Film-shaped heater

Abstract

The present invention addresses the problem of providing a film-shaped heater having higher insulation properties. Said problem is solved by this film-shaped heater, which has a heat-generating layer interposed between a first insulating layer and a second insulating layer, and has a main surface with projections and recesses thereon. Defining D1 as the shortest distance in a direction parallel to the main surface at a location X where the distance between the heat-generating layer and another heat-generating layer is shortest in a cross-section obtained by cutting said heater in a direction parallel to the thickness direction, and D2 as the length of a section at the location X where an A layer in contact with one main surface of the heat-generating layer and a B layer in contact with another main surface are in mutual contact and said mutual contact is in a direction parallel to the main surfaces, D2 / D1 is at least 0.6 but less than 1.

Description

Film-type heater

[0001] This disclosure relates to a film-type heater.

[0002] Several sheet-type heaters have been proposed conventionally.

[0003] Patent Document 1 describes a planar heater comprising a planar heating element and an insulating layer that adheres closely to and covers the planar heating element, which is attached to the curved surface of a support, characterized in that the insulating layer has irregularities formed on its surface, and the arrangement direction of the irregularities on the insulating layer surface portion that stretches during attachment is inclined with respect to the stretching direction.

[0004] Patent No. 4655255

[0005] It is preferable that the film-type heater has higher insulation properties due to the insulating layer. Furthermore, it is preferable that the film-type heater exhibits minimal localized heating. This disclosure provides a film-type heater with higher insulation properties and minimal localized heating.

[0006] This disclosure relates to a film-type heater in which a heating layer is sandwiched between a first insulating layer and a second insulating layer, wherein the main surface has irregularities, and at a location X where the shortest distance is between one heating layer and another heating layer in a cross-section obtained by cutting in a direction parallel to the thickness direction, the shortest distance in the direction parallel to the main surface is D1, and at that location X, when layer A, which is in contact with one main surface of the heating layer, and layer B, which is in contact with the other main surface, are in contact with each other, and the length of the contact portion in the direction parallel to the main surface is D2, D2 / D1 is 0.6 or more and less than 1.

[0007] Such a film-like heater will also be referred to as the "heater of this disclosure" below.

[0008] According to this disclosure, it is possible to provide a film-type heater that has higher insulation properties and less localized heating.

[0009] Figure 1(a) is a schematic view of the main surface of the heater of this disclosure as seen from the direction perpendicular thereto, and Figure 1(b) is a cross-sectional view taken along line A-A in Figure 1(a). Figure 2 is a thermographic image of the film heater obtained in Example 2.

[0010] The heater of this disclosure will be described with reference to the figures. The heater of this disclosure is not limited to the embodiments shown in the figures. All figures are schematic diagrams, and the dimensions and size of the heater of this disclosure may differ from those shown in the figures.

[0011] Figure 1(a) is a schematic diagram of the main surface of the heater of this disclosure as viewed from the direction perpendicular to it, and Figure 1(b) is a cross-sectional view taken along line A-A in Figure 1(a). However, in Figure 1(b), the gap between the two heating layers 7 is shown as large and does not match the size of the gap in Figure 1(a).

[0012] The heater 1 of this disclosure consists of a heating layer 7 sandwiched between a first insulating layer 3 and a second insulating layer 5. The main surfaces of the first insulating layer 3, the heating layer 7, and the second insulating layer 5 are in close contact with each other. In addition, the ratio (D2 / D1) of the length of the portion where the first insulating layer 3 and the second insulating layer 5 are in contact (D2, described later) to the shortest distance (D1, described later) between one heating layer 7 and another heating layer 7 is within a specific range. In this case, at least a portion of the end surface of the heating layer 7 does not adhere well to the first insulating layer 3 and / or the second insulating layer 5, resulting in a gap. For example, Figure 1(b) shows a state where the first insulating layer 3 is not in close contact with the end surface of the heating layer 7, and a gap V is formed surrounded by the end surface of the heating layer 7, the main surface of the first insulating layer 3, and the main surface of the second insulating layer 5. By having this gap V, the heater of this disclosure exhibits the effect of suppressing localized overheating. This is because the air in the gap V provides thermal insulation. The inventors estimate that by optimizing the ratio of D2 / D1 and the size and shape of this gap V, improvements in insulation and suppression of localized heating will be achieved.

