Polyester film having resin thin film layer

Abstract

Provided is a polyester film having good electrostatic adhesion. Disclosed is a polyester film having a polyester substrate film and a resin thin film layer on at least one surface of the polyester substrate film, wherein the polyester substrate film contains 0.01-950 ppm by mass of an ionic compound having a dissociation energy Q (kJ / mol) of anions and cations of 850 or less.

Description

Polyester film with a thin resin layer

[0001] This application claims priority based on Japanese Patent Application Nos. 2023-177741, 2024-031431, 2024-031434, 2024-055982, 2024-055985, 2024-055986, 2024-076078, 2024-094269, 2024-094270, 2024-113434, 2024-113436, and 2024-113437. The contents of these patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a polyester film having a thin resin layer.

[0003] BACKGROUND ART Polyester films, typified by polyethylene terephthalate, have been used for a variety of applications because of their excellent mechanical properties, heat resistance, electrical insulation, chemical resistance, and the like.

[0004] Polyester films are often provided with a thin resin layer to optimize the surface properties according to the application. In particular, stretched films of polyethylene terephthalate and polyethylene naphthalate have poor adhesion to adhesives, printing inks, coating agents, etc., so an easy-adhesion layer may be provided to compensate for this, or a lubricant layer may be provided to adjust the slipperiness of the film.

[0005] Polyester films are usually produced by melt-extruding a sheet from an extruder and bringing it into close contact with the surface of a rotating cooling drum or the like to produce an unstretched film, which is then used as an unstretched film, or by further uniaxially or biaxially stretching the unstretched film to produce a stretched film. An in-line method, in which a thin resin layer is provided during the film production process, is often adopted.

[0006] Furthermore, in order to improve the uniformity of the thickness of these unstretched and stretched films and to increase the production speed, it is necessary to quickly and evenly adhere the melt-extruded sheet to the surface of a cooling drum or the like.

[0007] A widely known method for achieving adhesion is the electrostatic adhesion method, in which electrodes are provided between the extrusion die and the cooling rotating drum, a high voltage is applied to the electrodes, static electricity is deposited on the surface of the molten sheet, and the molten sheet is then adhered to the surface of the cooling rotating drum by electrostatic force.

[0008] In the electrostatic adhesion method, it is effective to increase the amount of charge on the surface of the molten sheet material, and it is known that an effective way to increase the amount of charge is to reduce the resistivity of the polyester raw material. Methods for reducing the resistivity include adding a compound of an alkali metal (Group 1) or an alkaline earth metal (Group 2).

[0009] However, these methods tend to cause the added metals to precipitate as foreign matter, which can cause defects in the film or reduce transparency. Therefore, methods have been proposed to reduce the amount of precipitated foreign matter by optimizing the amount and timing of addition of these metals (for example, Patent Document 1).

[0010] Japanese Patent Application Laid-Open No. 2002-327053

[0011] In particular, in recent years, polyester films have become essential in fields requiring high precision, such as optical films, process films, and high-barrier films. There is a demand for polyesters that can be produced with high productivity using electrostatic adhesion methods, and in particular for polyester films with high clarity that have good electrostatic adhesion and few problems caused by precipitation of additives.

[0012] In view of the above circumstances, one of the objects of the present invention is to provide a polyester film having good electrostatic adhesion, in particular a polyester film having high clarity, which can be used for various applications, and which has excellent adhesion to adhesives, printing inks, coating agents, etc.

[0013] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by blending, in a polyester film having a resin thin film layer on at least one side of a polyester substrate film, 0.01 ppm by mass or more but 950 ppm by mass or less of an ionic compound having an anion-cation dissociation energy Q (kJ / mol) of 850 or less into the polyester substrate film. As a result of further investigations, the present inventors have completed the present invention.

[0014] The present invention includes the following embodiments: [Item 1] A polyester film having a polyester substrate film and a resin thin film layer on at least one surface of the polyester substrate film, wherein the polyester substrate film contains 0.01 mass ppm to 950 mass ppm of an ionic compound having an anion-cation dissociation energy Q (kJ / mol) of 850 or less. [Item 2] A polyester film having a melt resistivity of 20×10 ８ Item 3. The polyester film according to item 1, wherein the melt resistivity of the polyester substrate film (or the melt resistivity of the resin constituting the polyester substrate film) is 0.001 × 10 ８Item 4: The polyester film according to any one of Items 1 to 3, wherein the thickness of the resin thin film layer is 0.001 μm or more and 1 μm or less. Item 5: The polyester film according to any one of Items 1 to 4, wherein the resin thin film layer contains at least one resin selected from polyester resin, acrylic resin, and polyurethane resin. Item 6: The polyester film according to any one of Items 1 to 5, wherein the resin in the resin thin film layer is crosslinked. Item 7: The polyester film according to any one of Items 1 to 6, wherein the resin thin film layer contains particles. Item 8: The polyester film according to any one of Items 1 to 7, wherein the surface roughness (Ra) of the resin thin film layer is 0.5 to 100 nm. Item 9: The polyester film according to any one of Items 1 to 8, wherein the ionic radius of at least one of the anions and cations constituting the ionic compound is 10 Å or less. Item 10: The absolute value of the average charge density of at least one of the anions and cations constituting the ionic compound is 0.0025 e / Å. ２ 0.075e / Å or more ２ [Item 11] The polyester film according to any one of items 1 to 10, wherein the ionic radius of the cation constituting the ionic compound is 2 Å or more. [Item 12] The absolute value of the average charge density of the cation constituting the ionic compound is 0.015 e / Å or less. ２ [Item 13] The polyester film according to any one of Items 1 to 12, wherein the polyester substrate film contains the ionic compound in an amount of less than 100 ppm by mass. [Item 14] The polyester film according to any one of Items 1 to 13, wherein a resin constituting the polyester substrate film is polyethylene terephthalate and / or polyethylene naphthalate.

[0015] According to the present invention, it is possible to provide a polyester film having good electrostatic adhesion, in particular a polyester film having high clarity, which can be used for various applications and has excellent adhesion to adhesives, printing inks, coating agents, etc.

[0016] [Polyester film] The polyester film of the present invention preferably has a polyester substrate film and a resin thin film layer on at least one side thereof. In this specification, the term "polyester film" refers to one having a resin thin film layer. On the other hand, the melt-extruded portion described below, which does not contain the resin thin film layer, is referred to as the polyester substrate film, and may be simply referred to as the substrate film.

[0017] In this specification, the term "polyester film" refers to a film in which the main component of the resin (hereinafter sometimes referred to as "raw material resin") constituting the polyester substrate film is a polyester resin, and hereinafter may be simply referred to as a "film." The term "main component" refers to the component present in the largest amount among the raw material resins. The proportion of the polyester resin is preferably selected from a range of 50% by mass or more relative to 100% by mass of the raw material resin, for example, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The raw material resin of the film may be polyester resin alone, but when a resin other than polyester resin is combined with polyester resin, the proportion of the polyester resin is preferably selected from a range of 50% by mass or more but less than 100% by mass relative to 100% by mass of the raw material resin, for example, 70% by mass or more but less than 99% by mass.

[0018] (Polyester Resin Used in Base Film) In this specification, the term "polyester resin" refers to a resin having a dicarboxylic acid component and a glycol component as repeating units, or a resin having a hydroxycarboxylic acid component as repeating units, and the repeating units may be a mixture of both.

[0019] Examples of the dicarboxylic acid component include aromatic dicarboxylic acid components such as terephthalic acid, isophthalic acid, 1,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and sodium sulfoisophthalate; alicyclic dicarboxylic acid components such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acid components such as malonic acid, succinic acid, maleic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, and dimer acid; and heterocycle-containing dicarboxylic acid components such as furandicarboxylic acid. The dicarboxylic acid components may be used alone or in combination of two or more.

[0020] Examples of glycol components include aliphatic glycol components such as ethylene glycol, diethylene glycol (DEG), triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, neopentyl glycol, and 1,6-hexanediol; alicyclic glycol components such as 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, spiroglycol, and isosorbide; and aromatic glycol components such as p-xylylene glycol, m-xylylene glycol, and an ethylene oxide adduct of bisphenol A. The glycol components may be used alone or in combination of two or more.

[0021] Examples of the hydroxycarboxylic acid component include lactic acid (lactide), glycolic acid, 3-hydroxypropionic acid, 6-hydroxycaproic acid (ε-caprolactone), etc. The hydroxycarboxylic acid component may be used alone or in combination of two or more.

[0022] Specific polyester resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polycyclohexylene dimethylene terephthalate (PCT), polyethylene furanoate (PEF), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene succinate lactate (PBSL), polybutylene adipate terephthalate (PBAT), polyethylene succinate (PES), etc., and polyethylene terephthalate (PET) and / or polyethylene naphthalate (PEN) are particularly preferred. In this specification, when a polyester resin is specified by the above-mentioned name, the total of the polymerization components (dicarboxylic acid component and glycol component and / or hydroxycarboxylic acid component) of the polyester resin is taken as 100 mol%, and the total of the polymerization components based on the name is preferably 60 mol% or more. For example, in the case of polyethylene terephthalate (PET), it refers to a polyester resin in which the total amount of terephthalic acid components and ethylene glycol components is 60 mol% or more of the total polymerization components. The polyester resin preferably contains 70 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, and particularly preferably 90 mol% or more of the polymerization components based on the name, and may even contain 95 mol% or more, 97 mol% or more, or 98 mol% or more of the polymerization components based on the name. Note that multimers such as dimers and trimers of glycol components, such as diethylene glycol, generated as by-products are considered to be outside the polymerization components based on the name. The upper limit of the polymerization components based on the name of the total polymerization components is 100 mol%, but when producing a polyester resin using a dicarboxylic acid component and a glycol component, a multimer of the glycol component may be copolymerized, and the upper limit may be 99.5 mol% or even 99 mol%.

[0023] Furthermore, the polyester resin may contain, as copolymerization components, trifunctional or higher polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid; trifunctional or higher polyfunctional alcohol components such as trimethylolpropane and pentaerythritol. The copolymerization components may be used alone or in combination of two or more. When the total acid components are 100 mol% and the total alcohol components are 100 mol%, the total amount of the polyfunctional carboxylic acid components and the polyfunctional alcohol components is preferably 5 mol% or less, more preferably 3 mol% or less. The lower limit of the total amount of the polyfunctional carboxylic acid components and the polyfunctional alcohol components is not particularly limited and may be 0 mol% or 0.1 mol%.

[0024] The dicarboxylic acid component, glycol component, and hydroxycarboxylic acid component may be derived from petroleum, but if biomass-derived components are industrially available, biomass-derived components are preferred.

[0025] As the terephthalic acid component (or ethylene terephthalate component), bis(2-hydroxyethyl) terephthalate (BHET) obtained by chemical recycling may be used.

[0026] The polyester resin may be a single type or a mixture of multiple types with different compositions, and the polyester film may contain the polyester resin as a single layer or multiple layers with different compositions.

[0027] In the case of polyester resins of the same composition, a biomass-derived polyester resin and a petroleum-derived polyester resin may be mixed and used, or a recycled polyester resin and a non-recycled polyester resin may be mixed and used.

[0028] In particular, it is preferable to use recycled PET obtained by collecting used PET bottles and the like.

[0029] The lower limit of the intrinsic viscosity (sometimes referred to as inherent viscosity or IV) of the polyester resin is preferably 0.45 dl / g, more preferably 0.5 dl / g, and even more preferably 0.55 dl / g. The upper limit of the intrinsic viscosity of the polyester resin is preferably 1.2 dl / g, more preferably 1 dl / g, even more preferably 0.9 dl / g, and particularly preferably 0.8 dl / g. In one embodiment, the intrinsic viscosity of the polyester resin is preferably 0.45 dl / g or more and 1.2 dl / g or less. By setting the intrinsic viscosity within the above range, the mechanical properties of the film are ensured, and stable production is facilitated while suppressing the generation of foreign matter and discoloration due to thermal degradation during film formation. The intrinsic viscosity of the polyester resin can be measured at 30°C using an Ostwald viscometer by dissolving the polyester resin in a mixed solvent of phenol (6 parts by mass) and 1,1,2,2-tetrachloroethane (4 parts by mass).

[0030] The lower limit of the acid value (sometimes referred to as AV) of the polyester resin is preferably 0 eq / ton, more preferably 1 eq / ton, even more preferably 3 eq / ton, and particularly preferably 5 eq / ton. The upper limit of the acid value of the polyester resin is preferably 50 eq / ton, more preferably 40 eq / ton, and even more preferably 30 eq / ton. In one embodiment, the acid value of the polyester resin is preferably selected from a range of 30 eq / ton or less, and may be, for example, a range of 1 eq / ton to 30 eq / ton. The acid value of the polyester resin can be measured by dissolving the polyester resin in benzyl alcohol and titrating it with an ethanolic potassium hydroxide solution using phenol red as an indicator.

[0031] The raw material resin, such as a polyester resin, preferably has a thermal stability parameter (TS) indicating heat resistance of 0.5 or less. By setting the TS within this range, high heat resistance is achieved. Furthermore, by suppressing the decrease in molecular weight due to the progression of thermal decomposition and the generation of low-molecular-weight oligomers, foreign matter and defects in the film can be reduced, and deterioration of processability can be prevented. Furthermore, cutting of the molded product caused by foreign matter can also be suppressed, preventing deterioration of productivity. For example, the raw material resin composition (polyester resin composition) is placed in a glass ampoule, and after nitrogen substitution, the glass ampoule is sealed under a reduced pressure of 13.3 kPa (nitrogen atmosphere). The raw material resin composition is heat-treated for 2 hours at a temperature 40°C higher than the melting point of the raw material resin, and the intrinsic viscosity of the raw material resin composition is measured and calculated using the following formula: TS = 0.245 {[IV] f2 －１．４７ -[IV] i －１．４７} [IV] i and [IV] f2 indicate the intrinsic viscosity of the raw material resin composition before and after the heat treatment, respectively.

[0032] It is preferable that there is little foreign matter in the polyester film. The total number of particles of 5 μm or more in the polyester film (or polyester resin) is preferably 15 or less, more preferably 14 or less, even more preferably 13 or less, even more preferably 12 or less, particularly preferably 11 or less, and most preferably 10 or less, and may be less than 10 or even 5 or less. By keeping it within this range, the film and molded product obtained by film formation have a high degree of clarity. The total number of particles can be determined, for example, by observing 20 fields of view with a field area of ​​718 μm × 583 μm using a phase contrast microscope at 100x magnification and counting the number of particles of 5 μm or more using an image analyzer.

[0033] When the polyester resin is PET, the polyester resin may contain cyclic trimer (CT). The CT content is usually 1.1% by mass or less, preferably 1% by mass or less. In order to prevent contamination of film production equipment due to CT and to prevent an increase in haze due to heating of the film, the CT content is more preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less, and most preferably 0.5% by mass or less. In terms of productivity of the polyester resin, the lower limit of the CT content is preferably 0.3% by mass, more preferably 0.33% by mass, and even more preferably 0.35% by mass. The CT content can be determined, for example, by precisely weighing 100 mg of a pulverized sample, dissolving it in 3 mL of a hexafluoroisopropanol / chloroform mixture (volume ratio = 2 / 3), further diluting it with 20 mL of chloroform, adding 10 mL of methanol to this to precipitate the polymer, filtering it, evaporating the filtrate to dryness, and adjusting the volume to a constant volume with 10 mL of dimethylformamide, and then quantifying it by high performance liquid chromatography.

[0034] The polymerization catalyst for raw material resins such as polyester resins is not particularly limited, and examples thereof that can be used include antimony compounds such as diantimony trioxide, antimony pentoxide, antimony acetate, and antimony glycolate; germanium compounds such as germanium dioxide; aluminum compounds such as aluminum acetate; titanium compounds such as organic titanium compounds; manganese compounds such as manganese acetate; and mixtures of two or more of these. Among these, at least one selected from antimony compounds such as diantimony trioxide, germanium compounds such as germanium dioxide, aluminum compounds, and titanium compounds is preferred in terms of the transparency and availability of the resulting polyester resin.

[0035] The lower limit of the Sb content in a raw material resin such as a polyester resin is preferably 40 ppm by mass, more preferably 50 ppm by mass, even more preferably 60 ppm by mass, particularly preferably 70 ppm by mass, and most preferably 76 ppm by mass. The lower limit of the Sb content may be 78 ppm by mass or 80 ppm by mass. The upper limit of the Sb content is preferably 400 ppm by mass, more preferably 350 ppm by mass, even more preferably 300 ppm by mass, particularly preferably 250 ppm by mass, and may be less than 250 ppm by mass, most preferably 200 ppm by mass. In one embodiment, the Sb content is preferably 40 ppm by mass or more and 400 ppm by mass or less.

[0036] The lower limit of the Ge content in a raw material resin such as a polyester resin is preferably 10 ppm by mass, more preferably 20 ppm by mass, and even more preferably 30 ppm by mass. The upper limit of the Ge content is preferably 200 ppm by mass, more preferably 150 ppm by mass, and even more preferably 100 ppm by mass. In one embodiment, the Ge content is preferably 10 ppm by mass or more and 200 ppm by mass or less.

[0037] The lower limit of the Ti content in a raw material resin such as a polyester resin is preferably 1 ppm by mass, more preferably 2 ppm by mass, even more preferably 3 ppm by mass, particularly preferably 4 ppm by mass, and most preferably 5 ppm by mass. The upper limit of the Ti content is preferably 50 ppm by mass, more preferably 40 ppm by mass, even more preferably 30 ppm by mass, particularly preferably 25 ppm by mass, and most preferably 20 ppm by mass. In one embodiment, the Ti content is preferably 1 ppm by mass or more and 50 ppm by mass or less.

[0038] The lower limit of the Mn content in a raw material resin such as a polyester resin is preferably 10 ppm by mass, more preferably 20 ppm by mass, and even more preferably 25 ppm by mass. The upper limit of the Mn content is preferably 100 ppm by mass, more preferably 80 ppm by mass, and even more preferably 70 ppm by mass. In one embodiment, the Mn content is preferably 10 ppm by mass or more and 100 ppm by mass or less.

[0039] The lower limit of the Al content in a raw material resin such as a polyester resin is preferably 1 ppm by mass, more preferably 3 ppm by mass, even more preferably 5 ppm by mass, particularly preferably 7 ppm by mass, and most preferably 10 ppm by mass. The upper limit of the Al content is preferably 100 ppm by mass, more preferably 70 ppm by mass, even more preferably 50 ppm by mass, particularly preferably 40 ppm by mass, and most preferably 30 ppm by mass, and may even be 20 ppm by mass. By keeping it below the above upper limit, foreign matter can be further suppressed. In one embodiment, the Al content is preferably 1 ppm by mass or more and 100 ppm by mass or less.

[0040] By setting the amount of polymerization catalyst within the above range, polymerization can be carried out within an appropriate time, ensuring resin productivity, preventing discoloration of the resin and generation of foreign matter due to deterioration, and preventing generation of foreign matter due to precipitation or aggregation of the catalyst metal.

[0041] It is also preferable to further add a phosphorus compound to raw material resins such as polyester resins. Adding a phosphorus compound makes it easier to suppress the precipitation of metals used as polymerization catalysts. In addition, using an aluminum compound and a phosphorus compound in combination as a polymerization catalyst is preferable because it can increase the activity of the polymerization catalyst.

[0042] The phosphorus compound is not particularly limited, but it is preferable to use a phosphonic acid compound, a phosphinic acid compound, etc., because they have a large effect of improving the catalytic activity. Among these, it is more preferable to use a phosphonic acid compound, because they have a particularly large effect of improving the catalytic activity.

[0043] Among the above phosphorus compounds, phosphorus compounds having a phosphorus element and a phenol structure in the same molecule are preferred. The phosphorus compound having a phosphorus element and a phenol structure in the same molecule is not particularly limited, but it is preferred to use one or more compounds selected from the group consisting of phosphonic acid compounds having a phosphorus element and a phenol structure in the same molecule and phosphinic acid compounds having a phosphorus element and a phenol structure in the same molecule, as this has a large effect of improving the catalytic activity, and it is more preferred to use one or more phosphonic acid compounds having a phosphorus element and a phenol structure in the same molecule, as this has a very large effect of improving the catalytic activity of aluminum.

[0044] Examples of phosphorus compounds having a phosphorus element and a phenol structure in the same molecule include P(=O)R １ (OR ２ ) (OR ３ ) a phosphonic acid compound represented by P(=O)R １ R ４ (OR ２ ) and the like. １ represents a hydrocarbon group having 1 to 50 carbon atoms and containing a phenol structure, or a hydrocarbon group having 1 to 50 carbon atoms and containing a phenol structure and a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. ４ represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms and containing a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. ２ and R ３ R each independently represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms containing a substituent such as a hydroxyl group or an alkoxyl group. However, the hydrocarbon group may contain a branched chain structure, an alicyclic structure such as cyclohexyl, or an aromatic ring structure such as phenyl or naphthyl. ２ and R ４ The ends of may be bonded together.

[0045] Examples of phosphorus compounds having a phosphorus element and a phenol structure in the same molecule include p-hydroxyphenylphosphonic acid, dimethyl p-hydroxyphenylphosphonate, diethyl p-hydroxyphenylphosphonate, diphenyl p-hydroxyphenylphosphonate, bis(p-hydroxyphenyl)phosphinic acid, methyl bis(p-hydroxyphenyl)phosphinate, phenyl bis(p-hydroxyphenyl)phosphinate, p-hydroxyphenylphosphinic acid, methyl p-hydroxyphenylphosphinate, and phenyl p-hydroxyphenylphosphinate.

[0046] Examples of phosphorus compounds having a phosphorus element and a phenol structure in the same molecule include, in addition to the phosphorus compounds exemplified above, phosphorus compounds having a phosphorus element and a hindered phenol structure (e.g., a phenol structure in which an alkyl group having a tertiary carbon (preferably an alkyl group having a tertiary carbon at the benzylic position, such as a t-butyl group or a thexyl group; a neopentyl group, etc.) is bonded to one or two ortho-positions of a hydroxyl group) in the same molecule. Phosphorus compounds having a phosphorus element and a structure of the following formula A in the same molecule are preferred, and among these, dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate shown in the following formula B is more preferred.

[0047] (In Chemical Formula A, * represents a bond.)

[0048] (In Formula B, X １ and X ２ each independently represents hydrogen or an alkyl group having 1 to 4 carbon atoms.

[0049] In the above formula B, X １ and X ２ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably an alkyl group having 1 or 2 carbon atoms. In particular, a diethyl ester having 2 carbon atoms is preferred because Irganox 1222 (manufactured by BASF) is commercially available and easily available.

[0050] Furthermore, when an aluminum compound is used as the polymerization catalyst, it is also preferable to add a lithium compound such as lithium acetate. The lower limit of the Li content in the raw material resin such as a polyester resin is preferably 1 mass ppm, more preferably 3 mass ppm, and even more preferably 5 mass ppm. The upper limit of the Li content in the raw material resin such as a polyester resin is preferably 50 mass ppm, more preferably 30 mass ppm, and even more preferably 20 mass ppm. In one embodiment, the Li content in the raw material resin such as a polyester resin is preferably 1 mass ppm or more and 50 mass ppm or less.

[0051] The lower limit of the total content of Mg and Ca in a raw material resin such as a polyester resin is preferably 0 ppm by mass (below the detection limit), more preferably 0.01 ppm by mass, even more preferably 0.1 ppm by mass, and particularly preferably 0.5 ppm by mass. The upper limit of the total content of Mg and Ca is preferably 50 ppm by mass, more preferably 40 ppm by mass, even more preferably 30 ppm by mass, still more preferably 20 ppm by mass, particularly preferably 10 ppm by mass, and most preferably 5 ppm by mass. By keeping the content below the above upper limit, the generation of foreign matter can be further suppressed.

[0052] The lower limit of the Mg content in a raw material resin such as a polyester resin is preferably 0 ppm by mass (below the detection limit), more preferably 0.01 ppm by mass, even more preferably 0.1 ppm by mass, and particularly preferably 0.5 ppm by mass. The upper limit of the Mg content is preferably 10 ppm by mass, more preferably 9 ppm by mass, even more preferably 8 ppm by mass, particularly preferably 7 ppm by mass, and most preferably 6 ppm by mass. By keeping the Mg content at or below the above upper limit, the generation of foreign matter can be further suppressed.

[0053] The lower limit of the total alkali metal content in raw material resins such as polyester resins is preferably 0 ppm by mass (below the detection limit), more preferably 0.1 ppm by mass, and even more preferably 0.5 ppm by mass. The upper limit of the total alkali metal content is preferably 18 ppm by mass, more preferably 16 ppm by mass, even more preferably 15 ppm by mass, particularly preferably 14 ppm by mass, and most preferably 13 ppm by mass. By keeping the content below the above upper limit, coloration of the polyester film can be further suppressed.

[0054] The lower limit of the Na content in a raw material resin such as a polyester resin is preferably 0 ppm by mass (below the detection limit), more preferably 0.1 ppm by mass, and even more preferably 0.5 ppm by mass. The upper limit of the Na content is preferably 13 ppm by mass, more preferably 10 ppm by mass, even more preferably 7 ppm by mass, particularly preferably 5 ppm by mass, and most preferably 3 ppm by mass. By keeping the Na content below the above upper limit, coloration of the polyester film can be further suppressed.

[0055] In particular, by keeping the content of alkali metals such as Na in raw resins such as polyester resins below the above upper limit, discoloration can be suppressed even when the resin has a large thermal history, such as when the extrusion temperature during film production is high, when the piping is long and the residence time at high temperatures is long, or when recovered materials such as film edges are mixed as raw materials for the resin.

[0056] It is not necessary to exclude the above-mentioned Ca, Mg, and alkali metals. Even if these metals are present, stable electrostatic adhesion by the ionic compound is possible, and by keeping the content within the above range, foreign matter and coloration are suppressed, resulting in a film that can be stably produced.

[0057] The lower limit of the Mn content in a raw material resin such as a polyester resin is preferably 0 ppm by mass (below the detection limit). The upper limit of the Mn content is preferably 22 ppm by mass, more preferably 20 ppm by mass, even more preferably 18 ppm by mass, and particularly preferably 16 ppm by mass. By keeping the Mn content below the above upper limit, the generation of foreign matter and coloration can be further suppressed.

