JP2008091308A - Ptc planar heating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new PTC planar heating element which has both of an excellent PTC property and a low initial electric resistance and has an excellent heating function without causing a partial overheat and has an excellent flexibility and an excellent form stability and has a thin thickness as well. <P>SOLUTION: The PTC planar heating element includes a planar heating sheet made of a PTC electro-conductive composition, composed of carbon black or graphite, paraffine and a thermoplastic elastomer, which is impregnated into or coated on a long textile fabric made of a synthetic fiber and is calcined, and an insulating films are coated on both sides of the sheet and then a heating soaking sheet is coated on one side or both sides of the sheet and moreover the following conditions (1) to (5) are satisfied: (1) A thickness is in a range of 0.6 mm to 1.5 mm, (2) D<SB>20</SB>is in a range of 250 W/m<SP>2</SP>to 600 W/m<SP>2</SP>, (3) D<SB>25</SB>/D<SB>45</SB>is 2 or less, (4) D<SB>45</SB>/D<SB>80</SB>is 10 or more and (5) D<SB>25</SB>/D<SB>80</SB>is 20 or more, wherein D<SB>25</SB>, D<SB>45</SB>, D<SB>80</SB>are power flux densities at 25°C, 45°C and 80°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Detailed Description of the Invention

  The present invention relates to a PTC sheet heating element, and more particularly to a PTC sheet heating element suitable for floor heating.

Conventionally, as an electric heating element for floor heating, a resistance heating element that does not have self-temperature controllability (PTC characteristic: an abbreviation of a positive temperature coefficient of electric resistance, and the electric resistance increases as the temperature rises), for example, nichrome Heating elements using wires are widely used. However, this fatal defect of the heating element has a danger that the temperature will rise abnormally to an unpreferably high range for practical use or safety, and the risk of abnormal overheating especially in a blocked place is remarkable. Therefore, a complicated overheat prevention mechanism was indispensable. Moreover, since it is a linear heating element, in order to use it as a heating element for heating the entire surface like a planar heating element, a special arrangement of nichrome wires and a high-performance heat equalizing material are required. .
In addition, it is known that a conductive paint having PTC characteristics is impregnated or applied to, for example, a fiber cloth and then fired, and this is used as a planar heating element. Paraffin is known as an imparting agent for imparting PTC characteristics to a conductive paint. In general, paraffin has a low melting point and is usually 60 ° C. or lower. Such a conductive paint using paraffin has a defect that a planar heating element obtained therefrom is softened at a relatively low temperature.

The PTC conductive paint using paraffin used for the planar heating element is composed of carbon black or graphite as a conductive substance, paraffin as a PTC imparting agent, a resin component of a thermoplastic resin as a structural material, and a solvent. What is common is. A typical production method for obtaining a planar heating element from such a PTC conductive paint comprises a step of impregnating or coating the paint on a fiber fabric or film and then firing. The conventional planar heating element obtained in this way has (1) lack of flexibility and inferior bending resistance, and cracking occurs due to repeated bending, and the resistance is changed to a level that cannot be ignored. 2 ▼ As mentioned above, the heat resistance is not only lacking due to the low melting point of paraffin, but also the heating function is inferior due to the PTC characteristics being exhibited at a temperature that is too low, or If an excellent PTC characteristic (high PTC magnification) is imparted with the aim of preventing abnormal overheating, the initial electric resistance becomes too high, that is, it is difficult to combine the excellent PTC characteristic with a low initial electric resistance. This is a typical application of a planar heating element having defects such as the fact that a planar heating element with a large calorific value cannot be obtained, and (4) that there is an inevitable change over time after long-term use. Suitable for floor heating system What is extremely small.
In a method of impregnating or applying a conductive paint to a fiber cloth to obtain a planar heating element, a cotton cloth is generally used as the fiber cloth. However, in the case of using a fabric made of such short fibers, the heat generation sheet obtained by impregnation or baking after application is likely to generate so-called blemishes and beards, and the electrical resistance value which is the most important item of the heat generation sheet It has been found that there is a drawback that is difficult to control. In other words, the beards and whiskers become non-negligible fluctuation factors in the electric resistance value of the heat generating sheet. It is possible to press down the whiskers and beards by a method such as a press, but there is a limit. Also, even if you temporarily hold down a beard or beard, there is a risk that it will be restored afterwards.
On the other hand, in the case of a method of applying a conductive paint to a film to obtain a planar heating element, there is a problem that the film and the generated conductive coating film are apt to peel off with respect to the heating sheet obtained by baking. To do. In particular, there is a high risk of peeling due to repeated bending. Therefore, in order to prevent this, it is necessary to use a conductive paint having a very good adhesion performance to the film, but it is very difficult to select a conductive paint suitable for this.

