Film for metal lamination, film foil, film foil for battery current collector, and battery current collector

Abstract

The present invention contributes to improvement of the electrochemical stability of a film for metal lamination.　Disclosed is a film for metal lamination, which has a resin layer on at least one surface of a polyester film, wherein the ratio (β / α) of the peak intensity (β) after a test to the peak intensity (α) before the test satisfies formula (1).　Formula (1): (peak intensity (β) after test) / (peak intensity (α) before test) > 0.46

Description

Metal lamination film, film foil, film foil for battery current collector, and battery current collector

[0001] The present invention relates to a film for metal lamination, a film foil, a film foil for a battery current collector, and a battery current collector.

[0002] Polyester films are used in a variety of fields due to their excellent transparency, optical properties, dimensional stability, mechanical strength, heat resistance, chemical resistance, electrical properties, etc. Specifically, they are widely used as magnetic recording materials, packaging materials, solar cell applications, separators for liquid crystal polarizers, substrates for dry film resists, electrode substrates, release films for molding green sheets for multilayer ceramic capacitors, as well as optical films such as anti-reflection films, diffusion sheets, and prism sheets, and films for label printing.

[0003] Current collectors for secondary batteries may have a laminated structure in which the surface of a substrate made of polyester film is covered with a thin metal film. Such laminated current collectors using a substrate are effective in that they have a current interrupting function in which the substrate melts and deforms, causing the thin metal film to rupture when abnormal heat is generated due to an internal short circuit or the like (see Patent Documents 1 and 2).

[0004] JP-A-10-40919 JP-A 10-40920

[0005] However, current collectors having a structure in which a metal layer is laminated on the surface of a substrate made of a polyester film have issues such as reductive decomposition of the polyester film within the operating range during charging and discharging of a lithium-ion battery. Therefore, the inventors' investigations have revealed that further improvement is necessary from the viewpoint of electrochemical stability, particularly charge and discharge durability.

[0006] The present invention has been made in view of the above circumstances, and provides a film for metal lamination that can contribute to improving the electrochemical stability of polyester films used in applications where a metal layer is laminated.

[0007] The present invention also provides a film for metal lamination that can contribute to improving the charge / discharge durability of secondary batteries such as lithium ion batteries.

[0008] The present inventors have conducted extensive research in light of the above problems and have found that the above problems can be solved by providing the following configuration.

[0009] [1] A film for metal lamination having a resin layer on at least one surface of a polyester film, wherein the ratio (β / α) of the peak intensity (β) after the test to the peak intensity (α) before the test satisfies the following formula (1): [Formula] Peak intensity after the test (β) / Peak intensity before the test (α)>0.46 ... (1) [Peak intensity (α) before the test] The peak intensity (α) before the test is a peak intensity (α) of 1650 to 1800 cm in a Raman spectrum (Rmα) measured in a cross-sectional region of the polyester film included in the test film (sα) within a range of 1 μm in the thickness direction from one surface of the polyester film. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmα). -1 The peak intensity (β) after the test is defined as the peak intensity of 1650 to 1800 cm in the Raman spectrum (Rmβ) measured in a cross-sectional region within 1 μm in the thickness direction from one surface of the polyester film included in the test film (sβ) after the test described below. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmβ). -1The peak intensity is defined as a peak intensity when the peak intensity due to the skeletal vibration of the benzene ring appearing in the range is set to 1. [Test film (sβ) after test] A test film (sα) was prepared by laminating a copper layer on the resin layer side of the metal lamination film, and a separator and lithium foil were laminated in this order on the copper layer side of the test film (sα). An electrolyte solution obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) was added so that the test film (sα), separator, and lithium foil were immersed, and the resultant was sealed to prepare a test coin cell (diameter 20 mm, height 3.2 mm). A current density of 0.09 mA / cm was applied to the test coin cell. 2 A current was applied at a constant current for 10 hours, and then at a current density of 0.09 mA / cm 2 After a cycle of passing a current in the reverse direction under the conditions of 1000 kJ / s, 100 kJ / s, and a constant current for 10 hours was repeated a total of 10 times, the test film removed from the test coin cell was designated as the test film (sβ) after the test. [2] The metal lamination film according to [1], in which the resin contained in the resin layer satisfies the following requirement. (Requirement) When a voltammogram (Vb) obtained by linear sweep voltammetry measurement under the following conditions is compared with a voltammogram (Vp) obtained by linear sweep voltammetry measurement under the same conditions except that the resin contained in the resin layer or the monomer components constituting the resin are dissolved in the following electrolyte at a concentration of 0.5 mmol / L or more, no reduction current is observed at a different potential. [Linear sweep voltammetry measurement conditions] Working electrode: An electrode prepared by dispersing a mixture of natural carbon powder, sodium carboxymethyl cellulose, and styrene-butadiene rubber (mass ratio 98:1:1) in water, coating the mixture on copper foil, and drying it. Reference electrode and counter electrode: Lithium metal wire. Electrolyte: Electrolyte in which lithium hexafluorophosphate was dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7). Sweep rate: 1 mV / sec. Sweep range: Natural potential (approximately 3.2 V) → 0 V (vs. Li / Li +). [3] The film for metal lamination according to [1] or [2], wherein the resin layer contains at least one selected from the group consisting of polyolefin resins, (meth)acrylic resins, polyalkylene glycols, and compounds having a glycidyl ether group. [4] The film for metal lamination according to any one of [1] to [3], wherein the resin layer contains a compound having a glycidyl ether group or a reaction product of a compound having a glycidyl ether group and at least one or more compounds. [5] The film for metal lamination according to any one of [1] to [4], wherein the resin layer contains polyglycerol polyglycidyl ether or a reaction product of polyglycerol polyglycidyl ether and at least one or more compounds. [6] The film for metal lamination according to [3], wherein the content of the at least one selected from the group consisting of polyolefin resins, (meth)acrylic resins, polyalkylene glycols, and compounds having a glycidyl ether group is 70% by mass or more relative to the total mass of the resin layer (non-volatile components). [7] The film for metal lamination according to any one of [1] to [6], wherein the thickness of the resin layer is less than 1 μm. [8] The film for metal lamination according to any one of [1] to [7], wherein the resin layer is formed directly on the surface of the polyester film. [9] A film foil, obtained by laminating a metal layer on the resin layer side of the film for metal lamination according to any one of [1] to [8].

[10] The film foil according to [9], wherein the metal layer is any one of a metal vapor deposition layer, a metal plating layer, and a metal sputtering layer.

[11] The film foil according to [9] or

[10] , wherein the metal layer contains at least one selected from the group consisting of copper, aluminum, nickel, chromium, and alloys containing two or more of these.

[12] A film foil for a battery current collector, obtained by using the film foil according to any one of [9] to

[11] .

[13] A battery current collector, obtained by laminating an electrode layer on the surface of the metal layer of the film foil for battery current collector according to

[12] .

[14] The battery current collector according to

[13] , wherein the battery in the battery current collector is a lithium ion battery or a sodium ion battery.

[15] Use of the following laminated film for producing a film foil for a battery current collector or a battery current collector.A laminated film having a resin layer on at least one surface of a polyester film, wherein the ratio (β / α) of the peak intensity (β) after the test to the peak intensity (α) before the test satisfies the following formula (1): [Formula] Peak intensity after the test (β) / Peak intensity before the test (α)>0.46 ... (1) [Peak intensity (α) before the test] The peak intensity (α) before the test is a value of 1650 to 1800 cm in a Raman spectrum (Rmα) measured in a cross-sectional region of the polyester film contained in the test film (sα) within a range of 1 μm in the thickness direction from one surface, prepared by laminating a copper layer on the resin layer side of the laminated film. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmα). -1 The peak intensity (β) after the test is defined as the peak intensity of 1650 to 1800 cm in the Raman spectrum (Rmβ) measured in a cross-sectional region within 1 μm in the thickness direction from one surface of the polyester film included in the test film (sβ) after the test described below. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmβ). -1 The peak intensity is defined as a peak intensity when the peak intensity due to the skeletal vibration of the benzene ring appearing in the range is set to 1. [Test film (sβ) after test] A test film (sα) was prepared by laminating a copper layer on the resin layer side of the laminated film, and a separator and lithium foil were laminated in this order on the copper layer side of the test film (sα). An electrolyte solution obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) was added so that the test film (sα), separator, and lithium foil were immersed, and the resultant was sealed to prepare a test coin cell (diameter 20 mm, height 3.2 mm). A current density of 0.09 mA / cm was applied to the test coin cell. 2 A current was applied at a constant current for 10 hours, and then at a current density of 0.09 mA / cm 2After repeating this cycle of passing a current in the reverse direction under the conditions of a constant current for 10 hours 10 times in total, the test film removed from the test coin cell is designated as the test film (sβ) after the test.

[0010] The present invention can contribute to improving the electrochemical stability of a film for metal lamination containing a polyester film as a substrate, and one embodiment of the present invention can contribute to improving the charge-discharge durability of a secondary battery.

[0011] FIG. 1 is a diagram showing a Raman spectrum of Example 1. FIG. 2 is a diagram showing a Raman spectrum of Example 2. FIG. 3 is a diagram showing a Raman spectrum of Example 3. FIG. 4 is a diagram showing a Raman spectrum of Example 4. FIG. 5 is a diagram showing a Raman spectrum of Comparative Example 1. FIG. 6 is a diagram showing voltammograms by linear sweep voltammetry of Examples and Comparative Examples. FIG. 7 is a diagram for explaining peak intensities of Raman spectra. FIG. 8 is a diagram showing a schematic cross section of one embodiment of the present invention. FIG. 9 is a diagram showing a schematic cross section of one embodiment of the present invention.

[0012] Next, an example of an embodiment of the present invention will be described, but the present invention is not limited to the embodiment described below.

[0013] <<Film for Metal Lamination>> A film for metal lamination according to one embodiment of the present invention (hereinafter also referred to as "the film" or "laminate film") preferably has a resin layer on at least one surface of a polyester film as a base film. The film is suitable for applications involving laminating metals because it has excellent electrochemical stability, particularly durability against polyester decomposition, and also good adhesion to metals. In particular, the film is particularly suitable for applications such as electrode current collectors having a laminated structure in which metal layers are stacked, because it has excellent charge and discharge durability.

[0014] The present film is a film for metal lamination having a resin layer on at least one surface of a polyester film, and it is preferable that the ratio (β / α) of the peak intensity (β) after the test to the peak intensity (α) before the test satisfies the following formula (1): Peak intensity (β) after the test / Peak intensity (α) before the test>0.46 (1)

[0015] [Peak intensity after test (β) / Peak intensity before test (α)] The ratio (β / α) shown in the above formula (1) is the ratio of the peak intensity derived from the C═O stretching vibration before and after the test, i.e., indicates the decomposition durability or charge / discharge durability of the polyester film. If the ratio (β / α) exceeds 0.46, the polyester film will have excellent decomposition durability or charge / discharge durability. From the viewpoint of significantly achieving the effects of the present invention, the ratio (β / α) is preferably 0.50 or more, more preferably 0.60 or more, even more preferably 0.70 or more, particularly preferably 0.75 or more, particularly preferably 0.80 or more, and particularly preferably 0.90 or more, with the upper limit being preferably 1.20 or less, more preferably 1.10 or less, and even more preferably 1.00±0.05. If the ratio is within the above range, the decomposition resistance of the polyester film can be further improved, and the charge / discharge durability of the film can be improved when applied to, for example, lithium-ion batteries, etc.

[0016] Methods for controlling the ratio (β / α) within the above range include, but are not limited to, the type of resin constituting the resin layer, the components blended with the resin, their content ratios, the thickness of the resin layer, the film formation method, etc. Preferably, a method using a component that does not exhibit a redox reaction within the desired operating potential range is effective. In addition, by hardening the resin layer to an appropriate degree, it is possible to prevent the electrolyte from penetrating the resin layer and the electrolyte from eluting the resin layer, which is effective.

[0017] [Measurement of Peak Intensities (α) and (β)] The measurement of the peak intensity (α) before the test according to the above formula (1) is carried out using a test film (sα) in which a copper layer is laminated on the resin layer side of the present film. The test film (sα) is prepared, for example, by providing a copper layer on the surface side of the resin layer of the present film using a vacuum deposition device or the like. The test film has a layer structure of "copper layer / resin layer / substrate layer (polyester film)". Details are as described in the Examples below.

[0018] The peak intensity (α) before the test was 1650 to 1800 cm in the Raman spectrum (Rmα) measured in a cross-sectional region within 1 μm in the thickness direction from one surface (surface on the resin layer side) of the polyester film (base layer) included in the test film (sα). -1 The peak intensity (α) is a peak intensity due to C═O stretching vibration appearing in the range of 1550 to 1650 cm in the Raman spectrum (Rmα). -1 The peak intensity derived from the skeletal vibration of the benzene ring, which appears in the range of

[0019] The peak intensity (α) before the test will be explained with reference to Fig. 7. In Fig. 7, symbols A1 and the like have the following meanings. A1: Scattering intensity on the low wavenumber side in the specified wavenumber range. A2: Wavenumber on the low wavenumber side in the specified wavenumber range. B1: Scattering intensity on the high wavenumber side in the specified wavenumber range. B2: Wavenumber on the high wavenumber side in the specified wavenumber range. P1: Highest scattering intensity in the specified wavenumber range. P2: Wavenumber at P1. Q1: Scattering intensity at P2 on the line (BL) connecting two points A1, A2 and B1, B2.

[0020] First, the 1650-1800 cm in the Raman spectrum (Rmα) before the test -1 The peak intensity due to the C═O stretching vibration appearing in the range of 1650 cm in the Raman spectrum (Rmα) is calculated. -1 is wave number A2, 1800 cm -1 is the wave number B2. 1650-1800 cm in the Raman spectrum (Rmα) -1 The peak intensity due to the C═O stretching vibration appearing in the range (wavenumber range of A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1650 cm -1 (wave number A2) and the measurement point of the scattering intensity (A1) at 1800 cm -1 The measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. That is, the measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. -1The peak intensity due to the C═O stretching vibration appearing in this range is determined by subtracting the value of Q1 from the value of P1 (P1−Q1).

[0021] Next, the 1550 to 1650 cm in the Raman spectrum (Rmα) before the test -1 The peak intensity due to the skeletal vibration of the benzene ring, which appears in the range of 1550 cm in the Raman spectrum (Rmα), is calculated. -1 is wave number A2, 1650 cm -1 is the wave number B2. -1 The peak intensity due to the skeletal vibration of the benzene ring appearing in the range (wavenumber range of A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1550 cm -1 (wave number A2) and the measurement point of scattering intensity (A1) at 1650 cm -1 The measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. That is, the measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. -1 The peak intensity due to the skeletal vibration of the benzene ring appearing in the range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0022] Then, 1650 to 1800 cm in the Raman spectrum (Rmα) before the test -1 The peak intensity (P1-Q1) due to the C═O stretching vibration appearing in the range of 1550 to 1650 cm in the Raman spectrum (Rmα) was -1 The peak intensity (α) is determined by converting the peak intensity (P1-Q1) derived from the skeletal vibration of the benzene ring that appears in the range of 1.

[0023] The Raman spectrum can be measured using a Raman spectrometer. Measurement conditions include an excitation laser wavelength of 785 nm, a laser intensity (maximum output) of 30 mW, and an exposure time of 0.25 seconds. Details are as described in the Examples below.

[0024] Next, the measurement of the peak intensity (β) after the test will be described. The measurement of the peak intensity (β) after the test is carried out by preparing a test coin cell using the test film (sβ) after the test.

[0025] [Preparation of Test Coin Cell] First, prepare a test coin cell (diameter 20 mm, height 3.2 mm). For example, prepare a CR2032 type coin cell including a main case, a cap case, a spacer, a washer, and a gasket (O-ring). Such a coin cell can be a commercially available product (for example, a coin cell manufactured by Hosensha).

[0026] The test coin cell contains a laminated structure of "lithium foil / separator / copper layer / resin layer / base layer (polyester film)." The test coin cell is fabricated, for example, by placing a gasket and a test film (sα) in the main case under an argon atmosphere, placing the separator so that its surface faces the copper layer of the test film (sα), and dripping a predetermined electrolyte solution. Next, lithium foil, a spacer, a washer, and a cap case are sequentially placed on the separator, and the cap case and main case are sealed using a coin cell crimping machine or the like. Details are as described in the Examples below.

[0027] The separator is a component that electrically and physically separates electrodes of opposite polarity in an electrochemical device and allows ions to pass between them, and can be any of the common separators used in lithium ion batteries. For example, separators made of polypropylene or polyethylene are suitable. Alternatively, a glass filter may be used as the separator.

[0028] The electrolyte used was obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2). The electrolyte was added to the test coin cell so that the test film (sα), separator, and lithium foil were immersed in the solution. When dissolving lithium bis(fluorosulfonyl)imide in the mixed solvent, the lithium bis(fluorosulfonyl)imide was dissolved in a manner calculated so that the lithium coordination number was 4, assuming that sulfolane has a coordination number of 1 and dimethoxyethane has a coordination number of 2. If necessary, an electrolyte capable of electrolytically depositing and dissolving lithium metal during testing can also be used. The electrolyte solution is generally prepared by dissolving the electrolyte in a solvent. Examples of the solvent include acetonitrile, propionitrile, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, fluoroethylene carbonate, sulfolane, dimethyl sulfoxide, 1,2-dimethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran. The above solvents may be used alone or in combination. Examples of the electrolyte include lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate.

[0029] [Test Treatment (Li Deposition and Dissolution Reaction Treatment)] The test coin cell was set in the device, and a current density of 0.09 mA / cm 2 After applying a current at a constant current for 10 hours to electrolytically deposit lithium on the copper layer of the test film, the current density was 0.09 mA / cm 2 A current is passed in the reverse direction under the conditions of 1000 kJ / s, ...

[0030] After repeating the cycle a total of 10 times as described above, the test coin cell is disassembled under an argon atmosphere, the test film (sβ) is taken out, and the Raman spectrum is measured in the same manner as described above to determine the peak intensity (β).

