Metal layer-integrated polypropylene film, film capacitor, and method for producing metal layer-integrated polypropylene film

Abstract

To provide a metal layer-integrated polypropylene film capable of imparting short-circuit resistant properties to a film capacitor even when high voltage is applied at a temperature of 100°C or higher.SOLUTION: Provided is a metal layer-integrated polypropylene film with a polypropylene film and a metal layer laminated on one or both surfaces of the polypropylene film. The metal layer-integrated polypropylene film, which, when subjected to a static load of 2 MPa in a machine direction (MD) and heated at a temperature ramp rate of 10°C per minute from 25°C, for an elongation rate at 25°C of 0%, exhibits an elongation rate at 100°C of 0% or more and 1.8% or less, an elongation rate at 120°C of 0% or more and 2.3% or less, and an elongation rate at 130°C of 0% or more and 2.7% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a metal layer integrated polypropylene film, a film capacitor, and a method for manufacturing a metal layer integrated polypropylene film.

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, biaxially oriented polypropylene films have the property of thermal shrinkage. For example, as in Patent Document 1, in order to reduce the thermal shrinkage rate of the polypropylene film before laminating the metal layer, it is necessary to select a raw material resin that can produce a polypropylene film that hardly shrinks thermally. There is a problem that the range of selection of the raw material resin becomes narrow.

[0005] In addition, in order to obtain a polypropylene film with a low heat shrinkage rate (the polypropylene film before laminating the metal layer), its manufacturing conditions, for example, the manufacturing conditions of the cast sheet (for example, the melting temperature of the raw material resin, the casting temperature, etc.), and the stretching treatment conditions when stretching the cast sheet to form a polypropylene film (for example, the temperature during stretching, the stretching ratio, the nip pressure, etc.) become very limited, and it may be difficult to balance with other qualities (for example, electrical properties such as dielectric breakdown strength). Also, the selection of the raw material resin to reduce the heat shrinkage rate of the polypropylene film may also sacrifice other properties (for example, withstand voltage properties, etc.).

[0006] In addition, Patent Document 2 discloses a technique for suppressing the peeling of a metallicon electrode by setting the heat shrinkage rate of the polypropylene film before laminating the metal layer and the heat shrinkage rate of the metal layer-integrated polypropylene film after laminating the metal layer within a predetermined range.

[0007] On the other hand, as a result of the inventor's study, in the process of manufacturing the capacitor using the polypropylene film, in the process of forming the metal layer, and subsequent winding process, aging process, metallicon spraying process, etc., a certain amount of heat history is applied to the polypropylene film. Therefore, even if the heat shrinkage rate of the polypropylene film is reduced, when a film capacitor is formed using the obtained metal layer-integrated polypropylene film and the film capacitor is exposed to a high-temperature atmosphere, the element shape changes, the gap between the winding layers changes, or the distortion and wrinkles of the flat curve portion of the element occur, resulting in a problem that the withstand voltage and insulation properties are likely to decrease, and a short circuit is likely to occur when a high voltage is applied. The inventor focused on the elongation rate of the metal layer-integrated polypropylene film at high temperatures and tried to obtain a film with stable thermo-mechanical properties by applying heat (heat history) equal to or greater than that of the subsequent process (aging process) to the metallized film after the vapor deposition process in advance.

[0008] Under such circumstances, the main object of the present invention is to provide a metal layer integrated polypropylene film that can endow a film capacitor with the property of not short-circuiting even when a high voltage is applied at a high temperature of 100 °C or higher.

Means for Solving the Problems

[0009] The inventors of the present invention conducted intensive studies to solve the above problems. As a result, in a metal layer integrated polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, when heated at a temperature increase rate of 10 °C / min from 25 °C with a static load of 2 MPa applied in the MD direction, it was found that by setting the elongation rates at 100 °C, 120 °C, and 130 °C within specific ranges of 0% or more respectively, a film capacitor having high withstand voltage and high insulation properties in a high-temperature atmosphere can be obtained. That is, in the present invention, it was found that the above problems can be solved by setting the elongation rate within a predetermined range of 0% or more (i.e., not thermally shrinking), rather than the thermal shrinkage described in Patent Document 2. The present invention was completed by further studies based on such findings.

[0010] That is, the present invention includes the following. 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, When the metal layer integrated polypropylene film is heated at a temperature increase rate of 10 °C / min from 25 °C with a static load of 2 MPa applied in the MD direction, if the elongation rate at 25 °C is 0%, the elongation rate at 100 °C is 0% or more and 1.8% or less, the elongation rate at 120 °C is 0% or more and 2.3% or less, and the elongation rate at 130 °C is 0% or more and 2.7% or less. A metal layer integrated polypropylene film. Item 2. The metal layer integral polypropylene film according to Item 1, wherein when heated at a temperature rising rate of 10°C / min from 25°C while applying a static load of 2 MPa in the MD direction, the elongation gradient from 30°C to 100°C is 0.010% / °C or more and 0.030% / °C or less. Item 3. The metal layer integral polypropylene film according to Item 1 or 2, wherein in a graph showing the relationship between temperature and elongation rate obtained by heating the metal layer integral polypropylene film at a temperature rising rate of 10°C / min from 25°C while applying a static load of 2 MPa in the MD direction, the temperature of the inflection point is 130°C or more. Item 4. The metal layer integral polypropylene film according to any one of Items 1 to 3, having a thickness of 0.8 μm or more and 3.5 μm or less. Item 5. The metal layer integral polypropylene film according to any one of Items 1 to 4, which is for a capacitor. Item 6. A film capacitor having the wound metal layer integral polypropylene film according to any one of Items 1 to 5, or having a configuration in which a plurality of the metal layer integral polypropylene films according to any one of Items 1 to 5 are laminated. Item 7. A method for manufacturing a metal layer integral polypropylene film having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, comprising: a metal layer laminating step of laminating a metal layer on one or both sides of the polypropylene film to obtain a metal layer integral polypropylene film; a heating step of heating the metal layer integral polypropylene film obtained in the metal layer laminating step at a temperature of 100°C or more and 130°C or less. The method for manufacturing a metal layer integral polypropylene film, comprising the above steps.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a metal layer integrated polypropylene film that can impart to a film capacitor the property of not short-circuiting even when a high voltage is applied under a high temperature of 100°C or higher. Further, according to the present invention, it is possible to provide a film capacitor using the metal layer integrated polypropylene film and the metal layer integrated polypropylene film.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] The metal layer integrated polypropylene film according to the present embodiment is 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 according to the present embodiment, when heated at a temperature rising rate of 10°C / min from 25°C in a state where a static load of 2 MPa is applied in the MD (Machine Direction) direction (also referred to as the flow direction or the longitudinal direction), assuming that the elongation rate at 25°C is 0%, the elongation rate at 100°C is 0% or more and 1.8% or less, the elongation rate at 120°C is 0% or more and 2.3% or less, and the elongation rate at 130°C is 0% or more and 2.7% or less. By having such characteristics, the metal layer integrated polypropylene film according to the present embodiment can impart to the film capacitor the property of not short-circuiting even when a high voltage is applied under a high temperature of 100°C or higher when a film capacitor is formed using the metal layer integrated polypropylene film. Hereinafter, the metal layer integrated polypropylene film according to the present embodiment will be described in detail.

