JP2016188361A - Biaxially oriented polypropylene film for capacitor, metal film laminated film, and film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polypropylene film for capacitor which exhibits excellent withstanding voltage characteristics and reliability at high temperature even in the application for a capacitor for high voltage.SOLUTION: A biaxially oriented polypropylene film for capacitor which contains a polypropylene resin having a thickness (t1) by a micrometer method of 1-3 μm and a mesopentad fraction (mmmm) of 95% or more and less than 98%, and has an orientation parameter PMD in a longitudinal direction and an orientation parameter PTD in a width direction satisfying the following expression (1): 0.80≤PMD+PTD≤0.95. In expression (1), PMD=(A841/A809)/(5.8+(A841/A809)),PTD=(B841/B809)/(5.8+(B841/B809)), A841 is an absorption peak area at a wavelength of 841 cmin FT-IR when having polarized a light source in a longitudinal direction and measured the polarized light source, A809 is an absorption peak area at a wavelength of 809 cmin FT-IR when having polarized a light source in a longitudinal direction and measured the polarized light source, B841 is an absorption peak area at a wavelength of 841 cmin FT-IR when having polarized a light source in a width direction and measured the polarized light source, and B809 is an absorption peak area at a wavelength of 809 cmin FT-IR when having polarized a light source in a width direction and measured the polarized light source.SELECTED DRAWING: None

Description

  The present invention relates to a biaxially oriented polypropylene film suitable for packaging, industrial use, and the like. More specifically, the present invention relates to a capacitor for a capacitor having excellent productivity while maintaining a very high voltage resistance as a capacitor dielectric. The present invention relates to an axially oriented polypropylene film, a metal film laminated film, and a film capacitor.

  Biaxially oriented polypropylene films are excellent in transparency, mechanical properties, electrical properties, etc., and are therefore used in various applications such as packaging, tapes, cable wrapping, and electrical applications including capacitors.

  Among these, the capacitor application is particularly preferably used for high voltage capacitors because of its excellent withstand voltage characteristics and low loss characteristics, not limited to DC applications and AC applications.

  Recently, various types of electrical equipment are being converted into inverters, and accordingly, there is an increasing demand for miniaturization and large capacity of capacitors. In response to the demands of such markets, especially automobile applications (including hybrid car applications), solar power generation and wind power generation applications, while improving the voltage resistance of biaxially oriented polypropylene film, maintaining productivity and processability, A further reduction in film thickness is indispensable.

  Such a biaxially oriented polypropylene film needs to be highly oriented in the film plane from the viewpoint of voltage endurance, productivity, and processability. Since high orientation in the film plane requires stretching at a high magnification during film formation, this facilitates in-plane alignment, but easily breaks the film during film formation due to deterioration of stretchability. Therefore, it is not always sufficient in terms of productivity and cost in actual use, such as a significant reduction in productivity (for example, Patent Documents 1 and 2).

  Patent Document 2 discloses a technique for enhancing the in-plane orientation of a film by stretching a polypropylene resin having high stereoregularity having an isotactic degree of 98% or more at a low temperature and a high magnification. However, with the manufacturing method disclosed in Patent Document 2, it has been difficult to sufficiently maintain productivity in actual use.

  Furthermore, Patent Document 3 discloses a method for controlling the in-plane orientation of the film by adding a certain amount of low molecular weight component to the raw material resin under normal film forming conditions. However, in the manufacturing method disclosed in Patent Document 3, there is a limit to the high orientation in the film plane, and the withstand voltage is not always sufficient for applications requiring a high withstand voltage of 450 V / μm or higher at a high temperature of 120 ° C. I can not say.

  Furthermore, Patent Document 4 discloses a method of stably stretching at a high magnification by adding a stretching aid. However, in the production method disclosed in Patent Document 4, it is necessary to add at least one kind of petroleum resin substantially free of polar groups and / or terpene resin substantially free of polar groups as a stretching aid. Since the additive reduces the withstand voltage of the film, the withstand voltage was insufficient in applications where a high withstand voltage of 450 V / μm or more was required at a high temperature of 120 ° C.

  Furthermore, Patent Document 5 discloses a method of stretching in the longitudinal direction and the width direction in simultaneous biaxial stretching by the tenter method or sequential biaxial stretching, and then stretching in the longitudinal direction again, or two-stage stretching in the longitudinal direction. After performing, the method of extending | stretching a film at high magnification is disclosed by the method of extending | stretching to the width direction. However, in the production method disclosed in Patent Document 5, there is a limit to the high orientation in the film plane, and the withstand voltage is insufficient for applications requiring a high withstand voltage of 450 V / μm or higher at a high temperature of 120 ° C. there were.

International Publication No. 2012-121256 JP-A-2-129905 JP 2010-254868 A JP 2004-161799 A JP 2005-64067 A

  The present invention is intended to provide a biaxially oriented polypropylene film for capacitors that exhibits excellent voltage resistance, reliability, and productivity in high voltage capacitor applications.

  The above-described problems can be achieved by the following biaxially oriented polypropylene film for capacitors.

  It includes a polypropylene resin having a thickness (t1) measured by a micrometer method of 1 to 3 μm, a mesopentad fraction (mmmm) of 95% or more and less than 98%, and an orientation parameter PMD in the longitudinal direction and an orientation parameter PTD in the width direction. A biaxially oriented polypropylene film for capacitors that satisfies the following formula (1).

0.80 ≦ PMD + PTD ≦ 0.95 (1)
However,
PMD = (A841 / A809) / (5.8+ (A841 / A809))
PTD = (B841 / B809) / (5.8+ (B841 / B809))
A841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction A809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction B841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in a width direction B809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in a width direction

  Since the present invention can provide a biaxially oriented polypropylene film having excellent in-plane orientation, it can be applied to various uses such as packaging use, tape use, electrical use including cable wrapping and capacitors, and in particular. It is suitable for use as a capacitor, preferably for automobiles, solar power generation and wind power generation.

  The biaxially oriented polypropylene film for capacitors of the present invention preferably contains a polypropylene resin having a mesopentad fraction (mmmm) of 95% or more and less than 98%. In particular, as the polypropylene resin, the content of the above-described polypropylene resin is more preferably 90 to 100% by mass, further preferably 95 to 100% by mass, and more preferably 100% by mass with respect to the entire film.

  Moreover, it is preferable that thickness (t1) is 1-3 micrometers.

  Furthermore, it is important that the orientation parameter PMD in the longitudinal direction and the orientation parameter PTD in the width direction satisfy the following expression (1).

0.80 ≦ PMD + PTD ≦ 0.95 (1)
However,
PMD = (A841 / A809) / (5.8+ (A841 / A809))
PTD = (B841 / B809) / (5.8+ (B841 / B809))
A841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction A809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction B841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in a width direction B809: capacitors of the absorption peak area present invention FT-IR wavelengths 809cm ^-1 measured by polarized light source in a width direction As a resin used for the biaxially oriented polypropylene film for use, as described above, the mesopentad fraction (mmmm) is preferably 95% or more and less than 98% from the viewpoint of voltage resistance and film forming stability. Preferably they are 96% or more and less than 98%, More preferably, they are 97% or more and less than 98%. If the mesopentad fraction (mmmm) is less than 95%, the crystallinity of the film is lowered, and the mechanical strength and dielectric breakdown strength of the film may be inferior and the voltage resistance may be lowered. Further, if the mesopentad fraction (mmmm) is 98% or more, stretching becomes difficult, and the film formation stability may be inferior particularly at a film formation speed of 200 m / min or more.

  The biaxially oriented polypropylene film for capacitors of the present invention preferably has a thickness (t1) of 1 μm or more and 3 μm or less by the micrometer method from the viewpoints of capacitor size, capacity, voltage resistance, and productivity. Note that the thickness (t1) of the film by the micrometer method is an index representing the maximum thickness of the film because it is measured including the protrusions even when there are protrusions. When the thickness (t1) of the film is less than 1 μm, the mechanical strength and dielectric breakdown strength may be inferior in terms of performance, and the productivity may be inferior. On the other hand, when the film thickness (t1) exceeds 3 μm, the balance between the capacitor size and the capacity is poor, and it is difficult to stretch at a high magnification from the viewpoint of production, resulting in poor production stability.

