Exterior material for power storage device, production method therefor, and power storage device

Abstract

Provided is an exterior material for a power storage device which excels in formability and heat resistance.　The exterior material for a power storage device is composed of a multilayer body that comprises a base material layer, a barrier layer, and a heat-fusible resin layer, in that order. The base material layer is a polyester film containing polyethylene terephthalate and polybutylene terephthalate at a mass ratio of 65 / 35 to 90 / 10. The tensile elongation at break of the polyester film in the width direction is 90 to 155%.

Description

Exterior material for power storage device, manufacturing method thereof, and power storage device

[0001] The present invention relates to an exterior material for an electricity storage device, a method for producing the same, and an electricity storage device. More particularly, the present invention relates to an exterior material for an electricity storage device that has excellent formability and heat resistance, a method for producing the same, and an electricity storage device.

[0002] In an electricity storage device, a packaging material (external packaging material) is used to seal electrodes, an electrolyte, etc. Conventionally, metal packaging materials have been widely used.

[0003] Meanwhile, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., lithium-ion batteries are being required to have a variety of shapes as well as to be thinner and lighter. However, the metal exterior materials that have been widely used up until now have had the problem of difficulty in keeping up with the diversification of shapes and also of having limitations on how much weight they can achieve.

[0004] Therefore, in recent years, pouches made of a laminate of a metal foil such as aluminum foil and a plastic film have come into use as packaging materials that can be easily processed into various shapes and can be made thinner and lighter. In such packaging materials, recesses are typically formed by cold-forming the laminate, and power storage device elements such as electrodes and electrolytes are placed in the spaces formed by the recesses. The laminates are then heat-sealed to obtain lithium-ion batteries or the like containing the power storage device elements inside the packaging material. Polyamide has been widely used as the substrate for such laminates due to its excellent formability. In addition to formability, such packaging materials may require moisture resistance, hermetic sealing, puncture resistance, insulation, heat resistance, cold resistance, and chemical resistance. Therefore, laminate structures consisting of, from the outside, a polyester film, a polyamide film, a metal foil, and a sealant film have also been considered. Additionally, in recent years, electronic devices have been required to be smaller and thinner, and sharp corners of the pouches have been considered to efficiently install lithium-ion batteries together with printed circuit boards and other components inside the pouches. Furthermore, from the viewpoint of further increasing the capacity and energy density of the battery per volume by increasing the content volume (volume of the storage section) per pouch, there has been increasing emphasis in recent years on the development of films that have excellent formability that allows for the formation of deeper recesses in cold forming such as deep drawing. For example, polyester films containing polybutylene terephthalate as a main component have been disclosed (Patent Documents 1 and 2).

[0005] JP 2012-077292 A International Publication No. 2014 / 017457

[0006] However, the inventors' investigations have revealed that when a bag is formed by heat sealing using a laminate containing the polyester film described in Patent Documents 1 and 2, problems arise, such as whitening of the surface of the heat-sealed polyester film due to the low heat resistance of the polyester film in the laminate, resulting in a deterioration in the surface appearance of the obtained bag, or the laminate fusing to the heat seal bar used for heat sealing.Furthermore, the inventors' investigations have revealed that when the content of polybutylene terephthalate is reduced to improve heat resistance, problems arise, such as damage to the recesses when attempting to form deep recesses, even if a polyamide with excellent deep-drawability is laminated.

[0007] In view of these circumstances, the present inventors have conducted extensive research and have found that in an exterior packaging material for an electricity storage device composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, by containing polyethylene terephthalate and polybutylene terephthalate in a specific ratio as the base layer and controlling the tensile elongation at break in the width direction within a specific range, local stress concentration during molding is suppressed and stress uniformity is promoted, thereby achieving excellent moldability and making it possible to achieve both excellent heat resistance that can withstand heat fusion.

[0008] That is, the present invention provides the following. [1] A packaging material for an electricity storage device composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, wherein the base layer is a polyester film containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 65 / 35 to 90 / 10, and the polyester film has a tensile elongation at break in the width direction of 90% or more and 155% or less. [2] The packaging material for an electricity storage device according to [1], which includes a polyamide layer between the base layer and the barrier layer. [3] The packaging material for an electricity storage device according to [1] or [2], wherein the polyester film has a tensile yield stress in the longitudinal direction of 80 MPa or more and 105 MPa or less. [4] The packaging material for an electricity storage device according to any of [1] to [3], wherein the polyester film has a tensile yield stress in the width direction of 65 MPa or more and 110 MPa or less. [5] The packaging material for an electricity storage device according to any one of [1] to [4], wherein the polyester film has a tensile breaking elongation in the longitudinal direction of 110% or more and 190% or less. [6] The packaging material for an electricity storage device according to any one of [1] to [5], wherein the polyester film has a tensile breaking stress in the longitudinal direction of 160 MPa or more and 260 MPa or less and a tensile breaking stress in the width direction of 190 MPa or more and 290 MPa or less. [7] The packaging material for an electricity storage device according to any one of [1] to [6], wherein the tensile breaking elongation in the width direction of the polyester film is equal to or less than the tensile breaking elongation in the longitudinal direction of the polyester film. [8] The packaging material for an electricity storage device according to any one of [1] to [7], wherein the tensile breaking stress in the width direction of the polyester film is equal to or greater than the tensile breaking stress in the longitudinal direction of the polyester film. [9] The packaging material for an electricity storage device according to any one of [1] to [8], wherein a slope of a curve corresponding to the section from the yield point to the break point in a stress-strain curve of the polyester film is 0.60 MPa / % or more and 1.20 MPa / % or less in the longitudinal direction and 1.00 MPa / % or more and 1.80 MPa / % or less in the width direction.

[10] The packaging material for an electricity storage device according to [9], wherein an absolute value of a difference between the slope of the curve in the longitudinal direction and the slope of the curve in the width direction is 1.10 MPa / % or less.

[11] The packaging material for an electricity storage device according to any one of [1] to

[10] , wherein the melting point (1st run) of the polyester film is 230°C or higher.

[12] The packaging material for an electricity storage device according to any one of [1] to

[11] , wherein an adhesive layer is provided between the base material layer and the barrier layer.

[13] The packaging material for an electricity storage device according to any one of [1] to

[12] , wherein a polyamide layer composed of a stretched film is provided between the base material layer and the barrier layer.

[14] The packaging material for an electricity storage device according to any one of [1] to

[13] , wherein the barrier layer contains aluminum.

[15] The packaging material for an electricity storage device according to any one of [1] to

[14] , wherein the polyester film is formed as a laminate of two or more layers.

[16] The packaging material for an electricity storage device according to any one of [1] to

[15] , wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order.

[17] The packaging material for an electricity storage device according to any one of [1] to

[16] , wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order, and the thickness of the intermediate layer is greater than the thickness of the surface layer.

[18] The packaging material for an electricity storage device according to any one of [1] to

[17] , wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order, and the ratio of the thicknesses of the layers (thickness of the surface layer:thickness of the intermediate layer:thickness of the surface layer) is 1-1.6:8-12:1-1.6.

[19] The packaging material for an electricity storage device according to any one of [1] to

[18] , wherein the polyester film is formed as a laminate of two or more layers, and the material composition of one surface layer is different from the material composition of at least one of the other layers.

[20] The packaging material for an electricity storage device according to any one of [1] to

[19] , wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order, and the material composition of the surface layer is different from the material composition of the intermediate layer.

[21] The exterior packaging material for an electricity storage device according to any one of [1] to

[20] , wherein the polyester film is constituted by a laminate of two or more layers, and the content of polyethylene terephthalate in one surface layer is higher than the content of polyethylene terephthalate in at least one of the other layers.

[22] The packaging material for an electricity storage device according to any one of [1] to

[21] , wherein the polyester film is composed of a laminate of two or more layers, the polyethylene terephthalate content in one surface layer being greater than the polyethylene terephthalate content in at least one of the other layers, and the surface layer being the outermost layer of the laminate.

[23] The packaging material for an electricity storage device according to any one of [1] to

[22] , wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order, the polyethylene terephthalate content in the surface layer being greater than the polyethylene terephthalate content in the intermediate layer.

[24] The packaging material for an electricity storage device according to any one of [1] to

[23] , wherein the polyester film is composed of a laminate of two or more layers, and one surface layer contains polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10.

[25] The packaging material for an electricity storage device according to any one of [1] to

[24] , wherein the polyester film is composed of a laminate of two or more layers, one surface layer containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10, and the surface layer is located on the outermost layer side of the laminate.

[26] The packaging material for an electricity storage device according to any one of [1] to

[25] , wherein the polyester film has a surface layer, an intermediate layer, and a surface layer in this order, and the surface layer contains polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10.

[27] The packaging material for an electricity storage device according to any one of [1] to

[26] , wherein differential scanning calorimetry of the polyester film shows one melting peak during heating in at least one of a first run and a second run.

[28] The packaging material for an electricity storage device according to any one of [1] to

[27] , which has a coating layer on at least one surface of the polyester film.

[29] The packaging material for an electricity storage device according to any one of [1] to

[28] , which has a coating layer on at least one surface of the polyester film, and which contains a long-chain alkyl group-containing compound and a melamine compound in a mass ratio of 95 / 5 to 5 / 95.

[30] The packaging material for an electricity storage device according to any one of [1] to

[29] , wherein the polyethylene terephthalate contained in the polyester film has an intrinsic viscosity of 0.50 dL / g or more.

[31] The packaging material for an electricity storage device according to any one of [1] to

[30] , wherein the polybutylene terephthalate contained in the polyester film has an intrinsic viscosity of 0.70 dL / g or more.

[32] The packaging material for an electricity storage device according to any one of [1] to

[31] , wherein the polyester film is a biaxially stretched film, and the product of the stretch ratio in the width direction and the stretch ratio in the longitudinal direction of the polyester film is greater than 15.5.

[33] The packaging material for an electricity storage device according to any one of [1] to

[32] , wherein the polyester film is a biaxially stretched film, and the difference between the stretch ratio in the width direction and the stretch ratio in the longitudinal direction of the polyester film is 0.3 or more.

[34] The packaging material for an electricity storage device according to any one of [1] to

[33] , wherein the polyester film is a biaxially stretched film, and the ratio of the stretching ratio in the width direction to the stretching ratio in the longitudinal direction of the polyester film (stretching ratio in the width direction / stretching ratio in the longitudinal direction) is 1.2 or more and 1.7 or less.

[35] An electricity storage device, wherein an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the packaging material for an electricity storage device according to any one of [1] to

[34] .

[36] A method for producing a packaging material for an electricity storage device, comprising a step of obtaining a laminate by laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, wherein the polyester film used for the base layer contains polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 65 / 35 to 90 / 10, and the tensile breaking elongation of the polyester film in the width direction is 90% or more and 155% or less.

[37] The method for producing an exterior material for an electricity storage device according to

[36] , wherein the step of obtaining the laminate is a step of obtaining a laminate including at least a base layer, a polyamide layer, a barrier layer, and a heat-sealable resin layer in this order, and the polyester film has a tensile yield stress in the longitudinal direction of 80 MPa or more and 105 MPa or less, a tensile yield stress in the width direction of 65 MPa or more and 110 MPa or less, and a tensile elongation at break in the longitudinal direction of 110% or more and 190% or less.

[0009] According to the present invention, it is possible to provide an electrical storage device packaging material that is excellent in formability and heat resistance. Furthermore, according to the present invention, it is also possible to provide a method for manufacturing the electrical storage device packaging material, and an electrical storage device that uses the electrical storage device packaging material.

[0010] It is a schematic cross-sectional view showing an example of the cross-sectional structure of the electrical storage device packaging material of the present invention. It is a schematic plan view of the electrical storage device packaging material of the present invention when viewed from above. It is a schematic cross-sectional view taken along the line AA' in FIG.

[0011] The present invention will be described in more detail below based on embodiments of the present invention, but is not limited to these embodiments. In this specification, when "X to Y" (X and Y are any numbers) is expressed, the endpoints and the range are included unless otherwise specified. That is, it means that X, the range between X and Y, and Y are included. Furthermore, in this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and can mean three possibilities: X only, Y only, or X and Y. Furthermore, in this specification, the term "film" is also intended to include "sheet," and the term "sheet" is also intended to include "film." Furthermore, in this specification, the term "main component" means a component that has a significant impact on the properties of the material. The content of this component is the component that is most abundant in the entire material, and is typically 60% by mass or more of the entire material, preferably 65% ​​by mass or more, more preferably 70% by mass or more, and may be 80 to 100% by mass, or 90 to 100% by mass.

[0012] <<Present Exterior Material>> A exterior material for an electricity storage device according to one embodiment of the present invention (hereinafter may be referred to as "the present exterior material") is composed of a laminate including, in this order, a base material layer 1, a first adhesive layer 2, a polyamide layer 3, a second adhesive layer 4, a barrier layer 5, and a heat-sealable resin layer 6, as shown in Fig. 1 , although not limited thereto, with the base material layer 1 being the outermost layer and the heat-sealable resin layer 6 being the innermost layer. That is, when assembling a battery, the heat-sealable resin layers 6 located on the periphery of the battery element are heat-sealed to each other to seal the battery element, thereby sealing the battery element.

[0013] The thickness (total thickness) of the laminate constituting the present packaging material is not particularly limited, but is, for example, about 300 μm or less, preferably about 250 μm or less, about 220 μm or less, about 180 μm or less, about 155 μm or less, or about 120 μm or less from the viewpoint of cost reduction, improvement of energy density, etc. Furthermore, the thickness (total thickness) of the laminate constituting the present packaging material is preferably about 35 μm or more, about 45 μm or more, or about 60 μm or more from the viewpoint of maintaining the function of the present packaging material of protecting the electricity storage device elements. Furthermore, preferred thickness (total thickness) ranges of the laminate constituting the present packaging material are, for example, about 35 to 300 μm, about 35 to 250 μm, about 35 to 220 μm, about 35 to 180 μm, about 35 to 155 μm, about 35 to 120 μm, about 45 to 300 μm, about 45 to 250 μm, about 45 to 220 μm, about 45 to 180 μm, about 45 to 155 μm, about 45 to 120 μm, about 60 to 300 μm, about 60 to 250 μm, about 60 to 220 μm, about 60 to 180 μm, about 60 to 155 μm, and about 60 to 120 μm, with about 60 to 250 μm being particularly preferred.

[0014] In this packaging material, the ratio of the total thickness of the base material layer 1, the first adhesive layer 2 which is provided as needed, the polyamide layer 3 which is provided as needed, the second adhesive layer 4 which is provided as needed, the barrier layer 5, the heat-sealable resin layer 6, and the third adhesive layer which is provided as needed to the thickness (total thickness) of the laminate which constitutes this packaging material is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

[0015] In this packaging material, the MD (machine direction) and TD (transverse direction) of the barrier layer 5 described below can usually be determined during its manufacturing process. When the barrier layer 5 is made of aluminum alloy foil, linear lines called rolling marks are formed on the surface of the metal foil in the rolling direction (RD) of the metal foil. Since the rolling marks extend along the rolling direction, the rolling direction of the metal foil can be determined by observing the surface of the metal foil. Furthermore, during the manufacturing process of a laminate, the MD of the laminate usually coincides with the RD of the metal foil, so the MD of the laminate can be identified by observing the surface of the metal foil of the laminate and identifying the rolling direction (RD) of the metal foil. Furthermore, since the TD of the laminate is perpendicular to the MD of the laminate, the TD of the laminate can also be identified.

[0016] Furthermore, if the MD of the packaging material cannot be determined due to rolling marks on the aluminum alloy foil, it can be determined by the following method. One method for determining the MD of the packaging material is to observe the cross section of the heat-sealable resin layer of the packaging material using an electron microscope to confirm the sea-island structure. In this method, the direction parallel to the cross section in which the average diameter of the island shapes in the direction perpendicular to the thickness direction of the heat-sealable resin layer is largest can be determined as the MD. Specifically, the longitudinal cross section of the heat-sealable resin layer and each cross section at an angle of 10 degrees from the direction parallel to the longitudinal cross section to the direction perpendicular to the longitudinal cross section (a total of 10 cross sections) are observed using an electron microscope to confirm the sea-island structure. Next, the shape of each individual island is observed in each cross section. For each island shape, the linear distance connecting the leftmost end perpendicular to the thickness direction of the heat-sealable resin layer to the rightmost end in the perpendicular direction is defined as the diameter y. For each cross section, the average of the diameters y of the top 20 island shapes in order of largest diameter y is calculated. The direction parallel to the cross section in which the average diameter y of the island shape is the largest is determined to be the MD.

[0017] Layers forming the packaging material for an electricity storage device <Substrate layer 1> The substrate layer 1 is a layer provided for the purpose of exhibiting functions such as heat resistance, formability, and dimensional stability during lamination as the substrate of the packaging material, and is a layer composed of a specific polyester film (hereinafter sometimes referred to as "the polyester film").

[0018] From the viewpoint of achieving both formability and heat resistance of the packaging material, the polyester film has a mass ratio (PET / PBT) of polyethylene terephthalate (PET) to polybutylene terephthalate (PBT) of 65 / 35 to 90 / 10. In the mass ratio of polyethylene terephthalate (PET) to polybutylene terephthalate (PBT) contained in the polyester film, the mass ratio of polyethylene terephthalate (PET) is, for example, preferably 67 or more, more preferably 69 or more, even more preferably 70 or more, and particularly preferably 71 or more. Furthermore, for example, it is preferably 88 or less, more preferably 87 or less, even more preferably 86 or less, particularly preferably 85 or less, even particularly preferably 83 or less, even more particularly preferably 82 or less, and even more particularly preferably 80 or less. In the mass ratio of polyethylene terephthalate (PET) to polybutylene terephthalate (PBT) contained in the polyester film, the mass ratio of polybutylene terephthalate (PBT) is, for example, preferably 12 or more, more preferably 13 or more, even more preferably 14 or more, even more preferably 15 or more, particularly preferably 17 or more, even more particularly preferably 18 or more, and even more particularly preferably 20 or more. Also, for example, it is preferably 33 or less, more preferably 31 or less, even more preferably 30 or less, and particularly preferably 29 or less.The mass ratio in the polyester film is about 65 / 35 to 90 / 10, for example, about 67 / 33 to 90 / 10, about 69 / 31 to 90 / 10, about 70 / 30 to 90 / 10, about 71 / 29 to 90 / 10, or about 65 / 35 to 88 / 12, for example, about 67 / 33 to 88 / 12, about 69 / 31 to 88 / 12, or about 70 / 3 Approximately 0 to 88 / 12, approximately 71 / 29 to 88 / 12, approximately 65 / 35 to 87 / 13, for example, approximately 67 / 33 to 87 / 13, approximately 69 / 31 to 87 / 13, approximately 70 / 30 to 87 / 13, approximately 71 / 29 to 87 / 13, approximately 65 / 35 to 86 / 14, approximately 67 / 33 to 86 / 14, approximately 69 / 31 to 86 / 14, approximately 70 / 30 to 86 / 1 4, 71 / 29 to 86 / 14, 65 / 35 to 85 / 15, 67 / 33 to 85 / 15, 69 / 31 to 85 / 15, 70 / 30 to 85 / 15, 7 1 / 29~85 / 15, 65 / 35~83 / 17, 67 / 33~83 / 17, 69 / 31~83 / 17, 70 / 30~83 / 17, 71 / 29~ 67 / 33 to 82 / 18, about 69 / 31 to 82 / 18, about 70 / 30 to 82 / 18, about 71 / 29 to 82 / 18, about 65 / 35 to 80 / 20, about 67 / 33 to 80 / 20, about 69 / 31 to 80 / 20, about 70 / 30 to 80 / 20, about 71 / 29 to 80 / 20. If the mass ratio (PET / PBT) is outside the above range, it becomes difficult to achieve both moldability and heat resistance.

