JPH0714664A - Sheet-like heater and manufacture thereof - Google Patents

Abstract

PURPOSE:To transmit heat to a subject matter effectively, reduce the number of part items and processes to achieve low cost, and achieve compact size, light weight, and thin thickness. CONSTITUTION:A sheet-like heater 1 is provided with disc-shaped heat generation bodies 2... each comprising a static characteristic thermister, a pair of metal terminals 3, 3 comprising a metallic mesh or porous metal plate or of a linear or thin and flat form connected to electrodes 2a... in the heat generation bodies 2... respectively, and an electric insulation coating member 5 for coating the whole body of these and insulating them from the exterior. The electric insulation coating member 5 comprises synthetic resin in which filler material including long fibers are included, and it is integrally formed by compression molding. The heat generation body 2 is fixed with synthetic resin around it and passing holes in the metal terminals 3, 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element made of, for example, barium titanate-based porcelain semiconductor having PTC (Positive Temperature Coefficient) characteristics which can be used in many application fields as a constant temperature heater or a local heating heater. The present invention relates to a planar heater used and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a planar heater using a plate-shaped heating element made of a barium titanate-based ceramic semiconductor which is a positive temperature coefficient thermistor having a self-temperature control function has been considered. This planar heater does not require a temperature control circuit for maintaining a constant heat generation temperature or an overheat prevention circuit for preventing overheating, and has extremely high safety. Further, in the above-described sheet heater, electrodes are provided on the front and back surfaces of the heating element, and lead wires are soldered to these electrodes to connect to an external power source, and the electrodes are insulated from the object to be heated and the surface ( In order to make the heat generating surface smooth and to evenly transfer the heat generated by the heating element to the object to be heated, from a molded article of ceramics such as alumina, which has excellent electrical insulation, heat resistance, mechanical strength and thermal conductivity. The heating element is covered with a case or an insulating sheet made of a thermoplastic resin or the like.

In the above-mentioned conventional sheet heater, since the lead wire is directly soldered to the electrodes provided on the front and back surfaces of the heating element, a convex portion is formed on that portion, and the case or the insulating sheet is used. If a space (gap) is created between the heating element and the heating element, the thermal conductivity between the heating element and the object to be heated will decrease. The case is provided with a concave portion in accordance with the portion, and attention is paid to the adhesion between the case and the heating element.

[0004]

However, in the above-mentioned conventional sheet heater, when the heating element is covered with an insulating sheet, the heating element is fixed to the insulating sheet so that the heating element does not move in the insulating sheet. Therefore, an adhesive or the like must be used for that purpose. In addition, when the heating element is covered with a case made of a ceramic molded product, this case needs to be separately prepared in advance, and the planar heater becomes thicker, and the number of parts and the number of steps for manufacturing the planar heater are increased. However, there is a problem that the cost increases and the cost increases. Further, since the above case is formed of ceramics, it is poor in workability, and since it takes time to form unevenness in its shape, it is necessary to use a case having a low heat-generating temperature and no heat-resistant case. Further, the above problem becomes more serious.

Therefore, it is possible to easily insulate while maintaining the smoothness of the surface (heating surface), efficiently transmit the heat generated by the heating element to the object to be heated, and coat the heating element. There is a demand for a planar heater that can fix a heating element to an insulating material that is used, and that is small, lightweight, and thin.

[0006]

In order to solve the above-mentioned problems, the planar heater of the present invention is provided with electrodes on the upper and lower surfaces of a flat plate-shaped heating element made of a positive temperature coefficient thermistor. In the planar heater, a pair of metal terminals made of a metal net or a perforated metal plate or a linear or elongated flat shape electrically connected to the electrodes, respectively, and a pair electrically connected to these metal terminals, respectively. Of the present invention, and an electrically insulating coating member that covers the entire surface and electrically insulates from the outside. The electrically insulating coating member is made of a synthetic resin containing a filler containing long fibers. It is characterized by being integrally formed by compression molding.

In order to solve the above-mentioned problems, the planar heater according to the second aspect of the invention is a planar heater in which electrodes are provided on the upper and lower surfaces of a flat plate-shaped heating element made of a positive temperature coefficient thermistor. A pair of metal terminals electrically connected to the electrodes, a metal mesh or a perforated metal plate or a linear shape, and an elongated flat shape, and a pair of power supply lines electrically connected to the metal terminals, respectively. An insulating member that is provided between the metal terminals and that prevents contact between the metal terminals, and an electrically insulating coating member that covers the whole and electrically insulates from the outside, and the electrically insulating coating member is provided. It is characterized in that it is made of a synthetic resin mixed with a filler containing long fibers and is integrally formed by compression molding.

In order to solve the above-mentioned problems, a sheet heater according to a third aspect of the present invention includes a plurality of heating elements each composed of a positive temperature coefficient thermistor having electrodes provided on the upper and lower surfaces thereof, and the heating elements arranged above and below. A pair of conductive terminals that are electrically connected to the electrodes of the heating element by sandwiching between them, a lead wire connected to each conductive terminal, and an electrically insulating covering member that covers the heating element and the conductive terminals. It is characterized in that the conductive terminal is made of carbon cloth.

In order to solve the above problems, the sheet heater according to the invention of claim 4 is the sheet heater of claim 3, wherein the electrically insulating coating member is sandwiched by upper and lower conductive terminals. It is characterized in that it is composed of a spacer made of an insulator having a hole for disposing the heating element and an insulating surface layer covering the heating element and the conductive terminal.

In order to solve the above-mentioned problems, the sheet heater according to the invention of claim 5 is the sheet heater of claim 4, wherein the spacer includes either chopped strands or roving cloth. It is made of resin, and the insulating surface layer is made of fiber-reinforced synthetic resin.

In order to solve the above-mentioned problems, a method for manufacturing a planar heater according to a sixth aspect of the present invention includes a pair of heating elements, each of which is composed of a positive temperature coefficient thermistor having electrodes on its upper and lower surfaces. After sandwiching the conductive terminals made of metal or carbon cloth from the top and bottom, and then sandwiching the upper and lower conductive terminals from both sides with a pair of glass cloth or glass mat, set it in the mold, and then set the thermosetting resin liquid in the mold. And then the thermosetting resin liquid is cured to form an insulating surface layer covering the heating element and the conductive terminal.

