JP2000133503A - Manufacture of organic positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an organic positive temperature coefficient thermistor in which an initial resistance value is small at room temperature, PTC characteristics rise sharply, and which designates large change in the resistance values, by a method wherein ball-like Ni powders forming a plurality of projections as a conductive substance are prepared, and are mixedly kneaded with a crystalline polymer to form a thermistor element body. SOLUTION: In this manufacture of an organic positive temperature coefficient thermistor, a crystalline polymer is mixedly kneaded with a specified amount of ball-like Ni powders having a plurality of projections as a conductive substance in the crystalline polymer. As the crystalline polymer, polyvinylidene fluoride, polyethylene, polyethylene oxide, t-4-polybutadiene, polyethylene acrylate, ethylene-ethylacrylate copolymer, etc., are used. Furthermore, as conductive particles having a plurality of projections, the ball-like Ni powders having such respective physical characteristics as a mean particle size is 3 to 7 μm are used and an apparent density of 1.8 to 2.7 (g/cc), and a specific surface area of 0.34 to 0.44 (m2/g).

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, and more particularly, to a characteristic in which a resistance value rapidly increases in a specific temperature range when a temperature rises, that is, a positive temperature coefficient (PTC).
The present invention relates to a method for producing 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, but it is necessary to increase the filling amount. 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.

[0007] In addition, it is also known that 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 a method for producing 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.

[0009]

According to the first aspect of the present invention,
In a method for producing an organic positive temperature coefficient thermistor having a thermistor body in which a conductive substance is dispersed in a crystalline polymer,
The method includes a step of preparing a spherical Ni powder having a large number of protrusions as the conductive substance, and kneading the Ni powder with a crystalline polymer to obtain a thermistor body.

According to a second aspect of the present invention, the Ni powder has an apparent density in a range of 1.8 to 2.7 g / cc.

According to a third aspect of the present invention, the Ni powder comprises:
The specific surface area is in the range of 0.3 to 0.44 (m ² / g).

According to a fourth aspect of the present invention, in the method of manufacturing an organic positive temperature coefficient thermistor having a thermistor body in which a conductive material is dispersed in a crystalline polymer, a large number of protrusions are formed as the conductive material. It is characterized by including a step of preparing a chain-like Ni powder in which spherical Ni powders are connected in a chain-like manner, and kneading this into a crystalline polymer to obtain a thermistor body.

According to a fifth aspect of the present invention, the chain Ni powder has an apparent density of 0.5 to 0.95 (g / cc).
It is characterized by being within the range.

According to a sixth aspect of the present invention, the chain Ni powder has a specific surface area in a range of 0.58 to 0.63 (m ² / g).

According to the method for producing an organic positive temperature coefficient thermistor according to claims 1 to 3, the crystalline polymer is filled with spherical Ni powder having a large number of projections.
Compared with the case where spherical conductive particles are filled, tunnel current easily flows between spherical Ni powders having a large number of projections due to their shapes, thereby improving conductivity and improving initial resistance at room temperature. And the distance between the conductive particles is larger than that of the spherical particles, so that an organic positive temperature coefficient thermistor having a steep rise of PTC characteristics and a large change in resistance value can be obtained.

According to the method of manufacturing an organic positive temperature coefficient thermistor according to claims 4 to 6, the crystalline polymer is filled with a conductive substance having a shape in which spherical Ni powders having a large number of projections are connected in a chain. Since it is a thing, compared with the case where the spherical conductive particles are filled, it has a large number of protrusions and is connected in a chain, so that more tunnel current flows,
As a result, the conductivity becomes good, the initial resistance value at room temperature is small, and the interval between the conductive particles is larger than that of a true sphere, so that the rise of the PTC characteristic is sharp and a large change in the resistance value occurs. An organic positive temperature coefficient thermistor can be obtained.

[0017]

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

The organic positive temperature coefficient thermistor of the first embodiment comprises a crystalline polymer and a predetermined amount of spherical Ni powder having a large number of projections kneaded as a conductive substance with the crystalline polymer. .

FIG. 1 shows a micrograph of the organic positive temperature coefficient thermistor.

As is clear 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 polyethylene, polyethylene oxide, and t-polyvinylidene fluoride.
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 kind of the crystalline polymer can be appropriately selected according to the desired performance, use and the like.

As the conductive particles having many projections, spherical Ni powder having many projections (manufactured by Inco Limited) is used.

This 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 a 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 obtained by kneading a crystalline polymer and a conductive polymer having a shape in which a spherical Ni powder having a large number of projections is connected to the crystalline polymer. It is obtained by doing.

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

As is clear 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 substances, 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 A 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 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. 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 more 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 filamentous chain Ni powder (average particle size of 2.2 to 2.8 μm, manufactured by Inco Limited) was used as the conductive substance. 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, on both surfaces of this molded product, N
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 has 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 filamentous 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 filamentous 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 protrusions 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.

[0059]

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 protrusions has a good conductivity since tunnel current flows easily in the spherical Ni powder having a large number of protrusions as compared with a case where a spherical conductive material is used as a filler. As a result, an organic positive temperature coefficient thermistor having a small initial resistance value at normal temperature and a relatively large spacing between conductive particles, easily breaking a conductive path, sharply rising a PTC characteristic and exhibiting a large resistance value change. The manufacturing method which can do it can be provided.

According to the fourth 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 can be compared with a 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 manufacturing method can provide an organic positive temperature coefficient thermistor in which the rise of the PTC characteristic is steep and a large change in resistance is exhibited.

[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 (6)

[Claims] 1. A method for producing an organic positive temperature coefficient thermistor having a thermistor element in which a conductive substance is dispersed in a crystalline polymer, wherein a spherical Ni powder having a large number of projections is prepared as the conductive substance. And kneading the mixture with a crystalline polymer to obtain a thermistor body. A method for producing an organic positive temperature coefficient thermistor, comprising: 2. The Ni powder has an apparent density of 1.8.
The method for producing an organic positive temperature coefficient thermistor according to claim 1 , wherein the temperature is in the range of -2.7 g / cc. 3. The Ni powder has a specific surface area of 0.3.
3. The method for producing an organic positive temperature coefficient thermistor according to claim 1, wherein the temperature is within a range of 0.44 (m ² / g). 4. 4. A method for producing an organic positive temperature coefficient thermistor having a thermistor body in which a conductive substance is dispersed in a crystalline polymer, wherein the conductive substance comprises a chain of spherical Ni powder having a large number of projections formed thereon. Chain N linked in a circle
A method for producing an organic positive temperature coefficient thermistor, comprising a step of preparing i powder and kneading it with a crystalline polymer to obtain a thermistor body. 5. The method for producing an organic positive temperature coefficient thermistor according to claim 4, wherein said chain Ni powder has an apparent density in a range of 0.5 to 0.95 (g / cc). . 6. The organic positive temperature coefficient thermistor according to claim 4, wherein the chain Ni powder has a specific surface area in a range of 0.58 to 0.63 (m ² / g). Production method.