Polyester film

Abstract

To provide a polyester film which has little influence on basic characteristics such as transparency, surface properties, mechanical strength, and dimensional stability, can reduce the amount of carbon dioxide generated during incineration, and is excellent in appearance.SOLUTION: A polyester film having a layer A containing a polyester resin (X) and a flame retardant (Y), wherein a phosphorus element content in the polyester film is 50 to 10000 ppm by mass, and the polyester film satisfies at least one of the following requirements (1) and (2): (1) The L * value of a film having a total thickness equivalent to 500 μm is 95.5 or more. (2) The spectral reflectance of a film having a total thickness of 500 μm is 88.5% or more at 500nm wavelengths.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester film. [Background technology]

[0002] Polyester films have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and also have excellent cost performance, so they are used in a variety of applications.

[0003] However, while waste plastics such as polyester film have traditionally been disposed of by landfilling or dumping in the ocean, it is becoming increasingly difficult to secure landfill sites, and ocean dumping is becoming an environmental problem because plastics do not decompose. Thermal recycling is also practiced, in which waste plastic is incinerated and the heat is reused for power generation or heating, but this poses the problem of carbon dioxide emissions, which contribute to global warming.

[0004] Therefore, technologies have been developed to reduce the generation of carbon dioxide during incineration. For example, Patent Document 1 discloses a carbon dioxide emission reducing resin composition having a high carbon dioxide absorption effect, in which a mixture of a carbon dioxide absorbent and a dispersant is subjected to a dispersion treatment and then added to a resin, thereby enabling the carbon dioxide absorbent, which has poor compatibility with the resin, to be dispersed in the resin without agglomeration.

[0005] Furthermore, Patent Document 2 discloses a technique for suppressing the generation of carbon dioxide when incinerated in a resin film for a card, a laminate for a card that is thick because it has a plurality of resin films, and the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-14157 [Patent Document 2] Japanese Patent Application Publication No. 2019-214633 Summary of the Invention [Problem to be solved by the invention]

[0007] However, since it is undesirable that the basic properties of polyester film are deteriorated by including a substance that can reduce the amount of carbon dioxide generated during incineration, there is a demand for the substance to have minimal impact on the basic properties, and further improvements are required.

[0008] Furthermore, the inventors' investigations revealed that the polyester film tends to have a lower brightness due to the use of substances that can reduce the amount of carbon dioxide generated, making it appear black, and that further improvement is needed from the standpoint of design (appearance), etc.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned circumstances, and the problem to be solved is to provide a polyester film that has little effect on basic properties such as transparency, surface properties, mechanical strength, and dimensional stability, can reduce the amount of carbon dioxide generated when incinerated, and further has excellent design properties (appearance). [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by incorporating a predetermined amount of a flame retardant into a polyester film. Specifically, the present inventors have found that the above-mentioned problems can be solved by having the following configuration. The present invention has the following aspects.

[0011] [1] A polyester film having a layer A containing a polyester resin (X) and a flame retardant (Y), the phosphorus content in the polyester film is 50 to 10,000 ppm by mass, A polyester film that satisfies at least one of the following requirements (1) and (2): (1) L when the total thickness is equivalent to 500 μm *Value is 95.5 or higher. (2) When made into a film with a total thickness equivalent to 500 μm, the spectral reflectance at a wavelength of 500 nm is 88.5% or more. [2] The polyester film according to [1], wherein the amount of carbon dioxide generated is 2400 mg / g or less according to the <Method for measuring and calculating the amount of carbon dioxide generated> shown below. <Method for measuring and calculating carbon dioxide emissions> Carbon dioxide generated from the polyester film is measured under the following conditions using a differential thermal balance-mass spectrometer, and the amount of carbon dioxide generated is calculated from the ion chromatogram peak area of ​​m / z=44 and a calibration curve prepared from a standard sample. ·Heating conditions: temperature 25℃~1000℃, speed 10℃ / min Atmosphere: Simulated air (He + O2, He: 80 vol%, O2: 20 vol%) Gas flow rate: 300mL / min Container: Pt cup ·MS settings: EMS 1mA, SEM 1200V, m / z≒10~410(EI) Preparation: Calcium oxalate monohydrate Calibration curve: Create a two-point calibration using the ion chromatogram peak area (m / z=44) of the standard versus the theoretical amount of carbon dioxide generated. [3] The polyester film according to [1] or [2], wherein the content of the flame retardant (Y) is 0.005 to 1 part by mass, as a phosphorus content in the polyester film, per 100 parts by mass of the polyester resin (X). [4] The polyester film according to any one of [1] to [3], which has a carbon dioxide emission reduction rate of 1% or more based on the following <Method for measuring and calculating carbon dioxide emission amount> and <Method for calculating carbon dioxide emission reduction rate>. <Method for measuring and calculating carbon dioxide emissions> Carbon dioxide generated from the polyester film is measured under the following conditions using a differential thermal balance-mass spectrometer, and the amount of carbon dioxide generated is calculated from the ion chromatogram peak area of ​​m / z=44 and a calibration curve prepared from a standard sample. ·Heating conditions: temperature 25℃~1000℃, speed 10℃ / min Atmosphere: Simulated air (He + O2, He: 80 vol%, O2: 20 vol%) Gas flow rate: 300mL / min Container: Pt cup ·MS settings: EMS 1mA, SEM 1200V, m / z≒10~410(EI) Preparation: Calcium oxalate monohydrate Calibration curve: Create a two-point calibration using the ion chromatogram peak area (m / z=44) of the standard versus the theoretical amount of carbon dioxide generated. <Calculation method for carbon dioxide emission reduction rate> The reduction rate of carbon dioxide generation (%) is calculated by the following formula using the amount of carbon dioxide generation (p1) generated from the polyester film described in [1] to [3], calculated in the above <Method for measuring and calculating the amount of carbon dioxide generation>, and the amount of carbon dioxide generation (p0) generated from a polyester film having the same composition as the polyester film but not containing the flame retardant (Y). Carbon dioxide emission reduction rate (%) = {1-(p1÷p0)} x 100 [5] The polyester film according to any one of [1] to [4], wherein the flame retardant (Y) is a phosphorus compound having an aromatic ring. [6] The polyester film according to any one of [1] to [4], wherein the flame retardant (Y) is a compound having a P═O bond. [7] The polyester film according to any one of [1] to [4], wherein the flame retardant (Y) contains a compound having a structural unit of the following formula (1): [ka] [In formula (1), n ​​is an integer, A is a divalent organic group, Q1 and Q2 are divalent aromatic groups, and Z is a group having an ester-forming functional group. [8] The polyester film according to any one of [1] to [4], wherein the flame retardant (Y) contains a compound having a structural unit of the following formula (9-1): [ka] [In formula (9-1), n ​​is an integer of 2 to 40.] [9] The polyester film according to any one of [1] to [8], which has a flame retardancy of VTM-1 or less at a thickness of 38 μm in a UL94 vertical flame test in accordance with ASTM D4804.

[10] The polyester film according to any one of [1] to [9], wherein the amount of gas generated based on peaks detected in a retention time range of 6 to 20 minutes by gas chromatography mass spectrometry (GC-MS) is less than 9 μg / g.

[11] The polyester film according to any one of [1] to

[10] , wherein the amount of gas generated based on a peak derived from the flame retardant (Y) detected in a retention time range of 28 to 31 minutes by gas chromatography mass spectrometry (GC-MS) is less than 2 μg / g.

[12] The polyester film according to any one of [1] to

[11] , wherein the polyester resin (X) contains polyethylene terephthalate.

[13] The polyester film according to any one of [1] to

[12] , which is stretched in at least one direction.

[14] The polyester film according to any one of [1] to

[13] , which has a laminated structure of at least three layers including a surface layer, an intermediate layer, and another surface layer.

[15]

[14] The polyester film according to

[14] , wherein both of the surface layers are the A layer.

[16]

[14] The polyester film according to

[14] , wherein at least one of the surface layers is the layer A, and the content of the flame retardant (Y) in the one surface layer is 50 to 13,000 ppm by mass in terms of the phosphorus content in the one surface layer.

[17]

[14] The polyester film according to

[14] , wherein at least one of the surface layers is the layer A, and the content of the flame retardant (Y) in the one surface layer is 0.005 to 1.3 parts by mass, as a phosphorus content in the one surface layer, per 100 parts by mass of the polyester resin (X).

[18] A method for reducing the amount of carbon dioxide generated during incineration, using the polyester film according to any one of [1] to

[17] . [Effects of the Invention]

[0012] According to the present invention, a polyester film is provided which has little effect on basic properties such as transparency, surface properties, mechanical strength, and dimensional stability, can reduce the amount of carbon dioxide generated during incineration, and has excellent design properties (appearance). DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, an example of an embodiment of the present invention will be described, but the present invention is not limited to the embodiment described below.

[0014] <<<Polyester film>>> A polyester film according to one embodiment of the present invention (hereinafter also referred to as "the film") has a layer A containing a polyester resin (X) and a flame retardant (Y), and the phosphorus content in the film is preferably 50 to 10,000 ppm by mass. Furthermore, the present film preferably satisfies at least one of the following requirements (1) and (2), and more preferably satisfies both of the following requirements (1) and (2). (1) L when the total thickness is equivalent to 500 μm * Value is 95.5 or higher. (2) When made into a film with a total thickness equivalent to 500 μm, the spectral reflectance at a wavelength of 500 nm is 88.5% or more.

[0015] The present film may have a single-layer structure consisting of only Layer A, or a multilayer structure having at least Layer A (i.e., a laminated film). When the present film has a multilayer structure, it may have a two-layer structure, a three-layer structure, or may have four or more layers without departing from the gist of the present invention, and the number of layers is not particularly limited. However, from the viewpoint of responding to thinning and reducing the number of manufacturing steps, a single-layer structure or a multilayer structure of three or less layers is preferred. When there are a plurality of layers A, the components constituting the layers A and the contents thereof may be the same or different from each other.

[0016] The thickness of the present film is not limited to, but is, for example, 100 μm or less, preferably 5 to 90 μm, more preferably 10 to 80 μm, and even more preferably 15 to 70 μm, and may also be 20 to 60 μm, 25 to 50 μm, etc. The thickness of this film is measured at five random locations on the surface with a 1 / 1000 mm dial gauge, and the average of the measurements is taken as the thickness.

[0017] When the present film has a multilayer structure of two or more layers, the thickness of the film constituting the surface layer is not limited to the following, but is, for example, 1 to 25 μm, preferably 1.4 to 20 μm, more preferably 1.8 to 15 μm, even more preferably 2 to 10 μm, and even more preferably 3 to 7 μm. Specifically, but not limited to, for example, in the case of the present film consisting of at least three layers of "surface layer / one or more intermediate layers / surface layer," the thickness of each surface layer is, for example, 1 to 25 μm, preferably 1.4 to 20 μm, more preferably 1.8 to 15 μm, even more preferably 2 to 10 μm, and even more preferably 3 to 7 μm. The thickness of the intermediate layer is, for example, 3 to 80 μm, preferably 4 to 70 μm, more preferably 5 to 60 μm, and even more preferably 10 to 50 μm. In addition, in the thickness cross-sectional direction of the present film, the surface layer preferably occupies 1 to 25% of the thickness from the film surface, more preferably 2 to 25%, even more preferably 3 to 23%, and even more preferably 4 to 22% of the thickness.

[0018] Further, this film may be an unstretched film (sheet) or a stretched film. Among them, it is preferably a stretched film stretched in one axial direction or biaxially and stretched in at least one direction. Among them, a biaxially stretched film is more preferable in terms of excellent balance of mechanical properties and flatness.

