Biaxially oriented polypropylene film

Abstract

In the Raman spectrum along the principal orientation axis, 905–935 cm⁻¹ -1 The range and 770-790cm -1 The maximum peak intensity Ic in the range of 800-820 cm -1 A biaxially oriented polypropylene film in which the ratio Ic / Ip of the maximum peak intensity Ip in the range is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T℃ and the storage modulus in the direction perpendicular to the principal orientation axis in the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less. The present invention aims to provide a biaxially oriented polypropylene film that is excellent in processability, quality, and voltage resistance under high-temperature environments, and is suitable for use as a dielectric in film capacitors.

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polypropylene film, which is particularly suitable for use in film capacitor applications. [Background technology]

[0002] In recent years, the majority of electrical equipment has been converted to inverters, and consequently, the demand for smaller and larger capacity film capacitors has become even stronger. In response to this demand, particularly in fields such as automobiles (including electric vehicles and hybrid cars), electric aircraft, solar power generation, and wind power generation, there is a need for further thinning and improved heat resistance of the film, which is the dielectric of film capacitors, in addition to improving the voltage resistance and quality, and maintaining the processability in the fabrication of film capacitor elements.

[0003] For film to be used as a dielectric in film capacitors in the aforementioned field, it is important that the film possesses excellent heat resistance at the ambient temperature (maintaining molecular chain orientation, etc.) and stable electrical performance (withstand voltage, etc.) in a temperature range 10°C to 20°C higher than the ambient temperature. Furthermore, considering future applications in power semiconductors using silicon carbide (SiC), it is said that the ambient temperature for film capacitors will be higher, and it is estimated that the requirements for heat resistance will become even greater.

[0004] Currently, polypropylene film, which has relatively good heat resistance and voltage resistance among polyolefin films, is used as the dielectric for film capacitors. However, as described in Non-Patent Document 1, its upper limit of operating temperature is said to be approximately 110°C. However, due to the above circumstances, there is a need for further improvements in heat resistance and voltage resistance of film capacitors, and film capacitor films are required to have improved dielectric breakdown voltage in high-temperature environments exceeding 110°C. In other words, it has been extremely difficult for conventional polypropylene films to stably maintain voltage resistance in such temperature environments.

[0005] To miniaturize film capacitors and improve their heat resistance, various approaches have been considered, such as thinning the film, using films with high dielectric constants, and using films with glass transition temperatures exceeding the operating temperature range of film capacitors.

[0006] For example, films with improved processability have been proposed by co-extruding and co-stretching when forming laminates of cyclic olefin resins and polypropylene (e.g., Patent Documents 1 and 2). Films with enhanced thermal dimensional stability in high-temperature environments have also been proposed by blending cyclic olefin resins and polypropylene, followed by film formation and biaxial stretching (e.g., Patent Document 3). Furthermore, films with enhanced thermal dimensional stability in high-temperature environments have been proposed by blending polymers having alicyclic structures in their side chains with polypropylene, followed by film formation and biaxial stretching (e.g., Patent Document 4). In addition, films with improved rigidity and room-temperature dielectric strength have been proposed by generating polyvinylcyclohexane, which has nucleating agent properties, during the pre-polymerization stage and adding a small amount to the polypropylene, then biaxially stretching the resulting polypropylene composition (e.g., Patent Documents 5, 6, and 7). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2017 / 022706 [Patent Document 2] Japanese Patent Publication No. 2018-034510 [Patent Document 3] Special Publication No. 2020-521867 [Patent Document 4] International Publication No. 2024 / 228352 [Patent Document 5] Japanese Patent Publication No. 2022-514249 [Patent Document 6] Japanese Patent Application Publication No. 02-135245 [Patent Document 7] Japanese Patent Application Publication No. 62-122009

Non-Patent Literature

[0008]

Non-Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, since the base layer of the film in Patent Document 1 has a laminated structure composed of a cyclic olefin resin alone, it is difficult to increase the stretching stress by increasing the stretching magnification or lowering the stretching temperature, and it is difficult to form a uniform film structure. Defects with low breakdown voltage increase at room temperature or in a high-temperature environment, and it is hard to say that the quality and performance as a film capacitor are sufficient. The film in Patent Document 2 also has a base layer of a laminated structure composed of a cyclic olefin resin, and an elastomer is contained to improve the stretchability and increase the area stretching magnification. However, regarding the reduction of defects with low breakdown voltage in a high-temperature environment, it is not satisfactory, and it is hard to say that the performance as a film capacitor is sufficient.

[0010] The film in Patent Document 3 is simply a film formed by blending a cyclic olefin resin and polypropylene, so it is difficult to increase the stretching magnification. Also, the film in Patent Document 4 is also a film formed by blending a polymer having an alicyclic structure in the side chain and polypropylene and then subjected to film formation and biaxial stretching, and it is difficult to increase the stretching magnification. The films of Patent Documents 3 and 4 above also have difficulty in increasing the stretching stress by increasing the stretching magnification or lowering the stretching temperature and forming a uniform film structure. Defects with low breakdown voltage increase at normal temperature or in a high-temperature environment, and it is hard to say that the processability and quality as a film and the performance as a film capacitor are sufficient.

[0011] The film of Patent Document 5 is a film obtained by biaxially orienting polypropylene to which a polymer - based α - crystal nucleating agent such as polyvinylcyclohexane is added at 1% by weight or less. Although the crystallization temperature increases due to the addition of the polymer - based α - crystal nucleating agent, the longitudinal stretching temperature is high, and the dielectric breakdown voltage performance at high temperatures is insufficient. The film of Patent Document 6 is a stretched film comprising a crystalline propylene polymer composition containing 0.1 wtppm to 10 wt% of polyvinylcyclohexane as a nucleating agent, and having a crystallization temperature of 128°C or higher. However, the stretching ratio is low in both the longitudinal and transverse directions, and the dielectric breakdown voltage performance at high temperatures is insufficient. For a biaxially oriented polypropylene film containing polyvinylcyclohexane that acts as an α - crystal nucleating agent, it is difficult to increase the areal stretching ratio during stretching at an appropriate temperature. Conversely, if the addition amount of polyvinylcyclohexane is reduced to suppress the decrease in stretchability, the nucleating effect is insufficient, and it is difficult to enhance the withstand voltage property in a high - temperature environment.

[0012] The film of Patent Document 7 is obtained by stretching polypropylene containing 0.05 to 10000 wtppm of a polymer of vinylcycloalkane in at least one axial direction, but the disclosed addition amount of polyvinylcyclohexane and the stretching ratio in each direction are low. Therefore, the film of Patent Document 7 is difficult to use in a high - temperature environment.

[0013] That is, with the methods of Patent Documents 1 to 7, it was difficult to obtain a film having both processability, quality, and withstand voltage property in a high - temperature environment. Therefore, an object of the present invention is to provide a biaxially oriented polypropylene film that is excellent in processability, quality, and withstand voltage property in a high - temperature environment and can be suitably used as a dielectric of a film capacitor.

Means for Solving the Problems

[0014] In order to solve the above problems, the biaxially oriented polypropylene film of the present invention has the following constitution. That is, in the Raman spectrum in the main orientation axis direction, the biaxially oriented polypropylene film of the present invention has a range of 905 - 935 cm -1 and a range of 770 - 790 cm -1The maximum peak intensity Ic in the range of 800-820 cm -1 This is a biaxially oriented polypropylene film in which the ratio Ic / Ip of the maximum peak intensity Ip in the range is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T℃ and the storage modulus in the direction perpendicular to the principal orientation axis in the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less.

[0015] Furthermore, the biaxially oriented polypropylene film of the present invention can also be in the following forms, and as shown below, metal film laminated films, film capacitors, power control units, and electric vehicles can be obtained using these. (1) In the Raman spectrum along the principal orientation axis, 905–935 cm⁻¹ -1 The range and 770-790cm -1 The maximum peak intensity Ic in the range of 800-820 cm -1 A biaxially oriented polypropylene film in which the ratio Ic / Ip of the maximum peak intensity Ip in the range is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T℃ and the storage modulus in the direction perpendicular to the principal orientation axis in the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less. (2) The biaxially oriented polypropylene film according to (1), wherein E(150) is 1.10 GPa or more and 4.00 GPa or less. (3) The biaxially oriented polypropylene film according to (1) or (2), wherein the shrinkage stress in the direction of the principal orientation axis at 150°C when the temperature is raised at 10°C / min is 0.01 MPa or more and 4.0 MPa or less. (4) A biaxially oriented polypropylene film according to any one of (1) to (3), wherein the average value of the domain length in the direction of the principal orientation axis is 0.01 μm or more and 1.0 μm or less in a cross section in the direction of the principal orientation axis and the film thickness direction. (5) A biaxially oriented polypropylene film according to any one of (1) to (4), wherein the melting point Tm is 165.0°C or higher and 170.0°C or lower when the temperature is raised from 30°C to 250°C at 20°C / min, then cooled from 250°C to 30°C at 20°C / min, and then raised again from 30°C to 250°C at 20°C / min. (6) A biaxially oriented polypropylene film according to any one of (1) to (5), wherein, when all constituent components are considered as 100% by mass, the total amount of resin X other than polypropylene is greater than 0.1% by mass but less than 10.0% by mass. (7) A biaxially oriented polypropylene film according to any one of (1) to (6), wherein, when all constituent components are considered as 100% by mass, the total amount of resin X other than polypropylene is greater than 0.1% by mass but less than 3.0% by mass. (8) The biaxially oriented polypropylene film according to (6) or (7), wherein the resin X other than polypropylene is amorphous. (9) A biaxially oriented polypropylene film according to any one of (6) to (8), wherein the resin X other than polypropylene does not have a nucleating agent effect on polypropylene. (10) A biaxially oriented polypropylene film according to any one of (6) to (9), wherein the glass transition temperature of the resin X other than polypropylene is 110°C or more and 160°C or less. (11) A biaxially oriented polypropylene film according to any one of (6) to (10), wherein the glass transition temperature of the resin X other than polypropylene is 140°C or higher and 153°C or lower. (12) A biaxially oriented polypropylene film according to any one of (6) to (11), wherein the resin X other than polypropylene contains a cyclohexane structure in its side chain. (13) A biaxially oriented polypropylene film according to any of (1) to (12), wherein the mesopentade fraction is 0.976 or higher. (14) A biaxially oriented polypropylene film according to any of (1) to (13) for use as a dielectric in a film capacitor. (15) A metal film laminated film having a metal film on at least one side of a biaxially oriented polypropylene film as described in any of (1) to (14). (16) In the Raman spectrum in the direction of the main alignment axis, 905 to 935 cm -1 In the range of and 770 to 790 cm -1 The ratio Ic / Ip of the maximum peak intensity Ic in the range of to the maximum peak intensity Ip in the range of 800 to 820 cm -1 is 0.01% or more and 10% or less, and when the sum of the storage elastic modulus in the direction of the main alignment axis and the storage elastic modulus in the direction orthogonal to the film plane in the direction of the main alignment axis at T °C is defined as E(T), E(150) / E(25) is 0.090 or more and 0.300 or less, and it is a metal film laminated film having a metal film on at least one side. (17) The metal film laminated film according to (16), wherein the E(150) is 1.10 GPa or more and 4.00 GPa or less. (18) The metal film laminated film according to (16) or (17), wherein the shrinkage stress in the direction of the main alignment axis at 150 °C when the temperature is raised at 10 °C / min is 0.01 MPa or more and 4.0 MPa or less. (19) The metal film laminated film according to any one of (16) to (18), wherein in the cross section in the main alignment axis direction - film thickness direction, the average value of the domain length in the main alignment axis direction is 0.01 μm or more and 1.0 μm or less. (20) The melting point Tm when the temperature is raised from 30 °C to 250 °C at 20 °C / min, cooled from 250 °C to 30 °C at 20 °C / min, and then raised from 30 °C to 250 °C at 20 °C / min is 165.0 °C or more and 170.0 °C or less, and the metal film laminated film according to any one of (16) to (19). (21) The metal film laminated film according to any one of (16) to (21), which contains a resin X other than polypropylene in a total amount of more than 0.1 mass% and less than 10.0 mass% when the constituent components excluding the metal film are 100 mass%. (22) The metal film laminated film according to any one of (16) to (22), which contains a resin X other than polypropylene in a total amount of more than 0.1 mass% and less than 3.0 mass% when the constituent components excluding the metal film are 100 mass%. (23) The metal film laminated film according to (21) or (22), wherein the resin X other than the polypropylene is amorphous. (24) A metal film laminated film according to any one of (21) to (23), wherein the resin X other than polypropylene does not have a nucleating agent effect on polypropylene. (25) A metal film laminate according to any one of (21) to (24), wherein the glass transition temperature of the resin X other than polypropylene is 110°C or more and 160°C or less. (26) A metal film laminate according to any one of (21) to (25), wherein the glass transition temperature of the resin X other than polypropylene is 140°C or higher and 153°C or lower. (27) The metal film laminated film according to any one of (21) to (26), wherein the resin X other than polypropylene contains a cyclohexane structure in its side chain. (28) A metal film laminate according to any of (16) to (27), wherein the mesopentade fraction is 0.976 or higher. (29) A film capacitor having a metal film laminated film as described in any of (15) to (28). (30) A power control unit having the film capacitor described in (29). (31) An electric vehicle having the power control unit described in (30). [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a biaxially oriented polypropylene film that is excellent in quality, processability, and voltage resistance under high-temperature environments, and is suitable for use as a dielectric in film capacitors under high-temperature environments. [Modes for carrying out the invention]

[0017] The biaxially oriented polypropylene film of the present invention will be described in detail below. The biaxially oriented polypropylene film of the present invention exhibits a Raman spectrum in the direction of the principal orientation axis of 905-935 cm⁻¹. -1 The range and 770-790cm -1 The maximum peak intensity Ic in the range of 800-820 cm -1This is a biaxially oriented polypropylene film in which the ratio Ic / Ip of the maximum peak intensity Ip in the range is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T℃ and the storage modulus in the direction perpendicular to the principal orientation axis in the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less.

