Carbon nanotube heater

Abstract

A connection sheet part (21) of a CNT heater (1) is constituted by a sheet-like CNT molded body, and connects a pair of electrodes (22). The connection sheet part (21) generates heat by being supplied with electric power. An additional conductive part (23) is laminated on the connection sheet part (21). On the connection sheet part (21), a heating suppression region (212) is set in which the temperature upon supply of electric power is lower than the temperature of a surrounding portion. The additional conductive part (23) is disposed in a disposition region of an outer peripheral region (213) surrounding the periphery of the heating suppression region (212) and in contact with the peripheral edge of the heating suppression region (212), the disposition region including a region intersecting a first virtual straight line that passes through the center of the heating suppression region (212) and that extends in the X-direction. The conductivity of the additional conductive part (23) in the Y-direction is higher than the conductivity of the connection sheet part (21) in the Y-direction.

Description

Carbon nanotube heater

[0001] The present invention relates to a carbon nanotube heater. [Reference to related applications] This application claims the benefit of priority from Japanese Patent Application JP2024-220933 filed on December 17, 2024, and all disclosures of the said application are incorporated herein.

[0002] In recent years, it has been proposed to form a large number of carbon nanotubes into various shapes and use them in various products such as heaters and sensors. For example, Japanese Patent Laid-Open No. 2021-131931 (Document 1) discloses a carbon nanotube heater including a pair of electrodes, a sheet-shaped carbon nanotube molded body connecting between the pair of electrodes, and a sheet-shaped insulating member covering the carbon nanotube molded body from both sides in the thickness direction. In this carbon nanotube heater, when an electric current flows between the pair of electrodes, the sheet-shaped carbon nanotube molded body generates heat.

[0003] By the way, when there is a portion on the object to which the carbon nanotube heater is attached where heating is to be avoided, in the carbon nanotube heater, it is conceivable to provide a through hole by removing a region (hereinafter also referred to as a "heating suppression region") overlapping the portion of the object where heating is to be avoided. However, when providing a through hole in a carbon nanotube heater such as that of Document 1, it is necessary to form through holes in the carbon nanotube molded body and the insulating member, and further, in order to prevent leakage of electricity from the periphery of the through hole, etc., it is also necessary to form the through hole of the insulating member smaller than the through hole of the carbon nanotube molded body. Therefore, there is a possibility that the manufacture of the carbon nanotube heater becomes complicated.

[0004] The present invention is directed to a carbon nanotube heater, and aims to simplify the manufacture of the carbon nanotube heater while suppressing the temperature rise in the heating suppression region.

[0005] One aspect of the present invention is a carbon nanotube heater comprising: a pair of electrodes arranged side by side in a first direction; a connecting sheet portion made of a sheet-like carbon nanotube molded body extending in the first direction and a second direction perpendicular to the first direction and connecting the pair of electrodes, which generates heat when power is supplied; an additional conductive portion laminated on the connecting sheet portion and having a conductivity in the second direction higher than that of the connecting sheet portion; and a sheet-like covering portion covering the connecting sheet portion and the additional conductive portion from both sides in a third direction perpendicular to the first and second directions. A heating suppression region is set on the connecting sheet portion, in which the temperature when power is supplied is lower than that of the surrounding area. The additional conductive portion is arranged in an arrangement region that includes a region within the outer peripheral region surrounding the heating suppression region and in contact with the periphery of the heating suppression region, which intersects with a first virtual straight line extending in the first direction through the center of the heating suppression region.

[0006] According to the present invention, it is possible to simplify the manufacturing of carbon nanotube heaters while suppressing the temperature rise in the heating suppression region.

[0007] Aspect 2 of the present invention is a carbon nanotube heater according to aspect 1, wherein the arrangement region of the additional conductive portion includes all of the region in the outer peripheral region that is located on both sides of the first virtual line with respect to the second direction and between a pair of second virtual lines that are parallel to the first virtual line. The pair of second virtual lines are equidistant from the first virtual line with respect to the second direction. The distance between the pair of second virtual lines in the second direction is half the maximum length of the heating suppression region in the second direction.

[0008] A third aspect of the present invention is the carbon nanotube heater according to aspect 2, wherein the arrangement region of the additional conductive portion includes the entire outer peripheral region.

[0009] Aspect 4 of the present invention is a carbon nanotube heater according to any one of aspects 1 to 3, wherein the orientation of the carbon nanotubes in the connecting sheet portion is parallel to the first direction.

[0010] Aspect 5 of the present invention is a carbon nanotube heater according to any one of aspects 1 to 3 (or any one of aspects 1 to 4), wherein the additional conductive part is a metal foil or a metal plate.

[0011] Aspect 6 of the present invention is a carbon nanotube heater according to any one of aspects 1 to 3 (or any one of aspects 1 to 4), wherein the additional conductive portion is a sheet-shaped carbon nanotube molded body in which the orientation of the carbon nanotubes is different from that of the connecting sheet portion.

[0012] Aspect 7 of the present invention is a carbon nanotube heater according to aspect 6, wherein the orientation of the carbon nanotubes in the connecting sheet portion is parallel to the first direction. The orientation of the carbon nanotubes in the additional conductive portion is in a direction inclined with respect to the first direction.

[0013] Embodiment 8 of the present invention is a carbon nanotube heater according to Embodiment 7, wherein the orientation of the carbon nanotubes in the additional conductive portion is parallel to the second direction.

[0014] Aspect 9 of the present invention is a carbon nanotube heater according to aspect 6 (or any one of aspects 6 to 8), wherein the additional conductive portion is provided along the entire length of the connecting sheet portion in the second direction.

[0015] Embodiment 10 of the present invention is a carbon nanotube heater according to any one of embodiments 1 to 3 (or any one of embodiments 1 to 9), wherein the connecting sheet portion, the additional conductive portion, and the coating portion are flexible.

[0016] The aforementioned objectives, as well as other objectives, features, embodiments, and advantages, will be revealed by the detailed description of the present invention below, with reference to the attached drawings.

[0017] This is a plan view of a CNT heater according to the first embodiment. This is a cross-sectional view of a CNT heater. This is a plan view of a CNT heater. This is a diagram showing the temperature distribution in the CNT heater of the embodiment. This is a diagram showing the temperature distribution in the CNT heater of the embodiment. This is a diagram showing the temperature distribution in the CNT heater of the embodiment. This is a diagram schematically representing the current flow in a CNT heater. This is a plan view of a CNT heater. This is a plan view of a CNT heater according to the second embodiment. This is a cross-sectional view of a CNT heater.

