JP7514435B2 - Gas barrier film, laminate, and packaging container - Google Patents

Description

The present invention relates to a gas barrier film, a laminate, and a packaging container.

Polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), which are thermoplastic resins with excellent heat resistance and mechanical properties, are used in a wide variety of fields, including plastic films, electronics, energy, packaging materials, and automobiles. In particular, biaxially oriented polyester films are widely used in industrial and packaging fields because of their excellent balance of mechanical strength (i.e. mechanical properties), heat resistance, dimensional stability, chemical resistance, optical properties, etc., and cost.

In recent years, with the growing demand for the creation of a recycling-oriented society, the use of recycled raw materials has been promoted in the field of materials. Used PET bottles are also recycled for polyester. It is said that using recycled polyester leads to a reduction in _CO2 emissions. For these reasons, it is desirable to increase the proportion of recycled polyester used even slightly.

For example, Patent Document 1 discloses a biaxially oriented polyester film made using polyester obtained by mechanically recycling PET bottles, i.e., mechanically recycled polyester.

However, used polyester products such as used PET bottles have varying levels of contamination depending on the contents and storage environment, making it difficult to thoroughly remove contaminants through mechanical recycling.

A polyester that is recycled using a method different from mechanical recycling is known as chemically recycled polyester, which is obtained by breaking down the polyester contained in used polyester products to the monomer level and then repolymerizing it (see Patent Documents 3 and 4).

For example, Patent Document 2 discloses a vapor-deposited resin film that includes a polyester film made from chemically recycled polyester and a vapor-deposited film.

Japanese Patent No. 6036099 Patent No. 6984718 JP 2000-169623 A JP 2000-302707 A

Chemically recycled polyester is often polymerized by solid-state polymerization to make it easier to mold into PET bottles, so the intrinsic viscosity of chemically recycled polyester is often higher than that of polyesters used in typical biaxially oriented polyester films.

In the process of considering using chemically recycled polyester not for PET bottles but for the production of biaxially oriented polyester films that constitute gas barrier films, the inventors discovered a problem in that films using chemically recycled polyester tend to break easily when stretched, and therefore the film production speed may have to be excessively slowed down.

The present invention aims to provide a gas barrier film that can reduce the environmental impact, inhibit or reduce film breakage that may occur during stretching, and has excellent mechanical properties (specifically, tensile strength and puncture strength) and gas barrier properties. The present invention also aims to provide a laminate that includes the gas barrier film, and a packaging container that includes the laminate.

In order to solve this problem, the present invention has the following configuration [1].
[1]
A biaxially oriented polyester film;
and an inorganic thin film layer;
The biaxially oriented polyester film comprises chemically recycled polyester,
The intrinsic viscosity of the biaxially oriented polyester film is 0.50 dl/g or more and 0.70 dl/g or less,
The biaxially oriented polyester film has a melting point of 251° C. or higher.
Gas barrier film.
Here, "chemically recycled polyester" refers to polyester obtained by decomposing polyester contained in used polyester products down to the monomer level and then polymerizing it again.

In [1], the biaxially oriented polyester film contains chemically recycled polyester. Here, "the biaxially oriented polyester film contains chemically recycled polyester" means that, when the biaxially oriented polyester film contains multiple layers, at least one of the multiple layers contains chemically recycled polyester.

According to [1], the biaxially oriented polyester film constituting the gas barrier film contains chemically recycled polyester, which reduces the environmental impact.

Moreover, by having the intrinsic viscosity of the biaxially oriented polyester film be 0.70 dl/g or less, it is possible to prevent the stress (i.e., the stretching stress) during stretching in the biaxially oriented polyester film manufacturing process from becoming excessively large, and as a result, it is possible to suppress or reduce breakage of the film that may occur during stretching.

Furthermore, by having an intrinsic viscosity of 0.50 dl/g or more for the biaxially oriented polyester film, the mechanical properties, specifically tensile strength and puncture strength, can be improved.

By having the intrinsic viscosity of the biaxially oriented polyester film be 0.50 dl/g or more, the gas barrier properties of the gas barrier film can also be improved. This will be explained. Since low molecular weight components are incorporated into the polyester during the polymerization process, the larger the molecular weight of the polyester, the less low molecular weight components there are. According to [1], by having the intrinsic viscosity of the biaxially oriented polyester film be 0.50 dl/g or more, the amount of low molecular weight components can be limited to a certain level or less, and as a result, the occurrence of defects in the inorganic thin film layer 31 that may be caused by low molecular weight components can be reduced or suppressed. Therefore, the gas barrier properties of the gas barrier film can be improved. Specifically, the transmission of oxygen gas and water vapor can be suppressed or reduced.

When a sealant layer is formed on a gas barrier film, the intrinsic viscosity of the biaxially oriented polyester film is 0.50 dl/g or more, so that the peel strength between the gas barrier film and the sealant layer can be improved. This is thought to be because the decrease in peel strength caused by low molecular weight components that can act as plastic components can be suppressed.

Furthermore, biaxially oriented polyester film has a melting point of 251°C or higher, making it highly heat resistant.

The present invention preferably further comprises the following configurations [2] and subsequent sections.

[2]
The gas barrier film according to [1], having a puncture strength of 0.50 N/μm or more.

According to [2], a product (e.g., a packaging container) having excellent strength can be produced using the gas barrier film. For example, a packaging container that is difficult to puncture can be produced using the gas barrier film.

[3]
The gas barrier film according to [1] or [2], wherein the content of the chemically recycled polyester in the biaxially oriented polyester film is 20% by mass or more.

According to [3], the environmental impact can be further reduced.

[4]
The gas barrier film according to any one of [1] to [3], further comprising a coating layer between the biaxially oriented polyester film and the inorganic thin film layer.

According to [4], the adhesion between the biaxially oriented polyester film and the coating layer, and the adhesion between the coating layer and the inorganic thin film layer can be adjusted by the coating layer.

[5]
The gas barrier film according to [4], wherein the coating layer contains a resin containing an oxazoline group.

According to [5], the adhesion between the coating layer and the inorganic thin film layer can be increased. This is because the oxazoline group has excellent affinity with the inorganic thin film layer and can react with oxygen vacancies in the inorganic oxide or metal hydroxides that may occur during the formation of the inorganic thin film layer.

[6]
The gas barrier film according to any one of [1] to [5], further comprising a protective layer provided on the inorganic thin film layer.
Here, the term "protective layer" refers to a layer capable of reinforcing the gas barrier property of the inorganic thin film layer.

According to [6], the permeation of oxygen gas and water vapor can be further suppressed or reduced.

[7]
The gas barrier film according to [6], wherein the protective layer contains a urethane resin.

According to [7], the adhesion between the protective layer and the inorganic thin film layer can be increased. This is because the urethane bonds in the urethane resin have polarity and interact with the inorganic thin film layer. In addition, the degree of damage that may be sustained by the inorganic thin film layer when a bending load is applied to the gas barrier film can be reduced. This is because the amorphous portion in the urethane resin has flexibility.

[8]
The gas barrier film according to any one of [1] to [7], wherein the inorganic thin film layer contains a composite oxide of silicon oxide and aluminum oxide.

According to [8], it is possible to achieve both flexibility and density in the inorganic thin film layer.

[9]
[1] to [8], and
At least one of a sealant layer and an adhesive layer;
Laminate.

According to [9], when the laminate includes a sealant layer, a product including the laminate (e.g., a packaging container) can be produced by heat sealing. When the laminate includes an adhesive layer, a product including the laminate (e.g., a packaging container) can be produced by pressurization.

[10]
A packaging container comprising the laminate according to [9].

The present invention can reduce the environmental impact, inhibit or reduce film breakage that may occur during stretching, and provide a gas barrier film with excellent mechanical properties (specifically, tensile strength and puncture strength) and gas barrier properties.

1 is a schematic cross-sectional view of a gas barrier film according to one embodiment. 1 is a schematic cross-sectional view of a gas barrier film according to one embodiment. 1 is a schematic cross-sectional view of a gas barrier film according to one embodiment. 1 is a schematic cross-sectional view of a gas barrier film according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment. 1 is a schematic cross-sectional view of a laminate according to one embodiment.

1. Introduction
Hereinafter, an embodiment of the present invention will be described.
In the following description, polyethylene terephthalate may be referred to as PET or PET. In other words, these terms are used as synonyms.
Machine Direction (hereinafter, referred to as "MD") may be referred to as the longitudinal direction. That is, MD and longitudinal direction are used as synonyms.
Transverse Direction (hereinafter, referred to as "TD") may be referred to as width direction. That is, TD and width direction are used as synonyms.
In describing the embodiments of the present invention, it may be expressed as "the first layer 81, the second layer 82, and the third layer 83 are arranged in this order in the thickness direction of the biaxially oriented polyester film 8." This expression allows for the presence of other layers between the first layer 81 and the second layer 82, or between the second layer 82 and the third layer 83. Other expressions (i.e., similar expressions) that include the description that multiple layers are "arranged in this order" are also applicable.

2. Gas Barrier Film
1, in one embodiment, the gas barrier film 7 includes a biaxially oriented polyester film 8 and an inorganic thin film layer 31. Since the gas barrier film 7 includes the inorganic thin film layer 31, the transmission of oxygen gas and water vapor can be suppressed or reduced.

As shown in FIG. 2, the gas barrier film 7 may further include a coating layer 32. Specifically, the gas barrier film 7 may include a coating layer 32 between the biaxially oriented polyester film 8 and the inorganic thin film layer 31. This allows the coating layer 32 to adjust the adhesion between the biaxially oriented polyester film 8 and the coating layer 32, and the adhesion between the coating layer 32 and the inorganic thin film layer 31. In at least a portion of the gas barrier film 7, the biaxially oriented polyester film 8, the coating layer 32, and the inorganic thin film layer 31 can be arranged in this order in the thickness direction of the gas barrier film 7. The coating layer 32 can connect the biaxially oriented polyester film 8 and the inorganic thin film layer 31.

As shown in FIG. 3, the gas barrier film 7 may further include a protective layer 33 provided on the inorganic thin film layer 31. That is, the gas barrier film 7 may further include a protective layer 33 adjacent to the inorganic thin film layer 31. For example, the gas barrier film 7 may include a biaxially oriented polyester film 8, a coating layer 32, an inorganic thin film layer 31, and a protective layer 33. In at least a portion of the gas barrier film 7, the biaxially oriented polyester film 8, the coating layer 32, the inorganic thin film layer 31, and the protective layer 33 can be arranged in this order in the thickness direction of the gas barrier film 7. The protective layer 33 can further suppress or reduce the transmission of oxygen gas and water vapor.

The gas barrier film 7 may be printed or otherwise processed as necessary.

<2.1. Biaxially oriented polyester film>
The biaxially oriented polyester film 8 contains chemically recycled polyester, which reduces the environmental impact.

Chemically recycled polyester is polyester obtained by breaking down polyester contained in used polyester products down to the monomer level and then polymerizing it again. Because chemically recycled polyester is produced using polyester contained in used polyester products as the raw material, it reduces the burden on the environment. Furthermore, chemically recycled polyester is more hygienic than mechanically recycled polyester, as foreign matter (such as catalysts, coloring components, different types of plastics, and metals) is removed during the recycling process.

An example of a polyester that can be decomposed to the monomer level is a used polyester product. The used polyester product may be, for example, in the form of a bale, flake, or pellet. A preferred used polyester product is a used PET bottle.

One method for breaking down polyester to the monomer level is to crush and wash PET bottle bales, add at least ethylene glycol (EG) and a catalyst to the flakes, and heat them to break them down into bis-2-hydroxyethyl terephthalate (BHET) (hereinafter sometimes referred to as the "BHET method") (see Patent Document 3, i.e., JP 2000-169623 A). Another method for breaking down polyester to the monomer level is the method described in Patent Document 4 (JP 2000-302707 A). Of course, polyester may be broken down to the monomer level by methods other than those exemplified here.

Regarding the BHET method, an example of the procedure for decomposing polyethylene terephthalate that constitutes used PET bottles to obtain BHET will be described here.
The PET bottle bales are put into a crusher and wet crushed. In the wet crushing, the PET bottle bales can be crushed in washing water (for example, tap water or groundwater to which detergent has been added as necessary). The washing water may be at room temperature or may be warmed.
The wash water together with the PET bottle flakes are discharged from the crusher and subjected to gravity separation to remove foreign matter (e.g. metal, stones, glass, sand).
The flakes are then rinsed with ion-exchanged water and, if necessary, centrifuged for dehydration.
After melting the flakes, a catalyst and excess ethylene glycol are added and heated (i.e., depolymerization is performed). This allows the polyethylene terephthalate that constitutes the flakes to be depolymerized, and as a result, a depolymerized liquid in which BHET is dissolved in ethylene glycol can be obtained. Note that it is preferable to melt the flakes while they contain moisture (for example, the state in which they contain moisture after centrifugal dehydration).
Foreign matter (e.g., different plastics, metals, glass) floating or settling in the depolymerization liquid is removed. Since the melting point of the cyclic oligomers in the depolymerization liquid is higher than that of polyethylene terephthalate, low molecular weight components such as the cyclic oligomers can also be removed by filtration.
The depolymerized liquid is passed through activated carbon (i.e., made to pass through) and then through an ion exchange resin. By passing the depolymerized liquid through activated carbon, coloring components (e.g., pigments, dyes, and compounds generated by thermal degradation of organic matter) can be removed. By passing the depolymerized liquid through an ion exchange resin, catalysts (e.g., polymerization catalysts, depolymerization catalysts) and metal ions can be removed.
Next, the depolymerized liquid is cooled to precipitate BHET, and then the BHET and ethylene glycol are subjected to solid-liquid separation.
To remove any residual ethylene glycol from the BHET (i.e., to concentrate the BHET), vacuum evaporation is performed.
The concentrated BHET is subjected to molecular distillation.
By such a procedure, high-purity BHET can be obtained. Although the operation of performing solid-liquid separation of BHET and ethylene glycol and then vacuum evaporation has been described here, ethylene glycol may be distilled from the depolymerized liquid instead of this operation.

Examples of chemically recycled polyesters include chemically recycled polyethylene terephthalate (hereinafter sometimes referred to as "chemically recycled PET"), chemically recycled polybutylene terephthalate, and chemically recycled polyethylene-2,6-naphthalate. Of course, these may contain copolymerization components. Chemically recycled PET is preferred because it is easy to obtain and has excellent mechanical properties and heat resistance. These may be used alone or in combination of two or more types.

The chemically recycled polyester may be copolymerized with other components. Examples of dicarboxylic acid components as copolymerization components include isophthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, adipic acid, sebacic acid, and ester-forming derivatives thereof. Examples of diol components as copolymerization components include diethylene glycol, hexamethylene glycol, neopentyl glycol, and cyclohexanedimethanol. Similarly, polyoxyalkylene glycols such as polyethylene glycol and polypropylene glycol can also be mentioned. These may be used alone or in combination. In addition, considering that isophthalic acid is generally copolymerized with PET constituting PET bottles to improve moldability into bottles, it is preferable that the chemically recycled PET contains at least an isophthalic acid component as a copolymerization component.

When the mole number of all dicarboxylic acid components in the chemically recycled polyester is taken as 100 mole%, the mole number of the copolymerization components is preferably 10 mole% or less, more preferably 8 mole% or less, even more preferably 5 mole% or less, and even more preferably 3 mole% or less. The mole number of the copolymerization components is preferably 0.1 mole% or more, more preferably 1 mole% or more, and even more preferably 2 mole% or more. The chemically recycled polyester may contain one or more types of copolymerization components that satisfy such a suitable mole number of the copolymerization components.

When the chemically recycled polyester is chemically recycled PET, when the moles of all dicarboxylic acid components in the chemically recycled PET are taken as 100 mole%, the moles of isophthalic acid components are preferably 10 mole% or less, more preferably 8 mole% or less, even more preferably 5 mole% or less, and even more preferably 3 mole% or less. The moles of isophthalic acid components are preferably 0.1 mole% or more, more preferably 1 mole% or more, and even more preferably 2 mole% or more. The chemically recycled PET may contain one or more types of isophthalic acid components that satisfy such a suitable mole number of the isophthalic acid components.

The intrinsic viscosity of the chemically recycled polyester is preferably 0.50 dl/g or more, more preferably 0.55 dl/g or more, and even more preferably 0.57 dl/g or more. If it is 0.50 dl/g or more, the amount of low molecular weight components in the chemically recycled polyester can be limited to a certain level, so that the yellowish color that the biaxially oriented polyester film 8 may exhibit can be reduced. On the other hand, the intrinsic viscosity of the chemically recycled polyester is preferably 0.90 dl/g or less, more preferably 0.85 dl/g or less, even more preferably 0.80 dl/g or less, even more preferably 0.75 dl/g or less, and even more preferably 0.69 dl/g or less. If it is 0.90 dl/g or less, the intrinsic viscosity of the biaxially oriented polyester film 8 can be limited to a certain level or less, so that the stress (i.e., stretching stress) during stretching in the manufacturing process of the biaxially oriented polyester film 8 can be further prevented from becoming excessively large, and as a result, film breakage that may occur during stretching can be further suppressed or reduced. The chemically recycled polyester may contain one or more types that satisfy such a suitable intrinsic viscosity.

In the molecular weight distribution curve obtained by gel permeation chromatography (GPC) of chemically recycled polyester, the area ratio of the region with a molecular weight of 1000 or less may be 3.5% or less, 3.0% or less, 2.5% or less, 2.2% or less, or 2.0% or less of the total peak area. On the other hand, this area ratio may be 0.8% or more, 1.0% or more, or 1.2% or more.

The melt resistivity at 285°C in the chemically recycled polyester may be, for example, ^30.0x108 Ω·cm or less, ^25.0x108 Ω·cm or less, 20.0x108 Ω·cm or less, or ^15.0x108 Ω·cm or less. The melt resistivity at 285°C in the chemically recycled polyester may be, for example, ^0.5x108 Ω·cm or more, ^1.5x108 Ω·cm or more, ^{3.0x108 Ω} ·cm or more, or ^5.0x108 Ω·cm or more. The melt resistivity of the chemically recycled polyester is preferably higher than that of the fossil fuel-derived polyester and the mechanically recycled polyester described later. The chemically recycled polyester may contain one or more types that satisfy such a suitable melt resistivity.

Although chemically recycled polyester may contain alkaline earth metal compounds, it is preferable that it is substantially free of them. Since the catalyst and metal ions are removed during the recycling process, chemically recycled polyester can be polymerized with a catalyst other than alkaline earth metal compounds (e.g., a germanium-based catalyst or an antimony-based catalyst) to contain no or almost no alkaline earth metal compounds.

The content of alkaline earth metal compounds in the chemically recycled polyester may be, for example, less than 30 ppm, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, or 0 ppm, based on alkaline earth metal atoms (i.e., in terms of alkaline earth metal atoms).
Here, the content of the alkaline earth metal compound is the mass of the alkaline earth metal compound based on alkaline earth metal atoms relative to the mass of the chemically recycled polyester (i.e., mass of the alkaline earth metal compound based on alkaline earth metal atoms/mass of the chemically recycled polyester).
The chemically recycled polyester may contain one or more of such alkaline earth metal compounds satisfying the preferable content.

The content of magnesium compounds in the chemically recycled polyester may be, for example, less than 30 ppm, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, or 0 ppm, based on magnesium atoms (i.e., in terms of magnesium atoms). The chemically recycled polyester may contain one or more types of magnesium compounds that satisfy such a suitable magnesium compound content.

The content of phosphorus compounds in the chemically recycled polyester may be 10 ppm or more, 15 ppm or more, 20 ppm or more, or 30 ppm or more based on phosphorus atoms (i.e., in terms of phosphorus atoms), while the content of phosphorus compounds may be 300 ppm or less, 200 ppm or less, or 100 ppm or less based on phosphorus atoms.
Here, the content of the phosphorus compound is the mass of the phosphorus compound based on phosphorus atoms relative to the mass of the chemically recycled polyester (i.e., mass of the phosphorus compound based on phosphorus atoms/mass of the chemically recycled polyester).
The chemically recycled polyester may contain one or more of such phosphorus compound(s) that satisfy the suitable phosphorus compound content.

The content of chemically recycled polyester is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the biaxially oriented polyester film 8 is taken as 100% by mass. If it is 10% by mass or more, the environmental load can be further reduced. On the other hand, the content of chemically recycled polyester is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, when the biaxially oriented polyester film 8 is taken as 100% by mass.

