Wrapping material for cell, production method thereof, cell, and polyester film

Abstract

To provide a technique for restraining curl after molding, while improving moldability, in a wrapping material for a cell consisting of a laminate including a barrier layer, a heat-seal resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer.MEANS FOR SOLVING THE PROBLEM: A wrapping material for a cell is composed of a laminate including at least a barrier layer, a heat-seal resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer, and when the infrared absorption spectrum of 18 directions is acquired from 0° to 180° at a pitch of 10°, on the surface of the polyester film, by using total reflection method of Fourier transformation infrared spectroscopy, the ratio (surface orientation: Ymax / Ymin) of the maximum value Ymax and the minimum value Ymin of the ratio (Y1340 / Y1410) of the absorption peak intensity at 1,340 cm-1 of the infrared absorption spectrum, and the absorption peak intensity Y1410 at 1,410 cm-1 is in the range of 1.4-2.7.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Various types of batteries have been developed, but in all batteries, packaging materials are essential components for sealing battery elements such as electrodes and electrolytes. Conventionally, metallic packaging materials have been widely used for battery packaging.

[0003] Meanwhile, in recent years, batteries are being required to have a variety of shapes and to be thin and lightweight in line with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc. However, the metallic battery packaging materials that have been widely used in the past have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations in terms of weight reduction.

[0004] In recent years, a film-like laminate in which a substrate, a barrier layer, and a heat-sealable resin layer are laminated in this order has been proposed as a battery packaging material that can be easily processed into various shapes and can be made thinner and lighter (see, for example, Patent Document 1). In such battery packaging materials, generally, recesses are formed by cold forming, and battery elements such as electrodes and electrolyte are placed in the spaces formed by the recesses, and the heat-sealable resin layers are heat-sealed to each other to obtain a battery in which the battery elements are housed inside the battery packaging material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-287971 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, with the demand for smaller and thinner batteries, there has been a demand for even thinner packaging materials for batteries.

[0007] However, when the thickness of each layer of the battery packaging material is reduced, the peripheral portion of the recess formed in the battery packaging material curls (curves), which may hinder the accommodation of the battery element and the thermal fusion of the thermally adhesive resin layer, thereby reducing the production efficiency of the battery. In particular, battery packaging materials used for large secondary batteries such as secondary batteries for automobiles have a problem in that the curl has a very large effect on the productivity of the battery due to their large size.

[0008] In addition, when the outer surface (substrate surface) of a battery is made of, for example, a nylon film, if an electrolyte adheres to the surface of the battery during the manufacturing process of the battery, the outer surface of the battery is corroded (whitened) and becomes defective. For this reason, a stretched polyester film is sometimes used as the substrate to improve the chemical resistance and electrolyte resistance of the outer surface of the battery. However, the present inventors have found that the above-mentioned curling is particularly likely to occur in a battery packaging material laminated with a stretched polyester film. Furthermore, there is a problem that the moldability is easily reduced when the thickness of the battery packaging material is reduced, and in particular, there is a problem that a stretched polyester film is harder and less moldable than a polyamide film.

[0009] Under these circumstances, a main object of the present invention is to provide a technology for improving formability and suppressing curling after molding in a battery packaging material consisting of a laminate including a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems. As a result, in a battery packaging material composed of a laminate including at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer, when infrared absorption spectra were obtained in 18 directions at intervals of 10° from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, the infrared absorption spectrum of the polyester film at 1340 cm -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) in the range of 1.4 or more and 2.7 or less, the moldability is excellent and furthermore, curling after molding is effectively suppressed. The present invention was completed based on these findings and through further investigations.

[0011] That is, the present invention provides the following aspects. Item 1. The laminate is made of at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer, When infrared absorption spectra were obtained in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min) is in the range of 1.4 or more and 2.7 or less. Item 2. The battery packaging material according to Item 1, wherein the ratio of the thickness of the heat-sealable resin layer to the thickness of the polyester film is less than 3. Item 3. The battery packaging material according to Item 1 or 2, wherein the heat-sealable resin layer has a thickness of 100 μm or less. Item 4. The battery packaging material according to any one of Items 1 to 3, wherein the polyester film has a birefringence of 0.016 or more. Item 5. A battery, comprising a battery element including at least a positive electrode, a negative electrode, and an electrolyte, housed in a package formed from the battery packaging material according to any one of Items 1 to 4. Item 6. The method includes a step of laminating at least a polyester film, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, When the total reflection method of Fourier transform infrared spectroscopy was used to obtain infrared absorption spectra of the polyester film in 18 directions at intervals of 10° from 0° to 180° on the surface of the polyester film, -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. Item 7. A polyester film for use as a packaging material for batteries, When infrared absorption spectra were obtained in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. Item 8. When the total reflection method of Fourier transform infrared spectroscopy is used to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of a polyester film, the 1340 cm -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) is in the range of 1.4 or more and 2.7 or less, as packaging material for batteries. Effect of the Invention

[0012] According to the present invention, it is possible to provide a packaging material for batteries which is composed of a laminate including a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer, and which has excellent formability and is effectively prevented from curling after forming. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing an example of a cross-sectional structure of a battery packaging material of the present invention. [Diagram 2] 1 is a diagram showing an example of a cross-sectional structure of a battery packaging material of the present invention. [Diagram 3] 1 is a diagram showing an example of a cross-sectional structure of a battery packaging material of the present invention. [Figure 4] 1 is a diagram showing an example of a cross-sectional structure of a battery packaging material of the present invention. [Diagram 5]FIG. 2 is a schematic diagram for explaining a method for evaluating curl. [Figure 6] FIG. 2 is a schematic diagram for explaining a method for evaluating curl. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The battery packaging material of the present invention is composed of a laminate including at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a polyester film located on the other side of the barrier layer. When infrared absorption spectra are obtained in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, -1 Absorption peak intensity Y 1340 (CH2 wobbling vibration) and 1410cm -1 Absorption peak intensity Y 1410 (C=C stretching vibration) (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. The battery packaging material of the present invention will be described in detail below.

[0015] In this specification, the notation "~" indicating a numerical range indicates that the value is equal to or greater than the numerical value on the left side and equal to or less than the numerical value on the right side. For example, the notation of a numerical range "X~Y" means that the value is equal to or greater than X and equal to or less than Y.

[0016] 1.Laminated structure of battery packaging material 1, the battery packaging material 10 of the present invention is composed of a laminate including a polyester film 1, a barrier layer 3, and a heat-sealable resin layer 4 in this order. In the battery packaging material of the present invention, the polyester film 1 is the outermost layer, and the heat-sealable resin layer 4 is the innermost layer. That is, when the battery is assembled, the heat-sealable resin layers 4 located on the periphery of the battery element are heat-sealed to each other to seal the battery element, thereby sealing the battery element.

[0017] The battery packaging material of the present invention may have an adhesive layer 2 between the polyester film 1 and the barrier layer 3, as required, for the purpose of enhancing adhesion therebetween, as shown in, for example, Fig. 2. Also, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-sealable resin layer 4, as required, for the purpose of enhancing adhesion therebetween. Also, as shown in Fig. 4, a surface coating layer 6 or the like may be provided on the outer side of the polyester film 1 (the side opposite to the heat-sealable resin layer 4), as required.

[0018] The total thickness of the laminate constituting the battery packaging material of the present invention is not particularly limited, but from the viewpoint of exhibiting high moldability while making the total thickness of the laminate as thin as possible and further effectively suppressing curling after molding, it is preferably about 160 μm or less, more preferably about 35 to 155 μm, and even more preferably about 45 to 120 μm. Even when the thickness of the laminate constituting the battery packaging material of the present invention is thin, for example, 160 μm or less, according to the present invention, it is possible to effectively suppress curling after molding while maintaining excellent moldability.

