Laminate exterior material

Abstract

Provided is a laminate exterior material 1 in which a base layer 12 is bonded to one surface of a metal foil layer 10 with an adhesive layer 11, and a heat-fusible resin layer 14 is bonded to the other surface, wherein a stress σ at 150% elongation of an adhesive cured product constituting the adhesive layer 11 is 30 MPa-50 MPa, and a thickness T1 of the adhesive layer 11 is 1.5 μm-5.0 μm.

Description

Laminate exterior materials

[0001] The present invention relates to a laminate exterior material used as a packaging material for, for example, notebook computers, mobile phones, in-vehicle batteries, stationary secondary batteries (lithium ion secondary batteries), all-solid-state batteries, and capacitors.

[0002] A commonly used packaging material of this type is a laminate exterior material in which a base layer such as a polyamide film is laminated to one side of a metal foil layer and a heat-sealable resin layer is laminated to the other side as a sealant layer.

[0003] In the laminate exterior material, the metal foil layer and the base material layer, and the metal foil layer and the sealant layer are bonded together with an adhesive. The adhesive undergoes volumetric shrinkage upon curing, but by making the adhesive layer thinner, it is possible to suppress the occurrence of wrinkles, curls, and the like in the laminate exterior material. Furthermore, making the adhesive layer thinner is expected to have the effects of reducing costs and shortening the curing time.

[0004] Regarding the physical properties of the adhesive layer, Patent Document 1 proposes improving the formability of the laminate exterior material by providing the adhesive layer with a good balance of the contradictory physical properties of flexibility and rigidity.

[0005] Patent No. 6698275

[0006] When thinning the adhesive layer, there is a problem in that if the adhesive layer between the base material layer and the metal foil layer that forms the outer surface of the case is made thinner, delamination becomes more likely to occur due to moisture caused by changes in the environment or deformation caused by external stress.

[0007] On the other hand, Patent Document 1 is a technology that aims to improve formability by varying the hardness and flexibility of the adhesive layer, rather than by thinning the adhesive layer, and therefore does not achieve the effects of reducing costs or shortening curing time by thinning the adhesive layer.

[0008] In view of the above-mentioned background art, the present invention provides a laminate exterior material that can suppress delamination caused by thinning of the adhesive layer and thereby enjoy the benefits of thinning.

[0009] That is, the present invention has the configurations described in the following [1] to [6].

[0010] [1] A laminate exterior material in which a base material layer is bonded to one surface of a metal foil layer via an adhesive layer, and a heat-fusible resin layer is bonded to the other surface, wherein the stress σ of a cured adhesive material constituting the adhesive layer at 150% elongation is 30 MPa to 50 MPa, and the thickness of the adhesive layer is 1.5 μm to 5.0 μm.

[0011] [2] The laminate exterior material according to the preceding paragraph 1, wherein the cured adhesive has a tensile modulus of 200 MPa to 500 MPa at an elongation of 2% to 4%.

[0012] [3] The laminate exterior material according to the preceding paragraph 1 or 2, wherein the tensile breaking stress of the cured adhesive is 40 MPa or more.

[0013] [4] The laminate exterior material according to any one of items 1 to 3, wherein the adhesive strength between the base material layer and the metal foil layer is 2 N / 15 mm to 30 N / 15 mm.

[0014] [5] The laminate exterior material according to any one of the preceding items 1 to 4, wherein at least the surface of the substrate layer facing the metal foil layer is formed of polyamide.

[0015] [6] The laminate exterior material according to any one of items 1 to 5, wherein the adhesive strength between the base material layer and the metal foil layer after immersion in 40°C warm water for 168 hours is 2N / 15 mm or more.

[0016] In the laminate exterior material described in [1] above, the stress σ of the cured adhesive constituting the adhesive layer joining the substrate layer and the metal foil layer at 150% elongation is 30 MPa to 50 MPa, so that even though the thickness is a thin layer of 1.5 μm to 5.0 μm, the rigidity of the adhesive layer is maintained against volume changes due to moisture or heat in the resin layer including the substrate layer and deformation of the laminate exterior material due to external stress, and the adhesive layer conforms to the substrate layer, thereby preventing delamination. Moreover, the thinning of the adhesive layer has the effect of reducing costs and shortening curing time.

