Position detection device

Abstract

To provide a position detection device capable of accurately estimating a touch position regardless of the touch position.SOLUTION: A position detection device 1 detects a touch position on a position detection sheet 10 on which a first electrode layer 11 and a second electrode layer 13 are laminated with a dielectric layer 12 held therebetween. The position detection sheet 10 is in a shape that is in line symmetry with respect to a central axis CL (point symmetry with respect to a central point C). At both ends in the detection direction of the first electrode layer 11, a sheet electrode E1 and a sheet electrode E2 are attached to positions in line symmetry with respect to the central axis CL (point symmetry with respect to the central point C). On the second electrode layer 13, a sheet electrode E3 and a sheet electrode E4 connected to a common line are attached to the positions in line symmetry with respect to the central axis CL (point symmetry with respect to the central point C).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a position detection device that detects a touch position. [Background technology]

[0002] A position detection device has been proposed that uses a sheet having capacitance to detect a touch position (see, for example, Patent Documents 1 and 2).

[0003] 7 is an equivalent circuit diagram of a conventional position detection device 2 viewed from the side. The position detection device 2 includes a position detection sheet 20 having capacitance, which includes a first electrode layer 21, a dielectric layer 22, and a second electrode layer 23, with the dielectric layer 22 sandwiched between the first electrode layer 21 and the second electrode layer 23.

[0004] The first electrode layer 21 has a resistance component and uses a stretchable electrode film. Resistors R1 to R4 indicate the resistance component of the first electrode layer 21. The dielectric layer 22 is made of a material that has a high dielectric constant and is soft (has a low Young's modulus), such as a dielectric elastomer. The second electrode layer 23 has zero resistance component and uses a stretchable electrode film. Capacitors C1 to C5 indicate the capacitance component of the position detection sheet 20.

[0005] A first terminal T1 and a second terminal T2 are provided at both ends of the first electrode layer 21. A third terminal T3, which is a connection terminal to a common line such as ground, is provided at one end of the second electrode layer 23. An AC power source AC and a current detection resistor RS are connected in series between the common line to which the third terminal T3 is connected and the second terminal T2. An AC voltage from the AC power source AC is applied to the second terminal T2 via the current detection resistor RS.

[0006] The position detection device 2 estimates the touch position on the first electrode layer 21 based on the end voltage Vdet of the first terminal T1. For example, when position P2 on the first electrode layer 21 is pressed, the dielectric layer 22 near P2 contracts, reducing the inter-electrode distance, and increasing the capacitance of capacitor C2. The current flowing through the capacitor is expressed as vin × 2πfC. That is, as C (capacitance) increases, the current also increases. This increased current flows through resistor R1, increasing the voltage drop across resistor R1. As a result, the end voltage Vdet is lower than the voltage V0 when no point is pressed. Similarly, when P5 is pressed, the capacitance of capacitor C5 increases, increasing the current flowing through capacitor C5. This increased current flows through resistors R1 to R4, increasing the voltage drop across resistors R1 to R4, and the end voltage Vdet1 is significantly lower than when P2 is pressed. That is, the current distribution on the first electrode layer 21 changes depending on the touch position. Therefore, the edge voltage Vdet changes depending on the touch position as shown in FIG. 8(a), and therefore the touch position can be estimated.

[0007] However, as shown in FIG. 8(a), the position detection accuracy of the edge voltage Vdet changes depending on the pressure of the touch. Therefore, the position detection device 2 estimates the pressure by detecting the current value flowing through the current detection resistor RS as the input current Idet input to the second terminal T2. The total capacitance value of the capacitors C1 to C5 increases when the first electrode layer 21 is touched. The stronger the touch, the greater the total capacitance value of the capacitors C1 to C5. As C (capacitance) increases, the current increases. In other words, as the total capacitance value increases, the input current Idet input to the second terminal T2 increases. When the touch is performed with the same strength and area, the total capacitance value does not depend on the touch position. Therefore, the position detection device 2 can estimate the pressure value using the input current Idet, regardless of the touch position, as shown in FIG. 8(b). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2005-530996 [Patent Document 2] Special Publication No. 2017-521656 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the conventional technology, the closer the touch position is to the second terminal T2, to which the AC voltage from the AC power supply AC is input, the lower the detection sensitivity becomes. That is, as shown in Figure 8(a), when the touch position is P1, which is closest to the second terminal T2, to which the AC voltage from the AC power supply AC is input, there is no change in the amount of voltage drop across the resistors R1 to R5, and therefore there is almost no change in the end voltage Vdet. In other words, it is difficult to distinguish this from when no part of the touch panel is being touched.