[0018] The inventors of the present invention have conducted extensive research to solve the aforementioned problems and have concluded that the films described in Patent Documents 1 to 7 are of low quality, prone to breakage during processing, resulting in low yield, and have a shortened lifespan when used as dielectrics for film capacitors for extended periods, as follows.

[0019] The films described in Patent Documents 1 to 3 contain a cyclic olefin resin (hereinafter referred to as COP) having a cyclic olefin in its main chain to increase its dielectric strength at high temperatures. This improves heat resistance by incorporating COP into polypropylene and then stretching it. However, the dispersibility of COP in polypropylene and the deformation-following ability of the COP domains during stretching may be insufficient, resulting in a decrease in the stretchability of the unstretched film (especially the COP domains). Based on this problem, it was hypothesized that increasing the stretching temperature to improve the stretchability of the COP domains would make the polypropylene molecular chains more prone to relaxation, especially in high-temperature environments, and that using the resulting film as a dielectric in a film capacitor would shorten the lifespan of the film capacitor.

[0020] The film described in Patent Document 4 is obtained by dry blending 10% or more by mass of a polymer having an alicyclic structure in its side chains with polypropylene and then biaxially stretching it. However, it is difficult to increase the area stretching ratio during stretching at an appropriate temperature, and it is necessary to raise the stretching temperature or lower the stretching ratio for film formation. Therefore, it is thought that such films increase the low-voltage breakdown area at room temperature and high temperatures, leading to a decrease in quality and a shortening of the lifespan of film capacitors when used as dielectrics for film capacitors over long periods.

[0021] The films described in Patent Documents 5 and 6 use raw materials to which polyvinylcyclohexane, which acts as a nucleating agent, has been added. However, because the crystallization temperature (Tc) is high, the degree of crystallinity of the α-crystal in the cast film becomes too high, resulting in poor stretchability. Therefore, it is difficult to increase the area stretching ratio during stretching at an appropriate temperature. Based on this problem, we hypothesized that if the stretching temperature is increased or the stretching ratio is decreased, the molecular chains of polypropylene will relax more easily, especially in high-temperature environments, and the lifespan of the film capacitor will be shortened when the resulting film is used as a dielectric in a film capacitor.

[0022] The film described in Patent Document 7 has a low amount of polyvinylcyclohexane added and low stretching ratios in each direction, resulting in insufficient dielectric breakdown voltage performance at high temperatures. Furthermore, the polypropylene used as the raw material is polymerized using a Ziegler-Natta catalyst capable of polymerizing highly isotactic polypropylene, and a catalyst in which a small amount of vinylcycloalkane has been pre-polymerized. Based on the manufacturing method, this is thought to be crystalline polyvinylcyclohexane, similar to that described in Patent Document 6, and is presumed to have an α-crystallization nucleation effect on polypropylene.

[0023] Based on the above considerations, the inventors conducted further studies and succeeded in inventing a biaxially oriented polypropylene film that solves the above problems.

[0024] Here, "film" refers to a sheet-like molded article whose main component is a thermoplastic resin. "Main component" refers to a component that accounts for 80% or more but less than 100% by mass when the total constituent components of the object (film, layer, etc.) are considered as 100% by mass. "Biaxial orientation" means having molecular orientation in two orthogonal directions. A biaxially oriented film can be obtained by stretching a sheet in two orthogonal directions (usually the longitudinal and width directions). The longitudinal direction refers to the direction in which the film travels during the manufacturing process (the winding direction in the case of a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the film surface.

[0025] A polypropylene film refers to a film whose main component is polypropylene. However, if multiple types of polypropylene are included, even if the content of each individual polypropylene is less than 80% by mass of the total film, if the sum of all polypropylenes reaches 80% by mass or more, it will be considered a polypropylene film. Furthermore, polypropylene refers to a resin in which, when the total constituent units of the resin are set to 100 mol%, constituent units derived from propylene are more than 50 mol% but not exceeding 100 mol%.

[0026] Furthermore, the biaxially oriented polypropylene film of the present invention is not a microporous film and therefore does not have a large number of pores. In other words, the biaxially oriented polypropylene film of the present invention refers to a biaxially oriented polypropylene film other than a microporous film. Here, a microporous film is defined as a film having a pore structure that penetrates both surfaces of the film and possessing permeability such that the transmission time of 100 ml of air measured at a temperature of 23°C and a relative humidity of 65% using a Type B Gurley tester of JIS P 8117 (1998) is 5,000 seconds / 100 ml or less.

[0027] The biaxially oriented polypropylene film of the present invention has a storage modulus E(150) / E(25) of 0.090 or more and 0.300 or less, where E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T°C and the storage modulus in the direction perpendicular to the principal orientation axis within the film plane. Here, T represents the temperature (°C) at which the storage modulus is measured. For example, E(150) refers to the sum of the storage modulus in the direction of the principal orientation axis at 150°C and the storage modulus in the direction perpendicular to the principal orientation axis within the film plane. Note that E(150) and E(25) can be measured by the dynamic viscoelastic method, and the details of the measurement method will be described later.

[0028] A ratio of E(150) / E(25) of 0.090 or higher indicates that the biaxially oriented polypropylene film suppresses molecular chain relaxation even in high-temperature environments of 150°C, where it is not normally intended for use. In other words, it means that the biaxially oriented polypropylene film is a film with a structure that is very stable against heat. Therefore, even at high temperatures, areas that break down at low voltage are less likely to occur, and when such a biaxially oriented polypropylene film is used as a dielectric for a film capacitor, the lifespan of the film capacitor is improved, and the miniaturization of the film capacitor becomes easier. From the above viewpoint, the ratio of E(150) / E(25) in the biaxially oriented polypropylene film of the present invention is 0.090 or higher, preferably 0.098 or higher, more preferably 0.108 or higher, even more preferably 0.118 or higher, and particularly preferably 0.128 or higher. Furthermore, from the above viewpoint, a higher E(150) / E(25) ratio is preferable for the biaxially oriented polypropylene film of the present invention, but from the viewpoint of feasibility and thermal shrinkage, it is preferably 0.300 or less, preferably 0.250 or less, and more preferably 0.200 or less.

[0029] Effective methods for adjusting the E(150) / E(25) of the biaxially oriented polypropylene film of the present invention to 0.090 or more and 0.300 or within the above preferred range include, for example, raising the temperature of the biaxially oriented polypropylene film from 30°C to 250°C at 20°C / min, then lowering the temperature from 250°C to 30°C at 20°C / min, and then raising the temperature again from 30°C to 250°C at 20°C / min to set the melting point Tm (melting point of polypropylene) to 165.0°C or higher; setting the glass transition temperature (Tg) of the resin X other than polypropylene (hereinafter sometimes simply referred to as resin X) to 135°C or higher (if there are multiple types of resin X, at least one such component should be included); and performing biaxial stretching at an appropriate temperature as described later, with an area stretching ratio of 45 times or more.

[0030] The principal orientation axis direction in the biaxially oriented polypropylene film of the present invention will be described below. The principal orientation axis direction refers to the direction in which the molecular chain orientation of polypropylene is greatest within the film plane. When biaxial stretching is performed in the manufacture of a biaxially oriented polypropylene film, stretching is usually performed in the longitudinal direction and the width direction, but generally, the direction with the larger stretching ratio becomes the principal orientation axis direction. If the stretching direction (longitudinal direction and width direction) is specified but the stretching ratio is unknown, the direction with the larger storage modulus at 25°C can be designated as the principal orientation axis direction.

[0031] As described above, if the stretching direction and stretching ratio are known, the principal orientation axis direction can be easily determined. However, in the case of a film where these are unknown, the principal orientation axis direction direction can be determined by the following method. Specifically, cut a rectangle with a length of 50 mm and a width of 10 mm and take a sample. <1> Sample <1> Define the direction of the longer side as 0°. Next, create a sample rectangle of the same size such that the direction of the longer side is rotated 15° to the right from the 0° direction. <2> Collect a sample, and then rotate the rectangular sample by 15° in the direction of the longer side in the same manner as below. <3> ~ <12> A sample is taken. Next, each rectangular sample is set in the dynamic viscoelasticity measuring device with an initial chuck distance of 20 mm so that the longer side is the tensile direction (measurement direction), and the storage modulus at 25°C is calculated as described below. The longer side of the sample with the highest storage modulus is defined as the principal orientation axis of the biaxially oriented polypropylene film, and the direction perpendicular to this in the film plane is defined as the direction perpendicular to the principal orientation axis of the biaxially oriented polypropylene film in the film plane (hereinafter sometimes referred to as the direction perpendicular to the principal orientation axis).

[0032] If the width of a biaxially oriented polypropylene film sample is less than 50 mm and the above tensile test cannot be performed, the crystal orientation of the α(110) plane can be measured using wide-angle X-rays as follows, and the principal orientation axis direction can be determined based on the following criteria. Specifically, X-rays (CuKα rays) are incident perpendicular to the film surface, and the crystal peak at 2θ = approximately 14° (α(110) plane) is scanned in the circumferential direction. The direction with the highest diffraction intensity in the obtained diffraction intensity distribution can be considered the principal orientation axis direction, and the direction perpendicular to that within the film plane can be considered the direction perpendicular to the principal orientation axis direction.

[0033] The biaxially oriented polypropylene film of the present invention exhibits a Raman spectrum in the direction of the principal orientation axis of 905-935 cm⁻¹. -1 The range and 770-790cm -1 The maximum peak intensity Ic in the range of 800-820 cm -1 The ratio Ic / Ip of the maximum peak intensity Ip within the specified range is between 0.01% and 10%. When a resin other than polypropylene with an alicyclic structure in its main chain or side chain is used as resin X, Ic depends on the orientation state and amount of resin X in the biaxially oriented polypropylene film, and Ip depends on the orientation state and amount of polypropylene in the biaxially oriented polypropylene film, in the direction of the main orientation axis. Resins with an alicyclic structure in the main chain are 905-935 cm². -1 Resins with absorption peaks originating from molecular chains in the range of 770-790 cm² and alicyclic structures in their side chains exhibit the same absorption peaks. -1 Polypropylene has absorption peaks derived from molecular chains in the range of 800-820 cm². -1 It has absorption peaks originating from molecular chains within this range. When the above-mentioned resin X is used, Ic / Ip indicates the orientation state and abundance of resin X relative to polypropylene in a biaxially oriented polypropylene film. Ic / Ip can be measured by Raman spectroscopy, and details of the measurement method will be described later.

[0034] By setting the Ic / Ip ratio to 10% or less, the biaxially oriented polypropylene film of the present invention has fewer defects that could induce dielectric breakdown at low voltages. Therefore, such a biaxially oriented polypropylene film is of high quality, and yield reduction can be expected when used as a film capacitor. From the above viewpoint, the Ic / Ip ratio in the biaxially oriented polypropylene film of the present invention is 905 to 935 cm². -1 If a peak exhibiting the maximum peak intensity Ic exists within this range, it is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. Also, 770~790cm -1 When a peak exhibiting the maximum peak intensity Ic exists within the range, the Ic / Ip ratio in the biaxially oriented polypropylene film of the present invention is preferably 8.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, particularly preferably 2.0% or less, and most preferably 1.0% or less. From the above viewpoint, in all of the above cases, a smaller Ic / Ip ratio is preferable for the biaxially oriented polypropylene film of the present invention, but from the viewpoint of dielectric strength in high-temperature environments, it is preferably 0.01% or more, preferably 0.05% or more, and more preferably 0.1% or more.