[0012]

According to the first aspect of the invention, the pair of metal terminals are electrically connected to the electrodes provided on the upper surface and the lower surface of the flat plate-shaped heating element made of the positive temperature coefficient thermistor. And a pair of power supply lines are electrically connected to each other and are entirely covered with an electrically insulating coating member to be electrically insulated from the outside. Therefore, the surface temperature of the electrically insulating covering member rises rapidly to a predetermined temperature after the heating element is energized, and when the temperature reaches the predetermined temperature, the temperature is kept stable, so that the heat generated by the heating element is prevented. It is possible to efficiently transfer the heat to the object to be heated through the electrically insulating covering member.

The electrically insulating covering member is made of synthetic resin containing a filler containing long fibers and is integrally formed by compression molding. Therefore, it is possible to make the heat generation surface smooth and thin the coating by the electrically insulating coating member.

Further, since the metal terminal is formed of a wire mesh, a perforated metal plate, a linear shape, or an elongated flat shape, when the electrically insulating covering member is integrally formed by compression molding, the heating element is It is fixed by the synthetic resin that has passed through the hole of the metal terminal. For this reason, the number of parts and the number of steps can be reduced, the cost can be reduced, and the size, weight and thickness can be reduced. Further, so-called unitization is possible and mass production is possible.

According to the second aspect of the invention, the pair of metal terminals are electrically connected to the electrodes provided on the upper surface and the lower surface of the heating element made of the positive temperature coefficient thermistor, respectively.
A pair of power supply lines are electrically connected to these metal terminals, respectively, and are entirely covered with an electrically insulating coating member to be electrically insulated from the outside. Therefore, the surface temperature of the electrically insulating covering member rises rapidly to a predetermined temperature after the heating element is energized, and when the temperature reaches the predetermined temperature, the temperature is kept stable, so that the heat generated by the heating element is prevented. It is possible to efficiently transfer the heat to the object to be heated through the electrically insulating covering member.

The electrically insulating covering member is made of synthetic resin containing a filler containing long fibers and is integrally formed by compression molding. Therefore, it is possible to make the heat generation surface smooth and thin the coating by the electrically insulating coating member.

Further, since the metal terminal is made of a wire mesh, a perforated metal plate, a linear shape, or an elongated flat shape, when the electrically insulating covering member is integrally formed by compression molding, the heating element is It is fixed by the synthetic resin that has passed through the hole of the metal terminal. Therefore, the number of parts and the number of steps can be reduced, and the cost can be reduced. Further, so-called unitization is possible and mass production is possible.

Moreover, since the insulating member for preventing the metal terminals from contacting each other is provided between the metal terminals, the insulation between the metal terminals can be performed more reliably.

According to the structure of claim 3, since the conductive terminal made of carbon cloth is adopted instead of the metal terminal of claim 1, the weight is lighter and the coefficient of thermal expansion is smaller than that of the metal terminal. . Therefore, it is possible to realize a planar heater which is light and hard to break. Moreover, since the conductive terminal made of carbon cloth can be made thin and inexpensive, the planar heater can be made even thinner and the cost can be reduced.

According to the structure of claim 4, in addition to the effect of claim 3, the manufacture of the planar heater becomes easy. For example, of the electrically insulating coating members, existing spacers are used, and after assembling the heating element, the conductive terminals and the spacers, only the insulating surface layer is formed by using a mold to form a planar surface. It becomes possible to manufacture a heater.

According to the structure of claim 5, in addition to the effect of claim 4, it is possible to realize a planar heater having an electrically insulating coating member which is lightweight, has high electric insulation, and has a small thermal expansion coefficient.

According to the structure of claim 6, the thermosetting resin liquid is injected into the mold with the heating element, the conductive terminal and the glass cloth or the glass mat set in the mold. It can be small. Therefore, the heating element and the conductive terminal are not damaged. Moreover, it is possible to manufacture a planar heater having a uniform insulating surface and a constant thickness.

[0023]

[Embodiment 1] FIG. 1 shows an embodiment of the present invention.
The following is a description with reference to FIG.
In the following description, a planar heater having five heating elements inside will be taken as an example.

As shown in FIG. 1, the sheet heater 1 according to the present embodiment has a flat and substantially disc shape, and as shown in FIGS. 2 and 3, the flat disc-shaped heating element 2 ... , A disk-shaped metal terminal 3.3, a lead wire 4.4 as a power supply line,
And an electrically insulating coating member 5. The heating elements 2 are arranged at a central position in the planar heater 1 and at a total of five positions separated by a predetermined distance from the central position in four directions.
It is in close contact with 3. Further, the heating elements 2 ... Are provided with electrodes 2a, 2a formed on their upper and lower surfaces by applying, for example, silver paint.

The heating element 2 has a positive temperature coefficient (Positive Tempe).
a ceramics semiconductor whose main raw material is barium titanate or the like,
It is a positive temperature coefficient thermistor as a heat sensitive element having a characteristic that it has a low resistance from room temperature to the Curie temperature Tc (rapid change temperature), but its resistance value sharply increases when it exceeds the Curie temperature Tc. Due to this characteristic, when a voltage is applied to the heating element 2, the resistance value is small at first and a large current flows because of a low temperature. As a result, the temperature rises rapidly, while the temperature rises to the Curie temperature Tc. When it exceeds, the resistance value sharply increases, so that the temperature does not rise above a certain temperature and the certain temperature is kept stable. That is, the heating element 2
Has a self-temperature control function. Therefore, the sheet heater 1
Consumes less power, can omit the temperature control circuit and overheat prevention circuit, and can be downsized. Further, there is no fear of ignition due to local overheating. In addition, this heating element 2
Has a Curie temperature Tc of about 30 to 25 depending on the material composition.
Since it can be arbitrarily set in the range of 0 ° C., the heating element 2 in the present embodiment can realize the surface temperature of the electrically insulating coating member 5 effective for heating the object to be heated, and can achieve safety and power saving. The Curie temperature Tc may be set in consideration.

As the metal terminals 3 and 3 described above, when using a metal net or a perforated metal plate having excellent thermal conductivity (however, in FIG. 3, the metal terminals 3 and 3 are shown as a metal mesh for convenience of description), It is formed in a size slightly smaller than the main body of the planar heater 1. The metal terminals 3, 3 function as an electrode plate that energizes the heating elements 2 ... And as a heat transfer plate that transfers the heat generated by the heating elements 2 to the entire surface of the electrically insulating coating member 5. Has both.

