Adhesive film for metal terminal, metal terminal with adhesive film for metal terminal, electricity storage device using said adhesive film for metal terminal, and method for manufacturing electricity storage device

Abstract

To provide an adhesive film for a metal terminal which exhibits high adhesion strength to a metal terminal when the film is heated and pressurized a plurality of times before being adhered to the metal terminal.SOLUTION: In an adhesive film for a metal terminal interposed between a metal terminal electrically connected to an electrode of a power storage device element and an exterior material for the power storage device that seals the power storage device element, after standing for 12 seconds in a heating and pressurizing environment with a temperature of 180°C and a surface pressure of 0.0067 MPa and further standing for one hour in an environment with a temperature of 25°C, the tensile elastic modulus A measured in an environment with a temperature of 25°C is 490 MPa or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an adhesive film for a metal terminal, a metal terminal with an adhesive film for a metal terminal, an electricity storage device using the adhesive film for a metal terminal, and a method for manufacturing an electricity storage device. [Background technology]

[0002] Various types of electricity storage devices have been developed to date, and in all electricity storage devices, exterior materials for electricity storage devices have become essential components for sealing electricity storage device elements such as electrodes and electrolytes. Metal exterior materials for electricity storage devices have traditionally been widely used as exterior materials for electricity storage devices. However, in recent years, with the increasing performance of electric vehicles, hybrid electric vehicles, personal computers, cameras, mobile phones, and the like, electricity storage devices are being required to have a variety of shapes, as well as to be thinner and lighter. However, the metal exterior materials for electricity storage devices that have traditionally been widely used have the drawbacks of being difficult to keep up with the diversification of shapes and also having limitations on how much they can be made lighter.

[0003] Therefore, in recent years, a laminate sheet in which a base material layer / adhesive layer / barrier layer / thermal adhesive resin layer are laminated in this order has been proposed as an electrical storage device packaging material that can be easily processed into a variety of shapes and can achieve thinning and weight reduction. When such a film-like electrical storage device packaging material is used, the electrical storage device elements are sealed in the electrical storage device packaging material by heat-sealing the peripheral edge of the electrical storage device packaging material with the innermost thermal adhesive resin layers facing each other.

[0004] Metal terminals protrude from the heat-sealed portions of the exterior material for an electricity storage device, and the electricity storage device elements sealed with the exterior material for an electricity storage device are electrically connected to the outside via the metal terminals, which are electrically connected to the electrodes of the electricity storage device elements. That is, the portions of the heat-sealed exterior material for an electricity storage device where the metal terminals are present are heat-sealed in a state where the metal terminals are sandwiched between the heat-sealable resin layers. Because the metal terminals and the heat-sealable resin layer are made of different materials, adhesion is likely to decrease at the interface between the metal terminals and the heat-sealable resin layer.

[0005] For this reason, an adhesive film is sometimes disposed between the metal terminal and the heat-sealable resin layer in order to improve adhesion therebetween. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-79638 Summary of the Invention [Problem to be solved by the invention]

[0007] Such adhesive films are required to have high adhesion to the exterior packaging material for the electricity storage device and to the metal terminals.

[0008] In the process of bonding a metal terminal and an exterior material for an electric storage device via an adhesive film, it is common to perform multiple heating and pressure applications, such as a temporary bonding process to the metal terminal and a final bonding process. The temporary bonding process is a process of temporarily attaching the adhesive film to the metal terminal and removing air bubbles, while the final bonding process is a process of bonding the adhesive film to the metal terminal by applying heat and pressure once or multiple times at higher temperatures than in the temporary bonding process. The inventors have found that if the adhesive film is heated and pressed prior to the final bonding process and then further heated and pressed in the final bonding process, the adhesive strength of the adhesive film to the metal terminal may be reduced due to the effects of multiple heating and pressure applications. Depending on the degree of reduction in adhesive strength, the adhesive strength between the exterior material for an electric storage device and the metal terminal via the adhesive film may be insufficient.

[0009] In light of these circumstances, the present disclosure has as its main object the provision of an adhesive film for metal terminals that exhibits high adhesive strength to metal terminals when subjected to multiple cycles of heating and pressure before being bonded to the metal terminal. Furthermore, the present disclosure also has as its object the provision of a metal terminal with an adhesive film for metal terminals, an electricity storage device using the adhesive film for metal terminals, and a method for manufacturing the electricity storage device. [Means for solving the problem]

[0010] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. As a result, they found that an adhesive film for a metal terminal that has a tensile modulus of elasticity measured in an environment at 25°C after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then left to stand for one hour in an environment at a temperature of 25°C, exhibits high adhesive strength to the metal terminal when heated and pressurized multiple times before being bonded to the metal terminal. The present disclosure was completed through further research based on this finding.

[0011] That is, the present disclosure provides the inventions of the following aspects. An adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element, The adhesive film for metal terminals has a tensile modulus A of 490 MPa or more when measured in an environment at 25°C after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide an adhesive film for metal terminals that exhibits high adhesive strength to metal terminals when heated and pressurized multiple times before being bonded to the metal terminal. Furthermore, according to the present disclosure, it is also possible to provide a metal terminal with the adhesive film for metal terminals, an electricity storage device using the adhesive film for metal terminals, and a method for manufacturing an electricity storage device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic plan view of an electricity storage device according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view taken along line AA' in FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view taken along line BB' in FIG. [Figure 4] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 5] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 7] 1 is a schematic cross-sectional view of an adhesive film for metal terminals according to the present disclosure. [Figure 8] 1 is a schematic cross-sectional view of an exterior packaging material for an electricity storage device according to the present disclosure. [Figure 9] FIG. 2 is a schematic diagram of a stress-strain curve obtained by a tensile test of an adhesive film for a metal terminal. [Figure 10] This is a schematic cross-sectional view of an adhesive film / metal terminal / adhesive film laminate (metal terminal with adhesive film for metal terminal) obtained in an example by sandwiching a metal terminal between two adhesive films and heat-sealing them. [Figure 11] FIG. 2 is a schematic diagram illustrating a method for evaluating water vapor barrier properties (moisture content) in the examples. [Figure 12] FIG. 2 is a schematic diagram showing MD, TD, and thickness direction (y) in a production line for an adhesive film for a metal terminal. DETAILED DESCRIPTION OF THE INVENTION

[0014] The adhesive film for metal terminals of the present disclosure is an adhesive film for metal terminals that is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element. The adhesive film for metal terminals of the present disclosure is characterized in that, after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then being left to stand for 1 hour in an environment at a temperature of 25°C, the tensile modulus A measured in an environment at a temperature of 25°C is 490 MPa or more. Note that the treatment of leaving the film to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa is a treatment that simulates the heat and pressure applied in the temporary bonding step and the main bonding step.

[0015] According to the adhesive film for metal terminals of the present disclosure, the tensile modulus after the heating and pressurizing environment is set to 490 MPa or more, and therefore, when the film is heated and pressurized multiple times before being adhered to the metal terminal, the film can exhibit high adhesive strength to the metal terminal.

[0016] The present disclosure also provides an electricity storage device comprising at least an electricity storage device element having a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device that encapsulates the electricity storage device element, and metal terminals electrically connected to the positive electrode and the negative electrode, respectively, and protruding outside the exterior material for an electricity storage device, wherein the adhesive film for a metal terminal of the present disclosure is interposed between the metal terminal and the exterior material for an electricity storage device. The adhesive film for a metal terminal of the present disclosure, an electricity storage device using the adhesive film for a metal terminal, and a method for manufacturing the electricity storage device are described in detail below.

[0017] In this specification, numerical ranges indicated with "to" mean "greater than or equal to" or "less than or equal to." For example, the expression 2 to 15 mm means 2 mm or greater and 15 mm or less.

[0018] 1. Adhesive film for metal terminals The adhesive film for metal terminals of the present disclosure is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element. Specifically, as shown in Figures 1 to 3, for example, an adhesive film for metal terminal 1 of the present disclosure is interposed between a metal terminal 2 electrically connected to an electrode of an electricity storage device element 4 and an exterior material for an electricity storage device 3 that seals the electricity storage device element 4. The metal terminal 2 protrudes outside the exterior material for an electricity storage device 3 and is sandwiched between the exterior material for an electricity storage device 3, via the adhesive film for metal terminal 1, at a peripheral portion 3a of the heat-sealed exterior material for an electricity storage device 3. In the present disclosure, the heating temperature when heat-sealing the exterior material for an electricity storage device is typically in the range of about 160 to 190°C, and the pressure is typically in the range of about 1.0 to 2.0 MPa. The temporary bonding process of the adhesive film for metal terminals to the metal terminal is carried out, for example, under conditions of a temperature of about 140 to 160°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 3 to 6, while the main bonding process is carried out, for example, under conditions of a temperature of about 160 to 240°C, a pressure of about 0.01 to 1.0 MPa, a time of about 3 to 15 seconds, and a number of times of about 1 to 3.

[0019] The adhesive film 1 for metal terminals of the present disclosure is provided to improve adhesion between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device. Improved adhesion between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device improves the sealing performance of the electricity storage device element 4. As described above, when the electricity storage device element 4 is heat-sealed, the electricity storage device element is sealed such that the metal terminal 2 electrically connected to the electrode of the electricity storage device element 4 protrudes outside the exterior packaging material 3 for an electricity storage device. At this time, the metal terminal 2 made of metal and the heat-sealable resin layer 35 (a layer made of a heat-sealable resin such as polyolefin) located in the innermost layer of the exterior packaging material 3 for an electricity storage device are made of different materials. Therefore, without using such an adhesive film, the sealing performance of the electricity storage device element is likely to be reduced at the interface between the metal terminal 2 and the heat-sealable resin layer 35.

[0020] The adhesive film 1 for metal terminals of the present disclosure may be a single layer as shown in FIG. 4 or a multilayer as shown in FIGS. 5 to 7, provided that the tensile modulus A, described below, is 490 MPa or greater. The adhesive film 1 for metal terminals of the present disclosure is preferably a multilayer. When the adhesive film 1 for metal terminals of the present disclosure is a multilayer, it preferably includes a structure in which at least the substrate 11 and the first polyolefin layer 12a are laminated, as shown in FIGS. 5 to 7, and more preferably includes a structure in which at least the first polyolefin layer 12a, the substrate 11, and the second polyolefin layer 12b are laminated in this order, as shown in FIGS. 6 and 7. Furthermore, in the adhesive film for metal terminals 1 of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are preferably located on the surfaces of both sides, respectively.

[0021] In the adhesive film for metal terminal 1 of the present disclosure, at least one of the first polyolefin layer 12a and the second polyolefin layer 12b preferably contains an acid-modified polyolefin, and it is more preferable that the first polyolefin layer 12a and the second polyolefin layer 12b contain an acid-modified polyolefin. Furthermore, the substrate 11 preferably contains a polyolefin. As described below, the first polyolefin layer 12a and the second polyolefin layer 12b are preferably acid-modified polypropylene layers formed from acid-modified polypropylene. Furthermore, the substrate 11 is preferably a polypropylene layer formed from polypropylene.

