JPH11329886A - Metallized plastic film and film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To additionally provide a discharge electrode through a simple method so as to provide a metallized plastic film capacitor of high safety and reliability. SOLUTION: In a plastic film whose both sides or one side is metallized, one side 13 of a split electrode 12 marked off by a margin 11 which extends in a lengthwise direction and in a crosswise direction of the film is formed of a curve, or a line or lines at an angle with the crosswise direction of the film, and non-metallized parts 14 are formed. When a capacitor is manufactured, the split electrodes 12 are partly removed, whereby discharge electrodes 16 which are determined in shape by the non-metallized parts 14 are obtained, so that a capacitor provided with discharge electrodes can be manufactured through the same process with a conventional capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for a capacitor and a film capacitor.

[0002]

2. Description of the Related Art Generally, a metallized film for a capacitor is composed of a metallized portion formed on the film surface and serving as an internal electrode of the capacitor, and a non-metallized portion called a margin extending in the longitudinal direction of the film. However, as for a capacitor used in a power supply section or the like where particularly high safety is required, when a part of the capacitor is broken down as shown in FIG. In order to prevent this, a margin extending in the film width direction is formed at regular intervals, and the internal electrode is divided. In addition, as shown in FIG. A type in which a bridge-like gate acting as a fuse is provided between the terminal and a film end communicating with an external electrode has become widespread.

However, a capacitor with a fuse function has high safety against smoke and ignition, etc., but the capacity of the capacitor is reduced by the operation of the fuse, and in the worst case, the capacitor may not function as a capacitor. In recent years, the development of a new security mechanism to replace this has been sought, one of which is the addition of a discharge electrode.

As shown in FIGS. 6 (a) and 6 (b), the discharge electrode 61 is formed by a metal electrode connected to the external electrode of the capacitor and a discharge gap between the metal electrodes, which is added to the exterior part of the capacitor. When an overvoltage or surge is applied to the capacitor, the capacitor has a function of preventing a dielectric breakdown of the capacitor body by causing discharge between the metal electrodes and releasing an excessive voltage. In addition, safety can be further enhanced by combining with the above-mentioned capacitor having a fuse function.

[0005]

However, while a capacitor with a fuse function can be manufactured in almost the same process as a general capacitor, a discharge electrode is newly formed by bonding a metal piece to the capacitor. In addition, an additional step is required, and the production cost is significantly increased, so that the feasibility is poor.

Accordingly, an object of the present invention is to provide a highly safe and reliable metallized plastic film capacitor to which a discharge electrode is added by a simple method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, in a metallized plastic film for a capacitor in which internal electrodes are divided, the shape of the sides constituting the divided electrodes is defined, and a part of the divided electrodes is removed (hereinafter referred to as burn-off treatment). 2) to form two types of electrodes, the capacitor internal electrode (divided electrode) and the discharge electrode, on the same film.

The burn-off processing is a processing method used for securing the insulation distance at the winding start and winding end surfaces in a wound capacitor, and its mechanism is as shown in FIG. 4 (a). Then, a discharge is caused between the burn-off electrode 42 and the portion 43 to be processed while the metallized plastic film 41 is being fed, so that the metal of the portion 43 to be processed is sequentially scattered. Thus, the process is performed while the electrode 44 forming a pair with the burn-off electrode 42 is electrically connected as indicated by an arrow 45.

Therefore, as shown in FIG. 4 (b), when there is a cut-shaped non-metallized portion 47 on the side 46 at the end of the burn-off process of the divided electrode divided by the margin, the cut-off causes the electrode 44 to be cut off. Is lost and a portion 48 remains as a metallized portion without being burned off.

[0010] The shape of the portion 48 remaining as a metallized portion after the burn-off process is determined by the shape of the side 46 at the end of the burn-off process of the divided electrode. It is possible to form two types of electrodes, a capacitor internal electrode (divided electrode) and a discharge electrode.

