JP2018157055A - Metallized film for capacitor and capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallized film for a capacitor and a capacitor using the same capable of obtaining high moisture resistance.SOLUTION: A metallized film obtained by forming a metal layer on one side of a polypropylene film is a metallized polypropylene film for a capacitor in which a silicone oil layer or a fluorine oil layer of 0.02 to 0.2 μg/cmis formed on the surface of the metal layer, and a wetting index is 33 to 50 mN/m, a wetting index of the surface opposite to the metal layer of the polypropylene film is 33 to 45 mN/m, and the charge amount is in the range of -15 to +15 V.SELECTED DRAWING: None

Description

  The present invention relates to a metallized film for a capacitor and a capacitor using the same.

  Conventionally, capacitors using an organic polymer film as a dielectric have been widely used. For example, as exemplified in Patent Document 1 and Patent Document 2, a metal layer is formed by alternately winding a polyester film and a metal foil, or performing metal vapor deposition on the film, and winding the film. Or the technique of obtaining a capacitor | condenser by laminating | stacking is known.

  When a metal layer is formed on a film by vacuum deposition, aluminum or zinc is generally widely used as a metal to be used in terms of ease of deposition, cost, and electrical characteristics.

  A capacitor using a film having a thin metal layer as described above has a problem that the metal thin film is oxidized under high temperature and high humidity, the capacitor capacity gradually decreases, and finally cannot be put into practical use. In order to improve the problem of moisture resistance, as exemplified in Patent Document 3, a technique for forming an organic compound on a deposited layer is known.

  Conventionally, in the technique exemplified in Patent Document 3, for example, a metallized film is wound in an element, and the adhesiveness between film layers formed in the process of forming a capacitor element by pressing or heat treatment is not sufficient, and a fine gap is formed. As a result, it has been found that wet air enters from the end surface of the metallicon of the capacitor and oxidizes and degrades the metal layer.

JP-A-63-182351 JP 63-194318 A JP-A-10-128908

  With the conventional methods as described above, moisture resistance has become insufficient with the recent severe use of electronic components.

  In view of the background of such prior art, the present invention is to provide an excellent metallized film for a capacitor having extremely high moisture resistance, and a capacitor using the same.

  As a result of intensive studies by the inventors, by making each surface of the metallized film a specific range, it is possible to ensure adhesion between layers and improve moisture resistance when evaluated as a capacitor element. This is what we have achieved.

The present invention employs the following means in order to solve such problems.
That is, it is a metallized film formed by forming a metal layer on one side of a polypropylene film, and a 0.02-0.2 μg / cm ² silicone oil layer or fluorine oil layer is formed on the surface of the metal layer. And a wetting index of 33 to 50 mN / m, a wetting index on the side opposite to the metal layer of the polypropylene film is 33 to 45 mN / m, and a charge amount is in the range of −15 to +15 V. It is a film.

  ADVANTAGE OF THE INVENTION According to this invention, the metallized film for capacitors which can acquire the extremely high moisture resistance which was not obtained conventionally can be provided. According to the present invention, the film capacitor can cope with a more severe environment.

  In the metallized film for a capacitor of the present invention, a polypropylene film is used as the dielectric of the capacitor. Polypropylene film is suitable for securing moisture resistance as a capacitor because of its high withstand voltage and low water absorption. The polymer used for the polypropylene film of the present invention may be a copolymer of propylene and another α-olefin (for example, ethylene, butene, etc.) in addition to a homopolymer, and may be a polypropylene and another α-olefin polymer (for example, A blended product with polyethylene, polybutene, etc.) may be used. In the present invention, a homopolymer is particularly preferred, and the isotactic degree (hereinafter referred to as II) is particularly preferably 96% or more. A simultaneous or sequential biaxially stretched film is preferred, but a uniaxially stretched or unstretched film may also be used.

  The polypropylene film in the present invention preferably has a surface roughness Ra of 0.01 to 0.10 μm, more preferably 0.02 to 0.07 μm. An additive may be added to the polypropylene film in the present invention in order to impart surface formation, oxidation prevention, and other functions.