[0022] Specific examples of preferred laminate structures for the adhesive film 1 for metal terminals of the present disclosure include a two-layer structure of acid-modified polypropylene layer / polypropylene layer; a three-layer structure in which acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order; and a five-layer structure in which acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order.Of these, a two-layer structure of acid-modified polypropylene layer / polypropylene layer; and a three-layer structure in which acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order are more preferred, and a three-layer structure in which acid-modified polypropylene layer / polypropylene layer / acid-modified polypropylene layer are laminated in this order are particularly preferred.

[0023] When the adhesive film 1 for metal terminals of the present disclosure is placed between the metal terminal 2 of the electricity storage device 10 and the exterior material 3 for the electricity storage device, the surface of the metal terminal 2 made of metal and the heat-sealable resin layer 35 (a layer formed from a heat-sealable resin such as polyolefin) of the exterior material 3 for the electricity storage device are adhered via the adhesive film 1 for metal terminals.

[0024] The adhesive film 1 for metal terminals of the present disclosure has a tensile modulus A of 490 MPa or more when measured in a 25°C environment after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then left to stand for 1 hour in a 25°C environment. To ensure high adhesion strength to metal terminals when the film is heated and pressurized multiple times before being bonded to the metal terminal, the tensile modulus A is preferably about 520 MPa or more, more preferably about 550 MPa or more, even more preferably about 569 MPa or more, and even more preferably about 573 MPa or more. The upper limit of the tensile modulus A is about 850 MPa or less, preferably about 800 MPa or less to improve the impact absorption energy described below. Furthermore, to provide an adhesive film 1 for metal terminals with excellent flexibility (good evaluation in a bending test described below), the upper limit is preferably about 680 MPa or less, more preferably about 610 MPa or less. Preferred ranges for the tensile modulus A include about 490 to 850 MPa, about 490 to 800 MPa, about 490 to 680 MPa, about 490 to 610 MPa, about 520 to 850 MPa, about 520 to 800 MPa, about 520 to 680 MPa, about 520 to 610 MPa, about 550 to 850 MPa, about 550 to 800 MPa, about 550 to 680 MPa, about 550 to 610 MPa, about 569 to 850 MPa, about 569 to 800 MPa, about 569 to 680 MPa, about 569 to 610 MPa, about 573 to 850 MPa, about 573 to 800 MPa, about 573 to 680 MPa, and about 573 to 610 MPa. From the viewpoint of obtaining an adhesive film 1 for a metal terminal that exhibits high adhesive strength to a metal terminal while being excellent overall in flexibility, thickness change rate, and impact absorption energy, as described below, the overall preferable range of the tensile modulus A is about 500 to 550 MPa. The tensile modulus A is measured as follows.

[0025] <Tensile modulus A after heating and pressing> The tensile modulus after heating and pressurization at 180°C and 0.0067 MPa for 12 seconds is measured using the following procedure. First, the adhesive film for metal terminals is cut into strips with a width (TD) of 15 mm and a length (MD) of 50 mm. The MD and TD of the adhesive film for metal terminals can be determined by observing the sea-island structure of the cross section of the adhesive film for metal terminals in the thickness direction. The shape of the islands observed in the MD cross section is generally elongated compared to the TD cross section. Next, the adhesive film for metal terminals is sandwiched between two tetrafluoroethylene-ethylene copolymer films (ETFE films, 100 μm thick), placed on a hot plate heated to 180°C, and a 500 g sponge-attached weight is placed on top. The film is left to stand for 12 seconds, and then immediately left to stand at atmospheric pressure and 25°C for 1 hour to obtain a test specimen. Next, at atmospheric pressure and 25°C, a Tensilon universal testing machine (for example, A&D's RTG-1210) is used to obtain a stress-strain curve for the test piece at a tensile speed of 300 mm / min and a chuck distance of 30 mm. The tensile modulus A of the adhesive film for metal terminals after heating and pressurization is determined from the slope of the line connecting the two points of 0.05% and 0.25% strain.

[0026] The adhesive film 1 for metal terminals of the present disclosure has a tensile modulus B, measured in an environment at 25°C before exposure to a heated and pressurized environment, of, for example, about 900 MPa or less. From the viewpoint of providing an adhesive film 1 for metal terminals with excellent flexibility (good evaluation in the bending test described below), it is preferably about 700 MPa or less. Furthermore, from the viewpoint of enhancing the stiffness of the adhesive film 1 for metal terminals and facilitating alignment with the metal terminal, the tensile modulus B is preferably about 400 MPa or more. Preferred ranges for the tensile modulus B include about 400 to 900 MPa and about 400 to 700 MPa, with about 400 to 700 MPa being particularly preferred. From the viewpoint of providing an adhesive film 1 for metal terminals with high adhesive strength to metal terminals and overall good flexibility, thickness change rate, and impact absorption energy, as described below, the tensile modulus B is preferably in the range of 420 to 600 MPa, or even 420 to 480 MPa. The tensile modulus B is measured as follows.

[0027] <Tensile modulus B before heating and pressing> In accordance with the provisions of JIS K7161-1 (ISO527-1), the tensile modulus B of the adhesive film for metal terminals (before the heat and pressure application described above in "Tensile modulus A after heat and pressure application") is measured in a 25°C environment. Specifically, the adhesive film for metal terminals is cut into strips with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, a stress-strain curve of the test piece of the adhesive film for metal terminals is obtained using a Tensilon universal testing machine (e.g., A&D RTG-1210) at a tensile speed of 300 mm / min and a chuck distance of 30 mm in a 25°C environment. The tensile modulus B of the adhesive film for metal terminals before heat and pressure application is calculated from the slope of the line connecting the two points at 0.05% and 0.25% strain.

[0028] The tensile modulus of the adhesive film 1 for metal terminals of the present disclosure can be adjusted by the laminate structure, the melting point, MFR, thickness, thickness ratio of each layer, and further by the conditions of the T-die, inflation, etc. in the production of the adhesive film 1 for metal terminals (e.g., extrusion width from the T-die, stretching ratio, stretching speed, heat treatment temperature, etc.).

[0029] From the viewpoint of obtaining an adhesive film 1 for a metal terminal having excellent flexibility (good evaluation in a bending test described below), the adhesive film 1 for a metal terminal of the present disclosure has a difference in tensile modulus, calculated by subtracting the value of the tensile modulus B from the value of the tensile modulus A, of, for example, -250 to 200 MPa. From the viewpoint of exhibiting high adhesive strength to a metal terminal when the film is subjected to multiple heating and pressure treatments before being bonded to the metal terminal, it is preferable that this difference be large, preferably 5 MPa or more, more preferably 20 MPa or more, and even more preferably 40 MPa or more. The upper limit of the difference in tensile modulus is generally 120 MPa or less. Preferred ranges for the difference in tensile modulus include about 5 to 120 MPa, about 20 to 120 MPa, and about 40 to 120 MPa. From the viewpoint of obtaining an adhesive film 1 for a metal terminal that exhibits high adhesive strength to a metal terminal while also being good overall in terms of flexibility, thickness change rate, and impact absorption energy, as described below, a preferred range is about 40 to 75 MPa.

[0030] In order to ensure a high adhesive strength to a metal terminal when the film is heated and pressurized multiple times before being bonded to the metal terminal, the adhesive film 1 for a metal terminal of the present disclosure has a lower yield stress of preferably 17.0 MPa or more, more preferably 18.0 MPa or more, and also preferably 28.0 MPa or less, more preferably 26.0 MPa or less, as determined from a graph showing the relationship between stress (MPa) and strain (mm) (stress-strain curve) obtained by a tensile test performed in accordance with JIS K7127 at a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. Preferred ranges for the lower yield stress include about 17.0 to 28.0 MPa, about 17.0 to 26.0 MPa, about 18.0 to 28.0 MPa, and about 18.0 to 26.0 MPa, with about 18.0 to 26.0 MPa being particularly preferred. Moreover, a range of the lower yield stress that is generally preferable in terms of adhesion, flexibility, and conformability is about 17.0 to 18.0 MPa. The method for measuring the lower yield stress is as follows.

[0031] <Lower yield stress after heating and pressing> The method conforms to the JIS K7127 regulations and involves conducting a tensile test at a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. From the obtained stress-strain curve, the stress at the lower yield point L (see the schematic diagram in Figure 9) (lower yield point stress) is determined.

[0032] The lower yield stress of the adhesive film 1 for metal terminals of the present disclosure can be adjusted by the laminate structure, the melting point, MFR, thickness, thickness ratio of each layer, and further by the conditions of the T-die, inflation, etc. in the production of the adhesive film 1 for metal terminals (for example, the extrusion width from the T-die, the stretching ratio, the stretching speed, the heat treatment temperature, etc.).

[0033] Furthermore, the adhesive film 1 for metal terminal of the present disclosure preferably has a thickness change rate close to 100% before and after heating and pressing for 12 seconds under conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa (i.e., there is little or no change in thickness before and after heating and pressing), specifically, 90 to 100% is preferred, 95 to 100% is more preferred, and 96 to 100% is even more preferred. When the thickness change rate is within these ranges, the adhesive film 1 for metal terminal does not change significantly in thickness during heat fusion bonding between the adhesive film 1 for metal terminal and the exterior material 10 for an electrical storage device, thereby preventing voids from forming between them. The thickness change rate is calculated using the formula: (thickness of the adhesive film for metal terminal after heating and pressing) / (thickness of the adhesive film for metal terminal before heating and pressing) × 100.

[0034] Furthermore, the impact absorption energy calculated from the area enclosed by the stress-strain curve obtained in the above-mentioned <Tensile modulus A after heating and pressurizing> is preferably about 90 MPa or more, more preferably about 140 MPa or more, and is also preferably about 400 MPa or less, more preferably about 300 MPa or less, with a preferred range being around 90 to 400 MPa. Materials with a small impact absorption energy value tend to break easily without significant deformation, while materials with a large impact absorption energy value tend to break after significant deformation, and can be said to be tough materials that do not break easily.

[0035] The total thickness of the adhesive film 1 for metal terminal of the present disclosure is, from the viewpoint of improving conformability to the shape of the metal terminal 2, for example, about 120 μm or more, preferably about 140 μm or more, and more preferably about 150 μm or more. The upper limit of the total thickness of the adhesive film 1 for metal terminal of the present disclosure is, for example, about 200 μm. Preferred ranges for the total thickness of the adhesive film 1 for metal terminal of the present disclosure include about 120 to 200 μm, about 140 to 200 μm, and about 150 to 200 μm. Furthermore, from the viewpoint of providing an adhesive film 1 for metal terminal that exhibits high adhesive strength to the metal terminal while being generally excellent in terms of flexibility, rate of change in thickness, and impact energy absorption, a thickness of about 145 to 155 μm is particularly preferred.