[0019] 2. Layers that form the battery packaging material [Polyester film 1] In the battery packaging material of the present invention, the polyester film 1 is the layer located on the outermost layer side and functions as a substrate.

[0020] In the battery packaging material of the present invention, infrared absorption spectra were obtained for the surface of the polyester film in 18 directions at intervals of 10° from 0° to 180° using the total reflection method of Fourier transform infrared spectroscopy, and the infrared absorption spectrum of 1340 cm-1 Absorption peak intensity Y 1340 (CH2 pitch vibration) and 1410cm -1 Absorption peak intensity Y 1410 (C=C stretching vibration) (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min In the battery packaging material of the present invention, the surface orientation degree (Y max / Y min When the surface orientation degree (Y ) of the polyester film is in the range of 1.4 to 2.7, the polyester film has excellent moldability and effectively suppresses curling after molding. The mechanism behind this is considered as follows. max / Y min ) is in the range of 1.4 to 2.7, the polyester molecules constituting the polyester film have a high crystal orientation, and shrinkage of the polyester film during molding is suppressed. As a result, it is believed that curling after molding is effectively suppressed while exhibiting excellent moldability.

[0021] Specific measurement conditions for the infrared absorption spectrum are as follows. The infrared absorption spectrum on the surface of the polyester film can be measured in a state where the polyester film is laminated on a battery packaging material, so long as the surface of the polyester film is exposed. In addition, when a surface coating layer 6 or the like described below is laminated on the surface of the polyester film 1, the surface coating layer 6 can be removed to expose the surface of the polyester film, and the measurement can be performed. In addition, the infrared absorption spectrum of the polyester film of the present invention described below is measured on a single layer polyester film under the following measurement conditions.

[0022] (Infrared absorption spectrum measurement conditions) Measurements are performed using a Fourier transform infrared spectrophotometer with single reflection ATR method under the following conditions. Wavenumber resolution: 8cm-1 IRE:Ge Incident angle: 30° Polarizer: Wire grid, S-polarized Baseline: Average value of intensity in the wavenumber range from 1800 cm-1 to 2000 cm-1 Absorption peak intensity Y 1340 : The maximum peak intensity in the wavenumber range from 1335 cm-1 to 1342 cm-1 minus the baseline value Absorption peak intensity Y 1410 : The maximum peak intensity in the wavenumber range from 1400 cm-1 to 1410 cm-1 minus the baseline value

[0023] To obtain infrared absorption spectra in 18 directions, the polyester film sample was placed horizontally on the sample holder and rotated by 10° each time with the Ge crystal placed on top of the sample. The incidence angle is the angle between the perpendicular line (normal line) and the incident light.

[0024] The degree of surface orientation (Y max / Y min ) is not particularly limited as long as it is in the range of 1.4 to 2.7, but from the viewpoint of providing excellent moldability while suppressing curling after molding and improving moldability, the lower limit is preferably about 1.6 or more, and the upper limit is preferably about 2.4 or less. max / Y min ) is preferably in the range of about 1.4 to 2.4, about 1.6 to 2.7, or about 1.6 to 2.4.

[0025] The degree of surface orientation as described above: Y max / Y min The polyester film having the above formula (1) can be produced by appropriately adjusting the stretching method, stretching ratio, stretching speed, cooling temperature, heat setting temperature, and the like when producing the polyester film.

[0026] In addition, in the battery packaging material of the present invention, the birefringence of the polyester film is preferably 0.016 or more. That is, in the refractive index measurement of the polyester film, the birefringence (nx-ny) calculated by measuring the refractive index (nx) in the slow axis direction, which is the direction in which the refractive index is large, and the refractive index (ny) in the fast axis direction, which is the direction perpendicular to the slow axis, is preferably 0.016 or more. By having the birefringence of the polyester film be 0.016 or more, curling after molding is more effectively suppressed while exhibiting better moldability. This mechanism can be considered as follows. That is, since the birefringence of the polyester film is 0.016 or more, the crystal orientation of the polyester molecules constituting the polyester film is high, and the shrinkage of the polyester film during molding is suppressed, and as a result, it is considered that curling after molding is more effectively suppressed while exhibiting better moldability.

[0027] Specific conditions for measuring the birefringence are as follows: The birefringence of a polyester film is measured on a polyester film used for a packaging material for batteries.

[0028] (Conditions for measuring birefringence) The birefringence of the polyester film can be measured using a phase difference measuring device. The measurement wavelength is 550 nm, and the incident angle is 10 degrees. The thickness of the polyester film used to calculate the birefringence is measured using a micrometer. The average refractive index of the polyester film used to calculate the birefringence is assumed to be 1.6200.

[0029] From the viewpoint of suppressing curling after molding and further improving moldability, the lower limit of the birefringence is preferably about 0.019 or more, and the upper limit is preferably about 0.056 or less, more preferably about 0.050 or less, even more preferably about 0.042 or less, even more preferably about 0.026 or less, and particularly preferably about 0.022 or less. Preferred ranges of the birefringence include about 0.016 to 0.056, about 0.016 to 0.050, about 0.016 to 0.042, about 0.016 to 0.026, about 0.016 to 0.022, about 0.019 to 0.056, about 0.019 to 0.050, about 0.019 to 0.042, about 0.019 to 0.026, and about 0.019 to 0.022.

[0030] The refractive index (nx) of the polyester film in the slow axis direction is preferably about 1.68 to 1.70, and the refractive index (ny) of the polyester film in the fast axis direction is preferably about 1.64 to 1.68.

[0031] The polyester film having the birefringence as described above has the above-mentioned surface orientation degree: Y max / Y min Similarly, it can be produced by appropriately adjusting the stretching method, stretching ratio, stretching speed, cooling temperature, heat setting temperature, etc., used in producing the above-mentioned polyester film.

[0032] The polyester film is preferably a stretched polyester film, more preferably a biaxially stretched polyester film The stretched polyester film is a polyester film that has been stretched during the production process of the polyester film.

[0033] Specific examples of polyesters constituting the polyester film include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymerized polyesters mainly composed of ethylene terephthalate as a repeating unit, copolymerized polyesters mainly composed of butylene terephthalate as a repeating unit, etc. Specific examples of copolymerized polyesters mainly composed of ethylene terephthalate as a repeating unit include copolymerized polyesters mainly composed of ethylene terephthalate as a repeating unit polymerized with ethylene isophthalate (hereinafter abbreviated as polyethylene (terephthalate / isophthalate)), polyethylene (terephthalate / isophthalate), polyethylene (terephthalate / adipate), polyethylene (terephthalate / sodium sulfoisophthalate), polyethylene (terephthalate / sodium isophthalate), polyethylene (terephthalate / phenyl-dicarboxylate), polyethylene (terephthalate / decane dicarboxylate), etc. Specific examples of copolymer polyesters containing butylene terephthalate as the main repeating unit include copolymer polyesters in which butylene terephthalate is the main repeating unit and is polymerized with butylene isophthalate (hereinafter abbreviated as polybutylene (terephthalate / isophthalate)), polybutylene (terephthalate / adipate), polybutylene (terephthalate / sebacate), polybutylene (terephthalate / decanedicarboxylate), polybutylene naphthalate, etc. These polyesters may be used alone or in combination of two or more.

[0034] The thickness of the polyester film 1 is not particularly limited, but from the viewpoint of improving formability and effectively suppressing curling after molding, it is preferably 50 μm or less. From the viewpoint of further improving formability in addition to suppressing curling, it is preferably about 4 to 30 μm, more preferably about 16 to 25 μm. Note that, as described later, when the polyester film 1 has a multilayer structure, the thickness of the polyester film layer located on the outermost layer side is preferably about 4 to 16 μm, more preferably about 9 to 12 μm.

[0035] The polyester film 1 may be a single layer or a multi-layer (multi-layer structure). When the polyester film 1 is a multi-layer, at least one polyester film layer located on the outermost layer side (opposite to the barrier layer 3) has the above-mentioned surface orientation degree: Y max / Y min It is sufficient that the range of the above is satisfied.

