JPH07120607B2 - Capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved capacitor,
More specifically, the dielectric loss tangent (hereinafter,
(referred to as tan δ) does not change.

[Prior Art] A capacitor is known in which a biaxially oriented polyester film is wound or laminated with a so-called metallized polyester film obtained by vapor-depositing a metal such as a metal such as aluminum or zinc.

[Problems to be Solved by the Invention] However, the conventional capacitors described above have the following drawbacks.

Tan δ changes with the passage of time, and especially in a high temperature and high humidity atmosphere, tan δ increases in a relatively short time,
Its value also tends to change.

Furthermore, the capacitance decreases with the passage of time, and a stable capacitance cannot be obtained.

[Means for Solving Problems] The present invention has been made to solve the above-mentioned drawbacks of conventional capacitors. The capacitor of the present invention is mainly composed of a layer (A) formed by mixing a phenoxy resin and a polyisocyanate. , Biaxially oriented polyester film (B)
And a metallized polyester film comprising a vapor-deposited metal layer (C), which is wound or laminated.

A capacitor formed by winding or laminating a metallized polyester film is well known as described above, and the present invention can achieve the intended object of the present invention in any of the winding or laminating type. .

The polyester in the present invention is a polymer compound having an ester bond in the molecular main chain, which is obtained by more polycondensation of a dicarboxylic acid and a diol, and typical polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and the like. And those obtained by copolymerizing them with comonomers such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, diethylene glycol, polyethylene glycol and polytetramethylene glycol. Especially preferred for the present invention is polyethylene terephthalate (hereinafter referred to as PET). Known additives in this polyester, for example, stabilizers such as phosphorous acid and its ester, titanium dioxide, fine particle silica, calcium carbonate,
Powders of talc, kaolin, etc. may be included as lubricants.

The biaxially oriented polyester film (B) referred to in the present invention is a biaxially oriented polyester film obtained by melt-extruding the above polyester polymer to form a sheet, stretching and orienting in a biaxial direction, and subjecting it to heat treatment. . The stretching method of the polyester film may be either a sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then in the transverse direction, or a simultaneous biaxial stretching method in which it is simultaneously stretched in the longitudinal and transverse directions.

The thickness of the polyester film is preferably 0.2 to 2 μm, more preferably 0.2 to 1.5 μm.

The center line average roughness (Ra) of the surface of the biaxially oriented polyester film is preferably 0.015 to 0.05.

Further, it is preferable that at least one surface of the polyester film is subjected to corona discharge treatment, and metal is vapor-deposited on the surface. When corona treatment is applied, the atmospheric gas has an oxygen concentration of 0.
It is preferably carried out in an atmosphere of 1% by volume or less of nitrogen, carbon dioxide, argon or the like. The applied energy of corona discharge is preferably about 1 to 6 KJ / m ² .

The vapor-deposited metal layer (C) of the present invention means aluminum,
It is a thin film metal layer formed by vapor deposition of zinc, copper or an alloy thereof. The vapor deposition method is not particularly limited, for example, electrothermal heating dissolution vapor deposition method, ion beam vapor deposition method,
A sputtering method or the like can be used. In addition, the thickness of the vapor deposition film is preferably in the range of 10Å to 5000Å, which is 1 to 10Ω when expressed as the film resistance in the case of an aluminum film.
It will be in the range of / □.

The phenoxy resin referred to in the present invention has the general formula (Here, R _{1 to} R ₇ are a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.). Typical examples thereof are resins represented by R ₁ , R ₂ = CH ₃ , and R _{3 to} R ₇ = H.

The polyisocyanate referred to in the present invention is a compound containing two or more isocyanate groups per molecule, for example, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, 4,4'4 "-triisocyanate triphenylmethane, hexamethylene. Examples thereof include condensates of 3 mol of diisocyanate and 1 mol of trimethylolpropane, and various other isocyanate compounds.

