INPUT DEVICE

Abstract

An input device with a simple configuration, capable of detecting the approach and contact of a detection target and pressure exerted by the detection target, is provided. The input device comprises a first electrode, an elastic dielectric provided on the back side of the first electrode, a second electrode in which the elastic dielectric is provided between the second electrode and the first electrode, a detector that detects the approach and contact of a detection target with the first electrode and pressure exerted by the first electrode on the detection target based on an output from the first electrode, and a third electrode provided adjacent to the second electrode.

Description

Input Devices

[0001] The present disclosure relates to an input device.

[0002] Conventionally, there has been a touch panel comprising a touch sensor substrate that is rectangular in plan view and has a sensor electrode formed thereon that detects the position of a touch by an indicator; a cover panel that is fixed to one surface of the touch sensor substrate and is pressed by the indicator; a first electrode that is formed outside the display area on the surface of the cover panel opposite the surface that is pressed by the indicator; and a second electrode that is formed outside the display area on the one surface of the touch sensor substrate.

[0003] When viewed in a plane, at least a portion of the first electrode and the second electrode overlap, the second electrode is formed in at least one corner portion of the touch sensor substrate and is electrically separated from the sensor electrode, and the change in distance between the first electrode and the second electrode when the surface of the cover panel that is pressed by the indicator is pressed is measured as a change in capacitance between the first electrode and the second electrode, thereby detecting the pressure with which the indicator presses the touch sensor substrate through the cover panel, and further comprising a ground electrode formed on the outer periphery of the first electrode on the cover panel (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2021-125158

[0005] Conventional touch panels have a large number of components and are not simple in configuration because they have separate sensor electrodes for detecting a touch position and first and second electrodes for detecting pressure.

[0006] Therefore, an object of the present invention is to provide an input device that can detect the proximity, contact, and pressure of a detection object with a simple configuration.

[0007] An input device according to an embodiment of the present disclosure includes a first electrode, an elastic dielectric provided on the back side of the first electrode, a second electrode provided between the first electrode and the elastic dielectric, a detection unit that detects the proximity, contact, and pressure of a detection object relative to an operation surface located on the front side of the first electrode based on the output of the first electrode, and a third electrode provided adjacent to the second electrode.

[0008] It is possible to provide an input device that can detect the proximity, contact, and pressure of an object to be detected with a simple configuration.

[0009] 9 is a diagram showing a planar configuration of an input device 100 according to an embodiment. FIG. 9 is a diagram showing a cross section taken along the arrows A-A in FIG. 1. FIG. 9 is a diagram showing voltages applied to each electrode. FIG. 9 is a diagram showing a cross-sectional configuration of a simulation model of a comparative input device 10. FIG. 9 is a diagram showing simulation results of electric field distribution in the comparative input device 10. FIG. 9 is a diagram showing capacitance characteristics in the comparative input device 10. FIG. 9 is a diagram showing capacitance characteristics in the comparative input device 10. FIG. 9 is a diagram showing a cross-sectional configuration of a simulation model of an input device 100 according to an embodiment. FIG. 9 is a diagram showing simulation results of electric field distribution in the input device 100. FIG. 9 is a diagram showing capacitance characteristics in the input device 100. FIG. 9 is a diagram showing a cross-sectional structure of an input device 100A according to a first modified example of the embodiment. FIG. 9 is a plan view showing an input device 100C according to a second modified example of the embodiment. FIG. 9 is a diagram showing a planar configuration of an input device 100D according to a third modified example of the embodiment. FIG. 9 is a diagram showing a cross-sectional view taken along the arrows A-A in FIG.

[0010] Hereinafter, an embodiment to which the input device of the present disclosure is applied will be described.

[0011] <Embodiment> FIG. 1 is a diagram showing the planar configuration of an input device 100 according to an embodiment. FIG. 2 is a diagram showing a cross section taken along the line A-A in FIG. 1. The following description will be given by defining an XYZ coordinate system. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. For ease of explanation, the -Z direction may be referred to as the lower side or bottom, and the +Z direction may be referred to as the upper side or top, but this does not represent a universal vertical relationship. Furthermore, a planar view refers to a view from the XY plane. Furthermore, the length, width, thickness, etc. of each part may be exaggerated below to make the configuration easier to understand.

[0012] <Configuration of Input Device 100> The input device 100 includes a top panel 101, a substrate 102, an elastic dielectric 103, a substrate 104, a first electrode 110, a second electrode 120, a third electrode 130, a detection unit 140, a drive unit 141, and an MCU (micro controller unit) 150. The detection unit 140 and the MCU 150 are shown in FIG. 2 together with a user's fingertip FT.

