WO2012029760A1

WO2012029760A1 - Polyester film and method for producing same

Info

Publication number: WO2012029760A1
Application number: PCT/JP2011/069564
Authority: WO
Inventors: 正志中野; 西川　高宏; 伊藤　正道; 友彦小田川; 晴紀安田; 佳幸柚原
Original assignee: 倉敷紡績株式会社; 長瀬産業株式会社
Priority date: 2010-08-30
Filing date: 2011-08-30
Publication date: 2012-03-08
Also published as: TW201229102A; JPWO2012029760A1; JP5914339B2; WO2012029499A1; JPWO2012029761A1; TW201223995A; TW201221544A; WO2012029761A1

Abstract

The objective of the present invention is to provide a polyester film having a sufficiently superior hydrolysis resistance and that is improved in heat resistance and weather resistance, and to provide a method for producing the polyester film. The biaxially oriented polyester film contains an polyester resin formed by the polycondensation of an alcohol component containing the diol compound represented by general formula I (in the formula: ring A is one of either a cyclohexane ring or a benzene ring; n1 is an integer from 0 to 4; and R¹ is a hydrogen atom or an alkyl group) and a carboxylic acid component containing the dicarboxylic acid compound represented by general formula II (in the formula: ring B is the other of either a cyclohexane ring or a benzene ring; n2 is an integer from 0 to 4; R² is a hydrogen atom or an alkyl group; and R³ is a hydrogen atom or an alkyl group), and the tensile strength retention rate after 100 hours of a pressure cooker test is at least 50%. In the method for producing the polyester film, after producing a precursor film containing the polyester resin, the precursor film is biaxially stretched.

Description

Polyester film and method for producing the same

The present invention relates to a polyester film, particularly a hydrolysis-resistant polyester film, and a method for producing the same.

Since polyethylene terephthalate (PET) films are generally excellent in heat resistance and weather resistance, they are often used for solar cell back sheets and motor insulation films. However, since the PET film is poor in hydrolysis resistance, for example, when used in a solar cell backsheet, there is a risk of deterioration of the filler and corrosion of the wiring due to permeation of water vapor (moisture) during long-term use. It could not be said that there was sufficient reliability.

As a hydrolysis-resistant film material, a polyester (so-called PCTA) obtained by polycondensation of a diol component composed of 1,4-cyclohexanedimethanol and a dicarboxylic acid component composed of terephthalic acid and isophthalic acid is known (for example, PCTA). Patent Document 1). However, although the PCTA film is superior in hydrolysis resistance to the PET film, it does not have sufficient hydrolysis resistance. Further, the PCTA film has a problem that it has poor heat resistance and weather resistance as compared with the PET film.

JP 2008-227203 A

An object of the present invention is to provide a polyester film that is sufficiently excellent in hydrolysis resistance, improved in heat resistance and weather resistance, and a method for producing the same.

The present invention is a biaxially oriented polyester film containing a polyester resin formed by polycondensation of at least a diol component and a dicarboxylic acid component,
The diol component is of the general formula (I);

Wherein ring A is a cyclohexane ring or a benzene ring; n1 is an integer from 0 to 4; R ¹ is selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms, and n1 is 2 When the integer is from 4 to 4, the 2 to 4 R ¹ are each independently selected from the group).
The dicarboxylic acid component is of the general formula (II);

(Wherein ring B is a benzene ring when ring A is a cyclohexane ring, and is a cyclohexane ring when ring A is a benzene ring; n2 is an integer from 0 to 4; R ² is a hydrogen atom and Selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, and when n2 is an integer of 2 to 4, the 2 to 4 R ² are each independently selected from the group; ³ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms).
The present invention relates to a polyester film having a tensile strength retention ratio of 50% or more after 100 hours of a pressure cooker test at 120 ° C., 100% RH and 2 atm.

The present invention also relates to a method for producing a polyester film in which a precursor film containing the polyester resin is produced and then the precursor film is biaxially stretched.

The polyester film of the present invention is sufficiently excellent in hydrolysis resistance and has good heat resistance and weather resistance.

It is a schematic block diagram of an example of the solar cell provided with the polyester film of this invention. It is sectional drawing of the back surface protection sheet for solar cell modules of one Embodiment of the invention which concerns on the basic application (Japanese Patent Application No. 2010-192520) of this application. It is a schematic sectional drawing of the solar cell module of one Embodiment of the invention which concerns on the basic application of this application. 6 is a graph showing the change over time in the tensile strength retention rate in the pressure cooker test for the films of Examples 1 and 2 and Comparative Examples 1 to 3 according to the basic application of the present application. 6 is a graph showing the change over time in the tensile elongation retention rate in the pressure cooker test for the films of Examples 1 and 2 and Comparative Examples 1 to 3 according to the basic application of the present application. It is a figure which shows the X-ray-diffraction result of the film of Examples 1 and 2 and the comparative example 2 which concern on the basic application of this application.

The polyester film according to the present invention is a biaxially oriented film containing a specific polyester resin. Biaxial orientation means that the polymer molecules constituting the film are oriented mainly in two directions different from each other in the in-plane direction of the film, preferably in two directions substantially perpendicular to each other. For example, it can be achieved by biaxial stretching described later. In the present invention, by using a film containing a specific polyester resin as a biaxially oriented film, sufficiently excellent hydrolysis resistance is exhibited as compared with a film that is not biaxially oriented, heat resistance and weather resistance. Can be improved.

<Polyester resin>
The specific polyester resin (hereinafter simply referred to as “polyester resin A”) contained in the polyester film of the present invention is a polyester resin obtained by polycondensation of at least a diol component and a dicarboxylic acid component, and the diol component is A diol compound represented by the general formula (I) is included, and a dicarboxylic acid component includes a dicarboxylic acid compound represented by the following general formula (II).

(Diol component)

In formula (I), ring A is a cyclohexane ring or a benzene ring, preferably a cyclohexane ring. The two methylol groups on ring A are in a 1,2-substituted, 1,3-substituted or 1,4-substituted relationship, preferably 1,3-substituted or 1,4-substituted, more preferably 1, 4-Substitutional relationship.
n1 is an integer of 0 to 4, preferably 0 or 1, more preferably 0.
R ¹ is selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, an i-propyl group, and an n-propyl group. R ¹ is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom. When n1 is an integer of 2 to 4, the 2 to 4 R ^{1 s} are each independently selected from the above group, and preferably are simultaneously hydrogen atoms.

Specific examples of the diol compound represented by the general formula (I) include, for example, a cyclohexane diol compound represented by the general formula (Ia) and a benzene diol compound represented by the general formula (Ib). A cyclohexane diol compound is preferred.

In formulas (Ia) and (Ib), n1 and R ¹ are the same as in formula (I).

The cyclohexane diol compound represented by the general formula (Ia) is a diol compound in which the ring A is a cyclohexane ring in the general formula (I). Specific examples thereof include, for example, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-bis (hydroxymethyl) -3,4,5,6-tetra. Methyl-cyclohexane, 1,3-bis (hydroxymethyl) -2,4,5,6-tetramethyl-cyclohexane, 1,4-bis (hydroxymethyl) -2,3,5,6-tetramethyl-cyclohexane, etc. Is mentioned. 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol are preferred, and 1,4-cyclohexanedimethanol is more preferred.

The benzene diol compound represented by the general formula (Ib) is a diol compound in which the ring A is a benzene ring in the general formula (I). Specific examples thereof include, for example, 1,2-bis (hydroxymethyl) benzene, 1,3-bis (hydroxymethyl) benzene, 1,4-bis (hydroxymethyl) benzene, 1,2-bis (hydroxymethyl)- 3,4,5,6-tetramethyl-benzene, 1,3-bis (hydroxymethyl) -2,4,5,6-tetramethyl-benzene, 1,4-bis (hydroxymethyl) -2,3 5,6-tetramethyl-benzene) and the like. 1,3-bis (hydroxymethyl) benzene and 1,4-bis (hydroxymethyl) benzene are preferable, and 1,4-bis (hydroxymethyl) benzene is more preferable.

The diol component may contain other diol compounds in addition to the diol compound represented by the general formula (I). As the other diol compound, a diol compound used as a polyester film raw material can be used, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,2-butane. Aliphatic acids such as diol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, polyalkylene glycol Examples thereof include diol compounds and diphenyl diol compounds such as 2,2-bis (4′-β-hydroxyethoxyphenyl) propane.