[0018] Figure 1 is a plan view showing a carbon nanotube heater 1 (hereinafter also referred to as "CNT heater 1") according to a first embodiment of the present invention. Figure 2 is a cross-sectional view of the CNT heater 1 taken at position II-II in Figure 1. In Figure 2, the components of the CNT heater 1 are drawn spaced apart in the vertical direction to facilitate understanding of the figure. The CNT heater 1 is a relatively thin sheet-like heater used, for example, to heat an object.

[0019] In Figures 1 and 2, three mutually orthogonal directions are indicated by arrows as the X, Y, and Z directions. In the examples shown in Figures 1 and 2, the X and Y directions are horizontal directions perpendicular to each other, and the Z direction is the up and down direction. The same applies to other figures. In the following explanation, the X, Y, and Z directions will also be referred to as the "first direction," "second direction," and "third direction," respectively. Note that when the CNT heater 1 is actually used, the Z direction does not necessarily need to coincide with the direction of gravity (i.e., the vertical direction).

[0020] In the example shown in Figure 1, the shape of the CNT heater 1 in plan view (i.e., the shape of the CNT heater 1 when viewed along the Z direction) is a roughly rectangular shape with each side roughly parallel to the X or Y direction. The shape of the CNT heater 1 in plan view is not limited to a rectangle and may be changed in various ways, such as a square, trapezoid, or circle.

[0021] The CNT heater 1 comprises a carbon nanotube device 2 (hereinafter also referred to as "CNT device 2") and a coating portion 3. In the example shown in Figure 1, the shape of the CNT device 2 and the coating portion 3 in plan view is also a substantially rectangular shape with each side substantially parallel to the X or Y direction. The shape of the CNT device 2 and the coating portion 3 in plan view is not limited to a rectangle, but can be changed in various ways, such as a square, trapezoid, or circle.

[0022] The CNT device 2 is a substantially sheet-shaped heating element that generates heat when power is supplied to it. In this specification, "sheet-shaped" means a shape in which the thickness in the Z direction is thin relative to the size in the X and Y directions, and it may or may not be flexible. Specifically, the sheet-shaped member may or may not be deformable by human force. Furthermore, in this specification, "sheet-shaped" is a concept that also includes shapes called "film-shaped" and shapes called "flat plate-shaped".

[0023] The CNT device 2 comprises a connecting sheet portion 21, a pair of electrodes 22, and an additional conductive portion 23. The pair of electrodes 22 are arranged side by side in the X direction (i.e., the first direction) and are substantially parallel to each other. The pair of electrodes 22 are arranged at substantially the same position with respect to the Y direction (i.e., the second direction) and face each other while being spaced apart in the X direction. In the example shown in Figure 1, the shape of each electrode 22 in plan view is a substantially rectangular strip extending substantially parallel to the Y direction. The pair of electrodes 22 are sheet-like conductive members having substantially the same shape. Each electrode 22 is, for example, a metal foil formed of copper (Cu). The thickness of each electrode 22 is, for example, 20 μm to 300 μm, preferably 40 μm to 100 μm. The material, shape, and size of each electrode 22 can be varied.

[0024] The connecting sheet portion 21 is a sheet-like member that extends in the X and Y directions (i.e., substantially perpendicular to the Z direction) between the pair of electrodes 22, connecting the pair of electrodes 22. In the example shown in Figure 1, the shape of the connecting sheet portion 21 in plan view is a substantially rectangle with each side substantially parallel to the X or Y direction. In Figure 1, parallel diagonal lines are drawn on the connecting sheet portion 21 to facilitate understanding of the figure. In addition, different parallel diagonal lines are drawn on the additional conductive portion 23. Two types of parallel diagonal lines are drawn in the region where the connecting sheet portion 21 and the additional conductive portion 23 overlap.

[0025] The size of the connecting sheet portion 21 varies depending on the performance required of the CNT heater 1. The length of the connecting sheet portion 21 in the X direction is, for example, 30 mm to 500 mm. The length of the connecting sheet portion 21 in the Y direction is, for example, 30 mm to 1000 mm. The size and shape of the connecting sheet portion 21 in plan view can be changed in various ways.

[0026] The connecting sheet portion 21 is composed of a sheet-like carbon nanotube molded body (hereinafter also referred to as "CNT molded body") formed from a large number of carbon nanotubes. The connecting sheet portion 21 is conductive and electrically connects the pair of electrodes 22. In the example shown in Figures 1 and 2, the connecting sheet portion 21 is a laminated sheet-like member in which multiple carbon nanotube sheets are stacked in the Z direction. That is, the Z direction is the thickness direction of the connecting sheet portion 21 and the stacking direction of the multiple carbon nanotube sheets (hereinafter also referred to as "CNT sheets").

[0027] The number of layers of CNT sheets in the connecting sheet section 21 is, for example, 5 to 400 layers. The number of layers of CNT sheets in the connecting sheet section 21 is, for example, approximately the same over substantially the entire surface of the connecting sheet section 21, and the thickness of the connecting sheet section 21 is approximately the same over substantially the entire surface of the connecting sheet section 21. However, the number of layers of CNT sheets in the connecting sheet section 21 is not limited to this range and may be varied in a range of 1 or more layers. Also, the thickness of the connecting sheet section 21 does not necessarily have to be approximately the same over substantially the entire surface and may differ from part to part.

[0028] The orientation of the carbon nanotubes in the connecting sheet portion 21 (i.e., the direction in which the carbon nanotubes extend) is approximately parallel to the X direction. In other words, in the multiple layers of CNT sheets constituting the connecting sheet portion 21, the numerous carbon nanotubes constituting each CNT sheet extend approximately parallel to the X direction (i.e., the first direction).

[0029] The X-direction ends of the connecting sheet portion 21 are fixed to a pair of electrodes 22. For example, the electrodes 22 are folded and pressed with the ends of the connecting sheet portion 21 sandwiched between them, thereby fixing the connecting sheet portion 21 and the electrodes 22. Alternatively, the ends of the connecting sheet portion 21 located on the electrodes 22 may be covered with metal foil, and the connecting sheet portion 21 may be fixed to the electrodes 22 by joining the metal foil to the electrodes 22. The connecting sheet portion 21 may be fixed to the electrodes 22 by methods other than those described above.

