JP2000133502A - Organic positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the rate of change of a resistance value by a method, wherein in an organic positive temperature coefficient thermistor in which a Ni electrode is provided on both faces of a sheet-like forming body of a thermistor element body containing conductive particles as a filler in a crystalline polymer, ball-like Ni powders formed with a plurality of projections as the conductive particles are used. SOLUTION: This organic positive temperature coefficient thermistor comprises a crystalline polymer, and a specified amount of ball-like Ni powders having a plurality of projections mixedly kneaded in the crystalline polymer as a conductive substance. As the crystalline polymer, polyvinylidene fluoride, polyethylene, polyethylene oxide, t-4-polybutadiene, polyethylene acrylate, etc., are used. According to the organic positive temperature coefficient thermistor, a tunnel current is easy to flow due to the plurality of projections of a plurality of conductive particles, and an initial resistance value is at normal temperatures small, and contact points between conductive particles are easy to cut, so that PTC characteristics rise sharply and large change in the resistant values can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic positive temperature coefficient thermistor.
The present invention relates to an organic positive temperature coefficient thermistor having a temperature coefficient.

[0002]

2. Description of the Related Art Conventionally, an organic positive temperature coefficient thermistor having PTC characteristics in which a fine metal powder, carbon black or the like is dispersed in a crystalline polymer such as polyethylene or polypropylene is known in the art. For example, U.S. Patent No.
This is disclosed in, for example, Japanese Patent Nos. 3591526 and 3673121.

[0003] By the way, the PTC characteristic shows a sharp volume expansion when the crystalline polymer changes from crystalline to amorphous at the melting point, so that the particles of the conductive fine powder dispersed in the crystalline polymer are dispersed. This occurs because the spacing is expanded and the contact resistance between the particles increases rapidly.

Such an organic positive temperature coefficient thermistor can be used, for example, as a temperature detector or a self-control type heater. However, the performance required of the organic positive temperature coefficient thermistor is such that the rise of the PTC characteristic is steep and a large resistance value is obtained. It is necessary to show a change and to have a small initial resistance value at room temperature.

[0005]

However, conventional organic positive temperature coefficient thermistors are often filled with carbon black as a conductive substance. In this case, the filling amount is increased to reduce the initial resistance value. Needed. In such a case, there has been a problem that the rate of change in resistance becomes small and application to a heater or the like becomes difficult.

[0006] In addition, there is also known one in which general metal fine powder particles are filled as a conductive substance.
Similarly, in order to reduce the initial resistance value, it is necessary to increase the filling amount, and in such a case, a large change rate cannot be obtained, so that it has not been put to practical use.

Accordingly, an object of the present invention is to provide an organic positive temperature coefficient thermistor having a small initial resistance value at room temperature, a sharp rise in PTC characteristics and a large change in resistance value.

[0008]

The organic positive temperature coefficient thermistor according to claim 1 is provided with Ni electrodes on both surfaces of a sheet-like molded body of a thermistor body containing conductive particles as a filler in a crystalline polymer. Organic positive temperature coefficient thermistor,
The conductive particles include spherical Ni powder on which a large number of protrusions are formed.

The organic positive temperature coefficient thermistor according to claim 2 is an organic positive temperature coefficient thermistor having a Ni-electrode provided on both surfaces of a sheet-shaped molded body of a thermistor body containing conductive particles as a filler in a crystalline polymer. In addition, the conductive particles include powder in which spherical Ni powders on which a large number of protrusions are formed are connected in a chain.

[0010] According to the organic positive temperature coefficient thermistor of the first aspect, the crystalline polymer has a spherical Ni having a large number of protrusions.
Since it is filled with powder, spherical Ni with a larger number of protrusions than when filled with spherical conductive particles is used.
Tunnel currents tend to flow between powders due to their shape, which results in good conductivity, low initial resistance at room temperature, and a large spacing between conductive particles as compared to spherical ones. The rise of the PTC characteristic is steep and exhibits a large change in resistance value. In addition, since the Ni electrode made of the same material as the filler is provided, the characteristics are further improved.

