JP2020124905A - Metal layer-integrated polypropylene film, film capacitor and method for producing metal layer-integrated polypropylene film - Google Patents

Abstract

To provide a metal layer-integrated polypropylene film capable of suppressing peeling of a metallikon electrode while securing room for material selection of a polypropylene film and room for adjustment of production conditions of a polypropylene film.SOLUTION: There is provided a metal layer-integrated polypropylene film having a polypropylene film and a metal layer laminated on one surface or both surfaces of the polypropylene film, wherein when a thermal shrinkage in a first direction of a polypropylene film before laminating a metal layer is defined as A and a thermal shrinkage in a first direction of the metal layer-integrated polypropylene film is defined as B, the thermal shrinkage ratio [(thermal shrinkage B)/(thermal shrinkage A)] between a thermal shrinkage A and a thermal shrinkage B is 0.25 or more and 0.60 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a metal layer-integrated polypropylene film, a film capacitor, and a method for producing a metal layer-integrated polypropylene film.

The polypropylene film has excellent electrical characteristics such as high withstand voltage and low dielectric loss characteristics, and also has high humidity resistance. Therefore, it is widely used in electronic devices and electric devices. Specifically, for example, it is used as a film used for a high-voltage capacitor; a filter capacitor for a power conversion circuit such as a converter and an inverter, a smoothing capacitor, and the like.

Particularly, in recent years, polypropylene film has begun to be widely used as a capacitor for an inverter power supply device that controls a drive motor of an electric vehicle, a hybrid vehicle, or the like. BACKGROUND OF THE INVENTION Inverter power supply capacitors used in automobiles and the like are required to have small size, light weight, high capacity, and high reliability over a long temperature range over a wide temperature range (eg, -40°C to 90°C).

Here, the dielectric loss means that a part of the electric energy applied to the dielectric is lost as heat energy, and the dielectric loss tangent (hereinafter, also referred to as “tan δ”) is an index indicating the degree of the dielectric loss. .. Tan δ is defined by the ratio of the real part (resistance) and the imaginary part (reactance) of the complex impedance. The larger the value of tan δ, the larger the ratio of lost as heat energy to the added electric energy. When the capacitor is used for a long period of time, tan δ of the capacitor increases due to various causes. When tan δ rises, a large amount of heat may be generated during use as a capacitor, which may cause deterioration of reliability such as deterioration of characteristics. Therefore, even if it is used for a long period of time, it is required that the increase in tan δ be small.

Patent Document 1 describes a polypropylene film for capacitors, which has a heat shrinkage in the length direction of 3.0% or less and a heat shrinkage in the width direction of 0% or more and 1.0% or less. 1). Also, when the thermal shrinkage of the polypropylene film for capacitors exceeds 3.0% in the length direction, wrinkles are likely to occur due to the heat received from the vapor-deposited metal during vapor deposition processing, and dimensional stability during high temperature processes such as heat treatment during capacitor production. It is described that the property is poor and stable capacitor characteristics cannot be obtained (paragraph [0008]). Further, when the heat shrinkage ratio of the polypropylene film for capacitors in the width direction exceeds 1.0%, the end face of the capacitor element is curled in the high temperature process such as heat treatment at the time of manufacturing the capacitor to increase the contact resistance with the metallikon metal. Furthermore, it is described that stable capacitor characteristics cannot be obtained because the dielectric loss tangent of the capacitor is deteriorated (paragraph [0009]). In Patent Document 1, since the heat shrinkage rate of the polypropylene film for capacitors before the vapor deposition step is set to be smaller than a predetermined value, the heat shrinkage rate of the polypropylene film for capacitors before the metal layer is laminated is made small. Therefore, it is considered that the purpose is to obtain stable capacitor characteristics.

JP-A-11-273991

However, since a polypropylene film generally has a property of thermal shrinkage, in order to reduce the heat shrinkage rate of the polypropylene film before laminating the metal layer, as in Patent Document 1, it is preferable to heat the film as much as possible. It is necessary to select a raw material resin that can produce a polypropylene film that does not shrink. Therefore, there is a problem that the range of selection of the raw material resin is narrowed.
In addition, manufacturing conditions for obtaining a polypropylene film having a low thermal shrinkage (polypropylene film before laminating a metal layer) (for example, manufacturing conditions for a cast sheet (for example, melting temperature of raw material resin, casting temperature, etc.), casting In some cases, it may be difficult to set the conditions for the stretching treatment conditions (for example, the stretching temperature, the stretching ratio, the nip pressure, etc.) when the sheet is stretched to form the polypropylene film.
Furthermore, the selection of the raw material resin and the adjustment of the production conditions for reducing the heat shrinkage rate of the polypropylene film may sometimes sacrifice other characteristics (for example, withstand voltage characteristics).

The present invention has been made in view of the above-described problems, and an object thereof is to suppress the peeling of the metallikon electrode while ensuring the room for selecting the material of the polypropylene film and the room for adjusting the manufacturing conditions of the polypropylene film. An object of the present invention is to provide a polypropylene film having a metal layer integrated therein. Moreover, the objective of this invention is providing the film capacitor which has the said polypropylene film integrated with a metal layer. Moreover, the objective of this invention is providing the manufacturing method of the said metal layer integrated polypropylene film.

The present inventors diligently studied a metal layer-integrated polypropylene film. As a result, if the heat shrinkage rate of the metal layer-integrated polypropylene film after laminating the metal layer on the polypropylene film is significantly changed compared with the heat shrinkage rate of the polypropylene film before laminating the metal layer, the capacitor It was found that peeling of the metallikon electrode was suppressed when used as. As a reason for this, the present inventors have found that the heat shrinkage rate of the metal layer-integrated polypropylene film after laminating the metal layer on the polypropylene film is large as compared with the heat shrinkage rate of the polypropylene film before laminating the metal layer. If the number decreases, the metal layer-integrated polypropylene film is more resistant to heat shrinkage even if it is further subjected to heat history. It is presumed that the relative displacement on the contact surface of is suppressed. Then, by adopting the following configuration, a metal layer-integrated polypropylene film capable of suppressing peeling of the metallikon electrode while ensuring room for selection of polypropylene film material and room for adjusting polypropylene film manufacturing conditions. They have found that they can be provided, and have completed the present invention.

The metal layer-integrated polypropylene film according to the present invention,
Polypropylene film,
A metal layer-integrated polypropylene film having a metal layer laminated on one side or both sides of the polypropylene film,
When the heat shrinkage rate in the first direction of the polypropylene film before laminating the metal layer is A and the heat shrinkage rate in the first direction of the metal layer-integrated polypropylene film is B, the heat shrinkage rate A and the heat shrinkage The heat shrinkage ratio [(heat shrinkage B)/(heat shrinkage A)] with the ratio B is 0.25 or more and 0.60 or less.

According to the above configuration, since the metal layer is laminated on one side or both sides of the polypropylene film, it can be used for a film capacitor in which the polypropylene film is a dielectric and the metal layer is an electrode.
Further, according to the above configuration, since the heat shrinkage ratio is 0.60 or less, the polypropylene film shrinks relatively greatly after the metal layer is laminated, as compared with before the metal layer is laminated. Can be said. That is, since the heat shrinkage ratio is 0.60 or less, the metal layer-integrated polypropylene film has already undergone a large heat shrinkage, and even if it is subjected to a heat history, the heat shrinkage is less likely to occur. There is. As a result, relative displacement of the contact surface between the metal layer-integrated polypropylene film and the metallikon electrode due to long-term use after being made into a capacitor is suppressed, and peeling of the metallikon electrode can be suppressed.
In general, polypropylene films have the property of shrinking by heat. Therefore, by intentionally shrinking the polypropylene film significantly in the step of laminating the metal layer, the metal layer is laminated as compared to before the metal layer is laminated (before the heat is applied when the metal layer is laminated). It is relatively easy to reduce the heat shrinkage rate after the heat treatment (to set the heat shrinkage rate ratio to 0.60 or less). That is, in the present invention, the heat shrinkage ratio can be set to 0.60 or less by adjusting the conditions when laminating the metal layers, so that the range of selection for the material resin can be kept wide. .. For example, unlike Patent Document 1, there is no restriction that a raw material resin that reduces the heat shrinkage rate of the polypropylene film before laminating the metal layer must be selected. Further, it is not necessary to adjust the production conditions of the polypropylene film so that the heat shrinkage rate of the polypropylene film before laminating the metal layer becomes small.
Moreover, since the heat shrinkage ratio is 0.25 or more, the dimensional stability is excellent.
As described above, according to the above-mentioned configuration, since the heat shrinkage ratio is 0.60 or less, there is room for selection of the material of the polypropylene film and room for adjustment of the production conditions of the polypropylene film, and the heat shrinkage is possible. Since the rate ratio is 0.60 or less, peeling of the metallikon electrode can be suppressed.

Note that Patent Document 1 seems to attempt to suppress the curling of the end face of the capacitor element by reducing the heat shrinkage rate of the polypropylene film for capacitors in the width direction, and thereby to suppress the peeling of the metallikon electrode. .. That is, it seems that the polypropylene film for capacitors is trying to suppress peeling due to shrinkage in the direction away from the metallikon electrode surface.
On the other hand, in the present invention, the first direction means the MD direction (longitudinal direction, flow direction, vertical direction). Then, in the present invention, the wound metal layer-integrated polypropylene film is tightened by heat shrinkage, and it is intended to suppress shear peeling at the contact surface between the metal layer-integrated polypropylene film and the metallikon electrode, which is caused by tightening. ..
As described above, the present invention and Patent Document 1 can have the same purpose in terms of suppressing peeling of the metallikon electrode, but are completely different as means for solving the problems. That is, in the present invention, since the heat shrinkage ratio is set to 0.60 or less, shear peeling at the contact surface between the metal layer-integrated polypropylene film and the metallikon electrode is suppressed, while in Patent Document 1, By reducing the heat shrinkage ratio of the polypropylene film for capacitors in the width direction, peeling due to the polypropylene film for capacitors shrinking in the direction away from the metallikon electrode surface is suppressed, and the solution means is completely different.