  Although the thickness of the polypropylene film used by this invention is not specifically limited, The range of 0.5 micrometer-20 micrometers is preferable. By making thickness into this range, the effect of this invention can be exhibited more highly. More preferably, the thickness of the polypropylene film is in the range of 0.7 μm to 13 μm, and more preferably in the range of 1.0 μm to 6 μm.

  The metallized film of the present invention has a metal layer on at least one side of the film. The method for forming the metal layer is not particularly limited. For example, it can be formed using a method such as vapor deposition, sputtering, ion plating, or plating. Industrially preferred is a metal layer formed by vacuum deposition. When the vacuum deposition method is used, the film of the present invention can be produced efficiently.

  Preferred examples of the material for the metal layer in the present invention include aluminum, zinc, tin, nickel, chromium, iron, copper, titanium, and alloys containing these. From the viewpoint of the electrical characteristics and productivity of the capacitor, zinc, aluminum, or an alloy containing them is preferably used. More preferably, the metal layer contains 90% by mass or more of aluminum. Specifically, it is preferable from the viewpoint of moisture resistance to use aluminum alone or an aluminum alloy containing 90% by mass or more of aluminum.

  The thickness of the metal layer is preferably 1 to 100 nm. In particular, the thinner the metal layer, the more preferable the vapor deposition film according to the prior art, since the electrode deterioration under high humidity is accelerated, so that the effect of the present invention is remarkably exhibited. Preferably it is 1-40 nm. If it is thinner than 1 nm, the film resistance becomes too high, which may affect the electrical characteristics of the capacitor.

  The film resistance of the metal layer is preferably in the range of 0.5 to 50Ω / □, more preferably 1.5 to 40Ω / □, and further preferably 3 to 30Ω / □. If the film resistance is less than 0.5Ω / □, the original capacitor characteristics may not be obtained, for example, a self-healing failure occurs and the insulation resistance deteriorates. On the other hand, if it exceeds 30Ω / □, the series equivalent resistance may increase and the dielectric loss tangent (tan δ) may deteriorate. The film resistance can be controlled within the above range by controlling the thickness of the metal layer and selecting the metal species.

The metallized film of the present invention needs to have a 0.02-0.2 μg / cm ² silicone oil layer or fluorine oil layer formed on the surface of the metallized film on the metal layer side. The silicone oil or fluorine oil according to the present invention has a role of covering the metal layer and protecting the metal layer from moisture. Although not particularly limited, preferred examples include perfluoroalkyl polyethers, dimethylpolysiloxanes, and methylphenyl silicones.

  As the silicone oil, dimethylpolysiloxane or methylphenylsilicone oil is preferable, and methylphenyldimethylpolysiloxane is particularly preferable from the viewpoint of moisture resistance. As the organic-modified silicone oil, alkyl-modified silicone oil, fluorine-modified silicone oil, alcohol-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil and the like can be preferably used.

The thickness of the silicone oil layer or fluorine oil layer is preferably 0.02 to 0.2 μg / cm ² , more preferably 0.03 to 0.1 μg / cm ² . If it is less than 0.02 μg / cm ² , the moisture resistance is not exhibited remarkably, and if it is 0.2 μg / cm ² or more, the element winding property of the capacitor may deteriorate.

  In the present invention, the method for adhering a silicone oil layer or a fluorine oil layer (hereinafter referred to as an oil layer) to the film is not particularly limited. For example, the solvent component is evaporated after being diluted with an organic solvent and applied with a slit die coater. For example, a method of evaporating and spraying a heated substance from a dot-like or fine slit-like nozzle can be used as long as it is vaporized by heating in a vacuum. The latter method is preferable because, for example, when a metal layer is formed by vacuum vapor deposition, an oil layer formation step is provided in the vacuum vapor deposition machine, so that there is an advantage of good productivity and an oil layer can be formed with high uniformity. .