[0010] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a position detection device that can accurately estimate a touch position regardless of the touch position. [Means for solving the problem]

[0011] In order to achieve the above object, the position detection device according to the present invention is configured as follows. The position detection device of the present invention is a position detection device that detects a touch position on a position detection sheet in which a first electrode layer and a second electrode layer are stacked with a dielectric layer sandwiched between them, and the position detection sheet has a shape that is linearly symmetrical with respect to a central axis that is perpendicular to the detection direction in which the touch position is detected, and a first sheet electrode and a second sheet electrode are attached to both ends of the detection direction of the first electrode layer in positions that are linearly symmetrical with respect to the central axis, and a third sheet electrode and a fourth sheet electrode connected to a common line are attached to the second electrode layer in positions that are linearly symmetrical with respect to the central axis, and is characterized by comprising: a detection unit that detects a second end voltage of the second sheet electrode and a first input current to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and detects the first end voltage of the first sheet electrode and the second input current to the second sheet electrode when an AC voltage is applied to the second sheet electrode; and a position estimation unit that estimates the touch position based on the first end voltage, the second end voltage, the first input current, and the second input current. Furthermore, a position detection device according to the present invention is a position detection device that detects a touch position on a position detection sheet in which a first electrode layer and a second electrode layer are stacked with a dielectric layer sandwiched between them, wherein the position detection sheet has a shape that is point-symmetrical with respect to a center point of a detection direction in which the touch position is detected, and a first sheet electrode and a second sheet electrode are attached to both ends of the detection direction of the first electrode layer in positions that are point-symmetrical with respect to the center point, and a third sheet electrode and a fourth sheet electrode connected to a common line are attached to the second electrode layer in positions that are point-symmetrical with respect to the center point, and the position detection device is characterized by comprising: a detection unit that detects a second end voltage of the second sheet electrode and a first input current to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and detects the first end voltage of the first sheet electrode and the second input current to the second sheet electrode when an AC voltage is applied to the second sheet electrode; and a position estimation unit that estimates the touch position based on the first end voltage, the second end voltage, the first input current, and the second input current. [Effects of the Invention]

[0012] The position detection device of the present invention can improve the difference in sensitivity depending on the touch position even if inexpensive electrode films with resistance components are used for the first and second electrode layers, and can obtain pressure information that is independent of the touch position, so that the accurate touch position can be estimated regardless of the touch position. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an example of the configuration of a position detection device according to the present invention. [Figure 2] 10A and 10B are diagrams illustrating an example of the arrangement of sheet electrodes in a second electrode layer. [Figure 3] 2 is an equivalent circuit of the position detection device shown in FIG. [Figure 4] 2 is a diagram showing an example of a detection result of the position detection device shown in FIG. 1. [Figure 5] FIG. 10 is a diagram showing another example of the configuration of a position detection device according to the present invention. [Figure 6] FIG. 10 is a diagram showing another example of the configuration of a position detection device according to the present invention. [Figure 7] FIG. 1 is a diagram illustrating an example of the configuration of a conventional position detection device. [Figure 8] FIG. 1 is a diagram illustrating the operation of a conventional position detection device. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

[0015] 1, the position detection device 1 of this embodiment includes a position detection sheet 10 having capacitance, a detection switching unit 3, a detection unit 4, and a position estimation unit 5. The position detection device 1 detects a touch position on the position detection sheet 10 in the X-axis direction. That is, the X-axis direction is the touch position detection direction in which the touch position is detected.

[0016] The position detection sheet 10 is a sheet arranged on the XY plane shown in Fig. 1, and includes a first electrode layer 11, a dielectric layer 12, and a second electrode layer 13, with the dielectric layer 12 sandwiched between the first electrode layer 11 and the second electrode layer 13. Although the position detection sheet 10 is shown as a flat surface in Fig. 1, it may be curved in either or both of the X-axis direction and the Y-axis direction.

