Polyester film for battery current collector, film foil for battery current collector, and battery current collector

Abstract

To improve the uniformity of a metal layer formed on a polyester film for a battery current collector, and to improve the productivity of a film foil for a battery current collector using the polyester film.SOLUTION: A polyester film for a battery current collector satisfies the following (1) and (2). (1) The static friction coefficient μs, measured by overlapping side A, which is one surface, with side B, which is the other surface, is 0.26 or more and 0.75 or less. (2) The ratio (SaB / SaA) of the arithmetic mean height Sa (SaA) of side A, which is one surface, to the arithmetic mean height Sa (SaB) of side B, which is the other surface, is 1 or more and less than 1.2 (SaB≥SaA).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Secondary batteries such as lithium ion batteries are widely used in various products such as vehicles and portable devices. An electrode for such a secondary battery is formed, for example, by providing an electrode active material layer containing an electrode active material on the surface of an electrode current collector. This electrode current collector is a sheet-shaped conductive member and forms a part of the conductive path from the electrode active material layer to the electrode terminal. Electrode current collectors for secondary batteries are sometimes constructed with a laminated structure in which the surface of a resin substrate is covered with a thin metal film. Such laminated electrode current collectors using a resin substrate have a current interrupting function in which the resin substrate melts and deforms, causing the thin metal film to break, when abnormal heat is generated due to an internal short circuit or the like (see Patent Document 1). For example, it has been proposed to use a polyester film as the resin substrate (see Patent Documents 2 and 3).

[0003] In addition, in the process of providing metal layers consisting of thin metal films on both sides of a polyester film for battery current collectors, for example, metals that have been heated and vaporized are successively solidified and attached to a film that has been brought into close contact with a cooling roll in a vacuum chamber, thereby providing each metal layer on both sides of the film. From the viewpoint of improving the decrease in productivity caused by insufficient adhesion of the film to the cooling roll, and the decrease in homogeneity of each metal layer caused by a lack of balance in the air escaping behavior and cooling efficiency between the cooling rolls, it has been proposed to specify the relationship in surface roughness between the front and back surfaces of a biaxially oriented polyester film and to specify the coefficient of friction between the front and back surfaces (see Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-311146 A [Patent Document 2] Japanese Patent Application Publication No. 10-40919 [Patent Document 3] Japanese Patent Application Publication No. 10-40920 [Patent Document 4] JP 2014-220187 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the inventors' investigations have revealed that the polyester film for battery current collectors in Patent Document 4 still does not provide satisfactory uniformity or productivity for the metal layers formed on both sides of the film, and further improvement is required.

[0006] Therefore, the present invention has been made in consideration of the above-mentioned situation, and an object of the present invention is to provide a polyester film for a battery current collector, which can contribute to improving the uniformity of the metal layer formed on the film and improving the productivity of a film foil for a battery current collector using the polyester film. [Means for solving the problem]

[0007] As a result of intensive research conducted in view of the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A polyester film for use in a battery current collector, which satisfies the following (1) and (2): (1) The static friction coefficient μs measured by overlapping one surface, side A, with the other surface, side B, is 0.26 or more and 0.75 or less. (2) The ratio (SaB / SaA) of the arithmetic mean height Sa (SaA) of one surface, side A, to the arithmetic mean height Sa (SaB) of the other surface, side B, is 1 or more and less than 1.2 (wherein SaB≧SaA). [2] The polyester film for a battery current collector according to [1], which further satisfies the following (3): (3) The ratio (RaB / RaA) of the arithmetic mean roughness Ra (RaA) of side A, which is one surface, to the arithmetic mean roughness Ra (RaB) of the other surface, side B, is 1 or more and less than 1.2 (however, RaB≧RaA). [3] The polyester film for a battery current collector according to [1] or [2], which further satisfies the following (4): (4) The ratio (RzB / RzA) of the ten-point average roughness Rz (RzA) of side A, which is one surface, to the ten-point average roughness Rz (RzB) of the other surface, side B, is 1 or more and less than 1.5 (however, RzB≧RzA). [4] The polyester film for a battery current collector according to any one of [1] to [3], which further satisfies the following (5): (5) The surface free energy of the A surface (γ SV A) and the surface free energy of the other surface, B (γ SV The absolute value of the difference with B) is 5.5 mN / m or less. [5] The polyester film for a battery current collector according to any one of [1] to [4], which further satisfies the following (6): (6) The surface free energy of the A surface (γ SV A) and the surface free energy of the other surface, B (γ SV B) (γ SV B / γ SV A) is 1.15 or less (however, γ SV B ≧ γ SV A). [6] The polyester film for a battery current collector according to any one of [1] to [5], which has a crystalline melting temperature (Tm) of 258° C. or lower as determined by differential scanning calorimetry (DSC). [7] The polyester film for a battery current collector according to any one of [1] to [6], wherein an arithmetic mean height Sa (SaA) of side A, which is one surface, and an arithmetic mean height Sa (SaB) of side B, which is the other surface, are 15 nm or less. [8] The surface free energy of the A surface (γ SV The surface free energy (γ SV The polyester film for a battery current collector according to any one of [1] to [7], wherein B) is 20 mN / m or more. [9] The polyester film for a battery current collector according to any one of [1] to [8], which has a shrinkage rate of 1% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 120° C. for 5 minutes.

[10] The polyester film for a battery current collector according to any one of [1] to [9], which has a shrinkage rate of 2% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 150° C. for 5 minutes.

[11] The polyester film for a battery current collector according to any one of [1] to

[10] , which has a shrinkage rate of 4% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 180° C. for 5 minutes.

[12] The polyester film for a battery current collector according to any one of [1] to

[11] , which contains a polyethylene naphthalate-based copolymer (A).

[13] The polyester film for a battery current collector according to

[12] , wherein the content of the polyethylene naphthalate copolymer (A) in the polyester film is 50% by mass or more.

[14] The polyester film for a battery current collector according to

[12] or

[13] , wherein the polyethylene naphthalate-based copolymer (A) contains naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) and contains a bisphenol-ethylene oxide adduct and ethylene glycol as the diol component (a-2).

[15] The polyester film for a battery current collector according to

[14] , wherein the dicarboxylic acid component (a-1) contains 80 mol % or more of naphthalenedicarboxylic acid.

[16] The polyester film for a battery current collector according to

[14] or

[15] , wherein the diol component (a-2) contains a bisphenol-ethylene oxide adduct in an amount of 1 mol % or more and 49 mol % or less.

[17] The polyester film for a battery current collector according to any one of [1] to

[16] , which has a thickness of 1 μm or more and 12 μm or less.

[18] The polyester film for a battery current collector according to any one of [1] to

[17] , which has a coating layer.

[19] The polyester film for a battery current collector according to any one of [1] to

[18] , wherein the battery is a lithium ion battery.

[20] A film foil for a battery current collector, comprising the polyester film for a battery current collector according to any one of [1] to

[19] and a metal layer. [twenty one] The film foil for a battery current collector according to

[20] , wherein the metal layer is made of copper or aluminum. [twenty two] The film foil for a battery current collector according to

[20] or

[21] , wherein the metal layer is provided by any one of vapor deposition, plating, or sputtering. [twenty three] The film foil for a battery current collector according to any one of

[20] to

[22] , wherein the metal layer has a two-layer structure. [twenty four] The film foil for a battery current collector according to any one of

[20] to

[23] , wherein the battery is a lithium ion battery. [twenty five] A battery current collector comprising an electrode layer on the metal layer of the film foil for a battery current collector according to any one of

[20] to

[24] .

[26] The battery current collector according to

[25] , wherein the battery is a lithium ion battery. Effect of the Invention

[0009] The polyester film for battery current collector of the present invention can contribute to improving the uniformity of the metal layer formed on the film, and can also contribute to improving the productivity of the film foil for battery current collector using the polyester film. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a schematic structure of a film foil according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a metal layer according to an embodiment of the present invention having a two-layer structure. [Diagram 3] FIG. 2 is a cross-sectional view showing a schematic structure of a film foil in a case where the metal layer according to one embodiment of the present invention has a two-layer structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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.

[0012] <<Polyester film>> The polyester film for a battery current collector of the present invention (hereinafter also referred to as "the present film") preferably satisfies the following requirements. (1) The static friction coefficient μs measured by overlapping one surface, side A, with the other surface, side B, is 0.26 or more and 0.75 or less. (2) The ratio (SaB / SaA) of the arithmetic mean height Sa (SaA) of one surface, side A, to the arithmetic mean height Sa (SaB) of the other surface, side B, is 1 or more and less than 1.2 (wherein SaB≧SaA).

[0013] This film can effectively suppress the occurrence of slippage, shifting, twisting, wrinkles, etc. on the conveying rolls during the manufacturing process of the film foil for battery current collectors, and also has good adhesion to the cooling rolls, resulting in an excellent balance of air escape behavior between the cooling rolls and cooling efficiency. Furthermore, since thermal energy from deposition, sputtering, etc. is applied uniformly to both sides of the film, this can contribute to improving the uniformity of each metal layer formed on both sides of the film, and can also contribute to improving the productivity of the film foil for battery current collectors using this polyester film. On the other hand, if a film does not satisfy the above (1) and (2), for example, the running or transportability of the film tends to be insufficient, the air escape behavior tends to be insufficient, or the thermal energy applied to both sides of the film tends to be uneven, making it difficult to achieve a high degree of both the productivity and uniformity described above.

[0014] <Physical properties of polyester film> [Static friction coefficient μs] The static friction coefficient μs measured by overlapping the A side, which is one surface of the film, and the B side, which is the other surface, is preferably 0.26 to 0.75, and from the viewpoint of achieving high compatibility between the productivity and homogeneity, it is 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 is outside the above range, for example, the running property or transportability of the film tends to be insufficient. The static friction coefficient μs is measured by the method described in the examples.

[0015] [Ratio of arithmetic mean height Sa (SaB / SaA)] The ratio of the arithmetic mean heights Sa of the present film (SaB / SaA, which is the ratio of the arithmetic mean height SaA of any surface A, which is one of the surfaces, to the arithmetic mean height SaB of any surface B, which is the other surface) is preferably 1 or more and less than 1.2, and from the viewpoint of achieving a high degree of both the productivity and homogeneity described above, is 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, there is a tendency for the thermal energy applied to both surfaces of the film to become unbalanced, and it is difficult to effectively suppress the occurrence of curling in the film after deposition. The ratio of the arithmetic mean height Sa can be appropriately set 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, or the like. The ratio of the arithmetic mean heights Sa (SaB / SaA) is based on the condition SaB≧SaA. For example, when the values ​​of the arithmetic mean heights Sa of the respective surfaces are different, the relatively larger value is used as the numerator to determine the ratio.

[0016] The arithmetic mean height Sa of the present film (the arithmetic mean height SaA of any side A which is one surface and / or the arithmetic mean height SaB of any side B which is the other surface) is preferably 15 nm or less, more preferably 10 nm or less, even more preferably 8 nm or less, still 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 surfaces of the film. On the other hand, the lower limit of the arithmetic mean height Sa is not particularly limited, but is, for example, preferably 0.6 nm or more, more preferably 0.8 nm or more, even more preferably 1 nm or more, and particularly preferably 1.2 nm or more. The arithmetic mean height Sa can be appropriately set within the above range, and is not limited to the following, 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 Sa is within the above range for both the arithmetic mean height SaA of any surface A, which is one of the surfaces, and the arithmetic mean height SaB of any surface B, which is the other surface. By setting the arithmetic mean height in this manner, the surface area per unit projected area is small, and damage caused by heat during deposition or sputtering is easily suppressed, making it easier to control the thickness of the metal layer more uniformly and also having an effect in suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkling of the film after deposition.