[0031] The peak intensity (β) after the test was 1650 to 1800 cm in the Raman spectrum (Rmβ) measured in a cross-sectional region within 1 μm in the thickness direction from one surface (surface on the resin layer side) of the polyester film (substrate layer) included in the test film (sβ) after the test. -1 The peak intensity (β) is a peak intensity due to C═O stretching vibration appearing in the range of 1550 to 1650 cm in the Raman spectrum (Rmβ). -1 The peak intensity derived from the skeletal vibration of the benzene ring, which appears in the range of

[0032] The peak intensity (β) after the test will be described with reference to FIG. 7. First, the peak intensity (β) after the test in the range of 1650 to 1800 cm -1 The peak intensity due to the C=O stretching vibration appearing in the range of 1650 cm in the Raman spectrum (Rmβ) is calculated. -1 is wave number A2, 1800 cm -1 is the wave number B2. 1650-1800 cm in the Raman spectrum (Rmβ) -1 The peak intensity due to the C═O stretching vibration appearing in the range (wavenumber range of A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1650 cm -1 (wave number A2) and the measurement point of the scattering intensity (A1) at 1800 cm -1 The measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. That is, the measurement points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measurement points of the scattering intensity (B1) at wavenumber B2. -1 The peak intensity due to the C═O stretching vibration appearing in this range is determined by subtracting the value of Q1 from the value of P1 (P1−Q1).

[0033] Next, after the test, the Raman spectrum (Rmβ) was measured at 1550 to 1650 cm -1 The peak intensity due to the skeletal vibration of the benzene ring, which appears in the range of 1550 cm in the Raman spectrum (Rmβ), is calculated. -1 is wave number A2, 1650 cm -1 is the wave number B2. -1The peak intensity due to the skeletal vibration of the benzene ring appearing in the range (wavenumber range of A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1550 cm -1 (wave number A2) and the measurement point of scattering intensity (A1) at 1650 cm -1 The measured points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measured points of the scattering intensity (B1) at wavenumber B2. That is, the measured points of the scattering intensity (B1) at wavenumber B2 are shown by a straight line connecting the measured points of the scattering intensity (B1) at wavenumber B2. -1 The peak intensity due to the skeletal vibration of the benzene ring appearing in the range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0034] After the test, the Raman spectrum (Rmβ) showed a peak at 1650 to 1800 cm -1 The peak intensity (P1-Q1) due to the C═O stretching vibration appearing in the range of 1550 to 1650 cm in the Raman spectrum (Rmβ) was -1 The peak intensity (P1-Q1) derived from the skeletal vibration of the benzene ring appearing in the range is set to 1, and the peak intensity (β) is determined by conversion.

[0035] As described above, the peak intensity ratio (β / α) is the ratio of the peak intensities derived from the C═O stretching vibration before and after the test, i.e., indicates the decomposition durability or charge-discharge durability of the polyester film. Therefore, if the ratio (β / α) exceeds 0.46, the polyester film will have excellent decomposition durability or charge-discharge durability.

[0036] [Layer structure of film for metal lamination] The laminate structure of the present film may be a structure in which a resin layer is formed on only one side of a polyester film, or a structure in which a resin layer is formed on both sides of a polyester film. Furthermore, a resin layer may be formed directly on the surface of the polyester film, or another layer may be provided between the polyester film and the resin layer. The polyester film and resin layer constituting the present film will be described in detail below.

[0037] <Polyester Film (Substrate Film)> The polyester film preferably contains polyester as the main component resin. The "main component resin" refers to the resin that is contained in the polyester film in the largest proportion, for example, a resin that accounts for 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more (including 100% by mass) of the resins that constitute the polyester film. The polyester film is preferably a film containing polyester as the main component. The "main component" refers to the component that is contained in the largest proportion of the components (100% by mass) that constitute the film, meaning that polyester accounts for 50% by mass or more, particularly 70% by mass or more, particularly 80% by mass or more, and even 90% by mass or more, and may even be 100% by mass.

[0038] [Polyester] The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming properties and productivity, it is preferably 0.45 to 1 dL / g, more preferably 0.5 to 0.9 dL / g, even more preferably 0.55 to 0.8 dL / g, and particularly preferably 0.6 to 0.75 dL / g. When two or more polyesters with different intrinsic viscosities are used, the intrinsic viscosity refers to the intrinsic viscosity of a mixed polyester. The intrinsic viscosity can be measured according to a conventional method. For example, 1 g of polyester is precisely weighed, dissolved in 100 mL of a 50 / 50 (mass ratio) phenol / tetrachloroethane solvent, and the viscosity can be measured at 30°C using a viscosity measuring device (for example, "VMS-022UPC-F10" manufactured by Rigo Co., Ltd.).

[0039] The polyester may be a homopolyester or a copolymer polyester, and specifically includes a polyester obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0040] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, and aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid.

[0041] Examples of the diol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, polytetramethylene ether glycol, dimer diol, and bisphenols (bisphenol compounds such as bisphenol A, bisphenol F, or bisphenol S, or derivatives thereof, or ethylene oxide adducts thereof).

[0042] Representative polyesters include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate.

[0043] Examples of the copolymer polyester include a copolymer polyester containing a third component as a copolymerization component other than the compound that is the main component of the dicarboxylic acid component constituting the polyester and the compound that is the main component of the diol component.

[0044] In particular, from the viewpoint of significantly achieving the effects of the present invention, the polyester film preferably contains polyethylene naphthalate (hereinafter also referred to as "PEN") or a polyethylene naphthalate-based copolymer (A) (hereinafter also referred to as "PEN-based copolymer") as the polyester, and more preferably contains a PEN-based copolymer. The content of the PEN or PEN-based copolymer in the polyester film is preferably 50% by mass or more, more preferably 70% by mass, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more (including 100% by mass) of the resin constituting the polyester film and / or the components constituting the polyester film. Note that, when the polyester film has a laminated structure, it is preferable that the content of PEN or PEN-based copolymer (A) contained in each layer satisfies the above. Alternatively, the polyester film may be a mixture of PEN and a PEN-based copolymer.

[0045] Specifically, the PEN copolymer contains a dicarboxylic acid component (a-1) and a diol component (a-2), and more specifically, contains a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1), and ethylene glycol as the diol component (a-2), and contains a copolymerization component in at least one of the dicarboxylic acid component (a-1) and the diol component (a-2).

[0046] The PEN copolymer preferably contains 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more of the dicarboxylic acid component (a-1), and even more preferably all (100 mol %) of the dicarboxylic acid component (a-1) is a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid. By adjusting the content of naphthalenedicarboxylic acid in the dicarboxylic acid component (a-1) to 80 mol % or more, it becomes easier to adjust the shrinkage rate to a desired range, for example. 2,6-naphthalenedicarboxylic acid is the most preferred naphthalenedicarboxylic acid.

[0047] The PEN copolymer preferably contains ethylene glycol in the diol component (a-2) in an amount of 51 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, particularly preferably 80 mol% or more, and especially preferably 90 mol% or more. On the other hand, the amount of ethylene glycol in the diol component (a-2) is preferably 99 mol% or less, more preferably 98 mol% or less, even more preferably 97 mol% or less, particularly preferably 96 mol% or less, and especially preferably 95 mol% or less.

[0048] The PEN copolymer preferably contains 20 mol % or less, more preferably 10 mol % or less, of a copolymerizable component in the dicarboxylic acid component (a-1). It is even more preferable that all of the dicarboxylic acid component (a-1) is a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, i.e., the copolymerizable component is 0 mol %. The PEN copolymer also contains 49 mol % or less, more preferably 40 mol % or less, even more preferably 30 mol % or less, particularly preferably 20 mol % or less, and especially preferably 10 mol % or less, of a copolymerizable component in the diol component (a-2). The copolymerizable component in the diol component (a-2) is preferably 1 mol % or more, more preferably 2 mol % or more, even more preferably 3 mol % or more, particularly preferably 4 mol % or more, and especially preferably 5 mol % or more.

[0049] When the main component is 2,6-naphthalenedicarboxylic acid, examples of copolymerization components added to the dicarboxylic acid component (a-1) include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; and aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid. From the viewpoint of moldability, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, and 3,4-furandicarboxylic acid are preferred. These copolymerization components can be used alone or in combination of two or more.

[0050] Furthermore, examples of copolymerization components that can be added to the diol component (a-2) include diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, polytetramethylene ether glycol, dimer diol, and bisphenols (bisphenol compounds such as bisphenol A, bisphenol F, or bisphenol S, or derivatives thereof, or ethylene oxide adducts thereof). As the bisphenol, it is preferable to use a bisphenol-ethylene oxide adduct, and it is particularly preferable to use a bisphenol A-ethylene oxide adduct. These copolymerization components can be used alone or in combination of two or more.

[0051] For example, the PEN copolymer may contain a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) and a bisphenol-ethylene oxide adduct such as bisphenol A-ethylene oxide adduct and ethylene glycol as the diol component (a-2). In this PEN copolymer, the dicarboxylic acid component (a-1) contains preferably 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and particularly preferably 100 mol % of naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid. Furthermore, in this PEN copolymer, the diol component (a-2) contains a bisphenol-ethylene oxide adduct such as a bisphenol A-ethylene oxide adduct in an amount of preferably 1 mol % to 49 mol %, more preferably 2 mol % to 40 mol %, even more preferably 3 mol % to 30 mol %, particularly preferably 4 mol % to 20 mol %, and especially preferably 5 mol % to 10 mol %; and the diol component (a-2) contains ethylene glycol in an amount of preferably 51 mol % to 99 mol %, more preferably 60 mol % to 98 mol %, even more preferably 70 mol % to 97 mol %, particularly preferably 80 mol % to 96 mol %, and especially preferably 90 mol % to 95 mol %.

[0052] Typically, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is by-produced from the ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol by-produced from ethylene glycol varies depending on the polycondensation method, but is approximately 5 mol% or less of the ethylene glycol. In the present invention, 5 mol% or less of diethylene glycol is defined as by-product diethylene glycol, and the by-product diethylene glycol is also included in ethylene glycol and is distinguished from a copolymerization component. On the other hand, depending on the diethylene glycol content, more specifically, when diethylene glycol is contained in excess of 5 mol%, diethylene glycol is treated as a copolymerization component rather than as a by-product diethylene glycol.

[0053] [Polymerization Catalyst] The polycondensation catalyst used in the polycondensation of polyester is not particularly limited, and conventionally known compounds can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds. Among these, titanium compounds and antimony compounds are preferred from the viewpoint of productivity. When using the above titanium compounds as the polymerization catalyst, the titanium content in the polyester film is preferably 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm. When the polyester film is multilayered, the titanium content in the entire film should be within the above range, and it is particularly desirable that the titanium content in each layer be within the above range. By controlling the titanium compound content to the above upper limit or less, deterioration of the polyester during the melt extrusion process can be prevented, preventing the resulting film from becoming strongly yellowish. Furthermore, controlling the content to the above lower limit or more improves polymerization efficiency, reduces costs, and facilitates the production of a film with sufficient strength. As described above, when using a polyester containing a titanium compound derived from a polymerization catalyst, it is preferable to incorporate a phosphorus compound into the polyester to reduce the activity of the titanium compound and prevent degradation during the melt extrusion process. Considering the productivity and thermal stability of the polyester, alkyl acid phosphates such as orthophosphoric acid and ethyl acid phosphate are preferred as phosphorus compounds. The phosphorus content in the polyester film is preferably 1 to 300 ppm, more preferably 3 to 200 ppm, and even more preferably 5 to 100 ppm. By controlling the phosphorus compound content to below the upper limit, the phosphorus compound can be prevented from causing gelation or foreign matter. Furthermore, by controlling the content to above the lower limit, the activity of the titanium compound can be sufficiently reduced, preventing the resulting film from having a yellowish tint. When the polyester film is multilayered, the phosphorus content in the titanium-containing layer should be within the above range.

[0054] [Particles] Particles can also be incorporated into polyester films. Typically, the inclusion of particles in polyester films provides easy lubricity and prevents scratches during each process, improving handleability. The type of particles incorporated into polyester films is not particularly limited as long as they are capable of providing easy lubricity. Examples include inorganic particles such as silica, amorphous silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide; crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles; and organic particles such as calcium oxalate and ion exchange resins. These particles can be used alone or in combination of two or more. Furthermore, precipitated particles obtained by precipitating and finely dispersing a portion of a metal compound, such as a catalyst, during the polyester production process can also be used. Among these, silica particles and calcium carbonate particles are preferred because they are particularly effective even in small amounts.

[0055] The shape of the particles to be used is not particularly limited, and any of spherical, blocky, rod-like, flat, etc. may be used. There are also no particular limitations on the hardness, specific gravity, color, etc.

[0056] The average particle size of the particles is typically 0.01 to 5 μm, preferably 0.03 to 4 μm, more preferably 0.05 to 3.5 μm, and even more preferably 0.1 to 3 μm. An average particle size within this range can achieve both easy handling and transparency of the polyester film. When the particles are in powder form, the average particle size can be determined by measuring the powder using a centrifugal sedimentation particle size distribution analyzer (e.g., Shimadzu Corporation's "SA-CP3" model) and determining the particle size at an integrated volume fraction of 50% (d50) in the equivalent spherical distribution. The average particle size of particles in a film, layer, or resin can be determined by observing the diameters of 10 or more particles using a scanning electron microscope (SEM) and measuring the particle diameters, and then calculating the average value. In the case of non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0057] When particles are incorporated into a polyester film, it is preferred that the polyester film be a laminate having a surface layer and an intermediate layer, and that the particles be incorporated into the surface layer.

[0058] The method for adding particles to a polyester film is not particularly limited, and any conventionally known method can be used. For example, particles can be added at any stage of polyester production, but it is preferable to add particles after the completion of the esterification or transesterification reaction.

[0059] The particle content in the polyester film depends on the average particle size, but is usually 8000 ppm or less, preferably 5000 ppm or less, more preferably 3000 ppm or less, by mass in the particle-containing layer. The particle content in the particle-containing layer is not particularly limited, and is, for example, 50 ppm or more, preferably 100 ppm or more.

[0060] The resin layer described below may be provided on a particle-containing layer of the polyester film, or on a layer that does not substantially contain particles. Furthermore, the surface of the polyester film opposite to the surface on which the resin layer is provided (the opposite surface) may be a layer that does not substantially contain particles, or may be a layer that contains particles. Furthermore, by providing a particle-containing layer on one or both of the surface on which the resin layer is provided and the opposite surface, the winding property is improved. To impart excellent smoothness to at least one surface of the polyester film, the surface layer on the smooth surface side may contain particles or may be substantially free of particles. However, to obtain a film with extremely high smoothness, it is preferable that the surface layer be substantially free of particles. Note that "substantially free of particles" means that particles are not intentionally contained, specifically, that the particle content (particle concentration) is less than 50 ppm by mass, more preferably 40 ppm or less, and even more preferably 30 ppm or less. In this case, by laminating a resin layer on the surface layer on the smooth surface side and / or the surface layer on the side opposite the smooth surface, the handling property of the film when wound into a roll can be improved. In particular, from the viewpoint of maintaining the smoothness of the film and improving the handling properties, it is preferable that at least one surface be made smooth and that a resin layer be laminated on the opposite surface.

[0061] In addition to the above-mentioned particles, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film as needed. The polyester film may also contain other resins besides polyester as long as the effects of the present invention are not impaired. Other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polyether ether ketone resins, polyether ketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine-based resins.

[0062] [Layer Structure of Polyester Film, etc.] The polyester film may be composed of a single layer, or may be composed of a laminate of two or more layers, and is preferably composed of a laminate of three or more layers. There is no particular upper limit on the number of layers, but it is preferably about 10 layers or less. Examples of polyester films composed of a laminate of two or more layers include layer structures such as "first layer (surface layer) / second layer (surface layer)" and "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)." Among these, a polyester film composed of three layers, i.e., "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," is preferred. When the polyester film has a structure of "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," it is preferable that the thickness of the second layer (intermediate layer) be thicker than the thicknesses of the first layer (surface layer) and the third layer (surface layer). The thickness ratio of each layer (first layer (surface layer):second layer (intermediate layer):third layer (surface layer)) is not particularly limited, but is preferably 1.0-1.6:8.0-12:1.0-1.6, more preferably 1.0-1.5:8.5-11.5:1.0-1.5, and even more preferably 1.0-1.4:9.0-11:1.0-1.4.

[0063] Furthermore, when the polyester film has a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)" structure, it is preferable that the material composition forming the second layer (intermediate layer) is different from the material composition forming the first layer (surface layer), and it is preferable that the material composition forming the second layer (intermediate layer) is different from the material composition forming the third layer (surface layer). It is more preferable that the material composition forming the second layer (intermediate layer) is different from the material composition forming the first layer (surface layer) and the third layer (surface layer). It is even more preferable that the material composition forming the second layer (intermediate layer) is different from the material composition forming the first layer (surface layer) and the third layer (surface layer), and that the material composition forming the first layer (surface layer) and the third layer (surface layer) is the same. Furthermore, when the polyester film has a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)" structure, it is preferable that it has a two-type three-layer structure. Specifically, it is preferable that the polyester film contains three layers, the layers are made of two different material compositions, and the material compositions constituting the first layer (surface layer) and the third layer (surface layer) are the same.

[0064] Furthermore, when the polyester film is a laminate of two or more layers, it is preferable to use a laminate having two layers with different properties. Such a laminate can impart different characteristics to each layer, thereby achieving multi-functionality. Specifically, although not particularly limited, for example, in the case of a polyester film consisting of a three-layer laminate formed by laminating a surface layer, an intermediate layer, and another surface layer in this order, one or both of the surface layers can be made into a layer containing inorganic particles such as silica, organic particles, or additives such as the lubricant described above, so that the surface layer and the intermediate layer have different properties, thereby achieving multi-functionality.

[0065] The thickness (total thickness) of the polyester film is preferably 1 μm to 300 μm, more preferably 1 μm to 200 μm, even more preferably 1 μm to 150 μm, particularly preferably 1 μm to 100 μm, and especially preferably 1 μm to 80 μm. The thickness (total thickness) of the polyester film can be appropriately set within the above range, and may be, for example, 5 μm to 70 μm, 10 μm to 65 μm, or 20 μm to 60 μm. The thickness of the polyester film was measured at five random locations within the plane using a 1 / 1000 mm dial gauge, and the average of the measurements was used.