[0036] In order to improve pinhole resistance and insulation when used as a battery package, the one side of the barrier layer 3 may be laminated (multilayered) with at least one of a resin film and a coating made of a different material in addition to the polyester film to form a substrate. Examples of other resin films used for the substrate include resin films made of polyamide, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenolic resin, polyetherimide, polyimide, and mixtures or copolymers thereof. A specific example of a structure in which the polyester film 1 and a resin film made of a different material are laminated is a multilayer structure in which a polyester film and a polyamide film are laminated.

[0037] Specific examples of polyamides constituting the polyamide film include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 6,6; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (I represents isophthalic acid, T represents terephthalic acid) that contain structural units derived from terephthalic acid and / or isophthalic acid, and aromatic polyamides such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); polyamides copolymerized with lactam components or isocyanate components such as 4,4'-diphenylmethane diisocyanate; polyesteramide copolymers and polyetheresteramide copolymers that are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and copolymers of these. These polyamides may be used alone or in combination of two or more. Polyamide films have excellent stretchability and can prevent whitening due to resin cracking during molding, and are therefore suitable for use as a resin film used as a substrate together with the polyester film 1.

[0038] Specific examples of the case where the substrate has a multi-layer structure of polyester film 1 and where the resin film is provided include a laminate of polyester film and nylon film, and a laminate of multiple polyester films, and more preferably a laminate of stretched polyester film and stretched nylon film, and a laminate of multiple stretched polyester films. For example, when the substrate has a two-layer structure, it is preferable to have a structure in which a polyester film and a polyamide film are laminated, or a structure in which a polyester film and a polyester film are laminated, and more preferably a structure in which polyethylene terephthalate and nylon are laminated, or a structure in which polyethylene terephthalate and polyethylene terephthalate are laminated. In addition, since the polyester film is unlikely to discolor when an electrolyte solution adheres to the surface, for example, a laminate having a nylon film and a polyester film in this order from the barrier layer 3 side can be configured to have excellent electrolyte resistance. The thickness of the polyester film that is not located in the outermost layer or the resin film other than the polyester film is preferably 3 to 25 μm.

[0039] When the base material is a multi-layer structure of polyester film 1, or when the base material is configured to include the resin film, the polyester film 1 and each resin film may be bonded via an adhesive, or may be directly laminated without an adhesive. When bonding without an adhesive, for example, a method of bonding in a thermally molten state such as a co-extrusion method, a sandwich lamination method, or a thermal lamination method may be mentioned. When bonding via an adhesive, the adhesive used may be a two-component curing adhesive or a one-component curing adhesive. Furthermore, the bonding mechanism of the adhesive is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a thermal melting type, a thermal pressure type, an electron beam curing type, an ultraviolet ray curing type, and the like. Specific examples of the adhesive include the same adhesives as those exemplified in the adhesive layer 2. The thickness of the adhesive may also be the same as that of the adhesive layer 2.

[0040] In the present invention, from the viewpoint of improving the moldability of the battery packaging material, it is preferable that a lubricant is attached to the surface of the battery packaging material. The lubricant may be contained in the polyester film 1 or the surface coating layer 6, or the lubricant may be present on the surface of the battery packaging material. The lubricant present on the outermost surface of the battery packaging material may be a lubricant contained in the resin constituting the polyester film 1 or the surface coating layer 6 that has been exuded, or a lubricant may be applied to the surface of the battery packaging material. The lubricant is not particularly limited, but is preferably an amide-based lubricant. Specific examples of the lubricant include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, and unsaturated fatty acid bisamides. Specific examples of the saturated fatty acid amides include lauric acid amides, palmitic acid amides, stearic acid amides, behenic acid amides, and hydroxystearic acid amides. Specific examples of the unsaturated fatty acid amides include oleic acid amides and erucic acid amides. Specific examples of the substituted amide 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. Specific examples of the methylol amide include methylol stearic acid amide. Specific examples of the saturated fatty acid bisamide 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 adipic acid amide, and N,N'-distearyl sebacic acid amide. Specific examples of the unsaturated fatty acid bisamide include ethylene bisoleamide, ethylene biserucamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacamide, etc. Specific examples of the fatty acid ester amide include stearamide ethyl stearate, etc.Specific examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearylisophthalic acid amide, etc. The lubricant may be used alone or in combination of two or more kinds.

[0041] When a lubricant is present on the surface of the polyester film 1, the amount of the lubricant is not particularly limited, but is preferably about 3 mg / m in an environment of a temperature of 24° C. and a relative humidity of 60%. 2 More preferably, 4 to 15 mg / m 2 about 5 to 14 mg / m 2 The degree of

[0042] The total thickness of the polyester film 1 and the other resin films (total thickness of the substrate) is not particularly limited, but is preferably about 50 μm or less from the viewpoint of effectively suppressing curling after molding while improving moldability. Moreover, from the viewpoint of further improving moldability in addition to suppressing curling, the thickness is preferably about 4 to 30 μm, more preferably about 16 to 25 μm.

[0043] [Adhesive layer 2] In the battery packaging material of the present invention, the adhesive layer 2 is a layer that is provided between the polyester film 1 or the above-mentioned resin film and the barrier layer 3, as necessary, in order to firmly bond them together.

[0044] The adhesive layer 2 is formed of an adhesive capable of bonding the polyester film 1 or the above-mentioned resin film to the barrier layer 3. The adhesive used to form the adhesive layer 2 may be a two-component curing adhesive or a one-component curing adhesive. Furthermore, the adhesive used to form the adhesive layer 2 is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a thermal melting type, a thermal pressure type, etc.

[0045] Specific examples of adhesive components that can be used to form the adhesive layer 2 include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolymerized polyester; polyether-based adhesives; polyurethane-based adhesives; epoxy-based resins; phenol-based resins; polyamide-based resins such as nylon 6, nylon 66, nylon 12, and copolymerized polyamide; polyolefin-based resins such as polyolefin, carboxylic acid-modified polyolefin, and metal-modified polyolefin; polyvinyl acetate-based resins; cellulose-based adhesives; (meth)acrylic resins; polyimide-based resins; polycarbonate; amino resins such as urea resins and melamine resins; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; and silicone-based resins. These adhesive components may be used alone or in combination of two or more. Among these adhesive components, polyurethane-based adhesives are preferable. In addition, the adhesive strength of these adhesive component resins can be increased by using an appropriate curing agent in combination. The curing agent is appropriately selected from polyisocyanates, polyfunctional epoxy resins, oxazoline group-containing polymers, polyamine resins, acid anhydrides, etc., depending on the functional groups of the adhesive components. As these adhesive components and curing agents, polyurethane adhesives made of various polyols (adhesive components having hydroxyl groups) and polyisocyanates are preferred. More preferred are two-component curing polyurethane adhesives made of polyols such as polyester polyols, polyether polyols, and acrylic polyols as the main component, and aromatic or aliphatic polyisocyanates as the curing agent.

[0046] The thickness of the adhesive layer 2 is not particularly limited as long as it functions as an adhesive layer, but may be, for example, about 1 to 10 μm, and preferably about 2 to 5 μm.

[0047] [Barrier layer 3] In the battery packaging material, the barrier layer 3 is a layer that has the function of preventing water vapor, oxygen, light, and the like from penetrating into the inside of the battery in addition to improving the strength of the battery packaging material. The barrier layer 3 is preferably a metal layer, that is, a layer formed of a metal. Specific examples of metals constituting the barrier layer 3 include aluminum, stainless steel, and titanium, and aluminum is preferred. The barrier layer 3 can be formed, for example, of 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 these vapor deposition films, and is preferably formed of a metal foil, and more preferably formed of an aluminum alloy foil. From the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 3 during the production of the battery packaging material, it is more preferable that the barrier layer be formed from 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).

