JP2021077747A - Film for film capacitor and film capacitor - Google Patents

Abstract

To provide a film for a film capacitor capable of achieving a film capacitor with high withstand voltage strength of a small variation.SOLUTION: The film for a film capacitor is composed of a cured product with a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups. An F5 value indicating a stress at 5% elongation is 55 MPa or more.SELECTED DRAWING: Figure 2

Description

The present invention relates to a film for a film capacitor and a film capacitor.

As a kind of capacitor, a film capacitor having a structure in which a first metal layer and a second metal layer facing each other across the resin film are arranged while using a flexible resin film as a dielectric is known. .. Such a film capacitor is produced, for example, by winding or laminating a resin film on which a first metal layer is formed and a resin film on which a second metal layer is formed.

For example, Patent Document 1 describes a film for a film capacitor including a resin layer having a linear convex portion on the first surface and a linear concave portion on the second surface, and is 1 cm on the second surface of the resin layer. ^A film for a film capacitor is disclosed in which the total length of the linear recesses per 2 is 3 m or less, and the average depth of the linear recesses is 0.01 μm or more and 1.3 μm or less.

International Publication No. 2019/0695440

Patent Document 1 discloses a film for a film capacitor having a dielectric breakdown strength as a withstand voltage strength of more than 350 V / μm. However, assuming use in a harsh environment such as in-vehicle use, a film capacitor having a higher withstand voltage strength and less variation is desired, and a film for a film capacitor capable of realizing such a film capacitor is required. ing. On the other hand, although Patent Document 1 describes the withstand voltage strength of the film for film capacitors, there is no description about the withstand voltage strength of the film capacitor and its variation, so there is room for improvement.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a film for a film capacitor capable of realizing a film capacitor having a high withstand voltage strength and a small variation thereof. Another object of the present invention is to provide a film capacitor having the above-mentioned film for a film capacitor.

In the first aspect, the film for a film capacitor of the present invention comprises a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and has a 5% elongation stress. It is characterized in that the indicated F5 value is 55 MPa or more.

In the second aspect, the film for a film capacitor of the present invention comprises a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and has a yield stress of 70 MPa or more. It is characterized by being.

In the third aspect, the film for a film capacitor of the present invention comprises a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and has a static friction coefficient and a dynamic friction coefficient. Both are characterized in that they are 0.50 or less.

In the first aspect, the film capacitor of the present invention comprises a dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and the dielectric film. A metal layer provided on at least one of the main surfaces of the above is provided, and the F5 value indicating the stress at 5% elongation of the dielectric film is 55 MPa or more.

In the second aspect, the film capacitor of the present invention comprises a dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and the dielectric film. A metal layer provided on at least one of the main surfaces of the above is provided, and the yield stress of the dielectric film is 70 MPa or more.

In a third aspect, the film capacitor of the present invention comprises a dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and the dielectric film. A metal layer provided on at least one of the main surfaces of the above is provided, and both the static friction coefficient and the dynamic friction coefficient of the dielectric film are 0.50 or less.

According to the present invention, it is possible to provide a film for a film capacitor capable of realizing a film capacitor having a high withstand voltage strength and a small variation thereof. Further, according to the present invention, it is possible to provide a film capacitor having the film for the film capacitor.

It is a perspective schematic diagram which shows an example of the film capacitor of this invention. It is sectional drawing which shows the part corresponding to the line segment A1-A2 in FIG. It is a perspective schematic diagram which shows an example of the laminated body in FIG. 1 and FIG. It is a plane schematic diagram which shows an example of the metal layer provided with the fuse part.

Hereinafter, the film for a film capacitor of the present invention and the film capacitor of the present invention will be described. The present invention is not limited to the following configuration, and may be appropriately modified without departing from the gist of the present invention. In addition, a combination of a plurality of individual preferred configurations described below is also the present invention.

[Film capacitor]
As an example of the film capacitor of the present invention, a so-called winding type film in which a film containing a metallized film having a metal layer provided on at least one main surface of a dielectric film is wound in a laminated state. The capacitor will be described below. The film capacitor of the present invention may be a so-called laminated film capacitor in which the above films are laminated.

FIG. 1 is a schematic perspective view showing an example of the film capacitor of the present invention. FIG. 2 is a schematic cross-sectional view showing a portion corresponding to the line segments A1-A2 in FIG. FIG. 3 is a schematic perspective view showing an example of the laminated body in FIGS. 1 and 2.

In the present specification, the stacking direction and the width direction of the film capacitor are the directions defined by the arrows T and W, respectively, as shown in FIGS. 1, 2, and 3. In the winding type film capacitor, it can be said that there are a plurality of stacking directions, but in the present specification, the direction is defined by the arrow T. Here, the stacking direction T and the width direction W are orthogonal to each other.

