JP7020395B2 - Polypropylene film, metal layer integrated polypropylene film, film capacitor, and film roll - Google Patents

Description

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

The polypropylene film has excellent electrical characteristics such as high withstand voltage and low dielectric loss characteristics, and also has high moisture resistance. Therefore, it is widely used in electronic devices and electrical devices. Specifically, it is used as a film used for, for example, high voltage capacitors, various switching power supplies, filter capacitors (for example, converters, inverters, etc.), smoothing capacitors, and the like.

In recent years, there has been a demand for further miniaturization and higher capacity of capacitors. In order to improve the capacitance without changing the volume of the capacitor, it is preferable to make the film as a dielectric thin. Therefore, there is a demand for a film having a thinner thickness.

However, the thin polypropylene film has a problem that wrinkles and unwinding are likely to occur in the element winding process when manufacturing a capacitor. Therefore, there are cases where fine irregularities are formed on the surface of the polypropylene film to roughen the surface, with the main purpose of improving the slipperiness during the element winding process and facilitating the element winding process.

In Patent Document 1, the thickness is 1 to 3 μm, and when one film surface is the A side and the other side is the B side, the number of protrusions existing on the A side per 0.1 mm ² (Pa). The number of protrusions present on the B surface per 0.1 mm ² (Pb), the 10-point average roughness of the A surface (SRzA), and the 10-point average roughness of the B surface (SRzB) satisfy a predetermined relationship. A biaxially stretched polypropylene film for a capacitor is disclosed (see claim 1).
In Patent Document 1, as an effect of the biaxially stretched polypropylene film for a capacitor having the above-described configuration, even a thin film is excellent in processing suitability, and a wide range of atmospheric temperatures from low temperature (-40 ° C) to high temperature (150 ° C). It is described that it exhibits high withstand voltage even under conditions (see paragraph [0023]). Regarding the processing suitability, it is specifically described that the rate of occurrence of wrinkles and deviations is small when the element winding processing is performed (see paragraph [0122] and paragraph [0123]).

Further, in Patent Document 2, the film has protrusions on both sides, and the height (PhZ) of the most protrusions among the protrusions on each side is 100 nm or more and less than 400 nm on both sides, and 0.1 mm ² on each side. A biaxially oriented polypropylene film having a number of protrusions (Pc) per protrusion (Pc) of 150 or more and less than 500 on both sides is disclosed (see claim 1).
Patent Document 2 states that, as an effect of the biaxially oriented polypropylene film having the above-described configuration, it has a surface having a large number of low-height protrusions on both sides of the film, so that it has a high withstand voltage resistance, especially in an AC voltage capacitor application. , It is described that it has suitable element workability and excellent squealing characteristics (see paragraph [0025]). Regarding the element processability, it is specifically described that the rate of occurrence of wrinkles and deviations is small when the element winding process is performed (see paragraph [098] and paragraph [0099]).

International Publication No. 2013/146637 International Publication No. 2012/002123

The polypropylene film for a capacitor has a step of being wound in a roll shape in the manufacturing process even before the element is wound to manufacture the capacitor. Specifically, in the step of biaxially stretching an unstretched cast sheet, the polypropylene film after biaxially stretching is once wound into a roll. Further, the polypropylene film wound in a roll shape in the above step is then rewound (unwound), a metal layer such as a thin-film deposition film is formed on one surface, and the polypropylene film is wound again.

The present inventors have diligently studied polypropylene films for capacitors. As a result, even when a polypropylene film having a roughened surface is used in order to improve the slipperiness during element winding processing, when the film on which the metal layer is formed is rewound, the vapor-deposited surface and the film are formed. It was found that the non-deposited surface may be blocked and wrinkles may occur in the film in the flow direction. In addition, in this specification, blocking means that the polypropylene film of the upper layer and the polypropylene film of the lower layer which are wound and contacted are brought into close contact with each other by the pressure of winding or the like.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a polypropylene film capable of suppressing blocking of a polypropylene film integrated with a metal layer wound in a roll shape. .. The present invention also provides a metal layer-integrated polypropylene film having the polypropylene film, a film capacitor having the metal layer-integrated polypropylene film, and a film roll in which the polypropylene film is wound in a roll shape. It is in.

The present inventors have diligently studied the above findings. As a result, they have found that it is possible to suppress blocking of the polypropylene film wound in a roll shape by adopting the following configuration, and have completed the present invention.

The polypropylene film according to the present invention is
A polypropylene film having a first surface and a second surface.
Contains polypropylene resin as the main component,
The Svk value (Svk _A ) of the first surface is 0.005 μm or more and 0.030 μm or less.
The Spk value (Spk _A ) of the first surface is more than 0.035 μm and 0.080 μm or less.
The Svk value (Svk _B ) of the second surface is 0.005 μm or more and 0.030 μm or less.
The second surface is characterized in that the Spk value (Spk _B ) is 0.015 μm or more and 0.035 μm or less.

Here, the Svk value and the Spk value are parameters defined by the surface texture parameter (ISO 25178-2: 2007). The Svk value refers to the average height of the protruding valleys below the curve obtained by removing the protruding peaks and valleys from the bearing curve. The Spk value refers to the average height of the protruding peaks on the curve obtained by removing the protruding peaks and valleys from the bearing curve.

In the polypropylene film, a metal layer is formed on either one or both of the first surface and the second surface, and when the polypropylene film is wound, the first surface and the first surface are formed in a state where the metal layer is formed. The surface of 2 will come into contact. According to the above configuration, the Spk value of the first surface (Spk _A ), the Spk value of the first surface (Spk _A ), the Svk value of the second surface (Svk _B ), and the Spk of the second surface. The value (Spk _B ) is within the above numerical range, and both sides of the polypropylene film are roughened. Further, on the premise that both sides are roughened, the degree of roughening is different within the above numerical range. Therefore, the contact area between the first surface and the second surface when the polypropylene film is wound becomes smaller, and the gap between the first surface and the second surface due to the appropriate coarse protrusion can be maintained. Excellent cushioning. As a result, as can be seen from the examples, blocking can be suppressed.

Further, in general, the polypropylene film is wound by using a plurality of transport rolls and applying tension to the polypropylene film in order to prevent wrinkles and meandering. Therefore, not only one surface touches the transport roll, but both surfaces touch the transport roll and the winding is performed.
According to the above configuration, since both sides of the polypropylene film are roughened, the slipperiness to the transport roll is suitable for both sides when the polypropylene film after being biaxially stretched is wound into a roll shape. .. As a result, suitable transportability is obtained, wrinkles and unwinding are suppressed, and element winding workability is improved.

Here, considering only the transportability, it is preferable that the degree of roughening is about the same for the first surface and the second surface. However, considering the withstand voltage, it is preferable that the degree of roughening differs between the first surface and the second surface. This point will be described below.
Generally, the thickness of the film is such that the apex of the convex portion is the end of the thickness when the surface is uneven. That is, when unevenness exists on both the first surface and the second surface, the distance from the apex of the convex portion existing on the first surface to the apex of the convex portion existing on the second surface is The thickness of the film.
Here, the thickness of the core portion is the thickness obtained by subtracting the height of the convex portion of the first surface and the height of the convex portion of the second surface. Therefore, if a polypropylene film having both roughened surfaces is used, the thickness of the core portion becomes thin, leakage current is likely to occur, and the withstand voltage resistance is lowered.
Therefore, in the present invention, (1) the Svk value (Svk _A ) of the first surface and the Svk value (Svk _B ) of the second surface are about the same, that is, the depth of the valley portion is the first. While the surface and the second surface are moderately roughened on both sides to the same extent, (2) the Spk value (Spk _B ) of the second surface is used as the Spk value (Spk _A ) of the first surface for the coarse protrusions. It is configured to be smaller than the above to secure the thickness of the core part. Based on the above, it was decided to maintain the withstand voltage while also having the transportability due to the roughened surface.

As described above, according to the present invention, it is possible to suppress blocking, and further, it is possible to have both transportability and withstand voltage.

The polypropylene film having the above configuration is preferably used for capacitors.

The Spk value (Spk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _{B) of the second surface, and the Spk value (Spk B )} of the second surface are The polypropylene film within the above numerical range can suppress blocking, and further has both transportability and withstand voltage, so that it can be suitably used for a capacitor.

The polypropylene film having the above structure is preferably biaxially stretched.

When biaxially stretched, the Spk value of the first surface (Spk _A ), the Spk value of the first surface (Spk _A ), the Svk value of the second surface (Svk _B ), and the second surface It is easy to use a polypropylene film whose Spk value (Spk _B ) is within the above numerical range.

The polypropylene film having the above structure has a ratio Sq _B / Sq _A of the Sq value (Sq _A ) of the first surface to the Sq value (Sq _B ) of the second surface of 0.4 to 1.0. Is preferable.

Here, the Sq value is a parameter defined by the surface texture parameter (ISO 25178-2: 2007), and is the value of the root mean square of the height data in the defined region.

When the ratio Sq _B / Sq _A is 0.4 to 1.0, blocking after forming the metal layer can be suppressed while maintaining the strength of dielectric breakdown. As a result, it is preferable because it leads to the suppression of wrinkles at the time of feeding in the subsequent slitting process.

In the polypropylene film having the above structure, the ratio Sa _B / Sa _A of the Sa value (Sa _A ) of the first surface to the Sa value (Sa _B ) of the second surface is 0.6 to 1.0. Is preferable.

Here, the Sa value is a parameter defined by the surface texture parameter (ISO 25178-2: 2007), and is an arithmetic mean value of the absolute value of the height data in the defined region.

When the ratio Sa _B / Sa _A is 0.6 to 1.0, the amount of accompanying air accompanying the running of the film becomes close on the front and back. As a result, meandering of the film is suppressed, which leads to suppression of end face misalignment of small winding in the slitting process of the metal layer integrated film, which is preferable.

In the polypropylene film having the above configuration,
The polypropylene resin is
In the molecular weight differential distribution curve, 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 (Log (M) = 6.0). The difference when the differential distribution value is 100% (reference), hereinafter also referred to as "differential distribution value difference _DM ") is 8.0% or more, and the linear polypropylene resin A.
In the molecular weight differential distribution curve, the difference (differential distribution value difference DM) obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log ( _M ) = 4.5 is obtained. With a linear polypropylene resin B of less than 8.0%,
It preferably contains a long-chain branched polypropylene resin C polymerized using a metallocene catalyst.

The inclusion of the linear polypropylene resin A and the linear polypropylene resin B having different differences in the differential distribution values means that they include two types of linear polypropylene resins having different quantitative relationships between the high molecular weight component and the low molecular weight component. Means. Therefore, the unstretched polypropylene film (cast sheet) containing the linear polypropylene resin A and the linear polypropylene resin B is in a finely mixed state (phase separated state). Since the arrangement of the resin components constituting the film is complicated by stretching such an unstretched polypropylene film, it is considered that the withstand voltage at high temperature is improved as compared with the case where one kind of linear polypropylene resin is used alone. ..
In addition, the present inventors have discovered that when a long-chain branched polypropylene resin C polymerized using a metallocene catalyst is contained, a large amount of β crystals are formed on the specific cast sheet. Then, since the β crystal is transferred to the α crystal by stretching the cast sheet containing the β crystal, the polypropylene film obtained by the stretching has an arc (omitted) due to the difference in density between the β crystal and the α crystal. It was discovered that irregularities in the shape are formed and the surface can be suitably roughened.
In addition to containing the linear polypropylene resin A and the linear polypropylene resin B having different differences in the differential distribution values, the film is composed of the long-chain branched polypropylene resin C polymerized using a metallocene catalyst. It is possible to improve the withstand voltage resistance of the stretched film by complicating the arrangement of the resin components to be formed, and to form finely divided (omitted) arc-shaped irregularities to realize a more suitable roughened surface. ..
As described above, when the polypropylene film contains the linear polypropylene resin A, the linear polypropylene resin B, and the long-chain branched polypropylene resin C, the withstand voltage at high temperature is made more suitable, and the rough surface is more suitable. It will be possible to realize the conversion.
If a long-chain branched polypropylene resin obtained by cross-linking modification with a peroxide is used instead of the long-chain branched polypropylene resin C polymerized using a metallocene catalyst, the long-chain branched polypropylene obtained by cross-linking modification with a peroxide is used. Due to the α-crystal nucleation effect of the resin, the formation of α-crystals is promoted on the cast sheet, and the formation of β-crystals is greatly suppressed. Even if the cast sheet containing α crystals is stretched, the transition of crystallites does not occur, so that unevenness is difficult to form. Therefore, in order to roughen the polypropylene film, the long-chain branched polypropylene resin C polymerized using a metallocene catalyst is suitable.

Further, the polypropylene film integrated with a metal layer according to the present invention is
With the polypropylene film
It is characterized by having a metal layer laminated on one side or both sides of the polypropylene film.

According to the above configuration, since it has a metal layer laminated on one side or both sides of the polypropylene film, it can be used for a film capacitor using the polypropylene film as a dielectric and the metal layer as an electrode. Further, since the polypropylene film suppresses blocking and has both transportability and withstand voltage, the polypropylene film integrated with a metal layer having the polypropylene film can be suitably manufactured and has resistance. It has a voltage property.

Further, the film capacitor according to the present invention is characterized by having the wound metal layer integrated polypropylene film or having a structure in which a plurality of the metal layer integrated polypropylene films are laminated.

