Film Capacitors

Abstract

A film capacitor (1) of the present invention comprises a laminate (40) obtained by laminating metalized films (11, 12) each provided with a metal layer (15, 16) on a surface of a dielectric resin film (13, 14) containing a thermosetting urethane resin, wherein: the laminate (40) has a flat columnar shape formed by deforming a wound body (40a) which is obtained by winding the metalized films (11, 12) in a laminated state; a cross-sectional shape of the laminate (40) in a plane parallel to the lamination direction of the metalized films (11, 12) has a flat shape having a major axis (x) and a minor axis (y); the flat shape comprises a linear section (L) arranged substantially in the center in the extension direction of the major axis (x) and configured so as to include straight lines (La, Lb) substantially parallel to the major axis (x), and curved sections (C1, C2) arranged at both ends of the linear section (L) in the extension direction of the major axis (X) and configured so as to include curves (Ca, Cb); and the flat shape satisfies formula (1) below.　(1) 0≤f≤0.3 [where f is a number represented by f=1-(a / b), when the length of the major axis (x) is set to be L1 and the length of the linear part (L) is set to be L2, a is a number represented by a=[(L1–L1) / 2], and when the length of the minor axis (y) is set to be L3, b is a number represented by b=L3 / 2].

Description

[Technical field]

[0001] The present invention relates to a film capacitor. [Background technology]

[0002] One type of capacitor is a film capacitor, which uses a flexible resin film as a dielectric and has a first metal layer and a second metal layer facing each other with the resin film in between. This type of film capacitor is produced, for example, by winding a first dielectric film on which a first metal layer made of aluminum or the like is formed, and a second dielectric film on which a second metal layer made of aluminum or the like is formed.

[0003] Capacitors produced in this manner are usually cylindrical, but in order to increase volumetric efficiency, they are sometimes used after being deformed to have a flattened cross-sectional shape.

[0004] Patent Document 1 discloses a capacitor element having an oval cross section formed by winding and flattening a metallized film, which is made of a dielectric film made of polypropylene and has metal vapor deposition electrodes formed on it, around a core so that the pair of metal vapor deposition electrodes face each other via the dielectric film.

[0005] Patent Document 2 discloses a capacitor element in which a composite film roll is formed by wrapping an exterior film around the outer periphery of a metallized film roll and fixing the roll by thermal welding, and then press-molding the roll so that the aspect ratio is 0.6 or less. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-81007 A [Patent Document 2] JP 2015-70125 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when flattening, excessive force is applied to the metallized film, which can reduce the reliability of the capacitor, such as by causing the capacitor to lose its self-healing function in the event of a short circuit.

[0008] The purpose of Patent Document 1 is to increase volumetric efficiency by making the capacitor smaller and thinner, but it does not mention the relationship between the detailed shape of the flat body and the reliability of the capacitor.

[0009] Patent Document 2 describes the relationship between the heat welding method of the exterior film and the flatness of the element, but does not describe the relationship between the detailed shape of the flat body and the reliability of the capacitor.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a film capacitor that has high volumetric efficiency and is less likely to cause short circuits. [Means for solving the problem]

[0011] The film capacitor of the present invention comprises a laminate formed by laminating a metallized film having a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin, the laminate being a flat columnar shape formed by deforming a wound body formed by winding the metallized film in a laminated state, the cross-sectional shape of the laminate in a plane parallel to the lamination direction of the metallized film being a flat shape having a major axis and a minor axis, the flat shape having a straight line portion located approximately in the center in the direction in which the major axis extends and including a straight line approximately parallel to the major axis, and curved portions located at both ends of the straight line portion in the direction in which the major axis extends and including a curve, and the flat shape is a shape that satisfies the following formula (1). 0≦f≦0.3 (1) [wherein f is a number expressed by f=1-(a / b), a is a number expressed by a=[(L1-L2) / 2] when the length of the major axis is L1 and the length of the straight portion is L2, and b is a number expressed by b=L3 / 2 when the length of the minor axis is L3.] Effect of the Invention

[0012] According to the present invention, it is possible to provide a film capacitor which has high volumetric efficiency and is less likely to cause short circuits. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view illustrating a typical example of a film capacitor of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a perspective view that typically illustrates a roll formed by rolling up a metallized film. [Figure 4] FIG. 4 is a perspective view that typically illustrates an example of a laminate that constitutes the film capacitor of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining a method for determining boundaries between straight line portions and curved line portions. [Figure 6] FIG. 6 is a diagram showing a schematic cross-sectional shape of the laminate shown in FIG. 1 when cut along the line VI-VI. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The film capacitor of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual preferable configurations of the present invention described below.

