Metal-layer integrated polypropylene film

Abstract

To provide a metal layer integrated type polypropylene film having a processing suitability at a certain level as well as capable of obtaining a capacitor having an electrostatic capacitance stability at a certain level, and furthermore, capable of obtaining a capacitor excellent in an insulation resistance stability in a high-temperature high-voltage load.SOLUTION: A metal layer integrated type polypropylene film includes a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film. The metal layer integrated type polypropylene film has a cumulative dielectric breakdown point number density of 1000 pcs / m2 or less, after a cumulative direct current voltage application test at 20°C and 350 to 425 V / μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a metal-layer integrated polypropylene film, etc. [Background technology]

[0002] Polypropylene film possesses excellent electrical properties such as high voltage resistance and low dielectric loss characteristics, as well as high moisture resistance. Therefore, it is widely used in electronic and electrical equipment. Specifically, it is used as a film in applications such as high-voltage capacitors, various switching power supplies, filter capacitors (e.g., converters, inverters, etc.), and smoothing capacitors.

[0003] In particular, in recent years, polypropylene film has begun to be widely used as a capacitor for inverter power supply equipment that controls drive motors in electric vehicles and hybrid vehicles. Capacitors for inverter power supply equipment used in automobiles and the like are required to be small, lightweight, have high capacity, and have high reliability over long periods of time. Patent document 1 describes a projection of 0.1 mm 2 A biaxially oriented polypropylene film for capacitors is disclosed, in which the number of particles per unit area and the 10-point average roughness satisfy a predetermined relationship. Patent Document 1 describes the effects of the biaxially oriented polypropylene film for capacitors with the above configuration, including excellent processability even as a thin film, and high dielectric strength under a wide range of ambient temperature conditions from low temperatures (-40°C) to high temperatures (150°C). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2013 / 146367 [Overview of the project] [Problems that the invention aims to solve]

[0005] Particularly for films for in-vehicle use (e.g., for xEVs), due to the demands for miniaturization and high efficiency, the need for further thinning is increasing. However, thin polypropylene films have low processing suitability. For example, in the element winding process when manufacturing capacitors, there are problems such as wrinkles and displacement being likely to occur.

[0006] In addition, based on the increasing need for long-term reliability, the present inventor has focused on the fact that not only the capacitance stability during long-term use but also the insulation resistance stability under high-temperature and high-voltage loads is particularly important. Here, capacitance / insulation resistance stability means that when the capacitor is used, the change from the initial value of the capacitance / insulation resistance is small. If the insulation resistance significantly decreases under high-temperature and high-voltage loads, the leakage current will increase rapidly, causing thermal runaway and ultimately leading to short circuits and ignition.

[0007] Furthermore, during the progress of the research, the present inventor has focused on the fact that the physical property values in the state of the metal layer integrated polypropylene film used for capacitor manufacturing are important.

[0008] Therefore, an object of the present invention is to provide a metal layer integrated polypropylene film that can obtain a capacitor having a certain level of processing suitability and a certain level of capacitance stability, and further can obtain a capacitor having excellent insulation resistance stability under high-temperature and high-voltage loads.

Means for Solving the Problems

[0009] In view of the above problems, while conducting intensive research, the present inventor has a metal layer integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, and the cumulative insulation breakdown point density after a cumulative DC voltage application test at 20°C and 350 - 425 V / μm is {1000} pieces / m 2We have found that the above problems can be solved with a metal-layer integrated polypropylene film as described below. Based on this finding, the inventors have conducted further research and completed the present invention. That is, the present invention encompasses the following aspects.

[0010] Item 1. A metal-layer integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, wherein the cumulative dielectric breakdown point density after a cumulative DC voltage application test at 20°C and 350-425 V / μm is 1000 points / m². 2 The following is a polypropylene film with an integrated metal layer.

[0011] Item 2. The metal-layer integrated polypropylene film according to Item 1, wherein the thickness of the polypropylene film is 1.0 to 3.0 μm.

[0012] Item 3. The metal-layer integrated polypropylene film according to item 1 or 2, wherein the polypropylene film has a thermal shrinkage rate of 0 to 8% in a first direction and a thermal shrinkage rate of -2 to 2% in a second direction perpendicular to the first direction under processing conditions of 120°C for 15 minutes.

[0013] Item 4. A metal-layer integrated polypropylene film according to any one of items 1 to 3, wherein the polypropylene film has a thermal shrinkage rate of 0 to 10% in a first direction and a thermal shrinkage rate of -1 to 5% in a second direction perpendicular to the first direction under processing conditions of 140°C for 15 minutes.

[0014] Item 5. A metal-layer integrated polypropylene film according to any one of items 1 to 4, wherein the tensile modulus of the polypropylene film in a first direction is 1.5 GPa or more, and the tensile modulus of the polypropylene film in a second direction perpendicular to the first direction is 3 GPa or more.

[0015] Item 6. A metal-layer integrated polypropylene film according to any one of items 1 to 5, wherein the polypropylene film is a biaxially oriented film.

[0016] Item 7. A metal-layer integrated polypropylene film according to any one of items 1 to 6, wherein the polypropylene film is a single-layer film.

[0017] Item 8. A metal-layer integrated polypropylene film as described in any of items 1 to 7, for use in capacitors.

[0018] Item 9. A capacitor comprising a metal-layer-integrated polypropylene film as described in any of Items 1 to 8.

[0019] Item 10. The capacitor according to item 9, comprising a winding of a metal-layer-integrated polypropylene film as described in any of items 1 to 8. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a metal-layer integrated polypropylene film that not only provides a capacitor with a certain level of processability and capacitance stability, but also a capacitor with excellent insulation resistance stability under high temperature and high voltage loads. [Brief explanation of the drawing]

[0021] [Figure 1] This is a schematic perspective view illustrating metal-layer integrated polypropylene films prepared as examples and comparative examples. 1: Metal-layer integrated polypropylene film, 2: Biaxially oriented polypropylene film, 3: Metal-deposited electrode, 3a: Metal-deposited layer, 3b: Electrode removal section, 4: Insulating margin [Figure 2]This is a schematic diagram illustrating the manufacturing method of a metal-layer integrated polypropylene film according to the examples and comparative examples. 1: Metal-layer integrated polypropylene film, 1R: Metal-layer integrated polypropylene film roll, 2: Biaxially oriented polypropylene film, 2a: Evaporation surface, 2b: Cooling roll contact surface, 2R: Biaxially oriented polypropylene film roll, 101: Dielectric film supply section, 102: Insulation margin formation section, 103: Special vapor deposition pattern margin formation section, 103d: Plate roll, 104: Evaporation section, 104a: Metal vapor generation section, 104b: Metal vapor generation section (for electrode extraction section generation), 104c: Cooling roll, 105: Static electricity removal section, 105a: DC magnetron discharge electrode, 105b: DC magnetron discharge electrode, 105c: DC magnetron discharge electrode, 105d: DC magnetron discharge electrode, 106: Metal-layer integrated film winding section [Figure 3] This is a schematic diagram of a device for measuring cumulative dielectric breakdown point density. 1: Metal-layer integrated polypropylene film, 1a: Metal vapor-deposited surface, 201: Brass plate, 202: Conductive rubber, 203: Aluminum foil, 204: Insulating polypropylene film (5 μm), 204a: Window, 205: Cylindrical brass electrode, 206: Resistor element (10 kΩ), 207: DC power supply, 301: Cumulative dielectric breakdown point density test device [Modes for carrying out the invention]

[0022] In this specification, the terms “contains” and “includes” include the concepts of “contains,” “includes,” “substantially consist of,” and “consist solely of.”

[0023] In this specification, examples are also given of ranges obtained by arbitrarily swapping the upper and / or lower limits among multiple ranges, based on the ranges consisting of the upper and / or lower limits described for each parameter.

[0024] In this specification, "greater than or equal to X" (where X is a negative value) refers to the range of X ~ 0 and values ​​greater than 0. Furthermore, "less than or equal to X" (where X is a negative value) refers to the range of X and negative values ​​with an absolute value greater than X.

[0025] 1. Metal-layer integrated polypropylene film In one aspect, the present invention relates to a metal layer integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, wherein the cumulative insulation breakdown point density after a cumulative DC voltage application test at 20 ° C and 350 to 425 V / μm is 1000 pieces / m 2 The present invention relates to a metal layer integrated polypropylene film (which may also be referred to as "the metal layer integrated polypropylene film of the present invention" in this specification). Further, the polypropylene film (the polypropylene film without the metal layer laminated) of the metal layer integrated polypropylene film of the present invention may be referred to as "the polypropylene film of the present invention" in this specification. These will be described below.

[0026] The cumulative insulation breakdown point density (the cumulative insulation breakdown point density at 20 ° C at 425 V / μm) of the metal layer integrated polypropylene film of the present invention after a cumulative DC voltage application test at 20 ° C and 350 to 425 V / μm is 1000 pieces / m 2 The following is true. The cumulative insulation breakdown point density is 1000 pieces / m 2 By being the following, it is possible not only to obtain a capacitor that exhibits processing suitability at a certain level and has capacitance stability at a certain level, but also to obtain a capacitor having excellent insulation resistance stability under high temperature and high voltage load. The cumulative insulation breakdown point density is preferably 900 pieces / m 2 More preferably, it is 800 pieces / m 2 Even more preferably, it is 700 pieces / m 2 Even more preferably, it is 600 pieces / m 2 Particularly preferably, it is 500 pieces / m 2 Even more particularly preferably, it is 400 pieces / m 2 Even more particularly preferably, it is 300 pieces / m 2 Even more particularly preferably, it is 200 pieces / m 2 Particularly preferably, it is 100 pieces / m 2 The following is true. Among the particularly preferred embodiments, the cumulative insulation breakdown point density is preferably 50 pieces / m2 More preferably 20 pieces / m 2 More preferably 10 pieces / m 2 More preferably 5 pieces / m 2 The following is particularly preferable: 0 pieces / m 2 That is the case.

[0027] The cumulative dielectric breakdown point density is measured by setting the metal-layer integrated polypropylene film in the measuring device in the configuration shown in Figure 3, and measuring as follows: Under 20°C conditions, a DC voltage of 350 V / μm is applied for 1 minute, and the number of dielectric breakdown points in the window area (100 mm × 10 mm) of the insulating polypropylene film is visually counted. After counting, a DC voltage of 375 V / μm is applied for 1 minute, and the cumulative dielectric breakdown points in the window area of ​​the insulating polypropylene film are visually counted. Next, the DC voltage is increased by 25 V / μm increments, and this operation is repeated up to 425 V / μm, thereby applying the DC voltage cumulatively. The test is performed on five metal-layer integrated polypropylene films, and the average value of the cumulative dielectric breakdown points at 20°C at 425 V / μm is used as the value for the window area (100 mm × 10 mm = 1,000 mm²) of the insulating polypropylene film. 2 = 0.001m 2 Divide by ) to obtain the cumulative dielectric breakdown point density at 425 V / μm at 20°C (unit: points / m 2 )

[0028] Figure 3 and the details of the measurement method are as follows. Figure 3 is a schematic diagram to explain the measurement of cumulative dielectric breakdown point density. First, a brass plate 201 (320 mm x 250 mm), conductive rubber 202 (280 mm x 150 mm), and aluminum foil 203 (280 mm x 150 mm) are sequentially laminated on top of the aluminum foil 203, with an insulating polypropylene film 204 (300 mm x 210 mm, window 100 mm x 10 mm) having a square-shaped cutout (100 mm x 10 mm) in the center (hereinafter referred to as "window 204a") covering the outer perimeter of the aluminum foil 203.