Polyester resin A has a diol component among the diol compounds represented by the above general formula (I) from the viewpoint of hydrolysis resistance, cost, extrusion moldability and crystallinity (stretchability). ) Preferably includes a 1,4-diol compound in which the two methylol groups on ring A are in a 1,4-substituted relationship, and more preferably the 1,4-diol compound (particularly 1,4-cyclohexanedi). Methanol).

The content ratio of the diol compound represented by the general formula (I) with respect to the total diol component is preferably 50 mol% or more from the viewpoint of hydrolysis resistance, cost, extrusion moldability, and crystallinity (stretchability). Preferably it is 80 mol% or more, Most preferably, it is 95 mol% or more. A diol component may contain 2 or more types of diol compounds represented by the said general formula (I), and those total content ratios should just be in the said range in that case.

In addition to the diol component described above, the polyester resin A contains, for example, a trifunctional or higher polyhydric alcohol component such as trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, hexanetriol as a constituent monomer. Also good.

The content ratio of the trifunctional or higher polyhydric alcohol component to the total alcohol component is usually 50 mol% or less, preferably 20 mol% or less.

(Dicarboxylic acid component)

In formula (II), ring B is a benzene ring when ring A is a cyclohexane ring, and is a cyclohexane ring when ring A is a benzene ring. The two —COOR ³ groups on ring B are in a 1,2-substituted, 1,3-substituted or 1,4-substituted relationship, preferably 1,3-substituted or 1,4-substituted, more preferably There is a 1,4-substitution relationship.
n2 is an integer of 0 to 4, preferably 0 or 1, more preferably 0.
R ² is selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group include the same alkyl groups exemplified in the description of R ¹ . R ² is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom. When n2 is an integer of 2 to 4, the 2 to 4 R ² are each independently selected from the above group, and preferably are simultaneously hydrogen atoms.
Two R ^{3 s} are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group include the same alkyl groups exemplified in the description of R ¹ . Preferable R ³ is each independently a hydrogen atom or a methyl group, more preferably a hydrogen atom at the same time.

Specific examples of the dicarboxylic acid compound represented by the general formula (II) include, for example, a benzene dicarboxylic acid compound represented by the general formula (IIa) and a cyclohexane dicarboxylic acid compound represented by the general formula (IIb). It is done. A benzene dicarboxylic acid compound is preferred.

Wherein (IIa) and (IIb), n2, ^{R 2} and ^{R 3} are the same as those in the formula (II).

The benzene dicarboxylic acid compound represented by the general formula (IIa) is a dicarboxylic acid compound in which the ring B is a benzene ring in the general formula (II). Specific examples thereof include, for example, terephthalic acid, isophthalic acid, orthophthalic acid, 5-tert-butylisophthalic acid, phthalic acid, 4,4-biphenyldicarboxylic acid, 4,4-biphenylsulfone dicarboxylic acid, methyl terephthalate, isophthalic acid Methyl, methyl phthalate, 1,2-dicarboxyl-3,4,5,6-tetramethyl-benzene, 1,3-dicarboxyl-2,4,5,6-tetramethyl-benzene, 1,4- And dicarboxyl-2,3,5,6-tetramethyl-benzene. Preferred are terephthalic acid, methyl terephthalate, isophthalic acid, and methyl isophthalate.

The cyclohexane-based dicarboxylic acid compound represented by the general formula (IIb) is a dicarboxylic acid compound in which the ring B is a cyclohexane ring in the general formula (II). Specific examples thereof include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-dicarboxyl-3,4,5,6-tetramethyl-cyclohexane. 1,3-dicarboxyl-2,4,5,6-tetramethyl-cyclohexane, 1,4-dicarboxyl-2,3,5,6-tetramethyl-cyclohexane and the like. 1,4-cyclohexanedicarboxylic acid is preferred.

The dicarboxylic acid component may contain other dicarboxylic acid compounds in addition to the dicarboxylic acid compound represented by the general formula (II). As other dicarboxylic acid compounds, dicarboxylic acid compounds used as raw materials for polyester films can be used. For example, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid) Naphthalene dicarboxylic acid compounds such as 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, diphenyl dicarboxylic acid compounds such as 4,4′-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, etc. Examples include aliphatic dicarboxylic acid compounds.

Polyester resin A has a dicarboxylic acid component among the dicarboxylic acid compounds represented by the general formula (II) from the viewpoint of hydrolysis resistance, cost, extrusion moldability, and crystallinity (stretchability). It is preferable that the two —COOR ³ groups on ring B in (II) include a 1,4-dicarboxylic acid compound in a 1,4-substituted relationship, more preferably the 1,4-dicarboxylic acid compound and the above-mentioned Including a 1,3-dicarboxylic acid compound in which the two —COOR ³ groups on ring B in general formula (II) are in a 1,3-substituted relationship, most preferably 1,4-dicarboxylic acid compounds (especially terephthalic acid ) And a 1,3-dicarboxylic acid compound (especially isophthalic acid).

The content ratio of the dicarboxylic acid compound represented by the general formula (II) with respect to the total dicarboxylic acid component is preferably 50 mol% or more from the viewpoint of hydrolysis resistance, cost, extrusion moldability, and crystallinity (stretchability). More preferably, it is 80 mol% or more, and most preferably 95 mol% or more. When the dicarboxylic acid component contains two or more kinds of dicarboxylic acid compounds represented by the above general formula (II), the total content thereof may be within the above range.

Polyester resin A may contain a monocarboxylic acid component and / or a trifunctional or higher polyvalent carboxylic acid component as a constituent monomer in addition to the above-described dicarboxylic acid component.

The polyester resin A also preferably has a glass transition temperature of 40 to 250 ° C., particularly 70 to 200 ° C.
The glass transition temperature can be measured based on JIS K7121.

The polyester resin A also preferably has a melting point of 180 to 350 ° C, particularly 200 to 300 ° C.
The melting point can be measured based on JIS K7121.

The polyester resin A can be produced by polycondensing the above-described monomer components by a known method, or can be obtained as a commercial product.
As a commercial item of the polyester resin A, copolyester (copolyester) 13319 (made by Eastman) etc. are mentioned, for example. Copolyester 13319 (Eastman) is a polycondensate of 1,4-cyclohexanedimethanol with terephthalic acid and isophthalic acid.

In the polyester film, the polyester resin A may contain two or more kinds of polyester resins A having different monomer compositions, glass transition temperatures, melting points and / or carboxyl terminal concentrations within the above-described ranges.

The polyester film of the present invention may contain other polymers in addition to the above-mentioned polyester resin A, but from the viewpoint of further improving hydrolysis resistance, the polymer component in the polyester film is composed only of the above-mentioned polyester resin A. Is preferred.

The content ratio of the polyester resin A to the polymer component in the polyester film is preferably 60% by weight or more, more preferably 80% by weight or more, and still more preferably 95% by weight or more, from the viewpoint of further improving hydrolysis resistance. And most preferably 100% by weight.

In a range that does not adversely affect the performance such as hydrolysis resistance and film forming property, for example, polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polytrimethylene terephthalate; Other polymers such as polyetherimide, polyphenylene sulfite, polyether sulfone, and polyphenylene ether may be contained in the polyester film.

<Additives>
In addition to the polymers described above, the polyester film may contain additives such as antioxidants, ultraviolet absorbers, colorants, light stabilizers, lubricants, crystal nucleating agents, and flame retardants. From the viewpoint of heat resistance, the polyester film preferably contains an antioxidant. From the viewpoint of weather resistance, the polyester film preferably contains an ultraviolet absorber.

As the antioxidant, those used as an antioxidant in the polyester film field can be used, and examples thereof include a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant.

A phenolic antioxidant is an organic compound containing a phenolic skeleton, and a phenolic skeleton-containing organic compound conventionally used as a phenolic antioxidant in the field of polyester film can be used. The phenolic antioxidant can be obtained as a commercial product.
Commercially available phenolic antioxidants include, for example, Sumilizer GA-80 (manufactured by Sumitomo Chemical Co., Ltd.), Adekastab AO-60, Adekastab AO-330 (both manufactured by ADEKA), Irganox 245 (manufactured by BASF), Sianox 1790 (manufactured by CYTEC).

