JP2000200673A - Flat heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent thermorunaway caused by the riss of the heating tempera ture, to uniformize the heating temperature, and to minimize the individual difference in the heating temperature by setting the ratio of the resistance of a heating layer under some equilibrium heating temperature to the maximum resistance of the heating layer between the equilibrium heating temperature and a temperature higher than that by a prescribed temperature to a prescribed times. SOLUTION: A flat heating element is constituted of a pair of comb-shaped electrodes 2 provided on a substrate 1 and a heating layer 3 of a conductive ink composition. The ratio (Rmax/RG) of the equilibrium resistance RG of the heating layer 3 under an equilibrium heating temperature TG to the maximum resistance Rmax of the heating layer 3 under a heating temperature range TG-(TG+40 deg.C) is set to 5-606 times. When Rmax/RG is 5 times or less, thermorunaway caused by rising the heating temperature cannot be prevented to have a possibility of causing burning damage by the thermorunaway. On the other hand, if exceeding 106 times, there is no problem in its characteristics, however, in many cases, no conductive ink composition superior in workability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet heating element using a conductive ink composition, and more particularly to a sheet heating element used for heating equipment such as floor heating and for preventing dew condensation on a mirror, and having good PTC characteristics (positive temperature). Coefficient characteristic), can sufficiently prevent thermal runaway due to an increase in heat generation temperature, has a small difference in heat generation temperature within the sheet heat generator, and is unlikely to cause individual differences in heat generation temperature.

[0002]

2. Description of the Related Art A planar heating element is obtained by printing or applying a conductive ink composition on a substrate to form a heating layer having an arbitrary thickness and shape.
Heretofore, it has been used as a special shape or a small heating element. As a conductive ink composition used for the sheet heating element, a base polymer such as a crystalline polymer or an amorphous polymer and a conductive material such as carbon black, metal powder, and graphite are dispersed in a solvent. Are used.

A conductive ink composition using a crystalline polymer such as polyethylene as a base polymer is an excellent conductive ink composition capable of forming a coating film exhibiting a steep PTC characteristic with a rise in temperature. The PTC characteristic is manifested when the chain of the conductive substance is broken by the volume expansion of the crystalline polymer due to a temperature change, and the resistance increases accordingly. For this reason, a conductive ink composition using a crystalline polymer exhibiting a steep PTC characteristic is used in a planar heating element obtained by applying or printing the same, for example, when the ambient temperature rises. This has the advantage that thermal runaway due to temperature rise can be prevented and burnout can be suppressed.

However, the conductive ink composition using the crystalline polymer cannot obtain properties suitable for coating or printing because the base polymer does not dissolve in a solvent. Productivity decreases,
In addition, there is a problem that gelation easily occurs during low-temperature storage. Furthermore, the coating film obtained by printing or coating this on a substrate has insufficient mechanical strength and flexibility,
Had been a problem.

[0005] There is also a conductive ink composition using a non-crystalline polymer such as ethylene-propylene rubber as a base polymer. Since the base polymer is dissolved in the solvent, the conductive ink composition has properties suitable for application or printing, and has excellent workability during application or printing.

However, since the conductive ink composition using this non-crystalline polymer has a moderate thermal expansion due to a rise in temperature, the PTC characteristics of a coating film obtained using the same are also moderate. Therefore, for example, when the ambient temperature rises, or when the sheet heating element is exposed to adiabatic conditions,
There is a concern that the heat generation temperature may rise and cause burnout due to thermal runaway, which has been a problem. Therefore, it is necessary to provide an overheating prevention mechanism or the like corresponding to the use environment in a sheet heating element using this, which has been a problem.

Further, a conductive ink composition using both a crystalline polymer and an amorphous polymer as a base polymer has been proposed. Specifically, non-crystalline polymers such as natural rubber and synthetic rubber, crystalline polymer particles such as polyethylene and polyester incompatible with the non-crystalline polymers, conductive carbon black, graphite and inorganic fillers Have been proposed. This conductive ink composition has both the advantages of the crystalline polymer particles and the advantages of the non-crystalline polymer, and in particular, exhibits excellent stability with a small decrease in resistance even in an extremely cold environment. It is a thing.