[0017] In the laminate exterior material described in [2] above, the tensile modulus of the cured adhesive constituting the adhesive layer is 200 MPa to 500 MPa at 2% to 4% elongation, so that the stress on the metal foil layer and the stress on the base material layer are well balanced, and delamination is unlikely to occur regardless of the thickness of the adhesive layer.

[0018] In the laminate exterior material described in [3] above, the tensile breaking stress of the cured adhesive that constitutes the adhesive layer is 40 MPa or more, so when the laminate exterior material is molded into a three-dimensional case or when external stress is applied to the molded case, the adhesive layer is less likely to break under stress, regardless of the thickness of the adhesive layer.

[0019] The laminate exterior material described in [4] above has an adhesive strength between the base material layer and the metal foil layer of 2 N / 15 mm to 30 N / 15 mm, so that the two layers are less likely to come off, and delamination caused by the adhesive layer being too hard can be suppressed.

[0020] In the laminate exterior material described in [5] above, at least the surface of the base material layer facing the metal foil layer is formed of polyamide, and therefore has good conformability to the metal foil layer and good formability.

[0021] The laminate packaging material described in [6] above has a bonding strength between the base material layer and the metal foil layer of 2 N / 15 mm or more after immersion in hot water, and therefore has a high effect of suppressing delamination.

[0022] Fig. 4 is a cross-sectional view of one embodiment of the laminate exterior material of the present invention. Fig. 5 is an SS curve showing the relationship between stress and strain of a cured adhesive material. Fig. 6 is an SS curve of various cured adhesive materials. Fig. 7 is a cross-sectional view of a forming tool used in deep drawing of a laminate exterior material. Fig. 8 is a perspective view of a formed product produced using the deep drawing forming tool of Fig. 4.

[0023] One embodiment of the laminated exterior material according to the present invention is shown in Figure 1. This laminated exterior material is used, for example, as a material for an exterior body (case) for a lithium ion secondary battery.

[0024] In the laminate exterior material 1, a base material layer 12 is bonded to one surface of a metal foil layer 10 via a first adhesive layer 11, and a heat-sealable resin layer 14 is bonded to the other surface of the metal foil layer 10 via a second adhesive 13, and these are laminated together. When the laminate exterior material 1 is used as a battery case, the base material layer 12 becomes the outer surface of the case, and the heat-sealable resin layer 14 becomes the inner surface of the case.

[0025] The first adhesive layer 11 is an adhesive layer defined by the present invention, and the cured adhesive constituting the adhesive layer has the following physical properties and is limited in thickness to achieve a thin adhesive layer. The cured adhesive is an adhesive in a state in which the adhesive is made fluid by adding a solvent or the like to the adhesive, is applied to the metal foil layer 10 and / or the base material layer 12, the metal foil layer 10 and the base material layer 14 are superimposed, and the adhesive is cured under conditions appropriate for the adhesive, i.e., when the production of the laminate exterior material 1 is completed.

[0026] FIG. 2 is an example of an S-S curve (stress-strain curve) showing the relationship between stress σ (MPa) and strain (elongation) ε (%) of a cured adhesive. The cured adhesive must have a stress σ of 30 MPa to 50 MPa at 150% elongation. In FIG. 2, the S-S curve a indicates that the stress at 150% elongation of the cured adhesive falls within the range of 30 MPa to 50 MPa. By maintaining the stress σ at 150% elongation within this range, the rigidity of the first adhesive layer 11 can be maintained and the adhesive layer 12 can follow the deformation of the laminate exterior material 1 due to external stress or volumetric changes caused by moisture or heat in the resin layer containing the substrate layer 12, thereby preventing delamination of the substrate layer 12. If the stress σ is less than 30 MPa (S-S curve b in FIG. 2), it becomes difficult to maintain the rigidity of the first adhesive layer 11, and the effect of suppressing delamination is reduced. On the other hand, if the stress σ exceeds 50 MPa (SS curve c in FIG. 2), the material becomes too hard and its ability to conform to the base material layer 12 decreases, reducing the effect of suppressing delamination. A particularly preferable range of the stress σ at 150% elongation is 33 MPa to 45 MPa.