[0066] When the polyester film is a laminate of two or more layers, the thickness of each film constituting each layer is not particularly limited, but is, for example, 1 μm or more, preferably 1.5 μm or more, and may be 2 μm or more, and is, for example, 100 μm or less, preferably 80 μm or less, 70 μm or less, etc. Specifically, although not particularly limited, in the case of a polyester film composed of three layers, for example, "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)", it is preferable that the first layer (surface layer) and the third layer (surface layer) have thicknesses of 1 μm to 5 μm and 1.5 μm to 4 μm, respectively, and that the second layer (intermediate layer) have thicknesses of 15 μm to 60 μm and 20 μm to 50 μm.

[0067] The polyester film may be a non-stretched film (sheet) or a stretched film. Among these, a stretched film stretched uniaxially or biaxially is preferred. Among these, a biaxially stretched film is more preferred in terms of excellent balance of mechanical properties and flatness. The biaxially stretched film refers to a film in which the refractive index in the longitudinal direction (MD) and width direction (TD) of the film is higher than the refractive index in the thickness direction, and is usually obtained by stretching the film in the longitudinal and width directions.

[0068] [Method for Producing Polyester Film] A method for producing a polyester film will now be described in detail, but is not limited to the following method. For example, when producing a biaxially stretched film, a preferred method is to extrude dried polyester pellets as described above from a die using a melt extrusion device such as an extruder as a molten sheet, and then cool and solidify the sheet on a cooling roll such as a rotating cooling drum to obtain an unstretched sheet. Here, cooling is performed, for example, to a temperature below the glass transition point of the polymer to obtain a substantially amorphous unoriented sheet (unstretched sheet). Furthermore, to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the cooling roll, and an electrostatic adhesion method and / or a liquid application adhesion method are preferably used.

[0069] The unstretched sheet is then stretched biaxially. In this case, the unstretched sheet is first stretched in one direction using a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times.

[0070] Next, the film is stretched in a direction perpendicular to the first stretching direction. In this case, the stretching temperature is usually 70 to 170°C, preferably 75 to 160°C, and the stretching ratio is usually 3 to 7 times, preferably 3.5 to 6 times.

[0071] Subsequently, the film is heat-treated under tension or relaxation of 30% or less at a temperature of typically 180 to 270°C, preferably 190 to 260°C, to obtain a biaxially stretched film. This heat treatment is also called a heat setting process. The heat treatment may be performed in two or more stages at different temperatures. Alternatively, cooling may be performed in a cooling zone after the heat treatment. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester constituting the film, more specifically, preferably in the range of 100 to 160°C, and preferably under relaxation of 1.0 to 2.5% in the width direction. This cooling may be performed in two or more stages at different temperatures. In the above-mentioned stretching, a method of performing unidirectional stretching in two or more stages can also be employed. In this case, it is preferable to perform the heat treatment so that the final stretch ratios in both directions are within the above-mentioned ranges.

[0072] A simultaneous biaxial stretching method can also be employed in the production of polyester films. In the simultaneous biaxial stretching method, the unstretched sheet is simultaneously stretched and oriented in the machine direction (longitudinal direction) and width direction (transverse direction) under temperature control, typically at 70 to 120°C, preferably 80 to 110°C. The area stretching ratio is preferably 4 to 50 times, more preferably 7 to 35 times, and even more preferably 10 to 25 times. Subsequently, the sheet is heat-treated under tension or relaxation of 30% or less, typically at a temperature of 170 to 250°C, to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus employing the above-described stretching method, conventionally known stretching methods, such as a screw system, a pantograph system, and a linear drive system, can be employed.

[0073] <Others> In order to suppress the amount of ester cyclic trimer precipitation after heat treatment, the polyester film can also be produced using a polyester with a low content of ester cyclic trimer as the raw material. Various known methods can be used to produce a polyester with a low content of ester cyclic trimer, such as a method of solid-state polymerization after polyester production. Furthermore, the amount of ester cyclic trimer precipitation after heat treatment can be suppressed by forming a polyester film with a three-layer or more structure and using a polyester raw material with a low content of ester cyclic trimer as the outermost layer of the polyester film. Furthermore, the polyester can be obtained by esterification or transesterification, followed by melt polycondensation under reduced pressure at a higher reaction temperature.

[0074] <Resin Layer> In order to further improve the decomposition durability or charge / discharge durability of the polyester film as the base film, it is preferable that a resin layer formed from a resin composition is formed on at least one surface of the polyester film. The "resin" constituting the resin layer of the present invention means the main component involved in film formation, and specifically includes one or more selected from the group consisting of binder resins and crosslinking agents. The binder resin and crosslinking agent may be appropriately selected and used within a range that does not impair the effects of the present invention.

[0075] [Binder Resin] Examples of the binder resin include (meth)acrylic resins, ion-conductive polymer compounds, polyurethane resins, polyolefin resins, polyvinyl alcohol, polyesters, etc. These may be used alone or in combination of two or more.

[0076] ((Meth)acrylic Resin) A (meth)acrylic resin is a polymer (polyacrylic resin, polymethacrylic resin) composed of polymerizable monomers including acrylic or methacrylic monomers. These may be homopolymers or copolymers, or copolymers with polymerizable monomers other than acrylic or methacrylic monomers. A (meth)acrylic polymer is a polymer having structural units derived from (meth)acrylic acid or (meth)acrylic acid alkyl esters. A (meth)acrylic polymer may be a polymer of at least one selected from (meth)acrylic acid and (meth)acrylic acid alkyl esters, or a copolymer of at least one selected from these with at least one other monomer, such as styrene or a styrene derivative, or a monomer containing a hydroxyl group. Furthermore, such a polymer may be a copolymer of another polymer (e.g., polyester, polyurethane, etc.), such as a block copolymer or a graft copolymer. For example, the (meth)acrylic resin may be a (meth)acrylic-modified polyester resin or a (meth)acrylic-modified polyurethane resin. The (meth)acrylic resin may also be a polymer (or a mixture of polymers, in some cases) obtained by polymerizing a polymerizable monomer in a polyester solution or polyester dispersion, or a polymer (or a mixture of polymers, in some cases) obtained by polymerizing a polymerizable monomer in a polyurethane solution or polyurethane dispersion. The polyesters and polyurethanes used in the (meth)acrylic resins can be appropriately selected from the polyesters and polyurethanes exemplified for use in the resins described below. However, as described below, in order to effectively suppress the reductive decomposition of the polyester film, it is preferable that no reduction current be observed in a voltammogram obtained by linear sweep voltammetry measurement. Therefore, it is preferable that the proportion of the polyester skeleton portion in the (meth)acrylic-modified polyester resin is small. Similarly, it is preferable that the proportion of the urethane skeleton portion in the (meth)acrylic-modified polyurethane resin is small.In order to further improve adhesion to polyester films, the (meth)acrylic resin may contain one or more groups selected from the group consisting of a carboxy group, a hydroxy group, an amino group, a methylol group, and a cyano group. Among these, acrylic resins containing a carboxy group are preferred.

[0077] The polymerizable monomer is not particularly limited, but examples thereof include carboxy group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and salts thereof; hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyfumarate, and monobutylhydroxyitaconate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate. alkyl(meth)acrylate esters; nitrogen-containing monomers such as (meth)acrylamide, diacetone acrylamide, or (meth)acrylonitrile; nitrogen-containing monomers containing a hydroxyl group such as N-methylol(meth)acrylamide; styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and vinyltoluene; vinyl esters such as vinyl propionate; silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl halides such as vinyl chloride and vinylidene chloride; and conjugated dienes such as butadiene.

[0078] Among the above (meth)acrylic resins, polymers obtained by polymerizing polymerizable monomers including acrylic or methacrylic monomers are preferred, and it is more preferred that the polymerizable monomers include alkyl(meth)acrylic acid esters. Furthermore, it is preferred that the coating solution containing the (meth)acrylic resin is diluted with a solvent to form a coating solution, and it is preferred that the solvent contains water as the main solvent (50% by mass or more). From this perspective, the acrylic resin is also preferably a polymer obtained by polymerizing alkyl(meth)acrylic acid esters and polymerizable monomers including a hydroxyl group-containing monomer, a carboxyl group-containing monomer, or other hydrophilic group-containing monomer. Furthermore, the (meth)acrylic resin may be, for example, an emulsion polymer obtained by polymerizing a polymerizable monomer in the presence of a surfactant.

[0079] (Ion-conductive polymer compound) The ion-conductive polymer compound is a polymer compound containing an ion-conductive functional group, and examples thereof include ammonium group-containing compounds, polyether compounds, sulfonic acid compounds, betaine compounds, etc. Among these, ammonium group-containing compounds are preferred from the viewpoints of maintaining smoothness and forming a coating film.

[0080] The ammonium group-containing compound refers to a compound having an ammonium group in the molecule, and is preferably a polymer compound having an ammonium group. For example, a polymer containing a monomer having an ammonium group and an unsaturated double bond as a component can be used.

[0081] Specific examples of such polymers include polymers having, as repeating units, the constituent elements represented by the following formula (1): Homopolymers or copolymers of these, and copolymers of these with a plurality of other components may also be used.

[0082]

[0083] In the above "Chemical Formula 1", R 1 , R 2are each independently a hydrogen atom, an alkyl group, a phenyl group, or the like, and these alkyl groups and phenyl groups may be substituted with the groups shown below. Examples of the substitutable groups include a hydroxy group, an amide group, an ester group, an alkoxy group, a phenoxy group, a naphthoxy group, a thioalkoxy group, a thiophenoxy group, a cycloalkyl group, a trialkylammonium alkyl group, a cyano group, and a halogen atom. 1 and R 2 may be chemically bonded, for example, -(CH2) m -(m=an integer of 2 to 5), -CH(CH3)CH(CH3)-, -CH=CH-CH=CH-, -CH=CH-CH=N-, -CH=CH-N=C-, -CHOCH2-, -(CH2)2O(CH2)2-, and the like.

[0084] X in the above "Chemical Formula 1" - is, for example, a halogen ion, a sulfonate, a phosphate, a nitrate, an alkyl sulfonate, a carboxylate, and the like.

[0085] The above polymers, i.e., polymers containing a monomer having an ammonium group and an unsaturated double bond as a component, may be copolymerized with other monomers from the viewpoint of improving film-forming properties and obtaining stable coatings. Examples of such other monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate, and acrylamides such as n-methylolacrylamide.

[0086] The number average molecular weight of the ammonium group-containing compound is preferably 1,000 to 500,000, more preferably 2,000 to 350,000, even more preferably 5,000 to 200,000, particularly preferably 10,000 to 100,000, and especially preferably 10,000 to 80,000. By setting the molecular weight to 1,000 or more, it is possible to prevent the strength of the coating film from weakening and to easily improve heat resistance stability. Furthermore, by setting the molecular weight to 500,000 or less, it is possible to prevent the viscosity of the coating liquid from increasing and to easily improve handleability and coatability.

[0087] (Polyurethane Resin) A polyurethane resin is a polymer compound having a urethane bond in the molecule, and is preferably water-dispersible or water-soluble. In order to impart water-dispersibility or water-solubility, it is preferable to introduce a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a sulfonyl group, a phosphate group, or an ether group into the polyurethane resin. Among the above hydrophilic groups, a carboxyl group or a sulfonic acid group is preferred in terms of adhesion to a polyester film.

[0088] Polyurethane resins can be obtained by conventional methods, such as by reacting a hydroxyl group-containing compound with an isocyanate. Polyols are preferably used as raw materials for the hydroxyl group-containing compound, including polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

[0089] Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

[0090] Examples of the polyester polyols include those obtained from polycarboxylic acids or their acid anhydrides and polyhydric alcohols. Examples of polycarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, and isophthalic acid. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, and 1 ,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamines, lactonediols, and the like.

[0091] Examples of the polycarbonate polyols include polycarbonate diols obtained by dealcoholization reaction of polyhydric alcohols with dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, etc., and specifically include poly(1,6-hexylene) carbonate and poly(3-methyl-1,5-pentylene) carbonate.

[0092] Examples of polyisocyanate compounds used to obtain polyurethane resins include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidenedicyclohexyl diisocyanate.

[0093] A chain extender may be used when synthesizing the polyurethane resin. The chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group, and generally, a chain extender having two hydroxyl groups or two amino groups can be mainly used.

[0094] Examples of chain extenders having two hydroxyl groups include glycols such as aliphatic glycols such as ethylene glycol, propylene glycol, and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; and ester glycols such as neopentyl glycol hydroxypivalate.

[0095] Examples of chain extenders having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine; aliphatic diamines such as ethylenediamine, propanediamine, hexanediamine, 2,2-dimethyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine; and alicyclic diamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, 1,4-diaminocyclohexane, and 1,3-bisaminomethylcyclohexane.

[0096] It should be noted that polyurethane resins require careful selection because a reduction current may be observed in a voltammogram obtained by the following linear sweep voltammetry measurement. When using a polyurethane resin, it is preferable to perform linear sweep voltammetry measurement of the polyurethane resin and select a polyurethane resin in which a reduction current is unlikely to be observed, or preferably no reduction current is observed, in the obtained voltammogram.

[0097] (Polyolefin Resin) Examples of polyolefin resins include homopolymers obtained by polymerizing α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene, and copolymers containing α-olefins as the main monomer component. Among these, polyethylene-based resins containing ethylene as the main monomer component and polypropylene-based resins containing propylene as the main monomer component are preferred. Here, the term "main monomer component" refers to a monomer component that accounts for 50% by mass or more and 100% by mass or less of the resin.

[0098] (Polyethylene-Based Resin) The polyethylene-based resin is not particularly limited as long as it is a resin containing ethylene as the main monomer component, and examples thereof include low-density polyethylene, linear low-density polyethylene, linear very low-density polyethylene, medium-density polyethylene, high-density polyethylene, etc. Furthermore, the polyethylene-based resin may be an ethylene homopolymer, or a copolymer containing ethylene as the main monomer component and another copolymerizable monomer component.

[0099] Examples of the other copolymerizable monomer component (comonomer) include α-olefins having 3 to 10 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, vinyl esters, such as vinyl acetate and vinyl propionate, unsaturated carboxylic acid esters, such as methyl (meth)acrylate and ethyl (meth)acrylate, and ionomers thereof, and unsaturated compounds, such as conjugated dienes and non-conjugated dienes. The proportion of the other copolymerizable monomer component is not particularly limited, but is usually 30% by mass or less, and more preferably 15% by mass or less.

[0100] Examples of the copolymer include copolymers or multicomponent copolymers containing ethylene as a main monomer component and one or more comonomers selected from the other copolymerizable monomer components described above, or mixtures thereof.

[0101] Among the above polyethylene-based resins, low-density polyethylene, linear low-density polyethylene, linear very low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene (meth)acrylic acid ester copolymer, and ionomer resin are preferred, with linear low-density polyethylene being particularly preferred.

[0102] Furthermore, the linear low-density polyethylene is preferably a linear low-density polyethylene containing at least one α-olefin selected from the group consisting of 1-butene, 1-hexene, and 4-methyl-1-pentene as a comonomer. The proportion of these comonomer components is not particularly limited, but is usually 30% by mass or less, and more preferably 15% by mass or less. The inclusion of these comonomer components can enhance the flexibility and transparency of the film.

[0103] The method for producing the polyethylene resin is not particularly limited, and examples thereof include known polymerization methods using known olefin polymerization catalysts, such as slurry polymerization, solution polymerization, bulk polymerization, and gas phase polymerization using multi-site catalysts typified by Ziegler-Natta catalysts or single-site catalysts typified by metallocene catalysts, as well as bulk polymerization using a radical initiator.

[0104] The melting point of the polyethylene resin is preferably 70 to 130°C, more preferably 80 to 120°C. A melting point within this range is preferable because the film has a good balance of flexibility, strength, and heat resistance. The melting point is the crystalline melting peak temperature (Tm) (°C) determined from a thermogram measured using a differential scanning calorimeter (DSC) by heating approximately 10 mg of resin from -50°C to 200°C at a heating rate of 10°C / min, holding at 200°C for 1 minute, then cooling to -50°C at a cooling rate of 10°C / min, and again heating to 200°C at a heating rate of 10°C / min.

[0105] The melt flow rate (MFR) of the polyethylene resin is not particularly limited, but is typically 0.1 g / 10 min or higher, preferably 0.5 to 18 g / 10 min, and more preferably 1 to 15 g / 10 min. An MFR of 0.1 g / 10 min or higher provides stable extrusion processability, while an MFR of 20 g / 10 min or lower provides stable film formation during molding and minimizes thickness unevenness, reductions in mechanical strength, and other variations. The MFR is a value measured in accordance with JIS K 7210-1 (2014), under measurement conditions of 190°C and a load of 2.16 kg.

[0106] The density of the polyethylene resin is 0.880 to 0.980 g / cm 3 is preferably 0.890 to 0.960 g / cm 3 More preferably, it is 0.900 to 0.940 g / cm 3 It is particularly preferable that the density is 0.880 to 0.980 g / cm 3It is preferable that the density is in the range of 100 to 1500 nm because the balance of strength, adhesiveness, and flexibility is excellent. Here, the density is a value measured in accordance with JIS K 7112 (1999).

[0107] ((Polypropylene-based resin)) The polypropylene-based resin is not particularly limited as long as it is a resin containing propylene as the main monomer component, and may be a propylene homopolymer or a copolymer containing propylene as the main monomer component and other copolymerizable monomer components. The polypropylene-based resin may be used alone, or two or more types differing in copolymerizable monomer components, their compositions, physical properties, etc. may be used in combination.

