JP2010018789A - Polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film with less increase in haze induced by heat treatment, excellent in dimension stability without requiring a specific raw material and process. <P>SOLUTION: The polyester film includes a polyester layer (layer P) containing a polyester resin (A) and a polyester resin (B), wherein the polyester resin (B) is dispersed in the polyester resin (A) as a dispersion with a flantness of at least 3 in the polyester layer (layer P) and satisfies at least one, the following requirement (I) or (II). The requirement (I) is that the polyester resin (B) comprises an alicyclic diol component and/or an aromatic diol component as a diol component, and the total content of alicyclic diol and the aromatic diol in the polyester layer (layer P) is ≥0.2 to ≤10 mol% based on the amount of the diol components in the polyester layer (layer P). The requirement (II) is that the polyester resin (B) comprises at least one dicarboxylic acid selected from the group consisting of an alicyclic dicarboxylic acid component, isophthalic acid component and naphthalene dicarboxylic acid component, and the total content of alicyclic dicarboxylic acid component, isophthalic acid component and naphthalene dicarboxylic acid component in the polyester layer (layer P) is ≥0.2 and ≤10 mol% based on the amount of dicarboxylic acid component in the polyester layer (layer P). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyester film. Specifically, the present invention relates to a polyester film having excellent transparency and a small haze increase due to heat treatment.

  Aromatic polyester resins typified by polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are inexpensive resins that have both heat resistance and transparency, and can be stretched to form a high mechanical strength. Can do. Therefore, in addition to various magnetic materials such as various industrial materials such as photographic, solar cell, mold release, process, electrical insulation, electronic material, and laminate, various packaging materials, magnetic tape, etc. It has excellent transparency, heat resistance, mechanical properties, dimensional stability, chemical resistance, etc., and is used in various fields such as optical films for displays. It is widely used from thin to thick. For example, as a base film for a prism lens sheet, a base film for a diffusion plate, a base film for a touch panel, and a base film for an AR (anti-reflection) film, excellent strength and dimensional stability are required. A film of 100 μm or more is preferably used. Moreover, about the process use etc., the film of 50 micrometers or less in thickness is used suitably.

  When using a polyester film in these various applications, it is almost always used that having various functional layers such as an easy adhesion layer, a gas barrier layer, a release layer, a flame retardant layer, and a light diffusion layer formed on the surface thereof. . As these functional layer forming methods, techniques such as coating, vapor deposition, sputtering, plasma CVD, ion plating, etc. are used. In most of the processing methods, the polyester film is exposed to high temperatures during processing. become. Therefore, the polyester film is required to have excellent handleability, heat resistance and dimensional stability during processing. Furthermore, a film used for optical applications is required to maintain excellent transparency even after processing, and to maintain excellent transparency even when exposed to high temperatures during use.

  However, generally, when a polyester film is exposed to a high temperature, oligomers originally contained in the polyester film, oligomers generated by thermal degradation, and the like are deposited on the film surface. As a result, there have been problems such as process contamination, reduced transparency (increased haze), defects at the time of forming the functional layer, reduced functionality of the functional layer, and deteriorated characteristics during long-term use.

  On the other hand, in order to impart oligomer resistance to the polyester film, a method of forming a layer having oligomer block on the surface and blocking the oligomer with the layer to suppress the surface (Patent Document 1), cyclohexanedimethanol on the polyester A method of adding a copolyester (Patent Document 2) has been proposed.

JP-A 63-267540 JP 2005-60449 A

  However, the technique of Patent Document 1 has a problem that it is necessary to use an expensive raw material, the number of manufacturing steps is increased, and the productivity is low. Further, in the technique of Patent Document 2, sufficient effects cannot be exhibited unless a very large amount of cyclohexanedimethanol copolymerized polyester is added to the polyester. As a result, generation of oligomers can be suppressed, but heat resistance is not sufficient and dimensional stability is achieved. There was a problem of inferiority.

  Accordingly, it is an object of the present invention to provide a polyester film that does not require special raw materials and processes, has a small haze increase due to heat treatment, and is excellent in dimensional stability.

In order to solve the above problems, the present invention has the following configuration. That is, the polyester film of the present invention is a polyester film having a polyester layer (P layer) containing a polyester resin (A) and a polyester resin (B), and in the polyester layer (P layer), the polyester resin (B ) Is dispersed in the polyester resin (A) as a dispersion having a flatness of 3 or more and satisfies at least one of the following conditions (I) or (II).
(I) The polyester resin (B) has an alicyclic diol component and / or an aromatic diol component as a diol component, and the alicyclic diol component and the aromatic diol component in the polyester layer (P layer). The total content is 0.2 mol% or more and 10 mol% or less with respect to the amount of the diol component in the polyester layer (P layer).
(II) The polyester resin (B) has, as a dicarboxylic acid component, one or more dicarboxylic components selected from the group consisting of an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component, and the polyester layer The total content of the alicyclic dicarboxylic acid component, the isophthalic acid component and the naphthalenedicarboxylic acid component in the (P layer) is 0.2 mol% or more to the amount of the dicarboxylic acid component in the polyester layer (P layer) 10 It is characterized by being not more than mol%.

  The polyester film of the present invention does not require any special raw materials and processes, and can provide a polyester film that has a small haze increase due to heat treatment and is excellent in dimensional stability.

  The polyester film of the present invention needs to be a polyester film having a polyester layer (P layer) containing a polyester resin (A) and a polyester resin (B).

  In the present invention, in the polyester layer (P layer), the polyester resin (B) needs to be dispersed as a dispersion in the polyester resin (A).

  In the polyester film of the present invention, the polyester resin (A) and the polyester resin (B) are: 1) polycondensation of a dicarboxylic acid component or an ester-forming derivative thereof (hereinafter collectively referred to as “dicarboxylic acid component”) and a diol component; It can be obtained by the combination of 2) polycondensation of a compound having a carboxylic acid or carboxylic acid derivative skeleton and a hydroxyl group in one molecule, and 1) 2).

  In 1), the dicarboxylic acid component constituting the polyester resin includes malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, and azelain. Aliphatic dicarboxylic acids such as acid, methylmalonic acid and ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid , 5-Natri Representative examples are dicarboxylic acids such as musulfoisophthalic acid, phenylendanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9′-bis (4-carboxyphenyl) fluorenic acid, and ester derivatives thereof. However, it is not limited to these. Moreover, these may be used independently or may be used in multiple types as needed.

  Also, dicarboxy compounds obtained by adding oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid, and derivatives thereof, and a combination of a plurality of the oxyacids to the carboxy terminus of the dicarboxylic acid component described above. Preferably used.

  Examples of the diol component constituting the polyester resin in 1) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3. -Aliphatic diols such as butanediol, cycloaliphatic diols such as cyclohexanedimethanol, spiroglycol and isosorbide, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'- Representative examples include diols such as aromatic diols such as bis (4-hydroxyphenyl) fluorene, but are not limited thereto. Moreover, these may be used independently or may be used in multiple types as needed.

  In addition, dihydroxy compounds obtained by adding diols to the hydroxy terminal of the diol component described above are also preferably used. Diols used include ethylene glycol, 1,2-propanediol 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, neopentyl glycol, 1, Aliphatic diols such as 5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′bis (4′-β-hydroxyethoxyphenyl) propane, 1,2-cyclohexane Alicyclic diols such as dimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′- Such as bis (4-hydroxyphenyl) fluorene Such as aromatic diol, and the like. In these diol components, different diols may be added to the two hydroxy ends of the diol, and a plurality of diols may be linked. When a plurality are connected, different diols may be mixed.

  In 2), examples of the compound having a carboxylic acid or a carboxylic acid derivative skeleton and a hydroxyl group in one molecule include oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, and oxyacids thereof. And a dicarboxy compound to which a plurality of is added.

  The polyester resin (A) and the polyester resin (B) used for the polyester film of the present invention can be obtained by polycondensation by appropriately combining the above compounds.

The polyester film of the present invention requires that the polyester resin (B) is dispersed as a dispersion having a flatness of 3 or more in the polyester resin (A) in the polyester layer (P layer), and It is necessary that the polyester film satisfies at least one of the conditions (I) and (II).
(I) The polyester resin (B) has an alicyclic diol component and / or an aromatic diol component as a diol component, and the alicyclic diol component and the aromatic diol component in the polyester layer (P layer). The total content is 0.2 mol% or more and 10 mol% or less with respect to the amount of the diol component in the polyester layer (P layer).
(II) The polyester resin (B) has, as a dicarboxylic acid component, one or more dicarboxylic components selected from the group consisting of an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component, and the polyester layer The total content of the alicyclic dicarboxylic acid component, the isophthalic acid component and the naphthalenedicarboxylic acid component in the (P layer) is 0.2 mol% or more to the amount of the dicarboxylic acid component in the polyester layer (P layer) 10 Must be less than mol%.

  With such a configuration, a polyester film having a small increase in haze due to heat treatment and excellent dimensional stability can be obtained. The mechanism will be described.

  In the polyester film, the main cause of the increase in haze due to heating is mainly due to oligomers contained in the film (for example, in the case of PET film, especially cyclic trimer oligomers). It happens by becoming a fault. A general polyester film is often composed of a crystalline polyester resin. In a polyester film obtained by biaxially stretching such a crystalline polyester resin, a portion where the polyester resin is crystallized by orientation (hereinafter referred to as orientation). Crystallized part) and amorphous part. Here, the oligomer component centering on the cyclic trimer has a high affinity with the amorphous part, and a large amount exists in the amorphous part. This amorphous part is in a thermally unstable state as compared to the oriented crystallized part, and when subjected to heat, the molecular mobility is increased and the system is transferred in a direction in which the energy becomes stable. That is, the amorphous part is transferred to the crystallized part by heat. When such a system transition occurs, the oligomer component centered on the cyclic trimer that has been present inside the amorphous part is excluded to the outside. As a result, the oligomer component precipitates on the film surface and becomes a white defect that increases haze.