[0015] The following embodiments are merely examples, and it goes without saying that partial replacement or combination of the configurations shown in the different embodiments is possible. From the second embodiment onwards, a description of the matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects due to similar configurations will not be mentioned in each embodiment.

[0016] The drawings shown below are schematic, and the dimensions and aspect ratios may differ from the actual products.

[0017] The film capacitor of the present invention comprises a laminate formed by laminating a metallized film having a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin, the laminate being a flat columnar shape formed by deforming a wound body formed by winding the metallized film in a laminated state, the cross-sectional shape of the laminate in a plane parallel to the lamination direction of the metallized film being a flat shape having a major axis and a minor axis, the flat shape having a straight line portion located approximately in the center in the direction in which the major axis extends and including a straight line approximately parallel to the major axis, and curved portions located at both ends of the straight line portion in the direction in which the major axis extends and including a curve, and the flat shape is a shape that satisfies the following formula (1). 0≦f≦0.3 (1) [wherein f is a number expressed by f=1-(a / b), a is a number expressed by a=[(L1-L2) / 2] when the length of the major axis is L1 and the length of the straight portion is L2, and b is a number expressed by b=L3 / 2 when the length of the minor axis is L3.]

[0018] FIG. 1 is a perspective view that illustrates an example of a film capacitor of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. The film capacitor 10 shown in FIG. 1 includes a laminate 40, and a first external electrode 41 and a second external electrode 42 connected to both end faces of the laminate 40. As shown in FIG. 2, laminate 40 is formed by rolling up first metallized film 11 and second metallized film 12 in a laminated state. First metallized film 11 includes first dielectric resin film 13 and first metal layer (counter electrode) 15 provided on the surface of first dielectric resin film 13. Second metallized film 12 includes a second dielectric resin film 14 and a second metal layer (counter electrode) 16 provided on the surface of second dielectric resin film 14.

[0019] 2, the first metal layer 15 and the second metal layer 16 face each other with the first dielectric resin film 13 or the second dielectric resin film 14 sandwiched therebetween. Furthermore, the first metal layer 15 is electrically connected to a first external electrode 41, and the second metal layer 16 is electrically connected to a second external electrode 42.

[0020] The first dielectric resin film 13 and the second dielectric resin film 14 may have different configurations, but desirably have the same configuration.

[0021] The first metal layer 15 is formed on one surface of the first dielectric resin film 13 so as to reach one side edge but not to reach the other side edge. On the other hand, the second metal layer 16 is formed on one surface of the second dielectric resin film 14 so as not to reach one side edge but to reach the other side edge. The first metal layer 15 and the second metal layer 16 are composed of, for example, an aluminum layer.

[0022] FIG. 3 is a perspective view that typically illustrates a roll formed by rolling up a metallized film. As shown in Figures 2 and 3, the first dielectric resin film 13 and the second dielectric resin film 14 are wound in a stacked state so that the end of the first metal layer 15 that reaches the side edge of the first dielectric resin film 13 and the end of the second metal layer 16 that reaches the side edge of the second dielectric resin film 14 are both exposed from the stacked films, thereby forming a wound body 40a, and the first metal layer 15 and the second metal layer 16 are stacked while maintaining their exposed ends.

[0023] In the wound body 40a, the second dielectric resin film 14 is wound so that it is on the outside of the first dielectric resin film 13, and the first metal layer 15 and the second metal layer 16 of each of the first dielectric resin film 13 and the second dielectric resin film 14 face inward. A cavity 50a is provided in the center of the wound body 40a.

[0024] FIG. 4 is a perspective view that typically illustrates an example of a laminate that constitutes the film capacitor of the present invention. Laminate 40 shown in Fig. 4 can be obtained, for example, by pressing wound body 40a shown in Fig. 3. At this time, cavity 50a is also deformed to become cavity 50. The cross-sectional shape of laminate 40 in a plane parallel to the lamination direction of the metallized films is a flat shape having a major axis and a minor axis. By pressing the wound body 40a, the volume efficiency can be improved. In addition, the surface parallel to the stacking direction of the metallized film of the laminate 40 corresponds to a surface perpendicular to the axial direction of the flat column (the direction in which the column extends) and a surface perpendicular to the winding axis of the wound body 40a used when producing the laminate 40.