[0013] In the heater 1 of this disclosure, it is preferable that at least one main surface of the heating layer 7 is covered by a first insulating layer 3 or a second insulating layer 5, and it is preferable that both main surfaces of the heating layer 7 are covered by the first insulating layer 3 or the second insulating layer 5. In Figure 1(a), the location where the heating layer 7 is located is indicated by a dotted line.

[0014] When the heater 1 of this disclosure is viewed from a direction perpendicular to its main surface, the heating layer 7 preferably forms a strip-shaped electrical channel, as shown in Figure 1(a). In this case, as shown in Figure 1(b), the heater 1 of this disclosure has irregularities on its main surface. This is because the main surface of the heater 1 of this disclosure is recessed where the heating layer 7 does not exist. By having an irregular shape, the heater 1 of this disclosure can have high thermal insulation properties when installed in piping or the like. Such a strip-shaped electrical channel can be formed, for example, by patterning metal foil, metal mesh, or metal fiber sheet. The shape of the electrical channel in the heating layer is not limited.

[0015] Here, for example, as shown in Figure 1(b), a region including the area where the distance between one heating layer 7 and another heating layer 7 is shortest in a cross-section obtained by cutting the heater 1 of the present disclosure in a direction parallel to the thickness direction (a direction parallel to the perpendicular to the main surface of the heater 1 of the present disclosure). In Figure 1(a), this corresponds to the area labeled X. In other words, location X refers to the area in the heater 1 of the present disclosure where the gap between one heating layer 7 and another heating layer 7 is smallest. However, location X is the area where the distance between one heating layer 7 and another heating layer 7 is 500 μm or more and is the shortest.

[0016] Then, when the heater 1 of this disclosure is cut in a direction parallel to the thickness direction at such location X to obtain a cross-section as shown in Figure 1(b), the shortest distance between one heating layer 7 and another heating layer 7 in the direction parallel to the main surface of that cross-section (the left-right direction in Figure 1(b)) is defined as D1.

[0017] Furthermore, at location X, layer A, which is in contact with one main surface of the heating layer 7, and layer B, which is in contact with the other main surface, are in contact with each other. Here, layers A and B are layers in contact with the heating layer 7. In the embodiment shown in Figure 1, the first insulating layer 3 and the second insulating layer 5 are in contact with the heating layer 7, so the first insulating layer 3 corresponds to layer A and the second insulating layer 5 corresponds to layer B. That is, layer A may be a different layer from the first insulating layer 3, or it may be the first insulating layer 3 itself. Similarly, layer B may be a different layer from the second insulating layer 5, or it may be the second insulating layer 5 itself. In addition, in the heater of this disclosure, the heating layer is sandwiched between the first insulating layer and the second insulating layer, and there may be another layer between the first insulating layer and the heating layer 7, or between the second insulating layer and the heating layer 7, that does not correspond to either the first insulating layer or the second insulating layer. If such another layer exists, that other layer corresponds to layer A or layer B.

[0018] The first insulating layer and the second insulating layer may each consist of multiple layers. For example, if multiple insulating sheets are stacked and in close contact with the heating layer 7, these multiple insulating sheets are treated together as the first insulating layer or the second insulating layer. In the embodiment shown in Figure 1(b), the second insulating layer 5 consists of four insulating sheets. In such a case, the collection of the four insulating sheets is considered the second insulating layer 5. Also, for example, if the insulating sheets are bonded to the heating layer with an adhesive, the adhesive usually has insulating properties, so the layer consisting of the insulating sheets and the adhesive is treated together as the first insulating layer or the second insulating layer.