According to the organic positive temperature coefficient thermistor of the second aspect, the crystalline polymer has a spherical Ni having a large number of protrusions.
Since the powder is filled with a conductive material in a shape linked in a chain, it has a large number of protrusions and is connected in a chain, A larger tunnel current flows, thereby improving the conductivity, reducing the initial resistance value at room temperature, and increasing the interval between the conductive particles as compared with a true spherical particle, so that the rise of the PTC characteristic is increased. It exhibits a steep and large resistance change. Also, Ni made of the same material as the filler is used.
Since the electrodes are provided, the characteristics are further improved.

[0012]

Embodiments of the present invention will be described below in detail.

The organic positive temperature coefficient thermistor according to the first embodiment comprises a crystalline polymer and a predetermined amount of spherical Ni powder having a large number of projections kneaded with the crystalline polymer as a conductive substance. . A micrograph of this organic positive temperature coefficient thermistor is shown in FIG.

As is apparent from the photograph shown in FIG. 1, according to the organic positive temperature coefficient thermistor of the present embodiment, a tunnel current easily flows due to a large number of projections of a large number of conductive particles. The resistance is good, the initial resistance at room temperature is small, and the distance between conductive particles is large compared to spherical ones. Obtainable.

As the crystalline polymer, polyvinylidene fluoride is used.

Examples of the crystalline polymer include polyvinylidene fluoride, polyethylene, polyethylene oxide, t-
4-polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, polyester, polyamide, polyether, polycaprolactam, fluorinated ethylene-propylene copolymer, chlorinated polyethylene, chlorosulfonated Examples include ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride, polycarbonate, polyacetal, polyalkylene oxide, polyphenylene oxide, polysulfone, and fluororesin.

The type of the crystalline polymer can be appropriately selected according to the desired performance, application and the like.

As the conductive particles having a large number of projections, spherical Ni powders (manufactured by Inco Limited) having a large number of projections are used.

The Ni powder is produced, for example, by the carbonyl method, and is obtained by converting nickel carbonyl having a purity of 99.99% by the following chemical formula.

Ni (CO) ₄ → Ni + 4CO The average particle size is 3 to 7 μm (measured by fish-sub-sieve method), and the apparent density is 1.8 to 2.7 (g / c).
c) The specific surface area has physical properties of 0.34 to 0.44 (m ² / g).

Next, a second embodiment will be described.

The organic positive temperature coefficient thermistor according to the second embodiment is formed by kneading a crystalline polymer and a spherical Ni powder having a large number of projections as a conductive substance connected to the crystalline polymer. It can be obtained by

FIG. 2 shows a micrograph of the organic positive temperature coefficient thermistor.

As is apparent from the photograph shown in FIG. 2, according to the organic positive temperature coefficient thermistor of the present embodiment, a large number of protrusions of each of the conductive substances make it easy for a tunnel current to flow, thereby increasing the conductivity. As a result, the initial resistance value at room temperature is small, and the distance between the conductive particles is large, so that the conductive path is easily cut off, so that the rise of the PTC characteristic is sharp and a large change in the resistance value can be obtained.

The use of polyvinylidene fluoride as the crystalline polymer is the same as in the first embodiment.

As each of the conductive materials, a filament-like chain Ni powder (manufactured by Inco Limited) is used.

The average particle size of the filamentous chain Ni powder is 2.2 to 2.8 μm (measured by a fish-sub-sieve method), and the apparent density is 0.5 to 0.95 (g).
/ Cc), and the specific surface area is 0.58 to 0.63 (m ² /
g) each physical property.

The details will be described below.

Example 1 Spherical Ni powder having a large number of protrusions as a conductive substance using polyvinylidene fluoride as a crystalline polymer (average particle size: 3.0 to 7.0 μm, manufactured by Inco Limited)
Was added to the polyvinylidene fluoride in an amount of 30 parts by weight, kneaded with a Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd.), and then press-molded into a sheet having a thickness of 0.7 mm. gave.

Further, N electrodes are formed on both sides of the molded product as electrodes.
The i-foil was pressed and punched out into a disk having a diameter of 10 mm to obtain a sample.

Next, the PTC characteristics of this sample were measured. In this measurement, the temperature of the sample was raised and lowered in a thermostat, the resistance at each predetermined temperature was measured, and the relationship between the temperature and the resistance was obtained. FIG. 3 shows the measurement results.

