JP2003017227A - Plane heating element and heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane heating element, and its heating method, which realizes quick heating without using a power source with complicated control circuit. SOLUTION: The plane heating element has a second electric heating layer laminated on a first electric heating layer through an insulation layer, both heating layers connected to power source enabled to be opened or closed independently. Further, a substrate can also be laminated on the surface of the first and/or second electric heating layers. The method of heating is to heat both the first and the second heating layers by turning on electricity, to begin with, and then, to turn off electricity either for the first or the second heating layer before the temperature balancing time of the first and the second heating layers to get the temperature of the plane heating element balanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface heating element suitable as a heat source for generating heat with a flat and uniform temperature distribution.
In particular, the present invention relates to a surface heating element having a short heating time and an excellent rapid heating property and a heating method thereof.

[0002]

2. Description of the Related Art Surface heating elements are used for floor heating, electric carpets,
It is widely used as a heat source for consumer applications such as snow melting heaters and industrial applications such as heat insulation of pipes and tanks. Examples of the conventional surface heating element include (1) a sheet obtained by kneading conductive powder in a thermoplastic resin, and (2)
It is known that a conductive powder is mixed with a silicone resin or an organic vehicle to form a paste, and the paste is formed on a substrate by using a thick film printing technique.

For example, as the form of the above (1), as disclosed in Japanese Patent Publication No. 54-13625, a thermoplastic resin such as polyethylene, a conductive carbon such as graphite or carbon black is used. The conductive powder is formed by blending and kneading, and is molded into a sheet. The conductive powder is mixed in the resin, and the physical contact between the conductive powder provides electrical continuity. Further, in such a surface heating element, the resin has an extremely large coefficient of thermal expansion between the conductive powder and the thermoplastic resin, and the resin exhibits a larger coefficient of expansion at a temperature equal to or higher than the glass transition point. The spacing between the particles of the blended conductive powder expands as the temperature rises, and at the glass transition point or higher, the spread becomes extremely large, exhibiting a positive temperature characteristic (PTC characteristic) of electrical resistance. Therefore, it becomes difficult for an electric current to flow in the heating element before and after that temperature, and the self-temperature control is possible.

On the other hand, as the form of the above (2),
For example, there is one disclosed in Japanese Examined Patent Publication (Kokoku) No. 58-15913, the details of which are described in Silicone Resin Varnish,
There is described a surface heating element produced by mixing graphite powder, an organic solvent, a fluidity adjusting agent and the like, coating the mixture on a substrate, and then firing the mixture at a temperature of 250 to 450 ° C.

[0005]

However, in the case of the above-mentioned form (1), since the positive temperature characteristic of the electric resistance (volume resistivity), a large voltage is applied at room temperature to generate a large amount of heat (unit: Even if the time (per unit area) is increased, when the temperature reaches a high temperature, the electric resistance rapidly increases, the current value decreases, the calorific value decreases, and the temperature does not rise excessively. Therefore, it is possible to raise the temperature all at once to a temperature at which the resistance value changes greatly. However, since the thermoplastic resin is the main component, a high-temperature surface heating element has a drawback. Also, during repeated thermal expansion of the resin, the contact state and arrangement state of the carbon particles in the resin matrix may change, the control temperature may change, or the temperature may rise above the control temperature for further control. There was a problem that the property was remarkably deteriorated and a fire occurred. Further, in order to improve such problems, improvements such as crosslinking of resins have been proposed. However, there remain problems that the material is special, the cost is high, and the labor of processing is increased.

On the other hand, in the case of the form (2), since the heating element itself does not have the self-temperature controllability, the above-mentioned problems derived from the self-temperature controllability can be avoided, but the ultimate temperature is Since the area, resistance value, and applied voltage are determined, the rate of temperature rise cannot be controlled, and the rapid heating property is poor. Of course, it is also possible to perform feedback temperature control in which the temperature is measured with a temperature sensor such as a thermocouple and the power supplied to the surface heating element is controlled by a thyristor or the like based on the measured value. However, for that purpose, it becomes necessary to add a control circuit to the power supply.