In the metal layer-integrated polypropylene film having the above structure, the heat shrinkage A in the first direction of the polypropylene film before laminating the metal layer is preferably 2.0% or more and 10.0% or less.

If the heat shrinkage A in the first direction of the polypropylene film before laminating the metal layer is 2.0% or more and 10.0% or less, there is room for selection of polypropylene film material and room for adjustment of polypropylene film manufacturing conditions. Can be secured more.

The metal layer-integrated polypropylene film having the above structure is preferably used for capacitors.

The metal layer-integrated polypropylene film is suitable for capacitors because it can secure room for selection of polypropylene film material and room for adjustment of polypropylene film manufacturing conditions, and can suppress peeling of the metallikon electrode. Can be used for

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

When the polypropylene film is biaxially stretched, the heat shrinkage in the first direction of the polypropylene film tends to be larger than that before the biaxial stretching. Therefore, when the polypropylene film is biaxially stretched, it is easy to obtain a metal layer-integrated polypropylene film having the heat shrinkage ratio of 0.60 or less.

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

Further, the method for producing a metal layer-integrated polypropylene film according to the present invention,
Step A of preparing a polypropylene film,
A method for producing a metal layer-integrated polypropylene film, comprising: a step B in which a metal layer is laminated on one surface or both surfaces of the polypropylene film prepared in the step A to obtain a metal layer integrated polypropylene film,
When the heat shrinkage rate in the first direction of the polypropylene film prepared in the step A is A and the heat shrinkage rate B in the first direction of the metal layer-integrated polypropylene film obtained in the step B, the heat shrinkage rate A And the heat shrinkage ratio B of the heat shrinkage ratio [(heat shrinkage ratio B)/(heat shrinkage ratio A)] is 0.25 or more and 0.60 or less.

According to the above configuration, since the raw material resin and the manufacturing conditions in which the heat shrinkage ratio is 0.25 or more and 0.60 or less may be adopted, there is room for selection of materials for manufacturing the metal layer-integrated polypropylene film. And there is room for adjustment of manufacturing conditions. Further, since the heat shrinkage ratio is 0.60 or less, it is possible to suppress peeling of the metallikon electrode when used as a capacitor.

The polypropylene film prepared in the step A preferably has a heat shrinkage A in the first direction of 2.0% or more and 10.0% or less.

If the heat shrinkage A in the first direction of the polypropylene film before laminating the metal layer is 2.0% or more and 10.0% or less, there is room for selection of polypropylene film material and room for adjustment of polypropylene film manufacturing conditions. Can be secured more.

According to the present invention, it is possible to provide a metal layer-integrated polypropylene film capable of suppressing the peeling of the metallikon electrode while securing room for material selection of the polypropylene film and room for adjusting the manufacturing conditions of the polypropylene film. it can. In addition, it is possible to provide a film capacitor having the polypropylene film integrated with the metal layer. Moreover, the manufacturing method of the said polypropylene film integrated with a metal layer can be provided.

It is a typical perspective view for explaining a metal layer integrated polypropylene film produced as an example and a comparative example. It is a schematic diagram for demonstrating the manufacturing method of the metal layer integrated polypropylene film which concerns on an Example and a comparative example.

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

In this specification, the expressions "containing" and "including" include the concepts of "containing", "including", "consisting essentially of" and "consisting solely of".

In this specification, "element", "capacitor", "capacitor element", and "film capacitor" mean the same thing.

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

The metal layer integrated polypropylene film according to the present embodiment,
Polypropylene film,
A metal layer-integrated polypropylene film having a metal layer laminated on one side or both sides of the polypropylene film,
When the heat shrinkage rate in the first direction of the polypropylene film before laminating the metal layer is A and the heat shrinkage rate in the first direction of the metal layer-integrated polypropylene film is B, the heat shrinkage rate A and the heat shrinkage The heat shrinkage ratio [(heat shrinkage B)/(heat shrinkage A)] with the ratio B is 0.25 or more and 0.60 or less.

In the present specification, the first direction means the MD direction (Machine Direction) of the polypropylene film. That is, in this embodiment, the first direction is preferably the MD direction. However, in the present embodiment, the first direction is not limited to the MD direction, and any direction can be set as the first direction. Hereinafter, a case where the first direction is the MD direction will be described. In this specification, the direction orthogonal to the MD direction is the TD direction (Transverse Direction) (also referred to as “width direction or lateral direction”).

In the present specification, the metallikon electrode means an external electrode provided on a side surface on which a metal layer-integrated polypropylene film is laminated and electrically connected to a metal layer as an internal electrode.

The metal layer-integrated polypropylene film according to the present embodiment has a heat shrinkage ratio [(heat shrinkage B)/(heat shrinkage A)] of heat shrinkage A and heat shrinkage B of 0.60 or less. It is preferably 0.58 or less, more preferably 0.55 or less, still more preferably 0.49 or less, and particularly preferably 0.48 or less. Since the heat shrinkage ratio is 0.60 or less, it can be said that the polypropylene film is relatively shrunk after the metal layer is laminated, as compared with before the metal layer is laminated. That is, since the heat shrinkage ratio is 0.60 or less, the metal layer-integrated polypropylene film has already undergone a large heat shrinkage, and even if it is subjected to a heat history, the heat shrinkage is less likely to occur. There is. As a result, relative displacement of the contact surface between the metal layer-integrated polypropylene film and the metallikon electrode due to long-term use after being made into a capacitor is suppressed, and peeling of the metallikon electrode can be suppressed.
In general, polypropylene films have the property of shrinking by heat. Therefore, by intentionally shrinking the polypropylene film significantly in the step of laminating the metal layer, the metal layer is laminated as compared to before the metal layer is laminated (before the heat is applied when the metal layer is laminated). It is relatively easy to reduce the heat shrinkage rate after the heat treatment (to set the heat shrinkage rate ratio to 0.60 or less). That is, in the present embodiment, the heat shrinkage ratio can be set to 0.60 or less by adjusting the conditions when laminating the metal layers, so that the range of selection for the material resin can be kept wide. it can. For example, unlike Patent Document 1, there is no restriction that a raw material resin that reduces the heat shrinkage rate of the polypropylene film before laminating the metal layer must be selected. Further, it is not necessary to adjust the production conditions of the polypropylene film so that the heat shrinkage rate of the polypropylene film before laminating the metal layer becomes small.
The heat shrinkage ratio is 0.25 or more, preferably 0.28 or more, more preferably 0.30 or more, still more preferably 0.40 or more, and particularly preferably 0. It is 45 or more. Since the heat shrinkage ratio is 0.25 or more, the dimensional stability is excellent during the heat treatment after winding the element.
As described above, according to the metal layer-integrated polypropylene film according to the present embodiment, since the heat shrinkage ratio is 0.60 or less, there is room for selection of polypropylene film materials and room for adjustment of polypropylene film manufacturing conditions. And the heat shrinkage ratio is 0.60 or less, it is possible to suppress the peeling of the metallikon electrode. This point is also clear from the examples.

<Method of measuring heat shrinkage B in the first direction of the metal layer-integrated polypropylene film>
The metal layer-integrated polypropylene film is cut into a rectangle having a width of 20 mm and a length of 130 mm to prepare a measurement sample. At this time, the first direction (MD direction in this embodiment) is cut out as the length direction. Three measurement samples are prepared. In addition, in the metal layer integrated polypropylene film, when there is a portion where the metal layer is formed on the polypropylene film and a portion where the metal layer is not formed (when the metal layer is patterned on the polypropylene film), measurement When cutting out the sample, a portion having a width of 20 mm and a length of 130 mm where the metal layer is formed and not a heavy edge is cut out. Next, a 100 mm-long portion of the measurement sample is measured with a ruler, and a marked line is attached to the portion. Next, the three measurement samples are held in a hot air circulation type constant temperature bath at 120° C. for 15 minutes with no load. Then, it cools at room temperature (23 degreeC), and measures a dimension. The rate of dimensional change after heating with respect to the dimension of 100 mm before heating at 120° C. is referred to as heat shrinkage rate B. Specifically, it is as in the following formula.
(Heat shrinkage B)=[[(dimension before heating)-(dimension after heating)]/(dimension before heating)]×100(%)
The measurement conditions other than those described here are in accordance with JIS C 2151:2006 “21. Dimensional change”.
More specifically, the method described in the examples is used.

The method for measuring the heat shrinkage rate A is the same as the method for measuring the heat shrinkage rate B except that a polypropylene film before laminating a metal layer is used instead of the metal layer-integrated polypropylene film as the measurement sample. Is.

The method of adjusting the heat shrinkage ratio is not particularly limited. For example, the heat shrinkage rate B may be adjusted after selecting a material according to the purpose from various materials (raw material resin, etc.). That is, if the heat shrinkage ratio B is adjusted, the heat shrinkage ratio can be set to 0.25 or more and 0.60 or less, so that there is room for selecting a material for the polypropylene film.