[0019] [Tensile Breaking Elongation] The tensile breaking elongation in the width direction (TD) of the polyester film is 90% or more and 155% or less, from the viewpoint of achieving both the formability and heat resistance of the packaging material. That is, the tensile breaking elongation in the width direction (TD) is 90% or more, preferably 95% or more, more preferably 100% or more, even more preferably 105% or more, and particularly preferably 110% or more. Also, it is 155% or less, preferably 153% or less, more preferably 150% or less, even more preferably 148% or less, even more preferably 145% or less, particularly preferably 140% or less, and even particularly preferably 130% or less. The tensile elongation at break in the transverse direction (TD) of the polyester film is in the range of 90 to 155%, for example, about 95 to 155%, about 100 to 155%, about 105 to 155%, about 110 to 155%, about 90 to 153%, about 95 to 153%, about 100 to 153%, about 105 to 153%, about 110 to 153%, about 90 to 150%, about 95 to 150%, about 100 to 150%, about 105 to 150%, about 110 to 150%, about 90 to 153%. about 48%, about 95 to 148%, about 100 to 148%, about 105 to 148%, about 110 to 148%, about 90 to 145%, about 95 to 145%, about 100 to 145%, about 105 to 145%, about 110 to 145%, about 90 to 140%, about 95 to 140%, about 100 to 140%, about 105 to 140%, about 110 to 140%, about 90 to 130%, about 95 to 130%, about 100 to 130%, about 105 to 130%, and about 110 to 130%. If the tensile elongation at break in the transverse direction (TD) of the polyester film is outside the above range, it becomes difficult to achieve both formability and heat resistance. Furthermore, from the viewpoint of achieving a high degree of both formability and heat resistance of the packaging material, the tensile elongation at break in the machine direction (MD) of the polyester film is preferably 110% or more and 190% or less. That is, the tensile elongation at break in the machine direction (MD) is, for example, 110% or more, preferably 120% or more, more preferably 128% or more, even more preferably 135% or more, and particularly preferably 145% or more. Also, for example, it is 190% or less, preferably 188% or less, more preferably 182% or less, and even more preferably 180% or less.The range of the tensile elongation at break in the machine direction (MD) of the polyester film is, for example, about 110 to 190%, about 120 to 190%, about 128 to 190%, about 135 to 190%, about 145 to 190%, about 110 to 188%, about 120 to 188%, about 128 to 188%, about 135 to 188%, about 145 to 188%, about 110 to 182%, about 120 to 182%, about 128 to 182%, about 135 to 182%, about 145 to 182%, about 110 to 180%, about 120 to 180%, about 128 to 180%, about 135 to 180%, and about 145 to 180%.

[0020] From the viewpoint of achieving both formability and heat resistance of the packaging material, the tensile break elongation in the width direction (TD) of the polyester film is preferably equal to or less than the tensile break elongation in the longitudinal direction (MD) of the polyester film (tensile break elongation in the width direction (TD)≦tensile break elongation in the longitudinal direction (MD)), and more preferably less than the tensile break elongation in the longitudinal direction of the polyester film (tensile break elongation in the width direction (TD)<tensile break elongation in the longitudinal direction (MD)). Furthermore, for example, the difference between the tensile break elongation in the width direction (TD) and the tensile break elongation in the longitudinal direction (MD) of the polyester film (tensile break elongation in the longitudinal direction (MD) [%]−tensile break elongation in the width direction (TD) [%]) is, for example, about 5 to 60%, preferably about 8 to 55%, and more preferably about 10 to 52%. The difference between the tensile elongation at break in the width direction (TD) and the tensile elongation at break in the longitudinal direction (MD) of the polyester film (tensile elongation at break in the longitudinal direction (MD) [%] - tensile elongation at break in the width direction (TD) [%]) may be 50% or less, 46% or less, 42% or less, 36% or less, 32% or less, 28% or less, or 24% or less.

[0021] [Tensile Yield Stress] The tensile yield stress in the machine direction (MD) of the polyester film is preferably 80 MPa or more and 105 MPa or less, from the viewpoint of achieving a high level of both formability and heat resistance of the packaging material. That is, the tensile yield stress in the machine direction (MD) is, for example, 80 MPa or more, preferably 81 MPa or more, more preferably 82 MPa or more, and even more preferably 83 MPa or more. Also, for example, it is 105 MPa or less, preferably 103 MPa or less, more preferably 102 MPa or less, and even more preferably 100 MPa or less. The range of the tensile yield stress in the longitudinal direction (MD) of the polyester film is, for example, about 80 to 105 MPa, about 81 to 105 MPa, about 82 to 105 MPa, about 83 to 105 MPa, about 80 to 103 MPa, about 81 to 103 MPa, about 82 to 103 MPa, about 83 to 103 MPa, about 80 to 102 MPa, about 81 to 102 MPa, about 82 to 102 MPa, about 83 to 102 MPa, about 80 to 100 MPa, about 81 to 100 MPa, about 82 to 100 MPa, or about 83 to 100 MPa. The tensile yield stress in the width direction (TD) of the polyester film is preferably 65 MPa or more and 110 MPa or less, from the viewpoint of achieving a high level of both formability and heat resistance of the packaging material. That is, the tensile yield stress in the transverse direction (TD) is preferably 65 MPa or more, 68 MPa or more, more preferably 72 MPa or more, and even more preferably 75 MPa or more, and is preferably 110 MPa or less, 109 MPa or less, more preferably 107 MPa or less, and even more preferably 105 MPa or less. The range of the tensile yield stress in the width direction (TD) of the polyester film is, for example, about 65 to 110 MPa, about 68 to 110 MPa, about 72 to 110 MPa, about 75 to 110 Pa, about 65 to 109 MPa, about 68 to 109 MPa, about 72 to 109 MPa, about 75 to 109 Pa, about 65 to 107 MPa, about 68 to 107 MPa, about 72 to 107 MPa, about 75 to 107 Pa, about 65 to 105 MPa, about 68 to 105 MPa, about 72 to 105 MPa, and about 75 to 105 MPa.

[0022] [Tensile Breaking Stress] The tensile breaking stress in the machine direction (MD) of the polyester film is preferably 160 MPa or more and 260 MPa or less, from the viewpoint of achieving a high degree of both formability and heat resistance of the packaging material. That is, the tensile breaking stress in the machine direction (MD) is, for example, 160 MPa or more, preferably 170 MPa or more, more preferably 175 MPa or more, even more preferably 180 MPa or more, particularly preferably 190 MPa or more, even more particularly preferably 195 MPa or more, and even more particularly preferably 200 MPa or more. Also, for example, it is 260 MPa or less, preferably 255 MPa or less, more preferably 250 MPa or less, even more preferably 245 MPa or less, particularly preferably 240 MPa or less, even more particularly preferably 235 MPa or less, even more particularly preferably 230 MPa or less, and even more particularly preferably 227 MPa or less. The tensile stress at break in the longitudinal direction (MD) of the polyester film is, for example, about 160 to 260 MPa, preferably about 170 to 255 MPa, more preferably about 175 to 250 MPa, even more preferably about 180 to 245 MPa, particularly preferably about 190 to 240 MPa, even more particularly preferably about 195 to 245 MPa, and even more particularly preferably about 200 to 240 MPa. The tensile stress at break in the transverse direction (TD) of the polyester film is preferably 190 MPa or more and 290 MPa or less, from the viewpoint of achieving a high level of both formability and heat resistance of the packaging material. That is, the tensile stress at break in the transverse direction (TD) is, for example, 190 MPa or more, preferably 200 MPa or more, more preferably 220 MPa or more, even more preferably 230 MPa or more, and particularly preferably 240 MPa or more. The tensile stress at break in the transverse direction (TD) of the polyester film is, for example, about 190 to 290 MPa, preferably about 200 to 290 MPa, more preferably about 220 to 285 MPa, even more preferably about 230 to 280 MPa, and particularly preferably about 240 to 282 MPa.

[0023] From the viewpoint of achieving both formability and heat resistance of the packaging material, the tensile breaking stress in the width direction (TD) of the polyester film is preferably equal to or greater than the tensile breaking stress in the longitudinal direction (MD) of the polyester film (tensile breaking stress in the width direction (TD) ≧ tensile breaking stress in the longitudinal direction (MD)), and more preferably exceeds the tensile breaking stress in the longitudinal direction (MD) of the polyester film (tensile breaking stress in the width direction (TD) > tensile breaking stress in the longitudinal direction (MD)). Furthermore, for example, the difference between the tensile breaking stress in the width direction (TD) and the tensile breaking stress in the longitudinal direction (MD) of the polyester film (tensile breaking stress in the width direction (TD) [MPa] - tensile breaking stress in the longitudinal direction (MD) [MPa]) is, for example, 5 to 80 MPa, preferably about 8 to 75 MPa, and more preferably about 10 to 70 MPa. The difference between the tensile breaking stress in the width direction (TD) and the tensile breaking stress in the longitudinal direction (MD) of the polyester film (tensile breaking stress in the width direction (TD) [MPa] - tensile breaking stress in the longitudinal direction (MD) [MPa]) may be 65 MPa or less, 60 MPa or less, 55 MPa or less, 50 MPa or less, 45 MPa or less, 40 MPa or less, or 35 MPa or less.

[0024] The tensile yield stress, tensile elongation at break, and tensile stress at break can be measured with reference to JIS K 7161-1 (2014). Specifically, a sample piece is taken from a polyester film, and the tensile yield stress, tensile elongation at break, and tensile stress at break can be measured in each of the machine direction (MD) and the transverse direction (TD) using a tensile tester with reference to JIS K 7161-1 (2014). Measurement conditions include an atmosphere of 23°C and 50% RH, a chuck distance of 50 mm for the test piece, and a pulling speed of 200 mm / min. In this specification, "tensile elongation at break" refers to either "tensile strain at break" or "nominal tensile strain at break" (JIS K7161-1 (2014)). This refers to either "tensile strain at break" or "nominal tensile strain at break" depending on the characteristics of the stress / strain curve of the film being measured.

[0025] [Slope of the curve corresponding to the section from the yield point to the break point in the stress-strain curve] From the viewpoint of achieving a high level of both formability and heat resistance of the packaging material, the slope of the curve in the longitudinal direction (MD) of the polyester film is preferably 0.60 MPa / % or more and 1.20 MPa / % or less. That is, from the viewpoint of achieving a high level of both formability and heat resistance of the packaging material, the slope of the curve in the longitudinal direction (MD) is, for example, 0.60 MPa / % or more, preferably 0.65 MPa / % or more, more preferably 0.68 MPa / % or more. Also, for example, it is 1.20 MPa / % or less, preferably 1.10 MPa / % or less, more preferably 1.05 MPa / % or less, even more preferably 1.00 MPa / % or less, particularly preferably 0.98 MPa / % or less, and even more particularly preferably 0.97 MPa / % or less. The range of the slope of the curve in the machine direction (MD) of the polyester film is, for example, about 0.60 to 1.20 MPa / %, preferably about 0.60 to 1.10 MPa / %, more preferably about 0.65 to 1.05 MPa / %, even more preferably about 0.65 to 1.00 MPa / %, particularly preferably about 0.68 to 0.98 MPa / %, and even more particularly preferably about 0.68 to 0.97 MPa / %. The slope of the curve in the width direction (TD) of the polyester film is preferably 1.00 MPa / % or more and 1.80 MPa / % or less, from the viewpoint of achieving a high level of both formability and heat resistance of the packaging material. That is, the slope of the curve in the width direction (TD) is, for example, 1.00 MPa / % or more, preferably 1.05 MPa / % or more, more preferably 1.10 MPa / % or more, even more preferably 1.15 MPa / % or more, particularly preferably 1.20 MPa / % or more, even more particularly preferably 1.30 MPa / % or more, even more particularly preferably 1.35 MPa / % or more, and even more particularly preferably 1.40 MPa / % or more. Also, for example, it is 1.80 MPa / % or less, preferably 1.75 MPa / % or less, more preferably 1.70 MPa / % or less, even more preferably 1.65 MPa / % or less, may be 1.60 MPa / % or less, may be 1.55 MPa / % or less, may be 1.50 MPa / % or less, or may be 1.45 MPa / % or less.The range of the slope of the curve in the width direction (TD) of the polyester film is, for example, about 1.00 to 1.80 MPa / %, preferably about 1.05 to 1.75 MPa / %, more preferably about 1.10 to 1.70 MPa / %, even more preferably about 1.15 to 1.65 MPa / %, particularly preferably about 1.20 to 1.60 MPa / %, even more particularly preferably about 1.30 to 1.55 MPa / %, even more particularly preferably about 1.35 to 1.50 MPa / %, and even more particularly preferably about 1.40 to 1.45 MPa / %.

[0026] [Absolute value of the difference in slope between the longitudinal direction (MD) and the transverse direction (TD)] In this polyester film, from the viewpoint of achieving a high degree of both formability and heat resistance of this packaging material, the absolute value of the difference between the slope (MPa / %) of the curve corresponding to the section from the yield point to the break point in the stress-strain curve in the longitudinal direction (MD) and the slope (MPa / %) of the curve corresponding to the section from the yield point to the break point in the stress-strain curve in the transverse direction (TD) is, for example, 1.10 MPa / % or less, preferably 1.05 MPa / % or less, more preferably 1.00 MPa / % or less, even more preferably 0.95 MPa / % or less, particularly preferably 0.90 MPa / % or less. Also, for example, it is 0.20 MPa / % or more, preferably 0.25 MPa / % or more, more preferably 0.30 MPa / % or more, even more preferably 0.35 MPa / % or more, particularly preferably 0.40 MPa / % or more. The range of the absolute value of the difference in slope in the present polyester film is, for example, about 0.20 to 1.10 MPa / %, preferably about 0.25 to 1.05 MPa / %, more preferably about 0.30 to 1.00 MPa / %, even more preferably about 0.35 to 0.95 MPa / %, and particularly preferably about 0.40 to 0.90 MPa / %.

[0027] The slope of the stress-strain curve corresponding to the section between the yield point and the break point and the absolute value of the difference can be measured with reference to JIS K 7161-1 (2014). Specifically, a sample piece is taken from the polyester film, and the slope of the stress-strain curve corresponding to the section between the yield point and the break point is measured in each of the longitudinal direction (MD) and the transverse direction (TD) using a tensile tester with reference to JIS K 7161-1 (2014). The measurement conditions are an atmosphere of 23°C and 50% RH, a chuck distance of 50 mm for the test piece, and a tensile speed of 200 mm / min. The slope of each stress-strain curve is calculated using the least squares method of a regression line. The calculation conditions are one measurement point every 0.1 seconds, and data from 100 or more points is used.

[0028] The tensile yield stress and tensile elongation at break can be controlled within the above ranges by appropriately setting, for example, the mass ratio of polyethylene terephthalate and polybutylene terephthalate, the stretching ratio during film production, the preheating / stretching temperature, the heat setting temperature, etc., as described below.

[0029] The present packaging material for an electricity storage device, which contains polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) in a specific range, such as 65 / 35 to 90 / 10, and has the present polyester film with the tensile elongation at break in the width direction (TD) controlled to a specific range, serves as a base material layer 1, and is composed of a laminate having the base material layer 1, a barrier layer 5, and a heat-sealable resin layer 6, at least in this order, can achieve excellent formability and can also achieve excellent heat resistance that can withstand heat fusion.

[0030] Furthermore, the polyester film contains polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) in a specific ratio, such as 65 / 35 to 90 / 10, and has a tensile elongation at break in the transverse direction (TD) controlled to a specific range. The polyester film serves as a substrate layer 1, and the substrate layer 1, a polyamide layer 3, a barrier layer 5, and a heat-sealable resin layer 6 are laminated together in this order to achieve excellent formability and excellent heat resistance that can withstand heat fusion.

[0031] Specifically, the present packaging material includes a base layer 1 composed of a polyester film containing polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) in a specific ratio, such as 65 / 35 to 90 / 10, with the transverse direction (TD) tensile break elongation controlled within a specific range. Preferably, the base layer 1 is composed of a polyester film containing polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) in a specific ratio, such as 65 / 35 to 90 / 10, with the longitudinal direction (MD) and transverse direction (TD) tensile yield stress and tensile break elongation controlled within specific ranges. This suppresses localized stress concentration during molding and promotes stress uniformity, thereby preventing breakage and enabling the formation of deeper recesses than conventional methods during deep drawing. Furthermore, it also suppresses deterioration of the pouch surface appearance during heat sealing and adhesion to the heat seal bar. As described above, the present packaging material is extremely useful in terms of its excellent formability and heat resistance, and can be suitably used, for example, as a packaging material for a relatively large-sized electricity storage device, specifically, one having a deeper recess. For example, by increasing the content volume (volume of the storage section) per pouch obtained from the present packaging material, the capacity and energy density of the battery per the same volume can be further increased.

[0032] The structure of the polyester film will be described in more detail below.

[0033] [Polyethylene terephthalate (PET)] The polyethylene terephthalate constituting the present polyester film may be a homopolyethylene terephthalate consisting solely of ethylene terephthalate repeating units, or a copolymerized polyethylene terephthalate containing ethylene terephthalate as the main repeating unit. Such a copolymerized polyethylene terephthalate preferably contains 70 mol % or more, more preferably 80 mol % or more, or may be 90 mol % to 98 mol %. These may be used alone or in combination of two or more.

[0034] In copolymerized polyethylene terephthalate, examples of copolymerizable monomers include dibasic acid components other than terephthalic acid and its lower alcohol esters, and glycol components other than ethylene glycol. Examples of such dibasic acid components include aromatic or aliphatic polybasic acids such as isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and succinic acid, as well as esters thereof. Examples of glycol components include alkylene glycols such as diethylene glycol, propylene glycol, butylene glycol, trimethylene glycol, hexamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and 1,3-octanediol; aromatic alcohols such as bisphenol A and 4,4'-dihydroxybiphenyl; and alkylene oxide adducts such as an ethylene oxide diadduct of bisphenol A and a propylene oxide diadduct of bisphenol A.

[0035] Specifically, examples of copolymerized polyethylene terephthalate include polyester copolymers in which ethylene terephthalate is the main repeating unit and ethylene isophthalate are copolymerized (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), and polyethylene (terephthalate / decanedicarboxylate).

[0036] From the viewpoints of moldability and heat resistance, the intrinsic viscosity of polyethylene terephthalate is preferably 0.50 dL / g or more, more preferably 0.53 dL / g or more, even more preferably 0.57 dL / g or more, and particularly preferably 0.60 dL / g or more. The intrinsic viscosity is preferably 1.00 dL / g or less, more preferably 0.96 dL / g or less, even more preferably 0.93 dL / g or less, and particularly preferably 0.90 dL / g or less. The intrinsic viscosity of polyethylene terephthalate is preferably in the range of 0.50 to 1.00 dL / g, more preferably 0.53 to 0.96 dL / g, even more preferably 0.57 to 0.93 dL / g, and particularly preferably 0.60 to 0.90 dL / g. The intrinsic viscosity of polyethylene terephthalate can be appropriately set within the above range, and is not limited to the following, but may be, for example, 0.60 to 0.80 dL / g, 0.60 to 0.75 dL / g, etc.

[0037] [Polybutylene terephthalate (PBT)] The polybutylene terephthalate constituting the present polyester film may be a homopolybutylene terephthalate consisting solely of butylene terephthalate repeating units, or a copolymer polybutylene terephthalate mainly composed of butylene terephthalate repeating units. Such copolymer polybutylene terephthalate preferably contains 70 mol % or more, more preferably 80 mol % or more, or even 90 mol % to 98 mol % of butylene terephthalate repeating units. These may be used alone or in combination of two or more.

[0038] In copolymerized polybutylene terephthalate, examples of the monomers to be copolymerized include dibasic acid components other than terephthalic acid and its lower alcohol esters, and glycol components other than 1,4-butanediol. Examples of such dibasic acid components include aromatic or aliphatic polybasic acids such as isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and succinic acid, as well as esters thereof. On the other hand, examples of glycol components include alkylene glycols such as ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexanedimethanol, and 1,3-octanediol; aromatic alcohols such as bisphenol A and 4,4'-dihydroxybiphenyl; and alkylene oxide adducts such as an ethylene oxide diadduct of bisphenol A and a propylene oxide diadduct of bisphenol A.

[0039] Specifically, examples of copolymerized polybutylene terephthalate include copolymer polyesters in which butylene terephthalate is the main repeating unit and butylene isophthalate are polymerized (hereinafter abbreviated as polybutylene (terephthalate / isophthalate)), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), and the like.