That is, an object of the present invention is to provide a surface heating element which has a short heating time and an excellent rapid heating property without using a power source using a complicated control circuit or a special electric heating material. is there. It is also to provide such a heat generation method.

[0008]

[Means for Solving the Problems] In order to solve the above problems,
In the surface heating element of the present invention, in the surface heating element using the electric heating layer that generates heat by Joule heat, the second heating layer is laminated on the first heating layer via the insulating layer, and both heating layers are: Each of them can be opened and closed independently and is connected to a power supply.

With such a structure, the surface heating element can quickly reach the desired equilibrium temperature in a short period of time when the temperature rises early in the heat generation. Therefore, when it is used for a heating device or the like, a quick heating effect is obtained, and the temperature rising time is short and the rapid heating property is excellent. In addition, it is not necessary to use a special electrothermal material such as a material having PTC characteristics, and by using an ordinary resistor, stable heat generation characteristics can be obtained without deterioration over time due to the effect of repeated thermal expansion of the resin. it can. Further, even if the temperature control circuit is not specially attached to the power source, a constant temperature can be maintained if only the current value is kept constant.

Further, the surface heating element of the present invention has the above-mentioned constitution, and further, on the surface of the first electric heating layer and / or the second electric heating layer,
The base material is laminated.

With such a structure, the electrothermal layer can be supported by the base material, and the mechanical strength of the surface heating element can be reinforced.

The heat generating method of the present invention uses one of the above surface heating elements to first energize both the first electric heating layer and the second electric heating layer to generate heat, and then the first electric heating layer and the second electric heating layer. At a time point before the temperature equilibration time of the two electric heating layers, energization to either the first electric heating layer or the second electric heating layer was stopped, and the surface heating element was subjected to temperature equilibration.

By adopting such a method, it is possible to accelerate the rise of the temperature in the initial stage of heat generation and reach the desired equilibrium temperature in a short time. Therefore, when it is used for a heating device or the like, a quick heating effect can be obtained, and thus the temperature rising time can be shortened and a rapid heating property can be realized. Further, even if the temperature control circuit is not specially attached to the power source, a constant temperature can be maintained if only the current value is kept constant.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

[Outline] First, FIG. 1A is a cross-sectional view illustrating one embodiment of a surface heating element of the present invention. Figure 1 (A)
The surface heating element 100 shown in FIG.
The second electrothermal layer 12 is laminated with the base material 30 laminated on the surface (lower surface of the drawing) of the first electrothermal layer, and both electrothermal layers 11 and 12 are A pair of dedicated electrodes 4 each formed independently of each other in contact with the heating layer
1 and 42 can independently energize.
In addition, in FIG. 1 (A), the base material 30 is provided only on one surface of the first heating layer of both heating layers, but as shown in FIG. 1 (B), one surface of each heating layer is provided. Substrates 30a, 30b
May be provided, and the base material may be a multi-layer, such as a configuration in which both base material layers 30a and 30b sandwich both electric heating layers from both sides. Of course, these base materials are not indispensable, but when the shape cannot be maintained from the viewpoint of mechanical strength only by the electrothermal layer, the structure in which the base materials are laminated is preferable.

A plan view of FIG. 3 shows a planar view of one embodiment of the surface heating element 100 having the structure as shown in FIG. 1 (A). Further, FIG. 3 also shows an example of wiring for heating such a surface heating element 100.

That is, in FIG. 3, the surface heating element 100 is
The power cables 310 and 320 are connected to a common power source 400 so that the first electric heating layer 11 and the second electric heating layer 12 can be independently energized. That is, the first electric heating layer 11
A power cable 310 connected to a power source 400 via a switch 210 is connected to the pair of electrodes 41 dedicated to the first heating layer, and the second heating layer 12 is connected to the second heating layer. A power cable 320 connected to a power source 400 via a switch 220 is connected to the pair of electrodes 42 provided exclusively for the layers. If wiring is performed in this manner, a heat generating method with excellent rapid heating property is possible.

