JPH06112089A - Film capacitor and manufacturing film thereof - Google Patents

Abstract

PURPOSE:To protect a film capacitor against corrosion as much as possible so as to prevent, it from deteriorating in capacitance due to corrosion by a method wherein ceramic oxide is evaporated on an aluminum thin film. CONSTITUTION:An aluminum thin film is evaporated on a film base F1 through an aluminum evaporator 16. Furthermore, oxides of one or more elements selected out of Si, Ti, Zr, Sn, Y, and indium-tin oxide are evaporated thereon as much as 0.1 to 10mg/m<2> preferably 0.3 to 3mg/m<2> through a ceramic evaporator 17. By this setup, ceramic oxide adheres concentrating on defective points (kinks, steps, others) imperfect in atomic arrangement on the surface of the aluminum thin film, so that the aluminum thin film can be locally enhanced in withstand voltage and improved in resistance to corrosion and breakdown strength at defective points. Therefore, 2 corona discharge hardly occurs between metal thin films, and the metal films are less corroded, so that a capacitor of this design can be elongated in service life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallized plastic film capacitor using aluminum or its alloy as a metal thin film and a film for producing the same, and in particular, an improvement for preventing corrosion of metal thin film. Regarding

[0002]

2. Description of the Related Art A metallized plastic film capacitor of this type is generally manufactured through the following steps. First, as shown in FIG. 3 (cross-sectional view in the width direction of the film), a non-deposited portion 4A having a constant width along a side edge is formed on the upper surface of the dielectric film base material 4 having a constant width and long.
Except for the above, a metal thin film 3 made of aluminum, zinc, or an alloy thereof is formed to form a first capacitor manufacturing film 1.

Next, like the film 1, a second capacitor manufacturing film 2 is formed by forming a metal thin film 5 on the upper surface of a dielectric film substrate 6 except for the margin non-deposited portion 6A. The margin non-deposited portions 4A, 6A are located on opposite sides, and the non-deposited portions 4A, 6A are overlaid on the first capacitor manufacturing film 1 so as to be located inward of the edge of the other film. .

Further, after winding the laminated film (1 + 2) into a cylindrical shape, electrodes 8 of zinc, solder, etc. are formed on both ends of the wound body 7 by a spraying method or the like, as shown in FIG.
A lead wire 9 is connected to each electrode 8 and the whole is covered with an exterior 10 to complete the product.

[0005]

By the way, when the metal thin films 3 and 5 are formed of aluminum or its alloy,
It has excellent corrosion resistance as compared with the case of using zinc, and has an advantage of excellent self-healing property because the film thickness can be reduced to about 50 to 70% of that of zinc. The self-healing property means that when a voltage breakdown occurs in the weak points of the film base materials 4 and 6 and the respective metal thin films 3 and 5 are short-circuited, the short-circuit current causes the metal thin films 3 and 5 around the destroyed parts to evaporate. It is the function of maintaining the function of the capacitor.

On the other hand, however, when aluminum is used, a weak corona discharge is liable to occur between the metal thin films 3 and 5, and the corona discharge causes a spot-like corrosion called Al ₂ O ₃ as a main composition. However, the effective area of the metal coatings 3 and 5 decreases at a rate faster than the loss due to self-recovery, and the rate of decrease of the capacitor capacity over time is large. It was

Therefore, the present inventors tried an experiment for preventing corrosion by coating the metal thin films 3 and 5 with various materials, and as a result, Si and T were deposited on the metal thin film.
It has been found that vapor deposition of oxides of i, Zr, etc. improves the withstand voltage of the metal thin film, reduces the frequency of corona discharge, and improves the corrosion resistance of the metal thin film.

Further, when the thickness of the ceramic protective film was variously changed and the withstand voltage property and the corrosion resistance were evaluated,
Even if the protective film is made as thin as 0.3 mg / m ² (mass film thickness of about 1.5 angstrom), which is considered to be a porous film instead of a dense film, the effect of improving withstand voltage and corrosion resistance can be obtained. I discovered a new phenomenon.

A large amount of corona discharge is generated in the Al thin film because a portion of the surface of the Al thin film having a large binding energy (kink, step, etc.) is bound to oxygen by Al.
It is considered that when the oxide grows and Al oxide having a high specific resistance is generated over a wide range, the voltage stress concentrates on that portion.