By winding this metallized plastic film, a discharge is generated when an abnormal voltage is applied to the capacitor, and a discharge electrode having a function of protecting the capacitor body is formed. The metallized plastic film capacitor having a high value can be obtained without adding a special discharge electrode adding step.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to a metallized plastic film for a capacitor having divided electrodes on both sides or one side separated by a margin extending in the longitudinal direction and the width direction of the film. A capacitor characterized in that, of the sides constituting the electrode, at least one side formed by a margin extending in the width direction is formed by a curve or a line or a plurality of lines oblique to the film width direction. Metallized plastic film, which has an effect that two types of electrodes, a capacitor internal electrode and a discharge electrode, can be obtained by burn-off processing.

According to a second aspect of the present invention, at least one cut-shaped non-metallized portion is provided on at least one side of the sides constituting the divided electrodes formed by a margin extending in the width direction. The metallized plastic film for a capacitor according to claim 1, which has an effect that two types of electrodes, a capacitor internal electrode and a discharge electrode, can be obtained by a burn-off process.

According to a third aspect of the present invention, the metallized plastic film for a capacitor according to the first or second aspect is wound, and a part of the film surface is burned off, so that the inside of the film winding portion is formed. Alternatively, the present invention is a plastic film capacitor characterized by forming a discharge electrode on the outer periphery, and has a function of obtaining a plastic film capacitor having high safety and hardly reducing the capacity by a simple method.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 shows a metallized plastic film for a capacitor of the present invention and a state after a burn-off process.

The metallized plastic film shown in FIG. 1 is obtained by metallizing polyethylene terephthalate by aluminum evaporation. The surface of the metallized plastic film has a margin 11, which is a non-metallized portion extending in the longitudinal direction and the width direction of the film, and a capacitor 11. Metallized split electrode 12 serving as internal electrode
And the side 1 of the side of the split electrode 12 which is the burn-off end
3 is formed by cut-shaped non-metallized portions 14 formed at two places near the center and near the film edge connected to the capacitor external electrodes.

The upper part of FIG. 1 shows the film surface shape after the burn-off process. Most of the divided electrodes 12 are scattered by the burn-off process, and the cut-off non-metallized portions 14 cause the metal having the discharge gap 15 to have a discharge gap 15. The discharge electrode 16 is formed as an oxidized portion.

It should be noted that here, the side 1 at the end of burn-off
Although the description is given using the example in which the cut-shaped non-metallized portion 14 is formed in 3, the same effect can be obtained by changing the number, shape and size of the cuts.
Discharge electrodes of various shapes can be formed by the side 13 serving as a burn-off terminal being constituted by a line or a plurality of lines oblique to a curve or a film width direction,
The same effect can be obtained for each. In particular, the type in which the non-metallized portion 22 in the form of an acute cut is formed on the side 21 at the burn-off end as shown in FIG. 2A can shorten the distance of the discharge gap 23, It has the feature of operating with a low voltage surge,
As shown in FIG. 2B, in the type in which the arc 25 or the side 25 which is the burn-off end is formed by a series of polygons in a saw-tooth shape, the discharge electrode 26 formed by the burn-off process has a chain line shape. When the discharge occurs, the discharge electrode is scattered, and the energy of the surge is consumed. Further, as shown in FIG.
In the type in which the side 27 serving as the burn-off end is inclined with respect to the film width direction, an arbitrary width can be obtained according to the angle of the side 27 and the position of the fuse 28 or the cut-shaped non-metallized portion without reducing the area of the divided electrode. It has the feature that the discharge gap 29 can be formed. Appropriate shapes can be selected depending on the use and use condition of the capacitor such as the number and magnitude of applied surges.

Although a description is given here using a film in which polyethylene terephthalate is metallized by vapor deposition of aluminum, a case where another plastic film such as polyethylene naphthalate or polypropylene is used as a base film, Similar effects can be obtained when other metals such as zinc, nickel and the like are metallized by vapor deposition or sputtering.

Although the description has been made using a metallized plastic film having one side metallized and not provided with a fuse portion, a case where both sides are metallized or a position which is continuous with the side which is the burn-off end of the split electrode is used. A similar effect can be obtained even when a fuse portion is provided in the first embodiment.

(Embodiment 2) FIG. 3 shows a basic structure of a capacitor internal element using a metallized plastic film for a capacitor of the present invention.

