JP6466015B1 - Polypropylene film, metal layer integrated polypropylene film, and film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene film suitable for producing a capacitor capable of reducing the rate of decrease in insulation resistance value in a life test in a capacitor and having reliability capable of withstanding long-term use.
SOLUTION: The crystallite size determined by using the Scherrer equation from the half-value width of the reflection peak of the α crystal (040) plane measured by wide-angle X-ray diffraction method is 12.2 nm or less, and in an environment of 100 ° C. A polypropylene film having a volume resistivity of 6 × 10 ¹⁴ Ω · cm or more calculated from Formula I from the current value at the time when 1 minute has passed after applying a voltage at a potential gradient of 200 V / μm. Here, the formula I is: volume resistivity = [(effective electrode area) × (applied voltage)] / [(thickness of polypropylene film) × (current value)].
[Selection figure] None

Description

  The present invention relates to a polypropylene film, a metal layer integrated polypropylene film, and a film capacitor.

  Polypropylene films have excellent electrical characteristics such as high voltage resistance and low dielectric loss characteristics, and also have high moisture resistance, and are widely used in electronic equipment and electrical equipment. Specifically, it is used for high voltage capacitors, various switching power supplies, filter capacitors (for example, converters, inverters, etc.), smoothing capacitors, and the like.

Regarding the polypropylene film, Patent Document 1 describes that the reliability may be impaired when the volume resistivity at 110 ° C. is less than 5 × 10 ¹⁴ Ω · cm (Patent Document 1). (See paragraph 0028).

  The reliability of Patent Document 1 is considered to mean the strength of a capacitor against a high voltage application for a short time, that is, the strength against dielectric breakdown in a short time of the capacitor. This is based on the description in paragraphs 0141, 0147, 0148 to 0151 of Patent Document 1. This description means that a voltage of 300 VDC is applied to the capacitor element, and that the applied voltage is repeatedly increased at 50 VDC / 1 minute after 10 minutes at that voltage, and that the capacitance is lower than the initial value. After increasing the voltage until it decreased to 10% or less, the capacitor element was disassembled, the state of breakdown was examined, and the statement that the reliability was evaluated and through-type breakdown was observed to evaluate the reliability. It is a description to the effect that it has been adopted or not.

International Publication No. 2016/182003

  A distinction should be made between the strength of a capacitor against short-term dielectric breakdown and the reliability that it can withstand long-term use of the capacitor, ie the strength against dielectric degradation. One reason for this is that although it is superior in strength against dielectric breakdown in a short time, it may be inferior in strength against insulation degradation.

  As an indicator of long-term reliability, the present inventor initially adopted a degree of decrease in capacitance in a life test, represented by 1000 hours of DC 700 V applied to a capacitor.

  However, although the degree of decrease in capacitance is small, the inventor has noticed that reliability that can withstand long-term use may not be ensured.

  Based on such knowledge, the present inventor has conducted intensive studies, and as a result, by suppressing the decrease in the insulation resistance (IR) value in the life test of the capacitor, it is highly reliable to withstand long-term use. It has been found that a capacitor can be obtained. Specifically, first, the inventor has noticed that although the degree of decrease in capacitance is small, the decrease in insulation resistance value may be large. In such a case, if the life test is continued, it is clear that the performance is suddenly reduced due to the exponential decrease of the capacitance due to the decrease of the insulation resistance value. Therefore, it can be said that although the degree of decrease in capacitance is suitable for evaluating the degree of deterioration within the life test period, it is not suitable for evaluating the degree of deterioration progress after the life test. On the other hand, it can be said that the rate of decrease in the insulation resistance value is an index suitable for evaluating the degree of deterioration within the life test period and also for evaluating the degree of progress of deterioration after the life test.

  However, it has been unclear how the decrease in insulation resistance value in the life test can be suppressed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to reduce the rate of decrease in the insulation resistance value of the life test in the capacitor, and to provide a reliable capacitor that can withstand long-term use. It is to provide a polypropylene film suitable for production. Another object of the present invention is to provide a metal layer integrated polypropylene film having a polypropylene film and a film capacitor having a metal layer integrated polypropylene film.

  In order to achieve this object, the present inventor has intensively studied and has completed the present invention.

The polypropylene film of the first aspect in the present invention is
The crystallite size determined using the Scherrer equation from the half-value width of the reflection peak of the α crystal (040) plane measured by wide-angle X-ray diffraction is 12.2 nm or less,
A voltage is applied at a potential gradient of 200 V / μm in an environment of 100 ° C., and the volume resistivity calculated by the formula I from the current value at the time when 1 minute has elapsed is 6 × 10 ¹⁴ Ω · cm or more.
Volume resistivity = [(Effective electrode area) × (Applied voltage)] / [(Polypropylene film thickness) × (Current value)]
It is.

  In the present invention and the present specification, “element”, “capacitor”, “capacitor element”, and “film capacitor” are the same.

The reason why the decrease rate of the insulation resistance value in the life test of the capacitor element made of the polypropylene film of the first aspect is small is that the crystallite size is 12.2 nm or less, and the volume resistivity measured by the above method. Is 6 × 10 ¹⁴ Ω · cm or more. It is expected that the smaller the crystallite size, the smaller the leakage current of the film capacitor due to its morphological effect. However, the leakage current of the film capacitor is not determined only by the crystallite size. As a result of intensive studies by the present inventors, a voltage is applied to a polypropylene film with a very large potential gradient of 200 V / μm at a specific temperature. It has been found that it is also affected by the volume resistivity when applied. Here, the volume resistivity is one index indicating the ease of current leakage in the polypropylene film, and the volume resistivity is deeply related not only to the crystallite size but also to at least the molecular internal structure such as the molecular arrangement. The inventor thinks.

The volume resistivity measuring method for specifying the polypropylene film of the first aspect is excellent in accuracy. This will be described below.
Conventionally, in the general volume resistivity measurement method of film, the number of digits is a reliable number as the accuracy of the measured value, and the numerical value (coefficient) more detailed than the number of digits is regarded as an error range. ing. When the volume resistivity of the polypropylene film is 3 × 10 ¹⁴ Ω · cm, the number of digits of the volume resistivity indicates 10 ¹⁴ , and the coefficient (detailed numerical value) indicates 3.
In contrast, the present inventors applied a voltage with a potential gradient of 200 V / μm in a 100 ° C. environment, and obtained the volume resistivity calculated by the above formula I from the current value at the time when 1 minute had elapsed. It is specified as a matter of department. The volume resistivity is a physical property obtained with higher accuracy than the conventional digit level. In other words, the accuracy of the volume resistivity in the present invention extends not only to the number of digits but also to the coefficient. In the volume resistivity measurement method of the present invention, one of the reasons for improving the accuracy is that the potential gradient is constant (200 V / μm in the present invention).
In general, the volume resistivity is constant regardless of the voltage within the range in which Ohm's law is established. However, in the region where the Ohm's law is not satisfied (high electric field region), the volume resistivity varies depending on the voltage at the time of measurement. Specifically, the higher the voltage at the time of measurement (the higher the potential gradient), the lower the resistance value.
In the present invention, the volume resistivity is obtained with a constant potential gradient. For example, when the volume resistivity of a plurality of types of films is measured, the conventional method has almost the same volume resistivity because the number of digits is the same. It is possible to give a clearly different value for what was evaluated as
On the other hand, it can be said that the volume resistivity measuring method described in Patent Document 1 has low accuracy. In Patent Document 1, a volume resistivity is calculated from a volume resistance value at the time when 1 minute has passed after applying a voltage of 100 V (see paragraph 0137). When applying the voltage, the film thickness is not considered. For example, the film of Example 8 has a thickness of 2.3 μm, and the potential gradient is about 43.5 V / μm (100 V / 2.3 μm). On the other hand, the film of Example 9 has a thickness of 5.8 μm, and the potential gradient is about 17.2 V / μm (100 V / 5.8 μm). As described above, in the region where the Ohm's law is not satisfied (high electric field region), the volume resistivity varies depending on the voltage at the time of measurement. Therefore, in the volume resistivity measurement method as in Patent Document 1, It can be said that the accuracy is low.

  In the polypropylene film of the first aspect, the first heating melting point in the differential scanning calorimetry is preferably 165 ° C. or higher. When the melting point is 165 ° C. or higher, the current hardly propagates and the rate of decrease in the insulation resistance value after the life test can be kept low.

  The polypropylene film of the first aspect is preferably for a capacitor. Since the polypropylene film of the first aspect can reduce the rate of decrease in the insulation resistance value of the life test in the capacitor, it can be suitably used for producing a capacitor having reliability that can withstand long-term use.

  The polypropylene film of the first aspect is preferably a biaxially stretched film. When a biaxially stretched film is used, it is easy to obtain a polypropylene film that satisfies the crystal size and the volume resistivity.