Further, the film roll according to the present invention is characterized in that the polypropylene film is wound in a roll shape.

According to the present invention, it is possible to provide a polypropylene film capable of suppressing blocking of a polypropylene film integrated with a metal layer wound in a roll shape. Further, it is possible to provide a polypropylene film integrated with a metal layer having the polypropylene film, a film capacitor having the polypropylene film integrated with the metal layer, and a film roll in which the polypropylene film is wound in a roll shape.

(A) is a perspective view schematically showing crater-like fine irregularities, (b) is a cross-sectional view thereof, and (c) is a vertical cross section of (b) along the I-I'line. It is a figure. It is a figure which shows an example of the projection image which projected the part of the fine unevenness | height of 0.02 μm or more on the film surface using the optical interferometry type non-contact surface shape measuring machine. (A) to (c) are schematic plan views for explaining a method of determining a virtual annulus.

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

In the present specification, the expressions "contains" and "contains" include the concepts of "contains", "contains", "substantially consists", and "consists of only".
In the present specification, "element", "capacitor", "capacitor element", and "film capacitor" mean the same thing.

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

The polypropylene film according to this embodiment is
Contains polypropylene resin as the main component,
The Svk value (Svk _A ) of the first surface is 0.005 μm or more and 0.030 μm or less.
The Spk value (Spk _A ) of the first surface is more than 0.035 μm and 0.080 μm or less.
The Svk value (Svk _B ) of the second surface is 0.005 μm or more and 0.030 μm or less.
The second surface is characterized in that the Spk value (Spk _B ) is 0.015 μm or more and 0.035 μm or less.

The Svk value (Svk _A ) of the first surface is preferably 0.007 μm or more and 0.025 μm or less, more preferably 0.008 μm or more and 0.020 μm or less, and further preferably 0.009 μm or more and 0.015 μm or less.
The Spk value (Spk _A ) of the first surface is preferably 0.040 μm or more and 0.075 μm or less, more preferably 0.043 μm or more and 0.060 μm or less, and further preferably 0.045 μm or more and 0.055 μm or less.
The Svk value (Svk _B ) of the second surface is preferably 0.007 μm or more and 0.025 μm or less, more preferably 0.008 μm or more and 0.020 μm or less, and further preferably 0.009 μm or more and 0.015 μm or less.
The Spk value (Spk _B ) of the second surface is preferably 0.017 μm or more and 0.033 μm or less, more preferably 0.018 μm or more and 0.030 μm or less, and further preferably 0.020 μm or more and 0.025 μm or less.

In the polypropylene film, a metal layer is formed on either one or both of the first surface and the second surface, and when the polypropylene film is wound, the first surface and the first surface are formed in a state where the metal layer is formed. The surface of 2 will come into contact. According to the polypropylene film, the Spk value (Spk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the second surface. The Spk value (Spk _B ) is within the above numerical range, and both sides of the polypropylene film are roughened. Further, on the premise that both sides are roughened, the degree of roughening is different within the above numerical range. Therefore, the contact area between the first surface and the second surface when the polypropylene film is wound becomes smaller, and the gap between the first surface and the second surface due to the appropriate coarse protrusion can be maintained. Excellent cushioning. As a result, as can be seen from the examples, blocking can be suppressed.

Further, in general, the polypropylene film is wound by using a plurality of transport rolls and applying tension to the polypropylene film in order to prevent wrinkles and meandering. Therefore, not only one surface touches the transport roll, but both surfaces touch the transport roll and the winding is performed.
According to the polypropylene film, both sides of the polypropylene film are roughened, so that when the polypropylene film after being biaxially stretched is wound into a roll, the slipperiness to the transport roll is suitable for both sides. be. As a result, suitable transportability is obtained, wrinkles and unwinding are suppressed, and element winding workability is improved.

Here, considering only the transportability, it is preferable that the degree of roughening is about the same for the first surface and the second surface. However, considering the withstand voltage, it is preferable that the degree of roughening differs between the first surface and the second surface. This point will be described below.
Generally, the thickness of the film is such that the apex of the convex portion is the end of the thickness when the surface is uneven. That is, when unevenness exists on both the first surface and the second surface, the distance from the apex of the convex portion existing on the first surface to the apex of the convex portion existing on the second surface is The thickness of the film.
Here, the thickness of the core portion is the thickness obtained by subtracting the height of the convex portion of the first surface and the height of the convex portion of the second surface. Therefore, if a polypropylene film having both roughened surfaces is used, the thickness of the core portion becomes thin, leakage current is likely to occur, and the withstand voltage resistance is lowered.
Therefore, in the present embodiment, (1) the Svk value (Svk _A ) of the first surface and the Svk value (Svk _B ) of the second surface are about the same, that is, the depth of the valley is the first. (2) For coarse protrusions, the Spk value (Spk _B ) of the second surface is changed to the Spk value (Spk _A ) of the first surface, while the surface of the surface and the second surface are moderately roughened on both sides. ) To ensure the thickness of the core. Based on the above, it was decided to maintain the withstand voltage while also having the transportability due to the roughened surface.

As described above, according to the polypropylene film according to the present embodiment, it is possible to suppress blocking, and further, it is possible to have both transportability and withstand voltage.

The Svk value (Svk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the Spk value of the second surface (Svk B). Spk _B ) is obtained by measuring the surface shape using a light interferometry non-contact surface shape measuring machine and using a three-dimensional surface roughness evaluation method. Since the "three-dimensional surface roughness evaluation method" evaluates the height of the entire surface of the film, the shape of the film surface is evaluated three-dimensionally. Therefore, it is possible to grasp local fine changes and variations of the surface to be measured, and to evaluate more accurate surface roughness. Not just the height of the protrusions (two-dimensional surface roughness evaluation by general center line average roughness Ra etc.), but the three-dimensional average height of the protruding peaks and the average height of the protruding valleys. By evaluating the film surface roughness using the film, blocking can be suppressed. In addition, it is possible to have a configuration having both good transportability and withstand voltage.

More specifically, the Svk value (Svk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the second surface. The surface Spk value (Spk _B ) is a value measured by using "VertScan 2.0 (model: R5500GML)" manufactured by Ryoka System Co., Ltd. as an optical interferometry non-contact surface shape measuring machine.
Hereinafter, the details of the measurement method will be described.
First, using the WAVE mode, a 530 white filter and a 1 × BODY lens barrel are applied, and a measurement of 470.92 μm × 353.16 μm per field of view is performed using an × 10 objective lens. This operation is performed at 10 locations at 1 cm intervals in the flow direction from the central location in both the flow direction and the width direction of the target sample (polypropylene film).
Next, the obtained data is subjected to noise removal processing by a median filter (3 × 3), and then Gaussian filter processing with a cutoff value of 30 μm is performed to remove undulation components. As a result, the state of the roughened surface can be appropriately measured.
Next, analysis is performed using the "ISO parameter" in the plug-in function "bearing" of the analysis software "VS-Viewer" of "VertScan 2.0".
Finally, the average value is calculated for each of the values (Svk _A , Spk _A , Svk _B , Spk _B , Sq _A , Sq _B , Sa _A , Sa _B , Sk _A , Sk _B ) obtained at the above 10 locations. do. As described above, the Svk value (Svk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the second surface. The Spk value (Spk _B ) is obtained. Further, Sq _A , Sq _B , Sa _A , Sa _B , Sk _A , and Sk _B are also obtained in the same manner.
More specifically, the method described in the examples is used.

The polypropylene film has a ratio Sq _B / Sq _A of the Sq value (Sq _A ) of the first surface to the Sq value (Sq _B ) of the second surface of 0.4 to 1.0. It is preferably 0.45 to 0.8, more preferably 0.48 to 0.7.
The Sq _A is preferably 0.020 μm to 0.080 μm, more preferably 0.025 μm to 0.070 μm.
The Sq _B is preferably 0.005 μm to 0.030 μm, more preferably 0.010 μm to 0.025 μm.

When the ratio Sq _B / Sq _A is 0.4 to 1.0, blocking after forming the metal layer can be suppressed while maintaining the strength of dielectric breakdown. As a result, it is preferable because it leads to the suppression of wrinkles at the time of feeding in the subsequent slitting process.
The detailed measurement method of the Sq value (Sq _A ) of the first surface, the Sq value (Sq _B ) of the second surface, and the ratio Sq _B / Sq _A is as described in Examples.

The polypropylene film has a Sa _B / Sa _A ratio of the Sa value (Sa _A ) of the first surface to the Sa value (Sa _B ) of the second surface of 0.6 to 1.0. It is preferably 0.65 to 0.9, more preferably 0.7 to 0.8.
The Sa _A is preferably 0.005 μm to 0.025 μm, more preferably 0.009 μm to 0.020 μm.
The Sa _B is preferably 0.005 μm to 0.025 μm, more preferably 0.007 μm to 0.015 μm.

When the ratio Sa _B / Sa _A is 0.6 to 1.0, the amount of accompanying air accompanying the running of the film becomes close on the front and back. As a result, meandering of the film is suppressed, which leads to suppression of end face misalignment of small winding in the slitting process of the metal layer integrated film, which is preferable.
The detailed measurement method of the Sa value (Sa _A ) of the first surface, the Sa value (Sa _B ) of the second surface, and the ratio Sa _B / Sa _A is as described in the examples.

The polypropylene film has a Sk _B / Sk _A ratio of the Sk value (Sk _A ) of the first surface to the Sk value (Sk _B ) of the second surface of 0.6 to 1.0. It is preferably 0.7 to 0.9, more preferably 0.75 to 0.85, and even more preferably 0.75 to 0.85.
The Sk _A is preferably 0.030 μm to 0.070 μm, more preferably 0.035 to 0.060.
The Sk _B is preferably 0.010 μm to 0.050 μm, and more preferably 0.020 μm to 0.040 μm.

Here, the Sk value is a parameter defined by the surface texture parameter (ISO 25178-2: 2007), and is the difference between the upper level and the lower level of the curve obtained by removing the protruding peaks and protruding valleys from the bearing curve. Is.

When the ratio Sk _B / Sk _A is 0.6 to 1.0, blocking after forming the metal layer can be suppressed while maintaining the strength of dielectric breakdown. As a result, it is preferable because it leads to the suppression of wrinkles at the time of feeding in the subsequent slitting process.
The detailed measurement method of the Sk value (Sk _A ) of the first surface, the Sk value (Sk _B ) of the second surface, and the ratio Sk _B / Sk _A is as described in the examples.

The Svk value (Svk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the Spk value (Spk _B ) of the second surface. ), The Sq value of the first surface (Sq _A ), the Sq value of the second surface (Sq _B ), the ratio Sq _B / Sq _A , the Sa value of the first surface (Sa _A ), the above. The Sa value (Sa _B ) of the second surface, the ratio Sa _B / Sa _A , the Sk value of the first surface (Sk _A ), the Sk value of the second surface (Sk _B ), and the ratio. The method of setting Sk _B / Sk _A within the above numerical range is not particularly limited, but (i) selection of the type of resin (raw material resin) constituting the polypropylene film, stereoregularity, molecular weight distribution, and differential distribution. Value difference _DM , (ii) content of each resin in the entire polypropylene film, (iii) longitudinal and horizontal stretching ratios during stretching, and stretching temperature, (iv) types of additives (particularly nucleating agents). It can be adjusted as appropriate depending on the selection and its content.

_A method of making the Svk value (Svk A) of the first surface different from the Svk value (Svk _B ) of the second surface, the Spk value (Spk _A ) of the first surface and the second surface. A method of making the Spk value (Spk _B ) different, a method of making the Sq value (Sq _A ) of the first surface different from the Sq value (Sq _B ) of the second surface, Sa of the first surface. A method of making the value (Sa _A ) different from the Sa value (Sa _B ) of the second surface, the Sk value (Sk _A ) of the first surface and the Sk value (Sk _B ) of the second surface. The method for making the difference is not particularly limited, but for example, a cast sheet is produced with the first surface as the surface on the cast roll side and the second surface as the surface on the air knife side, and the cast sheet is biaxial. It can be adjusted by stretching.

Both sides of the polypropylene film may be roughened by crater-like fine irregularities. 1 (a) is a perspective view schematically showing crater-like fine irregularities, FIG. 1 (b) is a cross-sectional view thereof, and FIG. 1 (c) is an I-I of (b). 'It is a vertical cross-sectional view with a line. It should be noted that FIGS. 1 (a) to 1 (c) are schematic views for explaining the “ellipse” and do not show the surface shape of the polypropylene film or the like according to the examples described later.
Most of the crater-shaped fine irregularities are formed by, for example, using an optical microscope or the like to form a pair of arcs curved in opposite directions, or a substantially arc shape (hereinafter, the arc shape and the substantially arc shape are collectively referred to as "(omitted) arc". Also called "shape"). When two (omitted) arc-shaped parts that form an observed pair are complemented (interpolated) and connected, an elliptical shape or a substantially elliptical shape (hereinafter, the elliptical shape and the substantially elliptical shape are collectively referred to as "(omitted) elliptical shape". Also called).
The two (omitted) arc-shaped portions forming this pair form a protrusion and a recess between the protrusions (see FIG. 1 (a)). The protrusions and dents form the crater-like fine irregularities (see FIGS. 1 (b) and 1 (c)). The two (omitted) arc shapes are combined to form a circular shape or a substantially circular shape (hereinafter, the circular shape and the substantially circular shape are collectively referred to as "(omitted) circular shape") or (omitted) elliptical shape. In some cases. In this case, the cross section of the protrusion is an annular or substantially annular (hereinafter, the annular and the substantially annular are collectively referred to as "(abbreviated) annular") or an elliptical ring or a substantially elliptical ring (hereinafter, an elliptical ring and an elliptical ring). The abbreviated elliptical ring is collectively referred to as "(omitted) elliptical ring"). In addition, it may be observed as a single (abbreviated) arc shape without forming a pair.

