JPH052961A - Polymer switch and its manufacture - Google Patents

Abstract

PURPOSE:To construct a switching element at a low cost through simple manufacturing processes, which is equipped with a good performance and with a wide scope of application by forming electrode on both sides of an electroconductive composite film consisting of a plurality of resin sorts, having different melting point, which are filled with a certain amount of electroconductive filler. CONSTITUTION:A resin material of a low melting point near 80 deg.C such as polypentene-1 and another resin material having a high melting point over 100 deg.C such as polyethylene are filled with electroconductive filler - for example, powder of carbon black - in an amount of 40wt.% each approximately by means of the melt and knead method. These composite materials are mixed together in a mix proportion of for example 40:60 by wt. by means of the melting and kneading method so that the high melting point material constitutes a continuous layer while the low melting point material constitutes a non-continued layer, and thus a resultant electroconductive resin composite is fabricated. This composite is subjected to film formation process using the melting and extrusion method, and electrodes are formed on both sides of this film through non- electrolytic Cu plating, etc. Thus a polymer switch is accomplished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent / heat protection element for electronic equipment, and more particularly to a polymer switch which is excellent in switching performance and is inexpensive, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as an element having a switching function for protecting an electric circuit of this type, an element using BaTiO ₃ system ceramics is known. BaTiO
₃ ceramics is a typical example of a material having a PTC characteristic (a characteristic in which the resistance value increases as the temperature rises), and an element formed using this material has a BaTiO ₃ content due to the temperature rise.
_If the Curie point of ₃ is exceeded, the resistance value will change abruptly, which is effective as an overcurrent / heating protection element. As a switching element of this type using an organic material, a carbon black-filled polyethylene crosslinked material is known. This device utilizes the increase in resistance value due to the disconnection of conductive paths of carbon black one after another due to the volume change of up to several tens of percent due to the melting of the polymer with the increase in temperature.

[0003]

In the conventional PTC element using BaTiO ₃ -based ceramics, there is a lower limit of the specific resistance value in the steady state due to the inherent properties of the ceramic, and durability against high voltage and large current. There are drawbacks, such as limitations, and their applications have also been limited. In addition, the PTC element using the cross-linked polyethylene filled with carbon black can secure a low resistance in the steady state,
And since it is possible to manufacture protective elements for various circuits from those with large flow capacity to high voltage, it is effective for overcurrent and heat protection in the area that could not be covered by the above ceramics, but polyethylene crosslinking is effective. A special radiation (electron beam) cross-linking technology is used for this purpose, and the degree of cross-linking influences the switching function of the device, making it difficult to set the conditions for radiation cross-linking. Has a problem that it lacks versatility because it is quite limited. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a switching element which is simple to manufacture, has good switching performance, and has a wide application range, and a manufacturing method thereof.

[0004]

The first aspect of the present invention relates to a polymer switch, which comprises a plurality of resin materials having different melting points filled with a predetermined amount of conductive filler. It is characterized in that a conductive composite film and electrodes are formed on both surfaces of the conductive composite film. And the second invention of the present invention is an invention relating to a method for producing a polymer switch, comprising the step of obtaining a conductive resin composite composed of a plurality of resin materials having different melting points filled with a predetermined amount of conductive filler, Of a conductive resin composite into a film having a predetermined thickness by a melt extrusion method to obtain a conductive composite film, a film of a predetermined shape is cut from the conductive composite film, and electrodes are formed on both surfaces of the conductive composite film to obtain a switching element. It is characterized by consisting of.

In order to achieve the above-mentioned object of the present invention, the following means were taken to realize a polymer switch having a switching function for protecting an electric circuit.

