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

Abstract

To provide a polyester-based film capable of forming a packaging bag with excellent drop resistance.SOLUTION: A film for a packaging material of the present invention has at least a polyester layer X and a polyester layer Y, wherein the polyester layer X contains copolyester (x) having structural units derived from a dicarboxylic acid component and a diol component, the diol component containing alicyclic diol and acyclic aliphatic diol having a branched chain, and the polyester layer Y contains copolyester (y) having structural units derived from a dicarboxylic acid component and a diol component, the diol component containing alicyclic diol and acyclic aliphatic diol having a branched chain.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a packaging film, a packaging material, a laminate, and a method for producing a packaging film. [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 widely used in beverage and food containers, packaging materials, molded products, optical films, and more.

[0003] In recent years, environmental problems such as global warming have become more serious, and there is a demand for reducing the volume of packaging materials such as packages, and efforts are being made to promote recycling so that used packaging materials can be reused as resources. In response to this trend, conventional packaging materials often use film laminates obtained by heat-sealing or laminating a biaxially oriented film as a base film with a sealant film made primarily of polyethylene, polypropylene, or the like as the innermost layer. While such film laminates are endowed with various functions such as shelf life by combining multiple materials with different properties, they have had the problem of being difficult to recycle after use.

[0004] For this reason, in recent years, development of polyester films in which sealability is imparted to polyethylene terephthalate (PET) has been progressing (for example, Patent Documents 1 to 3). In the examples of Patent Documents 1 to 3, EG (ethylene glycol), BD (1,4-butanediol), NPG (neopentyl glycol), CHDM (1,4-cyclohexanedimethanol), and DEG (diethylene glycol) are used as polyhydric alcohol components, which are raw materials for polyester, respectively.

[0005] Patent Document 4 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] International Publication No. 2020 / 213471 Brochure [Patent Document 4] 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, it is required that the polyester film have not only heat seal strength but also film strength against impacts, drops, 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 the problems of the conventional technology, the present inventors have carried out investigations with the aim of providing a polyester film that can be used to form packaging bags that are excellent in 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 copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, the diol component containing an alicyclic diol and a branched acyclic aliphatic diol; A packaging film, wherein the polyester layer Y contains a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol. [2] The packaging film according to [1], wherein the branched acyclic aliphatic diol has a branched chain having two or more carbon atoms. [3] The packaging film according to [1] or [2], 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. [4] The film for packaging materials according to any one of [1] to [3], which has a breaking displacement of 9.1 mm or more in a hydroshot test. [5] The film for packaging materials according to any one of [1] to [4], which has an impact energy of more than 0.5 J in a hydroshot test. [6] The film for packaging materials according to any one of [1] to [5], wherein the diol component of the copolymer polyester (x) further contains diethylene glycol. [7] The packaging film 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 packaging film according to any one of [1] to [7], wherein the acyclic aliphatic diol having a branched chain in the copolymer polyester (x) is at least one selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol. [9] The film for packaging materials according to any one of [1] to [8], wherein the diol component of the copolymerized polyester (y) further contains diethylene glycol.

[10] The packaging film 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 packaging film according to any one of [1] to

[10] , wherein the acyclic aliphatic diol having a branched chain in the copolymer polyester (y) is at least one selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

[12] The polyester layer X contains a copolymer polyester (x-1) having structural units derived from a dicarboxylic acid component and a diol component and a copolymer polyester (x-2) having structural units derived from a dicarboxylic acid component and a diol component, The film for packaging material according to any one of [1] to

[11] , wherein the diol component constituting the copolymerized polyester (x-1) contains an alicyclic diol, and the diol component constituting the copolymerized polyester (x-2) contains an acyclic aliphatic diol having a branched chain.

[13] The polyester layer Y contains a copolymer polyester (y-1) having structural units derived from a dicarboxylic acid component and a diol component and a copolymer polyester (y-2) having structural units derived from a dicarboxylic acid component and a diol component, The film for packaging material according to any one of [1] to

[12] , wherein the diol component constituting the copolymerized polyester (y-1) contains an alicyclic diol, and the diol component constituting the copolymerized polyester (y-2) contains an acyclic aliphatic diol having a branched chain.

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

[13] , further comprising a polyester layer Z.

[15] The film for packaging materials according to

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

[16] The packaging film according to

[14] or

[15] , wherein the polyester layer Z contains a copolymerized polyester (z-1) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and / or an acyclic aliphatic diol.

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

[14] to

[16] , which has 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 branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X is 0.5 to 30 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 branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 0.5 to 20 mol %.

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

[21] , further comprising particles, the content of which is 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 relative to the total mass of the polyester layer X.

[24] The total content (mol%) of the alicyclic diol unit relative to all diol units in all polyesters contained in the polyester layer X and the branched acyclic aliphatic diol unit relative to all diol units in all polyesters contained in the polyester layer X is defined as P, When the total content (mol%) of the alicyclic diol unit relative to all diol units in all polyesters contained in the polyester layer Y and the content (mol%) of the branched acyclic aliphatic diol unit relative to all diol units in all polyesters contained in the polyester layer Y is Q, The film for packaging materials according to any one of [1] to

[23] , wherein P≧Q.

[25] The film for packaging materials according to

[24] , wherein the PQ value is 4 to 30 mol%.

[26] The film for packaging materials according to

[24] or

[25] , wherein the P / Q value is 1.1 to 3.5.

[27] The film for packaging material 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, calculated by dividing the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y.

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

[27] , wherein the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer X is 1.1 to 5, calculated by dividing the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer Y.

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

[28] , wherein the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X is 1 to 5, when divided by the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X.

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

[29] , wherein the content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 0.5 to 4, calculated by dividing the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y.

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

[30] , wherein the total content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X and the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X divided by the content (mol%) of diethylene glycol units relative to all diol units in all polyesters contained in the polyester layer X is 2 to 8.

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

[31] , wherein the total content (mol%) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y and the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y divided by the content (mol%) of diethylene glycol units relative to all diol units in all polyesters contained in the polyester layer Y is 1.5 to 7.5.

[33] A packaging film having at least a polyester layer X and a polyester layer Y, A packaging film, wherein at least one selected from a polyester layer X and a polyester layer Y contains a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an acyclic aliphatic diol having a branched chain with two or more carbon atoms.

[34] The polyester layer X contains a copolymer polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an acyclic aliphatic diol having a branched chain having two or more carbon atoms; The packaging film according to

[33] , wherein the polyester layer Y comprises a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component comprises an acyclic aliphatic diol having a branched chain having two or more carbon atoms.

[35] A film for packaging material, comprising a copolymer polyester having structural units derived from a dicarboxylic acid component and a diol component, the diol component comprises an alicyclic diol and a branched acyclic aliphatic diol; The total content (mol%) of the alicyclic diol unit and the branched acyclic aliphatic diol unit relative to all diol units in all polyesters contained in a region from one side of the film to 50% of the entire thickness is A packaging film that is higher than the total content (mol%) of alicyclic diol units and branched acyclic aliphatic diol units relative to all diol units in all polyester contained in a region extending from the other side of the film through 50% of the overall thickness.

[36] The packaging film according to

[35] , wherein the total content (mol%) of alicyclic diol units and branched acyclic aliphatic diol units relative to all diol units in all polyesters increases continuously from one side of the film to the other side.

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

[14] to

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

[38] A packaging material comprising the film for packaging material according to any one of [1] to

[37] .

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

[37] .

[40] A packaging material having the laminate according to

[39] .

[41] A method for producing a packaging film having at least a polyester layer X and a polyester layer Y, comprising: the polyester layer X contains a copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, the diol component containing an alicyclic diol and a branched acyclic aliphatic diol; the polyester layer Y contains a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, the diol component containing an alicyclic diol and a branched acyclic aliphatic diol; a step of laminating and stretching a resin composition constituting the polyester layer X and the polyester layer Y; a step of performing heat setting treatment after the step of performing stretching, A method for manufacturing a packaging film, in which the heat setting temperature in the heat setting step is 200°C or higher but lower than 250°C.

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

[41] , wherein the heat setting temperature in the step of performing heat setting is 220°C or higher and 235°C or lower. [Effects 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 INVENTION

[0012] The present invention will be described in detail below. The following description may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, when "X to Y" (X and Y are arbitrary numbers) is used, it means "X or more and Y or less" unless otherwise specified, and also includes "preferably greater than X" or "preferably less than Y." Furthermore, when "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the meaning "preferably greater than X" or "preferably less than Y." In the following description, the terms "film" and "sheet" are not clearly distinguished from each other, and the term "film" includes the term "sheet," and the term "sheet" includes the term "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) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol. The polyester layer Y contains a copolymer polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol. The polyester film is preferably used as a packaging film.

[0014] A second embodiment of the present invention relates to a polyester film (hereinafter also referred to as "the polyester film") having at least a polyester layer X and a polyester layer Y. Here, at least one selected from the polyester layer X and the polyester layer Y contains a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an acyclic aliphatic diol having a branched chain with two or more carbon atoms. The polyester film of the second embodiment is also preferably a film for packaging materials.

[0015] In the second embodiment, it is preferred that both the polyester layer X and the polyester layer Y contain a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, and that the diol component contains an acyclic aliphatic diol having a branched chain with two or more carbon atoms. Specifically, it is preferred that the polyester layer X contains a copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, and that the diol component contains an acyclic aliphatic diol having a branched chain with two or more carbon atoms, and that the polyester layer Y contains a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and that the diol component contains an acyclic aliphatic diol having a branched chain with two or more carbon atoms.

