CN112703111A

CN112703111A - Polyamide-based laminated film and method for producing same

Info

Publication number: CN112703111A
Application number: CN201980050200.9A
Authority: CN
Inventors: 松本真实
Original assignee: Unitika Ltd
Current assignee: Unitika Ltd
Priority date: 2018-07-31
Filing date: 2019-07-30
Publication date: 2021-04-23
Anticipated expiration: 2039-07-30
Also published as: CN112703111B; JP7336142B2; JPWO2020027089A1; TW202015916A; WO2020027089A1

Abstract

The present invention addresses the problem of providing a polyamide-based laminated film that exhibits excellent electrolyte resistance even when the protective layer is thin. The polyamide-based laminated film of the present invention is characterized by comprising a polyamide-based film base (11) and a protective layer (12) formed on at least one surface of the base, wherein (1) the protective layer (12) is formed so as to be in direct contact with the surface of the polyamide-based film base (11); (2) at least 1 protective layer (12) is disposed as the outermost surface layer of the polyamide-based laminated film; (3) the protective layer (12) contains a copolyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and in which the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of structural units derived from dicarboxylic acid; (4) the thickness of the protective layer is 1.5 μm or less.

Description

Polyamide-based laminated film and method for producing same

Technical Field

The present invention relates to a polyamide-based laminated film used for packaging or coating various products, particularly electronic components, electronic devices, and the like.

Background

Conventionally, a laminate film including a polyamide film has been often used as an exterior material of a battery (a lithium ion secondary battery or the like). As a representative example, a laminate in which a polyamide film, an aluminum foil, and a sealing layer are laminated in this order is known. In a lithium ion secondary battery using this laminate as a casing, the laminate is processed into a container shape such that the polyamide film is disposed on the outside of the battery and the sealing layer is disposed on the inside (inside of the battery). After the electrodes and the like are packed in the container, an electrolyte is injected.

In manufacturing such a lithium ion secondary battery, a step of injecting an electrolyte solution into the battery, a step of heat-sealing an exterior material after the injection, and the like are performed. In these steps, the electrolyte solution may spill out and adhere to the polyamide film on the outer side of the exterior material. Since the polyamide film has low resistance to an electrolytic solution (electrolytic solution resistance), when the polyamide film is disposed on the outer side as in the laminate, the surface of the film is whitened or a decomposition reaction occurs when the electrolytic solution adheres to the polyamide film. As a result, appearance defects of the product, a decrease in strength of the film, and the like may be caused. Further, when the electrolytic solution enters from the deteriorated portion of the polyamide film and comes into contact with the aluminum foil, there is a concern that the aluminum foil is corroded. In this case, the exterior material loses its required strength.

In order to solve the above-described problems, a method of providing a protective layer on the outer surface of the polyamide film has been proposed. For example, patent document 1 discloses an exterior material using a polyethylene terephthalate film as a protective layer. Patent document 2 discloses an exterior material using a film obtained by stretching a laminate of a polyester film and a polyamide film. Patent documents 3 to 5 disclose exterior materials in which a coating layer containing a specific resin is laminated as a protective layer on the outermost layer.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2002-56824

Patent document 2: japanese patent laid-open publication No. 2013-240938

Patent document 3: japanese patent laid-open No. 2000-123799

Patent document 4: japanese patent laid-open No. 2014-176999

Patent document 5: japanese patent laid-open publication No. 2014-176998

Disclosure of Invention

Problems to be solved by the invention

The exterior material of patent documents 1 to 2 uses a polyester film as a protective layer of a polyamide film. However, since a step of laminating a polyester film is required in addition to a step of providing an adhesive layer between a polyamide film and a polyester film, the production process becomes complicated, and cost reduction is hindered. In addition, the total weight of the battery is disadvantageous in terms of weight reduction of the battery because the weight of the adhesive increases.

The coating layers disclosed in patent documents 3 to 5 contain resin components such as polyvinylidene chloride and polyurethane. However, in order to impart a sufficient protective function to the electrolytic solution, it is necessary to secure a thickness of at least 1 μm or more as the protective layer. Therefore, the material cost of the protective layer itself increases, and the energy cost required for the drying step also increases, which is economically disadvantageous. In addition, since the protective layer is formed by the post-coating method, the number of steps increases, which may increase the cost, and the heat generated in the drying step may adversely affect the physical properties of the base film.

Accordingly, a main object of the present invention is to provide a polyamide-based laminated film which can exhibit excellent electrolyte resistance even when the protective layer is thin.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by providing a protective layer comprising a specific copolyester resin on the surface of a polyamide film, and have completed the present invention.

That is, the present invention relates to the following polyamide-based laminated film and a method for producing the same.

1. A polyamide-based laminated film comprising a polyamide-based film substrate and a protective layer formed on at least one surface of the substrate,

(1) the protective layer is formed so as to be in direct contact with the surface of the polyamide film base material;

(2) at least 1 protective layer is disposed as the outermost surface layer of the polyamide-based laminated film;

(3) the protective layer contains a copolyester resin containing a dicarboxylic acid component and a diol component as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is contained in an amount of 50 mol% or more based on 100 mol% of a structural unit derived from a dicarboxylic acid; and

(4) the thickness of the protective layer is 1.5 μm or less.

2. The polyamide-based laminated film according to the above item 1, which satisfies the following formula (1):

(HzX) - (Hz0) < 3.0 … formula (1)

(wherein Hz0 is a haze value measured according to JIS K7136, HzX is a haze value measured in the same manner as Hz0 after an electrolyte solution in which LiPF is added to a mixed solution containing ethylene carbonate/diethyl carbonate/methylethyl carbonate at a volume ratio of 1: 1: 1 (volume ratio) is adhered to a protective layer after Hz0 is measured, and the protective layer is kept at 23 ℃ and 50% RH for 12 hours₆Diluted to a concentration of 1 mol/L. )

And Hz0 is in the range below 10.

3. The polyamide laminated film according to item 1 above, wherein the surface roughness (Ra) of the protective layer is 45nm or less.

4. The polyamide laminated film as described in the above item 1, wherein the glass transition temperature of the copolyester resin is 60 to 145 ℃.

5. The polyamide-based laminated film according to item 1 above, wherein the protective layer further comprises at least 1 of a melamine resin, an isocyanate compound, a carbodiimide compound, and an oxazoline compound.

6. The polyamide laminated film according to any one of the above items 1 to 5, wherein the polyamide laminated film is laminated such that the protective layer is in direct contact with at least one surface of the polyamide film base material, and the polyamide laminated film is a laminate comprising:

(a) a laminate comprising a protective layer, a polyamide film base material, a barrier layer, and a heat-sealing layer in this order; or (b) a laminate comprising a protective layer, a polyamide-based film substrate, a protective layer, a barrier layer, and a heat-sealing layer in this order.

7. The polyamide-based laminated film according to any one of the above items 1 to 6, which is used for packaging an article.

8. A battery, comprising:

a power generation element including a negative electrode, a positive electrode, a separator, and an electrolyte; and

an exterior material for packaging the power generating element,

the exterior material is the polyamide-based laminate film according to any one of the above items 1 to 5, and the protective layer is disposed as an outermost layer of the battery.

9. A method for producing a polyamide-based laminated film according to any one of claims 1 to 5, comprising:

(1) a step of applying a coating liquid for forming a protective layer, which contains a copolyester resin containing a dicarboxylic acid component and a diol component as constituent components, and 50 mol% or more of dicarboxylic acid components having a naphthalene skeleton out of 100 mol% of the dicarboxylic acid components, to an unstretched polyamide film or a uniaxially stretched polyamide film; and

(2) and stretching the polyamide film having the coating film obtained by the coating to obtain a polyamide laminated film having a protective layer formed on one or both surfaces of a biaxially stretched film stretched in the MD and TD.

Effects of the invention

According to the present invention, a polyamide-based laminated film can be provided which can exhibit excellent electrolyte resistance even when the protective layer is thin.

In particular, since the protective layer of the polyamide-based laminated film of the present invention contains the copolyester resin in which the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more among the acid components, even if the thickness of the protective layer is 1.5 μm or less, excellent electrolyte resistance can be exhibited. Therefore, even when the electrolytic solution adheres, whitening, decomposition reaction, and the like of the polyamide film can be effectively suppressed. As a result, the strength of the polyamide-based laminated film can be maintained.

Further, since the surface roughness of the protective layer is small (the unevenness is small), the droplets are less likely to be retained even when the electrolytic solution adheres thereto. Therefore, the deterioration of the protective layer due to the adhesion of the electrolytic solution for a long time can be prevented.

Further, since the thickness of the protective layer is small, the polyamide-based laminated film can be made thin, and therefore, even when the polyamide-based laminated film is coated in a state of being closely adhered to the package, excellent molding follow-up properties can be obtained. Therefore, the resin composition is suitably used for a lithium ion secondary battery outer covering material and the like which require adhesiveness and the like.

Since the thickness of the protective layer is as thin as 1.5 μm or less, it can be easily formed under relatively mild heat treatment conditions, and therefore, the influence on the physical properties of the polyamide film substrate can be minimized. This also contributes to the realization of a polyamide-based laminate film that has excellent electrolyte resistance, mechanical properties, blocking resistance, and the like.

In particular, an electrolyte solution used in a lithium ion secondary battery is a conductive liquid prepared by dissolving an ionic substance in a polar solvent. Lithium hexafluorophosphate (LiPF) is generally used as the ionic substance₆)。LiPF₆When reacted with water, hydrofluoric acid (hydrogen fluoride) is produced as a strongly acidic medium. Therefore, when the electrolyte adheres to the air, moisture in the air and LiPF in the electrolyte may be mixed₆Reacting to produce hydrofluoric acid. The polyamide film used for the exterior material of the lithium ion secondary battery is dissolved by the hydrofluoric acid. In contrast, the polyamide-based laminated film of the present invention has the specific protective layer as described above, and therefore includes LiPF₆Etc., the strength of the polyamide film can be maintained without deterioration.

