JP6682937B2 - Biaxially oriented polypropylene film for capacitors, laminated metal film, and film capacitors - Google Patents

Description

  The present invention relates to a biaxially oriented polypropylene film suitable for packaging, industrial use, and the like, and more specifically, as a dielectric for a capacitor, while maintaining extremely high withstand voltage, it has excellent productivity. The present invention relates to an axially oriented polypropylene film, a metal film laminated film, and a film capacitor.

  The biaxially oriented polypropylene film is excellent in transparency, mechanical properties, electrical properties, and the like, and is therefore used in various applications such as packaging applications, tape applications, cable wrapping, and electrical applications including capacitors.

  Among them, the capacitor use is particularly preferably used not only for DC and AC applications but also for high voltage capacitors because of its excellent withstand voltage characteristics and low loss characteristics.

  Recently, various electrical equipments are being converted to inverters, and accordingly, demands for miniaturization and large capacity of capacitors are further increasing. In response to such demands in the market, especially in automobile applications (including hybrid vehicle applications), solar power generation, and wind power generation applications, while improving the withstand voltage of biaxially oriented polypropylene film and maintaining productivity and processability, Further thinning is becoming an essential situation.

  Such a biaxially oriented polypropylene film requires high orientation in the film plane from the viewpoint of withstand voltage, productivity, and processability. Since high in-plane orientation of the film requires stretching at a high magnification during film formation, this tends to cause in-plane orientation, but film tearing during film formation due to deterioration of stretchability. Therefore, it cannot be said that productivity and cost are not always sufficient in actual use, such as markedly reduced productivity (for example, Patent Documents 1 and 2).

  Further, Patent Document 2 discloses a method of increasing the in-plane orientation of a film by stretching a polypropylene resin having a high stereoregularity with an isotacticity of 98% or more at a low temperature and a high ratio. However, with the manufacturing method disclosed in Patent Document 2, it was difficult to maintain sufficient productivity in actual use.

  Furthermore, Patent Document 3 discloses a method of controlling the in-plane orientation of a film by incorporating a certain amount of a low molecular component into a raw material resin under normal film forming conditions. However, in the production 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 more at a high temperature of 120 ° C. I can not say.

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

  Further, in Patent Document 5, simultaneous biaxial stretching by a tenter method, or a method of stretching in the longitudinal direction and width direction in successive biaxial stretching and then stretching again in the longitudinal direction, or a two-stage stretching in the longitudinal direction After carrying out the method, a method of stretching the film at a high ratio by a method of stretching in the width direction or the like is disclosed. However, in the manufacturing method disclosed in Patent Document 5, there is a limit to the high orientation in the film plane, and the withstand voltage is insufficient in applications requiring a high withstand voltage of 450 V / μm or more at a high temperature of 120 ° C. there were.

International publication 2012-1212256 JP-A-2-129905 JP, 2010-254868, A JP 2004-161799 A JP-A-2005-64067

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

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

  The polypropylene resin has a thickness (t1) of 1 to 3 μm and a mesopentad fraction (mmmm) of 95% or more and less than 98%, and has a longitudinal alignment parameter PMD and a widthwise alignment parameter PTD. 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: FT-IR absorption peak area at a wavelength of 841 cm ⁻¹ measured with the light source polarized in the width direction B809: FT-IR absorption peak area at a wavelength of 809 cm ⁻¹ measured with the light source polarized in the width direction

  INDUSTRIAL APPLICABILITY Since the present invention can provide a biaxially oriented polypropylene film having excellent in-plane orientation, it can be applied to various applications such as packaging applications, tape applications, electrical applications including cable wrapping and capacitors, and particularly, It is suitable for use in capacitors, 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-mentioned polypropylene resin is more preferably 90 to 100% by mass, further preferably 95 to 100% by mass, and more preferably 100% by mass, based on the entire film.

  The thickness (t1) is preferably 1 to 3 μm.

  Further, 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: FT-IR absorption peak area at a wavelength of 841 cm ⁻¹ measured by polarizing the light source in the width direction B809: FT-IR absorption peak area at a wavelength of 809 cm ⁻¹ of the FT-IR measured by polarizing the light source in the width direction The resin used for the biaxially oriented polypropylene film for use preferably has a mesopentad fraction (mmmm) of 95% or more and less than 98%, as described above, from the viewpoint of voltage resistance and film-forming stability. It is preferably 96% or more and less than 98%, more preferably 97% or more and less than 98%. If the mesopentad fraction (mmmm) is less than 95%, the crystallinity of the film may be lowered, and the mechanical strength and dielectric breakdown strength of the film may be poor and the withstand voltage may be lowered. Further, when the mesopentad fraction (mmmm) is 98% or more, stretching becomes difficult, and film forming stability may be poor particularly at a film forming speed of 200 m / min or more.

  The biaxially oriented polypropylene film for capacitors of the present invention preferably has a film thickness (t1) measured by a micrometer method of 1 μm or more and 3 μm or less from the viewpoint of capacitor size, capacity, withstand voltage and productivity. The thickness (t1) of the film measured by the micrometer method is an index indicating the maximum thickness of the film because it is measured including the projections even if they exist. When the thickness (t1) of the film is less than 1 μm, mechanical strength and dielectric breakdown strength may be poor in terms of performance, and productivity may also be poor. When the thickness (t1) of the film exceeds 3 μm, the balance between the capacitor size and the capacity is poor, and it may be 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 expression (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. It is more preferably 0.83 or more and 0.95 or less, and even more preferably 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 reduced and the withstand voltage is likely to be reduced. Further, 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 poor.