[0019] <> As described above, this film preferably has an A layer containing a polyester resin (X) and a flame retardant (Y).

[0020] <Polyester resin (X)> The A layer preferably contains a polyester resin (X) as the main component resin. The main component resin means the resin with the largest mass ratio among the resins constituting the A layer of this film, and is 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more of the resins constituting the A layer of this film, and may be 100% by mass.

[0021] Also, the content of the polyester resin (X) contained in the A layer is not limited to the following, but for example, 80% by mass or more is preferable, more preferably 85% by mass or more, further preferably 90% by mass or more, particularly preferably 92% by mass or more, and may also be 94% by mass or more, 96% by mass or more, 98 - 99% by mass, etc.

[0022] The polyester resin (X) may be either an aliphatic polyester resin or an aromatic polyester resin. The polyester resin (X) may be used singly or in combination of two or more types, or may be used in combination of an aliphatic polyester resin and an aromatic polyester resin. Among these, it is preferable to contain an aromatic polyester resin, and more preferable to contain only an aromatic polyester resin. That is, it is more preferable that Layer A contains an aromatic polyester resin as the main component resin. The aromatic polyester resin refers to a polyester resin having an aromatic group in at least one of the polycarboxylic acid unit and the polyhydric alcohol unit constituting the polyester resin (X).

[0023] The aromatic polyester resin may be a homopolyester or a copolymer polyester.

[0024] The homopolyester is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of aliphatic glycols include ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Representative homopolyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene-2,6-naphthalate (PEN). In terms of versatility, PET is more preferred for this film.

[0025] On the other hand, the dicarboxylic acid component of the copolymer polyester may be one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, etc. The glycol component may be one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol, etc. The copolymer polyester contains an aromatic compound in the dicarboxylic acid component and / or the glycol component. When the aromatic polyester resin is a copolymer polyester, it is preferably a copolymer containing 30 mol% or less of a third component, more preferably 60 mol% or more, preferably 80 mol% or more of ethylene terephthalate units or ethylene-2,6-naphthalate units, and from the viewpoint of versatility, it is even more preferably 60 mol% or more, preferably 80 mol% or more of ethylene terephthalate units.

[0026] The aromatic polyester resin may be a single type or may contain multiple different types of polyester resins. The aromatic polyester resin preferably contains PET, more preferably contains only PET. That is, the polyester resin (X) of the present film preferably contains PET, more preferably contains only PET. The PET is preferably a homopolyester.

[0027] The polymerization catalyst for the polyester resin (X) is not particularly limited, and a conventionally known compound can be used. Examples of the polymerization catalyst include titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds. Among these, at least one of titanium compounds and antimony compounds is preferred.

[0028] The intrinsic viscosity of the polyester resin (X) is not particularly limited, but from the viewpoints of film-forming properties and productivity, it is preferably 0.45 to 1 dL / g, more preferably 0.5 to 0.9 dL / g, even more preferably 0.55 to 0.8 dL / g, and particularly preferably 0.6 to 0.75 dL / g. When two or more polyesters with different intrinsic viscosities are used, the intrinsic viscosity refers to the intrinsic viscosity of the mixed polyester. The intrinsic viscosity can be measured by a conventional method. For example, 1 g of polyester from which components incompatible with the polyester have been removed is precisely weighed, dissolved in 100 mL of a 50 / 50 (mass ratio) phenol / tetrachloroethane mixed solvent, and the viscosity can be measured at 30°C using a viscosity measuring device.

[0029] In order to suppress the amount of precipitation of oligomer components, the film may be produced using a polyester resin (X) having a low content of oligomer components as a raw material. As a method for producing a polyester resin having a low content of oligomer components, various known methods can be used, such as a method of solid-state polymerization after production of the polyester resin.

[0030] The polyester resin (X) may contain particles mainly for the purposes of imparting lubricity and preventing scratches during each process. The type of particles is not particularly limited as long as they are capable of imparting lubricity, and examples thereof include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the production process of the polyester resin (X) can also be used.

[0031] The shape of the particles is not particularly limited, and may be, for example, spherical, blocky, rod-like, flat, or the like. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc. These particles may be used alone or in combination of two or more types as required.

[0032] The average particle size of the particles is usually preferably 5 μm or less, more preferably 0.01 to 3 μm. By having the average particle size within this range, the film is given an appropriate surface roughness, ensuring good slip properties and smoothness. The average particle size of the particles may also be 0.1 to 2.8 μm, 0.5 to 2.6 μm, 1 to 2.5 μm, etc.

[0033] When the particles are powder, the average particle size can be determined by measuring the powder using a centrifugal sedimentation particle size distribution analyzer and determining the particle size at an integrated volume fraction of 50% (d50) in the equivalent spherical distribution. The average particle size of particles in a film, layer, or resin can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope (SEM) and averaging the measured diameters. In this case, for non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0034] When particles are contained, the particle content is preferably less than 5% by mass, more preferably 0.0003 to 3% by mass, and even more preferably 0.001 to 2% by mass, based on the total mass of the layer in which the particles are contained. By keeping the particle content within this range, the transparency and slipperiness of the film become good.

[0035] When particles are contained in Layer A, the particle content is preferably 0.01 to 0.25 mass %, more preferably 0.02 to 0.2 mass %, and even more preferably 0.05 to 0.15 mass %, relative to the total mass of Layer A. When the particle content is in this range, the transparency and slipperiness of the film are good.

[0036] The method for incorporating the particles is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage in the production of the polyester resin (X), but it is preferable to add them after the completion of the esterification or transesterification reaction.

[0037] <Flame retardant (Y)> The flame retardant (Y) preferably contains one or more compounds selected from phosphorus compounds having an aromatic ring and compounds having a P=O bond, from the viewpoints of being highly effective in reducing the amount of carbon dioxide generated during incineration and having little effect on the basic properties of the film.Moreover, the flame retardant (Y) more preferably contains a compound having an aromatic ring and a P=O bond.

[0038] The compound having a P=O bond may be an aromatic phosphate ester having a structure of an ester reaction product between an aromatic compound having a phenolic hydroxyl group and optionally further having other substituents and phosphoric acid. The compound having a P=O bond may be a phosphate monoester, a phosphate diester, or a phosphate triester, as long as the effects of the present invention can be obtained.

[0039] Examples of the aromatic compound having a phenolic hydroxyl group include phenol and naphthol. Examples of the substituent that the aromatic compound may have include a lower alkyl group such as a methyl group. The substituent in the compound having a P=O bond may be singular or plural, and when plural substituents are present, they may be the same or different. The compound having a P=O bond can be obtained, for example, by reacting phosphorus oxychloride with a phenol that may have a substituent, and is also commercially available.

[0040] Examples of the compound having a P=O bond include an aromatic condensed phosphate ester represented by formula (1) having a structure in which two phosphate esters are condensed, and an aromatic phosphate ester represented by formula (2).

[0041] [ka]

[0042] In the formulas (1) and (2), Ar1 is preferably a divalent group represented by the following formula (3) or (4), and Ar2 is preferably independently a monovalent group represented by the following formula (5): In formula (5), R1 independently represents a hydrogen atom or an alkyl group, and when R1 is an alkyl group, it is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms, and even more preferably a methyl group.

[0043] [ka]

[0044] Ar2 in the aromatic condensed phosphate ester represented by formula (1) and the aromatic phosphate ester represented by formula (2) may be the same or different as long as the effects of the present invention are obtained.

[0045] The phenylene group represented by the formula (3) may be any of an o-phenylene group, an m-phenylene group, and a p-phenylene group, as long as the effects of the present invention can be obtained, and may be the same or different in the aromatic condensed phosphate ester.

[0046] The position at which the phenylene group of the divalent group represented by formula (4) is bonded to the phosphorus atom of the phosphate moiety may be ortho, meta, or para to the central hydrocarbon group, as long as the effects of the present invention are obtained.

[0047] The position of the phenylene group represented by formula (5) that bonds to the oxygen atom of the phosphate moiety may be any of the 2nd, 4th, and 5th positions, assuming that the positions of R1 are the 1st and 3rd positions, as long as the effects of the present invention are obtained.

[0048] The aromatic condensed phosphate ester can be obtained, for example, by reacting phosphorus oxychloride with a dihydric phenol compound and phenol, methylphenol, or dimethylphenol, and is also available as a commercial product.

[0049] Preferred specific examples of the aromatic condensed phosphate ester represented by formula (1) include compounds represented by the following formulas (1-1) to (1-3), and preferred specific examples of the aromatic phosphate ester represented by formula (2) include compounds represented by the following formulas (2-1) to (2-3).

[0050] [ka]

[0051] [ka]

[0052] Commercially available aromatic condensed phosphate esters and aromatic phosphate esters include, for example, TPP: triphenyl phosphate, TXP: trixylenyl phosphate, CDP: cresyl phenyl phosphate, TCP: tricresyl phosphate, PX-110: cresyl di-2,6-xylenyl phosphate, CR-733S: resorcinol bis(diphenyl phosphate), CR-741: bisphenol A bisdiphenyl phosphate, PX200: 1,3-phenylene-teslakis(2,6-dimethylphenyl)phosphate, PX201: 1,4-phenylene-tetrakis(2,6-dimethylphenyl)phosphate, and PX202: 4,4′-biphenylene-tetrakis(2,6-dimethylphenyl)phosphate, all manufactured by Daihachi Chemical Industry Co., Ltd.

[0053] Among these, it is preferable that the aromatic phosphate ester contains an aromatic condensed phosphate ester (compound A) represented by the following formula (1-1), from the viewpoint of having a high effect of reducing the amount of carbon dioxide generated during incineration and having little effect on the basic properties of the film.

[0054] [ka]

[0055] During the condensation reaction of the aromatic condensed phosphate ester (compound A) represented by the formula (1-1), an aromatic phosphate ester (compound B) represented by the formula (2-1) may be produced. In such a case, the mass ratio of the aromatic condensed phosphate ester (compound A) to the aromatic phosphate ester (compound B) (compound A:compound B) may be about 80:20 to 99:1, 90:10 to 99:1, or 95:5 to 99:1.

[0056] Examples of the flame retardant (Y) include, in addition to the aromatic condensed phosphate ester represented by the formula (1) and the aromatic phosphate ester represented by the formula (2), condensed phosphite esters, phosphazene compounds, and the like.

[0057] The condensed phosphite ester is preferably a compound represented by the following formula (6).

[0058] [ka]

[0059] In the formula (6), R2 independently represents a group having an aromatic ring, R3 independently represents an organic group, and X represents a divalent organic group.

[0060] In the formula (6), examples of the group having an aromatic ring represented by R2 include an aryl group, or an alkyl or cycloalkyl group substituted with an aryl group. The aryl group, or the alkyl or cycloalkyl group substituted with an aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, a halogen atom, and an aryl halide group. Furthermore, the group may be a combination of these substituents, or a combination of these substituents bonded together via an oxygen atom, a sulfur atom, a nitrogen atom, or the like.

[0061] In the formula (6), examples of the organic group represented by R3 include an alkyl group, a cycloalkyl group, and an aryl group. The alkyl group, the cycloalkyl group, and the aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, a halogen atom, and an aryl halide group. The organic group may also be a group combining these substituents, or a group combining these substituents by bonding them via an oxygen atom, a sulfur atom, a nitrogen atom, or the like.

[0062] In the formula (6), the divalent organic group represented by X refers to a group having a valence of two or more obtained by removing one hydrogen atom from the organic group represented by R. Examples of such groups include alkylene groups, phenylene groups, substituted phenylene groups, and polynuclear phenylene groups derived from bisphenols.

