JPH0927385A - Planar heating element - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a planar heating element capable of sufficiently preventing local heat generation, reducing resistance change with time, and manufacturing at low cost. SOLUTION: Two electrode covering members 4 each covering an electrode 3 are attached to a sheet-like heat generating resistance sheet 2 at a predetermined distance from each other, and the electrode covering member 4 has a positive electric resistance value which increases with an increase in temperature. PTC with temperature coefficient characteristics
The heat generating resistance sheet 2 does not have the positive temperature coefficient characteristic.

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 having a positive temperature coefficient characteristic, for example, as a heater for snow melting on a road or a roof, a heater for floor heating, or an antifogging heater for a mirror. Available.

[0002]

BACKGROUND ART Due to snow melting on a road, a planar heating element is embedded near the surface of the road to heat the planar heating element. Further, the sheet heating element is integrated with a heat storage material to be used as a floor heating unit. This planar heating element is a planar heating resistance sheet formed by melting conductive particles such as carbon black in a thermoplastic resin, and provided with a pair of electrodes, and when a current is applied between these electrodes, The sheet is heated by the Joule heat.

The heat generating resistance sheet of the sheet heating element has a positive temperature coefficient characteristic (PTC) in which the electric resistance value increases as the temperature rises.
Characteristics), a temperature difference occurs in the heat generating part depending on the environment temperature and heat dissipation condition. For example, the heat generating resistance sheet radiates heat in two directions in its central region, but radiates heat not only in the front and back but also in three directions including the side regions in both side regions, so that the surface of the central region has both sides. It tends to be hotter than on the surface of the area. When this tendency becomes stronger, when the heat generating resistance sheet has a positive temperature coefficient characteristic, the temperature of the central region becomes extremely higher than the temperatures of the both side regions, and only the central region generates heat. Occurs.

Therefore, conventionally, a soaking plate is provided on the entire surface of the sheet-like heat-generating resistance sheet, or a soaking plate is provided only at a high temperature portion to prevent local heat generation (Japanese Patent Laid-Open No. Sho 61-96). 54
-156242). Further, in the conventional sheet heating element, when a heating resistance sheet is formed from a thermoplastic resin and conductive particles, heat treatment and pressure treatment are performed in order to reduce changes in resistance over time and changes due to thermal history. As a problem in each application, there is a large difference between the resistance value at room temperature and the resistance value at a temperature at which heat generation is stable, so there is a large difference between the power at rush time and the power at stable time, which requires devising when designing the breaker. It is necessary to increase the contract power.

[0005]

However, in the above-mentioned conventional example, the thickness of the heat equalizing plate becomes large, or the shape of the heat equalizing plate becomes complicated, which is not only inconvenient to handle, but also the manufacturing cost is high. Is a factor that increases. Further, in the case of arranging the heat equalizing plate only in the high temperature portion, the thickness of the planar heating element becomes very large, which is not suitable for use as a thin heater. In addition, since heat treatment and pressure treatment are performed when the heat-generating resistance sheet is formed from the thermoplastic resin and the conductive particles, the number of manufacturing processes increases, which is another factor that increases the manufacturing cost. An object of the present invention is to sufficiently prevent local heat generation, to reduce resistance change over time, and to manufacture at low cost. Furthermore, resistance change is small up to an assumed heat generation temperature, and the resistance value is higher than a certain temperature. An object is to provide a planar heating element having increasing properties.

[0006]

Therefore, according to the present invention, the PTC characteristic of the heat generating resistance sheet is eliminated, or the PTC characteristic of the heat generating resistance sheet is set higher than the PTC characteristic of at least a portion of the electrode coating member in the vicinity of the electrode. The above-mentioned object is achieved by decreasing the upper magnification or raising the rising temperature. Specifically, the sheet heating element of the present invention is a sheet heating element in which a plurality of electrode coating members each coating an electrode are attached to a sheet heating resistance sheet at a predetermined distance from each other. In the vicinity of at least one electrode of the member is a PTC layer having a positive temperature coefficient characteristic in which the electric resistance value increases as the temperature rises, and the heating resistance sheet does not have the positive temperature coefficient characteristic,
Alternatively, the rising ratio is smaller than that of the PTC layer or has a higher positive temperature coefficient characteristic than that of the PTC layer in a temperature range below the temperature at which the PTC layer has the maximum rising ratio. And

