Film for packaging material, packaging material, laminate, and method for producing film for packaging material

Abstract

To provide a polyester-based film capable of forming a packaging bag with excellent drop resistance.SOLUTION: The present invention relates to a film for packaging material at least comprising a polyester layer X and a polyester layer Y. The polyester layer X contains a copolyester (x) comprising a copolymer of a dicarboxylic acid component and a diol component, where the dicarboxylic acid component includes terephthalic acid and other dicarboxylic acids, and the diol component includes an alicyclic diol. The polyester layer Y contains a copolyester (y) comprising a copolymer of a dicarboxylic acid component and a diol component, where the dicarboxylic acid component includes terephthalic acid and other dicarboxylic acids, and the diol component includes an alicyclic diol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a film for packaging material, a packaging material, a laminate, and a method for producing a film for packaging material. [Background technology]

[0002] Polyester has excellent properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance and gas barrier properties, and is also readily available at a reasonable price, making it highly versatile and currently used in a wide range of applications including beverage and food containers and packaging materials, molded products and optical films.

[0003] In recent years, environmental problems such as global warming have become serious, and packaging materials such as packages are required to be reduced in volume, and recycling is being promoted to reuse used packaging materials as resources. In response to this, conventional packaging materials often use film laminates obtained by heat sealing or laminating a sealant film made mainly of polyethylene or polypropylene as the innermost layer to a biaxially oriented film as a base film. In such film laminates, various functions such as storage stability are imparted by combining multiple materials with different properties, but there is a problem that recycling after use is difficult.

[0004] For this reason, in recent years, polyester films in which sealing properties have been imparted to polyethylene terephthalate (PET) have been developed (for example, Patent Documents 1 and 2). In the examples of Patent Documents 1 and 2, EG (ethylene glycol), BD (1,4-butanediol), NPG (neopentyl glycol), CHDM (1,4-cyclohexanedimethanol), and DEG (diethylene glycol) are used as polyhydric alcohol components that are raw materials for polyester, respectively.

[0005] Patent Document 3 discloses a polyester resin for sealants in which 80 mol % or more of the carboxylic acid components are aromatic dicarboxylic acids, and the glycol components are 50 to 80 mol % of ethylene glycol, 3 to 20 mol % of neopentyl glycol, and 5 to 35 mol % of diethylene glycol, and a laminate obtained by laminating the same. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 175313 Brochure [Patent Document 2] Patent No. 6724447 [Patent Document 3] Japanese Patent Application Publication No. 10-139869 Summary of the Invention [Problem to be solved by the invention]

[0007] When a polyester film is used as a packaging material, the polyester film is required to have not only heat seal strength but also film strength against impact, dropping, etc. In particular, when the polyester film is used for a pouch product, the polyester film is required to have excellent drop resistance. However, conventional polyester films do not have sufficient drop resistance, and further improvement is required.

[0008] Therefore, in order to solve such problems of the conventional technology, the present inventors have carried out studies with the aim of providing a polyester film capable of forming a packaging bag having excellent drop resistance. [Means for solving the problem]

[0009] Examples of specific embodiments of the present invention are given below.

[0010] [1] A packaging film having at least a polyester layer X and a polyester layer Y, The polyester layer X contains a copolymer polyester (x) composed of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol; A packaging film, wherein the polyester layer Y contains a copolymer polyester (y) consisting of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component containing terephthalic acid and other dicarboxylic acids, and the diol component containing an alicyclic diol. [2] The packaging film according to [1], wherein the heat seal strength when the polyester layers X are sealed together under conditions of 140°C, 0.2 MPa, and 1 second is 15 N / 15 mm or more. [3] The film for packaging materials according to [1] or [2], which has a breaking point displacement of 9.1 mm or more in a hydroshot test. [4] The film for packaging materials according to any one of [1] to [3], which has an impact energy of more than 0.5 J in a hydroshot test. [5] The film for packaging materials according to any one of [1] to [4], wherein the diol component of the copolymer polyester (x) further contains ethylene glycol. [6] The film for packaging materials according to any one of [1] to [5], wherein the other dicarboxylic acid of the copolymer polyester (x) contains isophthalic acid. [7] The film for packaging materials according to any one of [1] to [6], wherein the alicyclic diol of the copolymerized polyester (x) is at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. [8] The film for packaging materials according to any one of [1] to [7], wherein the diol component of the copolymer polyester (y) further contains ethylene glycol. [9] The film for packaging materials according to any one of [1] to [8], wherein the other dicarboxylic acid of the copolymer polyester (y) contains isophthalic acid.

[10] The film for packaging materials according to any one of [1] to [9], wherein the alicyclic diol of the copolymerized polyester (y) is at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol.

[11] The polyester layer X comprises a copolymer polyester (x-1) composed of a copolymer of a dicarboxylic acid component and a diol component and a copolymer polyester (x-2) composed of a copolymer of a dicarboxylic acid component and a diol component, The film for packaging material according to any one of [1] to

[10] , wherein a dicarboxylic acid component constituting the copolymer polyester (x-1) contains terephthalic acid and another dicarboxylic acid, and a diol component constituting the copolymer polyester (x-2) contains an alicyclic diol.

[12] The film for packaging materials according to

[11] , wherein the other dicarboxylic acid of the copolymer polyester (x-1) contains isophthalic acid.

[13] The polyester layer Y comprises a copolymer polyester (y-1) composed of a copolymer of a dicarboxylic acid component and a diol component and a copolymer polyester (y-2) composed of a copolymer of a dicarboxylic acid component and a diol component, The film for packaging material according to any one of [1] to

[12] , wherein a dicarboxylic acid component constituting the copolymer polyester (y-1) contains terephthalic acid and another dicarboxylic acid, and a diol component constituting the copolymer polyester (y-2) contains an alicyclic diol.

[14] The film for packaging materials according to

[13] , wherein the other dicarboxylic acid of the copolymer polyester (y-1) contains isophthalic acid.

[15] The film for packaging materials according to any one of [1] to

[14] , further comprising a polyester layer Z.

[16] The packaging film according to

[15] , wherein the polyester layer Z contains homopolyethylene terephthalate (z) as a main component resin.

[17] The film for packaging materials according to

[15] or

[16] , having a polyester layer X, a polyester layer Y and a polyester layer Z in this order.

[18] The film for packaging materials according to any one of [1] to

[17] , wherein the total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is 2 to 40 mol %.

[19] The film for packaging materials according to any one of [1] to

[18] , wherein the total content of the other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is 2 to 35 mol %.

[20] The film for packaging materials according to any one of [1] to

[19] , wherein the total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 1 to 25 mol %.

[21] The film for packaging materials according to any one of [1] to

[20] , wherein the total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer Y is 1 to 25 mol %.

[22] The film for packaging material according to any one of [1] to

[21] , further comprising particles, the content of the particles being 20 to 2000 ppm by mass relative to the total mass of the film for packaging material.

[23] The film for packaging materials according to any one of [1] to

[22] , wherein the polyester layer X further contains particles, and the content of the particles is 100 to 3000 ppm by mass with respect to the total mass of the polyester layer X.

[24] The total content (mol%) of the total alicyclic diol unit content (mol%) relative to the total diol units in the entire polyester contained in the polyester layer X and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units in the entire polyester contained in the polyester layer X is P, When the total content (mol%) of the alicyclic diol unit relative to the total diol units in the entire polyester contained in the polyester layer Y and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units in the entire polyester contained in the polyester layer Y is Q, The film for packaging material according to any one of [1] to

[23] , wherein P≧Q.

[25] The film for packaging materials according to

[24] , having a PQ value of 4 to 30 mol%.

[26] The film for packaging materials according to

[24] or

[25] , having a P / Q value of 1.1 to 3.5.

[27] The film for packaging materials according to any one of [1] to

[26] , wherein the content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer X is 1.1 to 5, wherein the content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y is 1.1 to 5.

[28] The film for packaging materials according to any one of [1] to

[27] , wherein the content (mol %) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X is 1.1 to 5, wherein the content (mol %) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is 1.1 to 5.

[29] The film for packaging materials according to any one of [1] to

[28] , wherein a content (mol %) of alicyclic diol units in all diol units in all polyesters contained in the polyester layer X is divided by a content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in the polyester layer X, and the value is 1 to 5.

[30] The film for packaging materials according to any one of [1] to

[29] , wherein the content (mol %) of alicyclic diol units in all diol units in all polyesters contained in the polyester layer Y is 0.5 to 3, wherein the content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in the polyester layer Y is 0.5 to 3.

[31] A film for packaging material, comprising a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, The dicarboxylic acid component includes terephthalic acid and other dicarboxylic acids, and the diol component includes an alicyclic diol; The total content (mol%) of the alicyclic diol unit relative to the total diol units in the entire polyester and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units contained in the region from one side of the film to 50% of the entire thickness is A packaging film having a content (mol%) of alicyclic diol units relative to all diol units in all polyester and a content (mol%) of other dicarboxylic acid units relative to all dicarboxylic acid units contained in the region from the other side of the film through 50% of the overall thickness.

[32] The packaging film according to

[31] , wherein the total content (mol%) of the alicyclic diol units relative to the total diol units in all polyester and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units increases continuously from one side of the film to the other side of the film.

[33] The film for packaging materials according to any one of

[15] to

[30] , further comprising a barrier layer on the polyester layer Z.

[34] A packaging material having the film for packaging material according to any one of [1] to

[33] .

[35] A laminate having the film for packaging material according to any one of [1] to

[33] .

[36] A packaging material having the laminate according to

[35] .

[37] A method for producing a packaging film having at least a polyester layer X and a polyester layer Y, comprising the steps of: The polyester layer X contains a copolymer polyester (x) composed of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol; The polyester layer Y contains a copolymer polyester (y) composed of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acid components, and the diol component contains an alicyclic diol; A step of laminating a resin composition constituting the polyester layer X and the polyester layer Y and stretching the resin composition; The stretching step is followed by a heat setting step, A method for producing a packaging film, in which the heat setting temperature in the step of heat setting is 200°C or higher and lower than 250°C.