  As described above, it is important that the biaxially oriented polypropylene film for capacitors of the present invention satisfies the following formula (1).

0.80 ≦ PMD + PTD ≦ 0.95 (1)
In the above formula (1), the value of PMD + PTD is preferably 0.80 or more and 0.95 or less. More preferably, it is 0.83 or more and 0.95 or less, More preferably, it is 0.85 or more and less than 0.95.
If the value of PMD + PTD is less than 0.80, the in-plane orientation is lowered and the withstand voltage is likely to be lowered. On the other hand, if the value of PMD + PTD is larger than 0.95, the in-plane orientation becomes too high, and the film forming stability may be inferior.

  The inventors of the present invention have a high correlation between the withstand voltage of the film, the in-plane orientation degree, and the productivity, and the process with a high in-plane orientation degree and good productivity for improving the withstand voltage. Thus, it has been found that it is important to enable and control both performance and production.

  In order to control the value of PMD + PTD to 0.80 or more and 0.95 or less, the longitudinal stretching preheating temperature is 100 to 120 ° C., the longitudinal stretching temperature is 100 to 120 ° C., and the longitudinal stretching ratio is 5.5 to 8.0 times. It is preferable to adjust to. When the longitudinal stretching preheating temperature and the longitudinal stretching temperature are low and / or the longitudinal stretching ratio is high, PMD + PTD may be too high and film formation stability may be poor. Moreover, when the longitudinal stretching preheating temperature and the longitudinal stretching temperature are high and / or the longitudinal stretching ratio is low, PMD + PTD may be too low and the voltage resistance may be poor.

  In addition, the biaxially oriented polypropylene film for capacitors of the present invention preferably satisfies the following formulas (2) and (3) simultaneously in the above invention.

0.15 ≦ PMD ≦ 0.35 (2)
0.50 ≦ PTD ≦ 0.70 (3)
In the above formulas (2) and (3), the PMD value is preferably 0.15 or more and 0.35 or less. More preferably, they are 0.18 or more and 0.32 or less, More preferably, they are 0.20 or more and 0.30 or less. If the PMD value is less than 0.15, the in-plane orientation becomes too low and the voltage resistance may be inferior. Also, if the value of PMD is larger than 0.35, since the orientation is extremely advanced, it is difficult to stretch in the MD direction (longitudinal direction), and problems such as film breakage are likely to occur, and the film forming stability is remarkably improved. May be inferior.

  On the other hand, the value of PTD is preferably 0.50 or more and 0.70 or less. More preferably, it is 0.53 or more and 0.67 or less, More preferably, it is 0.55 or more and 0.65 or less. Similar to PMD, if the PTD is less than 0.50, the in-plane orientation becomes too low and the voltage resistance may be inferior. Also, if the PTD value is greater than 0.70, the orientation is extremely advanced, making it difficult to stretch in the TD direction (width direction), and tearing in the stenter is likely to occur, resulting in stable film formation. May be inferior.

  Moreover, it is preferable that the breaking strength (fMD) of the longitudinal direction of the biaxially oriented polypropylene film for capacitors of the present invention is 200 MPa or more and 350 MPa or less. More preferably, it is 220 MPa or more and 330 MPa or less, More preferably, it is 240 MPa or more and 300 MPa or less. When the breaking strength (fMD) is less than 200 MPa, the mechanical strength is lowered and the voltage resistance may be inferior. On the other hand, when the breaking strength (fMD) is higher than 350 MPa, the mechanical strength becomes excessively high, and the production stability such as deterioration in handling property during processing may be inferior.

  In order to control the breaking strength (fMD) in the longitudinal direction to 200 MPa or more and 350 MPa or less, a polypropylene resin having a mesopentad fraction (mmmm) of 95% or more, a longitudinal stretching temperature of 100 to 120 ° C., and a longitudinal stretching ratio of 5. It is preferable to adjust to 5 to 8.0 times. When the mesopentad fraction (mmmm) is low and / or the longitudinal stretching temperature is high and / or the longitudinal stretching ratio is low, the breaking strength (fMD) in the longitudinal direction tends to decrease. Further, when the mesopentad fraction (mmmm) is high and / or the longitudinal stretching temperature is low and / or the longitudinal stretching ratio is high, the breaking strength (fMD) in the longitudinal direction tends to be improved. The longitudinal stretch ratio has the greatest influence on the breaking strength (fMD) in the longitudinal direction.

Moreover, it is preferable that the breaking strength (fTD) of the width direction of the biaxially oriented polypropylene film for capacitors of the present invention is 250 MPa or more and 450 MPa or less. More preferably, it is 280 MPa or more and 420 MPa or less, More preferably, it is 300 MPa or more and 400 MPa or less. When the breaking strength (fTD) is less than 250 MPa, the mechanical strength is lowered and the voltage resistance may be inferior. On the other hand, when the breaking strength (fMD) is higher than 450 MPa, the mechanical strength and the heat shrinkage rate are too high, and the production stability may be inferior, particularly, the workability during vapor deposition is lowered.
In order to control the breaking strength (fTD) in the width direction to 250 MPa or more and 450 MPa or less, a polypropylene resin having a mesopentad fraction (mmmm) of 95% or more is used, the transverse stretching temperature is 140 to 170 ° C., and the transverse stretching ratio is set. It is preferable to stretch 7 to 13 times. When the mesopentad fraction is low and / or the transverse stretching temperature is low and / or the transverse draw ratio is low, the breaking strength (fTD) in the width direction tends to decrease. Moreover, when the mesopentad fraction is high and / or the transverse stretching temperature is high and / or the transverse stretching ratio is high, the breaking strength (fTD) in the width direction tends to be improved.

  The biaxially oriented polypropylene film for capacitors of the present invention preferably has a longitudinal elongation at break (EMD) of 40% or more and 120% or less. More preferably, they are 50% or more and 110% or less, More preferably, they are 60% or more and 100% or less. When the elongation at break (EMD) in the longitudinal direction is less than 40%, the rigidity of the film becomes too high, the elongation is small, and production stability such as conveyance stability and vapor deposition processability may be inferior. On the other hand, if the elongation at break (EMD) in the longitudinal direction is higher than 120%, the rigidity becomes too low, the elongation is large, and the production stability and the voltage resistance such as transport stability and vapor deposition processability may be inferior.

  In order to control the elongation at break (EMD) in the longitudinal direction to 40% or more and 120% or less, it is preferable to adjust the longitudinal stretching temperature to 100 to 120 ° C. and the longitudinal stretching ratio to 5.5 to 8.0 times. When the longitudinal stretching temperature is high and / or the longitudinal stretching ratio is low, the elongation at break (EMD) in the longitudinal direction tends to be improved. Further, when the longitudinal stretching temperature is low and / or the longitudinal stretching ratio is high, the elongation at break (EMD) in the longitudinal direction tends to decrease. The longitudinal stretching temperature has the greatest influence on the elongation at break (EMD) in the longitudinal direction.

  Moreover, it is preferable that the biaxially oriented polypropylene film for capacitors of the present invention has a longitudinal elongation at break (EMD) and a longitudinal strength at break (fMD) satisfying the following formula (4).

1.8 ≦ fMD / EMD ≦ 4.0 [MPa /%] (4)
In said formula (4), it is preferable that the value of fMD / EMD is 1.8 MPa /% or more and 4.0 MPa /% or less. More preferably, it is 2.0 MPa /% or more and 3.8 MPa /% or less, More preferably, it is 2.4 MPa /% or more and 3.6 MPa /% or less. If the value of fMD / EMD is less than 1.8 MPa /%, the rigidity becomes too low and the workability may be deteriorated or the withstand voltage may be inferior. On the other hand, if fMD / EMD is larger than 4.0 MPa /%, the rigidity in the MD direction becomes too high, and stretching in the MD direction becomes difficult, which may result in poor film formation stability.

