JPS61194813A - Metalized plastic film capacitor - 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 Field of Industrial Application The present invention relates to a dry capacitor used mainly for communications and electrical equipment.

Conventional technology Conventional dry capacitors are made of polypropylene (PP), polyethylene terephthalate (PET), polystyrene (
Aluminum (Aj or Zinc (Z)
n) was vapor-deposited to form an electrode, which was then wound to form a capacitor element, or an A2 foil electrode was wound together with a film to form a capacitor element. In the case of vapor-deposited electrodes, metallicon is applied to the capacitor element thus created, a lead wire is welded or soldered to the metallicon, a terminal fitting is attached to the tip of the lead wire, the capacitor is stored in a capacitor case, and resin is poured onto the capacitor element and lead wire. It was mold hardened and made into a resin mold type. In addition, an electrode structure has been proposed in which the resistance value of the vapor-deposited electrode is lower on the electrode lead-out side and higher on the margin side (that is, the electrode lead-out side is thicker and the margin side is thinner), and the energy during self-recovery is kept low, making it difficult to damage the capacitor. things were being done. However, with conventional dry capacitors, partial discharge occurs when a voltage of around 260 V or more is applied to the capacitor, and it is extremely difficult to provide a dry capacitor with a rated voltage of around 400 V or more with a potential gradient of 65 v/μ or more. Met. It was thought that this was because corona discharge occurs continuously during actual use, which causes the dielectric film to deteriorate and break down. If the evaporation electrode is A1, in addition to that! The electrode disappeared in the form of water droplets, resulting in a capacity reduction that exceeded the standard, resulting in an inconvenient result similar to destruction.

Considering that these causes are due to corona discharge, SiO or S was added to give the plastic film corona resistance.
Some proposals have been made to deposit 102 onto plastic films by vapor deposition or sputtering. Japanese Patent Publication No. 52-240 discloses a method for producing an electrically insulating material in which 1 to 1.5 μm of SiO, SiO, or Ca is deposited on an insulator of polyethylene terephthalate, polyimide, or polycarbonate foil or polyamide plastic fiber.
It has been proposed to deposit films of inorganic electrically insulating materials, such as F2, by evaporation or sputtering. In this prior document, SiO was formed on the surface of polyethylene terephthalate foil.
An inorganic film of about 1 to 1.6 μm was deposited on the conductor plate, and a rod electrode was placed across a 5 g gap.
An AC voltage is applied between the conductor plate and the rod electrode to generate a concentrated corona, and the withstand voltage with and without an inorganic film is compared. According to K, the case with an inorganic film has the withstand voltage for twice as long. Furthermore, Japanese Patent Application Laid-Open No. 49-46200 discloses a method in which a corona shield layer containing silicon carbide mixed in an insulating face is provided in order to improve the visible corona starting voltage, and an insulating film layer is formed on the surface of the corona shield layer so as not to entrain air. is proposed.

In addition, in Japanese Patent Application No. 149788/1988, 10 to 1
oooo We are proposing a method of forming a silicon oxide film. According to this, 10 to 100 people are placed on the lower plate electrode.
An organic film to which a silicon oxide film of 0.00000000000000000000000000000 is attached is placed, a perforated organic film is placed on top of this, and an upper flat plate electrode is arranged to sandwich these films, and an alternating current voltage is applied. The characteristics of the time taken to break down at a voltage higher than the corona starting voltage were investigated, and it was shown that the silicon oxide film can withstand 5 to 10 times longer.

Our experiments show that the silicon oxide films that have been proposed in the past can extend the lifespan of plastic films by 2 to 10 times.
Even if the thickness is 4000 Å or more, the lifespan will not be extended indefinitely.

In our experiments, when the silicon oxide film is less than 1000 Å, the longevity of the plastic film in the electrode configuration of the above-mentioned reference hardly appears. This is thought to be because the silicon oxide film scatters and disappears in a very short time due to the discharge energy when corona discharge occurs, and is not useful for improving corona resistance. Also 30o
Even in the case of a thick film of O ~ 4000 Å or more, the reason why it is several times or less is due to cracks that occur in the silicon oxide film, and the higher the voltage, the lower the discharge energy. This occurs in a short period of time, and the plastic begins to deteriorate from this cracked area, leading to destruction. Conventionally, oxidized silicon was applied to the surface of such plastic films.
The reason why films with J3 coatings were not put into practical use as films for capacitors, for example, were still at the idea stage, because while the costs were extremely high, their corona resistance was constantly improving. Due to this, dry capacitors with conventional structures were not put into practical use because large corona discharges were unavoidable.