The biaxially oriented polyester film 8 preferably contains fossil fuel-derived polyester, i.e., virgin polyester. Fossil fuel-derived polyester is polyester obtained by condensation polymerization of a diol compound derived from a fossil fuel and a dicarboxylic acid compound derived from a fossil fuel. Fossil fuel-derived polyesters generally have a wider range of choices than chemically recycled polyesters, and the use of fossil fuel-derived polyesters can broaden the range over which the physical properties of the biaxially oriented polyester film 8 can be adjusted.

Examples of fossil fuel-derived polyesters include fossil fuel-derived polyethylene terephthalate (hereinafter sometimes referred to as "fossil fuel-derived PET"), fossil fuel-derived polybutylene terephthalate, and fossil fuel-derived polyethylene-2,6-naphthalate. Of course, these may contain copolymerization components. Fossil fuel-derived PET is preferred because it can reduce costs and has excellent mechanical properties and heat resistance, and fossil fuel-derived homo-PET is more preferred. Note that homo-PET may contain a diethylene glycol component that is unavoidably contained. Note that these may be used alone or in combination of two or more types.

The intrinsic viscosity of the fossil fuel-derived polyester is preferably 0.50 dl/g or more, more preferably 0.55 dl/g or more, and even more preferably 0.57 dl/g or more. If it is 0.50 dl/g or more, the amount of low molecular weight components in the fossil fuel-derived polyester can be limited to a certain level, so that the yellowish color that the biaxially oriented polyester film 8 may exhibit can be reduced. On the other hand, the intrinsic viscosity of the fossil fuel-derived polyester is preferably 0.75 dl/g or less, more preferably 0.70 dl/g or less, even more preferably 0.68 dl/g or less, even more preferably 0.66 dl/g or less, and even more preferably 0.65 dl/g or less. If it is 0.75 dl/g or less, it is possible to further prevent the stress (i.e., stretching stress) during stretching in the manufacturing process of the biaxially oriented polyester film 8 from becoming excessively large, and as a result, it is possible to further suppress or reduce the breakage of the film that may occur during stretching. The fossil fuel-derived polyester may contain one or more types that satisfy such a suitable intrinsic viscosity.

In the molecular weight distribution curve obtained by gel permeation chromatography (GPC) of fossil fuel-derived polyester, the area ratio of the region with a molecular weight of 1000 or less may be 3.5% or less, 3.0% or less, or 2.8% or less of the total peak area. On the other hand, this area ratio may be 1.0% or more, 1.5% or more, 1.8% or more, or 2.0% or more.

The melt resistivity at 285°C of the fossil fuel-derived polyester may be, for example, 2.0x108 Ω·cm or less, ^1.5x108 Ω· ^cm or less, ^1.0x108 Ω·cm or less, ^0.5x108 Ω·cm or less, or ^0.4x108 Ω·cm or less. The melt resistivity at 285°C of the fossil fuel-derived polyester may be, for example, ^0.05x108 Ω·cm or more, or ^0.1x108 Ω·cm or more. The fossil fuel-derived polyester may contain one or more types of polyesters that satisfy such suitable melt resistivities.

The fossil fuel-derived polyester preferably contains an alkaline earth metal compound. The alkaline earth metal compound may be added to the fossil fuel-derived polyester, for example, as a polymerization catalyst for producing the fossil fuel-derived polyester, or may be added to reduce the melt resistivity of the biaxially oriented polyester film 8.

The content of alkaline earth metal compounds in the fossil fuel-derived polyester is, for example, preferably 30 ppm or more, preferably 35 ppm or more, preferably 40 ppm or more, and preferably 45 ppm or more, based on alkaline earth metal atoms (i.e., calculated as alkaline earth metal atoms).
Here, the content of the alkaline earth metal compound is the mass of the alkaline earth metal compound based on the alkaline earth metal atom relative to the mass of the fossil fuel-derived polyester (i.e., mass of the alkaline earth metal compound based on the alkaline earth metal atom/mass of the fossil fuel-derived polyester).
The fossil fuel-derived polyester may contain one or more types of alkaline earth metal compounds that satisfy such a suitable alkaline earth metal compound content.

The content of magnesium compounds in the fossil fuel-derived polyester is, for example, preferably 30 ppm or more, more preferably 35 ppm or more, more preferably 40 ppm or more, and more preferably 45 ppm or more, based on magnesium atoms (i.e., in terms of magnesium atoms). The fossil fuel-derived polyester may contain one or more types of magnesium compounds that satisfy such a suitable magnesium compound content.

The content of phosphorus compounds in the fossil fuel-derived polyester may be 10 ppm or more, 15 ppm or more, 20 ppm or more, or 30 ppm or more based on phosphorus atoms (i.e., in terms of phosphorus atoms), while the content of phosphorus compounds may be 300 ppm or less, 200 ppm or less, or 100 ppm or less based on phosphorus atoms.
Here, the content of the phosphorus compound is the mass of the phosphorus compound on a phosphorus atom basis relative to the mass of the fossil fuel-derived polyester (i.e., mass of the phosphorus compound on a phosphorus atom basis/mass of the fossil fuel-derived polyester).
The fossil fuel-derived polyester may contain one or more types of phosphorus compounds that satisfy such a suitable phosphorus compound content.

The content of fossil fuel-derived polyester is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the biaxially oriented polyester film 8 is taken as 100% by mass. If it is 5% by mass or more, the range in which the physical properties of the biaxially oriented polyester film 8 can be adjusted can be further expanded. On the other hand, the content of fossil fuel-derived polyester is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, when the biaxially oriented polyester film 8 is taken as 100% by mass.

The biaxially oriented polyester film 8 may or may not contain mechanically recycled polyester. Mechanically recycled polyester is polyester obtained from used polyester products without going through an operation of decomposing the polyester contained in the used polyester products to the monomer level. Mechanically recycled polyester is obtained, for example, by crushing and washing used polyester products and, if necessary, regenerating them into flakes or pellets.

In the molecular weight distribution curve obtained by gel permeation chromatography (GPC) of the mechanically recycled polyester, the area ratio of the region with a molecular weight of 1000 or less may be 4.5% or less of the total peak area, or 4.0% or less. On the other hand, this area ratio may be 2.5% or more, 3.0% or more, or 3.2% or more.

It is preferable that the biaxially oriented polyester film 8 does not substantially contain mechanically recycled polyester. The content of mechanically recycled polyester is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, when the biaxially oriented polyester film 8 is taken as 100% by mass. It is preferable that the biaxially oriented polyester film 8 does not contain any mechanically recycled polyester.

The biaxially oriented polyester film 8 may contain biomass polyester.

When the biaxially oriented polyester film 8 is taken as 100% by mass, the polyester content (i.e., the content of polyester including chemically recycled polyester) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

The biaxially oriented polyester film 8 may contain resins other than polyester (e.g., chemically recycled polyester, fossil fuel-derived polyester).

It is preferable that the biaxially oriented polyester film 8 further contains particles. Here, "the biaxially oriented polyester film 8 contains particles" means that, when the biaxially oriented polyester film 8 contains multiple layers, at least one of the multiple layers contains particles.

Examples of the particles include inorganic particles and organic particles. Examples of the inorganic particles include silica (silicon oxide) particles, alumina (aluminum oxide) particles, titanium dioxide particles, calcium carbonate particles, kaolin particles, crystalline glass filler, kaolin particles, talc particles, silica-alumina composite oxide particles, and barium sulfate particles. Among these, silica particles, calcium carbonate particles, and alumina particles are preferred, and silica particles and calcium carbonate particles are more preferred. Silica particles are particularly preferred because they can reduce haze. On the other hand, examples of the organic particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. Among these, acrylic resin particles are preferred. Examples of the acrylic resin particles include particles made of polymethacrylate, polymethyl acrylate, or derivatives thereof. These may be used alone or in combination.

The weight average particle diameter of the particles is preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1.5 μm or more. If it is 0.5 μm or more, unevenness can be formed on the surface of the biaxially oriented polyester film 8. Therefore, slipperiness can be imparted to the biaxially oriented polyester film 8. In addition, air that may be trapped when the biaxially oriented polyester film 8 is wound into a roll can be easily removed, reducing the occurrence of appearance defects such as wrinkles and air bubbles. On the other hand, the weight average particle diameter of the particles is preferably 4.0 μm or less, more preferably 3.8 μm or less, and even more preferably 3.0 μm or less. If it is 4.0 μm or less, the occurrence of coarse protrusions on the biaxially oriented polyester film 8 can be prevented.

The particle content in the biaxially oriented polyester film 8 is preferably 100 ppm or more. When the particle content is 100 ppm or more, the biaxially oriented polyester film 8 can be further provided with slipperiness and the occurrence of poor appearance can be further reduced. On the other hand, the particle content in the biaxially oriented polyester film 8 is preferably 1000 ppm or less, more preferably 800 ppm or less. When the particle content is 1000 ppm or less, the arithmetic mean height Sa and the maximum projection height Sp of the surface of the biaxially oriented polyester film 8 can be prevented from becoming excessively high. In addition, since the voids that may occur in the biaxially oriented polyester film 8 can be reduced, the deterioration of transparency due to the voids can be suppressed.
Here, the particle content is the mass of the particles relative to the mass of the biaxially oriented polyester film 8 (that is, mass of the particles/mass of the biaxially oriented polyester film 8).

The biaxially oriented polyester film 8 may further contain additives such as antioxidants, heat stabilizers, antistatic agents, UV absorbers, plasticizers, and pigments.

In the molecular weight distribution curve obtained by gel permeation chromatography (GPC) of the biaxially oriented polyester film 8, the area ratio of the region with a molecular weight of 1000 or less is preferably 5.5% or less of the total peak area. By making it 5.5% or less, that is, by setting an upper limit of the content of components with a molecular weight of 1,000 or less (i.e., low molecular weight components), the yellowish color that the biaxially oriented polyester film 8 may exhibit can be reduced. By making this area ratio 5.5% or less, the gas barrier property of the gas barrier film 7 can also be improved. Specifically, the permeation of oxygen gas and water vapor can be suppressed or reduced. This is thought to be because the occurrence of defects in the inorganic thin film layer 31 that may be caused by low molecular weight components can be reduced or suppressed.
By setting this area ratio to 5.5% or less, when a sealant layer is formed on the gas barrier film 7, the peel strength between the gas barrier film 7 and the sealant layer can be improved. This is believed to be because it is possible to suppress a decrease in peel strength due to low molecular weight components that can act as plastic components.

This area ratio may be 5.4% or less, 5.3% or less, 5.2% or less, 5.1% or less, or 5.0% or less.

In addition, the area ratio of the region with a molecular weight of 1000 or less is preferably 1.9% or more of the total peak area.
By making the content of the low molecular weight component 1.9% or more, that is, by setting a lower limit for the content of the low molecular weight component, it is possible to ensure the content of the low molecular weight component capable of acting like a plasticizer.
By being 1.9% or more, the molecular weight of the polyester contained in the biaxially oriented polyester film 8 can also be limited to a certain level or less. This will be explained. Since low molecular weight components are incorporated into the polyester during the polymerization process, the higher the molecular weight of the polyester, the fewer low molecular weight components there are, and the lower the molecular weight of the polyester, the more low molecular weight components there are. According to this embodiment, since the area ratio of the region with a molecular weight of 1000 or less is 1.9% or more, that is, since low molecular weight components exist to a certain level or more, the molecular weight of the polyester contained in the biaxially oriented polyester film 8 can be limited to a certain level or less.
Therefore, the stress during stretching in the manufacturing process of the biaxially oriented polyester film 8 (i.e., stretching stress) can be prevented from becoming excessively large, and as a result, film breakage that may occur during stretching can be suppressed or reduced.
This area ratio may be 2.0% or more, 2.2% or more, 2.4% or more, 2.6% or more, 2.8% or more, or 3.0% or more.

The color b ^* value per 1 μm of thickness of the biaxially oriented polyester film 8 is preferably 0.067 or less, more preferably 0.060 or less, and even more preferably 0.050 or less. If it is 0.067 or less, the yellowish color that the biaxially oriented polyester film 8 may exhibit can be limited. Therefore, for example, when a printed layer is formed on the biaxially oriented polyester film 8, the effect of the color tone of the biaxially oriented polyester film 8 on the appearance (i.e., external appearance) of the printed layer can be reduced. Also, for example, when a packaging container is produced using the gas barrier film 7, the effect of the color tone of the biaxially oriented polyester film 8 on the appearance of the contents can be reduced.

The intrinsic viscosity of the biaxially oriented polyester film 8 is 0.50 dl/g or more, preferably 0.51 dl/g or more. Since the intrinsic viscosity is 0.50 dl/g or more, the mechanical properties, specifically, the tensile strength and puncture strength, can be improved.
The intrinsic viscosity of the biaxially oriented polyester film 8 of 0.50 dl/g or more can also improve the gas barrier properties of the gas barrier film 7. This will be explained. Since low molecular weight components are incorporated into polyester during the polymerization process, the larger the molecular weight of the polyester, the less low molecular weight components there are. The intrinsic viscosity of the biaxially oriented polyester film 8 of 0.50 dl/g or more can limit the amount of low molecular weight components to a certain level or less, and as a result, the occurrence of defects in the inorganic thin film layer 31 that may be caused by the low molecular weight components can be reduced or suppressed. Therefore, the gas barrier properties of the gas barrier film 7 can be improved. Specifically, the permeation of oxygen gas and water vapor can be suppressed or reduced.
By setting the intrinsic viscosity of the biaxially oriented polyester film 8 to 0.50 dl/g or more, when a sealant layer is formed on the gas barrier film 7, the peel strength between the gas barrier film 7 and the sealant layer can be improved. This is believed to be because the decrease in peel strength caused by low molecular weight components that can act as plastic components can be suppressed.
On the other hand, the intrinsic viscosity of the biaxially oriented polyester film 8 is 0.70 dl/g or less, preferably 0.65 dl/g or less. Since the intrinsic viscosity is 0.70 dl/g or less, the stress (i.e., stretching stress) during stretching in the manufacturing process of the biaxially oriented polyester film 8 can be prevented from becoming excessively large, and as a result, the breakage of the film that may occur during stretching can be suppressed or reduced.

The surface crystallinity of at least one surface of the biaxially oriented polyester film 8 is preferably 1.10 or more, more preferably 1.15 or more, even more preferably 1.20 or more, and even more preferably 1.25 or more.
The crystallization rate increases as the molecular weight of the polyester decreases, so the surface crystallinity of the biaxially oriented polyester film 8 increases as the molecular weight of the polyester contained in the biaxially oriented polyester film 8 decreases.
If the surface crystallinity is 1.10 or more, not only can the molecular weight of the polyester contained in the biaxially oriented polyester film 8 be further limited to a certain level or less, but also the amount of low molecular weight components that can act like plasticizers can be further limited to a certain level or more. Therefore, the stress during stretching in the manufacturing process of the biaxially oriented polyester film 8 (i.e., stretching stress) can be further prevented from becoming excessively large, and as a result, the breakage of the film that may occur during stretching can be further suppressed or reduced.

Similarly, the surface crystallinity of both sides of the biaxially oriented polyester film 8 is preferably 1.10 or more, more preferably 1.15 or more, even more preferably 1.20 or more, and even more preferably 1.25 or more.

The surface crystallinity of at least one side of the biaxially oriented polyester film 8 is preferably 1.35 or less, more preferably 1.34 or less, even more preferably 1.33 or less, even more preferably 1.32 or less, even more preferably 1.31 or less, even more preferably 1.30 or less, even more preferably 1.29 or less, and even more preferably 1.28 or less. If it is 1.35 or less, the biaxially oriented polyester film 8 can be prevented from becoming excessively brittle (i.e., the toughness can be prevented from becoming excessively poor), and the mechanical properties, specifically, tensile strength and puncture strength, can be improved.

Similarly, the surface crystallinity of both sides of the biaxially oriented polyester film 8 is preferably 1.35 or less, more preferably 1.34 or less, even more preferably 1.33 or less, even more preferably 1.32 or less, even more preferably 1.31 or less, even more preferably 1.30 or less, even more preferably 1.29 or less, even more preferably 1.28 or less.

The degree of surface crystallinity is determined by ATR-IR. That is, it is determined by obtaining a spectrum by attenuated total reflection using a Fourier transform infrared spectrophotometer. The degree of surface crystallinity is the intensity ratio between the absorption appearing near 1340 cm ^-1 and the absorption appearing near 1410 cm ^-1 , specifically, the intensity at 1340 cm ^-1 /the intensity at 1410 cm ^-1 . The absorption appearing near 1340 cm ^-1 is absorption due to deformation vibration of CH ₂ (trans structure) of ethylene glycol. On the other hand, the absorption appearing near 1410 cm ^-1 is absorption unrelated to crystals or orientation.
The ATR-IR measurement is carried out under the following conditions:
FT-IR: BioRad DIGILAB FTS-60A/896
Single reflection ATR attachment: golden gate MKII (SPECAC)
Internal reflection element: Diamond Incident angle: 45°
Resolution: 4 ^cm
Number of times accumulated: 128

The biaxially oriented polyester film 8 has a melting point of 251°C or higher, preferably 252°C or higher. Since it is 251°C or higher, it has excellent heat resistance. On the other hand, the biaxially oriented polyester film 8 has a melting point of preferably 270°C or lower, more preferably 268°C or lower. If it is 270°C or lower, it is possible to prevent the viscosity from becoming excessively high when melt extruding the raw material polyester (e.g., chemically recycled polyester) for forming the biaxially oriented polyester film 8, and as a result, high-speed film production is possible.

The melt resistivity at 285°C in the biaxially oriented polyester film 8 is preferably ^1.0x108 Ω·cm or less, more preferably ^0.5x108 Ω·cm or less, and even more preferably ^0.25x108 Ω·cm or less. If it is ^1.0x108 Ω·cm or less, when the film-like polyester composition melt-extruded in the biaxially oriented polyester film 8 is adhered to the cooling drum by the electrostatic adhesion casting method in the manufacturing process of the biaxially oriented polyester film 8, it is possible to effectively charge the surface of the polyester composition with static electricity, so that the polyester composition can be well adhered to the cooling drum. Therefore, it is possible to suppress the occurrence of pinner bubbles (i.e., streak-like defects caused by air getting between the polyester composition and the cooling drum) without excessively lowering the film-forming speed. The film-forming speed is the running speed (m/min) of the biaxially oriented polyester film 8 when the biaxially oriented polyester film 8 is wound around the master roll. The film-forming speed can be calculated by multiplying the cast speed by the MD stretch ratio. On the other hand, the melt resistivity may be, for example, 0.01× ¹⁰ Ω·cm or more, 0.03× ¹⁰ Ω·cm or more, or 0.05× ¹⁰ Ω·cm or more. If the melt resistivity is 0.01× ¹⁰ Ω·cm or more, the generation of foreign matter (for example, foreign matter caused by alkaline earth metal compounds that can reduce the melt resistivity) can be suppressed or reduced.

The melt resistivity of the biaxially oriented polyester film 8 can be adjusted by the content of the alkaline earth metal compound and the content of the phosphorus compound in the biaxially oriented polyester film 8. For example, the alkaline earth metal atom (hereinafter sometimes referred to as "M2") constituting the alkaline earth metal compound has the effect of lowering the melt resistivity, so the melt resistivity can be lowered by increasing the content of the alkaline earth metal compound. On the other hand, although the phosphorus compound itself is thought not to have the effect of lowering the melt resistivity of the biaxially oriented polyester film 8, it contributes to a decrease in the melt resistivity in the presence of the alkaline earth metal compound. Although the reason for this is not clear, it is thought that the inclusion of the phosphorus compound can suppress the generation of foreign matter and increase the amount of charge carriers.

Examples of alkaline earth metal compounds include hydroxides of alkaline earth metals, aliphatic dicarboxylates (acetates, butyrates, etc., preferably acetates), aromatic dicarboxylates, and salts with compounds having phenolic hydroxyl groups (salts with phenols, etc.). Examples of alkaline earth metals include magnesium, calcium, strontium, and barium. Magnesium is preferred. More specifically, magnesium hydroxide, magnesium acetate, calcium acetate, strontium acetate, and barium acetate are examples. Magnesium acetate is preferred. The alkaline earth metal compounds can be used alone or in combination of two or more. Although there are definitions of alkaline earth metals that do not include magnesium in the alkaline earth metals, in this specification, alkaline earth metal is used as a term that includes magnesium. In other words, in this specification, alkaline earth metal refers to an element in Group IIa of the periodic table.