[0027] The thickness T1 of the first adhesive layer 11 must be 1.5 μm to 5.0 μm. By reducing the thickness T1 of the first adhesive layer 11, the formability of the laminate exterior material 1 can be improved, costs can be reduced, and the curing time of the adhesive can be shortened in the manufacturing process of the laminate exterior material 1. If the thickness T1 exceeds 5.0 μm, these effects of thinning the laminate exterior material 1 are reduced. As the thickness T1 becomes thinner, costs can be reduced and the curing time can be shortened, but if the thickness T1 is less than 1.5 μm, the adhesive strength will be low. The preferred thickness T1 of the first adhesive layer 11 is 2.5 μm to 4.5 μm, and from the viewpoints of formability and cost reduction, a thickness of 3.5 μm or less is particularly preferred.

[0028] As described above, the laminate 1 can prevent delamination without losing the advantage of thinning the first adhesive layer 11 .

[0029] The cured adhesive material constituting the first adhesive layer 11 preferably further has the following physical properties. (Tensile Modulus) The tensile modulus at 2% to 4% elongation, obtained from the S-S curve of the cured adhesive material, is preferably 200 MPa to 500 MPa. The tensile modulus is the slope of the S-S curve at 2% to 4% elongation. When the tensile modulus is within the above range, the balance between the stress on the metal foil layer 10 and the stress on the base material layer 12 of the first adhesive layer 11 is good, making delamination less likely to occur regardless of the thickness T1 of the first adhesive layer 11. A particularly preferred tensile modulus is 230 MPa to 450 MPa. (Tensile Stress at Break) The tensile stress at break (stress at the break point of the S-S curve) of the cured adhesive material is preferably 40 MPa or more. If the tensile stress at break is 40 MPa or more, the first adhesive layer 11 is less likely to be broken by stress, regardless of the thickness T1 of the first adhesive layer 11, when the laminate exterior material 1 is molded into a three-dimensional case or when external stress is applied to the molded case. A particularly preferred tensile stress at break is 42 MPa or more. (Adhesion Strength) The adhesive strength of the first adhesive layer 11 between the base material layer 12 and the metal foil layer 10 is preferably 2 N / 15 mm to 30 N / 15 mm. When the adhesive strength is in the above range, the two layers are less likely to come apart, and delamination caused by the first adhesive layer 11 being too hard can be suppressed. A preferred adhesive strength is 4 N / 15 mm to 20 N / 15 mm.

[0030] The adhesive constituting the first adhesive layer 11 is not limited in composition as long as it has the above-described physical properties. For example, polyurethane-based adhesives, epoxy-based adhesives, olefin-based adhesives, and acrylic-based adhesives can be used. The curing type of the adhesive is also not limited, and examples include two-component curing adhesives, energy ray-curing adhesives such as ultraviolet-curing adhesives and electron beam-curing adhesives (adhesives containing photoradical polymerization initiators, adhesives containing photocationic polymerization initiators), and thermosetting adhesives. (Adhesive Strength After Immersion in Warm Water) The laminate exterior material 1 constituting the battery case is in contact with moisture contained in the air. In the laminate exterior material 1, contact with moisture is one of the causes of delamination. Therefore, the delamination suppression effect of the first adhesive layer 11 can be evaluated based on the adhesive strength after an accelerated deterioration treatment in which the laminate material 1 is immersed in warm water, in addition to the evaluation of the adhesive strength described above. The present invention recommends a laminate exterior material 1 in which the adhesive strength between the base material layer 12 and the metal foil 10 after immersion in 40°C hot water for 168 hours is 2 N / 15 mm or more, and evaluates the laminate exterior material 1 as having a high delamination suppression effect. A particularly preferred adhesive strength after immersion in hot water is 2 N / 15 mm to 15 N / 15 mm. The adhesive strength is measured after immersing the laminate exterior material 1 in 40°C hot water for 168 hours and then immediately after removing it from the hot water.