[0016] A third embodiment of the present invention relates to a polyester film (hereinafter also referred to as "the polyester film") comprising a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, wherein the diol component comprises an alicyclic diol and a branched acyclic aliphatic diol, and the combined content (mol%) of the alicyclic diol units and the branched acyclic aliphatic diol units relative to all diol units in all polyester in a region extending from one side of the film through 50% of the overall thickness is higher than the combined content (mol%) of the alicyclic diol units and the branched acyclic aliphatic diol units relative to all diol units in all polyester in a region extending from the other side of the film through 50% of the overall thickness. In the third embodiment, the polyester film may be a single-layer film. The combined content (mol%) of the copolymerized components (alicyclic diol component and branched acyclic aliphatic diol component) varies across the thickness of the single-layer film. The polyester film in the third embodiment is also preferably a film for packaging materials.

[0017] In the third embodiment, it is preferable that the total content (mol%) of alicyclic diol units and branched acyclic aliphatic diol units relative to all diol units in the entire polyester increases continuously from one side of the film to the other side. For example, the total content (mol%) of copolymerized units (alicyclic diol units and branched acyclic aliphatic diol units) may be 0 mol% on one side of the film, but the total content (mol%) of copolymerized units (alicyclic diol units and branched acyclic aliphatic diol units) preferably increases continuously to about 10 to 50 mol% on the other side of the film. In this specification, "continuously increasing" means that the total content (mol%) of copolymerized units (alicyclic diol units and branched acyclic aliphatic diol units) increases at a substantially constant rate in the thickness direction. For example, when a film is divided into 10 layers in the thickness direction, a stepwise increase in the total content (mol%) of copolymerization units (alicyclic diol units and branched acyclic aliphatic diol units) in each of the 10 divided layers is also included in the term "continuously increasing." In the third embodiment, the side having a higher total content (mol%) of copolymerization units (alicyclic diol units and branched acyclic aliphatic diol units) exhibits excellent heat sealability.

[0018] In the first to third embodiments of the present invention, the polyester film has the above-described structure, allowing the formation of packaging bags with excellent drop resistance. Furthermore, the polyester film has the above-described structure, exhibiting excellent heat-sealing properties. Additionally, the polyester film can be made of polyester materials for all of its constituent resin components, making it easy to realize packaging materials made of a single material and in a single sheet (single layer). Therefore, the polyester film has excellent recyclability.

[0019] The polyester film may be a non-stretched film (sheet) or a stretched film. A uniaxially or biaxially stretched film is preferred. A biaxially stretched film is preferred because of its excellent balance of mechanical properties and flatness.

[0020] The polyester film may contain optional components in addition to polyester. Examples of optional components include particles (inorganic and organic particles), UV absorbers, antioxidants, antistatic agents, and heat stabilizers. The polyester film preferably contains particles, and more preferably 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 inclusion of particles in the polyester film can impart slipperiness to the polyester film and prevent scratches during each process. The particle content 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, relative to the total mass of the polyester film. The particle content 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, relative to the total mass of the polyester film.

[0021] <Polyester layer X> In the first and second embodiments, 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.

[0022] The polyester layer X contains a copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component. In a first embodiment, the diol component of the copolymerized polyester (x) contains an alicyclic diol and a branched acyclic aliphatic diol. In a second embodiment, the diol component of the copolymerized polyester (x) preferably contains a branched acyclic aliphatic diol having two or more carbon atoms.

[0023] In this specification, the term "copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component" refers to a copolymerized polyester obtained by copolymerizing one dicarboxylic acid component, one diol component, and another copolymerization component. Specifically, the term encompasses polyesters 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 a copolymerized polyester contains two or more dicarboxylic acid components, the dicarboxylic acid component other than the dicarboxylic acid component with the largest content among the dicarboxylic acid components is referred to as the "dicarboxylic acid copolymerized component." When a copolymerized polyester contains two or more diol components, the diol component other than the diol component with the largest content among the diol components is referred to as the "diol copolymerized component." In this embodiment, the "copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component" is preferably a polyester obtained by copolymerizing one dicarboxylic acid component and two or more diol components. In the first embodiment, the "diol copolymerization component" preferably contains at least an alicyclic diol and an acyclic aliphatic diol having a branched chain, and in the second embodiment, the "diol copolymerization component" preferably contains at least an acyclic aliphatic diol having a branched chain with two or more carbon atoms.

[0024] 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.

[0025] 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% of the total thickness of the polyester film, and more preferably 15 to 25%.

[0026] (copolymer polyester (x)) In the first embodiment, the copolymer polyester (x) is a copolymer having structural units derived from a dicarboxylic acid component and a diol component, and the copolymer polyester (x) preferably has a structural unit derived from a terephthalic acid component (hereinafter also referred to as a terephthalic acid unit), a structural unit derived from an ethylene glycol component (hereinafter also referred to as an ethylene glycol unit), a structural unit derived from an alicyclic diol component (hereinafter also referred to as an alicyclic diol unit), and a structural unit derived from a branched acyclic aliphatic diol component (hereinafter also referred to as a branched acyclic aliphatic diol unit). In the first embodiment, the copolymer polyester (x) preferably has an alicyclic diol unit and a branched acyclic aliphatic diol as structural units derived from the diol copolymerization component.

[0027] In a second embodiment, the copolymer polyester (x) is a copolymer having structural units derived from a dicarboxylic acid component and a diol component, and the copolymer polyester (x) preferably has a structural unit derived from a terephthalic acid component (hereinafter also referred to as a terephthalic acid unit), a structural unit derived from an ethylene glycol component (hereinafter also referred to as an ethylene glycol unit), and a structural unit derived from an acyclic aliphatic diol having a branched chain with two or more carbon atoms (hereinafter also referred to as an acyclic aliphatic diol unit having a branched chain with two or more carbon atoms). In the second embodiment, the copolymer polyester (x) preferably has an acyclic aliphatic diol having a branched chain with two or more carbon atoms as a structural unit derived from a diol copolymerization component.

[0028] Examples of the alicyclic diol constituting the copolymer 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; norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5-norbornanedimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalindimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among these, 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] In the first embodiment, the acyclic aliphatic diol constituting the copolymer polyester (x) has a branched chain. The number of branched chains possessed by the acyclic aliphatic diol may be 1 or more, preferably 2 or more, and more preferably 2 or 3. Examples of the branched acyclic aliphatic diol include neopentyl glycol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

[0030] In particular, the acyclic aliphatic diol preferably has a branched chain having two or more carbon atoms. In the second embodiment, the acyclic aliphatic diol has a branched chain having two or more carbon atoms. The number of carbon atoms in the branched chain is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The acyclic aliphatic diol having a branched chain may have at least one branched chain having the above-mentioned number of carbon atoms, and preferably has two or more branched chains having the above-mentioned number of carbon atoms. When the acyclic aliphatic diol has two or more branched chains, the respective branched chains may have the same or different numbers of carbon atoms, but preferably have different numbers of carbon atoms.

[0031] The acyclic aliphatic diol having a branched chain having two or more carbon atoms is preferably one or more selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol, more preferably one or more selected from the group consisting of 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2,2-diethyl-1,3-propanediol, and even more preferably 2-butyl-2-ethyl-1,3-propanediol. These acyclic aliphatic diols are primary alcohols and therefore prone to transesterification, and because they have two or more branched chains, they may be prone to inhibiting regular packing of molecular chains, which can lead to reduced crystallinity in the resulting film and improved drop resistance.

[0032] In this embodiment, the inclusion of a branched acyclic aliphatic diol as a copolymerization component is expected to prevent regular packing of polymer chains, resulting in a decrease in the crystallinity of the polyester layer X. A polyester layer X with reduced crystallinity is thought to have improved film flexibility, thereby improving drop resistance and seal strength. It is also thought to have improved transparency. This effect is more pronounced with an acyclic aliphatic diol having a branched chain with two or more carbon atoms. On the other hand, by setting the number of carbon atoms in the branched chain to a predetermined value or less, the flexibility of the diol component itself and the copolymerized polyester (x) can be increased, thereby more effectively improving impact resistance and drop resistance. Furthermore, increasing the flexibility of the diol component itself and the copolymerized polyester (x) can absorb and disperse impact, thereby suppressing breakage and damage to the polyester film.

[0033] Examples of other diol components (diol components excluding alicyclic diols and acyclic aliphatic diols having a branched chain containing two or more carbon atoms; hereinafter, also referred to as "other diol components") constituting the copolymer polyester (x) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. One or more of these diol components may be used. Among these, the copolymer polyester (x) preferably contains, as the other diol component, one or more selected from ethylene glycol and diethylene glycol, and more preferably contains diethylene glycol. The copolymer polyester (x) also preferably contains, as the other diol component, ethylene glycol and diethylene glycol. For example, the copolymerized polyester (x) preferably contains, as diol-derived units, ethylene glycol units, alicyclic diol units, and branched acyclic aliphatic diol units, and more preferably ethylene glycol units, diethylene glycol units, alicyclic diol units, and branched acyclic aliphatic diol units. When the copolymerized polyester (x) contains structural units derived from the copolymerization components in addition to ethylene glycol units, the polymerization stability of the copolymerized polyester and the heat resistance and strength of the polyester film can be improved, and when a packaging bag is formed from the polyester film, drop resistance can be improved.

[0034] Typically, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, a portion of the ethylene glycol is modified to form diethylene glycol, which is then incorporated into the polyester skeleton. This diethylene glycol is referred to as "by-product diethylene glycol," and the amount of by-product diethylene glycol varies depending on the type of polycondensation (transesterification, direct polycondensation), etc., but is approximately 1 to several mol% of the ethylene glycol. Therefore, in the present invention, ethylene glycol includes diethylene glycol in an amount of 2 mol% or less per 100 mol% of the diol component constituting a polyester (including copolymerized polyester) using ethylene glycol as one of the raw materials. However, when the amount exceeds 2 mol%, it can be determined that diethylene glycol is used as a copolymerization component.