[0017] The arithmetic mean height Sa is one of the surface roughness parameters (ISO 25178), which is a three-dimensional extension of the two-dimensional Ra, and is obtained by dividing the volume of the part surrounded by the surface shape curved surface and the mean surface by the measured area. Specifically, when the surface is the XY plane and the height direction is the Z axis, A is the defined area (the whole image), and Z(x, y) is the height of the image point (x, y) from the surface at height 0, and it is expressed by the following formula [Mathematical formula 1]. More specifically, it can be measured by the method described in the examples below.

[0018]

number

[0019] [Ratio of arithmetic mean roughness Ra (RaB / RaA)] In order to achieve a high degree of both productivity and uniformity in the present film, the ratio of arithmetic mean roughness Ra (RaB / RaA, which is the ratio of the arithmetic mean roughness RaA of any surface A, which is one of the surfaces, to the arithmetic mean roughness RaB of any surface B, which is the other surface) 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 upper limit value described above, for example, there is a tendency for the thermal energy applied to both surfaces of the film to become unbalanced, and it is difficult to effectively suppress the occurrence of curling in the film after deposition. The ratio of the arithmetic mean roughness Ra can be appropriately set 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, or the like. The ratio of arithmetic mean roughness Ra (RaB / RaA) is based on the condition that RaB≧RaA. For example, when the values ​​of arithmetic mean roughness Ra of each surface are different, the relatively larger value is used as the numerator to determine the ratio.

[0020] The arithmetic mean roughness Ra of the present film (the arithmetic mean roughness RaA of any surface A, which is one of the surfaces, and / or the arithmetic mean roughness RaB of any surface B, which is the other surface) is preferably 0.05 μm or less, more preferably 0.045 μm or less, even more preferably 0.04 μm or less, and particularly preferably 0.038 μm or less, from the viewpoint of further improving the uniformity of each metal layer formed on both surfaces of the film. The lower limit of the arithmetic mean roughness Ra is not particularly limited, and is, for example, 0.008 μm or more, 0.01 μm or more, 0.013 μm or more, etc. It is particularly preferable that the arithmetic mean roughness Ra of any one surface, that is, surface A, RaA, and the arithmetic mean roughness Ra of any other surface, that is, surface B, RaB, are both within the above range. By setting the arithmetic mean roughness in this manner, the surface area per unit projected area is small, and damage caused by heat during deposition or sputtering is easily suppressed, so that it becomes easier to control the thickness of the metal layer more uniformly and it is also effective in suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkling of the film after deposition. The arithmetic mean roughness Ra is one of the line roughness parameters (JIS B0601 (1994)) and indicates the average value of the average height difference from the average surface. Specifically, when a portion of a reference length L is sampled and the average line of this sampled portion is taken as the x-axis and the direction of the longitudinal magnification as the y-axis, and the roughness curve is expressed as y=Z(x), it can be calculated from the following formula [Mathematical formula 2]. More specifically, it can be measured by the method described in the examples below.

[0021]

number

[0022] [Ratio of ten-point average roughness Rz (RzB / RzA)] In order to achieve a high degree of both productivity and uniformity in the present film, the ratio of ten-point average roughness Rz (RzB / RzA, which is the ratio of ten-point average roughness RzA of any surface A, which is one of the surfaces, to ten-point average roughness RzB of any surface B, which is the other surface) is preferably 1 or more and less than 1.5, more preferably 1 or more and 1.4 or less, and even more preferably 1 or more and 1.3 or less. If the ratio of ten-point average roughness Rz exceeds the upper limit value described above, for example, there is a tendency for the thermal energy applied to both surfaces of the film to become unbalanced, and it is difficult to effectively suppress the occurrence of curling in the film after deposition. The ratio of ten-point average roughness Rz (RzB / RzA) is based on the condition that RzB≧RzA. For example, when the ten-point average roughness Rz values ​​of each surface are different, the larger value is used as the numerator to determine the ratio.

[0023] The ten-point average roughness Rz of the present film (ten-point average roughness RzA of any surface A, which is one of the surfaces, and / or ten-point average roughness RzB of any surface B, which is the other surface) is preferably 0.3 μm or less, more preferably 0.25 μm or less, even more preferably 0.2 μm or less, and particularly preferably 0.18 μm or less, from the viewpoint of further improving the uniformity of each metal layer formed on both surfaces of the film. The lower limit of the ten-point average roughness Rz is not particularly limited, and is, for example, 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 RzA of any surface A, which is one of the surfaces, and the ten-point average roughness RzB of any surface B, which is the other surface, are both within the above range. By setting the ten-point average roughness in this range, the surface area per unit projected area is small and damage caused by heat during deposition or sputtering is easily suppressed, making it easier to control the thickness of the metal layer more uniformly and also having an effect in suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkling of the film after deposition. The ten-point average roughness Rz is one of the line roughness parameters (JIS B0601 (1994)) and is obtained by measuring in a direction perpendicular to the direction in which the linear concave portions are continuous. More specifically, it can be measured by the method described in the examples below.

[0024] [Ratio of maximum cross-sectional height Rt (RtB / RtA)] In the present film, from the viewpoint of achieving a high degree of both the productivity and uniformity described above, 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, side A, to the maximum cross-sectional height RtB of any surface, side B,) is preferably 1 or more and 1.2 or less, more preferably 1 or more and 1.15 or less, and even more preferably 1 or more and 1.1 or less. The ratio of the maximum cross-sectional heights Rt (RtB / RtA) is based on the condition that RtB≧RtA. For example, when the values ​​of the maximum cross-sectional heights Rt of the respective faces are different, the relatively larger value is used as the numerator to determine the ratio.

[0025] The maximum cross-sectional height Rt of the present film (the maximum cross-sectional height RtA of any surface A, which is one surface, and / or the maximum cross-sectional height RtB of any surface B, which is the other surface) 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 surfaces of the film. The lower limit of the maximum cross-sectional height Rt is not particularly limited, and is, for example, 0.15 μm or more, 0.2 μm or more, 0.25 μm or more, etc. It is particularly preferable that the maximum cross-sectional height RtA of any surface A, which is one of the surfaces, and the maximum cross-sectional height RtB of any surface B, which is the other surface, are both within the above range. By setting the maximum cross-sectional height in this manner, the surface area per unit projected area is small, and damage caused by heat during deposition, sputtering, etc. is easily suppressed, making it easier to control the thickness of the metal layer more uniformly and also having an effect in suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkling of the film after deposition. The maximum cross-sectional height Rt is one of the line roughness parameters (JIS B0601 (1994)) and is calculated as the sum of the maximum peak height and the maximum valley depth. More specifically, it can be measured by the method described in the Examples below.

[0026] [Root mean square height Sq ratio (SqB / SqA)] The root mean square height Sq ratio of the present film (SqB / SqA, which is the ratio of the root mean square height SqA of any surface A, which is one of the surfaces, to the root mean square height SqB of any surface B, which is the other surface) is preferably 1 or more and 1.9 or less, and from the viewpoint of achieving a high degree of both the productivity and uniformity described above, it is more preferably 1 or more and 1.8 or less, and even more preferably 1 or more and 1.7 or less. The ratio of the root mean square height Sq can be appropriately set within the above range, and is not limited to the following, but may be, for example, 1.5 or less, 1.4 or less, etc. The ratio of the root mean square heights Sq (SqB / SqA) is based on the condition that SqB≧SqA. For example, when the root mean square heights Sq of the respective faces are different, the relatively larger value is used as the numerator to determine the ratio.

[0027] The root mean square height Sq of the present film (root mean square height SqA of any surface A, which is one surface, and / or 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 surfaces of the film. On the other hand, the lower limit of the root mean square height Sq is not particularly limited, but is, for example, preferably 0.8 nm or more, more preferably 1 nm or more, even more preferably 1.5 nm or more, and particularly preferably 2 nm or more. The root mean square height Sq can be appropriately set within the above range, and is not limited to the following, but may be, for example, 8 nm or less, 6 nm or less, 5 nm or less, etc. By setting such a root mean square height, the surface area per unit projected area is small and damage caused by heat during deposition or sputtering is easily suppressed, making it easier to control the film thickness to be more uniform and also having an effect of suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkles of the film after deposition. It is particularly preferable that the root mean square height SqA of any surface A, which is one of the surfaces, and the root mean square height SqB of any surface B, which is the other surface, are both within the above range. The root mean square height Sq is one of the surface roughness parameters (ISO 25178), and is a three-dimensional extension of the two-dimensional Rq. That is, it is the root mean square value of the height data in a defined area, and is a parameter equivalent to the standard deviation of the distance from the average surface, and can be calculated from the following formula [Equation 3]. More specifically, it can be measured by the method described in the Examples below.

[0028]

number

[0029] [Ratio of maximum cross-sectional height St (StB / StA)] The ratio of the maximum cross-sectional heights St of the present film (StB / StA, which is the ratio of the maximum cross-sectional height StA of any surface A, which is one of the surfaces, to the maximum cross-sectional height StB of any surface B, which is the other surface) is preferably 1 or more and 2.6 or less, and from the viewpoint of achieving a high degree of both the productivity and homogeneity described above, it is more preferably 1 or more and 2.4 or less, and even more preferably 1 or more and 2.2 or less. The ratio of the maximum cross-sectional height St can be appropriately set 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. The ratio of the maximum cross-sectional heights St (StB / StA) is based on the condition StB≧StA. For example, when the values ​​of the maximum cross-sectional heights St of the respective faces are different, the relatively larger value is used as the numerator to determine the ratio.

[0030] The maximum cross-sectional height St of the present film (the maximum cross-sectional height StA of any side A which is one surface and / or the maximum cross-sectional height StB of any side 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 enhancing the homogeneity of each metal layer formed on both surfaces of the film. On the other hand, the lower limit of the maximum cross-sectional height St is not particularly limited, but is, for example, preferably 30 nm or more, more preferably 40 nm or more, even more preferably 48 nm or more, and particularly preferably 50 nm or more. The maximum cross-sectional height St can be appropriately set within the above range, and is not limited to the following, but may be, for example, 300 nm or less, 250 nm or less, 200 nm or less, etc. By setting the maximum cross-sectional height in this manner, the surface area per unit projected area is small, and damage caused by heat during deposition or sputtering is easily suppressed, making it easier to control the film thickness to be more uniform in the metal layer, and is also effective in suppressing curling of the film after deposition. In addition, partial heat shrinkage can also be suppressed, which in turn leads to the suppression of curling and wrinkles in the film after deposition. It is particularly preferable that the maximum cross-sectional height StA of any surface A, which is one of the surfaces, and the maximum cross-sectional height StB of any surface B, which is the other surface, are both within the above range. The maximum profile height St is one of the surface roughness parameters (ISO 25178), which is a three-dimensional extension of the two-dimensional Rt, and is the sum (total of absolute values) of the maximum peak height and the maximum valley depth in a defined area. More specifically, it can be measured by the method described in the Examples below.