As shown in FIGS. 1 and 2, the film capacitor 10 is provided on the laminated body 40, the first external electrode 41 provided on one end face of the laminated body 40, and the other end face of the laminated body 40. It has a second external electrode 42 and the like. Here, both end faces of the laminated body 40 face each other in the width direction W.

As shown in FIGS. 2 and 3, the laminated body 40 is a wound body in which the first metallized film 11 and the second metallized film 12 are wound in a state of being laminated in the stacking direction T. .. That is, the film capacitor 10 is a winding type film capacitor having a laminated body 40 which is also such a winding body.

In the film capacitor 10, from the viewpoint of reducing the height of the film capacitor 10, the cross-sectional shape of the laminated body 40 is pressed into a flat shape such as an ellipse or an oval, and the cross-sectional shape of the laminated body 40 is a perfect circle. It is preferable that the shape has a small thickness.

The film capacitor 10 may have a columnar winding shaft. The winding shaft is arranged on the central axis of the first metallized film 11 and the second metallized film 12 in the wound state, and the first metallized film 11 and the second metallized film 12 are arranged. It serves as a winding shaft when winding the twelve.

The first metallized film 11 has a first dielectric film 13 and a first metal layer 15 provided on one main surface of the first dielectric film 13.

The first metal layer 15 is provided so as to reach one side edge of the first metallized film 11 and not reach the other side edge of the first metallized film 11 in the width direction W.

The second metallized film 12 has a second dielectric film 14 and a second metal layer 16 provided on one main surface of the second dielectric film 14.

The second metal layer 16 is provided so as not to reach one side edge of the second metallized film 12 but to reach the other side edge of the second metallized film 12 in the width direction W.

In the laminated body 40, the end portion of the first metal layer 15 on the side reaching the side edge of the first metallized film 11 is exposed on one end surface of the laminated body 40, and the second metal layer 16 is formed. The adjacent first metallized film 11 and the second metallized film 12 are arranged so that the end portion on the side reaching the side edge of the second metallized film 12 is exposed to the other end surface of the laminated body 40. It is deviated in the width direction W.

Since the laminated body 40 is wound in a state where the first metallized film 11 and the second metallized film 12 are laminated in the stacking direction T, the first metal layer 15 and the first dielectric are formed. It can be said that it is a wound body in which the body film 13, the second metal layer 16, and the second dielectric film 14 are wound in a state of being laminated in order in the stacking direction T.

In the laminated body 40, the first metallized film 11 is inside the second metallized film 12, the first metal layer 15 is inside the first dielectric film 13, and the second metal layer 16 is inside. The first metallized film 11 and the second metallized film 12 are wound in a state of being laminated in the stacking direction T so as to be inside the second dielectric film 14. That is, the first metal layer 15 and the second metal layer 16 face each other with the first dielectric film 13 or the second dielectric film 14 interposed therebetween.

The second metal layer 16 may be provided not on one main surface of the second dielectric film 14 but on the other main surface of the first dielectric film 13. In this case, in the laminated body 40, the first metal layer 15 is provided on one main surface of the first dielectric film 13, and the second metal layer 16 is provided on the other main surface. The metallized film and the second dielectric film 14 are wound in a state of being laminated in the stacking direction T.

As the first dielectric film 13 and the second dielectric film 14, the film for a film capacitor of the present invention, which will be described later, is used.

Examples of the constituent materials of the first metal layer 15 and the second metal layer 16 include metals such as aluminum, zinc, titanium, magnesium, tin, and nickel, respectively.

The compositions of the first metal layer 15 and the second metal layer 16 may be different from each other, but are preferably the same as each other.

The thicknesses of the first metal layer 15 and the second metal layer 16 are preferably 5 nm or more and 40 nm or less, respectively.

The thickness of the first metal layer 15 can be specified by observing the cut surface of the first metallized film 11 in the thickness direction using a transmission electron microscope (TEM). The thickness of the second metal layer 16 can be specified in the same manner.

It is preferable that the first metal layer 15 and the second metal layer 16 are each provided with a fuse portion.

FIG. 4 is a schematic plan view showing an example of a metal layer provided with a fuse portion. As shown in FIG. 4, the first metal layer 15 is provided with a plurality of divided electrode portions 61, an electrode portion 62, and a fuse portion 63.

The plurality of divided electrode portions 61 are separated by an insulating slit 64, and are portions facing the second metal layer 16 in the laminated body 40.

The electrode portion 62 is adjacent to the plurality of divided electrode portions 61 with the insulating slit 64 interposed therebetween, and is a portion of the laminated body 40 that does not face the second metal layer 16.

The fuse portion 63 is a portion that connects each of the divided electrode portions 61 and the electrode portion 62, and is thinner than the divided electrode portion 61 and the electrode portion 62.

The electrode pattern of the first metal layer 15 provided with the fuse portion is disclosed in, for example, JP-A-2004-363431 and JP-A-5-251266, etc., in addition to the electrode pattern shown in FIG. It may be an electrode pattern. The same applies to the electrode pattern of the second metal layer 16 provided with the fuse portion.