[0030] Each electrode 22 is connected to the connecting sheet portion 21 at its X-direction end, extending over approximately its entire length in the Y-direction. In the example shown in Figure 1, the (+Y) end of each electrode 22 extends slightly to the (+Y) side from the (+Y) edge of the connecting sheet portion 21. The (-Y) end of each electrode 22 extends relatively far to the (-Y) side from the (-Y) edge of the connecting sheet portion 21 and protrudes in the (-Y) direction from the (-Y) edge of the covering portion 3. The portion of each electrode 22 that protrudes from the covering portion 3 in the (-Y) direction becomes a terminal for supplying power to the CNT heater 1. Power is supplied to the connecting sheet portion 21 via these terminals of the pair of electrodes 22, causing the connecting sheet portion 21 to heat up.

[0031] A heating suppression region 212 is provided on the connecting sheet portion 21. The heating suppression region 212 is a region where the temperature rise must be suppressed when power is supplied to the connecting sheet portion 21 and heat is generated. The heating suppression region 212 overlaps with the portion of an object (i.e., the object to be heated) on which heating by the CNT heater 1 should be suppressed (hereinafter also referred to as the "temperature rise suppression portion") when the CNT heater 1 is attached to the object. As will be described later, the CNT heater 1 is provided with an additional conductive portion 23, so that when power is supplied to the connecting sheet portion 21, the temperature of the heating suppression region 212 becomes lower than the temperature of the surrounding portion of the connecting sheet portion 21. As a result, heating of the temperature rise suppression portion of the object is suppressed, and the temperature rise of the temperature rise suppression portion is suppressed.

[0032] In the example shown in Figure 1, the shape of the heating suppression region 212 in plan view is approximately circular and is located approximately in the center of the connecting sheet portion 21 in the X and Y directions. In Figure 1, the periphery of the heating suppression region 212 is shown by a dashed line (the same applies to the outer peripheral region 213 described later). The maximum length of the heating suppression region 212 in the X direction (diameter in the example shown in Figure 1) is, for example, 1.2% to 50% of the maximum length of the connecting sheet portion 21 in the X direction. The maximum length of the heating suppression region 212 in the Y direction (diameter in the example shown in Figure 1) is, for example, 0.6% to 50% of the maximum length of the connecting sheet portion 21 in the Y direction. Note that the shape, size, and position of the heating suppression region 212 on the connecting sheet portion 21 can be varied.

[0033] The additional conductive portion 23 is a conductive sheet-like member laminated on the connecting sheet portion 21 around the heating suppression region 212 of the connecting sheet portion 21. In the example shown in Figure 1, the additional conductive portion 23 is a substantially annular member provided along the periphery of the heating suppression region 212, extending almost the entire circumference around the heating suppression region 212. Specifically, the shape of the additional conductive portion 23 in plan view is a substantially annular shape that extends around the entire circumference around the heating suppression region 212. The center of the additional conductive portion 23 substantially coincides with the center of the heating suppression region 212. If we refer to the annular (for example, substantially annular) region on the connecting sheet portion 21 that surrounds the heating suppression region 212 and is in contact with the periphery of the heating suppression region 212 as the outer peripheral region 213, then the additional conductive portion 23 is arranged on the connecting sheet portion 21 over almost the entire circumference of the outer peripheral region 213. In other words, the area on the connecting sheet portion 21 where the additional conductive portion 23 is located includes the outer peripheral region 213 over substantially its entire circumference. In the example shown in Figure 1, the outer peripheral region 213 has substantially the same shape as the additional conductive portion 23 in plan view and substantially coincides with the additional conductive portion 23.

[0034] In the examples shown in Figures 1 and 2, the additional conductive portion 23 is provided on the main surface of the connecting sheet portion 21 on the (+Z) side. The additional conductive portion 23 may also be provided on the main surface of the connecting sheet portion 21 on the (-Z) side, or on the main surfaces of both the (+Z) and (-Z) sides of the connecting sheet portion 21 (the same applies to the additional conductive portions 23a and 23b described later).

[0035] In the example shown in Figure 1, the inner periphery of the additional conductive portion 23 substantially overlaps with the periphery of the heating suppression region 212 of the connecting sheet portion 21 over almost its entire circumference in a plan view. In other words, the inner diameter of the additional conductive portion 23 (i.e., the diameter of the inner periphery) is approximately the same as the diameter of the heating suppression region 212. The outer diameter of the additional conductive portion 23 (i.e., the diameter of the outer periphery) is larger than the diameter of the heating suppression region 212. The radial width of the additional conductive portion 23 (i.e., the difference between the outer diameter and the inner diameter) is, for example, 1% to 30% of the diameter of the heating suppression region 212. Note that the inner diameter of the additional conductive portion 23 may be larger than the diameter of the heating suppression region 212 (i.e., the inner diameter of the outer periphery region 213).

[0036] The additional conductive portion 23 is, for example, a metal foil or metal plate made of stainless steel or the like. The thickness of the additional conductive portion 23 is, for example, 5 μm to 200 μm, and is substantially the same over substantially the entire surface of the additional conductive portion 23. The conductivity of the additional conductive portion 23 is higher than the conductivity of the connecting sheet portion 21. Specifically, the conductivity of the additional conductive portion 23 in the Y direction is higher than the conductivity of the connecting sheet portion 21 in the Y direction, and the conductivity of the additional conductive portion 23 in the X direction is higher than the conductivity of the connecting sheet portion 21 in the X direction.

[0037] Furthermore, the conductivity of the additional conductive portion 23 only needs to be higher than that of the connecting sheet portion 21, at least in the Y direction. That is, the conductivity of the additional conductive portion 23 in the X direction may be the same as, or lower than, that of the connecting sheet portion 21 in the X direction. Also, the additional conductive portion 23 does not necessarily have to be made of metal; for example, it may be formed from a conductive resin film or conductive ceramics.

