Sheet heater

Abstract

To provide a sheet-like heater, capable of securing followability (flexibility) while suppressing leakage of current.SOLUTION: In a sheet-like heater, a first resin film layer, a first adhesion layer, a heating layer, a second adhesion layer, a second resin film layer, a third adhesion layer and a third resin film layer are stacked in this order. Principal planes of the respective neighboring layers are in tight contact with each other. All of the first, second and third resin film layers are made of a material with a relative dielectric constant of 1 to 2.5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sheet heater.

Background Art

[0002] Conventionally, several sheet heaters have been proposed. For example, Patent Document 1 describes a planar heater comprising a foil-shaped, plate-shaped, wire-shaped or fibrous metal heating element, a lead wire connected to the heating element side terminal portion of the metal heating element, and two heat-sealable fluororesin films that sandwich the metal heating element and the tip portion of the lead wire and heat-seal each other. The tip portion of the lead wire consists of a conductor exposed portion having a lead wire side terminal portion connected to the heating element side terminal portion and the tip portion of a conductor coating portion, and the coating member at the tip portion of the conductor coating portion is formed of a heat-sealable material. According to such a planar heater, it can be used by directly immersing it in water or a chemical solution, and it is excellent in chemical resistance, waterproofness, and corrosion resistance, and can obtain a stable life over a long period of time. Therefore, it is described that it can be used for heating blood, chemical solutions in the medical field where foreign matter contamination is avoided, and cleaning chemical solutions used in the electronic and semiconductor manufacturing processes.

[0003] Further, Patent Document 2 describes a sheet heater having a layered structure, comprising a sheet-shaped base material, a first resin layer made of a first resin agent attached to the main surface of the sheet-shaped base material, a mixed layer A connected to the first resin layer and made of a mixture of the first resin agent and metal fibers, a metal fiber layer connected to the mixed layer A and made only of the metal fibers and containing air inside, a mixed layer B connected to the metal fiber layer and made of a mixture of the metal fibers and a second resin agent, and a second resin layer connected to the mixed layer B and made of the second resin agent. And such a sheet heater is described as being excellent in rapid heating property and heat uniformity, and being a sheet heater that is difficult to break.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, a heater is required to suppress leakage current. Further, when the heater is used for heating a heated object whose surface such as a pipe is not flat, flexibility (flexibility) to the heated object is required.

[0006] Here, in order to suppress the former leakage current, generally a method of increasing the thickness of the insulating layer is used. However, when the insulating layer is thickened, the flexibility (flexibility) to the latter heated object (such as a pipe) deteriorates. That is, suppression of leakage current and ensuring of flexibility (flexibility) are in a trade-off relationship and are difficult to achieve both at the same time.

[0007] An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a sheet-like heater that suppresses leakage current and ensures flexibility (flexibility).

