JP2724821B2 - Planar heating element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a planar heating element having a metal foil heating circuit pattern, wherein a temperature detecting electrode and a plastic thermistor are provided so that the heating circuit also serves as one of the temperature detecting electrodes. The present invention relates to an improvement of a sheet heating element having a temperature detecting function integrated with a thermosensitive resin material made of a material. (Background technology) Wide area heaters, such as electric carpets, have a flat heating element with a temperature detection function, instead of a cord-shaped heating element and a cord-shaped temperature detection wire, and feel the unevenness of the cord. It is used because it is not thin, can be finished thinly, and it is easy to obtain uniform heat generation. An example of the configuration is as shown in FIG. In the figure, 1 is a heating circuit, 2 is a temperature detecting electrode, 3 is a split electrode, 4 is a thermosensitive resin film, 5 is an insulating film, and 6 is a coupling agent. Then, between the two metal foils 1, 2 and 3 made of aluminum foil or the like, a plastic thermistor material obtained by adding an ionic additive to polyamide-based nylon 12 is used as the heat-sensitive resin film 4, The heat generating circuit 1 and the temperature detecting electrode 2 are disposed on the metal foil at positions facing each other via a heat-sensitive resin material, and both outer surfaces thereof are covered with an insulating film 5. In such a configuration, the reliability of the temperature detection function is the most important, and there is a problem particularly at the interface between the electrode and the thermosensitive resin material. That is, the adhesive force between the electrode and the thermosensitive resin is sufficiently strong, and the temperature-impedance characteristic of the thermosensitive resin can be accurately detected. Therefore, in the case of a sheet heating element using a conventional polyamide-based heat-sensitive resin material, use an aminosilane-based coupling agent (Japanese Patent Publication No. 61-15824) to provide sufficient space between the electrode and the heat-sensitive resin material. In addition to obtaining a sufficient adhesive force, the temperature-impedance characteristic of the thermosensitive resin material is accurately detected. The reason for this is that when using a coupling agent, its thickness is formed in tens of angstroms. Because the thickness of the ring agent is sufficiently thin, the impedance value of the coupling agent layer is sufficiently small compared to the impedance value of the thermosensitive resin material, so that it is possible to accurately detect the temperature-impedance characteristics of the thermosensitive resin material in practical use. Was something. However, in the case of a sheet heating element using a conventional polyamide-based heat-sensitive resin material, the temperature-impedance characteristic is large due to the moisture absorption of the heat-sensitive resin material due to its hygroscopicity, as shown in FIG. There was a problem that the temperature could change and accurate temperature control could not be performed. This hygroscopicity does not have moisture permeability because the heating circuit and the temperature detection electrode are made of metal foil, but it does not cover the front surface, so it gradually changes over time,
Heat was generated, and if this was continued, it changed in the drying direction, and if it was stored in a highly humid place, it constantly changed, for example, it changed in the moisture absorption direction, making it difficult to use. (Object of the Invention) The present invention relates to a sheet heating element made of a metal foil, which is extremely stable with little change in temperature-impedance characteristic due to moisture absorption, and which exhibits a large B constant up to a high temperature range and has high safety. It is another object of the present invention to provide a planar heating element having a temperature detecting function. (Disclosure of the Invention) In order to achieve the above object, the present invention provides a thermosensitive resin film layer containing PVC as a main component between a pair of metal foils having at least one heating circuit pattern and a temperature detection electrode pattern. In a planar heating element provided with an insulating film attached to both outer surfaces, the metal foil is attached to both sides of the PVC-based heat-sensitive resin film layer via an adhesive mainly containing a vinyl-based resin. An object of the present invention is to provide a planar heating element characterized by being combined. Next, examples of the present invention will be described. It should be noted that the embodiments are merely examples, and it is needless to say that various changes or improvements can be made without departing from the spirit of the present invention. FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a heating circuit, 2 is a temperature detecting electrode, 3 is a split electrode, 5 is an insulating film, 7 is a heat-sensitive resin film mainly composed of PVC, and 8 is an adhesive mainly composed of vinyl resin. In the present invention, as the heat-sensitive resin material, a soft PVC-based material having less hygroscopicity than the pyramide-based resin is used. In Examples, the average degree of polymerization P = 1300
A film obtained by adding 25 parts of a pyromellitic acid-based plasticizer, 5 parts of a tribasic stabilizer, and 1.5 parts of a quaternary ammonium salt as an ionic additive to a PVC resin of The size of about 40 to 200 microns is suitable for strength, flexibility and manufacturing process. Further, the heat generating circuit 1 and the temperature detecting electrode 2 made of metal foil are preferably made of an ammonium foil, a copper foil, an iron foil, or the like, and are preferable for forming a pattern by etching or designing a resistance value. Further, an adhesive 8 having a thickness of about 0.5 to 2 μm and containing a vinyl resin as a main component is provided on both sides of the thermosensitive resin film layer 7 between the thermosensitive resin agent 7 and the metal foil electrodes 1, 2, 3. And ensuring the adhesive strength between the thermosensitive resin material and the metal foil electrode,
