Battery packaging material, method for producing the same, battery, and polyester film

Abstract

To provide a packaging material for a battery that is composed of a laminate having a barrier layer, a heat-fusible resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer, which suppresses curling after molding while improving moldability.MEANS FOR SOLVING THE PROBLEM: A packaging material for a battery is composed of a laminate having at least a barrier layer, a heat-fusible resin layer positioned on one surface side of the barrier layer, and a polyester film positioned on the other surface side of the barrier layer, wherein when an infrared absorption spectrum in 18 directions with 10° intervals from 0° to 180° on the surface of the polyester film is acquired by using a total reflection method of Fourier transformation infrared spectroscopy, a ratio (surface orientation degree: Ymax / Ymin) of a maximum value Ymax to a minimum value Ymin of a ratio (Y1340 / Y1410) of absorption peak intensity Y1340 at the infrared absorption spectrum of 1,340 cm-1 to absorption peak intensity Y1410 at 1,410 cm-1 is within a range of 1.4 to 2.7.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Conventionally, various types of batteries have been developed. In all batteries, a packaging material is an essential member for sealing battery elements such as electrodes and electrolytes. Conventionally, metal packaging materials have been widely used for battery packaging.

[0003] On the other hand, in recent years, with the improvement in performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, etc., batteries are required to have various shapes, and are also required to be thinner and lighter. However, conventionally widely used metal battery packaging materials have the disadvantages that it is difficult to follow the diversification of shapes and there is also a limit to weight reduction.

[0004] Therefore, in recent years, as a battery packaging material that can be easily processed into various shapes and can achieve thinning and weight reduction, a film-like laminate in which a base material / barrier layer / heat-sealable resin layer are sequentially laminated has been proposed (for example, see Patent Document 1). In such a battery packaging material, generally, a recess is formed by cold forming, battery elements such as electrodes and electrolytic solution are arranged in the space formed by the recess, and the heat-sealable resin layers are heat-sealed 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

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, with the requirements for miniaturization and thinning of batteries, there has been an increasing demand for further thinning of battery packaging materials.

[0007] However, when the thickness of each layer of the battery packaging material is reduced, the peripheral edge of the recess formed in the battery packaging material curls (bends), which may inhibit the accommodation of battery elements and the heat sealing of the heat-sealable resin layer, and may reduce the production efficiency of the battery. In particular, battery packaging materials used for large secondary batteries such as automotive secondary batteries have a problem that the influence of curl on battery productivity is very large due to their large size.

[0008] Also, when the outer surface of the battery (substrate surface) is composed of, for example, a nylon film, if electrolyte adheres to the surface of the battery during the battery manufacturing process, the outer surface of the battery will be eroded (whitened) and become defective. Therefore, in order to improve the chemical resistance and electrolyte resistance of the battery outer surface, a stretched polyester film may be used as the substrate. However, the inventors have found that the above-mentioned curl is particularly likely to occur in battery packaging materials laminated with a stretched polyester film. Furthermore, when the thickness of the battery packaging material is reduced, there is a problem that the formability is likely to decrease. In particular, a stretched polyester film is harder and has inferior formability compared to a polyamide film.

[0009] Under such circumstances, the main object of the present invention is to provide a technique for improving formability and suppressing curl after forming in a battery packaging material comprising a laminate including a barrier layer, a heat-sealable resin layer located on one surface side of the barrier layer, and a polyester film located on the other surface side of the barrier layer.

Means for Solving the Problems

[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 Min 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 a packaging material for a battery, which 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 thickness of the heat-sealable resin layer is 100 μm or less. Item 4. The battery packaging material according to any one of Items 1 to 3, wherein the birefringence of the polyester film is 0.016 or more. Item 5. A battery in which a battery element including at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed of the battery packaging material according to any one of Items 1 to 4. Item 6. It includes a step of obtaining a laminate by laminating at least a polyester film, a barrier layer, and a heat-sealable resin layer in this order. As the polyester film, when using the total reflection method of Fourier transform infrared spectroscopy to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film, the absorption peak intensity Y at 1340 cm -1 in it 1340 and the absorption peak intensity Y at 1410 cm -1 in it 1410 The ratio (Y 1340 / Y 1410 ) of the maximum value Y max and the minimum value Y min of (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. A method for manufacturing a battery packaging material using such a material. Item 7. A polyester film for use in a battery packaging material, When using the total reflection method of Fourier transform infrared spectroscopy to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film, the absorption peak intensity Y at 1340 cm -1 in it 1340 and the absorption peak intensity Y at 1410 cm -1 in it 1410 The ratio (Y1340 / Y 1410 ) maximum value Y max and minimum value Y min ratio (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less, a polyester film. Item 8. When obtaining infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of a polyester film using the total reflection method of Fourier transform infrared spectroscopy, at 1340 cm -1 absorption peak intensity Y 1340 and, at 1410 cm -1 absorption peak intensity Y 1410 ratio (Y 1340 / Y 1410 ) maximum value Y max and minimum value Y min ratio (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less, use of the polyester film as a battery packaging material.

Advantages of the Invention

[0012] According to the present invention, there is provided a battery packaging material composed of a laminate including a barrier layer, a heat-sealable resin layer located on one surface side of the barrier layer, and a polyester film located on the other surface side of the barrier layer, which has excellent moldability and effectively suppresses curl after molding.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[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 surface side of the barrier layer, and a polyester film located on the other surface side of the barrier layer. When using the total reflection method of Fourier transform infrared spectroscopy to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film, the absorption peak intensity Y -1 at 1340 cm 1340 (CH2 vertical rocking vibration), and the absorption peak intensity Y -1 at 1410 cm 1410 (C=C stretching vibration), the ratio (Y 1340 / Y 1410 ) of the maximum value Y max and the minimum value Y min (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. Hereinafter, the battery packaging material of the present invention will be described in detail.

[0015] In this specification, the notation "~" indicating a numerical range means that it is not less than the numerical value attached to its left side and not more than the numerical value attached to its right side. For example, the notation of the numerical range "X~Y" means not less than X and not more than Y.

[0016] 1. Laminated structure of packaging material for battery 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, as shown in FIG. 1 for example. In the battery packaging material of the present invention, the polyester film 1 is on the outermost layer side, and the heat-sealable resin layer 4 is on the innermost layer. That is, when assembling the battery, the heat-sealable resin layers 4 located at the periphery of the battery element are heat-sealed together 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, if necessary, for the purpose of enhancing their adhesiveness, as shown in FIG. 2 for example. Further, an adhesive layer 5 may be provided between the barrier layer 3 and the heat-sealable resin layer 4, if necessary, for the purpose of enhancing their adhesiveness. 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), if necessary.