[0025] Here, the larger the size of the cavity 50a provided in the center of the wound body 40a, the more flat the cross-sectional shape of the laminate 40 can be. That is, by adjusting the size of the cavity 50a in the wound body 40a, the cross-sectional shapes of the laminate 40 and the cavity 50 can be adjusted.

[0026] [Laminate] The film capacitor of the present invention includes a laminate in which a metallized film having a metal layer provided on the surface of a dielectric resin film containing a thermosetting urethane resin is laminated. The laminate has a flat shape obtained by deforming a roll in which metallized films are laminated and wound.

[0027] The metallized film is formed by providing a metal layer on the surface of a dielectric resin film containing a thermosetting urethane resin.

[0028] In the film capacitor of the present invention, the dielectric resin film contains, for example, a thermosetting urethane resin that is a cured product of a first organic material having a hydroxyl group (OH group) and a second organic material having an isocyanate group (NCO group). Specifically, the thermosetting urethane resin is a cured product obtained by reacting a hydroxyl group contained in the first organic material with an isocyanate group contained in the second organic material.

[0029] The first organic material may be an organic polymer having a hydroxyl group and a benzene ring in the repeating unit, such as a phenoxy resin. As the phenoxy resin, for example, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, etc. are preferable.

[0030] Examples of the second organic material include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), etc. Among these compounds, MDI or TDI is preferred. These compounds may contain modified polyisocyanates, and these compounds may be used in combination.

[0031] In the film capacitor of the present invention, the dielectric resin film may contain additives for imparting other functions. For example, smoothness can be imparted by adding a leveling agent. The additive may be a material having a functional group that reacts with a hydroxyl group and / or an isocyanate group and that forms part of the crosslinked structure of the cured product. Examples of such materials include resins having at least one functional group selected from the group consisting of an epoxy group, a silanol group, and a carboxyl group.

[0032] In the film capacitor of the present invention, the CR value, which is the product of the capacitance value of the film capacitor and the insulation resistance value measured after leaving it to stand in an atmosphere at a temperature of 125°C for 1 hour and then applying a voltage of 150 V / μm for 1 minute, is preferably 250 Ω·F or more, and more preferably 500 Ω·F or more. A capacitor with a CR value of 250 Ω·F or more under the above conditions can be said to have high resistance to high temperatures.

[0033] The thermosetting urethane resin means a urethane resin that can be cured by heat, and does not limit the curing method. Therefore, as long as it is a urethane resin that can be cured by heat, urethane resin cured by a method other than heat (for example, light, electron beam, etc.) is also included in the thermosetting urethane resin. Depending on the material, the reaction may start due to the reactivity of the material itself, and those that proceed to cure without necessarily applying heat or light from the outside are also considered to be thermosetting urethane resins.

[0034] The dielectric resin film may contain a thermoplastic resin or a silicone resin in addition to the thermosetting urethane. Examples of the thermoplastic resin include polypropylene, polyethersulfone, polyetherimide, and polyarylate.

[0035] The metal layer is provided on the surface of the dielectric resin film. The thickness of the metal layer is not particularly limited, but is preferably 5 nm or more and 40 nm or less.

[0036] The thickness of the metal layer can be determined by observing a cross section of the metallized film in the thickness direction using a transmission electron microscope (TEM).

[0037] Examples of materials constituting the metal layer include metals such as aluminum, zinc, titanium, magnesium, tin, and nickel.

[0038] The metal layer may be provided on both sides of the dielectric resin film, or on only one side. When a metal layer is provided on both sides of the dielectric resin film, a dielectric resin film having no metal layers on both sides (non-metallized film) and a dielectric resin film having metal layers on both sides (double-sided metallized film) are laminated and wound to obtain a wound body. On the other hand, when a metal layer is provided only on one surface of the dielectric film, two dielectric resin films having a metal layer on one side (single-sided metallized film) are laminated so that the metal layers do not come into contact with each other, and then wound to obtain a wound body.

[0039] The metal layer may include a fuse portion.

