JP2014157727A - Laminate film for battery outer packaging and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate film for battery outer packaging which has high sealing strength and interlayer adhesive strength, is excellent in heat resistance, electrolyte resistance and adhesiveness with a tab sealing layer, has a small environmental load, and can be inexpensively manufactured.SOLUTION: A laminate film 10 for battery outer packaging is formed by laminating at least a base material layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a sealant layer 5 in this order. The sealant layer 5 is formed from a polyethylene resin containing a linear low density polyethylene (LLDPE) as a main component, and has a sealant main layer of which an MFR is 0.1 g/10 min or more and 3 g/10 min or less, a density is 0.918 g/cmor more and 0.950 g/cmor less, and a tensile modulus is 100 MPa or more and 1,500 MPa or less.

Description

  The present invention relates to a laminate film for battery exterior and a method for producing the same. More specifically, the present invention relates to a battery body having a liquid, gel polymer, or solid electrolyte in a battery such as a lithium battery (lithium primary or secondary battery), a lithium ion secondary battery, or a polymer battery. The present invention relates to a laminate film for battery exterior packaging and a method for producing the same. The present invention also relates to a battery using the laminate film for battery exterior.

  In recent years, lithium batteries, lithium ion secondary batteries, and the like have been developed as thin and small batteries used in mobile phones, personal computers, automobiles, and the like. Conventionally, a metal can type has been used as an exterior material of these batteries. However, in recent years, since the degree of freedom in design of the battery is high and the weight can be further reduced, the base material layer and the sealant layer are used. A polymer film is used for the barrier layer, a metal foil is used for the barrier layer, and a laminated film of the base material layer / barrier layer / sealant layer formed by laminating them together, and the sealant layers are heat sealed to form a bag or a case What has been processed to have been used.

Some battery exterior materials are called pouch type or embossed type depending on the packaging form of the battery body. The pouch type is a three-side seal, four-side seal, pillow type, or other bag-shaped type. On the other hand, the embossed type has a recess in one or both exterior materials, and the battery body is stored in this recess. There is a shape in which the buttocks are sealed by heat sealing.
The battery exterior laminate film constituting these battery exterior materials requires high sealing strength as a basic packaging member and strong puncture resistance against external stress, but for the following reasons: There is also a demand for excellent anti-electrolytic solution resistance, high sealing properties and interlayer adhesion in a high temperature environment.

That is, in a lithium battery, together with a positive electrode material and a negative electrode material as battery contents, a polar solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate as an electrolyte solution, and LiPF ₆ and LiBF ₄ as electrolytes. What mix | blended lithium salts, such as these, is used. Since these electrolyte solvents have high penetrability into the polymer film, the adhesive strength of the seal portion decreases due to penetration of the solvent of the electrolyte into the laminated film of the exterior material, and the adhesive strength between the layers. Decline is a problem.
Furthermore, in the battery, a hydrolytic reaction occurs between a slight amount of moisture contained in the electrode, active material, electrolyte, etc., moisture entering from the outside through the cross section of the seal layer, and lithium salt of the electrolyte. Produces. This hydrofluoric acid penetrates into the sealant layer of the laminated film of the exterior material and causes metal corrosion of the barrier layer, further promoting the decrease in the adhesion between the sealant layer and the barrier layer and the decrease in the adhesive strength of the seal part. Will be allowed to.
In addition, the lithium battery is assumed to have been left in a car in midsummer, and even when left in a high temperature environment at 60 to 80 ° C., it needs heat resistance to maintain the sealing strength and the adhesive strength between the layers. It becomes.

  For this reason, the laminated film as a battery outer packaging material is required to be much better than other packaging materials in terms of the sealability between sealant layers and the adhesive strength between layers. Is done.

Conventionally, in order to impart corrosion resistance to hydrofluoric acid generated from an electrolytic solution, it has been proposed to subject the aluminum foil used for the barrier layer to a surface treatment.
For example, Patent Document 1 discloses a laminate composed of a base material layer, an adhesive layer, a chemical conversion treatment layer, aluminum, a chemical conversion treatment layer, an acid-modified PP film layer, and an innermost layer, and the chemical conversion treatment is a phosphoric acid chromate treatment. A polymer battery packaging material characterized by the above has been proposed.
Patent Document 2 proposes a laminate using an aluminum foil subjected to chemical conversion treatment with a chemical conversion treatment liquid composed of three components of a phenol resin, a chromium fluoride (trivalent) compound, and phosphoric acid.
Patent Document 3 proposes a battery packaging material using an aluminum foil that has been subjected to a chemical conversion treatment with a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound and a phosphorus compound.
However, the chemical conversion treatment performed in Patent Documents 1 to 3 is also referred to as a coating-type chemical conversion treatment, and the treatment liquid has an influence on the human body, has a large environmental load, and environmental pollution such as soil contamination is often a problem. Therefore, it is not preferable to apply such a chemical conversion treatment to the aluminum foil of the barrier layer.

  The following are further proposed as laminated films for battery exterior materials.

In Patent Document 4, in a laminate comprising an outermost layer / barrier layer / sand resin layer / sealant layer, a boehmite-treated aluminum foil is used as a barrier layer, the sealant layer has a density of 0.925 g / cm ³ or more and a heat of fusion. A battery exterior material using a layer made of an ethylene-α-olefin copolymer having a peak top of 115 ° C. or higher has been proposed. In Patent Document 4, a sandwich lamination method is employed for molding a sand resin layer as an adhesive layer.

  Patent Document 5 includes an outer layer, an aluminum foil, an inner layer, and a laminate in which at least a chemical conversion treatment layer is provided on the inner layer side of the aluminum foil, and a resin layer that contacts the chemical conversion treatment layer surface is made of an acid-modified olefin resin. A laminated body characterized by laminating a single layer film of a chemical conversion treatment layer and an acid-modified olefin resin or a co-extruded film of an acid-modified olefin resin and one or more olefin resins by a thermal lamination method and a method for producing the same are proposed. Has been.

In Patent Documents 6 and 7, as a method of manufacturing a packaging material for a battery, a chemical conversion treatment is performed on both surfaces of aluminum with an aqueous solution composed of a phenol resin, a chromium fluoride (3) compound, and phosphoric acid, and a substrate is formed on one surface. A laminate obtained by dry laminating and then laminating a polyethylene film or polypropylene film as a heat-sealable film layer on the other surface by sandwich lamination using acid-modified polyethylene resin or acid-modified polypropylene resin as an adhesive resin. A manufacturing method is disclosed in which heating is performed at or above the softening point of the adhesive resin by post-heating.
In Patent Documents 8 and 9, as a method for producing a polymer battery packaging material, phosphoric acid chromate treatment is performed on both surfaces of aluminum, a base material is dry laminated on one surface, and then an adhesive resin and an innermost layer are coated on the other surface. A method is disclosed in which a resin (heat seal layer) is co-extruded to form a laminate and heated by post-heating under conditions equal to or higher than the softening point of the adhesive resin.

  Patent Document 10 discloses a laminated film for a battery formed of a laminate composed of a biaxially stretched polyester film layer, a biaxially stretched nylon film layer, a metal foil layer, and a thermoadhesive resin layer. In addition, those using linear low density polyethylene, medium density polyethylene, polypropylene, and acid-modified polypropylene have been proposed. In Patent Document 10, as a method of laminating a heat-adhesive resin layer and a metal foil layer, a heat-adhesive resin such as acid-modified polypropylene is used as a film between the metal foil layer and the film of the heat-adhesive resin layer. Extrude is described.

  Patent Document 11 includes a base material layer, an adhesive layer, a chemical conversion treatment layer, aluminum, a chemical conversion treatment layer, an adhesive resin layer, and an innermost resin layer. The adhesive resin layer is acid-modified polyethylene, and the innermost resin layer has a density of 0.00. A packaging material for a lithium battery is disclosed, which is a medium-density polyethylene composed of 935 or more and MFR 1 to 10 g / 10 min, and is an adhesive resin layer and an innermost resin layer formed by coextrusion.

JP 2011-138789 A JP 2004-98409 A JP 2003-236980 A JP 2003-62932 A JP 2004-74419 A JP 2001-307684 A JP 2001-202927 A JP 2001-229887 A JP 2001-202928 A JP 2011-142091 A JP 2002-93386 A

  In the battery exterior material of Patent Document 4 using a layer made of an ethylene-α-olefin copolymer as the sealant layer, the heat seal strength of the laminate specifically produced in the example is about 6.5 N / 15 mm. It is weak and cannot be used as a battery exterior material. In addition, since the sandwich lamination method is used instead of the inflation molding method for forming the sand resin layer as the adhesive layer, a high fluidity resin with a high MFR must be selected, and the adhesive resin layer is not sealed when sealing. There is a problem that it becomes fluidized, the thickness is reduced, and the adhesive strength between the barrier layer and the aluminum foil is insufficient. That is, unlike the case where the resin extruded by the sandwich lamination method is extruded by the inflation method, the resin is usually extruded at a high temperature of 50 to 100 ° C. or higher than the melting point. This causes thermal degradation when extruding and deteriorates the seal strength and electrolyte resistance.

  In the laminate of Patent Document 5, in order to firmly bond the aluminum foil and the acid-modified resin, the chemical conversion treatment layer is heated above the softening point of the acid-modified olefin resin and below the melting point, and bonded by a thermal lamination method. After forming the laminate, it is necessary to perform a two-stage heat treatment in which the intermediate laminate is reheated so as to be equal to or higher than the melting point of the acid-modified olefin resin, which increases processing costs. Moreover, also in this patent document 5, similarly to patent documents 1-3, environmental pollution resulting from the chemical conversion process by a phosphoric acid chromate process becomes a problem.