[0018] The total thickness of the laminate constituting the battery packaging material of the present invention is not particularly limited. However, from the viewpoint of making the total thickness of the laminate as thin as possible while exhibiting high formability and effectively suppressing curl 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 as thin as 160 μm or less, according to the present invention, excellent formability can be provided while effectively suppressing curl after molding.

[0019] 2. Each layer forming the packaging material for battery [Polyester film 1] In the battery packaging material of the present invention, the polyester film 1 is a layer located on the outermost layer side and functions as a base material.

[0020] In the battery packaging material of the present invention, regarding the surface of the polyester film, using the total reflection method of Fourier transform infrared spectroscopy, infrared absorption spectra in 18 directions are obtained at 10° intervals from 0° to 180°, and the 1340 cm of the infrared absorption spectrum-1 Absorption peak intensity Y in 1340 (CH2 rocking vibration) and 1410 cm -1 Absorption peak intensity Y in 1410 (C=C stretching vibration), and the ratio (Y 1340 / Y 1410 ) has a maximum value Y max and a minimum value Y min The ratio of (surface orientation degree: Y max / Y min ) is in the range of 1.4 to 2.7. In the battery packaging material of the present invention, due to the surface orientation degree (Y max / Y min ) of the polyester film being in the range of 1.4 to 2.7, it has excellent formability, and furthermore, curl after molding is effectively suppressed. This mechanism can be considered as follows. That is, since the surface orientation degree (Y max / Y min ) of the polyester film is in the range of 1.4 to 2.7, the crystal orientation of the polyester molecules constituting the polyester film is high, and the shrinkage of the polyester film during molding is suppressed. As a result, it is considered that excellent formability is exhibited while curl after molding is effectively suppressed.

[0021] Specific measurement conditions for the infrared absorption spectrum are as follows. The measurement of the infrared absorption spectrum on the surface of the polyester film can be performed in a state where the surface of the polyester film is exposed, that is, in a state laminated on the battery packaging material. Also, when the surface coating layer 6 etc. described later is laminated on the surface of the polyester film 1, the measurement can be performed after removing the surface coating layer 6 so that the surface of the polyester film is exposed. Further, the measurement of the infrared absorption spectrum for the polyester film of the present invention described later is performed on a single-layer polyester film under the following measurement conditions.

[0022] (Measurement conditions for infrared absorption spectrum) Measurement is performed using the single reflection ATR method with a Fourier transform infrared spectrophotometer under the following conditions. Wavenumber resolution: 8 cm-1 IRE: Ge Angle of incidence: 30° Polarizer: wire grid, S polarization Baseline: average value of intensity in the range of wavenumber 1800 cm-1 to 2000 cm-1 Absorption peak intensity Y 1340 : value obtained by subtracting the value of the baseline from the maximum value of the peak intensity in the range of wavenumber 1335 cm-1 to 1342 cm-1 Absorption peak intensity Y 1410 : value obtained by subtracting the value of the baseline from the maximum value of the peak intensity in the range of wavenumber 1400 cm-1 to 1410 cm-1

[0023] The acquisition of the infrared absorption spectrum in 18 directions was performed by horizontally placing the polyester film as a sample in the sample holder and rotating the Ge crystal placed on the sample by 10° each time. The angle of incidence is the angle between the perpendicular (normal line) and the incident light.

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

[0025] The surface orientation degree as described above: Y max / Y min The polyester film having such a surface orientation degree can be produced by appropriately adjusting, for example, the stretching method, stretching ratio, stretching speed, cooling temperature, heat setting temperature, etc. when producing the polyester film.

[0026] Further, in the battery packaging material of the present invention, it is preferable that the birefringence of the polyester film is 0.016 or more. That is, in the measurement of the refractive index of the polyester film, the birefringence (nx - ny) calculated by measuring the refractive index (nx) in the slow axis direction, which is the direction with a large refractive index, and the refractive index (ny) in the fast axis direction, which is the direction orthogonal to the slow axis direction, is preferably 0.016 or more. When the birefringence of the polyester film is 0.016 or more, while exhibiting more excellent moldability, curling after molding is more effectively suppressed. 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. As a result, it is considered that while exhibiting more excellent moldability, curling after molding is more effectively suppressed.

[0027] Specific measurement conditions for the birefringence are as follows. The measurement of the birefringence of the polyester film is performed on the polyester film used for the battery packaging material.

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

[0029] As for the birefringence, from the viewpoint of further improving the formability in addition to suppressing curl after molding, the lower limit 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, still more preferably about 0.042 or less, still more preferably about 0.026 or less, and particularly preferably about 0.022 or less. The preferable range of the birefringence is 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, about 0.019 to 0.022.

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

[0031] The polyester film having the birefringence as described above has the surface orientation degree: Y max / Y min Similar to the above, for example, it can be produced by appropriately adjusting the stretching method, stretching ratio, stretching speed, cooling temperature, heat setting temperature, etc. when producing the aforementioned polyester film.

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

[0033] Examples of the polyester constituting the polyester film include, specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, a copolymer polyester having ethylene terephthalate as a main repeating unit, a copolymer polyester having butylene terephthalate as a main repeating unit, and the like. Further, examples of the copolymer polyester having ethylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing ethylene isophthalate with ethylene terephthalate as a main repeating unit (hereinafter abbreviated following polyethylene(terephthalate / isophthalate)), polyethylene(terephthalate / isophthalate), polyethylene(terephthalate / adipate), polyethylene(terephthalate / sodium sulfoisophthalate), polyethylene(terephthalate / sodium isophthalate), polyethylene(terephthalate / phenyl-dicarboxylate), polyethylene(terephthalate / decanedicarboxylate), and the like. Further, examples of the copolymer polyester having butylene terephthalate as a main repeating unit include, specifically, a copolymer polyester obtained by polymerizing butylene isophthalate with butylene terephthalate as a main repeating unit (hereinafter abbreviated following polybutylene(terephthalate / isophthalate)), polybutylene(terephthalate / adipate), polybutylene(terephthalate / sebacate), polybutylene(terephthalate / decanedicarboxylate), polybutylene naphthalate, and the like. 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 curl after molding, it is preferably 50 μm or less. Further, from the viewpoint of further enhancing formability in addition to suppressing curl, it is preferably about 4 to 30 μm, more preferably about 16 to 25 μm. In addition, as described later, when the polyester film 1 has a multilayer structure, the thickness of one layer of the polyester film 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 multilayer (multilayer structure). When the polyester film 1 is a multilayer, at least one layer of the polyester film located on the outermost layer side (the side opposite to the barrier layer 3) has the surface orientation degree: Y max / Y min should satisfy the range.