In the production method of the present invention, since the specific coating liquid for forming the protective layer can be applied by in-line coating (japanese: インラインコート) to form the protective layer, a polyamide-based laminate film excellent in the electrolyte resistance as described above can be produced on an industrial scale at low cost. In particular, since the thickness of the protective layer can be as thin as 1.5 μm or less, it can be easily formed by in-line coating under relatively mild conditions, and as a result, the influence on the physical properties of the polyamide-based film substrate and the like can be minimized. In this regard, it is also useful to realize a polyamide-based laminate film which is excellent in electrolyte solution resistance, mechanical properties, blocking resistance and the like.

In the production method of the present invention, the specific coating liquid for forming the protective layer is applied in-line to form the protective layer, and therefore the surface of the protective layer can be made more flat. This also contributes to improvement in electrolyte resistance. Although the cause thereof is not clear, it is presumed to be caused by the following mechanism of action. In the inline coating method, the coating film obtained from the coating liquid for forming the protective layer is subjected to stretching and heat treatment together with the polyamide film, and the stretching and heat treatment simultaneously form a high-density film mainly composed of a copolyester resin, so that the surface of the protective layer becomes smooth and a surface with less surface irregularities can be formed. As a result, it is presumed that the protective layer surface is a surface having few irregularities, and therefore, the electrolytic solution is not likely to remain even if it adheres thereto, and a protective layer having high protective performance against the electrolytic solution can be obtained.

The polyamide-based laminated film of the present invention having such characteristics is suitably used for applications where there is a concern that an electrolytic solution (or an acidic liquid) may adhere. In particular, the laminate is suitable for use as a packaging material for various batteries (particularly, laminate type batteries) typified by lithium ion secondary batteries.

Drawings

Fig. 1 is a view showing an embodiment of a polyamide-based laminated film of the present invention.

Fig. 2 is a view showing an embodiment of the polyamide-based laminated film of the present invention.

Fig. 3 is a conceptual diagram illustrating a method for measuring the thickness accuracy of the polyamide-based laminated film of the present invention.

Fig. 4 is an external view showing a battery using the polyamide-based laminate film of the present invention as an exterior material.

Fig. 5 is a schematic view showing the structure of a battery using the polyamide-based laminated film of the present invention as an exterior material.

Fig. 6 is a schematic diagram showing the structure of a battery using the polyamide-based laminated film of the present invention as an exterior material.

Detailed Description

1. Polyamide-based laminated film

The polyamide-based laminated film of the present invention (film of the present invention) is characterized by comprising a polyamide-based film substrate and a protective layer formed on at least one surface of the substrate,

(3) the protective layer contains a copolyester resin which contains a dicarboxylic acid component and a diol component as constituent components, and in which the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of structural units derived from dicarboxylic acid; and

(4) the thickness of the protective layer is 1.5 μm or less.

A. Layer Structure of the inventive film

As described above, the film of the present invention is basically composed of a polyamide-based laminated film including a polyamide-based film substrate and a protective layer formed on at least one surface of the substrate. That is, the laminate basically has a structure in which a protective layer is formed so as to be adjacent to one side or both sides of a polyamide film base material without an adhesive layer interposed therebetween.

Fig. 1 shows an example of the layer structure of the film of the present invention. Fig. 1A shows a laminate (inventive film) 10 in which a protective layer 12 is laminated on one surface of a polyamide film base material 11. Fig. 1B shows a laminate (inventive film) 10' in which

protective layers

12 and 12 are laminated on both sides of a polyamide film base 11. In these cases, the protective layer of either case is configured as the outermost surface layer (outermost layer). By exposing the protective layer as the outermost surface layer in this manner, for example, when a package (bag or the like) using the film of the present invention is produced with the protective layer facing outward, the contents of the package can be protected from the outside.

In the film of the present invention, as long as the protective layer is formed directly on the polyamide-based film substrate as described above and at least 1 protective layer is disposed as the outermost surface layer, other layers may be further laminated. Examples thereof include a barrier layer (gas barrier layer, water vapor barrier layer, etc.), a printing layer, a heat-sealing layer (adhesive layer, sealing layer, heat-sealing layer), a primer layer (anchor coating layer), an antistatic layer, a vapor-deposited layer, an ultraviolet absorbing layer, and an ultraviolet blocking layer.

Fig. 2 shows an example of the layer structure of a polyamide-based laminated film in which other arbitrary layers are laminated in addition to a polyamide-based film base material and a protective layer. Fig. 2A shows a laminate 20 in which a barrier layer 13 and a heat-sealing layer 14 are further laminated in this order on the laminate 10 of fig. 1A. In this laminate 20, the barrier layer 13 and the heat-seal layer 14 are laminated on the surface of the polyamide film base 11 on which the protective layer 12 is not formed, and thus the protective layer 12 is maintained in an exposed state as the outermost surface layer. Fig. 2B shows a laminate 20 'in which a barrier layer 13 and a heat-sealing layer 14 are further laminated in this order on the laminate 10' of fig. 1B. In this laminate 20', the barrier layer 13 and the heat-sealing layer 14 are laminated on the protective layer 12 on either side of the polyamide film base 11, but the other protective layer 12 is left exposed as the outermost surface layer. In addition, as shown in fig. 2, in the case where the film of the present invention has a heat-fusion layer, the heat-fusion layer is disposed as the outermost surface layer.

Hereinafter, in addition to the polyamide-based film base material and the protective layer constituting the film of the present invention, each of the arbitrary layers will be described.

A-1. Polyamide-based film substrate

The polyamide film base material is a base material (core material) of the film of the present invention, and is usually provided in the form of a film formed in advance. The polyamide-based film substrate may have a single-layer structure, or may have a multilayer structure in which 2 or more polyamide-based films are laminated. In the case of a multilayer structure, the layers may have the same composition or different compositions.

The polyamide-based film base material contains a polyamide-based resin as a main component, and may contain other components. In this case, the content ratio of the polyamide resin in the polyamide film base is not limited, but is preferably 70 to 100% by mass, particularly 90 to 99.5% by mass.

As the polyamide resin, any thermoplastic resin that can be melt-molded and has an amide bond (-CONH-) in its molecule may be used, and known or commercially available resins can be used. Thus, for example, polyamides obtained by polycondensation of lactams, omega-amino acids or dibasic acids with diamines are mentioned.

The lactams include, for example,. epsilon. -caprolactam, enantholactam, caprylolactam, and laurolactam.

Examples of the omega-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid.

The dibasic acids include, for example: adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecanedioic acid, eicosanedioic acid, 2, 4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, xylylenedicarboxylic acid, and the like.

The diamines include, for example: ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, 2,4 (or 2,4,4) -trimethylhexamethylenediamine, cyclohexanediamine, bis- (4, 4' -aminocyclohexyl) methane, m-xylylenediamine, and the like.

As the polymer obtained by polycondensing them or the copolymer thereof, for example:

nylon

6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 9T, 10T, 6I, MXD6 (poly m-xylylene adipamide), 6/6.6, 6/12, 6/6T, 6/6I, 6/MXD6 and the like. These may be used in 1 or 2 or more. Among these, the polyamide resin preferably contains nylon 6 from the viewpoint of excellent balance between heat resistance and mechanical properties.

The relative viscosity of the polyamide resin used for the polyamide film substrate is not particularly limited, but is preferably about 1.5 to 5.0, and more preferably 2.0 to 4.0. If the relative viscosity of the polyamide is less than 1.5, the mechanical properties of the resulting film may be significantly reduced. On the other hand, if the relative viscosity exceeds 5.0, the film formability of the film is easily impaired. The relative viscosity was measured by using an Ubbelohde viscometer to obtain a sample solution (liquid temperature 25 ℃) in which polyamide was dissolved in 96% sulfuric acid to have a concentration of 1.0 g/dl.

As described above, the polyamide-based film base material may contain other components in addition to the polyamide-based resin within a range not to impair the effects of the present invention. Other components include known or commercially available additives. More specifically, examples thereof include metals (metal ions), pigments, heat stabilizers, antioxidants, weather-resistant agents, flame retardants, plasticizers, mold release agents, reinforcing agents (fillers), and the like. In particular, as the heat stabilizer or the antioxidant, hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and the like are suitably used.

In order to improve the sliding property of the film, it is preferable that at least 1 of the inorganic lubricant and the organic lubricant is contained in a range where the surface roughness (Ra) satisfies 45nm or less. Specific examples of the lubricant include inorganic lubricants such as clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass hollow spheres (Japanese: ガラスバルーン), carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, and layered silicate; organic lubricants such as erucamide, oleamide, stearamide, ethylene bis oleamide, hexamethylene bis stearamide, and hexamethylene bis oleamide methylene bis stearamide.

The thickness of the polyamide-based film substrate is not particularly limited, but is preferably 4 to 30 μm, and more preferably 5 to 25 μm. If the thickness is less than 4 μm, the mechanical strength tends to be insufficient, and the moldability tends to be lowered. On the other hand, if the thickness exceeds 30 μm, the weight increases, and it becomes difficult to use the film for applications where weight reduction is desired. If the mechanical strength is sufficient, the thinner one can enclose more electrolyte, and therefore, it is preferable to secure the content amount and the electric capacity.

In addition, from the viewpoint of mechanical strength, the polyamide-based film substrate is preferably a stretched substrate. That is, a structure having orientation is preferable. In this case, the stretching may be either uniaxial stretching or biaxial stretching, but the orientation by biaxial stretching is particularly preferable. The stretch ratio can be appropriately set within the range described below.

The polyamide film base material preferably has a surface on at least one side of which a known surface treatment such as a corona treatment, a plasma treatment, or an ozone treatment is performed in order to improve the adhesion force between layers constituting the laminate when the laminate is produced. The surface roughness is particularly preferably 10nm or more. Further, from the viewpoint of electrolyte resistance and improvement of blocking resistance, it is preferably the same as or above the surface roughness of the protective layer surface. That is, in the present invention, "protective layer surface roughness ≦ polyamide base material film surface roughness" is preferable.

A-2 protective layer

The protective layer contains a copolyester resin containing a dicarboxylic acid component and a diol component (glycol component) as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of structural units derived from dicarboxylic acid (hereinafter, this specific copolyester resin is referred to as "copolyester resin a"). As such a copolyester resin a, for example, there can be suitably used: a copolymer obtained by polycondensation of the dicarboxylic acid component and the diol component.

