Input Devices

Abstract

Provided is an input device with which it is possible, using a simple structure, to detect proximity, contact, and pressing force of an object being detected.　The input device includes: a first electrode; an elastic dielectric body provided on the reverse side of the first electrode; a second electrode provided sandwiching the elastic dielectric body together with the first electrode; a detection unit for detecting proximity, contact and pressing force on the first electrode of an object being detected, on the basis of the output of the first electrode; and a third electrode provided adjacent to the second electrode.

Description

[Technical field]

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

[0002] Conventionally, there has been a touch panel that includes a touch sensor substrate that is rectangular in plan view and has sensor electrodes formed thereon for detecting a touch position 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 a 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] At least a portion of the first electrode and the second electrode overlap in a planar view, the second electrode is formed in at least one corner portion of the touch sensor substrate and is electrically isolated from the sensor electrode, and a change in distance between the first electrode and the second electrode when a 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 touch sensor substrate is pressed through the cover panel by the indicator, 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). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-125158 A Summary of the Invention [Problem to be solved by the invention]

[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 a pressure.

[0006] Therefore, an object of the present invention is to provide an input device capable of detecting the proximity, contact, and pressure of a detection object with a simple configuration. [Means for solving the problem]

[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 an output of the first electrode, and a third electrode provided adjacent to the second electrode. Effect of the Invention

[0008] It is possible to provide an input device capable of detecting the proximity, contact, and pressure of a detection object with a simple configuration. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a planar configuration of an input device 100 according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Diagram 3] FIG. 4 is a diagram showing voltages applied to each electrode. [Figure 4A] FIG. 2 is a diagram showing a cross-sectional configuration of a simulation model of the input device 10 for comparison. [Figure 4B] 13 is a diagram showing a simulation result of an electric field distribution in the input device 10 for comparison. FIG. [Figure 5A] FIG. 11 is a diagram showing capacitance characteristics in the input device 10 for comparison. [Figure 5B] FIG. 11 is a diagram showing capacitance characteristics in the input device 10 for comparison. [Figure 5C]FIG. 11 is a diagram showing capacitance characteristics in the input device 10 for comparison. [Figure 6A] 2 is a diagram showing a cross-sectional configuration of a simulation model of the input device 100 according to the embodiment. FIG. [Figure 6B] 13 is a diagram showing a simulation result of an electric field distribution in the input device 100. FIG. [Figure 6C] 3 is a diagram showing capacitance characteristics in the input device 100. FIG. [Figure 7] FIG. 11 is a diagram showing a cross-sectional structure of an input device 100A according to a first modified example of the embodiment. [Figure 8] FIG. 11 is a plan view showing an input device 100C according to a second modified example of the embodiment. [Figure 9] FIG. 13 is a diagram showing a planar configuration of an input device 100D according to a third modified example of the embodiment. [Figure 10] 10 is a cross-sectional view taken along the line AA in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 a planar configuration of an input device 100 according to an embodiment. FIG. 2 is a diagram showing a cross section taken along the line AA in FIG. 1. In the following, an XYZ coordinate system is defined and described. A direction parallel to the X axis (X direction), a direction parallel to the Y axis (Y direction), and a direction parallel to the Z axis (Z direction) are mutually orthogonal. In the following, for convenience of description, the -Z direction side may be referred to as the lower side or bottom, and the +Z direction side as the upper side or top, but these do not represent a universal relationship between the top and bottom. In addition, a planar view refers to a view in the XY plane. In the following, the length, width, thickness, etc. of each part may be exaggerated 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 (contacting) 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. Although the input device 100 can be operated with something other than the fingertip FT, the following description will be given assuming that it is operated with the fingertip FT.

[0014] The input device 100 detects the proximity, contact, and pressure of the user's fingertip on the operation surface of the top panel 101 of the FT, 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 remotely operate the operation target device, or may be provided integrally with the operation target device. The input device 100 may be portable, or may be fixedly installed on a wall surface 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, with the top surface being an operation surface on which a user touches with a fingertip FT to perform an operation input. A 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 to 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] As an example, the first electrode 110 has a rectangular shape in a plan view, 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 a 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 provided to detect the pressing by the fingertip FT based on the mutual capacitance with 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 the substrate 102 is capable of bending when pressed from above, similar to the top panel 101. The substrate 102 may be, for example, a transparent substrate made of polyimide.

[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 providing the substrate 102 on the elastic dielectric 103. In other words, the elastic dielectric 103 being provided below (on the back side) of the first electrode 110 includes both a case in which 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 in which 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. Since the elastic dielectric 103 is elastically deformable, when a user presses a portion of the operation surface of the top panel 101 directly above the detection electrode 111 downward with a fingertip FT, 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 is rectangular in plan view. Here, a form in which the second electrode 120 is square in plan view will be described. As described above, the first electrode 110 may be directly provided on the upper surface of the elastic dielectric 103 without providing the substrate 102 on the elastic dielectric 103, so the second electrode 120 may be provided with the elastic dielectric 103 sandwiched between the first electrode 110 and the second electrode 120.