  In the methods of Patent Documents 6 and 7, since the sandwich lamination method is adopted for forming the adhesive resin layer, the adhesive resin layer is fluidized at the time of sealing, and the thickness is reduced and the barrier layer aluminum foil is formed. There is a problem that the adhesive strength is insufficient, and there is a problem that the seal strength and the electrolytic solution resistance deteriorate due to thermal deterioration during extrusion at a high temperature.

  The methods of Patent Documents 8 and 9 are based on a so-called extrusion lamination method in which an adhesive resin is directly extruded onto an aluminum surface by a co-extrusion method. Similar to the sandwich lamination method, a high fluidity resin having a high MFR as an adhesive resin. The adhesive resin layer is fluidized at the time of sealing, the thickness becomes thin and the adhesive strength with aluminum is insufficient, and the sealing strength and electrolyte resistance deteriorate due to thermal deterioration during extrusion at high temperatures. There is a problem to do. In addition, as in Patent Documents 1 to 3, there is a problem of environmental pollution caused by the phosphoric acid chromate treatment.

  In Patent Document 10, since acid-modified polypropylene is used as the adhesion-strengthening resin layer, the electrolytic solution resistance is inferior.

  In Patent Document 11, since the innermost resin layer is made of medium density polyethylene, it is inferior in tear resistance. Therefore, when medium density polyethylene is laminated and formed into a case as an aluminum laminate film, it tends to be whitened and has resistance to electrolyte. Is inferior. In addition, there is a drawback that the adhesiveness of the sealing member used for sealing with the electrode tab to the polypropylene resin, that is, the adhesiveness to the tab seal layer is inferior.

As described above, various types of laminated films have been proposed as battery exterior materials in the past. However, since the optimum selection has not been made in terms of the resin properties and film forming method of the sealant layer, and the bonding method, High strength and interlayer adhesion strength, excellent resistance to electrolytic solution and heat, excellent adhesion to the tab seal layer, and there are no environmental pollution problems that can be manufactured at low cost. The actual situation is not.
The present invention solves the above-mentioned problems, and the object of the present invention is to provide high sealing strength and interlayer adhesion strength, excellent electrolytic solution resistance and heat resistance, and excellent adhesiveness with the tab seal layer, and the environment. The present invention provides a laminate film for battery exterior that can be manufactured at low cost by a method with less load.

  As a result of diligent study, the inventors of the present invention have a battery exterior laminate film in which at least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer are laminated in this order. By using a high-viscosity, high-density polyethylene resin mainly composed of specific linear low-density polyethylene (LLPE), the barrier layer is resistant to electrolysis without chemical treatment such as chromate treatment with a large environmental load. Liquid form, heat resistance, and high adhesive strength can be obtained. Also, it has excellent adhesion to the tab seal layer. Furthermore, an inflation molding method that extrudes the film-forming material from an annular die is used to form a sealant layer. By adopting it, it is possible to obtain a homogeneous film having no difference in physical properties such as longitudinal and lateral tensile strength and elongation, and this film is obtained by using the acid-modified polyethylene of the second adhesive layer. Bonding with the metal foil of the barrier layer by thermal lamination method through an adhesive resin, promotes the crystallinity of the acid-modified polyethylene resin of the sealant layer and the second adhesive layer, and is resistant to electrolyte, heat and interlayer It has been found that a laminate film for battery exterior having excellent adhesiveness can be obtained.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A battery exterior laminate film in which at least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer are laminated in this order, and the sealant layer is linear made of polyethylene resin composed mainly of low density polyethylene (LLPE), and, MFR0.1g / 10min or 3 g / 10min or less, density of 0.918 g / cm ³ or more 0.950 g / cm ³ or less, a tensile modulus of 100MPa or more A laminate film for battery exterior, having a sealant main layer of 1500 MPa or less.

[2] The second adhesive layer is made of a polyethylene resin containing LLPE as a main component, at least a part of the polyethylene resin is acid-modified, and has an MFR of 0.1 g / 10 min to 3 g / 10 min, density 0 .920g / cm ³ or more 0.950 g / cm ³ or less, a tensile laminate film for a battery exterior according to [1], wherein the or less elastic modulus 100MPa or more 1000 MPa.

[3] The density of either or both of the sealant main layer and the second adhesive layer is 0.928 g / cm ³ or more, and the density difference between the two is 0.015 g / cm ³ or less. The laminate film for battery exterior according to [1] or [2], which is characterized.

[4] The laminate film for battery exterior according to any one of [1] to [3], wherein the barrier layer is made of an aluminum foil that has not been subjected to chromium conversion treatment.

[5] The laminate film for battery exterior according to any one of [1] to [4], wherein the barrier layer is made of an aluminum foil having a boehmite film formed on a surface thereof.

[6] An inflation molding step of forming the sealant main layer forming film by an inflation molding method in which the film forming material for the sealant main layer is extruded from an annular die, and a sealant layer having the sealant main layer forming film The method for producing a laminate film for battery exterior according to any one of [1] to [5], further comprising a thermal lamination step of bonding to the barrier layer by a thermal lamination method through two adhesive layers.

[7] The battery exterior according to [6], wherein the second adhesive layer is a film formed by an inflation molding method in which a film forming material of the second adhesive layer is extruded from an annular die. Method for manufacturing laminated film.

[8] In the thermal lamination step, heat lamination is performed by heating the sealant layer side of the laminate film for battery exterior with a heating roll having a temperature of 20 ° C. or more higher than the melting point of the sealant layer [6] or [7] The method for producing a laminate film for battery exterior according to [7].

[9] In the thermal lamination step, when the barrier layer and the sealant layer are bonded to each other through the second adhesive layer, the non-bonded surface on the sealant layer side is 20 ° C. or higher than the melting point of the sealant layer. Any one of [6] to [8], wherein a heat-resistant resin film made of a resin other than polyethylene resin having a high melting point is laminated and thermally laminated, and then the heat-resistant resin film is peeled off from the sealant layer. Manufacturing method for laminate film for battery exterior.

[10] A battery comprising the laminate film for battery exterior according to any one of [1] to [5].

  According to the present invention, a battery having high sealing strength and interlayer adhesive strength, excellent electrolytic solution resistance and heat resistance, excellent adhesiveness with a tab seal layer, and can be manufactured at low cost by a method with little environmental load. An exterior laminate film is provided, and by using this battery exterior laminate film, the battery can be reduced in weight, thickness, size, cost, long-term durability, and reliability.

It is sectional drawing which shows embodiment of the laminate film for battery exteriors of this invention. It is the schematic of the thermal lamination process which shows an example of the manufacturing method of the laminated film for battery exteriors of this invention. It is a perspective view which shows an example of the battery exterior material using the laminate film for battery exteriors of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a laminate film for battery exterior of the present invention, and FIG. 2 is a schematic view of a thermal lamination process showing an example of a method for producing a laminate film for battery exterior of the present invention. 3 is a perspective view showing an example of a battery exterior material using the laminate film for battery exterior of the present invention. However, FIGS. 1-3 shows an example of embodiment of this invention, The laminate film for battery exteriors of this invention, and a battery exterior material are not limited to what is shown in FIGS. . Moreover, the manufacturing method of the laminate film for battery exteriors of this invention is not limited to what passes through the thermal lamination process shown in FIG.

In this specification, the tensile modulus of the resin or the resin composition is measured at 1 mm / min using a Tensilon tensile tester with a strip-like sample having a width of 15 mm based on ISO 1184-1970 with a distance between chucks of 100 mm. Value. Further, MFR (melt flow rate) was measured at 190 ° C. and a load of 2.16 kgf in the case of a polyethylene resin, an acid-modified polyethylene resin, or a resin composition containing these as a main component based on the JIS K7210A method. In the case of a polypropylene resin or a polypropylene resin composition, it is a value measured at 230 ° C. and a load of 2.16 kgf. The density of the resin is determined by the JISK7112A method (submersion method in water).
Moreover, melting | fusing point is calculated | required by the melting peak temperature when it measures by DSC (differential scanning calorimeter) with the temperature increase rate of 10 degree-C / min.

[Laminate film for battery exterior]
As shown in FIG. 1, the laminate film 10 for battery exterior of the present invention has at least a base layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a sealant layer 5 laminated in this order. The sealant layer 5 is made of a polyethylene resin mainly composed of linear low density polyethylene (LLPE), and has an MFR of 0.1 g / 10 min to 3 g / 10 min, and a density of 0.918 g / cm ^{3 to} 0. It has a sealant main layer having a tensile elastic modulus of 100 MPa or more and 1500 MPa or less, and 950 g / cm ³ or less.

<Base material layer>
The base material layer 1 in the present invention reinforces the barrier layer 3 to prevent damage to the barrier layer 3 due to external force due to piercing or the like, and the battery outer laminate film itself during processing of the battery outer laminate film. It is a layer for preventing breakage and may be a single layer or a laminate of two or more layers.
The base material layer 1 is required to be excellent in mechanical strength and heat resistance, and is preferably made of a resin film having a high tensile elastic modulus.

  Preferred resins used for the base material layer 1 include polyamide (PA), polyamideimide (PAI), polyimide (PI), polyacetal (POM), polyarylate (Par), polycarbonate (PC), polyethylene terephthalate (PET), Polyalkylene terephthalate (PAT) such as polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polymethyl methacrylate (PMMA), polyphenylene oxide (PPE) , Polyethersulfone (PES), polymethylpentene (TPX), polyoxybenzylene (POB), liquid crystalline polyester, polysulfone (PSF), polyphenylene sulfide (PP ), Poly bisamide triazole, polyaminobismaleimide, polyether imide (PEI), polyetheretherketone (PEEK), include one or more mixtures of these thermoplastic resins such as acrylic.

  Among these, polycarbonate (PC), polybutylene terephthalate (PBT), polyalkylene terephthalate (PAT) such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyamide (PA), Polyphenylene sulfide (PPS), polyamideimide (PAI), and polyimide (PI) are preferable.