In the present invention, when a current is passed between the electrodes, heat is generated in the heat generating resistance sheet.
Since there is no TC characteristic, or the rising ratio is smaller or the rising temperature is higher than that of the PTC layer, even if the heat radiation state differs between the central region and the both side regions, for example, local heat generation in the heating resistor sheet. Does not occur. Moreover, since the PTC layer having a positive temperature coefficient characteristic is provided in the vicinity of at least one electrode of the electrode covering member, the merit of the positive temperature coefficient characteristic of the conventional sheet heating element can be maintained. Furthermore, since a member that does not have a large positive temperature coefficient characteristic is used as the heat generation resistance sheet, the proportion of the portion having a positive temperature coefficient characteristic with a large change in resistance is reduced as a whole of the sheet heating element, and the overall resistance change with time. Can be made smaller. Therefore, the heat treatment for molding the heat generating resistance sheet is not required, so that the manufacturing cost of the sheet heating element can be reduced. Further, by adjusting and changing the ratio of the PTC layer (electrode covering member) and the specific resistance value to the resistance value of the heating resistance sheet, it is possible to variably design the temperature at which the resistance value of the entire heater increases. Therefore, the characteristics according to each application can be easily obtained.

Here, within a range in which the rising coefficient of the positive temperature coefficient characteristic of the heating resistance sheet is equal to or lower than the temperature at which the maximum rising coefficient of the PTC layer is reached, the rising coefficient of the positive temperature coefficient characteristic of the PTC layer is 0.5. The temperature may be set as follows, and the rising temperature of the positive temperature coefficient characteristic of the heating resistance sheet may be 5 ° C. higher than the rising temperature of the positive temperature coefficient characteristic of the PTC layer.
It may be higher than the above.

If the positive temperature coefficient characteristic of the heat generating resistance sheet is large, local heat generation is likely to occur when a temperature difference occurs on the surface of the heat generating resistance sheet. In order to prevent this, it is necessary to reduce the positive temperature coefficient characteristic of the heat generating resistance sheet. Therefore, the rising ratio of the positive temperature coefficient characteristic of the heating resistance sheet with respect to the PTC layer is set to 0.5 or less as described above within the temperature range below the maximum rising ratio of the PTC layer, or the heating resistance sheet is set to the PTC layer. In contrast, if the rising temperature of the positive temperature coefficient characteristic is increased by 5 ° C. or more as described above, local heat generation on the surface of the heat generating resistance sheet can be surely prevented, and the positive temperature coefficient characteristic of the PTC layer can reduce the temperature. Control becomes possible.

The PTC layer may be molded from a heat-generating composition having a thermoplastic resin and conductive particles, or an inorganic material. Further, the heat generating resistance sheet may be formed from a heat generating composition having a thermoplastic resin and conductive particles, an inorganic material, or a metal material. In addition, the heat conductive sheet and the PTC layer are thermally integrated so that the heat resistive sheet and the PTC layer have an insulating layer (for example, a PET film or a PE film) between them and a heat conductive material ( For example, a structure in which they are connected by a metal plate) may be used.

If the heat generating resistance sheet and the PTC layer are connected by a heat conducting material, the heat of the heat generating resistance sheet is directly transmitted to the electrodes, and the effect of the positive temperature coefficient characteristic can be exhibited. Here, if the heating resistor sheet and the PTC layer are directly connected with the heat conducting material, the current flows through the heating conductor material and does not flow through the heating resistor sheet. In the invention, the heat generating resistance sheet and the PTC
By providing an insulating layer between the layer and the heat conductive material, the current can flow reliably through the heat generating resistance sheet, and the heat generating effect can be secured.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, in each of the embodiments, the same components are designated by the same reference numerals, and description thereof will be omitted or simplified. 1 and 2 show a sheet heating element 1 according to a first embodiment of the present invention. FIG. 1 is a perspective view in which a part of the planar heating element 1 is cut away, and FIG. 2 is a plan view thereof. In these figures, the sheet heating element 1 is
A heat generating resistance sheet 2 formed by being formed into a flat rectangular shape;
The heating resistance sheet 2 is provided with two electrode covering members 4 which are respectively wound around the ends and cover the electrodes 3, and an exterior material made of a PET film or the like provided as needed.

The heating resistance sheet 2 is a sheet-shaped nichrome,
Sheet metal materials such as stainless steel and aluminum etching materials, sheet ITO materials and sheet conductive inorganic materials, sheet organic materials, or amorphous resins such as polystyrene (PS), methacrylic resin (PMMA), and vinyl chloride. It does not have a positive temperature coefficient characteristic (PTC characteristic) in which the resistance value increases as the temperature rises. The heating resistance sheet 2 has a thickness of 0.1 to 5 mm, preferably 0.1 to 5 mm.
~ 2mm, its width is 2.5mm ~ 6000mm, and its length is not limited. The electrodes 3 are formed by arranging a plurality of (four in the figure) single parallel wires 3A of the electrode conductive wires in parallel and in a flat plate shape in a line, and the single wires 3A have a thickness of 2 mm or less and 0.1 mm or more. Yes, but the specific thickness is a single line 3
It is determined in relation to the number of A. Note that the electrode 3 is not limited to the single wire 3A of the illustrated electrode lead wire,
You may comprise from a metal tape and a conductive paste.