[0031] The adhesive strength in this section refers to the adhesive strength of a laminated exterior material that has been subjected to accelerated deterioration treatment by immersion in hot water, while the adhesive strength in the previous section refers to the adhesive strength of a laminated exterior material that has not been subjected to accelerated deterioration treatment. (Substrate Layer) The substrate layer 12 is a layer located on the outer surface when the laminated exterior material 1 is used as a case, and is made of a heat-resistant resin that does not melt at the heat-sealing temperature during heat-sealing. The heat-resistant resin preferably has a melting point 10°C or more higher than the melting point of the heat-sealing resin that constitutes the heat-sealing resin layer 14, which is the sealant layer, and is particularly preferably a heat-resistant resin with a melting point 20°C or more higher than the melting point of the heat-sealing resin. Examples of the heat-resistant resin include polyamide film, polyester film, and polyolefin film, and stretched films of these are preferably used. Examples of the polyamide film include biaxially oriented polyamide 6 film (PA6) film and biaxially oriented polyamide 66 (PA66) film. Examples of the polyester film include biaxially oriented polyethylene terephthalate (PET) film, biaxially oriented polyethylene naphthalate (PEN) film, biaxially oriented polybutylene terephthalate (PBT) film, and polyethylene furanoate (PEF) film. Examples of the polyolefin film include biaxially oriented polypropylene (OPP) film. Among the above-mentioned films, polyamide film is preferred because of its good conformability to the metal foil layer 10 and good formability.

[0032] The base layer 12 can be either a single-layer film or a multi-layer film. However, in the case of a multi-layer film, it is preferable that the surface on the metal foil layer 10 side, i.e., the surface bonded to the first adhesive layer 11, is formed of polyamide, which has good conformability to the metal foil layer 10. An example of a multi-layer film is a multi-layer film of a PET film and a polyamide film. The multi-layer film can be produced by co-extrusion, dry lamination, or the like.

[0033] Furthermore, it is preferable that the film constituting the base layer 12 does not exhibit a yield point in the S-S curve. For films that exhibit a yield point, the stress difference between the upper yield point and the lower yield point is preferably less than 2 MPa. A base layer 12 having such physical properties is less likely to undergo sudden deformation due to external stress, and therefore less likely to cause delamination.

[0034] The preferred thickness of the substrate layer 12 is 10 μm to 50 μm, and even more preferably 10 μm to 30 μm. (Materials of Other Layers) In the laminate exterior material of the present invention, preferred materials for constituting layers other than the first adhesive layer and the substrate layer are as follows.

[0035] The metal foil layer 10 serves to impart gas barrier properties to the laminate exterior material 1, preventing the intrusion of oxygen and moisture. The metal foil layer 10 is not particularly limited, but examples include aluminum foil, copper foil, stainless steel foil, nickel foil, and titanium foil, with aluminum foil being commonly used. The thickness of the metal foil layer 10 is preferably 10 μm to 100 μm. A thickness of 20 μm or more can prevent the occurrence of pinholes during rolling when manufacturing the metal foil, while a thickness of 100 μm or less can reduce stress during stretch forming and drawing, improving formability. A particularly preferred thickness is 15 μm to 50 μm.

[0036] The metal foil layer 10 is preferably subjected to a chemical conversion treatment at least on the surface of the metal foil on the side of the heat-fusible resin layer 14 (the surface on the side of the second adhesive layer 13). By subjecting this surface to a chemical conversion treatment, corrosion of the metal foil surface by contents (battery electrolyte, food, medicine, etc.) can be sufficiently prevented. For example, a chemical conversion coating is formed by subjecting the metal foil to the following chromate treatment. In a chromate treatment method, for example, a chemical conversion treatment is performed by applying to the surface of a degreased metal foil one of the following solutions: 1) an aqueous solution of a mixture containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides; 2) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium (III) salts; or 3) an aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium (III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and non-metal salts of fluorides.

[0037] Other chemical conversion treatments include titanate treatment and zirconium treatment.

[0038] The heat-sealable resin layer 14 is a layer located on the inner surface when used as a case, and provides the laminated exterior material 1 with excellent chemical resistance, even against highly corrosive electrolytes used in lithium-ion secondary batteries, etc., and also plays a role in imparting heat-sealing properties to the laminated exterior material 1.

[0039] Although not particularly limited, the heat-sealable resin layer 14 is preferably an unstretched thermoplastic resin film layer. Although not particularly limited, the unstretched thermoplastic resin film layer is preferably composed of an unstretched film made of at least one thermoplastic resin selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers, in terms of chemical resistance and heat sealability.