[0035] Effective methods for adjusting the Ic / Ip of the biaxially oriented polypropylene film of the present invention to 0.01% or more and 10% or within the above preferred range include, for example, using a resin X having an alicyclic structure in the main chain or side chains and adjusting its amount to a suitable range, using a masterbatch state in which resin X has been pre-melted and kneaded with polypropylene under the conditions described later, and biaxially stretching the film at an appropriate temperature described later to an area stretching ratio of 45 times or more.

[0036] The biaxially oriented polypropylene film of the present invention preferably has an E(150) of 1.10 GPa or more and 4.00 GPa or less, from the viewpoint of further improving the lifespan of the film capacitor when used as a dielectric for the film capacitor. By setting E(150) to 1.10 GPa or more, when the biaxially oriented polypropylene film is used as a dielectric for the film capacitor, it becomes possible to maintain a high level of molecular chain orientation even at high temperatures of 150°C, thereby further improving the lifespan of the film capacitor. From the above viewpoint, the E(150) of the biaxially oriented polypropylene film of the present invention is preferably 1.10 GPa or more, more preferably 1.17 GPa or more, even more preferably 1.27 GPa or more, and particularly preferably 1.35 GPa or more. From the above viewpoint, the higher the E(150) of the biaxially oriented polypropylene film of the present invention, the better, but from the viewpoint of feasibility and compatibility with other properties, it is preferably 4.00 GPa or less and more preferably 3.00 GPa or less.

[0037] As a method for adjusting E(150) of the biaxially oriented polypropylene film of the present invention to the above preferred range, in addition to the same method as for adjusting E(150) / (E25) to the preferred range, effective methods include setting the area stretching ratio to 50 times or more (preferably 55 times or more) during biaxial stretching, setting the stretching temperature in the longitudinal direction to 149°C or less (preferably 147°C or less), setting the stretching temperature in the width direction to 167°C or less, and using polypropylene with a high mesopentade fraction, which is an indicator of crystallinity.

[0038] The biaxially oriented polypropylene film of the present invention is preferably such that, when used as a dielectric in a film capacitor, the shrinkage stress in the direction of the principal orientation axis at 150°C, when heated at 10°C / min, is between 0.01 MPa and 4.0 MPa, from the viewpoint of further improving the lifespan of the film capacitor. Hereinafter, the shrinkage stress in the direction of the principal orientation axis at 150°C may be referred to as P(150), and this can be measured by thermomechanical analysis (TMA) (details of the measurement method will be described later).

[0039] By setting P(150) to 4.0 MPa or less, the biaxially oriented polypropylene film exhibits low potential shrinkage stress at film capacitor operating temperatures, which can further improve the lifespan of film capacitors when used as a dielectric. Furthermore, it becomes possible to increase the processing temperature, and even when setting a higher aging temperature when used as a dielectric for film capacitors, deformation of the film capacitor can be suppressed, making it suitable from the viewpoint of productivity and reliability.

[0040] From the above viewpoint, the P(150) of the biaxially oriented polypropylene film of the present invention is preferably 4.0 MPa or less, more preferably 3.2 MPa or less, even more preferably 2.2 MPa or less, particularly preferably 1.4 MPa or less, and most preferably 1.1 MPa or less. From the above viewpoint, the lower the P(150) of the biaxially oriented polypropylene film of the present invention, the better, but from the viewpoint of compatibility with high-temperature characteristics, it is preferably 0.01 MPa or more, and more preferably 0.05 MPa or more.

[0041] Effective methods for adjusting the P(150) of the biaxially oriented polypropylene film of the present invention to the above preferred range include, for example, setting the stretching ratio in the direction of the principal orientation axis to 11 times or more, and setting the relaxation rate after stretching in that direction to 15% or more.

[0042] From the viewpoint of producing a more uniform and high-quality film, the biaxially oriented polypropylene film of the present invention preferably has an average domain length in the direction of the principal orientation axis in the principal orientation axis-film thickness cross-section of the present invention that is 0.01 μm or more and 1.0 μm or less. As described above, the biaxially oriented polypropylene film of the present invention mainly consists of polypropylene, so normally, polypropylene mainly exists as the matrix, and if components such as resin X are incompatible with polypropylene, these components mainly exist as domains. The principal orientation axis-film thickness cross-section refers to the cross-section obtained when the biaxially oriented polypropylene film is cut by a plane parallel to the principal orientation axis and perpendicular to the film surface. The average domain length in the direction of the principal orientation axis may be referred to as the domain length D below.

[0043] The details of the method for measuring the domain length D will be described later, but by setting the domain length D to 1.0 μm or less, a uniform structure with polypropylene as the main matrix is ​​obtained, making it possible to provide a higher quality biaxially oriented polypropylene film. From the above viewpoint, the domain length D of the biaxially oriented polypropylene film of the present invention is preferably 1.0 μm or less, more preferably 0.8 μm or less, even more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less. From the above viewpoint, it is preferable for the domain length D of the biaxially oriented polypropylene film of the present invention to be somewhat small, but from the viewpoint of feasibility and dielectric strength in high-temperature environments, it is preferably 0.01 μm or more, and more preferably 0.05 μm or more.

[0044] Effective methods for adjusting the domain length D of the biaxially oriented polypropylene film of the present invention to the above preferred range include, for example, using a resin other than polypropylene that has an alicyclic structure in its side chains as the resin X, melt-kneading the resin X and polypropylene under the conditions described below using a biaxial kneader with an L / D ratio of 40 or more, and biaxially stretching at an appropriate temperature and magnification range described below.

[0045] The biaxially oriented polypropylene film of the present invention preferably has a melting point Tm of 165.0°C or higher and 170.0°C or lower when heated from 30°C to 250°C at a rate of 20°C / min, then cooled from 250°C to 30°C at a rate of 20°C / min, and then heated again from 30°C to 250°C at a rate of 20°C / min. Tm can be measured by a known DSC, and the details of the measurement method will be described later, but Tm is the melting peak temperature when a sample of the biaxially oriented polypropylene film that has been melted and solidified is heated again, and usually the influence of the crystalline state of the film is removed in the first heating. Therefore, Tm indicates the melting point of the polypropylene constituting the biaxially oriented polypropylene film.

[0046] By setting the Tm to 165°C or higher, the E(150) / (25) and E(150) of the biaxially oriented polypropylene film are improved, and the lifespan of the film capacitor is improved when the biaxially oriented polypropylene film is used as the dielectric of the film capacitor. From the above viewpoint, the Tm of the biaxially oriented polypropylene film of the present invention is preferably 165.0°C or higher, more preferably 166.0°C or higher, and even more preferably 167.0°C or higher. From the above viewpoint, the higher the Tm of the biaxially oriented polypropylene film of the present invention, the better, but from the viewpoint of feasibility, it is preferably 170.0°C or lower, and more preferably 169.0°C or lower.

[0047] As a method for adjusting the Tm of the biaxially oriented polypropylene film of the present invention to the above preferred range, for example, it is effective to set the amount of polypropylene with a melting point of 165.5°C or higher (preferably 166.0°C or higher) in the total constituent components of the biaxially oriented polypropylene film to 80% by mass or more (preferably 85% by mass or more).

[0048] The mesopentad fraction of the biaxially oriented polypropylene film of the present invention is preferably 0.976 or higher, more preferably 0.980 or higher, even more preferably 0.983 or higher, and particularly preferably 0.985 or higher, from the viewpoint of heat resistance. The mesopentad fraction is an indicator of the stereoregularity of polypropylene and is measured by nuclear magnetic resonance (NMR) spectroscopy (details of the measurement method will be described later). Polypropylene with a higher mesopentad fraction has higher crystallinity, resulting in a higher degree of crystallinity and melting point, making it suitable for use at high temperatures and therefore preferable. There is no particular upper limit specified for the mesopentad fraction of the biaxially oriented polypropylene film, but from the viewpoint of feasibility, it is set to 1.000.

[0049] As a method for adjusting the mesopentad fraction of the biaxially oriented polypropylene film of the present invention to the above preferred range, for example, increasing the amount of polypropylene added, which has a high mesopentad ratio, is effective.

[0050] When using a biaxially oriented polypropylene film as a dielectric for a film capacitor, from the viewpoint of miniaturizing the film capacitor, its thickness is preferably 10 μm or less, more preferably 6.0 μm or less, even more preferably 3.5 μm or less, and particularly preferably 3.0 μm or less. From the viewpoint of suppressing film breakage during film formation, the thickness of the biaxially oriented polypropylene film is preferably 1.0 μm or more, and more preferably 1.5 μm or more. By making the thickness of the biaxially oriented polypropylene film 10 μm or less, the heat resistance improvement effect of resin X can be further enhanced, improving the voltage resistance in high-temperature environments and also reducing the size of the film capacitor element. The thickness of the biaxially oriented polypropylene film can be measured with a known electronic micrometer, and the details will be described later.

[0051] The thickness of biaxially oriented polypropylene film can be adjusted by known methods. Specifically, the thickness of biaxially oriented polypropylene film can be reduced by reducing the gap between the lip of the die, reducing the amount of molten resin discharged from the extruder, increasing the rotation speed of the casting drum, increasing the stretching ratio, etc.

[0052] The resin used to obtain the biaxially oriented polypropylene film of the present invention will be described in detail below. The biaxially oriented polypropylene film may be simply referred to as "film" below. Furthermore, if upper and lower limits are specified separately for the preferred range below, their combination can be arbitrary.

[0053] In the biaxially oriented polypropylene film of the present invention, the melt flow rate (MFR) of the polypropylene used as the main component (hereinafter sometimes referred to as polypropylene A) is preferably 5.0 g / 10 min or less, more preferably 4.0 g / 10 min or less, even more preferably 3.5 g / 10 min or less, and particularly preferably 3.0 g / 10 min or less. A melt flow rate (MFR) of polypropylene A of 5.0 g / 10 min or less allows for stretching under high-stress conditions, resulting in high tension in the molecular chains and making it easier to achieve a more uniform film structure. The MFR of polypropylene can be measured by the method described later.

[0054] In the biaxially oriented polypropylene film of the present invention, from the viewpoint of heat resistance, it is preferable that polypropylene A is linear polypropylene.

[0055] In the biaxially oriented polypropylene film of the present invention, the melting point of the raw material polypropylene A is preferably 165.5°C or higher, more preferably 166.0°C or higher, even more preferably 166.5°C or higher, and particularly preferably 167.0°C or higher. A melting point of polypropylene A of 165.5°C or higher helps to suppress the relaxation of molecular chains in high-temperature environments when the film is formed. The melting point of polypropylene can be measured by DSC, and the details will be described later.

[0056] In the biaxially oriented polypropylene film of the present invention, the mesopentade fraction of polypropylene A is preferably 0.976 or higher from the viewpoint of heat resistance when used as a biaxially oriented polypropylene film. From the above viewpoint, it is more preferably 0.980 or higher, even more preferably 0.983 or higher, particularly preferably 0.985 or higher, and most preferably 0.987 or higher. The mesopentade fraction is an index indicating the stereoregularity of polypropylene and is measured by nuclear magnetic resonance (NMR) spectroscopy (details of the measurement method will be described later). Polypropylene with a higher value of this fraction has higher crystallinity, resulting in higher crystallinity and melting point, making it suitable for use at high temperatures and therefore preferable. There is no particular upper limit for the mesopentade fraction of polypropylene A, but from the viewpoint of feasibility, it is set to 1.000.

[0057] To obtain polypropylene with such high stereoregularity, methods such as washing the resin powder obtained with a solvent such as n-heptane, or appropriately selecting a catalyst and / or co-catalyst and selecting its composition are preferably employed.

[0058] The polypropylene A used in the biaxially oriented polypropylene film of the present invention is preferably a homopolymer of propylene, in other words, homopolypropylene. However, a copolymer of propylene containing other unsaturated hydrocarbons as copolymer components may be used as long as it does not impair the objectives of the present invention. Examples of copolymer components included in the propylene copolymer include ethylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, and 5-methyl-2-norbornene. Here, homopolypropylene refers to a resin in which propylene units are present in an amount of 99.5 mol% or more and 100 mol% or less when the total constituent units of the resin are set to 100 mol%.