(a) Copolyester resin A

Dicarboxylic acid component

The dicarboxylic acid component is not particularly limited, and examples thereof include: aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 2, 3-naphthalenedicarboxylic acid, 4-dicarboxybiphenyl, phenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, and sodium 5-sulfonedicarboxylic acid (Japanese: 5- ナトリウムスルホンジカルボン acid); aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, dimer acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid; alicyclic dicarboxylic acids such as 1, 4-cyclohexanedicarboxylic acid; hydroxycarboxylic acids such as p-hydroxybenzoic acid, and the like. These may be used in 1 or 2 or more.

Of these, examples of the dicarboxylic acid component having a naphthalene skeleton (hereinafter also referred to as "dicarboxylic acid component A") include 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 2, 3-naphthalenedicarboxylic acid, and the like. Among them, in the present invention, 2, 6-naphthalenedicarboxylic acid is particularly preferable from the viewpoint of small steric hindrance and high crystallinity.

In the present invention, the dicarboxylic acid component a is contained in the dicarboxylic acid-derived structural unit (100 mol%) at usually 50 mol% or more, particularly preferably 60 mol% or more, further more preferably 70 mol% or more, and most preferably 80 mol% or more. This ensures higher resistance to electrolyte solution. The upper limit of the content of the dicarboxylic acid component is not particularly limited, and may be usually about 95 mol%.

In this case, the content of the dicarboxylic acid component other than the dicarboxylic acid component a (hereinafter referred to as "dicarboxylic acid component B") is not particularly limited, and is usually about 1 to 50 mol%, and particularly preferably 5 to 45 mol%, in the dicarboxylic acid-derived structural unit (100 mol%).

In the present invention, terephthalic acid is particularly preferably used as the dicarboxylic acid component B from the viewpoint of small steric hindrance and high crystallinity. When terephthalic acid is contained, the content of terephthalic acid in the dicarboxylic acid-derived structural unit (100 mol%) is not particularly limited, but is usually about 3 to 50 mol%, particularly preferably 5 to 45 mol%, and most preferably 10 to 40 mol%. Therefore, in the present invention, the dicarboxylic acid component can be suitably used in a composition containing 2, 6-naphthalenedicarboxylic acid and terephthalic acid. More specifically, there may be mentioned: the dicarboxylic acid-derived structural unit (100 mol%) has a composition in which the dicarboxylic acid-derived structural unit (100 mol%) contains 50 mol% or more of 2, 6-naphthalenedicarboxylic acid and 5 mol% or more of terephthalic acid. Thus, for example, it is also possible to employ: the dicarboxylic acid-derived structural unit (100 mol%) has a composition comprising 55 to 90 mol% of 2, 6-naphthalenedicarboxylic acid and 5 to 45 mol% of terephthalic acid, based on the dicarboxylic acid-derived structural unit (100 mol%).

In the present invention, the dicarboxylic acid component B may contain an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, but since a larger content thereof may lower the electrolyte resistance of the protective layer, the content of the aliphatic dicarboxylic acid is preferably 20 mol% or less, particularly preferably 15 mol% or less, and most preferably 5 mol% or less, among the constituent units derived from dicarboxylic acid (100 mol%).

In the case of using the dicarboxylic acid component B, the mixing ratio (molar ratio) of the dicarboxylic acid component a to the dicarboxylic acid component B is usually 50: 50-98: about 2, particularly preferably 80: 20-95: about 5.

Diol component

The diol component is not particularly limited, and examples thereof include: aliphatic dihydroxy compounds such as ethylene glycol, diethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; alicyclic dihydroxy compounds such as 1, 4-cyclohexanedimethanol and spiroglycol; and aromatic dihydroxy compounds such as bisphenol A. These may be used in 1 or 2 or more.

Among these, aliphatic dihydroxy compounds are preferable from the viewpoint of enhancing the electrolyte resistance, and among them, aliphatic dihydroxy compounds having 4 or less carbon atoms are more preferable. More specifically, at least 1 kind of ethylene glycol, diethylene glycol, 1, 2-propylene glycol, and 1, 3-propylene glycol may be mentioned.

The aliphatic dihydroxy compound is preferably contained in a proportion of usually 50 mol% or more, particularly preferably 60 mol% or more, further preferably 70 mol% or more, and most preferably 80 mol% or more, in a constituent unit (100 mol%) derived from a diol component. The upper limit of the content is set to 100 mol%, for example, but not limited thereto.

In the present invention, for example, an aliphatic diol having 5 or more carbon atoms such as 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol may be contained, but since the electrolyte resistance is liable to decrease when the content is too high, the content of the aliphatic diol having 5 or more carbon atoms is preferably about 0 to 25 mol% in 100 mol% of the structural units derived from the diol component.

Other copolymerization Components

When the copolyester resin A is made into an aqueous coating liquid for forming a protective layer, the dicarboxylic acid component B preferably contains a compound having a sulfo group (-SO)₃H) The dicarboxylic acid component (c) of (a), particularly preferably an aromatic dicarboxylic acid having a sulfo group). For example, at least 1 kind of isophthalic acid 5-sulfonic acid, isophthalic acid 2-sulfonic acid, isophthalic acid 4-sulfonic acid, terephthalic acid sulfonic acid, and 4-sulfonaphthalene-2, 6-dicarboxylic acid is preferable, and isophthalic acid 5-sulfonic acid is particularly preferable from the viewpoint of cost. That is, a dicarboxylic acid component having no naphthalene skeleton and having a sulfo group is preferably used as the dicarboxylic acid component B. In the case of a compound belonging to the dicarboxylic acid A, B, the content of the compound may be calculated as the dicarboxylic acid B.

The content of the dicarboxylic acid component having a sulfo group is preferably 3.5 to 30 mol%, more preferably 4 to 20 mol%, and even more preferably 4 to 10 mol% based on 100 mol% of the structural units derived from the dicarboxylic acid.

Physical Properties of copolyester resin A

The glass transition temperature of the copolyester resin A is preferably 60 ℃ or higher, particularly preferably 80 ℃ or higher, and most preferably 100 ℃ or higher. When the glass transition temperature is less than 60 ℃, the binding force between the molecular chains constituting the copolyester resin is weakened, and thus the electrolyte resistance may be poor.

On the other hand, as described later, the film of the present invention is preferably produced by applying a coating liquid for forming a protective layer to a polyamide film which has not been stretched or uniaxially stretched, and then stretching, but when the glass transition temperature of the copolyester resin a becomes high, the stretch following property with the polyamide film is lowered, and the film is likely to be cut, and therefore the glass transition temperature is preferably 145 ℃ or lower, more preferably 140 ℃ or lower.

In addition, the copolyester resin a may have a crosslinked structure. For example, the crosslinked structure can be formed by using a crosslinking agent that reacts with a carboxyl group or a hydroxyl group as a terminal group of the copolyester resin a. As a result, more excellent electrolyte resistance, physical properties, and the like can be exhibited. The crosslinking agent is not particularly limited as long as the above reaction can be carried out, but preferably contains at least 1 of a melamine resin, an isocyanate compound, a carbodiimide compound, and an oxazoline compound. These may be known or commercially available.

The crosslinking agent is preferably contained in the protective layer in an amount of 0.1 to 15% by mass, particularly preferably 0.1 to 10% by mass, and most preferably 2.5 to 7.5% by mass. By setting within such a range, more excellent electrolyte resistance and the like can be obtained.

Synthesis of copolyester resin A

The copolyester resin a can be synthesized basically according to a known method for producing a copolyester resin, except that the specific dicarboxylic acid component and diol component described above are used. That is, the copolyester resin a is preferably produced by a production method including a step of subjecting a dicarboxylic acid component containing 50 mol% or more of a dicarboxylic acid component having a naphthalene skeleton to a polycondensation reaction with a diol component in 100 mol% of the dicarboxylic acid component.

As the dicarboxylic acid component (dicarboxylic acid compound), in addition to the above-exemplified dicarboxylic acids, at least 1 of derivatives thereof such as metal salts thereof, acid anhydrides thereof, ester compounds thereof, and the like can be used. As these compounds, the same compounds as those used for synthesizing a known copolyester resin can be used.

As the diol component (diol compound), at least 1 kind of derivatives such as metal salts thereof, acid anhydrides thereof, and ester compounds thereof can be used in addition to the above-mentioned exemplified diols. These compounds themselves may be the same compounds as those used for synthesizing known copolyester resins.

The mixing ratio of the carboxylic acid component and the diol component may be appropriately set within a range in which a predetermined polycondensation reaction can be sufficiently performed, and generally, the ratio of the carboxylic acid component to the diol component is set in the following molar ratio: diol component 1: 0.5-1: the range of 1.5 may be set, but is not limited thereto.

Further, a polymerization catalyst may be added to the raw materials as needed. The polymerization catalyst is not limited, and a known catalyst can be used, and for example, a titanium-based catalyst such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate can be suitably used. The amount of the polymerization catalyst to be added is not particularly limited, and may be usually 5X 10 relative to 1 mole of the carboxylic acid component^-5～5×10^-4The molar range is appropriately adjusted.

The reaction system may be a liquid phase reaction, and the reaction can be carried out particularly in the absence of a solvent because the diol component is usually in a liquid state. An organic solvent can be used as necessary. In addition, as for the reaction atmosphere, the pressure may be any of normal pressure, reduced pressure (including vacuum), or increased pressure. The atmosphere gas may be an inert gas atmosphere such as nitrogen or argon.

The reaction is preferably carried out in 2 stages, the 2 stages comprising: the transesterification step in the 1 st stage and the polymerization step in the 2 nd stage.

The reaction temperature in the transesterification step is not particularly limited as long as the components are all melted, and may be usually set to about 200 to 260 ℃. The reaction time depends on the reaction temperature, and generally may be in the range of about 1 to 5 hours.