[0063] In the formula (6), one or two R3 and X may together form a ring structure. Examples of such ring structures include a cycloalkyl structure and an aryl structure. The ring structure may also be a spiro ring structure containing a phosphorus atom to which two R3 and X are bonded via an oxygen atom.

[0064] An example of a commercially available condensed phosphite is "Fireguard (registered trademark) FCX-210" manufactured by Teijin Limited.

[0065] The phosphazene compound is an organic compound having a -P=N- bond in the molecule, and preferably includes at least one compound selected from the group consisting of a cyclic phosphazene compound represented by the following formula (7), a chain phosphazene compound represented by the following formula (8), and a crosslinked phosphazene compound obtained by crosslinking at least one phosphazene compound selected from the group consisting of the following formulas (7) and (8) with a crosslinking group.

[0066] [ka]

[0067] In formula (7), a is an integer of 3 to 25, and R4s independently represent an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, an amino group, a hydroxy group, an aryl group, or an alkylaryl group, and it is preferable that at least one of them is an aryl group or an alkylaryl group.

[0068] [ka]

[0069] In formula (8), b is an integer of 3 to 10,000, R5 independently represents an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, an aryloxy group, an amino group, a hydroxy group, an aryl group, or an alkylaryl group, and at least one of them is preferably an aryl group. R6 represents at least one selected from a -N=P(OR5)3 group and a -N=P(O)OR5 group.

[0070] In the formulas (7) and (8), examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, and a dodecyl group. Of these, an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, a pentyl group, or a hexyl group, is preferred, and an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, or a propyl group, is particularly preferred.

[0071] In the formulas (7) and (8), examples of the cycloalkyl group include cycloalkyl groups having 5 to 14 carbon atoms such as cyclopentyl and cyclohexyl groups, and cycloalkyl groups having 5 to 8 carbon atoms are preferred.

[0072] In the formulas (7) and (8), examples of the alkenyl group include alkenyl groups having 2 to 8 carbon atoms, such as a vinyl group and an allyl group. Examples of the cycloalkenyl group include cycloalkenyl groups having 5 to 12 carbon atoms, such as a cyclopentyl group and a cyclohexyl group.

[0073] In the formulas (7) and (8), examples of the alkynyl group include alkynyl groups having 2 to 8 carbon atoms, such as an ethynyl group or a propynyl group, and alkynyl groups having an aryl group as a substituent, such as an ethynylbenzene group.

[0074] In the formulas (7) and (8), examples of the aryl group include aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a tolyl group, a xylyl group, a trimethylphenyl group, and a naphthyl group. Of these, aryl groups having 6 to 10 carbon atoms are preferred, and a phenyl group is particularly preferred.

[0075] In the formulas (7) and (8), examples of the alkylaryl group include aralkyl groups having 6 to 20 carbon atoms, such as a benzyl group, a phenethyl group, and a phenylpropyl group. Of these, an aralkyl group having 7 to 10 carbon atoms is preferred, and a benzyl group is particularly preferred.

[0076] Among these, R4 in the formula (7) and R5 in the formula (8) are preferably an aryl group or an arylalkyl group. By using such an aromatic phosphazene compound, the thermal stability of a composition containing a polyester resin can be effectively improved. From this viewpoint, R4 and R5 are more preferably an aryl group, and particularly preferably a phenyl group.

[0077] Examples of the cyclic and / or chain phosphazene compounds represented by formula (7) and formula (8) include phenoxyphosphazene; (poly)tolyloxyphosphazenes such as o-tolyloxyphosphazene, m-tolyloxyphosphazene, and p-tolyloxyphosphazene; (poly)xylyloxyphosphazenes such as o,m-xylyloxyphosphazene, o,p-xylyloxyphosphazene, and m,p-xylyloxyphosphazene; and o,m,p-trimethylphenyloxyphosphazene. (poly)phenoxytolyloxyphosphazenes such as phenoxy o-tolyloxyphosphazene, phenoxy m-tolyloxyphosphazene, and phenoxy p-tolyloxyphosphazene; (poly)phenoxyxylyloxyphosphazenes such as phenoxy o,m-xylyloxyphosphazene, phenoxy o,p-xylyloxyphosphazene, and phenoxy m,p-xylyloxyphosphazene; and phenoxy o,m,p-trimethylphenyloxyphosphazene. Among these, cyclic and / or chain phenoxyphosphazenes are preferred.

[0078] As the cyclic phosphazene compound represented by formula (7), a cyclic phenoxyphosphazene in which R4 is a phenyl group is particularly preferred. Examples of such cyclic phenoxyphosphazene compounds include compounds such as phenoxycyclotriphosphazene, octaphenoxycyclotetraphosphazene, and decafenoxycyclopentaphosphazene, which are obtained by isolating cyclic chlorophosphazenes such as hexachlorocyclotriphosphazene, octachlorocyclotetraphosphazene, and decachlorocyclopentaphosphazene from a mixture of cyclic and linear chlorophosphazenes obtained by reacting ammonium chloride with phosphorus pentachloride at a temperature of 120 to 130°C, and then substituting the cyclic chlorophosphazenes with phenoxy groups. Furthermore, the cyclic phenoxyphosphazene compound is preferably a compound represented by formula (7) in which a is an integer of 3 to 8, and may also be a mixture of compounds with different a's.

[0079] In formula (7), the average of a is preferably 3 to 5, and more preferably 3 to 4. Among these, a mixture of compounds in which those in which a=3 are 50% by mass or more, those in which a=4 are 10 to 40% by mass, and those in which a=5 or more are 30% by mass or less in total is preferred.

[0080] As the chain phosphazene compound represented by formula (8), a chain phenoxyphosphazene compound in which R5 is a phenyl group is particularly preferred. Examples of such chain phenoxyphosphazene compounds include compounds obtained by ring-opening polymerization of hexachlorocyclotriphosphazene obtained by the above-mentioned method at a temperature of 220 to 250°C, and substituting the resulting linear dichlorophosphazene having a degree of polymerization of 3 to 10,000 with a phenoxy group. In the above-mentioned linear phenoxyphosphazene compound represented by formula (8), b is preferably 3 to 1,000, more preferably 3 to 1000, and even more preferably 3 to 25.

[0081] Examples of the crosslinked phosphazene compound include compounds having a crosslinked structure of a 4,4'-diphenylene group, such as a compound having a crosslinked structure of 4,4'-sulfonyldiphenylene (i.e., a bisphenol S residue), a compound having a crosslinked structure of a 2,2-(4,4'-diphenylene)isopropylidene group, a compound having a crosslinked structure of a 4,4'-oxydiphenylene group, and a compound having a crosslinked structure of a 4,4'-thiodiphenylene group.

[0082] As the bridged phosphazene compound, a bridged phenoxyphosphazene compound obtained by crosslinking a cyclic phenoxyphosphazene compound in which R4 in formula (7) is a phenyl group via the crosslinking group, or a bridged phenoxyphosphazene compound obtained by crosslinking a chain phenoxyphosphazene compound in which R5 in formula (8) is a phenyl group via the crosslinking group, is preferred from the viewpoint of flame retardancy, and a bridged phenoxyphosphazene compound obtained by crosslinking a cyclic phenoxyphosphazene compound via the crosslinking group is more preferred. The content of phenylene groups in the bridged phenoxyphosphazene compound is usually 50 to 99.9%, preferably 70 to 90%, based on the total number of phenyl groups and phenylene groups in the cyclic phosphazene compound represented by formula (7) and / or the chain phenoxyphosphazene compound represented by formula (8). It is particularly preferable that the bridged phenoxyphosphazene compound is a compound having no free hydroxyl groups in its molecule.

[0083] In the present film, the phosphazene compound is preferably at least one selected from the group consisting of a cyclic phenoxyphosphazene compound represented by the formula (7) and a crosslinked phenoxyphosphazene compound obtained by crosslinking the cyclic phenoxyphosphazene compound represented by the formula (7) via a crosslinking group, from the viewpoint of flame retardancy and mechanical properties of the resin composition containing the polyester resin. An example of a commercially available phosphazene compound is FP-110 manufactured by Fushimi Pharmaceutical Co., Ltd.

[0084] As the flame retardant (Y), a compound represented by the following formula (9) is particularly preferred.

[0085] [ka]

[0086] In formula (9), n is an integer, A is preferably a divalent organic group, Q1 and Q2 are preferably divalent aromatic groups, and Z is preferably a group having an ester-forming functional group.

[0087] In formula (9), n is preferably an integer of 2 to 40, more preferably an integer of 10 to 30, and even more preferably an integer of 15 to 25.

[0088] In formula (9), examples of the divalent organic group represented by A include lower alkylene groups such as a methylene group, an ethylene group, a 1,2-propylene group, and a 1,3-propylene group, arylene groups such as a 1,3-phenylene group and a 1,4-phenylene group, and substituted arylene groups such as 1,3-xylylene and 1,4-xylylene.

[0089] In formula (9), examples of the divalent aromatic groups represented by Q1 and Q2 include divalent groups represented by formulas (3) and (4). Q1 and Q2 may be the same or different as long as the effects of the present invention are achieved.

[0090] In formula (9), examples of the group having an ester-forming functional group represented by Z include a group derived from a hydroxycarboxylic acid having 2 to 7 carbon atoms, and a group derived from a monoester of a dicarboxylic acid having 2 to 7 carbon atoms and a diol having 2 to 7 carbon atoms. When Z is a group derived from a monoester of a dicarboxylic acid having 2 to 7 carbon atoms and a diol having 2 to 7 carbon atoms, A may be bonded to a moiety derived from the dicarboxylic acid or to a moiety derived from the diol.

[0091] The compound represented by formula (9) is preferably a compound in which a group having an ester-forming functional group represented by Z forms a polyester structure, i.e., a compound having a structure in which the structural unit represented by formula (9) is repeated multiple times. Examples of such compounds include compounds having a structural unit represented by the following formula (9-1).

[0092] [ka]

[0093] In the formula (9-1), n ​​is an integer of 2 to 40, preferably an integer of 10 to 30, and more preferably an integer of 15 to 25.

[0094] The use of a compound having the structural unit of formula (9-1) is preferred from the viewpoints of suppressing blackening during molding, resulting in excellent film appearance, and being less likely to generate odors during heating. While the reason why a compound having the structural unit of formula (9-1) exhibits the above-mentioned excellent effects is unclear, the present inventors speculate that it is related to the fact that it is less affected by hydrolysis. That is, if a compound having such a structural unit undergoes hydrolysis, decomposition products (e.g., phenolic decomposition products) are immobilized within the structure and therefore less likely to volatilize. Furthermore, it is believed that the compound is stable and capable of recyclization through a re-dehydration reaction. This is believed to result in a film with an excellent appearance with less blackening, and also less likely to generate odor problems due to sublimation or volatilization of decomposition products.

[0095] Furthermore, examples of the flame retardant (Y) include phosphinic acid flame retardants such as phosphinates and diphosphinates.

[0096] Examples of the phosphinate or diphosphinate include a compound represented by formula (10) and a compound represented by formula (11).

[0097] [ka]

[0098] In formula (10), R 1 and R 2 each independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms. M represents a calcium ion, an aluminum ion, a magnesium ion, or a zinc ion. m is a natural number representing the valence of M.

[0099] In equation (10), R 1 and R 2are each independently a linear or branched alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and are preferably a methyl group, an ethyl group, a propyl group, or a phenyl group. M represents a calcium ion, an aluminum ion, a magnesium ion, or a zinc ion. m is a natural number representing the valence of M, and is preferably 2 or 3.

