled water ・ ・ ・ 51.6 parts

-Preparation of coating solution for forming a reflective layer-
Each component shown below was mixed to prepare a coating solution for forming a reflective layer.
(Composition of coating solution for reflection layer formation)
-Titanium dioxide dispersion (dispersion of white pigment) ... 80.0 parts-Silanol-modified polyvinyl alcohol ... 19.2 parts [R1130, manufactured by Kuraray Co., Ltd., solid content: 7%]
・ Polyoxyalkylene alkyl ether (surfactant) ・ ・ ・ 3.0 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
Oxazoline compound (crosslinking agent) 2.0 parts [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25%]
・ Distilled water: 7.8 parts

-Formation of reflective layer-
The obtained coating solution for forming the first polymer layer was applied to one side of the support and dried at 180 ° C. for 1 minute. The amount of white pigment (titanium dioxide) was 5.5 g / m ² , and the thickness was 5 A reflective layer having a thickness of 5 μm was formed.

<Formation of back layer>
-Preparation of pigment dispersion-
Each component in the following composition was mixed, and the mixture was subjected to dispersion treatment for 1 hour using a dynomill type disperser.
(Composition of pigment dispersion)
Titanium dioxide (white pigment, volume average particle size 0.42 μm) 39.9 parts [Taipeku R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content 100%]
Polyvinyl alcohol: 16.0 parts [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10%]
・ Surfactant [Demol EP, manufactured by Kao Corporation, solid content: 25%] ・ ・ ・ 0.5 part ・ Distilled water ・ ・ ・ 51.6 parts

-Preparation of coating solution for back layer formation-
Each component shown in the composition below was mixed to prepare a coating solution for forming the back surface layer.
(Composition of the coating solution for forming the back layer)
-Acrylic / silicone binder (silicone resin) ... 362.3 parts [Ceranate WSA-1070, manufactured by DIC, solid content: 40%]
Carbodiimide compound (crosslinking agent) 48.3 parts [Carbodilite V-02-L2, manufactured by Nisshinbo Co., Ltd., solid content: 40%]
Surfactant: 9.7 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
・ Pigment dispersion liquid: 157.0 parts ・ Distilled water: 422.7 parts

-Formation of back layer-
The obtained back surface layer forming coating solution was applied to the surface of the support 1 opposite to the surface on which the first polymer layer was formed so that the amount of the silicone-based resin was 3.0 g / m ² in terms of the coating amount. It was dried at 1 ° C. for 1 minute to form a back layer having a dry thickness of 3 μm.

<Formation of back surface protective layer>
-Preparation of coating solution for forming the back surface protective layer-
Each component shown to the following composition was mixed and the coating liquid for back surface protective layer formation was prepared.
(Composition of the coating solution for forming the back surface protective layer)
-Fluorine binder (fluorine resin) ... 362.3 parts [Obligato SW0011F, manufactured by AGC Co-Tech, solid content: 40%]
-Carbodiimide compound (crosslinking agent) 24.2 parts [Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Ltd., solid content: 40%]
-Surfactant ... 24.2 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
・ Distilled water ... 703.8 parts

-Formation of back surface protective layer-
The obtained coating solution for forming the back surface protective layer was applied on the back surface layer so that the amount of the fluorine-based resin was 2.0 g / m ² in terms of the coating amount, dried at 180 ° C. for 1 minute, and dried. A back protective layer having a thickness of about 2 μm was formed.

  By the above method, a reflective layer was formed on one surface of the polyester film obtained in Example 1, and a back surface layer and a back surface protective layer were formed on the opposite surface to prepare a back sheet.

<Adhesiveness>
[A] Adhesiveness before wet heat aging The sample was cut into a width of 20 mm x 150 mm to prepare two sample pieces. These two sample pieces are arranged so that the easy-adhesive layer side is on the inside, and an EVA sheet (EVA sheet manufactured by Mitsui Chemicals Fabro Co., Ltd .: SC50B) cut between them is 20 mm wide × 100 mm long. It was made to adhere to EVA by hot pressing using a vacuum laminator (vacuum laminator manufactured by Nisshinbo Co., Ltd.). The bonding conditions at this time were as follows.
Using a vacuum laminator, evacuation was performed at 128 ° C. for 3 minutes, and then pressure was applied for 2 minutes to temporarily bond. Thereafter, the main adhesion treatment was performed in a dry oven at 150 ° C. for 30 minutes. In this way, a sample for adhesion evaluation was obtained in which the 20 mm portion from one end of the two sample pieces adhered to each other was not bonded to EVA, and the EVA sheet was bonded to the remaining 100 mm portion.

The EVA non-bonded portion of the obtained sample for adhesion evaluation was sandwiched between upper and lower clips with Tensilon (RTC-1210A manufactured by ORIENTEC), a tensile test was performed at a peeling angle of 180 ° and a pulling speed of 300 mm / min, and the adhesive strength was measured. .
Based on the measured adhesive strength, ranking was performed according to the following evaluation criteria. Among these, ranks 4 and 5 are practically acceptable ranges.
<Evaluation criteria>
5: Adhesion was very good (6 N / mm or more)
4: Adhesion was good (4N / mm or more and less than 6 / mm)
3: Adhesion was slightly poor (3 / mm or more and less than 4 N / mm)
2: Adhesion failure occurred (2N / mm or more and less than 3N / mm)
1: Adhesion failure was remarkable (less than 2 N / mm)

[B] Adhesiveness after wet heat aging The obtained adhesion evaluation sample was held for 48 hours (wet heat aging) at 120 ° C. and 100% RH, and then bonded in the same manner as in [A] above. The force was measured. Based on the measured adhesive strength after wet heat, the adhesive strength was evaluated by the same method as in [A] above. Among these, ranks 3, 4, and 5 are practically acceptable ranges.