The reaction temperature in the polymerization reaction step is not particularly limited as long as the polymerization of the initial condensate (ester compound) can be carried out, and may be usually set to about 200 to 260 ℃. The reaction time depends on the reaction temperature, and generally may be in the range of about 1 to 5 hours. Particularly, in the polymerization reaction step, it is preferably carried out under reduced pressure or vacuum, more specifically, it is preferably 1X 10^-5 About 1X 10 Pa. Therefore, it can be set to, for example, 1 × 10^-4About 1X 5Pa, or may be set to 1X 10^-5～1×10^-1Pa or so.

Since the obtained reaction product is usually in a liquid state at normal temperature and normal pressure, it can be used as it is as a raw material of a coating agent for forming a protective layer. If necessary, the reaction product in liquid form may be subjected to a treatment such as solid-liquid separation or purification, and then separated. Thus, copolyester resin A was obtained.

In the present invention, the copolyester resin a may be further reacted with a crosslinking agent in order to impart a crosslinked structure to the copolyester resin a as required. When the crosslinking agent is contained, the crosslinking density of the protective layer is increased by the reaction with either or both of the carboxyl group and the hydroxyl group as the terminal group of the copolymerized polyester resin, and therefore, the electrolyte resistance of the protective layer can be further improved. In the case of the in-line coating method, the compound having a significant effect of improving the electrolyte resistance of the protective layer by the crosslinking agent is at least 1 of the blocked isocyanate and the oxazoline, and the oxazoline is particularly preferable.

The amount of the crosslinking agent to be added may be adjusted as long as it is contained in the protective layer in a specific ratio as described above, and may be adjusted within a range of about 1 to 15 parts by mass relative to 100 parts by mass of the copolyester resin a. When the crosslinking agent is added, the crosslinking agent may be added to and mixed with the copolyester resin a and held for a certain period of time. The holding temperature in this case is not particularly limited, and is usually about 5 to 30 ℃. The holding time is usually about 0 to 120 hours.

(b) Composition and physical Properties of protective layer

As described above, the protective layer contains the copolyester resin a, and the content of the copolyester resin a in the protective layer is preferably 70 to 100 mass%, and particularly preferably 80 to 95 mass%.

Therefore, the protective layer may contain components other than the copolyester resin a within a range not to impair the effects of the present invention. Examples thereof include: various additives such as lubricants, heat stabilizers, antioxidants, reinforcing materials (fillers), pigments, anti-deterioration agents, weather-resistant agents, flame retardants, plasticizers, mold release agents, and crosslinking agents. These may use the same additives as those suitable for the foregoing polyamide-based film substrate.

In particular, examples of the lubricant include: organic lubricants such as ethylene bisstearamide, organic particles such as acrylic particles, and inorganic particles such as silica. Since these may also function as an anti-blocking agent, it is preferable to add 1 or 2 or more of the above lubricants.

Examples of the heat stabilizer, the antioxidant and the deterioration inhibitor include: hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, or mixtures of these.

Examples of the reinforcing material include: clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminum silicate, magnesium silicate, glass hollow spheres, carbon black, zinc oxide, zeolite, hydrotalcite, metal fibers, metal whiskers, ceramic whiskers, potassium titanate whiskers, boron nitride, graphite, glass fibers, carbon fibers, and the like. These may be added in 1 or 2 or more.

From the viewpoint of further improving the electrolyte resistance, an inorganic layered compound may be further contained. The inorganic layered compound is an inorganic compound in which single crystal layers (japanese: crystal body run) are superposed to form a layered structure, and specifically, zirconium phosphate (phosphate derivative type compound), chalcogenide, lithium aluminum composite hydroxide, graphite, clay mineral, and the like are exemplified, and a substance that swells or cracks in a solvent is particularly preferable.

The thickness of the protective layer is required to be 1.5 μm or less, and particularly preferably 1 μm or less, from the viewpoints of improvement in productivity due to reduction in drying time, blocking resistance, and the like. The protective layer having a thickness of more than 1.5 μm may be uneven in the protective layer forming step or the drying step, may be deteriorated in productivity due to a long heat treatment time, may be economically disadvantageous due to an increase in cost of the coating solution, and may be inferior in blocking resistance.

On the other hand, the lower limit of the thickness of the protective layer is preferably 0.05 μm or more, particularly preferably 0.1 μm or more, more preferably 0.2 μm or more, and most preferably 0.4 μm or more, in order to sufficiently improve the resistance to an acidic liquid such as an electrolytic solution.

The surface roughness Ra of the protective layer surface (exposed surface) is not particularly limited, but is preferably 45nm or less, more preferably 40nm or less, and most preferably 35nm or less, from the viewpoint of improving the electrolyte resistance. If the surface roughness of the protective layer exceeds 45nm, the electrolyte may easily remain on the protective layer, and the electrolyte resistance may be impaired. The lower limit value of the surface roughness Ra may be, for example, 20nm or 15nm, but is not limited thereto. As described later, the surface roughness can be controlled to 45nm or less by forming a protective layer by an in-line coating method using a predetermined coating liquid for forming a protective layer.

A-3. other layers

As described above, the film of the present invention may have various layers laminated as necessary, in addition to the polyamide-based film base material and the protective layer. The same layers as those used for known packaging materials and the like can be used for each layer itself. As shown in fig. 2, the film of the present invention is effective as a battery exterior material, for example, a laminate comprising a protective layer/polyamide-based film base material/barrier layer/heat-sealing layer, a laminate comprising a protective layer/polyamide-based film base material/protective layer/barrier layer/heat-sealing layer, or the like. Preferred embodiments of the barrier layer and the heat-sealing layer will be described below.

Barrier layer

The barrier layer is particularly required to be a barrier layer that can exhibit gas barrier properties (oxygen barrier properties) and water vapor barrier properties, and a known or commercially available layer or film having barrier properties such as a metal foil or a vapor deposition film can be used. Among them, metal foils which are widely used are preferable. The metal foil is preferably an aluminum foil, but is not limited thereto. For example, various barrier layers used for exterior materials of lithium ion secondary batteries may be used.

The thickness of the barrier layer is not particularly limited, but is preferably about 20 to 200 μm, and more preferably 30 to 150 μm.

Further, it is preferable to perform surface treatment suitable for a lithium ion secondary battery exterior material on one or both surfaces of the barrier layer. Examples of the surface treatment include chemical conversion treatment and chromate treatment. In particular, these surface treatments are preferably applied to the side of the barrier layer that is in contact with the thermal bond.

Thermal welding layer

The heat-sealing layer is not particularly limited as long as it can be heat-sealed, and a known layer suitable for use in, for example, an exterior material of a lithium ion secondary battery can be used. Specifically, a polyvinyl chloride film, a polyolefin film, or the like can be suitably used. Examples of the polyolefin include polyethylene, polypropylene, a copolymer mainly composed of polypropylene, and acid-modified products thereof. Any of a stretched film and an unstretched film may be used for the heat-fusion layer.

The method for forming the heat-fusible layer is not particularly limited, and any method such as a method of applying a coating liquid containing a heat-fusible component, a method of laminating a film obtained by molding a resin composition containing a heat-fusible component into a film in advance, and the like can be used.

The thickness of the heat-sealing layer is not particularly limited as long as the desired heat-sealability can be obtained, but is generally preferably about 20 to 200 μm, and more preferably 30 to 100 μm.

B. Properties of the inventive film

The thickness (total thickness) of the film of the present invention can be appropriately set according to the use, the method of use, and the like. For example, when the film of the present invention is used as a battery exterior material, it is preferably about 10 to 25 μm, and more preferably 15 to 25 μm.

In addition, it is desirable that the film of the present invention has high thickness accuracy (thickness uniformity). That is, the standard deviation value with respect to the average thickness is usually preferably 0.200 or less, particularly preferably 0.180 or less, and most preferably 0.160 or less.

The above-described thickness accuracy evaluation method was performed as follows. After the film of the present invention was humidity-conditioned at 23 ℃ x 50% RH for 2 hours, as shown in fig. 3, a reference direction (0 degree direction) was designated around an arbitrary point a on the film, and then 8 lines L1 to L8 of 100mm in total were drawn from 8 directions, i.e., a center point a toward the reference direction (a), a 45 degree direction (b), a 90 degree direction (c), a 135 degree direction (d), a 180 degree direction (e), a 225 degree direction (f), a 270 degree direction (g), and a 315 degree direction (h), respectively, which were clockwise rotated with respect to the reference direction. On each straight line, the thickness was measured at intervals of 10mm from the center point A (10 points were measured) by a length measuring instrument "HEIDENHAIN-METRO MT 1287" (manufactured by Heidenhain Co.). Fig. 3 shows, as an example, a state in which a measurement point (10 points) is determined when L2 in the 45-degree direction is measured. Then, the average value of the measured values at 80 points in total of the data measured on all the straight lines was calculated, and the average thickness was used as the average thickness, and the standard deviation value from the average thickness was calculated. The reference direction is not particularly limited, and for example, MD in the stretching step in the film production may be used as the reference direction.

In the present invention, the average thickness and the standard deviation may be based on a point (point a) at any position of the polyamide film, and in particular, in the obtained polyamide film wound up on a film roll, it is more preferable that the average thickness and the standard deviation are within the above ranges at any point of the following 3 points. Point 3 is located at the following positions: a) a position near the center of the roll width and corresponding to half the roll amount; b) a position near the right end of the roll width and corresponding to half the roll amount; and c) a position near the left end of the roll width and near the end of the roll.

The film of the present invention has excellent electrolyte resistance, and preferably satisfies the following formula (1) as an index thereof.

(HzX) - (Hz0) < 3.0 … formula (1)

Hz 0: haze value measured according to Japanese Industrial Standard "JIS K7136". The measurement of the haze value may be performed using a commercially available measuring device (for example, a haze meter "NDH 4000" manufactured by japan electric color corporation).

HzX: after Hz0 was measured, the haze value was measured in the same manner as Hz0 after 12 hours at 23 ℃ and 50% RH in a state where an electrolyte solution shown below was allowed to adhere to the protective layer.

The electrolyte is used: in a solution containing ethylene carbonate/diethyl carbonate/ethyl methyl carbonate ═ 1: 1: 1 (volume ratio) mixed solution is mixed with LiPF₆And diluting the obtained liquid to a concentration of 1 mol/L. 10ml of this electrolyte solution was dropped onto the protective layer side, and the resultant was left to stand with the electrolyte solution adhered thereto at 23 ℃ and 50% RH for 12 hours. Thereafter, the electrolyte on the protective layer was wiped off with gauze and Hz0 was measured.