[0036] <When the adhesive film for metal terminal of the present disclosure is a single layer> When the adhesive film for metal terminals of the present disclosure is a single layer, the adhesive film for metal terminals 1 of the present disclosure is preferably composed of a first polyolefin layer 12a having the physical properties described above.

[0037] <When the adhesive film for metal terminal of the present disclosure is multilayered> When the adhesive film for metal terminals of the present disclosure is multilayered, it is preferable that the adhesive film for metal terminals 1 of the present disclosure is a laminate having at least a structure in which a substrate 11 and a first polyolefin layer 12a are laminated together, and has the properties described above, and it is preferable that the adhesive film for metal terminals 1 of the present disclosure is a laminate having at least a structure in which a first polyolefin layer 12a, a substrate 11, and a second polyolefin layer 12b are laminated together in this order, and has the properties described above.

[0038] The substrate 11, the first polyolefin layer 12a, and the second polyolefin layer 12b will be described in detail below.

[0039] [Base material 11] In the adhesive film for a metal terminal 1, the substrate 11 is a layer that functions as a support for the adhesive film for a metal terminal 1, and is provided as needed.

[0040] The material forming the substrate 11 is not particularly limited. Examples of materials that can be used to form the substrate 11 include polyolefin, polyamide, polyester, epoxy resin, acrylic resin, fluororesin, silicone resin, phenolic resin, polyetherimide, polyimide, polycarbonate, and mixtures and copolymers thereof, with polyolefin being particularly preferred. That is, the material forming the substrate 11 is preferably a resin containing a polyolefin skeleton, such as polyolefin or acid-modified polyolefin. Whether the resin forming the substrate 11 contains a polyolefin skeleton can be determined by, for example, infrared spectroscopy, gas chromatography mass spectrometry, or the like.

[0041] Specific examples of polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous 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); ethylene-butene-propylene terpolymers; etc. Among these polyolefins, polyethylene and polypropylene are preferred, and polypropylene is more preferred.

[0042] Specific examples of polyamides include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, nylon 46, and copolymers of nylon 6 and nylon 66; hexamethylenediamine-isophthalic acid-terephthalic acid copolymer polyamides such as nylon 6I, nylon 6T, nylon 6IT, and nylon 6I6T (where I represents isophthalic acid and T represents terephthalic acid) containing structural units derived from terephthalic acid and / or isophthalic acid; 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, which are copolymers of copolymerized polyamides with polyesters or polyalkylene ether glycols; and copolymers thereof. These polyamides may be used alone or in combination of two or more.

[0043] Specific examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, copolymer polyesters whose repeating units are mainly ethylene terephthalate, copolymer polyesters whose repeating units are mainly butylene terephthalate, etc. Specific examples of copolymer polyesters whose repeating units are mainly ethylene terephthalate include copolymer polyesters in which ethylene terephthalate is the main repeating unit and is 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 / decanedicarboxylate), 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.

[0044] The substrate 11 may also be made of a nonwoven fabric formed from the above resin. When the substrate 11 is a nonwoven fabric, the substrate 11 is preferably made of the above-mentioned polyolefin, polyamide, or the like.

[0045] Furthermore, by blending a colorant into the substrate 11, the substrate 11 can be made into a layer containing a colorant. Furthermore, light transmittance can be adjusted by selecting a resin with low transparency. When the substrate 11 is a film, a colored film or a film with low transparency can be used. When the substrate 11 is a nonwoven fabric, a nonwoven fabric using a fiber or binder containing a colorant or a nonwoven fabric with low transparency can be used.

[0046] The melt mass flow rate (MFR) of the substrate 11 at 230°C is preferably 8g / 10 min or less, more preferably 4g / 10 min or less, from the viewpoint of exhibiting higher adhesive strength to the metal terminal when heated and pressed multiple times before being bonded to the metal terminal while satisfying the above-mentioned properties, and is preferably 1g / 10 min or more, more preferably 2g / 10 min or more, from the viewpoint of obtaining an adhesive film 1 for metal terminal with excellent flexibility (good evaluation in the bending test described below), and preferred ranges include about 1 to 8g / 10 min, about 1 to 4g / 10 min, about 2 to 8g / 10 min, and about 2 to 4g / 10 min. When the substrate layer 11 is a polyolefin layer (a layer formed from polyolefin), it is particularly suitable that the MFR value of the polyolefin layer satisfies the above value. The melt mass flow rate (MFR) of the substrate 11 is a value (g / 10 min) at 230° C. measured in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011).

[0047] The melting point of the substrate 11 is preferably 130°C or higher, more preferably 150°C or higher, from the viewpoint of exhibiting higher adhesive strength to the metal terminal when heated and pressed multiple times before being bonded to the metal terminal while satisfying the above-mentioned properties, and is preferably 190°C or lower, more preferably 170°C or lower, from the viewpoint of providing an adhesive film 1 for a metal terminal with excellent flexibility (good evaluation in the bending test described below), with preferred ranges being about 130 to 190°C, or about 150 to 170°C. The melting point of the substrate 11 is measured by the method described in the Examples.

[0048] When the substrate 11 is made of a resin film, the surface of the substrate 11 may be subjected to a known adhesion-facilitating treatment such as corona discharge treatment, ozone treatment, or plasma treatment, if necessary.

[0049] The thickness of substrate 11 is preferably at least about 50 μm, more preferably at least about 60 μm, even more preferably at least about 80 μm, and even more preferably at least about 90 μm, from the viewpoint of exhibiting high adhesive strength to the metal terminal when multiple heating and pressure applications are performed before bonding to the metal terminal. It is also preferably at most about 150 μm, more preferably at most about 130 μm, and even more preferably at most about 120 μm. Preferred ranges include about 50 to 150 μm, about 50 to 130 μm, about 50 to 120 μm, about 60 to 150 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 150 μm, about 80 to 130 μm, about 80 to 120 μm, about 90 to 150 μm, about 90 to 130 μm, and about 90 to 120 μm. Of these, about 90 to 120 μm is particularly preferred.

[0050] [First and second polyolefin layers 12a, 12b] The adhesive film 1 for metal terminals of the present disclosure preferably includes a first polyolefin layer 12a. When the adhesive film 1 for metal terminals of the present disclosure is composed of a single layer, the adhesive film 1 for metal terminals preferably includes a first polyolefin layer 12a as shown in FIG. 4. When the adhesive film 1 for metal terminals of the present disclosure is composed of multiple layers, it preferably includes a configuration in which at least the substrate 11 and the first polyolefin layer 12a are laminated, and more preferably includes a configuration in which at least the first polyolefin layer 12a, the substrate 11, and the second polyolefin layer 12b are laminated in this order, as shown in FIGS. 6 and 7. In the adhesive film 1 for metal terminals of the present disclosure, the first polyolefin layer 12a and the second polyolefin layer 12b are preferably located on the surfaces of both sides, respectively.

[0051] Furthermore, at least one of the first polyolefin layer 12a and the second polyolefin layer 12b preferably contains an acid-modified polyolefin, and more preferably, the first polyolefin layer 12a and the second polyolefin layer 12b contain an acid-modified polyolefin. At least one of the first and second polyolefin layers 12a, 12b may be formed from an acid-modified polyolefin; one of the first and second polyolefin layers 12a, 12b may be formed from an acid-modified polyolefin and the other from a polyolefin; or both the first and second polyolefin layers 12a, 12b may be formed from an acid-modified polyolefin. Acid-modified polyolefins have a high affinity with metals and heat-sealable resins such as polyolefins. Furthermore, polyolefins have a high affinity with heat-sealable resins such as polyolefins. Therefore, in the adhesive film 1 for metal terminals of the present disclosure, by disposing a layer formed from an acid-modified polyolefin on the metal terminal 2 side, excellent adhesion can be achieved at the interface between the adhesive film 1 for metal terminals and the metal terminal 2 and the heat-sealable resin layer 35. Furthermore, by placing a layer formed from polyolefin on the heat-sealable resin layer 35 side of the packaging material 10 for an electrical storage device, even better adhesion can be achieved at the interface between the adhesive film 1 for metal terminals and the heat-sealable resin layer 35.

[0052] The adhesive film 1 for metal terminals is preferably a laminate having, in order, a first polyolefin layer 12a, a substrate 11, and a second polyolefin layer 12b. The adhesive film 1 for metal terminals has a laminate structure in which the first polyolefin layer 12a, the substrate 11, and the second polyolefin layer 12b are laminated in this order, for example, as shown in Figures 6 and 7. As described above, the adhesive film 1 for metal terminals is particularly preferably a three-layer structure in which an acid-modified polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order, or a three-layer structure in which a polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order. In addition, when the adhesive film 1 for metal terminals has a three-layer structure in which a polypropylene layer / a polypropylene layer / an acid-modified polypropylene layer are laminated in this order, the acid-modified polypropylene layer constituting one side is positioned on the metal terminal 2 side, and the polypropylene layer constituting the other side is positioned on the heat-sealable resin layer 35 side of the packaging material 10 for an electrical storage device, thereby enabling the adhesive film 1 for metal terminals to form particularly favorable adhesion between the packaging material 10 for an electrical storage device and the metal terminal 2.

[0053] In the first and second polyolefin layers 12a and 12b, the acid-modified polyolefin is not particularly limited as long as it is an acid-modified polyolefin, but preferred examples include polyolefins graft-modified with an unsaturated carboxylic acid or anhydride thereof.

[0054] Specific examples of acid-modified polyolefins include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous polypropylenes such as homopolypropylene, polypropylene block copolymers (e.g., propylene-ethylene block copolymers), and polypropylene random copolymers (e.g., propylene-ethylene random copolymers); and ethylene-butene-propylene terpolymers. Among these polyolefins, polyethylene and polypropylene are preferred.

[0055] The acid-modified polyolefin may be a cyclic polyolefin. For example, a carboxylic acid-modified cyclic polyolefin is a polymer obtained by copolymerizing a cyclic polyolefin by substituting an α,β-unsaturated carboxylic acid or an anhydride thereof for some of the monomers constituting the cyclic polyolefin, or by block polymerizing or graft polymerizing an α,β-unsaturated carboxylic acid or an anhydride thereof with a cyclic polyolefin.

[0056] The acid-modified cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, preferred are cyclic alkenes, and more preferred are norbornene. Styrene is also an example of a constituting monomer.

[0057] Examples of carboxylic acids or anhydrides thereof used for acid modification include maleic acid, acrylic acid, itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride. When the first and second polyolefin layers 12a and 12b are analyzed by infrared spectroscopy, a peak derived from maleic anhydride is preferably detected. For example, when maleic anhydride-modified polyolefin is measured by infrared spectroscopy, a peak derived from maleic anhydride is detected at a wave number of 1760 cm. -1 Near and wave number 1780cm -1 A peak derived from maleic anhydride is detected around . When the first and second polyolefin layers 12a, 12b are layers composed of maleic anhydride-modified polyolefin, a peak derived from maleic anhydride is detected when measured by infrared spectroscopy. However, if the degree of acid modification is low, the peak becomes small and may not be detected. In such cases, analysis can be performed by nuclear magnetic resonance spectroscopy.

