JPH10223356A - Ptc heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate electrode forming and provide a light-weight PTC heater with superior flexibility at low cost by providing a PTC material main body surface having a positive temperature resistance coefficient mixed with a thermal plastic resin and a conductive carbon particle with a flexible porous base material in which a conductive circuit is formed so as to obtain conduction of both of the top and bottom faces in advance. SOLUTION: A thermal plastic resin and a conductive carbon particle are heated above a melting temperature, mixed, and molded in a given shape, and pressure-cooled, and a PTC material 1 is obtained. On one side of this a non- woven cloth 2 in which a conductive circuit of flexible porous base material is formed and on the other side a plain non-woven cloth 3 are thermally pressure-welded by a heat press, bonded with a PTC material, and molded. Thereby, power can be supplied non-uniformly all through the PTC material from one side, the PTC material is reinforced with the plain non-woven cloth 3, in particular, bending breakage strength is large, and a structure ensuring large deformation at a normal temperature is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC heater having a positive coefficient of resistance ("PTC" characteristic), and more particularly, to a PTC heater which is lightweight, excellent in flexibility and capable of reducing cost.

[0002]

2. Description of the Related Art Conventionally, ceramic-based PTC heaters have been widely used as PTC heaters utilizing positive temperature characteristics. However, the ceramic PTC heater has problems that it is heavy and brittle due to its material properties, and that the moldability is poor and the product shape is limited. As a solution to this problem, an organic PTC heater comprising a mixture of a thermoplastic resin and conductive carbon particles has been proposed, and its use is expanding due to its light weight, excellent flexibility, excellent workability, and low cost. is there. However, organic PTC
In the case where a metal foil electrode is formed by thermocompression bonding on the surface of a PTC material body conventionally proposed as a heater,
After the electrodes are formed, the elongation is hindered by the metal foil, so PT
There has been a problem that the flexibility inherent in the C material body is impaired, and it is difficult to assemble it into another part by performing post-processing or deformation such as bending. Also,
When a complicated conductive circuit pattern is formed, there is a problem that processing of a metal foil and formation of an electrode are complicated and complicated.
Further, there is a problem in that the advantages of the organic PTC material, such as light weight and low cost, which are features of the organic PTC material, are lost due to an increase in weight due to the metal foil and an increase in processing cost due to pattern formation.

[0003] On the other hand, resin molded articles having a flexible porous substrate, for example, a nonwoven fabric on the surface, are used for many purposes (Japanese Utility Model Laid-Open No. 61-42804, etc.). In order to form the nonwoven fabric on the surface of the resin molded product, a part of the surface of the resin as the base material is melted, and this is permeated into the inside of the nonwoven fabric and pressure-bonded while exuding to the surface. That is,
The surface of the nonwoven fabric is covered with a resin material, thereby exhibiting strong adhesion.

However, when a conductive paste is applied after the non-woven fabric is thermocompression-bonded to a resin molded product, the result is the same as applying the conductive paste to the resin molding material itself. There were problems such as lack of properties.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to form an electrode on an organic PTC material easily, without deteriorating the characteristics of the material, light weight, excellent flexibility and low cost. The present invention provides a PTC heater capable of performing the following.

[0006]

Under such circumstances, the present inventor has conducted intensive studies, and as a result, has previously formed a conductive circuit capable of obtaining conduction between the front and back surfaces on a nonwoven fabric by screen printing of a conductive paste. It has been found that the above object can be achieved by thermocompression-bonding this to the surface of an organic PTC material, and the present invention has been completed. That is, the present invention provides, on the surface of a PTC material body having a positive temperature coefficient of resistance composed of a mixture of a thermoplastic resin and conductive carbon particles,
An object of the present invention is to provide a PTC heater provided with a flexible porous substrate on which a conductive circuit capable of obtaining conduction between the front and back surfaces is formed in advance.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic resin used in the present invention is not particularly limited.
Examples include polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, polyethylene terephthalate, and fluororesin. The thermoplastic resins can be used alone or in combination of two or more.

The conductive carbon particles used in the present invention are not particularly limited, but include carbon black, carbon fiber, carbon graphite, and carbon black.
Examples include carbon-based materials such as carbon beads, which are usually used in the form of particles of about 0.001 to 100 μm.