Means for Solving the Problems

[0008] The inventor of the present invention has intensively studied to solve the above problems and completed the present invention. The present invention is as follows (1) to (8). (1) A first resin film layer, a first adhesive layer, a heating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, and a third resin film layer are laminated in this order, and the main surfaces of adjacent layers are in close contact with each other, The first resin film layer, the second resin film layer, and the third resin film layer are all made of a material having a relative dielectric constant of 1 to 2.5, a sheet-like heater. (2) Further, A fourth adhesive layer and a fourth resin film layer are laminated in this order on the outside of the third resin film layer, or, in addition to the fourth adhesive layer and the fourth resin film layer on the outside of the third resin film layer, a fifth adhesive layer and a fifth resin film layer are laminated in this order, or, in addition to the fourth adhesive layer, the fourth resin film layer, the fifth adhesive layer and the fifth resin film layer on the outside of the third resin film layer, a sixth adhesive layer and a sixth resin film layer are laminated in this order, or, in addition to the fourth adhesive layer, the fourth resin film layer, the fifth adhesive layer, the fifth resin film layer, the sixth adhesive layer and the sixth resin film layer on the outside of the third resin film layer, a seventh adhesive layer and a seventh resin film layer are laminated in this order, the main surfaces of adjacent layers are in close contact with each other, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer and the seventh resin film layer are all made of a material having a relative permittivity of 1 to 2.5, and the sheet-like heater according to (1) above. (3) At least one selected from the group consisting of the first resin film layer, the second resin film layer, the third resin film layer, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer and the seventh resin film layer is made of a fluororesin, and the sheet-like heater according to (1) or (2) above. (4) Any of the first resin film layer, the second resin film layer, the third resin film layer, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer and the seventh resin film layer is made of a material having a relative permittivity of 2.2 or less, and the sheet-like heater according to any of (1) to (3) above. (5) The sheet heater according to any one of (1) to (4) above, wherein at least one selected from the group consisting of the first resin film layer, the second resin film layer, the third resin film layer, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer, and the seventh resin film layer has a thickness of 10 to 300 μm. (6) The sheet heater according to any one of (1) to (5) above, wherein the heating layer is made of a metal fiber sheet. (7) The sheet heater according to any one of (1) to (6) above, wherein at least one selected from the group consisting of the first adhesive layer, the second adhesive layer, the third adhesive layer, the fourth adhesive layer, the fifth adhesive layer, the sixth adhesive layer, and the seventh adhesive layer has a thickness of 5 to 100 μm. (8) The sheet heater according to any one of (1) to (7) above, having a total thickness of 100 to 1000 μm.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a sheet heater that suppresses leakage current and ensures followability (flexibility).

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] The present invention will be described. The present invention relates to a sheet heater in which a first resin film layer, a first adhesive layer, a heat generating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, and a third resin film layer are laminated in this order, and the main surfaces of adjacent layers are in close contact with each other. The first resin film layer, the second resin film layer, and the third resin film layer are all made of a material having a relative dielectric constant of 1 to 2.5. Such a sheet heater is also referred to as "the heater of the present invention" hereinafter.

[0012] A cross-section of the heater of the present invention is shown in FIG. 1. FIG. 1 is a schematic cross-sectional view showing the heater 1 of the present invention when cut in a direction perpendicular to its main surface. However, the dimensions in FIG. 1 may be different from the actual ones (the same applies to FIGS. 2 and 3 described later).

[0013] As shown in FIG. 1, in the heater 1 of the present invention, a first resin film layer 11, a first adhesive layer 21, a heat generating layer 5, a second adhesive layer 22, a second resin film layer 12, a third adhesive layer 23, and a third resin film layer 13 are laminated in this order, and the main surfaces of adjacent layers are in close contact with each other. When the heater 1 of the present invention is brought into close contact with a heated object 30 such as a pipe, as shown in FIG. 1, the first resin film layer 11 is on the outside, that is, the main surface of the third resin film layer 13 is brought into close contact with the outer surface of the heated object 30.

[0014] It is preferable that in the heater of the present invention, a fourth adhesive layer and a fourth resin film layer are further laminated in this order outside the third resin film layer in the heater 1 of the present invention. Such a preferred embodiment of the heater of the present invention is also referred to as "the heater 1A of the present invention" hereinafter.

[0015] It is preferable that in the heater of the present invention, a fifth adhesive layer and a fifth resin film layer are further laminated in this order outside the fourth resin film layer in the heater 1A of the present invention. Such a preferred embodiment of the heater of the present invention is also referred to as "the heater 1B of the present invention" hereinafter.

[0016] The heater of the present invention preferably has a sixth adhesive layer and a sixth resin film layer laminated in this order on the outside of the fifth resin film layer in the heater 1B of the present invention. Such a preferred embodiment of the heater of the present invention is also referred to as "the heater 1C of the present invention" below.

[0017] The heater of the present invention preferably has a seventh adhesive layer and a seventh resin film layer laminated in this order on the outside of the sixth resin film layer in the heater 1C of the present invention. Such a preferred embodiment of the heater of the present invention is also referred to as "the heater 1D of the present invention" below.