[38] The method for producing a packaging film according to

[37] , wherein the heat setting temperature in the step of performing heat setting is 220°C or higher and 235°C or lower. Effect of the Invention

[0011] According to the present invention, a polyester film capable of forming a packaging bag having excellent drop resistance can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below. The following description may be based on a representative embodiment or a specific example, but the present invention is not limited to such an embodiment. In this specification, when "X to Y" (X and Y are any numbers) is expressed, it includes "X or more and Y or less" as well as "preferably greater than X" or "preferably smaller than Y" unless otherwise specified. In addition, when "X or more" (X is any number) or "Y or less" (Y is any number) is expressed, it also includes "preferably greater than X" or "preferably less than Y". In the following description, "film" and "sheet" are not clearly distinguished from each other, and when "film" is referred to, it includes "sheet", and when "sheet" is referred to, it includes "film".

[0013] (Polyester film) The first embodiment of the present invention relates to a polyester film having at least a polyester layer X and a polyester layer Y (hereinafter, also referred to as "the polyester film"). Here, the polyester layer X contains a copolymer polyester (x) consisting of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol. The polyester layer Y contains a copolymer polyester (y) consisting of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol. The polyester film is preferably a film for packaging materials.

[0014] The second embodiment of the present invention relates to a polyester film (hereinafter also referred to as "the polyester film") comprising a copolymerized polyester consisting of a copolymer of a dicarboxylic acid component and a diol component, in which the dicarboxylic acid component comprises terephthalic acid and other dicarboxylic acids, the diol component comprises an alicyclic diol, and the total content (mol%) of the alicyclic diol unit relative to the total diol units in the entire polyester contained in the region from one side of the film to 50% of the entire thickness and the content (mol%) of the other dicarboxylic acid unit relative to the total dicarboxylic acid unit is higher than the total content (mol%) of the alicyclic diol unit relative to the total diol units in the entire polyester contained in the region from the other side of the film to 50% of the entire thickness. In the second embodiment, the polyester film may be a single-layer film. The total content (mol%) of the copolymerization components (other dicarboxylic acid components and alicyclic diol components) changes in the thickness direction of the single-layer film. The polyester film in the second embodiment is also preferably a film for packaging materials.

[0015] In the second embodiment, it is preferable that the total content (mol%) of the alicyclic diol unit relative to the total diol unit in the entire polyester and the content (mol%) of the other dicarboxylic acid unit relative to the total dicarboxylic acid unit increases continuously from one side to the other side of the film. For example, the total content (mol%) of the copolymerization components (other dicarboxylic acid components and alicyclic diol components) may be 0 mol% on one side of the film, but the total content (mol%) of the copolymerization components (other dicarboxylic acid components and alicyclic diol components) increases continuously to about 10 to 50 mol% on the other side of the film. In this specification, the term "continuously increasing" means that the total content (mol%) of the polymerization components (other dicarboxylic acid components and alicyclic diol components) increases at a substantially constant rate in the thickness direction. For example, when the film is divided into 10 layers in the thickness direction, a stepwise increase in the total content (mol%) of the copolymerization components (other dicarboxylic acid components and alicyclic diol components) in each of the 10 divided layers is also included in "continuously increasing". In the second embodiment, the surface side having a higher total content (mol%) of the copolymerization components (other dicarboxylic acid components and alicyclic diol components) exhibits excellent heat sealability.

[0016] In the first and second embodiments of the present invention, since the polyester-based film has the above-mentioned structure, a packaging bag having excellent drop resistance can be formed. Furthermore, since the polyester-based film has the above-mentioned structure, it exhibits excellent heat sealability. In addition, since all of the resin components constituting the polyester-based film can be polyester materials, it is easy to realize a packaging material made of a single material and a single sheet (single layer). Therefore, the polyester-based film has excellent recyclability.

[0017] The polyester film may be a non-stretched film (sheet) or a stretched film. Of these, a uniaxially or biaxially stretched film is preferred. Of these, a biaxially stretched film is preferred in terms of excellent balance of mechanical properties and flatness.

[0018] The polyester film may contain optional components in addition to polyester. Examples of optional components include particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers. Among them, the polyester film preferably contains particles, and more preferably contains inorganic particles. Examples of inorganic particles include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide. By including particles in the polyester film, it is possible to impart slipperiness to the polyester film and prevent scratches in each process. The content of the particles is preferably 20 ppm by mass or more, more preferably 50 ppm by mass or more, and even more preferably 100 ppm by mass or more, based on the total mass of the polyester film. The content of the particles is preferably 2000 ppm by mass or less, more preferably 1800 ppm by mass or less, even more preferably 1650 ppm by mass or less, and particularly preferably 1500 ppm by mass or less, based on the total mass of the polyester film.

[0019] <Polyester layer X> In the first embodiment, the polyester film has a polyester layer X. The polyester layer X is a layer having heat sealability and functions as a sealing layer. The sealing layer becomes the innermost layer when forming a packaging bag, for example.

[0020] The polyester layer X contains a copolymer polyester (x) made of a copolymer of a dicarboxylic acid component and a diol component. Among the components constituting the copolymer polyester (x), the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol.

[0021] In this specification, the term "copolymerized polyester consisting of a copolymer of a dicarboxylic acid component and a diol component" means a copolymerized polyester obtained by copolymerizing one dicarboxylic acid component and one diol component as well as a copolymerization component. In other words, it means a polyester obtained by copolymerizing two or more dicarboxylic acid components and one diol component, one dicarboxylic acid component and two or more diol components, or two or more dicarboxylic acid components and two or more diol components. When the copolymerized polyester contains two or more dicarboxylic acid components, the dicarboxylic acid components other than the dicarboxylic acid component with the highest content among the dicarboxylic acid components are referred to as "other dicarboxylic acids" or "dicarboxylic acid copolymerization components", and when the copolymerized polyester contains two or more diol components, the diol components other than the diol component with the highest content among the diol components are referred to as "other diols" or "diol copolymerization components".

[0022] The polyester layer X may contain only the copolymer polyester (x) as a resin, or may contain a copolymer polyester other than the copolymer polyester (x), or may further contain a homopolyester, or may further contain "other components" as necessary.

[0023] The thickness of the polyester layer X is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the polyester layer X is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The thickness of the polyester layer X is preferably 10 to 30% and more preferably 15 to 25% of the total thickness of the polyester film.

[0024] (Copolymer polyester (x)) The copolymer polyester (x) is a copolymer of a dicarboxylic acid component and a diol component, and the copolymer polyester (x) is not particularly limited as long as it has a terephthalic acid unit, another dicarboxylic acid unit, and an alicyclic diol unit. For example, the copolymer polyester (x) may be a copolymer of terephthalic acid, another dicarboxylic acid, and an alicyclic diol, or may be a blend of a copolymer containing terephthalic acid and another dicarboxylic acid and a copolymer containing terephthalic acid and an alicyclic diol. In this specification, the other dicarboxylic acid is a dicarboxylic acid other than terephthalic acid.

[0025] Examples of other dicarboxylic acids contained in the copolymer polyester (x) as a dicarboxylic acid component include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, eicosanoic acid, and derivatives thereof; alicyclic dicarboxylic acids or dimer acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, and cyclooctanedicarboxylic acid. Among them, the other dicarboxylic acids are preferably adipic acid, sebacic acid, dimer acid, and isophthalic acid, more preferably aromatic dicarboxylic acids, and even more preferably isophthalic acid. The "other dicarboxylic acids" may be one type or a combination of two or more types.

[0026] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is preferably 2 mol% or more, more preferably 3 mol% or more, even more preferably 4 mol% or more, and particularly preferably 5 mol% or more. The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is preferably 35 mol% or less, more preferably 30 mol% or less, even more preferably 25 mol% or less, even more preferably 20 mol% or less, and particularly preferably 18 mol% or less. The "total content of other dicarboxylic acid units" refers to the total amount of two or more other dicarboxylic acids when two or more other dicarboxylic acids are used in combination with terephthalic acid.

[0027] The content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is preferably 65 mol% or more, more preferably 70 mol% or more, even more preferably 75 mol% or more, even more preferably 80 mol% or more, and particularly preferably 82 mol% or more. The content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is preferably 98 mol% or less, more preferably 97 mol% or less, even more preferably 96 mol% or less, and particularly preferably 95 mol% or less.

[0028] Examples of the alicyclic diol constituting the copolymerized polyester (x) include cyclohexanediols such as 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol; cyclohexanedimethanols such as 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; norbornane dimethanols such as 2,3-norbornane dimethanol and 2,5-norbornane dimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalin dimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among them, the alicyclic diol is preferably a cyclohexanediol or a cyclohexanedimethanol, and is preferably at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. Among these, 1,4-cyclohexanedimethanol in which the methylol group is at the para position is particularly preferred from the viewpoint of excellent stability.

[0029] Examples of the diol components other than the alicyclic diol in the diol components constituting the copolymerized polyester (x) (hereinafter, also referred to as "other diol components") include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, neopentyl glycol, bisphenol, and derivatives thereof may also be used. These diol components may be used alone or in combination. Among them, the diol component other than the alicyclic diol is preferably ethylene glycol, and the copolymerized polyester (x) preferably contains an ethylene glycol unit and an alicyclic diol unit as diol-derived units. When the copolymer polyester (x) contains ethylene glycol units and alicyclic diol units, the polymerization stability of the copolymer polyester and the heat resistance and strength of the polyester film tend to be improved.

[0030] In addition, when polyester is usually produced (polycondensed) using ethylene glycol as one of the raw materials, a part of the ethylene glycol is modified to become diethylene glycol, which is introduced into the polyester skeleton. This diethylene glycol is called "by-product diethylene glycol", and the amount of the by-product varies depending on the type of polycondensation (ester exchange method, direct polycondensation), etc., but is about 1 to 5 mol% of the ethylene glycol. Therefore, in the present invention, 5 mol% or less of diethylene glycol in 100 mol% of the diol component constituting the polyester (including copolymer polyester) using ethylene glycol as one of the raw materials is included in ethylene glycol.

[0031] The total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is preferably 2 mol% or more, more preferably 4 mol% or more, even more preferably 6 mol% or more, even more preferably 8 mol% or more, and particularly preferably 10 mol% or more. The total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, and even more preferably 26 mol% or less. When two or more alicyclic diols are used in combination, the "total content of alicyclic diol units" refers to the total amount of two or more alicyclic diols. By setting the content of alicyclic diol units contained in the polyester layer X within the above range, the drop resistance and seal strength of the polyester film are improved, and the heat resistance and film strength are easily maintained.

[0032] The total content of diol units other than alicyclic diols relative to all diol units in all polyesters contained in polyester layer X is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more. The total content of diol units other than alicyclic diols relative to all diol units in all polyesters contained in polyester layer X is preferably 98 mol% or less, more preferably 96 mol% or less, even more preferably 94 mol% or less, even more preferably 92 mol% or less, and particularly preferably 90 mol% or less. By setting the content of diol units other than alicyclic diols contained in polyester layer X within the above range, it is easy to improve the drop resistance and seal strength of the polyester film.