  Therefore, in the present invention, an increase in haze at the time of heating is suppressed by providing an amorphous part that is not crystallized by heating inside the film.

  Specifically, by dispersing an amorphous polyester resin (B) satisfying at least one of the above (I) or (II) in the crystalline polyester resin (A), a polyester resin ( The amorphous region consisting of B) is clearly formed. Since this amorphous region is made of an amorphous polyester resin, it hardly crystallizes even when subjected to heat treatment. Therefore, the oligomer component centering on the cyclic trimer can be sufficiently trapped in the amorphous region, and precipitation of the oligomer can be prevented. Further, the region other than the amorphous region is a region made of the crystalline polyester resin (A). The region made of the crystalline polyester resin (A) can be oriented and crystallized by stretching. Therefore, high thermal dimensional stability can be imparted to the film by sufficiently orienting and crystallizing the film by stretching or the like.

  Conventionally, in order to improve oligomer resistance, a method using a low crystalline polyester resin has been used. This method is a method for suppressing thermal crystallization of an amorphous part by using a low crystalline polyester resin for the polyester resin constituting the film. However, on the other hand, oriented crystallization due to stretching or the like is also inhibited, so that it is inevitable that the more the oligomer resistance is improved, the lower the thermal dimensional stability is.

  The polyester resin (A) used in the present invention preferably has crystallinity as described above. By using a resin having crystallinity as the polyester resin (A), it becomes possible to further enhance orientation crystallization by stretching and heat treatment, and as a result, a polyester film having more excellent mechanical strength and dimensional stability can be obtained. . Here, having crystallinity means that the resin is heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN) according to JIS K7122 (1999), In a differential scanning calorimetry chart of 2ndRUN obtained by holding for 5 minutes in the state and then rapidly cooling to 25 ° C. or less and again raising the temperature from room temperature to 300 ° C. at a rate of 20 ° C./min. It is a resin in which an exothermic peak accompanying crystallization is observed. More specifically, it refers to a resin having a crystallization enthalpy ΔHcc determined from the area of the exothermic peak of 1 J / g or more. In the polyester film of the present invention, the polyester resin (A) is preferably a resin having a crystallization enthalpy ΔHcc of 5 J / g or more, more preferably 10 J / g or more, and even more preferably 15 J / g or more. By making the crystallization enthalpy of the polyester resin (A) in the above-mentioned range in the polyester film of the present invention, it becomes possible to further enhance the orientation crystallization by stretching and heat treatment, and as a result, more excellent mechanical strength and dimensional stability. Polyester film.

  Here, specific examples of the polyester resin (A) that can be suitably used in the present invention will be described.

  First, a case where the polyester resin (A) is a polyester resin obtained by the method 1) will be described. In this case, from the viewpoints of crystallinity, heat resistance, and mechanical strength, it is preferable to use an aromatic dicarboxylic acid or an ester-forming derivative thereof as the dicarboxylic acid component constituting the polyester resin. Specifically, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4 ′ -Diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylendanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, diphenic acid, and ester derivatives thereof, trimellitic acid, pyromellitic acid And polyfunctional acids such as ester derivatives thereof are preferably used. Particularly preferred are terephthalic acid and 2,6-naphthalenedicarboxylic acid. Therefore, in the present invention, polyethylene terephthalate (hereinafter sometimes abbreviated as PET), polyethylene-2,6-naphthalenedicarboxylate, polypropylene terephthalate, polybutylene terephthalate and the like obtained using such a dicarboxylic acid component are polyester resins. It is preferable to use as (A).

  Next, the case where the polyester resin (A) is a polyester resin obtained by the method 2) will be described. In this case, it is preferable to use d-lactide as a compound having a carboxylic acid or carboxylic acid derivative skeleton and a hydroxyl group in one molecule. Therefore, in the present invention, it is preferable to use D-polylactic acid obtained by polycondensation of d-lactide as the polyester resin (A).

  By making the polyester resin mentioned above into the polyester resin (A), high crystallinity and mechanical strength can be imparted when the film is formed while maintaining high transparency. Among them, polyethylene terephthalate (PET) is particularly preferable because it is inexpensive and can be used for a wide variety of applications. The melting point of the polyester resin used is preferably 250 ° C. or higher in view of heat resistance, and preferably 300 ° C. or lower in terms of productivity.

  In the polyester resin (A) used in the present invention, a copolymer component may be introduced into the above-described resin in a range where the crystallinity is not lost. The amount of the copolymerization component is not particularly limited, but from the viewpoint of transparency, stretchability, film-forming property, moldability, etc., when using the method 1), both the dicarboxylic acid component and the diol component are the respective components. Preferably, they are 1 mol% or more and 40 mol% or less, More preferably, they are 10 mol% or more and 20 mol% or less.

  Moreover, it is preferable that the intrinsic viscosity of the polyester resin (A) used for this invention is 0.60 or more and 1.0 or less. More preferably, it is 0.62 or more and 0.9 or less, More preferably, it is 0.68 or more and 0.85 or less, Especially preferably, it is 0.70 or more and 0.80. An intrinsic viscosity of 0.60 or less is not preferable because the oligomer component originally contained in the polyester resin (A) increases and the oligomer resistance of the formed film may be lowered. On the other hand, if it exceeds 1.0, it becomes difficult to form a film by stably extruding the resin, or even if it can, a large number of oligomers are generated due to thermal deterioration during melt film formation, and the oligomer resistance of the formed film Is not preferred because it may decrease. By setting the intrinsic viscosity of the polyester resin (A) used in the present invention to 0.60 or more and 1.0 or less, it is possible to impart oligomer resistance while having stable film forming properties.

  The polyester resin (B) is preferably amorphous as described above. By using an amorphous resin as the polyester resin (B), as will be described later, a film having higher oligomer resistance (a film having a small increase in haze due to heat treatment) can be obtained. Here, the term “amorphous” means that the resin is heated from 25 ° C. to 300 ° C. at a temperature rising rate of 20 ° C./min (1stRUN) according to JIS K7122 (1999), and the state In the differential scanning calorimetry chart of 2ndRUN obtained by rapidly cooling to 25 ° C. or less after holding for 5 minutes and then increasing the temperature from room temperature to 300 ° C. at a temperature increase rate of 20 ° C./min. The exothermic peak accompanying this is not observed, or even if it is observed, it is a resin having a crystallization enthalpy of less than 1 J / g.

  Next, specific examples of the polyester resin (B) that can be suitably used in the present invention will be described.

First, the case where the polyester resin (B) is a polyester resin obtained by the method 1) will be described. In this case, polyester having PET, polyethylene-2,6-naphthalene dicarboxylate, polypropylene terephthalate, polybutylene terephthalate, etc. as a basic structure, and a diol component and / or dicarboxylic acid component described below copolymerized in the basic structure. It is preferable to use the resin as the polyester resin (B). Examples of copolymerizable diol components include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, cyclopropanediol, cyclobutanediol, cyclopentadiol, cyclohexanediol, cyclohexanediol, Heptanediol, cyclooctanediol, cyclopropanedimethanol, cyclobutanedimethanol, cyclopentadimethanol, cycloheptanedimethanol, cyclooctanediol, tricyclo (5.2.1.0 ^2.6 ) decanedimethanol, β, β, β Alicyclic diols such as', β'-tetramethyl-2,4,8,10-tetraoxaspiro [5,5] undecane-3,9-diethanol, 2,6-decalindimethanol, spiroglycol, Bisphenol A, 1, - benzene dimethanol, 1,4-benzene dimethanol, 9,9'-bis (4-phenoxyethanol) and aromatic diols such as fluorene. The amount of copolymerization is not particularly limited as long as the condition (I) or (II) is satisfied, but it is 10 mol% or more and less than 100 mol%, more preferably, based on the amount of the diol component of the polyester resin (B). It is 20 mol% or more and less than 100 mol%. By making the amount of copolymerization into such a range, it can be set as the film (film with a small raise of the haze by heat processing) excellent in oligomer resistance.

Examples of the copolymerizable dicarboxylic acid component include adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclopropane dicarboxylic acid, cyclobutane dicarboxylic acid, cyclopentane dicarboxylic acid, cyclohexane dicarboxylic acid, cycloheptane dicarboxylic acid, and cyclooctane dicarboxylic acid. Acid, cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid, cycloheptanedicarboxylic acid, cyclooctanedicarboxylic acid, tricyclo (5.2.1.0 ^2.6 ) decanedicarboxylic acid, β, β, β ′, β ′ -Alicyclic dicarboxylic acids such as tetramethyl-2,4,8,10-tetraoxaspiro [5,5] undecane-3,9-dicarboxylic acid, 2,6-decalin dicarboxylic acid, isophthalic acid component and naphthalenedica Such as carbon acid components. The amount of copolymerization is not particularly limited as long as the condition (I) or (II) is satisfied, but it is more preferably 10 mol% or more and less than 100 mol% with respect to the amount of the dicarboxylic acid component of the polyester resin (B). Is 20 mol% or more and less than 100 mol%. By making the amount of copolymerization into such a range, it can be set as the film (film with a small raise of the haze by heat processing) excellent in oligomer resistance.

  Next, the case where the polyester resin (B) is a polyester resin obtained by the method 2) will be described. In this case, it is preferable to use, as the polyester resin (B), a resin in which D-polylactic acid is a basic component and l-lactide or a copolymerizable diol component / dicarboxylic acid component is copolymerized in the basic component. The amount of copolymerization is not particularly limited as long as the above condition (I) or (II) is satisfied. For example, D-polylactic acid obtained by polycondensation of d-lactide is used as a basic component, and l-lactide is added thereto. When 1-lactide is copolymerized, the copolymerization amount of l-lactide is preferably 1 mol% or more and 99 mol% or less, more preferably 5 mol% or more and 95 mol% or less.