[0018] The cross-section of the heater 1D of the present invention is shown in FIG. 2. FIG. 2 is a schematic cross-sectional view showing the heater 1D of the present invention when cut in a direction perpendicular to its main surface. As shown in FIG. 2, the heater 1D of the present invention has a first resin film layer 11, a first adhesive layer 21, a heat-generating layer 5, a second adhesive layer 22, a second resin film layer 12, a third adhesive layer 23, a third resin film layer 13, a fourth adhesive layer 24, a fourth resin film layer 14, a fifth adhesive layer 25, a fifth resin film layer 15, a sixth adhesive layer 26, a sixth resin film layer 16, a seventh adhesive layer 27, and a seventh resin film layer 17 laminated in this order, and the main surfaces of adjacent layers are in close contact with each other.

[0019] When the heater 1D of the present invention is brought into close contact with a heated object 30 such as a pipe, as shown in FIG. 2, the first resin film layer 11 is on the outside, that is, the main surface of the seventh resin film layer 17 is brought into close contact with the outer surface of the heated object 30.

[0020] The heater of the present invention may further have another layer (including an adhesive layer and / or a resin film layer). For example, another layer may be provided on the outside of the first resin film layer 11 in the heater 1 of the present invention. Also, for example, another layer (e.g., one or more adhesive layers and one or more resin film layers) may be provided on the outer surface of the seventh resin film layer 17 in the heater 1D of the present invention.

[0021] <Resin film layer> The heater of the present invention preferably includes a first resin film layer, a second resin film layer, and a third resin film layer, more preferably further includes a fourth resin film layer, still more preferably further includes a fourth resin film layer and a fifth resin film layer, yet still more preferably further includes a fourth resin film layer, a fifth resin film layer, and a sixth resin film layer, and most preferably further includes a fourth resin film layer, a fifth resin film layer, a sixth resin film layer, and a seventh resin film layer. Hereinafter, when simply referred to as "resin film layer", it shall mean any of the first resin film layer to the seventh resin film layer.

[0022] In the heater of the present invention, the resin film layer is made of a material having a relative dielectric constant of 1 to 2.5, preferably 2.2 or less. In this case, leakage current can be suppressed and followability (flexibility) can also be ensured. In the present invention, the relative dielectric constant means a value obtained by measurement at 25°C and 1 kHz.

[0023] Examples of the material having a relative dielectric constant of 1 to 2.5 include fluororesins and U-PE (ultra-high molecular weight polyethylene). Examples of the fluororesin having a relative dielectric constant of 1 to 2.5 include PFA (copolymer of ethylene tetrafluoride and perfluoroalkoxyethylene), FEP (ethylene tetrafluoride - hexafluoropropylene copolymer), and PTFE (polytetrafluoroethylene). Among these, PTFE (polytetrafluoroethylene) can be preferably used. In the heater of the present invention, each of the first resin film layer to the seventh resin film layer may all be made of the same kind of material, or at least some of the layers may be made of different kinds of materials.

[0024] The thickness of the resin film layer is not particularly limited, but is preferably 10 to 300 μm, and more preferably 25 to 200 μm. Moreover, it is preferable that the thickness of the first resin film layer is 25 to 200 μm, and the thickness of each of the second resin film layer to the seventh resin film layer is 25 to 150 μm.

[0025] Here, the thickness of the resin film layer shall be determined as follows. After obtaining an enlarged photograph (200 times) of a cross-section in a direction perpendicular to the main surface of the heater of the present invention as shown in FIGS. 1 and 2, in the enlarged photograph, the thickness of the resin film layer is measured at 100 randomly selected locations, and their simple average value is obtained. Then, the obtained average value is taken as the thickness of that layer. Note that the thickness of the heating layer and each adhesive layer described later also means the value obtained by measuring by the same method.

[0026] The shape and size of the main surface of the resin film layer are not particularly limited. It is preferable that the shape and size of the main surface of the resin film layer are the same as or slightly larger than the shape and size of the main surface of the heating layer described later.

[0027] <Adhesive layer> The heater of the present invention preferably includes a first adhesive layer, a second adhesive layer, and a third adhesive layer, and further preferably has a fourth adhesive layer, and further preferably has a fourth adhesive layer and a fifth adhesive layer, and further preferably has a fourth adhesive layer, a fifth adhesive layer, and a sixth adhesive layer, and further preferably has a fourth adhesive layer, a fifth adhesive layer, a sixth adhesive layer, and a seventh adhesive layer. Hereinafter, when simply referred to as "adhesive layer", it shall mean any of the first adhesive layer to the seventh adhesive layer.