  The inventors of the present invention have conducted intensive studies and found that there is a high correlation between the withstand voltage property of the film, the in-plane orientation degree, and the productivity, and the in-plane orientation degree is high for the improvement of the withstand voltage process, and the process has good productivity. By doing so, it was 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 If the longitudinal stretching preheating temperature and the longitudinal stretching temperature are low and / or the longitudinal stretching ratio is high, PMD + PTD may become too high and film forming stability may be poor. If 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 withstand voltage may be poor.

  Further, the biaxially oriented polypropylene film for capacitors of the present invention preferably satisfies the following formulas (2) and (3) at the same time in the above invention.

0.15 ≦ PMD ≦ 0.35 (2)
0.50 ≦ PTD ≦ 0.70 (3)
In the above formulas (2) and (3), the value of PMD is preferably 0.15 or more and 0.35 or less. It is more preferably 0.18 or more and 0.32 or less, and even more preferably 0.20 or more and 0.30 or less. If the value of PMD is less than 0.15, the in-plane orientation becomes too low and the withstand voltage may be poor. Further, if the PMD value is larger than 0.35, the orientation is extremely advanced, making it difficult to stretch in the MD direction (longitudinal direction), and problems such as film breakage are likely to occur, resulting in remarkable film formation stability. It may be inferior.

  On the other hand, the PTD value is preferably 0.50 or more and 0.70 or less. It is more preferably 0.53 or more and 0.67 or less, and even more preferably 0.55 or more and 0.65 or less. Similar to PMD, when the PTD is less than 0.50, the in-plane orientation becomes too low, and the withstand voltage property may deteriorate. Further, when the PTD value is larger than 0.70, the orientation is extremely advanced, so that it becomes difficult to stretch in the TD direction (width direction), and breakage or the like in the stenter is likely to occur, resulting in film formation stability. It may be inferior.

  Further, the breaking strength (fMD) in the longitudinal direction of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 200 MPa or more and 350 MPa or less. It is more preferably 220 MPa or more and 330 MPa or less, and even more preferably 240 MPa or more and 300 MPa or less. If the breaking strength (fMD) is less than 200 MPa, the mechanical strength may decrease and the withstand voltage may be poor. Further, if the breaking strength (fMD) is higher than 350 MPa, the mechanical strength becomes too high, which may result in poor production stability such as deterioration of handling property during processing.

  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 is used, the longitudinal stretching temperature is 100 to 120 ° C., and the longitudinal stretching ratio is 5. It is preferably adjusted to 5 to 8.0 times. If 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. If 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 stretching ratio has the greatest effect on the breaking strength (fMD) in the longitudinal direction.

The breaking strength (fTD) in the width direction of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 250 MPa or more and 450 MPa or less. It is more preferably 280 MPa or more and 420 MPa or less, and further preferably 300 MPa or more and 400 MPa or less. If the breaking strength (fTD) is less than 250 MPa, the mechanical strength may decrease and the withstand voltage may be poor. If the breaking strength (fMD) is higher than 450 MPa, the mechanical strength and the heat shrinkage ratio may be too high, and in particular, the production stability may be deteriorated due to a decrease in workability during vapor deposition.
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 It is preferable to stretch 7 to 13 times. If the mesopentad fraction is low and / or the transverse stretching temperature is low and / or the transverse stretching ratio is low, the transverse breaking strength (fTD) tends to decrease. If 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 breaking elongation (EMD) in the longitudinal direction of 40% or more and 120% or less. It is more preferably 50% or more and 110% or less, still more preferably 60% or more and 100% or less. If the breaking elongation (EMD) in the longitudinal direction is less than 40%, the rigidity of the film becomes too high, the elongation is small, and the production stability such as transport stability and vapor deposition processability may be poor. If the elongation at break (EMD) in the longitudinal direction is higher than 120%, the rigidity may be too low, the elongation may be large, and the production stability such as transport stability and vapor deposition processability and the withstand voltage may be poor.

  In order to control the breaking elongation (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. If the longitudinal stretching temperature is high and / or the longitudinal stretching ratio is low, the breaking elongation (EMD) in the longitudinal direction tends to be improved. If the longitudinal stretching temperature is low and / or the longitudinal stretching ratio is high, the breaking elongation (EMD) in the longitudinal direction tends to decrease. The longitudinal stretching temperature has the greatest effect on the breaking elongation (EMD) in the longitudinal direction.

  In the biaxially oriented polypropylene film for capacitors of the present invention, the breaking elongation (EMD) in the longitudinal direction and the breaking strength (fMD) in the longitudinal direction preferably satisfy the following formula (4).

1.8 ≦ fMD / EMD ≦ 4.0 [MPa /%] (4)
In the above formula (4), the value of fMD / EMD is preferably 1.8 MPa /% or more and 4.0 MPa /% or less. It is more preferably 2.0 MPa /% or more and 3.8 MPa /% or less, and even more preferably 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 may be too low, which may result in poor workability and poor withstand voltage. Further, if fMD / EMD is more 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 forming stability.

  The centerline average roughness (SRa) on both sides of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 10 to 40 nm, more preferably 15 to 35. When the center line average roughness (SRa) is larger than 40 nm, air may easily enter between layers when films are laminated, which may lead to deterioration of the capacitor and variation in capacity. In addition, when a metal layer is formed on the film, punctures may occur in the metal layer, which lowers the dielectric breakdown voltage at high temperatures and the withstand voltage such as in the capacitor life test. It may be a cause. When the center line average roughness (SRa) is less than 10 nm, the film becomes extremely slippery and the handling property is poor, or when the capacitor is impregnated with insulating oil, the insulating oil does not uniformly penetrate between the film layers. Instead, the capacity may change significantly during continuous use, or the self-healing property may deteriorate.