A polymer switch is formed by forming a conductive composite film formed by filling a predetermined amount of conductive filler in a plurality of resin materials having different melting points, and forming electrodes on both surfaces of the conductive composite film. . here,
As the conductive filler, metal-based fillers such as copper, silver, nickel and aluminum or carbon-based fillers such as carbon fiber, graphite and carbon black are effective. Further, as the resin material having a different melting point, a low melting point resin material having a melting point in the vicinity of the upper limit of the temperature range to be compensated for the electronic device, and even when the low melting point resin material is completely melted to cause a large volume change It is preferable to employ a high melting point resin material having a high melting point that does not reach the melting point and having good film moldability by extrusion molding. Normal,
Since the upper limit of the compensation temperature range of electronic equipment is around 80 ° C., as the low melting point resin material having a melting point around this, polypentene-1 (Tm: 75 ° C.), polyisoprene (Tm: 74 ° C.), polypropylene Oxide (Tm:
75 ° C.), polychloroprene (Tm: 80 ° C.) and the like are preferable, but are not limited to these, of course.
Any material having a melting point near 80 ° C. can be applied. In addition, the high melting point resin material needs to have a higher melting point than the low melting point resin material. However, if the melting point is too high, it will be difficult to form a composite by melting and kneading with a low melting point resin material, so care must be taken. However, various polyethylenes (Tm: 100 from low density to high density)
℃ ~ 137 ℃), polybutene-1 (Tm: 126 ℃),
Polypropylene (Tm: 176 ° C), Polyoxymethylene (Tm: 181 ° C), Polyvinylidene chloride (T
m: 198 ° C.), polyvinyl chloride (Tm: 212)
C.), polycarbonate (Tm: 220.degree. C.), polyethylene terephthalate (Tm: 267.degree. C.) and the like are suitable. Of course, these are not particularly limited. Further, the resin composite system is not limited to a combination of a set of a low melting point resin material and a high melting point resin material, and may be a combination of several kinds of resin materials.

A polymer switch is constructed by forming a conductive composite film made of a high melting point resin material and a low melting point resin material filled with a predetermined amount of conductive filler, and electrodes on both sides of the conductive composite film. Also in this case, the resin composite system is not limited to a combination of a low melting point resin material and a high melting point resin material, but may be a combination of several kinds of resin materials.

A predetermined amount of conductive filler is filled in a high melting point resin material by a melt-kneading method to prepare a conductive high melting point resin composite, and similarly, a predetermined amount of the conductive filler is melted in the low melting point resin material. A conductive low-melting point resin composite is prepared by filling by a kneading method, and then the conductive high-melting point resin composite and the conductive low-melting point resin composite thus prepared are melt-kneaded at a predetermined temperature. A conductive resin composite is prepared by compounding in a ratio, and further, a conductive composite film having a predetermined thickness is prepared by a melt extrusion method using the conductive resin composite, and the conductive composite film having a predetermined shape is formed. A polymer switch is manufactured by cutting out a film and forming electrodes on both surfaces of the film to form an element. In this case, the ratio of the conductive high-melting point resin composite and the conductive low-melting point resin composite in the conductive resin composite, the conductive high-melting point resin composite is a continuous layer, the conductive low-melting point resin composite Is preferably a discontinuous layer.

A high melting point resin material and a low melting point resin material are compounded at a predetermined ratio by a melt kneading method to prepare a resin composite, and a predetermined amount of a conductive filler is melt-kneaded in the resin composite. To prepare a conductive resin composite, and using the conductive resin composite to prepare a conductive composite film having a predetermined thickness by a melt extrusion method, and cutting a film having a predetermined shape from the conductive composite film. A polymer switch is manufactured by forming electrodes on both surfaces of the device to form an element. In this case, it is desirable that the high melting point resin material and the low melting point resin material be in a continuous layer and the low melting point resin material be a discontinuous layer in the resin composite.

A conductive filler is filled in a low melting point resin material in a predetermined amount by a melt-kneading method to prepare a conductive low melting point resin composite, and the high melting point resin material and the conductive low melting point resin composite are mixed in a predetermined amount. A conductive resin composite is produced by compounding by a melt kneading method in a ratio, and the conductive resin composite is formed into a film having a predetermined thickness by a melt extrusion method to produce a conductive composite film, and the conductive composite film is obtained. A polymer switch is manufactured by cutting out a film of a predetermined shape from, and forming electrodes on both sides of the film to form an element. In this case, the proportion of the high melting point resin material and the conductive low melting point resin composite in the conductive resin composite is such that the high melting point resin material is a continuous layer and the conductive low melting point resin composite is a discontinuous layer. It is desirable to do so.