The method for adjusting the heat shrinkage ratio B is not particularly limited, but can be adjusted, for example, under the conditions for laminating the metal layer on the polypropylene film. Specific conditions for laminating the metal layer on the polypropylene film include (i) the temperature of the cooling roll, (ii) the temperature of the evaporation source, and (iii) the thickness of the metal layer.
The temperature of the cooling roll is usually set low in order to prevent the polypropylene film from losing heat, but if set to a high value, the polypropylene film can be greatly heat-shrunk during metal layer lamination, The heat shrinkage ratio B of the obtained metal layer-integrated polypropylene film tends to be small. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less.
If the temperature of the evaporation source is set higher, the polypropylene film can be largely heat-shrunk when the metal layers are laminated, and the heat shrinkage ratio B of the obtained metal-layer-integrated polypropylene film tends to be smaller. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less.
The thicker the metal layer, the longer it will be exposed to heat due to the stacking of the metal layers. Therefore, if the thickness is set to a large value, the polypropylene film can be largely heat-shrunk by being exposed to heat for a long time when the metal layers are laminated, and the heat shrinkage rate B of the obtained metal-layer-integrated polypropylene film can be reduced. It tends to be possible. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less.

As another example of the method of adjusting the heat shrinkage ratio B, there is a method of laminating a metal layer on a polypropylene film and then performing a post heat treatment. By performing the post-heat treatment, the metal layer-integrated polypropylene film before being made into a product can be thermally shrunk, and as a result, the heat shrinkage rate B of the metal layer-integrated polypropylene film as a product can be made small. .. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less.

The heat shrinkage rate B is preferably 2.4% or less, more preferably 2.3% or less, further preferably 2.2% or less, and particularly preferably 2.1% or less. When the heat shrinkage rate B is 2.4% or less, relative displacement between the metal layer integrated polypropylene film and the metallikon electrode due to long-term use after being formed into a capacitor is further suppressed. As a result, peeling of the metallikon electrode can be further suppressed. This point is also clear from the examples. The heat shrinkage ratio B is, for example, 0.5% or more, 0.8% or more, 1.0% or more. When the heat shrinkage B is 0.5% or more, the element is preferably wound tightly during the heat treatment after winding the element. As a result, the voids between the films are removed and the shape is stabilized. In addition, withstand voltage can be improved.

The heat shrinkage A (heat shrinkage in the first direction of the polypropylene film before laminating the metal layer) is preferably 2.0% or more, more preferably 3.1% or more, further 3.5% or more. It is preferably 4.0% or more and particularly preferably. When the heat shrinkage ratio A is 2.0% or more, there is more room to select a material for the polypropylene film and room to adjust the production conditions for the polypropylene film. In other words, there are few restrictions that a raw material resin must be selected so that the heat shrinkage rate (heat shrinkage rate A) of the polypropylene film before laminating the metal layer becomes small. The upper limit of the heat shrinkage ratio A is not particularly limited, but is, for example, 9.0% or less, 8.0% or less, 7.5% or less, from the viewpoint of the production of the polypropylene film.

As described above, in this embodiment, it is preferable to use a polypropylene film having a heat shrinkage ratio A of 2.0% or more. That is, it is not necessary to manufacture a polypropylene film having a small heat shrinkage A. Therefore, there is room for selecting a material for the polypropylene film. Therefore, it is relatively easy to obtain a polypropylene film having a heat shrinkage ratio A of 2.0% or more, and it may be selected from various materials (raw resin, etc.).

The thickness of the metal layer-integrated polypropylene film is preferably 0.8 μm or more, more preferably 1.2 μm or more, still more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. The thickness of the polypropylene film is preferably 3.5 μm or less, more preferably 3.0 μm or less, further preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

The thickness of the metal layer-integrated polypropylene film refers to a value measured according to JIS-C2330, except that it is measured at 100±10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu.

In the metal layer-integrated polypropylene film, the dimensional change rate in the first direction at 120° C. is preferably −0.40% or more, more preferably −0.30% or more, and further preferably −0.26%. That is all. When the dimensional change rate in the first direction at 120° C. is −0.40% or more, it is possible to prevent the dimensional change of the film from becoming too large when used as a capacitor element at high temperature. As a result, peeling of the metallikon electrode can be suppressed more favorably. The dimensional change rate in the first direction at 120° C. is preferably 0.30% or less, more preferably 0% or less, even more preferably −0.01% or less, and particularly preferably −0.05% or less.
In the present embodiment, the dimensional change rate in the first direction at 120° C. can be controlled by the temperature of the evaporation source, the thickness of the metal layer, and the like. For example, when the first direction is the MD direction, the MD dimensional change rate tends to increase in the negative direction as the temperature of the evaporation source decreases. Further, for example, when the first direction is the MD direction, the MD dimension change rate tends to increase in the negative direction as the thickness of the metal layer increases (that is, the MD dimension change rate is lower. Tends to be).
The dimensional change rate in the first direction at 120° C. is a value measured by the TMA method, and more specifically according to the method described in the examples.

The polypropylene film included in the metal layer-integrated polypropylene film as a product after laminating the metal layers will be described below. That is, in the following, whether or not before laminating the metal layer, or after laminating the metal layer, unless otherwise specified, when referred to as "polypropylene film", unless otherwise specified, It is described as meaning a polypropylene film after laminating a metal layer.

The thickness of the polypropylene film is preferably 0.8 μm or more, more preferably 1.2 μm or more, further preferably 1.5 μm or more, particularly preferably 2.0 μm or more. The thickness of the polypropylene film is preferably 3.5 μm or less, more preferably 3.0 μm or less, further preferably 2.9 μm or less, and particularly preferably 2.8 μm or less.

When the thickness of the polypropylene film is 3.0 μm or less, the capacitance per unit volume of the capacitor element can be increased, so that it can be suitably used for capacitors. Further, from the viewpoint of film-forming stability of the film, and from the viewpoint of suppressing an increase in the heat shrinkage ratio B (from the viewpoint of suppressing that the shrinkage ratio exceeds 0.6), the thickness of the polypropylene film The thickness can be 0.8 μm or more.
This point will be described in detail below.
The thinner the polypropylene film, the greater the capacitance per unit volume. More specifically, the capacitance C is expressed as follows using the dielectric constant ε, the electrode area S, and the dielectric thickness d (thickness d of the polypropylene film).
C=εS/d
Here, in the case of a film capacitor, the thickness of the electrode is three orders of magnitude or less thinner than the thickness of the polypropylene film (dielectric), so ignoring the volume of the electrode, the volume V of the capacitor is expressed as follows. To be done.
V=Sd
Therefore, the electrostatic capacity C/V per unit volume is expressed as follows from the above two equations.
C/V=ε/d ²
As can be seen from the above equation, the capacitance per unit volume (C/V) is inversely proportional to the square of the polypropylene film thickness. Further, the dielectric constant ε is determined by the material used. Then, unless the material is changed, the capacitance per unit volume (C/V) can be improved only by reducing the thickness.
The electrode area does not affect the electrostatic capacity (C/V) per unit volume. This point will be described below.
It is assumed that a capacitor is manufactured by winding a film having the same material and the same thickness. For example, assume that the number of turns (the number of turns) is increased and the winding is performed ten times longer (the electrode area is ten times larger). Then, the capacitance is increased by 10 times, but the volume is also increased by 10 times, so that the capacitance per unit volume (C/V) does not change even if the electrode area changes.
The above description is idealized for ease of understanding. In other words, in practice, for example, there may be a slight gap between the films, the influence of the fringe effect at the electrode end, and the like, so that the capacitance per unit volume (C In some cases, there may be some changes in the value of /V). However, it can be seen that, in general, the capacitance per unit volume (C/V) depends on the polypropylene film thickness.
From the above, it is preferable that the thickness of the polypropylene film is as thin as possible within the range where the withstand voltage property is ensured. Therefore, the thickness of the polypropylene film is preferably 3.0 μm or less.
On the other hand, when the polypropylene film is thin, the heat shrinkage ratio B tends to be large. When the heat shrinkage ratio B increases, the shrinkage ratio also increases. Therefore, if the thickness is too thin, the metallikon electrode may peel off when the capacitor is used for a long period of time. Therefore, the thickness of the polypropylene film is preferably 0.8 μm or more.

The thickness of the polypropylene film in the present invention and the present specification is obtained by subtracting the thickness of the metal layer (the thickness of the metal layer calculated from the membrane resistance) from the thickness of the metal layer-integrated polypropylene film. Stipulated as being allowed.
The thickness of the metal layer in the metal layer-integrated polypropylene film is preferably 0.1 to 10 nm. When the thickness of the metal layer is 0.1 to 10 nm, the thickness of the metal layer-integrated polypropylene film and the thickness of the polypropylene film show the same value in the measuring method described in this example.

The polypropylene film may be a biaxially stretched film, a uniaxially stretched film, or an unstretched film. Of these, a biaxially stretched film is preferable. When the polypropylene film is biaxially stretched, the heat shrinkage in the first direction of the polypropylene film tends to be larger than that before the biaxial stretching. Therefore, when the polypropylene film is biaxially stretched, it is easy to obtain a metal layer-integrated polypropylene film having the heat shrinkage ratio of 0.60 or less.

The polypropylene film preferably has a plane orientation coefficient ΔP of 0.010 to 0.016, more preferably 0.011 to 0.0155, and further preferably 0.0115 to 0.015. ..