  In order to control the center line average roughness (SRa) to 10 to 40 nm, it is preferable to adjust the cooling drum temperature to 70 to 100 ° C. If 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.

  The 10-point average roughness (SRz) on both surfaces of the biaxially oriented polypropylene film for capacitors of the present invention is preferably 500 to 1,000 nm, more preferably 600 to 900 nm. If the 10-point average roughness (SRz) is larger than 1,000 nm, air may easily enter between layers when films are laminated, resulting in poor balance between the capacitor size and the capacity, and in AC (alternating current) applications, capacitors due to partial discharge May lead to deterioration. In addition, when a metal film is laminated on the film, hole withdrawal occurs in the metal film and the withstand voltage decreases from the viewpoint of insulation breakdown voltage at high temperature and device life, or electric charge is concentrated when voltage is applied and insulation defects It may be a cause. When the 10-point average roughness (SRz) is less than 500 nm, the film becomes extremely slippery and poor in handleability, or when the capacitor is impregnated with the insulating oil, the insulating oil is uniformly permeated between the film layers. Instead, the capacity may change significantly during continuous use, or the self-healing property may deteriorate.

  In order to control the 10-point average roughness (SRz) to 500 to 1,000 nm, it is preferable to set the cooling drum temperature to 70 to 100 ° C and the longitudinal stretching preheating temperature to 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 the branched chain polypropylene (H) described below is contained in an amount of 0.05 to 10% by mass, the film surface is densely roughened, so that the cooling drum is adjusted even at a low temperature of 100 to 120 ° C in the longitudinal stretching preheating temperature. It is possible to adjust the 10-point average roughness (SRz) to 500 to 1,000 nm only by using.

  In addition, the values of the above-mentioned protrusion height, the number of protrusions, 10-point average roughness (SRz), center line average roughness (SRa), etc. are based on JIS B-0601 (1982) and are manufactured by Kosaka Laboratory Ltd. It can be measured using a contact three-dimensional fine shape measuring instrument (ET-30HK) "and a" 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%. Reducing the glossiness means making the unevenness of the film surface dense, which increases the number of protrusions per unit area and increases the roughness density. When the glossiness is reduced to less than 125%, the protrusion height and the number of protrusions increase, and the withstand voltage at high temperature of the capacitor easily decreases. On the other hand, when the glossiness exceeds 145%, the film layers are very unlikely to slip, making it difficult to form a flat capacitor element, or sufficient clearance between the film layers cannot be maintained, resulting in poor self-healing and safety. It may drop 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. Moreover, when the temperature of the cooling drum 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. The surface wetting tension of a polypropylene film is usually 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 of at least one surface is 37 mN / m or more, the adhesiveness with the metal film is excellent, and the safety of the capacitor can be enhanced. Further, when the wetting tension exceeds 50 mN / m, the adhesion between the films becomes high, and when the film is unwound from a roll during vapor deposition processing, blocking may be strong and the film may be broken.

  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 which is the main raw material of the biaxially oriented polypropylene film for capacitors of the present invention, polypropylene resins which are 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 portion (CXS) of 4% by mass or less and a mesopentad fraction (mmmm) of 95% or more and less than 98%. If these are not satisfied, the film-forming stability may be poor and the withstand voltage 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., and has a low stereoregularity component and a low stereoregular component. It is considered to correspond to components that are difficult to crystallize, such as molecular weight components. When the content of the cold xylene-soluble portion (CXS) is higher than 4% by mass, problems such as thermal dimensional stability of the film and reduction of dielectric breakdown voltage at high temperature may occur.

  The mesopentad fraction (mmmm) of the linear polypropylene according to the present invention is preferably 95% or more and less than 98%. It is more preferably 96% or more and less than 98%, further preferably 97% or more and less than 98%. The mesopentad fraction (mmmm) is an index showing the stereoregularity of the crystalline phase of polypropylene measured by the nuclear magnetic resonance method (NMR method), and the higher the numerical value, the higher the crystallinity and the dielectric breakdown at high temperature. The voltage becomes high. If the mesopentad fraction (mmmm) is too high, stretching may be difficult and the film forming stability may be poor. In order to obtain a linear polypropylene having high stereoregularity, a method of washing a polypropylene resin powder obtained with a solvent such as n-heptane, a catalyst and / or a cocatalyst, and a composition are appropriately selected. The method of carrying out is preferably adopted.

  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), and 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 adopted.

  The linear polypropylene used in the present invention is mainly composed of a homopolymer of propylene, but within a range not impairing the object of the present invention, the linear polypropylene includes a copolymerization component composed of other unsaturated hydrocarbons. May be included. Further, as a resin raw material for the biaxially oriented polypropylene film for capacitors of the present invention, linear polypropylene may be blended with a copolymer of propylene and other unsaturated hydrocarbons. Examples of such a copolymerization component or a monomer component constituting the blended product include ethylene, propylene (in the case of a copolymerized blended product), 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 etc. are mentioned. From the viewpoint of dielectric breakdown resistance and dimensional stability, the copolymerization amount or blending amount is preferably less than 1 mol% and the blending amount is less than 10% by mass.