[0011]

The operation principle of the polymer switch manufactured according to the present invention will be described by exemplifying the polymer switch described above. This type of polymer switch is shown in FIG.
As shown in, the conductive filler dispersed in the low-melting resin material and the high-melting resin material in a steady state forms a myriad of conductive paths throughout the composite, and thus has a low specific resistance and an appropriate conductivity. However, since the coefficient of thermal expansion of the resin material is larger than that of the conductive filler as the temperature of the element rises, the path of the conductive filler is gradually cut as shown in FIG. It comes to show characteristics. Then, when the temperature reaches the melting point of the low melting point resin material, the low melting point resin composite is first melted. Since melting of such a low melting point resin composite causes a volume increase of several tens of percent, as shown in FIG. 1 (c), the path of the conductive filler in the low melting point resin composite causes thermal expansion. It is cut off more than time, and the resistance value rises sharply. For such PTC characteristics, infinite resistance-temperature characteristics can be selected by changing the type of resin material and the ratio of composite. In this case, since the high melting point resin composite does not reach the melting point, the high melting point resin composite serves as a support and the shape of the element is maintained.

As described above, when the temperature of the electronic device rises and reaches the upper limit of the compensation temperature range, the conductive state of the polymer switch is cut off. Therefore, if the polymer switch is incorporated in the circuit of the electronic device in series. It can protect the electric circuit from overcurrent and overheat.

Since various combinations of resin composite systems can be applied as the resin composite for the polymer switch of the present invention, it is possible to select a material having general versatility as compared with conventional switching elements. it can.

Also, as the manufacturing method, since a known resin compounding technique can be used, it is not necessary to use a dangerous and special technique such as radiation crosslinking, and an inexpensive switching element can be obtained by a simple technique. be able to.

[0015]

Embodiments of the present invention will be described below in more detail with reference to the drawings. In this example, polypentene-1 (Tm: 75 ° C.) was used as the low melting point resin material.
High-density polyethylene (Tm: 13)
1 ° C.) will be described by exemplifying a polymer switch using carbon black as a conductive filler, but it is not limited to this system. In Examples 1 to 3 below, the binary system of the low melting point resin material and the high melting point resin material was exemplified as the combination of the resin materials, but by combining a plurality of resin materials having different melting points at a predetermined ratio. , PTC characteristics can be freely designed.

Example 1 Polypentene-1 and polyethylene were each filled with about 40% by weight of carbon black powder by a melt-kneading method. Then, the carbon black-filled composites thus prepared were composited by a melt kneading method to prepare a polypentene-1 / polyethylene-based conductive resin composite. In this case, the mixing ratio of carbon black-filled polypentene-1 and carbon black-filled polyethylene was 40:60 by weight. Further, using the conductive resin composite, a conductive film having a thickness of 300 μm is formed by a melt extrusion method, and the conductive film is 10 mm thicker than the conductive film.
A disk-shaped sample of φ was cut out, and electrodes having a thickness of 10 to 15 μm were formed on both surfaces of the sample by electroless copper plating to form a polymer switch.

The polymer switch thus produced was placed in a thermostatic chamber to obtain the PTC of the electric resistance as the temperature rose.
The properties were measured. FIG. 2 is a diagram showing the PTC characteristics of the above-mentioned polypentene-1 / polyethylene-based polymer switch measured as described above in terms of the resistance value (Ω, vertical axis) and temperature (° C., horizontal axis). The resistance value of the element maintains a resistance of 10 ^-1 or less in a steady state and shows good conductivity, but the resistance value gradually rises as the element temperature rises, and rapidly increases near 80 ° C. Initially, the resistance value reaches 10 ⁴ ohms or more at around 125 ° C. After that, the element temperature was returned to the steady temperature, the temperature was raised again, and the cycle test was repeated about 10 times. In each case, the PTC characteristics similar to those in FIG. 2 were obtained, and it was confirmed that there was reproducibility.
The resistance change of 10 ⁵ Ω or more due to such temperature change is due to the operation principle described in the section of the action. That is, the gradual increase in resistance value at the initial stage of temperature rise is due to thermal expansion, and the abrupt increase in resistance value at 80 ° C. or higher is due to melting of the low melting point resin material.

Example 2 Using the same composite system as in Example 1, a polymer switch was produced by changing the production method. First, polypentene-1 and polyethylene are compounded in a weight ratio of 40:60 by a melt-kneading method, and then, 40 wt% of carbon black powder is filled in this resin composite by a melt-kneading method, and polypentene- A 1 / polyethylene-based conductive resin composite was produced. Furthermore, a polymer switch was constructed by using the conductive resin composite in the same manner as in Example 1. The polymer switch thus produced was placed in a thermostatic chamber, and the PTC characteristic of electric resistance with temperature rise was measured. As a result, the same PTC characteristic as that shown in FIG. 2 was obtained.

