Piezoelectric sensor and position detection device

Abstract

To enable easy amplification processing of output voltage based on a piezoelectric effect output from a sensor element.SOLUTION: A piezoelectric sensor includes a substrate, a lower electrode, a first piezoelectric layer, a common electrode, a second piezoelectric layer, an upper electrode, and a signal amplification unit that outputs an amplification signal obtained by amplifying a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode. The signal amplification unit includes a first amplification circuit that amplifies the first detection signal, a second amplification circuit that amplifies the amplification signal of the first amplification circuit, a third amplification circuit that amplifies the amplification signal of the first amplification circuit with a smaller amplification ratio than the second amplification circuit, a fourth amplification circuit that amplifies the second detection signal, a fifth amplification circuit that amplifies the amplification signal of the fourth amplification circuit, and a sixth amplification circuit that amplifies the amplification signal of the fourth amplification circuit with a smaller amplification ratio than the fifth amplification circuit.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a piezoelectric sensor and a position detection device. [Background technology]

[0002] Conventionally, a sensor element using the piezoelectric effect is known, in which a piezoelectric body is sandwiched between two electrodes and an external force is applied so as to distort the piezoelectric body, thereby generating a voltage between the two electrodes. A position detection device is also known that detects the position where an external force is applied by arranging a plurality of such sensor elements (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-163531 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such a position detection device, a sensor element is disposed for each position to be detected. In this case, the number of sensor elements increases as the number of positions to be detected increases, which causes a problem that the position detection device becomes complicated. Therefore, a piezoelectric sensor that can identify the position to which an external force is actually applied from among multiple pressure application positions according to the output voltage of the sensor element without disposing multiple sensor elements is desired. The voltage range of the voltage output by the sensor element of such a piezoelectric sensor becomes large corresponding to the number of positions to be detected, which can make it difficult to amplify and process the output voltage.

[0005] The present invention has been made in consideration of these points, and an object of the present invention is to make it possible to easily amplify an output voltage based on the piezoelectric effect output from a sensor element. [Means for solving the problem]

[0006] In a first aspect of the present invention, a signal amplifier includes a substrate, a lower electrode formed on the substrate, a first piezoelectric layer having a piezoelectric body formed on the lower electrode, a common electrode formed on the first piezoelectric layer, a second piezoelectric layer having a piezoelectric body formed on the common electrode, an upper electrode formed on the second piezoelectric layer, and a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal by amplifying the first detection signal and the second detection signal. the signal amplifier unit has a first amplifier circuit that amplifies the first detection signal by a first amplification factor, a second amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a second amplification factor, a third amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a third amplification factor smaller than the second amplification factor, a fourth amplifier circuit that amplifies the second detection signal by a fourth amplification factor, a fifth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a fifth amplification factor, and a sixth amplification circuit that amplifies the signal amplified by the fourth amplifier circuit by a sixth amplification factor smaller than the fifth amplification factor.

[0007] In a second aspect of the present invention, there is provided a substrate, a lower electrode formed on the substrate, a first piezoelectric layer having a piezoelectric body formed on the lower electrode, a common electrode formed on the first piezoelectric layer, a second piezoelectric layer having a piezoelectric body formed on the common electrode, an upper electrode formed on the second piezoelectric layer, and a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal obtained by amplifying the first detection signal and the second detection signal, wherein the signal amplifier outputs the first detection signal. a first amplifier circuit that amplifies a frequency component exceeding a predetermined frequency from the signal amplified by the first amplifier circuit; a third amplifier circuit that amplifies a frequency component equal to or lower than the predetermined frequency from the signal amplified by the first amplifier circuit; a fourth amplifier circuit that amplifies the second detection signal by a fourth amplification factor different from the first amplification factor of the first amplifier circuit; a fifth amplifier circuit that amplifies a frequency component exceeding a predetermined frequency from the signal amplified by the fourth amplifier circuit;

[0008] The input / output amplifier may further include a first high-frequency filter provided between the first amplifier circuit and the second amplifier circuit, the first high-frequency filter passing frequency components exceeding a predetermined frequency of the signal amplified by the first amplifier circuit; a first low-frequency filter provided between the first amplifier circuit and the third amplifier circuit, the first low-frequency filter passing frequency components equal to or lower than a predetermined frequency of the signal amplified by the first amplifier circuit; a second high-frequency filter provided between the fourth amplifier circuit and the fifth amplifier circuit, the first low-frequency filter passing frequency components exceeding a predetermined frequency of the signal amplified by the fourth amplifier circuit; and a second low-frequency filter provided between the fourth amplifier circuit and the sixth amplifier circuit, the first low-frequency filter passing frequency components equal to or lower than a predetermined frequency of the signal amplified by the fourth amplifier circuit.