[0019] The definitions of the first insulating layer and the second insulating layer will be explained later.

[0020] Then, let D2 be the length of the portion where the first insulating layer 3 (layer A) and the second insulating layer 5 (layer B) are in contact (the length of the contact portion in a direction parallel to the main surface).

[0021] In the heater 1 of this disclosure, D2 / D1 is 0.6 or more and less than 1, preferably 0.8 to 0.95, and more preferably 0.88 to 0.93. This is because the insulating properties of the heater of this disclosure are further enhanced and localized heating is reduced.

[0022] In the heater of the present disclosure, when the main surface is viewed from the direction perpendicular to it, the area of ​​the main surface is S1, and the area of ​​the heating layer in the region where the heating layer exists at any point in the thickness direction of the main surface is S2, then S2 / S1 is preferably 0.2 to 0.9, more preferably 0.3 to 0.9, and even more preferably 0.5 to 0.9. When the main surface of the heater of the present disclosure is viewed from the direction perpendicular to it, for example as shown in Figure 1(a), the area of ​​the first insulating layer 3 that makes up the main surface is S1, and the area of ​​the heating layer in the region where the heating layer 7 exists is S2.

[0023] In the heater of this disclosure, when a cross-section is obtained by cutting in a direction parallel to the thickness direction as shown in Figure 1(b), T1 is the average value of the thicknesses of the two heating layers 7, 7 at location X, and T2 is the total thickness of the first insulating layer 3 and layer A, then T1 / T2 is preferably 0.1 to 3, more preferably 0.3 to 2.5, and even more preferably 0.5 to 2. Note that if the first insulating layer is layer A, T2 represents the thickness of the first insulating layer.

[0024] In the heater of this disclosure, when a cross-section is obtained by cutting in a direction parallel to the thickness direction as shown in Figure 1(b), T1 is the average value of the thicknesses of the two heating layers 7, 7 at location X, and T3 is the sum of the thicknesses of the second insulating layer 5 and the B layer, T1 / T3 is preferably 0.1 to 3, more preferably 0.12 to 1, and even more preferably 0.15 to 0.5. Note that when the second insulating layer is the B layer, T3 means the thickness of the second insulating layer.

[0025] The thickness of each layer constituting the heater of this disclosure is determined by observing a cross-section obtained by cutting in a direction parallel to the thickness direction as shown in Figure 1(b) using an optical microscope to obtain a magnified photograph (200x), then measuring the thickness of each layer at 30 randomly selected locations in the magnified photograph, and taking a simple average of these measurements (simple average value).

[0026] <First insulating layer, second insulating layer> The heater of this disclosure has a first insulating layer and a second insulating layer. In the heater of this disclosure, the volume resistivity is measured in accordance with JIS C 2139 and the value is 10 × 10 10A layer with a density of Ω·m or greater shall be designated as the first or second insulating layer.

[0027] The insulating layer is preferably made of materials such as PET (polyethylene terephthalate), PI (polyimide), PP (polypropylene), PE (polyethylene), PEN (polyethylene naphthalate), TAC (triacetylcellulose), or ceramic. This is because these materials have high insulating properties. Among these, an insulating layer made of PI (polyimide) is preferred because it has excellent heat resistance and insulating properties.

[0028] The insulating layer preferably possesses both insulating and thermal conductivity.

[0029] The first insulating layer and the second insulating layer may be the same or different. Alternatively, multiple layers with different insulating properties (e.g., insulating sheets) may be stacked on top of each other to form the first insulating layer or the second insulating layer as a whole.

[0030] The thickness of the insulating layer is not limited, but is preferably 25 to 500 μm, and more preferably 50 to 200 μm.

[0031] The shape and size of the main surface of the insulating layer are not particularly limited. However, since the insulating layer serves to electrically insulate the heating layer from other layers, the size of the main surface of the insulating layer is usually the same as or larger than the main surface of the heating layer.