The phosphorus-based antioxidant is an organic compound containing a phosphorus atom, and a phosphorus atom-containing organic compound conventionally used as a phosphorus-based antioxidant in the field of polyester film can be used. Phosphorous antioxidants can be obtained as commercial products.
Examples of commercially available phosphorous antioxidants include Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), Adeka Stub PEP-36 (manufactured by ADEKA), Irgafos 38, Irgafos 168 (both manufactured by BASF), and the like.

The sulfur-based antioxidant is an organic compound containing a sulfur atom, and a sulfur atom-containing organic compound conventionally used as a sulfur-based antioxidant in the polyester film field can be used. The sulfur-based antioxidant can be obtained as a commercial product.
Examples of commercially available sulfur-based antioxidants include Sumilyzer MB (manufactured by Sumitomo Chemical Co., Ltd.) and Adeka Stub AO-412S (manufactured by ADEKA).

The content of the antioxidant is preferably 0.03 to 2.5% by weight with respect to the polymer component in the polyester film from the viewpoint of heat resistance. When two or more kinds of antioxidants are contained, the total amount thereof may be within the above range.

From the viewpoint of further improving the heat resistance, the phenol-based antioxidant, the phosphorus-based antioxidant and the sulfur-based antioxidant are each 0.05 to 2.0% by weight, particularly 0.1 to 1%, based on the polymer component. 0.0 is preferable.

As the UV absorber, those used as UV absorbers in the field of polyester film can be used, and examples thereof include benzoxazine UV absorbers, triazine UV absorbers, and benzotriazole UV absorbers.

The benzoxazine-based ultraviolet absorber is an organic compound containing a benzoxazine skeleton, and a benzoxazine skeleton-containing organic compound conventionally used as a benzoxazine-based ultraviolet absorber in the field of polyester film can be used. A benzoxazine-based ultraviolet absorber can be obtained as a commercial product.
Examples of commercially available benzoxazine-based ultraviolet absorbers include Siasorb UV-3638 (manufactured by CYTEC).

The triazine-based ultraviolet absorber is an organic compound containing a triazine skeleton, and a triazine skeleton-containing organic compound conventionally used as a triazine-based ultraviolet absorber in the polyester film field can be used. Triazine ultraviolet absorbers can be obtained as commercial products.
Examples of commercially available triazine ultraviolet absorbers include Tinuvin 1577ED and Tinuvin 479 (both manufactured by BASF).

The benzotriazole ultraviolet absorber is an organic compound containing a benzotriazole skeleton, and a benzotriazole skeleton-containing organic compound conventionally used as a benzotriazole ultraviolet absorber in the field of polyester films can be used. A benzotriazole type ultraviolet absorber can be obtained as a commercial product.
Examples of commercially available products of benzotriazole-based ultraviolet absorbers include SUMISORB 250 (manufactured by Sumitomo Chemical Co., Ltd.), ADK STAB LA-31 (manufactured by ADEKA), and Tinuvin 234 (manufactured by BASF).

The content of the ultraviolet absorber is preferably 0.1 to 2.0% by weight, particularly 0.15 to 1.5% by weight, based on the polymer component in the polyester film, from the viewpoint of weather resistance. When 2 or more types of ultraviolet absorbers are contained, the total amount thereof may be within the above range.

From the viewpoint of further improving the weather resistance and heat resistance, a phenol-based antioxidant, a phosphorus-based antioxidant and a sulfur-based antioxidant are contained within the above ranges, and further an ultraviolet absorber, particularly benzoxazine. 0.1 to 2.0% by weight, in particular, 0.1% to 2.0% by weight of one or more UV absorbers selected from the group consisting of UV-based UV absorbers, triazine-based UV absorbers, and benzotriazole-based UV absorbers. It is preferably contained at 15 to 1.5.

As the colorant, any pigment and dye used in the polyester film field can be used. The content of the colorant is not particularly limited as long as the object of the present invention is achieved, and for example, 1 to 30% by weight with respect to the polymer component is preferable.

<Production method of polyester film>
The polyester film of the present invention can be produced by the following method.
For example, the polyester resin A and other polymers and additives contained as required are mixed in a predetermined ratio, melted and kneaded to produce a precursor film, and then the obtained precursor film is biaxially stretched. .

A known method can be adopted as a method for producing the precursor film. For example, a mixture of desired components may be melted and kneaded with a twin screw extruder, and the kneaded product may be extruded from a T die and then cooled.

The thickness of the precursor film is not particularly limited, and is, for example, 100 to 2000 μm, preferably 120 to 1000 μm.

Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in the MD direction and the TD direction, or after stretching in one direction of the MD direction or the TD direction, stretching is performed in the other direction. Sequential biaxial stretching may be performed. Preferably simultaneous biaxial stretching is performed. In consideration of normal productivity and manufacturability, the sequential stretching method is generally used. However, the film formed by simultaneous biaxial stretching has better film formability than the film subjected to sequential biaxial stretching. This is because the hydrolysis resistance is improved after the maintenance. In particular, simultaneous biaxial stretching is preferred in view of the higher level of hydrolysis resistance required in the case of solar cell backsheets. On the other hand, desired hydrolysis resistance cannot be obtained even if uniaxial stretching is performed instead of biaxial stretching. In the present specification, the MD direction is a so-called flow direction, and means the direction (longitudinal direction) of the precursor film taken from the extruder. The TD direction is a so-called width direction and means a direction orthogonal to the MD direction.

When performing biaxial stretching, the stretching ratio and the stretching temperature are not particularly limited as long as the object of the present invention is achieved, but the following ranges are preferable. This is because the hydrolysis resistance is further improved.

The draw ratio is within a range in which breakage of 2.0 times or more does not occur in both the MD direction and the TD direction, and is preferably 2.0 to 5.0 times from the viewpoint of further improving the hydrolysis resistance, and more preferably 2.3 to 3.5 times. The draw ratios in the MD direction and the TD direction are preferably approximated. Specifically, when the MD direction draw ratio is P _MD and the TD direction draw ratio is P _TD , “P _TD −P _MD ” is preferably −0.5 to +0.5, more preferably −0. .3 to +0.3. In addition, the draw ratio of MD direction is a ratio based on MD direction length just before extending | stretching. The stretching ratio in the TD direction is a ratio based on the length in the TD direction immediately before stretching.

When the glass transition temperature of the polymer component constituting the film is Tg _P (° C.), the stretching temperature is usually Tg _P or higher and Tg _P + 40 ° C. or lower, from the viewpoint of further improving hydrolysis resistance, preferably Tg _P above, _Tg P + 30 ° C. or less, more preferably Tg _P more or less _Tg P + 25 ℃. The stretching temperature is the atmospheric temperature at which stretching is performed. When the polymer component is composed of two or more kinds of polymers, the Tg _P of the polymer component is the sum of values obtained by multiplying the glass transition temperature of each polymer by the content ratio of the polymer.

After biaxial stretching, heat setting is usually performed. The heat setting is a process for fixing the orientation of the polymer molecules by holding the stretched film at a temperature equal to or higher than the stretching temperature. The heat setting temperature is Tg _P + 50 ° C. or higher, Mp _P or lower, preferably Tg _P + 100 ° C. when the glass transition temperature of the polymer component constituting the film is Tg _P (° C.) and the melting point is Mp _P (° C.). The Mp _{P is} −20 ° C. or lower. The heat setting temperature is an atmospheric temperature for holding the film. When the polymer component is composed of two or more types of polymers, the Mp _P of the polymer component is the sum of values obtained by multiplying the melting point of each polymer by the content ratio of the polymer.

<Polyester film>
The thickness of the polyester film of the present invention is not particularly limited, and is, for example, 20 to 150 μm, preferably 25 to 125 μm.

The polyester film of the present invention exhibits extremely excellent hydrolysis resistance. Specifically, in the polyester film of the present invention, for example, the tensile strength retention after 100 hours of a pressure cooker test at 120 ° C., 100% RH and 2 atm is 50% or more, preferably 80% or more, and most preferably 90%. Achieve at least%.
In the polyester film of the present invention, the tensile strength retention rate after 150 hours of the pressure cooker test is preferably 10% or more, more preferably 40% or more, and most preferably 50% or more.
The pressure cooker test is an accelerated test for evaluating the hydrolysis resistance of the film, and is performed by a method described later.

