JPS62279619A - Capacitor with self-guard function - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a capacitor with a self-safety function used mainly in electrical equipment requiring a safety device.

Conventional technology Conventional capacitors with a built-in safety device house the capacitor element in a metal case, seal it by impregnating it with wax or insulating oil, and utilize the deformation of the case due to the pressure increase inside the case when the capacitor breaks. There were types that electrically cut the capacitor lead pieces to prevent capacitors from bursting or catching fire, and types that had a built-in current fuse or temperature fuse to prevent capacitors from bursting or catching fire.

Furthermore, by treating the evaporated electrode of the capacitor during or after evaporation, a current path part is provided that allows current to flow only in a limited area between the contact part with the metallicon and the capacitance formation part, so that the current flowing to the capacitance formation part is reduced. All of the current flows through this path, and the total electrode length is divided into multiple parts to form a capacitor from multiple independent capacitance forming parts.
There is a type with a self-protection function that prevents bursting and ignition by separating only the destroyed capacitor forming part by electrically cutting off the current path leading to the capacitor forming part by the current at the time of destruction.

Self-protection type capacitors are expected to be used more and more widely in the future due to their safety and economic efficiency, but a common requirement for capacitors used by Shinkin Banks is the demand for lower costs. Capacitor potential gradient technology has become necessary, such as applying a higher rated voltage than before to a film with the same thickness as before, or using a thinner film than before even though the rated voltage is the same as before. In the case of capacitors with safety features, a new technology was needed to achieve a similar high potential gradient.

In order to achieve a high potential gradient, it is necessary that the film has a weak point like the conventional one and can completely self-heal (self-heal: SH) even if a voltage higher than that of the conventional film is applied. In other words, it is necessary to improve the SH properties of the entire film.

One possible way to meet this demand is to deposit electrodes thinly, keep the energy when the electrodes scatter low, and prevent deterioration of the dielectric. It is true that this method increases the short-term breakdown voltage of the capacitor, and the effect is significant. The problem in this case is that if the electrode is aluminum (A2),
In a life test in a high-temperature atmosphere, it can be said that the thinner the electrode and the higher the electrode surface resistance, the greater the capacity reduction. This is from the metal 8λ to the insulator A4203.
This is because the thinner the electrode, the faster the Al2O2 portion spreads. Due to these factors, the electrode surface resistance of the conventional AC capacitor in which l is vapor-deposited is suppressed to less than 607 points. When the electrode is made of zinc (Zn), this problem of capacitance reduction does not become a problem even if the electrode has a sheet resistance of about 100QZ, and a high potential gradient can be achieved. However, when the electrode surface resistance exceeds 30Q/hole, unlike the case of the A2 foil electrode, the contact between the metallicon and the vapor-deposited electrode, which is originally weak, becomes even weaker, and -δ increases. To solve this problem, a stepped evaporation electrode is used in which the evaporation electrode on the contact side is deposited thicker than the evaporation electrode on the capacitor formation side. In this way, when the electrodes are made of Zn, increasing the potential gradient of the capacitor is being considered.

Problems that the invention aims to solve However, in the case of Zn electrodes, compared to Afl electrodes, SH properties are worse than conventional ones, and this causes a decrease in the CR value (capacitance x insulation resistance), which is a measure of the insulation performance of a capacitor. It tends to appear after 1,000 hours have passed.

A more decisive problem is that in the case of stepped evaporation electrodes, even if a current path section is formed in the thick-film evaporation electrode on the contact side for the purpose of operating the self-protection function, the breakdown current in the capacitance forming section where the evaporation electrode is thin is small. Therefore, the current path section cannot be cut, and a small destructive current continues to flow, eventually leading to smoke and ignition, and the self-protection function cannot be achieved.

The present invention can achieve both high SH property and self-safety function even if the design potential gradient of the capacitor with self-protection function is increased, and even in high-temperature life tests, the capacitance decrease is increased and the insulation property is maintained over a long period of time. The present invention aims to provide a capacitor with a self-protection function that is resistant to deterioration.