[0058] When either the first or second polyolefin layer 12a, 12b is formed from a polyolefin, examples of the polyolefin include the same polyolefins as those exemplified above as the acid-modified polyolefins or acid-modified cyclic polyolefins.

[0059] The first and second polyolefin layers 12a and 12b may each be formed of a single resin component or a blend polymer of two or more resin components.Furthermore, the first and second polyolefin layers 12a and 12b may each be formed of a single layer or two or more layers of the same or different resin components.

[0060] Furthermore, the first and second polyolefin layers 12a and 12b may each contain a filler, if necessary. When the first and second polyolefin layers 12a and 12b contain a filler, the filler functions as a spacer, making it possible to effectively prevent short circuits between the metal terminal 2 and the barrier layer 33 of the electrical storage device packaging material 3. The particle size of the filler is approximately 0.1 to 35 μm, preferably approximately 5.0 to 30 μm, and more preferably approximately 10 to 25 μm. The content of the filler is approximately 5 to 30 parts by mass, more preferably approximately 10 to 20 parts by mass, per 100 parts by mass of the resin component forming the first and second polyolefin layers 12a and 12b.

[0061] The filler may be either inorganic or organic. Examples of inorganic fillers include carbon (carbon, graphite), silica, aluminum oxide, barium titanate, iron oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, titanium oxide, calcium aluminate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, and calcium carbonate. Examples of organic fillers include fluororesins, phenolic resins, urea resins, epoxy resins, acrylic resins, benzoguanamine-formaldehyde condensates, melamine-formaldehyde condensates, cross-linked polymethyl methacrylates, and cross-linked polyethylenes. From the standpoints of shape stability, rigidity, and content resistance, aluminum oxide, silica, fluororesins, acrylic resins, and benzoguanamine-formaldehyde condensates are preferred, with spherical aluminum oxide and silica being particularly preferred. The filler can be mixed into the resin components forming the first and second polyolefin layers 12a, 12b by melt-blending the two components in advance using a Banbury mixer or the like to form a masterbatch and then mixing the masterbatch in a predetermined ratio, or by directly mixing the filler with the resin components.

[0062] The first and second polyolefin layers 12a and 12b may each contain a pigment, if necessary. Various inorganic pigments can be used as the pigment. A specific example of the pigment is carbon (carbon, graphite), which is one of the fillers listed above. Carbon (carbon, graphite) is a material commonly used inside electricity storage devices and is unlikely to leach into the electrolyte. Furthermore, the pigment has a significant coloring effect, and a sufficient coloring effect can be obtained with an amount that does not impair adhesion. Furthermore, the pigment does not melt due to heat, and the apparent melt viscosity of the added resin can be increased. Furthermore, the pigment prevents the pressurized portion from becoming thin during thermal adhesion (heat sealing), thereby providing excellent sealing between the electricity storage device exterior material and the metal terminal.

[0063] When a pigment is added to the first and second polyolefin layers 12a, 12b, the amount of the pigment added is, for example, about 0.05 to 0.3 parts by mass, preferably about 0.1 to 0.2 parts by mass, per 100 parts by mass of the resin components forming the first and second polyolefin layers 12a, 12b when carbon black with a particle size of approximately 0.03 μm is used. Adding a pigment to the first and second polyolefin layers 12a, 12b makes it possible to detect the presence or absence of the adhesive film for metal terminal 1 using a sensor or to visually inspect the film. When a filler and a pigment are added to the first and second polyolefin layers 12a, 12b, the filler and pigment may be added to the same first and second polyolefin layers 12a, 12b. However, to avoid impairing the thermal adhesiveness of the adhesive film for metal terminal 1, it is preferable to add the filler and pigment separately to the first and second polyolefin layers 12a, 12b.

[0064] The first and second polyolefin layers 12a, 12b can each be composed of a polyolefin film or an acid-modified polyolefin film. When the first and second polyolefin layers 12a, 12b are composed of a polyolefin film or an acid-modified polyolefin film, the adhesive film for a metal terminal can be suitably produced by laminating a resin film formed from the polyolefin or acid-modified polyolefin onto the substrate 11 using, for example, a dry lamination method. Alternatively, the adhesive film for a metal terminal can be suitably produced by extruding the resin constituting the first and second polyolefin layers 12a, 12b onto the substrate 11.

[0065] The melt mass flow rate (MFR) at 230°C of the first and second polyolefin layers 12a, 12b is preferably about 5 g / 10 min or more, more preferably about 7 g / 10 min or more, and even more preferably about 8 g / 10 min or more, from the viewpoint of improving conformability to the shape of the metal terminal while satisfying the above-mentioned properties, and is preferably about 11 g / 10 min or less, more preferably about 10 g / 10 min or less, and preferred ranges include about 5 to 11 g / 10 min, about 5 to 10 g / 10 min, about 7 to 11 g / 10 min, about 7 to 10 g / 10 min, about 8 to 11 g / 10 min, and about 8 to 10 g / 10 min. The melt mass flow rates (MFR) of the first and second polyolefin layers 12a, 12b are values ​​(g / 10 min) measured at 230°C in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011). When at least one of the first and second polyolefin layers 12a, 12b is an acid-modified polyolefin layer, it is particularly preferable that the MFR value of the acid-modified polyolefin layer satisfies the above value.

[0066] Furthermore, from the viewpoint of improving conformability to the shape of the metal terminal while satisfying the above-mentioned properties, the melting points of the first and second polyolefin layers 12a, 12b are preferably about 120° C. or higher, more preferably about 130° C. or higher, and are preferably about 160° C. or lower, more preferably about 150° C. or lower, with preferred ranges being about 120 to 160° C., about 120 to 150° C., about 130 to 160° C., or about 130 to 150° C. The melting points of the first and second polyolefin layers 12a, 12b are measured by the method described in the Examples.

[0067] When the first and second polyolefin layers 12a, 12b made of resin films are laminated on the surface of the substrate 11, the surfaces of the first and second polyolefin layers 12a, 12b facing the substrate 11 may be subjected to a known adhesion-facilitating treatment such as corona discharge treatment, ozone treatment, plasma treatment, etc. In particular, corona discharge treatment enhances the adhesion between the substrate 11 and the first polyolefin layer 12a and second polyolefin layer 12b, thereby providing excellent sealing between the exterior material for an electricity storage device and the metal terminal.

[0068] The thickness of the first and second polyolefin layers 12a, 12b is preferably about 10 μm or more, more preferably about 15 μm or more, and is preferably about 50 μm or less, more preferably about 45 μm or less, and even more preferably 30 μm or less, from the viewpoint of exhibiting higher adhesive strength to a metal terminal when multiple heating and pressure applications are performed before bonding to the metal terminal. Preferred thickness ranges for the first and second polyolefin layers 12a, 12b include about 10 to 50 μm, about 10 to 45 μm, about 10 to 30 μm, about 15 to 50 μm, about 15 to 45 μm, and about 10 to 30 μm, respectively, with 10 to 30 μm being particularly preferred.

[0069] The ratio of the thickness of the substrate 11 to the total thickness of the first and second polyolefin layers 12a, 12b is preferably about 0.7 or more, more preferably about 1.0 or more, and is preferably about 4.0 or less, more preferably about 2.0 or less, from the viewpoint of exhibiting high adhesive strength to a metal terminal when subjected to multiple heating and pressure cycles before bonding to the metal terminal while satisfying the above-described characteristics. Preferred ranges include about 0.7 to 4.0, about 0.7 to 2.0, about 1.0 to 4.0, and about 1.0 to 2.0, with about 1.0 to 4.0 being particularly preferred. In particular, when at least one of the first and second polyolefin layers 12a, 12b is an acid-modified polypropylene layer, if the thickness ratio of the acid-modified polypropylene layer in the adhesive film for metal terminal 1 satisfies these values, deterioration of the water vapor barrier property is suppressed. Suppressing deterioration of the water vapor barrier property is expected to extend the life and long-term stability of the electricity storage device. From this viewpoint, the ratio is preferably within the above upper limit.

[0070] Furthermore, the ratio of the total thickness of the adhesive film for metal terminal 1 to 100% and the total thickness of the first and second polyolefin layers 12a, 12b is preferably about 15 to 60%, more preferably about 20 to 40%.

[0071] [Adhesion promoter layer 13] The adhesion promoter layer 13 is a layer that is provided as needed for the purpose of firmly adhering the substrate 11 to the first and second polyolefin layers 12a, 12b (see FIG. 7). The adhesion promoter layer 13 may be provided on only one side between the substrate 11 and the first and second polyolefin layers 12a, 12b, or on both sides.

[0072] The adhesion promoter layer 13 can be formed using known adhesion promoters such as isocyanate-based, polyethyleneimine-based, polyester-based, polyurethane-based, and polybutadiene-based. From the viewpoint of further improving electrolyte resistance, it is preferable to form the layer using an isocyanate-based adhesion promoter. Among the isocyanate-based adhesion promoters, those containing an isocyanate component selected from triisocyanate monomer and polymeric MDI provide excellent laminate strength and show little decrease in laminate strength after immersion in an electrolyte. It is particularly preferable to form the adhesive layer using an adhesion promoter made from triphenylmethane-4,4',4"-triisocyanate, a triisocyanate monomer, or polymethylene polyphenyl polyisocyanate, a polymeric MDI (NCO content of approximately 30%, viscosity of 200 to 700 mPa·s). It is also preferable to form the adhesive layer using tris(p-isocyanatephenyl)thiophosphate, a triisocyanate monomer, or a two-component curing adhesion promoter that uses a polyethyleneimine-based compound as the main component and polycarbodiimide as the crosslinking agent.

[0073] The adhesion promoter layer 13 can be formed by coating and drying using a known coating method such as bar coating, roll coating, or gravure coating. The amount of the adhesion promoter to be applied is 20 to 100 mg / m when the adhesion promoter is made of triisocyanate. 2 Approximately, preferably 40 to 60 mg / m 2 In the case of adhesion promoters made of polymeric MDI, the concentration is 40 to 150 mg / m 2 Approximately, preferably 60 to 100 mg / m 2 In the case of a two-component curing adhesion promoter that uses polyethyleneimine as the main component and polycarbodiimide as the crosslinking agent, the adhesive strength is about 5 to 50 mg / m 2 about 10 to 30 mg / m 2 Triisocyanate monomer is a monomer with three isocyanate groups in one molecule, and polymeric MDI is a mixture of MDI and MDI oligomers formed by polymerizing MDI, and is represented by the following formula:

[0074] [ka]

[0075] The adhesive film 1 for metal terminals of the present disclosure can be produced, for example, by laminating first and second polyolefin layers 12a, 12b, respectively, on both surfaces of a substrate 11. The substrate 11 and the first and second polyolefin layers 12a, 12b can be laminated by known methods such as extrusion lamination or thermal lamination. When the substrate 11 and the first and second polyolefin layers 12a, 12b are laminated via an adhesion promoter layer 13, for example, the adhesion promoter that constitutes the adhesion promoter layer 13 can be applied to the substrate 11 by the above-mentioned method and dried, and the first and second polyolefin layers 12a, 12b can be laminated on top of the adhesion promoter layer 13.