In the polypropylene film of the first aspect, the sum of the tensile strength in the first direction and the tensile strength in the direction orthogonal to the first direction is 450 to 600 MPa, and the elongation at break in the first direction and the first direction are The total elongation at break in the direction perpendicular to the first direction is 150 to 220%, and the sum of the tensile modulus in the first direction and the tensile modulus in the direction perpendicular to the first direction is preferably 5 to 10 GPa.
When the tensile strength is within the numerical range, the tensile strength at a high temperature is relatively large. Therefore, even if it is used for a long time at high temperature, it can suppress that a crack etc. arise. As a result, it is possible to suitably improve the long-term withstand voltage at high temperatures while maintaining the effect that the rate of decrease of the insulation resistance value in the capacitor is small.
In addition, if the breaking elongation is within the numerical range, it has an appropriate breaking elongation in two orthogonal directions, so that in the molding process, molding failure is suppressed due to unstretched parts and undrawn portions. Therefore, while maintaining the effect that the decrease rate of the insulation resistance value in the capacitor is small, the continuous productivity is also excellent.
When the tensile elastic modulus is within the numerical range, the tensile elastic modulus at a high temperature is relatively large. Therefore, even if it is used for a long time at high temperature, it can suppress that a crack etc. arise. As a result, it is possible to suitably improve the long-term withstand voltage at high temperatures while maintaining the effect that the reduction rate of the insulation resistance value in the capacitor is small.

  The second aspect of the present invention relates to a metal layer integrated polypropylene film. The metal layer-integrated polypropylene film of the second aspect has the polypropylene film of the first aspect and a metal layer laminated on one side or both sides of the polypropylene film. Since the metal layer-integrated polypropylene film of the second aspect has a polypropylene film, it is possible to reduce the rate of decrease in the insulation resistance value of the life test in the capacitor, and to manufacture a capacitor having reliability that can withstand long-term use. Suitable for

  A third aspect of the present invention relates to a film capacitor. The film capacitor of a 3rd aspect has the metal layer integrated polypropylene film wound.

The fourth aspect of the present invention relates to the use of a polypropylene film as a capacitor film. The use of the polypropylene film of the fourth aspect as a capacitor film is as follows:
The crystallite size determined using the Scherrer equation from the half-value width of the reflection peak of the α crystal (040) plane measured by wide-angle X-ray diffraction is 12.2 nm or less,
A voltage is applied at a potential gradient of 200 V / μm in an environment of 100 ° C., and the volume resistivity calculated by the formula I from the current value at the time when 1 minute has elapsed is 6 × 10 ¹⁴ Ω · cm or more.
Volume resistivity = [(Effective electrode area) × (Applied voltage)] / [(Polypropylene film thickness) × (Current value)]
The use of a polypropylene film as a capacitor film.

  According to the present invention, since the rate of decrease in the insulation resistance value of the life test in a capacitor can be reduced, it is possible to provide a polypropylene film suitable for manufacturing a capacitor having reliability that can withstand long-term use. The present invention can also provide a metal layer integrated polypropylene film having a polypropylene film and a film capacitor having a metal layer integrated polypropylene film.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited only to these embodiments.

  In this specification, the expressions “containing” and “including” include the concepts of “containing”, “including”, “consisting essentially of”, and “consisting only of”.

Since the polypropylene film according to this embodiment is not a microporous film, it does not have a large number of pores.
The polypropylene film according to this embodiment may be composed of two or more layers, but is preferably composed of a single layer.

In the polypropylene film according to the present embodiment, the crystallite size obtained by using the Scherrer formula from the half-value width of the reflection peak of the α crystal (040) plane measured by the wide-angle X-ray diffraction method (XRD method) is 12. The volume resistivity calculated by the formula I is 6 × 10 ¹⁴ Ω · cm or more from the current value at the time when 1 minute has passed when a voltage is applied at a potential gradient of 200 V / μm in an environment of 100 ° C. Formula I is shown below.
Volume resistivity = [(Effective electrode area) × (Applied voltage)] / [(Polypropylene film thickness) × (Current value)]
Here, the volume resistivity is R _V (Ω · cm), the effective electrode area is A _E (cm ² ), the applied voltage is V _A (V), the thickness of the polypropylene film is T _F (cm), and the current value is If C _E (A),
R _V = (A _E × V _A ) ÷ (T _F × C _E ).

A method for measuring the volume resistivity will be described in detail. In the following description, measurement conditions not specifically described are based on JIS C 2139.
First, a volume resistivity measuring jig (hereinafter, also simply referred to as “jig”) is placed in a constant temperature bath of 100 ° C. environment. The configuration of the volume resistivity measuring jig is as follows. A DC power supply and a DC ammeter are connected to each electrode of the jig.
<Jig for measuring volume resistivity>
Main electrode (diameter 50mm)
Counter electrode (diameter 85mm)
Ring-shaped guard electrode surrounding the main electrode (outer diameter 80mm, inner diameter 70mm)
Each electrode is made of copper plated with gold, and a conductive rubber is stuck on the surface in contact with the sample. The conductive rubber used is EC-60BL (W300) manufactured by Shin-Etsu Silicone Co., Ltd., and the glossy surface of the conductive rubber is pasted so as to contact the gold-plated copper.

  Next, a polypropylene film (hereinafter also referred to as a sample) is placed in an environment of 23 ° C. and 50% RH for 24 hours. Then, a sample is set to the jig in a thermostat. Specifically, the main electrode and the guard electrode are brought into close contact with one surface of the polypropylene film, the counter electrode is brought into close contact with the other surface, and the polypropylene film and each electrode are brought into close contact with a load of 5 kgf. Then, let stand for 30 minutes.

  Next, a voltage is applied to the sample so that the potential gradient is 200 V / μm.

After applying the voltage, the current value at 1 minute is read, and the volume resistivity is calculated by the following formula. In addition, 2290-10 (DC power supply) manufactured by Keithley is used for voltage application, and 2635B (DC ammeter) manufactured by Keithley is used for current value measurement.
Volume resistivity = [(Effective electrode area) × (Applied voltage)] / [(Polypropylene film thickness) × (Current value)]

Here, the effective electrode area is obtained by the following equation.
(Effective electrode area) = π × [[[(Diameter of main electrode) + (Inner diameter of guard electrode)] / 2] / 2] ²
Here, assuming that the effective electrode area is A _E (cm ² ), the diameter of the main electrode is D _M (cm), and the inner diameter of the guard electrode is D _G (cm), A _E = π × [{(D _M + D _G ) ÷ 2} ÷ ^2] is ^2, it can be said that _{a E = π × (D M} + D G) 2/16.

  In this embodiment, the effective electrode area is not the area of the main electrode, and the effective electrode area is the same or closer to the main electrode than the main electrode among the separated portions of the main electrode and the guard electrode. . As a result, a more accurate current value can be measured.

  The volume resistivity measuring method in the present embodiment has higher accuracy than the digit number level. One of the reasons for improving accuracy is that the potential gradient is constant (in this embodiment, 200 V / μm). Further, in the present embodiment, the effective electrode area is not the area of the main electrode, and the portion of the separation between the main electrode and the guard electrode that is the same as the main electrode or closer to the main electrode is the effective electrode area. Therefore, it is possible to measure the current value more accurately than when the area of the main electrode is the effective electrode area.

The volume resistivity of the polypropylene film is 6 × 10 ¹⁴ Ω · cm or more. An example of the upper limit of the volume resistivity is 1 × 10 ¹⁶ Ω · cm. The volume resistivity of the polypropylene film is preferably 8.0 × 10 ¹⁴ Ω · cm or more, and more preferably 1.0 × 10 ¹⁵ Ω · cm or more. The volume resistivity of the polypropylene film is preferably 5.0 × 10 ¹⁵ Ω · cm or less, more preferably 3.0 × 10 ¹⁵ Ω · cm or less, and further preferably 2.0 × 10 ¹⁵ Ω · cm or less. . When the volume resistivity is less than 6 × 10 ¹⁴ Ω · cm, it is difficult to reduce the rate of decrease of the insulation resistivity in the life test in the film capacitor due to leakage of current due to the molecular internal structure (molecular arrangement, etc.). Become.

  The crystallite size of the polypropylene film is 12.2 nm or less. Considering the viewpoint of mechanical strength and the lamellar (folded crystal) thickness of the polymer chain, the lower limit of the crystallite size is usually considered to be around 10 nm. The crystallite size is calculated using the Scherrer equation from the half-value width of the reflection peak of the α crystal (040) plane measured by the wide-angle X-ray diffraction method. The Scherrer equation is expressed as equation (1) below.

式（１）において、Ｄは結晶子サイズ（ｎｍ）、Ｋは定数（形状因子）、λは使用Ｘ線波長（ｎｍ）、βは半価幅、θは回折ブラッグ角である。Ｋとして０．９４を用いる。λとして０．１５４１８ｎｍを用いる。

In equation (1), D is the crystallite size (nm), K is a constant (shape factor), λ is the X-ray wavelength used (nm), β is the half width, and θ is the diffraction Bragg angle. 0.94 is used as K. 0.15418 nm is used as λ.

  The crystallite size of the polypropylene film is preferably 10.5 nm or more, more preferably 11.0 nm or more, and further preferably 11.5 nm or more. When the crystallite size exceeds 12.2 nm, it becomes difficult to reduce the rate of decrease in the insulation resistivity of the life test in the film capacitor due to leakage of current due to the crystal form.