  Moreover, it is preferable that the centerline average roughness (SRa) of both surfaces of the biaxially oriented polypropylene film for capacitors of the present invention is 10 to 40 nm, and more preferably 15 to 35. If the center line average roughness (SRa) is greater than 40 nm, air may easily enter between the layers when the films are laminated, leading to deterioration of the capacitor and variation in capacitance. In addition, when a metal layer is formed on the film, holes in the metal layer are generated and the withstand voltage such as dielectric breakdown voltage at high temperature and capacitor life test is reduced. It may be a cause. In addition, when the center line average roughness (SRa) is less than 10 nm, the film is extremely difficult to slip and the handling property is inferior, or when the capacitor is impregnated with the insulating oil, the insulating oil uniformly penetrates between the film layers. However, the capacity change during continuous use may increase or the self-healing property may decrease.

  In order to control the center line average roughness (SRa) to 10 to 40 nm, the cooling drum temperature is preferably adjusted to 70 to 100 ° C. When the cooling drum temperature is low, SRa tends to decrease. Further, when the cooling drum temperature is high, the center line average roughness (SRa) tends to be improved.

  Moreover, it is preferable that 10-point average roughness (SRz) of both surfaces of the biaxially oriented polypropylene film for capacitors of the present invention is 500 to 1,000 nm, and more preferably 600 to 900 nm. If the 10-point average roughness (SRz) is greater than 1,000 nm, air is likely to enter between the layers when the films are laminated, and the capacitor size and capacity balance deteriorates. May lead to deterioration. In addition, when a metal film is laminated on the film, holes in the metal film are generated and the withstand voltage decreases from the standpoint of dielectric breakdown voltage and device life at high temperatures, or charges are concentrated when voltage is applied, resulting in insulation defects. It may be a cause. If the 10-point average roughness (SRz) is less than 500 nm, the film is extremely difficult to slip and the handling property is poor, or when the capacitor is impregnated with the insulating oil, the insulating oil uniformly penetrates between the film layers. However, the capacity change during continuous use may increase or the self-healing property may decrease.

  In order to control the 10-point average roughness (SRz) to 500 to 1,000 nm, it is preferable that the cooling drum temperature is 70 to 100 ° C. and the longitudinal stretching preheating temperature is 100 to 140 ° C. When the cooling drum temperature is low and / or the longitudinal stretching preheating temperature is low, the 10-point average roughness (SRz) tends to decrease. Further, when the cooling drum temperature is high and / or the longitudinal stretching preheating temperature is high, the 10-point average roughness (SRz) tends to be improved. When 0.05 to 10% by mass of branched polypropylene (H) described later is contained, the surface of the film is roughened precisely, so that adjustment of the cooling drum is possible even at a low temperature of 100 to 120 ° C. in the longitudinal stretching preheating temperature. The 10-point average roughness (SRz) can be adjusted to 500 to 1,000 nm only by the above.

  The above-mentioned projection height, number of projections, 10-point average roughness (SRz), centerline average roughness (SRa), and the like are based on JIS B-0601 (1982) "Non-stressed by Kosaka Laboratory Co., Ltd." It can be measured using a “contact three-dimensional fine shape measuring instrument (ET-30HK)” and “three-dimensional roughness analyzer (MODEL SPA-11)”. Details of measurement conditions and the like will be described later.

  The glossiness of the surface of the biaxially oriented polypropylene film for capacitors of the present invention is preferably in the range of 125 to 145%, more preferably 130 to 140%. Decreasing the gloss level means that the unevenness of the film surface is made dense, and the number of protrusions per unit area increases and the roughness density increases. When the glossiness is lowered to less than 125%, the withstand voltage at a high temperature as a capacitor tends to decrease due to an increase in the height and the number of protrusions. On the other hand, if the glossiness exceeds 145%, the film layers are very difficult to slip, making it difficult to form a flat capacitor element, and sufficient clearance between the film layers cannot be maintained, and self-healing and security are achieved. It may decrease extremely.

  In order to control the glossiness to 125 to 145%, it is preferable to adjust the cooling drum temperature to 70 to 100 ° C. When the cooling drum temperature is low, the glossiness tends to improve. Further, when the cooling drum temperature is high, the glossiness tends to decrease.

  The surface wetting tension of at least one surface of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 37 to 50 mN / m, and more preferably 39 to 48 mN / m. Usually, the surface wetting tension of a polypropylene film is about 30 mN / m, but the surface wetting tension can be increased by, for example, corona discharge treatment, plasma treatment, glow treatment, or flame treatment. When the surface wetting tension on at least one surface is 37 mN / m or more, the adhesion to the metal film is excellent, and the safety of the capacitor can be enhanced. On the other hand, when the wetting tension exceeds 50 mN / m, the adhesion between the films becomes high, and when the film is unwound from the roll during the vapor deposition process, the film may break strongly.

  Next, raw materials such as polypropylene used for the biaxially oriented polypropylene film for capacitors of the present invention will be described.

  As the polypropylene resin that is the main raw material of the biaxially oriented polypropylene film for capacitors of the present invention, a polypropylene resin usually used for packaging materials and capacitors can be used (hereinafter referred to as linear polypropylene for convenience). The linear polypropylene used in the present invention is preferably a polypropylene having a cold xylene soluble part (CXS) of 4% by mass or less and a mesopentad fraction (mmmm) of 95% or more and less than 98%. If these conditions are not satisfied, the film-forming stability may be inferior or the voltage resistance may be reduced.

  The cold xylene soluble part (CXS) of the linear polypropylene according to the present invention is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. The cold xylene-soluble part (CXS) is a polypropylene component dissolved in xylene when polypropylene is completely dissolved in xylene at 135 ° C. and then precipitated at 20 ° C. This is considered to correspond to a component that is difficult to crystallize, such as a molecular weight component. When the cold xylene soluble part (CXS) is higher than 4% by mass, problems such as a decrease in the thermal dimensional stability of the film and a breakdown voltage at high temperatures may occur.

  The mesopentad fraction (mmmm) of the linear polypropylene according to the present invention is preferably 95% or more and less than 98%. More preferably, it is 96% or more and less than 98%, More preferably, it is 97% or more and less than 98%. The mesopentad fraction (mmmm) is an index indicating the stereoregularity of the crystalline phase of polypropylene measured by nuclear magnetic resonance (NMR) method. The higher the numerical value, the higher the crystallinity and the higher the dielectric breakdown. The voltage increases. If the mesopentad fraction (mmmm) is too high, stretching may be difficult and film formation stability may be poor. In order to obtain linear polypropylene having such a high stereoregularity, a method of washing polypropylene resin powder obtained with a solvent such as n-heptane, selection of a catalyst and / or promoter, and selection of a composition are appropriately selected. The method of performing etc. is employ | adopted preferably.

  The linear polypropylene used in the present invention preferably has a melt flow index (MFR) of 1 to 10 g / 10 min (230 ° C., 21.18 N load), particularly preferably 2 to 5 g / 10 min ( 230 ° C., 21.18 N load). In order to set the melt flow index (MFR) of the linear polypropylene to the above value, a method of controlling the average molecular weight or the molecular weight distribution is employed.

  The linear polypropylene used in the present invention is mainly composed of a homopolymer of propylene. However, the linear polypropylene is composed of other unsaturated hydrocarbon copolymer components, etc., as long as the object of the present invention is not impaired. You may contain. Further, as a resin raw material of the biaxially oriented polypropylene film for capacitors of the present invention, a linear polypropylene may be blended with a copolymer of propylene and other unsaturated hydrocarbons. Examples of the monomer component constituting such a copolymer component or blend include, for example, ethylene, propylene (in the case of a copolymer blend), 1-butene, 1-pentene, 3-methylpentene-1, 3 -Methylbutene-1,1-hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl -2-norbornene and the like. From the viewpoint of dielectric breakdown resistance and dimensional stability, the copolymerization amount or blend amount is preferably less than 1 mol% in copolymerization amount and less than 10 mass% in blend amount.

  In addition, the linear polypropylene used in the present invention has various additives (for example, a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, and an antiblocking agent within a range not impairing the object of the present invention. Agents, fillers, viscosity modifiers, anti-coloring agents).

