Films for metal lamination, film foils, film foils for battery current collectors, and battery current collectors

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

[Technical Field]

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

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

[0003] In current collectors for secondary batteries, a laminated current collector is sometimes used in which the surface of a polyester film substrate is covered with a thin metal film. A laminated current collector using such a substrate is effective in that it has a current interruption function in which the substrate melts and deforms and the thin metal film breaks when abnormal heat generation occurs due to an internal short circuit or the like (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-40919 [Patent Document 2] Japanese Patent Application Publication No. 10-40920 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, current collectors having a structure in which a metal layer is laminated on the surface of a polyester film substrate have problems such as reductive decomposition of the polyester film during the operating range of charging and discharging lithium-ion batteries. Therefore, the inventors' research has revealed that further improvements are needed in terms of electrochemical stability, and especially in terms of charge-discharge durability.

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

[0007] Furthermore, the present invention provides a metal lamination film that can contribute to improving the charge-discharge durability of secondary batteries such as lithium-ion batteries. [Means for solving the problem]

[0008] In view of the above problems, the inventors have conducted thorough studies and have found that the above problems can be solved by having the following configuration. The present invention has the following aspects.

[0009] [1] A metal lamination 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 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 testing refers to 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), 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 measuring the peak intensity (α) in the 1650-1800 cm⁻¹ range in the thickness direction from one of the surfaces. -1This peak intensity originates from the C=O stretching vibration and appears in the range of 1550-1650 cm². -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 after testing (β)] 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 1 μm thickness range from one of the surfaces described above after the test. -1 This peak intensity originates from the C=O stretching vibration and appears in the range of 1550-1650 cm². -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 to the test film (sα), separator, and lithium foil so as to immerse them, and the device 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 applied 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] The metal lamination film described in [1], 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 the resin contained in the resin layer or the monomer components constituting the resin are dissolved in the electrolyte under the following conditions at a concentration of 0.5 mmol / L or more, 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 ml / L in a mixed solvent of ethylene carbonate and ethylmethyl carbonate (volume ratio 3:7). Sweep speed: 1mV / sec. Sweep range: Natural potential (approx. 3.2V) → 0V (vs Li / Li + ). [3] The metal lamination film according to [1] or [2], wherein the resin layer contains at least one selected from the group consisting of polyolefin resin, (meth)acrylic resin, polyalkylene glycol, and compounds having a glycidyl ether group. [4] The metal lamination film 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 other compound. [5] A metal lamination film 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 compound. [6] The metal lamination film according to [3], wherein the content of at least one selected from the group consisting of the above-mentioned polyolefin resin, (meth)acrylic resin, polyalkylene glycol, and compounds having a glycidyl ether group is 70% by mass or more with respect to the total mass of the above-mentioned resin layer (non-volatile component). [7] A metal lamination film according to any one of [1] to [6], wherein the thickness of the resin layer is less than 1 μm. [8] A metal lamination film according to any one of [1] to [7], wherein the above resin layer is formed directly on the surface of the polyester film. [9] A film foil comprising a metal layer laminated on the resin layer side surface of a metal lamination film as described in any of [1] to [8].

[10] The film foil according to [9], wherein the above metal layer is any 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 comprises 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, made using the film foil described in any of [9] to

[11] .

[13] A battery current collector comprising an electrode layer laminated on the surface of a metal layer of a film foil for battery current collectors described in

[12] .

[14] The battery current collector according to

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

[15] 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 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 test (β) / Peak intensity before test (α) > 0.46 …(1) [Peak intensity before test (α)] The peak intensity before test (α) is the peak intensity derived from the C=O stretching vibration appearing in the range of 1650 to 1800 cm in the Raman spectrum (Rmα) measured in the cross-sectional area 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 to 1650 cm in the Raman spectrum (Rmα) is taken as 1. -1 in the range of is used. -1 [Peak intensity after test (β)] The peak intensity after test (β) is the peak intensity derived from the C=O stretching vibration appearing in the range of 1650 to 1800 cm in the Raman spectrum (Rmβ) measured in the cross-sectional area of 1 μm in the thickness direction from one surface of the polyester film included in the test film (sβ) after the following test. 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 to 1650 cm in the Raman spectrum (Rmβ) is taken as 1. -1 in the range of is used. -1 [Test film (sβ) after test] A test film (sα) obtained by laminating a copper layer on the resin layer side of the laminated film is produced, a separator and a lithium foil are laminated in this order on the copper layer side of the test film (sα), and an electrolytic solution obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is added and sealed so that the test film (sα), the separator and the lithium foil are immersed to produce a test coin cell (diameter 20 mm, height 3.2 mm). A current is passed through the test coin cell under the conditions of a current density of 0.09 mA / cm 2 , constant current, and 10 hours, and then a current density of 0.09 mA / cm 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. [Effects of the Invention]

[0010] According to the present invention, it is possible to improve the electrochemical stability of metal lamination films containing a polyester film as a base material. Furthermore, according to one embodiment of the present invention, it is possible to improve the charge-discharge durability of secondary batteries. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the Raman spectrum of Example 1. [Figure 2] This figure shows the Raman spectrum of Example 2. [Figure 3] This figure shows the Raman spectrum of Example 3. [Figure 4] This figure shows the Raman spectrum of Example 4. [Figure 5] This figure shows the Raman spectrum of Comparative Example 1. [Figure 6] This figure shows voltammograms obtained by linear sweep voltammetry of examples and comparative examples. [Figure 7] This is a diagram illustrating the peak intensity of the Raman spectrum. [Figure 8] This diagram schematically shows a cross-section of one embodiment of the present invention. [Figure 9] This diagram schematically shows a cross-section of one embodiment of the present invention. [Modes for carrying out the invention]

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

[0013] <<Film for metal lamination>> A metal lamination film according to one embodiment of the present invention (hereinafter also referred to as "this film" or "laminated film") preferably has a resin layer on at least one surface of a polyester film as a base film. This film is suitable for applications involving metal lamination because it has excellent electrochemical stability, particularly resistance to polyester degradation, as well as good adhesion to metals. In particular, this film is especially suitable for applications such as electrode current collectors having a laminated structure with a metal layer, due to its excellent charge-discharge durability.

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

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

[0016] The method for controlling the ratio (β / α) within the above range is not limited to the following, but for example, the ratio (β / α) can be controlled within the above range by appropriately adjusting the type of resin constituting the resin layer, the components blended with the resin, their respective content ratios, the thickness of the resin layer, the film-forming method, etc. Preferably, a method using components that do not exhibit oxidation-reduction reactions within the desired operating potential range is effective. Furthermore, by hardening the resin layer to the required degree, it is possible to prevent the penetration of the electrolyte into the resin layer and the dissolution of the resin layer by the electrolyte, which is effective.

[0017] [Measurement of peak intensity (α) and (β)] The peak intensity (α) of formula (1) above is measured before the test using a test film (sα) in which a copper layer is laminated on the resin layer side of the main film. The test film (sα) is prepared, for example, by attaching a copper layer to the surface side of the resin layer of the main film using a vacuum deposition apparatus or the like. The test film has a layer structure of "copper layer / resin layer / base layer (polyester film)". Further details are described in the examples below.

[0018] The peak intensity (α) before the test is measured in the Raman spectrum (Rmα) within a cross-sectional area of ​​1 μm in the thickness direction from one surface (the resin layer side surface) of the polyester film (substrate layer) contained in the above test film (sα), specifically in the range of 1650-1800 cm⁻¹. -1 The peak intensity appearing in the range originates from the C=O stretching vibration, and the above peak intensity (α) is in the 1550-1650 cm range of the above Raman spectrum (Rmα). -1 The peak intensity derived from the benzene ring skeletal vibration appearing in this range is taken as the peak intensity converted to 1.

[0019] The peak intensity (α) before the test will be explained with reference to Figure 7. In Figure 7, the symbols A1, etc., mean the following: A1: Scattering intensity on the low-wavenumber side within the specified wavenumber range. A2: The lower wavenumber within the specified wavenumber range. B1: Scattering intensity on the high-wavenumber side within the specified wavenumber range. B2: The higher wavenumber within the specified wavenumber range. P1: The highest scattering intensity within the specified wavenumber range. P2: Wavenumber at P1. Q1: What is the scattering intensity at P2 on the straight line (BL) connecting two points A1 and A2, and B1 and B2?

[0020] First, the Raman spectrum (Rmα) before the test (1650-1800 cm⁻¹) -1 We determine the peak intensity originating from the C=O stretching vibration that appears in the range. Referring to Figure 7, the 1650 cm⁻¹ peak in the Raman spectrum (Rmα) -1 Wave number A2, 1800cm -1 This corresponds to wavenumber B2. This is the 1650-1800 cm² range in the Raman spectrum (Rmα). -1 The peak intensity originating from the C=O stretching vibration appearing within the range (wavenumber range A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1650 cm². -1 The measurement point of the scattering intensity (A1) at wavenumber A2, and 1800 cm -1 It is represented by a straight line connecting the measurement point of the scattering intensity (B1) at wavenumber (B2). That is, in the Raman spectrum (Rmα) before the test, 1650~1800 cm⁻¹ -1 The peak intensity originating from the C=O stretching vibration that appears within this range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0021] Next, the Raman spectrum (Rmα) before the test (1550-1650 cm⁻¹) -1 We determine the peak intensity originating from the benzene ring skeletal vibrations that appear in the range. Referring to Figure 7, the peak intensity at 1550 cm² in the Raman spectrum (Rmα) is determined. -1 Wave number A2, 1650cm -1 This corresponds to wavenumber B2. This is the 1550-1650 cm⁻¹ range in the Raman spectrum (Rmα). -1 The peak intensity originating from the benzene ring skeletal vibration appearing within the range (wavenumber range A2 to B2) is determined with the baseline (BL) as the reference (0). The baseline (BL) is 1550 cm². -1The measurement point of the scattering intensity (A1) at wavenumber A2, and 1650 cm -1 It is represented by a straight line connecting the measurement point of the scattering intensity (B1) at wavenumber (B2). That is, in the Raman spectrum (Rmα) before the test, 1550-1650 cm⁻¹ -1 The peak intensity originating from the benzene ring skeletal vibrations appearing within this range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0022] And, in the Raman spectrum (Rmα) before the test, 1650-1800 cm⁻¹ -1 The peak intensity (P1-Q1) originating from the C=O stretching vibration appearing in the range is in the Raman spectrum (Rmα) between 1550 and 1650 cm⁻¹. -1 The peak intensity (α) is determined by converting the peak intensity (P1-Q1) originating from the benzene ring skeletal vibrations appearing in this range to 1.

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

[0024] Next, we will explain how to measure the peak intensity (β) after the test. The peak intensity (β) after the test is measured by preparing a test coin cell using the test film (sβ) after the test.

[0025] [Preparation of test coin cells] First, prepare a test coin cell (20 mm in diameter, 3.2 mm in height). For example, prepare a CR2032 type coin cell including the main case, cap case, spacer, washer, and gasket (O-ring). Commercially available coin cells can be used as appropriate (for example, coin cells manufactured by Hosen Co., Ltd.).

[0026] The test coin cell contains a laminated structure consisting of "lithium foil / separator / copper layer / resin layer / base layer (polyester film)". A test coin cell is manufactured, for example, by placing a gasket and a test film (sα) inside the main case in an argon atmosphere, positioning the separator so that its surface faces the copper layer of the test film (sα), and dropping a predetermined electrolyte onto it. Then, lithium foil, a spacer, a washer, and a cap case are sequentially placed on top of the separator, and the cap case and the main case are sealed using a coin cell crimping machine or the like. Further details are described in the embodiments below.

[0027] The above-mentioned separator is a component that electrically and physically separates electrodes of opposite polarity within an electrochemical device and allows ions flowing between them to pass through. A general-purpose separator used for lithium-ion batteries can be used as appropriate. For example, separators made of polypropylene or polyethylene can be suitably used. Alternatively, a glass filter may be used as the separator.