[0040] The metal layer may be provided on the entirety of one surface of the dielectric resin film, or may be provided on only a portion of the surface.

[0041] The static coefficient of friction between the surface of the metallized film on which the metal layer is provided and the surface of the metallized film on which the metal layer is not provided is preferably 0.3 or more and 1.5 or less. The static friction coefficient is measured in accordance with JIS K 7125-1999. When the static friction coefficient is within this range, the metallized film has favorable slip properties and is smoothly flattened, making it easier to adjust the flat shape, which is the cross-sectional shape of the laminate, to a shape that satisfies formula (1).

[0042] The laminate has a flattened columnar shape obtained by deforming a roll in which metallized films are laminated and wound. The cross-sectional shape of the laminate in a plane parallel to the lamination direction of the metallized films is a flat shape having a major axis and a minor axis.

[0043] The flat shape has straight lines and curved lines. The straight line portion is a portion that is disposed approximately in the center in the direction in which the major axis extends and that includes a straight line that is approximately parallel to the major axis. The curved portions are portions that are disposed on both ends of the straight portion in the direction in which the major axis extends, and are configured to include curves.

[0044] The straight and curved portions are identified by the following procedure. First, two straight lines approximately parallel to the long axis are identified from the flat shape, and the portion surrounded by the two straight lines is defined as a straight line section. The straight line section is an approximately rectangular shape formed by the two straight lines and the line segments connecting the ends of the two straight lines. Next, the portion of the flat shape excluding the straight line portion is defined as the curved line portion. Therefore, the boundary between the straight line portion and the curved line portion is a straight line.

[0045] If the boundary between the straight line and curved line is unclear, the boundary is determined as the point where the angle between the tangent at each point constituting the outer shape of the curved line and the straight line constituting the straight line is 10°. In other words, the angle between the tangent at each point of the curved line and the straight line constituting the straight line is calculated starting from the point closest to the straight line. The point where the angle between the tangent and the straight line is 10° is the starting point of the curved line.

[0046] FIG. 5 is a diagram for explaining a method for determining boundaries between straight line portions and curved line portions. In the cross-sectional shape of the laminate shown in FIG. 5, it is assumed that the boundary between the straight line portion L and the curved line portion C2 is unclear, and the boundary between the straight line portion and the curved line portion is determined. FIG. 5 shows an extension line X0 extending the straight line portion L towards the curved portion C2, and tangent lines X1, X2, and X3 at arbitrary points P1, P2, and P3 on the curve Cb. Here, the angle between the tangent X1 and the extension X0 at the point P1 is 5°. The angle between the tangent X2 and the extension X0 at the point P2 is 10°. Furthermore, the angle between the tangent X3 and the extension X0 at the point P3 is 15°. Therefore, the point P2 where the tangent line X2, which makes an angle of 10° with the straight line constituting the straight line portion, touches the curved portion Cb is the starting point of the curved portion C2.

[0047] The flat shape is a shape that satisfies the following formula (1). 0≦f≦0.3 (1) f is a number expressed as f=1-(a / b). The number a is expressed by a=[(L1-L2) / 2], where L1 is the length of the major axis and L2 is the length of the straight portion. b is a number expressed as b=L3 / 2.

[0048] When the cross-sectional shape of the laminate satisfies the above formula (1), it can be said that uneven force is unlikely to be applied to the metallized films at the curved portion, so that even if the film capacitor experiences a dielectric breakdown, it will not short out and the dielectric will be restored. When the cross-sectional shape of the laminate has an f-value exceeding 0.3, the laminate is not smoothly flattened, and an abnormal force is applied to the metallized film in the straight line portion. If a dielectric breakdown occurs in the part where the abnormal force is applied to the metallized film, the dielectric breakdown cannot be restored and a short circuit occurs. On the other hand, in the cross-sectional shape of the laminate, if the f value is less than 0, the distance between the metallized films is increased in the curved portion, resulting in a decrease in capacitance and a decrease in dielectric breakdown strength. Furthermore, it becomes difficult to restore the insulation when a dielectric breakdown occurs.