[0108] Examples of the other copolymerizable monomer components (comonomers) include α-olefins having 2 to 20 carbon atoms, such as ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene; dienes, such as divinylbenzene, 1,4-cyclohexadiene, dicyclopentadiene, cyclooctadiene, and ethylidene norbornene; vinyl acetate, (meth)acrylic acid, (meth)acrylic acid esters, glycidyl (meth)acrylate, vinyl alcohol, ethylene glycol, maleic anhydride, styrene, and cyclic olefins. The polypropylene-based resin may be a multi-component copolymer containing two or more of the other copolymerizable monomer components described above. When the polypropylene-based resin contains a monomer component other than propylene and ethylene, 1-butene is preferred as the monomer component.

[0109] The polypropylene resin may be a block copolymer, a random copolymer, or a graft copolymer.

[0110] The melting point of the polypropylene resin is preferably 70 to 170° C., more preferably 80 to 160° C. If the melting point is within this range, the film will have a good balance of flexibility, strength, and heat resistance, which is preferable.

[0111] The melt flow rate (MFR) of the polypropylene resin is not particularly limited, but is usually 0.2 g / 10 min or more, preferably 0.5 to 18 g / 10 min, and more preferably 1 to 15 g / 10 min. An MFR of 0.2 g / 10 min or more stabilizes extrusion processability, while an MFR of 20 g / 10 min or less enables stable film formation during molding and reduces thickness unevenness, reduction or variation in mechanical strength, etc., which is preferable.

[0112] (Polyvinyl Alcohol) Polyvinyl alcohol is a compound having a polyvinyl alcohol moiety. For example, conventionally known polyvinyl alcohols can be used, including modified compounds in which polyvinyl alcohol has been partially acetalized or butyralized. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is typically 100 or higher, preferably in the range of 300 to 40,000. A degree of polymerization of 100 or higher facilitates improving the water resistance of the resin layer. Furthermore, the degree of saponification of polyvinyl alcohol is not particularly limited, but saponified polyvinyl acetates having a degree of saponification of typically 70 mol% or higher, preferably in the range of 70 to 99.9 mol%, more preferably 80 to 97 mol%, and even more preferably 86 to 95 mol% are practically used.

[0113] (Polyalkylene glycol) Examples of polyalkylene glycols include polymethylene glycol, polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, polyhexamethylene glycol, polyalkylene glycols having structural units derived from two or more glycols such as a copolymer of ethylene oxide and propylene oxide, and branched polyalkylene glycols using polyfunctional alcohols such as glycerin. These may be used alone or in combination of two or more.

[0114] The number average molecular weight of the polyalkylene glycol is, for example, preferably 200 to 20,000, more preferably 500 to 15,000, and even more preferably 1,000 to 10,000. The number average molecular weight is calculated based on the hydroxyl value measured in accordance with JIS K 1577:2007.

[0115] The content of the binder resin in the resin layer is preferably 10 to 99% by mass, more preferably 20 to 95% by mass, even more preferably 30 to 90% by mass, particularly preferably 35 to 88% by mass, and especially preferably 40 to 86% by mass, based on the total mass of the resin layer (non-volatile components). Depending on the type of binder resin, the content of the binder resin may be more than 99% by mass, 99.5% by mass or more, or even 100% by mass, based on the total mass of the resin layer (non-volatile components).

[0116] [Crosslinking Agent] The crosslinking agent is not particularly limited, and a conventionally known crosslinking agent can be used. Examples of the crosslinking agent include melamine compounds, oxazoline compounds, epoxy compounds, carbodiimide compounds, isocyanate compounds, and silane coupling compounds. These may be used alone or in combination of two or more.

[0117] (Melamine Compound) A melamine compound is a compound having a melamine skeleton within the compound. Examples include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures thereof. Examples of alkylolation include methylolation, ethylolation, isopropylolation, n-butylolation, and isobutyrolation. Among these, methylolation is preferred from the viewpoint of reactivity. Alcohols used for etherification include methanol, ethanol, isopropanol, n-butanol, and isobutanol, with methanol being more preferred. Furthermore, the melamine compound may be either a monomer or a dimer or higher polymer, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be further used to increase the reactivity of the melamine compound.

[0118] (Oxazoline Compound) An oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferred. The oxazoline compound can be obtained by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of addition-polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These may be used alone or in combination of two or more. Of these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, and a cyclohexyl group); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated amides such as N-alkyl(meth)acrylamides, N-alkyl(meth)acrylamides, and N,N-dialkyl(meth)acrylamides (the alkyl group can be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. These may be used alone or in combination of two or more.The oxazoline compound may have a polyalkylene oxide chain such as a polyethylene oxide chain, and for example, a (meth)acrylate having a polyalkylene oxide chain may be used as another monomer. From the viewpoint of improving adhesion to polyester films, the amount of oxazoline groups in the oxazoline compound is preferably in the range of 0.5 to 10 mmol / g, more preferably 1 to 9 mmol / g, and even more preferably 3 to 8 mmol / g.

[0119] (Epoxy Compound) The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. with a hydroxyl group or an amino group, polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc. Among these, polyepoxy compounds are preferred from the viewpoint of better adhesion of polyester films, etc.

[0120] Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, etc. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, etc. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, and examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0121] (Carbodiimide Compound) A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. From the viewpoint of better adhesion of the polyester film, a polycarbodiimide compound having two or more carbodiimide structures in the molecule is more preferred.

[0122] Carbodiimide compounds can be synthesized by conventionally known techniques, and generally involve the condensation reaction of a diisocyanate compound. The diisocyanate compound is not particularly limited, and both aromatic and aliphatic diisocyanates can be used. Specific examples include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate.

[0123] The content of carbodiimide groups contained in the carbodiimide compound is, in terms of carbodiimide equivalent (the weight [g] of the carbodiimide compound required to provide 1 mol of carbodiimide groups), usually in the range of 100 to 1,000, preferably 250 to 800, and more preferably 300 to 700.

[0124] Furthermore, within the scope of the present invention, in order to improve the water solubility or water dispersibility of the polycarbodiimide compound, a surfactant may be added, or a hydrophilic monomer such as a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, or a hydroxyalkyl sulfonate may be added.

[0125] (Isocyanate Compound) The isocyanate compound is a compound having an isocyanate or an isocyanate derivative structure, such as a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), and isopropylidenedicyclohexyl diisocyanate. Further examples include polymers and derivatives of these isocyanates, such as biuretized products, isocyanurated products, urethodionated products, and carbodiimide-modified products. These may be used alone or in combination of two or more.

[0126] When used in the form of a blocked isocyanate, examples of the blocking agent include bisulfites; phenolic compounds such as phenol, cresol, and ethylphenol; alcohol compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as isobutanoylmethyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; lactam compounds such as ε-caprolactam and δ-valerolactam; amine compounds such as diphenylaniline, aniline, and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; and oxime compounds such as formaldehyde oxime, acetaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used alone or in combination of two or more.

[0127] The isocyanate compound may be used alone or as a mixture or bond with various polymers. In order to improve the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or bond with a polyester resin or a polyurethane resin.

[0128] (Silane Coupling Compound) A silane coupling compound is an organosilicon compound having an organic functional group and a hydrolyzable group such as an alkoxy group in one molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl group-containing compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing compounds such as p-styryltrimethoxysilane and p-styryltriethoxysilane; (meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; (meth)acryl group-containing compounds such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)- Examples of suitable compounds include amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane; isocyanurate group-containing compounds such as tris(trimethoxysilylpropyl)isocyanurate and tris(triethoxysilylpropyl)isocyanurate; and mercapto group-containing compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane. These compounds may be used alone or in combination of two or more.

[0129] The content of the crosslinking agent contained in the resin layer is preferably 0.1 to 90% by mass, more preferably 1 to 70% by mass, even more preferably 3 to 50% by mass, particularly preferably 5 to 30% by mass, and especially preferably 8 to 25% by mass, relative to the total mass of the resin layer (non-volatile components).

[0130] [Surfactant] The resin composition forming the resin layer may contain a surfactant. Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0131] Examples of anionic surfactants include sulfonic acid surfactants such as alkyl sulfonates, alkylaryl sulfonates, and ester sulfonates; phosphoric acid surfactants such as alkyl phosphate esters or salts thereof, and polyoxyalkylene alkyl ether phosphate esters or salts thereof; sulfate ester surfactants such as alkyl sulfate esters and alkyl ether sulfate ester salts; and carboxylate surfactants such as alkyl fatty acid salts.

[0132] Examples of sulfonic acid type anionic surfactants include alkyl sulfonates such as decyl sulfonate, dodecyl sulfonate, tetradecyl sulfonate, hexadecyl sulfonate, and octadecyl sulfonate; alkyl aryl sulfonates such as butyl benzene sulfonate, hexyl benzene sulfonate, octyl benzene sulfonate, decyl benzene sulfonate, dodecyl benzene sulfonate, tetradecyl benzene sulfonate, hexadecyl benzene sulfonate, octadecyl benzene sulfonate, dibutyl naphthalene sulfonate, and triisopropyl naphthalene sulfonate; and ester sulfonates such as dibutyl sulfosuccinate, dioctyl sulfosuccinate, dodecyl sulfoacetic acid ester, and nonylphenoxy polyethylene glycol sulfoacetic acid ester. Among these, those in which the alkyl group has 8 or more carbon atoms, preferably 10 to 22, and more preferably 12 to 18 carbon atoms, are preferred. As the salt, a metal salt is preferred, and in particular, an alkali metal salt such as lithium, sodium or potassium is more preferred, and a sodium salt is even more preferred.

[0133] Examples of phosphoric acid type anionic surfactants include alkyl phosphoric acid esters or salts thereof such as butyl phosphate, butyl phosphate ester salts, hexyl phosphate, hexyl phosphate ester salts, octyl phosphate, octyl phosphate ester salts, decyl phosphate, decyl phosphate ester salts, lauryl phosphate, lauryl phosphate ester salts, tetradecyl phosphate, tetradecyl phosphate ester salts, hexadecyl phosphate, hexadecyl phosphate ester salts, stearyl phosphate, and stearyl phosphate salts; polyoxyethylene butyl ether phosphate, polyoxyethylene butyl ether phosphate salts, polyoxyethylene hexyl ether phosphate, polyoxyethylene hexyl ether phosphate salts, polyoxyethylene octyl ether phosphate, polyoxyethylene octyl ether phosphate salts, polyoxyethylene decyl ether phosphate; and polyoxyalkylene alkyl ether phosphates or salts thereof, such as ethylene decyl ether phosphate salt, polyoxyethylene lauryl ether phosphate salt, polyoxyethylene lauryl ether phosphate salt, polyoxyethylene tetradecyl ether phosphate salt, polyoxyethylene tetradecyl ether phosphate salt, polyoxyethylene hexadecyl ether phosphate salt, polyoxyethylene hexadecyl ether phosphate salt, polyoxyethylene stearyl ether phosphate salt, polyoxyethylene stearyl ether phosphate salt, polyoxypropylene octyl ether phosphate salt, polyoxypropylene octyl ether phosphate salt, polyoxypropylene decyl ether phosphate salt, polyoxypropylene decyl ether phosphate salt, polyoxypropylene lauryl ether phosphate salt, and polyoxypropylene lauryl ether phosphate salt. Among these, alkyl phosphate salts and polyoxyalkylene alkyl ether phosphates or salts thereof are preferred from the viewpoint of surfactant performance.

[0134] Furthermore, with regard to alkyl phosphate ester salts, the number of carbon atoms in the alkyl group is 4 or more, preferably 4 to 22, and more preferably in the range of 6 to 12, and with regard to polyoxyalkylene alkyl ether phosphate esters or salts thereof, the number of carbon atoms in the alkyl group is 4 or more, preferably 6 to 22, and more preferably in the range of 8 to 18. Furthermore, as the salt, metal salts and amine salts are preferred, and in particular, alkali metal salts such as lithium, sodium, and potassium, alkylamine salts, and alcoholamine salts are more preferred, and sodium salts and monoethanolamine salts are even more preferred.

[0135] Examples of nonionic surfactants include ester types in which a polyhydric alcohol such as glycerin or a sugar is ester-bonded to a fatty acid, ether types such as polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether, ester-ether types in which an alkylene oxide is added to a fatty acid or a polyhydric alcohol fatty acid ester, and amide types such as fatty acid alkanolamide in which a hydrophobic group and a hydrophilic group are connected via an amide bond. Among these, ester types, ether types, and ester-ether types are preferred in terms of heat resistance.

[0136] Examples of ester-type and ester-ether-type nonionic surfactants include glycerol fatty acid esters such as glycerol mono(di)laurate, glycerol mono(di)stearate, glycerol, glycerol mono(di)oleate, diglycerol mono(di)stearate, and triglycerol mono(di)stearate; polyoxyalkylene glycerol fatty acid esters such as polyoxyethylene glycerol mono(di)laurate, polyoxyethylene glycerol mono(di)stearate, polyoxypropylene glycerol mono(di)laurate, polyoxypropylene glycerol mono(di)stearate, polyoxybutylene glycerol mono(di)laurate, and polyoxybutylene glycerol mono(di)stearate; polyoxyethylene mono(di)laurate, and polyoxyethylene mono(di)stearate. sorbitan fatty acid esters such as sorbitan mono(di)laurate, sorbitan mono(di)palmitate, sorbitan mono(di)stearate, sorbitan mono(di)oleate; and polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxypropylene sorbitan monolaurate, and polyoxypropylene sorbitan monostearate.

[0137] Among these, from the viewpoint of compatibility with polyesters, etc., glycerin fatty acid esters, polyoxyalkylene glycerin fatty acid esters, and polyoxyalkylene fatty acid esters are preferred, and glycerin fatty acid esters and polyoxyalkylene glycerin fatty acid esters, which are fatty acid esters having a glycerin skeleton, are more preferred. In addition, it is desirable that the number of carbon atoms in the alkyl group is 8 or more, preferably 10 to 22, and more preferably 12 to 18.

[0138] Examples of ether-type nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene isodecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyldodecyl ether, polyoxypropylene lauryl ether, polyoxypropylene cetyl ether, polyoxypropylene stearyl ether, polyoxypropylene oleyl ether, polyoxybutylene lauryl ether, polyoxybutylene cetyl ether, polyoxybutylene stearyl ether, and polyoxybutylene oleyl ether; and polyoxyalkylene phenyl ethers such as polyoxyethylene triphenyl phenyl ether, polyoxyethylene tribenzyl phenyl ether, and polyoxyethylene distyrene phenyl ether.

[0139] Examples of cationic surfactants include quaternary ammonium salts such as alkylammonium salts and alkylbenzylammonium salts, and amine salts such as N-methylbishydroxyethylamine fatty acid ester hydrochloride.

[0140] Examples of the quaternary ammonium salt type cationic surfactant include alkyl ammonium salts such as octyltrimethylammonium salt, decyltrimethylammonium salt, lauryltrimethylammonium salt, tetradecyltrimethylammonium salt, hexadecyltrimethylammonium salt, stearyltrimethylammonium salt, octyldimethylethylammonium salt, decyldimethylethylammonium salt, lauryldimethylethylammonium salt, tetradecyldimethylethylammonium salt, hexadecyldimethylethylammonium salt, octyltriethylammonium salt, lauryltriethylammonium salt, hexadecyltriethylammonium salt, and didecyldimethylammonium salt; and alkyl benzyl ammonium salts such as octyldimethylbenzylammonium salt, decyldimethylbenzylammonium salt, lauryldimethylbenzylammonium salt, tetradecyldimethylbenzylammonium salt, hexadecyldimethylbenzylammonium salt, stearyldimethylbenzylammonium salt, tributylbenzylammonium salt, and trihexylbenzylammonium salt.

[0141] The number of carbon atoms in the alkyl group is usually 4 or more, preferably 6 to 22, and more preferably 8 to 18. Examples of the counter ion of the ammonium group include halogen ions, sulfonate ions, sulfate ions, phosphate ions, nitrate ions, and carboxylate ions.

[0142] Examples of amphoteric surfactants include betaine surfactants such as alkylbetaine, amino acid surfactants such as alkylamino fatty acid salts, and amine oxide surfactants such as alkylamine oxide.

[0143] Examples of betaine-type amphoteric surfactants include octyldimethylaminoacetic acid betaine, decyldimethylaminoacetic acid betaine, lauryldimethylaminoacetic acid betaine, tetradecyldimethylaminoacetic acid betaine, hexadecyldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, octanoic acid amidopropyl betaine, decanoic acid amidopropyl betaine, lauric acid amidopropyl betaine, tetradecanoic acid amidopropyl betaine, hexadecanoic acid amidopropyl betaine, and stearic acid amidopropyl betaine.

[0144] The content of the surfactant in the resin layer is preferably 0.1 to 10% by mass, more preferably 0.3 to 8% by mass, and even more preferably 0.4 to 6% by mass, based on the total mass of the resin layer (non-volatile components).

[0145] [Particles] The resin composition forming the resin layer may contain particles. Details of such particles are the same as those described in the section on [Particles] contained in the polyester, but the average particle size of the particles is preferably 0.01 to 1 μm, more preferably 0.02 to 0.9 μm, even more preferably 0.03 to 0.8 μm, particularly preferably 0.04 to 0.7 μm, and especially preferably 0.05 to 0.6 μm.

[0146] The content of the particles in the resin layer is preferably 0.1 to 20 mass %, more preferably 0.3 to 16 mass %, even more preferably 0.5 to 14 mass %, and particularly preferably 0.7 to 12 mass %, relative to the total mass of the resin layer (non-volatile components).

[0147] [Other Components] In addition to the above components, the resin layer may further contain additives such as antifoaming agents, coatability improvers, thickeners, organic lubricants, ultraviolet absorbers, antioxidants, foaming agents, dyes, and pigments, as appropriate, within the scope of the present invention.

[0148] [Solvent] The resin composition forming the resin layer may be diluted with a solvent to form a coating liquid. That is, the resin composition may be applied to a polyester film as a liquid coating liquid, and then dried and cured as necessary to form a resin layer. The components constituting the resin layer may be dissolved in a solvent or dispersed in a solvent. When a coating liquid is formed, the concentration of all nonvolatile components of the resin composition in the coating liquid is preferably 0.1 to 50% by mass. If the concentration is 0.1% by mass or more, a resin layer of the desired thickness can be efficiently formed. On the other hand, if the concentration is 50% by mass or less, the viscosity during coating can be reduced, thereby improving the appearance of the resin layer and increasing the stability of the coating liquid.