In this manner, the haze value before dropping of the electrolyte was Hz0, and the haze value measured after leaving for 12 hours after dropping of the electrolyte was HzX.

As described above, the value of the formula (1) is usually less than 3, particularly preferably 2 or less, further preferably 1.8 or less, and most preferably 1 or less. When the value of the above formula (1) is large, corrosion due to an electrolyte solution occurs, and as a result, whitening occurs, indicating poor electrolyte resistance. The lower limit of this value is not particularly limited, and may be, for example, 0.1.

The haze value (Hz0) of the film of the present invention before dropping of the electrolytic solution is not particularly limited, but is preferably 10 or less, and more preferably 5 or less, when the film is used for applications requiring transparency in particular. The lower limit of the haze value (Hz0) is not particularly limited, and may be, for example, about 0.1.

Further, as an index of excellent electrolyte resistance, the film of the present invention preferably satisfies the following formula (2).

(HzY) - (Hz0) < 3.0 … formula (2)

HzY: after Hz0 was measured, the haze value was measured in the same manner as Hz0 after 24 hours at 23 ℃ and 50% RH in a state where an electrolyte solution shown below was allowed to adhere to the protective layer.

The electrolyte is used: in a solution containing ethylene carbonate/diethyl carbonate/ethyl methyl carbonate ═ 1: 1: 1 (volume ratio) mixed solution is mixed with LiPF₆And diluting the obtained liquid to a concentration of 1 mol/L. 10ml of the electrolyte solution was dropped onto the protective layer side to attach the electrolyte solution, and the resultant was left at 23 ℃ and 50% RH for 24 hours. Thereafter, the electrolyte on the protective layer was wiped off with gauze and Hz0 was measured.

In this manner, the haze value before dropping of the electrolyte was Hz0, and the haze value measured after leaving for 24 hours after dropping of the electrolyte was HzY.

The value of the above formula (2) is usually less than 3, particularly preferably 2.6 or less, further more preferably 2 or less, further more preferably 1.8 or less, and most preferably 1 or less. The lower limit of this value is not particularly limited, and may be, for example, about 0.1.

As described above, the film of the present invention satisfying the above formula (1) or satisfying the above formulae (1) to (2) can more reliably exhibit excellent electrolyte resistance. That is, the haze hardly changes after the electrolyte solution was left to stand for 12 hours after the adhesion, and the haze hardly changes after the standing for 24 hours. This can be expected to be: even when left for a long time in a state where the electrolytic solution is adhered, the haze change before and after the adhesion is effectively suppressed, and the appearance change or the decrease in the tensile strength is effectively suppressed.

2. Production of polyamide-based laminated film

The film of the present invention can be suitably produced by a method for producing a polyamide-based laminated film, which comprises the steps of:

(1) a step of applying a coating liquid for forming a protective layer, which contains a copolyester resin containing a dicarboxylic acid component and a diol component as constituent components and having a naphthalene skeleton of 50 mol% or more of 100 mol% of a dicarboxylic acid-derived structural unit, to an unstretched polyamide film or a uniaxially stretched polyamide film (application step); and

(2) and a step (stretching step) of stretching the polyamide film having the coating film obtained by the coating step to obtain a polyamide laminated film having a protective layer formed on one side or both sides of the biaxially stretched film after stretching in the MD direction and the TD direction.

In the production of the film of the present invention, the method for forming the protective layer is not limited, and any of, for example, an in-line coating method, a post-coating method, and the like can be used.

In particular, in the present invention, an in-line coating method is preferably employed. Namely, the following method is preferably employed: an unstretched film or a uniaxially stretched film on which a coating film based on the protective layer forming coating liquid has been formed is stretched together with the coating film. Therefore, a production method including the above-described coating method and stretching method can be suitably employed. In the present invention, by using the in-line coating method, the protective layer can be made smooth as compared with the post-coating method, and as a result, the protective layer can be formed thinly and uniformly. In addition, as described above, the electrolyte resistance of the protective layer containing the copolyester resin is also improved.

In the production method of the present invention, the order of the coating step and the stretching step is not particularly limited as long as the above-described steps are provided. For example, a method of 1) applying a coating liquid for forming a protective layer on an unstretched polyamide film and then simultaneously or successively biaxially stretching; 2) in the sequential biaxial stretching method, any of methods such as a method of applying a coating liquid for forming a protective layer on a uniaxially stretched polyamide film and then stretching the film in a direction (MD direction or TD direction) orthogonal to the uniaxial direction is used. The respective steps will be specifically described below.

Coating step

In the coating step, a coating liquid for forming a protective layer (coating liquid of the present invention) containing a copolyester resin (copolyester resin a) containing a dicarboxylic acid component and a diol component as constituent components and having a naphthalene skeleton of 50 mol% or more of 100 mol% of a structural unit derived from dicarboxylic acid is applied to one side or both sides of an unstretched polyamide film or a uniaxially stretched polyamide film.

In this case, the unstretched polyamide film or uniaxially stretched polyamide film may be used as the polyamide film base material of the film of the present invention, and a film produced by a known method may be used as it is.

For example, an unstretched polyamide film can be obtained by molding a melt-kneaded product containing a polyamide resin into a film shape. The melt-kneaded product can be prepared by a known method. For example, the resin composition can be produced by molding a melt-kneaded product obtained by melting a resin composition containing a polyamide resin into a film. This can be done by using known or commercially available equipment. For example, a melt extruder with a T die may be used. That is, first, a starting material (for example, a granular raw material) is supplied to a hopper, plasticized and melted in a melt extruder, and the molten and kneaded product is extruded from a T die attached to the tip of the extruder into a sheet form, and cooled and solidified by a casting roll. At this time, the melt-kneaded product can be pressed against the casting roll by air to obtain an unstretched film.

In the resin composition, various additives may be added as required in addition to the polyamide resin. Examples of the additive include additives to be added to a polyamide film base material.

The uniaxially stretched polyamide film may be obtained by uniaxially stretching the above-described unstretched polyamide film, for example.

The coating liquid of the present invention contains a copolyester resin containing a dicarboxylic acid component and a diol component as constituent components, and the dicarboxylic acid component having a naphthalene skeleton is 50 mol% or more of 100 mol% of the dicarboxylic acid component. Such copolyester resin may use the resins mentioned in the foregoing.

The method for producing the coating liquid of the present invention can be carried out by dissolving or dispersing the copolyester resin a in a solvent. That is, the coating liquid of the present invention can be prepared in the form of a solution or dispersion.

The solvent is not particularly limited, and examples thereof include, in addition to water, alcohols such as methanol, ethanol, and isopropanol; cellosolves such as butyl cellosolve; toluene, Methyl Ethyl Ketone (MEK), cyclohexanone, SOLVESSO, isophorone, xylene, methyl isobutyl ketone (MIBK), ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate and the like. These may be used in 1 or 2 or more. In the present invention, a mixed solvent of a) water or b) water and a water-soluble organic solvent is preferably used. That is, from the viewpoint of workability, environment, and the like, the protective layer forming coating liquid is preferably an aqueous coating agent containing water as a main component and is water-soluble or an aqueous dispersion, and more preferably an aqueous dispersion from the viewpoint of coatability. In this case, the crosslinking agent is preferably an aqueous crosslinking agent as well. For the purpose of shortening the drying step, improving the stability of the coating liquid, and the like, an organic solvent such as alcohol may be contained in a small amount.

The concentration of the copolyester resin A in the coating liquid of the present invention can be appropriately set according to the kind of the copolyester resin used, and is usually about 3 to 40% by mass, and particularly preferably 5 to 20% by mass.

The coating liquid of the present invention may contain other components in addition to the copolyester resin a within a range not impairing the effects of the present invention. For example, various additives as described above can be blended.

The solid content concentration of the coating liquid for forming a protective layer containing a copolyester resin used in the present invention is preferably adjusted as appropriate according to the standards of a coating apparatus and a drying/heat treatment apparatus. However, too thin a coating liquid is difficult to form a protective layer having a thickness sufficient to exhibit resistance to an acidic liquid such as an electrolytic solution, and a problem that a long time is required in a subsequent drying step is likely to occur. On the other hand, a coating liquid having an excessively high concentration is not likely to become uniform, and a problem is likely to occur in coating properties. From such a viewpoint, the solid content concentration of the coating liquid for forming a protective layer is preferably about 5 to 70 mass%, but is not limited thereto.

The coating liquid for forming a protective layer containing a copolyester resin used in the present invention may be prepared by a known method using a furnace (japanese: dissolution vessel) equipped with a stirrer, or the like.

The method for coating with the coating liquid of the present invention is not particularly limited, and a known method can be suitably used. For example, a gravure roll coating method, a reverse roll coating method, a wire bar coating method, an air knife coating method, a curtain coating method, a blade coating method, a die coating method, a dip coating method, a bar coating method, or the like can be used, and a method in which these methods are combined can also be used.

After the coating liquid of the present invention is applied, the solvent may be removed by drying as necessary, but the coating liquid may be supplied to the stretching step in a liquid film or semi-dried film state before drying.

The drying step after coating is not particularly limited, and may be performed by a known method, such as drying in a drying atmosphere such as an oven, drying by contact with a hot roll, drying in a stretching machine, or the like. The drying temperature is not particularly limited, and may be set to a range of about 30 to 160 ℃. The drying time may be set appropriately according to the drying temperature, and is generally set within a range of 0.5 to 10 minutes.

Drawing step

After the coating step, the polyamide film having the coating film obtained by the coating step is stretched to obtain a polyamide laminated film having a protective layer formed on one side or both sides of a biaxially stretched film stretched in the MD direction and the TD direction.

Before the stretching step, the unstretched film or the uniaxially stretched film is preferably preheated. The preheating temperature is not limited, but is usually 180 to 250 ℃, particularly preferably 200 to 245 ℃, and particularly preferably 210 to 240 ℃. By the preheating, a biaxially stretched film having good physical properties can be obtained more reliably. The preheating time is generally preferably about 0.5 to 5 seconds, although it depends on the preheating temperature and the like.