[0049] Fig. 6 is a diagram showing a schematic cross-sectional shape of the laminate when the laminate shown in Fig. 1 is cut along line VI-VI. Therefore, Fig. 6 omits the state in which the metallized films constituting the laminate are wound, and the external electrodes formed on the end faces of the laminate. The cross-sectional shape of the laminate 40 shown in Fig. 6 is a flat shape having a major axis x and a minor axis y. The cross-sectional shape of the laminate 40 also has a straight line portion L and curved lines C1 and C2. The straight line portion L is configured to include straight lines La and Lb parallel to the major axis x. The curved lines C1 and C2 are disposed at both ends of the straight line portion L in the direction in which the major axis x extends, and are configured to include curved lines Ca and Cb, respectively. The length of the curved portions C1 and C2 in a direction substantially parallel to the major axis x is given by [(length L1 of the major axis x)-(length L2 of the straight portion L)] / 2=a.

[0050] In the cross-sectional shape of the laminate 40 shown in FIG. 6, the length of the major axis x, the length of the straight line portion L, and the length of the minor axis y are L1, L2, and L3, respectively. 6, when the length L1 of the major axis x is 1, the length L2 of the straight line portion L is 0.648, and the length L3 of the minor axis y is 0.365. Therefore, f is 1-[(1-0.648) / 0.365]≈0.036.

[0051] In the film capacitor of the present invention, a cavity or a winding core may be disposed in the center of the laminate.

[0052] In the film capacitor of the present invention, the ratio [XL / YL] of the interlayer distance XL between the metallized films in the curved portions to the interlayer distance YL between the metallized films in the straight portions is preferably 0 or more and 1 or less, and more preferably 0.45 or more and 1.0 or less.

[0053] The interlayer distance YL between the metallized films in the straight portion can be calculated from the thickness of the straight portion from the center of the laminate, the average thickness of the metallized films that make up the straight portion, and the number of turns (number of layers) of the metallized films that make up the straight portion. First, the thickness t from the center of the laminate in the straight line section L is the interlayer distance YL between the metallized films in the straight line section and the average thickness t of the metallized films constituting the straight line section. FL and the number of turns (number of layers) n of the metallized film that constitutes the straight portion, is expressed by the following formula (2). t L =(YL+t FL )×(n-1)+t FL (2) The interlayer distance YL between the metallized films in the straight line portion is expressed by the following formula (3), which is a modification of the above formula (2). YL = (t L -t FL ) / (n-1)-t FL (3) Moreover, by modifying the above formula (3), it can also be expressed as the following formula (4). YL = [(t L)-(t FL ×n)] / (n-1) (4)

[0054] On the other hand, the interlayer distance XL between the metallized films in the curved portion can be calculated from the thickness of the curved portion from the center of the laminate, the average thickness of the metallized films constituting the straight portions, and the number of turns (number of layers) of the metallized films constituting the curved portion. First, the thickness t of the laminate from the center of the curved section C is the interlayer distance XL between the metallized films in the curved section and the average thickness t of the metallized films constituting the straight section. FL and the number of turns (number of layers) n of the metallized film that constitutes the curved portion, is expressed by the following formula (5). t C =(XL+t FL )×(n-1)+t FL (5) The interlayer distance XL between the metallized films in the curved portion is expressed by the following formula (6), which is a modification of the above formula (5). XL=(t C -t FL ) / (n-1)-t FL (6) Moreover, by modifying the above formula (6), it can also be expressed as the following formula (7). XL=[(t C )-(t FL ×n)] / (n-1) (7) Here, when determining the interlayer distance XL between the metallized films in the curved portion, the average thickness t FL The reason for using this will be explained. The interlayer distance XL between metallized films in the curved portion in this specification is not the interlayer distance between metallized films in the curved portion of an actual film capacitor, but the distance between the metallized films calculated under the assumption that the thickness of the metallized film does not change due to the flattening process. The thickness of the metallized film in the straight sections does not change due to the flattening process, and furthermore, the thickness of the metallized film before the flattening process does not change between the straight sections and the curved sections, so the thickness of the metallized film in the curved sections before the flattening process is considered to be equal to the thickness of the metallized film in the straight sections after the flattening process. For the above reasons, in determining the interlayer distance XL between the metallized films in the curved sections, the average thickness t FL is used. Therefore, when the thickness of the metallized film is reduced by the flattening treatment, the interlayer distance XL between the metallized films may become a negative value.