The electrode covering member 4 is formed in a long shape, and two heat generating resistance sheets 2 are fused together on both sides along the length direction. The electrode covering member 4 has a thickness of 0.3 mm
It is formed in a rectangular cross section of 5 mm and a width of 0.5 mm to 30 mm, preferably 1 mm to 10 mm. The electrode covering member 4 is manufactured by a co-extrusion method in which a plurality of single wires 3A of electrode wires are passed through a die of an extruder in a parallel state without crossing each other, and the exothermic composition is extruded together with these electrode wires. .

The electrode coating member 4 is a PTC layer having a positive temperature coefficient characteristic which is formed from a heat generating composition containing a thermoplastic resin and conductive particles. As the thermoplastic resin, a crystalline thermoplastic resin is preferable, and specifically, a polyolefin resin and a copolymer resin thereof, a polyamide resin, a polyacetal resin, a thermoplastic polyester resin,
Examples thereof include polyphenylene oxide, nonyl resin, and polysulfone.

Examples of the polyolefin resin include polyethylenes such as high-density polyethylene, medium- and low-density polyethylene, linear low-density polyethylene, polypropylene such as isotactic polypropylene and syndiotactic polypropylene, polybutene, 4- Methyl pentene-1 resin etc. can be mentioned. Also, the first
In embodiments of the present invention, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer, etc. Copolymers of olefins and vinyl compounds, such as ethylene-acrylate copolymers and ethylene-vinyl chloride copolymers, fluorine-containing ethylene polymers, and modified products thereof can also be used.

As the vinyl acetate resin, for example,
Examples thereof include a vinyl acetate resin, polyvinyl acetoacetal, and polyvinyl butyral. Examples of the polyamide resin include nylon 6, nylon 8, nylon 11, nylon 66, nylon 610 and the like. The polyacetal may be a homopolymer or a copolymer. Examples of the thermoplastic polyester resin include polyethylene terephthalate and polybutylene terephthalate. Further, as the crystalline thermoplastic resin, in addition to the above,
For example, diene-based polymers and copolymers such as trans-1,3-polyisoprene and syndiotactic-1,2-polybutadiene can also be used.

The various crystalline thermoplastic resins may be used alone or in combination of two or more as a polymer blend or the like. However, among the various types of crystalline thermoplastic resins, high-density polyethylene, low-density polyethylene, linear polyethylene, ethylene-vinyl acetate copolymer, olefin copolymers such as ethylene-ethyl acrylate copolymer, and trans -1,4-polyisoprene and the like are preferred. The various crystalline thermoplastic resins described above can also be used as a composition with other polymers and additives as required.

Examples of the conductive particles include granular materials such as carbon black particles and graphite particles, iron (F
e), fine particles of metal such as nickel (Ni), platinum (Pt), copper (Cu), silver (Ag), and gold (Au); powders such as metal powder and metal oxide powder; Examples include fibrous materials, conductive inorganic materials (such as ITO), and inorganic materials having a positive temperature coefficient such as barium titanate (BaTio3) and strontium titanate (SrTio3). Among these, granular materials such as carbon black particles and graphite particles, particularly carbon black particles are preferable. The various conductive particles may be used alone or in combination of two or more. As the particle size of the conductive particles,
There is no particular limitation, but for example, the average particle size is usually 10 to 200 n.
m, preferably 15 to 100 nm. When the conductive particles are fibrous, the aspect ratio is usually 1 to 1000,
It is preferably about 1 to 100.

The weight ratio of the crystalline resin to the conductive particles is usually 10 to 80:90 to 20, preferably 55 to 75:45 to 25. If the mixing ratio of the conductive particles is less than this range, the resistance value of the electrode covering member 4 increases, and the sheet heating element 1 may not generate sufficient heat in practical use. If it is larger than the range, the positive temperature coefficient characteristic will not be sufficiently exhibited. The specific resistance value of the heat-generating composition of the electrode coating member 4 can be appropriately selected according to the specifications and purposes, but in the usual case, it is 10 to 50000.
Ω · cm, preferably 40 to 20000 Ω · cm. The electrode covering member 4 is obtained by mixing and molding the crystalline resin and the conductive particles, and at the time of or after the molding, the thermoplastic crystalline resin in the exothermic composition is crosslinked to form the exothermic composition. Preferably, it is cured. When this exothermic composition is cured, the positive temperature characteristics are improved and defects due to thermal deformation or thermal softening of the sheet heating element can be prevented.

