JP5471451B2 - Easy-adhesive white polyester film for solar cells - Google Patents

Description

  The present invention relates to an easily adhesive white polyester film for solar cells and a backsheet using the same. Specifically, when it is used for a solar cell backsheet, it is not only excellent in hydrolysis resistance and long-term thermal stability, but also when used on the surface of the solar cell backsheet in contact with the sealant, it is high temperature and humidity. The present invention also relates to a white polyester film excellent in adhesion with a sealant and a back sheet using the same.

  In recent years, solar cells have attracted attention as an energy means to replace petroleum energy that causes global warming, and the demand for solar cells has increased. A solar cell is a solar power generation system that directly converts solar energy into electricity. As a solar cell element, semiconductors such as single crystal silicon, polycrystalline silicon, and amorphous silicon, compound-based materials, and organic dyes are used. Yes. Recently, the ratio of thin-film solar cell elements in which the thickness of silicon is reduced in order to reduce raw materials, energy required for production, and costs has been increasing. In order to protect such elements over a long period of time (approximately 20 years or more), such a solar cell element is generally wired in series or in parallel with several to several tens of solar cell elements. Done and unitized. A unit incorporated in this package is called a solar cell module.

  Here, a solar cell module generally covers a surface to which sunlight is applied with glass, fills a gap with a sealing material for a solar electronic element, and has a plurality of layers such as a heat-resistant and weather-resistant plastic material called a back sheet on the back surface. It is the structure protected by the protective sheet which consists of a structure. As a sealing material filling the solar cell element, an olefin resin such as ethylene / vinyl acetate copolymer resin (hereinafter EVA) or polyvinyl butyral resin (hereinafter PVB) is used. Using these sealing materials, a module is produced by superposing the glass substrate / sealing material / solar cell element / sealing material / back sheet and then heat-pressing with a vacuum laminator or the like. The sealing material has a role of adhering and fixing the solar cell element, preventing moisture from entering from the outside, and protecting the solar cell element.

  As a solar cell backsheet, from the solar cell element side (encapsulant side) to polyester film / adhesive / polyester film (colored) / metal or metal oxide thin film layer (moisture-proof layer) / adhesive / fluorine Those having a laminated structure such as a film (antifouling layer) have been proposed. In particular, for the purpose of improving the photoelectric conversion efficiency, in order to reflect and efficiently absorb the light transmitted through the solar cell element (particularly, the thin film solar cell element), the solar cell element side (sealing material side) A white polyester film may be employed as the polyester film (Patent Document 1). Such a back sheet has a role of protecting the solar cell element from external moisture and contamination over a long period of time. Therefore, the durability of the polyester film used for the solar cell backsheet is important. In particular, in the polyester film on the solar cell element side that is in direct contact with the sealing material, the adhesion with the sealing material is also important. However, a surface-untreated polyester film cannot obtain sufficient adhesiveness with a sealing material and is required to be improved. As a method for improving the adhesion of the polyester film, it has been proposed to provide an adhesive layer containing a resin or a crosslinking agent (Patent Documents 2 to 5).

JP 2009-182188 A JP 2006-152013 A JP 2006-320991 A JP 2007-48944 A JP 2007-136911 A

  By using a white polyester film as described above, it is possible to reflect sunlight and increase power generation efficiency. On the other hand, a solar cell module used outdoors under severe environmental conditions is expected to have a long life of 20 years or more. However, a white polyester film requires a large amount of particles to be added to a polyester base material. Therefore, in order to improve the dispersibility and mixing state thereof, a raw material is prepared by premixing two or more kinds of materials. In addition, the resin tends to deteriorate due to a large heat history due to a long melting time in the normal extrusion process, etc., and there is a problem that the durability is poor when used as a solar cell under high temperature and high humidity Met.

  In recent years, solar cells have been developed from conventional rooftops to installation in large-scale solar power plants such as desert areas. In such an environment, the sunshine time is long, and it is exposed to high temperatures for a long time. Furthermore, the solar cell module has been increased in size and output, and a temperature increase due to the increase in size and a temperature increase in the electrode / connector part due to the increase in output have occurred. In such a situation where long-term thermal stability is increasingly required, it has been considered that sufficient durability cannot be achieved only by improvement by conventional hydrolysis resistance.

  Furthermore, with the progress of thinning of solar cell elements, sunlight easily passes through the silicon thin film and reaches the back sheet directly. Therefore, depending on the application, the backsheet is becoming a problem of decomposition and deterioration due to light irradiation. In addition, in a large-scale photovoltaic power generation system, a vast solar cell module is installed, so that depending on the application, the backsheet may be decomposed and deteriorated due to reflection from the ground.

  Furthermore, not only the initial adhesiveness but also the adhesive property for a long period of time under high temperature and high humidity in the sealing material easy-adhesive film used as a member on the solar cell element side that is in direct contact with the sealing material. Was considered necessary. However, the easy-adhesive polyester film for solar cells as disclosed in the above patent document still has insufficient adhesiveness, and a decrease in adhesive strength is unavoidable particularly in long-term use under high temperature and high humidity. It was a thing.

  In addition, various composition types including additives such as a crosslinking agent and an ultraviolet absorber have come to be used for the sealing material from the viewpoint of improving productivity and preventing deterioration. Therefore, there is a demand for a highly versatile and easy-to-adhere film that exhibits the same degree of adhesion to various sealing materials.

  In view of the above problems, the present invention has good hydrolysis resistance and long-term thermal stability under high temperature and high humidity, and excellent durability even under light irradiation, and can withstand harsh environments. Easily for solar cells that have strong adhesiveness, hardly cause deterioration of adhesiveness under high temperature and high humidity, which has been considered inevitable in the past, and has good adhesiveness to various sealing materials An adhesive white polyester film is provided.

  As a result of intensive studies to solve the above problems, the present inventor has detected and identified that the polyester catalyst type used for the film substrate has an influence on the thermal deterioration in the polyester film having the coating layer on at least one side. By using a polyester polyester film polymerized with a polymerization catalyst, and by using a specific coating layer, it exhibits excellent hydrolysis resistance and outstanding long-term thermal stability as a polyester film for solar cells. The inventor has found a surprising effect that it exhibits strong adhesiveness that can withstand even in an environment, and also exhibits excellent adhesiveness even under high temperature and high humidity.

The above-described problem can be achieved by the following solution means.
Polyester polymerized using a polycondensation catalyst containing aluminum and / or a compound thereof and a phosphorus compound having an aromatic group in the molecule is a main constituent, the whiteness is 50 or more, and the average particle size is 0. A white polyester film containing 3 to 50% by weight of fine particles of 1 to 3 μm, an acid value of the film of 1 (eq / ton) to 30 (eq / ton) and a thickness of 20 to 500 μm; The main component is a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and the infrared spectrum of the coating layer has an absorbance around 1460 cm ⁻¹ derived from an aliphatic polycarbonate component (A ₁₄₆₀ ) and 1530 cm ⁻¹ derived from a urethane component. Coating having a ratio (A ₁₄₆₀ / A ₁₅₃₀ ) to the absorbance (A ₁₅₃₀ ) in the vicinity of 0.70 to 1.60 An easily adhesive white polyester film for solar cells having a layer.

  In the easily adhesive white polyester film for solar cells of the present invention, the adhesive layer exhibits strong adhesiveness, and is particularly excellent in adhesiveness (humidity heat resistance) under high temperature and high humidity. Moreover, the white polyester film layer of the substrate has light reflection efficiency and excellent durability under high temperature and high humidity, and further has long-term thermal stability. In addition to the above properties, it also has excellent durability under light irradiation. Therefore, as a preferred embodiment of the present invention, when the easily adhesive white polyester film for solar cells of the present invention is used as a member of a back sheet, not only the adhesiveness with a sealing material is good, but also high temperature and high humidity. In processing, both the adhesion and the mechanical properties of the film are kept high and are therefore useful in solar cells.

(White polyester film)
The polycondensation catalyst used when polymerizing the polyester which is the main constituent of the polyester film for solar cells of the present invention is a catalyst containing aluminum and / or a compound thereof and a phosphorus compound having an aromatic group in the molecule, A catalyst containing an aluminum salt of a phosphorus compound, or a catalyst containing at least one selected from the compounds represented by the general formula (5).

  As said aluminum and / or an aluminum compound, a well-known aluminum compound other than metallic aluminum can be used without limitation.

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

  The addition amount of the aluminum and / or aluminum compound is preferably 0.001 to 0.05 mol% with respect to the number of moles of all constituent units of the carboxylic acid component such as dicarboxylic acid or polycarboxylic acid of the obtained polyester. More preferably, it is 0.005-0.02 mol%. If the addition amount is less than 0.001 mol%, the catalytic activity may not be sufficiently exerted. If the addition amount is 0.05 mol% or more, the thermal stability or thermal oxidation stability is deteriorated, resulting from aluminum. Occurrence of foreign matters or increased coloring may be a problem. As described above, the polymerization catalyst of the present invention has a great feature in that it exhibits a sufficient catalytic activity even when the addition amount of the aluminum component is small. As a result, thermal stability and thermal oxidation stability are excellent, and foreign matters and coloring caused by aluminum can be reduced.

  Although it does not specifically limit as a phosphorus compound which comprises the said polycondensation catalyst, When the 1 type, or 2 or more types of compound chosen from the group which consists of a phosphonic acid type compound and a phosphinic acid type compound is used, the improvement effect of a catalyst activity is large and preferable. . Among these, when one or two or more phosphonic acid compounds are used, the effect of improving the catalytic activity is particularly large and preferable.

  The phosphonic acid-based compound and the phosphinic acid-based compound are compounds having structures represented by the following formulas (6) and (7), respectively.

  Examples of the phosphonic acid compounds include dimethyl methylphosphonate, diphenyl methylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, dimethyl benzylphosphonate, diethyl benzylphosphonate, and the like.

  Examples of the phosphinic acid-based compound include diphenylphosphinic acid, methyl diphenylphosphinate, phenyl diphenylphosphinate, phenylphosphinic acid, methyl phenylphosphinate, and phenylphenylphosphinate.

  As the phosphinic acid compound, compounds represented by the following formulas (8) and (9) are preferably used.

  In the polycondensation catalyst of the present invention, among the above phosphorus compounds, it is necessary to use a compound having an aromatic ring structure in the molecule in order to obtain sufficient catalytic activity.

  Moreover, as a phosphorus compound which comprises the said polycondensation catalyst, when the compound represented by following General formula (10)-(11) is used, especially the improvement effect of a catalyst activity is large and preferable.

(In formulas (10) to (11), R ¹ and R ⁴ are each independently hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and having 1 to 50 carbon atoms. R ² and R ³ each independently represent hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a hydroxyl group or an alkoxyl group, provided that each hydrocarbon group is a hydrocarbon group; May contain an alicyclic structure such as cyclohexyl or an aromatic ring structure such as phenyl or naphthyl.)

As a phosphorus compound which comprises the said polycondensation catalyst, the compound whose R < ¹ >, R < ⁴ > is group which has an aromatic ring structure in said formula (10)-(11) is especially preferable.

  Examples of the phosphorus compound constituting the polycondensation catalyst include, for example, dimethyl methylphosphonate, diphenyl methylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, dimethyl phosphophosphonate, diethyl benzylphosphonate, and diphenylphosphine. Examples include acid, methyl diphenylphosphinate, phenyl diphenylphosphinate, phenylphosphinic acid, methyl phenylphosphinate, and phenylphenylphosphinate. Of these, dimethyl phenylphosphonate and diethyl benzylphosphonate are particularly preferred.

The amount of the phosphorus compound added is preferably 5 × 10 ^{−7 to} 0.01 mol based on the number of moles of all constituent units of the carboxylic acid component such as dicarboxylic acid and polyvalent carboxylic acid of the polyester obtained. Preferably it is 1 * 10 < ^-6 > -0.005 mol.

  The phosphorus compound having a phenol part constituting the polycondensation catalyst in the same molecule is not particularly limited as long as it is a phosphorus compound having a phenol structure, but a phosphonic acid compound having a phenol part in the same molecule, When one or two or more compounds selected from the group consisting of phosphinic acid compounds are used, the effect of improving the catalytic activity is greatly preferred. Among these, when a phosphonic acid compound having one or two or more phenol moieties in the same molecule is used, the effect of improving the catalytic activity is particularly large and preferable.

  Moreover, as a phosphorus compound which has the phenol part which comprises the said polycondensation catalyst in the same molecule, the compound etc. which are represented with following General formula (12), (13) are mentioned. Among these, it is particularly preferable to use the following formula because catalytic activity is improved.