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

[0037] Examples of the polyamide constituting the polyamide film include, specifically, aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 6,6; nylon 6I, nylon 6T, nylon 6IT, nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid), etc., which are hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides containing structural units derived from terephthalic acid and / or isophthalic acid, and polyamides containing aromatic groups such as polymetaxylylene adipamide (MXD6); alicyclic polyamides such as polyaminomethylcyclohexyl adipamide (PACM6); furthermore, polyamides copolymerized with a lactam component or an isocyanate component such as 4,4'-diphenylmethane-diisocyanate, and polyester amide copolymers and polyether ester amide copolymers that are copolymers of a copolymer polyamide with a polyester or a polyalkylene ether glycol; and these copolymers and the like. These polyamides may be used alone or in combination of two or more. The polyamide film is excellent in stretchability and can prevent the occurrence of whitening due to resin cracking during molding, and is preferably used as a resin film used for a substrate together with the polyester film 1.

[0038] When the base material has a multilayer structure of polyester film 1 and when the resin film is provided, specific examples include a laminate of a polyester film and a nylon film, and a laminate in which a plurality of polyester films are laminated. A laminate of a stretched polyester film and a stretched nylon film, and a laminate in which a plurality of stretched polyester films are laminated are more preferable. For example, when the base material 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. A structure in which polyethylene terephthalate and nylon are laminated, or a structure in which polyethylene terephthalate and polyethylene terephthalate are laminated is more preferable. Further, since the polyester film is less likely to change color when, for example, an electrolytic solution adheres to the surface, by having a laminate having a nylon film and a polyester film in this order from the side of the barrier layer 3, a configuration excellent in electrolytic solution resistance can be achieved. 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 has a multilayer structure of polyester film 1 and when it has a configuration including the resin film, polyester film 1 and each resin film may be adhered via an adhesive, or may be directly laminated without an adhesive. When adhering without an adhesive, for example, methods of adhering in a thermally melted state such as a coextrusion method, a sandwich lamination method, and a thermal lamination method can be mentioned. Further, when adhering via an adhesive, the adhesive used may be a two-component curing type adhesive or a one-component curing type adhesive. Furthermore, the adhesion mechanism of the adhesive is not particularly limited, and it may be any of a chemical reaction type, a solvent volatilization type, a thermal melting type, a hot pressing type, an electron beam curing type, an ultraviolet ray curing type, etc. Specific examples of the adhesive include the same ones as the adhesives exemplified in the adhesive layer 2. Also, the thickness of the adhesive can be the same as that of the adhesive layer 2.

[0040] In the present invention, from the viewpoint of enhancing the moldability of the battery packaging material, it is preferable that a lubricant adheres 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. Further, the lubricant present on the outermost surface of the battery packaging material may be one that exudes the lubricant contained in the resin constituting the polyester film 1 or the surface coating layer 6, or it may be one obtained by applying a lubricant to the surface of the battery packaging material. The lubricant is not particularly limited, but 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, unsaturated fatty acid bisamides, etc. Specific examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, etc. Specific examples of unsaturated fatty acid amides include oleic acid amide, erucic acid amide, etc. Specific 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, N-stearyl erucic acid amide, etc. Further, specific examples of methylol amides include methylol stearic acid amide, etc. Specific 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 adipic acid amide, N,N'-distearyl sebacic acid amide, etc. Specific examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacic acid amide, etc. Specific examples of fatty acid ester amides include stearamide ethyl stearate, etc.Specific examples of the aromatic bisamide include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearyl isophthalic acid amide, and the like. The lubricant may be used alone or in combination of two or more.

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

[0042] The total thickness (total thickness of the base material) of the polyester film 1 and the other resin film is not particularly limited, but from the viewpoint of enhancing moldability and effectively suppressing curl after molding, it is preferably about 50 μm or less. Further, from the viewpoint of further enhancing moldability in addition to suppressing curl, it 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 provided between the polyester film 1 or the aforementioned resin film and the barrier layer 3 as necessary in order to firmly adhere them.

[0044] The adhesive layer 2 is formed of an adhesive capable of adhering the polyester film 1 or the aforementioned resin film and the barrier layer 3. The adhesive used for forming the adhesive layer 2 may be a two-component curing type adhesive or a one-component curing type adhesive. Further, the adhesive used for forming the adhesive layer 2 is not particularly limited, and any of chemical reaction type, solvent evaporation type, hot melt type, hot press type, etc. may be used.

[0045] As the adhesive component that can be used for forming the adhesive layer 2, specifically, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and copolyester; polyether adhesives; polyurethane adhesives; epoxy resins; phenolic resins; polyamide resins such as nylon 6, nylon 66, nylon 12, and copolyamide; polyolefin resins such as polyolefin, carboxylic acid-modified polyolefin, and metal-modified polyolefin, polyvinyl acetate resins; cellulose adhesives; (meth)acrylic resins; polyimide resins; polycarbonate; amino resins such as urea resin and melamine resin; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; silicone resins, etc. may be mentioned. These adhesive components may be used alone or in combination of two or more. Among these adhesive components, preferably a polyurethane adhesive may be mentioned. Also, the resins serving as these adhesive components can increase the adhesive strength by using an appropriate curing agent in combination. The curing agent is appropriately selected from polyisocyanate, polyfunctional epoxy resin, oxazoline group-containing polymer, polyamine resin, acid anhydride, etc., according to the functional group of the adhesive component. As these adhesive components and curing agent, preferably a two-component curing type polyurethane adhesive composed of various polyols (substances having a hydroxyl group among the adhesive components) and polyisocyanate may be mentioned. More preferably, a two-component curing type polyurethane adhesive using polyols such as polyester polyol, polyether polyol, and acrylic polyol as the main agent and an aromatic or aliphatic polyisocyanate as the curing agent may be mentioned.

[0046] Regarding the thickness of the adhesive layer 2, there is no particular limitation as long as the function as an adhesive layer is exhibited. For example, it is about 1 to 10 μm, preferably about 2 to 5 μm.

[0047] [Barrier layer 3] In the battery packaging material, the barrier layer 3 is a layer that, in addition to improving the strength of the battery packaging material, has a function of preventing water vapor, oxygen, light, etc. from entering the battery. The barrier layer 3 is preferably a metal layer, that is, a layer formed of a metal. Specifically, examples of the metal constituting the barrier layer 3 include aluminum, stainless steel, titanium, etc., and preferably aluminum. The barrier layer 3 can be formed, for example, by a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, a film provided with these vapor deposition films, etc., and is preferably formed by a metal foil, and more preferably formed by an aluminum alloy foil. From the viewpoint of preventing wrinkles and pinholes from occurring in the barrier layer 3 during the manufacture of the battery packaging material, the barrier layer is, for example, 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), etc., and is more preferably formed.