Crosslinking of the crystalline thermoplastic resin is carried out by using a crosslinking agent and / or
Alternatively, radiation can be used. The cross-linking agent can be appropriately selected and determined from organic peroxides, sulfur compounds, oximes, nitroso compounds, amine compounds, polyamine compounds, etc., depending on the type of crystalline thermoplastic resin. For example, when the crystalline thermoplastic resin is a polyolefin resin or the like, an organic peroxide can be used as a suitable crosslinking agent. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl cumyl peroxide, te.
rt-Butyl hydroperoxide, 2,5-dimethyl-
2,5-di (tert-butylperoxy) hexyne-3,
1,1-bis (tert-butylperoxyisopropyl)
Benzene, 1,1-bis (tert-butylperoxy)-
3,3,5-trimethylcyclohexane, n-butyl-
4,4-bis (tert-butylperoxy) valerate,
2,2-bis (tert-butylperoxy) butane, tert
-Butyl peroxybenzene etc. can be mentioned.

Of these, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3 is particularly preferable.
Are preferred. In addition, these various organic peroxides are 1
The seeds may be used alone, or if necessary, a crosslinking aid such as triallyl cyanurate, divinylbenzene, triallyl isocyanurate may be added. The amount of the organic peroxide used is usually 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the crystalline resin. If this proportion is less than 0.01 parts by weight, crosslinking will be insufficient and the positive temperature coefficient characteristics will not be sufficiently exhibited, and problems such as a decrease in resistance in the high temperature region tend to occur. On the other hand, if the amount exceeds 5 parts by weight, the degree of cross-linking becomes too high, resulting in deterioration of moldability and deterioration of positive temperature coefficient characteristics.

FIG. 3 is a graph showing the positive temperature coefficient characteristics of the electrode coating member 4 and the heat generating resistance sheet 2. In FIG. 3, P indicates the positive temperature coefficient characteristic of the electrode covering member 4, and the rising magnification Xp is calculated by the following formula. Xp = R / R ₂₅ where R is a resistance value at a temperature T, and R ₂₅ is a temperature 2
The resistance value at 5 ° C. is shown. Maximum startup magnification Xp max is Xp m
It is shown by ax = Rpmax / R ₂₅ . On the other hand, S is PT
This shows the positive temperature coefficient characteristic of the heat generating resistance sheet 2 having no C characteristic, and its maximum rising ratio is 0.

Specifically, the electrode coating member 4 is made of ethylene-
When the heating resistance sheet 2 is formed of ethyl acrylate copolymer (EEA) and carbon black (CB) and the heating resistance sheet 2 is formed of a composition of an amorphous resin such as polystyrene (PS) and carbon black, an electrode is used. As shown in FIG. 4 (A), the positive temperature coefficient characteristic P of the covering member 4 is such that the resistance value increases with the temperature rise, and the positive temperature coefficient characteristic S of the heating resistance sheet 2 is shown in FIG. 4 (B). As shown in, even if the temperature rises, the resistance value does not change significantly. The positive temperature coefficient characteristic (P + S) of the entire sheet heating element 1 is shown in FIG.
As shown in (C), the characteristic is shown that the resistance value increases as the temperature increases. In the graph of FIG. 4 (C), the dotted line shows the case of only the heating resistance sheet 2.

Therefore, according to the first embodiment, the two electrode covering members 4 respectively covering the electrodes 3 are attached to the planar heating resistance sheet 2 at a predetermined distance from each other, and the electrode covering members 4 are attached to each other. Since the PTC layer has a positive temperature coefficient characteristic in which the electric resistance value increases as the temperature rises, and the heating resistance sheet 2 has a structure not having the positive temperature coefficient characteristic, when a current is passed between the electrodes 3, Although heat is dissipated by the heat generating resistance sheet 2, local heat generation does not occur in the heat generating resistance sheet 2 in this heat dissipation even if, for example, the heat dissipation state is different between the central region and the both side regions. Moreover, the positive temperature coefficient characteristics required for the sheet heating element 1 can be ensured by the electrode coating member 4. Furthermore, the heating resistance sheet 2
Does not have a positive temperature coefficient characteristic, it is possible to reduce the proportion of the portion of the sheet heating element 1 having a positive temperature coefficient characteristic with a large change in resistance and reduce the change over time in the overall resistance. Therefore, the heat treatment for molding the heating resistance sheet 2 is not required, and the manufacturing cost can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment differs from the first embodiment in that the heat generating resistance sheet has a positive temperature coefficient characteristic, and the other structures are the same as those in the first embodiment. The second aspect of the present invention is shown in FIGS.
The sheet heating element 11 according to the embodiment is shown.
FIG. 5 is a perspective view in which a part of the planar heating element 11 is cut away,
FIG. 6 is a plan view thereof. In these figures, the sheet heating element 11 is composed of a heating resistor sheet 12 formed by molding a heating composition into a flat rectangular shape and a heating resistor sheet 2 provided on both ends of the heating resistor sheet 2 to cover the electrodes 3. The electrode covering member 4 of the book and an exterior material made of a PET film or the like provided as needed are provided.