[0048] The thickness of the barrier layer 3 is not particularly limited as long as it exhibits a barrier function against water vapor and the like. From the viewpoint of reducing the thickness of the battery packaging material, the thickness is preferably about 100 μm or less, more preferably about 10 to 100 μm, and even more preferably about 10 to 80 μm.

[0049] In addition, it is preferable that at least one surface, preferably both surfaces, of the barrier layer 3 are chemically treated in order to stabilize adhesion and prevent dissolution and corrosion. Here, the chemical conversion treatment refers to a treatment for forming an acid-resistant film on the surface of the barrier layer. In the present invention, the barrier layer 3 may be provided with an acid-resistant film on one surface, may be provided with an acid-resistant film on both surfaces, or may not be provided with an acid-resistant film. Examples of the chemical conversion treatment include chromate treatment using a chromium compound such as chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromate acetyl acetate, chromium chloride, and potassium chromium sulfate; phosphate treatment using a phosphate compound such as sodium phosphate, potassium phosphate, ammonium phosphate, and polyphosphoric acid; and chromate treatment using an aminated phenol polymer having repeating units represented by the following general formulas (1) to (4). In the aminated phenol polymer, the repeating units represented by the following general formulas (1) to (4) may be contained alone or in any combination of two or more types.

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] 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 2In the general formulae (1) to (4), X and R are the same or different and each represents a hydroxyl group, an alkyl group, or a hydroxyalkyl group. 1 and R 2 Examples of the alkyl group represented by the formula (I) include linear or branched alkyl groups 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 2 Examples of the hydroxyalkyl group represented by the formula (1) to (4) include linear or branched alkyl groups having 1 to 4 carbon atoms substituted with one hydroxy 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 group and the hydroxyalkyl group represented by the formulas may be the same or different. In the 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 the repeating units represented by the formulas (1) to (4) is preferably, for example, about 500 to 1,000,000, and more preferably about 1,000 to 20,000.

[0055] As a chemical conversion treatment method for imparting corrosion resistance to the barrier layer 3, a method is exemplified in which fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, and tin oxide, or barium sulfate are dispersed in phosphoric acid, and then baking is performed at 150° C. or higher to form an acid-resistant film on the surface of the barrier layer 3. A resin layer in which a cationic polymer is crosslinked with a crosslinking agent may be further formed on the acid-resistant film. Examples of the cationic polymer include polyethyleneimine, an ionic polymer complex consisting of a polymer having polyethyleneimine and a carboxylic acid, a primary amine-grafted acrylic resin in which a primary amine is graft-polymerized to an acrylic main skeleton, polyallylamine or a derivative thereof, and aminophenol. These cationic polymers may be used alone or in combination of two or more. Examples of the crosslinking agent include a compound 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 a silane coupling agent. These crosslinking agents may be used alone or in combination of two or more.

[0056] As a specific method for providing the acid-resistant film, for example, at least the inner layer surface of the aluminum alloy foil is first degreased by a known treatment method such as an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method, and then a treatment liquid (aqueous solution) mainly composed of a metal phosphate such as a chromium phosphate, a titanium phosphate, a zirconium phosphate, or a zinc phosphate, or a mixture of these metal salts, or a treatment liquid (aqueous solution) mainly composed of a nonmetallic phosphate and a mixture of these nonmetallic salts, or a treatment liquid (aqueous solution) consisting of a mixture of these and a water-based synthetic resin such as an acrylic resin, a phenolic resin, or a urethane resin, is applied to the degreased surface by a known coating method such as a roll coating method, a gravure printing method, or a dipping method to form an acid-resistant film. For example, treatment with a chromium phosphate-based treatment solution results in an acid-resistant coating made of chromium phosphate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc., while treatment with a zinc phosphate-based treatment solution results in an acid-resistant coating made of zinc phosphate hydrate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc.

[0057] As another example of a specific method for providing an acid-resistant coating, for example, at least the inner layer surface of the aluminum alloy foil is first degreased by a well-known treatment method such as an alkali immersion method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method, and then the degreased surface is subjected to a well-known anodizing treatment to form an acid-resistant coating.

[0058] 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.

[0059] 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 that functions as the base material during embossing, prevent dissolution and corrosion of the aluminum surface, particularly aluminum oxide present on the aluminum surface, caused by hydrogen fluoride produced by a reaction between an electrolyte and water, and improve the adhesion (wettability) of the aluminum surface, preventing delamination between the layer that functions as the base material and aluminum during heat fusion, and in the case of embossed types, preventing delamination between the layer that functions as the base material and aluminum during press molding. Among the substances that form acid-resistant coatings, an aqueous solution composed of three components, phenol resin, chromium (III) fluoride compound, and phosphoric acid, is applied to the aluminum surface and dried and baked, providing good results.

[0060] 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 the phosphate may be blended in an amount of about 1 to 100 parts by mass per 100 parts by mass of the cerium oxide. It is preferable that the acid-resistant coating has a multilayer structure further including a layer having a cationic polymer and a crosslinking agent that crosslinks the cationic polymer.

[0061] 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.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.

[0062] The phosphoric acid or the phosphate is preferably a condensed phosphoric acid or a condensed phosphate.

[0063] The chemical conversion treatment may be performed using only one type of chemical conversion treatment, or may be performed using a combination of two or more types of chemical conversion treatment. Furthermore, these chemical conversion treatments may be performed using one type of compound alone, or may be performed using a combination of two or more types of compounds. Among the chemical conversion treatments, chromate treatment and chemical conversion treatments combining a chromium compound, a phosphoric acid compound, and an aminated phenol polymer are preferred. Among the chromium compounds, chromate compounds are preferred.

[0064] Specific examples of the acid-resistant coating include those containing at least one of phosphate, chromate, fluoride, and triazine thiol. Also preferred are acid-resistant coatings containing a cerium compound. As the cerium compound, cerium oxide is preferred.

[0065] Specific examples of the acid-resistant film include a phosphate-based film, a chromate-based film, a fluoride-based film, and a triazine thiol compound film. The acid-resistant film may be one of these films, or a combination of two or more of them. Furthermore, the acid-resistant film may be formed by degreasing the chemically treated surface of the aluminum alloy foil, using a treatment liquid made of a mixture of a metal phosphate and a water-based synthetic resin, or a treatment liquid made of a mixture of a nonmetal phosphate and a water-based synthetic resin.

[0066] The composition of the acid-resistant film can be analyzed, for example, by using time-of-flight secondary ion mass spectrometry. + and Cr + A peak originating from at least one of the above is detected.

[0067] The surface of the aluminum alloy foil is preferably provided with an acid-resistant film 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 film on the surface of the aluminum alloy foil of the battery packaging material can be confirmed by X-ray photoelectron spectroscopy. Specifically, first, the heat-sealable resin layer, adhesive layer, etc. laminated on the aluminum alloy foil in the battery packaging material are physically peeled off. Next, the aluminum alloy foil is placed in an electric furnace and organic components present on the surface of the aluminum alloy foil are removed at about 300°C for about 30 minutes. Then, the presence of these elements is confirmed by X-ray photoelectron spectroscopy of the surface of the aluminum alloy foil.

[0068] The amount of the acid-resistant film formed on the surface of the barrier layer 3 in the chemical conversion treatment is not particularly limited. For example, in the case of the above-mentioned chromate treatment, 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 1.0 to 40 mg, calculated as phosphorus, and the aminated phenol polymer is contained in an amount of about 1.0 to 200 mg, preferably about 5.0 to 150 mg, calculated as phosphorus, per unit area.

[0069] 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 3 and the heat-sealable resin layer. The thickness of the acid-resistant coating can be measured by observation with a transmission electron microscope, or a combination of observation with a transmission electron microscope and energy dispersive X-ray spectroscopy or electron energy loss spectroscopy.