  Further, in the linear polypropylene used in the present invention, various additives (for example, a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, an anti-blocking agent) may be added to the extent that the object of the present invention is not impaired. 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, as the antioxidant, a phenolic one having steric hindrance is preferable, and when a plurality of antioxidants are mixed and used, at least one kind is preferably a high molecular weight type having a molecular weight of 500 or more. Examples of the antioxidant include various ones. For example, 1,3,5-trimethyl-2,4 together with 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4). , 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, IRGANOX1010 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, blocking at high temperature due to bleed-out of these antioxidants may adversely affect the capacitor element. A more preferable content is 0.1 to 0.9 mass%, and a particularly preferable content is 0.2 to 0.8 mass%.

  A crystal nucleating agent can be added to the linear polypropylene used in the present invention within the range not deviating from the object of the present invention. As the crystal nucleating agent, α crystal nucleating agent (dibenzylidene sorbitols, sodium benzoate, etc.), β crystal nucleating agent (potassium 1,2-hydroxystearate, magnesium benzoate, N, N′-dicyclohexyl-2,6) -Amide compounds such as naphthalene dicarboxamide, quinanaclidone compounds, etc.), as well as branched polypropylene (H) described later. As the crystal nucleating agent, it is preferable to contain a branched-chain polypropylene (H) having an α crystal or β crystal crystal nucleating agent effect by itself. In the biaxially oriented polypropylene film for capacitors according to the present invention, when an α crystal nucleating agent or a β crystal nucleating agent other than the branched chain polypropylene (H) is added, it may be difficult to obtain a desired surface roughness, In some cases, the electrical properties may be adversely affected, such as a decrease in volume resistivity at high temperature, and the content is preferably less than 0.1% by mass, more preferably substantially not added. Is preferred.

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

  In this case, it is preferable that the branched polypropylene (H) 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, polypropylene is heated to 230 ° C. using a melt tension tester manufactured by Toyo Seiki Co., Ltd., and molten polypropylene is extruded at an extrusion speed of 15 mm / min to form a strand, which is 6.4 m / min. The tension at the time of drawing at a speed is measured, and it is defined as the melt tension (unit: cN). Further, the melt flow index (MFR) measured at 230 ° C. is a value measured with a load of 21.18 N according to JIS-K7210 (1999) (unit: g / 10 minutes).

  The branched-chain 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 formability. Those in the range of 20 g / 10 minutes are preferable, and those in the range of 1 to 10 g / 10 minutes are more preferable. The melt tension of the branched polypropylene (H) is preferably in the range of 1 to 30 cN, more preferably 2 to 20 cN. When the melt tension is low, the uniformity of the protrusions is poor, and coarse protrusions are easily formed. The higher the melt tension, the higher the uniformity of the protrusions, and the more likely it is that a dense surface is formed (the number of protrusions per unit area is large).

  When the biaxially oriented polypropylene film for capacitors of the present invention contains a branched-chain polypropylene (H), the melt crystallization temperature of ordinary polypropylene can be increased to 115 ° C or higher, while it is around 110 ° C. . When the dielectric film causes a dielectric breakdown for some reason, the generated discharge energy causes the evaporated metal around the discharge part to scatter, and the film itself partially melts. Normally, when the ambient temperature of the capacitor is high, it is difficult to recrystallize and recover the insulating property, but by adding branched-chain polypropylene (H), it becomes easier to recrystallize by increasing the melt crystallization temperature, and safety is improved. Can be improved.

To obtain a branched polypropylene (H) whose melt tension (MS) and melt flow index (MFR) measured at 230 ° C. satisfy 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-62-1212704, 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 and "Daploy HMS-PP" manufactured by Borealis (e.g., WB130HMS, WB135HMS). However, among these, PF-814 obtained by electron beam crosslinking is preferably used because the gel component in the resin is small. The branched polypropylene (H) used in the biaxially oriented polypropylene film for capacitors of the present invention preferably has 5 or less internal 3-substituted olefins per 10,000 carbon atoms. The presence of this internal 3-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) having a melt tension (MS) and a melt flow index (MFR), measured at 230 ° C., satisfying the above formula (5) of 0. The content is preferably from 5 to 10% by mass, more preferably from 0.5 to 8% by mass, and further preferably from 1 to 5% by mass. When the content of the branched-chain 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. When 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 device processability may be formed.

  When the biaxially oriented polypropylene film for capacitors of the present invention is composed of a linear polypropylene and a branched polypropylene (H), it is observed when the melting point is measured by the method described below and when it is measured by 2nd-Run. At least two melting peaks appear. That is, it has a shoulder peak (148-157 degreeC) in addition to a 1st melting peak (temperature 160-172 degreeC). This makes it possible to form a dense surface having uniform protrusions and few coarse protrusions. Further, by adding the branched-chain polypropylene (H) to the biaxially oriented polypropylene film for capacitors in the above proportion, an excellent characteristic surface shape with excellent uniformity of protrusions and less coarse protrusions,- It is possible to produce a biaxially oriented polypropylene film for capacitors, which exhibits excellent processability and high withstand voltage even under a wide range of ambient temperature conditions of 40 ° C. to 105 ° C.

  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 applies 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 may be deteriorated, and the dielectric breakdown voltage may be decreased when used as a capacitor. In order to set the ash content within this range, it is important to use a raw material with a small amount of catalyst residue, but a method such as reducing contamination from the extrusion system during film formation as much as possible, for example, a bleed time of 1 hour or more, A method such as thoroughly washing the route with a polymer before actually starting film formation can be adopted.

