JPH0259613B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to metallized film capacitors. Specifically, the present invention relates to a large-capacity, small-sized capacitor that has long-term reliability in terms of environmental resistance, particularly moisture and heat resistance, and a method for manufacturing the same. Metallized film capacitors are generally manufactured by providing a metal vapor-deposited thin film on a plastic film such as polycarbonate, polyester, or polypropylene, and then winding or laminating the film.
Compared to foil-type capacitors, which are manufactured by laminating plastic film and aluminum foil, capacitors can be made more compact, and are becoming increasingly popular as they meet the demands for smaller and more compact electronic devices. but,
Long-term reliability, especially performance stability in high-temperature and high-humidity environments, is not always satisfied.
Changes in capacitance, etc. tended to occur during use. For this reason, countermeasures have been taken, such as wrapping with tape, cases, etc., and dipping with epoxy resin, etc., but these have resulted in inconveniences such as complicated processes and increased dimensions of the finished product. The inventors conducted a detailed study on changes in capacitance, especially under high temperature and high humidity environments, and found that
It has been found that there is a deep relationship between the adhesion of the metal-deposited thin film to the base film. In other words, although biaxially stretched plastic film has excellent electrical, mechanical, thermal, and material properties required as a material for film capacitors, it generally has poor surface activity and is unsatisfactory in adhesion to metal-deposited thin films. In particular, the metal thin film easily deteriorates or comes off in the presence of moisture. The present inventors observed changes in the metal vapor deposited film under the harsh conditions of immersion in hot water, and found that if a specific resin layer was provided on the surface of the biaxially stretched film in advance, the durability of the metal vapor deposited film would be significantly improved. The present invention was developed based on the knowledge that this can be improved. That is, (A) a mixture of alkyd resin and melamine and/or urea resin (B) a mixture of acrylic resin and melamine and/or urea resin (C) water-dispersible polyurethane with a 100% modulus of 80 kg/cm ² or more Alternatively, aluminum or zinc is vapor-deposited on a biaxially stretched thermoplastic resin film having a thermosetting resin film with a thickness of 0.1μ or less selected from a mixture of polyurethane polyurea and melamine on the surface, and the film is used as a dielectric material. This is a film capacitor with excellent moisture and heat resistance that uses a metal vapor-deposited film as an electrode. Furthermore, as a method for manufacturing the capacitor of the present invention, the coating resin layer is provided before the stretching of the base film is completed, and good adhesion between the coating resin and the base film can be obtained by stretching the base film together with the base film in at least one direction. Furthermore, it has been found that a film having a coating film of the minimum necessary thickness can be produced uniformly and efficiently. That is, on a thermoplastic resin film that is unstretched or stretched only in one direction, (A) a mixture of alkyd resin and melamine and/or urea resin (B) a mixture of acrylic resin and melamine and/or urea resin (C) 100 A solution or aqueous dispersion of a resin selected from a water-dispersible polyurethane or a mixture of polyurethane polyurea and melamine having a % modulus of 80 Kg/ ^cm2 or more is coated and dried, followed by biaxial or perpendicular stretching direction. After stretching, aluminum or zinc is vacuum-deposited on a film obtained by heat treatment at a temperature range of 5 to 50°C below the melting point of the base film, and the deposited film is wound or laminated. This is an excellent method for manufacturing film capacitors. The base film in the present invention is a biaxially stretched thermoplastic resin film, and the target film is a film used in a film capacitor that requires improvement in heat and humidity resistance, but polyester film,
It is particularly effective for so-called crystalline resin films that undergo crystallization by biaxial stretching, such as polypropylene films. In particular, the most excellent small film capacitor can be obtained when applied to a biaxially stretched polyester film that satisfies the requirements for processing and final performance of the capacitor and is easy to obtain an extremely thin and uniform film. The coating resin in the present invention is a so-called thermosetting resin solution or dispersion that undergoes a curing reaction at room temperature or by heating after coating film formation, and is selected from the following three types. (A) Consists of a mixture of alkyd resin and melamine and/or urea resin, the mixing ratio of which is:
It can be appropriately determined depending on the type of base film and coating process. It is also possible to add nitrocellulose to adjust the viscosity if necessary. Mixtures of these resins can also be used dissolved in organic solvents or in water emulsion or aqueous form. (B) Consists of a mixture of acrylic resin and melamine and/or urea resin, the mixing ratio of which can be appropriately determined depending on the type of base film and the coating process. These mixtures can also be dissolved in organic solvents or used in the form of water emulsions or aqueous forms. (C) A mixture of water-dispersible polyurethane or polyurethane with a 100% modulus of 80 kg/cm ² or more and melamine, the mixing ratio of which can be appropriately selected depending on the type of base film and coating process. Water-dispersible polyurethane is a so-called forced emulsification type polyurethane obtained by mixing and kneading a prepolymer with a terminal -NCO group with water, an emulsifier, and a chain extender to advance polymerization at the same time as emulsification and dispersion. So-called ionomer-type polyurethane (self-emulsifying polyurethane) obtained by introducing ionic groups into the chain to impart hydrophilicity and stably dispersing it in water without the aid of an emulsifier, or water-soluble polyurethane made mainly from water-soluble polyol. Polyurethane, etc., can be applied, but the 100% modulus of the coating film is 80
A relatively hard resin of Kg/cm ² or more is required, and can be adjusted appropriately by adding melamine. Here, 100% modulus is a value measured in accordance with JISK6301. It is sufficient for the thickness of the coating layer to be 0.1 μm or less, and the thinner the better, as long as uniform coating is possible. For example, if the base film is 1.5μ, even 0.03μ is sufficiently effective, and it is not a good idea to make the coating layer thicker due to the need for smaller capacitors.