[0055] The thickness of the straight and curved portions from the center of the laminate, the average thickness of the metallized films, and the number of layers of the metallized films can be measured by observing a cut surface of the film capacitor cut in a direction perpendicular to the lamination direction of the metallized films with a scanning electron microscope, etc. The average thickness of the metallized film is the average value of the thicknesses of all the metallized films present on the minor axis of the flat shape, which is the cross-sectional shape of the laminate at the cut surface, in the case of the straight portions, and is the average value of the thicknesses of all the metallized films present on the major axis of the flat shape, which is the cross-sectional shape of the laminate at the cut surface, in the case of the curved portions.

[0056] Interlayer distance YL between metallized films in the straight line portion is, for example, the distance between second metal layer 16 constituting second metallized film 12 and first dielectric resin film 13 constituting first metallized film 11 in Fig. 2. However, Fig. 2 shows an example in which interlayer distance YL between metallized films in the straight line portion is zero.

[0057] On the other hand, in curved sections, the interlayer distance between metallized films may shrink or expand depending on how easily the metallized films slide against each other. When the ratio [XL / YL] is 0 or more and 1 or less, the interlayer distance between the metallized films constituting the curved portion is within an appropriate range, so that the metallized films constituting the curved portion are not subjected to abnormal forces, and therefore the insulation recovery function can be fully exerted.

[0058] If the ratio [XL / YL] exceeds 1, the metallized film at the curved portion may slip too much or may be pulled during deformation of the laminate, resulting in an excessively long interlayer distance between the metallized films at the curved portion. If dielectric breakdown occurs at the curved portion in such a case, the dielectric recovery function of the metallized film may not be exerted, resulting in a short circuit. Furthermore, a decrease in capacitance and a decrease in dielectric breakdown strength may easily occur.

[0059] On the other hand, when the ratio [XL / YL] is less than 0, it is considered that abnormal force is applied to the metallized film in the curved section, where the distance between the metallized films is almost the same, causing the thickness of the metallized film to become thin or deformed. In such a case, if dielectric breakdown occurs in the curved section, the dielectric recovery function of the metallized film is not exerted, leading to a short circuit. Furthermore, a decrease in capacitance and a decrease in dielectric breakdown strength are also likely to occur. The ratio [XL / YL] is less than 0 when the interlayer distance XL of the metallized film constituting the curved portion has a negative value. The negative film interlayer distance XL is calculated and has no relation to the actual distance between the metallized films. A negative film interlayer distance XL is a state in which there is almost no film interlayer distance and the metallized film constituting the curved portion is pushed or stretched excessively during the flattening process, making the film thickness in the curved portion thinner than the average thickness.

[0060] A cavity 50 is provided in the center of the laminate 40 shown in FIG. The thickness of the straight line portion L from the center of the laminate 40 is indicated by the double arrow t LThe thickness of the curved portion C2 from the center side of the laminate 40 is indicated by a double-headed arrow t C The length is indicated by In the laminate 40 shown in FIG. 6, the thickness t C is equal to a=(L1-L2) / 2. When a winding core is provided in the center of the laminate instead of a cavity, the interlayer distance between the metallized films can be determined by replacing the cavity in the above procedure with the winding core.

[0061] In the laminate 40 shown in FIG. 6, the cavity 50 has a predetermined thickness tv, so that the thickness t L However, b does not coincide with L3 / 2. On the other hand, when the laminate 40 does not have a cavity 50 or a winding core, the thickness t L But b=L3 / 2.

[0062] In determining the straight and curved portions in the cross-sectional shape of the laminate, the thickness of one or two metallized films is to be ignored, i.e., the step that occurs at the point where the winding of the metallized film ends is not to be taken into consideration. Similarly, in determining the shape of the cavity present inside the laminate, the step that occurs at the point where the winding of the metallized film begins is not taken into consideration.

[0063] It is preferable that the curved portion has an outer shape that is composed only of curves. When the outer shape of the curved portion is formed only from curves, it becomes easier to distribute the force applied to the metallized films that make up the laminate.