Means for Solving the Problems For this purpose, in the present invention, at least one electrode of a capacitor made of a metallized plastic film is composed of a plurality of divided electrodes, and the sheet resistance of each divided electrode is set to 6 to 6.
The electrode thickness is limited to a range of 30Ω/□, and the electrode thickness is not an uneven thickness electrode as in the case of stepped vapor deposition electrodes, but a uniform thickness electrode within the range of variation obtained under certain manufacturing conditions. .

In addition, at least on the metallized side of the metallized plastic film, superimpose it on the metallized side and apply S of 50 to 10 o
tO, SiO2, glass, Af), 203. Eel
.

MgO, T to, T to2. Bad, Cab
, CaO2, Ta2O3゜T a Or WO3, M
It is formed by forming an oxide insulating layer consisting of at least one layer of OO3, ZrO2, or MOO2. When using 29 single-sided metallized films, a film with an oxide insulating layer formed on the non-metalized side may also be used, or when using a double-sided metalized plastic film and a non-metalized plastic film, a non-metalized film may be used. An oxide insulating layer may be formed on at least one side of the metallized plastic film. When forming an oxide insulating layer on a non-metalized surface, it is preferable to perform corona treatment on the non-metalized surface in advance. A capacitor element is constructed by laminating or winding these metallized plastic films. Further, at the end of the winding of the wound capacitor element, a thermoplastic stretched plastinoplast or ilm having a heat deformation temperature of 80° C. or lower is further wound as a protective film. The heat distortion temperature here is the value of ASTM De4a (1a, eKp/crA), which tests the bulk properties of plastic materials. If you pay attention to the heat distortion temperature, you can fully demonstrate the effect of the protective film. The winding core around which the wound capacitor element is wound is a winding core having a maximum surface roughness of 100 μm or less.

Function The present invention enables high potential gradient design of a capacitor with a self-protection function. In case of self-recoverable breakdown before final breakdown, the capacitor with self-protection function will not melt the current bus part and the electrode will scatter, resulting in clean SHL,
In addition, the current bus section is required to have a self-protection function by melting down in case of destruction to the extent that it leads to final destruction.

Conventional capacitors with a self-protection function having an electrode surface resistance of about 2 to 5 Ω/□ have a rated design potential gradient of about 60 v/μm as an upper limit. When the conventional type is raised to about 70V/μm, a large SH occurs, and although it does not lead to final destruction, the current path section is fused due to the large SH current, resulting in a large capacity reduction, making it impractical. It ends up. On the other hand, in the case of an electrode in which the metallicon side where the current bus part is provided is thicker and the margin side is thinner, the SH current becomes smaller when a high potential gradient is applied.
Not only does the current path portion not melt due to this small SH current, but there are many cases where the current path portion does not melt even at the time of final breakdown, making it difficult to call it a self-protection type. Furthermore, when the electrode is made of A2, the thinness of the electrode allows it to change from Au to Af at high temperatures! , 203 results in a large capacity reduction, which also makes it impractical.

On the other hand, in the case of uniformly thick electrodes whose sheet resistance falls within the range of 6 to 30 Q/m, the rated design potential gradient is 7.
Even in the case of 0v/μm, the current path part does not melt against self-recoverable damage, as in the case of conventional self-protecting capacitors with uniform thickness electrodes in the range of 2 to tsΩ/□. It has been found that, in the event of a breakdown that is severe enough to cause only the broken electrode to scatter and result in SHL, and final breakdown, the current bus part will melt and fully exhibit its self-protection function. In the case of the present invention, even though the current at the time of final breakdown is smaller than that of the conventional one, the current path portion is also thinner in the same way as the electrode. We believe this is because the bus section can be fused. Electrode surface resistance is 30
If it exceeds Q/mouth, contact with the metallicon becomes poor and Isnδ increases. Moreover, the long-term stability of the vapor-deposited electrode is poor, which is not preferable. In the present invention, an oxide insulating layer is formed on top of an electrode that can ensure good SH properties and self-protection function even under a high potential gradient. The thickness of the oxide insulating layer is preferably 50 to 1000. One way to activate the self-safety function is to scatter the vapor-deposited electrodes in a certain pattern through discharge treatment to form electrode divisions and current bus sections, but the two layers of the electrode and oxide insulating layer are oxidized. This is because the discharge treatment can be performed at once in the same way as in the case where there is no physical insulating layer. Moreover, if the number exceeds 1000, cracks are likely to occur. The oxide insulating layer is mainly an oxide insulating layer of an inorganic material such as a metal. The inorganic oxide insulating layer can be simply and dryly formed by vapor deposition, sputtering, or the like.