[0031] When the present film is a laminate including a resin layer or the like, it is preferable that the surface characteristics of the front and back surfaces, which are the outermost layers of such a laminate, are within the above ranges.

[0032] The method for adjusting the surface characteristics Sa, Ra, Rz, Rt, St, Sq and the static friction coefficient μs of the above-mentioned film to the above range is not particularly limited, and various methods such as transfer processing such as embossed roll transfer, embossed belt transfer, embossed film transfer, sandblasting, shot blasting, etching, engraving, surface crystallization, etc. can be used. Since it is easy to continuously and uniformly form surface irregularities while extruding the molten resin into a film, a method of roughening by casting a film-like molten resin on a cast roll is preferred. In this case, the surface roughness of the resin film can be adjusted by adjusting the arithmetic mean roughness of the cast roll. In addition, it is also possible to adjust the surface properties by appropriately adjusting the particle size, shape, and content of the particles in the film, or by adding an appropriate amount of a crystal nucleating agent. Furthermore, it is also possible to adjust the film formation conditions such as the stretching temperature, stretching ratio, uniformity of widthwise stretching, relaxation rate, and cooling temperature. A method of performing an electrical surface treatment such as a corona discharge treatment or an atmospheric pressure glow discharge treatment can also be used. In addition, when a functional layer such as a resin layer or a release layer is separately provided by coating or the like, this can be achieved by appropriately adjusting the composition of the coating liquid used, the coating thickness, the coating conditions, the dispersion state of the particles blended in the coating liquid, the timing of coating (inline or offline, etc.), etc.

[0033] [Absolute value of the difference in surface free energy] The absolute value of the difference in surface free energy of this film (surface free energy γ SV The surface free energy γ of surface A and any other surface B SV B) is preferably 7 mN / m or less, and from the viewpoint of achieving both the productivity and homogeneity at a high level, 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, particularly preferably 1 mN / m or less, and most preferably 0.8 mN / m or less. The lower limit is preferably 0 mN / m, but may be 0.03 mN / m, 0.08 mN / m, 0.1 mN / m, 0.15 mN / m, 0.17 mN / m, or 0.2 mN / m.

[0034] [Ratio of surface free energy (γ SV B / γ SV A) The ratio of the surface free energy of this film (the surface free energy γ SV The surface free energy γ of surface A and any other surface B SV The ratio of B is γ SV B / γ SV A) is preferably 1 or more and 2 or less, and from the viewpoint of achieving a high degree of both productivity and homogeneity as described above, is more preferably 1 or more and 1.5 or less, and even more preferably 1 or more and 1.2 or less. Also, it is preferably 1.15 or less, more preferably 1 or more and 1.15 or less, particularly preferably 1 or more and 1.1 or less, particularly preferably 1 or more and 1.06 or less, and most preferably 1 or more and 1.03 or less. In addition, the surface free energy ratio (γ SV B / γ SV A) is γ SV B ≧ γ SV A is a condition, for example, the surface free energy γ SV When the values ​​are different, the relatively larger value is used as the numerator to determine the ratio.

[0035] The surface free energy of this film, γ SV (The surface free energy γ SV The surface free energy γ of surface A and any other surface B SV From the viewpoint of further improving the uniformity and adhesion of each metal layer formed on both sides of the film, B) is, for example, preferably 20 mN / m or more, more preferably 25 mN / m or more, even more preferably 30 mN / m or more, and particularly preferably 35 mN / m or more. On the other hand, the surface free energy γ SV The lower limit is not particularly limited, but is, for example, 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 of any surface A SV The surface free energy γ of surface A and any other surface B SV It is particularly preferable that both of B's ​​are within the above range.

[0036] Surface free energy is composed of the sum of components of intermolecular forces. The intermolecular forces are classified into dispersion forces, orientation forces, induction forces, and hydrogen bonding forces, which respectively constitute the surface free energy as a dispersion component (Dispersion), a polar component (Polar), an induction component (Induction), and a hydrogen bonding component (Hydrogen). Of these components, the inductive components are very weak and can be ignored, and the hydrogen bonding components can be grouped together in the polar components.

[0037] In the present invention, the surface free energy γ SV Each component (variance component γ SV d and the polar component γ SV p ) is a value determined by the following measurement and calculation methods. First, the following γ LV1 , γLV1 d and γ LV1 p The contact angle (θ1) between the first liquid and the surface to be measured, and γ LV2 , γ LV2 d and γ LV2 p The contact angle (θ2) between the second liquid, whose contact angle is known, and the surface to be measured is measured. Next, these values ​​are substituted into the following formulas (I-1) and (I-2), and the surface free energy γ of the resin layer surface to be measured is calculated from the simultaneous equations of the following formulas (I-1) and (I-2). SV The variance component of γ SV d and the polar component γ SV p In both cases, the units are mN / m.

[0038] (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)

[0039] Gamma SV d : Surface free energy γ of the surface to be measured SV Variance components of Gamma SV p : Surface free energy γ of the surface to be measured SV Polar component of Gamma LV1 : surface tension of the first liquid Gamma LV2 : surface tension of the second liquid θ1: contact angle of the first liquid θ2: Contact angle of the second liquid Gamma LV1 d : Dispersive component of the surface tension of the first liquid Gamma LV1 p : Polar component of the surface tension of the first liquid Gamma LV2 d : Dispersive component of the surface tension of the second liquid Gamma LV2 p : the polar component of the surface tension of the second liquid

[0040] The above formulas (I-1) and (I-2) are derived from the following Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula and the following Young's formula. OWRK theoretical formula: Gamma 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: Gamma SV =γ SL +γ LV cosθ (wherein, γ SL is the interfacial tension between the surface being measured and the liquid.)

[0041] The method for adjusting the surface free energy of the film surface to the above range is not particularly limited, but for example, it can be adjusted by the composition of the film surface. In particular, when the film is a laminate including a resin layer (particularly a coating layer), it is effective to adjust by the composition of each resin composition forming the resin layer and the thickness of the resin layer. In addition, by bringing the composition of the surface or resin layer on the A-side surface, which is one surface, closer to the composition of the surface or resin layer on the B-side surface, which is the other surface, specifically by making the resin compositions 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 blending a hydrophilic group-containing compound in addition to a binder resin and / or a crosslinking agent that are commonly used, the surface free energy value can be easily increased and can be easily adjusted to a desired value. The hydrophilic group-containing compound is not particularly limited as long as it contains a hydrophilic group. The hydrophilic group of the hydrophilic group-containing compound is a functional group that forms a weak bond with a water molecule by hydrogen bonding or the like, and examples of the hydrophilic group-containing compound include a hydroxyl group, a carboxyl group, an amide group, and a thiol group. Specific examples of the hydrophilic group-containing compound include compounds containing (meth)acryloyl groups, polyvinyl alcohol, glycerin, polyglycerin, alkylene oxide adducts of glycerin or polyglycerin, polyalkylene oxides, etc. Among them, polyvinyl alcohol and compounds containing (meth)acryloyl groups are preferred from the viewpoint of adhesion to the metal layer. In addition, the hydrophilic group-containing compound is preferably a polymer containing a structural unit having a hydrophilic group from the viewpoint of adhesion to the metal layer.

[0042] [Crystal melting temperature (Tm)] The crystalline melting temperature (Tm) of the present film as determined by differential scanning calorimetry (DSC) is preferably 258°C or lower. When the crystalline melting temperature (Tm) is 258°C or lower, for example, the temperature at which melting insulation begins to melt during a short circuit is lowered, and therefore the cessation and prevention of a runaway reaction due to a short circuit is initiated quickly. From this viewpoint, the crystalline melting temperature (Tm) is preferably 256°C or lower, more preferably 254°C or lower, and even more preferably 252°C or lower. On the other hand, from the viewpoint of moldability and strength retention during high-temperature treatment, the crystalline melting temperature (Tm) is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher.

[0043] The method for adjusting the crystalline melting temperature (Tm) to the above range is not particularly limited, and it can be adjusted, for example, by the type and content of the polyester constituting the present film.

[0044] [Shrinkage rate] The shrinkage rate of the present film when heat-treated at 120°C for 5 minutes is preferably 1.2% or less in either the longitudinal direction (MD) or the transverse direction (TD) from the viewpoint of suppressing a decrease in adhesion with the metal layer or deformation of the film, more preferably 1.1% or less, even more preferably 1% or less, and particularly preferably 0.9% or less. The lower limit of the shrinkage rate (120°C, 5 minutes) is not particularly limited, but is usually about -0.5%, 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 transverse direction (TD).

[0045] From the same viewpoint, the shrinkage rate of the present film when heat-treated at 150°C for 5 minutes is preferably 2.2% or less in either the longitudinal direction (MD) or the transverse 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 about -0.5%, 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 transverse direction (TD). From the same viewpoint, the shrinkage rate of the present film when heat-treated at 180°C for 5 minutes is preferably 4% or less in either the longitudinal direction (MD) or the transverse 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 about -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 transverse direction (TD).

[0046] The method for adjusting the above shrinkage ratios (120°C, 5 minutes), (150°C, 5 minutes), and (180°C, 5 minutes) to the above ranges is not particularly limited, and can be adjusted, for example, by the type and content of polyester constituting the present film, the particle size and content of particles if particles are contained, the film-forming conditions of the present film, etc. These shrinkage ratios can be measured by the method described in the Examples.

[0047] The longitudinal direction (MD) of the film refers to the direction in which the film advances during the film production process, i.e., the winding direction of the film roll, and is also called the machine direction or longitudinal direction. The transverse direction (TD) of the film refers to the direction parallel to the film surface and perpendicular to the longitudinal direction, i.e., the direction parallel to the central axis of the roll when the film is in a roll form, and is also called the transverse direction.

[0048] [Layer structure, thickness, etc. of this film] The layer structure of the present film is not particularly limited, and may be a single layer structure or a laminated (multi-layer) structure. When the present film has a laminated structure, the present film may be a two-layer structure, a three-layer structure, or may be a four-layer structure or more, as long as it does not deviate from the gist of the present invention. The number of layers to be laminated is not particularly limited, but is preferably 10 layers or less. If there are 10 layers or less, the thickness of each layer is sufficient, so that the lamination property during film formation is sufficient, flow marks and the like are unlikely to occur, and the quality of the film is sufficiently maintained.

[0049] The film may be a non-stretched film (sheet) or a stretched film. Of these, a stretched film stretched in a uniaxial or biaxial direction is preferable. Of these, a biaxially stretched film is more preferable in terms of excellent balance of mechanical properties and flatness. The biaxially stretched film means a film in which the refractive index in the longitudinal direction (MD) and width direction (TD) of the film is higher than the refractive index in the thickness direction, and is usually obtained by stretching the film in the longitudinal direction and width direction.

[0050] The thickness (total thickness) of the present film is preferably 1 μm to 12 μm, more preferably 1 μm to 10 μm, even more preferably 2 μm to 8 μm, particularly preferably 3 μm to 7 μm, and especially preferably 4 μm to 6 μm. The thickness of the present film was measured at five random points on the surface with a 1 / 1000 mm dial gauge, and the average was used as the thickness.