[0064] In the film capacitor of the present invention, when a boundary line between the curved portion and the straight portion is assumed, it is preferable that the difference between the maximum and minimum distances from the center point of the boundary line in the short axis direction to the outer edge of the curved portion is 35% or less of the value represented by [(a+b) / 2]. When the difference between the maximum and minimum values ​​is 35% or less of the value represented by [(a+b) / 2], the outer shape of the curved portion will be close to an arc that constitutes a perfect circle, making it easier to distribute the force applied to the metallized film. When the curve that constitutes the curved portion is a semicircle of a perfect circle, the distance from the center point in the minor axis direction of the boundary between the curved portion and the straight portion to the outer edge of the curved portion at every point is the same as a and b. Therefore, the difference between the maximum and minimum distances from the center point to the outer edge of the curved portion is zero, and the ratio of the above difference to the value indicated by [(a+b) / 2] is zero%.

[0065] In the laminate 40 shown in FIG. 6, the distance Ln from the center point p in the minor axis y direction of the boundary between the curved portion C2 and the straight portion L to an arbitrary point on the outer edge (curve Cb) of the curved portion C2 is equal to a and b. Here, if the difference between the maximum and minimum values ​​of the distance Ln is 35% or less of the value represented by [(a+b) / 2], the value of the distance Ln is close to a and b, and the shape of the curved portion is close to an arc that constitutes a perfect circle. Therefore, the force applied to the metallized film is easily dispersed, and abnormal forces are less likely to be applied to the metallized film.

[0066] [External electrode] The film capacitor of the present invention may include external electrodes. The external electrodes are provided on end faces of the laminate in a direction perpendicular to the lamination direction of the metallized films so as to be in contact with the metal layers.

[0067] The external electrodes are preferably made of zinc, aluminum, tin, alloys thereof, or the like.

[0068] The external electrodes may be formed by, for example, thermal spraying.

[0069] The thickness of the external electrodes is not particularly limited, but may be 0.5 mm or more and 5 mm or less.

[0070] The film capacitor of the present invention may include lead terminals connected to external electrodes and a housing case. When the film capacitor of the present invention is provided with a housing case, it is preferable that the film capacitor is housed in the housing case with lead terminals connected to the external electrodes, and that the film capacitor housed in the housing case is sealed with a sealing resin.

[0071] The film capacitor of the present invention can be applied to known applications, but is particularly suitable for use in environments with large temperature changes, particularly at high temperatures.Since the life of the equipment can be extended, the film capacitor is suitable for use in power electronics equipment such as electric compressors / pumps, chargers, DC-DC converters, and drive inverters mounted on automobiles and industrial equipment.

[0072] [Manufacturing method of film capacitors] Next, an example of a method for producing the film capacitor of the present invention will be described. The dielectric resin film constituting the film capacitor of the present invention can be produced by forming a resin solution containing a first organic material having a hydroxyl group and a second organic material having an isocyanate group into a film, and then curing it by heat treatment.

[0073] Next, a metal layer is formed on one surface of the dielectric resin film thus prepared to obtain a metallized film. The metal layer can be formed by a method such as vapor deposition. At this time, the metal layer is formed so that a strip-shaped insulating portion is formed on one side edge of one surface of the dielectric resin film.

[0074] Next, prepare two metallized films, each of which has a metal layer formed on one side of a dielectric resin film. One of the two metallized films is rotated 180 degrees around the lamination direction as an axis so that the positions of the insulating parts are staggered, and the two are stacked with a predetermined distance shifted in the width direction, and then wound to obtain a wound body.

[0075] Next, the obtained wound body is sandwiched in a direction perpendicular to the width direction and pressed into a flat shape to obtain a flat columnar laminate. At this time, by adjusting various conditions such as the thickness of the metallized film, the number of turns, the volume of the cavity in the center of the wound body, and the pressing pressure, the cross-sectional shape of the laminate is adjusted to satisfy the following formula (1). 0≦f≦0.3 (1)

[0076] Next, external electrodes are formed on the end faces of the laminate to obtain a film capacitor as shown in Figure 1. Methods for forming external electrodes on the end faces of the laminate include thermal spraying.

[0077] If necessary, the obtained film capacitor may be connected to lead terminals, housed in an exterior case, and sealed with a sealing resin. EXAMPLES

[0078] EXAMPLES Hereinafter, examples of the film capacitor of the present invention will be described more specifically. However, the present invention is not limited to these examples.

[0079] Example 1 First, a mixed solution of phenoxy resin and 4,4-phenylmethane diisocyanate was molded into a film and heat-cured to obtain a dielectric resin film with a thickness of 2.89 μm. A 10 nm thick aluminum layer was formed by vapor deposition on one surface of the obtained dielectric resin film to prepare a metallized film.