[0048] The thickness of the barrier layer 3 is not particularly limited as long as it exhibits a barrier function against water vapor, etc., but from the viewpoint of reducing the thickness of the battery packaging material, it 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, at least one surface, preferably both surfaces, of the barrier layer 3 is preferably subjected to chemical conversion treatment for stabilizing adhesion, preventing dissolution and corrosion, etc. 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 have an acid-resistant film on one side, may have acid-resistant films on both sides, or may not have 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 metaphosphate, acetylacetate chromate, chromium chloride, potassium chromium sulfate; phosphate treatment using a phosphate compound such as sodium phosphate, potassium phosphate, ammonium phosphate, polyphosphoric acid; chromate treatment using an aminoated phenol polymer having repeating units represented by the following general formulas (1) to (4), etc. In the aminoated 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.

[0050]

Chemical formula

[0051]

Chemical formula

[0052]

Chemical formula

[0053]

Chemical formula

[0054] In 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. Also, R 1 and R 2each independently represents a hydroxyl group, an alkyl group, or a hydroxyalkyl group. In General Formulas (1) to (4), X, R 1 and R 2 Examples of the alkyl group represented by 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. Further, examples of the hydroxyalkyl group represented by X, R 1 and R 2 include linear or branched alkyl groups having 1 to 4 carbon atoms with one hydroxy group substituted, 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. In General Formulas (1) to (4), the alkyl groups and hydroxyalkyl groups represented by X, R 1 and R 2 may be the same or different from each other. In 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 the repeating unit represented by General Formulas (1) to (4) is preferably about 500 to 1,000,000, more preferably about 1,000 to 20,000.

[0055] Also, as a chemical conversion treatment method for imparting corrosion resistance to the barrier layer 3, a coating obtained by dispersing fine particles of metal oxides such as aluminum oxide, titanium oxide, cerium oxide, tin oxide, and barium sulfate in phosphoric acid is applied, and a baking treatment is performed at 150°C or higher to form an acid-resistant film on the surface of the barrier layer 3. Further, a resin layer obtained by crosslinking a cationic polymer with a crosslinking agent may be further formed on the acid-resistant film. Here, examples of the cationic polymer include polyethyleneimine, an ion-polymer complex composed of polyethyleneimine and a polymer having a carboxylic acid, a primary amine graft acrylic resin obtained by graft-polymerizing a primary amine onto an acrylic main skeleton, polyallylamine or its derivative, and aminophenol. As these cationic polymers, only one type may be used, or two or more types may be used in combination. Also, 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. As these crosslinking agents, only one type may be used, or two or more types may be used in combination.

[0056] Also, as a specific method for providing the acid-resistant film, for example, as one example, at least the inner layer side surface of the aluminum alloy foil is first degreased by well-known treatment methods such as the alkali immersion method, electrolytic cleaning method, pickling method, electrolytic pickling method, and acid activation method. Then, a treatment liquid (aqueous solution) mainly composed of a metal phosphate such as a chromic phosphate, titanium phosphate, zirconium phosphate, 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) composed of a mixture of these and an aqueous synthetic resin such as an acrylic resin, a phenolic resin, or a urethane resin is applied by a well-known coating method such as the roll coating method, the gravure printing method, or the dipping method to form an acid-resistant film. For example, when treated with a chromic phosphate-based treatment liquid, it becomes an acid-resistant film composed of chromic phosphate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc. When treated with a zinc phosphate-based treatment liquid, it becomes an acid-resistant film composed of zinc phosphate hydrate, aluminum phosphate, aluminum oxide, aluminum hydroxide, aluminum fluoride, etc.

[0057] Also, as another example of a specific method for providing the acid-resistant film, for example, at least the inner layer side surface of the aluminum alloy foil is first degreased by well-known treatment methods such as the alkali immersion method, electrolytic cleaning method, pickling method, electrolytic pickling method, and acid activation method. Then, a well-known anodic oxidation treatment is performed on the degreased surface to form an acid-resistant film.

[0058] Also, as another example of the acid-resistant film, phosphate-based and chromic acid-based films can be mentioned. Examples of the phosphate-based include zinc phosphate, iron phosphate, manganese phosphate, calcium phosphate, chromic phosphate, etc. Examples of the chromic acid-based include chromic chromate, etc.

[0059] Also, as another example of the acid-resistant film, by forming an acid-resistant film such as phosphate, chromate, fluoride, triazine thiol compound, etc., delamination prevention between aluminum and the layer functioning as a base material during embossing is achieved. Hydrogen fluoride generated by the reaction of electrolyte and moisture prevents dissolution and corrosion of the aluminum surface, particularly dissolution and corrosion of aluminum oxide present on the aluminum surface. Also, it improves the adhesiveness (wettability) of the aluminum surface, prevents delamination between the layer functioning as a base material and aluminum during heat fusion, and shows the effect of preventing delamination between the layer functioning as a base material and aluminum during press forming in the emboss type. Among the substances for forming the acid-resistant film, an aqueous solution composed of three components of phenol resin, chromium(III) fluoride compound, and phosphoric acid is preferably applied to the aluminum surface and has good drying and baking treatment.

[0060] Also, the acid-resistant film includes a layer having cerium oxide, phosphoric acid or phosphate, an anionic polymer, and a crosslinking agent for crosslinking the anionic polymer. The phosphoric acid or phosphate may be blended in an amount of about 1 to 100 parts by mass with respect to 100 parts by mass of the cerium oxide. It is preferable that the acid-resistant film has a multilayer structure further including a layer having a cationic polymer and a crosslinking agent for crosslinking the cationic polymer.

[0061] Furthermore, it is preferable that the anionic polymer is poly(meth)acrylic acid or its salt, or a copolymer mainly composed of (meth)acrylic acid or its salt. Also, it is preferable that the crosslinking agent is at least one selected from the group consisting of a compound having any one of functional groups of isocyanate group, glycidyl group, carboxyl group, oxazoline group and a silane coupling agent.

[0062] Also, it is preferable that the phosphoric acid or phosphate is condensed phosphoric acid or condensed phosphate.

[0063] The forming treatment may be performed with only one type of forming treatment, or may be performed by combining two or more types of forming treatments. Furthermore, these forming treatments may be performed using a single compound alone, or may be performed using a combination of two or more compounds. Among the forming treatments, chromate treatment, or a forming treatment combining a chromium compound, a phosphate compound, and an aminated phenol polymer, etc. is preferable. Among the chromium compounds, chromic acid compounds are preferable.

[0064] Specific examples of the acid-resistant film include those containing at least one of phosphate, chromate, fluoride, and triazine thiol. Also, an acid-resistant film containing a cerium compound is also preferable. As the cerium compound, cerium oxide is preferable.

