JP2022085740A - Planar heating element - Google Patents

Abstract

To provide a planar heating element which is thin and is excellent in flexibility.SOLUTION: A planar heating element has: an electrically insulating film base material 1 composed of a polyurethane resin; a planar heating layer 3 that is provided on the electrically insulating film base material, and contains a carbon material selected from carbon nanomaterials such as a carbon nanotube, a graphene platelet and a carbon nanofiber, and a resin; a pair of electrode layers 2 arranged so as to be connected to the planar heating layer; and an electrically insulating coating layer 4 coating the planer heating layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a planar heating element.

Since the planar heating element can be formed thin and can be made flexible, it is used in various fields, and configurations according to the applications in each field have been proposed. For example, in applications where flexibility is required, which is used as a heat source for heating, a heating element and an electrode are formed on a base material made of cloth or resin, and a planar heating element having a structure covered with a covering material is used. Proposed.

For example, in Patent Document 1, a cloth base material, a conductive elastomer layer formed on at least one surface of the cloth base material, electrodes arranged for the conductive elastomer, and arrangements for the surfaces thereof. A planar heating element having an insulating layer is disclosed.

Further, Patent Document 2 describes a flexible base material, a flexible resin film bonded on the flexible base material, a comb-shaped electrode printed and formed on the flexible resin film by a conductive paste, and a polymer resistance. It has a polymer resistor printed and formed by body ink, a flexible coating material that covers them, and a woven fabric that is disposed on one or both sides of a flexible base material as an elongation restricting portion against stress. A planar heating element is disclosed.

Japanese Unexamined Patent Publication No. 63-236283 Japanese Unexamined Patent Publication No. 2007-179767

However, in Patent Document 1, since the cloth base material and the conductive elastomer layer are both thick, there are problems in terms of thinning, flexibility, and weight.
Further, in Patent Document 2, since the non-woven fabric is provided as the elongation restricting portion in order to secure the strength of the printing process at the time of manufacturing, the thickness is increased by that amount. Further, since the comb-shaped electrode is used and the electrode (branch electrode) is also provided in the region of the heat generating surface, the flexibility is reduced.
An object of the present invention is to provide a thin, flexible planar heating element.

(1) An electrically insulating film base material made of polyurethane resin and
A planar heat generating layer provided on the electrically insulating film base material and containing a carbon material and a resin,
A pair of electrode layers arranged connected to the planar heat generating layer,
A planar heating element having an electrically insulating coating layer covering the planar heating layer.
(2) The planar heating element according to (1), wherein the thickness of the planar heating element is in the range of 10 to 100 μm.
(3) The planar heating element according to (1) or (2), wherein the volume resistivity of the planar heating element is in the range of 300 to 500 μΩm.
(4) The planar heating element according to any one of (1) to (3), wherein the resin of the planar heating layer is a polyurethane resin.
(5) The planar heating element according to any one of (1) to (4), wherein the planar heating element contains a carbon nanomaterial as the carbon material.
(6) The thickness of the electrode layer is in the range of 10 to 200 μm, and the thickness is in the range of 10 to 200 μm.
The thickness of the electrically insulating coating layer is in the range of 5 to 200 μm, and the thickness is in the range of 5 to 200 μm.
The planar heating element according to any one of (1) to (5), wherein the thickness of the electrically insulating film base material is in the range of 5 to 500 μm.

According to the present invention, it is possible to provide a thin, highly flexible planar heating element.

It is sectional drawing of the planar heating element by embodiment of this invention. It is a top view of the planar heating element according to the embodiment of this invention. It is a figure which shows the heat generation behavior of the planar heating element of the Example of this invention.

Hereinafter, preferred embodiments of the present invention will be described.
First, the basic structure of the planar heating element according to the present embodiment will be described with reference to the cross-sectional view of FIG. 1 and the plan view of FIG. FIG. 1 is a cross-sectional view taken along the line AA of FIG.
In FIG. 1, reference numeral 1 is an electrically insulating film base material, reference numeral 2 is an electrode layer, reference numeral 3 is a planar heat generating layer, and reference numeral 4 is an electrically insulating coating layer. In FIG. 2, the planar heating layer 3 under the electrically insulating coating layer 4 can be seen, and the electrode layer 2 under the planar heating layer 3 can be seen so that the positions of the members on the lower layer side can be seen. It is drawn like this.