[0014] In this specification, "~" in a numerical range means "or more" and "or less". That is, the notation α~β means α or more and β or less, or β or more and α or less, and includes α and β as the range.

[0015] Also, in this specification, a metallized electrode refers to an external electrode provided on the side surface where a metal layer-integrated polypropylene film is laminated and electrically connected to the metal layer as an internal electrode.

[0016] As described above, when the metal layer-integrated polypropylene film according to this embodiment is heated at a temperature increase rate of 10 °C / min from 25 °C under a static load of 2 MPa in the MD direction, if the elongation rate at 25 °C is set to 0%, the elongation rate at 100 °C is 0% or more and 1.8% or less, the elongation rate at 120 °C is 0% or more and 2.3% or less, and the elongation rate at 130 °C is set to 0% or more and 2.7% or less. That is, in the metal layer-integrated polypropylene film according to this embodiment, it is not the characteristics of the polypropylene film before forming the metal layer in a high-temperature environment, but the elongation rate of the metal layer-integrated polypropylene film in which the metal layer is formed on the polypropylene film in a high-temperature environment (100 °C, 120 °C, and 130 °C) is set within a specific range of 0% or more. Since the elongation rate is 0% or more, the metal layer-integrated polypropylene film according to this embodiment does not thermally contract in a high-temperature environment. The film capacitor formed from the metal layer-integrated polypropylene film is less likely to undergo thermal changes such as thermal elongation / contraction in the capacitor winding direction (corresponding to the MD of the film) even when exposed to a high-temperature environment. As a result, the gap between the winding layers does not change, and in a flat-type element, the distortion and wrinkles of the flat curved portion disappear. Therefore, even when a high voltage is applied in a high-temperature environment, the capacitor is less likely to be short-circuited and damaged.

[0017] In the metal layer-integrated polypropylene film of this embodiment, in order to provide the elongation rate at each of the above temperatures, for example, it is preferable to adopt a method of heat-treating the metal layer-integrated polypropylene film under predetermined conditions, such as the manufacturing method described later. The specific method of heat treatment will be described in detail in the section on the manufacturing method of the metal layer-integrated polypropylene film described later.

[0018] From the viewpoint of more preferably exhibiting the effects of the present invention, the elongation rate at 100°C is preferably 0 to 1.7%, more preferably 0 to 1.5%, and still more preferably 0 to 1%. Further, the elongation rate at 120°C is preferably 0 to 2.2%, more preferably 0 to 2%, and still more preferably 0 to 1.9%. Further, the elongation rate at 130°C is preferably 0 to 2.6%, more preferably 0 to 2.5%, and still more preferably 0 to 2.4%.

[0019] <Relationship between Temperature and Elongation Rate of Metal Layer-Integrated Polypropylene Film> The expansion and contraction rates at these respective temperatures are values measured by using a thermo-mechanical analyzer (TMA), applying a static load of 2 MPa in the MD direction to the metal layer-integrated polypropylene film, heating it at a temperature increase rate of 10°C / min from 25°C, and obtaining a graph showing the relationship between temperature and elongation rate. More specifically, it is based on the method described in the examples.

[0020] Further, from the viewpoint of more preferably exhibiting the effects of the present invention, when the metal layer-integrated polypropylene film of the present embodiment is heated at a temperature increase rate of 10°C / min from 25°C while a static load of 2 MPa is applied in the MD direction, the elongation gradient (i.e., the average coefficient of linear expansion) from 30°C to 100°C is preferably 0.010 to 0.030% / °C, more preferably 0.020 to 0.025. The elongation gradient can be specified based on the graph obtained by the method described in the <Relationship between Temperature and Elongation Rate of Metal Layer-Integrated Polypropylene Film>.

[0021] Further, from the viewpoint of more preferably exerting the effects of the present invention, in a graph showing the relationship between temperature and elongation rate obtained by heating the metal layer-integrated polypropylene film of the present embodiment under a static load of 2 MPa at a temperature increase rate of 10 °C / min from 25 °C, the temperature at the inflection point is preferably 130 °C or higher, more preferably 140 °C or higher. The temperature at the inflection point is, for example, 160 °C or lower, 150 °C or lower. The inflection point can be specified based on the graph obtained by the method described in <Relationship between temperature and elongation rate of the metal layer-integrated polypropylene film>. Note that the inflection point means the inflection point that first appears from the temperature increase start temperature of 25 °C in the above graph. That is, there is no inflection point on the lower temperature side than the inflection point.

[0022] In the present embodiment, the thickness of the metal layer-integrated polypropylene film is preferably 0.8 μm or more, more preferably 1.2 μm or more, still more preferably 1.5 μm or more, still more preferably 1.6 μm or more, still more preferably 1.7 μm or more, and particularly preferably 1.8 m or more. Further, the thickness of the polypropylene film is preferably 3.5 μm or less, more preferably 3.0 μm or less, still more preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

[0023] The thickness of the metal layer-integrated polypropylene film refers to the value measured in accordance with JIS-C2330, except that it is measured at 100 ± 10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu Co., Ltd. More specifically, it is based on the method described in the examples.