It is preferable that the polypropylene film has an elliptic density _DA of the first surface of 85 to 120 pieces / mm ² and an elliptic density _DB of the second surface of 1 to 12 pieces / mm ² .
The elliptic density _DA is more preferably 85 to 110 pieces / mm ² , and further preferably 90 to 105 pieces / mm ² .
The elliptic density _DB is more preferably 3 to 11 pieces / mm ² , and even more preferably 4 to 10 pieces / mm ² .

The elliptic density refers to the total number of the following (X) and the following (Y) observed using a digital microscope (for example, a digital microscope VHX-2000 manufactured by KEYENCE CORPORATION) per unit area. Hereinafter, the shape of the following (X) and the shape of the following (Y) are collectively referred to as an "ellipse".
When the length of one axis is L μm and the length of the other axis is S μm, those satisfying S ≦ L and 1 ≦ L ≦ 300 are referred to as “ellipses” to be considered when calculating the ellipse density. Those that do not meet this are not considered when calculating the ellipse density (not counted as an "ellipse" when calculating the ellipse density).
(X) A (omitted) circular shape or an (omitted) elliptical shape formed by combining two (omitted) arc-shaped protrusions forming the above pair.
(Y) An (omitted) elliptical shape composed of interpolating and connecting two (omitted) arc shapes forming the above pair.

The specific method for measuring the elliptical density is the method described in the examples.

When the polypropylene film is wound, the elliptic density _DA of the first surface is 85 to 120 pieces / mm ² , and the elliptic density _DB of the second surface is 1 to 12 pieces / mm ² . The contact area between the first surface and the second surface can be made smaller.
Specifically, when the ellipse density _DA of the first surface is 85 to 120 pieces / mm ² , it can be said that the number of "ellipses" is relatively large. Therefore, it is more roughened. On the other hand, when the ellipse density _DB of the second surface is 1 to 12 pieces / mm ² , it can be said that the number of "ellipses" is relatively small. Therefore, although the surface is roughened, the degree is small.
As described above, if the elliptic density _DA of the first surface is 85 to 120 pieces / mm ² and the elliptic density _DB of the second surface is 1 to 12 pieces / mm ² , in the slit processing. It is possible to prevent the film from meandering to the left and right and causing the end faces of the small windings to be uneven. As a result, as can be seen from the examples, the slit process workability can be improved.

Further, when the elliptic density _DA of the first surface is 85 to 120 pieces / mm ² and the elliptic density _DB of the second surface is 1 to 12 pieces / mm ² , both sides of the polypropylene film are covered. Since the surface is more preferably roughened, the slipperiness to the transport roll is more suitable for both sides when the polypropylene film after being biaxially stretched is wound into a roll. As a result, more suitable transportability is obtained, and wrinkles and unwinding are further suppressed.

Here, considering only the transportability, it is preferable that the degree of roughening is about the same for the first surface and the second surface. However, considering the withstand voltage, it is preferable that the degree of roughening differs between the first surface and the second surface. Generally, when the surface is roughened, the thin portion (concave concave portion) of the film causes a leakage current. Therefore, if the elliptic density _DB of the second surface is smaller than the elliptic density _DA of the first surface, the number of irregularities that can cause leakage current can be reduced. Specifically, when the elliptic density _DB of the second surface is 1 to 12 pieces / mm ² , it can be said that the number of irregularities that can cause leakage current is small. As a result, the configuration is such that the withstand voltage resistance is more preferably maintained, and the transportability due to the roughening is more preferably combined.

The polypropylene film has an average major axis length _LA of 20 to 80 μm of the _ellipses constituting the elliptical density _DA of the first surface, and the average of the ellipses constituting the elliptic density DB of the second surface. The major axis length _LB is preferably 30 to 100 μm.
The average major axis length _LA is more preferably 30 to 70 μm, and even more preferably 40 to 68 μm.
The average major axis length _LB is more preferably 35 to 90 μm, and even more preferably 40 to 80 μm.

The average major axis length _LA is the average value of the major axis of the "ellipse" observed in the measurement of the ellipse density _DA .
The average major axis length _LB is the average value of the major axis of the "ellipse" observed in the measurement of the _ellipse density DB.

The specific measurement method of the average major axis length _LA and the average major axis length _LB is based on the method described in the examples.

When the average major axis length _LA of the ellipses constituting the elliptical density _DA of the first surface is 20 to 80 μm, the elliptic density _DA of the first surface is likely to be within the numerical range. Further, when the average major axis length _LB of the _ellipse constituting the elliptical density DB of the second surface is 30 to 100 μm, the elliptical density _DB of the second surface is likely to be within the numerical range. ..

The polypropylene film has an elliptical perfection _PA of an _ellipse constituting the elliptic density _DA of the first surface of 30 to 70%, and an elliptical perfection of an ellipse constituting the elliptic density DB of the second surface. The degree P _B is preferably 15 to 50%.
The elliptical perfect fifth _PA is more preferably 35 to 65%, further preferably 40 to 60%.
The elliptical perfect fifth P _B is more preferably 20 to 45%, still more preferably 25 to 40%.

The ellipse perfect fifth is a value obtained as follows.
First, as a light interference type non-contact surface shape measuring machine, "VertScan 2.0 (model R5500GML)" manufactured by Ryoka System Co., Ltd. is used, and a 530 white filter and a 1 × BODY lens barrel are applied in WAVE mode. , X10 objective lens is used to obtain surface shape data of 470.92 μm × 353.16 μm per field of view. This operation is performed at 10 locations at 1 cm intervals in the flow direction from the central location in both the flow direction and the width direction of the target sample (polypropylene film).
Next, the obtained data is subjected to noise removal processing by a median filter (3 × 3), and then Gaussian filter processing with a cutoff value of 30 μm is performed to remove undulation components.
From the projection images (see FIG. 2) of the surface shape data of each of the 10 locations obtained as described above, three crater projection images consisting of paired arcs are extracted.
FIG. 2 is a diagram showing an example of a projected image in which a portion of fine irregularities having a height of 0.02 μm or more is projected onto a film surface using a light interference type non-contact surface shape measuring device. Note that FIG. 2 is an image shown for facilitating visual understanding of the “projected image”, and is not a projected image of a polypropylene film or the like according to an embodiment described later.
In extracting the crater projection image, three crater projection images based on different β-type spherulites that do not overlap with each other are extracted. The three extraction methods extract quartiles (first quartile, second quartile (ie, median) and third quartile) in the area of the visual ellipse. I will do it. For example, when N crater projection images are confirmed, the first quartile is [(3 + N) / 4] th, the second quartile is [(1 + N) / 2] th, and the third quartile. The crater projection image having the largest area [(1 + 3N) / 4] as a number is extracted. If the first quartile to the third quartile obtained by substituting N have a decimal point, the first quartile to the third quartile are integers after the decimal point. Is rounded off. Specifically, for example, when nine crater projection images are confirmed, the crater projection images having the third, fifth, and seventh areas are extracted. Further, for example, when 12 crater projection images are confirmed, the crater projection images of the 4th, 7th, and 9th areas are extracted.
Next, for each of the three extracted crater projection images, the total length Lt of the paired arcs and the total circumference length of the virtual ring including the paired arcs are measured as Lc, and the ratio (Lt) is measured. / Lc) is calculated. Then, the obtained total 30 values of the ratio are averaged to obtain the average value α of the ratio (Lt / Lc).

The virtual ring is determined and Lt and Lc are measured by using the plug-in function "edge curve length" of the analysis software "VS-Viewer" of the optical interferometric non-contact surface shape measuring device VertScan 2.0. The specific procedure is as follows.
3 (a) to 3 (c) are schematic plan views for explaining a method of determining a virtual ring.
(1) First, as shown in FIG. 3A, the two points most distant from each other on the arc 30a and the arc 30b are designated as P ₁ and P ₂ , and a straight line connecting P ₁ and P ₂ (hereinafter, a straight line). (It is called P1 _- P2).) _Is determined.
( ₂ ) Then, as shown in FIG. 3 (b), a portion located on one side of the straight line (P1 _- P2) (in _FIG . 3, above the straight line (P1 _- P2)). From the shapes (positional data) of the arcs 30a and 30b of, an ellipse (E ₀ ) _having a straight line (P1 _−P2 ) as the major axis is derived by the least squares method. Then, the curve forming the ellipse (E ₀ ) (a part of the circumference of the ellipse (E ₀ )) complements the portion between the arc 30a and the arc 30b on one side to form a complementary line 40a. In FIG. 3, the ellipse (E ₀ ) other than the portion corresponding to the complementary line 40a is not shown.
(3) Then, as shown in FIG. 3 (c), the portion located on the other side of the straight line (P1 _- P2) (in _FIG . ₃ , the lower side than the straight line (P1 _- P2)). From the shapes (positional data) of the arcs 30a and 30b, an ellipse (E ₁ ) having _a straight line (P1 _−P2 ) as the major axis is derived by the least squares method. Then, the curve forming the ellipse (E ₁ ) (a part of the circumference of the ellipse (E ₁ )) complements the portion between the arc 30a and the arc 30b on the other side to form a complementary line 40b. In FIG. 3, the ellipse (E ₁ ) other than the portion corresponding to the complementary line 40b is not shown.
(4) The annulus shown in FIG. 3C in which the complementary lines 40a and 40b thus determined and the arcs 30a and 30b are connected is a virtual annulus.
(5) Then, the height profile of the fine unevenness 20 showing the height of the fine unevenness 20 at each position with respect to each position (distance when the point with the circumference is used as a reference) on the circumference of the virtual annulus is obtained. draw. From this height profile, Lt and Lc in the crater projection image G corresponding to the portion having a height of 0.02 μm or more are read.
When implementing the least squares method, 30 position data (n = 30) are used respectively.

When the elliptical perfection _PA is 40 to 60% and the elliptic perfection _PB is 25 to 35%, blocking after the formation of the metal layer can be suppressed while maintaining the strength of dielectric breakdown. As a result, it is preferable because it leads to the suppression of wrinkles at the time of feeding in the subsequent slitting process.

The DC dielectric breakdown strength ES of the polypropylene film at 100 ° C. is preferably 510 V _DC / μm or more, more preferably 525 V _DC / μm or more, and further preferably 540 V _DC / μ m or more. The higher the DC dielectric breakdown strength ES of the polypropylene film at 100 ° C. is, the more preferable, but for example, it is 600 V _DC / μm or less, 570 V _DC / μm or less, and 550 V _DC / μm or less.

The DC dielectric breakdown strength ES of the polypropylene film at 120 ° C. is preferably 485 V _DC / μm or more, and more preferably 490 V _DC / μm or more. The higher the DC dielectric breakdown strength ES of the polypropylene film at 125 ° C. is, the more preferable, but for example, it is 600 V _DC / μm or less and 550 V _DC / μm or less.

The ash content of the polypropylene film is preferably 6 × 10 ppm or less (60 ppm or less), more preferably 5 × 10 ppm or less (50 ppm or less), and 4 × 10 ppm or less (40 ppm or less) with respect to the polypropylene film. Is more preferable, and 3 × 10 ppm or less (30 ppm or less) is particularly preferable. The ash content is preferably 0 × 10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1 × 10 ppm or more (10 ppm or more). When the ash content is within the numerical range, the electrical characteristics of the capacitor are further improved while suppressing the formation of polar small molecule components. The ash content refers to a value obtained by the method described in Examples.

The polypropylene film has a thickness of preferably 9.5 μm or less, more preferably 6.0 μm or less, further preferably 3.0 μm or less, further preferably 2.9 μm or less, and particularly preferably 2.8 μm or less. More preferably, it is 5.5 μm or less. The thickness of the polypropylene film is preferably 0.8 μm or more, more preferably 1.0 μm or more, further preferably 1.4 μm or more, further preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. In particular, when it is in the range of 1.4 to 6.0 μm, 1.5 to 3.0 μm, 1.5 to 2.9 μm, etc., the slit process processability and the vapor deposition process are performed even though the polypropylene film is very thin. It is preferable because it is excellent in blocking suppression property and element winding processability at the time.

When the thickness is 9.5 μm or less, the capacitance can be increased, so that it can be suitably used for a capacitor. Further, from the viewpoint of manufacturing, the thickness can be 0.8 μm or more.

The thickness of the polypropylene film refers to a 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.

The polypropylene film may be a biaxially stretched film, a uniaxially stretched film, or a non-stretched film. Among them, the Spk value (Spk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the second surface. A biaxially stretched film is preferable from the viewpoint that the Spk value (Spk _B ) can be easily kept within the above numerical range.