In addition, since the catalyst and metal ions are removed from chemically recycled polyester during the recycling process, it contains no or substantially no alkaline earth metal compounds. Therefore, the content of alkaline earth metal compounds can be adjusted by using chemically recycled polyester in combination with other polyesters (for example, fossil fuel-derived polyesters or masterbatches to which alkaline earth metal compounds have been added).

The content of the alkaline earth metal compound in the biaxially oriented polyester film 8 is preferably 20 ppm or more, more preferably 22 ppm or more, and even more preferably 24 ppm or more, based on the alkaline earth metal atom (i.e., in terms of alkaline earth metal atom). On the other hand, the content of the alkaline earth metal compound is preferably 400 ppm or less, more preferably 350 ppm or less, and even more preferably 300 ppm or less, based on the alkaline earth metal atom. If it is 400 ppm or less, the generation of foreign matter and coloration caused by the alkaline earth metal compound can be suppressed.
Here, the content of the alkaline earth metal compound is the mass of the alkaline earth metal compound based on alkaline earth metal atoms relative to the mass of the biaxially oriented polyester film 8 (i.e., the mass of the alkaline earth metal compound based on alkaline earth metal atoms/mass of the biaxially oriented polyester film 8).

The content of magnesium compounds in the biaxially oriented polyester film 8 is preferably 20 ppm or more, more preferably 22 ppm or more, and even more preferably 24 ppm or more, based on magnesium atoms (i.e., in terms of magnesium atoms). On the other hand, the content of magnesium compounds is preferably 400 ppm or less, more preferably 350 ppm or less, and even more preferably 300 ppm or less, based on magnesium atoms.

Examples of phosphorus compounds include phosphoric acids (phosphoric acid, phosphorous acid, hypophosphorous acid, etc.), and esters thereof (alkyl esters, aryl esters, etc.), as well as alkylphosphonic acids, arylphosphonic acids, and esters thereof (alkyl esters, aryl esters, etc.). Preferred phosphorus compounds include phosphoric acid, aliphatic esters of phosphoric acid (alkyl esters of phosphoric acid, etc.; for example, mono-C1-6 alkyl esters of phosphoric acid such as monomethyl phosphate, monoethyl phosphate, and monobutyl phosphate, di-C1-6 alkyl esters of phosphoric acid such as dimethyl phosphate, diethyl phosphate, and dibutyl phosphate, tri-C1-6 alkyl esters of phosphoric acid such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate), aromatic esters of phosphoric acid (mono-, di-, or tri-C6-9 aryl esters of phosphoric acid such as triphenyl phosphate and tricresyl phosphate), aliphatic esters of phosphorous acid (alkyl esters of phosphorous acid, etc.; for example, trimethyl phosphite, hypomethyl phosphate, etc.), Examples of phosphorous compounds include mono-, di-, or tri-C1-6 alkyl esters of phosphorous acid such as tributyl phosphate, alkyl phosphonic acids (C1-6 alkyl phosphonic acids such as methyl phosphonic acid and ethyl phosphonic acid), alkyl phosphonic acid alkyl esters (mono- or di-C1-6 alkyl esters of C1-6 alkyl phosphonic acids such as dimethyl methyl phosphonate and dimethyl ethyl phosphonate), aryl phosphonic acid alkyl esters (mono- or di-C1-6 alkyl esters of C6-9 aryl phosphonic acids such as dimethyl phenyl phosphonate and diethyl phenyl phosphonate), and aryl phosphonic acid aryl esters (mono- or di-C6-9 aryl esters of C6-9 aryl phosphonic acids such as diphenyl phenyl phosphonate). Particularly preferred phosphorus compounds include phosphoric acid and trialkyl phosphates (trimethyl phosphate, etc.). These phosphorus compounds can be used alone or in combination of two or more.

The content of the phosphorus compound in the biaxially oriented polyester film 8 is preferably 10 ppm or more, more preferably 11 ppm or more, and even more preferably 12 ppm or more, based on phosphorus atoms (i.e., in terms of phosphorus atoms). When it is 10 ppm or more, the melt resistivity can be effectively reduced. In addition, the generation of foreign matter can be suppressed. The content of the phosphorus compound may be 20 ppm or more, 40 ppm or more, or 50 ppm or more, based on phosphorus atoms. On the other hand, the content of the phosphorus compound is preferably 600 ppm or less, more preferably 550 ppm or less, and even more preferably 500 ppm or less, based on phosphorus atoms. When it is 600 ppm or less, the generation of diethylene glycol can be reduced. The content of the phosphorus compound may be 400 ppm or less, 200 ppm or less, or 100 ppm or less, based on phosphorus atoms.
Here, the content of the phosphorus compound is the mass of the phosphorus compound based on phosphorus atoms relative to the mass of the biaxially oriented polyester film 8 (i.e., mass of the phosphorus compound based on phosphorus atoms/mass of the biaxially oriented polyester film 8).

In the biaxially oriented polyester film 8, the mass ratio of alkaline earth metal atoms (i.e., M2) to phosphorus atoms (P), i.e., the ratio of M2 mass to P mass (M2 mass/P mass), is preferably 1.0 or more, more preferably 1.1 or more, even more preferably 1.2 or more, even more preferably 1.3 or more, and even more preferably 1.4 or more. If it is 1.0 or more, the melt resistivity of the biaxially oriented polyester film 8 can be effectively reduced. On the other hand, this mass ratio is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. If it is 5.0 or less, the generation of foreign matter and coloration can be suppressed.

When the number of moles of all dicarboxylic acid components in the biaxially oriented polyester film 8 is taken as 100 mol%, the number of moles of the isophthalic acid component is preferably 0.1 mol% or more, more preferably 0.15 mol% or more, even more preferably 0.2 mol% or more, and even more preferably 0.4 mol% or more. If it is 0.1 mol% or more, when a sealant layer is provided on the gas barrier film 7, the peel strength between the gas barrier film 7 and the sealant layer can be improved. On the other hand, the number of moles of the isophthalic acid component is preferably 3.0 mol% or less, more preferably 2.5 mol% or less, even more preferably 2.2 mol% or less, and even more preferably 2.0 mol% or less. If it is 3.0 mol% or less, it is possible to prevent the crystallinity from being excessively reduced, and therefore it is possible to prevent the heat resistance and mechanical properties (specifically, tensile strength and puncture strength) from being excessively reduced. In addition, it is possible to reduce the thickness unevenness of the biaxially oriented polyester film 8, and it is also possible to limit the heat shrinkage rate of the biaxially oriented polyester film 8.

The tensile strength of the biaxially oriented polyester film 8 in at least one direction is preferably 180 MPa or more, more preferably 185 MPa or more, and even more preferably 190 MPa or more. If the tensile strength is 180 MPa or more, the biaxially oriented polyester film 8 can be used to produce products (e.g., packaging containers) with excellent strength.

Similarly, the tensile strength of the biaxially oriented polyester film 8 in the MD (i.e., 0° direction), 45° direction, TD (i.e., 90° direction), and 135° direction is preferably 180 MPa or more, more preferably 185 MPa or more, and even more preferably 190 MPa or more.

The tensile strength of the biaxially oriented polyester film 8 in at least one direction is preferably 350 MPa or less, more preferably 340 MPa or less, and even more preferably 330 MPa or less. If it is 350 MPa or less, the stress (i.e., stretching stress) during stretching in the manufacturing process of the biaxially oriented polyester film 8 can be further prevented from becoming excessively large, and as a result, film breakage that may occur during stretching can be further suppressed or reduced. The tensile strength may be 320 MPa or less.

Similarly, the tensile strength of the biaxially oriented polyester film 8 in the MD (i.e., 0° direction), 45° direction, TD (i.e., 90° direction), and 135° direction is preferably 350 MPa or less, more preferably 340 MPa or less, and even more preferably 330 MPa or less. The tensile strength may be 320 MPa or less.

The puncture strength of the biaxially oriented polyester film 8 is preferably 0.50 N/μm or more, more preferably 0.52 N/μm or more, and even more preferably 0.55 N/μm or more. If it is 0.50 N/μm or more, the gas barrier film 7 can be used to produce a product (e.g., a packaging container) with excellent strength. For example, the gas barrier film 7 can be used to produce a packaging container that is difficult to puncture.

The heat shrinkage rate of the biaxially oriented polyester film 8 in the longitudinal direction, i.e., the MD, is preferably 2.0% or less, and more preferably 1.8% or less. If it is 2.0% or less, the frequency of deformation and wrinkles due to heat can be reduced when the biaxially oriented polyester film 8 is subjected to secondary processing such as deposition processing and printing processing. The heat shrinkage rate in the MD may be, for example, 0.5% or more, or 0.8% or more.

The thermal shrinkage rate of the biaxially oriented polyester film 8 in the width direction, i.e., TD, is preferably -1.0% or more and 1.0% or less, and more preferably -0.8% or more and 0.8% or less. If it is -1.0% or more and 1.0% or less, the frequency of deformation and wrinkles due to heat can be reduced when secondary processing such as deposition processing and printing processing is performed.

The thickness of the biaxially oriented polyester film 8 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 9 μm or more. If the thickness is 5 μm or more, the biaxially oriented polyester film 8 has excellent rigidity, and therefore the frequency of wrinkles occurring when the biaxially oriented polyester film 8 is wound up can be reduced. On the other hand, the thickness of the biaxially oriented polyester film 8 is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and particularly preferably 25 μm or less. The thinner the thickness, the more cost can be reduced.

As shown in FIG. 4, the biaxially oriented polyester film 8 preferably includes a first layer 81 (hereinafter also referred to as "surface layer 81"), a second layer 82 (hereinafter also referred to as "center layer 82"), and a third layer 83 (hereinafter also referred to as "surface layer 83"). The first layer 81, the second layer 82, and the third layer 83 are arranged in this order in the thickness direction of the biaxially oriented polyester film 8. Note that other layers may be present between the first layer 81 and the second layer 82, or between the second layer 82 and the third layer 83.

The first layer 81, i.e., the surface layer 81, preferably contains chemically recycled polyester. If the first layer 81 contains chemically recycled polyester, the environmental impact can be further reduced.

The explanation of the chemically recycled polyester in the first layer 81 will be omitted because it overlaps with the explanation above (i.e., the explanation of the chemically recycled polyester in the biaxially oriented polyester film 8). Therefore, the explanation of the chemically recycled polyester in the biaxially oriented polyester film 8 can also be treated as the explanation of the chemically recycled polyester in the first layer 81.

The content of chemically recycled polyester is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the first layer 81 is taken as 100% by mass. If it is 10% by mass or more, the environmental load can be further reduced. On the other hand, the content of chemically recycled polyester is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, when the first layer 81 is taken as 100% by mass.

It is preferable that the first layer 81 contains a fossil fuel-derived polyester. The description of the fossil fuel-derived polyester in the first layer 81 will be omitted because it overlaps with the above description (i.e., the description of the fossil fuel-derived polyester in the biaxially oriented polyester film 8). Therefore, the description of the fossil fuel-derived polyester in the biaxially oriented polyester film 8 can also be used as the description of the fossil fuel-derived polyester in the first layer 81.

The content of the fossil fuel-derived polyester is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the first layer 81 is taken as 100% by mass. If it is 5% by mass or more, a certain degree of width can be secured within which the physical properties of the first layer 81 can be adjusted. On the other hand, the content of the fossil fuel-derived polyester can be 100% by mass or less, when the first layer 81 is taken as 100% by mass. The content of the fossil fuel-derived polyester is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

The first layer 81 may contain other polyesters, such as mechanically recycled polyester and biomass polyester.

When the first layer 81 is taken as 100% by mass, the polyester content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

The first layer 81 may contain a resin other than polyester.

It is preferable that the first layer 81 further contains particles. When the first layer 81 contains particles, it is possible to form unevenness on the surface of the biaxially oriented polyester film 8. This makes it possible to impart slipperiness to the biaxially oriented polyester film 8. In addition, air that may be trapped when the biaxially oriented polyester film 8 is wound into a roll can be easily removed, reducing the occurrence of appearance defects such as wrinkles and air bubbles.

The description of the particles in the first layer 81 will be omitted because it overlaps with the above description (i.e., the description of the particles in the biaxially oriented polyester film 8). Therefore, the description of the particles in the biaxially oriented polyester film 8 can also be treated as the description of the particles in the first layer 81.

The particle content in the first layer 81 is preferably 500 ppm or more, more preferably 600 ppm or more, and even more preferably 700 ppm or more. If it is 500 ppm or more, the biaxially oriented polyester film 8 can be further provided with slipperiness and the occurrence of defective appearance can be further reduced. On the other hand, the particle content in the first layer 81 may be 3000 ppm or less, 2000 ppm or less, or 1500 ppm or less.
Here, the particle content is the mass of the particles relative to the mass of the first layer 81 (i.e., mass of the particles/mass of the first layer 81).

The thickness of the first layer 81 is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. The thickness of the first layer 81 is preferably 7 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

The description of the third layer 83, i.e., the surface layer 83, will be omitted because it overlaps with the description of the first layer 81. Therefore, the description of the first layer 81 can also be treated as the description of the third layer 83. For example, the description of the chemically recycled polyester, the fossil fuel-derived polyester, the particles, the thickness, etc. of the first layer 81 can be treated as the description of the third layer 83. Of course, the first layer 81 and the third layer 83 can be independent of each other in terms of composition, physical properties (e.g., thickness), etc. Thus, for example, the composition of the first layer 81 and the third layer 83 may be the same or different. The thickness of both layers may be the same or different.

The second layer 82, i.e., the central layer 82, preferably contains chemically recycled polyester. If the second layer 82 contains chemically recycled polyester, the environmental impact can be further reduced.

The explanation of the chemically recycled polyester in the second layer 82 is omitted because it overlaps with the explanation above (i.e., the explanation of the chemically recycled polyester in the biaxially oriented polyester film 8). Therefore, the explanation of the chemically recycled polyester in the biaxially oriented polyester film 8 can also be treated as the explanation of the chemically recycled polyester in the second layer 82.

The content of chemically recycled polyester is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the second layer 82 is taken as 100% by mass. If it is 10% by mass or more, the environmental load can be further reduced. On the other hand, the content of chemically recycled polyester is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, when the second layer 82 is taken as 100% by mass.

The second layer 82 preferably contains a fossil fuel-derived polyester. The description of the fossil fuel-derived polyester in the second layer 82 is omitted because it overlaps with the above description (i.e., the description of the fossil fuel-derived polyester in the biaxially oriented polyester film 8). Therefore, the description of the fossil fuel-derived polyester in the biaxially oriented polyester film 8 can also be used as the description of the fossil fuel-derived polyester in the second layer 82.

The content of the fossil fuel-derived polyester is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, when the second layer 82 is taken as 100% by mass. If it is 5% by mass or more, a certain degree of width can be secured within which the physical properties of the second layer 82 can be adjusted. On the other hand, the content of the fossil fuel-derived polyester is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, when the first layer 81 is taken as 100% by mass.

The second layer 82 may contain other polyesters, such as mechanically recycled polyester and biomass polyester.

When the second layer 82 is taken as 100% by mass, the polyester content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more.

The second layer 82 may contain a resin other than polyester.

The second layer 82 may or may not contain particles. The description of the particles in the second layer 82 overlaps with the above description (i.e., the description of the particles in the biaxially oriented polyester film 8), so it is omitted. Therefore, the description of the particles in the biaxially oriented polyester film 8 can also be treated as the description of the particles in the second layer 82. If the second layer 82 does not contain particles, voids that may occur around the particles will not occur, so odor components can be prevented from escaping the biaxially oriented polyester film 8. In addition, it is also advantageous in terms of cost because it is easy to mix and use recovered raw materials from edge parts generated in the film production process and recycled raw materials from other film production processes at the appropriate time.

The particle content in the second layer 82 may be 3000 ppm or less, 2000 ppm or less, 1500 ppm or less, 1000 ppm or less, 500 ppm or less, 100 ppm or less, 50 ppm or less, or 0 ppm or less.
Here, the particle content is the mass of the particles relative to the mass of the second layer 82 (i.e., mass of the particles/mass of the second layer 82).

The thickness of the second layer 82 is preferably greater than the thickness of the first layer 81 and the thickness of the third layer 83. The thickness of the second layer 82 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 9 μm or more. If the thickness is 5 μm or more, the biaxially oriented polyester film 8 has excellent rigidity, so that the frequency of wrinkles occurring when the biaxially oriented polyester film 8 is wound up can be reduced. On the other hand, the thickness of the biaxially oriented polyester film 8 is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The thinner the thickness, the more cost can be reduced.

The composition patterns of the first layer 81, the second layer 82, and the third layer 83 will now be described in more detail.
As a first composition pattern (hereinafter, also referred to as "composition pattern A"), a pattern in which the first layer 81 contains chemically recycled polyester, the second layer 82 contains chemically recycled polyester, and the third layer 83 contains chemically recycled polyester can be mentioned. According to composition pattern A, since the chemically recycled polyester with a small amount of impurities constitutes both surface layers of the biaxially oriented polyester film 8, defects in the biaxially oriented polyester film 8 can be reduced. The explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern A is omitted because it overlaps with the above explanation (i.e., the explanation of the first layer 81, the second layer 82, and the third layer 83). Therefore, the above explanation can also be treated as the explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern A. Therefore, the first layer 81 may contain polyester other than chemically recycled polyester, the second layer 82 may contain polyester other than chemically recycled polyester, and the third layer 83 may contain polyester other than chemically recycled polyester.
As a second composition pattern (hereinafter, also referred to as "composition pattern B"), a pattern can be mentioned in which the first layer 81 contains chemically recycled polyester, and neither the second layer 82 nor the third layer 83 contains chemically recycled polyester. According to composition pattern B, the chemically recycled polyester with a small amount of impurities constitutes the surface layer of the biaxially oriented polyester film 8, so that defects in the biaxially oriented polyester film 8 can be reduced. The explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern B is omitted because it overlaps with the above explanation (i.e., the explanation of the first layer 81, the second layer 82, and the third layer 83). Therefore, the above explanation can also be treated as the explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern B. Therefore, the first layer 81 may contain polyester other than chemically recycled polyester.
In the composition pattern B, it is preferable that the second layer 82 and/or the third layer 83 contains mechanically recycled polyester. This can further increase the ratio of recycled raw materials, which means that the environmental load can be further reduced.
A third composition pattern (hereinafter, also referred to as "composition pattern C") may be a pattern in which the second layer 82 contains chemically recycled polyester, and neither the first layer 81 nor the third layer 83 contains chemically recycled polyester. The explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern C will be omitted because it overlaps with the above explanation (i.e., the explanation of the first layer 81, the second layer 82, and the third layer 83). Therefore, the above explanation can also be treated as the explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern C. Therefore, the second layer 82 may contain a polyester other than chemically recycled polyester.
In the composition pattern C, it is preferable that the first layer 81 and/or the third layer 83 contains mechanically recycled polyester. This can further increase the ratio of recycled raw materials, which means that the environmental load can be further reduced.
A fourth composition pattern (hereinafter, also referred to as "composition pattern D") may be a pattern in which the first layer 81 contains chemically recycled polyester, the second layer 82 contains chemically recycled polyester, and the third layer 83 does not contain chemically recycled polyester. According to composition pattern D, the chemically recycled polyester with a small amount of impurities constitutes the surface layer of the biaxially oriented polyester film 8, so that defects in the biaxially oriented polyester film 8 can be reduced. The explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern D is omitted because it overlaps with the above explanation (i.e., the explanation of the first layer 81, the second layer 82, and the third layer 83). Therefore, the above explanation can also be treated as the explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern D. Therefore, the first layer 81 may contain polyester other than chemically recycled polyester, and the second layer 82 may contain polyester other than chemically recycled polyester.
In the composition pattern D, it is preferable that the third layer 83 contains mechanically recycled polyester. This can further increase the ratio of recycled materials, which means that the environmental impact can be further reduced.
A fifth composition pattern (hereinafter, also referred to as "composition pattern E") is a pattern in which the first layer 81 contains chemically recycled polyester, the second layer 82 does not contain chemically recycled polyester, and the third layer 83 contains chemically recycled polyester. According to composition pattern E, the chemically recycled polyester with few impurities constitutes both surface layers of the biaxially oriented polyester film 8, so that defects in the biaxially oriented polyester film 8 can be reduced. The explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern E is omitted because it overlaps with the above explanation (i.e., the explanation of the first layer 81, the second layer 82, and the third layer 83). Therefore, the above explanation can also be treated as the explanation of the first layer 81, the second layer 82, and the third layer 83 in composition pattern E. Therefore, the first layer 81 may contain a polyester other than the chemically recycled polyester, and the third layer 83 may contain a polyester other than the chemically recycled polyester.
In the composition pattern E, it is preferable that the second layer 82 contains mechanically recycled polyester. This can further increase the ratio of recycled materials, which means that the environmental load can be further reduced.