However, the planar heating element using the conductive ink composition cannot sufficiently prevent thermal runaway due to a rise in the heat generation temperature, for example, when exposed to adiabatic conditions, resulting in burnout due to thermal runaway. There was a risk of causing such a problem, which was a problem. In addition, there has been a problem that the heating temperature in the planar heating element is non-uniform and the individual difference in the heating temperature is large.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances, and can solve such a problem, prevent a thermal runaway due to a rise in heat generation temperature, and furthermore, generate a planar heat generation. An object of the present invention is to provide a planar heating element having a uniform heat generation temperature in the body and a small individual difference in the heat generation temperature.

[0010]

An object of the present invention is to provide a planar heating element comprising a substrate provided with a pair of comb-shaped electrodes and having a heating layer made of a conductive ink composition formed thereon. In a state in which one side of the body is not in contact with the heat insulator, the equilibrium heat generation temperature _TG after voltage application is 35 to 110 ° C,
And there equilibrium heating temperature T _G, the resistance value R _G of the heat generating layer in the balanced heating temperature T _G between 40 ° C. higher temperature T _G +40 than this equilibrium heating temperature T _G, the maximum resistance value Rm of the heat generating layer
The ratio Rmax / R _G and ax is 5-10 ⁶ times, the comb electrodes are of the electrode interval 2 to 40 mm, the conductive ink composition comprises a solvent, a crystalline polymer, the non The problem can be solved by a planar heating element containing a crystalline polymer and a conductive material.

In the above-mentioned planar heating element, the conductive ink composition contains a solvent, a crystalline polymer, an amorphous polymer, and a conductive material, and the crystalline polymer is Having an average particle diameter of 0.2 to 100 μm, wherein the amorphous polymer has a crystallinity of 5% or less, and the weight ratio of the crystalline polymer to the amorphous polymer is 30 : 70-
It is desirable that the ratio be 95: 5.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is a plan view showing an example of the sheet heating element of the present invention, and FIG. 2 is a sectional view of the sheet heating element shown in FIG.
1 and 2, reference numeral 1 denotes a substrate. On this substrate 1, a pair of comb-shaped electrodes 2 and a heating layer 3 made of a conductive ink composition are provided. The comb electrode 2
Are formed in a direction parallel to the longitudinal direction of the substrate 1 and a plurality of linear comb portions 2a formed in parallel with each other in a direction perpendicular to the longitudinal direction of the substrate 1, and one end of the comb portion 2a And a connecting part 2b to which the parts are connected. The two comb-shaped electrodes 2 having the same interval between the comb portions 2a
Are arranged so that they face each other, and at a predetermined electrode interval d, the comb portion 2a of the other comb-shaped electrode 2 is located between the comb portions 2a of the other comb-shaped electrode 2.

FIG. 3 is a graph showing the relationship between the temperature of the sheet heating element and the resistance value. In FIG. 3, the symbol _TG is
The symbol _TG + 40 indicates an equilibrium heat generation temperature, and the symbol _TG + 40 indicates a temperature 40 ° C. higher than the equilibrium heat generation temperature _TG . In the present invention, the term “equilibrium heating temperature T _G ” refers to a heat generation after voltage application when a predetermined AC or DC voltage is applied while at least one surface of the sheet heating element is not in contact with the heat insulator. The temperature when the temperature reaches equilibrium and becomes constant. Further, a range from the above-mentioned equilibrium heat generation temperature _TG to a temperature _TG + 40 that is 40 ° C. higher than the equilibrium heat generation temperature _TG is referred to as “heat generation temperature range _{TG to TG} + 40”.

Further, in the present invention, as shown in FIG. 3, the resistance value of the heat generating layer 3 at the equilibrium heat generation temperature _TG is referred to as "equilibrium resistance value R _G ". Further, as shown in FIG. 3, the maximum resistance value of the heat generation layer 3 within the heat generation temperature range T _{G to} T _G +40 is referred to as “maximum resistance value Rmax”.
Then, the maximum resistance value Rmax and the balanced resistance value R _G
(Maximum resistance value Rmax / balanced resistance value R _G ) is abbreviated as “resistance value ratio Rmax / R _G ”.