The polypropylene film and the polypropylene film integrated with a metal layer are each wound in a roll shape, and are preferably in the form of a film roll. The film roll may or may not have a winding core. The film roll preferably has a winding core. The material of the winding core of the film roll is not particularly limited. Examples of the material include paper (paper tube), resin, fiber reinforced plastic (FRP), metal and the like. Examples of the resin include polyvinyl chloride, polyethylene, polypropylene, phenol resin, epoxy resin, acrylonitrile-butadiene-styrene copolymer and the like. Examples of the plastic constituting the fiber reinforced plastic include polyester resin, epoxy resin, vinyl ester resin, phenol resin, thermoplastic resin and the like. Examples of the fibers constituting the fiber-reinforced plastic include glass fiber, aramid fiber (Kevlar (registered trademark) fiber), carbon fiber, polyparaphenylene benzoxazole fiber (Zylon (registered trademark) fiber), polyethylene fiber, and boron fiber. Can be mentioned. Examples of the metal include iron, aluminum, stainless steel and the like. The winding core of the film roll also includes a winding core formed by impregnating a paper tube with the resin. In this case, the material of the winding core is classified as a resin.

As described above, the polypropylene film contains a polypropylene resin as a main component. In the present specification, the content of polypropylene resin as a main component means that the polypropylene resin is contained in an amount of 50% by mass or more with respect to the entire polypropylene film (when the entire polypropylene film is 100% by mass). The content of the polypropylene resin with respect to the entire polypropylene film is preferably 75% by mass or more, more preferably 90% by mass or more. The upper limit of the content of the polypropylene resin is, for example, 100% by mass, 98% by mass, or the like with respect to the entire polypropylene film.

The polypropylene resin is not particularly limited, and one type may be used alone, or two or more types may be used in combination. As the polypropylene resin, a polypropylene resin that forms β-type spherulites when used as a cast sheet is particularly suitable.

Examples of the polypropylene resin include linear polypropylene resins. The linear polypropylene resin can be used alone or in combination of two or more. Among them, it is preferable to use the following linear polypropylene resin A and / or the following linear polypropylene resin B. In particular, it is preferable to use the following linear polypropylene resin A and the following linear polypropylene resin B in combination. The following linear polypropylene resin A and the following linear polypropylene resin B are preferably homopolypropylene resins. As the combined use of the following linear polypropylene resin A and the following linear polypropylene resin B, the following resin A-1 and the following resin B-1, the following resin A-2 and the following resin B-2, the following resin A-3 and the following resin B-3, a combination of the following resin A-4 and the following resin B-4 may be mentioned as suitable. However, in the present invention, the polypropylene resin is not limited to the following resins.
<Linear polypropylene resin A>
(Linear polypropylene resin A-1)
In the molecular weight differential distribution curve, 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 (M) = 6. When the differential distribution value at 0 is 100% (reference), the linear polypropylene resin is 8.0% or more.
(Linear polypropylene resin A-2)
A linear polypropylene resin having a heptane insoluble content (HI) of 98.5% or less.
(Linear polypropylene resin A-3)
A linear polypropylene resin having a melt flow rate (MFR) of 4.0 to 10.0 g / 10 min at 230 ° C.
(Linear polypropylene resin A-4)
A linear polypropylene resin having a weight average molecular weight Mw of 340,000 or less.
<Linear polypropylene resin B>
(Linear polypropylene resin B-1)
In the molecular weight differential distribution curve, 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 (M) = 6. When the differential distribution value at 0 is 100% (reference), the linear polypropylene resin is less than 8.0%.
(Linear polypropylene resin B-2)
A linear polypropylene resin having a heptane insoluble content (HI) of more than 98.5%.
(Linear polypropylene resin B-3)
A linear polypropylene resin having a melt flow rate (MFR) of less than 4.0 g / 10 min at 230 ° C. (particularly a linear polypropylene resin having a melt flow rate (MFR) of 0.1 to 3.9 g / 10 min).
(Linear polypropylene resin B-4)
A linear polypropylene resin having a weight average molecular weight Mw of more than 340,000.

The weight average molecular weight Mw of the linear polypropylene resin A is preferably 250,000 or more. The weight average molecular weight Mw of the linear polypropylene resin A is preferably 450,000 or less, more preferably 400,000 or less, further preferably 350,000 or less, and 340,000 or less. Is particularly preferable. When the weight average molecular weight Mw of the linear polypropylene resin A is 250,000 or more and 450,000 or less, the resin fluidity becomes appropriate. As a result, the thickness of the cast sheet can be easily controlled, and a thin stretched film can be easily produced. In addition, the thickness of the cast sheet and the stretched film is less likely to be uneven, and appropriate stretchability can be obtained, which is preferable.

The molecular weight distribution [(weight average molecular weight Mw) / (number average molecular weight Mn)] of the linear polypropylene resin A is preferably 5.5 or more and 12.0 or less, and 7.0 or more and 12.0 or less. It is more preferably 7.5 or more and 11.0 or less, particularly preferably 8.0 or more and 11.0 or less, and even more preferably 9.0 or more and 11.0 or less. ..

The molecular weight distribution [(z average molecular weight Mz) / (number average molecular weight Mn)] of the linear polypropylene resin A is preferably 15.0 or more and 70.0 or less, and 20.0 or more and 60.0 or less. More preferably, it is more preferably 25.0 or more and 50.0 or less.

When the respective molecular weight distributions of the linear polypropylene resin A are within the above preferable ranges, unevenness is less likely to occur in the thicknesses of the cast sheet and the stretched film, and appropriate stretchability can be obtained, which is preferable.

In the present specification, the weight average molecular weight (Mw), number average molecular weight (Mn), Z average molecular weight and molecular weight distribution (Mw / Mn and Mz / Mn) of the linear polypropylene resin A and the linear polypropylene resin B are gel permeations. It is a value measured using an ion chromatograph (GPC) device. In the present specification, it is a value measured using HLC-8121GPC-HT (trade name) of 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) HTs manufactured by Tosoh Corporation are connected and used. The column temperature is set to 140 ° C., and trichlorobenzene is flowed as an eluent at a flow rate of 1.0 ml / 10 minutes to obtain measured values of Mw and Mn. A calibration curve with respect to the molecular weight M is prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured values are converted into the molecular weight of polypropylene using the Q-factor to obtain Mw, Mn and Mz. Further, the logarithm of the base 10 of the molecular weight M is referred to as a logarithmic molecular weight (“Log (M)”).

Further, 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 long-chain branched polypropylene C are obtained by gel permeation chromatography (GPC). It is a value measured using the device. More specifically, it is measured by a high temperature GPC-MALS measurement, that is, a high temperature GPC device (HLC-8121GPC / HT; manufactured by Tosoh) equipped with a light scattering detector (DAWN EOS; manufactured by Wyatt Technology). As columns, TSKgel guardcolumn HHR (30) (7.8 mm ID x 7.5 cm) and three TSKgel GMH-HR-H (20) HT (7.8 mm ID x 30 cm) manufactured by Tosoh Corporation are connected. To use. The column temperature is set to 140 ° C., and trichlorobenzene is flowed as an eluent at a flow rate of 1.0 ml / min to obtain measured values of Mw and Mn.

The linear polypropylene resin A preferably has a differential distribution value difference _DM of 8.0% or more, and the linear polypropylene resin A has a differential distribution value difference _DM of 8.0% or more and 18.0% or less. It is more preferably 9.0% or more and 17.0% or less, and particularly preferably 10.0% or more and 16.0% or less.

The fact that the differential distribution value difference DM of the linear polypropylene resin A is _8.0 % or more and 18.0% or less means that a component having a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter, “low molecular weight component”). ”) As a typical distribution value, a component with a logarithmic molecular weight Log (M) = 4.5 and a component with a molecular weight of around 1 million on the high molecular weight side (hereinafter, also referred to as“ high molecular weight component ”). It can be understood that the low molecular weight component is more than 8.0% or more and 18.0% or less when compared with the component having Log (M) = 6.0 as a distribution value.
That is, for example, in the case where the molecular weight distribution Mw / Mn is 7.0 to 12.0, even if the molecular weight distribution Mw / Mn is 7.0 to 12.0, the molecular weight distribution width is simply wide. It only shows that, and the quantitative relationship between the high molecular weight component and the low molecular weight component in it is unknown. Therefore, the linear polypropylene resin A contains a large amount of components having a molecular weight of 10,000 to 100,000 in a proportion of 8.0% or more and 18.0% or less as compared with the components having a molecular weight of 1 million.

When the differential distribution value difference DM of the linear polypropylene resin A is _8.0 % or more and 18.0% or less, the low molecular weight component is 8.0% or more and 18.0% when compared with the high molecular weight component. Includes a large amount at a rate of% or less. Therefore, it becomes easy to obtain the surface of the film in the present embodiment, which is preferable.

The differential distribution value is a value obtained as follows using GPC. A curve (generally also referred to as an "elution curve") indicating the intensity over time obtained by a GPC differential refractometer (RI) detector is used. Using the calibration curve obtained using standard polystyrene, the time axis is converted to a logarithmic molecular weight (Log (M)) to convert the elution curve into a curve showing the strength against 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, assuming that the total area of the curve showing the intensity is 100%. The differential distribution curve is obtained by differentiating this integral distribution curve with Log (M). Therefore, the "differential distribution" means the differential distribution of the concentration fraction with respect to the molecular weight. From this curve, the differential distribution value at a specific Log (M) is read.

The mesopentad fraction ([mm mm]) of the linear polypropylene resin A is preferably 99.8% or less, more preferably 99.5% or less, and further preferably 99.0% or less. preferable. The mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, still more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is appropriately improved due to the moderately high stereoregularity, and the withstand voltage under high temperature is improved. On the other hand, the rate of solidification (crystallization) during molding of the cast sheet becomes appropriate, and the cast sheet has an appropriate stretchability.

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

The heptane insoluble content (HI) of the linear polypropylene resin A is preferably 96.0% or more, more preferably 97.0% or more. The heptane insoluble content (HI) of the linear polypropylene resin A is preferably 99.5% or less, more preferably 98.5% or less, still more preferably 98.0% or less. Here, the larger the heptane insoluble content, the higher the stereoregularity of the resin. When the heptane insoluble content (HI) is 96.0% or more and 99.5% or less, the crystallinity of the resin is appropriately improved due to the moderately high stereoregularity, and the withstand voltage at high temperature is improved. do. On the other hand, the rate of solidification (crystallization) during molding of the cast sheet becomes appropriate, and the cast sheet has an appropriate stretchability. The method for measuring heptane insoluble matter (HI) is as described in Examples.

The ash content of the linear polypropylene resin A is preferably 6 × 10 ppm or less (60 ppm or less), more preferably 5 × 10 ppm or less (50 ppm or less), further preferably 4 × 10 ppm or less (40 ppm or less), and 3 ×. 10 ppm or less (30 ppm or less) is particularly preferable. The ash content of the linear polypropylene resin A is preferably 0 × 10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1 × 10 ppm or more (10 ppm or more). When the ash content of the linear polypropylene resin A is within the above preferable range, the electrical characteristics as a capacitor are further improved while suppressing the formation of polar small molecule components. The ash content refers to a value obtained by the method described in Examples.

The melt flow rate (MFR) of the linear polypropylene resin A at 230 ° C. is preferably 1.0 to 15.0 g / 10 min, more preferably 2.0 to 10.0 g / 10 min, and 4 It is more preferably 9.0 to 10.0 g / 10 min, and particularly preferably 4.3 to 6.0 g / 10 min. When the MFR of polypropylene A at 230 ° C. is within the above range, unstable flow such as melt fracture is unlikely to occur because the flow characteristics in the molten state are excellent, and fracture during stretching is suppressed. Therefore, since the film thickness uniformity is good, there is an advantage that the formation of a thin-walled portion where dielectric breakdown is likely to occur is suppressed. The method for measuring the melt flow rate is as described in the examples.

The content of the linear polypropylene resin A is preferably 55% by mass or more, more preferably 60% by mass or more, assuming that the total polypropylene resin in the polypropylene film is 100% by mass. The content of the linear polypropylene resin A is preferably 99.9% by mass or less, more preferably 90% by mass or less, and 85% by mass, assuming that the total polypropylene resin in the polypropylene film is 100% by mass. It is more preferably% or less, and particularly preferably 80% by mass or less.

The weight average molecular weight Mw of the linear polypropylene resin B is preferably 300,000 or more, more preferably 330,000 or more, further preferably more than 340,000, and further preferably 350,000 or more. It is preferable, and it is particularly preferable that it exceeds 350,000. The weight average molecular weight Mw of the linear polypropylene resin B is preferably 400,000 or less, and more preferably 380,000 or less.

The molecular weight distribution [(weight average molecular weight Mw) / (number average molecular weight Mn)] of the linear polypropylene resin B is preferably 7.0 or more and 9.0 or less, and 7.5 or more and 8.9 or less. It is more preferable, and it is further preferable that it is 7.5 or more and 8.5 or less.

The molecular weight distribution [(z average molecular weight Mz) / (number average molecular weight Mn)] of the linear polypropylene resin B is preferably 20.0 or more and 70.0 or less, and 25.0 or more and 60.0 or less. More preferably, it is more preferably 25.0 or more and 50.0 or less.

When the respective molecular weight distributions of the linear polypropylene resin B are within the above preferable ranges, unevenness is less likely to occur in the thicknesses of the cast sheet and the stretched film, and appropriate stretchability can be obtained, which is preferable.

