Polypropylene film, polypropylene film integrated with metal layer, film capacitor, and film roll

Abstract

The objective of this invention is to provide a polypropylene film that provides a film capacitor with superior voltage withstand properties at high temperatures. This objective is achieved by a polypropylene film characterized by having a first side and a second side, wherein, according to the surface properties parameters specified in ISO 25178, the Sku value of either the first side or the second side is 40 or less, and / or the Spc value of either the first side or the second side is 16 (1 / mm) or less.

Description

Technical Field

[0001] This invention relates to polypropylene films, polypropylene films with integrated metal layers, film capacitors, film rolls, etc. Background Technology

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

[0003] In recent years, polypropylene film has been widely used as capacitors in inverter power supply equipment for controlling drive motors in electric vehicles, hybrid vehicles, and other similar applications. Capacitors used in inverter power supply equipment for automobiles and other applications are required to be small, lightweight, high-capacitance, and demand high reliability over long periods.

[0004] Patent document 1 discloses that the protrusion is 0.1 mm in length. 2 A biaxially stretched polypropylene film for capacitors, wherein the number of points and the average roughness of 10 points satisfy a specified relationship. Patent Document 1 describes that, as an effect of the biaxially stretched polypropylene film for capacitors with the above-described structure, even thin films have excellent processing adaptability and exhibit high voltage resistance even under a wide range of atmosphere temperature conditions from low temperature (-40°C) to high temperature (150°C).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2013 / 146367 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] From the perspective of the long-term reliability of the capacitors mentioned above, capacitors used in automobiles and other applications that can operate at high temperatures are required to have high voltage withstand capability at high temperatures.

[0010] The objective of this invention is to provide a polypropylene film that enables the production of film capacitors with superior voltage resistance at high temperatures.

[0011] Solution for solving the problem

[0012] The inventors conducted in-depth research in view of the above-mentioned problems and found that the above-mentioned problems can be solved by using a polypropylene film characterized by having a first side and a second side, wherein, in the surface property parameters specified by ISO 25178, the Sku value of either the first side or the second side is 40 or less, and / or the Spc value of either the first side or the second side is 16 (1 / mm) or less. Based on this insight, the inventors conducted further research and completed the present invention. That is, the present invention includes the following methods.

[0013] Item 1. A polypropylene film, characterized in that it is a polypropylene film having a first side and a second side, wherein, among the surface properties parameters specified by ISO 25178, the Sku value of either the first side or the second side is 40 or less, and / or the Spc value of either the first side or the second side is 16 (1 / mm) or less.

[0014] Item 2. The polypropylene film according to Item 1, wherein, when the surface with high wetting tension as measured by JIS K6768:1999 is designated as the first surface and the surface with low wetting tension is designated as the second surface, the value obtained by dividing the Sku value of the second surface by the Sku value of the first surface is 1.0000 or less, and / or, the value obtained by dividing the Spc value of the second surface by the Spc value of the first surface is 1.0000 or less.

[0015] Item 3. The polypropylene film according to Item 1 or 2, wherein the Sku value of either the first side or the second side is 20 or less, and / or the Spc value of either the first side or the second side is 13 (1 / mm) or less.

[0016] Item 4. The polypropylene film according to any one of items 1 to 3, comprising linear polypropylene resin B and long-chain branched polypropylene resin C,

[0017] The linear polypropylene resin B exhibits a molecular weight differential distribution curve where the difference between the differential distribution value at log(M) = 4.5 and the differential distribution value at log(M) = 6.0 is less than 8.0%, and its melt flow rate at 230°C is less than 4.0 g / 10 min.

[0018] The long-chain branched polypropylene resin C is polymerized using a metallocene catalyst.

[0019] Item 5. The polypropylene film according to Item 4, further comprising linear polypropylene resin A, wherein the difference between the differential distribution value of the logarithmic molecular weight Log(M) = 4.5 and the differential distribution value of Log(M) = 6.0 in the differential molecular weight distribution curve is less than 8.0%, and the melt flow rate at 230°C is 4.0 g / 10 min or more.

[0020] Item 6. The polypropylene film according to any one of items 1 to 5, wherein it is a biaxially stretched polypropylene film.

[0021] Item 7. The polypropylene film according to any one of items 1 to 6, having a thickness of 1.4 to 6.0 μm.

[0022] Item 8. A polypropylene film according to any one of items 1 to 7, used in a capacitor.

[0023] Item 9. A metal-integrated polypropylene film comprising any one of items 1 to 8, and a metal layer laminated on a first side or both sides of the polypropylene film.

[0024] Item 10. A thin-film capacitor comprising the integral polypropylene film with a metal layer as described in Item 9.

[0025] Item 11. A film roll, which is formed by winding a polypropylene film according to any one of items 1 to 8 into a roll.

[0026] The effects of the invention

[0027] According to the present invention, a polypropylene film can be provided that provides a film capacitor with superior voltage resistance at high temperatures. Detailed Implementation

[0028] In this specification, the expressions “containing” and “comprising” include the concepts of “containing”, “comprising”, “substantially composed of” and “composed of only”.

[0029] In this specification, "component," "capacitor," "capacitor component," and "film capacitor" refer to the same object.

[0030] The polypropylene film of the present invention is not a microporous film and therefore does not have a large number of pores.

[0031] The polypropylene film of the present invention can be composed of two or more layers, preferably a single layer.

[0032] The polypropylene film of the present invention is characterized in that it is a polypropylene film having a first side and a second side, wherein, among the surface property parameters specified by ISO 25178, the Sku value of either the first side or the second side is 40 or less, and / or the Spc value of either the first side or the second side is 16 (1 / mm) or less.

[0033] The SKU value of either the first or second surface is preferably 30 or less, more preferably 20 or less, even more preferably 16 or less, even more preferably 14 or less, particularly preferably 12 or less, even more preferably 10 or less, even more preferably 9 or less, and even more preferably 8 or less. There is no particular limitation on the lower limit of this SKU value; for example, it can be 0.1, 0.5, 1, 2, or 3.

[0034] Sku refers to the kurtosis, a measure of the sharpness of a surface, indicating the steepness (sharpness) of its height distribution. Therefore, an Sku value of 40 or less on either the first or second surface means that the steep peaks and valleys on one side of the film surface are below a specified value. Consequently, the distance between the valleys on one side and the valleys on the opposite side of the film becomes relatively longer, reducing leakage current and contributing to improved lifetime performance (insulation breakdown strength, capacitance change rate).

[0035] Regarding the polypropylene film of the present invention, in one embodiment, the SKU value of the side opposite to the side with a SKU value of 40 or less is preferably 500 or more, more preferably 1000 or more, and even more preferably 1500 or more. By distributing a metal layer on this side, the thickness of the metal film on the shaded side of the steep peaks or steep valleys of the surface becomes relatively thin, thus making it easier for the fuse to trip and easier to prevent short-circuit faults in the capacitor element. There is no particular upper limit to this value; for example, it can be 10000, 7000, 5000, or 4000.

[0036] In one embodiment of the polypropylene film of the present invention, when the side with high wetting tension as measured by JIS K6768:1999 is designated as the first side and the side with low wetting tension is designated as the second side, the value obtained by dividing the SKU value of the second side by the SKU value of the first side is preferably 1.0000 or less. This value is more preferably 0.5000 or less, even more preferably 0.1000 or less, even more preferably 0.0500 or less, particularly preferably 0.0100 or less, and even more preferably 0.0050 or less. It should be noted that in this case, the SKU value of the second side is 40 or less.

[0037] The Spc value of either the first or the second surface is preferably 14 (1 / mm) or less, more preferably 13 (1 / mm) or less, even more preferably 12 (1 / mm) or less, even more preferably 11 (1 / mm) or less, and particularly preferably 10 (1 / mm) or less. There is no particular limitation on the lower limit of this Spc value, for example, it can be 0.1 (1 / mm), 0.5 (1 / mm), 1 (1 / mm), 2 (1 / mm), 4 (1 / mm), or 6 (1 / mm).

[0038] Spc represents the average principal curvature of the peaks on the surface. A small Spc value indicates that the point of contact with other objects is curved, while a large Spc value indicates that the point of contact with other objects is sharp. Therefore, a Spc value of 16 (1 / mm) or less on either the first or second surface means that there are fewer steep peaks on one side of the film surface. Thus, when the micrometer thickness is the same as that measured by mechanical thickness measurement, the distance between the valleys on one side of the film and the valleys on the opposite side is relatively longer, the leakage current is reduced, and this contributes to the improvement of lifetime performance (insulation breakdown strength, capacitance change rate).

[0039] Regarding the polypropylene film of the present invention, in one embodiment, the Spc value of the side opposite to the side with a Spc value of 16 (L / mm) or less is preferably 150 (L / mm) or more, more preferably 200 (L / mm) or more, and even more preferably 250 (L / mm) or more. By providing a metal layer on this side, the thickness of the metal film on the shaded side of the steep peaks or steep valleys of the surface becomes relatively thin, thus the fuse is easily disconnected, and short-circuit faults of the capacitor element are easily prevented. There is no particular upper limit to this value, for example, it is 1500 (L / mm), 1200 (L / mm), 1000 (L / mm) or 900 (L / mm).

[0040] In one embodiment of the polypropylene film of the present invention, when the side with high wetting tension as measured by JIS K6768:1999 is designated as the first side and the side with low wetting tension is designated as the second side, the value obtained by dividing the Spc value of the second side by the Spc value of the first side is preferably 1.0000 or less. This value is more preferably 0.5000 or less, even more preferably 0.2000 or less, even more preferably 0.1000 or less, particularly preferably 0.0500 or less, and even more preferably 0.0400 or less. It should be noted that in this case, the Spc value of the second side is 16 (1 / mm) or less.

[0041] In one embodiment of the polypropylene film of the present invention, the wetting tension of the first side is, for example, 32-50 mN / m, 34-45 mN / m, or 35-40 mN / m.

[0042] In one embodiment of the polypropylene film of the present invention, the wetting tension of the second side is, for example, less than 30 mN / m.

[0043] In one embodiment of the polypropylene film of the present invention, the difference between the wetting tension value (mN / m) of the first side and the wetting tension value (mN / m) of the second side is preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more.

[0044] In one embodiment of the polypropylene film of the present invention, the Sa value of the side opposite to the side with an Sku value of 40 or less (e.g., the first side) is, for example, 0.0040 μm or more and 0.0600 μm or less, 0.0080 μm or more and 0.0300 μm or less, or 0.0100 μm or more and 0.0200 μm or less.

[0045] In one embodiment of the polypropylene film of the present invention, the Sq value of the side opposite to the side with an Sku value of 40 or less (e.g., the first side) is, for example, 0.0080 μm or more and 0.1000 μm or less, 0.0150 μm or more and 0.0700 μm or less, or 0.0200 μm or more and 0.0400 μm or less.

[0046] In one embodiment of the polypropylene film of the present invention, the Sa value of the side (e.g., the second side) with an Sku value of 40 or less is, for example, 0.0020 μm or more and 0.0600 μm or less, 0.0040 μm or more and 0.0300 μm or less, or 0.0060 μm or more and 0.0200 μm or less.

[0047] In one embodiment of the polypropylene film of the present invention, the Sq value of the side (e.g., the second side) with an Sku value of 40 or less is, for example, 0.0030 μm or more and 0.0800 μm or less, 0.0060 μm or more and 0.0500 μm or less, or 0.0090 μm or more and 0.0300 μm or less.

[0048] In one embodiment of the polypropylene film of the present invention, the Sa value of the side opposite to the side with a Spc value of 16 (1 / mm) or less (e.g., the first side) is, for example, 0.0040 μm or more and 0.0600 μm or less, 0.0080 μm or more and 0.0300 μm or less, or 0.0100 μm or more and 0.0200 μm or less.

[0049] In one embodiment of the polypropylene film of the present invention, the Sq value of the side opposite to the side with a Spc value of 16 (1 / mm) or less (e.g., the first side) is, for example, 0.0080 μm or more and 0.1000 μm or less, 0.0150 μm or more and 0.0700 μm or less, or 0.0200 μm or more and 0.0400 μm or less.

[0050] In one embodiment of the polypropylene film of the present invention, the Sa value of the face (e.g., the second face) with a Spc value of 16 (1 / mm) or less is, for example, 0.0020 μm or more and 0.0600 μm or less, 0.0040 μm or more and 0.0300 μm or less, or 0.0060 μm or more and 0.0200 μm or less.

[0051] In one embodiment of the polypropylene film of the present invention, the Sq value of the face (e.g., the second face) with a Spc value of 16 (1 / mm) or less is, for example, 0.0030 μm or more and 0.0800 μm or less, 0.0060 μm or more and 0.0500 μm or less, or 0.0090 μm or more and 0.0300 μm or less.

[0052] The values ​​of Sku, Spc, Sa, and Sq were measured according to method (4-4) of Experiments 1 and 2 described later.