  In the polyester film of the present invention, the polyester resin (B) in the polyester layer (P layer) needs to satisfy at least one of the above conditions (I) or (II). The total content of the diol component and the aromatic diol component is preferably 0.5 mol% or more and 9 mol or less, more preferably 1 mol based on the amount of the diol component in the polyester layer (P layer). % To 9 mol%, more preferably 1.5 mol% to 8 mol%, particularly preferably 2 mol% to 8 mol%. If it is less than 0.2 mol%, the oligomer resistance may be lowered, which is not preferable. If it exceeds 10 mol%, the heat resistance of the film is lowered, and the dimensional change is large when exposed to high temperatures. This is not preferable. In the polyester film of the present invention, by setting the copolymerization component to 0.2 mol% or more and 10 mol% or less, it is possible to obtain a film having a small increase in haze by heat treatment and having excellent dimensional stability.

  The total content of the alicyclic dicarboxylic acid component, isophthalic acid component and naphthalenedicarboxylic acid component in the polyester layer (P layer) is 0 with respect to the amount of the dicarboxylic acid component in the polyester layer (P layer). It is preferably from 5 mol% to 9 mol%, more preferably from 1 mol% to 9 mol%, still more preferably from 1.5 mol% to 8 mol%, particularly preferably from 2 mol% to 8 mol%. It is as follows. If it is less than 0.2 mol%, the oligomer resistance may be lowered, which is not preferable. If it exceeds 10 mol%, the heat resistance of the film is lowered, and the dimensional change is large when exposed to high temperatures. This is not preferable. In the polyester film of the present invention, by setting the copolymerization component to 0.2 mol% or more and 10 mol% or less, it is possible to obtain a film having a small increase in haze by heat treatment and having excellent dimensional stability.

  In addition, in the polyester film of the present invention, in order to disperse the polyester resin (B) in the polyester resin (A), the polyester resin (B) is converted to the polyester under a state where the transesterification reaction does not occur as much as possible. It can carry out by mixing with resin (A). As a specific method thereof, (1) a method of adding a compound having a function of inhibiting a transesterification reaction (hereinafter referred to as a transesterification inhibitor), (2) a polyester resin having low compatibility with the polyester resin (A) is polyester. Examples thereof include a method used as the resin (B), (3) a method using the method (1) and the method (2) in combination. Here, examples of the compound having a function of inhibiting the transesterification reaction in the method (1) are represented by monostearyl phosphate, distearyl phosphate, a mixture of monostearyl phosphate and distearyl phosphate, and the like. Examples thereof include alkyl phosphoric acid and ester compounds thereof. Alkyl phosphoric acid and these ester-derived compounds have a catalyst deactivation effect of the polymerization catalyst contained in the film. By deactivating the polymerization catalyst, the ester exchange reaction between the polyester resin (A) and the polyester resin (B) As a result, the polyester resin (B) can be more easily dispersed as a dispersion in the polyester resin (A). The addition amount of the transesterification inhibitor added to the film is preferably 0.01% by weight or more and 2% by weight or less, more preferably 0.02% by weight or more and 1% by weight or less, still more preferably, with respect to the entire P layer. Is 0.03% by weight or more and 1% by weight or less, particularly preferably 0.05% by weight or more and 0.5% by weight or less. In the polyester film of the present invention, if the transesterification inhibitor is less than 0.01% by weight, the effect of inhibiting transesterification is insufficient, and it is difficult to disperse the polyester resin (B) in the polyester resin (A). Become. As a result, the oligomer trapping ability is lowered, and an increase in haze due to heat treatment may be increased, or dimensional stability may be lowered. On the other hand, if it exceeds 2% by weight, thermal degradation of the polyester resin (A) and the polyester resin (B) is promoted and melt film formation may not be possible. Moreover, even if the melt can be formed, the oligomer resistance and mechanical strength of the resulting film may be significantly reduced, or the transesterification inhibitor may bleed out and the transparency of the film may be impaired. . In the polyester film of the present invention, by adding the transesterification inhibitor in an amount of 0.01% by weight or more and 2% by weight or less, the polyester resin (B) is replaced with the polyester resin (B) while maintaining the mechanical strength and transparency. A) can be dispersed in the polyester film, and as a result, a polyester film having a small increase in haze due to heat treatment and excellent dimensional stability can be obtained.

  The method (2) uses a combination of polyester resins having low compatibility, and forcibly kneads them by, for example, applying high shear so that the polyester resin (B) is added to the polyester resin (A). This is a method of dispersion.

  For example, when polyethylene terephthalate is used as the polyester resin (A), it is preferable to use a polyester resin satisfying at least one of the following (I ′) or (II ′) as the polyester resin (B).

  (I ′) The polyester resin (B) has an alicyclic diol component and / or an aromatic diol component, and the polyester resin (B) has a content of the alicyclic diol component and the aromatic diol component. Resin whose sum total is 35 mol% or more with respect to the quantity of the diol component in this polyester resin (B). The total content is preferably 40 mol% or more. Although an upper limit is not specifically defined, It is preferable that it is 95 mol% or less from the point of the dispersibility to a polyester resin (A).

  (II ′) The polyester resin (B) has one or more dicarboxylic components selected from the group consisting of an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component, and in the polyester resin (B) Resin whose sum total of content of this alicyclic dicarboxylic acid component, this isophthalic acid component, and this naphthalene dicarboxylic acid component is 40 mol% or more with respect to the quantity of the dicarboxylic acid component in this polyester resin (B). The total content is preferably 45 mol% or more. Although an upper limit is not specifically defined, It is preferable that it is 95 mol% or less from the point of the dispersibility to a polyester resin (A).

  In addition, when employ | adopting the method of said (3) (method which combined the method of (1), and the method of (2)), as polyester resin (B), not only the above-mentioned thing but following (I ' A polyester resin satisfying at least one of ') and (II' ') can also be preferably used.

  (I ″) The polyester resin (B) has an alicyclic diol component and / or an aromatic diol component, and the polyester resin (B) contains the alicyclic diol component and the aromatic diol component. Is a resin having a total of 10 mol% or more based on the amount of the diol component in the polyester resin (B). The total content is preferably 40 mol% or less.

  (II ′) The polyester resin (B) has one or more dicarboxylic components selected from the group consisting of an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component, and the polyester resin (B) Resin in which the total content of the alicyclic dicarboxylic acid component, the isophthalic acid component and the naphthalenedicarboxylic acid component is 15 mol% or more and 40 mol% or less with respect to the amount of the dicarboxylic acid component in the polyester resin (B) .

  Moreover, in the polyester film of the present invention, when using PET as the polyester resin (A), as a more preferable copolymer component as the polyester resin (B), from the viewpoint of the effect of preventing the oligomer precipitation of the formed polyester film, The diol component is preferably an alicyclic diol, and the dicarboxylic acid component is preferably an alicyclic dicarboxylic acid. More preferably, cyclohexane dimethanol is particularly suitable as the diol component and cyclohexane dicarboxylic acid is particularly suitable as the dicarboxylic acid component from the viewpoint of the price of the monomer and the transparency of the formed film.

  In the polyester film of the present invention, the content of the polyester resin (B) in the polyester layer (P layer) is preferably 0.5% by weight or more and 15% by weight or less with respect to the entire P layer. More preferably, it is 0.8 to 12 weight%, More preferably, it is 1 to 10 weight%. If the content of the polyester resin (B) is less than 0.5% by weight, the oligomer trapping ability is insufficient, and it is not preferable because it whitens after the heat treatment, and if it exceeds 15% by weight, the heat resistance of the film decreases. The dimensional change may become large when exposed to high temperatures. In the polyester film of the present invention, by making the content of the polyester resin (B) 0.5% by weight or more and 15% by weight or less, the film has a small increase in haze due to heat treatment and has dimensional stability. be able to.

  In the present invention, it is necessary that the polyester resin (B) is dispersed as a dispersion having a flatness of 3 or more in the polyester layer (P layer).

The flatness of the dispersion here refers to the ratio a / d between the average thickness d in the film thickness direction of the dispersion and the major axis length a of the main surface, and the following procedures (1) to (7) Is required.
(1) Using a microtome, a thin film slice-like observation sample is produced without crushing the film cross section in the thickness direction. Samples are prepared in two types: a MD cross-section thin film section cut in a direction parallel to the longitudinal direction (MD) direction of the film and a TD cross-section thin film section cut in a direction parallel to the width direction (TD) direction.
(2) Obtain an image obtained by magnifying and magnifying the obtained MD cross-sectional thin film section at 100000 times using a transmission electron microscope (TEM) (transmission electron microscope “H-7100FA” manufactured by Hitachi, Ltd.). The observation place shall be determined randomly within the polyester layer (P layer). Further, when it is difficult to discriminate the dispersion in the image, the film is dyed in advance using osmium acid, ruthenium oxide or the like as appropriate. Note that the thickness direction of the film and the vertical direction of the image are made to coincide. Further, when the dispersion does not enter at 100000 times, an image obtained by shifting the observation position is obtained, and the images are joined together without any gap to obtain an observation image.
(3) The average thickness and major axis length in the film thickness direction are determined for the dispersion of the polyester resin (B) in the polyester layer (P layer) confirmed in the image. Here, the major axis length is the length of a line segment when a line segment A connects from one end (left end) to the other end (right end) of the dispersion in a direction parallel to the film surface direction. The average thickness in the film thickness direction is the line segment C from one end (upper end) to the other end (lower end) of the dispersion passing through the midpoint B of the line segment A and perpendicular to the line segment A. It is the length of the line segment when tied with. The same operation is performed on at least 20 dispersions observed in the image, and the average thickness and major axis length in the MD thickness direction and the TD cross section in the MD cross section and the TD cross section, respectively, are obtained.
(4) Randomly change the film cutting location, perform the same operations as (1) to (3) 10 times in total, and use the average value of the major axis length obtained for each to determine the length in the final MD section. Get the axial length. Similarly, let the average value of the average thickness of a film thickness direction be the average thickness dMD of the film thickness direction in the final MD cross section.
(5) The TD cross-section thin film slice is also measured in the same manner as the MD cross-section thin film slice, and the major axis length in the final TD cross section and the average thickness in the film thickness direction in the final TD cross section are obtained.
(6) The longer major axis length a in the final MD cross section and the average thickness in the film thickness direction in the final TD cross section is the final major axis length a, and the film at that time The average thickness in the thickness direction is defined as the final average thickness d.
(7) The value (a / d) obtained by dividing the major axis length a obtained in (6) above by the average thickness d in the film thickness direction is defined as the flatness of the dispersion.