[0029] As described above, the metal-layer integrated polypropylene film 1 is layered on top of the laminated insulating polypropylene film 204, ensuring that it does not extend beyond the outer periphery of the insulating polypropylene film 204. At this time, the metal-deposited surface 1a of the metal-layer integrated polypropylene film 1 is facing upwards, and the metal-deposited layer 3a covers the window 204a of the insulating polypropylene film 204. However, if a special vapor deposition pattern margin is formed on the metal-layer integrated polypropylene film 1, it is preferable that the portion overlapping the window 204a be the portion of the metal-deposited layer 3a without the special margin, i.e., the solid vapor-deposited portion of the metal-deposited layer 3a. In this manner, the metal-layer integrated polypropylene film 1 layered on top of the insulating polypropylene film 204 has a cooling roll contact surface 2b that contacts the surface of the aluminum foil 203 through the window 204a of the insulating polypropylene film 204.

[0030] Furthermore, regarding the metal-layer integrated polypropylene film 1 superimposed on the insulating polypropylene film 204 as described above, a cylindrical brass electrode 205 (25 mm in diameter, 65 mm in height) is placed on the metal vapor deposition layer 3a at a location away from the window 204a. At this time, the cylindrical brass electrode 205 is in contact with the metal vapor deposition layer 3a.

[0031] The cylindrical brass electrode 205 is electrically connected to the DC power supply 207 via an overcurrent prevention resistor element (10kΩ) 206. The brass plate 201 is also electrically connected directly to the DC power supply 207. The cumulative dielectric breakdown point density test apparatus 301 is configured as described above.

[0032] By measuring the cumulative dielectric breakdown point density of the metal-layer integrated polypropylene film 1 using the cumulative dielectric breakdown point density tester 301, the dielectric strength of the metal-layer integrated polypropylene film when used as a capacitor can be predicted at the stage of the metal-layer integrated polypropylene film, without having to manufacture a capacitor. When a high voltage is applied from the DC power supply 207 to the cumulative dielectric breakdown point density tester 301, dielectric breakdown occurs at the areas of the metal-layer integrated polypropylene film 1 that are weak in terms of dielectric strength. When dielectric breakdown occurs, heat is generated instantaneously, causing the metal vapor-deposited layer 3a to evaporate and the insulation to recover (self-healing). Areas where self-healing has occurred appear as a cloudy white area because the metal vapor-deposited layer 3a is gone. By counting the number of areas where self-healing has occurred (hereinafter referred to as "dielectric breakdown points") after applying a predetermined voltage for a certain period of time, the dielectric strength of the metal-layer integrated polypropylene film can be evaluated.

[0033] The dielectric breakdown point depends on the dielectric strength of the metal-layer integrated polypropylene film 1 and the properties of the metal-deposited layer 3a. In other words, the ease with which the metal-deposited layer 3a evaporates also affects the magnitude of the dielectric breakdown point. Since the cumulative dielectric breakdown point density tester 301 uses the metal-deposited layer 3a as the upper conductor, it is possible to observe characteristics that are close to those of an actual capacitor.

[0034] The cumulative dielectric breakdown point density test involves gradually increasing the voltage at regular intervals from a predetermined starting voltage to a predetermined ending voltage, applying the voltage for a set period of time, and repeatedly counting the cumulative dielectric breakdown points of the metal-layer integrated polypropylene film 1 each time (the cumulatively counted number will be referred to as "cumulative dielectric breakdown points" below). After repeating this process until the ending voltage is reached, the cumulative dielectric breakdown points of the metal-layer integrated polypropylene film 1 are measured over the area of ​​window 204a (100mm × 10mm = 1,000mm²). 2 = 0.001m 2 Divide by ) and calculate the cumulative dielectric breakdown point density (unit: points / m). 2This is carried out by determining the cumulative dielectric breakdown point density. Because the window 204a allows voltage to be applied to a constant area and surface discharge is prevented, it is possible to measure the cumulative dielectric breakdown point density of a metal-layer integrated polypropylene film with higher accuracy.

[0035] The polypropylene film of the present invention preferably has a thermal shrinkage rate of 0 to 8% (more preferably 0 to 6%, even more preferably 0 to 4%) in the first direction under processing conditions of 120°C for 15 minutes, and a thermal shrinkage rate of -2 to 2% (more preferably -1 to 1%) in the second direction perpendicular to the first direction. In this specification, if the polypropylene film of the present invention is a biaxially oriented polypropylene film, the first direction is preferably the MD direction (Machine Direction) of the polypropylene film, and the second direction is preferably the TD direction (Transverse Direction) of the polypropylene film. When the thermal shrinkage rate in the first direction is 0% or more (i.e., the thermal expansion rate is 0% or less) under processing conditions of 120°C for 15 minutes, and the thermal shrinkage rate in the second direction is -2% or more (i.e., the thermal expansion rate is 2% or less), and the thermal shrinkage rate in the first direction is 8% or less (i.e., the thermal expansion rate is -8% or more), and the thermal shrinkage rate in the second direction is 2% or less (i.e., the thermal expansion rate is -2% or more), the thermal expansion and contraction of the film on the cooling roll during metal vapor deposition processing can be further suppressed, conveying wrinkles can be suppressed, the adhesion of the polypropylene film to the cooling roll can be further improved, thermal damage can be suppressed, and the dielectric strength of the metal-layer integrated polypropylene film can be further improved.

[0036] The heat shrinkage rate (120°C heat shrinkage rate) (unit: %) under processing conditions of 120°C for 15 minutes is measured as follows. The sample used for measurement is cut from a roll, but the size of the sample is 130 mm in the first direction and 20 mm in the second direction when measuring the 120°C heat shrinkage rate in the first direction, and 20 mm in the first direction and 130 mm in the second direction when measuring the 120°C heat shrinkage rate in the second direction. Three samples are prepared for measuring the 120°C heat shrinkage rate in the first direction and three samples are prepared for measuring the 120°C heat shrinkage rate in the second direction. Next, for the three samples to be measured for the 120°C heat shrinkage rate in the first direction, mark a gauge line 15 mm from each end of the 130 mm in the first direction. At this time, the distance between the gauge lines will be 100 mm. Similarly, for the three samples to be measured for the 120°C heat shrinkage rate in the second direction, mark a gauge line 15 mm from each end of the 130 mm in the second direction. At this point, the distance between the markings will be 100 mm. Next, each marked sample is suspended without load in a 120°C hot air circulating constant temperature bath, with the 130 mm cut portion facing vertically, and held for 15 minutes. After that, it is cooled to room temperature (23°C), and the distance between the markings is measured with a ruler, and the following formula is used: Thermal shrinkage rate (%) = (gauge before heating - gauge after heating) / gauge before heating × 100 The thermal shrinkage rate (%) is calculated for each sample using the specified method. The average of the thermal shrinkage rates of three samples measured for thermal shrinkage rate at 120°C in the first direction is taken as the thermal shrinkage rate at 120°C in the first direction (%). Similarly, the average of the thermal shrinkage rates of three samples measured for thermal shrinkage rate at 120°C in the second direction is taken as the thermal shrinkage rate at 120°C in the second direction (%). For measurement conditions other than those described herein, the method is in accordance with "25. Dimensional change" of JIS C 2151:2019.

[0037] The polypropylene film of the present invention preferably has a thermal shrinkage rate of 0 to 10% (more preferably 0 to 8%, even more preferably 0 to 7%) in the first direction under processing conditions of 140°C for 15 minutes, and a thermal shrinkage rate of -1 to 5% (more preferably 0 to 4%) in the second direction perpendicular to the first direction. When the thermal shrinkage rate in the first direction is 0% or more (i.e., the thermal expansion coefficient is 0% or less), and the thermal shrinkage rate in the second direction is -1% or more (i.e., the thermal expansion coefficient is 1% or less), and the thermal shrinkage rate in the first direction is 10% or less (i.e., the thermal expansion coefficient is -10% or more), and the thermal shrinkage rate in the second direction is 5% or less (i.e., the thermal expansion coefficient is -5% or more), the thermal expansion and shrinkage of the film on the cooling roll during metal deposition processing can be further suppressed, conveying wrinkles can be suppressed, the adhesion of the polypropylene film to the cooling roll can be further improved, thermal damage can be suppressed, and the dielectric strength of the metal-layer integrated polypropylene film can be further improved.

[0038] The thermal shrinkage rate (140°C thermal shrinkage rate) (unit: %) under processing conditions of 140°C for 15 minutes is calculated using the same method as for the 120°C thermal shrinkage rate, except that the 120°C hot air circulating constant temperature bath is changed to a 140°C hot air circulating constant temperature bath. This method calculates the 140°C thermal shrinkage rate (%) in the first direction and the 140°C thermal shrinkage rate (%) in the second direction.

[0039] The polypropylene film of the present invention preferably has a tensile modulus of elasticity of 1.5 GPa or more (more preferably 2.0 GPa or more) in the first direction and a tensile modulus of elasticity of 3.0 GPa or more (more preferably 4.0 GPa or more) in the second direction perpendicular to the first direction. When the tensile modulus of elasticity in the first direction is 1.5 GPa or more and the tensile modulus of elasticity in the second direction is 3.0 GPa or more, transport wrinkles during metal deposition processing can be further suppressed, the adhesion of the polypropylene film to the cooling roll can be further improved, thermal damage can be suppressed, and the dielectric strength of the metal-layer integrated polypropylene film can be further improved. In one embodiment of the present invention, the tensile modulus of elasticity of the polypropylene film of the present invention is not particularly limited in any direction, but can be substantially limited to 6.0 GPa.

[0040] The tensile modulus (in GPa) is measured in accordance with JIS K-7127 (1999). The sample used for measurement is cut from a roll. When measuring the tensile modulus in the first direction, the sample size is 200 mm in the first direction and 15 mm in the second direction. When measuring the tensile modulus in the second direction, the sample size is 15 mm in the first direction and 200 mm in the second direction. After cutting the sample, a tensile test is performed using a tensile and compression testing machine (manufactured by Minebea Co., Ltd.) under the following test conditions: measurement temperature 23°C, chuck distance 100 mm, and tensile speed 200 mm / min. Then, the tensile modulus (GPa) in the first direction and the tensile modulus (GPa) in the second direction are determined by automatic analysis using data processing software built into the testing machine.

[0041] The polypropylene film of the present invention preferably has a thickness of 9.5 μm or less, more preferably 6.0 μm or less, even more preferably 3.0 μm or less, even more preferably 2.9 μm or less, particularly preferably 2.8 μm or less, and particularly most preferably 2.5 μm or less. Furthermore, the thickness of the polypropylene film of the present invention is preferably 0.8 μm or more, more preferably 1.0 μm or more, even more preferably 1.4 μm or more, even more preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. In particular, when the thickness is within the range of 1.0 to 6.0 μm, 1.0 to 3.0 μm, 1.0 to 2.9 μm, etc., it is preferable because the polypropylene film is very thin yet exhibits excellent slitting process processability, blocking suppression during the deposition process, and element winding processability. When the thickness is 9.5 μm or less, the capacitance can be increased, making it suitable for use as a capacitor. Furthermore, from a manufacturing standpoint, the thickness can be 0.8 μm or more.

[0042] The film thickness will be measured in accordance with JIS-C2330, except that it will be measured at 100±10kPa using a Citizen Seimitsu MEI-11 paper thickness gauge.

[0043] The haze value of the polypropylene film of the present invention is not particularly limited, but is, for example, 2.2 to 5.0%, preferably 2.3 to 4.5%, more preferably 2.5 to 4.5%, even more preferably 2.5 to 4.0%, and even more preferably 2.5 to 3.5%.

[0044] The haze value is measured as follows: Using a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.), the measurement is performed in accordance with JIS K 7136:2000. The sample size is 50 mm x 100 mm.

[0045] The polypropylene film of the present invention may be a biaxially oriented film, a uniaxially oriented film, or an unoriented film. Among these, a biaxially oriented film is preferred.

[0046] The layer structure of the polypropylene film of the present invention is not particularly limited. The film of the present invention may be a single layer consisting of one layer, or it may be a plurality of layers having the same or different compositions. The polypropylene film of the present invention is preferably a film consisting of one or more film-like molded layers, and more preferably a single-layer film (a film consisting of one film-like molded layer). The polypropylene film of the present invention contains a polypropylene resin as a main component. In this specification, "containing a polypropylene resin as a main component" means that the polypropylene film contains 50% by mass or more of polypropylene resin relative to the entire polypropylene film (when the entire polypropylene film is considered to be 100% by mass). The content of the polypropylene resin relative to the entire polypropylene film is preferably 75% by mass or more, and more preferably 90% by mass or more. The upper limit of the content of the polypropylene resin relative to the entire polypropylene film is, for example, 100% by mass, 98% by mass, etc.