The polyester film of the present invention has good heat resistance. For example, heat resistance is improved as compared with a precursor film before biaxial stretching. Specifically, in the polyester film of the present invention, the tensile strength retention after 100 hours of oven test at 200 ° C. is 5% or more, preferably 50% or more, more preferably 80% or more. In the present invention, based on the molecular behavior specific to the polyester resin A in the biaxially oriented film, the tensile strength retention rate may exceed 100% and may be about 150%.
The oven test is an accelerated test for evaluating the heat resistance of the film, and is performed by a method described later.

Furthermore, the polyester film of the present invention has good weather resistance. For example, the weather resistance is improved as compared with the precursor film before biaxial stretching. Specifically, in the polyester film of the present invention, the tensile strength retention after 500 hours of the sunshine weatherometer test is 25% or more, preferably 40% or more, more preferably 50% or more.
The sunshine weatherometer test is an accelerated test for evaluating the weather resistance of a film, and is performed by a method described later.

The polyester film of the present invention is useful for applications requiring hydrolysis resistance, heat resistance and weather resistance, particularly hydrolysis resistance, such as back sheets for solar cells and insulating films for motors.
The polyester film of the present invention is used, for example, in the solar cell shown in FIG. 1 when used in a solar cell backsheet. FIG. 1 is a schematic configuration diagram of an example of a solar cell 1. In FIG. 1, a solar cell 1 includes an element sealing layer 2 in which a solar cell element 22 provided with wiring 21 is embedded, a surface protective layer 3 that protects the surface side of the element sealing layer 2, and the element sealing. The back sheet layer 4 that protects the back side of the stop layer 2 is provided, and a frame 5 is mounted at the end. The backsheet layer 4 has, in order from the element sealing layer 2 side, a light reflecting layer 41, a gas barrier layer 42, and a hydrolysis-resistant layer 43, and the hydrolysis-resistant layer 43 is made of the polyester film of the present invention. Yes. The backsheet layer 4 is not limited to the above structure as long as it has a hydrolysis-resistant layer 43 outside the gas barrier layer 42, and the hydrolysis-resistant layer 43 only needs to be made of the polyester film of the present invention. .

Example / Comparative Example A mixture comprising the components shown in Table 1 or Table 2 was melted and kneaded by a twin screw extruder, and the kneaded product was extruded from a T die and then cooled to obtain a precursor film. The precursor film was biaxially stretched and heat-set under the stretching conditions described in Table 1 or Table 2. The heat setting was performed by maintaining the tension during stretching at a predetermined temperature.
As PCTA, copolyester 13319 (manufactured by Eastman, polycondensate of 1,4-cyclohexanedimethanol with terephthalic acid and isophthalic acid, Tg 92 ° C., melting point 285 ° C.) was used.
As the PET, polyethylene terephthalate (Mn 15000, Tg 75 ° C., melting point 265 ° C., terminal carboxyl group concentration 30 equivalent / ton) was used.

Hydrolysis resistance (Condition 1)
The film was allowed to stand for 100 hours in a high-temperature, high-humidity and high-pressure tank at 120 ° C., 100% RH and 2 atm (pressure cooker test). The film is removed from the bath, the tensile strength was measured to determine a retention M ₁ with respect to the tensile strength before the test. The tensile strength was measured according to JIS K7127; 1999 in the MD direction.
◎; 90% ≦ M ₁ (best);
○: 80 ≦ M ₁ <90% (good);
Δ: 50 ≦ M ₁ <80% (no problem in practical use);
X: M ₁ <50% (practical problem).

Hydrolysis resistance (Condition 2)
A pressure cooker test was conducted in the same manner as the evaluation method for hydrolysis resistance (Condition 1) except that the film was left in the high-temperature, high-humidity, high-pressure tank for 150 hours. It was determined retention M ₂ with respect to the intensity. Since the condition 2 is a very severe evaluation conditions as compared with the condition 1, the hydrolysis resistance in the present invention, retention M ₁ measured at the conditions 1 is equal rank "△" or more, Regardless of the evaluation result of Condition 2, it is within the allowable range. Also recognized as retention M ₂ measured in the condition 2 is significantly better achieved level if rank "△" or more. However, when M ₂ = 0, it is not recognized that it is extremely excellent.
◎; 50 ≦ M ₂
O; 40 ≦ M ₂ <50%;
Δ: 10 ≦ M ₂ <40%.
X: M ₂ <10%.

Heat resistance The film was allowed to stand for 100 hours in a hot-air circulating oven set to an atmosphere of 200 ° C. The film is removed from the oven, the tensile strength was measured to determine a retention M ₃ with respect to the tensile strength before the test. The tensile strength was measured according to JIS K7127; 1999 in the MD direction.
A; 80 ≦ M ₃ (best);
○: 50 ≦ M ₃ <80% (good);
Δ: 30 ≦ M ₃ <50% (no problem in practical use);
×: M ₃ <30% (practical problem).

Weather resistance A sunshine weatherometer test was conducted with a weather resistance tester specified in JIS B7753. The weathering tester is an accelerated weathering tester that irradiates a sample with ultraviolet light and sprays water, and the black panel temperature is 63 ° C., followed by irradiation for 102 minutes, and spraying for 18 minutes as a cycle. The film was left for 500 hours. The film is removed from the tester, the tensile strength was measured to determine a retention M ₄ for tensile strength before the test. The tensile strength was measured according to JIS K7127; 1999 in the MD direction.
◎; 50 ≦ M ₄ (best);
O; 40 ≦ M ₄ <50% (good);
Δ: 30 ≦ M ₄ <40% (no problem in practical use);
X: M ₄ <30% (practical problem).

In Table 1 and Table 2, the stretching conditions were as follows.
Biaxial stretching ⁽¹⁾ conditions: Stretched in the MD and TD directions simultaneously. Stretch ratio (MD × TD) 3 × 3, stretch temperature 110 ° C., heat setting temperature 230 ° C.
Biaxial stretching ⁽²⁾ conditions: Stretched simultaneously in the MD and TD directions. Stretch ratio (MD × TD) 2.1 × 2.1, stretch temperature 110 ° C., heat setting temperature 230 ° C.
Biaxial stretching ⁽³⁾ conditions: After stretching in the MD direction, stretching was performed in the TD direction. Stretch ratio (MD × TD) 2.8 × 2.8, stretch temperature 115 ° C., heat setting temperature 230 ° C.
Uniaxial stretching ⁽⁴⁾ condition: Stretched only in the MD direction. Stretch ratio (MD) 3, stretch temperature 110 ° C, heat setting temperature 230 ° C.
Biaxial stretching ⁽⁵⁾ conditions: Stretched in the MD and TD directions simultaneously. Stretch ratio (MD × TD) 1.8 × 1.8, stretch temperature 110 ° C., heat setting temperature 230 ° C.

The polyester film of the present invention is useful for applications requiring hydrolysis resistance, heat resistance and weather resistance, particularly hydrolysis resistance, for example, back sheets for solar cells and insulating films for motors.

1: Solar cell 2: Element sealing layer 3: Surface protective layer 4: Back sheet layer 5: Frame body 21: Wiring 22: Solar cell element 41: Light reflecting layer 42: Gas barrier layer 43: Hydrolysis resistant layer

The entire content of the basic application (Japanese Patent Application No. 2010-192520) of the present application is cited below as a part of the present specification.

Description [Title of Invention] Copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate, protective sheet for solar cell module, and solar cell module [Technology] Field]

The present invention relates to a copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate, a protective sheet for a solar cell module, and a solar cell module.
[Background technology]

Solar cell power generation systems are expected as a clean energy source to replace fossil fuels. In general, a solar cell power generation system uses a solar cell module in which an element group in which several to several tens of solar cell elements are wired in series or in parallel is protected by various packages. The solar cell module is generally covered with white plate tempered glass on the surface directly irradiated with sunlight, a solar cell element group is arranged below it, and the gap is filled with transparent ethylene, vinyl, acetate resin, etc. The back surface is protected by a sheet made of a weather resistant plastic material or the like (for example, Patent Documents 1 and 2).

