Planar heating element, laminate, vehicle interior material, and light emitting display device

Abstract

To provide a planar heating element capable of performing light rendition without reducing production efficiency and with a simple configuration, while preventing uneven tactile, and a laminate, a vehicle interior material, and a light emitting display device which include the planar heating element.SOLUTION: A planar heating element 10 includes a substrate 15 that includes an elastic rubber body 11, and a heating layer 20 that is disposed on one surface 15A of the substrate 15.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a planar heating element used as a heating device, a laminate including the planar heating element, an interior material for a vehicle, and a light-emitting display device.

Background Art

[0002] Conventionally, a heater may be attached to an interior material of a vehicle such as an automobile in order to improve the comfort of passengers in a cold environment. As an interior material with a heater attached, for example, the interior material described in Patent Document 1 is known as the prior art. The interior material described in Patent Document 1 includes a heat generating portion and a heat radiating portion provided so as to be in contact with the heat generating portion and including a molded body containing a first resin and a first fiber. Thereby, the surface heating temperature of the interior material described in Patent Document 1 becomes uniform. In the interior material described in Patent Document 1, grooves or the like are provided in the members constituting the interior material, and it is considered that by arranging the interior material inside the grooves, the unevenness of the nichrome wire does not appear on the surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when grooves or the like are provided in the members constituting the interior material as in Patent Document 1, there is a problem that the number of processing steps of the interior material increases and the production efficiency decreases. In addition, there may be a case where it is desired to transmit light from a light source such as an LED through the interior material to achieve a light effect of the interior material. In this case, the light transmissivity of the interior material described in Patent Document 1 is insufficient, and the light effect of the interior material may not be achieved. Furthermore, simply enclosing the grooves, the nichrome wire has no flexibility, and the flexibility of the interior material described in Patent Document 1 may become insufficient.

[0005] Therefore, an object of the present invention is to provide a planar heating element capable of light effects while preventing an uneven touch feeling with a simple configuration without reducing production efficiency.

Means for Solving the Problems

[0006] As a result of intensive studies, the present inventor has found that the above problems can be solved by disposing a heating layer on one surface of a base material including an elastic rubber body, and has completed the following present invention. That is, the present invention provides the following [1] to

[15] . [1] A planar heating element including a base material containing an elastic rubber body and a heating layer disposed on one surface of the base material. [2] The planar heating element according to [1] above, wherein the heating layer is disposed so as to be in direct contact with the elastic rubber body. [3] The planar heating element according to [1] above, wherein an underlayer is formed on the surface of the base material in contact with the heating layer. [4] The planar heating element according to any one of [1] to [3] above, wherein at least a part of the heating layer is buried inside the surface of the elastic rubber body. [5] The planar heating element according to any one of [1] to [4] above, wherein the heating layer is formed by a printing method. [6] The planar heating element according to any one of [1] to [5] above, wherein the rubber constituting the elastic rubber body is silicone rubber. [7] The planar heating element according to [6] above, wherein the rubber constituting the elastic rubber body contains a silicone gel. [8] The planar heating element according to any one of [1] to [7] above, wherein the surface roughness Ra of the surface of the base material on the side where the heating layer is provided is 5 μm or less. [9] The planar heating element according to any one of [1] to [8] above, wherein the heating layer has a thickness of 100 μm or less and is formed of a conductive material.

[10] A laminate including the planar heating element according to any one of [1] to [9] and a skin adhered to the planar heating element directly or via another layer.

[11] The skin is the laminate according to

[10] above, which is adhered to the surface of the planar heating element on the side where the heating layer is provided.

[12] The laminate according to

[10] or

[11] above, in which at least a part of the heating layer is embedded inside the surface of the elastic rubber body.

[13] An interior material for a vehicle, comprising the planar heating element according to any one of [1] to [9] above, or the laminate according to any one of

[10] to

[12] above.

[14] The interior material for a vehicle according to

[13] above, in which the heating layer is arranged on the interior side and the base material is arranged on the side opposite to the interior side.

[15] A light-emitting display device, comprising the planar heating element according to any one of [1] to [9] above, or the laminate according to any one of

[10] to

[12] above, and a light source.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a planar heating element capable of light effects, a laminate, an interior material for a vehicle, and a light-emitting display device, which have a simple structure, prevent an uneven tactile sensation, and can be produced with high production efficiency without reducing the production efficiency.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] <Planar heating element> Hereinafter, the planar heating element of the present invention will be described with reference to embodiments. FIG. 1 shows a planar heating element according to an embodiment of the present invention. As shown in FIG. 1, a planar heating element 10 according to an embodiment includes a base material 15 made of an elastic rubber body 11 and a heating layer 20 disposed on one surface 15A of the base material 15.

[0010] By having the above configuration, when the planar heating element 10 is in use or when it is assembled to a vehicle interior material or the like, at least a part of the heating layer 20 can be buried inside the elastic rubber body 11 by being pressed from the surface side where the heating layer 20 of the planar heating element 10 is provided. Therefore, it is possible to prevent the surface on the side where the heating layer 20 is provided from having an uneven tactile sensation. Further, since the base material 15 is made of the elastic rubber body 11, it can have light transmissivity. Therefore, the planar heating element 10 can transmit the light of a light source 40 described later and can perform light effects and the like. Furthermore, since no special processing such as providing grooves in the base material 15 is required, the planar heating element 10 can be manufactured with high production efficiency. Note that the light source 40 is preferably disposed on the side of the surface (back surface 15B) opposite to the surface (surface 15A) on which the heating layer 20 of the base material 15 is provided.

[0011] Hereinafter, each member constituting the planar heating element will be described in more detail. [Base material and elastic rubber body] The elastic rubber body 11 is made of rubber. Thereby, the light transmissivity of the vehicle interior material can be improved, and light effects can be achieved with the planar heating element. The elastic rubber body 11 is preferably a non-foamed body. Examples of the rubber constituting the elastic rubber body 11 include silicone rubber, acrylic rubber, urethane rubber, fluororubber, and the like. These rubbers may be used alone or in combination of two or more.

[0012] It is preferable to use silicone rubber as the rubber in the elastic rubber body 11 among those described above. By using silicone rubber for the elastic rubber body, flexibility and light transmittance are improved. In addition, since silicone rubber has high thermal conductivity, heat generated by a light source such as an LED can be dissipated more efficiently. Therefore, for example, when a planar heating element is not used in summer or the like, heating by light from the light source can be prevented, and unnecessary heating of the planar heating element in summer or the like can be prevented. From the viewpoints of flexibility and light transmittance, silicone gel is preferable among silicone rubbers, and it is preferable that the rubber constituting the elastic rubber body contains silicone gel. The silicone gel is not particularly limited, but is preferably a gel-like material obtained by controlling the crosslinking density of an addition-type liquid silicone rubber to 1 / 5 to 1 / 10 of the normal value and curing it. Examples of the silicone gel suitable for the elastic rubber body 11 include "Pantel GEL" manufactured by Sekisui Polymertec Co., Ltd.