[0058] The lower limit of the Cu content in a raw material resin such as a polyester resin is preferably 0 ppm by mass (below the detection limit). The upper limit of the Cu content is preferably 160 ppm by mass, more preferably 150 ppm by mass. By keeping the Cu content below the upper limit, the generation of foreign matter and coloration can be further suppressed.

[0059] In order to increase the productivity of the polyester resin while suppressing the generation of foreign matter, it is preferable to set the Sb content in the raw material resin such as a polyester resin to 76 ppm by mass or more and the Mg content to 10 ppm by mass or less. Also, in order to increase the productivity of the raw material resin such as a polyester resin while suppressing the generation of foreign matter, it is preferable to set the Sb content in the raw material resin such as a polyester resin to 76 ppm by mass or more and the Cu content to 160 ppm by mass or less.

[0060] The lower limit of the total metal content in a raw material resin such as a polyester resin is preferably 1 ppm by mass, more preferably 2 ppm by mass, even more preferably 3 ppm by mass, particularly preferably 4 ppm by mass, and most preferably 5 ppm by mass. The upper limit of the total metal content is preferably 500 ppm by mass, more preferably 450 ppm by mass, even more preferably 400 ppm by mass, particularly preferably 300 ppm by mass, and most preferably 250 ppm by mass. By keeping it below the above upper limit, the generation of foreign matter and coloration can be further suppressed. In one embodiment, the total metal content is preferably 1 ppm by mass or more and 500 ppm by mass or less.

[0061] The metal content in the raw resin can be calculated by pretreating the sample (e.g., by pre-carbonizing, ashing, acid treatment, and dissolving) to prepare a measurement solution, and measuring the element concentration in the resulting measurement solution with a high-frequency inductively coupled plasma (ICP) optical emission analyzer (e.g., SPECTROBLUE, manufactured by Hitachi High-Tech Science Corp.). Note that if it is difficult to perform the measurement at the wavelengths described in the examples below, other wavelengths may be used with reference to literature.

[0062] (Biomass PET) Of the polyester resins, it is also preferable to use biomass-derived PET (bioPET) as the PET.

[0063] Bio-PET contains at least one of the polymerization components, ethylene glycol and terephthalic acid, derived from biomass. When the ethylene glycol contains biomass-derived ethylene glycol, the biomass-derived ethylene glycol accounts for preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, particularly preferably 80% by mass or more, and particularly preferably 90% by mass or more of the total ethylene glycol, and may be 100% by mass or more. When the terephthalic acid contains biomass-derived terephthalic acid, the biomass-derived ethylene glycol accounts for preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more of the total terephthalic acid, and may be 100% by mass or more of biomass-derived terephthalic acid.

[0064] Bio-PET may be used without being mixed with petroleum-derived PET, or may be used in combination with petroleum-derived PET.

[0065] Of the raw material resins (particularly PET) of polyester films, biomass PET is preferably 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, and 95% by mass or more, in that order; more preferably more than 95% by mass, even more preferably 96% by mass or more, particularly preferably 97% by mass or more, and most preferably 100% by mass.

[0066] The total carbon in the raw resin of polyester film (especially PET) is radioactive carbon (C １４ ) The content of biomass-derived carbon measured is preferably 2% or more, 6% or more, 10% or more, 14% or more, 16% or more, 18% or more, or 19% or more, in that order, and most preferably exceeds 19%. When biomass-derived ethylene glycol is used only for the ethylene glycol, the theoretical upper limit of the biomass-derived carbon content is 20%. When biomass-derived terephthalic acid is also used, the biomass-derived carbon content may exceed 20%, with higher values ​​being preferred, so the most preferred value is 100%, but it may also be 95% or less, 90% or less, 80% or less, or 70% or less.

[0067] The above is a ratio based on carbon, but if hydrogen and oxygen are also added and the calculation is based on the mass of the biomass raw material, and if the entire amount of ethylene glycol is considered to be derived from biomass and the entire amount of terephthalic acid is considered to be derived from petroleum, the calculated ratio is 31.25 mass%.

[0068] Carbon dioxide in the atmosphere contains １４ Since carbon dioxide is contained in the atmosphere at a certain rate (105.5 pMC), plants that grow by absorbing carbon dioxide from the atmosphere, such as corn, contain １４ It is known that the carbon content is about 105.5 pMC. １４ It is also known that almost no carbon is contained in the polyester resin. １４ The biomass ratio can be calculated by measuring the ratio of carbon derived from biomass (biomass ratio). The biomass ratio can be calculated, for example, by measuring the ratio of radiocarbon (C １４ ) measurement.

[0069] When producing a polyester film from bio-PET, the addition of an ionic compound may be carried out in the same manner as for petroleum-derived PET, but a method using a masterbatch is preferred. The masterbatch PET may be petroleum-derived, biomass-derived, or a mixture of both.

[0070] The polyester film may be made of two or more layers, with at least one layer containing biomass-derived PET.

[0071] Bio-PET is preferably produced using an aluminum compound as a polymerization catalyst.

[0072] (Chemical Recycled PET) Of the polyester resins, it is also preferable to use polyethylene terephthalate (chemically recycled PET or CR-PET) polymerized using bis-2-hydroxyethyl terephthalate (chemically recycled BHET or CR-BHET) obtained by chemical recycling as the PET.

[0073] The chemically recycled BHET is preferably obtained by heating PET in the presence of ethylene glycol to depolymerize it. The original PET is preferably post-consumer PET, and examples thereof include PET bottles collected from the streets, containers such as trays, fibers and products, waste products before production, B-grade products not shipped to the market, edge portions gripped during film stretching, slit offcuts, and molded products returned due to complaints, etc. The original PET may contain terephthalic acid and / or ethylene glycol derived from petroleum or biomass. The original PET may also be a mechanically recycled molded product. The original PET may be a single type or a mixture of two or more types.

[0074] The original PET is typically subjected to a depolymerization process after being crushed, washed, and cleaned of foreign matter.

[0075] Chemically recycled BHET may contain linear dimers and higher polymers, and may also contain mono-2-hydroxyethyl terephthalate, terephthalic acid, ethylene glycol, and the like.

[0076] The total acid value and hydroxyl value of the chemically recycled BHET is preferably 6,500 eq / ton or more, more preferably 7,000 eq / ton or more, and even more preferably 7,500 eq / ton or more. The upper limit of this total is preferably 9,500 eq / ton, more preferably 9,000 eq / ton, and even more preferably 8,500 eq / ton. In one embodiment, the total is preferably 6,500 eq / ton or more and 9,500 eq / ton or less. By setting the total within this range, productivity can be ensured while maintaining sufficient purity.

[0077] The chemically recycled BHET may contain a dicarboxylic acid component other than terephthalic acid and / or a glycol component other than ethylene glycol. Examples of dicarboxylic acid components other than terephthalic acid include naphthalenedicarboxylic acid and isophthalic acid. The dicarboxylic acid components other than terephthalic acid may be used alone or in combination of two or more. Examples of glycol components other than ethylene glycol include diethylene glycol, neopentyl glycol, cyclohexanedimethanol, trimethylene glycol, tetramethylene glycol, an ethylene glycol or propylene glycol adduct of bisphenol A, and an ethylene glycol or propylene glycol adduct of bisphenol S. The glycol components other than ethylene glycol may be used alone or in combination of two or more.

[0078] The amounts of the dicarboxylic acid components of the terephthalic acid component and the glycol components other than ethylene glycol in the chemically recycled BHET are each independently preferably 2 mol % or less, more preferably 1.5 mol % or less, even more preferably 1 mol % or less, particularly preferably 0.7 mol % or less, and most preferably 0.5 mol % or less, when the dicarboxylic acid components and the glycol components are each taken as 100 mol %. Furthermore, as described above, the chemically recycled BHET is preferably obtained by depolymerizing PET, including recycled PET from the market. Although recycled PET from the market may contain components other than PET for adjusting crystallinity or physical properties, from the standpoint of cost, it is preferable to use the BHET with the components other than PET still added, rather than selecting only pure PET from the recycled material or purifying the BHET to a level where components other than terephthalic acid and ethylene glycol are not detectable. Therefore, the amount of the dicarboxylic acid component other than terephthalic acid and the amount of the glycol component other than ethylene glycol may each independently be present in an amount of preferably 0.01 mol % or more, more preferably 0.05 mol % or more, assuming that the dicarboxylic acid component and the glycol component are each 100 mol %.

[0079] The lower limit of the amount of chemically recycled BHET relative to the amount of BHET used in producing CR-PET is preferably 50% by mass, more preferably 60% by mass, even more preferably 70% by mass, particularly preferably 80% by mass, and most preferably 90% by mass, and may even be 100% by mass.

[0080] CR-PET may be mixed with a PET resin other than chemically recycled PET resin. When PET is blended with a polyester resin other than PET, CR-PET may be used as the PET.

[0081] The polyester film may be made of two or more layers, and at least one layer may contain chemically recycled PET resin.

[0082] Of the raw material resins (particularly PET) of the polyester film, CR-PET is preferably 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, in that order, and may be more than 95% by mass, 96% by mass or more, 97% by mass or more, or even 100% by mass. Note that even in masterbatches containing high concentrations of additives such as ionic compounds and lubricants, the CR-PET contained in the masterbatch is counted as chemically recycled resin.

[0083] When producing a polyester film from CR-PET, the addition of an ionic compound may be carried out in the same manner as for non-chemically recycled PET, but a method using a masterbatch is preferred. The polyester resin of the masterbatch may be CR-PET, a material other than CR-PET, or a mixture of both.

[0084] CR-PET is preferably produced using an aluminum compound as a polymerization catalyst.

[0085] (Recycled Polyester Resin) It is also preferable to use recycled polyester resin as the polyester resin. The recycled polyester resin is usually a recycled polyester resin molded product that has not been used or has been used.

[0086] Examples of recovered molded products include PET bottles collected from the streets, containers such as trays, fiber and film products, products discarded before being cut into products during manufacturing, products that were not shipped to the market as B-grade products, edge portions that are gripped during film stretching, offcuts from slits, and molded products that have been returned due to complaints, etc. These may be single items with known origins, such as recovered PET bottles or edge portions of films, or may be a mixture of items from different origins. Among these, the recovered polyester resin is preferably derived from recovered PET bottles, and preferably contains 90% by mass or more, and even 95% by mass or more, of components derived from recovered PET bottles.

[0087] The recovered polyester resin may be in the form of, for example, chips, flakes, powder, etc., and may be obtained by pulverizing the recovered molded articles described above. However, from the viewpoint of ease of handling, it is preferable to melt the recovered molded articles and pelletize them.

[0088] The recovered polyester resin preferably contains a total of 50 mol% or more of terephthalic acid components and ethylene glycol components, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more, of the polymerization components (dicarboxylic acid components, glycol components, and / or hydroxycarboxylic acid components) of the polyester resin taken as 100 mol%. Examples of copolymerization components that may be optionally contained include divalent or higher carboxylic acid components other than terephthalic acid, divalent or higher alcohol components other than ethylene glycol, and hydroxycarboxylic acid components, specific examples of which are as described above.

[0089] The recovered polyester resin preferably contains at least one selected from antimony, titanium, and germanium, i.e., the recovered polyester resin is preferably produced using at least one polymerization catalyst selected from antimony compounds, titanium compounds, and germanium compounds, and among these, recovered polyester resins containing antimony and germanium are preferred.

[0090] The total content of antimony, titanium, and germanium in the recovered polyester resin is preferably 2 ppm by mass or more, more preferably 5 ppm by mass or more, even more preferably 10 ppm by mass or more, still more preferably 30 ppm by mass or more, and particularly preferably 50 ppm by mass or more. The total content is preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, even more preferably 300 ppm by mass or less, and particularly preferably 250 ppm by mass or less. In one embodiment, the total content is preferably 2 ppm by mass or more and 500 ppm by mass or less, more preferably 5 ppm by mass or more and 400 ppm by mass or less, even more preferably 10 ppm by mass or more and 300 ppm by mass or less, and particularly preferably 50 ppm by mass or more and 250 ppm by mass or less.

[0091] The recycled polyester resin may contain additives such as a colorant, a lubricant (particularly lubricant particles), an ultraviolet absorber, a melt resistivity adjuster, an antistatic agent, an antioxidant, a heat stabilizer, etc. The additives may be used alone or in combination of two or more.

[0092] The intrinsic viscosity of the recovered polyester resin is preferably 0.5 dl / g or more, more preferably 0.55 dl / g or more, and even more preferably 0.57 dl / g or more. The intrinsic viscosity of the recovered polyester resin is preferably 0.8 dl / g or less, more preferably 0.75 dl / g or less, and even more preferably 0.73 dl / g or less. In one embodiment, the intrinsic viscosity of the recovered polyester resin is preferably 0.5 dl / g or more and 0.8 dl / g or less, more preferably 0.55 dl / g or more and 0.75 dl / g or less, and even more preferably 0.57 dl / g or more and 0.73 dl / g or less.

[0093] The recycled polyester resin is preferably PET recycled from PET bottles for beverages, etc. PET recycled from PET bottles for beverages, etc. is sometimes called "bottle recycled PET." The recycled polyester resin preferably contains 70% by mass or more of recycled PET from bottles, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may even contain 100% by mass.

[0094] The recycled polyester resin (particularly recycled bottle PET) may contain an isophthalic acid component as a copolymerization component, and when the total acid components are taken as 100 mol%, the lower limit of the content of the isophthalic acid component is preferably 0.02 mol%, more preferably 0.05 mol%, even more preferably 0.1 mol%, particularly preferably 0.2 mol%, and most preferably 0.3 mol%. The upper limit of the content of the isophthalic acid component is preferably 5 mol%, more preferably 4 mol%, even more preferably 3 mol%, particularly preferably 2.5 mol%, and most preferably 2 mol%. In one embodiment, the content of the isophthalic acid component is preferably 0.02 mol% or more and 5 mol% or less.

[0095] Diethylene glycol is not only contained in polyester resins as a by-product of ethylene glycol during polyester polymerization, but may also be added during polymerization to adjust crystallization.

[0096] The lower limit of the diethylene glycol component content of the recycled polyester resin (particularly recycled bottle PET), when the total glycol components are taken as 100 mol%, is preferably 0.5 mol%, more preferably 0.8 mol%, even more preferably 1 mol%, particularly preferably 1.2 mol%, and most preferably 1.4 mol%. The upper limit of the diethylene glycol component content is preferably 5 mol%, more preferably 4 mol%, even more preferably 3.5 mol%, and particularly preferably 3 mol%. In one embodiment, the diethylene glycol component content is preferably 0.5 mol% or more and 5 mol% or less.

[0097] The upper limit of the copolymerization components other than isophthalic acid and diethylene glycol in the recovered polyester resin (particularly recycled PET from bottles) is preferably 3 mol %, more preferably 2.5 mol %, and even more preferably 2 mol %, assuming that the total acid components are 100 mol % and the total glycol components are 100 mol %, respectively.

[0098] The total amount of copolymerization components of the recycled polyester resin (particularly recycled bottle PET) is preferably 0.5 mol% or more, more preferably 1 mol%, even more preferably 1.5 mol%, and particularly preferably 2 mol%, when the sum of all acid components and all glycol components is 200 mol%. The upper limit of this total amount is preferably 7 mol%, more preferably 6 mol%, even more preferably 5 mol%, and particularly preferably 4 mol%. If the total amount is equal to or less than the upper limit, the heat resistance and mechanical strength of the resulting polyester film can be prevented from decreasing, and there is no need to limit the amount of recycled polyester resin added. In one embodiment, the total amount is preferably 0.5 mol% or more and 7 mol% or less.

[0099] The recycled polyester resin may be mixed with a virgin polyester resin. When PET is blended with a polyester resin other than PET, recycled PET from bottles may be used as the PET.

[0100] The polyester film may have two or more layers, and at least one of the layers may contain the recycled polyester resin.

[0101] Of the raw material resins (particularly polyester resins) of polyester films, the recovered polyester resin may account for 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, or may be more than 95% by mass, 96% by mass or more, 97% by mass or more, or even 100% by mass. Incidentally, even in the case of a masterbatch containing a high concentration of additives such as an ionic compound or a lubricant, the recovered polyester resin contained in the masterbatch is also counted as recovered polyester resin.

[0102] When producing a polyester film using recycled polyester resin, the addition of an ionic compound may be carried out in the same manner as with virgin polyester resin, but a method using a masterbatch is preferred. The polyester resin in the masterbatch may be virgin polyester resin, recycled polyester resin, or a mixture of both. The polyester resin in the masterbatch may also contain CR-PET.

[0103] (Resins Other Than Polyester Resins) Resins other than polyester resins may be resins that are compatible with polyester resins or resins that are incompatible with polyester resins. Examples of resins other than polyester resins include thermoplastic resins such as polystyrene; polycarbonate; polyolefins such as polypropylene, polymethylpentene, and polycyclic olefins; polyamides such as 6-nylon and 6,6-nylon; polyetheramide; polyamideimide; polyimide; polyetherimide; polysulfone; and polyethersulfone. These may be used alone or in combination of two or more.

[0104] (Ionic Compound) Ionic compounds can control (e.g., reduce) the melt resistivity, for example. It is believed that the mechanism by which the melt resistivity is controlled is that, when a voltage is applied, cations and anions constituting the ionic compound migrate in the raw resin in a molten state, causing a bias in the charge in the raw resin.

[0105] In this specification, an ionic compound refers to a salt composed of a cation and an anion. Examples of ionic compounds include metal salts containing alkali metals, alkaline earth metals, transition metals (metals of Groups 3 to 11), and metals of Groups 12 to 16; and ionic liquids obtained by combining organic or inorganic cations with organic or inorganic anions. Among these, ionic liquids are more preferred because of their good dispersibility in the raw resin and the ability to control the melt resistivity of the raw resin with the addition of a small amount. Any one of the ionic compounds may be used alone, or two or more may be used in combination. When two or more ionic compounds are used in combination, they may be used in combination with metal salts, with ionic liquids, or with a metal salt and an ionic liquid; however, a combination of ionic liquids or a combination of a metal salt and an ionic liquid is more preferred.

[0106] The amount of ionic compound added (which can be read as content) in the resin constituting the film is greater than 0 ppm by mass, preferably 0.01 ppm by mass or more, more preferably 0.1 ppm by mass or more, and even more preferably 0.5 ppm by mass or more, based on the mass of the raw material resin (particularly polyester resin). The amount of ionic compound added is preferably 950 ppm by mass or less, more preferably 800 ppm by mass or less, and even more preferably 700 ppm by mass or less. In one embodiment, the amount of ionic compound added is preferably 0.01 ppm by mass or more and 950 ppm by mass or less, more preferably 0.1 ppm by mass or more and 800 ppm by mass or less, and even more preferably 0.5 ppm by mass or more and 700 ppm by mass or less. By being within the above range, it is possible to highly exhibit moldability and processability while suppressing the generation of foreign matter, etc. The amount of the ionic compound added may be 500 ppm by mass or less, 250 ppm by mass or less, or 150 ppm by mass or less. The amount of the ionic compound added may be less than 100 ppm by mass, 99 ppm by mass or less, 95 ppm by mass or less, 90 ppm by mass or less, 70 ppm by mass or less, 50 ppm by mass or less, 40 ppm by mass or less, 30 ppm by mass or less, 20 ppm by mass or less, or 10 ppm by mass or less. Furthermore, it may be less than 10 ppm by mass, 9 ppm by mass or less, 8 ppm by mass or less, or 7 ppm by mass or less. The amount of the ionic compound added can be appropriately set depending on the type of ionic compound and the melt resistivity of the resin constituting the film.

[0107] Reducing the amount of ionic compound added has the advantages of, for example, making it less likely for the ionic compound to bleed out onto the film surface, making it easier to suppress contamination of the film production line, and reducing changes over time in adhesion properties with adhesives, coating layers, printing inks, etc. Therefore, one method is to consider compatibility with the resin and select an ionic compound that can efficiently reduce melt resistivity even when added in a small amount.

[0108] The relationship between the amount R of the ionic compound added and the dissociation energy Q preferably satisfies the following formula (1) and / or formula (2): R≦0.15×Q+890 (1) R≦−20×Q+16000 (2) (where R is the amount (ppm by mass) of the ionic compound added to the raw resin, and Q is the dissociation energy (kJ / mol) of the anion and cation constituting the ionic compound.) When multiple types of ionic compounds are used in combination, R is the sum of the amounts of each ionic compound i added (R=ΣR ｉ ), and Q is the mass fraction (R ｉ / R) and Q (Q ｉ ) and the sum of the products (Q = Σ(R ｉ / R)Q ｉ )

[0109] Formula (1) shows that ionic compounds with small dissociation energy are more likely to dissociate into cations and anions more efficiently, and therefore can exhibit electrostatic applicability even in small amounts. When R satisfies formula (1), the conductivity of the raw resin can be prevented from becoming too high, and sparks can be prevented from occurring when a voltage is applied to the raw resin to impart an electric charge, enabling stable production. Furthermore, there is no risk of the raw resin being damaged, such as by scratches, holes, or breakage, which would make it difficult to process the raw resin using an electric charge.

[0110] Equation (2) shows that ionic compounds with smaller dissociation energy can have a high degree of clarity even when present in large quantities. This is presumably because ionic compounds with larger dissociation energy have stronger bonds between cations and anions, and the ionic compounds themselves tend to aggregate and become foreign matter, which reduces the clarity of the raw resin.

[0111] It is more preferable that the dissociation energy of the ionic compound and the amount of the ionic compound added to the raw material resin satisfy both of formulas (1) and (2). In this case, a film having high clarity and exhibiting high moldability and processability can be provided, and a method for producing the same can be provided.

[0112] The dissociation energy Q (kJ / mol) of the anion and cation constituting the ionic compound is preferably 850 or less, more preferably 800 or less, even more preferably 700 or less, even more preferably 600 or less, particularly preferably 500 or less, and most preferably 400 or less. The dissociation energy Q may be 0 or greater or greater than 0, and is not limited thereto. The lower limit is, for example, 10, preferably 50, or may be 100, 150, 200, or 250. By setting the dissociation energy Q within this range, the electrostatic applicability during melting of the raw material resin is improved, and high moldability and processability can be achieved. This is believed to be due to the fact that the ionic interaction is appropriately weakened, making it easier to dissociate into ions when a voltage is applied.

[0113] The average charge density (e / Å) of the anions and cations that constitute the ionic compound ２ The absolute values ​​of the average charge densities (e / Å) of the anions and cations are preferably 0.0025 or more, more preferably 0.003 or more, and even more preferably 0.0035 or more, and may be 0.0038 or more. ２ ) are each independently preferably 0.075 or less, more preferably 0.07 or less, even more preferably 0.065 or less, and may be 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.015 or less. In one embodiment, the average charge density (e / Å) of at least one ion selected from the anions and cations is ２ The absolute values ​​of the average charge densities (e / Å) of both the anions and cations are preferably 0.0025 or more and 0.075 or less, more preferably 0.003 or more and 0.07 or less, and even more preferably 0.0035 or more and 0.065 or less. ２) is preferably 0.0025 or more and 0.075 or less, more preferably 0.003 or more and 0.07 or less, and even more preferably 0.0035 or more and 0.065 or less. By setting it within this range, the electrostatic applicability during melting of the raw material resin is improved, and high moldability and processability can be achieved. This is thought to be because the ionic interaction with counter ions is a factor affected by the average charge density of anions or cations, and by setting the absolute value of the average charge density within this range, it becomes easier to dissociate into ions when a voltage is applied.

[0114] Furthermore, the average charge density (e / Å) of the anions constituting the ionic compound ２ The lower limit of the absolute value of the average charge density of the anions constituting the ionic compound may be 0.0038 or 0.004, and the upper limit may be 0.015, 0.01, 0.0095, 0.009, or 0.008. In one embodiment, the absolute value of the average charge density of the anions constituting the ionic compound is preferably 0.0038 or more and 0.015 or less.

[0115] The average charge density (e / Å) of the cations constituting the ionic compound ２ The lower limit of the absolute value of (e / Å) may be 0.0038, 0.004, or 0.0045, and the upper limit may be 0.02, 0.015, 0.0145, 0.013, 0.01, or 0.008. In one embodiment, the average charge density (e / Å) of the cations constituting the ionic compound is ２ ) is preferably 0.0038 or more and 0.015 or less.

[0116] Either the ionic radius of the anion constituting the ionic compound (hereinafter also referred to as the anion radius) or the ionic radius of the cation constituting the ionic compound (hereinafter also referred to as the cation radius) is preferably 1 Å or more, more preferably 1.5 Å or more, and may be 2 Å or more. Either the anion radius or the cation radius is preferably 10 Å or less, more preferably 5 Å or less, and particularly preferably 4 Å or less. In one embodiment, the ionic radius (or either the anion radius or the cation radius) of at least one of the anions and cations constituting the ionic compound is preferably 10 Å or less, more preferably 1 Å or more and 10 Å or less, and even more preferably 1.5 Å or more and 5 Å or less. Furthermore, it is preferable that the ionic radius (or the anion radius or the cation radius) of at least one of the anions and cations constituting the ionic compound is 2 Å or more. The ionic radius is a factor that affects the average charge density of the ions. By setting the ionic radius within this range, electrostatic applicability during melting is improved, and high moldability and processability can be achieved.

[0117] It is preferable that both the anion radius and the cation radius are within the above ranges. On the other hand, the lower limit of the anion radius may be 2.5 Å, 2.6 Å, 2.65 Å, 2.7 Å, 2.8 Å, 2.9 Å, or 3 Å. In one embodiment, the anion radius is preferably 2.5 Å or more and 10 Å or less. The lower limit of the cation radius may be 1.4 Å, 1.5 Å, 1.7 Å, 2 Å, or 2.2 Å. The upper limit of the cation radius may be 3.7 Å or more and 3.5 Å. In one embodiment, the cation radius is preferably 1.4 Å or more and 3.7 Å or less.