The first external electrode 41 is provided on one end surface of the laminated body 40, and is connected to the first metal layer 15 by coming into contact with the exposed end portion of the first metal layer 15.

From the viewpoint of connectivity between the first metal layer 15 and the first external electrode 41, in one end face of the laminate 40, the first metallized film 11 has a width with respect to the second metallized film 12. It is preferable that it protrudes in the direction W.

The second external electrode 42 is provided on the other end surface of the laminated body 40, and is connected to the second metal layer 16 by contacting the exposed end portion of the second metal layer 16.

From the viewpoint of connectivity between the second metal layer 16 and the second external electrode 42, at the other end face of the laminate 40, the second metallized film 12 has a width with respect to the first metallized film 11. It is preferable that it protrudes in the direction W.

Examples of the constituent materials of the first external electrode 41 and the second external electrode 42 include metals such as zinc, aluminum, tin, and zinc-aluminum alloy.

The compositions of the first external electrode 41 and the second external electrode 42 may be different from each other, but are preferably the same as each other.

The first external electrode 41 and the second external electrode 42 are preferably formed by spraying the metal as described above onto one end face and the other end face of the laminate 40, respectively.

The configuration of the laminated body 40 may be different from the configuration as shown in FIG. For example, in the first metallized film 11, the first metal layer 15 is divided into two metal layers in the width direction W, one metal layer reaches one side edge of the first metallized film 11, and the other. The metal layer may be provided so as to reach the other side edge of the first metallized film 11. In this case, in the first metal layer 15, one metal layer is connected to the first external electrode 41, and the other metal layer is connected to the second external electrode 42, while the second metal layer 16 is connected. Is provided so as not to be connected to both the first external electrode 41 and the second external electrode 42, a capacitor can be formed between the first metal layer 15 and the second metal layer 16.

[Film for film capacitors]
The film for a film capacitor of the present invention is used as a dielectric film in the film capacitor of the present invention, for example, the above-mentioned first dielectric film 13 and second dielectric film 14.

The film for a film capacitor of the present invention comprises a cured product of a first organic material having a plurality of hydroxyl groups (OH groups) and a second organic material having a plurality of isocyanate groups (NCO groups). More specifically, the film for a film capacitor of the present invention comprises a cured product obtained by reacting a hydroxyl group of a first organic material with an isocyanate group of a second organic material.

When the cured product is obtained by the above-mentioned reaction, the uncured portion of the starting material may remain in the film for the film capacitor. That is, the film for a film capacitor of the present invention may contain at least one of a hydroxyl group and an isocyanate group. In this case, the film for a film capacitor of the present invention may contain either a hydroxyl group or an isocyanate group, or may contain both a hydroxyl group and an isocyanate group.

The presence of hydroxyl groups and / or isocyanate groups in the film for film capacitors of the present invention can be confirmed by using a Fourier transform infrared spectrophotometer (FT-IR).

The first organic material has a plurality of hydroxyl groups, and more specifically, it is composed of a polyol having a plurality of hydroxyl groups in the molecule.

Examples of the polyol include polyvinyl acetal such as polyvinyl acetal acetal, polyether polyol such as phenoxy resin, polyester polyol and the like.

The first organic material preferably has an epoxy group. In particular, as the first organic material, a phenoxy resin is preferable, and a phenoxy resin which is a high molecular weight bisphenol A type epoxy resin having an epoxy group at the terminal is more preferable.

As the first organic material, a plurality of types of organic materials may be used in combination.

The weight average molecular weight (Mw) of the first organic material is preferably 55,000 or more. When the weight average molecular weight of the first organic material is 55,000 or more, the heat resistant temperature of the film capacitor is sufficiently increased. On the other hand, if the weight average molecular weight of the first organic material is too large, the viscosity of the resin solution used in producing a film for a film capacitor becomes high, which makes it difficult to mold on a substrate such as a polyethylene terephthalate film. Become. From such a viewpoint, the weight average molecular weight of the first organic material is preferably 100,000 or less.

The weight average molecular weight of the first organic material means the weight average molecular weight measured by gel permeation chromatography (GPC) and calculated with reference to a polystyrene standard sample.

The second organic material has a plurality of isocyanate groups, and more specifically, it is composed of a polyisocyanate having a plurality of isocyanate groups in the molecule. The second organic material functions as a curing agent that cures the resin solution when producing a film for a film capacitor by reacting with the hydroxyl group of the first organic material to form a crosslinked structure.

Examples of the polyisocyanate include aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), and aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI). The polyisocyanate may be a modified product of these polyisocyanates, for example, a modified product having carbodiimide, urethane, or the like.

As the second organic material, aromatic polyisocyanate is preferable, MDI or TDI is more preferable, and MDI is further preferable. As the MDI, for example, a polypeptide MDI or a monomeric MDI can be used.

As the second organic material, a plurality of types of organic materials may be used in combination.