[0053] The dielectric breakdown strength (DCES120°C) of the polypropylene film of the present invention under DC voltage at 120°C is preferably 500V. DC / μm or larger, preferably 550V DC / μm or larger, and more preferably 580V DC / μm or larger, with 595V being particularly preferred. DC / μm or higher. A high upper limit for the insulation breakdown strength at DC voltage and 120°C is preferred, for example, 650V. DC / μm, 630V DC / μm, etc.

[0054] The insulation breakdown strength is a value measured according to the method in (4-5) of the following embodiments.

[0055] The ash content of the polypropylene film of the present invention is preferably 6 × 10 ppm or less (60 ppm or less), more preferably 5 × 10 ppm or less (50 ppm or less), further preferably 4 × 10 ppm or less (40 ppm or less), and particularly preferably 3.5 × 10 ppm or less (35 ppm or less), relative to the aforementioned polypropylene film. The above-mentioned ash content is preferably 0 × 10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1 × 10 ppm or more (10 ppm or more). If the above-mentioned ash content is within the above-mentioned value range, the formation of polar low-molecular-weight components is suppressed, and the electrical characteristics as a capacitor are further improved.

[0056] The ash content was measured according to the method described in (4-6) of the following embodiments.

[0057] The thickness of the polypropylene film of the present invention is preferably 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 especially 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. Especially within the ranges of 1.4 to 6.0 μm, 1.5 to 3.0 μm, and 1.5 to 2.9 μm, even though the polypropylene film is very thin, its processability in the slitting process, its adhesion inhibition during the vapor deposition process, and its component winding processability remain excellent, and are therefore preferred.

[0058] If the thickness is 9.5 μm or less, the capacitance can be increased, making it suitable for use as a capacitor. However, from a manufacturing point of view, the thickness can be 0.8 μm or more.

[0059] The thickness is a value measured according to the method of (4-1) in the following embodiment.

[0060] The haze of the polypropylene film of the present invention is preferably 1.8 to 4.5, more preferably 1.8 to 4.0, and even more preferably 1.9 to 3.5.

[0061] The haze was measured according to the method in (4-2) of the following embodiments.

[0062] The polypropylene film of the present invention can be a biaxially stretched film, a uniaxially stretched film, or an unstretched film. From the viewpoint that it is easy to set the Sku value of either the first or second side within a specified range and / or easy to set the Spc value of either the first or second side within a specified range, a biaxially stretched film is preferred.

[0063] The polypropylene film and the metal-integrated polypropylene film of the present invention are respectively wound into rolls, preferably in the form of film rolls. The film rolls may or may not have a core. Preferably, the film rolls have a core. The material of the core of the film roll is not particularly limited. Examples of such materials include paper (paper tubes), resin, fiber-reinforced plastic (FRP), and metal. Examples of such resins include polyvinyl chloride, polyethylene, polypropylene, phenolic resin, epoxy resin, and acrylonitrile-butadiene-styrene copolymer. Examples of such plastics constituting the fiber-reinforced plastic include polyester resin, epoxy resin, vinyl ester resin, phenolic resin, and thermoplastic resin. Examples of such fibers constituting the fiber-reinforced plastic include glass fiber, aramid fiber (Kevlar fiber), carbon fiber, poly(p-phenylenebenzoxazole) fiber (Zylon fiber), polyethylene fiber, and boron fiber. Examples of such metals include iron, aluminum, and stainless steel. The core of the aforementioned film roll also includes a core formed by impregnating a paper tube with the aforementioned resin. In this case, the material of the aforementioned core is classified as resin.

[0064] The polypropylene film of the present invention contains polypropylene resin as a main component. In this specification, "containing polypropylene resin as a main component" means that, relative to the total polypropylene film (when the total polypropylene film is set to 100% by mass), it contains 50% by mass or more of polypropylene resin. The aforementioned content of polypropylene resin relative to the total polypropylene film is preferably 75% by mass or more, more preferably 90% by mass or more. The upper limit of the aforementioned content of polypropylene resin relative to the total polypropylene film is, for example, 100% by mass or 98% by mass.

[0065] The aforementioned polypropylene resin is not particularly limited; it can be used alone or in combination with two or more. Specifically, the aforementioned polypropylene resin is suitable for forming β-type spherulites when forming cast sheets.

[0066] As the aforementioned polypropylene resin, linear polypropylene resin can be cited as an example. Linear polypropylene resin can be used alone or in combination of two or more. From the viewpoint of easily adjusting the Sku value of either the first or second surface to an appropriate range and / or easily adjusting the Spc value of either the first or second surface to an appropriate range, the following linear polypropylene resin A and / or the following linear polypropylene resin B are preferred. The following linear polypropylene resin B is particularly preferred, and the following linear polypropylene resin A and the following linear polypropylene resin B are more preferably used in combination. The following linear polypropylene resin A and the following linear polypropylene resin B are preferably homopolymer polypropylene resins. However, in this invention, the polypropylene resin described above is not limited to the following resins.

[0067] <Linear polypropylene resin A>

[0068] A linear polypropylene resin, wherein the difference between the differential distribution value at log molecular weight Log(M) = 4.5 and the differential distribution value at Log(M) = 6.0 in the molecular weight differential distribution curve is less than 8.0%, and the melt flow rate at 230°C is greater than 4.0 g / 10 min.

[0069] <Linear polypropylene resin B>

[0070] A linear polypropylene resin, wherein the difference between the differential distribution value at log molecular weight Log(M) = 4.5 and the differential distribution value at Log(M) = 6.0 is less than 8.0% in the differential molecular weight distribution curve, and the melt flow rate at 230°C is less than 4.0 g / 10 min.

[0071] The weight-average molecular weight (Mw) of the aforementioned linear polypropylene resin A is preferably 250,000 or more. Furthermore, the weight-average molecular weight (Mw) of the aforementioned linear polypropylene resin A is preferably 450,000 or less, more preferably 400,000 or less, even more preferably 350,000 or less, and particularly preferably 340,000 or less. When the weight-average molecular weight (Mw) of the aforementioned linear polypropylene resin A is 250,000 or more and 450,000 or less, the resin flowability becomes moderate. As a result, the thickness of the cast sheet is easily controlled, and the production of thin stretched films becomes easier. In addition, uneven thickness is less likely to occur in the cast sheet and the stretched film, and moderate stretchability can be obtained, which is therefore preferable.

[0072] The molecular weight distribution of the above-mentioned linear polypropylene resin A [(weight average molecular weight Mw) / (number average molecular weight Mn)] is preferably 5.0 or more and 11.0 or less, more preferably 6.0 or more and 10.0 or less, even more preferably 6.5 or more and 9.0 or less, and particularly preferably 6.8 or more and 8.5 or less.

[0073] The molecular weight distribution of the above-mentioned linear polypropylene resin A [(z-average molecular weight Mz) / (number-average molecular weight Mn)] is preferably 12.0 or more and 60.0 or less, more preferably 16.0 or more and 50.0 or less, and even more preferably 20.0 or more and 40.0 or less.

[0074] When the molecular weight distributions of the linear polypropylene resin A described above are within the preferred range, uneven thickness is less likely to occur in the cast film and the stretched film, and moderate stretchability can be obtained, which is therefore preferred.

[0075] The difference in the differential distribution values ​​of the above-mentioned linear polypropylene resin A (the difference obtained by subtracting the differential distribution value of Log(M) = 6.0 from the differential distribution value of Log(M) = 4.5 in the molecular weight differential distribution curve) is less than 8.0%, more preferably 7.0% or less, even more preferably 0% or more and 6.0% or less, and particularly preferably 2.0% or more and 5.5% or less.

[0076] The meso-pentameric component ratio ([mmmm]) of the aforementioned linear polypropylene resin A is preferably 99.8% or less, more preferably 99.5% or less, and even more preferably 99.0% or less. Furthermore, the aforementioned meso-pentameric component ratio is preferably 94.0% or more, more preferably 95.0% or more, even more preferably 96.0% or more, and particularly preferably 97.0% or more. When the meso-pentameric component ratio is within the above-mentioned range, based on a moderately high stereoregularity, the crystallinity of the resin is moderately improved, and the voltage resistance at high temperatures is improved. On the other hand, the curing (crystallization) speed during cast sheet molding becomes moderate, resulting in moderate stretchability.

[0077] The heptane-insoluble substance (HI) content of the aforementioned linear polypropylene resin A is preferably 96.0% or more, more preferably 97.0% or more, and even more preferably 98.0% or more. Furthermore, the heptane-insoluble substance (HI) content of the aforementioned linear polypropylene resin A is preferably 99.5% or less, more preferably 99.0% or less. Here, a higher content of heptane-insoluble substance indicates a higher stereoregularity of the resin. When the heptane-insoluble substance (HI) content is 96.0% or more and 99.5% or less, based on the moderately high stereoregularity, the crystallinity of the resin is moderately improved, and the voltage resistance at high temperatures is improved. On the other hand, the curing (crystallization) speed during cast sheet molding becomes moderate, resulting in moderate stretchability.

[0078] The ash content of the aforementioned linear polypropylene resin A is preferably 6×10 ppm or less (60 ppm or less), more preferably 5×10 ppm or less (50 ppm or less), further preferably 4×10 ppm or less (40 ppm or less), and particularly preferably 3×10 ppm or less (30 ppm or less). Furthermore, the ash content of the aforementioned linear polypropylene resin A is preferably 0×10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1×10 ppm or more (10 ppm or more). When the ash content of the aforementioned linear polypropylene resin A is within the above-mentioned preferred range, the formation of polar low-molecular-weight components is suppressed, and the electrical properties as a capacitor are further improved.

[0079] The melt flow rate (MFR) of the aforementioned linear polypropylene resin A at 230°C is 4.0 g / 10 min or more, preferably 4.0 to 10.0 g / 10 min, and particularly preferably 4.0 to 6.0 g / 10 min. When the MFR of polypropylene A at 230°C is within the above range, it exhibits excellent flow characteristics in the molten state, thus reducing the likelihood of unstable flow such as melt fracture. Furthermore, fracture during stretching is also suppressed. Therefore, due to the good film thickness uniformity, it has the advantage of suppressing the formation of thin-walled portions that are prone to insulation breakdown.

[0080] When the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned linear polypropylene resin A is preferably 55% by mass or more, more preferably 60% by mass or more. When the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned linear polypropylene resin A is preferably 99.9% by mass or less, more preferably 90% by mass or less, further preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0081] The weight-average molecular weight (Mw) of linear polypropylene resin B is preferably 300,000 or more, more preferably 330,000 or more, even more preferably over 340,000, even more preferably over 350,000, and particularly preferably over 350,000. Furthermore, the weight-average molecular weight (Mw) of linear polypropylene resin B is preferably 400,000 or less, more preferably 380,000 or less.

[0082] The molecular weight distribution of the above-mentioned linear polypropylene resin B [(weight average molecular weight Mw) / (number average molecular weight Mn)] is preferably 7.0 or more and 9.0 or less, more preferably 7.5 or more and 8.9 or less, and even more preferably 7.5 or more and 8.5 or less.

[0083] The molecular weight distribution of the above-mentioned linear polypropylene resin B [(z-average molecular weight Mz) / (number-average molecular weight Mn)] is preferably 20.0 or more and 70.0 or less, more preferably 25.0 or more and 60.0 or less, and even more preferably 25.0 or more and 50.0 or less.

[0084] When the molecular weight distributions of the linear polypropylene resin B described above are within the preferred range, uneven thickness is less likely to occur in the cast film and the stretched film, and moderate stretchability can be obtained, which is therefore preferred.

[0085] The difference in the differential distribution value of the above-mentioned linear polypropylene resin B is preferably less than 8.0%, more preferably -20.0% or more and less than 8.0%, even more preferably -10.0% or more and less than 7.9%, and particularly preferably -5.0% or more and less than 7.5%.

[0086] The meso-pentameric component ratio ([mmmm]) of the aforementioned linear polypropylene resin B is preferably less than 99.8%, more preferably 99.5% or less, and even more preferably 99.0% or less. Furthermore, the aforementioned meso-pentameric component ratio is preferably 94.0% or more, more preferably 94.5% or more, and even more preferably 95.0% or more. When the meso-pentameric component ratio is within the above-mentioned range, based on a moderately high stereoregularity, the crystallinity of the resin is moderately improved, and the voltage resistance at high temperatures is improved. On the other hand, the curing (crystallization) speed during cast sheet molding becomes moderate, resulting in moderate stretchability.

[0087] The heptane-insoluble substance (HI) content of the aforementioned linear polypropylene resin B is, for example, 97% or more, preferably 97.5% or more, more preferably 98% or more, even more preferably more than 98.5%, and particularly preferably 98.6% or more. Furthermore, the heptane-insoluble substance (HI) content of the aforementioned linear polypropylene resin B is preferably 99.5% or less, more preferably 99% or less.