  In the metallized film of the present invention, the wettability index of the metal layer side surface of the metallized film needs to be 33 to 50 mN / m, and the metallized film of the present invention is a metal layer of the metallized film. It is necessary that the wetting index of the opposite surface is 33 to 45 mN / m.

  Originally, the surface activity of the surface of the deposited metal layer, that is, the wetting index is high, and in aluminum, the value is 54 mN / m or more. By forming a silicone oil layer or a fluorine oil layer as exemplified above on this, the wetting index generally decreases, and may be 22 or less if some types of fluorine oil with high water repellency are used. .

  In order to form these oils as an oil layer, and to make the wetting index of the surface on the metal side within the scope of the present application, a polymer containing many OH groups, COOH groups, C═O bonds and other polar groups is included in the oil layer. Either select the material, or after forming the oil layer, perform plasma discharge treatment to activate the surface and introduce polar groups, or perform corona treatment in the air or in an oxygen or nitrogen atmosphere. The method to introduce is mention | raise | lifted.

In the case of forming a metal layer and then an oil layer in a vacuum evaporator, it is most preferable in terms of production efficiency to perform plasma discharge treatment in a vacuum vapor deposition machine. In this case, as the material for the oil layer, it is preferable to select a material having a wetting index of 25 to 33 mN / m when formed into a film.
In order to improve moisture resistance, the wetting index of the surface of the metallized film on the metal layer side is more preferably 33 to 45 mN / m, and further preferably 34 to 40 mN / m.

  For the surface opposite the metal layer side of the metallized film of the present invention, the wet index of the untreated polypropylene film is 30-32 mN / m, and in order to make this within the scope of the present application Means can be applied. Most commonly, the corona treatment is performed in air or in an oxygen or nitrogen atmosphere. However, if corona treatment is performed on both sides of the polypropylene film before vapor deposition, there is a concern of blocking each other when wound up. As a preferable means, during vacuum deposition, plasma discharge treatment is performed in vacuum to activate the surface and introduce polar groups, or after forming a metal layer, corona in the atmosphere or in an oxygen or nitrogen atmosphere. There is a method for performing the processing.

  The wetting index of the surface opposite to the metal layer side of the metallized film of the present invention is more preferably 34 to 40 mN / m, and even more preferably 34 to 37 mN / m. It is preferable in order to improve and thus improve moisture resistance.

  The metallized film of the present invention needs to have a charge amount in the range of −15 to + 15V. By setting the amount of charge within this range, the handling performance when winding the element is improved, and the film moves freely (slips) to some extent without being stuck due to charging during press or heat treatment, resulting in a result. As a result, it is possible to reduce wrinkles and gaps inherent in the capacitor element, prevent moisture from entering from the fine gaps as described above, and improve moisture resistance.

  Next, although one aspect | mode of the manufacturing method of the metallized film of this invention is described below, this invention is not limited to this.

  The polypropylene film is unwound from the unwinding shaft in the vacuum vapor deposition machine and guided to the cooling drum. While the polymer film is cooled on a cooling drum, it is heated and melted from an evaporation source by an induction heating method, a resistance heating method, an electron beam method, etc., and the flying metal is deposited. After the cooling drum, a container provided with a thin slit-shaped nozzle is arranged, and a substance that becomes an oil layer is heated, evaporated, and sprayed therein. By directing this nozzle toward the polymer film, an oil layer is formed on the surface.

  Subsequently, plasma discharge treatment is simultaneously performed on the metal layer side and the opposite surface side in a vacuum. It is important that the plasma discharge electrodes have the same shape and structure as possible so as to face each other so as to be sandwiched between the passing films. Thereby, it is possible to prevent the charge distribution during the plasma discharge treatment from being biased to either positive or negative, and the charge amount of the film can be controlled within the range of the present application.