[0149] The solvent is not particularly limited, and either water or an organic solvent can be used. From the viewpoint of environmental protection, it is preferable to prepare an aqueous coating solution using water as the main solvent (at least 50% by mass of the total solvent). The water content is preferably at least 60% by mass, more preferably at least 70% by mass. The aqueous coating solution may contain a small amount of organic solvent. The specific amount of organic solvent should be equal to or less than the amount of water on a mass basis, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less of the solvent. Examples of organic solvents used in combination with water include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These can be used alone or in combination. By appropriately selecting and adding these organic solvents to the aqueous coating liquid as needed, the stability and coatability of the coating liquid may be improved in some cases.

[0150] Furthermore, when only an organic solvent is used as the solvent, examples of such organic solvents include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, heptane, isooctane, esters such as ethyl acetate, butyl acetate, ketones such as ethyl methyl ketone, isobutyl methyl ketone, alcohols such as ethanol, 2-propanol, ethers such as diisopropyl ether, dibutyl ether, etc. These may be used alone or in combination, taking into consideration solubility, coatability, boiling point, etc.

[0151] It is assumed that the resin layer contains unreacted components of the resin composition, reacted compounds, or a mixture thereof. Analysis of the components in the resin layer can be performed by, for example, TOF-SIMS, ESCA, or X-ray fluorescence.

[0152] When resin layers are provided on both sides of the present film, it is preferable, but not limited to, that the resin compositions (non-volatile components) forming each resin layer are the same or substantially the same. Note that "substantially the same" implies that the content of each non-volatile component constituting each resin composition is within a range of ±5% by mass, and that, if different components are contained, the total mass of the different components is less than 5% by mass. It is more preferable that the content of each non-volatile component constituting each resin composition is within a range of ±3% by mass, and even more preferable that it is within a range of ±1% by mass. If different components are contained, it is more preferable that the total mass of the different components is less than 3% by mass, and even more preferable that it is less than 1% by mass.

[0153] [Method for forming resin layer] The method for forming the resin layer is not particularly limited, and conventionally known methods can be used as appropriate, but it is preferable to form a resin layer by coating the above-mentioned resin composition on a polyester film and, if necessary, performing treatments such as drying, curing, heat treatment, etc. The coating method is not particularly limited, and for example, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used.

[0154] The above-mentioned forming method includes in-line coating carried out within the polyester film production process, and off-line coating in which a polyester film that has already been produced is coated outside the system, with in-line coating being preferred.

[0155] In-line coating is a method in which a polyester or resin composition forming a polyester film is melt-extruded and stretched, and then coated at any stage before heat setting and winding up. Usually, coating is performed on an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding up, but it is preferable to coat a stretched uniaxially stretched film.

[0156] For example, in the case of sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (MD) is coated and then stretched in the transverse direction (TD) is particularly preferred. This method has the advantage of being cost-effective because film formation and resin layer formation can be carried out simultaneously.

[0157] The thickness (after drying) of the resin layer formed as described above is preferably 2 μm or less, more preferably less than 1 μm, from the viewpoint of improving the decomposition durability and charge / discharge durability of the polyester film. Specifically, for example, it is preferably 0.01 μm or more and 2 μm or less, more preferably 0.015 μm or more and 1 μm or less, even more preferably 0.017 μm or more and less than 1 μm, and even more preferably 0.02 μm or more and 0.5 μm or less. The thickness of the resin layer can be appropriately set within the above range, for example, 0.03 μm or more and 0.1 μm or less, 0.035 μm or more and 0.08 μm or less, 0.04 μm or more and 0.075 μm or less, etc.

[0158] The amount of non-volatile components applied in the coating is not limited to the following, but is preferably 0.001 to 1 g / m 2 is preferable, and more preferably 0.005 to 0.7 g / m 2 , and even more preferably 0.01 to 0.5 g / m 2The coating amount is based on the non-volatile components, excluding volatile components such as solvents.

[0159] The coating amount of the nonvolatile component is the coating amount in the present film, for example, the coating amount after drying and stretching when drying and stretching are performed. The coating amount of the nonvolatile component is expressed as a mass per unit area and can also be said to be an index of the thickness of the resin layer.

[0160] [Preferred embodiment of resin layer] From the viewpoint of further enhancing the decomposition durability or charge / discharge durability of the polyester film as the base film, it is preferable that the present film has a reduction-decomposition-resistant resin layer formed from a resin composition on at least one surface of the polyester film. That is, it is preferable that the present film has a reduction-decomposition-resistant resin layer formed from a resin composition containing a reduction-decomposition-resistant resin on at least one surface of the polyester film. That is, it is preferable that the resin layer is a reduction-decomposition-resistant resin layer.

[0161] The resin forming the resin layer in the present film is selected from resins that are suitable for the operating potential of the battery, for example, 0 to 4 V (Li / Li + ) in which it is not oxidized or reduced. Specifically, the lower the level of the highest occupied molecular orbital (HOMO), the better the oxidation resistance, and the higher the level of the lowest unoccupied molecular orbital (LUMO), the better the reduction resistance. Therefore, a resin having a structure that satisfies these requirements is preferred. Thus, by providing such a resin layer on a polyester film, it becomes easier to prevent the polyester film from coming into contact with a metal layer, and in a battery using a polyester film as a current collector foil, it is possible to effectively suppress redox decomposition of the polyester film.

[0162] From the viewpoint of effectively suppressing reductive decomposition of the polyester film, it is preferable that the resin forming the resin layer in the present film does not show a reduction current in a voltammogram obtained by linear sweep voltammetry measurement. Specifically, it is preferable that the following requirements be satisfied. (Requirements) When a voltammogram (Vb) obtained by linear sweep voltammetry measurement under the following conditions (measurement of only the electrolyte solution (blank)) is compared with a voltammogram (Vp) obtained by linear sweep voltammetry measurement under the same conditions except that the resin contained in the resin layer or the monomer components constituting the resin are dissolved in the electrolyte solution at a concentration of 0.5 mmol / L or more, no reduction current is observed at a different potential. [Linear Sweep Voltammetry Measurement Conditions] Working electrode: An electrode prepared by dispersing a mixture of natural carbon powder, sodium carboxymethylcellulose, and styrene-butadiene rubber (mass ratio 98:1:1) in water, coating the mixture on copper foil, and then drying. Reference electrode and counter electrode: Lithium metal wire. Electrolyte: Electrolyte in which lithium hexafluorophosphate is dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7). Sweep rate: 1 mV / sec. Sweep range: Natural potential (approximately 3.2 V) → 0 V (Li / Li + ).

[0163] By using a resin that satisfies the above requirements as the resin forming the resin layer in the present film (or the monomer components that constitute the resin when the resin is not soluble in the electrolyte solution), and confirming that the resin is not easily decomposed, it is possible to prevent, for example, elution into the electrolyte solution, and effectively suppress redox decomposition.

[0164] From this viewpoint, suitable examples of resins include, but are not limited to, one or more selected from the group consisting of polyolefin resins, (meth)acrylic resins, compounds having a glycidyl ether group, and polyalkylene glycols. Among these, compounds having a glycidyl ether group are particularly preferred from the viewpoint of preventing elution into the electrolyte solution, and from the viewpoint of film-forming properties and adhesion to the metal layer. Furthermore, although not limited to, it is also suitable to use one or more selected from the group consisting of polyolefin resins, (meth)acrylic resins, and polyalkylene glycols together with a compound having a glycidyl ether group. For example, it is suitable to use a compound having a glycidyl ether group in combination with a (meth)acrylic resin (particularly an acrylic resin).

[0165] From the same viewpoint as above, the content of at least one selected from the group consisting of the polyolefin resin, (meth)acrylic resin, polyalkylene glycol, and compound having a glycidyl ether group is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, still more preferably 85% by mass or more, even more preferably 90% by mass or more, particularly preferably 95 to 100% by mass, or may be 96 to 99.5% by mass, relative to the total mass of the resin layer (non-volatile components).

[0166] (Compound Having a Glycidyl Ether Group) The compound having a glycidyl ether group is preferably a compound containing at least two glycidyl ether groups in the molecule, more preferably a compound containing three or more glycidyl ether groups, and even more preferably a compound containing four to five glycidyl ether groups. Furthermore, the compound having a glycidyl ether group may have a hydroxyl group in the molecule, and the number of hydroxyl groups in the molecule may be one or more, two or more, or two to three.

[0167] The mass average molecular weight (Mw) of the compound having a glycidyl ether group is, for example, preferably 200 to 2000, and more preferably 550 to 1800. The mass average molecular weight (Mw) means the mass average molecular weight measured by gel permeation chromatography (GPC) using polystyrene as a standard.

[0168] The epoxy equivalent of the compound having a glycidyl ether group (the number of grams of resin containing 1 gram equivalent of epoxy groups [g / eq]) is preferably 50 to 300 g / eq, more preferably 1100 to 250 g / eq, even more preferably 120 to 200 g / eq, and even more preferably 140 to 190 g / eq. The epoxy equivalent is measured in accordance with JIS K 7236 (2009).

[0169] Specific examples of compounds having a glycidyl ether group include glycidyl ether polyepoxides derived from aliphatic polyols, more specifically ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyethylene glycol diglycidyl ether, polyoxypropylene diol diglycidyl ether, polyoxypropylene triol triglycidyl ether, poly(oxypropylene-oxyethylene)triol triglycidyl ether, and polyglycerol polyglycidyl ether. Among these, glycerol polyglycidyl ether and polyglycerol polyglycidyl ether are preferred, with polyglycerol polyglycidyl ether being particularly preferred.

[0170] The resin forming the resin layer in the present film may also include a reaction product of at least two compounds, including a compound having a glycidyl ether group. Examples of reaction products derived from a compound having a glycidyl ether group include condensation reaction products between heterogeneous molecules, such as heat, between a functional group (e.g., an amino group, a hydroxyl group, a carboxylic acid group) in another component (another compound) of the resin composition constituting the resin layer, or a functional group (e.g., a hydroxyl group, a carboxylic acid group, or a carboxylate group) introduced to improve water dispersibility, and the glycidyl ether group of a compound having a glycidyl ether group. The resin may also be a reaction product between compounds having a glycidyl ether group.

[0171] The resin forming the resin layer in the present film may include a reaction product of at least two compounds including polyglycerol polyglycidyl ether. Examples of reaction products derived from polyglycerol polyglycidyl ether include condensation reaction products between heterogeneous molecules, such as heat, between functional groups such as amino groups, hydroxyl groups, carboxylic acid groups, or hydroxyl groups, carboxylic acid groups, or carboxylate groups introduced to improve water dispersibility in other components (other compounds) in the resin composition constituting the resin layer and the glycidyl ether groups of polyglycerol polyglycidyl ether. The reaction product may also be a reaction product between polyglycerol polyglycidyl ethers.

[0172] The content of at least one resin selected from the group consisting of a compound having a glycidyl ether group, a polyolefin resin, a (meth)acrylic resin, and a polyalkylene glycol in the resin layer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95 to 100% by mass, or may be 96 to 99.5% by mass, relative to the total mass of the resin layer (non-volatile components).

[0173] (Surfactant) The resin layer preferably contains at least one selected from the group consisting of a polyolefin resin, a (meth)acrylic resin, a compound having a glycidyl ether group, and a polyalkylene glycol, and further contains a surfactant. By containing a surfactant in the resin layer, it is possible to improve the coatability onto the polyester film and prevent coating defects.

[0174] Examples of such surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Among these, nonionic surfactants are preferred from the viewpoint of the stability of the coating liquid after preparation. Among nonionic surfactants, ether-type nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers, and ester-ether-type nonionic surfactants in which alkylene oxide is added to a fatty acid or a polyhydric alcohol fatty acid ester are preferred, and polyoxyethylene alkyl ethers and ester-ether-type nonionic surfactants in which ethylene oxide is added to a polyhydric alcohol fatty acid ester are more preferred. Among such ester-ether-type nonionic surfactants, ester-ether-type nonionic surfactants in which ethylene oxide is added to acetylene glycol (average EO addition mole number of 4 to 10) are preferred.

[0175] From the viewpoint of improving coatability, the HLB value of the nonionic surfactant is preferably 16 or less, more preferably 15 or less, and even more preferably 14 or less. There is no particular restriction on the lower limit of the HLB value, but it is usually 2 and may be 4. The HLB value is the balance between hydrophilicity and hydrophobicity used in the field of surfactants, and is determined by commonly used calculation formulas such as the Griffin, Davis, Kawakami formula, and organic conceptual diagram methods. Alternatively, the HLB value listed in a catalog or the like may be used.

[0176] When the resin composition forming the resin layer contains a surfactant, the content thereof is preferably in the range of 0.1 to 10% by mass, more preferably 0.3 to 8% by mass, and even more preferably 0.4 to 6% by mass, relative to the total mass of the resin layer (non-volatile components). By setting the surfactant content to 0.1% by mass or more, the coating liquid can be applied stably. On the other hand, by setting the surfactant content to 10% by mass or less, coating unevenness can be suppressed.

[0177] <<Physical Properties of the Present Film>> It may be preferable that the present film has, for example, the following physical properties: However, the following descriptions of the physical properties do not limit the present invention in any way.

[0178] [Static Friction Coefficient μs] The static friction coefficient μs measured by overlapping one surface, side A, of the present film with the other surface, side B, is preferably 0.26 to 0.75, more preferably 0.28 to 0.72, still more preferably 0.3 to 0.7, particularly preferably 0.31 to 0.6, and especially preferably 0.32 to 0.5. If the static friction coefficient μs is outside the above range, for example, the running or transportability of the film tends to be insufficient.

[0179] The static friction coefficient μs is measured by the following method. A test piece measuring 15 × 160 mm was cut out from the film before copper deposition, and the static friction coefficient between one side of the test piece and the other side was measured. Specifically, one side of the test piece was held in contact with the other side for 15 seconds before the start of the test, and then measurement was carried out in the machine direction (MD) under the following conditions. The sample was humidified for at least 6 hours before measurement. - Apparatus: Parallel movement type friction tester (MCS-300) manufactured by Yokohama Systems Research Institute - Sliding piece: Total mass 104 g (contact area is a square with one side of 12 mm) - Test speed: 20 mm / min - Temperature: 23°C ± 2°C - Relative humidity: 50% ± 10%

[0180] [Ratio of arithmetic mean heights Sa (SaB / SaA)] The ratio of the arithmetic mean heights Sa of the present film (SaB / SaA, which is the ratio of the arithmetic mean height SaA of any one surface, namely, side A, to the arithmetic mean height SaB of any one surface, namely, side B) is preferably 1 or more and less than 1.2, more preferably 1 or more and 1.19 or less. If the ratio of the arithmetic mean heights Sa exceeds the above-mentioned upper limit, for example, there is a tendency for the thermal energy applied to both sides of the film to become unbalanced, making it difficult to effectively suppress the occurrence of curl in the film after vapor deposition. The ratio of the arithmetic mean heights Sa can be appropriately set within the above-mentioned range and is not limited to the following, and may be, for example, 1.18 or less, 1.16 or less, 1.14 or less, etc. Note that the ratio of the arithmetic mean heights Sa (SaB / SaA) satisfies the condition SaB≧SaA. For example, if the values ​​of the arithmetic mean heights Sa of the respective surfaces are different, the larger value is used as the numerator to determine the ratio.

[0181] The arithmetic mean height Sa of the present film (the arithmetic mean height SaA of any one surface, i.e., side A, and / or the arithmetic mean height SaB of any other surface, i.e., side B) is preferably 15 nm or less, more preferably 10 nm or less, even more preferably 8 nm or less, even more preferably 7 nm or less, particularly preferably 5 nm or less, and especially preferably 4 nm or less, from the viewpoint of further enhancing the uniformity of each metal layer formed on both surfaces of the film. On the other hand, the lower limit of the arithmetic mean height Sa is not particularly limited, but is, for example, preferably 0.6 nm or more, more preferably 0.8 nm or more, even more preferably 1 nm or more, and particularly preferably 1.2 nm or more. The arithmetic mean height Sa can be appropriately set within the above range and is not limited to the following, and may be, for example, 3.2 nm or less, 3.0 nm or less, 2.5 nm or less, etc. It is particularly preferable that the arithmetic mean height SaA of any one surface, i.e., side A, and the arithmetic mean height SaB of any other surface, i.e., side B, are both within the above range.

[0182] The arithmetic mean height Sa is one of the surface roughness parameters (ISO 25178), and is a three-dimensional extension of the two-dimensional Ra, obtained by dividing the volume of the area enclosed by the surface shape curved surface and the mean surface by the measured area. Specifically, when the surface is the XY plane and the height direction is the Z axis, A is the defined area (the entire image), and Z(x, y) is the height from the surface at height 0 of the image point (x, y), and it can be expressed as in the following formula [1].

[0183]

[0184] [Ratio of arithmetic mean roughness Ra (RaB / RaA)] In the present film, the ratio of arithmetic mean roughness Ra (RaB / RaA, which is the ratio of the arithmetic mean roughness RaA of any one surface, namely, side A, to the arithmetic mean roughness RaB of any other surface, namely, side B) is, for example, preferably 1 or more and 1.25 or less, more preferably 1 or more and less than 1.2. If the ratio of arithmetic mean roughness Ra exceeds the above upper limit, for example, there is a tendency for the thermal energy applied to both sides of the film to become unbalanced, and it is difficult to effectively suppress the occurrence of curl in the film after vapor deposition. The ratio of arithmetic mean roughness Ra can be appropriately set within the above range and is not limited to the following, and may be, for example, 1.16 or less, 1.14 or less, 1.12 or less, etc. The ratio of arithmetic mean roughnesses Ra (RaB / RaA) is based on the condition that RaB≧RaA. For example, if the values ​​of arithmetic mean roughness Ra of each surface are different, the numerator is used to determine the ratio, with the relatively larger value being used as the numerator.