[0047] The polypropylene resin is not particularly limited, and one type may be used alone, or two or more types may be used in combination. Among the polypropylene resins, those that form β-type spherulites when used as a cast sheet are preferred.

[0048] Linear polypropylene resin is preferred, and linear homopolypropylene resin is more preferred.

[0049] For polypropylene resins, a lower total ash content is preferable for electrical properties. The total ash content is preferably 50 ppm or less, more preferably 40 ppm or less, and even more preferably 30 ppm or less, based on the polypropylene resin. The lower limit of the total ash content is, for example, 2 ppm or 5 ppm. A lower total ash content means fewer impurities such as polymerization catalyst residue.

[0050] In the polypropylene film of this embodiment, the polypropylene resin may include, for example, only the first polypropylene resin described below, or it may include the first polypropylene resin together with the second polypropylene resin described below.

[0051] The polypropylene resin may contain a first polypropylene resin. When the polypropylene resin contains a first polypropylene resin, the content of the first polypropylene resin is preferably 50% by weight or more, more preferably 55% by weight or more, and even more preferably 60% by weight or more, relative to 100% by weight of the polypropylene resin. As an upper limit, the content of the first polypropylene resin can be, for example, 100% by weight or less, 99% by weight or less, 98% by weight or less, 95% by weight or less, relative to 100% by weight of the polypropylene resin, and preferably 90% by weight or less, more preferably 85% by weight or less, and even more preferably 80% by weight or less, relative to 100% by weight of the polypropylene resin. Thus, the polypropylene film of this embodiment can contain a first polypropylene resin as its main component. As the first polypropylene resin, for example, isotactic polypropylene can be given.

[0052] The weight-average molecular weight Mw of the first polypropylene resin is preferably 250,000 or more and less than 400,000, more preferably 260,000 or more and 370,000 or less, and even more preferably 270,000 or more and 350,000 or less. When Mw is 250,000 or more and less than 400,000, the resin flowability is appropriate, the thickness of the cast raw material sheet is easy to control, and it is easy to produce a thin stretched film with good thickness uniformity. Furthermore, when Mw is 250,000 or more and less than 350,000, the resin flowability is even more appropriate, the thickness of the cast raw material sheet is easier to control, and it is even easier to produce a thin stretched film with good thickness uniformity.

[0053] The number-average molecular weight Mn of the first polypropylene resin is preferably 30,000 to 52,000, more preferably 32,000 to 50,000, and even more preferably 34,000 to 48,000.

[0054] The z-average molecular weight Mz of the first polypropylene resin is preferably 600,000 to 1,650,000, more preferably 700,000 to 1,600,000.

[0055] The molecular weight distribution (Mw / Mn) of the first polypropylene resin is preferably 5.0 or higher, more preferably 5.5 or higher. The Mw / Mn of the first polypropylene resin is preferably 11.0 or lower, and more preferably 10.0 or lower. A Mw / Mn of 5.0 or higher and 11.0 or lower for the first polypropylene resin is preferable because it allows for appropriate resin fluidity during biaxial stretching, making it easy to obtain an ultra-thin biaxially oriented propylene film with uniform thickness. The molecular weight distribution Mw / Mn is the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn.

[0056] The molecular weight distribution (Mz / Mn) of the first polypropylene resin is preferably 10 to 60, more preferably 12 to 50, and even more preferably 15 to 45. The molecular weight distribution Mz / Mn is the ratio of the z-average molecular weight Mz to the number-average molecular weight Mn.

[0057] In this specification, the weight-average molecular weight (Mw), number-average molecular weight (Mn), z-average molecular weight (Mz), and molecular weight distribution (Mw / Mn, and Mz / Mn) of the polypropylene resin are values ​​measured using a gel permeation chromatograph (GPC) instrument. More specifically, the values ​​are measured using the HLC-8121GPC-HT (product name), a high-temperature GPC measuring instrument with a built-in differential refractometer (RI) manufactured by Tosoh Corporation. Three TSKgel GMHHR-H(20)HT columns manufactured by Tosoh Corporation are used in conjunction as the GPC column. The column temperature is set to 140°C, and trichlorobenzene is flowed as the eluent at a flow rate of 1.0 ml / 10 min to obtain the measured values ​​of Mw and Mn. A calibration curve for the molecular weight M is created using standard polystyrene manufactured by Tosoh Corporation, and the measured values ​​are converted to polystyrene values ​​to obtain Mw, Mn, and Mz.

[0058] The melt flow rate (MFR) of the first polypropylene resin at 230°C is preferably 8.0 g / 10 min or less, more preferably 7.0 g / 10 min or less, and even more preferably 6.0 g / 10 min or less. Furthermore, a melt flow rate of 3.5 g / 10 min or more at 230°C is preferred. The melt flow rate at 230°C is measured in accordance with JIS K 7210-1999, under a load of 2.16 kg at 230°C. The unit g / 10 min of the melt flow rate is also referred to as dg / min.

[0059] The heptane-insoluble content of the first polypropylene resin is preferably 97.0% or more. The heptane-insoluble content is preferably 98.5% or less. A higher heptane-insoluble content indicates higher stereoregularity of the resin. When the heptane-insoluble content (HI) is 97.0% or more and 98.5% or less, the moderately high stereoregularity moderately improves the crystallinity of the polypropylene resin in the polypropylene film, improving its dielectric strength at high temperatures. Furthermore, the solidification (crystallization) rate during casting of the raw material sheet becomes moderate, resulting in moderate stretchability. The method for measuring the heptane-insoluble content (HI) is as described in the examples.

[0060] The total ash content of the first polypropylene resin is preferable to be as low as possible for electrical properties. The total ash content is preferably 50 ppm or less, more preferably 40 ppm or less, and even more preferably 30 ppm or less, based on the first polypropylene resin. The lower limit of the total ash content is, for example, 2 ppm or 5 ppm.

[0061] The polypropylene resin may further contain a second polypropylene resin. The polypropylene film of this embodiment preferably contains a second polypropylene resin in addition to the first polypropylene resin, and it is even more preferable that the resins constituting the polypropylene film are the first polypropylene resin and the second polypropylene resin.

[0062] When the polypropylene resin contains a second polypropylene resin, the content of the second polypropylene resin is preferably 50% by weight or less, more preferably 49% by weight or less, even more preferably 45% by weight or less, and particularly preferably 40% by weight or less, based on 100% by weight of the polypropylene resin. Furthermore, when the polypropylene resin contains a second polypropylene resin, the lower limit of the content of the second polypropylene resin can be, for example, 1% by weight or more, 2% by weight or more, or 5% by weight or more, based on 100% by weight of the polypropylene resin, and preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, based on 100% by weight of the polypropylene resin. Examples of the second polypropylene resin include isotactic polypropylene.

[0063] The Mw of the second polypropylene resin is preferably 300,000 or more, more preferably 350,000 or more. The Mw of the second polypropylene resin is preferably 450,000 or less, more preferably 400,000 or less.

[0064] The Mn content of the second polypropylene resin is preferably 40,000 to 54,000, more preferably 42,000 to 50,000, and even more preferably 44,000 to 48,000.

[0065] The Mz of the second polypropylene resin is preferably more than 1,550,000 and less than or equal to 2,000,000, and more preferably between 1,580,000 and 1,700,000.

[0066] In the second polypropylene resin, the ratio of Mw to Mn (Mw / Mn) is preferably 5.5 or higher, more preferably 7.0 or higher, and particularly preferably 7.5 or higher. The upper limit of Mw / Mn in the second polypropylene resin is, for example, 11.0, 10.0, 9.0, 8.5, etc.

[0067] In the second polypropylene resin, the ratio of Mz to Mn (Mz / Mn) is preferably 30 to 40, more preferably 33 to 37.

[0068] The melt flow rate at 230°C for the second polypropylene resin is preferably less than 4.0 g / 10 min, more preferably 3.9 g / 10 min or less, and even more preferably 3.8 g / 10 min or less. Furthermore, the melt flow rate at 230°C is preferably 1.0 g / 10 min or more, more preferably 1.5 g / 10 min or more, and even more preferably 2.0 g / 10 min or more.

[0069] The heptane-insoluble content of the second polypropylene resin is preferably 97.5% or more, more preferably 98.0% or more, even more preferably over 98.5%, and particularly preferably 98.6% or more. Furthermore, the heptane-insoluble content is preferably 99.5% or less, and more preferably 99.0% or less.

[0070] The total ash content of the second polypropylene resin is preferable to be low for electrical properties. The total ash content is preferably 50 ppm or less, more preferably 40 ppm or less, and even more preferably 30 ppm or less, based on the second polypropylene resin. The lower limit of the total ash content is, for example, 2 ppm or 5 ppm.

[0071] The total amount of the first polypropylene resin and the second polypropylene resin can be, for example, 90% or more by weight, 95% or more by weight, or 100% by weight, when the total amount of polypropylene resin is considered to be 100% by weight.

[0072] The aforementioned polypropylene resin can be produced using generally known polymerization methods. There are no particular limitations, as long as a polypropylene resin suitable for use in the polypropylene film of this embodiment can be produced. Examples of such polymerization methods include gas-phase polymerization, bulk polymerization, and slurry polymerization.

[0073] Polymerization may be a single-stage polymerization using one polymerization reactor, or it may be a multi-stage polymerization using at least two polymerization reactors. Furthermore, hydrogen or comonomers may be added to the reactor as molecular weight modifiers.

[0074] A generally known Ziegler-Natta catalyst can be used as the catalyst for polymerization, and is not particularly limited as long as the polypropylene resin can be obtained. The catalyst may also contain co-catalyst components and donors. By adjusting the catalyst and polymerization conditions, the molecular weight, molecular weight distribution, etc., can be controlled.

[0075] The molecular weight, molecular weight distribution, etc., of the aforementioned polypropylene resin can be adjusted by appropriately selecting, for example, (i) the polymerization method and conditions such as temperature and pressure during polymerization, (ii) the form of the reactor during polymerization, (iii) whether or not additives are used, the type and amount used, and (iv) the type and amount of catalyst used.

[0076] Specifically, the molecular weight, molecular weight distribution, etc., of the polypropylene resin can be adjusted, for example, by a multi-stage polymerization reaction. Examples of multi-stage polymerization reactions include the following methods.

[0077] First, in the first polymerization step, propylene and a catalyst are supplied to the first polymerization reactor. Along with these components, hydrogen, as a molecular weight modifier, is mixed in the amount necessary to reach the required molecular weight of the polymer. The reaction temperature is approximately 70-100°C, and the residence time is approximately 20-100 minutes, for example, in the case of slurry polymerization. Multiple reactors can be used, for example, in series. In this case, the polymerization product from the first step is continuously sent to the next reactor along with additional propylene, catalyst, and molecular weight modifier, and then a second polymerization is carried out, in which the molecular weight is adjusted to be lower or higher than that of the first polymerization step. By adjusting the yield (production amount) of the first and second reactors, it is possible to adjust the composition (constitution) of high molecular weight and low molecular weight components.

[0078] Furthermore, the molecular weight and molecular weight distribution of the polypropylene resin can also be adjusted by peroxidative decomposition. For example, a method using peroxidation treatment with decomposition agents such as hydrogen peroxide or organic peroxides can be used.

[0079] When peroxides are added to disintegrating polymers such as polypropylene, hydrogen abstraction reactions occur from the polymer. Some of the resulting polymer radicals recombine and undergo crosslinking reactions, but most radicals undergo secondary decomposition (β-cleavage), separating into two polymers with smaller molecular weights. In other words, the higher the molecular weight component, the higher the probability of decomposition. This increases the amount of low molecular weight components, allowing for adjustment of the molecular weight distribution.