As shown in FIGS. 1 and 2, a pair of line-shaped electrode layers 2 are arranged in parallel at predetermined intervals (W) on the electrically insulating film base material 1. The planar heat generating layer 3 is arranged on the electrically insulating base material 1 so as to cover the upper surface of these electrode layers 2. The electrically insulating coating layer 4 is arranged on the electrically insulating base material 1 so as to cover the planar heat generating layer 3. By supplying power to the pair of electrode layers 2, a current flows through the planar heat generating layer between the pair of electrode layers 2 to generate heat. The portion of the planar heat-generating layer 3 between the two electrode layers 2 becomes a heat-generating region, and the length W between the two electrode layers 2 and the length L of the portion where the electrode layer 2 is formed are the heat-generating regions. Corresponds to the vertical and horizontal lengths.
In this example, the planar heating layer 3 is arranged so as to cover the upper surface of the electrode layer 2, and the lower surface of the planar heating layer 3 and the upper surface of the electrode layer 2 are connected to each other, but on the planar heating layer 3. The electrode layer 2 may be provided to connect the upper surface of the planar heat generating layer 3 and the lower surface of the electrode layer 2.

The electrically insulating film base material in the embodiment of the present invention is made of a resin formed into a film or a sheet. Resins used for the electrically insulating base material include polyimide resin, polyamideimide resin, polyamide resin, fluororesin, vinyl chloride resin, polyethylene resin, polypropylene resin, ethylene vinyl acetate resin, polyethylene terephthalate resin, polyurethane resin, and acrylic resin. Can be mentioned. From the viewpoint of flexibility (for example, elongation) and solvent resistance, polyethylene resin, polypropylene resin, ethylene vinyl acetate resin, and polyurethane resin are preferable. Polyethylene resin, polypropylene resin, and polyurethane resin are preferable from the viewpoint of flexibility (for example, elongation rate), solvent resistance, and chemical resistance (acid resistance, alkali resistance). Among these, polyurethane resin is particularly preferable from the viewpoint of adhesiveness (adhesiveness) to the planar heat generating layer and wettability to a paint (for example, carbon dispersion) for forming the planar heating layer at the time of manufacture. Polyurethane resin is a liner-type thermoplastic polymer composed of soft segments and hard segments, and has hard segments strongly aggregated by strong hydrogen bonds between urethane groups, which are bonding units, and flexible soft segments (polyurethane). Since the balance of the chains) has flexibility, toughness, and elasticity, it is possible to form an electrically insulating film base material having excellent flexibility and toughness.

The thickness of the electrically insulating film base material in the embodiment of the present invention can be set in the range of 5 to 500 μm, preferably 5 μm or more, more preferably 10 μm or more, and 50 μm or more from the viewpoint of strength as a base material. More preferably, it is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less from the viewpoint of thinning and flexibility.

The electrically insulating coating layer in the embodiment of the present invention covers the planar heat generating layer (when the electrode layer is on the planar heating layer, it covers the electrode layer and the planar heating layer), and has electrical insulating properties. However, the resin layer that can be formed by coating is preferable from the viewpoint of adhesiveness (adhesiveness) to the planar heat generating layer and the film substrate and ease of coating. Various resin coating materials (insulating paints) can be used as the material for forming the electrically insulating coating layer. Alternatively, the above-mentioned electrically insulating film base material can also be used as the electrically insulating coating layer. In this case, the film base material on the lower layer side and the outer peripheral edge of the film base material (electrically insulating coating layer) on the upper layer side can be bonded to each other by fusion-sealing.
Examples of the resin constituting the electrically insulating coating layer include the above-mentioned resins constituting the electrically insulating base material, which have flexibility (for example, elongation), adhesiveness to the planar heat generating layer (adhesiveness), and the like. Polyurethane resin is particularly preferable from the viewpoint of wettability to the coating material, solvent resistance, and chemical resistance (acid resistance, alkali resistance). For example, the electrically insulating coating layer made of polyurethane resin can be formed by using a urethane-based polymer coating agent.

The thickness of the electrically insulating coating layer in the embodiment of the present invention can be set in the range of 5 to 200 μm, and is preferably 5 μm or more, more preferably 10 μm or more, and further 20 μm or more from the viewpoint of the strength of the coating layer and the step covering property. It is preferable, from the viewpoint of thinning and flexibility, 200 μm or less is preferable, 150 μm or less is more preferable, and 100 μm or less is further preferable.