The method of carrying out the preheating is not particularly limited. For example, it is possible to suitably employ: the method is carried out by setting the temperature of hot air blown to the film passing through the preheating zone of the stretcher to the above-described temperature range.

The method of setting the stretching temperature to the above temperature is not limited, and it is preferable to set the temperature of hot air blown to the film passing through the stretching zone of the stretching machine to the above temperature range. In this case, the time for the polyamide film to pass through the stretching zone is preferably about 0.5 to 5 seconds.

As the stretching method, since the biaxially stretched film of the present invention is to be obtained finally, a simultaneous biaxial stretching method or a sequential biaxial stretching method can be employed. Further, as a classification by the stretching apparatus, for example, a tube method, a tenter method, or the like can be used. In the present invention, a stretching method based on a tenter method is preferable particularly in terms of quality stability and dimensional stability. Therefore, a tenter simultaneous biaxial stretching method or a tenter sequential biaxial stretching method can be suitably employed.

In the case of using the sequential biaxial stretching method as the stretching method, the film of the present invention having a protective layer formed on a predetermined biaxially stretched film can be obtained by coating a protective layer forming coating liquid on a film uniaxially stretched in the MD or TD in advance and then stretching the film in a direction (TD or MD) orthogonal to the uniaxial direction.

The stretching ratio is not particularly limited, and generally, the stretching ratio may be about 2.0 to 4.5 times in each of the MD direction and TD direction. In this case, the stretching ratios in the MD direction and the TD direction may be the same or different from each other. In this way, a stretched film excellent in physical properties such as tensile strength and tensile elongation can be obtained.

The stretching temperature is not limited, and may be appropriately set within a range of 220 ℃ or less depending on, for example, the stretching method, the use of the film of the present invention, the use form, and the like.

For example, in the sequential biaxial stretching method, an unstretched film is first stretched in a uniaxial direction at a stretching temperature of 40 to 80 ℃ (preferably 50 to 65 ℃), and then a coating liquid for forming a protective layer is applied. The uniaxially stretched film coated with the coating liquid for forming a protective layer can be dried at 50 to 220 ℃ in the same manner as in the simultaneous biaxial stretching method. Then, the uniaxially stretched film coated with the coating liquid for forming a protective layer is stretched in the orthogonal direction at a stretching temperature of 200 ℃ or lower (preferably 90 to 190 ℃) to obtain a biaxially stretched film. When the sequential biaxial stretching is performed, it is preferable to perform the sequential biaxial stretching by a roll stretching method and a tenter stretching method in combination. That is, after stretching in the uniaxial direction (TD direction or MD direction) by a roll (generally, a device that stretches while passing over 2 or more rolls), stretching in a direction substantially perpendicular to the uniaxial direction (TD direction or MD direction) by tentering may be performed to perform biaxial stretching.

For example, in the simultaneous biaxial stretching method, it is preferable that after drying at 50 to 220 ℃ in the drying step, the unstretched film coated with the coating liquid for forming the protective layer is simultaneously biaxially stretched at a stretching temperature of 215 ℃ or lower (preferably 190 to 210 ℃). When the unstretched film is simultaneously biaxially stretched, it is preferably stretched by a tenter method, a LISIM biaxial stretching method, or the like.

The film stretched in the stretching step is preferably further subjected to a heat treatment. The heat treatment temperature is not particularly limited, but is usually preferably about 190 to 220 ℃, and more preferably 195 to 215 ℃. If the heat treatment temperature is less than 190 ℃, the coating film of the copolyester resin may be insufficiently formed, and a protective layer having insufficient resistance to the electrolytic solution may be formed. In addition, when a curing agent is added, the crosslinking reaction may not proceed sufficiently, and the effect of adding a crosslinking agent may not be obtained. On the other hand, if the heat treatment temperature exceeds 220 ℃, the strength of the polyamide film may be reduced. In the case where the crosslinking reaction does not proceed sufficiently in the heat treatment, the aging treatment may be performed after the stretching is completed. The time for the heat treatment may be appropriately set according to the heat treatment temperature, and is preferably about 1 to 15 seconds in general.

The heat treatment method is not particularly limited, and for example, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, and the like can be used. Among them, a method of blowing hot air is preferable from the viewpoint of uniform and accurate heating. For example, a method of performing heat-fixing treatment by blowing hot air having been set in the above-described temperature range to the film passing through the heat-fixing zone of the stretcher.

Other procedures

The method of laminating the layers is not particularly limited, and for example, any of the following methods can be employed: the method comprises the following steps: a) a method of forming a coating film using a coating liquid, b) a method of laminating a film formed in advance, c) a method of forming a vapor deposition film by a PVD method, a CVD method, or the like. In the case of b), any of a method of laminating via an adhesive, a method of laminating by simultaneous extrusion molding, and the like may be employed. In particular, when the film of the present invention is used for a battery exterior material such as a lithium ion secondary battery, a known method for producing an exterior material may be used. In this case, lamination can be performed using a known adhesive.

For example, in the case of lamination with a barrier layer, the following method can be employed: a method of dry lamination, thermal lamination, or the like of a laminate comprising a protective layer/polyamide film base material or a laminate comprising a protective layer/polyamide film base material/protective layer and a metal foil for forming a barrier layer or the like via a two-component type urethane adhesive or the like.

As a method for joining the barrier layer and the heat-fusible layer, a known method (dry lamination, heat lamination, extrusion lamination, sandwich lamination, or the like) can be used.

On the surface of the polyamide film, the barrier layer, and the heat-sealing layer of the layer to be formed with the adhesive, other layers such as an anchor coat layer and a primer layer may be provided as necessary, as long as the effects of the present invention are not impaired.

3. Use of polyamide-based laminated film

The film of the present invention can be used for various purposes, and particularly, can be suitably used as a packaging material. That is, it can be utilized as a packaging material for packaging the contents. The contents are not limited, and for example, electronic parts, chemical products, cosmetics, medical supplies (medical equipment), drinks and foods, and the like can be packaged.

In particular, the film of the present invention can be suitably used as a packaging material for a lithium ion battery, and when the film of the present invention is used as a packaging material, the film of the present invention (particularly, a polyamide base material layer) can be protected from an electrolyte solution by the protective layer. As a result, problems due to corrosion of the exterior material and the like can be effectively suppressed or prevented.

Generally, an electrolyte solution used in a lithium ion secondary battery is a conductive liquid prepared by dissolving an ionic substance (particularly, a lithium salt) in a polar solvent such as carbonate. Examples of the lithium salt include a lithium salt that generates hydrofluoric acid (hydrogen fluoride) by reacting with water. More specifically, the following may be exemplified: lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) And the like fluorine-containing lithium salts. Therefore, when the electrolyte adheres to the air, the moisture in the air reacts with the lithium salt containing fluorine in the electrolyte to generate hydrofluoric acid. This hydrofluoric acid may dissolve a polyamide film used for a lithium ion secondary battery exterior material. In contrast, in the film of the present invention, since the polyamide base material layer is covered with the specific protective layer, even when the electrolytic solution comes into contact with the exterior material (particularly, the protective layer), the exterior material can be effectively protected with high resistance to the electrolytic solution, and as a result, a highly reliable lithium ion secondary battery can be provided. Therefore, the film of the present invention can be suitably used as, for example, a lithium ion secondary battery casing material, and can also be applied to a lithium ion secondary battery formed by embossing or deep drawing. In addition, even if the electrolyte adheres to the exterior material in the production of the lithium ion secondary battery, the performance as the exterior material of the lithium ion secondary battery can be maintained well.

When used as a packaging material, the form thereof is not particularly limited, and for example, it can be used as a packaging bag or a packaging container. The packaging bag can be used as various bag bodies such as a pillow bag, an accessory bag, and a stand bag. The bag body can be formed by a known method.

Further, the present invention also includes a product (packaged product) in which the content is packaged by the packaging material or the packaging bag as described above. In this case, the packaged state includes, for example: and a state in which the contents are sealed from the outside by a packaging material or a packaging bag.

4. Battery with a battery cell

The present invention includes a battery, characterized by comprising: a power generation element including a negative electrode, a positive electrode, a separator, and an electrolyte; and an exterior material for packaging the power generating element; the outer casing is the film of the present invention, and the protective layer is disposed as the outermost layer of the battery.

The film of the present invention can be suitably used for a laminate type (pouch type) battery. Therefore, for example, a method of filling and sealing the power generating element after the film of the present invention is formed into a concave shape (container shape) in advance may be employed, or a method of encapsulating and molding the film of the present invention after the power generating element is placed on the film of the present invention.

The power generating element is not particularly limited, and a known or commercially available power generating element may be used. Further, the battery may be either a primary battery or a secondary battery. For example, lithium ion batteries, nickel hydride batteries, nickel cadmium batteries, and the like can be given.

A schematic of the cell is shown in fig. 4. The battery 40 has a structure in which the power generating element 41 is covered with the exterior material including the film 10 of the present invention. More specifically, the power generating element 21 is covered with the film 10 of the present invention so that the surface of the protective layer 10a of the film 10 of the present invention is the outside.

The power generating element 41 in fig. 4 includes: a positive electrode including a positive electrode active material and a current collector, a separator, a negative electrode including a negative electrode active material and a current collector, an electrolyte solution, and the like (all not shown). The positive electrode and the negative electrode each have a lead (tab) 43 extending from an end thereof.

A lithium ion battery is exemplified, and the following configuration can be adopted. Examples of the positive electrode active material include lithium salts such as lithium manganate, and metallic lithium, and the like, and the positive electrode active material collects currentAn example of the body is aluminum foil. Examples of the separator include microporous films such as polyethylene and polypropylene. Examples of the negative electrode active material include graphite, lithium salts such as lithium manganate, metallic lithium, and the like can be used, and examples of the positive electrode current collector include aluminum foil. The electrolyte solution may be lithium tetrafluoroborate (LiBF)₄) Lithium hexafluorophosphate (LiPF)₆) And a solution in which lithium salt is dissolved in Ethyl Carbonate (EC), Ethyl Methyl Carbonate (EMC), propylene carbonate, or the like.