(In the formulas (12) to (13), R1 is a hydrocarbon group having 1 to 50 carbon atoms containing a phenol part, a substituent such as a hydroxyl group, a halogen group, an alkoxyl group or an amino group, and a carbon number 1 to 1 containing a phenol part. Each represents a hydrocarbon group having 50. R ⁴ independently represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms containing a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. R ² and R ³ each independently represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a substituent such as a hydroxyl group or an alkoxyl group. The hydrogen group may have a branched structure or the ends of cyclo R ² and R ⁴ may be bonded to each other.)

  Examples of the phosphorus compound having the phenol moiety in the same molecule include p-hydroxyphenylphosphonic acid, dimethyl p-hydroxyphenylphosphonate, diethyl p-hydroxyphenylphosphonate, diphenyl p-hydroxyphenylphosphonate, bis ( p-hydroxyphenyl) phosphinic acid, methyl bis (p-hydroxyphenyl) phosphinate, phenyl bis (p-hydroxyphenyl) phosphinate, p-hydroxyphenylphenylphosphinic acid, methyl p-hydroxyphenylphenylphosphinate, p-hydroxy Phenylphenylphosphinic acid phenyl, p-hydroxyphenylphosphinic acid, p-hydroxyphenylphosphinic acid methyl, p-hydroxyphenylphosphinic acid phenyl and the following formulas (14) to (1) A compound represented by), and the like. Among these, a compound represented by the following formula (16) and dimethyl p-hydroxyphenylphosphonate are particularly preferable.

  As the compound represented by the above formula (16), for example, SANKO-220 (manufactured by Sanko Co., Ltd.) can be used.

  By adding a phosphorus compound having these phenol moieties in the same molecule during the polymerization of the polyester, the catalytic activity of the aluminum compound is improved and the thermal stability of the polymerized polyester is also improved.

As the addition amount of the phosphorus compound having the phenol part in the same molecule, 5 × 10 ⁻⁷ to the number of moles of all constituent units of the carboxylic acid component such as dicarboxylic acid and polycarboxylic acid of the obtained polyester 0.01 mol is preferable, and more preferably 1 × 10 ^{−6 to} 0.005 mol.

  Moreover, it is preferable to use a metal salt compound of phosphorus as the phosphorus compound. The phosphorus metal salt compound is not particularly limited as long as it is a metal salt of a phosphorus compound. However, it is preferable to use a metal salt of a phosphonic acid compound because of its large effect of improving the catalytic activity. Examples of the metal salt of the phosphorus compound include a monometal salt, a dimetal salt, and a trimetal salt.

  Further, among the above phosphorus compounds, when the metal part of the metal salt is selected from Li, Na, K, Be, Mg, Sr, Ba, Mn, Ni, Cu, Zn, the catalytic activity is improved. The effect is large and preferable. Of these, Li, Na, and Mg are particularly preferable.

  When at least one selected from the compounds represented by the following general formula (18) is used as the phosphorus metal salt compound, the effect of improving the catalytic activity is greatly preferred.

(In formula (18), R ¹ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms. R ² represents Represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group, and a hydrocarbon group having 1 to 50 carbon atoms, wherein R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. Or a hydrocarbon group having 1 to 50 carbon atoms including carbonyl, l is an integer of 1 or more, m is 0 or an integer of 1 or more, (l + m) is 4 or less, and M is a (l + m) valence. Represents a metal cation, n represents an integer of 1 or more, and the hydrocarbon group may contain an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl.

Examples of R ¹ include phenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 4-biphenyl, 2-biphenyl, and the like. Examples of R ² include hydrogen, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, long-chain aliphatic group, phenyl group, naphthyl group, Examples thereof include a substituted phenyl group, a naphthyl group, and a group represented by —CH ₂ CH ₂ OH. Examples of R ³ O ⁻ include hydroxide ions, alcoholate ions, acetate ions, and acetylacetone ions.

  Among the compounds represented by the general formula (18), it is preferable to use at least one selected from the compounds represented by the following general formula (19).

(In formula (19), R ¹ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms. R ³ represents Hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group, or a hydrocarbon group having 1 to 50 carbon atoms including carbonyl, l is an integer of 1 or more, m is 0 or an integer of 1 or more, (L + m) is 4 or less, M represents a (l + m) -valent metal cation, and the hydrocarbon group may contain an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl. )

Examples of R ¹ include phenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 4-biphenyl, 2-biphenyl, and the like. Examples of R ³ O ⁻ include hydroxide ions, alcoholate ions, acetate ions, and acetylacetone ions.

  Among the above phosphorus compounds, the use of a compound having an aromatic ring structure is preferable because the effect of improving the catalytic activity is great.

  Among the above formulas (19), when M is selected from Li, Na, K, Be, Mg, Sr, Ba, Mn, Ni, Cu, and Zn, the effect of improving the catalytic activity is greatly preferred. Of these, Li, Na, and Mg are particularly preferable.

  Examples of the metal salt compound of phosphorus include lithium [ethyl (1-naphthyl) methylphosphonate], sodium [ethyl (1-naphthyl) methylphosphonate], magnesium bis [ethyl (1-naphthyl) methylphosphonate], potassium [( 2-naphthyl) methylphosphonic acid ethyl], magnesium bis [(2-naphthyl) methylphosphonic acid ethyl], lithium [benzylphosphonic acid ethyl], sodium [benzylphosphonic acid ethyl], magnesium bis [benzylphosphonic acid ethyl], beryllium bis [ Benzyl phosphonate], strontium bis [benzyl phosphonate], manganese bis [benzyl phosphonate], sodium benzyl phosphonate, magnesium bis [benzyl phosphonate], sodium [(9-anthry ) Ethyl methylphosphonate], magnesium bis [(9-anthryl) methylphosphonate ethyl], sodium [ethyl 4-hydroxybenzylphosphonate], magnesium bis [4-hydroxybenzylphosphonate ethyl], sodium [4-chlorobenzylphosphonic acid] Phenyl], magnesium bis [ethyl 4-chlorobenzylphosphonate], sodium [methyl 4-aminobenzylphosphonate], magnesium bis [methyl 4-aminobenzylphosphonate], sodium phenylphosphonate, magnesium bis [ethyl phenylphosphonate] ], Zinc bis [ethyl phenylphosphonate] and the like.

  Among these, lithium [ethyl (1-naphthyl) methylphosphonate], sodium [ethyl (1-naphthyl) methylphosphonate], magnesium bis [ethyl (1-naphthyl) methylphosphonate], lithium [ethyl benzylphosphonate], Sodium [ethyl benzylphosphonate], magnesium bis [ethyl benzylphosphonate], sodium benzylphosphonate, magnesium bis [benzylphosphonic acid] are particularly preferred.

  The metal salt compound of phosphorus which is another preferable phosphorus compound constituting the polycondensation catalyst is composed of at least one selected from the compounds represented by the following general formula (20).

(In Formula (20), R ¹ and R ² each independently represent hydrogen and a hydrocarbon group having 1 to 30 carbon atoms. R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. R ⁴ represents a hydrocarbon group having 1 to 50 carbon atoms, including hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, an alkoxyl group, or a carbonyl group. Examples of R ⁴ O ⁻ include hydroxide ion, alcoholate ion, acetate ion, acetylacetone ion, etc. l represents an integer of 1 or more, m represents 0 or an integer of 1 or more, and (l + m) represents 4 or less. M represents a (l + m) -valent metal cation, n represents an integer of 1 or more, and the hydrocarbon group contains an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl. Moyo .)

  Among these, it is preferable to use at least one selected from compounds represented by the following general formula (21).

(In formula (21), M ^{n +} represents an n-valent metal cation. N represents 1, 2, 3 or 4.)

  Among the above formulas (20) or (21), when M is selected from Li, Na, K, Be, Mg, Sr, Ba, Mn, Ni, Cu, Zn, the effect of improving the catalytic activity is obtained. Largely preferred. Of these, Li, Na, and Mg are particularly preferable.

  Examples of the metal salt compound of the specific phosphorus include lithium [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate], sodium [3,5-di-tert-butyl-4-hydroxybenzylphosphone]. Ethyl], sodium [3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid], potassium [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid], magnesium bis [3, 5-di-tert-butyl-4-hydroxybenzylphosphonic acid ethyl], magnesium bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid], beryllium bis [3,5-di-tert-butyl -Methyl 4-hydroxybenzylphosphonate], strontium bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl], barium bis [3,5-di-tert-butyl] -Phenyl-4-hydroxybenzylphosphonate], manganese bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonate ethyl], nickel bis [3,5-di-tert-butyl-4-hydroxybenzylphosphone] Ethyl acrylate], copper bis [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate], zinc bis [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate] and the like. It is done. Among these, lithium [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate], sodium [ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate], magnesium bis [ Ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate] is particularly preferred.

  Another embodiment of the present invention is a polyester polymerization catalyst comprising at least one selected from aluminum salts of phosphorus compounds. You may use combining the aluminum salt of a phosphorus compound with another aluminum compound, a phosphorus compound, a phenol type compound, etc.

  The aluminum salt of the phosphorus compound, which is a preferred component constituting the polycondensation catalyst, is not particularly limited as long as it is a phosphorus compound having an aluminum part, but the use of an aluminum salt of a phosphonic acid compound improves the catalytic activity. Is preferable. Examples of the aluminum salt of the phosphorus compound include a monoaluminum salt, a dialuminum salt, and a trialuminum salt.

  Among the aluminum salts of the phosphorus compounds, the use of a compound having an aromatic ring structure is preferable because the effect of improving the catalytic activity is great.

  As the aluminum salt of the phosphorus compound constituting the polymerization catalyst, at least one selected from the compounds represented by the following general formula (34) is preferably used because the effect of improving the catalytic activity is great.

(In formula (22), R ¹ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms. R ² represents Represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group, and a hydrocarbon group having 1 to 50 carbon atoms, wherein R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. Or it represents a C1-C50 hydrocarbon group containing carbonyl, l represents an integer of 1 or more, m represents 0 or an integer of 1 or more, and (l + m) represents 3. n represents an integer of 1 or more. The hydrocarbon group may contain an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl.)

Examples of R ¹ include phenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 4-biphenyl, 2-biphenyl, and the like. Examples of R ² include hydrogen, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, long-chain aliphatic group, phenyl group, naphthyl group, Examples thereof include a substituted phenyl group, a naphthyl group, and a group represented by —CH ₂ CH ₂ OH. Examples of R ³ O ⁻ include hydroxide ions, alcoholate ions, ethylene glycolate ions, acetate ions, and acetylacetone ions.

  Examples of the aluminum salt of the phosphorus compound include an aluminum salt of ethyl (1-naphthyl) methylphosphonate, an aluminum salt of (1-naphthyl) methylphosphonic acid, an aluminum salt of ethyl (2-naphthyl) methylphosphonate, and an ethyl benzylphosphonate. Aluminum salt, aluminum salt of benzylphosphonic acid, aluminum salt of ethyl (9-anthryl) methylphosphonate, aluminum salt of ethyl 4-hydroxybenzylphosphonate, aluminum salt of ethyl 2-methylbenzylphosphonate, 4-chlorobenzylphosphonic acid Examples thereof include an aluminum salt of phenyl, an aluminum salt of methyl 4-aminobenzylphosphonate, an aluminum salt of ethyl 4-methoxybenzylphosphonate, and an aluminum salt of ethyl phenylphosphonate.

  Among these, an aluminum salt of ethyl (1-naphthyl) methylphosphonate and an aluminum salt of ethyl benzylphosphonate are particularly preferable.

  Another embodiment is a polyester polymerization catalyst comprising at least one selected from aluminum salts of phosphorus compounds represented by the following general formula (23). The aluminum salt of the phosphorus compound may be used in combination with other aluminum compounds, phosphorus compounds, phenolic compounds, and the like.

(In formula (23), R ¹ and R ² each independently represent hydrogen and a hydrocarbon group having 1 to 30 carbon atoms. R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. R ⁴ represents a hydrocarbon group having 1 to 50 carbon atoms, including hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, an alkoxyl group, or a carbonyl group. l represents an integer of 1 or more, m represents 0 or an integer of 1 or more, and (l + m) represents 3. n represents an integer of 1 or more, and the hydrocarbon group is an alicyclic structure such as cyclohexyl, a branched structure, or phenyl. Or may contain an aromatic ring structure such as naphthyl.)

  Among these, it is preferable to use at least one selected from compounds represented by the following general formula (24).

(In the formula (24), R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a hydroxyl group or an alkoxyl group. R ⁴ represents hydrogen and 1 carbon atom. Represents a hydrocarbon group having 1 to 50 carbon atoms, including 1 to 50 hydrocarbon group, hydroxyl group or alkoxyl group, or carbonyl, l represents an integer of 1 or more, m represents 0 or an integer of 1 or more, and (l + m) represents 3 The hydrocarbon group may contain an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl.)