[0017] The position detection sheet 10 (first electrode layer 11, dielectric layer 12, second electrode layer 13) is configured in a shape that is line-symmetric with respect to a central axis CL in the Y-axis direction. The position detection sheet 10 may also be shaped in point symmetry with respect to a central point C in the X-axis and Y-axis directions. In the following description, when the position detection sheet 10 has a point-symmetric shape, line symmetry can be appropriately referred to as point symmetry.

[0018] The first electrode layer 11 uses an electrode film that has a resistance component and is stretchable. Sheet electrodes E1 and E2, such as metal tapes or metal pads with zero resistance component, are attached to both ends of the first electrode layer 11 in the X-axis direction, respectively, in positions that are line-symmetrical with respect to the central axis CL. There are no particular restrictions on the shapes of the sheet electrodes E1 and E2. The first terminal T1 is connected to a wire drawn from the sheet electrode E1, and the second terminal T2 is connected to a wire drawn from the sheet electrode E2.

[0019] The dielectric layer 12 is made of a material that has a high dielectric constant and is soft (has a low Young's modulus), such as a dielectric elastomer.

[0020] An electrode film that has a resistance component and is stretchable is used for the second electrode layer 13. There is no need to assume that the second electrode layer 13 has no resistance component, as has been the case in the past. A stretchable electrode film that has no resistance component is expensive, but the second electrode layer 13 can be made of an inexpensive material that is the same as the first electrode layer 11, which makes it possible to reduce material costs, manufacturing costs, parts management costs, etc.

[0021] Sheet electrodes E3 and E4, such as metal tape or metal pads with zero resistance and connected to a common line such as ground, are attached to the ends of the second electrode layer 13 in positions symmetrical with respect to the central axis CL. The third terminal T3 is connected to a wire drawn from the sheet electrode E3, and the fourth terminal T4 is connected to a wire drawn from the sheet electrode E4.

[0022] The shape and number of the sheet electrodes E3 and E4 are not particularly limited, and the sheet electrodes E3 and E4 may be attached as shown in Figures 2(a) and 2(b). Note that since the position detection sheet 10 shown in Figure 1 is also point-symmetric, the sheet electrodes E3 and E4 may be attached at positions that are point-symmetric with respect to the center point C, as shown in Figures 2(c) to 2(e). Alternatively, the sheet electrodes E3 and E4 may be shared and attached to surround the end of the second electrode layer 13, as shown in Figure 2(g). In this case, the shapes of the sheet electrodes E3 and E4 are configured to be line-symmetric with respect to the central axis CL (line-symmetric with respect to the central axis CL).

[0023] The detection switching unit 3 switches between applying the AC voltage supplied from the AC power source AC via the current detection resistor RS to the first terminal T1 or the second terminal T2. When applying the AC voltage to the first terminal T1, the detection switching unit 3 connects the second terminal T2 to the detection unit 4. When applying the AC voltage to the second terminal T2, the detection switching unit 3 connects the first terminal T1 to the detection unit 4.

[0024] The detection unit 4 detects an end voltage Vdet1 of the first terminal T1 when an AC voltage is applied to the second terminal T2, and an end voltage Vdet2 of the second terminal T2 when an AC voltage is applied to the first terminal T1, and outputs the end voltage Vdet1 and end voltage Vdet2 to the position estimation unit 5. In addition, the detection unit 4 detects an input current Idet1 when an AC voltage is applied to the first terminal T1, and an input current Idet2 when an AC voltage is applied to the second terminal T2, based on the voltage across the current detection resistor RS, and outputs the input current Idet1 and input current Idet2 to the position estimation unit 5.

[0025] The position estimation unit 5 estimates the touch position on the first electrode layer 11 using the end voltages Vdet1 and Vdet2 and the input currents Idet1 and Idet2.

[0026] 3 is an equivalent circuit when the position detection device 1 is viewed from the Y direction. Capacitors C1 to C5 represent the capacitance components of the position detection sheet 10. Resistors R1 to R4 represent the resistance components of the first electrode layer 11. Resistors R5 to R8 represent the resistance components of the second electrode layer 13.

[0027] 3(a) shows a state in which, as a first detection operation, an AC voltage from an AC power source AC is applied to the second terminal T2 (seat electrode E2) via a current detection resistor RS. When the AC voltage is applied to the second terminal T2, the detection switching unit 3 connects the first terminal T1 to the detection unit 4. Therefore, the detection unit 4 detects the voltage of the first terminal T1 (seat electrode E1) as an edge voltage Vdet1 and outputs it to the position estimation unit 5. The detection unit 4 also detects the current flowing through the current detection resistor RS as an input current Idet2 to the second terminal T2 (seat electrode E2) and outputs it to the position estimation unit 5.