[0051] When the present film has a laminated structure of two or more layers, the ratio of the thickness (T1) of one outermost layer to the thickness (T2) of the other outermost layer (T2 / T1: with the proviso that T2≧T1) is preferably 1 or more and 1.8 or less, more preferably 1 or more and 1.5 or less, and even more preferably 1 or more and 1.2 or less, in order to prominently exhibit the effects of the present invention.

[0052] <Polyester> The present film preferably contains polyester as a main component resin. The above-mentioned "main component resin" means the resin that is contained in the present film in the largest proportion, for example, a resin that occupies 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more (including 100% by mass) of the resins that constitute the present film. The present film is preferably a film containing polyester as a main component. The above-mentioned "main component" refers to the component that is the largest among the components (100% by mass) constituting the present film, and means that polyester accounts for 50% by mass or more, particularly 70% by mass or more, of which 80% by mass or more, and further 90% by mass or more.

[0053] The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming property or productivity, it is preferably 0.45 to 1 dL / g, more preferably 0.5 to 0.9 dL / g, even more preferably 0.55 to 0.8 dL / g, and particularly preferably 0.6 to 0.75 dL / g. When two or more polyesters with different intrinsic viscosities are used, the intrinsic viscosity refers to the intrinsic viscosity of the mixed polyester. The intrinsic viscosity can be measured according to a conventional method, for example, using an Uperohde viscometer and using a solvent of phenol:tetrachloroethane=1:1 at 30°C.

[0054] The polyester used as the raw material of the present film is not particularly limited, and may be a homopolyester or a copolymer polyester. Specific examples include polyesters obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0055] Examples of the dicarboxylic acid component 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-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, and aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid.

[0056] Examples of the diol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, polytetramethylene ether glycol, dimer diol, and bisphenols (bisphenol compounds such as bisphenol A, bisphenol F, or bisphenol S, or derivatives thereof, or ethylene oxide adducts thereof).

[0057] Representative polyesters include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate.

[0058] The copolymer polyester may be one containing 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 a copolymerization component.

[0059] In particular, from the viewpoint of significantly achieving the effects of the present invention, the present film preferably contains, as the polyester, polyethylene naphthalate (hereinafter also referred to as "PEN") or a polyethylene naphthalate-based copolymer (A) (hereinafter also referred to as "PEN-based copolymer (A)"), and more preferably contains a PEN-based copolymer (A). The content of the PEN or PEN-based copolymer (A) in the present film is preferably 50 mass % or more in the resin constituting the present film and / or in the components constituting the present film, more preferably 70 mass % or more, even more preferably 80 mass % or more, and particularly preferably 90 mass % or more (including 100 mass %). In the case where the present film has a laminated structure, it is preferable that the content of PEN or the PEN-based copolymer (A) contained in each layer satisfies the above. Also, a mixture of PEN and the PEN-based copolymer (A) may be used.

[0060] The PEN copolymer (A) specifically includes a dicarboxylic acid component (a-1) and a diol component (a-2), and more specifically includes a naphthalene dicarboxylic acid such as 2,6-naphthalene dicarboxylic acid as the dicarboxylic acid component (a-1), and ethylene glycol as the diol component (a-2), and contains a copolymerization component in at least one of the dicarboxylic acid component (a-1) and the diol component (a-2).

[0061] The PEN copolymer (A) 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 making the content of naphthalenedicarboxylic acid in the dicarboxylic acid component (a-1) 80 mol% or more, for example, the shrinkage rate can be easily adjusted to a desired range. Incidentally, 2,6-naphthalenedicarboxylic acid is the most preferable naphthalenedicarboxylic acid.

[0062] The PEN copolymer (A) 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.

[0063] The PEN copolymer (A) preferably contains 20 mol % or less, more preferably 10 mol % or less of a copolymerization component in the dicarboxylic acid component (a-1), and even more preferably, all of the dicarboxylic acid component (a-1) is a naphthalene dicarboxylic acid such as 2,6-naphthalene dicarboxylic acid, i.e., the copolymerization component is 0 mol %. The PEN copolymer (A) contains the copolymerization component in the diol component (a-2) at 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 copolymerization component in the diol component (a-2) is preferably 1 mol% or more, more preferably 2 mol% or more, even more preferably 3 mol% or more, particularly preferably 4 mol% or more, and especially preferably 5 mol% or more.

[0064] When the main component is 2,6-naphthalenedicarboxylic acid, examples of copolymerization components added to the dicarboxylic acid component (a-1) include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, benzophenone dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 3,3'-diphenyl dicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid; and aliphatic dicarboxylic acids such as cyclohexane dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid. From the viewpoint of moldability, isophthalic acid, 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, and 3,4-furandicarboxylic acid are preferred. These copolymerization components can be used alone or in combination of two or more.

[0065] Examples of copolymerization components added to the diol component (a-2) include diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, polytetramethylene ether glycol, dimer diol, bisphenols (bisphenol compounds such as bisphenol A, bisphenol F, or bisphenol S, or derivatives thereof, or ethylene oxide adducts thereof). From the viewpoint of maintaining film strength, bisphenols are more preferred, and as bisphenols, it is preferable to use bisphenol-ethylene oxide adducts, and it is particularly preferable to use bisphenol A-ethylene oxide adducts. These copolymerization components can be used alone or in combination of two or more.

[0066] That is, the PEN copolymer (A) preferably contains a naphthalene dicarboxylic acid such as 2,6-naphthalene dicarboxylic acid as the dicarboxylic acid component (a-1) and a bisphenol-ethylene oxide adduct such as bisphenol A-ethylene oxide adduct and ethylene glycol as the diol component (a-2). In this PEN copolymer (A), the dicarboxylic acid component (a-1) contains a naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid in an amount of preferably 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and particularly preferably 100 mol %. In addition, in this PEN copolymer (A), the diol component (a-2) contains a bisphenol-ethylene oxide adduct such as a bisphenol A-ethylene oxide adduct in an amount of preferably 1 mol% to 49 mol%, more preferably 2 mol% to 40 mol%, even more preferably 3 mol% to 30 mol%, particularly preferably 4 mol% to 20 mol%, and especially preferably 5 mol% to 10 mol%, and contains ethylene glycol in an amount of preferably 51 mol% to 99 mol%, more preferably 60 mol% to 98 mol%, even more preferably 70 mol% to 97 mol%, particularly preferably 80 mol% to 96 mol%, and especially preferably 90 mol% to 95 mol%.

[0067] In addition, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is usually 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 is about 5 mol% or less of ethylene glycol. In the present invention, 5 mol% or less of diethylene glycol is defined as by-product diethylene glycol, and the by-product diethylene glycol is also included in ethylene glycol and is distinguished from the copolymerization component. On the other hand, depending on the content of diethylene glycol, more specifically, when diethylene glycol is contained in excess of 5 mol%, diethylene glycol is treated as a copolymerization component rather than as a by-product diethylene glycol.

[0068] In addition, when the present film has a multilayer structure, the type and content of the copolymerization component constituting the PEN-based copolymer (A) contained in any layer, preferably in each layer, may be the same as above, and the resin constituting each layer and the PEN-based copolymer (A) in each layer may be the same as or different from each other.

[0069] <Polymerization catalyst> The polycondensation catalyst used in polycondensing polyester is not particularly limited, and a conventionally known compound can be used, for example, titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, calcium compounds, etc. Among them, titanium compounds and antimony compounds are preferred from the viewpoint of productivity.

[0070] <particle> The film may contain particles. In general, the inclusion of particles in a polyester film provides the film with good lubricity and prevents scratches during each process, improving the handling properties. The type of particles contained in the present film is not particularly limited as long as it is a particle that can impart slipperiness, and examples thereof include inorganic particles such as 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 alone or in combination of two or more. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

[0071] The shape of the particles to be used is not particularly limited, and any of spherical, blocky, rod-like, flat, etc. may be used. There is also no particular limit to the hardness, specific gravity, color, etc.

[0072] The particles have an average particle size of usually 0.01 to 5 μm, preferably 0.03 to 4 μm, more preferably 0.05 to 3.5 μm, and even more preferably 0.1 to 3 μm. If the average particle size is within this range, the present film can have both easy handling and transparency. In addition, when the particles are powder, the average particle size of the particles can be the particle size (d50) at an accumulated volume fraction of 50% in the equivalent sphericity distribution measured using a centrifugal sedimentation type particle size distribution measuring device (e.g., Shimadzu Corporation's "SA-CP3 type"). The average particle size of the particles in the film, layer, or resin can be determined by observing 10 or more particles with a scanning electron microscope (SEM) to measure the diameters of the particles and calculating the average value. In this case, in the case of non-spherical particles, the average value of the longest diameter and the shortest diameter can be measured as the diameter of each particle.

[0073] When particles are incorporated into the present film, it is preferred that the film be a laminate having a surface layer and an intermediate layer, and that the particles be incorporated into the surface layer.

[0074] The method of adding particles to the present film is not particularly limited, and any conventionally known method can be used. For example, the particles can be added at any stage of the polyester production, but it is preferable to add the particles after the esterification or transesterification reaction is completed.

[0075] <Other> In order to suppress the amount of precipitation of oligomer components, the film may be produced using a polyester having a low content of oligomer components as a raw material. As a method for producing a polyester having a low content of oligomer components, various known methods can be used, for example, a method of performing solid phase polymerization after the production of a polyester. The present film may be configured with three or more layers, and the surface layer of the present film may be a layer made of a polyester raw material having a low content of oligomer components, thereby suppressing the amount of precipitation of oligomer components. The polyester may be obtained by melt polycondensation under reduced pressure at a higher reaction temperature after esterification or transesterification.

[0076] In addition to the above-mentioned particles, conventionally known ultraviolet absorbents, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the present film as required. Furthermore, the present film may contain resins other than polyester as long as the effects of the present invention are not impaired. Examples of other resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, and fluorine-based resins.

[0077] <Resin layer> A preferred embodiment of the present film is a laminate including a resin layer, and among these, a laminate including a coating layer formed by coating or the like as the resin layer is preferred. The resin layer is not particularly limited, but for example, it is formed by applying a resin composition for forming the resin layer to a polyester film, and if necessary, subjecting the applied resin composition to treatments such as drying, curing, and heat treatment.

[0078] The resin composition forming the resin layer is not particularly limited, but preferably contains particles. Details of such particles are the same as those described in the <Particles> section above, and the average particle size of the particles is preferably 0.01 to 1 μm, more preferably 0.02 to 0.9 μm, even more preferably 0.03 to 0.8 μm, particularly preferably 0.04 to 0.7 μm, and especially preferably 0.05 to 0.6 μm.

[0079] When resin layers are provided on both sides of the present film, the ratio (d2 / d1: d2≧d1) of the average particle size (d1) of the particles contained in one resin layer to the average particle size (d2) of the particles contained in the other resin layer is, although not limited thereto, preferably 1 to 10, more preferably 1 to 9, and even more preferably 1 to 8. In other words, it is preferable not to incorporate into the present film a combination of particles that falls outside the above range.

[0080] The content of the particles in the resin layer is preferably 0.1 to 20 mass %, more preferably 0.3 to 16 mass %, even more preferably 0.5 to 14 mass %, and particularly preferably 0.7 to 12 mass %, based on the total mass of the resin layer (non-volatile components).

[0081] The resin composition forming the resin layer may contain any known components, for example, a resin, a crosslinking agent, an antifoaming agent, a coatability improver, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, a solvent, etc.