In the polypropylene film in this embodiment, a combination of the requirement that the volume resistivity is 6 × 10 ¹⁴ Ω · cm or more and the requirement that the crystallite size is 12.2 nm or less is important. In order to obtain a polypropylene film satisfying a volume resistivity of 6 × 10 ¹⁴ Ω · cm or more and satisfying a crystallite size of 12.2 nm or less, in a biaxial stretching, a tenter stretching angle (hereinafter referred to as “lateral stretching angle”). ) Is adjusted to 8.5 ° to 14 °, and the stretching temperature of the tenter (hereinafter referred to as “lateral stretching temperature”) is preferably adjusted to 156 ° C. or more and less than 160 ° C. The transverse stretching angle is preferably 8.5 ° or more, more preferably 9 ° or more. The transverse stretching angle is preferably 13 ° or less, more preferably 12 ° or less, and still more preferably 11 ° or less. When the transverse stretching angle is less than 8.5 °, it is difficult to obtain the volume resistivity defined by the polypropylene film of this embodiment. The transverse stretching temperature is preferably 157 ° C. or higher, more preferably 158 ° C. or higher. The transverse stretching temperature is preferably 159.5 ° C or lower, more preferably 159 ° C or lower. The transverse stretching angle is defined as follows.
<Horizontal stretch angle>
Both ends of the first line segment constituting the width of the polypropylene film at the starting point of the horizontal stretching are defined by the first end and the second end, and both ends of the second line segment forming the width of the polypropylene film at the end of the horizontal stretching are defined as the third line. When the first end and the fourth end are defined to be located on one side of a reference imaginary straight line extending in the flow direction from the midpoint of the first line segment, the first end and the fourth end are defined. An angle formed by a first imaginary straight line connecting the three ends and a second imaginary straight line extending from the first end along the flow direction.

  The reason why the volume resistivity and the crystallite size can be adjusted by stretching the tenter (hereinafter referred to as “lateral stretching”) is that the crystallite size due to “breakage of the crystal” increases as strain increases in the transverse stretching process. It is considered that there is an increase in anisotropy of molecular arrangement due to “rearrangement of crystals” as well as miniaturization occurs. This will be described. The present inventor pays attention to the transverse stretching process and tracks the change in crystallite size and the change in molecular arrangement in the transverse stretching process. As a result, as the strain increases, the crystallite size becomes finer and the molecular It was found that the increase in anisotropy in the array proceeds. In the stretching process, when the increase in anisotropy in the molecular arrangement proceeds, the crystallite size generally increases due to orientation crystallization, but the result is that the miniaturization of the crystallite size has progressed. It is thought that "crystal destruction" occurred.

  In order to control “breakage of crystal” and “rearrangement of crystal”, it is considered that control of stretching energy is important. The stretching energy can be estimated as an area obtained by “stress s × time t” of a dynamic curve in a plane having time t on the horizontal axis and stress s on the vertical axis.

  The stretching energy can be controlled by the transverse stretching angle, the transverse stretching temperature, the stretching ratio, the type of polypropylene resin, the physical properties of the polypropylene resin, and the like. For example, the smaller the transverse stretching angle, the smaller the strain rate and the smaller the stress s applied to the polypropylene film. The stress s increases as the transverse stretching temperature decreases.

  Although the stretching energy depends not only on the transverse stretching angle, transverse stretching temperature, etc., but also on the polypropylene film transport speed in the transverse stretching process, it is preferable to positively change the transport speed in order to adjust the stretching energy. Absent. This is because the conveyance speed greatly affects operability such as yield and production efficiency.

  Therefore, it is preferable to adjust the volume resistivity and the crystallite size to be in the range defined by the polypropylene film of this embodiment by appropriately setting at least the transverse stretching angle and / or the transverse stretching temperature. As the lateral stretching temperature is increased, the volume resistivity tends to decrease and the crystallite size tends to increase, and as the lateral stretching temperature is decreased, the volume resistivity tends to increase and the crystallite size is increased. It tends to be smaller. In addition, as the lateral stretching angle is increased, the volume resistivity tends to increase and the crystallite size tends to increase. As the lateral stretching angle is decreased, the volume resistivity tends to decrease and the crystallite size also increases. It tends to be smaller. However, if the transverse stretching angle is too small, the tendency of the crystallite size may change and the crystallite size may increase.

Further, the surface temperature of the metal drum when forming an unstretched cast raw sheet, the stretching temperature in the flow direction (longitudinal stretching temperature or longitudinal stretching temperature), and / or the stretching ratio in the flow direction (longitudinal stretching ratio or More preferably, the volume resistivity and the crystallite size are adjusted so as to be in the range defined by the polypropylene film of the present embodiment by the longitudinal stretching ratio).
The surface temperature of the metal drum is preferably 105 ° C. or lower, and more preferably 100 ° C. or lower. The surface temperature of the metal drum is preferably 95 ° C. or higher. When the surface temperature of the metal drum is lower than 95 ° C., it may be difficult to obtain the volume resistivity and / or crystallite size defined by the polypropylene film of this embodiment.
The stretching temperature in the flow direction is preferably 127 ° C to 139 ° C. When the stretching temperature in the flow direction is lower than 127 ° C or higher than 139 ° C, it is difficult to obtain a crystallite size defined by the polypropylene film of the present embodiment. Moreover, it is preferable that the draw ratio of a flow direction is 3.0-4.3 times. When the draw ratio in the flow direction exceeds 4.3 times, it becomes difficult to obtain a crystallite size defined by the polypropylene film of the present embodiment.

  The polypropylene film preferably has an ash content of 50 ppm or less, more preferably 40 ppm or less, and even more preferably 30 ppm or less.

  In order to improve electrical characteristics, it is preferable that the ash content is as low as possible. Therefore, when the ash content contained in the polypropylene film is 35 ppm or less, the electrical characteristics are more excellent.

  In the polypropylene film, the first heating melting point in differential scanning calorimetry is preferably 165 ° C. or higher. When the melting point is 165 ° C. or higher, the current hardly propagates and the rate of decrease in the insulation resistance value after the life test is small. Melting | fusing point becomes like this. Preferably it is 166 degreeC or more, More preferably, it is 167 degreeC or more, More preferably, it is 168 degreeC or more. The upper limit of the melting point is, for example, 178 ° C., preferably 177 ° C.

  In the polypropylene film, the first heating melting enthalpy in differential scanning calorimetry is preferably 90 J / g or more and 120 J / g or less, more preferably 92 J / g or more and 117 J / g or less, and more preferably 95 J / g or more and 115 J / g. / G or less is more preferable.

  It is preferable that the melting enthalpy of the polypropylene film is 90 J / g or more because the crystal becomes strong. On the other hand, if it is 89 J / g or less, the heat resistance of the capacitor is significantly lowered.

  The melting point / melting enthalpy can be obtained by cutting a 5 mg sample from a polypropylene film, enclosing it in an aluminum pan, and performing input compensation differential scanning calorimetry with a differential scanning calorimeter (Diamond DSC manufactured by Perkin Elmer). . In the measurement, the temperature is increased (fast run) at 20 ° C./min from 30 ° C. to 280 ° C. in a nitrogen atmosphere.

  The polypropylene film preferably has a thickness in the range of 0.5 to 22 μm, more preferably in the range of 0.8 to 10 μm, and more preferably in the range of 0.9 to 7 μm. More preferably, it is more preferably in the range of 1 to 5 μm, still more preferably in the range of 1.1 to 3 μm, and particularly preferably in the range of 1.2 to 2.9 μm. In particular, when the thickness of the polypropylene film is in the range of 1.1 to 3 μm or 1.2 to 2.9 μm, since it is a thin film, excellent capacitance can be obtained when it is used as a capacitor element, and the thin film In spite of being a film, the effect of reducing the insulation resistance value of the life test in the capacitor and having the reliability that can withstand long-term use is obtained, which is a preferable mode.

  When the thickness is 22 μm or less, the capacitance can be increased, and therefore it can be suitably used for a capacitor. From the viewpoint of manufacturing, the thickness can be set to 0.5 μm or more.

  The thickness of a polypropylene film means the value measured based on JIS-C2330 except having measured at 100 +/- 10kPa using the paper thickness measuring device MEI-11 made from Citizen Seimitsu.

  The polypropylene film contains a polypropylene resin. 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 or 98% by mass with respect to the entire polypropylene film. The polypropylene resin may contain one kind of polypropylene resin alone or may contain two or more kinds of polypropylene resins. The polypropylene resin contained in the polypropylene film is preferably a homopolypropylene resin.

  Here, when two or more kinds of polypropylene resins are contained in the polypropylene film, the polypropylene resin having the larger content is referred to as “main component polypropylene resin” in the present specification. Moreover, when the polypropylene resin contained in the said polypropylene film is 1 type, the said polypropylene resin is called "the main component polypropylene resin" in this specification.

  Hereinafter, in the present specification, when it is referred to as “polypropylene resin” without particularly specifying whether or not it is a main component, unless otherwise specified, a polypropylene resin as a main component, and a polypropylene resin other than the main component, Means both. For example, when it is described that “the weight average molecular weight Mw of the polypropylene resin is preferably 250,000 to 450,000,” the weight average molecular weight Mw of the polypropylene resin as a main component is 250,000 to 450,000. It means that the following is preferable and that the weight average molecular weight Mw of the polypropylene resin other than the main component is preferably 250,000 to 450,000.

  The weight average molecular weight Mw of the polypropylene resin is preferably 250,000 or more and 450,000 or less, and 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 raw sheet, and it becomes easy to produce a thin stretched film. Moreover, moderate stretchability can be given to the cast raw fabric sheet. When using 2 or more types of polypropylene resins, it is preferable to use together the polypropylene resin whose Mw is 250,000 or more and less than 345,000 and the polypropylene resin whose Mw is 345,000 or more and 450,000 or less.