[0100] [ka]

[0101] In formula (11), R 4 and R 5 R each independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms. 3 represents a linear or branched alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, an alkylarylene group having 7 to 10 carbon atoms, or an arylalkylene group having 7 to 10 carbon atoms. M represents a calcium ion, an aluminum ion, a magnesium ion, or a zinc ion. n is a natural number representing the valence of M. n, a, and b are natural numbers that satisfy the relational expression 2×b=n×a.

[0102] In equation (11), R 4 and R 5 R each independently represents a linear or branched alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and is preferably a methyl group, an ethyl group, a propyl group, or a phenyl group. 3represents a linear or branched alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, an alkylarylene group having 7 to 10 carbon atoms, or an arylalkylene group having 7 to 10 carbon atoms, and is preferably a methylene group, an ethylene group, a propylene group, or a phenylene group. M represents a calcium ion, an aluminum ion, a magnesium ion, or a zinc ion. n is a natural number representing the valence of M. n, a, and b are natural numbers that satisfy the relational expression 2×b=n×a. n is preferably 2 or 3. b is preferably 1, 2, or 3, and more preferably 1 or 3. a is preferably 1 or 2.

[0103] Specific examples of phosphinates or diphosphinates include those produced in an aqueous medium using phosphinic acid and a metal carbonate, metal hydroxide, or metal oxide. Phosphinates or diphosphinates are basically monomeric compounds, but depending on the reaction conditions and environment, they may become polymeric phosphinates with a condensation degree of 1 to 3.

[0104] Examples of phosphinic acids or diphosphinic acids include dimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinic acid, methyl-n-propylphosphinic acid, methanedi(methylphosphinic acid), benzene-1,4-di(methylphosphinic acid), methylphenylphosphinic acid, and diphenylphosphinic acid.

[0105] Examples of the phosphinate include calcium dimethylphosphinate, magnesium dimethylphosphinate, aluminum dimethylphosphinate, zinc dimethylphosphinate, calcium ethylmethylphosphinate, magnesium ethylmethylphosphinate, aluminum ethylmethylphosphinate, zinc ethylmethylphosphinate, calcium diethylphosphinate, magnesium diethylphosphinate, aluminum diethylphosphinate, zinc diethylphosphinate, calcium methyl-n-propylphosphinate, magnesium methyl-n-propylphosphinate, aluminum methyl-n-propylphosphinate, zinc methyl-n-propylphosphinate, calcium methylphenylphosphinate, magnesium methylphenylphosphinate, aluminum methylphenylphosphinate, zinc methylphenylphosphinate, calcium diphenylphosphinate, magnesium diphenylphosphinate, aluminum diphenylphosphinate, and zinc diphenylphosphinate.

[0106] Examples of diphosphinates include calcium methane di(methylphosphinate), magnesium methane di(methylphosphinate), aluminum methane di(methylphosphinate), zinc methane di(methylphosphinate), calcium benzene-1,4-di(methylphosphinate), magnesium benzene-1,4-di(methylphosphinate), aluminum benzene-1,4-di(methylphosphinate), and zinc benzene-1,4-di(methylphosphinate).

[0107] Among these phosphinates or diphosphinates, aluminum ethylmethylphosphinate, aluminum diethylphosphinate, and zinc diethylphosphinate are preferred. Commercially available phosphinates or diphosphinates include EXOLIT OP1230 (aluminum phosphinate) and OP1400 manufactured by Clariant.

[0108] (Preferred Flame Retardant) The flame retardant (Y) contained in Layer A of the present film preferably contains a compound having a structural unit of the formula (9) (particularly, the formula (9-1)). When Layer A contains a compound having a structural unit of the formula (9) (particularly, the formula (9-1)), the amount of carbon dioxide generated when the present film is incinerated is highly reduced, and the basic properties of the film are not significantly affected. In addition, for example, blackening during molding (film formation) is particularly effectively suppressed, resulting in a polyester film with particularly excellent appearance and design properties. Furthermore, since Layer A contains a compound having a structural unit of the formula (9) (particularly the formula (9-1)), the film is highly effective in reducing the amount of carbon dioxide generated when incinerated, and has little effect on the basic properties of the film. In addition, the film is particularly effective in suppressing the generation of odors during heating (during film formation or melting), resulting in a polyester film that is particularly safe and easy to recycle.

[0109] In preparing the present film, the flame retardant (Y) and the polyester resin (X) may be premixed and then melt-kneaded, or the flame retardant (Y) may be added to the molten polyester resin (X) and then kneaded. Alternatively, a resin compound such as a masterbatch may be prepared by either of these methods, and then the polyester resin (X) may be melt-kneaded with the resin compound.

[0110] <Antioxidant (Z)> Layer A may further contain an antioxidant (Z). Suitable examples of the antioxidant (Z) include primary antioxidants (radical scavengers) such as phenol-based antioxidants, amine-based antioxidants, quinone-based antioxidants, and nitroso-based antioxidants, and conventionally known antioxidants can be used as appropriate.

[0111] In preparing the present film, the antioxidant (Z) and the polyester resin (X) may be premixed and then melt-kneaded, or the antioxidant (Z) may be added to the molten polyester resin (X) and then kneaded. Alternatively, a resin compound such as a masterbatch may be prepared by either of these methods, and then the polyester resin (X) may be melt-kneaded with the resin compound.

[0112] The content of the antioxidant (Z) is, for example, 0.005 to 3 parts by mass, 0.01 to 2 parts by mass, 0.03 to 1 part by mass, or 0.05 to 0.8 parts by mass relative to 100 parts by mass of the polyester resin (X).

[0113] <Reaction mechanism> The mechanism by which this film, which has layer A containing flame retardant (Y), can reduce the amount of carbon dioxide generated during incineration is not clear, but it is assumed to be as follows. Typically, the thermal decomposition of polyester resin begins with the thermal cleavage of its main chain. It is known that during thermal cleavage, a chain reaction occurs through the generation of radicals. Furthermore, during incineration, it readily reacts with oxygen in the air. These reactions increase the amount of oxygen atoms in the decomposed product during incineration of polyester resin, and the decomposition of the main chain progresses. Flame retardant (Y) has a radical trapping effect and promotes dehydration and carbonization through its own oxidative decomposition. These effects allow flame retardant (Y) to inhibit the reaction between polyester resin and oxygen in the air. In other words, by having layer A containing flame retardant (Y), the decomposition and carbonization of the main chain proceeds while suppressing the increase in the amount of oxygen atoms in the decomposition product during incineration. As a result, the amount of carbon dioxide generated during incineration is reduced.

[0114] In addition, since antioxidant (Z) is known to inhibit oxidation by terminating radical chains, antioxidant (Z) can also reduce the amount of carbon dioxide generated by inhibiting the increase in the amount of oxygen atoms in the decomposition products during incineration.

[0115] <Other additives> This film can contain additives that are usually used in ordinary film materials, etc., as necessary. For example, pigments, ultraviolet absorbers, infrared absorbers, ultraviolet reflectors, infrared reflectors, heat stabilizers, antistatic agents, plasticizers, nucleating agents, molecular chain extenders, crosslinking agents, fillers for resin strengthening, etc. can be mentioned. The content of these additives other than the filler for resin strengthening is not particularly limited, but is 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.7% by mass or less, etc., based on the entire A layer. The content of the filler for resin strengthening is not particularly limited, but is 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, etc., based on the entire A layer.

[0116] <<Layers other than the A layer>> This film may have layers other than the aforementioned A layer. The layer other than the A layer preferably contains a polyester resin as the main component resin. This "main component resin" means the resin with the largest mass ratio among the resins constituting the layer other than the A layer of this film, and means 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, 90% by mass or more of the resins constituting the layer other than the A layer of this film, and may be 100% by mass.

[0117] Also, the content of the polyester resin contained in the layer other than the A layer is not limited below, but for example, 80% by mass or more is preferable, more preferably 85% by mass or more, still more preferably 90% by mass or more, particularly preferably 92% by mass or more, and may also be 94% by mass or more, 96% by mass or more, 98 - 99% by mass, etc.

[0118] The specific and preferred embodiments of the polyester resin contained in the layer other than the A layer are the same as those of the polyester resin (X) contained in the aforementioned A layer, and all of these can be incorporated. That is, the polyester resin contained in the layer other than the A layer, and the polymerization catalysts, particles, and other additives exemplified for the polyester resin are the same as those of the polyester resin (X) in the A layer, and the polymerization catalysts, particles, and other additives exemplified for the polyester resin (X).

[0119] (Phosphorus content in this film) The present film is a polyester film having a layer A containing a polyester resin (X) and a flame retardant (Y), and the phosphorus content in the present film is preferably 50 to 10,000 ppm by mass, more preferably 60 to 9,000 ppm by mass, even more preferably 70 to 8,000 ppm by mass, still more preferably 80 to 7,000 ppm by mass, and even more preferably 90 to 6,500 ppm by mass. If the content is 50 ppm by mass or more, the carbon dioxide reduction effect during incineration is sufficiently exhibited. On the other hand, if the content is 10,000 ppm by mass or less, the carbon dioxide reduction effect is exhibited without impairing the incineration property of the film. The lower limit of the phosphorus content in the present film may be, for example, 100 ppm by mass or more, 150 ppm by mass or more, 200 ppm by mass or more, 220 ppm by mass or more, 250 ppm by mass or more, 300 ppm by mass or more, 400 ppm by mass or more, 500 ppm by mass or more, 600 ppm by mass or more, 700 ppm by mass or more, 750 ppm by mass or more, 800 ppm by mass or more, 900 ppm by mass or more, 1000 ppm by mass or more, 1500 ppm by mass or more, etc.

[0120] The phosphorus content in this film includes not only phosphorus derived from the flame retardant (Y) but also all phosphorus derived from other than the flame retardant (Y), if any. Specifically, this includes phosphorus contained in additives (co-catalysts, stabilizers, etc.) and particles used in the production of the raw polyester.

[0121] (Flame retardant (Y) content in this film, etc.) The content of the flame retardant (Y) in the present film is preferably 50 to 10,000 ppm by mass, more preferably 60 to 9,000 ppm by mass, even more preferably 70 to 8,000 ppm by mass, even more preferably 80 to 7,000 ppm by mass, and even more preferably 90 to 6,500 ppm by mass, in terms of the phosphorus content in the present film (content calculated as phosphorus element). If the content is 50 ppm by mass or more, the carbon dioxide reduction effect during incineration is sufficiently exhibited. On the other hand, if the content is 10,000 ppm by mass or less, the carbon dioxide reduction effect is exhibited without impairing the incineration property of the film. The lower limit of the content of the flame retardant (Y) in the present film may be, for example, 100 ppm by mass or more, 150 ppm by mass or more, 200 ppm by mass or more, 220 ppm by mass or more, 250 ppm by mass or more, 300 ppm by mass or more, 400 ppm by mass or more, 500 ppm by mass or more, 600 ppm by mass or more, 700 ppm by mass or more, 750 ppm by mass or more, 800 ppm by mass or more, 900 ppm by mass or more, 1000 ppm by mass or more, 1500 ppm by mass or more, etc.