  Although the base material layer 1 may be an unstretched film or a stretched film, it is preferably a stretched film from the viewpoint of mechanical strength and heat resistance, and particularly preferably a biaxially stretched film. In particular, a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film or a biaxially stretched polyamide film is preferable because it has a high tensile elastic modulus and is inexpensive.

  The base material layer 1 has a role for preventing pinhole generation of the barrier layer 2 due to deformation such as external piercing during assembly as a battery, and press processing generally performed when pouching or embossing. In order to play a role in preventing damage to the laminate film for battery exterior during the overhanging process, a certain degree of elastic modulus and thickness are required.

  The tensile elastic modulus of the base material layer 1 is usually 2000 MPa or more, preferably 2200 MPa or more, and particularly preferably 2400 MPa or more. The upper limit of the tensile elastic modulus is not particularly defined, but the tensile elastic modulus of the preferred resin as described above is usually 6000 MPa or less.

  Moreover, the thickness of the base material layer 1 is preferably 10 μm or more and 50 μm or less. When the thickness of the base material layer 1 is larger than 50 μm, the laminate film for battery exterior becomes too high in rigidity and not only is difficult to process such as press working, but also the surface density tends to increase and the weight cannot be reduced. . Moreover, when the thickness of the base material layer 1 is less than 10 μm, the puncture resistance may be affected. The thickness of the base material layer 1 is particularly preferably 12 μm or more and 30 μm or less.

  When the battery exterior laminate film is an embossed exterior material as illustrated in FIG. 3, the base material layer 1 also needs to be slidable with the mold during press molding. It is preferable to improve the slipperiness by applying a lubricant to the surface (the outermost surface of the laminate film for battery exterior) or providing unevenness.

  However, when a lubricant is used, there is a concern about the problem of mold contamination due to the lubricant. Therefore, it is particularly preferable that the surface of the base material layer 1 is uneven to reduce the coefficient of friction with the mold. . In this case, the unevenness of the surface of the base material layer 1 is a surface measured in an area of 40 μm × 40 μm using a laser microscope VK8500 manufactured by Keyence Co., Ltd. under the measurement conditions of lens 100 times, pitch 0.01 μm, shutter speed AUTO, gain 835. The average value obtained by measuring the roughness Ra at four points is preferably 0.3 μm or more and 1.0 μm or less. If Ra is smaller than the lower limit, the slipping property tends to be insufficient, and if Ra is larger than the upper limit, dust tends to adhere to the unevenness. A preferable surface roughness Ra of the base material layer 1 is not less than 0.35 μm and not more than 0.70 μm.

<First adhesive layer>
The first adhesive layer 2 is a layer for adhering the base material layer 1 and the barrier layer 3. When the base material layer 1 and the barrier layer 3 are bonded together by a dry lamination method, the first adhesive layer 2 is used for dry lamination. Adhesive, for example, aliphatic polyester, aromatic polyester, polyethyleneimine, polyether, cyanoacrylate, urethane, organic titanium, polyetherurethane, epoxy, polyesterurethane, imide, isocyanate Various adhesives such as those based on polyolefin, polyolefin, silicone, and acrylic can be used.
Among these adhesives, aromatic polyester-based, polyolefin-based, and acrylic-based adhesives are preferable because of their excellent resistance to electrolytic solution.

  When further electrolytic solution resistance is required, the base material layer 1 and the barrier layer 3 may be bonded together by a thermal lamination method using an acid-modified resin film for the first adhesive layer 2.

  Although the thickness of the 1st contact bonding layer 2 is not limited, Usually, it is about 1-10 micrometers.

<Barrier layer>
The barrier layer 3 is a layer for preventing (barrier) the entry of moisture from the outside into the battery, has no pinhole, and has a high tensile strength as a laminate film for battery exterior. It is required to have crack resistance against deformation and elongation during embossing and pouching.

As the barrier layer 3, a metal foil (metal layer) is preferable, and an aluminum foil is particularly preferable. Further, from the viewpoint of crack resistance during press working or embossing, an aluminum foil excellent in extensibility is preferable, and an aluminum foil containing 0.3 wt% or more and 3.0 wt% or less of iron is preferable. If the iron content is less than this range, the elongation tends not to be sufficient. If the iron content is more than this range, the problem of corrosion of the barrier layer 3 due to hydrofluoric acid generated from the electrolytic solution tends to occur. . The preferable iron content of the aluminum foil is not less than 0.5% by weight and not more than 1.7% by weight.
Moreover, although hard aluminum foil and soft aluminum foil exist in aluminum foil, since the soft aluminum foil which performed annealing treatment has a softness | flexibility, it is preferable.

The thickness of the barrier layer 3 such as an aluminum foil is preferably 9 μm or more and 60 μm or less, and particularly preferably 20 μm or more and 50 μm or less in order to achieve both thinning and barrier properties.
In addition, although the metal foil (metal layer) shape | molded previously is normally used for the barrier layer 3, the aspect which forms the barrier layer 3 by a vapor deposition method or the apply | coating method is also included, for example.

<Surface treatment of aluminum foil>
The surface of the aluminum foil suitable as a barrier layer in the present invention may be subjected to a surface treatment for imparting corrosion resistance. However, in the present invention, the surface treatment of the aluminum foil is not necessarily required.
That is, in the present invention, as will be described later, a linear low density polyethylene (LLPE) having specific physical properties is used as a film forming material for the sealant layer, and preferably a film formed by inflation molding is subjected to a temperature gradient. By attaching to the aluminum foil through the second adhesive layer by the applied thermal lamination method, it is possible to sufficiently secure the electrolytic solution resistance and corrosion resistance even for the aluminum foil that has not been surface-treated. Therefore, in the present invention, the surface treatment of the aluminum foil is not necessarily required, and in particular, it is preferable not to perform a surface treatment having a problem of environmental pollution such as a chromium chemical conversion treatment described later.

  When surface treatment is performed on an aluminum foil as a barrier layer, a known treatment is used as the surface treatment. For example, chromate chromate treatment, phosphoric acid chromate treatment, phosphoric acid-chromate treatment, chromate treatment, alkali Examples thereof include chromium-based chemical conversion treatment such as chromate treatment and coating-type chromate treatment, coating-type non-chromium treatment such as zirconium, titanium, and zinc phosphate, boehmite treatment, and anodizing treatment. In addition to these treatments, corona treatment, plasma treatment, flame treatment, and other treatments for imparting polar groups to the surface of the aluminum foil are performed to enhance corrosion resistance by enhancing adhesion to the second adhesive layer. May be. Two or more of these processes may be combined. However, it is preferable not to perform the chromium-based chemical conversion treatment as described above.

Among the above surface treatments, boehmite treatment that has a low environmental burden and can be surface treated at low cost is preferable.
The boehmite treatment is a treatment for forming an aluminum hydrated oxide film (boehmite film) having a boehmite crystal structure on the surface of the aluminum foil by holding the aluminum foil in high-temperature boehmite-treated water for a certain period of time.

  The preferred boehmite-treated water contains deionized water and an alkali such as triethanolamine and ammonia in an amount of 0.1 wt% to 2 wt%, preferably 0.3 wt% to 1 wt%, more preferably 0. The boehmite treatment is performed by heating such boehmite-treated water to 90 to 100 ° C., and the aluminum foil for 20 seconds to 5 minutes, preferably 20 seconds. It can be performed by immersing for 1 minute.

  By such boehmite treatment, an aluminum foil having a boehmite film having a thickness of preferably 0.1 μm or more and 1 μm or less, more preferably 0.1 μm or more and 0.8 μm or less, and further preferably 0.2 μm or more and 0.4 μm or less. If present, in heat lamination with an acid-modified polyethylene resin layer, which will be described later, which is preferably used as the second adhesive layer, strong adhesiveness can be obtained and a laminate film for battery exterior having excellent electrolytic solution resistance can be obtained. . If the thickness of the boehmite film is thinner than the above range, the effect of improving the adhesiveness by the boehmite treatment cannot be sufficiently obtained, and if it is thicker than the above range, the boehmite crystal is easily detached from the interface with the aluminum foil, which is not preferable. .

<Sealant layer>
The sealant layer 5 has a tab seal layer (usually variously wound around the electrode tab in order to reinforce the heat sealability during processing as a battery exterior material, the resistance to electrolyte solution, and the adhesion to the electrode tab. Adhesion with polyethylene, polypropylene monolayer or laminated film is required. The sealant layer 5 in the present invention is made of a polyethylene resin mainly composed of linear low density polyethylene (LLPE), and has an MFR of 0.1 g / 10 min to 3 g / 10 min and a density of 0.918 g / cm ^{3 to} 0.950 g /. It has a sealant main layer having a cm ³ or less and a tensile modulus of 100 MPa to 1500 MPa.
In the present invention, the sealant main layer may contain components other than the polyethylene resin as long as the above conditions are satisfied.
The sealant layer 5 may have a single-layer structure composed of only the above-mentioned sealant main layer, or may have a laminated structure of two or more layers of the sealant main layer and other layers.

  Polyethylene resin is a polymer whose melting point is lower than that of polypropylene resin, but is a polymer in which molecules are cross-linked by repeated application of heat, and for long-term exposure in a high-temperature environment of 80 to 90 ° C. required for use as a battery exterior material. It is difficult to cut molecules and has better long-term heat resistance than polypropylene.

  Furthermore, polyethylene has a high melt tension, flexibility, resistance to deformation when processed as a battery exterior material, hardly whitening during deformation, and excellent cold resistance. In addition, polyethylene has a higher density than polypropylene and has high resistance to moisture from the outside and a carbonate-based solvent that is a polar solvent for the electrolytic solution.