[0118] By selecting an ionic compound with low dissociation energy and by selecting an ionic compound with a large ionic radius for the cation and anion and a small absolute value of the average charge density, it becomes easier to maintain the melt resistivity within an appropriate range even when the amount added is reduced. The ions of the above-mentioned ionic compounds have good compatibility with the polyester resin without being excessively constrained, which is thought to lead to a stable effect of reducing the melt resistivity and suppressing aggregation. Among these, it is preferable to select an ionic compound with a large ionic radius and a small absolute value of the average charge density as the cation. Furthermore, by using an anion with a large ionic radius and a small absolute value of the average charge density, it becomes easier to suppress foreign matter, even when a metal such as magnesium or calcium is used as the cation.

[0119] The anion radius, cation radius, average charge density of the anion, and average charge density of the cation can be calculated using, for example, quantum chemistry calculation software "Gaussian 16" by the COSMO method according to the following procedure.

[0120] First, the anion and cation structures are optimized in vacuum. The density functional (DFT) method is used for the structure optimization. The functional is BVP86, the basis function is TZVP, and the fitting basis function is DGA1. The opt keyword is set. Next, based on the structure optimized in vacuum, structure optimization is performed under conditions where the molecular surface is shielded with a conductor. The same DFT method, functional, basis function, and fitting basis function as in vacuum are used for the structure optimization. The opt scrf = (cpcm, read) keyword is set. Furthermore, radii = klamt is set as an additional option. Next, based on the structure optimized under conditions where the molecular surface is shielded with a conductor, the COSMO method is used. The same DFT method, functional, basis function, and fitting basis function as in vacuum are used for the COSMO method. By specifying scrf=cosmors as a keyword, a file containing charge information when the surface of the molecule is shielded with a conductor is output.

[0121] The anion radius and cation radius are calculated by approximating the molecular shape to a sphere based on the volume described in the file output by the COSMO method.

[0122] The average charge density of anions and the average charge density of cations can be calculated by dividing the charges of anions and cations by the surface area using the surface area listed in the file output by the COSMO method. If necessary, unit conversion was performed using 1 Bohr = 0.529117 Å.

[0123] Dissociation energy is calculated by subtracting the sum of the energies of the anions and cations that make up an ionic compound from the energy of the ionic compound. (Dissociation energy) = (Energy of anion) + (Energy of cation) - (Energy of ionic compound). The total energy calculated by geometry optimization in vacuum is used for the energies of anions, cations, and ionic compounds. The density functional (DFT) method is used for geometry optimization. The functional used is BVP86, the basis function used is TZVP, and the fitting basis function used is DGA1. Set opt ​​as the keyword. The dissociation energy is calculated using the energy when geometry optimization is complete.

[0124] In one embodiment, the ionic compound is a metal salt. The metal salt preferably contains an alkali metal and / or an alkaline earth metal. Examples of alkali metals include lithium, sodium, and potassium, and examples of alkaline earth metals include magnesium, calcium, and barium. These may be used alone or in combination of two or more.

[0125] When a metal salt is used as the ionic compound, the total amount of metals (particularly alkali metals and alkaline earth metals) in a raw material resin such as a polyester resin is preferably 80 ppm by mass or less, more preferably 70 ppm by mass or less, 60 ppm by mass or less, 50 ppm by mass or less, 40 ppm by mass or less, 30 ppm by mass or less, 20 ppm by mass or less, 10 ppm by mass or less, and 5 ppm by mass or less. The total amount may also be 0% by mass (below the detection limit).

[0126] Examples of the form of the metal salt include hydroxides, aliphatic carboxylates (acetates, butyrates, etc., preferably acetates), aromatic carboxylates, salts with compounds having a hydroxyl group (salts with phenols, etc.), etc. Any of these may be used alone or in combination of two or more.

[0127] In one embodiment, the ionic compound preferably includes at least one compound that is liquid at a temperature of 100°C and a pressure of 1 atmosphere, particularly an ionic liquid. In this specification, an ionic liquid refers to a salt that becomes liquid at a relatively low temperature compared to common inorganic salts and has a melting point of 100°C or lower. In addition to being non-volatile and having a low viscosity, ionic liquids are characterized by having excellent dissolving power for organic and inorganic compounds due to their high polarity based on their aprotic ionic structure. Methods that can be used to synthesize ionic liquids include, for example, an anion exchange method, an acid ester method, and a neutralization method.

[0128] The anion constituting the ionic compound may be either an inorganic anion or an organic anion, and is not particularly limited. Specific anion species include, for example, Cl － ,Br － , I － , AlCl ４ － , Al ２ Cl ７ － , B.F. ４ － , P.F. ６ － , ClO ４ － , NO ３ － , C.H. ３ COO － (Abbreviation: AA), CF ３ COO － , C.H. ３ SO ３ － , C.F. ３ SO ３ － , C ４ F ９ SO ３ － , (CF ３SO ２ ) ２ N － , (C ２ F ５ SO ２ ) ２ N － , (C ３ F ７ SO ２ ) ２ N － , (C ４ F ９ SO ２ ) ２ N － , (CF ３ SO ２ ) ３ C － , AsF ６ － , SbF ６ － , NbF ６ － , TaF ６ － , F(HF) ｎ － (n is an integer of 1 or more, for example, an integer of 1 to 5), (CN) ２ N － (abbreviation: DCA), C ４ F ９ SO ３ － , (C ２ F ５ SO ２ ) ２ N － , C ３ F ７ COO － , (CF ３ SO ２ ) (CF ３ CO)N － , C ９ H １９ COO － , (CH ３ ) ２ P.O. ４ － (abbreviation: DMP), (C ２ H ５ ) ２ P.O. ４ － , C ２ H ５ OSO３ － , C ６ H １３ OSO ３ － , C ８ H １７ OSO ３ － , C.H. ３ (OC ２ H ４ ) ２ OSO ３ － , C ６ H ４ (CH ３ ) SO ３ － , (C ２ F ５ ) ３ PF ３ － , C.H. ３ CH(OH)COO － , and (FSO ２ ) ２ N － Among them, (CF) is preferred because of its large ionic radius, small absolute value of average charge density, and excellent electrostatic applicability. ３ SO ２ ) ２ N － (Abbreviation: TFSI), (FSO ２ ) N － (abbreviation: FSI) is preferred.

[0129] The cation constituting the ionic compound is not particularly limited, but is preferably an organic compound cation, since it can increase the ionic radius and reduce the absolute value of the average charge density. By using an organic compound as the cation, the cation radius can be increased (for example, 2 Å or more) and the absolute value of the average charge density can be reduced (for example, 0.015 e / Å). ２ Among the cations of organic compounds, cations of nitrogen-containing compounds are preferred. The cation of the nitrogen-containing compound is preferably at least one selected from the group consisting of the following (1) to (16):

[0130] (1) Pyridinium cations such as 1-ethylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-hexyl-3-methylpyridinium cation, and 1-butyl-3,4-dimethylpyridinium cation;

[0131] (2) Pyrrolidinium cations such as 1,1-dimethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-methyl-1-propylpyrrolidinium cation, 1-methyl-1-butylpyrrolidinium cation, 1-methyl-1-pentylpyrrolidinium cation, 1-methyl-1-hexylpyrrolidinium cation, 1-methyl-1-heptylpyrrolidinium cation, 1-ethyl-1-propylpyrrolidinium cation, 1-ethyl-1-butylpyrrolidinium cation, 1-ethyl-1-pentylpyrrolidinium cation, 1-ethyl-1-hexylpyrrolidinium cation, 1-ethyl-1-heptylpyrrolidinium cation, 1,1-dipropylpyrrolidinium cation, 1-propyl-1-butylpyrrolidinium cation, 1,1-dibutylpyrrolidinium cation, and pyrrolidinium-2-one cation;

[0132] (3) piperidinium cations such as 1-propylpiperidinium cation, 1-pentylpiperidinium cation, 1,1-dimethylpiperidinium cation, 1-methyl-1-ethylpiperidinium cation, 1-methyl-1-propylpiperidinium cation, 1-methyl-1-butylpiperidinium cation, 1-methyl-1-pentylpiperidinium cation, 1-methyl-1-hexylpiperidinium cation, 1-methyl-1-heptylpiperidinium cation, 1-ethyl-1-propylpiperidinium cation, 1-ethyl-1-butylpiperidinium cation, 1-ethyl-1-pentylpiperidinium cation, 1-ethyl-1-hexylpiperidinium cation, 1-ethyl-1-heptylpiperidinium cation, 1,1-dipropylpiperidinium cation, 1-propyl-1-butylpiperidinium cation, and 1,1-dibutylpiperidinium cation;

[0133] (4) pyrrolium cations such as 2-methyl-1-pyrrolium cation;

[0134] (5) Indolium cations such as 1-ethyl-2-phenylindolium cation and 1,2-dimethylindolium cation;

[0135] (6) carbazolium cations such as 1-ethylcarbazolium cation;

[0136] (7) morpholinium cations such as N-ethyl-N-methylmorpholinium cation;

[0137] (8) Imidazolium cations such as 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1,2-dimethyl-3-propylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-dimethylimidazolium cation, 1-(2-methoxyethyl)-3-methylimidazolium cation, and 1-allyl-3-methylimidazolium cation;

[0138] (9) Tetrahydropyrimidinium cations such as 1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3,4-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, and 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation;

[0139] (10) Dihydropyrimidinium cations such as 1,3-dimethyl-1,4-dihydropyrimidinium cation, 1,3-dimethyl-1,6-dihydropyrimidinium cation, 1,2,3-trimethyl-1,4-dihydropyrimidinium cation, 1,2,3-trimethyl-1,6-dihydropyrimidinium cation, 1,2,3,4-tetramethyl-1,4-dihydropyrimidinium cation, and 1,2,3,4-tetramethyl-1,6-dihydropyrimidinium cation;

[0140] (11) Pyrazolium cations such as 1-methylpyrazolium cation, 2-methylpyrazolium cation, 3-methylpyrazolium cation, 1-ethyl-2-methylpyrazolium cation, 1-ethyl-2,3,5-trimethylpyrazolium cation, 1-propyl-2,3,5-trimethylpyrazolium cation, and 1-butyl-2,3,5-trimethylpyrazolium cation;

[0141] (12) Pyrazolinium cations such as 1-ethyl-2,3,5-trimethylpyrazolinium cation, 1-propyl-2,3,5-trimethylpyrazolinium cation, and 1-butyl-2,3,5-trimethylpyrazolinium cation;

[0142] (13) Tetraalkylammonium cations such as tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, tetrapentylammonium cation, tetrahexylammonium cation, and tetraheptylammonium cation;

[0143] (14) Trialkylsulfonium cations such as trimethylsulfonium cation, triethylsulfonium cation, tributylsulfonium cation, trihexylsulfonium cation, diethylmethylsulfonium cation, dibutylethylsulfonium cation, and dimethyldecylsulfonium cation;

[0144] (15) Tetraalkylphosphonium cations such as tetramethylphosphonium cation, tetraethylphosphonium cation, tetrabutylphosphonium cation, tetrahexylphosphonium cation, tetraoctylphosphonium cation, triethylmethylphosphonium cation, tributylethylphosphonium cation, trimethyldecylphosphonium cation, diallyldimethylammonium cation, and tributyl-(2-methoxyethyl)phosphonium cation;

[0145] (16) N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation, glycidyltrimethylammonium cation, diallyldimethylammonium cation, N,N-dimethyl-N-ethyl-N-propylammonium cation, N,N-dimethyl-N-ethyl-N-butylammonium cation, N,N-dimethyl-N-ethyl-N-pentylammonium cation, N,N-dimethyl-N-ethyl-N-hexylammonium cation, N,N-dimethyl-N-ethyl-N-heptylammonium cation, N,N-dimethyl N,N-ethyl-N-nonylammonium cation, N,N-dimethyl-N,N-dipropylammonium cation, N,N-dimethyl-N-propyl-N-butylammonium cation, N,N-diethyl-N-propyl-N-butylammonium cation, N,N-dimethyl-N-propyl-N-pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-propyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-hexylammonium cation, N,N-dimethyl-N-butyl-N-heptylammonium, N,N-diethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-pentyl-N-hexylammonium cation, N,N-dimethyl-N,N-dihexylammonium cation, trimethylheptylammonium cation, N,N-diethyl-N-methyl-N-propylammonium cation, N,N-diethyl-N-methyl-N-pentylammonium cation, N,N-diethyl-N-methyl-N-heptylammonium cation, N,N-diethyl-N- Propyl-N-pentylammonium cation, trimethyldecylammonium cation, triethylmethylammonium cation, triethylpropylammonium cation, triethylpentylammonium cation, triethylheptylammonium cation, tributylethylammonium cation, N,N-dipropyl-N-methyl-N-ethylammonium cation, N,N-dipropyl-N-methyl-N-pentylammonium cation, N,N-dipropyl-N-butyl-N-hexylammonium cation, N,N-dipropyl-N,Examples of tetraalkylammonium cations include N-dihexylammonium cation, N,N-dibutyl-N-methyl-N-pentylammonium cation, N,N-dibutyl-N-methyl-N-hexylammonium cation, trioctylmethylammonium cation, and N-methyl-N-ethyl-N-propyl-N-pentylammonium cation.

[0146] In the above, the alkyl is preferably an alkyl having 1 to 10 carbon atoms, and may be an alkyl having 1 to 8 carbon atoms, an alkyl having 1 to 6 carbon atoms, an alkyl having 1 to 4 carbon atoms, an alkyl having 1 to 3 carbon atoms, or an alkyl having 1 or 2 carbon atoms. Of the above, from the viewpoint of high thermal stability, imidazolium cations such as 1-ethyl-3-methylimidazolium cation (abbreviation: EMIM), 1,3-dimethylimidazolium cation (abbreviation: MMIM), and 1-allyl-3-methylimidazolium cation (abbreviation: AMIM) are preferred, and pyrrolidinium cations such as 1-(2-methoxyethyl)-1-methylpyrrolidinium cation (abbreviation: MEMP) are particularly preferred.

[0147] Specific examples of the ionic compound are appropriately selected from the combinations of the cations and anions described above, and include, for example, 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium hexafluorophosphate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium trifluoromethanesulfonate, 1-butyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylpyridinium bis(pentafluoroethanesulfonyl) ) imide, 1-hexylpyridinium tetrafluoroborate, 1,1-dimethylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-ethylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl- 1-hexylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-heptylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-hexylpyrrolidinium bis(trifluoromethanesulfonyl)imide ) imide, 1-ethyl-1-heptylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1,1-dipropylpyrrolidinium bis(triple oromethanesulfonyl)imide, 1-propyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1,1-dibutylpyrrolidinium bis(triple oromethanesulfonyl)imide, 1-propylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide, 1,1-dimethylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-ethylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-butylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-hexylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-heptylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-propylpiperidinium bis (trifluoromethanesulfonyl)imide, 1-ethyl-1-butylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-pentylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-hexylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-heptylpiperidinium bis(trifluoromethanesulfonyl)imide, 1,1-dipropylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-propyl-1-butylpiperidinium bis(trifluoromethanesulfonyl)imide, 1,1-dibutylpiperidinium bis(trifluoromethanesulfonyl)imide,1-dimethylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-ethylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-butylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-pentylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-hexylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-heptylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-propylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-butylpyrrolidinium pyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-pentylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-hexylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-heptylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1,1-dipropylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-propyl-1-butylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1,1-dibutylpyrrolidinium bis(pentafluoroethanesulfonyl)imide, 1-propylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-pentylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1,1-dimethylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-ethylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-propylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-butylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-pentylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-hexylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-methyl-1-heptylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-propylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1 -butylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-pentylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-hexylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-1-heptylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1,1-dipropylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1-propyl-1-butylpiperidinium bis(pentafluoroethanesulfonyl)imide, 1,1-dibutylpiperidinium bis(pentafluoroethanesulfonyl)imide, 2-methyl-1-pyrrolium tetrafluoroborate, 1-ethyl-2-phenylindolium tetrafluoroborate, 1,2-Dimethylindolium tetrafluoroborate, 1-ethylcarbazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium trifluoroacetate, 1-ethyl-3-methylimidazolium heptafluorobutyrate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium perfluorobutanesulfonate, 1-ethyl-3-methylimidazolium difluoromethanesulfonate Cyanamide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tris(trifluoromethanesulfonyl)methide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium heptafluorobutyrate , 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium perfluorobutanesulfonate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium trifluoromethane sulfonate, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-2,3-dimethylimidazolium tetrafluoroborate, 1,2-dimethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide, 1-methylpyrazolium tetrafluoroborate, 2-methylpyrazolium tetrafluoroborate, 1-ethyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)imide, 1-propyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3,5-trimethylpyrazolium bis(pentafluoroethanesulfonyl)imide, 1-propyl-2,3,5-trimethylpyrazolium bis(pentafluoroethanesulfonyl)imide, 1-butyl-2,3,5-trimethylpyrazolium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)trifluoroacetamide, 1-propyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-2,3,5-trimethylpyrazolium bis(trifluoromethanesulfonyl)trifluoroacetamide, 1-ethyl-2,3, 5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)imide, 1-propyl-2,3,5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3,5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3,5-trimethylpyrazolinium bis(pentafluoroethanesulfonyl)imide, 1-propyl-2,3,5-trimethylpyrazolinium bis(pentafluoroethanesulfonyl)imide, 1-butyl-2,3,5-trimethylpyrazolinium bis(pentafluoroethanesulfonyl)imide, 1-ethyl-2,3,5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)trifluoroacetamide, 1-propyl-2,3,5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-2,3,5-trimethylpyrazolinium bis(trifluoromethanesulfonyl)trifluoroacetamide, tetrapentylammonium trifluoromethanesulfonate, tetrapentylammonium bis(trifluoromethanesulfonyl)imide, tetrahexylammonium trifluoromethanesulfonate, tetrahexylammonium bis(trifluoromethanesulfonyl)imide, tetrabutylammonium trifluoromethanesulfonate, tetrabutylammonium bis(trifluoromethanesulfonyl)imide, diallyldimethylammonium tetrafluoroborate, diallyldimethylammonium trifluoromethanesulfonate, diallyldimethylammonium bis(trifluoromethanesulfonyl)imide, diallyldimethylammonium bis(pentafluoroethanesulfonyl)imide, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, N,N-diethyl -N-methyl-N-(2-methoxyethyl)ammonium trifluoromethanesulfonate, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(pentafluoroethanesulfonyl)imide, glycidyltrimethylammonium trifluoromethanesulfonate, glycidyltrimethylammonium bis(trifluoromethanesulfonyl)imide, glycidyltrimethylammonium bis(pentafluoroethanesulfonyl)imide, tetraoctylphosphonium trifluoromethane sulfonate, tetraoctylphosphonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-heptylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-ethyl-N-nonylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N,N-dipropylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-propyl-N-butylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-propyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-propyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl N,N-dimethyl-N-butyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-butyl-N-heptylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N-pentyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dimethyl-N,N-dihexylammonium bis(trifluoromethanesulfonyl)imide, trimethylheptylammonium ammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-heptylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-propyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, triethylpropylammonium bis(trifluoro methanesulfonyl)imide, triethylpentylammonium bis(trifluoromethanesulfonyl)imide, triethylheptylammonium bis(trifluoromethanesulfonyl)imide, N,N-dipropyl-N-methyl-N-ethylammonium bis(trifluoromethanesulfonyl)imide, N,N-dipropyl-N-methyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-dipropyl-N-butyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dipropyl-N,Examples of such an imide include N-dihexylammonium bis(trifluoromethanesulfonyl)imide, N,N-dibutyl-N-methyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-dibutyl-N-methyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide, trioctylmethylammonium bis(trifluoromethanesulfonyl)imide, N-methyl-N-ethyl-N-propyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, 1-butylpyridinium(trifluoromethanesulfonyl)trifluoroacetamide, 1-butyl-3-methylpyridinium(trifluoromethanesulfonyl)trifluoroacetamide, 1-ethyl-3-methylimidazolium(trifluoromethanesulfonyl)trifluoroacetamide, N-ethyl-N-methylmorpholinium thiocyanate, and 4-ethyl-4-methylmorpholinium methyl carbonate. These may be used alone or in combination of two or more. Among these, from the viewpoint of exhibiting excellent melt resistivity, a combination of an imidazolium cation and a bis(trifluoromethanesulfonyl)imide anion (abbreviation: TFSI) or a bis(fluorosulfonyl)imide anion (abbreviation: FSI), or a combination of a pyrrolidinium cation and TFSI or FSI is preferred, a combination of an imidazolium cation and TFSI or FSI is more preferred, a combination of a 1,3-dialkylimidazolium cation and TFSI or FSI is particularly preferred, and a combination of a 1-ethyl-3-methylimidazolium cation (abbreviation: EMIM) and bis(trifluoromethanesulfonyl)imide (abbreviation: TFSI) is most preferred.

[0148] The content of the ionic compound in the polyester film and the content of the ionic compound in the masterbatch described below can be measured, for example, by liquid chromatography mass spectrometry. Since the ease of decomposition and volatility of the cation and anion of the ionic compound may differ, the content of the ionic compound in the polyester film can be the total amount of the detected cation and anion. The preferred content of the ionic compound in the polyester film is the same as above.

[0149] Examples of methods for adding an ionic compound include the following methods (A) to (C).

[0150] (A) Method of adding an ionic compound to a raw material resin (particularly a polyester resin) in advance Method (A) includes, for example, a method of adding an ionic compound during polymerization of a polyester resin. The timing of addition may be any stage before the start of the esterification reaction, during the reaction, or after completion of the reaction. In addition, when adding the ionic compound during the esterification reaction, it is preferable to add the ionic compound after the esterification reaction rate has reached preferably 95% or more, more preferably 97% or more, from the viewpoint of ensuring uniformity.

[0151] When adding the ionic compound, it may be dissolved in a solvent (for example, water, an organic solvent such as ethylene glycol, etc.) and added in order to ensure accurate supply. The organic solvent to be used is not particularly limited, and can be selected from aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, heptane, and octane; alcohol solvents such as methanol, ethanol, propanol, butanol, and benzyl alcohol; glycol solvents such as ethylene glycol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone; ether solvents such as diethyl ether and tetrahydrofuran; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, 1,3-dimethylimidazolidinone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone; lactone solvents such as γ-butyrolactone; and phenolic solvents such as phenol, taking into consideration the solubility of the ionic compound, miscibility with the raw material resin, and reactivity with the raw material resin. Among these, ketone solvents such as methyl ethyl ketone and acetone, alcohol solvents such as methanol and ethanol, and glycol solvents such as ethylene glycol are preferred from the viewpoint of solubility of the ionic compound, and are also preferred from the viewpoint of not interfering with the polycondensation reaction when the polycondensation step is carried out in the coexistence of an ionic compound. These solvents can be used alone or in combination of two or more.

[0152] The ionic compound may be added after the raw resin (particularly polyester resin) is produced and chipped, but before melt-kneading to form a polyester film. For example, the ionic compound may be added after the raw resin (particularly polyester resin) is chipped and dried (particularly immediately before drying). In this case, as in the above, it is preferable to add the ionic compound dissolved in a solvent (e.g., water, organic solvent, etc.), and the solvent preferably has a boiling point below the drying temperature (e.g., 135°C or below).

[0153] (B) Method of melt-kneading a raw material resin (particularly a polyester resin) and adding an ionic compound In method (B), similarly to method (A), it is preferable to add the ionic compound after dissolving it in a solvent (e.g., water, an organic solvent, etc.). Note that method (B) also includes a method of adding an ionic compound to a raw material resin that has been melt-kneaded during film formation.

[0154] (C) A method of blending a first raw material resin composition (such as a polyester resin composition) containing an ionic compound (particularly at a high concentration) with a second raw material resin (such as a polyester resin) or a second raw material resin composition (such as a polyester resin composition) containing the second raw material resin (such as a polyester resin composition) that does not contain an ionic compound, or that contains an ionic compound at a lower concentration than the first raw material resin composition, or that has a higher melt resistivity than the first raw material resin composition.

[0155] The above method (C) will be described in more detail below. In the following description, a polyester resin composition which is an example of the first raw material resin composition and which contains a polyester resin and an ionic compound having an anion-cation dissociation energy Q (kJ / mol) of 850 or less will be referred to as polyester resin composition A, a polyester resin used in polyester resin composition A will be referred to as polyester resin A, and a polyester resin which is an example of the second raw material resin and has a melt resistivity greater than that of polyester resin composition A will be referred to as polyester resin B.

[0156] In one embodiment, the method (C) is preferably a method including a step of mixing (particularly melt-mixing) a polyester resin A, a polyester resin composition A containing an ionic compound having an anion-cation dissociation energy Q (kJ / mol) of 850 or less, and a polyester resin B having a melt resistivity greater than that of the polyester resin composition A. In this method, the polyester resin B preferably has high melt resistivity and weak electrostatic adhesion, and by mixing it with the polyester resin composition A containing the ionic compound, the melt resistivity can be reduced and good electrostatic adhesion can be obtained.

[0157] (Polyester Resin Composition A) The polyester resin composition A may be referred to as an ionic compound masterbatch or an electrostatic adhesion agent masterbatch, or simply as a masterbatch (MB).

[0158] The polyester resin A is preferably selected from the polyester resins described above, specifically PET, PEN, PTT, PBT, PCT, PEF, PLA, PBS, PBSA, PBSL, PBAT, and PES. Furthermore, polyester resin A and polyester resin B are preferably polyester resins having the same main polymerization components (dicarboxylic acid component, glycol component, and / or hydroxycarboxylic acid component), but they do not necessarily have to be strictly identical. When the total amount of the polymerization components (dicarboxylic acid component, glycol component, and / or hydroxycarboxylic acid component) of the polyester resin is taken as 100 mol%, the total amount of the polymerization components that differ between polyester resin A and polyester resin B is preferably 7 mol% or less, more preferably 5 mol% or less, even more preferably 3 mol% or less, and particularly preferably 2 mol% or less. It may be 0 mol% or more. (Specific Example) In the above specific example, the difference in terephthalic acid component among all dicarboxylic acid components is 1 mol %, and the difference in ethylene glycol component among all glycol components is 0.4 mol %, for a total difference of 1.4 mol %.

[0159] When there are a plurality of polyester resins A and B, the composition is calculated as an average.

