Metal layer integrated polypropylene film

Abstract

To provide a metal layer-integrated type polypropylene film in which, while having excellent processing suitability when making capacitor, a capacitor having excellent voltage resistance and capacitance stability against high voltage can be obtained.SOLUTION: Provided is a metal layer-integrated type polypropylene film, which is a metal layer-integrated polypropylene film that comprises a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, and in which the elastic modulus in the first direction of the metal layer-integrated polypropylene film is 3.27 to 3.80 GPa.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a metal layer-integrated polypropylene film and the like. [Background technology]

[0002] Polypropylene films have excellent electrical properties such as high voltage resistance and low dielectric loss, and also have high moisture resistance. Therefore, they are widely used in electronic devices and electrical equipment. Specifically, they are used as films for filter capacitors and smoothing capacitors in power conversion circuits such as high-voltage capacitors, converters, and inverters.

[0003] In particular, in recent years, polypropylene films have begun to be widely used as capacitors for inverter power supplies that control drive motors in electric vehicles, hybrid vehicles, etc. Capacitors for inverter power supplies used in automobiles, etc. are required to be small, lightweight, high capacity, and highly reliable over a long period of time. Summary of the Invention [Problem to be solved by the invention]

[0004] In the course of research, the inventors have focused on the voltage resistance and capacitance stability against high voltage of the capacitor, among other things, in terms of the reliability of the capacitor. Through intensive research, the inventors have found that the voltage resistance and capacitance stability against high voltage of the capacitor can be improved by adjusting the elastic modulus of the film. However, even if these two performances are good, the processability during the manufacture of the capacitor may be poor (e.g., buckling or wrinkling of the end faces of the capacitor element). This may have a negative effect on the performance of the capacitor.

[0005] Therefore, an object of the present invention is to provide a metal layer-integrated polypropylene film that has excellent processability when producing a capacitor, and that can provide a capacitor that has excellent voltage resistance and capacitance stability against high voltage. [Means for solving the problem]

[0006] The present inventors have conducted intensive research in view of the above problems, and have found that the above problems can be solved by a metal layer-integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, the metal layer-integrated polypropylene film having an elastic modulus in a first direction of 3.27 to 3.80 GPa. The present inventors have conducted further research based on this finding, and have completed the present invention. That is, the present invention includes the following aspects.

[0007] Item 1. A metal layer-integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, The metal layer-integrated polypropylene film has an elastic modulus in a first direction of 3.27 to 3.80 GPa.

[0008] Item 2. The metal layer-integrated polypropylene film according to Item 1, wherein the polypropylene film has an elastic modulus in a first direction of 2.70 to 3.30 GPa.

[0009] Item 3. The metal layer-integrated polypropylene film according to item 1 or 2, wherein the protrusion peak height (Rpk) on the metal layer side surface is 0.050 to 0.078 μm.

[0010] Item 4. The metal layer-integrated polypropylene film according to any one of Items 1 to 3, having a film resistance of 1 to 25 Ω / sq.

[0011] Item 5. The metal layer-integrated polypropylene film according to any one of Items 1 to 4, wherein the metal layer-integrated polypropylene film has an elastic modulus in a first direction of 3.28 to 3.60 GPa.

[0012] Item 6. The metal layer-integrated polypropylene film according to any one of Items 1 to 5, wherein the protrusion peak height (Rpk) on the metal layer side surface is 0.059 to 0.078 μm.

[0013] Item 7. The metal layer-integrated polypropylene film according to any one of Items 1 to 6, wherein the polypropylene film is a biaxially stretched film.

[0014] Item 8. The metal layer-integrated polypropylene film according to any one of Items 1 to 7, wherein the polypropylene film has a thickness of 0.8 to 3.5 μm.

[0015] Item 9. The metal layer-integrated polypropylene film according to any one of Items 1 to 8, wherein the polypropylene film is a single-layer film.

[0016] Item 10. The metal layer-integrated polypropylene film according to any one of Items 1 to 9, which is for a capacitor.

[0017] Item 11. A capacitor comprising the metal layer-integrated polypropylene film according to any one of items 1 to 10.

[0018] Item 12. The capacitor according to item 11, comprising a roll of the metal layer-integrated polypropylene film according to any one of items 1 to 10. Effect of the Invention

[0019] According to the present invention, it is possible to provide a metal layer-integrated polypropylene film which has excellent processability during the production of a capacitor, and which can provide a capacitor having excellent voltage resistance and capacitance stability against high voltage. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic perspective view for explaining a metal layer-integrated polypropylene film produced as an example and a comparative example. [Diagram 2]FIG. 2 is a schematic diagram for explaining a method for producing a metal layer-integrated polypropylene film according to the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In this specification, the expressions "contain" and "comprise" include the concepts of "contain", "include", "consist essentially of" and "consist only of".

[0022] 1. Polypropylene film with metal layer In one aspect, the present invention relates to a metal layer-integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, the metal layer-integrated polypropylene film having an elastic modulus in a first direction of 3.27 to 3.80 GPa (sometimes referred to as "metal layer-integrated polypropylene film of the present invention" in this specification). The polypropylene film (polypropylene film not laminated with a metal layer) of the metal layer-integrated polypropylene film of the present invention is sometimes referred to as "polypropylene film of the present invention" in this specification. These will be described below.

[0023] The metal layer-integrated polypropylene film of the present invention has an elastic modulus in the first direction (hereinafter, sometimes referred to as "elastic modulus A") of 3.27 to 3.80 GPa. When the elastic modulus A satisfies a predetermined range, the film can exhibit a good balance of good processability during the preparation of a capacitor, and the voltage resistance and capacitance stability of the capacitor against high voltage. Although no limiting interpretation is desired, it is considered that by setting the elastic modulus within a specific range, the stress during the preparation of a capacitor (particularly during winding) can be adjusted to an appropriate level while adjusting the gap between the films to an appropriate level of self-healing action, and thus the film can exhibit a good balance of good processability during the preparation of a capacitor, and the voltage resistance and capacitance stability of the capacitor against high voltage. From the viewpoint of these characteristics, the elastic modulus A is preferably 3.27 to 3.70 GPa, more preferably 3.28 to 3.60 GPa, even more preferably 3.28 to 3.55 GPa, and even more preferably 3.28 to 3.50 GPa. In a particularly preferred embodiment, the elastic modulus A is 3.30 GPa or more, 3.35 GPa or more, 3.40 GPa or more, or 3.45 GPa or more.

[0024] Regarding the elastic modulus A, the first direction is any direction of the metal layer-integrated polypropylene film of the present invention, and is not particularly limited. By obtaining a capacitor (preferably a capacitor including a wound body) from the metal layer-integrated polypropylene film of the present invention with the same direction as the "first direction" or the opposite direction as the longitudinal direction, it is possible to obtain a capacitor that exhibits good processability during capacitor fabrication, and further has excellent voltage resistance and capacitance stability against high voltage. The first direction is preferably the MD (machine direction) of the metal layer-integrated polypropylene film.

[0025] The elastic modulus A is measured in accordance with JIS K 7127:1999 as follows. A rectangular sample having a length of 150 mm and a width of 10 mm is cut out from the metal layer-integrated polypropylene film of the present invention. At this time, the sample is cut out so that the first direction is the length direction. The sample is set in the chuck of a tensile tester (Tensilon universal tester RTG-1210 manufactured by A&D Co., Ltd.) with a chuck distance of 50 mm, and a tensile test is performed at a test speed of 300 mm / min. The temperature during the tensile test is 23°C. The elastic modulus (unit: GPa) is calculated by dividing the load value at the time of sample destruction in the tensile test by the cross-sectional area of ​​the sample before the tensile test (thickness x width of the sample before the tensile test: 10 mm). The tensile test is performed five times, and the average value is taken as the elastic modulus A (GPa).