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 withstand voltage and handling, and particularly by the micrometer method. When the film thickness (t1) is in the range of 1 μm or more and 3 μm or less, the performance is effectively exhibited. A more preferable thickness is 1.2 μm or more and 2.8 μm or less, and a further 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 the electrode configuration, it may be either a foil wound capacitor or a metal vapor deposition film capacitor, and is also preferably used for an oil immersion type capacitor impregnated with insulating oil or a dry type capacitor that does not use insulating oil at all. To be From the viewpoint of shape, it may be a winding type or a stacking type. However, due to the characteristics of the film of the present invention, it is particularly preferably used as a metal evaporated film capacitor.

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

  First, regarding the metal film constituting the metal film laminated film, as the metal species constituting the metal film, metals such as aluminum, zinc, copper, gold, silver, nickel and chromium, and / or mixtures and alloys thereof are used. , Compounds are exemplified. Of these, aluminum, zinc alone, alloys, or mixtures thereof are excellent in terms of cost and performance. The metal film may have a single-layer structure or a multi-layer structure. Examples of the method for providing the metal film include a vacuum vapor deposition method of forming a metal film by heating and melting and evaporating a metal in a vacuum, and a method of coating a metal powder with a suitable 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 20 Ω / □, and more preferably 5 to 10 Ω / □. If the film resistance is less than 1Ω / □, the capacitor is likely to be broken due to current concentration. Further, when the film resistance exceeds 20 Ω / □, 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 a winding type having more excellent withstand voltage characteristics is preferable. If the capacitor is of the wound type, it is preferable that the capacitor has an elliptical cross section and the ratio of the major axis to the minor axis of the ellipse is 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-mentioned characteristics. The method of biaxial stretching, inflation simultaneous biaxial stretching method, simultaneous stenter biaxial stretching method, can be obtained by any of the stenter sequential biaxial stretching method, among them, film-forming stability, thickness uniformity, of the film From the viewpoint of controlling high rigidity and dimensional stability, it is preferable to adopt the stenter sequential biaxial stretching method.

  Next, a method for producing the biaxially oriented polypropylene film of the present invention by the stenter sequential biaxial stretching method will be described, but the method is not necessarily limited thereto.

  First, a branched polypropylene (H) is blended with a linear polypropylene at a predetermined ratio, 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 capacitors of the present invention, it is necessary to properly generate β crystals, and it is preferable to appropriately control the temperature of the cooling drum in order to properly generate β crystals. . In order to efficiently generate β crystals, it is preferable to maintain the resin temperature at which the β crystal generation efficiency is maximum for a predetermined time, and the temperature is usually 115 to 135 ° C. The holding time is preferably 1 second or more.

  In order to realize these conditions, the process can be appropriately determined according to the resin temperature, the extrusion rate, 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 or more. Further, the temperature of the cooling drum to be selected is preferably 70 to 100 ° C, more preferably 72 to 98 ° C, and particularly preferably 75 to 90 ° C. If the temperature of the cooling drum is higher than 100 ° C., β crystal formation may proceed excessively, so that voids may be generated in the film and the dielectric breakdown resistance may deteriorate. On the other hand, if the cooling drum temperature is lower than 70 ° C., β crystals may not be generated, and a smooth surface with poor element processability may be formed.

  As a method for adhering the unstretched sheet to the cooling drum, any of an electrostatic application method, an adhering method utilizing surface tension of water, an air knife method, a press roll method, an underwater casting method and the like may be used. However, the air knife method is preferable because it has good flatness and can control the surface roughness.

  Next, this unstretched sheet is biaxially stretched. First, the unstretched sheet is preheated by passing through a longitudinally stretched preheating roll. The temperature of the longitudinal stretching preheating roll is preferably 100 to 120 ° C, more preferably 103 to 117 ° C, and further preferably 105 to 115 ° C. If the longitudinal stretching preheating roll temperature is less than 100 ° C., the amount of heat may be insufficient during longitudinal stretching due to insufficient preheating of the film, and the film may be broken due to excessive stretching stress. When the temperature of the longitudinal stretching preheating roll is higher than 120 ° C., the in-plane orientation of the film is hard to proceed, and the strength of the film may decrease. The temperature of the longitudinal stretching preheating roll is preferably the same as the temperature of the longitudinal stretching roll from the viewpoint of reaching the stretching temperature of the unstretched sheet before the longitudinal stretching.

Subsequently, the unstretched film is passed through a longitudinal stretching roll to be longitudinally stretched, and then cooled to room temperature. The longitudinal stretching method includes a single-drawing method and a multi-stage drawing method, but the single-drawing method, which can draw at a higher drawing speed and enhances 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 further preferably 105 to 115 ° C. If the temperature of the longitudinal stretching roll is less than 100 ° C., the film may have insufficient heat during longitudinal stretching and may be broken due to excessive stretching stress. 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 decrease. Further, the longitudinal stretching ratio is preferably 5.5 to 8.0 times, more preferably 6.0 to 8.0 times, and further preferably 6.5 to 8.0 times. If the longitudinal stretching ratio is less than 5.5 times, the in-plane orientation of the film may decrease. On the other hand, if the longitudinal stretching ratio is higher than 8.0 times, the film may be broken and the film-forming stability may be significantly deteriorated. 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, and particularly preferably 3 The range is 0.0 × 10 ^{6 to} 5.0 × 10 ⁶ % / min. If the longitudinal stretching rate is less than 1.0 × 10 ⁶ % / min, the in-plane orientation may be difficult to proceed and the withstand voltage may be poor. On the other hand, when the longitudinal stretching speed is higher than 5.0 × 10 ⁶ % / min, the film may be broken and the film formability may be significantly deteriorated.

