JPH0449601A - Planar heater - Google Patents

Abstract

PURPOSE:To improve a function of self-control of temperature by connecting a constant-resistance body to an organic PTC sheet in series electrically and by setting the resistance value of the constant-resistance body to be larger than that of organic PTC. CONSTITUTION:An organic PTC sheet 1 prepared by dispersing conductive particles in an macromolecular material, an insulating layer 2 laminated on one main surface of this organic PTC sheet 1, a constant-resistance body 3 laminated on the main surface of the insulating layer 2 on the opposite side to the main surface of the layer whereon it is laminated on the organic PTC sheet 1, and electrodes 4 connecting the organic PTC sheet 1 with the constant-resistance body 3 in series electrically, are provided and the resistance value of the constant-resistance body 3 at a temperature of 25 deg.C is set to be larger than that of the organic PTC 1 at 25 deg.C. As to the insulating layer, a resistance body constituted mainly of carbon is stuck on the whole of one main surface of a poly-ethylene terephthalate(PET) sheet and an organic PTC sheet is stuck on the whole of the other main surface of the sheet. As for the organic PTC sheet, a sheet prepared by dispersing carbon black in an ethylene vinyl acetate copolymer and molding is used; and the opposite ends of a laminate are coated with an Ag paste, so as to form the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a planar heating element constructed using an organic positive temperature coefficient thermistor (hereinafter abbreviated as organic PTC) sheet.

[Conventional technology]

Materials made by dispersing conductive particles in organic polymeric materials exhibit positive resistance-temperature characteristics. Such materials have excellent formability, so they can be formed into sheets, for example, to provide self-temperature control. It is used as a functional sheet heating element.

On the other hand, as a heating element with self-temperature control function, BaT
i0. Type ceramics are used, but because they are ceramics, it is difficult to form them into a planar or thin plate shape. Furthermore, since it is made of ceramic, it lacks flexibility and is difficult to use as a sheet heating element.

On the other hand, in the case of organic PTC, since it is mainly composed of an organic polymer material, it is easy to process it into a sheet shape.

Furthermore, since it is easy to obtain a flexible sheet, it is easy to use it as a sheet heating element.

[Problem to be solved by the invention]

However, the planar heating element using the PTC sheet does not have sufficient self-temperature control function, which is a feature of PTC, and it is difficult to control the temperature with high precision.
11 in terms of self-temperature control function and set temperature accuracy.
PTC is inferior to PTC using BaTiOs ceramics. This is an organic PTC sheet and BaTiOs
This is because their resistance-temperature characteristic curves are different.

As shown in Figure 2, in organic PTC, in the region where the resistance change ratio to the resistance value at 25°C is 10 times or less,
Compared to BaTiOs, there is less resistance change due to temperature changes.Therefore, the heat generation temperature changes easily due to changes in ambient temperature or variations in resistance value, and BaT has a self-temperature control function.
There was a problem that it was inferior to iO3, and therefore its usable applications were limited. In addition, in Fig. 2, the resistance change ratio R/Rzs on the vertical axis is 25° of the resistance value at that temperature.
The ratio to the resistance value at C is shown.

In addition, in the resistance temperature characteristic curve shown in Figure 2, if the stable point of heat generation is set in a region where the resistance change ratio is 10 times or more, organic P
The temperature gradient of the resistance-temperature curve of TC is the same as that of BaTi0. This is equivalent to the case of . However, when attempting to stabilize the resistance change ratio in such a high magnification range, voltage concentration tends to occur due to the temperature gradient between the heater electrodes, and the heater does not function as a planar heating element. In addition, the current when the power is turned on is ten times or more the current when the power is stable, which causes the problem that the power supply capacity must be made larger than necessary.

Therefore, an object of the present invention is to provide a planar heating element using organic PTC with improved self-temperature control function.

(Means for Solving the Problems) The planar heating element of the present invention includes an organic PTC sheet formed by dispersing conductive particles in an organic polymer material, and an insulating layer laminated on one main surface of the organic PTC sheet. And, the existence of the insulating layer!
A constant resistor laminated on the main surface opposite to the main surface laminated on the PTc sheet, and an electrode electrically connecting the organic PTC sheet and the constant resistor in series,
It is characterized in that the resistance value at 25°C is greater than the resistance value at 25°C of IIPTc.