[0028] Furthermore, as the electrolyte, an electrolyte obtained by dissolving lithium bis(fluorosulfonyl)imide in a mixed solvent of sulfolane and dimethoxyethane (molar ratio 1:2) is used, and this electrolyte is added to the test coin cell so that the test film (sα), separator, and lithium foil are immersed in it. When dissolving lithium bis(fluorosulfonyl)imide in the above mixed solvent, the coordination number to lithium ions should be calculated by considering sulfolane as 1-coordinate and dimethoxyethane as 2-coordinate, and then dissolving lithium bis(fluorosulfonyl)imide so that its lithium coordination number is 4. If necessary, an electrolyte capable of electrolytically dissolving and dissolving lithium metal can be used in the test. Electrolytes are generally prepared by dissolving the electrolyte in a solvent. Examples of solvents 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. Furthermore, the above solvent may be used alone or as a mixture of multiple materials. Examples of electrolytes include lithium bis(fluorosulfonyl)imide, lithium hexafluoride phosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate.

[0029] [Test treatment (Li precipitation and dissolution reaction treatment)] The test coin cell is placed in the device, and the current density is 0.09 mA / cm². 2 After electrolysis of lithium onto the copper layer of the test film by applying a constant current for 10 hours, the current density was 0.09 mA / cm². 2 Then, lithium is leached by applying a current in the reverse direction under constant current conditions for 10 hours. This processing cycle is repeated a total of 10 times. Further details are described in the examples below.

[0030] As described above, after repeating the cycle a total of 10 times, the test coin cell is disassembled under an argon atmosphere, the test film (sβ) is removed, 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 testing is measured in the Raman spectrum (Rmβ) within a cross-sectional area of ​​1 μm in the thickness direction from one surface (the resin layer side) of the polyester film (substrate layer) contained in the test film (sβ) after testing, specifically in the range of 1650-1800 cm⁻¹. -1 The peak intensity appearing in the range is derived from the C=O stretching vibration, and the above peak intensity (β) is in the 1550-1650 cm range of the above Raman spectrum (Rmβ). -1 The peak intensity derived from the benzene ring skeletal vibration appearing in this range is taken as the peak intensity converted to 1.

[0032] The peak intensity (β) after the test will be explained with reference to Figure 7. First, in the Raman spectrum (Rmβ) after the test, 1650-1800 cm⁻¹ -1 Determine the peak intensity originating from the C=O stretching vibration that appears in the range. In the Raman spectrum (Rmβ), the peak intensity at 1650 cm² is determined.-1 Wave number A2, 1800cm -1 This corresponds to wavenumber B2. This is the 1650-1800 cm⁻¹ range in the Raman spectrum (Rmβ). -1 The peak intensity originating from the C=O stretching vibration appearing within the range (wavenumber range A2 to B2) is determined using the baseline (BL) as the reference (0). The baseline (BL) is 1650 cm². -1 The measurement point of the scattering intensity (A1) at wavenumber A2, and 1800 cm -1 It is represented by a straight line connecting the measurement point of the scattering intensity (B1) at wavenumber (B2). That is, in the Raman spectrum (Rmβ) from 1650 to 1800 cm⁻¹ -1 The peak intensity originating from the C=O stretching vibration that appears within this range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0033] Next, in the Raman spectrum (Rmβ) after the test, 1550-1650 cm⁻¹ -1 Determine the peak intensity originating from the benzene ring skeletal vibrations that appear in the range. Refer to Figure 7, and the peak intensity at 1550 cm⁻¹ in the Raman spectrum (Rmβ) -1 Wave number A2, 1650cm -1 This corresponds to wavenumber B2. This is the 1550-1650 cm⁻¹ range in the Raman spectrum (Rmβ). -1 The peak intensity originating from the benzene ring skeletal vibration appearing within the range (wavenumber range A2 to B2) is determined with the baseline (BL) as the reference (0). The baseline (BL) is 1550 cm². -1 The measurement point of the scattering intensity (A1) at wavenumber A2, and 1650 cm -1 It is represented by a straight line connecting the measurement point of the scattering intensity (B1) at wavenumber (B2). That is, in the Raman spectrum (Rmβ) after the test, 1550-1650 cm⁻¹ -1 The peak intensity originating from the benzene ring skeletal vibrations appearing within this range is determined by subtracting the value of Q1 from the value of P1 (P1-Q1).

[0034] And, in the Raman spectrum (Rmβ) after the test, 1650-1800 cm⁻¹ -1The peak intensity (P1-Q1) originating from the C=O stretching vibration appearing in the range is shown in the Raman spectrum (Rmβ) at 1550-1650 cm⁻¹. -1 The peak intensity (β) is determined by converting the peak intensity (P1-Q1) originating from the benzene ring skeletal vibrations appearing in this range to 1.

[0035] As mentioned above, the ratio of peak intensities (β / α) is the ratio of peak intensities derived from C=O stretching vibration before and after the test, that is, it indicates the decomposition durability or charge / discharge durability of the polyester film. Therefore, if the ratio (β / α) exceeds 0.46, it indicates excellent decomposition durability or charge / discharge durability.

[0036] [Layer structure of metal lamination film] The laminated structure of this film may consist of a resin layer formed on only one side of the polyester film, or a structure in which resin layers are formed on both sides of the polyester film. Furthermore, the 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 that constitute this film will be described in detail below.

[0037] <Polyester film (base film)> The polyester film preferably has polyester as its main component resin. The "main component resin" refers to the resin that makes up the largest proportion of the resins constituting the polyester film, 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 constituting the polyester film. Furthermore, the polyester film is preferably a film whose main component is polyester. The term "main component" above refers to the most abundant component among the components (100% by mass) that make up the film, meaning that polyester accounts for 50% by mass or more, particularly 70% by mass or more, among which 80% by mass or more, and even more specifically 90% by mass or more, and may be 100% by mass.

[0038] [polyester] The intrinsic viscosity of the above 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 above intrinsic viscosity refers to the intrinsic viscosity of these mixed polyesters. The intrinsic viscosity can be measured according to conventional methods. For example, 1 g of polyester is accurately weighed, 100 mL of a phenol / tetrachloroethane mixed solvent (50 / 50 mass ratio) is added to dissolve it, and the viscosity can be measured at 30°C using a viscosity measuring device (for example, "VMS-022UPC·F10" manufactured by Rigosha).

[0039] Polyester may be homopolyester or copolymer polyester. Specifically, examples include polyesters obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0040] Examples of the above-mentioned dicarboxylic acid components include naphthalenedicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid; aromatic dicarboxylic acids such as 2,5-frandicarboxylic acid, 2,4-frandicarboxylic acid, 3,4-frandicarboxylic 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.

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

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

[0043] Examples of copolymerized polyesters include copolymerized polyesters that contain a third 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, as copolymerized components.

[0044] In particular, the polyester film preferably contains polyethylene naphthalate (hereinafter also referred to as "PEN") or polyethylene naphthalate copolymer (A) (hereinafter also referred to as "PEN copolymer") as the polyester, and more preferably contains a PEN copolymer, from the viewpoint of significantly demonstrating the effects of the present invention. The content of 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) in the resin constituting the polyester film and / or in the components constituting the polyester film. Furthermore, in the case of a laminated polyester film, it is preferable that the content of PEN or PEN-based copolymer (A) in each layer satisfies the above requirements. A mixture of PEN and PEN-based copolymer is also acceptable.

[0045] The above-mentioned PEN-based copolymer specifically comprises a dicarboxylic acid component (a-1) and a diol component (a-2), more specifically, the dicarboxylic acid component (a-1) comprises a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, and the diol component (a-2) comprises ethylene glycol, with at least one of the dicarboxylic acid component (a-1) and the diol component (a-2) containing a copolymer component.

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

[0047] The above PEN-based copolymer preferably contains 51 mol% or more of ethylene glycol in the diol component (a-2), 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 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 above PEN copolymer preferably contains a copolymer component in the dicarboxylic acid component (a-1) in a quantity of 20 mol% or less, more preferably 10 mol% or less, and even more preferably all of the dicarboxylic acid component (a-1) is a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, i.e., the copolymer component is 0 mol%. Furthermore, the above PEN-based copolymer contains copolymer components in the diol component (a-2) preferably 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. On the other hand, the copolymer components in the diol component (a-2) preferably contain 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] Examples of copolymer components to be added to the above dicarboxylic acid component (a-1) include, when 2,6-naphthalenedicarboxylic acid is the main component, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-frandicarboxylic acid, 2,4-frandicarboxylic acid, 3,4-frandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic 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-frandicarboxylic acid, 2,4-frandicarboxylic acid, and 3,4-frandicarboxylic acid are preferred. These copolymer components can be used individually or in combination of two or more.

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

[0051] For example, the above PEN-based copolymer includes a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1), and a bisphenol-ethylene oxide adduct such as a bisphenol A-ethylene oxide adduct and ethylene glycol as the diol component (a-2). In this PEN-based copolymer, the dicarboxylic acid component (a-1) preferably contains 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 100 mol% of a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid. Furthermore, in this PEN-based copolymer, the diol component (a-2) preferably contains bisphenol-ethylene oxide adducts such as bisphenol A-ethylene oxide adducts in an amount of 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 ethylene glycol preferably in an amount of 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] Normally, when polyester is manufactured (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is produced as a by-product from ethylene glycol. In this specification, this diethylene glycol is referred to as by-product diethylene glycol. The amount of diethylene glycol produced as a by-product from ethylene glycol varies depending on the type of polycondensation, but it is approximately 5 mol% or less of the ethylene glycol. In this invention, diethylene glycol of 5 mol% or less is considered by-product diethylene glycol, and this by-product diethylene glycol is also included in ethylene glycol and distinguished from copolymer components. On the other hand, depending on the content of diethylene glycol, more specifically, if the content of diethylene glycol exceeds 5 mol%, the diethylene glycol is treated as a copolymer component rather than as by-product diethylene glycol.

[0053] [Polymerization catalyst] There are no particular restrictions on the polycondensation catalyst used when polycondensing polyester; 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. In the case of polyester using the above titanium compound as a polymerization catalyst, the titanium element content in the polyester film is preferably in the range of 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm. Furthermore, if the polyester film is multilayered, the titanium content of the entire film should be within the above range, but it is especially desirable that the titanium content of each layer be within the above range. By keeping the titanium compound content below the above upper limit, degradation of the polyester during the melt-extrusion process can be prevented, thus preventing the formation of a film with a strong yellowish tint. Furthermore, setting the content above the lower limit improves polymerization efficiency, lowers costs, and makes it easier to obtain a film with sufficient strength. As described above, when using polyester containing titanium compounds derived from polymerization catalysts, it is preferable to blend a phosphorus compound into the polyester to reduce the activity of the titanium compounds in order to suppress degradation during the melt extrusion process. As the phosphorus compound, alkyl acid phosphates such as orthophosphoric acid and ethyl acid phosphate are preferred, considering the productivity and thermal stability of the polyester. The phosphorus content in the polyester film is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, and even more preferably 5 to 100 ppm. By keeping the phosphorus compound content below the above upper limit, it is possible to prevent the phosphorus compound from causing gelation or foreign matter. Furthermore, by keeping it above the above lower limit, the activity of the titanium compound can be sufficiently reduced, preventing the film from becoming yellowish. Furthermore, if the polyester film is multilayered, it is preferable that the phosphorus content in the layer containing titanium element be within the above range.

[0054] [particle] It is also possible to incorporate particles into polyester film. Typically, the inclusion of particles in polyester film provides slipperiness, prevents damage during each process, and improves handling. The types of particles to be included in the polyester film are not particularly limited as long as they can impart slipperiness. 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, as well as 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 can be used individually or in combination of two or more types. Furthermore, precipitated particles obtained by precipitating and finely dispersing a portion of metal compounds such as catalysts during the polyester manufacturing process can also be used. Among these, silica particles and calcium carbonate particles are particularly preferred because they are effective even in small amounts.

[0055] The shape of the particles used is not particularly limited; spherical, lumpy, rod-shaped, flattened, etc., may be used. Furthermore, there are no particular restrictions on their hardness, specific gravity, color, etc.