In order to achieve high orientation in the film plane in the present invention, the unstretched sheet is subjected to a low temperature of 100 to 120 ° C., 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 end portion of the unstretched sheet is significantly thicker than the central portion of the unstretched sheet, which is a product after stretching, because the end portion 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 amount of heat becomes insufficient at the ends of the thick sheet, the film breaks, and the productivity is significantly reduced.

  Therefore, in the present invention, first, an edge cooler (for example, a small air cooler) is installed on a cooling roll, and when the molten polymer is cooled and solidified into an unstretched sheet on the cooling roll, only the end portion of the unstretched sheet is cooled. 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 of the end portion of the unstretched sheet may proceed, 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 is deteriorated, the crystallinity unevenness occurs in the longitudinal direction of the unstretched sheet, and the productivity may be lowered 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 together with the method of rapidly cooling the end portion of the unstretched sheet by the above edge cooler on the cooling roll, and unstretched. It is preferable to use a method in which heat is applied only to the edges of the sheet to enhance the stretchability. The edge heater temperature is preferably 120 to 160 ° C, more preferably 125 to 155 ° C, and particularly preferably 130 to 150 ° C. If the edge heater temperature is higher than 160 ° C., the end portion 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 the edge heater may be broken during stretching.

  After that, the end portion of the stretched film is held by a clip and guided to a stenter, and stretched at 140 to 170 ° C., more preferably 150 to 160 ° C., in the width direction by 7 to 13 times, and more preferably 8 to 12 times. Then, while applying a relaxation of 2 to 20% in the width direction, heat fixing is performed at a temperature of 140 to 160 ° C. After that, the film is guided to the outside of the stenter through a cooling process at 100 to 150 ° C., the clip at the end of the film is released, the film edge is slit in the winder process, and the film product roll is wound. Before winding the film, it is preferable to perform corona discharge treatment in air, nitrogen, carbon dioxide gas or a mixed gas thereof in order to improve the adhesion of the metal to be vapor-deposited on the surface to be vapor-deposited.

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. Corona discharge treatment is performed at a strength of 20 to 30 W · min / m ² to impart adhesiveness to the deposited metal. In the present invention, the method for providing a metal film on the surface of the above-mentioned biaxially oriented polypropylene film for capacitors to form a metal film laminated film is not particularly limited, but for example, at least one surface of the polypropylene film is vapor-deposited with aluminum to form a film capacitor. A method of providing a metal film such as an aluminum vapor deposition film to be the internal electrode of is preferably used. At this time, other metal components such as nickel, copper, gold, silver, chromium and zinc may be vapor-deposited simultaneously with or sequentially with aluminum. Further, 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 subjected to annealing treatment or heat treatment at a specific temperature. Further, for insulation or other purposes, at least one surface of the metal film laminated film may be coated with polyphenylene oxide or the like.

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

  Aluminum is vapor-deposited under reduced pressure on one side of a polypropylene film. At that time, vapor deposition is performed in a stripe shape having a margin portion running in the longitudinal direction of the film. Next, a blade is placed at the center of each vapor deposition portion on the surface and the center of each margin portion to slit the tape-shaped take-up reel having a margin on one side. Two tape-shaped take-up reels each having a left or right margin, one for the left margin and one for the right margin, are stacked and wound in a width direction so that the vapor deposition portion protrudes from the margin portion. To get

  When performing vapor deposition on both sides, vapor-deposit in a stripe shape that has a margin portion that runs in the longitudinal direction of one surface, and stripe so that the longitudinal margin portion is located in the center of the backside vapor deposition portion on the other surface. Vapor deposition. Next, a tape-shaped take-up reel is manufactured by inserting a blade into the center of the margin on each of the front and back sides and slitting the both sides and having a margin on one side (for example, if there is a margin on the right side of the front surface, a margin on the left side of the back surface). The obtained reel and one undeposited laminated film are wound one on top of the other so that the metallized film protrudes from the laminated film in the width direction and is wound to obtain a wound body.

  A core material can be removed from the wound body prepared as described above and pressed, and metallikons are sprayed on both end faces to form external electrodes, and lead wires can be welded to the metallikons to obtain a wound film capacitor. The film capacitor has a wide variety of uses such as railroad cars, automobiles (hybrid cars, electric cars), solar power generation / wind power generation, and general household appliances. The film capacitor of the present invention is also suitable for these uses. Can be used.

  The method of measuring the characteristic value and the method of evaluating the effect 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 5 points of data measured under the conditions of an incident angle of 60 ° and a light receiving angle of 60 ° by using a digital variable angle gloss meter UGV-5D manufactured by Suga Test Instruments Co., Ltd. And

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

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

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

<Preparation of sample>
A 5 mg sample is sealed in an aluminum pan for measurement. If the film is metal-deposited, it is appropriately removed.

<Measurement>
The film is melted / recrystallized / remelted in the following steps (a) → (b) → (c). Regarding the melting point of the resin, the melting peak temperature on the highest temperature side among the melting peaks observed at 2nd-Run was taken as the melting point. Further, the peak temperature on the highest temperature side among the crystallization peak temperatures observed when the temperature was lowered was defined as the melting crystallization temperature.
It measured 3 times and made the average value the melting point.