[0028] 3(b) shows a state in which, as a second detection operation, an AC voltage from an AC power source AC is applied to the first terminal T1 (seat electrode E1) via the current detection resistor RS. When the AC voltage is applied to the first terminal T1, the detection switching unit 3 connects the second terminal T2 to the detection unit 4. Therefore, the detection unit 4 detects the voltage of the second terminal T2 (seat electrode E2) as an edge voltage Vdet2 and outputs it to the position estimation unit 5. The detection unit 4 also detects the current flowing through the current detection resistor RS as an input current Idet1 to the first terminal T1 (seat electrode E1) and outputs it to the position estimation unit 5.

[0029] The second electrode layer 13 has a shape that is line-symmetrical with respect to the central axis CL, and the sheet electrodes E3 and E4 connected to the common line are attached to the ends of the second electrode layer 13 at positions that are line-symmetrical with respect to the central axis CL. Therefore, as shown in Figures 3(a) and 3(b), even if resistance components (resistors R5 to R8) exist in the second electrode layer 13, the first detection operation and the second detection operation can be performed under the same conditions.

[0030] Therefore, the end voltages Vdet1 and Vdet2 are symmetrical with respect to the central axis CL, as shown in Fig. 4(a). As a result, by performing a calculation process (for example, subtraction process: Vdet1-Vdet2) using the end voltages Vdet1 and Vdet2, it is possible to obtain a calculation result proportional to the touch position, as shown in Fig. 4(b), and to improve the difference in sensitivity depending on the touch position.

[0031] Similarly, the input currents Idet1 and Idet2 are symmetrical with respect to the central axis CL, as shown in Fig. 4(c). As a result, by performing calculations using the input currents Idet1 and Idet2 (for example, averaging: (Idet1+Idet2) / 2), pressure information that is independent of the touch position can be obtained, as shown in Fig. 4(d).

[0032] The position estimation unit 5 performs calculations using the end voltages Vdet1 and Vdet2 to obtain position information that does not vary in sensitivity depending on the touch position. The position information using Vdet1 and Vdet2 includes pressure information. Therefore, the position estimation unit 5 performs calculations using the input currents Idet1 and Idet2 to obtain pressure information that is independent of the touch position. The position estimation unit 5 can accurately estimate the touch position on the first electrode layer 11 by correcting the position information obtained using Vdet1 and Vdet2 with the pressure information obtained using the input currents Idet1 and Idet2.

[0033] 5 has a five-layer structure in which the second electrode layer 13, the dielectric layer 12, the first electrode layer 11, the dielectric layer 12, and the second electrode layer 13 are stacked in this order. The position detection sheet 10a detects the position of a touch on the second electrode layer 13. Therefore, the position detection sheet 10a prevents the first electrode layer 11 from coming into contact with the human body, thereby preventing noise from being mixed into the detected end voltage Vdet and input current Idet.

[0034] 6 is configured such that a position detection sheet 10 that detects a touch position in the X-axis direction and a position detection sheet 10 that detects a touch position in the Y-axis direction are laminated with an insulating layer 14 sandwiched between them. The position detection sheet 10b can detect a touch position on the XY plane.

[0035] As described above, this embodiment is a position detection device 1 that detects a touch position on a position detection sheet 10 in which a first electrode layer 11 and a second electrode layer 13 are laminated with a dielectric layer 12 sandwiched therebetween. The position detection sheet 10 has a shape that is line-symmetrical with respect to a central axis CL that is perpendicular to the detection direction (X-axis direction) in which a touch position is detected. A first sheet electrode (sheet electrode E1) and a second sheet electrode (sheet electrode E2) are attached to both ends of the first electrode layer 11 in the detection direction at positions line-symmetrical with respect to the central axis CL, and a third sheet electrode (sheet electrode E3) and a fourth sheet electrode ( The touch panel further includes a detection unit 4 that detects a second end voltage (end voltage Vdet2) of the second sheet electrode and a first input current (input current Idet1) to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and a position estimation unit 5 that estimates a touch position based on the first end voltage, the second end voltage, the first input current, and the second input current. With this configuration, even if inexpensive electrode films having resistance components are used for the first electrode layer 11 and the second electrode layer 13, the difference in sensitivity depending on the touch position can be improved, and pressure information that is independent of the touch position can be obtained, so that the accurate touch position can be estimated regardless of the touch position.