[0026] The polypropylene film of the present invention preferably has an elastic modulus in the first direction (hereinafter sometimes referred to as "elastic modulus B") of 2.70 to 3.30 GPa. By making the elastic modulus B satisfy a predetermined range and adjusting the lamination conditions of the metal layer as described below, it is possible to easily adjust the elastic modulus A of the metal layer-integrated polypropylene film of the present invention to the above-mentioned predetermined range. The elastic modulus B is preferably 2.70 to 3.20 GPa, more preferably 2.70 to 3.10 GPa, even more preferably 2.70 to 3.08 GPa, and even more preferably 2.72 to 3.06 GPa. In a particularly preferred embodiment, the elastic modulus B is 2.80 GPa or more, 2.85 GPa or more, 2.90 GPa or more, or 2.95 GPa or more.

[0027] The definition of the first direction regarding the elastic modulus B is the same as the definition of the first direction regarding the elastic modulus A. The method for measuring the elastic modulus B is the same as the method for measuring the elastic modulus A, except that the polypropylene film of the present invention is used instead of the metal layer-integrated polypropylene film of the present invention.

[0028] From the viewpoint of exhibiting a good processing suitability in the preparation of a capacitor, and a well-balanced voltage resistance and capacitance stability against high voltage of the capacitor, the metal layer-integrated polypropylene film of the present invention preferably has a protrusion peak height (Rpk) of 0.050 to 0.078 μm on the metal layer side surface. When metal layers are laminated on both sides of the polypropylene film of the present invention, the protrusion peak height (Rpk) of either (preferably both) of the metal layer side surfaces is preferably 0.050 to 0.078 μm. The protrusion peak height (Rpk) is preferably 0.055 to 0.078 μm, more preferably 0.059 to 0.078 μm, and even more preferably 0.061 to 0.077 μm. In a particularly preferred embodiment, the protrusion peak height (Rpk) is 0.074 μm or less, 0.072 μm or less, 0.070 μm or less, or 0.068 μm or less.

[0029] The method for measuring the peak height (Rpk) of the protruding part is as follows. A "VertScan2.0 (model: R5500GML)" manufactured by Ryoka Systems Co., Ltd. is used as an optical interference type non-contact surface shape measuring instrument. The metal layer integrated polypropylene film of the present invention is cut into an arbitrary size of about 20 cm in the flow direction as a measurement sample, and set on the measurement stage using an electrostatic contact plate or the like in a state where wrinkles are sufficiently removed. The measurement is performed in WAVE mode, with a 530white filter and a 1×BODY lens barrel applied, and a 10x objective lens used to measure (353.16 μm×470.92 μm) per field of view. This operation is performed for 10 points at 1 cm intervals in the flow direction from the center of the surface of the measurement sample in both the flow direction and width direction. Next, the obtained data is subjected to noise removal processing using a median filter (3×3), and then Gaussian filter processing with a cutoff value of 30 μm is performed to remove waviness components. This makes it possible to properly measure the surface condition. Next, analysis is performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software of "VertScan2.0", Rpk is obtained, and the average value of the values ​​obtained at the above 10 locations is calculated as the protrusion peak height (Rpk) on the metal layer side surface of the metal layer-integrated polypropylene film of the present invention.

[0030] The thickness of the metal layer-integrated polypropylene film of the present invention is preferably 0.8 μm or more, more preferably 1.2 μm or more, even more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. The thickness of the metal layer-integrated polypropylene film of the present invention is preferably 3.5 μm or less, more preferably 3.0 μm or less, even more preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

[0031] The thickness of the metal layer-integrated polypropylene film of the present invention is a value measured in accordance with JIS-C2330, except that the thickness is measured at 100±10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu Co., Ltd.

[0032] The thickness of the polypropylene film of the present invention is preferably 0.8 μm or more, more preferably 1.2 μm or more, even more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. The thickness of the polypropylene film of the present invention is preferably 3.5 μm or less, more preferably 3.0 μm or less, even more preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

[0033] When the polypropylene film of the present invention has a thickness of 3.0 μm or less, the capacitance per unit volume of the film when made into a capacitor can be increased, so that the film can be suitably used for a capacitor. From the viewpoint of film formation stability, the polypropylene film of the present invention can have a thickness of 0.8 μm or more.

[0034] This point will be explained in detail below.

[0035] The thinner the polypropylene film, the greater the capacitance per unit volume. More specifically, capacitance C is expressed as follows using dielectric constant ε, electrode area S, and dielectric thickness d (thickness d of the polypropylene film): C=εS / d

[0036] Here, in the case of a film capacitor, the thickness of the electrodes is three or more orders of magnitude thinner than the thickness of the polypropylene film (dielectric), so if the volume of the electrodes is ignored, the volume V of the capacitor can be expressed as follows: V=Sd

[0037] Therefore, from the above two equations, the capacitance per unit volume, C / V, is expressed as follows: C / V=ε / d 2

[0038] As can be seen from the above formula, the capacitance per unit volume (C / V) is inversely proportional to the square of the polypropylene film thickness. Also, the dielectric constant ε is determined by the material used. Therefore, unless the material is changed, it is not possible to improve the capacitance per unit volume (C / V) other than by reducing the thickness.

[0039] The electrode area does not affect the capacitance per unit volume (C / V). This point will be explained below.

[0040] Consider the case where a capacitor is made by winding a film of the same material and the same thickness. For example, suppose the number of turns is increased and the film is wound 10 times longer (the electrode area is 10 times larger). This increases the capacitance by 10 times, but the volume also increases by 10 times, so the capacitance per unit volume (C / V) does not change even if the electrode area changes.

[0041] The above explanation is idealized for ease of understanding. In reality, for example, there may be a small gap between the films, or there may be a fringe effect at the electrode ends, so the capacitance per unit volume (C / V) may vary slightly depending on the area. However, it can be understood that the capacitance per unit volume (C / V) is generally determined by the polypropylene film thickness.

[0042] For these reasons, it is preferable that the thickness of the polypropylene film of the present invention is as thin as possible while ensuring the voltage resistance, and therefore the thickness of the polypropylene film of the present invention is preferably 3.0 μm or less.

[0043] The thickness of the polypropylene film of the present invention can be obtained by subtracting the thickness of the metal layer (the thickness of the metal layer converted from the film resistance) from the thickness of the metal layer-integrated polypropylene film of the present invention.

[0044] The thickness of the metal layer in the metal layer-integrated polypropylene film of the present invention is preferably 0.1 to 10 nm. When the thickness of the metal layer is 0.1 to 10 nm, the thickness of the metal layer-integrated polypropylene film of the present invention and the thickness of the polypropylene film of the present invention show approximately the same values ​​when measured by the method described in this example.

[0045] The polypropylene film of the present invention may be a biaxially stretched film, a uniaxially stretched film, or a non-stretched film, and is preferably a biaxially stretched film.

[0046] The layer structure of the polypropylene film of the present invention is not particularly limited. The film of the present invention may be a single layer consisting of one layer, or may be a multi-layer having the same or different compositions. The polypropylene film of the present invention is preferably a film consisting of one or more film-like molded layers, and more preferably a single-layer film (a film consisting of one film-like molded layer).

[0047] The layer structure of the metal layer in the metal layer-integrated polypropylene film of the present invention is not particularly limited. The metal layer may be a single layer or may be a plurality of layers having the same or different compositions. The polypropylene film of the present invention is not particularly limited in terms of its constituent material as long as it contains a polypropylene resin.

[0048] The content of the polypropylene resin is preferably 90% by mass or more, more preferably 95% by mass or more, based on the entire polypropylene film of the present invention (when the entire polypropylene film is taken as 100% by mass). The upper limit of the content of the polypropylene resin is, for example, 100% by mass, 98% by mass, etc., based on the entire polypropylene film of the present invention. The polypropylene resin may contain one type of polypropylene resin alone, or may contain two or more types of polypropylene resins.

[0049] When the polypropylene film of the present invention contains two or more polypropylene resins, the polypropylene resin with the greater content is referred to herein as the "main polypropylene resin." When the polypropylene film of the present invention contains only one polypropylene resin, the polypropylene resin is referred to herein as the "main polypropylene resin."

[0050] Hereinafter, in this specification, when the term "polypropylene resin" is used without specifying whether it is the main component or not, it means both the polypropylene resin as the main component and the polypropylene resin other than the main component unless otherwise specified. For example, when it is described that "the weight average molecular weight Mw of the polypropylene resin is preferably 250,000 or more and 450,000 or less," it means that the weight average molecular weight Mw of the polypropylene resin as the main component is preferably 250,000 or more and 450,000 or less, and that the weight average molecular weight Mw of the polypropylene resin other than the main component is preferably 250,000 or more and 450,000 or less.