The biaxially oriented polyester film 8 can be produced by feeding the raw materials for forming the first layer 81 to the first extruder, the raw materials for forming the second layer 82 to the second extruder, and the raw materials for forming the third layer 83 to the third extruder, and then melting them and feeding them from the first, second, and third extruders to a T-die, laminating them in the T-die, extruding them from the T-die, solidifying them on a cooling drum, and biaxially stretching them. Of course, these raw materials may also be fed from the first, second, and third extruders to a feed block, laminating them in the feed block, and extruding them from the T-die. Note that methods other than the T-die method, such as the tubular method, may also be used.

Examples of raw materials for forming the first layer 81 include chemically recycled polyester, fossil fuel-derived polyester, particle-containing master batch, and alkaline earth metal compound/phosphorus compound-containing master batch (hereinafter sometimes referred to as "MP master batch"). It is preferable to use at least these as raw materials for forming the first layer 81.

The particle-containing master batch may include polyester and particles (e.g., silica). The particle-containing master batch may include particles (e.g., silica) at the highest concentration of the individual raw materials for forming the first layer 81.

The polyester of the particle-containing masterbatch may be a chemically recycled polyester, a fossil fuel-derived polyester, a mechanically recycled polyester, or a biomass polyester. Of these, chemically recycled polyester and fossil fuel-derived polyester are preferred, and fossil fuel-derived polyester is more preferred.

The particle content in the particle-containing masterbatch is preferably 5000 ppm or more, more preferably 10000 ppm or more, and even more preferably 20000 ppm or more. On the other hand, the particle content in the particle-containing masterbatch may be 1,000,000 ppm or less, 200,000 ppm or less, or 100,000 ppm or less.
Here, the content of particles is the mass of the particles relative to the mass of the particle-containing masterbatch (that is, mass of particles/mass of particle-containing masterbatch).

On the other hand, the MP master batch (i.e., a master batch containing an alkaline earth metal compound and a phosphorus compound) can contain a polyester, an alkaline earth metal compound, and a phosphorus compound. Of the individual raw materials for forming the first layer 81, the MP master batch contains the highest concentration of an alkaline earth metal compound and also contains the highest concentration of a phosphorus compound.

The polyester of the MP masterbatch may be a chemically recycled polyester, a fossil fuel-derived polyester, a mechanically recycled polyester, or a biomass polyester. Of these, chemically recycled polyester and fossil fuel-derived polyester are preferred, and fossil fuel-derived polyester is more preferred. The MP masterbatch can be produced, for example, by adding a large amount of an alkaline earth metal compound and a phosphorus compound when polymerizing polyester.

The content of the alkaline earth metal compound in the MP master batch is, for example, preferably 200 ppm or more, preferably 400 ppm or more, preferably 600 ppm or more, and preferably 700 ppm or more, based on the alkaline earth metal atoms (i.e., in terms of alkaline earth metal atoms). The content of the alkaline earth metal compound may be, for example, 3000 ppm or less, 2000 ppm or less, or 1500 ppm or less, based on the alkaline earth metal atoms.
Here, the content of the alkaline earth metal compound is the mass of the alkaline earth metal compound based on the alkaline earth metal atom relative to the mass of the MP master batch (i.e., mass of the alkaline earth metal compound based on the alkaline earth metal atom/mass of the MP master batch).

The content of the magnesium compound in the MP master batch is, for example, preferably 200 ppm or more, preferably 400 ppm or more, preferably 600 ppm or more, and preferably 700 ppm or more, based on the magnesium compound atoms (i.e., in terms of magnesium compound atoms). The content of the alkaline earth metal compound may be, for example, 3000 ppm or less, 2000 ppm or less, or 1500 ppm or less, based on the magnesium compound atoms.

The content of the phosphorus compound in the MP master batch is, for example, preferably 150 ppm or more, more preferably 300 ppm or more, even more preferably 350 ppm or more, and even more preferably 400 ppm or more, based on phosphorus atoms (i.e., in terms of phosphorus atoms). On the other hand, the content of the phosphorus compound may be 1000 ppm or less, 800 ppm or less, or 700 ppm or less, based on phosphorus atoms.
Here, the content of the phosphorus compound is the mass of the phosphorus compound on a phosphorus atom basis relative to the mass of the MP master batch (i.e., mass of the phosphorus compound on a phosphorus atom basis/mass of the MP master batch).

In addition, instead of the MP master batch, an alkaline earth metal compound-containing master batch and a phosphorus compound-containing master batch may be used. The alkaline earth metal compound-containing master batch may contain polyester and an alkaline earth metal compound. This master batch contains the alkaline earth metal compound at the highest concentration among the individual raw materials for forming the first layer 81. The phosphorus compound-containing master batch may contain polyester and a phosphorus compound. This master batch contains the phosphorus compound at the highest concentration among the individual raw materials for forming the first layer 81.

Examples of raw materials for forming the second layer 82 include chemically recycled polyester, polyester derived from fossil fuels, and master batches containing alkaline earth metal compounds and phosphorus compounds (i.e., MP master batches). It is preferable to use at least these as raw materials for forming the second layer 82.

The explanation of the MP master batch in the second layer 82 will be omitted because it overlaps with the explanation above (i.e., the explanation of the MP master batch in the first layer 81). Therefore, the explanation of the MP master batch in the first layer 81 can also be treated as the explanation of the MP master batch in the second layer 82.

The explanation of the raw materials for forming the third layer 83 will be omitted because it overlaps with the explanation of the raw materials for forming the first layer 81. Therefore, the explanation of the raw materials for forming the first layer 81 can also be treated as the explanation of the raw materials for forming the third layer 83. Of course, the raw materials for forming the first layer 81 and the raw materials for forming the third layer 83 can be independent of each other. Thus, for example, these raw materials may be the same or different.

It is preferable to dry these raw materials (specifically, the raw materials for forming the first layer 81, the second layer 82, and the third layer 83) before supplying them to the extruder. For drying, for example, a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer can be used.

The raw materials for forming the first layer 81 are supplied to a first extruder, the raw materials for forming the second layer 82 to a second extruder, and the raw materials for forming the third layer 83 to a third extruder, and after melting, they are led from the first, second, and third extruders to a T-die or feed block, where they can be laminated. These raw materials are preferably melted at a temperature above the melting point of the polyester in the raw materials and between 200°C and 300°C.

The polyester composition in the form of a film can be extruded from the T-die and cast onto a cooling drum. This allows the polyester composition to be rapidly cooled and solidified, resulting in a substantially unoriented, unstretched film. The surface temperature of the cooling drum is preferably 40°C or lower.

The unstretched film can then be biaxially stretched. Biaxial stretching can improve mechanical properties such as tensile strength. The biaxial stretching can be simultaneous biaxial stretching or sequential biaxial stretching. Of these, sequential biaxial stretching is preferred. In sequential biaxial stretching, it is preferred to stretch the unstretched film in the longitudinal direction, i.e., MD, and then stretch the sheet after MD stretching in the width direction, i.e., TD. This allows the production of a biaxially oriented polyester film 8 with excellent thickness uniformity at a relatively high film-forming speed.

The temperature at which the unstretched film is stretched in the longitudinal direction, i.e., the MD stretching temperature, is preferably 80°C or higher and 130°C or lower. The stretching ratio at this time, i.e., the MD stretching ratio, is preferably 3.3 times or higher and 4.7 times or lower. If the temperature is 80°C or higher and 4.7 times or lower, the shrinkage stress in the longitudinal direction can be reduced, the bowing phenomenon can be reduced, and the variation and distortion of the molecular orientation and thermal shrinkage rate in the width direction of the biaxially oriented polyester film 8 can be reduced.

The method of stretching the unstretched film in the longitudinal direction may be, for example, a method of stretching in multiple stages between multiple rolls, or a method of stretching by heating with an infrared heater or the like. The latter method is preferred because it is easier to raise the temperature, it is easier to locally heat the film, and it is possible to reduce scratches and defects caused by the rolls.

At least one surface of the film stretched in the longitudinal direction may be subjected to a surface treatment such as corona treatment or plasma treatment as required. At least one surface of the film stretched in the longitudinal direction may be coated with a resin dispersion or resin solution as required. This can provide functions such as easy slippage, easy adhesion, and antistatic properties. Note that both surface treatment such as corona treatment or plasma treatment and coating with a resin dispersion or resin solution may be performed.

The film stretched in the longitudinal direction is introduced into a tenter device, both ends of the film are held by clips, and the film is heated to a specified temperature with hot air. The film is then transported in the longitudinal direction while the distance between the clips is increased, allowing the film to be stretched in the width direction.

The preheating temperature when stretching the film in the width direction is preferably 100°C or higher and 130°C or lower. If the temperature is 100°C or higher, the shrinkage stress generated when stretching in the longitudinal direction can be reduced, the bowing phenomenon can be reduced, and the variation and distortion of the molecular orientation and thermal shrinkage rate in the width direction of the biaxially oriented polyester film 8 can be reduced.

The temperature at which the film is stretched in the width direction, i.e., the TD stretching temperature, is preferably 105°C or higher and 135°C or lower. If it is 105°C or higher, the longitudinal stretching stress caused by TD stretching can be reduced, and the increase in the bowing phenomenon can be suppressed. If it is 135°C or lower, even if a polyester with a temperature-rise crystallization temperature of about 130°C (e.g., chemically recycled polyester) is used, film breakage that may occur during stretching can be suppressed or reduced.

The stretching ratio when stretching the film in the width direction, i.e., the TD stretching ratio, is preferably 3.5 times or more and 5.0 times or less. If it is 3.5 times or more, a high yield is likely to be obtained in terms of material balance, and a decrease in mechanical strength can be suppressed, and an increase in thickness unevenness in the width direction can also be suppressed. If it is 5.0 times or less, breakage of the film that may occur during stretching can be suppressed or reduced.

The biaxially stretched film can be heated for heat setting. The heat setting temperature is preferably 220°C or higher and 250°C or lower. If it is 220°C or higher, it is possible to prevent the heat shrinkage rate from becoming excessively high in both the longitudinal and width directions. This improves the thermal dimensional stability during secondary processing. If it is 250°C or lower, it is possible to suppress an increase in the bowing phenomenon, and to reduce the variation and distortion of the molecular orientation and heat shrinkage rate in the width direction of the biaxially oriented polyester film 8.

A heat relaxation treatment can be performed in conjunction with the heat setting treatment or separately from the heat setting treatment. The relaxation rate in the width direction in the heat relaxation treatment is preferably 4% or more and 8% or less. If it is 4% or more, the thermal shrinkage rate in the width direction can be prevented from becoming excessively high. Therefore, the thermal dimensional stability during secondary processing can be improved. If it is 8% or less, the longitudinal stretching stress in the center of the width direction of the film can be prevented from becoming excessively large, and an increase in the bowing phenomenon can be suppressed.

During the thermal relaxation process, the restraining force in the width direction decreases until the biaxially stretched film shrinks due to thermal relaxation, causing the film to slacken under its own weight, or the film may swell due to the accompanying air currents of hot air blown out from nozzles installed above and below the film. As such, the film is in a condition in which it is prone to vertical movement, so the amount of change in the orientation angle of the biaxially oriented polyester film 8 is prone to large fluctuations. To keep the film parallel, for example, the wind speed of the hot air blown out from the nozzles can be adjusted.

Corona discharge treatment, glow discharge treatment, flame treatment, and surface roughening treatment may be performed. Anchor coat treatment, etc. may also be performed.

The wide biaxially oriented polyester film 8 stretched in this manner may be wound up into a roll using a winder device. In other words, a master roll may be produced.

The width of the master roll is preferably 5,000 mm or more and 10,000 mm or less. If it is 5,000 mm or more, the cost per film area can be reduced in the subsequent secondary processing such as the slitting process, deposition processing, and printing processing.

The length of the master roll is preferably 10,000 m or more and 100,000 m or less. If it is 10,000 m or more, the cost per film area can be reduced in the subsequent secondary processing such as the slitting process, deposition processing, and printing processing.

The master roll may be slit and then wound into a roll, i.e., a film roll may be produced.

The winding width of the film roll is preferably 400 mm or more and 3000 mm or less. If it is 400 mm or more, the frequency of changing the film roll during the printing process can be reduced, and costs can be reduced. If it is 3000 mm or less, the roll width is not excessively large, and the roll weight can be prevented from becoming excessively heavy. In other words, the handling properties are good.

The length of the film roll is preferably 2000 m or more and 65000 m or less. If it is 2000 m or more, the frequency of changing the film roll during the printing process can be reduced, and costs can be reduced. If it is 65000 m or less, the roll diameter is not excessively large, and the roll weight can be prevented from becoming excessively heavy. In other words, the handling properties are good.

The core used for the film roll is not particularly limited, and for example, a cylindrical core made of plastic, metal, or paper with a diameter of 3 inches (37.6 mm), 6 inches (152.2 mm), 8 inches (203.2 mm), etc. can be used.

<2.2. Inorganic thin film layer>
The inorganic thin film layer 31, i.e., the deposition layer 31, may contain an inorganic oxide. Examples of the inorganic oxide include oxides of silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), and yttrium (Y). As a material for forming the inorganic thin film layer 31, silicon oxide (i.e., silica), aluminum oxide (i.e., alumina), and a mixture of silicon oxide and aluminum oxide are preferred. Among them, a composite oxide of silicon oxide and aluminum oxide is more preferred because it can achieve both flexibility and denseness of the inorganic thin film layer 31. In other words, it is preferred that the inorganic thin film layer 31 contains a composite oxide of silicon oxide and aluminum oxide. In this composite oxide, the mixture ratio of silicon oxide and aluminum oxide is a mass ratio in terms of metal atoms, i.e., a mass ratio in terms of metal atoms, and Al is preferably 20% by mass or more and 70% by mass or less. If it is 20% by mass or more, the gas barrier property is excellent. When the content is 70 mass % or less, excessive hardness of the inorganic thin film layer 31 can be prevented. Note that the silicon oxide referred to here is various silicon oxides such as SiO and _SiO2, or mixtures thereof, and the aluminum oxide is various aluminum oxides such as AlO and _{Al2O3 ,} or mixtures thereof.

The inorganic thin film layer 31 may be a metal vapor deposition layer. Examples of metals for the metal vapor deposition layer include magnesium, aluminum, titanium, chromium, iron, nickel, copper, zinc, silver, tin, platinum, and gold. Of these, aluminum is preferred. In other words, it is preferred that the inorganic thin film layer 31 is an aluminum vapor deposition layer.

The thickness of the inorganic thin film layer 31 may be, for example, 1 nm or more, 5 nm or more, 10 nm or more, or 20 nm or more. The thickness of the inorganic thin film layer 31 may be, for example, 200 nm or less, 100 nm or less, or 50 nm or less.

The inorganic thin film layer 31 may be a single layer structure, or may be a structure of two or more layers. When the inorganic thin film layer 31 is a structure of two or more layers, those layers can be independent from each other in terms of composition, physical properties (e.g., thickness), etc.

The inorganic thin film layer 31 can be formed by, for example, physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. When forming a silicon oxide/aluminum oxide-based thin film by vacuum deposition, for example, a mixture of SiO ₂ and Al ₂ O ₃ or a mixture of SiO ₂ and Al can be used as the deposition raw material. These deposition raw materials are preferably in the form of particles. The size of the particles is preferably such that the pressure during deposition does not change. For example, the particle diameter is preferably 1 mm to 5 mm. For heating, methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be used. It is also possible to introduce oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc. as a reactive gas, or to adopt reactive deposition using means such as ozone addition and ion assist. Furthermore, the film formation conditions can be changed as desired by applying a bias to the deposition target (a laminated film to be subjected to deposition), heating or cooling the deposition target, etc. The deposition material, reactive gas, bias, heating/cooling of the deposition target, etc. can be changed in the same manner when the sputtering method or CVD method is adopted.

<2.3. Covering layer>
The composition for forming the coating layer 32, i.e., the anchor coat layer 32, preferably contains a resin containing an oxazoline group, i.e., a polymer containing an oxazoline group. The resin containing an oxazoline group can act as a curing agent, i.e., a crosslinking agent. The resin containing an oxazoline group can increase the adhesion between the coating layer 32 and the inorganic thin film layer 31. This is because the oxazoline group has excellent affinity with the inorganic thin film layer 31 and can react with oxygen deficiency parts of inorganic oxides and metal hydroxides that may occur during the formation of the inorganic thin film layer 31. In addition, the unreacted oxazoline group present in the coating layer 32 can react with carboxylic acid terminals (for example, carboxylic acid terminals that may be generated by hydrolysis) that may occur in the biaxially oriented polyester film 8 and the coating layer 32, and therefore can form crosslinks.

The oxazoline group content of the resin having oxazoline groups is preferably 5.1 mmol/g or more, and more preferably 6.0 mmol/g or more. If it is 5.1 mmol/g or more, it may be easy to leave the oxazoline groups in the coating layer 32. On the other hand, the oxazoline group content of the resin having oxazoline groups is preferably 9.0 mmol/g or less, and more preferably 8.0 mmol/g or less. The resin may contain one or more types that satisfy such a suitable oxazoline group content.

The content of the resin having an oxazoline group is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on 100% by mass of the total resin components of the composition for forming the coating layer 32. The content of the resin having an oxazoline group is preferably 85% by mass or less, and more preferably 80% by mass or less.

The composition for forming the coating layer 32 preferably contains a resin containing a carboxy group. This allows the carboxy group to react with the oxazoline group, forming a crosslink. Examples of resins containing a carboxy group include urethane-, polyester-, acrylic-, titanium-, isocyanate-, imine-, and polybutadiene-based resins. Of these, urethane-, polyester-, and acrylic-based resins are preferred. From the viewpoint of adhesion, urethane resins are preferred. On the other hand, acrylic resins are preferred from the viewpoint of water resistance. These may be used alone or in combination of two or more types.

The acid value of the resin containing a carboxy group is preferably 40 mgKOH/g or less, and more preferably 30 mgKOH/g or less. If it is 40 mgKOH/g or less, the flexibility of the coating layer 32 can be prevented from being excessively reduced. On the other hand, the acid value may be 1 mgKOH/g or more, or 2 mgKOH/g or more. The resin may contain one or more types that satisfy such a suitable acid value.

The content of the resin having a carboxy group is preferably 15% by mass or more, and more preferably 20% by mass or more, based on 100% by mass of the total resin components of the composition for forming the coating layer 32. The content of the resin having a carboxy group is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

The composition for forming the coating layer 32 may or may not contain a silane coupling agent. The silane coupling agent preferably has one or more organic functional groups in the molecule. When the silane coupling agent has multiple organic functional groups (i.e., one or more) in the molecule, the multiple organic functional groups may be the same or different. In other words, the multiple organic functional groups can be independent of each other. Examples of organic functional groups include alkoxy groups, amino groups, epoxy groups, and isocyanate groups.

The composition for forming the coating layer 32 may contain a solvent. Examples of the solvent include aromatic solvents such as benzene and toluene, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, and polyhydric alcohol derivatives such as ethylene glycol monomethyl ether.

The coating layer 32 can be formed by applying a composition for forming the coating layer 32 to the biaxially oriented polyester film 8 and drying it.

<2.4. Protective layer>
The protective layer 33 is a layer that can reinforce the gas barrier property of the inorganic thin film layer 31. In other words, the protective layer 33 plays a role in improving the gas barrier property of the gas barrier film 7.