The differential distribution value difference DM of the linear polypropylene resin B is preferably less than 8.0%, more preferably _-20.0 % or more and less than 8.0%, and -10.0% or more. It is more preferably 7.9% or less, and particularly preferably −5.0% or more and 7.5% or less.

The mesopentad fraction ([mm mm]) of the linear polypropylene resin B is preferably less than 99.8%, more preferably 99.5% or less, and further preferably 99.0% or less. preferable. The mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, still more preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is appropriately improved due to the moderately high stereoregularity, and the withstand voltage under high temperature is improved. On the other hand, the rate of solidification (crystallization) during molding of the cast sheet becomes appropriate, and the cast sheet has an appropriate stretchability.

The heptane insoluble content (HI) of the linear polypropylene resin B is preferably 97.5% or more, more preferably 98% or more, still more preferably 98.5% or more, and particularly preferably 98. It is 6.6% or more. The heptane insoluble content (HI) of the linear polypropylene resin B is preferably 99.5% or less, more preferably 99% or less.

The ash content of the linear polypropylene resin B is preferably 6 × 10 ppm or less (60 ppm or less), more preferably 5 × 10 ppm or less (50 ppm or less), further preferably 4 × 10 ppm or less (40 ppm or less), and 3 ×. 10 ppm or less (30 ppm or less) is particularly preferable. The ash content of the linear polypropylene resin B is preferably 0 × 10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, and particularly preferably 1 × 10 ppm or more (10 ppm or more). When the ash content of the linear polypropylene resin B is within the above preferable range, the electrical characteristics as a capacitor are further improved while suppressing the formation of polar small molecule components. The ash content refers to a value obtained by the method described in Examples.

The melt flow rate (MFR) of the linear polypropylene resin B at 230 ° C. is preferably 0.1 g / 10 min or more. The melt flow rate (MFR) of the linear polypropylene resin B at 230 ° C. is preferably 6.0 g / 10 min or less, more preferably 5.0 g / 10 min or less, and 4.0 g / 10 min or less. It is more preferably less than 3.9 g / 10 min or less, and particularly preferably 3.9 g / 10 min or less.

When the linear polypropylene resin B is used as the polypropylene resin, the content of the linear polypropylene resin B is preferably 10% by mass or more, assuming that the total polypropylene resin in the polypropylene film is 100% by mass. It is more preferably 15% by mass or more, and further preferably 20% by mass or more. Similarly, the content of the linear polypropylene resin B is preferably 45% by mass or less, more preferably 40% by mass or less, assuming that the total polypropylene resin in the polypropylene film is 100% by mass. ..

When the linear polypropylene resin A and the linear polypropylene resin B are used in combination as the polypropylene resin, assuming that the total polypropylene resin is 100% by mass, 55 to 90% by weight of the linear polypropylene resin A and 45 to 45 to It is preferable to contain 10% by weight of the linear polypropylene resin B, and more preferably 60 to 85% by weight of the linear polypropylene resin A and 40 to 15% by weight of the linear polypropylene resin B. It is particularly preferable to contain 60 to 80% by weight of the linear polypropylene resin A and 40 to 20% by weight of the linear polypropylene resin B.

When the polypropylene resin contains the linear polypropylene resin A and the linear polypropylene resin B, the polypropylene film is in a finely mixed state (phase separated state) of the linear polypropylene resin A and the linear polypropylene resin B. Therefore, the withstand voltage resistance at high temperatures is improved.

The linear polypropylene resin can be produced by using a generally known polymerization method. As long as the linear polypropylene resin that can be used for the polypropylene film of the present embodiment can be produced, there is no particular limitation. Examples of such a polymerization method include a vapor phase polymerization method, a bulk polymerization method and a slurry polymerization method.

The polymerization may be a single-stage (one-stage) polymerization using one polymerization reactor, or may be a multi-stage polymerization using at least two or more polymerization reactors. Further, hydrogen or a comonomer may be added to the reactor as a molecular weight adjusting agent.

A generally known Ziegler-Natta catalyst can be used as the catalyst for the polymerization, and the linear polypropylene resin is not particularly limited as long as it can be obtained. The catalyst may contain a co-catalyst component or a donor. By adjusting the catalyst and polymerization conditions, the molecular weight, molecular weight distribution, stereoregularity and the like can be controlled.

The molecular weight, molecular weight distribution, differential distribution value difference _DM , etc. of the linear polypropylene resin are, for example, (i) each condition such as the polymerization method and the temperature and pressure at the time of polymerization, and (ii) the reactor at the time of polymerization. It can be adjusted by appropriately selecting the form, (iii) presence / absence of additive, type and amount used, (iv) type and amount of catalyst, and the like.

Specifically, the molecular weight, molecular weight distribution, differential distribution value difference _DM , and the like of the linear polypropylene resin can be adjusted, for example, by a multi-stage polymerization reaction. As the multi-stage polymerization reaction, for example, the following method can be exemplified.

First, in the first polymerization step, propylene and a catalyst are supplied to the first polymerization reactor. Along with these components, hydrogen as a molecular weight modifier is mixed in the amount required to reach the required molecular weight of the polymer. In the case of slurry polymerization, for example, the reaction temperature is about 70 to 100 ° C., and the residence time is about 20 minutes to 100 minutes. Multiple reactors can be used, for example, in series. In this case, the polymerization product of the first step is continuously sent to the next reactor together with additional propylene, a catalyst and a molecular weight modifier, and subsequently, the molecular weight is reduced to a lower molecular weight or a higher molecular weight than the first polymerization step. The adjusted second polymerization is carried out. By adjusting the yield (production amount) of the first and second reactors, it is possible to adjust the composition (composition) of the high molecular weight component and the low molecular weight component.

Further, the molecular weight, molecular weight distribution, differential distribution value difference _DM and the like of the linear polypropylene resin can be adjusted by peroxidation decomposition. For example, a method of peroxidation treatment with a decomposing agent such as hydrogen peroxide or organic peroxide can be exemplified.
When a peroxide is added to a disintegrating polymer such as polypropylene, a hydrogen abstraction reaction occurs from the polymer, and the generated polymer radicals are partially recombined to cause a cross-linking reaction, but most of the radicals are secondary decomposition (β cleavage). ), And it is divided into two polymers with smaller molecular weight. That is, the higher the molecular weight component, the higher the probability that the decomposition will proceed. As a result, the low molecular weight component is increased, and the composition of the molecular weight distribution can be adjusted.

When adjusting the content of low molecular weight components by blending (resin mixing), it is preferable to dry-mix or melt-mix at least two or more different molecular weight resins. In general, two types of polypropylene mixed systems in which an additive resin having a higher or lower average molecular weight than that of the main resin is mixed in an amount of about 1 to 40% by mass is preferable because the amount of low molecular weight components can be easily adjusted. It will be used.

Further, in the case of this mixing adjustment, a melt flow rate (MFR) may be used as a guideline for the average molecular weight. In this case, it is preferable that the difference in MFR between the main resin and the added resin is about 1 to 30 g / 10 minutes from the viewpoint of convenience in adjustment.

As the linear polypropylene resin, a commercially available product can also be used.

The polypropylene resin preferably contains a long-chain branched polypropylene resin. Among the long-chain branched polypropylene resins, the long-chain branched polypropylene resin C (hereinafter, also referred to as “long-chain branched polypropylene resin C”) obtained by polymerizing propylene using a metallocene catalyst is preferable. Specifically, when the polypropylene resin contains the long-chain branched polypropylene resin C, a large amount of β crystals are formed on the cast sheet. Then, since the β crystal is transferred to the α crystal by stretching the cast sheet containing the β crystal, the polypropylene film obtained by the stretching has an arc (omitted) due to the difference in density between the β crystal and the α crystal. It is preferable in that unevenness of the shape is formed and the surface can be preferably roughened.
Above all, it is more preferable that the polypropylene resin contains the linear polypropylene resin A and the long-chain branched polypropylene resin C.
Further, it is more preferable that the polypropylene resin contains the linear polypropylene resin A and the linear polypropylene resin B, and also contains the long-chain branched polypropylene resin C. The linear polypropylene resin A and the linear polypropylene resin B differ in the differential distribution value difference _DM , the heptane insoluble component (HI), and / or the melt flow rate (MFR), etc., and are in a finely mixed state (phase separated state). Therefore, by stretching such an unstretched polypropylene film, the arrangement of the resin components constituting the film becomes complicated. Therefore, in addition to containing the linear polypropylene resin A and the linear polypropylene resin B having different differential distribution value differences _DM , heptane insoluble content (HI), and / or melt flow rate (MFR), etc., the long chain The inclusion of the branched polypropylene resin C improves the withstand voltage resistance of the stretched film by complicating the arrangement of the resin components constituting the film, and forms finer (omitted) arc-shaped irregularities, which is more suitable. It is possible to achieve a rough surface.
If a long-chain branched polypropylene resin obtained by cross-linking modification with a peroxide is used instead of the long-chain branched polypropylene resin C polymerized using a metallocene catalyst, the long-chain branched polypropylene obtained by cross-linking modification with a peroxide is used. Due to the α-crystal nucleation effect of the resin, the formation of α-crystals is promoted on the cast sheet, and the formation of β-crystals is greatly suppressed. Even if the cast sheet containing α crystals is stretched, the transition of crystallites does not occur, so that unevenness is difficult to form. Therefore, in order to roughen the polypropylene film, the long-chain branched polypropylene resin C polymerized using a metallocene catalyst is suitable.

The metallocene catalyst is generally a metallocene compound that forms a polymerization catalyst that produces olefin macromers. The long-chain branched polypropylene resin C obtained by polymerizing propylene using a metallocene catalyst is preferable because the branched chain length and the branch chain spacing of polypropylene are appropriate and excellent compatibility with linear polypropylene can be obtained. .. Further, it is preferable because a uniform composition and a uniform surface shape can be obtained. In the production of long-chain branched polypropylene resin C, other conditions other than the type and amount of catalyst used, such as (i) polymerization method and conditions such as temperature and pressure during polymerization, and (ii) during polymerization. The form of the reactor, (iii) the presence or absence of additives, the type and amount of additives, etc. are determined in consideration of the molecular weight, molecular weight distribution, differential distribution value difference DM, etc. of the long-chain branched _{polypropylene} resin C to be produced. The conditions can be the same as those described in the section of the method for producing a linear polypropylene resin.

The weight average molecular weight Mw of the long-chain branched polypropylene resin C is preferably 150,000 or more and 600,000 or less, more preferably 200,000 or more and 500,000 or less, and further preferably 250,000 or more and 450,000 or less. It is preferable, and it is particularly preferable that it is 350,000 or more and 420,000 or less. When the weight average molecular weight Mw of the long-chain branched polypropylene resin C is 150,000 or more and 600,000 or less, the resin fluidity becomes appropriate. As a result, the thickness of the cast sheet can be easily controlled, and a thin stretched film can be easily produced. In addition, the thickness of the cast sheet and the stretched film is less likely to be uneven, and appropriate stretchability can be obtained, which is preferable.

The molecular weight distribution [(weight average molecular weight Mw) / (number average molecular weight Mn)] of the long-chain branched polypropylene resin C is preferably 1.5 or more and 4.5 or less, and 1.8 or more and 4.2 or less. It is more preferably 2.0 or more and 4.0 or less, particularly preferably 2.1 or more and 3.9 or less, and particularly preferably 2.2 or more and 3.0 or less. ..

The [(z average molecular weight Mz) / (number average molecular weight Mn)] of the long-chain branched polypropylene resin C is preferably 4.0 or more and 9.0 or less, and is 4.2 or more and 8.8 or less. Is more preferable, and it is more preferably 4.5 or more and 8.5 or less, and particularly preferably 5.0 or more and 8.2 or less.

The molecular weight, molecular weight distribution, differential distribution value difference DM, and the like of the long-chain branched polypropylene resin C can be controlled by _adjusting the catalyst and the polymerization conditions as described above.

The heptane insoluble content (HI) of the long-chain branched polypropylene resin C is preferably 98.0% or more, more preferably 98.2% or more, still more preferably 98.5% or more. The heptane insoluble content (HI) of the long-chain branched polypropylene resin C is preferably 99.5% or less, more preferably 99.0% or less. When the HI of the long-chain branched polypropylene resin C is in the above preferable range, β crystals are more preferably formed on the cast sheet, and as a result, the surface of the polypropylene film according to the present embodiment can be suitably roughened. ..

The ash content of the long-chain branched polypropylene resin C is preferably 45 × 10 ppm or less (450 ppm or less), more preferably 40 × 10 ppm or less (400 ppm or less). The ash content of the long-chain branched polypropylene resin C is preferably 0 × 10 ppm or more, more preferably 1 ppm or more, further preferably 5 ppm or more, further preferably 1 × 10 ppm or more (10 ppm or more), and further preferably 10 × 10 ppm or more (10 ppm or more). 100 ppm or more) is even more preferable, and 20 × 10 ppm or more (200 ppm or more) is particularly preferable. When the ash content of the long-chain branched polypropylene resin C is in the above preferable range, β crystals are more preferably formed on the cast sheet, and as a result, the surface of the polypropylene film according to the present embodiment can be suitably roughened. ..