[0051] The weight average molecular weight Mw of the polypropylene resin is preferably 250,000 to 450,000, more preferably 250,000 to 400,000, even more preferably 250,000 to 370,000, and even more preferably 290,000 to 370,000. When the weight average molecular weight Mw of the polypropylene resin is 250,000 to 450,000, the resin fluidity is moderate. As a result, it is easy to control the thickness of the cast raw sheet, and it is easy to prepare a thin stretched film with good thickness uniformity. In addition, from the viewpoint of mechanical properties, thermo-mechanical properties, stretch moldability, etc. of the biaxially stretched polypropylene film, the weight average molecular weight Mw is preferably 250,000 to 450,000. When two or more polypropylene resins are used, it is preferable to use a polypropylene resin having an Mw of 250,000 to 330,000 and a polypropylene resin having an Mw of 330,000 to 450,000 in combination.

[0052] The number average molecular weight Mn of the polypropylene resin is preferably 30,000 or more and 53,000 or less, more preferably 33,000 or more and 52,000 or less, even more preferably 38,000 or more and 52,000 or less, and even more preferably 43,000 or more and 52,000 or less.

[0053] The z-average molecular weight Mz of the polypropylene resin is preferably 500,000 or more and 2,100,000 or less, more preferably 700,000 or more and 1,900,000 or less, and even more preferably 700,000 or more and 1,700,000 or less.

[0054] The molecular weight distribution of the polypropylene resin [(weight average molecular weight Mw) / (number average molecular weight Mn)] is preferably 5 to 12, more preferably 5 to 11, even more preferably 6 to 11, even more preferably 6 to 10, and particularly preferably 7 to 10. When the molecular weight distribution of the polypropylene resin [(weight average molecular weight Mw) / (number average molecular weight Mn)] is 5 to 12, it is preferable because appropriate resin fluidity is obtained during biaxial stretching, and it is easy to obtain an extremely thin biaxially stretched propylene film without thickness unevenness.

[0055] The molecular weight distribution [(z-average molecular weight Mz) / (number-average molecular weight Mn)] of the polypropylene resin is preferably 10 or more and 70 or less, more preferably 15 or more and 60 or less, even more preferably 20 or more and 50 or less, even more preferably 25 or more and 50 or less, and particularly preferably 30 or more and 45 or less.

[0056] In this specification, the weight average molecular weight (Mw), number average molecular weight (Mn), z-average molecular weight (Mz), and molecular weight distribution (Mw / Mn and Mz / Mn) of the polypropylene resin are values ​​measured using a gel permeation chromatograph (GPC) device. More specifically, they are values ​​measured using a high-temperature GPC measuring device with built-in differential refractometer (RI) manufactured by Tosoh Corporation, HLC-8121GPC-HT (product name). As the GPC column, three TSKgel GMHHR-H(20)HT columns manufactured by Tosoh Corporation are connected and used. The column temperature is set to 140°C, and trichlorobenzene is passed as an eluent at a flow rate of 1.0 ml / 10 min to obtain measured values ​​of Mw and Mn. A calibration curve for the molecular weight M is prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured values ​​are converted to polystyrene values ​​to obtain Mw, Mn, and Mz. Here, the logarithm to the base 10 of the molecular weight M of standard polystyrene is called the logarithmic molecular weight ("Log(M)").

[0057] In the molecular weight differential distribution curve of the polypropylene resin, the difference obtained by subtracting the differential distribution value when the logarithmic molecular weight Log(M) is 6.0 from the differential distribution value when Log(M) is 4.5 (hereinafter also referred to as "differential distribution value difference DM") is preferably -5% or more and 14% or less, more preferably -4% or more and 12% or less, and even more preferably -4% or more and 10% or less.

[0058] In addition, the phrase "the difference (differential distribution value difference DM) obtained by subtracting the differential distribution value when Log(M)=6.0 from the differential distribution value when Log(M)=4.5 is -5% or more and 14% or less" can be understood to mean that, when comparing a component with a logarithmic molecular weight Log(M)=4.5, which is a representative distribution value of components with a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter also referred to as "low molecular weight components"), with a component with a molecular weight of around Log(M)=6.0, which is a representative distribution value of components with a molecular weight of around 1 million on the high molecular weight side (hereinafter also referred to as "high molecular weight components"), if the difference is positive, there is more low molecular weight components, and if the difference is negative, there is more high molecular weight components.

[0059] That is, for example, in the case where the molecular weight distribution Mw / Mn is 5 to 12, the fact that the molecular weight distribution Mw / Mn is 5 to 12 merely indicates the width of the molecular weight distribution width, and does not indicate the quantitative relationship between the high molecular weight components and the low molecular weight components therein. Therefore, from the viewpoints of resin fluidity, stretch moldability, and thickness uniformity, it is preferable to use the polypropylene resin such that the differential distribution value difference between the components having a molecular weight of 10,000 to 100,000 and the component having a molecular weight of 1,000,000 is -5% or more and 14% or less.

[0060] The differential distribution value is a value obtained by using GPC as follows. A curve showing intensity against time (generally called "elution curve") obtained by a GPC differential refractive index (RI) detector is used. A calibration curve obtained by using standard polystyrene is used to convert the time axis into logarithmic molecular weight (Log(M)), thereby converting the elution curve into a curve showing intensity against Log(M). Since the RI detection intensity is proportional to the component concentration, if the total area of ​​the curve showing intensity is taken as 100%, an integral distribution curve against the logarithmic molecular weight Log(M) can be obtained. The differential distribution curve is obtained by differentiating this integral distribution curve by Log(M). Therefore, "differential distribution" means the differential distribution of the concentration fraction against the molecular weight. From this curve, the differential distribution value at a specific Log(M) is read.

[0061] The mesopentad fraction ([mmmm]) of the polypropylene resin is preferably less than 98.0%, more preferably 97.5% or less, even more preferably 97.4% or less, and particularly preferably 97.0% or less. The mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, and even more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is appropriately improved due to the moderately high stereoregularity, and the initial voltage resistance and long-term voltage resistance are improved, while the desired stretchability can be obtained due to the moderate solidification (crystallization) speed when forming the cast raw sheet.

[0062] The mesopentad fraction ([mmmm]) is an index of stereoregularity that can be obtained by high-temperature nuclear magnetic resonance (NMR) measurement. In this specification, the mesopentad fraction ([mmmm]) refers to a value measured using a high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR), JNM-ECP500, manufactured by JEOL Ltd. The observation nucleus is 13C (125MHz), the measurement temperature is 135°C, and o-dichlorobenzene (ODCB: a mixed solvent of ODCB and deuterated ODCB (mixture ratio = 4 / 1) is used as the solvent for dissolving the polypropylene resin. The measurement method using high-temperature NMR can be performed by referring to the method described in, for example, "Japan Analytical Chemistry and Polymer Analysis Research Roundtable, New Edition Polymer Analysis Handbook, Kinokuniya Shoten, 1995, p. 610". A more detailed measurement method for the mesopentad fraction ([mmmm]) is described in the Examples.

[0063] The heptane insoluble content (HI) of the polypropylene resin is preferably 96.0% or more, more preferably 97.0% or more. The heptane insoluble content (HI) of the polypropylene resin is preferably 99.5% or less, more preferably 99.0% or less. Here, the higher the heptane insoluble content, the higher the stereoregularity of the resin. When the heptane insoluble content (HI) is 96.0% or more and 99.5% or less, the moderately high stereoregularity leads to a moderate improvement in the crystallinity of the resin, and the voltage resistance at high temperatures is improved. On the other hand, the rate of solidification (crystallization) during cast raw sheet molding becomes moderate, and the resin has moderate extensibility. The heptane insoluble content (HI) is measured by the method described in the Examples.

[0064] The melt flow rate (MFR) of the polypropylene resin is preferably 1.0 to 8.0 g / 10 min, more preferably 1.5 to 7.0 g / 10 min, and further preferably 2.0 to 6.0 g / 10 min. The melt flow rate of the polypropylene resin is measured by the method described in the Examples.