[0088] The ash content of the aforementioned linear polypropylene resin B is preferably 6 × 10 ppm or less (60 ppm or less), more preferably 5 × 10 ppm or less (50 ppm or less), further preferably 4 × 10 ppm or less (40 ppm or less), and particularly preferably 3 × 10 ppm or less (30 ppm or less). Furthermore, the ash content of the aforementioned linear polypropylene resin B is preferably 0 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1 × 10 ppm or more (10 ppm or more). When the ash content of the aforementioned linear polypropylene resin B is within the above-mentioned preferred range, the formation of polar low-molecular-weight components is suppressed, and the electrical properties as a capacitor are further improved.

[0089] The melt flow rate (MFR) of the aforementioned linear polypropylene resin B at 230°C is less than 4.0 g / 10 min. Preferably, the melt flow rate (MFR) of the aforementioned linear polypropylene resin B at 230°C is 0.1 g / 10 min or more, more preferably 1.0 g / 10 min or more, and even more preferably 1.5 g / 10 min or more. Furthermore, the melt flow rate (MFR) of the aforementioned linear polypropylene resin B at 230°C is preferably 3.5 g / 10 min or less, more preferably 3.0 g / 10 min or less.

[0090] When using the aforementioned linear polypropylene resin B as the polypropylene resin, if the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned linear polypropylene resin B is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. Similarly, when the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned linear polypropylene resin B is preferably 45% by mass or less, more preferably 40% by mass or less. In one embodiment (particularly when the aforementioned linear polypropylene resin B is not used in combination with the aforementioned linear polypropylene resin A), if the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned linear polypropylene resin B is 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0091] When using the above-mentioned linear polypropylene resin A and linear polypropylene resin B in combination, if the total polypropylene resin is set to 100% by mass, it is preferable to include 55 to 90% by weight of the above-mentioned linear polypropylene resin A and 45 to 10% by weight of the above-mentioned linear polypropylene resin B, more preferably 60 to 85% by weight of the above-mentioned linear polypropylene resin A and 40 to 15% by weight of the above-mentioned linear polypropylene resin B, and particularly preferably 60 to 80% by weight of the above-mentioned linear polypropylene resin A and 40 to 20% by weight of the above-mentioned linear polypropylene resin B.

[0092] When the aforementioned polypropylene resin includes the aforementioned linear polypropylene resin A and the aforementioned linear polypropylene resin B, the aforementioned polypropylene film becomes a finely mixed state (phase-separated state) of linear polypropylene resin A and linear polypropylene resin B, thus improving its voltage resistance at high temperatures.

[0093] The aforementioned linear polypropylene resin can generally be manufactured using known polymerization methods. There are no particular limitations as long as a linear polypropylene resin suitable for use in polypropylene films can be produced. Examples of such polymerization methods include gas-phase polymerization, bulk polymerization, and slurry polymerization.

[0094] Polymerization can be a single-step (one-step) polymerization using a single polymerization reactor, or a multi-step polymerization using at least two or more polymerization reactors. Furthermore, hydrogen or comonomers can be added to the reactor as molecular weight regulators.

[0095] The catalyst used in polymerization can typically be a well-known Ziegler-Natta catalyst, with no particular limitation as long as the aforementioned linear polypropylene resin can be obtained. The catalyst may contain co-catalyst components or donors. By adjusting the catalyst and polymerization conditions, the molecular weight, molecular weight distribution, and stereoregularity can be controlled.

[0096] The molecular weight, molecular weight distribution, and differential distribution values ​​of the aforementioned linear polypropylene resin can be adjusted, for example, by appropriately selecting (i) the polymerization method and various conditions such as temperature / pressure during polymerization, (ii) the shape of the reactor during polymerization, (iii) the presence, type, and amount of additives, and (iv) the type and amount of catalysts.

[0097] Specifically, the difference D between the molecular weight, molecular weight distribution, and differential distribution values ​​of the aforementioned linear polypropylene resin M Adjustments, for example, can be made through a multi-step polymerization reaction. As an example of a multi-step polymerization reaction, the following method can be illustrated.

[0098] First, in the first polymerization step, propylene and a catalyst are supplied to the first polymerization reactor. Hydrogen, acting as a molecular weight regulator, is mixed with these components in the amount required to achieve the desired polymer molecular weight. For example, in the case of slurry polymerization, the reaction temperature is approximately 70–100°C, and the residence time is approximately 20–100 minutes. Multiple reactors can be used, for example, in series. In this case, the polymerization product from the first step, along with additional propylene, catalyst, and molecular weight regulator, is continuously fed to the next reactor, where a second polymerization is carried out to adjust the molecular weight to be either lower or higher than that of the first polymerization step. By adjusting the output (production rate) of the first and second reactors, the composition (structure) of the high-molecular-weight and low-molecular-weight components can be adjusted.

[0099] Furthermore, the molecular weight, molecular weight distribution, and differential distribution differences of the aforementioned linear polypropylene resin can also be adjusted through peroxidation decomposition. For example, a method based on peroxidation treatment using decomposing agents such as hydrogen peroxide or organic peroxides can be illustrated.

[0100] Adding peroxides to disintegrating polymers like polypropylene triggers a hydrogen abstraction reaction, where hydrogen is removed from the polymer. Some of the resulting polymer free radicals rebond and undergo cross-linking, but most of the free radicals undergo secondary decomposition (β-cleavage), breaking down into two polymers with smaller molecular weights. In other words, higher molecular weight components are more likely to decompose. Therefore, increasing the amount of low molecular weight components can adjust the molecular weight distribution.

[0101] When adjusting the content of low molecular weight components through blending (resin mixing), at least two resins with different molecular weights can be dry-blended or melt-blended. Generally, it is preferable to use a polypropylene blend system in which approximately 1 to 40% by mass of an additive resin with an average molecular weight that is higher or lower than that of the main resin to easily adjust the amount of low molecular weight components.

[0102] Alternatively, in this mixed adjustment case, melt flow rate (MFR) can also be used as a benchmark for average molecular weight. In this case, it is good from the point of view to facilitate adjustment when the difference in MFR between the main resin and the added resin is set to about 1~30 g / 10 min.

[0103] Commercially available products can also be used as the linear polypropylene resin mentioned above.

[0104] From the viewpoint that it is easy to adjust the Sku value of either the first or second side to an appropriate range and / or to easily adjust the Spc value of either the first or second side to an appropriate range, the aforementioned polypropylene resin preferably includes a long-chain branched polypropylene resin. Among the aforementioned long-chain branched polypropylene resins, a long-chain branched polypropylene resin C (hereinafter also referred to as "long-chain branched polypropylene resin C") obtained by polymerizing propylene using a metallocene catalyst is preferred. Specifically, when the aforementioned polypropylene resin includes the aforementioned long-chain branched polypropylene resin C, a large number of β crystals are formed in the cast sheet. Moreover, by stretching the cast sheet containing β crystals, the β crystals are transformed into α crystals. Therefore, due to the density difference between β crystals and α crystals, the polypropylene film obtained by stretching forms (approximately) arc-shaped unevenness, which can appropriately roughen the surface, which is preferred.

[0105] The aforementioned polypropylene resin more preferably includes the aforementioned linear polypropylene resin A and / or the aforementioned linear polypropylene resin B and includes the aforementioned long-chain branched polypropylene resin C, and more preferably includes the aforementioned linear polypropylene resin B and the aforementioned long-chain branched polypropylene resin C.

[0106] Furthermore, the aforementioned polypropylene resin particularly preferably comprises the aforementioned linear polypropylene resin A and the aforementioned linear polypropylene resin B, and also comprises the aforementioned long-chain branched polypropylene resin C. The differences in differential distribution values, heptane-insoluble matter (HI), and / or melt flow rate (MFR) between linear polypropylene resin A and linear polypropylene resin B result in a finely mixed state (phase separation state). Therefore, stretching such an unstretched polypropylene film complicates the configuration of the resin components constituting the film. Therefore, by including linear polypropylene resin A and linear polypropylene resin B, which differ in differential distribution values, heptane-insoluble matter (HI), and / or melt flow rate (MFR), and further including long-chain branched polypropylene resin C, the voltage resistance of the stretched film can be improved by complicating the configuration of the resin components constituting the film, and a finely refined (approximately) arc-shaped unevenness can be achieved, resulting in a more suitable roughening.

[0107] It should be noted that if a long-chain branched polypropylene resin obtained by crosslinking modification using peroxides is used instead of long-chain branched polypropylene resin C obtained by polymerization using a metallocene catalyst, the α-crystal nucleation effect of the long-chain branched polypropylene resin obtained by crosslinking modification using peroxides promotes the formation of α-crystals in the cast film and significantly inhibits the formation of β-crystals. Even when the cast film containing α-crystals is stretched, no microcrystal transformation occurs, making it difficult to form uneven surfaces. Therefore, long-chain branched polypropylene resin C polymerized using a metallocene catalyst is suitable for roughening the polypropylene film surface.

[0108] Metallocene catalysts are typically metallocene compounds that form polymerization catalysts that generate olefin macromonomers. Long-chain branched polypropylene resin C obtained by polymerizing propylene using a metallocene catalyst has suitable branch lengths and spacing, resulting in excellent compatibility with linear polypropylene, and is therefore preferred. Furthermore, it yields a uniform composition and a uniform surface shape, which is also preferred. In the manufacture of long-chain branched polypropylene resin C, all conditions except for the type and amount of catalyst used, such as (i) polymerization method and temperature / pressure during polymerization, (ii) reactor configuration during polymerization, and (iii) the presence, type, and amount of additives, can be the same as those described in the method for manufacturing linear polypropylene resin above, taking into account the molecular weight, molecular weight distribution, and differential distribution differences of the manufactured long-chain branched polypropylene resin C.

[0109] The weight-average molecular weight (Mw) of the aforementioned long-chain branched polypropylene resin C is preferably 150,000 or more and 600,000 or less, more preferably 200,000 or more and 500,000 or less, even more preferably 250,000 or more and 450,000 or less, and particularly preferably 350,000 or more and 420,000 or less. When the weight-average molecular weight (Mw) of the aforementioned long-chain branched polypropylene resin C is 150,000 or more and 600,000 or less, the resin flowability becomes moderate. As a result, the thickness of the cast sheet is easily controlled, and the production of thin stretched films becomes easier. In addition, uneven thickness of the cast sheet and the stretched film is less likely to occur, and moderate stretchability can be obtained, which is therefore preferred.

[0110] The molecular weight distribution of the above-mentioned long-chain branched polypropylene resin C [(weight average molecular weight Mw) / (number average molecular weight Mn)] is preferably 1.5 or more and 4.5 or less, more preferably 1.8 or more and 4.2 or less, even more preferably 2.0 or more and 4.0 or less, particularly preferably 2.1 or more and 3.9 or less, and particularly preferably 2.2 or more and 3.0 or less.

[0111] The [(z-average molecular weight Mz) / (number-average molecular weight Mn)] of the aforementioned long-chain branched polypropylene resin C is preferably 4.0 or more and 9.0 or less, more preferably 4.2 or more and 8.8 or less, even more preferably 4.5 or more and 8.5 or less, and particularly preferably 5.0 or more and 8.2 or less.

[0112] As mentioned above, the molecular weight, molecular weight distribution, and differential distribution value of the aforementioned long-chain branched polypropylene resin C can be controlled by adjusting the catalyst and polymerization conditions.

[0113] The heptane-insoluble substance (HI) content of the aforementioned long-chain branched polypropylene resin C is preferably 98.0% or more, more preferably 98.2% or more, and even more preferably 98.5% or more. Furthermore, the heptane-insoluble substance (HI) content of the aforementioned long-chain branched polypropylene resin C is preferably 99.5% or less, more preferably 99.0% or less. When the HI content of the aforementioned long-chain branched polypropylene resin C is within the above-mentioned preferred range, β-crystals are more appropriately formed in the cast film, resulting in a suitable surface roughening of the polypropylene film.

[0114] The ash content of the aforementioned long-chain branched polypropylene resin C is preferably 45 × 10 ppm or less (450 ppm or less), more preferably 40 × 10 ppm or less (400 ppm or less). Furthermore, the ash content of the aforementioned long-chain branched polypropylene resin C is preferably 0 ppm or more, more preferably 1 ppm or more, even more preferably 5 ppm or more, even more preferably 1 × 10 ppm or more (10 ppm or more), even more preferably 10 × 10 ppm or more (100 ppm or more), and particularly preferably 20 × 10 ppm or more (200 ppm or more). When the ash content of the aforementioned long-chain branched polypropylene resin C is within the above-preferred range, β-crystals are more appropriately formed in the cast film, resulting in a suitable surface roughening of the polypropylene film.

[0115] The melt flow rate (MFR) of the aforementioned long-chain branched polypropylene resin C at 230°C is preferably 0.1 to 12 g / 10 min, more preferably 0.5 to 5 g / 10 min, even more preferably 0.7 to 3.5 g / 10 min, and particularly preferably 1.0 to 2.2 g / 10 min. When the MFR of the aforementioned long-chain branched polypropylene resin C at 230°C is within the above range, the flow characteristics in the molten state are excellent, thus preventing unstable flow such as melt fracture. In addition, fracture during stretching is also suppressed. Therefore, the film thickness uniformity is good, thus having the advantage of suppressing the formation of thin-walled portions that are prone to insulation breakdown.