[0038] The covering portion 3 is a sheet-like member that covers substantially the entire surface of the connecting sheet portion 21 and the additional conductive portion 23 from both sides in the Z direction. Specifically, substantially the entire portion of the connecting sheet portion 21, including the heat suppression region 212, the portion overlapping with the additional conductive portion 23 in the Z direction, and the portion outside the additional conductive portion 23 (i.e., radially outward), is covered by the covering portion 3. The covering portion 3 also covers the portion of the pair of electrodes 22, excluding the (-Y) end, from both sides in the Z direction. In the example shown in Figure 2, the covering portion 3 comprises a first covering portion 31 that contacts the main surface of the connecting sheet portion 21 on the (+Z) side, and a second covering portion 32 that contacts the main surface of the connecting sheet portion 21 on the (-Z) side. The first covering portion 31 and the second covering portion 32 are joined to each other by an adhesive or the like around the connecting sheet portion 21 and the pair of electrodes 22, with the connecting sheet portion 21, the pair of electrodes 22, and the additional conductive portion 23 sandwiched between them. The covering portion 3 may also be made by folding a single sheet material in half.

[0039] The covering portion 3 (i.e., the first covering portion 31 and the second covering portion 32) is an insulator with lower conductivity than the connecting sheet portion 21, each electrode 22, and the additional conductive portion 23. The covering portion 3 is, for example, a resin sheet formed from a resin such as polyimide. The covering portion 3 is, for example, a transparent or translucent material. In the example shown in Figure 1, the covering portion 3 is flexible. The connecting sheet portion 21 and the additional conductive portion 23 are also flexible. Therefore, the CNT heater 1 is flexible.

[0040] Next, examples of the CNT heater 1 will be described with reference to Table 1. In Examples 1 to 4, power was supplied between the pair of electrodes 22 in the CNT heater 1 described above, and after the temperature of the connecting sheet portion 21 stabilized, the temperatures T1, T2, and T3 at the positions indicated by the rectangles labeled P1, P2, and P3 in Figure 3 were measured. The temperatures T1, T2, and T3 were measured using a thermograph manufactured by Optex FA Co., Ltd. In Examples 1 to 4, the current flowing between the pair of electrodes 22 was changed.

[0041]

[0042] In Examples 1 to 4, the shape of the connecting sheet portion 21 in plan view is a roughly rectangular shape with lengths of 100 mm and 60 mm in the X and Y directions, respectively. The number of layers of CNT sheets in the connecting sheet portion 21 is 40. The heat suppression region 212 is located approximately in the center of the connecting sheet portion 21 in the X and Y directions. The shape of the heat suppression region 212 in plan view is a roughly circular shape with a diameter of 12 mm. The pair of electrodes 22 are metal foils made of Cu. The covering portion 3 is a resin sheet made of polyimide.

[0043] In Examples 1 to 4, the shape of the additional conductive portion 23 in plan view is approximately annular, with an inner diameter of 12 mm and an outer diameter of 15 mm, respectively. The center of the additional conductive portion 23 substantially coincides with the center of the heating suppression region 212. The additional conductive portion 23 is a metal foil with a thickness of 50 μm, made of stainless steel.

[0044] In Examples 1 to 4, the above-mentioned position P1 is a position 1.5 mm away from the end on the (+Y) side of the outer peripheral edge of the additional conductive portion 23 in the (+Y) direction at the center of the connection sheet portion 21 in the X direction. The position P2 is a position 1.5 mm away from the end on the (-X) side of the outer peripheral edge of the additional conductive portion 23 in the (-X) direction at the center of the connection sheet portion 21 in the Y direction. The position P3 is a position on the center of the heat suppression region 212 (that is, the center of the additional conductive portion 23). That is, the position P3 is a position included in the region inside the additional conductive portion 23 surrounded by the additional conductive portion 23, and the positions P1 and P2 are positions included in the region outside (that is, on the outer side in the radial direction) of the additional conductive portion 23.

[0045] In Example 1, the current flowing between the pair of electrodes 22 is 0.4 A. The temperature T1 of the CNT heater 1 at the position P1 was 72.7°C. The temperature T2 of the CNT heater 1 at the position P2 was 78.8°C. The temperature T3 of the CNT heater 1 at the position P3 was 66.0°C, which was lower than the temperatures T1 and T2. FIG. 4 is a diagram showing the temperature distribution in the CNT heater 1 of Example 1. In FIG. 4, in the region corresponding to the connection sheet portion 21, the whitish portion is a high-temperature portion with a relatively high temperature, and the portion with a higher density than the high-temperature portion (for example, the blackish portion) is a low-temperature portion with a relatively low temperature (the same applies to FIGS. 5 to 7).

[0046] In Example 2, the current flowing between the pair of electrodes 22 is 0.6 A. The temperature T1 of the CNT heater 1 at the position P1 was 97.4°C. The temperature T2 of the CNT heater 1 at the position P2 was 113.0°C. The temperature T3 of the CNT heater 1 at the position P3 was 76.9°C, which was lower than the temperatures T1 and T2. FIG. 5 is a diagram showing the temperature distribution in the CNT heater 1 of Example 2.

[0047] In Example 3, the current flowing between the pair of electrodes 22 is 0.7 A. The temperature T1 of the CNT heater 1 at the position P1 was 123.6 °C. The temperature T2 of the CNT heater 1 at the position P2 was 153.6 °C. The temperature T3 of the CNT heater 1 at the position P3 was 90.1 °C, which was lower than the temperatures T1 and T2. FIG. 6 is a diagram showing the temperature distribution in the CNT heater 1 of Example 3.

[0048] In Example 4, the current flowing between the pair of electrodes 22 is 0.9 A. The temperature T1 of the CNT heater 1 at the position P1 was 157.0 °C. The temperature T2 of the CNT heater 1 at the position P2 was 194.3 °C. The temperature T3 of the CNT heater 1 at the position P3 was 98.6 °C, which was lower than the temperatures T1 and T2. FIG. 7 is a diagram showing the temperature distribution in the CNT heater 1 of Example 4.

[0049] In the CNT heater 1, by providing the additional conductive portion 23 around the heating suppression region 212, the conductivity in the Y direction increases at the portions near the ends on the (+X) side and (-X) side of the heating suppression region 212. Therefore, as schematically shown by the arrow in FIG. 8, the current flowing through the connection sheet portion 21 between the pair of electrodes 22 flows along the additional conductive portion 23, avoiding the heating suppression region 212 and flowing to the sides of the heating suppression region 212 (that is, the (+Y) side and (-Y) side). For this reason, as shown in Examples 1 to 4, in the connection sheet portion 21, the temperature of the heating suppression region 212 becomes lower than the temperature of the region around the heating suppression region 212 (that is, the temperature of the region other than the heating suppression region 212).