The weight ratio of the first organic material to the second organic material (first organic material / second organic material) is preferably 10/90 or more, more preferably 20/80 or more, and further. It is preferably 30/70 or more. The weight ratio of the first organic material to the second organic material (first organic material / second organic material) is preferably 90/10 or less, more preferably 80/20 or less. , More preferably 70/30 or less. In particular, the weight ratio of the first organic material to the second organic material (first organic material / second organic material) is preferably larger than 50/50.

The film for a film capacitor of the present invention may contain additives for adding various functions. Examples of the additive include a leveling agent for imparting smoothness. The additive preferably has a functional group that reacts with a hydroxyl group and / or an isocyanate group, and forms a part of the crosslinked structure of the cured product. Examples of such an additive include a resin having at least one functional group selected from the group consisting of a hydroxyl group, an epoxy group, a silanol group, and a carboxyl group.

When the film for a film capacitor of the present invention is used as the first dielectric film 13 and the second dielectric film 14 described above, the compositions of the first dielectric film 13 and the second dielectric film 14 are different from each other. They may be different, but preferably they are the same.

The film for a film capacitor of the present invention is produced by forming a resin solution containing a first organic material and a second organic material into a film on a substrate such as polyethylene terephthalate film, and then heat-treating and curing the film. Will be done. The obtained film for a film capacitor is used in a state of being peeled off from a base material.

The thickness of the film for a film capacitor of the present invention is preferably 1 μm or more and 10 μm or less, and more preferably 3 μm or more and 5 μm or less. If the thickness of the film for a film capacitor of the present invention is smaller than 1 μm, it may become brittle. When the thickness of the film for a film capacitor of the present invention is larger than 10 μm, defects such as cracks due to the molding process of the resin solution may occur.

The thickness of the film for a film capacitor of the present invention can be measured using an optical film thickness meter.

When the film for a film capacitor of the present invention is used as the first dielectric film 13 and the second dielectric film 14 described above, the thicknesses of the first dielectric film 13 and the second dielectric film 14 are different from each other. They may be different, but preferably they are the same.

In the process of manufacturing a film capacitor, tensile stress may be applied to the film for the film capacitor, for example, by winding the film for the film capacitor. When tensile stress is applied to the film for film capacitors, the deformation mode of the film for film capacitors may shift from elastic deformation to plastic deformation. When a film for a film capacitor is plastically deformed, fracture occurs at the micro level, so that the withstand voltage strength of the obtained film capacitor may decrease and the variation may increase.

In the first aspect of the film for a film capacitor of the present invention, the F5 value indicating the stress at 5% elongation is 55 MPa or more. Since the F5 value of the film capacitor film is 55 MPa or more, even if a tensile stress is applied to the film capacitor film, the film capacitor film does not undergo plastic deformation and does not break at the micro level. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

In the film for a film capacitor of the present invention, if the F5 value becomes too large, the film tends to become brittle and the workability tends to be significantly lowered. From such a viewpoint, in the first aspect of the film for a film capacitor of the present invention, the F5 value is preferably 200 MPa or less.

The F5 value of the film for a film capacitor of the present invention is determined as follows. First, a measurement sample having a width of 5 mm and a length of 20 mm is cut out from the film for a film capacitor. Here, the length direction of the measurement sample is preferably the same as the direction in which tensile stress is applied to the film for the film capacitor in the process of manufacturing the film capacitor, for example, the winding direction of the film for the film capacitor. After that, the measurement sample is installed in, for example, the dynamic viscoelastic device "RSA3" manufactured by TA Instruments, and the measurement gap (distance between chucks) is 6 mm, and the extension rate is 1% in the length direction. Pull to. Then, the stress when the measurement sample is stretched by 5% is read, and the value is defined as the F5 value.

The F5 value of the film for film capacitors of the present invention is (1) the weight ratio of the first organic material to the second organic material, (2) the resin concentration in the resin solution, and (3) the heat treatment conditions of the resin solution. Etc. are controlled. As a preferable combination of these (1) to (3), (1) the weight ratio of the first organic material to the second organic material (first organic material / second organic material) is 30/70 or more. , 70/30 or less, (2) Resin concentration in resin solution is 15% by weight or more, 25% by weight or less, (3) Regarding heat treatment conditions of resin solution, heat treatment temperature is 130 ° C or more, 140 ° C or less, heat treatment time 2 hours or more and 10 hours or less.

In the second aspect of the film for a film capacitor of the present invention, the yield stress is 70 MPa or more. Since the yield stress of the film for film capacitors is 70 MPa or more, even if a tensile stress is applied to the film for film capacitors, the film for film capacitors does not undergo plastic deformation and fracture at the micro level does not occur. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

In the second aspect of the film for a film capacitor of the present invention, the yield stress is preferably 80 MPa or more. On the other hand, in the film for a film capacitor of the present invention, if the yield stress becomes too large, the film tends to become brittle and the workability tends to be significantly lowered. From such a viewpoint, in the second aspect of the film for a film capacitor of the present invention, the yield stress is preferably 200 MPa or less.

