JP2001023760A - Sheet heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform temperature or desirable temperature distribution on the whole surface when a heating material is heated by partially stacking second conductive resin on the conductive surface of a heating element, and covering the both surfaces of the heating element with an electrical insulating sheet. SOLUTION: A heating element is formed by uniformly forming, by coating for example, first conductive resin on the surface of an electric insulating base material. A sheet heating element 6 is formed by stacking in a belt shape for example second conductive resin to the heat element. The sheet heating element 6 is covered with an electrical insulating sheet 7. Parts 10, 10' where the second conductive resin is stacked on the heating element have the conductive resin layer connected in parallel to electrodes 4, 4' and have lower resistance value than parts 9 where the conductive resin layer is not stacked and a smaller amount of generated heat. Therefore, by the area ratio of the parts 10, 10' and the combination of electric resistances of the heating element and the second conductive resin, desirable amount of generated heat and heating distribution can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sheet heating element,
More specifically, the present invention relates to a planar heating element configured such that a uniform temperature distribution or a desired temperature distribution can be obtained in a whole portion where the planar heating element is in contact when an object to be heated is heated.

[0002]

2. Description of the Related Art Conventionally, floor heating, prevention of fogging of mirrors, heating of photosensitive drums and fixing rolls of copiers, prevention of freezing of parabolic antennas, heating of pets, various planar heating elements as heaters for home saunas and the like. Is used. For example,
Conductive material in which a metal resistance wire is stretched around an electrically insulating substrate to form a planar heating element, or an insulating substrate such as glass cloth or an electrically insulating sheet in which carbon powder or metal powder is dispersed in synthetic resin A sheet heating element in which a sheet heating element is formed by impregnating, applying or printing a resin to form a sheet heating element, and the sheet heating element is covered with an electrically insulating sheet is used.

[0003] Each of these planar heating elements is manufactured and used in various shapes such as a rectangular shape, a cylindrical shape, and a circular shape according to the purpose of use.

However, such a planar heating element has the following disadvantages. That is, since the sheet heating element is generally formed so that the calorific value becomes uniform,
When current is applied and heated only in the state of the planar heating element, the entire surface shows a relatively uniform temperature distribution. On the other hand, when the object to be heated is heated by using these sheet heating elements, the temperature becomes low around the object to be heated in contact with the end face of the sheet heating element due to a large amount of heat radiation. For this reason, the temperature is high in the central portion of the object to be heated, and the temperature is low in the peripheral portion, so that the entire surface cannot be maintained at a uniform temperature.

For example, conventionally, when a planar heating element is used for floor heating, a plurality of planar heating elements are usually arranged and attached to a floor material, and a plurality of the planar heating elements are arranged and laid. Since there is an electrode and an insulating portion between them, a temperature drop in that portion was inevitable. Therefore, although the area in contact with the central part of the planar heating element is warm, the temperature in the part in contact with the end does not rise and a sufficient effect as floor heating cannot be obtained, while the end part becomes warm. However, when the total heat generation is set to be high, there is a disadvantage that the peripheral portion becomes warm, but the central portion becomes too hot.

Further, when a planar heating element is attached to the entire surface of the mirror and heated as an anti-fog mirror, the anti-fog effect can be obtained at the central portion of the mirror, but the peripheral portion has a large amount of heat radiation, so the temperature is high. However, there was a disadvantage that it was not possible to prevent fogging of the peripheral portion. Furthermore, in the case where the photosensitive drum of the copying machine is heated and kept warm by the sheet heating element formed in a cylindrical shape, the center of the drum is heated to an appropriate temperature, but is heated at the end of the sheet heating element. Where the temperature is low, the toner cannot be uniformly attached to the copy paper.

[0007] As a solution to these problems, for example,
When a metal resistance wire is wound around an electrically insulating base material to form a heating element, a uniform temperature distribution can be obtained by increasing the winding pitch at the end, but a large flat heating can be obtained. There was a disadvantage that it could not be easily manufactured with the body and was not suitable for mass production. Further, when forming a planar heating element by holding a conductive resin by impregnating, coating or printing an electrically insulating base material, the amount of heat generation can be reduced by partially changing the holding amount of the conductive resin. An adjustment method can also be adopted, but in this case, it is difficult to arbitrarily set the holding amount of the conductive resin, and a planar heating element having an arbitrary heat generation distribution cannot be obtained.