[0033] In this embodiment, the content (mol %) of alicyclic diol units in all diol units in all polyesters contained in polyester layer X divided by the content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in polyester layer X is preferably 1 to 5, more preferably 1.1 to 4, even more preferably 1.2 to 3.7, and particularly preferably 1.3 to 3.5. By setting the relationship between the contents of alicyclic diol units and other dicarboxylic acid units contained in polyester layer X within the above range, it becomes easier to improve the seal strength while increasing the drop resistance of the polyester film.

[0034] The copolymer polyester (x) in which an alicyclic diol is copolymerized has a high intrinsic viscosity (IV), and thus it is easy to achieve both excellent mechanical properties and good film-forming properties. For example, the intrinsic viscosity of the copolymer polyester (x) is preferably 0.66 to 0.86 dL / g, and more preferably 0.68 to 0.84 dL / g. The intrinsic viscosity of the copolymer polyester (x) is preferably higher than that of a general homopolyester, and specifically, is preferably 0.03 to 0.25 dL / g higher, and more preferably 0.05 to 0.22 dL / g higher.

[0035] In particular, the copolymerized polyester (x) in which an alicyclic diol such as 1,4-cyclohexanedimethanol (CHDM) is copolymerized has multiple conformations, and therefore, when it is subjected to an impact, the conformational change of cyclohexane occurs, so that the impact energy is absorbed and the molecular chain is less likely to break, and this allows the polyester film to exhibit excellent drop resistance. In addition, other dicarboxylic acids such as isophthalic acid (IPA) can increase the seal strength of the film. The copolymerized polyester (x) in which an alicyclic diol such as 1,4-cyclohexanedimethanol (CHDM) is copolymerized has good compatibility with polyesters in which other dicarboxylic acids other than terephthalic acid such as isophthalic acid (IPA) are copolymerized, so that the film forming property is good and the occurrence of delamination is suppressed, and as a result, it becomes easier to achieve both seal strength and drop resistance. For this reason, by blending an alicyclic diol and other dicarboxylic acid at a predetermined concentration as the copolymerization component, it becomes possible to improve the seal strength while increasing the drop resistance.

[0036] (Copolymer polyester (x-1) / Copolymer polyester (x-2)) The polyester layer X may contain two or more kinds of copolymer polyesters instead of the copolymer polyester (x). In this case, the polyester layer X may contain, for example, a copolymer polyester (x-1) consisting of a copolymer of a dicarboxylic acid component and a diol component, and a copolymer polyester (x-2) consisting of a copolymer of a dicarboxylic acid component and a diol component. Here, the dicarboxylic acid component constituting the copolymer polyester (x-1) contains terephthalic acid and other dicarboxylic acids, and the diol component constituting the copolymer polyester (x-2) contains an alicyclic diol. More specifically, the polyester layer X preferably contains a copolymer polyester (x-1) which is a copolymer of terephthalic acid, other dicarboxylic acids, and a diol component, and a copolymer polyester (x-2) which is a copolymer of terephthalic acid, an alicyclic diol, and other diol components.

[0037] The copolymer polyester (x-1) contains terephthalic acid units, other dicarboxylic acid units, and diol units. In this embodiment, the diol units in the copolymer polyester (x-1) are units derived from diols other than alicyclic diols. Examples of the other dicarboxylic acids in the copolymer polyester (x-1) include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples of the other dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, eicosanoic acid, and derivatives thereof; and alicyclic dicarboxylic acids or dimer acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, and cyclooctanedicarboxylic acid. Among them, it is preferable that the copolymer polyester (x-1) contains isophthalic acid as the other dicarboxylic acid unit. That is, the copolymer polyester (x-1) preferably has terephthalic acid units, isophthalic acid units, and one kind of diol (excluding alicyclic diol) units.

[0038] Examples of the diol component in the copolymer polyester (x-1) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, neopentyl glycol, bisphenol, and derivatives thereof may also be used. Among them, it is preferable that the copolymer polyester (x-1) contains ethylene glycol as a diol component. That is, it is particularly preferable that the copolymer polyester (x-1) has a terephthalic acid unit, an isophthalic acid unit, and an ethylene glycol unit.

[0039] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in the copolymer polyester (x-1) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more. The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in the copolymer polyester (x-1) is preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 42 mol% or less. On the other hand, in the copolymer polyester (x-1), the content of terephthalic acid units relative to the total dicarboxylic acid units is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 58 mol% or more. Also, in the copolymer polyester (x-1), the content of terephthalic acid relative to the content of terephthalic acid units (100 mol%) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less.

[0040] The copolymer polyester (x-2) contains an alicyclic diol unit. In this embodiment, the diol unit in the copolymer polyester (x-2) preferably contains other diol units (excluding alicyclic diols) in addition to the alicyclic diol units. In particular, the copolymer polyester (x-2) preferably contains one kind of dicarboxylic acid unit, an alicyclic diol unit, and other diol units (excluding alicyclic diols).

[0041] Examples of the alicyclic diol constituting the copolymer polyester (x-2) include cyclohexanediols such as 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol; cyclohexanedimethanols such as 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; norbornane dimethanols such as 2,3-norbornane dimethanol and 2,5-norbornane dimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalin dimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among them, the alicyclic diol is preferably a cyclohexanediol or a cyclohexanedimethanol, and is preferably at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. Among these, 1,4-cyclohexanedimethanol in which the methylol group is at the para position is particularly preferred from the viewpoint of excellent stability.

[0042] The other diol constituting the copolymer polyester (x-2) may be the diol constituting the copolymer polyester (x-1). Among them, the other diol constituting the copolymer polyester (x-2) is preferably ethylene glycol.

[0043] The one dicarboxylic acid constituting the copolymer polyester (x-2) may be an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, or diphenyldicarboxylic acid. Among them, the one dicarboxylic acid constituting the copolymer polyester (x-2) is preferably terephthalic acid. That is, the copolymer polyester (x-2) more preferably contains terephthalic acid units, alicyclic diol units, and ethylene glycol units, and particularly preferably contains terephthalic acid units, 1,4-cyclohexanedimethanol units, and ethylene glycol units.

[0044] The total content of alicyclic diol units relative to all diol units in the copolymer polyester (x-2) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more. The total content of alicyclic diol units relative to all diol units in the copolymer polyester (x-2) is preferably 50 mol% or less, more preferably 45 mol% or less, even more preferably 40 mol% or less, and even more preferably 37 mol% or less. On the other hand, in the copolymer polyester (x-2), the content of other diol units relative to the total diol units is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, and even more preferably 63 mol% or more. Also, in the copolymer polyester (x-2), the content of other diol units relative to the total diol units is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, even more preferably 80 mol% or less, and particularly preferably 75 mol% or less.

[0045] The content of the copolymer polyester (x-1) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the total polyester contained in the polyester layer X. The content of the copolymer polyester (x-1) is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, and particularly preferably 60% by mass or less, based on the total polyester contained in the polyester layer X. The content of the copolymer polyester (x-2) is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, based on the total polyester contained in the polyester layer X. The content of the copolymer polyester (x-2) is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less, based on the total polyester contained in the polyester layer X.

[0046] The intrinsic viscosity of the copolymer polyester (x-1) is preferably 0.6 dL / g or more, more preferably 0.63 dL / g or more, and even more preferably 0.65 dL / g or more. The upper limit of the intrinsic viscosity of the copolymer polyester (x-1) is not particularly limited, but is preferably 0.83 dL / g or less, more preferably 0.8 dL / g or less, even more preferably 0.76 dL / g or less, and even more preferably 0.73 dL / g or less.

[0047] The intrinsic viscosity of the copolymer polyester (x-2) is preferably 0.7 dL / g or more, more preferably 0.75 dL / g or more, even more preferably 0.77 dL / g or more, and even more preferably 0.8 dL / g or more. The upper limit of the intrinsic viscosity of the copolymer polyester (x-2) is not particularly limited, but is preferably 1 dL / g or less, more preferably 0.95 dL / g or less, even more preferably 0.9 dL / g or less, and even more preferably 0.86 dL / g or less.

[0048] The polyester layer X may contain a copolymer polyester other than the copolymer polyester (x-1) and the copolymer polyester (x-2), or a homopolyester. In particular, the polyester layer X preferably contains a homopolyester in addition to the copolymer polyester (x-1) and the copolymer polyester (x-2). Here, the term "homopolyester" refers to a polyester obtained by polycondensation of one kind of dicarboxylic acid component and one kind of diol component. In this embodiment, the homopolyester is preferably homopolyethylene terephthalate (also simply referred to as "polyethylene terephthalate"). In this case, the homopolyethylene terephthalate may also contain 1 to 5 mol% of by-product diethylene glycol, and even in such a case, it is included in the homopolyethylene terephthalate.

[0049] When the polyester layer X contains a homopolyester, the content of the homopolyester is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, based on the total polyester contained in the polyester layer X. Moreover, the content of the homopolyester is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the total polyester contained in the polyester layer X.

[0050] (optional ingredient) The polyester layer X may contain optional components other than those described above, as necessary. Examples of the optional components include particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0051] Among them, the polyester layer X preferably contains particles, and more preferably contains inorganic particles. Examples of inorganic particles include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide. The polyester film contains particles, which can impart slipperiness to the polyester film and prevent scratches in each process. The content of the particles is preferably 100 ppm by mass or more, more preferably 300 ppm by mass or more, and even more preferably 500 ppm by mass or more, based on the total mass of the polyester layer X. The content of the particles is preferably 3000 ppm by mass or less, more preferably 2700 ppm by mass or less, even more preferably 2500 ppm by mass or less, and particularly preferably 2300 ppm by mass or less, based on the total mass of the polyester film.

[0052] <Polyester layer Y> In the first embodiment, the polyester film is a laminated film having a polyester layer Y on one side of a polyester layer X that can function as a sealing layer, as described above. When the polyester film is composed of two layers, polyester layer X and polyester layer Y, polyester layer Y is the layer that is on the opposite side to the contents, i.e., the outer side, when the polyester film is used as a packaging material, etc. Also, when the polyester film is composed of three layers, polyester layer X, polyester layer Y, and polyester layer Z, as described later, polyester layer Y is preferably an intermediate layer.