[0050] In the CNT heater 1 illustrated in FIG. 1, the additional conductive portion 23 is provided over the entire circumference around the heating suppression region 212 (that is, over the entire circumference of the outer peripheral region 213), but it is not limited to this. The additional conductive portion 23 may be provided only at a part of the periphery of the heating suppression region 212. For example, in the CNT heater 1a shown in FIG. 9, two additional conductive portions 23a each having a substantially arc shape are arranged in a region of the connection sheet portion 21 around the heating suppression region 212 excluding the vicinity of the ends on the (+Y) side and (-Y) side of the heating suppression region 212.

[0051] The area where the additional conductive portion 23a is located includes at least the area C1 of the outer peripheral region 213 that intersects with the first virtual line L1 extending in the X direction through the center C0 of the heating suppression region 212. In Figure 9, area C1 is enclosed by a dashed line. The heating suppression region 212 and the outer peripheral region 213 are also shown by dashed lines. Preferably, the area where the additional conductive portion 23a is located includes the area of ​​the outer peripheral region 213 that extends 30° circumferentially on both the (+Y) side and the (-Y) side of the area C1. In other words, preferably, the area where the additional conductive portion 23a is located includes all of the area of ​​the outer peripheral region 213 that is located on both sides of the first virtual line L1 with respect to the Y direction and between a pair of second virtual lines L2 that are parallel to the first virtual line L1. In other words, it is preferable that the additional conductive portion 23a is provided in the entire area of ​​the outer peripheral region 213 from one of the pair of second virtual lines L2 to the other. The pair of second virtual lines L2 are equidistant from the first virtual line L1 in the Y direction. The distance between the pair of second virtual lines L2 in the Y direction is half the maximum length of the heating suppression region 212 in the Y direction (i.e., the diameter of the heating suppression region 212). If the shape of the heating suppression region 212 in plan view is not circular, the center C0 of the heating suppression region 212 means the centroid of the heating suppression region 212 in plan view.

[0052] As described above, the CNT heaters 1 and 1a comprise a pair of electrodes 22, a connecting sheet portion 21, additional conductive portions 23 and 23a, and a covering portion 3. The pair of electrodes 22 are arranged side by side in a first direction (i.e., the X direction). The connecting sheet portion 21 is made of a sheet-shaped CNT molded body. The connecting sheet portion 21 extends in the X direction and in a second direction perpendicular to the X direction (i.e., the Y direction), connecting the pair of electrodes 22. The connecting sheet portion 21 generates heat when power is supplied to it. The additional conductive portions 23 and 23a are laminated on the connecting sheet portion 21. The covering portion 3 is a sheet-shaped member. The covering portion 3 covers the connecting sheet portion 21 and the additional conductive portions 23 and 23a from both sides in a third direction perpendicular to the X and Y directions (i.e., the Z direction).

[0053] A heating suppression region 212 is provided on the connecting sheet portion 21, where the temperature when power is supplied is lower than that of the surrounding area. The additional conductive portions 23 and 23a are positioned in a region of the outer peripheral region 213 that surrounds the heating suppression region 212 and is in contact with the periphery of the heating suppression region 212, and includes a region C1 that intersects with a first virtual straight line L1 that extends in the X direction through the center C0 of the heating suppression region 212. The conductivity of the additional conductive portions 23 and 23a in the Y direction is higher than the conductivity of the connecting sheet portion 21 in the Y direction.

[0054] As a result, in the connecting sheet portion 21, conductivity in the Y direction (i.e., the second direction) is increased near the portion of the connecting sheet portion 21 that faces the pair of electrodes 22 in the X direction (i.e., the first direction) within the periphery of the heating suppression region 212 (i.e., within the outer peripheral region 213). Therefore, current attempting to flow into the heating suppression region 212 can be diverted to both sides of the heating suppression region 212 in the Y direction, thereby suppressing the inflow of current into the heating suppression region 212. As a result, the temperature rise of the heating suppression region 212 when the CNT heaters 1, 1a are energized can be suppressed. Furthermore, compared to the case where through holes are formed in the connecting sheet portion as described above, the manufacturing of the CNT heater 1 can be simplified. In other words, by using the above structure for the CNT heater 1, the temperature rise of the heating suppression region 212 can be suppressed while simplifying the manufacturing of the CNT heater 1.

[0055] As described above, the arrangement region of the additional conductive parts 23, 23a preferably includes the entire region of the outer peripheral region 213 located between the pair of second virtual lines L2. The pair of second virtual lines L2 are located on both sides of the first virtual line L1 with respect to the Y direction. The pair of second virtual lines L2 are parallel to the first virtual line L1. The pair of second virtual lines L2 are located equidistant from the first virtual line L1 with respect to the Y direction. The distance between the pair of second virtual lines L2 in the Y direction is half the maximum length of the heating suppression region 212 in the Y direction (in the above example, the diameter of the heating suppression region 212).

[0056] In this way, by providing additional conductive portions 23, 23a in the outer peripheral region 213 in a relatively close and relatively wide area relative to the pair of electrodes 22, the inflow of current into the heating suppression region 212 can be further suppressed. As a result, the temperature rise of the heating suppression region 212 when the CNT heaters 1, 1a are energized can be further suppressed.

[0057] As described above, it is preferable that the area in which the additional conductive portion 23 is arranged includes the entire circumference of the outer peripheral region 213. This further suppresses the inflow of current into the heating suppression region 212, thereby further suppressing the temperature rise of the heating suppression region 212 when the CNT heaters 1, 1a are energized.

[0058] As described above, it is preferable that the orientation of the carbon nanotubes in the connecting sheet portion 21 is parallel to the X direction. This makes it possible to reduce the resistance of the connecting sheet portion 21 between the pair of electrodes 22.

[0059] As described above, the additional conductive portions 23 and 23a are preferably metal foils or metal plates. This makes it easy to provide additional conductive portions 23 and 23a on the connecting sheet portion 21 that have a higher conductivity in the Y direction than the connecting sheet portion 21.

[0060] As described above, it is preferable that the connecting sheet portion 21, the additional conductive portions 23, 23a, and the covering portion 3 are flexible. This allows the CNT heaters 1, 1a to be easily deformed to suit the installation location, thereby increasing the degree of freedom in the installation location of the CNT heaters 1, 1a.