[0160] Furthermore, when the polyester resin used as the raw material for the polyester film is a copolymer polyester resin or when a plurality of polyester resins with different compositions are blended, the above is not limitative. When the polyester resin used as the raw material for the polyester film is a copolymer polyester resin, the polyester resin A may be a polyester resin B instead of the above-listed PET or the like, to produce a masterbatch to form the polyester resin composition A. Furthermore, when a plurality of polyester resins with different compositions are blended, it is also a preferred embodiment to make the polyester resin composition A by adding an ionic compound to one or more of the polyester resins.

[0161] The amount of the ionic compound added to the polyester resin composition A is preferably 1% by mass (10,000 ppm by mass) or less, more preferably 5,000 ppm by mass or less, even more preferably 2,000 ppm by mass or less, and particularly preferably 1,000 ppm by mass or less. The amount of the ionic compound added can be appropriately optimized depending on the melt resistivity of the resin constituting the film to be obtained and the dissociation energy of the ionic compound. If the ionic compound has a small dissociation energy, the melt resistivity can be reduced with a smaller amount, and the amount of the ionic compound added to the polyester resin composition A can also be reduced.

[0162] The amount of the ionic compound added to the polyester resin composition A may be 950 ppm by mass or less, 900 ppm by mass or less, 850 ppm by mass or less, 700 ppm by mass or less, 500 ppm by mass or less, 400 ppm by mass or less, 250 ppm by mass or less, 150 ppm by mass or less, 90 ppm by mass or less, 40 ppm by mass or less, 20 ppm by mass or less, 10 ppm by mass or less, or 9 ppm by mass or less.

[0163] The amount of the ionic compound added to the polyester resin composition A is preferably 1 ppm by mass or more, more preferably 2 ppm by mass or more, even more preferably 3 ppm by mass or more, particularly preferably 4 ppm by mass or more, and particularly preferably 5 ppm by mass or more. In one embodiment, the amount of the ionic compound added to the polyester resin composition A is preferably 1 ppm by mass or more and 10,000 ppm by mass or less.

[0164] The amount added can be read as the content.

[0165] The polyester resin composition A preferably satisfies the above formulas 1 and 2.

[0166] The method for adding the ionic compound to the polyester resin A includes, for example, the above-mentioned methods (A) to (C).

[0167] The concentration C1 of the ionic compound contained in the polyester resin composition A is preferably 3 times or more, more preferably 5 times or more, even more preferably 8 times or more, and particularly preferably 10 times or more, the concentration C2 of the ionic compound contained in the substrate film (or raw material resin such as polyester resin). Furthermore, the concentration C1 is preferably 10,000 times or less, more preferably 1,000 times or less, even more preferably 500 times or less, particularly preferably 200 times or less, and most preferably 100 times or less, the concentration C2. In one embodiment, the concentration C1 is preferably 3 times or more and 10,000 times or less the concentration C2.

[0168] The upper limit of the melt resistivity of the polyester resin composition A is preferably 5×10 ８ Ω cm, and more preferably 2×10 ８ Ω cm, and more preferably 1×10 ８ Ω cm, and particularly preferably 0.5×10 ８ Ω cm, and most preferably 0.1×10 ８ The lower limit of the melt resistivity of the polyester resin composition A is preferably 0.0001×10 ８ Ω cm, and more preferably 0.0005×10 ８ Ω cm, and more preferably 0.001 × 10８ Ω cm, and particularly preferably 0.005×10 ８ Ω cm, and most preferably 0.01×10 ８ In one embodiment, the melt resistivity of polyester resin composition A is 0.0001×10 ８ Ω・cm or more 0.1×10 ８ By setting the viscosity in the above range, economical production becomes easy, and the components can be mixed uniformly, which makes stable production easier.

[0169] The polyester resin composition A may contain components other than the polyester resin A and the ionic compound. Specific examples of such components include colorants such as pigments, lubricants (particularly lubricant particles), ultraviolet absorbers, antistatic agents, antioxidants, heat stabilizers, and resins other than the polyester resin A. The components other than the polyester resin A and the ionic compound may be used alone or in combination of two or more.

[0170] A lubricant (particularly lubricant particles) is often added to a film to ensure smoothness and enable winding. Such a film can usually be produced by a method including a step of blending a polyester resin that does not contain (or contains at a low concentration of) a lubricant (particularly lubricant particles) with a polyester resin composition (lubricant masterbatch) in which a lubricant (particularly lubricant particles) has been added (or added at a high concentration) to the polyester resin. It is also a preferred method to add an ionic compound to this lubricant masterbatch to form a polyester resin composition A.

[0171] (Lubricant Masterbatch) The lubricant masterbatch will now be described. Examples of lubricants include oxides, carbonates, silicates, sulfates, and aluminates of metals such as titanium, aluminum, silicon, calcium, magnesium, and barium. More specifically, examples include titanium dioxide, alumina, aluminosilicate, silicon dioxide (silica), calcium oxide, calcium carbonate, and barium sulfate, as well as particles of naturally occurring talc, mica, kaolinite, and zeolite, but are not limited to these. The lubricants may be used alone or in combination of two or more.

[0172] The lower limit of the average particle size of the lubricant is preferably 0.1 μm, more preferably 0.2 μm, even more preferably 0.3 μm, particularly preferably 0.4 μm, and most preferably 0.5 μm. The upper limit of the average particle size of the lubricant is preferably 5 μm, more preferably 4 μm, even more preferably 3 μm, particularly preferably 2.7 μm, and most preferably 2.5 μm. In one embodiment, the average particle size of the lubricant is preferably 0.1 μm or more and 5 μm or less. By setting the particle size within the above range, unevenness is efficiently formed on the film surface, imparting the effect of imparting handleability such as slipperiness and runnability, while suppressing an increase in haze and the formation of coarse protrusions. The average particle size of the lubricant can be determined, for example, by photographing particles using an electron microscope, randomly selecting and observing 100 unagglomerated particles, and averaging their equivalent circle diameters to determine the average particle size. The particles to be measured may be those before addition, but it is also possible to dissolve the lubricant master batch or film in a solvent that dissolves polyester resin, filter it through a membrane filter such as PTFE, and measure the particles captured on the filter.

[0173] The lower limit of the amount of lubricant relative to the lubricant masterbatch is preferably 1000 ppm by mass, more preferably 2000 ppm by mass, even more preferably 3000 ppm by mass, particularly preferably 4000 ppm by mass, and most preferably 5000 ppm by mass. The upper limit of the amount of lubricant relative to the lubricant masterbatch is preferably 70000 ppm by mass, more preferably 50000 ppm by mass, even more preferably 40000 ppm by mass, particularly preferably 30000 ppm by mass, and most preferably 20000 ppm by mass. In one embodiment, the amount of lubricant relative to the lubricant masterbatch is preferably 1000 ppm by mass or more and 70000 ppm by mass or less.

[0174] When polyester resin composition A is produced as a lubricant masterbatch, it is preferable to add a lubricant to polyester resin A so that the amount of lubricant is a preferred amount. When the amount of lubricant relative to the lubricant masterbatch is within the above range, there is no need to add a large amount of lubricant masterbatch, and there is no risk of deterioration in color tone and heat resistance or increased production costs. In addition, there is no risk of lubricant aggregation occurring, which would lead to an increase in the number of coarse defects (coarse particles) after blending and dilution.

[0175] The lubricant masterbatch can be produced, for example, by adding a lubricant during polymerization of the polyester resin, or by melt-kneading the lubricant after producing the polyester resin.

[0176] When a lubricant is added during polymerization of a polyester resin, the timing of adding the lubricant to the polyester resin is not particularly limited, but adding the lubricant during the esterification (or transesterification) step or between the end of the esterification (or transesterification) step and the start of the polycondensation step is preferred, since it can be uniformly dispersed in the polyester resin. The lubricant is preferably added as a slurry of ethylene glycol.

[0177] Examples of methods for adding an ionic compound to a lubricant masterbatch include a method of adding an ionic compound to a polyester resin composition for a lubricant masterbatch, a method of adding an ionic compound or an ionic compound masterbatch when melt-kneading a polyester resin and a lubricant, a method of melt-kneading a polyester resin composition for an ionic compound masterbatch with a lubricant masterbatch, and a method of melt-kneading a lubricant masterbatch with an ionic compound masterbatch.

[0178] The film can also be produced by a method including, for example, blending a polyester resin that does not contain an ultraviolet absorber (or contains it at a low concentration) with a polyester resin composition (ultraviolet absorber masterbatch) in which an ultraviolet absorber has been added (or added at a high concentration) to the polyester resin. A preferred method is to add an ionic compound to this ultraviolet absorber masterbatch to form polyester resin composition A. Examples of ultraviolet absorbers include organic and inorganic ultraviolet absorbers, with organic ultraviolet absorbers being preferred from the viewpoint of transparency. Examples of organic ultraviolet absorbers include benzophenones, benzotriazoles, acrylonitriles, cyclic iminoesters, and combinations thereof.

[0179] Examples of the benzophenone-based ultraviolet absorber, benzotriazole-based ultraviolet absorber, and acrylonitrile-based ultraviolet absorber include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2' , 4,4'-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(5-chloro(2H)-benzotriazol-2-yl)-4-methyl-6-(tert-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol, and the like.

[0180] Examples of cyclic iminoester ultraviolet absorbers include 2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, and 2-phenyl-3,1-benzoxazin-4-one.

[0181] From the viewpoint of durability, benzothazole-based ultraviolet absorbers and / or cyclic iminoester-based ultraviolet absorbers are particularly preferred.

[0182] Another preferred method is to incorporate an ionic compound into the UV absorber masterbatch to produce polyester resin composition A. The UV absorber concentration in the UV absorber masterbatch is preferably 5 to 30% by mass to uniformly disperse the UV absorber and economically compound it. The UV absorber masterbatch is preferably prepared using a kneading extruder at an extrusion temperature of at least the melting point of the polyester resin but not exceeding 290°C for 1 to 15 minutes. This extrusion temperature and extrusion time range can suppress both loss of the UV absorber and a decrease in the viscosity of the UV absorber masterbatch. This extrusion time range also enables more uniform mixing of the UV absorber. Additives such as stabilizers, color adjusters, and antistatic agents may be added as needed. An ionic compound or an ionic compound masterbatch may be added to the polyester resin composition for the UV absorber masterbatch, a UV absorber may be added to the polyester resin composition for the ionic compound masterbatch, or the UV absorber masterbatch and the ionic compound masterbatch may be melt-kneaded together.

[0183] (Polyester Resin B) The melt resistivity of the polyester resin B is higher than that of the polyester resin composition A, and is 1×10 ８ The melt resistivity of polyester resin B is preferably 5×10 ８ More preferably, it is 10×10 Ω cm or more. ８ The upper limit of the melt resistivity of the polyester resin B is not particularly limited, but is preferably 10,000×10 ８Ω cm, and more preferably 1000×10 ８ In one embodiment, the melt resistivity of polyester resin B is 1×10 ８ Ω・cm or more 10000×10 ８ It is preferably Ω·cm or less.

[0184] In one preferred embodiment, polyester resin B includes one selected from biomass PET, chemically recycled PET, and recycled polyester resin.

[0185] The polyester resin B may contain a colorant such as a pigment, a lubricant (particularly lubricant particles), an ultraviolet absorber, an antistatic agent, an antioxidant, a heat stabilizer, a resin other than polyester resin, and the like.

[0186] The shape of the polyester resin composition A and the polyester resin B is preferably chips, and the shape may be any shape, such as a sphere, an oval sphere (rugby ball shape), a cylinder, or a bale (hamburger steak shape). The mass of the chips is preferably 10 to 100 mg, more preferably 15 to 70 mg, and even more preferably 20 to 50 mg. When the polyester resin composition A and the polyester resin B are dry blended, it is preferable to make the chip shapes and masses of the two similar in order to reduce segregation during feeding. When the chip mass of the polyester resin composition A and the chip mass of the polyester resin B are set to 1, the smaller mass (including when the masses are the same) is preferably 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, and particularly preferably 0.75 or more. The upper limit is preferably 1.

[0187] Examples of methods for mixing polyester resin composition A and polyester resin B include: a method in which chips are mixed in advance and then added through the same inlet of an extruder; a method in which chips are added through separate inlets of an extruder; a method in which polyester resin composition A is melted in a separate extruder and then merged with the extruder for polyester resin B; and a method in which polyester resin composition A and polyester resin B are melted in separate extruders and then mixed together in yet another extruder.

[0188] When mixing the polyester resin composition A and the polyester resin B, a lubricant masterbatch may be used in combination, or an ultraviolet absorber masterbatch may be used in combination, or other additives may be added directly or as a masterbatch.

[0189] The amount of polyester resin A relative to the total amount of polyester resin composition A and polyester resin B is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, particularly preferably 0.5% by mass or more, and most preferably 1% by mass or more. The amount of polyester resin A is preferably 33% by mass or less, more preferably 20% by mass or less, even more preferably 12.5% ​​by mass or less, and particularly preferably 10% by mass or less. In one embodiment, the amount of polyester resin A is preferably 0.01% by mass or more and 33% by mass or less. By setting the amount within the above range, the ionic compound can be added stably, enabling high-speed and stable film formation, which is advantageous in terms of cost, and a polyester film with few defects and coloration can be obtained.

[0190] In order to keep the amount of ionic compound added small and thereby reduce film discoloration and contamination of the film manufacturing equipment, it is preferable to add an ionic compound having an ionic dissociation energy within the above range. However, the dissociation energy of the ionic compound itself to be added may be outside the above range, as long as ion exchange or the like occurs within the film and an ionic compound whose ionic dissociation energy is substantially within the above range is produced.

[0191] Specifically, multiple ionic compounds with dissociation energies outside the above range may be added to the film, causing ion exchange or the like in the film to produce a combination of anions and cations such that the dissociation energy is substantially within the above range. In this case, polyester resin composition A may be added to produce a combination of anions and cations such that the dissociation energy falls within the above range, or polyester resin compositions A may be separately prepared to produce a combination of anions and cations such that the dissociation energy falls within the above range when mixed, and then these compositions may be mixed. The content of ionic compounds in the film can be the total amount of the combination of anions and cations that corresponds to the ionic compounds among the detected cations and anions.

[0192] The polyester film may be a multilayer film containing two or more polyester layers. The multilayer film may be, for example, a coextruded film (CCF). In the case of a multilayer film, it is preferable that at least one layer contains an ionic compound, and a layer not containing an ionic compound may also be present.

[0193] In the case of a multilayer film having three or more layers, the outermost layers on both sides may be layers that do not contain an ionic compound, and the inner layers may be layers that contain an ionic compound. By adopting such a configuration, bleeding out of the ionic compound can be suppressed.

[0194] When the film has layers that do not contain an ionic compound, the layers containing the ionic compound preferably account for 30% or more of the total thickness of the film, more preferably 50% or more, even more preferably 60% or more, particularly preferably 70% or more, and most preferably 90% or more. The layers containing the ionic compound preferably account for 99% or less of the total thickness of the film, more preferably 96% or less, even more preferably 94% or less, and particularly preferably 92% or less. In one embodiment, the layers containing the ionic compound preferably account for 30% or more and 99% or less of the total thickness of the film.

[0195] It is preferable to adjust the amount of the ionic compound added to the layer containing the ionic compound so that the melt resistivity of all layers falls within an appropriate range.

[0196] Other typical configurations of the multilayer film include, for example, a configuration of two or more layers in which one outermost layer contains a lubricant (particularly lubricant particles) and the other outermost layer does not contain a lubricant (particularly lubricant particles); a configuration in which the outermost layers on both sides contain a lubricant (particularly lubricant particles) and at least one of the inner layers does not contain a lubricant (particularly lubricant particles); a configuration in which the outermost layers on both sides do not contain a lubricant (particularly lubricant particles) and at least one of the inner layers contains a lubricant (particularly lubricant particles); and a configuration in which the outermost layers on both sides do not contain an ultraviolet absorber and at least one of the inner layers contains an ultraviolet absorber. Any combination or composite (for example, a layer containing an ionic compound and an ultraviolet absorber, a layer containing an ionic compound and a lubricant (particularly lubricant particles), etc.) is possible.

[0197] [Resin Thin Film Layer] The polyester film of the present invention preferably has a resin thin film layer on at least one surface. Examples of the resin thin film layer include an easy-adhesion layer for improving adhesion, a lubricant-containing layer for adjusting slippage, and an antistatic layer. The resin thin film layer may have multiple functions or may have multiple layers. The resin thin film layer may be provided on both sides. In this case, the resin thin film layers on both sides may have the same composition, or may have different compositions. The thickness of the resin thin film layer on both sides may also be the same or different.

[0198] Resins used in the resin thin film layer are preferably polyester resins, polyurethane resins, acrylic resins, polyolefin resins, polyamide resins, etc., and these can be used alone or in combination of two or more. Among these, it is more preferable to include at least one selected from polyester resins, polyurethane resins, and acrylic resins. In particular, it is preferable to include a polyester resin in terms of adhesion to the polyester substrate film. The polyester resin may be used as a polyurethane prepolymer.

[0199] [Polyester Resin for Resin Thin Film Layer] Examples of polyester resins for the resin thin film layer include the same polyester resins as those used for the polyester substrate film, but copolymer polyesters are preferred in terms of adhesion to the polyester substrate film and other materials when processing the polyester film, solvent solubility for producing a coating agent for providing the resin thin film layer, film-forming properties, etc. The polymerization components of the copolymer polyester can be arbitrarily selected from dicarboxylic acid components, glycol components, and hydroxycarboxylic acid components used for the polyester resin.

[0200] Copolymerized polyesters having specific names such as copolymerized PET and copolymerized PEN preferably have a total of 75 mol% or less of the polymerization components based on the name, assuming that the total of the polymerization components (dicarboxylic acid component, glycol component, and / or hydroxycarboxylic acid component) is 100 mol%. For example, in the case of copolymerized PET, a copolymerized polyester in which the total amount of terephthalic acid component and ethylene glycol component is 75 mol% or less of all polymerization components is preferred. When the polyester resin used in the resin thin film layer has a specific name, the polymerization components based on the name are more preferably 70 mol% or less, even more preferably 65 mol% or less, and even more preferably 60 mol% or less. Note that the polyester resin for the resin thin film layer does not necessarily require the polymerization components based on the name, but the lower limit of the polymerization components based on the name may be 5 mol% or 10 mol% due to ease of polymerization, etc.

[0201] When the polyester resin used in the base film is a polyester resin mainly containing an aromatic dicarboxylic acid component, such as PET or PEN, the polyester resin for the resin thin film layer preferably contains 50 mol% or more of the aromatic dicarboxylic acid component, more preferably 60 mol% or more, and even more preferably 70 mol% or more, of the aromatic dicarboxylic acid component, assuming that the total dicarboxylic acid component is 100 mol%. Furthermore, to improve the weather resistance of the resin thin film layer, the aromatic dicarboxylic acid component in the polyester resin for the resin thin film layer is preferably present in a large amount, such as 80 mol% or more, 90 mol% or more, or even 95 mol% or more. When the aromatic dicarboxylic acid component is 90 mol% or more, from the viewpoint of adhesion, it is preferable that the aromatic dicarboxylic acid component be of multiple types, preferably two or more types selected from terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. In this case, the aromatic dicarboxylic acid component in the largest amount is preferably 85 mol% or less, more preferably 80 mol% or less, and even more preferably 75 mol% or less. The aromatic dicarboxylic acid component may be combined with an aliphatic dicarboxylic acid component, such as sebacic acid.

[0202] On the other hand, when the polyester resin used for the base film is a polyester resin mainly containing an aliphatic dicarboxylic acid component, or a polyester resin mainly containing a hydroxycarboxylic acid component, from the viewpoint of adhesion to the base film, the aromatic dicarboxylic acid component of the dicarboxylic acid component of the polyester resin for the resin thin film layer is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less.

[0203] The glycol component of the polyester resin for the resin thin film layer preferably contains a straight-chain (unbranched) glycol component such as ethylene glycol, diethylene glycol, 1,6-hexanediol, etc., and also preferably contains a branched glycol component. The branched structure is thought to contribute to stress relaxation in the resin thin film layer and to provide favorable adhesion. Examples of branched glycol components include 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol. The branched glycol component may be used alone or in combination of two or more.

[0204] The lower limit of the molar ratio of the branched glycol component is preferably 10 mol%, more preferably 15 mol%, and even more preferably 20 mol%, when the total glycol components are taken as 100 mol%. On the other hand, the upper limit of the molar ratio of the branched glycol component is preferably 80 mol%, more preferably 70 mol%, and particularly preferably 60 mol%. In one embodiment, the molar ratio of the branched glycol component is preferably 10 mol% or more and 80 mol% or less.

[0205] When the polyester resin used in the base film is a polyester resin mainly composed of an aromatic dicarboxylic acid component, such as PET or PEN, the interference fringes that occur due to interference at both interfaces of the resin thin film layer can be suppressed by increasing the refractive index of the resin thin film layer.

[0206] In order to increase the refractive index of the resin thin film layer, it is preferable to use a dicarboxylic acid component having a condensed ring structure, such as a naphthalenedicarboxylic acid component, as the dicarboxylic acid component of the polyester resin for the resin thin film layer. When the total dicarboxylic acid components are 100 mol%, the lower limit of the molar ratio of the dicarboxylic acid component having a condensed ring structure is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, particularly preferably 40 mol%, and most preferably 50 mol%. The upper limit of the molar ratio of the dicarboxylic acid component having a condensed ring structure is preferably 95 mol%, more preferably 90 mol%, even more preferably 85 mol%, particularly preferably 80 mol%, and most preferably 75 mol%. In one embodiment, the molar ratio of the dicarboxylic acid component having a condensed ring structure is preferably 10 mol% or more and 95 mol% or less.

[0207] When a dicarboxylic acid component having a fused ring structure is used, it is preferable to use a glycol component having 4 or more carbon atoms. As the glycol component having 4 or more carbon atoms, at least one selected from butanediol, pentanediol, hexanediol, nonanediol, decanediol, dodecanediol, and dimer diol is preferable. In addition, these glycol components are preferably those having a primary hydroxy group because of ease of polymerization.

[0208] When the total glycol components are taken as 100 mol%, the lower limit of the molar ratio of glycol components having 4 or more carbon atoms is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly preferably 25 mol%. The upper limit of the molar ratio of glycol components having 4 or more carbon atoms is preferably 80 mol%, more preferably 70 mol%, even more preferably 60 mol%, and particularly preferably 50 mol%. In one embodiment, the molar ratio of glycol components having 4 or more carbon atoms is preferably 10 mol% or more and 80 mol% or less.

[0209] When a dicarboxylic acid component having a condensed ring structure is used, it is also preferable to combine it with an aliphatic dicarboxylic acid component. The aliphatic dicarboxylic acid component is preferably at least one selected from adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and dimer acid. When the total dicarboxylic acid components are taken as 100 mol%, the upper limit of the molar ratio of the aliphatic dicarboxylic acid is preferably 50 mol%, more preferably 40 mol%, even more preferably 30 mol%, particularly preferably 20 mol%, and most preferably 15 mol%. By using this composition, it is easy to achieve suitable adhesion while increasing the refractive index of the resin thin film layer.

[0210] The polyester resin for the resin thin film layer is preferably water-soluble or water-dispersible. To impart the above properties to the polyester resin, for example, methods include copolymerizing a compound (e.g., a dicarboxylic acid) containing a hydrophilic group such as a sulfonic acid (salt) group, a carboxylic acid (salt) group, or a phosphoric acid (salt) group; or copolymerizing fumaric acid, maleic acid, or the like into the polyester resin to introduce a double bond, followed by graft polymerization of acrylic acid or the like. Among these, a method of copolymerizing a dicarboxylic acid component having a sulfonic acid (salt) group is preferred from the viewpoint of imparting hydrophilicity while maintaining a low acid value of the polyester resin and controlling its reactivity with a crosslinking agent. Examples of dicarboxylic acid components having a sulfonic acid (salt) group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid, or alkali metal salts, amine salts, and ammonium salts thereof. Of these, 5-sulfoisophthalic acid or its salts are preferred.

[0211] The lower limit of the sulfonic acid (salt) group content in the polyester resin for the resin thin film layer (the total amount of sulfonic acid (salt) group-containing dicarboxylic acid components and sulfonic acid (salt) group-containing glycol components when all dicarboxylic acid components are 100 mol % and all glycol components are 100 mol %) is preferably 1 mol %, more preferably 3 mol %, and even more preferably 5 mol %. The upper limit of the sulfonic acid (salt) group content is preferably 15 mol %, more preferably 12 mol %, and even more preferably 10 mol %. In one embodiment, the sulfonic acid (salt) group content is preferably 1 mol % or more and 15 mol % or less. By setting it within the above range, it becomes easier to achieve both water solubility or water dispersibility and water resistance of the resin thin film layer.

[0212] The lower limit of the midpoint glass transition temperature (Tg) of the polyester resin for the resin thin film layer is preferably 20°C, more preferably 30°C, even more preferably 35°C, and particularly preferably 40°C. The upper limit of the Tg is preferably 90°C, more preferably 85°C, even more preferably 80°C, and particularly preferably 75°C. In one embodiment, the Tg is preferably 20°C or higher and 90°C or lower. By setting it within the above range, good adhesion can be achieved.

[0213] The upper limit of the acid value of the polyester resin for the resin thin film layer is preferably 20 KOHmg / g, more preferably 15 KOHmg / g, even more preferably 10 KOHmg / g, and particularly preferably 8 KOHmg / g. The lower limit of the acid value may be preferably 0 KOHmg / g, more preferably 0.5 KOHmg / g. By making the acid value equal to or greater than the lower limit, reactivity when crosslinking with isocyanate or the like can be increased, and weather resistance can be improved. In one embodiment, the acid value is preferably 0 KOHmg / g or more and 20 KOHmg / g or less.

[0214] The lower limit of the number average molecular weight of the polyester resin for the resin thin film layer is preferably 5,000, more preferably 8,000, even more preferably 10,000, and particularly preferably 12,000. The upper limit of the number average molecular weight is preferably 40,000, more preferably 35,000, even more preferably 30,000, and particularly preferably 28,000. By keeping the number average molecular weight at or below the above upper limit, the resin thin film layer can be made tough and have good adhesion. In one embodiment, the number average molecular weight is preferably 5,000 or more and 40,000 or less. In this specification, the number average molecular weight can be measured, for example, by gel permeation chromatography (GPC) in terms of polystyrene in the case of polyester resins.