[0053] The polyester layer Y contains a copolymer polyester (y) made of a copolymer of a dicarboxylic acid component and a diol component. Among the components constituting the copolymer polyester (y), the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol.

[0054] The polyester layer Y may consist of only the copolymer polyester (y), or may contain a copolymer polyester other than the copolymer polyester (y), or may further contain a homopolyester, or may further contain "other components" as necessary.

[0055] The thickness of the polyester layer Y is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The thickness of the polyester layer Y is preferably 150 μm or less, more preferably 120 μm or less, even more preferably 100 μm or less, even more preferably 70 μm or less, and particularly preferably 50 μm or less. The thickness of the polyester layer Y is preferably 40 to 80% of the total thickness of the polyester film.

[0056] (Copolymer polyester (y)) The copolymer polyester (y) is a copolymer of a dicarboxylic acid component and a diol component, and the copolymer polyester (y) is not particularly limited as long as it has a terephthalic acid unit, another dicarboxylic acid unit, and an alicyclic diol unit. For example, the copolymer polyester (y) may be a copolymer of terephthalic acid, another dicarboxylic acid, and an alicyclic diol, or may be a blend of a copolymer containing terephthalic acid and another dicarboxylic acid and a copolymer containing terephthalic acid and an alicyclic diol. In this specification, the other dicarboxylic acid is a dicarboxylic acid other than terephthalic acid.

[0057] Examples of other dicarboxylic acids contained in the copolymer polyester (y) as a dicarboxylic acid component include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, eicosanoic acid, and derivatives thereof; alicyclic dicarboxylic acids or dimer acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, and cyclooctanedicarboxylic acid. Among them, adipic acid, sebacic acid, dimer acid, and isophthalic acid are preferable, aromatic dicarboxylic acids are more preferable, and isophthalic acid is even more preferable. The "other dicarboxylic acids" may be one type or a combination of two or more types.

[0058] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 0.5 mol% or more, more preferably 1 mol% or more, even more preferably 2 mol% or more, and particularly preferably 3 mol% or more. The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and even more preferably 13 mol% or less. The "total content of other dicarboxylic acid units" refers to the total amount of two or more other dicarboxylic acids when two or more other dicarboxylic acids are used in combination with terephthalic acid.

[0059] The content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 70 mol% or more, more preferably 75 mol% or more, even more preferably 80 mol% or more, and even more preferably 85 mol% or more. The content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 99.5 mol% or less, more preferably 99 mol% or less, even more preferably 98 mol% or less, and even more preferably 97 mol% or less.

[0060] Examples of the alicyclic diol constituting the copolymerized polyester (y) include cyclohexanediols such as 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol; cyclohexanedimethanols such as 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; norbornane dimethanols such as 2,3-norbornane dimethanol and 2,5-norbornane dimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalin dimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among them, the alicyclic diol is preferably a cyclohexanediol or a cyclohexanedimethanol, and is preferably at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. Among these, 1,4-cyclohexanedimethanol in which the methylol group is at the para position is particularly preferred from the viewpoint of excellent stability.

[0061] Examples of the diol component other than the alicyclic diol in the diol component constituting the copolymerized polyester (y) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, neopentyl glycol, bisphenol, and derivatives thereof may also be used. These diol components can be used alone or in combination. Among them, the diol component other than the alicyclic diol is preferably ethylene glycol, and the copolymerized polyester (y) preferably contains an ethylene glycol unit and an alicyclic diol unit as a diol-derived unit. When the copolymer polyester (y) contains ethylene glycol units and alicyclic diol units, the polymerization stability of the copolymer polyester and the heat resistance and strength of the polyester film tend to be improved.

[0062] In addition, when polyester is usually produced (polycondensed) using ethylene glycol as one of the raw materials, a part of the ethylene glycol is modified to become diethylene glycol, which is introduced into the polyester skeleton. This diethylene glycol is called "by-product diethylene glycol", and the amount of the by-product varies depending on the type of polycondensation (ester exchange method, direct polycondensation), etc., but is about 1 to 5 mol% of the ethylene glycol. Therefore, in the present invention, 5 mol% or less of diethylene glycol in 100 mol% of the diol component constituting the polyester (including copolymer polyester) using ethylene glycol as one of the raw materials is included in ethylene glycol.

[0063] The total content of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y is preferably 1 mol% or more, more preferably 2 mol% or more, even more preferably 3 mol% or more, even more preferably 4 mol% or more, and particularly preferably 5 mol% or more. The total content of alicyclic diol units relative to all diols in all polyesters contained in polyester layer Y is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and even more preferably 13 mol% or less. When two or more alicyclic diols are used in combination, the "total content of alicyclic diol units" refers to the total amount of two or more alicyclic diols.

[0064] The total content of diol units other than alicyclic diols relative to all diol units in all polyesters contained in polyester layer Y is preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, and even more preferably 87 mol% or more. The total content of diol units other than alicyclic diols relative to all diol units in all polyesters contained in polyester layer Y is preferably 99 mol% or less, more preferably 98 mol% or less, even more preferably 97 mol% or less, even more preferably 96 mol% or less, and particularly preferably 95 mol% or less.

[0065] The content (mol %) of alicyclic diol units in all diol units in all polyesters contained in the polyester layer Y divided by the content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in the polyester layer Y is preferably 0.5 to 3, more preferably 0.8 to 2.5, even more preferably 1 to 2.2, and even more preferably 1.2 to 2. By setting the relationship between the contents of alicyclic diol units and other dicarboxylic acid units contained in the polyester layer Y within the above range, it becomes easier to improve the seal strength while increasing the drop resistance of the polyester film.

[0066] The copolymerized polyester (y) in which an alicyclic diol is copolymerized has a relatively high intrinsic viscosity (IV), and it is easy to achieve both excellent mechanical properties and good film-forming properties. For example, the intrinsic viscosity of the copolymerized polyester (y) is preferably 0.66 to 0.86 dL / g, and more preferably 0.68 to 0.84 dL / g. The intrinsic viscosity of the copolymerized polyester (y) is preferably higher than that of a general homopolyester, specifically, it is preferably 0.03 to 0.25 dL / g higher, and more preferably 0.05 to 0.22 dL / g higher.

[0067] In particular, polyester (y) copolymerized with cyclohexanedimethanol has multiple conformations, and when it is impacted, the conformational change of cyclohexane occurs, absorbing the impact energy and making it difficult for the molecular chain to break, which allows the polyester film to exhibit excellent drop resistance. Polyesters copolymerized with alicyclic diols such as 1,4-cyclohexanedimethanol (CHDM) and polyesters copolymerized with dicarboxylic acids other than terephthalic acid such as isophthalic acid (IPA) have good compatibility, which improves film formability and suppresses the occurrence of interlayer peeling, making it easier to achieve both interlayer adhesion and drop resistance.

[0068] (Copolymer polyester (y-1) / Copolymer polyester (y-2)) The polyester layer Y may contain two or more kinds of copolymer polyesters instead of the copolymer polyester (y). In this case, the polyester layer Y may contain, for example, a copolymer polyester (y-1) consisting of a copolymer of a dicarboxylic acid component and a diol component, and a copolymer polyester (y-2) consisting of a copolymer of a dicarboxylic acid component and a diol component. Here, the dicarboxylic acid component constituting the copolymer polyester (y-1) contains terephthalic acid and other dicarboxylic acids, and the diol component constituting the copolymer polyester (y-2) contains an alicyclic diol. More specifically, the polyester layer Y preferably contains a copolymer polyester (y-1) which is a copolymer of terephthalic acid, other dicarboxylic acids, and a diol component, and a copolymer polyester (y-2) which is a copolymer of terephthalic acid, an alicyclic diol, and other diol components.

[0069] The copolymer polyester (y-1) contains terephthalic acid units, other dicarboxylic acid units, and diol units. In this embodiment, the diol units in the copolymer polyester (y-1) are units derived from diols other than alicyclic diols. Examples of other dicarboxylic acids in the copolymer polyester (y-1) include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples of such other dicarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, eicosanoic acid, and derivatives thereof; and alicyclic dicarboxylic acids or dimer acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, and cyclooctanedicarboxylic acid. Among these, it is preferable that the copolymer polyester (y-1) contains isophthalic acid as the other dicarboxylic acid unit. That is, the copolymer polyester (y-1) preferably has terephthalic acid units, isophthalic acid units, and one kind of diol (excluding alicyclic diol) units.

[0070] Examples of the diol component in the copolymer polyester (y-1) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, neopentyl glycol, bisphenol, and derivatives thereof may also be used. Among them, it is preferable that the copolymer polyester (y-1) contains ethylene glycol as a diol component. That is, it is particularly preferable that the copolymer polyester (y-1) has a terephthalic acid unit, an isophthalic acid unit, and an ethylene glycol unit.

[0071] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in the copolymer polyester (y-1) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more. The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in the copolymer polyester (y-1) is preferably 42 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less. On the other hand, in the copolymer polyester (y-1), the content of terephthalic acid units relative to the total dicarboxylic acid units is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 70 mol% or more. Also, in the copolymer polyester (y-1), the content of terephthalic acid relative to the content of terephthalic acid units (100 mol%) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less.

[0072] The copolymer polyester (y-2) contains an alicyclic diol unit. In this embodiment, the diol unit in the copolymer polyester (y-2) preferably contains other diol units (excluding alicyclic diols) in addition to the alicyclic diol units. In particular, the copolymer polyester (y-2) preferably contains one kind of dicarboxylic acid unit, an alicyclic diol unit, and other diol units (excluding alicyclic diols).

[0073] Examples of the alicyclic diol constituting the copolymerized polyester (y-2) include cyclohexanediols such as 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol; cyclohexanedimethanols such as 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; norbornane dimethanols such as 2,3-norbornane dimethanol and 2,5-norbornane dimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalin dimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among them, the alicyclic diol is preferably a cyclohexanediol or a cyclohexanedimethanol, and is preferably at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol. Among these, 1,4-cyclohexanedimethanol in which the methylol group is at the para position is particularly preferred from the viewpoint of excellent stability.

[0074] The other diol constituting the copolymer polyester (y-2) may be the diol constituting the copolymer polyester (y-1). Among them, the other diol constituting the copolymer polyester (y-2) is preferably ethylene glycol.