[0035] In the first embodiment, 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. Furthermore, 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, even more preferably 25 mol% or less, and particularly preferably 20 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 the two or more alicyclic diols. By setting the content of alicyclic diol units in the polyester layer X within the above range, the drop resistance and seal strength of the polyester film can be improved, and the heat resistance and film strength can be further increased. In the second embodiment, the polyester contained in the polyester layer X may also contain an alicyclic diol unit, and in this case, the content of the alicyclic diol unit may be within the above range.

[0036] The total content of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer X is preferably 0.5 mol% or more, more preferably 1 mol% or more, even more preferably 1.5 mol% or more, even more preferably 2 mol% or more, and particularly preferably 2.5 mol% or more. Furthermore, the total content of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer X is preferably 30 mol% or less, more preferably 25 mol% or less, even more preferably 20 mol% or less, even more preferably 15 mol% or less, and particularly preferably 10 mol% or less. When two or more branched acyclic aliphatic diols are used in combination, the "total content of acyclic aliphatic diol units" refers to the total amount of two or more branched acyclic aliphatic diols. By setting the content of branched acyclic aliphatic diol units in polyester layer X within the above range, the drop resistance and seal strength of the polyester film can be improved, and the heat resistance and film strength can be further enhanced. In the second embodiment, the total content of acyclic aliphatic diol units having a branched chain with two or more carbon atoms is preferably within the above range.

[0037] The total content of structural units derived from other diol components (other diol units) relative to all diol units in all polyesters contained in polyester layer X is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. Furthermore, the total content of structural units derived from other diol components (other diol units) relative to all diol units in all polyesters contained in polyester layer X is preferably 97.5 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. In particular, the content of ethylene glycol units is preferably within the above range. By setting the content of diol units other than alicyclic diols contained in polyester layer X within the above range, the drop resistance and seal strength of the polyester film can be easily improved.

[0038] In particular, the total content of structural units (diethylene glycol units) derived from diethylene glycol components relative to all diol units in all polyesters contained in the polyester layer X is preferably 1.5 mol% or more, more preferably 2 mol% or more, even more preferably 3 mol% or more, even more preferably 3.5 mol% or more, and particularly preferably 4 mol% or more. Furthermore, the total content of structural units (diethylene glycol units) derived from diethylene glycol components relative to all diol units in all polyesters contained in the polyester layer X is preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 12 mol% or less, even more preferably 10 mol% or less, and particularly preferably 7 mol% or less. By setting the content of diethylene glycol units in the polyester layer X within the above range, the crystallinity of the polyester layer X can be reduced while maintaining hydrolysis resistance, resulting in more effective enhancement of seal strength. By setting the content of diethylene glycol units in the polyester layer X within the above range, the flexibility of the polyester layer X can be increased, thereby more effectively enhancing impact resistance, drop resistance, and transparency.

[0039] The copolymer polyester (x) may contain, as a structural unit derived from a dicarboxylic acid component, a structural unit derived from a dicarboxylic acid component other than a terephthalic acid unit (hereinafter also referred to as "other dicarboxylic acid unit"). Examples of the other dicarboxylic acid include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples 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. The other dicarboxylic acids may be one type or a combination of two or more types.

[0040] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When two or more other dicarboxylic acids are used in addition to terephthalic acid, the "total content of other dicarboxylic acid units" refers to the total amount of the two or more other dicarboxylic acids.

[0041] The content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X is preferably 70 mol% or more, more preferably 75 mol% or more, even more preferably 80 mol% or more, even more preferably 85 mol% or more, and particularly preferably 90 mol% or more. Alternatively, the content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer X may be 100 mol%.

[0042] In this embodiment, 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 branched acyclic aliphatic diol units relative to all diol 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 branched acyclic aliphatic diol units contained in polyester layer X within the above ranges, it becomes easier to improve the drop resistance of the polyester film and also improve the seal strength.

[0043] Copolymer polyester (x) copolymerized with an alicyclic diol has a high intrinsic viscosity (IV), which facilitates the achievement of both superior mechanical properties and good film-forming properties. For example, the intrinsic viscosity of copolymer polyester (x) is preferably 0.66 to 0.86 dL / g, more preferably 0.68 to 0.84 dL / g. Furthermore, the intrinsic viscosity of copolymer polyester (x) is preferably higher than that of a general homopolyester, specifically, preferably 0.03 to 0.25 dL / g higher, more preferably 0.05 to 0.22 dL / g higher.

[0044] In particular, copolymerized polyesters (x) copolymerized with alicyclic diols such as 1,4-cyclohexanedimethanol (CHDM) have multiple conformations. When impacted, the cyclohexane undergoes conformational transformation, absorbing the impact energy and reducing molecular chain fracture. This allows polyester films to exhibit excellent drop resistance. Furthermore, the inclusion of a branched acyclic aliphatic diol as a copolymerization component is expected to disrupt the regular packing of polymer chains, resulting in reduced crystallinity of the polyester film. Polyester films with reduced crystallinity are thought to have increased flexibility, resulting in improved drop resistance and improved seal strength. Transparency is also expected to be improved. Thus, the combined use of an alicyclic diol and a branched acyclic aliphatic diol as copolymerization components can enhance drop resistance while also improving seal strength.

[0045] (copolymer polyester (x-1) / copolymer polyester (x-2)) In the first embodiment, the polyester layer X may contain two or more copolymerized polyesters instead of the copolymerized polyester (x). In this case, the polyester layer X may contain, for example, a copolymerized polyester (x-1) having structural units derived from a dicarboxylic acid component and a diol component, and a copolymerized polyester (x-2) having structural units derived from a dicarboxylic acid component and a diol component. In this case, it is preferable that the diol component constituting the copolymerized polyester (x-1) contains an alicyclic diol, and the diol component constituting the copolymerized polyester (x-2) contains a branched acyclic aliphatic diol. More specifically, it is preferable that the polyester layer X contains a copolymerized polyester (x-1) containing an alicyclic diol unit as a copolymerization component in addition to a dicarboxylic acid unit and a diol unit, and a copolymerized polyester (x-2) containing a branched acyclic aliphatic diol unit as a copolymerization component in addition to a dicarboxylic acid unit and a diol unit.

[0046] The copolymer polyester (x-1) contains alicyclic diol units as copolymerization components in addition to terephthalic acid units and diol units. Examples of the alicyclic diol constituting the copolymer polyester (x-1) 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; norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5-norbornanedimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalindimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among these, 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.

[0047] In this embodiment, the other diol units in the copolymer polyester (x-1) are units derived from diols other than alicyclic diols and branched acyclic aliphatic diols. Examples of the diol component (other 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, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. One or more of these diol components may be used. In particular, the copolymer polyester (x-1) preferably contains one or more diols selected from ethylene glycol and diethylene glycol, and more preferably ethylene glycol, as the other diol component. That is, it is particularly preferable that the copolymer polyester (x-1) has terephthalic acid units, ethylene glycol units, and alicyclic diol units.

[0048] The copolymer polyester (x-2) contains, in addition to terephthalic acid units and diol units, a branched acyclic aliphatic diol unit as a copolymerization component. Examples of the branched acyclic aliphatic diol constituting the copolymer polyester (x-2) include neopentyl glycol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

[0049] Among these, the acyclic aliphatic diol having a branched chain preferably has a branched chain having 2 or more carbon atoms, and more preferably has two branched chains having 2 or more carbon atoms. When the acyclic aliphatic diol has two or more branched chains having 2 or more carbon atoms, the respective branched chains may have the same number of carbon atoms or different numbers of carbon atoms, but preferably have different numbers of carbon atoms.

[0050] The acyclic aliphatic diol having a branched chain having two or more carbon atoms is preferably one or more selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol, more preferably one or more selected from the group consisting of 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2,2-diethyl-1,3-propanediol, and even more preferably 2-butyl-2-ethyl-1,3-propanediol. These acyclic aliphatic diols are primary alcohols and therefore prone to transesterification, and because they have two or more branched chains, they may be prone to inhibiting regular packing of molecular chains, which can lead to reduced crystallinity in the resulting film and improved drop resistance.

[0051] In this embodiment, the other diol units in the copolymer polyester (x-2) are units derived from diols other than alicyclic diols and branched acyclic aliphatic diols. Examples of the diol component (other diol component) in the copolymer polyester (x-2) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. One or more of these diol components may be used. In particular, the copolymer polyester (x-2) preferably contains one or more selected from ethylene glycol and diethylene glycol as the other diol component, and more preferably contains ethylene glycol and diethylene glycol. That is, it is particularly preferable that the copolymer polyester (x-2) has terephthalic acid units, ethylene glycol units, alicyclic diol units and diethylene glycol units.

[0052] The copolymer polyester (x-1) and the copolymer polyester (x-2) may contain structural units derived from dicarboxylic acid components other than terephthalic acid units (hereinafter also referred to as "other dicarboxylic acid units") as structural units derived from dicarboxylic acid components. Examples of other dicarboxylic acids include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples 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. The other dicarboxylic acids may be one type or a combination of two or more types.

[0053] The total content of alicyclic diol units relative to all diol units in copolymer polyester (x-1) 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 copolymer polyester (x-1) 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.

[0054] The total content of branched acyclic aliphatic diol units relative to all diol units in copolymer polyester (x-2) is preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 10 mol% or more, and particularly preferably 12 mol% or more. The total content of branched acyclic aliphatic diol units relative to all diol units in copolymer polyester (x-2) is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, even more preferably 25 mol% or less, and particularly preferably 20 mol% or less.

[0055] When the copolymer polyester (x-1) and / or the copolymer polyester (x-2) contain a structural unit (diethylene glycol unit) derived from a diethylene glycol component as a unit derived from a diol other than an alicyclic diol and a branched acyclic aliphatic diol, the content of the diethylene glycol unit relative to the total diol units in each copolymer polyester is preferably 3 mol% or more, more preferably 4 mol% or more, even more preferably 5 mol% or more, and even more preferably 6 mol% or more. Furthermore, the content of the diethylene glycol unit relative to the total diol units in each copolymer polyester is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, even more preferably 12 mol% or less, and particularly preferably 10 mol% or less.