[0032] <Adhesives> As mentioned above, an adhesive can be used to attach a layer to the heating layer. If the adhesive forms an insulating layer, then the layer made of the adhesive constitutes at least a part of the insulating layer. When an adhesive is used to sandwich the heating layer between the first insulating layer and / or the second insulating layer, if the adhesive forms an insulating layer, then the layer made of the adhesive is considered to be part of the first insulating layer and / or the second insulating layer, and these layers are treated as layer A or layer B. On the other hand, if the adhesive does not form an insulating layer, then the layer made of the adhesive is treated as layer A or layer B. Typically, a layer made of adhesive has insulating properties, so when the first insulating layer and / or the second insulating layer are bonded to the heater of this disclosure using an adhesive, the layer made of the adhesive is considered to be part of the first insulating layer and / or the second insulating layer.

[0033] As the adhesive, for example, acrylic adhesives, silicone adhesives, rubber-based elastomers, thermosetting adhesives, thermoplastic adhesives, fluorine-based adhesives and the like can be used. Further, an adhesive sheet made of the same material can be used instead of the adhesive.

[0034] <Heat Generating Layer> The heat generating layer included in the heater of the present disclosure will be described. The heat generating layer is preferably a sheet-shaped member that generates heat when energized. Further, as described above, it is preferably formed by patterning so as to serve as a belt-shaped electrical flow path. Furthermore, the heat generating layer may be one in which wires made of a heat-generating metal such as nichrome wire are arranged so as to form a layer as a whole.

[0035] The heat generating layer may be, for example, a metal foil, a sheet-shaped metal mesh, a sheet-shaped metal fiber, or a carbon sheet.

[0036] The material of the heat generating layer is not particularly limited as long as it generates heat when energized, and stainless steel is preferable because of its high heat resistance and chemical resistance, but Cu (copper), Al (aluminum), Ni (nickel), nichrome, or carbon may also be used.

[0037] The thickness of the heat generating layer is preferably 20 to 250 µm, more preferably 30 to 150 µm.

[0038] The shape and size of the main surface of the heat generating layer can be appropriately adjusted according to the shape and size of the object to be heated on which the heater of the present disclosure is installed.

[0039] The resistance value of the heat generating layer is preferably 5 to 800 Ω, more preferably 10 to 300 Ω. If the resistance value is too low, excessive output may lead to excessive temperature; conversely, if the resistance value is too high, insufficient output may cause it to take a long time for the temperature to rise. Here, the resistance of the heat generating layer is a value determined in accordance with JIS C 2525.

[0040] The heating layer is preferably composed mainly of sheet-like metal fibers or sheet-like metal mesh using metal fibers, and more preferably of sheet-like metal fiber mesh. Here, "mainly" means 70% by mass or more. That is, it is preferable that 70% by mass or more of the heating layer is metal fibers. It is more preferable that the proportion of metal fibers in the heating layer be 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0041] The proportion of metal fibers contained in the heating layer shall be determined by the following method: The surface of the heating layer is magnified 1,000 times using a scanning electron microscope (SEM) to obtain an SEM image. The area occupied by metal fibers (excluding voids) within the field of view is determined using an image processing device, converted to a volume ratio by raising it to the power of 3 / 2, and then multiplied by the specific gravity to obtain a mass ratio, thereby calculating the metal fiber content.

[0042] The metal mesh is preferably made of stainless steel due to its high heat resistance and chemical resistance. The weaving method of the metal mesh is not particularly limited and may be plain weave, twill weave, plain tatami weave, or twill tatami weave, but plain weave is more preferable.

[0043] The mesh size of the metal mesh is preferably 16 to 800 mesh, more preferably 150 to 280 mesh, and preferably around 200 mesh.