[0116] When the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned long-chain branched polypropylene resin C is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, particularly preferably 2% by mass or more, and even more preferably 2.5% by mass or more. Furthermore, when the total polypropylene resin content in the polypropylene film is set to 100% by mass, the content of the aforementioned long-chain branched polypropylene resin C is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, particularly preferably 7% by mass or less, and even more preferably 5% by mass or less. The aforementioned polypropylene film may contain one or more of the aforementioned long-chain branched polypropylene resin C.

[0117] Representative commercially available products of the aforementioned long-chain branched polypropylene resin C include, for example, MFX3 and MFX6 manufactured by Japan Polypropylene Corporation, and MFX8 manufactured by Japan Polypropylene Corporation.

[0118] The methods for determining the above-mentioned physical properties of polypropylene resins are as follows. The average molecular weight and molecular weight distribution of linear polypropylene resins were measured according to the method described in Example (2-1) below. The average molecular weight and molecular weight distribution of branched polypropylene resins were measured according to the method described in Example (2-2) below. The difference in differential distribution values ​​was measured according to the method described in Example (2-3) below. The heptane-insoluble content was measured according to the method described in Example (2-4) below. The proportion of racemic five-unit components was measured according to the method described in Example (2-5) below. The melt flow rate was measured according to the method described in Example (2-6) below. The ash content was measured according to the method described in Example (2-7) below.

[0119] The aforementioned polypropylene film may contain resins other than polypropylene resin (hereinafter also referred to as "other resins"). "Other resins" generally refers to resins other than the polypropylene resin that is the main component resin, and there are no particular limitations as long as the target polypropylene film can be obtained. Examples of other resins include, for instance, polyethylene, poly(1-butene), polyisobutylene, poly(1-pentene), poly(1-methylpentene), and other polyolefins other than polypropylene; copolymers of α-olefins such as ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-butene copolymers; vinyl monomer-diene monomer random copolymers such as styrene-butadiene random copolymers; and vinyl monomer-diene monomer-vinyl monomer random copolymers such as styrene-butadiene-styrene block copolymers. The aforementioned polypropylene film may contain an amount that does not adversely affect the target polypropylene film. Relative to 100 parts by weight of polypropylene resin, the aforementioned polypropylene film preferably contains 10 parts by weight or less of other resins, more preferably 5 parts by weight or less. Furthermore, relative to 100 parts by weight of polypropylene resin, the aforementioned polypropylene film preferably contains 0.1 parts by weight or more of other resins, more preferably 1 part by weight or more.

[0120] In addition to resin components, the aforementioned polypropylene film may also contain at least one additive. "Additive" generally refers to any additive used in polypropylene, and there are no particular limitations as long as the desired polypropylene film can be obtained. Additives include, for example, nucleating agents (α-crystal nucleating agents, β-crystal nucleating agents), antioxidants, chlorine absorbers, UV absorbers, and other necessary stabilizers, lubricants, plasticizers, flame retardants, antistatic agents, inorganic fillers, and organic fillers. Examples of such inorganic fillers include barium titanate, strontium titanate, and alumina. When using the aforementioned additives, they can be included in an amount that does not adversely affect the target polypropylene film.

[0121] There are no particular restrictions on the use of "nucleating agents" as long as they are commonly used in polypropylene and can produce the target polypropylene film.

[0122] Examples of nucleating agents include α-crystal nucleating agents that preferentially nucleate α-crystals and β-crystal nucleating agents that preferentially nucleate β-crystals.

[0123] Organic nucleating agents used as α-crystal nucleating agents include dispersible and soluble nucleating agents. Examples of dispersible nucleating agents include phosphate ester metal salt nucleating agents, carboxylic acid metal salt nucleating agents, and rosin metal salt nucleating agents. Examples of soluble nucleating agents include sorbitol-based nucleating agents, nonitol-based nucleating agents, xylitol-based nucleating agents, and amide-based nucleating agents.

[0124] Examples of β-crystal nucleating agents include amide-based nucleating agents, dicarboxylic acid metal salt or polycarboxylic acid 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.

[0125] Nucleating agents can be dry-blended or melt-blended with polypropylene raw materials, granulated, and then used. Alternatively, they can be fed into an extruder along with the polypropylene granules. By using nucleating agents, the surface roughness of the film can be adjusted to the desired roughness. A representative commercially available example of a nucleating agent is NJSTAR NU-100 manufactured by Shin Nippon Rikka Co., Ltd., which is a β-crystal nucleating agent. When the aforementioned polypropylene film contains a β-crystal nucleating agent, its content relative to the mass of the resin component (when the resin component is considered as a whole, it is by mass) is preferably 1 to 1000 ppm by mass, more preferably 50 to 600 ppm by mass.

[0126] There are no particular restrictions on the use of an "antioxidant" as long as it is commonly referred to as an antioxidant and can be used in polypropylene to obtain the target polypropylene film. Antioxidants are generally used for two purposes. One purpose is to inhibit thermal and oxidative degradation within the extruder, and the other purpose is to help inhibit degradation during long-term use of the film as a capacitor and improve capacitor performance. Antioxidants that inhibit thermal and oxidative degradation within the extruder are also called "primary agents," while antioxidants that help improve capacitor performance are also called "secondary agents."

[0127] Two antioxidants can be used for both purposes, or one antioxidant can be used for both purposes.

[0128] Examples of primary agents include 2,6-di-tert-butyl-p-cresol (generic name: BHT). Primary agents are typically added to suppress thermal and oxidative degradation within the extruder during the preparation of the polypropylene resin composition described in the manufacturing method of the polypropylene film described later. Antioxidants added to the polypropylene resin composition for this purpose are almost entirely consumed during the molding process within the extruder, leaving virtually no residue in the film after film formation. Therefore, when the aforementioned polypropylene film contains a primary agent, its content relative to the mass of the resin component (when the resin component is considered as a whole, it is by mass) is typically less than 100 ppm by mass.

[0129] As secondary agents, hindered phenolic antioxidants with carbonyl groups can be cited as examples.

[0130] There are no particular restrictions on "hindered phenolic antioxidants with carbonyl groups" as long as they are generally considered to be hindered phenolic antioxidants with carbonyl groups and can yield the target polypropylene film.

[0131] Examples of hindered phenolic antioxidants with carbonyl groups include: triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (trade name: IRGANOX 245), 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: IRGANOX 259), pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: IRGANOX 1010), 2,2-thiodiethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: IRGANOX 1035), and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (trade name: IRGANOX). 1076), N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-phenylpropionamide) (trade name: IRGANOX1098), etc., especially preferred is pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which has high molecular weight, good compatibility with polypropylene, low volatility and excellent heat resistance.

[0132] To suppress degradation that accelerates with prolonged use, the aforementioned polypropylene film may contain one or more hindered phenolic antioxidants (secondary agents) having carbonyl groups. When the aforementioned polypropylene film contains one or more hindered phenolic antioxidants having carbonyl groups, their content relative to the mass of the resin component (when the resin component is considered as a whole, by mass) is preferably 4000 ppm by mass or more and 6000 ppm by mass or less, more preferably 4500 ppm by mass or more and 6000 ppm by mass or less. From the viewpoint of exhibiting appropriate effects, it is preferable that the content of the hindered phenolic antioxidant having carbonyl groups in the film is 4000 ppm by mass or more and 6000 ppm by mass or less.

[0133] Polypropylene films containing a carbonyl-based hindered phenolic antioxidant that is compatible with polypropylene at the molecular level in an optimal specific range exhibit improved long-term durability and are therefore preferred.

[0134] There are no particular limitations on the term "chlorine absorbent" as long as it is commonly referred to as a chlorine absorbent and can be used in polypropylene to obtain the target polypropylene film. Examples of chlorine absorbents include, for example, 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 target polypropylene film.

[0135] The polypropylene film of the present invention is preferably biaxially stretched. When the polypropylene film of the present invention is a biaxially stretched polypropylene film, the biaxially stretched polypropylene film can be manufactured by commonly known methods for manufacturing biaxially stretched polypropylene films. For example, a polypropylene resin composition can be obtained by mixing linear polypropylene resin A, linear polypropylene resin B, and long-chain branched polypropylene resin C with other resins, additives, etc., as needed, and a cast sheet can be made from this polypropylene resin composition, followed by biaxial stretching of the cast sheet.

[0136] <Preparation of Polypropylene Resin Compositions>

[0137] There are no particular limitations on the method for preparing the above-mentioned polypropylene resin composition, and the following methods can be cited: a method of dry mixing the polymer powder or granules of linear polypropylene resin A, linear polypropylene resin B and long-chain branched polypropylene resin C with other resins and additives as needed using a mixer; a method of feeding the polymer powder or granules of linear polypropylene resin A, linear polypropylene resin B and long-chain branched polypropylene resin C with other resins and additives as needed into a mixer for melt mixing to obtain a melt-blended resin composition, etc.

[0138] There are no particular restrictions on the type of mixer or compounding machine. A compounding machine can be any of the single-screw, twin-screw, or multi-screw types. In the case of twin-screw or multi-screw types, it can be any type of compounding machine that rotates in the same direction or in different directions.

[0139] When using melt blending for co-blending, the blending temperature is not particularly limited as long as good blending can be achieved. A range of 170–320°C is preferred, more preferably 200–300°C, and even more preferably 230–270°C. To suppress resin deterioration during blending, inactive gases such as nitrogen can be purged into the mixer. The melt-blended resin is typically granulated to an appropriate size using a known granulator, thereby obtaining granules of the melt-blended resin composition.

[0140] When preparing polypropylene resin compositions, for the purpose of suppressing thermal and oxidative degradation in the extruder, a primary antioxidant as described in the above-mentioned additives section may be added.

[0141] When the polypropylene resin composition contains a primary agent, its content relative to the mass of the resin component (by mass when the resin component is considered as a whole) is preferably 1000 ppm to 5000 ppm by mass. The antioxidant for this purpose is almost entirely consumed during the molding process in the extruder, leaving virtually no residue in the film after film formation.

[0142] The hindered phenolic antioxidant with a carbonyl group described in the above-mentioned additives section can be added to the polypropylene resin composition as a secondary agent.

[0143] When a polypropylene resin composition contains a hindered phenolic antioxidant with a carbonyl group, its content relative to the mass of the resin component (when the resin component is considered as a whole, by mass) is preferably 100 ppm to 10,000 ppm by mass, more preferably 5,500 ppm to 7,000 ppm by mass. A considerable amount of the hindered phenolic antioxidant with a carbonyl group is also consumed within the extruder.

[0144] When a polypropylene resin composition does not contain a primary agent, more hindered phenolic antioxidants with carbonyl groups can be used. This is because the consumption of hindered phenolic antioxidants with carbonyl groups increases within the extruder. When a polypropylene resin composition does not contain a primary agent but includes a hindered phenolic antioxidant with a carbonyl group, its content relative to the mass of the resin component (by mass when the resin component is considered as a whole) is 6000 ppm to 8000 ppm by mass or less.

[0145] <Production of Cast Film>

[0146] Cast sheets can be obtained by feeding pre-prepared dry-mixed resin compositions and / or granular melt-blended resin compositions into an extruder, heating and melting them, passing them through a filter, and then heating and melting them again to a temperature preferably 170°C to 320°C, more preferably 200°C to 300°C, and extruding them from a T-die. The extruded sheets are then cooled and solidified using at least one metal roller maintained at a temperature preferably 40°C to 140°C, more preferably 80°C to 140°C, further preferably 90°C to 140°C, particularly preferably 90°C to 120°C, and even more particularly preferably 90°C to 105°C (casting temperature). At this time, it is preferable to press the molten resin composition onto the metal roller using an air knife. It should be noted that the side in contact with the metal roller is the first side, and the opposite side (the side with the air knife) is the second side.

[0147] The thickness of the cast film is not particularly limited as long as the target polypropylene film can be obtained. It is preferably 0.05mm to 2mm, and more preferably 0.1mm to 1mm.

[0148] It should be noted that during the production process of cast sheets (especially in the extruder), polypropylene is mostly subjected to 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 in the extruder (inhibiting oxidation), screw shape in the extruder (shear force), internal shape of the T-die during casting (shear force), amount of antioxidant added (inhibiting oxidation), and winding speed during casting (elongation force).

[0149] <Stretching treatment>

[0150] The biaxially stretched polypropylene film described above can be manufactured by stretching the cast sheet. As a stretching method, a successive biaxial stretching method is preferred. In the successive biaxial stretching method, the cast sheet is first held at a temperature preferably 135-150°C, more preferably 140-146°C, and passed through rollers with a speed difference, stretched 3-7 times along the flow direction, and immediately cooled to room temperature. By appropriately adjusting the temperature of this longitudinal stretching process, the Sku value of either the first or second side can be easily adjusted to an appropriate range, and / or the Spc value of either the first or second side can be easily adjusted to an appropriate range. Next, the stretched film is fed into a tenter frame and, preferably at a temperature of 150°C or higher, more preferably 150-180°C, stretched laterally in the width direction to 3-11 times, then relaxed, heat-set, and wound into a roll.