In the sheet heating element of the present invention, at least one surface of the sheet heating element is not in contact with the heat insulator,
When an AC or DC voltage is applied, the equilibrium heat generation temperature _TG is in the range of 35 to 110 ° C. When the equilibrium heat generation temperature _TG is less than 35 ° C., the commercial value of the sheet-shaped heat generator generally decreases, which is not preferable. On the other hand, if the temperature exceeds 110 ° C., the substrate 1 and the heat generating layer 3 themselves are apt to be thermally deteriorated, which is not preferable.

The equilibrium heating temperature _TG varies depending on the type of the conductive ink composition used for the sheet heating element, the thickness of the heating layer 3, the electrode interval d of the comb-shaped electrode 2, and the like. Depending on the method of changing the distance d,
It is adjusted so as to be in the above-mentioned range.

The planar heating element has a heating temperature range T
_It can be used at _{G to TG} +40, and the resistance value ratio Rmax / _RG is 5 to 10 ⁶ times, preferably 10 to 10 times.
10 ⁶ fold, more preferably, is assumed to be 20 to 10 ⁶ times.

If the ratio Rmax / _RG of the resistance value is less than five times, the following inconveniences occur, which is not preferable. (1) Since the resistance value does not increase even if the heat generation temperature rises,
For example, when the planar heating element is in an adiabatic state, thermal runaway due to an increase in heat generation temperature cannot be prevented, and burnout due to thermal runaway may occur. (2) Since the difference in resistance between the high-temperature portion and the low-temperature portion in the planar heating element is small and the effect of reducing the difference in the heating temperature in the planar heating element cannot be obtained, the difference in the heating temperature in the planar heating element is not obtained. Becomes larger. Therefore, the individual difference of the heat generation temperature is also large. On the other hand, if it exceeds 10 ⁶ times, there is no problem in properties, but it is often not possible to obtain a conductive ink composition having excellent workability, which is not preferable.

The resistance value ratio Rmax / _RG differs depending on the type of the conductive ink composition used for the sheet heating element, the thickness of the heat generating layer 3, the electrode interval d of the comb-shaped electrode 2, and the like. The distance is adjusted so as to fall within the above range by a method of changing the electrode interval d of the second.

As the substrate 1 used for the planar heating element, a resin film of polyethylene terephthalate (PET), polyimide, polyvinyl chloride or the like having a thickness of about 10 to 100 μm is generally used. When considering the use of a material, a material having a high heat-resistant temperature is desirable.

As the comb-shaped electrode 2, a desired comb-shaped pattern is formed on the substrate 1 by a screen printing method or the like, or a copper foil or an aluminum foil having a thickness of about 10 to 50 μm is formed through an adhesive. And a comb-shaped electrode 2 formed by bonding a metal foil such as a silver foil or the like, preferably a copper foil, and performing an etching process to form a desired comb-shaped pattern.

As the comb-shaped electrode 2, the inter-electrode distance d of the comb-shaped electrode 2 is 2 to 40 mm, preferably,
Those having a size of 3 to 30 mm are used. It is not preferable to use a comb-shaped electrode 2 having an electrode spacing d of less than 2 mm, because a problem such as a short circuit between the electrodes due to foreign matter easily occurs. On the other hand, when a thickness exceeding 40 mm is used, the difference in the heat radiation state between the portion in contact with the comb-shaped electrode 2 in the heating layer 3 and the portion farthest from the comb-shaped electrode 2 becomes large. This is not preferable because the heat generation temperature tends to be non-uniform. In addition, this increases the individual difference in the heat generation temperature, which is not preferable.

The distance d between the electrodes of the comb-shaped electrode 2 has a correlation with the temperature of the heat generated in the sheet-shaped heating element. The narrower the distance d between the electrodes of the comb-shaped electrode 2, the higher the temperature of the sheet-shaped heating element can be obtained. Conversely, as the electrode interval d of the comb-shaped electrode 2 is increased, a planar heating element having a lower heating temperature is obtained, and it is preferable that the planar heating element is determined according to the use of the planar heating element. Furthermore, the electrode interval d of the comb-shaped electrode 2 is changed by the equilibrium heating temperature _TG and the resistance value ratio Rmax, which change with the electrode interval d.
/ _RG is adjusted and determined to be within the desired numerical range.

The heating layer 3 is made of a conductive ink composition. As the conductive ink composition used here, the equilibrium heating temperature T of the sheet heating element using the same is used.
_It is preferable that _G is 35 to 110 ° C. and the resistance value ratio Rmax / _RG is 5 to 10 ⁶ times. Specifically, a solvent, a crystalline polymer, a non-crystalline polymer, A conductive ink composition containing a conductive substance is preferably used.

The crystalline polymer used in the conductive ink composition has an average particle size of 0.2 to 100 μm.
m, preferably 1 to 50 μm. When the average particle diameter is less than 0.2 μm, the viscosity of the ink increases, and it becomes unsuitable for application or printing,
This is not preferable because the productivity of the planar heating element using the same decreases. In addition, when the particles having an average particle diameter exceeding 100 μm are used, problems such as pinholes are likely to occur in a coating film obtained by using the particles, which is not preferable.

As the crystalline polymer, for example,
Polyamide, polyester, low molecular weight polyethylene, polypropylene, trans-polybutadiene, polyoxymethylene, polystyrene, polyoxyethylene, polyoxypropylene, polyvinyl chloride and the like are used. Specifically, for example, a crystalline polyamide (trade name: polyamide S-1962, melting point: 117 ° C., manufactured by Sanyo Chemical Industries), a crystalline polyester (trade name: Alonmelt PES-110, manufactured by Toagosei Chemical), and the like are preferably used.

As the non-crystalline polymer used here, any polymer can be used as long as it has a crystallinity of 5% or less. For example, ethylene and vinyl acetate, acrylic acid, Copolymers with acrylates, maleic acid, etc., polyesters, natural rubbers, various synthetic rubbers such as isoprene rubber, nitrile rubber, ethylene propylene rubber, alkyl acrylate polymers and the like are used. Specifically, for example, a saturated polyester (trade name: Byron 200, manufactured by Toyobo) is preferably used.

As the conductive substance, conductive carbon black, graphite, metal powder and the like are used. The conductive carbon black here has a small structure and a relatively large particle size of about 30 to 150 μm, for example, HAF, SRF, GPF,
Those classified by type names such as FEF and FT are used. As the graphite, flakes of natural graphite and artificial graphite, clay lumps and the like are used.

As the solvent, those capable of dissolving the non-crystalline polymer well and stably dispersing the crystalline polymer are preferable. For example, hydrocarbon solvents such as toluene, xylene, mineral spirit, solvent naphtha, tetralin, and polyhydric alcohol derivative solvents such as butyl cellosolve, cellosolve acetate, butyl carbitol, carbitol acetate, n-butyl acetate, methoxybutyl acetate And ester solvents such as γ-butyrolactone are preferably used.

The preparation of such a conductive ink composition is as follows.
It is performed by adding and dispersing a crystalline polymer, an amorphous polymer, and a conductive substance in a solvent. These operations are performed by a wet dispersing device such as a Dyno mill or a 3
This is performed using a roll or the like. Further, the degree of dispersion of the conductive ink composition is confirmed using a particle gauge or the like. In some cases, it is preferable to add the crystalline polymer to the solvent after using such a dispersing device.

In this preparation, the weight ratio of the crystalline polymer to the non-crystalline polymer in the solvent is from 30:70 to 95:
5, preferably 50:50 to 85:15. If the weight ratio is less than 30:70, it is not preferable because good PTC characteristics cannot be obtained. If the ratio exceeds 95: 5, properties suitable for application or printing cannot be obtained, and the mechanical strength and flexibility of a coating film obtained by printing or applying the composition on a substrate are insufficient. Is not preferred.

The amount of the conductive substance added to the solvent is determined according to the use of the sheet heating element, the interval between the comb-shaped electrodes, and is not particularly limited. 5 to 8 per 100 parts by weight of the total
It is preferably about 0 parts by weight. Further, the amount of the solvent used here is not particularly limited, but is preferably about 80 to 400 parts by weight based on 100 parts by weight of the total of the crystalline polymer and the non-crystalline polymer.

In order to manufacture the planar heating element of the present invention, a comb-shaped electrode 2 is provided on a substrate 1, and the conductive ink composition is applied or printed on the electrode 2 to form a heating layer 3. This is done by: The comb-shaped electrode 2 is formed by a screen printing method or a method in which an electrode material such as a silver foil is attached to the substrate 1 with an adhesive or the like and subjected to etching or the like to form a comb-shaped pattern having a desired electrode spacing d. It is performed by a method or the like.

The application or printing of the conductive ink composition can be performed by any method capable of obtaining a coating film having a uniform thickness. For example, screen printing, a method using a knife coater, or a method using a gravure coater It is preferably carried out by using such a method. The applied or printed conductive ink composition is heated to about 80 to 15 using a heater or a furnace.
By drying at a temperature of 0 ° C. for about 1 to 30 minutes, the heat generating layer 3 having a thickness of about 10 to 50 μm is obtained.

In such a sheet heating element, since the resistance value ratio Rmax / _RG is 5 to 10 ⁶ times, the equilibrium heating temperature _TG is slightly lower than the temperature at which the resistance value changes rapidly. Becomes Therefore, for example, when the sheet heating element is in an adiabatic state, the resistance value greatly increases as the heating temperature increases, and the heating temperature is reduced to the heating temperature range _{TG to TG} + 4.
It is possible to maintain the temperature within 0. That is, thermal runaway due to an increase in the heat generation temperature can be sufficiently prevented, and burnout due to thermal runaway can be prevented. In addition, since the difference in resistance between the high-temperature portion and the low-temperature portion in the planar heating element is large, an effect of alleviating the difference in the heating temperature in the planar heating element is obtained, and the heating temperature in the planar heating element is reduced. Is small. Therefore, the individual difference in the heat generation temperature is also small.

Further, the electrode interval d of the comb-shaped electrode 2 is 2 to
Since it is 40 mm, short-circuiting between electrodes due to foreign matter and the like is unlikely to occur, and the heat generation temperature in the planar heating element is uniform,
The individual difference of the heat generation temperature is small. In addition, since the equilibrium heating temperature _TG in a state where at least one surface of the sheet heating element is not in contact with the heat insulator is 35 to 110 ° C., the applicable temperature range is wide, and it can be used in many applications. Can be done.

Further, the conductive ink composition for forming the heat generating layer 3 contains a solvent, a crystalline polymer, an amorphous polymer, and a conductive material, wherein the crystalline polymer is Having an average particle diameter of 0.2 to 100 μm, wherein the amorphous polymer has a crystallinity of 5% or less, and the weight ratio of the crystalline polymer to the amorphous polymer is 30 : 70-
By setting the ratio to 95: 5, the sheet heating element can obtain a high PTC resistance change magnification, and the resistance value ratio Rmax
It is possible to obtain a sheet heating element having a ratio / _RG of 5 to 10 ⁶ times. Further, the sheet heating element is excellent in flexibility and mechanical strength and can be easily manufactured.

In the sheet heating element of the present invention, in order to further increase the uniformity of the heat generation temperature in the sheet heating element, at least a part of the back surface of the substrate 1 is provided with a thermal conductivity such as a metal pad. A planar heating element to which a high substance is attached may be used.

[0039]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. (Test Example 1) A crystalline polyamide having a mean particle size of 40 μm (trade name: polyamide S-1962, melting point: 11) in 200 parts by weight of carbitol acetate
60 ° C., 7 ° C., manufactured by Sanyo Chemical Co., Ltd., and 40 parts by weight of a non-crystalline polymer copolymerized polyester (trade name: Byron 200, manufactured by Toyobo) are dispersed, and then carbon black (trade name: Denka Black, electric) 30 parts by weight (manufactured by Kagaku Kogyo) were added, and the mixture was stirred and kneaded with a three-roll mill to prepare a conductive ink composition.

Next, screen printing was carried out on the substrate 1 provided with a pair of silver comb-shaped electrodes 2 having an electrode spacing d of 10 mm using the conductive ink composition.
Dry for 200 minutes, width 200mm, length 400mm, thickness 10
A heating layer 3 having a thickness of about 12 μm was formed, and a sheet heating element shown in FIGS. 1 and 2 was prepared. An aluminum layer with an adhesive layer was attached to the entire back surface of the sheet heating element, and this was used as a test piece.