[0122] The content of the flame retardant (Y) in the present film is preferably 0.005 to 1 part by mass, more preferably 0.006 to less than 1 part by mass, even more preferably 0.007 to 0.9 parts by mass, and even more preferably 0.008 to 0.8 parts by mass, relative to 100 parts by mass of the polyester resin (X), in terms of the phosphorus content in the present film. The lower limit of the content in the present film may be, for example, 0.01 parts by mass or more, 0.02 parts by mass or more, 0.04 parts by mass or more, 0.1 parts by mass or more, 0.15 parts by mass or more, 0.2 parts by mass or more, 0.25 parts by mass or more, or 0.3 parts by mass or more.

[0123] In general, the amount of flame retardant blended is often more than 1 part by mass in terms of phosphorus content per 100 parts by mass of resin in order to exert a flame-retardant effect. However, in the present film, the content of the flame retardant (Y) is 50 to 10,000 ppm by mass in terms of phosphorus content in the present film, which is less than the amount generally used as a flame retardant. In other words, the present film does not impart flame retardancy to the polyester film, but rather exerts the effect of reducing carbon dioxide emissions during incineration without impairing the incineration property of the film.

[0124] The content of the flame retardant (Y) in the present film can be measured by the method described in the Examples. Alternatively, the content of the flame retardant (Y) in the present film can be measured as the phosphorus content in the present film by cutting out a sample from the film and measuring the phosphorus content using ICP-OES or the like. Specifically, when measuring the phosphorus content of the entire film, the entire film can be cut out as is and used as a sample, and when measuring the phosphorus content of each layer constituting the film, each layer can be separated using a microtome or the like and used as a sample.

[0125] <<Preferred embodiment>> The present film preferably has a laminated structure of at least three layers, including a surface layer, an intermediate layer, and another surface layer. Of these, it is more preferable that, when the present film has such a laminated structure, only one of the surface layers is Layer A, and it is even more preferable that both surface layers are Layer A, and it is particularly preferable that the film has a three-layer structure of "surface layer that is Layer A / intermediate layer that is not Layer A / surface layer that is Layer A." By using this film in a laminated structure of at least three layers, with at least one surface layer, preferably both surface layers, being Layer A, it is possible to effectively reduce the amount of carbon dioxide generated during incineration. Although the mechanism by which this occurs is unclear, the present inventors speculate as follows. Because combustion progresses from the surface layer, intermediate layers that are not layer A cannot effectively reduce carbon dioxide emissions during the initial stage of incineration. On the other hand, if the flame retardant (Y) is concentrated in the surface layer, the initial oxidative decomposition reaction during incineration is efficiently suppressed by the aforementioned reaction mechanism, forming a carbonized layer. Furthermore, when the surface layer is a carbonized layer, oxygen in the air is inhibited from reacting with the polyester resin in the intermediate layer, reducing combustion. As a result, it is believed that by using a laminate structure of at least three layers for this film and making at least one surface layer, or preferably both surface layers, layer A, it is possible to effectively reduce the amount of carbon dioxide generated during incineration.

[0126] When the present film has a laminated structure of at least three layers, with at least one surface layer, preferably both surface layers, designated as Layer A, the content of the flame retardant (Y) in the surface layer, in terms of the phosphorus content in the surface layer, is preferably 50 to 13,000 ppm by mass, more preferably 60 to 12,000 ppm by mass, even more preferably 70 to 8,000 ppm by mass, even more preferably 80 to 7,000 ppm by mass, even more preferably 90 to 6,000 ppm by mass, and even more preferably 100 to 5,500 ppm by mass. When the content is 50 ppm by mass or more, the effect of incorporating the flame retardant (Y) in the surface layer can be fully exerted, and the carbon dioxide reduction effect when the present film is incinerated can be fully exerted. On the other hand, when the content is 13,000 ppm by mass or less, the carbon dioxide reduction effect can be exerted without impairing the incineration property of the film. The lower limit of the content of the flame retardant (Y) in the surface layer may be, for example, 200 ppm by mass or more, 400 ppm by mass or more, 600 ppm by mass or more, 700 ppm by mass or more, 800 ppm by mass or more, 1000 ppm by mass or more, 1200 ppm by mass or more, 1300 ppm by mass or more, 1400 ppm by mass or more, 1500 ppm by mass or more, 1700 ppm by mass or more, 1900 ppm by mass or more, 2000 ppm by mass or more, 2200 ppm by mass or more, 2400 ppm by mass or more, 2600 ppm by mass or more, 2800 ppm by mass or more, 3000 ppm by mass or more, and the like.

[0127] When the present film has a laminated structure of at least three layers and at least one surface layer, preferably both surface layers, are Layer A, the content of the flame retardant (Y) in the surface layer, as phosphorus content in the surface layer, is preferably 0.005 to 1.3 parts by mass, more preferably 0.006 to 1.2 parts by mass, and even more preferably 0.007 to 1.1 parts by mass, per 100 parts by mass of the polyester resin (X). The lower limit of the content of the flame retardant (Y) in the surface layer may be, for example, 0.01 parts by mass or more, 0.02 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, 0.15 parts by mass or more, 0.2 parts by mass or more, 0.25 parts by mass or more, 0.3 parts by mass or more, and the upper limit may be, for example, 1 part by mass or less, 0.9 parts by mass or less, 0.8 parts by mass or less, etc.

[0128] The content of the flame retardant (Y) in the surface layer can be measured by the method described in the Examples. For example, the content of the flame retardant (Y) in the surface layer can be measured by cutting out a film as a sample to measure the phosphorus content in the surface layer using ICP-OES or the like. Specifically, when measuring the phosphorus content in the surface layer constituting the film, the surface layer can be separated using a microtome or the like to obtain a sample, and the phosphorus content can be measured using ICP-OES or the like. The content of the flame retardant (Y) in the intermediate layer can also be measured in the same way.

[0129] It is particularly preferred that both surface layers are layers A and that the content of the flame retardant (Y) in each surface layer satisfies the above. In such a case, the type and content of the flame retardant (Y) in each surface layer may be the same or different as long as they satisfy the above.

[0130] <<<Polyester film manufacturing method>>> Next, the method for producing the present film will be specifically described, but the present film is not limited to the following production example. Preferably, the present film is produced by first producing an unstretched sheet, which is then stretched in two directions to obtain a biaxially stretched polyester film.

[0131] The unstretched sheet is preferably obtained by feeding the above-mentioned polyester resin (X) and, if necessary, particles and other additives to an extruder, mixing them appropriately, extruding the mixture from a die of the extruder as a molten sheet, and cooling and solidifying it on a rotating cooling drum. In this case, it is preferable to increase the adhesion between the sheet and the rotating cooling drum in order to improve the flatness of the sheet, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably used. When the present film has a multilayer structure, it is preferable to co-extrude the layers by a co-extrusion method to form an unstretched sheet having a multilayer structure.

[0132] The polyester resin (X) as a raw material may be fed to an extruder in the form of pellets or the like after being appropriately dried, and particles and other additives may be appropriately blended into the pellets. The flame retardant (Y) and the antioxidant (Z) can be used as described above. For example, they may be premixed with the polyester resin and then melt-kneaded, or the flame retardant (Y) and the antioxidant (Z) may be added to the molten polyester resin (X) and then kneaded, or they may be first made into a resin compound such as a masterbatch.

[0133] The unstretched sheet is then stretched uniaxially and then biaxially. Specifically, the unstretched sheet is first stretched in one direction using a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 2.8 to 6 times, and more preferably 3 to 5.5 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction. In this case, the stretching temperature is usually 70 to 170°C, preferably 80 to 150°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times, and more preferably 3.6 to 5.5 times.

[0134] Subsequently, it is preferable to perform a heat setting treatment at a temperature of 180 to 270°C under tension or relaxation of 30% or less, preferably 10% or less, and more preferably 7% or less to obtain a biaxially stretched polyester film. The heat setting temperature is preferably 190°C or higher, more preferably 195°C or higher, and even more preferably 200°C or higher. The heat setting temperature is not particularly limited, but is preferably 240°C or lower, more preferably 230°C or lower, even more preferably 225°C or lower, and even more preferably 220°C or lower. The heat setting time is preferably 3 to 15 seconds, more preferably 4 to 14 seconds, and even more preferably 5 to 13 seconds. After the heat setting step, the film may be cooled in a cooling zone under a relaxation of 0 to 20%, 0.5 to 15%, preferably 1 to 10%, and more preferably 1.5 to 7%. The cooling temperature is, for example, preferably about 120 to 160°C, more preferably about 130 to 150°C. In the stretching, a method in which unidirectional stretching is performed in two or more stages may also be employed. In this case, it is preferable to perform the stretching so that the final stretch ratios in both directions are within the above-mentioned ranges.

[0135] The present film can also be produced by simultaneous biaxial stretching, which involves simultaneously stretching and orienting the unstretched sheet in the machine direction and width direction under temperature control, typically at 70 to 120°C, and preferably at 80 to 110°C, at a stretching ratio of 4 to 50, preferably 7 to 35, and more preferably 10 to 25 times in area. Subsequently, it is preferable to perform a heat setting treatment at a temperature of 170 to 250°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. Preferred conditions for the heat setting treatment are as described above. Regarding the simultaneous biaxial stretching device employing the above-mentioned stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be used.

[0136] The longitudinal direction of the film refers to the direction in which the film advances during the film production process, i.e., the winding direction of the film roll. The width direction refers to the direction parallel to the film surface and perpendicular to the longitudinal direction, i.e., the direction parallel to the central axis of the roll when the film is in a roll shape.

[0137] <<<Physical properties of polyester film>>> (carbon dioxide emissions) When the film is heated from 25°C to 1000°C at a temperature increase rate of 10°C / min in a simulated air atmosphere, the amount of carbon dioxide generated is preferably 2500mg / g or less. If the amount of carbon dioxide generated exceeds 2500mg / g, the effect of reducing carbon dioxide emissions during incineration may be insufficient. From the viewpoint of achieving an excellent carbon dioxide reduction effect during incineration, the amount of carbon dioxide generated is preferably 2400 mg / g or less, more preferably 2100 mg / g or less, and even more preferably 1600 mg / g or less. The lower limit of the amount of carbon dioxide generated is preferably as small as possible, and is sufficient as long as it is 0 mg / g or more, but it can be said that the effect is sufficient even if it is, for example, 500 mg / g or more or 1000 mg / g or more. The amount of carbon dioxide generated can be measured by the method described in the Examples.

[0138] (carbon dioxide emission reduction rate) When the film is heated from 25°C to 1000°C at a temperature increase rate of 10°C / min in a simulated air atmosphere, the reduction rate of carbon dioxide generation is preferably 1% or more, more preferably 10% or more, even more preferably 25% or more, even more preferably 45% or more, even more preferably 60% or more, even more preferably 65% ​​or more, and even more preferably 75% or more. If the reduction rate of carbon dioxide generation is equal to or greater than the lower limit, a sufficient carbon dioxide reduction effect can be obtained during incineration. The higher the upper limit of the carbon dioxide generation reduction rate, the better, and 100% is ideal, but the effect can also be said to be sufficient if it is, for example, 95% or less, 90% or less, 85% or less, or 80% or less. The carbon dioxide generation reduction rate can be measured and calculated by the method described in the Examples.

[0139] (tensile breaking strength) The tensile strength at break in the machine direction (MD) of the present film is preferably 120 MPa or more, more preferably 150 MPa or more, even more preferably 170 MPa or more, even more preferably 190 MPa or more, and even more preferably 210 MPa or more. The upper limit of the MD tensile strength at break is preferably as large as possible, and may be, for example, 340 MPa or less, 320 MPa or less, or 300 MPa or less. The tensile strength at break in the transverse direction (TD) of the present film is preferably 180 MPa or more, more preferably 200 MPa or more, even more preferably 220 MPa or more, even more preferably 240 MPa or more, even more preferably 250 MPa or more, and particularly preferably 260 MPa or more. The upper limit of the TD tensile strength at break is preferably as high as possible, and may be, for example, 400 MPa or less, 380 MPa or less, or 360 MPa or less. If the tensile strength at break is within the above range, the film can be said to have excellent durability, and is therefore likely to be adopted in a variety of fields, which is preferable. The tensile strength at break can be measured by the method described in the Examples.