For example, Si○, Sin, glass, An203. Bo
o.

MgO, Ti○, T102, Ba○, CaO
, CeO2, Ta2O3゜Ta ○ , WO3, MoO
s, Zr021M002, etc., and the same applies to other inorganic oxide insulating layers. This oxide insulating layer has two major functions.

One is to cut off the supply of oxygen to the electrodes. In particular, when the electrode is 8λ, the capacity decrease is large especially in the life test at high temperature because the metal A2 is oxidized and changed to an insulator called 812o3. What prevents such oxidation of the electrode is an oxide/material insulating layer. This is because the electrode surface resistance cannot maintain its initial value unless it is an insulator, and organic substances are not stable and will eventually decompose and cause oxidation of the electrode.

The other one is to make it easier for the self-security function to function. In particular, when the dielectric is polypropylene (PP) and the electrodes are thin as in the present invention, the adhesion between the films is extremely poor, which is disadvantageous for SH. Electrode scattering due to SH is larger as there is a gap between films, and clean SH is generated. In other words, recovery of insulation properties is improved. The oxide insulating layer of the present invention has the function of reducing the adhesion between films when films having thin electrodes are present. Therefore, a small and clean SH is generated until the final breakdown occurs, but when the final breakdown occurs, since the adhesion is poor, a relatively large current flows and the current bus portion is fused. A capacitor using a film with an oxide insulating layer formed only on the metallized side of a single-sided metallized film, a capacitor using a film with an oxide insulating layer formed on the non-metalized side, and a capacitor using a film with an oxide insulating layer formed on the non-metalized side, and oxidation on either side. There is a difference in the SH number when an overvoltage is applied compared to a capacitor using a film that does not form an insulating layer. The SH number is highest when an oxide insulating layer is formed on both sides, and the SH number is lowest when an oxide insulating layer is not formed on both sides.

However, if the adhesion is increased by using a film that does not form an oxide insulating layer, the self-protection function may not function.

Observations have also been made that capacitors with an oxide insulating layer formed on their electrodes can also slightly suppress the occurrence of partial discharges. We believe that this is because the presence of the insulating layer suppresses electron emission from the electrode.

Since the adhesion between the film layers of the capacitor according to the present invention is slightly lower than that of a capacitor without an oxide insulating layer, it is necessary to tighten the end portion of the capacitor element firmly. For this purpose, a stretched film having a heat deformation temperature of 80° C. or lower, such as a PP film, is wound as a protective film. This is because the protective film needs to sufficiently tighten the capacitor element during vacuum high temperature aging at 80 to 110'C. polyethylene terephthalate(
Films combined with PET) or paper are not preferred.

Further, in the capacitor according to the present invention, the function of the oxide insulating layer is extremely large, and therefore, if this oxide insulating layer peels off or cracks occur, the effectiveness and shift will be significantly reduced. In this sense, the surface shape of the capacitor core is also an extremely important issue. For example, when using a plastic molded product for the winding core, special care must be taken, as the surface roughness of the molded product will vary depending on the plastic material, molding temperature, etc. Polybutylene terephthalate (PBT) molded products have particularly poor surface conditions, and in the case of capacitors made of the present invention, the film is crimped to the core by the tightening of the capacitor during high-temperature vacuum aging, and an oxide insulating layer is formed on the film near the core. Cracks are observed. Cracks tend to occur on uneven parts where the maximum surface roughness exceeds 100 μm, and cracks are not observed in PET molded products, glass tubes, and cores made by winding up plastic films without such unevenness. Ta.