Since the sealant main layer according to the present invention has moderate flexibility among polyethylene resins and is excellent in adhesiveness with various tab seal layers that are wound around electrode tabs, linear low density polyethylene ( A polyethylene resin containing LLPE as a main component is used.
As used herein, the main component refers to a component that is contained most in a weight ratio in a material obtained by blending a plurality of components.

In the present invention, linear low density polyethylene (LLPE) means a copolymer of ethylene and an α-olefin having about 4 to 20 carbon atoms, and is a specific example of a branched side chain composed of an α-olefin. Include various comonomers such as butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, tetracene-1, and octadecene-1. Two or more of these α-olefins may be used in combination. Further, if an α-olefin having about 4 to 20 carbon atoms is used as a comonomer, propylene may be further used as a comonomer.
This branched side chain based on α-olefin facilitates molecular entanglement not only with polyethylene but also with polypropylene at the time of melting, and the sealant layers (that is, a laminate structure of two or more layers of a sealant main layer and another layer) In this case, the adhesion between the sealant main layer and other layers), the sealant layer and the second adhesive layer, and the sealant layer and the tab seal layer can be enhanced.

  Any linear low-density polyethylene (LLPE) can be used as long as the MFR, density, and tensile modulus of the main layer of the sealant can be in a specific range. Of these, linear low-density polyethylene having at least one side chain of butene-1, hexene-1, and octene-1 is preferable because it has appropriate flexibility, and hexene-1, octene-1 is particularly preferable. Is preferable because of its excellent resistance to electrolytic solution. Although the manufacturing method of linear low density polyethylene (LLPE) is not limited, The well-known method of manufacturing polyolefin resin is employable.

  In the polyethylene resin of the sealant main layer in the present invention, a polyethylene resin other than linear low density polyethylene (LLPE) can be blended. Polyethylene resins other than linear low density polyethylene (LLPE) are not limited, and specific examples include high density polyethylene (HDPE), medium density polyethylene, and low density polyethylene (LDPE). Here, the low-density polyethylene (LDPE) does not include the above-mentioned linear low-density polyethylene (LLPE), and usually includes what is called a high-pressure method low-density polyethylene. The production method of high density polyethylene (HDPE), medium density polyethylene, and low density polyethylene (LDPE) is not limited, and a known method can be adopted, but it is usually produced by a Ziegler catalyst, a metallocene catalyst, or the like. Is preferred.

  A preferred constituent material of the sealant main layer is mainly composed of linear low-density polyethylene (LLPE) so as to have an appropriate high density that can provide good inflation molding stability, heat resistance, and electrolytic solution resistance. It is a blend material with density polyethylene (HDPE) and / or low density polyethylene (LDPE), especially LLPE 50 wt% to 100 wt%, HDPE 5 wt% to 45 wt%, LDPE 1 wt% to 30 wt% The material is preferable in terms of inflation molding stability, heat resistance, and resistance to electrolyte solution penetration. In particular, when low density polyethylene (LDPE) is blended, the long chain branching of LDPE increases the entanglement with the LLPE molecular chain, which is preferable because the tension at the time of melting increases, thereby stabilizing the film forming property at the time of inflation molding, There exists an effect which the intensity | strength of the film obtained improves. In this case, the optimum blending ratio is LLPE 50 wt% or more and 95 wt% or less, HDPE 5 wt% or more and 40 wt% or less, and LDPE 1 wt% or more and 25 wt% or less.

  As described above, linear low-density polyethylene includes copolymers obtained by copolymerizing various comonomer species such as butene-1, hexene-1, 4-methylpentene-1, and octene-1 as branched side chains. There is no particular limitation as long as it satisfies the later-described density and MFR suitable for the main layer, and among these, a straight chain having at least one side chain of hexene-1 and octene-1 is particularly preferable. It contains 50% by weight or more of linear low density polyethylene, and a blend material in which high density polyethylene and / or low density polyethylene is further blended with such linear low density polyethylene is an electrolyte solution resistant, tab seal layer and Adhesiveness, inflation moldability, heat resistance during thermal lamination, adhesion to the second adhesive layer, acid resistance to hydrogen fluoride, press or overhang processing Because of its excellent in the whitening resistance, etc., it preferred.

  The sealant main layer may contain a resin other than the polyethylene resin as long as the effects of the present invention are not impaired. The resin other than the polyethylene resin is not limited. For example, an ethylene-based resin obtained by copolymerizing ethylene and a comonomer other than an α-olefin, such as an ethylene-vinyl acetate copolymer or an ethylene-vinyl alcohol copolymer; a propylene-based resin Vinyl chloride resin, polyamide resin, polyester resin, polycarbonate resin and the like. In addition, when a resin other than the polyethylene resin is contained in a large amount as the sealant main layer, since the effect of using the above-described polyethylene resin may be impaired, these resins are included in the sealant main layer. It is preferable to use in the range of not more than wt%, preferably not more than 15 wt%.

In the present invention, the sealant layer 5 has a sealant main layer mainly composed of linear low density polyethylene (LLPE) as described above, so that the electrolytic solution resistance and the sealing performance can be improved. When it is necessary to improve the adhesion with the layer, a specific acid-modified polyethylene resin may be used for the sealant layer.
Here, with respect to the type of acid used for modification of the polyethylene resin and the modification method, the acid and modification method in the resin constituting the second adhesive layer 4 described later can be similarly employed.

However, acid-modified resins have lower heat resistance than non-acid-modified resins, especially when low molecular weight components are deposited during film formation by the sand lamination method or extrusion lamination method that forms films at high temperatures. There is. When such a layer is used as the innermost layer, that is, a layer that is in direct contact with the electrolytic solution, from the portion where the low molecular weight component is deposited, to the inner layer of hydrofluoric acid generated by the solvent of the electrolytic solution or the hydrolysis of the electrolytic solution This may accelerate the penetration of the electrolyte and may cause a problem in the resistance to the electrolyte. For this reason, the sealant main layer is preferably an acid-modified polyethylene resin with a low modification rate or a polyethylene resin layer that is not acid-modified.
Here, “low modification rate” specifically means a modification rate of 0.1% by weight or less, preferably 0.05% by weight or less.

  Further, the sealant main layer has an ethylene-propylene copolymer, an ethylene-butene copolymer, a propylene-butene copolymer, an ethylene-butene-propylene copolymer, an ethylene-propylene copolymer, as long as the effects of the present invention are not impaired. Olefin elastomers such as propylene-diene copolymers, various elastomer components such as styrene elastomers, polyester elastomers, polyamide elastomers, antioxidants, thermal stabilizers, various plasticizers, light stabilizers, ultraviolet absorbers, Various additives such as a neutralizing agent, a lubricant, an antifogging agent, an antiblocking agent, a crosslinking agent, a crosslinking aid, a colorant, a flame retardant, and a dispersing agent can be added.

In the present invention, the sealant main layer, MFR0.1g / 10min or 3 g / 10min or less, density of 0.918 g / cm ³ or more 0.950 g / cm ³ or less, or less than the tensile modulus of 100 MPa 1500 MPa.

  If the MFR of the sealant main layer is larger than 3 g / 10 min, the fluidity is too high and a flow due to the melting of the resin occurs at the time of sealing, and the thickness of the seal portion is insufficient to cause a decrease in the sealing strength. Furthermore, the molecular weight is lowered, the permeability to hydrofluoric acid generated from the electrolytic solution is increased, and the barrier layer is corroded. The preferred MFR of the sealant main layer is 2 g / 10 min or less, more preferably 1.5 g / 10 min or less. The lower limit of the MFR of the sealant main layer is 0.1 g / 10 min or more, particularly 0.3 g / 10 min or more, because it is necessary to have a level in which the film forming property does not have a problem when the film is formed by the inflation molding method. If present, it is preferable because high-speed moldability and high seal strength in inflation molding can be maintained.

The density of the sealant main layer needs to be 0.918 g / cm ³ or more. If the density of the sealant main layer is smaller than this, the solvent resistance and the electrolytic solution resistance deteriorate. In order to block moisture from the outside and to increase resistance to hydrofluoric acid generated by hydrolysis of the electrolytic solution and moisture, the density of the sealant main layer should be high. It is 920 g / cm ³ or more, particularly preferably 0.923 g / cm ³ or more. The upper limit of the density of the sealant main layer needs to be in a range that does not impair the flexibility of the polyethylene resin, and the upper limit of the density is 0.950 g / cm ³ or less, adhesion to the tab seal layer, acid resistance to hydrogen fluoride, Considering the whitening resistance in pressing or overhanging processing, the upper limit of the density is preferably 0.945 g / cm ³ or less.
The means for setting the density of the sealant main layer within the above range is not limited, but besides the optimization of the polyethylene resin and the modification rate, as described above, a resin other than the polyethylene resin or the polyethylene resin is used in combination. For example, optimizing the mixing ratio.

In the present invention, the density of either the sealant main layer or the second adhesive layer 4 described later is preferably 0.928 g / cm ³ or more. In that case, the density difference between the two is 0.015 g. / Cm ³ or less is preferable.
That is, although the density of either one or both of the sealant main layer and the second adhesive layer 4 is 0.928 g / cm ³ or more, the solvent resistance and the electrolytic solution resistance are excellent. The density of the sealant main layer is preferably higher than the density of the second adhesive layer 4 to be described later, and the density of the sealant main layer is preferably 0.001 g / cm ³ or more, more preferably than the density of the second adhesive layer 4. Is preferably 0.002 g / cm ³ or more in terms of solvent resistance and electrolyte resistance. However, it is preferable that the density difference between the sealant main layer and the second adhesive layer 4 is small because the warpage of the film due to the difference in crystallinity after thermal lamination is small, and this density difference is 0.015 g / cm ^3. Hereinafter, it is particularly preferably 0.012 g / cm ³ or less.
When the density of both the sealant main layer and the second adhesive layer 4 is less than 0.928 g / cm ³ , sufficient solvent resistance and electrolyte resistance may not be obtained.