[0075] In addition, examples of the one dicarboxylic acid constituting the copolymer polyester (y-2) include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid. Among them, it is preferable that the one dicarboxylic acid constituting the copolymer polyester (y-2) is terephthalic acid. That is, it is more preferable that the copolymer polyester (y-2) contains terephthalic acid units, alicyclic diol units, and ethylene glycol units, and it is particularly preferable that the copolymer polyester (y-2) contains terephthalic acid units, 1,4-cyclohexanedimethanol units, and ethylene glycol units.

[0076] The total content of alicyclic diol units relative to all diol units in the copolymer polyester (y-2) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more. The total content of alicyclic diol units relative to all diol units in the copolymer polyester (y-2) is preferably 50 mol% or less, more preferably 45 mol% or less, even more preferably 40 mol% or less, and even more preferably 37 mol% or less. On the other hand, in the copolymer polyester (y-2), the content of other diol units relative to the total diol units is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, and even more preferably 63 mol% or more. Also, in the copolymer polyester (y-2), the content of other diol units relative to the total diol units is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, even more preferably 80 mol% or less, and particularly preferably 75 mol% or less.

[0077] The content of the copolymer polyester (y-1) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 12% by mass or more, based on the total polyester contained in the polyester layer Y. The content of the copolymer polyester (y-1) is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the total polyester contained in the polyester layer Y. The content of the copolymer polyester (y-2) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 12% by mass or more, based on the total amount of polyester contained in the polyester layer Y. The content of the copolymer polyester (y-2) is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and even more preferably 38% by mass or less, based on the total amount of polyester contained in the polyester layer Y.

[0078] The intrinsic viscosity of the copolymer polyester (y-1) is preferably 0.6 dL / g or more, more preferably 0.63 dL / g or more, and even more preferably 0.65 dL / g or more. The upper limit of the intrinsic viscosity of the copolymer polyester (y-1) is not particularly limited, but is preferably 0.83 dL / g or less, more preferably 0.8 dL / g or less, even more preferably 0.76 dL / g or less, and even more preferably 0.73 dL / g or less.

[0079] The intrinsic viscosity of the copolymer polyester (y-2) is preferably 0.7 dL / g or more, more preferably 0.75 dL / g or more, even more preferably 0.77 dL / g or more, and even more preferably 0.8 dL / g or more. The upper limit of the intrinsic viscosity of the copolymer polyester (y-2) is not particularly limited, but is preferably 1 dL / g or less, more preferably 0.95 dL / g or less, even more preferably 0.9 dL / g or less, and even more preferably 0.86 dL / g or less.

[0080] The polyester layer Y may contain a copolymer polyester other than the copolymer polyester (y-1) and the copolymer polyester (y-2), or a homopolyester. In particular, the polyester layer Y preferably contains a homopolyester in addition to the copolymer polyester (y-1) and the copolymer polyester (y-2). Here, the term "homopolyester" refers to a polyester obtained by polycondensation of one kind of dicarboxylic acid component and one kind of diol component. In this embodiment, the homopolyester is preferably homopolyethylene terephthalate (also simply referred to as "polyethylene terephthalate"). In this case, the homopolyethylene terephthalate may also contain 1 to 5 mol% of by-product diethylene glycol, and even in such a case, it is included in the homopolyethylene terephthalate.

[0081] When the polyester layer Y contains a homopolyester, the content of the homopolyester is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total polyester contained in the polyester layer Y. Furthermore, the content of the homopolyester is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less, based on the total polyester contained in the polyester layer Y.

[0082] (optional ingredient) The polyester layer Y may contain optional components other than those described above, as necessary. Examples of the optional components include particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0083] (Relationship between polyester layer X and polyester layer Y) When the total content (mol%) of the total alicyclic diol unit content (mol%) relative to the total diol units in all polyesters contained in polyester layer X and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units is P, and the total content (mol%) of the alicyclic diol unit content (mol%) relative to the total diol units in all polyesters contained in polyester layer Y and the content (mol%) of other dicarboxylic acid units relative to the total dicarboxylic acid units is Q, it is preferable that P ≧ Q. In other words, the sum of the total alicyclic diol unit content and the other dicarboxylic acid unit content in polyester layer X is preferably the same as or higher than the sum of the total alicyclic diol unit content and the other dicarboxylic acid unit content in polyester layer Y.

[0084] The PQ value is preferably 4 mol% or more, more preferably 6 mol% or more, even more preferably 8 mol% or more, and even more preferably 10 mol% or more. The PQ value is preferably 30 mol% or less, more preferably 25 mol% or less, and even more preferably 20 mol% or less.

[0085] The P / Q value is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.8 or more.The P / Q value is preferably 3.5 or less, more preferably 3.2 or less, even more preferably 3 or less, and even more preferably 2.8 or less.

[0086] By setting the relationship between the values ​​of P and Q under the above conditions, the balance between drop resistance and seal strength can be improved. For example, a copolymerized polyester containing an alicyclic diol component such as 1,4-cyclohexanedimethanol (CHDM) has multiple conformations, so that when the content is simply increased, the drop resistance increases, but the seal strength tends not to increase with respect to the amount added, especially when the intrinsic viscosity is high. On the other hand, a copolymerized polyester containing other dicarboxylic acid components such as isophthalic acid (IPA) increases the seal strength, but the drop resistance is not likely to be good, so that the drop resistance of the film is expected to decrease. For this reason, in this polyester-based film, by setting the relationship between the values ​​of P and Q in at least the polyester layers X and Y under the above conditions, a concentration gradient of the copolymerized components (alicyclic diol and other dicarboxylic acid components) is formed in the thickness direction when viewed as a whole polyester-based film, and it becomes easier to impart drop resistance while maintaining heat seal strength. In addition, in this embodiment, by setting the relationship between the values ​​of P and Q under the above conditions, a concentration gradient of the copolymerized components can be formed in the thickness direction from the polyester layer X to the polyester layer Z. By providing such a concentration gradient of the copolymerization component, the interlayer adhesion can be increased, and delamination is less likely to occur. It is presumed that the increased interlayer adhesion allows the force to be transmitted smoothly when an impact is applied, and the drop resistance is more effectively increased. In addition, the increased interlayer adhesion improves the strength of the entire film, and the heat seal strength and drop resistance of the film can be more effectively achieved.

[0087] The value obtained by dividing the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer X by the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.4 or more. In addition, the value obtained by dividing the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer X by the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y is preferably 5 or less, more preferably 4.5 or less, and even more preferably 4 or less.

[0088] The value obtained by dividing the content (mol%) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X by the content (mol%) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. In addition, the value obtained by dividing the content (mol%) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X by the content (mol%) of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 5 or less, more preferably 4.5 or less, even more preferably 4 or less, and even more preferably 3.5 or less.

[0089] The ratio of the thickness of the polyester layer Y to the thickness of the polyester layer X (thickness of the polyester layer Y / thickness of the polyester layer X) is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 2 or more. The ratio of the thickness of the polyester layer Y to the thickness of the polyester layer X (thickness of the polyester layer Y / thickness of the polyester layer X) is preferably 6 or less, more preferably 5 or less, and even more preferably 4.5 or less. By setting the ratio of the thickness of the polyester layer Y to the thickness of the polyester layer X within the above range, a good balance between drop resistance and seal strength can be achieved.

[0090] <Polyester layer Z> In the first embodiment, the polyester film may further have a polyester layer Z. In this case, it is preferable to provide the polyester layer Z as the outermost layer outside the polyester layer Y. That is, the polyester film preferably has the polyester layer X, the polyester layer Y, and the polyester layer Z in this order. In the polyester film, the polyester layer Z is the layer on the side opposite to the content side, i.e., the outermost layer, when the polyester film is used as a packaging material or the like.

[0091] The polyester layer Z is preferably a layer containing homopolyethylene terephthalate (z) as a main component resin. When the polyester layer Z contains homopolyethylene terephthalate (z) as a main component resin, the heat resistance and film strength can be improved. This makes it possible to increase the heat seal temperature, and as a result, the heat seal strength can be increased. In addition, by making the outermost layer a layer containing homopolyethylene terephthalate (z) as a main component resin, printability can also be improved.

[0092] The term "main component resin" refers to the resin that is contained in the largest amount among the resins that constitute the polyester layer Z. The main component resin preferably accounts for 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more (including 100% by mass) of the resins that constitute the polyester layer Z.

[0093] From the viewpoints of reducing production costs, increasing the interlayer affinity between the polyester layer X and the polyester layer Y and the polyester layer Z, and increasing recyclability, it is preferable that the homopolyester that may be contained in the polyester layer X and the polyester layer Y and the homopolyethylene terephthalate (z) contained in the polyester layer Z are the same resin.

[0094] The polyester layer Z may be composed solely of homopolyethylene terephthalate (z), or may contain a resin (z-1) other than homopolyethylene terephthalate (z).

[0095] The thickness of the polyester layer Z is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the polyester layer Z is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. The thickness of the polyester layer Z is preferably 10 to 40% of the total thickness of the polyester film.

[0096] The polyester-based film preferably has a polyester layer X, a polyester layer Y, and a polyester layer Z in this order, and in this case, it is preferable that the laminate structure has a total content (mol%) of copolymerization components (other dicarboxylic acid components and alicyclic diol components) that decreases successively from the polyester layer X to the polyester layer Z. This allows the polyester layer X to exhibit high sealant strength while the polyester layer Z contributes to improving strength, thereby achieving a good balance between drop resistance and seal strength. In addition, the polyester layer Z has high heat resistance, which can improve printability and processability.

[0097] In other words, with regard to the total content (mol%) of the alicyclic diol unit relative to all diol units in all polyesters (including copolymerized polyesters) contained in each layer, and the content (mol%) of all other dicarboxylic acid units relative to all dicarboxylic acid units, it is preferable that polyester layer X≧polyester layer Y≧polyester layer Z, and it is particularly preferable that polyester layer X>polyester layer Y>polyester layer Z.

[0098] When the relationship of the total copolymerization component contents in each layer is polyester layer X≧polyester layer Y≧polyester layer Z, the interlayer affinity between the layers is higher than when polyester layer X<polyester layer Y or polyester layer Y<polyester layer Z, and the force is transmitted more smoothly during the peeling process when measuring the heat seal strength. As a result, the polyester film can achieve excellent heat seal strength.

[0099] Whether or not the polyester film has a concentration gradient of all copolymerization components in each layer in the thickness direction of the film can be confirmed, for example, by the presence or absence of an inflection point in the concentration gradient of the copolymerization components in the thickness direction of the film. The inflection point can be examined by preparing an oblique cut surface of the film using SAICAS (registered trademark) and obtaining negative secondary ion peak intensity data using a time-of-flight secondary ion mass spectrometer TOF-SIMS.