[0013] (Addition-type liquid silicone rubber) The addition-type liquid silicone rubber contains vinyl group-containing organopolysiloxane as the main agent, hydrogen organopolysiloxane as the crosslinking agent, and a platinum compound as the catalyst.

[0014] Examples of vinyl group-containing organopolysiloxanes include dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, methyltrifluoropropylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-methyltrifluoropropylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-methyltrifluoropropylsiloxane-methylvinylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-vinylmethylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylsiloxane-vinylmethylsiloxane-diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, vinylmethylsiloxane-methyltrifluoropropylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylpolysiloxane blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-methylvinylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-diphenylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, methyltrifluoropropylpolysiloxane blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-methyltrifluoropropylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-methyltrifluoropropylsiloxane-methylvinylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylpolysiloxane blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups,Linear diorganopolysiloxanes such as dimethylsiloxane·methylvinylsiloxane·diphenylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, methyltrifluoropropylpolysiloxane blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane·methyltrifluoropropylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane·methyltrifluoropropylsiloxane·methylvinylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, dimethylpolysiloxane blocked at both ends with trivinylsiloxy groups, dimethylsiloxane·methylvinylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, dimethylsiloxane·diphenylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, dimethylsiloxane·methylvinylsiloxane·diphenylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, methyltrifluoropropylpolysiloxane blocked at both ends with trivinylsiloxy groups, dimethylsiloxane·methyltrifluoropropylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, dimethylsiloxane·methyltrifluoropropylsiloxane·methylvinylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, and branched-chain organopolysiloxanes containing a small amount of organosilsesquioxane units (for example, methylsilsesquioxane units; (CH3)SiO, 3 / 2 ) in the main chain of each of the linear diorganopolysiloxanes exemplified above.

[0015] Although the viscosity of the vinyl group-containing organopolysiloxane is not particularly limited, from the viewpoints of the handling workability of the silicone rubber composition obtained by mixing the raw materials of the silicone gel, the strength of the obtained silicone gel, and good fluidity, the viscosity at 23°C is preferably 50 to 100,000 mPa·s, and more preferably 100 to 10,000 mPa·s. The viscosity can be measured with a rotational viscometer.

[0016] Hydrogen organopolysiloxanes include, for example, 1,1,3,3 - tetramethyldisiloxane, 1,1,3,3,5,5 - hexamethyltrisiloxane, 1,3,5,7 - tetramethylcyclotetrasiloxane, methylhydrogen siloxane cyclic polymer, methylhydrogen siloxane·dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)silylmethylsilane, tris(dimethylhydrogensiloxy)silylphenylsilane, dimethylhydrogen siloxy - terminated dimethylpolysiloxane, dimethylhydrogen siloxy - terminated methylhydrogen polysiloxane, dimethylhydrogen siloxy - terminated methylhydrogen siloxane·dimethylsiloxane copolymer, dimethylhydrogen siloxy - terminated methylhydrogen siloxane·diphenylsiloxane copolymer, dimethylhydrogen siloxy - terminated methylhydrogen siloxane·dimethylsiloxane·diphenylsiloxane copolymer, trimethylsiloxy - terminated methylhydrogen polysiloxane, trimethylsiloxy - terminated dimethylsiloxane·methylhydrogen siloxane copolymer, trimethylsiloxy - terminated methylhydrogen siloxane·diphenylsiloxane copolymer, trimethylsiloxy - terminated methylhydrogen siloxane·diphenylsiloxane·dimethylsiloxane copolymer, and the like.

[0017] The viscosity of the hydrogen organopolysiloxane is preferably from 0.1 to 1,000 mPa·s, more preferably from 1 to 500 mPa·s. If the viscosity of the hydrogen organopolysiloxane is too low, the viscosity of the resulting silicone rubber composition will also be low, resulting in poor workability. In addition, the resulting silicone gel may become too hard. If the viscosity of the hydrogen organopolysiloxane is too high, the viscosity of the resulting silicone rubber composition will also be high, which may have an adverse effect on workability.

[0018] The blending amount of the hydrogen organopolysiloxane is such that the number of hydrogen atoms (SiH groups) bonded to silicon atoms in the hydrogen organopolysiloxane is 0.01 to 3, preferably 0.05 to 2, more preferably 0.2 to 1.5, per vinyl group bonded to a silicon atom in the whole composition (especially the vinyl group-containing organopolysiloxane). When the number of hydrogen atoms (SiH groups) bonded to silicon atoms in this hydrogen organopolysiloxane is less than 0.01 per vinyl group in the whole silicone rubber composition, a silicone gel cannot be obtained. Also, when it is more than 3, the heat resistance of the silicone gel decreases.

[0019] Examples of the platinum compound include platinum black, chloroplatinic acid, alcohol-modified products such as chloroplatinic acid; complexes of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes, acetylene alcohols, etc.

[0020] The blending amount of the platinum compound may be an effective amount and can be appropriately increased or decreased according to the desired curing rate. Usually, based on the mass of the platinum group metal atoms, it is in the range of usually 0.1 to 10000 mass ppm, preferably 1 to 5000 mass ppm, with respect to the total amount of the vinyl group-containing organopolysiloxane and the hydrogen organopolysiloxane. If this blending amount is too large, the heat resistance of the obtained silicone gel may decrease.

[0021] In addition, the addition-type liquid silicone rubber may further contain a reaction inhibitor to adjust the pot life. Examples of the reaction inhibitor include methylvinylcyclotetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohols, hydroperoxides, etc.

[0022] In addition, in order to increase the strength, the addition-type liquid silicone rubber may further contain a reinforcing material. Examples of the reinforcing material include reinforcing silica, quartz powder, iron oxide, alumina, vinyl group-containing silicone resin, etc.

[0023] The addition-type liquid silicone rubber may further contain additives such as pigments, mold release agents, heat-resistant agents, flame retardants, fluidity regulators, anti-settling agents, and adhesion improvers.

[0024] The elastic rubber body 11 is not particularly limited, but can be manufactured by curing a rubber composition containing a rubber component. The curing time of the rubber composition can be adjusted, for example, by the amount of catalyst added and the curing temperature. More specifically, the elastic rubber body 11 may be manufactured, for example, by supplying each raw material of the rubber composition to a mixer such as a kneading device, mixing them in the mixer, obtaining a sheet-shaped rubber composition, and then curing the obtained rubber composition. When curing the rubber composition, the rubber composition may be cured at room temperature, but when curing the rubber composition in a short time, it is preferable to heat the rubber composition.