[0215] [Polyurethane Resin for Resin Thin Film Layer] As the polyol for the polyurethane resin for the resin thin film layer, prepolymers such as polyester, polycarbonate, polyether, etc. are preferably used.

[0216] The polyester prepolymer is similar to the polyester resin for the resin thin film layer described above, but the upper limit of the number average molecular weight is preferably 10,000, more preferably 8,000, and even more preferably 6,000. The lower limit of the number average molecular weight of the polyester prepolymer is preferably 1,000, more preferably 1,500, and even more preferably 2,000. In one embodiment, the number average molecular weight of the polyester prepolymer is preferably 1,000 or more and 10,000 or less.

[0217] The polycarbonate used as the polycarbonate prepolymer is, for example, a lower dialkylene carbonate (e.g., C ２－４ It can be obtained by transesterification of a carbonate ester such as dialkylene carbonate or diphenyl carbonate with a diol, or by reacting a diol with phosgene.

[0218] Examples of diols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, and bisphenols. Among these, polycarbonate (polyhexamethylene carbonate diol) using 1,6-hexanediol is preferred in terms of solubility, weather resistance, and the like. The above diols may be copolymerized in addition to 1,6-hexanediol, but the amount of 1,6-hexanediol in all diols is preferably 60 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more.

[0219] The lower limit of the number average molecular weight of the polycarbonate prepolymer is preferably 500, more preferably 1000, and even more preferably 1500. The upper limit of the number average molecular weight of the polycarbonate prepolymer is preferably 5000, more preferably 4000, and even more preferably 3000. In one embodiment, the number average molecular weight of the polycarbonate prepolymer is preferably 500 or more and 5000 or less.

[0220] Examples of polyether prepolymers include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethylene glycol-polypropylene glycol block copolymers.

[0221] The lower limit of the number average molecular weight of the polyether prepolymer is preferably 200, more preferably 300, and even more preferably 400. The upper limit of the number average molecular weight of the polyether prepolymer is preferably 3000, more preferably 2500, and even more preferably 2000. In one embodiment, the number average molecular weight of the polyether prepolymer is preferably 200 or more and 3000 or less.

[0222] By setting the number average molecular weight of each prepolymer within the above range, the concentration of urethane bonds can be maintained within an appropriate range, making it easier to achieve both the properties of the prepolymer and the properties of the urethane resin, such as film toughness.

[0223] These prepolymers may be used singly or in combination of two or more. Specific examples of the preferred combinations include a combination of a polyether prepolymer and a polycarbonate prepolymer, and a combination of a polyether prepolymer and a polyester prepolymer.

[0224] Examples of polyisocyanates include aromatic aliphatic diisocyanates such as xylylene diisocyanate and 4,4'-diphenylmethane diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanatomethyl)cyclohexane; aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; and polyisocyanates in which one or more of these compounds are pre-added with trimethylolpropane, etc. Aliphatic isocyanates or alicyclic diisocyanates are preferred, and alicyclic diisocyanates are particularly preferred, because they are less likely to yellow, can be easily formed into a flexible coating, and when a photocurable resin layer is provided on the easy-adhesion layer, stress due to shrinkage and swelling is easily alleviated, resulting in good adhesion.

[0225] Furthermore, a chain extender can be used for the polyurethane resin. Examples of the chain extender include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; aminoalcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; and water.

[0226] To impart water solubility or water dispersibility to polyurethane resins, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular structure. From the viewpoint of moisture resistance, it is preferable to introduce weakly acidic carboxylic acid (salt) groups. Nonionic groups such as polyoxyalkylene groups can also be introduced.

[0227] To introduce carboxylic acid (salt) groups into a polyurethane resin, it is preferable to introduce a polyol compound having a carboxylic acid group, such as dimethylolpropionic acid or dimethylolbutanoic acid, as a copolymerization component and neutralize the polyol with a salt-forming agent. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine; N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine; and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of two or more.

[0228] When a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component to impart water solubility to a polyurethane resin, the molar ratio of the polyol compound having a carboxylic acid (salt) group in the polyurethane resin is preferably 3 to 60 mol%, and more preferably 5 to 40 mol%, when the total polyisocyanate components of the polyurethane resin are taken as 100 mol%. When the molar ratio is 3 mol% or more, water dispersion is easy. Furthermore, when the molar ratio is 60 mol% or less, excellent water resistance and moist heat resistance are achieved.

[0229] Alternatively, a chain extender having a tertiary amino group in the molecule may be used. Examples of the chain extender having a tertiary amino group in the molecule include N-alkyldialkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, N-alkyldiaminoalkylamines such as N-methyldiaminoethylamine and N-ethyldiaminoethylamine, and triethanolamine, and one type may be used alone or two or more types may be used in combination.

[0230] The chain extender having a tertiary amino group can be neutralized with an acid or quaternized with a quaternizing agent to improve its water solubility or water dispersibility. Examples of the acid include organic acids such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malic acid, malonic acid, and adipic acid, and inorganic acids such as hydrochloric acid, phosphoric acid, and nitric acid. These acids can be used alone or in combination of two or more. Examples of the quaternizing agent include alkyl halides such as benzyl chloride and methyl chloride, and sulfates such as dimethyl sulfate and diethyl sulfate. These quaternizing agents can be used alone or in combination of two or more.

[0231] The lower limit of the number average molecular weight of the polyurethane resin is preferably 3,000, more preferably 5,000, and even more preferably 7,000. The upper limit of the number average molecular weight of the polyurethane resin is preferably 70,000, and more preferably 50,000. In one embodiment, the number average molecular weight of the polyurethane resin is preferably 3,000 or more and 70,000 or less.

[0232] The lower limit of the Tg of the polyurethane resin is preferably −60° C., more preferably −50° C., and even more preferably −40° C. The upper limit of the Tg of the polyurethane resin is preferably 60° C., more preferably 40° C., and even more preferably 20° C., and may be 0° C. or −5° C. In one embodiment, the Tg of the polyurethane resin is preferably −60° C. or higher and 60° C. or lower.

[0233] [Acrylic Resin for Resin Thin Film Layer] The acrylic resin for the resin thin film layer preferably contains a hydrocarbyl acrylate and / or hydrocarbyl methacrylate as the main monomer component, and is copolymerized with an acrylate and / or methacrylate having another functional group. In this specification, acrylate and methacrylate may be collectively referred to as (meth)acrylate. Examples of the hydrocarbyl group of the hydrocarbyl (meth)acrylate include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, lauryl, and stearyl; cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl; and aralkyl groups such as benzyl and phenylethyl. One type of hydrocarbyl (meth)acrylate may be used alone, or two or more types may be used in combination, but two or more types may be used in combination. Among these, alkyl (meth)acrylates are preferably used, and C １－４ It is more preferable to use an alkyl (meth)acrylate, and even more preferable to use at least one selected from methyl methacrylate, ethyl methacrylate, and ethyl acrylate.

[0234] Examples of the (meth)acrylate having another functional group include the following, and one or more of these can be used. - Hydroxy group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate; - Amide group-containing monomers such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, and N-phenylacrylamide; - Polyalkylene oxide (meth)acrylate monomers such as polyethylene oxide (meth)acrylate, propylene oxide (meth)acrylate, polytetramethylene glycol (meth)acrylate, and polyethylene oxide-propylene oxide (meth)acrylate; - Amino group-containing monomers such as N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate; - Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate. Monomers containing a carboxyl group or a salt thereof, such as acrylic acid, methacrylic acid, and salts thereof (alkali metal salts such as lithium salt, sodium salt, potassium salt, etc.)

[0235] The acrylic resin may also contain a copolymerizable monomer. Examples of the copolymerizable monomer include styrene, vinyl acetate, acrylonitrile, methacrylonitrile, maleic anhydride, carboxyl group-containing monomers such as fumaric acid, maleic acid, crotonic acid, and itaconic acid, and salts thereof; and sulfonic acid group-containing monomers such as styrene sulfonic acid and vinyl sulfonic acid, and salts thereof. The copolymerizable monomers may be used alone or in combination of two or more.

[0236] The lower limit of the midpoint glass transition point (Tg) of the acrylic resin is preferably 0°C, more preferably 10°C, and even more preferably 15°C. The upper limit of the Tg of the acrylic resin is preferably 90°C, more preferably 80°C, and even more preferably 70°C. In one embodiment, the Tg of the acrylic resin is preferably 0°C or higher and 90°C or lower. By setting it within the above range, excellent adhesiveness can be exhibited over a wide temperature range, and flexibility can also be ensured.

[0237] The lower limit of the number average molecular weight of the acrylic resin is preferably 100,000, more preferably 200,000, and even more preferably 300,000. The upper limit of the number average molecular weight of the acrylic resin is preferably 1,000,000, more preferably 800,000, and even more preferably 600,000. In one embodiment, the number average molecular weight of the acrylic resin is preferably 100,000 or more and 1,000,000 or less.

[0238] In order to make an acrylic resin water-soluble or water-dispersible, methods such as introducing a carboxylate group or a sulfonate group into the acrylic resin using the above-mentioned monomers, introducing an amino group into the acrylic resin, or introducing polyethylene oxide into the acrylic resin can be mentioned.

[0239] [Other Resins] The resin thin film layer may contain resins other than the polyester resin, polyurethane resin, and acrylic resin described above, such as polyamide, polystyrene, styrene-acrylic copolymer, styrene-butadiene copolymer, polycarbonate, and polyvinyl alcohol-based resin.

[0240] In particular, the addition of a polyvinyl alcohol-based resin increases the affinity of the resin thin film for aqueous coating agents and the like, and exhibits good adhesion when a polyester film and a polarizer made of polyvinyl alcohol are laminated using an aqueous adhesive.

[0241] The polyvinyl alcohol resin is not particularly limited as long as it is recognized as a polyvinyl alcohol resin. Specific examples include polyvinyl alcohol obtained by saponifying polyvinyl acetate; derivatives thereof; saponified copolymers of vinyl acetate with copolymerizable monomers; and modified polyvinyl alcohol obtained by acetalizing, urethanizing, etherifying, grafting, phosphate esterifying, or the like of polyvinyl alcohol. Examples of the monomer include unsaturated carboxylic acids and esters thereof, such as maleic acid (anhydride), fumaric acid, crotonic acid, itaconic acid, and (meth)acrylic acid; α-olefins such as ethylene and propylene; (meth)allylsulfonic acid (sodium); sodium sulfonate (monoalkyl maleate); sodium disulfonate alkyl maleate; N-methylolacrylamide; alkali salts of acrylamidoalkylsulfonic acid; N-vinylpyrrolidone; and N-vinylpyrrolidone derivatives. These polyvinyl alcohol resins may be used alone or in combination.

[0242] Suitable polyvinyl alcohol-based resins include vinyl alcohol-vinyl acetate copolymers, vinyl alcohol-vinyl butyral copolymers, and ethylene-vinyl alcohol copolymers, and among these, vinyl alcohol-vinyl acetate copolymers and / or ethylene-vinyl alcohol copolymers are preferred. The degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of the viscosity of the coating liquid, it is preferable that the degree of polymerization is 3000 or less. It is preferable that the degree of polymerization of the polyvinyl alcohol-based resin is 300 or more.

[0243] The copolymerization ratio of vinyl alcohol in a polyvinyl alcohol-based resin can be expressed by the saponification degree. The saponification degree of the polyvinyl alcohol-based resin is not particularly limited as long as excellent adhesiveness is exhibited, but is preferably 60 mol% or more. More preferably, the upper limit of the saponification degree of the polyvinyl alcohol-based resin is 95 mol% or less, and preferably 85 mol% or less. The saponification degree of the polyvinyl alcohol-based resin is preferably 65 mol% or more and 83 mol% or less, more preferably 68 mol% or more and 80 mol% or less, even more preferably 70 mol% or more and less than 80 mol%, even more preferably 71 mol% or more and 78 mol% or less, and particularly preferably 73 mol% or more and 75 mol% or less. When the saponification degree of the polyvinyl alcohol-based resin is equal to or greater than the above-mentioned lower limit, the resin has suitable adhesiveness to aqueous adhesives and polarizers, and forms a nanophase-separated structure with polyester resins, etc. in the resin thin film layer, thereby achieving high levels of adhesion to the substrate film, adhesion to aqueous resins, and adhesion to non-water-soluble adhesives, etc. Furthermore, when the degree of saponification of the polyvinyl alcohol-based resin is equal to or less than the above upper limit (or less), a nanophase-separated structure can be more suitably formed with the polyester resin, etc. The degree of saponification of the polyvinyl alcohol-based resin can be determined by the amount of alkali consumption required for hydrolysis of copolymerization units such as vinyl acetate or by composition analysis by NMR.

[0244] The content of the polyvinyl alcohol-based resin in the resin thin film layer is preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less. When the content of the polyvinyl alcohol-based resin is equal to or more than the lower limit, the PVA surface fraction is increased, which is suitable for adhesion to the polarizer and the aqueous resin. On the other hand, when the content of the polyvinyl alcohol-based resin is equal to or less than the upper limit, it is suitable for adhesion to the polyester substrate film.

[0245] (Crosslinking Agent) The resin of the resin thin film layer is preferably crosslinked. By making the resin thin film layer have a crosslinked structure, blocking is less likely to occur after the film is wound up and stored. Furthermore, when the film is used, when coating or printing is performed on the resin thin film layer, the resin thin film layer does not dissolve and maintains its shape, and high adhesion can be maintained without being affected by the coating or printing conditions. Furthermore, by incorporating a crosslinking agent into the resin thin film layer, a nanophase separation structure can be more suitably formed. When the resin contains a polyvinyl alcohol-based resin, crosslinking between hydroxyl groups of the polyvinyl alcohol-based resin makes it easier for the polyvinyl alcohol-based resin to aggregate, which is thought to result in the formation of a suitable separation structure.

[0246] The crosslinking agent is not particularly limited as long as it has the ability to crosslink with functional groups in the resin (hydroxyl groups in the case of polyvinyl alcohol-based resins), and examples thereof include melamine compounds, isocyanate compounds, carbodiimide compounds, oxazoline compounds, epoxy compounds, and mixtures of two or more of these. From the viewpoint of the stability over time of the coating liquid, at least one selected from melamine compounds, isocyanate compounds, carbodiimide compounds, and oxazoline compounds is preferred. Furthermore, in the case of polyvinyl alcohol-based resins, the crosslinking agent preferably contains a melamine compound or an isocyanate compound from the viewpoint of favorable crosslinking reaction with hydroxyl groups.

[0247] The isocyanate compound may be a low-molecular or high-molecular diisocyanate or a trivalent or higher polyisocyanate. Examples of the isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenyl aromatic diisocyanates such as xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane; aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; and trimers of these isocyanate compounds. Further examples include polymeric terminal isocyanate group-containing compounds obtained by reacting an excess amount of these isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine, or high-molecular-weight active hydrogen compounds such as polyester polyols such as polycaprolactone-based polyester polyols, polyether polyols, and polyamides.

[0248] Furthermore, it is also preferable to impart water solubility or water dispersibility to the isocyanate compound. Methods for imparting water solubility or water dispersibility to the isocyanate compound include the same methods as those for imparting water solubility or water dispersibility to the polyurethane resin, as well as a method using a water-soluble polymer such as polyethylene glycol as the polymeric active hydrogen compound, and a method of reacting a portion of the isocyanate groups with polyethylene glycol monoalkyl (methyl, ethyl, etc.) ether. In this case, it is preferable to use a trivalent or higher isocyanate compound or a trimer.

[0249] The isocyanate compound is preferably a blocked isocyanate compound, which makes it possible to more suitably improve the stability of the coating liquid over time.

[0250] The blocked isocyanate compound can be prepared by subjecting the above-mentioned isocyanate compound and a blocking agent to an addition reaction using a conventionally known method.

[0251] Examples of the blocking agent include bisulfite compounds such as sodium bisulfite; pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 4-nitro-3,5-dimethylpyrazole; phenolic compounds such as phenol and cresol, and aliphatic alcohol compounds such as methanol and ethanol; active methylene compounds such as dimethyl malonate, diethyl malonate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; acid amide compounds such as acetanilide and acetic acid amide, and lactam compounds such as ε-caprolactam and δ-valerolactam; acid imide compounds such as succinimide and maleimide; oxime compounds such as acetaldoxime, acetone oxime, and methyl ethyl ketoxime; and amine compounds such as diphenylaniline, aniline, and ethyleneimine.

[0252] The lower limit of the boiling point of the blocking agent is preferably 150°C, more preferably 160°C, even more preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the blocking agent, the more suppressed is the evaporation of the blocking agent by the drying process after coating of the coating liquid or by heat addition during the film formation process in the case of an in-line coating method, thereby suppressing the occurrence of minute unevenness on the coated surface and improving the transparency of the film. The upper limit of the boiling point of the blocking agent is not particularly limited, but is preferably about 300°C from the viewpoint of productivity. In one embodiment, the boiling point of the blocking agent is preferably 150°C or higher and 300°C or lower. Since the boiling point is related to the molecular weight, it is preferable to use a blocking agent with a large molecular weight in order to increase the boiling point of the blocking agent, and the molecular weight of the blocking agent is preferably 50 or higher, more preferably 60 or higher, and even more preferably 80 or higher.

[0253] The upper limit of the dissociation temperature of the blocked isocyanate is preferably 200°C, more preferably 180°C, even more preferably 160°C, particularly preferably 150°C, and most preferably 120°C. The blocking agent dissociates during the drying process after application of the coating solution or during the film formation process in the case of an in-line coating method, generating regenerated isocyanate groups. This allows the crosslinking reaction with polyurethane resins and the like to proceed, improving adhesion. When the dissociation temperature of the blocked isocyanate is below the above temperature, dissociation of the blocking agent proceeds sufficiently, resulting in good adhesion, particularly good moist heat resistance.

[0254] In one embodiment, it is preferable that the dissociation temperature of the blocked isocyanate is 120° C. or lower, and the boiling point of the blocking agent is 150° C. or higher. Examples of such blocking agents include the aforementioned sodium bisulfite, 3,5-dimethylpyrazole, 3-methylpyrazole, dimethyl malonate, diethyl malonate, acetone oxime, and methyl ethyl ketoxime. Among these, pyrazole compounds typified by 3,5-dimethylpyrazole and 3-methylpyrazole are preferred from the viewpoints of moist heat resistance and yellowing.

[0255] The melamine compound may have a substituent group -(CH ２ )ｎ Examples of suitable melamine compounds include melamine resins substituted with -O-R (wherein n is an integer of 1 to 3, and R is an alkyl group having 1 to 4 carbon atoms), where R in the formula is preferably methyl. The number of the above-mentioned substituents per melamine structure is preferably 3 to 6. Specific examples of melamine compounds include M-3, MK, M-6, M-100, MC, and the like from the Sumitex Resin series manufactured by Sumitomo Chemical Co., Ltd., and methylated melamine resins MW-22, MX-706, MX-042, and the like manufactured by Sanwa Chemical Co., Ltd.

[0256] A melamine compound may be used in combination with an epoxy compound and / or an oxazoline compound, but in that case, the content of the epoxy compound and / or the oxazoline compound is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 2% by mass, and particularly preferably less than 1% by mass. When the content is equal to or less than the above upper limit, when the resin in the resin thin film layer contains a polyester resin and a polyvinyl alcohol-based resin, the surface fraction of the polyvinyl alcohol-based resin can be kept high regardless of the ratio of the two, and excellent adhesion can be achieved.

[0257] In addition, an isocyanate compound may be used in combination with an epoxy compound and / or an oxazoline compound, and in that case, the content of the epoxy compound and / or the oxazoline compound is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 2% by mass, and particularly preferably less than 1% by mass. When the content is equal to or less than the above upper limit, when the resin in the resin thin film layer contains a polyester resin and a polyvinyl alcohol-based resin, the surface fraction of the polyvinyl alcohol-based resin can be kept high regardless of the ratio of the two, and excellent adhesion can be achieved.

[0258] The content of the crosslinking agent in the resin thin film layer is preferably 2% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, and even more preferably 8% by mass to 30% by mass. When the content of the crosslinking agent is equal to or greater than the lower limit, it is suitable for crosslinking the resin (particularly polyvinyl alcohol-based resin), and when it is equal to or less than the upper limit, it is suitable for exhibiting adhesive properties due to the resin.

[0259] (Additives) Additives such as surfactants, antioxidants, catalysts, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, and nucleating agents may be added to the resin thin film layer.

[0260] In order to further improve the slipperiness and blocking resistance of the film, it is also a preferred embodiment to add particles to the resin thin film layer. Examples of particles to be contained in the resin thin film layer in the present invention include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, and mixtures of two or more of these. The inorganic particles can also be used in combination with other common inorganic particles, such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride. Examples of the particles include organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles.

[0261] The average particle size of the particles in the resin thin film layer (average particle size based on the number of particles measured by SEM or TEM; the same applies below) is preferably 0.04 to 2 μm, more preferably 0.1 to 1 μm. When the average particle size of the particles is 0.04 μm or more, sufficient irregularities are formed on the film surface, resulting in excellent handling properties such as slipperiness and winding ability of the film, and excellent processability during lamination. When the average particle size of the particles is 2 μm or less, particle shedding can be suppressed. The particle concentration in the resin thin film layer is preferably 1 to 20% by mass, more preferably 5 to 15% by mass, of the solid component.

[0262] When a film having a resin thin film layer of the present invention is used in optical equipment or for modification, interference fringes may occur, impairing the appearance. This is thought to be due to the influence of thin film interference caused by reflection at the upper and lower interfaces of the resin thin film layer when a hard coat or the like is provided on the resin thin film layer. Methods for suppressing thin film interference include increasing the refractive index of the resin thin film layer. Methods for increasing the refractive index include introducing a condensed ring structure into the polyester resin as described above, but also preferably adding high refractive index particles to the resin thin film layer.

[0263] As the high refractive index particles, metal oxide particles having a refractive index of 1.7 or more and 3 or less are preferred. The refractive index is measured at a wavelength of 589 nm, for example. Examples of such metal oxides include TiO ２ (refractive index 2.7), ZnO (refractive index 2.0), Sb ２ O ３ (refractive index 1.9), SnO ２ (refractive index 2.1), ZrO ２ (refractive index 2.4), Nb ２ O ５ (refractive index 2.3), CeO ２ (refractive index 2.2), Ta ２ O ５ (refractive index 2.1), Y ２ O ３ (refractive index 1.8), La ２ O ３ (refractive index 1.9), In ２ O ３ (refractive index 2.0), Cr ２ O ３ (refractive index 2.5), and composite oxides containing these metal atoms. Examples of composite oxides include TiO ２ -ZrO ２ (mass ratio of 1 / 4 to 4 / 1) These high refractive index particles can be used alone or in combination of two or more.

[0264] The average particle size of the high refractive index particles is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and particularly preferably 20 nm or more. The average particle size of the high refractive index particles is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, and particularly preferably 60 nm or less. In one embodiment, the average particle size of the high refractive index particles is preferably 5 nm or more and 200 nm or less. By setting the particle size within the above range, aggregation is less likely to occur and transparency is good.

[0265] The high refractive index particles may be surface-treated. Surface treatments include physical surface treatments such as plasma discharge treatment and corona discharge treatment, and chemical surface treatments using a coupling agent, with chemical surface treatments using a coupling agent being preferred. As the coupling agent, organoalkoxymetal compounds (e.g., titanium coupling agents, silane coupling agents) are preferably used.

[0266] The content of the high-refractive-index particles in the resin thin film layer is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and particularly preferably 8% by mass or more. The content of the high-refractive-index particles is preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, particularly preferably 20% by mass or less, and most preferably 15% by mass or less. In one embodiment, the content of the high-refractive-index particles is preferably 2% by mass or more and 70% by mass or less.

[0267] The lower limit of the dried thickness of the resin thin film layer is preferably 0.001 μm, more preferably 0.005 μm, even more preferably 0.01 μm, and particularly preferably 0.02 μm. The upper limit of the dried thickness of the resin thin film layer is preferably 1 μm or less, more preferably 0.5 μm or less, even more preferably 0.3 μm or less, and particularly preferably 0.2 μm. In one embodiment, the dried thickness of the resin thin film layer is preferably 0.001 μm or more and 1 μm or less. By setting the thickness within the above range, adhesion can be ensured and blocking can be suppressed.

[0268] The resin thin film layer can be provided by dissolving or dispersing the above resin in a solvent, and optionally adding additives such as particles to the coating liquid, and applying the coating liquid to the substrate film.

[0269] The solvent may be either an organic solvent such as toluene, ethyl acetate, or methyl ethyl ketone, or an aqueous solvent, but is preferably water alone or a mixture of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include ethanol, isopropanol, 1-butanol, ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, tetrahydrofuran, acetone, and methyl ethyl ketone.

[0270] The solid content concentration of the coating liquid is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The solid content concentration of the coating liquid is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. In one embodiment, the solid content concentration of the coating liquid is preferably 1% by mass or more and 30% by mass or less.

[0271] In one embodiment, a resin thin film layer is obtained by applying a coating liquid to a substrate film, followed by heating to dry and crosslink the coating liquid. Examples of the coating method include reverse roll coating, gravure coating, kiss coating, die coating, roll brush coating, spray coating, air knife coating, wire bar coating, pipe doctor coating, impregnation coating, and curtain coating.

[0272] The drying and crosslinking temperature is preferably 60 to 200° C., more preferably 70 to 180° C., and even more preferably 80 to 170° C. Before coating with the coating liquid, the coated surface of the substrate film may be subjected to corona treatment, plasma treatment, or the like.

[0273] The coating onto the substrate film may be carried out either by an offline method carried out after the substrate film is formed, or by an in-line method carried out during the film formation, but the in-line method is preferred.

[0274] [Method for producing (film-forming) polyester film] The method for producing (film-forming) polyester film preferably includes the steps of feeding raw materials such as a polyester resin into an extruder, melt-kneading the materials, and then extruding the materials through a die having a long, narrow slit onto a cooling roll to obtain an unstretched film. In one embodiment, the raw materials may include a polyester resin composition A and a polyester resin B.