The exothermic resistance sheet 12 is formed by extruding the exothermic composition into a sheet-like or film-like surface and has a thickness of 0.1 to 5 mm, preferably,
It is 0.1 to 2 mm, its width is 2.5 mm to 6000 mm, and its length is not limited. Electrode coating members 4 are fused to both ends of the heat generating resistance sheet 12 by heat sealing or ultrasonic sealing. The exothermic composition of the exothermic resistance sheet 12 has a positive temperature coefficient characteristic.

In the second embodiment, the thermoplastic resin used for the heat generating composition of the heat generating resistance sheet 12, particularly,
The crystalline thermoplastic resin and the thermoplastic resin used for the heat generating composition of the electrode coating member 4, particularly the crystalline thermoplastic resin, may be the same kind or different from each other. However, it is usually desirable to use the same kind in order to keep the adhesiveness by heat fusion better. The conductive particles used for the heat generating composition of the heat generating resistance sheet 12 and the conductive particles used for the heat generating composition of the electrode coating member 4 may be of the same type or different from each other. In order to make the positive temperature coefficient characteristics different between the electrode coating member 4 and the heating resistance sheet 12, the blending ratio of the thermoplastic resin is adjusted.

In FIG. 3, S ₁ and S ₂ show the positive temperature coefficient characteristics of the heating resistance sheet 12, of which S ₁ is the maximum rising ratio of the electrode covering member 4 whose rising ratio constitutes the PTC layer. In the range below the temperature, the temperature is lower than that of the electrode coating member 4, and S ₂ indicates that the rising temperature is higher than that of the electrode coating member 4. Maximum startup magnification of electrode coating member 4
The positive temperature coefficient characteristic S ₁ of the heat generating resistance sheet 12 is smaller than the positive temperature coefficient characteristic P of the electrode covering member 4 in a range equal to or lower than the temperature Tp max at the time of Xp max. That is, the heating resistance sheet 12
Xs <Xp, where Xs is the startup magnification of
Xs ≦ 0.5Xp. Further, the positive temperature coefficient characteristic S ₂ of the heating resistance sheet 12 has a higher rising temperature than that of the electrode coating member 4. That is, assuming that the rising temperature is the temperature when the resistance value R is 2 × R ₂₅ , the rising temperature when the electrode covering member 4 is 2 × Rp ₂₅ is tp, and the heating resistance sheet 12 is 2 × R _25. The rising temperature at Rs ₂₅ is ts. The rising temperature tp is lower than the rising temperature ts (0 ° C. <ts-tp), and the difference between tp and ts is preferably 5 ° C. or more (5 ° C. ≦ ts-tp), more preferably 1
It is 0 ° C. or higher (10 ° C. ≦ ts-tp).

Specifically, the electrode coating member 4 is made of ethylene-
In the case where the exothermic composition of ethyl acrylate copolymer (EEA) and carbon black (CB) is used and the exothermic resistance sheet 12 is formed of the exothermic composition of high density polyethylene (HDPE) and carbon black, the electrode is As shown in FIG. 7 (A), the positive temperature coefficient characteristic P of the covering member 4 is such that the resistance value increases as the temperature rises, and the positive temperature coefficient characteristic S ₂ of the heating resistance sheet 12 is shown in FIG.
As shown in (B), the resistance value increases as the temperature rises.
Is different from the positive temperature coefficient characteristic P of. In FIG. 7A, the rising temperature tp of the electrode coating member 4 is 67 ° C.
In (B), the rising temperature ts of the heating resistance sheet 12 is 1
The temperature is 20 ° C., and the rising temperature tp of the electrode covering member 4 is 53 ° C. higher than the rising temperature ts of the heating resistance sheet 12. As shown in FIG. 7C, the entire sheet heating element 11 has a characteristic that the resistance value increases as the temperature rises. This characteristic, in particular, the temperature at which the specific resistance value increases, is variable depending on the ratio and specific resistance value of the electrode coating member 4 (PTC layer). In the graph of FIG. 7 (C), the dotted line shows the case of only the heat generation resistance sheet 12.