[0065] When the polypropylene film of the present invention contains two or more kinds of polypropylene resins, the main polypropylene resin preferably has a weight average molecular weight Mw of 250,000 or more and less than 345,000 and an MFR of 4 g / 10 min or more and 8 g / 10 min or less. When the polypropylene film of the present invention contains two or more kinds of polypropylene resins, the polypropylene resins other than the main resin preferably have a weight average molecular weight Mw of 345,000 or more and 450,000 or less and an MFR of 1 g / 10 min or more and less than 4 g / 10 min (more preferably 1 g / 10 min or more and 3.9 g / 10 min or less).

[0066] The polypropylene resin can be produced by a generally known polymerization method, for example, a gas phase polymerization method, a bulk polymerization method, and a slurry polymerization method.

[0067] The polymerization may be a single-stage polymerization using one polymerization reactor, or a multi-stage polymerization using two or more polymerization reactors. The polymerization may be carried out by adding hydrogen or a comonomer as a molecular weight modifier to the reactor.

[0068] The catalyst used in the polymerization can be a generally known Ziegler-Natta catalyst, and is not particularly limited as long as the polypropylene resin can be obtained. The catalyst may contain a cocatalyst component or a donor. By adjusting the catalyst and polymerization conditions, the molecular weight, molecular weight distribution, stereoregularity, etc. can be controlled.

[0069] The molecular weight distribution of the polypropylene resin can be adjusted by resin mixing (blending). For example, a method of mixing two or more resins having different molecular weights or molecular weight distributions can be mentioned. In general, a two-type polypropylene mixture in which the main resin is 55% by mass or more and 90% by mass or less, assuming that the total resin is 100% by mass, and a resin having a higher or lower average molecular weight than the main resin is mixed is preferable because it is easy to adjust the amount of low molecular weight components.

[0070] When the above-mentioned mixing and adjusting method is adopted, the melt flow rate (MFR) may be used as a guide for the average molecular weight. In this case, it is preferable that the difference in MFR between the main resin and the additive resin is about 1 to 30 g / 10 min from the viewpoint of convenience during adjustment.

[0071] The method for mixing the resins is not particularly limited, and examples thereof include a method in which polymer powders or pellets of the main resin and the additive resin are dry-blended using a mixer or the like, and a method in which polymer powders or pellets of the main resin and the additive resin are fed to a kneader and melt-kneaded to obtain a blended resin.

[0072] The mixer and the kneader are not particularly limited. The kneader may be of a single screw type, a twin screw type, or a multi-screw type having more than one screw. In the case of a twin or more screw type, the kneader may be of either a co-rotating or counter-rotating type.

[0073] In the case of blending by melt kneading, the kneading temperature is not particularly limited as long as a good kneaded product is obtained. In general, it is in the range of 200°C to 300°C, and from the viewpoint of suppressing deterioration of the resin, 230°C to 270°C is preferable. In addition, in order to suppress deterioration during kneading and mixing of the resin, an inert gas such as nitrogen may be purged into the kneader. The melt kneaded resin may be pelletized to an appropriate size using a generally known granulator. In this way, mixed polypropylene raw material resin pellets can be obtained.

[0074] The total ash content resulting from polymerization catalyst residues and the like contained in the polypropylene raw material resin is preferably 50 ppm or less based on the polypropylene resin (100 parts by weight).

[0075] The total ash content (total ash content contained in the polypropylene raw material resin) is preferably 5 ppm or more and 35 ppm or less, more preferably 5 ppm or more and 30 ppm or less, and even more preferably 10 ppm or more and 25 ppm or less, in order to improve the electrical characteristics as a capacitor while suppressing the generation of polar low molecular weight components.

[0076] The polypropylene film of the present invention may contain an additive. The "additive" is not particularly limited as long as it is an additive generally used in polypropylene resins.

[0077] Examples of the additives include antioxidants, chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, inorganic fillers, organic fillers, etc. Examples of the inorganic fillers include barium titanate, strontium titanate, aluminum oxide, etc. The polypropylene resin may contain the additives in an amount that does not adversely affect the polypropylene film of the present invention.

[0078] The metal layer functions as an electrode when the metal layer-integrated polypropylene film of the present invention is used as a capacitor. The metal used in the metal layer may be, for example, a single metal such as zinc, lead, silver, chromium, aluminum, copper, or nickel, a mixture of a plurality of metals, or an alloy of a plurality of metals. In consideration of the environment, economy, and capacitor performance, zinc and aluminum are preferred.

[0079] 2. Manufacturing method of metal layer integrated polypropylene film Next, the method for producing the metal layer-integrated polypropylene film of the present invention will be described. Note that the metal layer-integrated polypropylene film of the present invention is preferably produced by the method for producing the metal layer-integrated polypropylene film described below, but it does not have to be produced by the method for producing the metal layer-integrated polypropylene film described below.

[0080] The method for producing the metal layer-integrated polypropylene film of the present invention comprises the steps of: A step A of preparing a polypropylene film of the present invention; A step B of laminating a metal layer on one or both sides of the polypropylene film of the present invention prepared in the step A to obtain the metal layer-integrated polypropylene film of the present invention; At least

[0081] First, step A will be described.

[0082] When the polypropylene film of the present invention is a biaxially oriented polypropylene film, the cast raw sheet before stretching for producing the biaxially oriented polypropylene film can be produced as follows. However, the production method of the cast raw sheet according to the present embodiment is not limited to the method described below.

[0083] First, resin pellets, dry-mixed resin pellets, or resin pellets previously prepared by melt-kneading are fed into an extruder and heated to melt.

[0084] The melt-kneading temperature varies depending on the type of thermoplastic resin, but in the case of polypropylene resin, the extruder temperature during heating and melting is preferably 220 to 280° C., more preferably 230 to 270° C. The resin temperature during heating and melting is preferably 220 to 280° C., more preferably 230 to 270° C. The resin temperature during heating and melting is a value measured by a thermometer inserted in the extruder.

[0085] The extruder temperature and resin temperature during heat melting are selected taking into consideration the physical properties of the resin used. By setting the resin temperature during heat melting within the above-mentioned range, deterioration of the resin can be suppressed.

[0086] Next, the molten resin is extruded into a sheet using a T-die, and then cooled and solidified on at least one metal drum to form an unstretched cast raw sheet.

[0087] The surface temperature of the metal drum (the temperature of the metal drum that first comes into contact after extrusion) is preferably 50 to 100° C., and more preferably 80 to 100° C. The surface temperature of the metal drum can be determined depending on the physical properties of the resin used, etc.

[0088] The thickness of the cast raw sheet is not particularly limited as long as the polypropylene film of the present invention can be obtained, but is usually preferably 0.05 mm to 2 mm, and more preferably 0.1 mm to 1 mm.

[0089] The polypropylene film of the present invention can be suitably produced as follows, although the method for producing the polypropylene film of the present invention is not limited to the method described below.

[0090] The polypropylene film of the present invention can be produced by subjecting the resin cast raw sheet to a stretching treatment. The stretching is preferably biaxial stretching in which the sheet is oriented biaxially in the machine direction and the transverse direction, and the stretching method is preferably a sequential biaxial stretching method. In the sequential biaxial stretching method, for example, the cast raw sheet is first kept at a temperature of 100 to 170°C, passed between rolls having a speed difference, and stretched 3 to 7 times in the MD direction (machine direction, machine direction). The nip pressure is 0.35 to 0.5 MPa.

[0091] The temperature during MD stretching is preferably 100 to 170° C., more preferably 120 to 160° C., and even more preferably 130 to 150° C. The stretch ratio during MD stretching is preferably 3 to 7 times, more preferably 4 to 6 times, and even more preferably 4 to 5 times. The nip pressure during MD stretching is preferably 0.35 to 0.45 MPa, more preferably 0.36 to 0.44 MPa, and even more preferably 0.37 to 0.43 MPa.

[0092] After stretching in the MD direction, the sheet is introduced into a tenter and stretched 3 to 11 times in the TD direction (transverse direction, width direction). The temperature during stretching in the TD direction is preferably 155 to 170°C. Thereafter, the sheet is relaxed 2 to 10 times and heat-set. As a result, a biaxially stretched polypropylene film is obtained.