When the plane orientation coefficient ΔP of the polypropylene film is within the above range, it is possible to reduce the dielectric breakdown at high temperature and high voltage while controlling the heat shrinkage ratio appropriately.

<Plane orientation coefficient ΔP>
In the present specification, the “plane orientation coefficient ΔP” means the plane orientation coefficient ΔP (where ΔP=ΔP=ΔP=calculated from the birefringence values ΔNyz and ΔNxz in the thickness direction of the polypropylene film obtained by optical birefringence measurement). (ΔNyz+ΔNxz)/2).
In the present specification, the “birefringence value ΔNyz” with respect to the thickness direction of the polypropylene film refers to the birefringence value ΔNyz with respect to the thickness direction obtained by optical birefringence measurement. More specifically, the principal axis in the in-plane direction of the film is the x-axis and the y-axis, and the thickness direction of the film (direction normal to the in-plane direction) is the z-axis. When the slow axis in the higher direction is the x-axis, the birefringence value ΔNyz is the value obtained by subtracting the three-dimensional refractive index in the z-axis direction from the three-dimensional refractive index in the y-axis direction.

In the present specification, the “birefringence value ΔNxz” in the thickness direction of the polypropylene film refers to the birefringence value ΔNxz in the thickness direction obtained by optical birefringence measurement, and more specifically, the x-axis. The value obtained by subtracting the three-dimensional refractive index in the z-axis direction from the three-dimensional refractive index in the (slow axis) direction is the birefringence value ΔNxz.

In the present embodiment, in order to measure the “birefringence value ΔNyz” in the thickness direction of the polypropylene film, specifically, a phase difference measuring device RE-100 manufactured by Otsuka Electronics Co., Ltd. is used. The measurement of retardation (phase difference) is performed using a tilt method. More specifically, the principal axis in the in-plane direction of the film is the x-axis and the y-axis, and the thickness direction of the film (direction normal to the in-plane direction) is the z-axis. The slow axis in the higher direction is the x axis. Retardation values are obtained when the x-axis is tilted and the z-axis is tilted by 10° in the range of 0° to 50°. From the obtained retardation value, the y-axis direction with respect to the thickness direction (z-axis direction) was used by the method described in Non-Patent Document "Yu Awaya, Introduction to Polarizing Microscopes of Polymer Materials, pp. 105-120, 2001". The birefringence ΔNyz of is calculated. First, for each inclination angle φ, the measured retardation value R is divided by the inclination-corrected thickness d to obtain R/d. For each R/d of φ=10°, 20°, 30°, 40°, 50°, obtain the difference from the R/d of φ=0°, and divide them by sin2r (r: refraction angle). The birefringence ΔNzy at each φ is set, and the positive and negative signs are reversed to obtain the birefringence value ΔNyz. The birefringence value ΔNyz is calculated as the average value of ΔNyz at φ=20°, 30°, 40°, and 50°. In the successive stretching method, for example, when the stretching ratio in the TD direction (width direction) is higher than the stretching ratio in the MD direction (flow direction), the TD direction becomes the slow axis (x axis) and the MD direction becomes y. It becomes an axis. When polypropylene is used, the value of the refraction angle r at each inclination angle of polypropylene is that described on page 109 of the above document.

In addition, in the present embodiment, the “birefringence value ΔNxz” in the thickness direction of the polypropylene film is obtained as described above from the value obtained by dividing the retardation value R measured at the inclination angle φ=0° by the thickness d. The birefringence value ΔNxz is calculated by dividing ΔNzy.
A more specific measuring method of the plane orientation coefficient is according to the method described in Examples.

The polypropylene film contains a polypropylene resin, and the constituent material thereof is not particularly limited as long as the heat shrinkage ratio is 0.25 or more and 0.60 or less.

The content of the polypropylene resin is preferably 90% by mass or more, and more preferably 95% by mass or more based on the entire polypropylene film (when the entire polypropylene film is 100% by mass). The upper limit of the content of the polypropylene resin is, for example, 100% by mass or 98% by mass with respect to the entire polypropylene film. The polypropylene resin may contain one kind of polypropylene resin alone, or may contain two or more kinds of polypropylene resin. The polypropylene resin is preferably a homopolypropylene resin.

Here, when two or more kinds of polypropylene resins are contained in the polypropylene film, the polypropylene resin having the larger content is referred to as “main component polypropylene resin” in the present specification. Further, when the polypropylene film contains one type of polypropylene resin, the polypropylene resin is referred to as “main component polypropylene resin” in the present specification.

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

The weight average molecular weight Mw of the polypropylene resin is preferably 250,000 or more and 450,000 or less, and more preferably 250,000 or more and 400,000 or less. When the weight average molecular weight Mw of the polypropylene resin is 250,000 or more and 450,000 or less, the resin fluidity becomes appropriate. As a result, the thickness of the cast original fabric sheet can be easily controlled, the thickness uniformity is good, and a thin stretched film can be easily produced. In addition, the weight average molecular weight Mw is preferably 250,000 or more and 450,000 or less from the viewpoint of mechanical properties, thermo-mechanical properties, stretch moldability, etc. of the biaxially oriented polypropylene film. When two or more polypropylene resins are used, it is preferable to use the polypropylene resin having Mw of 250,000 or more and less than 330,000 and the polypropylene resin having Mw of 330,000 or more and 450,000 or less in combination.
The number average molecular weight Mn of the polypropylene resin is preferably 30,000 or more and 53,000 or less, and more preferably 33,000 or more and 52,000 or less.
The z-average molecular weight Mz of the polypropylene resin is preferably 500,000 or more and 2100000 or less, and more preferably 700,000 or more and 1700000 or less.

The molecular weight distribution [(weight average molecular weight Mw)/(number average molecular weight Mn)] of the polypropylene resin is preferably 5 or more and 12 or less, more preferably 5 or more and 11 or less, and 5 or more and 10 or less. Is more preferable. When the polypropylene resin has a molecular weight distribution [(weight average molecular weight Mw)/(number average molecular weight Mn)] of 5 or more and 12 or less, appropriate resin fluidity can be obtained during biaxial stretching and ultrathinization without unevenness in thickness can be achieved. It is preferable because the obtained biaxially stretched propylene film is easily obtained.
The molecular weight distribution [(z average molecular weight Mz)/(number average molecular weight Mn)] of the polypropylene resin is preferably 10 or more and 70 or less, more preferably 15 or more and 60 or less, and 15 or more and 50 or less. Is more preferable.

In the present specification, the weight average molecular weight (Mw), number average molecular weight (Mn), z average molecular weight (Mz), and molecular weight distribution (Mw/Mn and Mz/Mn) of the polypropylene resin are gel permeation. It is a value measured using a chromatograph (GPC) device. More specifically, it is a value measured using HLC-8121GPC-HT (trade name), a high temperature GPC measuring instrument with a built-in differential refractometer (RI) manufactured by Tosoh Corporation. As a GPC column, three TSKgel GMHHR-H(20)HT manufactured by Tosoh Corporation are connected and used. The column temperature is set to 140° C., and trichlorobenzene is flown as an eluent at a flow rate of 1.0 ml/10 minutes to obtain measured values of Mw and Mn. A calibration curve for the molecular weight M is prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured value is converted into a polystyrene value to obtain Mw, Mn and Mz. Here, the logarithm of the base 10 of the molecular weight M of standard polystyrene is referred to as logarithmic molecular weight (“Log(M)”).

In the molecular weight differential distribution curve, the polypropylene resin has a difference obtained by subtracting the differential distribution value at Log(M)=6.0 from the differential distribution value at Log(M)=4.5 (hereinafter, “Differential distribution value difference D _M ”) is preferably −5% or more and 14% or less, more preferably −4% or more and 12% or less, and −4% or more and 10% or less. Is more preferable.
In addition, "the difference (differential distribution value difference D _M ) 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 − "5% or more and 14% or less" means a typical distribution of components having a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter, also referred to as "low molecular weight component") based on the Mw value of the polypropylene resin. Log(M) as a representative distribution value of a component having a logarithmic molecular weight Log(M)=4.5 as a value and a component having a molecular weight of about 1,000,000 on the high molecular weight side (hereinafter, also referred to as “high molecular weight component”) It can be understood that when the difference is positive, the low molecular weight component is more, and when the difference is negative, the high molecular weight component is more.

That is, for example, when the case where the molecular weight distribution Mw/Mn is 5 to 12 is taken as an example, even if the molecular weight distribution Mw/Mn is 5 to 12, it merely represents the width of the molecular weight distribution. However, the quantitative relationship between the high molecular weight component and the low molecular weight component therein is not known. Therefore, from the viewpoint of resin fluidity, stretch moldability, and thickness uniformity, the polypropylene resin has a differential distribution value difference of −5% when a component having a molecular weight of 10,000 to 100,000 is compared with a component having a molecular weight of 1,000,000. It is preferable to use polypropylene resin so that the content is 14% or less.

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

The polypropylene resin has a mesopentad fraction ([mmmm]) of preferably less than 98.0%, more preferably 97.5% or less, further preferably 97.4% or less, and 97. It is particularly preferably not more than 0.0%. Further, the mesopentad fraction is preferably 94.0% or more, more preferably 94.5% or more, and further preferably 95.0% or more. When the mesopentad fraction is within the above numerical range, the crystallinity of the resin is moderately improved due to the moderately high stereoregularity, and the initial withstand voltage property and the withstand voltage property over a long period of time are improved, while the cast raw sheet A desired stretchability can be obtained by an appropriate solidification (crystallization) rate at the time of molding.

