JP4534712B2 - Electrolytic capacitor - Google Patents

Description

  The present invention relates to an electrolytic capacitor used in various electronic devices.

  With the increase in frequency of electronic equipment, there is a demand for a large-capacity electrolytic capacitor excellent in equivalent series resistance (hereinafter referred to as “ESR”) characteristics in the high-frequency region even in an electrolytic capacitor as an electronic component. Recently, in order to reduce ESR in such a high frequency region, a solid electrolytic capacitor using a solid electrolyte such as a conductive polymer having a higher electric conductivity than a conventional driving electrolyte has been studied and commercialized. Has been. Also, in response to the demand for larger capacity, a wound solid that has a configuration in which a conductive polymer is filled in a capacitor element wound with a separator interposed between an anode foil and a cathode foil Electrolytic capacitors have been commercialized.

  The conductive polymer used in the solid electrolyte is a cation component utilizing a metal ion reduction reaction, as represented by a method of polymerizing 3,4-ethylenedioxythiophene with ferric p-toluenesulfonate. 3,4-ethylenedioxythiophene chemically oxidized by an oxidant / dopant agent acting as a dopant and a second chloride chloride which also acts as an oxidant / dopant agent using pyrrole monomer. Polypyrrole chemically oxidized and polymerized with iron or persulfate is known.

  However, since the solid electrolytic capacitor as described above uses only the solid electrolyte with poor repairability of the dielectric oxide film as the electrolyte, the leakage current is increased as compared with the conventional electrolytic capacitor using the driving electrolytic solution. As a result, short circuit failures due to the occurrence of defects in the dielectric oxide film and dielectric oxide films are likely to occur, making it difficult to construct a capacitor with a high withstand voltage.

  On the other hand, for the purpose of improving the above-described problem, a wound electrolytic capacitor has been proposed in which both a solid electrolyte made of a conductive polymer and a driving electrolyte are used as a cathode lead material. This wound electrolytic capacitor is made conductive with a separator polymer such as manila paper or kraft paper, or a porous polymer or synthetic fiber nonwoven fabric separator with a conductive polymer that is chemically oxidized and polymerized as a persulfate, an oxidizing agent and a dopant. It is configured using a conductive separator and a driving electrolyte.

As prior art document information related to the invention of this application, for example, the following patent documents 1 and 2 are known.
Japanese Patent Laid-Open No. 01-090517 Japanese Patent Application Laid-Open No. 07-249543

  However, the wound electrolytic capacitor using both the solid electrolyte made of the conventional conductive polymer and the driving electrolyte as the cathode lead material has characteristics even depending on the driving electrolyte used in combination with the conductive separator. It changes a lot. In particular, the anionic component of the dopant agent is easily dedoped and eluted into the driving electrolyte solution, so that the conductivity of the conductive polymer is remarkably lowered, and the thermal stability of the electrolytic capacitor is poor. There is a problem that the change of ESR with time is large.

  As a countermeasure against the dedoping, dedoping can be reduced by selecting a dopant agent, but the material is expensive and the manufacturing conditions of the conductive polymer are difficult.

  In addition, chemical oxidation polymerization of 3,4-ethylenedioxythiophene and the like is performed using a transition metal oxidizer / dopant having an oxidation-reduction action of metal ions such as ferric p-toluenesulfonate which is difficult to be dedoped. Although a method is also known, when a capacitor element having this structure is impregnated with a driving electrolyte solution to form an electrolytic capacitor, the remaining metal ion component is dissolved and precipitated by an electrochemical reaction in the driving electrolyte solution. There are problems such as increasing the leakage current of the electrolytic capacitor.

  An object of the present invention is to solve such a conventional problem and to provide a highly reliable electrolytic capacitor having a low ESR in a high frequency region.

In order to achieve the above object, the present invention is constituted by winding an anode foil having a roughened surface and forming a dielectric oxide film, and a cathode foil with a conductive separator interposed therebetween. In an electrolytic capacitor comprising a capacitor element, a bottomed cylindrical metal case that contains the capacitor element together with a driving electrolyte, and a sealing member that seals the opening of the metal case, the capacitor is attached to the conductive separator . Each of the conductive polymer and the driving electrolyte solution includes at least one selected from ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide .

  As described above, according to the present invention, even if the anion component of the dopant agent of the conductive separator is dedoped, the anion component of the non-transition metal oxidant present in the driving electrolyte is incorporated into the conductive polymer. Therefore, there is an effect that it is possible to obtain a highly reliable electrolytic capacitor with low ESR in a high frequency region.

  In addition, by containing an antioxidant in the additive, it is possible to suppress oxidative deterioration of the conductive separator and to suppress a decrease in electrical conductivity. Therefore, an electrolytic capacitor having a low ESR and a high reliability in a high frequency region can be obtained. It becomes possible to provide. When the antioxidant is used in combination with an acid, the reaction activity is increased and the effect is further improved.