Fig. 5 is a sectional view showing an example of a battery using the film body of the present invention as an exterior material. In the battery 50, the film 10 of the present invention as an exterior material is folded in two so that the protective layer 10a is positioned outside, and the power generating element 41 is mounted therein. The surface of the film 10 of the present invention on the side opposite to the protective layer is a heat-seal layer surface 10b, and the adhesive portion S1 is formed by heat-sealing in a state where the end portions thereof face each other. In the contact portion S1, the lead 43 is sandwiched between the heat-fusion bonding layers. In fig. 4, only 1 lead 43 is shown for simplicity, but actually, a positive electrode lead and a negative electrode lead are provided.

When the battery shown in fig. 5 is assembled, the power generating element 41 provided with the lead 43 is covered with the film 10 of the present invention so that the lead is exposed to the outside. In the coating, the power generating element 21 is coated by bonding the heat-bonding layer surfaces 10b of the film 10 of the present invention to each other. In this case, a part is not joined to secure the injection port of the electrolyte. Next, the injection port is filled with the electrolyte solution, and then the injection port is sealed by heat sealing. In this manner, the power generating element 21 is sealed with the film 10 of the present invention as an exterior material.

Fig. 6 is a schematic diagram showing a cross section of a battery according to another embodiment. The battery 60 has a power generating element (power generating element) 41 for connecting to an external lead 43, and the periphery thereof is covered with 2 sheets of the

films

10 and 10 of the present invention. Both ends of the

films

10, 10 of the present invention are sealed by the adhesive portions S1, S2 by heat sealing or the like. Lead 43 extends to be exposed to the outside from an electrode in battery 60, and can take out the current from power generating element 41 to the outside. In fig. 6, only 1 lead 43 is shown for simplicity, but actually, a positive electrode lead and a negative electrode lead are provided.

When the battery 60 shown in fig. 6 is assembled, the power generating element 41 including the lead 43 is covered with the

films

10 and 10 of the present invention so that the lead is exposed to the outside. In the coating, the power generating element 21 is coated by joining the heat-seal layer surfaces 10b and 10b of the 2

films

10 and 10 of the present invention to each other by heat-sealing. In this case, a part is not joined to secure the injection port of the electrolyte. Next, the injection port is filled with the electrolyte solution, and then the injection port is sealed by heat sealing. In this manner, the power generating element 41 was sealed with 2 sheets of the

films

10 and 10 of the present invention.

Examples

The following examples and comparative examples are provided to more specifically explain the features of the present invention. However, the scope of the present invention is not limited by the examples. In the following description, "parts" means "parts by mass".

Example 1

(1) Synthesis of copolyester resin A

Dicarboxylic acid components (709.4 parts of 2, 6-naphthalenedicarboxylic acid, 26.6 parts of terephthalic acid, and 56.2 parts of sodium 5-sulfoisophthalate), diol components (176.7 parts of ethylene glycol, 126.2 parts of diethylene glycol, and 336.8 parts of 1, 6-hexanediol), and 0.26 part of tetrabutyl titanate as a polymerization catalyst were charged into a reactor, and the inside of the system was replaced with nitrogen. Then, the reactor was warmed to 200 ℃ while stirring these raw materials at 1000 rpm.

Subsequently, the temperature was gradually raised to 260 ℃ over 4 hours and subjected to transesterification. Thereafter, the pressure was gradually reduced at 250 ℃ and the polycondensation reaction was carried out at 0.35mmHg for 1.5 hours. The specified copolyester resin was prepared in this manner.

(2) Preparation of coating liquid for Forming protective layer

The obtained copolyester resin was finely pulverized, 30 parts of the copolyester resin and 70 parts of water were added to a dissolution tank, and dissolved while stirring at 80 to 95 ℃ for 2 hours, thereby obtaining an aqueous solution having a concentration of 30 mass% as a coating liquid for forming a protective layer.

(3) Production of stretched film (simultaneous biaxial stretching)

A polyamide resin (nylon 6, "A1030 BRF" manufactured by Unitika corporation, relative viscosity: 3.1) was extruded into a sheet form from a T die at 260 ℃ using an extruder equipped with a T die. Then, the film was closely adhered to a casting roll whose surface temperature was adjusted to 18 ℃ and rapidly cooled, and the amount of the polyamide resin to be supplied was adjusted so that the thickness of the polyamide film obtained after stretching became 15 μm.

Subsequently, the unstretched film was passed through a water absorption treatment device with a water temperature of 50 ℃ and the coating liquid for forming the protective layer was applied to one surface of the unstretched film by a spray coating method so that the dried thickness became 0.70 μm, dried at 150 ℃, and then introduced into a simultaneous biaxial stretcher. The coated unstretched film was subjected to simultaneous biaxial stretching in the MD direction by 3.0 times and in the TD direction by 3.3 times at a preheating temperature of 200 ℃ and a stretching temperature of 190 ℃ in a simultaneous biaxial stretcher. Then, heat treatment was performed at a heat treatment temperature of 210 ℃ for 3 seconds to form a protective layer on one surface of the polyamide film. Further, the other surface having no protective layer was subjected to corona treatment, thereby obtaining a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm.

(4) Production of Polyamide-based laminated film

The surface of the obtained stretched film, on which the protective layer was not laminated, was coated in an amount of 5g/m²A two-pack polyurethane adhesive (TM-K55/CAT-10L, manufactured by Toyo Morton) was applied and dried at 80 ℃ for 10 seconds. An aluminum foil (50 μm thick) was bonded to the adhesive-coated surface. Then, the above adhesive was applied to the aluminum foil surface under the same conditions, dried, and an unstretched polypropylene film (GHC, 50 μm thick, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was laminated as a heat-sealing layer, and subjected to aging treatment at 40 ℃ for 72 hours in an atmosphere. In this manner, a polyamide-based laminated film was obtained in which "protective layer/polyamide film/aluminum foil/heat-sealing layer" were laminated in this order.

Examples 2 to 19 and comparative examples 1 to 6

A polyamide-based laminated film was produced in the same manner as in example 1, except for the conditions shown in table 1 and described below. Note that, in table 1, an example using the post-coating method is indicated by 1.

[ Table 1]

< As for example 2 >

(2) Preparation of coating liquid for Forming protective layer

The copolyester resin described in example 1 and the oxazoline-based crosslinking agent (WS 300, manufactured by japan catalyst corporation) described in table 1 were added so that the content of the crosslinking agent was 5 mass% based on the solid content of the copolyester resin, and the resulting mixture was further mixed with pure water so that the solid content of the mixture of the copolyester resin and the crosslinking agent became 9 mass%, thereby obtaining a coating liquid for forming a protective layer.

(3) Production of stretched film (simultaneous biaxial stretching)

A stretched film was obtained in the same manner as in example 1, except that the heat treatment temperature when the protective layer was formed on one side of the polyamide film was changed to the value shown in table 1.

< As for example 5 >

(1) Synthesis of copolyester resin A

A copolyester resin was obtained by polymerization in the same manner as in example 1, except that the blending ratio of the dicarboxylic acid component and the diol component was changed to the composition shown in table 1.

(2) Preparation of coating liquid for Forming protective layer

A crosslinking agent was added to the above copolyester resin under the conditions shown in table 1, and pure water was used to obtain a 9 mass% coating solution for forming a protective layer.

(3) Production of stretched film (sequential biaxial stretching)

A polyamide resin (nylon 6, manufactured by Unitika, A1030BRF, relative viscosity 2.7) was extruded into a sheet form from a T die at 260 ℃ using an extruder equipped with a T die. Then, the film was closely adhered to a casting roll whose surface temperature was adjusted to 18 ℃ to rapidly cool the film, and the amount of the polyamide resin to be supplied was adjusted so that the thickness of the polyamide film obtained after stretching became 15 μm.

Then, the unstretched film was stretched in the MD to a stretching magnification of 2.80 times by passing it through a stretching roll heated to 54 to 62 ℃. Next, the protective layer forming coating liquid was applied to one side of the stretched film using a gravure coater so that the dried thickness became 0.70 μm, and the film was stretched in the TD direction at a preheating temperature of 60 ℃ and a stretching temperature of 90 ℃ to a stretching ratio of 3.2 times. Further, the heat treatment was performed at a heat treatment temperature of 215 ℃ for 3 seconds. The polyamide film was further subjected to corona treatment on the side having no protective layer. Thus, a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm was obtained.

< As for example 6 >

A polyamide-based laminated film was produced in the same manner as in example 5, except that the heat treatment temperature was changed as shown in table 1.

< examples 3 to 4, 9, 16 to 18, and comparative example 2 >

A polyamide-based laminated film was obtained in the same manner as in example 2, except that the composition of the coating liquid for forming the protective layer and the heat treatment temperature at the time of forming the protective layer were set to the conditions shown in table 1.

< examples 6 to 8, 10 to 15 >

A polyamide-based laminated film was obtained in the same manner as in example 5, except that the composition of the coating liquid for forming the protective layer and the heat treatment temperature at the time of forming the protective layer were set to the conditions shown in table 1.

< As for example 19 >

(3) Production of stretched film (simultaneous biaxial stretching)

Subsequently, the unstretched film was passed through a water absorption treatment device with a water temperature of 50 ℃ and then introduced into a simultaneous biaxial stretcher, and simultaneous biaxial stretching was performed at a preheating temperature of 200 ℃ and a stretching temperature of 190 ℃ by 3.0 times in the MD direction and 3.3 times in the TD direction. Then, heat treatment was performed at a heat treatment temperature of 210 ℃ for 3 seconds. One side is then corona treated. Thus, a stretched film having a film thickness of 15 μm was obtained.

Further, the obtained stretched film was introduced into a gravure coater, and the coating liquid for forming a protective layer obtained in example 2 was applied so that the final coating thickness became 0.7 μm, and was dried by passing through a 5-zone drying furnace [ region 1(80 ℃) → region 2(100 ℃.) → region 3(120 ℃.) → region 4(110 ℃.) → region 5(80 ℃) ] taking 3 seconds, thereby obtaining a stretched film having a film thickness of 15 μm and a protective layer thickness of 0.70 μm.