In this way, the capacitor of the present invention exhibits little capacity loss in high-temperature life tests even under high potential gradients, and
This becomes a capacitor that can fully operate its self-safety function.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 illustrates the metallized plastic film of this example. The diagonal lines from the upper left to the lower right represent the deposited electrodes, and the diagonal lines from the upper right to the lower left represent the oxide insulation formed on the deposited electrodes. It represents a layer. At least one of the vapor-deposited electrodes constituting the capacitor is divided into divided electrodes 2 such that current path portions 1 and electrode division portions 3 are formed during or after vapor deposition to constitute a plurality of independent capacitance forming portions. In Fig. 1, an oxide insulating layer 5 is formed on the vapor deposited electrode and the margin 4, leaving the current bus part 1, in order to obtain good contact with the metallicon.However, if -δ is not too large, the current It may be formed on the entire vapor deposited electrode including the bus portion 1, or there is no problem if the margin 4 is formed by an oil margin and the oxide insulating layer 5 is difficult to be formed on the margin.

FIG. 2 is a sectional view taken along line AA' in FIG. 1, and shows a vapor deposited electrode 6 and an oxide insulating layer 5 formed on a glass film T. FIG. 3 is a sectional view taken along line BB' in FIG.

FIG. 4 is a cross-sectional view corresponding to the cross-sectional view taken along line A-A' in FIG. 1 when an oxide insulating layer is also formed on the non-metallized surface side, and FIGS. - A cross-sectional view corresponding to the cross-sectional view along the B' line, each showing the plastic film 7.
If the oxide insulating layer 5 is also formed on the non-metalized surface side of This shows the case where an oxide insulating layer is also formed thereon. A similar formation method is also applicable when a capacitor is constructed by a combination of a double-sided metallized film and a non-metalized film, and in any of these cases, it is not necessary to form an oxide insulating layer in the margin portion. FIG. 8 shows a conventional example of a single-sided metallized plastic film, in which a 2-5Ω pattern is applied on the plastic film 17 to have a self-protection function.
A vapor deposition electrode 16 of /□ is formed.

FIG. 9 shows an element of a wound type capacitor, and the winding core is a first-wound film winding core 8 made of plastic film. Figure 10 also shows the element of a wound type capacitor, in this case a hard core 9 made of plastic molded product.
is wrapped around.

In either case, the maximum surface roughness of the core surface of the cores 8 and 9 was 100 μm or less, and no cracks occurred in the oxide insulating layer. FIG. 11 shows a multilayer type capacitor element, in which case the ratio (pass ratio) of the width of the current bus portion to the length of the divided electrodes can be a factor of 100. In other words, the self-safety function operates even if the divided electrode width is kept in contact with the metallic contact without forming a special current bus section. FIG. 12 is an embodiment of the present invention.
The results of an 80'Q life test of a capacitor using double-deposited, single-sided metallized polypropylene film show that one film is treated with current bus sections and electrode splitting to exhibit a self-protection function, but the other film is not. The film thickness is 6 μm and the capacitor is 20 μF. O mark 10 indicates the characteristics of an example capacitor according to the present invention in which the oxide insulating layer is formed only on the metallized side, and Δ mark 11 also represents an example capacitor according to the present invention, in which the oxide insulating layer is formed only on the metallized side. The graph shows the characteristics when is formed on both the metallized side and the non-metallized side. 0 mark 12 indicates the characteristics when the oxide insulating layer is not formed on either surface, although the conditions are the same as ○ and Δ.

In either case, the electrodes are of uniform thickness and have an electrode surface resistance of 8 to 12 Ω/□. It can be seen that the capacitance of the capacitor marked 0 in which no oxide insulating layer is formed has a large capacitance reduction, whereas the capacitance of the example capacitor according to the present invention has a small capacitance reduction. Note that the applied voltage was 672v.

Table 1 summarizes the capacity reduction after an initial voltage withstand test of applying 660 V for 1 minute when a metallized plastic film is wound as an example of the present invention and the type of film wrapped around the outer periphery as a protective film is changed. It is something that

Table 1 The metallized plastic film was made of polypropylene film, the film thickness was 8 μm, the capacitance was 20 μF, and a voltage was applied at room temperature. With PET and paper, which have a high heat distortion temperature, the protective film does not shrink sufficiently during vacuum aging at 80 to 110 degrees Celsius, and the winding of the capacitor at the end of the winding is loose, resulting in a large decrease in capacity at the initial withstand voltage. ,
Capacity decrease during volupling is kept small. In the capacitor of the present invention, in which the adhesion between film layers is lower than that of conventional films, it is also an important requirement what kind of film is used as the protective film.