[Electrical Heat Layer] The first electric heat layer 11 and the second electric heat layer 12 can be formed by, for example, silk screen printing conductive ink in which conductive powder is dispersed in a resin binder. .

As the conductive powder, for example, conductive carbon (graphite or the like), conductive particles of metal or metal oxide such as silver, copper, nickel, ITO or scale-like foil pieces are used. Further, as the binder resin, for example, ethylene-vinyl acetate copolymer, acrylic resin, silicone resin, polyimide resin, polyester resin, polyamide resin, etc. are used. The conductive powder is usually added in an amount of about 100 to 3000 parts by mass with respect to 100 parts by mass of the resin binder. And the thickness of each layer of the 1st electric heating layer and the 2nd electric heating layer is usually formed to about 5 to 1000 μm.

The method for forming each electrothermal layer is not particularly limited. For example, in addition to the above-mentioned silk screen printing, printing methods such as gravure printing, flexo printing, offset printing, roll transfer printing, etc. It can be formed in a desired pattern on top. Alternatively, a resin composition obtained by kneading a conductive powder in a resin binder is calendered,
A film can also be formed into a sheet by a melt extrusion method, a casting method, or the like. In this case, the sheet may be formed without a base material, but this sheet may be laminated with the base material later.

[Electrodes] The electrodes 41 and 42 are for connecting to a power source so that each electric heating layer can be independently energized,
It is formed by printing conductive ink or laminating conductive foil. For example, as the conductive ink, an ink is used in which conductive powder made of metal or metal oxide particles such as copper, silver, ITO, tin oxide, or flaky foil pieces is added to a resin binder. Further, for example, a conductive foil made of the above metal or metal oxide is attached and laminated.

[Insulating Layer] The insulating layer 20 is the first heating layer 11
It has a function of preventing a current from flowing between the second heating layer 12 and the second heating layer 12 and thereby individually and independently controlling the heat generated by the energization of each heating layer. The insulating layer is made of a material having sufficient electric insulation and heat resistance that does not cause strength deterioration, deformation, melting, alteration, combustion, etc. at a desired equilibrium temperature during a desired use time. . For example, a sheet made of a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, ethylene-terephthalate-isophthalate copolymer, polyarylate, etc., and preferably a biaxially stretched sheet is used. Alternatively, polyvinyl fluoride, polyvinylidene fluoride, poly 4
It is also possible to use a resin sheet made of a fluororesin such as ethylene fluoride or an ethylene-4fluoride ethylene copolymer, or a polyimide resin. A flame retardant may be added to these resins in order to impart flame retardancy. As the flame retardant, aluminum hydroxide, magnesium hydroxide, molybdenum oxide, diantimony trioxide, etc. are used. The insulating layer may be formed by adhering the previously formed resin sheet to the electrothermal layer by a method such as heat fusion or dry lamination. Alternatively, a desired pattern can be formed by a printing method such as silk screen printing, gravure printing, flexographic printing, offset printing, roll transfer printing and the like. As the resin binder of the ink used, for example, acrylic resin, polyester resin, polyimide resin, silicone resin or the like is used. The thickness of the insulating layer is usually 20 to
It is about 300 μm.

[Substrate] The substrate 30 (or 30a, 30
Although b) is basically not essential, it is preferably laminated on one side or both sides of the surface heating element for electrical insulation, reinforcement of the surface heating element, and support. Therefore, the base material is laminated on the surface of the first electric heating layer, the surface of the second electric heating layer, or the surface of the first electric heating layer and the surface of the second electric heating layer.

As such a base material, a sheet-shaped material, a plate-shaped material or the like can be used. As the sheet-shaped substrate, one having electrical insulation and heat resistance, and more preferably nonflammable or flame retardant can be used. For example, it is a sheet of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polyarylate, and more preferably a biaxially stretched sheet is used. The thickness is not particularly limited, but is usually 20 to
It is about 300 μm.

As the sheet-shaped base material, a resin sheet or the like made of fluororesin such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-4 fluoroethylene copolymer or the like, or silicone rubber , Fluororubber, urethane rubber, SBR (styrene butadiene rubber), EPDM (ethylene propylene diene rubber),
A rubber sheet made of rubber such as NBR (nitrile butadiene rubber), CPE (chlorinated polyethylene rubber), TPE (thermoplastic elastomer) can also be used.

Further, as the sheet-shaped base material, a flame-retardant non-woven fabric or woven fabric (for example, one made of fibers such as glass, asbestos, quartz) or a vinyl chloride resin sheet can be used.

As the plate-shaped base material, for example, one made of glass, pottery, porcelain, alumina, phenol resin, various resins listed above as the sheet-shaped base material, or the like can be used.

[Heating of Surface Heating Element] By the way, in order to heat the surface heating element, an electric current is passed through each heating layer to generate heat by Joule heat.
Either is fine. In order to keep the calorific value constant, a power source with stabilized current or voltage is preferable. Also,
As a matter of course, switches (210 and 220 in FIG. 3) that can independently open and close the energization of each heating layer are attached. Further, in order to prevent short circuit and other overcurrent, it is preferable to install a fuse or a breaker. In addition, as shown in FIG. 3, one power source common to each heating layer is used as a power source, and while the current from the one power source is being supplied to each heating layer, it is divided into two currents, and each current is separated. You may open and close independently with a switch. Alternatively, although not shown, separate power supplies (two in total) may be prepared for each heating layer, and current may be supplied from each power supply to each heating layer through an individual switch.

Next, as a heat generating method of the present invention, a method suitable for causing the above-mentioned surface heating element of the present invention to generate heat will be described.

The heating method of the present invention uses the above-mentioned surface heating element of the present invention as a heating element. First, both the first electric heating layer and the second electric heating layer are energized to generate heat, and then the first electric heating layer is heated. Before reaching the temperature equilibration time of the bed and the second heating layer,
This is a method in which energization to either the first electric heating layer or the second electric heating layer is stopped and the surface heating element is temperature-balanced by the heat generation of only the remaining one electric heating layer. According to this method, the temperature rising time is shortened and rapid heating is obtained without using a power source using a complicated control circuit.

Next, the present heating method will be described in detail with reference to FIG. 2, focusing on the heating timing.

First, as shown in FIG. 2A, the temperature rise characteristics when the first heating layer is independently energized with a predetermined current, that is, a function of the temperature T with respect to the (elapsed) time t after the start of energization. The relationship is T ₁ (t), the equilibrium time in that case, that is,
The time when the first electric heating layer reaches the temperature equilibrium (saturation) state is t
^c ₁ and the equilibrium (saturation) temperature of the first heating layer are T ^sat ₁ . In addition, the temperature rise characteristic when the second electric heating layer is independently energized with a predetermined current is T ₂ (t), the equilibrium time in that case is t ^c ₂ ,
Let the equilibrium (saturation) temperature of the heating layer be T ^sat ₂ . In this case, the equilibrium temperature and the equilibrium time are the current value, the volume resistivity and the specific heat (capacity) of the heating layer, the thermal conductivity, the thickness, the width, the ambient temperature, whether the current is AC or DC, and especially when AC is used. It depends on factors such as its frequency and the dielectric loss tangent of the heating layer at that frequency.

In the present invention, the energization currents of the first electrothermal layer and the second electrothermal layer may be the same or different from each other. Further, the volume specific resistance (dielectric loss) and the thickness width of the first electric heating layer and the second electric heating layer may be the same or different from each other. These conditions may be appropriately selected depending on the application, required characteristics and the like.