[0056] Furthermore, the average particle size is typically 0.01 to 5 μm or less, preferably 0.03 to 4 μm, more preferably 0.05 to 3.5 μm, and even more preferably 0.1 to 3 μm. Within this range of average particle size, both the handling properties and transparency of the polyester film can be achieved. Furthermore, if the particles are in powder form, the average particle size can be determined by using a centrifugal sedimentation particle size distribution analyzer (e.g., Shimadzu Corporation's "SA-CP3" model) to measure the particle size distribution at 50% of the cumulative volume fraction (d50). For particles in films, layers, or resins, the average particle size can be determined by observing 10 or more particles with a scanning electron microscope (SEM), measuring the diameter of each particle, and taking the average value. In the case of non-spherical particles, the average of the longest and shortest diameters can be used as the diameter of each particle.

[0057] When incorporating particles into a polyester film, it is preferable to use a laminate having a surface layer and an intermediate layer, with the particles being incorporated into the surface layer.

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

[0059] The particle content in the polyester film depends on the average particle size, but in the particle-containing layer, it is usually 8000 ppm or less by mass, preferably 5000 ppm or less, and more preferably 3000 ppm or less. Furthermore, 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 later may be provided on a layer of polyester film containing particles, or on a layer substantially free of particles. Furthermore, the side of the polyester film opposite to the side on which the resin layer is provided (the opposite side) may be a layer substantially free of particles, or a layer containing particles. Additionally, by making one or both of the sides on which the resin layer is provided and the opposite side a layer containing particles, winding properties are improved. When providing excellent smoothness to at least one surface of a polyester film, the surface layer on the smooth side may contain particles or may not contain particles substantially. However, when obtaining an extremely smooth film, it is preferable that it not contain particles substantially. Furthermore, "substantially absent" means intentionally absent, and specifically means 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 side and / or on the surface layer on the opposite side of the smooth side, the handling performance when winding the film into a roll can be improved. In particular, from the viewpoint of improving handling performance while maintaining the smoothness of the film, it is preferable to keep at least one side smooth and laminate the resin layer on the opposite side.

[0061] In addition to the particles mentioned above, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc., may be added to the polyester film as needed. Furthermore, the polyester film may contain other resins besides polyester, as long as they do not impair the effects of the present invention. 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, polyamide-imide resins, polyamide-bismaleimide resins, polyetherimide resins, polyetherether ketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine resins.

[0062] [Layer structure of polyester film, etc.] The polyester film may be composed of a single layer, or of two or more layers, and preferably of three or more layers. There is no particular upper limit to the number of layers, but it is preferable to have 10 layers or less. Examples of polyester films composed 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, "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," is preferred. When the polyester film is "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)," it is preferable that the thickness of the second layer (intermediate layer) is greater than the thickness of the first layer (surface layer) and the third layer (surface layer). The ratio of the thicknesses 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 consists of a "first layer (surface layer) / second layer (intermediate layer) / third layer (surface layer)", 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), and 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 the material composition forming the first layer (surface layer) and the third layer (surface layer) is the same. Specifically, it is preferable that the polyester film contains three layers, that there are two types of material compositions forming these layers, and that the material compositions of the first layer (surface layer) and the third layer (surface layer) are the same.

[0064] Furthermore, if the polyester film is a laminate of two or more layers, it is preferable to have a laminate having two layers with different properties. With such a laminate, each layer can be given different characteristics, making it multifunctional. Specifically, although there are no particular limitations, for example, if the polyester film consists of a three-layer laminate of a surface layer, an intermediate layer, and another surface layer in that order, then one or both of the surface layers can be made to contain additives such as the above-mentioned lubricants, such as inorganic particles like silica or organic particles, so that the properties of the surface layer and the intermediate layer are different from each other, making it multifunctional.

[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 also be set appropriately within the above range, for example, 5 μm to 70 μm, 10 μm to 65 μm, 20 μm to 60 μm, etc. The thickness of the polyester film was measured at five unspecified points within the surface using a 1 / 1000 mm dial gauge, and the average of these measurements was used as the thickness.

[0066] When the polyester film is a laminate of two or more layers, the thickness of each layer is not particularly limited, but is, for example, 1 μm or more, preferably 1.5 μm or more, and may also be 2 μm or more, or, for example, 100 μm or less, preferably 80 μm or less, 70 μm or less, etc. Specifically, although there are no particular limitations, for example, in the case of a polyester film composed of three layers, "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) are 1 μm to 5 μm and 1.5 μm to 4 μm respectively, and the second layer (intermediate layer) is 15 μm to 60 μm and 20 μm to 50 μm.

[0067] The polyester film may be an unoriented film (sheet) or an oriented film. Among these, an oriented film stretched in either a uniaxial or biaxial direction is preferred. Of these, a biaxially oriented film is more preferred due to its superior balance of mechanical properties and flatness. A biaxially oriented film refers to a film in which the refractive index in the longitudinal direction (MD) and the width direction (TD) is higher than the refractive index in the thickness direction, and is usually obtained by stretching the film in both the longitudinal and width directions.

[0068] [Method for manufacturing polyester film] The following describes a specific method for manufacturing polyester film, but it is not limited to the method described below. For example, when manufacturing a biaxially oriented film, it is preferable to extrude the dried polyester pellets mentioned above as a molten sheet from a die using a melt extrusion device such as an extruder, and then cool and solidify them with 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, in order to obtain a substantially amorphous, unoriented sheet (unstretched sheet). Furthermore, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the cooling roll, and electrostatic application adhesion and / or liquid coating adhesion methods are preferably employed.

[0069] Next, the obtained unstretched sheet is stretched in two directions. In this case, first, the unstretched sheet is stretched in one direction using a roll or tenter type stretcher. 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 material 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] Next, a heat treatment is performed at a temperature of typically 180-270°C, preferably 190-260°C, under tension or with a relaxation of 30% or less, to obtain a biaxially oriented film. This heat treatment is also called the heat setting process. The heat treatment may be carried out in two or more stages at different temperatures. Furthermore, cooling may be performed in a cooling zone after heat treatment. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester constituting the film, more specifically, it is preferably in the range of 100 to 160°C, and preferably carried out under a relaxation of 1.0 to 2.5% in the width direction. This cooling may be carried out in two or more stages at different temperatures. In the stretching described above, a method can be adopted in which stretching is performed in two or more stages in one direction. In that case, it is preferable to perform the stretching so that the final stretching ratios in both directions fall within the above ranges.

[0072] Furthermore, simultaneous biaxial stretching can also be used in the production of polyester film. Simultaneous biaxial stretching is a method of simultaneously stretching and oriented the above-mentioned unstretched sheet in the machine direction (longitudinal direction) and width direction (transverse direction) while the temperature is controlled, usually at 70 to 120°C, preferably 80 to 110°C. The stretching ratio is preferably 4 to 50 times, more preferably 7 to 35 times, and even more preferably 10 to 25 times in terms of area. Then, heat treatment is carried out at a temperature of typically 170-250°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. For the simultaneous biaxial stretching apparatus employing the above stretching method, conventional known stretching methods such as screw type, pantograph type, and linear drive type can be used.

[0073] <Other> Polyester films can also be manufactured using polyester with a low ester cyclic trimer content as a raw material, in order to suppress the amount of ester cyclic trimer precipitation after heat treatment. Various known methods can be used to manufacture polyester with a low ester cyclic trimer content, such as solid-phase polymerization after polyester production. Furthermore, the polyester film may be constructed with three or more layers, and the outermost layer of the polyester film may be made from a polyester raw material with a low ester cyclic trimer content to suppress the amount of ester cyclic trimer precipitation after heat treatment. Alternatively, the polyester may be obtained by esterification or transesterification, followed by further increasing the reaction temperature and melt polycondensation under reduced pressure.

[0074] <Resin layer> From the viewpoint of further improving the degradation resistance or charge / discharge resistance of the polyester film, which is the base film, it is preferable to form a resin layer made of a resin composition on at least one surface of the polyester film. In this invention, the "resin" constituting the resin layer refers to 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 this invention.

[0075] [Binder resin] Examples of the binder resins mentioned above include (meth)acrylic resins, ionic conductive polymer compounds, polyurethane resins, polyolefin resins, polyvinyl alcohol, and polyester. These may be used individually or in combination of two or more types.

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

[0077] The polymerizable monomers mentioned above are not particularly limited, but include, for example, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and their salts; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutyl hydroxyfumarate, and monobutyl hydroxyitaconate; and methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, etc. Examples include alkyl (meth)acrylic acid esters; nitrogen-containing monomers such as (meth)acrylamide, diacetone acrylamide, or (meth)acrylonitrile; nitrogen-containing monomers containing hydroxyl groups 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 (meth)acrylic resins mentioned above, polymers obtained by polymerizing polymerizable monomers containing acrylic and methacrylic monomers are preferred, and it is more preferable that the polymerizable monomers contain alkyl (meth)acrylic acid esters. Furthermore, it is preferable to dilute the coating solution containing the (meth)acrylic resin with a solvent to make a coating solution, and it is preferable that the solvent is mainly water (50% by mass or more). From this viewpoint, polymers obtained by polymerizing alkyl (meth)acrylic acid esters and polymerizable monomers containing hydroxyl group monomers, carboxyl group-containing monomers, and other hydrophilic group-containing monomers are also preferred. In addition, the (meth)acrylic resin may be an emulsion polymer obtained by polymerizing polymerizable monomers in the presence of a surfactant, for example.

[0079] (Ionic conductive polymer compounds) Ionic conductive polymer compounds are polymer compounds containing ionic conductive functional groups, such as ammonium group-containing compounds, polyether compounds, sulfonic acid compounds, and betaine compounds. Among these, ammonium group-containing compounds are preferred from the viewpoint of maintaining smoothness and forming a coating.

[0080] An ammonium group-containing compound refers to a compound that has an ammonium group in its molecule, and it is preferable that it be 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 the constituent elements shown in the following formula "Chemical Formula 1" as repeating units. These may be homopolymers, copolymers, or copolymers of multiple other components.

[0082] [ka]

[0083] In the above "Chemical Formula 1", R 1 , R 2 Each of these is independently a hydrogen atom, an alkyl group, a phenyl group, etc., and these alkyl groups and phenyl groups may be substituted with the groups listed below. Substitutable groups include, for example, hydroxyl groups, amide groups, ester groups, alkoxy groups, phenoxy groups, naphthoxy groups, thioalkoxy groups, thiophenoxy groups, cycloalkyl groups, trialkylammonium alkyl groups, cyano groups, halogens, etc. Also, R 1 and R 2 The bonds may be chemically bonded, for example, -(CH2) m Examples include -(m=an integer from 2 to 5), -CH(CH3)CH(CH3)-, -CH=CH-CH=CH-, -CH=CH-CH=N-, -CH=CH-N=C-, -CH2OCH2-, -(CH2)2O(CH2)2-, etc.

[0084] X in "Chemical Formula 1" above- Examples include halogen ions, sulfonates, phosphates, nitrates, alkyl sulfonates, carboxylates, and so on.

[0085] Among the polymers described above, that is, polymers containing monomers having an ammonium group and an unsaturated double bond as components, copolymers with other monomers may be used to enhance film-forming properties and obtain a stable coating. Other monomers include, for example, 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. Setting the molecular weight to 1,000 or more prevents a decrease in the strength of the coating film and makes it easier to improve heat resistance stability. Furthermore, setting the molecular weight to 500,000 or less prevents the viscosity of the coating liquid from becoming too high, making it easier to improve handling and coating properties.

[0087] (Polyurethane resin) Polyurethane resin is a polymer compound having urethane bonds within its molecule, and is preferably water-dispersible or water-soluble. To impart water dispersibility or water solubility, it is preferable to introduce hydrophilic groups such as hydroxyl groups, carboxyl groups, sulfonic acid groups, sulfonyl groups, phosphate groups, and ether groups into the polyurethane resin. Among the above hydrophilic groups, carboxyl groups or sulfonic acid groups are preferred from the viewpoint of adhesion to polyester films.