[0044] The metal fibers used in the sheet-like metal mesh preferably have a fiber diameter of 0.01 to 0.1 mm, and more preferably 0.03 to 0.06 mm. Furthermore, the metal mesh is preferably constructed as a sheet (metal mesh sheet) by weaving such metallic fibers. Here, the metal mesh sheet may consist only of metal fibers, but it may also include non-metallic fibers (for example, resin fibers that function as a binder) in addition to metal fibers, to the extent that it does not hinder heat generation.

[0045] Metal mesh sheets have a basis weight of 150 to 1300 g / m². 2preferably 150 to 300 g / m 2 and more preferably . The basis weight is a value determined in accordance with JIS P 8124.

[0046] The density of the metal mesh sheet is 1 to 6 g / cm 3 preferably 2 to 5 g / cm 3 and more preferably . The density of the metal mesh sheet is calculated in accordance with JIS P 8118 as density (g / cm 3 ) = basis weight (g / m 2 ) / (thickness (mm) × 1000).

[0047] In the sheet-like metal fiber, it is preferable that the metal fiber has an equal-area circle equivalent diameter of a cross-section of 2 to 100 µm (preferably 5 to 20 µm) and a length of 2 to 20 mm. The equal-area circle equivalent diameter means the diameter of a circle having the same area as the area of the cross-section. Further, the heat-generating layer is preferably formed into a sheet shape (metal fiber sheet) by innumerable such metallic fibers intricately entangled with each other. The metal fiber sheet may be composed only of metal fibers, but in addition to the metal fibers, it may also contain components other than metal fibers (for example, resin fibers having a function as a binder) within a range that does not impair heat-generating properties. Here, the metal fibers constituting the metal fiber sheet are in contact with each other to such an extent that electricity can flow. It is preferable that the metal fibers are connected to each other at the contact points. For example, it is preferable that the metal fibers are fused to each other at the contact points by having a history of solidification after a part of the metal fibers is melted by sintering at a high temperature.

[0048] The metal fiber sheet is preferably a SUS fiber sheet because of its high heat resistance and chemical resistance. Examples of the SUS fiber sheet include stainless steel fiber sheets (for example, Tommy Fyrec SS, manufactured by Tomoegawa Paper Co., Ltd.).

[0049] The metal fiber sheet has a basis weight of 25 g / m 2 or more is preferable, 50 g / m 2 or more is more preferable. Further, 1000 g / m 2 or less is preferable, 200 g / m 2The following is more preferable. The basis weight shall be the value obtained in accordance with JIS P 8124.

[0050] The density of the metal fiber sheet is 1.0 to 10.0 g / cm³. 3 Preferably, it is 1.4 to 2.0 g / cm³. 3 It is more preferable that the concentration be 1.7 g / cm³. 3 It is preferable that the density is within a certain range. The density of the metal fiber sheet shall be in accordance with JIS P 8118, with a density of (g / cm³). 3 )=Basic weight (g / m 2 The value obtained by ) / (thickness (mm) × 1000) shall be used.

[0051] Metal fiber sheets can be manufactured by either a dry-laid nonwoven fabric manufacturing method or a wet-laid papermaking method. When manufactured by the wet-laid papermaking method, countless metallic fibers with an equivalent diameter of 2 to 100 μm and a length of 2 to 20 mm are stirred in a dispersion medium (water, organic solvent, etc.), then an organic flocculant is added, and the sheet is formed using a rectangular papermaking machine (such as those manufactured by Toyo Seiki Co., Ltd.), and then dried using a ferrotype drying device until the basis weight is 50 to 1100 g / m². 2 A dried sheet is obtained. Then, by firing at 400 to 1300°C, a metal fiber sheet is obtained. In principle, it is preferable that no organic flocculant remains in the metal fiber sheet.

[0052] <Sheet-like Substrate> The heater of this disclosure may have a sheet-like substrate on the outer side (main surface side where the heating layer is not present) of the first insulating layer and / or the second insulating layer. However, if the sheet-like substrate has insulating properties, it may be considered as part of the first insulating layer or the second insulating layer.