According to the studies by the present inventors, it is possible to prevent the generation and growth of Al oxide by bonding a ceramic oxide other than Al oxide to a portion of the surface of the Al thin film having a large binding energy. Therefore, even if the protective film is not a dense film but a porous film, it is presumed that the effect of improving the withstand voltage property and the corrosion resistance can be obtained.

On the other hand, in general, when the corrosion resistance of the metal surface is increased by using a SiO thin film or the like, the thickness of the SiO thin film is 10
It is well known that the effect of improving the corrosion resistance cannot be obtained unless it is set to about 100 Å or more. Further, the present applicant previously proposed in Japanese Patent Application No. 62-316513, a structure in which a SiO thin film is formed on a zinc vapor deposition film to enhance the corrosion resistance of the zinc thin film, but in the case of zinc, corrosion does not occur. It has been proved that the thin porous SiO thin film as described above cannot obtain the effect of improving the corrosion resistance.

The present invention has been made on the basis of the above findings, and an object thereof is to provide a film capacitor capable of preventing the occurrence of corrosion as much as possible and preventing the decrease of the capacitor capacity due to corrosion and a film for producing the same. There is.

[0013]

The constitution of the present invention will be specifically described below. In the film for producing a capacitor of the present invention, a metal thin film having at least its surface layer made of aluminum or an aluminum alloy is formed on the upper surface of a plastic film substrate, and Si, T is further formed on this metal thin film.
0.1-10 m of oxide of one or more substances selected from i, Zr, Sn, Y and indium tin oxide.
g / m ² , more preferably 0.3 to 3 mg / m ^{2 is} vapor-deposited.

Further, the film capacitor of the present invention comprises a winding body formed by winding two sheets of the above-mentioned capacitor manufacturing film so that the metal thin film and the film base material are alternately superposed, and each metal thin film. It is characterized by comprising a pair of electrodes respectively connected to each other, and a winding body and an exterior for sealing the electrodes.

As the film substrate, any substance that has been used for the same purpose can be used, and for example, polyethylene terephthalate, polystyrene, polypropylene, polycarbonate, polytetrafluoroethylene, polyethylene and the like are suitable. The thickness and width of the film substrate are arbitrarily set as needed.

The metal thin film is deposited by a vacuum deposition method or the like, and the thickness thereof is not limited, but preferably 50 to 50.
It is about 500 Å. Within this range, the self-healing property is good. Aluminum alloys that can be used as the metal thin film other than pure aluminum include Al.
-Zn alloy, Al-Ti alloy, etc.

When the amount of deposited ceramics is less than 0.1 mg / m ² , the oxide does not sufficiently adhere to the incomplete portions (kinks, steps, etc.) on the surface of the metal thin film, and the withstand voltage and Corrosion resistance cannot be increased sufficiently. In addition, when the amount of deposited ceramics is thicker than 10 mg / m ² , not only the vapor-deposited film may be thermally deformed but also the manufacturing cost is improved. As ceramics, Si, Ti, Z
It has been confirmed by the present inventors that the effect of the present invention is particularly good when an oxide of one or more substances selected from r, Sn, Y and indium tin oxide (ITO) is used. ing.

The film for producing a capacitor of the present invention can be produced, for example, by an apparatus as shown in FIG. In the figure, reference numeral 11 is an uncoiler in which a wide and long strip-shaped dielectric film base material F1 is wound and held; The nucleation vaporizer 14, the masking oil sprayer 15, the aluminum vaporizer 16, and the ceramic vaporizer 17 are arranged in this order from the uncoiler 11 side, and all of them are housed in a vacuum container (not shown).

In order to manufacture a film for manufacturing a capacitor with this apparatus, first, the uncoiler 11 to the vapor deposition drum 12 are used.
While moving the film base material F1 to the recoiler 13 through the above, a metal such as tin, silver or copper is vapor-deposited by the nucleation vaporizer 14. The metal thus deposited serves as a nucleus for subsequent aluminum deposition and promotes the formation of an aluminum thin film.

Next, the oil sprayer 15 sprays linear oil on the film base material F1 at equal intervals in the width direction, and the aluminum vapor deposition device 16 deposits an aluminum thin film on the film base material F1. Then,
Aluminum does not adhere to the oil adhered portion, and a strip-shaped non-deposited portion is formed. Furthermore, the ceramic vapor deposition device 1
The ceramic oxide is vapor-deposited on the aluminum thin film according to 7, and the product is rolled up by the recoiler 13. At this time, Si, Ti, Zr, Sn, Y, indium + tin itself may be used as the vapor deposition material instead of using the oxide ceramics as the vapor deposition material. In the case of the present invention, since the deposited film is extremely thin, these are converted into oxides during the deposition process.