[0028] The adhesive layer serves to bond the main surfaces of the resin film layer and the heating layer to each other, or the main surfaces between two resin film layers to each other. The material of the adhesive layer is not particularly limited as long as it can serve such a role. As the adhesive layer, it is preferable to use fluororubber, silicone-based adhesive, fluorine-based elastomer (such as PFA). In the heater of the present invention, each of the first to seventh adhesive layers may all be made of the same material, or at least some of the layers may be made of different materials.

[0029] The adhesive layer is preferably made of a material having a relative dielectric constant of 1 to 7, more preferably made of a material having a relative dielectric constant of 1 to 4. In this case, leakage current is suppressed and the adhesion performance is also excellent.

[0030] The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 20 to 50 μm.

[0031] <Heating layer> In the heater of the present invention, the heating layer is in the form of a layer, plate, foil, sheet, or a similar form. The shape of the main surface is not particularly limited. For example, as shown in FIG. 3, the heating layer 5 in a patterned form may be used.

[0032] The thickness of the heating layer is preferably 10 to 600 μm, more preferably 20 to 150 μm, and even more preferably about 35 μm.

[0033] The heating layer preferably generates heat when energized. For example, a foil-shaped metal that generates heat when energized can be used as the heating layer. Also, for example, a metal fiber sheet formed by processing linear or fibrous metals into a layer can be preferably used as the heating layer. Examples of the metal fiber sheet include a metal fiber non-woven fabric, a metal fiber woven fabric, and a metal fiber mesh.

[0034] When the heating layer is a metal fiber sheet, the metal fibers constituting the metal fiber sheet are preferably metal fibers having an equivalent diameter of a circle with an equal cross-sectional area of 2 to 100 μm (preferably 5 to 20 μm) and a length of 2 to 20 mm. And the metal fiber sheet is preferably formed by countless such metal fibers being intricately intertwined into a sheet shape.

[0035] Here, it is preferable that the metal fiber sheets are in contact with each other to such an extent that they can conduct electricity. Also, it is preferable that the metal fibers are connected at the contact points. For example, by sintering at a high temperature, after a part of the metal fibers has melted and then solidified, it is preferable that the metal fibers are fused at the contact points by having a history of solidification.

[0036] The material of the metal fibers is preferably stainless steel. Examples of metal fiber sheets made of stainless steel fibers include stainless steel fiber sheets (Tommy Filec SS, manufactured by Kawanakajima Pulp Co., Ltd.). The material of the metal fibers may also be Cu (copper), Al (aluminum), Ni (nickel), or nichrome.

[0037] The basis weight of the metal fiber sheet is preferably 25 g / m 2 or more, and preferably 50 g / m 2 or more. Also, it is preferably 1000 g / m 2 or less, and more preferably 200 g / m 2 or less.

[0038] The density of the metal fiber sheet is preferably 1.0 to 5.0 g / cm 3 and more preferably 1.4 to 2.0 g / cm 3 and most preferably about 1.7 g / cm 3 .

[0039] The metal fiber sheet can be manufactured by either a dry nonwoven fabric manufacturing method or a wet papermaking method. When manufacturing by the wet papermaking method, after stirring innumerable metal fibers with an equivalent circle diameter of the cross-section of 2 to 100 μm and a length of 2 to 20 mm in a dispersion medium (such as water or an organic solvent), an organic coagulant or the like is added, and the sheet is formed using a rectangular hand papermaking device (manufactured by Toyo Seiki Co., Ltd., etc.), and a dry sheet with a basis weight of 50 to 1100 g / m 2 is obtained using a ferrotype drying device. Thereafter, when fired at 400 to 1300 °C, a metal fiber sheet is obtained. When a metal fiber sheet is obtained by such a manufacturing method, in principle, no organic coagulant remains in the metal fiber sheet.

[0040] The total thickness of the heater of the present invention is preferably 100 to 1000 μm, and more preferably 300 to 600 μm.