[0070] The chemical conversion treatment is carried out by applying a solution containing a compound used to form an acid-resistant film to the surface of the barrier layer by a bar coating method, a roll coating method, a gravure coating method, a dipping method, or the like, and then heating the barrier layer so that the temperature of the barrier layer is about 70 to 200° C. In addition, before the chemical conversion treatment is carried out on the barrier layer, the barrier layer may be subjected to a degreasing treatment in advance by an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or the like. By carrying out the degreasing treatment in this manner, the chemical conversion treatment of the surface of the barrier layer can be carried out more efficiently.

[0071] [Thermal adhesive resin layer 4] In the battery packaging material of the present invention, the heat-sealable resin layer 4 corresponds to the innermost layer, and is a layer that seals the battery element by heat-sealing the heat-sealable resin layers together during assembly of the battery.

[0072] The resin component used in the heat-sealable resin layer 4 is not particularly limited as long as it is heat-sealable, and examples thereof include polyolefin, cyclic polyolefin, carboxylic acid-modified polyolefin, and carboxylic acid-modified cyclic polyolefin. That is, the resin constituting the heat-sealable resin layer 4 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 4 can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, it is found that the maleic anhydride-modified polyolefin has a peak at a wave number of 1760 cm. -1 Nearby and wave number 1780cm -1 A peak derived from maleic anhydride is detected around this peak. However, if the degree of acid modification is low, the peak may be small and not detectable. In that case, analysis can be performed using nuclear magnetic resonance spectroscopy.

[0073] 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 polyolefins, polyethylene and polypropylene are preferable.

[0074] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefins constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomers constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, preferred are cyclic alkenes, and more preferred are norbornene. Styrene can also be used as a constituting monomer.

[0075] The carboxylic acid-modified polyolefin is a polymer modified by block polymerization or graft polymerization of the polyolefin 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.

[0076] The carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin with an α,β-unsaturated carboxylic acid or its anhydride, or by block-polymerizing or graft-polymerizing an α,β-unsaturated carboxylic acid or its anhydride to the cyclic polyolefin. The cyclic polyolefin to be modified with the carboxylic acid 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.

[0077] Among these resin components, preferred are carboxylic acid-modified polyolefins; more preferred are carboxylic acid-modified polypropylenes.

[0078] The thermally adhesive resin layer 4 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. Furthermore, the thermally adhesive resin layer 4 may be formed of only one layer, or may be formed of two or more layers of the same or different resin components.

[0079] The heat-sealable resin layer 4 may contain a lubricant. The lubricant present on the surface of the heat-sealable resin layer 4 may be a lubricant exuded from the resin constituting the heat-sealable resin layer 4, or may be a lubricant applied to the surface of the heat-sealable resin layer 4. When the heat-sealable resin layer 4 contains a lubricant, the moldability of the battery packaging material can be improved. The lubricant is not particularly limited, and a known lubricant can be used, for example, the lubricant exemplified in the polyester film 1 above. The lubricant may be used alone or in combination of two or more kinds. The amount of the lubricant present on the surface of the heat-sealable resin layer 4 is not particularly limited, and from the viewpoint of improving the moldability of the electronic packaging material, it is preferably 10 to 50 mg / m in an environment of a temperature of 24° C. and a relative humidity of 60%. 2 about 15 to 40 mg / m 2 The degree of

[0080] As described above, in recent years, with the demand for smaller and thinner batteries, there is a demand for even thinner battery packaging materials. For this reason, it is also required to make the thickness of the heat-sealable resin layer located in the innermost layer of the battery packaging material as thin as possible. However, when the ratio of the thickness of the heat-sealable resin layer to the thickness of the substrate becomes small, the periphery of the recess formed in the battery packaging material curls (curves), which may hinder the storage of the battery element and the heat fusion of the heat-sealable resin layer, thereby reducing the production efficiency of the battery. In particular, battery packaging materials used for large secondary batteries such as secondary batteries for automobiles have a problem that the curl has a very large effect on the productivity of the battery due to their large size.

[0081] When the ratio of the thickness of the heat-sealable resin layer 4 to the thickness of the polyester film 1 becomes small (for example, when the thickness of the polyester film 1 is taken as 1, the ratio of the thickness of the heat-sealable resin layer 4 to the thickness of the polyester film 1 (thickness of the heat-sealable resin layer / thickness of the polyester film) is 4 or less), the battery packaging material tends to curl significantly after molding. However, in the battery packaging material of the present invention, max / Y min ) is in the range of 1.4 to 2.7, so that curling after molding is effectively suppressed while providing excellent moldability. In the battery packaging material of the present invention, from the viewpoint of suitably suppressing curling after molding, the upper limit of the ratio of the thickness of the heat-sealable resin layer 4 to the thickness of the polyester film 1 (thickness of heat-sealable resin layer / thickness of polyester film) is preferably 4 or less, more preferably less than 3, even more preferably 2 or less, and the preferred lower limit is 1 or more. A preferred range is 1 or more and 4 or less, a more preferred range is 1 or more and less than 3, and a more preferred range is 1 or more and 2 or less.

[0082] From the viewpoint of suppressing curling after molding while making the battery packaging material as thin as possible, the thickness of the heat-sealable resin layer 4 is preferably about 100 μm or less, more preferably about 40 μm or less, and the lower limit is about 15 μm or more. The preferred range of the thickness of the heat-sealable resin layer 4 is preferably about 15 to 100 μm, more preferably about 15 to 40 μm.

[0083] [Adhesive layer 5] In the battery packaging material of the present invention, the adhesive layer 5 is a layer that is provided, if necessary, between the barrier layer 3 and the heat-sealable resin layer 4 in order to firmly bond them together.

[0084] The adhesive layer 5 is formed of a resin capable of bonding the barrier layer 3 and the heat-sealable resin layer 4. The adhesive mechanism, the type of adhesive component, and the like of the resin used to form the adhesive layer 5 may be the same as those of the adhesive layer 2. The resin used to form the adhesive layer 5 may also be a polyolefin resin such as polyolefin, cyclic polyolefin, carboxylic acid-modified polyolefin, or carboxylic acid-modified cyclic polyolefin exemplified in the heat-sealable resin layer 4. That is, the resin constituting the adhesive layer 5 may or may not contain a polyolefin skeleton, and preferably contains a polyolefin skeleton. The resin constituting the adhesive layer 5 can be analyzed by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like, and the analysis method is not particularly limited. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, the wavelength of the maleic anhydride-modified polyolefin is 1760 cm. -1 Nearby and wave number 1780cm -1 A peak derived from maleic anhydride is detected around 1000 nm. However, if the degree of acid modification is low, the peak may be small and not detected. In that case, analysis can be performed by nuclear magnetic resonance spectroscopy. From the viewpoint of excellent adhesion between the barrier layer 3 and the heat-sealable resin layer 4, the polyolefin is preferably a carboxylic acid-modified polyolefin, and particularly preferably a carboxylic acid-modified polypropylene.

[0085] Furthermore, from the viewpoint of making the battery packaging material thinner while having excellent shape stability after molding, the adhesive layer 5 may be a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. The acid-modified polyolefin may be the same as the carboxylic acid-modified polyolefin and the carboxylic acid-modified cyclic polyolefin exemplified in the heat-sealable resin layer 4. The adhesive layer 5 is preferably a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group, a compound having an oxazoline group, and a compound having an epoxy group, and is particularly preferably a cured product of a resin composition containing at least one selected from the group consisting of a compound having an isocyanate group and a compound having an epoxy group. The adhesive layer 5 preferably contains at least one selected from the group consisting of a urethane resin, an amide ester resin, and an epoxy resin, and more preferably contains a urethane resin and an epoxy resin. The adhesive layer 5 is more preferably a cured product of a resin composition containing at least one of these and the acid-modified polyolefin. In addition, if unreacted compounds such as a compound having an isocyanate group, a compound having an oxazoline group, or a curing agent such as an epoxy resin remain in the adhesive layer 5, the presence of the unreacted compounds can be confirmed by a method selected from, for example, infrared spectroscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), etc.