[0065] Also, specific examples of the acid-resistant film include phosphate-based films, chromate-based films, fluoride-based films, triazine thiol compound films, etc. As the acid-resistant film, one of these may be used, or a combination of multiple types may be used. Furthermore, as the acid-resistant film, after degreasing the formed surface of the aluminum alloy foil, it may be formed from a treatment liquid composed of a mixture of a metal phosphate and an aqueous synthetic resin, or a treatment liquid composed of a mixture of a non-metal phosphate and an aqueous synthetic resin.

[0066] Note that the analysis of the composition of the acid-resistant film can be performed using, for example, time-of-flight secondary ion mass spectrometry. By analyzing the composition of the acid-resistant film using time-of-flight secondary ion mass spectrometry, for example, peaks derived from at least one of Ce + and Cr + are detected.

[0067] It is preferable that the surface of the aluminum alloy foil is provided with an acid-resistant film containing at least one element selected from the group consisting of phosphorus, chromium, and cerium. Note that the inclusion 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 for battery packaging materials can be confirmed using X-ray photoelectron spectroscopy. Specifically, first, in the battery packaging material, physically peel off the heat-sealable resin layer, adhesive layer, etc. laminated on the aluminum alloy foil. Next, put the aluminum alloy foil into an electric furnace and remove the organic components present on the surface of the aluminum alloy foil at about 300 °C for about 30 minutes. Then, use X-ray photoelectron spectroscopy on the surface of the aluminum alloy foil to confirm the inclusion of these elements.

[0068] Regarding the amount of the acid-resistant film formed on the surface of the barrier layer 3 in the chemical conversion treatment, there is no particular limitation. For example, in the case of performing the above-mentioned chromate treatment, per 1 m 2 of the surface of the barrier layer 3, the chromium compound is about 0.5 to 50 mg in terms of chromium, preferably about 1.0 to 40 mg, the phosphorus compound is about 0.5 to 50 mg in terms of phosphorus, preferably about 1.0 to 40 mg, and the aminophenol polymer is preferably contained at a ratio of about 1.0 to 200 mg, preferably about 5.0 to 150 mg.

[0069] The thickness of the acid-resistant film is not particularly limited, but from the viewpoints of the cohesion of the film and the adhesion to the barrier layer 3 and the heat-sealing resin layer, it is preferably about 1 nm to 10 μm, more preferably about 1 to 100 nm, and even more preferably about 1 to 50 nm. Note that the thickness of the acid-resistant film 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 for forming an acid-resistant film onto the surface of the barrier layer by means such as the bar coating method, roll coating method, gravure coating method, dipping method, etc., and then heating the barrier layer so that its temperature reaches about 70 to 200 °C. Further, before subjecting the barrier layer to the chemical conversion treatment, the barrier layer may be preliminarily subjected to a degreasing treatment by means such as the alkali dipping method, electrolytic cleaning method, acid cleaning method, electrolytic acid cleaning method, etc. By performing the degreasing treatment in this way, it becomes possible to perform the chemical conversion treatment on the surface of the barrier layer more efficiently.

[0071] [Heat-sealable 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 in which the heat-sealable resin layers are heat-sealed to each other during battery assembly to seal the battery element.

[0072] The resin component used for the heat-sealable resin layer 4 is not particularly limited as long as it can be heat-sealed. For example, polyolefin, cyclic polyolefin, carboxylic acid-modified polyolefin, carboxylic acid-modified cyclic polyolefin can be mentioned. That is, the resin constituting the heat-sealable resin layer 4 may or may not contain a polyolefin backbone, and it is preferable to contain a polyolefin backbone. Whether the resin constituting the heat-sealable resin layer 4 contains a polyolefin backbone can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc., and the analysis method is not particularly limited. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of wavenumber 1760 cm -1 and in the vicinity of wavenumber 1780 cm -1 . However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy.

[0073] Specific examples of the polyolefin include polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; polypropylene such as homopolypropylene, block copolymers of polypropylene (e.g., block copolymers of propylene and ethylene), random copolymers of polypropylene (e.g., random copolymers of propylene and ethylene); and terpolymers of ethylene-butene-propylene. Among these polyolefins, polyethylene and polypropylene are preferably mentioned.

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

[0075] 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 the modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, itaconic anhydride, etc.

[0076] The carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a part of the monomers constituting the cyclic polyolefin by replacing it 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 onto the cyclic polyolefin. The cyclic polyolefin to be carboxylic acid-modified is the same as described above. Further, 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, preferably a carboxylic acid-modified polyolefin; more preferably a carboxylic acid-modified polypropylene can be mentioned.

[0078] The heat-sealable resin layer 4 may be formed of a single resin component alone, or may be formed of a blend polymer in which two or more resin components are combined. Further, the heat-sealable resin layer 4 may be composed of only one layer, but may be formed of two or more layers with the same or different resin components.

[0079] The heat-sealable resin layer 4 may contain a lubricant. Further, the lubricant present on the surface of the heat-sealable resin layer 4 may be one obtained by exuding the lubricant contained in the resin constituting the heat-sealable resin layer 4, or may be one obtained by applying a lubricant 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 known lubricants can be used. For example, those exemplified in the above polyester film 1 can be mentioned. The lubricant may be used alone or in combination of two or more. 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, in an environment of a temperature of 24°C and a relative humidity of 60%, preferably 10 to 50 mg / m 2 level, more preferably 15 to 40 mg / m 2 level can be mentioned.

[0080] As described above, in recent years, with the demand for miniaturization and thinning of batteries, there has been an increasing requirement for further thinning of the packaging materials for batteries. For this reason, it is required to make the thickness of the heat-sealing 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-sealing resin layer to the thickness of the base material becomes small, the peripheral portion of the recess formed in the battery packaging material curls (curves), which inhibits the accommodation of the battery element and the heat-sealing of the heat-sealing resin layer, and may reduce 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 influence of curl on the productivity of the battery is very large because of their large size.

[0081] When the ratio of the thickness of the heat-sealing resin layer 4 to the thickness of the polyester film 1 becomes small (for example, when the thickness of the polyester film 1 is set to 1, the ratio of the thickness of the heat-sealing resin layer 4 to the thickness of the polyester film 1 (thickness of the heat-sealing resin layer / thickness of the polyester film) is 4 or less), the curl after molding of the battery packaging material tends to increase. However, in the battery packaging material of the present invention, since the surface orientation degree (Y max / Y min ) is in the range of 1.4 to 2.7, it has excellent moldability and effectively suppresses the curl after molding. In the battery packaging material of the present invention, from the viewpoint of preferably suppressing the curl after molding, the preferable upper limit of the ratio of the thickness of the heat-sealing resin layer 4 to the thickness of the polyester film 1 (thickness of the heat-sealing resin layer / thickness of the polyester film) is 4 or less, more preferably less than 3, still more preferably less than 2, and the preferable lower limit is 1 or more. The preferable range is 1 or more and 4 or less, the more preferable range is 1 or more and less than 3, and the still more preferable range is 1 or more and less than 2.