[0080] When adjusting the content of low molecular weight components by blending (resin mixing), it is preferable to dry-mix or melt-mix at least two resins with different molecular weights. Generally, a two-polypropylene mixture system, in which a main resin is mixed with an additive resin having a higher or lower average molecular weight in an amount of about 1 to 40% by mass, is preferred because it makes it easier to adjust the amount of low molecular weight components.

[0081] Furthermore, in this mixing process, the melt flow rate (MFR) can be used as a guideline for the average molecular weight. In this case, it is preferable to keep the difference in MFR between the main resin and the additive resin to approximately 1-30 g / 10 min for convenience during the mixing process.

[0082] Commercially available polypropylene resins can also be used.

[0083] The polypropylene film of the present invention may contain other resins other than polypropylene resin (hereinafter also referred to as "other resins"). "Other resins" generally refer to resins other than polypropylene resin, which is the main component resin, and are not particularly limited as long as the desired polypropylene film can be obtained. Examples of other resins include other polyolefins other than polypropylene, such as polyethylene, poly(1-butene), polyisobutene, poly(1-pentene), and poly(1-methylpentene); copolymers of α-olefins such as ethylene-propylene copolymer, propylene-butene copolymer, and ethylene-butene copolymer; vinyl monomer-diene monomer random copolymers such as styrene-butadiene random copolymer; and vinyl monomer-diene monomer-vinyl monomer random copolymers such as styrene-butadiene-styrene block copolymer. The polypropylene film of the present invention may contain other resins in an amount that does not adversely affect the desired polypropylene film. The polypropylene film of the present invention may preferably contain 10 parts by mass or less, more preferably 5 parts by mass or less, of the other resin per 100 parts by mass of polypropylene resin. Furthermore, the polypropylene film of the present invention may preferably contain 0.1 parts by mass or more, and more preferably 1 part by mass or more, of another resin per 100 parts by mass of polypropylene resin.

[0084] The polypropylene film of the present invention may further contain at least one additive in addition to the resin component. "Additive" refers to any additive generally used in polypropylene, and is not particularly limited as long as the desired polypropylene film can be obtained. Examples of additives include nucleating agents (α-crystal nucleating agents, β-crystal nucleating agents), antioxidants, necessary stabilizers such as chlorine absorbers and ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, inorganic fillers, and organic fillers. Examples of inorganic fillers include barium titanate, strontium titanate, and aluminum oxide. When using the additive, it can be included in an amount that does not adversely affect the desired polypropylene film.

[0085] The "nucleating agent" is not particularly limited as long as it is commonly used with polypropylene and can be used to obtain the desired polypropylene film.

[0086] Examples of nucleating agents include α-crystal nucleating agents that preferentially nucleate α-crystals and β-crystal nucleating agents that preferentially nucleate β-crystals.

[0087] Among α-crystal nucleating agents, organic nucleating agents include dispersed nucleating agents and dissolving nucleating agents. Dispersed nucleating agents include phosphate ester metal salt nucleating agents, carboxylic acid metal salt nucleating agents, and rosin metal salt nucleating agents. Dissolving nucleating agents include sorbitol-based nucleating agents, nonitol-based nucleating agents, xylitol-based nucleating agents, and amide-based nucleating agents.

[0088] Examples of β-crystal nucleating agents include amide-based nucleating agents, di- or polycarboxylate metal salt-based nucleating agents, quinacridone-based nucleating agents, aromatic sulfonic acid-based nucleating agents, phthalocyanine-based nucleating agents, and tetraoxaspiro compound-based nucleating agents.

[0089] The nucleating agent can be dry-blended or melt-blended with the polypropylene raw material and used as pellets, or it can be fed into an extruder together with the polypropylene pellets. By using a nucleating agent, the surface roughness of the film can be adjusted to a desired roughness. A typical example of a commercially available nucleating agent is NJester NU-100 manufactured by Shin-Nippon Rika Co., Ltd., which is used as a β-crystal nucleating agent. When the polypropylene film of the present invention contains a β-crystal nucleating agent, its content is preferably 1 to 1000 ppm by mass, more preferably 50 to 600 ppm by mass, relative to the mass of the resin component (by mass when the resin component is considered as the whole).

[0090] An "antioxidant" is generally referred to as an antioxidant and is used with polypropylene. There are no particular restrictions on the type of antioxidant used, as long as it can produce the desired polypropylene film. Antioxidants are generally used for two purposes. One purpose is to suppress thermal and oxidative degradation in the extruder, and the other purpose is to suppress degradation during long-term use as a film for capacitors and to contribute to improving capacitor performance. Antioxidants that suppress thermal and oxidative degradation in the extruder are also called "primary agents," and antioxidants that contribute to improving capacitor performance are also called "secondary agents."

[0091] Two types of antioxidants may be used for these two purposes, or one type of antioxidant may be used for both purposes.

[0092] Examples of primary agents include 2,6-di-tert-butyl-para-cresol (generic name: BHT). Primary agents can usually be added to the polypropylene resin composition during the preparation of the polypropylene resin composition, as described later in the method for producing polypropylene films, in order to suppress thermal degradation and oxidative degradation in the extruder. Antioxidants added to the polypropylene resin composition for this purpose are almost entirely consumed during the molding process in the extruder, and almost none remain in the film after film formation. Therefore, when the polypropylene film of the present invention contains a primary agent, its content is usually less than 100 ppm by mass relative to the mass of the resin component (by mass when the resin component is considered as the whole).

[0093] Examples of secondary agents include hindered phenol antioxidants having a carbonyl group.

[0094] "Hindered phenol antioxidant having a carbonyl group" usually refers to a hindered phenol antioxidant having a carbonyl group, and is not particularly limited as long as the desired polypropylene film can be obtained.

[0095] Examples of hindered phenol antioxidants having a carbonyl group include triethylene glycol-bis[3-(3-tertiary-butyl-5-methyl-4-hydroxyphenyl)propionate] (product name: Irganox 245), 1,6-hexanediol-bis[3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate] (product name: Irganox 259), pentaerythrultyl tetrakis[3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate] (product name: Irganox 1010), and 2,2-thio-diethylenebis[3-(3,5-di-tertiary- Examples include butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1035), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1076), and N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide) (trade name: Irganox 1098). However, pentaerythrutyl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is particularly preferred because it has a high molecular weight, excellent compatibility with polypropylene, low volatility, and excellent heat resistance.

[0096] The polypropylene film of the present invention may contain one or more hindered phenol antioxidants (secondary agents) having a carbonyl group, for the purpose of suppressing deterioration that progresses over time during long-term use. When the polypropylene film of the present invention contains one or more hindered phenol antioxidants having a carbonyl group, the content thereof is preferably 2000 ppm by mass or more and 6000 ppm by mass or less, and more preferably 3000 ppm by mass or more and 6000 ppm by mass or less, relative to the mass of the resin component (by mass when the resin component is considered as the whole). A content of 2000 ppm by mass or more and 6000 ppm by mass or less of hindered phenol antioxidants having a carbonyl group in the film is preferable from the viewpoint of achieving appropriate effects.

[0097] A polypropylene film containing a hindered phenol antioxidant having a carbonyl group that has good molecular compatibility with polypropylene, in an optimal range of amounts, is preferable because it improves long-term durability.

[0098] The term "chlorine absorbent" generally refers to a chlorine absorbent used with polypropylene, and is not particularly limited as long as it can be used to obtain the desired polypropylene film. Examples of chlorine absorbents include metal soaps such as calcium stearate. When using such a chlorine absorbent, it can be included in an amount that does not adversely affect the desired polypropylene film.

[0099] Figure 1 is a schematic perspective view illustrating one embodiment of the metal-layer integrated polypropylene film of the present invention. As shown in Figure 1, the metal-layer integrated polypropylene film 1 comprises a biaxially oriented polypropylene film 2 and a metal-deposited electrode 3 laminated on the biaxially oriented polypropylene film 2 such that an insulating margin 4 (insulating groove: the length in the width direction is not particularly limited as long as the area of ​​the metal-deposited electrode 3 does not become too small and significantly impair the capacitance when used as a capacitor, but for example, 2 mm or more) is left at one end in the film width direction. The metal-deposited electrode 3 comprises a metal-deposited layer 3a laminated on the biaxially oriented polypropylene film 2 so as to be in direct contact with the biaxially oriented polypropylene film 2, and an electrode extraction portion 3b formed on a part of the upper surface of the metal-deposited layer 3a. The metal-deposited layer 3a functions as an electrode when the metal-layer integrated polypropylene film is used as a capacitor. The electrode extraction portion 3b is the portion known as the heavy edge.

[0100] As the metal used in the metal deposition layer 3a and the electrode extraction section 3b, for example, individual metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, mixtures of several of these, and alloys thereof can be used. However, considering the environment, economy, and capacitor performance, zinc and aluminum are preferred.

[0101] The layer structure of the metal layer is not particularly limited. The metal layer may be a single layer or multiple layers having the same or different compositions.

[0102] The thickness of the metal vapor-deposited layer 3a and the electrode extraction portion 3b is controlled by the film resistance (resistance per unit area, unit: Ω / sq). Since the resistance is inversely proportional to the thickness, a lower film resistance corresponds to a thicker film. When the metal-layer integrated polypropylene film 1 is used as a capacitor, dielectric breakdown may occur at points in the metal-layer integrated polypropylene film 1 that are weak in terms of dielectric strength. When dielectric breakdown occurs, heat is generated instantaneously, causing the metal vapor-deposited layer 3a to evaporate and the insulation to recover (self-healing). The evaporation of the metal vapor-deposited layer 3a (the occurrence of self-healing) restores the function of the capacitor, making it possible to continue using it.

[0103] The ease with which the metal vapor-deposited layer 3a evaporates (ease of self-healing) varies depending on the film resistance (film thickness). The film resistance of the metal vapor-deposited layer 3a is preferably 1 Ω / sq or higher, and more preferably 5 Ω / sq or higher. If the film resistance is lower than 1 Ω / sq, evaporation of the metal vapor-deposited layer 3a becomes difficult (self-healing becomes difficult), which is undesirable because it increases the risk of leakage current flowing due to dielectric breakdown and ignition due to heat generation.

[0104] The film resistance of the metal vapor-deposited layer 3a is preferably 30 Ω / sq or less, and more preferably 27 Ω / sq or less. If the film resistance exceeds 30 Ω / sq, evaporation of the metal vapor-deposited layer 3a is more likely to occur (self-healing is more likely to occur), which is undesirable because it significantly reduces the capacitance of the capacitor.

[0105] The film resistance of the electrode extraction section 3b (heavy edge) is preferably 1Ω / sq or more and 7Ω / sq ​​or less, and more preferably 2Ω / sq or more and 6Ω / sq or less.

[0106] 2. Method for manufacturing polypropylene film The polypropylene film of the present invention is preferably biaxially oriented, as described above. When the polypropylene film of the present invention is a biaxially oriented polypropylene film, it can be manufactured by a generally known method for manufacturing biaxially oriented polypropylene films. For example, it can be manufactured by preparing a cast sheet from a polypropylene resin composition obtained by mixing a first polypropylene resin and a second polypropylene resin, or the first polypropylene resin, together with other resins, additives, etc., as needed, and then biaxially oriented the cast sheet.

[0107] In one embodiment of the present invention, as described below, it is preferable to set the heating and melting temperature in the cast sheet manufacturing process to a relatively high temperature, the cooling drum temperature in the cast sheet manufacturing process to a relatively high temperature, the longitudinal stretching temperature to a relatively high temperature, and to appropriately adjust other stretching conditions. Furthermore, in one embodiment of the present invention, it is preferable to set the heating and melting temperature in the cast sheet manufacturing process to a relatively high temperature, and to set the cooling drum temperature or the longitudinal stretching temperature in the cast sheet manufacturing process to a relatively high temperature.