[0080] Next, two of these metallized films were stacked together and wound to obtain a wound body, the cross-sectional shape of which was a doughnut shape with a roughly circular cavity in the center.

[0081] The wound body was then pressed to obtain a laminate. The cross-sectional shape of the laminate was a flat shape having a major axis and a minor axis, as well as straight and curved portions, as shown in Figure 6. The dimensions of the flat shape were as follows: Long axis x length L1: 25.1 mm Length of straight section L2: 18.0 mm Length of minor axis y L3: 9.4 mm Thickness t from the center of the straight section of the laminate L :4.70mm Thickness t from the center of the curved part of the laminate C :3.55mm The average thickness t of the metallized film that constitutes the straight section FL : 2.9μm Number of layers of metallized film: 1220 sheets The f value and XL / YL were calculated from these dimensions, and the results are shown in Table 1.

[0082] Zinc was sprayed onto the end faces of the laminate to form external electrodes, thereby producing the film capacitor according to Example 1.

[0083] (Examples 2 to 5, Comparative Examples 1 to 5) Except for changing the f value of the dielectric resin film as shown in Table 1, the external electrodes were produced in the same manner as in Example 1.

[0084] [Load test] A voltage of 100 V / μm was applied to the film capacitors of each Example and Comparative Example in an atmosphere of 125° C. The voltage was increased by 100 V / μm every hour, and then a load was applied in which the voltage was maintained for one hour. This load application operation was repeated until the film capacitor underwent dielectric breakdown and the capacitance became 0, or until the film capacitor was shorted. The film capacitors that underwent dielectric breakdown and the capacitance became 0 were rated as ◯, and the film capacitors that shorted were rated as ×. The results are shown in Table 1.

[0085] [Table 1]

[0086] The results in Table 1 show that the film capacitor according to the embodiment can restore insulation without short-circuiting until the capacitance becomes zero. From the above, it was found that the film capacitor of the present invention is less likely to cause a short circuit. [Explanation of symbols]

[0087] 10. Film Capacitors 11 First metallized film 12 Second metallized film 13 First dielectric resin film 14 Second dielectric resin film 15 First Metal Layer 16 Second Metal Layer 40 Laminate 40a Winding body 41 First external electrode 42 Second external electrode 50a, 50 cavities C1, C2 curved section Ca,Cb curve L Straight section L1 major axis length L2 Straight section length L3 minor axis length La, Lb straight line Any point on the P1, P2, P3 curves t V Cavity thickness x major axis X0 Extension line extending the straight section to the curved section Tangent at any point on the X1, X2, X3 curve t C Thickness from the center of the laminate at the curved section y minor axis t L Thickness from the center of the laminate in the straight section

Claims

1. The laminate includes a metallized film having a metal layer provided on a surface of a dielectric resin film containing a thermosetting urethane resin, the laminate has a flattened columnar shape obtained by deforming a roll obtained by rolling the metallized film in a stacked state, a cross-sectional shape of the laminate in a plane parallel to a lamination direction of the metallized film is a flat shape having a major axis and a minor axis, A winding core is not disposed in the center of the laminate, the flat shape has a straight line portion disposed at a substantially center in a direction in which the long axis extends and including a straight line substantially parallel to the long axis, and curved lines disposed at both ends of the straight line portion in a direction in which the long axis extends and including a curved line, The flat shape satisfies the following formula (1), a ratio [XL / YL] of an interlayer distance XL between the metallized films constituting the curved portion to an interlayer distance YL between the metallized films constituting the straight portion in a cross section of the laminate in a plane parallel to the stacking direction of the metallized film is 0 or more and 1 or less. 0≦f≦0.3 (1) [wherein f is a number expressed by f=1-(a / b), and a is the length of the long axis L １ The length of the straight line portion is L ２ When a=[(L １ -L ２ ) / 2], and b is the length of the minor axis L ３ When b = L ３ / 2.]

2. The film capacitor according to claim 1 , wherein each of the curved portions has an outer shape that is formed only by curves.

3. 3. The film capacitor according to claim 1, wherein, when a boundary line between the curved portion and the straight portion is assumed, the difference between the maximum and minimum distances from the center point of the boundary line in the short axis direction to the outer edge of the curved portion is 35% or less of the value represented by [(a + b) / 2].

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