  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 more preferably 5 or more and 10 or less. Is more 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 15 or more and 50 or less. Is more preferable.

  In this specification, the weight average molecular weight (Mw), the number average molecular weight (Mn), the z average molecular weight, and the molecular weight distribution (Mw / Mn and Mz / Mn) of the polypropylene resin are determined by gel permeation chromatography (GPC). ) Value measured using an apparatus. More specifically, this is a value measured using HLC-8121GPC-HT (trade name) of a differential refractometer (RI) built-in type high temperature GPC measuring machine manufactured by Tosoh Corporation. As a GPC column, three TSKgel GMHHR-H (20) HT manufactured by Tosoh Corporation are connected and used. The column temperature is set to 140 ° C., and trichlorobenzene is allowed to flow as an eluent at a flow rate of 1.0 ml / 10 minutes 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 into polystyrene values to obtain Mw, Mn, and Mz. Here, the logarithm of the bottom 10 of the molecular weight M of standard polystyrene is referred to as logarithmic molecular weight (“Log (M)”).

In the molecular weight differential distribution curve of the polypropylene resin, the difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log (M) = 4.5 is Log ( When the differential distribution value when M) = 6.0 is 100% (reference), it is preferably −5% or more and 14% or less, more preferably −4% or more and 12% or less, and −4 It is more preferable that it is 10% or less.
In addition, “the difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when logarithmic molecular weight Log (M) = 4.5 is −5% or more and 14% or less. Is a logarithmic molecular weight Log (M) as a typical distribution value of a component having a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter also referred to as “low molecular weight component”) from the Mw value of the polypropylene resin. = 4.5 and a component with Log (M) = 6.0 as a typical distribution value of a component having a molecular weight of about 1 million on the high molecular weight side (hereinafter also referred to as “high molecular weight component”). When compared, 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.

  In other words, even though the molecular weight distribution Mw / Mn is 5 to 12, it merely represents the breadth of the molecular weight distribution width, and the quantitative relationship between the high molecular weight component and the low molecular weight component therein is not known. Absent. Therefore, from the viewpoint of stable film forming property and thickness uniformity of the raw sheet, the polypropylene resin has a broad molecular weight distribution and at the same time a component having a molecular weight of 10,000 to 100,000 in order to appropriately contain a low molecular weight component. It is preferable to use a polypropylene resin so that the differential distribution value difference is -5% or more and 14% or less compared to the component having a molecular weight of 1,000,000.

  The differential distribution value is a value obtained as follows using GPC. A curve (generally also referred to as “elution curve”) showing the intensity with respect to time obtained by a differential refraction (RI) detector of GPC is used. Using the calibration curve obtained with standard polystyrene, the elution curve is converted into a curve showing the intensity with respect to Log (M) by converting the time axis into logarithmic molecular weight (Log (M)). Since the RI detection intensity is proportional to the component concentration, an integral distribution curve with respect to the logarithmic molecular weight Log (M) can be obtained when the total area of the curve indicating the intensity is 100%. The differential distribution curve is obtained by differentiating the integral distribution curve with Log (M). Therefore, “differential distribution” means a differential distribution with respect to the molecular weight of the concentration fraction. From this curve, the differential distribution value at a specific Log (M) is read.

  The heptane-insoluble content (HI) of the polypropylene resin is preferably 96.0% or more, more preferably 97.0% or more. Further, the heptane insoluble content (HI) of the polypropylene resin is preferably 99.5% or less, more preferably 99.0% or less. Here, the heptane-insoluble content indicates that the greater the stereoregularity of the resin, the greater the amount. When the heptane-insoluble content (HI) is 96.0% or more and 99.5% or less, the crystallinity of the resin is moderately improved due to the reasonably high stereoregularity, and the voltage resistance at high temperature is improved. . On the other hand, the rate of solidification (crystallization) at the time of forming the cast original fabric sheet becomes moderate, and it has moderate stretchability.

  The mesopentad fraction ([mmmm]) of the polypropylene resin is preferably 94.0% or more, and more preferably 95.0% or more. In addition, the mesopentad fraction of the polypropylene resin is preferably 97.5% or less, and more preferably 97.0% or less. By using such a polypropylene resin, the crystallinity of the resin is moderately improved by the reasonably high stereoregularity, and the initial voltage resistance and the voltage resistance over a long period are improved. On the other hand, desired stretchability can be obtained by an appropriate solidification (crystallization) rate when the cast raw sheet is formed.

  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 observation nucleus is 13C (125 MHz), the measurement temperature is 135 ° C., and a solvent for dissolving the polypropylene resin is ortho-dichlorobenzene (ODCB: ODCB and deuterated ODCB mixed solvent (mixing ratio = 4/1). For the measurement method by high temperature NMR, refer to, for example, the method described in “Japan Analytical Chemistry / Polymer Analysis Research Roundtable, New Edition Polymer Analysis Handbook, Kinokuniya, 1995, p. 610”. It can be carried out.

The measurement mode is single pulse proton broadband decoupling, the pulse width is 9.1 μsec (45 ° pulse), the pulse interval is 5.5 sec, the number of integration is 4500 times, and the shift reference is CH ₃ (mmmm) = 21.7 ppm. .
The pentad fraction representing the degree of stereoregularity is a combination of the quintet (pentad) of the consensus “meso (m)” arranged in the same direction and the consensus “rasemo (r)” arranged in the opposite direction (mmmm and mrrm). Etc.) based on the integrated value of the intensity of each signal derived from. Each signal derived from mmmm, mrrm and the like can be assigned with reference to, for example, “T. Hayashi et al., Polymer, 29, 138 (1988)”. A more detailed method for measuring the mesopentad fraction ([mmmm]) is according to the method described in Examples.

  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 2.0 to 6.0 g / min. More preferably, it is 10 minutes. The method for measuring the melt flow rate of the polypropylene resin is according to the method described in the examples.

  When two or more types of polypropylene resins are contained in the polypropylene film, the main component polypropylene resin has at least a weight average molecular weight Mw of 250,000 or more and less than 345,000 and an MFR of 4 to 8 g / 10 min. Is preferred. Moreover, when the polypropylene resin contained in the said polypropylene film is 2 or more types, as for polypropylene resin other than a main component, the weight average molecular weight Mw is 345,000 or more and 450,000 or less, and MFR is 1 g / 10min or more and 4 g. / 10 min or less (more preferably 1 g / 10 min or more and 3.9 g / 10 min or less).

  Polypropylene resin can be generally produced using a known polymerization method. Examples of the polymerization method include a gas phase polymerization method, a bulk polymerization method, and a slurry polymerization method.

  The polymerization may be single-stage (one-stage) polymerization using one polymerization reactor or multi-stage polymerization using two or more polymerization reactors. The polymerization may be performed by adding hydrogen or a comonomer as a molecular weight modifier in the reactor.

  As the catalyst for the polymerization, generally known Ziegler-Natta catalysts can be used, and are not particularly limited as long as a polypropylene resin can be obtained. The catalyst may contain a promoter component and a donor. The molecular weight, molecular weight distribution, stereoregularity, etc. can be controlled by adjusting the catalyst and polymerization conditions.

  The molecular weight distribution of the polypropylene resin can be adjusted by resin mixing (blending). For example, a method of mixing two or more types of resins having different molecular weights or molecular weight distributions. In general, when a resin having a higher average molecular weight or a lower resin is used as the main resin and the resin as a whole is 100% by mass, the main resin is mixed in two types of polypropylene having a main resin content of 55% by mass to 90% by mass. The system is preferable because it is easy to adjust the amount of low molecular weight components.

  In addition, when employ | adopting the mixing adjustment method, you may use a melt flow rate (MFR) as a standard of average molecular weight. In this case, the difference in MFR between the main resin and the additive resin is preferably about 1 to 30 g / 10 minutes from the viewpoint of convenience during adjustment.

  The method of mixing the resin is not particularly limited, but a method of dry blending the main resin and additive resin polymerized powder or pellets using a mixer or the like, a main resin and additive resin polymerized powder, or pellets Is supplied to a kneader and melt-kneaded to obtain a blend resin.

  The mixer and the kneader are not particularly limited. The kneader may be either a single screw type, a twin screw type, or a multi-screw type higher than that. In the case of a screw type with two or more axes, either a kneading type rotating in the same direction or rotating in a different direction may be used.

  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 is preferably 230 ° C. to 270 ° C. from the viewpoint of suppressing deterioration of the resin. Further, an inert gas such as nitrogen may be purged into the kneader in order to suppress deterioration during resin kneading and mixing. The melt-kneaded resin may be pelletized to an appropriate size using a generally known granulator. Thereby, a mixed polypropylene raw material resin pellet can be obtained.

  It is preferable that the total ash resulting from the polymerization catalyst residue contained in the polypropylene raw resin is as small as possible in order to improve the electrical characteristics. The total ash content is preferably 50 ppm or less, more preferably 40 ppm or less, and particularly preferably 30 ppm or less, based on the polypropylene resin (100 parts by weight).

  The polypropylene resin may contain an additive. Examples of the additive include an antioxidant, a chlorine absorbent, an ultraviolet absorbent, a lubricant, a plasticizer, a flame retardant, and an antistatic agent. The polypropylene resin may contain an additive in an amount that does not adversely affect the polypropylene film.