Since the solar cell module is used outdoors, sufficient durability and weather resistance are required in its configuration, material structure, and the like. In particular, the solar cell module protective sheet (particularly the back surface protective sheet) is required to have weather resistance, particularly hydrolysis resistance. This is because the protective sheet may be decomposed and peeled off by moisture such as rain while being used outdoors for a long time, which may cause corrosion of the exposed wiring and affect the output of the module. .
[Prior art documents]
[Patent Literature]

[Patent Document 1] JP 2000-243999 [Patent Document 2] JP 2008-235603 [Summary of Invention]
[Problems to be solved by the invention]

Although various film materials have been studied as a base material for the back surface protection sheet for solar cell modules, film materials having good hydrolysis resistance have not yet been provided.

For example, a polyethylene terephthalate (PET) film or a polyethylene naphthalate (PEN) film has insufficient hydrolysis resistance and cannot be practically used as a base material for a back protective sheet for a solar cell module.

Then, an object of this invention is to provide the film excellent in hydrolysis resistance, the protection sheet for solar cell modules using the same, and a solar cell module.
[Means for solving problems]

As a result of intensive studies, the present inventors have found that a copolymer film of specific 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate has excellent hydrolysis resistance and is used for a solar cell module. The present invention has been conceived by finding it suitable for a base material for a protective sheet.

The present invention provides a copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate having a glass transition temperature measured by DMA method of 130 ° C. or higher.

The present invention also provides a copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate having a glass transition temperature measured by the TMA method of 200 ° C. or higher. .

In addition, the present invention provides a co-polymerization of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate having a maximum peak in the range of 22 ° ≦ 2θ ≦ 24 ° in X-ray diffraction. Provide a coalesced film.
These copolymer films of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate are excellent in hydrolysis resistance.

The present invention provides a protective sheet for a solar cell module, comprising at least one copolymer film of any of the above 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate. Such a protective sheet for a solar cell module is excellent in hydrolysis resistance and can withstand long-term use of the solar cell module. The protective sheet for a solar cell module is particularly preferably used as a back surface protective sheet for a solar cell module.

The present invention includes a filling layer including a solar cell element, a surface protection sheet disposed on the surface of the filling layer, and a back surface protection sheet disposed on the back surface of the filling layer, the surface protection sheet and the back surface protection sheet. At least one of the above provides a solar cell module having a copolymer film of any of the aforementioned 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate.
[The invention's effect]

ADVANTAGE OF THE INVENTION According to this invention, the film excellent in hydrolysis resistance, the protection sheet for solar cell modules, and the module for solar cells can be provided.
[Brief description of drawings]

FIG. 2 is a cross-sectional view of a back protective sheet for a solar cell module according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of a solar cell module according to an embodiment of the present invention.
FIG. 4 is a graph showing changes with time in tensile strength retention in a pressure cooker test for the films of Examples 1 and 2 and Comparative Examples 1 to 3.
FIG. 5 is a graph showing the change over time in tensile elongation retention in the pressure cooker test for the films of Examples 1 and 2 and Comparative Examples 1 to 3.
FIG. 6 is a diagram showing the X-ray diffraction results of the films of Examples 1 and 2 and Comparative Example 2.
[Mode for Carrying Out the Invention]

Hereinafter, preferred embodiments of the present invention will be described in detail.

The copolymer film of 1,4-cyclohexylene dimethylene terephthalate and 1,4-cyclohexylene dimethylene isophthalate of this embodiment is composed of 1,4-cyclohexylene dimethylene terephthalate and 1,4-cyclohexylene dimethylene. It consists of a resin composition containing a copolymer with isophthalate (hereinafter referred to as “copolymer A”).

The molar ratio of terephthalate to isophthalate is not particularly limited, but is usually 99.9: 0.1 to 50:50, preferably about 99: 1 to 70:30. The intrinsic viscosity (IV value) of the copolymer A is preferably 0.5 to 1.0 dl / g, and more preferably 0.75 to 1.0 dl / g. The IV value is obtained as follows. That is, copolymer A is dissolved in a mixed solvent of 60% by mass of phenol and 40% by mass of 1,1,2,2-tetrachloroethylene so as to have a concentration of 0.5 g / 100 ml. Using a capillary viscometer, the drop time of the solution in the capillary viscometer is measured at 25 ° C., and this is taken as ts. Moreover, the drop time in the capillary viscometer only of a solvent is measured, and this is set to. The IV value is obtained by the formula of IV value = [ln (ts / to)] / 0.5. “Ln” represents the base of the natural logarithm.

The content ratio of the copolymer A in the resin composition containing the copolymer A is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and 70 to 100% by mass from the viewpoint of further improving the hydrolysis resistance. % Is more preferable.

The resin composition containing the copolymer A may appropriately include organic substances other than the copolymer A, inorganic substances, and various additives. Examples of organic substances other than the copolymer A include cyclic and linear copolymer A oligomers, monomers of the acid component and glycol component constituting the copolymer A, low molecular weight reactants derived therefrom, and other than the copolymer A And various additives. As resins other than the copolymer A, thermoplastic polyesters such as PET, PBT, PEN, polypropylene naphthalate, polybutylene naphthalate, etc., thermosetting polyester, nylon 6, nylon 66, nylon 11, nylon 12, etc. Examples thereof include polyamide, polycarbonate, polyacetal, polystyrene, ABS resin, polyurethane, fluororesin, silicon resin, polyphenylene sulfite resin, cellulose, polyphenylene ether resin, and copolymer resins thereof.

Examples of inorganic substances include inorganic fillers such as glass fiber, carbon fiber, talc, mica, wollastonite, kaolin clay, layered silicate, calcium carbonate, titanium dioxide, and silica dioxide, inorganic lubricants, polymerization catalyst residues, and the like.

Additives include organic and inorganic dyes and pigments, matting agents, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, color adjusting agents, antioxidants, ultraviolet absorbers, crystal nucleating agents. , Whitening agents, lubricants, impurity scavengers, thickeners, surface conditioners and the like. Among these, it is preferable to include a heat stabilizer and a trapping agent for low molecular weight volatile impurities. As the heat stabilizer, pentavalent and / or trivalent phosphorus compounds, hindered phenol compounds and the like are preferable, and as a trapping agent for low molecular weight volatile impurities, polymers and oligomers of polyamide and polyesteramide, amide groups and amine groups are preferred. Preferred are low molecular weight compounds having

The copolymer A film of this embodiment has a glass transition temperature measured by DMA method of 130 ° C. or higher. The glass transition temperature measured by the DMA method is preferably 140 ° C. or higher, more preferably 150 ° C. or higher. Although there is no upper limit of the glass transition temperature measured by the DMA method, it is usually 200 ° C. or lower, preferably 180 ° C. or lower, preferably 170 ° C. or lower, and more preferably 160 ° C. or lower.

The DMA method is the following method. That is, the test piece is heated from room temperature at a rate of 5 ° C./min, the dynamic viscoelasticity and loss tangent of the test piece are measured using a viscoelasticity measuring device, and the glass transition temperature is calculated from the peak temperature of the loss tangent. Can be requested. The measurement frequency is 1 Hz.

Further, the copolymer A film of this embodiment has a glass transition temperature measured by the TMA method of 200 ° C. or higher. The glass transition temperature measured by the TMA method is preferably 210 ° C. or higher, more preferably 220 ° C. or higher, still more preferably 230 ° C. or higher, and particularly preferably 235 ° C. or higher. Although there is no upper limit of the glass transition temperature measured by the TMA method, it is usually 260 ° C. or lower, preferably 255 ° C. or lower, more preferably 250 ° C. or lower, and further preferably 245 ° C. or lower.

The TMA method is the following method. That is, the temperature of the test piece is raised from room temperature at a rate of 10 ° C./min, the amount of thermal expansion in the thickness direction is measured using a thermal analyzer, and a graph showing the relationship between the temperature and the amount of thermal expansion is drawn. . A tangent line is drawn on the curves before and after the glass transition point, and the glass transition temperature can be obtained from the intersection of the tangent lines.

Further, the copolymer A film of this embodiment has a maximum peak in the range of 22 ° ≦ 2θ ≦ 24 ° in X-ray diffraction.

The copolymer A film of this embodiment is excellent in hydrolysis resistance. The reason why the copolymer A film according to this embodiment has such characteristics is not clear, but one factor is as follows.
The characteristics relating to the glass transition temperature and the maximum peak described above are related to the fact that the copolymer A in the copolymer A film of the present embodiment is crystallized to some extent. And it is thought that hydrolysis resistance becomes high when the copolymer A is crystallized to some extent (preferably 20% or more, more preferably 30% or more in crystallinity).