[0056] The content of ethylene glycol units relative to all diol units in each of the copolymer polyesters (x-1) and / or (x-2) is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 58 mol% or more, and even more preferably 62 mol% or more. The content of ethylene glycol units relative to all diol units in each copolymer polyester is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and even more preferably 82 mol% or less.

[0057] 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, even more preferably 20% by mass or more, still more preferably 25% by mass or more, and particularly preferably 30% by mass or more, based on the total amount of 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 amount of polyester contained in the polyester layer X. The content of the copolymer polyester (x-2) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, based on the total amount of polyester contained in the polyester layer X. The content of the copolymer polyester (x-2) is preferably 75% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less, based on the total amount of polyester contained in the polyester layer X.

[0058] 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. There is no particular upper limit to the intrinsic viscosity of the copolymer polyester (x-1), but it 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.

[0059] 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. There is no particular upper limit to the intrinsic viscosity of the copolymer polyester (x-2), but it 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.

[0060] 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, "homopolyester" refers to a polyester obtained by polycondensation of one dicarboxylic acid component and one 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 several mol % of by-product diethylene glycol, and even in such a case, it is included in the homopolyethylene terephthalate.

[0061] 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 amount of polyester contained in the polyester layer X. Furthermore, 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 amount of polyester contained in the polyester layer X.

[0062] (optional ingredient) The polyester layer X may contain optional components other than those described above, as necessary, such as particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0063] In particular, 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 inclusion of particles in the polyester film can impart slipperiness to the polyester film and prevent scratches during each process. The particle content 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, relative to the total mass of the polyester layer X. The particle content 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, relative to the total mass of the polyester layer X.

[0064] <Polyester layer Y> In the first and second embodiments, 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 faces away from the contents, i.e., the outer side, when the polyester film is used as a packaging material, etc. Furthermore, when the polyester film is composed of three layers, polyester layer X, polyester layer Y, and polyester layer Z, as described below, polyester layer Y preferably serves as an intermediate layer.

[0065] The polyester layer Y contains a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component. In a first embodiment, the diol component of the copolymerized polyester (y) contains an alicyclic diol and a branched acyclic aliphatic diol. In a second embodiment, the diol component of the copolymerized polyester (y) preferably contains a branched acyclic aliphatic diol having two or more carbon atoms.

[0066] The polyester layer Y may be composed 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.

[0067] 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.

[0068] (copolymer polyester (y)) In the first embodiment, the copolymer polyester (y) is a copolymer having structural units derived from a dicarboxylic acid component and a diol component, and the copolymer polyester (y) preferably has terephthalic acid units, ethylene glycol units, alicyclic diol units, and branched acyclic aliphatic diol units. In the first embodiment, the copolymer polyester (y) preferably has alicyclic diol units and branched acyclic aliphatic diol units as structural units derived from the diol copolymerization component.

[0069] In a second embodiment, the copolymer polyester (y) is a copolymer having structural units derived from a dicarboxylic acid component and a diol component, and the copolymer polyester (y) preferably has a structural unit derived from a terephthalic acid component (hereinafter also referred to as a terephthalic acid unit), a structural unit derived from an ethylene glycol component (hereinafter also referred to as an ethylene glycol unit), and a structural unit derived from an acyclic aliphatic diol having a branched chain with two or more carbon atoms (hereinafter also referred to as an acyclic aliphatic diol unit having a branched chain with two or more carbon atoms). In the second embodiment, the copolymer polyester (y) preferably has an acyclic aliphatic diol having a branched chain with two or more carbon atoms as a structural unit derived from a diol copolymerization component.

[0070] Examples of the alicyclic diol constituting the copolymer 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; norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5-norbornanedimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalindimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among these, 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.

[0071] In the first embodiment, the acyclic aliphatic diol constituting the copolymerized polyester (y) has a branched chain. The number of branched chains possessed by the acyclic aliphatic diol may be 1 or more, and preferably 2. Examples of the acyclic aliphatic diol having a branched chain include neopentyl glycol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

[0072] In particular, the acyclic aliphatic diol preferably has a branched chain having two or more carbon atoms. In the second embodiment, the acyclic aliphatic diol has a branched chain having two or more carbon atoms. The number of carbon atoms in the branched chain is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The acyclic aliphatic diol having a branched chain may have at least one branched chain having the above-mentioned number of carbon atoms, and preferably has two or more branched chains having the above-mentioned number of carbon atoms. Note that when the acyclic aliphatic diol has two or more branched chains, the respective branched chains may have the same number of carbon atoms or different numbers of carbon atoms.

[0073] The acyclic aliphatic diol having a branched chain having two or more carbon atoms is preferably one or more selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol, more preferably one or more selected from the group consisting of 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2,2-diethyl-1,3-propanediol, and even more preferably 2-butyl-2-ethyl-1,3-propanediol. These acyclic aliphatic diols are primary alcohols and therefore prone to transesterification, and because they have two or more branched chains, they may be prone to inhibiting regular packing of molecular chains, which can lead to reduced crystallinity in the resulting film and improved drop resistance.

[0074] Examples of other diol components (diol components excluding alicyclic diols and acyclic aliphatic diols having a branched chain containing two or more carbon atoms; hereinafter, also referred to as "other diol components") constituting the copolymer polyester (y) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. One or more of these diol components may be used. In particular, the copolymer polyester (y) preferably contains one or more diol components selected from ethylene glycol and diethylene glycol, and more preferably contains ethylene glycol and diethylene glycol. For example, the copolymerized polyester (y) preferably contains, as diol-derived units, ethylene glycol units, alicyclic diol units, and branched acyclic aliphatic diol units, and more preferably ethylene glycol units, alicyclic diol units, branched acyclic aliphatic diol units, alicyclic diol units, and branched acyclic aliphatic diol units. When the copolymerized polyester (y) contains structural units derived from the copolymerization components in addition to ethylene glycol units, the polymerization stability of the copolymerized polyester and the heat resistance and strength of the polyester film can be improved, and when a packaging bag is formed from the polyester film, drop resistance can be improved.

[0075] Typically, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, a portion of the ethylene glycol is modified to form diethylene glycol, which is then incorporated into the polyester skeleton. This diethylene glycol is referred to as "by-product diethylene glycol," and the amount of by-product diethylene glycol varies depending on the type of polycondensation (transesterification, direct polycondensation), etc., but is approximately 1 to several mol% of the ethylene glycol. Therefore, in the present invention, ethylene glycol includes diethylene glycol in an amount of 2 mol% or less per 100 mol% of the diol component constituting a polyester (including copolymerized polyester) using ethylene glycol as one of the raw materials. However, when the amount exceeds 2 mol%, it can be determined that diethylene glycol is used as a copolymerization component.

[0076] In the first embodiment, the total content of alicyclic diol units relative to all diol units in all polyesters contained in the 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. Furthermore, the total content of alicyclic diol units relative to all diols in all polyesters contained in the polyester layer Y is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, even more preferably 13 mol% or less, and particularly preferably 10 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 the two or more alicyclic diols. By setting the content of alicyclic diol units in the polyester layer Y within the above range, the drop resistance of the polyester film can be improved, and the heat resistance and film strength can be further increased. In the second embodiment, the polyester contained in the polyester layer Y may also contain an alicyclic diol unit, and in this case, the content of the alicyclic diol unit may be within the above range.

[0077] The total content of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is preferably 0.5 mol% or more, more preferably 1 mol% or more, even more preferably 1.5 mol% or more, even more preferably 2 mol% or more, and particularly preferably 2.5 mol% or more. Furthermore, the total content of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 12 mol% or less, even more preferably 10 mol% or less, and particularly preferably 7 mol% or less. When two or more branched acyclic aliphatic diols are used in combination, the "total content of acyclic aliphatic diol units" refers to the total amount of the two or more branched acyclic aliphatic diols. By setting the content of branched acyclic aliphatic diol units in the polyester layer Y within the above range, the drop resistance of the polyester film can be improved, and the heat resistance and film strength can be further enhanced. In the second embodiment, the total content of acyclic aliphatic diol units having a branched chain with two or more carbon atoms is preferably within the above range.

[0078] The total content of structural units derived from other diol components (other diol units) relative to all diol 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. Furthermore, the total content of structural units derived from other diol components (other diol units) 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.

[0079] In particular, the total content of structural units (diethylene glycol units) derived from diethylene glycol components relative to all diol 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 1.4 mol% or more, and even more preferably 1.8 mol% or more. Furthermore, the total content of structural units (diethylene glycol units) derived from diethylene glycol components relative to all diol units in all polyesters contained in polyester layer Y is preferably 15 mol% or less, more preferably 12 mol% or less, even more preferably 10 mol% or less, even more preferably 7 mol% or less, and particularly preferably 5 mol% or less. By setting the content of diethylene glycol units in polyester layer Y within the above range, the crystallinity of copolymerized polyester (y) can be reduced, and as a result, impact resistance, drop resistance, and transparency can be more effectively improved.

[0080] The copolymerized polyester (y) may contain, as a structural unit derived from a dicarboxylic acid component, a structural unit derived from a dicarboxylic acid component other than a terephthalic acid unit (hereinafter also referred to as "other dicarboxylic acid unit"). Examples of other dicarboxylic acids include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples 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, adipic acid, sebacic acid, dimer acid, and isophthalic acid are preferred, aromatic dicarboxylic acids are more preferred, and isophthalic acid is even more preferred. The other dicarboxylic acids may be one type or a combination of two or more types.