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

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

[0090] Examples of the above 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, isophthalic acid, etc. 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, 1 Examples include ,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, etc.

[0091] Examples of the above-mentioned polycarbonate-based polyols include polycarbonate diols obtained by a de-alcoholization reaction from polyhydric alcohols with dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, etc. Specifically, poly(1,6-hexylene) carbonate, poly(3-methyl-1,5-pentylene) carbonate, etc.

[0092] Polyisocyanate compounds used to obtain polyurethane resins include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having aromatic rings 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 isopropylidene dicyclohexyl diisocyanate.

[0093] When synthesizing polyurethane resins, chain extenders may be used. There are no particular restrictions on the chain extender as long as it has two or more active groups that react with isocyanate groups. Generally, chain extenders having two hydroxyl groups or amino groups can be used.

[0094] Examples of chain extenders having two hydroxyl groups include 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] Furthermore, since a reduction current may be observed in the voltammogram obtained by the linear sweep voltammetry measurement described below for polyurethane resins, care must be taken when selecting a polyurethane resin. When using a polyurethane resin, it is preferable to perform a linear sweep voltammetry measurement and select a polyurethane resin in which a reduction current is unlikely to be observed, or preferably not observed at all, in the resulting voltammogram.

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

[0098] ((Polyethylene resin)) Polyethylene resins are not particularly limited as long as they are resins in which ethylene is the main monomer component, and examples include low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, medium-density polyethylene, and high-density polyethylene. Furthermore, the polyethylene resin may be an ethylene homopolymer, or it may be a copolymer in which ethylene is the main monomer component and other copolymerizable monomer components.

[0099] Examples of the other copolymerizable monomer components (comonomers) mentioned above 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 their ionomers; and unsaturated compounds such as conjugated and unconjugated dienes. The proportion of the other copolymerizable monomer components is not particularly limited, but is usually 30% by mass or less, and more preferably 15% by mass or less.

[0100] Examples of the copolymers mentioned above include copolymers or polypolymers in which ethylene is the main monomer component and one or more comonomers selected from the other copolymerizable monomer components mentioned above, or mixed compositions thereof.

[0101] Among the polyethylene resins mentioned above, low-density polyethylene, linear low-density polyethylene, linear ultra-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, as the linear low-density polyethylene, linear low-density polyethylene is preferred in which at least one α-olefin selected from the group consisting of 1-butene, 1-hexene, and 4-methyl-1-pentene is used 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 described above is not particularly limited and includes known polymerization methods using known olefin polymerization catalysts, such as slurry polymerization, solution polymerization, bulk polymerization, and gas-phase polymerization using multi-site catalysts such as Ziegler-Natta type catalysts or single-site catalysts such as metallocene catalysts, as well as bulk polymerization using radical initiators.

[0104] The melting point of the polyethylene resin described above is preferably 70 to 130°C, and more preferably 80 to 120°C. A melting point within this range is preferable because it provides a good balance between the flexibility, strength, and heat resistance of the film. The melting point is the crystal melting peak temperature (Tm) (°C) obtained from a thermogram measured using a differential scanning calorimetry (DSC) when approximately 10 mg of the resin is heated from -50°C to 200°C at a heating rate of 10°C / min, held at 200°C for 1 minute, cooled down to -50°C at a cooling rate of 10°C / min, and then heated again to 200°C at a heating rate of 10°C / min.

[0105] The melt flow rate (MFR) of the polyethylene resin described above is not particularly limited, but is usually 0.1 g / 10 min or more, preferably 0.5 to 18 g / 10 min, and more preferably 1 to 15 g / 10 min. If the MFR is 0.1 g / 10 min or more, the extrusion processability is stable, and if it is 20 g / 10 min or less, stable film formation is possible during molding, and variations in thickness, reduction in mechanical strength, etc., are reduced, which is preferable. 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 above polyethylene resin is 0.880 to 0.980 g / cm³. 3 Preferably, it is 0.890 to 0.960 g / cm³. 3 It is more preferable that the concentration be 0.900-0.940 g / cm³. 3 It is particularly preferable that the density be 0.880-0.980 g / cm³. 3 Within this range, it is preferable because it offers an excellent balance of strength, adhesiveness, and flexibility. Here, density is a value measured in accordance with JIS K 7112 (1999).

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

[0108] Examples of the above-mentioned other copolymerizable monomer components (comonomers) include ethylene, α-olefins having 2 to 20 carbon atoms such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, as well as 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 above-mentioned polypropylene resin may also be a polypolymer containing two or more of the above-mentioned other copolymerizable monomer components. When the polypropylene resin has monomer components other than propylene and ethylene, 1-butene is preferred as the monomer component.

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

[0110] The melting point of the above-mentioned polypropylene resin is preferably 70 to 170°C, and more preferably 80 to 160°C. A melting point within this range is preferable because it provides a good balance between the flexibility, strength, and heat resistance of the film.

[0111] The melt flow rate (MFR) of the above 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 ensures stable extrusion processability, and an MFR of 20 g / 10 min or less allows for stable film formation during molding, while also reducing thickness variations, decreases in mechanical strength, and other issues, which is preferable.

[0112] (Polyvinyl alcohol) Polyvinyl alcohol refers to a compound having a polyvinyl alcohol moiety. Conventional known polyvinyl alcohols can be used, including modified compounds such as those partially acetalized or butyralized. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or higher, preferably in the range of 300 to 40000. A degree of polymerization of 100 or higher makes it easier to improve the water resistance of the resin layer. Furthermore, the degree of saponification of polyvinyl alcohol is not particularly limited, but polyvinyl acetate saponified with a degree of saponification of 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%, is commonly used in practice.

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

[0114] The number-average molecular weight of polyalkylene glycol is 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 binder resin content 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, relative to the total mass of the resin layer (non-volatile components). Depending on the type of binder resin, the binder resin content may be more than 99% by mass, 99.5% or more by mass, or 100% by mass, relative to the total mass of the resin layer (non-volatile components).

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

[0117] (Melamine compound) Melamine compounds are compounds that have a melamine skeleton in 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-butyrolation, and isobutyrolation. Among these, methylolation is preferred from the viewpoint of reactivity. Suitable alcohols for etherification include methanol, ethanol, isopropanol, n-butanol, and isobutanol, with methanol being more preferred among these. Furthermore, the melamine compound may be a monomer, a polymer of two or more units, or a mixture thereof. In addition, a compound in which urea or the like is co-condensed with a portion of the melamine can be used, and a catalyst can be used to further increase the reactivity of the melamine compound.

[0118] (Oxazoline compounds) Oxazoline compounds are compounds having an oxazoline group in their molecule, and polymers containing an oxazoline group are particularly preferred. These can be obtained by polymerization of 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. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers, for example (meth)acrylic acid esters such as alkyl (meth)acrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and their salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth Examples include unsaturated amides such as acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); 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 individually or in combination of two or more. Furthermore, the oxazoline compound may have polyalkylene oxide chains such as polyethylene oxide chains, and for example, (meth)acrylates having polyalkylene oxide chains may be used as other monomers. 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) Epoxy compounds are compounds that have epoxy groups in their molecules. Examples include condensates of hydroxyl groups or amino groups such as epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, as well as polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. Among these, polyepoxy compounds are preferred from the viewpoint of better adhesion to polyester films.

[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, and trimethylolpropane polyglycidyl ether. 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, and polytetramethylene glycol diglycidyl ether. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether, while examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0121] (Carbodiimide compounds) A carbodiimide compound is a compound having a carbodiimide structure, specifically a compound having one or more carbodiimide structures in its molecule. However, from the viewpoint of better adhesion to polyester films, polycarbodiimide compounds having two or more carbodiimide structures in their molecule are more preferable.

[0122] Carbodiimide compounds can be synthesized using conventionally known techniques, and generally involve the condensation reaction of diisocyanate compounds. The diisocyanate compound is not particularly limited and can be either aromatic or aliphatic. Specifically, 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 amount of carbodiimide groups contained in a carbodiimide compound is typically in the range of 100 to 1000, preferably 250 to 800, and more preferably 300 to 700, in terms of carbodiimide equivalents (weight [g] of the carbodiimide compound required to give 1 mol of carbodiimide groups).

[0124] Furthermore, to the extent that it does not impair the spirit of the present invention, surfactants may be added, or hydrophilic monomers such as polyalkylene oxides, quaternary ammonium salts of dialkylamino alcohols, and hydroxyalkyl sulfonates may be added to improve the water solubility and water dispersibility of the polycarbodiimide compound.

[0125] (Isocyanate compounds) Isocyanate compounds are compounds having an isocyanate derivative structure, such as isocyanates or blocked isocyanates. Examples of isocyanates include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl 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 isopropylidene dicyclohexyl diisocyanate. Furthermore, polymers and derivatives of these isocyanates, such as biuretized, isocyanurateized, uretdioneized, and carbodiimide-modified compounds, are also mentioned. These may be used individually or in combination of two or more.

[0126] When used in the form of blocked isocyanates, examples of blocking agents include: bisulfites; phenolic compounds such as phenol, cresol, and ethylphenol; alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as methyl isobutanoylacetate, 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, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used individually or in combination of two or more.

[0127] Furthermore, isocyanate compounds may be used alone or as mixtures or binders with various polymers. It is preferable to use mixtures or binders with polyester resins or polyurethane resins in order to improve the dispersibility and crosslinking properties of the isocyanate compounds.

[0128] (Silane coupling compounds) Silane coupling compounds are organosilicon compounds that contain both an organic functional group and a hydrolyzable group such as an alkoxy group within a single molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 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)acrylic group-containing compounds such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)- Examples 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 may be used individually or in combination of two or more.

[0129] The amount 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, based on the total mass of the resin layer (non-volatile components).

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

[0131] Examples of anionic surfactants include sulfonic acid types such as alkyl sulfonates, alkylaryl sulfonates, and ester sulfonates; phosphate types such as alkyl phosphate esters or their salts, polyoxyalkylene alkyl ether phosphate esters or their salts; sulfate ester types such as alkyl sulfate salts and alkyl ether sulfate salts; and carboxylate types 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; alkylaryl sulfonates such as butylbenzene sulfonate, hexylbenzene sulfonate, octylbenzene sulfonate, decylbenzene sulfonate, dodecylbenzene sulfonate, tetradecylbenzene sulfonate, hexadecylbenzene sulfonate, octadecylbenzene sulfonate, dibutylnaphthalene sulfonate, and triisopropylnaphthalene sulfonate; and ester sulfonates such as dibutyl sulfosuccinate SL salt, dioctyl sulfosuccinate ester salt, dodecyl sulfoacetate ester salt, and nonylphenoxypolyethylene glycol sulfoacetate ester salt. Among these, alkyl groups with 8 or more carbon atoms are preferred, preferably 10 to 22, and more preferably 12 to 18. Furthermore, metal salts are preferred as the salt, alkali metal salts such as lithium, sodium, and potassium are more preferred, and sodium salts are even more preferred.

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

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

[0135] Examples of nonionic surfactants include ester types in which polyhydric alcohols such as glycerin and sugars are ester-bonded to fatty acids, ether types such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers, ester-ether types in which alkylene oxides are added to fatty acids or polyhydric alcohol fatty acid esters, and amide types such as fatty acid alkanolamides in which hydrophobic and hydrophilic groups are connected by amide bonds. Among these, ester types, ether types, and ester-ether types are preferred when considering 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; and polyoxyethylene mono(di)laurate and polyoxyethylene mono(di)stearate. Examples include polyoxyalkylene fatty acid esters such as polyoxyethylene mono(di)oleate, polyoxypropylene mono(di)laurate, and polyoxypropylene mono(di)stearate; sorbitan fatty acid esters such as sorbitan mono(di)laurate, sorbitan mono(di)palmitate, sorbitan mono(di)stearate, and 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, glycerin fatty acid esters, polyoxyalkylene glycerin fatty acid esters, and polyoxyalkylene fatty acid esters are preferred from the viewpoint of compatibility with polyester, and glycerin fatty acid esters and polyoxyalkylene glycerin fatty acid esters, which are fatty acid esters having a glycerin skeleton, are more preferred. Furthermore, it is desirable that the alkyl group has 8 or more carbon atoms, preferably 10 to 22, and more preferably 12 to 18.