The mixing ratio of the thermoplastic resin and the conductive carbon particles is not particularly limited, and can be appropriately selected according to the type of the resin and the conductive carbon particles, but is usually 30 to 80:70 by weight. It is preferably in the range of 20 to 20.

The PTC material of the present invention is prepared by, for example, uniformly kneading a thermoplastic resin and conductive carbon particles using a mixing roll heated to a temperature not lower than the melting temperature of the resin, and then heating and pressing the mixture. It can be obtained by, for example, molding into a predetermined shape such as a sheet or film, and then cooling under pressure. The thickness of the PTC material is 0.1
It is preferably about 10 to 10 mm.

In the present invention, a conductive circuit for providing conduction between the front and back surfaces is formed in advance on a flexible porous substrate. The flexible porous base material is flexible, and since the PTC material to be treated with the flexible base material penetrates to the back surface to form a layer having good adhesion, a porous resin film, Woven fabrics and non-woven fabrics can be mentioned, but non-woven fabrics are particularly preferred from the viewpoint of thickness stability and material cost.

The material of the non-woven fabric is not particularly limited, and includes polyester, polyamide, polyacetal, aramid, glass and the like. Of these, aramid and glass are preferably used when heat resistance is particularly required. . As the base material of the nonwoven fabric, any of a single fiber and a long fiber can be used. However, when performing thermocompression bonding, in order to allow the PTC material to permeate and obtain a strong bond,
Preferably, the thickness is 50 to 200 μm and the density is 0.2 to 0.6 g / cm ³ .

The method for forming a conductive circuit on the flexible porous substrate is not particularly limited, but it is simple, a desired conductive circuit can be formed in a free shape, temperature unevenness can be reduced, and a temperature gradient can be reduced. From the viewpoint of quick adjustment and low cost, a method of screen-printing a conductive paste containing one or more of silver, copper, carbon and the like is preferable. In the case of this method, since the conductive paste penetrates the flexible porous material, a conductive circuit in which conduction between the front and back surfaces can be easily obtained is formed.

The method of forming the flexible porous substrate having the conductive circuit formed on the PTC material is not particularly limited, but the flexible porous substrate is subjected to thermocompression bonding using a hot press. A method of bonding to the surface of the material is preferred. For continuous formation, a thermal transfer method using a hot roll is preferred.

The nonwoven fabric having the conductive circuit formed on the surface of the PTC material can be formed in various forms. For example, as shown in FIG. 1, a conductive circuit is formed on one side of the PTC material 1. The nonwoven fabric 2 can be formed, and a plain nonwoven fabric 3 can be provided on the back surface. With such a formation form, power can be supplied evenly to the entire PTC material from one side, and the PTC material can be reinforced by a plain nonwoven fabric.
In particular, it is possible to obtain a structure in which the bending fracture strength is increased and which can withstand large deformation at room temperature. Further, as shown in FIG. 2, a nonwoven fabric 2 having a conductive circuit formed on both surfaces of the PTC material 1 can be provided. In such a formation mode, unlike FIG. 1, the conductive direction is the thickness direction of the PTC material, so that more stable performance can be obtained. The shape of the conductive circuit is not particularly limited, and any of a comb shape, a waveform shape, and the like can be used.

The use of the PTC heater of the present invention is as follows.
Although not particularly limited, the present invention is particularly suitable for applications requiring a curved surface, for example, a heater for a hot curler of hair.

[0017]

According to the present invention, an electrode can be easily provided on an organic PTC material on which an electrode is difficult to be formed. This greatly simplifies the operation as compared with the conventional electrode formation using a metal foil, and can be manufactured more inexpensively and quickly. Further, the PTC heater is lightweight and excellent in flexibility without sacrificing the characteristics of the organic material. Also, if installed together with a plain nonwoven fabric,
The TC material is reinforced, the thermal deformation is greatly reduced, the bending strength at room temperature is large, and the degree of freedom of post-processing is further increased.

[0018]

The present invention will be described in more detail with reference to the following examples, which are merely illustrative and do not limit the present invention.