[0108] 2-1. Preparation of polypropylene resin composition There are no particular limitations on the method for preparing the polypropylene resin composition, but examples include a method of dry blending the first polypropylene resin and the second polypropylene resin, or polymerized powder or pellets of the first polypropylene resin, together with other resins, additives, etc. as needed, using a mixer, or a method of supplying the first polypropylene resin and the second polypropylene resin, or polymerized powder or pellets of the first polypropylene resin, together with other resins, additives, etc. as needed, to a kneader and melt-kneading to obtain a melt-blended resin composition.

[0109] Mixers and kneaders are not particularly limited. Kneaders may be single-screw, twin-screw, or multi-screw types. In the case of twin-screw or multi-screw types, either co-rotating or staggered rotation kneading is acceptable.

[0110] In the case of blending by melt kneading, the kneading temperature is not particularly limited as long as good kneading is achieved, but it is preferably in the range of 170 to 320°C, more preferably in the range of 200 to 300°C, and even more preferably in the range of 230 to 270°C. To suppress deterioration during the kneading of the resin, an inert gas such as nitrogen may be purged into the kneader. The melt-kneaded resin can be pelletized to an appropriate size using a generally known granulator to obtain pellets of the melt-blended resin composition.

[0111] When preparing a polypropylene resin composition, a primary agent as an antioxidant, as described in the section on additives above, may be added to suppress thermal degradation and oxidative degradation in the extruder.

[0112] When the polypropylene resin composition contains a primary agent, its content is preferably 1,000 ppm to 5,000 ppm by mass relative to the mass of the resin component (by mass when the resin component is considered as the whole). This antioxidant is almost entirely consumed during the molding process in the extruder, and almost none remains in the film after film formation.

[0113] A hindered phenol antioxidant having a carbonyl group, as described in the section on additives above, can be added to the polypropylene resin composition as a secondary agent.

[0114] When a polypropylene resin composition contains a hindered phenol antioxidant having a carbonyl group, its content is preferably 100 ppm to 10,000 ppm by mass, and more preferably 3,000 ppm to 7,000 ppm by mass, relative to the mass of the resin component (by mass when the resin component is considered as a whole). A considerable amount of the hindered phenol antioxidant having a carbonyl group is consumed in the extruder.

[0115] When a polypropylene resin composition does not contain a primary agent, a larger amount of hindered phenol antioxidant containing a carbonyl group can be used. This is because the consumption of hindered phenol antioxidant containing a carbonyl group increases in the extruder. When a polypropylene resin composition does not contain a primary agent and contains a hindered phenol antioxidant containing a carbonyl group, its content is 4000 ppm to 8000 ppm by mass relative to the mass of the resin components (by mass when the resin components are considered as a whole).

[0116] 2-2. Preparation of the cast sheet Cast sheets can be obtained by supplying pellets of a pre-made dry blend resin composition and / or melt blend resin composition to an extruder, heating and melting them, passing them through a filter, heating and melting them to a relatively high temperature, preferably 255°C to 320°C, more preferably 260°C to 300°C, and even more preferably 265°C to 280°C, and extruding them from a T-die, and then cooling and solidifying them in at least one metal drum held at a relatively high temperature, preferably 96°C to 120°C, more preferably 96°C to 110°C, and even more preferably 96°C to 100°C (cast temperature). At this time, it is preferable to press the extruded resin composition against the metal drum with an air knife. The side that contacts the metal drum becomes the first surface, and the opposite side (the side with the air knife) becomes the second surface.

[0117] The thickness of the cast sheet is not particularly limited as long as the desired polypropylene film can be obtained, but is preferably 0.05 mm to 2 mm, more preferably 0.1 mm to 1 mm.

[0118] Furthermore, during the production process of cast sheets (especially inside the extruder), polypropylene inevitably undergoes some degree of thermal degradation (oxidative degradation) and shear degradation. The degree of such degradation, i.e., changes in molecular weight distribution and stereoregularity, can be suppressed by nitrogen purging inside the extruder (inhibition of oxidation), the screw shape inside the extruder (shear force), the internal shape of the T-die during casting (shear force), the amount of antioxidant added (inhibition of oxidation), and the winding speed during casting (extension force).

[0119] 2-3. Stretching process The biaxially oriented polypropylene film can be manufactured by stretching the cast sheet. A sequential biaxial stretching method is preferred as the stretching method. In the sequential biaxial stretching method, first the cast sheet is kept at a relatively high temperature, preferably 142-180°C, more preferably 143-160°C, and even more preferably 144-150°C, and passed between rolls with a speed difference to be stretched preferably 3-7 times, more preferably 4-6 times, in the flow direction, and immediately cooled to room temperature. Subsequently, the stretched film is led to a tenter and transversely stretched 3-11 times (preferably 8-11 times) in the width direction at a temperature preferably 150-160°C, more preferably 150-159°C, even more preferably 150-158°C, and even more preferably 150-157°C, then relaxed and heat-set, and wound into a roll shape.

[0120] The longitudinal stretching speed is preferably 100 to 100,000% / sec, more preferably 1,000 to 80,000% / sec, even more preferably 60,000 to 70,000% / sec, and even more preferably 65,000 to 70,000% / sec. The transverse stretching speed is preferably 10 to 800% / sec, more preferably 100 to 600% / sec, even more preferably 300 to 400% / sec, and even more preferably 300 to 350% / sec.

[0121] The film, wound in a roll, is subjected to an aging treatment in an atmosphere of approximately 20-45°C. After being unwound (or fed out), it is slit (cut) to the desired product width using a slitter or similar tool, and then each section is wound again.

[0122] This stretching process results in a film with excellent mechanical strength and rigidity.

[0123] It is preferable to perform corona discharge treatment on the polypropylene film online or offline after the stretching and heat setting processes are completed. Corona discharge treatment can improve the adhesive properties in subsequent processes such as metal vapor deposition. Corona discharge treatment can be performed using known methods. It is preferable to use air, carbon dioxide, nitrogen gas, or a mixture thereof as the atmospheric gas.

[0124] 3. Method for manufacturing a metal-layer integrated polypropylene film The metal-layer-integrated polypropylene film of the present invention can be obtained, for example, by a method that includes the step of laminating a metal layer on one or both sides of the polypropylene film of the present invention. Examples of methods for laminating a metal layer on one or both sides of the polypropylene film of the present invention include vacuum deposition and sputtering. From the viewpoint of productivity and economic efficiency, vacuum deposition is preferred. Examples of vacuum deposition methods include the crucible method and the wire method, but are not particularly limited, and the most suitable method can be selected as appropriate.

[0125] In the vacuum deposition method described above, the thickness of the metal layer is controlled by the film resistance. In the vacuum deposition method, the film resistance of the metal deposition layer 3a is preferably 1Ω / □Ω / sq or higher, and more preferably 5Ω / □Ω / sq or higher. Furthermore, the film resistance of the metal deposition layer 3a is preferably 30Ω / □Ω / sq or lower, and more preferably 27Ω / □Ω / sq or lower.

[0126] The film resistance of the electrode extraction section 3b (heavy edge) is preferably 1Ω / □Ω / sq or more and 7Ω / □Ω / sq or less, and more preferably 2Ω / □Ω / sq or more and 6Ω / □Ω / sq or less.

[0127] While there are no particular limitations on the margin pattern when laminating metal layers by vapor deposition, it is preferable to apply a pattern including so-called special margins, such as a fishnet pattern or a T-margin pattern, to one side of the film in order to improve characteristics such as the safety of the capacitor. This enhances safety and is effective in preventing capacitor failure and short circuits.

[0128] Any method known to form a margin, such as the tape method or the oil method, can be used without any limitations.

[0129] After laminating a metal layer on one or both sides of the polypropylene film of the present invention, a post-heat treatment may be performed. Examples of post-heat treatment conditions include applying silicone oil heated to 120-130°C.

[0130] A preferred method for manufacturing the metal-layer-integrated polypropylene film of the present invention will be described below with reference to Figure 2. As will be described later, the cumulative dielectric breakdown point density can be suppressed by controlling the deposition conditions (mainly the voltage-to-rate ratio per unit width of the cooling roll and the discharge amount).

[0131] Figure 2 is a schematic diagram illustrating a method for manufacturing a metal-layer integrated polypropylene film. It is preferable to manufacture the metal-layer integrated polypropylene film using the manufacturing apparatus described below. As shown in Figure 2, the manufacturing apparatus for a metal-layer integrated polypropylene film comprises a dielectric film supply unit 101, an insulating margin formation unit 102, a special vapor deposition pattern margin formation unit 103, a metal vapor deposition unit 104, a DC magnetron discharge electrode 105, and a metal-layer integrated film winding unit 106.

[0132] The dielectric film supply unit 101 supports a biaxially oriented polypropylene film roll 2R around which the biaxially oriented polypropylene film 2 is wound, and supplies the biaxially oriented polypropylene film 2. The biaxially oriented polypropylene film 2 supplied from the biaxially oriented polypropylene film roll 2R is transported to the insulation margin forming unit 102.

[0133] The insulating margin forming section 102 applies oil in a pattern corresponding to the insulating margin 4 pattern to the metal vapor-deposited surface 2a of the biaxially oriented polypropylene film 2 to form an oil mask. The oil mask is intended to prevent metal particles from adhering to the portion that will become the insulating margin in the metal layer integrated polypropylene film 1 during the vapor deposition process. The insulating margin forming section 102 vaporizes oil stored in an oil tank and applies the oil directly to the metal vapor-deposited surface 2a of the polypropylene film 2 through a nozzle (slit) provided in the tank to form an oil mask.

[0134] The special vapor deposition pattern margin forming unit 103 applies oil to the metal vapor deposition surface 2a of the biaxially oriented polypropylene film 2 in a pattern that roughly corresponds to the electrode pattern of the metal vapor deposition layer 3a, thereby forming an oil mask. The oil mask prevents metal particles from adhering to the longitudinal and transverse margins of the metal layer-integrated polypropylene film 1 during the vapor deposition process. The special vapor deposition pattern margin forming unit 103 includes an oil tank 103a, an anilox roll 103b, a transfer roll 103c, a plate roll 103d, and a backup roll 103e. The oil tank 103a vaporizes the stored oil and ejects it from a nozzle. The anilox roll 103b and the transfer roll 103c rotate with the oil ejected from the nozzle of the oil tank 103a adhering to their outer surfaces. The backup roll 103e faces the plate roll 103d via the polypropylene film 2 and contacts the cooling roll contact surface 2b of the biaxially oriented polypropylene film 2.

[0135] The biaxially oriented polypropylene film 2, having passed through the insulating margin formation section 102 and the special vapor deposition pattern margin formation section 103, is transported to the vapor deposition section 104.

[0136] The vapor deposition unit 104 comprises metal vapor generation units 104a and 104b, and a cooling roll 104c facing the metal vapor generation units 104a and 104b via a biaxially oriented polypropylene film 2. The metal vapor generation unit 104a generates metal vapor by supplying it to a heated boat by passing an electric current through a metal wire, which is the material of the metal vapor deposition layer 3a, and deposits this metal vapor onto the metal vapor deposition surface 2a of the biaxially oriented polypropylene film 2. The metal vapor generation unit 104b generates metal vapor by heating and evaporating the metal that is the material of the electrode extraction unit 3b, and deposits it on top of the metal vapor deposition layer 3a that has been previously formed on the metal vapor deposition surface 2a of the biaxially oriented polypropylene film 2 by the metal vapor generation unit 104a. As a result, the metal vapor deposition layer in the electrode extraction unit 3b becomes thicker than the metal vapor deposition layer in the other parts, forming a heavy edge structure. Furthermore, the metal vapor generated in the metal vapor generation sections 104a and 104b adheres to the parts of the biaxially oriented polypropylene film 2 other than the oil mask, thereby forming the metal vapor deposition electrode 3.

