JP2616991B2 - Electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrolytic capacitor used for various electronic devices.

[Prior art] A conventional aluminum electrolytic capacitor is formed by roughening a high-purity aluminum foil to increase its surface area, then forming an anode foil having a dielectric oxide film formed by anodic oxidation and roughening the aluminum foil. Wrap the cathode foil together with the separator and impregnate the driving electrolyte to form a capacitor element,
The capacitor element is housed in a bottomed cylindrical case, and the open end of the case is sealed with a sealing plate to obtain a completed product.

The separator used in the above-mentioned conventional aluminum electrolytic capacitor is manila paper or kraft paper, but recently, the use of a thermoplastic resin microporous film has also been proposed, and is disclosed in Japanese Patent Application Laid-Open No. 61-13614. The publication describes an aluminum electrolytic capacitor using a polyethylene microporous film as a separator.

[Problem to be Solved by the Invention] Such an aluminum electrolytic capacitor is required to have the following characteristics.

(1) To facilitate the movement of ionogen in the driving electrolyte,
Good electrolyte permeability to reduce loss.

(2) The holding amount of the driving electrolyte is large.

(3) No short circuit between the poles occurs.

That is, as a separator, the porosity is high, the number of through holes is large, and the distance between the electrodes is substantially shortened.
Ideally, the through-hole is not bent, has a substantially uniform size, and has a small thickness.

Conventionally used manila paper or kraft paper is made of crossed cellulose fibers, so the through hole that serves as a path from the anode to the cathode is complicatedly bent, and the distance between the electrodes is long. . In addition, the density of cellulose used for the separator is about 1.5 g / cm ³ , and those which can be currently used as the separator have a porosity of 50 to 60%.
Less than and low. If the porosity exceeds 70%, cellulose can be made, but the structure is extremely non-uniform, and when used as a separator, the size of the through-holes is uniform and uniform characteristics can be obtained. Can not.

Meanwhile, a technique using a thermoplastic resin microporous film as a separator has also been developed. However, for example, when a microporous film made of polypropylene is used, although the safety against short-circuit between poles is increased, currently available ones have a porosity of at most about 40%,
In addition, the shape and size of the through-holes are not uniform, and there is a drawback that the required bottom loss cannot be obtained in an electrolytic capacitor using this as a separator.

Also, the use of polyethylene microporous film as a thermoplastic resin microporous film has been attempted,
Also in this case, what is currently provided has a complicatedly bent through hole, and the distance between the electrodes is very long. Therefore, the distance that the ionogen must travel becomes longer,
There are drawbacks such as preventing the fast movement of the ionogen between the electrodes in the high frequency region and the inability of the ionogen to move between the electrodes to cope with an increase in the viscosity of the driving electrolyte at a low temperature. That is, the performance of the aluminum electrolytic capacitor using this separator is inferior in the high frequency region and the low temperature region.

The present invention relates to a technique for improving the above-mentioned drawbacks of the conventional aluminum electrolytic capacitor, and provides an electrolytic capacitor exhibiting stable performance under a wide range of use conditions.

[Means for Solving the Problems] The present invention is a microporous film having a large number of micropores obtained by stretching a thermoplastic resin, wherein the micropores are
A group of unstretched plate-like planes formed at predetermined intervals in a direction perpendicular to the stretching direction of the film, and stretch-oriented fibrils formed at predetermined intervals in the direction of stretching of the film and joining adjacent unstretched plate-like planes An anode foil made of a valve action metal having an anodic oxide film formed thereon and a cathode foil opposed thereto are laminated and wound through a separator made of a thermoplastic resin microporous film which is a through hole formed by the group. The present invention relates to an electrolytic capacitor comprising a capacitor element being turned.

In particular, the thickness of the unstretched plate-like plane is 0.1 to 0.5 μm, the diameter of the stretch-oriented firil is 0.03 to 0.15 μm, and the average pore diameter of the micropores of the microporous film is 0.1 to 0.3.
An electrolytic capacitor using a microporous film made of a thermoplastic resin having a pore size of 60 μm and a porosity of 60 to 75% as a separator has excellent performance and is preferred.

The porosity of the microporous film is preferably in the range of 60 to 75%. If the porosity is less than 60%, the movement of ionogen is hindered or the amount of the driving electrolyte retained is reduced, so that when the electrolytic capacitor is used for a long time, the characteristics are easily deteriorated due to the loss of the driving electrolytic wave, which is called a so-called drip-up. It is not preferable. On the other hand, when the porosity exceeds 75%, the film strength required as a separator cannot be maintained.

If the thickness of the unstretched plate-like plane exceeds 0.5 μm, or if the diameter of the stretch-oriented fibrils exceeds 0.15 μm, the porosity of the microporous film decreases and the performance of the electrolytic capacitor decreases, which is not preferable. .