< comparative example 1 >

A polyamide-based laminated film was obtained in the same manner as in example 19, except that the composition of the coating liquid for forming a protective layer was changed to the composition shown in table 1 and the thickness of the protective layer was changed to 2.00 μm.

< comparative example 3 >

A polyamide-based laminated film was obtained in the same manner as in comparative example 1, except that the coating liquid for forming a protective layer was changed to a commercially available PVDC coating liquid ("Saran Latex L549").

< comparative example 4 >

A polyamide-based laminated film was obtained in the same manner as in example 1, except that the coating liquid for forming the protective layer was changed to the same PVDC coating liquid as in comparative example 3, and the heat treatment temperature at the time of forming the protective layer was changed.

< comparative example 5 >

A polyamide-based laminated film was obtained in the same manner as in comparative example 1, except that the coating liquid for forming the protective layer was changed to a saturated polyester resin emulsion (kokusu oil and fat co., ltd. a-110F).

< comparative example 6 >

A polyamide-based laminated film was obtained in the same manner as in example 1, except that the coating liquid for forming the protective layer was changed to the same saturated polyester resin emulsion as in comparative example 5, and the heat treatment temperature at the time of forming the protective layer was changed.

Test example 1

The following properties were measured for each of the polyamide-based laminated films obtained in examples and comparative examples. The results are shown in Table 2. "not measurable" in table 2 indicates that wrinkles or the like occur after the electrolyte adheres, and the surface of the polyamide-based laminated film is deformed, and thus cannot be measured.

(1) Composition of copolyester resin

Measurement was carried out using an "ECZ 400R NMR apparatus" manufactured by Japan electronic division¹H-NMR was obtained from the peak integrated intensity ratio of proton of each copolymerization component in the obtained graph.

(2) Glass transition temperature of copolyester resin

The temperature was measured at a temperature rise rate of 20 ℃ per minute using a differential scanning calorimeter (Diamond DSC) manufactured by Perkin Elmer corporation.

(3) Thickness of protective layer

The obtained polyamide-based laminated film was embedded with an epoxy resin, subjected to surface processing (Japanese: surface し), and then subjected to RuO₄Staining (1 day) and collecting sections with a thickness of 90nm (set value) using a microtome. The cutting temperature was set at 23 ℃ C. and the humidity at 50% RH (the periphery of the sample, the knife, and the chamber), and the cutting speed was set at 0.6 mm/min. The obtained sample was measured for the thickness of the protective layer by transmission measurement at an accelerating voltage of 100kV using a TEM "JEM-1230" manufactured by Japan Electron Ltd.

(4) Uneven thickness of laminate film (thickness accuracy)

As shown in fig. 3, after the obtained polyamide-based laminated film was subjected to humidity conditioning at 23 ℃ and 50% RH for 2 hours, a reference direction (0 degree direction) was specified centering on an arbitrary point a on the film, and then 8 lines of 100mm in total were drawn from the center point a in 8 directions, i.e., a 45 degree direction, a 90 degree direction, a 135 degree direction, a 180 degree direction, a 225 degree direction, a 270 degree direction, and a 315 degree direction, which are clockwise rotated with respect to the reference direction. On each straight line, the thickness was measured (10 points were measured) at 10mm intervals from the center point a by a length measuring instrument "HEIDENHAIN-METRO MT 1287" (manufactured by Heidenhain corporation), the average value of the measured values at 80 points in total of the data measured on all the straight lines was calculated, and the standard deviation value with respect to the average thickness was calculated using the average thickness. The reference direction is not particularly limited, and for example, MD in the stretching step in the film production may be used as the reference direction.

(5) Surface roughness

The surface roughness of the protective layer surface and the polyamide film base surface of the obtained polyamide laminated film was measured at 10 points arbitrarily according to japanese industrial standard "JIS B0601-2013" using a contact surface roughness measuring instrument "Suefcorder SE 500A" manufactured by mini sakawa research, ltd., and the calculated average value was set to Ra.

(6) Resistance to electrolyte solution

Using the obtained polyamide-based laminated film, the electrolyte resistance was evaluated for 3 kinds of standing times of 6 hours, 12 hours, and 24 hours as shown below.

First, the haze value of the obtained polyamide-based laminated film was measured according to japanese industrial standard "JIS K7136" using a haze meter (NDH4000) manufactured by japan electrochromism corporation. This was set as the haze (Hz0) before dropping of the electrolyte.

Next, 3 samples were prepared in which the opening of a glass shallow tray (diameter 200mm) was covered with a polyamide-based laminated film so that the protective layer formed the surface. In each sample, 10ml of an electrolyte (a mixture containing ethylene carbonate/diethyl carbonate/methylethyl carbonate in a volume ratio of 1/1/1) was dropped onto the protective layer₆And diluted to a concentration of 1 mol/L), the electrolytic solution was attached to the protective layer.

Of the 3 samples, 3 samples were prepared in which the standing time at 23 ℃ and 50% RH was 6 hours, 12 hours, and 24 hours after the adhesion of the electrolyte. For the 3 samples, after being left for each time, the electrolyte on the protective layer was wiped off with gauze, and measurement was performed in the same manner as described above using a japan electrochromatography haze meter (NDH4000) according to japanese industrial standard "JIS K7136".

The haze value measured after leaving the electrolyte at 23 ℃ and 50% RH for 6 hours after the attachment was HzW, the haze value measured after leaving the electrolyte for 12 hours was HzX, and the haze value measured after leaving the electrolyte for 24 hours was HzY.

Then, differences from Hz0 before dropping of the electrolyte were calculated in each case, (HzW) - (Hz0), (HzX) - (Hz0), (HzY) - (Hz 0).

In the above calculation results, a value that is in line with practicality is less than 3.0, particularly preferably less than 2.0, and further most preferably less than 1.0.

(7) Moistening

The wetting was measured according to Japanese Industrial Standard "JIS K6768". When the measured value is 42dyn or more, the evaluation is good.

(8) Blocking resistance

The obtained polyamide-based laminated film was stacked (in the case where the protective layer was formed on one side, the protective layer was stacked on the base material layer, and in the case where the protective layer was formed on both sides, the protective layer was stacked on the protective layer) and placed on a platen at 300g/cm²In the state of the weight, the plate was left standing in a thermostatic bath at a temperature of 40 ℃ and a humidity of 50% RH for 24 hours. Thereafter, the sample was cut into a long strip having a width of 15mm × a length of 100mm, and peeled at a speed of 200mm/min using a tensile tester Autograph AG-I (manufactured by Shimadzu corporation), and the highest value was defined as a peel strength value. Regarding the peel strength value, 50g/15mm or less was evaluated as "O" for blocking resistance, more than 50g/15mm and less than 80g/15mm was evaluated as "Δ" for blocking resistance, and 80g/15mm or more was evaluated as "X" for blocking resistance. In terms of practicality, the blocking resistance "Δ" or more is essential.

[ Table 2]

The polyamide-based laminated films obtained in examples 1 to 19 exhibited good electrolyte resistance and good blocking resistance, without changing the appearance of the polyamide film for at least 12 hours or more, even if the electrolyte solution was deposited on the protective layer, because the protective layer contained the copolyester resin having the composition specified in the present invention and had a thickness of 1.5 μm or less. Particularly, the protective layer containing a dicarboxylic acid component having a naphthalene skeleton in an amount of 80 mol% or more and a crosslinking agent having a glass transition temperature of 80 ℃ or more is excellent in electrolyte resistance.

On the other hand, the polyamide-based laminated films obtained in comparative examples 1,3 and 5 had poor blocking resistance because the protective layer had a large thickness and could not be sufficiently dried in a short drying step of 3 seconds, although they exhibited electrolyte resistance.

In comparative examples 2,4, and 6, since the composition of the protective layer defined in the present invention was not satisfied, when the thickness of the protective layer was as thin as 1.50 μm or less, sufficient electrolyte resistance could not be obtained, and when the electrolyte adhered to the protective layer, the polyamide-based laminated film whitened and the appearance was significantly impaired. In comparative example 5, even when the protective layer was thick, the polyamide-based laminated film still whitened and the appearance was significantly impaired.

Claims

(4) the thickness of the protective layer is 1.5 μm or less.

2. The polyamide-based laminate film according to claim 1, which satisfies the following formula (1):

(HzX) - (Hz0) < 3.0 … formula (1)

And Hz0 is in the range below 10,

in formula (1), Hz0 is a haze value measured according to JIS K7136, and HzX is a haze value measured in the same manner as Hz0 after being held at 23 ℃ and 50% RH for 12 hours in a state where an electrolyte is attached to a protective layer after the measurement of Hz0, the electrolyte being a solution containing, in a volume ratio of 1: 1: 1 ethylene carbonate/diethyl carbonate/ethyl methyl carbonate mixture LiPF is added₆Diluted to a concentration of 1 mol/L.

3. The polyamide-based laminate film according to claim 1, wherein the protective layer has a surface roughness Ra of 45nm or less.

4. The polyamide-based laminate film according to claim 1, wherein the glass transition temperature of the copolyester resin is 60 to 145 ℃.

5. The polyamide-based laminate film according to claim 1, wherein the protective layer further comprises at least 1 of a melamine resin, an isocyanate compound, a carbodiimide compound, and an oxazoline compound.

6. The polyamide-based laminated film according to any one of claims 1 to 5, wherein the polyamide-based laminated film is laminated such that a protective layer is in direct contact with at least one surface of a polyamide-based film base material, and the polyamide-based laminated film is a laminate comprising:

(a) a laminate comprising a protective layer, a polyamide film base material, a barrier layer, and a heat-sealing layer in this order; or

(b) A laminate comprising a protective layer, a polyamide-based film substrate, a protective layer, a barrier layer, and a heat-sealing layer in this order.

7. The polyamide-based laminated film according to any one of claims 1 to 6, which is used for packaging an article.

8. A battery, comprising:

an exterior material for packaging the power generating element,

the outer covering material is the polyamide-based laminate film according to any one of claims 1 to 6, and the protective layer is disposed as an outermost layer of the battery.

9. A method for producing a polyamide-based laminated film according to any one of claims 1 to 6, comprising: