Capacitance sensor having heater function and capacitance sensor unit

Abstract

A capacitance sensor (10) having a heater function comprises: a conductive part (30) that forms capacitance with an object (100) to be detected; and a base material (20) that has electrical insulation properties and holds the conductive part (30). The conductive part (30) comprises a first conductive layer (40) that generates heat by electrical resistance, and a second conductive layer (70) that is in contact with the first conductive layer (40) and electrically connected to the first conductive layer (40). The electrical resistivity (ρ2) of the second conductive layer (70) is higher than the electrical resistivity (ρ1) of the first conductive layer (40). The second conductive layer (70) is provided with a non-overlapping portion (72) that does not overlap the first conductive layer (40) in a plan view.

Description

Capacitive sensor with heater function and capacitive sensor unit

[0001] The present invention relates to a capacitive sensor having a heater function, and a capacitive sensor unit equipped with the capacitive sensor. For designated countries where incorporation by reference is permitted, the contents described in Japanese Patent Application No. 2024-189245, filed in Japan on October 28, 2024, are incorporated herein by reference and constitute part of this specification.

[0002] A grip sensor is known that comprises a sensor wire arranged in a nonwoven fabric and a control circuit unit electrically connected to the sensor wire via a harness (see, for example, Patent Document 1). The control circuit unit includes a sensor circuit and a power supply unit. The sensor circuit detects the driver gripping the steering wheel by detecting a change in capacitance in the sensor wire. Meanwhile, the power supply unit warms the steering wheel by passing an electric current through the sensor wire, causing it to heat up.

[0003] Japanese Patent Publication No. 2018-142411

[0004] In the grip sensor described above, the sensor wire, which functions as a capacitive sensor, is also used as a heating element. However, because this sensor wire is made of thin metal wire such as copper wire, the detection area formed by the sensor wire is small when it functions as a capacitive sensor, resulting in a problem of low sensitivity for the capacitive sensor.

[0005] The problem that this invention aims to solve is to provide a capacitive sensor and a capacitive sensor unit that can improve sensitivity.

[0006] [1] Embodiment 1 of the present invention is a capacitive sensor having a heater function, comprising: a conductive part that forms a capacitance with an object to be detected; and a substrate that has electrical insulating properties and holds the conductive part, wherein the conductive part comprises: a first conductive layer that generates heat due to electrical resistance; and a second conductive layer that contacts the first conductive layer and is electrically connected to the first conductive layer, wherein the electrical resistivity of the second conductive layer is higher than the electrical resistivity of the first conductive layer, and the second conductive layer has a non-overlapping portion that does not overlap with the first conductive layer in a plan view.

[0007] [2] Embodiment 2 of the present invention is a capacitance sensor of Embodiment 1 in which the second conductive layer overlaps with the first conductive layer in a plan view and has an overlapping portion to which the non-overlapping portion is connected.

[0008] [3] Embodiment 3 of the present invention is a capacitance sensor according to Embodiment 1 or 2 in which, in a plan view, the area of ​​the second conductive layer is larger than the area of ​​the first conductive layer.

[0009] [4] Embodiment 4 of the present invention is a capacitance sensor in any one of embodiments 1 to 3, wherein the first conductive layer has a linear pattern extending in a linear manner, and the second conductive layer has a planar pattern, and the linear pattern is included in the planar pattern in a planar view.

[0010] [5] Embodiment 5 of the present invention is a capacitance sensor in any one of embodiments 1 to 4, wherein the first conductive layer has a mesh pattern with openings, and the non-overlapping portion overlaps with the openings in a plan view.

[0011] [6] Embodiment 6 of the present invention is a capacitance sensor of Embodiment 5 in which the second conductive layer covers the mesh pattern or has a planar pattern on which the mesh pattern is superimposed.

[0012] [7] Embodiment 7 of the present invention is a capacitance sensor in any one of embodiments 1 to 4, wherein the first conductive layer has a plurality of linear patterns arranged at intervals, and the non-overlapping portion overlaps with the portion between the plurality of linear patterns in a plan view.

[0013] [8] Embodiment 8 of the present invention is a capacitance sensor of embodiment 7 in which the second conductive layer covers the plurality of linear patterns or has a planar pattern in which the plurality of linear patterns are superimposed.

[0014] [9] Embodiment 9 of the present invention is a capacitance sensor in any one of embodiments 1 to 8, wherein the first conductive layer is provided on the substrate and the second conductive layer is provided on the substrate so as to cover the first conductive layer.

[0015]

[10] Embodiment 10 of the present invention is a capacitance sensor in any one of embodiments 1 to 8, wherein the second conductive layer is provided on the substrate and the first conductive layer is provided on the second conductive layer.

[0016]

[11] Embodiment 11 of the present invention is a capacitance sensor unit comprising one capacitance sensor from embodiments 1 to 10, a sensor circuit that applies a voltage to the conductive part and detects a change in capacitance, and a heater circuit that generates heat in the first conductive layer by passing an electric current through the first conductive layer.

[0017] In the present invention, the conductive part includes a first conductive layer that generates heat due to electrical resistance, and a second conductive layer that contacts the first conductive layer and is electrically connected to the first conductive layer. Since the electrical resistivity of the second conductive layer is higher than that of the first conductive layer, the first conductive layer can function as a heater. Further, in the present invention, since the second conductive layer contacts the first conductive layer and is electrically connected to the first conductive layer, both the first and second conductive layers can function as a capacitance sensor. Furthermore, in the present invention, since the second conductive layer includes a non-overlapping portion that does not overlap with the first conductive layer in a plan view, the area of the detection area can be increased, and the sensitivity of the capacitance sensor can be improved.

[0018] FIG. 1 is a plan view showing a capacitance sensor unit in an embodiment of the present invention. FIG. 2 is a plan view showing a capacitance sensor in an embodiment of the present invention. FIG. 3 is an enlarged view of part III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a plan view showing a modified example of the first conductive layer in an embodiment of the present invention. FIG. 6 is a cross-sectional view of a capacitance sensor in another embodiment of the present invention, corresponding to FIG. 4. FIG. 7 is a cross-sectional view of a capacitance sensor in still another embodiment of the present invention, corresponding to FIG. 4. FIG. 8(a) is a diagram for explaining the charging of charges to the second conductive layer in Comparative Example 1, and FIG. 8(b) is a diagram for explaining the charging of charges to the second conductive layer in an embodiment of the present invention. FIG. 9 is a graph showing the results of a heat generation experiment of the capacitance sensor. FIG. 10 is a graph showing the results of a sensitivity experiment of the capacitance sensor.

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] FIG. 1 is a plan view showing a capacitance sensor unit 1 in the present embodiment. FIG. 2 is a plan view showing a capacitance sensor 10 in the present embodiment, FIG. 3 is an enlarged view of part III in FIG. 2, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3.

[0021] As shown in FIG. 1, the capacitance sensor unit 1 in the present embodiment includes a capacitance sensor 10 and a control device 80. The capacitance sensor 10 has a function as a capacitance sensor that forms a capacitance with a detection object 100 (see FIG. 4). Further, in addition to the function as the capacitance sensor described above, the capacitance sensor 10 also has a function as a heater that generates heat by electrical resistance.

[0022] Although not particularly limited, the capacitance sensor unit 1 can be used as a steering wheel grip detection sensor for a vehicle. For example, the capacitance sensor 10 is installed along the circumferential direction on the rim portion of the steering hole, and the sensor circuit 81 (described later) of the control device 80 detects a change in the capacitance formed between the capacitance sensor 10 and the driver's hand 100, thereby detecting the gripping of the steering wheel by the driver. On the other hand, the capacitance sensor 10 generates heat by electrical resistance according to the current from the heater circuit 82 (described later) of the control device 80, thereby warming the steering wheel.

[0023] Note that the use of the capacitance sensor unit 1 is not limited to the above-described steering wheel grip detection sensor. For example, the capacitance sensor unit 1 may be used as a touch screen for a smartphone or a tablet device, a track pad for a personal computer, a switch portion for a home appliance, a control panel for a vehicle, a seating sensor for a vehicle, or a seating sensor for a toilet seat. At this time, the heater function of the capacitance sensor 10 can be used, for example, for defrosting, ensuring the normal operation of the capacitance sensor unit 1 in a low-temperature environment, or warming a human body.

[0024] As shown in Figures 2 to 4, the capacitance sensor 10 is a wiring board comprising a base material 20 and a conductive part 30. The conductive part 30 comprises a first conductive layer 40, connecting wires 51 and 52, terminals 61 and 62, and a second conductive layer 70. The first conductive layer 40, connecting wires 51 and 52, and terminals 61 and 62 are provided on the base material 20. The second conductive layer 70 is provided on the base material 20 so as to cover the first conductive layer 40. That is, the first conductive layer 40 is interposed between the base material 20 and the second conductive layer 70. In Figure 2, the second conductive layer 70 is shown with a dashed line to make the first conductive layer 40 easier to see.

[0025] The base material 20 is a film-like member having electrical insulating properties. This base material 20 may also be flexible. This base material 20 is made of, for example, an electrically insulating resin material. While not particularly limited, specific materials that constitute this base material 20 include polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), polyetheretherketone (PEEK), and aramid.

[0026] The first conductive layer 40 has a mesh pattern 41 in plan view, comprising a plurality of first fine lines 411 and a plurality of second fine lines 412. These first and second fine lines 411 and 412 correspond to an example of a "linear pattern" in an embodiment of the present invention, and the mesh pattern 41 corresponds to an example of a "mesh pattern" in an embodiment of the present invention.

[0027] Multiple first thin wires 411 are in the first direction D １ The multiple first fine wires 411 are provided on the base material 20 so as to extend along the first direction D. These multiple first fine wires 411 extend parallel to each other and are arranged at equal intervals. On the other hand, the multiple second fine wires 412 extend along the first direction D. １ A second direction D that is orthogonal to the first direction. ２The first and second fine wires 411 are provided on the base material 20 so as to extend along the first and second fine wires 411. These multiple second fine wires 412 also extend parallel to each other and are arranged at equal intervals. The first and second fine wires 411 and 412 intersect with each other, and these first and second fine wires 411 and 412 form a mesh pattern 41 having a mesh-like planar shape. This mesh pattern 41 has openings 413 that are demarcated by the first and second fine wires 411 and 412.

[0028] In Figure 3, the line width of the first thin line 411 and the line width of the second thin line 412 are the same, but the line width of the first thin line 411 and the line width of the second thin line 412 may be different. Also, in Figure 3, the spacing between the first thin lines 411 and the spacing between the second thin lines 412 are the same, but the spacing between the first thin lines 411 and the spacing between the second thin lines 412 may be different. Furthermore, in Figure 3, the intersection angle between the first thin line 411 and the second thin line 412 is a right angle, but the intersection angle between the first thin line 411 and the second thin line 412 may be an acute or obtuse angle.

[0029] This first conductive layer 40 is made of a conductive material and has a relatively low electrical resistivity ρ １ The first conductive layer 40 is made of a metallic material having good conductivity, although it is not particularly limited. Specific examples of the metallic material constituting the first conductive layer 40 include silver, copper, and aluminum. The first conductive layer 40 is formed on the substrate 20 using, for example, a subtractive method, a fully additive method, or a semi-additive method. Alternatively, the first conductive layer 40 may be formed using physical vapor deposition (PVD) such as vacuum deposition or sputtering, or chemical vapor deposition (CVD). The first conductive layer 40 formed by these methods is made of bulk metal.

[0030] Alternatively, the first conductive layer 40 may be formed by printing a conductive paste onto the substrate 20 and allowing it to solidify (harden). The conductive paste is composed of conductive particles and a binder resin mixed with water or a solvent and various additives. This conductive paste has a relatively low electrical resistivity ρ １This is a low-resistance conductive paste that can form a first conductive layer 40 having the following properties.

[0031] Specific examples of conductive particles contained in this low-resistance conductive paste include silver, copper, nickel, tin, bismuth, zinc, indium, and palladium, as well as alloys thereof. Specific examples of binder resins contained in the conductive paste include acrylic resin, polyester resin, epoxy resin, vinyl resin, urethane resin, phenolic resin, polyimide resin, silicone resin, and fluororesin. Furthermore, examples of solvents contained in the conductive paste include α-terpineol, butyl carbitol acetate, butyl carbitol, 1-decanol, butyl cellsolve, diethylene glycol monoethyl ether acetate, and tetradecane.

[0032] While not particularly limited, in this embodiment, it is preferable to use a silver paste, in which silver is the main component of conductive particles, or a copper paste, in which copper is the main component of conductive particles, as the low-resistance conductive paste. Alternatively, metal salts may be used as the conductive particles contained in the conductive paste. Examples of metal salts include the salts of the metals mentioned above. Furthermore, the binder resin may be omitted from the conductive paste. That is, a sintered conductive paste without a binder resin may be used instead of the conductive paste. Alternatively, conductive ink may be used instead of the conductive paste.

[0033] The method of applying the conductive paste is not particularly limited, but either a contact application method or a non-contact application method may be used. Specific examples of contact application methods include screen printing, gravure printing, offset printing, gravure offset printing, and flexographic printing. On the other hand, specific examples of non-contact application methods include inkjet printing, spray application, dispensing application, and jet dispensing. Furthermore, the heat source for curing the conductive paste is not particularly limited, but examples include electric ovens, infrared ovens, far-infrared (IR) furnaces, near-infrared (NIR) furnaces, and laser irradiation devices, and a combination of these heat treatments may also be used.

[0034] The connecting wires 51, 52 and terminals 61, 62 are provided on the base material 20. Connecting wire 51 is connected to one end of the mesh pattern 41 (the right end in Figure 2). The ends of the multiple fine wires 411, 412 provided on the mesh pattern 41 are connected to this connecting wire 51. Terminal 61 is connected to this connecting wire 51. On the other hand, connecting wire 52 is connected to the other end of the mesh pattern 41 (the left end in Figure 2). The ends of the multiple fine wires 411, 412 provided on the mesh pattern 41 are connected to this connecting wire 52. Terminal 62 is connected to this connecting wire 52. These connecting wires 51, 52 and terminals 61, 62 are made of the same material as the first conductive layer 40 described above. These connecting wires 51, 52 and terminals 61, 62 are formed in the same process as the first conductive layer 40 and are formed integrally with the first conductive layer 40.

[0035] The connecting wires 51, 52 and terminals 61, 62 may be made of a different material than the first conductive layer 40. The materials that make up the connecting wires 51, 52 and the materials that make up the terminals 61, 62 may be different. The connecting wires 51, 52 and terminals 61, 62 may be formed in a process separate from the first conductive layer 40. The terminals 61, 62 may be formed in a process separate from the connecting wires 51, 52.

[0036] The second conductive layer 70 is provided on the substrate 20 so as to cover the first conductive layer 40. In addition to covering the first conductive layer 40, the second conductive layer 70 covers a portion of one connection line 51 and a portion of the other connection line 52, and has a rectangular planar pattern (a so-called solid pattern) that is larger than the mesh pattern 41 of the first conductive layer 40. Therefore, in a plan view, the entire mesh pattern 41 is contained within the second conductive layer 70, and the entire first conductive layer 40 is covered by the second conductive layer 70. Also, in a plan view, the area of ​​the second conductive layer 70 is larger than the area of ​​the first conductive layer 40.

[0037] As shown in Figures 3 and 4, the second conductive layer 70 comprises an overlapping portion 71 and a non-overlapping portion 72. The overlapping portion 71 is the portion that overlaps with the first conductive layer 40 in a plan view. In this embodiment, since the first conductive layer 40 has a mesh pattern 41, the overlapping portion 71 also has a mesh-like planar shape corresponding to the shape of the mesh pattern 41. Specifically, the overlapping portion 71 overlaps with the first fine wires 411 of the first conductive layer 40 and also overlaps with the second fine wires 412 of the first conductive layer 40. On the other hand, the non-overlapping portion 72 is the portion that does not overlap with the first conductive layer 40 in a plan view. In this embodiment, the non-overlapping portion 72 overlaps with the openings 413 of the mesh pattern 41 of the first conductive layer 40 in a plan view.

[0038] The overlapping portion 71 and the non-overlapping portion 72 are integrally formed and interconnected. The overlapping portion 71 is in direct contact with the first conductive layer 40 at its lower surface 711. The non-overlapping portion 72 is also in direct contact with the first conductive layer 40 at its side surface 721. Therefore, the second conductive layer 70 is in contact with the first conductive layer 40 at multiple locations 711, 721, and the second conductive layer 70 is electrically connected to the first conductive layer 40.

[0039] This second conductive layer 70 is also made of a conductive material. In this embodiment, the electrical resistivity ρ of the first conductive layer 40 described above is １ Higher electrical resistivity ρ ２ (ρ２ > ρ １ ). Although not particularly limited, for example, the electrical resistivity ρ of the second conductive layer 70 ２ is 10 times or more the electrical resistivity ρ of the first conductive layer 40 １ (ρ ２ ≥ ρ １ × 10), or the electrical resistivity ρ of the second conductive layer 70 ２ is 100 times or more the electrical resistivity ρ of the first conductive layer 40 １ (ρ ２ ≥ ρ １ × 100). Here, the "electrical resistivity" in the present embodiment is the electrical resistivity (specific resistance) ρ that can be calculated by the following formula (1). However, in the following formula (1), R is the resistance value of the conductor, L is the length of the conductor, and A is the cross-sectional area of the conductor.

[0040]

[0041] The second conductive layer 70 is formed by printing a conductive paste on the base material 20 and curing it. This conductive paste is a high-resistance conductive paste capable of forming the second conductive layer 70 having a relatively high electrical resistivity ρ ２ .

[0042] Specific examples of such high-resistance conductive pastes include carbon paste. Specific examples of the conductive particles contained in the carbon paste include carbon-based materials such as graphite, carbon black (furnace black, acetylene black, and ketjen black), carbon nanotubes, and carbon nanofibers. Note that carbon ink may be used instead of the above carbon paste.

[0043] Note that, as the material constituting the second conductive layer 70, instead of the above-described carbon paste, a conductive polymer such as PEDOT / PSS or indium tin oxide (ITO) may be used. In this case, instead of the above-described printing method, the second conductive layer 70 may be formed by a physical vapor deposition method (PVD) such as vacuum evaporation or sputtering, or a chemical vapor deposition method (CVD).

[0044] Furthermore, if a bulk metal layer is formed as the first conductive layer 40 by the subtractive method described above, the second conductive layer 70 may be formed using a low-resistance conductive paste such as a silver paste with silver as the main component of conductive particles, or a copper paste with copper as the main component of conductive particles.

[0045] The planar shape of the first conductive layer 40 is not particularly limited as long as it has a linear pattern. The first conductive layer 40 may have a linear pattern 42 as shown in Figure 5. Figure 5 is a plan view showing a modified example of the first conductive layer 40 in an embodiment of the present invention.

[0046] In the modified example shown in Figure 5, the first conductive layer 40 has four linear patterns 42. These four linear patterns 42 extend linearly between connecting lines 51 and 52 and are arranged at equal intervals from one another. The second conductive layer 70 is provided on the substrate 20 so as to cover these four linear patterns 42. In addition to the linear patterns 42, the second conductive layer 70 covers a portion of one connecting line 51 and a portion of the other connecting line 52. Therefore, in a plan view, the entirety of the four linear patterns 42 is contained within the second conductive layer 70, and the entirety of the first conductive layer 40 is covered by the second conductive layer 70. Also, in a plan view, the area of ​​the second conductive layer 70 is larger than the area of ​​the first conductive layer 40.

[0047] In the modified example shown in Figure 5, since the first conductive layer 40 has a linear pattern 42, the overlapping portion 71 of the second conductive layer 70 also has a linear shape that extends in a manner corresponding to the linear pattern 42. On the other hand, the non-overlapping portion 72 of the second conductive layer 70 overlaps with the portion between the linear patterns 42 in a plan view.

[0048] The number of linear patterns 42 on the first conductive layer 40 is not particularly limited to those described above. Also, although all linear patterns 42 have the same line width in Figure 5, the line widths of the linear patterns 42 may differ. Also, although the linear patterns 42 are arranged at equal intervals in Figure 5, the intervals between the first thin lines 411 do not have to be equal. Furthermore, the shape of the linear patterns on the first conductive layer 40 is not particularly limited to those described above. For example, the first conductive layer 40 may have meandering linear patterns.

[0049] Furthermore, as shown in Figure 6, a second conductive layer 70 may be provided on the substrate 20, and the first conductive layer 40 may be provided on the second conductive layer 70. Figure 6 is a cross-sectional view of a capacitance sensor in another embodiment of the present invention, and corresponds to Figure 4.

[0050] In the configuration shown in Figure 6, the second conductive layer 70 has an electrical resistivity ρ of the first conductive layer 40. １ Higher electrical resistivity ρ ２ (ρ ２ >ρ １ The second conductive layer 70 is formed by printing the carbon paste described above onto the substrate 20 and curing it. Alternatively, instead of carbon paste, a conductive polymer such as PEDOT / PSS or indium tin oxide (ITO) may be used as the material for the second conductive layer 70. In this case, instead of the printing method described above, the second conductive layer 70 may be formed by a physical vapor deposition (PVD) method such as vacuum deposition or sputtering, or by a chemical vapor deposition (CVD) method.

[0051] On the other hand, the first conductive layer 40 is formed by printing a low-resistance conductive paste, such as silver paste or copper paste, onto the second conductive layer 70 and curing it. Alternatively, the first conductive layer 40 may be formed by depositing a metal material with relatively low electrical resistivity, such as silver, copper, or aluminum, onto the second conductive layer 70 using a physical vapor deposition (PVD) method such as vacuum deposition or sputtering, or a chemical vapor deposition (CVD) method.

[0052] In the configuration shown in Figure 6, the overlapping portion 71 of the second conductive layer 70 has a mesh-like planar shape corresponding to the shape of the mesh pattern 41 of the first conductive layer 40. In this embodiment, the overlapping portion 71 is in direct contact with the first conductive layer 40 at its upper surface 712, and the overlapping portion 71 is electrically connected to the first conductive layer 40. On the other hand, the non-overlapping portion 72 of the second conductive layer 70 overlaps with the opening 413 of the mesh pattern 41 of the first conductive layer 40 in a plan view and is not in contact with the first conductive layer 40. This non-overlapping portion 72 is formed integrally with the overlapping portion 71 and is electrically connected to the first conductive layer 40 via the overlapping portion 71.

[0053] Alternatively, as shown in Figure 7, the first conductive layer 40 may be provided on the substrate 20, and the second conductive layer 70 may be provided on the substrate 20 so as to be located only within the openings 413 of the mesh pattern 41. Figure 7 is a cross-sectional view of a capacitance sensor in yet another embodiment of the present invention, and corresponds to Figure 4. In the embodiment shown in Figure 7, the second conductive layer 70 has only a non-overlapping portion 72 corresponding to the openings 413, and does not have an overlapping portion 71. The non-overlapping portion 72 is in direct contact with the first conductive layer 40 at its side surface 721, and the second conductive layer 70 is electrically connected to the first conductive layer 40.

[0054] As shown in Figure 1, the control device 80 of the capacitance sensor unit 1 includes a sensor circuit 81 and a heater circuit 82. Although not particularly limited, this control device 80 is a circuit board that supplies current and applies voltage to the capacitance sensor 10. For example, this control device 80 alternately switches between sensor control by the sensor circuit 81 and heat generation control by the heater circuit 82. Power is supplied to this control device 80 from, for example, the vehicle's auxiliary battery (not shown). The control device 80 and the capacitance sensor 10 are electrically connected, for example, via a wire harness (not shown).

[0055] The heater circuit 82 is connected to both terminals 61 and 62, and generates heat in the first conductive layer 40 by passing current through it. In this embodiment, the electrical resistivity ρ of the second conductive layer 70 ２The electrical resistivity ρ of the first conductive layer 40 is １ It is higher than (ρ ２ >ρ １ ), the resistance value R of the second conductive layer 70 ２ The resistance value R of the first conductive layer 40 is １ It is larger than (R ２ > R １ Therefore, when the first conductive layer 40 generates heat as a heater, current also flows through the second conductive layer 70, but the power generated in the first conductive layer 40 (V ０ ２ / R １ ) generates power (V) in the second conductive layer 70. ０ ２ / R ２ (V) will be larger than ０ ２ / R １ >V ０ ２ / R ２ The first conductive layer 40 mainly generates heat. Note that the above voltage V ０ This is the voltage value applied to the capacitance sensor 10 by the heater circuit 82.

[0056] On the other hand, the sensor circuit 81 is connected to one terminal 61 and applies a voltage to the first conductive layer 40 to form a capacitance between the object to be detected 100 (see Figure 4) and the first conductive layer 40. In this embodiment, the second conductive layer 70 is in contact with the first conductive layer 40 and electrically connected, so a capacitance is also formed between the object to be detected 100 and the second conductive layer 70. At this time, the second conductive layer 70 has a non-overlapping portion 72 that does not overlap with the first conductive layer 40 in a plan view, and the area of ​​the detection area is increased, so the sensitivity of the capacitance sensor 10 can be improved. For example, this sensor circuit 81 outputs an AC signal to the first and second conductive layers 40 and 70, and detects the change in capacitance by detecting a change in the frequency of the AC signal caused by the approach or contact of the object to be detected 100.

[0057] Furthermore, in this embodiment, a low electrical resistivity ρ １The second conductive layer 70 is in contact with the first conductive layer 40, which has a high electrical resistivity ρ, and is electrically connected to the first conductive layer 40. ２ This has a reduced effect on the sensitivity of the capacitance sensor. Figure 8(a) illustrates the charging of the second conductive layer 70 in the capacitance sensor 10' of Comparative Example 1, and Figure 8(b) illustrates the charging of the second conductive layer 70 in the capacitance sensor 10 of this embodiment.

[0058] Specifically, as shown in Figure 8(a), in the capacitance sensor 10' of Comparative Example 1, which does not have the first conductive layer 40, the second conductive layer 70 has a relatively high electrical resistivity ρ ２ Because of this, it takes time to fill the portion of the second conductive layer 70 that is away from the terminals 61 and 62 (the central portion of the second conductive layer 70 in Figure 8(a)) with charge 200.

[0059] In contrast, in this embodiment, as described above, the first conductive layer 40 has a relatively low electrical resistivity ρ １ In addition, the second conductive layer 70 is in contact with the first conductive layer 40 and electrically connected. Therefore, as shown in Figure 8(b), the charge 200 can be filled into the portion of the second conductive layer 70 that is far from the terminals 61 and 62 via the first conductive layer 40, and the second conductive layer 70 can be filled with charge quickly. In other words, in this embodiment, the rate at which the charge 200 is filled into the second conductive layer 70 is faster than in the comparative example shown in Figure 8(a).

[0060] As described above, in this embodiment, the conductive portion 30 comprises a first conductive layer 40 that generates heat due to electrical resistance, and a second conductive layer 70 that is in contact with the first conductive layer 40 and is electrically connected to the first conductive layer, and the electrical resistivity ρ of the second conductive layer 70 ２ The electrical resistivity ρ of the first conductive layer 40 is １ Since it is higher than ρ, the first conductive layer 40 can function as a heater. In this case, the first conductive layer 40 has a low electrical resistivity ρ １ Because it has this feature, the heat-generating portion can be extended to a wide area, and the capacitance sensor 10 can be used as a large-area heater.

[0061] Furthermore, in this embodiment, since the second conductive layer 70 is in contact with the first conductive layer 40 and electrically connected to the first conductive layer 40, both the first and second conductive layers 40 and 70 can function as capacitance sensors. Moreover, in this embodiment, since the second conductive layer 70 has a non-overlapping portion 72 that does not overlap with the first conductive layer 40 in a plan view, the area of ​​the detection area can be increased, and the sensitivity of the capacitance sensor 10 can be improved.

[0062] Capacitive sensors according to Example 1, Example 2, and Comparative Example 2 were fabricated. Example 1 is a capacitive sensor having the structure shown in Figures 2 to 4, having a mesh pattern made of silver as the first conductive layer, and a planar pattern formed by printing and curing carbon paste as the second conductive layer. Example 2 has the same configuration as Example 1, except that the planar pattern of the second conductive layer is formed by printing and curing a paste containing PEDOT / PSS. Comparative Example 2 has the same configuration as Example 1, except that it does not have a second conductive layer.

[0063] Then, heat generation experiments and sensitivity experiments were conducted for Examples 1 and 2, and Comparative Example 2 described above. In the heat generation experiments, the voltage applied to the capacitance sensor from the heater circuit was gradually increased, and the temperature of the capacitance sensor was measured for each applied voltage. As shown in Figure 9, Examples 1 and 2 had heat generation performance equivalent to that of Comparative Example 2. Figure 9 is a graph showing the results of the heat generation experiment of the capacitance sensor.

[0064] On the other hand, in the sensitivity experiment, the capacitance value was measured when a person's finger was in contact with the upper surface of the glass laminated on the capacitance sensor, and when the finger was not in contact with the glass surface, and the difference between these values ​​was calculated. The results are shown in Figure 10. Figure 10 is a graph showing the results of the sensitivity experiment of the capacitance sensor. As shown in Figure 10, the difference in capacitance values ​​was sufficiently large in Examples 1 and 2, whereas in Comparative Example 2, a large difference in capacitance values ​​could not be obtained.

[0065] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0066] 1...Capacitance sensor unit 10...Capacitance sensor 20...Substrate 30...Conductive part 40...First conductive layer 41...Mesh pattern 411, 412...Fine wires 413...Opening 42...Linear pattern 51, 52...Connecting wires 61, 62...Terminals 70...Second conductive layer 71...Overlapping portion 711...Bottom surface 712...Top surface 72...Non-overlapping portion 721...Side surface 80...Control device 81...Sensor circuit 82...Heater circuit 100...Detected object 200...Charge

Claims

1. A capacitance sensor having a heater function, comprising: a conductive part that forms a capacitance with an object to be detected; and a substrate that has electrical insulating properties and holds the conductive part, wherein the conductive part comprises: a first conductive layer that generates heat due to electrical resistance; and a second conductive layer that contacts the first conductive layer and is electrically connected to the first conductive layer, wherein the electrical resistivity of the second conductive layer is higher than the electrical resistivity of the first conductive layer, and the second conductive layer has a non-overlapping portion that does not overlap with the first conductive layer in a plan view.

2. A capacitance sensor according to claim 1, wherein the second conductive layer overlaps with the first conductive layer in a plan view and has an overlapping portion to which the non-overlapping portion is connected.

3. A capacitance sensor according to claim 1 or 2, wherein, in a plan view, the area of ​​the second conductive layer is larger than the area of ​​the first conductive layer.

4. A capacitance sensor according to any one of claims 1 to 3, wherein the first conductive layer has a linear pattern extending in a linear manner, and the second conductive layer has a planar pattern, and the linear pattern is included in the planar pattern in a planar view.

5. A capacitance sensor according to any one of claims 1 to 4, wherein the first conductive layer has a mesh pattern with openings, and the non-overlapping portion overlaps with the openings in a plan view.

6. A capacitance sensor according to claim 5, wherein the second conductive layer covers the mesh pattern or has a planar pattern on which the mesh pattern is superimposed.

7. A capacitance sensor according to any one of claims 1 to 4, wherein the first conductive layer has a plurality of linear patterns arranged at intervals, and the non-overlapping portions overlap with the portions between the plurality of linear patterns in a plan view.

8. A capacitance sensor according to claim 7, wherein the second conductive layer covers the plurality of linear patterns or has a planar pattern in which the plurality of linear patterns are superimposed.

9. A capacitance sensor according to any one of claims 1 to 8, wherein the first conductive layer is provided on the substrate and the second conductive layer is provided on the substrate so as to cover the first conductive layer.

10. A capacitance sensor according to any one of claims 1 to 8, wherein the second conductive layer is provided on the substrate and the first conductive layer is provided on the second conductive layer.

11. A capacitance sensor unit comprising: a capacitance sensor according to any one of claims 1 to 10; a sensor circuit that applies a voltage to the conductive part and detects a change in capacitance; and a heater circuit that generates heat in the first conductive layer by passing an electric current through the first conductive layer.

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