Preferably, the resistance value of the constant resistor at 25°C is set to be 10 times or more the resistance value of the organic PTC at 25°C.

[Effect]

A constant resistor is electrically connected in series to the organic PTC sheet. Moreover, the resistance value of the constant resistor at 25°C is larger than the resistance value of the 11PTc at 25°C,
Preferably, it is set to 10 times or more. Therefore, when electricity is applied, most of the power is consumed on the constant resistor side in the initial state. In addition, as the constant resistor generates heat, the organic @PTC sheet is warmed, and the resistance value of the organic PTC sheet increases.
Power consumption on the organic PTC sheet side increases, and as a result, stable heat generation is obtained due to the self-temperature side mst ability of the organic PTC sheet.

Note that if the resistance value of the constant resistor at 25°C is 10 times or more the resistance value of the organic PTC sheet at 25°C, it will stabilize at the steep temperature gradient of the resistance-temperature characteristic curve, so the heat generation temperature will decrease. becomes even more stable.

That is, in the present invention, by electrically connecting a constant resistor to an organic PTC sheet in series, the resistance temperature characteristics of the entire planar heating element can be determined by utilizing not only the PTC sheet but also the resistance value of the resistor. It is characterized by an improved curve.

[Explanation of Examples]

The present invention will be explained below using examples.

A polyethylene terephthalate (PET) sheet with a size of 50 x 100 x 0.1 mm was prepared as the back insulation layer. This PET
Thickness 0 consisting mainly of carbon on the entire surface of one main surface of the sheet
．． A 3m long carbon resistor is pasted, and there is one on the other main surface! A PTC sheet was attached. As the organic PTC sheet, a sheet formed by dispersing carbon black in ethylene vinyl acetate copolymer and molded to a thickness of 0.5 m was used. This one! The resistance-temperature characteristics of the PTC sheet are shown by solid lines in FIG. 4. Ag paste was applied to both ends of the laminate obtained as described above to form electrodes.

The structure of the obtained planar heating element is shown in Figs. 1(a) and (b).
In FIGS. 1(a) and 1(b), 1 is an organic PTC sheet, 2 is a PET sheet as an insulating layer, 3 is a carbon resistor as a constant resistor, and 4.5a and 5b are electrodes. Note that the electrode 4 is provided to electrically connect the organic PTC sheet 1 and the carbon resistor 3 in series, and the electrodes 5a and 5b are terminal electrodes for connection with the outside. It is.

When the sheet heating element obtained as described above was energized and its resistance temperature characteristics were measured, the results shown by the broken line in FIG. 4 were obtained.

Stop comparison ■1 50X100XO as used in the examples.

A 1-inch PPT sheet was prepared, and an organic PTC sheet was attached to one main surface in the same manner as in the example. Ag paste was applied to both ends of the laminate thus obtained to form electrodes, thereby constructing the planar heating element shown in FIG. 3. In Figure 3, 1 is an organic PTC sheet, 2 is a PET sheet, and 6a
, 6b indicate electrodes.

Comparison 1 Comparative Example 2 A planar heating element was constructed in exactly the same manner as Comparative Example 1, except that the resistance-temperature characteristic curve of the organic PTC sheet shown by the dashed line in FIG. 4 was used. .

In addition, in FIG. 4, the thin line indicates the resistance value (constant resistance value) of the carbon resistor used in the example.

The planar heating elements of Examples and Comparative Examples 1.2 above were attached to an aluminum plate with a thickness of 0.5 m coated with an insulation coating, and AC
40V was applied. The ambient temperature at that time is 110℃ and 2
The heat generation temperature and power consumption at 5°C are shown in Table 1 below.

Table 1 As is clear from Table 1, the heat generation temperature is low only in Comparative Example 1. This is because in the sheet heating element of Comparative Example 1, voltage concentration occurs within the heating element, and This is because it is linear, which means that it cannot be used as a sheet heating element.