  The polypropylene film may contain a resin other than the polypropylene resin (hereinafter also referred to as “other resin”). Other resins include polyolefins other than polypropylene such as polyethylene, poly (1-butene), polyisobutene, poly (1-pentene), poly (1-methylpentene); ethylene-propylene copolymer, propylene-butene copolymer Copolymers, copolymers of α-olefins such as ethylene-butene copolymers; vinyl monomers-diene monomer random copolymers such as styrene-butadiene random copolymers; styrene-butadiene-styrene block copolymers Examples thereof include a vinyl monomer such as a coalescence-diene monomer-vinyl monomer random copolymer. The polypropylene film may contain such other resins in an amount that does not adversely affect the polypropylene film.

  When making a polypropylene film into a biaxially stretched polypropylene film, the cast original fabric sheet before extending | stretching for manufacturing a biaxially stretched polypropylene film can be produced as follows.

First, polypropylene resin pellets, dry-mixed polypropylene resin pellets, or mixed polypropylene resin pellets prepared by melting and kneading in advance are supplied to an extruder and melted by heating.
5-40 rpm is preferable and, as for the rotation speed of the extruder at the time of heat-melting, 10-30 rpm is more preferable. Moreover, 220-280 degreeC is preferable and the extruder preset temperature at the time of heat-melting has more preferable 230-270 degreeC. Moreover, 220-280 degreeC is preferable and the resin temperature at the time of heat-melting has more preferable 230-270 degreeC. The resin temperature at the time of heating and melting is a value measured by a thermometer inserted in an extruder.
Note that the number of revolutions of the extruder, the set temperature of the extruder, and the resin temperature during heating and melting are selected in consideration of the physical properties of the crystalline thermoplastic resin to be used. In addition, deterioration of resin can also be suppressed by making the resin temperature at the time of heat-melting in such a numerical range.

Next, the molten resin is extruded into a sheet shape using a T die, and cooled and solidified with at least one metal drum (also referred to as a cast drum), thereby forming an unstretched cast raw sheet.
As described above, the surface temperature of the metal drum (the temperature of the metal drum that first contacts after extrusion) is preferably 105 ° C. or less, and more preferably 100 ° C. or less. The surface temperature of the metal drum is preferably 95 ° C. or higher. The surface temperature of the metal drum can be determined according to the physical properties of the polypropylene resin used.

The melt flow rate (MFR) of the cast original fabric sheet is preferably 1.0 to 9.0 g / 10 min, more preferably 2.0 to 8.0 g / 10 min, and 3.0 to 7. More preferably, it is 0 g / 10 min.
The thickness of the cast original fabric sheet is not particularly limited as long as a polypropylene film can be obtained, but is usually preferably 0.05 mm to 2 mm, more preferably 0.1 mm to 1 mm. preferable.

  The polypropylene film can be produced by subjecting a polypropylene cast original fabric sheet to a stretching treatment. The stretching is preferably biaxial stretching that is biaxially oriented longitudinally and laterally, and the sequential biaxial stretching method is preferred as the stretching method. As a sequential biaxial stretching method, for example, as described above, first, the cast raw sheet is maintained at a temperature of 127 to 145 ° C. and passed between rolls provided with a speed difference to be 3 to 4.3 times in the flow direction. Stretch. Subsequently, the sheet is guided to a tenter and stretched 3 to 11 times in the lateral direction. Thereafter, relaxation and heat fixation are performed 2 to 10 times. As described above, a biaxially stretched polypropylene film is obtained.

In the biaxially stretched polypropylene film of the present embodiment, the total tensile strength in the first direction and the tensile strength in the direction orthogonal to the first direction is preferably 450 MPa or more, more preferably 470 MPa or more, More preferably, it is 480 MPa or more. The total of the tensile strength in the first direction and the tensile strength in the direction perpendicular to the first direction is preferably 600 MPa or less, more preferably 570 MPa or less, and further preferably 530 MPa or less, It is particularly preferably 525 MPa or less.
In this specification, the 1st direction intends MD direction (Machine Direction) of a biaxially-stretched polypropylene film. That is, in the present embodiment, the first direction is preferably the MD direction. However, in the present embodiment, the first direction is not limited to the MD direction, and any direction can be set as the first direction.
Hereinafter, a case where the first direction is the MD direction will be described. In the present specification, the direction orthogonal to the MD direction is the TD direction (Transverse Direction) (also referred to as “width direction or horizontal direction”).
The biaxially stretched polypropylene film of the present embodiment preferably has a total (T _MD + T _TD ) of tensile strength in the MD direction (T _MD ) and tensile strength in the TD direction (T _TD ) of 450 MPa or more. More preferably, it is more preferably 480 MPa or more. Here, the tensile strength of the polypropylene film of this embodiment is a value obtained by the measurement method described in the examples. Further, the total tensile strength of the polypropylene film of the present embodiment _(T MD ₊ T _TD) is preferably not more than 600 MPa, more preferably at most 570 MPa, more preferably at most 530 MPa, 525MPa It is particularly preferred that When the total of the tensile strength in the MD direction and the tensile strength in the TD direction of the polypropylene film at 23 ° C. (described in JIS-C2151), which is the measurement temperature, is within the above preferred ranges, the tensile strength at high temperatures is also compared. Become bigger. Therefore, even if it is used for a long time at high temperature, it can suppress that a crack etc. arise. As a result, it is possible to suitably improve the long-term withstand voltage at high temperatures while maintaining the effect of the present embodiment that the rate of decrease in the insulation resistance value in the capacitor is small.
The ratio of the tensile strength in the TD direction to the tensile strength in the MD direction (T _TD / _TMD ) of the tensile strength of the polypropylene film of the present embodiment is preferably 2.00 or less, more preferably 1.80 or less, 1.70 or less is more preferable, and 1.58 or less is particularly preferable. _Further, T TD _{/ T MD} is more preferably 1.10 or more, more preferably 1.50 or more. When T _TD / _TMD is within the above preferred ranges, the tensile strength in the width direction is large while having a tensile strength that is relatively balanced in two orthogonal directions. For this reason, in the molding process, the drawing failure due to unstretched parts and undrawn portions is suppressed and molding is performed. Therefore, continuous production is achieved while maintaining the effect of the present embodiment that the decrease rate of the insulation resistance value in the capacitor is small. Excellent in properties.

The biaxially stretched polypropylene film of the present embodiment preferably has a total elongation (E _MD + E _TD ) of 150% or more in the MD direction breaking elongation (E _MD ) and the TD direction breaking elongation (E _TD ), It is more preferably 160% or more, and further preferably 170% or more. Here, the breaking elongation of the polypropylene film of this embodiment is a value obtained by the measurement method described in the examples. In addition, the total (E _MD + E _TD ) of the breaking elongation of the polypropylene film of the present embodiment is preferably 220% or less, more preferably 200% or less, further preferably 190% or less, and 185 % Or less is particularly preferable. When the sum of the breaking elongation in the MD direction and the breaking elongation in the TD direction of the polypropylene film at 23 ° C. (described in JIS-K7127), which is the measurement temperature, is appropriate in the two orthogonal directions, Therefore, in the molding process, the drawing failure due to unstretched parts and undrawn portions is suppressed, and the effect of the present embodiment that the decrease rate of the insulation resistance value in the capacitor is small is maintained. However, it also has excellent continuous productivity.
The ratio of the breaking elongation in the TD direction to the breaking elongation in the MD direction (E _TD / E _MD ) of the breaking elongation of the polypropylene film of this embodiment is preferably 0.70 or less, more preferably 0.60 or less. 0.50 or less is particularly preferable. Further, E _TD / E _MD is preferably 0.20 or more, more preferably 0.30 or more, and further preferably 0.35 or more. When E _TD / E _MD is within each of the above preferred ranges, the formation of defects at the time of capacitor element production is suppressed by having a relatively balanced elongation at break in two orthogonal directions, and therefore it is easy to maintain voids between film layers. . As a result, it is possible to suitably improve the long-term withstand voltage at high temperatures while maintaining the effect of the present embodiment that the rate of decrease of the insulation resistance value in the capacitor is small.

The biaxially stretched polypropylene film of the present embodiment preferably has a total of the tensile elastic modulus (M _MD ) in the _MD direction and the tensile elastic modulus (M _TD ) in the TD direction (M _MD + M _TD ) of 5 GPa or more. More preferably, it is 2 GPa or more. Here, the tensile elastic modulus of the polypropylene film of the present embodiment is a value obtained by the measurement method described in the examples. In addition, the total tensile modulus (M _MD + M _TD ) of the polypropylene film of this embodiment is preferably 10 GPa or less, more preferably 8 GPa or less, and even more preferably 7.5 GPa or less. . When the total of the tensile elastic modulus in the MD direction and the tensile elastic modulus in the TD direction of the polypropylene film at 23 ° C. (described in JIS-K7127), which is the measurement temperature, is within the above preferred ranges, the tensile elasticity at high temperatures. The rate is also relatively large. Therefore, even if it is used for a long time at high temperature, it can suppress that a crack etc. arise. As a result, it is possible to suitably improve the long-term withstand voltage at high temperatures while maintaining the effect of the present embodiment that the rate of decrease of the insulation resistance value in the capacitor is small.
The ratio of the tensile elastic modulus in the TD direction and the tensile elastic modulus in the MD direction (M _TD / M _MD ) of the tensile elastic modulus of the polypropylene film of the present embodiment is preferably 2.0 or less, and preferably 1.9 or less, 1.7 or less is more preferable, and 1.6 or less is more preferable. Further, M _TD / M _MD is preferably 1.0 or more, and more preferably 1.1 or more. When M _TD / M _MD is within the above-described preferable ranges, the tensile elastic modulus in the width direction is large while having a tensile elastic modulus relatively balanced in the two orthogonal directions. For this reason, in the molding process, the drawing failure due to unstretched parts and undrawn portions is suppressed and molding is performed. Therefore, continuous production is achieved while maintaining the effect of the present embodiment that the decrease rate of the insulation resistance value in the capacitor is small. Excellent in properties.