[0082] [Resin [Binder]] The resin is not particularly limited, and a conventionally known resin can be used. Specifically, it is a polymeric compound having a number average molecular weight (Mn) of 1000 or more as measured by gel permeation chromatography (GPC) and has film-forming properties, and examples of such polymeric compounds include (meth)acrylic resins, ion-conductive polymeric compounds, polyurethane resins, polyvinyl alcohol, and polyesters. These may be used alone or in combination of two or more. Among these, (meth)acrylic resins are preferred from the viewpoints of maintaining smoothness and forming a film.

[0083] ((Meth)acrylic resin) The (meth)acrylic resin is a polymer made of polymerizable monomers including acrylic and methacrylic monomers. These may be homopolymers or copolymers, or copolymers with polymerizable monomers other than acrylic and methacrylic monomers. The (meth)acrylic polymer is a polymer having a structural unit derived from (meth)acrylic acid or (meth)acrylic acid alkyl esters. The (meth)acrylic polymer may be at least one polymer selected from (meth)acrylic acid and (meth)acrylic acid alkyl esters, or may be a copolymer of at least one selected from these and at least one monomer other than these, such as styrene or a styrene derivative, or a monomer containing a hydroxyl group. In addition, the (meth)acrylic resin may be a copolymer of the polymer with another polymer (e.g., polyester, polyurethane, etc.), such as a block copolymer or a graft copolymer. For example, the (meth)acrylic resin may be a (meth)acrylic-modified polyester resin or a (meth)acrylic-modified polyurethane resin. It may also be a polymer (or a mixture of polymers in some cases) obtained by polymerizing a polymerizable monomer in a polyester solution or polyester dispersion, or a polymer (or a mixture of polymers in some cases) obtained by polymerizing a polymerizable monomer in a polyurethane solution or polyurethane dispersion. The above-mentioned polyesters and polyurethanes used in the (meth)acrylic resins can be appropriately selected from those exemplified as polyesters and polyurethanes used in the resins described later. The (meth)acrylic resin may also contain a hydroxy group or an amino group in order to further improve the adhesion to the polyester film.

[0084] The polymerizable monomer is not particularly limited, but examples thereof include carboxy group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and salts thereof; hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyfumarate, and monobutylhydroxyitaconate; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate. alkyl (meth)acrylic acid esters; nitrogen-containing monomers such as (meth)acrylamide, diacetone acrylamide, or (meth)acrylonitrile; nitrogen-containing monomers containing a hydroxyl group, such as N-methylol (meth)acrylamide; styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and vinyl toluene; 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.

[0085] Among the above (meth)acrylic resins, a polymer obtained by polymerizing a polymerizable monomer including an acrylic or methacrylic monomer is preferred, and the polymerizable monomer more preferably includes an alkyl (meth)acrylic acid ester. In addition, the coating liquid including the (meth)acrylic resin is preferably diluted with a solvent to obtain a coating liquid, and the solvent is preferably water as the main solvent (50 mass% or more). From this viewpoint, the acrylic resin is also preferably a polymer obtained by polymerizing a polymerizable monomer including an alkyl (meth)acrylic acid ester and a hydrophilic group-containing monomer such as a monomer containing a hydroxyl group or a monomer containing a carboxyl group. In addition, the (meth)acrylic resin may be, for example, an emulsion polymer obtained by polymerizing a polymerizable monomer in the presence of a surfactant.

[0086] (Ion-conductive polymer compound) The ionically conductive polymer compound is a polymer compound containing an ionically conductive functional group, and examples of such polymer compounds include ammonium group-containing compounds, polyether compounds, sulfonic acid compounds, betaine compounds, etc. Among these, ammonium group-containing compounds are preferred from the viewpoints of maintaining smoothness and forming a coating film.

[0087] The ammonium group-containing compound means a compound having an ammonium group in the molecule, and is preferably a polymeric compound having an ammonium group. For example, a polymer containing an ammonium group and a monomer having an unsaturated double bond as a component can be used.

[0088] Specific examples of such polymers include polymers having a repeating unit that is a component represented by the following formula (1): These may be homopolymers or copolymers, or may be copolymerized with a plurality of other components.

[0089] [ka]

[0090] In the above formula (1), R 1 , R 2 are each independently a hydrogen atom, an alkyl group, a phenyl group, or the like, and these alkyl groups and phenyl groups may be substituted with the groups shown below. Examples of the substitutable groups include a hydroxyl group, an amide group, an ester group, an alkoxy group, a phenoxy group, a naphthoxy group, a thioalkoxy group, a thiophenoxy group, a cycloalkyl group, a trialkylammonium alkyl group, a cyano group, and halogens. 1 and R 2 may be chemically bonded, for example, -(CH2) m -(m = an integer of 2 to 5), -CH(CH3)CH(CH3)-, -CH=CH-CH=CH-, -CH=CH-CH=N-, -CH=CH-N=C-, -CH2OCH2-, -(CH2)2O(CH2)2- and the like.

[0091] X in the above formula (1)- is, for example, a halogen ion, a sulfonate, a phosphate, a nitrate, an alkylsulfonate, a carboxylate, and the like.

[0092] Among the above-mentioned polymers, i.e., polymers containing a monomer having an ammonium group and an unsaturated double bond as a component, from the viewpoint of improving film-forming properties and obtaining a stable coating, the polymers may be copolymerized with other monomers. Examples of other monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate; and acrylamides such as n-methylolacrylamide.

[0093] The number average molecular weight of the ammonium group-containing compound is preferably 1000 to 500000, more preferably 2000 to 350000, even more preferably 5000 to 200000, particularly preferably 10000 to 100000, and especially preferably 10000 to 80000. By making the molecular weight 1000 or more, it is possible to prevent the strength of the coating film from being weakened, and it is easy to improve the heat resistance stability. In addition, by making the molecular weight 500000 or less, it is possible to prevent the viscosity of the coating liquid from being increased, and it is easy to improve the handling property and the coating property.

[0094] (Polyurethane resin) The polyurethane resin is a polymeric compound having a urethane bond in the molecule, and is preferably water-dispersible or water-soluble. In order to impart water-dispersibility or water-solubility, it is preferable to introduce a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a sulfonyl group, a phosphoric acid group, or an ether group into the polyurethane resin. Among the above hydrophilic groups, a carboxyl group or a sulfonic acid group is preferable from the viewpoint of adhesion to a polyester film.

[0095] The polyurethane resin is obtained by a conventional method, for example, by the reaction of a hydroxyl group-containing compound with an isocyanate. As the hydroxyl group-containing compound used as a raw material, polyol is preferably used, for example, polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

[0096] Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

[0097] Examples of the polyester polyols include those obtained from polyvalent carboxylic acids or their acid anhydrides and polyhydric alcohols. Examples of the polyvalent carboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, and isophthalic acid. Examples of the 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 ,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamines, lactonediols, and the like.

[0098] Examples of the polycarbonate-based polyols include polycarbonate diols obtained by dealcoholization reaction of polyhydric alcohols with dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, etc., and specifically, poly(1,6-hexylene) carbonate, poly(3-methyl-1,5-pentylene) carbonate, etc.

[0099] Examples of polyisocyanate compounds used to obtain polyurethane resins include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidenedicyclohexyl diisocyanate.

[0100] A chain extender may be used when synthesizing the polyurethane resin. The chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group, and generally, a chain extender having two hydroxyl groups or two amino groups can be mainly used.

[0101] Examples of chain extenders having two hydroxyl groups include glycols such as aliphatic glycols such as ethylene glycol, propylene glycol, and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; and ester glycols such as neopentyl glycol hydroxypivalate.

[0102] 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.

[0103] (Polyvinyl alcohol) Polyvinyl alcohol is a compound having a polyvinyl alcohol moiety, and for example, conventionally known polyvinyl alcohols can be used, including modified compounds in which polyvinyl alcohol is partially acetalized or butyralized. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably in the range of 300 to 40,000. When the degree of polymerization is 100 or more, the water resistance of the resin layer is easily improved. In addition, the degree of saponification of polyvinyl alcohol is not particularly limited, but a polyvinyl acetate saponification product having a degree of saponification of 70 mol % or more, 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 practically used.

[0104] The content of the resin in the resin layer is preferably 10 to 99 mass%, more preferably 20 to 95 mass%, even more preferably 30 to 90 mass%, particularly preferably 35 to 88 mass%, and especially preferably 40 to 86 mass%, relative to the total mass of the resin layer (non-volatile components).

[0105] [Crosslinking agent] The crosslinking agent is not particularly limited, and a conventionally known crosslinking agent can be used. Examples of the crosslinking agent include melamine compounds, oxazoline compounds, epoxy compounds, carbodiimide compounds, isocyanate compounds, and silane coupling compounds. Among them, melamine compounds and oxazoline compounds are preferred, and melamine compounds are more preferred. These may be used alone or in combination of two or more.

[0106] (Melamine compounds) The melamine compound is a compound having a melamine skeleton in the compound, and examples thereof include alkylolated melamine derivatives, compounds obtained by reacting an alkylolated melamine derivative with an alcohol to partially or completely etherify the compound, and mixtures thereof. Examples of alkylolation include methylolation, ethylolation, isopropylolation, n-butyrolation, isobutyrolation, etc. Among these, methylolation is preferred from the viewpoint of reactivity. As the alcohol used for etherification, methanol, ethanol, isopropanol, n-butanol, isobutanol, etc. are preferably used, and among these, methanol is more preferred. The melamine compound may be either a monomer or a dimer or higher polymer, or a mixture of these may be used. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be further used to increase the reactivity of the melamine compound.

[0107] (Oxazoline compounds) The oxazoline compound is a compound having an oxazoline group in the molecule, and in particular, a polymer containing an oxazoline group is preferred, and can be obtained by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition polymerizable oxazoline group-containing monomer 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 suitable because it is easily available industrially. The other monomer is not limited as long as it is a monomer that can be copolymerized with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (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, styrenesulfonic acid, and salts thereof (sodium salts, potassium salts, ammonium salts, tertiary amine salts, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylic acid esters such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salts, potassium salts, ammonium salts, tertiary amine salts, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; ) 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 alone or in combination of two or more. The oxazoline compound may have a polyalkylene oxide chain such as a polyethylene oxide chain, and for example, a (meth)acrylate having a polyalkylene oxide chain may be used as another monomer. From the viewpoint of improving adhesion to polyester film, 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.

[0108] (Epoxy compounds) The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. with a hydroxyl group or an amino group, polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc. Among these, polyepoxy compounds are preferred from the viewpoint of better adhesion of polyester films, etc.

[0109] Examples of polyepoxy compounds include sorbitol polyglycidyl ether, 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, and examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylamino)cyclohexane, and the like.

[0110] (Carbodiimide compounds) A carbodiimide compound is a compound having a carbodiimide structure, i.e., a compound having one or more carbodiimide structures in its molecule. From the viewpoint of better adhesion of polyester films, etc., a polycarbodiimide compound having two or more carbodiimide structures in its molecule is more preferred.

[0111] Carbodiimide compounds can be synthesized by conventionally known techniques, and generally, condensation reaction of diisocyanate compounds is used. The diisocyanate compound is not particularly limited, and both aromatic and aliphatic compounds can be used. Specific examples include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate.