[0040] From the viewpoints of moldability and heat resistance, the intrinsic viscosity of polybutylene terephthalate is preferably 0.70 dL / g or more, more preferably 0.73 dL / g or more, even more preferably 0.77 dL / g or more, and particularly preferably 0.80 dL / g or more. The intrinsic viscosity is preferably 1.40 dL / g or less, more preferably 1.37 dL / g or less, even more preferably 1.33 dL / g or less, and particularly preferably 1.30 dL / g or less. The intrinsic viscosity of polybutylene terephthalate is preferably in the range of 0.70 to 1.40 dL / g, more preferably 0.73 to 1.37 dL / g, even more preferably 0.77 to 1.33 dL / g, and particularly preferably 0.80 to 1.30 dL / g. The intrinsic viscosity of polybutylene terephthalate can be appropriately set within the above range and is not limited to the following, but may be, for example, 0.80 to 1.20 dL / g, 0.80 to 1.10 dL / g, 0.80 to 1.00 dL / g, etc.

[0041] In addition, when two or more polyethylene terephthalates having different intrinsic viscosities are used, or when two or more polybutylene terephthalates having different intrinsic viscosities are used, the intrinsic viscosity refers to the intrinsic viscosity of a mixed polyester of these. The intrinsic viscosity can be measured in accordance with JIS K7367-1:2002 by a conventional method, for example, using an Ubbelohde viscometer at 30°C using a solvent of phenol:tetrachloroethane=1:1.

[0042] The polyester film constituting the base layer 1 may contain other resin components other than polyethylene terephthalate and polybutylene terephthalate, or other components such as additives, but is preferably composed primarily of polyethylene terephthalate. The total content of polyethylene terephthalate and polybutylene terephthalate is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 98 to 100% by mass, based on the total mass of the polyester film (i.e., the total mass of the base layer 1).

[0043] The other resin components and other components such as additives are not particularly limited, and examples thereof include lubricants, flame retardants, antiblocking agents, antioxidants, light stabilizers, tackifiers, antistatic agents, colorants, etc. These may be used alone or in combination of two or more.

[0044] The lubricant is not particularly limited, and examples thereof include inorganic particles such as silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate; organic particles obtained by polymerizing acrylic acid ester monomers, styrene monomers, silicone monomers, and the like, or organic particles obtained by copolymerizing these monomers, and organic fine particles such as acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles.

[0045] The average particle size of the lubricant is not particularly limited, but is usually 0.03 μm or more, preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.6 μm or more. It is usually 10 μm or less, preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less. The average particle size of the lubricant is usually 0.03 to 10 μm, preferably 0.1 to 6 μm, more preferably 0.3 to 5 μm, and even more preferably 0.6 to 4 μm. In this specification, the average particle size of the lubricant can be determined by observing 10 or more particles with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to measure the particle diameters and then averaging the measured values. In the case of non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0046] The content of the lubricant in the polyester film is not particularly limited, but is usually 0.001% by mass or more, preferably 0.004% by mass or more, more preferably 0.008% by mass or more, and even more preferably 0.01% by mass or more, relative to the total mass of the polyester film. The content of the lubricant is 3% by mass or less, preferably 1.5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.7% by mass or less. The content of the lubricant ranges from 0.001 to 3% by mass, preferably 0.004 to 1.5% by mass, more preferably 0.008 to 1% by mass, and even more preferably 0.01 to 0.7% by mass, relative to the total mass of the polyester film.

[0047] Furthermore, amide-based lubricants can be suitably used as the lubricant. Examples include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides. Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide. Examples of substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide. Examples of methylolamides include methylol stearic acid amide. Examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, etc. Examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, etc. Examples of fatty acid ester amides include stearamidoethyl stearate, etc. Examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, etc. These may be used alone or in combination of two or more.

[0048] When a lubricant is present on the surface of the polyester film, the amount of the lubricant is not particularly limited, but for example, about 3 mg / m 2 or more, preferably about 4 mg / m 2 Above, about 5mg / m 2The amount of lubricant present on the surface of the polyester film is, for example, about 15 mg / m 2 or less, preferably about 14 mg / m 2 Below, about 10mg / m 2 The preferred range of the amount of lubricant present on the surface of the base layer 1 is 3 to 15 mg / m 2 Degree, 3-14mg / m 2 Degree, 3-10mg / m 2 Degree, 4-15mg / m 2 Degree, 4-14mg / m 2 degree, 4-10mg / m 2 degree, 5-15mg / m 2 Degree, 5-14mg / m 2 degree, 5-10mg / m 2 The lubricant present on the surface of the polyester film may be a lubricant exuded from a resin constituting the polyester film, or a lubricant applied to the surface of the base layer 1.

[0049] The present polyester film may be composed of a single layer or a laminate of two or more layers, and preferably a laminate of three or more layers. The upper limit of the number of layers is not particularly limited, but is preferably about 10 or less. Examples of the present polyester film composed of a laminate of two or more layers include layer structures such as "first layer (surface layer) / second layer (surface layer)" and "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)." Among these, from the viewpoint of achieving both high formability and heat resistance, a present polyester film composed of three layers, i.e., "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," is preferred. When the polyester film has a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)" structure, the second layer (intermediate layer) is preferably thicker than the first layer (surface layer), the second layer (intermediate layer) is preferably thicker than the third layer (surface layer), and the second layer (intermediate layer) is more preferably thicker than the first layer (surface layer) and the third layer (surface layer). From the viewpoint of achieving both formability and heat resistance, the thickness ratio of each layer (first layer (surface layer):second layer (intermediate layer):third layer (surface layer)) is preferably 1.0-1.6:8.0-12:1.0-1.6, more preferably 1.0-1.5:8.5-11.5:1.0-1.5, and even more preferably 1.0-1.4:9.0-11.0:1.0-1.4.

[0050] When the polyester film is a laminate of two or more layers, it is preferable that the material composition of one surface layer is different from the material composition of at least one of the other layers.When the polyester film is a laminate of two or more layers, it is preferable that the material composition of one surface layer is different from the material composition of each of the other layers.

[0051] That is, for example, when the present polyester film is a laminate including one surface layer, the other surface layer, and one or more other layers located between the surface layers (layers of the laminate excluding both surface layers), it is preferable that the material composition of at least one of the other layers is different from the material composition of the one surface layer, and it is also preferable that the material composition of all of the other layers is different from the material composition of the one surface layer, and it is more preferable that the material composition of all of the other layers is different from the material composition of the one surface layer and the other surface layer. Furthermore, when the present polyester film is a laminate including one surface layer, the other surface layer, and one or more other layers located between the surface layers (layers of the laminate excluding both surface layers), it is even more preferable that the material composition of all of the other layers is different from the material composition of the one surface layer and the other surface layer, and that the material composition of the one surface layer and the other surface layer is the same.

[0052] Furthermore, when the present polyester film is a laminate of two or more layers, the material composition forming one surface layer may be different from the material composition forming the other surface layer. That is, when the present polyester film has a two-layer structure of "first layer (surface layer) / second layer (surface layer)," it is preferably a two-type two-layer structure. Specifically, it is preferable that the present polyester film contains two layers, and the layers are formed from two types of material compositions, with the material compositions forming the first layer (surface layer) and the second layer (surface layer) being different.

[0053] Furthermore, when the polyester film has a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)" structure, it is preferable that the material composition of the second layer (intermediate layer) is different from the material composition of the first layer (surface layer), and it is preferable that the material composition of the second layer (intermediate layer) is different from the material composition of the third layer (surface layer). It is more preferable that the material composition of the second layer (intermediate layer) is different from the material composition of the first layer (surface layer) and the third layer (surface layer). It is even more preferable that the material composition of the second layer (intermediate layer) is different from the material composition of the first layer (surface layer) and the third layer (surface layer), and that the material composition of the first layer (surface layer) and the third layer (surface layer) is the same. Furthermore, when the polyester film has a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)" structure, it is preferable that it has a two-type three-layer structure. Specifically, it is preferred that the polyester film contains three layers, the layers are made of two different material compositions, and the first layer (surface layer) and the third layer (surface layer) are made of the same material composition.

[0054] The phrase "different material compositions" means that the material compositions are not the same or are not substantially the same. "Not substantially the same" means that, when comparing the components constituting each material, the difference in the content of each component exceeds ±1% by mass, and / or, if different components are contained, the total content of the different components is 2% by mass or more relative to the total material.

[0055] When the polyester film is a monolayer, the mass ratio (PET / PBT) of the entire monolayer is preferably within the above range. When the polyester film is a laminate, the mass ratio (PET / PBT) of the entire laminate is preferably within the above range. When the polyester film is a laminate, the mass ratio (PET / PBT) of some of the layers constituting the laminate may be outside the above range, or the mass ratio (PET / PBT) of all of the layers constituting the laminate may be within the above range. The polyester film, which is composed of two or more layers, may be a laminate formed by co-extrusion of specified raw materials, or may be a laminate formed by laminating monolayer polyester films with an adhesive or the like. The polyester film, which is composed of two or more layers, may have a structure in which the polyester layers constituting each layer are in direct contact with each other, or may have a structure in which an adhesive layer is provided between the polyester layers constituting each layer. Specifically, for example, in a layer structure such as "first layer (surface layer) / second layer (surface layer)" or "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," the laminate may be a laminate in which the first layer (surface layer) and the second layer (surface layer) are in direct contact, a laminate in which one surface of the second layer (intermediate layer) is in direct contact with the first layer (surface layer) and the other surface of the second layer (surface layer) is in direct contact with the third layer (surface layer), a laminate in which an adhesive layer is provided between the first layer (surface layer) and the second layer (surface layer), or a laminate in which an adhesive layer is provided between one surface of the second layer (intermediate layer) and the first layer (surface layer) and an adhesive layer is provided between the other surface of the second layer (surface layer) and the third layer (surface layer). The adhesive layer is not particularly limited as long as it can bond the layers together, and can be appropriately selected from the adhesives exemplified for the first adhesive layer 2, second adhesive layer 4, and third adhesive layer described below.

[0056] In a preferred embodiment of the present polyester film, the polyester film is a laminate of two or more layers. From the viewpoint of effectively suppressing adhesion to a heat seal bar used for heat sealing, the content of polyethylene terephthalate in at least one or both surface layers is preferably 65% ​​by mass or more, 66% by mass or more, or 67% by mass or more, more preferably 68% by mass or more, 69% by mass or more, and even more preferably 70% by mass or more, or 71% by mass or more, based on the total amount of material constituting the surface layers. Alternatively, the content may be 100% by mass, but is preferably 97% by mass or less, 93% by mass or less, 90% by mass or less, 85% by mass or less, or 83% by mass or less, more preferably 82% by mass or less, and even more preferably 80% by mass or less. The content of polyethylene terephthalate in the surface layer is preferably 65 to 85% by mass, 66 to 85% by mass, more preferably 68 to 82% by mass, and even more preferably 70 to 80% by mass.

[0057] In an embodiment of the present polyester film, from the viewpoint of improving heat resistance to suppress deterioration of surface appearance due to surface whitening during heat fusion and suppressing adhesion of the laminate to a heat seal bar used for heat fusion, the present polyester film is composed of a laminate of two or more layers, and the present polyester film has a surface layer, an intermediate layer, and a surface layer in this order. Preferably, at least one or both surface layers contain polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10 (polyethylene terephthalate / polybutylene terephthalate), more preferably about 100 / 0 to 91 / 9, and even more preferably about 100 / 0 to 92 / 8. Furthermore, it is preferable that the surface layer is present on the outermost layer side of the packaging material for an electricity storage device.

[0058] In an embodiment of the present polyester film, the improved heat resistance prevents deterioration of the surface appearance due to surface whitening during heat fusion and prevents the laminate from adhering to a heat seal bar used for heat fusion. For this purpose, the polyester film is composed of two or more laminate layers, and the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order. The content of polyethylene terephthalate in at least one or both surface layers is preferably 65% ​​by mass or more, 66% by mass or more, 67% by mass or more, more preferably 68% by mass or more, 69% by mass or more, even more preferably 70% by mass or more, 71% by mass or more, based on the total amount of material constituting the surface layer. The content of polyethylene terephthalate in the surface layer is preferably 85% by mass or less, 83% by mass or less, more preferably 82% by mass or less, and even more preferably 80% by mass or less. The content of polyethylene terephthalate in the surface layer is preferably 65 to 85% by mass, 66 to 85% by mass, more preferably 68 to 82% by mass, and even more preferably 70 to 80% by mass.

[0059] In an embodiment of the present polyester film, from the viewpoint of improving heat resistance to suppress deterioration of surface appearance due to surface whitening during heat fusion and suppressing adhesion of the laminate to a heat seal bar used for heat fusion, in the present polyester film composed of a laminate of two or more layers, the polyethylene terephthalate content in one surface layer is preferably higher than the polyethylene terephthalate content in at least one of the other layers, and more preferably higher than the polyethylene terephthalate content in all of the other layers. Furthermore, the surface layer with the higher polyethylene terephthalate content is preferably located on the outermost layer side of the packaging material for an electrical storage device. Specifically, for example, when the present polyester film has a two-layer structure of "first layer (surface layer) / second layer (surface layer)," the polyethylene terephthalate content in one surface layer is preferably higher than the polyethylene terephthalate content in the other surface layer.

[0060] In the present polyester film having a surface layer, an intermediate layer and another surface layer in this order, it is preferable that the polyethylene terephthalate content in at least one or both of the surface layers is higher than the polyethylene terephthalate content in the intermediate layer.

[0061] That is, in the present polyester film composed of a laminate of two or more layers, the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting one surface layer of the polyester film is preferably greater than the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting at least one of the other layers, or the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting all of the other layers. For example, the difference between the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting one surface layer of the polyester film and the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting each of the other layers (the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting the surface layer minus the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting each of the other layers) is, for example, about 3 to 30 mass %, preferably about 5 to 25 mass %, and more preferably about 10 to 20 mass %.

[0062] Furthermore, in the present polyester film having a surface layer, an intermediate layer, and another surface layer in this order, the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting one surface layer of the polyester film is preferably greater than the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting the intermediate layer. For example, the difference between the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting one surface layer of the polyester film and the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting the intermediate layer (the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting the surface layer - the content (mass %) of polyethylene terephthalate relative to the total amount of materials constituting the intermediate layer) is, for example, about 3 to 30 mass %, preferably about 5 to 25 mass %, and more preferably about 10 to 20 mass %.

[0063] When the present polyester film is composed of a laminate of two or more layers, or when it is composed of a laminate having a surface layer, an intermediate layer, and another surface layer in this order, particularly when the compositions of the materials constituting each layer are different, or when the polyethylene terephthalate content of the surface layer is higher than the polyethylene terephthalate content of at least one of the other layers, particularly when the polyethylene terephthalate content of the surface layer is higher than the polyethylene terephthalate content of the intermediate layer, it is not easy to adjust various tensile properties such as the tensile breaking elongation to within the desired range. However, through extensive studies by the present inventors, it has become possible to control various tensile properties to within the desired range by appropriately adjusting and setting, as described below, for example, the mass ratio of polyethylene terephthalate to polybutylene terephthalate, the stretch ratio during film production, the preheating / stretching temperature, the heat setting temperature, etc. Furthermore, when the polyester film is composed of a laminate of two or more layers, or when it is composed of a laminate having a surface layer, an intermediate layer and another surface layer in that order, particularly when the compositions of the materials constituting each layer are different, or further when the polyethylene terephthalate content of the surface layer is higher than the polyethylene terephthalate content of at least one of the other layers, particularly when the polyethylene terephthalate content of the surface layer is higher than the polyethylene terephthalate content of the intermediate layer, it becomes easier for the packaging material to achieve both excellent formability and excellent heat resistance that can withstand heat fusion.

[0064] The thickness (total thickness) of the polyester film is not particularly limited, but is, for example, about 4 μm or more, for example, about 6 μm or more, preferably about 8 μm or more, more preferably about 10 μm or more, even more preferably about 12 μm or more, or about 15 μm or more. The thickness (total thickness) of the polyester film is, for example, about 100 μm or less, for example, about 60 μm or less, for example, about 40 μm or less, preferably about 30 μm or less, more preferably about 28 μm or less, even more preferably about 26 μm or less. The thickness (total thickness) of the polyester film may range, for example, from about 4 to 100 μm, from about 6 to 100 μm, from about 8 to 100 μm, from about 10 to 100 μm, from about 12 to 100 μm, from about 15 to 100 μm, from about 4 to 60 μm, from about 6 to 60 μm, from about 8 to 60 μm, from about 10 to 60 μm, from about 12 to 60 μm, from about 15 to 60 μm, from about 4 to 40 μm, from about 6 to 40 μm, from about 8 to 40 μm, from about 10 to 40 μm, from about 12 to 4 Preferred thicknesses are about 0 μm, about 15 to 40 μm, about 4 to 30 μm, about 6 to 30 μm, about 8 to 30 μm, about 10 to 30 μm, about 12 to 30 μm, about 15 to 30 μm, about 4 to 28 μm, about 6 to 28 μm, about 8 to 28 μm, about 10 to 28 μm, about 12 to 28 μm, about 15 to 28 μm, about 4 to 26 μm, about 6 to 26 μm, about 8 to 26 μm, about 10 to 26 μm, about 12 to 26 μm, and about 15 to 26 μm. When the polyester film is a laminate of two or more layers, the thickness of the resin film constituting each layer is not particularly limited, but is, for example, about 1 μm or more, preferably about 1.5 μm or more, and, for example, about 25 μm or less, preferably about 22 μm or less. The thickness of the resin film constituting each layer is, for example, about 1 to 25 μm, preferably about 1.5 to 22 μm. Specifically, although not particularly limited, in the case of the present polyester film composed of three layers of "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)", it is preferable that the first layer (surface layer) and the third layer (surface layer) have thicknesses of 1 μm to 2.8 μm and 1.8 μm to 2.6 μm, respectively, and the second layer (intermediate layer) have thicknesses of 15 μm to 23 μm and 18 μm to 22 μm.

[0065] Furthermore, when the present polyester film is a laminate of two or more layers, it is preferable that the laminate has two layers with different properties. Such a laminate allows each layer to have different characteristics, thereby achieving multifunctionality. Specifically, although not particularly limited, for example, in the case of the present polyester film consisting of a three-layer laminate formed by laminating a surface layer, an intermediate layer, and another surface layer in this order, one or both of the surface layers may contain inorganic particles such as silica or organic particles, or additives such as the lubricant described above, so that the surface layer and the intermediate layer have different properties, thereby achieving multifunctionality.

[0066] Furthermore, a coating layer may be further formed on the surface of the present polyester film from the viewpoint of adhesiveness, printability, etc. Although not particularly limited, for example, a coating layer can be formed on the surface of the present polyester film that is located on the barrier layer 5 side, more specifically, for example, on the surface of the present polyester film that is located on the first adhesive layer 2 side, thereby improving interlayer adhesion. The thickness of such a coating layer is, for example, about 0.01 to 1.0 μm, and the coating amount is 0.005 to 1 g / m 2 and preferably 0.01 to 0.6 g / m 2 More preferably, 0.02 to 0.3 g / m 2 Such a coating layer can be formed, for example, from an adhesive such as the adhesive exemplified for the first adhesive layer 2 described below.

[0067] Furthermore, although not particularly limited, a coating layer can be formed on, for example, the surface of the present polyester film opposite the barrier layer 5, more specifically, for example, the surface of the present polyester film opposite the first adhesive layer 2, thereby improving printability, etc. Furthermore, it can improve heat resistance and make it less likely that problems such as deterioration of the surface appearance due to surface whitening during heat fusion or fusion of the laminate to the heat seal bar used for heat fusion occur. The thickness of such a coating layer is, for example, about 0.01 to 0.7 μm, preferably about 0.01 to 0.4 μm, and more preferably about 0.1 to 0.2 μm. The coating amount of such a coating layer is, for example, 0.005 to 1 g / m 2 about 0.01 to 0.6 g / m2 about 0.02 to 0.3 g / m 2 about 0.03 to 0.1 g / m 2 That's about it.

[0068] Such a coating layer is not particularly limited, and can be formed from various synthetic resins such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, polyolefin, acid-modified polyolefin, polyester, epoxy resin, phenolic resin, fluororesin, cellulose ester, polyurethane, acrylic resin, polyamide, etc. These may be used alone or in combination of two or more. Furthermore, the coating layer may contain the above-mentioned lubricant, etc., as needed, to improve slip properties.