[0185] The arithmetic mean roughness Ra of the present film (the arithmetic mean roughness RaA of any one surface, i.e., side A, and / or the arithmetic mean roughness RaB of any other surface, i.e., side B) is preferably 0.05 μm or less, more preferably 0.045 μm or less, even more preferably 0.04 μm or less, and particularly preferably 0.038 μm or less, from the viewpoint of further improving the uniformity of each metal layer formed on both surfaces of the film. The lower limit of the arithmetic mean roughness Ra is not particularly limited, but may be, for example, 0.008 μm or more, 0.01 μm or more, 0.013 μm or more, etc. It is particularly preferable that the arithmetic mean roughness RaA of any one surface, i.e., side A, and the arithmetic mean roughness RaB of any other surface, i.e., side B, are both within the above-mentioned ranges. The arithmetic mean roughness Ra is one of the line roughness parameters (JIS B 0601 (1994)) and represents the average value of the average height difference from the mean plane. Specifically, when a portion of the reference length L is sampled and the average line of this sampled portion is taken as the x-axis and the direction of the longitudinal magnification is taken as the y-axis, and the roughness curve is expressed as y = Z(x), it can be calculated from the following formula [Mathematical Expression 2].

[0186]

[0187] [Ratio of Ten-Point Average Roughnesses Rz (RzB / RzA)] In order to achieve a high degree of both productivity and uniformity in the present film, the ratio of ten-point average roughnesses Rz (RzB / RzA, which is the ratio of the ten-point average roughness RzA of any one surface, namely, side A, to the ten-point average roughness RzB of any one surface, namely, side B) is preferably 1 or more and less than 1.5, more preferably 1 or more and 1.4 or less, and even more preferably 1 or more and 1.3 or less. If the ratio of ten-point average roughnesses Rz exceeds the above-mentioned upper limit, for example, there is a tendency for the thermal energy applied to both sides of the film to become unbalanced, making it difficult to effectively suppress curling in the film after deposition. Note that the ratio of ten-point average roughnesses Rz (RzB / RzA) is determined based on the condition that RzB≧RzA. For example, if the ten-point average roughness Rz values ​​of each surface are different, the larger value is used as the numerator to determine the ratio.

[0188] The ten-point average roughness Rz of the present film (the ten-point average roughness RzA of any one surface, namely, side A, and / or the ten-point average roughness RzB of any other surface, namely, side B) is preferably 0.3 μm or less, more preferably 0.25 μm or less, even more preferably 0.2 μm or less, and particularly preferably 0.18 μm or less, from the viewpoint of further enhancing the uniformity of each metal layer formed on both surfaces of the film. The lower limit of the ten-point average roughness Rz is not particularly limited, but may be, for example, 0.004 μm or more, 0.005 μm or more, 0.006 μm or more, etc. It is particularly preferred that the ten-point average roughness RzA of any one surface, namely, side A, and the ten-point average roughness RzB of any other surface, namely, side B, are both within the above-mentioned ranges. The ten-point average roughness Rz is one of the line roughness parameters (JIS B 0601 (1994)), and is determined by measuring in a direction perpendicular to the direction in which the recesses in the line direction are continuous.

[0189] [Ratio of Maximum Cross-Sectional Heights Rt (RtB / RtA)] In the present film, from the viewpoint of achieving a high degree of both productivity and uniformity, the ratio of maximum cross-section heights Rt (RtB / RtA, which is the ratio of the maximum cross-section height RtA of any surface, namely, side A, to the maximum cross-section height RtB of any surface, namely, side B) is preferably 1 or more and 1.2 or less, more preferably 1 or more and 1.15 or less, and even more preferably 1 or more and 1.1 or less. Note that the ratio of maximum cross-section heights Rt (RtB / RtA) satisfies the condition RtB≧RtA, and for example, when the values ​​of the maximum cross-section heights Rt of the respective surfaces are different, the larger value is used as the numerator to determine the ratio.

[0190] The maximum cross-sectional height Rt of the present film (the maximum cross-sectional height RtA of any one surface, namely, side A, and / or the maximum cross-sectional height RtB of any other surface, namely, side B) is preferably 0.5 μm or less, more preferably 0.48 μm or less, even more preferably 0.45 μm or less, and particularly preferably 0.4 μm or less, from the viewpoint of further enhancing the uniformity of each metal layer formed on both surfaces of the film. The lower limit of the maximum cross-sectional height Rt is not particularly limited, but may be, for example, 0.15 μm or more, 0.2 μm or more, 0.25 μm or more, etc. It is particularly preferable that the maximum cross-sectional height RtA of any one surface, namely, side A, and the maximum cross-sectional height RtB of any other surface, namely, side B, are both within the above-mentioned ranges. The maximum cross-sectional height Rt is one of the line roughness parameters (JIS B 0601 (1994)) and is calculated as the sum of the maximum peak height and the maximum valley depth.

[0191] [Root-mean-square height Sq ratio (SqB / SqA)] The root-mean-square height Sq ratio of the present film (SqB / SqA, which is the ratio of the root-mean-square height SqA of any one surface, namely, side A, to the root-mean-square height SqB of any one surface, namely, side B) is preferably 1 or more and 1.9 or less, and from the viewpoint of achieving a high degree of both productivity and uniformity as described above, is more preferably 1 or more and 1.8 or less, and even more preferably 1 or more and 1.7 or less. The root-mean-square height Sq ratio can be appropriately set within the above range and is not limited to the following, and may be, for example, 1.5 or less, 1.4 or less, etc. Note that the root-mean-square height Sq ratio (SqB / SqA) satisfies the condition SqB≧SqA. For example, when the root-mean-square heights Sq of the respective surfaces are different, the larger value is used as the numerator to determine the ratio.

[0192] The root-mean-square height Sq of the present film (the root-mean-square height SqA of any one of the surfaces, namely, side A, and / or the root-mean-square height SqB of any one of the surfaces, namely, side B) is preferably 15 nm or less, more preferably 14 nm or less, even more preferably 13 nm or less, particularly preferably 12 nm or less, and especially preferably 11 nm or less, from the viewpoint of further improving the uniformity of each metal layer formed on both surfaces of the film. On the other hand, the lower limit of the root-mean-square height Sq is not particularly limited, but is, for example, preferably 0.8 nm or more, more preferably 1 nm or more, even more preferably 1.5 nm or more, and particularly preferably 2 nm or more. The root-mean-square height Sq can be appropriately set within the above range and is not limited to the following, and may be, for example, 8 nm or less, 6 nm or less, 5 nm or less, etc. It is particularly preferable that the root-mean-square height SqA of any one of the surfaces, namely, side A, and the root-mean-square height SqB of any one of the surfaces, namely, side B, are both within the above range. The root mean square height Sq is one of the surface roughness parameters (ISO 25178) and is a three-dimensional extension of the two-dimensional Rq. In other words, it is the root mean square value of the height data in a defined area, and is a parameter equivalent to the standard deviation of the distance from the mean surface, and can be calculated using the following formula (3).

[0193]

[0194] [Ratio of Maximum Cross-Sectional Heights St (StB / StA)] The ratio of maximum cross-section heights St of the present film (StB / StA, which is the ratio of the maximum cross-section height StA of any surface A, which is one surface, to the maximum cross-section height StB of any surface B, which is the other surface) is preferably 1 or more and 2.6 or less, and from the viewpoint of achieving a high degree of both productivity and homogeneity as described above, it is more preferably 1 or more and 2.4 or less, and even more preferably 1 or more and 2.2 or less. The ratio of maximum cross-section heights St can be appropriately set within the above range and is not limited to the following, and may be, for example, 2 or less, 1.8 or less, etc. The lower limit of the ratio of maximum cross-section heights St may be 1.05 or 1.1. Note that the ratio of maximum cross-section heights St (StB / StA) satisfies the condition StB≧StA. For example, when the values ​​of the maximum cross-section heights St of each surface are different, the relatively larger value is used as the numerator to determine the ratio.

[0195] The maximum cross-sectional height St of the present film (the maximum cross-sectional height StA of any one of the surfaces, namely, side A, and / or the maximum cross-sectional height StB of any one of the surfaces, namely, side B) is preferably 600 nm or less, more preferably 550 nm or less, even more preferably 525 nm or less, particularly preferably 500 nm or less, and especially preferably 490 nm or less, from the viewpoint of further enhancing the uniformity of each metal layer formed on both surfaces of the film. On the other hand, the lower limit of the maximum cross-sectional height St is not particularly limited, but is, for example, preferably 30 nm or more, more preferably 40 nm or more, even more preferably 48 nm or more, and particularly preferably 50 nm or more. The maximum cross-sectional height St can be appropriately set within the above range and is not limited to the following, and may be, for example, 300 nm or less, 250 nm or less, 200 nm or less, etc. It is particularly preferable that the maximum cross-sectional height StA of any one of the surfaces, namely, side A, and the maximum cross-sectional height StB of any one of the surfaces, namely, side B, are both within the above range. The maximum cross-sectional height St is one of the surface roughness parameters (ISO 25178), which is a three-dimensional extension of the two-dimensional Rt, and is the sum (total of absolute values) of the maximum peak height and the maximum valley depth in a defined area.

[0196] It is preferable that the surface properties of the front and back surfaces, which are the outermost layers of the present film, are within the above ranges.

[0197] The arithmetic mean height Sa, maximum cross-sectional height St, and root-mean-square height Sq were specifically measured as follows. A film prior to metal deposition, such as copper, was measured using a non-contact surface / layer cross-sectional shape measurement system (VertScan® R550GML) manufactured by Ryoka Systems Co., Ltd., under the conditions of an eyepiece magnification of 1.0, an objective lens magnification of 50, and a measurement area of ​​178 μm length x 238 μm width. After fourth-order polynomial surface correction and median filter (3 × 3) processing, the arithmetic mean height Sa, maximum cross-sectional height St, and root-mean-square height Sq were calculated. The measurement was performed 10 times, and the average values ​​were used.

[0198] The arithmetic mean roughness Ra, ten-point mean roughness Rz, and maximum cross-sectional height Rt are specifically measured as follows. A film before metal deposition, such as copper, was measured in the longitudinal direction (MD) of the film using a contact surface roughness meter (Surf Coder SE3500) manufactured by Kosaka Laboratory Co., Ltd. under the following conditions: stylus tip radius 0.5 mm, evaluation length 2.5 mm, longitudinal magnification 20,000 times, lateral magnification 20 times, cutoff value 0.08 mm, and measurement speed 0.1 mm / sec. The arithmetic mean roughness Ra, ten-point mean roughness Rz, and maximum cross-sectional height Rt were determined. The measurement was performed 12 times, and the average of 10 points obtained by dividing the maximum and minimum values ​​was used as the measured value.

[0199] The method for adjusting the surface properties Sa, Ra, Rz, Rt, St, Sq, and static friction coefficient μs of the film to fall within the above ranges is not particularly limited, and various methods can be used, such as transfer processes such as embossing roll transfer, embossing belt transfer, and embossing film transfer, sandblasting, shot blasting, etching, engraving, and surface crystallization. A preferred method is to roughen the surface by casting a film of molten resin onto a casting roll, as this facilitates the formation of continuous, uniform surface irregularities while extruding the molten resin into a film. In this case, the surface roughness of the resin film can be adjusted by adjusting the arithmetic mean roughness of the casting roll. Furthermore, the surface properties can be adjusted by appropriately adjusting the particle size, shape, and content of particles in the film or by adding an appropriate amount of a crystal nucleating agent. Furthermore, this can also be achieved by adjusting film formation conditions such as the stretching temperature, stretching ratio, uniformity of widthwise stretching, relaxation rate, and cooling temperature. Electrical surface treatments such as corona discharge treatment and atmospheric pressure glow discharge treatment can also be used. Furthermore, when a functional layer such as a resin layer or a release layer is separately provided by coating or the like, this can be achieved by appropriately adjusting the formulation of the coating liquid used, the coating thickness, the coating conditions, the dispersion state of the particles blended in the coating liquid, the timing of coating (inline or offline, etc.), etc.

[0200] [Absolute Value of Difference in Surface Free Energy] The absolute value of the difference in surface free energy of the present film (surface free energy γ SV The surface free energy γ of surface A and any other surface B SVB) is preferably 7 mN / m or less, and from the viewpoint of achieving both the productivity and the homogeneity at a high level, it is more preferably 5.5 mN / m or less, even more preferably 5 mN / m or less, still more preferably 3 mN / m or less, particularly preferably 2 mN / m or less, particularly preferably 1.5 mN / m or less, particularly preferably 1 mN / m or less, and most preferably 0.8 mN / m or less. The lower limit is preferably 0 mN / m, but may be 0.03 mN / m, 0.08 mN / m, 0.1 mN / m, 0.15 mN / m, 0.17 mN / m, or 0.2 mN / m.

[0201] [Ratio of surface free energy (γ SV B / γ SV A) )] The ratio of the surface free energy of the film (the surface free energy γ of any surface A, which is one of the surfaces) SV The surface free energy γ of surface A and any other surface B SV γ is the ratio of B SV B / γ SV A) is preferably 1 or more and 2 or less, and from the viewpoint of achieving both the productivity and the homogeneity at a high level, it is more preferably 1 or more and 1.5 or less, and even more preferably 1 or more and 1.2 or less. It is also preferably 1.15 or less, more preferably 1 or more and 1.15 or less, particularly preferably 1 or more and 1.1 or less, particularly preferably 1 or more and 1.06 or less, and most preferably 1 or more and 1.03 or less. The surface free energy ratio (γ SV B / γ SV A) is γ SV B≧γ SV A is a condition, for example, the surface free energy γ SV If the values ​​are different, the larger value is used as the numerator to determine the ratio.

[0202] The surface free energy γ SV (The surface free energy γ of any surface A, which is one of the surfaces, SV The surface free energy γ of surface A and any other surface B SVFrom the viewpoint of further improving the uniformity and adhesion of the metal layers formed on both sides of the film, B) is, for example, preferably 20 mN / m or more, more preferably 25 mN / m or more, even more preferably 30 mN / m or more, and particularly preferably 35 mN / m or more. SV The lower limit of the surface free energy γ is not particularly limited, but is preferably 90 mN / m or less, more preferably 75 mN / m or less, even more preferably 60 mN / m or less, particularly preferably 55 mN / m or less, and especially preferably 50 mN / m or less. SV is the surface free energy γ of any surface A, which is one of the surfaces. SV The surface free energy γ of surface A and any other surface B SV It is particularly preferable that both of B's ​​are within the above range.

[0203] Surface free energy is composed of the sum of intermolecular force components. The intermolecular forces are classified into dispersion force, orientation force, induction force, and hydrogen bond force, and each of these constitutes surface free energy as a dispersion component (Dispersion), polar component (Polar), induction component (Induction), and hydrogen bond component (Hydrogen). Of these components, the induction component is very weak and can be ignored, and the hydrogen bond component can be lumped together with the polar component.

[0204] In the present invention, the surface free energy γ SV Each component (variance component γ SV d and polar component γ SV p ) is a value determined by the following measurement and calculation methods. LV1 , γ LV1 d and γ LV1 p The contact angle (θ1) between the first liquid and the surface to be measured is known, and the following γ LV2 , γ LV2 d and γ LV2 pThe contact angle (θ2) between the second liquid, whose value is known, and the surface to be measured is measured. Next, these values ​​are substituted into the following equations (I-1) and (I-2), and the surface free energy γ of the resin layer surface to be measured is calculated from the simultaneous equations (I-1) and (I-2) below. SV The variance component of γ SV d and the polar component γ SV p In both cases, the unit is mN / m.

[0205] (γ SV d ・γ LV1 d ) 1 / 2 + (γ SV p ・γ LV1 p ) 1 / 2 = γ LV1 (1+cosθ1) / 2...(I-1) (γ SV d ・γ LV2 d ) 1 / 2 + (γ SV p ・γ LV2 p ) 1 / 2 = γ LV2 (1+cosθ2) / 2...(I-2)

[0206] gamma SV d : Surface free energy γ of the surface to be measured SV Variance component of γ SV p : Surface free energy γ of the surface to be measured SV The polar component of γ LV1 : surface tension of the first liquid γ LV2 : surface tension of the second liquid θ1: contact angle of the first liquid θ2: contact angle of the second liquid γ LV1 d : dispersion component of the surface tension of the first liquid γ LV1 p : polar component of the surface tension of the first liquid γ LV2 d : dispersion component of the surface tension of the second liquid γ LV2 p: polar component of the surface tension of the second liquid

[0207] The above formulas (I-1) and (I-2) are derived from the following Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula and the following Young's formula: OWRK theoretical formula: γ SL = γ SV +γ LV -2 (γ SV d ・γ LV d ) 1 / 2 -2 (γ SV p ・γ LV p ) 1 / 2 Young's formula: γ SV = γ SL +γ LV cosθ (where γ SL is the interfacial tension between the surface to be measured and the liquid.)

[0208] There are no particular limitations on the method for adjusting the surface free energy of the film surface within the above range, but it can be adjusted, for example, by the composition of the film surface. Adjusting the composition of each resin composition forming the resin layer of the film and the thickness of the resin layer are particularly effective. Furthermore, by approximating the composition of the surface or resin layer on one surface (side A) with the composition of the surface or resin layer on the other surface (side B), specifically by making the resin compositions identical or substantially identical, it becomes easier to adjust the absolute value and ratio of the difference in surface free energy within the above range. In adjusting the resin layer composition, for example, by incorporating a hydrophilic group-containing compound in addition to a commonly used binder resin and / or crosslinking agent, it becomes easier to increase the surface free energy value and adjust it to the desired value. The hydrophilic group-containing compound is not particularly limited as long as it contains a hydrophilic group. The hydrophilic group of the hydrophilic group-containing compound is a functional group that forms a weak bond with water molecules via hydrogen bonding or the like, and examples thereof include a hydroxyl group, a carboxyl group, an amide group, and a thiol group. Specific examples of the hydrophilic group-containing compound include compounds containing a (meth)acryloyl group, polyvinyl alcohol, glycerin, polyglycerin, alkylene oxide adducts of glycerin or polyglycerin, and polyalkylene oxides. Among these, polyvinyl alcohol and compounds containing a (meth)acryloyl group are preferred from the viewpoint of adhesion to the metal layer. Furthermore, from the viewpoint of adhesion to the metal layer, the hydrophilic group-containing compound is preferably a polymer containing a structural unit having a hydrophilic group.