The melt flow rate (MFR) of the long-chain branched polypropylene resin C at 230 ° C. is preferably 0.1 to 12 g / 10 min, more preferably 0.5 to 5 g / 10 min, and 0.7 to 3.5 g / 10 min. More preferably, 1.0 to 2.2 g / 10 min is particularly preferable. When the MFR of the long-chain branched polypropylene resin C at 230 ° C. is within the above range, unstable flow such as melt fracture is unlikely to occur because the flow characteristics in the molten state are excellent, and fracture during stretching is also suppressed. .. Therefore, since the film thickness uniformity is good, there is an advantage that the formation of a thin-walled portion where dielectric breakdown is likely to occur is suppressed.

The content of the long-chain branched polypropylene resin C is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass, assuming that the entire polypropylene resin in the polypropylene film is 100% by mass. % Or more, particularly preferably 2% by mass or more, and more particularly preferably 2.5% by mass or more. Further, the content of the long-chain branched polypropylene resin C is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, assuming that the entire polypropylene resin in the polypropylene film is 100% by mass or less. It is particularly preferably 7% by mass or less, and more particularly preferably 5% by mass or less. The polypropylene film may contain one or more of the long-chain branched polypropylene resins C.

Typical commercially available products of the long-chain branched polypropylene resin C include, for example, MFX3 and MFX6 manufactured by Japan Polypropylene Corporation, MFX8 manufactured by Japan Polypropylene Corporation, and the like.

The polypropylene film may contain a resin other than the polypropylene resin (hereinafter, also referred to as “other resin”). The "other resin" is generally a resin other than the polypropylene resin which is the main component resin, and is not particularly limited as long as the target polypropylene film can be obtained. Examples of other resins include polyethylene, poly (1-butene), polyisobutene, poly (1-pentene), poly (1-methylpentene) and other polyolefins other than polypropylene, ethylene-propylene copolymers and propylene-. Butene copolymers, α-olefin copolymers such as ethylene-butene copolymers, vinyl monomer-diene monomer random copolymers such as styrene-butadiene random copolymers, styrene-butadiene-styrene Examples thereof include vinyl monomer-diene monomer-vinyl monomer random copolymer such as block copolymer. The polypropylene film can be contained in an amount that does not adversely affect the target polypropylene film. The polypropylene film may contain 10 parts by mass or less of another resin, more preferably 5 parts by mass or less, based on 100 parts by mass of the polypropylene resin. Further, the polypropylene film may contain 0.1 part by mass or more of another resin, more preferably 1 part by mass or more, based on 100 parts by mass of the polypropylene resin.

The polypropylene film may further contain at least one additive in addition to the resin component. The "additive" is an additive generally used for polypropylene, and is not particularly limited as long as the target polypropylene film can be obtained. Additives include, for example, nucleating agents (α-crystal nucleating agents, β-crystal nucleating agents), antioxidants, necessary stabilizers such as chlorine absorbers and ultraviolet absorbers, lubricants, plasticizers, and flame retardants. Includes agents, antistatic agents, inorganic fillers, organic fillers and the like. Examples of the inorganic filler include barium titanate, strontium titanate, aluminum oxide and the like. When the additive is used, it can be contained in an amount that does not adversely affect the target polypropylene film.

The "nucleating agent" is generally used for polypropylene, and is not particularly limited as long as the desired polypropylene film can be obtained.
Examples of the nucleating agent include an α-crystal nucleating agent that preferentially enucleates α-crystals and a β-crystal nucleating agent that preferentially enucleates β-crystals.
Among the α-crystal nucleating agents, examples of the organic nucleating agent include a dispersion-type nucleating agent and a dissolution-type nucleating agent. Examples of the dispersed nucleating agent include a phosphoric acid ester metal salt-based nucleating agent, a carboxylic acid metal salt-based nucleating agent, and a rosin metal salt-based nucleating agent. Examples of the dissolution-type nucleating agent include a sorbitol-based nucleating agent, a nonitol-based nucleating agent, a xylitol-based nucleating agent, and an amide-based nucleating agent.
Examples of β-crystal nucleating agents include amide-based nucleating agents, di or polycarboxylic acid metal salt-based nucleating agents, quinacridone-based nucleating agents, aromatic sulfonic acid-based nucleating agents, phthalocyanine-based nucleating agents, and tetraoxaspiro. Examples include compound-based nucleating agents.
The nucleating agent can be dry-blended or melt-blended with a polypropylene raw material and pelletized for use, or can be put into an extruder together with polypropylene pellets for use. By using a nucleating agent, the surface roughness of the film can be adjusted to a desired roughness. As an example of a typical commercial product of a nucleating agent, for example, as a β crystal nucleating agent, there is an NJester NU-100 manufactured by Shin Nihon Rika Co., Ltd. When the polypropylene film contains a β-crystal nucleating agent, the content thereof is preferably 1 to 1000 mass ppm (in terms of mass when the resin component is taken as a whole), and more preferably 50 to 50 to the mass of the resin component. It is 600 mass ppm.

The "antioxidant" is generally called an antioxidant, and is not particularly limited as long as it is used for polypropylene and the target polypropylene film can be obtained. Antioxidants are commonly used for two purposes. One purpose is to suppress thermal deterioration and oxidative deterioration in the extruder, and the other purpose is to contribute to suppressing deterioration and improving capacitor performance in long-term use as a film for capacitors. An antioxidant that suppresses thermal deterioration and oxidative deterioration in an extruder is also referred to as a "primary agent", and an antioxidant that contributes to improving capacitor performance is also referred to as a "secondary agent".

Two types of antioxidants may be used for these two purposes, or one type of antioxidant may be used for two purposes.

Examples of the primary agent include 2,6-di-tertiary-butyl-para-cresol (generic name: BHT). The primary agent is usually added for the purpose of suppressing thermal deterioration and oxidative deterioration in the extruder when preparing the polypropylene resin composition described in the method for producing a polypropylene film described later. Most of the antioxidant added to the polypropylene resin composition for this purpose is consumed in the molding process in the extruder, and hardly remains in the film after film forming. Therefore, when the polypropylene film contains a primary agent, the content thereof is usually less than 100 mass ppm (by mass when the resin component is taken as a whole) with respect to the mass of the resin component.

Examples of the secondary agent include a hindered phenolic antioxidant having a carbonyl group.

The "hindered phenolic antioxidant having a carbonyl group" is usually a hindered phenolic antioxidant having a carbonyl group, and is not particularly limited as long as the target polypropylene film can be obtained. ..

Examples of the hindered phenolic antioxidant having a carbonyl group include triethylene glycol-bis [3- (3-tertiary-butyl-5-methyl-4-hydroxyphenyl) propionate] (trade name: Irganox 245). ), 1,6-Hexanediol-bis [3- (3,5-ditershally-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 259), pentaerythrultyl tetrakis [3-( 3,5-Di-tersary butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010), 2,2-thio-diethylenebis [3- (3,5-di-tersary-butyl-4-) Hydroxyphenyl) propionate] (trade name: Irganox 1035), octadecyl-3- (3,5-di-tertiary-butyl-4-hydroxyphenyl) propionate (trade name: Irganox 1076), N, N'- Hexamethylenebis (3,5-ditershally-butyl-4-hydroxy-hydrocinnamamide) (trade name: Irganox 1098) and the like can be mentioned, but they have a high molecular weight and are highly compatible with polypropylene. Pentaerythrutyl tetrakis [3- (3,5-di-tertiarybutyl-4-hydroxyphenyl) propionate], which has low volatility and excellent heat resistance, is particularly preferable.

The polypropylene film may contain one or more kinds of hindered phenolic antioxidants (secondary agents) having a carbonyl group for the purpose of suppressing deterioration that progresses with time during long-term use. When the polypropylene film contains one or more kinds of hindered phenolic antioxidants having a carbonyl group, the content thereof is preferably relative to the mass of the resin component (by mass when the resin component is taken as a whole). It is 4000 mass ppm or more and 6000 mass ppm or less, more preferably 4500 mass ppm or more and 6000 mass ppm or less. It is preferable that the content of the hindered phenolic antioxidant having a carbonyl group in the film is 4000 mass ppm or more and 6000 mass ppm or less from the viewpoint of appropriate effect expression.

A polypropylene film containing a hindered phenolic antioxidant having a carbonyl group, which has good compatibility with polypropylene at the molecular level, in an optimum specific range is preferable because it improves long-term durability.

The "chlorine absorber" is generally called a chlorine absorber, and is not particularly limited as long as it is used for polypropylene and the target polypropylene film can be obtained. Examples of the chlorine absorber include metal soaps such as calcium stearate. When such a chlorine absorber is used, it can be contained in an amount that does not adversely affect the polypropylene film of interest.

The polypropylene film is preferably biaxially stretched. When the polypropylene film is a biaxially stretched polypropylene film, the biaxially stretched polypropylene film can be produced by a generally known method for producing a biaxially stretched polypropylene film. For example, a cast sheet from a polypropylene resin composition obtained by mixing a linear polypropylene resin A, a linear polypropylene resin B, and a long-chain branched polypropylene resin C together with other resins, additives, etc., if necessary. Can be produced by producing the cast sheet and then biaxially stretching the cast sheet.

<Preparation of polypropylene resin composition>
The method for preparing the polypropylene resin composition is not particularly limited, but a polymer powder or pellet of a linear polypropylene resin A, a linear polypropylene resin B, and a long-chain branched polypropylene resin C may be used as necessary. A method of dry blending using a mixer or the like together with the above resin, additives, etc., and polymer powders or pellets of linear polypropylene resin A, linear polypropylene resin B, and long-chain branched polypropylene resin C, if necessary. Examples thereof include a method of supplying the kneader together with other resins and additives and melt-kneading to obtain a melt-blended resin composition.

The mixer and kneader are not particularly limited. The kneader may be a single-screw screw type, a double-screw screw type, or a multi-screw screw type or more. In the case of a screw type with two or more axes, either a kneading type that rotates in the same direction or 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 good kneading can be obtained, but is preferably in the range of 170 to 320 ° C, more preferably in the range of 200 ° C to 300 ° C, and further preferably. Is in the range of 230 ° C to 270 ° C. In order to suppress deterioration during kneading and mixing of the resin, the kneader may be purged with an inert gas such as nitrogen. The melt-kneaded resin can be pelletized to an appropriate size using a generally known granulator to obtain pellets of the melt-blended resin composition.

When preparing the polypropylene resin composition, a primary agent as an antioxidant described in the above-mentioned additive section can be added for the purpose of suppressing thermal deterioration and oxidative deterioration in the extruder.
When the polypropylene resin composition contains a primary agent, the content thereof is preferably 1000 mass ppm to 5000 mass ppm (in terms of mass when the resin component is taken as a whole) with respect to the mass of the resin component. Most of the antioxidant for this purpose is consumed in the molding process in the extruder, and hardly remains in the film after film forming.

The hindered phenolic antioxidant having a carbonyl group described in the above-mentioned additive section can be added to the polypropylene resin composition as a secondary agent.
When the polypropylene resin composition contains a hindered phenolic antioxidant having a carbonyl group, the content thereof is preferably 100% by mass or more with respect to the mass of the resin component (by mass when the resin component is taken as a whole). It is 10000 mass ppm, more preferably 5500 mass ppm to 7000 mass ppm. Not a little in the extruder, a hindered phenolic antioxidant having a carbonyl group is also consumed.
When the polypropylene resin composition does not contain a primary agent, more hindered phenolic antioxidants having a carbonyl group can be used. This is because the consumption of the hindered phenolic antioxidant having a carbonyl group increases in the extruder. When the polypropylene resin composition does not contain a primary agent and contains a carbonyl group-based hindered phenolic antioxidant, its content is relative to the mass of the resin component (by mass when the resin component is taken as a whole). ) 6000 mass ppm to 8000 mass ppm or less.

<Making a cast sheet>
For the cast sheet, the dry blend resin composition and / or the pellets of the melt blend resin composition prepared in advance are supplied to an extruder, heated and melted, passed through a filtration filter, and then preferably at 170 ° C to 320 ° C. It is more preferably heated and melted to 200 ° C. to 300 ° C. and melted and extruded from the T die, preferably 40 ° C. to 140 ° C., more preferably 80 ° C. to 140 ° C., still more preferably 90 to 140 ° C., and particularly preferably 90 to 120 ° C. It can be obtained by cooling and solidifying with at least one metal drum maintained at a temperature of ° C., more preferably 90 to 105 ° C. (cast temperature). At this time, it is preferable to press the melt-extruded resin composition against the metal drum with an air knife. The surface on the side in contact with the metal drum is the first surface, and the surface on the opposite side (the surface on the air knife side) is the second surface.

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

In the process of producing the cast sheet (particularly in the extruder), polypropylene undergoes not a little thermal deterioration (oxidative deterioration) and shear deterioration. The degree of progress of such deterioration, that is, changes in molecular weight distribution and stereoregularity, are the nitrogen purge in the extruder (suppression of oxidation), the screw shape in the extruder (shearing force), and the internal shape of the T-die during casting (the internal shape of the T-die during casting). It can be suppressed by the shearing force), the amount of antioxidant added (oxidation suppression), the winding speed at the time of casting (elongation force), and the like.