As shown in Table 1, in Examples 1 to 37, it can be seen that both the wet heat resistance and the adhesion are highly evaluated, and a polyester film excellent in the wet heat resistance and the adhesion is obtained. On the other hand, in Comparative Examples 1 to 8, the elongation half time for evaluating the heat and moisture resistance is 120 h or less, or the evaluation of adhesion is 2 or less. From these results, it can be seen that Comparative Examples 1 to 8 cannot improve both the heat and moisture resistance and the adhesion.
In Examples 4 to 8, 9 and 10, 11 to 14, and 17 to 37, since the ketene imine compound is used as the end-capping agent, in addition to the high evaluation of both moist heat resistance and adhesion, It can be seen that the manufacturing aptitude is very excellent. In addition, among the ketene imine compounds, those having a molecular weight of 320 or more excluding the nitrogen atom constituting the ketene imine and the substituent bonded to the nitrogen atom, gas volatilization is suppressed very well, It can be seen that preferable manufacturing aptitude is realized.

  According to this invention, adhesiveness with the other member laminated | stacked on a polyester film can be improved. In addition, the moisture and heat resistance of the polyester film can be increased, and the strength of the polyester film can be sufficiently maintained in a high humidity environment. For this reason, the polyester film of this invention can be used suitably for the solar cell module backsheet, and its industrial applicability is high.

Claims (17)

A polyester film comprising polyester and a terminal sealant,
The average content of the terminal blocking agent with respect to the polyester is 0.1 to 10% by mass,
The polyester film, wherein the in-plane variation of the content of the end-capping agent is 2 to 20%.   2. The polyester film according to claim 1, wherein when the average content of the end-capping agent is Xave and the in-plane standard deviation is σx, 0.5 ≦ (σx / Xave) × 100 ≦ 5. .   The polyester film according to claim 1, wherein the end-capping agent is a chain carbodiimide compound, a cyclic carbodiimide compound, or a ketene imine compound. The polyester film according to claim 1 or 2, wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (1).

(In the general formula (1), R ₁ and R ₂ each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group; ₃ represents an alkyl group or an aryl group.) The polyester film according to claim 1 or 2, wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (2).

(In the general formula (2), R ₁ represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group. R ₂ represents L ₁ as a substituent. Represents an alkyl group, aryl group, alkoxy group, alkoxycarbonyl group, aminocarbonyl group, aryloxy group, acyl group or aryloxycarbonyl group, wherein R ₃ represents an alkyl group or an aryl group, and n is 1 to 4. Represents an integer, and L ₁ represents an n-valent linking group.)   In the said General formula (2), n is 3 or 4, The polyester film of Claim 5 characterized by the above-mentioned. The polyester film according to claim 1 or 2, wherein the terminal blocking agent is a ketene imine compound represented by the following general formula (3).

(In the general formula (3), R ₁ and R ₅ represent an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. R ₂ and R ₄ Represents an alkyl group having L ₂ as a substituent, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group or an aryloxycarbonyl group, wherein R ₃ and R ₆ are an alkyl group or an aryl group. L ₂ represents a single bond or a divalent linking group.)   The polyester film according to any one of claims 4 to 7, wherein a molecular weight of a portion excluding a nitrogen atom constituting the ketene imine of the ketene imine compound and a substituent bonded to the nitrogen atom is 320 or more. . It further contains a phosphorus compound so that the phosphorus element content is 30 to 600 ppm,
The polyester film according to any one of claims 1 to 8, wherein an in-plane variation of the phosphorus element content is 2 to 20%.   The polyester film according to claim 9, wherein 0.5 ≦ (σy / Yave) × 100 ≦ 5, where Yave is an average content of the phosphorus element and σy is an in-plane standard deviation.   The polyester film according to claim 1, further comprising fine particles, wherein the content of the fine particles is 0.5 to 10% by mass with respect to the polyester.   The polyester film according to claim 1, further comprising a void, wherein the void content is 5 to 50% with respect to a cross-sectional area of the polyester. Producing a mixture of a first composition comprising a polyester and an end-capping agent; and a second composition comprising a polyester and having a different content of the first composition and the end-capping agent;
A step of melting the mixture to form a film;
In the step of producing the mixture, the first composition and the second composition are mixed non-uniformly. The step of preparing the mixture includes the step of charging the first composition and the second composition into a kneading extruder,
The method for producing a polyester film according to claim 13, wherein in the step of adding, the amount of the first composition charged is varied.   The polyester film manufactured by the method of Claim 13 or 14.   The solar cell backsheet using the polyester film of any one of Claims 1-12 and Claim 15.   The module for solar cells using the solar cell amount backsheet of Claim 16.