[0025] (Thickness) The thickness of the elastic rubber body 11 is not particularly limited, but is preferably 0.5 to 100 mm, and more preferably 1 to 50 mm. When the thickness is within these ranges, the planar heating element 10 can be suitably used for vehicle interior materials. Also, by setting the thickness to be equal to or greater than the above lower limit value, the heating layer 20 can be easily buried inside the base material 15.

[0026] (Light transmittance) The elastic rubber body 11, that is, the base material 15, preferably has light transmittance in the thickness direction. When the base material 15 has light transmittance, for example, when light from the light source 40 is irradiated from the back surface 15B side of the base material 15, the light can pass through the base material 15 and perform a light effect on the surface side of the planar heating element. Specifically, it becomes possible to display necessary information by the light from the light source, perform lighting, video display, etc. inside the vehicle using the light source 40.

[0027] The total light transmittance in the thickness direction of the base material 15 may be, for example, 50% or more, preferably 70% or more, and more preferably 80% or more. When the total light transmittance of the elastic rubber body 11 is 50% or more, the base material 15 can be provided with sufficient light transmittance, and the light emitted from the light source 40 is likely to be emitted to the surface side of the surface heating element with a light amount of a certain amount or more. The higher the total light transmittance of the base material 15, the better, and it may be 100% or less, but practically it may be 99% or less, or 98% or less. The total light transmittance of the base material 15 can be within the above range, for example, by appropriately adjusting the thickness of the elastic rubber body 11, the type of rubber, and the type of additives such as pigments and dyes added to the rubber. However, it is easy to increase the total light transmittance by using silicone rubber. The total light transmittance can be measured, for example, in accordance with ASTM D1003 using a haze meter. The total light transmittance in the thickness direction of the base material 15 is the total light transmittance in the region where the elastic rubber body 11 is provided when only a part of the region of the base material 15 is constituted by the elastic rubber body 11 as described later.

[0028] (Durometer hardness) The measurement method of the durometer hardness of the elastic rubber body 11 varies depending on the hardness. Generally, it is measured under the condition that the durometer hardness falls within the range of 20 to 90. When measured using a type A durometer in accordance with JIS K6253-3:2012, it is preferably 20 or more and 80 or less. When the durometer hardness of the elastic rubber body 11 is 20 or more and 80 or less, it is further possible to achieve both the strength of the elastic rubber body 11 and a soft touch. From such a viewpoint, the durometer hardness of the elastic rubber body 11 is more preferably 20 or more and 70 or less, and even more preferably 20 or more and 65 or less. In addition, when the softer elastic rubber body 11 is measured using a type E durometer in accordance with JIS K6253-3:2012, it is preferably 20 or more and 90 or less. When the durometer hardness of the elastic rubber body 11 is 20 or more and 90 or less, it is further possible to achieve both the strength of the elastic rubber body 11 and a soft touch. From such a viewpoint, the durometer hardness of the elastic rubber body 11 is more preferably 30 or more and 90 or less, and even more preferably 40 or more and 90 or less. The durometer hardness of the elastic rubber body 11 can be measured in accordance with JIS K6253-3:2012 using, for example, an Asker rubber hardness meter manufactured by Kobunshi Keiki Co., Ltd.

[0029] (Surface roughness) It is preferable that the surface roughness Ra of the surface 15A of the base material 15 on the side where the heat generating layer 20 is provided is 5 μm or less, and more preferably 3 μm or less. Also, the smaller the surface roughness Ra of the surface 15A, the better, but practically it is preferably, for example, 1 μm or more. The surface 15A of the base material 15 may be composed of the surface of the elastic rubber body 11, but may also be formed by other materials than the elastic rubber body 11. Specifically, it may be formed by a resin layer (not shown) serving as a skin layer described later, an underlayer 16 (see FIG. 2), or the like.

[0030] Note that the surface roughness Ra can be set to a certain value or less as described above, for example, by adjusting the surface state of the elastic rubber body 11. Also, as described later, the surface roughness Ra can be lowered by forming a skin layer or an underlayer 16. Note that the surface roughness Ra is a value of the arithmetic mean roughness obtained in accordance with JIS B0601 (2001).

[0031] The base material 15 may be composed of a single elastic rubber body, but a layer other than the elastic rubber body may be provided on the surface of the base material 15. For example, a layer other than the elastic rubber body 11 may be provided on the surface 15A of the base material 15 where the heat generating layer 20 is provided. Specifically, a resin layer (not shown) serving as a skin layer described later may be provided, or an underlayer 16 such as a deterioration-resistant film or an adhesion coating film may be provided as shown in FIG. 2.

[0032] (Skin layer) The elastic rubber body 11 may have a skin layer (not shown) formed on at least one surface, and a heat generating layer 20 may be formed on the skin layer. The skin layer is preferably composed of a resin other than rubber. Examples of the resin constituting the skin layer include urethane resin, acrylic resin, polyester resin, polycarbonate resin, polyimide resin, and the like. The skin layer may be in the form of a film. The thickness of the skin layer on the surface 15A where the heat generating layer 20 is disposed is not particularly limited, but is preferably about 5 to 500 μm, more preferably 8 to 300 μm, and even more preferably 10 to 100 μm. By setting the thickness of the skin layer to a certain value or less, the flexibility of the base material 15 is not impaired, and it becomes easier to embed the heat generating layer 20 inside the elastic rubber body 11.

[0033] (Underlayer) In the base material 15, a base layer 16 may be provided on the surface 15A of the base material in contact with the heat generating layer 20 as shown in FIG. 2. Examples of the base layer 16 include a deterioration resistant film or an adhesion coating film. Further, the base layer 16 may have the functions of both of these films. The deterioration resistant film is a film for preventing the deterioration of the heat generating layer 20. By providing the deterioration resistant film on the base material 15, at least one of the oxidation resistance, sulfurization resistance, and moisture resistance of the heat generating layer 20, preferably all of them, can be improved.

[0034] When the base layer 16 is an adhesion coating film, the base layer 16 can improve the adhesion between the heat generating layer 20 and the elastic rubber body 11. Although the heat generating layer 20 may have insufficient adhesiveness when directly adhered to the elastic rubber body 11, the provision of the adhesion coating film can suppress the adhesion failure of the heat generating layer 20 to the base material 15.

[0035] The base layer 16 is preferably formed directly on the surface of the elastic rubber body 11, but may also be formed on the surface of a layer other than the elastic rubber body formed on the surface of the elastic rubber body 11, like the above-described skin layer. Further, when the base layer 16 is provided, the heat generating layer 20 described later is preferably formed directly on the base layer 16. Further, as shown in FIG. 2, the underlayer 16 may be provided on the entire surface 15A of the base material 15, but it does not have to be provided on the entire surface, and it is preferably provided at least in the region where the heat generating layer 20 described later is formed.