  FIG. 1 is a partially cutaway perspective view showing the structure of an electrolytic capacitor according to an embodiment of the present invention. In FIG. 1, reference numeral 19 denotes a capacitor element. The capacitor element 19 has an anode foil 11 made of an aluminum foil having a dielectric oxide film formed by anodizing after the surface is roughened by etching, and a surface by etching. The cathode foil 12 made of a roughened aluminum foil is wound with a conductive separator 13 covered with a conductive polymer interposed therebetween.

  14 and 15 are external lead-out anode and cathode leads connected to the anode foil 11 and the cathode foil 12, respectively, and 17 is a bottomed cylindrical aluminum housing the capacitor element 19 together with a driving electrolyte (not shown). The metal case 16 has a hole through which the anode lead 14 and the cathode lead 15 are inserted to seal the opening of the metal case 17, and 18 has a hole through which the anode lead 14 and the cathode lead 15 are inserted. It is an insulating seat plate made of an insulating resin mounted on the lever sealing member 16 side. A surface mount type electrolytic capacitor is formed by bending the anode lead 14 and the cathode lead 15 along a groove provided on the outer surface of the insulating seat plate 18.

  The conductive separator has at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon and glassy as a separator base material. It can be obtained by using a non-woven fabric to be contained and attaching a conductive polymer to this separator substrate by oxidative polymerization of a monomer using a non-transition metal oxidant and a dopant agent.

  The nonwoven fabric separator has extremely good adhesion and adhesion to the conductive polymer, and can lower ESR in the high frequency region.

  The non-transition metal-based oxidizing agent is at least one selected from ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide, and the dopant agent is benzenesulfonic acid, naphthalenesulfonic acid, toluenesulfonic acid, nitro One selected from phenol or a derivative thereof is used.

  The driving electrolyte basically comprises an organic solvent, a solute (acid [organic acid and inorganic acid] and base), an additive, and a non-transition metal oxidant used in a conductive polymer.

  Examples of the organic solvent include alcohols [methanol, ethanol, propanol, butanol, cyclobutanol, cyclohexanol, ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol] and the like. Examples of aprotic organic solvents include amides [N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, etc. ], Lactones [γ-butyrolactone, β-butyrolactone, α-valerolactone, γ-valerolactone, etc.], sulfoxides [sulfolane, 3-methylsulfolane, dimethyl sulfoxide], cyclic amides [ethylene carbonate, propylene carbonate, etc.] Nitrile [acetonitrile, etc.], oxide [dimethyl sulfoxide, etc.], imidazolidinone [3-methyl-1,3-oxazolidine-2-one, 1,3-diethyl-2-imidazolidinone, 1,3 -Dipropyl-2-imidazolidinone, 1-methyl 3-ethyl-2-imidazolidinone, 1,3,4-trimethyl-2-imidazolidinone, a 1,3,4,5-tetramethyl-2-imidazolidinone, etc.]. These organic solvents can be used alone or in combination.

  Solute acid components of the driving electrolyte include aliphatic carboxylic acids: ([saturated carboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatin Acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid , Stearic acid, behenic acid], [unsaturated carboxylic acids such as maleic acid, fumaric acid, itonic acid, acrylic acid, methacrylic acid, oleic acid]), aromatic carboxylic acids: (eg phthalic acid, isophthalic acid, terephthalic acid , Trimellitic acid, pyromellitic acid, benzoic acid, cinnamic acid, naphthoic acid), alicyclic polycarboxylic acids: (eg cyclohexene) -1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.), oxycarboxylic acid: (for example, salicylic acid, mandelic acid, resorcinic acid) and the like. Among these, thermal conductivity is high and thermal conductivity is preferable. Are also stable organic acids such as maleic acid, phthalic acid, benzoic acid, pyromellitic acid and resorcinic acid.

  Examples of the inorganic acid include carbon compounds, hydrogen compounds, boron compounds, sulfur compounds, nitrogen compounds, and phosphorus compounds. Examples of typical inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphoric acid ester, boric acid, borofluoric acid, tetrafluoroboric acid, and hexafluorophosphoric acid.

  The solute base component of the driving electrolyte is a compound having an alkyl-substituted amidine group, and examples thereof include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds and imidazoline compounds). Specifically, 1,8-diazabicyclo [5,4,0] undecene-7,1,5-diazabicyclo [4,3,0] nonene- which can provide a capacitor having high conductivity and excellent impedance performance 5, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2- (3′heptyl) imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, 1-methylbenzimidazole preferable. Further, a quaternary salt of a compound having an alkyl-substituted amidine group can be used as a base component, and an imidazole compound, a benzimidazole compound, or an alicyclic quaternized with an alkyl group having 1 to 11 carbon atoms or an arylalkyl group. Examples include amidine compounds (pyrimidine compounds and imidazoline compounds).