Examples of R ³ include hydrogen, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, long-chain aliphatic group, phenyl group, and naphthyl group. A substituted phenyl group, a naphthyl group, a group represented by —CH ₂ CH ₂ OH, and the like. Examples of R ⁴ O ⁻ include hydroxide ions, alcoholate ions, ethylene glycolate ions, acetate ions, and acetylacetone ions.

  Examples of the aluminum salt of the phosphorus compound include aluminum salt of ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, aluminum of methyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate. Salt, aluminum salt of isopropyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, aluminum salt of phenyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 3,5-di- Examples thereof include an aluminum salt of tert-butyl-4-hydroxybenzylphosphonic acid.

  Among these, an aluminum salt of ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate and an aluminum salt of methyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate are particularly preferable.

  Moreover, it is preferable to use a phosphorus compound having at least one P—OH bond as the phosphorus compound. The phosphorus compound having at least one P—OH bond is not particularly limited as long as it is a phosphorus compound having at least one P—OH in the molecule. Among these phosphorus compounds, the use of a phosphonic acid compound having at least one P—OH bond is preferable because the effect of improving the catalytic activity is great.

  Among the above phosphorus compounds, the use of a compound having an aromatic ring structure is preferable because the effect of improving the catalytic activity is great.

  When the phosphorus compound having at least one P—OH bond constituting the polycondensation catalyst is at least one selected from compounds represented by the following general formula (25), the effect of improving the catalytic activity is greatly preferred. .

(In formula (25), R ¹ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms. R ² represents Represents a hydrocarbon group having 1 to 50 carbon atoms including hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group, n represents an integer of 1 or more, and the hydrocarbon group represents an alicyclic structure such as cyclohexyl, It may contain a branched structure or an aromatic ring structure such as phenyl or naphthyl.)

Examples of R ¹ include phenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 4-biphenyl, 2-biphenyl, and the like. Examples of R ² include hydrogen, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, long-chain aliphatic group, phenyl group, naphthyl group, Examples thereof include a substituted phenyl group, a naphthyl group, and a group represented by —CH ₂ CH ₂ OH.

  Among the above phosphorus compounds, the use of a compound having an aromatic ring structure is preferable because the effect of improving the catalytic activity is great.

  Examples of phosphorus compounds having at least one P-OH bond include ethyl (1-naphthyl) methylphosphonate, (1-naphthyl) methylphosphonic acid, ethyl (2-naphthyl) methylphosphonate, ethyl benzylphosphonate, benzylphosphonic acid, 9-anthryl) ethyl methylphosphonate, ethyl 4-hydroxybenzylphosphonate, ethyl 2-methylbenzylphosphonate, phenyl 4-chlorobenzylphosphonate, methyl 4-aminobenzylphosphonate, ethyl 4-methoxybenzylphosphonate, etc. It is done. Of these, ethyl (1-naphthyl) methylphosphonate and ethyl benzylphosphonate are particularly preferred.

  A preferable phosphorus compound includes a specific phosphorus compound having at least one P-OH bond. The specific phosphorus compound having at least one P—OH bond, which is a preferable phosphorus compound constituting the polycondensation catalyst, means at least one compound selected from the compounds represented by the following general formula (26). To do.

(In formula (26), R ¹ and R ² each independently represent hydrogen and a hydrocarbon group having 1 to 30 carbon atoms. R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. And n represents an integer of 1 or more, even if the hydrocarbon group contains an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl. Good.)

  Among these, it is preferable to use at least one selected from compounds represented by the following general formula (27).

(In formula (27), R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a hydroxyl group or an alkoxyl group. The hydrocarbon group is an alicyclic ring such as cyclohexyl. It may contain a structure, a branched structure, or an aromatic ring structure such as phenyl or naphthyl.)

Examples of R ³ include hydrogen, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, long-chain aliphatic group, phenyl group, and naphthyl group. A substituted phenyl group, a naphthyl group, a group represented by —CH ₂ CH ₂ OH, and the like.

  Specific phosphorus compounds having at least one P—OH bond include ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 3,5-di-tert-butyl-4-hydroxybenzyl. Methyl phosphonate, isopropyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, phenyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 3,5-di-tert-butyl- Examples include octadecyl 4-hydroxybenzylphosphonate, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, and the like. Of these, ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate and methyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate are particularly preferred.

  A preferable phosphorus compound includes a phosphorus compound represented by the chemical formula (28).

(In the formula (28), R ¹ represents a hydrocarbon group having ¹ to 49 carbon atoms, or a hydrocarbon group having ¹ to 49 carbon atoms including a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and R ² , R ³ Each independently represents a hydrocarbon group having 1 to 50 carbon atoms including hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group, and the hydrocarbon group includes an alicyclic structure, a branched structure or an aromatic ring structure. You may go out.)

More preferably, at least one of R ¹ , R ² and R ^{3 in} the chemical formula (28) is a compound containing an aromatic ring structure.

  Specific examples of the phosphorus compound are shown below.

  The phosphorus compound having a large molecular weight is more preferable because it is less likely to be distilled off during polymerization.

  Another phosphorus compound that is preferably used as the polycondensation catalyst is at least one phosphorus compound selected from compounds represented by the following general formula (35).

(In the above formula (35), R ¹ and R ² each independently represent hydrogen and a hydrocarbon group having 1 to 30 carbon atoms. R ³ and R ⁴ are each independently hydrogen and hydrocarbon having 1 to 50 carbon atoms. Represents a hydrocarbon group having 1 to 50 carbon atoms including a group, a hydroxyl group or an alkoxyl group, n represents an integer of 1 or more, and the hydrocarbon group represents an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring such as phenyl or naphthyl. May contain structure.)

  Among the general formula (35), it is preferable to use at least one selected from the compounds represented by the following general formula (36) because the effect of improving the catalytic activity is high.

(In said formula (36), R < ³ >, R < ⁴ > represents a C1-C50 hydrocarbon group containing hydrogen, a C1-C50 hydrocarbon group, a hydroxyl group, or an alkoxyl group each independently. Hydrocarbon group. May contain an alicyclic structure such as cyclohexyl, a branched structure, or an aromatic ring structure such as phenyl or naphthyl.)

Examples of R ³ and R ⁴ include short chain aliphatic groups such as hydrogen, methyl and butyl groups, long chain aliphatic groups such as octadecyl, phenyl groups, naphthyl groups, substituted phenyl groups and naphthyl groups. An aromatic group such as a group, a group represented by —CH ₂ CH ₂ OH, and the like.

  Examples of the specific phosphorus compound include diisopropyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, di-n-butyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 3 , 5-di-tert-butyl-4-hydroxybenzylphosphonate dioctadecyl, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate diphenyl, and the like.

  Of these, dioctadecyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate and diphenyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate are particularly preferred.

  Another phosphorus compound that is preferably used as the polycondensation catalyst is at least one phosphorus compound selected from the compounds represented by chemical formula (37) and chemical formula (38).

  As the compound represented by the chemical formula (37), Irganox 1222 (manufactured by Ciba Specialty Chemicals) is commercially available. Moreover, Irganox1425 (made by Ciba Specialty Chemicals) is marketed as a compound shown by Chemical formula (38).

  Phosphorus compounds are generally well known as antioxidants, but it is not known that melt polymerization is greatly promoted when these phosphorus compounds are used in combination with conventional metal-containing polyester polymerization catalysts. Actually, even when a phosphorus compound is added to melt-polymerize polyester using a polymerization catalyst of an antimony compound, titanium compound, tin compound or germanium compound, which is a typical catalyst for polyester polymerization, to a substantially useful level. It is not observed that polymerization is accelerated.

  That is, by using the phosphorus compound in combination, a sufficient catalytic effect can be exhibited even if the content of aluminum in the polyester polymerization catalyst is small.

  The addition amount of the phosphorus compound is preferably 0.0001 to 0.1 mol%, preferably 0.005 to 0.05 mol%, based on the number of moles of all the structural units of the dicarboxylic acid component constituting the polyester. More preferably. When the addition amount of the phosphorus compound is less than 0.0001 mol%, the addition effect may not be exhibited. On the other hand, if added over 0.1 mol%, the catalytic activity as a polyester polymerization catalyst may be reduced. Further, the tendency of the change varies depending on the amount of aluminum added.

  By using aluminum compound as the main catalyst component without using a phosphorus compound, reducing the amount of aluminum compound added, and adding a cobalt compound, coloring due to a decrease in thermal stability when using an aluminum compound as the main catalyst Although it has been studied to prevent the thermal stability, the addition of the cobalt compound to the extent that it has sufficient catalytic activity also reduces the thermal stability. Therefore, it is difficult to make both compatible with this technique.

  By using the phosphorus compound having the above specific chemical structure, polycondensation does not cause problems such as deterioration of thermal stability and generation of foreign matter, and has a sufficient catalytic effect even if the addition amount of the metal-containing component as aluminum is small. A catalyst is obtained, and the thermal stability of the polyester film after melt molding is improved by using the polyester polymerized by the polycondensation catalyst.

  Moreover, even if it replaces with the said phosphorus compound and phosphoric acid esters, such as phosphoric acid and a trimethyl phosphoric acid, are added, the said addition effect is not seen. Furthermore, even if the above phosphorus compound is used in combination with a metal-containing polyester polycondensation catalyst such as a conventional antimony compound, titanium compound, tin compound, and germanium compound within the range of the preferable addition amount, the melt polymerization reaction is promoted. The effect is not recognized.

  On the other hand, in the present invention, in addition to aluminum or its compound, a small amount of alkali metal, alkaline earth metal and at least one selected from the compound may coexist as the second metal-containing component. The coexistence of such a second metal-containing component in the catalyst system is effective in improving productivity by obtaining a catalyst component having an increased reaction rate in addition to an effect of suppressing the formation of diethylene glycol, and thus a higher reaction rate. .

  A technique of adding an alkali metal compound or an alkaline earth metal compound to an aluminum compound to obtain a catalyst having sufficient catalytic activity is known. When such a known catalyst is used, a polyester having excellent thermal stability can be obtained. However, when a known catalyst using an alkali metal compound or an alkaline earth metal compound is used to obtain a practical catalytic activity, the amount of catalyst added Need to be more.

  When an alkali metal compound is used in combination, the amount of foreign matters resulting therefrom increases, and the frequency of filter replacement tends to be shortened or film defects tend to increase in the melt extrusion process during film production.

  In addition, when an alkaline earth metal compound is used in combination, when the practical activity is obtained, the thermal stability and thermal oxidation stability of the obtained polyester is lowered, coloring due to heating is large, and foreign matter is generated. The amount also increases.

When an alkali metal, an alkaline earth metal, or a compound thereof is added, the addition amount M (mol%) is 1 × 10 ⁻⁶ or more and 0 with respect to the number of moles of all polycarboxylic acid units constituting the polyester. It is preferably less than 1 mol%, more preferably 5 × 10 ^{−6 to} 0.05 mol%, still more preferably 1 × 10 ^{−5 to} 0.03 mol%, and particularly preferably 1 * 10 < ^-5 > -0.01 mol%.

  That is, since the amount of alkali metal or alkaline earth metal added is small, the reaction rate can be increased without causing problems such as a decrease in thermal stability, generation of foreign matter, and coloring. In addition, problems such as degradation of hydrolysis resistance do not occur.

When the added amount M of an alkali metal, alkaline earth metal, or compound thereof is 0.1 mol% or more, there are problems in product processing such as a decrease in thermal stability, an increase in foreign matter generation and coloring, and a decrease in hydrolysis resistance. The case that becomes. If M is less than 1 × 10 ⁻⁶ mol%, the effect is not clear even if it is added.

  The alkali metal or alkaline earth metal constituting the second metal-containing component preferably used in addition to the aluminum or a compound thereof includes Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba Is preferably at least one selected from the group consisting of alkali metals and compounds thereof.

  When an alkali metal or a compound thereof is used, Li, Na, and K are particularly preferable as the alkali metal. Examples of the alkali metal and alkaline earth metal compounds include saturated aliphatic carboxylates such as formic acid, acetic acid, propionic acid, butyric acid, and succinic acid, and unsaturated aliphatic carboxylates such as acrylic acid and methacrylic acid. , Aromatic carboxylates such as benzoic acid, halogen-containing carboxylates such as trichloroacetic acid, hydroxycarboxylates such as lactic acid, citric acid and salicylic acid, carbonic acid, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen carbonate, phosphorus Inorganic acid salts such as acid hydrogen, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid and bromic acid, and organic sulfonates such as 1-propanesulfonic acid, 1-pentanesulfonic acid and naphthalenesulfonic acid , Organic sulfates such as lauryl sulfate, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert-butyl Alkoxides such as alkoxy, chelate compounds and the like acetylacetonate, hydrides, oxides, and hydroxides and the like.