The wire mesh is made of, for example, iron, copper, stainless steel or the like. The mesh of the wire mesh, that is, the size of the mesh may be, for example, an opening (opening) of several tens of microns to several mm. In addition, a frame may be provided, for example, with the same material as the wire mesh on the peripheral portion of the wire mesh formed in a disc shape so that the lead wire 4 can be easily soldered. Furthermore, the thickness of the wire mesh is thin so that the planar heater 1 can be made lighter and thinner. In addition, the size of the mesh,
The thickness and forming method of the wire net are not particularly limited.

The perforated metal plate is formed, for example, by punching a copper plate, a phosphor bronze plate, an aluminum plate, a stainless plate or the like with a die or the like to open a large number of holes.
The diameter of the holes of the perforated metal plate may be smaller than the diameter of the heating elements 2 ..., For example, it may be about several mm. The thickness of the perforated metal plate is thin so that the planar heater 1 can be made lighter and thinner. The thickness of the perforated metal plate, the diameter of the hole, the forming method, the forming position, etc. are not particularly limited.

For each metal terminal 3, for example, a wire net and a perforated metal plate or a linear terminal, an elongated flat terminal, etc. may be used properly depending on the use, size, shape, etc. of the sheet heater 1. The metal terminal 3 and the back side metal terminal 3 do not necessarily have to be the same. For example, one metal terminal 3 may be a wire net and the other metal terminal 3 may be a perforated metal plate.

The heating elements 2, ... And the metal terminals 3, 3 are electrically connected by pressing the electrodes 2a of the heating element 2 and the metal terminals 3 against each other. Also, the metal terminal 3
3 and the lead wires 4 and 4 are electrically connected to the metal terminal 3 and
The lead wires 4 corresponding to the end surface side or the inner surface side of 3 are soldered, for example. still,
The heating elements 2, ... And the metal terminals 3, 3 may be electrically connected by, for example, pasting them with a conductive adhesive of epoxy resin / silver mixture.

The electrically insulating covering member 5 is integrally formed of a synthetic resin containing a filler containing long fibers.
The heating elements 2, ... And the metal terminals 3, 3 are covered and sealed, that is, sealed. Further, the electrically insulating covering member 5 is
The lead wires 4 and 4 should be prevented from being mechanically loaded on the soldered portions of the lead wires 4 and the metal terminals 3 to prevent disconnection.
The end portion of the metal terminal 3 side is also covered.

The glass fibers are generally classified into long fibers and short fibers by the manufacturing method. The above long fibers are used in this sense, and do not mean long fibers.

The above-mentioned synthetic resin has a small heat shrinkage ratio, is excellent in electrical insulation and mechanical strength, is heat resistant to withstand the heat generation temperature of the heat generating elements 2, and is waterproof so that moisture such as water vapor does not pass inside. It is necessary to have airtightness that does not allow air to pass inside, and to have good adhesion to the coating material of the lead wires 4 and 4, for example, unsaturated polyester resin, vinyl ester resin, A thermosetting resin such as an epoxy resin or a phenol resin, or a thermoplastic resin such as a polypropylene resin, a polyamide resin, or a polyethylene terephthalate resin is used. Incidentally, the synthetic resin is, for example, price, affinity with the filler to be used, molding method of the electrically insulating coating member 5, application and size of the planar heater 1,
The shape may be appropriately selected depending on the strength and various physical properties required of the planar heater 1. Further, the synthetic resin may contain a curing agent, a release agent, a low-shrinking agent, a coloring agent, a thickening agent and the like.

The above-mentioned filler (hereinafter referred to as "filler")
Must have excellent thermal conductivity, electrical insulation, and mechanical strength, must have heat resistance to withstand the heat generation temperature of the heating elements 2 ..., and must have good affinity with synthetic resin. For example, organic fiber, inorganic fiber, organic powder, inorganic powder or the like is used.

Examples of the organic fiber include cotton, wool,
Natural fibers such as hemp, chemical fibers such as rayon,
Synthetic fibers made of polyvinyl chloride resin, polyamide resin, wholly aromatic polyamide resin, saturated polyester resin or the like are used. As the inorganic fiber, for example, glass fiber, potassium titanate, boron, silicon carbide, alumina, polytitanocarbosilane and the like are used.

Further, as the organic powder, for example, rubber such as styrene-butadiene rubber is used. As the inorganic powder, for example, calcium carbonate, kaolin, clay, alumina, aluminum hydroxide, barium sulfate, lithopone, glass powder in the form of cut fibers or milled fibers, glass flakes, glass beads, glass microballoons, aluminosilicate microballoons. , Silica microballoons, wollastonite, boron nitride, fine particle silicon, ultra fine particle anhydrous silica,
Quartz powder, talc, mica, antimony trioxide, etc. are used.

The particle diameters of the above-mentioned organic powder and inorganic powder are not particularly limited. The forms of the organic powder and the inorganic powder are not particularly limited.

The above-mentioned filler is required for, for example, price, affinity with the synthetic resin to be used, method of molding the electrically insulating coating member 5, use and size, shape of the sheet heater 1, sheet heater 1. It may be appropriately selected depending on the strength and various physical properties. Moreover, the compounding amount of the filler with respect to the synthetic resin is not particularly limited. Each of the above fillers may be mixed alone with the synthetic resin, but it is necessary to include long fibers. Further, two or more kinds may be mixed and blended with the synthetic resin, if necessary. Furthermore, the method of mixing the synthetic resin and the filler is not particularly limited.

The above-mentioned electrically insulating coating member 5, that is, the sheet heater 1, is, for example, SMC (Sheet Molding Compoun).
Thermosetting resins such as d) and BMC (Bulk Molding Compound) are molded and manufactured by the heat compression molding method.
Further, a thermoplastic resin (stampable sheet) such as long-fiber-reinforced polypropylene resin or polyamide resin is molded and manufactured by a compression molding method in which a heated resin is cooled and compressed.

The molding and manufacturing of the planar heater 1 by the above SMC is performed by the following procedure. That is, first, a synthetic resin containing a filler (hereinafter referred to as a composite) is molded into three sheets each having a predetermined shape and size,
Two of these sheets are used as a top sheet and a bottom sheet, and a hole having a size capable of accommodating the heating elements 2 is opened at a predetermined position of the remaining one sheet to form a perforated sheet. The thickness and forming method of these sheets are not particularly limited.