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

A. Measuring conditions Device: Bruker, DRX-500
Measurement nucleus: ¹³ C nucleus (resonance frequency: 125.8 MHz)
Measurement concentration: 10wt%
Solvent: benzene / heavy orthodichlorobenzene = mass ratio 1: 3 mixed solution Measurement temperature: 130 ° C
Spin rotation speed: 12 Hz
NMR sample tube: 5 mm tube Pulse width: 45 ° (4.5 μs)
Pulse repetition time: 10 seconds Data point: 64K
Number of conversions: 10,000 times Measurement mode: Complete Decoupling
B. Analysis conditions Fourier transform was performed with LB (line broadening factor) set to 1.0, and the mmmm peak was set to 21.86 ppm. Peak division is performed using WINFIT software (manufactured by Bruker). At that time, the peaks on the high magnetic field side are divided into the following peaks, the attached software is automatically fitted to optimize the peak divisions, and then the total mmmm peak fraction is calculated using the mesopentad fraction. The ratio (mmmm) was used.
The measurement was performed 5 times, and the average value was used as the mesopentad fraction.

Peak (a) mrrm
(B) (c) rrrm (split as two peaks)
(D) rrrr
(E) mrmr
(F) mrmm + rmrr
(G) mmrr
(H) rmmr
(I) mmmr
(J) mmmm
(7) Number of Internally Trisubstituted Olefins The sample is dissolved in a solvent, and the number of internally trisubstituted olefins is determined using ¹ H-NMR under the following conditions.

A. Measurement conditions Device: JNM-ECX400P type nuclear magnetic resonance spectrometer manufactured by JEOL Ltd. Measurement nucleus: ¹ H nucleus (resonance frequency: 500 MHz)
Measurement concentration: 2wt%
Solvent: Heavy orthodichlorobenzene Measurement temperature: 120 ° C
Pulse width: 45 °
Pulse repetition time: 7 seconds Converted number: 512 times Measurement mode: non decoupling
B. Analytical conditions Based on the chemical shift of 7.10 ppm of ortho-dichlorobenzene, the signal in the 5.0 to 5.2 ppm region is assigned to the proton of the internal 3-substituted olefin, and the integral ratio with the broad signal of 0.5 to 2.0 ppm. Then, the proton ratio of the internal 3-substituted olefin is obtained.

(8) Cold xylene soluble part (CXS)
Dissolve 0.5 g of polypropylene film sample in 100 ml of 135 ° C xylene, allow to cool, recrystallize for 1 hour in a constant temperature water bath at 20 ° C, and then dissolve the polypropylene-based component in the filtrate by liquid chromatography. (X (g)). It is determined by the following formula using the precise amount value (X0 (g)) of 0.5 g of the sample.

CXS (mass%) = (X / X0) × 100
(9) Centerline average roughness (SRa), 10-point average roughness (SRz)
According to JIS B-0601 (1982), "Non-contact three-dimensional fine shape measuring instrument (ET-30HK)" and "three-dimensional roughness analyzer (MODEL SPA-11)" manufactured by Kosaka Laboratory Ltd. are used, and the following conditions are used. It was measured at. 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: 1 mm
Horizontal magnification: 200 times Vertical magnification: 20,000 times Cutoff: 0.25 mm
Width feed rate: 0.1 mm / sec Length feed pitch: 10 μm
Length direction feed number: 25 times Measurement direction: Film width direction (10) Orientation parameters (PMD, PTD)
The orientation parameters (PMD, PTD) were calculated based on the method described in the literature (YV KISSIN et al., Journal of Polymer Science: Polymer Physics Edition, Vol. 21, 2085-2096 (1983)).

  First, a polarizer was attached to the light source of the FT-IR device, 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 Speac
Resolution: 2 cm ^-1
Number of times of integration: 64 times In the infrared absorption spectrum measured, the three-point peak detection function of the analysis software “IR Solution” was performed under the following conditions to calculate the absorption peak areas at 841 cm ⁻¹ and 809 cm ⁻¹ . The “corrected area” output by peak detection was taken as the absorption peak area in each absorption peak.

3-point peak detection peak of 841cm ^-1: 840.99cm ^-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 equation to calculate the orientation parameters (PMD, PTD).

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: FT-IR wavelength 841 cm ⁻¹ absorption peak area measured by polarizing the light source in the width direction B809: FT-IR wavelength 809 cm ⁻¹ absorption peak area measured by polarizing the light source in the width direction Orientation parameter (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 of absorption of the absorption wavelength 809cm ^-1 wavelength 841cm ^-1.

(11) Breaking elongation and breaking strength A tensile test was performed under the following conditions using a tensile tester (Tensilon AMF / RTA-100 manufactured by Orientic Co., Ltd.). The elongation of the sample at the time of breaking the sample was taken as the breaking elongation, and the value obtained by dividing the load applied to the sample at the time of breaking the sample 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: length in the test direction 150 mm x width 10 mm
Initial chuck distance: 50 mm
Tensile speed: 300 mm / min (12) Membrane resistance of metal film A metal film laminated film was cut into a rectangle having a width of 10 mm and a full width (50 mm) in a width direction to obtain a sample, and a width of 30 mm was measured by a 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 (flat plate electrode method), an average value was obtained, and the average value was divided by the film thickness (μm) of the film measured by the micrometer method (described above) to obtain V / μm. It was written with.

(14) Evaluation of Vapor Deposition Capacitor Properties Aluminum was applied to the films obtained in each of the examples and comparative examples described later by a vacuum vapor deposition machine manufactured by ULVAC Co., Ltd. with a film resistance of 8Ω / □ and a margin portion in a direction perpendicular to the longitudinal direction. A vapor deposition pattern having a so-called T-shaped margin pattern provided with was provided to obtain a vapor deposition reel having a width of 50 mm.