[0024] Hereinafter, the polypropylene film included in the metal layer-integrated polypropylene film as a product after laminating the metal layer will be described. That is, hereinafter, when referring to the "polypropylene film" without particularly specifying whether it is before laminating the metal layer or after laminating the metal layer, it will be described as meaning the polypropylene film after laminating the metal layer unless otherwise specified.

[0025] The thickness of the polypropylene film is preferably 0.8 μm or more, more preferably 1.2 μm or more, still more preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. Also, the thickness of the polypropylene film is preferably 3.5 μm or less, more preferably 3.0 μm or less, still more preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

[0026] When the thickness of the polypropylene film is 3.0 μm or less, the capacitance per unit volume when used as a capacitor element can be increased, so it can be suitably used as a capacitor. Also, from the viewpoints of film formation stability and process passability (handleability) of the film, the thickness of the polypropylene film can be 0.8 μm or more. This point will be described in detail below.

[0027] The thinner the polypropylene film, the greater the capacitance per unit volume. More specifically, the capacitance C is expressed as follows using the dielectric constant ε, the electrode area S, and the dielectric thickness d (the thickness d of the polypropylene film). C = εS / d Here, in the case of a film capacitor, since the thickness of the electrode is three digits or more thinner than the thickness of the polypropylene film (dielectric), ignoring the volume of the electrode, the volume V of the capacitor is expressed as follows. V = Sd Therefore, from the above two equations, the capacitance per unit volume C / V is expressed as follows. C / V = ε / d 2 As can be seen from the above equation, 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. Then, it can be understood that unless the material is changed, the capacitance per unit volume (C / V) cannot be improved other than by reducing the thickness. Note that the electrode area does not affect the capacitance per unit volume (C / V). This point will be explained below.

[0028] Assume a case where a capacitor is fabricated by winding films of the same material and the same thickness. For example, suppose the number of turns (winding number) is increased and it is wound 10 times longer (the electrode area is 10 times larger). Then, the capacitance becomes 10 times, but the volume also becomes 10 times, so the capacitance per unit volume (C / V) does not change even if the electrode area changes. The above description is idealized for ease of understanding. That is, in reality, for example, there may be a slight gap between the films, or there may be an influence of the fringe effect at the electrode ends, etc., so there may be some change in the value of the capacitance per unit volume (C / V) according to the area. However, generally, it can be understood that the capacitance per unit volume (C / V) is determined by the thickness of the polypropylene film.

[0029] From the above, it is preferable that the thickness of the polypropylene film is as thin as possible within the range where insulation and / or breakdown voltage are ensured. Therefore, the thickness of the polypropylene film is preferably 3.0 μm or less. On the other hand, when the thickness of the polypropylene film becomes thin, the handleability becomes extremely poor, so the film formation and the capacitor fabrication work become extremely difficult, and the process passability tends to deteriorate. Furthermore, because it is thin, tearing (breaking), etc. may occur even in the film formation process, and the film formation tends to become unstable. Therefore, the thickness of the polypropylene film is preferably 0.8 μm or more.

[0030] The thickness of the polypropylene film in the present invention and in this specification is defined as being 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. The thickness of the metal layer in the metal layer-integrated polypropylene film 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 and the thickness of the polypropylene film show values of the same degree by the measurement method described in this example.

[0031] The polypropylene film is a biaxially stretched film. There are simultaneous biaxial stretching, sequential biaxial stretching, etc. for biaxial stretching, and any of them is acceptable. By subjecting the polypropylene film to biaxial stretching, the molecules are extremely strongly oriented, and various physical properties such as mechanical properties, thermal properties, and electrical properties are improved and / or stabilized, making it preferably used for industrial applications. However, on the other hand, when the biaxially stretched film is exposed to a certain amount of heat (high temperature), an action occurs where the orientation relaxes and tries to return to an unoriented state, resulting in so-called (thermal) shrinkage.

[0032] The polypropylene film preferably has a planar orientation coefficient ΔP of 0.010 to 0.016, more preferably 0.011 to 0.0155, and even more preferably 0.0115 to 0.015.

[0033] It is preferable that the planar orientation coefficient ΔP of the polypropylene film is within the above range because it can further reduce dielectric breakdown under high temperature and high voltage.

[0034] <Planar orientation coefficient ΔP> In this specification, the "planar orientation coefficient ΔP" refers to the planar orientation coefficient ΔP calculated from the values of the birefringence values ΔNyz and ΔNxz with respect to the thickness direction of the polypropylene film obtained by optical birefringence measurement (however, ΔP = (ΔNyz + ΔNxz) / 2). In this specification, the "birefringence value ΔNyz with respect to the thickness direction of the polypropylene film" refers to the birefringence value ΔNyz with respect to the thickness direction obtained by optical birefringence measurement. More specifically, taking the main axes in the in-plane direction of the film as the x-axis and y-axis, and the thickness direction of the film (the normal direction with respect to the in-plane direction) as the z-axis, and setting the slow axis in the direction with a higher refractive index in the in-plane direction as the x-axis, the value obtained by subtracting the three-dimensional refractive index in the z-axis direction from the three-dimensional refractive index in the y-axis direction is the birefringence value ΔNyz.

[0035] In addition, in this specification, the "birefringence value ΔNxz" with respect to the thickness direction of the polypropylene film refers to the birefringence value ΔNxz with respect to the thickness direction obtained by optical birefringence measurement. More specifically, the value obtained by subtracting the three-dimensional refractive index in the z-axis direction from the three-dimensional refractive index in the x-axis (slow axis) direction is the birefringence value ΔNxz.