[0013] A user performs an operation input to the input device 100 by touching (making contact with) the operation surface (upper surface) of the top panel 101 with a fingertip FT. The fingertip FT is an example of an object to be detected. The input device 100 can be operated with something other than the fingertip FT, but the following description will be given assuming that the input device 100 is operated with the fingertip FT.

[0014] The input device 100 detects the proximity, contact, and pressure of the user's fingertip FT to the operation surface of the top panel 101, and outputs data representing the content of the operation input to an operation target device connected to the input device 100. The input device 100 may be used to remotely control the operation target device, or may be provided integrally with the operation target device. The input device 100 may also be portable, or may be fixedly installable on a wall or the like.

[0015] The top panel 101 is, for example, a plate-like member made of transparent glass or resin that can bend when pressed from above, and is rectangular in plan view. The top surface is an operation surface that a user touches with their fingertip FT to perform operation input. The user can also press the top surface of the top panel 101 downward.

[0016] The first electrode 110 is disposed on the upper surface of the substrate 102 provided on the lower surface side of the top panel 101. The upper surface side (upper side) of the first electrode 110 is the front side facing the top panel 101, and the lower surface side (lower side) of the first electrode 110 is the back side opposite the front side. Therefore, the operation surface, which is the upper surface of the top panel 101, is located on the front side of the first electrode 110. The first electrode 110 is formed of a transparent electrode such as ITO (Indium Tin Oxide).

[0017] The first electrode 110 has a rectangular shape in a plan view, for example, and a square shape will be described here. The area of ​​the first electrode 110 is equal to the area of ​​the second electrode 120, and the first electrode 110 is disposed such that the entire outer edge of the first electrode 110 coincides with the outer edge of the second electrode 120 in a plan view.

[0018] The first electrode 110 is connected to the detection unit 140 via wiring. The first electrode 110 is provided to detect the proximity or contact of the fingertip FT based on the absolute self-capacitance of the first electrode 110. The absolute self-capacitance of the first electrode 110 is the capacitance Ct between the first electrode 110 and the fingertip FT shown in FIG. 2. The first electrode 110 is also provided to detect the pressing force of the fingertip FT based on the mutual capacitance between the first electrode 110 and the second electrode 120. The mutual capacitance is the capacitance Cp between the first electrode 110 and the second electrode 120 shown in FIG. 2.

[0019] The substrate 102 is a transparent substrate that holds the first electrode 110, and it is sufficient if it can bend when pressed from above, similar to the top panel 101. The substrate 102 may be, for example, a transparent polyimide substrate.

[0020] The elastic dielectric 103 is provided below (on the back side of) the substrate 102. Since the substrate 102 is provided below (on the back side of) the first electrode 110, the elastic dielectric 103 is provided below (on the back side of) the first electrode 110 with the substrate 102 sandwiched therebetween. Here, the first electrode 110 may be directly disposed on the upper surface of the elastic dielectric 103 without the substrate 102 being provided on the elastic dielectric 103. In other words, "the elastic dielectric 103 is provided below (on the back side of) the first electrode 110" means both a case where the elastic dielectric 103 is indirectly provided below (on the back side of) the first electrode 110 with the substrate 102 sandwiched therebetween, and a case where the elastic dielectric 103 is directly provided below (on the back side of) the first electrode 110 without the substrate 102 sandwiched therebetween. This also includes cases where an insulating layer or the like is provided between the first electrode 110 and the elastic dielectric 103 in place of the substrate 102, or where a structure such as an insulating layer is provided in addition to the substrate 102.

[0021] The elastic dielectric 103 is a transparent, elastically deformable dielectric material, and is made of, for example, urethane resin. The elastic dielectric 103 is provided at a position overlapping the top panel 101, the first electrode 110, and the substrate 102 in a plan view, and has a uniform thickness in the Z direction. Because the elastic dielectric 103 is elastically deformable, when a user presses downward with a fingertip FT onto a portion of the operation surface of the top panel 101 directly above the detection electrode 111, the elastic dielectric 103 bends and contracts, causing the first electrode 110 and the substrate 102 to be slightly displaced downward.

[0022] The second electrode 120 is provided on the upper surface of the substrate 104 disposed below the elastic dielectric 103. That is, the second electrode 120 is provided with the substrate 102 and the elastic dielectric 103 sandwiched between the second electrode 120 and the first electrode 110. As an example, the second electrode 120 has a rectangular shape in a planar view. Here, a form in which the second electrode 120 has a square shape in a planar view will be described. As described above, the first electrode 110 may be provided directly on the upper surface of the elastic dielectric 103 without providing the substrate 102 on the elastic dielectric 103, so it is sufficient that the second electrode 120 is provided with the elastic dielectric 103 sandwiched between the second electrode 120 and the first electrode 110.

[0023] The second electrode 120 and the first electrode 110 have similar electrode shapes, and their central positions coincide in a plan view. The area of ​​the second electrode 120 is equal to the area of ​​the first electrode 110. Therefore, the outer edge of the second electrode 120 is arranged to coincide with the outer edge of the first electrode 110.

[0024] The second electrode 120 is provided to detect downward pressure on the top panel 101 by the fingertip FT based on the mutual capacitance between the second electrode 120 and the first electrode 110. The second electrode 120 is made of a transparent conductive material such as an ITO film, for example.

[0025] The third electrode 130 is provided on the upper surface of the substrate 104 so as to surround the periphery of the second electrode 120 in a plan view. In other words, the third electrode 130 is provided adjacent to the second electrode 120. The third electrode 130 has a rectangular ring shape in a plan view. The third electrode 130 is arranged so that its center position coincides with the second electrode 120 and the first electrode 110 in a plan view.

[0026] The third electrode 130 is provided to shield stray capacitance from the ground (a structure at ground potential) surrounding the input device 100 when detecting proximity and contact of the fingertip FT with the operation surface of the top panel 101, and to stabilize the mutual capacitance between the first electrode 110 and the second electrode 120 when detecting a pressure by the fingertip FT. The third electrode 130 is, for example, made of a transparent conductive material such as an ITO film. As will be described in detail later, the third electrode 130 is provided to reduce leakage of the electric field from the second electrode 120 to the fingertip FT by attracting the electric field from the second electrode 120 to the third electrode 130. Therefore, "the third electrode 130 is provided adjacent to the second electrode 120" means that the third electrode 130 is disposed adjacent to the second electrode 120 and close enough to the second electrode 120 that leakage of the electric field from the second electrode 120 to the fingertip FT can be reduced by diverting it toward the third electrode 130.

[0027] Note that, here, a configuration will be described in which the third electrode 130 has a rectangular ring shape in a plan view and surrounds the periphery of the second electrode 120 in a plan view, but the third electrode 130 is not limited to a rectangular ring shape and may not be ring-shaped. For example, when the second electrode 120 is rectangular, the third electrode 130 may be four electrodes provided along the four sides of the second electrode 120. In this case, the third electrode 130 does not surround the entire periphery of the second electrode 120 in a plan view, but is provided adjacent to the second electrode 120.

[0028] The substrate 104 is a transparent substrate that holds the second electrode 120 and the third electrode 130. As an example, the substrate 104 may be a transparent polyimide substrate, similar to the substrate 102, but may also be a transparent glass or resin substrate that hardly bends even when the operation surface of the top panel 101 is pressed.

[0029] Note that, assuming that a display panel such as a liquid crystal display or organic electroluminescence (EL) display panel is disposed below the input device 100, a configuration in which the top panel 101, the first electrode 110, the substrate 102, the elastic dielectric 103, the second electrode 120, the third electrode 130, and the substrate 104 are transparent will be described. However, for example, if a display panel is not disposed, these do not have to be transparent. In this case, the top panel 101, the first electrode 110, the second electrode 120, and the third electrode 130 may be made of a conductive material rather than a transparent material, such as a metal plate.

[0030] The detection unit 140 is connected to the first electrode 110 and the MCU 150. The drive unit 141 is connected to the second electrode 120 and the third electrode 130 and the MCU 150. The detection unit 140 detects proximity, contact, and pressure of the user's fingertip FT on the operation surface of the top panel 101 based on the output of the first electrode 110. At this time, the drive unit 141 applies a driving voltage to the second electrode 120 and the third electrode 130. More specifically, the detection unit 140 detects proximity or contact of the fingertip FT with the operation surface based on the absolute self-capacitance of the first electrode 110, and detects pressure of the fingertip FT on the operation surface based on the mutual capacitance between the first electrode 110 and the second electrode 120. Such a detection unit 140 can be realized, for example, by an integrated circuit (IC).

[0031] The detection unit 140 converts the absolute self-capacitance (analog value) of the first electrode 110 and the mutual capacitance (analog value) between the first electrode 110 and the second electrode 120 into digital values, and outputs detection data representing the digital capacitance values ​​to the MCU 150. Note that the detection unit 140 applies a voltage to the first electrode 110 and the drive unit 141 drives the second electrode 120 and the third electrode 130 with voltages in a time-division manner. This will be described in detail later.

[0032] The MCU 150 determines the content of the operation input based on the detection data input from the detection unit 140, and outputs data representing the determined content of the operation input to the operation target device connected to the input device 100. When determining whether the fingertip FT is in proximity to or in contact with the operation surface, the MCU 150 makes the determination based on the detection data representing the absolute self-capacitance of the first electrode 110 input from the detection unit 140, and when determining whether the fingertip FT is pressing the operation surface, the MCU 150 makes the determination based on the detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120 input from the detection unit 140.

[0033] In addition, when the detection unit 140 detects the absolute self-capacitance of the first electrode 110 and the mutual capacitance between the first electrode 110 and the second electrode 120, the MCU 150 controls the voltages that the detection unit 140 and the drive unit 141 apply to the first electrode 110, the second electrode 120, and the third electrode 130 in a time-division manner.

[0034] <Voltage Applied to Each Electrode> Fig. 3 is a diagram showing the voltages applied to each electrode. Fig. 3 shows the voltages applied to the first electrode 110, the second electrode 120, and the third electrode 130 when obtaining detection data representing the absolute self-capacitance of the first electrode 110 and when obtaining detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120. The voltages shown in Fig. 3 are applied to the first electrode 110, the second electrode 120, and the third electrode 130 by the MCU 150 controlling the detection unit 140 and the drive unit 141. The detection unit 140 applies a voltage to the first electrode 110, and the drive unit 141 applies a voltage to the second electrode 120 and the third electrode 130.

[0035] When obtaining detection data representing the absolute self-capacitance of the first electrode 110, a sinusoidal voltage (AC voltage) having the same frequency, amplitude, and phase is applied to the first electrode 110, the second electrode 120, and the third electrode 130.

[0036] Although the self-capacitance can be detected by the first electrode 110 alone, using only the first electrode 110 would also detect the stray capacitance of the ground external to the input device 100, resulting in a large capacitance. As a result, it becomes difficult to increase the detection sensitivity. Therefore, in order to detect the absolute self-capacitance of the first electrode 110, the input device 100 applies an AC voltage having the same waveform to the second electrode 120 and the third electrode 130, thereby blocking the stray capacitance from the external ground with the second electrode 120 and the third electrode 130.

[0037] Since there is no potential difference between the first electrode 110 and the second and third electrodes 120 and 130, the capacitance of the first electrode 110 with respect to ground can be reduced, and the input device 100 can improve the detection sensitivity of the absolute self-capacitance at the first electrode 110. This makes it possible to detect a proximity state in which the fingertip FT is not in contact with the operation surface but is very close. In this way, when detecting the absolute self-capacitance, the second electrode 120 and the third electrode 130 are used as an active shield.

[0038] Furthermore, when obtaining detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120, the input device 100 applies an AC voltage (a predetermined AC voltage) to the second electrode 120, and maintains the first electrode 110 and the third electrode 130 at a constant potential. The AC voltage applied to the second electrode 120 is, for example, the same as the AC voltage applied to the first electrode 110, the second electrode 120, and the third electrode 130 to obtain detection data representing the absolute self-capacitance.

[0039] An AC voltage is applied to the second electrode 120 while the first electrode 110 is held at a constant potential to detect the movement of charge (current), so the second electrode 120 becomes the transmitting side (Tx) and the first electrode 110 becomes the receiving side (Rx).

[0040] When the first electrode 110 and the third electrode 130 are fixed at a constant potential and an AC voltage is applied to the second electrode 120, a potential difference occurs between the first electrode 110 and the second electrode 120, and the input device 100 can measure the movement of charge (current) due to mutual capacitance between the first electrode 110 and the second electrode 120. Note that as long as the potentials of the first electrode 110 and the third electrode 130 are constant, any DC voltage may be applied.

[0041] <Simulation Results of Comparative Input Device 10> Fig. 4A is a diagram showing a cross-sectional configuration of a simulation model of the comparative input device 10. Fig. 4B is a diagram showing simulation results of the electric field distribution in the comparative input device 10. Figs. 5A, 5B, and 5C are diagrams showing capacitance characteristics in the comparative input device 10. Here, before describing the simulation results of the input device 100 of the embodiment, the simulation results and problems of the comparative input device 10 will be described.

[0042] Regarding the Z-direction position of the fingertip FT, Z = 0 mm is the position where the fingertip FT is in contact with the operation surface. A positive Z value indicates that the fingertip FT is spaced upward from the operation surface, and a negative Z value indicates that the fingertip FT is pressing downward on the operation surface.

[0043] As shown in Fig. 4A, the comparative input device 10 has a configuration in which the third electrode 130 is removed from the input device 100 of the embodiment. Fig. 4A also shows a ground plate 11 on the underside of the substrate 104. The ground plate 11 is, for example, a ground layer of a circuit board or the like on which the input device 10 is installed.