[0036] The underlayer 16 is not particularly limited, but it may be formed of a resin composition containing a resin such as a thermosetting resin or a thermoplastic resin. Specific examples of the resin used for the underlayer 16 include urethane resins and acrylic resins. By using a urethane resin or an acrylic resin for the underlayer 16, it can be suitably used as a deterioration-resistant film for improving the above-described deterioration resistance or an adhesion coating film for improving the adhesiveness between the heat generating layer 20 and the elastic rubber body 11. The resin composition for forming the underlayer may contain additives and colorants other than the resin component, and may also contain a solvent and be diluted with the solvent.

[0037] The underlayer 16 is preferably formed by printing ink, and the printing ink may be a medium that is a colorless ink. When the underlayer 16 is formed by printing ink, it is preferably applied and formed on the surface of the elastic rubber body 11 or the surface of a layer other than the elastic rubber body such as a skin layer by a known printing method such as screen printing or inkjet printing. Since both the underlayer 16 and the heat generating layer 20 can be formed by a known printing method when the underlayer 16 is formed by printing ink, the planar heating element 10 can be efficiently manufactured even if the underlayer 16 is provided. The printing ink for forming the underlayer 16 is not particularly limited, and examples thereof include thermosetting ink, photocuring ink, and two-component curing ink composed of an acrylic resin or a urethane resin.

[0038] The thickness of the underlayer 16 is not particularly limited, but for example, it is preferably about 0.1 to 50 μm, and more preferably 0.5 to 20 μm.

[0039] Note that the above-described deterioration-resistant film is not limited to the configuration provided as the underlayer 16 on the surface 15A of the above-described base material 15, and may be formed on the surface on the side opposite to the surface on the base material 15 side of the heat-generating layer 20 described later. When the deterioration-resistant film is formed on the surface on the side opposite to the surface on the base material 15 side of the heat-generating layer 20, the underlayer 16 as the deterioration-resistant film provided on the surface of the elastic rubber body may be omitted, but it is preferable that the underlayer 16 as the deterioration-resistant film is formed. With such a configuration, since the deterioration-resistant film is formed on both the surface on the base material 15 side and the surface on the opposite side thereof for the heat-generating layer 20, the deterioration of the heat-generating layer 20 can be more effectively suppressed.

[0040] [Heat-generating layer] The heat-generating layer 20 disposed on one surface 15A of the base material 15 is not particularly limited as long as it is a conductive layer capable of generating heat by passing an electric current, but it is preferably a metal layer formed of a metal. Examples of the metal include metals or alloys such as silver, copper, gold, nickel, aluminum, and iron. Among them, it is preferable to use a metal with high ductility. Since the heat-generating layer 20 has high ductility and has a thickness below a certain level as described later, it easily follows the deformation of the planar heating element 10. Therefore, even if the planar heating element 10 is formed into a predetermined shape by vacuum forming or the like, the heat-generating layer 20 is less likely to be disconnected and can generate heat with low resistance and low voltage. Specific examples of the metal with high ductility include silver, copper, and gold. Among these, silver is preferable from the viewpoints of cost, ductility, durability, etc.

[0041] The heat-generating layer 20 preferably has a thickness T of 100 μm or less, and more preferably 50 μm or less. If the heat-generating layer 20 has a thickness T of 100 μm or less, during use, a part of the heat-generating layer 20 can be in a state of being buried inside the elastic rubber body 11, making it difficult to feel the uneven touch of the heating electrode. Therefore, the unevenness caused by the heat-generating layer 20 is less likely to appear on the surface on the side where the heat-generating layer 20 of the planar heating element 10 is provided during use or assembly, and the touch feeling is good. Also, when the thickness of the heat-generating layer is within the above range, it becomes significantly thinner than the base material 15 and the skin 31, and the presence or absence of the heat-generating layer has a smaller impact on the overall thickness. Therefore, it is possible to make it difficult to feel the uneven tactile sensation of the heat-generating electrodes. The thickness T of the heat-generating layer 20 is not particularly limited, but from the viewpoint of ensuring conductivity even after shaping, it is preferably a certain value or more. Specifically, it is preferably 5 μm or more, and more preferably 20 μm or more.

[0042] It is preferable to form wiring in the heat-generating layer 20. The planar shape of the heat-generating layer 20 is not particularly limited. As shown in FIG. 3, for example, a linear wiring extends while meandering from one terminal 20E to the other terminal 20E so that a certain region can be heated generally evenly. At this time, the heat-generating layer 20 has, for example, a plurality of straight portions 20A arranged in parallel, and one end or the other ends of adjacent straight portions 20A, 20A are alternately connected via connection portions 20B along the parallel direction, and the other ends of the straight portions 20A, 20A on both sides serve as the terminals 20E, 20E. The terminals 20E, 20E may have a larger width than the portions other than the terminals 20E. The heat-generating layer 20 may generate heat when a voltage is applied between the terminals 20E, 20E. Also, in another embodiment, the heat-generating layer 20 preferably has a planar shape such as a rectangle or a square. In this case, it is possible to heat the whole more uniformly. In this case, it is desirable to arrange electrodes for passing electricity at both ends of the heat-generating layer having a planar shape. For this heat-generating layer and the electrodes, in order to make the heat-generating layer uniform, it is necessary to make the resistance values between the electrodes and in the plane uniform. By doing so, when a voltage is applied, the heat-generating layer can be heated uniformly. In the case of a rectangle or a square, it is possible to make the resistance values between the electrodes uniform by suppressing the in-plane variation of the resistance value of the heat-generating layer. On the other hand, in the case of irregular shapes such as a trapezoid, an ellipse, or a circle, it is necessary to make the electric power flowing through the heat-generating layer uniform by making slits in the heat-generating layer or inserting auxiliary electrodes between the electrodes. Also, it is desirable that the resistance value of the electrode is lower than that of the heating layer. By doing so, it is possible to suppress the electrode portion from generating heat more than the heating layer. Also, when it has a flat shape, since there is no step in the heating layer, unevenness of the heating electrode can be eliminated.

[0043] As shown in FIGS. 1 and 2, the heating layer 20 preferably has a rectangular cross-section in which the width W is larger than the thickness T. Since the heating layer 20 has a rectangular cross-section, it becomes easier for a part of the heating layer 20 to be buried inside the elastic rubber body 11 during use or assembly. Also, the width W only needs to be sufficiently larger than the thickness T, for example, 1 to 1000 mm, preferably 2 to 700 mm, more preferably 3 to 200 mm. Note that the heating layer 20 preferably has the above width W for portions other than the terminal 20E.