Next, the metal terminal 3, the perforated sheet in which the heating elements 2 are fitted in the holes, and the other metal terminal 3 are placed on the lower sheet in this order at predetermined positions. Place the top sheet on top. Then, this laminate is placed in a mold (not shown) on a press molding machine, and pressed under predetermined conditions, that is, predetermined temperature, pressure, time, etc., to heat-harden the composite, and to form three sheets. Are integrated to form the electrically insulating coating member 5. As a result, the heating element 2
... and the metal terminals 3 and 3 are sealed and fixed inside the electrically insulating coating member 5, and the planar heater 1 is molded and manufactured.

Further, the planar heater 1 by the above BMC
The molding / manufacturing is performed by the following procedure. That is, first, after the composite is made into a paste, the paste-like composite is expanded by a predetermined amount. Next, the metal terminal 3, the heating element 2, ... And the paste-like composite, and the other metal terminal 3 are arranged in this order on the paste-like composite in this order, and the paste-like composite is further placed on the metal terminal 3. Expand a predetermined amount. After that, the composite is thermoset by pressing the laminate under predetermined conditions to form the electrically insulating coating member 5, and the planar heater 1 is obtained.

Further, the molding and manufacturing of the planar heater 1 made of the above-mentioned thermoplastic resin is carried out by the following procedure.
That is, first, the composite is formed into three sheets having a predetermined shape and size, and two of these sheets are used as the top sheet and the bottom sheet, while the remaining one sheet is perforated to form a perforated sheet. And The thickness and forming method of these sheets are not particularly limited.

Next, the above three sheets are heated to a predetermined temperature and sufficiently melted, and the perforated sheet in which the metal terminals 3, the heating elements 2 ... The metal terminals 3 are placed at predetermined positions in this order, and the top sheet is further placed on the metal terminals 3. Alternatively, the sheets may be sufficiently melted by heating in the order described above and then heating.
Then, install this laminate in the mold on the press molding machine,
By pressing under a predetermined condition, the composite is fused and cooled, and the three sheets are integrated to form the electrically insulating coating member 5, and the planar heater 1 is obtained.

The procedure for molding / manufacturing the planar heater 1 using SMC, BMC, and long fiber reinforced thermoplastic resin (stampable sheet) is not limited to the above procedure, but is not limited to electrical insulation. The procedure for forming and manufacturing the planar heater 1 by covering and sealing the heating elements 2 and the metal terminals 3 and 3 with the heat-resistant covering member 5 may be used. Also,
In compression molding, the perforated sheet may be omitted if there is no risk of the metal terminals 3, 3 contacting each other during pressing. In this case, the space between the heating element 2 and the metal terminals 3 and 3 is filled with the synthetic resin that has passed through the holes of the metal terminals 3 and 3.

However, when the fiber length of the filler is shorter than the size of the hole of the metal terminal 3, when the composite is placed on the upper and lower sides of the metal terminals 3 and pressed, the synthetic resin is caused by the pressure. And most of the filler passes through the hole of the metal terminal 3 and enters between the metal terminals 3 and 3, so that almost no composite remains above and below the metal terminals 3 and 3. Therefore, only the extremely thin electrically insulating coating member 5 is formed above and below the metal terminals 3, 3.
Part of the metal terminals 3, 3 is exposed on the surface of the electrically insulating coating member 5. That is, the electric insulation of the heating elements 2, ... And the metal terminals 3, 3 is not secured, and it becomes impossible to use it as a planar heater.

Further, in the above metal terminals 3 and 3,
Since the lead wire 4 is connected to the end surface side or the inner surface side of the metal terminals 3 and 3, the unevenness due to the connection of the lead wires 4 and 4 does not occur on the outer surface side of the metal terminal 3 and 3.
Therefore, it is not necessary to provide the electrically insulating coating member 5 with a thickness for absorbing the unevenness, and the electrically insulating coating member 5,
That is, the planar heater 1 can be formed thin. As a result, the planar heater 1 can be made smaller, lighter and thinner, and the heat generated by the heating elements 2 can be efficiently transferred to the object to be heated. Furthermore, since the surface (heat generating surface) of the electrically insulating coating member 5 is smooth and can be brought into close contact with the object to be heated, the heat transfer efficiency can be further improved.

The lead wires 4 and 4 are connected to a power cord (not shown), and are electrically connected to an external power source through this power cord. In addition, each heating element 2
They are connected in parallel with each other. The lengths of the lead wires 4 and the power cord are not particularly limited.

Since the sheet heater 1 having the above-mentioned structure uses the heating elements 2 made of positive temperature coefficient thermistors as the heating means, the temperature rises rapidly after energization, and when the temperature reaches a predetermined temperature, the temperature is maintained. Become. Therefore, the surface of the electrically insulating coating member 5 is quickly raised to a predetermined temperature, and the object to be heated can be quickly heated.

Next, a method for manufacturing the sheet heater 1 having the above-mentioned structure will be described in detail with reference to specific examples, but the present invention is not limited thereto. In addition, in the following specific examples, the shape of the planar heater is a flat rectangular shape.

Concrete Example: A planar heater was molded and manufactured by SMC. First, Showa Polymer Co., Ltd. SM
C (Product number: H8D6H, Composition: Polyester resin 33 wt%, 1
Inch long glass fiber 32wt%, other filler 35wt%,
Density: 1.8 g / cm ³ ) is cut into 14.5 cm squares into 3 sheets (weight of about 73 g per sheet), 2 sheets of which are the top sheet and the bottom sheet, while the remaining 1 sheet Five holes with a diameter of 15 mm were opened at predetermined positions on the sheet to prepare a perforated sheet. Also, the Curie temperature Tc is 70 ° C, and the resistance value is 150
A heating element having a resistance of Ω, a diameter of 15 mm and a thickness of 2.5 mm was used, and a metal wire having a mesh size of 2 mm and a lead wire soldered thereto was used as a metal terminal.

Next, the lower surface sheet is set, the metal terminals and the perforated sheet are placed in this order on the lower surface sheet, the heating element is fitted into the holes of the perforated sheet, and then the metal terminals and The top sheet was placed in this order. afterwards,
This laminate is pressed at a temperature of 160 ° C. and a pressure of 100 kg / cm ^{2 for} 4 minutes to heat-cure the polyester resin and integrate the three sheets into an electrically insulating coating member of 15 cm × 15 cm × about 5 mmt, that is, A planar heater was obtained. The electric insulation of the obtained sheet heater was good.