  Among these additives, selection of the type and amount of antioxidant is important from the viewpoint of long-term heat resistance. That is, the antioxidant is preferably a phenolic compound having steric hindrance, and when a mixture of a plurality of antioxidants is used, at least one is preferably a high molecular weight type having a molecular weight of 500 or more. Specific examples of the antioxidant include various examples. For example, 2,6-di-tert-butyl-p-cresol (BHT: molecular weight 220.4) and 1,3,5-trimethyl-2,4 , 6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (for example, IRGANOX (registered trademark) 1330 manufactured by BASF Japan Ltd .: molecular weight 775.2) or tetrakis [methylene-3 (3,5- Di-t-butyl-4-hydroxyphenyl) propionate] methane (for example, IRGANOX 1010 manufactured by BASF Japan Ltd .: molecular weight 1177.7) is preferably used in combination. The total content of these antioxidants is preferably in the range of 0.03 to 1.0 mass% with respect to the total amount of polypropylene. If the amount of the antioxidant is too small, the long-term heat resistance may be poor. If the amount of the antioxidant is too large, the capacitor element may be adversely affected by blocking at a high temperature due to bleeding out of these antioxidants. The more preferable content is 0.1 to 0.9% by mass, and particularly preferably 0.2 to 0.8% by mass.

  A crystal nucleating agent can be added to the linear polypropylene used in the present invention within a range not contrary to the object of the present invention. As crystal nucleating agents, α crystal nucleating agents (dibenzylidene sorbitols, sodium benzoate, etc.), β crystal nucleating agents (potassium 1,2-hydroxystearate, magnesium benzoate, N, N′-dicyclohexyl-2,6). -An amide compound such as naphthalene dicarboxamide, a quinanacridon compound, etc.) and a branched polypropylene (H) described later are exemplified. As the crystal nucleating agent, it is preferable to contain branched polypropylene (H) having a crystal nucleating agent effect of α crystal or β crystal by itself. In the biaxially oriented polypropylene film for capacitors according to the present invention, the addition of an α crystal nucleating agent other than the branched polypropylene (H) or β crystal nucleating agent makes it difficult to obtain the desired surface roughness. It may adversely affect electrical properties such as a decrease in volume resistivity at high temperatures, and the content is preferably less than 0.1% by mass, more preferably not substantially added. Is preferred.

  The biaxially oriented polypropylene film for capacitors of the present invention preferably contains branched polypropylene (H), and is further composed of a mixture of linear polypropylene and the branched polypropylene (H). Is preferred.

  In this case, the branched polypropylene (H) preferably has a melt tension (MS) and a melt flow index (MFR) measured at 230 ° C. that satisfy the following formula (5).

log (MS)> − 0.56 log (MFR) +0.74 (5)
Here, the melt tension measured at 230 ° C. is measured according to the melt flow index (MFR) measurement shown in JIS-K7210 (1999). Specifically, using a melt tension tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the polypropylene is heated to 230 ° C., and the molten polypropylene is discharged at an extrusion speed of 15 mm / min to form a strand, and this strand is 6.4 m / min. The tension at the time of drawing at the speed is measured and set as the melt tension (unit cN). The melt flow index (MFR) measured at 230 ° C. is a value (unit: g / 10 minutes) measured at a load of 21.18 N according to JIS-K7210 (1999).

  The branched polypropylene (H) used in the present invention preferably satisfies the above formula (5), but is not particularly limited, and has a melt flow index (MFR) of 1 to 1 from the viewpoint of film forming properties. What exists in the range of 20 g / 10min is preferable, and what exists in the range of 1-10 g / 10min is more preferable. Moreover, about the melt tension of branched polypropylene (H), what exists in the range of 1-30 cN is preferable, and what exists in the range of 2-20 cN is more preferable. If the melt tension is low, the uniformity of the protrusions is inferior and coarse protrusions are easily formed. The larger the melt tension, the higher the uniformity of the protrusions, and the more likely the surface formation is dense (the number of protrusions per unit area is large).

  When the biaxially oriented polypropylene film for capacitors of the present invention contains branched polypropylene (H), the melt crystallization temperature of ordinary polypropylene is about 110 ° C., whereas it can be increased to 115 ° C. or higher. . When the dielectric film causes a dielectric breakdown for some reason, the deposited metal around the discharge portion is scattered by the generated discharge energy, and the film itself is also partially melted. Usually, when the ambient temperature of the capacitor becomes high, it is difficult to recrystallize and it is difficult to recover the insulation. However, by adding a branched polypropylene (H), it becomes easier to recrystallize by increasing the melt crystallization temperature, thus ensuring safety. Can be improved.

To obtain a branched polypropylene (H) having a melt tension (MS) and a melt flow index (MFR) measured at 230 ° C. satisfying the above formula (5), an oligomer or polymer having a branched structure is blended. A method, a method of introducing a long chain branched structure into a polypropylene molecule as described in JP-A-62-1121704, a method described in Japanese Patent No. 2869606, or the like is preferably used. Specific examples of the branched polypropylene (H) satisfying the above formula (5) include “Profax PF-814” manufactured by Basell, “Daploy HMS-PP” manufactured by Borealis (for example, WB130HMS, WB135HMS). However, among these, PF-814 obtained by electron beam crosslinking is preferably used because it contains a small amount of gel component in the resin. The branched polypropylene (H) used in the biaxially oriented polypropylene film for capacitors of the present invention preferably has 5 or less internal trisubstituted olefins per 10,000 carbon atoms. The presence of this internal tri-substituted olefin can be confirmed by the proton ratio in the ¹ H-NMR spectrum.

  The biaxially oriented polypropylene film for capacitors of the present invention has a branched chain polypropylene (H) satisfying the above formula (5) having a melt tension (MS) and a melt flow index (MFR) measured at 230 ° C. of 0.000. It is preferable to contain 05-10 mass%, More preferably, it is 0.5-8 mass%, More preferably, it is 1-5 mass%. If the content of the branched polypropylene (H) is less than 0.05% by mass, the proportion of coarse protrusions may increase and the withstand voltage of the film may decrease. On the other hand, if the content of the branched polypropylene (H) is higher than 10% by mass, the crater shape on the film surface becomes too small, and a smooth surface with low element processability may be formed.

  When the biaxially oriented polypropylene film for capacitors of the present invention is composed of linear polypropylene and branched polypropylene (H), it is observed when the melting point is measured by the method described later and measured by 2nd-Run. At least two melting peaks appear. That is, it has a shoulder peak (148 to 157 ° C.) in addition to the first melting peak (temperature 160 to 172 ° C.). Thereby, it is possible to form a dense surface having uniform protrusions and less coarse protrusions. In addition, by adding the branched polypropylene (H) to the biaxially oriented polypropylene film for capacitors in the above-described ratio, an excellent characteristic surface shape having excellent protrusion uniformity and few coarse protrusions, and- A biaxially oriented polypropylene film for capacitors that exhibits excellent workability and high withstand voltage even under a wide range of atmospheric temperature conditions exceeding 40 ° C. to 105 ° C. can be produced.

  Further, the ash content of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 50 ppm or less (mass basis, the same shall apply hereinafter), more preferably 30 ppm or less, and particularly preferably 20 ppm or less. If the ash content is too large, the dielectric breakdown resistance of the film is lowered, and the dielectric breakdown voltage may be lowered when a capacitor is used. In order to make the ash content within this range, it is important to use a raw material with little catalyst residue, but a method of reducing contamination from the extrusion system as much as possible, for example, taking a bleed time of 1 hour or more, A method of sufficiently washing the path with a polymer before actually starting film formation can be employed.