[0036] In this embodiment, in order to measure the "birefringence value ΔNyz" with respect to the thickness direction of the polypropylene film, specifically, a retardation measuring device RE-100 manufactured by Otsuka Electronics Co., Ltd. is used. The measurement of retardation (phase difference) is performed using the tilt method. More specifically, the main axes in the in-plane direction of the film are the x-axis and the y-axis, and the thickness direction of the film (the normal direction with respect to the in-plane direction) is the z-axis. Among the in-plane directions, the slow axis in the direction with a higher refractive index is set as the x-axis. With the x-axis as the tilt axis, each retardation value is obtained when the film is tilted by 10° with respect to the z-axis in the range of 0° to 50°. From the obtained retardation values, the birefringence ΔNyz in the y-axis direction with respect to the thickness direction (z-axis direction) is calculated using the method described in the non-patent document "Hiroshi Awaya, Introduction to Polarizing Microscopy of Polymer Materials, pages 105 to 120, 2001". First, for each tilt angle φ, R / d is obtained by dividing the measured retardation value R by the thickness d corrected for tilt. For each R / d at φ = 10°, 20°, 30°, 40°, 50°, the difference from R / d at φ = 0° is obtained, and the result of dividing these differences by sin2r (r: refractive angle) is taken as the birefringence ΔNzy at each φ, and the sign is reversed to obtain the birefringence value ΔNyz. The birefringence value ΔNyz is calculated as the average value of ΔNyz at φ = 20°, 30°, 40°, 50°. For example, in the sequential stretching method, when the stretching ratio in the TD direction (width direction) is higher than the stretching ratio in the MD direction (flow direction), the TD direction becomes the slow axis (x-axis), and the MD direction becomes the y-axis. Also, when using polypropylene, the value of the refractive angle r at each tilt angle for polypropylene is the one described on page 109 of the above-mentioned document.

[0037] Further, in the present embodiment, the "birefringence value ΔNxz" in the thickness direction of the polypropylene film is calculated by dividing the retardation value R measured at an inclination angle φ = 0° by the thickness d, then dividing by the previously obtained ΔNzy to calculate the birefringence value ΔNxz.

[0038] The polypropylene film contains a polypropylene resin, and its constituent materials are not particularly limited.

[0039] 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 (when the entire polypropylene film is 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. The polypropylene resin may contain a single type of polypropylene resin alone or may contain two or more types of polypropylene resins. The polypropylene resin is preferably a homopolypropylene resin.

[0040] Here, when the polypropylene film contains two or more types of polypropylene resins, the polypropylene resin with the higher content is referred to as the "main component polypropylene resin" in this specification. When the polypropylene film contains only one type of polypropylene resin, that polypropylene resin is referred to as the "main component polypropylene resin" in this specification.

[0041] Hereinafter, in this specification, when "polypropylene resin" is mentioned without specifically stating whether it is the main component or not, unless otherwise specified, it means both the polypropylene resin as the main component and the polypropylene resin other than the main component. 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 both 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.

[0042] The weight average molecular weight Mw of the polypropylene resin is preferably 250,000 or more and 450,000 or less, more preferably 250,000 or more and 400,000 or less. When the weight average molecular weight Mw of the polypropylene resin is 250,000 or more and 450,000 or less, the resin fluidity becomes appropriate. As a result, it is easy to control the thickness of the cast base sheet, and it becomes easy to produce a thin stretched film with good thickness uniformity. Also, from the viewpoints of the mechanical properties, thermo-mechanical properties, stretch formability, etc. of the biaxially stretched polypropylene film, the weight average molecular weight Mw is preferably 250,000 or more and 450,000 or less. When two or more kinds of polypropylene resins are used, it is preferable to use in combination a polypropylene resin having the above Mw of less than 330,000 and a polypropylene resin having the above Mw of 330,000 or more and 450,000 or less. 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. 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 1,700,000 or less.

[0043] The molecular weight distribution [(weight average molecular weight Mw) / (number average molecular weight Mn)] of the polypropylene resin is preferably 5 or more and 12 or less, more preferably 5 or more and 11 or less, and even more preferably 5 or more and 10 or less. When the molecular weight distribution [(weight average molecular weight Mw) / (number average molecular weight Mn)] of the polypropylene resin is 5 or more and 12 or less, appropriate resin fluidity can be obtained during biaxial stretching, and it is easy to obtain an extremely thin biaxially stretched propylene film without thickness unevenness, which is preferable. 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, and even more preferably 15 or more and 50 or less.

[0044] 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) apparatus. More specifically, they are values measured using the HLC-8121GPC-HT (trade name), a high-temperature GPC measuring machine with a built-in differential refractometer (RI), manufactured by Tosoh Corporation. 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 flowed as the eluent at a flow rate of 1.0 ml / 10 minutes to obtain measured values of Mw and Mn. A calibration curve regarding its molecular weight M is created using standard polystyrene manufactured by Tosoh Corporation, and the measured values are converted to polystyrene values to obtain Mw, Mn, and Mz. Here, the logarithm of the bottom 10 of the molecular weight M of the standard polystyrene is referred to as the logarithmic molecular weight (“Log(M)”).

[0045] In the differential molecular weight distribution curve of the polypropylene resin, the difference obtained by subtracting the differential distribution value at Log(M) = 6.0 from the differential distribution value at Log(M) = 4.5 (hereinafter, also referred to as “differential distribution value difference D M ”) is preferably -5% or more and 14% or less. , more preferably -4% or more and 12% or less, still more preferably -4% or more and 10% or less. In addition, "the difference obtained by subtracting the differential distribution value at Log(M) = 6.0 from the differential distribution value at Log(M) = 4.5 (differential distribution value difference D M ) is -5% or more and 14% or less " means that, when comparing the component with Log(M) = 4.5, which is a representative distribution value of the component with a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter also referred to as "low molecular weight component"), with the component around Log(M) = 6.0, which is a representative distribution value of the component around a molecular weight of 1,000,000 on the high molecular weight side (hereinafter also referred to as "high molecular weight component"), from the value of Mw of the polypropylene resin, it can be understood that when the difference is positive, there are more low molecular weight components, and when the difference is negative, there are more high molecular weight components.

[0046] That is, for example, when taking the case where the molecular weight distribution Mw / Mn is 5 to 12 as an example, simply stating that the molecular weight distribution Mw / Mn is 5 to 12 only represents the width of the molecular weight distribution, and the quantitative relationship between the high molecular weight component and the low molecular weight component therein is not known. Therefore, from the viewpoints of resin fluidity, stretch moldability, and thickness uniformity, it is preferable to use a polypropylene resin such that the differential distribution value difference between the component with a molecular weight of 10,000 to 100,000 and the component with a molecular weight of 1,000,000 is -5% or more and 14% or less.