[0044] The heating layer 20 is preferably formed of a metal nanoink, and more preferably a metal nanoink paste. The metal nanoink is an ink in which metal nanomaterials such as metal nanoparticles, metal nanowires, and metal nanorods are dispersed by a dispersion medium such as water or an organic solvent, and may further contain a binder component that is a resin component, a dispersant, etc. as required. The resin component is not particularly limited, but a thermosetting resin or the like is preferably used. The type of metal used in the metal nanoink is as described above, and it is preferably a nanomaterial mainly composed of silver such as silver nanoparticles or silver nanowires. Therefore, the metal nanoink is preferably a silver nanoink, and more preferably a silver nanoink paste. Since the heating layer 20 is formed from a metal nanoink, it is likely to be able to generate heat with low resistance and low voltage. Generally, the elastic rubber body 11 constituting the base material 15 does not have a high insulation resistance, but since the heating layer 20 can generate heat at a low voltage, it is possible to prevent leakage from the base material 15 side.

[0045] Metal nanoparticles are particles with a particle size in the nanoscale. The average particle size of the metal nanoparticles is preferably 1 nm or more and less than 1000 nm, more preferably 1 to 300 nm, and even more preferably 5 to 100 nm. Note that the "average particle size" is the volume average particle size (median diameter, D50), and can be measured, for example, by a laser particle size distribution analyzer. Commercially available products can also be used as the metal nanoink. For example, products with the trade names "Dotite" (manufactured by Fujikura Kasei Co., Ltd.), "Conductive Paste Compatible with Molding Processing" (manufactured by Toyobo MSC Co., Ltd.), "Low Temperature Curing Type Conductive Paste" (manufactured by Taiyo Ink Manufacturing Co., Ltd.), etc. can be used.

[0046] The heating layer 20 is preferably formed by a printing method. For example, the heating layer 20 can be formed by applying a metal nanoink to the base material 15 by a known printing method such as screen printing or inkjet printing, followed by drying and, if necessary, heating. The metal nanoparticles may form a metal layer on the base material 15, for example, by pseudo-sintering or heat aggregation. Note that the heating temperature after applying the metal nanoink is, for example, 80 to 150°C, preferably 100 to 140°C. By setting the heating temperature to be equal to or higher than the above lower limit value, pseudo-sintering or heat aggregation becomes easier, and it becomes easier to obtain a material that can generate heat with low resistance and low voltage. Also, by setting the heating temperature to be equal to or lower than the above upper limit value, it is possible to prevent the base material containing the elastic rubber body from being thermally deteriorated. However, the heating layer 20 may be formed by other means than the metal nanoink. For example, it may be formed by a conductive material other than metal, or may be formed by a conductive polymer such as a polythiophene-based conductive polymer (PEDOT / PSS). When using a conductive polymer, a more flexible heating layer can be obtained, and a good tactile sensation can be obtained. Also, when using a conductive polymer, a transparent heating layer can be obtained, and by using a light-transmissive foam as the base material, a light-transmissive heater can be obtained. Further, the heating layer 20 may be formed by physical vapor deposition such as vacuum evaporation or sputtering of a metal film, or by plating. Also, the heating layer 20 may be formed by laminating a metal foil such as gold foil. Further, the heating layer 20 may be formed of a carbon material such as graphite, carbon nanotubes, graphene, or a carbon fiber fabric. In particular, by using carbon nanomaterials such as carbon nanotubes and carbon nanoparticles, a more flexible and optically transparent heating layer can be obtained. Furthermore, the heating layer 20 may be formed of a conductive ink in which conductive particles of carbon or metal are dispersed in a resin. One type of material for these heating layers may be used, or a mixture of multiple materials or a heating layer composed of multiple materials may be laminated in multiple layers and used.

[0047] As shown in FIG. 1, the heating layer 20 is preferably arranged so as to directly contact the surface of the elastic rubber body 11. By directly laminating the heating layer 20 on the surface of the elastic rubber body 11, it becomes easier to embed it inside the elastic rubber body 11. Also, a planar heating element 10 with a simple structure can be obtained, so that the planar heating element 10 can be manufactured with higher production efficiency.

[0048] However, the heating layer 20 does not necessarily have to be directly laminated on the surface of the elastic rubber body 11, and it may be formed so as to contact the surface of a member other than the elastic rubber body 11. For example, when the above-described underlayer 16 is formed on the surface 15A of the base material 15, the heating layer 20 is preferably formed so as to contact the underlayer 16. Also, when a resin layer is provided as a skin layer, the heating layer 20 may be formed so as to contact the resin layer. Note that the line width size of the heating layer is not particularly limited, and for example, it may be a size that covers the entire surface or substantially the entire surface of the elastic rubber body 11. The resistance value of the heating layer is not particularly limited, but is preferably less than 1 KΩ / sq, more preferably less than 500 Ω / sq, and particularly preferably less than 100 Ω / sq. When it is in this range, a heater of the same size can be heated at a lower voltage.

[0049] <Laminate> The planar heating element 10 may further be laminated with another member to form a laminate. An embodiment of the laminate is shown in FIG. 4. As shown in FIG. 4, the laminate 30 preferably includes the above-described planar heating element 10 and a skin 31 adhered to the planar heating element 10. The skin 31 is adhered to the surface of the planar heating element 10 on the side where the heating layer 20 is provided. Therefore, the skin 31 can decorate the surface of the planar heating element 10 on the side where the heating layer 20 is provided, and the laminate 30 including the skin 31 can be suitably used as a vehicle interior material.

[0050] Examples of the skin 31 include a polyvinyl chloride sheet, a resin sheet such as a mixed resin sheet of polyvinyl chloride and ABS resin, a thermoplastic elastomer sheet, a woven fabric, a knitted fabric, a non-woven fabric using natural fibers or artificial fibers, a fake leather such as artificial leather or synthetic leather, and a metal. Further, a material having a design such as a grain or wood grain pattern on the surface using genuine leather or a silicone stamper with unevenness transferred from stone, wood, etc. may be used. Further, the skin 31 may be provided with a large number of holes by punching or the like as appropriate in order to provide light transmissibility.