The biaxially oriented polypropylene film of the present invention is suitable for a thin film capacitor because it has a high rigidity and a high degree of orientation, and is excellent in voltage resistance and handling properties. When the film thickness (t1) is in the range of 1 μm or more and 3 μm or less, the performance is effectively expressed. A more preferable thickness is 1.2 μm or more and 2.8 μm or less, and a more preferable thickness is 1.5 μm or more and 2.5 μm or less.
The biaxially oriented polypropylene film for capacitors of the present invention is preferably used as a dielectric film for capacitors, but is not limited to the type of capacitor. Specifically, from the viewpoint of electrode configuration, either a foil wound capacitor or a metal vapor deposition film capacitor may be used, and it is also preferably used for an oil immersion type capacitor impregnated with insulating oil or a dry type capacitor not using insulating oil at all. It is done. Further, from the viewpoint of shape, it may be a winding type or a laminated type. However, it is particularly preferably used as a metal vapor deposition film capacitor because of the characteristics of the film of the present invention.

  Next, the metal film laminated film of the present invention will be described.

  First, regarding the metal film constituting the metal film laminated film, the metal species constituting the metal film include metals such as aluminum, zinc, copper, gold, silver, nickel, chromium, and / or mixtures and alloys thereof. And compounds. Among these, aluminum, zinc alone, an alloy, or a mixture is excellent in terms of cost and performance. Further, the metal film may have a single layer structure or a multilayer structure. Examples of the method for providing a metal film include a vacuum deposition method in which a metal film is formed by heating and melting and evaporating in a vacuum, and a method of coating metal powder with an appropriate binder resin. The vapor deposition method is excellent in terms of forming a vapor deposition film.

  The film resistance of the metal film is preferably 1 to 20Ω / □, and more preferably 5 to 10Ω / □. If the film resistance is less than 1Ω / □, the capacitor is easily destroyed due to current concentration. Further, when the film resistance exceeds 20Ω / □, the internal resistance increases, and the heat generation of the capacitor may increase when a large current flows.

  Next, a film capacitor using the metal film laminated film of the present invention will be described. The type of the capacitor may be a winding type or a laminated type, but is preferably a winding type with more excellent withstand voltage characteristics. If the type of the capacitor is a winding type, the shape of the capacitor is preferably an ellipse in cross section, and the ratio of the major axis to the minor axis of the ellipse is preferably 1.5 or more.

  The biaxially oriented polypropylene film for capacitors of the present invention can be obtained by biaxially stretching using a raw material that can give the above-described characteristics. The biaxial stretching method can be obtained by any of the inflation simultaneous biaxial stretching method, the stenter simultaneous biaxial stretching method, and the stenter sequential biaxial stretching method. Among them, the film forming stability, the thickness uniformity, In terms of controlling high rigidity and dimensional stability, it is preferable to employ a stenter sequential biaxial stretching method.

  Next, although the manufacturing method of the biaxially oriented polypropylene film of this invention by a stenter sequential biaxial stretching method is demonstrated, it is not necessarily limited to this.

  First, branched polypropylene (H) is blended at a predetermined ratio with linear polypropylene, melt extruded, passed through a filtration filter, extruded from a T die at a temperature of 220 to 280 ° C., and solidified on a cooling drum. An unstretched sheet is obtained. Here, in order to obtain the biaxially oriented polypropylene film for a capacitor of the present invention, it is necessary to appropriately generate β crystals, and it is preferable to appropriately control the temperature of the cooling drum so as to appropriately generate β crystals. . In order to efficiently produce β crystals, it is preferable to maintain the resin temperature at which the β crystal production efficiency is maximized for a predetermined time, which is usually 115 to 135 ° C. The holding time is preferably 1 second or longer.

  In order to realize these conditions, the process can be determined as appropriate according to the resin temperature, the extrusion amount, the take-up speed, etc., but from the viewpoint of productivity, the diameter of the cooling drum greatly affects the holding time. In addition, the diameter of the drum is preferably at least 1 m. Furthermore, the cooling drum temperature to be selected is preferably 70 to 100 ° C, more preferably 72 to 98 ° C, and particularly preferably 75 to 90 ° C. When the cooling drum temperature is higher than 100 ° C., β crystal formation proceeds too much, so that voids are generated in the film and the dielectric breakdown resistance may be lowered. On the other hand, if the cooling drum temperature is less than 70 ° C., β crystals are not generated, and a smooth surface inferior in device processability may be formed.

  As an adhesion method of the unstretched sheet to the cooling drum, any method of an electrostatic application method, an adhesion method using the surface tension of water, an air knife method, a press roll method, an underwater casting method, or the like may be used. However, the air knife method is preferable because the flatness is good and the surface roughness can be controlled.

  Next, this unstretched sheet is biaxially stretched. First, an unstretched sheet is preheated by passing it through a longitudinally stretched preheating roll. The temperature of the longitudinally stretched preheating roll is preferably 100 to 120 ° C, more preferably 103 to 117 ° C, and still more preferably 105 to 115 ° C. When the longitudinal stretching preheating roll temperature is less than 100 ° C., the amount of heat is insufficient at the time of longitudinal stretching due to insufficient preheating of the film, and the film may be broken due to excessive stretching stress. On the other hand, if the longitudinal stretching preheating roll temperature is higher than 120 ° C., the in-plane orientation of the film is difficult to proceed, and the strength of the film may be lowered. The temperature of the longitudinal stretching preheat roll is preferably the same as the temperature of the longitudinal stretching roll from the viewpoint of causing the temperature of the unstretched sheet to reach the stretching temperature before longitudinal stretching.

Subsequently, the unstretched film is stretched longitudinally through a longitudinal stretching roll, and then cooled to room temperature. The longitudinal stretching method includes a stretch method and a multi-stage stretch method, but the stretch method that can be stretched at a higher stretching speed and can enhance the in-plane orientation of the film is preferably used. The longitudinal stretching roll temperature is preferably 100 to 120 ° C, more preferably 103 to 117 ° C, and still more preferably 105 to 115 ° C. When the longitudinal stretching roll temperature is less than 100 ° C., the film becomes insufficient in heat during longitudinal stretching and may be broken due to excessive stretching stress. On the other hand, if the longitudinal stretching roll temperature is higher than 120 ° C., the in-plane orientation of the film is difficult to proceed, and the strength of the film may be lowered. The longitudinal draw ratio is preferably 5.5 to 8.0 times, more preferably 6.0 to 8.0 times, and still more preferably 6.5 to 8.0 times. If the longitudinal draw ratio is less than 5.5 times, the in-plane orientation of the film may be lowered. On the other hand, when the longitudinal draw ratio is higher than 8.0 times, the film may be broken and remarkably inferior in film formation. Furthermore, the longitudinal stretching speed is preferably 1.0 × 10 ^{6 to} 5.0 × 10 ⁶ % / min, more preferably 2.0 × 10 ^{6 to} 5.0 × 10 ⁶ % / min, particularly preferably 3 The range is from 0.0 × 10 ^{6 to} 5.0 × 10 ⁶ % / min. When the longitudinal stretching speed is less than 1.0 × 10 ⁶ % / min, in-plane orientation is difficult to proceed and the withstand voltage may be inferior. On the other hand, when the longitudinal stretching speed is higher than 5.0 × 10 ⁶ % / min, the film may be broken and remarkably inferior in film formability.

In order to achieve high film orientation in the present invention, the unstretched sheet is at a low temperature of 100 to 120 ° C., at a high magnification of 5.5 to 8.0 times, and 1.0 × 10 ^6. It is preferable to stretch at a high speed of ˜5.0 × 10 ⁶ % / min. However, in general, the thickness of the unstretched sheet end is significantly thicker than the center portion of the unstretched sheet that becomes the product after stretching because the end of the unstretched sheet is gripped by the clip of the stenter. Therefore, when the roll temperature is simply lowered, and the film is stretched at a high magnification and at a high speed, the end of the thick sheet becomes insufficient in heat, resulting in film breakage and a significant reduction in productivity.

  Therefore, in the present invention, first, an edge cooler (for example, a small air cooler) is installed on the cooling roll, and when the molten polymer is cooled and solidified on the unrolled sheet on the cooling roll, only the end of the unstretched sheet is used. It is preferable to quench and increase the amorphous component at the end of the unstretched sheet to impart stretchability. The temperature of the edge cooler is preferably 0 to 40 ° C, more preferably 5 to 35 ° C, and particularly preferably 10 to 30 ° C. If the edge cooler temperature is higher than 40 ° C., crystallization at the end of the unstretched sheet proceeds, and the stretchability may decrease. On the other hand, when the edge cooler temperature is lower than 0 ° C., the adhesion between the unstretched sheet and the cooling roll deteriorates, crystallinity unevenness occurs in the longitudinal direction of the unstretched sheet, and the productivity may decrease due to film breakage. .