[0040] The thickness of the heat-sealable resin layer 14 is preferably set to 20 μm to 100 μm. By setting the thickness to 20 μm or more, the occurrence of pinholes can be sufficiently prevented, and by setting the thickness to 100 μm or less, the amount of resin used can be reduced, thereby reducing costs. In particular, it is particularly preferable that the thickness of the heat-sealable resin layer 14 be set to 25 μm to 45 μm. The heat-sealable resin layer 14 may be a single layer or a multi-layer. An example of a multi-layer heat-sealable resin layer 14 is a three-layer film in which random polypropylene films are laminated on both sides of a block polypropylene film.

[0041] The second adhesive layer 13 is not particularly limited, but examples thereof include adhesive layers formed from polyurethane adhesives, acrylic adhesives, epoxy adhesives, polyolefin adhesives, elastomer adhesives, fluorine adhesives, acid-modified polypropylene adhesives, etc. The second adhesive layer 13 preferably has a thickness of 1 μm to 5 μm, and particularly preferably has a thickness of 2 μm to 4 μm.

[0042] The heat-fusible resin layer 14 can also be directly bonded to the metal foil layer 10 by utilizing its adhesive strength. A laminate exterior material in which the heat-fusible resin layer 14 is bonded directly to the metal foil layer 10 without the second adhesive layer 13 interposed therebetween is also included in the technical scope of the present invention.

[0043] Next, specific examples of the present invention will be described. However, the present invention is not limited to these examples. [Preparation of laminate exterior materials] In Examples 1 to 9 and Comparative Examples 1 to 4, laminate exterior materials 1 having the laminate structure shown in FIG. 1 were prepared. The laminate exterior materials 1 of each example differ only in the first adhesive layer 11, and the other materials are common. The common materials are as follows:

[0044] The metal foil layer 10 was an aluminum foil made of JIS H4160 A8079-O with a thickness of 45 μm. A chemical conversion treatment solution consisting of polyacrylic acid, a trivalent chromium compound, water, and alcohol was applied to both sides of this aluminum foil, and the resulting solution was dried at 180° C. to form a chemical conversion coating. The chromium deposition amount of this chemical conversion coating was 10 mg / m per side.２ is.

[0045] The substrate layer 12 is a biaxially oriented polyamide film having a thickness of 15 μm.

[0046] The heat-sealable resin layer 14 is an unstretched polypropylene film having a thickness of 80 μm.

[0047] The second adhesive layer 13 is a two-component curing maleic acid-modified polypropylene adhesive consisting of a base agent and a curing agent. An adhesive solution was prepared by blending 100 parts by weight of maleic acid-modified polypropylene (melting point 80°C, acid value 10 mgKOH / g) as the base agent with 8 parts by weight of an isocyanurate of hexamethylene diisocyanate (NCO content: 20% by weight) as the curing agent, and then adding a solvent. (First Adhesive Layer) Six types of two-component curing adhesives, A to F, shown in Table 1, were prepared. Table 1 shows the base agent, curing agent, and their blending ratios for each adhesive.

[0048]

[0049] (Physical Properties of Cured Adhesive) A solvent was added to each of the two-component curing adhesives A to F to prepare adhesive solutions with a solid content of 40% by mass. The adhesive solution was applied to A4-sized release paper using a bar coater in an automatic coating machine and then dried. The adhesive-coated release paper was then held in a thermo-hygrostat in an atmosphere of 60°C x 40% RH for 5 days to cure the adhesive, producing 50 mm x 200 mm adhesive films A to F. The cured adhesive film was then removed from the release paper and cut into the shape of a JIS K7127 Type 2 test piece. The thickness of the center was measured using a Mitutoyo microgauge and found to be 30 μm.

[0050] For adhesive films A to F, stress σ (MPa) versus strain ε (%) was measured in accordance with JIS K7127 (1999) using a Shimadzu Corporation Strograph (AGS-5kNX) tensile tester under conditions of sample length 100 mm, sample width 15 mm, rating distance 50 mm, and tensile speed 200 mm / min, and the S-S curve (stress-strain curve) shown in Figure 3 was created. The stress σ at 150% elongation, tensile modulus at 2% to 4% elongation, and tensile stress at break σ obtained from Figure 3 are shown in Table 1. (Preparation of laminate exterior materials of Examples 1 to 9 and Comparative Examples 1 to 4) A substrate layer 12 and a heat-sealable resin layer 14 were bonded to both sides of the metal foil layer 10 by dry lamination.