[0138] Examples of ether-type nonionic surfactants include 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, polyoxybutylene oleyl ether, and other polyoxyalkylene alkyl ethers, as well as polyoxyethylene triphenylphenyl ether, polyoxyethylene tripenzylphenyl ether, polyoxyethylene disstyrenephenyl ether, and other polyoxyalkylene phenyl ethers.

[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 quaternary ammonium salt type cationic surfactants include alkylammonium 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, didecyldimethylammonium salt, etc., and alkylbenzylammonium salts such as octyldimethylbenzylammonium salt, decyldimethylbenzylammonium salt, lauryldimethylbenzylammonium salt, tetradecyldimethylbenzylammonium salt, hexadecyldimethylbenzylammonium salt, stearyldimethylbenzylammonium salt, tributylbenzylammonium salt, trihexylbenzylammonium salt, etc.

[0141] Furthermore, 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 counterions for the ammonium group include halogen ions, sulfonates, sulfates, phosphates, nitrates, and carboxylates.

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

[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, lauryl acid amidopropyl betaine, tetradecanoic acid amidopropyl betaine, hexadecanoic acid amidopropyl betaine, and stearic acid amidopropyl betaine.

[0144] The surfactant content 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, relative to the total mass of the resin layer (non-volatile components).

[0145] [particle] 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 polyester, but the average particle size 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 particle content in the resin layer is preferably 0.1 to 20% by mass, more preferably 0.3 to 16% by mass, even more preferably 0.5 to 14% by mass, and particularly preferably 0.7 to 12% by mass, relative to the total mass of the resin layer (non-volatile components).

[0147] [Other ingredients] Furthermore, the resin layer may contain, to the extent that it does not impair the spirit of the present invention, additional additives such as defoaming agents, coating properties improvers, thickeners, organic lubricants, ultraviolet absorbers, antioxidants, foaming agents, dyes, and pigments as appropriate.

[0148] [solvent] The resin composition that forms the resin layer may be diluted with a solvent to form a coating solution. That is, the resin composition may be applied to a polyester film as a liquid coating solution, 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 used as a coating solution, the concentration of the total non-volatile components of the resin composition in the coating solution is preferably 0.1 to 50% by mass. If it is 0.1% by mass or more, a resin layer of the desired thickness can be efficiently formed. On the other hand, if it is 50% by mass or less, the viscosity during coating can be suppressed, thereby improving the appearance of the resin layer and increasing its stability in the coating solution.

[0149] There are no particular restrictions on the solvent used, and either water or an organic solvent can be used. From the viewpoint of environmental protection, it is preferable to use water as the main solvent (50% by mass or more of the total solvent) to make an aqueous coating solution. The water content is preferably 60% by mass or more, more preferably 70% by mass or more. The aqueous coating solution may contain a small amount of organic solvent. The specific amount of organic solvent should be less than or equal to the amount of water by mass, but for example, it should be 50% by mass or less, preferably 40% by mass or less, and 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 individually or in combination. By appropriately selecting and including these organic solvents in the aqueous coating solution as needed, the stability and coating properties of the coating solution can be improved.

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

[0151] Furthermore, it can be inferred that the resin layer contains unreacted components of the resin composition, reacted compounds, or mixtures thereof. Analysis of each component in the resin layer can be performed, for example, by TOF-SIMS, ESCA, or X-ray fluorescence.

[0152] When resin layers are provided on both sides of the 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. "Substantially the same" means that the content of each non-volatile component constituting each resin composition is within ±5% by mass, and if different components are included, the total mass of the content 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 ±3% by mass, and even more preferable that it is within ±1% by mass. If different components are included, it is more preferable that the total mass of the content 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 a resin layer] The method for forming the resin layer is not particularly limited, and conventionally known methods can be used as appropriate. However, it is preferable to coat the aforementioned resin composition onto a polyester film and, if necessary, perform treatments such as drying, curing, and heat treatment to form the resin layer. The coating method is not particularly limited, and conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating can be used.

[0154] The above-mentioned forming methods include in-line coating performed within the polyester film manufacturing process, or off-line coating performed outside the system on a polyester film that has already been manufactured, but in-line coating is preferred.

[0155] In-line coating is a method of coating a polyester or resin composition that forms a polyester film at any stage from melt extrusion and stretching to heat-setting and winding. Typically, coating is performed on an unstretched sheet obtained by melting and rapid cooling, a stretched uniaxially oriented film, a biaxially oriented film before heat-setting, or a film after heat-setting but before winding, but it is preferable to coat the stretched uniaxially oriented film.

[0156] For example, in sequential biaxial stretching, a method is preferred in which a uniaxially stretched film is coated after being stretched in the longitudinal direction (MD), and then stretched in the transverse direction (TD). This method offers cost advantages in manufacturing because film formation and resin layer formation can be carried out simultaneously.

[0157] The thickness of the resin layer formed as described above (after drying) is preferably 2 μm or less, and 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. Furthermore, 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 above coating is not limited to the following, but is between 0.001 and 1 g / m². 2 Preferably, and more preferably, 0.005 to 0.7 g / m 2 Even more preferably 0.01~0.5g / m 2 The application amount is based on the non-volatile components, excluding volatile components such as solvents.

[0159] The amount of non-volatile component applied refers to the amount applied to this film, and for example, if drying and stretching are performed, it refers to the amount applied after drying and stretching. Furthermore, the amount of non-volatile component applied can be said to be an indicator of the thickness of the resin layer, expressed as mass per unit area.

[0160] [Preferred embodiment of the resin layer] In order to further improve the degradation durability or charge / discharge durability of the polyester film base film, it is preferable to form a reduction-resistant resin layer formed by a resin composition on at least one surface of the polyester film. That is, it is preferable to form a reduction-resistant resin layer formed by a resin composition containing a reduction-resistant resin on at least one surface of the polyester film. In other words, it is preferable that the resin layer is a reduction-resistant resin layer.

[0161] The resin forming the resin layer in this film is the operating potential of the battery, for example, 0~4V (Li / Li + It is preferable to have a wide potential window in which oxidation or reduction does not occur within the range of ). Specifically, the lower the level of the highest occupied orbital (HOMO), the better the oxidation resistance, and the higher the level of the lowest unoccupied orbital (LUMO), the better the reduction resistance; therefore, a resin having a structure that satisfies these conditions is preferable. By providing such a resin layer on a polyester film, it becomes easier to prevent contact between the polyester film and the metal layer, and in batteries using polyester film as current collector foil, oxidation-reduction decomposition of the polyester film can be effectively suppressed.

[0162] In this film, it is preferable that the resin forming the resin layer does not show a reduction current in the voltammogram obtained by linear sweep voltammetry, from the viewpoint of effectively suppressing the reductive decomposition of the polyester film. Specifically, it is preferable that the following requirements are met. (Requirements) When comparing the voltammogram (Vb) obtained by linear sweep voltammetry measurement under the following conditions (measurement with only the electrolyte below (blank)) with the voltammogram (Vp) obtained by linear sweep voltammetry measurement under the same conditions as below, except that the resin contained in the resin layer or the monomer components constituting the resin is dissolved in the electrolyte below at a concentration of 0.5 mmol / L or more, 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: 1mV / sec. Sweep range: Natural potential (approx. 3.2V) → 0V (Li / Li + ).

[0163] By using a resin that satisfies the above requirements (or, if the resin does not dissolve in the electrolyte, the monomer components constituting the resin) as the resin forming the resin layer in this film, and confirming that it is resistant to decomposition, for example, it is possible to prevent elution into the electrolyte and effectively suppress oxidation-reduction decomposition.

[0164] From this viewpoint, suitable 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, and from the viewpoint of film-forming properties and adhesion to the metal layer. Furthermore, although not limited to the following, it is also preferable 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 preferable to use a compound having a glycidyl ether group in combination with a (meth)acrylic resin (particularly an acrylic resin).

[0165] The content of at least one selected from the group consisting of the above-mentioned polyolefin resin, (meth)acrylic resin, polyalkylene glycol, and compounds 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, even more preferably 85% by mass or more, even more preferably 90% by mass or more, particularly preferably 95-100% by mass, and may also be 96-99.5% by mass, based on the same viewpoint as above.

[0166] (Compounds containing a glycidyl ether group) The compounds having glycidyl ether groups are preferably compounds containing at least two glycidyl ether groups in the molecule, more preferably compounds containing three or more glycidyl ether groups, and even more preferably compounds containing four to five glycidyl ether groups. Furthermore, the compounds having glycidyl ether groups may also have hydroxyl groups 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 compounds having a glycidyl ether group is preferably 200 to 2000, and more preferably 550 to 1800. Note that the mass-average molecular weight (Mw) refers to the mass-average molecular weight with polystyrene as the standard, measured by gel permeation chromatography (GPC).

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

[0169] Specific examples of compounds having a glycidyl ether group include glycidyl ether-based polyepoxides derived from aliphatic polyols. More specifically, examples include 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, polyglycerol polyglycidyl ether, and the like. Among these, glycerol polyglycidyl ether and polyglycerol polyglycidyl ether are preferred, and polyglycerol polyglycidyl ether is particularly preferred.

[0170] Furthermore, the resin forming the resin layer in this film may include reaction products of at least two compounds, including a compound having a glycidyl ether group. Reaction products derived from the compound having a glycidyl ether group include condensation reaction products between different molecules due to heat, etc., between an amino group, hydroxyl group, carboxylic acid group, or functional group such as a hydroxyl group, carboxylic acid group, or carboxylic acid base introduced for water dispersibility improvement in other components (other compounds) in the resin composition constituting the resin layer and the glycidyl ether group of the compound having a glycidyl ether group. Reaction products between compounds having glycidyl ether groups may also be included.

[0171] As the resin for forming the resin layer in this film, it may contain a reaction product of at least two compounds including polyglycerol polyglycidyl ether. Examples of the reaction product generated from polyglycerol polyglycidyl ether include condensation reaction products between different molecules by heat or the like between functional groups such as amino groups, hydroxyl groups, carboxylic acid groups in other components (other compounds) in the resin composition constituting the resin layer, or hydroxyl groups, carboxylic acid groups, carboxylate groups, etc. introduced for improving water dispersibility, and the glycidyl ether group of polyglycerol polyglycidyl ether. Further, it may 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 contained in the resin layer, a polyolefin resin, a (meth)acrylic resin, and a polyalkylene glycol is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95 to 100% by mass, and may also be 96 to 99.5% by mass, based on the total mass of the resin layer (non-volatile components).

[0173] (Surfactant) The resin layer preferably further contains a surfactant together with one or more selected from the group consisting of a polyolefin resin, a (meth)acrylic resin, a compound having a glycidyl ether group, and a polyalkylene glycol. By containing a surfactant in the resin layer, it is possible to improve the coating property on the polyester film and prevent coating peeling.

[0174] Examples of such surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc. Among these, nonionic surfactants are preferred from the viewpoint of the stability of the coating solution after preparation, etc. Among nonionic surfactants, ether-type nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers, and ester-ether-type nonionic surfactants obtained by adding alkylene oxide to fatty acids or polyhydric alcohol fatty acid esters are preferred, and more preferably, ester-ether-type nonionic surfactants obtained by adding ethylene oxide to polyoxyethylene alkyl ethers and polyhydric alcohol fatty acid esters. Among such ester-ether-type nonionic surfactants, ester-ether-type nonionic surfactants obtained by adding ethylene oxide to acetylene glycol (average number of EO added moles: 4 to 10) are preferred.