[0081] The total content of other dicarboxylic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When two or more other dicarboxylic acids are used in addition to terephthalic acid, the "total content of other dicarboxylic acid units" refers to the total amount of the two or more other dicarboxylic acids.

[0082] 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, even more preferably 85 mol% or more, and particularly preferably 90 mol% or more. Alternatively, the content of terephthalic acid units relative to all dicarboxylic acid units in all polyesters contained in polyester layer Y may be 100 mol%.

[0083] The value obtained by dividing the content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in polyester layer Y by the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer Y is preferably 0.5 to 4, more preferably 0.8 to 3, even more preferably 1 to 2.5, and even more preferably 1.2 to 2.2. By setting the relationship between the contents of alicyclic diol units and branched acyclic aliphatic diol units contained in polyester layer Y within the above ranges, it becomes easier to improve the drop resistance of the polyester film and also to improve the seal strength.

[0084] Copolymerized polyester (y) copolymerized with an alicyclic diol has a relatively high intrinsic viscosity (IV), which facilitates the achievement of both superior mechanical properties and good film-forming properties. For example, the intrinsic viscosity of copolymerized polyester (y) is preferably 0.66 to 0.86 dL / g, more preferably 0.68 to 0.84 dL / g. Furthermore, the intrinsic viscosity of copolymerized polyester (y) is preferably higher than that of a general homopolyester, specifically, preferably 0.03 to 0.25 dL / g higher, more preferably 0.05 to 0.22 dL / g higher.

[0085] In particular, polyesters (y) copolymerized with alicyclic diols such as 1,4-cyclohexanedimethanol (CHDM) have multiple conformations. When impacted, the cyclohexane undergoes conformational transformation, absorbing the impact energy and reducing molecular chain fracture. This allows polyester films to exhibit excellent drop resistance. Furthermore, the inclusion of a branched acyclic aliphatic diol as a copolymerization component is expected to disrupt the regular packing of the polymer chains, resulting in reduced crystallinity of the polyester film. Polyester films with reduced crystallinity are thought to have improved drop resistance due to increased film flexibility. Thus, drop resistance can be improved by combining an alicyclic diol and a branched acyclic aliphatic diol as copolymerization components.

[0086] (Copolymer polyester (y-1) / Copolymer polyester (y-2)) In the first embodiment, the polyester layer Y may contain two or more copolymerized polyesters instead of the copolymerized polyester (y). In this case, the polyester layer Y may contain, for example, a copolymerized polyester (y-1) having structural units derived from a dicarboxylic acid component and a diol component, and a copolymerized polyester (y-2) having structural units derived from a dicarboxylic acid component and a diol component. In this case, it is preferable that the diol component constituting the copolymerized polyester (y-1) contains an alicyclic diol, and the diol component constituting the copolymerized polyester (y-2) contains a branched acyclic aliphatic diol. More specifically, it is preferable that the polyester layer Y contains a copolymerized polyester (y-1) containing an alicyclic diol unit as a copolymerization component in addition to a dicarboxylic acid unit and a diol unit, and a copolymerized polyester (y-2) containing a branched acyclic aliphatic diol unit as a copolymerization component in addition to a dicarboxylic acid unit and a diol unit.

[0087] The copolymer polyester (y-1) contains alicyclic diol units as copolymerization components in addition to terephthalic acid units and diol units. Examples of the alicyclic diol constituting the copolymer polyester (y-1) 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; norbornanedimethanols such as 2,3-norbornanedimethanol and 2,5-norbornanedimethanol; tricyclodecane dimethanol, pentacyclopentadecanedimethanol, 1,3-adamantanediol, 2,2-adamantanediol, decalindimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. Among these, 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.

[0088] The other diol units in the copolymerized polyester (y-1) are units derived from diols other than alicyclic diols and branched acyclic aliphatic diols. Examples of the diol components (other diol components) in the copolymerized polyester (y-1) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. These diol components may be used alone or in combination. In particular, the copolymerized polyester (y-1) preferably contains one or more diols selected from ethylene glycol and diethylene glycol, and more preferably ethylene glycol, as the other diol component. That is, it is particularly preferable that the copolymer polyester (y-1) has terephthalic acid units, ethylene glycol units, and alicyclic diol units.

[0089] The copolymer polyester (y-2) contains, in addition to terephthalic acid units and diol units, a branched acyclic aliphatic diol unit as a copolymerization component. Examples of the branched acyclic aliphatic diol constituting the copolymer polyester (y-2) include neopentyl glycol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

[0090] Among these, the acyclic aliphatic diol having a branched chain preferably has a branched chain having 2 or more carbon atoms, and more preferably has two branched chains having 2 or more carbon atoms. When the acyclic aliphatic diol has two or more branched chains having 2 or more carbon atoms, the respective branched chains may have the same number of carbon atoms or different numbers of carbon atoms, but preferably have different numbers of carbon atoms.

[0091] The acyclic aliphatic diol having a branched chain having two or more carbon atoms is preferably one or more selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol, more preferably one or more selected from the group consisting of 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and 2,2-diethyl-1,3-propanediol, and even more preferably 2-butyl-2-ethyl-1,3-propanediol. These acyclic aliphatic diols are primary alcohols and therefore prone to transesterification, and because they have two or more branched chains, they may be prone to inhibiting regular packing of molecular chains, which can lead to reduced crystallinity in the resulting film and improved drop resistance.

[0092] In this embodiment, the other diol units in the copolymerized polyester (y-2) are units derived from diols other than alicyclic diols and branched acyclic aliphatic diols. Examples of the diol components (other diol components) in the copolymerized polyester (y-2) include aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, bisphenol, and derivatives thereof may also be used. These diol components may be used alone or in combination. In particular, the copolymerized polyester (y-2) preferably contains one or more diols selected from ethylene glycol and diethylene glycol, and more preferably diethylene glycol, as the other diol component. The copolymer polyester (y-2) preferably contains ethylene glycol and diethylene glycol as other diol components. That is, the copolymer polyester (y-2) particularly preferably contains terephthalic acid units, ethylene glycol units, alicyclic diol units, and diethylene glycol units.

[0093] The copolymer polyester (y-1) and the copolymer polyester (y-2) may contain structural units derived from dicarboxylic acid components other than terephthalic acid units (hereinafter also referred to as "other dicarboxylic acid units") as structural units derived from dicarboxylic acid components. Examples of other dicarboxylic acids include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. More specifically, examples 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. The other dicarboxylic acids may be one type or a combination of two or more types.

[0094] The total content of alicyclic diol units relative to all diol units in copolymer polyester (y-1) 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 copolymer polyester (y-1) 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.

[0095] The total content of branched acyclic aliphatic diol units relative to all diol units in copolymer polyester (y-2) is preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 10 mol% or more, and particularly preferably 12 mol% or more. The total content of branched acyclic aliphatic diol units relative to all diol units in copolymer polyester (y-2) is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, even more preferably 25 mol% or less, and particularly preferably 20 mol% or less.

[0096] When the copolymer polyester (y-1) and / or the copolymer polyester (y-2) contain a structural unit (diethylene glycol unit) derived from a diethylene glycol component as a unit derived from a diol other than an alicyclic diol and a branched acyclic aliphatic diol, the content of the diethylene glycol unit relative to the total diol units in each copolymer polyester is preferably 3 mol% or more, more preferably 4 mol% or more, even more preferably 5 mol% or more, and even more preferably 6 mol% or more. Furthermore, the content of the diethylene glycol unit relative to the total diol units in each copolymer polyester is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, even more preferably 12 mol% or less, and particularly preferably 10 mol% or less.

[0097] The content of ethylene glycol units relative to all diol units in each of the copolymer polyesters (y-1) and / or (y-2) is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 58 mol% or more, and even more preferably 62 mol% or more. The content of ethylene glycol units relative to all diol units in each copolymer polyester is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and even more preferably 82 mol% or less.

[0098] The content of the copolymer polyester (y-1) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 14% by mass or more, and even more preferably 18% by mass or more, based on the total amount of 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 26% by mass or less, based on the total amount of 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, even more preferably 14% by mass or more, and even more preferably 18% 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 40% by mass or less, more preferably 35% by mass or less, even more preferably 32% by mass or less, and even more preferably 28% by mass or less, based on the total amount of polyester contained in the polyester layer Y.

[0099] 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. There is no particular upper limit to the intrinsic viscosity of the copolymer polyester (y-1), but it 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.

[0100] 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. There is no particular upper limit to the intrinsic viscosity of the copolymer polyester (y-2), but it 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.

[0101] 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, "homopolyester" refers to a polyester obtained by polycondensation of one dicarboxylic acid component and one 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 several mol % of by-product diethylene glycol, and even in such a case, it is included in the homopolyethylene terephthalate.

[0102] 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 amount of 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 amount of polyester contained in the polyester layer Y.

[0103] (optional ingredient) The polyester layer Y may contain optional components other than those described above, as necessary, such as particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0104] (Relationship between polyester layer X and polyester layer Y) When the total content (mol%) of alicyclic diol units (mol%) and branched acyclic aliphatic diol units (mol%) relative to all diol units in all polyesters contained in polyester layer X is defined as P, and the total content (mol%) of alicyclic diol units (mol%) and branched acyclic aliphatic diol units (mol%) relative to all diol units in all polyesters contained in polyester layer X is defined as Q, it is preferable that P≧Q. That is, the sum of the alicyclic diol unit content and the acyclic aliphatic diol unit content in polyester layer X is preferably the same as or higher than the sum of the alicyclic diol unit content and the acyclic aliphatic diol unit content in polyester layer Y.

[0105] 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.

[0106] 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.