[0009] When the thickness of the first piezoelectric layer is formed to be greater than the thickness of the second piezoelectric layer, the first amplification factor of the first amplifier circuit may be smaller than the fourth amplification factor of the fourth amplifier circuit, and when the thickness of the first piezoelectric layer is formed to be smaller than the thickness of the second piezoelectric layer, the first amplification factor of the first amplifier circuit may be larger than the fourth amplification factor of the fourth amplifier circuit.

[0010] The piezoelectric element may further include a plurality of pressure application sections formed on the upper electrode and arranged in a first direction parallel to the substrate and a second direction different from the first direction, to which pressure is applied from the outside, wherein the first piezoelectric layer has the piezoelectric elements formed such that the volume of the piezoelectric elements per unit area varies depending on the position of the pressure application sections arranged in the first direction in a plane parallel to the substrate, and the second piezoelectric layer has the piezoelectric elements formed such that the volume of the piezoelectric elements per unit area varies depending on the position of the pressure application sections arranged in the second direction in a plane parallel to the substrate.

[0011] The thicknesses of the first piezoelectric layer and the second piezoelectric layer may vary depending on the position of the pressure application portion.

[0012] In a third aspect of the present invention, there is provided a position detection device comprising the piezoelectric sensor of the first and second aspects, a plurality of pressure application sections formed on the upper electrode and to which pressure is applied from the outside, a signal receiving section that receives the amplified signal output from the signal amplifier section, a memory section that stores pressure application section data that associates the positions of the plurality of pressure application sections in a plane parallel to the substrate with reference values ​​of the amplified signals when pressure is applied to each of the pressure application sections, and an identification section that identifies the position of the pressure application section to which an external force is applied based on the amplified signal received by the signal receiving section and the pressure application section data. Effect of the Invention

[0013] According to the present invention, it is possible to easily amplify the output voltage based on the piezoelectric effect output from the sensor element. [Brief description of the drawings]

[0014] [Figure 1] 2 shows an example of the configuration of a position detection device 10 for comparison. [Diagram 2] 1 shows a first configuration example of a position detection device 100 according to the present embodiment. [Diagram 3] 2 shows a second configuration example of the position detection device 100 according to the present embodiment. [Figure 4] 3 shows a third configuration example of the position detection device 100 according to the present embodiment. [Diagram 5] 5 shows a schematic configuration of the pressure sensor 110 of the position detection device 100 of the third configuration example shown in FIG. [Figure 6] 13 shows a first calculation example of the maximum amplitude values ​​of the first detection signal and the second detection signal. [Figure 7] 13 shows a first calculation example of a ratio of maximum amplitude values ​​of a first detection signal and a second detection signal. [Figure 8] 13 shows a second calculation example of the maximum amplitude values ​​of the first detection signal and the second detection signal. [Figure 9] 13 shows a second calculation example of the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal. [Figure 10] 2 shows an example of the configuration of a piezoelectric sensor 300 according to the present embodiment. [Figure 11] 2 shows a modified example of the piezoelectric sensor 300 according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Configuration example of position detection device 10 for comparison> 1 shows a configuration example of a position detection device 10 for comparison. In this embodiment, three orthogonal axes are shown as an X-axis, a Y-axis, and a Z-axis. The position detection device 10 includes a pressure sensor 20 and a signal processing unit 30. The pressure sensor 20 includes a pressure application unit 40, a substrate 50, a sensor element 60, a base layer 70, a protective film 80, and wiring 90.