The mesopentad fraction ([mmmm]) is an index of stereoregularity that can be obtained by high temperature nuclear magnetic resonance (NMR) measurement. In the present specification, the mesopentad fraction ([mmmm]) refers to a value measured by using JNM-ECP500, a high temperature Fourier transform nuclear magnetic resonance apparatus (high temperature FT-NMR) manufactured by JEOL Ltd. 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 For the measurement method by high temperature NMR, refer to, for example, the method described in “Japan Analytical Chemistry/Polymer Analysis Research Round-table, New Edition Polymer Analysis Handbook, Kinokuniya Bookstore, 1995, p. 610”. A more detailed measuring method of the mesopentad fraction ([mmmm]) is according to the method described in the examples.

The heptane-insoluble content (HI) of the polypropylene resin is preferably 96.0% or more, more preferably 97.0% or more. Further, the heptane-insoluble matter (HI) of the polypropylene resin is preferably 99.5% or less, more preferably 99.0% or less. Here, the heptane insoluble content is higher, 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 an appropriately high stereoregularity, and the withstand voltage property at high temperature is improved. To do. On the other hand, the rate of solidification (crystallization) at the time of forming the cast raw sheet becomes appropriate, and the sheet has appropriate stretchability. The heptane insoluble matter (HI) is measured by the method described in Examples.

The melt flow rate (MFR) of the polypropylene resin is preferably 1.0 to 8.0 g/10 min, more preferably 1.5 to 7.0 g/10 min, and 2.0 to 6.0 g. More preferably, it is /10 min. The method for measuring the melt flow rate of the polypropylene resin is according to the method described in Examples.

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

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

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

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

The molecular weight distribution and the like of the polypropylene resin can be adjusted by resin mixing (blending). For example, a method of mixing two or more kinds of resins having different molecular weights or molecular weight distributions from each other can be mentioned. Generally, a mixture of two types of polypropylene having a main resin of 55% by mass or more and 90% by mass or less, where 100% by mass of the whole resin is a resin having an average molecular weight higher or lower than that of the main resin. The system is preferable because the amount of low molecular weight components can be easily adjusted.

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

The method for mixing the resins is not particularly limited, but a polymer powder of the main resin and the added resin, or a pellet, a method of dry blending using a mixer or the like, a polymer powder of the main resin and the added resin, or pellets. Is supplied to a kneading machine and melt-kneaded to obtain a blended resin.

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

In the case of blending by melt-kneading, the kneading temperature is not particularly limited as long as a good kneaded product can be obtained. Generally, it is in the range of 200°C to 300°C, and 230°C to 270°C is preferable from the viewpoint of suppressing deterioration of the resin. Further, in order to suppress deterioration at the time of kneading and mixing the resin, the kneading machine may be purged with an inert gas such as nitrogen. The melt-kneaded resin may be pelletized to an appropriate size using a generally known granulator. Thereby, the mixed polypropylene raw material resin pellets can be obtained.

The total ash content due to the polymerization catalyst residue and the like contained in the polypropylene raw material resin is preferably 50 ppm or less based on the polypropylene resin (100 parts by weight).

The total ash content (total ash content contained in the polypropylene raw material resin) is preferably 5 ppm or more and 35 ppm or less, and 5 ppm or more and 30 ppm or less, in order to improve the electrical characteristics of the capacitor while suppressing the generation of polar low-molecular components. The following is more preferable, and 10 ppm or more and 25 ppm or less is further preferable.

The polypropylene film may include an additive. The "additive" is generally an additive used in polypropylene resin, and is not particularly limited as long as a polypropylene film having the heat shrinkage ratio of 0.25 or more and 0.6 or less can be obtained. ..

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

The metal layer functions as an electrode when the polypropylene film integrated with the metal layer is used as a capacitor. As the metal used for the metal layer, for example, a simple metal such as zinc, lead, silver, chromium, aluminum, copper, nickel, a mixture of plural kinds thereof, an alloy thereof, or the like can be used. Considering economical efficiency and capacitor performance, zinc and aluminum are preferable.

Next, a method for manufacturing the metal layer-integrated polypropylene film according to the present embodiment will be described. The metal layer-integrated polypropylene film according to the present invention is preferably manufactured by the method for manufacturing a metal layer-integrated polypropylene film described below, but the method for manufacturing a metal layer-integrated polypropylene film described below. Need not be manufactured in.

The manufacturing method of the metal layer-integrated polypropylene film according to the present embodiment,
Step A of preparing a polypropylene film,
And at least a step B for obtaining a metal layer-integrated polypropylene film by laminating a metal layer on one side or both sides of the polypropylene film prepared in the step A,
When the heat shrinkage rate in the first direction of the polypropylene film prepared in the step A is A and the heat shrinkage rate B in the first direction of the metal layer-integrated polypropylene film obtained in the step B, the heat shrinkage rate A And the heat shrinkage ratio B [(heat shrinkage ratio B)/(heat shrinkage ratio A)] is 0.25 or more and 0.6 or less.

First, the step A will be described.

When the polypropylene film is a biaxially stretched polypropylene film, a cast original fabric sheet before stretching for producing the biaxially stretched polypropylene film can be produced as follows. However, the method for producing the cast raw fabric sheet according to the present embodiment is not limited to the method described below.

First, resin pellets, dry-mixed resin pellets, or resin pellets prepared by melt-kneading in advance are supplied to an extruder and heated and melted.
The temperature of the melt-kneading varies depending on the type of the thermoplastic resin, but in the case of the polypropylene resin, the extruder setting temperature during heating and melting is preferably 220 to 280°C, more preferably 230 to 270°C. The resin temperature during heating and melting is preferably 220 to 280°C, more preferably 230 to 270°C. The resin temperature at the time of heating and melting is a value measured by a thermometer inserted in the extruder.
The extruder set temperature and the resin temperature during heating and melting are selected in consideration of the physical properties of the resin used. It is also possible to suppress the deterioration of the resin by setting the resin temperature during heating and melting within the above numerical range.

Next, the molten resin is extruded into a sheet shape using a T-die, and cooled and solidified with at least one metal drum to form an unstretched cast raw sheet.
The surface temperature of the metal drum (the temperature of the metal drum that first contacts after extrusion) is preferably 50 to 100°C, more preferably 60 to 80°C. The surface temperature of the metal drum can be determined according to the physical properties of the resin used and the like.

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

The polypropylene film according to this embodiment can be suitably produced as follows. However, the method for producing the polypropylene film according to the present embodiment is not limited to the method described below.

The polypropylene film can be manufactured by subjecting the resin cast original fabric sheet to a stretching treatment. The stretching is preferably biaxial stretching in which the film is oriented biaxially in the longitudinal and transverse directions, and the sequential biaxial stretching method is preferred as the stretching method. As a sequential biaxial stretching method, for example, first, the cast raw fabric sheet is kept at a temperature of 100 to 170° C., and is passed between rolls provided with a speed difference, and is 3 to 7 times in the MD direction (flow direction, longitudinal direction) To stretch. The nip pressure is 0.35 to 0.5 MPa.
100-170 degreeC is preferable, as for the temperature at the time of MD extending|stretching, 120-160 degreeC is more preferable, 130-150 degreeC is further more preferable. The stretching ratio during MD stretching is preferably 3 to 7 times, more preferably 4 to 6 times, and even more preferably 4 to 5 times. The nip pressure during MD stretching is preferably 0.35 to 0.45 MPa, more preferably 0.36 to 0.44 MPa, and further preferably 0.37 to 0.43 MPa. The higher the nip pressure during MD direction stretching, the smaller the heat shrinkage, and the lower the nip pressure, the larger the heat shrinkage.
After stretching in the MD direction, the sheet is guided to a tenter and stretched 3 to 11 times in the TD direction (transverse direction, width direction). The temperature during stretching in the TD direction is preferably 155 to 170°C. After that, relaxation and heat fixation are applied by 2 to 10 times. By the above, a biaxially oriented polypropylene film is obtained.

The polypropylene film may be subjected to a corona discharge treatment online or offline after the stretching and heat-setting steps for the purpose of enhancing the adhesive property in a subsequent step such as a metal vapor deposition processing step. The corona discharge treatment can be performed using a known method. It is preferable to use air, carbon dioxide gas, nitrogen gas, or a mixed gas thereof as the atmosphere gas.

A polypropylene film can be obtained as described above. In particular, a polypropylene film having a heat shrinkage A in the first direction of 2.0% or more and 10.0% or less can be preferably obtained.

The process A of preparing the polypropylene film has been described above.

Next, step B of obtaining a polypropylene film integrated with a metal layer by laminating a metal layer on one side or both sides of the polypropylene film prepared in the step A will be described. However, the process B according to the present embodiment is not limited to the process described below.

In step B, a metal layer is laminated on one side or both sides of the polypropylene film in order to process it as a capacitor to obtain a metal layer-integrated polypropylene film.

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

As a vapor deposition condition in the vacuum vapor deposition method, the temperature of the cooling roll is preferably −23° C. or higher, more preferably −22° C. or higher, and further preferably −20° C. or higher. When the temperature of the cooling roll is −23° C. or higher, the polypropylene film can be largely heat-shrunk when the metal layers are laminated, and the heat shrinkage rate B of the obtained metal layer-integrated polypropylene film tends to be small. .. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less. From the viewpoint of preventing the heat loss of the polypropylene film, the temperature of the cooling roll is preferably −18° C. or lower, and more preferably −19° C. or lower.