[0076] The method for interposing the adhesive film 1 for a metal terminal between the metal terminal 2 and the exterior packaging material 3 for an electricity storage device is not particularly limited, and for example, as shown in Figures 1 to 3, the adhesive film 1 for a metal terminal may be wrapped around the metal terminal 2 in the portion where the metal terminal 2 is sandwiched by the exterior packaging material 3 for an electricity storage device. Furthermore, although not shown, in the portion where the metal terminal 2 is sandwiched by the exterior packaging material 3 for an electricity storage device, the adhesive film 1 for a metal terminal may be arranged on both sides of the metal terminal 2 so as to cross the two metal terminals 2.

[0077] [Metal terminal 2] The adhesive film 1 for metal terminals of the present disclosure is used by being interposed between a metal terminal 2 and an exterior material 3 for an electricity storage device. The metal terminal 2 (tab) is a conductive member electrically connected to an electrode (positive electrode or negative electrode) of an electricity storage device element 4, and is made of a metal material. The metal material constituting the metal terminal 2 is not particularly limited, and examples thereof include aluminum, nickel, copper, etc. For example, the metal terminal 2 connected to the positive electrode of a lithium ion electricity storage device is usually made of aluminum, etc. Furthermore, the metal terminal 2 connected to the negative electrode of a lithium ion electricity storage device is usually made of copper, nickel, etc.

[0078] To enhance electrolyte resistance, the surface of the metal terminal 2 is preferably subjected to a chemical conversion treatment. For example, when the metal terminal 2 is made of aluminum, specific examples of the chemical conversion treatment include known methods for forming a corrosion-resistant film using phosphates, chromates, fluorides, triazine thiol compounds, etc. Among the methods for forming a corrosion-resistant film, a preferred method is a phosphate chromate treatment using a compound consisting of three components: a phenolic resin, a chromium (III) fluoride compound, and phosphoric acid.

[0079] The size of the metal terminal 2 may be set appropriately depending on the size of the electricity storage device to be used. The thickness of the metal terminal 2 is preferably about 50 to 1000 μm, more preferably about 70 to 800 μm. The length of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm. The width of the metal terminal 2 is preferably about 1 to 200 mm, more preferably about 3 to 150 mm.

[0080] [Exterior materials for energy storage devices 3] The electrical storage device packaging material 3 may have a laminated structure including at least a substrate layer 31, a barrier layer 33, and a heat-sealable resin layer 35, in this order. FIG. 8 shows an example of the cross-sectional structure of the electrical storage device packaging material 3, in which the substrate layer 31, an optional adhesive layer 32, a barrier layer 33, an optional adhesive layer 34, and a heat-sealable resin layer 35 are laminated in this order. In the electrical storage device packaging material 3, the substrate layer 31 is the outer layer, and the heat-sealable resin layer 35 is the innermost layer. During assembly of the electrical storage device, the electrical storage device elements 4 are sealed by bringing the heat-sealable resin layers 35 located on the peripheries of the electrical storage device elements 4 into contact with each other and heat-sealing them, thereby sealing the electrical storage device elements 4. While FIGS. 1 to 3 illustrate an electrical storage device 10 using an embossed type electrical storage device packaging material 3 formed by embossing or the like, the electrical storage device packaging material 3 may be an unformed pouch type. The pouch type includes three-sided seal, four-sided seal, pillow type, etc., and any type may be used.

[0081] The thickness of the laminate constituting the electricity storage device packaging material 3 is not particularly limited, but from the viewpoints of cost reduction, improving energy density, and the like, the upper limit is preferably about 180 μm or less, about 160 μm or less, about 155 μm or less, about 140 μm or less, about 130 μm or less, or about 120 μm or less, and from the viewpoint of maintaining the function of the electricity storage device packaging material 3 to protect the electricity storage device elements 4, the lower limit is preferably about 35 μm or more, about 45 μm or more, about 60 μm or more, or about 80 μm or more, and preferred ranges are, for example, about 35 to 180 μm, 35 to 1 Examples include about 60 μm, about 35 to 155 μm, about 35 to 140 μm, about 35 to 130 μm, about 35 to 120 μm, about 45 to 180 μm, about 45 to 160 μm, about 45 to 155 μm, about 45 to 140 μm, about 45 to 130 μm, about 45 to 120 μm, about 60 to 180 μm, about 60 to 160 μm, about 60 to 155 μm, about 60 to 140 μm, about 60 to 130 μm, about 60 to 120 μm, about 80 to 180 μm, about 80 to 160 μm, about 80 to 155 μm, about 80 to 140 μm, about 80 to 130 μm, and about 80 to 120 μm.

[0082] (Base material layer 31) In the packaging material 3 for an electricity storage device, the base material layer 31 is a layer that functions as the base material of the packaging material for an electricity storage device, and is a layer that forms the outermost layer side.

[0083] The material for forming the base layer 31 is not particularly limited, as long as it has insulating properties. Examples of materials for forming the base layer 31 include polyester, polyamide, epoxy, acrylic, fluororesin, polyurethane, silicone resin, phenol, polyetherimide, polyimide, and mixtures or copolymers thereof. Polyesters such as polyethylene terephthalate and polybutylene terephthalate have the advantage of being highly resistant to electrolyte and being less susceptible to whitening due to adhesion of electrolyte, and are therefore preferably used as materials for forming the base layer 31. Furthermore, polyamide film has excellent stretchability and can prevent whitening due to resin cracking of the base layer 31 during molding, and is therefore preferably used as materials for forming the base layer 31.

[0084] The base layer 31 may be formed of a uniaxially or biaxially stretched resin film, or may be formed of an unstretched resin film. Among them, a uniaxially or biaxially stretched resin film, especially a biaxially stretched resin film, is preferably used as the base layer 31 because its heat resistance is improved by oriented crystallization.

[0085] Among these, the resin film forming the base layer 31 is preferably nylon or polyester, and more preferably biaxially oriented nylon or biaxially oriented polyester.

[0086] The base material layer 31 may be formed by laminating resin films made of different materials to improve pinhole resistance and insulation when used as a package for an electricity storage device. Specific examples include a multilayer structure in which a polyester film and a nylon film are laminated together, or a multilayer structure in which a biaxially oriented polyester film and a biaxially oriented nylon film are laminated together. When the base material layer 31 has a multilayer structure, the resin films may be bonded together via an adhesive, or may be laminated together directly without an adhesive. When bonding without an adhesive, examples of methods that bond the films in a hot-melt state include co-extrusion, sand lamination, and thermal lamination.

[0087] The base layer 31 may be made low-friction to improve formability. When making the base layer 31 low-friction, the coefficient of friction of the surface is not particularly limited, but may be, for example, 1.0 or less. To make the base layer 31 low-friction, for example, matte treatment, formation of a thin film layer of a slip agent, or a combination thereof may be used.

[0088] The thickness of the base layer 31 is, for example, about 10 to 50 μm, and preferably about 15 to 30 μm.

[0089] (Adhesive layer 32) In the packaging material 3 for an electricity storage device, the adhesive layer 32 is a layer that is disposed on the base material layer 31 as necessary in order to impart adhesion to the base material layer 31. In other words, the adhesive layer 32 is provided between the base material layer 31 and the barrier layer 33.

[0090] The adhesive layer 32 is formed of an adhesive capable of bonding the base material layer 31 and the barrier layer 33. The adhesive used to form the adhesive layer 32 may be a two-component curing adhesive or a one-component curing adhesive. The bonding mechanism of the adhesive used to form the adhesive layer 32 is not particularly limited, and may be any of a chemical reaction type, a solvent volatilization type, a hot melt type, a hot pressure type, or the like.

[0091] The resin component of the adhesive that can be used to form the adhesive layer 32 is preferably a polyurethane-based two-component curing adhesive; polyamide, polyester, or a blend resin of these with modified polyolefin, from the viewpoint of having excellent ductility, durability under high humidity conditions, yellowing prevention, and thermal degradation prevention during heat sealing, and effectively suppressing a decrease in the laminate strength between the base layer 31 and the barrier layer 33 and preventing delamination.

[0092] Furthermore, the adhesive layer 32 may be multi-layered with different adhesive components. When the adhesive layer 32 is multi-layered with different adhesive components, it is preferable to select a resin that has excellent adhesion to the base material layer 31 as the adhesive component disposed on the base material layer 31 side, and an adhesive component that has excellent adhesion to the barrier layer 33 as the adhesive component disposed on the barrier layer 33 side, from the viewpoint of improving the laminate strength between the base material layer 31 and the barrier layer 33. When the adhesive layer 32 is multi-layered with different adhesive components, specifically, preferred examples of the adhesive component disposed on the barrier layer 33 side include acid-modified polyolefin, metal-modified polyolefin, a mixed resin of polyester and acid-modified polyolefin, and a resin containing copolymer polyester.

[0093] The thickness of the adhesive layer 32 is, for example, about 2 to 50 μm, and preferably about 3 to 25 μm.

[0094] (Barrier layer 33) In the electrical storage device packaging material, the barrier layer 33 is a layer that not only improves the strength of the electrical storage device packaging material but also has the function of preventing water vapor, oxygen, light, and the like from penetrating into the electrical storage device. The barrier layer 33 is preferably a metal layer, i.e., a layer formed of a metal. Specific examples of metals constituting the barrier layer 33 include aluminum, stainless steel, and titanium, and aluminum is preferred. The barrier layer 33 can be formed, for example, from a metal foil, a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film provided with any of these vapor deposition films. It is preferably formed from a metal foil, and more preferably from an aluminum foil. From the viewpoint of preventing the occurrence of wrinkles or pinholes in the barrier layer 33 during the production of the packaging material for an electricity storage device, it is more preferable that the barrier layer be formed from a soft aluminum 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).

[0095] The thickness of the barrier layer 33 is preferably about 10 to 200 μm, and more preferably about 20 to 100 μm, from the viewpoint of making the packaging material for an electricity storage device thinner and making it less likely to produce pinholes during molding.

[0096] Furthermore, it is preferable that at least one surface, and preferably both surfaces, of the barrier layer 33 be chemically treated to stabilize adhesion, prevent dissolution and corrosion, etc. Here, chemical treatment refers to a treatment for forming a corrosion-resistant film on the surface of the barrier layer.

[0097] (adhesive layer 34) In the packaging material 3 for an electricity storage device, the adhesive layer 34 is a layer that is provided as needed between the barrier layer 33 and the heat-sealable resin layer 35 in order to firmly bond the heat-sealable resin layer 35.

[0098] The adhesive layer 34 is formed of an adhesive capable of bonding the barrier layer 33 and the heat-sealable resin layer 35. The composition of the adhesive used to form the adhesive layer is not particularly limited, and examples thereof include a resin composition containing an acid-modified polyolefin. Examples of acid-modified polyolefins include the same as those exemplified for the first and second polyolefin layers 12a and 12b.