[0051] The skin 31 preferably has light transmissibility. When the skin 31 has light transmissibility, the above-described base material 15 may also have light transmissibility. When the skin 31 and the base material 15 have light transmissibility, when light from the light source 40 is irradiated from the back surface 15B side of the base material, the light can pass through the base material 15 and the skin 31 to perform a light effect on the surface side of the planar heating element (laminate). The total light transmittance in the thickness direction of the skin 31 may be, for example, 10% or more, preferably 20% or more, more preferably 40% or more. When the total light transmittance of the skin 31 is 10% or more, sufficient light transmittance can be imparted to the skin 31, and the light emitted from the light source 40 is likely to be emitted to the surface side of the laminate with a light amount of a certain amount or more. The total light transmittance of the skin 31 may be 100% or less, for example, it may be 90% or less, or may be 80% or less. The total light transmittance of the skin 31 can be made within the above range, for example, by appropriately adjusting the type of the skin. In the case of woven fabrics, knitted fabrics, non-woven fabrics, etc., it can be adjusted by the mesh opening, apparent density, etc. Further, when punching is performed, it can also be adjusted by the size of the holes, the number per unit area of the holes, etc.

[0052] The skin 31 may have a printing layer or a printing film. The printing layer may be formed by printing on one surface of the skin 31. Further, the printing film may be formed by laminating on one surface of the skin 31. The printing film is a base film such as a polyester film such as a polyolefin film or a PET film, on which a printing layer is formed. As a method for forming the printing layer, known methods such as an inkjet method, a screen printing method, a gravure printing method, etc. can be appropriately used. The printing layer may display, for example, a logo, a pattern, an icon, etc.

[0053] The skin 31 may be directly adhered to the surface of the surface heating element 10 on the side where the heating layer 20 is provided. As shown in FIG. 4, the skin 31 may be partially adhered to the surface 15A of the base material 15 and partially adhered to the heating layer 20 and laminated on the surface heating element 10. However, the skin 31 does not necessarily have to be directly adhered to the planar heating element 10, and it may be adhered to the surface of the planar heating element 10 on the side where the heating layer 20 is provided via another layer (not shown) such as an adhesive layer. In this case, for example, a part of the skin 31 may be adhered to the base material 15 via another layer such as an adhesive layer, and a part may be adhered to the heating layer 20 via another layer such as an adhesive layer and laminated on the planar heating element 10. Furthermore, the skin 31 does not have to be adhered to the heating layer 20.

[0054] In addition, as shown in FIGS. 1 and 4, when the elastic rubber body 11 constitutes the surface 15A of the base material 15, the skin 31 may be directly adhered to the elastic rubber body 11 or adhered to the elastic rubber body 11 via another layer such as an adhesive layer. However, when the surface 15A of the base material 15 is provided with a skin layer composed of an underlayer 16 (see FIG. 2) or a surface resin layer (not shown), etc., the skin 31 may be directly adhered to the skin layer such as the underlayer 16 or the resin layer, or adhered to the skin layer such as the underlayer 16 or the resin layer via another layer such as an adhesive layer.

[0055] Examples of the method of adhering the skin 31 to the planar heating element 10 include an extrusion lamination method, an adhesive lamination method in which an adhesive is applied and then bonded, a heat lamination method (heat fusion method), a hot melt method, a high-frequency welder method, an electroless plating method, an electrolytic plating method, and a vapor deposition method for metals, etc., but it may be adhered by any method.

[0056] In the laminate 30, at least a part of the heating layer 20 may be buried inside from the surface of the elastic rubber body 11. At this time, the skin 31 may be adhered to the planar heating element 10 so as to press the heating layer 20 as shown in FIG. 4. With such a configuration, the laminate 30 can more appropriately prevent the surface on the side where the skin 31 is provided from having an uneven tactile sensation. However, the heat generating layer 20 does not necessarily need to be embedded in the elastic rubber body 11 by being pressed by the skin 31, and it may be pressed by other members or may be in a state of being embedded in the elastic rubber body 11 without being pressed. For example, it may be in a state of being embedded in the elastic rubber body 11 in the state of the planar heat generating body 10 without the skin 31 being provided.

[0057] <Light-emitting display device> As shown in FIGS. 1, 2, 4, and 5, the planar heat generating body and the laminate of the present invention can be combined with the light source 40 to form a light-emitting display device 50. The light source 40 is preferably disposed on the surface opposite to the surface 15A of the base material 15 (that is, the back surface 15B side). The light source 40 irradiates light onto the sheet for the light-emitting display device. The light from the light source 40 disposed on the back side can perform various light effects on the surface side through the planar heat generating body 10 or the planar heat generating body 10 and the skin 31.

[0058] The light source 40 may be any light source used as a light source for lighting devices and display devices such as fluorescent lamps, incandescent lamps, LEDs, and organic EL elements. Among these, LEDs and organic EL elements are preferred, and among them, LEDs are more preferred. An LED is also called a light-emitting diode. The light source 40 is shown as a surface light source in FIG. 1 and the like, but it may be a point light source. The size of the point light source is not particularly limited, and it may be a size of about 1 cm 2 or less, or a size of about 0.1 cm 2 or less, and for example, it may be a size of 0.001 cm 2 or more, or a size of 0.005 cm 2 or more. Also, the light source 40 may be single or plural. When there are a plurality of light sources 40, in order to display specific information, a plurality of light sources 40 may be arranged in a specific shape.

[0059] In addition, the light from the light source 40 can be used for various functions, such as lighting, video display, and alert display, or can be used as a light source for illuminating icons, logos, patterns, etc. formed by the printing layer on the skin. It can also be used, for example, to indicate the position of the heating layer 20 and the presence or absence of heat generation in the heating layer 20. Further, it may be light for indicating the operating positions of motion sensors, touch sensors, switches, etc. Therefore, although not shown, switches, touch sensors, etc. may be provided on the back side of the planar heating element.

[0060] For example, when the light from the light source 40 is used to indicate the presence or absence of heat generation in the heating layer 20, it is preferable that when an electric current flows through the heating layer 20, the light from the light source 40 is irradiated, and the light from the light source 40 indicates that the heating layer 20 is generating heat. Also, for example, by irradiating the light from the light source 40 around the heating layer 20 while not irradiating light at positions away from the heating layer 20, it is possible to indicate the position of the heating layer 20. Also, when indicating the operating positions of sensors, switches, etc., it is possible to illuminate the operating positions and not illuminate the surroundings of the operating positions, so that the operating positions can be recognized. At this time, the illumination may be made to blink or the like. Furthermore, for lighting and alert display inside the vehicle, it is advisable to use a plurality of point light sources or a surface light source. Also, as lighting, it may be used as interior lighting of the vehicle or as lighting for vehicle interior effects (for example, lighting that emits light in accordance with music).

[0061] The base material 15 may be entirely composed of the elastic rubber body 11, but as shown in FIG. 5, in addition to the region 61 composed of the elastic rubber body 11, a region 62 composed of the foam 12 may be provided. In this case, the heating layer 20 is preferably provided in the region 61 composed of the elastic rubber body 11. By using the foam 12, the weight of the base material 15 can be reduced, and it can also be suitably used for interior materials for vehicles, etc. In addition, the manufacturing cost of the base material can be reduced.