[0059] When polypropylene A contains copolymer components other than propylene, it is preferable that the copolymerization amount be less than 1 mol% from the viewpoint of dielectric breakdown voltage and heat resistance. Here, a copolymerization amount of components other than propylene being less than 1 mol% means that when the total constituent units of polypropylene A are set to 100 mol%, the constituent units other than propylene units are less than 1 mol%. In other words, this applies when polypropylene A is homopolypropylene or a polypropylene polymer with a copolymerization amount of less than 1 mol%. Similarly, it is also a preferred embodiment when a polypropylene polymer with a copolymerization amount of 1 mol% or more and homopolypropylene (or a polypropylene polymer with a copolymerization amount of less than 1 mol%) are mixed such that the constituent units other than propylene make up less than 1 mol% of the total.

[0060] The biaxially oriented polypropylene film of the present invention may contain branched polypropylene in order to suppress coarse protrusions on the film surface and to suppress film breakage during production. Here, branched polypropylene refers to polypropylene having one or more side chains with 6 or more carbon atoms in the molecular chain.

[0061] The biaxially oriented polypropylene film of the present invention preferably contains more than 0.1% by mass and less than 10.0% by mass of resin X other than polypropylene. Resin X refers to all resins that do not fall under the definition of polypropylene described above, and details of preferred resins will be described later, but if multiple types of resin X are included, the content of resin X is calculated by summing up all resins X.

[0062] The biaxially oriented polypropylene film of the present invention is preferably capable of stretching and processing under conditions of higher stress, such as high stretch ratios and low temperatures, and from the viewpoint of improving the quality and heat resistance of the film, the total content of resin X is preferably less than 10.0% by mass. From the above viewpoint, in the biaxially oriented polypropylene film of the present invention, the total content of resin X is preferably less than 10% by mass, more preferably 8.0% by mass or less, even more preferably 5.0% or less, and particularly preferably less than 3.0% by mass. On the other hand, by having a total content of resin X exceed 0.1% by mass, the heat resistance when the biaxially oriented polypropylene film is used as a dielectric in a film capacitor can be improved. From the above viewpoint, the total content of resin X in the biaxially oriented polypropylene film is preferably more than 0.1% by mass, and more preferably 0.5% by mass or more.

[0063] Here, resin X is preferably a resin having an alicyclic structure in its main chain or side chain, different from polypropylene, and more preferably a resin containing a total of 0.1 mol% to 100 mol% of constituent units 1 to 5 represented by the following chemical formulas, when the total constituent units are set to 100 mol%. Note that the constituent units included in the molecular chain of resin X may be any of the constituent units 1 to 5 below. Furthermore, a constituent unit refers to the smallest structural unit in the molecular chain of the resin that has 2 or more carbon atoms. For example, in polyethylene, constituent unit 6 is one in which both R1 and R2 are H, and in polyvinylcyclohexane synthesized by hydrogenating polystyrene, constituent unit 1 is one in which R1 to R6 are H.

[0064] [ka]

[0065] Other constituent units of resin X are arbitrary, but for example, constituent unit 6, represented by the following chemical formula, can be cited.

[0066] In constituent units 1 to 6, R1 to R8 represent H or any substituent, such as H, alkyl group, halogen group, nitro group, sulfone group, amide group, carbonyl group, carboxyl group, etc. Note that R1 to R8 may all be different, or two or more may be duplicates. Note that the wavy lines in constituent units 1 to 6 indicate that the chemical structure beyond that point is omitted.

[0067] However, from the viewpoint of increasing the degree of polymerization when manufacturing resin X, R1 is preferably H or a methyl group. Also, from the viewpoint of improving dispersibility in polypropylene (A), R2 to R8 are preferably H, a linear alkyl group having 1 to 30 carbon atoms such as a methyl group or an ethyl group, an isopropyl group, an isobutyl group, a sec-butyl group, etc.

[0068] In the biaxially oriented polypropylene film of the present invention, the heat resistance can be adjusted by adjusting the glass transition temperature of resin X by adjusting the molecular structure of resin X. For example, the glass transition temperature of resin X can be increased by increasing the ratio of constituent units 1 to 5 in resin X or decreasing the ratio of constituent unit 6. Furthermore, the heat resistance and quality of the biaxially oriented polypropylene film can also be adjusted by adjusting the content of resin X or by mixing multiple types of resin X. For example, the heat resistance of the biaxially oriented polypropylene film can be improved by mixing resin X with a high ratio of constituent units 1 to 5 and resin X with a high ratio of constituent unit 6, and increasing the mixing ratio of the former.

[0069] On the other hand, from the viewpoint of the quality of the biaxially oriented polypropylene film, it is preferable to reduce the ratio of constituent units 1 to 5 in resin X, reduce the content of resin X, and, when using multiple resin X, reduce the proportion of resin X with a high ratio of constituent units 1 to 5. In other words, the heat resistance and quality of the biaxially oriented polypropylene film are in a trade-off relationship from the viewpoint of the constituent units and content of resin X. From the viewpoint of achieving both, it is preferable to appropriately adjust the ratio of constituent units 1 to 5 in resin X, the content of resin X, and, when using multiple resin X, the proportion of resin X with a high ratio of constituent units 1 to 5.

[0070] The alicyclic structures contained in the side chains of constituent units 1 to 4 not only increase the glass transition temperature and improve heat resistance, but also contribute to increased affinity with polypropylene. Furthermore, if such alicyclic structures are present in the main chain rather than the side chains, the flexibility of the molecular chains decreases, reducing stability and stretchability during molding. On the other hand, when alicyclic structures are present in the side chains, the decrease in molecular chain flexibility is suppressed, making it possible to achieve both stability and stretchability during molding and a high glass transition temperature (heat resistance). In other words, it is preferable that the resin X in the biaxially oriented polypropylene film of the present invention contains a resin having an alicyclic structure in its side chains, and for the reasons described below, a resin having a cyclohexane structure in its side chains is more preferable.

[0071] Among the resins X, those containing constituent unit 1 are preferred because their synthesis method is industrially established and they can be synthesized by hydrogenating styrene-based polymers for which high-quality raw materials can be procured. Styrene-based polymers refer to polymers polymerized with styrene as one of the monomers, and examples include styrene-ethylene-butylene copolymer, styrene-ethylene copolymer, styrene-ethylene-propylene copolymer, styrene-butylene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-butylene-styrene copolymer, styrene-propylene-styrene copolymer, and polystyrene.

[0072] More specifically, industrially available resins X that can be suitably used in the biaxially oriented polypropylene film of the present invention include hydrides of polystyrene and hydrides of styrene-α-olefin copolymers. In particular, from the viewpoint of suppressing interfacial delamination in polypropylene and improving dispersibility to enhance E(150) / E(25) and E(150) as described later, it is more preferable to use a copolymer having at least one residue of ethylene or α-olefin and a vinylcyclohexane residue as the resin X, it is even more preferable to use a resin synthesized by hydrogenating the styrene and α-olefin-derived unsaturated bonds of a styrene-α-olefin block copolymer, and it is especially preferable to use polyvinylcyclohexane obtained by hydrogenating polystyrene.

[0073] Polyvinylcyclohexane is generally known to include crystalline isotactic polyvinylcyclohexane obtained by polymerization of vinylcyclohexane, and amorphous atactic polyvinylcyclohexane obtained by hydrogenation of atactic polystyrene. Crystalline isotactic polyvinylcyclohexane has been reported to be added with the expectation of acting as a nucleating agent for polypropylene (Japanese Patent No. 6592192, Japanese Patent No. 2075499, Macromolecules 2006, 39, 2832-2840).

[0074] In the biaxially oriented polypropylene film of the present invention, it is preferable that the resin X other than polypropylene is amorphous, from the viewpoint of ensuring stability and stretchability during molding, increasing the film's dielectric strength by stretching without forming insulation defects, and extending its lifespan. Here, whether or not the resin is amorphous can be determined by the method described later. Also, from the same viewpoint, it is preferable that the resin X other than polypropylene does not have a nucleating agent effect on polypropylene, and it is more preferable to use amorphous atactic polyvinylcyclohexane or a copolymer thereof. As described in the aforementioned non-patent literature and patent literature, isotactic polyvinylcyclohexane and syndiotactic polyvinylcyclohexane have melting points higher than 300°C, and if an amount suitable for enhancing the effect of the biaxially oriented polypropylene film of the present invention (described later) is included, the co-extrusion and moldability with polypropylene may deteriorate.

[0075] Whether or not resin X has a nucleating agent effect on polypropylene is determined by the crystallization temperature (Tmc) of polypropylene when resin X is mixed with polypropylene. Specifically, if Tmc is less than 115°C, it is determined that there is no nucleating agent effect, and if it is 115°C or higher, it is determined that there is a nucleating agent effect. In the secondary machine-oriented polypropylene film of the present invention, from the viewpoint of improving film-forming properties and productivity, it is preferable that resin X has substantially no nucleating agent effect. For example, polypropylene containing polyvinylcyclohexane by prepolymerization prior to propylene polymerization, as described in Patent Documents 5 and 6, has a Tmc of 122°C or higher due to the nucleating effect of the α-crystal of polyvinylcyclohexane. Using resin X that has substantially no nucleating agent effect and a Tmc of less than 115°C, rather than the resins described in Patent Documents 5 and 6, is also effective in improving the characteristics of film capacitors in high-temperature environments. Note that Tmc can be measured in accordance with JIS K7121-1987, and the details will be described later.

[0076] In other words, it is preferable that resin X is amorphous and does not have α-crystal nucleation activity, and therefore it is preferable that it is not obtained as a prepolymer of polypropylene.

[0077] Commercially available resins industrially usable as resin X in the biaxially oriented polypropylene film of the present invention include, for example, USI's "ViviOn" (registered trademark) series (1325, 0645, etc.), which are amorphous resins with alicyclic structures in the side chains, and Mitsubishi Chemical's "Tefablock" (registered trademark), which are amorphous polymers with alicyclic structures in the main chain. Other examples include Mitsui Chemicals' "APEL" (registered trademark) series (APL6015T, etc.) and Polyplastics' "TOPAS" (registered trademark) COC series (6013F-04, etc.). The "ViviOn" (registered trademark) series includes copolymers containing constituent unit 1 where R1 to R6 are all H and constituent unit 6 where R1 is H and R2 is an ethyl group, and homopolymers of constituent unit 1 where R1 to R6 are all H, but as described above, all can be suitably used. Among these, resins with alicyclic structures in the side chains are more preferably used.

[0078] The biaxially oriented polypropylene film of the present invention is not particularly limited in terms of its layer structure, but from the viewpoint of achieving both stretchability and heat resistance, it is preferable to have at least one layer containing both polypropylene and resin X. Generally, when the above-mentioned preferred resin X is used, polypropylene alone has superior stretchability compared to resin X, but inferior heat resistance. Therefore, by having a layer containing both polypropylene and resin X, a biaxially oriented polypropylene film with excellent stretchability and heat resistance can be obtained.

[0079] In the biaxially oriented polypropylene film of the present invention, it is preferable that the glass transition temperature of the resin X other than polypropylene is 110°C or higher and 160°C or lower. If multiple components corresponding to resin X are included, the requirement is satisfied if the glass transition temperature of one of them is within the above range. By adopting this configuration, the conformability of resin X to polypropylene during molding can be improved, making it easier to suppress the decrease in adhesion between resin X and polypropylene, which leads to a decrease in impact strength, and also making it possible to suppress the relaxation of polypropylene molecular chains even at high temperatures. As a result, a high-quality biaxially oriented polypropylene film can be obtained, and by using this as a dielectric in film capacitors, the lifespan of film capacitors can be extended.

[0080] Furthermore, from the viewpoint of increasing the temperature at which it can be used as a film capacitor, the biaxially oriented polypropylene film of the present invention is more preferably to contain a resin X having a glass transition temperature of 135°C or higher, even more preferably to contain a resin X having a glass transition temperature of 140°C or higher, and particularly preferably to contain a resin X having a glass transition temperature of 145°C or higher.

[0081] Generally, when cyclic olefin resins have a glass transition temperature of 135°C or higher, their stretchability decreases significantly when dispersed in polypropylene, making it difficult to achieve both quality and heat resistance sufficient for use as a dielectric in film capacitors under high-temperature conditions. The biaxially oriented polypropylene film of the present invention uses a resin having an alicyclic structure in its side chains as the heat-resistant resin X, and by appropriately adjusting the amount of additive, compounding conditions, and stretching conditions, stretchability can be maintained even when the glass transition temperature of resin X is higher than 145°C, achieving both heat resistance sufficient for use as a dielectric in film capacitors under high-temperature conditions and quality. On the other hand, from the viewpoint of moldability, the glass transition temperature of resin X is more preferably 160°C or lower, even more preferably 153°C or lower, and particularly preferably 150°C or lower.