Problems to be solved by the invention

Accordingly, an object of the present invention is to combine a high PTC magnification PTC characteristic and a low initial electrical resistance value, thus having a high heat generation function that does not cause abnormal local overheating in a blocked place, and excellent flexibility and An object of the present invention is to provide a novel planar heating element having good shape stability and a small thickness.
Further, another object of the present invention is that there is no fear of peeling of the conductive coating film from the substrate as seen in the film substrate use example, and generation of blemishes, whiskers, etc. is suppressed as much as possible, and thus stable electric It is an object of the present invention to provide a novel planar heating element having a resistance value and having a stable heat generation performance.

Means for solving the problem

  As a result of intensive studies by the inventors, the above object of the present invention has been industrially advantageously achieved by the present invention having the following constitution.

[1] A sheet-like heat generating sheet formed by impregnating, coating and firing a long-fiber fabric made of synthetic fiber with a PTC conductive composition made of carbon black or graphite, paraffin, and a thermoplastic elastomer is sequentially applied to both sides of the sheet. A PTC planar heating element comprising an insulating film coated with a soaking sheet on one or both sides and satisfying the following conditions (1) to (5);
▲ 1 ▼ thickness is in the range of 0.6mm~1.5mm ▲ 2 ▼ that _{D 25} is in the range of ^{250W / m 2 ~600W / m 2} ▲ 3 ▼ D 25 / D 45 is 2 (4) D ₄₅ / D ₈₀ is 10 or more (5) D ₂₅ / D ₈₀ is 20 or more, provided that D ₂₅ , D ₄₅ , and D ₈₀ are 25 ° C. and 45 ° C., respectively. , Which means power density at 80 ° C.
[2] The PTC planar heating element according to the above [1], wherein D ₂₅ / D ₈₀ is 30 or more.
[3] The PTC planar heating element according to any one of the above [1] and [2], wherein D ₄₅ / D ₈₀ is 15 or more.
[4] The PTC planar heating element as set forth in any one of [1] to [3], wherein a long fiber fabric made of synthetic fibers is woven with electrode wires.
[5] The PTC planar heating element according to any one of the above [1] to [4], wherein the long fiber fabric made of synthetic fibers is a polyester long fiber fabric.
[6] The PTC planar heating element according to any one of [1] to [5], wherein the soaking sheet is a resin film / aluminum laminate.
[7] The PTC planar heating element according to any one of [1] to [6], wherein the insulating film is a polyethylene terephthalate film.
[8] The PTC planar heating element according to any one of [1] to [7], wherein the PTC conductive composition further contains a crystalline thermoplastic resin.
[9] The PTC planar heating element according to any one of [1] to [8], wherein the PTC conductive composition further contains a thermosetting resin.
[10] The PTC surface according to any one of [1] to [9] above, wherein the amount of carbon black or graphite in the PTC conductive composition is in the range of 12 wt% to 22 wt%. Heating element.
[11] The PTC planar heating element according to any one of [1] to [10], wherein the paraffin has a melting point in the range of 70 ° C to 85 ° C.
[12] The PTC planar heating element according to any one of [1] to [11], which is for floor heating.