It functions as a material that does not significantly affect the detection of the temperature-impedance characteristic of the thermosensitive resin material. As the adhesive containing the vinyl resin as a main component, a solvent type vinyl acetate resin type, an emulsion type vinyl chloride / vinyl acetate copolymer type, a vinyl alcohol type, etc., alone or in combination. Used as a type. This vinyl-based adhesive layer is applied by one digit or more thicker than the thickness of the coupling agent in the conventional example, but the heat-sensitive resin material is an ion conductive type thermistor material obtained by adding an ionic additive to a PVC resin. Yes, because the adhesive layer is also composed of the same type of vinyl resin as the main component, the ionic conduction effectively contributes to the adhesive layer as well, or the resin material itself (with no ionic conduction) has a similar material-specific impedance. Therefore, it is considered that the adhesive layer does not affect the detection of the characteristics of the heat-sensitive resin material as a result that the dielectric constant is particularly similar and the impedance-related influence on the AC voltage is similar. FIG. 2 shows the temperature-impedance characteristic of the planar heating element of the present invention and the moisture absorption characteristic thereof. The change in the temperature-impedance characteristic during drying and moisture absorption due to the low hygroscopic property of the PVC resin is shown in FIG. It turns out that it is remarkably improved compared with the conventional product. In addition, in the figure, a comparative example in the case of bonding with an adhesive other than a vinyl-based adhesive is also described.
It can be seen that all of those containing an epoxy resin or the like as a main component show a marked deterioration in impedance at a high temperature side and deteriorate the thermistor characteristics. This is because the impedance of the adhesive layer has an impedance that is not negligible compared to the high-temperature impedance of the thermistor material, so that a large change appears in the overall characteristics. Next, a method for manufacturing the sheet heating element of the present invention will be described. First, a PVC-based thermosensitive resin material is formed into a film by a T-die method, a calendar method, an inflation method, etc., and an aluminum foil is bonded to both sides of the thermosensitive resin film while applying a vinyl adhesive by a dry lamination method. The pattern is printed with resist ink on both sides by gravure printing, then etched with ferric chloride, caustic soda, etc. to form a pattern, and then an insulating film made of polyester film etc. is pasted on both sides. . Further, the cross section is not limited to FIG. 1, but may be configured as shown in FIGS. (Effects of the Invention) As described above, the present invention provides a heat-sensitive resin film layer containing PVC as a main component between a pair of metal foils having at least one heating circuit pattern and a temperature detection electrode pattern, And, in a sheet heating element having an insulating film attached to both outer surfaces, the metal foil is attached to both sides of a heat-sensitive resin film layer mainly composed of PVC via an adhesive mainly composed of a vinyl resin. Therefore, when applied to an electric carpet, etc., because the impedance characteristics do not change much due to moisture absorption of the thermosensitive resin material, (a) it has an action of lowering the impedance on the high temperature side, so that accurate temperature control can be realized, and the appropriate temperature can be maintained at any time. (B) Low impedance on high temperature side (that is, high sensitivity temperature-impedance characteristics can be taken out as a signal as it is) Inevitably, in the actual use of large area heaters such as electric carpet,
The disadvantages of the prior art as a result of the use of partial insulation on a cushion or the like are solved as follows. The temperature of the part where the cushion is placed is too high,
The problem of discoloration of the tatami floor etc. is solved. The temperature of the part where the cushion is placed is too high,
Avoids the high temperature degradation phenomenon of the heat-sensitive resin film and extends the service life. High sensor sensitivity enables accurate temperature control,
The temperature can be controlled precisely to the temperature desired by the customer, and the partial heat insulation has the effect of making it difficult for burns to occur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an embodiment of a planar heating element according to the present invention, FIG. 2 is a relation between temperature and impedance of the heating element according to the present invention, and FIGS. FIG. 5 shows a conventional example, and FIG.
The figure shows the relationship between the temperature and the impedance. DESCRIPTION OF SYMBOLS 1 ... Heating circuit 2 ... Temperature detection electrode 3 ... Divided electrode 5 ... Insulating film 7 ... Thermosensitive resin film mainly composed of vinyl chloride 8 ... Bonding mainly composed of vinyl resin Agent.

Claims (1)

(57) [Claims] A sheet-like heating element in which a heat-sensitive resin film layer containing PVC as a main component is provided between a pair of metal foils having at least one heating circuit pattern and a temperature detection electrode pattern, and insulating films are attached to both outer surfaces. 2. The sheet heating element according to claim 1, wherein the heat-sensitive resin film layer mainly containing vinyl chloride is bonded to both sides of the heat-sensitive resin film layer via an adhesive mainly containing vinyl resin.