[0061] In CNT heaters 1 and 1a, the additional conductive parts 23 and 23a may be sheet-shaped CNT molded bodies in which the orientation of carbon nanotubes differs from that of the connecting sheet part 21. This allows the connecting sheet part 21 and the additional conductive parts 23 and 23a to be formed from the same material, thereby simplifying the manufacturing of CNT heaters 1 and 1a. For example, the additional conductive parts 23 and 23a may be laminated sheet-shaped CNT molded bodies in which multiple CNT sheets are stacked.

[0062] When the additional conductive portions 23, 23a are CNT molded bodies, it is preferable that the orientation of the carbon nanotubes in the connecting sheet portion 21 is parallel to the X direction, and the orientation of the carbon nanotubes in the additional conductive portions 23, 23a is inclined with respect to the X direction. This makes it possible to reduce the resistance of the connecting sheet portion 21 between the pair of electrodes 22, and to suitably make the conductivity of the additional conductive portions 23, 23a in the Y direction higher than the conductivity of the connecting sheet portion 21 in the Y direction. As a result, it is possible to suitably suppress the inflow of current into the heating suppression region 212 and suitably suppress the temperature rise of the heating suppression region 212 when the CNT heaters 1, 1a are energized.

[0063] More preferably, the orientation of the carbon nanotubes in the additional conductive portions 23, 23a is parallel to the Y direction (i.e., perpendicular to the X direction). This makes it possible to increase the difference between the conductivity of the additional conductive portions 23, 23a in the Y direction and the conductivity of the connecting sheet portion 21 in the Y direction. As a result, the temperature rise of the heating suppression region 212 when the CNT heaters 1, 1a are energized can be further suppressed.

[0064] Next, a CNT heater 1b according to a second embodiment of the present invention will be described. Figure 10 is a plan view showing the CNT heater 1b. Figure 11 is a cross-sectional view of the CNT heater 1b taken at position XI-XI in Figure 10. In the CNT heater 1b, an additional conductive part 23b, which has a different shape from the additional conductive part 23, is provided instead of the additional conductive part 23 shown in Figure 1. The other components of the CNT heater 1b are substantially the same as those of the CNT heater 1, and in the following description, the same reference numerals are used for components of the CNT heater 1b that correspond to components of the CNT heater 1.

[0065] In Figure 10, to facilitate understanding of the diagram, parallel diagonal lines are drawn on the connecting sheet portion 21, similar to Figure 1, and parallel diagonal lines are drawn on the additional conductive portion 23b, different from those on the connecting sheet portion 21. Two types of parallel diagonal lines are drawn in the region where the connecting sheet portion 21 and the additional conductive portion 23b overlap. In Figure 11, to facilitate understanding of the diagram, the components of the CNT heater 1b are drawn spaced apart vertically within the diagram.

[0066] The additional conductive portion 23b is a sheet-like member that is laminated on the connecting sheet portion 21 at the center of the connecting sheet portion 21 in the X direction. The additional conductive portion 23b is composed of a sheet-like CNT molded body formed from a large number of carbon nanotubes. In the example shown in Figures 10 and 11, the additional conductive portion 23b is a laminated sheet-like member in which a plurality of carbon nanotube sheets are laminated in the Z direction.

[0067] In the example shown in Figure 10, the shape of the additional conductive portion 23b in plan view is a substantially rectangular shape with one pair of sides substantially parallel to the X direction and the other pair of sides substantially parallel to the Y direction. The additional conductive portion 23b is provided over substantially the entire length of the connecting sheet portion 21 in the Y direction. The length of the additional conductive portion 23b in the Y direction is substantially the same as the length of the connecting sheet portion 21 in the Y direction. That is, the (+Y) side and (-Y) side edges of the additional conductive portion 23b substantially overlap with the (+Y) side and (-Y) side edges of the connecting sheet portion 21 in plan view.

[0068] The length of the additional conductive portion 23b in the X direction is greater than the maximum length (i.e., diameter) of the heating suppression region 212 in the X direction. The heating suppression region 212 is located between the (+X) side and the (-X) side edges of the additional conductive portion 23b. In other words, the (+X) side edge of the additional conductive portion 23b is spaced away from the heating suppression region 212 towards the (+X) side, and the (-X) side edge of the additional conductive portion 23b is spaced away from the heating suppression region 212 towards the (-X) side. The length of the additional conductive portion 23b in the X direction is less than the length of the connecting sheet portion 21 in the X direction. For example, the length of the additional conductive portion 23b in the X direction is 2.4% to 55% of the length of the connecting sheet portion 21 in the X direction. The size and shape of the additional conductive portion 23b in plan view can be varied.

[0069] The additional conductive portion 23b includes a through hole 231 that overlaps with the heating suppression region 212 of the connecting sheet portion 21 in a plan view. The through hole 231 of the additional conductive portion 23b penetrates the additional conductive portion 23b in the Z direction (i.e., the thickness direction). The through hole 231 is located, for example, approximately in the center of the additional conductive portion 23b in the X and Y directions. In the example shown in Figure 10, the shape of the through hole 231 in a plan view is approximately circular.

[0070] In the example shown in Figure 10, the size of the through-hole 231 in plan view is approximately the same as the size of the heating suppression region 212 in plan view. The center of the through-hole 231 approximately coincides with the center of the heating suppression region 212. That is, the periphery of the through-hole 231 overlaps with the periphery of the heating suppression region 212 (i.e., the inner periphery of the outer peripheral region 213) in plan view. Note that the shape, size, and position of the through-hole 231 on the additional conductive portion 23b may be changed in various ways to match the heating suppression region 212. Furthermore, the through-hole 231 does not necessarily have to be the same size as the heating suppression region 212, and the periphery of the through-hole 231 may be located outside (i.e., radially outward) the periphery of the heating suppression region 212.

[0071] The number of layers of CNT sheets in the additional conductive portion 23b is, for example, 3 to 100 layers. The number of layers of CNT sheets in the additional conductive portion 23b is, for example, substantially the same over substantially the entire surface of the additional conductive portion 23b, and the thickness of the additional conductive portion 23b is substantially the same over substantially the entire surface of the additional conductive portion 23b. However, the number of layers of CNT sheets in the additional conductive portion 23b is not limited to this range and may be varied in a range of 1 layer or more. Also, the thickness of the additional conductive portion 23b does not necessarily have to be substantially the same over substantially the entire surface and may differ from part to part.