(The capacitance of the capacitor is inversely proportional to the thickness of the film.) The steps after metal vapor deposition in the present invention are not particularly limited, and all conventional metallized film capacitor manufacturing steps can be applied. Laminated film and lacquer coating, which are commonly used for winding or laminating vapor deposited films, are also possible. Although the capacitor of the present invention exhibits good moisture and heat resistance even without an outer layer such as a tape, a case, or a resin dip, longer-term stability can be obtained by providing such external protection. Next, a method for manufacturing the capacitor of the present invention will be described. The capacitor of the present invention can of course use a coating film obtained by the so-called post-coating method in which the above-mentioned specific coating agent is applied to a biaxially stretched thermoplastic resin film, but the aim is to reduce the size and increase the capacity. Therefore, it is not a good idea to uniformly apply a coating to the required minimum thickness. A so-called unstretched film obtained by melt-extruding a thermoplastic resin into a film is coated, and the coated film is stretched in two steps simultaneously or sequentially in the longitudinal and transverse directions, or uniaxial stretching is performed by previously stretching the unstretched film in one direction, longitudinally or transversely. An in-line coating method in which a film is coated, and then the base film and the coating layer are simultaneously stretched in at least one direction by coating the film and then at least before the final stretching in a direction perpendicular to the aforementioned direction, yields a uniform thin film with high productivity. This is the best method and the adhesion of the coating layer to the base film is significantly improved. The coating method is not particularly limited, and for example, gravure roll coating, inverse roll coating, reverse roll coating, Meyer bar coating, air knife coating, etc. can be employed. After the coating layer and the base film are co-stretched, it is necessary to heat-treat at a temperature of 5 to 50°C below the melting point of the base film. When the heat treatment temperature is lower than 50°C below the melting point, the thermal dimensional stability of the base film is insufficient, distortion occurs during the capacitor processing process, and the moisture resistance of the final product is poor. If heat treated at a temperature higher than 5°C below the melting point, breakage will easily occur during film production.
Mechanical properties are also reduced. The above-mentioned heat setting treatment simultaneously accelerates the curing of the coating resin in a short period of time and is useful for forming a highly durable thin film. Comparative Experimental Example The following various coating solutions were applied to an unstretched polyester film with a thickness of 25μ using an 80μ Maya bar and dried to obtain a coating film with a coating thickness of 0.4μ. These films were preheated to 80°C using a tenter-type simultaneous biaxial stretching machine, stretched simultaneously 3.0 times in length and 3.3 times in width, and then heat-treated at 220°C for 5 seconds under tension. A thin metal aluminum film with a thickness of approximately 500 Å was provided on the coated surface of the obtained film by vacuum evaporation. For comparison, an uncoated film was similarly biaxially stretched, heat set, and aluminum vapor deposited. 40 to evaluate the water resistance of these films.
It was immersed in warm water at ℃ for 24 hours, and changes in the state of the aluminum vapor-deposited film were observed. The results are shown in Table 1. Coating liquid (A) Aminoalkyd resin coating liquid Phthalkyd M641-50 (manufactured by Hitachi Chemical KK)/
A resin mixture consisting of melamine 20 (manufactured by Hitachi Chemical KK)/nitrocellulose in a weight ratio of 63/27/10 was mixed with toluene/ethyl acetate/cyclohexane in a 6/6/20 weight ratio.