[0093] The polypropylene film may be subjected to corona discharge treatment online or offline after the stretching and heat setting processes in a post-process such as a metal deposition process, in order to enhance the adhesive properties. The corona discharge treatment can be performed using a known method. It is preferable to perform the treatment using air, carbon dioxide gas, nitrogen gas, or a mixture of these gases as the atmospheric gas.

[0094] Next, a description will be given of step B, in which a metal layer-integrated polypropylene film of the present invention is obtained by laminating a metal layer on one or both sides of the polypropylene film of the present invention prepared in step A. However, step B according to the present embodiment is not limited to the steps described below.

[0095] In step B, a metal layer is laminated on one or both sides of the polypropylene film of the present invention to obtain the metal layer-integrated polypropylene film of the present invention for processing into a capacitor.

[0096] Examples of the method for laminating a metal layer on one or both sides of the polypropylene film of the present invention include a vacuum deposition method and a sputtering method. From the viewpoints of productivity and economy, the vacuum deposition method is preferred. Examples of the vacuum deposition method include a crucible method and a wire method, but are not particularly limited, and an optimal method can be appropriately selected.

[0097] As a deposition condition in the vacuum deposition method, the temperature of the cooling roll is preferably -23°C or higher, more preferably -22°C or higher, and even more preferably -20°C or higher. When the temperature of the cooling roll is -23°C or higher, the elastic modulus of the polypropylene film tends to be increased when the metal layer is laminated. From the viewpoint of preventing the polypropylene film from being damaged by heat, the temperature of the cooling roll is preferably -16°C or lower, and more preferably -17°C or lower.

[0098] In the vacuum deposition method, the temperature of the evaporation source is controlled by the amount of current flow. As a deposition condition in the vacuum deposition method, the amount of current flow to the evaporation source is preferably 650 A or more, more preferably 700 A or more, and even more preferably 800 A or more. Increasing the amount of current flow (setting the temperature of the evaporation source higher) tends to increase the elastic modulus of the polypropylene film when the metal layer is laminated. From the viewpoint of preventing heat damage to the polypropylene film, the amount of current flow is preferably 900 A or less, and more preferably 850 A or less.

[0099] In the vacuum deposition method, the thickness of the metal layer is controlled by the film resistance. As a deposition condition in the vacuum deposition method, the film resistance is preferably 25Ω / sq or less, more preferably 20Ω / sq or less, in the case of an aluminum film. In the case of a zinc film, it is preferably 5Ω / sq or less, more preferably 4Ω / sq or less. The film resistance being small means that the thickness of the metal layer is thick. If the film resistance is made small (if the thickness of the metal layer is made thick), the metal layer will be exposed to heat for a long time for lamination. Therefore, if the film resistance is set to a large value, the elastic modulus of the polypropylene film tends to be increased by being exposed to heat for a long time during lamination of the metal layer. From the viewpoint of self-recovery (self-healing), the film resistance is preferably 1Ω / sq or more, more preferably 5Ω / sq or more, in the case of an aluminum film. In the case of a zinc film, it is preferably 1Ω / sq or more, more preferably 2Ω / sq or more. The term "self-healing" refers to the fact that when a defect occurs in the polypropylene film, the metal in the deposition layer is instantly evaporated by applied energy or the energy of the capacitor itself, and the function of the capacitor is restored. The thickness of the metal layer (film resistance) can be adjusted by the wire feed speed, deposition line speed, and evaporation source temperature, and the zinc film can be adjusted by the deposition line speed and evaporation source temperature.

[0100] The margin pattern when laminating the metal layer by vapor deposition is not particularly limited, but in order to improve the characteristics such as safety of the capacitor, it is preferable to apply a pattern including a so-called special margin, such as a fishnet pattern or a T-margin pattern, on one side of the film. This is effective in terms of increasing safety and preventing destruction and short circuits of the capacitor.

[0101] As a method for forming the margin, a generally known method such as a tape method or an oil method can be used without any limitation.

[0102] In the step B, a post-heat treatment may be further carried out after laminating a metal layer on one or both sides of the polypropylene film of the present invention. Examples of the conditions for the post-heat treatment include application of silicone oil heated to 120 to 130°C.

[0103] 3. Capacitor In one aspect, the present invention relates to a capacitor (sometimes referred to as "the capacitor of the present invention" in this specification) including the metal layer-integrated polypropylene film of the present invention. This will be described below.

[0104] The capacitor of the present invention is a capacitor that is excellent in voltage resistance and capacitance stability against high voltage.

[0105] For example, the capacitor of the present invention preferably has a withstand voltage of 405 V as measured by the voltage step-up test described in the Examples. DC More than 410V, preferably 410V DC More than 415V, preferably 415V DC Above 420V, more preferably 420V DC Above 430V, preferably 430V DC More preferably, 440V DC More than 450V, especially preferred DC The upper limit of the withstand voltage is not particularly limited, and may be, for example, 520V. DC , 510V DC, 500V DC , or 490V DC It is.

[0106] For example, the capacitor of the present invention preferably has a withstand voltage of 510 V as measured by a short-time withstand voltage test described in the Examples. DC More than 520V, preferably 520V DC More than 530V, preferably 530V DC Above 540V, more preferably 540V DC Above 550V, preferably 550V DC The upper limit of the withstand voltage is not particularly limited, and may be, for example, 610V. DC , 600V DC , 590V DC , or 580V DC It is.

[0107] For example, the capacitance change rate of the capacitor of the present invention measured by the method described in the Examples is preferably -0.27% or more, more preferably -0.26% or more, even more preferably -0.24% or more, still more preferably -0.22% or more, particularly preferably -0.20% or more, and particularly preferably -0.18% or more. The upper limit of the capacitance change rate is not particularly limited, and is, for example, 2%, 1%, 0.5%, 0.2%, or 0%.

[0108] In one embodiment of the present invention, the process of producing a capacitor involves, for example, winding a film. For example, two pairs of metal layer-integrated polypropylene films of the present invention are overlapped and wound so that the metal layers of the metal layer-integrated polypropylene film of the present invention and the polypropylene film of the present invention are alternately laminated, and further, the insulating margins are on opposite sides. In this case, it is preferable to laminate the two pairs of metal layer-integrated polypropylene films of the present invention with a shift of 1 to 2 mm. The winding machine used is not particularly limited, and for example, an automatic winding machine 3KAW-N2 type manufactured by Kaito Seisakusho Co., Ltd. can be used.

[0109] When producing a flat capacitor, after winding, the resulting wound product is usually pressed. Pressing promotes tightening of the capacitor and element formation. From the viewpoint of controlling and stabilizing the interlayer gap, the optimum pressure to be applied varies depending on the thickness of the film of the present invention, and is generally 2 to 20 kg / cm. 2 It is.

[0110] Next, metal is sprayed onto both end faces of the winding to provide metallikon electrodes, thereby completing a capacitor.

[0111] The capacitor is further subjected to a predetermined heat treatment. That is, the present invention includes a step of subjecting the capacitor to a heat treatment (hereinafter, sometimes referred to as "thermal aging"). The heat treatment temperature is not particularly limited, but is, for example, 80 to 190°C. The method of subjecting the capacitor to heat treatment may be appropriately selected from known methods including, for example, a method using a thermostatic bath under a vacuum atmosphere or a method using high-frequency induction heating. The time for which the heat treatment is performed is preferably 1 hour or more, more preferably 10 hours or more, from the viewpoint of obtaining mechanical and thermal stability, but is more preferably 20 hours or less, from the viewpoint of preventing molding defects such as heat wrinkles and molding.

[0112] By carrying out the heat treatment, the effect of heat aging can be obtained. Specifically, the gap between the films constituting the capacitor based on the metal layer-integrated polypropylene film of the present invention is reduced, corona discharge is suppressed, and the internal structure of the metal layer-integrated polypropylene film of the present invention is changed and crystallization is promoted. As a result, it is considered that the voltage resistance is further improved.

[0113] Lead wires are usually welded to the metallikon electrodes of the heat-aged capacitor. In order to impart weather resistance, particularly to prevent deterioration due to humidity, the capacitor is preferably encapsulated in a case and potted with epoxy resin.