  Among these alkali metals, alkaline earth metals or their compounds, when using strongly alkaline substances such as hydroxides, these tend to be difficult to dissolve in diols such as ethylene glycol or organic solvents such as alcohols. The solution must be added to the polymerization system in an aqueous solution, which may cause a problem in the polymerization process.

  Furthermore, when using strongly alkaline substances such as hydroxides, the polyester is liable to undergo side reactions such as hydrolysis during polymerization, and the polymerized polyester tends to be colored, and the hydrolysis resistance also decreases. Tend to.

  Accordingly, the alkali metal or the compound thereof, the alkaline earth metal or the compound thereof is preferably a saturated aliphatic carboxylate, unsaturated aliphatic carboxylate or aromatic carboxylate of the alkali metal or alkaline earth metal. , Halogen-containing carboxylate, hydroxycarboxylate, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen phosphate, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid, bromic acid Acid salts, organic sulfonates, organic sulfates, chelate compounds, and oxides. Among these, from the viewpoint of ease of handling, availability, and the like, it is preferable to use an alkali metal or alkaline earth metal saturated aliphatic carboxylate, particularly acetate.

  The polyester catalyst used in the present invention has catalytic activity not only in the polymerization reaction but also in the esterification reaction and transesterification reaction. For example, polymerization by an ester exchange reaction between an alkyl ester of a dicarboxylic acid such as dimethyl terephthalate and a glycol such as ethylene glycol is usually carried out in the presence of an ester exchange catalyst such as a titanium compound or a zinc compound. Instead, the catalyst described in the claims of the present invention can be used together with these catalysts. The catalyst has catalytic activity not only in melt polymerization but also in solid phase polymerization or solution polymerization, and it is possible to produce a polyester suitable for producing a polyester film by any method. In particular, in the present invention, it is preferable to use a polyester having an intrinsic viscosity of more than 0.60 dl / g in order to impart durability of the polyester film. However, in order to adjust the intrinsic viscosity, it is desirable to perform solid-phase polymerization after polymerization. .

  The polyester polymerization catalyst used in the present invention can be added to the reaction system at any stage of the polymerization reaction. For example, it can be added to the reaction system at any stage before and during the esterification reaction or transesterification reaction, immediately before the start of the polycondensation reaction, or at any stage during the polycondensation reaction. In particular, aluminum or a compound thereof is preferably added immediately before the start of the polycondensation reaction.

  The method for adding the polyester polycondensation catalyst used in the present invention is not particularly limited, but it may be added in the form of powder or neat, or in the form of a slurry or solution of a solvent such as ethylene glycol. May be. Further, aluminum metal or a compound thereof and other components, preferably those obtained by mixing the phenolic compound or phosphorus compound of the present invention in advance may be added, or these may be added separately. In addition, aluminum metal or a compound thereof and other components, preferably a phenolic compound or a phosphorus compound, may be added to the polymerization system at the same addition time, or may be added at different addition times.

  The polyester polycondensation catalyst used in the present invention preferably does not use other polymerization catalysts such as an antimony compound, a titanium compound, a germanium compound, and a tin compound, but there are problems in the properties, workability, and color tone of the polyester. An appropriate amount may be allowed to coexist within a range that does not occur.

  Specifically, the addition amount of the antimony compound is preferably 50 ppm or less in terms of antimony atoms, more preferably 30 ppm or less, with respect to the polyester obtained by polymerization. When the amount converted to antimony exceeds 50 ppm, metal antimony is precipitated, and the polyester becomes blackish, which is not preferable in appearance. Moreover, the foreign material resulting from a metal antimony increases and it is unpreferable especially in the use with a severe request | requirement with respect to a fault.

  The addition amount of the titanium compound is preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 2 ppm or less, and particularly preferably 1 ppm or less, in terms of titanium atom with respect to the polyester obtained by polymerization. If the titanium atom equivalent exceeds 10 ppm, the thermal stability of the resulting resin is significantly reduced.

  The addition amount of the germanium compound is preferably 20 ppm or less, more preferably 10 ppm or less, in terms of germanium atom, based on the polyester obtained by polymerization. If the germanium atom equivalent exceeds 20 ppm, it is not preferable because it is disadvantageous in terms of cost.

  The kind of the antimony compound, titanium compound, germanium compound and tin compound is not particularly limited.

  Specifically, examples of the antimony compound include antimony trioxide, antimony pentoxide, antimony acetate, and antimony glycoloxide. Of these, antimony trioxide is preferable.

  Examples of titanium compounds include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and titanium oxalate. Of these, tetra-n-butoxy titanate is preferred.

  Furthermore, examples of the germanium compound include germanium dioxide, germanium tetrachloride, etc. Among these, germanium dioxide is preferable.

  As tin compounds, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, triethyltin hydroxide, monobutylhydroxytin oxide, triisobutyltin adduct, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin sulfide, Examples thereof include dibutylhydroxytin oxide, methylstannoic acid, and ethylstannic acid, and the use of monobutylhydroxytin oxide is particularly preferable.

  The polyester used as a film raw material in the present invention is one or two or more selected from a polyhydric carboxylic acid containing a dicarboxylic acid and one or more of these ester-forming derivatives and a polyhydric alcohol containing a glycol. Or consisting of a hydroxycarboxylic acid and an ester-forming derivative thereof, or consisting of a cyclic ester.

  Preferred polyesters are those in which the main acid component is terephthalic acid or an ester-forming derivative thereof, or naphthalene dicarboxylic acid or an ester-forming derivative thereof, and the main glycol component is alkylene glycol.

  The polyester whose main acid component is terephthalic acid or its ester-forming derivative or naphthalene dicarboxylic acid or its ester-forming derivative is terephthalic acid or its ester-forming derivative and naphthalene dicarboxylic acid or its ester formation with respect to all acid components It is preferable that it is polyester containing 70 mol% or more in total of the functional derivatives, more preferably polyester containing 80 mol% or more, and still more preferably polyester containing 90 mol% or more.

  The polyester whose main glycol component is an alkylene glycol is preferably a polyester containing 70 mol% or more of the total amount of alkylene glycol with respect to all glycol components, more preferably a polyester containing 80 mol% or more, More preferably, it is a polyester containing 90 mol% or more.

  Dicarboxylic acids copolymerizable with terephthalic acid and naphthalenedicarboxylic acid do not reduce hydrolysis resistance, so orthophthalic acid, isophthalic acid, 4,4′-biphenyldicarboxylic acid, 4,4′-biphenylsulfonedicarboxylic acid 4,4′-biphenyl ether dicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p′-dicarboxylic acid, pamoic acid, anthracene dicarboxylic acid and the like, or ester formation thereof Sex derivatives are preferred. Further, a tri- or higher functional carboxylic acid component such as pyromellitic acid or trimellitic acid may be copolymerized.

  Examples of the glycol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1, 4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedi Alkylene glycol such as methanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, 1,12-dodecanediol, poly Aliphatic glycols exemplified by tylene glycol, polytrimethylene glycol, polytetramethylene glycol, hydroquinone, 4,4′-dihydroxybisphenol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-bis ( β-hydroxyethoxyphenyl) sulfone, bis (p-hydroxyphenyl) ether, bis (p-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) methane, 1,2-bis (p-hydroxyphenyl) ethane, bisphenol A , Bisphenol C, 2,5-naphthalenediol, and glycols obtained by adding ethylene oxide to these glycols, and the like.

  Among these glycols, alkylene glycol is preferable, and ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,4-cyclohexanedimethanol are more preferable. The alkylene glycol may contain a substituent or an alicyclic structure in the molecular chain, and two or more kinds may be used at the same time.

  Examples of polyhydric alcohols other than these glycols include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, hexanetriol and the like.

  Among these, polyesters particularly preferably used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, poly (1,4-cyclohexanedimethylene terephthalate), polyethylene naphthalate, polybutylene naphthalate, polypropylene naphthalate and these. Of these, polyethylene terephthalate and this copolymer are particularly preferable.

  Further, after polymerizing the polyester, the thermal stability of the polyester can be further enhanced by removing the catalyst from the obtained polyester or deactivating the catalyst by adding a phosphorus compound or the like.

  Since the film of the present invention uses a polyester obtained by polymerization using a specific catalyst species, the half life of elongation at break in a heat resistance test at 160 ° C. is 700 hours or more, more preferably 800 hours or more. By being in such a range, the film of the present invention can exhibit long-term thermal stability that can withstand long-term use even with large-sized and high-output solar cells.

  The film of the present invention preferably has an intrinsic viscosity (IV) value of 0.60 to 0.90 dl / g in order to obtain high heat resistance and hydrolysis resistance, more preferably 0.62 to 0.62. 0.85 dl / g, more preferably 0.65 to 0.8 dl / g. When the IV value is lower than 0.60 dl / g, the hydrolysis resistance and heat resistance are not sufficient, and when it is higher than 0.90 dl / g, the back pressure in the melting process becomes high, resulting in high productivity. Is not preferable, and thermal deterioration is promoted by shearing heat generation.

  The polyester as the film raw material preferably has an acid value of 1 (eq / ton) to 30 (eq / ton), more preferably 2 (eq / ton) to 20 (eq / ton), and still more preferably. It is 2 (eq / ton) or more and 16 (eq / ton) or less. If it exceeds 30 (eq / ton), a film having good hydrolysis resistance cannot be obtained. Polyesters of less than 1 (eq / ton) are difficult to produce industrially.

  The film of the present invention has a breaking elongation retention ratio of 60% or more, preferably 70% or more, more preferably 80% or more, which is an evaluation of hydrolysis resistance. If it is less than 60%, the durability as a solar battery back sheet is low and cannot be used. By controlling the acid value of the film, the hydrolysis resistance of the film of the present invention can be controlled within the above range.

  The film of this invention uses a white polyester film so that reflected light can be utilized from the point of the improvement of the photoelectric conversion efficiency of a solar cell. In order to exhibit effective light reflectivity, the whiteness degree of the white polyester film of the present invention is 50 or more, preferably 60 or more. If it is this range, the reflectance of light becomes high and is preferable.

  The film of the present invention contains fine particles having an average particle size of 0.1 to 3 μm in an amount of 3 to 50% by mass, preferably 4 to 25% by mass, based on the total mass of the film. If it is 0.1 μm or less or exceeds 3 μm, it is difficult to make the whiteness of the film 50 or more even if the addition amount is increased. Moreover, if it is less than 3 mass%, it will become difficult to make whiteness into 50 or more. If it exceeds 50% by mass, the film weight increases, making it difficult to handle it during processing.

In addition, the average particle diameter of this invention is calculated | required by the electron microscope method. Specifically, the following method is used.
The fine particles are observed with a scanning electron microscope, the magnification is appropriately changed according to the size of the particles, and the photographed image is enlarged and copied. Next, the outer circumference of each particle is traced for at least 200 fine particles selected at random. The equivalent circle diameter of the particles is measured from these trace images with an image analysis apparatus, and the average value of these is taken as the average particle diameter.

  As the fine particles of the present invention, inorganic or organic particles can be used. Examples of these fine particles include silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, acid value zinc, titanium oxide, zinc sulfide, and organic white pigment, but are not particularly limited. Absent. From the viewpoint of improving whiteness and productivity, titanium oxide or barium sulfate is preferable, and titanium oxide is more preferable. The titanium oxide may be either anatase type or rutile type. Further, the surface of the fine particles may be subjected to an inorganic treatment such as alumina or silica, or may be subjected to an organic treatment such as silicon or alcohol.

In a preferred embodiment of the film of the present invention, it is preferable to exhibit excellent durability even under light irradiation. Specifically, when UV irradiation is performed at 63 ° C., 50% Rh, irradiation intensity of 100 mW / cm ² for 100 hours, the elongation at break is preferably 35% or more, more preferably 40% or more. As described above, the film of the present invention is more suitable as a back sheet for a solar cell used outdoors because photodecomposition and deterioration are suppressed by light irradiation.

  In order to control the durability under light irradiation within the above range, it is preferable to add titanium dioxide fine particles mainly composed of rutile type to the film of the present invention. Titanium oxide is mainly known in two crystalline forms, rutile and anatase. The anatase has a very high spectral reflectance of ultraviolet rays, whereas the rutile type has a high absorption rate of ultraviolet rays (spectral spectroscopy). (Reflectance is small). The present inventor has paid attention to such a difference in spectral characteristics in the crystal form of titanium dioxide, and has improved the light resistance of the polyester film for solar cells by utilizing the rutile-type ultraviolet absorption performance. As a result, the present invention is excellent in film durability under light irradiation even when other ultraviolet absorbers are not substantially added. For this reason, problems such as contamination due to bleeding out of the ultraviolet absorber and a decrease in adhesion are unlikely to occur.