The gas barrier properties of the laminate 9 can be improved by forming the protective layer 33 from a composition containing a resin and a curing agent. This will be explained. In general, the inorganic thin film layer 31 has minute defects scattered therein. By forming the protective layer 33 by applying such a composition onto the inorganic thin film layer 31, the composition can be allowed to penetrate into the defective parts of the inorganic thin film layer 31, and as a result, the gas barrier properties of the laminate 9 can be improved.

Examples of the resin include urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins. These may be used alone or in combination of two or more.
Examples of the curing agent include epoxy-based, isocyanate-based, and melamine-based curing agents. These may be used alone or in combination of two or more.

Among these, urethane-based resins, i.e., urethane resins, are preferred. In other words, it is preferred that the protective layer 33 contains a urethane resin. The urethane resin can increase the adhesion between the protective layer 33 and the inorganic thin film layer 31. This is because the urethane bonds in the urethane resin have polarity and interact with the inorganic thin film layer 31. In addition, the degree of damage that may be sustained by the inorganic thin film layer 31 when a bending load is applied to the gas barrier film 7 can be reduced. This is because the amorphous portion in the urethane resin has flexibility.

The acid value of the urethane resin is preferably in the range of 10 mgKOH/g to 60 mgKOH/g. More preferably, it is in the range of 15 mgKOH/g to 55 mgKOH/g, and even more preferably, it is in the range of 20 mgKOH/g to 50 mgKOH/g. When the acid value of the urethane resin is in the above range, the liquid stability is improved when it is made into an aqueous dispersion, and the protective layer 33 can be uniformly deposited on the highly polar inorganic thin film, resulting in a good coat appearance.

The urethane resin preferably has a glass transition temperature (Tg) of 80°C or higher, and more preferably 90°C or higher. By making the Tg 80°C or higher, it is possible to reduce swelling of the protective layer 33 due to molecular motion during the moist heat treatment process (heating - keeping the temperature - cooling).

From the viewpoint of improving gas barrier properties, it is preferable that the urethane resin contains an aromatic or araliphatic diisocyanate component as a main constituent component. Among them, it is particularly preferable that the urethane resin contains a metaxylylene diisocyanate component. By using such a urethane resin, the cohesive strength of the urethane bond can be further increased due to the stacking effect between the aromatic rings, resulting in good gas barrier properties.

It is preferable that the proportion of aromatic or araliphatic diisocyanate in the urethane resin is 50 mol% or more (i.e., 50 mol% to 100 mol%) out of 100 mol% of the polyisocyanate component. The total proportion of aromatic or araliphatic diisocyanate is preferably 60 mol% to 100 mol%, more preferably 70 mol% to 100 mol%, and even more preferably 80 mol% to 100 mol%. As such a resin, the "Takelac (registered trademark) WPB" series commercially available from Mitsui Chemicals, Inc. can be suitably used. When the total proportion of aromatic or araliphatic diisocyanate is 50 mol% or more, good gas barrier properties are obtained.

From the viewpoint of improving the affinity with the inorganic thin film layer 31, it is preferable that the urethane resin has a carboxylic acid group (carboxyl group). In order to introduce a carboxylic acid (salt) group into the urethane resin, for example, a polyol compound having a carboxylic acid group, such as dimethylolpropionic acid or dimethylolbutanoic acid, may be introduced as a copolymerization component as a polyol component. In addition, after synthesizing the urethane resin containing a carboxylic acid group, it is possible to obtain a urethane resin in a water dispersion by neutralizing it with a salt forming agent. Examples of the salt forming agent include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone or in combination of two or more.

The composition for forming the protective layer 33 may contain a solvent. Examples of the solvent include aromatic solvents such as benzene and toluene, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, and polyhydric alcohol derivatives such as ethylene glycol monomethyl ether.

On the other hand, the protective layer 33 may be formed from a composition that undergoes polycondensation by a sol-gel method. This allows the formation of a protective layer 33 with high gas barrier properties, thereby improving the gas barrier properties of the laminate 9. Such a composition may contain an alkoxide represented by formula 1 and at least one of a polyvinyl alcohol resin and an ethylene-vinyl alcohol copolymer.
Formula 1 R ¹ _n M(OR ² ) _m
^R1 represents an organic group having 1 to 8 carbon atoms. ^R2 represents an organic group having 1 to 8 carbon atoms. M represents a metal atom. n represents an integer of 0 or more. m represents an integer of 1 or more. n+m represents the valence of M.
In addition, when there are a plurality of R ¹ in formula 1, the plurality of R ¹ can be independent from each other. When there are a plurality of R ² in formula 1, the plurality of R ² can be independent from each other.

As the alkoxide represented by formula 1, at least one of a partial hydrolyzate of an alkoxide and a condensate of the hydrolysis of an alkoxide can be used. It is not necessary that all of the alkoxy groups in the partial hydrolyzate of an alkoxide are hydrolyzed. As the condensate of the hydrolysis of an alkoxide, a dimer or higher of a partially hydrolyzed alkoxide, specifically a dimer to hexamer, can be used.

Examples of metal atoms represented by M include silicon, zirconium, titanium, and aluminum. Among these, silicon and titanium are preferred. Alkoxides of a single metal atom or a mixture of two or more different metal atoms may be used.

Examples of the organic group having 1 to 8 carbon atoms represented by ^R1 include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, an n-hexyl group, and an n-octyl group.

Examples of the organic group represented by ^R2 include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, an n-hexyl group, and an n-octyl group.

The composition may contain a silane coupling agent. Examples of the silane coupling agent include organoalkoxysilanes containing organic reactive groups. In particular, organoalkoxysilanes having epoxy groups are preferred. Examples of organoalkoxysilanes having epoxy groups include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. These may be used alone or in combination of two or more.

The composition may further contain, for example, a sol-gel catalyst, an acid, water, and an organic solvent.

2.5. Physical properties of gas barrier film
The oxygen gas permeability of the gas barrier film 7 may be, for example, 5.5 ml/( ^m2 ·day·MPa) or less, 5.0 ml/( ^m2 ·day·MPa) or less, 4.0 ml/( ^m2 ·day·MPa) or less, 3.5 ml/( ^m2 ·day·MPa) or less, or 3.0 ml/( ^m2 ·day·MPa) or less.

The water vapor permeability of the gas barrier film 7 may be, for example, 1.0 g/( ^m2 ·day) or less, 0.9 g/( ^m2 ·day) or less, or 0.8 g/( ^m2 ·day) or less.

The tensile strength of the gas barrier film 7 in at least one direction is preferably 180 MPa or more, more preferably 185 MPa or more, and even more preferably 190 MPa or more. If the tensile strength is 180 MPa or more, the gas barrier film 7 can be used to produce products (e.g., packaging containers) with excellent strength.

Similarly, the tensile strength of the gas barrier film 7 in the MD (i.e., 0° direction), 45° direction, TD (i.e., 90° direction), and 135° direction is preferably 180 MPa or more, more preferably 185 MPa or more, and even more preferably 190 MPa or more.

The tensile strength of the gas barrier film 7 in at least one direction is preferably 350 MPa or less, more preferably 340 MPa or less, and even more preferably 330 MPa or less. If it is 350 MPa or less, the stress (i.e., stretching stress) during stretching in the manufacturing process of the biaxially oriented polyester film 8 can be further prevented from becoming excessively large, and as a result, film breakage that may occur during stretching can be further suppressed or reduced. The tensile strength may be 320 MPa or less.

Similarly, the tensile strength of the gas barrier film 7 in the MD (i.e., 0° direction), 45° direction, TD (i.e., 90° direction), and 135° direction is preferably 350 MPa or less, more preferably 340 MPa or less, and even more preferably 330 MPa or less. The tensile strength may be 320 MPa or less.

The puncture strength of the gas barrier film 7 is preferably 0.50 N/μm or more, more preferably 0.52 N/μm or more, and even more preferably 0.55 N/μm or more. If the puncture strength is 0.50 N/μm or more, the gas barrier film 7 can be used to produce a product (e.g., a packaging container) with excellent strength. For example, the gas barrier film 7 can be used to produce a packaging container that is difficult to puncture.

The heat shrinkage rate of the gas barrier film 7 in the longitudinal direction, i.e., the MD, is preferably 2.0% or less, and more preferably 1.8% or less. If it is 2.0% or less, the frequency of deformation and wrinkles caused by heat can be reduced when the biaxially oriented polyester film 8 is subjected to secondary processing such as deposition processing and printing processing. The heat shrinkage rate in the MD may be, for example, 0.5% or more, or 0.8% or more.

The thermal shrinkage rate of the gas barrier film 7 in the width direction, i.e., TD, is preferably -1.0% or more and 1.0% or less, and more preferably -0.8% or more and 0.8% or less. If it is -1.0% or more and 1.0% or less, the frequency of deformation and wrinkles due to heat can be reduced when secondary processing such as deposition processing and printing processing is performed.

The thickness of the gas barrier film 7 is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 9 μm or more. If it is 5 μm or more, the gas barrier film 7 has excellent rigidity. On the other hand, the thickness of the gas barrier film 7 is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and particularly preferably 25 μm or less. The thinner the thickness, the more cost can be reduced.

<2.6. Uses of gas barrier films>
The gas barrier film 7 can be used for various purposes. For example, it can be suitably used as packaging containers, labels (e.g., labels to be wrapped around the body of a PET bottle), and exterior films for electronic components such as exteriors for lithium ion batteries. Among these, it can be suitably used for packaging containers. It can be particularly suitably used for food packaging containers.

<3. Laminate>
As shown in FIG. 5, in one embodiment, the laminate 9 includes a gas barrier film 7 and a sealant layer 21. The laminate 9 can include a biaxially oriented polyester film 8, a coating layer 32, an inorganic thin film layer 31, a protective layer 33, and a sealant layer 21. In at least a part of the laminate 9, the biaxially oriented polyester film 8, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. Since the laminate 9 includes the sealant layer 21, a product (e.g., a packaging container) including the laminate 9 can be manufactured by heat sealing. Note that, although a structure in which the laminate 9 includes the coating layer 32 and the protective layer 33 is shown here, the laminate 9 does not have to include these (the same applies below).

The sealant layer 21 is a layer that can be softened at a lower temperature than the biaxially oriented polyester film 8. That is, the sealant layer 21 can be melted at a lower temperature than the biaxially oriented polyester film 8. The sealant layer 21 may be formed, for example, of a hot melt adhesive, a film, or other materials. Examples of materials that constitute the sealant layer 21 include thermoplastic resins. Examples of materials that constitute the sealant layer 21 include polyethylene resins such as high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE), polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, and ionomer resins. The sealant layer 21 may contain one of these materials, or may contain two or more of them.

As polyethylene, biomass polyethylene is preferred from the viewpoint of further reducing the environmental load. Biomass polyethylene is polyethylene produced using biomass ethanol as a raw material. In particular, biomass polyethylene produced using fermented ethanol derived from biomass obtained from plant raw materials is preferred. Examples of plant raw materials include corn, sugar cane, beet, and manioc.

The sealant layer 21 may contain additives. Examples of additives include oxygen absorbers, plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, friction reducers, slip agents, release agents, antioxidants, ion exchange agents, antiblocking agents, and colorants.

The thickness of the sealant layer 21 may be, for example, 5 μm or more, or 7 μm or more. The thickness of the sealant layer 21 may be, for example, 50 μm or less, or 30 μm or less. The sealant layer 21 may be a single layer structure, or a two or more layer structure.

As shown in FIG. 6A, the laminate 9 can further include a printed layer 11. The laminate 9 can include the printed layer 11, a gas barrier film 7, and a sealant layer 21. In at least a portion of the laminate 9, the printed layer 11, the gas barrier film 7, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9.

The printing layer 11, i.e., the ink layer 11, can impart a design to the laminate 9. The design may be, for example, a pattern, design, picture, photograph, or figure, or a symbol such as a letter, code, or mark, or any combination of two or more of these. The design may be plain.

The shape of the printed layer 11 when viewed perpendicularly to the laminate 9 can be set as appropriate. When viewed perpendicularly to the laminate 9, the size of the printed layer 11 may be the same as the size of the biaxially oriented polyester film 8, or may be smaller than the size of the biaxially oriented polyester film 8.

The printed layer 11 may contain a resin. Examples of the resin include acrylic resin, urethane resin, polyester resin, vinyl chloride resin, vinyl acetate copolymer resin, and mixtures of two or more of these. The printed layer 11 may contain a colorant. Examples of the colorant include pigments and dyes. The printed layer 11 may contain additives. Examples of the additives include antistatic agents, light blocking agents, ultraviolet absorbing agents, plasticizers, lubricants, fillers, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants.

The printing layer 11 can be formed from ink. In addition to the above-mentioned components, the ink can contain, for example, a solvent. The ink may be ink made from raw materials derived from biomass.

The printing layer 11 can be formed by printing and drying ink. Printing methods include, for example, offset printing, gravure printing, and screen printing. Drying methods after printing include, for example, hot air drying, heated roll drying, and infrared drying.

As shown in FIG. 6B, in at least a portion of the laminate 9, the gas barrier film 7, the printing layer 11, and the sealant layer 21 may be arranged in this order in the thickness direction of the laminate 9.

7A, the laminate 9 may further include a sealant layer 22. For example, the laminate 9 may include a sealant layer 22, a printed layer 11, a gas barrier film 7, and a sealant layer 21. In at least a part of the laminate 9, the sealant layer 22, the printed layer 11, the gas barrier film 7, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. Of course, the laminate 9 having the laminated structure shown in FIG. 5 may further include a sealant layer 22. Of both sides of the laminate 9, it is preferable that one side is composed of the sealant layer 21 and the other side is composed of the sealant layer 22. In other words, it is preferable that one of the pair of outermost layers of the laminate 9 is the sealant layer 21 and the other is the sealant layer 22. The explanation of the sealant layer 22 will be omitted because it overlaps with the explanation of the sealant layer 21. Therefore, the explanation of the sealant layer 21 can also be treated as the explanation of the sealant layer 22.

As shown in FIG. 7B, in at least a portion of the laminate 9, the sealant layer 22, the gas barrier film 7, the printing layer 11, and the sealant layer 21 may be arranged in this order in the thickness direction of the laminate 9.

In the laminate 9, the role of the biaxially oriented polyester film 8 constituting the gas barrier film 7 is not particularly limited. For example, the biaxially oriented polyester film 8 may play a role of holding the above-mentioned layers (e.g., the sealant layer 21, the printed layer 11, and the inorganic thin film layer 31), that is, may play a role as a substrate. On the other hand, the biaxially oriented polyester film 8 may be used not as a substrate but for the purpose of improving some physical property of the laminate 9, such as strength. In other words, the biaxially oriented polyester film 8 used for that purpose plays a role as a support. In other words, the biaxially oriented polyester film 8 may play a role as a support.
When the biaxially oriented polyester film 8 serves as a support, another layer (for example, a resin film or a paper layer) can serve as a substrate.

When the biaxially oriented polyester film 8 serves as a substrate, the laminate 9 may further include a layer that serves as a support (hereinafter referred to as a "support layer"). On the other hand, when the biaxially oriented polyester film 8 serves as a support (i.e., a support layer), the laminate 9 may further include a layer that serves as a substrate (hereinafter referred to as a "substrate layer").

In Figures 5 to 7B, the laminate 9 has been explained with a focus on the gas barrier film 7. From here on, however, the laminate 9 will be explained with a focus on the base layer and support layer rather than the gas barrier film 7. In other words, the laminate 9 will be explained from a different perspective. Therefore, the explanation from here on may overlap with the explanation so far.

As shown in FIG. 8, in one embodiment, the laminate 9 includes a base layer 51, an inorganic thin film layer 31, and a sealant layer 21. In at least a portion of the laminate 9, the base layer 51, the inorganic thin film layer 31, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. Because the laminate 9 includes the sealant layer 21, a product (e.g., a packaging container) including the laminate 9 can be manufactured by heat sealing.

As shown in FIG. 9, the laminate 9 may further include a coating layer 32. Specifically, the laminate 9 may include the coating layer 32 between the substrate layer 51 and the inorganic thin film layer 31. The adhesion between the substrate layer 51 and the coating layer 32 and the adhesion between the coating layer 32 and the inorganic thin film layer 31 can be adjusted by the coating layer 32. In at least a part of the laminate 9, the substrate layer 51, the coating layer 32, the inorganic thin film layer 31, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. The coating layer 32 can connect the substrate layer 51 and the inorganic thin film layer 31.

As shown in FIG. 10, the laminate 9 may further include a protective layer 33 provided on the inorganic thin film layer 31. That is, the laminate 9 may further include a protective layer 33 adjacent to the inorganic thin film layer 31. For example, the laminate 9 may include a base layer 51, a coating layer 32, an inorganic thin film layer 31, a protective layer 33, and a sealant layer 21. In at least a portion of the laminate 9, the base layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. The protective layer 33 can further suppress or reduce the permeation of oxygen gas and water vapor.

A biaxially oriented polyester film 8 is used as the base layer 51. That is, the base layer 51 is a biaxially oriented polyester film 8. On the other hand, the base layer 51 may be a single layer structure or a structure of two or more layers. For example, the base layer 51 may be a laminate structure of the biaxially oriented polyester film 8 and a resin film (for example, a biaxially oriented nylon film).

As shown in FIG. 11A, the laminate 9 can further include a printed layer 11. The laminate 9 can include the printed layer 11, a substrate layer 51, a coating layer 32, an inorganic thin film layer 31, a protective layer 33, and a sealant layer 21. In at least a portion of the laminate 9, the printed layer 11, the substrate layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9.

As shown in FIG. 11B, in at least a portion of the laminate 9, the base layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, the printing layer 11, and the sealant layer 21 may be arranged in this order in the thickness direction of the laminate 9.

As shown in FIG. 12A, the laminate 9 may further include a sealant layer 22. For example, the laminate 9 may include the sealant layer 22, the print layer 11, the substrate layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, and the sealant layer 21. In at least a part of the laminate 9, the sealant layer 22, the print layer 11, the substrate layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9. Of course, the laminate 9 having the laminated structure shown in FIG. 8 to FIG. 10 may further include a sealant layer 22. Of both sides of the laminate 9, it is preferable that one side is composed of the sealant layer 21 and the other side is composed of the sealant layer 22. In other words, it is preferable that one of the pair of outermost layers of the laminate 9 is the sealant layer 21 and the other is the sealant layer 22.

As shown in FIG. 12B, in at least a portion of the laminate 9, the sealant layer 22, the base layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, the printing layer 11, and the sealant layer 21 may be arranged in this order in the thickness direction of the laminate 9.

As shown in FIG. 13, the laminate 9 can further include an intermediate layer 61. For example, the laminate 9 can include a base layer 51, a coating layer 32, an inorganic thin film layer 31, a protective layer 33, an intermediate layer 61, and a sealant layer 21. In at least a portion of the laminate 9, the base layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, the intermediate layer 61, and the sealant layer 21 can be arranged in this order in the thickness direction of the laminate 9.

The intermediate layer 61 may include a support layer, a gas barrier layer, a metal foil, or two or more of these. Of course, it may also include other layers, such as an adhesive layer, an adhesive resin layer, or an anchor coat layer. The intermediate layer 61 may also include a printing layer 11. When the intermediate layer 61 includes a support layer, some physical property of the laminate 9, such as strength, can be improved. When the intermediate layer 61 includes a gas barrier layer or metal foil, the gas barrier properties of the laminate 9 can be improved.

Examples of the support layer include a resin film and a paper layer. Examples of the resin film include a film containing one or more of the following resin materials: polyester, (meth)acrylic resin, polyolefin (e.g., polyethylene, polypropylene, polymethylpentene), vinyl resin, cellulose resin, ionomer resin, polyamide (nylon 6, nylon 6,6, polymetaxylylene adipamide (MXD6)). Of these, polyester is preferred. In other words, it is preferable that the resin film contains polyester. The resin film may be a stretched resin film or an unstretched resin film. The stretched resin film may be a uniaxially stretched resin film or a biaxially stretched resin film. Of these, a biaxially stretched resin film is preferred because of its excellent dimensional stability.

The paper layer may be, for example, fine paper, art paper, coated paper, resin-coated paper, cast-coated paper, paperboard, synthetic paper, impregnated paper, etc. The thickness of the paper layer is preferably, for example, 30 g/ ^m2 or more and 400 g/ ^m2 or less.

The paper layer and/or resin film can be laminated to the biaxially oriented polyester film 8 via other layers (e.g., an adhesive layer, an adhesive resin layer, an anchor coat layer).