(Test Example 2) The amount of carbon black added was 2
A sheet heating element was prepared in the same manner as in Test Example 1, except that the weight was 5 parts by weight. (Test Example 3) A sheet heating element was prepared in the same manner as in Test Example 1, except that the electrode interval d was 20 mm. (Test Example 4) A sheet heating element was prepared in the same manner as in Test Example 1, except that the electrode interval d was 25 mm. (Test Example 5) A sheet heating element was prepared in the same manner as in Test Example 1, except that the electrode interval d was 3 mm. (Test Example 6) A sheet heating element 3 was prepared in the same manner as in Test Example 1, except that the addition amount of carbon black was 20 parts by weight and the electrode interval d was 1 mm. (Test Example 7) A sheet heating element was prepared in the same manner as in Test Example 1, except that the addition amount of carbon black was 40 parts by weight and the electrode interval d was 50 mm.

Of the sheet heating elements of Test Examples 1 to 7 thus obtained, Test Examples 1 to 3 are examples of the present invention, and Test Examples 4 to 7 are: It is a comparative example.
Each of the sheet heating elements of Test Example 1 to Test Example 7 was 20
Each sheet was prepared, and the following items were measured and evaluated.

[T _G ] A planar heating element was suspended in an atmosphere of 20 ° C., and its temperature was measured to obtain an equilibrium temperature before voltage application. Then, a voltage of AC100V is applied between the electrodes,
The minimum temperature and the maximum temperature in the planar heating element 10 minutes after the voltage application were measured with a radiation thermometer, and the average value was defined as the equilibrium heating temperature _TG after the voltage application. [Variation in temperature of planar heating element] Temperature variation in one planar heating element at the equilibrium heating temperature _TG was evaluated. [Individual Difference] With respect to the sheet heating element in the same test example, the minimum value and the maximum value of the equilibrium heating temperature _TG were examined, and the temperature difference between individuals was obtained.

The resistance value of the heat generating layer 3 was measured when the [Rmax / R _G ] temperature was from the equilibrium temperature before voltage application to the equilibrium heat generation temperature T _G + 40 ° C. Next, the equilibrium heating temperature T _G
Resistance _RG of the heat generating layer 3 at the temperature and the heat generating temperature range _{TG to TG} +
The ratio Rma to the maximum resistance value Rmax of the heat generating layer 3 within 40
x ( _{TG- TG} + 40) / _RG ( _TG ) was determined. [Heat generation temperature after 10 minutes of heat insulation] [Heat generation temperature after 10 minutes of heat insulation] Urethane foam having a thickness of 50 mm, which is a heat insulator, is closely adhered to both surfaces of the sheet heating element to insulate it. A voltage was applied, and the temperature of the sheet heating element 10 minutes and 5 hours after the voltage application was measured using a thermocouple. Table 1 shows the results.

[0045]

[Table 1]

According to Table 1, in Test Examples 1 to 3, the heat generation temperature during adiabatic operation was 4 times lower than the equilibrium heat generation temperature _TG after voltage application.
The result was that it did not rise above 0 ° C. From this, it was confirmed that the heat generation temperature could be maintained within the heat generation temperature range T _{G to} T _G +40. Further, the variation in the temperature in the planar heating element and the individual difference were measured in Test Examples 4 and 5 in which the resistance value ratio Rmax / _RG was less than 5 times, and in a test in which the electrode interval was less than 2 mm. Example 6 was clearly smaller than Test Example 7 in which the electrode spacing was set to exceed 40 mm and the resistance value ratio Rmax / _RG was less than 5 times. In Test Example 5, the heat generation temperature during heat insulation increased with time, and a tendency for thermal runaway was observed.