In the measurement based on JIS-K7127, the breaking strength of the copolymer A film of this embodiment is preferably 80 MPa or more, more preferably 90 MPa or more, and more preferably 100 MPa or more in both the MD direction and the TD direction. More preferably it is.

In the measurement based on JIS-K7127, the elongation at break of the copolymer A film of this embodiment is preferably 150 MPa or less, more preferably 120 MPa or less, and more preferably 80 MPa or less in both the MD direction and the TD direction. More preferably.

The dielectric breakdown voltage of the present embodiment is preferably 90 kV / mm or more, more preferably 110 kV / mm or more, and further preferably 130 kV / mm or more in the measurement based on ASTM D-149. .

The thermal expansion coefficient (CTE) of this embodiment is preferably 80 ppm / ° C. or less, more preferably 60 ppm / ° C. or less in both the MD and TD directions, as measured by the TMA method (50 to 100 ° C.). Preferably, it is 40 ppm / ° C. or less.

The thickness of the copolymer A film of the present embodiment can be appropriately selected depending on the thickness of the back protective sheet for solar cell module and the required performance, but is preferably 10 μm to 500 μm, and preferably 20 μm to 300 μm. It is more preferable that the thickness is 30 μm to 200 μm. By setting it as such a range, while it becomes easy to manufacture a film, intensity | strength and rigidity increase and handling property and post-processability become easy. The thickness unevenness is preferably within ± 10%, more preferably within ± 7%, and further preferably within ± 5%.

The copolymer A film according to this embodiment can be produced as follows.
First, a copolymer A resin (for example, pellets) as a raw material is prepared. The copolymer A resin can be produced by polycondensing 1,4-cyclohexanedimethanol, terephthalic acid, and isophthalic acid by a known method. Further, for example, the copolymer A pellet is also commercially available from Eastman, for example, under the trade name “Eastman Copolyester 13319”.
And copolymer A resin is fuse | melted by heating, an additive is added as needed and the resin composition containing the copolymer A is obtained. Then, this resin composition is formed into a film. As a method for forming into a film, a melt molding method in which a resin composition containing the copolymer A is extruded from a die in a molten state, a solution in which the resin composition is dissolved in a solvent is applied onto a support, and then the solvent The solution cast method etc. which dry is mentioned. Of these, the melt molding method is most preferable because it is excellent in productivity and environmental suitability and can obtain a film in one step. As the melt molding method, a method using a T die or an I die, a water-cooled method, and an air-cooled inflation method are preferable.

Subsequently, the above-described copolymer A film according to this embodiment can be obtained by stretching the formed unstretched copolymer A film.

The stretching conditions and the stretching method are not particularly limited, and may be appropriately adjusted within a range in which the above glass transition temperature is obtained or a maximum peak is obtained in a predetermined angle range in X-ray diffraction.

For example, the stretching direction may be uniaxial or biaxial, but biaxial is preferred.

The stretching method is not particularly limited, and various methods such as roll stretching and tenter stretching can be used alone or in any combination.

The stretch ratio is not particularly limited. For example, it can be 2 to 5 times in the MD (machine direction) direction and 2 to 5 times in the TD (transverse direction) direction.

FIG. 2 shows an example of the configuration of the back surface protection sheet for solar cell modules of the present invention (hereinafter, sometimes simply referred to as “back surface protection sheet”). The back surface protection sheet 11 has a configuration in which

film base materials

30 and 32 having heat resistance are laminated on both surfaces of the gas barrier film 20. The gas barrier film 20 is obtained by providing a vapor deposition layer 12 made of an inorganic compound on one surface of a substrate 10. As the base material 10, the above-mentioned copolymer A film can be used.

The

film base materials

30 and 32 having heat resistance used in the present embodiment may be any film having heat resistance, such as a polyethylene terephthalate (PET) film or a vinyl fluoride resin (PVF) film, a vinylidene fluoride resin ( PVDF) film, trifluoroethylene chloride (PCTFE) film, ethylene-tetrafluoroethylene copolymer (ETFE) film, polytetrafluoroethylene (PTFE) film, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer Examples thereof include a fluorine-based substrate selected from (PFA) films. Moreover, the copolymer A film can also be used suitably as the

film base materials

30 and 32 which have heat resistance.

The thickness of the

film base materials

30 and 32 is not particularly limited, and is preferably 3 to 200 μm, and more preferably 6 to 30 μm.

The material of the vapor deposition layer 12 is not particularly limited, and examples thereof include aluminum oxide, silicon oxide, tin oxide, magnesium oxide, zinc oxide, and a mixture of two or more thereof. The thickness of the vapor deposition layer 12 is not particularly limited, and is preferably 5 to 300 nm, for example, and more preferably 10 to 150 nm.

As a method of laminating the gas barrier film 20 of this embodiment and the heat-resistant

film base materials

30 and 32, for example, a dry lamination laminating method can be employed for laminating. As an adhesive for dry lamination, it is necessary that the adhesive strength does not cause delamination due to deterioration when used outdoors for a long period of time, and that the adhesive does not turn yellow, etc., and is compatible with high heat resistance, moisture heat resistance, etc. Therefore, it is desirable to use a resin or the like as a main component of the vehicle constituting the adhesive which can be crosslinked or cured to form a three-dimensional network crosslinked structure. Specifically, the adhesive constituting the adhesive layer for laminating preferably forms a crosslinked structure by reaction energy consisting of heat or light in the presence of a curing agent or a crosslinking agent. For example, laminating by reaction energy consisting of heat or light in the presence of an aliphatic or alicyclic isocyanate such as a two-component curable polyurethane adhesive, or an isocyanate curing agent or crosslinking agent such as an aromatic isocyanate. When the adhesive for adhesive forms a crosslinked structure, a back protective sheet for a solar cell module excellent in heat resistance, weather resistance, moist heat resistance and the like can be produced.

In the above adhesive, as the aliphatic isocyanate, for example, 1,6-hexamethylene diisocyanate (HDI), as the alicyclic isocyanate, for example, isophorone diisocyanate (IPDI), as the aromatic isocyanate, for example, tri Range isocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthylene diisocyanate (NDI), tolidine diisocyanate (TODI), xylylene diisocyanate (XDI), and the like can be used.

In the adhesive, an ultraviolet absorber or a light stabilizer can be added in order to prevent ultraviolet degradation or the like. The amount used varies depending on the particle shape, density, etc., but is preferably about 0.1 to 10% by weight.

The adhesive can be applied, for example, by a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method, and the coating amount is 2 to 20 g / m ² (dry state) ) Position, preferably in the range of 3 to 10 g / m ² (dry state).

The back protective sheet for a solar cell module of the present invention thus obtained is particularly excellent in hydrolysis resistance because it has the above-mentioned copolymer A film. Therefore, such a back surface protection sheet for solar cells can protect the solar cells over a long period of time and is inexpensive.

In addition, the structure of the back surface protection sheet for solar cell modules is not limited to said structure.

For example, a transparent primer layer may be provided between the vapor-deposited layer 12 and the base material 10 in order to improve their adhesion. Examples of the resin for the transparent primer layer include a composite of a silane coupling agent or a hydrolyzate thereof, a polyol and an isocyanate compound.

Examples of the silane coupling agent include ethyltrimethoxysilane, vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. One or two or more of silane couplings such as γ-methacryloxypropylmethyldimethoxysilane or hydrolysates thereof can be used. Further, for example, those containing isocyanate groups such as γ-isocyanatopropyltriethoxysilane and γ-isocyanatopropyltrimethoxysilane, those containing mercapto groups such as γ-mercaptopropyltriethoxysilane, and γ-aminopropyltriethoxysilane There are those containing amino groups such as silane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, and γ-phenylaminopropyltrimethoxysilane. Further, those containing an epoxy group such as γ-glycidoxypropyltrimethoxysilane and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrimethoxysilane, vinyl (β-methoxyethoxy) silane, etc. Such a silane coupling agent may be added with alcohol or the like and added with a hydroxyl group or the like, and one or more of these may be used.

Examples of the polyol include those obtained by polymerizing acrylic acid derivative monomers such as ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxylbutyl methacrylate alone, and acrylic polyols obtained by copolymerizing with other monomers such as styrene. Is preferably used.