In the vacuum vapor deposition method, the temperature of the evaporation source is controlled by the amount of energization. As the vapor deposition conditions in the vacuum vapor deposition method, the amount of electricity supplied to the vaporization source is preferably 650 A or more, more preferably 700 A or more, and further preferably 800 A or more. When the energization amount is increased (when the temperature of the evaporation source is set to be high), the polypropylene film can be largely heat-shrunk when the metal layers are laminated, and the heat shrinkage rate B of the obtained metal-layer-integrated polypropylene film is reduced. Tend to be able to. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less. From the viewpoint of preventing the heat loss of the polypropylene film, the energization amount is preferably 900 A or less, and more preferably 850 A or less.

In the vacuum deposition method, the thickness of the metal layer is controlled by the film resistance. As the vapor deposition conditions in the vacuum vapor deposition method, the film resistance of the aluminum film is preferably 20 Ω/sq or less, and more preferably 17 Ω/sq or less. In the case of a zinc film, it is preferably 5 Ω/sq or less, more preferably 4 Ω/sq or less. The small film resistance means that the metal layer has a large thickness. If the film resistance is decreased (the thickness of the metal layer is increased), the metal layer is exposed to heat for a long time due to the lamination. Therefore, if the thickness is set to a large value, the polypropylene film can be greatly heat-shrinked by being exposed to heat for a long time when the metal layers are laminated, and the heat shrinkage rate B of the obtained metal layer-integrated polypropylene film can be reduced. It tends to be possible. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less. In the case of an aluminum film, the film resistance is preferably 1 Ω/sq or more, and more preferably 5 Ω/sq or more, from the viewpoint of self-healing property (self-healing property). In the case of a zinc film, it is preferably 1 Ω/sq or more, more preferably 2 Ω/sq or more. Note that the self-healing property means that when a defective portion occurs in the polypropylene film, the metal of the vapor deposition layer is instantly evaporated by the applied energy or the energy of the capacitor itself to restore the function of the capacitor. ..
The thickness (film resistance) of the metal layer can be adjusted by the vapor deposition line speed and the temperature of the evaporation source.

The margin pattern when depositing the metal layer by vapor deposition is not particularly limited, but a pattern including a so-called special margin such as a fishnet pattern or a T margin pattern from the viewpoint of improving characteristics such as security of the capacitor. Is preferably applied to one side of the film. It is also effective from the standpoint of enhancing safety and preventing capacitor destruction and short circuits.

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

In the step B, after the metal layer is laminated on one side or both sides of the polypropylene film, a post heat treatment may be further performed. By performing the post-heat treatment, the metal layer-integrated polypropylene film before being made into a product can be thermally shrunk, and as a result, the heat shrinkage rate B of the metal layer-integrated polypropylene film as a product can be made small. .. If the heat shrinkage ratio B can be reduced, the shrinkage ratio can easily be set to 0.6 or less. Examples of conditions for the post heat treatment include application of silicon oil heated to 120 to 130°C.

Heretofore, an example of the method for producing the metal layer-integrated polypropylene film having the shrinkage ratio of 0.25 or more and 0.60 or less has been described.

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

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 thereof is not exceeded.

[Polypropylene resin]
The polypropylene resins used to produce the polypropylene films of the Examples and Comparative Examples are shown in Table 1.
Resin A is a product manufactured by Prime Polymer Co. (Irganox (registered trademark) 1010 is added as an antioxidant at 5000 ppm, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane at 20 ppm is added. It is a resin whose molecular weight distribution is adjusted by subjecting it to peroxide decomposition treatment by melt-kneading with a granulator.
Resin B is a product manufactured by Prime Polymer Co., Ltd. (a resin containing 5000 ppm of Irganox (registered trademark) 1010 as an antioxidant).
Resin C is HPT-1 (a resin containing 5000 ppm of Irganox (registered trademark) 1010 as an antioxidant) manufactured by Korea Yuka Co., Ltd.
Table 1 shows the weight average molecular weight (Mw), number average molecular weight (Mn), z average molecular weight (Mz), molecular weight distribution (Mw/Mn), and molecular weight distribution (Mz/Mn) of each resin. These values are in the form of raw material resin pellets. The measuring method is as follows. Resin A, resin B and resin C are all homopolypropylene resins.

<Measurement of weight average molecular weight (Mw), number average molecular weight (Mn), z average molecular weight (Mz), molecular weight distribution (Mw/Mn), and molecular weight distribution (Mz/Mn) of polypropylene resin>
Using GPC (gel permeation chromatography) under the following conditions, the weight average molecular weight (Mw), number average molecular weight (Mn), z average molecular weight (Mz), molecular weight distribution (Mw/Mn) of each resin, and The molecular weight distribution (Mz/Mn) was measured.
Specifically, an HLC-8121GPC-HT type manufactured by Tosoh Corporation, which is a high temperature GPC device with a built-in differential refractometer (RI), was used. As a column, three TSKgel GMHHR-H(20)HT manufactured by Tosoh Corporation were connected and used. It was measured by flowing trichlorobenzene as a eluent at a column temperature of 140° C. at a flow rate of 1.0 ml/min. A calibration curve was prepared using standard polystyrene manufactured by Tosoh Corporation, and the measured value of the molecular weight was converted into the value of polystyrene to obtain a weight average molecular weight (Mw), a number average molecular weight (Mn), and a z-average. The molecular weight (Mz) was obtained. A molecular weight distribution (Mw/Mn) was obtained using the values of Mw and Mn. Further, a molecular weight distribution (Mz/Mn) was obtained using the values of Mz and Mn.

<Measurement of difference (differential distribution value difference D _M ) between differential distribution value when logarithmic molecular weight log(M)=4.5 and differential distribution value when logarithmic molecular weight log(M)=6.0>
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, a time curve (elution curve) of the intensity distribution detected by using an RI detector is converted into a distribution curve with respect to the molecular weight M (Log(M)) of standard polystyrene by using a calibration curve prepared using the above standard polystyrene. Converted Next, after obtaining an integral distribution curve for Log(M) in the case where the total area of the distribution curve is 100%, a derivative distribution with respect to Log(M) is obtained by differentiating this integral distribution curve with Log(M). The curve was obtained. From this differential distribution curve, the differential distribution values at Log(M)=4.5 and Log(M)=6.0 were read. The difference between the differential distribution value when Log(M)=4.5 and the differential distribution value when Log(M)=6.0 was defined as the differential distribution value difference D _M. The series of operations until obtaining the differential distribution curve was performed using the analysis software built in the used GPC measurement device. The results are shown in Table 1.

<Measurement of Mesopentad Fraction ([mmmm])>
Each resin was dissolved in a solvent and measured using a high temperature Fourier transform nuclear magnetic resonance apparatus (high temperature FT-NMR) under the following conditions. The results are shown in Table 1.
High temperature type nuclear magnetic resonance (NMR) device: manufactured by JEOL Ltd., high temperature type Fourier transform nuclear magnetic resonance device (high temperature FT-NMR), JNM-ECP500
Observation nucleus: ¹³ C (125 MHz)
Measurement temperature: 135℃
Solvent: Ortho-dichlorobenzene (ODCB: mixed solvent of ODCB and deuterated ODCB (mixing ratio=4/1))
Measurement mode: Single pulse proton broadband decoupling pulse width: 9.1 μsec (45° pulse)
Pulse interval: 5.5 sec
Accumulation frequency: 4,500 times Shift standard: CH ₃ (mmmm)=21.7 ppm
The pentad fraction, which represents the degree of stereoregularity, is the combination of a pair of pentads of "meso (m)" in the same direction and "racemo (r)" in the opposite direction (mmmm or mrrm). Etc.) was calculated as a percentage (%) from the integrated value of the intensity of each signal. Regarding the attribution of signals derived from mmmm, mrrm, etc., for example, the description of spectra such as “T. Hayashi et al., Polymer, 29, 138 (1988)” was referred to.

<Measurement of heptane insoluble matter (HI)>
Each resin was press-molded into a size of 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 matter was calculated from the sample mass before and after extraction. 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 resin pellets was measured using a melt indexer manufactured by Toyo Seiki Co., Ltd. according to JIS K 7210 condition M. Specifically, first, a sample weighed to 4 g was inserted into a cylinder at 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 for 30 seconds, and the MFR (g/10 min) was obtained. The above measurement was repeated 3 times, and the average value was used as the measured value of MFR. The results are shown in Table 1.

A polypropylene film and a metal layer-integrated polypropylene film were produced using the above resin, and the physical properties thereof were evaluated.

<Production of polypropylene film>
(Production Example 1)
The resin A is supplied to the extruder and melted at a temperature of 255° C., then extruded using a T die, wound around a metal drum whose surface temperature is kept at 94° C. to be solidified, and cast with a thickness of about 120 μm. A raw sheet was prepared. The obtained cast raw fabric sheet was passed between rolls having a speed difference at a temperature of 139° C., stretched 4.8 times in the MD direction (flow direction), and immediately cooled to room temperature (23° C.). At this time, the nip pressure was 0.40 MPa.
Next, it was introduced into a tenter and stretched 10 times in the TD direction (width direction) at a temperature of 163° C. to obtain a biaxially oriented polypropylene film.
Here, the nip pressure is a nip roll above a roll having a high rotation speed (a roll located at a position where stretching in the MD direction is started) of two rolls provided with a speed difference for longitudinal stretching. Is provided, and refers to the pressure applied to the film when the film passes between the high-speed roll and the nip roll.