On the other hand, the temperature rise characteristic T _{1+ 2} (t) when both the first heating layer and the second heating layer are simultaneously energized is shown in FIG.
As shown in (B). In this case, the equilibrium time is t ^c _{1 + 2} and the equilibrium temperature is T ^sat _{1 + 2} . However, of course, T
^{_{sat 1 + 2> T sat 1}} , and, and ^{_{T sat 1 + 2> T sa}} t 2.

Then, the insulating layer 20 as described with reference to FIG.
Using the surface heating element of the present invention having a structure in which the first electric heating layer 11 and the second electric heating layer 12 are laminated so that they can be independently energized, ,
A description will be given based on FIG.

First, first of all, the first and second electric heating layers 1
Energize 1 and 12 simultaneously. As a result, the temperature rising characteristics at the time of rising are similar to the temperature rising characteristics T _{1 + 2} (t) when both electric heating layers are energized, as indicated by the curve OA or OB in the figure. As a matter of course, as compared with the temperature rising characteristics T ₁ (t) and T ₂ (t) when each electric heating layer is energized independently, the rising is faster (that is, the temperature at the same time is higher).

Then, the equilibrium time of the first heating layer, and the second
At time t ^x, which is earlier than the equilibrium time of the heating layer,
Stop energizing one of the heating layers. In the figure, time t ^x ₁ (point A on the curve) earlier than both the equilibrium time of the first heating layer and the second heating layer
Then, when the energization of the second electric heating layer is stopped and only the first electric heating layer is kept energized, the energization of the first electric heating layer is stopped and the second electric heating layer is stopped at time t ^x ₂ (point B on the curve). Both cases are shown where only the layers are energized. As a matter of course, t ^x ₁ <t ^c ₁ , t ^x ₁
<T ^c ₂ , t ^x ₂ <t ^c ₁ , t ^x ₂ <t ^c ₂ .

After the energization of one of the heating layers is stopped, it transits to a transient state and quickly converges to the equilibrium temperature of the first heating layer or the second heating layer when the individual heating is performed. That is, time t ^x ₁ (point A)
When the power supply to the second heating layer is stopped at the point A, the temperature at the point A is still less than the equilibrium temperature T ^sat ₁ ,
The temperature is further increased due to the thermal inertia and the heat generation amount of the first electric heating layer. The temperature rising characteristic of this portion is a transient state T ₁ ^tran
(T) (AD part of the figure). And time t ^c ₁ '
At point (D), it converges to the original equilibrium temperature T ^sat ₁ of the first heating layer. Naturally, as is clear from the figure, t ^c ₁ '<t ^c ₁ , and the time for raising the temperature, that is, the equilibrium time is shortened.

Further, when the power supply to the first heating layer is stopped at time t ^x ₂ (point B), at point B, although the temperature is already above the equilibrium temperature T ^sat ₂ , heat dissipation Causes a temperature drop. The temperature rising characteristic of this portion is a transient state T ₂
^tran (t) (BC part of the figure). And time t
^c ₂ 'In (C point) the second electrical heating layer intrinsic equilibrium temperature T ^{sa t} ₂
Converge to. In this case as well, as is clear from the figure, t ^c ₂ '
<T ^c ₂ , and the time for raising the temperature, that is, the equilibrium time is shortened.

As in the case of OAD in FIG. 2C, the temperature is converged without exceeding the target value of the equilibrium temperature, or as in the case of OBC, the target value is exceeded. Whether the temperature is converged depends on the condition setting, and may be selected while taking into consideration the desired temperature control characteristic and other circumstances.
Generally, if the shortening of the equilibrium time (temperature rising time) is prioritized, a form like OBC is adopted. If priority is given not to let the temperature exceed the equilibrium temperature (target value), a form like OAD is adopted. Note that, as shown in FIG. 2C, in order to shorten the temperature raising (equilibrium) time, for example, a timer sets a predetermined energization stop time t ^x ₁ or t ^x _2.
Is set in advance, and the energization of a predetermined electric heating layer is stopped by the timer at a predetermined time t ^x ₁ or t ^x ₂ .