[0086] The curing agent is not particularly limited as long as it cures the acid-modified polyolefin. Examples of the curing agent include epoxy-based curing agents, polyfunctional isocyanate-based curing agents, carbodiimide-based curing agents, and oxazoline-based curing agents. In order to further increase the adhesion between the acid-resistant film and the adhesive layer 5, the adhesive layer 5 is preferably a cured product of a resin composition containing a curing agent having at least one selected from the group consisting of an oxygen atom, a heterocycle, a C=N bond, and a COC bond. Examples of the curing agent having a heterocycle include a curing agent having an oxazoline group and a curing agent having an epoxy group. Examples of the curing agent having a C=N bond include a curing agent having an oxazoline group and a curing agent having an isocyanate group. Examples of the curing agent having a COC bond include a curing agent having an oxazoline group, a curing agent having an epoxy group, and a urethane resin. The fact that the adhesive layer 5 is a cured product of a resin composition containing these curing agents can be confirmed by methods such as gas chromatography mass spectrometry (GCMS), infrared spectroscopy (IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS).

[0087] The epoxy curing agent is not particularly limited as long as it is a compound having at least one epoxy group. Examples of the epoxy curing agent include epoxy resins such as bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether.

[0088] The polyfunctional isocyanate curing agent is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of the polyfunctional isocyanate curing agent include isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymerized or nurated products thereof, mixtures thereof, and copolymers with other polymers.

[0089] The carbodiimide-based curing agent is not particularly limited as long as it is a compound having at least one carbodiimide group (-N=C=N-). As the carbodiimide-based curing agent, a polycarbodiimide compound having at least two carbodiimide groups is preferable.

[0090] The oxazoline-based curing agent is not particularly limited as long as it is a compound having an oxazoline skeleton, and specific examples of the oxazoline-based curing agent include the EPOCROS series manufactured by Nippon Shokubai Co., Ltd.

[0091] From the viewpoint of improving the adhesion between the barrier layer 3 and the thermally adhesive resin layer 4 by the adhesive layer 5, the curing agent may be composed of two or more kinds of compounds.

[0092] The content of the curing agent in the resin composition forming the adhesive layer 5 is preferably in the range of 0.1 to 50 mass%, more preferably in the range of 0.1 to 30 mass%, and even more preferably in the range of 0.1 to 10 mass%.

[0093] The thickness of the adhesive layer 5 is not particularly limited as long as it functions as an adhesive layer, but when the adhesive layer 2 is used, the thickness is preferably about 2 to 10 μm, more preferably about 2 to 5 μm. When the resin exemplified in the thermal adhesive resin layer 4 is used, the thickness is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. When the adhesive layer 5 is a cured product of an acid-modified polyolefin and a curing agent, the thickness is preferably about 30 μm or less, more preferably about 0.1 to 20 μm, and even more preferably about 0.5 to 5 μm. When the adhesive layer 5 is a cured product of a resin composition containing an acid-modified polyolefin and a curing agent, the adhesive layer 5 can be formed by applying the resin composition and curing it by heating or the like.

[0094] [Surface coating layer 6] In the battery packaging material of the present invention, a surface coating layer 6 may be provided on the polyester film 1 (the side of the polyester film 1 opposite to the barrier layer 3) as needed for the purpose of improving design, electrolyte resistance, abrasion resistance, formability, etc. The surface coating layer 6 is a layer located on the outermost layer when the battery is assembled.

[0095] The surface coating layer 6 can be formed from, for example, polyvinylidene chloride, polyester resin, urethane resin, acrylic resin, epoxy resin, etc. Among these, the surface coating layer 6 is preferably formed from a two-component curing resin. Examples of the two-component curing resin forming the surface coating layer 6 include a two-component curing urethane resin, a two-component curing polyester resin, and a two-component curing epoxy resin. The surface coating layer 6 may also contain an additive.

[0096] Examples of additives include fine particles having a particle size of 0.5 nm to 5 μm. The material of the additive is not particularly limited, and examples thereof include metals, metal oxides, inorganic substances, and organic substances. The shape of the additive is also not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and balloon-like. Specific examples of additives include talc, silica, graphite, kaolin, montmorillonite, synthetic mica, hydrotalcite, silica gel, zeolite, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, aluminum oxide, neodymium oxide, antimony oxide, titanium oxide, cerium oxide, calcium sulfate, barium sulfate, calcium carbonate, calcium silicate, lithium carbonate, calcium benzoate, calcium oxalate, magnesium stearate, alumina, carbon black, carbon nanotubes, high melting point nylon, crosslinked acrylic, crosslinked styrene, crosslinked polyethylene, benzoguanamine, gold, aluminum, copper, and nickel. These additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferable from the viewpoints of dispersion stability, cost, etc. Furthermore, the additives may be subjected to various surface treatments such as insulation treatment and high dispersibility treatment.

[0097] The content of the additive in the surface coating layer 6 is not particularly limited, but is preferably about 0.05 to 1.0 mass %, and more preferably about 0.1 to 0.5 mass %.

[0098] The method for forming the surface coating layer 6 is not particularly limited, and may be, for example, a method for coating one surface of the polyester film 1 with a two-component curing resin that forms the surface coating layer 6. When an additive is added, the additive may be added to the two-component curing resin, mixed, and then coated.

[0099] The thickness of the surface coating layer 6 is not particularly limited as long as the surface coating layer 6 exhibits the above-mentioned functions, and is, for example, 0.5 to 10 μm, preferably 1 to 5 μm.

[0100] 3. Manufacturing method of battery packaging material The method for producing the battery packaging material of the present invention is not particularly limited as long as a laminate in which each layer of a predetermined composition is laminated can be obtained. The method for producing the battery packaging material includes, for example, a step of laminating at least a polyester film, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate, and when infrared absorption spectra are obtained in 18 directions at intervals of 10° from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, the infrared absorption spectrum of the polyester film is obtained by measuring the wavelength of the infrared absorption spectrum at 1340 cm -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) in the range of 1.4 to 2.7.

[0101] An example of a method for producing the battery packaging material of the present invention is as follows. First, a laminate (hereinafter, sometimes referred to as "laminate A") is formed in which a polyester film 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order. Specifically, the laminate A can be formed by a dry lamination method in which an adhesive used for forming the adhesive layer 2 is applied and dried on the polyester film 1 or on the barrier layer 3, the surface of which has been chemically treated as necessary, by a coating method such as gravure coating or roll coating, and then the barrier layer 3 or the polyester film 1 is laminated and the adhesive layer 2 is cured.

[0102] Next, the adhesive layer 5 and the heat-fusible resin layer 4 are laminated in this order on the barrier layer 3 of the laminate A. For example, there may be mentioned (1) a method of laminating the adhesive layer 5 and the heat-sealable resin layer 4 on the barrier layer 3 of the laminate A by co-extruding them (co-extrusion lamination method), (2) a method of separately forming a laminate in which the adhesive layer 5 and the heat-sealable resin layer 4 are laminated, and laminating this on the barrier layer 3 of the laminate A by a thermal lamination method, (3) a method of laminating an adhesive for forming the adhesive layer 5 on the barrier layer 3 of the laminate A by an extrusion method or a solution coating, drying at a high temperature, and further baking, and laminating a heat-sealable resin layer 4 previously formed into a sheet-like film on this adhesive layer 5 by a thermal lamination method, and (4) a method of laminating the laminate A and the heat-sealable resin layer 4 via the adhesive layer 5 while pouring a molten adhesive layer 5 between the barrier layer 3 of the laminate A and the heat-sealable resin layer 4 previously formed into a sheet-like film (sandwich lamination method), and the like.