[0137] A voltage is applied to the cooling roll 104C, and the application of this voltage causes the cooling roll contact surface 2b of the biaxially oriented polypropylene film 2 to adhere closely to the cooling roll 104C, thereby cooling the biaxially oriented polypropylene film 2. The degree of adhesion of the cooling roll contact surface 2b to the cooling roll 104C is proportional to the applied voltage (V) to the cooling roll 104C, and inversely proportional to the width (m) and deposition speed (m / min) of the cooling roll. Therefore, the voltage-to-speed ratio per unit width of the cooling roll (unit: V·min / m) 2 The higher the voltage-to-speed ratio (V·min / m), the closer the cooling roll contact surface 2b of the biaxially oriented polypropylene film 2 is to the cooling roll 104C, increasing cooling efficiency and preventing thermal damage to the vapor-deposited metal. The voltage-to-speed ratio per unit width of the cooling roll is 0.20 V·min / m 2 More than 0.45V min / m 2The following is preferable: The voltage-to-speed ratio per unit width of the cooling roll is 0.20 V·min / m 2 If the ratio is smaller, the cooling roll contact surface 2b of the biaxially oriented polypropylene film 2 will not adhere sufficiently to the cooling roll 104C, resulting in poor cooling efficiency. This causes thermal damage to the biaxially oriented polypropylene film 2 or the metal-layer integrated polypropylene film 1, and as a result, the dielectric strength of the metal-layer integrated polypropylene film 1 decreases, leading to a reduced lifespan due to dielectric breakdown or overheating when used as a capacitor. Furthermore, if the voltage-to-speed ratio per unit width of the cooling roll is 0.45 V·min / m 2If the contact surface 2b of the biaxially oriented polypropylene film 2 with the cooling roll is sufficiently in contact with the cooling roll 104C, the cooling efficiency improves and thermal damage to the biaxially oriented polypropylene film 2 or the metal-layer integrated polypropylene film 1 is reduced. However, electrical discharge is more likely to occur between the biaxially oriented polypropylene film 2 and the roll 104C, or between the metal-layer integrated polypropylene film 1 and the roll 104C. If discharge occurs, the biaxially oriented polypropylene film 2 or the metal-layer integrated polypropylene film 1 will suffer electrical damage. Even if discharge does not occur, the metal-layer integrated polypropylene film 1 will become more easily charged, and when it is wound into a roll in the metal-layer integrated film winding section 106, electrical damage due to electrostatic discharge will occur, damaging the metal-layer integrated polypropylene film 1. When the biaxially oriented polypropylene film 2 or the metal-layer integrated polypropylene film 1 is damaged by electrical damage, its withstand voltage decreases, making it more susceptible to dielectric breakdown and reduced lifespan due to overheating when used as a capacitor. Furthermore, when the metal-layer integrated polypropylene film 1 becomes charged, its slipperiness deteriorates, making it more prone to wrinkles during winding in the metal-layer integrated film winding section 106 or during the element winding process in capacitor manufacturing. Also, during the pressing process after element winding in capacitor manufacturing, buckling is more likely to occur due to the deterioration of slipperiness caused by static charge. Wrinkles and buckling are undesirable because they damage the metal-layer integrated polypropylene film 1, leading to dielectric breakdown of the capacitor and reduced lifespan due to overheating. The voltage-speed ratio per unit width of the cooling roll is 0.24 V·min / m 2 Above, 0.41V min / m 2 The following are even more preferable.

[0138] The temperature of the cooling roll 104C is preferably -18°C or lower, and more preferably -19°C or lower, from the viewpoint of preventing thermal damage to the biaxially oriented polypropylene film 2 or the metal-layer integrated polypropylene film 1.

[0139] The metal-layer integrated polypropylene film 1, formed by forming a metal vapor deposition electrode 3 on a biaxially oriented polypropylene film 2 in a vapor deposition section 104, passes through the static electricity removal section 105. The static electricity removal section 105 is equipped with DC magnetron discharge electrodes 105a, 105b, 105c, and 105d. When argon gas is supplied and power is supplied to the DC magnetron discharge electrode sections 105a, 105b, 105c, and 105d, argon gas ions are generated. When the metal-layer integrated polypropylene film 1 passes through the static electricity removal section 105 with argon gas ions generated, the static electricity on the metal-layer integrated polypropylene film 1 is neutralized by the argon gas ions, preventing the metal-layer integrated polypropylene film roll 1R from becoming charged. The degree of electrostatic neutralization exerted by argon gas ions on the metal-layer integrated polypropylene film 1 can be expressed in terms of discharge amount. This discharge amount is proportional to the total power (W) of the DC magnetron discharge electrode sections 105a, 105b, 105c, and 105d, and inversely proportional to the width (m) of the DC magnetron discharge electrode section and the deposition rate (m / min). Here, the widths of each of the DC magnetron discharge electrode sections 105a, 105b, 105c, and 105d are the same, and the width (m) of the DC magnetron discharge electrode section is the width of each individual section, not the total width of the DC magnetron discharge electrode sections 105a, 105b, 105c, and 105d. The discharge amount is 1.5 W·min / m 2 Above, 3.7W min / m 2 The following is preferable: Discharge rate of 3.7 W·min / m 2 If the discharge rate is too high, the discharge at the DC magnetron discharge electrodes 105a, 105b, 105c, and 105d becomes too strong, causing electrical damage to the metal-layer integrated polypropylene film 1. Furthermore, even if no discharge occurs, the metal-layer integrated polypropylene film 1 becomes charged by argon gas ions. Also, if the discharge rate is 1.5 W·min / m², 2If the static charge is too small, the neutralization of static electricity in the metal-layer integrated polypropylene film 1 becomes insufficient, causing it to become charged. When the metal-layer integrated polypropylene film 1 is damaged by electrical damage, its dielectric strength decreases, making it more susceptible to dielectric breakdown and reduced lifespan due to overheating when used as a capacitor. Furthermore, when the metal-layer integrated polypropylene film 1 becomes charged, electrical damage occurs due to the discharge of static electricity from the metal-layer integrated polypropylene film 1 when it is wound into a roll shape in the metal-layer integrated film winding unit 106, causing damage to the metal-layer integrated polypropylene film 1. When the metal-layer integrated polypropylene film 1 is damaged, its dielectric strength decreases, making it more susceptible to dielectric breakdown and reduced lifespan due to overheating when used as a capacitor. In addition, when the metal-layer integrated polypropylene film 1 becomes charged, its slipperiness deteriorates, making it more prone to wrinkles during winding in the metal-layer integrated film winding unit 106 or during the element winding process in capacitor manufacturing. Furthermore, during the press processing process after element winding in capacitor manufacturing, buckling is more likely to occur due to the deterioration of slipperiness caused by the charge. Wrinkling and buckling are undesirable because they damage the metal-layer integrated polypropylene film 1, leading to dielectric breakdown of the capacitor and reduced lifespan due to overheating. The discharge rate is 1.9 W·min / m 2 Above, 3.3W min / m 2 The following are preferable.

[0140] The metal-layer integrated polypropylene film 1 that has passed through the static electricity removal section 105 is transported to the metal-layer integrated film winding section 106, where it is wound up to become a metal-layer integrated polypropylene film roll 1R.

[0141] Using the above manufacturing apparatus, a metal deposition electrode 3 can be formed on the metal deposition surface 2a of the polypropylene film 2 to obtain a polypropylene film 1 with an integrated metal layer.

[0142] 4. Capacitor In one embodiment, the present invention relates to a capacitor (which may be referred to herein as "the capacitor of the present invention") that includes the metal layer integrated polypropylene film of the present invention. This will be described below.

[0143] The capacitor of the present invention not only possesses a certain level of capacitance stability for long-term use, but also exhibits excellent insulation resistance stability under high-temperature, high-voltage loads.

[0144] For example, the capacitor of the present invention has a capacitance change rate, as measured by the high-temperature short-time withstand voltage test described in the examples, preferably -5% or more, more preferably -2% or more. The upper limit of this capacitance change rate is not particularly limited and may be, for example, 2%, 1%, 0.5%, 0.2%, or 0%.

[0145] For example, the capacitor of the present invention has a capacitance change rate measured by the 105°C lifetime test described in the examples, preferably -25% or more, more preferably -20% or more, and even more preferably -15% or more. The upper limit of this capacitance change rate is not particularly limited and may be, for example, 2%, 1%, 0.5%, 0.2%, or 0%.

[0146] For example, the capacitor of the present invention has an insulation resistance value, as measured by the 105°C lifetime test described in the examples, preferably 20 MΩ or more, more preferably 300 MΩ or more, even more preferably 500 MΩ or more, even more preferably 800 MΩ or more, and particularly preferably 1000 MΩ or more. The upper limit of this insulation resistance value is not particularly limited and may be, for example, 20000 MΩ, 15000 MΩ, or 13000 MΩ.

[0147] For example, the capacitor of the present invention has a capacitance change rate, as measured by the 115°C lifetime test described in the examples, preferably -30% or more, more preferably -25% or more, and even more preferably -20% or more. The upper limit of this capacitance change rate is not particularly limited and may be, for example, 2%, 1%, 0.5%, 0.2%, or 0%.

[0148] For example, the capacitor of the present invention has an insulation resistance value, as measured by the 115°C lifetime test described in the examples, preferably 20 MΩ or more, more preferably 100 MΩ or more, even more preferably 150 MΩ or more, even more preferably 200 MΩ or more, and particularly preferably 250 MΩ or more. The upper limit of this insulation resistance value is not particularly limited and may be, for example, 20,000 MΩ, 15,000 MΩ, or 13,000 MΩ.

[0149] For example, the capacitor of the present invention is measured by the high-voltage application test described in the examples. The insulation resistance is preferably 20 MΩ or more, more preferably 3000 MΩ or more, even more preferably 5000 MΩ or more, even more preferably 8000 MΩ or more, and particularly preferably 10000 MΩ or more. The upper limit of the insulation resistance is not particularly limited and may be, for example, 20000 MΩ, 15000 MΩ, or 13000 MΩ.

[0150] In one embodiment of the present invention, the process of manufacturing a capacitor involves, for example, winding a film. For example, two pairs of metal-layer integrated polypropylene films of the present invention are stacked and wound together so that the metal layer and the polypropylene film of the present invention are alternately laminated, and furthermore, so that the insulating margins are on opposite sides. In this case, it is preferable to stack the two pairs of metal-layer integrated polypropylene films of the present invention with a 1-2 mm offset so that the electrode extraction portions extend outside the insulating margin of the other pair. The winding machine used is not particularly limited, and for example, an automatic winding machine 3KAW-N2 manufactured by Kaito Manufacturing Co., Ltd. can be used.

[0151] When manufacturing flat-type capacitors, the resulting winding is usually pressed after winding. Pressing promotes winding tightness and element formation of the capacitor. The optimal pressure applied varies depending on the thickness of the film used in this invention, as it controls and stabilizes the interlayer gap, but the load is typically between 1 and 20 kgf / cm². 2 That is the case.

[0152] Next, a capacitor is fabricated by applying metal-coated electrodes to both ends of the wound material using thermal spraying.

[0153] Further heat treatment is applied to the capacitor. That is, the present invention includes a step of applying heat treatment to the capacitor (hereinafter sometimes referred to as "thermal aging"). The heat treatment temperature is not particularly limited, but for example, it is 80 to 190°C. The method of applying heat treatment to the capacitor is not particularly limited, but may be appropriately selected from known methods, such as using a constant temperature bath or high-frequency induction heating under atmospheric pressure or a vacuum atmosphere. The time for applying heat treatment is not particularly limited, but for example, when using a constant temperature bath under a vacuum atmosphere, it is preferable to apply it for 1 hour or more, more preferably for 3 hours or more, in order to obtain mechanical and thermal stability, but it is more preferable to apply it for 20 hours or less in order to prevent molding defects such as heat wrinkles and mold formation.

[0154] By applying heat treatment, the effects of thermal aging can be obtained. Specifically, the voids between the films constituting the capacitor based on the metal-layer integrated polypropylene film of the present invention are reduced, suppressing corona discharge when the capacitor is used, and furthermore, the internal structure of the metal-layer integrated polypropylene film of the present invention changes, promoting crystallization. As a result, it is believed that the voltage resistance will be further improved.

[0155] Lead wires are typically welded to the metallicon electrodes of a capacitor that has undergone thermal aging. Furthermore, although not particularly limited, it is preferable to enclose the capacitor in a case and pot it with epoxy resin to provide weather resistance and, in particular, prevent humidity degradation.