(Production Example 2)
Resin B and resin C were dry blended. The mixing ratio was (resin B):(resin C)=60:40 in terms of mass ratio. After that, the dry blended resin is supplied to an extruder, melted at a temperature of 255° C., then extruded using a T die, wound on a metal drum whose surface temperature is maintained at 91.5° C., and solidified, A cast original fabric sheet having a thickness of about 120 μm was produced. The obtained cast raw fabric sheet was passed between rolls having a speed difference at a temperature of 139° C., stretched 4.8 times in the MD direction (flow direction), and immediately cooled to room temperature (23° C.). At this time, the nip pressure was 0.40 MPa. Next, it was introduced into a tenter and stretched 10 times in the TD direction (width direction) at a temperature of 163° C. to obtain a biaxially oriented polypropylene film.

(Production Example 3)
A biaxially oriented polypropylene film was obtained in the same manner as in Production Example 2 except that the nip pressure was 0.30 MPa instead of 0.40 MPa.

<Measurement of heat shrinkage A in MD direction of polypropylene film before laminating metal layer>
The polypropylene film produced in Production Example was cut into a rectangle having a width of 20 mm and a length of 130 mm to prepare a measurement sample. At this time, the MD direction was cut as the length direction. Three measurement samples were prepared. Next, a 100 mm-long portion was measured with a ruler, and a marked line was attached to the portion. Next, the three measurement samples were held in a hot air circulation type constant temperature bath at 120° C. for 15 minutes with no load. Then, it cooled at room temperature (23 degreeC) and measured the dimension. The rate of change in the dimension after heating with respect to the dimension of 100 mm before heating at 120° C. was defined as the heat shrinkage rate A. Specifically, the following formula was used.
(Heat shrinkage rate A)=[[(dimension before heating)-(dimension after heating)]/(dimension before heating)]×100(%)
In addition, about conditions other than that described here, it was based on "21. Dimensional change" of JIS C2151:2006. The results are shown in Table 2.

<Production of metal layer integrated polypropylene film>
Using a vapor deposition device (manufactured by ULVAC, Inc., product name: roll-up type vacuum vapor deposition device EWE-060), a metal layer was laminated on the polypropylene film obtained in each production example under vapor deposition conditions shown in Table 2, A polypropylene film integrated with a metal layer according to a comparative example was obtained. Specifically, metal layer-integrated polypropylene films according to Examples and Comparative Examples were obtained as follows. The metal layer-integrated polypropylene films according to Examples and Comparative Examples all had a thickness of 2.5 μm. The thickness of the metal layer-integrated polypropylene film was measured according to JIS-C2330 except that it was measured at 100±10 kPa using a paper thickness measuring instrument MEI-11 manufactured by Citizen Seimitsu.

FIG. 1 is a schematic perspective view for explaining a metal layer-integrated polypropylene film produced as an example and a comparative example.
As shown in FIG. 1, the metal layer-integrated polypropylene film 1 produced in Examples and Comparative Examples includes a polypropylene film 2 and a metal vapor deposition electrode 3 laminated on the polypropylene film 2 so as to leave an insulation margin 4. Have. The metal vapor deposition electrode 3 has a metal vapor deposition layer 3a laminated on the polypropylene film 2 so as to be in direct contact with the polypropylene film 2, and an electrode lead-out portion 3b formed on a partial upper surface of the metal vapor deposition layer 3a. The electrode lead-out portion 3b is a so-called heavy edge.

FIG. 2 is a schematic diagram for explaining a method for manufacturing a metal layer-integrated polypropylene film according to Examples and Comparative Examples. The metal layer-integrated polypropylene films produced as Examples and Comparative Examples were produced by the production apparatus described below.
As shown in FIG. 2, the metal layer integrated polypropylene film manufacturing apparatus includes a dielectric film supply unit 101, an insulation margin forming unit 102, a pattern forming unit 103, a vapor deposition unit 104, and a winding roll 105. Prepare

The dielectric film supply unit 101 supports the dielectric film roll 2R around which the polypropylene film 2 (the polypropylene film manufactured in the manufacturing example) is wound, and supplies the dielectric film 2. The polypropylene film 2 supplied from the dielectric film roll 2R is conveyed to the insulation margin forming unit 102.

The insulation margin forming unit 102 applies oil having a pattern corresponding to the pattern of the insulation margin 4 to the surface 2a of the polypropylene film 2 to form an oil mask. The oil mask is for preventing metal particles from adhering to a portion of the metal layer-integrated polypropylene film 1 that serves as an insulation margin in the vapor deposition process. The insulation margin forming unit 102 vaporizes the oil stored in the oil tank and directly applies the oil to the one surface 2a of the polypropylene film 2 through a nozzle (slit) provided in the tank to form an oil mask.

The pattern forming unit 103 applies oil to the one surface 2a of the polypropylene film 2 in a pattern substantially corresponding to the electrode pattern of the metal vapor deposition layer 3a to form an oil mask. The oil mask is for preventing metal particles from adhering to the portions of the metal layer-integrated polypropylene film 1 which are vertical and horizontal margins in the vapor deposition process. The pattern forming unit 103 includes an oil tank 103a, an anilox roll 103b, a transfer roll 103c, a plate roll 103d, and a backup roll 103e. The oil tank 103a vaporizes the stored oil and ejects it from the nozzle. The anilox roll 103b and the transfer roll 103c rotate with the oil ejected from the nozzle of the oil tank 103a attached to the outer peripheral surfaces thereof. The backup roll 103e faces the plate roll 103d via the polypropylene film 2 and contacts the surface 2b of the polypropylene film 2.

The polypropylene film 2 that has passed through the insulating margin forming portion 102 and the pattern forming portion 103 is conveyed to the vapor deposition portion 104.

The vapor deposition unit 104 includes metal vapor generation units 104a and 104b, and a cooling roll 104c that faces the metal vapor generation units 104a and 104b with the polypropylene film 2 in between. The metal vapor generation unit 104a generates a metal vapor by supplying an electric current to a metal wire that is a material of the metal vapor deposition layer 3a on a heated boat to generate the metal vapor, and the metal vapor is supplied to the surface 2a of the polypropylene film 2. Vapor deposition. The metal vapor generation unit 104b heats and vaporizes the metal that is the material of the electrode extraction unit 3b to generate metal vapor, and the metal vapor deposition layer previously formed on the surface 2a of the polypropylene film 2 by the metal vapor generation unit 104a. It is vapor-deposited on top of 3a. As a result, the metal vapor deposition layer in the electrode extraction portion 3b portion becomes thicker than the metal vapor deposition layer in the other portions, and a heavy edge structure is formed. The metal vapor generated in the metal vapor generators 104a and 104b adheres to a portion other than the oil mask formed on the surface 2a of the polypropylene film 2 to form the metal vapor deposition electrode 3. The cooling roll 104b contacts the polypropylene film 2 to cool the polypropylene film 2.
The temperature of the metal vapor rises according to the amount of current (amount of energization) passed.
The thickness of the metal vapor deposition layer 3a is controlled by film resistance (resistance value per unit area). Since the resistance value is inversely proportional to the thickness, the lower the film resistance, the larger the film thickness.

The metal layer-integrated polypropylene film 1 formed by forming the metal vapor deposition electrode 3 on the polypropylene film 2 in the vapor deposition unit 104 is conveyed to the winding roll 105 and wound up.

The metal vapor deposition electrode 3 was formed on the surface 2a of the polypropylene film 2 using the above-mentioned manufacturing apparatus to obtain the polypropylene film 1 with integrated metal layer.

The thickness of the metal layer-integrated polypropylene film was measured according to JIS-C2330, except that the thickness was measured at 100±10 kPa using a paper thickness measuring device MEI-11 manufactured by Citizen Seimitsu.

<Membrane resistance measurement method>
A low resistance resistivity meter Loresta GX MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used to measure with a probe applied to the metal layer-integrated polypropylene film produced. The measurement was carried out at five solid parts near the center in the width direction of the film (a place other than the electrode lead-out part 3b), and the average value was taken as the film resistance.

<Measurement of heat shrinkage B in MD direction of polypropylene film integrated with metal layer>
The metal layer-integrated polypropylene films obtained in Examples and Comparative Examples were cut into rectangles having a width of 20 mm and a length of 130 mm to prepare measurement samples. At this time, the MD direction was cut as the length direction. Three measurement samples were prepared. Next, a 100 mm-long portion was measured with a ruler, and a marked line was attached to the portion. Next, the three measurement samples were held in a hot air circulation type constant temperature bath at 120° C. for 15 minutes with no load. Then, it cooled at room temperature (23 degreeC) and measured the dimension. The rate of dimensional change after heating with respect to 100 mm before heating at 120° C. was defined as the heat shrinkage rate B. Specifically, the following formula was used.
(Heat shrinkage B)=[[(dimension before heating)-(dimension after heating)]/(dimension before heating)]×100(%)
The measurement conditions other than those described here were in accordance with “21. Dimensional change” of JIS C2151:2006. The results are shown in Table 2.
Further, Table 2 also shows the heat shrinkage ratio [(heat shrinkage B)/(heat shrinkage A)] of the heat shrinkage A and the heat shrinkage B.