According to the above-mentioned manufacturing method, the vapor deposition of the ceramic coating can be carried out in parallel with the vapor deposition of the metal thin film, so that the productivity of the film for producing a capacitor is not lowered and the cost is low. There is.

The obtained film for producing a capacitor includes
As shown in FIG. 2, since the non-deposited portions 18 are formed at regular intervals, at the time of use, they are cut along the arrow C in the figure, and two sheets are laminated and wound as shown in FIG. Further, as shown in FIG. 4, electrodes 8 made of zinc, solder or the like are formed on both ends of the wound body 7 by a melting method or the like, and lead wires 9 are connected to the respective electrodes 8, respectively, and the whole is covered with an outer package. 1
The product is completed by covering with 0. The shape of the capacitor is not limited to the cylindrical shape as shown in FIG. 4, and may be any conventionally used product shape.

[0023]

EXAMPLES Next, the effects of the present invention will be demonstrated with reference to examples. Using the vapor deposition machine shown in FIG. 1, vacuum degree 1 × 10 ⁻⁴ To
At rr, an aluminum thin film was vapor-deposited to a thickness of about 300 angstroms on a 3.7 μm-thick polyester film, leaving a non-deposited portion for margin, and SiO was then deposited to a thickness of about 0.3 mg / m ² . It was vapor-deposited.

The obtained film for producing a capacitor is shown in FIG.
In the same manner as described above, a film having a width of 8.5 and a length of 13.5 m was cut, and two films were stacked and wound to form a film capacitor having a structure shown in FIG. However, the exterior 10 is not formed. In addition, as a comparative example, a film capacitor was prepared in the same manner except that SiO was not vapor-deposited.

With respect to each of the 10 film capacitors of the example and the comparative example, a durability test was conducted under the following experimental conditions to examine the change with time of the capacitor capacity. Experimental condition: Test temperature / humidity: 70 ° C. 80% RH accelerated experiment (C = 0.5 μF) The results are shown in Table 1.

[0026]

[Table 1]

As shown in the above table, the capacitance of the capacitor of the practical example hardly changed, while the capacitance of the capacitor of the comparative example decreased by almost 8%. When the capacitors were disassembled after the test was completed, the metal thin film of the comparative example had 5
While 15% was corrosive, the metal thin film of the example was not corrosive at all.

[0028]

As described above, the film capacitor and the film for producing the same according to the present invention are provided with a metal thin film made of aluminum or an aluminum alloy on the upper surface of a long plastic film base. An oxide of one or more substances selected from Si, Ti, Zr, Sn, Y, and ITO is added on the top of 0.1 to 10.
Since 10 mg / m ^{2 is} vapor-deposited, the ceramic oxide is concentrated on the surface of the metal thin film where the atomic arrangement is incomplete (kinks, steps, etc.), and the voltage resistance and corrosion resistance of the incomplete area are localized. Improve to. Therefore, corona discharge is less likely to occur between the metal thin films, the occurrence rate of corrosion can be reduced, and the life of the capacitor can be extended. Furthermore, since the metal thin film can be made thinner because corrosion is less likely to occur, it is possible to improve self-healing property as compared with the conventional product.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus for producing a film for producing a capacitor according to the present invention.

FIG. 2 is a plan view showing an example of a film for producing a capacitor of the present invention.

FIG. 3 is an enlarged cross-sectional view of a conventional capacitor manufacturing film.

FIG. 4 is an explanatory diagram of a conventional film capacitor.

[Explanation of symbols]

 F1 Film substrate F2 Capacitor manufacturing film 11 Uncoiler 12 Evaporation drum 13 Recoiler 14 Nucleating vaporizer 15 Masking oil sprayer 16 Aluminum vaporizer 17 Ceramic oxide vaporizer

Claims (2)

[Claims] 1. A surface of a plastic film substrate,
A metal thin film made of aluminum or an aluminum alloy is provided, and Si, Ti, Zr, Sn,
A film for producing a capacitor, comprising 0.1 to 10 mg / m ^{2 of} an oxide of one or more substances selected from Y and indium tin oxide. 2. A winding body formed by winding two sheets of the film for producing a capacitor according to claim 1 so that the metal thin film and the film base are alternately arranged, and each metal thin film. A film capacitor, comprising: a pair of electrodes respectively connected to each other, and a winding body and an exterior covering the electrodes.