[Application of Surface Heating Element] The application of the surface heating element according to the present invention is not particularly limited. For example, floor heating, electric carpet, heating of chairs and seats, consumer applications such as snow melting heaters, piping, It can be used for industrial applications such as keeping the tank warm.

[0042]

The present invention will be further described with reference to Examples and Comparative Examples.

Example 1 A surface heating element 100 having a sectional view as shown in FIG. 1A and a plan view as shown in FIG. 3 was produced as follows. A 250 mesh plate of silver paste (manufactured by Jujo Chemical Co., Ltd., trade name "JELCON SH-1") as a pair of first electrodes 41 on one side of a biaxially stretched polyethylene terephthalate sheet having a thickness of 188 μm as the base material 30. Silk screen printing using, and heating in an oven at 150 ° C. for 30 minutes to solidify, consisting of parallel straight lines with a line width of 5 mm, a length of 145 mm, and an electrode distance of 50 mm.
A counter electrode pattern having a film thickness of 8 μm was formed.

Next, a conductive carbon paste (manufactured by Jujo Chemical Co., Ltd., trade name "CH-2") was silk-screen printed in the same manner on the first electrode, and then in an oven at 120 ° C. for 20 minutes. 70m wide by heating and solidifying
The first electric heating layer 11 having a length of m, a length of 100 mm and a film thickness of 9 μm was formed. Since the first electrode 41 serves as an electrode terminal,
Overprinting was performed so that the carbon paste was not applied to a part of the first electrode 41.

Next, an insulating paste (manufactured by Jujo Chemical Co., Ltd., trade name "JELC") is formed so as to cover the first heating layer 11.
ON IN-15M ") is silk screen printed using a 200 mesh plate, and then UV (lamp intensity 12
The insulating layer 20 having a thickness of 18 μm was formed by irradiating with 0 W / cm ² and one metal halide lamp. The irradiation is carried out at a conveyor speed of 6 m / min and an irradiation distance of 10 cm.
It went on condition of. In order to secure the terminal portion of the first electrode 41, the insulating layer 20 is printed by overlapping printing so that the insulating paste does not cover a part (25 mm length) of the first electrode 41. It was

Next, a silver paste (trade name "Dotite XA-3006" manufactured by Toyobo Co., Ltd.) is silk-screen printed on the insulating layer 20 so as to overlap the first heating layer 11 using a 250 mesh plate. And then in the oven at 150 ° C,
It was heated and solidified for 30 minutes to form the second electrode 42 having a film thickness of 8 μm. The pattern of the second electrode 42 has a line width of 5 m at a position inside the first electrode 41 so as not to overlap the terminal lead-out portion of the first electrode 41 and parallel to the first electrode 41.
The counter electrode pattern was composed of parallel straight lines with m, length 130 mm, and electrode distance 30 mm.

Then, a conductive carbon paste (trade name "CH-2" manufactured by Jujo Chemical Co., Ltd.) was silk screen printed with a 250 mesh plate so as to cover the second electrode 42, and then 120 ° C. in an oven. 15 minutes, heated and solidified, width 50mm, length 100mm, film thickness 6μ
m second electric heating layer 12 was formed. In addition, in order to take an electrode terminal, a part of the second electrode 42 (for a length of 30 mm) was overprinted so that the carbon paste was not applied.

The surface heating element 100 obtained as described above.
Had a surface resistance of 20Ω / □, and a terminal resistance of 60Ω at the first electrode and 55Ω at the second electrode.

In this surface heating element, as shown in FIG.
When 12 V DC is supplied from the power source 400 to the first electrode 41 and the second electrode 42 independently of the power cables 310 and 320 via the switches 210 and 220, respectively,
The electric heating layer 11 and the second electric heating layer 12 generated heat and increased in temperature.
Table 1 shows the results of measuring the change with time of the surface temperature at that time together with the case of the comparative example. In addition, as a heat generation method,
At first, the first electric heating layer 11 and the second electric heating layer 12 are simultaneously energized, and after 30 seconds, the switch 220 is opened to open the second electric heating layer 12.
The energization of No. 1 was stopped, and thereafter, only the first electric heating layer 11 was energized.