The electrode layer in the embodiment of the present invention can be formed by using a conductive tape (for example, a conductive adhesive tape) or a conductive paste such as a silver paste. The thickness of the electrode layer can be set in the range of 10 to 200 μm, preferably 10 μm or more from a store with sufficient conductivity and strength, more preferably 20 μm or more, thinning and flexibility, and easy to cover steps with the electrode layer. From this point of view, 200 μm or less is preferable, and 100 μm or less is more preferable.

The planar heat generating layer in the embodiment of the present invention is a conductive film containing a carbon material and a resin. In this planar heat-generating layer, the carbon material as the conductive material is uniformly dispersed in the resin as the matrix. Therefore, the carbon material in the planar heating layer enables heat generation with a uniform temperature distribution in the planar heating layer with the minimum required content. Further, the planar heat generating layer is excellent in flexibility because the carbon material is in a dispersed state and the matrix is a resin. In addition, since the planar heating layer contains a resin, it has a high affinity with an electrically insulating film substrate made of a resin, and has excellent adhesiveness (adhesiveness) to the film substrate, so that it is difficult to peel off and has excellent durability. A planar heating element can be obtained.

The thickness of the planar heat generating layer in the embodiment of the present invention can be set in the range of 10 to 200 μm, preferably 10 μm or more, more preferably 20 μm or more, thinning, flexibility, and consumption from the viewpoint of obtaining sufficient strength and heat generation. From the viewpoint of power consumption, 200 μm or less is preferable, 100 μm or less is more preferable, and 80 μm or less is further preferable.

The volume resistivity of the planar heating layer in the embodiment of the present invention can be set in the range of 300 to 500 μΩm. If the planar heating layer has such a volume resistivity, a sufficient amount of heat can be obtained by applying a relatively low voltage of, for example, 30 V or less, for example, a power supply for a 12 V / 24 V vehicle or the sun. A low voltage power source such as a battery can be used. The voltage applied to the planar heating layer can be set, for example, in the range of 1 to 30V or in the range of 3 to 30V, depending on the distance between the electrodes of the planar heating element.

Examples of the carbon material contained in the planar heating layer in the embodiment of the present invention include carbon nanomaterials such as carbon nanotubes, graphene platelets, and carbon nanofibers, graphite, and carbon black, and a combination of two or more of these can be mentioned. You may use it. Among these carbon materials, carbon nanomaterials are preferable, and at least one carbon material selected from the group consisting of carbon nanotubes and graphene platelets is preferable. For example, a carbon material containing graphene platelet as a main material, a carbon material containing carbon nanotubes as a main material, a carbon material containing graphene platelet as a main material, and a carbon material containing carbon nanotubes can be used. In particular, in the carbon material containing graphene platelet as a main material, the ratio of graphene platelet in the carbon material is preferably 60% by mass or more, more preferably 70% by mass or more, while it is preferably 90% by mass or less, preferably 80% by mass. % Or less is more preferable, the ratio of other carbon materials (preferably carbon nanotubes) is preferably 40% by mass or less, more preferably 30% by mass or less, while 10% by mass or more is preferable, and 20% by mass or more is more preferable. .. In the carbon material containing carbon nanotubes as a main material, the ratio of carbon nanotubes in the carbon material is preferably 60% by mass or more, more preferably 70% by mass or more.

Examples of carbon nanotubes (CNTs) include single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), and MWNTs include, for example, two-walled, three-walled, and four-walled ones. The CNT has a diameter of 0.5 to 500 nm, preferably a diameter of 3 to 100 nm, and more preferably a diameter of 5 to 25 nm. The CNTs have a length of several mm, but for example, those having a length of 500 μm or less or 100 μm or less can be used, and those having an aspect ratio (ratio of length to diameter) of 5 or more can be used. It is preferable to use 50 or more, more preferably 100 or more.

Graphene platelets include single-layer graphene and multi-layer graphene in which single-layer graphene is stacked, and may contain both of these. As the graphene platelet, one having 1 to 100 layers of graphene can be used, preferably 10 to 90 layers, and more preferably 20 to 60 layers.
As the size of the graphene platelet, one having a thickness (length in the direction perpendicular to the graphene plane) of 100 nm or less can be used, preferably 10 nm or less, more preferably 1 nm or less, and the length (width) in the graphene plane direction. Is preferably 1 μm or more, and preferably 20 μm or less.

As the resin contained in the planar heat generating layer in the embodiment of the present invention, a resin that functions as a matrix resin and functions as a binder resin that can hold the carbon material in a dispersed state in the layer can be used. Further, a resin having an affinity with the resin constituting the electrically insulating film substrate to be used is preferable, and a resin of the same type is preferable.
Examples of the resin contained in the planar heat generating layer in the embodiment of the present invention include the same resin as the resin constituting the above-mentioned electrically insulating film base material. That is, the resin contained in the planar heating layer in the embodiment of the present invention includes a polyimide resin, a polyamideimide resin, a polyamide resin, a fluororesin, a vinyl chloride resin, a polyethylene resin, a polypropylene resin, an ethylene vinyl acetate resin, and a polyethylene terephthalate resin. , Polyurethane resin, acrylic resin and the like. From the viewpoint of flexibility (for example, elongation) and solvent resistance, polyethylene resin, polypropylene resin, ethylene vinyl acetate resin, and polyurethane resin are preferable. Polyethylene resin, polypropylene resin, and polyurethane resin are preferable from the viewpoint of flexibility (for example, elongation rate), solvent resistance, and chemical resistance (acid resistance, alkali resistance). Among these, polyurethane resin is particularly preferable from the viewpoint of adhesiveness (adhesiveness) to an electrically insulating film base material and coatability of a paint for forming a planar heat-generating layer (for example, a carbon dispersion) at the time of production. Further, as described above, the polyurethane resin is a linear type thermoplastic polymer composed of a soft segment and a hard segment, and is flexible with a hard segment strongly aggregated by a strong hydrogen bond between urethane groups which are bonding units. Since the balance of the soft segments (polyurethane chains) has flexibility, toughness, and elasticity, a planar heat-generating layer having excellent flexibility and toughness can be obtained.

The volume ratio of the carbon material contained in the planar heating layer (ratio of the planar heating layer to the constituent materials) in the embodiment of the present invention can be set in the range of 10 to 90%, and is in the range of 30 to 90%. Is preferable, and the range of 50 to 80% is more preferable. If the ratio of the carbon material is too small, the variation in volume resistivity becomes large, and it becomes difficult to obtain a uniform heat generation region. On the contrary, if the ratio of the carbon material is too large, the mechanical properties (particularly flexibility) and durability of the planar heat generating layer are deteriorated.
Further, the volume ratio of the resin contained in the planar heat generating layer (ratio to the constituent material of the planar heating layer) can be set in the range of 10 to 90%, preferably in the range of 10 to 70%, and preferably in the range of 20 to 70%. A range of 50% is more preferred. If the volume ratio of the resin is too small, the mechanical properties (especially flexibility), durability, and adhesiveness of the planar heating layer deteriorate, and conversely, if it is too large, the variation in volume resistivity becomes large and a uniform heat generation region. Will be difficult to obtain.
The volume ratio of the carbon material to the resin can be set in the range of 10 to 900 parts of the carbon material with respect to 100 parts of the resin, preferably 40 to 900 parts of the carbon material with respect to 100 parts of the resin, and the carbon material with respect to 100 parts of the resin. More preferably, 100 to 400 parts. If the ratio of the carbon material is too small, the variation in volume resistivity becomes large, and it becomes difficult to obtain a uniform heat generation region. On the contrary, if the ratio of the carbon material is too large, the ratio of the resin becomes small, and the mechanical properties (particularly flexibility), durability, and adhesiveness of the planar heat generating layer are lowered.

The planar heat generating layer in the embodiment of the present invention may contain a conductive material other than the carbon material as the conductive material as long as the desired effect can be obtained. As a material other than the carbon material, metal fine particles made of a metal such as silver, aluminum, and nickel can be used. From the viewpoint of heat generation efficiency, weight, dispersibility, etc., it is preferable that the ratio of the carbon material in the conductive material is large, and the ratio of the conductive material other than the carbon material is the ratio of the total of the conductive materials including the carbon material. It is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably all of the conductive materials are carbon materials.

The planar heat generating layer in the embodiment of the present invention is preferably a coating film formed by using a dispersion liquid of a carbon material. This coating film can be formed by applying a carbon dispersion liquid containing a carbon material and a resin onto an electrically insulating film substrate and drying the coating film. The thickness of the coating film can be set in the range of the thickness of the above-mentioned planar heat generating layer, and the coating basis weight (after drying) can be set in the range of 10 to 150 g / m ² to obtain sufficient thickness and heat generation. From the point of view, 10 g / m ² or more is preferable, 20 g / m ² or more is more preferable, 25 g / m ² or more is further preferable, 150 g / m ² or less is preferable, 120 g / m 2 or less is more preferable, and 120 g / m 2 or less is more preferable from the viewpoint of thinning and flexibility. More preferably, it is 100 g / m ² or less.

The carbon dispersion can be applied by a general coating method such as a roll coating method, a dipping method, a spin coating method, a spray method, or a printing method such as a screen printing method or an inkjet printing method. can. The coating method can be selected according to the viscosity of the carbon dispersion liquid, the content of the carbon material, the type of the dispersion medium, and the like. Compared to printing methods such as the screen printing method, the coating method does not require the strength of the base material, so a thin electrically insulating film base material can be used, which is advantageous in that the planar heating element is made thinner. be. In particular, the roll coating method using a doctor blade is preferable in that a uniform thin film can be formed.

The carbon dispersion used for forming the planar heating layer in the embodiment of the present invention contains a carbon material, a resin, and a dispersion medium, and if necessary, contains a conductive material other than the carbon material and various additives. May be.

Examples of the resin contained in the carbon dispersion liquid include the above-mentioned resin constituting the planar heat generating layer, and the resin may be dispersed in a dispersion medium or dissolved in a dispersion medium. From the viewpoint of reducing the viscosity of the carbon dispersion, it is preferable to disperse the resin. Since the carbon dispersion liquid containing the resin in a dispersed state has a low viscosity, it is suitable for a coating method and can form a uniform thin film.
As the resin contained in the carbon dispersion, a polyurethane resin is preferable, but an aqueous polyurethane resin is more preferable. Since the water-based polyurethane resin can be dispersed in water, it is possible to obtain a carbon dispersion liquid in which the resin is dispersed in an aqueous medium (water or a liquid containing water as a main component) together with the carbon material. As the aqueous polyurethane, a self-emulsifying type (ionomer type) in which a hydrophilic group is introduced into the polymer skeleton can be used.

Examples of the conductive material other than the carbon material contained in the carbon dispersion include the above-mentioned conductive material that may be used for the planar heat generating layer. Other additives contained in the carbon dispersion include auxiliary agents used in general dispersions such as dispersants, penetrants, stabilizers, viscosity modifiers (thickeners) and crosslinkers. ..

The concentration of the solid content containing the carbon material and the resin in the carbon dispersion can be set in the range of 10 to 65% by mass, preferably in the range of 30 to 60% by mass, more preferably in the range of 40 to 60% by mass. preferable. If the concentration of the solid content is too low, it becomes difficult to form a coating film having a uniform thickness and a dispersed state, and it takes a lot of time and energy to remove the dispersion medium at the time of coating. On the contrary, if the concentration of the solid content is too high, the viscosity becomes high and it becomes difficult to apply the coating film, or it becomes difficult to form a coating film having a uniform thickness and a dispersed state. The viscosity of the carbon dispersion can be set in the range of 0.1 to 100 Pa · s, preferably in the range of 1 to 50 Pa · s, and more preferably in the range of 1 to 10 Pa · s.

The production of a planar heating element according to the embodiment of the present invention can be carried out, for example, as follows.
First, a pair of line-shaped electrode layers are arranged and attached in parallel to each other on an electrically insulating film base material. Next, the carbon dispersion liquid is applied on the electrically insulating film base material so as to cover the electrode layer, and then the dispersion liquid is dried. The drying may be natural drying or forced drying by heating. The coating film after drying becomes a planar heat generating layer. Next, a resin coating material is applied and dried so as to cover the planar heat generating layer to form an electrically insulating coating layer. Instead of applying the resin coating material, the electrically insulating coating layer may be laminated with an electrically insulating film or a sheet, and the outer peripheral edge thereof may be heat-sealed and sealed. Further, the electrode layer may be formed on the planar heat generating layer after the planar heat generating layer is formed.

The planar heating element according to the embodiment of the present invention described above can adjust the resistance value between the electrodes according to the thickness of the planar heating layer, the length of the electrode layer, and the distance between the electrodes, and generates heat. Can be controlled. The control of heat generation of the planar heating element can be appropriately set according to the application target and the purpose of use. However, when applied to a seat heater as a heater for an automobile interior, for example, the distance between the electrodes is set in the range of 50 to 500 mm, for example. The range of 100 to 500 mm is preferable, the range of 150 to 500 mm is more preferable, the electrode length (length on the planar heating layer) can be set in the range of 50 to 1000 mm, and the range of 100 to 1000 mm is preferable. The range of 150 to 1000 mm is more preferable.