[0041] The heated object to which the heater of the present invention is adhered has a non-flat surface. And the heater of the present invention is used by attaching it to such a non-flat surface. The heated object to which the heater of the present invention is adhered preferably has a surface (curved surface) with curvature such as a pipe, and more preferably is a pipe.

Example

[0042] Examples of the present invention will be described below. The present invention is not limited to the aspects of the examples described below.

[0043] <Example 1> In Example 1, a sheet-shaped heater in which a first resin film layer, a first adhesive layer, a heat-generating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, and a third resin film layer were laminated in this order, and the main surfaces of adjacent layers were adhered to each other was created. That is, the sheet-shaped heater 1 of the aspect shown in FIG. 1 was created.

[0044] Also, in Example 1, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS100H (manufactured by AGC, Inc.) · Heat-generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer and third adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS100H (manufactured by AGC, Inc.) · Second resin film layer and third resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 410 μm

[0045] <Example 2> In Example 2, a sheet heater was created by laminating a first resin film layer, a first adhesive layer, a heat generating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, a third resin film layer, a fourth adhesive layer, and a fourth resin film layer in this order, with the main surfaces of adjacent layers being in close contact with each other. That is, the heater 1A of the present invention described above was created.

[0046] Also, in Example 2, the following were used for each layer. · First resin film layer: PTFE film, thickness 25 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, and fourth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, and fourth resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 460 μm

[0047] <Example 3> In Example 3, the heater 1A of the present invention was created in the same manner as in Example 2.

[0048] Also, in Example 3, the following were used for each layer. · First resin film layer: PTFE film, thickness 50 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, and fourth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, and fourth resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 485 μm

[0049] <Example 4> In Example 4, the heater 1A of the present invention similar to that of Example 2 was fabricated.

[0050] Also, in Example 4, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heating layer: Stainless steel fiber sheet, thickness 35 μm · Second, third, and fourth adhesive layers: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second, third, and fourth resin film layers: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 535 μm

[0051] <Example 5> In Example 5, the heater 1A of the present invention similar to that of Example 2 was fabricated.

[0052] Also, in Example 5, the following were used for each layer. · First resin film layer: PTFE film, thickness 150 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heating layer: Stainless steel fiber sheet, thickness 35 μm · Second, third, and fourth adhesive layers: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second, third, and fourth resin film layers: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 585 μm

[0053] <Example 6> In Example 6, the heater 1A of the present invention similar to that of Example 2 was fabricated.

[0054] In Example 6, the following were used for each layer. · First resin film layer: PTFE film, thickness 200 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, and fourth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, and fourth resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 635 μm

[0055] <Example 7> In Example 7, a sheet heater was fabricated in which a first resin film layer, a first adhesive layer, a heating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, a third resin film layer, a fourth adhesive layer, a fourth resin film layer, a fifth adhesive layer, and a fifth resin film layer were laminated in this order, and the main surfaces of adjacent layers were in close contact with each other. That is, the heater 1B of the present invention described above was fabricated.

[0056] In Example 7, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, fourth adhesive layer, and fifth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, fourth resin film layer, and fifth resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 660 μm

[0057] <Example 8> In Example 8, a sheet heater was created by laminating a first resin film layer, a first adhesive layer, a heat generating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, a third resin film layer, a fourth adhesive layer, a fourth resin film layer, a fifth adhesive layer, a fifth resin film layer, a sixth adhesive layer, and a sixth resin film layer in this order, with the main surfaces of adjacent layers in close contact with each other. That is, the heater 1C of the present invention described above was created.

[0058] Also, in Example 8, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, fourth adhesive layer, fifth adhesive layer, and sixth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, fourth resin film layer, fifth resin film layer, and sixth resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 785 μm

[0059] <Comparative Example 1> In Comparative Example 1, a sheet heater was created by laminating a first resin film layer, a first adhesive layer, a heat generating layer, a second adhesive layer, and a second resin film layer in this order, with the main surfaces of adjacent layers in close contact with each other.