[0103] When the surface coating layer 6 is provided, the surface coating layer 6 is laminated on the surface of the polyester film 1 opposite to the barrier layer 3. The surface coating layer 6 can be formed, for example, by applying the above-mentioned resin for forming the surface coating layer 6 to the surface of the polyester film 1. The order of the step of laminating the barrier layer 3 on the surface of the polyester film 1 and the step of laminating the surface coating layer 6 on the surface of the polyester film 1 is not particularly limited. For example, after the surface coating layer 6 is formed on the surface of the polyester film 1, the barrier layer 3 may be formed on the surface of the polyester film 1 opposite to the surface coating layer 6.

[0104] As described above, a laminate is formed consisting of the optional surface coating layer 6 / polyester film 1 / optional adhesive layer 2 / optional barrier layer 3 whose surface is chemically treated / adhesive layer 5 / thermally adhesive resin layer 4, and in order to strengthen the adhesiveness of the adhesive layer 2 or adhesive layer 5, the laminate may be subjected to a heat treatment such as a hot roll contact type, hot air type, near or far infrared type. Conditions for such heat treatment include, for example, about 150 to 250° C. for about 1 to 5 minutes.

[0105] In the battery packaging material of the present invention, each layer constituting the laminate may be subjected to a surface activation treatment such as corona treatment, blast treatment, oxidation treatment, ozone treatment, etc., as necessary, in order to improve or stabilize the film-forming properties, lamination processing, suitability for secondary processing of the final product (pouching, embossing), etc.

[0106] 4. Applications of battery packaging materials The battery packaging material of the present invention is used for a package for hermetically housing battery elements such as a positive electrode, a negative electrode, an electrolyte, etc. That is, a battery element including at least a positive electrode, a negative electrode, and an electrolyte can be housed in a package formed from the battery packaging material of the present invention to form a battery.

[0107] Specifically, a battery element including at least a positive electrode, a negative electrode, and an electrolyte is covered with the battery packaging material of the present invention in such a manner that a flange portion (a region where the heat-sealable resin layers contact each other) can be formed on the periphery of the battery element with the metal terminals connected to each of the positive electrode and the negative electrode protruding outward, and the heat-sealable resin layers of the flange portion are heat-sealed to provide a battery using the battery packaging material. When a battery element is housed in a package formed from the battery packaging material of the present invention, the package is formed so that the heat-sealable resin portion of the battery packaging material of the present invention is on the inside (the surface in contact with the battery element).

[0108] The battery packaging material of the present invention may be used for either primary or secondary batteries, but is preferably used for secondary batteries. The type of secondary battery to which the battery packaging material of the present invention is applied is not particularly limited, and examples thereof include lithium ion batteries, lithium ion polymer batteries, lead storage batteries, nickel-hydrogen storage batteries, nickel-cadmium storage batteries, nickel-iron storage batteries, nickel-zinc storage batteries, silver oxide-zinc storage 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 of the battery packaging material of the present invention.

[0109] 5. Polyester film The polyester film of the present invention is a polyester film used for a packaging material for batteries. When infrared absorption spectra are obtained for the surface of the polyester film in 18 directions at intervals of 10° from 0° to 180° using the total reflection method of Fourier transform infrared spectroscopy, the polyester film of the present invention has a peak at 1340 cm -1 Absorption peak intensity Y 1340 And, 1410cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) is in the range of 1.4 to 2.7. The specific configuration of the polyester film of the present invention is the same as that described in the above section "2. Each layer forming the battery packaging material [Polyester film 1]". EXAMPLES

[0110] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0111] Examples 1-7 and Comparative Examples 1-3 <Production of battery packaging materials> In each case, a barrier layer made of aluminum foil (JIS H4160:1994 A8021H-O) that had been chemically treated on both sides to form an acid-resistant film was laminated on a stretched polyethylene terephthalate film by a dry lamination method. Specifically, a two-liquid curing urethane adhesive (polyol compound and aromatic isocyanate compound) was applied to one side of the aluminum foil to form an adhesive layer (thickness 3 μm) on the barrier layer. Next, the adhesive layer on the barrier layer and the polyethylene terephthalate film were laminated, and then aging treatment was performed to produce a laminate of stretched polyethylene terephthalate film / adhesive layer / barrier layer. The chemical conversion treatment of the aluminum foil used as the barrier layer was performed using a treatment solution consisting of a phenolic resin, a chromium fluoride compound, and phosphoric acid, with a coating amount of chromium of 10 mg / m. 2 (dry weight) was applied to both sides of an aluminum foil by roll coating, and then baked.

[0112] Next, maleic anhydride modified polypropylene as an adhesive layer and random polypropylene as a heat-sealable resin layer were co-extruded onto the barrier layer of the obtained laminate, thereby laminating an adhesive layer / heat-sealable resin layer on the barrier layer. Next, the obtained laminate was aged and heated to obtain a battery packaging material in which a stretched polyethylene terephthalate film, an adhesive layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer were laminated in this order. The layer structure and thickness of each layer of the battery packaging material are as shown in Table 1.

[0113] [Table 1]

[0114] In Table 1, the numbers in parentheses in the layer configurations indicate thicknesses (μm).

[0115] <Measurement of surface orientation> For the surface of the stretched polyester film laminated to the battery packaging material and the surface of the single layer of stretched polyester film used for lamination, infrared absorption spectra were obtained in 18 directions at 10° intervals from 0° to 180° using the attenuated total reflection method (ATR) of Fourier transform infrared spectroscopy (FT-IR). -1 Absorption peak intensity Y 1340 (CH2 wobbling vibration) and 1410cm -1 Absorption peak intensity Y 1410 (C=C stretching vibration) (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation (Y max / Y min ) was calculated. The specific conditions for measuring the infrared absorption spectrum are as follows. The results are shown in Table 2.

[0116] (Infrared absorption spectrum measurement conditions) Spectrometer: Nicolet iS10 FT-IR manufactured by Thermo Fisher Scientific Attachment: Single reflection ATR attachment (Seagull) Detector: MCT (Hg Cd Te) Wavenumber resolution: 8cm-1 IRE:Ge Incident angle: 30° Polarizer: Wire grid, S-polarized Baseline: Average value of intensity in the wavenumber range from 1800 cm-1 to 2000 cm-1 Absorption peak intensity Y 1340 : The maximum peak intensity in the wavenumber range from 1335 cm-1 to 1342 cm-1 minus the baseline value Absorption peak intensity Y 1410 : The maximum peak intensity in the wavenumber range from 1400 cm-1 to 1410 cm-1 minus the baseline value

[0117] <Measurement of birefringence> The birefringence of the polyethylene terephthalate film was measured using a phase difference measuring device (KOBRA-WR manufactured by Oji Scientific Instruments). The measurement wavelength was 550 nm, and the incident angle was 10 degrees. The thickness of the polyethylene terephthalate film used to calculate the birefringence was a value measured using a micrometer (Digimatic Micrometer manufactured by Mitutoyo Corporation). The average refractive index of the polyester film used to calculate the birefringence was an assumed value of 1.6200. The results are shown in Table 2.