[0099] The thickness of the adhesive layer 34 is, for example, about 1 to 40 μm, and preferably about 2 to 30 μm.

[0100] (Thermal adhesive resin layer 35) In the packaging material 3 for an electricity storage device, the heat-sealable resin layer 35 corresponds to the innermost layer, and is a layer that seals the electricity storage device elements by heat-sealing the heat-sealable resin layers together when assembling the electricity storage device.

[0101] The resin component used in the heat-fusible resin layer 35 is not particularly limited as long as it is heat-fusible, and examples thereof include polyolefins and cyclic polyolefins.

[0102] Specific examples of the polyolefin include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; crystalline or amorphous 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 preferred.

[0103] The cyclic polyolefin is a copolymer of an olefin and a cyclic monomer, and examples of the olefin constituting the cyclic polyolefin include ethylene, propylene, 4-methyl-1-pentene, butadiene, and isoprene. Examples of the cyclic monomer constituting the cyclic polyolefin include cyclic alkenes such as norbornene; specifically, cyclic dienes such as cyclopentadiene, dicyclopentadiene, cyclohexadiene, and norbornadiene. Among these polyolefins, cyclic alkenes are preferred, and norbornene is more preferred. Styrene is also an example of a constituting monomer.

[0104] Among these resin components, preferred are crystalline or amorphous polyolefins, cyclic polyolefins, and blend polymers thereof; more preferred are polyethylene, polypropylene, copolymers of ethylene and norbornene, and blend polymers of two or more of these.

[0105] The heat-fusible resin layer 35 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 heat-fusible resin layer 35 may be formed of only one layer, or may be formed of two or more layers of the same or different resin components.

[0106] The thickness of the heat-fusible resin layer 35 is not particularly limited, but may be about 2 to 2000 μm, preferably about 5 to 1000 μm, and more preferably about 10 to 500 μm.

[0107] 2. Energy storage device 10 An electricity storage device 10 of the present disclosure comprises at least an electricity storage device element 4 having a positive electrode, a negative electrode, and an electrolyte, an exterior material for an electricity storage device 3 that seals the electricity storage device element 4, and metal terminals 2 that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude to the outside of the exterior material for an electricity storage device 3. The electricity storage device 10 of the present disclosure is characterized in that an adhesive film for a metal terminal 1 of the present disclosure is interposed between the metal terminal 2 and the exterior material for an electricity storage device 3. In other words, the electricity storage device 10 of the present disclosure can be produced by a method that includes a step of interposing an adhesive film for a metal terminal 1 of the present disclosure between the metal terminal 2 and the exterior material for an electricity storage device 3.

[0108] Specifically, an electricity storage device element 4 including at least a positive electrode, a negative electrode, and an electrolyte is placed in an electrical storage device packaging material 3, with metal terminals 2 connected to the positive and negative electrodes protruding outward, and the adhesive film 1 for metal terminals of the present disclosure is interposed between the metal terminals 2 and the heat-sealable resin layer 35, and the electrical storage device element 4 is covered around its periphery so as to form a flange portion of the electrical storage device packaging material (a region where the heat-sealable resin layers 35 come into contact with each other, i.e., the peripheral portion 3a of the electrical storage device packaging material), and the heat-sealable resin layers 35 of the flange portion are heat-sealed to provide an electrical storage device 10 using the electrical storage device packaging material 3. When the electrical storage device element 4 is housed using the electrical storage device packaging material 3, the electrical storage device packaging material 3 is used so that the heat-sealable resin layer 35 of the electrical storage device packaging material 3 faces inside (the surface in contact with the electrical storage device element 4).

[0109] The exterior material for an electricity storage device according to the present disclosure can be suitably used in electricity storage devices such as batteries (including condensers, capacitors, etc.). The exterior material for an electricity storage device according to the present disclosure may be used in either primary or secondary batteries, but is preferably used in secondary batteries. The type of secondary battery to which the exterior material for an electricity storage device according to the present disclosure is applied is not particularly limited, and examples include lithium ion batteries, lithium ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, condensers, and capacitors. Among these secondary batteries, lithium ion batteries and lithium ion polymer batteries are suitable applications for the exterior material for an electricity storage device according to the present disclosure. [Example]

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

[0111] Examples 1-16 and Comparative Examples 1-6 <Production of adhesive film for metal terminals> Polypropylene layers having the melting points and MFRs shown in Table 1 and the thicknesses shown in Table 2 were used as the substrates (hereinafter sometimes referred to as "PP layers"). Maleic anhydride-modified polypropylene (hereinafter sometimes referred to as "PPa") having the melting points and melt mass flow rates (MFRs) shown in Table 1 were used as the first polyolefin layer (PPa layer) and the second polyolefin layer (PPa layer). For Examples 1 to 12 and Comparative Example 3, a T-die extruder was used to extrude two types of polypropylene and maleic anhydride-modified polypropylene into three layers, thereby obtaining adhesive films for metal terminals in which a PPa layer / PP layer / PPa layer were laminated in that order. For Examples 13 to 16 and Comparative Examples 4 to 6, an inflation method was used to obtain adhesive films for metal terminals in which a PPa layer / PP layer / PPa layer were laminated in that order. Furthermore, for Comparative Examples 1 and 2, maleic anhydride-modified polypropylene (PPa) was extruded onto each side of a substrate (PP layer) made of polypropylene film (PP) using a T-die extruder, to obtain an adhesive film for metal terminals in which a PPa layer / PP layer / PPa layer was laminated in this order. The thicknesses of each layer of the PPa layer / PP layer / PPa layer are as shown in Table 2.

[0112] The physical properties of the adhesive film for metal terminals listed in Table 2, such as the tensile modulus, lower yield stress, water vapor barrier property, and thickness change rate, were adjusted by adjusting the melting point, MFR, thickness, and thickness ratio of the PPa layer and PP layer, as well as the conditions of the T-die and inflation in the production of adhesive film for metal terminals 1 (for example, the extrusion width from the T-die, the stretching ratio, the stretching speed, the heat treatment temperature, etc.).

[0113] <Melt point measurement> The melting points of the PP layer and PPa layer listed in Table 1 were measured using the following method. The melting peak temperature was measured twice using a differential scanning calorimeter (DSC, a Q200 differential scanning calorimeter manufactured by TA Instruments). Specifically, the PP layer or PPa layer was held at -20°C for 10 minutes and then heated from -20°C to 250°C at a heating rate of 10°C / min by DSC according to the procedure of JIS K7121:2012 (Method for measuring transition temperatures of plastics (JIS K7121:1987, Supplement 1)). The first melting peak temperature P (°C) was measured and then held at 250°C for 10 minutes. The temperature was then lowered from 250°C to -20°C at a cooling rate of 10°C / min and held for 10 minutes. Furthermore, the temperature was raised from -20°C to 250°C at a rate of 10°C / min, and the second melting peak temperature Q (°C) was measured. The flow rate of nitrogen gas was 50 ml / min. Using the above procedure, the first melting peak temperature P (°C) and the second melting peak temperature Q (°C) were determined, and the temperature with the highest peak was taken as the melting point.

[0114] <Melt Mass Flow Rate (MFR)> The melt mass flow rates (MFR) of the PP layer and PPa layer listed in Table 1 are values ​​(g / 10 min) at 230°C measured in accordance with the provisions of JIS K7210-1:2014 (ISO 1133-1:2011).

[0115] [Table 1]

[0116] <Tensile modulus B before heating and pressing> In accordance with the provisions of JIS K7161-1 (ISO527-1), the tensile modulus B of the adhesive film for metal terminals (before heating and pressurizing in the "Tensile modulus A after heating and pressurizing" section described below) was measured in a 25°C environment. Specifically, each adhesive film for metal terminals obtained in the Examples and Comparative Examples was cut into a strip with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, for the adhesive film for metal terminals, a stress-strain curve was obtained for the test piece using a Tensilon universal material testing machine (RTG-1210 manufactured by A&D Co., Ltd.) at a tensile speed of 300 mm / min and a chuck distance of 30 mm in a 25°C environment. The tensile modulus B of the adhesive film for metal terminals before heating and pressurizing was calculated from the slope of the line connecting the two points at 0.05% and 0.25% strain. The results are shown in Table 2.

[0117] <Tensile modulus A after heating and pressing> The tensile modulus after heating and pressing for 12 seconds at a temperature of 180°C and a surface pressure of 0.0067 MPa was measured using the following procedure. First, each adhesive film for metal terminals obtained in the Examples and Comparative Examples was cut into a strip with a width (TD) of 15 mm and a length (MD) of 50 mm. Next, the adhesive film for metal terminals was sandwiched between two tetrafluoroethylene-ethylene copolymer films (ETFE films, 100 μm thick) and placed on a hot plate heated to 180°C. A 500 g weight with a sponge was placed on top. The film was left to stand for 12 seconds, and then immediately left to stand for 1 hour at atmospheric pressure and 25°C to obtain a test piece. Next, a stress-strain curve was obtained for the test piece using a Tensilon universal testing machine (RTG-1210 manufactured by A&D Corporation) at atmospheric pressure and 25°C, with a tensile speed of 300 mm / min and a chuck distance of 30 mm. The tensile modulus A of the adhesive film for metal terminals after heating and pressurization was calculated from the slope of the line connecting the two points of 0.05% and 0.25% strain. The results are shown in Table 2.

[0118] <Lower yield stress after heating and pressing> The stress at the lower yield point L (see the schematic diagram in Figure 9) (lower yield point stress) was calculated from the stress-strain curve obtained by conducting a tensile test at a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm, in accordance with the JIS K7127 standard. The results are shown in Table 2.

[0119] <Water vapor barrier properties (moisture content)> First, an exterior packaging material for an electricity storage device (hereinafter, sometimes simply referred to as "exterior packaging material") was prepared by the following procedure. An aluminum alloy foil (35 μm thick) was laminated onto a substrate layer (25 μm thick) made of nylon film by dry lamination. Specifically, a two-component urethane adhesive (a polyol compound and an aromatic isocyanate compound) was applied to one side of a barrier layer made of aluminum alloy foil to form an adhesive layer (3 μm thick) on the aluminum alloy foil. Next, the adhesive layer on the aluminum alloy foil and the substrate layer were laminated, and then aging treatment was performed to prepare a substrate layer / adhesive layer / barrier layer laminate. Next, an adhesive layer (20 μm thick, placed on the metal layer side) made of maleic anhydride-modified polypropylene resin and a heat-sealable resin layer (15 μm thick, innermost layer) made of random polypropylene resin were co-extruded onto the barrier layer of the laminate, thereby laminating the adhesive layer / heat-sealable resin layer on the barrier layer. Next, the obtained laminate was heated at 190°C for 2 minutes to obtain an exterior packaging material for an electricity storage device in which a base layer, an adhesive layer, a barrier layer, an adhesive layer, and a heat-sealable resin layer were laminated in this order.