[0156] The capacitor of the present invention, utilizing the polypropylene film of the present invention, is suitable for use in high-temperature environments, is compact, and can be a high-capacitance capacitor (for example, a capacitance of 5 μF or more, preferably 10 μF or more, more preferably 20 μF or more, even more preferably 30 μF or more, and particularly preferably 40 μF or more. The upper limit of capacitance is not particularly limited, and can be, for example, 100 μF, 80 μF, 70 μF, or 60 μF). Therefore, the capacitor of the present invention can be used as a high-voltage capacitor, a filter capacitor and smoothing capacitor for various switching power supplies, converters and inverters, etc., used in electronic equipment and electrical equipment. Furthermore, the capacitor of the present invention can be suitably used as an inverter capacitor and converter capacitor for controlling drive motors in electric vehicles and hybrid vehicles, for which demand has been increasing in recent years. [Examples]

[0157] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Unless otherwise specified, parts and % refer to "parts by mass" and "mass %", respectively.

[0158] (1) Preparation of polypropylene resin Table 1 shows the polypropylene resins used to produce the biaxially oriented polypropylene films of the examples and comparative examples.

[0159] Resin A, shown in Table 1, is a product manufactured by Prime Polymer Co., Ltd. Resin B is S802M manufactured by Daehan Oil & Chemical Co., Ltd. Both resins A and B are linear homopolypropylene resins.

[0160] Table 1 shows the number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), molecular weight distribution (Mz / Mn), melt flow rate (MFR), and heptane-insoluble content (HI) of linear homopolypropylene resin. These values ​​are for the raw resin pellet form. The measurement method is as follows.

[0161] (1-1) Measurement of the number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of linear polypropylene resins. Using GPC (gel permeation chromatography), the number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of each resin were measured under the following conditions.

[0162] Specifically, a high-temperature GPC instrument with a built-in differential refractometer (RI), the HLC-8121GPC-HT model, manufactured by Tosoh Corporation, was used. Three TSKgel GMHHR-H(20)HT columns, also manufactured by Tosoh Corporation, were used in conjunction. Measurements were taken at a column temperature of 140°C, with trichlorobenzene flowing as the eluent at a flow rate of 1.0 ml / min. A calibration curve for the molecular weight M was created using standard polystyrene manufactured by Tosoh Corporation, and the measured values ​​were converted to the molecular weight of polypropylene using the Q-factor to obtain the number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz). The molecular weight distribution (Mw / Mn) was obtained using the Mw and Mn values. The molecular weight distribution (Mz / Mn) was also obtained using the Mz and Mn values.

[0163] (1-2) Measurement of Melt Flow Rate (MFR) For each resin, the melt flow rate (MFR) in the form of raw resin pellets was measured using a melt indexer from Toyo Seiki Co., Ltd., in accordance with condition M of JIS K 7210. Specifically, first, a 4g sample was placed in a cylinder heated to a test temperature of 230°C and preheated for 3.5 minutes under a load of 2.16kg. Then, the weight of the sample extruded from the bottom hole over 30 seconds was measured, and the MFR (g / 10min) was determined. The above measurement was repeated three times, and the average value was taken as the measured MFR. The results are shown in Table 1.

[0164] (1-3) Measurement of heptane insoluble matter (HI) For each resin, a sample of approximately 3 g was prepared by press molding to 10 mm × 35 mm × 0.3 mm. Next, approximately 150 mL of heptane was added and Soxhlet extraction was performed for 8 hours. The heptane-insoluble portion was calculated from the sample mass before and after extraction. The results are shown in Table 1.

[0165] (1-4) Physical properties of polypropylene resin

[0166] [Table 1]

[0167] (2) Preparation of biaxially oriented polypropylene film Resin A and resin B were dry-blended. The mixing ratio was (resin A):(resin B)=75:25 by mass. Then, the dry-blended resin was melted at a resin temperature of 270°C, extruded using a T-die, and solidified by winding it onto a metal drum maintained at a surface temperature of 98°C. This produced a cast sheet with a thickness of 115 μm. During this process, the molten extruded resin composition was pressed against the metal drum with an air knife while producing the cast sheet. The obtained unstretched cast sheet was kept at a temperature of 146°C, passed between rolls with a speed difference, and stretched five times in the flow direction at a stretching speed of 67300% / second, and immediately cooled to room temperature. Subsequently, the stretched film was guided to a tenter and stretched ten times in the width direction at a temperature of 155°C and a stretching speed of 335% / second, followed by relaxation and heat setting. Then, 25 W·min / m was applied to the film surface (metal drum contact side). 2 After performing corona discharge treatment in air at a processing speed, the material was wound up and subjected to aging treatment in an atmosphere of approximately 30°C. This resulted in a biaxially oriented polypropylene film with a thickness of 2.3 μm.

[0168] (3) Measurement of physical properties of biaxially oriented polypropylene film (3-1) Thickness measurement of biaxially oriented polypropylene film The thickness (in μm) of the biaxially oriented polypropylene film prepared in (2) above was measured. Specifically, the measurement was performed in accordance with JIS-C2330, except that it was measured at 100 ± 10 kPa using a Citizen Seimitsu MEI-11 paper thickness gauge. As a result, the thickness of the biaxially oriented polypropylene film was 2.3 μm.

[0169] (3-2) Measurement of 120°C heat shrinkage rate of biaxially oriented polypropylene film The heat shrinkage rate (120°C heat shrinkage rate) (unit: %) of the biaxially oriented polypropylene film prepared in (2) above was measured under the processing condition of 120°C for 15 minutes. Specifically, samples were cut from the roll. The sample size for measuring the 120°C heat shrinkage rate in the MD direction was 130 mm in the MD direction and 20 mm in the TD direction, and the sample for measuring the 120°C heat shrinkage rate in the TD direction was 20 mm in the MD direction and 130 mm in the TD direction. Three samples each were prepared for measuring the 120°C heat shrinkage rate in the MD direction and the 120°C heat shrinkage rate in the TD direction. Next, for the three samples for measuring the 120°C heat shrinkage rate in the MD direction, markings were made 15 mm from each end of the 130 mm MD direction. At this time, the distance between the markings was 100 mm. Similarly, for the three samples for measuring the 120°C heat shrinkage rate in the TD direction, markings were made 15 mm from each end of the 130 mm TD direction. At this time, the distance between the markings was 100 mm. Next, each sample with the markings was suspended without load in a 120°C hot air circulating constant temperature bath so that the direction in which it was cut to 130 mm was vertical, and held for 15 minutes. After that, it was cooled to room temperature (23°C), the distance between the markings was measured with a ruler, and the thermal shrinkage rate (%) for each sample was calculated using the following formula: Thermal shrinkage rate (%) = (distance between markings before heating - distance between markings after heating) / distance between markings before heating × 100.

[0170] The average of the heat shrinkage rates of three samples measured in the MD direction at 120°C was defined as the MD direction 120°C heat shrinkage rate (%). Similarly, the average of the heat shrinkage rates of three samples measured in the TD direction at 120°C was defined as the TD direction 120°C heat shrinkage rate (%).

[0171] For measurement conditions other than those described herein, we followed the "25. Dimensional changes" section of JIS C 2151:2019.

[0172] As a result, the 120°C heat shrinkage rate of the biaxially oriented polypropylene film was 3.7% in the MD direction, and 0.4% in the TD direction.

[0173] (3-3) Measurement of heat shrinkage rate of biaxially oriented polypropylene film at 140°C The thermal shrinkage rate (140°C thermal shrinkage rate) (unit: %) of the biaxially oriented polypropylene film prepared in (2) above was measured under the treatment condition of 140°C for 15 minutes. The 140°C thermal shrinkage rate (%) in the MD direction and the 140°C thermal shrinkage rate (%) in the TD direction were calculated using the same method as for the 120°C thermal shrinkage rate, except that the 120°C hot air circulating constant temperature bath was changed to a 140°C hot air circulating constant temperature bath.

[0174] As a result, the heat shrinkage rate of the biaxially oriented polypropylene film at 140°C in the MD direction was 6.1%, and the heat shrinkage rate at 140°C in the TD direction was 3.1%.

[0175] (3-4) Measurement of the tensile modulus of biaxially oriented polypropylene film The tensile modulus (GPa) of the biaxially oriented polypropylene film prepared in (2) above was measured in accordance with JIS K-7127 (1999). Specifically, samples were cut from the roll. The sample size for measuring the tensile modulus in the MD direction was 200 mm in the MD direction and 15 mm in the TD direction, and the sample for measuring the tensile modulus in the TD direction was 15 mm in the MD direction and 200 mm in the TD direction. Next, a tensile test was performed using a tensile and compression testing machine (manufactured by Minebea Co., Ltd.) under the test conditions (measurement temperature 23°C, chuck distance 100 mm, tensile speed 200 mm / min). Then, the tensile modulus in the MD direction (GPa) and the tensile modulus in the TD direction (GPa) were determined by automatic analysis using data processing software built into the testing machine.

[0176] As a result, the tensile modulus of the biaxially oriented polypropylene film was 2.76 GPa in the MD direction, and the tensile modulus of the TD direction was 4.56 GPa.

[0177] (3-5) Haze measurement of biaxially oriented polypropylene film The haze (in %) of the biaxially oriented polypropylene film prepared in (2) above was measured using a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136:2000. The sample was cut from a roll, with a sample size of 50 mm in the MD direction and 100 mm in the TD direction. As a result, the haze of the biaxially oriented polypropylene film was 3.1%.

[0178] (4) Production of film roll after cutting The biaxially oriented polypropylene film prepared in (2) above was unwound from the roll and cut in the width direction using a slitter. When winding the cut polypropylene film, a fiber-reinforced plastic core with an outer diameter of 176 mm was used, and a winding device equipped with a contact pressure roll was employed to apply surface pressure to the polypropylene film while winding. The cutting conditions were a speed of 300 m / min, winding force of 40 N / m, winding tension of 50 N / m, and winding surface pressure of 400 N / m. A rubber contact pressure roll with an outer diameter of 152 mm and a surface hardness of 40° was used, and a biaxially oriented polypropylene roll (post-cut film roll) with a width of 620 mm and a length of 75,000 m was produced. The film was visually inspected during winding to confirm that no wrinkles had formed. In addition, the end faces of the obtained post-cut film roll were inspected to confirm that no deviation of 2 mm or more had occurred.

[0179] (5) Preparation of polypropylene film with integrated metal layer <Example 1> Using a vapor deposition system (ULVAC, Inc., product name: EWE-060 roll-type vacuum deposition system), with a cooling roll temperature of -22°C and a voltage-to-speed ratio of 0.32 V·min / m per unit width of the cooling roll. 2 , discharge amount 2.5W min / m 2 Under these conditions, a special vapor deposition pattern margin and an insulating margin were formed on the cut film roll prepared in (4) above to impart film capacitor safety, and aluminum vapor deposition was performed so that the surface resistivity of the metal film was 20 Ω / sq, thereby obtaining a metal-layer integrated polypropylene film. A schematic diagram of the metal-layer integrated polypropylene film is shown in Figure 1. A schematic diagram of the manufacturing apparatus is shown in Figure 2.

[0180] <Example 2> The voltage-to-speed ratio per unit width of the cooling roll is 0.21 V·min / m. 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0181] <Example 3> The voltage-to-speed ratio per unit width of the cooling roll is 0.44 V·min / m. 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0182] <Example 4> Discharge rate: 1.6 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0183] <Example 5> Discharge rate: 3.6 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0184] <Example 6> The voltage-to-speed ratio per unit width of the cooling roll is 0.21 V·min / m. 2 The discharge rate is 3.6 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0185] <Comparative Example 1> The voltage-to-speed ratio per unit width of the cooling roll is 0.18 V·min / m. 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0186] <Comparative Example 2> The voltage-to-speed ratio per unit width of the cooling roll is 0.47 V·min / m. 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0187] <Comparative Example 3> Discharge rate: 1.3 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0188] <Comparative Example 4> Discharge rate: 3.9 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0189] <Comparative Example 5> The voltage-to-speed ratio per unit width of the cooling roll is 0.18 V·min / m. 2 The discharge rate is 3.9 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0190] <Comparative Example 6> The voltage-to-speed ratio per unit width of the cooling roll is 0.47 V·min / m. 2 The discharge rate is 3.9 W·min / m 2 A metal-layer integrated polypropylene film was obtained in the same manner as in Example 1, except for the aforementioned difference.