[0047] The differential distribution value is a value obtained as follows using GPC. A curve showing the intensity against time (generally also referred to as an "elution curve") obtained by a differential refractive index (RI) detector of GPC is used. By using a calibration curve obtained using standard polystyrene and converting the time axis to logarithmic molecular weight (Log(M)), the elution curve is converted into a curve showing the intensity against Log(M). Since the RI detection intensity is proportional to the component concentration, when the total area of the curve showing the intensity is set to 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 with respect to Log(M). Therefore, "differential distribution" means the differential distribution of the concentration fraction with respect to the molecular weight. The differential distribution value at a specific Log(M) is read from this curve.

[0048] The mesopentad fraction ([mmmm]) of the polypropylene resin is preferably less than 98.0%, more preferably 97.5% or less, still more preferably 97.4% or less, and particularly preferably 97.0% or less. Also, the mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, and still more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is moderately improved by moderately high stereoregularity, and the initial breakdown voltage resistance and the long-term breakdown voltage resistance are improved. On the other hand, a desired stretchability can be obtained by an appropriate solidification (crystallization) rate when forming a cast base sheet.

[0049] 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 apparatus (high-temperature FT-NMR), JNM-ECP500, manufactured by JEOL Ltd. The observed nucleus is 13It is C (125 MHz), the measurement temperature is 135 °C, and for the solvent that dissolves the polypropylene resin, o-dichlorobenzene (ODCB: a mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4 / 1) is used. The measurement method by high-temperature NMR can be carried out with reference to the method described in, for example, "Edited by the Japanese Society for Analytical Chemistry, Polymer Analysis Research Symposium, New Edition Polymer Analysis Handbook, Kiyokawa Shoten, 1995, page 610".

[0050] The heptane-insoluble content (HI) of the polypropylene resin is preferably 96.0% or more, more preferably 97.0% or more. Also, 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, due to moderately high stereoregularity, the crystallinity of the resin is moderately improved, and the withstand voltage property at high temperatures is improved. On the other hand, the solidification (crystallization) rate during the formation of the cast original sheet becomes moderate, and it has moderate stretchability.

[0051] 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 even more preferably 2.0 to 6.0 g / 10 min.

[0052] When there are two or more types of polypropylene resins contained in the polypropylene film, the main component polypropylene resin preferably has a weight average molecular weight Mw of at least 250,000 and less than 345,000, and an MFR of 4 to 8 g / 10 min. Also, when there are two or more types of polypropylene resins contained in the polypropylene film, the polypropylene resin other than the main component preferably has a weight average molecular weight Mw of at least 345,000 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).

[0053] The above-mentioned polypropylene resin can be produced using generally known polymerization methods. Examples of the polymerization methods include, for example, gas-phase polymerization method, bulk polymerization method, and slurry polymerization method.

[0054] The polymerization may be single-stage (one-step) polymerization using one polymerization reactor, or may be multi-stage polymerization using two or more polymerization reactors. Further, the polymerization may be carried out by adding hydrogen or a comonomer as a molecular weight regulator into the reactor.

[0055] As the catalyst for the polymerization, generally known Ziegler-Natta catalysts can be used, and it is not particularly limited as long as the above-mentioned 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.

[0056] The molecular weight distribution, etc. of the above-mentioned polypropylene resin can be adjusted by resin mixing (blending). For example, a method of mixing two or more resins having different molecular weights and molecular weight distributions can be mentioned. Generally, a two-component polypropylene blend system in which a resin having a higher average molecular weight or a lower average molecular weight than the main resin is added to the main resin, and the main resin is 55% by mass or more and 90% by mass or less based on 100% by mass of the total resin, is preferable because it is easy to adjust the amount of low molecular weight components.

[0057] When adopting the above-mentioned mixing and adjusting method, the melt flow rate (MFR) may be used as a measure of the average molecular weight. In this case, from the viewpoint of convenience during adjustment, the difference in MFR between the main resin and the added resin is preferably about 1 to 30 g / 10 minutes.

[0058] The method of resin mixing is not particularly limited, but examples include a method of dry blending the polymerization powder or pellets of the main resin and the added resin using a mixer or the like, and a method of supplying the polymerization powder or pellets of the main resin and the added resin to a kneader and melt-kneading to obtain a blended resin.

[0059] The mixer and the kneader are not particularly limited. The kneader may be of any of a single-screw type, a twin-screw type, or a multi-screw type with three or more screws. In the case of a twin-screw or multi-screw type, either a co-rotating or counter-rotating kneading type may be used.

[0060] In the case of blending by melt-kneading, the kneading temperature is not particularly limited as long as a good kneaded product is obtained. Generally, it is in the range of 200°C to 300°C, and from the viewpoint of suppressing resin deterioration, 230°C to 270°C is preferable. Also, 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 generally be pelletized to an appropriate size using a known pelletizer. Thereby, mixed polypropylene raw material resin pellets can be obtained.

[0061] The total ash content due to polymerization catalyst residues and the like contained in the polypropylene raw material resin is preferably 50 ppm or less based on 100 parts by weight of the polypropylene resin.

[0062] 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 suppress the generation of polar low-molecular components and improve the electrical characteristics as a capacitor.

[0063] The polypropylene film may contain an additive. The "additive" is generally an additive used for polypropylene resins and is not particularly limited as long as it does not inhibit the effects of the present invention.

[0064] Examples of the additive include antioxidants, chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, inorganic fillers, organic fillers, and the like. Examples of the inorganic filler include barium titanate, strontium titanate, aluminum oxide, and the like. The polypropylene resin may contain the additive in an amount that does not adversely affect the polypropylene film.

[0065] When the metal layer-integrated polypropylene film according to this embodiment is used as a capacitor, the metal layer functions as an electrode. Examples of the metal used for the metal layer include single metals such as zinc, lead, silver, chromium, aluminum, copper, nickel, mixtures of multiple types thereof, alloys thereof, etc. However, considering the environment, economy, capacitor performance, etc., zinc and aluminum are preferred.