[0023] The second electrode 120 and the first electrode 110 have similar electrode shapes, and their central positions coincide with each other 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 disposed so as to coincide with the outer edge of the first electrode 110.

[0024] The second electrode 120 is provided to detect a 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 disposed 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) around the input device 100 when detecting the proximity and contact of the fingertip FT to 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 the pressing by the fingertip FT. The third electrode 130 is made of a transparent conductive material such as an ITO film, for example. Although the details will be described later, the third electrode 130 is provided to reduce the wraparound of the electric field from the second electrode 120 to the fingertip FT by drawing the electric field from the second electrode 120 to the third electrode 130. Therefore, the third electrode 130 being provided adjacent to the second electrode 120 means that the third electrode 130 is arranged next to the second electrode 120 and close to the second electrode 120 so that the wraparound of the electric field from the second electrode 120 to the fingertip FT can be reduced by escaping to the third electrode 130 side.

[0027] Note that, here, a form 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 will be described, but the third electrode 130 is not limited to a rectangular ring shape, and may not be a ring shape. 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 like 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] In this embodiment, it is assumed that a display panel such as a liquid crystal or organic EL (Electroluminescence) panel is disposed below the input device 100, and 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, when 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 material that is not transparent but has conductivity, and may be a metal plate or the like.

[0030] The detection unit 140 is connected to the first electrode 110 and is also connected to the MCU 150. The drive unit 141 is connected to the second electrode 120 and the third electrode 130 and is also connected to the MCU 150. The detection unit 140 detects the proximity, contact, and pressure of the user's fingertip FT to 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 the proximity or contact of the fingertip FT to the operation surface based on the absolute self-capacity of the first electrode 110, and detects the pressure of the operation surface by the fingertip FT 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 IC (integrated circuit).

[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 capacitance in digital 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 voltage to the second electrode 120 and the third electrode 130 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-capacity 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> 3 is a diagram showing voltages applied to each electrode. FIG. 3 shows 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, the input device 100 detects even the stray capacitance of the ground outside the input device 100, resulting in a large electrostatic 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 by 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 the ground can be reduced, and the input device 100 can improve the detection sensitivity of the absolute self-capacitance at the first electrode 110. In this way, it becomes 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 holds 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-capacity.

[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 that 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 the mutual capacitance between the first electrode 110 and the second electrode 120. Note that since it is only necessary that the potentials of the first electrode 110 and the third electrode 130 are constant, any DC voltage may be applied.

[0041] <Simulation results of the input device 10 for comparison> 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 a simulation result of the electric field distribution in the comparative input device 10. Figs. 5A, 5B, and 5C are diagrams showing the capacitance characteristics of the comparative input device 10. Here, before describing the simulation result of the input device 100 of the embodiment, the simulation result 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 value of Z indicates that the fingertip FT is above the operation surface, and a negative value of Z 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 lower side 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 given the symbol Tx (transmitting side) and the first electrode 110 is given the symbol Rx (receiving side). This method of applying voltage corresponds to the method of applying voltage for obtaining 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] In Fig. 4B, arrows show the electric field distribution in the area enclosed by the dashed square in Fig. 4A. Along the large arrow A from Tx to the fingertip FT, a large amount of electric field is generated from the second electrode 120 (Tx) through the first electrode 110 (Rx) toward the fingertip FT, and it can be seen that a large amount of electric field is leaking into the fingertip FT. The same arrow A as the arrow A in Fig. 4B is also shown in Fig. 4A. This is because the electric potential of the fingertip FT is the ground potential, and therefore the electric field leaks from the second electrode 120 (Tx) to the fingertip FT.

[0046] 5A shows a simulation result 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 characteristic shows the characteristic of the detection data representing the absolute self-capacitance of the first electrode 110, and the solid line characteristic shows the characteristic of the detection data representing the mutual capacitance between the first electrode 110 and the second electrode 120.

[0047] Fig. 5B shows a simulation result 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 characteristic shows the characteristic of the detection data representing the absolute self-capacitance of the first electrode 110, and the solid line characteristic 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) versus 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 positive values ​​(Z=+20 mm) to negative values ​​(Z=approximately −1 mm). The characteristics in the section Z≧0 in FIG. 5C are the same as the characteristics of the solid line in FIG. 5A. The characteristics in the section Z<0 in FIG. 5C are represented by converting the horizontal axis of the characteristics of the solid line in FIG. 5B into the position in the Z direction.