[0120] Next, as shown in the schematic diagram of FIG. 11, the resulting packaging material 3 was cut into a square measuring 120 mm in length (MD) and 120 mm in width (TD) (FIG. 11a). Each adhesive film 1 for metal terminals (hereinafter sometimes simply referred to as "adhesive film") obtained in the Examples and Comparative Examples was cut into a rectangle measuring 120 mm in length (MD) and 10 mm in width (TD). The packaging material 10 was folded in half lengthwise with the heat-sealable resin layer facing inward, and two adhesive films for metal terminals were placed between the folded film and the folded film so that their length and width directions coincided, resulting in a laminate in which packaging material / adhesive film / adhesive film / packaging material were laminated in this order (FIG. 11b). The adhesive films were placed between the packaging materials 10 along the long sides to be heat-sealed (described below). Next, a heat seal bar (stainless steel plate) was used to heat-seal the layers of the laminate at the long and short sides of the laminate, creating a bag-like structure with one short side not heat-sealed. The heat sealing conditions for the long sides were as follows: a 10 mm-wide heat seal bar was used at 190°C, a pressure of 1.0 MPa, and a duration of 3 seconds, once (see s1 in Figure 11c). For the short sides, a 7 mm-wide heat seal bar was used at 190°C, a pressure of 2.0 MPa, and a duration of 3 seconds. Then, a 7 mm-wide heat seal bar was used at a position 3 mm inward from the short side, and a 190°C, a pressure of 2.0 MPa, and a duration of 3 seconds. That is, for short side 2, two heat seals were performed, each 3 mm apart, to achieve a width of 10 mm (see s2 in Figure 11c). Next, the heat-sealed portion on the long side was cut off along the long side so that the width was 3 mm, and the cut was allowed to dry in a dry room for one day (see Figure 11d). Next, approximately 3.0 g of a liquid (0% moisture content) consisting of ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1 was poured into the non-heat-sealed short side (Figure 11e). The non-heat-sealed short side was then heat-sealed in the same manner as the previous short side to form a sealed bag (Figure 11f). This sealed bag was then left to stand for 30 days in an environment at 60°C and 90% relative humidity. The moisture content of the liquid removed from the sealed bag was then measured by the Karl Fischer method in a dry room. The results are shown in Table 2.

[0121] <Thickness change rate> In the above-mentioned <Tensile modulus A after heating and pressing>, the thickness change rate was calculated for each adhesive film for metal terminal before and after heating and pressing for 12 seconds under conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa using the formula (thickness of adhesive film for metal terminal after heating and pressing) / (thickness of adhesive film for metal terminal before heating and pressing) × 100. The thickness change rate is the average value measured at three points in the MD direction of the adhesive film for metal terminal. The results are shown in Table 2.

[0122] <Measurement of adhesion strength between adhesive film for metal terminals and metal terminals> Aluminum (JIS H4160:1994 A8079H-O) measuring 50 mm in length, 22.5 mm in width, and 0.2 mm in thickness was prepared as the metal terminal. Each adhesive film for metal terminal obtained in the Examples and Comparative Examples was cut to a length of 45 mm and a width of 15 mm. The adhesive film for metal terminal was then placed on the metal terminal to obtain a metal terminal / adhesive film laminate. The metal terminal was laminated so that the longitudinal and lateral directions of the metal terminal coincided with the length and width directions of the adhesive film for metal terminal, respectively, and so that the centers of the metal terminal and the adhesive film for metal terminal were aligned. Next, a tetrafluoroethylene-ethylene copolymer film (ETFE film, thickness 100 μm) was placed on the adhesive film for metal terminal of the laminate (the surface of the adhesive film for metal terminal was covered with the ETFE film), and in this state, the laminate was placed on a hot plate heated to 180°C (with the metal terminal facing the hot plate), and a 500 g weight with a sponge was placed on top and left to stand for 12 seconds, whereby the adhesive film was heat-sealed to the metal terminal (surface pressure 0.0067 MPa, contact area 300 mm 2After heat fusion, the laminate was allowed to cool naturally to 25°C. Next, in a 25°C environment, the adhesive film for metal terminals was peeled from the metal terminal using a Tensilon universal material testing machine (RTG-1210, manufactured by A&D Corporation). The maximum strength at the time of peeling was taken as the adhesion strength to the metal terminal (N / 15 mm). The peel speed was 175 mm / min, the peel angle was 180°, and the chuck distance was 30 mm. The average value was taken as the average of three measurements. The treatment of leaving the laminate in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.016 MPa for 12 seconds simulates the heat and pressure applied in the temporary and main bonding processes described above. The results are shown in Table 2.

[0123] <Bending test> Each adhesive film for metal terminals obtained in the Examples and Comparative Examples was cut to a size of 100 mm in length (MD) and 15 mm in width (TD). A mandrel tester (metal rod with a diameter of 2 mm) was used to wrap the adhesive film. The MD of the adhesive film for metal terminals was perpendicular to the metal rod of the mandrel tester. A bending test was performed in this state, and the adhesive film for metal terminals was visually observed and evaluated according to the following criteria. The results are shown in Table 2. A: The adhesive film for metal terminals does not whiten in the wrapped area and returns to its original shape after wrapping. B: There is no whitening in the area where the adhesive film for metal terminals is wrapped, but it does not return to its original shape after wrapping and curls. C: Whitening of the area where the adhesive film for metal terminals is wrapped

[0124] <Conformity evaluation 1 (adhesive film / metal terminal)> A 200 μm thick aluminum foil (JIS H4160:1994 A8079H-O) was prepared as a metal terminal. Each adhesive film for metal terminal obtained in the Examples and Comparative Examples was also prepared. Next, the metal terminal was sandwiched between two adhesive films to obtain an adhesive film / metal terminal / adhesive film laminate. Next, the laminate sandwiched between two tetrafluoroethylene-ethylene copolymer films (ETFE films, 100 μm thick) was placed on a hot plate heated to 180°C, and a 500 g weight with a sponge was placed on top. The laminate was left standing for 12 seconds to thermally fuse the adhesive film to the metal terminal (surface pressure 0.0067 MPa, contact area 300 mm). 2 ) In this process, as shown in the schematic diagram of Figure 10, the metal terminal was sandwiched between the adhesive films, so that the metal terminal was surrounded by the adhesive film and a portion was formed where the two adhesive films were heat-sealed together. The heat-sealed laminate was allowed to cool naturally to 25°C, and the cross section in the thickness direction was observed with a laser microscope to evaluate the conformability of the adhesive film for metal terminals to the shape of the metal terminal according to the following criteria. The results are shown in Table 2. A: There are no air bubbles between the adhesive film for metal terminals and the metal terminals. B: There are no bubbles at the interface between the adhesive film for metal terminals and the metal terminal, but there are bubbles in the adhesive film for metal terminals near the interface. C: There are bubbles at the interface between the adhesive film for metal terminals and the metal terminals, and there are also bubbles in the adhesive film for metal terminals near the interface.

[0125] <Follow-up evaluation 2 (adhesive film / exterior material)> First, an adhesive film / metal terminal / adhesive film laminate was prepared using the same procedure as in the conformability evaluation 1. Next, the resulting laminate was sandwiched between two exterior materials and sealed using a heat seal tester at 180°C, a surface pressure of 1.0 MPa, and for 3 seconds to obtain a laminate in which the exterior material and the adhesive film were heat-sealed. The resulting laminate was allowed to cool to 25°C, and the cross section in the thickness direction was observed with a laser microscope. The conformability of the adhesive film for metal terminals to the shape of the exterior material for the power storage device was evaluated according to the following criteria. The results are shown in Table 2. A: There is no gap between the adhesive film for metal terminals and the exterior material for the energy storage device. B: There is a minute gap (diameter 10 μm or less) between the adhesive film for metal terminals and the exterior material for the power storage device. C: There is a gap (diameter greater than 10 μm) between the adhesive film for metal terminals and the exterior material for the energy storage device.

[0126] <Impact energy absorption> The impact absorption energy was calculated from the area enclosed by the stress-strain curve obtained in the above <Tensile modulus A after heating and pressurizing>. The results are shown in Table 2.

[0127] [Table 2]

[0128] In Table 2, the notation "-" means not measured.

[0129] The adhesive films for metal terminals of Examples 1 to 16 are adhesive films for metal terminals that are interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, and have a tensile modulus A of 490 MPa or more. As is clear from the results shown in Table 2, the adhesive films for metal terminals of Examples 1 to 16 having this configuration exhibit high adhesive strength to the metal terminal when heated and pressed multiple times before being adhered to the metal terminal.

[0130] In particular, the adhesive films for metal terminals of Examples 1 and 2 had sufficient adhesion strength of 45 N / 15 mm or more, and also had excellent flexibility (bending test), thickness change rate, and impact absorption energy.These adhesive films for metal terminals had good adhesion, flexibility, thickness change rate, and impact absorption energy, and were excellent in terms of overall balance of properties. That is, in the adhesive film for metal terminals of the present disclosure, the tensile modulus A is approximately 500 to 550 MPa, the tensile modulus B is 420 to 480 MPa, the difference between the tensile moduli A and B is 40 to 75 MPa, the total thickness of the adhesive film for metal terminals is 145 to 155 μm, the thickness of the substrate is 90 to 120 μm, the thicknesses of the first polyolefin layer and the second polyolefin layer are each 10 to 30 μm, and the ratio of the thickness of the substrate to the total thickness of the first and second polyolefin layers is 1.0 to 4.0, thereby resulting in an adhesive film for metal terminals with good adhesion, flexibility, rate of change in thickness, and impact absorption energy, and an excellent balance of overall properties.

[0131] Example 17 <Production of adhesive film for metal terminals> An unstretched polypropylene layer (hereinafter sometimes referred to as "CPP layer") having the melting point and MFR listed in Table 3 and the thickness listed in Table 4 was used as the substrate. Furthermore, polypropylene (PP) was used as the first polyolefin layer (PP layer), and maleic anhydride-modified polypropylene (PPa) was used as the second polyolefin layer (PPa layer), each having the melting point and melt mass flow rate (MFR) listed in Table 3. Polypropylene (PP) and maleic anhydride-modified polypropylene (PPa) were extruded on each side of the substrate made of unstretched polypropylene film (CPP layer) using a T-die extruder, to obtain an adhesive film for metal terminals in which the PP layer, CPP layer, and PPa layer were laminated in this order. The thicknesses of the PP layer, CPP layer, and PPa layer are as shown in Table 4.

[0132] The physical properties of the adhesive film for metal terminals listed in Table 4, such as the tensile modulus, lower yield stress, water vapor barrier property, and thickness change rate, were adjusted, as in Examples 1 to 16, by adjusting the melting point, MFR, thickness, and thickness ratio of the PP layer, PPa layer, and CPP layer, as well as the T-die conditions in the production of adhesive film for metal terminal 1 (e.g., extrusion width from the T-die, stretching ratio, stretching speed, heat treatment temperature, etc.).