[0191] (6) Measurement of physical properties of metal-layer integrated polypropylene film For the metal-layer integrated polypropylene films obtained in Examples 1 to 6 and Comparative Examples 1 to 6, the cumulative dielectric breakdown point density (cumulative dielectric breakdown point density at 20°C at 425V / μm) was measured after a cumulative DC voltage application test at 20°C and 350-425V / μm, using the configuration shown in Figure 3 and following the procedure below. Under a 20°C environment, a DC voltage of 350V / μm was applied for 1 minute, and the number of dielectric breakdown points in the window area (100mm x 10mm) of the insulating polypropylene film was visually counted. After counting, a DC voltage of 375V / μm was applied for 1 minute, and the cumulative dielectric breakdown points in the window area of ​​the insulating polypropylene film were visually counted. Next, the DC voltage was increased by 25V / μm increments, and this operation was repeated up to 425V / μm, thereby applying the DC voltage cumulatively. The test was conducted using five metal-layer integrated polypropylene films, and the average value of the cumulative dielectric breakdown point at 425 V / μm at 20°C was used, with the window area of ​​the insulating polypropylene film (100 mm × 10 mm = 1,000 mm²) being used. 2 = 0.001m 2 Divide by ) to obtain the cumulative dielectric breakdown point density at 425V / μm at 20℃ (unit: points / m 2 The following was calculated. The results are shown in Tables 2 and 3.

[0192] (7) Evaluation (7-1) Evaluation of press processing yield The metal-layer integrated polypropylene films prepared in the examples and comparative examples were slit into 30mm wide rolls. Next, one roll of the 30mm wide metal-layer integrated polypropylene film with an insulating margin (2mm in width) on the left side when viewed from the unwinding side, and another roll with an insulating margin (2mm in width) on the right side when viewed from the unwinding side, were used. The two rolls were combined so that the electrode extraction portion of each roll protruded more than the insulating margin of the other metal-layer integrated polypropylene film roll. Using a Kaito Manufacturing Co., Ltd. automatic winding machine 3KAW-N2, 1350 turns were performed at a winding speed of 4m / sec, a winding tension of 180g, and a contact roller contact pressure of 260g.

[0193] The element wound with the element has a load capacity of 5.9 kgf / cm².2 The material was then flattened by pressing.

[0194] For the flattened elements that underwent press processing, the sides were observed while the press load was still applied to check for buckling of the metal-layer integrated polypropylene film. All elements that showed buckling were deemed unacceptable. For all flattened elements, the percentage of flattened elements that passed the above criteria was calculated as the press processing yield rate α, and evaluated using the following criteria. The results are shown in Tables 2 and 3.

[0195] A: α = 100% B: 100% > α ≥ 80% C:80%>α.

[0196] (7-2) Performance evaluation of capacitors As described in (7-1) above, zinc metal was sprayed onto the end faces of the flattened elements while the press load was still applied. The spraying conditions were a feed rate of 20 mm / s, a spraying voltage of 21 V, and a spraying pressure of 0.4 MPa. Spraying was performed to a thickness of 0.6 mm to 0.7 mm to form the electrode extraction area, and the elements were heat-treated in a vacuum constant temperature bath at 120°C for 15 hours under a vacuum atmosphere to cure them. In this way, flattened film capacitors were obtained. Subsequently, lead wires were soldered to the end faces of the flattened film capacitors and sealed with epoxy resin. The epoxy resin was cured by heating at 90°C for 2.5 hours, followed by heating at 120°C for another 2.5 hours. The capacitance of all the finished capacitors was 50 μF (±3 μF). The obtained capacitors were used in the following six tests.

[0197] (7-2-1) High-temperature, short-time withstand voltage test of capacitors (rate of change in capacitance) The initial capacitance (C0) of the obtained capacitor was measured before testing using a Hioki E.E. Corporation LCR high-tester 3522-50. Next, a DC voltage of 325 V / μm was applied to the capacitor for 10 seconds in a constant temperature bath at 105°C. The capacitance of the capacitor after voltage application was measured in the same manner, and the capacitance change rate (ΔC) before and after the test was calculated using the following formula: ΔC = [(Capacitance after voltage application) - C0] / C0 × 100 (%) It was calculated using the method described below.

[0198] Next, a DC voltage of 350 V / μm was applied for 10 seconds in a constant temperature bath at 105°C, and the capacitance was measured in the same manner. Then, in the constant temperature bath at 105°C, the DC voltage was increased by 25 V / μm increments, and this operation was repeated until the voltage reached 425 V / μm, thereby applying a cumulative DC voltage. The test was performed on two samples, and the average value of the rate of change of capacitance at 425 V / μm was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0199] A: ΔC ≥ -2% B: -2% > ΔC ≥ -5% C:-5%>ΔC

[0200] (7-2-2) Capacitor life test at 105°C (rate of change in capacitance) The initial capacitance (C0) of the obtained capacitors before testing was measured using a Hioki E.E. Corporation LCR HiTester 3522-50. Next, the capacitors were subjected to a DC voltage of 325 V / μm for 1,500 hours in a constant temperature chamber at 105°C. The capacitance of the capacitors after 1,500 hours (C1500H105C) was similarly measured, and the capacitance change rate (ΔC105C) before and after voltage loading was calculated using the following formula: ΔC105C = (C1500H105C - C0) / C0. The test was performed on two samples, and the average value of the capacitance change rate (ΔC105C) was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0201] A: ΔC105C≧-15% B: -15% > ΔC105C ≥ -25% C:-25%>ΔC105C

[0202] (7-2-3) Capacitor life test at 105°C (insulation resistance value) The obtained capacitors were subjected to a DC voltage of 325 V / μm for 1,500 hours in a constant temperature bath at 105°C. A shielding box SME-8350 was connected to a Hioki Electric Corporation DSM8104 super insulation resistance meter. The capacitors after 1,500 hours were placed inside the shielding box, and a DC voltage of 500V was applied. The insulation resistance value (IR105C) was read after 1 minute. The test was performed on two samples, and the average of their insulation resistance values ​​(IR105C) was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0203] For measurement conditions other than those described herein, the specifications of JIS C 5101-16:2009, "4.2.4 Insulation Resistance," were followed.

[0204] A: IR105C ≥ 500MΩ B: 500MΩ > IR105C ≥ 20MΩ C:20MΩ>IR105C

[0205] (7-2-4) Capacitor life test at 115°C (rate of change in capacitance) The initial capacitance (C0) of the obtained capacitors before testing was measured using a Hioki E.E. Corporation LCR HiTester 3522-50. Next, the capacitors were subjected to a DC voltage of 325 V / μm for 1,500 hours in a constant temperature chamber at 115°C. The capacitance of the capacitors after 1,500 hours (C1500H115C) was measured in the same manner, and the capacitance change rate (ΔC115C) before and after voltage loading was calculated using the following formula: ΔC115C = (C1500H115C - C0) / C0. The test was performed on two samples, and the average value of the capacitance change rate (ΔC115C) was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0206] A: ΔC115C≧-20% B: -20% > ΔC115C ≥ -30% C:-30%>ΔC115C

[0207] (7-2-5) Capacitor life test at 115°C (insulation resistance value) The obtained capacitors were subjected to a DC voltage of 325 V / μm for 1,500 hours in a constant temperature bath at 115°C. A shielding box SME-8350 was connected to a Hioki Electric Corporation DSM8104 super insulation resistance meter. The capacitors after 1,500 hours were placed inside the shielding box, and a DC voltage of 500V was applied. The insulation resistance value (IR115C) was read after 1 minute. The test was performed on two samples, and the average of their insulation resistance values ​​(IR115C) was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0208] For measurement conditions other than those described herein, the specifications of JIS C 5101-16:2009, "4.2.4 Insulation Resistance," were followed.

[0209] A: IR115C ≥ 150MΩ B: 150MΩ > IR115C ≥ 20MΩ C:20MΩ>IR115C

[0210] (7-2-6) High-voltage application test of capacitors (insulation resistance value) The obtained capacitors were subjected to a 1200V DC voltage load for 10 minutes in a constant temperature bath at 105°C. A shielding box SME-8350 was connected to a HIOKI DSM8104 super insulation resistance meter, and the capacitors after 10 minutes were placed inside the shielding box. A 500V DC voltage was applied, and the insulation resistance value (IR10) after 1 minute was read. The test was performed on two samples, and the average of their insulation resistance values ​​(IR10) was evaluated according to the following criteria. The results are shown in Tables 2 and 3.

[0211] For measurement conditions other than those described herein, the specifications of JIS C 5101-16:2009, "4.2.4 Insulation Resistance," were followed.

[0212] A: IR10 ≥ 5000 MΩ B: 5000MΩ > IR10 ≥ 20MΩ C:20MΩ>IR10

[0213] [Table 2]

[0214] Table 3

Claims

1. A metal-layer integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, wherein the cumulative dielectric breakdown point density measured by the method described below is 1000 points / m². ２ The following is a polypropylene film with an integrated metal layer. (Method for measuring cumulative dielectric breakdown point density) The cumulative dielectric breakdown point density is measured by setting a metal-layer integrated polypropylene film in a measuring device and measuring it as follows. Here, the direction in which the DC voltage is applied in the measuring device is in the thickness direction of the metal-layer integrated polypropylene film. A DC voltage of 350 V / μm is applied for 1 minute in an environment of 20°C, then a DC voltage of 375 V / μm is applied for 1 minute in an environment of 20°C, then a DC voltage of 400 V / μm is applied for 1 minute in an environment of 20°C, and then a DC voltage of 425 V / μm is applied for 1 minute in an environment of 20°C. The test was conducted using five metal-layer integrated polypropylene films. The number of dielectric breakdown points was visually counted after applying a DC voltage of 425 V / μm, and the average value was calculated using the window area of ​​the insulating polypropylene film (100 mm x 10 mm = 1,000 mm²). ２ = 0.001 m ２ Divide the result by the cumulative dielectric breakdown point density (unit: points / m²) and use that value to determine the cumulative dielectric breakdown point density. ２ )

2. The metal layer integrated polypropylene film according to claim 1, wherein the thickness of the polypropylene film is 1.0 to 3.0 μm.

3. The metal-layer-integrated polypropylene film according to claim 1 or 2, wherein the polypropylene film has a thermal shrinkage rate of 0 to 8% in a first direction and a thermal shrinkage rate of -2 to 2% in a second direction perpendicular to the first direction under processing conditions of 120°C for 15 minutes.

4. The metal-layer-integrated polypropylene film according to any one of claims 1 to 3, wherein the polypropylene film has a thermal shrinkage rate of 0 to 10% in a first direction and a thermal shrinkage rate of -1 to 5% in a second direction perpendicular to the first direction under processing conditions of 140°C for 15 minutes.

5. The metal-layer-integrated polypropylene film according to any one of claims 1 to 4, wherein the tensile modulus of the polypropylene film in a first direction is 1.5 GPa or more, and the tensile modulus of the polypropylene film in a second direction perpendicular to the first direction is 3 GPa or more.

6. The metal layer integrated polypropylene film according to any one of claims 1 to 5, wherein the polypropylene film is a biaxially oriented film.

7. The metal layer integrated polypropylene film according to any one of claims 1 to 6, wherein the polypropylene film is a single-layer film.

8. A metal-layer integrated polypropylene film according to any one of claims 1 to 7, for use in capacitors.

9. A capacitor comprising a metal layer-integrated polypropylene film according to any one of claims 1 to 8.

10. The capacitor according to claim 9, comprising a winding of a metal layer-integrated polypropylene film according to any one of claims 1 to 8.

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