  In the polyester film of the present invention, the flatness obtained by the above-described method is more preferably 5 or more, further preferably 8 or more, and particularly preferably 10 or more. In the polyester film of the present invention, by dispersing the polyester resin (B) as a dispersion having a flatness of 3 or more in the polyester layer (P layer), a high oligomer trapping ability is expressed even with a smaller content, and heat treatment It is possible to further reduce the increase in haze.

  Here, in order to set the flatness to 3 or more, a sheet formed by dispersing the polyester resin (B) in the polyester resin (A) is 1 ′) the area stretch ratio is 1.5 times or more. Examples of such a method include uniaxial or biaxial stretching, 2 ′) rolling in the thickness direction so that the rolling rate is 90% or more, and 3 ′) using 1 ′) and 2 ′) in combination. Details of the method 1 ') will be described later. The area magnification is obtained by multiplying the draw ratio of the first axis by the draw ratio of the second axis. In the method 2 '), the rolling ratio (%) is obtained by dividing the thickness after rolling by the thickness before rolling and multiplying by 100.

  Further, in the polyester film of the present invention, in order to increase the flatness, 1 ") increase the area stretch ratio or the rolling rate, and in addition, 2") the polyester resin (B) in the polyester resin (A). 3 ") a method of reducing the glass transition temperature difference between the polyester resin (A) and the polyester resin (B), 4") a method using at least two of the above 1 ") to 3 '), etc. Is preferably used.

  In addition, although there is no restriction | limiting about the upper limit of flatness, it is 100 or less substantially from the point of the limit draw ratio of a polyester resin (A).

  That is, in the present invention, the dispersion form of the polyester resin (B) dispersed in the polyester layer (P layer) is a disc shape (including an elliptical disc), and the main surface of the disc-like dispersion is substantially the same as the film surface. Parallel is preferable. By forming the disk-like dispersion substantially parallel to the film surface, it is possible to efficiently trap the oligomer generated from the inside of the film and moving to the surface side, and the content of the polyester resin (B) is small. However, the increase in haze due to the heat treatment can be reduced.

  Here, “substantially parallel” means that the angle θ formed by the plane direction of the film and the main surface of the longitudinal disc-shaped dispersion is within 0 ± 15 °. More preferably, θ is within 0 ± 10 °, and further preferably θ is within 0 ± 5 °. By setting it as this range, it becomes possible to express high oligomer resistance.

  In the present invention, the average thickness d in the film thickness direction of the dispersion of the polyester resin (B) is preferably 1 nm or more and 200 nm or less. More preferably, they are 2 nm or more and 100 nm or less, More preferably, they are 3 nm or more and 50 nm or less, Especially preferably, they are 3 nm or more and 25 nm or less. If the average amount of the dispersion of the polyester resin (B) in the film thickness direction of the dispersion is less than 1 nm, the oligomer trapping capability is insufficient and whitening occurs after the heat treatment. This is not preferable because the properties may be greatly reduced and the unevenness in the surface of the oligomer resistance may increase.

  Here, in order to make the thickness d in the above range, the polyester resin (B) in the polyester resin (A) has a dispersion diameter of 3 μm or less, more preferably 1 μm or less, and even more preferably 500 nm or less. What was made into the sheet | seat by disperse | distributing to can be obtained by extending | stretching and compressing. The area stretch ratio and the rolling rate at this time may be appropriately adjusted according to the dispersion diameter of the polyester resin (B).

  In the polyester film of the present invention, by setting the average thickness d in the average film thickness direction of the dispersion in such a range, even if the content of the polyester resin (B) is the same amount, it is contained in a more finely dispersed state. Therefore, the oligomer trapping ability can be imparted uniformly in the film plane without impairing the transparency of the film.

  Moreover, various additives can be added to the polyester film of the present invention within a range where the effects of the present invention are not lost. Examples of additives that can be added and blended include, for example, organic fine particles, inorganic fine particles, dispersants, dyes, fluorescent brighteners, antioxidants, weathering agents, antistatic agents, mold release agents, thickeners, Examples include plasticizers, pH adjusters, and salts.

  Moreover, the polyester film or polyester layer (P layer) of the present invention may be oriented (stretched) in a uniaxial or biaxial direction. By orientation crystallization by stretching or the like, not only can the film have high mechanical strength and high dimensional stability, but the polyester resin (B) dispersed in the polyester resin (A) at the time of stretching is co-stretched, The polyester resin (B) can be made into a disk-like dispersion whose main surface is substantially parallel to the film surface direction, and as a result, a high oligomer trapping ability can be imparted even when added in a small amount.

  Moreover, the thickness of the polyester film of the present invention is not particularly limited, and an appropriate film thickness can be selected depending on the use, but generally it is preferably 1 μm or more and 500 μm or less. If the film thickness is less than 1 μm, tearing may easily occur during film formation. Moreover, when film thickness exceeds 500 micrometers, it may become difficult to wind up a film in roll shape.

Moreover, the polyester film of this invention may be formed only by the polyester layer (P layer) which satisfy | fills the above-mentioned requirements, and may be a laminated structure with another another layer. That is, another layer (for example, a polyester layer (P2 layer)) may be laminated on one side or both sides of the polyester layer (P layer) in which the polyester resin (B) is dispersed in the polyester resin (A). Furthermore, when the polyester layer (P2 layer) is laminated, the polyester layer (P layer) is positioned on the outermost layer, in particular, the polyester layer (P layer) that satisfies the above-described requirements is positioned on both side surface layers. A laminated structure having a polyester layer (P2) layer is more preferable in that the oligomer trapping effect by the polyester layer (P layer) is efficiently expressed, and the oligomer resistance is superior. In that case, it is preferable that the thickness of the said polyester layer (P layer) is 2% or more with respect to the thickness of the whole film, More preferably, it is 5% or more, More preferably, it is 8% or more. If it is less than 2%, the oligomer resistance may be inferior.
Moreover, when setting it as a laminated structure, it is preferable to use resin which has a polyethylene terephthalate as a main structural component as a polyester resin (A2) which comprises a polyester layer (P2 layer). By adopting such a configuration, it is possible to further improve transparency and thermal dimensional stability while maintaining oligomer resistance.

  In the polyester film of the present invention, the intrinsic viscosity [IVp] of the polyester layer (P layer) is preferably from 0.55 to 0.85 from the viewpoint of oligomer resistance and thermal dimensional stability. More preferably, they are 0.58 or more and 0.80 or less, More preferably, they are 0.60 or more and 0.75 or less. Moreover, in the case of a laminated structure, [IVp] is more preferably 0.65 or more, and further preferably 0.68 or more, from the viewpoint that the oligomer resistance can be further improved.

  When the polyester film of the present invention has a laminated structure, the difference [IVp]-[IVp2] between the intrinsic viscosity [IVp] of the polyester layer (P layer) and the intrinsic viscosity [IVp2] of the polyester layer (P2 layer) is 0. It is preferably 0.15 or less. When [IVp]-[IVp2] is larger than 0.15, the lamination interface is disturbed when the co-extrusion is carried out, and it is easy to break in the stretching process starting from the disturbance, so that stable film formation becomes difficult. Moreover, when [IVp]-[IVp2] is 0 or less, the intrinsic viscosity [IVp] of the polyester layer (P layer) becomes too low and the oligomer resistance decreases, or the polyester of the polyester layer (P2 layer) As a result of the molecular weight of the resin (A2) becoming too high and orientation crystallization by stretching becoming difficult, the thermal dimensional stability of the entire film may be deteriorated. In the polyester film of the present invention, [IVp]-[IVp2] can achieve both film forming properties, oligomer resistance, and thermal dimensional stability.

  The polyester film of the present invention has the above structure, and the total light transmittance is preferably 80% or more. The total light transmittance here is a value measured based on JIS-K7361 (1997 edition), and is the total light transmittance at a film thickness of 50 μm. More preferably, the total light transmittance is 85% or more, and still more preferably the total light transmittance is 88% or more.

  Further, in the polyester film of the present invention, the initial haze H0 is not particularly limited, but is preferably 3% or less particularly in applications requiring transparency of the film such as optical applications. The haze here is a value measured based on JIS-K7136 (2000 version) and is a haze at a film thickness of 50 μm. The initial haze is a term for distinguishing from the haze H1 of the film after heat treatment at 160 ° C. for 1 hour after film formation, which will be described later, and is not subjected to heat treatment exceeding 50 ° C. after film formation. Point to haze.

  The initial haze H0 is more preferably 2.5% or less, still more preferably 2.0% or less. Conventional processing steps can be applied by controlling the haze to 3% or less, and a polyester film applicable to optical applications can be obtained.

  Here, as a method of setting the initial haze H0 in the above range, a method of finely dispersing the polyester resin (B) in the polyester resin (A), an average thickness d in the film thickness direction of the dispersion of the polyester resin (B) And a method of reducing the refractive index difference between the polyester resin (A) and the polyester resin (B).

  Moreover, it is preferable that the difference (H1-H0) of the initial haze H0 and the haze H1 after heat-processing at 160 degreeC for 1 hour is 3% or less. More preferably, it is 2.5% or less, More preferably, it is 2.0% or less. By setting H1-H0 to 3% or less, transparency is not impaired, and the generated oligomer does not cause process contamination. In addition, the function of the functional layer can be sufficiently exhibited without causing defects during the formation of the functional layer due to the generated oligomer.

  Here, in order to make H1-H0 within the above range, it can be achieved by copolymerizing the polyester resin (B) with an alicyclic diol and / or an alicyclic dicarboxylic acid component.