[0275] The lower limit of the melting temperature (melting point) is preferably the melting point of the raw resin of the film + 5°C, more preferably the melting point + 10°C, even more preferably the melting point + 15°C, and particularly preferably the melting point + 20°C. The upper limit of the melting temperature (melting point) is preferably the melting point + 50°C, more preferably the melting point + 45°C, even more preferably the melting point + 40°C, and particularly preferably the melting point + 35°C. In one embodiment, the melting temperature is preferably the melting point + 5°C or more and the melting point + 50°C or less. By setting the melting temperature within the above range, it becomes easier to form a film of uniform thickness, and the generation of foreign matter and discoloration due to decomposition of the raw resin can be suppressed. For example, in the case of PET, the lower limit of the melting temperature is preferably 265°C, more preferably 270°C, and even more preferably 275°C. The upper limit of the melting temperature is preferably 310°C, more preferably 305°C, and even more preferably 300°C. In one embodiment, the melting temperature is preferably 265°C or more and 310°C or less. When the film is made of a plurality of raw resins, the melting point of the resin with the highest melting point is used as the melting point of the raw resin of the film. The melting point can be evaluated by the endothermic peak value from the results obtained under the following conditions using a differential scanning calorimeter (e.g., DSC7020 manufactured by Hitachi High-Tech Science Corporation). Sample: 5 mg Measurement conditions: 1st RUN (heating): Heating rate 10°C / min, rt → 250°C (hold for 3 minutes) 1st RUN (cooling): Heating rate -50°C / min, 250°C → 25°C 2nd RUN (heating): Heating rate 10°C / min, rt → 250°C

[0276] The electrostatic adhesion method is preferred as a method for adhering the molten raw material resin to the chill roll. The electrostatic adhesion method is a method in which an electrode is usually provided before (particularly immediately before) the molten raw material resin comes into contact with the chill roll, a voltage is applied to the electrode to charge the molten resin, and the molten resin is adhered to the chill roll by electrostatic force.

[0277] Examples of the electrode include wire-shaped and ribbon-shaped electrodes. The diameter Φ of the wire-shaped electrode is preferably 0.05 to 1 mm, particularly preferably 0.08 to 0.5 mm. The thickness of the ribbon-shaped electrode is preferably 0.05 to 1 mm, particularly preferably 0.08 to 0.5 mm, and the width of the ribbon-shaped electrode is preferably 3 to 50 mm, particularly preferably 5 to 40 mm. The electrodes may be used in combination with a plurality of types and sizes, such as a wire and a tape, or a small-diameter wire and a large-diameter wire. It is preferable that the electrodes be unwound from one side and wound up on the other side.

[0278] Examples of materials for the electrodes include tungsten, iron, nickel, cobalt, molybdenum, titanium, tantalum, aluminum, copper, stainless steel, etc., and alloys of these may also be used. The surfaces of the electrodes may also be plated with gold, platinum, etc.

[0279] The electrode is provided on the opposite side of the molten resin film from the cooling roll, and the distance from the molten resin film is preferably 2 to 50 mm, more preferably 3 to 30 mm, and even more preferably 4 to 20 mm. The electrode is preferably provided between the die outlet and the point where the cooling roll and the molten resin contact each other, and is provided preferably 1 to 50 mm upstream, more preferably 2 to 30 mm upstream from the point where the cooling roll and the molten resin contact each other.

[0280] The voltage is preferably 1 to 100 KV, more preferably 3 to 50 KV.

[0281] The electrostatic adhesion method may be used in combination with a mechanical adhesion method such as a vacuum box or an air knife, and it is particularly preferable to use it in combination with a method of blowing air onto both ends.

[0282] Since the melt resistivity of the raw material resin can be optimized, high adhesion can be obtained even when the film is formed at a high speed. For example, an unstretched film can be produced at a speed of 60 m / min or more, 80 m / min or more, 100 m / min or more, or 120 m / min or more. The upper limit of the speed is not limited because it depends on the overall capacity and cooling capacity of the extruder and film-forming machine, but is approximately 500 m / min, 400 m / min, or 300 m / min. In one embodiment, the speed is preferably 60 m / min or more and 500 m / min or less.

[0283] The cooled film may be used as an unstretched film, or may be subsequently stretched to form a stretched film. Stretching may be either uniaxial or biaxial. In uniaxial stretching, stretching may be in either the MD (longitudinal) direction or the TD (transverse) direction, or may be in an oblique direction. In biaxial stretching, any method such as sequential stretching, simultaneous biaxial stretching, or a combination of these may be used. In biaxial stretching, stretching may be performed in either MD followed by TD stretching, or in TD followed by MD stretching. MD stretching and TD stretching may be added and alternately repeated, or MD stretching and TD stretching may be performed in multiple stages.

[0284] The lower limit of the stretching ratio in uniaxial stretching is preferably 2, more preferably 2.5, even more preferably 2.8, particularly preferably 3, and most preferably 3.2. The upper limit of the stretching ratio in uniaxial stretching is preferably 8, more preferably 7, even more preferably 6, particularly preferably 5.5, and most preferably 5. In one embodiment, the stretching ratio in uniaxial stretching is preferably 2 to 8 times.

[0285] The lower limit of the stretching ratio in at least one of the biaxial stretching directions (main directions) is preferably 2, more preferably 2.5, even more preferably 2.8, particularly preferably 3, and most preferably 3.2. The upper limit of the stretching ratio in at least one of the biaxial stretching directions (main directions) is preferably 8, more preferably 7, even more preferably 6, particularly preferably 5.5, and most preferably 5. In one embodiment, the stretching ratio in at least one of the biaxial stretching directions (main directions) is preferably 2 to 8.

[0286] The lower limit of the stretching ratio in the other direction of biaxial stretching is preferably 1.05, more preferably 1.1, even more preferably 1.2, particularly preferably 1.3, and most preferably 1.5. The upper limit of the stretching ratio in the other direction of biaxial stretching is preferably 8, more preferably 7, even more preferably 6, particularly preferably 5.5, and most preferably 5. In one embodiment, the stretching ratio in the other direction of biaxial stretching is preferably 1.05 to 8.

[0287] The lower limit of the area ratio of biaxial stretching is preferably 4 times, more preferably 5 times, even more preferably 6 times, particularly preferably 7 times, and most preferably 8 times. The upper limit of the area ratio of biaxial stretching is preferably 25 times, more preferably 22 times, even more preferably 20 times, particularly preferably 18 times, and most preferably 16 times. In one embodiment, the area ratio of biaxial stretching is preferably 4 times or more and 25 times or less.

[0288] In the case of a typical biaxial stretching method in which MD stretching is followed by TD stretching, the lower limit of the MD stretching ratio is preferably 2.3 times, more preferably 2.6 times, and even more preferably 2.8 times. The upper limit of the MD stretching ratio is preferably 4.2 times, more preferably 3.8 times, and even more preferably 3.5 times. In one embodiment, the MD stretching ratio is preferably 2.3 times or more and 4.2 times or less.

[0289] The lower limit of the TD stretching ratio is preferably 2.8 times, more preferably 3 times, even more preferably 3.2 times, and particularly preferably 3.4 times. The upper limit of the TD stretching ratio is preferably 6 times, more preferably 5 times, even more preferably 4.5 times, particularly preferably 4.3 times, and most preferably 4 times. In one embodiment, the TD stretching ratio is preferably 2.8 times or more and 6 times or less.

[0290] The lower limit of the stretching temperature is preferably Tg + 0°C, more preferably Tg + 3°C, even more preferably Tg + 5°C, and particularly preferably Tg + 10°C. The upper limit of the stretching temperature is preferably Tg + 50°C, more preferably Tg + 40°C, even more preferably Tg + 35°C, and particularly preferably Tg + 30°C. In one embodiment, the stretching temperature is preferably Tg or higher and Tg + 50°C or lower. In this specification, Tg refers to the midpoint glass transition temperature defined in JIS K7121 (1987). In addition, in the case of a film in which multiple resins are mixed, it is the Tg of the molten mixture (the resin composition extruded onto the cooling roll).

[0291] In the case of PET, the lower limit of the stretching temperature is preferably 80° C., more preferably 83° C., and even more preferably 85° C. In the case of PET, the upper limit of the stretching temperature is preferably 130° C., more preferably 125° C., and even more preferably 120° C. In one embodiment, the stretching temperature in the case of PET is preferably 80° C. or higher and 130° C. or lower.

[0292] For PET, the lower limit of the MD stretching temperature is preferably 80° C., more preferably 83° C., and even more preferably 85° C. For PET, the upper limit of the MD stretching temperature is preferably 110° C., more preferably 105° C., and even more preferably 100° C. In one embodiment, the MD stretching temperature for PET is preferably 80° C. or higher and 110° C. or lower.

[0293] In the case of PET, the lower limit of the TD stretching temperature is preferably 85° C., more preferably 90° C., and even more preferably 95° C. In the case of PET, the upper limit of the TD stretching temperature is preferably 130° C., more preferably 125° C., and even more preferably 120° C. In one embodiment, the TD stretching temperature in the case of PET is preferably 85° C. or higher and 130° C. or lower. Note that the above temperatures are guidelines for the film temperature, and it is preferable to adjust the temperature of the heating roller, infrared heater, tenter, etc. so that the above temperatures are achieved during stretching.

[0294] The lower limit of the stretching speed (tenter) is preferably 10% / s, more preferably 15% / s, even more preferably 20% / s, and particularly preferably 25% / s. By setting the stretching speed to equal to or greater than the above lower limit, productivity can be increased. The upper limit of the stretching speed (tenter) is preferably 100% / s, more preferably 90% / s, even more preferably 80% / s, and particularly preferably 75% / s. By setting the stretching speed to equal to or less than the above upper limit, breakage can be suppressed and uniform stretching can be achieved. In one embodiment, the stretching speed (tenter) is preferably 10% / s or more and 100% / s or less. The stretching speed is determined based on the length before stretching as 100%.

[0295] The lower limit of the heat treatment temperature is preferably 120°C, more preferably 150°C, even more preferably 170°C, and particularly preferably 190°C. By setting the temperature at or above the lower limit, the thermal shrinkage rate of the film can be suppressed. The upper limit of the heat treatment temperature is preferably 250°C, more preferably 245°C, even more preferably 240°C, and particularly preferably 235°C. By setting the temperature at or below the upper limit, good flatness can be achieved. In one embodiment, the heat treatment temperature is preferably 120°C or higher and 250°C or lower.

[0296] The lower limit of the heat treatment time is preferably 2 seconds, more preferably 3 seconds, and even more preferably 5 seconds. The upper limit of the heat treatment time is preferably 120 seconds, more preferably 60 seconds, even more preferably 30 seconds, and particularly preferably 20 seconds. In one embodiment, the heat treatment time is preferably 2 seconds or more and 120 seconds or less.

[0297] The lower limit of the relaxation treatment temperature is preferably 100°C, more preferably 120°C, even more preferably 140°C, and particularly preferably 150°C. The upper limit of the relaxation treatment temperature is preferably the heat treatment temperature, more preferably the heat treatment temperature -5°C, even more preferably the heat treatment temperature -10°C, and may be, for example, 250°C or lower. In one embodiment, the relaxation treatment temperature is preferably 100°C or higher and the heat treatment temperature or lower, and may be 100°C or higher and 250°C or lower.

[0298] The lower limit of the relaxation rate is preferably 0.5%, more preferably 1%, and even more preferably 1.5%. By setting the rate at or above the lower limit, the thermal shrinkage rate can be effectively suppressed. The upper limit of the relaxation rate is preferably 5%, more preferably 4.5%, and even more preferably 4%. By setting the rate at or below the upper limit, the flatness can be improved. In one embodiment, the relaxation rate is preferably 0.5% or more and 5% or less.

[0299] Relaxation in the TD direction can be achieved, for example, by narrowing the clip width in a tenter. Examples of relaxation in the MD direction include cutting off or releasing the edge portions held by the clips in the tenter and slowing the film take-up speed below the film running speed in the tenter, narrowing the clip spacing using a simultaneous biaxial stretching machine, and transferring the film between a first-stage clip chain and a second-stage clip chain running slower than the first-stage clip chain.

[0300] The film is then typically cooled and wound up. The lower limit of the cooling temperature (at the tenter outlet) is preferably 40°C, more preferably 50°C, and even more preferably 60°C. The upper limit of the cooling temperature (at the tenter outlet) is preferably 140°C, more preferably 120°C, and even more preferably 100°C. In one embodiment, the cooling temperature (at the tenter outlet) is preferably 40°C or higher and 140°C or lower.

[0301] The lower limit of the film temperature during winding is preferably 10°C, more preferably 15°C, and even more preferably 18°C. The upper limit of the film temperature during winding is preferably 50°C, more preferably 40°C, and even more preferably 35°C. By keeping the temperature at or below the above upper limit, charging and scratches due to tight winding can be reduced. In one embodiment, the film temperature during winding is preferably 10°C or higher and 50°C or lower.

[0302] When the resin thin film layer is formed by the in-line method, the coating may be performed on an unstretched film or a uniaxially stretched film immediately before the film is introduced into a tenter, and the film may be dried in a dryer or the like before the film is introduced into the tenter. However, it is preferable to dry the film by utilizing the heat of the tenter. Crosslinking is preferably performed in a heat treatment step.

[0303] The melt resistivity of polyester resin to which no ionic compound is added varies depending on the polyester composition, the type and amount of catalyst, etc., and is 100 x 10 ８ Although the resistance may be Ω cm, by using an ionic compound (or polyester resin composition A), the melt resistivity can be reduced and electrostatic adhesion can be provided. In particular, for insulation, germanium, titanium, manganese, etc. are used as catalysts, and the amount of metal catalyst is reduced as much as possible to ensure high insulation, and the melt resistivity is set high in some cases, but when the amount of catalyst is increased to provide electrostatic adhesion, the catalyst may precipitate and that part may be prone to short circuiting, making it difficult to ensure sufficient insulation. However, by using an ionic compound (or polyester resin composition A), it is possible to reduce the melt resistivity while suppressing short circuits caused by foreign matter and ensure insulation.

[0304] The melt resistivity of the raw material resin (particularly polyester resin) after adding the ionic compound is preferably 20×10 ８ Ω cm or less, and more preferably 15×10 ８ Ω cm or less, and more preferably 10 × 10 ８ Ω cm or less, and particularly preferably 5×10 ８ Ω cm or less, and most preferably 2×10 ８ By setting the resistivity to the above upper limit or less, electrostatic adhesion can be imparted even to raw material resins (particularly polyester resins) that have high melt resistivity before the addition of the ionic compound.

[0305] In order to obtain a film formation at a higher speed, the melt resistivity of the raw material resin (particularly polyester resin) after adding the ionic compound is preferably 1×10 ８ Ω cm or less, and more preferably 0.8×10 ８ Ω cm or less, and more preferably 0.7×10 ８ Ω cm or less, and particularly preferably 0.6×10 ８ Ω cm or less, and most preferably 0.5×10 ８ The lower limit of the melt resistivity is preferably 0.001×10 ８ Ω cm, and more preferably 0.005×10 ８ Ω cm, and more preferably 0.01×10 ８ Ω cm, and particularly preferably 0.05×10 ８ Ω cm, and most preferably 0.1×10 ８ By making the resistivity equal to or greater than the lower limit, the charge of the film can be maintained and high electrostatic adhesion can be ensured. In addition, scratches, holes, breaks, etc. in the film due to sparks between the electrode and the molten resin can be suppressed. In one embodiment, the melt resistivity is 0.001 × 10 ８ Ω・cm or more 1×10 ８ It is preferably Ω·cm or less.

[0306] When the purpose is to further reduce the amount of foreign matter, or when high insulation properties are required, such as for insulation, the melt resistivity is 0.5 × 10 ８It may be 0.6×10 Ω cm or more, ８ Ω cm or more, and may be 0.7 × 10 ８ Ω cm or more, and may be 0.8×10 ８ It may be Ω cm or more, and may be 1×10 ８ The melt resistivity may be the melt resistivity after the polyester resin composition A and the polyester resin B are mixed.

[0307] In this specification, the melt resistivity is a resistivity value (unit: Ω cm) calculated from the amount of current that flows when a raw material resin such as a polyester resin is heated to a temperature 20°C higher than its melting point and a predetermined voltage is applied to the raw material resin in a molten state, and is a numerical value that serves as an index of the electrical conductivity of the raw material resin.

[0308] It is preferable that the melt resistivity of the raw material resin (particularly polyester resin) of the polyester film is within the above range.

[0309] When the polyester film is formed from a mixture (composition) of a plurality of polyester resins, it is preferable that the melt resistivity of the mixture is within the above range.

[0310] When the raw resin of the polyester film contains resins other than polyester resins or other additives, it is preferable that the melt resistivity of the entire raw resin composition is within the above range.

[0311] The melt resistivity of a film is measured by melting it at a temperature 20°C higher than the melting point of the raw resin, such as polyester resin, used in the film. When a film contains multiple raw resins, such as polyester resins, the melting point measured by melt-kneading the film can be used. Furthermore, when the melting point cannot be clearly detected, the melting point of the polymer of the largest amount of dicarboxylic acid component and the largest amount of glycol component among the main polymer components of the film can be used if the film contains a dicarboxylic acid component and a glycol component as the main polymer components. When the film contains a hydroxycarboxylic acid component as the main polymer component, the melting point of the polymer of the largest amount of hydroxycarboxylic acid component alone can be used. Multilayer films with different polyester resin compositions in each layer are treated similarly. For example, if ethylene terephthalate is the main repeating structural unit (terephthalic acid component is 50 mol% or more of the total acid components and ethylene glycol component is 50 mol% or more of the total glycol components), the measurement can be performed at 280°C.

[0312] [Substrate Film Properties] The lower limit of the film thickness is preferably 1 μm, more preferably 2 μm, even more preferably 3 μm, particularly preferably 5 μm, and most preferably 10 μm. The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, even more preferably 200 μm, particularly preferably 150 μm, and most preferably 100 μm. In one embodiment, the film thickness is preferably 1 μm or more and 300 μm or less. The film thickness can be measured, for example, in accordance with JIS K 7130-1999 Method A.

[0313] The lower limit of the intrinsic viscosity (IVf) of the film is preferably 0.4 dl / g, more preferably 0.45 dl / g, even more preferably 0.5 dl / g, particularly preferably 0.55 dl / g, and most preferably 0.6 dl / g. By setting it to equal to or higher than the above lower limit, the mechanical strength of the film can be ensured. The upper limit of the intrinsic viscosity (IVf) of the film is preferably 1.2 dl / g, more preferably 1 dl / g, even more preferably 0.9 dl / g, particularly preferably 0.8 dl / g, and most preferably 0.7 dl / g. By setting it to equal to or lower than the above upper limit, shear heat generation during melt extrusion can be suppressed, foreign matter and coloration can be reduced, and film formability can be improved. In one embodiment, the intrinsic viscosity (IVf) of the film is preferably 0.4 dl / g or more and 1.2 dl / g or less.

[0314] The lower limit of the acid value (AVf) of the film is preferably 3 eq / ton, more preferably 5 eq / ton, and even more preferably 7 eq / ton. The upper limit of the acid value (AVf) of the film is preferably 100 eq / ton, more preferably 80 eq / ton, even more preferably 75 eq / ton, particularly preferably 70 eq / ton, and most preferably 60 eq / ton. By keeping it below the above upper limit, foreign matter can be suppressed. In one embodiment, the acid value (AVf) of the film is preferably 3 eq / ton or more and 100 eq / ton or less.

[0315] The lower limit of the haze is preferably 0.1%, more preferably 0.2%. The upper limit of the haze is preferably 10%, more preferably 5%, even more preferably 3%, particularly preferably 2%, and most preferably 1%. In one embodiment, the haze is preferably 0.1% or more and 10% or less. By keeping the haze within the above range, the film can be preferably used in applications where transparency is required. The haze can be measured in accordance with JIS K 7136 using, for example, a haze meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0316] The lower limit of the total light transmittance is preferably 80%, more preferably 85%, even more preferably 88%, particularly preferably 89%, and most preferably 90%. The upper limit of the total light transmittance is preferably 99%, more preferably 97%, even more preferably 95%, and particularly preferably 94%. In one embodiment, the total light transmittance is preferably 80% or more and 99% or less. By setting it within the above range, it can be preferably used in applications where transparency is required. Note that the total light transmittance may include an inline coating (IC) layer such as an easy-adhesion layer, but is a value measured on a film that does not include a layer provided by post-processing such as an anti-reflection layer. The total light transmittance can be measured, for example, using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0317] The lower limit of the breaking elongation in at least one of the MD direction and the TD direction is preferably 30%, more preferably 40%, and even more preferably 50%. The upper limit of the breaking elongation is preferably 400%, more preferably 300%, and even more preferably 200%. In one embodiment, the breaking elongation is preferably 30% or more and 400% or less. Furthermore, the breaking elongation in both the MD direction and the TD direction may be within the above range.

[0318] The lower limit of the breaking strength in at least one of the MD and TD directions is preferably 30 MPa, more preferably 50 MPa, even more preferably 100 MPa, particularly preferably 150 MPa, and most preferably 180 MPa. The upper limit of the breaking strength is preferably 500 MPa, more preferably 450 MPa, even more preferably 400 MPa, and particularly preferably 350 MPa. In one embodiment, the breaking strength is preferably 30 MPa or more and 500 MPa or less. Moreover, the breaking strength in both the MD and TD directions may be in the above range.

[0319] The lower limit of the elastic modulus in at least one of the MD and TD directions is preferably 0.1 GPa, more preferably 0.5 GPa, even more preferably 1 GPa, even more preferably 1.5 GPa, particularly preferably 2 GPa, and most preferably 2.5 GPa. The upper limit of the elastic modulus is preferably 10 GPa, more preferably 8 GPa, even more preferably 7 GPa, and particularly preferably 6 GPa. In one embodiment, the elastic modulus is preferably 0.1 GPa or more and 10 GPa or less. Moreover, the elastic modulus in both the MD and TD directions may be in the above range.

[0320] The breaking elongation and breaking strength can be determined from a stress-strain curve obtained by cutting a test sample having a width of 15 mm and a length of 100 mm in the longitudinal direction of the film and conducting a tensile test using a tensile tester (Autograph AG-I manufactured by Shimadzu Corporation) under conditions of a gauge length of 50 mm and a tensile speed of 200 mm / min, in accordance with JIS K 7127. The elastic modulus can be determined from a tangent to the rising portion of the stress-strain curve.

[0321] The lower limit of the tear propagation resistance in at least one of the MD and TD directions is preferably 1 N / mm, more preferably 3 N / mm, and even more preferably 5 N / mm. The upper limit of the tear propagation resistance is preferably 30 N / mm, more preferably 25 N / mm, and even more preferably 20 N / mm. In one embodiment, the tear propagation resistance is preferably 1 N / mm or more and 30 N / mm or less. The tear propagation resistance in both the MD and TD directions may be within the above range. The tear propagation resistance is a value measured in accordance with the Elmendorf method of JIS P8116 (2000).

[0322] The lower limit of the impact strength is preferably 0.005 J / μm, more preferably 0.01 J / μm, even more preferably 0.02 J / μm, and particularly preferably 0.03 J / μm. The upper limit of the impact strength is preferably 0.2 J / μm, more preferably 0.15 J / μm, even more preferably 0.1 J / μm, and particularly preferably 0.08 J / μm. In one embodiment, the impact strength is preferably 0.005 J / μm or more and 0.2 J / μm or less. By setting the impact strength within the above range, the strength of the polyester film is ensured, stable film production is achieved, problems such as breakage during post-processing are suppressed, and the film can be used in accordance with the properties required for various applications. The impact strength can be measured in an atmosphere of 23°C using an impact sphere with a diameter of 1 / 2 inch using an impact strength measuring device (e.g., a film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd.).

[0323] The lower limit of the heat shrinkage rate in the maximum direction is preferably 0%, more preferably 0.1%, even more preferably 0.2%, and particularly preferably 0.3%. The upper limit of the heat shrinkage rate in the maximum direction is preferably 5%, more preferably 4%, even more preferably 3%, and particularly preferably 2%. In one embodiment, the heat shrinkage rate in the maximum direction is preferably 0% or more and 5% or less. The heat shrinkage rate in the maximum direction can be measured, for example, by the following method. (Measurement Method) After leaving the polyester film at rest in an environment of 25°C and 50% RH for 168 hours, a circle with a diameter of 80 mm and a straight line D with a length of approximately 50 mm, passing through the center of the circle and parallel to the TD direction of the film, are drawn. The diameter of the circle is measured continuously using an image dimension measuring device (Image Measure IM6500 manufactured by KEYENCE Corporation) by setting the direction of the straight line D to 0° and setting it every 1°, and the length of the diameter of the circle at each angle before heat treatment is determined. Next, the film is heat-treated at 150°C for 30 minutes, and then cooled for 10 minutes in an environment set at room temperature (25°C). The diameter of the circle at each angle after the heat treatment is measured in the same manner as before the heat treatment. Note that the heat treatment is performed on the polyester film alone. The heat shrinkage rate is calculated at each angle using the following formula: Heat shrinkage rate = (length before heat treatment - length after heat treatment) / length before heat treatment x 100. In this way, the heat shrinkage rate of the polyester film can be measured in the direction in which the heat shrinkage rate is greatest.

[0324] The lower limit of the dynamic friction coefficient of at least one surface is preferably 0.2, more preferably 0.3. By making it equal to or greater than the above lower limit, it is possible to prevent slippage during transport, etc. The upper limit of the dynamic friction coefficient of at least one surface is preferably 0.8, more preferably 0.7, and even more preferably 0.6. By making it equal to or less than the above upper limit, it is possible to facilitate winding. In one embodiment, the dynamic friction coefficient of at least one surface is preferably 0.2 or more and 0.8 or less. Furthermore, the dynamic friction coefficients of both surfaces may be within the above range.

[0325] The lower limit of the static friction coefficient of at least one surface is preferably 0.2, more preferably 0.25, and even more preferably 0.3. By making it equal to or greater than the above lower limit, it is possible to prevent slippage during transport, etc. The upper limit of the static friction coefficient of at least one surface is preferably 0.8, more preferably 0.7, and even more preferably 0.6. By making it equal to or less than the above upper limit, it is possible to facilitate winding. In one embodiment, the static friction coefficient of at least one surface is preferably 0.2 or more and 0.8 or less. Furthermore, the static friction coefficients of both surfaces may be within the above range.