Therefore, according to the second embodiment, the two electrode covering members 4 respectively covering the electrodes 3 are attached to the planar heating resistance sheet 12 at a predetermined distance from each other.
The electrode covering member 4 is a PTC layer having a positive temperature coefficient characteristic, and the heating resistance sheet 12 has an electrode covering in a range in which the rising ratio Xs is equal to or lower than the temperature Tp max at which the maximum rising ratio Xp max of the electrode covering member 4 is exhibited. Since the structure has a positive temperature coefficient characteristic that is smaller than the rising magnification Xp of the member 4 or that the rising temperature ts is higher than the rising temperature tp of the electrode covering member 4,
Similar to the embodiment described above, local heat generation does not occur in the heat generating resistance sheet 12, and the positive temperature coefficient characteristic required as a planar heating element can be ensured by the electrode covering member 4. Further, in the sheet heating element 1 as a whole, the proportion of the portion having the positive temperature coefficient characteristic in which the change in resistance is large is reduced, and the change in resistance over time can be reduced. Therefore, heat treatment is not required when molding the heat generating resistance sheet 12, so that the manufacturing cost can be reduced.

Further, in the second embodiment, the rising ratio Xs of the heating resistor sheet 12 is set to the rising ratio of the electrode covering member 4 in a range of the temperature Tp max or lower which indicates the maximum rising ratio Xp max of the electrode covering member 4. The upper magnification Xp is set to 0.5 or less, or the rising temperature ts of the heating resistance sheet 12 is set to the electrode covering member 4.
If it is higher than the rising temperature ts of 5 ° C. by 5 ° C. or more, local heat generation on the surface of the heat generating resistance sheet 12 can be surely prevented, and the temperature can be controlled by the positive temperature coefficient characteristic of the electrode coating member 4. Becomes

Next, a third embodiment of the present invention will be described with reference to FIGS. 8 to 10 show a sheet heating element 21 according to a third embodiment of the present invention. 8 is a perspective view in which a part of the planar heating element 21 is cut away, FIG. 9 is a plan view thereof, and FIG. 10 is a sectional view thereof. In these figures, the sheet heating element 21 is
The heat generating resistance sheet 12, the two electrode covering members 4 covering the electrodes 3, and the heat generating resistance sheet 12
And the insulating layer 22 that covers the electrode covering member 4, and the heat conductive sheet 23 that covers both surfaces of the heat generating resistance sheet 12 and the electrode covering member 4 from the outside of the insulating layer 22, and the heat generating resistance sheet 12 and the electrode covering member. 4 so as to be thermally integrated with the heat generating resistance sheet 12 and the electrode coating member 4 between the insulating layer 22.
The structure is connected by the heat conducting material 23 via the.

The heat conductive material 23 effectively transfers the heat generated in the heat generating resistance sheet 12 to the electrode coating member 4 which is a PTC layer, and is made of a metal such as copper, gold, silver, aluminum, iron or stainless steel. Is formed into a plate shape or a sheet shape, and is fixed to the insulating layer 22 with an adhesive tape, an adhesive, or the like. Insulating layer 22
Is a material for surely passing an electric current through the heating resistance sheet 12, and is made of a film having a high insulating effect such as polyethylene terephthalate (PET) or polyethylene (PE). That is, when the heat generating resistance sheet 12 and the electrode coating member 4 are directly connected by the heat conducting material 23, the current flows through the heat conducting material 23 and does not flow through the heat generating resistance sheet 12, and the heat generating resistance sheet 12 generates heat. Because there is a problem that disappears,
Heat generating resistance sheet 12, electrode covering member 4 and heat conducting material 2
This inconvenience was avoided by providing the insulating layer 22 between the insulating layer 22 and the insulating layer 22.

Therefore, according to the third embodiment, the second
In addition to achieving the same effect as in the above embodiment, the heat generating resistance sheet 12 and the electrode coating member 4 are interposed between the heat generating resistance sheet 12 and the electrode coating member 4 which is the PTC layer so as to be thermally integrated. Since the heat conductive material 23 is connected through the insulating layer 22, the heat of the heat generating resistance sheet 12 is directly transferred to the electrode 3, and the effect of the positive temperature coefficient characteristic can be effectively exhibited.

[0036]

[Examples] In order to confirm the effects of the embodiments,
An example will be described. [Example 1] Example 1 corresponds to the first embodiment, and the heating resistance sheet 2 is formed of an aluminum etching material. The aluminum etching material has a shape width of 245 mm and a length of 1 m, and its resistance value is 1 KΩ / m. 55 parts by weight of the electrode coating member 4 of ethylene-ethyl acrylate copolymer (EEA) [DPDJ6182; manufactured by Nippon Unicar Co., Ltd.] and 45 parts by weight of carbon black (CB).
It was formed from the exothermic composition of [Dia Black E; manufactured by Mitsubishi Kasei Kogyo Co., Ltd.]. Each electrode 3 was formed by arranging 10 single wires 3A in parallel without crossing each other.