[0082] Furthermore, to achieve both stretchability and heat resistance, two or more types of resin X may be included. Including both resin X with a glass transition temperature of 140°C or higher and resin X with a glass transition temperature lower than 140°C provides the effect of increased heat resistance from the former and the effect of improved quality due to improved film-forming properties from the latter. Note that "containing two or more types of resin X" means that the component corresponding to resin X is separated into two or more groups of components by known methods such as liquid chromatography or reprecipitation, the mole fraction of each constituent unit is determined for each group when the total constituent units of the component corresponding to resin A are set to 100 mol%, and when the mole fractions of the constituent units are compared between the groups, there is at least one group where the difference is 5 mol% or more. If measuring the mole fraction is difficult, the glass transition temperature of the resin can be measured after separating it into groups as described above, and if the glass transition temperatures of the components corresponding to resin X differ by 5°C or more, it can also be considered to contain two or more types of resin X.

[0083] In this invention, the glass transition temperature of the resin can be measured as follows in accordance with JIS K7121-1987. Using a differential scanning calorimeter, the resin is heated from 30°C to 260°C at a rate of 20°C / min in a nitrogen atmosphere, then held at 260°C for 5 minutes, and then cooled to 30°C at a rate of 20°C / min. Furthermore, after being held at 20°C for 5 minutes, the temperature is raised again from 30°C to 260°C at a rate of 20°C / min. The glass transition temperature (Tg) is calculated from the DSC curve obtained during the reheating process using the following formula. Note that the differential scanning calorimeter is not particularly limited as long as it is capable of measurement, and any known differential scanning calorimeter can be used, for example, the EXSTAR DSC6220 manufactured by Seiko Instruments. Glass transition temperature = (Extracorporeal glass transition start temperature + Extracorporeal glass transition end temperature) / 2.

[0084] The biaxially oriented polypropylene film of the present invention may contain various additives, such as organic particles, inorganic particles, nucleating agents, antioxidants, heat stabilizers, chlorine scavengers, lubricants, antistatic agents, antiblocking agents, fillers, viscosity modifiers, and anticoloring agents, as long as they do not impair the objectives of the present invention. These additives may be used individually or in combination. Furthermore, if the biaxially oriented polypropylene film has a laminated structure, these additives may be included in any layer.

[0085] When antioxidants are included among these additives, their type and amount are important from the viewpoint of long-term heat resistance. Specifically, such antioxidants should be sterically hindered phenolic types, and at least one of them should preferably be a high molecular weight type with a molecular weight of 500 or more. Various specific examples can be given, but for example, it is preferable to use 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (e.g., BASF's "Irganox"® 1330: molecular weight 775.2) or tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (e.g., BASF's "Irganox"® 1010: molecular weight 1,177.7) in combination with 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4).

[0086] The total content of high molecular weight antioxidants with a molecular weight of 500 or more is preferably in the range of 0.10 to 1.00 parts by mass per 100 parts by mass of the total resin. If the amount of antioxidant is too low, the long-term heat resistance may be poor, and if the amount of antioxidant is too high, blocking at high temperatures due to the bleed-out of these antioxidants may adversely affect the film capacitor element. From the above viewpoint, a more preferable content of the antioxidant is 0.10 to 0.70 parts by mass, and even more preferably 0.10 to 0.50 parts by mass per 100 parts by mass of the total resin. When the biaxially oriented polypropylene film has a laminated structure of two or more layers, it is preferable that each layer contains 0.10 to 0.50 parts by mass of high molecular weight antioxidants with a molecular weight of 500 or more, from the viewpoint of suppressing defects such as fish eyes and improving quality and dielectric strength.

[0087] The biaxially oriented polypropylene film of the present invention can be preferably used as a dielectric in film capacitors. The type of film capacitor is not limited; specifically, from the viewpoint of electrode configuration, it may be a wound film capacitor with metal foil and film, or a metal-deposited film capacitor. It can also be preferably used in oil-immersion type film capacitors impregnated with insulating oil, or in dry-type capacitors that do not use insulating oil at all. However, due to the properties of the biaxially oriented polypropylene film of the present invention, it is particularly preferably used as a metal-deposited film capacitor. From the viewpoint of shape, it may be wound or laminated (the film capacitor of the present invention will be described later).

[0088] Biaxially oriented polypropylene films typically have low surface energy, making it difficult to stably apply metal vapor deposition. Therefore, it is preferable to perform surface treatment before vapor deposition to improve adhesion with the metal film. Examples of surface treatments include corona discharge treatment, plasma treatment, glow treatment, and flame treatment.

[0089] The biaxially oriented polypropylene film of the present invention can be obtained by acquiring a polypropylene sheet using a resin composition mainly composed of polypropylene and containing resin X, and then performing biaxial stretching, heat treatment, and relaxation treatment. As for the biaxial stretching method, any of the following methods may be used: simultaneous inflation biaxial stretching, simultaneous tenter biaxial stretching, or sequential tenter biaxial stretching. Among these, sequential tenter biaxial stretching and simultaneous tenter biaxial stretching are preferred in terms of film formation stability, crystalline / amorphous structure, surface properties, and especially in terms of controlling mechanical properties and thermal dimensional stability while increasing the stretching ratio of the present invention, with sequential tenter biaxial stretching being more preferred.

[0090] The method for producing the biaxially oriented polypropylene film of the present invention will be described in more detail below, with an example of an embodiment having a layer containing polypropylene and resin X. However, the biaxially oriented polypropylene film of the present invention is not limited to those obtained by the following method.

[0091] First, in manufacturing the biaxially oriented polypropylene film of the present invention, it is preferable to pre-mix the resin X, polypropylene, and antioxidant in order to improve the dispersion state of the resin X and polypropylene and to increase the dielectric breakdown voltage of the resulting biaxially oriented polypropylene film at high temperatures.

[0092] While single-screw extruders and twin-screw extruders can be used for compounding, it is particularly preferable to use a twin-screw extruder from the viewpoint of achieving a good dispersion state. When using a twin-screw extruder, it is preferable that the ratio of the extruder screw length (L) to the extruder screw diameter (D), L / D, is between 40 and 80 from the viewpoint of suppressing the degradation of resin X and polypropylene while achieving a good dispersion state.

[0093] When compounding, the resin temperature is preferably within the following temperature range, from the viewpoint of suppressing the degradation of resin X and polypropylene while improving the dispersion state. First, the upper limit is preferably 280°C, and more preferably 270°C. From the same viewpoint, the lower limit is preferably 190°C.

[0094] Furthermore, from the viewpoint of further improving the dispersibility of resin X in polypropylene, it is preferable that the resin temperature is 50°C or more higher than the extruder's set temperature during compounding. The extruder's set temperature is the set temperature for the kneading portion where the resin has a high compression ratio after melting. From the above viewpoint, a difference of 60°C or more is more preferable. Also, from the viewpoint of processability, this temperature difference is preferably 90°C or less. Within the above range, a high level of shear heat is generated due to friction between molecular chains during the kneading of polypropylene and resin X, which can further improve the dispersibility of resin X.

[0095] From the viewpoint of the heat resistance of the resulting biaxially oriented polypropylene film, the content of resin X in the resin composition obtained by compounding is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and particularly preferably 9% by mass or more, when the total components to be compounded are considered as 100% by mass. On the other hand, from the viewpoint of improving the dispersibility of resin X and improving stretchability, the content of resin X in the resin composition obtained by compounding is preferably 45% by mass or less, and more preferably 40% by mass or less.

[0096] The amount of antioxidant is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, per 100 parts by mass of resin components in the resin composition obtained by the compound. The upper limit is 1.0 part by mass. Furthermore, it is preferable to add an inert gas from the viewpoint of suppressing the deterioration of the resin in the compound. From the viewpoint of economy and practicality, it is more preferable to use nitrogen gas as the inert gas.

[0097] Next, the resin composition obtained by compounding polypropylene is mixed as needed, and the amount of resin X is adjusted to a desired level (preferably 0.1% to 10.0% by mass when the total resin composition is considered to be 100% by mass), and then supplied to a single-screw extruder. After passing through a filter, the material is extruded in a sheet shape from a slit-shaped die. At this time, the extrusion temperature is preferably 200°C to 290°C. After that, the molten sheet material extruded from the slit-shaped die is solidified on a temperature-controlled casting drum to obtain a polypropylene sheet.

[0098] The biaxially oriented polypropylene film of the present invention preferably has at least one layer containing both polypropylene and resin X, from the viewpoint of achieving both heat resistance and stretchability. That is, if the biaxially oriented polypropylene film of the present invention has a single-layer structure, it is preferable that the biaxially oriented polypropylene film consists only of layers containing both polypropylene and resin X. If the biaxially oriented polypropylene film of the present invention has a laminated structure, from the viewpoint of suppressing film breakage when the area stretching ratio is increased, a two-layer structure of two types, such as layer A / layer B, or a three-layer structure of two types, such as layer B / layer A / layer B, is preferred. In the above configuration, it is preferable that at least layer A contains both polypropylene and resin X. In the above configuration, the resin X content in layer B is less than that of layer A, preferably less than 3.0% by mass, more preferably 1.0% by mass or less, and it is most preferable that layer B does not contain resin X. When layer B is laminated on both sides, the composition of layer B on both sides may be the same or different from each other. Furthermore, when the biaxially oriented polypropylene film of the present invention is manufactured in a laminated structure, the resin X may be contained in only one of the multiple layers, or it may be contained in two or more layers.

[0099] The method for forming the biaxially oriented polypropylene film of the present invention into a laminated structure is not particularly limited, but for example, the following method can be employed. A resin composition obtained by compounding polypropylene and resin X is mixed and supplied to a single-screw extruder as the raw material for layer A, and only polypropylene is supplied to another single-screw extruder as the raw material for layer B. Then, the molten resin is laminated in a two-layer structure of layer A / layer B, or a three-layer structure of layer B / layer A / layer B, using a feed block method by melt co-extrusion, and this is extruded in a sheet shape from a slit-shaped die and solidified on a temperature-controlled casting drum to obtain an unstretched polypropylene film.

[0100] Furthermore, regardless of whether the film has a single-layer or laminated structure, from the viewpoint of appropriately controlling crystal growth while cooling and solidifying the molten resin composition, the temperature of the casting drum is preferably 10°C to 110°C, and more preferably 10°C to 95°C.

[0101] Any of the following methods can be used to adhere the molten sheet to the casting drum: electrostatic application, adhesion using the surface tension of water, air knife method, press roll method, underwater casting method, or air chamber method. However, the air knife method is preferred because it provides good flatness and allows for control of surface roughness. It is also preferable to appropriately adjust the position of the air knife so that air flows downstream of the film formation to prevent vibration of the film. The air temperature of the air knife is preferably between 5°C and 130°C.

[0102] Next, the unstretched polypropylene film is biaxially stretched to achieve biaxial orientation. For biaxial orientation, either sequential biaxial stretching, where the film is stretched sequentially in the longitudinal and width directions, or simultaneous biaxial stretching, where the film is stretched simultaneously, may be used, but sequential biaxial stretching is more preferable. The case of sequential biaxial stretching will be described below.

[0103] First, during stretching, the unstretched polypropylene film is brought into contact with a roll set to a predetermined longitudinal stretching temperature and stretched longitudinally at a predetermined magnification. From the viewpoint of suppressing film breakage, the longitudinal stretching temperature is preferably 130°C or higher, and more preferably 135°C or higher. On the other hand, from the viewpoint of highly oriented molecular chains, the longitudinal stretching temperature is preferably 149°C or lower, more preferably 148°C or lower, and even more preferably 145°C or lower.

[0104] Furthermore, the longitudinal stretching ratio is preferably 4.7 times or more, more preferably 5.2 times or more, even more preferably 5.5 times or more, and particularly preferably 5.9 times or more, from the viewpoint of increasing the area stretching ratio and thus increasing the dielectric breakdown voltage at high temperatures. On the other hand, from the viewpoint of suppressing film breakage, the longitudinal stretching ratio is preferably 15 times or less, and more preferably 10 times or less. After stretching the unstretched polypropylene film in the longitudinal direction in this manner, it is cooled to room temperature to obtain a uniaxially oriented polypropylene film.

[0105] Next, the obtained uniaxially oriented polypropylene film is guided to the preheating chamber of the tenter while both ends in the width direction are held with clips, and preheated at a temperature of +10°C to +25°C above the ambient temperature of the downstream stretching chamber. After preheating, it is introduced into the stretching chamber and stretched in the width direction while both ends in the width direction of the uniaxially oriented polypropylene film are held with clips. At this time, the ambient temperature of the stretching chamber (stretching temperature in the width direction) is preferably 150°C or higher, more preferably 155°C or higher, from the viewpoint of uniformly stretching the layer containing resin X, which has a high glass transition temperature. On the other hand, from the viewpoint of maximizing the tension of the polypropylene molecular chains and improving heat resistance, the stretching temperature in the width direction is preferably 170°C or lower, more preferably 167°C or lower, even more preferably 165°C or lower, and particularly preferably 163°C or lower.

