JPH0582012A - Overcurrent protection element - Google Patents

Abstract

PURPOSE:To eliminate the corrosiveness to metal and a danger of the fire, and operate an overcurrent protection element appropriately independently from the influence of the environment by using carboxylic acid as dopant of the overcurrent protection element made of conductive high polymer, which includes dopant. CONSTITUTION:As carboxylic acid to be used for dopant, monatomic carboxylic acid such as formic acid, acetic acid or the like; diatomic carboxylic acid such as oxalic acid, malonic acid or the like; ketocarboxylic acid such as pyruvic acid or the like, amino acid such as glutamic acid or the like; aromatic carboxylic acid such as phthalic acid or the like are used. Especially, oxalic acid is desirable in consideration that the resistance is raised quickly to cut the current at an operation temperature of the element. Doping quantity is set at 20-50mol% of a monomer unit composing a conductive high polymer such as polyaniline or the like to be doped. The dopant included conductive high polymer compound is formed into an appropriate shape to manufacture an excess current protecting element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection device composed of a conductive polymer compound containing a dopant.

[0002]

2. Description of the Related Art An overcurrent protection device made of a conductive polymer compound containing a dopant is known from JP-A-59-134523, and as the dopant, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, borofluoric acid, etc. are known. Has been. In addition, JP-A-59-
Japanese Patent No. 134523 describes an overcurrent protection device using picric acid as a dopant.

[0003]

[Problems to be Solved by the Invention] However, hydrochloric acid, sulfuric acid,
Since nitric acid, perchloric acid, borofluoric acid, etc. are corrosive to metals, they cannot be used as an overcurrent protection element for circuits. Further, since picric acid is explosive, a risk of fire accompanies production, storage, transportation, etc. of an element containing it.

In a conductive polymer having hydrochloric acid as a dopant, the increase in resistance with temperature rise is largely due to oxidation by oxygen in the air. The rise in resistance is delayed. Then, when the element starts to operate, current concentrates inside. Therefore, there is a limit in improving the withstand voltage of the device. Further, if an oxygen impermeable coating is provided for insulation, or if it is used in an oxygen-free environment, the increase in resistance is significantly delayed, so that it does not function properly as an overcurrent protection element.

Therefore, an object of the present invention is to provide a dopant-containing overcurrent protection device which is safe without corrosiveness to metals or danger of fire and which operates properly regardless of the use environment. ..

[0006]

Means for Solving the Problems The present invention is achieved in order to achieve the above object, in an overcurrent protection device comprising a conductive polymer containing a dopant, wherein the dopant is a carboxylic acid. Provide a protection element.

Examples of the carboxylic acid used as a carboxylic acid dopant include monovalent carboxylic acids such as formic acid, acetic acid and propionic acid; divalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid and maleic acid. Acid; ketocarboxylic acid such as pyruvic acid;
Amino acids such as glutamic acid; aromatic carboxylic acids such as phthalic acid and picolinic acid. Among these,
Oxalic acid is particularly preferable because the resistance sharply rises when the temperature of the overcurrent protection element reaches the operating temperature and the current is instantaneously cut off.

The doping amount of the dopant may usually be 20 to 50 mol% of the monomer units constituting the polymer to which it is doped. The doping method is not particularly limited, and examples thereof include a chemical doping method and an electrochemical method.

Conductive Polymer Examples of the conductive polymer used include polyaniline, polypyrrole, polyacetylene, polythiophene and the like.

Manufacture of Device The device of the present invention is manufactured by molding the above-mentioned conductive polymer compound containing a dopant into an appropriate shape. As for the shape,
For example, a cylindrical shape, a disk shape, a sheet shape, etc. may be mentioned. A typical element has a cylindrical shape and is used by providing electrodes, which will be described later, at the upper and lower circular end portions.

The overcurrent protection element is usually used, for example, in a state of being sandwiched between two electrodes at the time of use. Examples of the material of this electrode include various metals such as gold, silver, copper, nickel, chromium, aluminum and indium, and carbon. In selecting these electrode materials, a material that allows ohmic contact with the conductive polymer to be used is used. As a method of attaching such an electrode, for example, a physical or chemical method such as baking, vapor deposition, electroless plating, conductive paste application, or a method of mechanically clamping and sandwiching two metal electrodes And so on.

In the device of the present invention, the electrodes described above do not necessarily have to be provided at the time of manufacture and sale. This is because, for example, when the device is mechanically clamped and clamped by a predetermined electrode or the like provided in advance in use as described above, it is not necessary to previously provide and place the electrode on the element.