In the sheet heating element 1 having this structure, the amount of heat generation changes depending on the ambient temperature, and the same favorable positive temperature coefficient characteristic as the conventional sheet heating element using the heating composition as the heating resistance sheet is obtained. showed that. This positive temperature coefficient characteristic is shown in FIG.
Is the same as that shown in. This is because the temperature of the electrode covering member 4 rises due to the temperature of the heat generating resistance sheet 2 being transmitted to the electrode 3, and the positive temperature coefficient characteristic functions in the electrode covering member 4. Further, one surface of the planar heating element 1 was covered with a heat insulating material (styrofoam) along the electrode 3 and a temperature difference of 20 ° C. was generated on the surface. However, the local heating observed in the conventional planar heating element is Did not occur. Lower limit temperature is -2
Cycle the heat history 15 times in the range of the upper limit temperature of 70 ° C at 0 ° C (heating / cooling rate; heating at 1 ° C / mm for 10 minutes
After lowering the temperature and holding for 50 minutes to move to the next temperature),
The change of the resistance value due to the heat history was −0.5% in Example 1, whereas it was −20% in the conventional planar heating element, and in Example 1, compared with the conventional planar heating element. The change in resistance value due to thermal history was reduced to 1/40 or less.

Example 2 Example 2 corresponds to the second embodiment, in which 80 parts by weight of the heat resistance sheet 12 is used for high density polyethylene (HDPE) [Idemitsu HDPE 230].
J; manufactured by Idemitsu Kosan Co., Ltd.) and 20 parts by weight of carbon black (CB) [diamond black E; manufactured by Mitsubishi Kasei Kogyo Co., Ltd.], and the electrode coating member 4 was the same as in Example 1. It was formed from an exothermic composition of ethylene-ethyl acrylate copolymer (EEA) and carbon black (CB). Each electrode 3 has 10 single wires 3A
Were arranged in parallel without crossing each other. The sheet heating element 11 having this structure showed good positive temperature coefficient characteristics for the same reason as in Example 1. This positive temperature coefficient characteristic is the same as that shown in FIG.

Further, one surface of the planar heating element 11 was covered with a heat insulating material (styrofoam) along the electrode 3 to generate a temperature difference of 20 ° C. on the surface, which was found in the conventional planar heating element. No local fever occurred. This is the heat resistance sheet 12
The melting point of the resin used in
This is because there is no rise of a large resistance value (positive temperature coefficient characteristic) below. At the same time, when an experiment based on heat history was conducted under the same conditions as in Example 1, the change in resistance value due to heat history was less than 1/10 of that of the conventional sheet heating element.

Comparative Example 60 parts by weight of ethylene-ethyl acrylate copolymer (EEA) [DPDJ6182;
The exothermic resistance sheet was composed of an exothermic composition of Nippon Unicar Co., Ltd.] and 40 parts by weight of carbon black (CB) [Dia Black E; manufactured by Mitsubishi Kasei Kogyo Co., Ltd.].
A similar exothermic composition and an electrode were co-extruded to form an elongated electrode covering member having a rectangular cross section, and the electrode covering member and the exothermic resistance sheet were fused by heat sealing or the like. When a soaking plate was attached to the planar heating element of this structure and electricity was applied, good positive temperature coefficient characteristics were exhibited depending on the temperature change. However, if one surface of the planar heating element is covered with a heat insulating material (styrofoam) along the electrodes and a temperature difference of 20 ° C. is generated on the surface, local heating occurs and good heating cannot be obtained. Also, a change of several tens of percent due to thermal history was observed.

The present invention is not limited to the configurations of the above-described embodiments, but includes the following modifications as long as the object of the present invention can be achieved. For example, in each of the above-described embodiments, the electrode coating member 4 is formed by coextrusion molding the electrode 3 in which a plurality of single wires 3A are arranged in parallel and in a flat plate shape and the heat generating composition, and has a rectangular cross section. However, in the present invention, the electrode provided on the electrode coating member 4 is formed by twisting a plurality of single wires to have a circular cross-section.
It may be formed from a thick single wire, and the sheet heating elements 1, 11 and 21 may be replaced by heating resistance sheets 2, 12 and 2.
The electrode wire formed by twisting a single wire of the electrode lead wire on the 2 itself or one thick electrode wire may be provided.