[0151] After the film is cured in an atmosphere of about 20~45℃, it is slit (cut) to the desired product width by a slitting machine while being unwound (released) and then wound up again.

[0152] Through this stretching process, a film with excellent mechanical strength and rigidity is produced. In addition, the surface irregularities are more clearly defined, resulting in a biaxially stretched film with a finely roughened surface.

[0153] For the aforementioned polypropylene film, corona discharge treatment can be performed online or offline after the stretching and heat setting processes. Corona discharge treatment improves adhesion properties in subsequent processes such as metal vapor deposition. The corona discharge treatment can be performed using known methods. Air, carbon dioxide, nitrogen, or mixtures thereof are preferably used as the atmosphere gas.

[0154] To process it into a capacitor, a metal layer can be laminated on the first or both sides of the aforementioned polypropylene film to form a polypropylene film with an integral metal layer. The aforementioned metal layer functions as an electrode. For example, the metal used in the aforementioned metal layer can be elemental metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, mixtures thereof, or alloys thereof. Considering environmental factors, economic considerations, and capacitor performance, zinc and aluminum are preferred.

[0155] Methods for laminating a metal layer on the first or both sides of the aforementioned polypropylene film include, for example, vacuum evaporation and sputtering. From the viewpoint of productivity and economy, vacuum evaporation is preferred. Examples of vacuum evaporation methods include crucible evaporation and resistance wire evaporation, but there are no particular limitations, and the optimal method can be selected appropriately.

[0156] The margin pattern when laminating metal layers by vapor deposition is not particularly limited. However, from the viewpoint of improving capacitor safety and other properties, it is preferable to apply a pattern containing a fishnet pattern or a T-edge pattern, or other special edge patterns, to one side of the thin film. This is also effective from the perspective of improving safety and preventing capacitor breakdown and short circuits.

[0157] The method of forming the edge can use commonly known methods such as the strip method and the oil method without any restrictions.

[0158] When forming a metal layer on the polypropylene film, the polypropylene film, which is wound into a roll, is unwound (released) to form a metal layer such as a vapor-deposited film on one or both sides, and then wound again.

[0159] The aforementioned metal-integrated polypropylene film can be laminated in multiple layers using conventional methods, or processed by element winding (winding) to form a film capacitor.

[0160] Specifically, a cutting blade is placed in the center of each edge of the integral metal-layer polypropylene film for slitting, and a winding spool with an edge on one side of the surface is made.

[0161] Next, using the left and right edge take-up spools, two sheets are overlapped and wound together such that the vapor-deposited portion protrudes beyond the edge in the width direction (element winding process). Then, the core material is pulled out from the winding and pressed. Next, external electrodes are formed on both end faces, and leads are then provided on the external electrodes. Thus, a wound-type thin-film capacitor is obtained.

[0162] Example

[0163] The present invention will now be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[0164] Experiment 1, which investigated the correlation between the Sku value and the subject matter of this application, and Experiment 2, which investigated the correlation between the Spc value and the subject matter of this application, were conducted. In each experiment, the examples and comparative examples were numbered consecutively starting from 1.

[0165] < Experiment 1 >

[0166] Experiment 1: (1) Preparation of polypropylene resin

[0167] The polypropylene resins used to manufacture the polypropylene films of the examples and comparative examples are shown in Table 1.

[0168] • Resin A1: Manufactured by Prime Polymer Co., Ltd.

[0169] • Resin A2: HC300BF manufactured by Borealis

[0170] • Resin A3: Manufactured by Prime Polymer Co., Ltd.

[0171] • Resin B1: S802M manufactured by Korea Oil & Chemical Co., Ltd.

[0172] • Resin B2: HPT-1 manufactured by Korea Oil & Chemical Industries Co., Ltd.

[0173] • Resin B3: HP600J manufactured by HMC POLYMERS

[0174] • Resin C1: MFX6 manufactured by Japan Polypropylene Corporation.

[0175] • Resin C2: WB135HMS manufactured by Borealis.

[0176] Resins A1, A2, and A3 are linear polypropylene resins, equivalent to linear polypropylene resin A or its corresponding resin. Resins B1, B2, and B3 are linear polypropylene resins, equivalent to linear polypropylene resin B. Resins A1, A2, A3, B1, B2, and B3 are all homopolymer polypropylene resins. Resin C1 is a branched polypropylene resin polymerized using a metallocene catalyst, equivalent to long-chain branched polypropylene resin C. Resin C2 is a branched polypropylene resin manufactured using peroxides, not a branched polypropylene resin polymerized using a metallocene catalyst.

[0177] Table 1 shows 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) for each resin. These values ​​are for the raw resin granules. The determination methods are as follows.

[0178] [Table 1]

[0179]

[0180] Experiment 1: (2) Determination of physical properties of polypropylene resin

[0181] Experiment 1: (2-1) Determination of various average molecular weights and molecular weight distributions of linear polypropylene resin

[0182] Using SEC (size exclusion chromatography), various average molecular weights and molecular weight distributions were determined under the following conditions.

[0183] Apparatus: HLC-8321GPC / HT (Detector: Differential Refractometer (RI)) (Manufactured by Tosoh Corporation)

[0184] Column: TSKgel guardcolumnH HR (30) HT (7.5mmI.D.×7.5cm)×1 piece+TSKgel GMH HR -H(20)HT(7.8mmI.D.×30cm)×3 pieces (manufactured by Tosoh Corporation)

[0185] Eluent: 1,2,4-Trichlorobenzene (for GPC production by Fujifilm and Kohden Chemical Co., Ltd.) + butylated hydroxytoluene (0.05%)

[0186] Flow rate: 1.0 mL / min

[0187] Detection condition: Polarity = (-)

[0188] Injection volume: 300μL

[0189] Column temperature: 140℃

[0190] System temperature: 40℃

[0191] Sample concentration: 1 mg / mL

[0192] Pretreatment: Weigh the sample, add solvent (1,2,4-trichlorobenzene with 0.1% butylated hydroxytoluene), and dissolve by shaking at 140°C for 1 hour. Then filter by heating using a 0.5 μm sintered filter. It should be noted that no undissolved matter was observed during visual inspection of the sample solution.

[0193] Standard curve: A standard curve was prepared using standard polystyrene manufactured by Tosoh Corporation, approximating a fifth-order curve. The molecular weight was converted to the molecular weight of polypropylene using the Q factor.

[0194] Based on the obtained standard curve and SEC chromatogram, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) were obtained using analytical software from the assay apparatus. The molecular weight distribution (Mw / Mn) was obtained using the values ​​of Mw and Mn. Additionally, the molecular weight distribution (Mz / Mn) was obtained using the values ​​of Mz and Mn.

[0195] Experiment 1: (2-2) Determination of various average molecular weights and molecular weight distributions of branched polypropylene resin

[0196] Using SEC-MALS (size exclusion chromatography with multi-angle light scattering detector), various average molecular weights and molecular weight distributions were determined under the following conditions. This method utilizes SEC to fractionate molecules by size and MALS to determine the absolute molecular weight and average molecular weight.

[0197] Device: HLC-8321GPC / HT (with built-in differential refractometer (RI)) (manufactured by Tosoh Corporation) Light scattering detector: DAWN HELEOS (manufactured by Wyatt Technology)

[0198] MALS laser wavelength: 664nm

[0199] Column: TSKgel guardcolumnH HR (30) HT (7.5mmI.D.×7.5cm)×1 piece+TSKgel GMH HR -H(20)HT(7.8mmI.D.×30cm)×3 pieces (manufactured by Tosoh Corporation)

[0200] Eluent: 1,2,4-Trichlorobenzene (for GPC production by Fujifilm and Kohden Chemical Co., Ltd.) + butylated hydroxytoluene (0.05%)

[0201] Flow rate: 1.0 mL / min

[0202] Injection volume: 300μL

[0203] Column temperature: 140℃

[0204] System temperature: 40℃

[0205] Sample concentration: 1 mg / mL

[0206] Pretreatment: Weigh the sample, add solvent (1,2,4-trichlorobenzene with 0.1% butylated hydroxytoluene), and dissolve by shaking at 140°C for 1 hour. Then filter by heating using a 0.5 μm sintered filter. It should be noted that no undissolved matter was observed during visual inspection of the sample solution.

[0207] Data processing was performed using Astra Ver. 5.3.4, a software developed by Wyatt Technology. The analysis was conducted under the following conditions.

[0208] • Determine the absolute molecular weight and radius of rotation from the Zimm diagram.

[0209] The refractive index (1.501) of 1,2,4-trichlorobenzene used in the calculation at 140 °C was obtained by approximating the refractive index values ​​at 20 °C and 135 °C.

[0210] • The refractive index concentration increment (dn / dc) of the sample was taken from the literature (-0.092 mL / g). Reference: K. Lederer and I. Mingozzi, Pure and Applied Chemistry, 69(5), 993-1006 (1997).

[0211] • In GPC-MALS, there are areas where the evaluation of absolute molecular weight and radius of rotation is difficult for the following reasons, therefore, the corresponding parts are removed from the scope of absolute molecular weight calculation and radius of rotation evaluation.

[0212] • Low concentration (both high molecular weight and low molecular weight sides): In the peak tailing part of the chromatogram, the sample concentration is insufficient, and adequate sensitivity cannot be obtained.

[0213] • Isotropic scattering (low molecular weight side only): When the molecular size is less than about 1 / 20 of the incident light wavelength, the scattered light does not show anisotropy, and the radius of rotation cannot be obtained in the measurement principle.

[0214] The radius of gyration (Rw), number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) are obtained through the above analysis. The molecular weight distribution (Mw / Mn) is obtained using the values ​​of Mw and Mn. Similarly, the molecular weight distribution (Mz / Mn) is obtained using the values ​​of Mz and Mn.

[0215] Experiment 1: (2-3) Difference in differential distribution values ​​(D) M Determination of )

[0216] Differential distribution value Of Difference (D) M The SEC chromatogram is obtained as follows: The SEC chromatogram is obtained using the method described in (2-1) above. The chromatogram is then converted into a differential molecular weight distribution curve using the analytical software built into the measuring device. The differential molecular weight distribution values ​​at Log(M) = 4.5 and Log(M) = 6.0 are read from this curve. The difference between the differential molecular weight distribution values ​​(D...) M The value is calculated by subtracting the differential molecular weight distribution value at Log(M) = 6.0 from the differential molecular weight distribution value at Log(M) = 4.5.

[0217] Experiment 1: (2-4) Determination of [HI] insoluble substances in heptane

[0218] For linear polypropylene resin, it was compressed into a 10mm × 35mm × 0.3mm shape to prepare approximately 3g of sample for analysis. Then, approximately 150mL of heptane was added, and Soxhlet extraction was performed for 8 hours. The heptane-insoluble content was calculated from the sample mass before and after extraction.

[0219] Experiment 1: (2-5) Determination of the proportion of racemic five-unit components [mmmm]

[0220] To analyze the stereoregularity of polypropylene resin, the proportion of racemic five-unit components was determined by dissolving the resin in a solvent and using a nuclear magnetic resonance (NMR) analyzer with a low-temperature probe under the following conditions.

[0221] Nuclear Magnetic Resonance (NMR) Device: Bruker AVANCE NEO 700

[0222] Probe: 10mm φ PABBO BB

[0223] Observation kernel: 13 C (176.07MHz)

[0224] Solvent: 1,1,2,2-Tetrachloroethane-d2

[0225] Concentration: Approximately 250 mg / 2.5 mL

[0226] Total number of times: 8,192

[0227] Temperature: 130℃

[0228] Benchmark: 5 connected propylene units (mmmm) = 21.86 ppm

[0229] Pulse width: 5.3μs

[0230] Observation time: 0.8s

[0231] Standby time: 2.2s

[0232] Measurement mode: power-gated decoupling (the NOE of all methyl carbons in the propylene unit is considered equal).

[0233] The pentad ratio, representing stereoregularity, is calculated as a percentage (%) of the intensity integral of each signal from combinations of pentads (mmmm, mrrm, etc.) derived from co-orienting pentads (monic (m)) and anti-orienting pentads (r). The attribution of signals from mmmm, mrrm, etc., is referenced, for example, to the spectral records in "T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988)".

[0234] Experiment 1: (2-6) Determination of Melt Flow Rate (MFR)

[0235] For each resin, the melt flow rate (MFR) of the raw resin granules was determined using a melt indexer from Toyo Seiki Co., Ltd., according to condition M of JIS K 7210. Specifically, firstly, a 4g sample was inserted into a barrel at 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 orifice within 30 seconds was measured, and the MFR (g / 10min) was calculated. This measurement was repeated three times, and the average value was taken as the measured MFR.

[0236] Experiment 1: (2-7) Determination of Ash Content

[0237] The ash content of each resin is determined as follows. Weigh approximately 200g of sample. Repeat the process of placing approximately 10g of sample into a platinum dish and burning it until all the sample is burned. Then, ashing is performed in an electric furnace at 800℃ for 40 minutes. The ash content (ppm) is determined from the obtained ash residue. This process is repeated twice, and the average value is taken as the ash content (ppm).