  Furthermore, in the present invention, an edge heater (for example, a small radiation heater) is installed on the longitudinal stretching roll in combination with the above-described method of rapidly cooling the edge of the unstretched sheet by the edge cooler on the cooling roll. It is preferable to use a method in which heat is applied only to the sheet edge to enhance stretchability. The edge heater temperature is preferably 120 to 160 ° C, more preferably 125 to 155 ° C, and particularly preferably 130 to 150 ° C. When the edge heater temperature is higher than 160 ° C., the end of the unstretched sheet may melt and break during stretching. On the other hand, if the edge heater temperature is lower than 120 ° C., the amount of heat applied to the end portion of the unstretched sheet is insufficient, and may break during stretching.

  Thereafter, the end of the stretched film is gripped with a clip and guided to a stenter, and stretched at 140 to 170 ° C., more preferably 150 to 160 ° C., 7 to 13 times in the width direction, more preferably 8 to 12 times. Next, heat setting is performed at a temperature of 140 to 160 ° C. while giving relaxation of 2 to 20% in the width direction. Then, it guide | induces to the outer side of a stenter through a cooling process at 100-150 degreeC, the clip of a film edge part is released, a film edge part is slit in a winder process, and a film product roll is wound up. Here, in order to improve the adhesion of the deposited metal to the surface to be deposited before winding the film, it is preferable to perform a corona discharge treatment in air, nitrogen, carbon dioxide or a mixed gas thereof.

In the case of a metal film laminated film in which a metal film is provided on the biaxially oriented polypropylene film for capacitors of the present invention, the surface on which the metal film is formed is treated in air, nitrogen, carbon dioxide gas or a mixed gas thereof. A corona discharge treatment is performed at a strength of 20 to 30 W · min / m ² to provide adhesion of the deposited metal. In the present invention, the method of providing a metal film on the surface of the above-described biaxially oriented polypropylene film for a capacitor to form a metal film laminated film is not particularly limited. For example, a film capacitor is obtained by evaporating aluminum or the like on at least one surface of a polypropylene film. A method of providing a metal film such as an aluminum vapor deposition film serving as an internal electrode is preferably used. At this time, other metal components such as nickel, copper, gold, silver, chromium, and zinc can be deposited simultaneously or sequentially with aluminum. In addition, a protective layer can be provided on the deposited film with oil or the like.

  In the present invention, if necessary, after the metal film is formed, the metal film laminated film can be annealed at a specific temperature or heat-treated. In addition, for insulation or other purposes, a coating of polyphenylene oxide or the like can be applied to at least one surface of the metal film laminated film.

  The metal film laminated film thus obtained can be laminated or wound by various methods to obtain a film capacitor. An example of a preferred method for producing a wound film capacitor is as follows.

  Aluminum is vapor-deposited on one side of the polypropylene film under reduced pressure. In that case, it vapor-deposits in the stripe form which has the margin part which runs in a film longitudinal direction. Next, a tape-shaped take-up reel having a blade with a margin on one side is formed by inserting a blade into the center of each vapor deposition portion and the center of each margin portion on the surface. Two tape-shaped take-up reels with margins on the left or right are wound on each other so that the vapor deposition part protrudes from the margin part in the width direction. Get.

  When vapor deposition is performed on both sides, the vapor deposition is performed in a stripe shape having a margin portion that runs in the longitudinal direction of one surface, and the other surface is striped so that the longitudinal margin portion is located at the center of the vapor deposition portion on the back side. Vapor deposition. Next, a tape-shaped take-up reel having a margin on one side of each of the front and back margin portions and making a slit on both sides (for example, a margin on the right side of the front surface and a left side margin on the back surface) is prepared. Two each of the obtained reel and undeposited laminated film are overlapped and wound so that the metallized film protrudes from the laminated film in the width direction, and a wound body is obtained.

  The core material is removed from the wound body produced as described above and pressed, and the metallicon is sprayed on both end faces to form external electrodes, and a lead wire is welded to the metallicon to obtain a wound film capacitor. Film capacitors are used in a wide variety of applications such as railway vehicles, automobiles (hybrid cars, electric cars), solar power generation / wind power generation, and general home appliances. The film capacitors of the present invention are also suitable for these applications. Can be used.

  The characteristic value measurement method and the effect evaluation method in the present invention are as follows.

(1) Film thickness (μm)
The micrometer method thickness was measured according to 7.4.1.1 of JIS C-2330 (2001).

(2) Gloss (Glossiness)
According to JIS K-7105 (1981), the average value of five data measured under the conditions of an incident angle of 60 ° and a light receiving angle of 60 ° using a digital variable angle gloss meter UGV-5D manufactured by Suga Test Instruments Co., Ltd. It was.

(3) Melt flow index (MFR)
According to JIS-K7210 (1999), measurement was performed at a measurement temperature of 230 ° C. and a load of 21.18N.

(4) Melt tension (MS)
It measured according to the apparatus for MFR measurement shown by JIS-K7210 (1999). Using a Toyo Seiki Seisakusho Co., Ltd. melt tension tester, heat the polypropylene to 230 ° C., discharge the molten polypropylene at an extrusion speed of 15 mm / min to form a strand, and determine the tension when the strand is drawn at a speed of 6.5 m / min. The melt tension was measured.

(5) Melting point, melt crystallization temperature (° C)
Measurement was performed under the following conditions using an RDC220 differential scanning calorimeter manufactured by Seiko Instruments Inc.

<Preparation of sample>
A 5 mg sample is sealed in an aluminum pan for measurement. In addition, when metal vapor deposition etc. are given to the film, it removes suitably.

<Measurement>
The film is melted / recrystallized / remelted in the following steps (a) → (b) → (c). The melting point of the resin was defined as the melting peak temperature on the highest temperature side among melting peaks observed at 2nd-Run. Further, the peak temperature on the highest temperature side among the crystallization peak temperatures observed when the temperature was lowered was taken as the melt crystallization temperature.
Three measurements were taken, and the average value was taken as the melting point.

(A) 1st-Run 30 ° C. → 280 ° C. (temperature increase rate 20 ° C./min)
(B) Temperature decrease After holding at 280 ° C. for 5 minutes, 280 ° C. → 30 ° C. (temperature decrease rate 20 ° C./min)
(C) 2nd-Run 30 ° C. → 280 ° C. (temperature increase rate 20 ° C./min)
(6) Mesopentad fraction (mmmm)
The sample was dissolved in a solvent, and the mesopentad fraction (mmmm) was determined under the following conditions using ¹³ C-NMR.

A. Measurement conditions Apparatus: manufactured by Bruker, DRX-500
Measurement nucleus: ¹³ C nucleus (resonance frequency: 125.8 MHz)
Measurement concentration: 10 wt%
Solvent: benzene / heavy orthodichlorobenzene = mass ratio 1: 3 mixed solution Measurement temperature: 130 ° C.
Spin rotation speed: 12Hz
NMR sample tube: 5 mm tube Pulse width: 45 ° (4.5 μs)
Pulse repetition time: 10 seconds Data point: 64K
Conversion count: 10,000 times Measurement mode: Complete Decoupling
B. Analysis condition LB (line broadening factor) was set to 1.0, and Fourier transform was performed to set the mmmm peak to 21.86 ppm. Peak splitting is performed using WINFIT software (manufactured by Bruker). At that time, the peak splitting from the peak on the high magnetic field side as follows, automatic fitting of the attached software is performed, and the peak splitting is optimized, and then the total peak fraction of mmmm is calculated as the mesopentad fraction. Rate (mmmm).
The measurement was performed 5 times, and the average value was defined as the mesopentad fraction.