  The greatest feature of the present invention is that it has excellent PTC characteristics, that is, by adopting a specific fabric substrate, adopting a specific PTC conductive composition, defining power density at a plurality of temperatures, specifying a thickness, etc. It has both high magnification PTC characteristics and high power density at 25 ° C., has excellent flexibility and good shape stability, and has a stable electric resistance value, and the conductive coating film is difficult to peel off. In addition, a thin sheet heating element having a small thickness is provided.

  In the present invention, the PTC conductive composition is composed of a resin component including graphite or carbon black, paraffin, and a thermoplastic elastomer. As a typical method of impregnating or applying such a PTC conductive composition to a long fiber fabric made of synthetic fibers, a PTC conductive coating made of a uniform mixture of this PTC conductive composition and an appropriate amount of solvent is prepared. A method of impregnating or applying this paint to a long-fiber fabric and then baking it is used. Graphite or carbon black is a conductivity imparting material, paraffin is a PTC imparting material, and a thermoplastic elastomer is a resin component that functions as a structural material, all of which are solid components. In the PTC conductive paint, the ratio of the solid component to the solvent is referred to as a solid solution ratio.

  In the present invention, the carbon black or graphite is preferably in the range of 13 to 22% by weight with respect to the total solid content. When this value is less than 13% by weight, the initial electric resistance becomes too high, and when it exceeds 22% by weight, it is difficult to obtain a desired high PTC magnification. Any kind of carbon black or graphite can be used. This conductive material is usually used in the form of a fine powder.

In the present invention, the paraffin preferably has a melting point in the range of 70 ° C to 85 ° C. If the melting point is less than 70 ° C, the heat resistance tends to be inferior and softening tends to occur at a low temperature. If the melting point exceeds 85 ° C, the temperature at which the PTC characteristics are sufficiently exerted becomes too high, and the temperature is separately controlled. Ingenuity is required, which is not preferable as a planar heating element for floor heating. A more preferable range of the melting point of paraffin is in the range of 73 ° C to 83 ° C. There are coal-based and petroleum-based paraffins from the origin, but any of them can be used in the present invention.
The weight ratio of paraffin to carbon black or graphite is preferably in the range of 2.3 to 3.5, and if it is less than 2.3, it becomes difficult to impart desired PTC characteristics, and 3.5 Exceeding this results in a drastic decrease in the concentration of carbon black, and the initial electrical resistance becomes too high.
In the present invention, the paraffin is preferably in the range of 60 wt% to 80 wt% with respect to the total amount of the resin component containing the thermoplastic elastomer and the paraffin. If this value is less than 60% by weight, it becomes difficult to impart desired PTC characteristics, and if it exceeds 80% by weight, the resin component as a structural material becomes too small, and the mechanical properties of the obtained planar heating element are reduced. The physical properties tend to be impaired. A more preferable range is 68% by weight to 78% by weight. The paraffin used in the present invention is preferably in the form of fine powder.

The thermoplastic elastomer that can be used in the present invention is not particularly limited, and examples thereof include styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene / butylene-styrene copolymers, and hydrogenation. Type styrene / butadiene random copolymer, dynamic vulcanization type polyolefin thermoplastic elastomer, polyester thermoplastic elastomer, polyamide thermoplastic elastomer, ethylene-vinyl acetate thermoplastic elastomer, polyvinyl chloride thermoplastic elastomer, fluoro rubber These include thermoplastic thermoplastic elastomers, trans-polyisoprene thermoplastic elastomers, and chlorinated polyethylene thermoplastic elastomers.
In the present invention, the use of such a thermoplastic elastomer is essential for imparting flexibility to the planar heating element. Of course, this thermoplastic elastomer functions as a structural material for the conductive paint.