[0066] Next, a method for manufacturing the metal layer-integrated polypropylene film according to this embodiment will be described. Note that the metal layer-integrated polypropylene film according to this embodiment is preferably manufactured by the method for manufacturing the metal layer-integrated polypropylene film described below, but it does not necessarily have to be manufactured by the method for manufacturing the metal layer-integrated polypropylene film described below.

[0067] The method for manufacturing the metal layer-integrated polypropylene film according to this embodiment is a metal layer lamination step of laminating a metal layer on one or both sides of the polypropylene film to obtain a metal layer-integrated polypropylene film, and a heating step of heating the metal layer-integrated polypropylene film obtained in the metal layer lamination step at a temperature of 100°C or higher and 130°C or lower. It comprises.

[0068] The cast master sheet before stretching for manufacturing the biaxially stretched polypropylene film can be produced as follows. However, the method for manufacturing the cast master sheet according to this embodiment is not limited to the method described below.

[0069] First, supply resin pellets, dry-mixed resin pellets, or resin pellets prepared by pre-melting and kneading to an extruder and heat and melt them. The temperature of melt-kneading varies depending on the type of thermoplastic resin. In the case of polypropylene resin, the set temperature of the extruder during heat melting is preferably 220 to 280°C, more preferably 230 to 270°C. Also, the resin temperature during heat melting is preferably 220 to 280°C, more preferably 230 to 270°C. The resin temperature during heat melting is the value measured by a thermometer inserted into the extruder. Note that the set temperature of the extruder and the resin temperature during heat melting are selected in consideration of the physical properties of the resin to be used. By setting the resin temperature within the above numerical range during heat melting, deterioration of the resin can also be suppressed.

[0070] Next, use a T-die to extrude the molten resin into a sheet shape, and cool and solidify it with at least one or more metal drums to form an unoriented cast base sheet. The surface temperature of the metal drum (the temperature of the metal drum that first contacts after extrusion) is preferably 50 to 100°C, more preferably 60 to 95°C. The surface temperature of the metal drum can be determined according to the physical properties of the resin to be used, etc.

[0071] The thickness of the cast base sheet is not particularly limited as long as the polypropylene film can be obtained, but it is usually preferably 0.05 mm to 2 mm, more preferably 0.1 mm to 1 mm.

[0072] The polypropylene film according to this embodiment can be preferably produced as follows. However, the production method of the polypropylene film according to this embodiment is not limited to the method described below.

[0073] The polypropylene film can be manufactured by performing a stretching process on the resin cast master sheet. The stretching is preferably biaxial stretching in which the film is oriented biaxially in the longitudinal and transverse directions. As the stretching method, either a simultaneous biaxial stretching method or a sequential biaxial stretching method may be used, but the sequential biaxial stretching method is preferred. As the sequential biaxial stretching method, for example, first, the cast master sheet is maintained at a temperature of 100 to 170°C and passed between rolls with a speed difference to be stretched 3 to 7 times in the MD direction (flow direction, longitudinal direction). The temperature during stretching in the MD direction is preferably 100 to 170°C, more preferably 120 to 160°C. Also, the stretching ratio during stretching in the MD direction is preferably 3 to 7 times, more preferably 4 to 6 times. After stretching in the MD direction, the sheet is guided to 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, relaxation and heat setting are performed 2 to 10 times. Thus, a biaxially stretched polypropylene film is obtained.

[0074] In the polypropylene film, for the purpose of enhancing the adhesion characteristics in a subsequent process such as a metal layer lamination process, corona discharge treatment may be performed online or offline after the stretching and heat setting processes. 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 mixed gas thereof as the atmosphere gas.

[0075] The polypropylene film can be obtained as described above.

[0076] A metal layer lamination process for laminating a metal layer on one or both sides of the polypropylene film to obtain a metal layer integrated polypropylene film will be described. However, Process B according to this embodiment is not limited to the processes described below.

[0077] In the metal layer lamination process, in order to process it as a capacitor, a metal layer is laminated on one or both sides of the polypropylene film to obtain a metal layer integrated polypropylene film.

[0078] As a method of laminating a metal layer on one or both sides of the polypropylene film, for example, a vacuum evaporation method or a sputtering method can be exemplified. From the viewpoints of productivity and economy, etc., the vacuum evaporation method is preferable. As the vacuum evaporation method, generally, a crucible method, a wire method, etc. can be exemplified, but it is not particularly limited, and an appropriate optimum one can be selected as appropriate.

[0079] As the deposition conditions in the vacuum evaporation method, the temperature of the cooling roll is preferably -23°C to 19°C or lower, more preferably -22°C or higher to 19°C or lower, and even more preferably adjusted to -22°C or higher to -18°C or lower. During deposition, by cooling the film with the cooling roll, heat loss (thermal degradation, thermal deformation) due to deposition heat can be suppressed.

[0080] In the vacuum evaporation method, the temperature of the evaporation source is controlled by the amount of electricity supplied. As the deposition conditions in the vacuum evaporation method, the amount of electricity supplied to the evaporation source is preferably 650 A or more, more preferably 700 A or more, and even more preferably 800 A or more. When the amount of electricity supplied is increased (if the temperature of the evaporation source is set higher), the temperature of the furnace rises and the evaporation amount of the metal increases, so that deposition can be carried out more efficiently. From the viewpoint of preventing heat loss of the polypropylene film, the amount of electricity supplied is preferably 900 A or less, and more preferably 850 A or less.