The yield stress of the film for a film capacitor of the present invention is determined as follows. First, a measurement sample having a width of 5 mm and a length of 20 mm is cut out from the film for a film capacitor. Here, the length direction of the measurement sample is preferably the same as the direction in which tensile stress is applied to the film for the film capacitor in the process of manufacturing the film capacitor, for example, the winding direction of the film for the film capacitor. After that, the measurement sample is installed in, for example, the dynamic viscoelastic device "RSA3" manufactured by TA Instruments, and the measurement gap (distance between chucks) is 6 mm, and the extension rate is 1% in the length direction. Pull to. Then, the yield stress corresponding to the yield point is read from the graph showing the obtained stress-strain relationship.

The yield stress of the film for film capacitors of the present invention is (1) the weight ratio of the first organic material to the second organic material, (2) the resin concentration in the resin solution, and (3) the heat treatment conditions of the resin solution. Etc. are controlled. As a preferable combination of these (1) to (3), (1) the weight ratio of the first organic material to the second organic material (first organic material / second organic material) is 30/70 or more. , 70/30 or less, (2) Resin concentration in resin solution is 15% by weight or more, 25% by weight or less, (3) Regarding heat treatment conditions of resin solution, heat treatment temperature is 130 ° C or more, 140 ° C or less, heat treatment time 2 hours or more and 10 hours or less.

In the third aspect of the film for a film capacitor of the present invention, both the coefficient of static friction and the coefficient of dynamic friction are 0.50 or less. Since both the static friction coefficient and the dynamic friction coefficient of the film for film capacitors are 0.50 or less, for example, when the film for film capacitors is wound to manufacture a film capacitor, a guide for feeding the film for film capacitors for winding. The film for the film capacitor becomes slippery with respect to the roll portion. Therefore, tensile stress is less likely to be applied to the film for the film capacitor. Therefore, the film for the film capacitor does not undergo plastic deformation and does not break at the micro level. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

In the third aspect of the film for a film capacitor of the present invention, both the coefficient of static friction and the coefficient of dynamic friction are preferably 0.48 or less. On the other hand, in the film for film capacitors of the present invention, if both the coefficient of static friction and the coefficient of dynamic friction are too small, for example, it becomes difficult to feed and wind the film for film capacitors. From such a viewpoint, in the third aspect of the film for a film capacitor of the present invention, both the coefficient of static friction and the coefficient of dynamic friction are preferably 0.3 or more.

The coefficient of static friction and the coefficient of dynamic friction of the film for a film capacitor of the present invention are determined as follows. First, two films for a film capacitor are prepared as measurement samples. Here, for both main surfaces of each measurement sample, the main surface that was on the base material side at the time of manufacture is defined as the release surface, and the main surface that was on the opposite side to the base material is defined as the dry surface. Further, the length direction of each measurement sample is preferably the same as the direction in which tensile stress is applied to the film for the film capacitor in the process of manufacturing the film capacitor, for example, the winding direction of the film for the film capacitor. Then, for one of the two measurement samples, a square plate is fixed to the release surface so that the dry surface is exposed. Further, for the other measurement sample, a square weight having a weight of 200 g is attached to the dry surface so that the release surface is exposed. After that, the release surface of the other measurement sample in which a weight is attached to the dry surface is placed on the dry surface of one measurement sample in which the plate is fixed to the release surface in the length direction. Are brought into contact with each other so that they are parallel to each other. Then, the weight attached to the dry surface of the other measurement sample is attached to, for example, a force gauge manufactured by Imada, and then pulled at a speed of 150 mm / min in the length direction. At this time, the maximum frictional force until the weight starts to move together with the other measurement sample is read, and the coefficient of static friction is calculated from that value. Further, the average frictional force from when the weight starts to move together with the other measurement sample to when it moves by 50 mm is read, and the dynamic friction coefficient is calculated from the value.

The static friction coefficient and dynamic friction coefficient of the film for film capacitors of the present invention are (1) the weight ratio between the first organic material and the second organic material, (2) the resin concentration in the resin solution, and (3) the resin solution. It is controlled by heat treatment conditions, etc. As a preferable combination of these (1) to (3), (1) the weight ratio of the first organic material to the second organic material (first organic material / second organic material) is 30/70 or more. , 70/30 or less, (2) Resin concentration in resin solution is 15% by weight or more, 25% by weight or less, (3) Regarding heat treatment conditions of resin solution, heat treatment temperature is 130 ° C or more, 140 ° C or less, heat treatment time 2 hours or more and 10 hours or less.