[0175] The HLB value of the nonionic surfactant is preferably 16 or less, more preferably 15 or less, and even more preferably 14 or less, from the viewpoint of improving coating properties. There is no particular lower limit to the HLB value, but it is usually 2, and may also be 4. The HLB value is a balance between hydrophilicity and hydrophobicity used in the field of surfactants, and is defined by commonly used calculation formulas, such as the Griffin, Davis, Kawakami formula, and organic conceptual diagrams. Alternatively, the HLB values ​​listed in catalogs, etc., may be used.

[0176] When the resin composition forming the resin layer contains a surfactant, its content 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 solution can be applied stably. On the other hand, by setting the surfactant content to 10% by mass or less, uneven coating can be suppressed.

[0177] <<Physical properties of this film>> This film may preferably possess the following physical properties, for example. However, the description of the following physical properties does 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) and the other surface (Side B) of the film, is preferably 0.26 to 0.75, more preferably 0.28 to 0.72, even 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 falls outside the above range, there is a tendency for the film's runability or transportability to become insufficient, for example.

[0179] The static friction coefficient μs is measured by the following method. A 15 x 160 mm test specimen was cut from the film before copper deposition, and the static friction coefficient between one side of the specimen and the other side was measured. Specifically, the two sides of the specimen were held in contact for 15 seconds before the start of the test, and then measurements were taken in the longitudinal direction (MD) under the following conditions. The sample was conditioned for at least 6 hours before measurement. • Equipment: Yokohama Systems Research Institute Co., Ltd. parallel-movement type friction testing machine (MCS-300) • Slide piece: Total mass 104g (contact area is a square with sides of 12mm) • Test speed: 20 mm / min ·Temperature: 23℃±2℃ • Relative humidity: 50% ± 10%

[0180] [Ratio of arithmetic mean heights Sa (SaB / SaA)] The ratio of the arithmetic mean heights Sa of this film (SaB / SaA, which is the ratio of the arithmetic mean height SaA of one surface A to the arithmetic mean height SaB of the other surface B) is preferably 1 or more and less than 1.2, and more preferably 1 or more and 1.19 or less. If the ratio of the arithmetic mean heights Sa exceeds the above upper limit, for example, the thermal energy applied to both sides of the film tends to become unbalanced, making it difficult to effectively suppress the occurrence of curl in the film after deposition. The ratio of the arithmetic mean height Sa can be set appropriately within the above range and is not limited to the following, but may be, for example, 1.18 or less, 1.16 or less, 1.14 or less, etc. Note that the ratio of arithmetic mean heights Sa (SaB / SaA) is based on the condition that SaB ≥ SaA. For example, if the arithmetic mean heights Sa of each face are different, the ratio is calculated using the relatively larger value as the numerator.

[0181] The arithmetic mean height Sa of this film (the arithmetic mean height SaA of any surface A and / or the arithmetic mean height SaB of any surface 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 improving the homogeneity of each metal layer formed on both sides of the film. On the other hand, the lower limit of the arithmetic mean height Sa is not particularly limited, but for example, it is 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 set appropriately within the above range and is not limited to the following, but 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 surface A and the arithmetic mean height SaB of any other surface B are both within the above range.

[0182] The arithmetic mean height Sa mentioned above is one of the surface roughness parameters (ISO 25178), and is an extension of the two-dimensional Ra to three dimensions. It is calculated by dividing the volume of the area enclosed by the surface shape curve and the mean plane by the measured area. Specifically, when the surface is the XY plane and the height direction is the Z axis, if A is the defined area (the entire image) and Z(x,y) is the height of the image point (x,y) from the plane with height 0, then it is expressed as shown in the following equation [Equation 1].

[0183]

number

[0184] [Ratio of arithmetic mean roughness Ra (RaB / RaA)] In this film, the ratio of arithmetic mean roughness Ra (RaB / RaA, which is the ratio of the arithmetic mean roughness RaA of one surface A to the arithmetic mean roughness RaB of the other surface B) is preferably, for example, 1 or more and 1.25 or less, and 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, the thermal energy applied to both sides of the film tends to become unbalanced, and it tends to be difficult to effectively suppress the occurrence of curl in the film after deposition. The ratio of the arithmetic mean roughness Ra can be set appropriately within the above range and is not limited to the following, but may be, for example, 1.16 or less, 1.14 or less, 1.12 or less, etc. Note that the ratio of arithmetic mean roughness Ra (RaB / RaA) is calculated under the condition that RaB ≥ RaA. For example, if the arithmetic mean roughness Ra values ​​of each surface are different, the ratio is calculated using the relatively larger value as the numerator.

[0185] The arithmetic mean roughness Ra of this film (the arithmetic mean roughness RaA of any surface A and / or the arithmetic mean roughness RaB of any surface 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 homogeneity of each metal layer formed on both sides of the film. The lower limit of the arithmetic mean roughness Ra is not particularly limited, but for example, it could be 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 surface A and the arithmetic mean roughness RaB of any other surface B are both within the above range. 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 average surface. Specifically, when a portion of reference length L is extracted, and the roughness curve is represented as y=Z(x) with the average line of this extracted portion as the x-axis and the direction of the vertical scaling as the y-axis, it can be calculated from the following formula [Equation 2].

[0186] [Number]

[0187] [Ratio (RzB / RzA) of the ten-point average roughness Rz] In this film, from the perspective of highly achieving both the above-mentioned productivity and homogeneity, the ratio of the ten-point average roughness Rz (RzB / RzA, which is the ratio of the ten-point average roughness RzA of any A surface on one side and the ten-point average roughness RzB of any B surface on the other side) 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. When the ratio of the ten-point average roughness Rz exceeds the above upper limit value, for example, there is a tendency for the thermal energy added to both sides of the film to become unbalanced, and there is a tendency that it is difficult to effectively suppress the occurrence of curl in the film after vapor deposition. The ratio of the ten-point average roughness Rz (RzB / RzA) is based on the condition that RzB ≥ RzA. For example, when the values of the ten-point average roughness Rz of each surface are different, the ratio is obtained by using the larger value as the numerator.

[0188] The ten-point average roughness Rz of this film (the ten-point average roughness RzA of any A surface on one side and / or the ten-point average roughness RzB of any B surface on the other side) 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 perspective of further enhancing the homogeneity of each metal layer formed on both sides of the film. Also, the lower limit value of the ten-point average roughness Rz is not particularly limited, but for example, it is 0.004 μm or more, 0.005 μm or more, 0.006 μm or more, etc. It is particularly preferable that the ten-point average roughness Rz is such that the ten-point average roughness RzA of any A surface on one side and the ten-point average roughness RzB of any B surface on the other side are both within the above range. Incidentally, the ten-point average roughness Rz is one of the line roughness parameters (JIS B 0601 (1994)), and it is obtained by measuring in the vertical direction so as to cross the direction in which the concave portions in the line direction are continuous.

[0189] [Ratio of maximum cross-sectional height Rt (RtB / RtA)] In this film, from the viewpoint of achieving a high degree of both productivity and homogeneity, the ratio of the maximum cross-sectional heights Rt (RtB / RtA, which is the ratio of the maximum cross-sectional height RtA of any surface A to the maximum cross-sectional height RtB of any surface 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 the maximum cross-sectional heights Rt (RtB / RtA) is based on the condition that RtB ≥ RtA. For example, if the maximum cross-sectional heights Rt of each face are different, the ratio is calculated using the relatively larger value as the numerator.

[0190] The maximum cross-sectional height Rt of this film (the maximum cross-sectional height RtA of any surface A and / or the maximum cross-sectional height RtB of any surface 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 improving the homogeneity of each metal layer formed on both sides of the film. The lower limit of the maximum cross-sectional height Rt is not particularly limited, but for example, it could be 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 surface A and the maximum cross-sectional height RtB of any other surface B are both within the above range. 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] [Ratio of root mean square heights Sq (SqB / SqA)] The ratio of the root mean square heights Sq of this film (SqB / SqA, which is the ratio of the root mean square height SqA of any surface A to the root mean square height SqB of any other surface B) is preferably 1 or more and 1.9 or less, and more preferably 1 or more and 1.8 or less, and even more preferably 1 or more and 1.7 or less, from the viewpoint of achieving a high degree of both productivity and homogeneity as described above. The ratio of the root mean square height Sq can be set appropriately within the above range and is not limited to the following, but for example, it may be 1.5 or less, 1.4 or less, etc. Note that the ratio of the root mean square heights Sq (SqB / SqA) is conditional on SqB ≥ SqA. For example, if the root mean square heights Sq of each face are different, the ratio is calculated using the relatively larger value as the numerator.

[0192] The root mean square height Sq of this film (the root mean square height SqA of any surface A, which is one surface, and / or the root mean square height SqB of any surface B, which is the other surface) 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 homogeneity of each metal layer formed on both sides of the film. On the other hand, the lower limit of the root mean square height Sq is not particularly limited, but for example, it is 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 set appropriately within the above range and is not limited to the following, but 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 Sq of one surface, which is any surface A, and the root mean square height SqB of the other surface, which is any surface B, are both within the above range. The root mean square height Sq is one of the surface roughness parameters (ISO 25178), and is an extension of the two-dimensional Rq to three dimensions. That is, it is the root mean square value of the height data in a defined area, and is a parameter that corresponds to the standard deviation of the distance from the mean surface, and can be calculated from the formula [Equation 3] below.

[0193]

number

[0194] [Ratio of maximum cross-sectional height St (StB / StA)] The ratio of the maximum cross-sectional heights St of this film (StB / StA, which is the ratio of the maximum cross-sectional height StA of any surface A to the maximum cross-sectional height StB of any surface B) is preferably 1 or more and 2.6 or less, and more preferably 1 or more and 2.4 or less, and even more preferably 1 or more and 2.2 or less, from the viewpoint of achieving a high degree of both productivity and homogeneity as described above. The ratio of the maximum cross-sectional height St can be set appropriately within the above range and is not limited to the following, but may be, for example, 2 or less, 1.8 or less, etc. The lower limit of the ratio of the maximum cross-sectional height St may be 1.05 or 1.1. Note that the ratio of the maximum cross-sectional heights St (StB / StA) is based on the condition that StB ≥ StA. For example, if the maximum cross-sectional heights St of each face are different, the ratio is calculated using the relatively larger value as the numerator.

[0195] The maximum cross-sectional height St of this film (the maximum cross-sectional height StA of any surface A, which is one surface, and / or the maximum cross-sectional height StB of any surface B, which is the other surface) 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 improving the homogeneity of each metal layer formed on both sides of the film. On the other hand, the lower limit of the maximum cross-sectional height St is not particularly limited, but for example, it is 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 set appropriately within the above range and is not limited to the following, but 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 surface A and the maximum cross-sectional height StB of any other surface B are both within the above range. The maximum cross-sectional height St is one of the surface roughness parameters (ISO 25178), and is an extension of the two-dimensional Rt to three dimensions. It is the sum (sum of absolute values) of the maximum peak height and the maximum valley depth in the defined region.

[0196] Furthermore, it is preferable that the surface characteristics of the front and back surfaces, which constitute the outermost layer of this film, fall within the above range.

[0197] The arithmetic mean height Sa, maximum cross-sectional height St, and root mean square height Sq are measured specifically as follows: For films before metal deposition such as copper, measurements were performed using a non-contact surface and layer cross-sectional shape measurement system (VertScan® R550GML) manufactured by Ryoka Systems Co., Ltd., under the conditions of eyepiece magnification of 1.0x, objective lens magnification of 50x, and measurement area of ​​178 μm vertical × 238 μm horizontal. After applying quartic polynomial surface correction and median filtering (3 × 3), 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 value was used.