When the polyester resin was thermoset by pressing under the same conditions except that the pressure was changed to 80 kg / cm ² , the same planar heater of 15 cm × 15 cm × about 5 mmt was obtained.

Concrete Example: Molding of a planar heater with a long fiber reinforced thermoplastic resin (stampable sheet)
It was manufactured. First of all, use a stamper sheet manufactured by Cape La Sheet Co., Ltd. (product number: C8010-N, composition: 60 wt% polypropylene resin, 40 wt% glass fiber, thickness: 0.85 mm)
It was cut into 4.5 cm squares to obtain two sheets, an upper sheet and a lower sheet. In addition, the company's stampable sheet (product number: C8040-N, composition: same as above, thickness: 3.3 mm)
After cutting into 14.5 cm square, five holes having a diameter of 15 mm were opened at predetermined positions to form a perforated sheet. Further, a heating element having a diameter of 15 mm and a thickness of 2.5 mm was used, and a metal wire having a mesh size of 2 mm to which a lead wire was soldered was used as a metal terminal.

Next, while heating the above-mentioned top sheet and bottom sheet using an infrared heater for 2 minutes and 30 seconds,
After heating the perforated sheet for about 4 minutes and 30 seconds to approximately 200 ° C, set the bottom sheet, and place the metal terminals and the perforated sheet on this bottom sheet in this order. After fitting the heating element into the hole, the metal terminal and the top sheet were further placed in this order. After that, this laminate is pressed at a temperature of 50 ° C and a pressure of 100 kg / cm ^{2 for} 40 seconds to fuse and cool the polypropylene resin, and the three sheets are integrated to form an electric insulation of 15 cm × 15 cm × 5 mmt. A covering member, that is, a planar heater was obtained. The electric insulation of the obtained sheet heater was good.

As described above, the sheet heater 1 having the above structure
Is the electrodes 2a, 2a provided on the upper and lower surfaces of the flat disk-shaped heating element 2 made of a positive temperature coefficient thermistor.
A pair of disk-shaped metal terminals 3 and 3 are electrically connected to each other, and a pair of lead wires 4 and 4 are electrically connected to these metal terminals 3 and 3, and further to the electrically insulating coating member 5. The whole is covered and electrically insulated from the outside. Therefore, the surface temperature of the electrically insulating coating member 5 rises rapidly to a predetermined temperature after the heating elements 2 are energized, and when the predetermined temperature is reached, the temperature is kept stable.
The heat generated by the heating elements 2 ... Can be efficiently transferred to the object to be heated through the electrically insulating coating member 5.

The electrically insulating coating member 5 is made of a synthetic resin containing a filler containing long reinforcing fibers and is integrally formed by compression molding. Therefore, the surface, that is, the heating surface can be made smooth, and the coating by the electrically insulating coating member 5 can be made thin.

Furthermore, since the metal terminals 3, 3 are composed of a wire mesh, a perforated metal plate, a linear terminal, an elongated flat terminal, etc., when the electrically insulating coating member 5 is integrally formed by compression molding. , Heating element 2 ... are metal terminals 3 and 3
It is fixed by the synthetic resin that has passed through the hole. For this reason, the number of parts and the number of steps can be reduced, the cost can be reduced, and the size, weight and thickness can be reduced. Also, so-called unitization is possible,
It can be mass-produced. The thickness of the sheet heater 1 is
Although it depends on the thickness of the heating elements 2, ..., For example, it can be about 3 mm.

The positions where the heating elements 2 are arranged are not limited to the above positions, of course, and may depend on the Curie temperature Tc of the heating elements 2 and the surface temperature of the sheet heater 1, for example. It may be appropriately arranged so as to be at the optimum position.

In the first embodiment described above, the planar heater 1 has been described by taking as an example the case where the five heating elements 2 are used. However, the number of the heating elements 2 is, of course, five. The size and shape of the planar heater 1 are not limited,
It may be appropriately changed depending on the application, the size of the heating element 2, the Curie temperature Tc, or the like. The shape of the heating element 2 is not limited to the above flat disk shape, and may be various shapes such as a flat rectangular shape and a triangular shape.
Further, if necessary, it may have a cylindrical shape having a through hole. Further, the shape of the metal terminals 3, 3 is not limited to the above disk shape, and may be various shapes such as an elliptical shape, a triangular shape, a quadrangular shape, and a linear shape.

Further, the shape, size, and thickness of the electrically insulating coating member 5, that is, the planar heater 1 are not limited to the above-mentioned flat and substantially disc shape, and may be any size or shape of the object to be heated. The shape, size, and thickness can be variously changed according to the shape, and various shapes such as a flat rectangular shape, a triangular shape, and an elliptical shape may be used. Furthermore, the metal terminals 3 may be formed in a disk shape, while the electrically insulating coating member 5 may be formed in a flat rectangular shape.

[Second Embodiment] The following will describe another embodiment of the present invention with reference to FIGS. 4 to 6. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, in the sheet heater 10 according to this embodiment, a spacer 11 as an insulating member is provided between the metal terminals 3 and 3. Spacer 11 above
Is required to have a small heat shrinkage ratio, excellent electrical insulation properties, mechanical strength, and heat resistance capable of withstanding the heat generation temperature of the heat generating element 2. For example, ceramics, thermoplastic resin, heat It is made of a curable resin, a synthetic resin that becomes the electrically insulating coating member 5, or the like. The metal terminal 3
In the case where the heat generated by the heating elements 2 ... Is sufficiently transmitted to the entire surface of the electrically insulating coating member 5 due to 3, the spacer 11 may be formed of a synthetic resin foam.

As shown in FIG. 5, the spacer 11 is formed in a disk shape having substantially the same size and shape as the metal terminals 3 and 3, and the center position of the spacer 11 and the center position thereof. .. are formed in a total of five positions spaced apart by a predetermined distance from each other. Each of the holes 11a ... Has a size capable of accommodating the heating element 2, and the thickness of the spacer 11 is equal to the thickness of the heating element 2. The spacer 11 is mounted between the metal terminals 3 and 3 at the time of molding / manufacturing the planar heater 10 so that the metal terminals 3 /
It is designed to prevent the three members from contacting each other and to position the heating elements 2 ...