  The polyester film of the present invention preferably has a melting point Tm obtained by differential scanning calorimetry (hereinafter referred to as DSC) of 245 ° C. or more and 265 ° C. or less. The melting point Tm here is the melting point Tm in the temperature raising process (temperature rising rate: 20 ° C./min) obtained by DSC, and from 25 ° C. to 300 ° C. by the method based on JIS K-7121 (1999). Heat at a heating rate of 20 ° C / min (1stRUN), hold in that state for 5 minutes, then rapidly cool to 25 ° C or less, and again increase from room temperature to 300 ° C at a heating rate of 20 ° C / min. The melting point Tm of the polyester film is defined as the peak top temperature of the 2ndRun crystal melting peak obtained. More preferably, the melting point Tm is 247 ° C. or higher and 262 ° C. or lower, more preferably 250 ° C. or higher and 260 ° C. or lower. If the melting point Tm is less than 245 ° C, the film may be inferior in heat resistance, and if the melting point Tm exceeds 265 ° C, extrusion may be difficult, which is not preferable. By making melting | fusing point Tm into 245 degreeC or more and 265 degrees C or less in the polyester film of this invention, it can be set as the polyester film which was compatible with heat resistance and workability.

  Here, in order to make melting | fusing point Tm in the said range, it can achieve by using what copolymerized the diol component and dicarboxylic acid component which were mentioned above as a polyester resin (B).

  The polyester film of the present invention preferably has a heat shrinkage rate of 1% or less when heat-treated at 150 ° C. for 30 minutes. By setting the heat shrinkage rate within the above range, a polyester film excellent in processability and flatness can be obtained when used in a state exposed to high temperature conditions. More preferably, it is 0.8% or less, More preferably, it is 0.5% or less.

  Here, in order to set the thermal shrinkage rate within the above range, the polyester film can be obtained by controlling the melting point Tm of the polyester film within the above range, followed by stretching and heat treatment by the above method. In addition, by adopting a laminated structure in which the intrinsic viscosity [IVp] of the polyester layer (P layer) and the intrinsic viscosity [IVp2] of the polyester layer (P2 layer) have the above-described relationship, a high oligomer resistance is exhibited, It becomes possible to further reduce the shrinkage rate.

  Further, the polyester film of the present invention preferably has a transmission b value of 0.5 or less, more preferably 0.3 or less. When the transmission b value is 0.5 or less, particularly in the case of optical film use, when the film is attached to the surface of the display device, the film is not deteriorated or discolored, and the film is used for the display device. When incorporated inside, it can be suitably used without impairing the color balance. The transmission b value is preferably −0.5 or more. If it is less than -0.5, the film will appear blue-black. If such a film is affixed to the surface of the display device, it will give a dark impression, and if the film is incorporated inside the display device, the balance of color and brightness may be impaired. It is not preferable because of its properties.

  Here, in order to make the transmission b value within the above range, the polyester resin (A) is processed into a sheet at a temperature of the melting point + 20 ° C. or lower in a nitrogen atmosphere using a resin controlled in the above color tone range. A method, a method of correcting the color tone using a fluorescent brightening agent, and the like are preferably used.

  The polyester film of the present invention includes an easy-adhesive layer for improving adhesion to coating agents, vapor deposition materials, etc. used in various processing steps, an easy-slip layer for improving the slipperiness of the film, A layer (functional layer) having another function such as a hard coat layer, an ultraviolet resistant layer for imparting ultraviolet resistance, and a flame retardant layer for imparting flame resistance may be provided in order to enhance impact properties.

  The component constituting the functional layer is not particularly limited as long as it has adhesiveness to the polyester film as the base layer, and is not particularly limited. For example, the component constituting the functional layer is an organic material. When the main component is a polyester resin, a polycarbonate resin, an epoxy resin, an alkyd resin, an acrylic resin, a urea resin, a urethane resin, or the like can be suitably used. Further, two or more different resins, for example, a polyester resin and a urethane resin, a polyester resin and an acrylic resin, or a urethane resin and an acrylic resin may be used in combination. Polyester resins, acrylic resins, and urethane resins are preferable, and polyester resins are particularly preferable.

  When such a functional layer contains a resin as a main component, it is preferable to use various crosslinking agents in combination with the above resin. By using a cross-linking agent in combination, it is possible to drastically improve moisture-resistant adhesion as well as heat-resistant adhesion. As a crosslinking agent used for the functional layer, when a crosslinkable functional group is copolymerized with a polyester resin, a urethane resin, or an acrylic resin, it is particularly preferable to use a crosslinking agent in combination. The resin constituting the functional layer and the crosslinking agent can be mixed and used at an arbitrary ratio. However, the crosslinking agent is 0.2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the resin in terms of improving adhesiveness. More preferably, it is 0.5 to 15 parts by weight, and particularly preferably 1 to 10 parts by weight. When the addition amount of the crosslinking agent is less than 0.2 parts by weight, the effect of the addition is small, and when it exceeds 20 parts by weight, the function as a functional layer (for example, adhesiveness) tends to decrease.

  In addition, it is preferable to add inorganic and organic fine particles in the functional layer in order to impart easy slipping and blocking resistance. In this case, the inorganic fine particles to be added include, for example, gold, silver, copper, platinum, palladium, rhenium, vanadium, osmium, cobalt, iron, zinc, ruthenium, praseodymium, chromium, nickel, aluminum, Metals such as tin, zinc, titanium, tantalum, zirconium, antimony, indium, yttrium, lanthanum, zinc oxide, titanium oxide, cesium oxide, antimony oxide, tin oxide, indium tin oxide, yttrium oxide, lanthanum oxide, zirconium oxide , Metal oxides such as aluminum oxide and silicon oxide, lithium fluoride, magnesium fluoride, aluminum fluoride, metal fluorides such as cryolite, metal phosphates such as calcium phosphate, carbonates such as calcium carbonate, barium sulfate Etc. Salts, and the like can be used other talc and kaolin. The organic fine particles are incompatible with the silicone resin, crosslinked fine particles such as crosslinked styrene, crosslinked acrylic, and crosslinked melamine, as well as the thermoplastic resin that constitutes the coating layer. The thermoplastic resin to be used can also be used as fine particles. The average particle size of the fine particles used is preferably from 0.001 μm to 5 μm, more preferably from 0.005 μm to 3 μm, particularly preferably from 0.01 μm to 2 μm, and still more preferably from 0.02 μm to 2 μm. The mixing ratio of the fine particles with respect to 100 parts by weight of the resin in the functional layer is not particularly limited, but is preferably 0.05 μm or more and 10 parts by weight or less, and more preferably 0.1 μm or more and 5 parts by weight or less in terms of solid content.

  In the functional layer, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic lubricant, a pigment, and a dye may be used as long as the effects of the present invention are not impaired. Further, a filler, an antistatic agent, a nucleating agent and the like may be blended.

  Next, although an example is demonstrated about the manufacturing method of the polyester film of this invention, this invention is not limited only to this example.

  The polyester resin used for the polyester film of the present invention can be obtained, for example, by subjecting a dicarboxylic acid component such as terephthalic acid or a derivative thereof and a diol component such as ethylene glycol to a transesterification reaction by a known method. In addition, as a method for causing the polyester resin (B) to contain an aliphatic diol component, an aromatic diol component, an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component as a copolymerization component, Polymerizing alicyclic diol components and aromatic diol components by adding alicyclic dicarboxylic acid components, isophthalic acid components, and naphthalenedicarboxylic acid components (or their ester derivatives) as dicarboxylic acid components. Can be obtained. As the polyester resin (B), “PET-G 6763” (PET in which 33 mol% of 1,4 cyclohexane dimethanol is copolymerized with respect to the total amount of the diol component) and the like are also preferably used. be able to.

  In addition, a conventionally known reaction catalyst (polymerization catalyst) (alkali metal compound, alkaline earth metal compound, zinc compound, lead compound, manganese compound, cobalt compound, aluminum compound, antimony compound, titanium compound, etc.) may be used for the polymerization. good. Furthermore, you may add a phosphorus compound etc. as a color tone regulator. More preferably, an antimony compound, a germanium compound, or a titanium compound is added as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is. Next, a method for obtaining the sheet of the present invention from the polyester resin will be described.

  In the case where the polyester film of the present invention has a single film structure consisting only of the polyester layer (P layer) in which the polyester resin (B) is dispersed in the polyester resin (A), the polyester resin (A) and the polyester resin dried as necessary A method (melt casting method) in which (B) is heated and melted in an extruder, extruded from a die onto a cast drum cooled, and processed into a sheet shape can be used. As another method, the polyester resin (A) and the polyester resin (B) are dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is removed from the film layer. It is also possible to use a method (solution casting method) or the like in which the material is dried and removed to be processed into a sheet shape.

  Moreover, the manufacturing method in the case where the film has a laminated structure including a polyester layer (P layer) and another layer (for example, a polyester layer (P2 layer)) is mainly composed of a thermoplastic resin as a material of each layer to be laminated. In this case, the raw materials for each layer are put into separate extruders, melted and coextruded onto a cast drum cooled from the die and processed into a sheet (coextrusion method), coated on a sheet made of a single film Layer material is put into an extruder, melt extruded and laminated while extruding from the die (melt laminating method), and the polyester layer (P layer) and the material to be laminated are prepared separately and heated by a heated roll group, etc. A method of pressure bonding (thermal lamination method), a method of bonding with an adhesive (adhesion method), and other materials for forming the material to be laminated are dissolved in a solvent, and the solution is prepared in advance. And a method of coating on a polyester layer was (coating method), and a method in which a combination of these can be used.

  In addition, when the material to be laminated is not a thermoplastic resin, the polyester layer and the material to be laminated are prepared separately and bonded together via an adhesive (adhesion method), or in the case of a curable material, the polyester layer The method of hardening by electromagnetic wave irradiation, heat processing, etc. after apply | coating on can be used.