  The tensile modulus of the main layer of the sealant is 100 MPa or more because it tends to cause material destruction when an external force such as deformation is applied if too much flexibility is applied. On the other hand, if it becomes too hard, it tends to become brittle. Since it becomes easy to peel between the barrier layer 3 which contacts through a layer, it is 1500 MPa or less. The tensile elastic modulus of the sealant main layer is more preferably 130 MPa to 1000 MPa, and particularly preferably 180 MPa to 900 MPa.

  The values of MFR, density, and tensile modulus described above refer to the characteristics of the material constituting the sealant main layer (or the sealant layer when the sealant layer is a single-layer structure of the sealant main layer). When a plurality of polyethylene resins are used in combination as a polyethylene resin or when a resin other than a polyethylene resin is contained, a sealant main layer (a sealant layer if the sealant layer is a single-layer structure of the sealant main layer) is configured. It means the value as a resin composition.

  In the present invention, since the sealant layer has a layer mainly composed of linear low-density polyethylene, the electrolytic solution resistance and the sealing performance can be improved. It is preferable to use a specific acid-modified polyethylene resin layer for the adhesive layer 4.

  Alternatively, the sealant layer may have a multilayer structure, and a laminated structure of the above-described sealant main layer mainly composed of linear low density polyethylene and a random polypropylene layer or a block polypropylene layer. That is, the sealant layer in the present invention has a good sealing strength with the tab seal layer used for the electrode tab portion even though it is composed of a single layer of the sealant main layer, but the tab seal layer used for the electrode tab portion. Depending on the material, sufficient seal strength may not be obtained. In such a case, the sealing strength of the electrode tab portion with the tab seal layer can be further improved by providing the sealant layer with the laminated structure as described above.

The thickness of the sealant main layer is preferably 3 μm or more and 80 μm or less, more preferably 10 μm or more and 60 μm or less, and particularly preferably 12 μm or more and 50 μm or less. If the thickness of the sealant main layer is thinner than the above range, the seal strength between the sealant layers may not be obtained. If it is thicker than the above range, the film forming property at the time of inflation molding is inferior and the thickness becomes uniform. In addition, the sealant layer is difficult to melt at the time of thermal lamination, and wrinkles and air entrainment may easily occur.
Also in the case of a sealant layer having a multilayer laminated structure, it is preferable that the total thickness falls within the above range.

  In addition, like the base material layer 1, the sealant layer 5 is formed on the surface (the surface opposite to the second adhesive layer 4) which is the outermost surface of the laminate film for battery exterior in order to improve the slipping property at the time of embossing. It is preferable to provide unevenness because a lubricant having a problem of mold contamination can be dispensed with. In this case, the surface roughness Ra of the unevenness imparting surface of the sealant layer 5 is preferably about 0.02 to 0.08 μm, particularly about 0.03 to 0.07 μm. Here, the surface roughness Ra of the sealant layer 5 is a value measured in the same manner as the surface roughness Ra of the substrate layer 1 described above. This surface irregularity can be imparted by a thermal lamination process described later.

<Second adhesive layer>
The second adhesive layer 4 is a layer for bonding the barrier layer 3 and the sealant layer 5, and the material thereof is not limited, but contains a polyethylene resin mainly composed of linear low density polyethylene (LLPE). In particular, the second adhesive layer 4 is made of a polyethylene resin containing LLPE as a main component, at least a part of the polyethylene resin is acid-modified, and has an MFR of 0.1 g / 10 min to 3 g / 10 min. , density 0.920 g / cm ³ or more 0.950 g / cm ³ or less, is preferably less than the tensile modulus of 100 MPa 1000 MPa. Moreover, the 2nd contact bonding layer 4 may contain components other than polyethylene resin.

  As mentioned above, polyethylene resin is a polymer whose melting point is lower than that of polypropylene resin, but is a polymer in which molecules are cross-linked by repeated application of heat, and it is long in a high temperature environment of 80 to 90 ° C. necessary for use as a battery exterior material. It is less susceptible to molecular cleavage with time exposure and has better long-term heat resistance than polypropylene.

Furthermore, polyethylene has a high melt tension, flexibility, resistance to deformation when processed as a battery exterior material, hardly whitening during deformation, and excellent cold resistance. In addition, polyethylene has a higher density than polypropylene and has high resistance to moisture from the outside and a carbonate-based solvent that is a polar solvent for the electrolytic solution.
Such polyethylene acid-modified resin is excellent in adhesion to metal foil such as aluminum foil constituting the barrier layer, and is subjected to chromium-based chemical conversion treatment or phosphorus-based chemical conversion treatment that causes environmental pollution to the aluminum foil. Even if it is not, a strong adhesive force can be obtained.

In the present invention, among polyethylene resins, a polyethylene resin mainly composed of linear low density polyethylene (LLPE) is used because it has moderate flexibility and excellent adhesion to a barrier layer such as an aluminum foil. It is preferable.
As used herein, the main component refers to a component that is contained most in a weight ratio in a material obtained by blending a plurality of components.

  In the present invention, linear low density polyethylene (LLPE) means a copolymer of ethylene and an α-olefin having about 4 to 20 carbon atoms as described above, and a branched side chain composed of an α-olefin. Specific examples thereof include various comonomers such as butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, tetracene-1, and octadecene-1. Two or more of these α-olefins may be used in combination. Further, if an α-olefin having about 4 to 20 carbon atoms is used as a comonomer, propylene may be further used as a comonomer. Among these, linear low density polyethylene having at least one side chain of butene-1, hexene-1, and octene-1 is preferable because it has appropriate flexibility. Although the manufacturing method of linear low density polyethylene (LLPE) is not limited, The well-known method of manufacturing polyolefin resin is employable.

  Polyethylene resins other than linear low density polyethylene (LLPE) can be blended in the polyethylene resin constituting the second adhesive layer 4, and as polyethylene resins other than the linear low density polyethylene (LLPE), Specific examples include, but are not limited to, high density polyethylene (HDPE), medium density polyethylene, and low density polyethylene (LDPE) exemplified as polyethylene resins other than LLPE in the sealant main layer.

  The polyethylene resin constituting the second adhesive layer 4 preferably includes a polyethylene resin that is at least partially acid-modified. Such an acid-modified polyethylene resin can be produced, for example, by modifying an unsaturated carboxylic acid and / or a derivative thereof into a polyethylene resin by graft polymerization.

  A preferred acid-modified polyethylene resin is an acid-modified polyethylene resin that is a blend material of linear low-density polyethylene (LLPE) and high-density polyethylene (HDPE), and this blend material has an LLPE of 50 wt% or more and 98 wt% or less. HDPE is preferably 2% by weight or more and 50% by weight or less in view of heat resistance and resistance to electrolyte solution penetration. Furthermore, in order to impart inflation molding stability, low density polyethylene (LDPE) may be blended as the third component. In this case, the blending ratio is LLPE 50% to 95% by weight, HDPE 5% to 40% by weight. % Or less, preferably 1% by weight or more and 30% by weight or less of LDPE.

  The unsaturated carboxylic acid and unsaturated carboxylic acid derivative used for acid modification of the polyethylene resin are not particularly limited, and examples thereof include dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid. Acids; Unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid; dicarboxylic acid anhydrides such as maleic anhydride, fumaric anhydride, itaconic anhydride, mesaconic anhydride, and derivatives such as amides, imides, esters, etc. Can be mentioned. Among these, maleic acid, maleic anhydride, acrylic acid, and methacrylic acid are preferably used, and maleic anhydride is particularly preferable.

  The method for modifying the polyethylene resin is not particularly limited. For example, a solution method in which a polyethylene resin is dissolved in an organic solvent and reacted with an acid (such as maleic anhydride) in the presence of a radical generator, polyethylene Examples thereof include a melting method in which a resin is heated and melted and reacted with an acid (such as maleic anhydride) in the presence of a radical generator.

The acid-modified polyethylene resin may be a linear low-density polyethylene (LLPE) as a main component, or other polyethylene resin that can be used in combination with this, for example, high-density polyethylene (HDPE). Or low density polyethylene (LDPE). Furthermore, an acid-modified polyethylene resin and a non-acid-modified polyethylene resin can be appropriately blended and used.
In addition, when other polyethylene resins are used together with linear low density polyethylene (LLPE), these polyethylene resins may be acid-modified in a mixed or coexisting state, or at least one of the polyethylene resins may be It may be previously modified with an acid, and this may be mixed with another polyethylene resin that has not been modified with an acid.

If the modification rate of the acid-modified polyethylene resin (content of acid groups in the acid-modified polyethylene resin) is too small, the effect of improving adhesiveness due to acid modification may not be obtained sufficiently. Since the heat resistance of the modified polyethylene resin tends to decrease, it is preferably 0.05% by weight or more and 10% by weight or less, particularly preferably 0.2% by weight or more and 5% by weight or less. Here, the modification rate of the acid-modified polyethylene resin can be confirmed by means such as infrared absorption spectrum analysis (IR) or titration. In addition, in the case of blending and using an acid-modified polyethylene resin and a non-acid-modified polyethylene resin, the modification rate refers to the modification rate in all polyethylene resins including a polyethylene resin not acid-modified. Shall mean.
In addition, as an acid-modified polyethylene resin, a commercial item can also be used. For example, it corresponds to the above from Mitsubishi Chemical Corporation, Modic (trade name) series, Mitsui Chemicals, Admer (trade name), etc. What is to be selected can be appropriately selected and used.