[0008]

SUMMARY OF THE INVENTION From the above, it is an object of the present invention to provide a planar heating element which can be easily manufactured and which can obtain a uniform temperature over the entire surface when heating an object to be heated.
Another object is to develop a planar heating element capable of obtaining a desired temperature distribution and a desired heat generation distribution.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have impregnated, coated or printed a first conductive resin on an electrically insulating base material. Forming a planar heating element by partially laminating a second conductive resin on a heating element having a uniform resistance distribution obtained by forming a parallel portion of conductive layers in the planar heating element. By
The present inventors have found that an arbitrary temperature distribution and an arbitrary heat generation distribution can be obtained relatively easily, and have reached the present invention.

That is, according to the present invention, there is provided a heating device having a uniform resistance distribution obtained by impregnating, coating or printing an electrically insulating base material with a first conductive resin and having a rectangular or similar shape. Electrodes are provided at two opposing peripheral ends on the element,
A planar heating element is formed by partially laminating a second conductive resin on the conductive surface of the heating element, and the front and back surfaces of the planar heating element are covered with an electrically insulating sheet. This is a planar heating element.

Further, the present invention has a uniform resistance distribution obtained by impregnating, coating or printing an electrically insulating substrate with a first conductive resin, and has a cylindrical or similar shape. Electrodes are provided at two opposing peripheral ends on the heating element, and a second conductive resin is partially laminated on a conductive surface of the heating element to form a sheet heating element. Characterized in that the front and back surfaces are covered with an electrically insulating sheet.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a sheet-like heating element obtained by impregnating, coating or printing a first conductive resin on an electrically insulating substrate such as glass cloth or electrically insulating film. Applies to sheet heating elements covered by sheets. The sheet heating element in the present invention includes any as long as the heating surface forms a sheet.
For example, a heating element having a flat shape, a cylindrical shape, a polygonal cylindrical shape, or the like is included in the planar heating element of the present invention.

An example of the present invention will be specifically described with reference to FIGS. FIG. 2 is an example (2) of a perspective plan view of the sheet heating element of the present invention. FIG. 3 is a sectional view taken along line AA ′ in FIG. The heating element 1 of the present invention is obtained by uniformly coating a first conductive resin 3 on a surface of an electrically insulating base material 2. Electrodes 4 and 4 ′ are provided at opposing peripheral ends of the heating element 1. The heating element 1 is provided with a second conductive resin 5.
Are partially (here, strip-shaped) laminated to form a planar heating element 6.
Are formed. The front and back surfaces of the sheet heating element 6 are covered with the electrically insulating sheets 7, 7 '. Further, power supply leads 8, 8 'are connected to the electrodes 4, 4'.

Here, a description will be given of the heat generation distribution in a portion along the vicinity of the line AA 'in FIG. The portion 10 where the second conductive resin 5 is laminated on the heating element 1 means that the conductive resin layer is connected in parallel to the electrodes 4 and 4 ′, and the portion 9 where the second conductive resin 5 is not laminated (that is, The resistance value is lower than that of the element 1 only). On the other hand, the value of the current flowing between the electrodes 4 and 4 ′ is the same in the unlaminated portion 9 and the laminated portion 10
Is the same. Therefore, according to Ohm's law, the calorific value of the laminated portion 10 is always smaller than that of the non-laminated portion 9. For this reason, in FIG. 2, a desired amount of heat is generated in the direction of the line AA ′ depending on the area ratio of the stacked portion 10 and the combination of the electric resistance values of the heating element 1 and the second conductive resin 5. And a desired heat generation distribution.

Further, as shown in FIG. 1, the second conductive resin 5 is laminated on the heating element 1 at the peripheral end where the electrode is not provided over the electrodes 4 and 4 ′ (laminated portion 10 ′). ) Can be set to a desired calorific value and a desired calorific value distribution.

FIGS. 4 to 6 show, in order to explain the concept of the present invention, a sheet heating element having a second conductive resin having a different lamination structure, the same size as the sheet heating element and a thickness of 5 mm. When the wooden plywood of the above was superimposed and energized and heated so that the center temperature of the wooden plywood was 40 ° C in an environment of 25 ° C, A-
Examples of the temperature distribution at the line A 'and the line BB' are shown. FIG. 7 shows an example of a temperature distribution in the case of a planar heating element in which the second conductive resin is not laminated, which is a conventional technique. 4 to 7, AA ′
The temperature distribution of the line portion is shown below the planar heating element, and the temperature distribution of the line BB 'is shown on the right side of the planar heating element.