[0238] Experiment 1: (3) Fabrication of polypropylene film

[0239] Example 1

[0240] Resins A1, B1, and C1 were dry-blended. The mixing ratio, by mass, was set as (Resin A1):(Resin B1):(Resin C1) = 63:34:3. Then, using the dry-blended resins, after melting at a resin temperature of 260°C, the mixture was extruded using a T-die and wound onto a metal roller with a surface temperature maintained at 97°C to solidify, thus producing a cast sheet. Simultaneously, the molten resin composition was pressed against the metal roller using an air knife while the cast sheet was being produced. The resulting unstretched cast sheet was held at 143°C and passed between rollers with a speed difference, stretched 4.6 times along the flow direction, and immediately cooled to room temperature. Next, the stretched film obtained by stretching the cast sheet along the flow direction was fed into a tenter frame and stretched 9.5 times along the width direction at a transverse stretching temperature of 155°C, followed by relaxation and heat setting. Next, a corona treatment was applied to one side of the film in an air atmosphere to achieve a wetting tension of 37±1 mN / m. Then, a biaxially stretched polypropylene film with a thickness of 2.3 μm was wound up. After winding up the biaxially stretched polypropylene film, it was placed in an atmosphere at about 40°C for 24 hours to perform a curing treatment, thus obtaining the biaxially stretched polypropylene film of Example 1.

[0241] Example 2

[0242] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2, and the mixture was wound onto a metal roller with the surface temperature maintained at 92°C to cure it and produce a cast sheet. Otherwise, the biaxially stretched polypropylene film of Example 2 was obtained in the same manner as in Example 1.

[0243] Example 3

[0244] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2. Otherwise, the biaxially stretched polypropylene film of Example 3 was obtained in the same manner as in Example 1.

[0245] Comparative Example 1

[0246] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2, and the mixture was wound onto a metal roller with the surface temperature maintained at 90°C to cure it and produce a cast sheet. The unstretched cast sheet was kept at a temperature of 145°C and passed between rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 1 was obtained in the same manner as in Example 1.

[0247] Comparative Example 2

[0248] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2, and the mixture was wound onto a metal roller with the surface temperature maintained at 96°C to cure it and produce a cast sheet. The unstretched cast sheet was kept at a temperature of 147°C and passed between rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 2 was obtained in the same manner as in Example 1.

[0249] Comparative Example 3

[0250] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2, and the unstretched cast sheet was kept at a temperature of 145°C and passed through rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 3 was obtained in the same way as in Example 1.

[0251] Comparative Example 4

[0252] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 2, and the resin was melted at a temperature of 250°C, wound onto a metal roller with a surface temperature maintained at 93°C, and cured to produce a cast sheet. The sheet was then stretched along the width direction at a transverse stretching temperature of 158°C. Otherwise, the biaxially stretched polypropylene film of Comparative Example 4 was obtained in the same manner as in Example 1.

[0253] [Table 2]

[0254]

[0255] Experiment 1: (4) Evaluation of the physical properties of polypropylene film

[0256] Experiment 1: (4-1) Thickness Measurement

[0257] The paper thickness was measured using a CITIZEN SEIMITSU CO., LTD. MEI-11 paper thickness gauge (measuring pressure 100 kPa, descent speed 3 mm / s, measuring terminal φ=16 mm, measuring force 20.1 N) at an environment of 23±2℃ and 50±5%RH. Samples were cut from rolls with at least 10 overlapping sheets, ensuring that wrinkles and air did not enter the film during cutting. Five measurements were performed on the 10-sheet overlapping samples, and the thickness was calculated by dividing the average of the five measurements by 10.

[0258] Experiment 1: (4-2) Determination of Haze

[0259] Haze was measured using a haze meter (NDH-5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K 7136:2000. The sample was cut from the roll, with the sample size set at 50 mm in the MD direction and 100 mm in the TD direction.

[0260] Experiment 1: (4-3) Determination of wetting tension

[0261] The wetting tension of the film surface was measured in an environment with a temperature of 23±2℃ and a humidity of 50±5%RH, according to JIS K6768:1999.

[0262] Experiment 1: (4-4) Determination of three-dimensional surface property parameters

[0263] For the biaxially stretched polypropylene films of the examples and comparative examples, the following three-dimensional surface properties parameters were determined by the following method, according to ISO 25178-2 (2007 draft).

[0264] • Sa: Arithmetic mean deviation

[0265] • Sq: Root-mean-square deviation

[0266] •Sku: kurtosis

[0267] It should be noted that the measurements were performed on both sides of the film separately using the following method.

[0268] As an optical interferometric non-contact surface shape measuring machine, the "VertScan2.0 (model: R5500GML)" manufactured by Ryoka Systems Inc. is used with the following configuration.

[0269] Manufacturer: Ryoka Systems Inc.

[0270] • Device Name: VertScan 2.0 (R5500GML-A150-AC)

[0271] • Measurement software: VS-Measure Version 5.05.0014

[0272] • CCD camera: SONY HR-50 1 / 3

[0273] • Objective lens: 10×

[0274] • Lens tube: 1 x Lens body

[0275] • Zoom lens: No relay

[0276] Wavelength filter: 530 white

[0277] Measurement mode: Wavelength (WAVE)

[0278] • Field of view size: 640×480 pixels

[0279] • Measurement area: 470.92μm × 353.16μm

[0280] A porous plate was placed on an electrostatic adsorption plate (150mm × 150mm), and the sample was fixed on it for measurement. In addition, 10 sites were measured at 1cm intervals along the flow direction, starting from the central part in both the flow direction and width direction of the target sample (polypropylene film).

[0281] Next, the obtained measurement data were processed sequentially as follows to calculate the surface property parameters.

[0282] Analysis software: VS-Viewer Version 5.05.0013

[0283] 1. Supplementing bad pixels based on the command "Supplement (Complete)"

[0284] 2. Noise Removal Based on Median (3×3) Filtering

[0285] 3. Fluctuation components are removed by applying Gaussian filtering with a cutoff value of 30μm.

[0286] 4. Calculations performed using the "ISO Parameters" plugin (S-Filter: None)

[0287] 5. Calculate the arithmetic mean of the values ​​(Sa, Sq, Sku) obtained from the measurement / analysis of the above 10 locations, and use this value.

[0288] Test 1: (4-5) Determination of Insulation Breakdown Strength

[0289] The insulation breakdown strength of biaxially stretched films was determined according to JIS C 2330:2010 6.2 b) and JIS C 2151:2006 17.2.2 (Insulation Breakdown Strength / DC Test / Plate Electrode Method). The lower electrode in the test was constructed by placing conductive rubber (manufactured by Hoshiwa Electric Co., Ltd., size 100mm×200mm, thickness 1mm, model E12S10) on a metallic plate (150mm×150mm, thickness 3mm). Forty-four tests were performed. Six high and six low values ​​were removed from the results, and the average of the remaining 32 tests was divided by the film thickness to obtain the insulation breakdown strength (V0.05). DC ( / μm). The measurement conditions are as follows.

[0290] Test piece: approximately 150mm × 150mm

[0291] Conditioning of the test piece: 30 minutes under atmospheric conditions.

[0292] Power supply: DC

[0293] Atmosphere: 120℃

[0294] Testing machine: TOS9213AS DC withstand voltage / insulation resistance tester manufactured by Kikusui Electronics Industries, Ltd.

[0295] Voltage rise rate: 100V / s

[0296] Current detection response speed: MID

[0297] Upper limit reference value: 5mA.

[0298] Experiment 1: (4-6) Determination of Ash Content

[0299] Weigh approximately 200g of the sample and transfer it to a platinum dish. Ash the sample at 800°C for 40 minutes. Determine the ash content (ppm) from the resulting ash residue.

[0300] Experiment 1: (5) Fabrication of metallized thin films and capacitors

[0301] While rewinding the polypropylene film roll, insulating edges and segmented electrode patterns are formed on the corona-treated surface using a ULVAC roll-up vacuum evaporation apparatus (EWE-060) through an oil mask. Aluminum is vapor-deposited to form electrodes on the film, and zinc is vapor-deposited to form thick edges (electrode conduction areas). This yields a metallized film roll with electrode patterns, exhibiting an Al metal film resistivity of 20 Ω / □ and a Zn metal film resistivity of 5 Ω / □.

[0302] It should be noted that in the determination of the resistance (surface resistivity ρs) of the metal film, the insulation resistance tester (Mitsubishi Analytech Co., Ltd. Loresta GP-MCP-T610) uses a thin film measurement electrode (PSP probe MCP-TP06PRMH112) and the measurement is performed in the following order.

[0303] 1. A four-probe electrode arranged roughly in a straight line is positioned to contact the effective electrode portion of the sample.

[0304] 2. A specified current is passed between the two probes on the outer side, and the potential difference generated between the two probes on the inner side is measured, thereby determining the film resistance value of the metal part.

[0305] 3. There is no particular limitation on the sample size, but since the distribution of electrical energy varies depending on the sample size being measured, the sample shape and size are input into the equipment to obtain the value by multiplying it by the resistivity correction factor (4.419).

[0306] This is because the thickness of the metal film (effective electrode portion) deposited on the polypropylene sheet is difficult to measure due to its thinness, which is only a few tens of nm. Therefore, the resistance (surface resistivity ρs) of the metal film is measured instead of the thickness.

[0307] The fabricated metallized film rolls were slit into 30mm wide pieces using a slitting machine to create small spools for winding the metallized film, with an insulating edge width of 2.0mm and a thickness width of 1.5mm. Using the fabricated small spools, the components were wound with a capacitance of approximately 50μF using a fully automated metallized film capacitor winding machine (3KAW-N2) from Kaito Manufacturing Co., Ltd., followed by pressing and flattening. For the flattened components, metal was sputtered onto the end faces to form thin-film electrode take-off sections, followed by heat treatment under vacuum at high temperature to cure the components. Leads were attached to the metal-sputtered sections, and the components were placed into a resin housing. Epoxy resin was filled into the gaps, and the resin was cured, thus obtaining a metallized film capacitor element for evaluation.

[0308] Experiment 1: (6) Evaluation of the characteristics of metallized thin films and capacitors

[0309] Experiment 1: (6-1) Determination of capacitance and dielectric loss tangent of capacitor

[0310] Install a four-terminal probe 9140 on an LCR HiTESTER-3522-50 manufactured by HIOKI Electric Co., Ltd. Clamp the two terminals (leads) of the capacitor using the four-terminal probe 9140, and apply an AC voltage of 0.1V, 1kHz through the built-in power supply of the LCR HiTESTER-3522-50. After the displayed value stabilizes (for example, approximately 30 seconds after application), read the capacitance and tanδ values. It should be noted that for measurement conditions other than those described here, refer to "4.2.2 Capacitance" and "4.2.3 Dielectric Loss Tangent (tanδ)" of JIS C 5101-16:2009.

[0311] Experiment 1: (6-2) Capacitor life test (rate of change of capacitance and safety)

[0312] A capacitor was continuously subjected to a DC voltage of 750V for 1000 hours in a high-temperature bath at 115℃. Based on the capacitor's capacitance before and after this load, the rate of change of capacitance before and after the voltage load was calculated using the following formula. The test was conducted using two samples, and the average value was used for evaluation.

[0313] (Rate of change of capacitance) = [(Capacitance after voltage load) - (Initial capacitance)] / (Initial capacitance) × 100 (%)

[0314] The capacity change rate after 1000 hours is preferably within -5%.

[0315] It should be noted that the insulation resistance was measured using the following method. A shielded box SME-8350 was connected to a DSM8104 insulation resistance meter manufactured by Hioki Electric Co., Ltd. A metallized film capacitor element was placed inside the shielded box, and a DC voltage of 500V was applied. The insulation resistance value was read after 1 minute. It should be noted that for measurement conditions other than those described here, JIS C 5101-16:2009, "4.2.4 Insulation Resistance", should be followed.

[0316] Furthermore, in determining short-circuit faults, a short-circuit fault is defined as an insulation resistance less than 100kΩ. Specifically, a short-circuit fault is defined as a resistance level exceeding the lower limit of the insulation resistance meter's measurement range (when no value is displayed).

[0317] There are roughly three types of capacitor failure modes. Among them, short-circuit failure also poses the following dangers: because the current continues to flow in the short-circuited capacitor, it will release heat due to Joule heating; and it will ignite due to the reaction with oxygen in the air when the outer packaging is damaged. Therefore, short-circuit failure cannot occur.

[0318] 1. Open circuit fault: A fault in which the capacitance is extremely reduced when the insulation resistance is high.

[0319] 2. Short circuit fault: A fault in which the insulation resistance value becomes extremely low.

[0320] 3. Capacitance variation: Faults where capacitor characteristics such as capacitance and loss exceed the standard.