Furthermore, it has been thought that corona deterioration becomes more pronounced in the presence of oxygen, and among other plastic materials, PP's corona resistance is particularly poor. Table 1 shows the order of corona resistance of plastic films, and is numbered in descending order of corona resistance. (IEEJ Technical Report (Part 1) No. 74, 1966) Table 1 As shown in Table 1, the corona resistance of PP film is poor;
In recent years, PP films have come to be used in large quantities for capacitors due to their excellent dielectric properties, and have come to be widely used not only in oil-immersed capacitors but also in dry capacitors.

In particular, the good dielectric properties of PP cannot be ignored when increasing the capacitance of capacitors and using films with high potential gradients.
The development of a PP film dry capacitor that can be used in both directions has been awaited.

Problems to be Solved by the Invention The present invention is designed to prevent capacitance reduction or destruction of a dry capacitor even when the potential gradient used is 65 V/μ or more.

Means to Solve the Problems To solve this problem, in the present invention, electrodes are formed on one side of a polypropylene film, with a low resistance part of 10Ω/□ or less on the electrode lead-out side (metallicon side) and a high resistance part of 20 to 200Ω/square on the margin side. The high resistance part is formed by evaporating zinc so that the width is at least W or more than the electrode width.
iO2t A 12203. B e○.

MgO, TiO, TiO2, BaO, CaO, CeO2
, Ta2O3゜Ta 20. , WO3, MoO2, Zr
O□ or M o O2t7) A metalized plastic film is formed by forming at least one metal oxide insulating layer, and a fixed amount of a pair of this m-built metal plastic film is wound around the outer periphery of the roll. The capacitor element is constructed by winding either a protective film made of cellulose fiber or glass fiber reinforced plastic. After this, apply metallicon, 1
Aging under reduced pressure at 20°C to 140°C. The pressure at the time of decompression is preferably 0.01 Torr or less. From then on, the process is the same as manufacturing conventional dry capacitors; the lead wires and terminal fittings are attached to the case, and the resin is poured and cured to complete the capacitor.

Function: In the capacitor of the present invention, corona discharge occurs significantly and K
It is characterized by its sharpness. In addition, there are cases where almost no corona discharge is detected during the life test. There is almost no decrease in capacity, and it can withstand a potential gradient of 90V/μ.

This is presumed to be due to the following effect.

(1) The protective film of paper, cellulose, or glass fiber reinforced plastic wrapped around the outer circumference of the capacitor element greatly suppresses the thermal expansion and contraction of the metallized PP film wrapped inside during high-temperature vacuum aging. It is possible to improve the adhesion between film layers after aging. This is because the protective film hardly undergoes thermal deformation, and compared to when a normal plastic film is used as a protective film, the expansion of the round capacitor in the radial direction at high temperatures is suppressed by strong pressure. This is because shrinkage in the axial direction is suppressed, and the film layers are pressed together while air and moisture between the film layers are also removed by reducing the pressure.

(2) Since the zinc-deposited surface is divided into a low-resistance part and a high-resistance part, and the high-resistance part is on a bar plate with the width of the electrode, the low-resistance parts overlap each other as in the case of conventional electrodes. In addition, when the film layers are brought into close contact with each other as mentioned above, there is a difference between a thick zinc layer and a thin zinc layer. A thinner zinc layer results in better adhesion. This has been confirmed by detecting the amount of corona discharge, where the amount of corona decreases significantly when the discharge is thin. In addition, it has been found that making the electrode thinner is effective when increasing adhesion in this way, but when the metal is A1, as has been attracting attention in recent years, even if no corona discharge is observed due to corrosion, it is possible to reduce the electrode thickness to Aλ2o3. As a result of this change, the electrode becomes transparent in the shape of a water drop and no longer functions as a stain electrode, resulting in a large decrease in capacity. Therefore, in order to increase the adhesion between the film layers and suppress the decrease in capacity, it is necessary to use zinc as an electrode material and make it thin. This is because even if zinc changes to ZnO, its conductivity does not decrease in the case of 812o3, so that it can function as an electrode.

(3) The function of the 50A to 1000A metal oxide insulating layer is currently unknown, but if this insulating layer is not present, sudden corona discharge will occur even if no corona discharge is observed after a long life test. dielectric breakdown occurs. Further, according to the evaluation test in the cited reference, when the metallized plastic film according to the present invention is exposed to corona discharge from the surface of the metal oxide insulating layer, its corona resistance is almost the same as that without the insulating layer. On the other hand, a capacitor was made by depositing An on a PP film, forming a metal oxide insulating layer on it, and leaving nothing attached to the other surface of the PP film. It was found that A12o3 was generated and the capacity decreased. However, in the capacitor of the present invention, neither capacitance reduction nor dielectric breakdown occurred, indicating that pp is less susceptible to deterioration.