By configuring the planar heating element in this manner, when the planar heating element is used in contact with the object to be heated, the entire surface can be set to a uniform temperature distribution or an arbitrary temperature distribution. it can. For example, by applying the planar heating element of the present invention as a heater for floor heating, the entire surface can be set to a substantially uniform temperature distribution.

The heating element according to the present invention is obtained by impregnating an electrically insulative substrate with a first conductive resin in which carbon powder or metal powder is dispersed in a synthetic resin solution, holding the impregnated resin by a method such as coating or printing. The resistor is fixed by heating, drying, or the like.

The electrically insulative substrate used in the present invention may be any as long as it can hold the first conductive resin uniformly, has mechanical strength, and has heat resistance and electrical insulation. The material is not particularly limited. For example,
Glass cloth, a glass cloth impregnated with an epoxy resin, and then cured by heating, a polyester sheet, a polyimide sheet, mica, or the like can be used.

The first conductive resin is a resin having electric conductivity, for example, graft carbon (registered trademark, manufactured by Ryoyu Kogyo Co., Ltd.), carbon powder, metal powder, metal oxide powder and the like. Is dispersed in a synthetic resin liquid. Here, the first conductive resin includes a material generally called a conductive paint, a conductive paste, or the like.
In the present invention, electrodes are provided at two opposite ends on the heating element. The electrode is usually provided by superposing a strip-shaped copper foil or the like on the first conductive resin surface held on the electrically insulating substrate.

In the present invention, the second conductive resin is laminated on the heating element so as to obtain a desired calorific value distribution, and has the same electrical conductivity as the first conductive resin. For example, graft carbon (registered trademark, manufactured by Ryoyu Kogyo Co., Ltd.), carbon powder, metal powder, metal oxide powder and the like are dispersed in a synthetic resin liquid.
Here, the second conductive resin generally includes a conductive paint,
It contains a substance called a conductive paste or the like.

Here, the second conductive resin may be of the same material and the same composition as the first conductive resin, or may be of a different material. Any material that does not cause thermal distortion when used as a body may be used. Further, the second conductive resin may use one kind of resistance value, or may use a conductive resin having partially different resistance value.

When the second conductive resin is laminated on the heating element, the second conductive resin is laminated on the surface holding the first conductive resin so that both are electrically connected to each other. Shaped heating element. There is no particular limitation on the method of laminating the second conductive resin on the heating element. For example, the method can be performed by printing, applying, or attaching a liquid second conductive resin. In the case of printing, it can be performed by a method such as screen printing, printing by jet injection, intaglio printing, or the like. In addition, lamination can be performed by spraying a solid second conductive resin.

The size, shape, thickness, and the like of the lamination surface of the second conductive resin are not particularly limited, and are appropriately determined according to the size, shape, and desired heat generation characteristics of the sheet heating element. Further, as a laminated shape, a band shape, a slit shape, a lattice pattern shape, a striped pattern shape, or the like can be used. After the heating element is laminated with the second conductive resin to form a sheet heating element, as it is, or after drying, heating and baking, the front and back surfaces of the heating element are covered with an electrically insulating sheet. The sheet heating element of the present invention.

As the electrically insulating sheet used here, a synthetic resin sheet such as silicon, polyester, polyamide or the like, a rubber sheet, an epoxy impregnated glass cloth, or the like is used. The coating with the electrically insulating sheet is usually performed by a method such as heating or pressure bonding. A power supply lead wire is connected to the electrode. Usually, the connection portion is buried with a resin or the like to provide insulation and water resistance.

The thickness of the electrically insulating substrate used for the heating element of the present invention is not particularly limited.
0 mm, preferably 0.03 to 0.5 mm, and more preferably 0.05 to 0.3 mm. In addition, the size and shape are not particularly limited, such as floor heating, mirrors, information devices, and any size depending on its use and installation location,
It can be rectangular, cylindrical, polygonal, and similar.

In the present invention, the amount of the first conductive resin held on the electrically insulating substrate of the heating element varies depending on the heat-resistant temperature of the electrically insulating sheet, the use of the sheet heating element, a desired temperature range, and the like. Although it cannot be specified unambiguously, the calorific value when used as a planar heating element per unit area is usually 0.005 to 1.5 watt / cm ² , preferably 0.1 to 1.5 watt / cm ² .
It is set so as to be 01 to 0.8 watt / cm ² .