This is the intermediate product wound by the winding shaft of the vapor deposition machine. The intermediate product is slit to a predetermined width to obtain a reel-like film.
In the plasma discharge treatment, a gas is locally introduced around the electrode. Although the kind of gas used is not specifically limited, For example, O2, Ar, CO, CO2 etc. are mentioned. Particularly preferred is O 2, Ar, or a mixed gas containing one or more of these.
In this case, it is preferable that the processing power density is 5 W · min / (m ² · single side) or more in order to control the film characteristics within the scope of the present application, and the processing power density on the metal layer surface and the opposite surface is the same. It is preferable to do this. More preferably, it is 10-30W * min / (m < ² > * single side | surface).

  Further, it is preferable to use a copper, titanium, aluminum, or stainless steel electrode for the plasma discharge electrode. In order to control the characteristics within the range of the present invention, the plasma discharge power source is preferably a pulsed DC power source, and the frequency is preferably 200 to 500 kHz.

  The metallized film thus obtained can be preferably used as a capacitor film, and can be laminated or wound by a known method to obtain a capacitor.

For example, the case of a wound film capacitor is illustrated. In the step of forming the metal layer on the above-described film, the metal layer is deposited in a stripe shape having a margin portion running in the longitudinal direction. Next, a blade is put in the center of each vapor deposition part on the surface and the center of each margin part and slit to form a tape-shaped take-up reel having a margin on the left or right side. Of the obtained reels, a little of the film with a margin on the left side and one film with a margin on the right side are slightly placed so that the film end surface on the non-margin side protrudes from the film end surface on the margin side in the width direction. Shift and superimpose and wind to obtain a wound body. The core material is removed from the wound body and pressed, and the metallicon is sprayed on both end faces to form external electrodes, and a lead wire is welded to the metallicon to obtain a wound capacitor element.
[Methods for measuring physical properties and methods for evaluating effects]
(1) Oil quantity Fluorescent X-ray analyzer Using a ZSX Primus II manufactured by Rigaku Denki Kogyo, the sample is cut to about 3 cm square, and measured by fluorescent X-ray analysis in a measurement atmosphere vacuum at a measurement spot diameter of 30 mm. went.

(2) Wetting index It measured according to JIS K-6768 (1999).

(3) Charge amount Using a surface potential meter S-211, manufactured by Kawaguchi Electric Mfg., Place the metallized film on a grounded aluminum plate with the metal layer side facing down, and measure the charge amount. did.

(4) Metal layer thickness ESCA analysis is performed from the surface of the metal layer while etching with argon ions under the following conditions to obtain an elemental composition profile in the depth direction. The point where the metal element is 50% or less is defined as the interface, and the distance (depth) from the surface to the interface is defined as the metal layer thickness. The etching rate was measured in advance by treating SiO ₂ under the same conditions and measuring the etching amount with a shape measuring machine, and the etching amount was converted from the etching rate of SiO ₂ .
Ion species: Argon ion beam intensity: 3 kV, 10 mA.

(5) Total thickness of metallized film According to JIS C 2151, the thickness of 10 metallized films was measured with an electronic micrometer, and the average of 5 points was divided by the number of metallized films (10). It was set as the film thickness.

(6) Aluminum ratio After 9 cm ^{2 of the} metallized film sample was dissolved in dilute nitric acid, it was dissolved in 20 ml, and the composition of each metal was determined by ICP emission spectroscopic analysis. As an ICP emission spectroscopic analyzer, SPS1200VR manufactured by Seiko Denshi Kogyo was used.

(7) Membrane resistance The resistance of a metal film between 100 mm electrodes was measured by a four-terminal method, and the measured value was divided by the measurement width and the distance between the electrodes to calculate the membrane resistance per 10 mm width and 10 mm distance between the electrodes. . The unit is displayed as Ω / □.

(8) Moisture resistance The obtained metallized film was wound around the following conditions to obtain a film capacitor. A high-temperature and high-humidity life test was performed by applying a DC voltage of 100 V / μm in an atmosphere of 95 ° C. × 85% RH with no exterior. In the average of 10 samples, the electrostatic capacity at 0 hour was defined as 100%, and the retention capacity of the electrostatic capacity after 1000 hours was determined as 90% or more as good and less than 90% as defective.
Capacitance: 1μF
Press temperature, pressure, time: 120 ° C., 30 kg / cm ² , 10 minutes Metallicon material: Teikoku Metal Industry TM801CN.