[0072] The orientation of the carbon nanotubes in the additional conductive portion 23b (i.e., the direction in which the carbon nanotubes extend) is in a direction inclined with respect to the orientation of the carbon nanotubes in the connecting sheet portion 21. As described above, when the orientation of the carbon nanotubes in the connecting sheet portion 21 is substantially parallel to the X direction, the orientation of the carbon nanotubes in the additional conductive portion 23b is in a direction inclined with respect to the X direction. In the examples shown in Figures 10 and 11, the orientation of the carbon nanotubes in the additional conductive portion 23b is substantially parallel to the Y direction (i.e., substantially perpendicular to the X direction).

[0073] The additional conductive portion 23b is conductive, and its conductivity in the Y direction is higher than that of the connecting sheet portion 21 in the Y direction. On the other hand, the conductivity of the additional conductive portion 23b in the X direction is lower than that of the connecting sheet portion 21 in the X direction. As a result, similar to the CNT heaters 1 and 1a described above, conductivity in the Y direction is higher in the vicinity of the portion of the heating suppression region 212 (i.e., the outer peripheral region 213) that faces the pair of electrodes 22 in the X direction. Therefore, current attempting to flow into the heating suppression region 212 is diverted to both sides of the heating suppression region 212 in the Y direction, and the inflow of current into the heating suppression region 212 is suppressed.

[0074] As described above, the CNT heater 1b comprises a pair of electrodes 22, a connecting sheet portion 21, an additional conductive portion 23b, and a covering portion 3, substantially the same as the CNT heater 1 described above. The pair of electrodes 22 are arranged side by side in a first direction (i.e., the X direction). The connecting sheet portion 21 is made of a sheet-shaped CNT molded body. The connecting sheet portion 21 extends in the X direction and in a second direction perpendicular to the X direction (i.e., the Y direction), connecting the pair of electrodes 22. The connecting sheet portion 21 generates heat when power is supplied to it. The additional conductive portion 23b is laminated on the connecting sheet portion 21. The covering portion 3 is a sheet-shaped member. The covering portion 3 covers the connecting sheet portion 21 and the additional conductive portion 23b from both sides in a third direction perpendicular to the X and Y directions (i.e., the Z direction).

[0075] A heating suppression region 212 is provided on the connecting sheet portion 21, where the temperature when power is supplied is lower than that of the surrounding area. The additional conductive portion 23b is positioned in the outer peripheral region 213 that surrounds the heating suppression region 212 and is in contact with the periphery of the heating suppression region 212, and includes a region C1 (see Figure 9) that intersects with a first virtual straight line L1 extending in the X direction through the center C0 of the heating suppression region 212. The conductivity of the additional conductive portion 23b in the Y direction is higher than the conductivity of the connecting sheet portion 21 in the Y direction.

[0076] As a result, in the connecting sheet portion 21, conductivity in the Y direction (i.e., the second direction) is increased near the portion of the connecting sheet portion 21 that faces the pair of electrodes 22 in the X direction (i.e., the first direction) within the periphery of the heating suppression region 212 (i.e., within the outer peripheral region 213). Therefore, current attempting to flow into the heating suppression region 212 is diverted to both sides of the heating suppression region 212 in the Y direction, thereby suppressing the inflow of current into the heating suppression region 212. As a result, the temperature rise of the heating suppression region 212 when the CNT heater 1b is energized can be suppressed. Furthermore, compared to the case where through holes are formed in the connecting sheet portion as described above, the manufacturing of the CNT heater 1b can be simplified. In other words, by using the above structure for the CNT heater 1b, the temperature rise of the heating suppression region 212 can be suppressed while simplifying the manufacturing of the CNT heater 1b.

[0077] The arrangement region of the additional conductive portion 23b preferably includes the entire region of the outer peripheral region 213 located between a pair of second virtual lines L2 (see Figure 9). The pair of second virtual lines L2 are located on both sides of the first virtual line L1 with respect to the Y direction. The pair of second virtual lines L2 are parallel to the first virtual line L1. The pair of second virtual lines L2 are equidistant from the first virtual line L1 with respect to the Y direction. The distance between the pair of second virtual lines L2 in the Y direction is half the maximum length of the heating suppression region 212 in the Y direction (in the above example, the diameter of the heating suppression region 212).

[0078] In this way, by providing the additional conductive portion 23b in the outer peripheral region 213 in a relatively close and relatively wide area relative to the pair of electrodes 22, the inflow of current into the heating suppression region 212 can be further suppressed. As a result, the temperature rise of the heating suppression region 212 when the CNT heater 1b is energized can be further suppressed.

[0079] The arrangement area of ​​the additional conductive portion 23b preferably includes the entire circumference of the outer peripheral region 213. This further suppresses the inflow of current into the heating suppression region 212, thereby further suppressing the temperature rise of the heating suppression region 212 when the CNT heater 1b is energized.

[0080] The connecting sheet portion 21, the additional conductive portion 23b, and the covering portion 3 are preferably flexible. This allows the CNT heater 1b to be easily deformed to fit the installation location, thereby increasing the flexibility of the installation location of the CNT heater 1b.

[0081] As described above, in the CNT heater 1b, the additional conductive portion 23b is a sheet-shaped CNT molded body in which the orientation of carbon nanotubes is different from that of the connecting sheet portion 21. This allows the connecting sheet portion 21 and the additional conductive portion 23b to be formed from the same material, thereby simplifying the manufacturing of the CNT heater 1b.

[0082] As described above, it is preferable that the orientation of the carbon nanotubes in the connecting sheet portion 21 is parallel to the X direction. This makes it possible to reduce the resistance of the connecting sheet portion 21 between the pair of electrodes 22. Furthermore, it is preferable that the orientation of the carbon nanotubes in the additional conductive portion 23b is inclined with respect to the X direction. This makes it possible to suitably increase the conductivity of the additional conductive portion 23b in the Y direction compared to the conductivity of the connecting sheet portion 21 in the Y direction. As a result, the inflow of current into the heating suppression region 212 can be suitably suppressed, and the temperature rise of the heating suppression region 212 when the CNT heater 1b is energized can be suitably suppressed.

[0083] More preferably, the orientation of the carbon nanotubes in the additional conductive portion 23b is parallel to the Y direction (i.e., perpendicular to the X direction). This makes it possible to increase the difference between the conductivity of the additional conductive portion 23b in the Y direction and the conductivity of the connecting sheet portion 21 in the Y direction. As a result, the temperature rise of the heating suppression region 212 when the CNT heater 1b is energized can be further suppressed.