[0047]

As described above, in the sheet heating element according to the present invention, the equilibrium heating temperature between the certain equilibrium heating temperature _TG and the temperature T _G +40 which is 40 ° C. higher than the equilibrium heating temperature _TG. the resistance value R _G of the heat generating layer in T _G, since the ratio Rmax / R _G between the maximum resistance value Rmax of the heat generating layer is from 5 to 10 ⁶ times, an equilibrium heating temperature T _G, the resistance value sharply changes The temperature can be set to a temperature slightly lower than the temperature to be performed. Therefore, for example, when the planar heating element is in a heat-insulating state, the resistance value greatly increases as the heating temperature increases, and the heating temperature can be maintained within the heating temperature range _{TG to TG} +40. it can. That is, it is possible to provide a planar heating element capable of sufficiently preventing thermal runaway due to an increase in the heat generation temperature and preventing burnout and the like due to thermal runaway. Also,
Since the difference in resistance between the high-temperature portion and the low-temperature portion in the planar heating element is large, the effect of reducing the difference in the heating temperature in the planar heating element is obtained, and the difference in the heating temperature in the planar heating element is reduced. be able to. Therefore, individual differences in the heat generation temperature can be reduced.

Further, the electrode interval between the comb-shaped electrodes is 2 to 40 mm.
Therefore, a short circuit between the electrodes due to foreign matter or the like is unlikely to occur, and the heat generation temperature in the sheet heating element is uniform, and the sheet heating element can have a small individual difference in the heat generation temperature.

Further, since at least one surface of the sheet heating element is not in contact with the heat insulator and the equilibrium heating temperature _TG after voltage application is 35 to 110 ° C., the applicable temperature range is wide, It can be used for many applications, for example,
It can be a planar heating element that can be used for applications such as prevention of dew condensation in a heat retention device, a heating facility, a mirror, and the like.

Further, the conductive ink composition contains a solvent, a crystalline polymer, a non-crystalline polymer, and a conductive material, and the crystalline polymer has an average particle diameter of 0.2. -10
0 μm, wherein the amorphous polymer has a crystallinity of 5% or less, and the weight ratio of the crystalline polymer to the amorphous polymer is 30:70 to 95: 5. As a result, a planar heating element capable of obtaining a high PTC resistance change magnification is obtained, and the equilibrium heating temperature between a certain equilibrium heating temperature T _G and a temperature T _G +40 which is 40 ° C. higher than the equilibrium heating temperature T _G. the resistance value R _G of the heat generating layer in T _G, the ratio Rmax / R _G between the maximum resistance value Rmax of the heat generating layer can be obtained planar heating element is 5 to 10 ⁶ times. Further, it is possible to obtain a sheet heating element which is excellent in flexibility and mechanical strength and can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a sheet heating element of the present invention.

FIG. 2 is a cross-sectional view of the sheet heating element shown in FIG.

FIG. 3 is a graph showing a relationship between a temperature of a sheet heating element and a resistance value.

[Explanation of symbols]

 1. . . Substrate, 2 ... comb electrode, 3 ... heating layer.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshifumi Nakajima 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. F-term in Fujikura Kasei Co., Ltd. R & D Laboratory (reference) JA57 JA69 KA06 KA12 MA12 MA14 NA13 NA20 PB05 PC08

Claims (2)

[Claims] 1. A planar heating element comprising a heating layer made of a conductive ink composition formed on a substrate provided with a pair of comb-shaped electrodes, wherein at least one surface of the planar heating element is in contact with a heat insulator. In a state where the temperature has not been adjusted, the equilibrium heat generation temperature _TG after voltage application is 35 to 110
A ° C., and is the equilibrium heat producing temperature T _G, the maximum of the equilibrium heating temperature T and the resistance value R _G of the heat generating layer in the balanced heating temperature T _G between 40 ° C. higher temperature T _G +40 than _G, the heat generating layer Resistance value Rm
The ratio Rmax / _RG with ax is 5 to 10 ⁶ times, the electrode spacing of the comb-shaped electrodes is 2 to 40 mm, and the conductive ink composition comprises a solvent, a crystalline polymer,
A planar heating element comprising an amorphous polymer and a conductive material. 2. The conductive ink composition comprises a solvent, a crystalline polymer, a non-crystalline polymer, and a conductive material, wherein the crystalline polymer has an average particle size of 0.2 to 0.2. 100 μm, wherein the non-crystalline polymer has a crystallinity of 5% or less, and the weight ratio of the crystalline polymer to the non-crystalline polymer is 3
2. The sheet heating element according to claim 1, wherein the ratio is 0:70 to 95: 5.