  The polypropylene film may be subjected to corona discharge treatment on-line or off-line after completion of the stretching and heat-setting steps in order to enhance the adhesive properties in a later step such as a metal vapor deposition step. The corona discharge treatment can be performed using a known method. It is preferable to use air, carbon dioxide gas, nitrogen gas, or a mixed gas thereof as the atmospheric gas.

  In order to process as a capacitor, a metal layer may be laminated on one side or both sides of a polypropylene film to form a metal layer integrated polypropylene film. The metal layer functions as an electrode. As the metal used for the metal layer, for example, a simple metal such as zinc, lead, silver, chromium, aluminum, copper, nickel, a mixture of plural kinds thereof, an alloy thereof or the like can be used. In view of economy and capacitor performance, zinc and aluminum are preferable.

  Examples of a method for laminating a metal layer on one or both sides of a polypropylene film include a vacuum deposition method and a sputtering method. From the viewpoint of productivity and economy, the vacuum deposition method is preferable. Examples of the vacuum deposition method generally include a crucible method and a wire method, but are not particularly limited, and an optimum one can be selected as appropriate.

  The margin pattern when the metal layer is laminated by vapor deposition is not particularly limited, but a pattern including a so-called special margin such as a fishnet pattern or a T margin pattern is used in order to improve the characteristics such as the safety of the capacitor. It is preferable to apply on one side of the film. It is effective from the viewpoint of improving the safety and preventing the destruction of the capacitor and the short circuit.

  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.

  The metal layer-integrated polypropylene film can be laminated by a conventionally known method or wound to form a film capacitor.

  The reduction rate of the insulation resistance value in the film capacitor is preferably 60% or less, more preferably 55% or less, and further preferably 50% or less. The lowering rate of the insulation resistance value is preferably smaller, but can be, for example, 10% or more and 30% or more. The decrease rate of the insulation resistance value is a value calculated by the following equation. Moreover, the measuring method of an insulation resistance value and the method of a life test are as follows.

<Measurement method of decrease rate of insulation resistance value in capacitor>
The insulation resistance value of the capacitor is evaluated using a super insulation resistance meter DSM8104 manufactured by Hioki Electric Co., Ltd. The reduction rate of the insulation resistance value is obtained by the following procedure. After allowing the capacitor to stand at 23 ° C. for 24 hours, a voltage is applied to the capacitor at a potential gradient of 200 V / μm (however, if the film thickness is 2 μm or more, 500 V), and the insulation resistance value after one minute has elapsed after application. Measure. This is defined as an insulation resistance value before the life test (hereinafter sometimes referred to as “IR ₀ ”). Next, the capacitor is removed from the super insulation resistance meter, and a voltage is continuously applied (loaded) for 1000 hours at a potential gradient of DC 280 V / μm with a DC high-voltage power source in a constant temperature bath at 105 ° C. After 1000 hours have elapsed, the capacitor is removed, and a discharge resistor is connected to the capacitor to remove static electricity. Next, the capacitor is allowed to stand for 24 hours at 23 ° C., and then the insulation resistance value of the element (hereinafter sometimes referred to as “IR ₁₀₀₀ ”) is measured to calculate the rate of decrease of the insulation resistance value. The rate of decrease of the insulation resistance value is evaluated by the average value of two capacitors.
[Decrease rate of insulation resistance value (%)] = [[(Insulation resistance value before life test) − (Insulation resistance value after life test)] / ((Insulation resistance value before life test)] × 100.
The reduction rate (also referred to as IR reduction rate) (%) of the insulation resistance value is also expressed as [(IR ₀ −IR ₁₀₀₀ ) / IR ₀ ] × 100 (%). Here, / means ÷, and / in this specification may also mean ÷.

  The rate of change in capacitance of the film capacitor after 1000 hours is preferably in the range of −5% to 0%, more preferably −0.1%.

<Measurement method of capacitance change rate ΔC in film capacitor after 1000 hours>
The capacitance of the capacitor is measured using an LCR high tester 3522-50 (frequency 1 kHz) manufactured by Hioki Electric Co., Ltd. The rate of change in capacitance is determined by the following procedure. First, after standing for 24 hours at 23 ° C. The condenser, initial electrostatic capacity before the life test (hereinafter sometimes referred to as "C _0".) Is measured. Next, the capacitor is removed from the LCR high tester 3522-50, and a voltage is continuously applied (loaded) for 1000 hours at a potential gradient of DC 280 V / μm with a DC high voltage power source in a constant temperature bath at 105 ° C. After 1000 hours have elapsed, the capacitor is removed, and a discharge resistor is connected to the capacitor to remove static electricity. Next, the capacitor is allowed to stand at 23 ° C. for 24 hours, and then the capacitance of the element (hereinafter sometimes referred to as “C ₁₀₀₀ ”) is measured to calculate the rate of change in capacitance. The capacitance change rate ΔC is [(C ₁₀₀₀ −C ₀ ) / C ₀ ] × 100 (%). The rate of change in capacitance is evaluated by the average value of two capacitors.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples, but these examples are for explaining the present invention and do not limit the present invention in any way. Unless otherwise specified, “part” and “%” in the examples represent “part by mass” and “% by mass”, respectively.

<Measurement of Weight Average Molecular Weight (Mw), Molecular Weight Distribution (Mw / Mn), Molecular Weight Distribution (Mz / Mn), and Differential Distribution Value of Polypropylene Resin>
Using GPC (gel permeation chromatography), the measurement was performed under the following conditions.
Measuring instrument: manufactured by Tosoh Corporation, differential refractometer (RI) built-in high temperature GPC HLC-8121GPC / HT type column: manufactured by Tosoh Corporation, three TSKgel GMHhr-H (20) HT, connected column temperature: 145 ° C.
Eluent: Trichlorobenzene Flow rate: 1.0 ml / min
A calibration curve was prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured molecular weight value was converted to a polystyrene value to obtain a Z-average molecular weight (Mz), a weight-average molecular weight (Mw), and a number-average molecular weight ( Mn) was obtained. The molecular weight distribution (Mz / Mn) was obtained using the values of Mz and Mn, and the molecular weight distribution (Mw / Mn) was obtained using the values of Mw and Mn.
The differential distribution value was obtained by the following method. First, a time curve (elution curve) of an intensity distribution detected using an RI detector is converted into a distribution curve with respect to the molecular weight M (Log (M)) of standard polystyrene using a calibration curve prepared using the standard polystyrene. Converted. Next, after obtaining an integral distribution curve for Log (M) when the total area of the distribution curve is 100%, the differential distribution for Log (M) is obtained by differentiating the integral distribution curve with Log (M). I was able to get a curve. From this differential distribution curve, differential distribution values when Log (M) = 4.5 and Log (M) = 6.0 were read. A series of operations until obtaining the differential distribution curve was performed using analysis software built in the GPC measurement apparatus used.

<Mesopentad fraction>
Polypropylene resin was dissolved in a solvent and measured using a high temperature Fourier transform nuclear magnetic resonance apparatus (high temperature FT-NMR) under the following conditions.
High-temperature nuclear magnetic resonance (NMR) apparatus: manufactured by JEOL Ltd., high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR), JNM-ECP500
Observation nucleus: 13C (125MHz)
Measurement temperature: 135 ° C
Solvent: Ortho-dichlorobenzene (ODCB: Mixed solvent of ODCB and deuterated ODCB (mixing ratio = 4/1))
Measurement mode: Single pulse proton broadband decoupling pulse width: 9.1 μsec (45 ° pulse)
Pulse interval: 5.5 sec
Integration count: 4,500 times Shift standard: CH3 (mmmm) = 21.7 ppm
The pentad fraction representing the degree of stereoregularity is a combination of a quintet (pentad) of a consensus “meso (m)” arranged in the same direction and a consensus “rasemo (r)” arranged in the same direction (mmmm or mrrm Etc.) was calculated as a percentage (%) from the integrated value of the intensity of each signal. Regarding the attribution of each signal derived from mmmm, mrrm, etc., for example, the description of spectra such as “T. Hayashi et al., Polymer, 29, 138 (1988)” was referred to.

<Thickness of film>
The thickness of the biaxially stretched polypropylene film was measured according to JIS-C2330 except that it was measured at 100 ± 10 kPa using a paper thickness measuring device MEI-11 manufactured by Citizen Seimitsu.

<Measurement of melt flow rate (MFR)>
For each resin, the melt flow rate (MFR) in the form of raw material resin pellets was measured according to the condition M of JIS K 7210 using a melt indexer manufactured by Toyo Seiki Co., Ltd. Specifically, first, a sample weighed to 4 g was inserted into a cylinder set at a test temperature of 230 ° C., and preheated for 3.5 minutes under a load of 2.16 kg. Thereafter, the weight of the sample extruded from the bottom hole in 30 seconds was measured to obtain MFR (g / 10 min). The above measurement was repeated three times, and the average value was taken as the MFR measurement value.