[0016] A plurality of pressure application units 40 are provided in the position detection device 10, and pressure is applied from the outside. FIG. 1 shows an example in which three pressure application units 40, a first pressure application unit 40A, a second pressure application unit 40B, and a third pressure application unit 40C, are provided in the position detection device 10. Pressure is applied to the pressure application units 40, for example, by an operation by a user or the like. As an example, the pressure application unit 40 is pressed by the fingertip of the user. The pressure application unit 40 is formed in the shape of, for example, a push button or a key button. Alternatively, the plurality of pressure application units 40 may be a plurality of regions that are divided by printing or the like on the upper surface of an elastic plate-like or film-like member. The pressure application unit 40 is attached to, for example, a housing not shown.

[0017] The substrate 50 has a surface approximately parallel to the XY plane, and components such as the sensor element 60 are formed on the surface. The substrate 50 is preferably a component for maintaining the strength of the position detection device 10. The substrate 50 is formed of, for example, a bendable material. In this case, the substrate 50 is a PEN (polyethylene naphthalate) film, a PET (polyethylene terephthalate) film, a flexible substrate, or the like.

[0018] A plurality of sensor elements 60 are formed on the substrate 50. The sensor elements 60 may be formed on the upper surface of a base layer 70 formed on the upper surface of the substrate 50. The base layer 70 is, for example, a cross-linked PVP (polyvinylpyrrolidone) film. The sensor elements 60 detect pressure applied from the outside. One sensor element 60 is provided corresponding to one pressure application section 40, and is arranged so as to detect that one pressure application section 40 is pressed. FIG. 1 shows an example in which three sensor elements 60 are formed on the substrate 50 corresponding to three pressure application sections 40. The sensor element 60 has a lower electrode 62, an upper electrode 64, and a piezoelectric layer 66.

[0019] The lower electrode 62 and the upper electrode 64 are formed of a conductive material. It is preferable that the lower electrode 62 and the upper electrode 64 include a metal material. The lower electrode 62 and the upper electrode 64 are formed with a piezoelectric layer 66 sandwiched therebetween.

[0020] The piezoelectric layer 66 is a portion where a piezoelectric body is formed on the upper surface of the lower electrode 62. The piezoelectric body is a ferroelectric material having a piezoelectric effect. The piezoelectric body is, for example, a polymer such as PVDF (polyvinylidene fluoride) or a piezoelectric ceramic such as PZT (lead zirconate titanate).

[0021] The protective film 80 is formed so as to cover the multiple sensor elements 60. The protective film 80 is made of a resin or the like. The protective film 80 is made of a polymer such as parylene. The pressure application unit 40 is provided on the protective film 80. The pressure application unit 40 may be provided so as to be in contact with the protective film 80 when not pressed, or alternatively, may be provided so as to have a gap between the pressure application unit 40 and the protective film 80.

[0022] The wiring 90 electrically connects the lower electrode 62 and the upper electrode 64 of the sensor element 60 to the signal processing unit 30. The wiring 90 is provided for each sensor element 60. The signal processing unit 30 detects the voltage generated from the sensor element 60 and identifies the sensor element 60 to which pressure has been applied among the multiple sensor elements 60. Furthermore, the signal processing unit 30 can identify the pressure application unit 40 corresponding to the identified sensor element 60 as the pressure application unit 40 to which an external force has been applied.

[0023] As described above, in the pressure sensor 20, the sensor element 60 is disposed in correspondence with the position of the pressure application unit 40 so that when the pressure application unit 40 is pressed, pressure is applied to the piezoelectric layer 66. The sensor element 60 generates a voltage between the lower electrode 62 and the upper electrode 64 according to the pressure applied to the piezoelectric layer 66 due to the piezoelectric effect.

[0024] 1, when the user presses the pressure application unit 40 with his / her finger, the sensor element 60 generates a voltage larger than the steady state voltage. When the user removes his / her finger from the pressure application unit 40 after pressing the pressure application unit 40 with his / her finger, the sensor element 60 generates a voltage smaller than the steady state voltage. The signal processing unit 30 identifies the sensor element 60 to which pressure has been applied, for example, by detecting the maximum amplitude value of such a detection waveform.