The adhesive layer can be formed of an adhesive, i.e., a laminating adhesive. For example, the laminating adhesive can be formed by applying the laminating adhesive to the biaxially oriented polyester film 8 and/or the paper layer and drying it. The laminating adhesive may be a one-component curing type or a two-component curing type. The laminating adhesive may be a solvent-based, water-based, or emulsion-based adhesive. Examples of laminating adhesives include vinyl-based adhesives, (meth)acrylic-based adhesives, polyamide-based adhesives, polyester-based adhesives, polyether-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, and rubber-based adhesives. These may be used alone or in combination of two or more.

The thickness of the adhesive layer may be, for example, 0.1 μm or more, or 1 μm or more. The thickness of the adhesive layer may be, for example, 10 μm or less, or 5 μm or less.

The adhesive resin layer contains a thermoplastic resin. Examples of the thermoplastic resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-maleic acid copolymer, and ionomer resin. In addition, examples of the thermoplastic resin include resins in which at least one of unsaturated carboxylic acids, unsaturated carboxylic acids, unsaturated carboxylic anhydrides, and ester monomers is graft-polymerized and/or copolymerized with a polyolefin resin. Examples of the resins include resins in which maleic anhydride is graft-modified with a polyolefin resin. These may be used alone or in combination of two or more.

The thickness of the adhesive resin layer may be, for example, 0.1 μm or more, 1 μm or more, 5 μm or more, or 10 μm or more. The thickness of the adhesive resin layer may be, for example, 100 μm or less, 50 μm or less, 10 μm or less, or 5 μm or less.

The anchor coat layer can be formed from a composition containing a resin and a curing agent. Examples of the resin include urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins. Among these, urethane-based, polyester-based, and acrylic-based resins are preferred. From the viewpoint of adhesion, urethane resins are preferred. On the other hand, from the viewpoint of water resistance, acrylic resins are preferred. These may be used alone or in combination of two or more. Examples of the curing agent include epoxy-based, isocyanate-based, and melamine-based curing agents. These may be used alone or in combination of two or more.

The composition for forming the anchor coat layer preferably contains a silane coupling agent. The silane coupling agent preferably has one or more organic functional groups in the molecule. When the silane coupling agent has multiple organic functional groups (i.e., one or more) in the molecule, the multiple organic functional groups may be the same or different. In other words, the multiple organic functional groups can be independent of each other. Examples of organic functional groups include an alkoxy group, an amino group, an epoxy group, and an isocyanate group.

The composition for forming the anchor coat layer may contain a solvent. Examples of the solvent include aromatic solvents such as benzene and toluene, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, and polyhydric alcohol derivatives such as ethylene glycol monomethyl ether.

The anchor coat layer can be formed by applying a composition for forming the anchor coat layer to the biaxially oriented polyester film 8 and drying it.

The thickness of the anchor coat layer may be, for example, 0.1 μm or more, or 0.2 μm or more. The thickness of the anchor coat layer may be, for example, 2 μm or less, or 1 μm or less.

The support layer may contain additives. Examples of additives include oxygen absorbers, plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, friction reducers, slip agents, release agents, antioxidants, ion exchange agents, antiblocking agents, and colorants.

A biaxially oriented polyester film 8 may be used as the support layer. That is, the support layer may be a biaxially oriented polyester film 8.

When a biaxially oriented polyester film 8 is used as the support layer, the biaxially oriented polyester film 8 may be used as the base layer 51, or a resin film may be used, or a paper layer may be used. In this way, when a biaxially oriented polyester film 8 is used as the support layer, it is not necessary to use a biaxially oriented polyester film 8 as the base layer 51.

When the biaxially oriented polyester film 8 is used as the support layer, the base layer 51 may be, for example, a biaxially oriented polyester film 8, a resin film other than the biaxially oriented polyester film 8, or a paper layer. Examples of the resin film include films containing one or more of the following resin materials: polyester, (meth)acrylic resin, polyolefin (e.g., polyethylene, polypropylene, polymethylpentene), vinyl resin, cellulose resin, ionomer resin, polyamide (nylon 6, nylon 6,6, polymetaxylylene adipamide (MXD6)). Polyester is preferred among them. In other words, it is preferable that the resin film contains polyester. The resin film may be a stretched resin film or an unstretched resin film. The stretched resin film may be a uniaxially stretched resin film or a biaxially stretched resin film. Among them, a biaxially stretched resin film is preferred because of its excellent dimensional stability.

The intermediate layer 61 may include a coating layer 32 on at least one surface of the support layer, or may include an inorganic thin film layer 31. The intermediate layer 61 may include a protective layer 33 (not shown).

The gas barrier layer contains a gas barrier resin. Examples of gas barrier resins include ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol, polyacrylonitrile, polyamide (e.g., nylon 6, nylon 6,6, polymetaxylylene adipamide (MXD6)), polyester, polyurethane, and (meth)acrylic resin. The gas barrier layer may contain two or more types of gas barrier resins. The gas barrier layer may further contain other resins and may further contain additives.

The thickness of the gas barrier layer may be, for example, 3 μm or more, 5 μm or more, or 7 μm or more. The thickness of the gas barrier layer may be, for example, 30 μm or less, or 20 μm or less.

Examples of metal foils include aluminum foil and magnesium foil. Of these, aluminum foil is preferred. Of these, aluminum foil containing iron is preferred from the viewpoint of pinhole resistance and ductility. The iron content is preferably 0.1 mass% or more, and more preferably 0.5 mass% or more, based on 100 mass% of the aluminum foil. On the other hand, the iron content is preferably 9.0 mass% or less, and more preferably 2.0 mass% or more.

The metal foil may be pretreated. Examples of pretreatment include degreasing, acid washing, and alkaline washing.

The thickness of the metal foil may be, for example, 3 μm or more, or 6 μm or more. The thickness of the metal foil may be, for example, 100 μm or less, or 25 μm or less.

As shown in FIG. 14, the laminate 9 may include a printed layer 11, a base layer 51, a coating layer 32, an inorganic thin film layer 31, a protective layer 33, an intermediate layer 61, and a sealant layer 21. In at least a portion of the laminate 9, the printed layer 11, the base layer 51, the coating layer 32, the inorganic thin film layer 31, the protective layer 33, the intermediate layer 61, and the sealant layer 21 may be arranged in this order in the thickness direction of the laminate 9.

Of course, the position of the printed layer 11 can be changed as appropriate. For example, in the laminate 9 having the laminate configuration shown in FIG. 13, the intermediate layer 61 may include the printed layer 11.

The laminate 9 having the laminated structure shown in FIG. 13 or FIG. 14 may further include a sealant layer 22 (not shown). Of both sides of the laminate 9, it is preferable that one side is constituted by the sealant layer 21 and the other side is constituted by the sealant layer 22. In other words, it is preferable that, of the pair of outermost layers of the laminate 9, one outermost layer is the sealant layer 21 and the other outermost layer is the sealant layer 22.

So far, the laminate 9 has been described as including the sealant layer 21 and, if necessary, the sealant layer 22, but of course, the present invention is not limited to this. The laminate 9 may include an adhesive layer in place of at least one of the sealant layer 21 and the sealant layer 22. The adhesive layer may be formed of an adhesive. Examples of adhesives include synthetic rubbers such as styrene butadiene rubber, acrylonitrile-butadiene rubber, and polyisobutylene rubber, as well as natural rubber, acrylic resins, silicone resins, and polypropylene. These may be used alone or in combination of two or more types.

In this way, the laminate 9 is
The film includes a base layer 51, an inorganic thin film layer 31, and a sealant layer 21 or an adhesive layer,
It can be said that at least the base layer 51 and the inorganic thin film layer 31 are composed of the gas barrier film 7 .
It is preferable that the laminate 9 further includes a coating layer 32. At least the base layer 51, the coating layer 32 and the inorganic thin film layer 31 may be composed of a gas barrier film 7.
It is preferable that the laminate 9 further includes a protective layer 33. At least the base layer 51, the inorganic thin film layer 31 and the protective layer 33 may be composed of the gas barrier film 7.
It is preferable that the laminate 9 further includes a coating layer 32 and a protective layer 33. At least the base layer 51, the coating layer 32, the inorganic thin film layer 31 and the protective layer 33 may be composed of the gas barrier film 7.

On the other hand, the laminate 9 is
The film includes a base layer 51, an inorganic thin film layer 31, an intermediate layer 61, and a sealant layer 21 or an adhesive layer,
It can also be said that the intermediate layer 61 includes the gas barrier film 7 .

The laminate 9 has been described above with reference to Fig. 5 to Fig. 14. More specific examples will now be given.
First, the meanings of the abbreviations are as follows:
CRF Biaxially oriented polyester film 8
PET Polyethylene terephthalate ONY Oriented nylon OPP Oriented polypropylene CPP Unoriented polypropylene PE Polyethylene PEF Polyethylene film Al Aluminum MO Metal oxide MOR Metal alkoxide

A specific example will be given below. In this example, the base layer 51 is a biaxially oriented polyester film 8.
(1) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / heat seal layer (PEF)
(2) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / heat seal layer (PE)
(3) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / anchor coat layer / heat seal layer (PE)
(4) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / anchor coat layer / adhesive resin layer (PE) / heat seal layer (PEF)
(5) Base layer (CRF) / inorganic thin film layer (Al) / adhesive layer (6) Base layer (CRF) / inorganic thin film layer (Al) / anchor coat layer / heat seal layer (PE)
(7) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / heat seal layer (PEF)
(8) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / heat seal layer (PE)
(9) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / anchor coat layer / heat seal layer (PE)
(10) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / anchor coat layer / adhesive resin layer (PE) / heat seal layer (PEF)
(11) Printing layer/base layer (CRF)/inorganic thin film layer (Al)/adhesive layer (12) Printing layer/base layer (CRF)/inorganic thin film layer (Al)/heat seal layer (PE)
(13) Printing layer/substrate layer (CRF)/inorganic thin film layer (Al)/anchor coat layer/heat seal layer (PE)

Further specific examples are given below. In the examples given here, the base layer 51 is also a biaxially oriented polyester film 8.
(1) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / support layer (ONY) / adhesive layer / heat seal layer (PEF)
(2) Base layer (CRF)/inorganic thin film layer (MO)/protective layer (MOR)/adhesive layer/protective layer (MOR)/inorganic thin film layer (MO)/support layer (PET)/adhesive layer/heat seal layer (CPP)
(3) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / inorganic thin film layer (Al) / support layer (PET) / adhesive layer / heat seal layer (CPP)
(4) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / support layer (ONY) / adhesive layer / heat seal layer (CPP)
(5) Heat seal layer (PEF) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / substrate layer (CRF) / adhesive layer / heat seal layer (PEF)
(6) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / support layer (PET) / adhesive layer / heat seal layer (PEF) / hot melt layer (hot melt adhesive)
(7) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / support layer (ONY) / heat seal layer (PE)
(8) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / support layer (ONY) / anchor coat layer / heat seal layer (PE)
(9) Heat seal layer (PEF) / adhesive layer / substrate layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / heat seal layer (PEF)
(10) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / support layer (ONY) / adhesive layer / heat seal layer (PEF)
(11) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (PET) / adhesive layer / heat seal layer (CPP)
(12) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / inorganic thin film layer (Al) / support layer (PET) / adhesive layer / heat seal layer (CPP)
(13) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / support layer (ONY) / adhesive layer / heat seal layer (CPP)
(14) Base material layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / support layer (PET) / adhesive layer / heat seal layer (PEF) / hot melt layer (hot melt adhesive)
(15) Heat seal layer (PEF) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / substrate layer (CRF) / printing layer / adhesive layer / heat seal layer (PEF)
(16) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / support layer (ONY) / heat seal layer (PE)
(17) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / support layer (ONY) / anchor coat layer / heat seal layer (PE)
(18) Heat seal layer (PEF) / adhesive layer / substrate layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / heat seal layer (PEF)

Further specific examples are given below. In the examples given here, the support layer is a biaxially oriented polyester film 8.
(1) Base layer (PET)/adhesive layer/inorganic thin film layer (Al)/support layer (CRF)/adhesive layer/heat seal layer (PEF)
(2) Base material layer (ONY)/anchor coat layer/adhesive resin layer (PE)/inorganic thin film layer (Al)/support layer (CRF)/anchor coat layer/adhesive resin layer (PE)/heat seal layer (PEF)
(3) Base material layer (paper)/adhesive layer/protective layer (MOR)/inorganic thin film layer (MO)/support layer (CRF)/adhesive layer/heat seal layer (CPP)
(4) Base layer (OPP)/adhesive layer/protective layer (MOR)/inorganic thin film layer (MO)/support layer (CRF)/adhesive layer/heat seal layer (CPP)
(5) Base layer (PET) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(6) Base layer (ONY)/adhesive layer/protective layer (MOR)/inorganic thin film layer (MO)/support layer (CRF)/adhesive layer/heat seal layer (CPP)
(7) Base layer (PET) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF) / hot melt layer (hot melt adhesive)
(8) Base layer (OPP) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(9) Base layer (PET) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (CPP)
(10) Base material layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / heat seal layer (PE)
(11) Base material layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(12) Base layer (OPP)/adhesive layer/protective layer (MOR)/inorganic thin film layer (MO)/support layer (CRF)/adhesive layer/heat seal layer (OPP)
(13) Base layer (PET) / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / heat seal layer (PE)
(14) Base layer (PET) / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(15) Base layer (PET) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / heat seal layer (PE)
(16) Base layer (PET) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(17) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / heat seal layer (PEF)
(18) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(19) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(20) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / support layer (PEF) / adhesive layer / support layer (CRF) / inorganic thin film layer (Al) / adhesive layer / heat seal layer (PEF)
(21) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / support layer (PEF) / adhesive layer / support layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / heat seal layer (PEF)
(22) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / support layer (PEF) / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(23) Heat seal layer (PEF) / adhesive layer / base layer (PET) / adhesive layer / support layer (PEF) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(24) Heat seal layer (PE) / base layer (paper) / adhesive resin layer (PE) / inorganic thin film layer (Al) / support layer (CRF) / heat seal layer (PE)
(25) Heat seal layer (PE) / base layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / heat seal layer (PE)
(26) Heat seal layer (PE) / base layer (paper) / adhesive resin layer (PE) / inorganic thin film layer (Al) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(27) Heat seal layer (PE) / base layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(28) Base layer (PET) / printing layer / adhesive layer / inorganic thin film layer (Al) / base layer (CRF) / adhesive layer / heat seal layer (PEF)
(29) Base material layer (ONY) / printing layer / anchor coat layer / adhesive resin layer (PE) / inorganic thin film layer (Al) / support layer (CRF) / anchor coat layer / adhesive resin layer (PE) / heat seal layer (PEF)
(30) Printing layer / substrate layer (paper) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (CPP)
(31) Base layer (OPP) / Printing layer / Adhesive layer / Protective layer (MOR) / Inorganic thin film layer (MO) / Support layer (CRF) / Adhesive layer / Heat seal layer (CPP)
(32) Base layer (PET) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(33) Base material layer (ONY) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (CPP)
(34) Base material layer (PET) / Printing layer / Adhesive layer / Protective layer (MOR) / Inorganic thin film layer (MO) / Support layer (CRF) / Adhesive layer / Heat seal layer (PE) / Hot melt layer (Hot melt adhesive)
(35) Base material layer (OPP) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(36) Base layer (PET) / Printing layer / Adhesive layer / Protective layer (MOR) / Inorganic thin film layer (MO) / Support layer (CRF) / Adhesive layer / Heat seal layer (CPP)
(37) Printing layer / substrate layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / heat seal layer (PE)
(38) Printing layer / substrate layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(39) Base layer (OPP) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (OPP)
(40) Base material layer (PET) / printing layer / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / heat seal layer (PE)
(41) Base material layer (PET) / printing layer / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(42) Base layer (PET) / Printing layer / Adhesive layer / Protective layer (MOR) / Inorganic thin film layer (MO) / Support layer (CRF) / Heat seal layer (PE)
(43) Base layer (PET) / Printing layer / Adhesive layer / Protective layer (MOR) / Inorganic thin film layer (MO) / Support layer (CRF) / Anchor coat layer / Heat seal layer (PE)
(44) Base layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / printing layer / adhesive layer / heat seal layer (PEF)
(45) Heat seal layer (PEF) / adhesive layer / substrate layer (PET) / printing layer / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(46) Heat seal layer (PEF) / adhesive layer / base layer (PET) / printing layer / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(47) Heat seal layer (PEF) / adhesive layer / substrate layer (PET) / printing layer / adhesive layer / support layer (PEF) / adhesive layer / support layer (CRF) / inorganic thin film layer (Al) / adhesive layer / heat seal layer (PEF)
(48) Heat seal layer (PEF) / adhesive layer / substrate layer (PET) / printing layer / adhesive layer / support layer (PEF) / adhesive layer / support layer (CRF) / inorganic thin film layer (MO) / protective layer (MOR) / adhesive layer / heat seal layer (PEF)
(49) Heat seal layer (PEF) / adhesive layer / substrate layer (PET) / printing layer / adhesive layer / support layer (PEF) / adhesive layer / inorganic thin film layer (Al) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(50) Heat seal layer (PEF) / adhesive layer / substrate layer (PET) / printing layer / adhesive layer / support layer (PEF) / adhesive layer / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(51) Heat seal layer (PE) / printing layer / base layer (paper) / adhesive resin layer (PE) / inorganic thin film layer (Al) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(52) Heat seal layer (PE) / printing layer / base layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / adhesive layer / heat seal layer (PEF)
(53) Heat seal layer (PE) / printing layer / base layer (paper) / adhesive resin layer (PE) / inorganic thin film layer (Al) / support layer (CRF) / anchor coat layer / heat seal layer (PE)
(54) Heat seal layer (PE) / printing layer / base layer (paper) / adhesive resin layer (PE) / protective layer (MOR) / inorganic thin film layer (MO) / support layer (CRF) / anchor coat layer / heat seal layer (PE)

In the above-mentioned specific examples, there are some laminates 9 in which the substrate layer 51 and the inorganic thin film layer 31 are adjacent to each other. In these laminates 9, a coating layer 32 may be provided between the substrate layer 51 and the inorganic thin film layer 31.

In the above-mentioned specific examples, there are some laminates 9 in which the support layer and the inorganic thin film layer 31 are adjacent to each other. In these laminates 9, a coating layer 32 may be provided between the support layer and the inorganic thin film layer 31.

The specific examples described above include some laminates 9 that include a protective layer 33 formed from a composition that includes MOR, i.e., a metal alkoxide. In these laminates 9, the protective layer 33 may be formed from a composition that includes a resin and a hardener.

Among the specific examples described above, there are some laminates 9 that include both a base layer 51 and a support layer. In these examples, both the base layer 51 and the support layer may be biaxially oriented polyester films 8.

The oxygen gas permeability of the laminate 9 may be, for example, 5.5 ml/( ^m2 ·day·MPa) or less, 5.0 ml/( ^m2 ·day·MPa) or less, 4.0 ml/( ^m2 ·day·MPa) or less, 3.5 ml/( ^m2 ·day·MPa) or less, or 3.0 ml/( ^m2 ·day·MPa) or less.

The water vapor permeability of the laminate 9 may be, for example, 1.0 g/(m ² ·day) or less, 0.9 g/(m ² ·day) or less, or 0.8 g/(m ² ·day) or less.

The laminate strength of the laminate 9 is preferably 3.0 N/15 mm or more, more preferably 3.5 N/15 mm or more, and even more preferably 4.0 N/15 mm or more. If it is 3.0 N/15 mm or more, when a sealant layer is provided on the gas barrier film 7, a product (such as a packaging container) that is difficult to peel between them can be produced. Here, the laminate strength of the laminate 9 is the peel strength measured by the method described below in "Laminate strength - gas barrier film" (see Examples).

The laminate 9 can be used for a variety of purposes. For example, it can be used as packaging containers, labels (e.g., labels to be wrapped around the body of PET bottles), and exterior films for electronic components, including the exterior of lithium-ion batteries. It is particularly suitable for use as packaging containers. It is particularly suitable for use as food packaging containers.