[0051] First, an adhesive solution of adhesives A to E shown in Table 2 was applied to one surface of the metal foil layer 10 as the first adhesive layer 11, and the first adhesive layer 11 was formed by heating and drying, and then the base material layer 12 was laminated on top of it. At this time, the amount of adhesive solution applied was adjusted so that the thickness T1 of the first adhesive layer 11 in the finished laminate exterior material 1 would be the thickness shown in Table 2. Next, a two-component curing adhesive solution for the second adhesive layer 13 was applied to the other surface of the metal foil layer 10, and the second adhesive layer 13 was formed by heating and drying, and then the heat-fusible resin layer 14 was laminated on top of it. At this time, the solid content of the adhesive was 2 g / m ２ The amount of adhesive solution applied was adjusted so that

[0052] Next, the above laminate was sandwiched between a rubber nip roll and a laminating roll heated to 100°C, and dry-laminated by thermocompression bonding, and then wound up on a roll shaft. Then, in the wound state on the roll shaft, it was aged at 40°C for 10 days to obtain a laminate exterior material 1. [Physical properties (adhesion strength) of laminate exterior material] First, the adhesive strength (N / 15 mm) between the base material layer 12 and the metal foil layer 10 in each of the produced laminate exterior materials 1 was measured by the following method specified in JIS K 6854-3 (1999).

[0053] A test specimen measuring 15 mm wide and 150 mm long was cut out from the laminate exterior material 1. Neoliver S-546 (manufactured by Sansai Kako Co., Ltd.) was applied as a release agent to the entire area of ​​the test specimen extending 10 mm from the end of the short side, i.e., the surface of the base material layer 12, the surface of the heat-sealable resin layer 14, and the three cross sections. The specimen was left to stand at room temperature for 1 hour, and then the release agent was wiped off. The metal foil layer 10 and the base material layer 12 were peeled from the end of the short side where the release agent was applied, and the region 10 mm from the end was divided into a first portion including the metal foil layer 10 and the heat-sealable resin layer 14 and a second portion including the base material layer 12.

[0054] Then, using a Strograph (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd., a first portion of the test specimen was held with one of two chucks, and a second portion was held with the other chuck, and the strength was measured when a T-peel test was performed at a tensile speed of 100 mm / min. The measured values ​​are shown in Table 2.

[0055] Furthermore, each laminate exterior material was evaluated for formability (occurrence of cracks, etc., and delamination), warm water resistance, and adhesive strength after immersion in warm water using the following test methods. Furthermore, based on the evaluation of these items, the laminate exterior material was comprehensively judged as good or bad. The evaluation results are shown in Table 2. (Formability) The prepared laminate exterior material 1 was cut into a rectangle to prepare a molding material 1A. As shown in FIG. 4, a deep drawing tool 30 (manufactured by Amada Co., Ltd.) equipped with a die 31, a punch 32, and a blank holder 33 was used to perform deep drawing to form a rectangular parallelepiped shape measuring 55 mm in length, 35 mm in width, and a depth D. The deep drawing was performed in such a manner that the top surface of the punch 32 was in contact with the heat-fusible resin layer 14 of the molding material 1A, causing the base layer 12 to protrude outward. The forming depth D was changed from 4.0 mm to 9.0 mm in 0.5 mm increments to produce molded products 35 with 11 different depths D.

[0056] The resulting 11 molded articles 35 (see FIG. 5) were then examined for the occurrence of cracks and delamination.

[0057] The presence or absence of cracks and pinholes was observed at four corners 36 (only three are shown) of the molded product 35, and moldability was evaluated according to the following criteria: The presence or absence of cracks and pinholes was checked by visually observing the presence or absence of transmitted light passing through the cracks or pinholes in a dark room.