[0100] (optional ingredient) The polyester layer Z may contain optional components other than those described above, as necessary. Examples of the optional components include particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0101] Among them, the polyester layer Z preferably contains particles, and more preferably contains inorganic particles. Examples of inorganic particles include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide. The polyester film contains particles, which can impart slipperiness to the polyester film and prevent scratches in each process. The content of the particles is preferably 100 mass ppm or more, more preferably 500 mass ppm or more, even more preferably 800 mass ppm or more, and even more preferably 1000 mass ppm or more, based on the total mass of the polyester layer Z. The content of the particles is preferably 4000 mass ppm or less, more preferably 3500 mass ppm or less, even more preferably 3000 mass ppm or less, and particularly preferably 2700 mass ppm or less, based on the total mass of the polyester film.

[0102] <Other layers> The polyester film may further have a polyester layer on the side of the polyester layer Z opposite to the polyester layer X, i.e., on the outside of the polyester layer Z. In this embodiment, by forming a polyester film made of a single material, it is possible to more effectively improve recyclability while maintaining drop resistance and sheet strength. The polyester layer provided on the outside of the polyester layer Z may be laminated via an adhesive layer.

[0103] The polyester film may also have a barrier layer (also referred to as the present barrier layer) on the side of the polyester layer Z opposite to the polyester layer X, i.e., on the outside of the polyester layer Z. Another layer may be laminated between the polyester layer Z and the barrier layer. The present barrier layer is a layer that can enhance the property of suppressing gas permeation (also referred to as "gas barrier property"), particularly the water vapor barrier property.

[0104] The inorganic substance serving as the main material constituting the present barrier layer may be, for example, one or more inorganic compounds selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxycarbonitride, aluminum oxide, aluminum nitride, aluminum oxynitride, and aluminum oxycarbide.

[0105] The barrier layer is preferably, for example, a PVD inorganic layer formed by a physical vapor deposition (PVD) method, a plasma-assisted deposition inorganic layer formed by a plasma-assisted deposition method, a CVD inorganic layer formed by a chemical vapor deposition (CVD) method, or a coated inorganic layer formed by a method in which inorganic particles are dispersed in an organic polymer and applied.

[0106] The barrier layer may be a single layer or a multi-layer structure of two or more layers. For example, as an example of a multi-layer structure of two or more layers, one layer may be an inorganic layer made of only an inorganic material, such as an inorganic oxide, and the other layer may be an inorganic-organic mixed layer made of an inorganic material, such as an inorganic oxide, and an organic material. By mixing an organic material with an inorganic material, a relatively flexible layer can be obtained, and by providing such a flexible layer, the gas barrier property may be improved. That is, the coarse protrusions of the base film may be the starting point for the generation of minute defects called pinholes on the surface of the inorganic layer, or the raw material may fly in clumps during thermal evaporation and adhere to the surface, causing minute defects on the surface of the inorganic layer, and the gas barrier properties may be reduced by gas passing through the voids caused by these defects. Therefore, by laminating a flexible layer as described above on the surface, the defects can be filled, and the gas barrier properties may be improved.

[0107] The thickness of the barrier layer (the total thickness of the inorganic layers when the inorganic layers are multi-layered) is preferably 0.1 nm to 500 nm, more preferably 1 to 300 nm, and even more preferably 5 to 100 nm. If the thickness of the barrier layer is within the above range, it is possible to ensure the desired gas barrier properties.

[0108] <Physical properties of this polyester film> The polyester film preferably has the following physical properties:

[0109] (Thickness of this polyester film) The total thickness of the polyester film is not particularly limited, and an appropriate thickness can be selected depending on the application. From the viewpoint of ensuring high heat sealability and performing barrier deposition and printing processing, the total thickness of the polyester film is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The upper limit of the total thickness of the polyester film is not particularly limited, but for example, it is preferably 260 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and even more preferably 120 μm or less. In this embodiment, the thickness of the polyester film, the composition of the layers constituting the polyester film, the heat setting treatment temperature during production, etc. can be appropriately adjusted to achieve a good balance between drop resistance and seal strength. In some cases, the drop resistance and seal strength are increased when the thickness of the polyester film is a certain level or more, and in such cases, the total thickness of the polyester film may be 30 μm or more, 35 μm or more, or 40 μm or more.

[0110] (Heat seal strength) When the polyester layers X of two sheets of the present polyester film, i.e., the sealing layers, are sealed together under conditions of 140°C, 0.2 MPa, and 1 second, the seal strength of the present polyester film is preferably 15N / 15mm or more, more preferably 16N / 15mm or more, even more preferably 17N / 15mm or more, even more preferably 18N / 15mm or more, even more preferably 19 / 15mm or more, and particularly preferably 20N / 15mm or more. By making the seal strength of the present polyester film within the above range, for example, when it is used as a packaging material, it can contribute to improving low-temperature sealability and airtightness, and it can also be suitably used as an antibacterial polyester film. The upper limit of the seal strength is not particularly limited, but it may be, for example, 50N / 15mm or less, or 45N / 15mm or less.

[0111] The heat seal strength of this polyester film is measured in accordance with JIS Z1707: 2019. Specifically, the seal surfaces (polyester layer X) are joined together and heat sealed at 140°C, 0.2 MPa, and pressure for 1 second, and the sealed area is cut to a width of 15 mm, and then the peel strength of the sealed area is measured using a tensile tester at a pulling speed of 300 mm / min.

[0112] (Displacement at break point in hydroshot test) The break displacement of the polyester film in the hydroshot test is preferably 9.1 mm or more, more preferably 9.5 mm or more, and even more preferably 10 mm or more. The upper limit of the break displacement is not particularly limited, but may be, for example, 20 mm or less, or 15 mm or less. By making the break displacement in the hydroshot test equal to or greater than the lower limit, the drop resistance can be more effectively improved, and the film can be suitably used for packaging liquids.

[0113] (Impact energy in hydroshot test) The impact energy of the polyester film in the hydroshot test is preferably more than 0.5 J, more preferably 0.6 J or more, and even more preferably 0.7 J or more. The upper limit of the impact energy in the hydroshot test is not particularly limited, but may be, for example, 3 J or less, or 2.5 J or less. By making the impact energy in the hydroshot test equal to or greater than the lower limit, the drop resistance can be more effectively improved, and the film can be suitably used for packaging liquids.

[0114] The measurement of the breaking point displacement and impact energy in the hydroshot test is carried out as follows: A sample film measuring 100 mm lengthwise and 100 mm widthwise is used, and a hydroshot high-speed impact tester (Shimadzu Corporation, Model HTM-1) is used to fix the sample film with clamps, and an impact core with a diameter of 1 / 2 inch is dropped at a speed of 3 m / sec onto the center of the sample film at a temperature of 23°C to apply an impact, and the amount of displacement (breaking point displacement) (mm) and energy (impact energy) (J) at the breaking point when the sample breaks are measured.

[0115] (Breaking strength) The polyester film has a breaking strength of preferably 50 MPa or more in both the machine direction (MD) and the transverse direction (TD), more preferably 60 MPa or more, and even more preferably 70 MPa or more. By making the breaking strength equal to or more than the above lower limit, for example, when used as a packaging material, it is possible to prevent breaking. The higher the breaking strength, the more preferable it is, but even if it is 170 MPa or less, it can be said that it is sufficient for practical use, and it may be 160 MPa or less. The breaking strength of the polyester film was measured by pulling a sample film in the machine direction (MD) or transverse direction (TD) at a speed of 200 mm / min using a tensile tester, and the strength at which the sample broke (fractured) (the value obtained by dividing the tensile load by the cross-sectional area of ​​the test piece) was taken as the breaking strength (MPa).

[0116] (Shrinkage rate) The present polyester-based film has a shrinkage rate of -5% to 5% in either the machine direction (MD) or the transverse direction (TD). By having a shrinkage rate in the range of -5% to 5%, the original shape can be maintained even in a high temperature environment, for example. From this viewpoint, the present polyester-based film has a shrinkage rate of -4% to 4% in either the machine direction (MD) or the transverse direction (TD) more preferably, -3% to 3%, and particularly preferably, -2% to 2%. The shrinkage rate is calculated by placing a sample film in a non-tensioned state in a hot air oven maintained at a specified temperature (100°C) and heat treating it for 5 minutes, measuring the length of the sample film before and after the treatment, and calculating the shrinkage rate using the following formula 1. Shrinkage rate (%) = {(sample length before heat treatment) - (sample length after heat treatment)} / (sample length before heat treatment) × 100 (Equation 1)

[0117] (Haze) The haze of the polyester film is preferably 15% or less, more preferably 10% or less, and even more preferably 6% or less. The lower the haze, the higher the transparency, and therefore the more preferable it is. The lower limit is about 0.01%. The haze is measured in accordance with JIS K7136:2000.

[0118] <Method of manufacturing the polyester film> As an example of the method for producing the polyester film, a case in which the polyester film is a biaxially stretched film will be described, although the method is not limited to the one described here.

[0119] The method for producing the polyester film preferably includes a step of laminating and stretching the resin compositions constituting at least the polyester layer X and the polyester layer Y, and a step of carrying out a heat setting treatment after the stretching step.

[0120] First, the resin compositions constituting each layer are prepared by a known method, and the resin compositions are separately fed into a twin-screw melt extruder to melt the resin compositions, and the amount of molten resin discharged is adjusted so that the thicknesses of the layers are in a predetermined thickness ratio, and each layer is extruded from a die, i.e., coextruded. This coextruded sheet is cooled and solidified on a rotating cooling drum to a temperature below the glass transition point of the polymer, to obtain a substantially amorphous unoriented sheet.

[0121] Next, the unoriented sheet is stretched in one direction by a roll or tenter type stretching machine, at a stretching temperature of usually 70 to 120° C., preferably 80 to 100° C., and a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Then, the film is stretched in a direction perpendicular to the first-stage stretching direction at a temperature of usually 70 to 40° C. and a stretch ratio of usually 3 to 7 times, preferably 3.5 to 6 times. In addition, in the stretching, a method in which stretching in one direction is performed in two or more stages can also be adopted.