From the measurement results shown in FIG. 3, the resistance value at room temperature is a very low value of 0.6Ω, but at the transition temperature, the resistance value rises sharply and the maximum resistance value is 3 × 10 ⁷ Ω. It can be seen that the rate of change is a high value of 10 ⁸ or more.

Further, even at a temperature of 176 ° C. or higher where the maximum resistance was exhibited, the resistance did not decrease and the sample did not deform due to heat.

As described above, the organic positive temperature coefficient thermistor of this embodiment has a low resistance value at room temperature and has a steep PTC characteristic.

Example 2 A disk-shaped sample was formed in the same manner as in Example 1 except that the content of the spherical Ni powder having many projections was changed to 20 parts by weight.

The PTC characteristics of this sample were measured in the same manner as in Example 1, and the measurement results shown in FIG. 4 were obtained. As is clear from FIG. 4, the resistance value at room temperature is as low as 1.4Ω, but at the transition temperature, the resistance value rises rapidly, the maximum resistance value becomes 5 × 10 ⁷ Ω, and the rate of change is Is 10 ⁷
It was higher than the above.

Example 3 A disk-shaped sample was formed in the same manner as in Example 1, except that the content of the spherical Ni powder having many projections was changed to 60 parts by weight.

The PTC characteristics of this sample were measured in the same manner as in Example 1, and the measurement results shown in FIG. 5 were obtained. As is clear from FIG. 5, the resistance value at room temperature is a very low value of 0.07Ω, but at the transition temperature, the resistance value rises sharply, and the maximum resistance value becomes 3 × 10 ⁶ Ω · cm. Become
The rate of change was as high as 10 ⁸ or more.

Example 4 Polyvinylidene fluoride was used as the crystalline polymer, and filamentary chain Ni powder (average particle size of 2.2 to 2.8 μm, manufactured by Inco Limited) was used as the conductive material. Filament-like chain Ni powder was added to vinylidene at a ratio of 30 parts by weight, kneaded with a lab plast mill, pressed into a sheet having a thickness of 0.7 mm, and then subjected to a crosslinking treatment.

Further, N electrodes were formed on both surfaces of this molded product as electrodes.
The i-foil was pressed and punched out into a disk having a diameter of 10 mm to obtain a sample.

Next, the PTC characteristics of this sample were measured. In this measurement, the temperature of the sample was raised and lowered in a thermostat, the resistance at each predetermined temperature was measured, and the relationship between the temperature and the resistance was obtained. FIG. 6 shows the measurement results.

From the measurement results shown in FIG. 6, the resistance value at room temperature is a very low value of 0.5Ω, but at the transition temperature, the resistance value rises sharply and the maximum resistance value is 2 × 10 ⁷ Ω. It can be seen that the resistance change rate is a high value of 10 ⁸ or more.

The resistance did not decrease even at a temperature of 176 ° C. or higher where the maximum resistance was exhibited, and the sample did not deform due to heat.

As described above, the organic positive temperature coefficient thermistor of this embodiment has a low resistance value at room temperature and a steep PTC characteristic.

Example 5 A disk-shaped sample was formed in the same manner as in Example 4, except that the content of the fermented chain Ni powder was changed to 20 parts by weight.

The PTC characteristics of this sample were measured in the same manner as in Example 1, and the measurement results shown in FIG. 7 were obtained. As is clear from FIG. 7, the resistance value at room temperature is as low as 1.2Ω, but at the transition temperature, the resistance value rises rapidly, the maximum resistance value becomes 4 × 10 ⁷ Ω, and the rate of change is Is 10 ⁷
It was higher than the above.

Example 6 A disk-shaped sample was formed in the same manner as in Example 4, except that the content of the fermented chain Ni powder was changed to 60 parts by weight.

The PTC characteristics of this sample were measured in the same manner as in Example 1, and the measurement results shown in FIG. 8 were obtained. As is clear from FIG. 8, the resistance value at room temperature is a very low value of 0.05Ω, but at the transition temperature, the resistance value rises sharply, and the maximum resistance value becomes 2 × 10 ⁶ Ω · cm. Become
The rate of change was as high as 10 ⁸ or more.