[0082] In addition, regarding the thickness of the heat-sealable resin layer 4, from the viewpoint of suppressing curl after molding while thinning the battery packaging material as much as possible, the upper limit is preferably about 100 μm or less, more preferably about 40 μm or less, and the lower limit is about 15 μm or more. Also, the preferable 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 provided between the barrier layer 3 and the heat-sealable resin layer 4 as necessary to firmly bond them.

[0084] The adhesive layer 5 is formed of a resin that can bond the barrier layer 3 and the heat-sealable resin layer 4. As the resin used for forming the adhesive layer 5, the adhesion mechanism, the type of adhesive component, etc. can be the same as those of the adhesives exemplified in the adhesive layer 2, for example. Also, as the resin used for forming the adhesive layer 5, polyolefin-based resins such as the polyolefins, cyclic polyolefins, carboxylic acid-modified polyolefins, and carboxylic acid-modified cyclic polyolefins exemplified in the above-mentioned heat-sealable resin layer 4 can also be used. That is, the resin constituting the adhesive layer 5 may or may not contain a polyolefin backbone, and it is preferable to contain a polyolefin backbone. Whether the resin constituting the adhesive layer 5 contains a polyolefin backbone can be analyzed by, for example, infrared spectroscopy, gas chromatography-mass spectrometry, etc., and the analysis method is not particularly limited. For example, when measuring maleic anhydride-modified polyolefin by infrared spectroscopy, peaks derived from maleic anhydride are detected in the vicinity of a wave number of 1760 cm -1 and in the vicinity of a wave number of 1780 cm -1 . However, if the degree of acid modification is low, the peak may become small and not be detected. In that case, it can be analyzed by nuclear magnetic resonance spectroscopy. From the viewpoint of excellent adhesion between the barrier layer 3 and the heat-sealable resin layer 4, as the polyolefin, carboxylic acid-modified polyolefin is preferable, and carboxylic acid-modified polypropylene is particularly preferable.

[0085] Furthermore, from the perspective of making a battery packaging material with excellent shape stability after molding while reducing the thickness of the battery packaging material, the adhesive layer 5 may be a cured product of a resin composition containing an acid-modified polyolefin and a curing agent. Examples of the acid-modified polyolefin preferably include the same ones as the carboxylic acid-modified polyolefin and the carboxylic acid-modified cyclic polyolefin exemplified in the heat-sealable resin layer 4. Also, 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 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. Further, 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. When unreacted products of curing agents such as a compound having an isocyanate group, a compound having an oxazoline group, and an epoxy resin remain in the adhesive layer 5, the presence of the unreacted products 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] Also, the curing agent is not particularly limited as long as it can cure the acid-modified polyolefin. Examples of the curing agent include epoxy-based curing agents, polyfunctional isocyanate-based curing agents, carbodiimide-based curing agents, oxazoline-based curing agents, and the like. Further, from the viewpoint of further enhancing 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 heterocyclic ring, a C=N bond, and a C-O-C bond. Examples of the curing agent having a heterocyclic ring include a curing agent having an oxazoline group, a curing agent having an epoxy group, and the like. Examples of the curing agent having a C=N bond include a curing agent having an oxazoline group, a curing agent having an isocyanate group, and the like. Examples of the curing agent having a C-O-C bond include a curing agent having an oxazoline group, a curing agent having an epoxy group, a urethane resin, and the like. Whether 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-based curing agent is not particularly limited as long as it is a compound having at least one epoxy group. Examples of the epoxy-based 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-based 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-based curing agent include isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), those obtained by polymerizing or nurating these, 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 or more carbodiimide groups is preferred.

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

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

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

[0093] The thickness of the adhesive layer 5 is not particularly limited as long as it exhibits the function as an adhesive layer. However, when using the adhesive exemplified in the adhesive layer 2, it is preferably about 2 to 10 μm, more preferably about 2 to 5 μm. Also, when using the resin exemplified in the heat-sealable resin layer 4, it is preferably about 2 to 50 μm, more preferably about 10 to 40 μm. Further, when it is a cured product of an acid-modified polyolefin and a curing agent, it 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, for the purpose of improving designability, electrolyte resistance, scratch resistance, formability, etc., a surface coating layer 6 may be provided on the upper side of the polyester film 1 (the side opposite to the barrier layer 3 of the polyester film 1) as necessary. The surface coating layer 6 is the outermost layer when the battery is assembled.

[0095] The surface coating layer 6 can be formed of, for example, polyvinylidene chloride, polyester resin, urethane resin, acrylic resin, epoxy resin, etc. Among these, the surface coating layer 6 is preferably formed of a two-component curable resin. Examples of the two-component curable resin for forming the surface coating layer 6 include two-component curable urethane resin, two-component curable polyester resin, two-component curable epoxy resin, etc. Further, additives may be blended in the surface coating layer 6.

[0096] Examples of the additive include fine particles with 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. Further, the shape of the additive is not particularly limited, and examples thereof include spherical, fibrous, plate-like, amorphous, and balloon-like shapes. Specific examples of the additive include talc, silica, graphite, kaolin, montmorillonite, 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, nickel, etc. These additives may be used alone or in combination of two or more. Among these additives, silica, barium sulfate, and titanium oxide are preferably used from the viewpoints of dispersion stability and cost. Further, various surface treatments such as insulation treatment and high dispersibility treatment may be applied to the surface of the additive.

[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% by mass, more preferably about 0.1 to 0.5% by mass.

[0098] The method for forming the surface coating layer 6 is not particularly limited, and examples thereof include a method of applying a two-component curable resin for forming the surface coating layer 6 on one surface of the polyester film 1. When adding an additive, the additive may be added to the two-component curable resin, mixed, and then applied.

[0099] The thickness of the surface coating layer 6 is not particularly limited as long as the above functions of the surface coating layer 6 are exhibited, and examples thereof include 0.5 to 10 μm, preferably 1 to 5 μm.

[0100] 3. Manufacturing method of packaging material for battery The manufacturing method of the packaging material for a battery of the present invention is not particularly limited as long as a laminate in which each layer having a predetermined composition is laminated can be obtained. As the manufacturing method of the packaging material for a battery, for example, it includes at least a step of laminating a polyester film, a barrier layer, and a heat-sealable resin layer in this order to obtain a laminate. As the polyester film, when obtaining infrared absorption spectra 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, the absorption peak intensity Y at 1340 cm -1 and the absorption peak intensity Y at 1410 cm 1340 , and the ratio (Y -1 / Y 1410 ) of the maximum value Y 1340 and the minimum value Y 1410 of the infrared absorption spectra (surface orientation degree: Y max / Y min ) is in the range of 1.4 to 2.7. max / Y min ) is in the range of 1.4 to 2.7 can be mentioned.