[0112] The content of carbodiimide groups contained in the carbodiimide compound is usually in the range of 100 to 1000, preferably 250 to 800, and more preferably 300 to 700, in terms of carbodiimide equivalent (the weight [g] of the carbodiimide compound required to provide 1 mol of carbodiimide groups).

[0113] Furthermore, within the scope of the present invention, in order to improve the water solubility or water dispersibility of the polycarbodiimide compound, a surfactant may be added, or a hydrophilic monomer such as a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, or a hydroxyalkylsulfonate may be added.

[0114] (Isocyanate compounds) The isocyanate compound is a compound having an isocyanate or an isocyanate derivative structure, such as a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethyl xylylene 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, methylene bis(4-cyclohexyl isocyanate), and isopropylidenedicyclohexyl diisocyanate. Further, examples of the polymers and derivatives of these isocyanates include biuretized products, isocyanurate products, uretdione products, carbodiimide modified products, etc. These may be used alone or in combination of two or more kinds.

[0115] When used in the form of blocked isocyanate, examples of the blocking agent 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 isobutanoyl methyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; lactam compounds such as ε-caprolactam and δ-valerolactam; amine compounds such as diphenylaniline, aniline, and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; and oxime compounds such as formaldehyde oxime, acetaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used alone or in combination of two or more.

[0116] The isocyanate compound may be used alone or as a mixture or bond with various polymers. In terms of improving the dispersibility and crosslinking property of the isocyanate compound, it is preferable to use a mixture or bond with a polyester resin or a polyurethane resin.

[0117] (Silane coupling compound) A silane coupling compound is an organosilicon compound that has an organic functional group and a hydrolyzable group such as an alkoxy group in one molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 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 of the compounds include 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, which are amino group-containing compounds; tris(trimethoxysilylpropyl)isocyanurate, tris(triethoxysilylpropyl)isocyanurate, and other isocyanurate group-containing compounds; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and other mercapto group-containing compounds. These compounds may be used alone or in combination of two or more.

[0118] The content of the above-mentioned crosslinking agent in the resin layer is preferably 0.1 to 90 mass %, more preferably 1 to 70 mass %, even more preferably 3 to 50 mass %, particularly preferably 5 to 30 mass %, and especially preferably 8 to 25 mass %, relative to the total mass of the resin layer (non-volatile components).

[0119] [solvent] The solvent is not particularly limited, and either water or an organic solvent can be used. From the viewpoint of environmental protection, it is preferable to prepare an aqueous coating liquid using water as the main solvent (50% by mass or more of the total solvent). The water content is preferably 60% by mass or more, more preferably 70% by mass or more. The aqueous coating liquid may contain a small amount of an organic solvent. The specific amount of the organic solvent is preferably equal to or less than the amount of water on a mass basis, and is, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less of the solvent. Examples of organic solvents used in combination with water include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These may be used alone or in combination of two or more.

[0120] In addition, when only an organic solvent is used as the above-mentioned solvent, examples of such an organic solvent include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, heptane, isooctane, esters such as ethyl acetate, butyl acetate, ketones such as ethyl methyl ketone, isobutyl methyl ketone, alcohols such as ethanol, 2-propanol, ethers such as diisopropyl ether, dibutyl ether, etc. These may be used alone or in combination of two or more kinds.

[0121] The resin composition forming the resin layer is prepared to a predetermined solid content concentration using the above-mentioned components. The solid content concentration (non-volatile component concentration) of the resin composition is preferably 0.1 to 99 mass%, more preferably 0.5 to 50 mass%, and even more preferably 1 to 30 mass%.

[0122] When resin layers are provided on both sides of the film, it is preferable that the resin compositions (non-volatile components) forming each resin layer are the same or substantially the same, although not limited thereto. Note that "substantially the same" implies that the content of each component of the non-volatile components constituting each resin composition is within the range of ±5% by mass, and when different components are contained, the total content of the different components is less than 5% by mass. It is more preferable that the content of each component of the non-volatile components constituting each resin composition is within the range of ±3% by mass, and even more preferable that it is within the range of ±1% by mass. When different components are contained, it is more preferable that the total content of the different components is less than 3% by mass, and even more preferable that it is less than 1% by mass.

[0123] [Method of forming resin layer] The method for forming the resin layer is not particularly limited, and a conventionally known method can be appropriately used, but it is preferable to form the resin layer by applying the above-mentioned resin composition to a polyester film and, if necessary, performing treatment such as drying, curing, heat treatment, etc. The application method is not particularly limited, and for example, a conventionally known application method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used.

[0124] The above-mentioned formation method includes in-line coating carried out within the polyester film production process, and off-line coating in which a polyester film that has already been produced is coated outside the system, with in-line coating being preferred.

[0125] In-line coating is a method in which a polyester or resin composition forming a polyester film is melt-extruded and stretched, and then coated at any stage before being heat-set and wound up. Usually, coating is performed on any of the unstretched sheets obtained by melting and quenching, stretched uniaxially stretched films, biaxially stretched films before heat-set, and films after heat-set and before being wound up, but it is preferable to coat the stretched uniaxially stretched films.

[0126] For example, in the case of sequential biaxial stretching, a method is preferred in which a uniaxially stretched film stretched in the longitudinal direction (MD) is coated and then stretched in the transverse direction (TD). This method has the advantage of being able to simultaneously form the film and the resin layer, and is advantageous in terms of production costs. In addition, since stretching is performed after coating, the thickness of the resin layer can be changed by the stretching ratio, and it is easier to control the arithmetic mean height Sa, etc., within a suitable range than offline coating.

[0127] The amount of the non-volatile component in the coating is not limited to the following, but is preferably 0.001 to 1 g / m 2 is preferable, and more preferably 0.005 to 0.7 g / m 2 , and even more preferably 0.01 to 0.5 g / m 2 The coating amount is based on the non-volatile component value excluding volatile components such as solvents.

[0128] When resin layers are formed on both sides of the present film to form the outermost layers, the ratio of the coating amount of non-volatile components for forming one resin layer (CT1) to the coating amount of non-volatile components for forming the other resin layer (CT2) (CT2 / CT1: CT2≧CT1) is preferably 1 or more and 5 or less, more preferably 1 or more and 3 or less, even more preferably 1 or more and 2 or less, and particularly preferably 1 or more and 1.5 or less, from the viewpoint of significantly achieving the effects of the present invention.

[0129] The coating amount of the non-volatile component is the coating amount in the present film, for example, the coating amount after drying and stretching in the case where drying and stretching are performed. The coating amount of the non-volatile component is expressed as a mass per unit area, and can also be said to be an index of the thickness of the resin layer.

[0130] <Manufacturing method of this film> Next, a method for producing the present film will be specifically described, but the method is not limited to the following method. For example, when producing a biaxially stretched film, a method is preferred in which the dried polyester pellets described above are extruded as a molten sheet from a die using a melt extrusion device such as an extruder, and then cooled and solidified with a cooling roll such as a rotating cooling drum to obtain an unstretched sheet. Here, the cooling is carried out, for example, to a temperature below the glass transition point of the polymer to obtain a substantially amorphous unoriented sheet (unstretched sheet). In addition, in order to improve the planarity of the sheet, it is preferable to increase the adhesion between the sheet and the cooling roll, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably adopted.

[0131] Next, the obtained unstretched sheet is stretched in biaxial directions. In this case, the unstretched sheet is first stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times.

[0132] Then, the film is stretched in a direction perpendicular to the first-stage stretching direction. In this case, the stretching temperature is usually 70 to 170° C., preferably 75 to 160° C., and the stretch ratio is usually 3 to 7 times, preferably 3.5 to 6 times.

[0133] Then, the film is heat-treated under tension or relaxation of 30% or less at a temperature of usually 180 to 270°C, preferably 190 to 260°C, to obtain a biaxially stretched film. This heat treatment is also called a heat setting step. The heat treatment may be performed in two or more steps with different temperatures. After the heat treatment, the film may be cooled in a cooling zone. The cooling temperature is preferably higher than the glass transition temperature (Tg) of the polyester constituting the film, and more specifically, is preferably in the range of 100 to 160° C. This cooling may be performed in two or more steps at different temperatures. In the above stretching, a method of stretching in one direction in two or more stages can be adopted. In that case, it is preferable to perform the stretching so that the final stretch ratios in both directions are each within the above range.

[0134] The present film can also be produced by a simultaneous biaxial stretching method, which involves simultaneously stretching and orienting the unstretched sheet in the machine direction (longitudinal direction) and width direction (transverse direction) under temperature control usually at 70 to 120° C., preferably 80 to 110° C., and 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 ratio. Then, the film is subsequently heat-treated under tension or under relaxation of 30% or less at a temperature of 170 to 250° C. to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching device employing the above-mentioned stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear drive method can be employed.

[0135] Furthermore, an example of a preferred method for producing the present film includes, for example, a production method having a first stretching step, a second stretching step, and a coating step of forming a resin layer between the first stretching step and the second stretching step. More specifically, a manufacturing method having an extrusion step of extruding an unstretched sheet, a primary stretching step of stretching the sheet in the MD direction, a secondary stretching step of stretching the stretched sheet obtained in the primary stretching step in the TD direction, and a coating step of forming a resin layer on the stretched sheet obtained in the primary stretching step between the primary stretching step and the secondary stretching step is preferred, and among these, a manufacturing method in which the coating step is an in-line coating step is more preferred.

[0136] In the above preferred embodiment, from the viewpoint of controlling the static friction coefficient μs and the arithmetic mean height Sa within suitable ranges, it is preferable to set the various conditions within the following ranges. That is, the extrusion temperature during melt extrusion from the die is preferably 250 to 325°C, more preferably 270 to 310°C. The temperature of the cooling roll is preferably 22 to 65°C, more preferably 24 to 55°C. In order to improve the flatness of the sheet, it is preferable to employ an electrostatic application adhesion method or a liquid application adhesion method.

[0137] The temperature condition in the first stretching step is preferably 80 to 130° C. The stretch ratio in the first stretching step is preferably 2.8 to 5 times, and further more preferably 2.9 to 4 times. The temperature condition in the second stretching step is preferably 90 to 140° C. The stretch ratio in the second stretching step is preferably 3 to 6 times.

[0138] The preheating temperature condition after the first stretching step and before the second stretching step is, for example, 75 to 100°C, and preferably 80 to 95°C. After the secondary stretching step, it is preferable to carry out a heat treatment at a predetermined temperature under tension or relaxation of 30% or less. The heat treatment temperature is, for example, 180 to 250°C, more preferably 200 to 230°C.

[0139] The cooling temperature after the heat treatment step is preferably, for example, 100 to 160° C. In particular, it is preferable to perform a cooling treatment at 100 to 160° C. under relaxation of, for example, 1.0 to 2.5% in the width direction, preferably under relaxation of 1.2 to 2.2% in the width direction.

[0140] <<Film foil>> The film foil for battery current collector of the present invention (hereinafter also referred to as "the present film foil") has a metal layer on the surface of the present film. The metal layer may be provided on at least one side of the present film, but it is more preferable to provide the metal layer on both sides. More specifically, as shown in FIG. 1, the present film foil 1 preferably comprises a polyester film 11 and metal layers 12 on both sides thereof.