[0106] From the viewpoint of improving the structural uniformity (quality) and heat resistance of the resulting biaxially oriented polypropylene film, the stretching ratio in the width direction is preferably 10.3 times or more, more preferably 11.2 times or more, even more preferably 11.7 times or more, and particularly preferably 12.5 times or more. On the other hand, from the viewpoint of stable film formation, the stretching ratio in the width direction is preferably 20.0 times or less, and more preferably 17.0 times or less.

[0107] In the manufacturing of the biaxially oriented polypropylene film of the present invention, it is preferable to include a heat treatment and a relaxation treatment step after biaxial stretching. In this step, it is preferable to perform a heat treatment at a temperature of 150°C to 170°C in a tenter atmosphere while tension-holding both ends in the width direction with clips and applying a relaxation of 2 to 30% in the width direction. This is preferable from the viewpoint of increasing the lifespan of the biaxially oriented polypropylene film when used as a dielectric in a film capacitor. From the above viewpoint, the heat treatment temperature is preferably 150°C to 165°C. Furthermore, the relaxation treatment rate is preferably 10% or more, more preferably 13% or more, even more preferably 15% or more, and particularly preferably 18% or more. On the other hand, from the viewpoint of improving the structural uniformity of the biaxially oriented polypropylene film, the relaxation treatment is more preferably 25% or less, and even more preferably 20% or less.

[0108] The area stretching ratio is preferably 45 times or more from the viewpoint of improving the structural uniformity of the biaxially oriented polypropylene film to achieve high quality, and from the viewpoint of improving structural uniformity (quality) and heat resistance by increasing the tension of the polypropylene molecular chains. In the present invention, the area stretching ratio is the product of the stretching ratio in the longitudinal direction and the stretching ratio in the width direction. From the viewpoint of improving the tension of the molecular chains and the structural uniformity of the biaxially oriented polypropylene film, the area stretching ratio is more preferably 55 times or more, even more preferably 63 times or more, and particularly preferably 70 times or more. There is no particular upper limit to the area stretching ratio, but from the viewpoint of feasibility, it is 100 times for sequential biaxial stretching and 150 times for simultaneous biaxial stretching.

[0109] After heat treatment and relaxation treatment, the biaxially oriented polypropylene film is guided to the outside of the tenter, and the clips at both ends in the width direction are released in a room temperature atmosphere. Then, the film edges are slit in the winding process and the biaxially oriented polypropylene film is wound into a roll. Before winding the biaxially oriented polypropylene film, it is preferable to perform a surface treatment such as corona discharge treatment on at least one side in air, nitrogen, carbon dioxide, or a mixture thereof in order to improve the adhesion of the vapor-deposited metal.

[0110] Next, a metal film laminated film using the biaxially oriented polypropylene film of the present invention, a film capacitor using the same, and a method for manufacturing them will be described.

[0111] The metal film laminate of the present invention has a metal film on at least one side of the biaxially oriented polypropylene film of the present invention. This metal film laminate can be obtained by providing a metal film on at least one side of the biaxially oriented polypropylene film of the present invention described above.

[0112] In the present invention, the method for forming the metal film is not particularly limited, but a preferred method is to deposit aluminum or an alloy of aluminum and zinc onto at least one side of a biaxially oriented polypropylene film to form a metal film such as a deposited film that will serve as the internal electrode of a film capacitor. At this time, other metal components such as nickel, copper, gold, silver, and chromium can be deposited simultaneously or sequentially with the aluminum. A protective layer such as oil can also be provided on the deposited film. If the surface roughness of the biaxially oriented polypropylene film differs between the front and back sides, it is preferable to provide the metal film on the smoother surface side to form a metal film laminated film, from the viewpoint of improving dielectric strength.

[0113] The metal film laminate of the present invention can be annealed or heat-treated at a specific temperature as needed after the metal film is formed. The annealing temperature is preferably in the range of t°C to (t+50)°C, where t[°C] is the temperature at which the film is intended to be used. Furthermore, a resin coating, such as polyphenylene oxide, can be applied to at least one side of the metal film laminate for insulation or other purposes.

[0114] The film capacitor of the present invention is made using the metal film laminated film of the present invention. That is, the film capacitor of the present invention has the metal film laminated film of the present invention. For example, the film capacitor of the present invention can be obtained by laminating or winding the above-described metal film laminated film of the present invention in various ways. A preferred manufacturing method for a wound film capacitor is as follows.

[0115] Aluminum is deposited onto one side of a biaxially oriented polypropylene film under reduced pressure. The aluminum is deposited in a stripe pattern with a margin running along the longitudinal direction. Next, a blade is inserted into the center of each deposited area and the center of each margin to create a tape-shaped reel with a margin on one side of the surface. Two of these tape-shaped reels, one with a left margin and one with a right margin, are stacked and wound together so that the deposited portion extends beyond the margin in the width direction, thereby obtaining a wound body.

[0116] When vapor deposition is performed on both sides, one side is vapor-deposited in a stripe pattern with a margin running along the longitudinal direction, and the other side is vapor-deposited in a stripe pattern so that the longitudinal margin is located in the center of the vapor-deposited area on the back side. Next, a blade is inserted into the center of the margin on both the front and back sides to make a slit, and a tape-shaped winding reel is created on both sides, each with a margin on one side (for example, if there is a margin on the right side of the front side, there will be a margin on the left side of the back side). The obtained reel and one unvapor-deposited laminated film are stacked on top of each other in the width direction so that the metallized film extends beyond the laminated film, and the two are wound together to obtain a wound body.

[0117] The metal film laminate of the present invention has a storage modulus of 0.090 or more and 0.300 or less when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T°C and the storage modulus in the direction perpendicular to the principal orientation axis within the film plane. Here, T means the temperature (°C) at which the storage modulus is measured. For example, E(150) refers to the sum of the storage modulus in the direction of the principal orientation axis at 150°C and the storage modulus in the direction perpendicular to the principal orientation axis within the film plane. E(150) and E(25) can be measured by the dynamic viscoelastic method as described above, and the details of the measurement method will be described later.

[0118] A ratio of E(150) / E(25) of 0.090 or higher indicates that molecular chain relaxation is suppressed even in a high-temperature environment of 150°C. In other words, it means that the metal film laminate has a structure that is very stable against heat. From the above viewpoint, the preferred range of E(150) / E(25) for the metal film laminate of the present invention is the same as that for the biaxially oriented polypropylene film described above, and the method for adjusting it to 0.090 or more and 0.300 or the above preferred range can also be the same as that for the biaxially oriented polypropylene film described above.

[0119] The metal film laminate of the present invention exhibits a Raman spectrum in the direction of the principal orientation axis of 905-935 cm⁻¹. -1 The range and 770-790cm -1 The maximum peak intensity Ic in the range of 800-820 cm -1 The ratio of the maximum peak intensity Ip within the specified range, Ic / Ip, is between 0.01% and 10%. By setting Ic / Ip to 10% or less, the metal film laminate of the present invention has fewer defects that could induce dielectric breakdown at low voltages. Therefore, such a metal film laminate is of high quality, and yield reduction can be expected when used as a film capacitor. From the above viewpoint, the preferred range of Ic / Ip for the metal film laminate of the present invention is the same as that for the biaxially oriented polypropylene film described above, and the method for adjusting it to 0.01% or more and 10% or the above preferred range can also be the same as that for the biaxially oriented polypropylene film described above.

[0120] Furthermore, in the metal film laminate of the present invention, from the same viewpoint as described above for the biaxially oriented polypropylene film, it is preferable that E(150), the shrinkage stress in the direction of the main orientation axis at 150°C when heated at 10°C / min, the average value of the domain length in the direction of the main orientation axis, the melting point Tm, the amount of resin X other than polypropylene, the glass transition temperature of resin X other than polypropylene, and the mesopentade fraction be within the preferred range for the biaxially oriented polypropylene film described above, and the means for achieving this can also be applied. However, with respect to the composition, the values ​​are those of the portion excluding the metal film. In addition, in the metal film laminate of the present invention, from the same viewpoint as described above for the biaxially oriented polypropylene film, it is also preferable that the resin X other than polypropylene contains a cyclohexane structure in its side chains, is amorphous, and does not have nucleating agent activity.

[0121] One method for obtaining a film capacitor of the present invention using the metal layer laminated film of the present invention is to remove the core material from the wound body prepared as described above, press it, spray Metallicon onto both end faces to form external electrodes, and weld lead wires to the Metallicon to form a wound film capacitor. Film capacitors have a wide range of applications, including power control units for electric vehicles such as electric cars, hybrid cars, and fuel cell vehicles, electric aircraft such as drones, railway vehicles, solar and wind power generation, and general home appliances, and the film capacitor of the present invention can be suitably used in these applications. In addition, the biaxially oriented polypropylene film of the present invention can be used in various applications such as battery current collection films, packaging films, release films, process films, sanitary products, agricultural products, building materials, and medical products, and can be particularly preferably used in applications that include a heating process in film processing.

[0122] The following describes the power control unit and electric vehicle of the present invention. The power control unit of the present invention has the film capacitor of the present invention. The power control unit is a system for managing power in an electric vehicle that has a mechanism driven by electricity. By equipping the power control unit with the film capacitor of the present invention, it is possible to miniaturize the power control unit itself, improve its heat resistance and increase its efficiency.

[0123] The electric vehicle of the present invention has the power control unit of the present invention. Here, an electric vehicle refers to an automobile having a mechanism driven by electricity, such as an electric vehicle, hybrid vehicle, or fuel cell vehicle. As described above, the power control unit of the present invention can be miniaturized and also has excellent heat resistance and efficiency, so when an electric vehicle is equipped with the power control unit of the present invention, it leads to improved fuel efficiency and other benefits. The same effect can be obtained when it is used in electric aircraft and other devices that use electricity as part of their power source. [Examples]

[0124] The present invention will be described in more detail below using examples, but the present invention is not limited to the embodiments described below.

[0125] [Measurement and evaluation methods] (1) Thickness The thickness of a biaxially oriented polypropylene film was measured at 10 arbitrary points in an atmosphere of 23°C and 65% RH using a contact-type electronic micrometer (K-312A) manufactured by Anritsu Corporation. The arithmetic mean of these 10 thicknesses was defined as the thickness of the biaxially oriented polypropylene film (unit: μm).

[0126] (3) E(150) / E(25) and E(150) A rectangular test specimen (5 mm wide x 20 mm long) cut from a biaxially oriented polypropylene film with the measurement direction as the longer side was mounted on the apparatus chuck under a 23°C atmosphere and cooled to -100°C. E' was measured from -100°C to 180°C after the start of heating. A viscoelastic-temperature curve was drawn using the dynamic viscoelastic method, and E' at 25°C was calculated. Next, with the longitudinal direction of the polypropylene film set to 0°, dynamic viscoelasticity was similarly measured for each direction forming angles of 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and 165° with respect to the longitudinal direction. The storage modulus E' at 25°C in each direction was calculated, and the direction showing the highest storage modulus E' was defined as the principal orientation axis direction, and the direction perpendicular to the principal orientation axis direction was defined as the principal orientation axis perpendicular direction. Subsequently, the storage modulus E' at 150°C and 25°C was read for each direction. The test was conducted with n=3, and the average values ​​of the storage modulus E' at 150°C and 25°C were taken as E(150) and E(25) in the measurement direction of the biaxially oriented polypropylene film, with the sum of the values ​​in the direction perpendicular to the principal orientation axis and the direction perpendicular to the principal orientation axis being used to calculate E(150) / E(25). The measurement equipment and conditions are as follows. <Measurement equipment and conditions> • Device: EXSTAR DMS6100 (manufactured by Seiko Instruments Inc.) • Geometry: Tension • Chuck spacing: 20mm • Frequency: 10Hz Distortion: 0.1-0.2% Temperature range: -100 to 200°C • Heating rate: 5°C / min • Measurement environment: Under nitrogen.