Comparative Example 1 A comparative sample was prepared in the same manner as in Example 3, except that the conductive substance was carbon black and the content was 40 parts by weight. FIG. 9 shows the measurement results of this comparative sample. As is clear from FIG. 9, the resistance at room temperature was about 0.2 Ω, the maximum resistance was 4 × 10 ⁴ Ω · cm, and the rate of change was about 10 ⁵ .

Comparative Example 2 A comparative sample was prepared in the same manner as in Example 1 except that the conductive substance was a spherical Ni powder (average particle size: 3 μm, manufactured by Inco Limited). FIG. 10 shows the measurement results of this comparative sample. As is clear from FIG. 10, the resistance value of this comparative sample at room temperature was about 9 × 10 ⁴ Ω, the maximum resistance value was 4 × 10 ⁸ Ω, and the rate of change was about 10 ³ .

As described in detail above, the organic positive temperature coefficient thermistor of the present embodiment has a relatively small amount of spherical Ni powder or filamentary chain Ni powder having a large number of projections as a conductive substance. Instead, it has both low resistance at room temperature and steep PTC characteristics, and is suitable for application to heaters and the like.

The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention.

[0053]

According to the present invention described in detail above, the following effects can be obtained by employing the above-described configuration.

According to the first aspect of the present invention, a spherical Ni powder having a large number of projections has a good conductivity since tunnel current flows easily in the spherical Ni powder having a large number of projections as compared with a case where a spherical conductive material is used as the filler. The present invention provides an organic positive temperature coefficient thermistor having a small initial resistance value at room temperature and a relatively large distance between conductive particles, so that a conductive path is easily cut off, a rise in PTC characteristics is steep, and a large change in resistance value is exhibited. be able to.

Since the Ni electrode made of the same material as the filler is provided, the characteristics are further improved.

According to the second aspect of the present invention, in the case of a conductive material having a shape in which spherical Ni powders having a large number of protrusions are connected, the protrusions are different from the case where a spherical conductive material is used as the filler. The tunnel current easily flows,
Good conductivity, low initial resistance at room temperature,
In addition, since the distance between the conductive particles is relatively large, the conductive path is easily broken, and the PTC characteristic rises steeply, and an organic positive temperature coefficient thermistor exhibiting a large change in resistance value can be provided. In addition, since the Ni electrode made of the same material as the filler is provided, even if the temperature is increased from room temperature to a high temperature, the characteristics are further improved such that deformation by heat does not occur.

[Brief description of the drawings]

FIG. 1 is a micrograph showing the structure of an organic positive temperature coefficient thermistor according to a first embodiment of the present invention.

FIG. 2 is a micrograph showing the structure of an organic positive temperature coefficient thermistor according to a second embodiment of the present invention.

FIG. 3 is a graph showing resistance temperature characteristics of the organic positive temperature coefficient thermistor of Example 1.

FIG. 4 is a graph showing resistance temperature characteristics of the organic positive temperature coefficient thermistor of Example 2.

FIG. 5 is a graph showing resistance-temperature characteristics of the organic positive temperature coefficient thermistor of Example 3.

FIG. 6 is a graph showing resistance temperature characteristics of the organic positive temperature coefficient thermistor of Example 4.

FIG. 7 is a graph showing resistance temperature characteristics of the organic positive temperature coefficient thermistor of Example 5.

FIG. 8 is a graph showing resistance temperature characteristics of the organic positive temperature coefficient thermistor of Example 6.

FIG. 9 is a graph showing resistance-temperature characteristics of the organic positive temperature coefficient thermistor of Comparative Example 1.

FIG. 10 is a graph showing the resistance temperature characteristics of the organic positive temperature coefficient thermistor of Comparative Example 2.

Claims (2)

[Claims] 1. Nitrogen on both surfaces of a sheet-like molded body of a thermistor body containing conductive particles as a filler in a crystalline polymer.
An organic positive temperature coefficient thermistor provided with said electrode, wherein said conductive particles comprise a spherical Ni powder having a large number of projections formed thereon. 2. Ni is applied to both sides of a sheet-like molded body of a thermistor body containing conductive particles as a filler in a crystalline polymer.
An organic positive temperature coefficient thermistor, comprising: an electrode provided with the above-mentioned electrode, wherein the conductive particles comprise a powder in which spherical Ni powders having a large number of projections are connected in a chain.