Solid content concentration 10 in mixed solvent consisting of 2/2 weight ratio
Coating liquid obtained by dissolving it so that it becomes %. (B) Thermosetting acrylic resin coating liquid Hitaroid 2405/Hitaroid 2602/Melan 20
(all manufactured by Hitachi Chemical KK) in a 40/30/30 weight ratio toluene/xylene/
A coating liquid obtained by dissolving n-butanol in a mixed solvent with a weight ratio of 1/1/1 to a solid content concentration of 10%. (C) Water-dispersible urethane resin coating liquid This is an anionic aliphatic polyester urethane aqueous dispersion. INPRANIL-
A coating solution with a solid content concentration of 10% is obtained by adding 300 parts by weight of ion-exchanged water to 100 parts by weight of DLH (manufactured by Bayer AG, solid content 40%) and stirring well. The 100% modulus of the coating film is 50Kg/cm ² . (D) Mixed coating solution of water-dispersible polyurethane and melamine 20 parts by weight of a 10% aqueous solution of trimethoxymethylmelamine was added to 100 parts by weight of the coating solution of (C) and stirred well. Coating liquid. 100% of coating film
Modulus is 105Kg/cm ² .

[Table] Example 1 and Comparative Examples 1 and 2 Polyethylene terephthalate was melt-extruded into a film to form an unstretched film with a thickness of 14μ,
The coating liquid C (Comparative Example 1) was applied to both sides of this film.
and D (Example 1) were coated so that the thickness after drying was 0.5μ on one side, and after drying, they were continuously fed into a tenter type simultaneous biaxial stretching machine and the preheating section
The film was simultaneously biaxially stretched 3.0 times in length and 3.3 times in width at 100°C and 85°C in the stretching section, passed through a heat treatment section at 150 to 230°C, cooled, and then rolled up. The resulting film is a double-sided coated biaxially oriented polyester film with a total thickness of 1.5μ with a coating of 0.05μ on each side. Vapor deposition width on the above film: 9mm, margin width: 1mm
A vertical strip of aluminum was vapor-deposited on both sides, micro-slit and wound together with a laminated film, and electrodes were attached to form a 0.1 μF film capacitor. For comparison, a wound type film capacitor was similarly made using an uncoated 1.5 μm thick polyester film that had been biaxially stretched by the same process (Comparative Example 2). Each capacitor was left in an atmosphere of 40°C and 95% RH, and changes in capacitance were examined after 500 and 1000 hours.
The results are shown in Table 2.

[Table] As is clear from Table 2, the moisture resistance of the capacitor corresponds well with the hot water immersion test results of the aluminum vapor-deposited film, and the film capacitor using the coating film of the present invention has significantly improved moisture resistance and load life. I understand that.

Claims (1)

[Scope of Claims] 1 (A) A mixture of an alkyd resin and a melamine and/or a urea resin (B) A mixture of an acrylic resin and a melamine and/or a urea resin (C) A mixture with a 100% modulus of 80 Kg/cm ² or more Aluminum or zinc is vapor-deposited on a biaxially stretched thermoplastic resin film having a thermosetting resin coating with a thickness of 0.1μ or less on the surface selected from water-dispersible polyurethane or a mixture of polyurethane polyurea and melamine. A film capacitor with excellent moisture and heat resistance, which uses a dielectric as a dielectric and a metal vapor-deposited film as an electrode. 2. The capacitor according to claim 1, wherein the biaxially stretched thermoplastic film is a polyester film. 3 A thermoplastic resin film that is unstretched or stretched only in one direction contains (A) a mixture of alkyd resin and melamine and/or urea resin (B) a mixture of acrylic resin and melamine and/or urea resin (C) 100% A solution or aqueous dispersion of a resin selected from a water-dispersible polyurethane or a mixture of polyurethane polyurea and melamine having a modulus of 80 kg/cm ² or more is coated and dried, and then biaxially or in a direction perpendicular to the stretching direction. After stretching, aluminum or zinc is vacuum-deposited on a film obtained by heat treatment at a temperature range of 5 to 50°C below the melting point of the base film, and the deposited film is wound or laminated, and has excellent moisture and heat resistance. A method of manufacturing a film capacitor.