[0321] In the above-mentioned capacitor life test, if neither of the two capacitor elements supplied for the test has a short circuit fault, it is considered to be in good safety condition; if either or both of the two capacitors has a short circuit fault, it is considered to be in poor safety condition.

[0322] Experiment 1: (7) Characteristic Evaluation Results

[0323] [Table 3]

[0324]

[0325] < Experiment 2 >

[0326] Experiment 2: (1) Preparation of polypropylene resin

[0327] The polypropylene resins used to manufacture the polypropylene films of the examples and comparative examples are shown in Table 4.

[0328] • Resin A1: Manufactured by Prime Polymer Co., Ltd.

[0329] • Resin A2: HC300BF manufactured by Borealis

[0330] • Resin A3: Manufactured by Prime Polymer Co., Ltd.

[0331] • Resin B1: S802M manufactured by Korea Oil & Chemical Co., Ltd.

[0332] • Resin B2: HPT-1 manufactured by Korea Oil & Chemical Industries Co., Ltd.

[0333] • Resin B3: HP600J manufactured by HMC POLYMERS

[0334] • Resin C1: MFX6 manufactured by Japan Polypropylene Corporation.

[0335] • Resin C2: WB135HMS manufactured by Borealis.

[0336] Resins A1, A2, and A3 are linear polypropylene resins, equivalent to linear polypropylene resin A or its corresponding resin. Resins B1, B2, and B3 are linear polypropylene resins, equivalent to linear polypropylene resin B. Resins A1, A2, A3, B1, B2, and B3 are all homopolymer polypropylene resins. Resin C1 is a branched polypropylene resin polymerized using a metallocene catalyst, equivalent to long-chain branched polypropylene resin C. Resin C2 is a branched polypropylene resin manufactured using peroxides, not a branched polypropylene resin polymerized using a metallocene catalyst.

[0337] Table 4 shows 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) for each resin. These values ​​are for the raw resin granules. The determination methods are as follows.

[0338] [Table 4]

[0339]

[0340] Experiment 2: (2) Determination of physical properties of polypropylene resin

[0341] Experiment 2: (2-1) Determination of various average molecular weights and molecular weight distributions of linear polypropylene resin

[0342] Using SEC (size exclusion chromatography), various average molecular weights and molecular weight distributions were determined under the following conditions.

[0343] Apparatus: HLC-8321GPC / HT (Detector: Differential Refractometer (RI)) (Manufactured by Tosoh Corporation)

[0344] Column: TSKgel guardcolumnH HR (30) HT (7.5mmI.D.×7.5cm)×1 piece+TSKgel GMH HR -H(20)HT(7.8mmI.D.×30cm)×3 pieces (manufactured by Tosoh Corporation)

[0345] Eluent: 1,2,4-Trichlorobenzene (for GPC production by Fujifilm and Kohden Chemical Co., Ltd.) + butylated hydroxytoluene (0.05%)

[0346] Flow rate: 1.0 mL / min

[0347] Detection condition: Polarity = (-)

[0348] Injection volume: 300μL

[0349] Column temperature: 140℃

[0350] System temperature: 40℃

[0351] Sample concentration: 1 mg / mL

[0352] Pretreatment: Weigh the sample, add solvent (1,2,4-trichlorobenzene with 0.1% butylated hydroxytoluene), and dissolve by shaking at 140°C for 1 hour. Then filter by heating using a 0.5 μm sintered filter. It should be noted that no undissolved matter was observed during visual inspection of the sample solution.

[0353] Standard curve: A standard curve was prepared using standard polystyrene manufactured by Tosoh Corporation, approximating a fifth-order curve. The molecular weight was converted to the molecular weight of polypropylene using the Q factor.

[0354] Based on the obtained standard curve and SEC chromatogram, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) were obtained using analytical software from the assay apparatus. The molecular weight distribution (Mw / Mn) was obtained using the values ​​of Mw and Mn. Additionally, the molecular weight distribution (Mz / Mn) was obtained using the values ​​of Mz and Mn.

[0355] Experiment 2: (2-2) Determination of various average molecular weights and molecular weight distributions of branched polypropylene resin

[0356] Using SEC-MALS (size exclusion chromatography with multi-angle light scattering detector), various average molecular weights and molecular weight distributions were determined under the following conditions. This method utilizes SEC to fractionate molecules by size and MALS to determine the absolute molecular weight and average molecular weight.

[0357] Device: HLC-8321GPC / HT (with built-in differential refractometer (RI)) (manufactured by Tosoh Corporation) Light scattering detector: DAWN HELEOS (manufactured by Wyatt Technology)

[0358] MALS laser wavelength: 664nm

[0359] Column: TSKgel guardcolumnH HR (30) HT (7.5mmI.D.×7.5cm)×1 piece+TSKgel GMH HR -H(20)HT(7.8mmI.D.×30cm)×3 pieces (manufactured by Tosoh Corporation)

[0360] Eluent: 1,2,4-Trichlorobenzene (for GPC production by Fujifilm and Kohden Chemical Co., Ltd.) + butylated hydroxytoluene (0.05%)

[0361] Flow rate: 1.0 mL / min

[0362] Injection volume: 300μL

[0363] Column temperature: 140℃

[0364] System temperature: 40℃

[0365] Sample concentration: 1 mg / mL

[0366] Pretreatment: Weigh the sample, add solvent (1,2,4-trichlorobenzene with 0.1% butylated hydroxytoluene), and dissolve by shaking at 140°C for 1 hour. Then filter by heating using a 0.5 μm sintered filter. It should be noted that no undissolved matter was observed during visual inspection of the sample solution.

[0367] Data processing was performed using Astra Ver. 5.3.4, a software developed by Wyatt Technology. The analysis was conducted under the following conditions.

[0368] • Determine the absolute molecular weight and radius of rotation from the Zimm diagram.

[0369] The refractive index (1.501) of 1,2,4-trichlorobenzene used in the calculation at 140 °C was obtained by approximating the refractive index values ​​at 20 °C and 135 °C.

[0370] • The refractive index concentration increment (dn / dc) of the sample was taken from the literature (-0.092 mL / g). Reference: K. Lederer and I. Mingozzi, Pure and Applied Chemistry, 69(5), 993-1006 (1997).

[0371] • In GPC-MALS, there are areas where the evaluation of absolute molecular weight and radius of rotation is difficult for the following reasons, therefore, the corresponding parts are removed from the scope of absolute molecular weight calculation and radius of rotation evaluation.

[0372] • Low concentration (both high molecular weight and low molecular weight sides): In the peak tailing part of the chromatogram, the sample concentration is insufficient, and adequate sensitivity cannot be obtained.

[0373] • Isotropic scattering (low molecular weight side only): When the molecular size is less than about 1 / 20 of the incident light wavelength, the scattered light does not show anisotropy, and the radius of rotation cannot be obtained in the measurement principle.

[0374] The radius of gyration (Rw), number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) are obtained through the above analysis. The molecular weight distribution (Mw / Mn) is obtained using the values ​​of Mw and Mn. Similarly, the molecular weight distribution (Mz / Mn) is obtained using the values ​​of Mz and Mn.

[0375] Experiment 2: (2-3) Difference in differential distribution values ​​(D) M Determination of )

[0376] Differential distribution value Of Difference (D) M The SEC chromatogram is obtained as follows: The SEC chromatogram is obtained using the method described in (2-1) above. Using the analytical software built into the measuring device, the chromatogram is converted into a differential molecular weight distribution curve. The differential molecular weight distribution values ​​at Log(M) = 4.5 and Log(M) = 6.0 are read from this curve. Differential molecular weight distribution values. Of Difference (D) M The value is calculated by subtracting the differential molecular weight distribution value at Log(M) = 6.0 from the differential molecular weight distribution value at Log(M) = 4.5.

[0377] Experiment 2: (2-4) Determination of heptane-insoluble substances [HI]

[0378] For linear polypropylene resin, it was compressed into a 10mm × 35mm × 0.3mm shape to prepare approximately 3g of sample for analysis. Then, approximately 150mL of heptane was added, and Soxhlet extraction was performed for 8 hours. The heptane-insoluble content was calculated from the sample mass before and after extraction.

[0379] Experiment 2: (2-5) Determination of the proportion of racemic five-unit components [mmmm]

[0380] To analyze the stereoregularity of polypropylene resin, the proportion of racemic five-unit components was determined by dissolving the resin in a solvent and using a nuclear magnetic resonance (NMR) analyzer with a low-temperature probe under the following conditions.

[0381] Nuclear Magnetic Resonance (NMR) Device: Bruker AVANCE NEO 700

[0382] Probe: 10mm φ PABBO BB

[0383] Observation kernel: 13 C (176.07MHz)

[0384] Solvent: 1,1,2,2-Tetrachloroethane-d2

[0385] Concentration: Approximately 250 mg / 2.5 mL

[0386] Total number of times: 8,192

[0387] Temperature: 130℃

[0388] Benchmark: 5 connected propylene units (mmmm) = 21.86 ppm

[0389] Pulse width: 5.3μs

[0390] Observation time: 0.8s

[0391] Standby time: 2.2s

[0392] Measurement mode: power-gated decoupling (the NOE of all methyl carbons in the propylene unit is considered equal).

[0393] The pentad ratio, representing stereoregularity, is calculated as a percentage (%) of the intensity integral of each signal from combinations of pentads (mmmm, mrrm, etc.) derived from co-orienting pentads (monic (m)) and anti-orienting pentads (r). The attribution of signals from mmmm, mrrm, etc., is referenced, for example, to the spectral records in "T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988)".

[0394] Experiment 2: (2-6) Determination of Melt Flow Rate (MFR)

[0395] For each resin, the melt flow rate (MFR) of the raw resin granules was determined using a melt indexer from Toyo Seiki Co., Ltd., according to condition M of JIS K 7210. Specifically, firstly, a 4g sample was inserted into a barrel at 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 orifice within 30 seconds was measured, and the MFR (g / 10min) was calculated. This measurement was repeated three times, and the average value was taken as the measured MFR.

[0396] Experiment 2: (2-7) Determination of Ash Content

[0397] The ash content of each resin is determined as follows. Weigh approximately 200g of sample. Repeat the process of placing approximately 10g of sample into a platinum dish and burning it until all the sample is burned. Then, ashing is performed in an electric furnace at 800℃ for 40 minutes. The ash content (ppm) is determined from the obtained ash residue. This process is repeated twice, and the average value is taken as the ash content (ppm).

[0398] Experiment 2: (3) Fabrication of polypropylene film

[0399] Example 1

[0400] Resins A1, B1, and C1 were dry-blended. The mixing ratio, by mass, was set as (Resin A1):(Resin B1):(Resin C1) = 63:34:3. Then, using the dry-blended resins, after melting at a resin temperature of 260°C, the mixture was extruded using a T-die and wound onto a metal roller with a surface temperature maintained at 97°C to solidify, thus producing a cast sheet. Simultaneously, the molten resin composition was pressed against the metal roller using an air knife while the cast sheet was being produced. The resulting unstretched cast sheet was held at 143°C and passed between rollers with a speed difference, stretched 4.6 times along the flow direction, and immediately cooled to room temperature. Next, the stretched film obtained by stretching the cast sheet along the flow direction was fed into a tenter frame and stretched 9.5 times along the width direction at a transverse stretching temperature of 155°C, followed by relaxation and heat setting. Next, a corona treatment was applied to one side of the film in an air atmosphere to achieve a wetting tension of 37±1 mN / m. Then, a biaxially stretched polypropylene film with a thickness of 2.3 μm was wound up. After winding up the biaxially stretched polypropylene film, it was placed in an atmosphere at about 40°C for 24 hours to perform a curing treatment, thus obtaining the biaxially stretched polypropylene film of Example 1.

[0401] Example 2

[0402] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5, and the mixture was wound onto a metal roller with the surface temperature maintained at 92°C to cure it and produce a cast sheet. Otherwise, the biaxially stretched polypropylene film of Example 2 was obtained in the same manner as in Example 1.

[0403] Example 3

[0404] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5. Otherwise, the biaxially stretched polypropylene film of Example 3 was obtained in the same manner as in Example 1.

[0405] Comparative Example 1

[0406] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5, and the mixture was wound onto a metal roller with the surface temperature maintained at 90°C to cure it and produce a cast sheet. The unstretched cast sheet was kept at a temperature of 145°C and passed between rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 1 was obtained in the same way as in Example 1.

[0407] Comparative Example 2

[0408] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5, and the mixture was wound onto a metal roller with the surface temperature maintained at 96°C to cure it and produce a cast sheet. The unstretched cast sheet was kept at a temperature of 147°C and passed between rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 2 was obtained in the same manner as in Example 1.

[0409] Comparative Example 3

[0410] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5, and the unstretched cast sheet was kept at a temperature of 145°C and passed through rollers with a speed difference to stretch it in the flow direction. Otherwise, the biaxially stretched polypropylene film of Comparative Example 3 was obtained in the same way as in Example 1.