  The second adhesive layer 4 may contain a resin other than the polyethylene resin as long as the effects of the present invention are not impaired. The resin other than the polyethylene resin is not limited. For example, an ethylene-based resin obtained by copolymerizing ethylene and a comonomer other than an α-olefin, such as an ethylene-vinyl acetate copolymer or an ethylene-vinyl alcohol copolymer; a propylene-based resin Vinyl chloride resin, polyamide resin, polyester resin, polycarbonate resin and the like. In addition, when the resin other than the polyethylene resin is contained in a large amount as the second adhesive layer 4, since the effect of using the above-described polyethylene resin may be impaired, these resins are used in the second adhesive layer. It is preferable to use in the range of 20% by weight or less, preferably 15% by weight or less.

  Further, the second adhesive layer 4 has an ethylene-propylene copolymer, an ethylene-butene copolymer, a propylene-butene copolymer, and an ethylene-butene-propylene copolymer as long as the effects of the present invention are not impaired. Olefin elastomers such as ethylene-propylene-diene copolymers, various elastomer components such as styrene elastomers, polyester elastomers, polyamide elastomers, antioxidants, thermal stabilizers, various plasticizers, light stabilizers, ultraviolet rays Various additives such as an absorbent, a neutralizing agent, a lubricant, an antifogging agent, an antiblocking agent, a crosslinking agent, a crosslinking aid, a colorant, a flame retardant, and a dispersing agent can be added.

Second adhesive layer, MFR0.1g / 10min or 3 g / 10min or less, density of 0.920 g / cm ³ or more 0.950 g / cm ³ or less, is preferably less than the tensile modulus of 100 MPa 1000 MPa.

  If the MFR of the second adhesive layer 4 is greater than 3 g / 10 min, the fluidity is too high and a flow due to melting of the resin occurs at the time of sealing, and the thickness of the seal portion is insufficient, which may cause a decrease in seal strength. is there. Furthermore, the molecular weight is lowered, the permeability to hydrofluoric acid generated from the electrolytic solution is increased, and the barrier layer may be corroded. The more preferable MFR of the second adhesive layer 4 is 2 g / 10 min or less, more preferably 1.5 g / 10 min or less. The lower limit of the MFR of the second adhesive layer 4 is preferably at least 0.1 g / 10 min since it is preferably at a level that does not cause a problem in film formation when the film is formed by an inflation molding method. .3 g / 10 min or more is preferable because high-speed moldability and high seal strength in inflation molding can be maintained.

In addition, the density of the second adhesive layer 4 is preferably 0.920 g / cm ³ or more. If the density is smaller than this, the solvent resistance and the electrolytic solution resistance may deteriorate. In order to block moisture from the outside and increase resistance to hydrofluoric acid generated by hydrolysis of the electrolytic solution and moisture, the density of the second adhesive layer 4 should be high, and more preferable density. the lower limit is at 0.923 g / cm ³ or more, and particularly preferably 0.925 g / cm ³ or more. The upper limit of the density of the second adhesive layer 4 is not particularly limited as long as the flexibility of the polyethylene resin is not impaired. Usually, the upper limit of the density is 0.950 g / cm ³ or less, and In consideration of adhesiveness, acid resistance to hydrogen fluoride, and resistance to whitening in pressing or overhanging, the upper limit of the density is preferably 0.945 g / cm ³ or less.
Means for bringing the density of the second adhesive layer 4 within the above range is not limited, but examples include a method of appropriately selecting a polyethylene resin to be used. In particular, optimization of the polyethylene resin used for acid modification, modification rate In addition to optimization, as described above, it is possible to use a polyethylene resin that is not acid-modified, a resin other than polyethylene resin, and the like to optimize the blending ratio.
The preferable relationship between the density of the second adhesive layer 4 and the density of the sealant main layer is as described above.

  Further, the tensile modulus of elasticity of the second adhesive layer 4 is preferably 100 MPa or more because it tends to cause material destruction when an external force such as deformation is applied if too much flexibility is applied. It is preferably 1000 MPa or less because it tends to become brittle and easily peels at the interface with the barrier layer. The tensile elastic modulus of the second adhesive layer 4 is more preferably 130 MPa to 800 MPa, and particularly preferably 180 MPa to 600 MPa.

  The values of MFR, density, and tensile modulus described above indicate the characteristics of the material constituting the second adhesive layer 4, and when a plurality of polyethylene resins are used in combination as the polyethylene resin, a resin other than the polyethylene resin is used. In the case of containing, it means a value as a resin composition.

  The thickness of the second adhesive layer 4 is preferably 3 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less, and particularly preferably 12 μm or more and 35 μm or less. If the thickness of the second adhesive layer 4 is thinner than the above range, it may not be possible to obtain sufficient adhesive strength for the adhesion between the barrier layer 3 and the sealant layer 5. If thicker than the above range, the sealant layer 5 The thickness of the electrode must be reduced, and the electrolyte solution resistance may be inferior.

[Method for producing laminated film for battery exterior]
Hereinafter, the case where the sealant layer has a single-layer structure of the above-described sealant main layer will be described as an example, and the method for producing the laminate film for battery exterior of the present invention will be described. In addition, what is necessary is just to form into a film by the coextrusion inflation molding method below, when making a sealant layer into the laminated structure of a sealant main layer and another layer.

The method for producing the laminate film for battery exterior of the present invention is not particularly limited, but at least the sealant layer is formed by an inflation molding method, and then the barrier layer and the barrier layer through the second adhesive layer by a thermal lamination method. It is preferable to bond them together.
In addition, a laminated film of the second adhesive layer and the sealant layer is formed in advance by the coextrusion inflation molding method (multilayer inflation molding method), and then the metal foil / second adhesive layer / sealant layer is formed by the thermal lamination method. It is good also as a laminated film. Further, the second adhesive layer and the sealant layer may be separately formed in advance, and these may be bonded together at the time of thermal lamination to form a laminated film of metal foil / second adhesive layer / sealant layer. Moreover, you may laminate by extruding a 2nd contact bonding layer between the sealant layer previously formed by the inflation molding, and the barrier layer bonded together with the base material layer.
In any case, if a high density and low MFR resin is selected as the sealant layer, that is, the main sealant layer, the crystallinity of the sealant layer and the second adhesive layer is increased during thermal lamination, and the crystal lamella of the sealant layer is increased. Electrolytic solution resistance is created, and the crystal lamellae of the acid-modified polyethylene resin of the second adhesive layer can easily enter the surface of the metal foil of the barrier layer, and high adhesive strength, heat resistance, and electrolytic solution resistance can be obtained.

  In addition, the metal foil of the barrier layer used for thermal lamination should be used as a laminated film in which a base material layer is bonded in advance through a first adhesive layer by a dry lamination method or the like. This is preferable because the side is cooled more slowly, crystallization proceeds, and a laminate film for battery exterior having excellent heat resistance and electrolytic solution resistance can be obtained.

  Thereafter, a film of a sealant layer and a second adhesive layer are respectively formed by an inflation molding method, and this is bonded to a barrier layer, preferably a base material layer bonded to the first adhesive layer, by thermal lamination. The method for producing the laminate film for battery exterior of the present invention will be described.

<Inflation molding>
Inflation molding is a method in which air or the like is placed in a melting tube made of a film forming material extruded from an annular die, inflated larger than the diameter of the annular die, and continuously taken and filmed while being cooled and solidified by air cooling or water cooling. Extrusion method.

  In the inflation molding method, the molten resin extruded from the extruder is formed into a tube shape, and the molten resin flows through an annular flow path using an inflation die. This flow path is between the outer die and the inner mandrel. Immediately after the molten resin film exits the annular die, air pressure is applied inside the tube to expand it. The expanded tube is configured to be tightened with a nip roll to maintain air pressure. The expanded tube (bubble) is cooled with air from the cooling ring above the die exit.

  Since the bubble grows in the extrusion direction (MD direction) and the circumferential direction (TD direction), the film speed at the nip roll must be much faster than the tube speed at the die exit. The film is stretched in the MD direction and expanded in the TD direction. The stretch ratio is expressed as the ratio between the final film speed and the initial speed, and the blow-up ratio is expressed as the ratio between the final tube diameter and the initial diameter (annular die diameter). The size of the blow-up ratio is from 1: 1 to 10: 1. A range is preferred, with a range of 1.3: 1 to 5: 1 being particularly preferred.

In general, polypropylene is often used as the resin for the battery exterior film from the viewpoint of heat resistance, and in order to emphasize low cost, it is manufactured by an extrusion lamination method, a sand lamination method, or a casting method. Often filmed polypropylene is used. However, since all of these films are formed by cooling the molten resin extruded from a T-shaped mold (strip-shaped resin discharge port), physical properties such as tensile strength, elongation, and tensile modulus in the MD and TD directions are obtained. Differences are likely to occur. Therefore, when used as a battery exterior film, at the time of press working or overhanging, wrinkles at the time of working tend to occur due to the difference in mechanical properties depending on the direction.
Further, as described above, since the highly elastic film of the base material layer is usually stretch-molded with a T-die, the difference in the MD / TD direction is likely to occur.

  For this reason, in the present invention, the sealant layer and further the second adhesive layer are less likely to cause a difference in physical properties in the MD / TD direction by inflation molding, and balance with the physical properties of the base material layer. In view of the above, it is preferable that the laminated film for battery exterior is formed by adjusting the blow-up ratio within the above range so as to eliminate anisotropy.

  As described above, the film formed by the inflation molding method is unlikely to have a difference in mechanical properties between the extrusion direction (MD direction) and the circumferential direction (TD direction) perpendicular to the extrusion direction, and is subjected to press processing and overhang processing. The laminated film has an advantage that wrinkles during processing are less likely to occur because there is little difference in mechanical properties depending on the direction.

  In addition, the resin raw material suitable for the inflation molding method requires characteristics such as a low MFR, a high molecular weight, a high melt tension, and a low processing temperature during film formation. The properties are different from those of resins used in extrusion laminating or sandwich laminating methods that are molded at high temperatures and require high MFR, high flow resin properties. For this reason, in the present invention, the low MFR resin as described above is used as the resin of the sealant main layer and the acid-modified polyethylene resin of the second adhesive layer, but these resins have low MFR properties and high melt tension. Depending on the properties, there is an advantage that high sealing strength can be easily obtained.