[0122] A heat setting process is provided after the stretching process. The heat setting temperature in the heat setting process is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher. The heat setting temperature is preferably less than 250°C, more preferably 240°C or lower, even more preferably 238°C or lower, even more preferably 235°C or lower, and particularly preferably 230°C or lower. The heat setting process is performed at the above temperature under tension or relaxation of 30% or less to obtain the present polyester film as a biaxially oriented film. By setting the heat setting temperature within the above range, the present polyester film can be prevented from becoming brittle, and the impact resistance and drop resistance can be improved. In addition, by appropriately adjusting the heat setting temperature and the blending of the copolymerization components constituting the polyester film, the balance between the drop resistance and seal strength of the present polyester film can be improved.

[0123] In addition, when producing the polyester-based film in the second embodiment, for example, when the molten resin composition is extruded into a film from an extruder, a method can be adopted in which a die equipped with electrodes is used to generate a concentration gradient by utilizing the difference in polarity of the resin composition.

[0124] <Applications of this polyester film> The polyester film of the present invention is preferably a film for packaging material, and may also be called a sealant film since it has a polyester layer X as a sealing layer.

[0125] This embodiment may relate to a packaging material including a film for packaging material. In this case, the present polyester-based film may be used as a packaging material as it is, or the present polyester-based film may be used as a component of the packaging material. When the present polyester-based film is used as a component of the packaging material, the packaging material may be a laminate, and such a laminate has a configuration in which the present polyester-based film is laminated with other layers. Examples of the other layers include films using polyethylene terephthalate, polyamide, polypropylene, polystyrene (syndiotactic polystyrene), polymethylpentene, polyimide, polytetrafluoroethylene, etc. In addition, as the other layer, a layer containing a metal such as aluminum or iron may be provided. Such a layer may be a vapor deposition layer, but may also be provided by laminating a film containing a metal such as aluminum or iron or bonding it with an adhesive or the like. By providing other layers in the packaging material, the strength and heat resistance of the packaging material can be increased, or functions according to the application can be imparted. Such a laminate is also preferably used as a packaging material. EXAMPLES

[0126] The features of the present invention will be described in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0127] <Materials used> [Preparation of polyester raw materials] The raw material composition (proportion of raw material monomers) of each polyester used in the examples and comparative examples is shown in Table 1. In Table 1, TPA is terephthalic acid, IPA is isophthalic acid, EG is ethylene glycol, and CHDM is 1,4-cyclohexanedimethanol. In producing polyester b, spherical silica particles having an average particle size of 4 μm were added as a lubricant in a ratio of 15,000 ppm based on the polyester. The intrinsic viscosity (IV) of polyesters a to d is a value measured by a method in which the polyester is dissolved in a 1:1 mixed solution of phenol:tetrachloroethane and the intrinsic viscosity (IV) is calculated from the elution time of this polyester solution.

[0128] [Table 1]

[0129] Example 1 As the raw material for polyester layer Z, polyester a and polyester b were mixed in a mass ratio of 89:11. As the raw material for polyester layer Y, polyester a, polyester c, and polyester d were mixed in a mass ratio of 59:22:19. As the raw material for polyester layer X, polyester a, polyester c, and polyester d were mixed in a mass ratio of 5:50:45, and mixed raw materials for forming each layer were prepared.

[0130] The mixed raw materials for polyester layer Z, polyester layer Y, and polyester layer X were each fed into a separate twin-screw extruder, and the mixed raw materials for polyester layer Z, polyester layer Y, and polyester layer X were heated and melted at 280° C. The amount of molten resin discharged was adjusted so that each layer had a predetermined thickness, and each layer was extruded from a die, and each was cooled and solidified with a cooling roll set at 25° C. to obtain an unstretched laminated film of three types and three layers (polyester layer Z / polyester layer Y / polyester layer X). Next, the obtained unstretched laminated film was stretched 3.3 times in the machine direction (MD) at 85°C using a roll stretching machine. Furthermore, after preheating at 95°C in a tenter, it was stretched 4.2 times in the transverse direction (TD) at 110°C. Finally, it was heat-treated at 230°C (heat setting temperature) to obtain a laminated film (sample) of three types and three layers (polyester layer Z: 9.3 μm, polyester layer Y: 31.4 μm, polyester layer X: 9.3 μm) with a thickness of 50 μm. The properties of the obtained laminated film were evaluated by the following method.

[0131] Example 2 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the heat setting temperature was changed to 225°C.

[0132] Example 3 The polyester layer X was prepared by mixing polyester a, polyester b, polyester c, and polyester d in a mass ratio of 5:5:45:45. The mass ratios of the raw materials and the film-forming conditions of each layer other than the polyester layer X were the same as in Example 1, and a laminated film (sample) with a thickness of 50 μm was obtained.

[0133] Example 4 Except for changing the heat setting temperature to 225°C, the same procedure as in Example 3 was carried out to obtain a laminated film (sample) having a thickness of 50 µm.

[0134] Example 5 The polyester layer X was prepared by mixing polyester b, polyester c, and polyester d in a mass ratio of 10:45:45. The mass ratios of the raw materials and the film-forming conditions of each layer other than the polyester layer X were the same as in Example 2, and a laminated film (sample) having a thickness of 50 μm was obtained.

[0135] Example 6 A laminated film (sample) having a thickness of 38 μm was obtained in the same manner as in Example 5, except that the thickness of the polyester layer Z was changed to 7.1 μm, the thickness of the polyester layer Y was changed to 23.8 μm, and the thickness of the polyester layer X was changed to 7.1 μm.

[0136] Example 7 The raw material for polyester layer X was prepared by mixing polyester b, polyester c, and polyester d in a mass ratio of 11:62:27. A laminated film (sample) having a thickness of 38 μm was obtained in the same manner as in Example 1, except that the thickness of polyester layer Z was changed to 7.1 μm, the thickness of polyester layer Y was changed to 23.8 μm, and the thickness of polyester layer X was changed to 7.1 μm.

[0137] Example 8 A 50 μm thick laminated film (sample) was obtained in the same manner as in Example 7, except that the thickness of polyester layer Z was changed to 9.3 μm, the thickness of polyester layer Y was changed to 31.4 μm, the thickness of polyester layer X was changed to 9.3 μm, and the heat setting temperature was changed to 225° C.

[0138] Example 9 Except for changing the heat setting temperature to 230°C, the same procedure as in Example 8 was carried out to obtain a laminated film (sample) having a thickness of 50 µm.

[0139] Example 10 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw materials for polyester layer Z were prepared by mixing polyester a and polyester b in a mass ratio of 91:9, the raw materials for polyester layer Y were prepared by mixing polyester a, polyester c, and polyester d in a mass ratio of 59:21:20, and the raw materials for polyester layer X were prepared by mixing polyester b, polyester c, and polyester d in a mass ratio of 6:50:44.

[0140] Comparative Example 1 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 2, except that the raw material for polyester layer Y was prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and the raw material for polyester layer X was prepared by mixing polyester a and polyester d in a mass ratio of 20:80.

[0141] Comparative Example 2 The raw material for polyester layer Z was prepared by mixing polyester a and polyester b in a mass ratio of 91:9, the raw material for polyester layer Y was prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and a laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that only polyester d was used as the raw material for polyester layer X.

[0142] Comparative Example 3 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw material for the polyester layer Y was prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and the raw material for the polyester layer X was prepared by mixing polyester a and polyester c in a mass ratio of 19:81.

[0143] Comparative Example 4 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the raw material for polyester layer Y was prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and the raw material for polyester layer X was prepared by mixing polyester a, polyester c, and polyester d in a mass ratio of 5:50:45.

[0144] Comparative Example 5 The raw material for polyester layer Y was prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and the raw material for polyester layer X was prepared by mixing polyester a and polyester d in a mass ratio of 20:80. Except for changing the heat setting temperature to 220°C, a laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 1.

[0145] <Evaluation method> The laminated films (samples) produced in the examples and comparative examples were evaluated as follows.

[0146] (1) Heat seal strength The heat seal strength (N / 15mm) of the laminated films (samples) produced in the examples and comparative examples was measured in accordance with JIS Z1707:2019. First, the sealing surfaces (polyester layers X) of the laminated films (samples) were placed together and heat sealed by applying pressure of 140°C, 0.2 MPa, and 1 second. The sealed portion was cut to a width of 15 mm, and the peel strength of the sealed portion was measured at a pulling speed of 300 mm / min using a tensile tester. The average value of three measured values ​​was taken as the heat seal strength.

[0147] (2) Breaking point displacement and impact energy in hydroshot tests The laminated films (samples) prepared in the examples and comparative examples were used as sample films measuring 100 mm in the vertical direction and 100 mm in the horizontal direction. Using a hydroshot high-speed impact tester (Shimadzu Corporation, "HTM-1 type"), the sample film was fixed with a clamp, and an impact core with a diameter of 1 / 2 inch was dropped at a drop speed of 3 m / s onto the center of the sample film at a temperature of 23°C to apply impact, and the displacement (breaking point displacement) (mm) and energy (impact energy) (J) at the breaking point when the sample broke were measured. The average values ​​of five measured values ​​were taken as the breaking point displacement (mm) and impact energy (J) in the hydroshot test.

[0148] (3) Drop resistance evaluation The sealed surfaces (polyester layers X) of the laminated films (samples) produced in the examples and comparative examples were made to face each other as inner surfaces, and the water content was set to 50 mL to produce a four-sided sealed pouch measuring 140 mm in length and 100 mm in width. The sealing conditions for producing the sealed pouch were 140°C, 0.2 MPa, and 2 seconds. The width of the sealed portion was 10 mm. Next, as a drop test, the above-mentioned sealed pouch was dropped vertically from a height of 50 cm, and then dropped horizontally (in a flat plane). A set of vertical and horizontal (flat) drops was performed, and five sets of drop tests were performed. In the vertical drop, the short sides of the four-side sealed pouch came into contact with the ground when dropped, and in the horizontal (flat) drop, the body (widest surface) of the four-side sealed pouch came into contact with the ground when dropped. The drop resistance was evaluated according to the following criteria. 〇 (Good): The bag did not break even once when five sets were dropped. × (Poor): The bag broke before dropping five sets (the bag broke in any of the drop tests of 1 to 5 sets).

[0149] In addition, the water content was increased to 100 mL for the laminated film (sample) produced in the example, and a four-sided sealed pouch measuring 150 mm in length and 110 mm in width was produced. The sealing conditions and the width of the sealed portion were the same as above. Next, a drop test was carried out in the same manner, and the drop resistance was evaluated according to the following criteria. ◎ (Excellent): The bag did not break even once when five sets were dropped. ◯ (Good): The bag broke after 2 to 4 sets were dropped. × (Poor): One set broke when dropped. For the laminated films (samples) produced in the comparative examples, a drop test using 100 mL of water and an evaluation of drop resistance were not performed. Therefore, the results in Table 3 are indicated as "-".