[0060] Also, in Comparative Example 1, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · Total thickness: 285 μm

[0061] <Comparative Example 2> In Comparative Example 2, in the same manner as in Comparative Example 1, a sheet heater was fabricated in which a first resin film layer, a first adhesive layer, a heat generating layer, a second adhesive layer, and a second resin film layer were laminated in this order, and the main surfaces of adjacent layers were in close contact with each other.

[0062] Also, in Comparative Example 1, the following were used for each layer. · First resin film layer: PTFE film, thickness 100 μm, relative permittivity = 2.1 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer: PTFE film, thickness 200 μm, relative permittivity = 2.1 · Total thickness: 385 μm

[0063] <Comparative Example 3> In Comparative Example 3, a heater having the same configuration as the heater 1A of the present invention in Example 2 was fabricated.

[0064] However, in Comparative Example 3, the following were used for each layer. · First resin film layer: PI coating, thickness 50 μm, relative permittivity = 3.5 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heat generating layer: Stainless steel fiber sheet, thickness 35 μm · Second, third, and fourth adhesive layers: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second, third, and fourth resin film layers: PI coating, thickness 50 μm, relative permittivity = 3.5 · Total thickness: 335 μm

[0065] <Comparative Example 4> In Comparative Example 4, a heater having the same configuration as the sheet heater 1C in Example 8 was fabricated.

[0066] However, in Comparative Example 4, the following were used for each layer. · First resin film layer: PI coating, thickness 50 μm, relative permittivity = 3.5 · First adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Heating layer: Stainless steel fiber sheet, thickness 35 μm · Second adhesive layer, third adhesive layer, fourth adhesive layer, fifth adhesive layer, and sixth adhesive layer: Fluororubber, thickness 25 μm, relative permittivity 2.8, AFLAS 100H (manufactured by AGC, Inc.) · Second resin film layer, third resin film layer, fourth resin film layer, fifth resin film layer, and sixth resin film layer: PI coating, thickness 50 μm, relative permittivity = 3.5 · Total thickness: 485 μm

[0067] <Measurement of leakage current> For each of the sheet heaters of Examples 1 to 8 and Comparative Examples 1 to 4 obtained as described above, the leakage current was measured. As the method for measuring the leakage current, a withstand voltage tester "HIOKI 3158 ac withstanding voltage hitester" manufactured by HIOKI was used. Then, of the two electrodes provided in the withstand voltage tester, one was connected to the heater of the present invention and the other was connected to an aluminum plate having a larger area than the heater. After that, the aluminum plate was placed on a horizontal plane, and the main surface of the heater of the present invention was overlapped so that the main surfaces were in contact with each other. Further, a weight was placed on top to bring the main surface of the aluminum plate into close contact with the main surface of the heater of the present invention. Then, a constant voltage (in this case, 0.2 kV or 1.5 kV) was applied and held for one minute, and the current flowing during that time was measured as the leakage current.

[0068] The leakage current was measured for each of the cases of 0.2 kV and 1.5 kV. Also, as shown in Table 1, for the case of 1.5 kV, the performance was evaluated according to the degree of leakage current and scored from 0 to 3 points. The results are shown in Table 2.

[0069] <Piping followability> For each of the sheet heaters of Examples 1 to 8 and Comparative Examples 1 to 4 obtained as described above, the piping followability was evaluated. Specifically, the ease of winding when each sheet heater was wound around a pipe was evaluated such that the first resin film layer was on the outside, that is, the second to sixth resin film layers were in close contact with the outer surface of the pipe. Here, pipes with diameters of Φ20 mm, Φ50 mm, and Φ100 mm were prepared, and for each pipe, evaluation was performed according to the criteria shown in Table 1 and scored from 0 to 3 points. The results are shown in Table 2.

[0070]

Table 1

[0071]

Table 2

[0072] Regarding the leakage current, in the case of the sheet heaters of Examples 1 to 8, low values were obtained in both the cases of 0.2 kV and 1.5 kV as shown in Table 2. In particular, in the cases of Example 7 and Example 8, the leakage current was low and received high evaluations (◎, 3 points). In contrast, the leakage current of the sheet heaters of Comparative Examples 1 to 4 was a high value exceeding 0.3 mA in the case of 1.5 kV, so low evaluations were given (×, 0 points).