  The content of the solute in the driving electrolyte solution of the present invention is usually 10 to 95% by weight, preferably 20 to 90% by weight, based on the weight of the driving electrolyte solution. Outside this range, the conductivity is significantly reduced.

  Examples of additives for the driving electrolyte of the present invention include phosphorus compounds (such as phosphate esters), boric acid compounds (boric acid, complex compounds of boric acid and polysaccharides [mannit, sorbit, etc.]), boron Complex compounds of acids and polyhydric alcohols (ethylene glycol, glycerin, etc.), nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p- Nitrophenol, etc.). Adding these additives may increase the spark voltage of the driving electrolyte and may be preferable.

  An antioxidant can also be added to the driving electrolyte. Examples of this antioxidant include phenol compounds, amine compounds, azo compounds, silane compounds, quinone compounds, carboxylic acid compounds, phenol, methylphenol, ethylphenol, pyrogallol, hydroquinone, pyrocatechol, tocophenol, butylhydroxyanisole, Dibutylhydroxytoluene, benzoquinone, naphthoquinone, anthraquinone, citric acid, ascorbic acid, ethylenediaminetetraacetic acid, quinic acid, rutin, flavonoid, γ-oryzanol, tocophenolbenzotriazole, 2,6-di-t-butyl-p-cresol, Stearyl propionate-β- (3,5-di-tert-butyl-4-hydroxyphenyl), 2,2′-methylene-bis (3-methyl-6-tert-butylphenol), dilaurylthiodipropina , Triphenyl phosphite, diphenylisodecyl phosphite, tris (nonylphenyl) phosphite, trisnonylphenyl phosphite, hydroxyanisole, 1,4-naphthalenediol, trimethylhydroquinone, 2,3-dimethylhydroquinone , Aminohydroquinone, aminophenol and the like.

  Further, the non-transition metal oxidant contained in the driving electrolyte solution is at least one selected from ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, and sodium hypochlorite.

  Hereinafter, specific examples will be described.

Example 1
First, an anode foil made of an aluminum foil having a surface roughened by an etching process and then a dielectric oxide film (formation voltage 10 V) formed by an anodic oxidation process, and a cathode foil obtained by etching the aluminum foil are electrically conductive separators. A capacitor element is produced by winding with (A) interposed.

The conductive separator (A) is made of a non-woven fabric mainly composed of polyethylene terephthalate (a base material thickness of 50 μm, a weight of 25 g / m ² ), ammonium persulfate (concentration 3% by weight) and 2-naphthalene. It is immersed in a mixed solvent of water and ethanol containing sulfonic acid (concentration 5% by weight) (impregnation amount: 15 mg / cm ² ), and this separator substrate is placed on a tank containing pyrrole monomer and sealed. The ambient temperature was kept at 40 ° C. for 5 minutes, and the product was taken out, washed for 5 minutes in warm water at 60 ° C., and dried at 105 ° C. (conductivity of the conductive separator (A): 2.4 S / cm).

  Subsequently, the capacitor element was immersed in each of the driving electrolytes (A) to (F) shown in (Table 1) under reduced pressure conditions (−700 mmHg), and the gaps of the capacitor element were impregnated with the driving electrolyte. .

  Next, each capacitor element has a bottomed cylindrical shape together with a resin vulcanized butyl rubber sealing material (composed of 30 parts of butyl rubber polymer, 20 parts of carbon and 50 parts of an inorganic filler, sealing body hardness: 70 IRHD [international rubber hardness unit]). After being inserted into the aluminum case, the opening of the aluminum case is sealed by curling treatment, and both lead terminals led out from the anode foil and the cathode foil are passed through an insulating seat plate made of polyphenylene sulfide, and the lead portion is The insulating seat plate was fixed by bending it into a flat shape.

  Finally, aging was performed by continuously applying a DC voltage of 6.3 V for 1 h (atmosphere temperature: 105 ° C.) to produce surface mount type electrolytic capacitors (size: diameter 10 mm × height 10 mm).

(Example 2)
A surface mount type electrolytic capacitor was produced in the same manner as in Example 1 except that in Example 1, the conductive separator (A) was used instead of the conductive separator (B) produced by the following method. did.

The conductive separator (B) is made of a separator base material (base material thickness 50 μm, weighing 25 g / m ² ) made of nonwoven fabric mainly composed of polyphenylene sulfide, potassium persulfate (concentration 3% by weight) and p- Immerse in a mixed solvent of water and ethanol containing toluenesulfonic acid (concentration 5% by weight) (impregnation amount: 15 mg / cm ² ), place this separator substrate on a tank containing pyrrole monomer and seal it In this state, the ambient temperature was kept at 40 ° C., and after leaving for 5 minutes, the product was taken out, washed in 60 ° C. warm water for 5 minutes, and then dried at 105 ° C. (conductivity of conductive separator (B): 2.2S / Cm).