[0101] As an example of the manufacturing method of the packaging material for a battery of the present invention, it is as follows. First, a laminate (hereinafter, may also be referred to as "laminate A") in which a polyester film 1, an adhesive layer 2, and a barrier layer 3 are laminated in this order is formed. The formation of the laminate A is specifically carried out 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 the barrier layer 3 whose surface is chemically converted as necessary by a coating method such as a gravure coating method or a roll coating method, and then the barrier layer 3 or the polyester film 1 is laminated to cure the adhesive layer 2.

[0102] Next, an adhesive layer 5 and a heat-sealable resin layer 4 are laminated in this order on the barrier layer 3 of the laminate A. For example, (1) a method of laminating by co-extruding the adhesive layer 5 and the heat-sealable resin layer 4 on the barrier layer 3 of the laminate A (co-extrusion lamination method), (2) 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) extruding or solution-coating an adhesive for forming the adhesive layer 5 on the barrier layer 3 of the laminate A, drying at a high temperature and further baking, etc. to laminate, and laminating the heat-sealable resin layer 4 previously formed into a sheet shape on this adhesive layer 5 by a thermal lamination method, (4) a method of laminating the laminate A and the heat-sealable resin layer 4 through the adhesive layer 5 while pouring the 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 shape (sandwich lamination method), etc. can be mentioned.

[0103] When providing the surface coating layer 6, 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 resin for forming the surface coating layer 6 to the surface of the polyester film 1. Note that 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 forming the surface coating layer 6 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 composed of the surface coating layer 6 / polyester film 1 / adhesive layer 2 (provided as necessary) / barrier layer 3 (surface may be chemical conversion-treated as necessary) / adhesive layer 5 / heat-sealable resin layer 4 is formed as necessary. However, in order to strengthen the adhesiveness of the adhesive layer 2 or the adhesive layer 5, it may be further subjected to a heat treatment such as a heat roll contact type, a hot air type, a near or far infrared type, etc. Examples of the conditions for such a heat treatment include 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 surface activation treatment such as corona treatment, blast treatment, oxidation treatment, ozone treatment, etc., as necessary, in order to improve or stabilize film-forming properties, lamination processing, suitability for final product secondary processing (pouch formation, embossing), etc.

[0106] 4. Use of packaging material for battery The battery packaging material of the present invention is used for a package for sealing and housing battery elements such as a positive electrode, a negative electrode, and an electrolyte. That is, a battery can be formed by housing a battery element including at least a positive electrode, a negative electrode, and an electrolyte in a package formed of the battery packaging material of the present invention.

[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 a state where metal terminals connected to each of the positive electrode and the negative electrode protrude outward, so that a flange portion (a region where heat-sealable resin layers contact each other) can be formed at the periphery of the battery element, and the heat-sealable resin layers of the flange portion are heat-sealed and sealed, thereby providing a battery using the battery packaging material. When housing a battery element in a package formed of the battery packaging material of the present invention, the package is formed such that the heat-sealable resin portion of the battery packaging material of the present invention is on the inner side (the surface in contact with the battery element).

[0108] The battery packaging material of the present invention may be used for either a primary battery or a secondary battery, but is preferably a secondary battery. The type of secondary battery to which the battery packaging material of the present invention is applied is not particularly limited, and examples include lithium-ion batteries, lithium-ion polymer 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, capacitors, and capacitors. Among these secondary batteries, lithium-ion batteries and lithium-ion polymer batteries are mentioned as preferred application targets for 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 battery packaging materials. The polyester film of the present invention uses the total reflection method of Fourier transform infrared spectroscopy to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film. When the infrared absorption spectra are obtained, the absorption peak intensity Y at 1340 cm -1 in the absorption peak intensity Y 1340 and 1410 cm -1 in the absorption peak intensity Y 1410 and the ratio (Y 1340 / Y 1410 ) of the maximum value Y max and the minimum value Y min of the ratio (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less. The specific configuration of the polyester film of the present invention is the same as the configuration described in the column of "[Polyester Film 1]" in each layer forming the battery packaging material above.

Examples

[0110] Examples and comparative examples are shown below to explain the present invention in detail. However, the present invention is not limited to the examples.

[0111] Examples 1-7 and Comparative Examples 1-3 <Manufacture of Battery Packaging Material> On a stretched polyethylene terephthalate film, a barrier layer made of aluminum foil (JIS H4160:1994 A8021H-O) with a chemical conversion treatment applied to both sides to form an acid-resistant film was laminated by the dry lamination method. Specifically, a two-component curable 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, after laminating the adhesive layer on the barrier layer and the polyethylene terephthalate film, an aging treatment was carried out to produce a laminate of stretched polyethylene terephthalate film / adhesive layer / barrier layer. Note that the chemical conversion treatment of the aluminum foil used as the barrier layer was carried out by applying a treatment solution composed of a phenolic resin, a chromium fluoride compound, and phosphoric acid to both sides of the aluminum foil by the roll coating method so that the coating amount of chromium was 10 mg / m 2 (dry mass), and then baking.

[0112] Next, on the barrier layer of the obtained laminate, maleic anhydride-modified polypropylene as an adhesive layer and random polypropylene as a heat-sealing resin layer were co-extruded to laminate an adhesive layer / heat-sealing 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-sealing resin layer were laminated in this order. The layer structure and the thickness of each layer of the battery packaging material are as shown in Table 1.

[0113]

Table 1

[0114] In Table 1, the numerical values in parentheses in the layer structure represent the thickness (μm).

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

[0116] (Measurement conditions of infrared absorption spectrum) Spectrometer: Nicolet iS10 FT-IR manufactured by Thermo Fisher Scientific Accessory: One-reflection ATR accessory (Seagull) Detector: MCT (Hg Cd Te) Wavenumber resolution: 8 cm-1 IRE: Ge Incident angle: 30° Polarizer: Wire grid, S polarization Baseline: Average value of intensity in the range of wavenumber 1800 cm-1 to 2000 cm-1 Absorption peak intensity Y 1340 : Value obtained by subtracting the baseline value from the maximum value of the peak intensity in the range of wavenumber 1335 cm-1 to 1342 cm-1 Absorption peak intensity Y 1410 : Value obtained by subtracting the baseline value from the maximum value of the peak intensity in the range of wavenumber 1400 cm-1 to 1410 cm-1