[0025] The position detection device 10 described above can function as an input device that detects a user's operation input. In the position detection device 10, for example, the sensor element 60A generates a voltage in response to the user pressing the first pressure application unit 40A with a finger. Therefore, the signal processing unit 30 can detect that the first pressure application unit 40A at a position corresponding to the sensor element 60A has been pressed in response to a predetermined voltage value being generated from the wiring 90 connected to the sensor element 60A. The signal processing unit 30 outputs the detected information of the pressure application unit 40 to an external circuit, device, or the like.

[0026] Thus, the position detection device 10 is configured as an input device such as a touch panel, a numeric keypad, a keyboard, etc. Since the position detection device 10 uses the piezoelectric effect, it can reduce false detection even when water droplets or dust are present, compared to input devices that use capacitance.

[0027] In such a position detection device 10, there may be cases where it is desired to improve the position detection resolution or increase the number of pressure application units 40 to which input is possible. In this case, a sensor element 60 must be arranged at each position where the pressure of the pressure sensor 20 is to be detected. However, by increasing the number of sensor elements 60, the arrangement of the sensor elements 60, the arrangement of the wiring 90, the circuit of the signal processing unit 30, etc. become complicated, which may make it difficult to manufacture, maintain, inspect, etc. the position detection device 10. Therefore, the position detection device according to this embodiment is capable of detecting the position of the pressure application unit 40 to which pressure is actually applied from among multiple pressure application units 40 without arranging multiple sensor elements 60, etc.

[0028] <First Configuration Example of Position Detection Device 100> Fig. 2 shows a first configuration example of the position detection device 100 according to this embodiment. In the position detection device 100 according to this embodiment, parts that operate substantially the same as those in the comparative position detection device 10 shown in Fig. 1 are given the same reference numerals, and duplicated explanations will be omitted. The position detection device 100 includes a pressure sensor 110 and a signal processing unit 150. The pressure sensor 110 includes a pressure application unit 40, a substrate 50, a base layer 70, a protective film 80, wiring 90, a lower electrode 120, an upper electrode 130, and a piezoelectric layer 140.

[0029] The lower electrode 120 is formed on a substrate 50. Fig. 2 shows an example in which the lower electrode 120 is formed on the upper surface of the underlayer 70. The lower electrode 120 is preferably formed as a single unit. The upper electrode 130 is formed on a piezoelectric layer 140. The upper electrode 130 is preferably formed on the upper surface of the piezoelectric layer 140. The upper electrode 130 is preferably formed as a single unit. The lower electrode 120 and the upper electrode 130 are formed of a conductive material.

[0030] The piezoelectric layer 140 is a portion where a piezoelectric body is formed on the lower electrode 120. The piezoelectric layer 140 is desirably formed on the upper surface of the lower electrode 120. The piezoelectric body is a ferroelectric material that has a piezoelectric effect. The piezoelectric body is, for example, a polymer such as PVDF (polyvinylidene fluoride) or a piezoelectric ceramic such as PZT (lead zirconate titanate).

[0031] As described above, the position detection device 100 according to this embodiment has a lower electrode 120, an upper electrode 130, and a piezoelectric layer 140 formed thereon, instead of the multiple sensor elements 60 of the comparative position detection device 10. In other words, the position detection device 100 has a common lower electrode 120 and a common upper electrode 130 sandwiched between them by the piezoelectric layer 140. The pressure application section 40 is formed on the upper electrode 130 with the protective film 80 interposed therebetween.

[0032] In the piezoelectric layer 140, the piezoelectric material is formed such that the volume of the piezoelectric material per unit area in a plane (XY plane) approximately parallel to the substrate 50 varies depending on the position of the pressure application section 40. Fig. 2 shows an example in which the thickness of the piezoelectric layer 140 varies depending on the position of the pressure application section 40. The piezoelectric effect of the piezoelectric layer 140 generates different voltages depending on the volume of the piezoelectric material to which pressure is applied, even when the same pressure is applied to the piezoelectric material.