[0053] When the heater of this disclosure includes a sheet-like substrate, the sheet-like substrate is preferably made of a material that has insulating and flexible properties, such as PET (polyethylene terephthalate), PI (polyimide), PP (polypropylene), PE (polyethylene), PEN (polyethylene naphthalate), or TAC (triacetylcellulose). The sheet-like substrate may also be made of a fluororesin. Examples of fluororesins include polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer. Furthermore, the sheet-like substrate may be a high-strength, high-insulating sheet made by impregnating glass, aramid (aromatic polyamide resin), carbon fiber, or other reinforcing fibers with a fluororesin.

[0054] The thickness of the sheet-like substrate is not particularly limited, but is preferably 25 to 500 μm, and more preferably 50 to 200 μm.

[0055] <Terminals, connecting wires, etc.> Preferably, the heating layer has terminals connected to it, connecting wires extending from the terminals, and the connecting wires connected to a power supply. Preferably, the heating layer is energized by supplying electricity from the power supply, causing the heating layer to generate heat. The terminals, wiring, and power supply mentioned here are not shown in Figure 1. These may be conventionally known.

[0056] In the heater of this disclosure, the peel strength of layers A and B is preferably 1 N / 10 mm or more, and more preferably 5 N / 10 mm or more. This is because contact between the heating elements of the heater of this disclosure is suppressed to ensure insulation and prevent short circuits. In addition, even when the heater is subjected to stress during installation on the object to be heated, such as when installed in piping, peeling of layers A and B is suppressed, making installation on the object to be heated easier.

[0057] The heater of this disclosure preferably has a stiffness of 10 to 500 mN, and more preferably 20 to 200 mN. This is because it allows the heater of this disclosure to stand on its own. In addition, even when the heater is subjected to stress during installation on a heated object, such as when installed in piping, its good flexibility makes installation on the heated object easy. Here, the stiffness is a value determined using a Gurley tester in accordance with JIS L-1085.

[0058] The thickness of the heater in this disclosure is not limited, but is preferably 1000 to 1500 μm, and more preferably 200 to 400 μm.

[0059] The heater of this disclosure preferably has an insulation resistance of 100 MΩ or more, more preferably 200 MΩ or more, and even more preferably 300 MΩ or more. The insulation resistance of the heater of this disclosure shall be the value obtained by measuring it using the method shown in the embodiments described later.

[0060] The present disclosure includes the following embodiments (1) to (6): (1) A film-like heater having a heating layer sandwiched between a first insulating layer and a second insulating layer, wherein the main surface has irregularities, and at a location X where the shortest distance between one heating layer and another heating layer in a cross-section obtained by cutting in a direction parallel to the thickness direction is D1, and at location X, when layer A, which is in contact with one main surface of the heating layer, and layer B, which is in contact with the other main surface, are in contact with each other, and the length of the contact portion in a direction parallel to the main surface is D2, D2 / D1 is 0.6 or more and less than 1. (2) The film-like heater according to (1) above, wherein the heating layer is made of metal fibers. (3) The film-like heater according to (1) or (2) above, wherein the peel strength of layer A and layer B is 1 N / 10 mm or more. (4) A film-type heater according to any of (1) to (3) above, wherein when the main surface is viewed from the direction perpendicular to it, the area of ​​the main surface is S1, and the area of ​​the region on the main surface where the heating layer exists at any point in the thickness direction is S2, and S2 / S1 is 0.2 to 0.9. (5) A film-type heater according to any of (1) to (4) above, wherein in a cross section obtained by cutting in a direction parallel to the thickness direction, when the average value of the thicknesses of the two heating layers at point X is T1, and the total thickness of the first insulating layer and the A layer is T2, T1 / T2 is 0.1 to 3. (6) A film-type heater according to any of (1) to (5) above, wherein in a cross section obtained by cutting in a direction parallel to the thickness direction, when the average value of the thicknesses of the two heating layers at point X is T1, and the total thickness of the second insulating layer and the B layer is T3, T1 / T3 is 0.1 to 3. (7) A film-type heater according to any of (1) to (6) above, wherein the fuzziness is 10 to 500 mN.