Example 3 Using the same composite system as in Example 1, a polymer switch was produced by changing the production method. First, about 40% by weight of carbon black powder is filled in polypentene-1 by a melt-kneading method to prepare a conductive low-melting resin composite, and then the conductive low-melting resin composite and polyethylene are mixed at a weight ratio of 40.
A polypentene-1 / polyethylene-based conductive resin composite was prepared by compounding in a ratio of 60 with the melt-kneading method. Furthermore, a polymer switch was constructed by using the conductive resin composite in the same manner as in Example 1. Place the polymer switch produced in this way in a constant temperature bath,
When the PTC characteristic of the electric resistance accompanying the temperature rise was measured, the same PTC characteristic as in FIG. 2 was obtained.

The characteristic shown in FIG. 2 is due to the temperature change of the polymer switch due to the change of ambient temperature, and can be useful when protecting the circuit from heat generation of the electronic device itself, for example, abnormal heat generation due to short circuit of the battery. .
On the other hand, even when an abnormal current flows in the circuit, the polymer switch similarly generates heat, and the circuit can be cut off by the same operation principle.

[0021]

The polymer switch manufactured according to the present invention exhibits an extremely excellent switching function because it exhibits a resistance change of 10 ⁵ ohms or more due to a temperature change, and this polymer switch is connected in series to a circuit of an electronic device. By incorporating it, the circuit of the electronic device can be easily protected from overcurrent and overheat. Moreover, since various combinations of resin composite systems can be applied as the resin composite for the polymer switch of the present invention, a versatile polymer switch can be constructed. Furthermore, in the method for producing the polymer switch of the present invention, since a known resin compounding technique can be used, it is not necessary to use a dangerous and special technique such as radiation crosslinking shown in the conventional technique, and a simple technique can be used. An inexpensive switching element can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an operating principle of a polymer switch.

FIG. 2 is a diagram showing a resistance value-temperature characteristic of a polymer switch.

Claims (5)

[Claims] 1. A polymer switch comprising: a conductive composite film made of a plurality of resin materials having different melting points filled with a predetermined amount of conductive filler; and electrodes formed on both surfaces of the conductive composite film. 2. A step of obtaining a conductive resin composite composed of a plurality of resin materials having different melting points filled with a predetermined amount of conductive filler, wherein the conductive resin composite is formed into a film having a predetermined thickness by a melt extrusion method. A process for producing a polymer switch, comprising the steps of obtaining a conductive composite film, cutting a film having a predetermined shape from the conductive composite film, and forming electrodes on both surfaces of the film to obtain a switching element. 3. A step of filling a predetermined amount of a conductive filler into a high melting point resin material by a melt-kneading method to obtain a conductive high melting point resin composite, and a predetermined amount of the conductive filler is melted and mixed into the low melting point resin material. Filling by kneading method to obtain a conductive low melting point resin composite, the conductive high melting point resin composite and the conductive low melting point resin composite are compounded at a predetermined ratio by a melt kneading method, and a conductive resin A step of obtaining a composite, a step of forming the conductive resin composite into a film having a predetermined thickness by a melt extrusion method to obtain a conductive composite film, cutting a film having a predetermined shape from the conductive composite film, and forming electrodes on both surfaces thereof. A method of manufacturing a polymer switch, which comprises the step of forming and obtaining a switching element. 4. A step of compounding a high-melting point resin material and a low-melting point resin material by a melt kneading method at a predetermined ratio to obtain a resin composite, wherein the resin composite is filled with a predetermined amount of a conductive filler. To obtain a conductive resin composite, a step of forming the conductive resin composite into a film having a predetermined thickness by a melt extrusion method to obtain a conductive composite film, cutting out a film having a predetermined shape from the conductive composite film, A method for producing a polymer switch, comprising the step of forming electrodes on both sides to obtain a switching element. 5. A step of filling a predetermined amount of a conductive filler in a low melting point resin material by a melt kneading method to obtain a conductive low melting point resin composite, a high melting point resin material and the conductive low melting point resin composite. To obtain a conductive resin composite by compounding by a melt kneading method at a predetermined ratio, a step of forming the conductive resin composite into a film having a predetermined thickness by a melt extrusion method to obtain a conductive composite film, A process for producing a polymer switch, comprising the steps of cutting a film having a predetermined shape from a flexible composite film and forming electrodes on both surfaces of the film to obtain a switching element.