JP2000235902A - PTC resistance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable and good PTC characteristics even in the repetitive use and with a little content of mixed conductive fillers by sheeting a conductive composition material containing a thermosetting resin and a metal flake conductive filler. SOLUTION: A PTC resistive element is a thermally cured PTC conductive composition containing a thermosetting resin and a metal flake conductive filler. The volume percentage ratio of the thermosetting resin to the filler is 15:85-35:65, the resistivity at 20 deg.C is 1 Ωcm or less and it exhibits a resistivity of 105 Ωcm or more at a switching temp. or less. In manufacturing the PTC resistive element, it is desirable to heat over desired switching temp. to thermally cure. The PTC composition exhibits stable PTC characteristics when the conductive filler is uniformly dispersed and hence it is desirable to make the conductive filler in a uniformly dispersed state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC resistance element, and more particularly, to a PTC (Positive Temperature Coeffic).
The present invention relates to a PTC resistance element for protecting an electric circuit using a PTC conductive composition having a characteristic of a positive temperature coefficient.

[0002]

2. Description of the Related Art As an electric circuit protection element used in electric equipment and electronic equipment including secondary batteries, an organic conductive composition in which a carbon-based conductive filler is dispersed in a crystalline polymer matrix is known. Have been.

In the organic conductive composition, while the temperature is lower than the crystal melting point of the crystalline polymer matrix, the carbon-based conductive filler is present only in the non-crystalline region of the crystalline polymer matrix, and has a chain structure. And exhibits a low resistivity due to a conductive mechanism in which electrons move through the conductive filler.

When the temperature rises and the crystalline polymer matrix begins to melt, the volume of the crystalline polymer matrix increases, so that the distance between the carbon-based conductive fillers in the crystalline polymer matrix is reduced. As a result, the conductive path is broken and the resistance increases.

An electric circuit protection element using the above operation principle includes a conductive composition which has a low resistance at room temperature and increases the resistance as the temperature rises to limit the current, particularly a desired switching temperature (the resistance is rapidly increased). A PTC conductive composition whose resistance rapidly increases at a rising temperature) is used.

[0006]

However, in order to obtain an element having good conductivity, the filling amount of the conductive filler must be increased. Therefore, it is conceivable to increase the filling of the conductive filler, but the conductive filler is 40 wt% or more based on the crystalline polymer matrix.
It is difficult to fill, and it has been difficult to manufacture a PTC resistance element.

Accordingly, an object of the present invention is to provide a PTC resistance element which is stable against repeated use and has good reproducibility of PTC characteristics even when the amount of conductive filler is small. .

[0008]

The PTC resistance element of the present invention is obtained by thermosetting a PTC conductive composition containing a thermosetting resin and a flake-shaped metal conductive filler. The ratio of the volume fraction to the volume fraction of the thermosetting resin is 15/85 to 35/65, the resistivity at 20 ° C. is 1 Ωcm or less, and the resistivity is 10 ⁵ Ωcm or more at a switching temperature or higher. .

When the PTC resistance element is manufactured, it is preferable that the PTC resistance element is heated to a desired switching temperature or higher and thermally cured. In the PTC conductive composition, if the dispersion state of the conductive filler is uniform, stable PTC characteristics are exhibited. Therefore, the dispersion state of the conductive filler is preferably uniform.

In the present invention, the type of thermosetting resin and curing agent to be used is selected based on a desired switching temperature,
By using a thermoplastic filler according to the purpose of use, 7
A conductive composition exhibiting stable PTC characteristics in a medium temperature range of 0 to 135 ° C. is obtained, and a metal flake conductive filler is dispersed in a one-component thermosetting resin. After application on the surface, a hot press is performed to improve conductivity and PTC characteristics.

That is, the present invention is a PTC resistance element obtained by forming a conductive composition containing a thermosetting resin and a metal flake conductive filler into a sheet shape as the PTC resistance element.

Further, according to the present invention, the metal conductive filler has an average particle diameter of 2 to 75 μm and a particle thickness of 0.2 to 75 μm.
The PTC resistance element is a flake-shaped particle having a 1 μm aspect ratio of 10 or more.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS PTC according to an embodiment of the present invention
An example of the resistance element will be described below.

[0014]

EXAMPLES Example 1 One-component epoxy resin (trade name;
(ECCOBOND) 80 parts by weight and a metal powder conductive filler; 20 parts by weight of silver powder (trade name: AgC-AO).
The conductive composition was uniformly dispersed to prepare a conductive composition.

Then, the thickness of one side is roughened to 25 μm.
Sandwiching the conductive composition between two rough surfaces of nickel foil of
After being pressurized and spread to a thickness of 300 μm, it was thermally cured at 150 ° C. for 15 minutes.

The PTC resistance element was prepared by cutting the conductive composition bonded to the nickel foil into a ring shape having an outer diameter of 10 mmφ and an inner diameter of 6 mmφ.

The resistance change of the PTC resistance element when the current was repeatedly interrupted was measured. As a result, the resistivity at room temperature becomes 0.8 Ωcm, which is 20% lower than that of a conventional PTC resistor element prepared by filling a crystalline polymer matrix with conductive filler of spherical particles (average particle size: 4 μm). Could be reduced.

When a voltage of 30 V and a current of 5 A are applied, switching is performed in 3 seconds, and even when current is repeatedly interrupted 10 times, the resistance value when cooled to room temperature by natural cooling is 1.3 times the initial resistance. Within this range, it was confirmed that a higher stability of PTC characteristics was obtained as compared with the conventionally used spherical silver powder, and that stable repetitive current interruption could be performed. The results are shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

Example 2 One-part epoxy resin (trade name: ECCOBOND) 80 parts by weight and an aspect ratio of 1
A conductive composition was prepared by adding 20 parts by weight of a metal flake conductive filler having a particle size of -100 to silver flake (trade name: PUFF-SILVER-X) and uniformly dispersing the same.

Next, one side is roughened to a thickness of 25 μm.
Sandwiching the conductive composition between two rough surfaces of nickel foil of
After being pressurized and spread to a thickness of 300 μm, it was thermally cured at 150 ° C. for 15 minutes.

As the PTC resistance element, the conductive composition bonded to the nickel foil was cut into a ring shape having an outer diameter of 10 mmφ and an inner diameter of 6 mmφ to produce a PTC resistance element of the present invention.

As a result of measuring the resistance value of the PTC resistance element of the present invention, it was confirmed that a conductive filler having a smaller thickness and a higher aspect ratio even with the same particle diameter exhibits more excellent conductivity. Table 3 shows the results.

[0025]

[Table 3]

From Table 3, it can be seen that a remarkable effect of improving the resistivity is seen at an aspect ratio of 10 or more.

[0027]

As described above, according to the present invention, it is possible to provide a PTC resistance element which is stable against repeated use and has good reproducibility of PTC characteristics even if the amount of conductive filler is small. Can be.

Claims (2)

[Claims] 1. A PTC resistance element for protecting an electric circuit, wherein the material is a conductive composition containing a thermosetting resin and a metal flake conductive filler, and the conductive composition is formed into a sheet. P characterized by comprising
TC resistance element. 2. The metal flake conductive filler has an average particle size of 2 to 75 μm and a particle thickness of 0.2 to 1 μm.
2. The PTC resistance element according to claim 1, wherein the PTC resistance element has an aspect ratio of 10 or more.