JPH0677008A - Heat-sensitive conductor - Google Patents

Abstract

PURPOSE:To obtain a new heat-sensitive conductor having the positive resistance temperature coefficient with which current application can be controlled by a method wherein electric resistance is suddenly increased when temperature is raised in excess of the set temperature. CONSTITUTION:This heat-sensing conductive wire is composed of a core wire made of conductive material consisting of one or more kinds of element belonging to 3B or 6B of the law of periodic table and having at least a nonconductive melting phase and a conductive crystalline phase, and an outer covering made of insulating material having the heat-resisting property higher than the melting point of the conductive material. It is desirable that the material mainly composed of chalcogenite compound is used as the conductive material which constitutes the core wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating resistance wire used for a sheet heating element or the like, or a heat-sensitive conductive wire used for a thermal fuse or the like.

[0002]

2. Description of the Related Art As a heating resistance wire for a sheet heating element or the like, a conductive wire in which a long thin metal wire is densely wound around a relatively short core wire, fine particles of metal, metal oxide, conductive carbon, or the like, or Conductive wire formed by linearly forming conductive material obtained by mixing fibers with polymer material, or conductive wire formed by depositing the above-mentioned conductive material on a core wire made of glass fiber or synthetic fiber, etc. Is known to be used.

A heating element using such a heating resistance wire may have an abnormal temperature rise when a failure of the temperature control mechanism occurs. Therefore, even if such a failure occurs, an abnormal temperature of the heating resistance wire may occur. In order to prevent the rise, it is desirable that the heating resistance wire itself has a temperature control characteristic. However, the resistance-temperature characteristic of the conventional conductive wire as described above is not sufficiently large to control the temperature.
Therefore, for example, a method of forming a conductive wire using a conductive material obtained by mixing a material such as a semiconductor having a large positive resistance / temperature coefficient with a polymer material has been proposed. Generally has the drawback that the electrical resistance easily changes depending on the environmental conditions such as temperature and humidity, and among others, the electrical resistance of a conductive wire coated with a conductive material on a non-conductive core wire also changes due to contact or friction. There is a problem.

[0004]

Under the above circumstances, according to the present invention, when the temperature becomes equal to or higher than the set temperature, the electric resistance rapidly increases and the energization can be restricted. It is intended to provide a novel heat-sensitive conductive wire having resistance and temperature coefficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive material comprising at least one element belonging to 3B to 6B of the Periodic Table, in which the melt phase is non-conductive and the crystalline phase is conductive. The heat-sensitive conductive wire of the present invention is characterized in that it comprises a core wire made of and a jacket made of an insulating material having a heat resistant temperature higher than the melting point of the conductive material.

The conductive material constituting the core of the heat-sensitive conductive wire of the present invention is obtained by heating the amorphous phase having a low conductivity obtained by cooling and solidifying the molten phase to a temperature higher than the crystallization temperature for phase conversion. In this case, it is particularly preferable that the main component is a chalcogen or chalcogenide compound.

The chalcogen or chalcogenide compound that can be used as the conductive material of the heat-sensitive conductive wire of the present invention is
For example, there are selenium, selenium-tellurium alloy, and the like, and it is also possible to use them as a chalcogenide compound in which metals such as gold, silver, and copper are appropriately mixed to adjust the conductivity.

[0008]

In the heat-sensitive conductive wire of the present invention, the core wire is melted while being wrapped in the outer cover made of a heat resistant insulating material at a temperature equal to or higher than the melting point of the conductive material forming the core wire, so that the electric resistance is rapidly increased. Therefore, energization is effectively suppressed. Next, when the once melted core wire solidifies due to a decrease in temperature and becomes a crystalline phase again, it returns to the same characteristics as the heat-sensitive conductive wire before melting.

When the molten conductive material does not have sufficient cooling time to crystallize when it solidifies, it becomes an amorphous phase and has a lower conductivity than when it is a crystalline phase. A heat-sensitive conductive wire having stable conductivity can be obtained by holding the wire in a heated state at a crystallization temperature or higher and converting it into a crystalline phase.

[0010]

【Example】

(Example 1) Selenium melted at 300 ° C was drawn out from a nozzle to form a wire, which was drawn to form a filament having a diameter of about 1 µm. Then, this selenium filament was immersed in a 17% dimethylformamide solution of polyamidecarboxylic acid, which is an equimolar reaction product of pyromellitic anhydride and p-phenylenediamine, and then pulled up, followed by coagulation in an 80% hydrous ethanol bath. , Wash with water and dry at 100 ℃,
A coated filament was formed. Further, this filament was heat-treated at 180 ° C. to completely polyimidize the outer cover and crystallize the core wire to obtain a heat-sensitive conductive wire A of the present invention having a diameter of about 1.5 μm.