[0140] (Tensile elongation at break) The tensile elongation at break in the machine direction (MD) of the present film is preferably 120% or more, more preferably 130% or more, even more preferably 140% or more, even more preferably 150% or more, even more preferably 160% or more, particularly preferably 170% or more, and especially preferably 180% or more. The upper limit of the tensile elongation at break in the MD is preferably as large as possible, and may be, for example, 280% or less, 260% or less, or 240% or less. The tensile elongation at break in the transverse direction (TD) of the present film is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 100% or more, even more preferably 105% or more, and particularly preferably 110% or more. The upper limit of the TD tensile elongation at break is preferably as large as possible, and may be, for example, 240% or less, 220% or less, or 200% or less. If the tensile elongation at break is within the above range, the present film can be said to have excellent durability, and is therefore likely to be adopted in a variety of fields, which is preferable. The tensile elongation at break can be measured by the method described in the examples.

[0141] (Young's modulus) The Young's modulus in the machine direction (MD) of the present film is preferably 2 GPa or more, more preferably 3 GPa or more, even more preferably 3.5 GPa or more, even more preferably 4 GPa or more, and even more preferably 4.5 GPa or more. The upper limit of the MD Young's modulus is preferably as large as possible, but may be, for example, 15 GPa or less, 10 GPa or less, or 8 GPa or less. The Young's modulus in the transverse direction (TD) of the present film is preferably 3 GPa or more, more preferably 4 GPa or more, even more preferably 4.5 GPa or more, even more preferably 5 GPa or more, even more preferably 5.5 GPa or more, particularly preferably 5.8 GPa or more, and particularly preferably 6 GPa or more. The upper limit of the MD Young's modulus is preferably as large as possible, and may be, for example, 15 GPa or less, 10 GPa or less, or 8 GPa or less. If the Young's modulus is within the above range, the film has sufficient strength and tends to be easily adopted in various fields, which is preferable. The Young's modulus can be measured by the method described in the Examples.

[0142] (Thermal shrinkage rate) The heat shrinkage of the present film in the machine direction (MD) when heat treated at 150°C for 30 minutes is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2.5% or less, even more preferably 2% or less, and particularly preferably 1.8% or less. The lower limit of the MD heat shrinkage when heat treated at 150°C for 30 minutes is the smaller the better, but it may be, for example, 0.3% or more, 0.6% or more, or 0.8% or more. The heat shrinkage of the present film in the transverse direction (TD) when heat treated at 150°C for 30 minutes is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, even more preferably 1.8% or less, even more preferably 1.5% or less, and even more preferably 1% or less. The lower limit of the heat shrinkage in the MD when heat treated at 150°C for 30 minutes is the smaller the better, but it may be, for example, 0.1% or more, 0.3% or more, or 0.5% or more. If the heat shrinkage rate when heat treated at 150°C for 30 minutes is within the above range, the film can be said to have excellent heat resistance, and is therefore favorable as it tends to be easily usable in applications where it may be exposed to high temperatures. The heat shrinkage rate can be measured by the method described in the examples.

[0143] (Flame retardant) The flame retardancy of the present film at a thickness of 38 μm in the UL94 vertical flame test in accordance with ASTM D4804 is preferably VTM-1 or less, more preferably VTM-2 or less. If the flame retardancy at a thickness of 38 μm is within the above range, the present film is preferable because it is easy to incinerate and has high energy efficiency when disposed of. The flame retardancy can be measured by the method described in the examples.

[0144] (Gas generation amount [retention time range 6 to 20 minutes]) The amount of gas generated by gas chromatography-mass spectrometry (GC-MS) of this film, based on peaks detected within a retention time range of 6 to 20 minutes, is preferably less than 9 μg / g, more preferably 7 μg / g or less, even more preferably 5 μg / g or less, even more preferably 3 μg / g or less, particularly preferably 2 μg / g or less, and especially preferably 1 μg / g or less. The lower limit of the amount of gas generated is not particularly limited, but is about 0 μg / g. If the amount of gas generated is within this range, odors generated during incineration, etc. are sufficiently suppressed, resulting in excellent safety and recyclability.

[0145] Furthermore, the amount of gas generated based on peaks detected in the retention time range of 6 to 17 minutes by gas chromatography-mass spectrometry (GC-MS) is preferably less than 9 μg / g, more preferably 7 μg / g or less, even more preferably 5 μg / g or less, even more preferably 3 μg / g or less, particularly preferably 2 μg / g or less, and especially preferably 1 μg / g or less. The lower limit of the amount of gas generated is not particularly limited, but is about 0 μg / g. If the amount of gas generated is within this range, odors generated during incineration or other disposal are sufficiently suppressed, resulting in excellent safety and recyclability.

[0146] Furthermore, the amount of gas generated based on the peak derived from the flame retardant (Y) detected in the retention time range of 6 to 20 minutes by gas chromatography mass spectrometry (GC-MS) is preferably less than 9 μg / g, more preferably 7 μg / g or less, even more preferably 5 μg / g or less, still more preferably 3 μg / g or less, particularly preferably 2 μg / g or less, and especially preferably 1 μg / g or less. The lower limit of the amount of gas generated is not particularly limited, but is about 0 μg / g. If the amount of gas generated is within this range, the odor generated during incineration or other disposal is sufficiently suppressed, resulting in excellent safety and recyclability.

[0147] (Gas generation amount [retention time range 28-31 minutes]) The amount of gas generated from this film, based on the peak derived from the flame retardant (Y) detected in the retention time range of 28 to 31 minutes by gas chromatography-mass spectrometry (GC-MS), is preferably less than 2 μg / g, more preferably 1.5 μg / g or less, even more preferably 1 μg / g or less, and even more preferably 0.5 μg / g or less. The lower limit of the amount of gas generated is not particularly limited, but is usually about 0 μg / g. If the amount of gas generated is within this range, odors generated during incineration, etc., are sufficiently suppressed, resulting in excellent safety and recyclability. Furthermore, the appearance of the film is excellent.

[0148] Furthermore, the odor of this film is sufficiently suppressed during film production, and the odor is also sufficiently suppressed both during film production and when incinerated, making it highly safe and recyclable.

[0149] (L * value, a * value, b * value) When this film is made into a film equivalent to a total thickness of 500 μm, * The value is preferably 95.5 or more, more preferably 95.8 or more, even more preferably 96 or more, and even more preferably 96.2 or more. * The value represents the brightness, and the larger the value is from 0 to 100, the brighter it becomes. * The upper limit of the value is not particularly limited, but is, for example, 98 or less, or 97 or less. * If the value is within this range, it is preferable in that, for example, the design (appearance) of the molded product is not impaired and the amount of CO2 generated when incinerated tends to be small, making it suitable for use as a packaging material, for example.

[0150] When this film is made into a film equivalent to a total thickness of 500 μm, * The value is preferably from -0.5 to 0.5, more preferably from -0.45 to 0.4, and even more preferably from -0.4 to 0.3. * If the value is within this range, it is preferable in that, for example, the design (appearance) of the molded product is not impaired and the amount of CO2 generated when incinerated tends to be small, making it suitable for use as a packaging material, for example.

[0151] When this film is made into a film equivalent to a total thickness of 500 μm, * The value is preferably from -0.5 to 1, more preferably from -0.4 to 0.95, and even more preferably from -0.3 to 0.9. * If the value is within this range, it is preferable in that, for example, the design (appearance) of the molded product is not impaired and the amount of CO2 generated when incinerated tends to be small, making it suitable for use as a packaging material, for example.

[0152] (Spectral reflectance [wavelength 500nm]) When this film is made into a film equivalent to a total thickness of 500 μm, the spectral reflectance at a wavelength of 500 nm is preferably 88.5% or more, more preferably 89% or more, and even more preferably 90% or more. The upper limit of the spectral reflectance is not particularly limited, but is usually about 99%, and may be about 98%. A spectral reflectance within this range is preferable, for example, because it does not impair the design (appearance) of the molded product and tends to produce less CO2 even when incinerated, making it suitable for use as a packaging material, for example.

[0153] The spectral reflectance, L * value, a * value, b * The value can be measured by the method described in the Examples. The term "film having a total thickness equivalent to 500 μm" means, for example, that when a test film is constructed by stacking multiple sheets of this film, the thickness of the test film is closest to 500 μm, but does not mean that the thickness is exactly 500 μm. For example, in the case of a 25 μm film of this film, 20 sheets of this film can be stacked, and in the case of a 38 μm film, 13 sheets of this film can be stacked. When measuring a film with a thickness greater than 500 μm, the test film can be sliced ​​to a thickness equivalent to 500 μm using, for example, a microtome.

[0154] (Haze) The haze of the present film is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, even more preferably 4% or less, even more preferably 3.5% or less, and may be 3.2% or less, 3% or less, etc. The lower limit of the haze may be as small as possible, and may be, for example, 0.3% or more, 0.7% or more, or 1% or more. If the haze is within the above range, the present film can be said to have excellent transparency, and tends to be easily usable in applications where maintaining the appearance is required, which is preferable. The haze can be measured by the method described in the Examples.

[0155] (Arithmetic mean roughness (Ra)) The arithmetic mean roughness (Ra) of the present film is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more, and is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 35 nm or less. If the arithmetic mean roughness (Ra) is within the above range, the present film can be said to have excellent slip properties, and is therefore likely to be easily adopted in a variety of fields, which is preferable. The arithmetic mean roughness (Ra) can be measured by the method described in the examples.

[0156] <<<Methods for reducing carbon dioxide emissions>>> As described above, the present film can reduce the amount of carbon dioxide generated during incineration. Therefore, the present film can provide a method for reducing the amount of carbon dioxide generated during incineration.

[0157] <<<Uses of polyester film>>> This film has little effect on basic properties such as transparency, surface texture, mechanical strength, and dimensional stability, and can reduce the amount of carbon dioxide emitted when incinerated. Therefore, this film can be used in a wide variety of fields, including packaging materials, magnetic recording materials, solar cell applications, separators for liquid crystal polarizers, substrates for dry film resists, and release films for molding green sheets for multilayer ceramic capacitors, as well as optical films such as anti-reflection films, diffusion sheets, and prism sheets, and films for label printing.

[0158] <<<Term Explanation>>> In this specification, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". In the present invention, "pseudo air" refers to a gas in which helium (He) and oxygen (O2) are mixed so that the ratio of He:O2 is 80 vol %:20 vol %. In this specification, when it is written "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". In this specification, when it is stated that the quantity is "X or more" (X is any number), it also means that the quantity is "preferably larger than X" unless otherwise specified, and when it is stated that the quantity is "Y or less" (Y is any number), it also means that the quantity is "preferably smaller than Y" unless otherwise specified. In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in the present specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and means three possibilities: X only, Y only, and X and Y. [Example]

[0159] 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 as long as it does not deviate from the gist of the present invention.

[0160] <Evaluation method> (1) Intrinsic viscosity (IV) of polyester 1 g of polyester, from which components incompatible with the polyester had been removed, was precisely weighed and dissolved in 100 mL of a 50 / 50 (mass ratio) phenol / tetrachloroethane mixed solvent. The viscosity was measured at 30°C using a viscosity measuring device "VMS-022UPC·F10" (manufactured by Rigo Co., Ltd.).