In order to prevent voltage concentration from occurring in the planar heating element of Comparative Example 1, it is necessary to set the heating stability point in the region where the resistance change ratio is 2 to 5 times the resistance value at room temperature. It becomes.

On the other hand, in the example, even if the room temperature changed by 35°C, the exothermic temperature changed only by 2.8 to 3.3°C.

On the other hand, in Comparative Example 1, the temperature changed by 15.2 to 16.8°C, and in Comparative Example 2, it changed by 10.1°C.

In the embodiment, this means that the resistance temperature characteristic curve is 1.0% of the room temperature resistance value. This is because when the resistance value exceeds 5 times, the resistance becomes steep, and even if the resistance change ratio is stabilized at about 2 to 3 times, the temperature change can be made small.

As described above, in the embodiment, the organic PTC sheet 1 and the carbon resistor 3, which is a constant resistor, are thermally surface-bonded via the PET sheet 2 and electrically connected in series. Furthermore, since the resistance value of the organic PTC sheet 4 at room temperature (25°C) is set lower than the resistance value of the carbon resistor 3, very stable self-temperature control is possible.
It can be seen that a planar heating element having m function is constructed.

In addition, when specifically configuring the planar heating element, in addition to the electrodes having the illustrated shapes, electrodes having other shapes such as a comb-like shape may be used.

〔Effect of the invention〕

As described above, in the planar heating element of the present invention, the constant resistor is laminated with the organic PTC sheet via an insulating layer and is electrically connected in series with the organic PTC sheet, and the constant resistor Since the resistance value at 25°C of the organic PTC sheet is made larger than that of the organic PTC sheet at 25°C,
When electricity is applied to generate heat, most of the power is initially consumed on the constant resistor side. In addition, the temperature of the heating element increases,
When the resistance value of organic PTC sheet increases,
Power consumption on the sheet side increases, and stable heat generation is obtained due to the self-temperature control function of the organic PTC sheet.

In other words, it is possible to provide a planar heating element having a very stable self-temperature control function and excellent temperature uniformity using an organic PTC sheet.

In particular, the resistance value of the constant resistor at 25°C is
By setting the resistance value at 25° C. to 10 times or more, it is possible to obtain a planar heating element that can realize an even more stable heating state.

Moreover, in the present invention, by electrically connecting the constant resistors in series, it is possible to exhibit an excellent self-temperature control function without making the stable point of heat generation on the resistance temperature characteristic curve very high. Gradient and voltage concentration are less likely to occur, and there is no need to increase the power supply capacity more than necessary.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a cross-sectional view and a plan view of a planar heating element according to an embodiment of the present invention, FIG. 2 is a diagram showing resistance temperature characteristic curves of an organic PTC sheet and BaTiOs ceramics, and FIG. The figure is a sectional view of the planar heating element of Comparative Example 1, and FIG. 4 is a diagram showing the resistance temperature characteristic curve of the entire PTC sheet, constant resistor, and planar heating element used in the example and comparative example. In the figure, 1 is a @PTC sheet, 2 is a PET sheet as an insulating layer, 3 is a carbon resistor as a constant resistor, 4 is an electrode, and 5a and 5b are electrodes. Figure 1 Figure 2 Figure 3 Si Meng La (Dc)

Claims (2)

[Claims] (1) An organic positive temperature coefficient thermistor sheet formed by dispersing conductive particles in an organic polymer material, an insulating layer laminated on one main surface of the organic positive temperature coefficient thermistor sheet, and an organic positive temperature coefficient thermistor sheet of the insulating layer. a constant resistor laminated on the main surface opposite to the main surface laminated on the organic positive temperature coefficient thermistor sheet, and an electrode provided to electrically connect the organic positive temperature coefficient thermistor sheet and the constant resistor in series. . A planar heating element, wherein the resistance value of the constant resistor at 25°C is selected to be larger than the resistance value of the organic positive temperature coefficient thermistor sheet at 25°C. (2) The planar heating element according to claim 1, wherein the resistance value at 25°C of the constant resistor is 10 times or more the resistance value at 25°C of the organic positive temperature coefficient thermistor.