JPH0454368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor constructed by winding a metallized film in which metal electrodes are formed on the surface of a dielectric film such as plastic film or paper by vapor deposition or the like.

At present, a large number of wound capacitors are produced using plastic film or paper as a dielectric. These capacitors can be roughly divided into capacitors that use metal foil for electrodes and capacitors that use metallized film that has electrodes formed by vacuum-depositing metal on one or both sides of a dielectric film. The former has the advantage that the manufacturing process is simple and inexpensive, but on the other hand, when winding,
Meandering of the metal foil in the width direction of the film tends to occur, and as a result, the dimensional accuracy of the insulation groove (usually called the margin part, hereinafter referred to as the margin part) provided at the edge of the film width direction and the electrode facing part are reduced. The drawback was that it did not produce enough information. If the dimensional accuracy is not sufficient as described above, there will be a disadvantage that a margin portion is formed more than necessary and the capacitance distribution after winding is not stable.

Furthermore, since metal foil is used for the electrodes, there is no self-healing function, and the electrodes have the drawbacks of being large.

On the other hand, since the latter uses the metallized surface as an electrode, it is easy to stabilize the dimensional accuracy of the margin part and electrode facing width, it can be made smaller, and it has the advantage of having a self-healing function.
After winding, the lead wire cannot be drawn out unless a metal material such as Zn or Sn is sprayed on both end faces of the metallized film to form an electrode extension part.
The drawback was that the manufacturing process was complicated and productivity was low.

In view of the current situation, the present inventors have proceeded with the development of a capacitor that combines the high productivity of film capacitors using metal foil for electrodes and the features of metallized film capacitors. As a result, a metallized film was constructed by forming an electrode with a thickness of 350 to 850 Å using a vacuum evaporation method or the like so as to provide a margin at the widthwise end of the dielectric film. Aluminum having a length of 50% of the length of the electrode so that the smooth surface with no unevenness of μ or more is located on the electrode surface side of the metallized film, and without facing with the dielectric film in between. A capacitor was developed in which foils were overlapped to have the same potential as the electrode surface, and the electrodes were drawn out using the aluminum foil.

The biggest technical point in the capacitor of the present invention is that we have found conditions that make it possible to draw out the electrodes directly from the electrodes, which was considered extremely difficult in the past, with something as simple as physically overlapping aluminum foil. That's true. The conditions are:
Use an electrode with a thickness of 350 to 850 Å. The aluminum foil used as an auxiliary electrode should have a smooth side with no irregularities of 0.2μ or more on the electrode surface, and should not be faced with a dielectric film in between. ,
The electrodes should be overlapped with a length of 50% or more of the length of the electrodes.

FIG. 1 shows the structure of essential parts of a capacitor according to an embodiment of the present invention. In the figure, 1 is a metallized film, and electrodes 1a and 1a each having a thickness of 350 to 850 Å are formed on both sides of the dielectric film. On one surface side, a margin portion is provided along one edge, and on the other surface side, a margin portion is provided along the other edge. Reference numeral 2 denotes a plastic laminated film, which is wound so as to be overlapped with the metallized film 1. Reference numerals 3 and 3 denote metal foils serving as auxiliary electrodes, one of which has a smooth surface with no unevenness of 0.2μ or more. These metal foils 3, 3 are placed on both sides of the metallized film 1 without facing each other with the film interposed therebetween, and their smooth surfaces A, A are opposed to the electrodes 1a, 1a of the metallized film 1. The two electrodes touch each other over 50% or more of the electrode length.

FIG. 2 shows the structure of the main part of another embodiment of the present invention. In the figure, 1 is a metallized film, and an electrode 1a with a thickness of 350 to 850 Å is formed on one side of the dielectric film, and the two films are overlapped and wound so that the margins are located on opposite sides. . A pair of metal foils 3, 3 as auxiliary electrodes are placed on both sides of the metallized film 1 without facing each other with the film in between, and each on the smooth surface A side where there are no irregularities of 0.2μ or more. Each of them is in contact with the electrode 1a of the metallized film 1 over 50% or more of the electrode length.

Figure 3 shows the thickness of the metallized film electrode and the results after 100 cycles of charge/discharge tests.
Zn is vapor-deposited. Note that the charging/discharging test conditions were such that one cycle consisted of applying a voltage twice the rated voltage between the terminals for 1 second, and then short-circuiting for 1 second.

Furthermore, FIG. 4 shows the results of an examination of the conditions under which the characteristics of a metallized film capacitor can be fully exhibited despite having a metal foil type structure. Figure 4 shows a DC withstand voltage test in which a DC voltage three times the rated voltage is applied to each capacitor for 2 to 3 seconds (number of non-defective products with no punctures)/(number of test pieces) x 100. This is the result.

As is clear from FIGS. 3 and 4, a capacitor having the excellent characteristics of the present invention cannot be obtained unless the electrode has a thickness of 350 to 850 Å. However, there is no significant difference between A1 and Zn as electrode materials.

Figure 5 shows the overlapping length ratio of the aluminum foil used as an auxiliary electrode to the electrode and the charge/discharge test 100.
It shows the value of dielectric loss tangent after cycling. All values before the test were 0.4 to 0.6%.

Further, FIG. 6 shows the state in which the aluminum foil used as the auxiliary electrode is superimposed on the electrode, that is, the surface state of the aluminum foil bonded to the electrode, and the results of the charge/discharge test. In Figure 6, characteristic C is
The product of the present invention, in which the smooth side with no unevenness of 0.2μ or more is bonded to the electrode by overlapping, characteristic D is 0.2 to 0.5μ.
This is a comparison product in which the rough surface side with uneven parts is overlapped and bonded to the electrode.

By the way, it is well known that the aluminum foil currently used for film capacitors and the like always has a smooth surface and a rough surface during manufacturing. As mentioned above, the capacitor of the present invention has a structure in which direct electrode extraction from the electrodes, which was conventionally considered difficult, is achieved by physically overlapping aluminum foils, so the results shown in FIGS. 5 and 6 are In particular, this is an important condition that is indispensable for perfecting the capacitor of the present invention. That is, they are superimposed on each electrode surface of the metallized film as an auxiliary electrode without facing each other with the film in between. It is necessary that the smooth side of the aluminum foil, which has no irregularities of 0.2μ or more, be overlapped with the electrode surface, and the overlapping length must be at least 50% of the electrode length.

As described above, in the capacitor of the present invention,
It can be produced using the same excellent production method as conventional metal foil type capacitors, and
Like metallized film capacitors, it is possible to obtain a stable and excellent capacitance distribution, and because it has a self-recovery function, it can be made smaller and lighter, and it also has various excellent capacitor characteristics. It is also possible to do this.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing the main structure of the capacitor of the present invention, and FIGS. 3, 4, 5, and 6 are diagrams for explaining the effects of the capacitor according to the present invention, respectively. It is. 1...Metalized film, 1a... Electrode, 2...
Laminated film, 3... Aluminum foil, A... Smooth surface.

Claims (1)

[Claims] 1 Constructed by winding a metallized film on which an electrode with a thickness of 350 to 850 Å is formed on the surface of a dielectric film, and the electrode surface of the metallized film has a smooth surface with no unevenness of 0.2μ or more. is in contact with the electrode surface of the metallized film and does not face each other with the metallized film in between, overlapping aluminum foil having a length of 50% or more of the electrode to have the same potential as the electrode surface, A capacitor characterized in that an electrode is drawn out using the aluminum foil.