[0062] When providing the light source 40, the elastic rubber body 11 constituting the region 61 may be irradiated with light from the light source 40, and a light effect may be performed in the region 61. As shown in FIG. 5, the foam body 12 may be provided with holes 63, and the elastic rubber body 11 may be fitted into the holes 63. Further, although not shown, the foam body 12 may be provided with notches, and the elastic rubber body 11 may be fitted into the notches.

[0063] The foam body 12 is a resin foam. Examples of the resin constituting the foam include polyolefin resins, urethane resins, acrylic resins, and elastomer resins. The resin used for the foam body 12 may be used alone or in combination of two or more. Among those described above, a polyolefin resin foam using a polyolefin resin as the resin is preferable. By using a polyolefin resin for the foam, flexibility and mechanical strength are improved.

[0064] (Polyolefin resin) Examples of the polyolefin resin include polyethylene resin, polypropylene resin, and ethylene-vinyl acetate copolymer. Among these, polypropylene resin is preferable. By using polypropylene resin, it is easy to impart heat resistance to the base material 15, and it can be suitably used as a planar heating element.

[0065] Examples of the polyethylene resin include low-density polyethylene (density: less than 0.930 g / cm 3 ), medium-density polyethylene (density: 0.930 g / cm 3 or more and less than 0.942 g / cm 3 ), high-density polyethylene (density: 0.942 g / cm 3 or more), and linear low-density polyethylene. The density of linear low-density polyethylene is preferably 0.870 to 0.910 g / cm 3 more preferably 0.875 to 0.907 g / cm 3 and even more preferably 0.880 to 0.905 g / cm 3is more preferable. As the polyethylene resin, a plurality of polyethylene resins can be used, and a polyethylene resin outside the above-described density range may also be used. Examples of the ethylene-vinyl acetate copolymer used as the polyolefin resin include ethylene-vinyl acetate copolymers containing 50% by mass or more of ethylene.

[0066] The polypropylene resin is not particularly limited, and examples thereof include propylene homopolymers (homopolypropylene) and copolymers of propylene and other olefins. The copolymer of propylene and other olefins may be any of a block copolymer, a random copolymer, and a random block copolymer, but a random copolymer (random polypropylene) is preferable. In the copolymer of propylene and other olefins, examples of the propylene-α-olefin containing, for example, preferably 75% by mass or more, more preferably 90% by mass or more of propylene can be mentioned. Examples of the other olefin copolymerized with propylene include α-olefins such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, and 1-decene, and ethylene is preferable among these. Therefore, as the random polypropylene, an ethylene-propylene random copolymer is more preferable.

[0067] When using a polypropylene resin as the polyolefin resin, the polypropylene resin may be used alone, or may be used in combination with other polyolefin resins other than the polypropylene resin or resins other than the polyolefin resin. For example, it may be used in combination with other polyolefin resins other than the polypropylene resin, or may be used in combination with resins other than the polyolefin resin. Examples of the resin other than the polyolefin resin include elastomer resins. Examples of the elastomeric resin include various rubber components such as ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), polybutadiene rubber, polyisoprene rubber, styrene-butadiene copolymer (SBR), or styrene rubber such as its hydrogenated product (HSBR). Also included are thermoplastic elastomers such as olefinic thermoplastic elastomers and styrenic thermoplastic elastomers. From the viewpoint of heat resistance, the higher the content of the polypropylene resin in the foam, the better. Based on the total amount of the resin contained in the foam, for example, 50 to 100% by mass is preferable, 70 to 100% by mass is more preferable, and 80 to 100% by mass is even more preferable.

[0068] Also, from the viewpoint of imparting both heat resistance and flexibility, a polypropylene-based elastomer containing a polypropylene resin and a rubber component is also preferable as the resin constituting the foam 12. As the polypropylene-based elastomer, the polypropylene resin and the rubber component may be separate or copolymerized. Polypropylene-based elastomers are classified into reactor-type simple blend type, dynamic crosslinking type, etc. depending on the production method, but the reactor type is preferable in that the domain diameter of the dispersed rubber component is small and the transparency is high. As such a reactor-type polypropylene-based elastomer, commercially available products such as "Catalloy" (manufactured by Sun Allomer Co., Ltd.) can also be used.

[0069] (Foaming agent) The foam 12 is preferably a foam obtained by foaming a foamable composition containing the above resin and a foaming agent. Examples of the foaming agent include thermal decomposition foaming agents, and as the thermal decomposition type foaming agent, organic foaming agents and inorganic foaming agents can be used. For the thermal decomposition type foaming agent, those having a decomposition temperature higher than the melting temperature of the resin are usually used. For example, those having a decomposition temperature of 140 to 270 °C may be used. Specific organic blowing agents include azo compounds such as azodicarbonamide, metal salts of azodicarboxylic acid (such as barium azodicarboxylate), azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, hydrazodicarbonamide, hydrazine derivatives such as 4,4'-oxybis(benzenesulfonylhydrazide) and toluenesulfonylhydrazide, semicarbazide compounds such as toluenesulfonyl semicarbazide, etc. Inorganic blowing agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, monosodium anhydrous citrate, etc. Among these, from the viewpoints of obtaining fine bubbles, economy, and safety, azo compounds are preferred, and azodicarbonamide is particularly preferred. These thermal decomposition type blowing agents can be used alone or in combination of two or more. The compounding amount of the thermal decomposition type blowing agent in the foaming composition may be adjusted according to the foaming ratio of the foam, but it is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and still more preferably 2 to 10 parts by mass with respect to 100 parts by mass of the resin.

[0070] However, as the blowing agent, blowing agents other than thermal decomposition blowing agents may be used, for example, physical blowing agents may be used. As the physical blowing agent, it is preferable to use a high-pressure inert gas. The inert gas is not particularly limited as long as it is inert to the resin composition and can be impregnated, and examples include carbon dioxide, butane gas, nitrogen gas, air, etc. These gases may be used in combination. Among these, from the viewpoint of easily increasing the foaming ratio of the foam, carbon dioxide and butane gas are preferred. The inert gas at the time of impregnation is preferably in a supercritical state or a subcritical state.

[0071] (Other Additives) The foam or foaming composition may be blended with additives generally used in foams, such as crosslinking agents, crosslinking aids, antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, fillers, decomposition temperature adjusters, etc., as necessary. Among these, it is preferable to use antioxidants and decomposition temperature adjusters.

[0072] (Expansion ratio) The foam 12 preferably has an expansion ratio of 4 to 50 cm 3 / g, more preferably 8 to 30 cm 3 / g, and even more preferably 10 to 20 cm 3 / g.

[0073] (Closed cell ratio) The foam 12 may be an open cell foam, a semi-closed cell foam, or a closed cell foam, but a closed cell foam is preferred.