  As described above, the titanium dioxide particles according to the present invention are mainly rutile type. Here, “main body” means that the amount of rutile titanium dioxide in all titanium dioxide particles exceeds 50% by mass. Moreover, it is preferable that the amount of anatase type titanium dioxide in all the titanium dioxide particles is 10 mass% or less. More preferably, it is 5 mass% or less, Most preferably, it is 0 mass% or less. If the content of anatase type titanium dioxide exceeds the above upper limit, the amount of rutile type titanium dioxide in the total titanium dioxide particles may be reduced, resulting in insufficient ultraviolet absorption performance. Since the photocatalytic action is strong, the light resistance tends to be lowered by this action. Rutile titanium dioxide and anatase titanium dioxide can be distinguished by X-ray structure diffraction and spectral absorption characteristics.

  The rutile-type titanium dioxide fine particles of the present invention may be subjected to inorganic treatment such as alumina or silica on the fine particle surface, or may be subjected to organic treatment such as silicon or alcohol. Rutile titanium dioxide may be subjected to particle size adjustment and coarse particle removal using a purification process before blending with the polyester composition. As industrial means of the purification process, for example, a jet mill or a ball mill can be applied as the pulverizing means, and as a classification means, for example, dry or wet centrifugation can be applied.

  Fine particles can be added to the film by using a known method, but a master batch method (MB method) in which a polyester resin and fine particles are mixed in an extruder in advance is preferable. Further, it is possible to adopt a method in which a polyester resin and fine particles which have not been dried in advance are put into an extruder and MB is produced while moisture and air are deaerated. Furthermore, it is preferable to prepare an MB using a polyester resin that has been slightly dried in advance to suppress an increase in the acid value of the polyester. In this case, a method of extruding while degassing, a method of extruding without deaeration with a sufficiently dried polyester resin, and the like can be mentioned.

  The film of the present invention may contain many fine cavities inside. By containing fine cavities inside, the electrical insulation of the film is improved, so that it is effective as a solar cell backsheet (particularly an inner layer member) that requires high electrical insulation. In that case, the apparent specific gravity is 0.7 or more and 1.3 or less, preferably 0.9 or more and 1.3 or less, more preferably 1.05 or more and 1.2 or less. If it is less than 0.7, the film is not elastic and processing at the time of producing the solar cell module becomes difficult. Even if the film exceeds 1.3, it is within the range of the film of the present invention. However, if the film exceeds 1.3, the film weight is so large that it may become an obstacle when considering the reduction in weight of solar cells. There is.

  The fine cavities can be formed from a thermoplastic resin that is incompatible with the fine particles and / or polyester described below. The term “cavity derived from a thermoplastic resin that is incompatible with fine particles or polyester” means that a void exists around the fine particle or the thermoplastic resin, and is confirmed by, for example, a cross-sectional photograph of the film using an electron microscope. Can do.

  The polyester used in the present invention may be optionally added with an incompatible thermoplastic resin, and is not particularly limited as long as it is incompatible with the polyester. Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, and cellulose resins. In particular, polystyrene resins or polyolefin resins such as polymethylpentene and polypropylene are preferably used.

  The mixing amount of these void forming agents, that is, the thermoplastic resin incompatible with the polyester, with respect to the polyester varies depending on the amount of the target void, but may be in the range of 3 to 20% by mass with respect to the entire film. More preferably, it is 5 to 18% by mass. And if it is less than 3 mass%, there exists a limit in increasing the production amount of a cavity. On the other hand, if it is 20% by mass or more, the stretchability of the film is remarkably impaired, and the heat resistance, strength, and waist strength are impaired.

  The polyester film for solar cells of the present invention can be a void-containing polyester film. The polyester film of the present invention may have a single layer or a laminated structure composed of two or more layers. The laminated structure includes a skin layer comprising a polyester layer containing many cavities derived from fine particles having an average particle size of 0.1 to 3 μm, and a polyester containing many cavities derived from a thermoplastic resin incompatible with polyester. It is also a preferred embodiment of the present invention to have a core layer composed of layers.

  The thickness of the polyester film used as the base material of the present invention is 20 to 500 μm, more preferably 25 to 450 μm, and still more preferably 30 to 300 μm. When the substrate thickness is thin, the influence of heat shrinkage is large, and the adhesiveness after high temperature and high humidity treatment may be reduced. If it is thick, it cannot be wound as a roll.

(Coating layer)
The easy-adhesive white polyester film for solar cells of the present invention is formed with a coating layer mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component, and the aliphatic polycarbonate is measured by infrared spectroscopy. that absorbance around 1460 cm ^-1 derived from the component ratio of _{(a 1460)} and 1530 cm ^-1 vicinity of absorbance from urethane component _{(a 1530) (a 1460 /} a 1530) is is from 0.70 to 1.60 is important. Here, the “main component” means that it is contained in an amount of 50% by mass or more, more preferably 70% by mass or more as the total solid component contained in the coating layer.

  As described in Patent Documents 1 to 4, it is desirable that the conventional technical common sense positively introduces a cross-linking structure in the formation of the coating layer in order to improve the durability of the coating layer, thereby forming a rigid and strong coating layer. It was thought. However, in the present invention, the polyurethane resin comprising an aliphatic polycarbonate polyol as a constituent component controls the absorbance by infrared spectroscopy within a certain range, thereby exhibiting strong adhesion and adhesion under high temperature and high humidity heat. As a result, the inventors have found a remarkable effect of improving the quality of the present invention and have reached the present invention. Although the mechanism of improving adhesiveness with such a configuration is not well understood, the present inventor thinks as follows.

  For example, when the module is packaged, thermocompression bonding is performed at a high temperature in a configuration in which a glass film / a sealing material / a polyester film having a coating layer (coating layer) is laminated. Under the present circumstances, stress arises between a film (coating layer) and a sealing material by the thermal contraction of the film at the time of high temperature adhesion. In particular, the generation of such stress can also vary depending on various kinds of sealing materials and bonding conditions. As a result, it was considered that the stress could not be alleviated and the adhesiveness with the sealing material was lowered. Furthermore, when such a laminated body is placed under high temperature and high humidity, degradation of the coating layer proceeds due to hydrolysis. As a result, it was considered that the above stress could not be endured, the sealing material was peeled off, and the adhesiveness under high temperature and high humidity was lowered. Therefore, in order to maintain high adhesion to the sealing material and high adhesiveness under high temperature and high humidity, instead of simply imparting durability by firmly crosslinking the coating layer, heat resistance, It is considered desirable to have a component that retains hydrolysis resistance and to be flexible enough to withstand the stress. However, merely having flexibility has a problem in coating strength. Therefore, it is most desirable to make these conflicting characteristics compatible.

In this invention, it is a coating layer which has as a main component the urethane resin which has aliphatic polycarbonate polyol as a structural component, Comprising: The light absorbency (A of 1460cm < ^-1 > vicinity derived from the aliphatic polycarbonate component measured by infrared spectroscopy ₁₄₆₀ ) and the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component is 0.70 to 1.60, so that the above characteristics are compatible. That is, the above-mentioned characteristics can be achieved by coexisting an aliphatic polycarbonate component having hydrolysis resistance and a urethane component exhibiting toughness at a predetermined ratio. This makes it possible to relieve stress caused by thermal shrinkage of the film during thermal bonding at high temperatures, so that strong adhesion to the sealing material can be obtained, and heat resistance can be achieved even in subsequent high-temperature and high-humidity environments. It is thought that the coating layer can be prevented from deteriorating because it retains hydrolysis resistance.

Here, the absorbance in the vicinity of 1460 cm ⁻¹ (A ₁₄₆₀ ) is derived from the bending vibration specific to the C—H bond in the methylene group contained in the aliphatic polycarbonate component. Therefore, the magnitude of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ depends on the amount of the aliphatic polycarbonate polyol component constituting the urethane resin present in the coating layer. On the other hand, the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ is derived from the bending vibration specific to the N—H bond contained in the urethane component. Therefore, the magnitude of the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ depends on the amount of the urethane component constituting the urethane resin present in the coating layer. Therefore, these absorbance ratios (A ₁₄₆₀ / A ₁₅₃₀ ) indicate that both components having different characteristics coexist in a specific ratio. In the present invention, the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is 0.70 to 1.60, but the lower limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 0.75, more preferably 0.00. 80. Moreover, the upper limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 1.50, more preferably 1.45, and even more preferably 1.40. When the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is less than 0.70, the amount of the hard urethane component is excessive, and the stress relaxation of the coating layer is lowered, so that the heat and moisture resistance is lowered. In addition, when the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) exceeds 1.55, the aliphatic component of the flexible aliphatic polycarbonate is excessively increased, and the strength of the coating layer is lowered, so that the coating strength and moisture and heat resistance are reduced. Decreases.

  According to the aspect described above, the present invention can exhibit strong adhesiveness with a sealing material and can improve adhesiveness (moisture heat resistance) under high temperature and high humidity. Further, the configuration of the present invention will be described in detail below.

  The urethane resin of the present invention includes at least a polyol component and a polyisocyanate component as constituent components, and further includes a chain extender as necessary. The urethane resin of the present invention is a polymer compound in which these constituent components are mainly copolymerized by urethane bonds. In this invention, it has an aliphatic polycarbonate polyol as a structural component of a urethane resin. Heat-moisture resistance can be improved by including a urethane resin containing an aliphatic polycarbonate polyol as a constituent component in the coating layer of the present invention. The components of these urethane resins can be specified by nuclear magnetic resonance analysis or the like.

  The diol component, which is a constituent component of the urethane resin of the present invention, needs to contain an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance. From the viewpoint of preventing yellowing by sunlight of the present invention, it is preferable to use an aliphatic polycarbonate polyol.

Examples of the aliphatic polycarbonate polyol include aliphatic polycarbonate diols and aliphatic polycarbonate triols, and aliphatic polycarbonate diols can be preferably used. Examples of the aliphatic polycarbonate diol that is a constituent of the urethane resin of the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl. -1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4- Aliphatic polycarbonate diols obtained by reacting one or more diols such as cyclohexanedimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate, and phosgene. It is below. The number average molecular weight of the aliphatic polycarbonate diol is preferably 1500 to 4000, and more preferably 2000 to 3000. When the number average molecular weight of the aliphatic polycarbonate diol is small, the ratio of the aliphatic polycarbonate component constituting the urethane resin is relatively small. Therefore, in order to make the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) within the above range, it is preferable to control the number average molecular weight of the aliphatic polycarbonate diol within the above range. If the number average molecular weight of the aliphatic polycarbonate diol is large, the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component increases, and the aliphatic component increases. The strength after processing may be reduced. When the number average molecular weight of the aliphatic polycarbonate diol is small, a strong urethane component increases, and stress due to thermal shrinkage of the base material cannot be relieved, and adhesiveness may be lowered.

  Examples of the polyisocyanate that is a component of the urethane resin of the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis (isocyanatomethyl) cyclohexane. Such as alicyclic diisocyanates such as hexamethylene diisocyanate and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate; Isocyanates. When aromatic isocyanate is used, there is a problem of yellowing, which may not be preferable. Moreover, since it becomes a hard coating film compared with an aliphatic type | system | group, it becomes impossible to relieve | moderate the stress by the heat shrink of a base material, and adhesiveness may fall.

Chain extenders include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol, polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol, ethylenediamine Diamines such as hexamethylenediamine and piperazine, aminoalcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water. In order to prevent a decrease in absorbance in the vicinity of 1530 cm ⁻¹ derived from the urethane component and to impart flexibility, straight chain and high molecular weight materials such as 1,4-butanediol, 1,6-hexanediol, and hexamethylenediamine are used. preferable.

  The coating method of the coating layer of the present invention is not particularly limited, and various off-line coating methods and in-line coating methods can be employed. However, from the viewpoint of productivity and environmental protection, the coating layer of the present invention is preferably provided by an in-line coating method described later using an aqueous coating solution. In this case, it is desirable that the urethane resin of the present invention is water-soluble. The “water-soluble” means that it dissolves in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

  In order to impart water solubility to the urethane resin, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. Since the sulfonic acid (salt) group is strongly acidic and it may be difficult to maintain moisture resistance due to its hygroscopic performance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group. Moreover, nonionic groups, such as a polyoxyalkylene group, can also be introduced.