  In the present invention, it is preferable to further use a crystalline thermoplastic resin as a resin component of the conductive paint. Such combined use imparts appropriate flexibility to the planar heating element in the case where the flexibility becomes excessive when only the thermoplastic elastomer is used. In this case, the amount of the crystalline thermoplastic resin used is preferably 35% by weight or less with respect to the thermoplastic elastomer. If it exceeds 35% by weight, the planar heating element becomes too rigid, which is not preferable. Of course, this crystalline thermoplastic resin also functions as a structural material for the conductive paint.

  The crystalline thermoplastic resin that can be used in the present invention is not particularly limited. For example, polyethylene, polypropylene, polyamide, polycarbonate, polyester, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyurethane, polyimide, modified polyphenylene ether, polysulfone, polysulfone Examples include arylate, polyethersulfone, polyetheretherketone, polyetherimide, polyphenylene sulfide, and polyparaxylene.

  When a crystalline thermoplastic resin is used in combination in the present invention, the crystalline thermoplastic resin and the thermoplastic elastomer are preferably selected in combination with those having a common monomer unit from the viewpoint of good compatibility between the two. That is, as a thermoplastic elastomer, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-ethylene-butylene-styrene copolymer, a hydrogenated styrene-butadiene random copolymer, etc. When using a styrenic thermoplastic elastomer, it is preferable to use polystyrene as the crystalline thermoplastic resin.

In the present invention, it is preferable to use a thermosetting resin in combination with the thermoplastic elastomer and / or the crystalline thermoplastic resin as the resin component of the conductive paint. Examples of such thermosetting resins include phenolic resins, epoxy resins, alkyd resins, polyurethane resins, and alkyd / melamine resins that are commonly used for coatings. Of these, alkyd resins and alkyd / melamine resins are preferably used. In the conductive paint used in the present invention, an embodiment in which these thermosetting resins are contained as a precursor is common.
The use of such a thermosetting resin is preferable in order to impart form stability to heat. In addition, this thermosetting resin functions as a structural material for the conductive paint in the present invention in combination with the thermoplastic elastomer and / or the crystalline thermoplastic resin.

In the present invention, it is necessary to cover both sides of the sheet heating sheet with an insulating film. Examples of the insulating film include a polyester film, a polyamide film, and a polypropylene film. A polyester film, particularly a polyethylene terephthalate film is preferably used.
Next, after coating the insulating film, it is necessary to coat a soaking sheet on one or both sides. The soaking sheet used in the present invention is not particularly limited, but an aluminum sheet, particularly an aluminum sheet / resin film laminate is preferably used. As the resin film, a polyester film and a polyolefin film are used, and a polyester film, particularly a polyethylene phthalate film is preferably used. Usually, this soaking sheet is covered with an adhesive or an adhesive.

The planar heating element according to the present invention needs to have a thickness in the range of 0.6 mm to 1.5 mm. If it is less than 0.6 mm, it becomes difficult to obtain a desired power density, and if it exceeds 1.5 mm, the application range as a planar heating element is narrowed, which is not preferable. One of the features of the planar heating element of the present invention is that it has high performance despite being extremely thin.
In the present invention, D ₂₅ , D ₄₅ , and D ₈₀ mean power densities at 25 ° C., 45 ° C., and 80 ° C., respectively.
In the present invention, it is necessary to satisfy the following conditions regarding the power density.
Condition _{1: D 25} is in the range of ^{250W / m 2 ~500W / m 2} .
Condition 2: D ₂₅ / D ₄₅ is 2 or less.
Condition 3: D ₄₅ / D ₈₀ is 10 or more.
Condition 4: D ₂₅ / D ₈₀ is 20 or more.
If D ₂₀ is less than 250 W / m ² , the initial heat generation amount is too small, and the rate of heating the object is undesirably slow, and if D ₂₀ exceeds 500 W / m ² , the initial heat generation amount is too large. It is difficult to reduce the calorific value at a specific temperature, for example, 80 ° C. in a normal heating system to a desired value, which is not preferable. On the other hand, if D ₂₅ / D ₄₅ exceeds 2, the heat generation capacity of the planar heating element is undesirably lowered with the passage of time of use. It is more preferable that this value is 1.7 or less. In the present invention, D ₄₅ / D ₈₀ needs to be 10 or more, and if it is less than 10, the amount of heat generated at a high temperature increases when the planar heating element is used for heating such as floor heating. This is not preferable because it is not only uneconomical but also requires a device for controlling the temperature separately. It is more preferable that this value is 13 or more.
In the present invention, D ₂₅ / D ₈₀ needs to be 20 or more, and it is preferable that the PTC magnification is sufficiently high such that it is 30 or more.