[0061] The present disclosure will be specifically described below with reference to examples. However, the present disclosure is not limited to these examples.

[0062] (Example 1) A heater of the present disclosure similar to that shown in Figure 1 was fabricated by the following method. First, three thermoplastic polyimide (PI) films with a thickness of 50 μm and the same shape were prepared and laminated. The resulting laminate corresponds to the second insulating layer 5 shown in Figure 1. Next, a patterned metal mesh sheet was prepared as shown in Figure 1(a). This corresponds to the heating layer 7 shown in Figure 1. Here, the metal mesh sheet is made of plain weave, has a mesh count of 200, and a thickness of 100 μm. The metal mesh sheet is also made of metal fibers, and the fiber diameter of the metal fibers is 0.03 mm. Next, one sheet of thermoplastic polyimide (PI) film identical to the three thermoplastic polyimide (PI) films that make up the second insulating layer 5 was prepared. As shown below, this corresponds to the first insulating layer 3 shown in Figure 1. Then, the aforementioned metal mesh sheet was sandwiched between this one thermoplastic polyimide (PI) film and the laminate made of the three thermoplastic polyimide (PI) films mentioned above, and then a heat press was performed on the laminate to obtain a film-like heater. Here, the heat pressing was performed using a vacuum heat press machine at 330°C for 10 minutes. In this way, a heater of the present disclosure similar to that shown in Figure 1 was obtained. The only difference from the one shown in Figure 1 is the number of second insulating layers. That is, in the embodiment shown in Figure 1, there are four second insulating layers 5, but in the film-like heater obtained in Example 1 (and similarly in Examples 2 to 4 described later), there are three thermoplastic polyimide (PI) films corresponding to the second insulating layer 5.

[0063] (Example 2) In Example 1, a metal mesh sheet with a thickness of 100 μm was used, but in Example 2, a metal mesh sheet with a thickness of 195 μm was used. Everything else was the same as in Example 1 to obtain a film-type heater.

[0064] (Example 3) In Example 1, a metal mesh sheet with a thickness of 100 μm was used, but in Example 3, a metal mesh sheet with a thickness of 200 μm was used. Everything else was the same as in Example 1 to obtain a film-type heater.

[0065] (Example 4) In Example 1, a metal mesh sheet with a thickness of 100 μm was used, but in Example 4, a metal mesh sheet with a thickness of 220 μm was used. Everything else was the same as in Example 1 to obtain a film-type heater.

[0066] <Measurement of D1 and D2> Next, each of the film heaters obtained in Examples 1 to 4 was cut in a direction parallel to the thickness direction to obtain a cross-section as shown in Figure 1(b). Then, D1 and D2 were measured in that cross-section. The results are shown in Table 1. Note that D1 and D2 were measured using a Keyence VHX-6000 optical microscope, digital microscope, and observed at 200x magnification.

[0067]

[0068] <Measurement of Insulation Resistance> For each film heater obtained in Examples 1 to 4, the insulation resistance was measured using an insulation resistance meter, analog megohmmeter, IR4041-10 / 11, manufactured by HIOKI E.E. CORPORATION. As a result, all film heaters had an insulation resistance value of 300 MΩ or higher.

[0069] <Evaluation of Localized Heating> The film heaters obtained in Examples 1 to 4 were each energized and heated to 200°C by applying a voltage of 100V. Then, the temperature distribution on the main surface of the film heater was observed using thermography. As a result, no localized heating was observed in any of the film heaters. Among these, the film heater of Example 2 showed the least amount of localized heating. Figure 2 shows a thermographic image of the film heater obtained in Example 2.

[0070] (Example 5) When obtaining a film-like heater by hot pressing, in Example 2 the process was carried out at 330°C for 10 minutes, while in Example 5 it was carried out at 330°C for 1 minute. All other aspects were the same as in Example 2 to obtain the film-like heater. When D1 and D2 were measured using the above method, the ratio of D2 / D1 was in the range of 0.6 or more and less than 1.