The layer (A) composed of the phenoxy resin and the polyisocyanate of the present invention is applied with a solution obtained by mixing the phenoxy resin and the polyisocyanate in a normal solution state, and the solvent is evaporated in a heating atmosphere at 70 to 200 ° C. to form a film. Complete by doing.

The mixing ratio of the phenoxy resin and the polyisocyanate is such that the equivalent ratio of the isocyanate group of the polyisocyanate to 1 equivalent of the hydroxyl group of the phenoxy resin is preferably 0.8 to 2.0,
The range is more preferably 0.9 to 1.5.

The thickness of the layer (C) composed of the phenoxy resin and the polyisocyanate is preferably 1 μm or less, and more preferably 0.1 to 1.0 with respect to the thickness of the polyester film.

The repeating unit of the layer constitution of the layer (A) comprising the phenoxy resin and polyisocyanate of the present invention, the biaxially oriented polyester film (B) and the vapor-deposited metal (C) is
(A) layer / (C) layer / (B) layer (A) layer / (C) layer /
(B) layer, (A) layer / (B) layer / (C) layer (A) layer /
(B) layer / (C) layer, (A) layer / (C) layer / (B) layer /
(C) layer / (A) layer (B) layer, (C) layer / (B) layer /
(C) layer (A) layer / (B) layer / (A) layer, (C) layer /
(B) layer (A) layer / (C) layer / (B) layer / (A) layer, and preferably (A) layer / (C) layer / (B) layer (A) layer / (C). ) Layer / (B) layer, (A) layer / (B) layer /
Layer (C) ((A) layer / (B) layer / (C) layer, more preferably (A) layer / (C) layer / (B) layer (A))
Layer / (C) layer / (B) layer (Here, / indicates a layer interface formed by vapor deposition or coating. The mark indicates that after two films are superposed to form a capacitor element. , Showing the heat-bonded layer interface).

When the thickness of the biaxially oriented polyester film of the present invention is small, for example, 0.2 to 2.0 μm, the polyester film and the polyolefin film are laminated in order to smoothly perform processing steps such as vapor deposition, coating and slitting. Films are preferred. The laminated structure of the laminated film is polyester film / polyolefin film, polyester film / polyolefin film /
Polyester film is preferred. The melting point of the polymer of the polyolefin film is preferably in the range of 110 to 140 ° C., and specifically, ethylene / propylene copolymer, butylene / propylene copolymer, ethylene / butylene / propylene copolymer, etc. are suitable. .

Next, a specific example of the method for manufacturing the capacitor of the present invention will be described.

Polyethylene terephthalate containing fine particle silica and the like is extrusion-molded to obtain a non-oriented sheet. Alternatively, the PET
And ethylene / propylene copolymer are melt-extruded by separate extruders, and the melts are merged to form a three-layer structure of PET / ethylene / propylene copolymer / PET to obtain a laminated non-oriented sheet. The sheet is heated to a temperature of 80 to 120 ° C., stretched 3 to 5 times in the longitudinal direction, then heated to a temperature of 90 to 130 ° C., stretched 3 to 5 times in the transverse direction, biaxially oriented, then ,
Heat treatment is performed at a temperature of 190 to 230 ° C. to obtain a biaxially oriented polyethylene terephthalate film. When heat treatment is performed, relaxation treatment is performed in the lateral direction, if necessary. This film is set in a vacuum vapor deposition apparatus, and a metal such as aluminum or zinc is vapor deposited to form a metal layer. Alternatively / or the film is set in a coating device, a mixed solution of phenoxy resin and polyisocyanate is applied, and 70-
Heat with heated air at 200 ° C for 5 to 300 seconds to evaporate the solvent,
A layer composed of a phenoxy resin and polyisocyanate is formed. The laminated film thus obtained is slit into a small width, two of these are laminated and wound to form a capacitor element, and heat pressing, taping, metallikon, voltage treatment, both end surface sealing, lead wire attachment are carried out by the following ordinary methods. Etc. to make a capacitor.