<Stretching treatment>
The biaxially stretched polypropylene film can be produced by subjecting the cast sheet to a stretching treatment. As the stretching method, a sequential biaxial stretching method is preferable. As a sequential biaxial stretching method, first, the cast sheet is kept at a temperature of preferably 100 to 180 ° C, more preferably 140 to 160 ° C, passed between rolls provided with a speed difference, and stretched 3 to 7 times in the flow direction. And immediately cool to room temperature. By appropriately adjusting the temperature of this longitudinal stretching step, β crystals are melted and transferred to α crystals, and unevenness becomes apparent. Subsequently, the stretched film is guided to a tenter and laterally stretched 3 to 11 times in the width direction at a temperature of preferably 160 ° C. or higher, more preferably 160 to 180 ° C., and then relaxed and heat-fixed to form a roll. Wind around.

The film wound in a roll shape is subjected to an aging treatment in an atmosphere of about 20 to 45 ° C., and then slit (cut) to a desired product width with a slitter or the like while being rewound (while being unwound). , Each is wound again.

By such a stretching step, a film having excellent mechanical strength and rigidity is obtained, and surface irregularities are further clarified to obtain a finely roughened biaxially stretched film.

The polypropylene film may be subjected to a corona discharge treatment online or offline after the stretching and heat fixing steps are completed. By performing the corona discharge treatment, the adhesive properties in the post-process such as the metal vapor deposition processing process can be improved. The corona discharge treatment can be performed by using a known method. It is preferable to use air, carbon dioxide gas, nitrogen gas, and a mixed gas thereof as the atmospheric gas.

In order to process it as a capacitor, a metal layer may be laminated on one side or both sides of the polypropylene film to form a polypropylene film integrated with a metal layer. The metal layer functions as an electrode. As the metal used for the metal layer, for example, elemental metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, mixtures of a plurality of them, alloys thereof, and the like can be used, but the environment. Zinc and aluminum are preferable in consideration of economic efficiency and capacitor performance.

As a method of laminating a metal layer on one side or both sides of the polypropylene film, for example, a vacuum vapor deposition method or a sputtering method can be exemplified. The vacuum vapor deposition method is preferable from the viewpoint of productivity and economy. As the vacuum vapor deposition method, a crucible method, a wire method, or the like can be generally exemplified, but the method is not particularly limited, and the optimum method can be appropriately selected.

The margin pattern when laminating the metal layer by vapor deposition is not particularly limited, but from the viewpoint of improving the characteristics such as the safety of the capacitor, a pattern including a so-called special margin such as a fishnet pattern or a T-margin pattern is used. It is preferably applied on one side of the film. It is effective in terms of improving safety, destroying capacitors, preventing short circuits, and so on.

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.

When forming a metal layer on the polypropylene film, the polypropylene film wound in a roll shape is rewound (unwound), and a metal layer such as a thin-film deposition film is formed on one or both surfaces, and again. It is wound.

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

Specifically, a blade is inserted in the center of each margin portion of the metal layer integrated polypropylene film and slit processing is performed to produce a take-up reel having a margin on one surface of the surface.
Here, in the polypropylene film, the Spk value (Spk _A ) of the first surface, the Spk value (Spk _A ) of the first surface, the Svk value (Svk _B ) of the second surface, and the second surface Since the Spk value (Spk _B ) of is within a predetermined numerical range, blocking is suppressed. Therefore, it is possible to prevent the polypropylene film from blocking and wrinkling in the flow direction during the slit processing.
Next, using a take-up reel with a left margin and a take-up reel with a right margin, two sheets are superposed and wound so that the vapor-filmed portion protrudes from the margin portion in the width direction (element winding processing). Next, the core material is removed from the winding body and pressed. Next, external electrodes are formed on both end faces, and lead wires are further provided on the external electrodes. From the above, a winding type film capacitor can be obtained.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Polypropylene resin]
Table 1 shows the polypropylene resins used to produce the polypropylene films of Examples and Comparative Examples.
The resin A1 shown in Table 1 is a product manufactured by Prime Polymer Co., Ltd. Resin A2 is a product manufactured by Prime Polymer Co., Ltd. The resin B1 is S802M manufactured by Korea Yuka Co., Ltd. Resin B2 is HPT-1 manufactured by Korea Yuka Co., Ltd. The resin B3 is manufactured by Korea Yuka Co., Ltd. Resin C1 is MFX6 manufactured by Japan Polypropylene Corporation. The resin X1 is WB135HMS (Double HMS-PP) manufactured by Borealis. MFX6 is a long-chain branched polypropylene resin polymerized using a metallocene catalyst. WB135HMS is a long-chain branched polypropylene resin obtained by cross-linking modification with a peroxide. The resin A1 and the resin A2 correspond to the linear polypropylene resin A. The resin B1, the resin B2, and the resin B3 correspond to the linear polypropylene resin B. The resin C1 corresponds to the long-chain branched polypropylene resin C. The resin A1, the resin A2, the resin B1, the resin B2, and the resin B3 are all homopolypropylene resins. Resin X2 is a product manufactured by Prime Polymer Co., Ltd. and is a linear homopolypropylene.
Table 1 shows the number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of each resin. These values are values in the form of raw material resin pellets. The measurement method is as follows.

<Measurement of number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of linear polypropylene resin>
Using GPC (Gel Permeation Chromatography), the number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mw / Mn) of each resin under the following conditions. The molecular weight distribution (Mz / Mn) was measured.
Specifically, an HLC-8121GPC-HT type, which is a high temperature GPC device with a built-in differential refractometer (RI) manufactured by Tosoh Corporation, was used. As a column, three TSKgel GMHR-H (20) HTs manufactured by Tosoh Corporation were connected and used. Trichlorobenzene was flowed as an eluent at a flow rate of 1.0 ml / min at a column temperature of 140 ° C. and measured. A calibration curve for the molecular weight M is created using standard polystyrene manufactured by Tosoh Corporation, and the measured values are converted into the molecular weight of polypropylene using the Q-factor, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) are converted. , And z average molecular weight (Mz) was obtained. The molecular weight distribution (Mw / Mn) was obtained using the values of Mw and Mn. Moreover, the molecular weight distribution (Mz / Mn) was obtained using the values of Mz and Mn.

<Measurement of number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) of long-chain branched polypropylene>
Using GPC (Gel Permeation Chromatography), polypropylene number average molecular weight (Mn), weight average molecular weight (Mw), z average molecular weight (Mz), molecular weight distribution (Mw / Mn), molecular weight distribution (Mw / Mn) under the following conditions. Mz / Mn) was measured.
An HLC-8121GPC-HT type high temperature GPC device with a built-in differential refractometer (RI) manufactured by Tosoh Corporation was used. As a column, three TSKgelGMHR-H (20) HTs manufactured by Tosoh Corporation were connected, and one TSKgelgradecolumnHHR (30) was used. At a column temperature of 140 ° C., 1.0 ml of 1,2-di-terriary-butyl-para-cresol (generic name: BHT) was added to 1,2,4-trichlorobenzene as an eluent at 0.05 wt%. The measurement was carried out at a flow rate of / min to obtain a number average molecular weight (Mn), a weight average molecular weight (Mw) and a z average molecular weight (Mz). The molecular weight distribution (Mz / Mn) was obtained by using the values of Mz and Mn, and the molecular weight distribution (Mw / Mn) was obtained by using the values of Mw and Mn. The measurement conditions are as follows.
GPC device: HLC-8121GPC / HT (manufactured by Tosoh)
Light scattering detector: DAWN EOS (Wyatt Technology),
Column: TSKgelgoldcolumnHHR (30) (7.8 mm ID x 7.5 cm) x 1 + TSKgelGMHHR-H (20) HT (7.8 mm ID x 30 cm) x 3 (manufactured by Tosoh)
Eluent: 0.05 wt% BHT on 1,2,4-trichlorobenzene
Flow velocity: 1.0 mL / min
Sample concentration: 2 mg / mL
Injection volume: 300 μL
Column temperature: 140 ° C
System temperature: 40 ° C
Pretreatment: The sample was precisely weighed, an eluent was added, and the sample was shaken and dissolved at 140 ° C. for 1 hour, and then heat-filtered with a 0.5 μm sintered metal filter.

<Measurement of differential distribution value when log molecular weight log (M) = 4.5, differential distribution value when log molecular weight log ( _M ) = 6.0, and differential distribution value difference DM>
For each resin, the differential distribution value when the logarithmic molecular weight log (M) = 4.5 and the differential distribution value when the logarithmic molecular weight log (M) = 6.0 were obtained by the following methods. First, the time curve (elution curve) of the intensity distribution detected by the RI detector is used as the distribution curve for the molecular weight M (Log (M)) of the standard polystyrene using the calibration curve prepared using the above 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 this integral distribution curve with Log (M). I got a curve. From this differential distribution curve, the differential distribution values when Log (M) = 4.5 and Log (M) = 6.0 were read. Further, the difference between the differential distribution value when Log (M) = 4.5 and the differential distribution value when Log ( _M ) = 6.0 was defined as the differential distribution value difference DM. A series of operations until the differential distribution curve was obtained was performed using the analysis software built in the GPC measuring device used. The results are shown in Table 1.

<Measurement of melt flow rate (MFR)>
For each resin, the melt flow rate (MFR) in the form of raw material resin pellets was measured using a melt indexer manufactured by Toyo Seiki Co., Ltd. according to the condition M of JIS K 7210. Specifically, first, a sample weighed to 4 g was inserted into a cylinder having a test temperature of 230 ° C., and preheated for 3.5 minutes under a load of 2.16 kg. Then, the weight of the sample extruded from the bottom hole was measured in 30 seconds to determine the MFR (g / 10 min). The above measurement was repeated 3 times, and the average value was taken as the measured value of MFR. The results are shown in Table 1.

<Measurement of heptane insoluble matter (HI)>
Each resin was press-molded to 10 mm × 35 mm × 0.3 mm to prepare a measurement sample of about 3 g. Next, about 150 mL of heptane was added and Soxhlet extraction was performed for 8 hours. The heptane insoluble content was calculated from the sample mass before and after extraction. The results are shown in Table 1.

<Measurement of ash content>
The ash content of each resin was measured as follows.
Approximately 200 g of the sample was weighed, transferred to a platinum dish and incinerated at 800 ° C. for 40 minutes. The ratio of ash content (ppm) was measured from the obtained ash content residue. The results are shown in Table 1.

<Mesopentad fraction>
Each resin was dissolved in a solvent and measured under the following conditions using a high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR).
High temperature nuclear magnetic resonance (NMR) device: JEM-ECP500, high temperature Fourier transform nuclear magnetic resonance (NMR) device manufactured by JEOL Ltd.
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
Number of integrations: 4,500 times Shift reference: CH3 (mmmm) = 21.7 ppm
The pentad fraction, which represents the degree of stereoregularity, is a combination (mmmm or mrrm) of a 5-series (pentad) of a mixture "meso (m)" arranged in the same direction and a mixture "racemo (r)" arranged in a different direction. Etc.), calculated as a percentage (%) from the integrated intensity of each signal. Regarding the attribution of each signal derived from mmmm, mrrm, etc., for example, the description of the spectrum such as "T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988)" was referred to.

Using the above-mentioned resin, polypropylene films of Examples and Comparative Examples were prepared and their physical properties were evaluated.

<Making polypropylene film>
(Example 1)
Resin A1, resin B1 and resin C1 were dry-blended. The mixing ratio was (resin A1) :( resin B1) :( resin C1) = 63: 34: 3 in terms of mass ratio. Then, using a dry-blended resin, the resin was melted at a resin temperature of 250 ° C., extruded using a T-die, wound around a metal drum whose surface temperature was maintained at 95 ° C., and solidified to prepare a cast sheet. At this time, a cast sheet was prepared while the melt-extruded resin composition was pressed against a metal drum with an air knife. The obtained unstretched cast sheet was kept at a temperature of 130 ° C., passed between rolls provided with a speed difference, stretched 4.5 times in the flow direction, and immediately cooled to room temperature. Subsequently, the stretched film was guided to a tenter, stretched 8 times in the width direction at a temperature of 158 ° C., then relaxed and heat-fixed, wound up, and aged in an atmosphere of about 40 ° C. in Example 1. The polypropylene film according to the above was obtained.

(Examples 2 to 5, Comparative Examples 1 to 6)
Polypropylene films according to Examples 2 to 5 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1 except that the mixing ratio at the time of dry blending of the raw material resin was changed as shown in Table 2. rice field.
However, in Comparative Example 6, a smooth cast sheet could not be produced due to the melt fracture during extrusion molding. Therefore, breakage occurred when the cast sheet was stretched.

(Examples 6 to 8, Comparative Example 7, Comparative Example 8)
Polypropylene films according to Examples 6 to 8, Comparative Example 7, and Comparative Example 8 were obtained in the same manner as in Example 1 except that the mixing ratio at the time of dry blending of the raw material resin was changed as shown in Table 2. rice field.

<Measurement of polypropylene film thickness>
The thickness of the polypropylene films of Examples and Comparative Examples was measured. Specifically, the measurement was performed in accordance with JIS-C2330 except that the measurement was performed at 100 ± 10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu. The results are shown in Table 3.