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

[0199] There are no particular limitations on the method for adjusting the aforementioned surface properties Sa, Ra, Rz, Rt, St, Sq and static friction coefficient μs of the film to the above range. For example, various methods can be used, such as transfer treatments like embossing roll transfer, embossing belt transfer, and embossing film transfer, sandblasting, shot blasting, etching, engraving, and surface crystallization. A method of roughening the surface by casting a film-like molten resin onto a cast roll is preferred because it is easy to continuously and uniformly form 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 cast roll. It is also possible to adjust the surface properties by appropriately adjusting the particle size, shape, and content of particles in the film, or by adding an appropriate amount of crystal nucleating agent. Furthermore, it is also possible to adjust the film manufacturing conditions such as the stretching temperature, stretching ratio, uniformity of stretching in the width direction, relaxation rate, and cooling temperature. Electrical surface treatments such as corona discharge treatment and atmospheric pressure glow discharge treatment can also be used. Furthermore, if functional layers such as resin layers or release layers are to be provided separately by coating, this can also be achieved by appropriately adjusting the formulation of the coating solution, the coating thickness, the coating conditions, the dispersion state of the particles incorporated in the coating solution, and the timing of the coating (in-line or offline, etc.).

[0200] [Absolute value of the difference in surface free energy] The absolute value of the difference in surface free energy of this film (the surface free energy γ of any surface A, which is one of the surfaces) SV Surface free energy γ of A and the other surface, which is any surface B. SVThe absolute value of the difference in B is preferably 7 mN / m or less, and from the viewpoint of achieving a high degree of both productivity and homogeneity as described above, it is more preferably 5.5 mN / m or less, even more preferably 5 mN / m or less, even more preferably 3 mN / m or less, particularly preferably 2 mN / m or less, especially preferably 1.5 mN / m or less, most 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 energies (γ SV B / γ SV A) The ratio of the surface free energies of this film (the surface free energy γ of any surface A, which is one of the surfaces) SV Surface free energy γ of A and the other surface, which is any surface B. SV The ratio of B is γ SV B / γ SV A) is preferably 1 to 2, and more preferably 1 to 1.5, and even more preferably 1 to 1.2, from the viewpoint of achieving a high degree of both productivity and homogeneity as described above. Furthermore, a value of 1.15 or less is preferred, more preferably 1 to 1.15, particularly preferably 1 to 1.1, especially preferably 1 to 1.06, and most preferably 1 to 1.03. Note that the ratio of surface free energies (γ SV B / γ SV A) is γ SV B Enγ SV This is conditional on A, for example, the surface free energy γ of each surface. SV If the values ​​are different, the ratio is calculated by using the relatively larger value as the numerator.

[0202] Surface free energy γ of this film SV (Surface free energy γ of any surface A, which is one of the surfaces) SV Surface free energy γ of A and the other surface, which is any surface B. SVB) is preferably, for example, 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, from the viewpoint of further enhancing the homogeneity and adhesion of each metal layer formed on both sides of the film. On the other hand, the surface free energy γ SV Although there is no particular limitation on the lower limit value, for example, it 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. The surface free energy γ SV is the surface free energy γ SV A of any A surface which is one surface and the surface free energy γ SV B of any B surface which is the other surface are both particularly preferably within the above range.

[0203] The surface free energy is composed of the sum of the components of intermolecular forces. The above intermolecular forces are classified into dispersion force, orientation force, induction force, and hydrogen bonding force, and the surface free energy is constituted by the dispersion component (Dispersion), polar component (Polar), induction component (Induction), and hydrogen bonding component (Hydrogen), respectively. Among these components, the induction component is very weak and can be ignored, and the hydrogen bonding component can be grouped into the polar component.

[0204] In the present invention, the respective components (dispersion component γ SV and polar component γ SV d ) of the surface free energy γ SV p are values obtained by the following measurement method and calculation method. First, the contact angle (θ1) between a first liquid for which the following γ LV1 , γ LV1 d and γ LV1 p are known and the surface of the measurement object, the following γ LV2 , γ LV2 d and γ LV2p The contact angle (θ2) between the second liquid, whose properties are known, and the surface of the object being measured is measured. Next, substitute these values ​​into equations (I-1) and (I-2) below, and from the simultaneous equations (I-1) and (I-2) below, the surface free energy γ of the resin layer surface to be measured can be obtained. SV Dispersion component γ SV d and polar component γ SV p Calculate the following. Note that all units are in 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] γ SV d : Surface free energy γ of the surface of the object being measured SV Dispersed components γ SV p : Surface free energy γ of the surface of the object being measured SV polar components 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] Furthermore, equations (I-1) and (I-2) above are derived from the theoretical formulas of Owens-Wendt-Rable-Kaelble (OWRK) and Young's formula, respectively. OWRK's 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 (However, in the formula, γ SL This is the tension at the interface between the surface of the object being measured and the liquid.

[0208] There are no particular limitations on the method for adjusting the surface free energy of the aforementioned film surface to the above range, but it can be adjusted, for example, by the composition of the film surface. In particular, it is effective to adjust it by the composition of each resin composition forming the resin layer of the film, or by the thickness of the resin layer. Furthermore, by making the composition of the surface and resin layer of one surface, side A, similar to that of the other surface, side B, specifically by making the resin composition the same or substantially the same, it becomes easier to adjust the absolute value or ratio of the difference in surface free energy to the above range. In adjusting the resin layer composition, for example, by incorporating a hydrophilic group-containing compound in addition to the 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 in a hydrophilic group-containing compound is a functional group that forms weak bonds with water molecules, such as hydrogen bonds, and examples include hydroxyl groups, carboxyl groups, amide groups, and thiol groups. Examples of hydrophilic group-containing compounds include compounds containing (meth)acryloyl groups, polyvinyl alcohol, glycerin, polyglycerin, alkylene oxide adducts of glycerin or polyglycerin, and polyalkylene oxides. Among these, polyvinyl alcohol and compounds containing (meth)acryloyl groups 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 constituent units having hydrophilic groups.

[0209] The surface free energy is measured specifically as follows: For measuring the contact angle, a contact angle meter (DMo-501 model) manufactured by Kyowa Interface Science Co., Ltd. was used. The contact angle was measured when 1 μL of pure water and methylene iodide were dropped onto a film before copper deposition, which had been conditioned for more than 24 hours at 23°C and 50% RH. The contact angle was taken 60 seconds after dropping each liquid onto the film. Using the obtained contact angles and the surface tension component values ​​of each liquid (Table 1), the surface free energy of the film surface was calculated using the Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula.

[0210] [Crystal melting temperature (Tm)] The crystal melting temperature (Tm) of this film, as determined by differential scanning calorimetry (DSC), is preferably 258°C or lower. When the crystal melting temperature (Tm) is 258°C or lower, for example, the starting temperature for molten insulation during a short circuit is lower, so the cessation and prevention of runaway reactions due to short circuits is initiated quickly. From this viewpoint, the crystal 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 moldability and strength retention during high-temperature processing, the crystal melting temperature (Tm) is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher.

[0211] There are no particular restrictions on the method for adjusting the crystal melting temperature (Tm) to the above range, but it can be adjusted, for example, by the type and content of polyester that makes up the film.

[0212] The crystal melting temperature Tm is measured specifically as follows: The crystal melting temperature (Tm) was measured using a PerkinElmer differential scanning calorimetry system (DSC 8500) in accordance with JIS K 7121 (2012) when the temperature was increased from 20°C to 300°C at a rate of 10°C per minute. The extreme value of the maximum endothermic peak was defined as the crystal melting temperature Tm. The analysis was performed by selecting the corresponding maximum endothermic peak range from the "Peak Area" option in the "Analysis" menu of the built-in software.

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

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

[0215] There are no particular restrictions on the method for adjusting the above shrinkage rates (120°C, 5 minutes), shrinkage rates (150°C, 5 minutes), and shrinkage rates (180°C, 5 minutes) to within the above ranges. For example, they can be adjusted by the type and amount of polyester constituting the film, the particle size and amount if particles are included, the film-forming conditions of the film, etc.

[0216] The contraction rate is measured specifically as follows: A 1.5cm x 15cm test film was subjected to heat treatment for 5 minutes in a hot air oven maintained at a predetermined temperature (120°C, 150°C, 180°C) in a tension-free state. The length of the test film was measured before and after the treatment, and the length was calculated using the following formula. Measurements were taken in both the longitudinal (MD) and width (TD) directions of the film. Shrinkage rate (%) = {(Sample length before heat treatment) - (Sample length after heat treatment)} ÷ (Sample length before heat treatment) × 100

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

[0218] <Metal layer> The metal forming the metal layer is not particularly limited, but examples include conductive metals such as aluminum, nickel, gold, silver, copper, cadmium, titanium, and alloys containing two or more of these. In particular, from the viewpoint of being commonly used as electrode current collectors (positive electrode current collectors) used in the positive electrode and electrode current collectors (negative electrode current collectors) used in the negative electrode of lithium-ion batteries, the above metal layer is preferably made of copper or aluminum. Here, "made of" means that it contains copper or aluminum as the main component. The above metal layer may also contain elements other than conductive metals.

[0219] The metal layer is preferably provided by vapor deposition, plating, or sputtering, and more specifically, conventionally known methods such as vacuum deposition, electrolytic plating, electroless plating, and sputtering can be used. In other words, the metal layer is preferably a metal vapor-deposited layer, a metal plated layer, or a metal sputtered layer.

[0220] The thickness of the metal layer is typically 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] Furthermore, the metal layer is preferably a two-layer structure. One example of such a configuration is a two-layer structure in which the metal layer consists of a metal layer provided on the film by vapor deposition or sputtering, and a metal layer provided on the metal layer by plating. In this case, the film foil will have a metal layer provided on both sides of the polyester film in the order of vapor deposition or sputtering and a metal layer provided by plating. By adopting such a two-layer structure, it is possible to make the film thinner and lighter than conventional metal foils while maintaining conventional performance, and to reduce costs compared to conventional metal foils.

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

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

[0224] <<Application>> Because this film and film foil exhibit excellent electrochemical stability, they are preferably applied to electrode substrates such as current collectors and tab leads in batteries, and especially to electrodes coated with active materials that undergo oxidation and reduction at low potentials. Furthermore, because this film also possesses metal adhesion properties, it can be suitably used in battery casing materials, metal wiring substrates, RF tags, and the like.

[0225] Among these, it is preferable to use it for battery current collectors. Examples of batteries include rechargeable batteries, secondary batteries, lithium-ion batteries, and sodium-ion batteries, and it is preferably used for lithium-ion batteries, and particularly preferably for lithium-ion secondary batteries. Accordingly, it is preferable that the current collector has a configuration exemplified by "electrode layer (positive electrode) / metal layer / resin layer / base layer (polyester film) / resin layer / metal layer / electrode layer (positive electrode)" for the positive electrode current collector, and "electrode layer (negative electrode) / metal layer / resin layer / base layer (polyester film) / resin layer / metal layer / electrode layer (negative electrode)" for the negative electrode current collector.

[0226] Furthermore, compared to electrodes with configurations such as "electrode layer (positive electrode) / metal layer / electrode layer (positive electrode) or electrode layer (negative electrode) / metal layer / electrode layer (negative electrode)", using this film contributes to thinning, weight reduction, and cost reduction, and also enables the stopping and prevention of runaway reactions due to short circuits.

[0227] <<Use of film foil for battery current collectors or laminated film for the manufacture of battery current collectors>> One embodiment of the present invention includes the use of the following laminated film for manufacturing a battery current collector film foil 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 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 testing refers to 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 laminated film, within a thickness range of 1 μm from one of the surfaces, with a peak intensity of 1650-1800 cm². -1 This peak intensity originates from the C=O stretching vibration and appears in the range of 1550-1650 cm².-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 after testing (β)] 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 1 μm thickness range from one of the surfaces described above after the test. -1 This peak intensity originates from the C=O stretching vibration and appears in the range of 1550-1650 cm². -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 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). The current density for the above test coin cell is 0.09 mA / cm². 2 The current was then applied 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.

[0228] Furthermore, the details of the composition or structure of the above-mentioned laminated film are the same as those of the present-mentioned film.

[0229] <<Explanation of terms>> In this specification, unless otherwise specified, "main component" means a component that has a significant effect on the properties of the material, and the content of this component is usually 50% by mass or more of the total 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 90-100% by mass. In this specification, the term "film" includes "sheets," and the term "sheet" includes "film." In this specification, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Furthermore, with respect to the numerical ranges described in stages in this specification, the upper or lower limit of one stage of the numerical range can be arbitrarily combined with the upper or lower limit of another stage of the numerical range. Furthermore, "X and / or Y (where X and Y are any combination)" means at least one of X and Y, and can mean X only, Y only, or X and Y. [Examples]

[0230] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following embodiments, unless it exceeds the scope of its essence.