Peak (a) mrrm
(B) (c) rrrrm (divided as two peaks)
(D) rrrr
(E) mrmr
(F) mrmm + rmrr
(G) mmrr
(H) rmmr
(I) mmmr
(J) mmmm
(7) Number of internal 3-substituted olefins A sample is dissolved in a solvent, and the number of internal 3-substituted olefins is determined under the following conditions using ¹ H-NMR.

A. Measurement conditions Apparatus: JNM-ECX400P type nuclear magnetic resonance spectrometer manufactured by JEOL Ltd. Measurement nucleus: ¹ H nucleus (resonance frequency: 500 MHz)
Measurement concentration: 2 wt%
Solvent: Heavy orthodichlorobenzene Measurement temperature: 120 ° C
Pulse width: 45 °
Pulse repetition time: 7 seconds Conversion count: 512 times Measurement mode: non decoupling
B. Analysis conditions Based on the chemical shift of orthodichlorobenzene of 7.10 ppm, the signal in the 5.0 to 5.2 ppm region is assigned to the proton of the internal trisubstituted olefin, and the integral ratio of the broad signal of 0.5 to 2.0 ppm. To determine the proton ratio of the internal trisubstituted olefin.

(8) Cold xylene soluble part (CXS)
After dissolving 0.5 g of a polypropylene film sample in 100 ml of xylene at 135 ° C. and allowing to cool, the polypropylene components dissolved in the filtrate after recrystallization in a constant temperature water bath at 20 ° C. for 1 hour are subjected to liquid chromatography. (X (g)). Using the precision value (X0 (g)) of 0.5 g of the sample, the following formula is used.

CXS (mass%) = (X / X0) × 100
(9) Centerline average roughness (SRa), 10-point average roughness (SRz)
According to JIS B-0601 (1982), using the “Non-contact three-dimensional fine shape measuring device (ET-30HK)” and “Three-dimensional roughness analyzer (MODEL SPA-11)” manufactured by Kosaka Laboratory Ltd. Measured with The measurement was repeated 10 times in the longitudinal direction, and the center line average roughness (SRa) and 10-point average roughness (SRz) were obtained as the average value.

Measurement length: 1mm
Horizontal magnification: 200 times Vertical magnification: 20,000 times Cut off: 0.25 mm
Width direction feed speed: 0.1 mm / sec Length direction feed pitch: 10 μm
Number of feeds in the length direction: 25 times Measurement direction: width direction of the film (10) Orientation parameters (PMD, PTD)
The orientation parameters (PMD, PTD) were calculated based on the method described in the literature (YV V KISSIN et al., Journal of Polymer Science: Polymer Phisics Edition, Vol. 21, 2085-2096 (1983)).

  First, a polarizer was attached to the light source of the FT-IR apparatus, the film was polarized in the MD direction and the TD direction, and the infrared absorption spectrum was measured under the following conditions.

FT-IR device: “FTIR-8400S” manufactured by Shimadzu Corporation
Analysis software: “IR Solution (ver. 1.6)” manufactured by Shimadzu Corporation
Polarizer attachment: “P / N 12500 Polarizer Mount” manufactured by Specac
Resolution: 2cm ^-1
Number of integrations: 64 times In the measured infrared absorption spectrum, the three-point peak detection function of the analysis software “IR Solution” was performed under the following conditions, and absorption peak areas at 841 cm ⁻¹ and 809 cm ⁻¹ were calculated. The “correction area” output by peak detection was defined as the absorption peak area at each absorption peak.

841 cm ⁻¹ three-point peak detection Peak: 840.99 cm ⁻¹
Base (H): 821.70 cm ⁻¹
Base (L): 794.70 cm ⁻¹
3-point peak detection peak of 809cm ^-1: 808.20cm ^-1
Base (H): 860.28 cm ⁻¹
Base (L): 823.63 cm ⁻¹
Next, the calculated absorption peak area was substituted into the following formula, and the orientation parameters (PMD, PTD) were calculated.

PMD = (A841 / A809) / (5.8+ (A841 / A809))
PTD = (B841 / B809) / (5.8+ (B841 / B809))
A841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction A809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction B841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in a width direction B809: absorption peak area orientation parameter of FT-IR wavelengths 809cm ^-1 measured by polarized light source in a width direction (PMD , PTD) is calculated from the absorption appears at 809cm ^-1 with an absorption appearing at 841cm ^-1 with parallel transition moment and the helical axis of the PP crystalline, nearly vertical transition moment and the helical axis of the PP crystals.

In the above, the constant 5.8 represents the ratio of the absorption coefficient at the wavelength 841 cm ^{−1 to} the absorption at the wavelength 809 cm ⁻¹ .

(11) Elongation at break and strength at break The tensile test was conducted under the following conditions using a tensile tester (Tensilon AMF / RTA-100 manufactured by Orientic Co., Ltd.). The elongation obtained by dividing the elongation of the sample at the time of sample breakage by the elongation at breakage and the load applied to the sample at the time of sample breakage by the cross-sectional area of the sample before the test was taken as the breaking strength. The measurement was performed 5 times for each sample, and the average value was evaluated.

Sample size: Test direction length 150mm x width 10mm
Initial chuck distance: 50mm
Tensile speed: 300 mm / min (12) Film resistance of metal film A metal film laminated film is cut into a rectangle having a full width (50 mm) in the width direction of 10 mm in the length direction to obtain a sample, which is between 30 mm in the width direction by the 4-terminal method. The resistance of the metal film was measured, and the obtained measurement value was multiplied by the measurement width (10 mm) to divide the distance between electrodes (30 mm) to calculate the film resistance per 10 mm × 10 mm. (Unit: Ω / □)
(13) Dielectric breakdown voltage of film (V / μm)
According to JIS C2330 (2001) 7.4.11.2 B method (plate electrode method), an average value is obtained, and divided by the micrometer method film thickness (μm) (described above) of the measured sample, V / μm The notation.

(14) Evaluation of vapor deposition capacitor characteristics The film obtained in each of Examples and Comparative Examples to be described later is made of aluminum with a vacuum vapor deposition machine manufactured by ULVAC, Inc., and a margin portion in a direction perpendicular to the longitudinal direction with a film resistance of 8Ω / □. A vapor deposition pattern having a so-called T-shaped margin pattern provided with a film was provided to obtain a vapor deposition reel having a width of 50 mm.

  Next, after winding the capacitor element with an element winding machine (KAW-4NHB) manufactured by Minato Manufacturing Co., Ltd. using this reel, and applying metallicon, heat treatment was performed at a temperature of 105 ° C. for 10 hours under reduced pressure, and lead Wires were attached to finish the capacitor element. The capacitance of the capacitor element at this time was 5 μF.

  Using 10 capacitor elements thus obtained, a voltage of 300 VDC is applied to the capacitor element at a high temperature of 120 ° C., and the applied voltage is gradually increased in steps of 50 VDC / 1 minute after 10 minutes at that voltage. A so-called step-up test was repeated. The capacitance change at this time was measured and plotted on a graph, and the value obtained by dividing the voltage at which the capacitance became 70% of the initial value by the micrometer film thickness (described above) is the withstand voltage of the capacitor. 450 V / μm or more was determined as a usable level.

  Hereinafter, an example is given and the effect of the present invention is further explained.

Example 1
Using a polypropylene resin made by Prime Polymer Co., Ltd. having a mesopentad fraction of 97.5% and a melt mass flow rate (MFR) of 2.6 g / 10 min as a linear polypropylene, it is supplied to an extruder at a temperature of 250 ° C., Melt extrusion was performed in a sheet form from a T-shaped slit die at a resin temperature of 250 ° C., and the molten sheet was cooled and solidified on a cooling drum held at 90 ° C. At that time, the end portion was rapidly cooled with a small air cooler having an air temperature of 20 ° C. Next, the unstretched sheet was gradually preheated to 110 ° C., and subsequently passed between rolls maintained at a temperature of 110 ° C. and provided with a difference in peripheral speed, and in the longitudinal direction at a stretching speed of 4.0 × 10 ⁶ % / min. Stretched to 0 times. At that time, the end of the unstretched sheet was heated to 150 ° C. and stretched with a small radiation heater having an output of 5.0 kW. Subsequently, the film was guided to a stenter, stretched 10 times in the width direction at a temperature of 158 ° C., then heat treated at 155 ° C. while giving 6% relaxation in the width direction, and then cooled to obtain a film thickness (t1). A 2.0 μm biaxially oriented polypropylene film was obtained. Furthermore, the drum surface side (A surface) of the biaxially oriented polypropylene film was subjected to corona discharge treatment in the atmosphere at a treatment strength of 25 W · min / m ² . The properties of the biaxially oriented polypropylene film thus obtained were as shown in Table 2.