[0044] Here, an AC voltage is applied to the second electrode 120, and the electric field distribution is calculated while the first electrode 110 is held at ground potential, so the second electrode 120 is labeled Tx (transmitting side) and the first electrode 110 is labeled Rx (receiving side). This method of applying voltage corresponds to the method of applying voltage to obtain detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120 in the input device 100 of the embodiment.

[0045] Figure 4B shows the electric field distribution in the area enclosed by the dashed square in Figure 4A, using arrows. Along the large arrow A pointing from Tx to the fingertip FT, a large amount of electric field is generated from the second electrode 120 (Tx) over the first electrode 110 (Rx) toward the fingertip FT, indicating that a large amount of electric field is leaking into the fingertip FT. The same arrow A as in Figure 4B is also shown in Figure 4A. This is because the electric potential of the fingertip FT is at ground potential, resulting in leakage of the electric field from the second electrode 120 (Tx) to the fingertip FT.

[0046] 5A shows the simulation results of the change in capacitance with respect to the position of the fingertip FT in the Z direction when the position of the fingertip FT is Z≧0. The dashed line shows the characteristic of the detection data representing the absolute self-capacitance of the first electrode 110, and the solid line shows the characteristic of the detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120.

[0047] 5B shows the simulation results of the change in capacitance with respect to the force (N) applied to the operation surface when the position of the fingertip FT is Z<0. The dashed line shows the characteristic of the detection data representing the absolute self-capacitance of the first electrode 110, and the solid line shows the characteristic of the detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120. The position in FIG. 5B where the pressing force is 0 (N) corresponds to the position in FIG. 5A where Z=0 mm.

[0048] FIG. 5C shows the results of a simulation of the change in capacitance (mutual capacitance between the first electrode 110 and the second electrode 120) with respect to the position of the fingertip FT in the Z direction. In FIG. 5C, the position of the fingertip FT in the Z direction ranges from a positive value (Z = +20 mm) to a negative value (Z = approximately -1 mm). The characteristics in the range Z ≥ 0 in FIG. 5C are the same as the characteristics indicated by the solid line in FIG. 5A. The characteristics in the range Z < 0 in FIG. 5C are represented by converting the horizontal axis of the characteristics indicated by the solid line in FIG. 5B into position in the Z direction.

[0049] Like the input device 100, the comparative input device 10 determines whether the fingertip FT is approaching or touching the operation surface based on detection data representing the absolute self-capacitance of the first electrode 110 input from the detection unit 140, and determines whether the fingertip FT is pressing the operation surface based on detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120 input from the detection unit 140.

[0050] Therefore, when determining whether or not the fingertip FT is approaching or touching the operation surface while no operation is being performed, the comparative input device 10 determines whether or not the fingertip FT is approaching or touching the operation surface based on the characteristics of the dashed line in FIG. 5A . As the fingertip FT approaches the operation surface, the capacitance changes so as to trace the characteristics of FIG. 5A from left to right. Therefore, the comparative input device 10 determines, for example, whether or not the fingertip FT is approaching the operation surface when the capacitance count value reaches the proximity determination threshold TH1, and whether or not the fingertip FT is touching the operation surface when the capacitance count value reaches the contact determination threshold TH2. As an example, the proximity determination threshold TH1 is 500, and the contact determination threshold TH2 is 1300. Note that the contact determination threshold TH2 must be set somewhat low to ensure reliable contact determination due to variations in capacitance values ​​between fingers. Therefore, the threshold value TH2 for contact determination shown in the example of Figure 5A is set to a value lower than the count value (approximately 4100) obtained at the position Z = 0 mm, and contact is determined at Z = approximately 1 mm, slightly before the position Z = 0 mm where the fingertip FT contacts the operation surface.

[0051] Furthermore, when determining whether or not there is a pressure after determining whether or not there is proximity and contact, the presence or absence of a pressure is determined based on the characteristics of the solid line shown in Fig. 5B. The mutual capacitance value when it is determined that the fingertip FT is in contact with the operation surface is used as a reference, and since the capacitance increases relative to the reference value as the pressure increases, the pressure may be calculated based on the difference between the measured capacitance value and the reference value, or a threshold value (e.g., 1000) may be set to determine whether or not there is a pressure.

[0052] As shown in the solid line characteristic in FIG. 5A (mutual capacitance between the first electrode 110 and the second electrode 120), when the count value of the absolute self-capacitance reaches the contact determination threshold TH2 (1300) at a position Z = approximately 1 mm and it is determined that the fingertip FT is in contact with the operation surface, the count value of the mutual capacitance is approximately -250. However, the count value of the mutual capacitance at a position Z = 0 mm drops to approximately -300. Furthermore, in the solid line characteristic in FIG. 5B (mutual capacitance between the first electrode 110 and the second electrode 120), the count value is approximately -300 when the pressing force is 0 N. The mutual capacitance becomes the same value as the mutual capacitance count value (approximately -250) at a position Z = approximately 1 mm in FIG. 5A at approximately 0.4 N. Therefore, when the pressing force is in the range from 0 N to approximately 0.4 N, the measured count value of the mutual capacitance falls below the reference value, making it impossible to calculate the pressing force and creating a dead zone.

[0053] Because of the existence of such a dead zone, when the pressure of the fingertip FT decreases from a pressed state, for example, if the fingertip FT repeatedly presses and approaches, the comparative input device 10 has difficulty distinguishing between pressing and approaching even if it tries to determine the operation state based on the capacitance count value using the characteristics of the solid lines shown in Figures 5A and 5B.

[0054] In other words, using FIG. 5C , when the pressure of the fingertip FT decreases from a pressed state, for example, if the fingertip FT repeatedly presses and approaches, it becomes difficult to distinguish between pressing and approaching even when the comparative input device 10 attempts to determine the operation state based on the capacitance value using the characteristics shown in FIG. 5C . As shown by the dashed circle around Z = 0 mm in the characteristics of FIG. 5C , the capacitance value drops around Z = 0 mm, and this section behaves like a dead zone. This drop in capacitance around Z = 0 mm is thought to be caused by the electric field leaking into the fingertip FT. In other words, when the electric field leaks between the second electrode 120 and the finger, the detected capacitance (mutual capacitance) decreases compared to when there is no finger around Z = 0 mm, and then increases with further pressure. Therefore, as described above, the pressure cannot be determined, resulting in a dead zone.

[0055] The input device 100 of the embodiment solves the above-mentioned problems and makes it possible to easily and accurately determine the operation state, particularly around Z = 0 mm, when determining the operation state using the mutual capacitance between the first electrode 110 and the second electrode 120.

[0056] <Simulation Results of Input Device 100 of Embodiment> Fig. 6A is a diagram showing a cross-sectional configuration of a simulation model of the input device 100 of the embodiment. Fig. 6B is a diagram showing simulation results of the electric field distribution in the input device 100. Fig. 6C is a diagram showing capacitance characteristics in the input device 100. Fig. 6C shows characteristics corresponding to the characteristics in Fig. 5C for the input device 10 for comparison.

[0057] Fig. 6B shows the electric field distribution when an AC voltage is applied to the second electrode 120 and the first electrode 110 and the third electrode 130 are held at ground potential in order to obtain detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120. The electric field distribution shown in Fig. 6B corresponds to the area surrounded by the dashed square in Fig. 6A.

[0058] As shown in FIG. 6B, an electric field is generated from the second electrode 120 (Tx) toward the third electrode 130 (GND) as indicated by arrow B, and therefore the electric field from the second electrode 120 (Tx) toward the fingertip FT is reduced compared to FIG. 4B.

[0059] 6C , the simulation result of the change in capacitance (mutual capacitance between the first electrode 110 and the second electrode 120) with respect to the position of the fingertip FT in the Z direction shows that the drop in capacitance value (dead zone) around Z = 0 mm is eliminated, and a substantially constant value is obtained in the direction in which the fingertip FT moves away from Z = 0 mm. When viewed from the positive Z coordinate, the capacitance count value is substantially constant up to Z = 0 mm, and the capacitance value increases sharply at Z = 0 mm.

[0060] The reason why the characteristics improved around Z=0 is thought to be that by providing the third electrode 130 around the second electrode 120 and keeping the third electrode 130 at ground potential when detecting the mutual capacitance, an electric field component is generated that flows from the second electrode 120 to the third electrode 130, as shown in FIG. 6B, and the electric field component that flows from the second electrode 120 to the fingertip FT is reduced.

[0061] In general, the electric field tends to be strongest at the end (edge) of an electrode. To effectively generate an electric field component that wraps around from the second electrode 120 to the third electrode 130, the following can be done. As shown in FIGS. 1 and 2 , the edge of the first electrode 110 and the edge of the second electrode 120 are very close to each other in a plan view. Therefore, to effectively generate an electric field component that wraps around from the second electrode 120 to the third electrode 130, the edges of the first electrode 110 and the second electrode 120 should be close to the inner edge of the rectangular ring of the third electrode 130 in a plan view.

[0062] <Effects> As described above, the input device 100 includes the first electrode 110, the second electrode 120 provided with the elastic dielectric 103 sandwiched between the first electrode 110 and the second electrode 120, the third electrode 130 provided adjacent to the second electrode 120, and the detection unit 140 that detects the proximity, contact, and pressure of the fingertip FT with respect to the operation surface located on the front side of the first electrode 110 based on the output of the first electrode 110. Therefore, with a simple configuration including the first electrode 110, the second electrode 120, and the third electrode 130, it is possible to detect the proximity, contact, and pressure of the fingertip FT based on the output of the first electrode 110.

[0063] Therefore, it is possible to provide an input device 100 that can detect the proximity, contact, and pressure of the fingertip FT with a simple configuration.

[0064] Furthermore, since the third electrode 130 is maintained at a constant potential when the detection unit 140 detects the pressure of the fingertip FT, the leakage of the electric field from the second electrode 120 to the fingertip FT can be reduced by diverting the electric field from the second electrode 120 to the fingertip FT to the third electrode 130 side. As a result, as shown in FIG. 6C , the characteristic of the change in capacitance (mutual capacitance between the first electrode 110 and the second electrode 120) with respect to the position of the fingertip FT in the Z direction eliminates the drop in the capacitance count value around Z = 0 mm. Therefore, it is possible to provide an input device 100 that can accurately determine the operation state around Z = 0 mm.

[0065] Furthermore, the detection unit 140 detects the proximity or contact of the fingertip FT based on the absolute self-capacitance of the first electrode 110, and detects the pressure of the fingertip FT based on the mutual capacitance between the first electrode 110 and the second electrode 120. Therefore, it is possible to provide an input device 100 with a simple configuration that can detect the proximity or contact of the fingertip FT with the operation surface and the pressure on the operation surface by utilizing the output of the first electrode 110.

[0066] Furthermore, when the detection unit 140 detects the proximity or contact of the fingertip FT, AC voltages of the same frequency and phase are applied to the first electrode 110, the second electrode 120, and the third electrode 130. This allows the second electrode 120 and the third electrode 130 to function as active shields, and the second electrode 120 and the third electrode 130 can shield stray capacitance from the external ground. Furthermore, since there is no potential difference between the first electrode 110 and the second electrode 120 and the third electrode 130, the capacitance of the first electrode 110 with respect to the ground can be reduced, thereby improving the detection sensitivity of the absolute self-capacitance of the first electrode 110. Furthermore, proximity states can also be detected.

[0067] Furthermore, the first electrode 110 and the third electrode 130 are held at a constant potential when the detection unit 140 detects the pressure of the fingertip FT, and a predetermined AC voltage is applied to the second electrode 120 when the detection unit 140 detects the pressure of the fingertip FT. This allows a potential difference to be generated between the first electrode 110 and the second electrode 120, making it possible to measure the mutual capacitance between the first electrode 110 and the second electrode 120. The amount of pressure can then be detected based on the mutual capacitance.

[0068] Furthermore, since the third electrode 130 is arranged to surround the second electrode 120, the second electrode 120 and the third electrode 130 can function as active shields to provide a greater shielding effect when shielding stray capacitance from ground, thereby improving the detection sensitivity of absolute self-capacitance at the first electrode 110.

[0069] Furthermore, the first electrode 110 and the second electrode 120 have electrode shapes that are similar to each other, and their central positions coincide when viewed in a plane, resulting in a symmetrical arrangement when viewed in a plane, with little directional bias when viewed in a plane, making it possible to provide an input device 100 that can determine the operation state with high accuracy.

[0070] <First Modification> Fig. 7 is a diagram showing a cross-sectional structure of an input device 100A according to a first modification of the embodiment. The detection unit 140 and the MCU 150 are omitted from Fig. 7 . The input device 100A has a configuration in which a shield electrode 160 is added to the input device 100 shown in Fig. 2 , and the shield electrode 160 is provided around the first electrode 110 in a plan view between the top panel 101 and the elastic dielectric 103. The shield electrode 160 may be, for example, rectangular and annular like the third electrode 130, or may be four electrodes provided along the four sides of the first electrode 110.

[0071] The same voltage as that applied to the third electrode 130 may be applied to the shield electrode 160. That is, when obtaining detection data representing the absolute self-capacitance of the first electrode 110, the same AC voltage as that applied to the first electrode 110, the second electrode 120, and the third electrode 130 may be applied to the shield electrode 160. Furthermore, when obtaining detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120, the shield electrode 160 may be held at the same constant potential as that of the third electrode 130. In this way, when obtaining detection data representing the absolute self-capacitance of the first electrode 110, stray capacitance from the external ground can be more effectively shielded, thereby further improving the detection sensitivity of the first electrode 110.