[0114] The capacitor of the present invention using the film of the present invention can be suitably used in a high-temperature environment, and can be a small-sized capacitor with a high capacity (for example, a capacitance of 5 μF or more, preferably 10 μF or more, more preferably 20 μF or more, even more preferably 30 μF or more, and particularly preferably 40 μF or more. The upper limit of the capacitance is not particularly limited, and is, for example, 100 μF, 80 μF, 70 μF, or 60 μF). Therefore, the capacitor of the present invention can be used as a high-voltage capacitor, a filter capacitor and a smoothing capacitor for various switching power supplies, converters, inverters, etc., which are used in electronic devices and electric devices. In addition, the capacitor of the present invention can be suitably used as an inverter capacitor, a converter capacitor, etc., which control the drive motor of electric vehicles and hybrid vehicles, which have become increasingly popular in recent years. EXAMPLES

[0115] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0116] (1) Preparation of resin The weight average molecular weight (Mw), number average molecular weight (Mn), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), molecular weight distribution (Mz / Mn), differential distribution value difference (DM), mesopentad fraction (mmmm), heptane insoluble matter (HI), and melt flow rate (MFR) of the resins used in the examples and comparative examples were measured. These measured values ​​are values ​​in the form of raw resin pellets. The measurement methods are as follows.

[0117] (1-1) Measurement of weight average molecular weight (Mw), number average molecular weight (Mn), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of polypropylene resin The weight average molecular weight (Mw), number average molecular weight (Mn), z-average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of the resin were measured using GPC (gel permeation chromatography) under the following conditions.

[0118] Specifically, a high-temperature GPC device with a built-in differential refractometer (RI), HLC-8121GPC-HT model, manufactured by Tosoh Corporation, was used. Three TSKgel GMHHR-H(20)HT columns manufactured by Tosoh Corporation were used in conjunction. Measurements were performed at a column temperature of 140°C, with trichlorobenzene as the eluent flowing at a flow rate of 1.0 ml / min. A calibration curve was prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured molecular weight values ​​were converted to polystyrene values ​​to obtain the weight average molecular weight (Mw), number average molecular weight (Mn), and z-average molecular weight (Mz). The molecular weight distribution (Mw / Mn) was obtained using the values ​​of Mw and Mn. The molecular weight distribution (Mz / Mn) was also obtained using the values ​​of Mz and Mn.

[0119] (1-2) Measurement of the difference (differential distribution value difference DM) between the differential distribution value when the logarithmic molecular weight log(M) = 4.5 and the differential distribution value when the logarithmic molecular weight log(M) = 6.0 For the resin, the differential distribution value at logarithmic molecular weight log(M)=4.5 and the differential distribution value at logarithmic molecular weight log(M)=6.0 were obtained by the following method. First, the time curve (elution curve) of the intensity distribution detected by the RI detector was converted into a distribution curve for the molecular weight M (Log(M)) of the standard polystyrene using a calibration curve prepared using the above-mentioned standard polystyrene. Next, an integral distribution curve for Log(M) was obtained when the total area of ​​the distribution curve was set to 100%, and then the integral distribution curve was differentiated by Log(M) to obtain a differential distribution curve for Log(M). From this differential distribution curve, the differential distribution values ​​at Log(M)=4.5 and Log(M)=6.0 were read. The difference between the differential distribution value at Log(M)=4.5 and the differential distribution value at Log(M)=6.0 was taken as the differential distribution value difference DM. The series of operations up to obtaining the differential distribution curve were performed using the analysis software built into the GPC measurement device used.

[0120] (1-3) Measurement of mesopentad fraction ([mmmm]) The resin was dissolved in a solvent and measured using a high-temperature Fourier transform nuclear magnetic resonance spectrometer (high-temperature FT-NMR) under the following conditions. The results are shown in Table 1. High-temperature nuclear magnetic resonance (NMR) instrument: JEOL Ltd., high-temperature Fourier transform nuclear magnetic resonance instrument (high-temperature FT-NMR), JNM-ECP500 Observed nucleus: 13C (125MHz) Measurement temperature: 135℃ Solvent: ortho-dichlorobenzene (ODCB: mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4 / 1)) Measurement mode: Single pulse proton broadband decoupling Pulse width: 9.1μsec (45° pulse) Pulse interval: 5.5sec Number of times: 4,500 Shift standard: CH3(mmmm)=21.7ppm

[0121] The pentad fraction, which indicates the degree of stereoregularity, was calculated as a percentage (%) from the integral intensity of each signal derived from a combination of five pentads (pentads) consisting of meso (m) pentads arranged in the same direction and racemo (r) pentads arranged in the opposite direction (mmmm, mrrm, etc.). The assignment of each signal derived from mmmm, mrrm, etc. was based on the spectral descriptions in, for example, T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988).

[0122] (1-4) Measurement of heptane insolubles (HI) The resin was press-molded to a size of 10 mm x 35 mm x 0.3 mm and weighed approximately 3 g. Next, about 150 mL of heptane was added and Soxhlet extraction was performed for 8 hours. The heptane insoluble matter was calculated from the sample mass before and after extraction.

[0123] (1-5) Measurement of Melt Flow Rate (MFR) The melt flow rate (MFR) of the resin in the form of raw resin pellets was measured using a melt indexer manufactured by Toyo Seiki Co., Ltd. in accordance with condition M of JIS K 7210. Specifically, a sample weighed to 4 g was inserted into a cylinder with a test temperature of 230°C, and preheated for 3.5 minutes under a load of 2.16 kg. The weight of the sample extruded from the bottom hole in 30 seconds was then measured, and the MFR (g / 10 min) was calculated. The above measurement was repeated three times, and the average value was taken as the measured MFR.

[0124] (1-6) Physical properties of resin The results are shown in Table 1.

[0125] [Table 1]

[0126] (2) Preparation of metal layer integrated polypropylene film <Example 1> Polypropylene resin A and polypropylene resin B were dry blended. The mixing ratio was resin A: resin B = 65:35 by mass ratio. The dry blended resin composition was then fed to an extruder, melted at a temperature of 255 ° C, extruded using a T-die, and solidified by wrapping around a metal drum whose surface temperature was kept at 94 ° C to produce a cast raw sheet having a thickness of about 120 μm. The obtained cast raw sheet was passed through rolls with a speed difference at a temperature of 139 ° C, stretched 4.7 times in the MD direction (flow direction), and immediately cooled to room temperature (23 ° C). At this time, the nip pressure was 0.40 MPa.

[0127] Next, the film was introduced into a tenter and stretched 10 times in the TD direction (width direction) at a temperature of 163° C. to obtain a biaxially stretched polypropylene film.

[0128] Here, nip pressure refers to the pressure applied to a film when it passes between a nip roll that rotates faster (the roll located at the point where stretching in the MD direction begins) of two rolls that have a speed difference for longitudinal stretching, and the nip roll that is provided above the roll that rotates faster (the roll located at the point where stretching in the MD direction begins).

[0129] Next, a metal layer was laminated on the obtained polypropylene film using a deposition apparatus (manufactured by ULVAC, product name: roll-type vacuum deposition apparatus EWE-060) to obtain a metal layer-integrated polypropylene film.

[0130] FIG. 1 is a schematic perspective view for explaining the produced metal layer-integrated polypropylene film.

[0131] As shown in Fig. 1, the produced metal layer-integrated polypropylene film 1 has a polypropylene film 2 and a metal vapor deposition electrode 3 laminated on the polypropylene film 2 so as to leave an insulating margin 4. The metal vapor deposition electrode 3 has a metal vapor deposition layer 3a laminated on the polypropylene film 2 so as to be in direct contact with the polypropylene film 2, and an electrode lead-out portion 3b formed on part of the upper surface of the metal vapor deposition layer 3a. The electrode lead-out portion 3b is a portion known as a heavy edge.

[0132] 2 is a schematic diagram for explaining the method for producing a metal layer-integrated polypropylene film. The metal layer-integrated polypropylene film was produced by a production apparatus described below.

[0133] As shown in FIG. 2, the manufacturing apparatus for the metal layer-integrated polypropylene film includes a dielectric film supply section 101, an insulating margin forming section 102, a pattern forming section 103, a vapor deposition section 104, and a take-up roll 105.