[0209] Specifically, the surface free energy is measured as follows. To measure the contact angle, a contact angle meter (DMo-501 model) manufactured by Kyowa Interface Science Co., Ltd. was used to measure the contact angle when 1 μL of pure water and methylene iodide were dropped onto a film before copper deposition that had been conditioned for 24 hours or more in an environment of 23°C and 50% RH. The contact angle measured 60 seconds after each liquid was dropped onto the film was used. Using the obtained contact angle and the surface tension component values ​​of each liquid (Table 1), the surface free energy of the film surface was calculated according to the Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula.

[0210] [Crystalline Melting Temperature (Tm)] The crystalline melting temperature (Tm) of the present film as determined by differential scanning calorimetry (DSC) is preferably 258°C or lower. If the crystalline melting temperature (Tm) is 258°C or lower, for example, the temperature at which melting insulation begins during a short circuit is lowered, thereby quickly starting to stop or prevent a runaway reaction due to a short circuit. From this perspective, the crystalline melting temperature (Tm) is preferably 256°C or lower, more preferably 254°C or lower, and even more preferably 252°C or lower. On the other hand, from the viewpoint of formability and strength retention during high-temperature treatment, the crystalline melting temperature (Tm) is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher.

[0211] The method for adjusting the crystalline melting temperature (Tm) to the above range is not particularly limited, but it can be adjusted, for example, by changing the type and content of the polyester constituting the present film.

[0212] Specifically, the crystalline melting temperature Tm was measured as follows. Using a PerkinElmer differential scanning calorimeter (DSC 8500), the crystalline melting temperature (Tm) that appeared when the temperature was raised from 20°C to 300°C at a rate of 10°C per minute was measured in accordance with JIS K 7121 (2012). The extreme value of the maximum endothermic peak was taken as the crystalline melting temperature Tm. The analysis was performed by selecting the corresponding maximum endothermic peak range from "Peak Area" in the "Analysis" menu of the built-in software.

[0213] [Shrinkage] The shrinkage of the present film when heat-treated at 120°C for 5 minutes is preferably 1.2% or less, more preferably 1.1% or less, even more preferably 1% or less, and particularly preferably 0.9% or less in either the longitudinal direction (MD) or the transverse direction (TD), from the viewpoint of suppressing a decrease in adhesion to the metal layer and deformation of the film. The lower limit of the shrinkage (120°C, 5 minutes) is not particularly limited, but is usually about -0.5%, preferably -0.3% or more. It is particularly preferred that the shrinkage (120°C, 5 minutes) be within the above range in both the longitudinal direction (MD) and the transverse direction (TD).

[0214] From the same viewpoint, the shrinkage percentage of the present film when heat-treated at 150°C for 5 minutes is preferably 2.2% or less, more preferably 2.1% or less, and even more preferably 2% or less, in either the longitudinal direction (MD) or the transverse direction (TD). The lower limit of the shrinkage percentage (150°C, 5 minutes) is not particularly limited, but is usually about -0.5%, preferably -0.1% or more. It is particularly preferred that the shrinkage percentage (150°C, 5 minutes) be within the above range in both the longitudinal direction (MD) and the transverse direction (TD). From the same viewpoint, the shrinkage percentage of the present film when heat-treated at 180°C for 5 minutes is preferably 4% or less, more preferably 3.8% or less, and even more preferably 3.5% or less, in either the longitudinal direction (MD) or the transverse direction (TD). The lower limit of the shrinkage percentage (180°C, 5 minutes) is not particularly limited, but is usually about -0.5%, preferably 0%. It is particularly preferable that the shrinkage rate (180°C, 5 minutes) is within the above range in both the machine direction (MD) and the transverse direction (TD).

[0215] The method for adjusting the shrinkage percentages (120°C, 5 minutes), (150°C, 5 minutes), and (180°C, 5 minutes) to fall within the above ranges is not particularly limited. For example, the adjustments can be made by the type and content of polyester constituting the present film, the particle size and content of particles if particles are contained, the film-forming conditions of the present film, etc.

[0216] Specifically, the shrinkage rate is measured as follows. A test film of 1.5 cm x 15 cm was heat-treated for 5 minutes in a hot air oven maintained at a predetermined temperature (120°C, 150°C, 180°C) in an untensioned state, and the lengths of the test film were measured before and after the treatment, and the shrinkage rate was calculated using the following formula. The measurements were taken in both the machine direction (MD) and the width direction (TD) of the film. Shrinkage rate (%) = {(sample length before heat treatment) - (sample length after heat treatment)} ÷ (sample length before heat treatment) x 100

[0217] <<Film Foil>> A film foil for a battery current collector using the metal lamination film of the present invention (hereinafter also referred to as "the film foil") has a metal layer on the surface of the film facing the resin layer. The metal layer may be provided on at least one side of the film, but it is more preferable to provide a metal layer on both sides. For example, as shown in Figure 8, it is more preferable to provide metal layers 12, 12 on both sides of resin layers 11b, 11b formed on both sides of a polyester film 11a.

[0218] <Metal Layer> The metal forming the metal layer is not particularly limited, but may be, for example, a conductive metal, such as aluminum, nickel, gold, silver, copper, cadmium, titanium, or an alloy containing two or more of these. Among these, the metal layer is preferably made of copper or aluminum, from the viewpoint of being widely used, for example, as an electrode current collector (positive electrode current collector) used in the positive electrode of a lithium ion battery or an electrode current collector (negative electrode current collector) used in the negative electrode. Here, "made of" means that copper or aluminum is contained as the main component. The metal layer may also contain elements other than the conductive metal.

[0219] The metal layer is preferably provided by any one of vapor deposition, plating, and sputtering, and more specifically, a conventionally known method such as vacuum vapor deposition, electrolytic plating, electroless plating, sputtering, etc. That is, the metal layer is preferably any one of a metal vapor deposition layer, a metal plated layer, and a metal sputtered layer.

[0220] The thickness of the metal layer is usually 0.01 to 100 μm, preferably 0.013 to 50 μm, more preferably 0.015 to 20 μm, and even more preferably 0.02 to 5 μm.

[0221] The metal layer preferably has a two-layer structure. One example of such a structure is a two-layer structure consisting of a metal layer formed on the film by vapor deposition or sputtering, and a metal layer formed on the metal layer by plating. In this case, the film foil has a metal layer formed on both sides of the polyester film by vapor deposition or sputtering, and a metal layer formed by plating, in that order. This two-layer structure allows for a thinner and lighter film than conventional metal foils while maintaining conventional performance, and also allows for cost reduction compared to conventional metal foils.

[0222] <<Battery Current Collector>> A battery current collector using the present film foil (hereinafter also referred to as "the present current collector") has an electrode layer on a metal layer. The electrode layer is formed by laminating a conventionally known electrode agent on the surface of the metal layer, and can be used as a battery electrode. The layer structure of the present current collector is not limited to the following, but is preferably, for example, "electrode layer 13 / metal layer 12 / resin layer 11b / polyester film (substrate layer) 11a / resin layer 11b / metal layer 12 / electrode layer 13" as shown in Figure 9.

[0223] Furthermore, the current collector can be used to manufacture batteries such as lithium ion batteries by conventionally known methods.

[0224] <<Applications>> Because the present film and film foil exhibit excellent electrochemical stability, they are preferably used for electrode substrates such as battery current collectors and tab leads, particularly electrodes coated with an active material that oxidizes and reduces at a base potential. In addition, because the present film also has metal adhesion, it can also be used favorably for battery exterior materials, metal wiring substrates, RF tags, etc.

[0225] Among these, it is preferable to use it for a battery current collector. Examples of the battery include a storage battery, a secondary battery, a lithium ion battery, and a sodium ion battery. The current collector is preferably used for a lithium ion battery, and particularly for a lithium ion secondary battery. Therefore, the current collector preferably has a structure exemplified by "electrode layer (positive electrode) / metal layer / resin layer / substrate layer (polyester film) / resin layer / metal layer / electrode layer (positive electrode)" for a positive electrode current collector, and "electrode layer (negative electrode) / metal layer / resin layer / substrate layer (polyester film) / resin layer / metal layer / electrode layer (negative electrode)" for a negative electrode current collector.

[0226] Furthermore, compared to electrodes having a configuration of, for example, "electrode layer (positive electrode) / metal layer / electrode layer (positive electrode) or electrode layer (negative electrode) / metal layer / electrode layer (negative electrode)," use of this film can contribute to thinner, lighter, and less costly electrodes, and can also stop or prevent runaway reactions caused by short circuits.

[0227] <<Use of Laminate Film for Manufacturing a Film Foil for a Battery Current Collector or a Battery Current Collector>> One embodiment of the present invention includes the use of the following laminate film for manufacturing a film foil for a battery current collector or a battery current collector. A laminate film having a resin layer on at least one surface of a polyester film, wherein the ratio (β / α) of the peak intensity after the test (β) to the peak intensity before the test (α) satisfies the following formula (1): [Formula] Peak intensity after the test (β) / Peak intensity before the test (α)>0.46 (1) [Peak intensity before the test (α)] The peak intensity before the test (α) is a peak intensity of 1650 to 1800 cm in a Raman spectrum (Rmα) measured in a cross-sectional region of the polyester film included in the test film (sα) within a range of 1 μm in the thickness direction from one surface of the polyester film. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmα). -1The peak intensity (β) after the test is defined as the peak intensity of 1650 to 1800 cm in the Raman spectrum (Rmβ) measured in a cross-sectional region within 1 μm in the thickness direction from one surface of the polyester film included in the test film (sβ) after the test described below. -1 However, the peak intensity due to the C═O stretching vibration appears in the range of 1550 to 1650 cm in the Raman spectrum (Rmβ). -1 The peak intensity is defined as a peak intensity when the peak intensity due to the skeletal vibration of the benzene ring appearing in the range is set to 1. [Test film (sβ) after test] A test film (sα) was prepared by laminating a copper layer on the resin layer side of the laminated film, and a separator and lithium foil were laminated in this order on the copper layer side of the test film (sα). An electrolyte solution obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) was added so that the test film (sα), separator, and lithium foil were immersed, and the resultant was sealed to prepare a test coin cell (diameter 20 mm, height 3.2 mm). A current density of 0.09 mA / cm was applied to the test coin cell. 2 A current was applied at a constant current for 10 hours, and then at a current density of 0.09 mA / cm 2 After repeating this cycle of passing a current in the reverse direction under the conditions of a constant current for 10 hours 10 times in total, the test film removed from the test coin cell is designated as the test film (sβ) after the test.

[0228] The details of the constitution and structure of the laminated film are the same as those of the present film.

[0229] <<Explanation of Terms>> In this specification, unless otherwise specified, the term "main component" refers to a component that has a significant effect on the properties of the material. The content of the component is typically 50% by mass or more of the entire material, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90 to 100% by mass. In this specification, the term "film" also includes the term "sheet," and the term "sheet" also includes the term "film." In this specification, when "X to Y" (X and Y are arbitrary numbers) is used, unless otherwise specified, it also includes the meaning of "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." Furthermore, with regard to numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. Furthermore, "X and / or Y (X and Y are arbitrary components)" means at least one of X and Y, and can mean three possibilities: X only, Y only, or X and Y.

[0230] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[0231] <Evaluation Method> (1) Preparation of Test Film A test film having a layer structure of "copper layer / resin layer / base layer (polyester film)" was prepared by providing a 30 nm thick copper layer (copper purity 99.9%) on the surface side of a polyester film (114 mm x 114 mm) having a resin layer using a vacuum deposition apparatus (EBX-10D, manufactured by ULVAC, Inc.). A comparative test film having a layer structure of "copper layer / base layer (polyester film)" was also prepared using a similar method (Comparative Example 1). The vacuum deposition conditions were a deposition vacuum of 4.0 x 10 -3 [Pa], the deposition time was 30 seconds, and the current value was 250 mA.

[0232] (2) Lithium Electrolytic Deposition and Dissolution Reaction Test (2-1) Preparation of Test Coin Cells Test coin cells were prepared using the test film. Specifically, a CR2032-type coin cell (20 mm diameter, 3.2 mm height, manufactured by Hosen Co., Ltd.) including a main case, cap case, spacer, washer, and gasket (O-ring) was prepared. A circular cut-out (17 mm diameter) of the test film was placed inside the main case in an argon atmosphere in a glove box, with the copper layer facing outward. A polypropylene monolayer separator was then placed on the test film, with the copper layer of the test film facing the surface of the separator. Next, an electrolyte solution prepared by dissolving lithium bis(fluorosulfonyl)imide (LiFSI) in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) was added dropwise, and lithium foil (purity 99.8%) was placed on the separator. When lithium bis(fluorosulfonyl)imide was dissolved in the mixed solvent, sulfolane was assumed to be mono-coordinated with lithium ions, and dimethoxyethane was assumed to be di-coordinated with lithium ions, and the lithium bis(fluorosulfonyl)imide was dissolved in the mixed solvent so that the lithium coordination number was four. Furthermore, a spacer, a washer, and a cap case were sequentially placed on the lithium foil, and the cap case and main case were sealed using a coin cell crimping machine to prepare a test coin cell. The test coin cell contained a laminated structure of "lithium foil / separator / copper layer / resin layer / base layer (polyester film)." The comparative test film contained a laminated structure of "lithium foil / separator / copper layer / base layer (polyester film)."

[0233] (2-2) Precipitation and dissolution reaction test The test coin cell was set in the device, and a current density of 0.09 mA / cm 2 A current was passed through the test film at a constant current density of 0.09 mA / cm for 10 hours to electrolytically deposit lithium onto the copper layer of the test film. 2A current was passed in the reverse direction under the conditions of 10 hours at a constant current. This cycle was repeated 10 times in total. The current density was measured based on the area (1.11 cm2) of the lithium foil as viewed from the normal direction (the vertical direction where the main case and cap case overlap). 2 ) was calculated based on

[0234] (3) Raman Spectroscopic Measurement A test piece was cut out from the test film, embedded in epoxy resin, and then cut out in the thickness direction using a microtome (UC7, manufactured by Leica). A Raman spectrum was measured in a 1 μm region (1 μm in the thickness direction × 1 μm in the direction perpendicular to the thickness direction) from the copper layer side surface of the resin layer toward the substrate layer (polyester film) using a Raman spectrometer (DXR3Xi, manufactured by Thermo Fisher Scientific). (Conditions) Excitation laser wavelength: 785 nm Laser intensity (maximum output): 30 mW Exposure time: 0.25 seconds Beam diameter: 0.9 μm Grating (diffraction grating): 400 lines / mm Accumulation count: 80 Aperture: 25 μm Objective lens: MPLFLN-BD100x (0.9 NA)

[0235] The Raman spectrum of the test film after the test was also measured in the same manner. That is, after the electrodeposition-dissolution cycle was repeated a total of 10 times, the test coin cell was disassembled in an argon atmosphere in a glove box, the test film was taken out, and the Raman spectrum was measured in the same manner as above.

[0236] (4) Peak Intensity of Raman Spectrum ((α), (β)) The Raman spectrum obtained above (vertical axis represents scattering intensity (Intensity) and horizontal axis represents Raman shift (cm -1 )) based on the graph shown as -1 The peak intensity (α) in the range of 1650 to 1800 cm in the test film after the test -1 The peak intensity (β) was calculated.

[0237] (5) Linear Sweep Voltammetry (LSV) Measurement In a glove box under an argon atmosphere, a non-aqueous electrolyte solution prepared by dissolving lithium hexafluorophosphate at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) was poured into a container, and the following working electrode, counter electrode, and reference electrode were immersed in the container. A potentiostat was operated to apply a voltage, and the potential was swept from the natural potential (approximately 3.2 V) to 0 V at a sweep rate of 1 mV / s. The horizontal axis represents voltage (V), and the vertical axis represents current density (mA / cm 2 ) and a voltammogram (blank) was obtained. (Working electrode, reference electrode, and counter electrode) Working electrode: A slurry solution prepared by dispersing a mixture of natural carbon powder, sodium carboxymethyl cellulose, and styrene butadiene rubber (mass ratio 98:1:1) in water was applied to the surface of copper foil, which was then dried and cut into strips to obtain a working electrode. Reference electrode and counter electrode: Lithium metal wire.

[0238] In addition, the following resin (A-1), resin (A-2), or dimethyl terephthalate (a model compound for polyester film) was dissolved in the nonaqueous electrolyte at 0.5 mmol / L or more, and a voltammogram was obtained under the same conditions as above.

[0239] <Materials used in the base film> Polyester (P-1): polyethylene terephthalate (intrinsic viscosity 0.64 dL / g, substantially no particles) Polyester (P-2): polyethylene terephthalate (intrinsic viscosity 0.65 dL / g, containing 0.2% by mass of amorphous silica having an average particle size of 2 μm)

[0240] <Materials used in resin layers> Resin (A-1): Polyglycerol polyglycidyl ether (epoxy equivalent 183 g / eq) Resin (A-2): Carboxy group-containing acrylic resin (Alphon UC-3000, manufactured by Toagosei Co., Ltd.) Resin (A-3): Carboxy group- and methylol group-containing acrylic resin (Nikasol RX-7013ED, manufactured by Nippon Carbide Industries Co., Ltd.) Resin (A-4): Carboxy group-containing acrylic resin (Alphon UC-3080, manufactured by Toagosei Co., Ltd.) Resin (A-5): Carboxy group-, cyano group-, and methylol group-containing acrylic resin (Nikasol PK-8012K, manufactured by Nippon Carbide Industries Co., Ltd.)

[0241] Surfactant (B-1): A nonionic surfactant containing polyoxyethylene alkyl ether as the main component and having an HLB of 13.3. Surfactant (B-2): An acetylene-based nonionic surfactant having polyethylene oxide in the side chain and having an HLB of 8.0.