(Example 3)
A surface mount type electrolytic capacitor was produced in the same manner as in Example 1 except that the conductive separator (A) was used in place of the conductive separator (C) produced by the following method in Example 1. did.

The conductive separator (C) is a separator base material (base material thickness 50 μm, weighing 25 g / m ² ) made of a nonwoven fabric mainly composed of polyamideimide, sodium persulfate (concentration 3% by weight) and p- Immerse in a mixed solvent of water and ethanol containing toluenesulfonic acid (concentration 5% by weight) (impregnation amount: 15 mg / cm ² ), place this separator substrate on a tank containing pyrrole monomer and seal it In this state, the ambient temperature was kept at 40 ° C., the product was left for 5 minutes, taken out, washed in 60 ° C. warm water for 5 minutes, and then dried at 105 ° C. (conductivity of conductive separator (C): 2.3S) / Cm).

Example 4
A surface mount type electrolytic capacitor was produced in the same manner as in Example 1 except that in Example 1, the conductive separator (A) was used instead of the conductive separator (D) produced by the following method. did.

The conductive separator (D) is a separator base material (base material thickness 50 μm, basis weight 25 g / m ² ) made of nylon and glass fiber nonwoven fabric, potassium persulfate (concentration 2% by weight) and hydrogen peroxide solution. (Separation 1% by weight) and 1-naphthalenesulfonic acid (concentration 5% by weight) in water and ethanol in a mixed solvent (impregnation amount: 15 mg / cm ² ) Placed on a bath containing dioxythiophene, kept in an airtight state at 40 ° C., left for 5 minutes, taken out, washed in 60 ° C. warm water for 5 minutes, and dried at 105 ° C. (Conductivity of conductive separator (C): 2.0 S / cm).

(Comparative Example 1)
A surface mount type electrolytic capacitor was fabricated in the same manner as in Example 1 except that Comparative Example A in Table 1 was used as the driving electrolyte in Example 1.

(Comparative Example 2)
A surface mount type electrolytic capacitor was produced in the same manner as in Example 1 except that Comparative Example B in Table 1 was used as the driving electrolyte in Example 1.

  Table 2 shows the results of measuring the electrical characteristics of the electrolytic capacitors of Examples 1 to 4 and Comparative Examples 1 and 2 after the initial state and the 105 ° C. load test.

  As is clear from Table 2, the electrolytic capacitors of Examples 1 to 4 were each made of non-transition metal oxidizers such as ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide water as the driving electrolyte. By adding, the electrical characteristics after a 105 ° C. load test are superior to Comparative Example 1 in which this is not added.

  In addition, the separator base material of the conductive separator can be the same regardless of whether it is a nonwoven fabric based on polyethylene terephthalate, a nonwoven fabric based on polyphenylene sulfide, a nonwoven fabric based on polyamideimide, or a nonwoven fabric of nylon and glass fiber. The electrical characteristics can be obtained.

  In addition, when an ammonium persulfate oxidant is used when forming the conductive separator, it is not always necessary to use ammonium persulfate as the driving electrolyte, and either potassium persulfate, sodium persulfate, or hydrogen peroxide water must be used. Use it.

  In addition, the electrical characteristics obtained by adding the antioxidant to the driving electrolyte are further improved as compared with the case where the antioxidant is not added.

  Furthermore, in the solute of the driving electrolyte, by including an acid component in excess of the base component, extremely good electrical characteristics can be obtained as compared with those using the general driving electrolyte of Comparative Example 2. Can do.

  Although the chip type electrolytic capacitor is used in the above embodiment, it goes without saying that the same effect can be obtained with an electrolytic capacitor that does not use an insulating seat plate.

The electrolytic capacitor according to the present invention has a special effect that the electric conductivity of the conductive polymer constituting the conductive separator does not deteriorate due to the driving electrolyte used in combination with the conductive separator. ESR is effectively reduced in the high frequency region,
In addition, it is useful for applications that require stable performance over a long period of time.

The partially cutaway perspective view which showed the structure of the electrolytic capacitor by one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Anode foil 12 Cathode foil 13 Conductive separator 14 Anode lead 15 Cathode lead 16 Sealing member 17 Metal case 18 Insulating seat 19 Capacitor element

Claims (1)

A capacitor element formed by winding an anode foil having a roughened surface and forming a dielectric oxide film, and a cathode foil with a conductive separator interposed therebetween, and driving the capacitor element In an electrolytic capacitor comprising a bottomed cylindrical metal case housed together with an electrolytic solution and a sealing member sealing an opening of the metal case, the conductive polymer attached to the conductive separator and the driving electrolytic solution An electrolytic capacitor comprising at least one selected from ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide .

Images