[0326] The dynamic friction coefficient and static friction coefficient can be measured, for example, using a Tensilon (RTG-1210) manufactured by AND Corporation under conditions of a metal load of 3.5 kg, a pulling speed of 200 mm / min, 23° C., and 65% RH.

[0327] The lower limit of the water vapor permeability converted to a thickness of 50 μm is preferably 1 g / m ２ 24h, more preferably 2g / m ２ 24h, more preferably 3g / m ２ 24h, particularly preferably 5g / m ２ 24h, most preferably 8g / m ２ The upper limit of the water vapor permeability converted to a thickness of 50 μm is preferably 100 g / m ２ 24h, more preferably 50g / m ２ 24h, more preferably 30g / m ２ 24h, particularly preferably 20g / m ２ 24h, most preferably 15g / m ２ 24 h. In one embodiment, the water vapor transmission rate is 1 g / m ２ ・100g / m for 24 hours or more ２ The water vapor transmission rate converted into a value for a thickness of 50 μm can be measured using a water vapor transmission rate measuring device (for example, "PERMATRAN-W 3 / 33MG" manufactured by MOCON) in accordance with JIS-K7129-B method.

[0328] The lower limit of the oxygen permeability converted to a thickness of 50 μm is preferably 10 cm３ / m ２ 24h MPa, more preferably 50 cm ３ / m ２ 24h MPa, more preferably 100cm ３ / m ２ 24h MPa, particularly preferably 150 cm ３ / m ２ 24h MPa, particularly preferably 200 cm ３ / m ２ 24h MPa, most preferably 250 cm ３ / m ２ The upper limit of the oxygen permeability converted to a thickness of 50 μm is preferably 1000 cm ３ / m ２ 24h MPa, more preferably 700 cm ３ / m ２ 24h MPa, more preferably 500 cm ３ / m ２ 24h MPa, particularly preferably 400 cm ３ / m ２ 24h MPa, particularly preferably 350 cm ３ / m ２ 24h MPa, most preferably 320 cm ３ / m ２ In one embodiment, the oxygen permeability converted to a thickness of 50 μm is 10 cm ３ / m ２ ・24h・MPa or more 1000cm ３ / m ２ The oxygen permeability can be measured using an oxygen permeability measuring device (for example, "OX-TRAN2 / 20" manufactured by MOCON) in accordance with the electrolytic sensor method (Appendix A) of JIS-K7126-2.

[0329] The lower limit of the surface roughness (Ra) of at least one surface is preferably 0.1 nm, more preferably 0.5 nm, even more preferably 0.8 nm, and particularly preferably 1 nm. The upper limit of the surface roughness (Ra) of at least one surface is preferably 100 nm, more preferably 50 nm, even more preferably 30 nm, particularly preferably 20 nm, and most preferably 10 nm. In one embodiment, the surface roughness (Ra) of at least one surface is preferably 0.1 nm or more and 100 nm or less. The surface roughness (Ra) of both surfaces may be within the above range.

[0330] The lower limit of the ten-point average surface roughness (Rzjis) of at least one surface is preferably 5 nm, more preferably 10 nm, even more preferably 15 nm, and particularly preferably 20 nm. The upper limit of the ten-point average surface roughness of at least one surface is preferably 500 nm, more preferably 400 nm, even more preferably 300 nm, and particularly preferably 250 nm. In one embodiment, the ten-point average surface roughness of at least one surface is preferably 5 nm or more and 500 nm or less. Furthermore, the ten-point average surface roughness of both surfaces may be within the above range. By setting it within the above range, smoothness, transparency, and clarity (low haze) can be ensured.

[0331] The surface roughness (Ra and Rzjis) can be measured in accordance with ISO 25178 using a non-contact surface shape measurement system (for example, VertScan R550H-M100 manufactured by Ryoka Systems Co., Ltd.).

[0332] The above film properties are typically preferred for PET or PEN films, but are also preferred for other polyester films. It is not necessary for a film to satisfy all of the above properties, and they can be selected appropriately depending on the application, the type of polyester, etc.

[0333] [Uses of Polyester Film] The polyester film of the present invention can be used for various applications. Examples of applications include, but are not limited to, the following: Optical films such as polarizer protective films, prism and lens sheets, and anti-reflection films; Surface protective films for image display devices and polarizing plates; Substrate films for transparent conductive films used in touch sensors, etc.; Process release films for ceramic green sheet production, dry film resists, etc., and functional thin film transfer films such as liquid crystal compound thin films; Insulating films for solar cell backsheets, motor insulation, and film capacitors, etc.; Circuit substrate films; Barrier film substrates; Light-reflecting films, light-shielding films; Paper-substitute void-containing films; Various packaging films; Heat-shrinkable films; Heat-molded films; Films for laminating metal plates.

[0334] The resin composition and production conditions of the polyester film can be adjusted to suit these applications, thereby optimizing the film properties. For example, when the polyester film is used in the optical system of an image display device, such as a polarizer protective film, the lower limit of the thickness is preferably 10 μm, more preferably 20 μm, and the upper limit of the thickness is preferably 150 μm, more preferably 100 μm.

[0335] In addition, the uniaxial orientation (stretching ratio) may be increased to enhance uniaxiality and increase retardation, thereby suppressing iridescence when used in an image display device. In this case, the retardation is preferably 1500 nm or more, more preferably 3000 nm or more, and can be 15000 nm or less, and can be 10000 nm or less. In this case, the lower limit of the refractive index difference between the slow axis direction of the film and the direction perpendicular thereto (fast axis direction) is preferably 0.05, more preferably 0.07, and even more preferably 0.08, and the upper limit is preferably 0.2, more preferably 0.15, and even more preferably 0.1. In this case, the lower limit of the NZ coefficient is preferably 1.3, more preferably 1.4, and even more preferably 1.5. The upper limit of the NZ coefficient is preferably 3, more preferably 2.7, and even more preferably 2.5.

[0336] Furthermore, when used in an optical system, it is also preferable to adjust the TD magnification and MD magnification by biaxial stretching to enhance isotropy. The thickness in this case can be selected from the same range as above. The retardation in this case is preferably 3500 nm or less, more preferably 3000 nm or less, even more preferably 2500 nm or less, particularly preferably 2000 nm or less, and most preferably 1500 nm or less. Furthermore, the retardation may be preferably less than 1500 nm, more preferably 1000 nm or less, even more preferably 500 nm or less, and particularly preferably 300 nm or less to form a non-retardation (low retardation) film. The lower limit of the retardation is 0 nm, but may actually be 10 nm or more, preferably 50 nm or more. The lower limit of the NZ coefficient in this case is preferably 3, more preferably 4, and even more preferably 5. The upper limit of the NZ coefficient is theoretically infinite, but in practice it is preferably 300, more preferably 200, and even more preferably 100.

[0337] The film provided with the resin thin film layer of the present invention exhibits good adhesion (adhesion) to adhesive layers, pressure-sensitive adhesive layers, various coating layers, printed layers, etc., which are applied to the surface of the resin thin film layer during use.

[0338] Examples of adhesives include rubber-based, heat-curable or radiation-curable epoxy-based, urethane-based, heat-curable or radiation-curable epoxy-acrylic, polyvinyl alcohol-based, starch-based, polyvinylpyrrolidone-based, glue, etc. These adhesives can be used to bond the film to other resin films, polarizers, metal plates, metal foils, paper, cloth, etc.

[0339] Examples of the coating layer include a hard coating layer, a low-reflection layer, an antireflection layer, an antistatic layer, an antifouling layer, a release layer, and a paint layer. These may be radiation-curable layers using acrylic or the like. They may also be prism layers or light-diffusing layers using radiation-curable resins.

[0340] Examples of the printed layer include layers printed with various solvent-based inks and radiation-curable inks.

[0341] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the invention by making appropriate modifications within the scope that is compatible with the spirit of the invention, and all of these modifications are included in the technical scope of the present invention.

[0342] [Melting Resistivity] After vacuum drying at 40°C for 16 hours, the raw resin composition was heated to a temperature 20°C higher than the melting point of the raw resin and melted. Two electrodes (stainless steel wires with a diameter of 0.6 mm) were placed in the raw resin composition, and a voltage of 120 V was applied to measure the current (io). This was applied to the following formula to calculate the resistivity value Si (Ω cm): Si (Ω cm) = (A / L) × (V / io) [A: area between electrodes (cm ２ ), L: distance between electrodes (cm), V: voltage (V), io: current (A)]

[0343] [Number of Coarse Particles] The raw resin composition was sandwiched between two cover glasses, melt-pressed to a thickness of 50 μm at a temperature 20° C. higher than the melting point of the raw resin, and rapidly cooled. After that, 20 fields of view with a field area of ​​718 μm × 583 μm were observed using a phase contrast microscope at 100x magnification, and the number of particles of 5 μm or larger was counted using an image analyzer.

[0344] [Amount of Oligomer] 100 mg of the pulverized sample was precisely weighed and dissolved in 3 mL of a hexafluoroisopropanol / chloroform mixture (volume ratio = 2 / 3), and then 20 mL of chloroform was added for dilution. 10 mL of methanol was added to this to precipitate the polymer, which was then filtered. The filtrate was evaporated to dryness and brought to a constant volume with 10 mL of dimethylformamide. The amount of cyclic trimer was then quantified using the following high-performance liquid chromatography method. Apparatus: L-7000 (Hitachi) Column: μ-Bondasphere C18 5μ 100 Å 3.9 mm × 15 cm (Waters) Solvent: Eluent A: 2% acetic acid / water (v / v) Eluent B: acetonitrile Gradient B%: 10 → 100% (0 → 55 min) Flow rate: 0.8 mL / min Temperature: 30°C Detector: UV-259 nm

[0345] [Thermal Stability Parameter (TS)] The raw resin composition was placed in a glass ampoule, and after replacing the atmosphere with nitrogen, the glass ampoule was sealed under a reduced pressure of 13.3 kPa (nitrogen atmosphere). The raw resin composition was then heat-treated for 2 hours at a temperature 40°C higher than the melting point of the raw resin, and the intrinsic viscosity of the raw resin composition was measured and calculated using the following formula: TS = 0.245 {[IV] f2 －１．４７ -[IV] i －１．４７} [IV] i and [IV] f2 indicate the intrinsic viscosity of the raw material resin composition before and after the heat treatment, respectively.

[0346] [Film formation stability] (Electrostatic application castability) The raw resin composition was dried at 135°C for 6 hours under a reduced pressure of 33 Pa. Thereafter, it was melted and filtered twice with 100 µm and 50 µm filters. A DC voltage of 6 kV was applied between an electrode placed on top of the melt-extruded film and a cooling roller to rapidly cool the sheet to adhere and solidify it. The casting speed was gradually increased, and the casting speed (m / min) at which uneven application occurred was judged and rated according to the following criteria: ◯: 50 m / min or more Δ: 30 m / min or more but less than 50 m / min ×: less than 30 m / min

[0347] [Melting point] Using a DSC7020 manufactured by Hitachi High-Tech Science Corporation, the melting point was evaluated as the endothermic peak value from the results obtained under the following conditions: Sample: 5 mg Measurement conditions: 1st run (heating): heating rate 10°C / min, rt → 250°C (hold for 3 minutes) 1st run (cooling): cooling rate -50°C / min, 250°C → 25°C 2nd run (heating): heating rate 10°C / min, rt → 250°C

[0348] [Amount of elements such as metals] The sample was pretreated to prepare a measurement solution, and the element concentration in the resulting measurement solution was measured using a high-frequency inductively coupled plasma (ICP) optical emission spectrometer (SPECTROBLUE, manufactured by Hitachi High-Tech Science Corporation) to calculate the element content in the sample. (Pretreatment) Sb, P, Ge The sample was weighed into a platinum crucible, 5 mL of a 5% yttrium nitrate ethanol solution was added, and pre-carbonization was performed on a hot plate to 400 ° C. Then, using a Yamato Scientific electric furnace FO610, ashing was performed at 550 ° C. for 8 hours. After ashing, 20 mL of 1.2 N hydrochloric acid was added, and the nitrate was dissolved to prepare a measurement solution. Ti, Mn, Al, Mg, Ca, K, Na, Li, Cu The sample was weighed into a platinum crucible and pre-carbonization was performed on a hot plate to 400 ° C. Thereafter, an ashing treatment was carried out at 550°C for 8 hours using a Yamato Scientific electric furnace FO610. After ashing, small amounts of 6.0N hydrochloric acid and hydrofluoric acid were added, and acid decomposition was carried out on a hot plate, followed by heat treatment until the acid was completely evaporated. After acid decomposition was completed, the solution was adjusted to the desired volume using 20mL of 1.2N hydrochloric acid, and the resulting solution was used as the measurement solution. (ICP optical emission analysis conditions) Plasma output: 1400W Plasma gas: 13.0L / min Auxiliary gas: 1.0L / min Nebulizer: Crossflow nebulizer Chamber: Scott chamber Measurement wavelength: See table below

[0349] [Glass transition temperature (Tg)] The midpoint glass transition temperature measured by DSC as specified in JIS K 7121 (1987) is used.

[0350] [Film Thickness] According to JIS K7130-1999 Method A, the thickness was measured using an electric micrometer (Militron 1245D, manufactured by Fine Leaf Co., Ltd.) after leaving the film to stand for 168 hours in an environment of 25°C and 50% RH.

[0351] [Intrinsic Viscosity IV] A polyester resin (or film) was dissolved in a mixed solvent of phenol (6 parts by mass) and 1,1,2,2-tetrachloroethane (4 parts by mass), and the intrinsic viscosity was measured at 30° C. using an Ostwald viscometer.

[0352] [Acid value] Polyester chips or films were freeze-pulverized and dried, and 0.2 g of the dried product was dissolved by heating in 10 mL of benzyl alcohol. The acid value was determined by titration with a 0.04 mol / L potassium hydroxide ethanol solution (80 mL of a 0.5 mol / L potassium hydroxide aqueous solution was diluted with ethanol to make 1 L) using phenol red as an indicator.

[0353] [Haze] Measurement was carried out in accordance with JIS K 7136. The haze meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd. was used as the measuring instrument.

[0354] [Total Light Transmittance] The total light transmittance was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0355] [Elongation at break, strength at break, and modulus of elasticity] According to JIS K 7127, a test sample measuring 15 mm wide and 100 mm long was cut out in the longitudinal direction of the film. The test sample was subjected to a tensile test using a tensile tester (Shimadzu Corporation, Autograph AG-I) with a gauge length of 50 mm and a tensile speed of 200 mm / min. The elongation at break and strength at break of the test sample were calculated from the obtained stress-strain curve. The modulus of elasticity was determined from the tangent to the rising portion of the stress-strain curve.

[0356] [Tear propagation resistance] This was measured according to the Elmendorf method of JIS P8116 (2000). The obtained value was divided by the film thickness (μm) and then multiplied by 10 to obtain a value per 10 μm thickness.

[0357] [Impact Strength] Measurements were made using an impact strength measuring device (product name: Film Impact Tester, serial number T-84-3) manufactured by Toyo Seiki Seisakusho, Ltd. A rectangular sample measuring 100 mm in the width direction of the film and 100 mm in the length direction of the film was cut out. The sample was then placed in the device, and the strength of the film against impact punching was measured in an atmosphere of 23°C using an impact sphere with a diameter of 1 / 2 inch. The strength converted into strength per 1 μm of thickness was taken as the impact strength, expressed in units of J / μm. The method for correcting the impact strength for thickness is as follows: (Impact Strength) = (Measured Value) ÷ (Thickness of Measurement Sample)

[0358] [150°C Heat Shrinkage in Maximum Direction] After leaving the polyester film for 168 hours in an environment of 25°C and 50% RH, a circle with a diameter of 80 mm and a line D with a length of approximately 50 mm, passing through the center of the circle and parallel to the TD direction of the film, were drawn. The circle and line D were drawn using a fine-tip pen capable of drawing black oil-based ink with a thickness of 0.5 mm or less, with constant pen pressure to ensure lines of as uniform thickness as possible. A template or compass can be used to draw the circle. The diameter of the circle was measured continuously using an image dimension measuring device (IMAGE MEASURE IM6500 manufactured by KEYENCE Corporation) in 1° increments, with the direction of line D set to 0°, and the length of the circle diameter at each angle before heat treatment was determined. Next, the film was heat-treated for 30 minutes using a gear oven set at 150°C, and then cooled for 10 minutes in an environment set at room temperature of 25°C. After that, the length of the circle diameter at each angle after heat treatment was determined in the same manner as before heat treatment. The heat treatment was performed on the polyester film alone. The heat shrinkage was evaluated at each angle using the following formula: Heat shrinkage = (length before heat treatment - length after heat treatment) / length before heat treatment x 100. In this way, the heat shrinkage of the polyester film was measured in the direction in which the heat shrinkage was greatest.

[0359] [Dynamic and static friction coefficients] Sample films were prepared by cutting out pieces of 400 mm lengthwise x 100 mm widthwise from the obtained film. These were aged for 12 hours in an atmosphere of 23°C and 65% RH. The sample was divided into pieces of 300 mm lengthwise x 100 mm widthwise for the slide platform and 100 mm lengthwise x 100 mm widthwise for the load. The slide platform sample was set on the slide platform, and the load sample was subjected to a metal load of 3.5 kg (the size of the base area was 39.7 mm ２ The static and dynamic friction coefficients of the metal load were measured using a Tensilon (RTG-1210) manufactured by AND Co. under the conditions of a pulling speed of 200 mm / min, 23°C, and 65% RH, and the average of three measurements was calculated. The friction between the same surfaces was measured.

[0360] [Water Vapor Permeability] In accordance with JIS-K7129-B method, the water vapor permeability under normal conditions was measured using a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON Co., Ltd.) in an atmosphere in which the temperature and humidity on the high humidity side around the sample during measurement were 40°C and 90% RH, respectively.

[0361] [Oxygen Permeability] In accordance with the electrolytic sensor method (Appendix A) of JIS-K7126-2, oxygen permeability was measured under normal conditions using an oxygen permeability measuring device ("OX-TRAN2 / 20" manufactured by MOCON Corporation) in an atmosphere in which the temperature and humidity on the high humidity side around the sample during measurement were 23°C and 65% RH, respectively.

[0362] [Surface roughness (Ra and Rzjis)] Each surface roughness parameter was measured in accordance with ISO 25178 using a non-contact surface shape measurement system (VertScan R550H-M100, manufactured by Ryoka Systems Co., Ltd.) under the following conditions: (Measurement conditions) Measurement mode: WAVE mode Objective lens: 10x 0.5x Tube lens Measurement area: 936 μm × 702 μm (Analysis conditions) Surface correction: 4th order correction Interpolation processing: Full interpolation ISO parameter processing: S-Filter 10 μm specified Measurements were taken at five points, and the average value was calculated.

[0363] The silica particle diameter was determined by laser diffraction of the dispersion of the added particles. The average particle diameter of high refractive index particles can also be determined by dynamic scattering during particle or film production. The sol was diluted with a dispersion medium, and measurements were performed using a submicron particle analyzer N4 PLUS (manufactured by Beckman Coulter) using the dispersion medium's parameters. The average particle diameter was calculated by cumulant calculation. Dynamic light scattering observes the average particle diameter of particles in the sol, and if particles aggregate, the average particle diameter of the aggregated particles is observed. The particle diameter of particles added to polyester was measured using a scanning electron microscope. 100 unagglomerated inorganic particles were randomly selected and observed, and the average particle diameter was calculated. The particle diameter was calculated as the circle-equivalent diameter. The circle-equivalent diameter was calculated by dividing the area of ​​the observed inorganic particles by π, calculating the square root, and then multiplying it by two. The area and circle-equivalent diameter were calculated using an image analyzer (Shimadzu Corporation, particle image analyzer iSpect-DIA-10).

[0364] [Polyester Composition] 20 mg of polyester resin was dissolved in 0.6 ml of a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform in a 1:9 (volume ratio) mixture, followed by centrifugation. The supernatant was then collected and subjected to H-NMR measurement under the following conditions: Apparatus: Fourier transform nuclear magnetic resonance apparatus (BRUKER, AVANCE NEO600) H resonance frequency: 600.13 MHz Lock solvent: deuterated chloroform Flip angle: 30° Data acquisition time: 4 seconds Delay time: 1 second Measurement temperature: 30°C Number of accumulations: 128

[0365] [Number Average Molecular Weight] 0.03 g of copolymerized polyester resin was dissolved in 10 ml of tetrahydrofuran, and the number average molecular weight was measured using a GPC-LALLS low-angle light scattering photometer LS-8000 (manufactured by Tosoh Corporation, tetrahydrofuran solvent, reference: polystyrene) at a column temperature of 30°C and a flow rate of 1 ml / min using a column (Shodex KF-802, 804, 806 manufactured by Showa Denko K.K.).

[0366] The content of EMIM-TFSI in the film was measured by the following analytical method. (Analysis Method) Approximately 50 mg of a sample obtained by cutting the film into small pieces was precisely weighed and dissolved in 1.5 mL of a solvent with a 2 / 3 mass ratio of HFIP / chloroform. 10 mL of chloroform was added to this solution, and then 5 mL of methanol was added to precipitate the resin, and the filtrate obtained by filtration was concentrated and dried. 5 mL of DMF was added to this, and the filtrate was appropriately diluted and then subjected to HPLC analysis. The HPLC conditions were as follows: Apparatus: Waters ACQUITY UPLC H Class Flow rate: 0.2 mL / min Column temperature: 40°C Injection volume: 5 μL The TFSI conditions were as follows: Column: Waters BEH C18 2.1 mm x 150 mm Mobile phase: A 0.1% formic acid, B ACN 0 min (5% B) -25 (98) -30 (98) The EMIM conditions were as follows: Column: TSKgel Amide 80 3 μm 2.1 mm x 150 mm Mobile phase: A 0.1% formic acid, B ACN 0 min (90% B) -10 (50) -15 (50) The MS was performed using a Waters Xevo G2-XS QTof instrument, with electrospray ionization (ESI) as the ionization method, with ESI negative for TFSI and ESI positive for EMIM.

[0367] [PVA Adhesion] A polyvinyl alcohol aqueous solution (PVA117 manufactured by Kuraray) adjusted to a solids concentration of 5% by mass was applied to the surface of a resin thin film layer formed using coating solutions CLB1 to 5 of a polyester film using a wire bar so that the thickness of the polyvinyl alcohol resin layer after drying was 2 μm, and the layer was dried at 70°C for 5 minutes. A red dye was added to the polyvinyl alcohol aqueous solution to facilitate evaluation. The prepared film to be evaluated was attached to a 5 mm thick glass plate with double-sided tape attached, with the side opposite the side on which the polyvinyl alcohol resin layer of the laminated film to be evaluated being attached to the double-sided tape. Next, 100 square-shaped cuts were made through the polyvinyl alcohol resin layer and reaching the base film using a cutter guide with a gap spacing of 2 mm. Next, adhesive tape (Cellotape (registered trademark) CT-24 manufactured by Nichiban Co., Ltd.; 24 mm width) was attached to the square-shaped cut surface. After the adhesive tape was applied, any air remaining at the interface was removed with an eraser to ensure complete adhesion, and the adhesive tape was then forcefully peeled off vertically five times. The number of squares in which the polyvinyl alcohol resin layer had not peeled off was counted, and a score of 90 or more was evaluated as ○. Note that partial peeling within a single square was also included in the number of peeled squares.

[0368] [Hard Coat (HC) Adhesion] (Formation of Hard Coat Layer) A coating solution for forming a hard coat layer having the following composition was applied to one surface of the resin thin film layer of the film using a #10 wire bar, and dried at 70°C for 1 minute to remove the solvent. Then, the film coated with the hard coat layer was irradiated with 300 mJ / cm using a high-pressure mercury lamp. ２The film was irradiated with ultraviolet light of 1000 W at ...

[0369] [Interference fringes] An optical adhesive polyester film having a hard coat formed on one side was cut into a 10 cm x 15 cm area to prepare a sample film. A black glossy tape (vinyl tape No. 21; black, manufactured by Nitto Denko Corporation) was attached to the side opposite the hard coat layer of the obtained sample film. The hard coat side of this sample film was placed on top, and a three-wavelength daylight light source (National Palook, FL 15EX-N 15W) was used as the light source. The sample film was observed obliquely from above at a position where the strongest reflection was observed (distance from the light source: 40 to 60 cm, angle: 15 to 45°). ○: No interference fringes were observed △: Very slight or weak interference fringes were observed ×: Interference fringes were observed

[0370] [Printing ink adhesion] Black letters were printed on the film using UV ink. Cellophane adhesive tape was attached to the printed area and then peeled off. If the printed letters remained on the film without peeling, it was evaluated as "good", and if even a part of the letters peeled off, it was evaluated as "bad".

[0371] [Polyester Resin Production Example] [Polyester Resin SbA-1] The esterification reactor was heated to 80°C, and terephthalic acid and ethylene glycol were charged at 2 moles per mole of terephthalic acid. While stirring, diantimony trioxide was added as a catalyst to give an Sb atom concentration of 70 ppm relative to the PET produced. Furthermore, 0.33 mol% of triethylamine relative to the terephthalic acid was added. The temperature was then increased by heating, and a pressurized esterification reaction was carried out at a gauge pressure of 0.34 MPa and 240°C. The pressure inside the esterification reactor was then returned to normal, and EMIM-TFSI was added as an ethylene glycol solution at 3 ppm relative to the PET produced. After the temperature was increased to 260°C over 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reactor, where it was gradually heated from 260°C to 280°C under reduced pressure, and then subjected to a polycondensation reaction at 285°C. After the polycondensation reaction was completed, the mixture was pelletized to obtain polyester resin SbA-1. The evaluation results are shown in Table 1.