Example 1 55 parts by weight of a high-density polyethylene (trade name "3300FP" manufactured by Mitsui Petrochemical Co., Ltd.) and 45 parts by weight of carbon black (trade name "Diablack G" manufactured by Mitsubishi Chemical Corporation) were mixed by a pressure kneader. Kneaded for 10 minutes. The kneaded material is heated and pressed by a hot press machine to form a sheet having a thickness of about 1 mm.
A TC material was produced. On the other hand, conductive paste (product name "#
Screen printing was performed to form a comb-shaped electrode 4 shown in FIG. 3 on the surface of a non-woven fabric (trade name: “H-8004” manufactured by Nippon Vileen Co., Ltd.) using polyester fiber (13 ”manufactured by NE Chemcat). . This is 140 °
C. for 30 minutes to obtain a nonwoven fabric having a strong conductive circuit capable of obtaining conduction between the front and back surfaces. Then, the P
A nonwoven fabric on which the electrode is printed is placed on one side of the TC material,
A plain nonwoven fabric was placed on the other side, and thermocompression-bonded using a hot press. Thus, a PTC heater having a cross section similar to that of FIG. 1 was obtained. The PTC heater is 45mm ×
A 100 mm rectangle having a thickness of 0.6 mm had a resistance of 18Ω at 25 ° C. A voltage of 30 V was applied to the heater, and the surface temperatures at six points as shown in FIG. 4 were measured before the test, and at 30, 60, and 300 seconds after the application. The results are shown in Table 1. Thus, the PTC heater obtained in this example had good uniformity of temperature distribution.

[0020]

[Table 1]

Example 2 Example 1 was repeated except that 52 parts by weight of low-density polyethylene (trade name "LF561M" manufactured by Mitsubishi Chemical Corporation) and 48 parts by weight of carbon black (trade name "Diablack G" manufactured by Mitsubishi Chemical Corporation) were used. According to the same method as in the above, a PTC material was produced.
Further, a nonwoven fabric having a conductive circuit was obtained in the same manner as in Example 1, and this was thermocompression-bonded to both surfaces of the PTC material with a hot press to obtain a PTC heater. The PTC heater was subjected to a flexural fracture strength test (JIS K7203), which was determined as a result of five measurements. The results are shown in Table 2.

Comparative Example 1 Only a PTC material having the same thickness as the PTC heater obtained in Example 2 and having no nonwoven fabric was obtained. The same bending fracture strength as in Example 2 was measured for the PTC material. The results are shown in Table 2.

[0023]

[Table 2]

Comparative Example 2 The PTC material used in Example 1 was used, and a metal foil 5 having a width of 3 mm was thermocompression-bonded thereto to produce a PTC heater 11 having a conductive circuit pattern as shown in FIG. . This was subjected to a bending test shown below. The results are shown in Example 1.
Table 3 shows the results of the PTC heaters.

(Flexibility test) A pipe 6 having a diameter of 30 mm is placed on the center of the surface of the PTC heater 10, and the PTC heater 10 is bent along the pipe 6 as shown in FIG. The state of adhesion or peeling of the electrode after 20 times is visually observed.

[0026]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a PTC heater according to an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of another embodiment of the PTC heater of the present invention.

FIG. 3 shows a conductive circuit pattern of the nonwoven fabric used in Example 1.

FIG. 4 is a plan view of the PTC heater of Example 1 showing measurement points of temperature.

FIG. 5 shows a plan view of a PTC heater of Comparative Example 2.

FIG. 6 shows a bending state of a PTC heater in a bending test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PTC material 2 Nonwoven fabric in which conductive circuit was formed 3 Plain nonwoven fabric 4 Conductive circuit pattern 5 Metal foil 6 Pipe 10, 11 PTC heater

Claims (4)

[Claims] 1. A flexible porous member in which a conductive circuit for obtaining conduction between the front and back surfaces is formed in advance on the surface of a PTC material body having a positive temperature coefficient of resistance, comprising a mixture of a thermoplastic resin and conductive carbon particles. A PTC heater comprising a porous substrate. 2. The PTC heater according to claim 1, wherein the flexible porous substrate is a non-woven fabric. 3. The PTC heater according to claim 1, wherein the conductive circuit is formed by screen printing of a conductive paste. 4. The PTC heater according to claim 1, wherein the flexible porous material is bonded to the surface of the PTC material body by thermocompression.