The film capacitor having the first aspect of the film for a film capacitor of the present invention as a dielectric film is the first aspect of the film capacitor of the present invention. That is, in the first aspect of the film capacitor of the present invention, the F5 value indicating the stress at 5% elongation of the dielectric film is 55 MPa or more. Since the F5 value of the dielectric film is 55 MPa or more, even if tensile stress is applied to the dielectric film, the dielectric film is not plastically deformed and fracture at the micro level does not occur. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

The film capacitor having the second aspect of the film for a film capacitor of the present invention as a dielectric film is the second aspect of the film capacitor of the present invention. That is, in the second aspect of the film capacitor of the present invention, the yield stress of the dielectric film is 70 MPa or more. Since the yield stress of the dielectric film is 70 MPa or more, even if a tensile stress is applied to the dielectric film, the dielectric film is not plastically deformed and fracture at the micro level does not occur. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

The film capacitor having the third aspect of the film for a film capacitor of the present invention as a dielectric film is the third aspect of the film capacitor of the present invention. That is, in the third aspect of the film capacitor of the present invention, both the coefficient of static friction and the coefficient of dynamic friction of the dielectric film are 0.50 or less. Since both the static friction coefficient and the dynamic friction coefficient of the dielectric film are 0.50 or less, for example, when the dielectric film is wound to manufacture a film capacitor, the guide roll portion for feeding the dielectric film for winding is used. On the other hand, the dielectric film becomes slippery. Therefore, tensile stress is less likely to be applied to the dielectric film. Therefore, the dielectric film is not plastically deformed and is not broken at the micro level. As a result, the withstand voltage strength of the obtained film capacitor is increased, and the variation is also reduced.

[Manufacturing method of film for film capacitors]
The film for a film capacitor of the present invention is produced, for example, by the following method.

<Step of preparing resin solution>
A resin solution is prepared by mixing a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups.

As the first organic material and the second organic material, those described above are used.

When preparing the resin solution, the first organic material and the second organic material may be dissolved in a solvent. In particular, it is preferable to dissolve the first organic material and the second organic material in a mixed solvent containing a first solvent selected from ketones and a second solvent selected from cyclic ether compounds.

Examples of the ketones for which the first solvent is selected include methyl ethyl ketone and diethyl ketone.

As the first solvent, a plurality of types of ketones may be used in combination.

Examples of the cyclic ether compound for which the second solvent is selected include tetrahydrofuran, tetrahydropyran and the like.

As the second solvent, a plurality of types of cyclic ether compounds may be used in combination.

When preparing the resin solution, the above-mentioned additives may be mixed with the first organic material and the second organic material.

The resin concentration in the resin solution is preferably 15% by weight or more and 25% by weight or less.

<Step of curing the resin solution>
The resin solution is formed into a film on a base material such as polyethylene terephthalate film, and then heat-treated to cure. As a result, a film for a film capacitor is produced on the base material. The obtained film for a film capacitor is used in a state of being peeled off from a base material.

Regarding the heat treatment conditions of the resin solution, the heat treatment temperature is preferably 130 ° C. or higher and 140 ° C. or lower. The heat treatment time is preferably 2 hours or more and 10 hours or less.

In the above-mentioned film manufacturing method for film capacitors, (1) the weight ratio of the first organic material to the second organic material, (2) the resin concentration in the resin solution, (3) the heat treatment conditions of the resin solution, etc. By adjusting, the F5 value of the film for film capacitors is controlled to 55 MPa or more. That is, according to the above-described method for producing a film for a film capacitor, the first aspect of the film for a film capacitor of the present invention can be produced.

Further, in the above-mentioned film manufacturing method for film capacitors, (1) the weight ratio of the first organic material to the second organic material, (2) the resin concentration in the resin solution, and (3) the heat treatment conditions of the resin solution. , Etc. are adjusted to control the yield stress of the film for film capacitors to 70 MPa or more. That is, according to the above-described method for producing a film for a film capacitor, the second aspect of the film for a film capacitor of the present invention can be produced.

Further, in the above-mentioned film manufacturing method for film capacitors, (1) the weight ratio of the first organic material to the second organic material, (2) the resin concentration in the resin solution, and (3) the heat treatment conditions of the resin solution. By adjusting, etc., both the static friction coefficient and the dynamic friction coefficient of the film for film capacitors are controlled to 0.50 or less. That is, according to the above-described method for producing a film for a film capacitor, the third aspect of the film for a film capacitor of the present invention can be produced.

[Manufacturing method of film capacitors]
The film capacitor of the present invention is manufactured by, for example, the following method.

<Process for producing metallized film>
First, a first dielectric film and a second dielectric film are produced as a film for a film capacitor by the above-mentioned method for producing a film for a film capacitor.

Then, a first metallized film is produced by depositing a metal on one main surface of the first dielectric film to form a first metal layer. At this time, in the width direction, the first metal layer is formed so as to reach one side edge of the first metallized film and not reach the other side edge of the first metallized film.

Further, a second metallized film is produced by depositing a metal on one main surface of the second dielectric film to form a second metal layer. At this time, the second metal layer is formed so as not to reach one side edge of the second metallized film in the width direction but to reach the other side edge of the second metallized film.