[0372] [Polyester Resin SbA-2] When the temperature of the esterification reactor reached 200°C, terephthalic acid was adjusted to 2 ton / hr, and a slurry consisting of 2 moles of ethylene glycol per mole of terephthalic acid was charged. While stirring, diantimony trioxide was added as a catalyst so that the Sb atom concentration relative to the produced PET was 70 ppm, and triethylamine was further added in an amount of 0.33 mol% relative to the terephthalic acid. Next, the temperature was increased by heating, and a pressurized esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240°C. Thereafter, the temperature was increased to 260°C over 15 minutes, and the resulting esterification reaction product was transferred to a polycondensation reactor, and the temperature was gradually increased from 260°C to 280°C under reduced pressure, followed by a polycondensation reaction at 285°C. After completion of the polycondensation reaction, the mixture was pelletized. The resulting polyester resin pellets were then dried at 135°C for 6 hours under a reduced pressure of 33 Pa and added in fixed amounts to a kneading extruder KZW15TW-45 / 60MG-NH(-2200) (manufactured by Technovel Co., Ltd.). While simultaneously feeding a fixed amount of EMIM-TFSI from a separate feed port using an automatic feeder, the mixture was melted and kneaded under conditions of an actual temperature of 270°C, a screw rotation speed of 200 rpm, and a discharge rate of 1.6 to 2.0 kg / h, and further granulated and pelletized to obtain polyester resin SbA-2. The evaluation results are shown in Table 1.

[0373] [Polyester Resins SbA-3 to 8, Sb-0, and SbB-1 to 5] Polyester resins SbA-3 to 8, Sb-0, and SbB-1 to 5 were produced in the same manner as polyester resin SbA-1, except that the type and amount of ionic compound added were changed as shown in Table 1. The evaluation results are shown in Table 1. Note that polyester resin SbA-8 is an example in which two types of ionic compounds were used in combination, with the amount of ionic compound added R (ppm) being 8 + 2 = 10, and the dissociation energy Q (kJ / mol) being (8 / 10) × 315 + (2 / 19) × 857 = 423.

[0374] [Polyester Resin SbA-9] Polyester Resin SbA-9 was prepared in the same manner as Polyester Resin SbA-1, except that the Sb content was adjusted to 100 ppm.

[0375] [Polyester Resin TiA-1 (Ti-Catalyzed PET)] The esterification reactor was heated to 80°C, and 2 moles of ethylene glycol were charged per mole of terephthalic acid. While stirring, 0.33 mole% of triethylamine was added to the terephthalic acid. The temperature was then increased by heating, and a pressurized esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240°C. The pressure inside the esterification reactor was then returned to normal, and EMIM-TFSI was added as an ethylene glycol solution to the resulting PET at 3 ppm, and tetra-n-butoxytitanium was added to the resulting PET at 7 ppm in terms of elemental Ti. After heating to 260°C over 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reactor, gradually heated from 260°C to 280°C under reduced pressure, and then subjected to a polycondensation reaction at 285°C. After the polycondensation reaction was completed, the mixture was pelletized to obtain polyester resin TiA-1. The evaluation results are shown in Table 1.

[0376] [Polyester Resin Ti-0 (Ti-Catalyzed PET)] Polyester Resin Ti-0 was produced in the same manner as Polyester Resin TiA-1, except that EMIM-TFSI was not added.

[0377] [Polyester Resin GeA-1 (Ge-Catalyzed PET)] Polyester Resin GeA-1 was produced in the same manner as Polyester Resin TiA-1, except that germanium dioxide was added as a water / ethylene glycol aqueous solution in place of tetra-n-butoxytitanium, so that the Ge element amount was 65 ppm relative to the produced PET.

[0378] [Polyester Resin AlA-1 (GS Catalyst PET)] (Preparation of Aluminum-Containing Ethylene Glycol Solution) A 20 g / L aqueous solution of basic aluminum acetate and an equal amount (volume ratio) of ethylene glycol were charged into a blending tank and stirred at room temperature (23°C) for several hours. After that, water was distilled off from the system while stirring under reduced pressure (3 kPa) at 50 to 90°C for several hours, to prepare an aluminum-containing ethylene glycol solution containing 20 g / L of an aluminum compound.

[0379] (Preparation of phosphorus-containing ethylene glycol solution) Irganox 1222 (manufactured by BASF Co., Ltd.) as a phosphorus compound was charged into a blending tank together with ethylene glycol, and the mixture was heat-treated at 175°C for 150 minutes while stirring under nitrogen substitution to prepare a phosphorus-containing ethylene glycol solution containing 50 g / L of the phosphorus compound.

[0380] (PET Polymerization) Polyester resin AlA-1 was produced in the same manner as polyester resin TiA-1, except that instead of tetra-n-butoxytitanium, an aluminum-containing ethylene glycol solution and a phosphorus-containing ethylene glycol solution were added to the produced PET so as to give 21 ppm of Al element and 45 ppm of P element. The aluminum-containing ethylene glycol solution and the phosphorus-containing ethylene glycol solution were mixed in advance and then added.

[0381] [Polyester Resin CRA-1Sb (Chemically Recycled PET)] Chemically recycled BHET was charged into a reactor equipped with a stirrer, and diantimony trioxide was added to the resulting PET to achieve 70 ppm Sb atoms. Furthermore, EMIM-TFSI was added as an ethylene glycol solution at 3 ppm relative to the resulting PET. The system temperature was then raised to 280°C over one hour, during which the system pressure was gradually reduced to 0.15 kPa. Under these conditions, a polycondensation reaction was carried out to obtain a polyester resin. The chemically recycled BHET used was obtained by alkaline hydrolysis of recovered PET bottles and polyester fibers in ethylene glycol, followed by purification processes such as filtration and distillation. The isophthalic acid content of the chemically recycled BHET was 1.0 mol% (relative to total acid components), and the diethylene glycol content was 1.2 mol% (relative to total acid components).

[0382] [Polyester Resin CRA-1Al (Chemically Recycled PET)] Chemically recycled BHET was charged into a reaction vessel equipped with a stirrer, and an aluminum-containing ethylene glycol solution and a phosphorus-containing ethylene glycol solution were added so that the amount of Al element was 21 ppm and the amount of P element was 45 ppm relative to the amount of the produced PET, and polyester resin CRA-1Al was produced in the same manner as polyester resin AlA-1.

[0383] [Polyester Resin CR-0Al (Chemical Recycled PET)] Polyester resin CR-0Al was produced in the same manner as CRA-1Al, except that EMIM-TFSI was not added.

[0384] [Polyester Resin BIA-1Sb (Bio-PET)] Polyester Resin BIA-1Sb was produced in the same manner as for Polyester Resin SbA-1, except that biomass-derived ethylene glycol was used instead of ethylene glycol.

[0385] [Polyester Resin BI-0Al (Bio-PET)] Esterification was carried out in the same manner as for Polyester Resin TiA-1, except that biomass-derived ethylene glycol was used instead of ethylene glycol. Thereafter, the pressure inside the esterification reactor was returned to normal pressure, and an aluminum-containing ethylene glycol solution and a phosphorus-containing ethylene glycol solution were added to the resulting PET so that the Al element amount was 21 ppm and the P element amount was 45 ppm. After the temperature was raised to 260°C over 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reactor, where it was gradually heated from 260°C to 280°C under reduced pressure, and then subjected to a polycondensation reaction at 285°C. After completion of the polycondensation reaction, the mixture was pelletized to obtain Polyester Resin BI-0Al.

[0386] [Polyester Resin BIA-1Al] Polyester Resin BIA-1Al was obtained in the same manner as for Polyester Resin BI-0, except that EMIM-TFSI was added in an amount of 3 ppm based on the produced PET.

[0387] [Polyester Resin PEN] A reaction vessel was charged with 100 parts by mass of ethylene glycol and 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate, and antimony acetate was added thereto so that the Sb atom concentration was 120 ppm relative to the PEN produced. Furthermore, 0.33 mol % of triethylamine relative to the dimethyl 2,6-naphthalenedicarboxylate and 150 ppm of trimethyl phosphate were added. The mixture was then heated to a temperature of 0.34 MPa and subjected to a pressurized esterification reaction at 245°C and a gauge pressure of 2.45 MPa. The temperature was then gradually increased to 285°C while reducing the pressure to 133 Pa, and a polycondensation reaction was then carried out at 285°C. Immediately prior to the end of the reaction, EMIM-TFSI was added to a concentration of 5 ppm. After stirring for 5 minutes, the reaction was terminated and the mixture was pelletized.

[0388] [Polyester Resin MR (Material Recycled PET)] Recycled PET beverage bottles were washed, crushed, and then pelletized. The isophthalic acid content was 1.5 mol% (relative to the total acid components), and the diethylene glycol content was 1.8 mol% (relative to the total acid components). The Sb content was 175 ppm, and the Ge content was 2.0 ppm. The IV was 0.64.

[0389] [Polyester Resin MB-1Sb] Polyester Resin MB-1Sb was produced in the same manner as Polyester Resin SbA-1, except that the amount of EMIM-TFSI was 80 ppm based on the produced PET.

[0390] [Polyester Resin MB-1BI] Polyester Resin MB-1BI was produced in the same manner as Polyester Resin BI-0, except that EMIM-TFSI was added in an amount of 80 ppm based on the produced PET.

[0391] [Polyester Resin MB-1CR] Polyester resin MB-1CR was produced in the same manner as polyester resin CRA-1Al, except that EMIM-TFSI was added in an amount of 80 ppm based on the produced PET.

[0392] [Polyester Resin MB-2Si1] Dried polyester resin Sb-0 and silica particles with an average particle size of 2.5 μm were charged into a twin-screw extruder and kneaded at 285°C to produce pellets of polyester resin MB-2Si1 containing 6000 ppm of silica particles.

[0393] [Polyester Resin MB-2Ca] The same procedure as for Polyester Resin MB-2Si1 was carried out except that calcium carbonate particles having an average particle size of 0.6 μm were used and the content was changed to 30,000 ppm.

[0394] [Polyester Resin MB-2Si2] Polyester Resin MB-2Si2 was prepared in the same manner as Polyester Resin MB-2Si1, except that porous colloidal silica having an average particle size of 0.06 μm was used and the content was changed to 10,000 ppm.

[0395] [Polyester Resin MB-2St] Polyester Resin MB-2St was prepared in the same manner as Polyester Resin MB-2Si1, except that porous colloidal silica having an average particle size of 0.2 μm and crosslinked polystyrene particles having an average particle size of 0.30 μm were used at contents of 20,000 ppm and 15,000 ppm, respectively.

[0396] [Polyester resin composition MB-1Sia] Pellets of polyester resin composition MB-1Sia were produced in the same manner as MB-2Si1, except that instead of polyester resin Sb-0, polyester resin Sb-0 and polyester resin composition SbA-2 were dry blended in a mass ratio of 9 / 1.

[0397] [Polyester Resin Composition MB-1Sib] The same procedure as in the production of MB-2Si1 was carried out, except that EMIM-TFSI was simultaneously fed from a separate feed port by an automatic feeder so that the concentration of EMIM-TFSI was 80 ppm relative to the polyester resin.

[0398] [Polyester Resin MB-3] 10 parts by mass of dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one) and 90 parts by mass of polyester resin SbA-1 were mixed, and pellets of polyester resin MB-3 containing the ultraviolet absorber were obtained using a kneading extruder.

[0399] [Polyester Resin Composition MB-1UV] The same procedure as for polyester resin MB-3 was carried out, except that polyester resin MB-1Sb was used instead of polyester resin SbA-1.

[0400] In the above preparation, all pellets were approximately 2.5 mm x 3.0 mm x 3.6 mm as measured by vernier calipers.

[0401] The properties of the obtained resin are shown in Table 1. The abbreviations for the anions and cations that make up the ionic compounds in Table 1 have the following meanings: (Anions) AA: acetic acid DCA: dicyanamide DMP: dimethyl phosphate FSI: bis(fluorosulfonyl)imide TFSI: bis(trifluoromethanesulfonyl)imide OA: oleic acid (Cations) AMIM: 1-allyl-3-methylimidazolium EMIM: 1-ethyl-3-methylimidazolium MEMP: 1-(2-methoxyethyl)-1-methylpyrrolidinium MMIM: 1,3-dimethylimidazolium

[0402]

[0403]

[0404]

[0405]

[0406] [Polymerization of Copolymerized Polyester Resin] A reaction vessel was charged with 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate, and a transesterification reaction was carried out over 4 hours at a temperature of 160° C. to 220° C. The temperature was then raised to 255° C., and the reaction system was gradually reduced in pressure, and then the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin.

[0407] [Production of Polyester Water Dispersion] 30 parts by mass of copolymerized polyester resin and 15 parts by mass of ethylene glycol-n-butyl ether were placed in a reaction vessel, heated to 110°C, and stirred to dissolve the resin. After the resin was completely dissolved, water was gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to produce a polyester water dispersion (CoPES-1).

[0408] Similarly, aqueous dispersions of copolymerized polyester resins having the copolymerization compositions shown in Table 2 were obtained. Sebacic acid was added after the end of the transesterification reaction and before the temperature was raised. The solid content was adjusted by the amount of water added.

[0409]

[0410] [Production of Polyurethane Water Dispersion] (PU-1) 43.75 parts by mass of 4,4-dicyclohexylmethane diisocyanate (HMDI), 12.85 parts by mass of dimethylol butanoic acid (DMBA), 153.41 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added to a reaction vessel, and the mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere. It was confirmed that the reaction solution had reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and then 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. Thereafter, the acetone and a portion of the water were removed under reduced pressure to prepare a water-soluble polyurethane resin solution (PU-1).

[0411] (PU-2) A water-soluble polyurethane resin solution (PU-2) was prepared in the same manner as in PU-1, except that the isocyanate was changed to 4,4'-diphenylmethane diisocyanate (MDI).

[0412] (PU-3) A water-soluble polyurethane resin solution (PU-3) was prepared in the same manner as in the polymerization of A1, except that 38.41 parts by mass of isophorone diisocyanate (IPDI), 6.95 parts by mass of dimethylolpropanoic acid (DMPA), and 158.99 parts by mass of polyhexamethylene carbonate diol were used.

[0413] (PU-4) Polyether prepolymer type HUX350 (manufactured by ADEKA, solid content 30%) was used.

[0414] PC: Polyhexamethylene carbonate HMDI: 4,4'-dicyclohexylmethane diisocyanate MDI: 4,4'-diphenylmethane diisocyanate DMBA: Dimethylolbutanoic acid DMPA: Dimethylolpropanoic acid

[0415] [Production of Isocyanate-Based Crosslinking Agent (Blocked Isocyanate)] (BI-1) A reaction vessel was charged with 100 parts by mass of a polyisocyanate compound having an isocyanurate structure (Duranate TPA, manufactured by Asahi Kasei Chemicals Corporation), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (number average molecular weight 750), and the mixture was maintained at 70°C for 4 hours under a nitrogen atmosphere. The reaction solution temperature was then lowered to 50°C, and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of the isocyanate group had disappeared, yielding a blocked polyisocyanate aqueous dispersion (BI-1). The solid content was adjusted by adding a diethylene glycol dimethyl ether / water (1 / 5 mass ratio) mixed solvent.

[0416] (BI-2) To 66.04 parts by mass of a polyisocyanate compound having an isocyanurate structure and 17.50 parts by mass of N-methylpyrrolidone, 25.19 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120°C, boiling point: 218°C) were added dropwise, and the mixture was maintained at 70°C for 1 hour under a nitrogen atmosphere. Thereafter, 5.27 parts by mass of dimethylolpropanoic acid was added dropwise. The infrared spectrum of the reaction solution was measured, and after it was confirmed that the absorption of the isocyanate group had disappeared, 5.59 parts by mass of N,N-dimethylethanolamine and water were added to obtain a blocked polyisocyanate aqueous dispersion (BI-2). The solid content was adjusted by the amount of water added.

[0417] (BI-3) A blocked polyisocyanate aqueous dispersion (BI-3) was obtained in the same manner as in BI-2, except that the blocking agent was changed to diethyl malonate.

[0418] (BI-4) A reaction vessel was conditioned under a nitrogen atmosphere, and 600 parts by mass of HMDI and 30 parts by mass of a trihydric alcohol polycaprolactone-based polyester polyol (manufactured by Daicel Chemical Industries, Ltd., PLACCEL 303, molecular weight 300) were charged. The temperature inside the reactor was maintained at 90°C for 1 hour with stirring to carry out a urethanization reaction. Thereafter, the temperature inside the reactor was maintained at 60°C, and an isocyanuration catalyst, tetramethylammonium caprylate, was added. When the yield reached 48%, phosphoric acid was added to terminate the reaction, yielding a polyisocyanate composition. Next, 100 parts by mass of the polyisocyanate composition, 19 parts by mass of methoxypolyethylene glycol having a molecular weight of 400 (manufactured by NOF Corporation, UNIOX M400) (reacts with 10% of all isocyanate groups in the polyisocyanate), and 37 parts of propylene glycol monomethyl ether acetate were charged, and the mixture was maintained at 80°C for 7 hours. Thereafter, the temperature of the reaction liquid was maintained at 50° C., and 38 parts by mass of methyl ethyl ketoxime was added dropwise. Measurement of the infrared spectrum of the reaction liquid showed that the isocyanate groups had disappeared, and an aqueous blocked polyisocyanate resin (BI-4) with a solid content concentration of 80% by mass was obtained.

[0419]

[0420] [Production of Oxazoline-Based Crosslinking Agent] A reaction vessel was charged with a mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium, and 4 parts by mass of a polymerization initiator (2,2'-azobis(2-amidinopropane) dihydrochloride). Meanwhile, a dropping funnel was charged with a mixture of 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, 32 parts by mass of methoxypolyethylene glycol acrylate (average number of moles of ethylene glycol added: 9 moles, manufactured by Shin-Nakamura Chemical Co., Ltd.), and 32 parts by mass of methyl methacrylate, and the mixture was added dropwise at 70°C over 1 hour under a nitrogen atmosphere. After completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin (OXA-1) having an oxazoline group with a solids concentration of 40% by mass.

[0421] [Polymerization of Carbodiimide-Based Crosslinking Agent] A reaction vessel was charged with 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400), and the mixture was stirred at 120°C for 1 hour. 26 parts by mass of 4,4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphorene-1-oxide (2% by mass relative to the total isocyanate) as a carbodiimidization catalyst were then added, and the mixture was stirred for an additional 5 hours at 185°C under a nitrogen stream. The infrared spectrum of the reaction solution was measured at a wavelength of 2200 to 2300 cm. －１ It was confirmed that the absorption of 1000 ppm had disappeared. The mixture was allowed to cool to 60° C., and 567 parts by mass of ion-exchanged water was added to obtain a carbodiimide water-soluble resin (CDI-1) with a solid content of 40% by mass.

[0422] [Epoxy-based crosslinking agent] Denacol (registered trademark) EX-521 (solid content concentration 100%) manufactured by Nagase ChemteX Corporation was used (EPX-1).

[0423] [Melamine-based crosslinking agent] Beckamin (registered trademark) M-3 (solid content concentration 60%) manufactured by DIC Corporation was used (MEL-1).

[0424] [Zirconia / titania mixed particles] A dispersion of zirconia particles (average particle size measured by dynamic light scattering: 19 nm) and a dispersion of titania particles (average particle size measured by dynamic light scattering: 35 nm) were produced according to the method described in the examples of JP 2017-95734 A. The resulting dispersions were mixed with zirconia particles / titania particles (75 / 25 mass ratio), and the concentration was adjusted with water to obtain a zirconia / titania mixed particle dispersion (Pw-1) with a solids concentration of 13 mass%.

[0425] [Tin oxide fine particles] Ceramace S-8 (solid content concentration 8% by mass) manufactured by Taki Chemical Industry Co., Ltd. was used (Pw-2).

[0426] [Silica Particles] PwA was a silica sol having an average particle size of 40 nm (solid content concentration 40% by mass), PwB was a silica sol having an average particle size of 450 nm (solid content concentration 40% by mass), and PwC was a silica sol having an average particle size of 100 nm (solid content concentration 40% by mass).

[0427] [Production of Coating Solution] The raw materials were mixed in the proportions shown in Table 4, and the coating solution was filtered through a 10 μm filter (nominal filtration accuracy: 95% cutoff of 10 μm particles). Although not shown in Table 4, a catalyst matching the type of crosslinking agent was added immediately before coating.

[0428]

[0429]

[0430]

[0431] [Example 1] A polyester resin was dried under reduced pressure (33 Pa) at 135°C for 6 hours, then fed to a single-screw extruder and melted at 285°C. The molten polymer was filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 95% cut of 20 μm particles), extruded into a sheet from a T-die, and then wound around a casting drum with a surface temperature of 30°C using an electrostatic casting method, followed by cooling and solidification to produce an unstretched film.

[0432] Casting was carried out at a speed of 60 m / min by providing a tungsten wire electrode between the nozzle of the extruder and the cooling drum and applying a voltage of 5 to 15 kV between the electrode and the casting drum.

[0433] Subsequently, this unstretched film was stretched in the machine direction by 3.3 times at 95° C. using rolls with different peripheral speeds.

[0434] The resin thin film layer coating solution (CLA-1) was applied to both sides of this uniaxially stretched PET film in a coating amount of 0.12 g / m after final stretching and drying. ２ After coating the coating solution so that the coating was uniform, the coating solution was introduced into a dryer and dried at 80° C. for 20 seconds.

[0435] The uniaxially stretched film on which the coating layer was formed was introduced into a tenter stretching machine, and while the edges of the film were held with clips, it was introduced into a hot air zone at a temperature of 125° C. and stretched 3.5 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 225° C. for 30 seconds, and then subjected to a 3% relaxation treatment in the TD direction. After cooling, both edges of the film were cut and then wound up to obtain a biaxially stretched PET film with a film thickness of 50 μm.

[0436] [Examples 2 to 32 and Comparative Examples 1 to 10] The resins shown in Table 1 were charged into an extruder in the same manner as in Example 1 to obtain biaxially stretched polyester films. In Example 10, the casting speed was 30 m / min. In Examples 18 to 32 and Comparative Examples 8 to 9, which used two or more resins, the resins were dry-blended in advance and then dried. In the case of PEN (Example 15), the melting temperature was 290°C, the roll temperature during longitudinal stretching was 110°C, and the tenter temperature was 135°C. For the easy-adhesion layers of Examples 24, 25, 31, and 32, CLA-1 without added particles was used.

[0437] In all Examples except Example 10, the casting speed was 50 m / min or more, enabling stable film formation at high speed. Furthermore, there were no sparks. Example 10 corresponds to a case where the amount of metal, such as a catalyst, was reduced for insulation applications, etc., but the film was able to effectively reduce melt resistivity and was less susceptible to short circuits. On the other hand, Comparative Examples 1 and 5 had good electrostatic adhesion and no sparks, but the amount of foreign matter in the film was high. Comparative Examples 2 and 7 had no problems with foreign matter, but had poor electrostatic adhesion. Comparative Example 6 had slightly poor electrostatic adhesion and a large amount of foreign matter. Comparative Examples 3 and 4 generated sparks, and film formation was unstable.

[0438] [Example 33] The resins for the surface layer and the intermediate layer were dry-blended, dried, and then charged into extruders for the surface layer and the intermediate layer, filtered with the same filter material, and then introduced into a two-kind, three-layer T-die, and a biaxially stretched film was obtained in the same manner. For the easy-adhesion layer, CLA-1 was used without adding particles. [Example 34] The resins for the surface layer and the intermediate layer were dry-blended, dried, and then charged into extruders for the surface layer and the intermediate layer, filtered with the same filter material, and then introduced into a two-kind, three-layer T-die, and an unstretched sheet was obtained. The resin thin film layer coating solution (CLA-1) was applied to both sides of the obtained unstretched sheet in a coating amount of 0.12 g / m after final stretching and drying. ２ The film was stretched 4.0 times in the width direction using a tenter at 125° C. The heat setting temperature was 190° C., and the film was subjected to a relaxation treatment of 2% in the TD direction. The thickness of the obtained film was 80 μm.

[0439] [Example 35] The unstretched sheet having an easy-adhesion layer obtained in Example 34 was stretched 2.2 times in the width direction and 6.5 times in the machine direction using a simultaneous biaxial stretching machine, and then heat-set at 225°C. The thickness of the obtained film was 40 µm.

[0440] The resins used, the film configuration, and the film properties are shown in Tables 7 to 9. The content of ionic compounds in the film obtained in Example 1 was measured and found to be 2.2 ppm by mass.

[0441]

[0442]

[0443] *1: CLA-1 without added particles was used.

[0444] *1: CLA-1 without added particles was used.

[0445] *1: CLA-1 without added particles was used.

[0446] The physical properties of the obtained film are shown in Tables 10 and 11.

[0447] (*1) The films of Examples 1 to 16 and 18 to 21 had almost the same properties, so the properties of the film of Example 1 are shown as a representative. (*2) Values ​​for the particle-containing layer

[0448] (*3) The films of Examples 26 to 30 had almost the same properties, so the properties of the film of Example 26 are shown as a representative example.

[0449]

[0450] Examples 1-2 to 1-17 The coating liquid was changed to that shown in Table 12, and the same procedure as in Example 1 was carried out.

[0451] Examples 34-2 to 34-8 The coating liquid was changed to that shown in Table 13, and the same procedure as in Example 34 was carried out.

[0452] The coating solution, adhesion evaluation, and interference fringe evaluation are shown in Tables 12 and 13.

[0453]

[0454]

Claims

1. A polyester film having a polyester base film and a thin resin layer on at least one side thereof, the polyester base film containing 0.01 ppm by mass or more and 950 ppm by mass or less of an ionic compound having an anion-cation dissociation energy Q (kJ / mol) of 850 or less.

2. The melt resistivity of the polyester base film is 20 x 10 ８ The polyester film according to claim 1, having a modulus of Ω·cm or less.

3. The melt resistivity of the polyester base film is 0.001 x 10 ８ The polyester film according to claim 2, having a modulus of Ω·cm or more.

4. The polyester film according to claim 1, wherein the thickness of the resin thin layer is from 0.001 μm to 1 μm.

5. The polyester film according to claim 1, wherein the resin thin film layer contains at least one resin selected from the group consisting of polyester resin, acrylic resin, and polyurethane resin.

6. The polyester film according to claim 1, wherein the resin in the resin thin film layer is crosslinked.

7. The polyester film according to claim 1, wherein the resin thin film layer contains particles.

8. The polyester film according to claim 1, wherein the surface roughness (Ra) of the resin thin film layer is 0.5 to 100 nm.

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