[0134] The dielectric film supplying unit 101 supports a dielectric film roll 2R around which the polypropylene film 2 is wound, and supplies the dielectric film 2. The polypropylene film 2 supplied from the dielectric film roll 2R is transported to an insulating margin forming unit .

[0135] The insulating margin forming unit 102 applies oil in a pattern corresponding to the pattern of the insulating margin 4 to the surface 2a of the polypropylene film 2 to form an oil mask. The oil mask is intended to prevent metal particles from adhering to the portion of the metal layer-integrated polypropylene film 1 that will become the insulating margin during the vapor deposition process. The insulating margin forming unit 102 vaporizes oil stored in an oil tank and applies the oil directly to one surface 2a of the polypropylene film 2 from a nozzle (slit) provided in the tank to form an oil mask.

[0136] The pattern forming unit 103 applies oil to one surface 2a of the polypropylene film 2 in a pattern that generally corresponds to the electrode pattern of the metal deposition layer 3a, forming an oil mask. The oil mask is intended to prevent metal particles from adhering to the vertical and horizontal margins of the metal layer-integrated polypropylene film 1 during the deposition process. The pattern forming unit 103 has an oil tank 103a, an anilox roll 103b, a transfer roll 103c, a printing roll 103d, and a backup roll 103e. The oil tank 103a vaporizes the stored oil and ejects it from a nozzle. The anilox roll 103b and the transfer roll 103c rotate with the oil ejected from the nozzle of the oil tank 103a attached to their outer circumferential surfaces. The backup roll 103e faces the printing roll 103d across the polypropylene film 2, and abuts against the surface 2b of the polypropylene film 2.

[0137] The polypropylene film 2 that has passed through the insulating margin forming section 102 and the pattern forming section 103 is transported to the deposition section 104.

[0138] The deposition unit 104 includes metal vapor generating units 104a and 104b, and a cooling roll 104c facing the metal vapor generating units 104a and 104b with the polypropylene film 2 interposed therebetween. The metal vapor generating unit 104a generates metal vapor by supplying a current to a wire made of metal (aluminum), which is the material of the metal vapor deposition layer 3a, onto a heated boat, and deposits the metal vapor on the surface 2a of the polypropylene film 2. The metal vapor generating unit 104b heats and evaporates the metal (aluminum), which is the material of the electrode extraction unit 3b, to generate metal vapor, which is deposited on the metal vapor deposition layer 3a previously formed on the surface 2a of the polypropylene film 2 by the metal vapor generating unit 104a. As a result, the metal vapor deposition layer on the electrode extraction unit 3b becomes thicker than the metal vapor deposition layer on the other parts, forming a heavy edge structure. The metal vapor generated by the metal vapor generating units 104a and 104b adheres to the parts of the polypropylene film 2 other than the oil mask formed on the surface 2a of the polypropylene film 2, forming the metal vapor deposition electrode 3. The cooling roll 104c comes into contact with the polypropylene film 2 to cool it.

[0139] The temperature of the metal vapor increases according to the amount of current (energy flow) passed through it.

[0140] The thickness of the metal deposition layer 3a is controlled by the film resistance (resistance per unit area). Since the resistance is inversely proportional to the thickness, the lower the film resistance, the thicker the film thickness.

[0141] Metal layer-integrated polypropylene film 1, which is formed by forming metal vapor deposition electrode 3 on polypropylene film 2 in vapor deposition section 104, is transported to take-up roll 105 and taken up.

[0142] Using the above manufacturing apparatus, a metal vapor deposition electrode was formed on one surface of a polypropylene film to obtain a metal layer-integrated polypropylene film. In this example, in the manufacturing apparatus for a metal layer-integrated polypropylene film, the temperature of the cooling roll 104c was -18°C, and the supply speed of the aluminum wire (diameter 1.3 mm) in the metal vapor generating section 104a was 370 mm / min.

[0143] <Example 2> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 1, except that instead of the resin composition having a mixing ratio of resin A:resin B = 65:35 by mass, resin C:resin D = 65:35 was used and the stretching ratio in the MD direction (machine direction) of the cast raw sheet was changed to 4.5 times.

[0144] <Example 3> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 2, except that the stretching ratio in the MD direction (machine direction) of the cast raw sheet was changed to 4.3 times.

[0145] <Comparative Example 1> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 2, except that the stretching ratio in the MD direction (machine direction) of the cast raw sheet was changed to 5.0 times.

[0146] <Comparative Example 2> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 2, except that the stretch ratio in the MD direction (machine direction) of the cast raw sheet was changed to 4.3 times and the temperature of the cooling roll 104c was changed to -24°C.

[0147] <Comparative Example 3> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 2, except that the stretch ratio in the MD direction (machine direction) of the cast raw sheet was changed to 4.5 times, the temperature of the cooling roll 104c was changed to -24°C, and the supply speed of the aluminum wire in the metal vapor generation section 104a was changed to 460 mm / min.

[0148] <Comparative Example 4> A polypropylene film and a metal layer integrated polypropylene film were obtained in the same manner as in Example 2, except that the stretch ratio in the MD direction (machine direction) of the cast raw sheet was changed to 4.3 times, the temperature of the cooling roll 104c was changed to -24°C, and the supply speed of the aluminum wire in the metal vapor generating section 104a was changed to 460 mm / min.

[0149] (3) Making the capacitor The metal layer-integrated polypropylene film prepared in the examples and comparative examples was slit to a width of 30 mm. Next, two sheets of the metal layer-integrated polypropylene film were laminated together. Using an automatic winding machine 3KAW-N2 manufactured by Kaito Seisakusho Co., Ltd., the laminated metal layer-integrated polypropylene film was wound 1350 turns at a winding tension of 176 g, a contact pressure of 255 g, and a winding speed of 4 m / s. The wound element was heat-treated at 120°C for 15 hours while being pressed with a load of 5.9 kg / cm2. Then, zinc metal was sprayed on the element end surface. The spraying conditions were a feed speed of 20 mm / s, a spraying voltage of 22 V, and a spraying pressure of 0.4 MPa, and the spraying was performed to a thickness of 0.7 mm. In this way, a flat capacitor was obtained. Lead wires were soldered to the end surface of the flat capacitor. Then, the flat capacitor was sealed with epoxy resin. The epoxy resin was cured by heating at 90° C. for 2.5 hours and then at 120° C. for another 2.5 hours. The capacitance of the resulting capacitor was 50 μF.

[0150] (4) Measurement and evaluation methods The polypropylene films, metal layer-integrated polypropylene films, and capacitors obtained in the examples and comparative examples were subjected to various measurements and evaluations by the following methods.

[0151] (4-1) Film thickness measurement The thicknesses of the polypropylene film and the metal layer-integrated polypropylene film were measured in accordance with JIS-C2330, except that they were measured at 100±10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu Co., Ltd.

[0152] (4-2) Measurement of elastic modulus The elastic modulus of the polypropylene film and the metal layer integrated polypropylene film was measured in accordance with JIS K 7127:1999. Specifically, a rectangular sample with a length of 150 mm and a width of 10 mm was cut out from each film. At this time, the sample was cut out so that the MD direction was the length direction. The sample was set in the chuck of a tensile tester (Tensilon universal tester RTG-1210 manufactured by A&D Co., Ltd.) with a chuck distance of 50 mm, and then a tensile test was performed at a test speed of 300 mm / min. The temperature during the tensile test was 23°C. The elastic modulus (GPa) was calculated by dividing the load value at the time of sample destruction in the tensile test by the cross-sectional area of ​​the sample before the tensile test (thickness x width of the sample before the tensile test, 10 mm). The tensile test was performed five times, and the average value was taken as the elastic modulus (GPa).

[0153] (4-3) Measurement of surface protrusion height (Rpk) The protruding peak height (Rpk) on the metal layer side surface of the metal layer-integrated polypropylene film was measured by the following measurement method. That is, a "VertScan2.0 (model: R5500GML)" manufactured by Ryoka Systems Co., Ltd. was used as an optical interference type non-contact surface shape measuring instrument. As a measurement sample, the metal layer-integrated polypropylene film was cut into an arbitrary size of about 20 cm in the flow direction, and in a state where wrinkles were sufficiently smoothed out, it was set on the measurement stage using an electrostatic contact plate or the like.