Examples of the isocyanate compound include monomers such as aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic xylene diisocyanate (XDI), hexadiisocyanate (HMDI), and polymers thereof. Or a derivative thereof can be used, and one or more of these can be used.

The thickness of the transparent primer layer is not particularly limited, but is preferably 0.001 to 2 μm, and preferably 0.03 to 0.5 μm.

Further, an overcoat layer having a gas barrier property may be further provided between the vapor deposition layer 12 and the film substrate 32. The overcoat layer includes, for example, a water-soluble polymer and one or more metal alkoxides or a hydrolyzate thereof, and a coating solution containing water or a water-alcohol mixed solution as a solvent is applied to the vapor deposition layer 12. Can be formed.

Examples of water-soluble polymers include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate.

Examples of the metal alkoxide include tetraethoxysilane and triisopropoxyaluminum.

Further, the vapor deposition layer 12 may be formed on both surfaces of the base material 10. In this case, you may form the above-mentioned transparent primer layer and overcoat layer with respect to both vapor deposition surfaces.

Moreover, the back surface protection sheet 11 for solar cell modules may not have any one or both of the

film base materials

30 and 32, and may be comprised only from the above-mentioned base material 10.

Next, a solar cell module using the solar cell back surface protective sheet of the present invention will be described. FIG. 3 is a schematic cross-sectional view showing the layer configuration of one embodiment of the solar cell module 100 including the solar cell back surface protective sheet of the present invention.

The solar cell module 100 of the present embodiment includes a solar cell module surface protection sheet 60, a front surface side filler layer 51, a solar cell element 50 as a photovoltaic element provided with a wiring 52, a back surface side filler layer 53, And the film base material 30 which has the said hydrolysis resistance of the said back surface protection sheet 11 is set as the structure arrange | positioned at the back surface side filler layer 53 side of the solar cell module 100. FIG. For each of these members, for example, by using a molding method such as a lamination method in which the members are integrated by, for example, vacuum suction, and heat-pressed, the above-described layers can be thermocompression-molded as an integrally formed body. Furthermore, the solar cell module 100 can be mounted with, for example, an aluminum frame (not shown).

As the normal solar cell module surface protection sheet 60 constituting the solar cell module, it has sunlight permeability, insulation, etc., and further has weather resistance, heat resistance, light resistance, water resistance, moisture resistance, It has various characteristics such as antifouling properties, etc., is excellent in physical or chemical strength, toughness, etc., is extremely durable, and further, because it protects solar cell elements as photovoltaic elements, It must be excellent in scratch resistance, shock absorption, and the like.

Specifically, known glass plates and the like, and further, for example, polyamide resins (various nylons), polyester resins, cyclic polyolefin resins, polystyrene resins, (meth) acrylic resins, polycarbonate resins, acetals Various resin films and sheets such as a resin and others can be used, and the copolymer A can also be suitably used. As the resin film or sheet, a biaxially stretched stretched film or sheet can be used. Further, the thickness of the resin film or sheet may be a minimum thickness necessary to maintain strength, rigidity, waist, etc. If it is too thick, there is a disadvantage that the cost increases, and the thickness is thin. If it is too high, strength, rigidity, waist and the like are lowered, which is not preferable. In the present embodiment, for the reasons described above, the thickness of the resin film or sheet is preferably 12 to 200 μm, more preferably 25 to 150 μm.

As the filler layer 51 laminated under the surface protection sheet 60 for the solar cell module constituting the solar cell module, sunlight enters through the surface protection sheet 60 and transmits and absorbs the transparency. It is necessary to have adhesiveness with a surface protection sheet and a back surface protection sheet. In addition, from the viewpoint of protecting the solar cell element as the photovoltaic element from having thermoplasticity in order to achieve the function of maintaining the smoothness of the surface of the solar cell element as the photovoltaic element. It is necessary to have excellent properties and shock absorption.

Specifically, as the filler layer, for example, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid, or acid-modified polyolefin resin, polyvinyl butyral resin, silicone resin, epoxy resin , (Meth) acrylic resins, and other resins can be used as a mixture of one or more. In the present embodiment, the resin constituting the filler layer is, for example, a crosslinking agent within a range that does not impair its transparency in order to improve weather resistance such as heat resistance, light resistance, and water resistance. Additives such as thermal antioxidants, light stabilizers, ultraviolet absorbers, photo-antioxidants, etc. can be arbitrarily added and mixed. In the present embodiment, the filler on the sunlight incident side is preferably an ethylene-vinyl acetate resin in consideration of performance and price such as weather resistance such as light resistance, heat resistance, and water resistance. It is a material. The thickness of the filler layer is preferably 200 to 1000 μm, more preferably 350 to 600 μm.

As the solar cell element 50 as a photovoltaic element constituting the solar cell module, a conventionally known one, for example, a crystalline silicon solar electronic element such as a single crystal silicon type solar cell element or a polycrystalline silicon type solar cell element, a single Amorphous silicon solar cell elements of junction type or tandem structure type, III-V compound semiconductor solar electronic elements such as gallium arsenide (GaAs) and indium phosphorus (InP), cadmium tellurium (CdTe) and copper indium selenide (CuInSe) ₂ ) Group II-VI compound semiconductor solar electronic device, organic solar cell device, etc. can be used. Furthermore, a thin film polycrystalline silicon solar cell element, a thin film microcrystalline silicon solar cell element, a hybrid element of a thin film crystalline silicon solar cell element and an amorphous silicon solar cell element, or the like can also be used.

The back-side filler layer 53 laminated under the photovoltaic element constituting the solar cell module is made of the same material as the front-side filler layer 51 laminated under the surface protection sheet for the solar cell module. Can be used. It is also necessary to have adhesiveness with the back surface protection sheet, and it has thermoplasticity to fulfill the function of maintaining the smoothness of the back surface of the solar cell element as a photovoltaic element, and further, the photovoltaic element From the viewpoint of protecting the solar cell element, it is necessary to have excellent scratch resistance, shock absorption and the like.

According to the solar cell module of the present invention, since the copolymer A film is used for at least one of the above-described back surface protection sheet and the surface protection sheet, the hydrolysis resistance of the back surface protection sheet or the surface protection sheet. High nature. Therefore, compared with the case where the conventional polyethylene terephthalate (PET) film or polyethylene naphthalate (PEN) film is used, it becomes possible to maintain the power output characteristics as a solar cell over a long period of time.

In addition, a solar cell module is not limited to said structure, Various structures are possible. For example, as the back surface protection sheet 11, those having various configurations as described above can be adopted. If necessary, it includes a filling layer including the solar cell element 50, a surface protection sheet 60 disposed on the surface of the filling layer, and a back surface protection sheet 11 disposed on the back surface of the filling layer. It suffices that at least one of the back surface protection sheets 11 includes the above-mentioned copolymer A film.
[Example]

Hereinafter, the contents of the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the following Example.

The following resin pellets were used as raw materials for the film. PEN is polyethylene naphthalate.
(1) Copolymer A (trade name: Eastman Copolyester 13319, manufactured by Eastman)
(2) PEN (manufactured by Teijin DuPont Films, trade name: Teonex Q51)
(3) 1,4-cyclohexanedimethanol / 2,2,4,4-tetramethyl-1,3-cyclobutanediol / terephthalic acid polycondensate (manufactured by Eastman, trade name: Eastman Tritan Copolyester FX200) , Referred to as “Copolymer B”.)

[Example 1]
The copolymer A (in the form of pellets) was melt-extruded to form a film, and further biaxially stretched to obtain a stretched copolymer A film having a thickness of 50 μm.

[Example 2]
A copolymer A film having a thickness of 100 μm was obtained in the same manner as in Example 1 except that the thickness was changed to 100 μm by changing the draw ratio.

[Comparative Example 1]
PEN (pellet form) was melt-extruded to form a film, and further biaxially stretched to obtain a stretched PEN film having a thickness of 25 μm.

[Comparative Example 2]
Copolymer A (pellet form) was melt-extruded to form a film, and an unstretched copolymer A film having a thickness of 110 μm was obtained.

[Comparative Example 3]
Copolymer B (pellet form) was melt-extruded to form a film, and an unstretched copolymer B film having a thickness of 100 μm was obtained.