<4. Packaging Containers>
The packaging container of this embodiment includes a laminate 9. That is, the packaging container of this embodiment can be produced using the laminate 9. Here, "the packaging container includes the laminate 9" means that when the packaging container is composed of a plurality of members, at least one member includes the laminate 9. Examples of the packaging container include packaging bags (i.e., pouches), lids, laminated tubes, paper containers, and paper cups (see, for example, Japanese Patent No. 6984717). The packaging container may be a food packaging container or a non-food packaging container. That is, the contents may be food or non-food. In particular, the packaging container is preferably a food packaging container.

Examples of packaging bags include standing pouches, pillow bags (i.e., hem-sealed bags), two-sided sealed bags, three-sided sealed bags, four-sided sealed bags, side-sealed bags, envelope-sealed bags, pleated sealed bags, flat-bottom sealed bags, square-bottom sealed bags, and bags with gussets.

5. Various modifications can be made to the above-described embodiment.
The above-described embodiment may be modified in various ways. For example, the above-described embodiment may be modified by selecting one or more of the following modifications.

In the above-described embodiment, the biaxially oriented polyester film 8 has a single layer structure, and the biaxially oriented polyester film 8 has a three-layer structure composed of a first layer 81, a second layer 82, and a third layer 83. However, the above-described embodiment is not limited to this structure. The biaxially oriented polyester film 8 may have a two-layer structure composed of a first layer 81 and a second layer 82. Of course, the biaxially oriented polyester film 8 may have a structure of four or more layers.

The present invention will be explained in more detail below with reference to examples and comparative examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." Note that polyesters A to G, which will be described later, may be collectively referred to as raw polyesters.

<Methods for measuring each physical property>
(Intrinsic Viscosity)
0.2 g of the sample (specifically, raw polyester and biaxially oriented polyester film) was dissolved in 50 ml of a mixed solvent of phenol/1,1,2,2-tetrachloroethane (60/40 (mass ratio)), and the intrinsic viscosity (IV) was measured using an Ostwald viscometer at 30° C. The unit of intrinsic viscosity is dl/g.

(Content of terephthalic acid component and isophthalic acid component)
A sample (specifically, raw polyester and biaxially oriented polyester film) was dissolved in a solvent in which chloroform D (manufactured by Eurisopp) and trifluoroacetic acid-D1 (manufactured by Eurisopp) were mixed at a volume ratio of 10:1. For this sample solution, proton NMR was measured using a nuclear magnetic resonance (NMR) spectrometer ("GEMINI-200" manufactured by Varian) under measurement conditions of a temperature of 23°C and an accumulation number of 64. In this NMR measurement, the peak intensity of a predetermined proton was calculated, and then the content (mol %) of the terephthalic acid component and the isophthalic acid component in 100 mol % of the acid component was calculated.

(Quantitative analysis of magnesium)
The samples (specifically, the raw polyester and the biaxially oriented polyester film) were decomposed by incineration in a platinum crucible, and then 6 mol/L hydrochloric acid was added and evaporated to dryness. The samples were dissolved in 1.2 mol/L hydrochloric acid, and the magnesium content was quantified using an inductively coupled plasma (ICP) emission spectrometer (Shimadzu Corporation, "ICPS-2000").

(Quantitative analysis of phosphorus)
The samples (specifically, raw polyester and biaxially oriented polyester film) were decomposed by dry incineration in the presence of sodium carbonate, or by wet decomposition in either a sulfuric acid/nitric acid/perchloric acid system or a sulfuric acid/hydrogen peroxide system to convert phosphorus to orthophosphoric acid. Next, molybdate was reacted in a 1 mol/L sulfuric acid solution to convert it to phosphomolybdic acid, which was then reduced with hydrazine sulfate to produce heteropoly blue, whose absorbance at 830 nm was measured with an absorptiometer (Shimadzu Corporation, "UV-150-02") (i.e., colorimetric determination was performed).

(Melting Resistivity)
The samples (specifically, the raw polyester and the biaxially oriented polyester film) were melted at 285° C., and then a pair of electrode plates was inserted therein and a voltage of 120 V was applied. The current at that time was measured, and the melt resistivity Si (Ω cm) was calculated based on the following formula.
Si = (A/I) x (V/io)
Here, A is the area of the electrodes (cm ² ), I is the distance between the electrodes (cm), V is the voltage (V), and io is the current (A).

(Area ratio of region with molecular weight of 1000 or less)
10 g of sample (specifically, raw polyester and biaxially oriented polyester film) was weighed in a 30 mL vial. A mixture of chloroform/HFIP=98/2 (volume ratio) was added to the vial and left to stand for 12 hours to dissolve the sample. The sample was then diluted with chloroform/hexafluoroisopropanol (HFIP)=98/2 (volume ratio) to prepare a 0.1% solution. The 0.1% solution was filtered with a 0.45 μm filter (GL Chromatodisc Non-aqueous N Type 13N, manufactured by GL Sciences). The filtrate was subjected to gel permeation chromatography (GPC) measurement under the following conditions.
Columns used: TSKgel Super HM-H × 2 and TSKgel Super H2000, manufactured by Tosoh Corporation
Column temperature: 40°C
Mobile phase: chloroform/HFIP=98/2 (volume ratio)
Flow rate: 0.6 mL / min
Injection volume: 20 μL
Detection: 254 nm (UV-Vis detector)
Molecular weight calibration: monodisperse polystyrene (manufactured by Tosoh Corporation)
Apparatus: Tosoh Corporation HLC-8300GPC
In the molecular weight distribution curve obtained by GPC measurement, the area ratio of the region having a molecular weight of 1000 or less was determined.
In general, in GPC analysis, the area outside the calibration curve is generally excluded from the calculation range of the GPC analysis. However, in this analysis, in order to more accurately determine the area proportion of the region with a molecular weight of 1000 or less, the GPC chromatogram area (i.e., the total peak area) was calculated including not only the area within the calibration curve but also the area outside the calibration curve.

(Thickness)
The thickness of the biaxially oriented polyester film was measured using a dial gauge in accordance with JIS K7130-1999 Method A.

(Melting Point)
A 5 mg sample (specifically, a biaxially oriented polyester film) was heated from 25° C. to 320° C. at a rate of 10° C./min using a differential scanning calorimeter (Shimadzu Corporation, “DSC60”), and the main peak top temperature of the endothermic curve accompanying melting was determined as the melting point.

(Tensile strength)
A test piece having a width of 15 mm and a length of 100 mm was cut out from the biaxially oriented polyester film. In accordance with JIS K 7127, the test piece was pulled using a tensile tester (Shimadzu Corporation's "Autograph AG-I") with a gauge length of 50 mm and a pulling speed of 200 mm/min. The tensile strength of the test piece, i.e., the tensile breaking strength, was calculated from the stress/strain curve obtained in this way. Using this procedure, the tensile strengths in the MD (i.e., 0° direction), 45° direction, TD (i.e., 90° direction), and 135° directions were obtained.

(Thermal shrinkage rate)
A test piece with a width of 10 mm and a length of 250 mm was cut out from the biaxially oriented polyester film. A pair of marks (i.e., a pair of benchmark lines) was made at 200 mm intervals along the length of the test piece, and the benchmark distance was measured under a tension of 5 gf. The test piece was heat-treated at 150°C for 30 minutes under no load, and the benchmark distance was then measured. From these measurement results, the thermal shrinkage was calculated using the following formula.
Heat shrinkage rate (%) = {(A - B) / A} x 100
Here, A is the gauge length before heat treatment, and B is the gauge length before heat treatment.
Using this procedure, the heat shrinkage rates in the MD and TD were determined.

(Color b ^* value)
Ten biaxially oriented polyester films were stacked and set in a colorimeter (ZE2000, manufactured by Nippon Denshoku Industries Co., Ltd.) to determine the color b ^* value using the reflection method. The color b ^* value per 1 μm of thickness was calculated using the following formula.
Color b ^* value per 1 μm thickness=(Color b ^* value when 10 biaxially oriented polyester films are stacked)/(10×thickness of biaxially oriented polyester film)

(Surface Crystallinity)
FT-IR ATR measurements were carried out on both the corona-treated and non-treated sides of the biaxially oriented polyester film under the following conditions: Spectra were obtained by attenuated total reflection using a Fourier transform infrared spectrophotometer.
FT-IR: BioRad DIGILAB FTS-60A/896
Single reflection ATR attachment: golden gate MKII (SPECAC)
Internal reflection element: Diamond Incident angle: 45°
Resolution: 4 ^cm
Number of times of accumulation: 128. The degree of surface crystallinity was calculated from the intensity ratio between the absorption appearing near 1340 cm ^-1 and the absorption appearing near 1410 cm ^-1 (intensity at 1340 cm ^-1 /intensity at 1410 cm ^-1 ). The absorption appearing near 1340 cm ^-1 is due to the bending vibration of CH ₂ (trans structure) of ethylene glycol. On the other hand, the absorption appearing near 1410 cm ^-1 is an absorption unrelated to crystals or orientation.

(Puncture Strength)
The puncture strength of a 5 cm square test piece cut out from the biaxially oriented polyester film was measured in accordance with JIS Z1707 using a digital force gauge ("ZTS-500N" manufactured by Imada Co., Ltd.), an electric measuring stand ("MX2-500N" manufactured by Imada Co., Ltd.), and a film puncture test jig ("TKS-250N" manufactured by Imada Co., Ltd.). Based on the puncture strength determined by this measurement (i.e., the puncture strength of the biaxially oriented polyester film), the puncture strength per 1 μm of thickness was also calculated.

(Laminate strength - biaxially oriented polyester film)
A urethane-based two-component curing adhesive (specifically, an adhesive obtained by mixing Mitsui Chemicals'"Takelac (registered trademark) A525S" and Mitsui Chemicals'"Takenate (registered trademark) A50" at a ratio of 13.5:1 (by mass)) was used to dry laminate the corona-treated surface of the biaxially oriented polyester film to a 70 μm-thick non-oriented polypropylene film (Toyobo's "P1147") as a polyolefin sealant layer, and the laminate was then aged at 40° C. for 4 days to produce a laminate. A test piece 15 mm wide and 200 mm long was cut out from the laminate to measure the peel strength (N/15 mm) of the bonding surface between the corona-treated surface of the biaxially oriented polyester film and the polyolefin resin layer. The peel strength was measured under conditions of a temperature of 23° C. and a relative humidity of 65%, using a Tensilon UMT-II-500 model manufactured by Toyo Baldwin Co., Ltd., at a tensile speed of 20 cm/min and a peel angle of 180°.

(Maximum Casting Speed)
The unstretched films produced while changing the rotation speed of the cooling drum stepwise were visually inspected for the presence or absence of pinner bubbles using a polarizing plate (manufactured by Nishida Kogyo Co., Ltd.) From this, the maximum casting speed was determined from the maximum rotation speed at which no pinner bubbles were generated.

(Film-forming ability)
The film formability of the biaxially oriented polyester film was evaluated according to the following criteria.
◯: No breakage occurred for 60 minutes or more, i.e., continuous film formation for 60 minutes or more was possible.
Δ: Break occurred at least once within 30 minutes or more and less than 60 minutes.
x: Break occurred at least once within 30 minutes.

(Lamination strength - gas barrier film)
A laminate was produced by the following procedure (hereinafter referred to as "Procedure A"): a urethane-based two-component curing adhesive (specifically, an adhesive obtained by mixing "Takelac (registered trademark) A525S" manufactured by Mitsui Chemicals, Inc. and "Takenate (registered trademark) A50" manufactured by Mitsui Chemicals, Inc. at a ratio of 13.5:1 (by mass)) was used to bond a 70 μm-thick non-oriented polypropylene film ("P1147" manufactured by Toyobo Co., Ltd.) as a polyolefin sealant layer to the inorganic thin film layer or protective layer of the gas barrier film, and then aging was performed at 40° C. for 4 days. The peel strength (N/15 mm) of the bonding surface between the gas barrier film and the polyolefin sealant layer was measured for a test piece having a width of 15 mm and a length of 200 mm cut from the laminate. The peel strength was measured at a temperature of 23° C. and a relative humidity of 65% using a Tensilon UMT-II-500 model manufactured by Toyo Baldwin Co., Ltd., at a tensile speed of 20 cm/min and a peel angle of 180°.

(Laminate strength after retort treatment)
The laminate produced by procedure A was kept in hot water at 130° C. for 30 minutes, and then dried for one day (specifically, 24 hours) at 40° C. A test piece 15 mm wide and 200 mm long was cut out from this laminate, and the peel strength (N/15 mm) of the bonding surface between the gas barrier film and the polyolefin sealant layer was measured by the method described above.

(Oxygen gas permeability)
For the laminate produced by procedure A, oxygen gas permeability was measured under normal conditions in an atmosphere of 23° C. and 65% relative humidity using an oxygen permeability measuring device ("OX-TRAN 2/20" manufactured by MOCON) in accordance with the electrolytic sensor method (Appendix A) of JIS-K7126-2. The oxygen gas permeability was measured in the direction in which oxygen gas permeated from the biaxially oriented polyester film side to the polyolefin sealant layer side.

(Oxygen gas permeability after retort treatment)
The laminate produced by procedure A was kept in hot water at 130° C. for 30 minutes, and then dried at 40° C. for one day (specifically, 24 hours). The oxygen gas permeability of this laminate was measured by the method described above.

(Water vapor permeability)
The laminate produced by procedure A was measured for water vapor permeability under normal conditions in an atmosphere of a temperature of 40° C. and a relative humidity of 90 RH% using a water vapor permeability measuring device ("PERMATRAN-W1A" manufactured by MOCON) in accordance with JIS-K7129-1992 Method B. The water vapor permeability was measured in the direction in which water vapor permeated from the biaxially oriented polyester film side to the polyolefin sealant layer side.

(Water vapor transmission rate after retort treatment)
The laminate produced by procedure A was kept in hot water at 130° C. for 30 minutes, and then dried for one day (specifically, 24 hours) at 40° C. The water vapor transmission rate of this laminate was measured by the method described above.

<Raw material polyester>
(Polyester B)
The collected and recovered PET bottles were crushed by circulating the cleaning liquid (specifically, 500g of liquid kitchen detergent was added to 1000L of water) in a wet grinder. Metal, sand, glass, and other foreign objects with high specific gravity were precipitated by a gravity separator connected to the wet grinder, and flakes were taken out from the upper layer. The flakes were rinsed with pure water and centrifuged. The recovered flakes were obtained by this procedure.
30 kg of melted recovered flakes in a wet state was mixed with a preheated mixture, specifically, a mixture of 150 kg of ethylene glycol and 150 g of zinc acetate dihydrate, in a stirred autoclave, and fractions with a boiling point lower than that of ethylene glycol, such as water and acetic acid, were removed.Then, the mixture was reacted for 4 hours at a temperature of 195°C to 200°C using a reflux condenser.
After the reaction was completed, the temperature of the contents of the reactor was lowered to 97° C. to 98° C., and the contents were filtered while still hot to remove suspended matter and precipitates.
The filtrate was further cooled, and after confirming that the crude BHET was completely dissolved, the filtrate was passed through an activated carbon bed at 50° C. to 51° C. and then through an anion/cation exchange mixed bed for 30 minutes, i.e., a pre-purification treatment was performed.
The pre-purified solution was charged into a stirring autoclave and heated to distill off excess ethylene glycol at normal pressure, thereby obtaining a molten solution of concentrated BHET.
The concentrated BHET melt was allowed to cool naturally while stirring under a nitrogen gas atmosphere, and then removed from the stirring autoclave to obtain a block of concentrated BHET flakes.
The block of fine pieces was heated to 130° C. and melted, and then fed to a thin-film vacuum evaporator by a metering pump, evaporated, and cooled and condensed to obtain purified BHET.
2650 kg of this purified BHET was fed at once to a dissolution tank purged with nitrogen, and after replacing with nitrogen again, dissolution was carried out at a temperature of 150° C. After completion of dissolution, the temperature of the dissolution tank was raised to 230° C. over 30 minutes while stirring. 2650 kg of the obtained BHET solution was transferred to a polycondensation reaction tank, and 300 ppm of antimony trioxide, 170 ppm of cobalt acetate, 55 ppm of phosphoric acid, and 0.3 wt % of titanium dioxide were added to the BHET solution relative to the amount of PET obtained (approximately 2000 kg of PET can be obtained from 2650 kg of BHET), and the temperature of the polycondensation reaction tank was gradually raised from 230° C. to 290° C. while stirring at 10 to 40 rpm, and the pressure was reduced to 40 Pa. When a predetermined stirring torque was reached, the polycondensation reaction vessel was purged with nitrogen to return to normal pressure and terminate the polycondensation reaction. The resulting mixture was discharged in the form of strands, cooled, and immediately cut to obtain polyester chips.
By this procedure, a chemically recycled polyester having an intrinsic viscosity of 0.59 dl/g, namely Polyester B, was obtained.

(Polyester A)
Polyester B (i.e., chemically recycled polyester with an intrinsic viscosity of 0.59 dl/g) was continuously fed to a crystallizer and crystallized at 150°C, then fed to a dryer and dried at 130°C for 10 hours. The dried polyester B was sent to a preheater and heated to 180°C, and then fed to a solid-state polymerizer. A solid-state polymerization reaction was carried out at 190°C for 24 hours under nitrogen gas to obtain a chemically recycled polyester with an intrinsic viscosity of 0.79 dl/g, i.e., polyester A.

(Polyester C)
A chemically recycled polyester having an intrinsic viscosity of 0.83 dl/g, that is, Polyester C, was obtained in the same manner as in Polyester A, except that the time for the solid-phase polymerization reaction was changed from 24 hours to 50 hours.

(Polyester D)
After washing out the remaining beverage and other foreign matter from the beverage PET bottle, the beverage PET bottle was crushed to obtain flakes. The flakes were mixed with a 3.5% by mass sodium hydroxide solution and washed by stirring at a flake concentration of 10% by mass, 85°C, and 30 minutes (i.e., alkaline washing was performed). The flakes taken out after the alkaline washing were washed with distilled water by stirring at a flake concentration of 10% by weight, 25°C, and 20 minutes. This water washing was performed two more times, changing the distilled water each time. The flakes after the water washing were dried and melted in an extruder, and the foreign matter was filtered out by passing them through a filter. The filters were installed in the extruder up to the third stage filter so that the mesh size was successively smaller. The mesh size of the third stage filter was 50 μm. In this manner, a mechanically recycled polyester with an intrinsic viscosity of 0.69 dl/g, i.e., polyester D, was obtained.

(Polyester E-1)
As polyester E-1, that is, as a fossil fuel-derived polyester, a polyester (manufactured by Toyobo) with an intrinsic viscosity of 0.62 dl/g and terephthalic acid/ethylene glycol = 100 mol%/100 mol% was used. In other words, homopolyethylene terephthalate (i.e. homoPET) with an intrinsic viscosity of 0.62 dl/g was used. It should be noted that both terephthalic acid and ethylene glycol were derived from fossil fuels, not from used polyester products.

(Polyester E-2)
As polyester E-2, that is, as a fossil fuel-derived polyester, a polyester (manufactured by Toyobo) was used, which had an intrinsic viscosity of 0.75 dl/g and a terephthalic acid/ethylene glycol ratio of 100 mol%/100 mol%. In other words, a homopolyethylene terephthalate (i.e., homoPET) with an intrinsic viscosity of 0.75 dl/g was used. It should be noted that both the terephthalic acid and the ethylene glycol were derived from fossil fuels, not from used polyester products.

(Polyester E-3)
As polyester E-3, that is, as a fossil fuel-derived polyester, a polyester (manufactured by Toyobo) was used, which had an intrinsic viscosity of 0.63 dl/g and a composition of terephthalic acid/ethylene glycol/isophthalic acid=92.1 mol%/98 mol%/7.9 mol%. That is, isophthalic acid-copolymerized polyethylene terephthalate (i.e., IPA-copolymerized PET) with an intrinsic viscosity of 0.63 dl/g was used. It should be noted that the terephthalic acid, ethylene glycol, and isophthalic acid were not derived from used polyester products but were derived from fossil fuels.