The internal element of the capacitor shown in FIG. 3 has a winding portion 31 formed by winding the metallized plastic film of the present invention.
And external electrodes 32 formed by spraying a metal on both ends of the winding part 31. The winding part 31 is composed of a divided electrode part 33 and a discharge electrode part 34 formed by performing a burn-off process at the start and end of winding. Further, the split electrode section 33 and the discharge electrode section 34
Are electrically connected to the outside of the capacitor via external electrodes 32 at both ends thereof. Therefore, the external electrode 32 has a structure in which it enters between the layers at both ends 35 of the discharge electrode portion 34.

The split electrode portion 33 forms the capacity of the capacitor, and the discharge electrode portion 34 discharges between the metal electrodes when an overvoltage or surge is applied to the capacitor to release an excessive voltage, thereby allowing the split electrode portion to discharge. It has the function of preventing dielectric breakdown of the portion 33.

Although the discharge electrode portion 34 is formed at the beginning and end of winding, the discharge electrode portion 34 is formed at the beginning or end of winding or in the middle of the divided electrode portion 33. The same effect can be obtained even when it is formed in place or divided into a plurality.

In this case, the external electrodes 32 are connected to both ends 35 of the discharge electrode portion 34 in order to secure conduction of the discharge electrode portion 34.
However, the same effect can be obtained even when the external electrode 32 covers the outer periphery of the winding portion 31.
Further, even if sufficient conduction between the external electrode 32 and the discharge electrode portion 34 is not ensured, the same can be achieved by making the discharge voltage of the discharge electrode portion 34 and the split electrode portion 33 different by impregnation of oil or resin. The effect can be obtained.

[0026]

As described above, according to the present invention, when an abnormal voltage is applied to a capacitor, a discharge electrode having a function of causing discharge and protecting a capacitor body is formed.
A highly safe and reliable metallized plastic film capacitor can be obtained without adding a special discharge electrode adding step.

[Brief description of the drawings]

FIG. 1 is a front view showing a metallized plastic film of the present invention and a state after a burn-off process.

FIG. 2 is a front view of a film surface shape example of the present invention and a discharge electrode shape obtained thereby.

FIG. 3 is a perspective view and a sectional view of a capacitor internal element using the metallized plastic film of the present invention.

FIG. 4 is a structural diagram showing a burn-off mechanism and a state when the film of the present invention is processed.

FIG. 5 is a front view of a conventional split electrode type metallized plastic film.

FIG. 6 is a front view and a sectional view of a conventional capacitor with a discharge electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Margin 12 Divided electrode 13 Side which becomes end of burn-off processing of divided electrode 14 Cut not-metallized part 15 Discharge gap 16 Discharge electrode 21 Side which becomes end of burn-off processing of split electrode 22 Noncut metal part of acute cut 23 Discharge gap 24 Arc forming side of split electrode 25 Side that becomes end of burn-off processing of split electrode 26 Discharge electrode 27 Side that becomes end of burn-off processing of split electrode 28 Cut-off non-metallized portion 29 Discharge gap 31 Winding portion 32 External electrode 33 Split electrode part 34 Discharge electrode part 35 Discharge electrode part both ends 41 Metallized plastic film 42 Burn-off electrode 43 Burn-off processed part 44 Electrode 45 Arrow indicating the flow of burn-off current 46 Edge to be the end of burn-off processing of split electrode 47 Notch Non-metallic part 48 burn-off Metallized part remaining after processing 61 Discharge electrode of conventional capacitor

Claims (3)

[Claims] 1. A metallized plastic film for capacitors having divided electrodes separated on both sides or one side by margins extending in the film longitudinal direction and in the width direction, wherein a margin extending in the width direction among sides constituting the divided electrodes is provided. A metallized plastic film for capacitors, wherein at least one of the formed sides is constituted by a line or a plurality of lines oblique to a curve or a film width direction. 2. A capacitor for a capacitor according to claim 1, wherein at least one cut-shaped non-metallized portion is provided on at least one side of the sides constituting the divided electrodes formed by a margin extending in the width direction. Metallized plastic film. 3. A discharge electrode is provided inside or on the outer periphery of a wound portion of a film by winding the metallized plastic film for a capacitor according to claim 1 or 2 and removing a part of the metal on the film surface. A plastic film capacitor characterized by being formed.