  In the present invention, in order to impart various properties such as mechanical properties, sealing properties, heat resistance, moldability, etc. as a battery exterior film while taking advantage of the low anisotropy of the film by the inflation molding method, Paying attention to the resin characteristics used in the method, by constructing the sealant layer having the specific resin and specific physical properties described above, the aluminum foil without the chromium conversion treatment is applied to the aluminum foil as the barrier layer. It is possible to obtain a laminate film for battery exterior that has excellent adhesiveness, can prevent moisture intrusion, has excellent resistance to electrolytic solution, and has high sealing strength.

<Thermal lamination method>
In the present invention, a sealant layer (film for forming a sealant layer) formed by an inflation method, preferably, a laminated film of a sealant layer and a second adhesive layer is thermocompression bonded by a thermal lamination method to adhere to the barrier layer. This is important for improving the resistance to electrolytic solution.

  The thermal lamination method uses two or more rolls, sandwiches two or more films between the rolls, moves the film while rotating at least one roll, and heats the film while heating at least one roll. Is a laminating method in which the material is heated and bonded. In this method, the line speed is slower than in the dry lamination and extrusion lamination methods, but since the cooling process is not rapid, it is easy to create processing conditions that promote crystallization of the resin.

In the present invention, a polyethylene resin mainly composed of a high density and highly crystalline linear low density polyethylene is used for the sealant layer, and the sealant layer and the second adhesive layer are melted and thermocompression bonded by a thermal lamination method. By adopting this method, the sealant layer and the second adhesive layer are crystallized, and the crystal lamella with the developed sealant layer has a barrier property against the electrolyte by promoting the crystallization by slowly cooling it in the cooling process. In addition, the polymer is entangled with the second adhesive layer composed of the same kind of polymer component, and is excellent in adhesiveness.
In addition, the crystal lamella developed in the second adhesive layer produces strong adhesion with the metal foil as the second adhesive layer and the barrier layer. As a result, the adhesive strength is increased and the crystal lamella particularly forms a boehmite film. This has the effect of entering into the pores of the boehmite film of the aluminum foil and realizing even higher adhesive strength and electrolyte resistance.

FIG. 2 shows a laminated film 14 of a second adhesive layer and a sealant layer by a thermal lamination method, and a base material layer / barrier layer laminated film 12 in which the base material layer is laminated and integrated with the barrier layer in advance by the first adhesive layer. The second adhesive layer / sealant layer laminated film 14 and the base material layer / barrier layer fed from the wound body 13 of the second adhesive layer / sealant layer laminated film The base material layer / barrier layer laminated film 12 fed from the laminated film wound body 11 and the heat-resistant resin film 16 fed from the heat-resistant film wound body 15 are heated and pressurized between the heating rolls 17A and 17B. As a result, the second adhesive layer side 14A of the second adhesive layer / sealant layer laminated film 14 and the barrier layer side 12A of the base material layer / barrier layer laminated film 12 are thermally laminated. That.
The heat-laminated laminate film 10 for battery exterior passes between the feed rolls 18A and 18B and is taken up by the take-up roll 20.
On the other hand, the heat-resistant resin film 16 is peeled off from the battery exterior laminate film 10 and wound up on a winding roll 19.

  In such a thermal lamination method, the heating temperature between the heating rolls 17A and 17B can be arbitrarily set at a temperature that reaches the temperature at which the second adhesive layer and the sealant layer melt, but the heating roll on the sealant layer side The temperature of 17A is 20 ° C. or more, preferably 25 to 100 ° C. higher than the melting point of the sealant layer (main sealant main layer), so that the cooling is further reduced in the cooling stage after heating, and the sealant layer and the second adhesive layer The lamellar crystal is easy to grow, which is preferable in terms of improving the adhesive strength between the sealant layer and the second adhesive layer and the adhesive strength between the second adhesive layer and the barrier layer. If the temperature of the heating roll 17A is lower than the lower limit, the sealant layer and the second adhesive layer tend not to melt and the adhesive strength tends to be insufficient. If the temperature is higher than the upper limit, the resin of the sealant layer and the second adhesive layer Tends to flow and the adhesive strength between the layers tends to decrease. The melting point of the sealant layer is usually about 120 to 168 ° C.

  In addition, the heating temperature in the thermal lamination is such that the temperature on the second adhesive layer side, that is, the temperature on the heating roll 17A and the temperature on the barrier layer side, that is, the temperature on the heating roll 17B is different. This is preferable because the crystal orientation of the acid-modified polyethylene resin of the adhesive layer 2 is further enhanced, crystal growth in the thickness direction is promoted, and the barrier layer is more strongly bonded. In this case, the temperature on the second adhesive layer side, that is, the temperature of the heating roll 17A is 170 ° C. or higher, for example, 200 ° C. or higher and 260 ° C. or lower, including the relationship with the melting point of the sealant layer. That is, the temperature of the heating roll 17B is less than 170 ° C., for example, 120 ° C. or more and 165 ° C. or less, and it is desirable to give a temperature difference of 10 ° C. or more, preferably 20 ° C. or more and 70 ° C. or less. If the temperature of the heating rolls 17A and 17B is too low, sufficient adhesion cannot be performed. However, if the temperature is too high, the resin deteriorates or melts and flows to reduce the thickness of the adhesive layer, resulting in sufficient adhesion. There is a tendency to disappear. Moreover, if the temperature difference between the two is too small, the effect of promoting crystal growth by providing the temperature difference cannot be sufficiently obtained, and excessively increasing this temperature difference is the setting temperature of each heating roll. It is difficult to meet the conditions.

In addition, when thermal lamination is performed at such a high temperature, the resin of the sealant layer may be welded to the heating roll. The purpose of preventing this welding is to promote the growth of the crystal lamella of the second adhesive layer on the surface of the barrier layer and the growth of the crystal lamella to the second adhesive layer of the sealant layer, thereby further strengthening the adhesion between the layers. For the purpose, it is preferable to overlap the heat resistant resin film 16 on the further outer side (non-bonded surface) of the sealant layer as shown in FIG. 2 and to peel off the heat resistant resin film 16 after thermal lamination.
At this time, a heat resistant resin film having a surface roughness Ra of 0.1 μm or more and 1 μm or less, preferably 0.25 μm or more and 0.75 μm or less by matting or the like in advance on at least the side of the heat resistant resin film that comes into contact with the sealant layer. When it is used, the unevenness of the heat-resistant film is thermally transferred to the sealant layer at the time of thermal lamination, and appropriate unevenness is imparted to the surface of the sealant layer, so that the slipperiness with the mold necessary for embossing can be obtained.

  The heat-resistant resin film 16 has excellent heat resistance, is not welded to the heating roll 17A during thermal lamination, and is not weldable to the sealant layer. For example, the melting point is higher than the temperature of the heating roll 17A, and the sealant layer A resin film made of a resin other than a polyethylene resin, which has a melting point of 20 ° C. or higher than the melting point and does not thermally bond with the polyethylene resin of the sealant layer is preferable. Particularly preferred is a thermoplastic resin film similar to the above-mentioned base material layer, which has a melting point 20 ° C. or more higher than the melting point of the sealant layer, for example, a melting point of 150 ° C. or more, preferably 200 to 350 ° C. Can be used. Specifically, a biaxially stretched PA film, a biaxially stretched PET film, a biaxially stretched PP film, a uniaxially stretched PP film, an unstretched PP film, and the like are preferable. The thickness of the heat resistant resin film 16 is usually 25 μm or more and 125 μm or less. If the heat-resistant resin film 16 is too thin, the crystal lamella growth promoting effect due to the provision of the heat-resistant resin film 16 may not be sufficiently obtained, and if it is too thick, the heating efficiency during thermal lamination tends to deteriorate. is there.

[Battery exterior materials]
The laminated film for battery exterior of the present invention can be processed into a battery exterior material according to a conventional method.
The battery exterior material forms an exterior body that wraps the battery body, and there are a pouch type and an emboss type depending on the type.

FIG. 3 shows an embodiment of an embossed type exterior material. The first exterior material 31 is formed with a recess that serves as a housing portion 31b of the battery body 30, and a flange (flange) 31a is formed at the periphery of the opening. Has been. The second exterior material 32 is a lid material that covers the opening of the first exterior material 31. As for the 1st exterior material 31, the inner wall side of the accommodating part 31b becomes a sealant layer, and as for the 2nd exterior material 32, the contact surface side to the 1st exterior material 31 becomes a sealant layer.
A film made of polypropylene or the like is wound as a tab seal layer (not shown) on the electrode tab where the electrode tabs 30A and 30B come into contact with the flange portion (flange) 31a and the second exterior member 32.
The battery is assembled by covering the second exterior member 32 with the first exterior member 31 with the electrode tabs 30A and 30B pulled out, and heat-sealing the periphery.

In addition to the embossed type exterior material having the recesses formed on one side in this way, there is a type in which the recesses are formed on both exterior materials. In addition, there is a type in which a lid piece portion corresponding to the second exterior material extends from the flange on one side of the first exterior material.
On the other hand, the pouch type has a bag shape such as a three-side seal type, a four-side seal type, and a pillow type.

  The laminate film for battery exterior of the present invention can be used as various battery exterior materials including embossed type, pouch type and the like.

[battery]
The battery of the present invention is one in which a battery body is enclosed in an exterior material made of the laminate film for battery exterior of the present invention, and in various batteries such as lithium batteries and fuel cells, it is light, thin, small, and low in cost. In addition, long-term durability and reliability can be improved.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples and comparative examples, the materials used for forming the sealant layer and the second adhesive layer are as shown in Table 1 below.
The acid-modified LLPE used as the second adhesive layer is mainly composed of LLPE having butene-1 as a side chain, and an ethylene-propylene copolymer (EPR) having an ethylene content of 70%. Acid-modified high-density polyethylene (HDPE) is blended.