In the present invention, the thickness for laminating the second conductive resin on the heating element is not particularly limited, but when formed as a planar heating element, the step between the laminated portion and the non-laminated portion is reduced. Usually, 0.0
It is from 0.01 to 1 mm, preferably from 0.005 to 0.1 mm, more preferably from 0.01 to 0.05 mm.

The size and shape of the portion where the second conductive resin is laminated on the heating element are not particularly limited, and are appropriately set according to the heat capacity of the object to be heated, the desired heat generation amount, and the desired temperature distribution. You. For example, when it is sufficient to maintain a uniform temperature distribution in only one direction, as shown in FIG. 4, a band-like laminated portion is provided in a middle portion between two electrodes in parallel with the electrodes. Further, as shown in FIG. 5, it is also possible to stack over two electrodes and along the peripheral edge where no electrodes are provided.

Further, in order to keep the entire surface at a substantially uniform temperature as in the case of floor heating, as shown in FIGS. 1 and 6, a second conductive resin is provided between two electrodes and The belt is laminated in a strip shape along the peripheral edge where the electrodes are not provided, and is further laminated in a band shape in parallel with the electrodes at an intermediate portion between the two electrodes except for the laminated portion. In addition, the shape of the second conductive resin laminated on the heating element may be a single continuous plate as shown in FIGS. 1 to 6 and may be divided into small widths or provided in the form of stepping stones. Can also.

In the present invention, the resistance value of the second conductive resin used for lamination is not particularly limited, and is appropriately selected so as to obtain a desired calorific value and temperature distribution when laminated on the heating element. Further, by partially changing the lamination amount of the second conductive resin, a planar heating element whose resistance value continuously changes in the planar heating element can be obtained. The ratio of the calorific value of the non-laminated portion and the calorific value of the laminated portion, that is, the ratio of the watt density is not particularly limited, but is appropriately selected so as to obtain a desired calorific value and temperature distribution. Therefore, the ratio of (non-laminated portion) / (laminated portion) is determined by the use of the sheet heating element.

In the present invention, the material, width, and thickness of the electrode vary depending on the size of the sheet heating element, the desired heat generation amount, and the like, and cannot be specified unconditionally.
A copper foil having a width of about 0.1 mm and a width of about 3 to 15 mm is used.

The thickness of the electrically insulating sheet when the sheet heating element is insulated and coated depends on the material of the electrically insulating sheet, the use of the sheet heating element, the use conditions, and the like, and cannot be specified unconditionally. 0.03 to 1.5 mm, preferably 0.
05-1 mm, more preferably 0.08-0.5 mm
It is.

The method and conditions for coating with an electrically insulating sheet are not particularly limited, but are usually carried out by pressure bonding under heating. For example, 100-250 ° C, 0.5-
It can be carried out by thermocompression bonding of about 30 kgf / cm ² . In addition, the size of the electrically insulating sheet for covering the sheet heating element usually has an area slightly larger than the size of the sheet heating element so that the covering is completely performed when heat-pressed. Used.

By thus configuring the planar heating element, conventionally, when the planar heating element is used for floor heating, only the central portion is warm and the peripheral portion is low in temperature, so that uniform heat cannot be maintained. However, according to the present invention, it is possible to efficiently maintain the temperature with a uniform temperature distribution without generating an overheated portion.

When the sheet heating element of the present invention is used to prevent fogging of the mirror, the entire surface can be uniformly heated. As a result, the fogging of the entire mirror can be prevented at a relatively low heating temperature. Can be prevented. In addition, when used as a food or drink insulation case, keep the entire food or drink in the case at an appropriate temperature without giving excessive heat to the food or drink placed in the center of the case. Can be.

The present invention is intended to obtain a uniform temperature distribution or a desired temperature distribution when heating an object to be heated by laminating a second conductive resin on the heating element. When the element has conductivity on both the front and back surfaces, the second conductive resin may be partially laminated on both the front and back surfaces of the heating element. However, such a configuration is the same as changing the amount and shape of the second conductive resin laminated on one surface of the heating element, and is included in the present invention.

Further, even when the present invention is applied to a cylindrical planar heating element, a uniform temperature distribution or a desired temperature distribution can be set by selecting a configuration as shown in FIGS. can do. In addition, a cylindrical planar heating element can be manufactured by using a cylindrical element as the shape of the heating element. Alternatively, a cylindrical planar heating element can be manufactured and then formed into a cylindrical shape. Can be manufactured. In addition, polygonal cylinders, frustoconical cylinders, and the like can be manufactured in the same manner.