  In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, as a polyol component, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymer component to form a salt. Neutralize with an agent. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, tri-n-butylamine, N such as N-methylmorpholine and N-ethylmorpholine. -N-dialkylalkanolamines such as alkylmorpholines, N-dimethylethanolamine, N-diethylethanolamine and the like. These can be used alone or in combination of two or more.

  In order to impart water solubility, when a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is the same as that of the urethane resin. When the total polyisocyanate component is 100 mol%, it is preferably 3 to 60 mol%, more preferably 5 to 40 mol%. If the composition molar ratio is less than 3 mol%, water dispersibility may be difficult. Moreover, when the said composition molar ratio exceeds 60 mol%, since water resistance falls, moist heat resistance may fall.

  The glass transition temperature of the urethane resin of the present invention is preferably less than 0 ° C, more preferably less than -5 ° C. When the glass transition temperature is less than 0 ° C., the viscosity is close to that of partially melted olefin resin such as EVA or PVB at the time of pressure bonding, contributing to the improvement of strong adhesiveness by partial mixing, From the viewpoint of stress relaxation of the coating layer, it is preferable because it is easy to achieve suitable flexibility.

  In the urethane resin of the present invention, a crosslinking group may be introduced into the resin itself in order to improve adhesion after high temperature and high humidity. A silanol group is preferred from the viewpoint of the stability over time of the coating solution and the effect of improving the crosslinking density.

  A resin other than the urethane resin of the present invention may be contained in order to improve adhesiveness. For example, a urethane resin, an acrylic resin, a polyester resin, or the like containing polyether or polyester as a constituent component can be used.

  In the present invention, a crosslinking agent may be contained in the coating layer. By including a crosslinking agent, it becomes possible to further improve the adhesiveness.

  In the present invention, two kinds of crosslinking agents may be mixed in order to improve the coating film strength. Moreover, in order to promote a crosslinking reaction, you may use a catalyst etc. suitably as needed.

  In the present invention, particles may be contained in the coating layer. Particles are (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, aluminum silicate, diatomaceous earth Inorganic particles such as soil, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide, (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / Butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, di Rirufutareto systems include organic particles of polyester or the like.

  The particles preferably have an average particle size of 1 to 500 nm. Although an average particle diameter is not specifically limited, If it is 1-100 nm from the point which maintains the transparency of a film, it is preferable.

  The particles may contain two or more kinds of particles having different average particle diameters.

  In addition, said average particle diameter measures the maximum diameter of the 10 or more particle | grains which exist in the cross section of a coating layer by image | photographing the cross section of a laminated film at a magnification of 120,000 times using a transmission electron microscope (TEM). And can be obtained as an average value of them.

  As content of particle | grains, 0.5 mass% or more and 20 mass% or less are preferable. When the amount is small, sufficient blocking resistance cannot be obtained. Further, scratch resistance is deteriorated. When the amount is large, the coating film strength decreases.

  The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be any of cationic, anionic and nonionic surfactants, but is preferably a silicon-based, acetylene glycol-based or fluorine-based surfactant. These surfactants are preferably contained in a range that does not impair the adhesiveness to the sealing material, for example, in the range of 0.005 to 0.5% by mass in the coating solution.

  In order to impart other functionality to the coating layer, various additives may be contained within a range that does not impair the adhesion with the sealing material. Examples of the additive include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, foam suppressors, antifoaming agents, preservatives, and antistatic agents.

  In the present invention, examples of the method for providing the coating layer on the polyester film include a method in which a coating solution containing a solvent, particles and a resin is applied to the polyester film and dried. Examples of the solvent include organic solvents such as toluene, water, and a mixed system of water and a water-soluble organic solvent. Preferably, water alone or a mixture of a water-soluble organic solvent and water is used from the viewpoint of environmental problems. preferable.

(Manufacture of easy-adhesive white polyester film for solar cells)
The production method of the white polyester film of the present invention is arbitrary, and is not particularly limited. For example, the white polyester film can be produced as follows. First, as a method of joining the skin layer to the film surface, after supplying the polyester resin of the skin layer containing fine particles and the polyester resin of the core layer containing an incompatible thermoplastic resin to separate extruders, It is most preferable to employ a coextrusion method in which layers are laminated in a molten state and extruded from the same die.

  Each raw material is mixed, put into an extruder, melted, extruded from a T-die, and adhered to a cooling roll to obtain an unstretched sheet. The unstretched sheet is further expanded by stretching between rolls having a speed difference (roll stretching), stretching by gripping and expanding by a clip (tenter stretching), stretching by expanding with air pressure (inflation stretching), and the like. Axial orientation treatment. By performing the orientation treatment, interfacial peeling occurs between the polyester / incompatible thermoplastic resin and between the polyester / fine particles, and many fine cavities appear. Therefore, the conditions for stretching / orienting the unstretched sheet are closely related to the formation of cavities.

  First, the first-stage longitudinal stretching process is the most important process for forming many fine cavities in the film. In the longitudinal stretching, stretching is performed between two or many rolls having different peripheral speeds. As a heating means at this time, a method using a heating roll or a method using a non-contact heating method may be used, or they may be used in combination. Among these, the most preferable stretching method is a method using both roll heating and non-contact heating. In this case, first, the film is preheated to a temperature not higher than 50 ° C. to a glass transition point of polyester using a heating roll, and then heated with an infrared heater.

  Next, the uniaxially stretched film thus obtained is introduced into a tenter and stretched 2.5 to 5 times in the width direction. A preferable stretching temperature at this time is 100 ° C to 200 ° C. The biaxially stretched film thus obtained is subjected to heat treatment as necessary. The heat treatment is preferably performed in a tenter, and is preferably performed in the range of the melting point Tm-50 ° C. to Tm of the polyester.

  In an arbitrary stage of the film manufacturing process, a coating solution is applied to at least one surface of the PET film to form the coating layer. There is no particular problem even if the coating layer is formed on both sides of the PET film. The solid content concentration of the resin composition in the coating solution is preferably 2 to 35% by weight, particularly preferably 4 to 15% by weight.

  Any known method can be used as a method for applying the coating solution to the PET film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. It is done. These methods are applied alone or in combination.

  In the present invention, the coating layer is formed by coating the coating solution on an unstretched or uniaxially stretched PET film, drying it, stretching in at least a uniaxial direction, and then performing a heat treatment.

In this invention, it is preferable that the thickness of the coating layer finally obtained is 10-3000 nm, and the coating amount after drying is 0.01-3 g / m < ² >. When the coating amount of the coating layer is less than 0.01 g / m ² , the effect on adhesiveness is almost lost. On the other hand, when the coating amount exceeds 3 g / m ² , haze increases.

(Back sheet for solar cell)
The solar cell backsheet of the present invention comprises a white polyester film having the coating layer as a constituent member. In particular, it is preferably used for the outermost layer that is in direct contact with the sealing material. With such a configuration, the solar cell backsheet of the present invention can exhibit strong adhesion to the encapsulant, and can exhibit good adhesion even under harsh environments over a long period of time. Therefore, it can contribute to moisture proof maintenance and barrier property improvement of the solar cell element. Furthermore, since the solar cell backsheet of the present invention exhibits good light reflectivity, it is suitable for improving the photoelectric conversion efficiency.

  As an aspect of the solar cell backsheet of the present invention, for example, a white polyester film having the coating layer / adhesive / metal foil or a film having a metal thin film layer / adhesive / polyvinyl fluoride film or polyester-based high durability A configuration such as a moisture-proof film is exemplified. Moreover, the structure which has the said coating layer on both surfaces may be sufficient as the white polyester film of this invention. The coating layer of the present invention can exhibit good adhesiveness with configurations other than the sealing material. Here, as the film having a metal foil or a metal thin film layer, a film having a water vapor barrier property can be suitably used.

  Examples of the metal include aluminum, tin, magnesium, silver, and stainless steel. Among them, aluminum and silver are preferable because they have a relatively high reflectance and are easily available industrially. The metal layer may be used as a metal foil, or may be laminated as a thin film on a polyester film or the like. As a method of laminating these metals as a thin film, a vacuum deposition method, a sputtering method, an ion plating method, a plasma vapor deposition method (CVD), or the like can be used.

  In the present invention, the respective layers of the white polyester film having the coating layer, the metal foil or the film having the metal thin film layer, the polyvinyl fluoride film or the polyester high durability moisture-proof film are integrated by vacuum suction or the like, and thermocompression bonded. A solar cell backsheet can be produced by using a conventional molding method such as a lamination method and thermocompression-molding each of the above layers as an integral molded body. In the above, in order to improve the adhesiveness etc. between each film, it is preferable to laminate | stack via an adhesive agent. Examples of the adhesive include (meth) acrylic resins, olefinic resins, vinyl resins, and other heat melting adhesives, solvent-based adhesives, photo-curing adhesives, etc. whose main component is a vehicle. It is done.

  Here, the high durability moisture-proof film is laminated for the purpose of improving the weather resistance. Examples of the high durability moisture-proof film include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer. Polymer (PFA), 4-Fluoroethylene-6-fluoropropylene copolymer (FEP), 2-Ethylene-4 fluoroethylene copolymer (ETFE), Poly-3-fluoroethylene (PCTFE), Polyfluoride Fluorine resin film such as vinylidene (PVDF) or polyfuca vinyl (PVF), or UV absorber for resin such as polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic A film made of a kneaded resin composition It is.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example and a comparative example, naturally this invention is not limited to a following example. The evaluation method used in the present invention is as follows.

(1) Intrinsic viscosity Based on JIS K7367-5, it measured at 30 degreeC, using p-chlorophenol as a solvent.

(2) Apparent density of film Four films were cut into 5 cm squares and used as samples. Four of these were overlapped, the thickness was changed with a micrometer, and arbitrary 10 locations were measured with four significant figures, and the average value of the stacked thickness was obtained. The average value was divided by 4 and rounded to 3 significant figures to obtain an average thickness per sheet (t: μm). The mass (w: g) of the four samples was measured using an automatic upper pan balance with four significant digits, and the apparent density was determined from the following equation. The apparent density was rounded to 3 significant figures.
Apparent density (g / cm ³ ) = (w × 10 ⁴ ) / (5.00 × 5.00 × 4 × t)

(3) Whiteness Whiteness This was carried out by using Nippon Denshoku Industries Co., Ltd. Z-1001DP according to JIS-L1015-1981-B method.

(4) Acid value The film and the raw material polyester resin were measured by the following method.

(I) Preparation of sample The film or the raw material polyester resin is pulverized, vacuum dried at 70 ° C. for 24 hours, and then weighed in a range of 0.20 ± 0.0005 g using a balance. The mass at that time is defined as W (g). A sample weighed with 10 ml of benzyl alcohol is added to a test tube, the test tube is immersed in a benzyl alcohol bath heated to 205 ° C., and the sample is dissolved while stirring with a glass rod. Samples with dissolution times of 3 minutes, 5 minutes, and 7 minutes are designated as A, B, and C, respectively. Next, a new test tube is prepared, and only benzyl alcohol is added and processed in the same procedure, and the samples when the dissolution time is 3 minutes, 5 minutes, and 7 minutes are designated as a, b, and c, respectively.
(Ii) Titration Titration is performed using a 0.04 mol / l potassium hydroxide solution (ethanol solution) whose factor is known in advance. Phenol red is used as the indicator, and the titration (ml) of the potassium hydroxide solution is determined with the end point being changed from yellowish green to light red. The titration amounts of samples A, B, and C are XA, XB, and XC (ml). The titration amounts of samples a, b, and c are Xa, Xb, and Xc (ml).
(Iii) Calculation of acid value Using the titration amounts XA, XB, and XC for each dissolution time, the titration amount V (ml) at a dissolution time of 0 minutes is determined by the least square method. Similarly, titration volume V0 (ml) is obtained using Xa, Xb, and Xc. Subsequently, an acid value is calculated | required according to following Formula.
Carboxyl terminal concentration (eq / ton) = [(V−V0) × 0.04 × NF × 1000] / W
NF: Factor of 0.04 mol / l potassium hydroxide solution

(5) Glass transition temperature Based on JIS K7121, the glass transition start temperature was calculated | required from the DSC curve using the differential scanning calorimeter (The Seiko Instruments Inc. make, DSC6200).