Other constituent members and sheet heater 1
The molding / manufacturing method of No. 0 is the same as that of the planar heater 1 of the first embodiment.

As described above, the spacer 11 is provided to prevent the metal terminals 3, 3 from coming into contact with each other. Therefore, in the above-described embodiment, the thickness of the spacer 11 is equal to the thickness of the heating element 2 ... However, the thickness of the spacer 11 is not limited to the above-described embodiment, and the thickness of the heating element 2 ... It should be equal to or thinner than the thickness. That is, as shown in FIG.
For example, the thickness of the spacer 11 may be approximately half the thickness of the heating elements 2. In this case, spacer 1
1 may be in contact with either one of the metal terminals 3 or 3, and may not be in contact with the metal terminals 3 or 3.

When the density of the material of the spacer 11 is smaller than the density of the composite of the electrically insulating coating member 5, the thickness of the spacer 11 is made equal to the thickness of the heating elements 2 ... It is possible to further reduce the weight. Further, the holes 11a of the spacer 11 ...
The diameter of the spacer 1 is not particularly limited as long as it is equal to or larger than the diameter of the heating element 2, and the spacer 1
1 may be slightly larger or slightly smaller than the metal terminals 3 and 3. Moreover, the spacer 11 may or may not have an affinity with the synthetic resin of the composite that becomes the electrically insulating coating member 5.

[Embodiment 3] Another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The sheet heater of the present embodiment has a metal terminal 3
As shown in FIG. 7, instead of 3, the conductive terminals 23, 23 made of carbon cloth are used, which is different from the above-described embodiment. The conductive terminal 23 made of carbon cloth is lighter in weight and has a smaller coefficient of thermal expansion than the metal terminal 3. Therefore, it is possible to realize a planar heater which is light and hard to break. Moreover, since the conductive terminal 23 made of carbon cloth can be made thin and inexpensive, the planar heater can be made even thinner and the cost can be reduced.

Further, the conductive terminal 23 and the lead wire 4 can be integrated with carbon cloth.

The carbon cloth for the conductive terminal 23 includes
For example, Carboron Z cloth and Carboron cloth GF-8P-21E manufactured by Nippon Carbon Co., Ltd. can be used.

Using the conductive terminals 23, 23 made of these carbon cloths, a planar heater was trial-produced by the same method as the manufacturing method shown in the specific example of the embodiment.
A good planar heater having a size of 5 cm × 15 cm × 2.9 mmt was obtained. That is, a planar heater thinner than the specific examples of the above-described examples was obtained. The same material as the material shown in the specific example of the above-described embodiment was used for the members other than the conductive terminal 23.

Further, conductive terminals 23 and 23 made of carbon fiber cloth GF-8P-21E manufactured by Nippon Carbon Co., Ltd.
When a sheet heater was manufactured by using the manufacturing method shown in the specific example of the above example, the sample size was 15 cm × 15 cm × 2.
A good planar heater of 9 mmt was obtained. That is,
A planar heater having a thickness thinner than that of the specific example of the above-described example was obtained. The same material as the material shown in the specific example of the above-described embodiment was used for the members other than the conductive terminal 23.

[Embodiment 4] Another embodiment of the present invention will be described below with reference to FIGS. 8 and 9. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The sheet heater of this embodiment has substantially the same structure as that of the above embodiment, as shown in FIGS. However, in FIG. 9, ring-shaped heating elements 2 ... Are used.

The planar heater of this embodiment is RTM (Resin
Since it is manufactured by the Transfer Molding method, the molding pressure can be smaller than that of the SMC method or BMC method of the above-mentioned embodiment. Therefore, the heating element 2 consisting of a PTC thermistor
Also, the metal terminal 3 or the conductive terminal 23 made of carbon cloth is not damaged. Further, it does not depend on the mesh of the metal terminal 3 and the size of the opening of the punched hole. Further, since the heating elements 2 are fixed by mold clamping and the low-viscosity resin is injected, the planar heater having a constant thickness can be manufactured without the spacer 11. Moreover, it is possible to form a uniform insulating surface layer on the surface.

Hereinafter, a method for manufacturing a planar heater by the RTM method will be described based on a concrete example.

First, five heating elements 2 ... Are sandwiched between metal terminals 3 made of stainless steel mesh. As the heating element 2, a PTC thermistor manufactured by Sekisui Plastics Co., Ltd. was used. The Curie temperature Tc of this PTC thermistor is
70 ℃, resistance value is 150Ω, outer diameter is 15mm, inner diameter is 5mm, and thickness is 2.5mm. The stainless mesh size is 14
It is 5mm x 145mm and the opening is 2mm.

Next, the upper and lower stainless steel meshes were further sandwiched by glass mats, set in a mold, and the mold was closed. As the glass mat, a glass chopped strand mat manufactured by Fuji Fiber Glass was used. It's size is 15
It has a size of 0 mm × 150 mm and a basis weight of 300 g / m ² . The type is FRP
The inner size of the mold is 150mm x 150mm x 6mm.

Then, 210 g of a low-viscosity resin mixture solution was injected into the mold with a resin injection machine at a pressure of 3 kg / cm ² . The resin mixture consists of 30 parts of aluminum hydroxide, 0.7 parts of BPO (benzoyl peroxide) and 0.3 parts of DMA (dimethylaniline) per 100 parts of unsaturated polyester resin (Rigolac 140R manufactured by Showa High Polymer Co., Ltd.). ing.

The mold filled with the resin mixture was held in an oven at 80 ° C. for 10 minutes to form an electrically insulating coating member 5 containing glass mat and polyester resin as main components. By taking out the molded product from the mold, an excellent thin planar heater having a thickness of 6 mm and having a surface temperature of 60 ° C. 2 minutes after the voltage application was obtained.

The resin-impregnated glass mat forms an insulating surface layer.

Next, a method of manufacturing a large thin flat heater by the RTM method will be described based on a concrete example.

First, 81 heating elements 2 were sandwiched between the metal terminals 3 made of punched aluminum plates at intervals of 100 mm in a grid pattern. The heating element 2 is the same as above. The size of the punched aluminum plate is 1000mm × 1000mm × 1mm and the opening is 12mm.

Next, the upper and lower punched aluminum plates were further sandwiched by a roving cloth, set in a mold, and the mold was closed. A product of Central Glass Co. was used for the roving cloth. The size of this is 1000mm × 1000mm, and the areal density is 320g / m.
^{Is 2} . The mold is made of FRP and the inner size of the mold is 1000
It is mm x 1000 mm x 5.2 mm.