[0081] In the vacuum evaporation method, the thickness of the metal layer is controlled by film resistance. As the evaporation conditions in the vacuum evaporation method, for an aluminum film, the film resistance is preferably 20 Ω / sq or less, and more preferably 17 Ω / sq or less. For a zinc film, it is preferably 5 Ω / sq or less, and more preferably 4 Ω / sq or less. The fact that the film resistance is small means that the thickness of the metal layer is large. From the viewpoint of self-healing property, for an aluminum film, the film resistance is preferably 1 Ω / sq or more, and more preferably 5 Ω / sq or more. For a zinc film, it is preferably 1 Ω / sq or more, and more preferably 2 Ω / sq or more. Note that the self-healing property means that when a defective part occurs in a polypropylene film or the like, the metal of the deposited layer instantaneously evaporates by the applied energy or the energy possessed by the capacitor itself, and the function of the capacitor is restored. When the metal layer is thick, it tends to be inferior in self-healing property. The thickness (film resistance) of the metal layer can be adjusted by the evaporation line speed and the temperature of the evaporation source (the total energization amount as described in full).

[0082] The margin pattern when laminating the metal layer by evaporation is not particularly limited. However, from the viewpoint of improving characteristics such as the 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 surface of the film. It is effective in terms of enhancing safety and preventing destruction and short circuits of the capacitor.

[0083] As the method for forming the margin, generally known methods such as the tape method and the oil method can be used without any limitation.

[0084] Next, a heating (heat treatment) step is performed in which the metal layer-integrated polypropylene film obtained in the metal layer lamination step is heated at a temperature of 100°C or higher and 130°C or lower. By performing this step, the heat history that the metal layer-integrated polypropylene film has received until then is canceled, so that even when the film capacitor is exposed to a high-temperature environment after being formed, thermal changes such as thermal expansion / contraction in the capacitor winding direction are less likely to occur. As a result, the gap between the winding layers does not change, and in the case of a flat element, the distortion and wrinkle formation of the flat curve portion disappear. Therefore, even when a high voltage is applied under a high-temperature environment, the capacitor is less likely to undergo short-circuit breakdown, and the film capacitor can be given the characteristic of not short-circuiting even when a high voltage is applied under a high temperature of 100°C or higher. Preferred specific examples of the heating step are as follows. The heating (heat treatment) step may be either a batch type or a roll-to-roll type. From the viewpoint of working efficiency (time), it is preferable to perform heating (heat treatment) in a roll-to-roll manner. In the batch type, for example, a metal layer-integrated polypropylene film roll (winding) that has been cut to a desired width for forming a capacitor or before cutting is placed in a constant-temperature bath set at a predetermined temperature and heat-treated for a predetermined time. The constant-temperature bath can be used without limitation, such as a general hot air (blowing) type constant-temperature bath, an induction heating type, an infrared type, etc. The heating time is not limited as long as the elongation rate according to the present invention can be achieved, but if the roll diameter is large (if the winding length is long), the heat treatment time will be longer accordingly. Although it depends on the roll diameter, generally, from the viewpoint of working efficiency, it is preferably about 5 minutes to 6 hours, and as short as possible, for example, about 1 hour or less. From the viewpoint of shortening the heat treatment time, the roll-to-roll method is preferably adopted. The film unwound from the roll is continuously guided into a heating furnace (zone), and the film coming out of the furnace is wound up to perform heat treatment. The heating furnace (zone) can be of any type, such as a blowing method or an infrared method. Also, instead of the heating furnace, a contact heating method using a plurality of heating rolls may be used. The processing speed is not limited as long as the elongation rate according to the present invention can be achieved, and it also depends on the length of the heating zone.Generally, it is effective to perform a heat treatment by providing a plurality of hot air heating zones each about several meters to a dozen or so meters in length, passing the unwound film through them over a period of 1 to 5 minutes, and then winding it up.

[0085] The metal layer integrated polypropylene film of this embodiment can be laminated by a conventionally known method or wound to form a film capacitor.

Examples

[0086] Examples and comparative examples are shown below to explain the present invention in detail. However, the present invention is not limited to the examples. Unless otherwise specified, "parts" and "%" indicate "parts by mass" and "mass%", respectively.

[0087] [Examples 1-5 and Comparative Examples 1-4] <Manufacture of Metal Layer Integrated Polypropylene Film> Polypropylene resin (weight average molecular weight: 300,000, molecular weight distribution: 6, meso-pentad fraction: 96.5%) with 5000 ppm of Irganox 1010 added as an antioxidant was supplied to an extruder, melted at a resin temperature of 250°C, then extruded using a T-die, and wound around a metal drum maintained at a surface temperature of 92°C to be solidified, thereby producing a cast master sheet with a thickness of about 125 μm. Subsequently, this unstretched cast master sheet was stretched 5 times in the flow direction at a temperature of 140°C, immediately cooled to room temperature, and then stretched 10 times in the transverse direction at a temperature of 165°C using a tenter to obtain a very thin biaxially stretched polypropylene film.

[0088] Next, using a vapor deposition apparatus (manufactured by ULVAC, product name: winding type vacuum vapor deposition apparatus EWE-060), an aluminum metal layer was formed on the obtained biaxially stretched polypropylene film so that the surface resistivity of the metal film became 20 Ω / sq to obtain a metal layer integrated polypropylene film (before heat treatment). At this time, by the oil margin method, after slitting, metal vapor deposition was performed so that the metal electrode 3 as shown in FIG. 1 was formed with an insulating margin 4 (insulating groove part: width direction length 1 mm) continuous in the longitudinal direction of the film at one end in the film width direction.

[0089] Next, after slitting the metal layer integrated polypropylene film (before heat treatment), heat treatment was performed under each condition (temperature, batch or roll-to-roll, time) described in Table 1 to obtain a metal layer integrated polypropylene film (after heat treatment) with a total width of 60 mm. The thickness of the metal layer integrated polypropylene film was the value measured by the method described below, and was as described in Table 1 respectively. In Comparative Example 1, the metal layer integrated polypropylene film was not heat treated. In Comparative Example 2, the biaxially stretched polypropylene film before forming the metal layer was heat treated in a batch at 100 °C for 10 minutes, but the metal layer integrated polypropylene film was not heat treated.

[0090] <Measurement of the Thickness of the Metal Layer Integrated Polypropylene Film> Under an environment of temperature 23 ± 2 °C and humidity 50 ± 5% RH, a paper thickness gauge MEI-11 (manufactured by Citizen Seimitsu Co., Ltd., measurement pressure 100 kPa, descent speed 3 mm / second, measurement terminal φ = 16 mm, measurement force 20.1 N) was used. Five measurements were performed on a sample of 10 stacked metal layer integrated polypropylene films so as not to allow wrinkles or air to enter, and the thickness was calculated by dividing the average value of the five measurements by 10.