[0242] Particles (C-1) Silica particles with an average particle size of 0.07 μm

[0243] [Comparative Example 1] A blend of polyester (P-1) and polyester (P-2) in a mass ratio of 92:8 (P-1:P-2) was used as the raw material for layer a, and polyester (P-1) alone was used as the raw material for layer b. Each was fed into an extruder, heated and melted at 285 ° C., and layer a was divided into two to form a two-kind, three-layer structure with layer a as the outermost layer (surface layer) and layer b as the intermediate layer. Co-extruded under extrusion conditions such that the thickness composition ratio was surface layer (a) / intermediate layer (b) / surface layer (a) = 1:8:1, and cooled and solidified while in close contact with a mirror-finished cooling drum with a surface temperature of 40 to 50 ° C. to produce an unstretched film. This film was stretched 3.4 times in the longitudinal direction while passing through a group of heated rolls at 85 ° C. to produce a uniaxially stretched film. Next, this uniaxially stretched film was introduced into a tenter stretching machine, stretched 4.3 times in the width direction at 110°C, further subjected to heat treatment at 235°C for 1 to 30 seconds, and then subjected to cooling treatment at 140°C under 2% relaxation in the width direction to obtain a biaxially stretched polyester film with a thickness of 50 μm.

[0244] [Example 1] Coating solution I shown in Table 1 below was coated on one surface of the biaxially stretched polyester film obtained in Comparative Example 1, and the coating solution was cured by heating in an oven at 100°C for 3 minutes and at 210°C for 1 minute to form a resin layer having a thickness (after drying) of 0.050 µm, thereby obtaining a laminated polyester film having a resin layer.

[0245] Example 2 A blend of polyester (P-1) and polyester (P-2) in a mass ratio of 92:8 (P-1:P-2) was used as the raw material for layer a, and polyester (P-1) alone was used as the raw material for layer b. Each was fed into an extruder, heated and melted at 285 ° C., and layer a was divided into two to form a two-kind, three-layer structure with layer a as the outermost layer (surface layer) and layer b as the intermediate layer. The resulting extrusion was co-extruded under the following conditions: thickness composition ratio of surface layer (a) / intermediate layer (b) / surface layer (a) = 1:8:1, and the resulting film was cooled and solidified while in close contact with a mirror-finished cooling drum with a surface temperature of 40 to 50 ° C. to produce an unstretched film. This film was stretched 3.4 times in the longitudinal direction while passing through a group of heated rolls at 85 ° C. to produce a uniaxially stretched film. Next, Coating Solution II shown in Table 1 below was applied to one surface of this uniaxially stretched film, and then this film was introduced into a tenter stretching machine, stretched 4.3 times in the width direction at 110°C, further subjected to heat treatment at 235°C, and then subjected to a 2% relaxation treatment in the width direction to form a biaxially stretched film having a thickness of 50 μm and a resin layer with a film thickness (after drying) of 0.040 μm, thereby obtaining the laminated polyester film of Example 2.

[0246] Examples 3 to 4 The laminated polyester films of Examples 3 and 4 were obtained in the same manner as in Example 2, except that Coating Solution II in Example 2 was changed to the coating solution shown in Table 1. Note that A-4' in Table 2 is a product obtained by neutralizing Resin (A-4) with aqueous ammonia. Neutralized product (A-4') of Resin (A-4) was obtained by adding Resin (A-4) to pure water, and neutralizing the mixture by adding aqueous ammonia while heating and stirring at 40°C. Note that the amount of aqueous ammonia added was such that the amount of ammonia was 1.2 equivalents relative to the carboxy groups of Resin (A-4) (calculated value).

[0247]

[0248] (Evaluation Results of Measurement of Peak Intensities ((α), (β)) of Raman Spectra) The peak intensities ((α), (β)) of the Raman spectra were determined for each of Examples 1 to 4 and Comparative Example 1. The results are shown in FIGS. 1 to 5 and Table 2.

[0249]

[0250] 5 and Table 2, the film of Comparative Example 1 shows a significant decrease in peak intensity after the test compared to the peak intensity due to C=O stretching vibration before the test, indicating that the polyester has been significantly reduced and decomposed, indicating that the film has poor charge-discharge durability. On the other hand, the results of FIGS. 1 to 4 and Table 2 indicate that the films of Examples 1 to 4 have excellent charge-discharge durability because the decrease in peak intensity due to the reduction of C=O bonds due to the reduction of the polyester can be significantly suppressed.

[0251] (Test Results of Linear Sweep Voltammetry Measurement) As shown in FIG. 6, when dimethyl terephthalate (a model compound of polyester film) was used (Reference Example), a reduction current (a downward convex peak) was clearly observed around 1.3 V, unlike the case of only the electrolyte solution (blank). On the other hand, in the case of the electrolyte solution using resin (A-1) or resin (A-2), no reduction current (a downward convex peak) was observed, as in the case of only the electrolyte solution (blank). From these results, it can be seen that a metal lamination film having a resin layer containing the resin has excellent charge and discharge durability.

[0252] Furthermore, as shown in FIG. 6, the electrolyte solution using resin (A-1) or resin (A-2) and the case of only the electrolyte solution (blank) exhibited roughly the same behavior. Specifically, in a graph plotting the potential and current density when the potential was swept from the natural potential (about 3.2 V) to 0 V at a sweep rate of 1 mV / s, the maximum value of the current density ratio calculated by the following method was small, 1.2, when resin (A-1) or resin (A-2) was used. On the other hand, the maximum value of the current density ratio when dimethyl terephthalate (Reference Example) was used was relatively large, 8.3. (Maximum value of current density ratio) This is the maximum value of the current density ratio obtained according to the following formula (2) at a specified potential. The specified potential is 0.0 V (Li / Li ＋ ) ~ 3.0V (Li / Li ＋ ) in the range of 0.05V (Li / Li ＋ If there is no current density data at a specified potential, the specified potential ±0.02V (Li / Li ＋The value of the current density in the range of [Formula] Current density ratio = |Current density at a specified potential when using resin (A-1), resin (A-2), or dimethyl terephthalate| / |Current density at a specified potential when using only the electrolyte (blank)| ... (2)

[0253] The results also show that a film for metal lamination having a resin layer containing the resin has excellent charge-discharge durability. The maximum value of the current density ratio in the present invention is not limited, but is, for example, preferably 8 or less, more preferably 6.5 or less, even more preferably 5 or less, still more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0254] Resin (A-3), resin (A-4), and resin (A-5) are insoluble in the electrolyte, making direct linear sweep voltammetry measurement difficult. However, because they are acrylic resins containing carboxy groups like resin (A-2), it is presumed from the results for resin (A-2) that they have excellent charge / discharge durability. In the case of resins (A-3), (A-4), and (A-5) that are insoluble in the electrolyte, linear sweep voltammetry measurement can be performed using the monomer components that make up the resin, as described above, to confirm that they are not easily decomposed.

[0255] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0256] The metal lamination film of the present invention exhibits excellent electrochemical stability and can therefore be suitably used in applications requiring electrochemical stability, such as battery components. Examples of battery components include current collectors and tab leads, and examples of batteries include lithium ion batteries and sodium ion batteries. Furthermore, since the metal lamination film of the present invention also has metal adhesion, it can also be suitably used in battery exterior materials, metal wiring substrates, RF tags, and the like.

[0257] 11a Polyester film 11b Resin layer 12 Metal layer 13 Electrode layer

Claims

1. A film foil for a battery current collector, comprising a polyester film having a resin layer on at least one surface, wherein the resin layer contains polyglycerol polyglycidyl ether or a reaction product of polyglycerol polyglycidyl ether and at least one compound, and the ratio of the peak intensity after the test (β) to the peak intensity before the test (α) (β / α) satisfies formula (1), wherein a metal layer is laminated on the surface of the resin layer side of the metal lamination film. [formula] Peak intensity after the test (β) / Peak intensity before the test (α) > 0.46 ... (1) [Peak intensity before testing (α)] The peak intensity (α) before testing refers to the Raman spectrum (Rmα) measured in a cross-sectional area of ​​the polyester film contained in the test film (sα), where a test film (sα) is prepared by laminating a copper layer on the resin layer side of the above-mentioned metal lamination film, and the peak intensity is measured in the range of 1 μm in the thickness direction from one of the surfaces. -1 This peak intensity originates from C=O stretching vibrations and appears in the range of 1550–1650 cm² in the above Raman spectrum (Rmα). -1 This is defined as the peak intensity when the peak intensity originating from the benzene ring skeletal vibration appearing in this range is set to 1. [Peak intensity (β) after testing] The peak intensity (β) after the test refers to the 1650–1800 cm⁻¹ range in the Raman spectrum (Rmβ) measured in a cross-sectional area of ​​the polyester film contained in the test film (sβ) within a thickness range of 1 μm from one of the surfaces described above after the test. -1 This peak intensity originates from C=O stretching vibrations and appears in the range of 1550–1650 cm⁻¹. -1 This is defined as the peak intensity when the peak intensity originating from the benzene ring skeletal vibration appearing in this range is set to 1. [Test film (sβ) after testing] A test film (sα) is prepared by laminating a copper layer on the resin layer side of the above-mentioned metal lamination film. A separator and lithium foil are then laminated in this order to the copper layer side of the test film (sα). An electrolyte obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is added so as to immerse the test film (sα), separator, and lithium foil, and the cell is sealed to produce a test coin cell (20 mm in diameter, 3.2 mm in height). The current density for the test coin cell is 0.09 mA / cm². 2 The current was then passed under constant current conditions for 10 hours, and the current density was then measured at 0.09 mA / cm². 2 After repeating a cycle of applying current in the reverse direction under constant current and 10 hours for a total of 10 cycles, the test film removed from the test coin cell is designated as the test film (sβ) after testing.

2. A film foil for a battery current collector, comprising a polyester film having a resin layer on at least one surface, wherein the thickness of the resin layer is less than 1 μm, and the ratio of the peak intensity after testing (β) to the peak intensity before testing (α) (β / α) satisfies formula (1), wherein a metal layer is laminated on the surface of the resin layer side of the metal lamination film. [formula] Peak intensity after the test (β) / Peak intensity before the test (α) > 0.46 ... (1) [Peak intensity before testing (α)] The peak intensity (α) before testing refers to the peak intensity originating from the C=O stretching vibration appearing in the 1650-1800 cm⁻¹ range in the Raman spectrum (Rmα) measured in a cross-sectional area of ​​the polyester film contained in the test film (sα), which is prepared by laminating a copper layer on the resin layer side of the above-mentioned metal lamination film, within a thickness range of 1 μm from one of the surfaces. However, this peak intensity is defined as the peak intensity when the peak intensity originating from the benzene ring skeleton vibration appearing in the 1550-1650 cm⁻¹ range in the above-mentioned Raman spectrum (Rmα) is set to 1. [Peak intensity (β) after testing] The peak intensity (β) after the test refers to the peak intensity originating from the C=O stretching vibration appearing in the 1650-1800 cm⁻¹ range in the Raman spectrum (Rmβ) measured in a cross-sectional area within a 1 μm thickness range from one surface of the polyester film contained in the test film (sβ) after the test described below. However, this peak intensity is defined as the peak intensity when the peak intensity originating from the benzene ring skeleton vibration appearing in the 1550-1650 cm⁻¹ range in the above Raman spectrum (Rmβ) is set to 1. [Test film (sβ) after testing] A test film (sα) is prepared by laminating a copper layer on the resin layer side of the above-mentioned metal lamination film. A separator and lithium foil are then laminated in this order to the copper layer side of the test film (sα). An electrolyte obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is added so that the test film (sα), separator, and lithium foil are immersed, and the cell is sealed to produce a test coin cell (20 mm in diameter, 3.2 mm in height). A current is passed through the test coin cell at a current density of 0.09 mA / cm², constant current, for 10 hours, and then the current is passed in the reverse direction at a current density of 0.09 mA / cm², constant current, for 10 hours. This cycle is repeated a total of 10 times, and the test film removed from the test coin cell is designated as the test film (sβ) after testing.

3. The film foil for a battery current collector according to claim 1 or 2, wherein the resin contained in the above resin layer satisfies the following requirements. (Requirements) When comparing the voltammogram (Vb) obtained by linear sweep voltammetry measurement under the following conditions with the voltammogram (Vp) obtained by linear sweep voltammetry measurement under the same conditions as below, except that 0.5 mmol / L or more of the resin contained in the resin layer or the monomer components constituting the resin is dissolved in the electrolyte under the following conditions, no reduction current is observed at different potentials. [Linear sweep voltammetry measurement conditions] Working electrode: An electrode prepared by dispersing a mixture of natural carbon powder, sodium carboxymethylcellulose, and styrene-butadiene rubber (mass ratio 98:1:1) in water, coating it onto copper foil, and then drying it. Reference electrode and counter electrode: Lithium metal wire. Electrolyte: An electrolyte prepared by dissolving lithium hexafluoride phosphate at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate and ethylmethyl carbonate (volume ratio 3:7). Sweep speed: 1 mV / sec. Sweep range: Natural potential (approx. 3.2V) → 0V (vs Li / Li + ).

4. The film foil for a battery current collector according to claim 1, wherein the content of the above reaction product is 70% by mass or more relative to the total mass of the above resin layer (non-volatile component).

5. The film foil for a battery current collector according to claim 1 or 2, wherein the resin layer is formed directly on the surface of the polyester film.

6. The film foil for a battery current collector according to claim 1 or 2, wherein the metal layer is any one of a metal vapor deposition layer, a metal plating layer, and a metal sputtering layer.

7. The film foil for a battery current collector according to claim 1 or 2, wherein the above metal layer comprises at least one selected from the group consisting of copper, aluminum, nickel, chromium, and alloys containing two or more of these.

8. A battery current collector comprising an electrode layer laminated on the surface of a metal layer of a film foil for battery current collectors according to claim 1 or 2.

9. The battery current collector according to claim 8, wherein the battery in the above-mentioned battery current collector is a lithium-ion battery or a sodium-ion battery.

10. Use of the following laminated films for the manufacture of battery current collector film foils or battery current collectors. A laminated film having a resin layer on at least one surface of a polyester film, wherein the resin layer contains polyglycerol polyglycidyl ether or a reaction product of polyglycerol polyglycidyl ether and at least one compound, and the ratio (β / α) of the peak intensity after the test to the peak intensity before the test (α) satisfies formula (1). [formula] Peak intensity after the test (β) / Peak intensity before the test (α) > 0.46 ... (1) [Peak intensity before testing (α)] The peak intensity (α) before the test refers to the peak intensity derived from the C=O stretching vibration appearing in the range of 1650-1800 cm -1 in the Raman spectrum (Rmα) measured in the cross-sectional area in the range of 1 μm in the thickness direction from one surface of the polyester film included in the test film (sα) obtained by laminating a copper layer on the resin layer side of the laminated film. However, it is the peak intensity when the peak intensity derived from the skeletal vibration of the benzene ring appearing in the range of 1550-1650 cm -1 in the Raman spectrum (Rmα) is taken as 1. [Peak intensity (β) after testing] The peak intensity (β) after the test refers to the 1650–1800 cm⁻¹ range in the Raman spectrum (Rmβ) measured in a cross-sectional area of ​​the polyester film contained in the test film (sβ) within a thickness range of 1 μm from one of the surfaces described above after the test. -1 This peak intensity originates from C=O stretching vibrations and appears in the range of 1550–1650 cm⁻¹. -1 This is defined as the peak intensity when the peak intensity originating from the benzene ring skeletal vibration appearing in this range is set to 1. [Test film (sβ) after testing] A test film (sα) is prepared by laminating a copper layer on the resin layer side of the above-mentioned laminated film. A separator and lithium foil are then laminated in this order on the copper layer side of the test film (sα). An electrolyte obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is added so as to immerse the test film (sα), separator, and lithium foil, and the cell is sealed to produce a test coin cell (20 mm in diameter, 3.2 mm in height). The current density for the above test coin cell is 0.09 mA / cm². 2 The current was then passed under constant current conditions for 10 hours, and the current density was then measured at 0.09 mA / cm². 2 After repeating a cycle of applying current in the reverse direction under constant current and 10 hours for a total of 10 cycles, the test film removed from the test coin cell is designated as the test film (sβ) after testing.

11. Use of the following laminated film for manufacturing a film foil for a battery current collector or a battery current collector. A laminated film having a resin layer on at least one surface of a polyester film, wherein the thickness of the resin layer is less than 1 μm, and the ratio of the peak intensity after the test (β) to the peak intensity before the test (α) (β / α) satisfies formula (1). [formula] Peak intensity after the test (β) / Peak intensity before the test (α) > 0.46 ... (1) [Peak intensity before testing (α)] The peak intensity (α) before the test refers to the peak intensity originating from the C=O stretching vibration appearing in the 1650-1800 cm⁻¹ range in the Raman spectrum (Rmα) measured in a cross-sectional area within a thickness range of 1 μm from one surface of the polyester film contained in the test film (sα), which is prepared by laminating a copper layer on the resin layer side of the laminated film described above. However, the peak intensity is defined as the peak intensity when the peak intensity originating from the benzene ring skeleton vibration appearing in the 1550-1650 cm⁻¹ range in the Raman spectrum (Rmα) is set to 1. [Peak intensity (β) after testing] The peak intensity (β) after the test refers to the peak intensity originating from the C=O stretching vibration appearing in the 1650-1800 cm⁻¹ range in the Raman spectrum (Rmβ) measured in a cross-sectional area within a 1 μm thickness range from one surface of the polyester film contained in the test film (sβ) after the test described below. However, this peak intensity is defined as the peak intensity when the peak intensity originating from the benzene ring skeleton vibration appearing in the 1550-1650 cm⁻¹ range in the above Raman spectrum (Rmβ) is set to 1. [Test film (sβ) after testing] A test film (sα) is prepared by laminating a copper layer on the resin layer side of the laminated film described above. A separator and lithium foil are then laminated in this order to the copper layer side of the test film (sα). An electrolyte obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is added so that the test film (sα), separator, and lithium foil are immersed, and the cell is sealed to produce a test coin cell (20 mm in diameter, 3.2 mm in height). A current is passed through the test coin cell at a current density of 0.09 mA / cm², constant current, for 10 hours, and then the current is passed in the reverse direction at a current density of 0.09 mA / cm², constant current, for 10 hours. This cycle is repeated a total of 10 times, and the test film removed from the test coin cell is designated as the test film (sβ) after the test.