[0069] When a coating layer is formed for the purpose of improving heat resistance, it is preferable that the coating layer contains a release agent and a crosslinking agent. There are no particular limitations on the release agent, and conventionally known compounds can be used. Examples of the release agent include long-chain alkyl group-containing compounds, waxes, fluorine compounds, and silicone compounds. Among these, at least one of long-chain alkyl group-containing compounds and waxes is preferred, and long-chain alkyl group-containing compounds are more preferred. The release agent may be used alone or in combination of two or more types.

[0070] A long-chain alkyl group-containing compound is a compound having a linear or branched alkyl group with a carbon number of typically 6 or more, preferably 8 or more, and more preferably 12 or more. Examples of alkyl groups include hexyl, octyl, decyl, lauryl, octadecyl, and behenyl. Examples of compounds having an alkyl group include various long-chain alkyl group-containing polymeric compounds, long-chain alkyl group-containing amine compounds, long-chain alkyl group-containing ether compounds, and long-chain alkyl group-containing quaternary ammonium salts. In consideration of heat resistance and stain resistance, polymeric compounds are preferred. Furthermore, from the viewpoint of effectively obtaining mold releasability, polymeric compounds having a long-chain alkyl group in the side chain are more preferred.

[0071] A polymer compound having a long-chain alkyl group in its side chain can be obtained by reacting a polymer having a reactive group with a compound having an alkyl group capable of reacting with the reactive group. Examples of the reactive group include a hydroxyl group, an amino group, a carboxyl group, and an acid anhydride. Examples of compounds having these reactive groups include polyvinyl alcohol, polyethyleneimine, polyethyleneamine, reactive group-containing polyester resins, and reactive group-containing poly(meth)acrylic resins. Among these, polyvinyl alcohol is preferred in terms of releasability and ease of handling.

[0072] Examples of compounds having an alkyl group capable of reacting with the reactive group include long-chain alkyl group-containing isocyanates such as hexyl isocyanate, octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, and behenyl isocyanate, long-chain alkyl group-containing acid chlorides such as hexyl chloride, octyl chloride, decyl chloride, lauryl chloride, octadecyl chloride, and behenyl chloride, long-chain alkyl group-containing amines, and long-chain alkyl group-containing alcohols. Among these, in consideration of releasability and ease of handling, long-chain alkyl group-containing isocyanates are preferred, and octadecyl isocyanate is particularly preferred.

[0073] Furthermore, polymeric compounds having long-chain alkyl groups in their side chains can also be obtained by polymerizing long-chain alkyl (meth)acrylates or copolymerizing long-chain alkyl (meth)acrylates with other vinyl group-containing monomers. Examples of long-chain alkyl (meth)acrylates include hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, and behenyl (meth)acrylate.

[0074] In addition to the long-chain alkyl group-containing compound, multiple types of conventionally known release agents may also be used in combination. Examples of conventionally known release agents include waxes, fluorine compounds, and silicone compounds. However, from the viewpoint of oligomer precipitation, the coating layer of the present invention is desirably formed with a non-silicone release agent. "Formed with a non-silicone release agent" means that the silicone compound content of the coating layer is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and most preferably not intentionally contained. Even if silicone compounds are not actively used, there is a possibility of contamination from foreign matter or dirt adhering to the film production line or equipment being mixed in.

[0075] The silicone compound is a compound having a silicone structure in the molecule, and examples thereof include silicone emulsion, acrylic-grafted silicone, silicone-grafted acrylic, amino-modified silicone, perfluoroalkyl-modified silicone, and alkyl-modified silicone.

[0076] The content of the release agent is not particularly limited, but from the viewpoint of release performance and strength, it is, for example, 5 to 97% by mass, preferably 10 to 95% by mass, more preferably 20 to 90% by mass, even more preferably 30 to 80% by mass, and still more preferably 40 to 70% by mass, based on the total non-volatile components of the coating layer.

[0077] When a long-chain alkyl group-containing compound is used as the release agent, its content is not particularly limited. From the viewpoints of release performance, strength, and heat resistance, the content is, for example, preferably 30 to 95 mass %, more preferably 40 to 90 mass %, even more preferably 45 to 85 mass %, and particularly preferably 50 to 80 mass %, based on the total non-volatile components of the coating layer.

[0078] The crosslinking agent can improve the strength of the coating layer, adhesion to the substrate, and heat resistance. Examples of crosslinking agents include melamine compounds, isocyanate compounds, oxazoline compounds, epoxy compounds, and carbodiimide compounds. Among these crosslinking agents, it is preferable to use melamine compounds or isocyanate compounds from the viewpoint of good coating film strength. Furthermore, from the viewpoint of excellent release properties of the coating layer, melamine compounds are preferred, and from the viewpoint of excellent heat resistance of the coating layer, isocyanate compounds are particularly preferred. Furthermore, two or more of these crosslinking agents may be used in combination.

[0079] The melamine compound refers to a compound having a melamine skeleton within the compound. Examples include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures thereof. Examples of alkylolation include methylolation, ethylolation, isopropylolation, n-butylolation, and isobutyrolation. Among these, methylolation is preferred from the viewpoint of reactivity. Furthermore, alcohols used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. From the viewpoint of improving coating film strength and improving adhesion between the coating layer and the polyester film, a partially etherified alkylolated melamine derivative is preferred, and an alkylol etherified with methyl alcohol is more preferred. Therefore, a more preferred form is a partially etherified melamine having a methylol group and a methoxymethyl group. The etherified alkylol group is preferably 0.5 to 5 equivalents, and more preferably 0.7 to 3 equivalents, relative to the unetherified alkylol group. The melamine compound may be a monomer or a dimer or higher polymer, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

[0080] The isocyanate compound is a compound having an isocyanate derivative structure, typified by a blocked isocyanate having a structure in which the isocyanate group of an isocyanate compound precursor is protected with a blocking agent. Examples of isocyanates include aliphatic isocyanate compounds, alicyclic isocyanate compounds, and aromatic isocyanate compounds. From the viewpoint of being able to react more highly and improving the heat resistance of the coating layer, these isocyanate compounds are more preferably compounds having multiple isocyanate groups, i.e., polyisocyanate compounds. Furthermore, when using an aqueous coating liquid, blocked isocyanates are more preferably used.

[0081] Examples of aliphatic polyisocyanate compounds include polyisocyanate compounds derived from aliphatic diisocyanates such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane and lysine diisocyanate, lysine triisocyanate, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, bis(2-isocyanatoethyl)2-isocyanatoglutarate, and compounds derived from these isocyanate compounds. Among these, hexamethylene diisocyanate is preferred because of its ease of industrial availability.

[0082] Examples of alicyclic polyisocyanate compounds include isophorone diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, hydrogenated xylylene diisocyanate, and compounds derived from these isocyanate compounds. Among these, isophorone diisocyanate is preferred in terms of weather resistance and ease of industrial availability.

[0083] Examples of aromatic polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and compounds derived from these isocyanate compounds.

[0084] Among these polyisocyanate compounds, aliphatic polyisocyanate compounds and alicyclic polyisocyanate compounds are preferred because of their excellent weather resistance. Furthermore, among the aliphatic polyisocyanate compounds, aliphatic polyisocyanate compounds derived from aliphatic diisocyanates are preferred. Among these, hexamethylene diisocyanate is particularly preferred. These isocyanate compounds may be used alone or in combination of two or more.

[0085] The blocked polyisocyanate compound can be synthesized by reacting the isocyanate group of the polyisocyanate compound with a blocking agent.

[0086] Examples of blocking agents include active methylene-based, oxime-based, pyrazole-based, alcohol-based, alkylphenol-based, phenol-based, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, amine-based, imine-based, and bisulfite-based blocking agents. Among these, active methylene-based blocking agents are preferred, particularly from the viewpoint of being less susceptible to changes in release properties after heating. Furthermore, two or more of these blocking agents may be used in combination.

[0087] Examples of active methylene-based blocking agents include isobutanoyl acetate, n-propanoyl acetate, n-butanoyl acetate, n-pentanoyl acetate, n-hexanoyl acetate, 2-ethylheptanoyl acetate, malonic acid ester, acetoacetate, acetylacetone, etc. Among these, isobutanoyl acetate, n-propanoyl acetate, n-butanoyl acetate, n-pentanoyl acetate, n-hexanoyl acetate, and 2-ethylheptanoyl acetate are preferred, more preferably isobutanoyl acetate, n-propanoyl acetate, and n-pentanoyl acetate, and even more preferably isobutanoyl acetate, in terms of excellent low-temperature curing properties and storage stability in the presence of water. More specifically, examples of isobutanoyl acetate esters include methyl isobutanoyl acetate, ethyl isobutanoyl acetate, n-propyl isobutanoyl acetate, isopropyl isobutanoyl acetate, n-butyl isobutanoyl acetate, isobutyl isobutanoyl acetate, t-butyl isobutanoyl acetate, n-pentyl isobutanoyl acetate, n-hexyl isobutanoyl acetate, 2-ethylhexyl isobutanoyl acetate, phenyl isobutanoyl acetate, and benzyl isobutanoyl acetate. Among these, methyl isobutanoyl acetate and ethyl isobutanoyl acetate are preferred. Examples of n-propanoyl acetate esters include methyl n-propanoyl acetate, ethyl n-propanoyl acetate, isopropyl n-propanoyl acetate, n-butyl n-propanoyl acetate, and t-butyl n-propanoyl acetate. Among these, methyl n-propanoyl acetate and ethyl n-propanoyl acetate are preferred. Examples of n-pentanoyl acetate esters include methyl n-pentanoyl acetate, ethyl n-pentanoyl acetate, isopropyl n-pentanoyl acetate, n-butyl n-pentanoyl acetate, t-butyl n-pentanoyl acetate, etc. Among these, methyl n-pentanoyl acetate and ethyl n-pentanoyl acetate are preferred.

[0088] In the active methylene-blocked isocyanate compound used in the coating layer, the active methylene-based blocking agents shown above can be used alone or in combination of two or more. As the active methylene-based blocking agent to be used in combination, dimethyl malonate and diethyl malonate are preferred in terms of excellent low-temperature curing properties and excellent heat resistance of the formed coating layer.

[0089] Examples of oxime-based blocking agents include formaldoxime, acetaldoxime, acetoneoxime, methylethylketoxime, and cyclohexanoneoxime.

[0090] Examples of pyrazole-based blocking agents include pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, etc. Examples of alcohol-based blocking agents include methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, etc.

[0091] Examples of alkylphenol-based blocking agents include monoalkylphenols such as n-propylphenol, isopropylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, and n-nonylphenol; and dialkylphenols such as di-n-propylphenol, diisopropylphenol, isopropyl cresol, di-n-butylphenol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, and di-n-nonylphenol.

[0092] Examples of phenol-based blocking agents include phenol, cresol, ethylphenol, styrenated phenol, and hydroxybenzoic acid esters.

[0093] Examples of mercaptan-based blocking agents include butyl mercaptan and dodecyl mercaptan.

[0094] Examples of the acid amide blocking agent include acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, and γ-butyrolactam.

[0095] Examples of the acid imide-based blocking agent include succinimide and maleimide.

[0096] Examples of imidazole-based blocking agents include imidazole and 2-methylimidazole.

[0097] Examples of urea-based blocking agents include urea, thiourea, and ethyleneurea.

[0098] Examples of amine-based blocking agents include diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, etc. Examples of imine-based blocking agents include ethyleneimine, polyethyleneimine, etc.

[0099] The blocked isocyanate compound used in the coating layer preferably contains a hydrophilic moiety. Examples of a method for adding a hydrophilic moiety to a blocked isocyanate compound include a method of reacting an isocyanate group of a precursor isocyanate compound with a hydrophilic compound having an active hydrogen.

[0100] Examples of hydrophilic compounds having active hydrogen that are used in the blocked isocyanate compound used in the coating layer include polyethylene glycol compounds, carboxylic acid group-containing compounds, sulfonic acid group-containing compounds, amine-containing compounds, etc. These hydrophilic compounds may be used alone or in combination of two or more.

[0101] Examples of polyethylene glycol compounds include monoalkoxypolyethylene glycol, polyethylene glycol, polyoxypropylene-polyoxyethylene copolymer diol, polyoxypropylene-polyoxyethylene block polymer diol, and the like. Among these, monoalkoxypolyethylene glycols such as monomethoxypolyethylene glycol and monoethoxypolyethylene glycol are particularly preferred.

[0102] The carboxylic acid group-containing compound may be a monohydroxycarboxylic acid, a dihydroxycarboxylic acid, or a derivative thereof, etc. Among the carboxylic acid group-containing compounds, a monohydroxycarboxylic acid or a dihydroxycarboxylic acid is preferred, and a monohydroxycarboxylic acid is more preferred.

[0103] Specific examples of the carboxylic acid group-containing compound include hydroxypivalic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and derivatives thereof, such as polycaprolactone diol and polyether polyol, which are prepared using these as initiators, and salts thereof.

[0104] Examples of sulfonic acid group-containing compounds include aminoethylsulfonic acid, ethylenediamino-propyl-β-ethylsulfonic acid, 1,3-propylenediamine-β-ethylsulfonic acid, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, and salts thereof.

[0105] Examples of the amine-containing compound include hydroxyl group-containing amino compounds, such as dimethylethanolamine and diethylethanolamine.

[0106] The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferred. The oxazoline compound can be prepared by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These can be used alone or in combination of two or more.

[0107] Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially.

[0108] The other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, and a cyclohexyl group); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylic acid esters such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; Examples of suitable monomers include unsaturated amides such as acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide (the alkyl group can be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. These monomers can be used alone or in combination.

[0109] The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensation products of epichlorohydrin with a hydroxyl group or an amino group of ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc., polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc.

[0110] Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, and ethylene glycol diglycidyl ether. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether. Examples of glycidyl amine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0111] The content of the crosslinking agent is not particularly limited, but from the viewpoint of release performance and strength, it is, for example, 3 to 80 mass %, preferably 5 to 70 mass %, more preferably 10 to 60 mass %, and even more preferably 15 to 50 mass %, based on the total non-volatile components of the coating layer.

[0112] When a melamine compound is used as the crosslinking agent, its content is not particularly limited, but from the viewpoints of mold release performance, strength, and heat resistance, it is preferably 5 to 70 mass %, more preferably 10 to 60 mass %, and particularly preferably 15 to 50 mass %, based on the total non-volatile components of the coating layer.

[0113] In an embodiment of the present polyester film, from the viewpoints of improving heat resistance, suppressing deterioration of surface appearance due to surface whitening during heat fusion, and effectively suppressing fusion to a heat seal bar used for heat fusion, the coating layer preferably contains, for example, a long-chain alkyl group-containing compound and a melamine compound, and more preferably the coating layer is mainly composed of the long-chain alkyl group-containing compound and the melamine compound. That is, the total content of the long-chain alkyl group-containing compound and the melamine compound relative to the total nonvolatile components of the coating layer is 60% by mass or more, preferably 65% ​​by mass or more, more preferably 70% by mass or more, even more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass.

[0114] From the same viewpoint, the coating layer preferably contains the long-chain alkyl group-containing compound and the melamine compound in a mass ratio of, for example, 95 / 5 to 5 / 95 (long-chain alkyl group-containing compound / melamine compound), more preferably 90 / 10 to 10 / 90, even more preferably 80 / 20 to 20 / 80, and particularly preferably 70 / 30 to 30 / 70.

[0115] From the same viewpoint, a preferred embodiment of the present packaging material is a packaging material for an electricity storage device, which is composed of a laminate that uses the present polyester film having a coating layer containing a long-chain alkyl group-containing compound and a melamine compound as a base layer, and that includes the base layer, a barrier layer, and a heat-sealable resin layer in this order, and is used to house the electricity storage device on the heat-sealable resin layer side.

[0116] The method for forming the coating layer is not particularly limited, and any conventionally known method can be used as appropriate, but it is preferable to form the coating layer by applying a predetermined material to a polyester film and, if necessary, performing treatments such as drying, curing, heat treatment, etc. The coating method is not particularly limited, and any conventionally known coating method can be used, such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc.

[0117] The polyester film is preferably a stretched film, such as a uniaxially stretched film or a biaxially stretched film, with a biaxially stretched film being preferred. Examples of stretching methods for forming a biaxially stretched film include sequential biaxial stretching, inflation, and simultaneous biaxial stretching, with sequential biaxial stretching being preferred. The biaxially stretched film refers to a film in which the refractive index in the longitudinal direction (MD) and transverse direction (TD) of the film is higher than the refractive index in the thickness direction, and is typically obtained by stretching the film in the longitudinal and transverse directions.

[0118] When the polyester film is a biaxially stretched film, the product of the stretch ratio in the width direction (TD) and the stretch ratio in the longitudinal direction (MD) of the polyester film (i.e., the stretch ratio in the width direction (TD) × the stretch ratio in the longitudinal direction (MD)) is preferably more than 15.5, more preferably 15.6 or more, and even more preferably 15.7 or more. The upper limit of the product of the stretch ratio in the width direction (TD) and the stretch ratio in the longitudinal direction (MD) of the polyester film is not particularly limited, but may be, for example, 19.5 or less, 19.3 or less, 19.0 or less, or 18.7 or less.

[0119] When the polyester film is a biaxially stretched film, the difference between the stretch ratio in the width direction (TD) and the stretch ratio in the longitudinal direction (MD) of the polyester film (stretch ratio in the width direction - stretch ratio in the longitudinal direction) is preferably 0.3 or more, more preferably 0.4 or more, even more preferably 0.5 or more, and still more preferably 0.6 or more. The upper limit of the difference between the stretch ratio in the width direction and the stretch ratio in the longitudinal direction of the polyester film is not particularly limited, but may be, for example, 2.0 or less, 1.8 or less, 1.6 or less, or 1.4 or less.

[0120] When the present polyester film is a biaxially stretched film, the ratio of the stretching ratio in the width direction of the polyester film to the stretching ratio in the longitudinal direction (stretching ratio in the width direction / stretching ratio in the longitudinal direction) is preferably 1.2 or more and 1.7 or less, more preferably 1.2 or more and 1.6 or less.

[0121] The stretching ratio is determined, for example, in the longitudinal direction from the ratio of the film transport speed before stretching to the film transport speed after stretching, and in the width direction from the ratio of the film width before stretching to the film width after stretching.

[0122] The melting point (Tm) of the first run of the polyester film is not particularly limited, but from the viewpoint of heat resistance in practical use, it is, for example, 230°C or higher, preferably 235°C or higher, and more preferably 240°C or higher. The melting point (Tm) of the first run of the polyester film is preferably 250°C or lower, more preferably 248°C or lower. The melting point (Tm) of the first run of the polyester film is preferably in the range of 235 to 250°C, more preferably 240 to 248°C. The melting point (Tm) of the second run of the polyester film is not particularly limited, but from the viewpoint of heat resistance, it is, for example, 223°C or higher, preferably 228°C or higher, and more preferably 233°C or higher. The melting point (Tm) of the second run of the polyester film is preferably 247°C or lower, more preferably 245°C or lower. The melting point (Tm) of the present polyester film in the first run is preferably in the range of 228 to 245°C, more preferably 233 to 243°C. The melting point (Tm) is measured in accordance with JIS K7121 (2012) using a differential scanning calorimeter (DSC) under conditions of -70 to 280°C, a heating rate of 10°C / min, a holding time of 10 minutes, and a cooling rate of 600°C / min. The peak top value of the melting peak observed during the first heating (melting peak temperature) is defined as the melting point of the first run, and the peak top value of the melting peak observed during the second heating (reheating) (melting peak temperature) is defined as the melting point of the second run.

[0123] Furthermore, the present polyester film preferably has a single melting peak during temperature rise in the first run and / or second run (a melting peak during temperature rise in at least one of the first run and the second run) measured by differential scanning calorimetry, and preferably has a single melting peak during both the first run and the second run. Having a single melting peak makes the polyester film less likely to soften at low temperatures. Therefore, when used as an exterior material for an electrical storage device, deterioration of the exterior material is easily prevented even when the battery dissipates heat and the exterior material is heated. Furthermore, there is also the advantage that the film can be stably produced even at a high heat setting temperature in the manufacturing method described below. The polyester film can be adjusted to have a single melting peak by compatibilizing PBT and PET.

[0124] The phrase "one melting peak observed during heating by differential scanning calorimetry" means that the number of melting peaks observed during reheating is one, as measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121 (2012) under conditions of -70 to 280°C, a heating rate of 10°C / min, a holding time of 10 minutes, and a cooling rate of 600°C / min. The melting peak of the first run is preferably observed at its peak top in the range of 230 to 250°C, more preferably in the range of 235 to 248°C, and even more preferably in the range of 240 to 248°C. The melting peak of the second run is preferably observed at its peak top in the range of 223 to 247°C, more preferably in the range of 228 to 245°C, and even more preferably in the range of 233 to 243°C.

[0125] The glass transition temperature (Tg) of the present polyester film is not particularly limited, but is, for example, 60°C or higher, preferably 61°C or higher, and more preferably 62°C or higher. The glass transition temperature (Tg) of the present polyester film is, for example, preferably 72°C or lower, more preferably 70°C or lower. The glass transition temperature (Tg) of the present polyester film is preferably in the range of 61 to 72°C, more preferably 62 to 70°C. The glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121 (2012), 3.(3), under conditions of −70 to 280°C, a heating rate of 10°C / min, a holding time of 10 minutes, and a cooling rate of 600°C / min, and the midpoint glass transition temperature during the reheating process is used.

[0126] [Method for Producing the Present Polyester Film] A known film-forming method can be appropriately adopted as a method for producing a polyester film. For example, a film-forming raw material containing polyester and other raw materials is melted, formed into a sheet, and stretched to increase strength, etc., to produce a desired polyester film. Although not particularly limited, the following production conditions are preferred from the viewpoint of controlling the tensile yield stress, tensile elongation at break, tensile breaking stress, and stress-strain curve of the present polyester film within the above-mentioned preferred ranges.

[0127] For example, in the sequential biaxial stretching method, a film-forming material containing polyester and other materials is melt-extruded through a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched sheet. The extrusion temperature during melt extrusion through the die is preferably 270°C or higher, more preferably 275°C or higher, even more preferably 280°C or higher, and preferably 300°C or lower, more preferably 295°C or lower, and even more preferably 290°C or lower. The preferred range of the extrusion temperature during melt extrusion through the die is preferably 270 to 300°C, more preferably 275 to 295°C, and even more preferably 280 to 290°C. The temperature of the cooling roll is preferably 10°C or higher, more preferably 15°C or higher, even more preferably 20°C or higher, and preferably 40°C or lower, more preferably 35°C or lower, and even more preferably 30°C or lower. The preferred range of the temperature of the cooling roll is preferably 10 to 40°C, more preferably 15 to 35°C, and even more preferably 20 to 30°C. In order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method can be appropriately adopted.

[0128] The temperature conditions in the primary stretching step, i.e., the stretching step in the machine direction (MD) (longitudinal stretching step), are, for example, preferably 60° C. or higher, more preferably 62° C. or higher, even more preferably 64° C. or higher, and preferably 75° C. or lower, more preferably 74° C. or lower, and even more preferably 73° C. or lower. A preferred range for the temperature conditions in the stretching step in the machine direction (MD) (longitudinal stretching step) is 60 to 75° C., more preferably 62 to 74° C., and even more preferably 64 to 73° C. The stretch ratio in the stretching step in the machine direction (MD) (longitudinal stretching step) is, for example, preferably 3 times or higher, more preferably 3.3 times or higher, even more preferably 3.4 times or higher, and preferably 4.2 times or lower, more preferably 4 times or lower, and even more preferably 3.8 times or lower. The preferred range of the stretching ratio in the longitudinal direction (MD) stretching step (longitudinal stretching step) is 3 to 4.2 times, more preferably 3.3 to 4 times, and even more preferably 3.4 to 3.8 times. The temperature conditions in the secondary stretching step, i.e., the width direction (TD) stretching step (transverse stretching step), are, for example, preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 85°C or higher, and preferably 120°C or lower, more preferably 110°C or lower, and even more preferably 105°C or lower. The preferred range of the temperature conditions in the width direction (TD) stretching step (transverse stretching step) is preferably 70 to 120°C, more preferably 80 to 110°C, and even more preferably 85 to 105°C. The stretching ratio in the width direction (TD) stretching step (transverse stretching step) is, for example, preferably 3.5 times or more, more preferably 3.8 times or more, even more preferably 4 times or more, and is preferably 6 times or less, more preferably 5.5 times or less, even more preferably 5.2 times or less. The preferred range of the stretching ratio in the width direction (TD) stretching step (transverse stretching step) is preferably 3.5 to 6 times, more preferably 3.8 to 5.5 times, even more preferably 4 to 5.2 times.

[0129] The preheating temperature conditions after the primary stretching step and before the secondary stretching step are, for example, preferably 65° C. or higher, more preferably 70° C. or higher, even more preferably 75° C. or higher, and preferably 110° C. or lower, more preferably 105° C. or lower, even more preferably 100° C. or lower. A preferred range for the preheating temperature conditions is 65 to 110° C., more preferably 70 to 105° C., even more preferably 75 to 100° C. The preheating time is, for example, preferably about 1 to 12 seconds, more preferably about 2 to 11 seconds, and even more preferably about 3 to 10 seconds. Furthermore, after the secondary stretching step, the heat setting temperature conditions in the heat setting step, which is carried out under tension or relaxation of 10% or less, preferably 7% or less, are, for example, preferably 180°C or higher, more preferably 190°C or higher, even more preferably 195°C or higher, particularly preferably 200°C or higher, and preferably 240°C or lower, more preferably 230°C or lower, even more preferably 225°C or lower, particularly preferably 220°C or lower. The preferred range of the heat setting temperature conditions is 180 to 240°C, more preferably 190 to 230°C, even more preferably 195 to 225°C, and particularly preferably 200 to 220°C. The heat setting time is, for example, preferably about 3 to 15 seconds, more preferably about 4 to 14 seconds, and even more preferably about 5 to 13 seconds.

[0130] After the heat setting step, the film may be cooled in a cooling zone under a relaxation of 0 to 20%, 0.5 to 15%, preferably 1 to 10%, and more preferably 1.5 to 7%. The cooling temperature is, for example, preferably about 120 to 160°C, and more preferably about 130 to 150°C.

[0131] By setting the preheating temperature, stretching temperature, and stretch ratio conditions slightly lower than usual and the heat setting temperature slightly higher than usual, it becomes easy to control the tensile yield stress, tensile elongation at break, tensile stress at break, and stress-strain curve characteristics within preferred ranges. Furthermore, by controlling them in this manner, local stress concentration during molding is suppressed and stress uniformity is promoted, thereby achieving both excellent moldability and excellent heat resistance that can withstand heat fusion. This compatibility of excellent moldability and heat resistance becomes even more pronounced when laminated with a polyamide layer.

[0132] <First Adhesive Layer 2> The first adhesive layer 2 is a layer that may be optionally included in the packaging material, and is provided between the polyester film that constitutes the base layer 1 and a layer adjacent to it on the inner side to bond them together. For example, it is a layer provided between the polyester film that constitutes the base layer 1 and the polyamide film that constitutes the polyamide layer 3, or between the polyester film that constitutes the base layer 1 and the barrier layer 5. The adhesive used for the first adhesive layer 2 is not particularly limited as long as it can bond the polyester film to a layer adjacent to it on the inner side, such as the polyamide film that constitutes the polyamide layer 3, and may be any adhesive such as a chemical reaction type, a solvent evaporation type, a hot melt type, or a thermocompression type. It may also be a two-component curing adhesive (two-component adhesive), a one-component curing adhesive (one-component adhesive), or a resin that does not involve a curing reaction.

[0133] The adhesive component contained in the adhesive is not particularly limited, but examples thereof include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymer polyesters; polyethers; polyurethanes; epoxy resins; phenolic resins; polyamides such as nylon 6, nylon 66, nylon 12, and copolymer polyamides; polyolefin-based resins such as polyolefins, cyclic polyolefins, acid-modified polyolefins, and acid-modified cyclic polyolefins; polyvinyl acetate; cellulose; (meth)acrylic resins; polyimides; polycarbonates; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone resins. These may be used alone or in combination with two or more. Among these, polyurethane adhesives are preferred. Furthermore, these adhesive components can also be used in combination with a curing agent to increase adhesive strength. Examples of the curing agent include polyisocyanates, multifunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, and acid anhydrides. These may be used alone or in combination of two or more.

[0134] Examples of polyurethane adhesives include those containing a base agent containing a polyol compound and a curing agent containing an isocyanate compound. For example, two-component curing polyurethane adhesives are preferred, which use a polyol such as polyester polyol, polyether polyol, or acrylic polyol as the base agent and an aromatic or aliphatic polyisocyanate as the curing agent. Furthermore, it is preferred to use, as the polyol compound, a polyester polyol having hydroxyl groups on the side chain in addition to the terminal hydroxyl groups of the repeating unit.

[0135] The first adhesive layer 2 may also contain a colorant, a thermoplastic elastomer, a tackifier, a filler, etc., as long as the adhesiveness is not impaired. Known colorants such as pigments and dyes can be used. These may be used alone or in combination of two or more.

[0136] Examples of pigments include organic pigments such as azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigothioindigo-based, perinone-perylene-based, isoindolenine-based, and bezimidazolone-based pigments; inorganic pigments such as carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, and iron-based pigments; fine powder of mica, fish scale foil, etc. These may be used alone or in combination of two or more.

[0137] The average particle size of the pigment is not particularly limited and is, for example, about 0.05 to 5 μm, preferably about 0.08 to 2 μm. The average particle size of the pigment is the median diameter measured with a laser diffraction / scattering particle size distribution measuring device.

[0138] The content of the pigment in the first adhesive layer 2 is not particularly limited as long as it colors the exterior material, and is, for example, about 5 to 60% by mass, and preferably about 10 to 40% by mass.

[0139] The first adhesive layer 2 may be a single layer or a laminate of two or more layers. The thickness (total thickness) of the first adhesive layer 2 is not particularly limited, but is, for example, about 1 to 10 μm, or about 1 to 5 μm.

[0140] <Polyamide Layer 3> The polyamide layer 3 is a layer that may be optionally included in the packaging material, is provided for the purpose of exhibiting excellent formability, and is a layer that is laminated to the base material layer 1. The polyamide layer 3 may be a layer that is laminated to the base material layer 1, optionally via the first adhesive layer 2. The polyamide for constituting the polyamide layer 3 is not particularly limited, but from the viewpoint of achieving both the moldability and heat resistance of the exterior material, aliphatic polyamides such as nylon 12, nylon 46, a copolymer of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) containing structural units derived from terephthalic acid and / or isophthalic acid, polyamides containing aromatics such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); polyamides copolymerized with a lactam component or an isocyanate component such as 4,4'-diphenylmethane-diisocyanate, polyesteramide copolymers and polyetheresteramide copolymers which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; copolymers thereof, etc. These may be used alone or in combination of two or more.

[0141] From the viewpoint of achieving both formability and heat resistance of the packaging material, the polyamide layer 3 is preferably composed of a stretched film, and in particular, a biaxially stretched polyamide film, particularly a biaxially stretched nylon film. Stretched polyamide films can be produced by conventionally known methods, and examples of stretching methods for forming biaxially stretched polyamide films include sequential biaxial stretching, inflation, and simultaneous biaxial stretching, with sequential biaxial stretching being preferred.

[0142] The polyamide layer 3 may be composed of a single layer or a laminate of two or more layers. The thickness (total thickness) of the polyamide layer 3 is not particularly limited, but from the viewpoint of exhibiting excellent moldability, it is preferably about 30 μm or less, more preferably about 28 μm or less, even more preferably about 25 μm or less, and is about 1 μm or more, more preferably about 5 μm or more, and even more preferably about 10 μm or more. The thickness (total thickness) of the polyamide layer 3 preferably ranges from about 1 to 30 μm, more preferably from about 5 to 28 μm, and more preferably from about 10 to 25 μm.

[0143] From the viewpoint of further improving moldability, the thickness ratio of the base layer 1 to the polyamide layer 3 (base layer 1:polyamide layer 3) is preferably in the range of about 2:1 to 1:5, more preferably in the range of about 1.5:1 to 1:4, and even more preferably in the range of about 1:1 to 1:3.

[0144] <Second adhesive layer 4> The second adhesive layer 4 is a layer that may be optionally included in the packaging material, and is a layer provided between the polyamide film that constitutes the polyamide layer 3 and the metal foil or the like that constitutes the barrier layer 5, which will be described later, in order to bond these two. The second adhesive layer 4 is the same as the content described in the <First adhesive layer 2> section above, and for example, the adhesive used in the second adhesive layer 4 is not particularly limited as long as it can bond the polyamide film that constitutes the polyamide layer 3 and the metal foil or the like that constitutes the barrier layer 5, and can be appropriately selected from the adhesives exemplified for the first adhesive layer 2.

[0145] The second adhesive layer 4 may be a single layer or a laminate of two or more layers. The thickness (total thickness) of the second adhesive layer 4 is not particularly limited, but is, for example, about 1 to 10 μm, about 1.5 to 5 μm, or about 2 to 4 μm.

[0146] <Barrier Layer 5> The barrier layer 5 is a layer that has the function of preventing water vapor, oxygen, light, and the like from penetrating into the battery. The barrier layer 5 is preferably a metal layer, i.e., a layer formed of a metal. Examples of metals that constitute the barrier layer 5 include aluminum, stainless steel, and titanium. Of these, aluminum is preferred. The barrier layer 5 can be formed, for example, from a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film provided with any of these vapor deposition films. Of these, a metal foil is preferred, and an aluminum alloy foil or stainless steel foil is more preferred. Furthermore, from the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 5 during the production of this packaging material, it is more preferable that the barrier layer 5 be made of a soft aluminum alloy foil such as annealed aluminum (JIS H4160:1994 A8021H-O, JIS H4160:1994 A8079H-O, JIS H4000:2014 A8021P-O, JIS H4000:2014 A8079P-O).

[0147] The barrier layer 5 may be formed of a single layer or a laminate of two or more layers. The thickness (total thickness) of the barrier layer 5 is not particularly limited as long as it exhibits a barrier function against water vapor, etc., but is, for example, about 10 μm or more, preferably about 20 μm or more, more preferably about 30 μm or more, still more preferably about 35 μm or more, about 40 μm or more, about 45 μm or more, or about 55 μm or more, and is preferably about 200 μm or less, more preferably about 150 μm or less, even more preferably about 100 μm or less, and even more preferably about 85 μm or less, and preferred ranges are about 10 to 200 μm, about 20 to 150 μm, about 30 to 100 μm, about 35 to 85 μm, and about 45 to 85 μm.

[0148] Furthermore, from the viewpoints of stabilizing adhesion and preventing dissolution and corrosion, it is preferable that at least one surface, preferably both surfaces, of the barrier layer 5 be chemically treated. Here, chemical conversion treatment refers to a treatment for forming an acid-resistant coating on the surface of the barrier layer 5. The barrier layer 5 may be provided with an acid-resistant coating on one surface, on both surfaces, or without an acid-resistant coating. Examples of chemical conversion treatments include chromate treatments using chromium compounds such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetylacetate, chromium chloride, and potassium chromium sulfate; phosphate treatments using phosphate compounds such as sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid; and chromate treatments using aminated phenolic polymers having repeating units represented by the following general formulas (1) to (4). The aminated phenolic polymers may contain one type of repeating unit represented by the following general formulas (1) to (4) alone, or any combination of two or more types.

[0149]

[0150]

[0151]

[0152]

[0153] In the general formulas (1) to (4), X represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group, or a benzyl group. 1 and R 2 are the same or different and represent a hydroxyl group, an alkyl group, or a hydroxyalkyl group. 1 and R 2 Examples of the alkyl group represented by X include a linear or branched alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. 1 and R 2Examples of the hydroxyalkyl group represented by the formula (1) include a linear or branched alkyl group having 1 to 4 carbon atoms substituted with one hydroxyl group, such as a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group. 1 and R 2 The alkyl groups and hydroxyalkyl groups represented by the general formulas (1) to (4) may be the same or different. In the general formulas (1) to (4), X is preferably a hydrogen atom, a hydroxyl group, or a hydroxyalkyl group. The number average molecular weight of the aminated phenol polymer having repeating units represented by the general formulas (1) to (4) is preferably, for example, 500 to 1,000,000, and more preferably 1,000 to 20,000.

[0154] Another example of a chemical conversion treatment method for imparting corrosion resistance to the barrier layer 5 is to coat the surface of the barrier layer 5 with a dispersion of fine particles of a metal oxide such as aluminum oxide, titanium oxide, cerium oxide, or tin oxide, or barium sulfate, in phosphoric acid, followed by baking at 150°C or higher to form an acid-resistant coating on the surface of the barrier layer 5. A resin layer in which a cationic polymer is crosslinked with a crosslinking agent may be further formed on the acid-resistant coating. Examples of cationic polymers include polyethyleneimine, an ionic polymer complex composed of a polymer having polyethyleneimine and a carboxylic acid, a primary amine-grafted acrylic resin in which a primary amine is graft-polymerized onto an acrylic main skeleton, polyallylamine or a derivative thereof, and aminophenol. These may be used alone or in combination of two or more. Examples of crosslinking agents include compounds having at least one functional group selected from the group consisting of an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and silane coupling agents. These may be used alone or in combination of two or more.

[0155] As a specific method for providing the acid-resistant coating, for example, at least the inner layer surface of the aluminum alloy foil is first degreased by a well-known method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then the degreased surface is coated by a well-known coating method such as roll coating, gravure printing, or dipping with a treatment liquid (aqueous solution) mainly composed of a metal phosphate such as a chromium phosphate, titanium phosphate, zirconium phosphate, or zinc phosphate, or a mixture of these metal salts, or a treatment liquid (aqueous solution) mainly composed of a non-metal phosphate and a mixture of these non-metal salts, or a treatment liquid (aqueous solution) consisting of a mixture of any of these with a water-based synthetic resin such as an acrylic resin, a phenolic resin, or a urethane resin, to form the acid-resistant coating. For example, when treated with a chromium phosphate-based treatment solution, an acid-resistant coating film made of chromium phosphate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc. is formed, and when treated with a zinc phosphate-based treatment solution, an acid-resistant coating film made of zinc phosphate hydrate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc. is formed.

[0156] As another example of a specific method for providing an acid-resistant coating, for example, at least the inner layer side surface of the aluminum alloy foil is first degreased by a well-known treatment method such as alkali immersion, electrolytic cleaning, acid pickling, electrolytic pickling, or acid activation, and then the degreased surface is subjected to a well-known anodizing treatment, thereby forming an acid-resistant coating.

[0157] Other examples of acid-resistant coatings include phosphate-based and chromate-based coatings. Phosphate-based coatings include zinc phosphate, iron phosphate, manganese phosphate, calcium phosphate, and chromium phosphate, while chromate-based coatings include chromium chromate.

[0158] Other examples of acid-resistant coatings include those made of phosphates, chromates, fluorides, triazine thiol compounds, etc., which prevent delamination between the aluminum and the layer functioning as the substrate during embossing, prevent dissolution and corrosion of the aluminum surface, particularly of aluminum oxide present on the aluminum surface, due to hydrogen fluoride produced by the reaction of an electrolyte with water, and improve the adhesion (wettability) of the aluminum surface, preventing delamination between the layer functioning as the substrate and the aluminum during heat fusion, and in the case of embossed types, preventing delamination between the layer functioning as the substrate and the aluminum during press molding. Among the substances that form acid-resistant coatings, an aqueous solution composed of three components, phenolic resin, chromium (III) fluoride compound, and phosphoric acid, applied to the aluminum surface and then dried and baked is effective.

[0159] The acid-resistant coating may include a layer having cerium oxide, phosphoric acid or a phosphate, an anionic polymer, and a crosslinking agent that crosslinks the anionic polymer, and the phosphoric acid or phosphate may be blended in an amount of 1 to 100 parts by mass per 100 parts by mass of the cerium oxide. Preferably, the acid-resistant coating has a multilayer structure that further includes a layer having a cationic polymer and a crosslinking agent that crosslinks the cationic polymer.

[0160] Furthermore, the anionic polymer is preferably poly(meth)acrylic acid or a salt thereof, or a copolymer mainly composed of (meth)acrylic acid or a salt thereof, and the crosslinking agent is preferably at least one selected from the group consisting of a compound having any one of a functional group of an isocyanate group, a glycidyl group, a carboxyl group, and an oxazoline group, and a silane coupling agent.