[Examples 1-9, Comparative Examples 1-3]
A laminate film for battery exterior was produced by the following method.
As the barrier layer, a JIS 8079-O material (soft aluminum foil containing 1.0% by weight of iron) having a thickness of 40 μm subjected to boehmite treatment was used.
Boehmite treatment was performed by immersing the aluminum foil in 95 ° C boehmite treated water in which triethanolamine was added to deionized water at a concentration of 0.5% by weight for 1 minute. A needle-like crystal film was formed.

Next, as a base material layer, a biaxially stretched polyamide film (tensile elastic modulus 2500 MPa, density 1.148 g / cm ³ ) having a thickness of 25 μm and a surface roughness Ra of 0.03 μm and subjected to a single-side corona treatment is used. Laminate one side of the aluminum foil and the corona-treated side of the biaxially stretched polyamide film via an adhesive layer for dry lamination (first adhesive layer) of .5μm aromatic polyester and polyisocyanate. It was.

  The film of the sealant layer and the second adhesive layer is made of the materials shown in Table-1 and Table-2, using a single-layer inflation molding machine extruded from an extruder with a diameter (barrel inner diameter) of 75 mm, an annular die diameter of 300 mm, Extruded from a spiral annular die with a die gap of 1.5 mm, taken up at a tube diameter of 560 mm, a blow-up ratio of 1.87, a take-up speed of 15 m / min, and the thicknesses of the second adhesive layer and sealant layer are shown in Table-2. Each monolayer film was formed while adjusting the extrusion amount of the extruder so as to achieve the predetermined thickness described.

  Using the film of the second adhesive layer and sealant layer obtained by the above-described method, as shown in FIG. 2, the surface of the second adhesive layer is on the aluminum foil side and the surface of the sealant layer is on the heat-resistant resin film side. The laminate was laminated with a dry lamination laminated film of biaxially stretched nylon film / aluminum foil by a thermal lamination method. In this thermal lamination, the temperature of the heating roll 17A on the sealant layer laminated film side was 200 ° C., and the temperature of the heating roll 17B on the biaxially oriented nylon film / aluminum foil laminated film side was 180 ° C. As the heat resistant resin film 16, a 75 μm thick PET film (melting point: 260 ° C.) was used. The surface of the PET film in contact with the sealant layer has irregularities with a surface roughness Ra of 0.06 μm.

The laminate film for battery exterior thus obtained was evaluated for laminate strength, seal strength, electrolytic solution resistance, and adhesive strength with the tab seal layer (tab seal strength) by the following methods. It was shown to.
In addition, the unevenness | corrugation of surface roughness Ra0.06micrometer was formed in the sealant layer surface of the obtained laminate film for battery exteriors by the surface unevenness | corrugation of PET film used as a heat resistant resin film.

<Lamination strength>
For the laminate strength between the aluminum foil and the second adhesive layer, a sample cut into a strip shape with a width of 15 mm was used, and the 180 ° peel strength at the interface between the aluminum foil and the second adhesive layer was measured using a Tensilon tensile test. It measured on the conditions of the tension speed of 50 mm / min using the machine, and this value was made into laminate strength.

<Seal strength>
The sealant layers of the two laminate films for battery exterior that were cut in advance to 65 mm × 65 mm were used at 220 ° C. over a seal width of 10 mm and a length of 65 mm using a heat sealer “OPL-200-10” with a single-side heater manufactured by Fuji Impulse. Then, heat sealing was performed under conditions of a sealing pressure of 0.45 MPa and a heat sealing time of 5 seconds, and the mixture was left standing at 23 ° C. for 24 hours or more, and then the seal portion was cut into a strip having a width of 15 mm to obtain a sample for measuring the seal strength.
The seal strength was measured at a pulling speed of 300 mm / min using a Tensilon tensile tester so that the sealant layers were peeled off from each other.

<Electrolytic solution resistance (laminate strength and seal strength after immersion in electrolytic solution)>
Using ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 (volume ratio) as a mixed solvent, 1 mol of lithium hexafluorophosphate was dissolved in this mixed solvent, and 1 mol / L of lithium hexafluorophosphate was dissolved. A solution electrolyte was prepared.
This electrolytic solution is put into a blow bottle made of PFA (perfluoroalkoxy fluororesin), and the above-mentioned seal strength measurement sample and unsealed laminate strength measurement sample are put in the electrolytic solution, and the lid is closed. The heat cycle of leaving in a constant temperature water bath at 80 ° C. for 12 hours and then returning to room temperature and returning to room temperature for 12 hours was repeated three times (total 80 ° C. for 36 hours, left at room temperature for 36 hours). The laminate strength and the seal strength were measured in the same manner as above.

<Tab seal strength>
A random PP film (Novatech EG6D 100 μm (thickness) film made by Nippon Polypro Co., Ltd.) cut into 65 mm × 65 mm as a tab seal film, and two sealant layers of a battery exterior laminate film previously cut into 65 mm × 65 mm Between the above, the random PP film cut into 65 mm × 65 mm is put, and a heat sealer “OPL-200-10” with one side heater manufactured by Fuji Impulse Co., Ltd. is used, and the seal pressure is 220 ° C. over a seal width of 10 mm and a length of 65 mm. Heat sealing was performed under the conditions of 0.45 MPa and a heat sealing time of 5 seconds. Then, after standing for 24 hours or more at 23 ° C., the strip was cut into three strips with a width of 15 mm, and the sealant layers of the above sample for measuring the seal strength were peeled off, and using a Tensilon tensile tester, the tensile speed was 300 mm. The adhesive strength with the tab seal film was measured at / min.

From Table 2, the laminate film for battery exterior having a sealant layer made of a polyethylene resin mainly composed of linear low density polyethylene (LLPE) satisfying the MFR, density and tensile modulus defined in the present invention is It turns out that it is excellent in adhesiveness, sealing performance, heat resistance, electrolyte solution resistance, and adhesiveness with a tab seal layer. On the other hand, in Comparative Examples 1 to 3 in which the sealant layer is composed of low-density polyethylene and / or high-density polyethylene, the sealing property, the electrolytic solution resistance, and the adhesiveness with the tab seal layer are poor.
In Table 2, “Comprehensive evaluation” was determined based on the following criteria as a battery exterior laminate film.
○: Laminate strength, seal strength, and tab seal strength are excellent.
Δ: Laminate strength, seal strength, and tab seal strength are at a usable level.
X: Laminate strength, seal strength, and tab seal strength are insufficient.

DESCRIPTION OF SYMBOLS 1 Base material layer 2 1st contact bonding layer 3 Barrier layer 4 2nd contact bonding layer 5 Sealant layer 10 Laminate film for battery exterior 12 Base material layer / barrier layer laminated film 14 2nd adhesion layer / sealant layer laminated film 16 Heat resistance Resin film 17A, 17B Heating roll 30 Battery body 31 First exterior material 32 Second exterior material

Claims (10)

A laminated film for battery exterior comprising at least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer laminated in this order, wherein the sealant layer is a linear low density polyethylene (LLPE) made of polyethylene resin as a main component, and, MFR0.1g / 10min or 3 g / 10min or less, density of 0.918 g / cm ³ or more 0.950 g / cm ³ or less, more tensile modulus 100 MPa 1500 MPa or less A laminate film for battery exterior, comprising a sealant main layer. The second adhesive layer is made of a polyethylene resin containing LLPE as a main component, at least a part of the polyethylene resin is acid-modified, and has an MFR of 0.1 g / 10 min to 3 g / 10 min, and a density of 0.920 g / The laminate film for battery exterior according to claim 1, wherein the laminate film has a tensile modulus of 100 MPa or more and 1000 MPa or less and a cm ³ or more and 0.950 g / cm ³ or less. The density of either or both of the sealant main layer and the second adhesive layer is 0.928 g / cm ³ or more, and the density difference between the two is 0.015 g / cm ³ or less. The laminate film for battery exterior according to claim 1 or 2.   The battery barrier laminate film according to any one of claims 1 to 3, wherein the barrier layer is made of an aluminum foil that is not subjected to chromium-based chemical conversion treatment.   5. The laminated film for battery exterior according to claim 1, wherein the barrier layer is made of an aluminum foil having a boehmite film formed on a surface thereof.   An inflation molding step of forming the sealant main layer forming film by an inflation molding method in which the film forming material of the sealant main layer is extruded from an annular die, and a sealant layer having the sealant main layer forming film are second bonded. The method for producing a laminate film for battery exterior according to any one of claims 1 to 5, further comprising a thermal lamination step of bonding to the barrier layer by a thermal lamination method through a layer.   The laminated film for battery exterior according to claim 6, wherein the second adhesive layer is a film formed by an inflation molding method in which a film forming material of the second adhesive layer is extruded from an annular die. Manufacturing method.   8. The heat lamination is performed by heating the sealant layer side of the laminate film for battery exterior with a heating roll having a temperature of 20 ° C. or more higher than the melting point of the sealant layer. Manufacturing method for laminate film for battery exterior.   In the thermal lamination step, when the barrier layer and the sealant layer are bonded together via the second adhesive layer, the melting point is 20 ° C. or more higher than the melting point of the sealant layer on the non-bonded surface on the sealant layer side. The battery exterior according to any one of claims 6 to 8, wherein a heat resistant resin film made of a resin other than polyethylene resin is stacked and thermally laminated, and then the heat resistant resin film is peeled off from the sealant layer. Method for manufacturing laminated film.   A battery comprising the laminate film for battery exterior according to any one of claims 1 to 5.

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