  Hereinafter, the present invention will be described in detail based on examples.

[Example 1]
On a polypropylene film having a thickness of 3.0 μm (“Torphan (registered trademark)” # 3E-Q273 manufactured by Toray Industries, Inc.), a film having a film resistance of 10Ω / cm is continuously formed by vacuum deposition at a line speed of 400 m / min. Vapor deposition was performed so that □ Next, phenylmethyldimethylpolysiloxane oil (SH702 made by Toray Dow Corning Silicone) was heat-deposited on the same surface (metal deposition surface). Subsequently, plasma electrodes are arranged evenly on both sides, and a plasma discharge treatment is performed on both sides by generating a 250 kHz, 4 kW plasma discharge using a pulsed DC power supply while supplying a small amount of O2 gas (processing power density E = 8 W). * Min / (m < ² > * single side)), this was wound up by the winding shaft and the aluminum vapor deposition film was obtained. Here, the amount of oil deposited was controlled so that the amount of oil adhesion was 0.05 μg / cm ² . When the above-mentioned moisture resistance evaluation was performed, the capacitance retention was 98% and the moisture resistance was good. The results are shown in Table 1.

[Example 2]
An aluminum vapor-deposited film was obtained in the same manner as in Example 1 except that the treatment power was adjusted and the treatment power density was 4 W · min / (m ² · single side). When the same moisture resistance evaluation as that of Example 1 was performed, the capacitance retention was 95% and the moisture resistance was good. The results are shown in Table 1.

[Comparative Example 1]
An aluminum vapor-deposited film was obtained in the same manner as in Example 1 except that the plasma discharge treatment was performed only on the metal layer surface and the treatment power density was 20 W · min / (m ² · single surface). When the same moisture resistance evaluation as that of Example 1 was performed, the capacitance retention was 80% and the moisture resistance was poor. The results are shown in Table 1.

[Comparative Example 2]
An aluminum vapor deposition film was obtained in the same manner as in Example 1 except that phenylmethyldimethylpolysiloxane oil was not formed on the metal vapor deposition surface. When the same moisture resistance evaluation as that of Example 1 was performed, the capacitance retention was 65% and the moisture resistance was good. The results are shown in Table 1.

[Comparative Example 3]
A power source of a different system is connected to the surface opposite to the metal layer surface side of the plasma discharge processing, the processing power density on the metal layer surface side is 8 W · min / (m ² · single side), and the processing power density on the opposite surface side is 20 W · min. An aluminum vapor-deposited film was obtained in the same manner as in Example 1 except that it was changed to / (m ² · single side). When the same moisture resistance evaluation as that of Example 1 was performed, the capacitance retention was 70% and the moisture resistance was good. The results are shown in Table 1.

  The capacitor obtained by the present invention is suitably used for electrical equipment for automobiles and trains and for controlling engines, motors, inverter smoothing capacitors, lighting, and the like.

Claims (4)

A metallized film formed by forming a metal layer on one side of a polypropylene film used as a dielectric of a film capacitor, wherein a 0.02 to 0.2 μg / cm ² silicone oil layer or fluorine is formed on the surface of the metal layer An oil layer is formed, the wetting index is 33 to 50 mN / m, the wetting index on the side opposite to the metal layer of the polypropylene film is 33 to 45 mN / m, and the charge amount is −15 to +15 V Range of metallized film for capacitors.   2. The metallized film for a capacitor according to claim 1, wherein the metal layer has a thickness of 1 to 100 nm and the metallized film has a thickness of 0.5 to 20 μm.   The metallized film for a capacitor according to claim 1 or 2, wherein the metal layer contains 90% by mass or more of aluminum with respect to 100% by mass of the metal layer.   The capacitor | condenser formed using the metallized film for capacitors in any one of Claims 1-3.