<Measurement of plane orientation coefficient>
<Retardation value>
First, the retardation values of the polypropylene films of Examples and Comparative Examples were measured by the tilt method as described below.
Measuring machine: Retardation measuring device RE-100 manufactured by Otsuka Electronics Co., Ltd.
Light source: LED light source with wavelength of 550 nm Measurement method: The angle dependence of retardation value was measured by the following tilt method. The main axis in the in-plane direction of the film is the x-axis and the y-axis, and the thickness direction of the film (the direction normal to the in-plane direction) is the z-axis. When the axis is the x-axis, each retardation value is obtained when the x-axis is the tilt axis and the z-axis is tilted by 10° in the range of 0° to 50°. For example, in the successive stretching method, when the stretching ratio in the TD direction (width direction) is higher than the stretching ratio in the MD direction (flow direction), the TD direction becomes the slow axis (x axis) and the MD direction becomes the y axis. ..

<Birefringence value and plane orientation coefficient ΔP>
From the retardation value, the plane orientation coefficient ΔP was calculated as follows, as described in Non-Patent Document “Yu Awaya, Introduction to Polarizing Microscopes for Polymer Materials, pp. 105-120, 2001”.
First, for each tilt angle φ, the measured retardation value R was divided by the tilt-corrected thickness d to obtain R/d. For each R/d of φ=10°, 20°, 30°, 40°, 50°, obtain the difference from the R/d of φ=0°, and divide them by sin2r (r: refraction angle). The birefringence ΔNzy at each φ was set, and the positive and negative signs were reversed to obtain the birefringence value ΔNyz. The birefringence value ΔNyz was calculated as the average value of ΔNyz at φ=20°, 30°, 40°, and 50°.
Next, the birefringence value ΔNxz was calculated by dividing the retardation value R measured at the inclination angle φ=0° by the value obtained by dividing the retardation value R by the thickness d.
Finally, the birefringence values ΔNyz and ΔNxz were substituted into the formula: ΔP=(ΔNyz+ΔNxz)/2 to obtain ΔP. As for the value of the refraction angle r at each inclination angle φ of polypropylene, the value described on page 109 of the above-mentioned non-patent document was used. The results are shown in Table 2.

<Increase rate of tan δ before and after thermal shock test and change rate of capacitance>
[Production of capacitors]
The metal layer-integrated polypropylene films prepared in Examples and Comparative Examples were slit into a width of 60 mm. Next, two metal layer-integrated polypropylene films were put together. Using the automatic winding machine 3KAW-N2 type manufactured by Minato Manufacturing Co., Ltd., the metal layer-integrated polypropylene films which were phased together were wound at 1137 turns at a winding tension of 250 g, a contact pressure of 880 g and a winding speed of 4 m/s. I went. The wound element was heat-treated at 120° C. for 15 hours while being pressed with a load of 5.9 kg/cm ² . Then, zinc metal was sprayed on the end face of the device. The spraying conditions were a feed rate of 15 mm/s, a spraying voltage of 22 V, and a spraying pressure of 0.3 MPa, and the spraying was carried out to a thickness of 0.7 mm. In this way, a flat type capacitor was obtained. A lead wire was soldered to the end face of the flat type capacitor. Then, the flat capacitor was sealed with an epoxy resin. The epoxy resin was cured by heating at 90° C. for 2.5 hours and then at 120° C. for 2.5 hours. The capacitance of the finished capacitor was 75 μF.

[Method of thermal shock test]
The capacitor for measurement produced above was put in a thermal shock tester (ESPEC TSA-101S-W), and a cycle of rapid temperature increase and decrease was repeated 500 times between a lower limit temperature of -40°C and an upper limit temperature of 105°C. Specifically, holding at −40° C. for 50 minutes and holding at 105° C. for 50 minutes were set as one set and repeated 500 times. The temperature was switched by blowing air at the set temperature and forcibly replacing it. Further, the temperature switching time was also included in the time of holding for 50 minutes.

[Measurement of tan δ and capacitance before and after thermal shock test]
About the produced capacitor element, the tan δ and the capacitance before and after the thermal shock test were measured by using LCR HiTester 3522-50 manufactured by Hioki Electric Co., Ltd. A 4-terminal probe 9140 was used as the test fixture. The specific measurement conditions were an applied voltage of 0.1 V and a frequency of 1 kHz. The measurement was performed for three capacitor elements, and the average value was used as the measured value.
Then, the rate of increase in tan δ was calculated by the following formula.
(Increase rate of tan δ)=[[(tan δ after thermal shock test)-(tan δ before thermal shock test)]/(tan δ before thermal shock test)]×100(%)
In addition, the rate of change in capacitance was determined by the following formula.
(Change rate of electrostatic capacity)=[[(electrostatic capacity after thermal shock test)-(electrostatic capacity before thermal shock test)]/(electrostatic capacity before thermal shock test)]×100(%)
The results are shown in Table 2.

[Evaluation]
When the increase rate of tan δ is 100% or less, it can be said that the peeling of the metallikon electrode can be suppressed more preferably. That is, when the metallikon electrode is peeled off, tan δ is increased due to the increase in resistance due to the limitation of the current path. However, if the increase rate of tan δ is 100% or less, the metallikon electrode is increased. It can be inferred that no large peeling occurred. Therefore, the case where the increase rate of tan δ is 100% or less was evaluated as A, and the case where it was more than 100% was evaluated as B. The results are shown in Table 2.

Here, even if the metallikon electrode is largely peeled off, the capacitance does not change significantly even if a slight electrical connection is obtained. On the other hand, if the electrostatic capacitance is largely changed before and after the thermal shock test, it means that a defect other than the separation of the metallikon electrode (for example, a defect in the metal layer) has occurred.
In Comparative Example 1-4, the rate of change in capacitance is within the range of -1.0% or more and 1.0% or less, and it is inferred that no trouble other than peeling of the metallikon electrode has occurred. Therefore, in Comparative Examples 1-4, it is inferred that the increase in tan δ is certainly due to the peeling of the metallikon electrode and not due to a defect other than peeling of the metallikon electrode.

<MD change rate at 120°C>
The dimensional change rate in the MD direction was obtained by temperature modulation TMA measurement using a thermomechanical analyzer (“SS-6000” manufactured by Seiko Instruments Inc.).
Strips were cut out from the metal layer-integrated polypropylene films produced in Examples and Comparative Examples so as to have a width of 30 mm in the measuring direction and a width of 4 mm in the direction orthogonal to the measuring direction to prepare samples. Three measurement samples were prepared. At this time, the sample was cut out so that the measurement direction of the sample coincided with the MD direction. The measurement conditions were such that the chuck distance was 15 mm, the measurement temperature range was 25° C. to 150° C., the temperature rising rate was 10° C./min, and the tensile load that was continuously applied to the sample piece was 20 mN. From the chuck distance (mm) when the furnace temperature reached 120° C., the dimensional change rate in the MD direction was calculated using the following formula.
[Dimensional change rate (%) in MD direction at 120°C] = [(distance between chucks at 120°C-distance between chucks at 25°C)/distance between chucks at 25°C] x 100
The average value of the three measured values was taken as the dimensional change rate (%) in the MD direction at 120°C.
The dimensional change rate is positive (plus) when the film size increases (expands) with temperature increase, and negative (minus) when the film size decreases (contracts) with temperature increase. Become. The results are shown in Table 2.

1 Polypropylene film integrated with metal layer 2 Polypropylene film 3 Metal deposition electrode 3a Metal deposition layer 3b Electrode extraction part 4 Insulation margin

Claims (9)

Polypropylene film,
A metal layer-integrated polypropylene film having a metal layer laminated on one side or both sides of the polypropylene film,
When the heat shrinkage rate in the first direction of the polypropylene film before laminating the metal layer is A and the heat shrinkage rate in the first direction of the metal layer-integrated polypropylene film is B, the heat shrinkage rate A and the heat shrinkage A metal layer-integrated polypropylene film, which has a heat shrinkage ratio [(heat shrinkage B)/(heat shrinkage A)] of 0.25 or more and 0.60 or less. The polypropylene film with a metal layer integrated therein according to claim 1, wherein a heat shrinkage ratio A in the first direction of the polypropylene film before laminating the metal layer is 2.0% or more and 10.0% or less. .. The dimensional change rate in the said 1st direction at 120 degreeC is -0.40% or more, The metal layer integrated polypropylene film of Claim 1 or 2 characterized by the above-mentioned. The plane orientation coefficient ΔP of the polypropylene film is 0.010 to 0.016, and the metal layer-integrated polypropylene film according to any one of claims 1 to 3, wherein. It is for capacitors, The polypropylene film integrated with a metal layer according to any one of claims 1 to 4. The said polypropylene film is biaxially stretched, The metal layer integrated polypropylene film of any one of Claims 1-5 characterized by the above-mentioned. It has the metal layer integrated polypropylene film according to any one of claims 1 to 6 that is wound, or a plurality of metal layer integrated polypropylene films according to any one of claims 1 to 6 are laminated. A film capacitor having the above structure. Step A of preparing a polypropylene film,
A method for producing a metal layer-integrated polypropylene film, comprising: a step B in which a metal layer is laminated on one surface or both surfaces of the polypropylene film prepared in the step A to obtain a metal layer integrated polypropylene film,
When the heat shrinkage rate in the first direction of the polypropylene film prepared in the step A is A and the heat shrinkage rate B in the first direction of the metal layer-integrated polypropylene film obtained in the step B, the heat shrinkage rate A And a heat shrinkage ratio B of the heat shrinkage ratio [(heat shrinkage ratio B)/(heat shrinkage ratio A)] is 0.25 or more and 0.60 or less, the production of a metal layer-integrated polypropylene film Method. The polypropylene film prepared in the step A has a heat shrinkage ratio A in the first direction of 2.0% or more and 10.0% or less, and the polypropylene film of the metal layer integrated type according to claim 8. Production method.

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