[0161] The phosphoric acid or phosphate is preferably a condensed phosphoric acid or a condensed phosphate.

[0162] The chemical conversion treatment may be performed using only one type of chemical conversion treatment, or two or more types of chemical conversion treatments in combination. Furthermore, these chemical conversion treatments may be performed using one type of compound alone, or two or more types of compounds in combination. Among the chemical conversion treatments, chromate treatments and chemical conversion treatments combining a chromium compound, a phosphate compound, and an aminated phenol polymer are preferred. Among chromium compounds, chromic acid compounds are preferred.

[0163] Specific examples of acid-resistant coatings include those containing at least one of phosphate, chromate, fluoride, and triazine thiol. Acid-resistant coatings containing a cerium compound are also preferred. The cerium compound is preferably cerium oxide.

[0164] Specific examples of the acid-resistant coating include phosphate-based coatings, chromate-based coatings, fluoride-based coatings, and triazine thiol compound coatings. The acid-resistant coating may be one of these, or a combination of two or more. Furthermore, the acid-resistant coating may be formed by degreasing the chemically treated surface of the aluminum alloy foil, using a treatment solution consisting of a mixture of a metal phosphate and an aqueous synthetic resin, or a treatment solution consisting of a mixture of a non-metal phosphate and an aqueous synthetic resin.

[0165] The composition of the acid-resistant film can be analyzed by, for example, time-of-flight secondary ion mass spectrometry. Analysis of the composition of the acid-resistant film using time-of-flight secondary ion mass spectrometry can reveal, for example, Ce + and Cr + A peak derived from at least one of the above is detected.

[0166] The surface of the aluminum alloy foil is preferably provided with an acid-resistant coating containing at least one element selected from the group consisting of phosphorus, chromium, and cerium. The presence of at least one element selected from the group consisting of phosphorus, chromium, and cerium in the acid-resistant coating on the surface of the aluminum alloy foil of the battery packaging material can be confirmed using X-ray photoelectron spectroscopy. Specifically, first, the heat-sealable resin layer 6, the second adhesive layer 4, and the like laminated on the aluminum alloy foil are physically peeled off. Next, the aluminum alloy foil is placed in an electric furnace and heated at approximately 300°C for approximately 30 minutes to remove organic components present on the surface of the aluminum alloy foil. Then, the presence of these elements is confirmed using X-ray photoelectron spectroscopy of the surface of the aluminum alloy foil.

[0167] The amount of the acid-resistant film formed on the surface of the barrier layer 5 in the chemical conversion treatment is not particularly limited. For example, in the case of the above-mentioned chromate treatment, the amount of the acid-resistant film formed on the surface of the barrier layer 5 is 2 It is desirable that the chromium compound is contained in an amount of about 0.5 to 50 mg, preferably about 1.0 to 40 mg, calculated as chromium, the phosphorus compound is contained in an amount of about 0.5 to 50 mg, preferably about 1 to 40 mg, calculated as phosphorus, and the aminated phenol polymer is contained in an amount of about 1 to 200 mg, preferably about 5 to 150 mg, calculated as phosphorus, per 1000 ml of the aqueous solution.

[0168] The thickness of the acid-resistant coating is not particularly limited, but is preferably about 1 nm to 10 μm, more preferably about 1 to 100 nm, and even more preferably about 1 to 50 nm, from the viewpoint of the cohesive strength of the coating and the adhesive strength with the barrier layer 5 and the heat-fusible resin layer. The thickness of the acid-resistant coating can be measured by observation with a transmission electron microscope, or by a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy.

[0169] The chemical conversion treatment is carried out by applying a solution containing a compound used to form the acid-resistant coating to the surface of the barrier layer 5 by bar coating, roll coating, gravure coating, immersion, or the like, and then heating the barrier layer 5 to a temperature of about 70 to 200° C. Furthermore, before the chemical conversion treatment is carried out on the barrier layer 5, the barrier layer 5 may be subjected to a degreasing treatment in advance by an alkali immersion method, electrolytic cleaning, acid cleaning, electrolytic acid cleaning, or the like. By carrying out such a degreasing treatment, the chemical conversion treatment on the surface of the barrier layer 5 can be carried out more efficiently.

[0170] <Heat-Fusible Resin Layer 6> The heat-fusible resin layer 6 corresponds to the innermost layer, and is a layer that seals the battery element by heat-fusing the heat-fusible resin layers 6 together during battery assembly.

[0171] The resin component used in the heat-sealable resin layer 6 is not particularly limited as long as it is heat-sealable, and examples thereof include polyolefin, cyclic polyolefin, carboxylic acid-modified polyolefin, carboxylic acid-modified cyclic polyolefin, etc. That is, the resin constituting the heat-sealable resin layer 6 may or may not contain a polyolefin skeleton, and preferably contains a polyolefin skeleton. The presence of a polyolefin skeleton in the resin constituting the heat-sealable resin layer 6 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, etc., and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, the wavelength is 1760 cm. -1 Nearby and wave number 1780 cm -1 A peak derived from maleic anhydride is detected around this point. However, if the degree of acid modification is low, the peak may be small and not be detected. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0172] Specific examples of the polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylenes such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), and random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and ethylene-butene-propylene terpolymers. Among these, polyethylene and polypropylene are preferred, and polypropylene is particularly preferred.

[0173] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Of these, cyclic alkenes are preferred, and norbornene is more preferred. Styrene can also be used as a constituting monomer.

[0174] The carboxylic acid-modified polyolefin is a polymer obtained by modifying the polyolefin by block polymerization or graft polymerization with a carboxylic acid. Examples of the carboxylic acid used for modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride.

[0175] The carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a cyclic polyolefin by substituting an α,β-unsaturated carboxylic acid or an anhydride thereof for some of the monomers constituting the cyclic polyolefin, or by block or graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof with a cyclic polyolefin. The carboxylic acid-modified cyclic polyolefin is the same as described above. The carboxylic acid used for the modification is the same as that used for the modification of the acid-modified polyolefin.

[0176] Of these resin components, preferred is carboxylic acid-modified polyolefin, and more preferred is carboxylic acid-modified polypropylene.

[0177] The heat-sealable resin layer 6 may contain a lubricant. The lubricant present on the surface of the heat-sealable resin layer 6 may be a lubricant exuded from the resin constituting the heat-sealable resin layer 6, or a lubricant applied to the surface of the heat-sealable resin layer 6. When the heat-sealable resin layer 6 contains a lubricant, the formability of the packaging material can be improved. The lubricant is not particularly limited, and known lubricants can be used, such as those exemplified for the polyester film above. These may be used alone, or two or more may be used in combination. The amount of lubricant present on the surface of the heat-sealable resin layer 6 is not particularly limited, and from the viewpoint of improving the formability of the packaging material, it is preferably 10 to 50 mg / m 2 about 15 to 40 mg / m 2 That's about it.

[0178] The heat-sealable resin layer 6 may be formed of one type of resin component alone, or may be formed of a blend polymer of two or more types of resin components. The heat-sealable resin layer 6 may be formed of a single layer or a laminate of two or more layers. The heat-sealable resin layer 6 may be formed of either a stretched film or an unstretched film.

[0179] The thickness (total thickness) of the heat-sealable resin layer 6 is about 15 to 100 μm, more preferably about 15 to 40 μm, from the viewpoint of making the battery packaging material as thin as possible while suppressing curling after molding.

[0180] In addition, the packaging material may have an adhesive layer (hereinafter sometimes referred to as a "third adhesive layer") provided between the barrier layer 5 and the heat-sealable resin layer 6, if necessary, for the purpose of enhancing the adhesion therebetween. The third adhesive layer is the same as that described in the <First adhesive layer 2> section above. For example, the adhesive used in the third adhesive layer provided between the barrier layer 5 and the heat-sealable resin layer 6 is not particularly limited as long as it can bond the metal foil or the like that constitutes the barrier layer 5 to the resin film or the like that constitutes the heat-sealable resin layer, and can be appropriately selected from the adhesives exemplified in <First adhesive layer 2>.

[0181] From the viewpoint of firmly adhering the third adhesive layer and the heat-sealable resin layer 6, the resin used to form the third adhesive layer preferably contains a polyolefin skeleton, and examples thereof include the polyolefins and acid-modified polyolefins exemplified for the heat-sealable resin layer 6 described above. Furthermore, from the viewpoint of firmly adhering the barrier layer 5 and the third adhesive layer, the third adhesive layer preferably contains an acid-modified polyolefin. Examples of acid-modified components include dicarboxylic acids such as maleic acid, itaconic acid, succinic acid, and adipic acid, as well as anhydrides thereof, acrylic acid, and methacrylic acid. Among these, maleic anhydride is preferred in terms of ease of modification and versatility. Furthermore, from the viewpoint of the heat resistance of the electrical storage device exterior material, the olefin component is preferably a polypropylene-based resin, and the third adhesive layer most preferably contains maleic anhydride-modified polypropylene.

[0182] When the resin used to form the third adhesive layer contains a polyolefin skeleton, it is preferable that the third adhesive layer contains a resin containing a polyolefin skeleton as its main component, it is more preferable that it contains an acid-modified polyolefin as its main component, and it is even more preferable that it contains an acid-modified polypropylene as its main component.

[0183] The inclusion of a polyolefin skeleton in the resin constituting the third adhesive layer can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. Furthermore, the inclusion of an acid-modified polyolefin in the resin constituting the adhesive layer can be determined by, for example, measuring a maleic anhydride-modified polyolefin by infrared spectroscopy, and finding a wavelength of 1760 cm -1 Nearby and wave number 1780 cm -1 Analysis is possible if a peak derived from maleic anhydride is detected near the peak. However, if the degree of acid modification is low, the peak may be small and not detectable. In this case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0184] A pre-formed resin film may be used as the third adhesive layer when the present packaging material is manufactured by laminating the third adhesive layer with the barrier layer 5, the heat-sealable resin layer 6, or the like. Alternatively, the heat-sealable resin that forms the third adhesive layer may be formed into a film on the surface of the barrier layer 5, the heat-sealable resin layer 6, or the like by extrusion molding, coating, or the like, to form the third adhesive layer from a resin film.

[0185] The thickness (total thickness) of the third adhesive layer is not particularly limited, but is preferably about 50 μm or less, about 40 μm or less, or about 30 μm or less. The thickness (total thickness) of the adhesive layer is preferably about 1 μm or more, about 5 μm or more, or 10 μm or more. The thickness (total thickness) of the third adhesive layer is preferably in the range of about 1 to 50 μm, about 5 to 40 μm, or about 10 to 30 μm. When using a resin exemplified for the heat-fusible resin layer 6, the third adhesive layer can be formed, for example, by extrusion molding the heat-fusible resin layer 6 and the third adhesive layer. Furthermore, when the heat-fusible resin layer 6 and the third adhesive layer are formed by co-extrusion molding, the total thickness of the heat-fusible resin layer 6 and the third adhesive layer has a lower limit of approximately 35 μm, approximately 55 μm, or approximately 75 μm, and an upper limit of approximately 45 μm, approximately 65 μm, or approximately 85 μm, and numerical ranges of approximately 35 to 45 μm, approximately 35 to 65 μm, approximately 35 to 85 μm, approximately 55 to 65 μm, approximately 55 to 85 μm, or approximately 75 to 85 μm.

[0186] Furthermore, the exterior packaging material may have a colored layer between the base material layer 1 and the first adhesive layer 2, or between the first adhesive layer 2 and the polyamide layer 3. The colored layer can be formed, for example, by applying ink containing a colorant to the surface of the target layer. Known colorants such as pigments and dyes can be used as colorants. Specific examples of the colorant are the same as those exemplified in the section <First adhesive layer 2>.

[0187] Furthermore, each layer constituting the laminate in the packaging material may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, or ozone treatment, as necessary, in order to improve or stabilize film-forming properties, lamination processing, suitability for secondary processing of the final product, and the like.

[0188] <Uses> The present packaging material is used in a package for hermetically housing an electricity storage device element such as a positive electrode, a negative electrode, an electrolyte, etc. That is, an electricity storage device can be made by housing an electricity storage device element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed from the present packaging material.

[0189] Specifically, an electricity storage device using the packaging material for an electricity storage device is provided by covering an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte with the packaging material in a state in which metal terminals connected to each of the positive electrode and negative electrode protrude outward, so that a flange portion (a region where the heat-sealable resin layers contact each other) is formed around the periphery of the electricity storage device element, and then heat-sealing the heat-sealable resin layers of the flange portion to form a hermetic seal. Note that when an electricity storage device element is housed in a package formed from the packaging material, the package is formed so that the heat-sealable resin portion of the packaging material is on the inside (the surface that contacts the electricity storage device element).

[0190] The present packaging material can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The present packaging material may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the present packaging material is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, semi-solid batteries, quasi-solid batteries, polymer batteries, all-resin batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the present packaging material.

[0191] <Method of Manufacturing the Present Exterior Material> The method of manufacturing the present exterior material is not particularly limited, as long as it uses a laminate in which the above-mentioned layers are laminated together. For example, first, a laminate (hereinafter sometimes referred to as "laminate A") is formed in which a base material layer 1, a first adhesive layer 2, and a polyamide layer 3 are laminated together in this order. Specifically, the formation of laminate A can be carried out by a dry lamination method in which an adhesive used to form the first adhesive layer 2 is applied to the base material layer 1 or the polyamide layer 3 by a coating method such as gravure coating or roll coating, and then dried, and the polyamide layer 3 or base material layer 1 is laminated thereon to cure the first adhesive layer 2. Next, a laminate (hereinafter sometimes referred to as "laminate B") is formed using laminate A in which a base material layer 1, a first adhesive layer 2, a polyamide layer 3, a second adhesive layer 4, and a barrier layer 5 are laminated together in this order. Specifically, the formation of the laminate B can be carried out by a dry lamination method in which the adhesive used to form the second adhesive layer 4 is applied by a coating method such as gravure coating or roll coating to the polyamide layer 3 or to the barrier layer 5, the surface of which has been chemically treated as necessary, and dried, and then the barrier layer 5 or the polyamide layer 3 is laminated on the laminate and cured the second adhesive layer 4. The procedure for forming the laminate B is not limited to the above-mentioned procedure, and the laminate B can also be formed by a dry lamination method in which the adhesive used to form the second adhesive layer 4 is applied by a coating method such as gravure coating or roll coating to the polyamide layer 3 or to the barrier layer 5, the surface of which has been chemically treated as necessary, and dried, and then the barrier layer 5 or the polyamide layer 3 is laminated on the laminate and cured the second adhesive layer 4, and then the adhesive used to form the first adhesive layer 2 is applied by a coating method such as gravure coating or roll coating to the base layer 1 or to the polyamide layer 3, and dried, and then the polyamide layer 3 or the base layer 1 is laminated on the laminate and cured the first adhesive layer 2. In addition, instead of laminate B, for example, a laminate (hereinafter sometimes referred to as "laminate B'") can be formed in which a base material layer 1, a first adhesive layer 2, and a barrier layer 5 are laminated in order.Specifically, the formation of the laminate B' can be carried out by a dry lamination method in which the adhesive used to form the first adhesive layer 2 is applied to the substrate layer 1 or to the barrier layer 5, the surface of which has been chemically treated as necessary, by a coating method such as gravure coating or roll coating, and then dried, and the barrier layer 5 or the substrate layer 1 is laminated thereon to cure the first adhesive layer 2. Next, a heat-fusible resin layer 6 is laminated on the barrier layer 5 of the laminate B or the laminate B'. When the heat-fusible resin layer 6 is directly laminated on the barrier layer 5, the heat-fusible resin layer 6 may be laminated on the barrier layer 5 of the laminate B or the laminate B' by a method such as thermal lamination or extrusion lamination. In addition, when the third adhesive layer is provided between the barrier layer 5 and the heat-sealable resin layer 6, for example, (1) a method of laminating the third adhesive layer and the heat-sealable resin layer 6 by extruding them onto the barrier layer 5 of the laminate B or the laminate B' (co-extrusion lamination method, tandem lamination method), (2) a method of separately forming a laminate in which the third adhesive layer and the heat-sealable resin layer 6 are laminated, and laminating this on the barrier layer 5 of the laminate B or the laminate B' by a thermal lamination method, or a method of forming a laminate in which the third adhesive layer is laminated on the barrier layer 5 of the laminate B or the laminate B', and laminating this on the heat-sealable resin layer 6 by a thermal lamination method. (3) a method (sandwich lamination method) in which a molten third adhesive layer is poured between the barrier layer 5 of the laminate B or the laminate B' and the heat-sealable resin layer 6 previously formed into a sheet, and the laminate B or the laminate B' and the heat-sealable resin layer 6 are bonded together via the third adhesive layer; (4) a method in which an adhesive for forming a third adhesive layer is solution-coated on the barrier layer 5 of the laminate B or the laminate B', followed by drying or baking, and then laminating the heat-sealable resin layer 6 previously formed into a sheet on this adhesive layer.

[0192] In the manner described above, for example, a laminate having a base material layer 1, a first adhesive layer 2, a barrier layer 5, and a heat-sealable resin layer 6 in this order, or a laminate having a base material layer 1, a first adhesive layer 2, a polyamide layer 3, a second adhesive layer 4, a barrier layer 5, and a heat-sealable resin layer 6 in this order, is formed, but if necessary, the laminate may be further subjected to a heat treatment in order to strengthen the adhesion of the first adhesive layer 2 and the second adhesive layer 4.

[0193] 2 and 3, in the packaging material 100 formed from the laminate 10, the housing portion 100a for the lithium-ion battery or the like is produced by cold forming using a molding die. The molding die is usually rectangular in plan view, and the housing portion 100a is also usually rectangular in plan view. The rectangular shape may have right-angled corners or may have rounded corners instead of right angles.

[0194] Since the present packaging material has excellent deep-draw formability, there are no particular limitations on the ratio (d / S) of the area (S) of the housing portion for a lithium ion battery or the like in a plan view to the recess depth (d), for example, 0.005 (mm / mm 2 ) or more, and further, 0.006 (mm / mm 2 ) or more, and further, 0.007 to 0.012 (mm / mm 2 ) In the case of a substantially rectangular shape without corner ridgelines R, the distance between the opposing sides of the molded product is measured, and the measurement is made for each of the long and short sides, and the product is taken as the area (S). In the case of a substantially rectangular shape with corner ridgelines R, the distance between the point where the ridgeline R on the side of the molded product ends and the same point opposite it is measured for each of the long and short sides, and the product is taken as the area (S). In the case of a non-substantially rectangular shape, the area of ​​the rectangle is calculated in the same way as for a substantially rectangular shape, and the sum of the combined areas is taken as the area (S). Specifically, for example, when the area (S) of the storage section 100a for a lithium ion battery or the like in a plan view is 1722.2 mm 2 In the case of (31.6 mm x 54.5 mm), the recess depth (d) can be, for example, 8 mm or more, 10 mm or more, or 12 to 20 mm.

[0195] There are no particular limitations on the production of a lithium-ion battery or the like housed in the present packaging material, but for example, when the housing section 100a is rectangular in plan view, it is preferable that the long side direction of the rectangular shape of the housing section in plan view corresponds to the MD of the present polyester film, and the short side direction of the rectangular shape of the housing section in plan view corresponds to the TD of the present polyester film.

[0196] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are based on mass.

[0197] First, the raw materials of the substrate layer used in the following Examples and Comparative Examples are as follows.