(6) Absorbance measurement by infrared spectroscopy The coating layer was shaved off about the obtained easily adhesive polyester film for solar cells, and a sample of about 1 mg was collected. A pressure was applied to the collected sample to prepare a coating layer sample piece (size: about 50 μm × about 50 μm) molded into a film having a thickness of about 1 μm. Further, a sample piece (blank sample piece) was prepared in the same manner as described above for a PET resin having the same quality as the base film as a blank sample.
The prepared sample piece was placed on a KBr plate, and an infrared absorption spectrum was measured by a microscopic transmission method under the following conditions. The infrared spectrum of the coating layer was determined as the difference spectrum between the infrared spectrum obtained from the coating layer sample piece and the spectrum of the blank sample piece.
Absorbance around 1460 cm ^-1 derived from an aliphatic polycarbonate component _{(A 1460)} is 1460 and the value of the absorption peak height having an absorption maximum in the region of ± 10 cm ^-1, the absorbance in the vicinity of 1530 cm ^-1 derived from urethane component (A ₁₅₃₀ ) is the value of the absorption peak height having an absorption maximum in the region of 1530 ± 10 cm ⁻¹ . The baseline was a line connecting the hems on both sides of each maximum absorption peak. The absorbance ratio was determined from the obtained absorbance by the following formula.
(Absorbance ratio) = A ₁₄₆₀ / A ₁₅₃₀

(Measurement condition)
Apparatus: FT-IR analyzer SPECTRA TECH IRμs / SIRM
Detector: MCT
Resolution: 4cm ^-1
Integration count: 128 times

(7) Hydrolysis resistance HAST (Highly Accelerated Temperature and Humidity Stress Test) standardized in JIS-60068-2-66 was performed. The equipment was EHS-221 manufactured by ESPEC CORP. Under the conditions of 105 ° C., 100% Rh, 0.03 MPa.
The film was cut into 70 mm × 190 mm, and the film was placed using a jig. Each film was placed at a distance where it did not touch. The treatment was performed for 200 hours under the conditions of 105 ° C., 100% Rh, 0.03 MPa.

(8) Light resistance In the accelerated light resistance test, an I-super UV tester SUV-W151 manufactured by Iwasaki Electric Co., Ltd. was used, and a continuous UV irradiation treatment was performed for 100 hours at 63 ° C., 50% Rh, irradiation intensity 100 mW / cm 2.

(9) Breaking elongation retention rate The hydrolysis resistance and light resistance were evaluated based on the breaking elongation retention rate. The elongation at break before and after each treatment was measured according to JIS C 2318-1997 5.3.31 (tensile strength and elongation), and the elongation at break was calculated according to the following formula.
Breaking elongation retention ratio (%) = [(breaking elongation after treatment) × 100] / (breaking elongation before treatment)

(10) Half-life of elongation at break in heat resistance test at 160 ° C. A strip sample having a length of 200 mm and a width of 10 mm was cut out and used in the longitudinal direction. In accordance with the method defined in JIS K-7127, the elongation at break was measured at 25 ° C. and 65% RH using a tensile tester. The distance between the initial pull chucks was 100 mm, and the pull speed was 300 m / min. The measurement was performed 20 times by changing the sample, and the average value (X) of the elongation at break was determined. In addition, a strip-shaped sample having a length of 200 mm and a width of 10 mm was put in a gear oven, left in an atmosphere of 160 ° C., then naturally cooled, and this sample was subjected to a tensile test under the same conditions as described above 20 times. The average value (Y) of elongation was determined. From the average values (X) and (Y) of the obtained elongation at break, the elongation retention was determined by the following equation.
Elongation retention (%) = (Y / X) × 100
The heat treatment time until the elongation retention was 50% or less was determined and defined as the half life of elongation at break.

(11) Adhesive The obtained easy-adhesive white polyester film for solar cells was prepared by cutting out 100 mm width × 100 mm length and EVA sheet cut into 70 mm width × 90 mm length, and the film (coating layer surface) / EVA / (Coating layer surface) A sample was prepared by stacking with a film structure and heat-pressing with a vacuum laminator under the bonding conditions described below. The prepared sample was cut out into a width of 20 mm and a length of 100 mm, attached to a SUS plate, and the peel strength between the film layer and the EVA layer was measured with a tensile tester under the conditions described below. The peel strength was determined as the average value of the portions that peeled stably after exceeding the maximum point. The ranking was based on the following criteria.
◎: 100 N / 20 mm or more, or film breakage of film ○: 75 N / 20 mm or more, less than 100 N / 20 mm Δ: 50 N / 20 mm or more, less than 75 N / 20 mm ×: less than 50 N / 20 mm

(Sample creation conditions)
Apparatus: Vacuum laminator NP-30 type LM-30x30 pressurization: 1 atmosphere EVA:
A. Standard cure type Sunvik Ultra Pearl PV (0.4μm)
Lamination process: 100 ° C. (vacuum 5 minutes, vacuum pressurization 5 minutes)
Cure process: Heat treatment 150 ° C (normal pressure 45 minutes)
II. Mitsui Fabro Solar EVA SC4 (0.4μm)
Lamination process: 130 ° C (vacuum 5 minutes, vacuum pressurization 5 minutes)
Cure process: 150 ° C (45 minutes at normal pressure)
B. Fast cure type Sunvik Ultra Pearl PV (0.45μm)
Lamination process: 135 ° C (vacuum 5 minutes, vacuum pressure 15 minutes)
II. Mitsui Fabro Solar Eva RC02B (0.45μm)
Lamination process: 150 ° C. (vacuum 5 minutes, vacuum pressure 15 minutes)

(Measurement condition)
Apparatus: Tensilon RTM-100 manufactured by Toyo BALDWIN
Peeling speed: 200 mm / min Peeling angle: 180 degrees

(12) Moisture and heat resistance The obtained easy-adhesive white polyester film for solar cells was left in an environment of 85 ° C. and 85% RH for 1000 hours in a high-temperature and high-humidity tank. Subsequently, the easily adhesive white polyester film for solar cells was taken out and allowed to stand at room temperature and humidity for 24 hours. Thereafter, the peel strength was measured by the same method as in (11) above, and ranked according to the following criteria.
◎: 100 N / 20 mm or more, or film breakage of film ○: 75 N / 20 mm or more, less than 100 N / 20 mm Δ: 50 N / 20 mm or more, less than 75 N / 20 mm ×: less than 50 N / 20 mm

(Polymerization of urethane resin A-1 containing aliphatic polycarbonate polyol)
In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, several 153.41 parts by mass of polyhexamethylene carbonate diol having an average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-1) having a solid content of 35%. The obtained polyurethane resin (A-1) had a glass transition temperature of -30 ° C.

(Polymerization of urethane resin A-2 containing aliphatic polycarbonate polyol)
In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 29.14 parts by mass of 4,4-diphenylmethane diisocyanate, 7.57 parts by mass of dimethylolbutanoic acid, several An average molecular weight of 3000 polyhexamethylene carbonate diol 173.29 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-2) having a solid content of 35%.

(Polymerization of urethane resin A-3 containing aliphatic polycarbonate polyol as a constituent)
In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 11.12 parts by mass of dimethylolbutanoic acid, hexane 1.97 parts by mass of diol, 143.40 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added, and 75 ° C. in a nitrogen atmosphere. The mixture was stirred for 3 hours to confirm that the reaction solution reached a predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin solution (A-3) having a solid content of 35%.

(Polymerization of silanol group-containing urethane resin A-4 containing aliphatic polycarbonate polyol as a constituent)
In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 38.41 parts by mass of isophorone diisocyanate, 6.95 parts by mass of dimethylolpropanoic acid, and a number average molecular weight of 2000 Polyhexamethylene carbonate diol 158.999 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and acetone 84.00 parts by mass as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that the equivalent amount was reached. Next, after cooling this reaction liquid to 40 degreeC, 4.37 mass parts of triethylamine was added, and the polyurethane prepolymer solution was obtained. Next, 3.84 parts by mass of γ- (aminoethyl) aminopropyltriethoxysilane, 1.80 parts by mass of 2-[(2-aminoethyl) amino] ethanol and 450 g of water were added, and the polyurethane prepolymer solution was dropped. And dispersed in water. Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble silanol group-containing polyurethane resin solution (A-4) having a solid content of 30%.

(Polymerization of urethane resin A-5 containing aliphatic polycarbonate polyol as a constituent)
A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 1000. A solution (A-5) was obtained.

(Polymerization of urethane resin A-6 containing aliphatic polycarbonate polyol as a constituent)
A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 5000. A solution (A-6) was obtained.

(Polymerization A-7 of Polyurethane Resin Containing Polyester Polyol)
A water-soluble polyurethane resin solution (A) having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 of the water-soluble polyurethane resin (A-1) was changed to a polyester diol having a number average molecular weight of 2000. -7) was obtained.

(Polymerization A-8 of Polyurethane Resin Containing Polyether Polyol)
A water-soluble polyurethane resin solution having a solid content of 35% (with a solid content of 35%), except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyether diol having a number average molecular weight of 2000. A-8) was obtained.

Example 1
(Preparation of polyethylene terephthalate resin (PET-I))
(1) Preparation of polycondensation catalyst solution (preparation of ethylene glycol solution of phosphorus compound)
After adding 2.0 liters of ethylene glycol to a flask equipped with a nitrogen introduction tube and a cooling tube at room temperature and normal pressure, while stirring at 200 rpm in a nitrogen atmosphere, Irganox 1222 (Ciba 39) represented by -200 g of Specialty Chemicals) was added. Further, 2.0 liters of ethylene glycol was added, the temperature was raised by changing the jacket temperature setting to 196 ° C., and the mixture was stirred under reflux for 60 minutes from the time when the internal temperature reached 185 ° C. or higher. Thereafter, the heating was stopped, the solution was immediately removed from the heat source, and the solution was cooled to 120 ° C. or less within 30 minutes while maintaining the nitrogen atmosphere. The mole fraction of Irganox 1222 in the obtained solution was 40%, and the mole fraction of the compound whose structure changed from Irganox 1222 was 60%.

(Preparation of aqueous solution of aluminum compound)
After adding 5.0 liters of pure water to a flask equipped with a cooling tube at room temperature and normal pressure, 200 g of basic aluminum acetate was added as a slurry with pure water while stirring at 200 rpm. Further, pure water was added so as to be 10.0 liters as a whole, and the mixture was stirred at normal temperature and pressure for 12 hours. Thereafter, the jacket temperature was changed to 100.5 ° C., the temperature was raised, and the mixture was stirred under reflux for 3 hours from the time when the internal temperature reached 95 ° C. or higher. Stirring was stopped and the mixture was allowed to cool to room temperature to obtain an aqueous solution.

(Preparation of ethylene glycol mixed solution of aluminum compound)
After adding an equal volume of ethylene glycol to the aqueous aluminum compound solution obtained by the above method and stirring for 30 minutes at room temperature, the internal temperature is controlled to 80 to 90 ° C., and the pressure is gradually reduced to reach 27 hPa while stirring for several hours. Water was distilled off from the system to obtain an ethylene glycol solution of an aluminum compound at 20 g / l. The peak integration value ratio of ²⁷ Al-NMR spectrum of the obtained aluminum solution was 2.2.

(2) Esterification reaction and polycondensation A high-speed stirrer is provided in the transfer line from the third esterification reaction tank to the first polycondensation reaction tank, comprising three continuous esterification reaction tanks and three polycondensation reaction tanks. 0.75 parts by mass of ethylene glycol with respect to 1 part by mass of high-purity terephthalic acid was continuously supplied to a slurry preparation tank. The prepared slurry is continuously supplied, the first esterification tank has a reaction temperature of 250 ° C. and 110 kPa, the second esterification reaction tank has 260 ° C. and 105 kPa, the third esterification reaction tank has 260 ° C. and 105 kPa, and the second ester A polyester oligomer was obtained by continuously adding 0.025 parts by mass of ethylene glycol to the chemical reaction tank. The oligomer is continuously transferred to a continuous polycondensation apparatus comprising three reaction tanks, and the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound prepared by the above method in an in-line mixer installed in the transfer line. Are continuously added while stirring with an agitating mixer so as to be 0.015 mol% and 0.036 mol% as aluminum atoms and phosphorus atoms with respect to the acid component in the polyester, respectively. Is 265 ° C., 9 kPa, the medium polycondensation reaction tank is 265-268 ° C., 0.7 kPa, the final polycondensation reaction tank is 273 ° C., 13.3 Pa, and the intrinsic viscosity is 0.59, the acid value is 10.5 ( eq / ton) of polyethylene terephthalate resin (PET-I).

(Preparation of polyethylene terephthalate resin (PET-II))
The polyethylene terephthalate resin (PET-I) prepared above is subjected to solid phase polymerization using a rotary vacuum polymerization apparatus under a reduced pressure of 0.5 mmHg at 220 ° C. for various times. A polyethylene terephthalate resin (PETII) having a concentration of 5.0 (eq / ton) was prepared.

(Preparation of fine particle-containing masterbatch)
50% by mass of rutile titanium dioxide having an average particle size of 0.3 μm (electron microscopic method) is mixed with 50% by mass of polyethylene terephthalate resin (PET-I), which is dried at 120 ° C. under 10 ⁻³ torr for about 8 hours in advance. The product was supplied to a vent type twin screw extruder, kneaded and extruded at 275 ° C. while degassing to prepare rutile type titanium dioxide fine particle-containing master batch (MB-I) pellets. The acid value of this pellet was 12.0 (eq / ton).