<Crystallite size>
The crystallite size of the biaxially stretched polypropylene film was measured using an XRD (wide angle X-ray diffraction) apparatus as follows.
Measuring instrument: Disrupted X-ray diffraction device MiniFlex300 manufactured by Rigaku
X-ray generation output: 30KV, 10mA
Irradiation X-ray: Monochromator monochromated CuKα ray (wavelength 0.15418 nm)
Detector: scintillation counter goniometer scan: 2θ / θ interlocking scan From the obtained data, diffraction reflection of α crystal (040) plane using analysis computer and integrated powder X-ray analysis software PDXL The half width of the peak was calculated. From the half width of the diffraction reflection peak of the obtained α crystal (040) plane, the crystallite size was determined using Scherrer's formula (D = K × λ / (β × Cos θ)). In the Scherrer equation, D is the crystallite size (nm), K is a constant (shape factor), λ is the used X-ray wavelength (nm), β is the half width obtained, and θ is the diffraction Bragg angle. . As K, 0.94 was adopted.

<Measurement of volume resistivity>
The specific measurement procedure of the volume resistivity is described below, but the measurement was performed in accordance with JIS C 2139 under conditions not specifically described.
First, a volume resistivity measuring jig (hereinafter, also simply referred to as “jig”) was placed in a constant temperature bath of 100 ° C. environment. The configuration of the volume resistivity measuring jig is as follows. A DC power supply and a DC ammeter are connected to each electrode of the jig.
<Jig for measuring volume resistivity>
Main electrode (diameter 50mm)
Counter electrode (diameter 85mm)
Ring-shaped guard electrode surrounding the main electrode (outer diameter 80mm, inner diameter 70mm)
Each electrode is made of copper plated with gold, and a conductive rubber is stuck on the surface in contact with the sample. The used conductive rubber is EC-60BL (W300) manufactured by Shin-Etsu Silicone Co., Ltd., and the glossy surface of the conductive rubber is pasted so as to contact the gold-plated copper.

  Next, the biaxially stretched polypropylene films (hereinafter also referred to as samples) of Examples and Comparative Examples were placed in an environment of 23 ° C. and 50% RH for 24 hours. Thereafter, the sample was set on a jig in a thermostat. Specifically, the main electrode and the guard electrode are adhered to one surface of the biaxially stretched polypropylene film, the counter electrode is adhered to the other surface, and the biaxially stretched polypropylene film and each electrode are adhered to each other with a load of 5 kgf. I let you. Then, it left still for 30 minutes.

  Next, a voltage was applied to the sample so that the potential gradient was 200 V / μm.

After applying the voltage, the current value at the time when 1 minute elapsed was read, and the volume resistivity was calculated by the following formula. Note that 2290-10 (DC power supply) manufactured by Keithley was used for voltage application, and 2635B (DC ammeter) manufactured by Keithley was used for current value measurement.
Volume resistivity = [(effective electrode area) × (applied voltage)] / [(biaxially oriented polypropylene film thickness) × (current value)]

Here, the effective electrode area was calculated | required by the following formula.
(Effective electrode area) = π × [[[(Diameter of main electrode) + (Inner diameter of guard electrode)] / 2] / 2] ²

<Tensile strength>
The tensile strength of the polypropylene film was measured according to JIS-C2151. The measurement direction was the MD direction (flow direction) and the TD direction (width direction). The temperature during the measurement was 23 ° C.

<Elongation at break / tensile modulus>
The elongation at break was measured according to JIS K-7127 (1999). Specifically, a tensile test is performed under the test conditions (measurement temperature 23 ° C., test piece length 140 mm, test length 100 mm, test piece width 15 mm, tensile speed 100 mm / min) using a tensile / compression tester (manufactured by Minebea Co., Ltd.). went. Subsequently, the elongation at break (%) and the tensile modulus (GPa) were determined by automatic analysis using data processing software built in the testing machine.

<Example 1>
[Example 1-1. Fabrication of cast sheet]
PP resin A1 [Mw = 320,000, Mw / Mn = 9.3, difference (D _M ) = 11.2 (“difference (D _M )” is a logarithmic molecular weight Log (M) in a differential distribution curve of molecular weight. = Difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when 4.5 = mesopentad fraction [mmmm] = 95%, MFR = 4.9 g / 10 min, prime Polymer] and PP resin B1 [Mw = 350,000, Mw / Mn = 7.7, difference (D _M ) = 7.2, mesopentad fraction [mmmm] = 96.5%, MFR = 3.8 g / 10 min, manufactured by Korea Oil Chemical Co., Ltd.) at a mass ratio of A1: B1 = 65: 35, melted at a resin temperature of 250 ° C., and then extruded using a T-die to maintain the surface temperature at 95 ° C. It was wound around a metal drum and solidified to produce a cast sheet .
[Example 1-2. Preparation of biaxially oriented polypropylene film]
The obtained unstretched cast original sheet was kept at a temperature of 130 ° C., passed between rolls provided with a speed difference, stretched 4 times in the flow direction, and immediately cooled to room temperature. Subsequently, the stretched film is guided to a tenter, stretched 10 times in the width direction at a temperature of 158 ° C. at a stretching angle of 9 °, and then wound by relaxing and heat setting, and aging in an atmosphere of about 30 ° C. A biaxially stretched polypropylene film having a thickness of 2.5 μm was obtained by the treatment.
[Example 1-3. Capacitor fabrication, insulation resistance reduction rate and capacitance change rate ΔC]
Next, using the obtained biaxially stretched polypropylene film, a capacitor was produced as follows. A metallized film including a metal film on one side of the biaxially stretched polypropylene film was obtained by subjecting the biaxially stretched polypropylene film to aluminum deposition with a T margin deposition pattern at a deposition resistance of 15Ω / □. After slitting to a width of 60 mm, the two metallized films were combined, and 1076 turns were wound using an automatic winder 3KAW-N2 manufactured by Minato Seisakusho Co., Ltd. at a winding tension of 250 g. The element wound element was heat-treated at 120 ° C. for 15 hours while being pressed, and then sprayed with zinc metal on the element end face to obtain a flat capacitor. Lead wires were soldered to the end face of the flat capacitor, and then sealed with epoxy resin. The capacitance of the completed capacitor was 75 μF (± 5 μF).
With respect to the obtained capacitor, a direct current was applied at a test environment temperature of 105 ° C. and a voltage of 700 V for 1000 hours, and then the insulation resistance value and capacitance were measured, and the rate of decrease in insulation resistance value and change in capacitance were measured. The rate ΔC was determined.

<Example 2>
In the production of the biaxially stretched polypropylene film, the biaxially stretched polypropylene film (thickness 2.5 μm) and the capacitor were prepared in the same manner as in Example 1 except that the biaxially stretched polypropylene film was guided to a tenter and stretched in the width direction at a temperature of 159 ° C. Fabricated and evaluated.

<Example 3>
A biaxially stretched polypropylene film (thickness) was produced in the same manner as in Example 1 except that the biaxially stretched polypropylene film was led to a tenter and stretched in the width direction at a temperature of 159 ° C at a stretch angle of 11 °. 2.5 μm) and a capacitor were prepared and evaluated.

<Example 4>
In the production of the biaxially stretched polypropylene film, a biaxially stretched polypropylene film (thickness) was obtained in the same manner as in Example 1 except that it was led to a tenter and stretched in the width direction at a temperature of 159 ° C at a stretch angle of 12 °. 2.5 μm) and a capacitor were prepared and evaluated.

<Example 5>
In the production of the cast raw sheet, PP resin B2 [Mw = 380,000, Mw / Mn = 8.3, difference (D _M ) = 0.6 in place of PP resin B1 (in the molecular weight distribution curve, the log molecular weight is 4 Difference obtained by subtracting the differential distribution value when the logarithmic molecular weight is 6 from the differential distribution value when .5, mesopentad fraction [mmmm] = 96.5%, MFR = 2.3 g / 10 min, manufactured by Korea Oil Chemical Co., Ltd.] A biaxially stretched polypropylene film (thickness 2.5 μm) and a capacitor were prepared and evaluated in the same manner as in Example 1 except that was used.

<Example 6>
In the production of the cast raw sheet, PP resin A2 [Mw = 270,000, Mw / Mn = 5.7, difference (D _M ) = 8.8, mesopentad fraction [mmmm] = 95% instead of PP resin A1 , MFR = 5.6 g / 10 min, made of prime polymer], except that PP resin B2 is used instead of PP resin B1 at a mass ratio of A2: B2 = 75: 25 to obtain a cast raw sheet Produced a biaxially stretched polypropylene film (thickness 2.5 μm) and a capacitor in the same manner as in Example 3, and evaluated them.

<Example 7>
A biaxially stretched polypropylene film (thickness: 2.5 μm) and a capacitor were prepared in the same manner as in Example 3 except that the cast original fabric sheet was obtained using only the PP resin B1 as a resin component in the production of the cast original fabric sheet. Fabricated and evaluated.