  In the present invention, a method for obtaining a PTC planar heating element satisfying the conditions (1) to (5) described in the claims is as follows. Condition (1) “thickness is in the range of 0.6 mm to 1.5 mm” is the condition for adjusting the thickness of the long-fiber fabric made of synthetic fibers and impregnating or applying the PTC conductive composition. This can be achieved by adjusting the thickness of the insulating film and the soaking sheet.

Conditions ▲ 1 ▼ with meeting the condition ▲ 2 ▼ "that _{D 25} is in the range of 250W ^{/ m 2} ~500W ^/ m 2", condition ▲ 3 ▼ _"D 25 _{/ D 45} is 2 or less In order to satisfy all of the conditions “4” “D ₄₅ / D ₈₀ is 10 or more” and “5” “D ₂₅ / D ₈₀ is 20 or more”, first of all, PTC conductive composition made of carbon black or graphite, paraffin, thermoplastic elastomer, specification of long fiber fabric made of synthetic fiber, and specification of impregnation amount or coating amount of PTC conductive composition to this As for the identification of the PTC conductive composition, (1) the melting point of the paraffin is in the range of 70 ° C to 85 ° C, and (2) the weight of the paraffin on the carbon black or graphite is The amount ratio is within the range of 2.3 to 3.5, and (3) within the range of 63 to 80% by weight with respect to the total amount of resin components and paraffin including the paraffin thermoplastic elastomer, and (4) It is preferable to set the condition that the carbon black is in the range of 13 to 22% by weight with respect to the total solid content. As the fiber fabric, a long fiber fabric made of synthetic fibers is essential, and PTC conductivity Specification of the amount of impregnation or application of the conductive composition must be adjusted in conjunction with the characteristics of the electrical resistance of the PTC conductive composition, and in the case of a PTC conductive composition with low resistance, the amount of impregnation or It is necessary to increase the amount of impregnation or the amount of application when the application amount is small, and vice versa.
In the present invention, it is essential to use a long-fiber woven fabric made of synthetic fibers as the base fiber fabric. Such synthetic fibers are not particularly limited, and examples thereof include polyester fibers, polyamide fibers, acrylic fibers, and vinylon fibers. Especially, when using a polyester film as an insulating film, it is preferable to use a polyester fiber.
In the present invention, it is preferable that the long-fiber fabric made of synthetic fibers is woven with electrode wires.
The use of a long fiber woven fabric made of synthetic fibers is essential to prevent defects that adversely affect the electrical resistance value such as hair and whisker on the planar heating element, and to obtain a planar heating element having a stable electrical resistance value. Plays an important role.

  In the present invention, a typical example of impregnating or applying the PTC conductive composition to a long fiber fabric made of synthetic fibers is a method using a PTC conductive coating. The production method of the PTC conductive paint is not particularly limited, but a typical production method is as follows. That is, it is manufactured by the following sequence of steps. (1) An aromatic solvent is put into a heated stirring vessel and heated to a temperature of 40 to 60 ° C. (2) A structural material such as a thermoplastic elastomer is added. (3) Paraffin is added and all solids are added. Continue stirring until the minutes are dissolved or fully dispersed, (4) add carbon black or graphite conductive fine powder, stir until a smooth paste is formed, and (5) add the paste to this Kneading until a substantially uniform dispersion of conductive fine powder is obtained.