[0036] Furthermore, in this embodiment, the position detection device 1 detects a touch position on a position detection sheet 10 in which a first electrode layer 11 and a second electrode layer 13 are laminated with a dielectric layer 12 sandwiched therebetween, and the position detection sheet 10 has a shape that is point-symmetrical with respect to a center point C in a detection direction (X-axis direction) in which the touch position is detected, and a first sheet electrode (sheet electrode E1) and a second sheet electrode (sheet electrode E2) are attached to both ends of the detection direction of the first electrode layer 11 at positions that are point-symmetrical with respect to the center point C, and a third sheet electrode (sheet electrode E3) and a fourth sheet electrode (sheet electrode E4) that are connected to a common line are attached to the second electrode layer 13. The touch panel further comprises a detection unit 4 that detects a second end voltage (end voltage Vdet2) of the second sheet electrode and a first input current (input current Idet1) to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and a position estimation unit 5 that estimates a touch position based on the first end voltage, the second end voltage, the first input current, and the second input current. With this configuration, even if inexpensive electrode films having resistance components are used for the first electrode layer 11 and the second electrode layer 13, the difference in sensitivity depending on the touch position can be improved, and pressure information that is independent of the touch position can be obtained, so that the accurate touch position can be estimated regardless of the touch position.

[0037] Furthermore, in this embodiment, the third sheet electrode and the fourth sheet electrode are shared and are attached so as to surround the end of the second electrode layer 13.

[0038] It is clear that the present invention is not limited to the above-described embodiments, and that each embodiment can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and the number, position, shape, etc. can be set to be suitable for implementing the present invention. Note that the same components are denoted by the same reference numerals in each drawing. [Explanation of symbols]

[0039] 1 Position detection device 3 Detection switching section 4. Detection unit 5 Position estimation part 10, 10a, 10b, Position detection sheet 11 First electrode layer 12 Dielectric layer 13 Second electrode layer 14 Insulating layer AC alternating current power supply E1, E2, E3, E4 sheet electrodes

Claims

1. A position detection device that detects a touch position on a position detection sheet in which a first electrode layer and a second electrode layer are stacked with a dielectric layer sandwiched therebetween, the position detection sheet has a shape that is symmetrical with respect to a central axis perpendicular to a detection direction in which a touch position is detected; a first sheet electrode and a second sheet electrode are attached to both ends of the first electrode layer in the detection direction at positions that are symmetrical with respect to the central axis, a third sheet electrode and a fourth sheet electrode connected to a common line are attached to the second electrode layer at positions symmetrical with respect to the central axis, a detection unit that detects a second end voltage of the second sheet electrode and a first input current to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and detects a first end voltage of the first sheet electrode and a second input current to the second sheet electrode when an AC voltage is applied to the second sheet electrode; a position estimation unit that estimates a touch position based on the first end voltage, the second end voltage, the first input current, and the second input current.

2. A position detection device that detects a touch position on a position detection sheet in which a first electrode layer and a second electrode layer are stacked with a dielectric layer sandwiched therebetween, the position detection sheet has a shape that is point-symmetrical with respect to a center point of a detection direction in which a touch position is detected, a first sheet electrode and a second sheet electrode are attached to both ends of the first electrode layer in the detection direction at positions symmetrical with respect to the center point; a third sheet electrode and a fourth sheet electrode connected to a common line are attached to the second electrode layer at positions symmetrical with respect to the center point; a detection unit that detects a second end voltage of the second sheet electrode and a first input current to the first sheet electrode when an AC voltage is applied to the first sheet electrode, and detects a first end voltage of the first sheet electrode and a second input current to the second sheet electrode when an AC voltage is applied to the second sheet electrode; a position estimation unit that estimates a touch position based on the first end voltage, the second end voltage, the first input current, and the second input current.

3. 3. The position detection device according to claim 1, wherein the third sheet electrode and the fourth sheet electrode are shared and are attached so as to surround an end portion of the second electrode layer.

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