According to the present invention, a desired temperature distribution is set by laminating the second conductive resin on the heating element as described above, and the heat generation distribution can be easily and arbitrarily changed with a small lamination thickness. No special material is required other than the second conductive resin. Further, since it is only necessary to laminate the second conductive resin, it can be easily manufactured. Further, any heat generation distribution can be manufactured.

[0040]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) (Production of planar heating element) Thickness 0.1 mm, width 310 mm,
A glass cloth having a length of 300 mm is uniformly impregnated with a first conductive resin in which graft carbon (registered trademark, manufactured by Ryoyu Kogyo Co., Ltd.) is dispersed in a synthetic resin liquid, and then dried and heated and fired. A heating element was manufactured. 0.035 mm thickness, 5 mm width, 30 length
An electrode was formed by superimposing 0 mm copper foil.

A silver paste (LS-500 manufactured by Asahi Chemical Laboratory), which is a second conductive resin having silver powder dispersed in a synthetic resin liquid, having the same shape as that shown in FIG. ) Is formed in a band shape by a screen printing method in a band shape across two electrodes provided on the heating element and along two peripheral edges where no electrodes are provided.
It was laminated over a length of 00 mm and a length of 30 mm, and was further laminated in an intermediate portion between the two electrodes excluding the laminated portion in a belt shape in a width of 150 mm and a length of 240 mm in parallel with the electrodes. Thereafter, drying and heating and baking were performed to obtain a planar heating element.

The surface heating element has a thickness of 0.2 m on the front and back surfaces.
A polyester film having a length of 330 mm, a width of 330 mm and a length of 320 mm was overlaid and heated and pressed to be insulated. Further, a power supply lead wire was connected to the electrode to obtain a sheet heating element. The electric resistance of the heating element used here was about 50 Ω / c.
m ² , the amount of silver paste contained in the second conductive resin laminate is 5 mg / cm ² , and the resistance value is about 300
Ω / cm ² . The above planar heating element is 5 m thick
m, a width of 330 mm, and a length of 320 mm were attached to a wood plywood to form a wood plywood integrated planar heating element (test body 1).

(Heating test) With the wood plywood part of the test piece 1 facing upward, it was floated 100 mm off the floor and placed horizontally, and 5 mm inward from the end face of the heating part in each of the width and length directions.
Thermocouples were attached at 20 points at 50 mm intervals and at 9 points evenly dividing the whole inside. In an environment of 25 ° C. and a humidity of 65%, the surface of the wood plywood, which is the center of the test piece 1, is heated by heating so that the temperature is 40 ° C. The temperature difference at the points inside was also measured. As a result, when the surface of the wood plywood was at 40 ° C., the point within 5 mm from the end face of the heat-generating portion of the sheet heating element was 37 to 38 ° C., and the temperature-side fixed point was 37 to 40 ° C.

Comparative Example 1 A sheet heating element was manufactured in the same manner as in Example 1 except that the production of the sheet heating element in Example 1 was performed without laminating the second conductive resin. . Further, a heating test was performed on the wood-plywood-integrated planar heating element manufactured in the same manner as in Example 1 using this planar heating element in the same manner as in Example 1. The temperature difference between the point 5 mm inside the end face and the point inside the end face was measured. As a result, when the surface of the wood plywood is at 40 ° C., the point 5 mm inward from the end face of the heat generating portion of the sheet heating element is 34 to 36 ° C., and the temperature distribution of the sheet heating element is 3 ° C.
The temperature was in the range of 4 to 40 ° C., and a decrease in temperature at both ends was observed.

(Example 2) (Manufacture of floor warming panel) Two sheet heating elements manufactured in the same manner as in Example 1 were stuck on a wood plywood having a thickness of 5 mm, a width of 320 mm and a length of 640 mm without gaps. And a floor warm panel (test body 2). As a result, a non-heat-generating portion having a total length of 20 mm was formed between the two sheet heating elements, including the electrode portion and the insulating portion.

(Heating Test) With the wood plywood part of the test piece 2 facing upward, float it 100 mm off the floor, place it horizontally, and place it on the center line of the non-heating part between the two sheet heating elements.
Thermocouples were attached at points at mm intervals and at 18 equal points on the heating section of the sheet heating element. 25 ° C, Humidity 65%
In the environment of (1), the surface of the wood plywood, which is the center of the sheet heating element, was heated by heating so that the temperature became 40 ° C., and the temperature difference between the surface of the wood plywood at the heating portion and the portion of the non-heating portion of the sheet heating element was measured. . As a result, the temperature of the surface of the wood plywood in the heat-generating portion of the planar heating element was 40 ° C, while the temperature of the non-heat-generating portion was 37 to 38 ° C, and the temperature difference was 2 to 3 ° C.