Estimating from these facts, it is considered that the metal oxide insulating layer functions not as a strong protective film against corona, but as a limiting film for oxygen molecules, oxygen ions, or moisture. In the case of metal A2, regardless of the presence or absence of corona, these substances are limited to some extent by the metal oxide insulating layer, and even if the amount reaching the metal surface is reduced, the A2 degree is sufficient.
3, but in the case of PP, this is insufficient to cause oxidative deterioration of this, and therefore it is thought that deterioration of PP is less likely to occur.

However, if the thickness of the metal oxide insulating layer is 500Å or more, defects such as cracks are likely to occur during the production of a continuous film, and if the thickness is within the range of 2000A to 5000A, this problem will not occur, but during the heat cycle of the capacitor. 1000, which is resistant to heat cycles, starts to become effective in stabilizing the characteristics.
It is necessary to suppress the film thickness within the range A.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a model diagram of the metallized plastic film capacitor of the present invention. An electrode having a low resistance part 2 of 10 Ω/□ or less on the metallicon 6 side and a high resistance part 3 of 20 to 200 Ω/square on the margin 6 side is formed on one side of the polypropylene film 1 by zinc evaporation, and on the other side. 60-100
A pair of metallized plastic films formed with a metal oxide insulating layer 4 is wound. FIG. 2 shows a cross section of a metallized plastic film capacitor according to the present invention. The winding core 1o is a plastic molded product or a thick polyethylene terephthalate film wound several turns.A metallized plastic film 7 according to the present invention is wound onto the winding core, and paper, cellulose fiber reinforced plastic, or A protective film 8 made of glass fiber reinforced plastic is wound around the protective film 8, and metallized silicone 9 is applied to both ends thereof to form a capacitor element. Figure 3 shows PP as a capacitor of the present invention.
The thickness of the film is 7.6μ, the low resistance part is 4 to 6Ω/hole, the high resistance part is 30 to 6oΩ/hole, the protective film is paper (the laminated thickness of paper is preferably 0.2m or more), and metal oxide insulation is used. 13 in which the layer is made of approximately 250 SiO layers, and 2 in which the layer is made of approximately 250 SiO layers.
It shows the change over time in the maximum amount of discharged charge for the case 14 formed by 60 8102 persons and the case 16 formed by about 250 T102 persons. Conventional type PP film thickness 9μ
AI! The maximum discharge charge of the capacitor 11 whose electrodes are formed by vapor-depositing Zn at 2 to 4 Ω/hole and the capacitor 12 whose electrodes are formed by vapor-depositing Zn at 3 to 4 Ω/hole is large, 1000 In both cases, destruction occurred within a certain amount of time. On the other hand, the capacitor of the present invention has a structure in which corona discharge is extremely difficult to occur, and the amount of discharge tends to decrease with time after energization, so that destruction does not occur. still,
The test in Figure 3 was conducted at room temperature and was applied at eooV for conventional type capacitors and 500V for capacitors of the present invention.
This is the result of applying a voltage of 66.7 in both cases.
The potential gradient is V/μ. All capacitances are 20μ
It is F. Further, in FIG. 3, corona discharge of 3001)C or less could not be detected due to the influence of noise, but even conventional type capacitors are hardly deteriorated at this level of discharge amount.

Effects of the Invention As described above, according to the present invention, it is possible to provide a dry capacitor that can be used satisfactorily even under conditions of potential gradient and capacitance that conventional capacitors could not withstand.

[Brief Description of the Drawings] Fig. 1 is a model diagram of a capacitor in an embodiment of the present invention, Fig. 2 is a cross-sectional view of the capacitor element, and Fig. 3 is a diagram showing changes over time in the maximum discharge amount of the capacitor. It is. 1...pp film, 2...Zrx vapor deposited electrode (low resistance part), 3...Zn vapor deposited electrode (high resistance part), 4...metal Oxide insulating layer, 5...
...Metallicon, 6...Margin, 7...
... Metallized plastic film and metal oxide forming film roll, 8... Protective film, 9...
...Metallicon, 1o... Winding core.

Claims (1)

[Claims] 1 on the metallicon side on one side of the polypropylene film.
An electrode having a low resistance part of 0 Ω/□ or less and a high resistance part of 20 to 200 Ω/□ with a width of at least 1/2 or more of the electrode width on the margin side is formed of zinc, and A pair of metalized plastic films with a metal oxide insulating layer of 60 to 1000 Å on the other side are wound around the outer periphery of a pair of metalized plastic films made of paper, cellulose fiber reinforced plastic, or glass fiber reinforced plastic. A metallized plastic film capacitor characterized by having a capacitor element formed by winding a film.