[0058] ○: No cracks or pinholes at 5.0 mm or more ×: Cracks or pinholes at 4.5 mm or less Delamination The appearance of the molded product 35 was visually observed, and formability was evaluated based on the molding depth D at which no delamination occurred. ⊚: 7.0 mm or more ◯: 5.0 mm to 6.5 mm ×: 4.5 mm or less (Warm Water Resistance) Five molded products 35 with a depth D of 5.0 mm were produced for each example using the deep drawing tool 30. These molded products 35 were immersed in warm water at 40°C for 168 hours. The appearance of the molded products 35 removed from the warm water was visually observed to check for any lifting or delamination, and evaluated according to the following criteria: ⊚: No delamination occurred in any of the five products. ◯: Delamination occurred in one product. ×: Delamination occurred in two or more products. (Adhesion strength after immersion in warm water) The process from cutting out the test specimen to branching the end of the test specimen into the first part and the second part was carried out in the same manner as the process in the above-mentioned "Physical properties (adhesion strength) of laminate exterior material".

[0059] Next, the test specimen with the branched end was immersed in warm water at 40°C for 168 hours, and then immediately removed from the warm water, the water was wiped off, and the base layer 12 was reinforced with Cellotape (registered trademark) (manufactured by Nichiban).

[0060] Then, in the same manner as in the measurement method in the above-mentioned "Physical properties (adhesive strength) of laminate exterior materials," a first portion of the test specimen was held with one chuck of a Strograph (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd., and a second portion was held with the other chuck, and the strength was measured when a T-peel was performed at a pulling rate of 100 mm / min.

[0061] That is, the method for measuring the adhesive strength after immersion in warm water is the same as the measurement method in the above-mentioned "Physical properties (adhesive strength) of laminate exterior materials" except that the test specimen was immersed in warm water and the base layer 12 was reinforced after immersion.

[0062] The measured bonding strength after immersion in hot water is shown in Table 2. <Overall evaluation> A sample with no "x" marks in the three evaluation items of formability (occurrence of cracks, etc.), formability (delamination), and hot water resistance was judged as ◯ (good), and a sample with an "x" mark was judged as x (poor).

[0063] Furthermore, all of the laminate exterior materials that were judged to be good (◯) in the above three items had an adhesive strength of 2 N / 15 mm or more after immersion in hot water, and there was no change in the overall evaluation based on the three items.

[0064]

[0065] From Table 2, it was confirmed that by specifying the stress at 150% elongation of the cured adhesive material constituting the first adhesive layer, it is possible to achieve a thinner adhesive layer while maintaining good moldability.

[0066] This application claims priority to Japanese Patent Application No. 2021-78490, filed on May 6, 2021, the disclosure of which constitutes part of this application in its entirety.

[0067] It should be understood that the terms and expressions used herein are used for the purpose of explanation and not for limiting interpretation, and do not exclude any equivalents of the features shown and described herein, but also allow various modifications within the claimed scope of the present invention.

[0068] The present invention can be used as a material for battery cases of lithium ion secondary batteries and the like.

[0069] REFERENCE SIGNS LIST 1... Laminate exterior material 10... Metal foil layer 11... First adhesive layer 12... Base material layer 13... Second adhesive layer 14... Heat-sealable resin layer

Claims

1. A laminate exterior material in which a base layer is bonded to one surface of a metal foil layer via an adhesive layer, and a heat-fusible resin layer is bonded to the other surface of the metal foil layer, A laminate exterior material, characterized in that the stress σ of the cured adhesive material constituting the adhesive layer at 150% elongation is 30 MPa to 50 MPa, and the thickness of the adhesive layer is 1.5 μm to 5.0 μm.

2. 2. The laminate exterior material according to claim 1, wherein the cured adhesive has a tensile modulus of elasticity of 200 MPa to 500 MPa when elongated by 2% to 4%.

3. 3. The laminate exterior material according to claim 1, wherein the cured product of the adhesive has a tensile breaking stress of 40 MPa or more.

4. 3. The laminate exterior material according to claim 1, wherein the adhesive strength between the base material layer and the metal foil layer is 2 N / 15 mm to 30 N / 15 mm.

5. 3. The laminate exterior material according to claim 1, wherein at least a surface of the base material layer facing the metal foil layer is made of polyamide.

6. 3. The laminate exterior material according to claim 1, wherein the adhesive strength between the base material layer and the metal foil layer after immersion in warm water at 40° C. for 168 hours is 2 N / 15 mm or more.