<Process for producing a laminate>
A laminated body (rolled body) is produced by stacking the first metallized film and the second metallized film in a state of being displaced by a predetermined distance in the width direction and then winding them. If necessary, the obtained laminate may be sandwiched from a direction perpendicular to the width direction and pressed into an elliptical cylindrical shape.

<Step of forming external electrodes>
By spraying a metal onto one end face of the laminate, the first external electrode is formed so as to be connected to the first metal layer.

Further, by spraying a metal onto the other end face of the laminated body, the second external electrode is formed so as to be connected to the second metal layer.

As described above, the film capacitor of the present invention as illustrated in FIGS. 1 and 2 is manufactured.

Hereinafter, an example in which the film for a film capacitor of the present invention and the film capacitor of the present invention are more specifically disclosed will be shown. The present invention is not limited to these examples.

[Manufacturing of film for film capacitors]
A film sample as a film for a film capacitor was produced by the following method.

<Step of preparing resin solution>
As the first organic material, a phenoxy resin having a plurality of hydroxyl groups was prepared. More specifically, as the phenoxy resin, a phenoxy resin which is a high molecular weight bisphenol A type epoxy resin having an epoxy group at the terminal was used.

Further, as a second organic material, MDI having a plurality of isocyanate groups was prepared. More specifically, as the above MDI, a polymeric MDI was used.

A resin solution was prepared by mixing the first organic material and the second organic material in various weight ratios and dissolving them in a mixed solvent of methyl ethyl ketone and tetrahydrofuran. The resin concentration in the resin solution was also changed in various ways.

<Step of curing the resin solution>
The resin solution was formed into a film on a polyethylene terephthalate film using a doctor blade coater to prepare an uncured film having a thickness of 3 μm. Then, the uncured film was heat-treated and cured, and peeled from the polyethylene terephthalate film.

From the above, film samples 1 to 16 were produced.

[Manufacturing of film capacitors]
Using the film sample produced as described above as a dielectric film, a film capacitor sample was produced by the following method.

<Process for producing metallized film>
First, two film samples 1 were prepared.

Then, a first metallized film was produced by depositing a metal on one main surface of one of the two film samples 1 to form a first metal layer. At this time, in the width direction, the first metal layer was formed so as to reach one side edge of the first metallized film and not reach the other side edge of the first metallized film.

Further, a second metallized film was produced by depositing a metal on one main surface of the other film sample 1 to form a second metal layer. At this time, the second metal layer was formed so as not to reach one side edge of the second metallized film in the width direction but to reach the other side edge of the second metallized film.

The electrode patterns of the first metal layer and the second metal layer were each provided with a fuse portion as shown in FIG.

<Process for producing a laminate>
A laminated body (rolled body) was produced by stacking the first metallized film and the second metallized film in a state of being displaced by a predetermined distance in the width direction and then winding them.

<Step of forming external electrodes>
By spraying a metal onto one end face of the laminate, the first external electrode was formed so as to be connected to the first metal layer.

Further, the second external electrode was formed so as to be connected to the second metal layer by spraying a metal onto the other end face of the laminated body.

Then, after attaching lead wires to each of the first external electrode and the second external electrode, they were covered with an exterior resin.

From the above, 50 film capacitor samples 1 were manufactured.

Similarly, using the film samples 2 to 16, 50 film capacitor samples 2 to 16 were produced.

[Evaluation]
The following evaluations were performed on the film samples 1 to 16 and the film capacitor samples 1 to 16.

<Evaluation 1>
For film samples 1 to 5, the F5 value was measured by the method described above.

Next, after applying a voltage to each of the 50 film capacitor samples 1 at an electric field strength of 100 V / μm for 10 minutes, each electric field strength is held for 10 minutes in increments of an electric field strength of 25 V / μm, and the capacitance is initially set. The electric field strength immediately before the value decreased by 5%, that is, immediately before the capacitance became 95% of the initial value was measured as the failure voltage. The measurement temperature was 125 ° C. Then, the failure voltages of the 50 film capacitor samples 1 were weibull plotted, and the value at which the failure frequency was 50% in the Weibull distribution was adopted as the withstand voltage strength of the film capacitor sample 1. Further, the lowest failure voltage among the failure voltages of the 50 film capacitor samples 1 was set as the minimum value of the withstand voltage strength of the film capacitor sample 1.

The withstand voltage strength and the minimum value of the withstand voltage strength were evaluated in the same manner for the film capacitor samples 2 to 5.

The F5 values of (1) film samples 1 to 5, (2) withstand voltage strength of film capacitor samples 1 to 5, and (3) withstand voltage strength of film capacitor samples 1 to 5 obtained as described above. The minimum value of is shown in Table 1. In Table 1, the film sample and the film capacitor sample are collectively referred to as "sample".