<Various physical properties>
With respect to the films of Examples 1 and 2 and Comparative Examples 1 to 3, the breaking strength, breaking elongation, glass transition temperature, melting point, dielectric breakdown voltage, specific gravity and thermal expansion coefficient were measured. Table 3 shows measurement methods and measurement values for each measurement.

<Hydrolysis test>
The films of Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a pressure cooker test (120 ° C., 100% RH (relative humidity), 2 atm). For each film, the tensile strength retention and tensile elongation retention after 50 hours, 100 hours, 150 hours and 200 hours were measured. The results are shown in FIGS. The films of Examples 1 and 2 had a slower decrease in tensile strength retention and tensile elongation retention than the films of Comparative Examples 1 to 3.

<Measurement of crystallinity>
About the film of Example 1, Example 2, and the comparative example 2, the powder X-ray diffraction by CuK (alpha) ray was performed, confirmation of the diffraction pattern and calculation of the crystallinity degree were performed. The measurement method and measurement conditions are as follows. Target: Cu, X-ray tube current: 40 mA, X-ray tube voltage: 45 kV, scanning range: 2θ = 4 to 65 °, step: 2θ = 0.01671 °, average time / step: 10.160 s, fixed diverging slit: 1/2 °, rotation speed: 60 rotations per minute, crystallinity analysis: Hermans method, pretreatment: none.

FIG. 4 shows the relationship between the angle 2θ formed by the X-ray incident direction and the reflection direction and the diffraction intensity. In the films of Examples 1 and 2, a clear sharp maximum peak was confirmed in the range of 22 ° ≦ 2θ ≦ 24 °, but no sharp peak was observed anywhere in the film of Comparative Example 2, and the film was amorphous. There was found. Moreover, when the crystallinity degree of the film of Example 1 and Example 2 was calculated | required based on FIG. 4, they were 42.8% and 39.7%, respectively.
In Examples 1 and 2, the second intensity peak appeared at 2θ = 16 to 17 °, and the third intensity peak appeared at 2θ = 19 to 20 °. The peak intensity ratio was about the second intensity peak / maximum peak = 0.1 to 0.2.
[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Back surface protection sheet for solar cell modules, 10 ... Base material, 12 ... Deposition layer, 20 ... Gas barrier film, 30, 32 ... Film base material, 50 ... Solar cell element, 51 ... Surface side filler layer, 52 ... Wiring, 53 ... back side filler layer, 60 ... surface protection sheet for solar cell module, 100 ... solar cell module.

Contents of Claims [Claim 1]
A copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate, having a glass transition temperature measured by DMA method of 130 ° C. or higher.
[Claim 2]
The copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to claim 1, having a glass transition temperature measured by TMA method of 200 ° C or higher.
[Claim 3]
3. The 1,4-cyclohexylenedimethylene terephthalate and the 1,4-cyclohexylenedimethylene isophthalate according to

claim

1 or 2 having a maximum peak in a range of 22 ° ≦ 2θ ≦ 24 ° in X-ray diffraction. Copolymer film.
[Claim 4]
A copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate having a glass transition temperature measured by TMA method of 200 ° C. or higher.
[Claim 5]
Copolymerization of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to claim 4, which has a maximum peak in the range of 22 ° ≤2θ≤24 ° in X-ray diffraction Combined film.
[Claim 6]
A copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate having a maximum peak in the range of 22 ° ≦ 2θ ≦ 24 ° in X-ray diffraction.
[Claim 7]
The copolymer of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to any one of claims 1 to 6, which is used for protecting the front or back surface of a solar cell module. the film.
[Claim 8]
A protective sheet for a solar cell module, comprising at least one copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to any one of claims 1 to 6. .
[Claim 9]
A back surface protection for a solar cell module, comprising at least one copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to any one of claims 1 to 6. Sheet.
[Claim 10]
A filling layer including a solar cell element; a surface protection sheet disposed on a surface of the filling layer; and a back surface protection sheet disposed on a back surface of the filling layer, wherein at least the surface protection sheet and the back surface protection sheet. One is a solar cell module having the copolymer film of 1,4-cyclohexylenedimethylene terephthalate and 1,4-cyclohexylenedimethylene isophthalate according to any one of claims 1 to 6.

Claims

A biaxially oriented polyester film containing a polyester resin obtained by polycondensation of at least a diol component and a dicarboxylic acid component,
The diol component is of the general formula (I);

Wherein ring A is a cyclohexane ring or a benzene ring; n1 is an integer from 0 to 4; R 1 is selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms, and n1 is 2 When the integer is from 4 to 4, the 2 to 4 R 1 are each independently selected from the group).
The dicarboxylic acid component is of the general formula (II);

(Wherein ring B is a benzene ring when ring A is a cyclohexane ring, and is a cyclohexane ring when ring A is a benzene ring; n2 is an integer from 0 to 4; R 2 is a hydrogen atom and Selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, and when n2 is an integer of 2 to 4, the 2 to 4 R 2 are each independently selected from the group; 3 each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms).
A polyester film having a tensile strength retention of 50% or more after 100 hours of a pressure cooker test at 120 ° C., 100% RH and 2 atm.
The polyester film according to claim 1, wherein ring A is a cyclohexane ring and ring B is a benzene ring.
The two methylol groups on ring A are in a 1,3-substituted or 1,4-substituted relationship;
3. The polyester film according to claim 1, wherein the two —COOR 3 groups on ring B are in a 1,3-substituted or 1,4-substituted relationship.
The diol component includes a 1,4-diol compound in which the two methylol groups on ring A in the general formula (I) are in a 1,4-substituted relationship;
The dicarboxylic acid component includes a 1,4-dicarboxylic acid compound in which the two —COOR 3 groups on the ring B in the general formula (II) are in a 1,4-substituted relationship, and two —COOR on the ring B. The polyester film according to any one of claims 1 to 3, comprising a 1,3-dicarboxylic acid compound in which three groups are 1,3-substituted.
The diol component comprises the 1,4-diol compound;
The polyester film according to claim 4, wherein the dicarboxylic acid component comprises the 1,4-dicarboxylic acid compound and the 1,3-dicarboxylic acid compound.
The 1,4-diol compound is 1,4-cyclohexanedimethanol;
The 1,4-dicarboxylic acid compound is terephthalic acid,
The polyester film according to claim 4 or 5, wherein the 1,3-dicarboxylic acid compound is isophthalic acid.
A biaxially oriented polyester film containing a polyester resin obtained by polycondensation of 1,4-cyclohexanedimethanol with terephthalic acid and isophthalic acid,
A polyester film having a tensile strength retention of 50% or more after 100 hours of a pressure cooker test at 120 ° C., 100% RH and 2 atm.
The polyester film according to any one of claims 1 to 7, wherein the biaxially oriented polyester film is obtained by biaxially stretching a film containing the polyester resin.
The polyester film according to claim 8, wherein the biaxial stretching is simultaneous biaxial stretching.
The polyester film according to any one of claims 1 to 9, wherein the tensile strength retention after 150 hours of the pressure cooker test is 10% or more.
The polyester film according to any one of claims 1 to 10, which has a tensile strength retention of 50% or more after 100 hours of an oven test at 200 ° C.
The polyester film according to any one of claims 1 to 11, which has a tensile strength retention of 40% or more after 500 hours of a sunshine weatherometer test.
The polyester film according to any one of claims 1 to 12, further comprising an antioxidant and an ultraviolet absorber.
The antioxidant is selected from the group consisting of phenolic antioxidants, phosphorus antioxidants and sulfur antioxidants;
The polyester film according to claim 13, wherein the ultraviolet absorber is selected from the group consisting of benzoxazine-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers.
A phenolic antioxidant, a phosphorus antioxidant and a sulfur antioxidant are each contained in an amount of 0.05 to 2.0% by weight based on the polymer component,
Contains one or more UV absorbers selected from the group consisting of benzoxazine UV absorbers, triazine UV absorbers, and benzotriazole UV absorbers in an amount of 0.1 to 2.0% by weight based on the polymer component The polyester film according to claim 14.
The polyester film according to any one of claims 1 to 15, which is used as a solar cell back sheet or a motor insulating film.
A method for producing a polyester film according to any one of claims 1 to 16,
The manufacturing method of the polyester film which biaxially stretches this precursor film, after manufacturing the precursor film containing the said polyester resin.