[0049] Similar to the input device 100, the comparative input device 10 determines whether the fingertip FT is in proximity to or in contact with the operation surface based on detection data representing the absolute self-capacity 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 the comparative input device 10 determines the presence or absence of proximity or contact from a state where no operation is being performed by the fingertip FT, the comparative input device 10 determines the presence or absence of proximity or contact based on the characteristics of the dashed line in FIG. 5A. When the fingertip FT approaches the operation surface, the capacitance changes so as to trace the characteristics of FIG. 5A from the left side to the right side. Therefore, the comparative input device 10 may determine the proximity of the fingertip FT when the count value of the capacitance reaches the threshold value TH1 for proximity determination, and may determine the contact of the fingertip FT when the count value of the capacitance reaches the threshold value TH2 for contact determination. As an example, the threshold value TH1 for proximity determination is 500, and the threshold value TH2 for contact determination is 1300. Note that the threshold value TH2 for contact determination must be set somewhat lower in order to reliably perform contact determination, since there is variation in the capacitance value depending on the finger. 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 of Z = 0 mm, and contact is determined at Z = approximately 1 mm, slightly before the position of Z = 0 mm where the fingertip FT contacts the operation surface.

[0051] In addition, when determining whether or not there is a press after determining whether or not there is proximity and contact, the presence or absence of a press is determined based on the characteristics of the solid line shown in Fig. 5B. Since 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 the capacitance increases relative to the reference value as the pressing force increases, the pressing force may be calculated according to the difference between the measured capacitance value and the reference value, or a threshold value (e.g., 1000) for determining the pressing force may be set to determine whether or not there is a press.

[0052] Incidentally, as shown in the solid line characteristic (mutual capacitance between the first electrode 110 and the second electrode 120) in FIG. 5A, when the count value of the absolute self-capacitance reaches the contact determination threshold value TH2 (1300) at the position of 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 the position of Z=0 mm drops to approximately -300. In addition, in the solid line characteristic (mutual capacitance between the first electrode 110 and the second electrode 120) shown in FIG. 5B, the count value is approximately -300 when the pressing force is 0 N, and it is approximately 0.4 N that the mutual capacitance becomes the same value as the count value (approximately -250) of the mutual capacitance at the position of Z=approximately 1 mm in FIG. 5A. Therefore, in the range of pressing force from 0 N to approximately 0.4 N, the measured count value of the mutual capacitance falls below the reference value, and the pressing force cannot be calculated, resulting in a dead zone.

[0053] Due to the existence of such a dead zone, when the pressure of the fingertip FT decreases from a pressed state, for example, when 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, when the pressure of the fingertip FT decreases from a pressed state, for example, when the fingertip FT repeats pressing and approaching, it becomes difficult to distinguish between pressing and approaching even if the comparative input device 10 tries 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. Such a drop in the capacitance value around Z=0 mm is considered to be caused by the wraparound of the electric field to the fingertip FT. That is, when the wraparound of the electric field occurs between the second electrode 120 and the finger, the detected capacitance (mutual capacitance) decreases compared to the state without the finger around Z=0 mm, and increases when the finger is pressed further. Therefore, as described above, the pressing cannot be determined and a dead zone occurs.

[0055] The input device 100 of the embodiment solves the problems described above, 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 the Input Device 100 of the Embodiment> Fig. 6A is a diagram showing a cross-sectional configuration of a simulation model of the input device 100 according to the embodiment. Fig. 6B is a diagram showing a simulation result of an electric field distribution in the input device 100. Fig. 6C is a diagram showing a capacitance characteristic in the input device 100. Fig. 6C shows a characteristic corresponding to the characteristic 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 an approximately 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 approximately 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 believed to be that by providing third electrode 130 around second electrode 120 and holding third electrode 130 at ground potential when detecting mutual capacitance, an electric field component is generated that circulates from second electrode 120 to third electrode 130 as shown in FIG. 6B, and the electric field component that circulates from second electrode 120 to fingertip FT is reduced.

[0061] In general, the electric field tends to be strongest at the end (edge) of an electrode. In order 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 position of the edge of the first electrode 110 and the position of the edge of the second electrode 120 are very close to each other in a plan view. Therefore, in order to effectively generate an electric field component that wraps around from the second electrode 120 to the third electrode 130, the positions of the edges of the first electrode 110 and the second electrode 120 and the position of the inner edge of the rectangular ring of the third electrode 130 can be made close to each other 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 capable of detecting the proximity, contact, and pressure of a fingertip FT with a simple configuration.

[0064] Furthermore, since the third electrode 130 is held at a constant potential when the detection unit 140 detects the pressing of the fingertip FT, the wraparound of the electric field from the second electrode 120 to the fingertip FT can be reduced by dissipating the wraparound of 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 is such that the drop in the capacitance count value around Z=0 mm is eliminated. 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 pressing 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 to the operation surface and the pressing of the operation surface by utilizing the output of the first electrode 110.