[0118] <Evaluation of moldability> Each battery packaging material obtained above was cut into a rectangle with a length (z direction) of 150 mm and a width (x direction) of 100 mm to prepare a test sample. The sample was cold-formed (one-stage drawing) into 10 samples each at a pressing pressure (surface pressure) of 0.9 MPa, with the forming depth changed in 0.5 mm increments from 0.5 mm, using a rectangular forming die (female die, surface has a maximum height roughness (nominal value of Rz) of 3.2 μm as specified in Table 2 of the surface roughness standard specimen for comparison in JIS B 0659-1:2002, Annex 1 (Reference)) with an aperture of 30 mm (x direction) and 50 mm (z direction). The corresponding forming die (male die, surface has a maximum height roughness (nominal value of Rz) of 1.6 μm as specified in Table 2 of the surface roughness standard specimen for comparison in JIS B 0659-1:2002, Annex 1 (Reference)). At this time, the above test sample was placed on the female mold so that the heat-sealable resin layer side was located on the male mold side, and molding was performed. The clearance between the male mold and the female mold was 0.5 mm. For the samples after cold molding, the deepest molding depth at which no pinholes or cracks occurred in the aluminum foil in any of the 10 samples was A mm, and the number of samples at which pinholes or the like occurred at the shallowest molding depth at which pinholes or the like occurred in the aluminum foil was B, and the value calculated by the following formula was taken as the limit molding depth of the battery packaging material. The results are shown in Table 2. Limit forming depth = A mm + (0.5 mm / 10 pieces) x (10 pieces - B pieces)

[0119] <Evaluation of curl after molding> Each battery packaging material obtained above was cut to prepare a strip of 150 mm in length (z direction) and 100 mm in width (x direction), which was used as a test sample. Next, using the molding die used in the evaluation of moldability, the test sample was placed on the female die so that the heat-sealable resin layer side was located on the male die side, and the test sample was pressed with a pressure (surface pressure) of 0.1 MPa so that the molding depth was 6 mm, and cold molding (pulled in one-stage molding) was performed. Details of the position where molding was performed are as shown in FIG. 5. As shown in FIG. 6, molding was performed at a position where the distance d between the rectangular molded part M and the end P of the battery packaging material 10 was 75 mm. Next, the battery packaging material 10 after molding was placed on a horizontal plane 20 as shown in FIG. 6, and the maximum value t of the vertical distance y from the horizontal plane 20 to the end P was taken as the maximum height of the curled part (molded curl (mm)). The results are shown in Table 2.

[0120] [Table 2]

[0121] In Tables 1 and 2, PET means oriented polyethylene terephthalate, DL means an adhesive layer, ALM means aluminum foil, PPa means an adhesive layer formed from maleic anhydride-modified polypropylene, and PP means a heat-sealable resin layer formed from random polypropylene. [Explanation of symbols]

[0122] 1. Polyester film 2 Adhesive layer 3. Barrier layer 4 Heat-fusible resin layer 5 Adhesive layer 6 Surface coating layer

Claims

1. The laminate is made up of at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a substrate located on the other side of the barrier layer, the substrate comprises a polyester film; The thickness of the polyester film is 50 μm or less, The thickness of the adhesive layer is 10 μm or less, the barrier layer is formed of an aluminum alloy foil, the barrier layer has a thickness of 10 μm or more and 80 μm or less; the heat-sealable resin layer is made of polypropylene, the thickness of the heat-fusible resin layer is 15 μm or more and 100 μm or less; The thickness of the adhesive layer is 2 μm or more and 50 μm or less (excluding 20 μm or less), When the total reflection method of Fourier transform infrared spectroscopy was used to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film, the 1340 cm -1 Absorption peak intensity Y 1340 And 1410 cm -1 Absorption peak intensity Y 1410 The ratio (Y 1340 / Y 1410 ) maximum value Y max and the minimum value Y min Ratio of surface orientation: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less.

2. The battery packaging material described in Claim 1, wherein the polyester film is multi-layered.

3. A packaging material for batteries as described in claim 1 or 2, wherein the ratio of the thickness of the heat-sealable resin layer to the thickness of the polyester film is less than 3.

4. A packaging material for batteries as described in claim 1 or 2, wherein the thickness of the heat-sealable resin layer is 15 μm or more and 40 μm or less.

5. A battery packaging material described in any one of claims 1 to 3, wherein the birefringence of the polyester film is 0.016 or more.

6. A battery, in which a battery element having at least a positive electrode, a negative electrode, and an electrolyte is contained in a package formed from the battery packaging material described in any one of claims 1 to 4.

7. A method for manufacturing a laminate comprising a step of laminating a substrate, an adhesive layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer in this order to obtain a laminate consisting only of the substrate, the adhesive layer, the barrier layer, the adhesive layer, and the heat-sealable resin layer, the substrate comprises a polyester film; The thickness of the polyester film is 50 μm or less, The thickness of the adhesive layer is 10 μm or less, the barrier layer is formed of an aluminum alloy foil, the barrier layer has a thickness of 10 μm or more and 80 μm or less; the heat-sealable resin layer is made of polypropylene, the thickness of the heat-fusible resin layer is 15 μm or more and 100 μm or less; The thickness of the adhesive layer is 2 μm or more and 50 μm or less (excluding 20 μm or less), The method for producing a battery packaging material uses a polyester film in which, when infrared absorption spectra are obtained on the surface of the polyester film in 18 directions at 10° increments from 0° to 180° using the total reflection method of Fourier transform infrared spectroscopy, the ratio of the maximum value Y max to the minimum value Y min of the ratio (Y 1340 / Y 1410 ) of the absorption peak intensity Y 1340 at 1340 cm −1 to the absorption peak intensity Y 1410 at 1410 cm −1 in the infrared absorption spectrum (degree of surface orientation: Y max / Y min ) is in the range of 1.4 to 2.

7.

8. A polyester film for use as a packaging material for batteries, comprising: the battery packaging material is composed of a laminate including at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a base material located on the other side of the barrier layer; the laminate is composed of only the base material, the adhesive layer, the barrier layer, the adhesive layer, and the heat-fusible resin layer, in this order; the substrate comprises a polyester film; The thickness of the polyester film is 50 μm or less, The thickness of the adhesive layer is 10 μm or less, the barrier layer is formed of an aluminum alloy foil, the barrier layer has a thickness of 10 μm or more and 80 μm or less; the heat-sealable resin layer is made of polypropylene, the thickness of the heat-fusible resin layer is 15 μm or more and 100 μm or less; The thickness of the adhesive layer is 2 μm or more and 50 μm or less (excluding 20 μm or less), A polyester film, wherein when infrared absorption spectra are obtained on the surface of the polyester film in 18 directions at 10° increments from 0° to 180° using the total reflection method of Fourier transform infrared spectroscopy, the ratio of the maximum value Y max to the minimum value Y min of the ratio (Y 1340 / Y 1410 ) of the absorption peak intensity Y 1340 at 1340 cm −1 to the absorption peak intensity Y 1410 at 1410 cm −1 in the infrared absorption spectrum (degree of surface orientation: Y max / Y min ) is in the range of 1.4 to 2.

7.

9. Use of a polyester film as a packaging material for batteries, wherein when infrared absorption spectra are obtained on the surface of a polyester film in 18 directions at 10° intervals from 0° to 180° using the total reflection method of Fourier transform infrared spectroscopy, the ratio of the maximum value Y max to the minimum value Y min of the ratio of the absorption peak intensity Y 1340 at 1340 cm -1 to the absorption peak intensity Y 1410 at 1410 cm -1 (Y 1340 / Y 1410 ) is in the range of 1.4 to 2.7, the battery packaging material is composed of a laminate including at least a barrier layer, a heat-sealable resin layer located on one side of the barrier layer, and a base material located on the other side of the barrier layer; the laminate is composed of only the base material, the adhesive layer, the barrier layer, the adhesive layer, and the heat-fusible resin layer, in this order; the substrate comprises a polyester film; The thickness of the polyester film is 50 μm or less, The thickness of the adhesive layer is 10 μm or less, the barrier layer is formed of an aluminum alloy foil, the barrier layer has a thickness of 10 μm or more and 80 μm or less; the heat-sealable resin layer is made of polypropylene, the thickness of the heat-fusible resin layer is 15 μm or more and 100 μm or less; The thickness of the adhesive layer is 2 μm or more and 50 μm or less (excluding 20 μm or less), Use of the polyester film as a packaging material for a battery.

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