Further, the single wire 3 of the electrode 3 is attached to the electrode covering member 4.
Although A is arranged in a line, in the present invention, the single wire 3A of the electrode 3 may be arranged in a plurality of lines. Further, the two electrode covering members 4 are fused to the heat generating resistance sheets 2, 12 and 22, but the number of the electrode covering members 4 may be three or more. Moreover, the cross-sectional shape of the electrode covering member 4 may be various shapes such as a trapezoid, a triangle, and a pentagon. Furthermore, in each of the above embodiments, all of the electrode covering member 4 is a PTC layer,
In the present invention, PT is provided near the electrode 3 in the electrode covering member 4.
It may be a C layer.

[0043]

According to the present invention, a plurality of electrode coating members, each of which covers an electrode, are attached to a sheet-like heat generating resistance sheet at a predetermined distance from each other, and at least the vicinity of the electrodes of the electrode coating member is electrically heated as the temperature rises. A PTC layer having a positive temperature coefficient characteristic with an increased resistance value is used, and the heating resistance sheet does not have the positive temperature coefficient characteristic, or the PTC is in a temperature range below the temperature at which the rising rate shows the maximum rising rate of the PTC layer. Since the structure has a positive temperature coefficient characteristic smaller than that of the layer or having a higher rising temperature than that of the PTC layer, it is possible to sufficiently prevent local heat generation, reduce resistance change over time, and manufacture at low cost. . Further, the rising temperature of the resistor can be arbitrarily adjusted by changing the ratio of the PTC layer and the specific resistance value with respect to the heat generating resistance sheet, and there is an advantage that the resistance change until the rising of the resistor can be designed to be small.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a sheet heating element according to a first embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a graph showing respective positive temperature coefficient characteristics of an electrode covering member and a heat generating resistance sheet.

FIG. 4A is a graph showing a positive temperature coefficient characteristic of an electrode covering member, FIG. 4B is a graph showing a positive temperature coefficient characteristic of a heating resistance sheet, and FIG. It is a graph which shows a positive temperature coefficient characteristic.

FIG. 5 is a partially cutaway perspective view of a sheet heating element according to a second embodiment of the present invention.

FIG. 6 is a plan view of FIG. 5;

7A is a graph showing a positive temperature coefficient characteristic of an electrode covering member, FIG. 7B is a graph showing a positive temperature coefficient characteristic of a heating resistance sheet, and FIG. It is a graph which shows a positive temperature coefficient characteristic.

FIG. 8 is a partially cutaway perspective view of a sheet heating element according to a third embodiment of the present invention.

FIG. 9 is a plan view of FIG.

FIG. 10 is a sectional view of FIG. 8;

[Explanation of symbols]

 1,11,21 Sheet heating element 2,12 Heating resistance sheet 3 Electrode 4 Electrode coating member (PTC layer) 22 Insulating layer 23 High thermal conductivity material

Claims (9)

[Claims] 1. A planar heating element in which a plurality of electrode coating members each coating an electrode are attached to a planar heating resistance sheet at a predetermined distance from each other, and at least a portion of the electrode coating member in the vicinity of the electrodes has a temperature. Is a PTC layer having a positive temperature coefficient characteristic in which the electrical resistance value increases with an increase in the temperature coefficient, and the heating resistance sheet does not have the positive temperature coefficient characteristic, or the rising rate is the maximum rising rate of the PTC layer. The sheet heating element is characterized in that it has a positive temperature coefficient characteristic that is smaller than that of the PTC layer or has a rising temperature higher than that of the PTC layer in a range not higher than the temperature. 2. The planar heating element according to claim 1, wherein the rising coefficient of the positive temperature coefficient characteristic of the heating resistance sheet is PT within a temperature range below the maximum rising coefficient of the PTC layer.
A planar heating element having a positive temperature coefficient characteristic of the C layer of 0.5 or less as a rising ratio. 3. The sheet heating element according to claim 1, wherein the rising temperature of the positive temperature coefficient characteristic of the heating resistance sheet is 5 ° C. higher than the rising temperature of the positive temperature coefficient characteristic of the PTC layer.
A sheet heating element characterized by being higher than the above. 4. The sheet heating element according to any one of claims 1 to 3, wherein the PTC layer is formed from a heating composition having a thermoplastic resin and conductive particles. body. 5. The sheet heating element according to claim 1, wherein the PTC layer is formed of an inorganic material. 6. The sheet heating element according to any one of claims 1 to 5, wherein the heating resistance sheet is formed from a heating composition having a thermoplastic resin and conductive particles. Heating element. 7. The sheet heating element according to claim 1, wherein the heating resistance sheet is formed of an inorganic material. 8. The sheet heating element according to claim 1, wherein the heating resistance sheet is formed of a metal material. 9. The sheet heating element according to claim 1, wherein the heating resistor sheet and the PT are arranged such that the heating resistor sheet and the PTC layer are thermally integrated.
A planar heating element characterized in that the C layer is connected with a material having good thermal conductivity via an insulating layer therebetween.