[0198] <<Base layer>> <Polyethylene terephthalate, etc.> PET (1): homopolyethylene terephthalate, intrinsic viscosity 0.64 dL / g PET (2): homopolyethylene terephthalate, intrinsic viscosity 0.85 dL / g PET MB (1): Polyethylene terephthalate-based masterbatch containing 0.55% by mass of spherical silica particles (average particle size 3.1 μm), intrinsic viscosity 0.61 dL / g PET MB (2): A polyethylene terephthalate-based masterbatch containing 10% by mass of spherical organic particles (average particle size 4.1 μm) obtained by polymerizing an acrylic acid ester monomer, a styrene monomer, and a silicone monomer, with an intrinsic viscosity of 0.60 dL / g

[0199] <Polybutylene terephthalate> PBT (1): Polybutylene terephthalate, manufactured by Mitsubishi Engineering Plastics Corporation, Novaduran (registered trademark) 5008, intrinsic viscosity 0.85 dL / g PBT (2): Polybutylene terephthalate, manufactured by Mitsubishi Engineering Plastics Corporation, Novaduran (registered trademark) 5026, intrinsic viscosity 1.26 dL / g

[0200] Biaxially stretched polyester films (PE1 to PE17) constituting the base layer were produced using the formulation and production conditions shown in Table 1 below. Specific details are as follows. The PET / PBT (mass ratio) shown in Table 1 is the mass ratio of PET and PBT contained in the entire biaxially stretched polyester film having the three-layer structure described below. Specifically, the PET / PBT mass ratio in the entire polyester film was calculated from the blending ratio of PET and PBT in each layer and the thickness ratio of each layer, and this mass ratio was rounded to one decimal place. In differential scanning calorimetry (DSC) described below, polyester films PE9 and PE14 had two melting peaks, while polyester films other than PE9 and PE14 had one melting peak.

[0201] <Polyester film (PE1)> 70% by mass of PET (1), 20% by mass of PBT (1), PET MB A mixed raw material obtained by mixing 10% by mass of PET (1) and 20% by mass of PBT (1) was used as the raw material for both surface layers, and a mixed raw material obtained by mixing 80% by mass of PET (1) and 20% by mass of PBT (1) was used as the raw material for the intermediate layer. The mixed raw materials for both surface and intermediate layers were fed into two extruders, melted at 280 ° C., and then co-extruded onto a cooling roll set at 25 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = 2.5 / 20 / 2.5 output), and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet was then stretched 3.5 times in the longitudinal direction (MD) at 73 ° C. using a roll stretching machine (longitudinal stretching). Furthermore, it was preheated in a tenter at 75 ° C. for 6 seconds, and then stretched 4.5 times in the width direction (TD) at 85 ° C. (transverse stretching). After stretching, the film was subsequently heat-set at 210°C for 8 seconds and then cooled to 140°C under 2% relaxation in the width direction to produce a biaxially stretched polyester film (PE1) having a thickness of 25 μm (each surface layer: 2.5 μm, middle layer: 20 μm).

[0202] <Polyester Films (PE2 to 5, PE8 to 13, PE15 to 16)> Biaxially stretched polyester films (PE2 to 5, PE8 to 13, PE15 to 16) each having a thickness of 25 μm were produced in the same manner as for the polyester film (PE1), except that the types of raw materials, the thickness ratio and blending proportions of each layer, and the production conditions were changed as shown in Table 1.

[0203] <Polyester film (PE6)> 68% by mass of PET (1), 20% by mass of PBT (1), PET MB A mixed raw material obtained by mixing 12% by mass of PET (1) and 20% by mass of PBT (1) was used as the raw material for both surface layers, and a mixed raw material obtained by mixing 80% by mass of PET (1) and 20% by mass of PBT (1) was used as the raw material for the intermediate layer. The mixed raw materials for both surface and intermediate layers were each fed into two extruders, melted at 280 ° C., and then co-extruded onto a cooling roll set at 25 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = discharge amount 2.1 / 20.8 / 2.1), and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet was then stretched 3.4 times in the longitudinal direction (MD) at 73 ° C. using a roll stretching machine (longitudinal stretching) to obtain a uniaxially stretched film. A coating solution having the following composition was applied to one side of this uniaxially stretched film in an amount of 0.05 g / m (after dry stretching). 2 The coating was applied so that a coating layer was formed. The film was then preheated in a tenter at 75°C for 7 seconds and then stretched 4.7 times in the width direction (TD) at 85°C (transverse stretching). After stretching, the film was subsequently heat-set at 209°C for 10 seconds and cooled to 140°C under 2% relaxation in the width direction to produce a biaxially stretched polyester film (PE6) having a coating layer and a thickness of 25 μm (each surface layer: 2.1 μm, middle layer: 20.8 μm).

[0204] [Coating liquid composition in non-volatile components] Aqueous dispersion of polyester resin 90% by mass Monomer composition: (acid component) polyester resin copolymerized with terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / / (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56 / 40 / 4 / / 70 / 20 / 10 (mol%) Melamine compound: hexamethoxymethylolmelamine 9% by mass Lubricant: silica particles with an average particle size of 0.07 μm 1% by mass

[0205] <Polyester film (PE7)> 68% by mass of PET (1), 20% by mass of PBT (1), PET MBA mixed raw material obtained by mixing PET (1) at a ratio of 12% by mass was used as the raw material for both surface layers, and a mixed raw material obtained by mixing PET (1) at a ratio of 80% by mass and PBT (1) at a ratio of 20% by mass was used as the raw material for the intermediate layer. The mixed raw materials for both surface layers and the intermediate layer were each fed into two extruders, melted at 280 ° C., and then co-extruded onto a cooling roll set at 25 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer 3.4 / 33.2 / 3.4 discharge amount), and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet was then stretched 3.5 times in the longitudinal direction (MD) at 76 ° C. using a roll stretching machine (longitudinal stretching). Furthermore, after preheating at 75 ° C. for 7 seconds in a tenter, it was stretched 4.6 times in the width direction (TD) at 85 ° C. (transverse stretching). After stretching, the film was heat-set at 210°C for 10 seconds and then cooled to 140°C under 2% relaxation in the width direction to produce a biaxially stretched polyester film (PE7) with a thickness of 40 μm (each surface layer: 3.4 μm, middle layer: 33.2 μm).

[0206] <Polyester film (PE14)> 65% by mass of PET (2), 20% by mass of PBT (2), PET MB A mixed raw material obtained by mixing PET (2) at a ratio of 15% by mass was used as the raw material for both surface layers, and a mixed raw material obtained by mixing PET (2) at a ratio of 45% by mass and PBT (2) at a ratio of 55% by mass was used as the raw material for the intermediate layer. The mixed raw materials for both surface layers and the intermediate layer were each fed into two extruders, melted at 280 ° C., and then co-extruded onto a cooling roll set at 25 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = 2.1 / 20.8 / 2.1 discharge amount), and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet was then stretched 3.8 times in the longitudinal direction (MD) at 70 ° C. using a roll stretching machine (longitudinal stretching). Furthermore, it was preheated in a tenter at 80 ° C. for 6 seconds, and then stretched 5.2 times in the width direction (TD) at 80 ° C. (transverse stretching). After stretching, the film was heat-set at 180°C for 8 seconds and then cooled to 140°C with 2% relaxation in the width direction to produce a biaxially stretched polyester film (PE14) with a thickness of 25 μm (each surface layer: 2.1 μm, middle layer: 20.8 μm).

[0207] <Polyester film (PE17)> 90% by mass of PET (1), PET MBA mixed raw material obtained by mixing PET (1) at a ratio of 10% by mass was used as the raw material for both surface layers, and a mixed raw material obtained by mixing PET (1) at a ratio of 80% by mass and PBT (1) at a ratio of 20% by mass was used as the raw material for the intermediate layer. The mixed raw materials for both surface layers and the intermediate layer were each fed into two extruders, melted at 280 ° C., and then co-extruded onto a cooling roll set at 25 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = discharge amount 2.5 / 20 / 2.5), and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet was then stretched 3.5 times in the longitudinal direction (MD) at 76 ° C. using a roll stretching machine (longitudinal stretching) to obtain a uniaxially stretched film. A coating solution having the following composition was applied to one side of this uniaxially stretched film in an amount (after dry stretching) of 0.03 g / m 2 The coating was applied so that a coating layer was formed. The film was then preheated in a tenter at 75°C for 7 seconds and then stretched 4.5 times in the width direction (TD) at 90°C (transverse stretching). After stretching, the film was subsequently heat-set at 210°C for 10 seconds and cooled to 140°C under 2% relaxation in the width direction to produce a biaxially stretched polyester film (PE17) having a coating layer and a thickness of 25 μm (each surface layer: 2.5 μm, middle layer: 20 μm).

[0208] [Coating Solution Composition in Nonvolatile Components] 60% by mass of a long-chain alkyl group-containing compound obtained by the following production method, in which octadecyl isocyanate was added to polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol%, <Production Method> 200 parts of xylene and 600 parts of octadecyl isocyanate were added to a four-neck flask and heated with stirring. Once the xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol% was added in small portions at 10-minute intervals over approximately 2 hours. After the polyvinyl alcohol addition was completed, the mixture was refluxed for another 2 hours to terminate the reaction. The reaction mixture was cooled to approximately 80°C and then added to methanol, resulting in the precipitation of a white precipitate. This precipitate was then filtered off, 140 parts of xylene was added, and the mixture was heated to completely dissolve the reaction product. Then, methanol was added again to cause precipitation. This procedure was repeated several times, and the precipitate was washed with methanol, dried, and pulverized. Melamine compound: hexamethoxymethylolmelamine (partially etherified melamine in which the ratio of methylol groups to methoxy groups is 1:2.2) 40% by mass

[0209]

[0210] Next, the raw materials of the polyamide layer and the like used in the following Examples and Comparative Examples are as follows: <<Polyamide Layer>> <Biaxially oriented polyamide 6 film (PA1)>> A polyamide film having a thickness of 25 μm, produced by biaxial orientation.

[0211] <<Barrier Layer>> <Aluminum alloy foil (ALM1)> Aluminum alloy foil with a thickness of 40 μm and 80 μm, having the composition of JIS H4160:1994 A8079H-O

[0212] <<Heat-Fusible Resin Layer>> <Polypropylene Resin> Polypropylene (PP1, thickness 22.5 μm and 40 μm) as a heat-fusible resin layer

[0213] <<Adhesive layer>> <Two-component curing urethane adhesive> Two-component curing urethane adhesive (polyol compound and aromatic isocyanate compound) <Polypropylene resin> Maleic anhydride modified polypropylene (PPa1, thickness 22.5 μm and 40 μm)

[0214] Using the polyester films (PE1 to PE17) for the base layer prepared above and various raw materials for the other layers, laminates according to the following examples and comparative examples were prepared.

[0215] Example 1: A barrier layer composed of an aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides was laminated onto a biaxially oriented polyamide film (PA1) as a polyamide layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied to one side of the aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides, forming an adhesive layer (3 μm thick after curing) on ​​the aluminum alloy foil (ALM1, thickness 40 μm). Next, the adhesive layer on the aluminum alloy foil and the polyamide film (PA1) were laminated, and then aging treatment was performed to produce a polyamide layer / adhesive layer / barrier layer laminate. Next, a polyester film (PE1) as a substrate layer was laminated onto the biaxially oriented polyamide film (PA1) by dry lamination in the same manner as described above, to produce a substrate layer / adhesive layer / polyamide layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which base material layer (25 μm) / adhesive layer (3 μm) / polyamide layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0216] [Examples 2 to 6 and 9 to 11, Comparative Examples 1 to 6] Laminates of Examples 2 to 6 and 9 to 11 and Comparative Examples 1 to 6 were produced in the same manner as Example 1, except that the polyester film (PE1) was changed to the polyester films (PE2 to PE13 and 15 to 17) shown in Table 2. Note that Example 6 is a laminate in which an adhesive layer is laminated on a coating layer formed on a base layer, and a polyamide layer, adhesive layer, barrier layer, adhesive layer, and heat-sealable resin layer are laminated in this order. Example 11 is a laminate in which an adhesive layer is laminated on the surface of the base layer on the side where no coating layer is formed, and a polyamide layer, adhesive layer, barrier layer, adhesive layer, and heat-sealable resin layer are laminated in this order.

[0217] [Examples 7, 13, and 14] A barrier layer composed of an aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides was laminated onto a biaxially oriented polyamide film (PA1) as a polyamide layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied to one side of the aluminum alloy foil (ALM1, thickness 80 μm) with an acid-resistant coating formed on both sides, forming an adhesive layer (thickness 3 μm after curing) on ​​the aluminum alloy foil (ALM1). Next, the adhesive layer on the aluminum alloy foil and the polyamide film (PA1) were laminated, and then aging treatment was performed to produce a polyamide layer / adhesive layer / barrier layer laminate. Next, a polyester film (PE5) as a substrate layer was laminated onto the biaxially oriented polyamide film (PA1) by dry lamination in the same manner as above, to produce a substrate layer / adhesive layer / polyamide layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 40 μm) as an adhesive layer and polypropylene (PP1, thickness 40 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which base material layer (25 μm) / adhesive layer (3 μm) / polyamide layer (25 μm) / adhesive layer (3 μm) / barrier layer (80 μm) / adhesive layer (40 μm) / heat-sealable resin layer (40 μm) were laminated in this order.

[0218] Example 8: A barrier layer composed of an aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides was laminated on a biaxially oriented polyamide film (PA1) as a polyamide layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides, forming an adhesive layer (3 μm thick after curing) on ​​the aluminum alloy foil (ALM1, thickness 80 μm). Next, the adhesive layer on the aluminum alloy foil and the polyamide film (PA1) were laminated, and then aging treatment was performed to produce a polyamide layer / adhesive layer / barrier layer laminate. Next, a polyester film (PE7) as a substrate layer was laminated on the biaxially oriented polyamide film (PA1) by dry lamination in the same manner as above, to produce a substrate layer / adhesive layer / polyamide layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 40 μm) as an adhesive layer and polypropylene (PP1, thickness 40 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which base layer (40 μm) / adhesive layer (3 μm) / polyamide layer (25 μm) / adhesive layer (3 μm) / barrier layer (80 μm) / adhesive layer (40 μm) / heat-sealable resin layer (40 μm) were laminated in this order.

[0219] Example 12 A laminate was obtained in the same manner as in Example 1, except that the biaxially oriented polyamide 6 film (PA1) was not laminated. Specifically, a barrier layer composed of an aluminum alloy foil (ALM1, thickness: 40 μm) with an acid-resistant coating formed on both sides was laminated on a polyester film (PE1) as a base layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides, forming an adhesive layer (thickness: 3 μm after curing) on ​​the aluminum alloy foil (ALM1). The adhesive layer and polyester film (PE1) were laminated, and the resulting laminate was subjected to an aging treatment to produce a base layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which the substrate layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0220] Comparative Example 7: A laminate was obtained in the same manner as in Comparative Example 1, except that the biaxially oriented polyamide 6 film (PA1) was not laminated. Specifically, a barrier layer composed of an aluminum alloy foil (ALM1, thickness: 40 μm) with an acid-resistant coating formed on both sides was laminated on a polyester film (PE8) as a base layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides, forming an adhesive layer (thickness: 3 μm after curing) on ​​the aluminum alloy foil (ALM1). The adhesive layer and polyester film (PE8) were laminated, and the resulting laminate was subjected to an aging treatment to produce a base layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which the substrate layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0221] Comparative Example 8: A laminate was obtained in the same manner as in Comparative Example 6, except that the biaxially oriented polyamide 6 film (PA1) was not laminated. Specifically, a barrier layer composed of an aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides was laminated on a polyester film (PE8) as a base layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides, forming an adhesive layer (3 μm thick after curing) on ​​the aluminum alloy foil (ALM1, 40 μm thick). The adhesive layer and polyester film (PE13) were then laminated, followed by aging treatment, to produce a base layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which the substrate layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0222] [Comparative Example 9] A barrier layer composed of an aluminum alloy foil (ALM1) with acid-resistant coatings formed on both sides was laminated on a polyester film (PE14) as a base layer by dry lamination. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1, 40 μm) with acid-resistant coatings formed on both sides, forming an adhesive layer (thickness 3 μm after curing) on ​​the aluminum alloy foil (ALM1). The adhesive layer and polyester film (PE14) were laminated together, and then aging treatment was performed to produce a base layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded onto the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which the substrate layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0223] <<Measurement Methods and Evaluation Methods>> The properties of the polyester film obtained above were measured by the following measurement methods, and the results are shown in Tables 2 and 3. The formability and heat resistance of the laminate obtained above were evaluated by the following methods, and the results are also shown in Tables 2 and 3. In Tables 2 and 3, the tensile yield stress (MPa), tensile elongation at break (%), and tensile stress at break (MPa) are measured values ​​rounded to one decimal place, the slope of the stress-strain curve is measured value rounded to two decimal places, and the difference in the slope of the stress-strain curve (MPa / %) is measured value obtained by calculating the ratio of the measured values ​​and rounded to two decimal places.

[0224] [Tensile Yield Stress, Tensile Breaking Elongation, and Tensile Breaking Stress of Polyester Film] A test piece for measuring tensile properties in the longitudinal direction (MD) of 15 mm x longitudinal direction (MD) of 150 mm was taken from a polyester film. A test piece for measuring tensile properties in the width direction (TD) of 15 mm x width direction (TD) of 150 mm was taken from a polyester film. The tensile yield stress, tensile break elongation (nominal tensile break strain), and tensile break stress of the polyester film were measured in the longitudinal direction (MD) using the test piece for measuring tensile properties in the longitudinal direction (MD) and in the width direction (TD) using the test piece for measuring tensile properties in the width direction (TD) using an "Autograph AGX-V" tensile tester manufactured by Shimadzu Corporation, with reference to JIS K 7161-1 (2014). The measurement was carried out in an atmosphere of 23° C. and 50% RH, with reference marks at 50 mm intervals in the center of each test piece, with a chuck distance of 50 mm and a pulling speed of 200 mm / min.

[0225] [Slope of the curve corresponding to the section from the yield point to the break point in the stress-strain curve of a polyester film, and the difference (absolute value) of the slope between MD and TD] A specimen for measuring tensile properties in the longitudinal direction (MD) measuring 15 mm x 150 mm was taken from a polyester film, and a specimen for measuring tensile properties in the width direction (TD) measuring 15 mm x 150 mm was taken from a polyester film. Using an "Autograph AGX-V" manufactured by Shimadzu Corporation, the slope of the stress-strain curve corresponding to the section from the yield point to the break point was measured in the longitudinal direction (MD) using the specimen for measuring tensile properties in the longitudinal direction (MD), and in the width direction (TD) using the specimen for measuring tensile properties in the width direction (TD) with reference to JIS K 7161-1 (2014). Measurements were performed in an atmosphere of 23°C and 50% RH, with gauge marks at 50 mm intervals in the center of each test specimen, a chuck distance of 50 mm, and a tensile speed of 200 mm / min. The slope of each stress-strain curve was calculated using the least squares method of the regression line. In the calculation, one measurement point was taken every 0.1 seconds, and calculations were performed using the LINEST function of the spreadsheet software "Microsoft Excel" manufactured by Microsoft Corporation using data from 100 or more points.

[0226] [Melting point (Tm) of polyester film] In accordance with JIS K7121 (2012), a polyester film was measured using a Diamond DSC (manufactured by PerkinElmer Japan) as a differential scanning calorimeter. The film was heated to the melting temperature from -70 to 280 ° C. at a heating rate of 10 ° C. / min, held for 10 minutes, then cooled to -70 ° C. at a cooling rate of 600 ° C. / min, and then heated again to -70 to 280 ° C. at a heating rate of 10 ° C. / min. The melting point was determined as the peak top value (melting peak temperature) of the melting peak observed during the first heating process, and the peak top temperature (melting peak temperature) of the melting peak observed during the second heating process was used as the melting point of the second run. When two or more melting peaks are observed, the temperature at the peak top position of the largest peak was used as the melting point.

[0227] [Glass Transition Temperature (Tg) of Polyester Film] In accordance with JIS K7121 (2012), a polyester film was measured using a Diamond DSC (manufactured by PerkinElmer Japan) as a differential scanning calorimeter. The polyester film was heated once to the melting temperature from −70 to 280° C. at a heating rate of 10° C. / min, held at that temperature for 10 minutes, and then cooled to −70° C. at a cooling rate of 600° C. / min. After that, the polyester film was heated again from −70 to 280° C. at a heating rate of 10° C. / min, and the midpoint glass transition temperature during the second heating process was measured.