(Polyester F)
When the temperature of the esterification reactor reached 200° C., a slurry consisting of 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was charged, and 0.017 parts by mass of antimony trioxide and 0.16 parts by mass of triethylamine were added as catalysts while stirring. The reactor was then heated to increase the temperature, and a pressurized esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240° C.
Thereafter, the inside of the esterification reactor was returned to normal pressure, and 0.071 parts by mass of magnesium acetate tetrahydrate was added, followed by 0.014 parts by mass of trimethyl phosphate. After heating to 260°C over 15 minutes, 0.012 parts by mass of trimethyl phosphate was added, followed by 0.0036 parts by mass of sodium acetate. 15 minutes after the addition of these, 3.0 parts by mass of an ethylene glycol slurry of amorphous silica particles with an average particle size of 2.7 μm was added based on the particle content. The obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was carried out under reduced pressure at 280°C to obtain a polyester F with an intrinsic viscosity of 0.61 dl/g.
Here, the ethylene glycol slurry of the above-mentioned irregular silica particles is a slurry obtained by mixing the irregular silica particles with ethylene glycol, dispersing the mixture using a high-pressure disperser, centrifuging the mixture to remove 35% of the coarse particles, and then filtering the mixture through a metal filter having a mesh size of 5 μm.
It should be noted that both terephthalic acid and ethylene glycol were derived from fossil fuels, not from used polyester products.

(Polyester G)
When the temperature of the esterification reactor reached 200° C., a slurry consisting of 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was charged, and 0.025 parts by mass of antimony trioxide and 0.16 parts by mass of triethylamine were added as catalysts while stirring. The reactor was then heated to increase the temperature, and a pressurized esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240° C.
Thereafter, the inside of the esterification reactor was returned to normal pressure, and 0.34 parts by mass of magnesium acetate tetrahydrate was added, followed by 0.042 parts by mass of trimethyl phosphate. After the temperature was raised to 260°C over 15 minutes, 0.036 parts by mass of trimethyl phosphate was added, followed by 0.0036 parts by mass of sodium acetate. The obtained esterification reaction product was transferred to a polycondensation reactor, and the temperature was gradually raised from 260°C to 280°C under reduced pressure, and then polycondensation reaction was carried out at 285°C. After the polycondensation reaction was completed, filtration was carried out using a stainless steel sintered filter with a pore size of 5 μm (initial filtration efficiency 95%) to obtain polyester G with an intrinsic viscosity of 0.62 dl/g. It should be noted that neither terephthalic acid nor ethylene glycol was derived from used polyester products, but from fossil fuels.

Additional explanations for Table 1: TPA is an abbreviation for terephthalic acid. EG is an abbreviation for ethylene glycol. IPA is an abbreviation for isophthalic acid.
In the TPA, EG, and IPA columns, "-" means not measured.
Mg indicates the content of magnesium compounds based on magnesium atoms. This content is the mass of magnesium compounds based on magnesium atoms relative to the mass of polyester (i.e., mass of magnesium compounds based on magnesium atoms/mass of polyester). Note that here, only the content of magnesium compounds among alkaline earth metal compounds is shown. This is because the raw polyester did not contain any alkaline earth metal compounds other than magnesium compounds (or it may be said that the amount was below the detection limit).
P represents the content of the phosphorus compound on a phosphorus atom basis. This content is the mass of the phosphorus compound on a phosphorus atom basis relative to the mass of the polyester (i.e., the mass of the phosphorus compound on a phosphorus atom basis/the mass of the polyester).

As shown in Table 1, among polyesters A, B, and C, polyester C had the highest intrinsic viscosity and the least amount of low molecular weight components. Polyester B had the lowest intrinsic viscosity and the most amount of low molecular weight components. In other words, the higher the intrinsic viscosity, the lower the content of low molecular weight components.

Polyester B (i.e., chemically recycled polyester) had a lower intrinsic viscosity than Polyester E-1 (i.e., fossil fuel-derived polyester), but the content of low molecular weight components was similar to that of Polyester E-1.

On the other hand, polyester D (i.e., mechanically recycled polyester) had a higher intrinsic viscosity than polyester E-1 (i.e., fossil fuel-derived polyester), but contained more low molecular weight components than polyester E-1.

<Preparation of biaxially oriented polyester film NAC1>
Using three extruders, a three-layered biaxially oriented polyester film NAC1 was produced. To form the base layer, i.e., the B layer, of the biaxially oriented polyester film NAC1, 50.0% by mass of polyester A, 42.0% by mass of polyester E-1, and 8.0% by mass of polyester G were used. On the other hand, to form a pair of surface layers, i.e., a pair of A layers, of the biaxially oriented polyester film NAC1, 50.0% by mass of polyester A, 39.0% by mass of polyester E-1, 3.0% by mass of polyester F, and 8.0% by mass of polyester G were used. The film production procedure will be described below.
The raw polyester for forming the A layer was dried and then fed to the first and third extruders and melted at 285°C, while the raw polyester for forming the B layer was dried and then fed to the second extruder and melted at 285°C. The molten polyester was introduced from each extruder to a T-die, laminated in the T-die to form an A layer/B layer/A layer (thickness 1 μm/10 μm/1 μm), extruded from the T-die, and cooled and solidified on a casting drum with a surface temperature of 25°C, i.e., a cooling drum. At that time, the film extruded from the T-die and before being in contact with the cooling drum was charged with a wire-shaped electrode with a diameter of 0.15 mm. The casting speed was 70 m/min. An unstretched film was produced by this procedure.
The unstretched film was heated to 120° C. with an infrared heater and stretched in one stage in the longitudinal direction (i.e., MD) at a stretching ratio of 4.0.
Subsequently, the film was stretched in the width direction (i.e., TD) at a preheating temperature of 120°C, a stretching temperature of 130°C, and a stretch ratio of 4.2 times using a tenter-type transverse stretching machine, heat-set at 245°C, and heat-relaxed by 5% in the width direction. The length of the width direction stretching zone was 12.2 m, and the width direction stretching speed (i.e., TD stretch ratio) was 122.66%/sec. Next, the A layer in contact with the cooling drum of the pair of A layers was subjected to a corona treatment under the condition of 40 W·min/ ^m2 , and then wound into a roll by a winder.
By this procedure, a master roll (wound length 60,000 m, width 8,000 mm) of biaxially oriented polyester film NAC1 having a thickness of 12 μm was obtained.
The biaxially oriented polyester film NAC1 was unwound from the master roll and slit to a width of 800 mm, while applying surface pressure with a contact roll and tension with a two-axis turret winder, and the slit biaxially oriented polyester film NAC1 was wound into a roll around a core having a diameter of 6 inches (152.2 mm).
By this procedure, a biaxially oriented polyester film NAC1 was obtained.

<Preparation of biaxially oriented polyester films NAC2, NAC3, NAC4, NAC5, NAC7, NAC8, NAC9, NAC10, and NAC12>
Biaxially oriented polyester films NAC2, NAC3, NAC4, NAC5, NAC7, NAC8, NAC9, NAC10, and NAC12 were produced in the same manner as the biaxially oriented polyester film NAC1, except that the mixing ratio of the raw polyester and the film-forming conditions were changed according to the formulation in Table 2. The casting speed was 70 m/min for all of them. The length of the transverse stretching zone was 12.2 m, and the transverse stretching speed (i.e., TD stretch ratio) was 122.66%/sec for all of them.

<Preparation of biaxially oriented polyester film NAC11>
Biaxially oriented polyester film NAC11 was produced in the same manner as biaxially oriented polyester film NAC1, except that the mixing ratio of raw polyester and film-forming conditions were changed according to the formulation in Table 2. The cast speed was 65 m/min. The length of the transverse stretching zone was 12.2 m, and the transverse stretching speed (i.e., TD stretch ratio) was 113.7%/sec.

<Preparation of biaxially oriented polyester film NAC6>
An unstretched film was obtained in the same manner as for the biaxially oriented polyester film NAC1, except that the mixing ratio of the raw polyesters was changed according to the recipe in Table 2. The casting speed was 70 m/min.
The unstretched film was held at its ends by clips of a tenter-type simultaneous biaxial stretching machine, and was run through a preheating zone at 120° C., and then simultaneously biaxially stretched 4.0 times in the longitudinal direction (i.e., MD) and 4.2 times in the transverse direction (i.e., TD) at 130° C. Next, the film was heat-treated at a temperature of 245° C. with a relaxation rate of 5% in the transverse direction, cooled to room temperature, and wound up to obtain a biaxially oriented polyester film NAC6 having a thickness of 12 μm.

A supplementary explanation is provided for Table 2. The "mixing ratio" shown in Table 2 is shown as a value when the total mass of the raw material polyesters used to form the target layer is taken as 100 mass %. For example, for the B layer in Example 1, it shows that the polyester A accounted for 50 mass % of the total mass of the polyesters A, E-1, and G used to form the B layer, which is 100 mass %.
The silica content is the mass of silica relative to the mass of the target layer (i.e., mass of silica/mass of target layer). The mass of the target layer means the total mass of the raw materials (e.g., polyester and particles) for forming the target layer. "CRPET" is a collective term for polyesters A, B, and C.
Mg indicates the content of magnesium compound on a magnesium atom basis. This content is the mass of magnesium compound on a magnesium atom basis relative to the mass of the biaxially oriented polyester film.
P indicates the content of the phosphorus compound on a phosphorus atom basis. This content is the mass of the phosphorus compound on a phosphorus atom basis relative to the mass of the biaxially oriented polyester film.

By replacing 80% by mass of polyester E-1 (i.e., fossil fuel-derived homo-PET with an intrinsic viscosity of 0.62 dl/g) with polyester C (i.e., chemically recycled polyester with an intrinsic viscosity of 0.83 dl/g), the intrinsic viscosity became too high and the film broke when stretched (see NAC7 and NAC9). Not only that, but the surface crystallinity was also excessively reduced. Even with the biaxially oriented polyester film NAC11, which had an excessively high intrinsic viscosity, the film broke when stretched and the surface crystallinity was excessively low.

By replacing 91% by mass of polyester E-1 (i.e., fossil fuel-derived homo-PET with an intrinsic viscosity of 0.62 dl/g) with polyester B (i.e., chemically recycled polyester with an intrinsic viscosity of 0.59 dl/g), the intrinsic viscosity became too low, the surface crystallinity became too high, and the tensile strength and puncture strength decreased (see NAC7 and NAC10). In addition, the color b ^* value became too high.

NAC12, a biaxially oriented polyester film with an excessively high content of isophthalic acid, had an excessively low melting point and surface crystallization, and was poor in tensile strength and puncture strength.

On the other hand, by replacing some of the polyester E-1 (specifically 50%, 20%, and 80% by mass) with polyester A (i.e., chemically recycled polyester with an intrinsic viscosity of 0.79 dl/g), biaxially oriented polyester films with excellent tensile strength, puncture strength, and heat resistance could be produced without breakage (see NAC7, NAC1, NAC2, and NAC3). Biaxially oriented polyester films could also be produced without breakage by simultaneous biaxial stretching (see NAC6).

By replacing some of the polyester E-1 (specifically 50% by mass, 80% by mass) with polyester B (i.e., chemically recycled polyester with an intrinsic viscosity of 0.59 dl/g), it was possible to produce biaxially oriented polyester films with excellent tensile strength, puncture strength, and heat resistance without breakage (see NAC7, NAC4, and NAC5).

<Preparation of biaxially oriented polyester films AC1 to AC8, AC10 and AC12>
A biaxially oriented polyester film AC1 was produced in the same manner as the biaxially oriented polyester film NAC1, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC2 was produced in the same manner as biaxially oriented polyester film NAC2, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC3 was produced in the same manner as biaxially oriented polyester film NAC3, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC4 was produced in the same manner as biaxially oriented polyester film NAC4, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC5 was produced in the same manner as biaxially oriented polyester film NAC5, except that the film after longitudinal stretching was coated with coating liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC6 was produced in the same manner as for biaxially oriented polyester film NAC6, except that Coating Liquid 1 was coated on an unstretched film by a fountain bar coating method, and the film was then introduced into a tenter while being dried.
Biaxially oriented polyester film AC7 was produced in the same manner as biaxially oriented polyester film NAC7, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC8 was produced in the same manner as biaxially oriented polyester film NAC8, except that the film after longitudinal stretching was coated with coating liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC10 was produced in the same manner as biaxially oriented polyester film NAC10, except that the film after longitudinal stretching was coated with coating liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.
Biaxially oriented polyester film AC12 was produced in the same manner as biaxially oriented polyester film NAC12, except that the film after longitudinal stretching was coated with Coating Liquid 1 by a fountain bar coating method and then dried while being introduced into a tenter.

(Coating Liquid 1)
The materials were mixed in the following mixing ratio to prepare coating solution 1 (i.e., a resin composition for coating layer).
Water 54.40% by weight
Isopropanol 25.00% by mass
Oxazoline group-containing resin 15.00% by mass
Acrylic resin 3.60% by mass
Urethane resin J 2.00% by mass

(Oxazoline Group-Containing Resin)
As the oxazoline group-containing resin, a commercially available water-soluble oxazoline group-containing acrylate ("Epocross (registered trademark) WS-300" manufactured by Nippon Shokubai Co., Ltd.; solid content 10%) was used. The amount of oxazoline groups in this resin was 7.7 mmol/g.

(acrylic resin)
As the acrylic resin, a 25% by mass emulsion of a commercially available acrylic acid ester copolymer ("Movinyl (registered trademark) 7980" with carboxyl groups, manufactured by Japan Coating Resins Co., Ltd.) was used. The acid value (theoretical value) of this acrylic resin was 4 mgKOH/g.

(Urethane resin J)
As urethane resin J, a commercially available polyester urethane resin dispersion ("Takelac (registered trademark) W605" manufactured by Mitsui Chemicals, Inc.; solid content 30% with carboxyl groups) was used. The acid value of this urethane resin was 25 mg KOH/g. The glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) was 100° C. The proportion of aromatic or araliphatic diisocyanate to the entire polyisocyanate component measured by ¹ H-NMR was 55 mol %.

<Examples 1 to 18 and Comparative Examples 1 to 12>
An inorganic thin film layer was formed on each of the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12 by the following two methods.
(Formation of inorganic thin film layer M-1)
To form the inorganic thin film layer M-1, the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12 were subjected to deposition of aluminum oxide. Specifically, the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12 were set on the unwinding side of a continuous vacuum deposition machine, and were wound up after being run over a cooled metal drum. At this time, the continuous vacuum deposition machine was depressurized to 10 ^-4 Torr or less, and 99.99% pure aluminum metal was loaded into an alumina crucible from the bottom of the cooled metal drum, and the aluminum metal was heated and evaporated, and oxygen was supplied into the vapor to cause an oxidation reaction, during which the aluminum metal was deposited on the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12. As a result, an aluminum oxide film having a thickness of 30 nm, i.e., the inorganic thin film layer M-1, was formed.
(Formation of inorganic thin film layer M-2)
To form the inorganic thin film layer M-2, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12 by electron beam deposition. Particulate SiO ₂ (purity 99.9%) and Al ₂ O ₃ (purity 99.9%) of about 3 mm to 5 mm were used as deposition sources. This resulted in a composite oxide layer with a thickness of 13 nm, i.e., inorganic thin film layer M-2. The composition of the composite oxide layer was SiO ₂ /A1 ₂ O ₃ (mass ratio) = 60/40.

Then, in some examples (i.e., Examples 3, 6, 9, 12, 15, and 18, and Comparative Examples 3, 6, 9, and 12), Coating Liquid 2 was applied onto the inorganic thin film layer by a wire bar coating method and dried at 200° C. for 15 seconds. In other words, a protective layer was formed. The coating amount after drying was 0.190 g/m ² (Dry).
(Coating Liquid 2)
The materials were mixed in the following ratio to prepare coating solution 2.
Water 60.00% by mass
Isopropanol 30.00% by mass
Urethane resin K 10.00% by mass
As urethane resin K, a commercially available dispersion of metaxylylene group-containing urethane resin ("Takelac (registered trademark) WPB341" manufactured by Mitsui Chemicals, Inc.; solid content 30%) was used. The acid value of this urethane resin was 25 mg KOH/g. The glass transition temperature (Tg) measured by DSC was 130° C. The proportion of aromatic or araliphatic diisocyanate to the entire polyisocyanate component measured by ¹ H-NMR was 85 mol %.

Using this procedure, the gas barrier films of Examples 1 to 18 and Comparative Examples 1 to 12 were produced.

"PEs film" in Table 3 is used as an abbreviation for biaxially oriented polyester film.

The gas barrier films using biaxially oriented polyester films NAC1 to NAC6 had low oxygen gas permeability and low water vapor permeability (see Examples 1 to 18). This was also the case after retort treatment. The gas barrier films using biaxially oriented polyester films NAC1 to NAC6 had high lamination strength.

On the other hand, the gas barrier film using the biaxially oriented polyester film NAC10 had high oxygen gas permeability and high water vapor permeability (see Comparative Examples 7 to 9). This was also the case after retort treatment. The gas barrier film using the biaxially oriented polyester film NAC10 had low lamination strength.

The gas barrier film using biaxially oriented polyester film NAC8 also had high oxygen gas permeability and water vapor permeability (see Comparative Examples 4 to 6). This was also the case after retort treatment. The gas barrier film using biaxially oriented polyester film NAC8 had low lamination strength.

Gas barrier films using biaxially oriented polyester film NAC7 had low laminate strength (see Comparative Examples 1 to 3).

<Examples 19 to 36 and Comparative Examples 13 to 24>
The gas barrier films of Examples 19 to 36 and Comparative Examples 13 to 24 were produced in the same manner as above, except that the biaxially oriented polyester films AC1 to AC8, AC10 and AC12 were used instead of the biaxially oriented polyester films NAC1 to NAC8, NAC10 and NAC12.

"PEs film" in Table 4 is used as an abbreviation for biaxially oriented polyester film.

The gas barrier films using biaxially oriented polyester films AC1 to AC6 had low oxygen gas permeability and low water vapor permeability (see Examples 19 to 36). This was also the case after retort treatment. The gas barrier films using biaxially oriented polyester films AC1 to AC6 had high laminate strength.

On the other hand, the gas barrier film using biaxially oriented polyester film AC10 had high oxygen gas permeability and high water vapor permeability (see Comparative Examples 19 to 21). This was also the case after retort treatment. The gas barrier film using biaxially oriented polyester film AC10 had low lamination strength.

The gas barrier film using biaxially oriented polyester film AC8 also had high oxygen gas permeability and water vapor permeability (see Comparative Examples 16 to 18). This was also the case after retort treatment. The gas barrier film using biaxially oriented polyester film AC8 had low lamination strength.

Gas barrier films using biaxially oriented polyester film AC7 had low laminate strength (see Comparative Examples 13 to 15).

Since the present invention relates to a gas barrier film, the present invention has industrial applicability.

7...gas barrier film, 8...biaxially oriented polyester film, 81...first layer, 82...second layer, 83...third layer, 9...laminate, 11...printed layer, 21...sealant layer, 22...sealant layer, 31...inorganic thin film layer, 32...anchor coat layer, 33...protective layer, 51...substrate layer, 61...intermediate layer

Claims (10)

A biaxially oriented polyester film;
and an inorganic thin film layer;
The biaxially oriented polyester film comprises chemically recycled polyester,
The chemically recycled polyester contains chemically recycled polyethylene terephthalate, and the chemically recycled polyethylene terephthalate contains at least an isophthalic acid component as a copolymerization component,
In the biaxially oriented polyester film, in a molecular weight distribution curve obtained by gel permeation chromatography, the area ratio of a region having a molecular weight of 1000 or less is 1.9% or more and 5.5% or less of a total peak area;
The intrinsic viscosity of the biaxially oriented polyester film is 0.50 dl/g or more and 0.70 dl/g or less,
The biaxially oriented polyester film has a melting point of 251° C. or higher.
Gas barrier film. The gas barrier film according to claim 1, having a puncture strength of 0.50 N/μm or more. The gas barrier film according to claim 1, wherein the content of the chemically recycled polyester in the biaxially oriented polyester film is 20% by mass or more. The gas barrier film according to claim 1, comprising a coating layer between the biaxially oriented polyester film and the inorganic thin film layer. The gas barrier film according to claim 4, wherein the coating layer contains a resin containing an oxazoline group. The gas barrier film according to claim 1, further comprising a protective layer provided on the inorganic thin film layer. The gas barrier film according to claim 6, wherein the protective layer contains a urethane resin. The gas barrier film according to claim 1, wherein the inorganic thin film layer contains a composite oxide of silicon oxide and aluminum oxide. A gas barrier film according to any one of claims 1 to 8,
At least one of a sealant layer and an adhesive layer;
Laminate. A packaging container comprising the laminate according to claim 9.