[0133] For the adhesive film for metal terminal of Example 17, the tensile modulus, yield stress after heating and pressing, impact absorption energy, water vapor barrier property, thickness change rate, bending test, and conformability evaluations 1 and 2 were each performed in the same manner as in Examples 1 to 16. The results are shown in Table 4.

[0134] [Table 3]

[0135] [Table 4]

[0136] The adhesive film for metal terminal of Example 17, like Examples 1 to 16, is an adhesive film for metal terminal interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, and has a tensile modulus A of 490 MPa or more. As is clear from the results shown in Table 4, the adhesive film for metal terminal of Example 17 having this configuration exhibits high adhesive strength to the metal terminal when heated and pressed multiple times before being adhered to the metal terminal.

[0137] As described above, the present disclosure provides the following aspects of the invention. Item 1. An adhesive film for metal terminals that is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that encapsulates the electricity storage device element, The adhesive film for metal terminals has a tensile modulus A of 490 MPa or more when measured in an environment at 25°C after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C. Item 2. The adhesive film for a metal terminal according to Item 1, wherein the adhesive film for a metal terminal has a tensile modulus B of 700 MPa or less when measured in an environment at a temperature of 25°C before being exposed to the heat and pressure environment. Item 3. An adhesive film for metal terminal according to Item 2, wherein the difference in tensile modulus calculated by subtracting the value of the tensile modulus B from the value of the tensile modulus A is 5 MPa or more. Item 4. The adhesive film for a metal terminal according to any one of Items 1 to 3, wherein the tensile modulus A of the adhesive film for a metal terminal is 680 MPa or less. Item 5. The adhesive film for metal terminal according to any one of Items 1 to 4, wherein the adhesive film for metal terminal has a lower yield stress of 17.0 MPa or more, as determined from a graph showing the relationship between stress (MPa) and strain (mm) obtained by a tensile test conducted in accordance with JIS K7127 at a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. Item 6. The adhesive film for metal terminal according to any one of Items 1 to 5, wherein the rate of change in thickness calculated by the following formula before and after heating and pressing for 12 seconds under conditions of a temperature of 180°C and a surface pressure of 0.0067 MPa is 90% or more and 100% or less. Thickness change rate = (thickness of adhesive film for metal terminals after heating and pressing / thickness of adhesive film for metal terminals before heating and pressing) x 100 Item 7. The adhesive film for a metal terminal according to any one of Items 1 to 6, wherein the adhesive film for a metal terminal has a thickness of 140 μm or more. Item 8. The adhesive film for metal terminal according to any one of Items 1 to 7, wherein the adhesive film for metal terminal is composed of a laminate having a first polyolefin layer, a substrate, and a second polyolefin layer in this order. Item 9. The adhesive film for metal terminals according to Item 8, wherein the ratio of the thickness of the substrate to the total thickness of the first polyolefin layer and the second polyolefin layer is 0.7 or more and 4.0 or less. Item 10. The adhesive film for metal terminal according to Item 8 or 9, wherein the thickness of the substrate is 50 μm or more and 150 μm or less. Item 11. The adhesive film for a metal terminal according to any one of Items 8 to 10, wherein the thickness of the first polyolefin layer and the second polyolefin layer is 10 μm or more and 50 μm or less. Item 12. The adhesive film for metal terminal according to any one of Items 8 to 11, wherein the melt mass flow rate at 230°C of at least one of the first polyolefin layer and the second polyolefin layer is 7.2 g / 10 min or more and 9.8 g / 10 min or less. Item 13. The adhesive film for metal terminal according to any one of Items 8 to 12, wherein the melt mass flow rate of the substrate at 230°C is 1.8 g / 10 min or more and 5.0 g / 10 min or less. Item 14. The adhesive film for metal terminal according to any one of Items 8 to 13, wherein the resin contained in the substrate contains a polyolefin skeleton. Item 15. The adhesive film for a metal terminal according to any one of Items 8 to 14, wherein the first polyolefin layer and the second polyolefin layer contain an acid-modified polyolefin. Item 16. The packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, Item 16. The adhesive film for a metal terminal according to any one of items 1 to 15, wherein the adhesive film for a metal terminal is interposed between the heat-sealable resin layer and the metal terminal. Item 17. A metal terminal with an adhesive film for a metal terminal, comprising the adhesive film for a metal terminal according to any one of items 1 to 16 attached to a metal terminal. Item 18. An electricity storage device including at least the electricity storage device element including a positive electrode, a negative electrode, and an electrolyte, the electricity storage device casing material that seals the electricity storage device element, and the metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and that protrude outside the electricity storage device casing material, Item 17. An electricity storage device, wherein the adhesive film for a metal terminal according to any one of items 1 to 16 is interposed between the metal terminal and the exterior material for an electricity storage device. Item 19. A method for manufacturing a battery including at least the electricity storage device element including a positive electrode, a negative electrode, and an electrolyte, the electricity storage device casing material that seals the electricity storage device element, and the metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and that protrude outside the electricity storage device casing material, Item 17. A method for producing an electricity storage device, comprising a step of interposing the adhesive film for metal terminal according to any one of items 1 to 16 between the metal terminal and the exterior material for an electricity storage device, and sealing the electricity storage device element with the exterior material for an electricity storage device. [Explanation of symbols]

[0138] 1. Adhesive film for metal terminals 2 metal terminals 3. Exterior materials for energy storage devices 3a Peripheral part of the exterior material for the electricity storage device 4. Energy storage device elements 10. Energy storage devices 11 Base material 12a First polyolefin layer 12b Second polyolefin layer 13 Adhesion promoter layer 31 Base material layer 32 Adhesive layer 33 Barrier Layer 34 Adhesive layer 35 Heat-fusible resin layer

Claims

1. An adhesive film for metal terminals, which is interposed between a metal terminal electrically connected to an electrode of an electricity storage device element and an exterior material for an electricity storage device that seals the electricity storage device element, The adhesive film for a metal terminal is composed of a laminate including at least a first polyolefin layer, a substrate, and a second polyolefin layer in this order, and the melting point of the substrate is 130°C or more and 190°C or less. The adhesive film for a metal terminal has a tensile modulus A of 490 MPa or more measured in an environment at a temperature of 25°C after being left to stand for 12 seconds in a heated and pressurized environment at a temperature of 180°C and a surface pressure of 0.0067 MPa, and then further left to stand for 1 hour in an environment at a temperature of 25°C; The adhesive film for metal terminals has a lower yield stress of 17.0 MPa or more, as determined from a graph showing the relationship between stress (MPa) and strain (mm) obtained by conducting a tensile test in accordance with the provisions of JIS K7127 under conditions of a temperature of 25°C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm.

2. The adhesive film for metal terminals according to claim 1, wherein the adhesive film for metal terminals has a tensile modulus B of 700 MPa or less when measured in an environment at a temperature of 25°C before being exposed to the heat and pressure environment.

3. 3. An adhesive film for metal terminal according to claim 2, wherein the difference in tensile modulus calculated by subtracting the value of the tensile modulus B from the value of the tensile modulus A is 5 MPa or more.

4. The adhesive film for a metal terminal according to any one of claims 1 to 3, wherein the tensile modulus A of the adhesive film for a metal terminal is 680 MPa or less.

5. The adhesive film for metal terminals is a method according to the provisions of JIS K7127, and is subjected to a tensile test under conditions of a temperature of 25 ° C, a tensile speed of 175 mm / min, and a chuck distance of 30 mm. The adhesive film for metal terminals according to any one of claims 1 to 4, wherein the lower yield stress obtained from a graph showing the relationship between stress (MPa) and strain (mm) is 18.0 MPa or more.

6. The thickness change rate calculated by the following formula before and after heating and pressing for 12 seconds under conditions of a temperature of 180 ° C. and a surface pressure of 0.0067 MPa is 90% or more and 100% or less. The adhesive film for metal terminals according to any one of claims 1 to 5. Thickness change rate = (thickness of adhesive film for metal terminal after heating and pressing / thickness of adhesive film for metal terminal before heating and pressing) x 100

7. The adhesive film for metal terminal according to any one of claims 1 to 6, wherein the thickness of the adhesive film for metal terminal is 140 µm or more.

8. The adhesive film for metal terminals according to any one of claims 1 to 7, wherein the adhesive film for metal terminals is composed of a laminate having a first polyolefin layer, a substrate, and a second polyolefin layer in this order.

9. 9. The adhesive film for metal terminal according to claim 8, wherein the ratio of the thickness of the substrate to the total thickness of the first polyolefin layer and the second polyolefin layer is 0.7 or more and 4.0 or less.

10. 10. The adhesive film for metal terminal according to claim 8, wherein the thickness of the substrate is 50 μm or more and 150 μm or less.

11. The adhesive film for metal terminals according to any one of claims 8 to 10, wherein the thickness of the first polyolefin layer and the second polyolefin layer is 10 µm or more and 50 µm or less.

12. The melt mass flow rate at 230 ° C. of at least one of the first polyolefin layer and the second polyolefin layer is 7.2 g / 10 min or more and 9.8 g / 10 min or less. The adhesive film for metal terminals according to any one of claims 8 to 11.

13. The adhesive film for metal terminals according to any one of claims 8 to 12, wherein the melt mass flow rate of the substrate at 230 ° C. is 1.8 g / 10 min or more and 5.0 g / 10 min or less.

14. The adhesive film for metal terminals according to any one of claims 8 to 13, wherein the resin contained in the substrate includes a polyolefin skeleton.

15. The adhesive film for metal terminals according to any one of claims 8 to 14, wherein the first polyolefin layer and the second polyolefin layer contain acid-modified polyolefin.

16. the packaging material for an electricity storage device is composed of a laminate including at least a base layer, a barrier layer, and a heat-sealable resin layer in this order, The adhesive film for metal terminals according to any one of claims 1 to 15, wherein the adhesive film for metal terminals is interposed between the heat-sealable resin layer and the metal terminal.

17. A metal terminal with an adhesive film for a metal terminal, comprising the adhesive film for a metal terminal according to any one of claims 1 to 16 attached to a metal terminal.

18. an electricity storage device including at least an electricity storage device element including a positive electrode, a negative electrode, and an electrolyte; an exterior material for an electricity storage device that seals the electricity storage device element; and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, An electricity storage device, comprising the adhesive film for metal terminals according to any one of claims 1 to 16 interposed between the metal terminals and the exterior material for electricity storage devices.

19. a method for manufacturing a battery including at least an electricity storage device element including a positive electrode, a negative electrode, and an electrolyte; an exterior material for an electricity storage device that seals the electricity storage device element; and metal terminals that are electrically connected to the positive electrode and the negative electrode, respectively, and protrude outside the exterior material for an electricity storage device, A method for manufacturing an electricity storage device, comprising a step of interposing the adhesive film for metal terminals according to any one of claims 1 to 16 between the metal terminals and the exterior material for electricity storage devices, and sealing the electricity storage device elements with the exterior material for electricity storage devices.

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