[0154] The measurements were performed in WAVE mode, with a 530 white filter and a 1x BODY lens barrel, and a 10x objective lens, measuring one field of view (353.16μm×470.92μm). This operation was performed at 10 points at 1cm intervals in the flow direction from the center in both the flow direction and width direction on the surface of the measurement sample.

[0155] Next, the obtained data was subjected to noise removal processing using a median filter (3 × 3), and then to Gaussian filter processing with a cutoff value of 30 μm to remove waviness components, making it possible to properly measure the surface condition.

[0156] Next, analysis was performed using the "ISO parameters" in the "Bearing" plug-in function of the "VS-Viewer" analysis software for "VertScan2.0" to determine Rpk, and the average value of the values ​​obtained at the above 10 locations was calculated to determine the protruding peak height (Rpk) on the metal layer side surface of the metal layer-integrated polypropylene film.

[0157] (4-4) Measurement of membrane resistance Measurements were taken by placing the probe on the metal layer-integrated polypropylene film using a low-resistance resistivity meter Loresta GX MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd. Measurements were taken at the active area near the center of the film width, and the average value of five points was taken as the film resistance.

[0158] (4-5) Measurement of capacitance change rate The initial capacitance of the capacitor before the test was measured using an LCR HiTester 3522-50 manufactured by Hioki E.E. Corporation. Next, a DC voltage of 1000V was applied to the capacitor at room temperature for 10 seconds. The capacitance of the capacitor after the voltage application was similarly measured, and the rate of change in capacitance before and after the test was calculated using the following formula: (rate of change in capacitance)=[(capacitance after voltage application)-(initial capacitance)] / (initial capacitance)×100(%).

[0159] (4-6) Voltage resistance measurement (4-6-1) Test 1 (Step-up test) The voltage resistance of the capacitor was measured by a voltage step-up test. Specifically, it was measured as follows. The obtained capacitor was placed in a thermostatic chamber and preheated to 105°C, then removed from the thermostatic chamber, and the capacitance was measured using a LCR high tester 3522-50 manufactured by HIOKI EE Corporation (initial capacitance). Next, a DC voltage of 600V was applied to the capacitor for 1 hour in a thermostatic chamber at 105°C. The capacitor after the voltage application was removed from the thermostatic chamber, and the capacitance was measured in the same manner, and the capacitance change rate before and after the test was calculated by the following formula: (change rate of capacitance) = [(capacitance after voltage application) - (initial capacitance)] / (initial capacitance) x 100 (%). Next, the capacitor was returned to the thermostatic chamber again, and a DC voltage of 650V was applied for 1 hour, and the capacitance was measured in the same manner. The voltage was increased by 50V at a time, and this operation was repeated until the capacitance change rate became -10%, and the voltage was applied cumulatively. The voltage at which the capacitance change rate reached -10% was divided by the thickness of the metal layer-integrated polypropylene film to determine the voltage resistance. The test was performed on two samples, and the average value was used for evaluation.

[0160] (4-6-2) Test 2 (Short-time pressure test) The voltage resistance of the capacitor was measured by a short-time voltage resistance test. Specifically, it was measured as follows. The initial capacitance of the obtained capacitor before the test was measured using an LCR high tester 3522-50 manufactured by Hioki E.E. Corporation. Next, a direct current voltage of 1000 V was applied to the capacitor at room temperature for 10 seconds. The capacitance of the capacitor after the voltage application was measured in the same manner, and the capacitance change rate before and after the test was calculated by the following formula: (change rate of capacitance) = [(capacitance after voltage application) - (initial capacitance)] / (initial capacitance) x 100 (%). Next, a direct current voltage of 1050 V was applied for 10 seconds, and the capacitance was measured in the same manner. The voltage was increased by 50 V at a time, and this operation was repeated until the capacitance change rate became -2%, and the voltage was applied cumulatively. The voltage when the capacitance change rate became -2% was divided by the thickness of the metal layer integrated polypropylene film prepared to obtain the voltage resistance. The test was performed on two samples, and the average value was used for evaluation.

[0161] (4-7) Evaluation of processability (degree of buckling and wrinkling on the end faces of the capacitor element) The shape stability of the end faces of the capacitor was evaluated (visual evaluation) according to the following criteria: ○: Almost no buckling or wrinkles. ×: Many buckling and wrinkles.

[0162] (5) Measurement and evaluation results The results are shown in Table 2. In Table 2, PP film indicates a polypropylene film, and MF indicates a metal layer-integrated polypropylene film.

[0163] [Table 2] [Explanation of symbols]

[0164] 1. Polypropylene film with metal layer 2 Polypropylene film 3 Metal evaporated electrode 3a Metal deposited layer 3b Electrode extraction part 4. Isolation Margin

Claims

1. A metal layer-integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, The metal layer-integrated polypropylene film has a tensile modulus (elastic modulus A) in a first direction of 3.27 to 3.80 GPa; The elastic modulus A is a value measured by the following method. , Polypropylene film with integrated metal layer. (Method of measuring elastic modulus A) The elastic modulus A is measured in accordance with JIS K 7127:1999 as follows. A rectangular sample having a length of 150 mm and a width of 10 mm is cut out from the metal layer-integrated polypropylene film. At this time, the sample is cut out so that the first direction is the length direction. The sample is set in the chuck of a tensile tester (Tensilon universal tester RTG-1210 manufactured by A&D Co., Ltd.) with a chuck distance of 50 mm, and a tensile test is performed at a test speed of 300 mm / min. The temperature during the tensile test is 23°C. The elastic modulus (unit: GPa) is calculated by dividing the load value at the time of sample destruction in the tensile test by the cross-sectional area of ​​the sample before the tensile test (thickness x width of the sample before the tensile test: 10 mm). The tensile test is performed five times, and the average value is taken as the elastic modulus A (GPa).

2. The metal layer-integrated polypropylene film according to claim 1, wherein the tensile modulus of elasticity (elastic modulus B) in the first direction of the polypropylene film is 2.70 to 3.30 GPa, and the elastic modulus B is a value measured by the following method. (Method of measuring elastic modulus B) The elastic modulus B is measured in accordance with JIS K 7127:1999 as follows. A rectangular sample having a length of 150 mm and a width of 10 mm is cut out from the polypropylene film. At this time, the sample is cut out so that the first direction is the length direction. The sample is set in the chuck of a tensile tester (Tensilon universal tester RTG-1210 manufactured by A&D Co., Ltd.) with a chuck distance of 50 mm, and a tensile test is performed at a test speed of 300 mm / min. The temperature during the tensile test is 23°C. The elastic modulus (unit: GPa) is calculated by dividing the load value at the time of sample destruction in the tensile test by the cross-sectional area of ​​the sample before the tensile test (thickness x width of the sample before the tensile test: 10 mm). The tensile test is performed five times, and the average value is taken as the elastic modulus B (GPa).

3. The metal layer-integrated polypropylene film according to claim 1 or 2, wherein the protrusion height (Rpk) on the metal layer side surface is 0.050 to 0.078 μm.

4. The metal layer-integrated polypropylene film according to any one of claims 1 to 3, having a film resistance of 1 to 25 Ω / sq.

5. The metal layer-integrated polypropylene film according to any one of claims 1 to 4, wherein the elastic modulus A is 3.28 to 3.60 GPa.

6. The metal layer-integrated polypropylene film according to any one of claims 1 to 5, wherein the protrusion height (Rpk) on the metal layer side surface is 0.059 to 0.078 μm.

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

8. The metal layer-integrated polypropylene film according to any one of claims 1 to 7, wherein the polypropylene film has a thickness of 0.8 to 3.5 µm.

9. The metal layer-integrated polypropylene film according to any one of claims 1 to 8, wherein the polypropylene film is a single layer film.

10. The metal layer-integrated polypropylene film according to any one of claims 1 to 9, which is for a capacitor.

11. A capacitor comprising the metal layer-integrated polypropylene film according to any one of claims 1 to 10.

12. The capacitor according to claim 11, comprising a roll of the metal layer-integrated polypropylene film according to any one of claims 1 to 10.

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