The thickness of the planar heating element according to the present embodiment having the above configuration can be set in the range of, for example, 50 to 1200 μm, and is preferably 50 μm or more, more preferably 80 μm or more, from the viewpoint of ensuring sufficient strength and durability. 100 μm or more is more preferable. On the other hand, from the viewpoint of thinness and flexibility, the thickness of the planar heating element is preferably 1200 μm or less, more preferably 1000 μm or less, further preferably 500 μm or less, and even if it is 200 μm or less, a good planar heating element can be provided. ..

Since the planar heating element according to the embodiment of the present invention is thin and has excellent flexibility, it is suitable for a heater that comes into contact with a human body, and can be used, for example, as an automobile interior heater such as an in-vehicle seat heater or a steering heater. .. According to another embodiment of the present invention, it is possible to provide an in-vehicle seat heater provided with a planar heating element.
The planar heating element according to the embodiment of the present invention has excellent flexibility and therefore has an excellent usability, and is resistant to deterioration even when repeatedly bent and has excellent durability. Further, when heating a wide range, uniform heat generation is possible for a heater using a metal wire, power saving is possible, and problems due to disconnection can be prevented. An in-vehicle seat heater provided with such a planar heating element is excellent in usability and durability, power saving, and reliability.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
A planar heating element having the structures shown in FIGS. 1 and 2 was prepared and evaluated as follows.
The planar heating element was prepared as follows.
First, a pair of line-shaped electrode layers 2 were formed with a conductive paste on an insulating film base material 1 made of a polyurethane resin. As the conductive paste, a silver paste (manufactured by Fujikura Kasei Co., Ltd., product name: Dotite FA-333) that cures at a relatively low temperature is used, and the heat treatment is performed at 120 ° C to soften the insulating base film. The electrode layer was formed without deformation.

Next, a dispersion liquid of a carbon material was applied so as to cover the electrode layer 2 and dried to form a planar heat generating layer 3. As the dispersion liquid of the carbon material, a carbon nanomaterial was used as the carbon material, an aqueous polyurethane resin was used as the resin, and a dispersion liquid containing water was used as the dispersion medium.
Next, a urethane-based polymer coating agent was applied onto the planar heat-generating layer 3 and dried to form an electrically insulating coating layer 4.

The size of the obtained planar heating element was as follows.
Thickness of electrically insulating film substrate: 100 μm
Thickness of planar heating layer: 50 μm
Vertical length of heat generation region (length W between electrodes on planar heat generation layer): 100 mm
Horizontal length of heat generation region (length L of electrode forming portion on planar heat generation layer): 100 mm
Thickness of electrically insulating coating layer: 20 μm

The obtained planar heating element was evaluated as follows.
(Heat generation performance and power consumption)
A comparison was made with the case where a planar heating element was mounted as a seat heater and a metal wire was mounted as a seat heater under the seat skin of the in-vehicle seat.
When the temperature of the seat skin surface was measured 3 minutes after the power of the seat heater was turned on, it was 31 ° C. in each case. It can be seen that the planar heating element of this embodiment has a heat generation performance equal to or higher than that when the metal wire is attached as a seat heater. After that, when the power of the seat heater was turned off and the temperature of the seat surface was measured 5 minutes later, the temperature dropped to 28 ° C. when the metal wire was attached, but 30 ° C. in the case of the planar heating element of this embodiment. Met. It can be seen that the planar heating element of this example has excellent heat retention. In addition, the power consumption when the planar heating element of this embodiment was attached could be reduced by 25% as compared with the case where the metal wire was attached.

(Fever behavior)
The epidermis was set on the prepared planar heating element, energized for 5 hours, and the temperature of the epidermis surface was measured. FIG. 3 shows the relationship between the energization time and the temperature of the upper surface of the epidermis. From this figure, it can be seen that the number of temperature control parts can be reduced because the surface temperature is stable.