The size of the through-holes of the microporous film (value measured using ethanol according to the half-dry method described in ASTMF316-80) is preferably in the range of 0.1 to 0.3 μm. (The shape of the through-holes of the microporous film of the present invention is substantially square, but is converted into a circle according to the method described above and expressed as an average pore diameter.) When the average pore diameter is less than 0.1 μm, the movement of ionogen becomes difficult. , 0.3 μm, due to minute projections on the surface of the metal foil constituting the electrode,
It is not preferable because a short circuit easily occurs between the electrodes.

The thermoplastic resin porous film used in the electrolytic capacitor of the present invention can be manufactured by the method described below.

The method is blown film molding, T-
A thermoplastic resin film having an appropriate degree of crystal orientation molded by a die film molding method or the like, preferably at a temperature about 15 to 70 ° C. lower than the melting point of the thermoplastic resin,
The film is heated for at least 50 seconds at a low temperature of not more than 50 ° C. higher than the boiling point of the medium from the freezing point of the medium in a medium such as nitrogen, carbon monoxide, methane, and ethane.
%, Preferably a method of stretching at a stretching ratio in the range of 10 to 150%, or a thermoplastic resin film having an appropriate degree of crystal orientation, preferably 15 to 15 to the melting point of the thermoplastic resin
The film is heat-treated at a temperature of about 70 ° C. for 3 seconds or more. Preferably, according to a stretching method such as a method of stretching at a stretching ratio in the range of 150 to 600%, a film having a large number of fine holes having a substantially square cross section on the entire surface and penetrating relatively linearly from one surface of the film to the other surface. It is manufactured.

Examples of the material of the thermoplastic resin microporous film produced by the above method include crystalline synthetic resins such as polyethylene, polypropylene, poly-4-methylpentene-1, and polytetrafluoroethylene. In particular, general-purpose resins having good workability such as polyethylene and polypropylene are preferable.

[Operation] With the above configuration, the porosity of the separator is high, and the through holes are formed perpendicular to the plane of the film. Has good permeability and bottom loss.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Examples and Comparative Examples) Five types of separators having materials, thicknesses, average pore diameters, and porosity as shown in Table 1 (Examples 1, 2, and 3 and Comparative Examples 1 and 2)
As shown in FIG. 1, both electrodes are opposed to each other between the aluminum anode electrolytic foil 1 and the aluminum cathode electrode foil 2 with the above-mentioned five types of separators 3 interposed therebetween, and are wound.
A 10 V, 330 μF aluminum electrolytic capacitor was manufactured and a performance test was performed.

Table 1 shows that these five types of electrolytic capacitors have a temperature
The capacitance, the tangent of the loss angle (tan δ) (in the case of a frequency f = 120 Hz), the impedance, and the occurrence ratio of short-circuit at ° C.

As is clear from the test results of the above Examples and Comparative Examples, the aluminum electrolytic capacitors of the present invention (Examples 1, 2, and 3) were
It was found that the tan δ and the impedance at −40 ° C. and -40 ° C. could be reduced, the short-circuit occurrence rate at the time of assembling the electrolytic capacitor was low, and the performance was good.

[Effects of the Invention] As described above, the electrolytic capacitor using the thermoplastic resin microporous film of the present invention as a separator,
Although the porosity of the separator is high and the through hole is formed perpendicular to the plane of the film, the distance between the electrodes is short, the loss is low, and it has excellent performance even under normal use conditions. In particular, the excellent performance is maintained even in a high frequency range or a low temperature range.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an element portion of an electrolytic capacitor. 1 ... Anode electrode foil, 2 ... Cathode electrode foil, 3 ... Separator, 4 ... Drawing lead.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Noriaki Shio 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Eiichi Kamei 3-10 Nakamiyakitamachi, Hirakata-shi, Osaka Ube Industries (56) References JP-A-1-113442 (JP, A) JP-A-63-164420 (JP, A)

Claims (3)

(57) [Claims] 1. A microporous film having a large number of micropores obtained by stretching a thermoplastic resin, wherein the micropores are
A group of unstretched plate-like planes formed at predetermined intervals in a direction perpendicular to the direction of stretching of the film, and stretch-oriented fibrils formed at predetermined intervals in the direction of stretching of the film and joining adjacent unstretched plate-like planes An anode foil made of a valve action metal having an anodic oxide film formed thereon and a cathode foil opposed thereto are laminated and wound through a separator made of a thermoplastic resin microporous film which is a through hole formed by the group. An electrolytic capacitor comprising a capacitor element that is turned. 2. The electrolytic capacitor according to claim 1, wherein the thickness of the unstretched plate-like plane is 0.1 to 0.5 μm, and the diameter of the stretch-oriented fibrils is 0.03 to 0.15 μm. 3. The microporous film having an average pore diameter of 0.
The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor has a porosity of 1 to 0.3 µm and a porosity of 60 to 75%.