Then, the low-viscosity resin mixture solution was injected into the mold at a pressure of ² kg / cm ² with a resin injection machine. The resin mixture is 100 parts of unsaturated polyester resin (Rigolac 162R manufactured by Showa High Polymer Co., Ltd.), 20 parts of calcium carbonate, and methyl ethyl ketone peroxide (MEKP).
O 55%) is 1.4 parts, cobalt naphthenate (NAPCO0.
6%) consists of 0.6 parts.

The mold in which the resin mixture was poured was allowed to stand at room temperature of 25 ° C. for 40 minutes to form an electrically insulating coating member 5 containing roving cloth and polyester resin as main components. By taking out the molded product from the mold, an excellent large-sized thin planar heater having a thickness of 5.2 mm and having a surface temperature of 60 ° C. in 1 minute 45 seconds after applying a voltage was obtained.

In the sheet heater corresponding to the invention of claim 3, a plurality of heating elements 2 ... Composed of positive temperature coefficient thermistors having electrodes 2a and 2a on the upper and lower surfaces, and the heating elements 2 ... The electrodes 2a of the heating element 2 ...
.A pair of conductive terminals 23.2 electrically connected to 2a
3 and lead wires 4 and 4 connected to each conductive terminal 23
And an electrically insulating coating member 5 covering the heating element 2 and the conductive terminals 23, 23.
・ 23 is a structure made of carbon cloth.

According to this, since the conductive terminals 23, 23 made of carbon cloth are used instead of the metal terminals 3, 3, the weight is lighter than that of the metal terminals 3.3.
The coefficient of thermal expansion is also small. Therefore, it is possible to realize a planar heater which is light and hard to break. Moreover, since the conductive terminals 23 made of carbon cloth can be made thin and inexpensive, the planar heater can be made even thinner and the cost can be reduced.

The planar heater corresponding to the invention of claim 4 is the planar heater of claim 3 as described above,
The electrically insulating coating member 5 includes the upper and lower conductive terminals 23, 23.
Sandwiched by the holes 11a for arranging the heating elements 2 ...
And a heating element 2, and the insulating surface layer covering the conductive terminals 23.

According to this, in addition to the effect of the third aspect, the manufacture of the planar heater becomes easy. For example, of the electrically insulating coating member 5, the existing spacer 11 is used, and after assembling the heating element 2 ..., the conductive terminals 23, 23 and the spacer 11, only the insulating surface layer is formed using a mold. The sheet heater can be manufactured by forming the sheet heater.

The sheet heater corresponding to the invention of claim 5 is the sheet heater of claim 4, as described above,
The spacer 11 is made of either chopped strand or roving cloth, and the insulating surface layer is made of fiber-reinforced synthetic resin.

According to this, in addition to the effect of the fourth aspect, it is possible to realize a planar heater having an electrically insulating coating member 5 which is lightweight, has high electric insulation, and has a small thermal expansion coefficient.

As described above, the method of manufacturing the planar heater according to the invention of claim 6 is as follows.
· A plurality of heating elements 2 made of a positive temperature coefficient thermistor provided with 2a are sandwiched from above and below by a pair of conductive terminals 23, 23 made of metal or carbon cloth, and further by a pair of glass cloth or glass mat. After setting in the mold with the conductive terminals 23 of 23 sandwiched from both sides, a thermosetting resin liquid is injected into the mold and the thermosetting resin liquid is cured, whereby the heating element 2 ... This is a structure in which an insulating surface layer covering the terminals 23 is formed.

According to this, the heating element 2, ..., The conductive terminal 2
Since the thermosetting resin liquid is injected into the mold in a state in which the mold 3 and 23 and the glass cloth or the glass mat are set in the mold, the molding pressure can be small. Therefore, the heating elements 2 and the conductive terminals 23, 23 are not damaged. Moreover,
It is possible to manufacture a flat heater having a uniform thickness and a uniform insulating surface.

[0096]

The sheet heater of the invention according to claim 1 is
As described above, a pair of metal nets or perforated metal plates electrically connected to the electrodes, or a pair of metal terminals having a linear or elongated flat shape, and a pair of power supply lines electrically connected to these metal terminals, respectively. And an electrically insulative covering member that covers the whole and electrically insulates from the outside. The electrically insulative covering member is made of a synthetic resin containing a filler containing long fibers, and is compression molded. Is integrally formed by.

As a result, the surface temperature of the electrically insulating coating member rises rapidly to a predetermined temperature after the heating element is energized, and when it reaches the predetermined temperature, the temperature is kept stable. It is possible to efficiently transfer the generated heat to the object to be heated through the electrically insulating coating member. Also,
The heating surface can be made smooth and the coating by the electrically insulating coating member can be made thin. Further, when the electrically insulating covering member is integrally formed by compression molding, the heating element is fixed by the synthetic resin that has passed through the hole of the metal terminal. Therefore, it is possible to reduce the number of parts and the number of steps, and it is possible to reduce the cost, and also it is possible to reduce the size, the weight, and the thickness. In addition, so-called unitization is possible and mass production can be performed together.

As described above, the planar heater according to the second aspect of the present invention includes a wire mesh or a perforated metal plate electrically connected to the electrodes, or a pair of metal terminals each having a linear or elongated flat shape, A pair of power supply lines electrically connected to the metal terminals respectively, an insulating member provided between the metal terminals and electrically insulating the metal terminals from each other, and a whole covering to electrically insulate the outside. An electric insulating covering member is provided, and the electric insulating covering member is made of synthetic resin mixed with a filler containing long fibers, and is integrally formed by compression molding.

As a result, the surface temperature of the electrically insulating coating member rises rapidly to a predetermined temperature after the heating element is energized, and when it reaches the predetermined temperature, the temperature is kept stable, so that the heating element is generated. It is possible to efficiently transfer the generated heat to the object to be heated through the electrically insulating coating member. Also,
The heating surface can be made smooth and the coating by the electrically insulating coating member can be made thin. Further, when the electrically insulating covering member is integrally formed by compression molding, the heating element is fixed by the synthetic resin that has passed through the hole of the metal terminal. Therefore, the number of parts and the number of steps can be reduced, and the cost can be reduced. Moreover, the insulation between the metal terminals can be performed more reliably. Therefore, it is possible to further reduce the size, weight, and thickness. Furthermore, so-called unitization is possible and mass production can be performed together.