[0107] By achieving the above-mentioned relationship between the P and Q values, a better balance between drop resistance and seal strength can be achieved. For example, copolymerized polyesters containing alicyclic diol components such as 1,4-cyclohexanedimethanol (CHDM) have multiple conformations. Therefore, simply increasing the content of these components, especially when the intrinsic viscosity is high, increases drop resistance, but seal strength tends to increase only slightly relative to the amount of added component. On the other hand, the inclusion of branched acyclic aliphatic diols such as 2-butyl-2-ethyl-1,3-propanediol as copolymerization components disrupts the regular packing of polymer chains, resulting in reduced crystallinity of polyester films. In polyester films with reduced crystallinity, increased flexibility improves drop resistance, but excessive film flexibility is expected to reduce drop resistance. Therefore, in the present polyester film, by satisfying the above-described relationship between the values ​​of P and Q in at least the polyester layers X and Y, a concentration gradient of the copolymerization components (alicyclic diol and branched acyclic aliphatic diol components) is formed in the thickness direction of the polyester film as a whole, making it easier to maintain heat seal strength while also imparting drop resistance. Furthermore, in this embodiment, by satisfying the above-described relationship between the values ​​of P and Q, a concentration gradient of the copolymerization 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 components, interlayer adhesion can be improved, making interlayer delamination less likely to occur. It is presumed that this improved interlayer adhesion allows for smooth transmission of force when an impact is applied, thereby more effectively improving drop resistance. Additionally, improved interlayer adhesion improves the overall strength of the film, more effectively achieving both heat seal strength and drop resistance.

[0108] 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. Furthermore, 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. By keeping this value within the above range, a good balance between drop resistance and seal strength can be achieved.

[0109] The value obtained by dividing the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer X by the content (mol%) of branched acyclic aliphatic 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 1.3 or more. Furthermore, the value obtained by dividing the content (mol%) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in polyester layer X by the content (mol%) of branched acyclic aliphatic 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, even more preferably 4 or less, and even more preferably 3.5 or less. By keeping this value within the above range, a good balance between drop resistance and seal strength can be achieved.

[0110] The value obtained by dividing the total content (mol%) of alicyclic diol units (relative to all diol units in all polyesters) and the content (mol%) of branched acyclic aliphatic diol units (relative to all diol units in all polyesters) contained in polyester layer X by the content (mol%) of diethylene glycol units (relative to all diol units in all polyesters) contained in polyester layer X is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3 or more. Furthermore, the value obtained by dividing the total content (mol%) of alicyclic diol units (relative to all diol units in all polyesters) and the content (mol%) of branched acyclic aliphatic diol units (relative to all diol units in all polyesters) contained in polyester layer X by the content (mol%) of diethylene glycol units (relative to all diol units in all polyesters) contained in polyester layer X is preferably 8 or less, more preferably 7.5 or less, and even more preferably 7 or less. By keeping this value within the above range, a good balance between drop resistance and seal strength can be achieved.

[0111] The value obtained by dividing the total content (mol%) of alicyclic diol units (relative to all diol units in all polyesters) and the content (mol%) of branched acyclic aliphatic diol units (relative to all diol units in all polyesters) contained in the polyester layer Y by the content (mol%) of diethylene glycol units (relative to all diol units in all polyesters) contained in the polyester layer Y is preferably 1.5 or more, more preferably 2 or more, and even more preferably 2.5 or more. Furthermore, the value obtained by dividing the total content (mol%) of alicyclic diol units (relative to all diol units in all polyesters) and the content (mol%) of branched acyclic aliphatic diol units (relative to all diol units in all polyesters) contained in the polyester layer Y by the content (mol%) of diethylene glycol units (relative to all diol units in all polyesters) contained in the polyester layer Y is preferably 7.5 or less, more preferably 7 or less, and even more preferably 6.5 or less. By keeping this value within the above range, drop resistance can be more effectively improved.

[0112] The ratio of the thickness of polyester layer Y to the thickness of polyester layer X (thickness of polyester layer Y / thickness of polyester layer X) is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 2 or more. Furthermore, the ratio of the thickness of polyester layer Y to the thickness of polyester layer X (thickness of polyester layer Y / thickness of 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 polyester layer Y to the thickness of polyester layer X within the above range, a good balance between drop resistance and seal strength can be achieved.

[0113] <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.

[0114] 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, it is possible to improve heat resistance and film strength. This also makes it possible to increase the heat sealing temperature, which in turn increases the heat sealing strength. Furthermore, by making the outermost layer a layer containing homopolyethylene terephthalate (z) as a main component resin, it is also possible to improve printability.

[0115] The term "main component resin" refers to the resin with the largest content among the resins constituting the polyester layer Z. The main component resin preferably accounts for 50% by mass or more, particularly 70% by mass or more, and particularly 80% by mass or more (including 100% by mass) of the resins constituting the polyester layer Z.

[0116] 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 improving 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.

[0117] The polyester layer Z may be composed solely of homopolyethylene terephthalate (z) or may contain a resin (z-1) other than homopolyethylene terephthalate (z).

[0118] The polyester layer Z may contain, as a resin (z-1) other than the homopolyethylene terephthalate (z), a copolymerized polyester (z-1) having structural units derived from a dicarboxylic acid component and a diol component. Examples of the diol component constituting the copolymerized polyester (z-1) include alicyclic diols and / or acyclic aliphatic diols. The acyclic aliphatic diol may be any diol other than ethylene glycol, and examples thereof include acyclic linear aliphatic diols having 3 or more carbon atoms and acyclic aliphatic diols having a branched chain. Examples of the alicyclic diols and acyclic aliphatic diols include the alicyclic diols and acyclic aliphatic diols constituting the copolymerized polyesters contained in the polyester layer X and the polyester layer Y.

[0119] 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.

[0120] The polyester film preferably comprises a polyester layer X, a polyester layer Y, and a polyester layer Z in this order. In this case, the laminate structure preferably has a total content (mol%) of copolymerization components (alicyclic diol component and branched acyclic aliphatic diol component) decreasing sequentially from polyester layer X to polyester layer Z. This allows the polyester layer X to exhibit high sealant strength while the polyester layer Z contributes to improving strength, resulting in a good balance between drop resistance and seal strength. Furthermore, the polyester layer Z has high heat resistance, which can improve printability and processability.

[0121] That is, with respect to the total content (mol%) of the alicyclic diol unit and the content (mol%) of the branched acyclic aliphatic diol component relative to all diol units of all polyesters (including copolymerized polyesters) contained in each layer, 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.

[0122] 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.

[0123] Whether or not the polyester film has a concentration gradient of all copolymer 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 copolymer components in the thickness direction of the film. The inflection point can be determined by preparing an obliquely 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.

[0124] (optional ingredient) The polyester layer Z may contain optional components other than those described above, as necessary, such as particles (inorganic particles and organic particles), ultraviolet absorbers, antioxidants, antistatic agents, and heat stabilizers.

[0125] In particular, 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 inclusion of particles in the polyester film can impart slipperiness to the polyester film and prevent scratches during each process. The particle content is preferably 100 ppm by mass or more, more preferably 500 ppm by mass or more, even more preferably 800 ppm by mass or more, and even more preferably 1000 ppm by mass or more, relative to the total mass of the polyester layer Z. The particle content is preferably 4000 ppm by mass or less, more preferably 3500 ppm by mass or less, even more preferably 3000 ppm by mass or less, and particularly preferably 2700 ppm by mass or less, relative to the total mass of the polyester layer Z.

[0126] <Other layers> The polyester film may further include 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 from 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.

[0127] The present polyester film may also have a barrier layer (also referred to as "the present barrier layer") on the side of polyester layer Z opposite to polyester layer X, i.e., on the outside of polyester layer Z. Another layer may be laminated between polyester layer Z and the barrier layer. The 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.

[0128] The inorganic substance that constitutes the main material of 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.

[0129] The barrier layer is preferably 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.

[0130] The barrier layer may have a single layer structure or a multi-layer structure of two or more layers. For example, in a multi-layer structure of two or more layers, one layer may be an inorganic layer made only of 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 providing such a flexible layer may improve the gas barrier properties. That is, coarse protrusions on the base film may act as starting points to cause minute defects called pinholes on the surface of the inorganic layer, or raw materials may fly in clumps during thermal evaporation and adhere to the surface, causing minute defects on the surface of the inorganic layer, and gas may pass through the voids caused by these defects, resulting in a decrease in gas barrier properties. Therefore, by laminating a flexible layer as described above on the surface, it is possible to fill the defects and improve the gas barrier properties in some cases.

[0131] The thickness of the barrier layer (the total thickness of the inorganic layers when the layer is a multi-layer structure) 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.

[0132] <Physical properties of this polyester film> The polyester film preferably has the following physical properties:

[0133] (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-sealing properties and performing barrier deposition and printing processes, 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 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, a good balance between drop resistance and seal strength can be achieved by appropriately adjusting the thickness of the polyester film, the composition of the layers constituting the polyester film, the heat setting temperature during production, and the like. A polyester film with a certain thickness or greater may improve drop resistance and seal strength. 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.

[0134] (Heat seal strength) When the polyester layers X of two sheets of the present polyester film are sealed together (i.e., the seal layers) at 140°C, 0.2 MPa, and 1 second, the seal strength of the present polyester film is preferably 15 N / 15 mm or more, more preferably 16 N / 15 mm or more, even more preferably 17 N / 15 mm or more, even more preferably 18 N / 15 mm or more, even more preferably 19 N / 15 mm or more, and particularly preferably 20 N / 15 mm or more. By maintaining the seal strength of the present polyester film within the above range, for example, when used as a packaging material, it can contribute to improved low-temperature sealing and airtightness, making it suitable for use as an antibacterial polyester film. The upper limit of the seal strength is not particularly limited, but it may be, for example, 50 N / 15 mm or less, or 45 N / 15 mm or less.