[0013]

[Function] Hydrochloric acid, nitric acid, etc. evaporate when the overcurrent protection element is heated and operate, and damage the surrounding electronic parts. For example, among carboxylic acids, oxalic acid, malonic acid, maleic acid, etc. Decomposes into H ₂ O, CO _2, CO and other electronic components that are not likely to damage electronic components. Further, for example, a carboxylic acid such as acetic acid having a high decomposition temperature is vaporized in a vapor state without being decomposed, but its influence on electronic parts is minor as compared with conventional hydrochloric acid or the like. When the former type of carboxylic acid, which decomposes at the operating temperature, is used as the dopant, the resistance rises particularly rapidly because these dopants decompose and the entire device is rapidly insulated.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Distilled water was added to 13.3 g of aniline and 18 ml of hydrochloric acid to prepare 1
After making 50 ml, the mixture was transferred to a 200 ml Erlenmeyer flask and kept at 0 ° C. Separately, an aqueous solution prepared by dissolving 15.3 g of ammonium peroxodisulfate in 25 ml of distilled water was added dropwise to the aqueous solution in the Erlenmeyer flask over 40 minutes. Polymerization was carried out while stirring for 24 hours. The obtained polymer was washed with water and then treated with aqueous ammonia to dedope the dopant hydrochloric acid.
Further, it was washed with water to obtain a polyaniline containing no dopant. This was immersed in 1M oxalic acid to obtain oxalic acid-doped polyaniline. After this was dried, a molded body having a diameter of 5 mm and a thickness of 1 mm was formed by press molding, and electrodes were formed with gold paste on both surfaces of the molded body to prepare an overcurrent protection element.

Examples 2-8 In Examples 2-8, instead of 1M oxalic acid, a 1M solution of maleic acid in ethanol, pyruvic acid (100%),
1M malonic acid, 1M ethanol solution of orthophthalic acid,
Acetic acid (100%), saturated aqueous solution of α-picolinic acid, or L-
An overcurrent protection element made of carboxylic acid-doped polyaniline was produced in the same manner as in Example 1 except that saturated aqueous solutions of glutamic acid were used.

Comparative Example Distilled water was added to 13.3 g of aniline and 18 ml of hydrochloric acid to make 1
After making 50 ml, the mixture was transferred to a 200 ml triangular flask and kept at 0 ° C. Separately, an aqueous solution prepared by dissolving 15.3 g of ammonium peroxodisulfate in 25 ml of distilled water was added dropwise to the aqueous solution in the Erlenmeyer flask over 40 minutes. Polymerization was carried out while stirring for 24 hours. The obtained hydrochloric acid-doped polyaniline was dried and then press-molded to form a molded body having a diameter of 5 mm and a thickness of 1 mm, and electrodes were formed on both sides of the molded body with a gold paste to manufacture an overcurrent protection device.

Characteristic test (1) When the element resistances of the overcurrent protection elements produced in Examples 1 to 8 and Comparative Example were measured, the results shown in Table 1 were obtained. (2) The temperature dependence of the volume resistivity of the conductive polyaniline produced in Examples 1, 4 and Comparative Example was measured, and the results shown in FIG. 1 were obtained. (3) A molded body was manufactured in the same manner as in Examples 1 to 4, 6 to 8 and Comparative Example, and left on the copper plate without forming an electrode for 10 days at room temperature in the atmosphere to examine the change of the copper plate. The results are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

EFFECT OF THE INVENTION Since the dopant-containing overcurrent protection device of the present invention has a carboxylic acid as a dopant, it has very weak or negligible corrosiveness to metals, and has no risk of explosiveness. It can also be used as an overcurrent protection device.

In particular, in the embodiment using oxalic acid or the like which decomposes at the operating temperature as a dopant, unlike the conventional device using hydrochloric acid or the like which requires oxidation by oxygen as a dopant, an increase in resistance of the device is caused by self-decomposition of the dopant. Because it happens
The resistance increase of the entire device occurs almost uniformly. Therefore,
The current does not concentrate locally. It also has high reliability in various atmospheres regardless of the presence or absence of oxygen.

[Brief description of drawings]

FIG. 1 shows the temperature dependence of volume resistivity for conductive polyaniline produced in Examples 1, 2 and 6, and Comparative Example.

Claims (3)

[Claims] 1. An overcurrent protection device comprising a conductive polymer containing a dopant, wherein the dopant is a carboxylic acid. 2. The overcurrent protection device according to claim 1, wherein the conductive polymer is polyaniline. 3. The overcurrent protection element according to claim 1 or 2, wherein the carboxylic acid is oxalic acid.