[0161] (2) Average particle size The particle size at an integrated volume fraction of 50% in the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation was taken as the average particle size d50.

[0162] (3) Reduction of carbon dioxide emissions (carbon dioxide emissions from polyester film and reduction rate of carbon dioxide emissions) Measurements were carried out using a thermobalance mass spectrometer (ThermoMASS) manufactured by Rigaku Corporation. The amount of carbon dioxide generated was calculated from the ion chromatogram peak area of ​​m / z = 44 and a calibration curve prepared from a standard sample. The calibration curve was prepared by two-point calibration using the ion chromatogram peak area (m / z = 44) of the standard sample versus the theoretical amount of carbon dioxide generated. The measurement conditions were as follows: Heating conditions: temperature 25℃~1000℃, speed 10℃ / min Atmosphere: Simulated air (He + O2, He: 80 vol%, O2: 20 vol%) Gas flow rate: 300 mL / min Container: Pt cup MS settings: EMS 1mA, SEM 1200V, m / z≒10~410(EI) Preparation: Calcium oxalate monohydrate

[0163] The reduction rate of carbon dioxide generation of the polyester films shown in Table 2 was calculated using the following formula from the amount of carbon dioxide generation (p1) generated from the polyester films of the Examples and the amount of carbon dioxide generation (p0) generated from the polyester films of the Comparative Examples, which had the same composition as the polyester films of the Examples except that they did not contain the flame retardant (Y). Carbon dioxide emission reduction rate (%) = {1-(p1÷p0)} x 100

[0164] (4) Design (color: spectral reflectance of polyester film, L * value, a * value, b * value) Spectral reflectance of polyester film (spectral reflectance at a wavelength of 500 nm), L * value, a * value, and b * The value was determined using a spectrophotometer "CM-3700d" manufactured by Konica Minolta Japan, Inc. as follows. Samples were taken by punching out a sample from a predetermined location on the polyester film using a round holder blade with a diameter of approximately 60 mm. The number of test sheets was determined so that the layer thickness (total thickness at the time of measurement) was closest to 500 μm. For example, 20 sheets of film should be stacked for a 25 μm film, and 13 sheets of film should be stacked for a 38 μm film. The measurement conditions were reflective conditions. The spectral reflectance (wavelength 500 nm), L * value, a * value, b * The values ​​were measured in an environment of 23° C. Details of the measurement equipment settings and color display conditions are as follows: Measuring equipment: CM-3700d (integrating sphere type d / 8) Measurement mode: Reflectance Average number of times: 3 ·Specular reflection light processing: SCI ·UV light amount: 100%FULL ·Measurement diameter: LAV (φ25.4mm) Target Mask: Large (LAV) Field of view setting: 2° field of view ·Light source: 1st C――C, 2nd D65――D65, 3rd A――A ·Measurement wavelength interval: 10nm (360~740nm)

[0165] (5) Transparency (haze of polyester film) Measurement was carried out in accordance with JIS K7136 using a haze meter (NDH2000) manufactured by Nippon Denshoku Industries Co., Ltd.

[0166] (6) Safety and recyclability 1 (Odor during polyester film production) A sensory evaluation test was conducted by five or more expert panelists to evaluate the odor of the polyester film during film formation. (Evaluation criteria) 〇...No odor. △...Weak odor. ×...Strong odor.

[0167] (7) Safety and recyclability 2 (amount of gas generated when polyester film is melted) According to the conditions shown below, the gas generated when the sample was heated was collected, and the components of the collected gas were separated and identified by GC-MS to obtain an ion chromatogram. The amount of gas generated was calculated based on the peaks detected in the retention time range of 6 to 20 minutes and the peaks detected in the retention time range of 28 to 31 minutes.

[0168] A 10 mg sample was placed in a quartz glass thermal desorption tube, both ends packed with quartz wool, and the tube was inserted into a thermal desorption apparatus (Gerstel TDU2) at 40 °C for 1 minute. The tube was then purged with helium. The tube was then heated to 280 °C at a rate of 720 °C / min and held at this temperature for 10 minutes to perform thermal extraction. During this heating period, the GC inlet filled with quartz wool was cooled to -150 °C and held at this temperature for 0.5 minutes to capture volatile components evolved from the sample. The components collected by cooling in the GC inlet were vaporized by rapidly heating the collection section to 300 °C at a rate of 720 °C / min and introduced into a GC column for GC-MS analysis. The GC-MS analysis conditions were as follows: [GC-MS conditions] GC-MS device: Agilent 7890GC / 5977MSD Column: Slightly polar column, J&W DB-5, 30m x 0.25mm ID, 0.25μm film thickness Oven temperature: 40°C (hold for 5 minutes) to 300°C (hold for 20 minutes), heating rate: 10°C / min Carrier gas: Helium Carrier gas flow rate: 1 mL / min (constant flow) Scan range: m / z=10-600

[0169] The sum of the areas of all peak components detected in the retention time range of 6 to 20 minutes in the ion chromatogram was calculated. Similarly, the sum of the areas of all peak components detected in the retention time range of 28 to 31 minutes in the ion chromatogram was calculated. Next, the sum of the peak areas detected as described above was converted into the amount of n-ecoisan using the calibration curve, and this was divided by the mass (M) of the measured sample to calculate the amount of gas generated per unit mass (ng / g) in terms of n-ecoisan.

[0170] The calibration curve was prepared by conventional methods, using GC-MS measurements of known concentrations of n-eicosane and plotting the amount of n-eicosane versus the peak area of ​​the detected gas. Specifically, GC-MS measurements were performed using n-eicosane (130 ng, 250 ng, 500 ng) in the same manner as described above, and the amount of n-eicosane versus the peak area of ​​the detected gas was plotted to prepare a calibration curve of the amount of n-eicosane added (Xa) versus the peak area (Ya). The peak area (Yb) obtained from the measurement of each sample was substituted into this calibration curve to determine the amount of generated gas (Xb), which was then divided by the mass (M) of the sample to calculate the amount of generated gas (μg / g). A blank measurement was carried out without inserting a sample, and the peaks detected in the blank measurement were not included in the quantitative calculation as they were derived from the measurement blank.

[0171] (8) Surface properties (arithmetic mean roughness (Ra) of polyester film) The arithmetic mean roughness of the polyester film surface was determined as follows using a surface roughness measuring instrument (SE-3500) manufactured by Kosaka Laboratory Co., Ltd. That is, a section of reference length L (2.5 mm) was cut out from the film cross-sectional curve obtained by measurement in the direction of its center line, and when the roughness curve y = f(x) was expressed with the center line of this cut out section as the x-axis and the direction of longitudinal magnification as the y-axis, the arithmetic mean roughness was the value given by the following formula, expressed in nm. Ten roughness curves were obtained from the sample film surface, and the arithmetic mean roughness was expressed as the average value of the arithmetic mean roughness of the cut out sections obtained from these roughness curves. The stylus tip radius was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

[0172]

number

[0173] (9) Mechanical Properties 1 (Tensile Strength and Elongation at Break of Polyester Film) A sample piece measuring 15 mm wide and 150 mm long was taken from a predetermined location on the polyester film, and the tensile strength and elongation at break were measured using an Autograph AGX-V manufactured by Shimadzu Corporation in a room controlled at a temperature of 23°C and a humidity of 50%RH. Using a tensile testing machine with a chuck distance of 50 mm, the sample film was subjected to a tensile test in the machine direction (MD) or the transverse direction (TD) at a speed of 200 mm / min. The strength (tensile load value divided by the cross-sectional area of ​​the test piece) when the sample broke (fractured) was defined as the breaking strength (MPa). The elongation (percentage of the difference between the gauge length at break and the gauge length before the test divided by the gauge length before the test) when the sample broke (fractured) was defined as the breaking elongation (%).

[0174] (10) Mechanical properties 2 (Young's modulus of polyester film) A sample film measuring 20 mm wide and 170 mm long was taken from a predetermined location on the polyester film, and Young's modulus was measured using an Autograph AGX-V manufactured by Shimadzu Corporation in a room regulated at a temperature of 23°C and a humidity of 50%RH. Tensile measurements were carried out in the machine direction (MD) and width direction of the sample film at a chuck distance of 120 mm and a tensile speed of 10 mm / min. E=Δσ / Δε (In the above formula, E is Young's modulus (GPa), Δσ is the stress difference (GPa) due to the original average cross-sectional area between two points on the line, and Δε is the strain difference between the same two points / initial length.) Measurements were taken at five points in each of the machine direction (MD) and the transverse direction (TD) of the film, and the average value was calculated for each.

[0175] (11) Dimensional stability (heat shrinkage rate of polyester film) A 1.5cm x 15cm sample film was heat-treated for 30 minutes in a hot air oven maintained at a specified temperature (150°C) under no tension, and the lengths of the sample film were measured before and after the treatment, and the elastic modulus was calculated using the following formula. Measurements were taken in both the machine direction (MD) and the cross direction (TD) of the film. Heat shrinkage rate (%) = {(sample length before heat treatment) - (sample length after heat treatment)} ÷ (sample length before heat treatment) × 100

[0176] (12) Flame retardancy Flame retardancy was evaluated in the UL94 vertical flame test in accordance with ASTM D4804. Specifically, a 200mm x 50mm sample film was rolled into a cylindrical shape, attached vertically to a clamp, and exposed to a 20mm flame for 3 seconds three times. Based on the burning behavior, the film was rated as VTM-0, VTM-1, VTM-2, or Not. The burning test was performed with the long side of the sample film facing MD.

[0177] (13) Measurement of flame retardant content in polyester film and on the surface The phosphorus content of each of the raw materials C and D was measured using ICP-OES (iCAP6500DUO manufactured by Thermo Fisher Scientific). XSTC-8 (phosphorus content 10 ppm by mass) manufactured by SPEX was used as the standard solution, and 500-fold dilution (phosphorus content 0.02 ppm by mass), 200-fold dilution (phosphorus content 0.05 ppm by mass), 100-fold dilution (phosphorus content 0.1 ppm by mass), and 33.3-fold dilution (phosphorus content 0.3 ppm by mass) were prepared to create a calibration curve. The sample (approximately 1 g) was weighed into a Kjeldahl flask and decomposed by wet decomposition using sulfuric acid, nitric acid, and hydrogen peroxide to prepare an acid solution. After cooling, the solution was diluted to a constant volume in a 50 ml measuring flask and used as the measurement solution. The wavelength used was 177.440 nm. From the obtained results, the content of the flame retardant in the polyester film was calculated as the phosphorus content based on the blending ratio of raw materials C and D in the polyester film. Furthermore, the content of the flame retardant in the surface layer was calculated as the phosphorus content based on the blending ratio of raw materials C and D in the polyester film and the ratio of the discharge amount of each layer when producing the polyester film. Furthermore, based on the above, the content of the flame retardant (Y) per 100 parts by mass of the polyester resin (X) in the film was calculated as the phosphorus content, and the content of the flame retardant (Y) per 100 parts by mass of the polyester resin (X) in the surface layer was calculated as the phosphorus content. The phosphorus content value obtained in this example can be considered to be the same as the actual phosphorus content in the film and the surface layer.