Comparative Example 2 A sheet heating element was manufactured in the same manner as in Example 2 except that the sheet heating element in Example 2 was manufactured without using the second conductive resin. . A heating test was performed on the thus obtained floor warming panel in the same manner as in Example 2, and the temperature difference between the surface of the wood plywood at the heat-generating portion and the non-heat-generating portion of the planar heating element was measured. As a result, the temperature of the surface of the wood plywood in the heat-generating portion of the sheet heating element was 40 ° C., whereas that of the non-heat-generating portion was 34 ° C., and the temperature difference was 6 ° C.

[0049]

According to the present invention, there is provided a planar heating element in which a planar heating element is formed by laminating a second conductive resin on a heating element, and the front and back surfaces of the heating element are insulated. And a sheet heating element having the following formula can be easily obtained. As a result, when the planar heating element is used as a heater for floor heating, a mirror, a photosensitive drum of a copying machine, etc., it is possible to impart a uniform temperature distribution to each of them. Furthermore, in the case of using a planar heating element having a locally increased calorific value for heat insulation of a food and drink heat insulation case or the like, the entire food or drink in the heat insulation case can be kept at a moderate and uniform temperature. It became so.

[Brief description of the drawings]

FIG. 1 is an example (1) of a perspective plan view of a planar heating element of the present invention.

FIG. 2 is an example (2) of a perspective plan view of the sheet heating element of the present invention.

FIG. 3A is a sectional view taken along line AA ′ in FIG. 2; (B) It is an enlarged view of the circle part of (a).

FIG. 4 is a plan perspective view of a planar heating element of the present invention and an example diagram (1) of a temperature distribution.

FIG. 5 is a plan view perspective diagram and an example diagram (2) of a temperature distribution of the sheet heating element of the present invention.

FIG. 6 is a plan perspective view and an example diagram (3) of a temperature distribution of the sheet heating element of the present invention.

FIG. 7 is a plan perspective view and an example of a temperature distribution in a conventional planar heating element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating element 2 Electric insulating base material 3 First conductive resin 4, 4 'electrode 5 Second conductive resin 6 Planar heating element 7, 7' Electric insulating sheet 8, 8 'Power supply lead 9th Portion where the second conductive resin is not laminated 10, 10 'Portion where the second conductive resin is laminated

Claims (7)

[Claims] 1. A heating element having a uniform resistance distribution obtained by impregnating, coating, or printing an electrically insulating base material with a first conductive resin and having a rectangular or similar shape. Electrodes are provided at two opposing peripheral ends, and a second conductive resin is partially laminated on the conductive surface of the heating element to form a planar heating element. A sheet heating element covered with an electrically insulating sheet. 2. A heating element having a uniform resistance distribution obtained by impregnating, coating, or printing an electrically insulating base material with a first conductive resin and having a cylindrical or similar shape. An electrode is provided at two peripheral ends facing each other, and a second conductive resin is partially laminated on a conductive surface of the heating element to form a planar heating element. Is coated with an electrically insulating sheet. 3. The first conductive resin and the second conductive resin include a synthetic resin containing at least one selected from grafted carbon, carbon powder, metal powder and metal oxide powder. Item 3. The sheet heating element according to Item 2. 4. The method according to claim 1, wherein the second conductive resin is laminated in a band shape in parallel with the electrodes at an intermediate portion between the two electrodes provided on the heating element. Sheet heating element. 5. The method according to claim 1, wherein the second conductive resin is laminated in a strip shape across the two electrodes provided on the heating element and along the peripheral edge where the electrodes are not provided. The planar heating element according to claim 2. 6. A second conductive resin is laminated in a strip shape across two electrodes provided on the heating element and along a peripheral edge where no electrode is provided, and further includes a heating element. The sheet heating element according to claim 1 or 2, wherein the sheet heating element is laminated in a band shape in parallel with the electrode at an intermediate portion between the two electrodes except for the laminated portion. 7. The sheet heating element according to claim 1, wherein the sheet heating element is cylindrical.
A planar heating element formed in a polygonal cylindrical shape or a similar shape.