[0066] In addition, when the detection unit 140 detects the proximity or contact of the fingertip FT, the first electrode 110, the second electrode 120, and the third electrode 130 are applied with an AC voltage of the same frequency and phase. Therefore, the second electrode 120 and the third electrode 130 can function as an active shield, and the second electrode 120 and the third electrode 130 can shield stray capacitance from the external ground. In addition, since there is no potential difference between the first electrode 110 and the second electrode 120 and the third electrode 130, the electrostatic capacitance of the first electrode 110 with respect to the ground can be reduced, and the detection sensitivity of the absolute self-capacitance at the first electrode 110 can be improved. Furthermore, the proximity state 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 pressing of the fingertip FT, and a predetermined AC voltage is applied to the second electrode 120 when the detection unit 140 detects the pressing of the fingertip FT. Therefore, a potential difference can be generated between the first electrode 110 and the second electrode 120, and the mutual capacitance between the first electrode 110 and the second electrode 120 can be measured. Then, the amount of pressing can be detected based on the mutual capacitance.

[0068] In addition, 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 an active shield to obtain a greater shielding effect when shielding stray capacitance from ground, thereby improving the detection sensitivity of the absolute self-capacitance at the first electrode 110.

[0069] Furthermore, the first electrode 110 and the second electrode 120 have similar electrode shapes 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 modified example of an embodiment. In Fig. 7, the detection unit 140 and the MCU 150 are omitted. 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 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 shield electrode 160 may be applied with the same voltage as that of the third electrode 130. 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. 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, the stray capacitance from the external ground can be more effectively shielded, and the detection sensitivity of the first electrode 110 can be further improved.

[0072] <Second Modification> Fig. 8 is a plan view showing an input device 100C of a second modified example 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 using a resistive electrode material, the second electrode 120, and the third electrode 130 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 the amount of charge detected by the detection unit 140 changes. Therefore, by placing the detection unit 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 a planar configuration of an input device 100D according to a third modified example 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.

[0076] The first electrode 110 is, for example, rectangular in plan view, and here is a square. 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 plan view. Therefore, the outer edge of the second electrode 120 is included within the outer edge of the first electrode 110 in plan view.

[0077] Moreover, the area of ​​the first electrode 110 is larger than the area of ​​the second electrode 120, and the entire outer edge of the first electrode 110 is disposed outside the outer edge of the second electrode 120 in a planar view. For example, the first electrode 110 and the second electrode 120 may have electrode shapes similar to each other, and may be configured so that their central positions coincide with each other in a planar 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 wraparound of the electric field from the second electrode 120 to the finger, but the area of ​​the first electrode 110 closer to the finger is increased to completely cover the second electrode 120, thereby further reducing the wraparound of the electric field between the second electrode 120 and the finger. Therefore, there is no reduction in the capacitance between the first electrode 110 and the second electrode 120, and no dead zone is generated, so that the detection unit 140 can reliably detect the press. In this way, when the area of ​​the first electrode 110 is larger than the area of ​​the second electrode 120, the wraparound of the electric field to the finger can be further suppressed than 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. However, 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 to Japanese patent application No. 2022-037453, filed on March 10, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0082] 101 Top Panel 102 Substrate 103 Elastic Dielectrics 104 Substrate 110 1st electrode 120 2nd electrode 130 3rd electrode 140 Detection unit 150 MCU

Claims

1. A first electrode; an elastic dielectric body provided on the rear side of the first electrode; a second electrode provided with the elastic dielectric sandwiched between the first electrode and the second electrode; a detection unit that detects the proximity, contact, and pressure of a detection object relative to an operation surface located on a front side of the first electrode based on an output of the first electrode; a third electrode provided adjacent to the second electrode; Including, The third electrode is maintained at a constant potential when the detection unit detects pressing of the detection object.

2. 2. The input device according to claim 1, wherein the detection unit detects 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.

3. 3. The input device according to claim 2, wherein the first electrode, the second electrode, and the third electrode are all applied with an AC voltage of the same frequency and phase when the detection unit detects proximity or contact of the detection object.

4. the first electrode and the third electrode are held at a constant potential when the detection unit detects the pressing of the detection object, The input device according to claim 2 , wherein a predetermined AC voltage is applied to the second electrode when the detection unit detects pressing of the detection object.

5. The input device according to claim 1 , wherein the third electrode is provided so as to surround the periphery of the second electrode.

6. The area of ​​the first electrode is larger than the area of ​​the second electrode, The input device according to claim 1 , wherein, in a plan view, an outer edge of the first electrode is entirely disposed outside an outer edge of the second electrode.

7. The input device according to claim 6 , wherein the first electrode and the second electrode have similar electrode shapes and have center positions that coincide with each other in a plan view.

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