[0150] (4) Breaking strength The laminated films (samples) produced in the examples and comparative examples were used as sample films of 1.5 cm x 15 cm. Using a tensile tester, the sample films were pulled in the machine direction (MD) or transverse direction (TD) at a speed of 200 mm / min, and the strength at which the sample broke (fractured) (the value obtained by dividing the tensile load value by the cross-sectional area of ​​the test piece) was taken as the breaking strength (MPa). The average value of three measured values ​​was taken as the breaking strength.

[0151] (5) Shrinkage rate The laminated films (samples) produced in the examples and comparative examples were used as sample films of 1.5 cm x 15 cm. The sample films were placed in a hot air oven maintained at a specified temperature (100°C) in a tension-free state and heat-treated for 5 minutes, and the lengths of the sample films before and after were measured to calculate the shrinkage rate using the following formula (1). The measurements were carried out in both the machine direction (MD) and the transverse direction (TD) of the film. Shrinkage rate (%) = {(sample length before heat treatment) - (sample length after heat treatment)} / (sample length before heat treatment) × 100 (Equation 1) The average of three measurements was taken as the shrinkage rate.

[0152] (6) Haze The haze (%) of the laminated films (samples) produced in the examples and comparative examples was measured in accordance with JIS K7136:2000 using a haze meter DH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. The average value of three measurements is shown in Table 3 as the haze.

[0153] [Table 2]

[0154] [Table 3]

[0155] In Table 3, for example, the CHDM component content (mol%) of polyester layer X means the ratio (mol%) of the total content of CHDM units to all diol units (100 mol%) contained in all polyesters (including copolymer polyesters) constituting polyester layer X. Also, the IPA component content (mol%) of polyester layer X means the ratio (mol%) of the total content of IPA units to all dicarboxylic acid units (100 mol%) contained in all polyesters (including copolymer polyesters) constituting polyester layer X. The same applies to the other layers. In addition, diethylene glycol units of 5 mol % or less out of 100 mol % of a diol component constituting a polyester (including a copolymer polyester) using ethylene glycol as one of the raw materials were considered to be included in ethylene glycol units.

[0156] When a four-side sealed pouch was produced from the laminated film obtained in the examples, it exhibited excellent drop resistance. On the other hand, in the comparative examples, the polyester layer X and the polyester layer Y did not satisfy the predetermined component composition, and therefore the drop resistance was poor.

[0157] In addition, since all of the resin components constituting the laminated films obtained in the examples are polyester (including copolymerized polyester), it is possible to form packaging materials using a single material system made of polyester material by, for example, laminating other polyester-based substrate films such as transparent barrier vapor-deposited PET or applying barrier vapor deposition or printing processing techniques, and it is also possible to achieve high recyclability. [Industrial Applicability]

[0158] The laminated film of the present invention has excellent drop resistance, and since all of the resin components constituting the film can be polyester materials, a packaging material made of a single material can be realized. The present invention can provide a packaging material that is excellent in drop resistance and recyclability.

Claims

1. A packaging film having at least a polyester layer X and a polyester layer Y, the polyester layer X contains a copolymer polyester (x) made of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, and the diol component contains an alicyclic diol; The polyester layer Y comprises a copolymer polyester (y) composed of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component comprises terephthalic acid and another dicarboxylic acid, and the diol component comprises an alicyclic diol.

2. 2. The packaging film according to claim 1, wherein the polyester layers X have a heat seal strength of 15 N / 15 mm or more when sealed together at 140° C. under 0.2 MPa for 1 second.

3. 2. The packaging film according to claim 1, which has a breaking displacement of 9.1 mm or more in a hydroshot test.

4. 2. The film for packaging materials according to claim 1, having an impact energy of more than 0.5 J in a hydroshot test.

5. The packaging film according to claim 1 , wherein the diol component of the copolymerized polyester (x) further comprises ethylene glycol.

6. The packaging film according to claim 1 , wherein the other dicarboxylic acid of the copolymer polyester (x) includes isophthalic acid.

7. The packaging film according to claim 1, wherein the alicyclic diol of the copolymerized polyester (x) is at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol.

8. The packaging film according to claim 1 , wherein the diol component of the copolymerized polyester (y) further comprises ethylene glycol.

9. The packaging film according to claim 1 , wherein the other dicarboxylic acid of the copolymer polyester (y) includes isophthalic acid.

10. The packaging film according to claim 1, wherein the alicyclic diol of the copolymerized polyester (y) is at least one selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,1-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol.

11. the polyester layer X comprises a copolymer polyester (x-1) made of a copolymer of a dicarboxylic acid component and a diol component, and a copolymer polyester (x-2) made of a copolymer of a dicarboxylic acid component and a diol component, 2. The packaging film according to claim 1, wherein the dicarboxylic acid component constituting the copolymer polyester (x-1) contains terephthalic acid and other dicarboxylic acids, and the diol component constituting the copolymer polyester (x-2) contains an alicyclic diol.

12. The packaging film according to claim 11, wherein the other dicarboxylic acid of the copolymer polyester (x-1) includes isophthalic acid.

13. the polyester layer Y comprises a copolymer polyester (y-1) composed of a copolymer of a dicarboxylic acid component and a diol component, and a copolymer polyester (y-2) composed of a copolymer of a dicarboxylic acid component and a diol component, 2. The packaging film according to claim 1, wherein the dicarboxylic acid component constituting the copolymer polyester (y-1) contains terephthalic acid and another dicarboxylic acid, and the diol component constituting the copolymer polyester (y-2) contains an alicyclic diol.

14. The packaging film according to claim 13, wherein the other dicarboxylic acid of the copolymer polyester (y-1) includes isophthalic acid.

15. The packaging film according to claim 1 , further comprising a polyester layer Z.

16. The packaging film according to claim 15, wherein the polyester layer Z contains homopolyethylene terephthalate (z) as a main component resin.

17. The packaging film according to claim 15 , comprising the polyester layer X, the polyester layer Y and the polyester layer Z in this order.

18. 2. The packaging film according to claim 1, wherein the total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is 2 to 40 mol %.

19. 2. The packaging film according to claim 1, wherein the total content of the other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is 2 to 35 mol %.

20. 2. The packaging film according to claim 1, wherein the total content of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 1 to 25 mol %.

21. 2. The packaging film according to claim 1, wherein the total content of the other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer Y is 1 to 25 mol %.

22. The packaging film according to claim 1, further comprising particles, the content of the particles being 20 to 2000 ppm by mass relative to the total mass of the packaging film.

23. 2. The packaging film according to claim 1, wherein the polyester layer X further comprises particles, and the content of the particles is 100 to 3000 ppm by mass based on the total mass of the polyester layer X.

24. the total content (mol %) of the total alicyclic diol unit content (mol %) relative to the total diol units in the entire polyester contained in the polyester layer X and the content (mol %) of other dicarboxylic acid units relative to the total dicarboxylic acid units in the entire polyester contained in the polyester layer X is denoted by P; When the total content (mol %) of the alicyclic diol unit relative to all diol units in the entire polyester contained in the polyester layer Y and the content (mol %) of other dicarboxylic acid units relative to all dicarboxylic acid units in the entire polyester contained in the polyester layer Y is Q, The packaging film according to claim 1 , wherein P≧Q.

25. The film for packaging materials according to claim 24, wherein the value of PQ is 4 to 30 mol%.

26. The packaging film according to claim 24, wherein the value of P / Q is 1.1 to 3.

5.

27. 2. The packaging film according to claim 1, wherein a content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is divided by a content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y, and the value is 1.1 to 5.

28. 2. The packaging film according to claim 1, wherein a content (mol %) of the other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer X is divided by a content (mol %) of the other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in the polyester layer Y, and the value is 1.1 to 5.

29. 2. The packaging film according to claim 1, wherein a content (mol %) of alicyclic diol units in all diol units in all polyesters contained in the polyester layer X is divided by a content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in the polyester layer X, and the value is 1 to 5.

30. 2. The packaging film according to claim 1, wherein a content (mol %) of alicyclic diol units in all diol units in all polyesters contained in the polyester layer Y is divided by a content (mol %) of other dicarboxylic acid units in all dicarboxylic acid units in all polyesters contained in the polyester layer Y, and the value is 0.5 to 3.

31. A packaging film comprising a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, The dicarboxylic acid component includes terephthalic acid and other dicarboxylic acids, and the diol component includes an alicyclic diol, the total content (mol %) of the alicyclic diol unit relative to the total diol units in the entire polyester and the content (mol %) of other dicarboxylic acid units relative to the total dicarboxylic acid units contained in a region from one side of the film to 50% of the entire thickness is a content (mol %) of alicyclic diol units relative to all diol units in all polyesters and a content (mol %) of other dicarboxylic acid units relative to all dicarboxylic acid units in the entire polyesters, the content (mol %) being higher than the total content of the alicyclic diol units relative to all diol units in all polyesters contained in a region from the other surface side of the film up to 50% of the entire thickness of the film.

32. 32. The packaging film according to claim 31, wherein the total content (mol %) of the alicyclic diol unit relative to all diol units in all polyesters and the content (mol %) of other dicarboxylic acid units relative to all dicarboxylic acid units increases continuously from one side to the other side of the film.

33. The packaging film according to claim 15, further comprising a barrier layer on the polyester layer Z.

34. A packaging material comprising the film for packaging material according to any one of claims 1 to 33.

35. A laminate comprising the packaging film according to any one of claims 1 to 33.

36. A packaging material comprising the laminate of claim 35.

37. A method for producing a packaging film having at least a polyester layer X and a polyester layer Y, comprising the steps of: the polyester layer X contains a copolymer polyester (x) made of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acids, the diol component contains an alicyclic diol, the polyester layer Y contains a copolymer polyester (y) composed of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid and other dicarboxylic acid components, and the diol component contains an alicyclic diol; a step of laminating and stretching a resin composition constituting the polyester layer X and the polyester layer Y; The stretching step is followed by a heat setting step, The method for producing a packaging film, wherein the heat setting temperature in the step of performing the heat setting treatment is 200° C. or higher and lower than 250° C.

38. The method for producing a packaging film according to claim 37, wherein the heat setting temperature in the step of performing the heat setting is 220°C or higher and 235°C or lower.

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