[0072] 8 is a plan view showing an input device 100C according to a second modification of the embodiment. The input device 100C has a configuration in which the input device 100 shown in FIG. 1 is elongated in the X direction. Therefore, the top panel 101, the elastic dielectric 103, the substrate 104, the first electrode 110, the second electrode 120, and the third electrode 130, which are made of a resistive electrode material, are elongated in the X direction.

[0073] Such an input device 100C can be used as a slider. As the position of the fingertip FT in the X direction changes, the resistance value seen from the connection end of the first electrode 110 changes, and therefore the amount of charge detected by the detection unit 140 changes. Therefore, by placing the detection units 140 on both ends of the first electrode 110 and calculating the ratio of the amounts of charge, the position of the fingertip FT in the X direction can be detected.

[0074] <Third Modification> Fig. 9 is a diagram showing the planar configuration of an input device 100D according to a third modification of the embodiment, and Fig. 10 is a diagram showing a cross section taken along the line AA in Fig. 9 .

[0075] In the input device 100D of the third modification, the area of ​​the first electrode 110 of the input device 100 shown in FIGS. 1 and 2 is made larger than the area of ​​the second electrode 120.

[0076] The first electrode 110 has a rectangular shape in a plan view, and is square in this example. The area of ​​the first electrode 110 is larger than the area of ​​the second electrode 120, and the first electrode 110 is disposed such that the entire outer edge of the first electrode 110 is located outside the outer edge of the second electrode 120 in a plan view. Therefore, the outer edge of the second electrode 120 is included within the outer edge of the first electrode 110 in a plan view.

[0077] Furthermore, the area of ​​the first electrode 110 is larger than the area of ​​the second electrode 120, and in a plan view, the entire outer edge of the first electrode 110 is disposed outside the outer edge of the second electrode 120. For example, the first electrode 110 and the second electrode 120 may have electrode shapes that are similar to each other, and may be configured so that their center positions coincide in a plan view.

[0078] In this modification, when detecting the mutual capacitance between the first electrode 110 and the second electrode 120, not only is the third electrode 130 held at a constant potential to reduce the leakage of the electric field from the second electrode 120 to the finger, but the area of ​​the first electrode 110 closest to the finger is increased to completely cover the second electrode 120, further reducing the leakage of the electric field between the second electrode 120 and the finger. Therefore, there is no decrease in the capacitance between the first electrode 110 and the second electrode 120, and no dead zone occurs, allowing the detection unit 140 to reliably detect a press. In this way, when the area of ​​the first electrode 110 is larger than the area of ​​the second electrode 120, the leakage of the electric field to the finger can be further reduced compared to when the areas are equal.

[0079] Therefore, it is possible to provide an input device 100 that can detect the proximity, contact, and pressure of the fingertip FT with a simple configuration and with higher accuracy.

[0080] The above describes an input device according to an exemplary embodiment of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0081] This international application claims priority based on Japanese Patent Application No. 2022-037453, filed on March 10, 2022, the entire contents of which are incorporated herein by reference.

[0082] REFERENCE SIGNS LIST 101 Top panel 102 Substrate 103 Elastic dielectric 104 Substrate 110 First electrode 120 Second electrode 130 Third electrode 140 Detection unit 150 MCU

Claims

1. An input device comprising: a first electrode; an elastic dielectric provided on the back side of the first electrode; a second electrode provided between the first electrode and the elastic dielectric; a detection unit that detects the proximity, contact, and pressure of a detection object against an operation surface located on the front side of the first electrode based on the output of the first electrode; and a third electrode provided adjacent to the second electrode.

2. The input device according to claim 1, wherein the third electrode is maintained at a constant potential when the detection unit detects the pressing of the object to be detected.

3. An input device as described in claim 1 or 2, wherein the detection unit detects the proximity or contact of the object to be detected based on the absolute self-capacitance of the first electrode, and detects pressure by the object to be detected based on the mutual capacitance between the first electrode and the second electrode.

4. An input device as described in claim 3, wherein an AC voltage of the same frequency and phase is applied to the first electrode, the second electrode, and the third electrode when the detection unit detects the proximity or contact of the object to be detected.

5. An input device according to claim 3 or 4, wherein the first electrode and the third electrode are maintained at a constant potential when the detection unit detects pressing of the object to be detected, and a predetermined AC voltage is applied to the second electrode when the detection unit detects pressing of the object to be detected.

6. An input device according to any one of claims 1 to 5, wherein the third electrode is provided so as to surround the periphery of the second electrode.

7. An input device according to any one of claims 1 to 6, wherein the area of ​​the first electrode is larger than the area of ​​the second electrode, and in a planar view, all of the outer edges of the first electrode are positioned outside the outer edges of the second electrode.

8. The input device according to claim 7, wherein the first electrode and the second electrode have similar electrode shapes and their central positions coincide in a plan view.

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