  Then, using this reel, the capacitor element was wound up with a device winding machine (KAW-4NHB) manufactured by Minato Manufacturing Co., Ltd., and after metallikoning, it was subjected to heat treatment at a temperature of 105 ° C. for 10 hours under reduced pressure, and then a lead. The wire was attached and the capacitor element was finished. At this time, the capacitance of the capacitor element was 5 μF.

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

  Hereinafter, the effects of the present invention will be further described with reference to examples.

(Example 1)
As a linear polypropylene, a polypropylene polymer manufactured by Prime Polymer Co., Ltd., which has a mesopentad fraction of 97.5% and a melt mass flow rate (MFR) of 2.6 g / 10 min, is supplied to an extruder at a temperature of 250 ° C., Melt extrusion was performed in a sheet shape 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 was rapidly cooled with a small air cooler having an air temperature of 20 ° C. Then, the unstretched sheet was gradually preheated to 110 ° C., continuously passed through rolls having a peripheral speed difference maintained at a temperature of 110 ° C., and stretched in the longitudinal direction at a rate of 4.0 × 10 ⁶ % / min. It was stretched to 0 times. At that time, the end portion 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 introduced into 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 having a thickness (t1) of A 2.0 μm biaxially oriented polypropylene film was obtained. Further, the drum surface side (A surface) of the biaxially oriented polypropylene film was subjected to corona discharge treatment in the atmosphere at a treatment intensity of 25 W · min / m ² . The properties of the biaxially oriented polypropylene film thus obtained are 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-sized 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)
Longitudinal stretching preheating roll temperature was 117 ° C., longitudinal stretching temperature was 117 ° C., longitudinal stretching ratio was 5.5 times, output of small radiator was 3.5 kW, and unstretched sheet edge temperature during longitudinal stretching was 140 ° C. Except for the above, the 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 4)
Longitudinal stretching preheating roll temperature was 117 ° C., longitudinal stretching temperature was 117 ° C., longitudinal stretching ratio was 7.0 times, output of small radiator was 3.5 kW, and unstretched sheet end temperature during longitudinal stretching was 140 ° C. Except for the above, the 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 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 % / A film was formed in the same manner as in Example 1 except that the amount was changed 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 % / A film was formed in the same manner as in Example 1 except that the amount was changed 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 having a mesopentad fraction of 95.0% was used, the longitudinal stretching ratio was 5.5 times, the output of a small radiator was 4.0 kW, and the film edge 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 radiator was 5.3 kW, and the end temperature of the unstretched sheet during longitudinal stretching was 155 ° C. The film was formed into a biaxially oriented polypropylene film. 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. Membrane 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. Membrane 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, the longitudinal stretching roll. A film was formed in the same manner as in Example 1 except that the above small radiator 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 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, but the film was broken by longitudinal stretching and could not be formed.

(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 by performing film formation in the same manner as in Example 1 except that the draw ratio 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 small air cooler temperature on the cooling roll is 10 ° C, the longitudinal 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 radiator is 3.0 kW. A biaxially oriented polypropylene film was obtained by performing film formation in the same manner as in Example 1 except that the end temperature of the film during longitudinal stretching was 150 ° C. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

(Comparative example 5)
Using polypropylene resin with a mesopentad fraction of 99.5%, the small air cooler on the cooling roll is turned off, the longitudinal 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 stretching ratio was 5.3 times, and the film formation was performed in the same manner as in Example 1 except that the small radiator on the longitudinal stretching 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, the longitudinal stretching. Film formation was performed in the same manner as in Example 1 except that the small radiator heater on the 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 7)
Using a linear polypropylene with a mesopentad fraction of 94.0%, the small air cooler on the cooling roll was turned off, the longitudinal preheating temperature was 140 ° C, the longitudinal stretching temperature was 140 ° C, and the longitudinal stretching speed was 2.5 × 10. ^A biaxially oriented polypropylene film was obtained in the same manner as in Example 1 except that ⁶ % / min, the longitudinal stretching ratio was 5.0, and the small radiator on the longitudinal stretching roll was turned off. The properties of the obtained biaxially oriented polypropylene film are shown in Table 2.

Claims (7)

The polypropylene resin has a thickness (t1) of 1 to 3 μm and a mesopentad fraction (mmmm) of 95% or more and less than 98%, and has a longitudinal alignment parameter PMD and a widthwise alignment parameter PTD. 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: FT-IR absorption peak area at a wavelength of 841 cm ⁻¹ measured with the light source polarized in the width direction B809: FT-IR absorption peak area at a wavelength of 809 cm ⁻¹ measured with the light source polarized in the width direction The biaxially oriented polypropylene film for capacitors according to claim 1, which simultaneously satisfies the following expressions (2) and (3).
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, which has a breaking strength (fMD) in the longitudinal direction of 200 MPa or more and 350 MPa or less and a breaking strength (fTD) in the width direction of 250 MPa or more and 450 MPa or less. The breaking elongation (EMD) in the longitudinal direction is 40% or more and 120% or less, and the breaking elongation (EMD) in the longitudinal direction and the breaking strength (fMD) in the longitudinal direction satisfy the following expression (4). A biaxially oriented polypropylene film for capacitors according to any one of 3 to 3.
1.8 ≦ fMD / EMD ≦ 4.0 [MPa /%] (4)   A metal film laminated film comprising a metal film 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.