[0135] Furthermore, when the polyester layers X of two sheets of the present polyester film are sealed together (i.e., the seal layers) at 160°C, 0.2 MPa, and 1 second, the seal strength of the present polyester film is preferably 15 N / 15 mm or more, more preferably 16 N / 15 mm or more, even more preferably 17 N / 15 mm or more, even more preferably 18 N / 15 mm or more, and even more preferably 19 N / 15 mm or more. By maintaining the seal strength of the present polyester film within the above range, for example, when used as a packaging material, it can contribute to improved low-temperature sealing and airtightness, making it suitable for use as an antibacterial polyester film. The upper limit of the seal strength is not particularly limited, but it may be, for example, 50 N / 15 mm or less, or 45 N / 15 mm or less.

[0136] 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 the peel strength of the sealed area is measured using a tensile tester at a pulling rate of 300 mm / min.

[0137] (Fracture displacement in hydroshot test) The breaking 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 breaking displacement is not particularly limited, but may be, for example, 20 mm or less or 15 mm or less. By making the breaking displacement in the hydroshot test equal to or greater than the lower limit, drop resistance can be more effectively improved, making the film suitable for use in packaging liquids.

[0138] (Impact energy in hydroshot test) The impact energy of the polyester film in a hydroshot test is preferably greater than 0.5 J, more preferably at least 0.6 J, and even more preferably at least 0.7 J. 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 setting the impact energy in the hydroshot test to the above lower limit or more, drop resistance can be more effectively improved, making the film suitable for use in packaging liquids.

[0139] The measurement of the fracture 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. A 1 / 2-inch diameter impact core is dropped onto the center of the sample film at a temperature of 23°C at a speed of 3 m / s to apply an impact, and the amount of fracture displacement (fracture displacement) (mm) and energy (impact energy) (J) at the time the sample breaks are measured.

[0140] (breaking strength) The breaking strength of the polyester film in both the machine direction (MD) and the transverse direction (TD) is preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more. By making the breaking strength equal to or greater than the above lower limit, for example, when used as a packaging material, breakage can be prevented. The higher the breaking strength, the better, but even if it is 170 MPa or less, it can be said that it is practically sufficient, and it may be 160 MPa or less. The breaking strength of the polyester film was measured by pulling the 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 value by the cross-sectional area of ​​the test piece) was taken as the breaking strength (MPa).

[0141] (shrinkage rate) The present polyester-based film preferably has a shrinkage rate of -5% to 5% in either the machine direction (MD) or the transverse direction (TD). A shrinkage rate of -5% to 5% allows the film to maintain its original shape, for example, even in a high-temperature environment. From this perspective, the present polyester-based film more preferably has a shrinkage rate of -4% to 4%, even more preferably -3% to 3%, and particularly preferably -2% to 2% in both the machine direction (MD) and the transverse direction (TD). The shrinkage rate is calculated by placing the 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)

[0142] (Haze) The haze of the polyester film is preferably 15% or less, more preferably 10% or less, and even more preferably 7% 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.

[0143] <Method of manufacturing the present polyester film> As an example of the method for producing the polyester film, a biaxially stretched polyester film will be described below, although the production method is not limited to the one described here.

[0144] 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 heat-setting the laminate after the stretching step.

[0145] First, the resin compositions constituting each layer are prepared by a known method, and each resin composition is separately fed into a twin-screw melt extruder to melt the resin compositions. The extrusion rate of the molten resin is adjusted so that the thickness of each layer is a predetermined thickness ratio, and each layer is extruded through 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 an unoriented sheet in a substantially amorphous state.

[0146] Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretching machine, at a stretching temperature of usually 70 to 120°C, preferably 80 to 100°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction, at a stretching temperature of usually 70 to 40° C. and a stretching ratio of usually 3 to 7 times, preferably 3.5 to 6 times. In addition, in the stretching, a method of performing stretching in one direction in two or more stages can also be adopted.

[0147] A heat setting step is performed after the stretching step. The heat setting temperature in the heat setting step 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. Heat setting is performed at the above temperature under tension or under 30% or less relaxation to obtain the present polyester film as a biaxially oriented film. Setting the heat setting temperature within the above range can prevent the present polyester film from becoming brittle, thereby improving its impact resistance and drop resistance. Furthermore, by appropriately adjusting the heat setting temperature and the composition of the copolymerization components constituting the polyester film, a better balance between the drop resistance and seal strength of the present polyester film can be achieved.

[0148] In addition, when producing the polyester-based film in the third embodiment, for example, when the molten resin composition is extruded into a film form 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.

[0149] <Uses of this polyester film> The polyester film is preferably a film for packaging materials, and is sometimes called a sealant film because it has a polyester layer X as a sealing layer.

[0150] This embodiment may relate to a packaging material including a packaging film. In this case, the polyester film may be used as a packaging material as is, or the polyester film may be used as a component of the packaging material. When the polyester 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 polyester film is laminated with another layer. Examples of the other layer include films using polyethylene terephthalate, polyamide, polypropylene, polystyrene (syndiotactic polystyrene), polymethylpentene, polyimide, polytetrafluoroethylene, etc. Furthermore, as the other layer, a layer containing a metal such as aluminum or iron may be provided. Such a layer may be a vapor-deposited layer, or may be provided by laminating a film containing a metal such as aluminum or iron or by bonding it with an adhesive. In the packaging material, the provision of another layer can increase the strength and heat resistance of the packaging material or impart functions according to the application. Such a laminate is also preferably used as a packaging material. [Example]

[0151] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0152] <Materials used> [Preparation of polyester raw materials] The raw material compositions (proportions of raw material monomers) of the polyesters used in the examples and comparative examples are shown in Table 1. In Table 1, TPA is terephthalic acid, IPA is isophthalic acid, EG is ethylene glycol, CHDM is 1,4-cyclohexanedimethanol, BEPG is 2-butyl-2-ethyl-1,3-propanediol, and DEG is diethylene glycol. When producing polyester b, spherical silica particles having an average particle size of 4 μm were added as a lubricant in a proportion of 15,000 ppm by mass relative to the polyester. The intrinsic viscosity (IV) of polyesters a to f was measured by dissolving the polyester in a 1:1 mixed solution of phenol:tetrachloroethane and calculating the intrinsic viscosity (IV) from the elution time of this polyester solution.

[0153] [Table 1]

[0154] 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 e were mixed in a mass ratio of 50:24:26. ​​As the raw material for polyester layer X, polyester b, polyester c, and polyester e were mixed in a mass ratio of 7:50:43, and mixed raw materials for forming each layer were prepared.

[0155] The mixed raw materials for polyester layer Z, polyester layer Y, and polyester layer X were each fed into separate twin-screw extruders, and the mixed raw materials for polyester layer Z, polyester layer Y, and polyester layer X were heated to 280°C and melted. The amount of molten resin discharged was adjusted so that each layer had a predetermined thickness, and each layer was extruded through a die. Each layer was then cooled and solidified with a cooling roll set at 25°C, yielding an unstretched laminate film of three types and three layers (polyester layer Z / polyester layer Y / polyester layer X). The resulting unstretched laminate film was then stretched 3.3 times in the machine direction (MD) at 85°C using a roll stretching machine. It was then preheated in a tenter at 95°C and 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 50µm-thick, three-type, three-layer laminate film (sample) with a thickness of 30µm (polyester layer Z: 9.3µm, polyester layer Y: 31.4µm, polyester layer X: 9.3µm). The properties of the resulting laminate film were evaluated using the following methods.

[0156] 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.

[0157] Example 3 The raw materials for the polyester layer Y were prepared by mixing polyester a, polyester c, and polyester e in a mass ratio of 57:21:22. The raw material mass ratios and film-forming conditions for each layer other than the polyester layer Y were the same as in Example 1, and a laminated film (sample) with a thickness of 50 μm was obtained.

[0158] Example 4 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 3, except that the heat setting temperature was changed to 225°C.

[0159] Example 5 A 38 μm thick laminated film (sample) was obtained in the same manner as in Example 3, except that the thickness of the polyester layer Z was changed to 12.0 μm, the thickness of the polyester layer Y to 30.0 μm, and the thickness of the polyester layer X to 8.0 μm.

[0160] Example 6 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 5, except that the heat setting temperature was changed to 225°C.

[0161] Example 7 The raw materials for the polyester layer Z were prepared by mixing polyester a, polyester b, and polyester f in a mass ratio of 79:11:10. The raw material mass ratios and film-forming conditions for each layer other than the polyester layer Z were the same as in Example 5, and a laminated film (sample) with a thickness of 50 μm was obtained.

[0162] Example 8 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 7, except that the heat setting temperature was changed to 225°C.

[0163] Example 9 The raw materials for the polyester layer Z were prepared by mixing polyester a, polyester b, and polyester c in a mass ratio of 79:11:10. The raw material mass ratios and film-forming conditions for each layer other than the polyester layer Z were the same as in Example 5, and a laminated film (sample) with a thickness of 50 μm was obtained.

[0164] Example 10 A laminated film (sample) having a thickness of 50 μm was obtained in the same manner as in Example 9, except that the heat setting temperature was changed to 225°C.

[0165] (Comparative Example 1) A 50 μm thick laminated film (sample) 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.

[0166] (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.

[0167] (Comparative Example 3) A 50 μm thick laminated film (sample) 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 and polyester c in a mass ratio of 19:81.

[0168] Comparative Example 4 A 50 μm thick laminated film (sample) was obtained in the same manner as in Example 1, except that the raw materials for polyester layer Y were prepared by mixing polyester a and polyester d in a mass ratio of 50:50, and the raw materials for polyester layer X were prepared by mixing polyester a, polyester c, and polyester d in a mass ratio of 5:50:45.

[0169] (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. 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 220°C.

[0170] <Evaluation method> The laminated films (samples) produced in the examples and comparative examples were evaluated as follows.