(Evaluation of durability)
The following durability tests were performed on the prepared planar heating element, and there was no significant change in appearance in any case.
<Low temperature bending test>
Prepare a planar heating element (100 x 100 mm) prepared as a sample, place a cylinder with a length of 100 mm and φ12 in the center of the sample under an atmosphere of -30 ° C, and place one side of the sample along the cylinder. Bend it so that it overlaps 180 ° on one side, and then return it to its original state. This was repeated 100 times, and the presence or absence of cracks and deformation of the planar heating element was confirmed.
<Heat resistance test>
The prepared planar heating element was placed in a constant temperature bath and held at 80 ° C. for 400 hours, and then the appearance was confirmed.
<Evaluation of solvent resistance and chemical resistance>
Solvent resistance and chemical resistance of the materials used can be evaluated based on ASTM D543.

(Evaluation of planar heating layer)
The following planar wear resistance test (wear resistance test) and coating film adhesion test (go board test) were performed on the formed coating film (planar heat-generating layer), and the results were excellent in wear resistance and adhesion. It turned out that there was.
<Plane wear resistance test>
The surface heating element was slid 10,000 times with the Gakushin type friction tester shown in JIS K5701-1 and the friction resistance test was performed to confirm the degree of surface wear.
<Coating film adhesion test>
A grid test was performed according to JIS K5600-5-6 to evaluate the adhesion of the coating film.

(Example 2)
A planar heating element was produced in the same manner as in Example 1 except that an electrically insulating coating layer was formed by using a vinyl chloride resin (PVC) -based coating agent instead of the urethane-based polymer coating agent. When the evaluation was performed in the same manner as in Example 1, the heat resistance was inferior to that of Example 1, but the other evaluation results were good.
Since the solvent resistance of the vinyl chloride resin (PVC) is inferior to that of the polyurethane resin, it can be said that the solvent resistance of the obtained planar heating element is also inferior to that of Example 1.

(Example 3)
A planar heating element was produced in the same manner as in Example 1 except that an electrically insulating coating layer was formed by using a polyethylene (PE) -based coating agent instead of the urethane-based polymer coating agent. When the evaluation was performed in the same manner as in Example 1, the heat resistance was inferior to that of Example 1, but the other evaluation results were good.

(Comparative Example 1)
A planar heating element was produced in the same manner as in Example 1 except that an insulating film base material made of polyethylene terephthalate (PET) resin was used instead of the insulating film base material made of polyurethane resin. When the evaluation was performed in the same manner as in Example, the adhesion test of the coating film was inferior to that in Example 1.
Further, since the solvent resistance and chemical resistance (alkali) of the polyethylene terephthalate (PET) resin are inferior to those of the polyurethane resin, the solvent resistance and chemical resistance (alkali) of the obtained planar heating element are also higher than those of Example 1. It can be said that it is inferior.

(Comparative Example 2)
A planar heating element was produced in the same manner as in Example 1 except that an insulating film base material made of vinyl chloride resin (PVC) was used instead of the insulating film base material made of polyurethane resin. When the evaluation was performed in the same manner as in Example 1, the adhesion test and the heat resistance test of the coating film were inferior to those of Example 1.
Further, since the solvent resistance of the vinyl chloride resin (PVC) is inferior to that of the polyurethane resin, it can be said that the solvent resistance of the obtained planar heating element is also inferior to that of Example 1.

1 Electrically insulating film base material 2 Electrode layer 3 Planar heat generating layer 4 Electrically insulating coating layer

Claims (6)

With an electrically insulating film base material made of polyurethane resin,
A planar heat generating layer provided on the electrically insulating film base material and containing a carbon material and a resin,
A pair of electrode layers arranged connected to the planar heat generating layer,
A planar heating element having an electrically insulating coating layer covering the planar heating layer. The planar heating element according to claim 1, wherein the thickness of the planar heating element is in the range of 10 to 200 μm. The planar heating element according to claim 1 or 2, wherein the volume resistivity of the planar heating element is in the range of 300 to 500 μΩm. The planar heating element according to any one of claims 1 to 3, wherein the resin of the planar heating layer is a polyurethane resin. The planar heating element according to any one of claims 1 to 4, wherein the planar heating element contains a carbon nanomaterial as the carbon material. The thickness of the electrode layer is in the range of 10 to 200 μm, and the thickness is in the range of 10 to 200 μm.
The thickness of the electrically insulating coating layer is in the range of 5 to 200 μm, and the thickness is in the range of 5 to 200 μm.
The planar heating element according to any one of claims 1 to 5, wherein the thickness of the electrically insulating film base material is in the range of 5 to 500 μm.

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