<Svk value of the first surface (Svk _A ), Spk value of the first surface (Spk _A ), Svk value of the second surface (Svk _B ), Spk value of the second surface (Spk _B ), first The Sq value of the first surface (Sq _A ), the Sq value of the second surface (Sq _B ), the Sa value of the first surface (Sa _A ), the Sa value of the second surface (Sa _B ), the first surface. Measurement of the Sk value of the surface (Sk _A ) and the Sk value of the second surface (Sk _B )>
Hereinafter, the first surface may be referred to as "A surface", and the second surface may be referred to as "B surface". In Table 3, the terms A-side and B-side may also be used.
As a light interference type non-contact surface shape measuring machine, "VertScan 2.0 (model: R5500GML)" manufactured by Ryoka System Co., Ltd. was used.
First, using the WAVE mode, a 530 white filter and a 1 × BODY lens barrel were applied, and a measurement of 470.92 μm × 353.16 μm was performed per field of view using an × 10 objective lens. This operation was performed at 10 locations at 1 cm intervals in the flow direction from the central location in both the flow direction and the width direction of the target sample (polypropylene film).
Next, the obtained data was subjected to noise removal processing by a median filter (3 × 3), and then Gaussian filter treatment with a cutoff value of 30 μm was performed to remove undulation components. As a result, the state of the roughened surface can be appropriately measured.
Next, the analysis was performed using the "ISO parameter" in the plug-in function "bearing" of the analysis software "VS-Viewer" of "VertScan 2.0".
Finally, the average value is calculated for each of the values (Svk _A , Spk _A , Svk _B , Spk _B , Sq _A , Sq _B , Sa _A , Sa _B , Sk _A , Sk _B ) obtained at the above 10 locations. did. As a result, the Svk value of the first surface (Svk _A ), the Spk value of the first surface (Spk _A ), the Svk value of the second surface (Svk _B ), and the Spk value of the second surface (Spk _B ). , Sq value of the first surface (Sq _A ), Sq value of the second surface (Sq _B ), Sa value of the first surface (Sa _A ), Sa value of the second surface (Sa _B ), first The Sk value (Sk _A ) of the first surface and the Sk value (Sk _B ) of the second surface were determined. The results are shown in Table 3. Table 3 also shows the values of the ratio Sq _B / Sq _A , the ratio Sa _B / Sa _A , and the ratio Sk _B / Sk _A.

<Measurement of ellipse density>
The elliptic densities of the first surface (A surface) and the second surface (B surface) of the polypropylene films of Examples and Comparative Examples were measured. Specifically, using a digital scope (Digital Microscope VHX-2000 manufactured by Keyence Co., Ltd.), lens magnification: 100 times, measurement method: reflection measurement, field of view range: 3.4 mm × 2.6 mm, each of polypropylene films. The surface was observed and the number of "ellipses" observed within the field of view was measured. After that, it was converted per unit area. The results are shown in Table 3.
When the length of one axis is L μm and the length of the other axis is S μm, those satisfying S ≦ L and 1 ≦ L ≦ 300 are defined as “ellipses” to be considered when calculating the ellipse density. Those that did not meet this were not considered when calculating the ellipse density (not counted as an "ellipse" when calculating the ellipse density).

<Measurement of average major axis length>
The mean value of the long axis of the ellipse observed in the measurement of ellipse density was calculated. The results are shown in Table 3.

<Measurement of ellipse perfect fifth>
First, as a light interference type non-contact surface shape measuring machine, "VertScan 2.0 (model R5500GML)" manufactured by Ryoka System Co., Ltd. is used, and a 530 white filter and a 1 × BODY lens barrel are applied in WAVE mode. , X10 objective lens was used to obtain surface shape data of 470.92 μm × 353.16 μm per field of view. This operation was performed at 10 locations at 1 cm intervals in the flow direction from the central location in both the flow direction and the width direction of the target sample (polypropylene film).
Next, the obtained data was subjected to noise removal processing by a median filter (3 × 3), and then Gaussian filter treatment with a cutoff value of 30 μm was performed to remove undulation components.
From the projected images of the surface shape data of each of the 10 locations obtained as described above, three crater projected images consisting of paired arcs were extracted. The projected image was a projected image in which the portion of the fine unevenness having a height of 0.02 μm or more was projected onto the film surface.
In extracting the crater projection images, three crater projection images based on different β-type spherulites, in which no overlap between arcs was observed, were extracted. The three extraction methods extract quartiles (first quartile, second quartile (ie, median) and third quartile) in the area of the visual ellipse. I decided.
Next, for each of the three extracted crater projection images, the total length Lt of the paired arcs and the total circumference length of the virtual ring including the paired arcs are measured as Lc, and the ratio (Lt) is measured. / Lc) was calculated. Then, a total of 30 values of the ratios obtained were averaged to obtain an average value α of the ratios (Lt / Lc).
The determination of the virtual ring and the measurement of Lt and Lc were performed using the plug-in function "edge curve length" of the analysis software "VS-Viewer" of the optical interferometric non-contact surface shape measuring device VertScan 2.0. The specific procedure is as follows.
(1) First, as shown in FIG. 3A, the two points most distant from each other on the arc 30a and the arc 30b are designated as P ₁ and P ₂ , and a straight line connecting P ₁ and P ₂ (hereinafter, a straight line). (It is called P1 _- P2).) _Is determined.
( ₂ ) Then, as shown in FIG. 3 (b), a portion located on one side of the straight line (P1 _- P2) (in _FIG . 3, above the straight line (P1 _- P2)). From the shapes (positional data) of the arcs 30a and 30b of, an ellipse (E ₀ ) _having a straight line (P1 _−P2 ) as the major axis is derived by the least squares method. Then, the curve forming the ellipse (E ₀ ) (a part of the circumference of the ellipse (E ₀ )) complements the portion between the arc 30a and the arc 30b on one side to form a complementary line 40a. In FIG. 3, the ellipse (E ₀ ) other than the portion corresponding to the complementary line 40a is not shown.
(3) Then, as shown in FIG. 3 (c), the portion located on the other side of the straight line (P1 _- P2) (in _FIG . ₃ , the lower side than the straight line (P1 _- P2)). From the shapes (positional data) of the arcs 30a and 30b, an ellipse (E ₁ ) having _a straight line (P1 _−P2 ) as the major axis is derived by the least squares method. Then, the curve forming the ellipse (E ₁ ) (a part of the circumference of the ellipse (E ₁ )) complements the portion between the arc 30a and the arc 30b on the other side to form a complementary line 40b. In FIG. 3, the ellipse (E ₁ ) other than the portion corresponding to the complementary line 40b is not shown.
(4) The annulus shown in FIG. 3C in which the complementary lines 40a and 40b thus determined and the arcs 30a and 30b are connected is a virtual annulus.
(5) Then, the height profile of the fine unevenness 20 showing the height of the fine unevenness 20 at each position with respect to each position (distance when the point with the circumference is used as a reference) on the circumference of the virtual annulus is obtained. draw. From this height profile, Lt and Lc in the crater projection image G corresponding to the portion having a height of 0.02 μm or more are read.
When implementing the least squares method, 30 position data (n = 30) are used respectively.

<Measurement of dielectric breakdown strength of polypropylene film (withstand voltage resistance evaluation)>
According to JIS C2330 (2001) 7.4.11.2 B method (plate electrode method), the dielectric breakdown voltage value of the polypropylene film was measured 12 times at 100 ° C. and 125 ° C. using a DC power supply. The dielectric breakdown voltage value _VDC is divided by the film thickness (μm), and the average value of 8 points excluding the upper 2 points and the lower 2 points in the 12 measurement results is the dielectric breakdown strength ES ( _VDC / μm). ). The results are shown in Table 3.
In Comparative Examples 1 and 4, the dielectric breakdown strength at 120 ° C. is less than 485 _VDC / μm, and it can be seen that the withstand voltage resistance is inferior.

<Blocking evaluation of metal vapor deposition rolls>
A metal layer-integrated polypropylene film was obtained by subjecting a biaxially stretched polypropylene film to an aluminum vapor deposition with a T-margin thin-film deposition pattern at a vapor deposition resistance of 15 Ω / □. The pattern vapor deposition was carried out according to the vacuum vapor deposition method by the wire method, and the heavy edge vapor deposition was carried out according to the vacuum vapor deposition method by the crucible method. The film used for vapor deposition had a width of 620 mm, and the film length after vapor deposition was 50,000 m. A blade was inserted in the center of each margin portion of the polypropylene film integrated with a metal layer having a width of 620 mm, and slitting was performed so as to form a small winding having a width of 30 mm and a length of 10,000 m at a slit speed of 350 m / min. At that time, AA is the case where no wrinkles in the flow direction due to blocking between the vapor-filmed surface and the non-deposited surface are observed in the metal vapor-deposited take-out portion, and A is the case where slight streaks that cannot be said to be wrinkles are observed. The case where wrinkles in the flow direction were observed at the end in the width direction was evaluated as B, and the case where wrinkles in the flow direction were also observed in the center in the width direction was evaluated as C. The results are shown in Table 3.

<Measurement of ash content>
The polypropylene films of Examples and Comparative Examples were measured as follows.
Approximately 200 g of the sample was weighed, transferred to a platinum dish and incinerated at 800 ° C. for 40 minutes. The ratio of ash content (ppm) was measured from the obtained ash content residue. The results are shown in Table 3.

<Slit process workability evaluation>
The metal vapor deposition winding having a width of 620 mm was slitted at a slit speed of 350 m / min so as to have a width of 30 mm and a length of 10,000 m, and was divided into 20 pieces in the width direction. As a result, the deviation of the end faces of all the 20 small windings obtained (the deviation length when the film meanders to the left and right during winding and the end faces of the small windings are uneven) is 0. If it is within 5%, A, if the end face deviation of all 20 small windings is within 1.0% of the slit width and the above A evaluation is not obtained, B, the end face deviation of all 20 small windings. Is within 2.0% of the slit width and does not correspond to the above A evaluation or B evaluation. C, There is one or more end face deviations of 20 small windings exceeding 2.0% of the slit width. Was evaluated as D. The results are shown in Table 3.

<Evaluation of element winding workability>
Of the small windings obtained by the slit workability evaluation, the winding reel with the left margin and the winding reel with the right margin are used, and two reels are overlapped and wound so that the vapor-deposited portion protrudes from the margin portion in the width direction. Turned (element winding processing). The winding was performed for 1360 turns with a winding tension of 200 g using an automatic winding machine 3KAW-N2 type manufactured by Minato Seisakusho Co., Ltd. At that time, visually observe from the beginning to the end of winding, those with wrinkles and misalignment were rejected, and the ratio of the number of rejected products to the total number of manufactured products was shown as a percentage and used as an index of workability. (Hereinafter referred to as element winding yield). The higher the element winding yield, the more preferable. 95% or more was evaluated as good "○", and less than 95% was evaluated as bad "x". The results are shown in Table 3.

<Manufacturing of capacitors and capacitance>
Using the polypropylene film obtained in the example, a capacitor was produced as follows. By subjecting the polypropylene film to aluminum vapor deposition with a T-margin vapor deposition pattern at a vapor deposition resistance of 15 Ω / □, a polypropylene film integrated with a metal layer containing a metal film on one side of the polypropylene film was obtained. After slitting to a width of 60 mm, two metal layer integrated polypropylene films are combined, and an automatic winder 3KAW-N2 type manufactured by Minato Seisakusho Co., Ltd. is used to wind 1076 turns at a winding tension of 250 g. went. The element wound element was heat-treated at 120 ° C. for 15 hours while being pressed, and then zinc metal was sprayed on the element end face to obtain a flat capacitor. Lead wires were soldered to the end faces of the flat capacitors and then sealed with epoxy resin. The capacitance of the completed capacitors was 75 μF (± 5 μF).

Claims (7)

A polypropylene film having a first surface and a second surface.
Contains polypropylene resin as the main component,
The Svk value (Svk _A ) of the first surface is 0.005 μm or more and 0.030 μm or less.
The Spk value (Spk _A ) of the first surface is more than 0.035 μm and 0.080 μm or less.
The Svk value (Svk _B ) of the second surface is 0.005 μm or more and 0.030 μm or less.
The Spk value (Spk _B ) of the second surface is 0.015 μm or more and 0.035 μm or less.
The polypropylene resin is
In the molecular weight differential distribution curve, 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 8.0% or more. Chain polypropylene resin A and
In the molecular weight differential distribution curve, 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 less than 8.0%. Chain polypropylene resin B and
Containing long chain branched polypropylene resin C polymerized using a metallocene catalyst ,
A polypropylene film characterized by being biaxially stretched . The polypropylene film according to claim 1, wherein the polypropylene film is for a capacitor. The claim is characterized in that the ratio Sq _B / Sq _A of the Sq value (Sq _A ) of the first surface and the Sq value (Sq _B ) of the second surface is 0.4 to 1.0. The polypropylene film according to 1 or 2 . The claim is characterized in that the ratio Sa _B / Sa _A of the Sa value (Sa _A ) of the first surface to the Sa value (Sa _B ) of the second surface is 0.6 to 1.0. The polypropylene film according to any one of 1 to 3 . The polypropylene film according to any one of claims 1 to 4 ,
A polypropylene film integrated with a metal layer, characterized by having a metal layer laminated on one side or both sides of the polypropylene film. A film capacitor having a wound metal layer-integrated polypropylene film according to claim 5 , or having a configuration in which a plurality of metal layer-integrated polypropylene films according to claim 5 are laminated. A film roll according to any one of claims 1 to 4 , wherein the polypropylene film is wound in a roll shape.

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