[0074] A closed cell foam is one in which most of the bubbles contained in the foam are closed cells. Specifically, the closed cell ratio is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. Also, the upper limit of the closed cell ratio is not particularly limited and is 100%.

[0075] Note that the closed cell ratio can be measured according to the method of ASTM D2856 (1998). Specifically, it may be measured as follows. First, a test piece having a planar square shape with a side length of 5 cm is cut out from the foam. Then, the thickness of the test piece is measured to calculate the apparent volume V1 of the test piece, and the weight W1 of the test piece is measured. Next, the volume V2 occupied by the bubbles is calculated based on the following formula. The density of the matrix resin constituting the test piece is ρ (g / cm 3 ). The volume V2 occupied by the bubbles = V1 - W1 / ρ Subsequently, immerse the test piece in distilled water at 23°C to a depth of 100 mm from the water surface, and apply a pressure of 15 kPa to the test piece over 3 minutes. Then, release the pressure in water, let it stand for 1 minute, take out the test piece from the water, remove the water adhering to the surface of the test piece, measure the weight W2 of the test piece, and calculate the continuous bubble rate F1 and the independent bubble rate F2 based on the following formula. Continuous bubble rate F1 (%) = 100×(W2 - W1) / V2 Independent bubble rate F2 (%) = 100 - F1

[0076] (Degree of crosslinking) The foam 12 is preferably a crosslinked foam, and more preferably an electron beam crosslinked body crosslinked by an electron beam. By being a crosslinked foam, especially an electron beam crosslinked body, the foam 12 has good durability, moldability, etc. The degree of crosslinking of the foam 12 is not particularly limited, but is, for example, 10 to 70% by mass, more preferably 20 to 60% by mass. By setting the degree of crosslinking of the foam 12 within the above range, it becomes easier to improve the mechanical strength, flexibility, etc. of the base material 15. Also, it becomes possible to appropriately foam the foam 12. The method for measuring the degree of crosslinking is as follows. Collect about 100 mg of test pieces from the foam, and accurately weigh the weight A (mg) of the test pieces. Next, immerse these test pieces in 30 cm of xylene at 120°C 3 leave for 24 hours, filter with a 200-mesh wire mesh, collect the insoluble matter on the wire mesh, vacuum dry it, and accurately weigh the weight B (mg) of the insoluble matter. From the obtained values, calculate the degree of crosslinking (% by mass) using the following formula. Degree of crosslinking (% by mass) = 100×(B / A)

[0077] The foam 12 is not particularly limited, but can be produced by foaming a foamable composition containing a resin component and a foaming agent with a foaming agent. At this time, foaming with a foaming agent may be performed by heating or the like. Also, the foam 12 is preferably obtained by crosslinking the foamable composition and foaming the crosslinked foamable composition. The foamable composition may contain additives as necessary in addition to the resin component and the foaming agent.

[0078] <Use> The planar heating element of the present invention is preferably used for vehicle interior materials, and more preferably used for vehicle interior materials as the laminate 30 provided with the skin 31. The planar heating element is particularly preferably used for vehicle interior materials in the automotive field, and preferably constitutes a ceiling material, a door, an instrument panel, etc. The planar heating element and the laminate of the present invention are used as a heating device in which the surface on the side where the heating layer of the planar heating element is provided generates heat by passing an electric current through the heating layer as described above. Therefore, by applying the planar heating element and the laminate to vehicle interior materials, it becomes possible to heat the vehicle interior materials. In the planar heating element 10, the heating layer 20 (that is, the skin 31 in the laminate 30) may be arranged on the interior side, and the base material 15 may be arranged on the side opposite to the interior side. The interior side is the side decorated by the vehicle interior material, and is the outer peripheral surface side of the attached body to which the vehicle interior material is attached.

[0079] The planar heating element and the laminate of the present invention are preferably formed into a desired shape by shaping and then used. The planar heating element and the laminate are preferably used as vehicle interior materials by being shaped. When the planar heating element and the laminate are shaped, the heating layer 20 may also be shaped together with the elastic rubber body 11 (base material 15) and the skin 31. Examples of the forming method of the planar heating element and the laminate include a stamping method, a vacuum forming method, a compression molding method, an injection molding method, etc. Among these, the stamping method and the vacuum forming method are preferred. As the vacuum forming method, either a male drawing vacuum forming method or a female drawing vacuum forming method can be adopted, but the male drawing vacuum forming method is more preferred.

[0080] When the planar heating element and the laminate of the present invention are used as vehicle interior materials as described above, of course, they may be combined with a light source and used as a light-emitting display device. In this case, since the heating layer is arranged on the interior side, it is possible to perform various effects inside the vehicle with the light from the light source arranged on the back side of the planar heating element.

Explanation of symbols

[0081] 10 planar heating element 11 elastic rubber body 12 foam 15 base material 15A surface 16 underlayer 20 heating layer 30 laminate 31 skin 40 light source 50 light-emitting display device

Claims

1. A planar heating element comprising a base material containing an elastic rubber body and a heating layer disposed on one surface of the base material.

2. The planar heating element according to Claim 1, wherein the heating layer is disposed so as to be in direct contact with the elastic rubber body.

3. The planar heating element according to Claim 1, wherein an underlayer is formed on the surface of the base material in contact with the heating layer.

4. The planar heating element according to Claim 1, wherein the heating layer is formed by a printing method.

5. The planar heating element according to any one of Claims 1 to 4, wherein at least a part of the heating layer is embedded inside the surface of the elastic rubber body.

6. The planar heating element according to any one of Claims 1 to 4, wherein the rubber constituting the elastic rubber body is silicone rubber.

7. The planar heating element according to Claim 6, wherein the rubber constituting the elastic rubber body contains silicone gel.

8. The planar heating element according to any one of Claims 1 to 4, wherein the surface roughness Ra of the surface of the base material on the side where the heating layer is provided is 5 μm or less.

9. The planar heating element according to any one of Claims 1 to 4, wherein the heating layer has a thickness of 100 μm or less and is formed of a conductive material.

10. A laminate comprising the planar heating element according to Claim 1 and a skin adhered to the planar heating element directly or via another layer.

11. The laminate according to Claim 10, wherein the skin is adhered to the surface of the planar heating element on the side where the heating layer is provided.

12. The laminate according to Claim 10, wherein at least a part of the heating layer is embedded inside the surface of the elastic rubber body.

13. An interior material for a vehicle comprising the planar heating element according to Claim 1 or the laminate according to Claim 10.

14. The interior material for a vehicle according to Claim 13, wherein the heating layer is disposed on the interior side and the base material is disposed on the side opposite to the interior side.

15. A light-emitting display device comprising the planar heating element according to Claim 1 or the laminate according to Claim 10 and a light source.

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