As described above, the sheet heater according to the third aspect of the present invention is obtained by sandwiching the heating element from above and below, with a plurality of heating elements made of positive temperature coefficient thermistors having electrodes on the upper and lower surfaces. A pair of conductive terminals electrically connected to the electrodes of the heating element, a lead wire connected to each conductive terminal, and an electrically insulating covering member that covers the heating element and the conductive terminals are provided. Since the conductive terminal is made of carbon cloth, it is possible to realize a sheet heater that is light and hard to break. Moreover, since the conductive terminal made of carbon cloth can be made thin and inexpensive, the flat heater can be made even thinner and the cost can be reduced.

As described above, the sheet heater according to the invention of claim 4 is the sheet heater of claim 3, wherein the electrically insulating coating member is sandwiched by the upper and lower conductive terminals and the heating element is arranged. In addition to the effect of claim 3, it is easy to manufacture the planar heater, since it is composed of a spacer made of an insulating material having a hole for heating and an insulating surface layer covering the heating element and the conductive terminal. Produce an effect.

As described above, the planar heater according to the invention of claim 5 is the planar heater according to claim 4, wherein the spacer is made of a synthetic resin containing either chopped strands or roving cloth. Since the insulating surface layer is made of fiber reinforced synthetic resin, in addition to the effect of claim 4, a planar heater having an electrically insulating coating member that is lightweight, has high electric insulation, and has a small thermal expansion coefficient is provided. There is an effect that can be realized.

As described above, in the method for manufacturing a planar heater according to the invention of claim 6, a plurality of heating elements composed of a positive temperature coefficient thermistor having electrodes on the upper and lower surfaces are used as a pair of metal or carbon. It is sandwiched from above and below by conductive terminals made of cloth, and further set in a mold with a pair of glass cloth or glass mat sandwiching the upper and lower conductive terminals from both sides, and then a thermosetting resin liquid is injected into the mold, By curing the thermosetting resin liquid, the insulating surface layer covering the heating element and the conductive terminals is formed, so that the molding pressure is small. Therefore, the heating element and the conductive terminal are not damaged. Moreover, it is possible to manufacture a planar heater having a uniform thickness and a uniform insulating surface layer.

[Brief description of drawings]

FIG. 1 is a perspective view of a sheet heater according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the above planar heater.

FIG. 3 is a perspective view of a heating element and a metal terminal, showing an internal structure of the above-mentioned sheet heater.

FIG. 4 is a sectional view of an essential part of a sheet heater according to another embodiment of the present invention.

5 is a perspective view of a spacer used in the planar heater of FIG.

FIG. 6 is a cross-sectional view of a main part of a planar heater in which a spacer is formed thinner than a heating element.

FIG. 7 shows another embodiment of the present invention and is a schematic exploded perspective view of a planar heater.

8A and 8B show another embodiment of the present invention. FIG. 8A is a schematic exploded perspective view of a sheet heater, and FIG. 8B shows a schematic configuration of the sheet heater. FIG.

9 is a ring-shaped heating element of FIG. 8, FIG. 9 (a) is a schematic exploded perspective view of a planar heater, and FIG. 9 (b) is a schematic configuration of the planar heater. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Planar heater 2 Heating element 2a Electrode 3 Metal terminal 4 Lead wire (feed line) 5 Electrically insulating covering member 10 Planar heater 11 Spacer (insulating member) 23 Conductive terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukitaka Kadowaki 4-5-27- Kuto, Oji-cho, Kitakatsuragi-gun, Nara 321 (72) Inventor Naoki Katsuta 4-5-27-Kuto, Oji-cho, Kitakatsuragi-gun, Nara 310

Claims (6)

[Claims] 1. A planar heater in which electrodes are provided on the upper and lower surfaces of a flat plate-shaped heating element made of a positive temperature coefficient thermistor, and a wire net or a perforated metal plate or wire electrically connected to the electrodes, respectively. , A pair of elongated flat metal terminals, a pair of power supply lines electrically connected to these metal terminals, and an electrically insulating coating member that covers the whole and is electrically insulated from the outside. The sheet heater, wherein the electrically insulating coating member is made of synthetic resin mixed with a filler containing long fibers and is integrally formed by compression molding. 2. A planar heater in which electrodes are provided on an upper surface and a lower surface of a plate-shaped heating element composed of a positive temperature coefficient thermistor, and a wire net or a perforated metal plate or wire electrically connected to the electrodes, respectively. Shape, a pair of elongated flat metal terminals, a pair of power supply lines electrically connected to the metal terminals, respectively, the insulating member provided between the metal terminals, to prevent contact between the metal terminals, An electrically insulating coating member for covering the whole and electrically insulating from the outside is provided, wherein the electrically insulating coating member is made of a synthetic resin containing a filler containing long fibers and is integrally formed by compression molding. A planar heater characterized by being formed in a uniform manner. 3. A plurality of heating elements made of a positive temperature coefficient thermistor with electrodes provided on the upper and lower surfaces, and a pair of conductive members electrically connected to the electrodes of the heating element by sandwiching the heating elements from above and below. A terminal, a lead wire connected to each conductive terminal, and an electrically insulating covering member that covers the heating element and the conductive terminal are provided, and the conductive terminal is made of carbon cloth. Sheet heater to be. 4. The electrically insulating coating member is a spacer made of an insulator having a hole portion for arranging a heating element sandwiched between upper and lower conductive terminals, and an insulating surface layer covering the heating element and the conductive terminal. The planar heater according to claim 3, characterized in that 5. The planar heater according to claim 4, wherein the spacer is made of synthetic resin containing either chopped strands or roving cloth, and the insulating surface layer is made of fiber reinforced synthetic resin. . 6. A plurality of heating elements made of a positive temperature coefficient thermistor having electrodes provided on the upper and lower surfaces are vertically sandwiched by a pair of conductive terminals made of metal or carbon cloth, and a pair of glass cloth or glass is further provided. Place the upper and lower conductive terminals on both sides with a mat and set it in the mold, then inject the thermosetting resin liquid into the mold and cure the thermosetting resin liquid to set the heating element and the conductive terminals. A method for manufacturing a planar heater, comprising forming an insulating surface layer to be covered.