  A typical method for obtaining a planar heating element from this PTC conductive coating is a method of impregnating, coating and firing a long fiber fabric made of synthetic fibers. When this method is described in detail, it is preferable to use a long-fiber woven fabric that contains electrode wires in advance, and as such a long-fiber woven fabric, polyester fiber, polyamide fiber, acrylic fiber, vinylon fiber, etc. Long fiber yarns made of synthetic fibers are arranged on warps and wefts, and copper wires or good conductive filaments (which become electrode wires) instead of them are arranged at predetermined intervals on a part of the warps and / or wefts. A long fiber fabric is mentioned. As a heating method for firing, for example, far-infrared irradiation, microwave irradiation, dielectric heating and the like can be used. However, the heating method is not limited to these, as long as appropriate temperature management is possible, A method in which the difference in the divergence rate of the solvent of the conductive paint hardly occurs between the surface and the inside of the produced coating film is preferable.

  The typical structure of the sheet heating element according to the present invention will be described. Two electrode wires are provided on the top of a 250 mm wide heating sheet, two electrodes are provided at both ends, and two electrodes are equally allocated inside. Are provided from the long fibers in the longitudinal direction of the sheet, and the electrode wire and the electrode were connected so as to be electrically connected to the heat generating sheet divided into three. Cover both sides of the heat generating sheet with an insulating film, and then cover with a soaking sheet. The length of the heat generating sheet is 600 mm, 1750 mm, and 2650 mm in typical specifications. For example, 10 pieces of 1750 mm length for 6 liters, 10 pieces of 2650 mm for 8 pieces, 15 pieces of 2650 mm pieces for 12 pieces, 3 pieces of 600 mm pieces for kitchen / toilet, Each is connected.

  The PTC planar heating element according to the present invention is used in various applications such as heating floor panels, greenhouse heating equipment, defrosting / water freeze prevention heaters, cookers, snow melting equipment, toilet seat devices, outdoor seats, and plants. It is suitably used for a dryer or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to this Example.

[Example 1]
2.9 kg of acetylene black (manufactured by Denki Kagaku): 4 kg of ethylene / propylene / styrene copolymer (manufactured by Shell: Kraton G1701), 1.1 kg of polystyrene, 7 kg of paraffin having a melting point of 80 ° C., and MEK / xylene = 20 / Add to 15 kg of 80 solvent mixture, stir well, knead with 3 rolls to make uniform paste, then dilute and stir with 15 kg xylene to adjust the coating solution containing heating material did.

On the other hand, the warp and weft are polyester long fiber fabrics using polyethylene terephthalate filament yarn (double use of 150 denier / 48 filaments) with a total fineness of 300 denier and a weaving density of 88 warp / inch and 41 weft / inch. As a highly conductive filament, two electrodes at both ends and two at the center 2 are formed by arranging five covering yarns obtained by winding a copper foil having a width of about 0.3 mm on the surface of a polyethylene terephthalate filament yarn of 275 dtex / f. A polyester long fiber woven fabric having a width of 250 mm, in which the book (equal allocation) was driven into a warp, was formed, the resulting woven fabric was immersed in the coating solution, lightly squeezed with a roll, and then fired. Thus, a PTC conductive sheet having a length of 600 mm was obtained. Both sides of this heat generation sheet are covered with an insulating film of a polyethylene terephthalate film (50 microns), and then a sheet of laminating a 25 micron polyethylene terephthalate film with a 40 micron aluminum foil. One side was coated so that it touched. A planar heating element was prepared so that the power density at 25 ° C. of the planar heating element generated by adjusting the squeezing with a roll, adjusting the solid content concentration of the coating liquid, and preliminary experiments was about 420 W / m ² . . Two electrode wires are provided at the top of the heat generating sheet, and two electrodes are provided at both ends, and two electrodes are provided in the longitudinal direction of the sheet in the longitudinal direction of the sheet, and are divided into three parts. The electrode wire and the electrode were connected so as to conduct electricity to the generated heat generation sheet. And it energized by 200V specification.
The characteristics of the obtained planar heating element were as follows.
(1) Thickness: 0.7mm
(2) Power density at 25 ° C .: 415 W / m ²
(3) Power density at 45 ° C .: 326 W / m ²
(4) Power density at 80 ° C .: 15 W / m ²
This planar heating element was extremely thin and flexible, had excellent heat generation performance, and had extremely high PTC magnification and excellent safety. Further, this planar heating element did not show any local overheating called a hot line or hot spot. Furthermore, the power density remained almost unchanged even after natural standing for 3 months.