[0228] [Moldability of Laminate] A test piece measuring 90 mm in the longitudinal direction (MD) × 150 mm in the transverse direction (TD) was taken from the laminate. The longitudinal direction (MD) of the laminate corresponded to the rolling direction (RD) of the aluminum alloy foil, and the transverse direction (TD) of the laminate corresponded to the TD of the aluminum alloy foil. The test piece was placed in a 25°C environment using a rectangular mold (female mold, surface roughness in maximum height (nominal Rz value) of 3.2 μm, corner R2.0 mm, ridge R1.0 mm) with a bore of 31.6 mm (MD) × 54.5 mm (TD). The surface roughness was measured in accordance with JIS B 0659-1:2002, Appendix 1 (Reference), Table 2 of the comparative surface roughness standard piece. The maximum height roughness (nominal Rz value) of the comparative surface roughness standard specimen, as specified in Table 2, is 1.6 μm. Using a corner R2.0 mm, ridge R1.0 mm, a pressing pressure (surface pressure) of 0.25 MPa, 23°C, and 50% RH, the forming depth was changed in 0.5 mm increments from a forming depth of 0.5 mm. Ten test specimens were cold-formed (single-stage drawing) to form a rectangular housing (a housing for a lithium ion battery) in plan view. The test specimens were placed on a female mold so that the heat-sealable resin layer was positioned on the male mold side. The clearance between the male and female molds was 0.3 mm. The cold-formed samples were irradiated with a penlight in a darkroom to check for pinholes or cracks in the aluminum alloy foil by light transmission. The deepest forming depth at which no pinholes or cracks occurred in the aluminum alloy foil in any of the 10 samples was defined as A mm, and the number of samples at which pinholes or the like occurred in the aluminum alloy foil at the shallowest forming depth was defined as B. The value calculated by the following formula was rounded to two decimal places to determine the limit forming depth of the exterior material for an electricity storage device: Limit forming depth = A mm + (0.5 mm / 10 samples) × (10 samples - B samples).

[0229] (Evaluation Criteria 1) A laminate with the same layer structure using PE8 of the same thickness was used as a "reference," and the limit forming depth was compared and evaluated. S... limit forming depth is reference + 1.5 mm or more A... limit forming depth is reference + 1 mm or more, but less than reference + 1.5 mm B... limit forming depth is reference + 0.5 mm or more, but less than reference + 1 mm C... limit forming depth is reference + 0 mm or more, but less than reference + 0.5 mm D... limit forming depth is less than reference

[0230] In Example 1 and Comparative Example 1, the "reference" refers to a laminate prepared as follows. (Preparation of Reference for Example 1) The polyester film (PE1) used as the base layer was replaced with a polyester film (PE8). Specifically, a barrier layer composed of an aluminum alloy foil (ALM1) with an acid-resistant coating formed on both sides was laminated by dry lamination onto a biaxially oriented polyamide film (PA1) used as a polyamide layer. Specifically, a two-component curing urethane adhesive was applied as an adhesive layer to one side of the aluminum alloy foil (ALM1, 40 μm) with an acid-resistant coating formed on both sides, forming an adhesive layer (3 μm thick after curing) on ​​the aluminum alloy foil (ALM1). Next, the adhesive layer on the aluminum alloy foil and the polyamide film (PA1) were laminated, and then aging treatment was performed to prepare a polyamide layer / adhesive layer / barrier layer laminate. Next, a polyester film (PE8) as a base layer was laminated on the biaxially stretched polyamide film (PA1) by dry lamination in the same manner as above to produce a base layer / adhesive layer / polyamide layer / adhesive layer / barrier layer laminate. Next, maleic anhydride-modified polypropylene (PPa1, thickness 22.5 μm) as an adhesive layer and polypropylene (PP1, thickness 22.5 μm) as a heat-sealable resin layer were co-extruded on the aluminum alloy foil (ALM1) to laminate the heat-sealable resin layer on the barrier layer, thereby producing a laminate in which the base layer (25 μm) / adhesive layer (3 μm) / polyamide layer (25 μm) / adhesive layer (3 μm) / barrier layer (40 μm) / adhesive layer (22.5 μm) / heat-sealable resin layer (22.5 μm) were laminated in this order.

[0231] (Preparation of References for Comparative Examples 1 and 7) The reference for the formability evaluation of Examples 1 to 11, 13, and 14, and Comparative Examples 1 to 6 listed in Table 2 is Comparative Example 1, and the reference for the formability evaluation of Example 12 and Comparative Examples 7 to 9 listed in Table 3 is Comparative Example 7. Since Comparative Example 1 originally uses "PE8," Comparative Example 1 and the reference for Comparative Example 1 are the same laminate. In other words, the formability evaluation of Comparative Example 1 shows the results of comparing the same laminate. Therefore, the evaluation is C (limit forming depth is reference +0 mm or more and less than +0.5 mm). For the same reason, Comparative Example 7 is also evaluated as C (limit forming depth is reference +0 mm or more and less than +0.5 mm).

[0232] (Evaluation Criterion 2) In order to confirm the effect of the presence or absence of a polyamide layer, Example 12 without a polyamide layer was used as a "reference," and the limit molding depth of Example 1 with a polyamide layer was evaluated using the same index as in Evaluation Criterion 1. The limit molding depth of Example 1 was equal to or greater than +1 mm and less than +1.5 mm of the reference compared to Example 12, and the evaluation was A.

[0233] [Heat resistance of laminate] A test piece measuring 120 mm in the longitudinal direction (MD) × 60 mm in the transverse direction (TD) was taken from the laminate. The test piece was folded so that the MD length was halved (60 mm) with the base layer facing outward, and the heat-fusible resin layers were aligned in the longitudinal direction (MD) and the transverse direction (TD). Using a heat seal tester "TP-701-B" manufactured by Tester Sangyo Co., Ltd., with a Teflon (registered trademark) coated seal bar surface, heat sealing was performed at a predetermined heat seal temperature of 200 to 230 ° C. shown in Tables 2 and 3 under the conditions of a surface pressure of 1.0 MPa, a sealing time of 3 seconds, a seal width of 7 mm, an ambient temperature of 23 ° C., and an ambient humidity of 50% RH. The surface appearance of the laminate after heat sealing and the presence or absence of welding of the laminate to the heat seal bar were visually observed and evaluated according to the following criteria. In Example 11, the test piece was folded with the coating layer facing outward, and heat-sealed according to the same procedure as above. The coating layer surface (corresponding to the laminate substrate surface) and the presence or absence of welding of the laminate to the heat seal bar were visually observed, and the evaluation was based on the following criteria. The "heat seal temperature" refers to the set temperature of the heat seal tester heat source. (Evaluation criteria) S... No change in the appearance of the laminate substrate surface, and no welding of the laminate substrate surface to the heat seal bar. A... Slight whitening of the laminate substrate surface, or slight welding of the laminate substrate surface to the heat seal bar. B... Whitening of the laminate substrate surface, or welding of the laminate substrate surface to the heat seal bar. C... Both whitening of the laminate substrate surface and welding of the laminate substrate surface to the heat seal bar.

[0234]

[0235] As described above, in conventional packaging materials for power storage devices for sealing electrodes, electrolytes, etc., when a bag is formed by heat sealing using a laminate containing a polyester film, the heat resistance of the laminate is low, so whitening occurs on the heat-sealed surface, deteriorating the surface appearance of the resulting bag, or the laminate is fused to the heat seal bar used for heat sealing. There are problems, and further, when the content of polybutylene terephthalate is reduced to improve heat resistance, even if a polyamide with excellent deep draw formability is laminated, there are problems such as damage to the periphery of the recess when attempting to form a deep recess. However, as shown in Tables 2 and 3, with the laminates of Examples 1 to 14 according to the present invention, changes in surface appearance and welding of the laminate to the heat seal bar can be sufficiently suppressed, and local stress concentration during molding is suppressed and stress uniformity is promoted. As a result, it is also excellent in deep draw formability, and it can be seen that both moldability and heat resistance can be achieved. The heat resistance of the laminates of Examples 1 to 8 at a heat sealing temperature of 230°C was evaluated as "C." However, since heat sealing is usually performed in a temperature range up to about 220°C, it can be said that the laminates of Examples 1 to 8 also have heat resistance sufficient for practical use.

[0236] Specifically, for example, as shown in Table 2, Example 1, which uses a polyester film (PE1) as the base layer, has relatively improved formability compared to the reference, which uses a polyester film (PE8) as the base layer. Furthermore, Example 1, which uses a polyester film (PE1) as the base layer, also has excellent heat resistance (note that the heat resistance is an absolute evaluation, not a relative evaluation with respect to the reference).

[0237] On the other hand, as shown in Tables 2 and 3, in the laminates of Comparative Examples 1 to 9, the mass ratio of polyethylene terephthalate to polybutylene terephthalate in the base layer was not controlled within the range of 65 / 35 to 90 / 10, and the tensile elongation at break in the width direction was not controlled within the range of 90% to 155%, so it can be seen that both formability and heat resistance were not achieved. Furthermore, for example, when a polyester film (PE8) containing only polyethylene terephthalate of the polyethylene terephthalate and polybutylene terephthalate and having a large MD tensile yield stress was used, as in Comparative Examples 1 and 7, it can be seen that although the heat resistance was excellent, both formability and heat resistance could not be achieved.

[0238] Furthermore, for example, even when a polyester film contains both polyethylene terephthalate and polybutylene terephthalate, when a polyester film (PE9) having a high polybutylene terephthalate content and low tensile yield stress in MD and TD is used as in Comparative Example 2, it is found that there is no effect of improving formability, heat resistance is insufficient, and both formability and heat resistance cannot be achieved. Furthermore, when a polyester film (PE10) having a high polybutylene terephthalate content and low TD tensile elongation at break and high TD tensile stress at break is used as in Comparative Example 3, it is found that there is no effect of improving formability, heat resistance is insufficient, and both formability and heat resistance cannot be achieved.

[0239] Similarly, even if a film contains both polyethylene terephthalate and polybutylene terephthalate, for example, when a polyester film (PE12) having a high polybutylene terephthalate content, a low MD tensile yield stress, and a low TD tensile break elongation is used, as in Comparative Example 5, there is no effect of improving formability, and both formability and heat resistance cannot be achieved. Furthermore, when a polyester film (PE13) having a high polybutylene terephthalate content, a low MD tensile yield stress, and a low TD tensile break elongation is used, as in Comparative Examples 6 and 8, heat resistance is insufficient, and both formability and heat resistance cannot be achieved.

[0240] Similarly, even if a film contains both polyethylene terephthalate and polybutylene terephthalate, for example, when a polyester film (PE14) is used that has a high polybutylene terephthalate content, a low MD tensile yield stress, a low TD tensile breaking elongation, and a low MD tensile breaking stress, as in Comparative Example 9, there is no effect of improving formability, and the heat resistance is insufficient, making it impossible to achieve both formability and heat resistance.

[0241] Furthermore, for example, even if a film contains polyethylene terephthalate and polybutylene terephthalate in the mass ratio range (65 / 35 to 90 / 10) specified in the present invention, when a polyester film (PE11) with a small tensile breaking stress in the MD is used, as in Comparative Example 4, the heat resistance is insufficient, and it is found that both formability and heat resistance cannot be achieved.

[0242] (Regarding the Presence or Absence of Polyamide Layer) As described above, in order to confirm the effect of the presence or absence of a polyamide layer, Example 12 without a polyamide layer was used as a reference, and the limit molding depth of Example 1 with a polyamide layer was evaluated using the same index as in the evaluation criterion 1. As a result, the limit molding depth of Example 1 was equal to or greater than the reference +1 mm and less than +1.5 mm compared to Example 12, and the evaluation was A. From this result, it can be seen that the effect of improving moldability can be obtained by forming a laminate having a polyamide layer.

[0243] Furthermore, among the examples using polyester films containing polyethylene terephthalate and polybutylene terephthalate in the mass ratio range specified in the present invention (65 / 35 to 90 / 10), it can be seen that films with a higher content of polyethylene terephthalate in the surface layer have better heat resistance, as shown in Examples 9 to 11, 13, and 14.

[0244] From the above, it has been demonstrated that an exterior packaging material for an electricity storage device, which uses a polyester film that satisfies all of the requirements of the present invention as a base material layer and includes a laminate having such base material layer, a polyamide layer, a barrier layer, and a heat-sealable resin layer in this order, can achieve a high level of both heat resistance and formability.

[0245] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0246] According to the present invention, it is possible to provide an exterior packaging material for an electricity storage device that has excellent formability and heat resistance, and is particularly suitable as a battery pouch (packaging body) for a relatively high-capacity lithium-ion battery.

[0247] REFERENCE SIGNS LIST 1 Base material layer 2 First adhesive layer 3 Polyamide layer 4 Second adhesive layer 5 Barrier layer 6 Heat-sealable resin layer

Claims

1. An exterior packaging material for an electricity storage device, which is composed of a laminate having at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, wherein the base layer is a polyester film containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 65 / 35 to 90 / 10, and the tensile elongation at break in the width direction of the polyester film is 90% or more and 155% or less.

2. The packaging material for an electricity storage device according to claim 1, further comprising a polyamide layer between the substrate layer and the barrier layer.

3. The packaging material for an electricity storage device according to claim 1 or 2, wherein the polyester film has a longitudinal tensile yield stress of 80 MPa or more and 105 MPa or less.

4. The packaging material for an electricity storage device according to any one of claims 1 to 3, wherein the polyester film has a tensile yield stress in the width direction of 65 MPa or more and 110 MPa or less.

5. The packaging material for an electricity storage device according to any one of claims 1 to 4, wherein the tensile elongation at break in the longitudinal direction of the polyester film is 110% or more and 190% or less.

6. The exterior packaging material for a storage battery device according to any one of claims 1 to 5, wherein the polyester film has a longitudinal tensile breaking stress of 160 MPa or more and 260 MPa or less, and a widthwise tensile breaking stress of 190 MPa or more and 290 MPa or less.

7. The packaging material for an electricity storage device according to any one of claims 1 to 6, wherein the tensile elongation at break in the width direction of the polyester film is equal to or less than the tensile elongation at break in the longitudinal direction of the polyester film.

8. The packaging material for an electricity storage device according to any one of claims 1 to 7, wherein the tensile breaking stress in the width direction of the polyester film is equal to or greater than the tensile breaking stress in the longitudinal direction of the polyester film.

9. The packaging material for an electricity storage device according to any one of claims 1 to 8, wherein the slope of the stress-strain curve of the polyester film corresponding to the section from the yield point to the break point is 0.60 MPa / % or more and 1.20 MPa / % or less in the longitudinal direction and 1.00 MPa / % or more and 1.80 MPa / % or less in the width direction.

10. The exterior packaging material for an electricity storage device according to claim 9, wherein the absolute value of the difference between the gradient of the curve in the longitudinal direction and the gradient of the curve in the width direction is 1.10 MPa / % or less.

11. The packaging material for an electricity storage device according to any one of claims 1 to 10, wherein the melting point (1st run) of the polyester film is 230°C or higher.

12. The packaging material for an electricity storage device according to any one of claims 1 to 11, which comprises an adhesive layer between the base material layer and the barrier layer.

13. The packaging material for an electricity storage device according to any one of claims 1 to 12, further comprising a polyamide layer made of a stretched film between the base layer and the barrier layer.

14. The packaging material for an electricity storage device according to any one of claims 1 to 13, wherein the barrier layer contains aluminum.

15. The packaging material for an electricity storage device according to any one of claims 1 to 14, wherein the polyester film is composed of a laminate of two or more layers.

16. The packaging material for an electricity storage device according to any one of claims 1 to 15, wherein the polyester film comprises a surface layer, an intermediate layer, and another surface layer in this order.

17. The exterior packaging material for an electricity storage device according to any one of claims 1 to 16, wherein the polyester film comprises a surface layer, an intermediate layer, and another surface layer in this order, and the thickness of the intermediate layer is greater than the thickness of the surface layer.

18. The exterior packaging material for an electricity storage device according to any one of claims 1 to 17, wherein the polyester film comprises a surface layer, an intermediate layer, and another surface layer in this order, and the ratio of the thicknesses of the layers (thickness of the surface layer:thickness of the intermediate layer:thickness of the surface layer) is 1-1.6:8-12:1-1.

6.

19. The exterior packaging material for an electricity storage device according to any one of claims 1 to 18, wherein the polyester film is composed of a laminate of two or more layers, and the material composition forming one of the surface layers is different from the material composition forming at least one of the other layers.

20. An exterior packaging material for an electricity storage device according to any one of claims 1 to 19, wherein the polyester film comprises a surface layer, an intermediate layer, and a surface layer in this order, and the material composition forming the surface layer is different from the material composition forming the intermediate layer.

21. An exterior packaging material for an electricity storage device according to any one of claims 1 to 20, wherein the polyester film is composed of a laminate of two or more layers, and the polyethylene terephthalate content in one surface layer is higher than the polyethylene terephthalate content in at least one of the other layers.

22. An exterior packaging material for an electricity storage device according to any one of claims 1 to 21, wherein the polyester film is composed of a laminate of two or more layers, the polyethylene terephthalate content in one surface layer being greater than the polyethylene terephthalate content in at least one of the other layers, and the surface layer being located on the outermost layer side of the laminate.

23. An exterior packaging material for an electricity storage device according to any one of claims 1 to 22, wherein the polyester film comprises a surface layer, an intermediate layer, and another surface layer in this order, and the content of polyethylene terephthalate in the surface layer is greater than the content of polyethylene terephthalate in the intermediate layer.

24. An exterior packaging material for an electricity storage device according to any one of claims 1 to 23, wherein the polyester film is composed of a laminate of two or more layers, one of the surface layers containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10.

25. An exterior packaging material for an electricity storage device according to any one of claims 1 to 24, wherein the polyester film is composed of a laminate of two or more layers, one of the surface layers containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10, and the surface layer is located on the outermost layer side of the laminate.

26. An exterior packaging material for an electricity storage device according to any one of claims 1 to 25, wherein the polyester film comprises a surface layer, an intermediate layer and another surface layer in this order, and the surface layer contains polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 100 / 0 to 90 / 10.

27. The packaging material for an electricity storage device according to any one of claims 1 to 26, wherein the polyester film exhibits one melting peak during temperature rise in at least one of the first and second runs as measured by differential scanning calorimetry.

28. The packaging material for an electricity storage device according to any one of claims 1 to 27, which has a coating layer on at least one surface of the polyester film.

29. An exterior packaging material for an electricity storage device according to any one of claims 1 to 28, having a coating layer on at least one surface of the polyester film, the coating layer containing a long-chain alkyl group-containing compound and a melamine compound in a mass ratio of 95 / 5 to 5 / 95.

30. An exterior packaging material for an electricity storage device according to any one of claims 1 to 29, wherein the polyethylene terephthalate contained in the polyester film has an intrinsic viscosity of 0.50 dL / g or more.

31. The packaging material for an electricity storage device according to any one of claims 1 to 30, wherein the polybutylene terephthalate contained in the polyester film has an intrinsic viscosity of 0.70 dL / g or more.

32. An exterior packaging material for an electricity storage device according to any one of claims 1 to 31, wherein the polyester film is a biaxially stretched film, and the product of the stretching ratio in the width direction and the stretching ratio in the longitudinal direction of the polyester film is greater than 15.

5.

33. An exterior packaging material for a storage battery device according to any one of claims 1 to 32, wherein the polyester film is a biaxially stretched film, and the difference between the stretching ratio in the width direction and the stretching ratio in the longitudinal direction of the polyester film is 0.3 or more.

34. An exterior packaging material for an electricity storage device according to any one of claims 1 to 33, wherein the polyester film is a biaxially stretched film, and the ratio of the stretching ratio in the width direction of the polyester film to the stretching ratio in the longitudinal direction (stretching ratio in the width direction / stretching ratio in the longitudinal direction) is 1.2 or more and 1.7 or less.

35. An electricity storage device in which an electricity storage device element having at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed from the exterior packaging material for an electricity storage device according to any one of claims 1 to 34.

36. A method for producing an exterior material for an electricity storage device, comprising a step of laminating at least a base layer, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, wherein the base layer is a polyester film containing polyethylene terephthalate and polybutylene terephthalate in a mass ratio of 65 / 35 to 90 / 10, and the tensile elongation at break in the width direction of the polyester film is 90% or more and 155% or less.

37. A method for producing an exterior material for an electricity storage device as described in claim 36, wherein the step of obtaining the laminate is a step of obtaining a laminate comprising at least a base layer, a polyamide layer, a barrier layer, and a heat-sealable resin layer in this order, and the polyester film has a longitudinal tensile yield stress of 80 MPa or more and 105 MPa or less, a width tensile yield stress of 65 MPa or more and 110 MPa or less, and a longitudinal tensile breaking elongation of 110% or more and 190% or less.

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