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

[0118] <Evaluation of formability> Each of the battery packaging materials obtained above was cut into a rectangle with a length (z direction) of 150 mm and a width (x direction) of 100 mm to obtain test samples. Using a rectangular mold (female mold, the surface has a maximum height roughness (Rz nominal value) of 3.2 μm as specified in Table 2 of the reference surface roughness standard piece attached to JIS B 0659-1:2002) with a diameter of 30 mm (x direction) and 50 mm (z direction), and a corresponding mold (male mold, the surface has a maximum height roughness (Rz nominal value) of 1.6 μm as specified in Table 2 of the reference surface roughness standard piece attached to JIS B 0659-1:2002), cold forming (drawing one-step forming) was performed on 10 samples each at a pressing pressure (surface pressure) of 0.9 MPa while changing the forming depth in 0.5 mm units from a forming depth of 0.5 mm. At this time, the above test samples were placed on the female mold so that the heat-sealable resin layer side was positioned on the male mold side for forming. Also, the clearance between the male mold and the female mold was set to 0.5 mm. For the samples after cold forming, the deepest forming depth at which no pinholes or cracks occurred in all 10 samples on the aluminum foil was defined as Amm, and the number of samples in which pinholes or the like occurred at the shallowest forming depth at which pinholes or the like occurred in the aluminum foil was defined as B. The value calculated by the following formula was defined as the limiting forming depth of the battery packaging material. The results are shown in Table 2. Limiting forming depth = Amm + (0.5 mm / 10 pieces) × (10 pieces - B pieces)

[0119] <Evaluation of curl after forming> Each battery packaging material obtained as described above was cut to produce strip pieces with a length (z-direction) of 150 mm and a width (x-direction) of 100 mm, and these were used as test samples. Next, using the molding die used in the evaluation of formability, the above test samples were placed on the female die such that the heat-sealable resin layer side was positioned on the male die side, and the test samples were pressed at a holding pressure (surface pressure) of 0.1 MPa so as to achieve a molding depth of 6 mm, and cold forming (drawing single-stage forming) was performed. The details of the position where the forming was carried out are as shown in Fig. 5. As shown in Fig. 6, forming was carried out at a position where the distance d between the rectangular forming portion M and the end portion P of the battery packaging material 10 was 75 mm. Next, the battery packaging material 10 after forming was placed on the 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 portion P was taken as the maximum height (molding curl (mm)) of the curled portion. The results are shown in Table 2.

[0120]

Table 2

[0121] In Table 1 and Table 2, PET means stretched polyethylene terephthalate, DL means the adhesive layer, ALM means the aluminum foil, PPa means the adhesive layer formed of maleic anhydride-modified polypropylene, and PP means the heat-sealable resin layer formed of random polypropylene.

Explanation of Signs

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

Claims

1. A battery packaging material composed of a laminate comprising 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, wherein the laminate is composed only of the substrate, an adhesive layer, the barrier layer, an adhesive layer, and the heat-sealable resin layer in this order, the substrate comprises a polyester film, the thickness of the substrate 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 thickness of the barrier layer is 10 μm or more and 80 μm or less, the heat-sealable resin layer is composed of polypropylene, the thickness of the heat-sealable resin layer is 15 μm or more and 100 μm or less, the thickness of the adhesive layer is 0.1 μm or more and 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, -1 Absorption peak intensity Y 1340 And 1410 cm -1 Absorption peak intensity Y 1410 Ratio to (Y 1340 / Y 1410 ) the maximum value Y max and the minimum value Y min Ratio of surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less.

2. The battery packaging material according to claim 1, wherein the ratio of the thickness of the heat-sealable resin layer to the thickness of the polyester film is less than 3.

3. The battery packaging material according to claim 1 or 2, wherein the thickness of the heat-sealable resin layer is 15 μm or more and 40 μm or less.

4. The battery packaging material according to any one of claims 1 to 3, wherein the birefringence of the polyester film is 0.016 or more.

5. A battery, wherein a battery element comprising at least a positive electrode, a negative electrode, and an electrolyte is housed in a package formed of the battery packaging material according to any one of claims 1 to 4.

6. 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 composed 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 substrate 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 thickness of the barrier layer is 10 μm or more and 80 μm or less, the heat-sealable resin layer is composed of polypropylene, the thickness of the heat-sealable resin layer is 15 μm or more and 100 μm or less, the thickness of the adhesive layer is 0.1 μm or more and 20 μm or less, As the polyester film, when infrared absorption spectra in 18 directions are obtained at 10° intervals from 0° to 180° on the surface of the polyester film using the total reflection method of Fourier transform infrared spectroscopy, the absorption peak intensity Y -1 at 1340 cm 1340 and the absorption peak intensity Y -1 at 1410 cm 1410 and the ratio (Y 1340 / Y 1410 ) of the maximum value Y max and the minimum value Y min (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less is used, a method for manufacturing a battery packaging material.

7. A polyester film for use in a battery packaging material, The battery packaging material is composed of at least a laminate including 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 only of, in order, the base material, an adhesive layer, the barrier layer, an adhesive layer, and the heat-sealable resin layer. The base material includes a polyester film. The thickness of the base material 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 thickness of the barrier layer is 10 μm or more and 80 μm or less. The heat-sealable resin layer is composed of polypropylene. The thickness of the heat-sealable resin layer is 15 μm or more and 100 μm or less. The thickness of the adhesive layer is 0.1 μm or more and 20 μm or less. When using the total reflection method of Fourier transform infrared spectroscopy to obtain infrared absorption spectra in 18 directions at 10° intervals from 0° to 180° on the surface of the polyester film, the absorption peak intensity Y -1 at 1340 cm 1340 and the absorption peak intensity Y -1 at 1410 cm 1410 The ratio (Y 1340 / Y 1410 ), the maximum value Y max and the minimum value Y min Ratio (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less, a polyester film.

8. When infrared absorption spectra in 18 directions are obtained at 10° intervals from 0° to 180° on the surface of a polyester film using the total reflection method of Fourier transform infrared spectroscopy, the absorption peak intensity Y -1 at 1340 cm 1340 and the absorption peak intensity Y -1 at 1410 cm 1410 and the ratio (Y 1340 / Y 1410 ), the ratio of the maximum value Y max and the minimum value Y min (surface orientation degree: Y max / Y min ) is in the range of 1.4 or more and 2.7 or less, for use as a battery packaging material of a polyester film, The battery packaging material is composed of at least a laminate including 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 only of, in order, the base material, an adhesive layer, the barrier layer, an adhesive layer, and the heat-sealable resin layer. The base material includes a polyester film. The thickness of the base material 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 thickness of the barrier layer is 10 μm or more and 80 μm or less. The heat-sealable resin layer is composed of polypropylene. The thickness of the heat-sealable resin layer is 15 μm or more and 100 μm or less. The thickness of the adhesive layer is 0.1 μm or more and 20 μm or less. Use of the polyester film for the battery packaging material.

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