Next, the metallized plastic film of the present invention is wound around a core, which is a PBT molded product, having irregularities with a maximum surface roughness exceeding 100 μm, vacuum aged at 100°C, and then rewound to remove the metal near the core. The metalized plastic film and the metalized plastic film of the present invention are wound on a core on which a commercially available PET film of 38 μm is wound, vacuum aged at 100°C, and then rewound to remove the metalized plastic near the core. Comparing with film, if the surface of the winding core has large irregularities like a PBT molded product, cracks will occur in the oxide insulating layer and electrodes at those parts, which will become electrical weak points. In order for the present invention to fully exhibit its effects, the metallized plastic film on which the oxide insulating layer is formed must be wound around a core that does not have large irregularities, such as a core of a plastic film winding or a glass tube. is necessary.

In addition to the effects of the invention, the capacitor of the present invention makes it possible to design a capacitor with a high potential gradient that has a safety function, and can realize smaller size, lighter weight, resource saving, and lower cost, and its industrial efficiency is great. It is.

[Brief explanation of drawings]

Figure 1 is a developed view of a metallized plastic film of a capacitor showing one embodiment of the present invention, and Figure 2 is a diagram of Figure 1 A-A'.
3 is a sectional view taken along line B-B' in FIG. 1; FIG. 4 is a sectional view of a metallized plastic film in another embodiment of the present invention corresponding to FIG. 2; FIG. 7 to 7 are cross-sectional views of a metallized plastic film in other embodiments of the present invention corresponding to FIG. 3, and FIG. 8 is a cross-sectional view of a metallized plastic film in a conventional example corresponding to FIG. FIG. 9 is a perspective view of a capacitor wound around a first-wound film core in another embodiment of the present invention, and FIG. 10 is a perspective view of a capacitor wound around a plastic molded product core in another embodiment of the present invention. Perspective view, 11th
The figure is a perspective view of a multilayer type capacitor according to another embodiment of the present invention, and FIG. 12 is a life test characteristic diagram of the embodiment of the present invention and a conventional capacitor. 1... Current path part, 2... Divided electrode, 5...
... Oxide insulating layer, 6... Evaporated electrode, 7...-Plastic film, 8, 9... Winding core. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 2 Fig. 7 Arasura Takufilm Fig. 4 Fig. 8/Otsu Fig. 9 Fig. 10 Fig. 12 Fig. 12

Claims (4)

[Claims] (1) In a capacitor with a self-protection function, in which at least one electrode of the capacitor is made of a metallized plastic film and is composed of a plurality of divided electrodes, an electrode of uniform thickness with a sheet resistance of 6 to 30 Ω/□ is used. A capacitor with a self-safety function characterized by having the following features: (2) In a capacitor with a self-protection function in which at least one electrode of the capacitor is made of a metallized plastic film and is composed of a plurality of divided electrodes, an electrode of uniform thickness with a sheet resistance of 6 to 30 Ω/□ is used. What is claimed is: 1. A capacitor with a self-protection function, comprising: a metallized plastic film; an oxide insulating layer is formed over at least the metallized surface of the metallized plastic film; (3) In a capacitor with a self-protection function in which at least one electrode of the capacitor is made of a metallized plastic film and is composed of a plurality of divided electrodes, an electrode of uniform thickness with a sheet resistance of 6 to 30 Ω/□ is used. Stretched film comprising a metallized plastic film with an oxide insulating layer overlaid on at least the metallized surface, and a protective film wrapped around the outer periphery of the capacitor element made of thermoplastic plastic with a heat distortion temperature of 80°C or less. A capacitor with a self-safety function characterized by: (4) In a capacitor with a self-protection function in which at least one electrode of the capacitor is made of a metallized plastic film and is composed of a plurality of divided electrodes, an electrode of uniform thickness with a sheet resistance of 6 to 30 Ω/□ is used. an oxide insulating layer is formed over at least the metallized surface of the metallized plastic film, and the surface shape of the core material around which the metallized plastic film is wound has a maximum surface roughness of 10
A capacitor with a self-protection function characterized by having unevenness of 0 μm or less.