[0141] <Metal layer> The metal forming the metal layer is not particularly limited as long as it is a metal having electrical conductivity, and examples thereof include aluminum, nickel, gold, silver, copper, cadmium, titanium, and the like. Among them, the metal layer is preferably made of copper or aluminum, from the viewpoint of being widely used, for example, as an electrode collector (positive electrode collector) used in a positive electrode of a lithium ion battery or an electrode collector (negative electrode collector) used in a negative electrode. Here, "made of" means that it contains copper or aluminum as a main component. The metal layer may contain elements other than the metal having electrical conductivity.

[0142] The metal layer is preferably provided by any one of vapor deposition, plating, and sputtering, and more specifically, a conventionally known method such as a vacuum vapor deposition method, an electroplating method, or a sputtering method can be used.

[0143] The thickness of the metal layer is usually 0.5 to 5 μm, preferably 0.7 to 3 μm, and more preferably 1 to 2 μm.

[0144] The metal layer is preferably a two-layer structure, and an example of such a form is a two-layer structure of metal layer 12, which is a metal layer 21 provided on the present film by vapor deposition or sputtering, and a metal layer 22 provided on metal layer 21 by plating (see FIG. 2). In such a case, the present film foil 1 has, on both sides of polyester film 11, metal layer 21 provided by vapor deposition or sputtering, and metal layer 22 provided by plating, in that order (see FIG. 3). By using such a two-layer structure, it is possible to make the foil thinner and lighter than conventional metal foils while maintaining the same performance, and it is also possible to reduce costs compared to conventional metal foils.

[0145] <<Battery current collector>> The battery current collector of the present invention (hereinafter also referred to as "the current collector") preferably comprises an electrode layer on a metal layer. The electrode layer is formed by laminating a conventionally known electrode agent on the surface of the metal layer, and can be used as an electrode for a battery. Furthermore, by using the current collector, a battery such as a lithium ion battery can be produced by a conventionally known method.

[0146] <<Application>> The present film and the present film foil can be used for battery current collectors, such as storage batteries, secondary batteries, and lithium ion batteries, and are preferably used for lithium ion batteries, and particularly preferably used for lithium ion secondary batteries. Therefore, the present current collector preferably has a configuration exemplified by electrode layer (positive electrode) / metal layer / polyester film / metal layer / electrode layer (positive electrode) for a positive electrode current collector, and electrode layer (negative electrode) / metal layer / polyester film / metal layer / electrode layer (negative electrode) for a negative electrode current collector.

[0147] In the manufacturing process of the film foil for battery current collectors, the present film can effectively suppress the occurrence of slippage, shifting, twisting, wrinkles, etc. on the transport roll during film transport, and has good adhesion to the cooling roll, so that the balance of the air escape behavior between the cooling rolls and the cooling efficiency is excellent. Moreover, since the thermal energy from deposition, sputtering, etc. is applied uniformly to both sides of the film, it can contribute to improving the homogeneity of each metal layer formed on both sides of the film, and can contribute to improving the productivity of the film foil for battery current collectors using the polyester film. Furthermore, compared to conventional battery current collectors for lithium-ion batteries that use metal foil, more specifically, electrode layer (positive electrode) / metal layer / electrode layer (positive electrode) or electrode layer (negative electrode) / metal layer / electrode layer (negative electrode), the use of this film contributes to the thinning, weight reduction, and cost reduction, and also makes it possible to stop and prevent runaway reactions caused by short circuits. In particular, because the crystal melting temperature Tm of this film is within a specific range, it is possible to lower the starting temperature of molten insulation during a short circuit, and contribute to stopping and preventing runaway reactions caused by molten insulation at an earlier stage.

[0148] <<Explanation of terms>> In this specification, unless otherwise specified, the term "main component" means a component that has a significant effect on the properties of the material, and the content of the component is usually 50% by weight or more of the entire material, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90 to 100% by mass. In this specification, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". In this specification, when it is written "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably larger than X" or "preferably smaller than Y". In addition, for numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. Furthermore, "X and / or Y (X and Y are optional)" means at least one of X and Y, and means the following three cases: X only, Y only, and X and Y. EXAMPLES

[0149] The present invention will now be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not deviate from the gist of the present invention.

[0150] <Evaluation method> (1) Static friction coefficient (μs) A test piece measuring 15 x 160 mm was cut out from the film before copper deposition, and the static friction coefficient between one side of the test piece and the other side was measured. Specifically, one side of the test piece was kept in contact with the other side for 15 seconds before the start of the test, and then measurements were made in the machine direction (MD) under the following conditions. The sample was conditioned for at least 6 hours before the measurement. Equipment: Parallel movement friction tester (MCS-300) manufactured by Yokohama Systems Research Institute Slider: Total mass 104g (contact area is a square with a side of 12mm) Test speed: 20mm / min ·Temperature: 23℃±2℃ Relative humidity: 50%±10%

[0151] (2) Arithmetic mean height Sa, maximum cross-sectional height St, root mean square height Sq The film before copper deposition was measured using a non-contact surface / layer cross-sectional shape measurement system (VertScan (registered trademark) R550GML) manufactured by Ryoka Systems Co., Ltd. under the conditions of eyepiece magnification 1.0x, objective lens magnification 50x, and measurement area 178μm length × 238μm width, and after fourth-order polynomial surface correction and median filter (3x3) processing, the arithmetic mean height Sa, maximum cross-sectional height St, and root-mean-square height Sq were obtained. The measurement was performed 10 times and the average value was calculated.

[0152] (3) Arithmetic mean roughness Ra, ten-point mean roughness Rz, maximum cross-sectional height Rt The film before copper deposition was measured in the longitudinal direction (MD) of the film using a contact type surface roughness meter (Surf Coder SE3500) manufactured by Kosaka Laboratory under the following conditions: stylus tip radius 0.5 mm, evaluation length 2.5 mm, longitudinal magnification 20,000 times, lateral magnification 20 times, cutoff value 0.08 mm, and measurement speed 0.1 mm / sec, and the arithmetic mean roughness Ra, ten-point mean roughness Rz, and maximum cross-sectional height Rt were obtained. The measurement was performed 12 times, and the average value of 10 points after dividing the maximum and minimum values ​​was used as the measured value.

[0153] (4) Crystal melting temperature Tm The crystal melting temperature (Tm) was measured when the temperature was raised from 20°C to 300°C at a rate of 10°C per minute using a PerkinElmer differential scanning calorimeter (DSC 8500) in accordance with JIS K7121 (2012). The extreme value of the maximum endothermic peak was taken as the crystal melting temperature Tm. The analysis was performed by selecting the corresponding maximum endothermic peak range from "Peak area" in the "Analysis" menu of the built-in software.

[0154] (5) Shrinkage rate A sample film of 1.5 cm x 15 cm was heat-treated for 5 minutes in a hot air oven maintained at a specified temperature (120°C, 150°C, 180°C) in an untensioned state, and the length of the sample film was measured before and after the treatment, and the elasticity was calculated using the following formula. The measurements were taken in both the machine direction (MD) and the width direction (TD) of the film. Shrinkage rate (%) = {(sample length before heat treatment) - (sample length after heat treatment)} ÷ (sample length before heat treatment) × 100

[0155] (6) Surface free energy The contact angle was measured using a Kyowa Interface Science contact angle meter (DMo-501 type) when 1 μL of pure water and methylene iodide were dropped onto a film before copper deposition that had been conditioned for more than 24 hours in an environment of 23°C and 50% RH. The contact angle was measured 60 seconds after each liquid was dropped onto the film. The surface free energy of the film surface was calculated using the Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula using the obtained contact angle and the surface tension component values ​​of each liquid (Table 1).

[0156] [Table 1]

[0157] (7) Curling of vapor-deposited film A vacuum deposition machine (MH59-0133) manufactured by Nippon Vacuum Engineering Co., Ltd. was used to apply a vacuum of 2×10 to one side (side A) of a biaxially oriented polyester film attached to a 14 cm square mold. -5Copper was evaporated on the other side (side B) under the same conditions as side A. The portion of the obtained vapor-deposited film with copper vapor-deposited on both sides was cut into an 80 mm square, and the degree of curling of the film when the other side (side B) was placed down was visually confirmed and evaluated according to the following criteria. (Evaluation Criteria) ◎: No curl ○: The ends curl slightly △: The ends are clearly curled ×: Large curls

[0158] (8) Intrinsic viscosity (IV) 1 g of polyester from which components incompatible with the polyester had been removed was precisely weighed out, dissolved in 100 mL of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio), and the viscosity was measured at 30 °C using a viscosity measuring device "VMS-022UPC·F10" (manufactured by Rigosha).

[0159] <Ingredients used> Raw material P1: homopolyethylene terephthalate (intrinsic viscosity = 0.65 dL / g) Raw material P2: Dicarboxylic acid component (a-1): 2,6-naphthalenedicarboxylic acid = 100 mol%, diol component (a-2): ethylene glycol = 95 mol%, bisphenol A-ethylene oxide adduct = 5 mol% polyethylene naphthalate copolymer (A) (intrinsic viscosity = 0.62 dL / g)

[0160] <Coating solution used> Coating solutions C1 to C6 shown in Table 2 were prepared using the following raw materials. <Component I> Aqueous dispersion of acrylic resin polymerized with the following composition Emulsion polymer of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylolacrylamide / acrylic acid = 65 / 21 / 10 / 2 / 2 (mass%) (emulsifier: anionic surfactant)

[0161] <Component II> A polymer compound with a number average molecular weight of 51,000, whose constituent unit is the methanesulfonate salt of 2-(dimethylammonium)ethyl methacrylate.