(Example 2) A selenium-tellurium alloy containing 10% by weight of tellurium melted at 320 ° C. was used to form a filament having a diameter of about 1 μm in the same manner as in Example 1. Then, the filament is immersed in a 10% p-chlorophenol solution of polyimide, which is an equimolar reaction product of 3,3 ', 4,4'-diphenyltetracarboxylic anhydride and 4,4'-diaminodiphenyl ether. Then, it was pulled up and solidified in a methanol bath to form a coated filament. This filament was heat-treated at 200 ° C. to completely dry the outer cover and crystallize the core wire to obtain a heat-sensitive conductive wire B of the present invention having a diameter of about 1.5 μm.

Reference Example The polyimide solution used in the second example was extruded from a spinning nozzle, coagulated in a methanol bath, and stretched at 300 ° C. to obtain a polyimide fiber having a diameter of about 2 μm. Then, this polyimide fiber was further twisted to obtain a weft yarn having a diameter of about 50 μm for producing a conductive woven fabric.

Test Example 1 Using the warp yarn having a diameter of about 50 μm obtained by twisting each of the heat-sensitive conductive wires A and B of the present invention produced as described above, and the weft produced in the reference example. Each of the satin-woven conductive woven fabrics was prepared. Cut these woven fabrics so that the warp length is about 10 cm, apply silver-based conductive paste to the cut end, and cure to form the electrode part.
A sheet heating element was obtained. When a thermocouple was attached to the surface of this sheet heating element and electricity was supplied from a 100 V AC power source connected to the electrode section, all exhibited good heat generation.

When the voltage applied to the sheet heating element was increased to raise the temperature, no current flowed and the heat generation stopped when the temperature exceeded 210 ° C.
Next, when these sheet heating elements were held in a constant temperature bath at 150 ° C. for about 30 minutes and cooled, and then an energization test was carried out again, good exothermic properties were reproduced.

(Example 3) A selenium-tellurium alloy containing 30% by weight of tellurium was crushed to 1 μm or less in a heat-shrinkable tube made of a fluororesin having an inner diameter of 0.6 mm (made by Mitsui DuPont Fluorochemical, Tefzel 200). Was filled in, vacuumed to seal both ends, and then heated to 260 ° C. to melt the selenium-tellurium alloy and compress the whole finely. This was once cooled and then heated again to 150 ° C. to crystallize the core wire to obtain a heat-sensitive conductive wire C of the present invention having an outer diameter of about 0.8 mm.

(Test Example 2) An end portion of the heat-sensitive conductive wire C was cut off, and a silver-based conductive paste was applied thereto and cured to form an electrode portion, and a heat-sensitive wire having a length of about 1 cm was prepared. On the other hand, a part of this heat-sensitive wire was placed and fixed on the hot plate with a thermocouple attached, and a voltage of 10 V was applied to the heat-sensitive wire to gradually increase the temperature of the hot plate while checking the conduction current. When the temperature of the plate exceeded 230 ° C, conduction of the heat-sensitive wire stopped. Next, when the temperature of the hot plate was gradually decreased, when the temperature of the hot plate reached 180 ° C., conduction of the heat-sensitive wire started again.

[0017]

EFFECTS OF THE INVENTION The heat-sensitive conductive wire of the present invention comprises a core wire made of a substance having a specific property as a conductive material, and the outside thereof is covered with an insulating material having a heat resistant temperature higher than the melting point of the core wire. Then, when the temperature becomes equal to or higher than a predetermined temperature, the conduction automatically stops. Therefore, when it is used as a heating wire, there is no risk of an accident due to abnormal heat generation, and when it is used as a sensor wire for detecting abnormal temperature, it has high sensitivity and there is no risk of malfunction. Moreover, it has the advantage that it is not easily damaged by mechanical external force, and even after the electrical connection is once stopped, it is restored to a complete initial state by heat treatment within a predetermined temperature range, and there is no deterioration in function.

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Claims (3)

[Claims] 1. A core wire made of a conductive material comprising at least one element belonging to 3B to 6B of the Periodic Table and having a non-conductive molten phase and a conductive crystalline phase, and the conductive material. And a jacket made of an insulating material having a heat resistant temperature higher than the melting point of the heat-sensitive conductive wire. 2. The heat-sensitive conductive wire according to claim 1, wherein the conductive material is formed by heating an amorphous core wire obtained by cooling and solidifying a molten phase to a crystallization temperature or higher. 3. The heat-sensitive conductive wire according to claim 1, wherein the conductive material contains chalcogen or a chalcogenide compound as a main component.