JPS6031202A - Resistance element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a conductive material having a characteristic (hereinafter referred to as P 1-C characteristic) in which a positive temperature coefficient of resistance rapidly increases in a specific temperature range when the temperature is increased. The present invention relates to a resistance element made of a polymer composition.

[Technical Background of the Invention] Conventionally, as a resistance element having PTC characteristics (hereinafter referred to as TC element), metal foil electrodes are coated on both sides of a flat element body made of barium titanate-based metal oxide. C is commonly used.

However, the reality is that such conventional I-C elements have a high specific resistance and a large heat capacity, so that they are used only for limited purposes.

On the other hand, a PTC element made of a conductive polymer composition in which conductive particles are uniformly dispersed in a crystalline polymer,
Due to its low specific resistance and small thermal mass, it has recently been investigated for application in fields where barium titanate-based [ ]O C elements cannot be used.

The p-rc characteristics of such conductive polymer compositions are such that the base crystalline polymer has -C at its melting point.
This phenomenon occurs when the conductive particles dispersed therein widen due to rapid volumetric expansion when changing from crystalline to amorphous.

This PTC element is a conductor with low resistance below the temperature at which the conductive polymer composition rapidly increases its electrical resistance (hereinafter referred to as a switching hot stone). The temperature rises to the switching temperature, which limits the current and protects equipment from destruction due to overcurrent, and when used as a heating element, prevents self-damage due to heating. .

Figures 1 and 2 show that metal foil electrodes 2.2 are pasted on both sides of a disk-shaped element body 1 made of conductive borine, and that the metal foil electrodes 2.2 are coated with Jζ for half a day. , relead wire 4.4
This figure shows an example of a P T'C element connected to the P T'C element.

However, the element main body 1 is formed by forming a conductive composition into a plate shape, which is a mixture of a crystalline polymer such as polyethylene, an adhesive polymer, and conductive particles such as conductive carbon.
Metal foil electrodes are bonded under heat and pressure to both sides to form the C element, and by irradiating the metal foil electrode with an electron beam, the conductive composition is crosslinked and heat resistance is imparted to the entire C element. There is C.

[Problems with the background art] PTC using such conventional conductive polymer compositions
In the device, cross-linking of the crystalline polymer by electron beam irradiation is performed after bonding the device body 1 and the metal foil electrode 2.2, so as shown in FIG. When hydrogen gas and other gases are generated, metal thermoelectric
- 2nd layer accumulates at the interface with the element body 1 to form bubbles 5,
These bubbles repeatedly expand and contract as a result of the heat cycle, and the internal pressure P1 at the time of expansion is U! against the metal foil electrode 2. ! There is a problem in that the metal foil electrode 2 acts as a separation force and causes the metal foil electrode 2 to be peeled off from the element body 1.

In addition, since the linear expansion coefficient of the metal foil electrode 2 is about 1/40 smaller than that of the element body 1, shear horns act on the adhesive interface between the two as a result of the heating noise. This was one of the factors that led to the peeling of the foil electrode.

Furthermore, although such conventional PTC cords have a flat surface, their thermal tliFll properties cannot necessarily be said to be good, and improvements in their heat dissipation properties are desired in applications where current carrying capacity is limited. was.

[Object of the Invention J The present invention has been made in response to such conventional circumstances.
It is an object of the present invention to provide a resistive element which has excellent adhesiveness between an electrode and an element body, and which has improved heat dissipation and current carrying capacity.

[Summary of the Invention] That is, the resistance element of the present invention is a resistance element comprising an element body made of a conductive polymer composition and an electrode closely adhered to the surface of the element body, sandwiching the element body.
1. The device is characterized in that the interface between the element body and the electrode is an uneven surface.

[Embodiment of the Invention] Hereinafter, one embodiment of the present invention will be described without showing the details in the drawings.

FIG. 4 is a perspective view showing one embodiment of the PTC element of the present invention;
FIG. 5 is a cutaway perspective view taken along line V-v. na d3
In each of the following figures, the same reference numerals are given to the same parts as in FIGS. 1 and 2.

In FIGS. 4 and 5, the resistance element of this example has PrC characteristics, which is made by blending a crosslinkable crystalline polymer with conductive particles such as conductive carbon and, if necessary, an adhesive polymer. A disk-shaped element body 1 made of a conductive polymer composition, and electrodes 2.2 coated on both sides thereof.
and a lead wire 4 connected to the center with solder 3.
It consists of 4.

However, in the resistance element of this embodiment, a plurality of annular protrusions 1a having a trapezoidal cross section are formed concentrically on both sides of the element body 1, and electrodes 2. is deposited to form a C structure.

The crystalline polymer "C" used in the conductive polymer composition of this example is, for example, polyolefin such as 111 density, medium density, or low density polyethylene or polypropylene. For example, there are ethylene-based polymers such as ethylene/ethyl acrylate-1 copolymer, ethylene/acid-resistant vinyl polymer, etc.

Further, the electrode 2.2 can also be formed by, for example, metal vapor deposition, metal plating, etc. other than metal foil having the same shape.

Since the resistance element constructed in this manner has an annular convex portion 1a having a trapezoidal cross section on both sides of the element main body 1, bubbles 5 made of hydrogen gas etc. generated by irradiation crosslinking, as shown in FIG.
The peeling force due to the internal pressure P+ during thermal expansion is reduced to p 1 cos α (<PI) by the rising angle α of the annular convex portion 1a.