  Further, when the polyester film of the present invention is a uniaxial or biaxially oriented film, as a preferred production method, first, raw materials are charged into an extruder (a plurality of extruders in the case of a laminated structure) and melted to form a die. The film is extruded (co-extruded in the case of a laminated structure), and cooled and solidified by static electricity on a cooled drum cooled to a surface temperature of 10 ° C. or higher and 60 ° C. or lower to produce an unstretched (unoriented) film.

  This unstretched film is led to a group of rolls heated to a temperature of 70 ° C. or higher and 140 ° C. or lower, stretched 3 to 4 times in the longitudinal direction (longitudinal direction, that is, the film traveling direction), and 20 to 50 ° C. It cools with the roll group of the following temperature, and obtains a uniaxial stretching (uniaxial orientation) film.

  Subsequently, while holding both ends of the uniaxially stretched film with clips, the film is guided to a tenter and heated in a temperature of 80 ° C. or higher and 150 ° C. or lower in a direction perpendicular to the longitudinal direction (“width direction” or “lateral direction”). It may be called “3” or more and 4 times or less. Thereby, the polyester resin (B) dispersed in the polyester resin (A) is also co-stretched to form a disk-like dispersion.

  The stretching ratio is 3 to 5 times in each of the longitudinal direction and the width direction, and the area ratio (vertical stretching ratio × lateral stretching ratio) is preferably 9 to 15 times. When the area magnification is less than 9 times, the strength of the obtained biaxially stretched film becomes insufficient. Conversely, when the area magnification exceeds 15 times, the film tends to be broken during stretching.

  As the biaxial stretching method, in addition to the sequential biaxial stretching method in which the stretching in the longitudinal direction and the width direction is separated as described above, the simultaneous biaxial stretching method in which the stretching in the longitudinal direction and the width direction is performed simultaneously. Either one does not matter.

  In order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and dimensional stability, it is preferably 1 at a temperature not lower than the melting point of the glass transition temperature Tg of the resin that is preferably a raw material in the tenter. A heat treatment is performed for at least 30 seconds and not more than 30 seconds, and after uniform cooling, it is cooled to room temperature.

  Moreover, in the said heat processing process, you may perform the relaxation process of 3% or more and 12% or less in the width direction or a longitudinal direction as needed.

  Next, as a method of forming a layer having a different function (functional layer) on the polyester film of the present invention, a vapor deposition method, a dry method such as a sputtering method, a wet method such as a plating method, or a plurality of extruders are used. , Polyester film raw material and functional layer raw material are melted in separate extruders and co-extruded on a cast drum cooled from the die (co-extrusion method), produced as a single film The raw material for the functional layer is put into an extruder and melt-extruded and laminated while extruding from the die (melt laminating method), the polyester film and the functional layer are prepared separately, and heated by a group of rolls, etc. A method of thermocompression bonding (thermal lamination method), a method of bonding via an adhesive (adhesion method), and other functional layer raw materials are dissolved in a solvent, and the solution is applied. A method of coating on a polyester film which had been beforehand prepared (coating method), and can be a method in which a combination of these is used.

  Here, among these methods described above, the coextrusion method and the coating method, which are easy to form the functional layer to be formed, are more preferable forming methods.

  As a method of forming the functional layer on the polyester film by the coextrusion method, using a plurality of extruders, the polyester film raw material and the functional layer raw material are melted in separate extruders and coextruded from the die, A sheet having a functional layer formed on the polyester film of the present invention can be obtained by tightly cooling and solidifying by static electricity on a drum cooled to a surface temperature of 10 ° C. or more and 60 ° C. or less.

  When the polyester film of the present invention is a uniaxially or biaxially stretched (oriented) film, an unstretched sheet in which the functional layer raw material and the polyester film raw material are laminated is the same as that described above. By extending | stretching by a method, the sheet | seat by which the whole was biaxially oriented can be obtained at a stretch, laminating | stacking a functional layer.

  In addition, as a method of forming a functional layer on the polyester film of the present invention by a coating method, an in-line coating method that is applied during the formation of the polyester film and an offline coating method that is applied to the polyester film after the formation are listed. Either can be used, but an in-line coating method is preferably used because it is more efficient at the same time as the polyester film and has high adhesion to the polyester film. Further, when coating, corona treatment or the like is preferably performed on the surface of the polyester film from the viewpoint of improving the wettability of the coating liquid onto the support and improving the adhesive strength.

  As a method for forming the functional layer on the polyester film by the coating method, a means for applying and drying a coating solution obtained by dissolving / dispersing the material constituting the functional layer in a solvent on the polyester film is preferably used. . In this case, the solvent to be used is arbitrary, but in the in-line coating method, it is preferable to use water as a main component from the viewpoint of safety. In that case, a small amount of an organic solvent that dissolves in water may be added in order to improve applicability and solubility. Examples of such organic solvents include aliphatic or alicyclic alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol, diols such as ethylene glycol, propylene glycol, and diethylene glycol, methyl cellosorb, Diol derivatives such as ethyl cellosolve propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as methyl acetate, ethyl acetate and amyl acetate, ketones such as acetone and methyl ethyl ketone, amides such as N-methylpyrrolidone Etc. and mixtures thereof may be used, but are not limited to these.

  In addition, when the functional layer is mainly composed of an inorganic material, among these methods described above, it is easy to control the formed functional layer and has excellent adhesion and uniformity to the base material, and a sputtering method and sputtering. A dry method such as a method is a more preferable forming method.

  As a method of forming a functional layer by a dry method, resistance heating vapor deposition, electron beam vapor deposition, induction heating vapor deposition, and vacuum vapor deposition methods such as plasma or ion beam assist method, reactive sputtering method, ion beam sputtering method, Sputtering methods such as ECR (electron cyclotron) sputtering, physical vapor deposition methods such as ion plating (PVD method), chemical vapor deposition methods using heat, light, plasma, etc. (CVD method), etc. Can be mentioned. When the functional layer is formed by the PVD method, it is preferable to increase the degree of vacuum in the system when the pressure is reduced before volatilization. By increasing the degree of vacuum in the system, it is possible to form an A layer that is dense and has few defects, and the functional layer can be formed uniformly.

  When the material constituting the functional layer is an organic / inorganic composite conductive material, it can be formed by appropriately selecting from the above-described manufacturing methods depending on the type, composition, and the like of the material used.

  The polyester film of the present invention can be formed by the above-mentioned process, and the obtained film has excellent transparency as compared with the conventional film, and the precipitation of oligomer is small after the processing process, resulting in an increase in haze. Is small. The polyester film of the present invention can be applied to various uses that take advantage of this feature. For example, base films for various optical sheets such as prism lens sheets, diffuser plates, touch panels, and AR (anti-reflection) films, photographs Suitable for various film materials such as various industrial films for film, solar cell, mold release, process, electrical insulation, electronic material, laminating, etc. Can be used.

[Characteristic evaluation method]
A. Flatness and average thickness d of the polyester resin (B)
According to the method described above, the flatness and average thickness d of the polyester resin (B) were determined.

B. Total light transmittance The total light transmittance of the polyester film in the film thickness direction was measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Co., Ltd.). In addition, in the film surface, it measured by changing 5 places or more, and it was set as the total light transmittance with the average value. Moreover, it calculated | required about both surfaces of the polyester film, and made it the transmittance | permeability of the polyester film with a lower numerical value.

C. Initial haze H0
The haze in the film thickness direction of the polyester film was measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Co., Ltd.). In addition, in the film surface, it measured by changing five places or more, and it was set as the initial stage haze H0 by the average value. Moreover, it calculated | required about both surfaces of the polyester film, and made it the initial stage haze H0 of the polyester film with a lower numerical value.

D. Difference between initial haze H0 and haze H1 after heat treatment at 160 ° C. for 1 hour (H1−H0)
A 200 mm × 150 mm size polyester film was heat-treated at 160 ± 3 ° C. for 1 hour, and the haze of the treated film was measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Co., Ltd.). In the film plane, the measurement was carried out by changing the location at 5 or more locations, and the average value was used as the haze H1 after the treatment. The obtained haze H1 and C.I. The difference (H1−H0) in the initial haze H0 obtained in the above was obtained.

E. Thermal shrinkage when heat-treated at 150 ° C. for 30 minutes Polyester film was cut into strips with a width of 1 cm and a length of 15 cm, and lines parallel to the width direction were drawn 2.5 cm inside from both ends in the length direction. The distance L0 between the parallel lines of the book was accurately measured. Next, the strip sample was heat-treated in a hot air oven at 150 ° C. for 30 minutes, and after cooling, the distance L1 between the two parallel lines was accurately measured. The thermal shrinkage rate (%) was calculated from the dimension before treatment and the dimension after treatment by the following formula.
Thermal contraction rate (%) = (L0−L1) / L0 × 100
In the measurement, when the length direction of the strip is parallel to the film MD direction and when parallel to the film TD direction, 10 samples are measured for each, and the thermal contraction rate in the MD direction with each average value, TD The heat shrinkage rate in the direction was taken.
The average of the obtained MD and TD heat shrinkage rates was used as the heat shrinkage rate of the present film, and was determined as follows. When thermal shrinkage is 0.5% or less: S
When 0.5% and 0.8% or less: A
If 0.8% and less than 1%: B
If it exceeds 1%: C
It was. In the case of S or A or B, the heat resistance is good, and S is the best.
F. Intrinsic viscosity IV
The resin used, and the intrinsic viscosity of the polyester layer (P2) and polyester layer (P2 layer) in the film were obtained by dissolving the P layer in 100 ml of orthochlorophenol (solution concentration C = 1.2 g / ml). The viscosity at 25 ° C. was measured using an Ostwald viscometer. Similarly, the viscosity of the solvent was measured. [Η] was calculated by the following formula (3) using the obtained solution viscosity and solvent viscosity, and the obtained value was used as the intrinsic viscosity (IV).
ηsp / C = [η] + K [η] ² · C (3)
(Where ηsp = (solution viscosity / solvent viscosity) −1, K is the Huggins constant (assuming 0.343)).
In addition, the intrinsic viscosity of the polyester layer (P layer) and the polyester layer (P2 layer) in the film is polished (as an example, a method of scraping from the surface using a single blade while measuring the thickness with a micrometer, etc.) Etc.) and the measurement was carried out after only the P layer and only the P2 layer, respectively.
G. Composition analysis of polyester resin and P layer The composition analysis of polyester resin and P layer is performed by hydrolyzing the polyester resin and P layer with alkali, and analyzing each component by gas chromatography or high performance liquid chromatography. The composition ratio was determined from the peak area. An example is shown below.
The dicarboxylic acid component and the polyfunctional acid component were measured by high performance liquid chromatography. The measurement conditions can be analyzed by a known method, and an example of the measurement conditions is shown below.