(Coating solution adjustment)
The following coating agent was mixed to prepare a coating solution.
Water 55.86% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 13.52 mass%
0.59% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.03 mass%
(Silicon, solid content concentration of 100% by mass)

(Production of film)
Next, the raw material of the layer (A) in which 50% by mass of the polyethylene terephthalate resin (PET-II) prepared as described above and 50% by mass of the previously prepared MB-I were mixed, and 70% by mass of PET-II. % And 30% by mass of MB-I as raw materials for layer (B), each charged into separate extruders, mixed and melted at 280 ° C., and then using a feed block, layer B on one side of layer A Were joined in a molten state. At this time, the discharge rate ratio of the A layer and the B layer was controlled using a gear pump. Subsequently, it was extruded onto a cooling drum adjusted to 30 ° C. using a T-die, and an unstretched sheet was prepared so as to be an A / B / A layer.

The obtained unstretched sheet was uniformly heated to 70 ° C. using a heating roll, and 3.3-fold roll stretching was performed at 90 ° C. Subsequently, after apply | coating the said coating liquid on the single side | surface of PET film by the roll coat method, it dried at 80 degreeC for 20 second. The final coating amount (after biaxial stretching) was adjusted so that the coating amount after drying was 0.15 g / m ² . The obtained uniaxially stretched film was led to a tenter, heated to 140 ° C. and transversely stretched 3.7 times, fixed in width and subjected to heat treatment at 220 ° C. for 5 seconds, and further at 220 ° C. in the width direction of 4%. By relaxing, an easily adhesive white polyester film for solar cells having a thickness of 188 μm (19/150/19) was obtained.

Comparative Example 1
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-5).

Comparative Example 2
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-6).

Comparative Example 3
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to a polyurethane resin (A-7).

Comparative Example 4
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to a polyurethane resin (A-8).

Comparative Example 5
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 5 μm.

Example 2
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-2).

Example 3
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-3).

Example 4
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 5
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 50 μm.

Example 6
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easy-adhesive white polyester film for solar cells was changed to 100 μm.

Example 7
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 350 μm.

Example 8
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily-adhesive white polyester film for solar cells.
61.51% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 8.11% by mass
0.35% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.03 mass%
(Silicon, solid content concentration of 100% by mass)

Example 9
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily-adhesive white polyester film for solar cells.
Water 41.71% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 27.05% by mass
1.18% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.06% by mass
(Silicon, solid content concentration of 100% by mass)

Example 10
(3) Manufacture of solar cell backsheet Adhesive white polyester film for solar cell of Example 1 / aluminum foil (30 μm) / polyvinyl fluoride film (38 μm) and bonded by dry lamination method for solar cell A backsheet was obtained.
Adhesive for dry laminate Takelac A-315 (Mitsui Chemicals) / Takenate A-10 (Mitsui Chemicals) = 9/1 (solid content ratio)

Example 11
(Preparation of cavity forming agent)
As raw materials, 20% by mass of polystyrene with a melt flow rate of 1.5 (manufactured by Nippon Polystyrene Co., Ltd., G797N), 20% by mass of vapor phase polymerization polypropylene with a melt flow rate of 3.0 (F300SP, manufactured by Idemitsu Petrochemical), and melt flow Rate 180 polymethylpentene (manufactured by Mitsui Chemicals: TPX DX-820) 60% by mass pellets were mixed, supplied to a twin screw extruder and kneaded sufficiently to prepare a cavity forming agent (MB-II).
An easy-adhesive white polyester film for solar cells was prepared in the same manner as in Example 1 except that PET-II: MB-I: MB-II was changed to 80: 12: 8 (mass%) as a raw material for the B layer. Obtained.

Comparative Example 6
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-5).

Comparative Example 7
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-6).

Comparative Example 8
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-7).

Comparative Example 9
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-8).

Comparative Example 10
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 5 μm.

Example 12
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-2).

Example 13
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to the polyurethane resin (A-3).

Example 14
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the polyurethane resin was changed to a silanol group-containing polyurethane resin (A-4).

Example 15
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the base material thickness of the easily adhesive white polyester film for solar cells was changed to 50 μm.

Example 16
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 100 μm.

Example 17
An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the substrate thickness of the easily adhesive white polyester film for solar cells was changed to 350 μm.

Example 18
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the coating solution was changed to the following.
61.51% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 8.11% by mass
0.35% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.03 mass%
(Silicon, solid content concentration of 100% by mass)

Example 19
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 11 except that the coating solution was changed to the following.
Water 41.71% by mass
Isopropanol 30.00% by mass
Polyurethane resin solution (A-1) 27.05% by mass
1.18% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Surfactant 0.06% by mass
(Silicon, solid content concentration of 100% by mass)

Comparative Example 11
An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that the acid value of the polyethylene terephthalate resin as the film material was 29.5 (PET-III).

Example 20
In the preparation of the fine particle-containing masterbatch, as a raw material, 50% by mass of polyethylene terephthalate resin (PET-I) mixed with 50% by mass of anatase-type titanium dioxide having an average particle size of 0.3 μm (electron microscopic method) is a vent type 2 The mixture was supplied to a shaft extruder, kneaded and extruded at 275 ° C. while degassing to prepare fine particle-containing master batch (MB-III) pellets. The acid value of this pellet was 11.9 (eq / ton). An easily adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that MB-III was used instead of the fine particle-containing master batch MB-I.

Comparative Example 12
In the preparation of a master batch containing fine particles, a polyethylene terephthalate resin having an undried intrinsic viscosity of 0.59 and an acid value of 10.5 (eq / ton) stored in a paper bag as a raw material in a place where temperature and humidity are not controlled (PET-I) 50 mass% mixed with 50 mass% of rutile titanium dioxide having an average particle size of 0.3 μm (electron microscopic method) is supplied to a vent type twin screw extruder, kneaded and 305 ° C. A masterbatch (MB-IV) pellet containing fine particles (titanium oxide) was prepared while degassing with a vacuum. The acid value of this pellet was 36.6 (eq / ton). An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that MB-IV was used instead of the fine particle-containing master batch MB-I.

Example 21
In the preparation of the master batch containing fine particles, barium sulfate having an average particle size of 0.6 μm was used instead of rutile titanium dioxide (MB-V), and it was used instead of MB-I as a raw material for the A layer. An easy-adhesion white polyester film for solar cells was obtained in the same manner as in Example 1.

Comparative Example 13
After transesterification using 100 parts by mass of dimethylene terephthalate, 64 parts by mass of ethylene glycol and 0.09 parts by mass of calcium acetate, trimethyl phosphate and antimony trioxide are polymerized at 0.03% by mass, and a rotary vacuum polymerization apparatus. Is used, and is subjected to solid phase polymerization at 220 ° C. under reduced pressure of 0.5 mmHg, and a polyethylene terephthalate resin (PET-IV) having a value intrinsic viscosity of 0.75 and a carboxyl terminal concentration of 8.0 (eq / ton). It was created. An easy-adhesive white polyester film for solar cells was obtained in the same manner as in Example 1 except that PET-IV was used instead of PET-II.

  The easy-adhesive white polyester film for solar cells of the present invention is not only excellent in hydrolysis resistance and long-term thermal stability, but also in adhesion to a sealing material and adhesion under high temperature and high humidity (moisture heat resistance). Since it is excellent, it is suitable as a member of the solar cell backsheet, particularly as the innermost base film of the solar cell backsheet.

Claims (13)

A white polyester film having a coating layer on at least one side,
The film is mainly composed of polyester polymerized using a polycondensation catalyst containing aluminum and / or a compound thereof and a phosphorus compound having an aromatic group in the molecule,
The whiteness is 50 or more,
Containing 3 to 50% by mass of fine particles having an average particle size of 0.1 to 3 μm,
The acid value of the film is 1 (eq / ton) or more and 30 (eq / ton) or less,
The thickness is 20 to 500 μm,
The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component,
The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component in the infrared spectrum of the coating layer. ) Is 0.70 to 1.60, an easily adhesive white polyester film for solar cells.   The easy-adhesive white polyester film for solar cells according to claim 1, wherein the fine particles are fine particles of titanium dioxide mainly composed of a rutile type.   3. The easily adhesive white polyester film for solar cells according to claim 1 or 2, wherein the film has a large number of fine cavities so that the apparent specific gravity of the film is 0.7 or more and 1.3 or less.   Polyester layer (skin layer) containing many cavities derived from fine particles having an average particle size of 0.1 to 3 μm, and polyester layer (core layer) containing many cavities derived from a thermoplastic resin incompatible with polyester The easily adhesive white polyester film for solar cells according to any one of claims 1 to 3, wherein is laminated.   The easily adhesiveness for solar cells according to any one of claims 1 to 4, wherein the phosphorus compound is one or more compounds selected from the group consisting of phosphonic acid compounds and phosphinic acid compounds. White polyester film. The solar cell according to claim 1, wherein the phosphorus compound is one or more selected from the group consisting of compounds represented by the following general formulas (1) to (2). Easy-adhesive white polyester film.

(Formula (1) and (2) in, R ^1, R ⁴ are each independently hydrogen, 1 to 50 carbon atoms hydrocarbon group, a hydroxyl group or 1 to 50 carbon atoms containing a halogen group, an alkoxyl group, or an amino group R ² and R ³ each independently represent hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a hydroxyl group or an alkoxyl group, provided that each hydrocarbon group is a hydrocarbon group; May contain an alicyclic structure or an aromatic ring structure.) The easily adhesive white polyester film for solar cells according to claim 6, wherein R ¹ and R ^{4 in the} general formulas (1) to (2) are groups having an aromatic ring structure.   The easily adhesive white polyester film for solar cells according to any one of claims 1 to 7, wherein the phosphorus compound has a phenol moiety in the same molecule. 9. The phosphorus compound having a phenol part in the same molecule is one or more selected from the group consisting of compounds represented by the following general formulas (3) to (4). Easy-adhesive white polyester film for solar cells.

(In the formulas (3) to (4), R ¹ is a carbon group having 1 to 50 carbon atoms including a phenol part, a hydroxyl group, a halogen group, an alkoxyl group, an amino group and a phenol part. R ⁴ represents each independently hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxyl group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms, R ² , R ³ each independently represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydrocarbon group having 1 to 50 carbon atoms including a hydroxyl group or an alkoxyl group, provided that the hydrocarbon group represents a branched structure, alicyclic structure or aromatic group. (It may contain a ring structure. The ends of R ² and R ⁴ may be bonded to each other.) A white polyester film having a coating layer on at least one side,
The film is mainly composed of polyester polymerized using a polycondensation catalyst containing an aluminum salt of a phosphorus compound,
The whiteness is 50 or more,
Containing 3 to 50% by mass of fine particles having an average particle size of 0.1 to 3 μm,
The acid value of the film is 1 (eq / ton) or more and 30 (eq / ton) or less,
The thickness is 20 to 500 μm,
The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component,
The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component in the infrared spectrum of the coating layer. ) Is 0.70 to 1.60, an easily adhesive white polyester film for solar cells. A white polyester film having a coating layer on at least one side,
The film is mainly composed of polyester polymerized using a polycondensation catalyst containing at least one selected from compounds represented by the following general formula (5),
The whiteness is 50 or more,
Containing 3 to 50% by mass of fine particles having an average particle size of 0.1 to 3 μm,
The acid value of the film is 1 (eq / ton) or more and 30 (eq / ton) or less,
The thickness is 20 to 500 μm,
The coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component,
The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component in the infrared spectrum of the coating layer. ) Is 0.70 to 1.60, an easily adhesive white polyester film for solar cells.

(In formula (7), R ¹ and R ² each independently represent hydrogen and a hydrocarbon group having 1 to 30 carbon atoms. R ³ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group or an alkoxyl group. R ⁴ represents a hydrocarbon group having 1 to 50 carbon atoms, including hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, a hydroxyl group, an alkoxyl group, or a carbonyl group. l represents an integer of 1 or more, m represents 0 or an integer of 1 or more, and (l + m) represents 4 or less, n represents an integer of 1 or more, and the hydrocarbon group represents an alicyclic structure, a branched structure, or an aromatic ring structure. May be included.)   The easily adhesive white polyester film for solar cells according to any one of claims 1 to 11, wherein the half life of elongation at break in a heat resistance test at 160 ° C is 700 hours or more.   The solar cell backsheet which laminated | stacked the easily adhesive white polyester film for solar cells in any one of Claims 1-12.