In addition, the shear no.j that acts in the radial direction of the element due to the difference in linear expansion coefficient between the metal foil electrode 2.2 and the element body 1 is alleviated by increasing the bonding area between the two, and the heat dissipation properties are also improved. Improved by increasing surface area.

Figure 7 shows 30 parts by weight of high-density polyethylene, ethylene.
Manufactured with a conductive polymer composition consisting of 30 parts by weight of ethyl acrylate copolymer and 40 parts by weight (6) parts of conductive carbon! ! PTC of the resistance element (diameter 2o) (example) with the structure shown in Figs. 4 to 6 and the conventional resistance element (diameter 2oIll11) shown in Fig. 1 (comparative example)
It is a graph showing characteristics and performance power characteristics.

In the same figure, a curve R shows the change in resistance of the semiconductive polymer composition of these resistance elements with respect to the change in temperature. From this curve, these resistor 11'L elements are 100 to 12
It can be seen that it has PTC characteristics with a dislocation temperature of 0°C.

Further, Wi+ to Wi3 are power consumption characteristic curves showing the relationship between temperature and consumption type horn when a constant current is passed through each resistance element. Here, Wi+ is the characteristic curve when a safe current that does not reach the switching temperature is passed through the resistance element of the comparative example, Wi 2 is the characteristic curve when an overcurrent is applied to the same resistance element, and Wi 3 is the characteristic curve of this example. There is a characteristic curve when a current larger than Wi2 is passed through the element. In addition, Wc1 and Wc2 indicate the cold lJI performance of the resistance element, WC+ is a comparative example, and Wc2 is a curve showing the relationship between the temperature change of the resistance element and the consumption type saw of the example.

It is clear from the graph in Figure 7 that when a safe current is passed through a conventional resistance element, the curve Wi + DoWC + Which intersection indicates that the resistance element reaches a stable state at a temperature lower than the switching temperature. (fixed at the power consumption of
A stable state is reached at the intersection of 2 and Wc+ in a high-temperature and high-resistance region that exceeds the switching temperature.

On the other hand, in the resistance element of the example, the annular convex portion 1al,
:J: Since the heat dissipation properties have been improved, a stable current flows even if the conventional resistance element is in the temperature range d3 where it is in an overcurrent state, as shown by curve WC2, and this allows even larger current to be loaded. However, as shown in the song mwi3, the temperature is stable below the intersection point C, which exceeds the switching temperature.

FIG. 8 is a graph showing the recovery characteristic curves of the resistance element of the embodiment of the present invention and the resistance element of the comparative example. As is clear from this graph, in this example, the heat dissipation is improved due to the formation of the annular convex portion, so it can be reused. can be written. In addition, at a3 in FIG. 8, the horizontal axis represents the time (seconds) after cutting off the circuit current of the element operating with high resistance, and the vertical axis represents the resistance value (Ω)'c of the element.

In the above embodiment, the interface between the element body and the electrode is trapezoidal, but the present invention is not limited to such an embodiment, and the surface of the convex portion 101 may be arcuate.

Further, as shown in FIG. 9, a large number of parallel protrusions 1b may be provided in parallel to the element body 1 in the shape of a sea 1.

[Effects of the Invention] As explained above, the resistance element of the present invention has the advantage that the interface between the element body and the electrode is formed into a concave curved surface, and the peeling force due to bubbles generated at the interface between the electrode and the element body is reduced. is reduced and durability is improved. Furthermore, since the heat dissipation property is improved, the current carrying capacity is increased and it becomes possible to use it frequently.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a conventional resistance element, Fig. 2 is a partially cutaway perspective view thereof, Fig. 3 is a sectional view of a main part illustrating the abrasion of the electrode by gas generated during crosslinking, and Fig. 4 5 is a perspective view showing an embodiment of the resistance element of the present invention, FIG. 5 is a partially cutaway perspective view thereof, and FIG. 6 shows a situation in which the peeling force of the electrode caused by the gas generated during crosslinking is reduced. Main part sectional view, No. 7
The figure shows PTC in resistance elements of an example of the present invention and a comparative example.
FIG. 8 is a graph showing the recovery characteristics, and FIG. 9 is a perspective view showing another embodiment of the present invention. 1...... Element body 1a...... Annular convex portion 1b...... Convex strip 2... ...Metallic 3...Solder 4...Lead wire 5...Bubble Fig. 1 Fig. 2 Fig. 3 Factor tMt+ Fig. 5 Fig. 6 Fig. 7 Fig. 0 Temperature ('C) Times (Sec)

Claims (5)

[Claims] (1) In a resistance element C, which comprises an element body made of a polymer composition II and an electrode closely adhered to the surface of the element body, the interface between the element body and the electrode has an uneven surface. A resistance element characterized by: (2) The resistance element according to claim 1]J4, wherein the uneven surface has a cross-sectional shape of a trapezoid or repeated circular arcs. (3) The resistive element according to claim 1 or 2, wherein the conductive polymer composition is a composition in which conductive particles are divided into a crystalline polymer. (4) The resistance element according to claim 3, wherein the crystalline polymer is a polyolefin. (5) Look at the conductive polymer composition! ) I cross-linked (
A resistance element according to claims 1 to 4.