As can be seen from Table 1, when the F5 value of the film is 55 MPa or more as in Samples 4 and 5, the withstand voltage strength of the film capacitor is 400 V / μm or more, which is a very good withstand voltage performance. Further, the minimum value of the withstand voltage strength of the film capacitor was 350 V / μm or more, and the variation in the withstand voltage strength was very small.

On the other hand, as can be seen from Table 1, when the F5 value of the film is smaller than 55 MPa as in Samples 1 to 3, the withstand voltage strength of the film capacitor is lower than 400 V / μm, and the withstand voltage strength of the film capacitor is further increased. The minimum value was lower than 300 V / μm. Therefore, there is a concern that the reliability of Samples 1 to 3 evaluated in a long-term high-temperature load test or the like will be low.

<Evaluation 2>
The yield stress of the film samples 6 to 10 was measured by the method described above.

Next, with respect to the film capacitor samples 6 to 10, the withstand voltage strength and the minimum value of the withstand voltage strength were evaluated in the same manner as in the evaluation 1 described above.

The yield stress of (1) film samples 6 to 10 and (2) withstand voltage strength of film capacitor samples 6 to 10 and (3) withstand voltage strength of film capacitor samples 6 to 10 obtained as described above. The minimum value of is shown in Table 2. In Table 2, the film sample and the film capacitor sample are collectively referred to as "sample".

As can be seen from Table 2, when the yield stress of the film is 70 MPa or more as in Samples 8 to 10, the withstand voltage strength of the film capacitor is 400 V / μm or more, which is a very good withstand voltage performance. Further, the minimum value of the withstand voltage strength of the film capacitor was 350 V / μm or more, and the variation in the withstand voltage strength was very small.

On the other hand, as can be seen from Table 2, when the yield stress of the film is smaller than 70 MPa as in Samples 6 and 7, the withstand voltage strength of the film capacitor is lower than 350 V / μm, and the withstand voltage strength of the film capacitor is further increased. The minimum value was lower than 200 V / μm. Therefore, there is a concern that the reliability of Samples 6 and 7 evaluated in a long-term high-temperature load test or the like will be low.

<Evaluation 3>
For the film samples 11 to 16, the coefficient of static friction and the coefficient of dynamic friction were measured by the method described above.

Next, with respect to the film capacitor samples 11 to 16, the withstand voltage strength and the minimum value of the withstand voltage strength were evaluated in the same manner as in the evaluation 1 described above.

The static friction coefficient and dynamic friction coefficient of (1) film samples 11 to 16 and the withstand voltage strength of film capacitor samples 11 to 16 and (3) film capacitor samples 11 to 16 obtained as described above. The minimum value of the withstand voltage strength is shown in Table 3. In Table 3, the film sample and the film capacitor sample are collectively referred to as "sample".

As can be seen from Table 3, when the coefficient of static friction and the coefficient of dynamic friction of the film are both 0.50 or less as in Samples 13 to 15, the withstand voltage strength of the film capacitor is 400 V / μm or more, which is a very good withstand voltage. Performance was obtained. Further, the minimum value of the withstand voltage strength of the film capacitor was 350 V / μm or more, and the variation in the withstand voltage strength was very small.

On the other hand, as can be seen from Table 3, when at least one of the static friction coefficient and the dynamic friction coefficient of the film is larger than 0.50 as in Samples 11, 12, and 16, the withstand voltage strength of the film capacitor is lower than 350 V / μm. Furthermore, the minimum value of the withstand voltage strength of the film capacitor was lower than 200 V / μm. Therefore, there is a concern that the reliability of Samples 11, 12, and 16 evaluated in a long-term high-temperature load test or the like will be low.

10 Film capacitor 11 First metallized film 12 Second metallized film 13 First dielectric film 14 Second dielectric film 15 First metal layer 16 Second metal layer 40 Laminated body 41 First External electrode 42 Second external electrode 61 Divided electrode part 62 Electrode part 63 Fuse part 64 Insulation slit T Stacking direction W Width direction

Claims (6)

It consists of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups.
A film for a film capacitor, characterized in that an F5 value indicating a stress at 5% elongation is 55 MPa or more. It consists of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups.
A film for a film capacitor, characterized in that the yield stress is 70 MPa or more. It consists of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups.
A film for a film capacitor, characterized in that both the coefficient of static friction and the coefficient of dynamic friction are 0.50 or less. A dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and
A metal layer provided on at least one main surface of the dielectric film.
A film capacitor characterized in that the F5 value indicating the stress at 5% elongation of the dielectric film is 55 MPa or more. A dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and
A metal layer provided on at least one main surface of the dielectric film.
A film capacitor characterized in that the yield stress of the dielectric film is 70 MPa or more. A dielectric film composed of a cured product of a first organic material having a plurality of hydroxyl groups and a second organic material having a plurality of isocyanate groups, and
A metal layer provided on at least one main surface of the dielectric film.
A film capacitor characterized in that both the coefficient of static friction and the coefficient of dynamic friction of the dielectric film are 0.50 or less.

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