(Example 2)
Biaxial orientation was carried out in the same manner as in Example 1 except that the longitudinal stretching ratio was 5.5 times, the output of the small radiation heater was 4.0 kW, and the end temperature of the unstretched sheet during longitudinal stretching was 140 ° C. A polypropylene film was obtained. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

Example 3
The longitudinal stretching preheating roll temperature is 117 ° C., the longitudinal stretching temperature is 117 ° C., the longitudinal stretching ratio is 5.5 times, the output of the small radiation heater is 3.5 kW, and the temperature at the end of the unstretched sheet during longitudinal stretching is 140 ° C. Except for the above, film formation was carried out in the same manner as in Example 1 to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

Example 4
The longitudinal stretching preheating roll temperature is 117 ° C., the longitudinal stretching temperature is 117 ° C., the longitudinal stretching ratio is 7.0 times, the output of the small radiation heater is 3.5 kW, and the temperature at the end of the unstretched sheet during longitudinal stretching is 140 ° C. Except for the above, film formation was carried out in the same manner as in Example 1 to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Example 5)
The temperature of the small air cooler on the cooling roll is 5 ° C., the longitudinal stretching preheating roll temperature is 108 ° C., the longitudinal stretching temperature is 108 ° C., the longitudinal stretching ratio is 7.5 times, and the longitudinal stretching speed is 4.5 × 10 ⁶ % / Except for the above, a film was formed in the same manner as in Example 1 to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Example 6)
The temperature of the small air cooler on the cooling roll is 15 ° C., the longitudinal stretching preheating roll temperature is 108 ° C., the longitudinal stretching temperature is 108 ° C., the longitudinal stretching ratio is 7.5 times, and the longitudinal stretching speed is 2.0 × 10 ⁶ % / Except for the above, a film was formed in the same manner as in Example 1 to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Example 7)
A linear polypropylene with a mesopentad fraction of 95.0% was used, except that the longitudinal stretching ratio was 5.5 times, the output of the small radiation heater was 4.0 kW, and the film end temperature during longitudinal stretching was 140 ° C. Film formation was performed in the same manner as in Example 1 to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Example 8)
Same as Example 1 except that the film thickness was 3.0 μm, the air cooler temperature on the cooling roll was 5 ° C., the output of the small radiation heater was 5.3 kW, and the unstretched sheet edge temperature during longitudinal stretching was 155 ° C. A biaxially oriented polypropylene film was obtained. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

Example 9
Manufactured in the same manner as in Example 1 except that the film thickness was 3.0 μm, the longitudinal stretching ratio was 5.5 times, the output of the small radiation heater was 4.0 kW, and the end temperature of the unstretched sheet during longitudinal stretching was 140 ° C. Filming was performed to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Example 10)
Manufactured in the same manner as in Example 1 except that the film thickness was 1.0 μm, the air cooler temperature on the cooling roll was 10 ° C., the output of the small radiation heater was 4.0 kW, and the film edge temperature during longitudinal stretching was 140 ° C. Filming was performed to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 1)
The air cooler on the cooling roll is turned off, the longitudinal stretching preheating temperature is 140 ° C., the longitudinal stretching temperature is 140 ° C., the longitudinal stretching speed is 2.5 × 10 ⁶ % / min, the longitudinal stretching ratio is 5.0 times, and the longitudinal stretching roll. A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the above small radiation heater was turned off. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 2)
Film formation was attempted in the same manner as in Example 1 except that the small air cooler on the cooling roll was turned off and the small radiation heater on the longitudinal stretching roll was turned off.

(Comparative Example 3)
Film thickness is 4.0 μm, small air cooler temperature on cooling roll is 0 ° C., longitudinal stretching preheating temperature is 120 ° C., longitudinal stretching temperature is 120 ° C., longitudinal stretching speed is 2.5 × 10 ⁶ % / min, longitudinal stretching. A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the magnification was 5.5 times, and the end temperature of the unstretched sheet during longitudinal stretching was 160 ° C. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 4)
The temperature of the small air cooler on the cooling roll is 10 ° C., the longitudinal stretching preheating temperature is 140 ° C., the longitudinal stretching temperature is 140 ° C., the longitudinal stretching speed is 2.5 × 10 ⁶ % / min, and the output of the small radiation heater is 3.0 kW. The biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the film end temperature during longitudinal stretching was 150 ° C. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 5)
A polypropylene resin with a mesopentad fraction of 99.5% is used, the small air cooler on the cooling roll is turned off, the longitudinal stretching preheating temperature is 145 ° C., the longitudinal stretching temperature is 145 ° C., and the longitudinal stretching speed is 2.5 × 10 ⁶ %. / Min, the longitudinal draw ratio was 5.3 times, and the film was formed in the same manner as in Example 1 except that the small radiation heater on the longitudinal draw roll was turned off to obtain a biaxially oriented polypropylene film. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 6)
The small air cooler on the cooling roll is turned off, the longitudinal stretching preheating temperature is 120 ° C., the longitudinal stretching temperature is 120 ° C., the longitudinal stretching speed is 2.5 × 10 ⁶ % / min, the longitudinal stretching ratio is 5.0 times, and the longitudinal stretching is performed. A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that the small radiation heater on the roll was turned off. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative Example 7)
A linear polypropylene with a mesopentad fraction of 94.0% is used, the small air cooler on the cooling roll is turned off, the longitudinal stretching preheating temperature is 140 ° C., the longitudinal stretching temperature is 140 ° C., and the longitudinal stretching speed is 2.5 × 10. ^A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that ⁶ % / min, the longitudinal draw ratio was 5.0 times, and the small radiation heater on the longitudinal draw roll was turned off. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

Claims (7)

It includes a polypropylene resin having a thickness (t1) measured by a micrometer method of 1 to 3 μm, a mesopentad fraction (mmmm) of 95% or more and less than 98%, and an orientation parameter PMD in the longitudinal direction and an orientation parameter PTD in the width direction. A biaxially oriented polypropylene film for capacitors that satisfies the following formula (1).
0.80 ≦ PMD + PTD ≦ 0.95 (1)
However,
PMD = (A841 / A809) / (5.8+ (A841 / A809))
PTD = (B841 / B809) / (5.8+ (B841 / B809))
A841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction A809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in the longitudinal direction B841: absorption peak area in the wavelength 841cm ^-1 of FT-IR measured by polarized light source in a width direction B809: absorption peak area in the wavelength 809cm ^-1 of FT-IR measured by polarized light source in a width direction The biaxially oriented polypropylene film for a capacitor according to claim 1, wherein the following formulas (2) and (3) are simultaneously satisfied.
0.15 ≦ PMD ≦ 0.35 (2)
0.50 ≦ PTD ≦ 0.70 (3)   The biaxially oriented polypropylene film for capacitors according to claim 1 or 2, wherein the breaking strength (fMD) in the longitudinal direction is 200 MPa or more and 350 MPa or less and the breaking strength (fTD) in the width direction is 250 MPa or more and 450 MPa or less. The longitudinal elongation at break (EMD) is 40% or more and 120% or less, and the longitudinal elongation at break (EMD) and the longitudinal breaking strength (fMD) satisfy the following formula (4). The biaxially oriented polypropylene film for capacitors according to any one of to 3.
1.8 ≦ fMD / EMD ≦ 4.0 [MPa /%] (4)   A metal film laminated film in which a metal film is provided on at least one surface of the biaxially oriented polypropylene film for capacitors according to claim 1.   The metal film laminated film according to claim 5, wherein the surface resistance of the metal film is in the range of 1 to 20 Ω / □.   A film capacitor comprising the metal film laminated film according to claim 5.