[0231] <Evaluation Method> (1) Preparation of test film A test film with a layer structure of "copper layer / resin layer / base layer (polyester film)" was prepared by applying a 30 nm thick copper layer (copper purity 99.9%) to the surface side of the resin layer of a polyester film (114 mm x 114 mm) having a resin layer, using a vacuum deposition apparatus (EBX-10D, ULVAC, Inc.). A comparative test film with a layer structure of "copper layer / base layer (polyester film)" was prepared using the same method (Comparative Example 1). The vacuum deposition conditions are: deposition vacuum degree 4.0 × 10⁻⁶ -3[Pa], deposition time 30 seconds, current value 250mA.

[0232] (2) Lithium electrolysis dissolution reaction test (2-1) Preparation of test coin cells A test coin cell was fabricated using a test film. Specifically, a CR2032 type coin cell (20mmφ, 3.2mm high, manufactured by Hosen Co., Ltd.) including the main case, cap case, spacer, washer, and gasket (O-ring) was prepared. Inside a glove box under an argon atmosphere, a circular piece (17mmφ) of the test film, folded so that the copper layer side faced outwards and partially connected, was placed inside the main case. A single-layer polypropylene separator was then placed on the test film so that the copper layer of the test film and the surface of the separator faced each other. Next, an electrolyte obtained 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 top of the separator. When dissolving lithium bis(fluorosulfonyl)imide in the above mixed solvent, the sulfolane was considered to be 1-coordinate to lithium ions, and the dimethoxyethane was considered to be 2-coordinate to lithium ions, and the lithium bis(fluorosulfonyl)imide was dissolved after calculation to achieve a lithium coordination number of 4. Furthermore, a test coin cell was fabricated by sequentially placing a spacer, washer, and cap case on the lithium foil, and then sealing the cap case and main case using a coin cell crimping machine. This test coin cell contains a laminated structure of "lithium foil / separator / copper layer / resin layer / base layer (polyester film)". In the case of the comparative test film, it contains 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 is placed in the device, and the current density is 0.09 mA / cm². 2Lithium was electrolytically extracted onto the copper layer of the test film by applying a constant current for 10 hours. Next, the current density was 0.09 mA / cm². 2 Then, a current was passed in the reverse direction under constant current and for 10 hours. This cycle was repeated a total of 10 times. The current density is calculated by viewing the lithium foil from the normal direction (the vertical direction where the main case and cap case overlap) over an area of ​​1.11 cm². 2 Calculated based on ).

[0234] (3) Raman spectroscopy A test specimen was cut from the test film, embedded in epoxy resin, and then a cross-section in the thickness direction was cut using a microtome (UC7, Leica). At this cross-section, 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) was measured using a Raman spectrometer (DXR3Xi, Thermo Fisher Scientific). (conditions) • Excitation laser wavelength: 785nm • Laser intensity (maximum output): 30mW Exposure time: 0.25 seconds • Beam diameter: 0.9 μm • Grating (diffraction grating): 400 lines / mm • Total number of uses: 80 • Aperture: 25 μm • Objective lens: MPLFLN-BD100x (0.9NA)

[0235] The Raman spectrum was measured in the same manner for the test film after the experiment. Specifically, after repeating the electrodeposition and dissolution cycle a total of 10 times, the test coin cell was disassembled in a glove box under an argon atmosphere, the test film was removed, and the Raman spectrum was measured in the same manner as described above.

[0236] (4) Peak intensities of the Raman spectrum ((α),(β)) The Raman spectrum obtained above (vertical axis: scattering intensity, horizontal axis: Raman shift (cm)) -1 Based on the graph shown as ), the 1650-1800 cm² of the test film before the test -1 Peak intensity (α) in the range, and the intensity of the test film at 1650-1800 cm after testing. -1 The peak intensity (β) was calculated.

[0237] (5) Linear sweep voltammetry (LSV) measurement In a glove box under an argon atmosphere, a container was injected with a non-aqueous electrolyte consisting of a mixed solvent of ethylene carbonate and ethylmethyl carbonate (volume ratio 3:7) in which lithium hexafluoride phosphate was dissolved at a concentration of 1 ml / L. The working electrode, counter electrode, and reference electrode described below were impregnated into this container, and a potentiostat was activated to apply a voltage. The potential was then 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 / cm²). 2 The data was plotted as follows, and a voltammogram (blank) was obtained. (Working pole, reference pole, and counter pole) • Working electrode: A working electrode obtained by coating the surface of copper foil with a slurry solution obtained by dispersing a mixture of natural carbon powder, sodium carboxymethylcellulose, and styrene-butadiene rubber (mass ratio 98:1:1) in water, drying it, and cutting it into strips. Reference electrode and counter electrode: Lithium metal wire.

[0238] Furthermore, resin (A-1), resin (A-2), or dimethyl terephthalate (a model compound for polyester film) was dissolved in the above non-aqueous electrolyte at a concentration of 0.5 mmol / L or higher, 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 particle-free) • Polyester (P-2): Polyethylene terephthalate (intrinsic viscosity 0.65 dL / g, contains 0.2% by mass of amorphous silica with an average particle size of 2 μm)

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

[0241] • Surfactant (B-1): A nonionic surfactant with an HLB of 13.3, mainly composed of polyoxyethylene alkyl ether. • Surfactant (B-2): Acetylene-based nonionic surfactant with polyethylene oxide in its side chain and an HLB of 8.0

[0242] • Silica particles (C-1) 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. Both were supplied to an extruder, heated and melted at 285°C, and layer a was divided into two to form the outermost layer (surface layer) and layer b as the intermediate layer, creating a 2-type, 3-layer structure. The extrusion conditions were set so that the thickness composition ratio of surface layer (a) / intermediate layer (b) / surface layer (a) = 1:8:1, and the film was co-extruded. The film was cooled and solidified while in close contact with a mirror-cooled drum with a surface temperature of 40-50°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 oriented film. Next, this uniaxially oriented film was guided into a tenter stretcher, stretched 4.3 times in the width direction at 110°C, and then subjected to a heat treatment at 235°C for 1 to 30 seconds. After that, it was cooled at 140°C with a 2% relaxation in the width direction to obtain a biaxially oriented polyester film with a thickness of 50 μm.

[0244] [Example 1] In Comparative Example 1, one surface of the biaxially oriented polyester film was coated with coating solution I shown in Table 1 below, and the film was heat-cured in an oven at 100°C for 3 minutes and then at 210°C for 1 minute to form a resin layer with a film 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. Both were supplied to an extruder, heated and melted at 285°C, and layer a was divided into two to form the outermost layer (surface layer) and layer b as the intermediate layer, creating a 2-type, 3-layer structure. The extrusion conditions were set so that the thickness composition ratio of surface layer (a) / intermediate layer (b) / surface layer (a) = 1:8:1, and the film was co-extruded. The film was cooled and solidified while in close contact with a mirror-cooled drum with a surface temperature of 40-50°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 oriented film. Next, coating solution II shown in Table 1 below was applied to one surface of the uniaxially oriented film. Then, the film was guided into a tenter stretcher and stretched 4.3 times in the width direction at 110°C. After further heat treatment at 235°C, a 2% relaxation treatment was performed in the width direction to obtain a biaxially oriented film with a thickness of 50 μm and a resin layer with a film thickness (after drying) of 0.040 μm, thus obtaining the laminated polyester film of Example 2.

[0246] [Examples 3-4] Laminated polyester films of Examples 3 and 4 were obtained in the same manner as in Example 2, except that coating solution II was changed to the coating solution shown in Table 1. Note that A-4' in Table 2 is obtained by neutralizing resin (A-4) with aqueous ammonia. The neutralized resin (A-4') was obtained by adding aqueous ammonia to resin (A-4) in pure water, heating and stirring at 40°C, and then neutralizing it. The amount of aqueous ammonia added was calculated to be 1.2 equivalents of ammonia relative to the carboxyl groups of resin (A-4).

[0247] [Table 1]

[0248] (Evaluation results of Raman spectrum peak intensity ((α),(β)) measurement) For each of Examples 1-4 and Comparative Example 1, the peak intensities ((α),(β)) of the Raman spectra were determined. The results are shown in Figures 1-5 and Table 2.

[0249] [Table 2]

[0250] As shown in Figure 5 and Table 2, the peak intensity of the film in Comparative Example 1 was significantly reduced after the test compared to the peak intensity derived from the C=O stretching vibration before the test. This indicates that the polyester underwent significant reductive decomposition, resulting in inferior charge-discharge durability. On the other hand, the results from Figures 1-4 and Table 2 show that the films of Examples 1-4 significantly suppress the decrease in peak intensity caused by the reduction of C=O bonds due to polyester reduction, indicating that they have excellent charge-discharge durability.

[0251] (Test results of linear sweep voltammetry measurement) As shown in Figure 6, when dimethyl terephthalate (a model compound for polyester film) was used (reference example), unlike the case with only the electrolyte (blank), a reduction current (downward convex peak) was clearly observed around 1.3V. On the other hand, in the electrolyte solution using resin (A-1) or resin (A-2), no reduction current (downward convex peak) was observed, similar to the case with the electrolyte solution alone (blank). These results indicate that a metal lamination film having a resin layer containing the resin in question exhibits excellent charge-discharge durability.

[0252] Furthermore, as shown in Figure 6, the electrolyte using resin (A-1) or resin (A-2) exhibited generally similar behavior to the electrolyte alone (blank). Specifically, in a graph plotting the potential and current density when the potential was swept from the natural potential (approximately 3.2V) to 0V at a sweep speed of 1mV / s, the maximum value of the current density ratio obtained using the method described below was small, at 1.2, when resin (A-1) or resin (A-2) was used. On the other hand, the maximum current density ratio when using dimethyl terephthalate (reference example) was relatively high at 8.3. (Maximum value of current density ratio) This is the maximum value of the current density ratio obtained according to the following equation (2) at the specified potential. The specified potential is 0.0V (Li / Li + )~3.0V(Li / Li + ) in the range of 0.05V (Li / Li + This refers to potentials in increments of 0.02V (Li / Li). If current density data is not available at the specified potential, the specified potential ±0.02V (Li / Li) will be used. + The current density values ​​within the range of ) shall be used. [formula] Current density ratio = |Current density at the specified potential when using resin (A-1), resin (A-2), or dimethyl terephthalate| / |Current density at the specified potential when using only electrolyte (blank)| ... (2)

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

[0254] Although resins (A-3), (A-4), and (A-5) are insoluble in the electrolyte and therefore difficult to measure directly using linear sweep voltammetry, they are acrylic resins containing carboxyl groups, similar to resin (A-2), and based on the results for resin (A-2), it can be inferred that they have excellent charge-discharge durability. As mentioned above, in the case of resins like (A-3), (A-4), and (A-5) that are insoluble in the electrolyte, it is sufficient to perform linear sweep voltammetry measurements using the monomer components that make up the resin to confirm that they are resistant to decomposition.

[0255] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that would be obvious to those skilled in the art are intended to fall within the scope of the present invention. [Industrial applicability]

[0256] The metal lamination film of the present invention exhibits excellent electrochemical stability, making it suitable for 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 possesses metal adhesion properties, it can be suitably used in battery casing materials, metal wiring substrates, RF tags, and the like. [Explanation of symbols]

[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. The film foil for a battery current collector according to Claim 1, wherein the thickness of the resin layer is less than 1 μm.

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 or 2, 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 that appears in the range of 1650 to 1800 cm -1 in the Raman spectrum (Rmα) measured in the cross-sectional area within a 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 that appears in the range of 1550 to 1650 cm -1 in the Raman spectrum (Rmα) 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 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 solution 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 laminated film according to claim 10, wherein the thickness of the resin layer is less than 1 μm.

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