[Example 2]
3.2 kg of acetylene black (manufactured by Denki Kagaku: Denka Black), 3.8 kg of ethylene / propylene / styrene copolymer (manufactured by Shell: Kraton G1701), 1.2 kg of polystyrene, 6.8 kg of paraffin having a melting point of 80 ° C., and MEK / Xylene = added to a solution consisting of 15 kg of a mixed solvent of 20/80, sufficiently stirred, kneaded with three rolls to make a uniform paste, diluted with 15 kg of xylene and stirred to produce a heating material The coating liquid containing was adjusted.

The same fabric as in Example 1 was dipped in the coating solution, lightly squeezed with a roll, and then fired. Thus, a planar heating element having a PTC conductivity length of 600 mm was obtained. Both sides of this exothermic sheet were covered with an insulating film of a polyethylene terephthalate film (50 microns), and then one side was covered with a sheet obtained by laminating a 40 micron aluminum foil on a 25 micron polyethylene terephthalate film. A planar heating element was prepared so that the power density at 25 ° C. of the planar heating element generated by adjusting the drawing with a roll, adjusting the solid content concentration of the coating liquid, and preliminary experiments, was about 450 W / m ² . . Two electrode wires are provided at the top of the heat generating sheet, and two electrodes are provided at both ends, and two electrodes are provided in the longitudinal direction of the sheet in the longitudinal direction of the sheet, and are divided into three parts. The electrode wire and the electrode were connected so as to conduct electricity to the generated heat generation sheet. And it energized by 200V specification.
The characteristics of the obtained planar heating element were as follows.
(1) Thickness: 0.69mm
(2) Power density at 25 ° C .: 455 W / m ²
(3) Power density at 45 ° C .: 364 W / m ²
(4) Power density at 80 ° C .: 20 W / m ²
This planar heating element was extremely thin and flexible, had excellent heat generation performance, and had extremely high PTC magnification and excellent safety. Further, this planar heating element did not show any local overheating called a hot line or hot spot. Furthermore, the power density remained almost unchanged even after natural standing for 3 months.

Example 3
2.5 kg of acetylene black (manufactured by Denki Kagaku): 3.8 kg of ethylene / propylene / styrene copolymer (manufactured by Shell: Kraton G1701), 1.2 kg of polystyrene, 7.5 kg of paraffin having a melting point of 80 ° C., and MEK / Xylene = added to a solution consisting of 15 kg of a mixed solvent of 20/80, sufficiently stirred, kneaded with three rolls to make a uniform paste, diluted with 15 kg of xylene and stirred to produce a heating material The coating liquid containing was adjusted.