Equipment: Shimadzu LC-10A
Column: YMC-Pack ODS-A 150 × 4.6 mm S-5 μm
120A
Column temperature: 40 ° C
Flow rate: 1.2ml / min
Detector: UV 240nm
The quantification of the diol component and the component having a hydroxyl group can be analyzed by a known method using gas chromatography. An example of measurement conditions is shown below.

Apparatus: Shimadzu 9A (manufactured by Shimadzu Corporation)
Column: SUPELCOWAX-10 capillary column 30m
Column temperature: 140 ° C. to 250 ° C. (heating rate 5 ° C./min)
Flow rate: Nitrogen 25ml / min
Detector: FID

  Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the present invention is not limited thereto.

Example 1
A polycondensation reaction is performed using terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component, magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. (PET) resin (polyester resin (A)) was obtained.

  Next, terephthalic acid is used as the dicarboxylic acid component, 67 mol% of ethylene glycol and 33 mol% of cyclohexanedimethanol as the diol component, and a polycondensation reaction is performed using magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A polyester resin (B) obtained by copolymerizing 33 mol% of methanol was obtained. The detailed composition of the polyester resin (B) is shown in the table.

  Next, 92.9 parts by weight of polyester resin (A) vacuum-dried at 180 ° C. for 2 hours, 7 parts by weight of polyester resin (B) dried in hot air at 70 ° C. for 6 hours, monostearyl phosphate / distearyl as transesterification inhibitors 0.1 parts by weight of a phosphoric acid mixture “ADK STAB” AX-71 (manufactured by ADEKA Corporation) was melted at a temperature of 280 ° C. in an extruder and introduced into a T die die.

  Next, the molten single layer sheet is extruded from the inside of the T die die into a molten single layer sheet, and the molten single layer sheet is closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. A layer film was obtained. Subsequently, the unstretched single layer film was preheated with a roll group heated to a temperature of 80 ° C., and then stretched 3.3 times in the longitudinal direction (longitudinal direction) using a heating roll having a temperature of 85 ° C. A uniaxially stretched film was obtained by cooling with a roll group at a temperature of ° C.

  While holding both ends of the obtained uniaxially stretched film with clips, it is guided to a preheating zone at a temperature of 90 ° C. in the tenter, and continuously in a heating zone at a temperature of 100 ° C. in a direction perpendicular to the longitudinal direction (width direction). The film was stretched 3.5 times. Subsequently, heat treatment was performed at a temperature of 210 ° C. for 20 seconds in the heat treatment zone in the tenter, and after further relaxation treatment in the 4% width direction at a temperature of 210 ° C., a further 3% width direction at a temperature of 140 ° C. The relaxation treatment was performed. Then, after uniform cooling, the film was wound up to obtain a biaxially stretched (biaxially oriented) film having a thickness of 50 μm.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the major axis length a, average thickness d, and flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, initial haze H0, haze H1 after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 2)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that 97.9 parts by weight of the polyester resin (A) and 2 parts by weight of the polyester resin (B) were used.
When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 3)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that 86.9 parts by weight of the polyester resin (A) and 13 parts by weight of the polyester resin (B) were used.
When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

Example 4
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that 98.9 parts by weight of the polyester resin (A) and 1 part by weight of the polyester resin (B) were used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 5)
Polyester resin (B) was subjected to a polycondensation reaction using terephthalic acid as the dicarboxylic acid component, 33 mol% ethylene glycol and 67 mol% cyclohexanedimethanol as the diol component, and magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyester resin (B) copolymerized with 67 mol% of cyclohexanedimethanol was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 6)
Polyester resin (B) was subjected to a polycondensation reaction using terephthalic acid as the dicarboxylic acid component, 33 mol% ethylene glycol and 67 mol% cyclohexanedimethanol as the diol component, and magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 2 except that the polyester resin (B) copolymerized with 67 mol% of cyclohexanedimethanol was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 7)
Polyester resin (B) was subjected to a polycondensation reaction using terephthalic acid as the dicarboxylic acid component, 33 mol% ethylene glycol and 67 mol% cyclohexanedimethanol as the diol component, and magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 3 except that the polyester resin (B) copolymerized with 67 mol% of cyclohexanedimethanol was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 8)
Polyester resin (B) was subjected to a polycondensation reaction using terephthalic acid as the dicarboxylic acid component, 33 mol% ethylene glycol and 67 mol% cyclohexanedimethanol as the diol component, and magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 4 except that 67 mol% cyclohexanedimethanol copolymerized polyester resin (B) was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Examples 9 to 12)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 5 to 8 except that no transesterification inhibitor was added.
Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Examples 13 and 14)
Polyester resin (B) is subjected to a polycondensation reaction using terephthalic acid as a dicarboxylic acid component, 60 mol% ethylene glycol and 40 mol% spiroglycol as diol components, and magnesium acetate, antimony trioxide and phosphorous acid as catalysts. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 5 and Example 9, except that the polyester resin (B) obtained by copolymerizing 40 mol% of spiroglycol was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although initial haze was high compared with Examples 1-12, it turned out that the raise of the haze by heat processing was small, and it turned out that it has the outstanding heat resistance.

(Examples 15 and 16)
As the polyester resin (B), 20 mol% of terephthalic acid and 80 mol% of cyclohexanedicarboxylic acid as dicarboxylic acid components, 40 mol% of ethylene glycol as diol components, 9,9'-bis (4-phenoxyethanol) fluorene (Osaka Gas Chemical Co., Ltd.) Example 5 and Example 5, respectively, except that 60 mol% of BPEF) was used and a polyester resin (B) copolymerized by polycondensation reaction using magnesium acetate, antimony trioxide and phosphorous acid as a catalyst was used. As in 9, a biaxially stretched polyester film having a thickness of 50 μm was obtained.

When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.
Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although initial haze was high compared with Example 13.14, it turned out that the raise of the haze by heat processing is small, and it has the outstanding heat resistance.

(Example 17)
Polyester resin (B) is a polycondensation reaction using 67 mol% terephthalic acid and 33 mol% cyclohexanedicarboxylic acid as the dicarboxylic acid component, ethylene glycol as the diol component, magnesium acetate, antimony trioxide, and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyester resin (B) copolymerized was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 18)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 17 except that 97.9 parts by weight of the polyester resin (A) and 2 parts by weight of the polyester resin (B) were used.
When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 19)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 17 except that 86.9 parts by weight of the polyester resin (A) and 13 parts by weight of the polyester resin (B) were used.
When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 20)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 17 except that 98.9 parts by weight of the polyester resin (A) and 1 part by weight of the polyester resin (B) were used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Examples 21 to 25)
Polyester resin (B) is subjected to a polycondensation reaction using 67 mol% of terephthalic acid as a dicarboxylic acid component, 33 mol of cyclohexanedicarboxylic acid, ethylene glycol as a diol component, and magnesium acetate, antimony trioxide, and phosphorous acid as catalysts. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 5 to 9 except that the copolymerized polyester resin (B) was used.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.

(Example 26)
As polyester resin (B), 67 mol% terephthalic acid and 33 mol isophthalic acid are used as the dicarboxylic acid component, ethylene glycol is used as the diol component, and polycondensation reaction is performed using magnesium acetate, antimony trioxide and phosphorous acid as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polymerized polyester resin (B) was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the haze increase value was large as compared with Example 1, it was found that each characteristic was excellent.

(Examples 27 and 28)
Polyester resin (B) is subjected to a polycondensation reaction using 33 mol% of terephthalic acid as a dicarboxylic acid component, 67 mol of cyclohexanedicarboxylic acid, ethylene glycol as a diol component, and magnesium acetate, antimony trioxide and phosphorous acid as catalysts. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 5 and 9 except that the copolymerized polyester resin (B) was used.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the haze increase value was large as compared with Example 1, it was found that each characteristic was excellent.

(Example 29)
As polyester resin (B), 70 mol% of terephthalic acid and 30 mol of 2,6-naphthalenedicarboxylic acid are used as a dicarboxylic acid component, ethylene glycol is used as a diol component, and magnesium acetate, antimony trioxide and phosphorous acid are used as catalysts. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyester resin (B) copolymerized by conducting a condensation reaction was used.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the haze increase value was large as compared with Example 1, it was found that each characteristic was excellent.

(Examples 30 and 31)
As the polyester resin (B), 40 mol% of terephthalic acid and 60 mol of 2,6-naphthalenedicarboxylic acid are used as the dicarboxylic acid component, ethylene glycol is used as the diol component, and magnesium acetate, antimony trioxide and phosphorous acid are used as the catalyst. A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 5 and Example 9 except that the polyester resin (B) copolymerized by conducting a condensation reaction was used.

Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the haze increase value was large as compared with Example 1, it was found that each characteristic was excellent.
(Examples 32, 33, 34)
As the polyester resin (A), a biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1, 5, and 9 except that a polyethylene terephthalate resin having an intrinsic viscosity of 0.75 and a melting point of 255 ° C. was obtained. .
Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that the haze increase due to the heat treatment can be further suppressed as compared with Examples 1, 5, and 9, and each characteristic is excellent.
(Examples 35, 36, and 37)
As the polyester resin (A), a biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1, 5, and 9 except that a polyethylene terephthalate resin having an intrinsic viscosity of 0.71 and a melting point of 255 ° C. was obtained. .
Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that the haze increase due to the heat treatment can be further suppressed as compared with Examples 1, 5, and 9, and each characteristic is excellent.
(Examples 38, 39, 40)
In a composite film forming apparatus having a main extruder and a sub-extruder, polyethylene terephthalate having an intrinsic viscosity of 0.65 obtained by the same method as in Example 1 was used as a raw material for the main layer (P2 layer) at a temperature of 180 ° C. After vacuum drying for a time, it was supplied to the main extruder side, melt-extruded at a temperature of 280 ° C., and then introduced into a T-die composite die. On the other hand, as a P-layer raw material, a mixture having the same composition as in Examples 1, 5, and 9 was supplied to the sub-extruder, and introduced into the T-die composite die after melt extrusion at a temperature of 280 ° C. Next, in the T-die composite die, the resin layer extruded from the sub-extruder is laminated on both surface layers of the resin layer extruded from the main extruder (resin layer extruded from the sub-extruder / extruded from the main extruder). Resin layer / resin layer extruded from the sub-extruder) and then co-extruded into a sheet to form a melt-laminated sheet, on the drum maintained at a surface temperature of 25 ° C. The solid film was adhered and cooled and solidified by an electrostatic charge method to obtain an unstretched laminated film.

The obtained unstretched laminated film was stretched in the same manner as in Example 1 to obtain a biaxially stretched film having a thickness of 50 μm. When the cross section of the obtained film was observed, it was found that the polyester layer (P layer) having the polyester resin (B) dispersed in a disc shape was formed on both surface layers of the polyester layer (P2 layer). The thickness of each P layer was 7 μm, for a total of 14 μm. Further, the major axis length a, average thickness d, and flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.
Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Compared with Examples 1, 5, and 9, it was excellent in initial haze and thermal shrinkage, and it was found that each characteristic was excellent.
(Examples 41, 42, 43)
A biaxially stretched film having a thickness of 50 μm, which is the same as in Examples 38, 39, and 40, except that the P layer material to be fed into the sub-extruder is the same as that in Examples 32, 33, and 34. Obtained.

  When the cross section of the obtained film was observed, it was found that the polyester layer (P layer) having the polyester resin (B) dispersed in a disc shape was formed on both surface layers of the polyester layer (P2 layer). The thickness of each P layer was 7 μm, for a total of 14 μm. Further, the major axis length a, average thickness d, and flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Compared with Examples 1, 5, and 9, the initial haze, the haze increase by heat treatment, and the heat shrinkage rate were excellent, and it was found that each characteristic was excellent.
(Examples 44, 45, 46)
A biaxially stretched film having a thickness of 50 μm, the same as in Examples 38, 39, and 40, except that the P-layer raw material to be fed into the sub-extruder is the same as that in Examples 35, 36, and 37, respectively. Obtained.

  When the cross section of the obtained film was observed, it was found that the polyester layer (P layer) having the polyester resin (B) dispersed in a disc shape was formed on both surface layers of the polyester layer (P2 layer). The thickness of each P layer was 7 μm, for a total of 14 μm. Further, the major axis length a, average thickness d, and flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Compared with Examples 1, 5, and 9, the initial haze, the haze increase by heat treatment, and the heat shrinkage rate were excellent, and it was found that each characteristic was excellent.
(Examples 47, 48, 49)
50 μm in the same manner as in Examples 38, 39, and 40, respectively, except that polyethylene terephthalate having an intrinsic viscosity of 0.75 obtained in Examples 32, 33, and 34 was used as the raw material for the P2 layer to be charged into the main extruder. A thick biaxially stretched polyester film was obtained.

  When the cross section of the obtained film was observed, it was found that the polyester layer (P layer) having the polyester resin (B) dispersed in a disc shape was formed on both surface layers of the polyester layer (P2 layer). The thickness of each P layer was 7 μm, for a total of 14 μm. Further, the major axis length a, average thickness d, and flatness of the dispersed polyester resin (B) were determined. The results are shown in the table.

Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. It was found that each characteristic was excellent.
(Examples 50, 51, and 52)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1, 5, and 9 except that the stretching ratio was 2.5 times in length and 2.5 times in width.
Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the haze and heat shrinkage rate after heat treatment were slightly worse than those of Examples 1, 5, and 9, respectively, it was found that they were excellent in various properties.

(Comparative Examples 1 and 7)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1 and 17, except that no transesterification inhibitor was added.

  When the cross section of the obtained film was observed, it was found that the dispersion of the polyester resin (B) could not be confirmed and was in a compatible state.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage ratio was good, it was found that the haze greatly increased after the heat treatment.

(Comparative Examples 2 and 8)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 2 and 18 except that no transesterification inhibitor was added.

  When the cross section of the obtained film was observed, it was found that the dispersion of the polyester resin (B) could not be confirmed and was in a compatible state.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage ratio was good, it was found that the haze greatly increased after the heat treatment.

(Comparative Examples 3 and 9)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 3 and 19 except that no transesterification inhibitor was added.
When the cross section of the obtained film was observed, it was found that the dispersion of the polyester resin (B) could not be confirmed and was in a compatible state.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although haze increase due to heat treatment was suppressed, it was found that the heat shrinkage rate was poor.

(Comparative Examples 4 and 10)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 4 and 20, except that no transesterification inhibitor was added.
When the cross section of the obtained film was observed, it was found that the dispersion of the polyester resin (B) could not be confirmed and was in a compatible state.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage rate was good, it was found that the haze increase after heat treatment was large.

(Comparative Examples 5 and 11)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1 and 17, except that 99.6 parts by weight of the polyester resin (A) and 0.3 parts by weight of the polyester resin (B) were used.
When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage ratio was good, it was found that the haze increased greatly after heat treatment.

(Comparative Examples 6 and 12)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Examples 1 and 17, except that the polyester resin (A) was 64.9 parts by weight and the polyester resin (B) was 35 parts by weight.

  When the cross section of the obtained film was observed, it was found that the polyester resin (B) was dispersed in a disc shape. Further, the average major axis length, average major axis length, and average flatness of the dispersed polyester resin (B) were determined.

  Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although haze increase due to heat treatment was suppressed, it was found that the heat shrinkage rate was poor.

(Comparative Examples 13 and 14)
A biaxially stretched polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that 100 parts by weight of the same polyester resin (A) as in Example 1 and 100 parts by weight of the polyester resin (A) in Example 32 were used.

Next, the total light transmittance, haze, haze after heat treatment, and heat resistance of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage ratio was good, it was found that the haze greatly increased after the heat treatment.
(Comparative Example 15)
The same as in Examples 35, 36, and 37 except that polyethylene terephthalate having an intrinsic viscosity of 0.75 and a melting point of 255 ° C. obtained in Examples 32, 33, and 34 was used as the P-layer raw material to be charged into the sub-extruder. Biaxially stretched polyester films having a thickness of 50 μm were obtained in the same manner as in Examples 38, 39, and 40, respectively.

  Next, the total light transmittance, haze, haze after heat treatment, and heat shrinkage of the obtained film were evaluated. The results are shown in the table. Although the heat shrinkage ratio was good, it was found that the haze greatly increased after the heat treatment.

  The polyester film of the present invention has excellent transparency as compared with a conventional film, and is characterized in that oligomer precipitation is small after the processing step and haze increase is small. It can be applied to various applications that take advantage of this feature. For example, base films for various optical sheets such as prism lens sheets, diffuser plates, touch panels, and AR (anti-reflection), photographs, solar cells, separation It can be suitably used as various film materials such as various industrial films for molds, processes, electrical insulation, electronic materials, laminating, various films for packaging materials, and films for magnetic tape.

Claims (8)

A polyester film having a polyester layer (P layer) containing a polyester resin (A) and a polyester resin (B), wherein the polyester resin (B) is in the polyester resin (A). A polyester film which is dispersed as a dispersion having a flatness of 3 or more and satisfies at least one of the following conditions (I) or (II).
(I) The polyester resin (B) has an alicyclic diol component and / or an aromatic diol component as a diol component, and the alicyclic diol component and the aromatic diol component in the polyester layer (P layer). The total content is 0.2 mol% or more and 10 mol% or less with respect to the amount of the diol component in the polyester layer (P layer).
(II) The polyester resin (B) has, as a dicarboxylic acid component, one or more dicarboxylic components selected from the group consisting of an alicyclic dicarboxylic acid component, an isophthalic acid component, and a naphthalenedicarboxylic acid component, and the polyester layer The total content of the alicyclic dicarboxylic acid component, the isophthalic acid component and the naphthalenedicarboxylic acid component in the (P layer) is 0.2 mol% or more to the amount of the dicarboxylic acid component in the polyester layer (P layer) 10 Must be less than mol%. The polyester film according to claim 1, wherein an average thickness d of the dispersion is 200 nm or less. The polyester film according to claim 1 or 2, wherein the initial haze H0 is 3% or less. The polyester film according to any one of claims 1 to 3, wherein a difference (H1-H0) between initial haze H0 and haze H1 after heat treatment at 160 ° C for 1 hour is 3% or less. Melting | fusing point is 245 degreeC or more and 265 degrees C or less, The polyester film in any one of Claims 1-4. The polyester film according to any one of claims 1 to 5, which has a heat shrinkage of 1% or less when heat-treated at 150 ° C for 30 minutes. The polyester film according to claim 1, wherein the polyester layer (P layer) is a biaxially oriented polyester layer. At least the polyester layer (P layer) is positioned on both surface layers, the inner layer has a polyester layer (P2) layer, and the intrinsic viscosity [IVp] of the polyester layer (P layer) is 0.65 or more and The difference [IVp]-[IVp2] between the intrinsic viscosity [IVp] of the polyester layer (P layer) and the intrinsic viscosity [IVp2] of the polyester layer (P2 layer) is 0 or more and 0.15 or less. The polyester film in any one.