<Example 8>
In the production of the cast raw sheet, PP resin A3 [Mw = 340,000, Mw / Mn = 8.1, difference (D _M ) = 4.8, mesopentad fraction [mmmm] = 97%, MFR = 4.0 g / 10 min, manufactured by Borealis], a biaxially stretched polypropylene film (thickness: 2.5 μm) and a capacitor were prepared and evaluated in the same manner as in Example 3 except that a cast raw sheet was obtained. went.

<Comparative Example 1>
In the production of the biaxially stretched polypropylene film, a biaxially stretched polypropylene film (thickness) was obtained in the same manner as in Example 1 except that it was led to a tenter and stretched in the width direction at a stretch angle of 15 ° and a temperature of 160 ° C. 2.5 μm) and a capacitor were prepared and evaluated.

<Comparative example 2>
In the production of the biaxially stretched polypropylene film, a biaxially stretched polypropylene film (thickness) was obtained in the same manner as in Example 1 except that it was guided to a tenter and stretched in the width direction at a stretching angle of 9 ° and a temperature of 160 ° C. 2.5 μm) and a capacitor were prepared and evaluated.

<Comparative Example 3>
A biaxially stretched polypropylene film (thickness: 2.5 μm) and a biaxially stretched polypropylene film were produced in the same manner as in Example 1 except that the biaxially stretched polypropylene film was led to a tenter and stretched in the width direction at a stretch angle of 5 °. A capacitor was produced and evaluated.

<Comparative example 4>
In the production of the biaxially stretched polypropylene film, a biaxially stretched polypropylene film (thickness) was obtained in the same manner as in Example 1 except that the biaxially stretched polypropylene film was guided to a tenter and stretched in the width direction at a stretch angle of 8 ° and a temperature of 160 ° C. 2.5 μm) and a capacitor were prepared and evaluated.

<Resin used in Examples 1-8 and Comparative Example 4>
The polypropylene resins used in Examples 1 to 8 and Comparative Example 4 are all homopolypropylene resins.

As shown in Table 1, the decrease rate of the insulation resistance value in the capacitor made of a biaxially stretched polypropylene film having a crystallite size of 12.2 nm or less and a volume resistivity of 6 × 10 ¹⁴ Ω · cm or more was small. . A capacitor made of a biaxially stretched polypropylene film having a crystallite size of 12.2 nm or less and a volume resistivity of 6 × 10 ¹⁴ Ω · cm or more has a capacitance change rate ΔC of −5% to 0 The capacitance was stable even after a direct current was applied for 1000 hours at a test environment temperature of 105 ° C. and a voltage of 700 V.

<Verification of volume resistivity measurement accuracy>
It was verified that the measurement accuracy of the volume resistivity measurement method in the present disclosure is higher than that of Patent Document 1 (International Publication No. 2016/182003). This will be described below.
Reference Example 1 is a test example that assumes the volume resistivity measurement method in Patent Document 1. Reference Example 2 is a test example for confirming how the measurement accuracy changes when the potential gradient is higher than that of Reference Example 1 compared to Reference Example 1.

(Reference Example 1)
A volume resistivity measuring jig, a DC power source, and a DC ammeter used in the above-described examples were prepared.
Next, a 2.3 μm biaxially stretched polypropylene film having the same thickness as that of Example 1 of Patent Document 1 (a biaxial film manufactured by Oji Holdings, different from the biaxially stretched polypropylene film of Example 1 described in Patent Document 1) The stretched polypropylene film) was set on the jig and held at 120 ° C. for 30 minutes. Thereafter, a voltage of 100 V was applied. That is, the potential gradient was 43 V / μm. As a result, a minute current of 0.1 to 0.5 nA level was measured when 1 minute passed after the voltage application.
Using this voltage and current results, the volume resistance value when the electrode area diameter was assumed to be 10 mm was found to be 6.8 × 10 ¹⁴ Ω · cm. This value is an average value of the reproduction test (n = 4). In addition, the volume resistance value when the diameter of the electrode area is assumed to be 10 mm was obtained because the diameter of the electrode area was set to 10 mm in the volume resistivity measurement method of Patent Document 1, and this was adjusted. is there.
This volume resistance value (6.8 × 10 ¹⁴ Ω · cm) was close to 6.5 × 10 ¹⁴ Ω · cm, which is the value of Example 1 of Patent Document 1. Therefore, it can be seen that the measurement method of Reference Example 1 is valid as a test assuming the measurement method of Patent Document 1.
Next, the standard deviation was obtained from the variation in the current measurement value of the reproduction test (n = 4). As a result, the standard deviation was 1.2 × 10 ¹⁴ Ω · cm. Moreover, as a result of calculating the coefficient of variation (Coefficient of variation), it was about 18%.
The coefficient of variation is a value obtained from the following.
(Coefficient of variation) = (Standard deviation) / (Average value)
Here, in Patent Document 1, measurement is performed at 110 ° C., while in Reference Example 1, measurement is performed at 120 ° C. This is due to the following reason.
When measured at 110 ° C. in the test method of Reference Example 1, the measured current value was smaller than that of Patent Document 1. Therefore, in order to reproduce the measurement method of Patent Document 1 more accurately, in Reference Example 1, measurement was performed at 120 ° C. When measuring at 110 ° C. in the test method of Reference Example 1, the reason why the measured current value is not the same as that of Patent Document 1 is that the biaxially stretched polypropylene film used for the measurement is the same as that of Patent Document 1 This is probably not the case.

(Reference Example 2)
Similar to Reference Example 1, a jig for volume resistivity measurement, a DC power source, and a DC ammeter used in the above-described examples were prepared.
Next, the same biaxially stretched polypropylene film used in Reference Example 1 was set on the jig and held at 120 ° C. for 30 minutes. Thereafter, in Reference Example 2, a voltage of 200 V was applied. That is, in Reference Example 2, the potential gradient was 87 V / μm. Except for the potential gradient, the current value was measured in the same manner as in Reference Example 1. As a result, a current of 11 to 12 nA was measured.
Using this voltage and current result, the volume resistance value when the diameter of the electrode area was assumed to be 10 mm was found to be 5.9 × 10 ¹³ Ω · cm. This value is an average value of the reproduction test (n = 4).
Next, the standard deviation was obtained from the variation in the current measurement value of the reproduction test (n = 4). As a result, the standard deviation was 3.3 × 10 ¹² Ω · cm. Moreover, as a result of calculating the coefficient of variation (Coefficient of variation), it was about 6%.

(Discussion)
As in Reference Example 1, in the volume resistivity measurement method of Patent Document 1, the current obtained is at the pA (picoampere) level and the value is not stable, but as in Reference Example 2, the current is at the nA (nanoampere) level. As a result, it can be seen that the value becomes stable.
In Reference Example 2, it is shown that when the potential gradient is 87 V / μm, the value is stable as compared with Reference Example 1 in which the potential gradient is 43 V / μm. Therefore, the potential gradient is 200 V / μm. It is understood that the value is further stabilized in comparison with the volume resistivity measurement method disclosed in Patent Document 1 (if the volume resistivity measurement method is used).
As mentioned above, it turns out that the precision of the measuring method of this volume resistivity in this indication is high.

Claims (12)

The crystallite size determined using the Scherrer equation from the half-value width of the reflection peak of the α crystal (040) plane measured by wide-angle X-ray diffraction is 12.2 nm or less,
A voltage is applied at a potential gradient of 200 V / μm in an environment of 100 ° C., and the volume resistivity calculated by the formula I from the current value at the time when 1 minute has elapsed is 6 × 10 ¹⁴ Ω · cm or more.
Volume resistivity = [(Effective electrode area) × (Applied voltage)] / [(Polypropylene film thickness) × (Current value)]
Is,
Polypropylene film.   The polypropylene film according to claim 1, wherein the melting point of fast heating in differential scanning calorimetry is 165 ° C or higher.   The polypropylene film according to claim 1 or 2, which is used for a capacitor.   The polypropylene film according to any one of claims 1 to 3, which is a biaxially stretched film. Total direction tensile strength perpendicular to the strength and the first direction pulling the first direction Ru 450~600MPa der,
The polypropylene film according to any one of claims 1 to 4. The total of the breaking elongation in the first direction and the breaking elongation in the direction orthogonal to the first direction is 150 to 220%.
The polypropylene film according to any one of claims 1 to 5. The sum of the tensile elastic modulus in the first direction and the tensile elastic modulus in the direction orthogonal to the first direction is 5 to 10 GPa.
The polypropylene film according to any one of claims 1 to 6. Ratio of tensile strength in the first direction and tensile strength in the direction perpendicular to the first direction (T _{Orthogonal direction} / T _{First direction} ) Is 1.10 or more and 2.00 or less,
The polypropylene film according to any one of claims 1 to 7. Ratio of elongation at break in the first direction and elongation at break in the direction perpendicular to the first direction (E _{Orthogonal direction} / E _{First direction} ) Is 0.20 or more and 0.70 or less,
The polypropylene film according to any one of claims 1 to 8. Ratio of tensile elastic modulus in the first direction and tensile elastic modulus in the direction orthogonal to the first direction (M _{Orthogonal direction} / M _{First direction} ) Is 1.0 or more and 2.0 or less,
The polypropylene film according to any one of claims 1 to 9. The polypropylene film according to any one of claims 1 to 10 ,
Having a metal layer laminated on one or both sides of the polypropylene film,
Metal layer integrated polypropylene film. The film capacitor which has the metal layer integrated polypropylene film of Claim 11 wound.