Comparative Example 1 With respect to the surface heating element 100 manufactured in Example 1, the heating method is changed from that in Example 1, and
The change in surface temperature with time was measured. As the heat generation method, electricity was applied only to the first electrothermal layer 11 from the beginning. The results are shown in Table 1.

[Comparative Example 2] With respect to the surface heating element 100 manufactured in Example 1, the heating method is changed from that in Example 1, and
The change in surface temperature with time was measured. As a heat generating method, electricity was applied only to the second electric heating layer 12 from the beginning. The results are shown in Table 1.

[0052]

[Table 1]

[Result Comparison] As shown in Table 1, Comparative Examples 1 and 2
In the heat generation method in (1), the temperature rising rate is slow, and the temperature rising rate decreases with time, and the temperature is kept rising gently even after 2 minutes or more. On the other hand, in the heat generation method of Example 1, the constant temperature was reached after 60 seconds, and the rapid heating property could be improved.

[0054]

(1) According to the surface heating element of the present invention, the temperature rises quickly in the initial stage of heat generation, and the desired equilibrium temperature can be reached in a short time. Therefore, when it is used for a heating device or the like, a quick heating effect is obtained, and the temperature rising time is short and the rapid heating property is excellent. In addition, it is not necessary to use a special electrothermal material such as a material having PTC characteristics, and by using an ordinary resistor, stable heat generation characteristics can be obtained without deterioration over time due to the effect of repeated thermal expansion of the resin. it can. In addition, the temperature rise time can be shortened simply by opening and closing the switch at a predetermined time without adding a temperature control circuit, and if the current value is kept constant, a constant temperature is maintained. it can. (2) Further, by forming a base material on the surface of the first electric heating layer and / or the second electric heating layer, the electric heating layer can be supported by the base material and the mechanical strength of the surface heating element can be reinforced. . (3) Further, according to the heat generation method of the present invention, it is possible to accelerate the rise of the temperature at the initial stage of heat generation and reach the desired equilibrium temperature in a short time. Therefore, when it is used for a heating device or the like, a quick heating effect can be obtained, and thus the temperature rising time can be shortened and a rapid heating property can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing some form examples of a surface heating element of the present invention.

FIG. 2 is an explanatory view detailing a heating method according to the present invention.

FIG. 3 is a plan view showing an example of a planar view shape of a surface heating element of the present invention and an example of wiring for the heating method.

[Explanation of symbols]

11 1st electric heating layer 12 2nd electric heating layer 20 Insulating layers 30, 30a, 30b Base material 41 1st electrode 42 2nd electrode 100 Surface heating element 210, 220 Switch 310, 320 Power supply cable 400 Power supply (DC stabilized power supply etc.) ) 500 thermometer (digital thermometer, etc.) 510 temperature sensor T _{1 + 2} ^sat equilibrium temperature T ₁ ^sat equilibrium temperature T ₂ ^sat equilibrium temperature

Claims (3)

[Claims] 1. A surface heating element using an electric heating layer which generates heat by Joule heat, wherein a second electric heating layer is laminated on a first electric heating layer with an insulating layer interposed therebetween, and both electric heating layers are independently formed. A surface heating element that can be opened and closed and connected to a power supply. 2. The surface heating element according to claim 1, wherein a base material is laminated on the surface of the first electric heating layer and / or the second electric heating layer. 3. The surface heating element according to claim 1 or 2,
First, both the first electric heating layer and the second electric heating layer are energized to generate heat, and then, before the temperature equilibration time of any of the first electric heating layer and the second electric heating layer, the first electric heating layer or the second electric heating layer is heated. (2) A heating method in which the power supply to any one of the heating layers is stopped and the surface heating element is temperature-balanced.