[0171] (1) Heat seal strength The heat seal strength (N / 15 mm) of the laminated films (samples) prepared 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 joined together and heat-sealed at 140°C or 160°C under a pressure of 0.2 MPa for 1 second. The sealed portion was cut to a width of 15 mm, and the peel strength of the sealed portion was measured using a tensile tester at a pulling rate of 300 mm / min. The average of three measurements was taken as the heat seal strength at each heat seal temperature.

[0172] (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 lengthwise and 100 mm widthwise. Using a Hydroshot high-speed impact tester (Shimadzu Corporation, Model HTM-1), the sample films were clamped and a 1 / 2-inch diameter impact core was dropped onto the center of the sample film at a temperature of 23°C at a speed of 3 m / s to apply impact. The displacement (mm) and impact energy (J) at the fracture point when the sample broke were measured. The average values ​​of five measurements were used as the fracture displacement (mm) and impact energy (J) in the Hydroshot test.

[0173] (3) Drop resistance evaluation The sealed surfaces (polyester layers X) of the laminated films (samples) produced in the Examples and Comparative Examples were placed inside each other, and a four-sided sealed pouch measuring 140 mm in length and 100 mm in width was produced with a water content of 50 mL. 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, for the drop test, the above-mentioned sealed pouch was dropped vertically from a height of 0.5 m, and then dropped horizontally (flat direction). Five sets of drop tests were conducted, each set consisting of a vertical drop and a horizontal drop (flat direction). When dropped vertically, the short sides of the four-side sealed pouch came into contact with the ground, and when dropped horizontally (flat direction), the body (widest surface) of the four-side sealed pouch came into contact with the ground. Drop resistance was evaluated according to the following criteria. A: When I dropped five sets, the bag did not break even once. B: The bag broke after dropping 2 to 4 sets. C: The bag broke when one set was dropped.

[0174] In addition, the water content of the laminated film (sample) produced in the examples was increased to either 100 mL or 150 mL, and the drop height was set to either 0.5 m, 1.0 m, or 1.2 m, and a four-side 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. A: When I dropped five sets, the bag did not break even once. B: The bag broke after dropping 2 to 4 sets. C: The bag broke when one set was dropped. The laminated films (samples) produced in the comparative examples were not subjected to drop tests using 100 mL and 150 mL of water and their drop resistance was not evaluated. Therefore, the results in Table 3 were marked "-".

[0175] (4) Breaking strength The laminated films (samples) produced in the examples and comparative examples were used as sample films measuring 1.5 cm x 15 cm. Using a tensile tester, the sample films were pulled in the machine direction (MD) or the 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 recorded as the breaking strength (MPa). The breaking strength was recorded as the average value of three measurements.

[0176] (5) Shrinkage rate The laminated films (samples) produced in the Examples and Comparative Examples were used to prepare sample films measuring 1.5 cm x 15 cm. The sample films were placed in a non-tensioned hot air oven maintained at a predetermined temperature (100°C) and heat-treated for 5 minutes. The lengths of the sample films before and after the treatment were measured, and the shrinkage ratio was calculated using the following formula (1). Measurements were taken in both the machine direction (MD) and the cross 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 value of three measurements was taken as the shrinkage rate.

[0177] (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.

[0178] [Table 2]

[0179] [Table 3]

[0180] In Table 3, for example, the CHDM component content (mol%) in 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 BEPG component content (mol%) in polyester layer X means the ratio (mol%) of the total content of BEPG units to all diol units (100 mol%) contained in all polyesters (including copolymer polyesters) constituting polyester layer X. The same applies to the other layers.

[0181] 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 polyester layer Y did not satisfy the predetermined component composition, and therefore the drop resistance was poor.

[0182] Furthermore, since all of the resin components constituting the laminated films obtained in the examples are polyester (including copolymer polyester), it is possible to form packaging materials using a single material system consisting of polyester material by, for example, laminating other polyester-based substrate films such as transparent barrier-deposited PET, or by applying barrier deposition or printing processing techniques, and it is also possible to achieve high recyclability. [Industrial Applicability]

[0183] 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 copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol, a polyester layer Y comprising a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component comprising an alicyclic diol and a branched acyclic aliphatic diol.

2. The packaging film according to claim 1 , wherein the acyclic aliphatic diol having a branched chain has a branched chain having two or more carbon atoms.

3. 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, 0.2 MPa, and 1 second.

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

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

6. The packaging film according to claim 1 , wherein the diol component of the copolymerized polyester (x) further contains diethylene glycol.

7. 2. 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. 2. The packaging film according to claim 1, wherein the acyclic aliphatic diol having a branched chain in the copolymerized polyester (x) is at least one selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

9. The packaging film according to claim 1 , wherein the diol component of the copolymerized polyester (y) further contains diethylene glycol.

10. 2. 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. 2. The packaging film according to claim 1, wherein the acyclic aliphatic diol having a branched chain in the copolymerized polyester (y) is at least one selected from the group consisting of 1,2-butanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, and 3-octyl-1,5-pentanediol.

12. the polyester layer X comprises a copolymer polyester (x-1) having structural units derived from a dicarboxylic acid component and a diol component and a copolymer polyester (x-2) having structural units derived from a dicarboxylic acid component and a diol component, 2. The packaging film according to claim 1, wherein the diol component constituting the copolymerized polyester (x-1) includes an alicyclic diol, and the diol component constituting the copolymerized polyester (x-2) includes a branched acyclic aliphatic diol.

13. the polyester layer Y comprises a copolymer polyester (y-1) having structural units derived from a dicarboxylic acid component and a diol component and a copolymer polyester (y-2) having structural units derived from a dicarboxylic acid component and a diol component, 2. The packaging film according to claim 1, wherein the diol component constituting the copolymerized polyester (y-1) includes an alicyclic diol, and the diol component constituting the copolymerized polyester (y-2) includes a branched acyclic aliphatic diol.

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

15. The packaging film according to claim 14, wherein the polyester layer Z contains homopolyethylene terephthalate (z) as a main component resin.

16. 15. The packaging film according to claim 14, wherein the polyester layer Z comprises a copolymerized polyester (z-1) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component comprises an alicyclic diol and / or an acyclic aliphatic diol.

17. The packaging film according to claim 14 , 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 branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X is 0.5 to 30 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 branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 0.5 to 20 mol %.

22. 2. 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 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. P represents the total content (mol %) of the alicyclic diol unit relative to all diol units in all polyesters contained in the polyester layer X and the content (mol %) of the branched acyclic aliphatic diol unit relative to all diol units in all polyesters contained in the polyester layer X; When the total content (mol %) of the alicyclic diol unit relative to all diol units in all polyesters contained in the polyester layer Y and the content (mol %) of the branched acyclic aliphatic diol unit relative to all diol units in all polyesters 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 P / Q value is 1.1 to 3.

5.

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

28. 2. The packaging film according to claim 1, wherein a value obtained by dividing the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X by the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 1.1 to 5.

29. 2. The packaging film according to claim 1, wherein a value obtained by dividing the content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X by the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X is 1 to 5.

30. 2. The packaging film according to claim 1, wherein a value obtained by dividing the content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y by the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y is 0.5 to 4.

31. 2. The packaging film according to claim 1, wherein a value obtained by dividing the total content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer X and the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer X by the content (mol %) of diethylene glycol units relative to all diol units in all polyesters contained in the polyester layer X is 2 to 8.

32. 2. The packaging film according to claim 1, wherein a value obtained by dividing the total content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in the polyester layer Y and the content (mol %) of branched acyclic aliphatic diol units relative to all diol units in all polyesters contained in the polyester layer Y by the content (mol %) of diethylene glycol units relative to all diol units in all polyesters contained in the polyester layer Y is 1.5 to 7.

5.

33. A packaging film having at least a polyester layer X and a polyester layer Y, a packaging film, wherein at least one selected from the polyester layer X and the polyester layer Y contains a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an acyclic aliphatic diol having a branched chain having two or more carbon atoms.

34. the polyester layer X contains a copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an acyclic aliphatic diol having a branched chain having two or more carbon atoms, 34. The packaging film according to claim 33, wherein the polyester layer Y comprises a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component comprises an acyclic aliphatic diol having a branched chain having two or more carbon atoms.

35. A packaging film comprising a copolymerized polyester having structural units derived from a dicarboxylic acid component and a diol component, the diol component comprises an alicyclic diol and a branched acyclic aliphatic diol, the total content (mol %) of the alicyclic diol unit and the content (mol %) of the branched acyclic aliphatic diol unit relative to all diol units in all polyesters contained in a region from one surface side of the film to 50% of the entire thickness is a film for packaging material, the film having a content (mol %) of alicyclic diol units relative to all diol units in all polyesters contained in a region extending from the other surface side of the film to 50% of the entire thickness of the film being higher than the total content (mol %) of branched acyclic aliphatic diol units.

36. 36. The packaging film according to claim 35, wherein the total content (mol%) of alicyclic diol units and branched acyclic aliphatic diol units relative to all diol units in all polyesters increases continuously from one surface side to the other surface side of the film.

37. The packaging film according to claim 14, further comprising a barrier layer on the polyester layer Z.

38. A packaging material comprising the packaging film according to any one of claims 1 to 37.

39. A laminate comprising the packaging film according to any one of claims 1 to 37.

40. A packaging material comprising the laminate of claim 39.

41. A method for producing a packaging film having at least a polyester layer X and a polyester layer Y, comprising: the polyester layer X contains a copolymerized polyester (x) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol, the polyester layer Y contains a copolymerized polyester (y) having structural units derived from a dicarboxylic acid component and a diol component, and the diol component contains an alicyclic diol and a branched acyclic aliphatic diol, a step of laminating and stretching a resin composition constituting the polyester layer X and the polyester layer Y; a step of performing heat setting treatment after the step of performing the stretching, The method for producing a packaging film, wherein the heat setting temperature in the step of performing the heat setting is 200°C or higher and lower than 250°C.

42. The method for producing a packaging film according to claim 41, 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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