[0091] <Manufacture of Film Capacitor> Two of the obtained metal layer integrated polypropylene films were used and overlapped. Using an automatic winder 3KAW-N2 type manufactured by Minato Seisakusho Co., Ltd., the overlapped metal layer integrated polypropylene films were wound 1137 turns at a winding tension of 250 g, a contact pressure of 880 g, and a winding speed of 4 m / s. The element wound with the element had a load of 5.9 kg / cm 2It was heat-treated at 120°C for 15 hours while pressing. Then, zinc metal was sprayed onto the end face of the element. As the spraying conditions, the feed rate was 15 mm / s, the spraying voltage was 22 V, and the spraying pressure was 0.3 MPa, and spraying was performed to a thickness of 0.7 mm. Thus, a flat film capacitor was obtained. Lead wires were soldered to the end faces of the flat film capacitor. Then, the flat film capacitor was encapsulated with an epoxy resin. The epoxy resin was cured by heating at 90°C for 2.5 hours and then further heating at 120°C for 2.5 hours. The capacitance of the completed film capacitor was 75 μF.

[0092] <Relationship between Temperature and Elongation Rate of Metal Layer Integrated Polypropylene Film> Using a thermo-mechanical measuring device (TMA)·TMA / SS6000 type manufactured by Seiko Instruments Inc., for a metal layer integrated polypropylene film sampled in a strip shape with a width of 4 mm and a length of 25 mm using a quartz tensile probe, while applying a static load of 2 MPa in the MD direction, heating was performed at a heating rate of 10°C / min from 25°C, and a graph showing the relationship between temperature and expansion / contraction rate (TMA (%)) was obtained. Also, for the obtained graph, the expansion / contraction rate (%) at 100°C, 120°C, and 130°C (with the expansion / contraction rate at 25°C being 0%), the elongation gradient (average expansion rate) from 30°C to 100°C, and the temperature of the inflection point (the first inflection point appearing from the start of heating) were read. The measurement conditions are summarized below. Measuring device: TMA / SS6000 type manufactured by Seiko Instruments Inc. Measuring probe: Quartz tensile probe Measuring mode: F mode (load control mode) Static load: 2 MPa Initial chuck distance: 15 mm Measuring temperature range: 25°C to 165°C Heating rate: 10°C / min Data sampling time: 0.5 sec

[0093] <Evaluation of Dielectric Withstanding Voltage in High Temperature Environment (Presence or Absence of Short Circuit)> The withstand voltage property of the film capacitor in a high-temperature environment was evaluated according to the following procedure. The results are shown in Table 1. First, a voltage of 480 Vdc / μm (DC 1200 V for a 2.5-μm-thick film capacitor) was applied to the film capacitor in a 150°C environment for 10 minutes. After discharging, next, the insulation resistance value (value after 1 minute of applying DC 500 V) of the film capacitor was measured at room temperature using a digital ultra-insulation microammeter DMS8104 type manufactured by Hioki Electric Co., Ltd., and the withstand voltage property (presence or absence of short circuit) was evaluated according to the following criteria. The results are shown in Table 1. A: It was determined that the resistance value was 0.05 MΩ or more (if the resistance value could not be displayed), and there was no short circuit. C: It was determined that the resistance value was less than 0.05 MΩ (the resistance value could not be displayed), and there was a short circuit.

[0094] <Evaluation of Insulation in High-Temperature Environment> The insulation property of the film capacitor in a high-temperature environment was evaluated according to the following procedure. The results are shown in Table 1. First, a voltage of 480 Vdc / μm (DC 1200 V for a 2.5-μm-thick film capacitor) was applied to the film capacitor in a 150°C environment for 10 minutes (withstand voltage test). After discharging, next, the insulation resistance value (value after 1 minute of applying DC 500 V) of the film capacitor was measured at room temperature using a digital ultra-insulation microammeter DMS8104 type manufactured by Hioki Electric Co., Ltd., and the insulation property was evaluated according to the following criteria. The results are shown in Table 1. A: The resistance value was 1 GΩ or more. C: The resistance value was less than 1 GΩ.

[0095]

Table 1

Explanation of Symbols

[0096] 1 Metal-layer integrated polypropylene film 2 Polypropylene film 3 Metal electrode 3a Metal layer 3b Electrode extraction part 4 Insulation 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, wherein the polypropylene film has a surface orientation coefficient ΔP of 0.010 to 0.016, the total ash content in the resin constituting the polypropylene film is 50 ppm or less, when the metal layer integrated polypropylene film is heated at a temperature rising rate of 10°C / min from 25°C with a static load of 2 MPa applied in the MD direction, the elongation gradient from 30°C to 100°C is 0.010% / °C or more and 0.030% / °C or less, for use in a capacitor, A metal layer integrated polypropylene film.

2. The metal layer integrated polypropylene film according to claim 1, wherein in a graph showing the relationship between temperature and elongation rate obtained by heating the metal layer integrated polypropylene film with a static load of 2 MPa applied in the MD direction at a temperature rising rate of 10°C / min from 25°C, the temperature of the inflection point is 130°C or higher.

3. The metal layer integrated polypropylene film according to claim 1 or 2, having a thickness of 0.8 μm or more and 3.5 μm or less.

4. A film capacitor having the wound metal layer integrated polypropylene film according to any one of claims 1 to 3, or having a structure in which a plurality of the metal layer integrated polypropylene films according to any one of claims 1 to 3 are laminated.

5. A method for producing a metal layer integrated polypropylene film according to any one of claims 1 to 4, having a polypropylene film and a metal layer laminated on one or both sides of the polypropylene film, a metal layer lamination step of laminating a metal layer on one or both sides of the polypropylene film to obtain a metal layer integrated polypropylene film, a heating step of heating the metal layer integrated polypropylene film obtained in the metal layer lamination step at a temperature of 100°C or higher and 130°C or lower, The method for producing a metal layer integrated polypropylene film comprising these steps.

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