[0178] <Materials used> Raw material A: polyethylene terephthalate (intrinsic viscosity = 0.65 dL / g) Raw material B: Masterbatch containing polyethylene terephthalate and 0.55% by mass of silica particles with an average particle size of 2.2 μm (intrinsic viscosity = 0.61 dL / g)

[0179] Raw material C: A masterbatch (intrinsic viscosity = 0.50 dL / g) in which a phosphorus compound having an aromatic ring is blended with polyethylene terephthalate to a phosphorus element content of 7700 μg / g and a phenolic antioxidant is added. The phosphorus compound having an aromatic ring comprises an aromatic condensed phosphate ester (compound A) represented by the following formula (1-1) and an aromatic phosphate ester (compound B) represented by the following formula (2-1), and the mass ratio of compound A to compound B (compound A:compound B) is 98:2. Compound B is a by-product of compound A.

[0180] [ka]

[0181] Raw material D: A masterbatch prepared by blending a phosphorus compound having an aromatic ring with polyethylene terephthalate in an amount of 28,000 μg / g in terms of elemental phosphorus. The phosphorus compound having an aromatic ring is a compound (compound C) having a structural unit of the following formula (9-1). Note that in the following formula (9-1), n ​​is an average of 18 (intrinsic viscosity = 0.43 dL / g).

[0182] [ka]

[0183] Example 1 The raw materials for both surface layers were prepared by mixing raw materials A, B, and D in proportions of 70%, 25%, and 5% by mass, respectively, and the raw material for the intermediate layer was prepared by mixing 100% raw material A. The raw materials for both surface and intermediate layers were each fed into two extruders and melted at 285°C. They were then co-extruded onto a cooling roll set at 25°C in a layer structure of two types and three layers (surface layer / intermediate layer / surface layer = discharge rate 4 / 40 / 4), and cooled and solidified to obtain an unstretched sheet. The resulting unstretched sheet was then stretched 3.2 times in the machine direction (MD) at 86°C using a roll stretching machine. It was then preheated to 100°C in a tenter and stretched 4.2 times in the transverse direction (TD) at 115°C. Finally, it was heat-set at 230°C and cooled to 140°C with 2% relaxation in the transverse direction (TD) to obtain a biaxially stretched polyester film with a thickness of 38 μm. The evaluation results are shown in Table 2.

[0184] (Examples 2 to 5, Comparative Examples 1 to 4) The same procedure as in Example 1 was carried out, except that the composition was as shown in Table 1 below. A biaxially stretched polyester film was obtained. The evaluation results are shown in Table 2. In Table 1, the numerical values ​​for the blending ratios of raw materials A to D are rounded to one decimal place. In Table 1, the content (ppm by mass) of the flame retardant (Y) in the film and the content (ppm by mass) of the flame retardant (Y) in the surface layer are calculated values ​​rounded to the nearest tenth. In Table 1, the content (parts by mass) of the flame retardant (Y) per 100 parts by mass of the polyester resin (X) in the film and the content (parts by mass) of the flame retardant (Y) per 100 parts by mass of the polyester resin (X) in the surface layer are calculated values ​​rounded to the nearest tenth. In Table 2, the amount of carbon dioxide generated is shown as a measured value rounded off to the first decimal place, and the reduction rate of carbon dioxide generated is shown as a calculated value rounded off to the first decimal place. * The values ​​are rounded to the second decimal place. * value and b * The values ​​shown are measured values ​​rounded to three decimal places. In Table 2, haze indicates a value obtained by rounding off the measured value to the first decimal place. In Table 2, gas generation amount indicates a value obtained by rounding off the measured value to the first decimal place. In Table 2, arithmetic mean roughness (Ra) indicates a value obtained by rounding off the measured value to the first decimal place. In Table 2, tensile breaking strength indicates a value obtained by rounding off the measured value to the first decimal place. In Table 2, tensile breaking elongation indicates a value obtained by rounding off the measured value to the first decimal place. In Table 2, Young's modulus indicates a value obtained by rounding off the measured value to the second decimal place. In Table 2, heat shrinkage indicates a value obtained by rounding off the measured value to the second decimal place. In Table 1, "*1" indicates the phosphorus element content.

[0185] [Table 1]

[0186] [Table 2]

[0187] As can be seen from the results in Table 2, the polyester films of Examples 1 to 5, which have Layer A containing the polyester resin (X) and the flame retardant (Y), can reduce the amount of carbon dioxide generated during incineration. Furthermore, the polyester films of Examples 1 to 5 did not show significant changes in basic properties such as transparency, surface properties, mechanical strength, and dimensional stability compared to the polyester film of Comparative Example 1, which did not contain flame retardant (Y), indicating that the flame retardant (Y) has little effect on the basic properties of the film.

[0188] Furthermore, although the polyester film of Example 2 and the polyester film of Example 3 have the same content of flame retardant (Y) in the polyester film, it is found that Example 3, which contains a larger amount of flame retardant (Y) in the surface layer, generates less carbon dioxide when incinerated. Therefore, it can be said that by including the flame retardant (Y) in at least one of the surface layers, the amount of carbon dioxide generated can be effectively reduced.

[0189] In addition, the polyester films of Examples 1 to 5 were L * Since the reflectance and spectral reflectance are equal to or greater than the predetermined values, the appearance is not blackened, and it is clear that the polyester film is excellent in appearance and design.

[0190] Furthermore, the polyester films of Examples 1 to 4 have a more suppressed odor during film formation and a reduced amount of gas generated during melting, which indicates that they are excellent in safety and recyclability. [Industrial Applicability]

[0191] The polyester film of the present invention has little effect on basic properties such as transparency, surface properties, mechanical strength, and dimensional stability, and can reduce the amount of carbon dioxide generated during incineration. It also has a high effect of suppressing blackening during molding, resulting in a polyester film with excellent appearance. Furthermore, it has a high effect of suppressing odor generation during heating, resulting in a polyester film with excellent safety. Therefore, the polyester film of the present invention can be used in a wide variety of fields, including magnetic recording materials, packaging materials, solar cell applications, separators for liquid crystal polarizers, substrates for dry film resists, and release films for forming green sheets for multilayer ceramic capacitors, as well as optical films such as antireflection films, diffusion sheets, and prism sheets, and films for label printing.

Claims

1. A polyester film having a layer A containing a polyester resin (X) and a flame retardant (Y), The phosphorus content in the polyester film is 50 to 10,000 ppm by mass, A polyester film that satisfies at least one of the following requirements (1) and (2): (1) L when made into a film equivalent to a total thickness of 500 μm ＊ The value is 95.5 or higher. (2) When made into a film equivalent to a total thickness of 500 μm, the spectral reflectance at a wavelength of 500 nm is 88.5% or more.

2. The polyester film according to claim 1, wherein the amount of carbon dioxide generated is 2,400 mg / g or less according to the <Method for measuring and calculating the amount of carbon dioxide generated> described below. <Method for measuring and calculating carbon dioxide emissions> Carbon dioxide generated from the polyester film under the following conditions is measured using a differential thermobalance-mass spectrometer, and the amount of carbon dioxide generated is calculated from the ion chromatogram peak area at m / z=44 and a calibration curve prepared from a standard sample. ・Heating conditions: temperature 25°C to 1000°C, speed 10°C / min Atmosphere: pseudo air (He + O ２ , He:80vol%, O ２ : 20 vol%) Gas flow rate: 300 mL / min ・Container: Pt cup ・MS settings: EMS 1mA, SEM 1200V, m / z≒10-410 (EI) ・Standard: calcium oxalate monohydrate Calibration curve: Prepared by two-point calibration from the ion chromatogram peak area (m / z=44) of the standard versus the theoretical amount of carbon dioxide generated.

3. 3. The polyester film according to claim 1, wherein the content of the flame retardant (Y) is 0.005 to 1 part by mass, as a phosphorus content in the polyester film, per 100 parts by mass of the polyester resin (X).

4. 3. The polyester film according to claim 1, wherein the reduction rate of carbon dioxide emission is 1% or more based on the following <Method for measuring and calculating carbon dioxide emission amount> and <Method for calculating reduction rate of carbon dioxide emission amount>. <Method for measuring and calculating carbon dioxide emissions> Carbon dioxide generated from the polyester film under the following conditions is measured using a differential thermobalance-mass spectrometer, and the amount of carbon dioxide generated is calculated from the ion chromatogram peak area at m / z=44 and a calibration curve prepared from a standard sample. ・Heating conditions: temperature 25°C to 1000°C, speed 10°C / min Atmosphere: pseudo air (He + O ２ , He:80vol%, O ２ : 20 vol%) Gas flow rate: 300 mL / min ・Container: Pt cup ・MS settings: EMS 1mA, SEM 1200V, m / z≒10-410 (EI) ・Standard: calcium oxalate monohydrate Calibration curve: Prepared by two-point calibration from the ion chromatogram peak area (m / z=44) of the standard versus the theoretical amount of carbon dioxide generated. <Calculation method for carbon dioxide emission reduction rate> The reduction rate (%) of carbon dioxide generation is calculated by the following formula using the amount of carbon dioxide generation (p1) generated from the polyester film according to claim 1 or 2 calculated by the above <Method for measuring and calculating the amount of carbon dioxide generation> and the amount of carbon dioxide generation (p0) generated from a polyester film having the same composition as the polyester film but not containing the flame retardant (Y). Carbon dioxide emission reduction rate (%) = {1 - (p1 ÷ p0)} x 100

5. The polyester film according to claim 1 or 2, wherein the flame retardant (Y) is a phosphorus compound having an aromatic ring.

6. The polyester film according to claim 1 or 2, wherein the flame retardant (Y) is a compound having a P═O bond.

7. The polyester film according to claim 1 , wherein the flame retardant (Y) comprises a compound having a structural unit represented by the following formula (1): 【Chemistry 1】 [In formula (1), n ​​is an integer, A is a divalent organic group, and Q １ and Q ２ is a divalent aromatic group, and Z is a group having an ester-forming functional group.

8. The polyester film according to claim 1 or 2, wherein the flame retardant (Y) comprises a compound having a structural unit represented by the following formula (9-1): 【Chemistry 2】 [In formula (9-1), n ​​is an integer of 2 to 40.]

9. 3. The polyester film according to claim 1, which has a flame retardancy of VTM-1 or less at a thickness of 38 μm in a UL94 vertical flame test in accordance with ASTM D4804.

10. 3. The polyester film according to claim 1, wherein the amount of gas generated is less than 9 μg / g based on peaks detected in a retention time range of 6 to 20 minutes by gas chromatography-mass spectrometry (GC-MS).

11. 3. The polyester film according to claim 1, wherein the amount of gas generated based on a peak derived from the flame retardant (Y) detected in a retention time range of 28 to 31 minutes by gas chromatography-mass spectrometry (GC-MS) is less than 2 μg / g.

12. The polyester film according to claim 1 or 2, wherein the polyester resin (X) comprises polyethylene terephthalate.

13. The polyester film according to claim 1 or 2, which is stretched in at least one direction.

14. 3. The polyester film according to claim 1, which has a laminate structure of at least three layers including a surface layer, an intermediate layer, and another surface layer.

15. The polyester film according to claim 14 , wherein both of the surface layers are the A layer.

16. 15. The polyester film according to claim 14, wherein at least one of the surface layers is the layer A, and the content of the flame retardant (Y) in the one surface layer is 50 to 13,000 ppm by mass, in terms of phosphorus content in the one surface layer.

17. 15. The polyester film according to claim 14, wherein at least one of the surface layers is the layer A, and the content of the flame retardant (Y) in the one surface layer, as expressed as a phosphorus content in the one surface layer, is 0.005 to 1.3 parts by mass per 100 parts by mass of the polyester resin (X).

18. A method for reducing the amount of carbon dioxide generated during incineration, using the polyester film according to claim 1 or 2.

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