[0127] (3) Ic / Ip Under the following apparatus and conditions, a cross-section in the direction of the principal orientation axis and thickness was cut from a biaxially oriented polypropylene film using a microtome. Polarized Raman spectroscopy (beam diameter 1 μm, measured with polarization parallel to the principal orientation axis) was performed at the center of the cross-section in the thickness direction. Subsequently, the 905-935 cm⁻¹ range was observed in the Raman band obtained from the measurement. -1and 770-790cm -1 Read the maximum peak intensity value within the range and use 700cm as a baseline correction. -1 The value obtained by subtracting the above value was defined as Ic. If there were no peaks in any of the above ranges, Ic=0. Also, 800~820cm -1 Read the maximum peak intensity value within the range and use 700cm as a baseline correction. -1 The value obtained by subtracting the above value was defined as Ip. Cross-sections were cut at five locations selected at least 1 cm away from the edge of the film and at least 1 cm away from the center of the cross-section measured previously. The average of the measured values ​​obtained for each cross-section was adopted as the Ic / Ip of the biaxially oriented polypropylene film. Polarized Raman spectra were obtained by incidenting linearly polarized light onto the biaxially oriented polypropylene film and detecting only the component parallel to the incident light from the resulting scattered light. However, to eliminate the anisotropy of the spectrometer, a λ / 4 plate was placed after the analyzer and before the grating to eliminate the polarization state of the scattered light before it was introduced into the grating. <Measuring device> Measurement device: inVia (manufactured by RENISHAW) <Measurement conditions> Measurement mode: Micro-Raman Objective lens: ×100 Beam diameter: 1 μm Light source: Semiconductor laser / 532nm Laser power: 300mW Diffraction grating: Single -3000gr / mm Slit: 65 μm Detector: CCD / RENISHAW 1024×256. Data points: 1 point / cm -1 That's all.

[0128] (4) Shrinkage stress in the principal orientation axis direction at 150°C (P(150)) Using a TMA (manufactured by SII Nanotechnology Co., Ltd., model TMA / SS6100), thermal shrinkage stress curves in the principal orientation axis direction were obtained under the following conditions, and the shrinkage stress at 150°C (MPa) was read from the obtained shrinkage stress curves. Measurements were performed three times in each direction, and the average value was adopted. The measurement conditions and the method for creating the thermal shrinkage stress curves are as follows. (a) Sample: 4mm wide x 20mm long (b) Initial load: 0.0 mN (c) Temperature program: Heats up from 30°C to 200°C at a heating rate of 10°C / min. (d) Creation of thermal shrinkage stress curves: The load (N) at each observed temperature is divided by the cross-sectional area (thickness × sample width) of the biaxially oriented polypropylene film to calculate the shrinkage stress (MPa) at each temperature, and a temperature-shrinkage stress curve (thermal shrinkage stress curve) is created.

[0129] (5) Melting point (Tm) and glass transition temperature (Tg), and amorphousness evaluation The melting point and glass transition temperature (Tg) of the biaxially oriented propylene film and the resin used were measured in accordance with JIS K7121-1987. Using a differential scanning calorimeter (Seiko Instruments EXSTAR DSC6220), 3 mg of the film or resin was heated from 30°C to 260°C at a rate of 20°C / min in a nitrogen atmosphere, held at 260°C for 5 minutes, and then cooled to 30°C at a rate of 20°C / min. After holding at 20°C for 5 minutes, the temperature was raised again from 30°C to 260°C at a rate of 20°C / min. In the DSC curve obtained during the reheating process, the peak temperature of the endothermic peak was defined as the melting point of the resin / Tm of the biaxially oriented propylene film, and the glass transition temperature (Tg) was calculated using the following formula. If multiple endothermic peaks were observed in a single measurement, the peak temperature of the endothermic peak with the highest peak temperature was used as the peak temperature for that measurement. Furthermore, if no endothermic peak was observed in resin X, it was determined to be amorphous. Glass transition temperature = (Extracorporeal glass transition start temperature + Extracorporeal glass transition end temperature) / 2.

[0130] (6) Crystallization temperature (Tmc) The crystallization temperature (Tmc) of each resin was measured according to JIS K7121-1987 as follows. Using a differential scanning calorimeter (Seiko Instruments EXSTAR DSC6220), 3 mg was heated from 30°C to 260°C at a rate of 20°C / min in a nitrogen atmosphere. Then, it was held at 260°C for 5 minutes, and then cooled down to 30°C at a rate of 20°C / min. The peak temperature of the exothermic peak obtained during the cooling process was measured. The same measurement was performed three times, and the average value of the obtained peak temperatures was taken as the crystallization temperature (Tmc). If multiple exothermic peaks were observed in a single measurement, the peak temperature of the exothermic peak with the highest peak temperature was taken as the peak temperature for that measurement.

[0131] (7) Evaluation of the nucleating agent activity of resin X on polypropylene A mixture of 98.5 parts by mass of Borealis AG's "Borclean" (trade name) HC300BF, a commercially available polypropylene raw material, 1 part by mass of resin X, and 0.5 parts by mass of antioxidant was prepared. The mixture was kneaded and extruded in a twin-screw extruder set to 260°C, and the strands were water-cooled and then chipped. The resulting chips were measured for Tmc (crystallization temperature) using the same measurement method as described above. If Tmc was less than 115°C, resin X was considered to have no nucleating agent activity; if Tmc was 115°C or higher, resin X was considered to have nucleating agent activity.

[0132] (8) Length of the domain in the direction of principal orientation in the film principal orientation axis-thickness direction cross section Using a microtome, ultrathin sections with a cross-section in the principal orientation axis direction and thickness direction were collected from a biaxially oriented polypropylene film (the principal orientation axis direction and thickness direction refers to a direction parallel to the principal orientation axis and perpendicular to the film surface). The collected sections were stained with RuO4, and the cross-sections were observed using a transmission electron microscope (TEM) under the following conditions, and images were acquired. At this time, since resin X stained blacker than polypropylene resin, the black-stained areas were treated as domains and the following measurements were performed. • Equipment: Hitachi, Ltd. Transmission Electron Microscope (TEM) HT7700 • Acceleration voltage: 100kV • Magnification: 20,000x The length of the domains along their principal orientation axis was measured by taking the length of each domain along its principal orientation axis in the acquired image. The five longest domains were selected, and their average length was taken as the domain's length along its principal orientation axis. If a selected domain had an end outside the field of view, the field of view was moved from one end to the other to acquire multiple images, and the length of the domain along its principal orientation axis was determined from the stitched-together image. If five domains could not be selected in one field of view, the field of view was moved to another, and observation continued until the measurement of five domains was completed.

[0133] (9) Melt Flow Rate (MFR) The MFR of the resin was measured in accordance with condition M of JIS K 7210-1 (2014). A load of 2.16 kg and a temperature of either 230°C or 260°C were selected as appropriate conditions.

[0134] (10) Mesopentad fraction To measure the mesopentad fraction of polypropylene resin or biaxially oriented polypropylene film, 1 g of polypropylene resin or biaxially oriented polypropylene film was freeze-dried and pulverized. The n-heptane-insoluble portion was recovered by extracting with n-heptane for 2 hours using the Soxhlet extraction method in 50 mL of water to remove impurities and additives from the polypropylene, and the sample was vacuum-dried at 130°C for 2 hours or more. The sample was then dissolved in a solvent. 13 The mesopentade fraction (mmmm) was determined using 1C-NMR under the following conditions. Measurement conditions • Equipment: Bruker DRX-500 • Measurement nucleus: 13 C nucleus (resonance frequency: 125.8MHz) ·Measurement concentration: 10% by weight • Solvent: Benzene: Deuthorthodichlorobenzene = 1:3 mixed solution (by volume) ·Measurement temperature: 130℃ • Spin speed: 12Hz • NMR sample tube: 5mm tube • Pulse width: 45° (4.5μs) • Pulse repetition time: 10 seconds • Data points: 64K • Total count: 10,000 times • Measurement mode: complete decoupling Analysis conditions A Fourier transform was performed with the LB (line broadening factor) set to 1, and the mmmm peak was determined to be 21.86 ppm. Peak splitting was performed using WINFIT software (Bruker). During this process, the peak splitting was performed from the high-field side as follows, and further automatic fitting by the software was performed to optimize the peak splitting. The sum of the peak fractions of mmmm and ss (spinning sideband peak of mmmm) was taken as the mesopentad fraction (mmmm). (1) mrrm (2)(3)rrrm (split into two peaks) (4)rrrr (5) mrmm+rmrr (6) mmrr (7) mmmr (8) ss (mmmm spinning sideband peak) (9) mmmm (10) rmmr The same sample was subjected to the same measurement five times, and the average of the obtained mesopentad fractions was taken as the mesopentad fraction of the sample.

[0135] (11) Performance evaluation of biaxially oriented polypropylene film <Quality Evaluation: Low-voltage breakdown index at room temperature> The extent to which defect regions, which are areas with low dielectric strength, existed in biaxially oriented polypropylene films manufactured under the conditions described in the Examples and Comparative Examples was measured in accordance with JIS C2330(2001)7.4.11.2 Method B (flat electrode method). However, for the lower electrode, a metal plate of the same dimensions as described in Method B of JIS C2330(2001)7.4.11.2 was used, along with "Conductive Rubber E-100" manufactured by Togawa Rubber Co., Ltd. <65> A film with the following markings was used. Dielectric breakdown voltage tests were performed 30 times in an atmosphere of 23℃, and the obtained values ​​were divided by the film thickness (measured in (1) above) to convert them to V / μm. The average of the 5 values ​​from the smallest to the smallest of the 30 measured values ​​(calculated values) was determined as the low-voltage breakdown value at room temperature. The smallness of the low-voltage breakdown value was evaluated as follows. From the following ranks, S, A, B, and C were considered pass and D was considered fail in terms of the quality of the film for film capacitors. S: The low-voltage breakdown value at room temperature was 550V / μm or higher. A: The low-voltage breakdown value at room temperature was 500V / μm or higher, but less than 550V / μm. B: The low-voltage breakdown value at room temperature was 400V / μm or higher, but less than 500V / μm. C: The low-voltage breakdown value at room temperature was 300V / μm or higher, but less than 400V / μm. D: The low-voltage breakdown value at room temperature was less than 300V / μm.

[0136] <High-temperature characteristics evaluation: High-temperature breakdown voltage> Biaxially oriented polypropylene films manufactured under the conditions described in the Examples and Comparative Examples were heated in an oven maintained at 135°C for 100 hours, removed from the oven, and allowed to stand at 23°C for 24 hours. Subsequently, the heat-treated biaxially oriented polypropylene films were heated in an oven maintained at 135°C for 5 minutes, and a dielectric breakdown voltage test was performed in that atmosphere according to JIS C2330(2001)7.4.11.2 Method B (flat electrode method), and the dielectric breakdown voltage was measured. However, for the lower electrode, a metal plate of the same dimensions as described in JIS C2330(2001)7.4.11.2 Method B, using "Conductive Rubber E-100" manufactured by Togawa Rubber Co., Ltd. <65> A sample with the following applied was used. Dielectric breakdown voltage tests were performed 30 times, and the obtained values ​​were divided by the thickness of the polypropylene film (measured in (1) above) to convert them to V / μm. The average of the 20 values ​​obtained by removing the 5 largest values ​​and the 5 smallest values ​​from the total of 30 measured values ​​(calculated values) was defined as the high-temperature breakdown voltage. Based on the high-temperature breakdown voltage calculated in this way, the dielectric strength characteristics at high temperatures were evaluated as follows, with S, A, B, and C being passable and D being a fail. S: The high-temperature breakdown voltage was 480 V / μm or higher. A: The high-temperature breakdown voltage was between 450V / μm and 480V / μm. B: The high-temperature breakdown voltage was 420V / μm or higher, but less than 450V / μm. C: The high-temperature breakdown voltage was 390 V / μm or higher and less than 420 V / μm. D: The high-temperature breakdown voltage was less than 390 V / μm.

[0137] <Evaluation of film capacitor characteristics> The wet tensile strength of each side of the polypropylene film was measured in accordance with JIS K 6768-1995. Aluminum was deposited onto the side with the higher wet tensile strength using a vacuum deposition machine manufactured by ULVAC, Inc., to achieve a film resistance of 10 Ω / sq. During deposition, a margin portion was created perpendicular to the longitudinal direction using masking oil, resulting in a so-called T-shaped margin pattern (longitudinal pitch (period) of 17 mm, fuse width of 0.5 mm). Depositional film A and deposition film B were then prepared, respectively, with a deposition pattern having a T-shaped margin. The obtained depositional films A and B were slit, respectively, to obtain depositional reels A and B with a film width of 50 mm (end margin width of 2 mm). Next, using a Kaito Manufacturing Co., Ltd. element winding machine (KAW-4NHB), the vapor-deposited reels A and B were stacked alternately, and the film capacitor elements were wound so that the element capacitance after finishing was 10 μF. After metallizing treatment, the elements were heat-treated for 6 hours under reduced pressure at 135°C, and lead wires were attached to finish them as film capacitor elements. A voltage of (film thickness (μm) × 250 VDC / μm) was applied to 20 of these film capacitor elements, and the capacitance of the 20 elements was measured after 500 hours at 125°C. The film capacitor characteristics were evaluated from the obtained element capacitance values ​​according to the following criteria. S and A mean suitable for use, B and C mean usable, and D means difficult to use. S: There were 16 or more elements with a capacitance of 9.5 μF or higher after testing. A: After testing, there were between 14 and 16 elements with a capacitance of 9.5 μF or higher. B: After testing, there were 12 or more but less than 14 devices with a capacitance of 9.5 μF or higher. C: After testing, there were between 10 and 12 devices with a capacitance of 9.5 μF or higher. D: Fewer than 10 devices had a capacitance of 9.5 μF or higher after testing.