[0084] Various modifications are possible for the CNT heaters 1, 1a, and 1b described above.

[0085] For example, the additional conductive parts 23, 23a do not necessarily need to be flexible and may be made of a rigid material. Also, the covering part 3 does not necessarily need to be flexible and may be made of a rigid material.

[0086] The pair of electrodes 22 do not necessarily have to be arranged substantially parallel to each other. For example, one electrode 22 may be arranged substantially parallel to the Y direction, and the other electrode 22 may be arranged to extend in a direction inclined with respect to the X and Y directions. Also, the shape of each electrode 22 in plan view does not necessarily have to be a rectangular strip; for example, it may be a substantially arc shape centered on the center of the heating suppression region 212.

[0087] The shape of the connecting sheet portion 21 in plan view does not necessarily have to be rectangular; for example, it may be approximately circular with the center of the heating suppression region 212 at its center.

[0088] The shape of the heating suppression region 212 of the connecting sheet portion 21 in plan view is not necessarily limited to a circle, but may be, for example, roughly rectangular. The same applies to the through hole 231 of the additional conductive portion 23b.

[0089] The orientation of the carbon nanotubes in the connecting sheet portion 21 does not necessarily have to be substantially parallel to the X direction; it may be in a direction inclined with respect to the X direction.

[0090] In the CNT heater 1a, the area where the additional conductive portion 23a is located only needs to include at least the area C1 that intersects the first virtual line L1 within the outer peripheral region 213, and does not necessarily need to include all of the area located between the pair of second virtual lines L2 within the outer peripheral region 213.

[0091] In the CNT heater 1b, the additional conductive portion 23b does not necessarily have to be provided along the entire length of the connecting sheet portion 21 in the Y direction. For example, the length of the additional conductive portion 23b in the Y direction may be greater than the maximum length (i.e., diameter) of the heating suppression region 212 in the Y direction, and less than the length of the connecting sheet portion 21 in the Y direction.

[0092] In the CNT heaters 1, 1a, and 1b, for example, the numerous carbon nanotubes constituting the connecting sheet portion 21 may be bonded to each other with an adhesive mainly composed of an aqueous polyvinyl alcohol (PVA) solution. The adhesive may be an epoxy, acrylic, or silicone rubber adhesive. The adhesive may also contain a conductive additive. The conductive additive may be, for example, metal fine particles such as silver (Ag), graphene (specifically, powder obtained by crushing sheet-like graphene), milled fiber, or carbon nanotube powder. The diameter of the conductive additive is preferably 10 μm or less, and more preferably less than 1 μm. Note that the adhesive does not necessarily contain a conductive additive.

[0093] In the CNT heaters 1, 1a, and 1b, for example, a reflective portion may be provided on the (-Z) side of the connecting sheet portion 21 to reflect heat from the connecting sheet portion 21. This reflective portion is, for example, a sheet-like member with a metal foil provided on the main surface of the (+Z) side of the heat insulating sheet. This allows heat from the connecting sheet portion 21 to be efficiently collected on the (+Z) side of the connecting sheet portion 21. Note that the reflective portion may be provided on the (+Z) side of the connecting sheet portion 21.

[0094] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other.

[0095] Although the invention has been described in detail, the above description is illustrative and not limiting. Therefore, it can be said that numerous modifications and embodiments are possible as long as they do not deviate from the scope of the present invention.

[0096] 1, 1a, 1b CNT heater 3 Covering portion 21 Connecting sheet portion 22 Electrode 23, 23a, 23b Additional conductive portion 212 Heat suppression region 213 Outer peripheral region 231 Through hole (of the additional conductive portion) C0 Center (of the heat suppression region) C1 Region L1 First virtual line L2 Second virtual line

Claims

1. A carbon nanotube heater comprising: a pair of electrodes arranged side by side in a first direction; a connecting sheet portion made of a sheet-like carbon nanotube molded body extending in the first direction and a second direction perpendicular to the first direction and connecting the pair of electrodes, which generates heat when power is supplied; an additional conductive portion laminated on the connecting sheet portion and having a conductivity in the second direction higher than that of the connecting sheet portion; and a sheet-like covering portion covering the connecting sheet portion and the additional conductive portion from both sides in a third direction perpendicular to the first and second directions, wherein a heating suppression region is set on the connecting sheet portion such that the temperature when power is supplied is lower than that of the surrounding area, and the additional conductive portion is arranged in a configuration region that includes a region that intersects with a first virtual straight line extending in the first direction through the center of the heating suppression region, among the outer peripheral region that surrounds the heating suppression region and is in contact with the periphery of the heating suppression region.

2. A carbon nanotube heater according to claim 1, wherein the arrangement region of the additional conductive portion includes all of the region of the outer peripheral region that is located on both sides of the first virtual line with respect to the second direction and between a pair of second virtual lines that are parallel to the first virtual line, the pair of second virtual lines are equidistant from the first virtual line with respect to the second direction, and the distance between the pair of second virtual lines in the second direction is half the maximum length of the heating suppression region in the second direction.

3. A carbon nanotube heater according to claim 2, wherein the arrangement region of the additional conductive portion includes the entire outer peripheral region.

4. A carbon nanotube heater according to any one of claims 1 to 3, wherein the orientation of the carbon nanotubes in the connecting sheet portion is parallel to the first direction.

5. A carbon nanotube heater according to any one of claims 1 to 3, wherein the additional conductive part is a metal foil or a metal plate.

6. A carbon nanotube heater according to any one of claims 1 to 3, wherein the additional conductive portion is a sheet-shaped carbon nanotube molded body in which the orientation of the carbon nanotubes is different from that of the connecting sheet portion.

7. A carbon nanotube heater according to claim 6, wherein the orientation of the carbon nanotubes in the connecting sheet portion is parallel to the first direction, and the orientation of the carbon nanotubes in the additional conductive portion is in a direction inclined with respect to the first direction.

8. A carbon nanotube heater according to claim 7, wherein the orientation of the carbon nanotubes in the added conductive portion is parallel to the second direction.

9. A carbon nanotube heater according to claim 6, wherein the additional conductive portion is provided along the entire length of the connecting sheet portion in the second direction.

10. A carbon nanotube heater according to any one of claims 1 to 3, wherein the connecting sheet portion, the additional conductive portion, and the coating portion are flexible.

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