[0071] (Example 6) When obtaining a film-like heater by hot pressing, in Example 2 the process was carried out at 330°C for 10 minutes, but in Example 6 the process was carried out at 290°C for 10 minutes. All other aspects were the same as in Example 2 to obtain the film-like heater. When D1 and D2 were measured using the above method, the ratio of D2 / D1 was in the range of 0.6 or more and less than 1.

[0072] <Measurement of Peel Strength> In each of the film-like heaters obtained in Examples 2, 5, and 6, a sample was obtained by cutting out the portion where the thermoplastic polyimide (PI) film corresponding to the first insulating layer (layer A) and the laminate consisting of three thermoplastic polyimide (PI) films corresponding to the second insulating layer (layer B) were in contact. Here, the sample was a rectangle of 5 mm × 50 mm. In addition, five samples were cut out from each film-like heater. Next, the peel strength of layers A and B in each sample was measured by a T-peel test. Here, a Tensilon universal material tester, RTC-1210A manufactured by A&D Company, Limited was used as the measuring device. The tensile speed of the test was set to 50 mm / min. The results are shown in Table 2.

[0073]

[0074] <Measurement of stiffness> Six samples were cut from the film heater obtained in Example 2. Each sample was sized such that the heating layer appeared in three locations in the cross-section obtained when cut in a direction parallel to its thickness, as shown in Figure 1(b). In addition, the heating layer was always present at the edges of the sample, and no areas where the first insulating layer and the second insulating layer were in contact were observed. The stiffness of the six samples was measured using a Gurley tester in accordance with JIS L-1085. The stiffness was measured for each of the two main surfaces of the sample, and the average value was taken as the stiffness value of that sample. The results are shown in Table 3.

[0075]

[0076] This application claims priority based on Japanese Patent Application No. 2025-48318, filed on 24 March 2025, and incorporates all of its disclosures herein.

[0077] 1 Heater of the present disclosure 3 First insulating layer 5 Second insulating layer 7 Heating layer V Gap

Claims

1. A film-type heater having a heating layer sandwiched between a first insulating layer and a second insulating layer, wherein the main surface has irregularities, and at a point X where the shortest distance between one heating layer and another heating layer is obtained by cutting in a direction parallel to the thickness direction, the shortest distance in the direction parallel to the main surface is D1, and at that point X, when layer A, which is in contact with one main surface of the heating layer, and layer B, which is in contact with the other main surface, are in contact with each other, and the length of the contact portion in the direction parallel to the main surface is D2, D2 / D1 is 0.6 or more and less than 1.

2. The film-like heater according to claim 1, wherein the heating layer is made of metal fibers.

3. The film-like heater according to claim 1 or 2, wherein the peel strength of the A layer and the B layer is 1 N / 10 mm or more.

4. A film-type heater according to any one of claims 1 to 3, wherein when the main surface is viewed from the direction perpendicular to it, the area of ​​the main surface is S1, and the area of ​​the region on the main surface where the heating layer exists at any point in the thickness direction is S2, and S2 / S1 is 0.2 to 0.

9.

5. In a cross-section obtained by cutting in a direction parallel to the thickness direction, when T1 is the average value of the thicknesses of the two heating layers at location X, and T2 is the total thickness of the first insulating layer and the A layer, T1 / T2 is 0.1 to 3, the film-like heater according to any one of claims 1 to 4.

6. In a cross-section obtained by cutting in a direction parallel to the thickness direction, when T1 is the average value of the thicknesses of the two heating layers at location X, and T3 is the total thickness of the second insulating layer and the B layer, T1 / T3 is 0.1 to 3, the film-like heater according to any one of claims 1 to 5.

7. A film-type heater according to any one of claims 1 to 6, wherein the fuzziness is 10 to 500 mN.

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