[0138] [Resin, etc.] The following resins and other materials were used to produce the biaxially oriented polypropylene films in each example and comparative example.

[0139] <Polypropylene> Polypropylene 1: Polypropylene manufactured by Prime Polymer Co., Ltd. (corresponding to polypropylene A in this invention) has a melting point of 168°C, a mesopentad fraction of 0.985, a melt flow rate (MFR) of 2.3 g / 10 min, and a Tmc of 112°C. Polypropylene 2: Homopolypropylene (Borealis AG polypropylene) with a melting point of 164°C, a mesopentad fraction of 0.970, a melt flow rate (MFR) of 3.3 g / 10 min, and a Tmc of 111°C. Polypropylene 3: Homopolypropylene (polypropylene manufactured by Korea Petrochemical Ind. Co., Ltd.) with a melting point of 165.5°C, a mesopentad fraction of 0.976, a melt flow rate (MFR) of 3.3 g / 10 min, and a Tmc of 111°C.

[0140] <Resins other than polypropylene X> Resin X1: USI's "ViviOn" (registered trademark), product name 0645. It is an amorphous resin (corresponding to resin X) with an alicyclic structure (cyclohexane structure) in its side chains. The MFR was 5.5 g / 10 min (260°C), the glass transition temperature was 147°C, the melting point was not confirmed, and it was amorphous. Furthermore, no nucleating agent activity was confirmed for polypropylene. Resin X2: USI's "ViviOn" (registered trademark), product name 1325. It is an amorphous resin (corresponding to resin X) with an alicyclic structure (cyclohexane structure) in its side chains. It has a MFR of 13 g / 10 min (260°C), a glass transition temperature of 128°C, and no melting point was confirmed; it is amorphous. Furthermore, no nucleating agent activity was confirmed for polypropylene. Resin X3: Polyplastics' "TOPAS" (registered trademark) 6013F-04 is an amorphous resin (corresponding to resin X) with an alicyclic structure in the main chain formed by copolymerizing ethylene and norbornene. Its MFR is 0.9 g / 10 min (230°C). Its glass transition temperature is 138°C, and no melting point was observed, indicating its amorphous nature. Furthermore, no nucleating agent activity was observed in polypropylene.

[0141] <Ingredients other than resin components> Antioxidant 1: IRGANOX® 1010, manufactured by Ciba Specialty Chemicals. Antioxidant 2: “H-BHT” manufactured by Honshu Chemical Industry Co., Ltd. <Pre-mixing raw materials> MB raw material (M1): Polypropylene 1 was mixed in an amount of 69.5 parts by mass, resin X1 in an amount of 30 parts by mass, and antioxidant in an amount of 0.5 parts by mass. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX44αIII, manufactured by Japan Steel Works, L / D: 52.5) ​​set to 195°C. After that, the strands were water-cooled and chipped. The resin temperature during compounding was +62°C compared to the extruder setting temperature, with Tm: 168°C and Tmc: 113°C. MB raw material (M2): The components were mixed in the following order: 69.5 parts by mass of polypropylene 1, 25.5 parts by mass of resin X1, 4.5 parts by mass of resin X2, and 0.5 parts by mass of antioxidant. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX44αIII, manufactured by Japan Steel Works, L / D: 52.5) ​​set to 190°C. The strands were then water-cooled and chipped. The resin temperature during compounding was +63°C compared to the extruder setting temperature, with Tm: 168°C and Tmc: 113°C. Raw material (M3): The components were mixed in an amount of 69.5 parts by mass of polypropylene 2, 30 parts by mass of resin X1, and 0.5 parts by mass of antioxidant. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX44αIII, manufactured by Japan Steel Works, L / D: 52.5) ​​set to 200°C. The strands were then water-cooled and chipped. The resin temperature during compounding was +55°C compared to the extruder's set temperature, with Tm: 164°C and Tmc: 111°C. Raw material (M4): The components were mixed in the following order: 69.5 parts by mass of polypropylene 1, 30 parts by mass of resin X3, and 0.5 parts by mass of antioxidant. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX44αIII, manufactured by Japan Steel Works, L / D: 52.5) ​​set to 195°C. The strands were then water-cooled and chipped. The resin temperature during compounding was +62°C compared to the extruder's set temperature, with Tm: 168°C and Tmc: 113°C. Raw material (M5): Polypropylene 1 was mixed in an amount of 69.5 parts by mass, resin X1 in an amount of 30 parts by mass, and antioxidant in an amount of 0.5 parts by mass. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX30α manufactured by Japan Steel Works, L / D: 38.5) set to 195°C. After that, the strands were water-cooled and chipped. The resin temperature during compounding was +62°C compared to the extruder setting temperature, with Tm: 168°C and Tmc: 113°C. Raw material (M6): Polypropylene 3 was mixed in an amount of 69.5 parts by mass, resin X1 in an amount of 30 parts by mass, and antioxidant in an amount of 0.5 parts by mass. Nitrogen gas was added, and the mixture was kneaded and extruded in a twin-screw extruder (TEX44αIII, manufactured by Japan Steel Works, L / D: 52.5) ​​set to 195°C. After the strands were water-cooled and chipped, the resin temperature during compounding was +62°C compared to the extruder setting temperature, with Tm: 166°C and Tmc: 112°C.

[0142] (Example 1) M 2 Using this method, polypropylene 1 is 97. 1A resin composition was prepared by mixing the components in the following proportions: parts by mass of resin X1, 2.21 parts by mass of resin X2, 0.39 parts by mass of resin X2, 0.15 parts by mass of antioxidant 1, and 0.15 parts by mass of antioxidant 2. This mixture was then supplied to a single-screw extruder. The resin composition was melted at 250°C in the single-screw extruder, and after removing foreign matter with an 80 μm cut sintered filter adjusted to 250°C, the molten resin composition was extruded in a sheet form from a T-die. Subsequently, the molten sheet was brought into close contact with a casting drum, whose surface temperature was maintained at 75°C, using an air knife (air temperature: 23°C), and cooled and solidified to obtain an unstretched polypropylene film. The unstretched polypropylene film was heated to 140°C in a group of rolls and stretched 5.9 times in the longitudinal direction between rolls with a difference in peripheral speed to obtain a uniaxially oriented polypropylene film. Next, the uniaxially oriented polypropylene film was guided to a tenter with multiple clips gripping both ends in the width direction. After preheating at 180°C, it was stretched to 12.6 times its original width at 163°C. Further heat treatment and relaxation treatment was performed at 157°C while providing 18% relaxation in the width direction. After that, the film was guided to the outside of the tenter, the clips were released, and the heat-treated film surface (the side in contact with the casting drum) was exposed to air at 25 W·min / m². 2 A biaxially oriented polypropylene film was obtained by performing corona discharge treatment at the specified treatment intensity. The evaluation results are shown in Table 1.

[0143] (Examples 2-10, Comparative Examples 2-3, 6) A biaxially oriented polypropylene film was obtained in the same manner as in Example 1, except that the raw material formulation and film-forming conditions were as shown in Table 1. The evaluation results are shown in Table 1. The film thickness was adjusted by increasing or decreasing the extrusion rate of the extruder.

[0144] (Comparative Examples 1, 4, 5) A biaxially oriented polypropylene film was obtained in the same manner as in Example 1, except that a resin composition prepared by mixing each component according to the raw material formulation in Table 1 was supplied to a single-screw extruder without using pre-mixed raw materials, and the film-forming conditions were as described in Table 1.

[0145] [Table 1]

[0146] The biaxially oriented polypropylene films described in Examples 1-10 and Comparative Examples 1-6 did not possess sufficient permeability to pass 100 ml of air through a Gurley tester (Type B, JIS P 8117 (1998)) at a temperature of 23°C and a relative humidity of 65%, resulting in a transmission time of 5,000 seconds / 100 ml or less. Therefore, they were not deemed to be microporous films. In each example and comparative example, the antioxidants 1 and 2 in the raw material formulation were used in equal amounts. Furthermore, for each example and comparative example, the aluminum-deposited biaxially oriented polypropylene films prepared in the aforementioned film capacitor characteristic evaluation were also evaluated for their film characteristics as described in Table 1 using the aforementioned measurement and analysis method, and values ​​equivalent to those of each biaxially oriented polypropylene film were obtained. [Industrial applicability]

[0147] The biaxially oriented polypropylene film of the present invention can be widely used in industrial applications such as film capacitors, packaging, release agents, and tapes. In particular, due to its excellent voltage resistance and reliability in high-temperature environments, it can be suitably used in film capacitors that operate under high temperatures and high voltages.

Claims

1. In the Raman spectrum along the principal orientation axis, 905–935 cm⁻¹ －１ The range and 770-790 cm －１ The maximum peak intensity Ic in the range of 800-820 cm －１ A biaxially oriented polypropylene film in which the ratio Ic / Ip of the maximum peak intensity Ip in the range is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T°C and the storage modulus in the direction perpendicular to the principal orientation axis in the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less.

2. The biaxially oriented polypropylene film according to claim 1, wherein E(150) is 1.10 GPa or more and 4.00 GPa or less.

3. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the shrinkage stress in the direction of the principal orientation axis at 150°C, when heated at 10°C / min, is 0.01 MPa or more and 4.0 MPa or less.

4. A biaxially oriented polypropylene film according to claim 1 or 2, wherein in a cross-section in the direction of the main orientation axis and the film thickness direction, the average value of the domain length in the direction of the main orientation axis is 0.01 μm or more and 1.0 μm or less.

5. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the melting point Tm is 165.0°C or higher and 170.0°C or lower when the temperature is raised from 30°C to 250°C at a rate of 20°C / min, then cooled from 250°C to 30°C at a rate of 20°C / min, and then further raised from 30°C to 250°C at a rate of 20°C / min.

6. The biaxially oriented polypropylene film according to claim 1 or 2, wherein, when all constituent components are considered as 100% by mass, the total amount of resin X other than polypropylene is greater than 0.1% by mass but less than 10.0% by mass.

7. The biaxially oriented polypropylene film according to claim 1 or 2, wherein, when all constituent components are considered as 100% by mass, the total amount of resin X other than polypropylene is greater than 0.1% by mass but less than 3.0% by mass.

8. The biaxially oriented polypropylene film according to claim 6, wherein the resin X other than polypropylene is amorphous.

9. The biaxially oriented polypropylene film according to claim 6, wherein the resin X other than polypropylene does not act as a nucleating agent for polypropylene.

10. The biaxially oriented polypropylene film according to claim 6, wherein the glass transition temperature of the resin X other than polypropylene is 110°C or higher and 160°C or lower.

11. The biaxially oriented polypropylene film according to claim 6, wherein the glass transition temperature of the resin X other than polypropylene is 140°C or higher and 153°C or lower.

12. The biaxially oriented polypropylene film according to claim 6, wherein the resin X other than polypropylene contains a cyclohexane structure in its side chain.

13. A biaxially oriented polypropylene film according to claim 1 or 2, wherein the mesopentad fraction is 0.976 or more.

14. A biaxially oriented polypropylene film according to claim 1 or 2, for use as a dielectric in a film capacitor.

15. A metal film laminated film having a metal film on at least one side of a biaxially oriented polypropylene film according to claim 1 or 2.

16. A metal film laminate, wherein, in the Raman spectrum along the principal orientation axis, the ratio Ic / Ip of the maximum peak intensity Ic in the ranges of 905-935 cm-1 and 770-790 cm-1 to the maximum peak intensity Ip in the range of 800-820 cm-1 is 0.01% or more and 10% or less, and when E(T) is the sum of the storage modulus in the direction of the principal orientation axis at T°C and the storage modulus in the direction perpendicular to the principal orientation axis within the film plane, E(150) / E(25) is 0.090 or more and 0.300 or less, and has a metal film on at least one side.

17. A film capacitor having a metal film laminated film as described in claim 15.

18. A power control unit having the film capacitor described in claim 17.

19. An electric vehicle having the power control unit described in claim 18.

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