[Measuring Method] The measuring method according to the present invention will be described below.

(1) Thickness of film and thickness of layer (C) composed of phenoxy resin and polyisocyanate The film was attached on a glass support in a wrinkle-free state, and this was applied to a stylus-type surface roughness. Measure the level difference between the place without the film (the place without the (C) layer) and the place with the film (the place with the (C) layer), and measure the value 10 times. The average value was defined as the film thickness (thickness of the (C) layer).

(2) Tan δ increase rate (Δ tan δ) and capacity decrease rate (Δc) of the capacitor are 1.2 μm or less polyethylene terephthalate film on the vapor deposition layer (Al film, electrical resistance of the vapor deposition film: 2Ω / □), and / or By providing a layer consisting of phenoxy resin and polyisocyanate, and making a 3μF winding type capacitor by a conventional method, place this capacitor in an atmosphere of 80 ° C, 85% RH,
Charge DC50V / μ and keep for 500 hours. Tan after 500 hours
From δ and the capacity c value, the change rate with respect to the initial tan δ and capacity is expressed in%.

(3) Dielectric breakdown voltage (BDV) of capacitor 1.2μm or less biaxially oriented polyethylene terephthalate with a vapor deposition layer (Al film, electrical resistance of vapor deposition film: 2Ω / □) or / or a layer consisting of phenoxy resin and polyisocyanate After that, a capacitor element having an electrostatic capacity of 3 μF is formed by a conventional method, the element is hot-pressed, and then an electrode is provided by a metallikon to obtain a wound capacitor. This capacitor is charged at a boosting rate of 50 V / sec, and the voltage when the capacitor breaks is divided by the thickness of the laminated film.
V value.

[Examples] Hereinafter, embodiments of the present invention will be described based on Examples.

Examples 1-3, Comparative Examples 1-3 Polyethylene terephthalate (IV: 0.62, average particle size 0.3μ
0.5% by weight of fine particle silica) was fed to the extruder,
It was melted at 80 ° C, discharged from the die in a sheet form, and adhered and solidified on a drum cooled at 25 ° C. This cast sheet was stretched 3.5 times in the longitudinal direction at 95 ° C and then stretched in the transverse direction at 100 ° C for 3.4 times.
After stretching twice, it was heat-treated for 6 seconds at 205 ° C. while relaxing in the width direction by 4% to obtain a biaxially stretched film having a thickness of 1.2 μm.

The film thus obtained is vapor-deposited and / or coated to form (A) layer / (B) layer / (C) layer,
(A) layer / (C) layer / (B) layer, (C) layer / (B) layer /
A laminated film of (C) layer and (A) layer / (B) layer / (A) layer was obtained. The method for forming the layer (A) composed of a phenoxy resin and a polyisocyanate is a mixed solution of a phenoxy resin (phenoxy resin PKHH, manufactured by Union Carbide) and polyisocyanate (“Coronate HL” manufactured by Nippon Polyurethane Co., Ltd.) A reaction equivalence ratio of 1: 1.1) was applied, air-dried at 70 ° C. for 2 seconds, and then treated with hot air at 130 ° C. for 10 seconds to form a layer having a film thickness of 0.3 μm.

Slit each film to 1 cm width (margin: 0.5 mm),
Two films were wound in layers and a capacitor element (capacitance 3 μF) having a repeating unit of the layer structure shown in Table 1 was prepared. The capacitor element is heat-pressed (temperature: 1
50 ° C, pressure: 4 kg / cm ² , time: 30 minutes), metallikon the electrodes on both ends, apply DC voltage 100 V / μ (film thickness) to both electrodes for 1 second, and perform self-healing to obtain a capacitor. . Breakdown voltage (BDV) of this capacitor,
Table 1 shows Δtan δ and Δc.