[0162] <Component III> Melamine compound: Hexamethoxymethylolmelamine

[0163] <Ingredient IVa> Silica particles (spherical) with an average particle size of 0.5 μm

[0164] <Component IVb> Silica particles (spherical) with an average particle size of 0.06 μm

[0165] [Table 2]

[0166] Example 1 Polyester (P1) was fed into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.09 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C1 in the same container so that the coating amount (after drying and stretching) was 0.09 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.2 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 2.0% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0167] Example 2 Polyester (P1) was fed into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the machine direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating solution C6 having the composition shown in Table 2 above was prepared, and the coating solution C6 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.08 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C6 in the same container so that the coating amount (after drying and stretching) was 0.08 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.7 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 1.9% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0168] Example 3 Polyester (P2) was fed into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.5 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating solution C3 having the composition shown in Table 2 above was prepared, and the coating solution C3 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.1 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C3 in the same container so that the coating amount (after drying and stretching) was 0.1 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.2 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 1.7% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0169] Example 4 Polyester (P2) was fed into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C4 having the composition shown in Table 2 above was prepared, and the coating liquid C4 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.1 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C4 in the same container so that the coating amount (after drying and stretching) was 0.1 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.2 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 1.7% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0170] Example 5 Polyester (P2) was fed into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.09 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C1 in the same container so that the coating amount (after drying and stretching) was 0.09 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.5 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 1.2% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0171] Example 6 Polyester (P2) was fed into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C2 having the composition shown in Table 2 above was prepared, and the coating liquid C2 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.1 g / m 2 One side (side B) of the uniaxially stretched film was coated with the coating solution C2 in the same container so that the coating amount (after drying and stretching) was 0.1 g / m on the opposite side (side A). 2 The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.2 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 1.7% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0172] Comparative Example 1 Polyester (P1) was fed into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating solution C5 having the composition shown in Table 2 above was prepared, and the coating solution C5 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.1 g / m 2 The coating was applied to one side (side B) of a uniaxially stretched film so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.2 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 2.0% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0173] Comparative Example 2 Polyester (P1) was fed into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.09 g / m 2 The coating was applied to one side (side B) of a uniaxially stretched film so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.2 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 2.0% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0174] Comparative Example 3 Polyester (P2) was fed into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then the coating amount (after drying and stretching) was quickly adjusted to 0.09 g / m 2 The coating was applied to one side (side B) of a uniaxially stretched film so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.2 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 2.0% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0175] Comparative Example 4 Polyester (P1) was put into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then quickly dispensed into two different containers and left to stand for about 1 hour. The coating liquid C1 in one container was stirred, and then quickly dispensed into two different containers until the coating amount (after drying and stretching) was 0.09 g / m 2 The coating solution C1 in the other container was applied to one side (side B) of the uniaxially stretched film so that the coating amount (after drying and stretching) was 0.09 g / m 2 The coating was applied to the opposite surface (side A) so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.7 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 1.9% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0176] Comparative Example 5 Polyester (P1) was fed into a twin-screw extruder, extruded at 280°C, and cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched three times in the longitudinal direction (MD) at 86°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then quickly dispensed into two different containers and left to stand for about 1 hour. The coating liquid C1 in one container was mixed with the coating liquid C1 so that the coating amount (after drying and stretching) was 0.09 g / m 2 The coating solution C1 in the other container was then stirred and the coating amount (after drying and stretching) was quickly adjusted to 0.09 g / m 2The coating was applied to the opposite side (side A) so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 90°C, and stretched 4.7 times in the transverse direction (TD) at 105°C. After stretching, the film was heat-set at 220°C and cooled to 140°C under 1.4% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0177] Comparative Example 6 Polyester (P2) was put into a twin-screw extruder, extruded at 300°C, and cooled and solidified on a cooling roll set at 50°C using an electrostatic adhesion method to obtain an unstretched sheet. The unstretched sheet obtained was then stretched 3.8 times in the longitudinal direction (MD) at 125°C using a roll stretching machine to obtain a uniaxially stretched film. A container filled with coating liquid C1 having the composition shown in Table 2 above was prepared, and the coating liquid C1 in the container was stirred, and then quickly dispensed into two different containers and left to stand for about 1 hour. The coating liquid C1 in one container was stirred, and then quickly dispensed into two different containers until the coating amount (after drying and stretching) was 0.09 g / m 2 The coating solution C1 in the other container was applied to one side (side B) of the uniaxially stretched film so that the coating amount (after drying and stretching) was 0.09 g / m 2 The coating was applied to the opposite surface (side A) so that the coating was as follows: The film was then introduced into a tenter stretching machine, preheated in the tenter at 120°C, and stretched 4.2 times in the transverse direction (TD) at 130°C. After stretching, the film was heat-set at 225°C and cooled to 140°C under 1.7% relaxation in the transverse direction to obtain a biaxially stretched polyester film with a thickness of 4 μm.

[0178] The static friction coefficient, surface properties, crystal melting temperature, shrinkage rate, surface free energy, and curl of the deposited film of each of the films obtained above were measured or evaluated according to the methods described above. The results are shown in Table 3. In addition, the numerical values ​​of the arithmetic mean height Sa, the root mean square height Sq, and the maximum cross-sectional height St in Table 3 are values ​​obtained by rounding off the measured values ​​to the third decimal place, the arithmetic mean roughness Ra, the ten-point mean roughness Rz, and the maximum cross-sectional height Rt are values ​​obtained by rounding off the measured values ​​to the fifth decimal place, and each ratio is a value obtained by rounding off the measured value ratio to the second decimal place. In addition, the crystal melting temperature Tm is a value obtained by rounding off the measured value to the first decimal place, and the shrinkage ratio is a value obtained by rounding off the measured value to the third decimal place. In addition, the surface free energy is a value calculated by the above theoretical formula and rounded off to the third decimal place, and the ratio is a value obtained by rounding off the measured value ratio to the second decimal place.

[0179] [Table 3]

[0180] As shown in Table 3, the static friction coefficient μs and the ratio of arithmetic mean height Sa (SaB / SaA) of the polyester films of Examples 1 to 6 are each controlled within a specific range. Therefore, the polyester films of the Examples can effectively suppress slippage, shifting, twisting, wrinkles, and the like on the transport rolls in the manufacturing process of the film foil for battery current collectors, and also have good adhesion to the cooling rolls, resulting in an excellent balance of the air release behavior between the cooling rolls and the cooling efficiency, and further, it can be seen that thermal energy from deposition, sputtering, and the like is applied uniformly to both sides of the film.

[0181] In particular, for example, the static friction coefficient μs and the ratio of the arithmetic mean height Sa (SaB / SaA) of the polyester films of Examples 1 to 6 are each controlled within a specific range. In addition, the absolute value and ratio of the difference in surface free energy are also controlled within a specific range. Therefore, for example, it is clearly understood that the thermal energy due to deposition, sputtering, etc. is applied uniformly to both sides of the film. Specifically, by controlling the static friction coefficient μs, the ratio of the arithmetic mean height Sa (SaB / SaA), and the absolute value and ratio of the difference in surface free energy within a specific range, the homogeneity and adhesion of the deposited metal layer are further improved, and for example, curling of the deposited film can be effectively suppressed.

[0182] On the other hand, the polyester films of Comparative Examples 1 to 6 have arithmetic mean height Sa ratios (SaB / SaA) that exceed the upper limit value specified in the present invention, and therefore, for example, it is difficult for thermal energy from deposition, sputtering, etc. to be applied uniformly to both sides of the film, and it is found that, for example, curling of the film after deposition cannot be effectively suppressed.

[0183] Specifically, for example, the polyester film of the comparative example has a ratio of arithmetic mean heights Sa (SaB / SaA) exceeding the upper limit specified in the present invention, which shows that, for example, thermal energy due to deposition, sputtering, etc. is applied non-uniformly to both sides of the film, etc. Specifically, because the ratio of arithmetic mean heights Sa (SaB / SaA) is large, for example, curling of the deposited film cannot be effectively suppressed. [Industrial Applicability]

[0184] The polyester film of the present invention can be used as a battery current collector, and is suitable for use as a battery current collector for storage batteries, secondary batteries, lithium ion batteries, etc., and is particularly suitable for use in lithium ion secondary batteries. [Explanation of symbols]

[0185] 1 Film foil 11 Polyester film 12 metal layer 21 Metal layer (evaporation or sputtering) 22 Metal layer (plating)

Claims

1. A polyester film for use in a battery current collector, which satisfies the following (1) and (2): (1) The static friction coefficient μs measured by overlapping one surface, side A, with the other surface, side B, is 0.26 or more and 0.75 or less. (2) The ratio (SaB / SaA) of the arithmetic mean height Sa (SaA) of one surface, side A, to the arithmetic mean height Sa (SaB) of the other surface, side B, is 1 or more and less than 1.2 (with the proviso that SaB≧SaA).

2. The polyester film for a battery current collector according to claim 1 , further satisfying the following (3): (3) The ratio (RaB / RaA) of the arithmetic mean roughness Ra (RaA) of side A, which is one surface, to the arithmetic mean roughness Ra (RaB) of the other surface, side B, is 1 or more and less than 1.2 (with the proviso that RaB≧RaA).

3. The polyester film for a battery current collector according to claim 1 or 2, which further satisfies the following (4): (4) The ratio (RzB / RzA) of the ten-point average roughness Rz (RzA) of side A, which is one surface, to the ten-point average roughness Rz (RzB) of the other surface, side B, is 1 or more and less than 1.5 (with the proviso that RzB≧RzA).

4. The polyester film for a battery current collector according to claim 1 or 2, which further satisfies the following (5): (5) The surface free energy (γ SV A) and the surface free energy (γ SV The absolute value of the difference from B) is 5.5 mN / m or less.

5. The polyester film for a battery current collector according to claim 1 or 2, which further satisfies the following (6): (6) The surface free energy (γ SV A) and the surface free energy (γ SV B) (γ SV B / γ SV A) is 1.15 or less (however, γ SV B ≧ γ SV A).

6. 3. The polyester film for a battery current collector according to claim 1, which has a crystalline melting temperature (Tm) of 258°C or lower as determined by differential scanning calorimetry (DSC).

7. 3. The polyester film for a battery current collector according to claim 1, wherein an arithmetic mean height Sa (SaA) of one surface, side A, and an arithmetic mean height Sa (SaB) of the other surface, side B, are 15 nm or less.

8. The surface free energy (γ SV A) and the other surface, surface B, have a surface free energy (γ SV 3. The polyester film for a battery current collector according to claim 1, wherein B) is 20 mN / m or more.

9. 3. The polyester film for a battery current collector according to claim 1, which has a shrinkage rate of 1% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 120°C for 5 minutes.

10. 3. The polyester film for a battery current collector according to claim 1, which has a shrinkage rate of 2% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 150°C for 5 minutes.

11. 3. The polyester film for a battery current collector according to claim 1, which has a shrinkage rate of 4% or less in both the machine direction (MD) and the transverse direction (TD) when heat-treated at 180°C for 5 minutes.

12. The polyester film for a battery current collector according to claim 1 or 2, comprising a polyethylene naphthalate-based copolymer (A).

13. The polyester film for a battery current collector according to claim 12 , wherein the content of the polyethylene naphthalate-based copolymer (A) in the polyester film is 50% by mass or more.

14. The polyethylene naphthalate copolymer (A) contains naphthalenedicarboxylic acid as the dicarboxylic acid component (a-1) and a bisphenol-ethylene oxide adduct and ethylene glycol as the diol component (a-2). The polyester film for a battery current collector according to claim 12.

15. The polyester film for a battery current collector according to claim 14, wherein the dicarboxylic acid component (a-1) contains 80 mol % or more of naphthalenedicarboxylic acid.

16. The polyester film for a battery current collector according to claim 14, wherein the diol component (a-2) contains 1 mol % or more and 49 mol % or less of a bisphenol-ethylene oxide adduct.

17. 3. The polyester film for a battery current collector according to claim 1, which has a thickness of 1 μm or more and 12 μm or less.

18. The polyester film for a battery current collector according to claim 1 or 2, which has a coating layer.

19. 3. The polyester film for a battery current collector according to claim 1, wherein the battery is a lithium ion battery.

20. A film foil for a battery current collector, comprising the polyester film for a battery current collector according to claim 1 or 2 and a metal layer.

21. The film foil for a battery current collector according to claim 20 , wherein the metal layer is made of copper or aluminum.

22. The film foil for a battery current collector according to claim 20 , wherein the metal layer is provided by any one of vapor deposition, plating, and sputtering.

23. The film foil for a battery current collector according to claim 20, wherein the metal layer has a two-layer structure.

24. 21. The film foil for a battery current collector according to claim 20, wherein the battery is a lithium ion battery.

25. A battery current collector comprising an electrode layer on the metal layer of the film foil for a battery current collector according to claim 20.

26. 26. The battery current collector of claim 25, wherein the battery is a lithium ion battery.

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