The same fabric as in Example 1 was dipped in the coating solution, lightly squeezed with a roll, and then fired. Thus, a planar heating element having a PTC conductivity length of 600 mm was obtained. Both sides of this exothermic sheet were covered with an insulating film of a polyethylene terephthalate film (50 microns), and then one side was covered with a sheet obtained by laminating a 40 micron aluminum foil on a 25 micron polyethylene terephthalate film. The planar heating element was prepared so that the power density at 25 ° C. of the planar heating element generated by adjusting the drawing with the roll, adjusting the solid content concentration of the coating liquid, and preliminary experiments, was about 340 W / m ² . . Two electrode wires are provided at the top of the heat generating sheet, and two electrodes are provided at both ends, and two electrodes are provided in the longitudinal direction of the sheet in the longitudinal direction of the sheet, and are divided into three parts. The electrode wire and the electrode were connected so as to conduct electricity to the generated heat generation sheet. And it energized by 200V specification.
The characteristics of the obtained planar heating element were as follows.
(1) Thickness: 0.71mm
(2) Power density at 25 ° C .: 342 W / m ²
(3) Power density at 45 ° C .: 260 W / m ²
(4) Power density at 80 ° C .: 8 W / m ²
This planar heating element was extremely thin and flexible, had excellent heat generation performance, and had extremely high PTC magnification and excellent safety. Further, this planar heating element did not show any local overheating called a hot line or hot spot. Furthermore, the power density remained almost unchanged even after natural standing for 3 months.

The invention's effect

  According to the present invention, by adopting a specific fabric base material such as a long-fiber woven fabric made of synthetic fibers, adopting a specific PTC conductive composition, defining power density at a plurality of temperatures, specifying a thickness, etc. Combines excellent PTC characteristics and high power density at 20 ° C., has excellent flexibility and good shape stability, and has a stable electrical resistance value, and the conductive coating film is difficult to peel off. A novel planar heating element having a small thickness has been provided.

Claims (12)

Insulating films are sequentially formed on both sides of a sheet heating sheet formed by impregnating, applying and firing a long fiber fabric made of synthetic fiber with a PTC conductive composition made of carbon black or graphite, paraffin, and a thermoplastic elastomer. A PTC sheet heating element that is coated with a soaking sheet on one or both sides and satisfies the following conditions (1) to (5);
▲ 1 ▼ thickness is in the range of 0.6mm~1.5mm ▲ 2 ▼ _{D 20} is in the range of ^{250W / m 2 ~600W / m 2} ▲ 3 ▼ D 25 / D 45 is 2 4) D ₄₅ / D ₈₀ is 10 or more. 5) D ₂₅ / D ₈₀ is 20 or more. However, D ₂₅ , D ₄₅ and D ₈₀ are 25 ° C., 45 ° C. and 80 ° C., respectively. This means the power density at. PTC planar heating element according to claim 1, D ₂₅ / _{D 80} is equal to or 30 or more. _D45 / _D80 is 15 or more, The PTC planar heating element in any one of Claim 1 and 2 characterized by the above-mentioned. The PTC planar heating element according to any one of claims 1 to 3, wherein a long fiber fabric made of synthetic fibers is woven with electrode wires. The PTC sheet heating element according to any one of claims 1 to 4, wherein the long-fiber fabric made of synthetic fibers is a polyester-based long-fiber fabric. The PTC planar heating element according to any one of claims 1 to 5, wherein the soaking sheet is a resin film / aluminum laminate. The PTC sheet heating element according to claim 1, wherein the insulating film is a polyethylene terephthalate film. The PTC sheet heating element according to any one of claims 1 to 7, wherein the PTC conductive composition further contains a crystalline thermoplastic resin. The PTC sheet heating element according to any one of claims 1 to 8, wherein the PTC conductive composition further contains a thermosetting resin. The PTC sheet heating element according to any one of claims 1 to 9, wherein the amount of carbon black or graphite in the PTC conductive composition is in the range of 12 wt% to 22 wt%. The PTC planar heating element according to any one of claims 1 to 10, wherein the melting point of paraffin is in the range of 70C to 85C. It is for floor heating, The PTC planar heating element in any one of Claims 1-11.