[0411] Comparative Example 4

[0412] The mixing ratio of the raw material resin during dry mixing was changed as shown in Table 5, and the resin was melted at a temperature of 250°C, wound onto a metal roller with a surface temperature maintained at 93°C, and cured to produce a cast sheet. The film was stretched along the width direction at a transverse stretching temperature of 158°C. Otherwise, the biaxially stretched polypropylene film of Comparative Example 4 was obtained in the same manner as in Example 1.

[0413] [Table 5]

[0414]

[0415] Experiment 2: (4) Evaluation of the physical properties of polypropylene film

[0416] Experiment 2: (4-1) Thickness Measurement

[0417] The paper thickness was measured using a CITIZEN SEIMITSU CO., LTD. MEI-11 paper thickness gauge (measuring pressure 100 kPa, descent speed 3 mm / s, measuring terminal φ=16 mm, measuring force 20.1 N) at an environment of 23±2℃ and 50±5%RH. Samples were cut from rolls with at least 10 overlapping sheets, ensuring that wrinkles and air did not enter the film during cutting. Five measurements were performed on the 10-sheet overlapping samples, and the thickness was calculated by dividing the average of the five measurements by 10.

[0418] Experiment 2: (4-2) Determination of Haze

[0419] Haze was measured using a haze meter (NDH-5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K 7136:2000. The sample was cut from the roll, with the sample size set at 50 mm in the MD direction and 100 mm in the TD direction.

[0420] Experiment 2: (4-3) Determination of wetting tension

[0421] The wetting tension of the film surface was measured in an environment with a temperature of 23±2℃ and a humidity of 50±5%RH, according to JIS K6768:1999.

[0422] Experiment 2: (4-4) Determination of three-dimensional surface property parameters

[0423] For the biaxially stretched polypropylene films of the examples and comparative examples, the following three-dimensional surface properties parameters were determined by the following method, according to ISO 25178-2 (2007 draft).

[0424] • Sa: Arithmetic mean deviation

[0425] • Sq: Root-mean-square deviation

[0426] • Spc: Arithmetic mean peak curvature

[0427] It should be noted that the measurements were performed on both sides of the film separately using the following method.

[0428] As an optical interferometric non-contact surface shape measuring machine, the "VertScan2.0 (model: R5500GML)" manufactured by Ryoka Systems Inc. is used with the following configuration.

[0429] Manufacturer: Ryoka Systems Inc.

[0430] • Device Name: VertScan 2.0 (R5500GML-A150-AC)

[0431] • Measurement software: VS-Measure Version 5.05.0014

[0432] • CCD camera: SONY HR-50 1 / 3

[0433] • Objective lens: 10×

[0434] • Lens tube: 1 x Lens body

[0435] • Zoom lens: No relay

[0436] Wavelength filter: 530 white

[0437] Measurement mode: Wavelength (WAVE)

[0438] • Field of view size: 640×480 pixels

[0439] • Measurement area: 470.92μm × 353.16μm

[0440] A porous plate was placed on an electrostatic adsorption plate (150mm × 150mm), and the sample was fixed on it for measurement. In addition, 10 sites were measured at 1cm intervals along the flow direction, starting from the central part in both the flow direction and width direction of the target sample (polypropylene film).

[0441] Next, the obtained measurement data were processed sequentially as follows to calculate the surface property parameters.

[0442] Analysis software: VS-Viewer Version 5.05.0013

[0443] 1. Supplementing bad pixels based on the command "Supplement (Complete)"

[0444] 2. Noise Removal Based on Median (3×3) Filtering

[0445] 3. Fluctuation components are removed by applying Gaussian filtering with a cutoff value of 30μm.

[0446] 4. Calculations performed using the "ISO Parameters" plugin (S-Filter: None)

[0447] 5. For the values ​​(Sa, Sq, Spc) obtained from the measurement / analysis of the above 10 locations, calculate their arithmetic mean and use this value. It should be noted that Spc may sometimes be negative due to the influence of the calculation definition in the analysis software; therefore, the arithmetic mean of the absolute values ​​obtained is set as Spc.

[0448] Test 2: (4-5) Determination of Insulation Breakdown Strength

[0449] The insulation breakdown strength of biaxially stretched films was determined according to JIS C 2330:2010 6.2 b) and JIS C 2151:2006 17.2.2 (Insulation Breakdown Strength / DC Test / Plate Electrode Method). The lower electrode in the test was constructed by placing conductive rubber (manufactured by Hoshiwa Electric Co., Ltd., size 100mm×200mm, thickness 1mm, model E12S10) on a metallic plate (150mm×150mm, thickness 3mm). Forty-four tests were performed. Six high and six low values ​​were removed from the results, and the average of the remaining 32 tests was divided by the film thickness to obtain the insulation breakdown strength (V0.05). DC ( / μm). The measurement conditions are as follows.

[0450] Test piece: approximately 150mm × 150mm

[0451] Conditioning of the test piece: 30 minutes under atmospheric conditions.

[0452] Power supply: DC

[0453] Atmosphere: 120℃

[0454] Testing machine: TOS9213AS DC withstand voltage / insulation resistance tester manufactured by Kikusui Electronics Industries, Ltd.

[0455] Voltage rise rate: 100V / s

[0456] Current detection response speed: MID

[0457] Upper limit reference value: 5mA.

[0458] Experiment 2: (4-6) Determination of Ash Content

[0459] Weigh approximately 200g of the sample and transfer it to a platinum dish. Ash the sample at 800°C for 40 minutes. Determine the ash content (ppm) from the resulting ash residue.

[0460] Experiment 2: (5) Fabrication of metallized thin films and capacitors

[0461] While rewinding the polypropylene film roll, insulating edges and segmented electrode patterns are formed on the corona-treated surface using a ULVAC roll-up vacuum evaporation apparatus (EWE-060) through an oil mask. Aluminum is vapor-deposited to form electrodes on the film, and zinc is vapor-deposited to form thick edges (electrode conduction areas). This yields a metallized film roll with electrode patterns, exhibiting an Al metal film resistivity of 20 Ω / □ and a Zn metal film resistivity of 5 Ω / □.

[0462] It should be noted that in the determination of the resistance (surface resistivity ρs) of the metal film, the insulation resistance tester (Mitsubishi Analytech Co., Ltd. Loresta GP-MCP-T610) uses a thin film measurement electrode (PSP probe MCP-TP06PRMH112) and the measurement is performed in the following order.

[0463] 1. A four-probe electrode arranged roughly in a straight line is positioned to contact the effective electrode portion of the sample.

[0464] 2. A specified current is passed between the two probes on the outer side, and the potential difference generated between the two probes on the inner side is measured, thereby determining the film resistance value of the metal part.

[0465] 3. There is no particular limitation on the sample size, but since the distribution of electrical energy varies depending on the sample size being measured, the sample shape and size are input into the equipment to obtain the value by multiplying it by the resistivity correction factor (4.419).

[0466] This is because the thickness of the metal film (effective electrode portion) deposited on the polypropylene sheet is difficult to measure due to its thinness, which is only a few tens of nm. Therefore, the resistance (surface resistivity ρs) of the metal film is measured instead of the thickness.

[0467] The fabricated metallized film rolls were slit into 30mm wide pieces using a slitting machine to create small spools for winding the metallized film, with an insulating edge width of 2.0mm and a thickness width of 1.5mm. Using the fabricated small spools, the components were wound with a capacitance of approximately 50μF using a fully automated metallized film capacitor winding machine (3KAW-N2) from Kaito Manufacturing Co., Ltd., followed by pressing and flattening. For the flattened components, metal was sputtered onto the end faces to form thin-film electrode take-off sections, followed by heat treatment under vacuum at high temperature to cure the components. Leads were attached to the metal-sputtered sections, and the components were placed into a resin housing. Epoxy resin was filled into the gaps, and the resin was cured, thus obtaining a metallized film capacitor element for evaluation.

[0468] Experiment 2: (6) Evaluation of the characteristics of metallized thin films and capacitors

[0469] Experiment 2: (6-1) Determination of capacitance and dielectric loss tangent of capacitor

[0470] Install a four-terminal probe 9140 on an LCR HiTESTER-3522-50 manufactured by HIOKI Electric Co., Ltd. Clamp the two terminals (leads) of the capacitor using the four-terminal probe 9140, and apply an AC voltage of 0.1V, 1kHz through the built-in power supply of the LCR HiTESTER-3522-50. After the displayed value stabilizes (for example, approximately 30 seconds after application), read the capacitance and tanδ values. It should be noted that for measurement conditions other than those described here, refer to "4.2.2 Capacitance" and "4.2.3 Dielectric Loss Tangent (tanδ)" of JIS C 5101-16:2009.

[0471] Experiment 2: (6-2) Capacitor life test (rate of change of capacitance and safety)

[0472] A capacitor was continuously subjected to a DC voltage of 750V for 1000 hours in a high-temperature bath at 115℃. Based on the capacitor's capacitance before and after this load, the rate of change of capacitance before and after the voltage load was calculated using the following formula. The test was conducted using two samples, and the average value was used for evaluation.

[0473] (Rate of change of capacitance) = [(Capacitance after voltage load) - (Initial capacitance)] / (Initial capacitance) × 100 (%)

[0474] The capacity change rate after 1000 hours is preferably within -5%.

[0475] It should be noted that the insulation resistance was measured using the following method. A shielded box SME-8350 was connected to a DSM8104 insulation resistance meter manufactured by Hioki Electric Co., Ltd. A metallized film capacitor element was placed inside the shielded box, and a DC voltage of 500V was applied. The insulation resistance value was read after 1 minute. It should be noted that for measurement conditions other than those described here, JIS C 5101-16:2009, "4.2.4 Insulation Resistance", should be followed.

[0476] Furthermore, in determining short-circuit faults, a short-circuit fault is defined as an insulation resistance less than 100kΩ. Specifically, a short-circuit fault is defined as a resistance level exceeding the lower limit of the insulation resistance meter's measurement range (when no value is displayed).

[0477] There are roughly three types of capacitor failure modes. Among them, short-circuit failure also poses the following dangers: because the current continues to flow in the short-circuited capacitor, it will release heat due to Joule heating; and it will ignite due to the reaction with oxygen in the air when the outer packaging is damaged. Therefore, short-circuit failure cannot occur.

[0478] 1. Open circuit fault: A fault in which the capacitance is extremely reduced when the insulation resistance is high.

[0479] 2. Short circuit fault: A fault in which the insulation resistance value becomes extremely low.

[0480] 3. Capacitance variation: Faults where capacitor characteristics such as capacitance and loss exceed the standard.

[0481] In the above-mentioned capacitor life test, if neither of the two capacitor elements supplied for the test has a short circuit fault, it is considered to be in good safety condition; if either or both of the two capacitors has a short circuit fault, it is considered to be in poor safety condition.

[0482] Experiment 2: (7) Characteristic Evaluation Results

[0483] [Table 6]

[0484]

Claims

1. A polypropylene film, characterized in that, It is a polypropylene film having a first side and a second side, wherein, in the surface properties parameters specified by ISO 25178, the Sku value of either the first side or the second side is 40 or less, and / or the Spc value of either the first side or the second side is 16 (1 / mm) or less.

2. The polypropylene film according to claim 1, wherein, When the surface with high wetting tension as measured by JIS K6768:1999 is designated as the first surface and the surface with low wetting tension is designated as the second surface, the value obtained by dividing the Sku value of the second surface by the Sku value of the first surface is 1.0000 or less, and / or the value obtained by dividing the Spc value of the second surface by the Spc value of the first surface is 1.0000 or less.

3. The polypropylene film according to claim 1, wherein, The Sku value of either the first or the second face is 20 or less, and / or the Spc value of either the first or the second face is 13 (1 / mm) or less.

4. The polypropylene film according to claim 1, comprising linear polypropylene resin B and long-chain branched polypropylene resin C. The linear polypropylene resin B exhibits a molecular weight differential distribution curve where the difference between the differential distribution value at log(M) = 4.5 and the differential distribution value at log(M) = 6.0 is less than 8.0%, and its melt flow rate at 230°C is less than 4.0 g / 10 min. The long-chain branched polypropylene resin C is polymerized using a metallocene catalyst.

5. The polypropylene film according to claim 4, further comprising linear polypropylene resin A, The linear polypropylene resin A has a molecular weight differential distribution curve in which the differential distribution value at log(M) = 4.5 is subtracted from the differential distribution value at log(M) = 6.0, and the difference is less than 8.0%, and the melt flow rate at 230°C is greater than 4.0 g / 10 min.

6. The polypropylene film according to any one of claims 1 to 5, wherein it is a biaxially stretched polypropylene film.

7. The polypropylene film according to any one of claims 1 to 5, wherein the thickness is 1.4 to 6.0 μm.

8. The polypropylene film according to any one of claims 1 to 5, used in a capacitor.

9. A metal-integrated polypropylene film comprising the polypropylene film according to any one of claims 1 to 5, and a metal layer laminated on a first side or both sides of the polypropylene film.

10. A film capacitor comprising the integral polypropylene film with a metal layer as described in claim 9.

11. A film roll, which is formed by winding a polypropylene film according to any one of claims 1 to 5 into a roll.

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