From the above results, it is understood that the capacitor characteristics are improved by forming the layer composed of the phenoxy resin and the polyisocyanate according to the present invention.

Examples 4 to 7 and Comparative Example 4 The following two types of raw materials (pellets) were prepared.

PET: IV 0.62, 0.5% by weight of wet synthetic silica with an average particle size of 0.3 μm.

EPC: Ethylene propylene random copolymer with an ethylene content of 6.5% by weight These two raw materials were separately fed to an extruder and melt-extruded at 280 ° C, and the melts were merged in a T-shaped die. , PET / EPC / PET had a three-layer structure, which was wound around a cooling drum at 25 ° C. to be cooled and solidified. This sheet was stretched 5 times in the longitudinal direction at 110 ° C and then stretched in the width direction at 110 ° C for 4.5 times.
After stretching twice, while relaxing at 215 ° C in the width direction by 5%,
Heat treatment was performed for 4 seconds to obtain a laminated biaxially stretched PET film. EPC
The thickness of the layer film was kept constant at 7 μm, the extrusion amount of the PET layer was changed, and the thickness of the PET film was adjusted, as shown in Table 2.

After vacuum-depositing aluminum (metal film resistance 2 Ω / □) on the PET surface of the film, a phenoxy resin (phenoxy resin PKHH, manufactured by Union Carbide) and polyisocyanate (“Coronate HL”, Nippon Polyurethane Industry ( Co., Ltd.) (reaction equivalent ratio 1: 1.1) was applied, air-dried at 70 ° C. for 2 seconds, and then treated with hot air at 130 ° C. for 10 seconds. This laminated film is slit to a width of 1 cm (margin 0.5 mm), the PET film is peeled off from the EPC layer surface, and these two films are wound by an element winding machine to form a capacitor element (electrostatic capacity 3 μF). Had made. The repeating unit of the layer structure of the capacitor element is (A) layer / (C) layer /
(B) layer (A) layer / (C) layer / (B) layer. The capacitor element was hot pressed by a conventional method, electrodes were metallikoned at both ends thereof, and a DC voltage of 100 V / μ (film thickness) was applied to both electrodes for 1 second to perform self-healing treatment to obtain a capacitor. The dielectric breakdown voltage (BDV), Δtan δ, and Δc of this capacitor are shown in Table 2.

Example 8 The surface of the biaxially oriented laminated PET film obtained according to Example 5 was subjected to corona discharge treatment under a mixed gas of oxygen concentration of less than 0.1 vol% and nitrogen of 90 vol% and carbon dioxide gas of 10 vol%. The surface wetting tension of the film after discharge treatment is 54 dyne / cm.
Met. The film was coated with a mixed solution of a phenoxy resin and a polyisocyanate in the same manner as in Example 5, and then formed into a capacitor, and its characteristics were measured.
It was as shown in the table.

From the above results, it is understood that the effect of the present invention is increased by subjecting the surface of the biaxially oriented polyester film of the present invention to corona discharge treatment to form a film deposited on the surface of the film.

Comparative Example 5 A vapor-deposited biaxially stretched polyethylene terephthalate laminated film obtained according to Example 5 was coated with an organic solvent solution of bisphenol-type polycarbonate on the vapor-deposited film surface, and was dried by heating in a hot air oven to give a film thickness of 0.2. μm. A capacitor was produced from the laminated film according to Example 5. The capacitor characteristics are shown in Table 2.

[Effects of the Invention] The ultrathin film capacitor according to the present invention has little change in tan δ and electrostatic capacity with time, especially under high humidity, and has a high dielectric breakdown voltage.

Claims (1)

[Claims] 1. A metallized polyester film mainly comprising a layer (A) in which a phenoxy resin and a polyisocyanate are mixed, a biaxially oriented polyester film (B) and a vapor-deposited metal layer (C) is wound or laminated. A capacitor characterized by being formed.