[0073] Regarding the piping followability, in the case of the sheet heaters of Examples 1 to 8, as shown in Table 2, they could be wound around any of the pipes. In contrast, in the case of the sheet heater of Comparative Example 4, it could not be wound around the thin pipes of Φ20 mm and Φ50 mm.

[0074] In order to evaluate whether the leakage current and the pipe followability are compatible, the product of the evaluation (score) of the leakage current and the evaluation (total score) of the pipe followability was obtained. As shown in the column of "Comprehensive Evaluation" in Table 2, in the case of the sheet heaters of Examples 1 to 8, the comprehensive evaluation was high in all cases.

Explanation of Signs

[0075] 1 Heater of the present invention 1D Preferred embodiment of the heater of the present invention 5 Heating layer 11 First resin film layer 12 Second resin film layer 13 Third resin film layer 14 Fourth resin film layer 15 Fifth resin film layer 16 Sixth resin film layer 17 Seventh resin film layer 21 First adhesive layer 22 Second adhesive layer 23 Third adhesive layer 24 Fourth adhesive layer 25 Fifth adhesive layer 26 Sixth adhesive layer 27 Seventh adhesive layer 30 Heated object

Claims

1. A first resin film layer, a first adhesive layer, a heating layer, a second adhesive layer, a second resin film layer, a third adhesive layer, and a third resin film layer are laminated in this order, and the main surfaces of adjacent layers are in close contact with each other. The first resin film layer, the second resin film layer, and the third resin film layer are all made of a material having a relative dielectric constant of 1 to 2.

5. The first adhesive layer, the second adhesive layer, and the third adhesive layer are all made of fluororubber, a sheet heater.

2. Furthermore, A fourth adhesive layer and a fourth resin film layer are laminated in this order on the outside of the third resin film layer, Or, In addition to the fourth adhesive layer and the fourth resin film layer on the outside of the third resin film layer, a fifth adhesive layer and a fifth resin film layer are laminated in this order, Or, In addition to the fourth adhesive layer, the fourth resin film layer, the fifth adhesive layer, and the fifth resin film layer on the outside of the third resin film layer, a sixth adhesive layer and a sixth resin film layer are laminated in this order, Or, In addition to the fourth adhesive layer, the fourth resin film layer, the fifth adhesive layer, the fifth resin film layer, the sixth adhesive layer, and the sixth resin film layer on the outside of the third resin film layer, a seventh adhesive layer and a seventh resin film layer are laminated in this order, The main surfaces of adjacent layers are in close contact with each other. The fourth resin film layer, the fifth resin film layer, the sixth resin film layer, and the seventh resin film layer are all made of a material having a relative dielectric constant of 1 to 2.

5. The fourth adhesive layer, the fifth adhesive layer, the sixth adhesive layer, and the seventh adhesive layer are all made of fluororubber, the sheet heater according to Claim 1.

3. At least one selected from the group consisting of the first resin film layer, the second resin film layer, the third resin film layer, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer, and the seventh resin film layer is made of a fluororesin, the sheet heater according to Claim 2.

4. The thickness of at least one selected from the group consisting of the first resin film layer, the second resin film layer, the third resin film layer, the fourth resin film layer, the fifth resin film layer, the sixth resin film layer, and the seventh resin film layer is 10 to 300 μm, the sheet heater according to Claim 2 or 3.

5. 5. The sheet heater according to claim 1, wherein the heat generating layer is made of a metal fiber sheet.

6. 6. The sheet-type heater according to claim 2, wherein at least one selected from the group consisting of the first adhesive layer, the second adhesive layer, the third adhesive layer, the fourth adhesive layer, the fifth adhesive layer, the sixth adhesive layer, and the seventh adhesive layer has a thickness of 5 to 100 μm.

7. 7. The sheet heater according to claim 1, wherein the total thickness is 100 to 1000 μm.

8. A pipe having a sheet-like heater described in any one of claims 1 to 7 wrapped around its surface so that the first resin film layer is on the outside.

9. The piping described in claim 8, having a diameter of φ20 to φ100 mm.

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