[0033] For example, when an external force is applied to the first pressure application section 40A, a part of the piezoelectric layer 140 to which pressure is applied in correspondence with the first pressure application section 40A directly below the first pressure application section 40A is defined as a first piezoelectric region 141. When an external force is applied to the second pressure application section 40B, a part of the piezoelectric layer 140 to which pressure is applied in correspondence with the second pressure application section 40B directly below the second pressure application section 40B is defined as a second piezoelectric region 142. Similarly, when an external force is applied to the third pressure application section 40C, a part of the piezoelectric layer 140 to which pressure is applied is defined as a third piezoelectric region 143.

[0034] 2, the thickness of the first piezoelectric region 141 in the direction perpendicular to the substrate 50 (Z-axis direction) is formed to be thinner than the thickness of the second piezoelectric region 142, and therefore the volume of the first piezoelectric region 141 is smaller than the volume of the second piezoelectric region 142. Similarly, the volume of the second piezoelectric region 142 is smaller than the volume of the third piezoelectric region 143.

[0035] The larger the volume of the piezoelectric body, the greater the amount of charge output from the piezoelectric body. Therefore, in the case of the pressure sensor 110 having the structure shown in FIG. 2, when an external force of a certain magnitude is applied to each of the first pressure application section 40A, the second pressure application section 40B, and the third pressure application section 40C, the voltages generated by the piezoelectric layer 140 are different from each other. For example, the magnitude of the voltage generated from the first piezoelectric region 141 when an external force of a certain magnitude is applied to the first pressure application section 40A is smaller than the magnitude of the voltage generated from the second piezoelectric region 142 when an external force of approximately the same magnitude as the external force is applied to the second pressure application section 40B. Therefore, by detecting the value of the voltage generated in the common lower electrode 120 and upper electrode 130, it is possible to determine which pressure application section 40 the external force has been applied to.

[0036] The wiring 90 transmits the voltages thus generated in the lower electrode 120 and the upper electrode 130 as detection signals to the signal processing unit 150. The signal processing unit 150 identifies the pressure application unit 40 to which the external force has been applied, based on the waveform (e.g., amplitude) of the detection signal output from the pressure sensor 110. The signal processing unit 150 has a signal receiving unit 160, an identifying unit 170, and a storage unit 180.

[0037] The signal receiving unit 160 receives the detection signals output from the upper electrode 130 and the lower electrode 120. The signal receiving unit 160 includes, for example, an amplifier circuit, an A / D conversion circuit, etc., and converts the received detection signals into digital signals. The signal receiving unit 160 supplies the converted digital signals to the identification unit 170.

[0038] The identifying unit 170 identifies the position of the pressure application unit 40 to which the external force is applied, based on the detection signal and the pressure application unit data received by the signal receiving unit 160. The pressure application unit data is data in which the positions of the multiple pressure application units 40 on a plane parallel to the substrate 50 are associated with reference values ​​of the detection signals when pressure is applied to each of the pressure application units 40.

[0039] For example, the average value of the maximum amplitude of the voltage generated from the first piezoelectric region 141 by pressing the first pressure application unit 40A with a finger is V1ave, and the allowable error value is ΔV. In this case, the reference value ST1 of the detection signal corresponding to the first pressure application unit 40A is a value (V1ave-ΔV) obtained by subtracting the allowable error value from the average value. Similarly, the reference value ST2 of the detection signal corresponding to the second pressure application unit 40B is a value (V2ave-ΔV) obtained by subtracting the allowable error value from the average value of the maximum amplitude of the voltage generated from the second piezoelectric region 142 by pressing the second pressure application unit 40B with a finger. Similarly, the reference value ST3 of the detection signal corresponding to the third pressure application unit 40C is V3ave-ΔV.

[0040] In this case, the identifying unit 170 identifies the pressure applying unit 40 to which the external force is applied as the first pressure applying unit 40A in response to, for example, the maximum amplitude value of the detection signal being smaller than the reference value ST2 and being equal to or greater than the reference value ST1. Similarly, the identifying unit 170 identifies the pressure applying unit 40 to which the external force is applied as the second pressure applying unit 40B in response to the maximum amplitude value of the detection signal being smaller than the reference value ST3 and being equal to or greater than the reference value ST2. The identifying unit 170 may also identify the pressure applying unit 40 to which the external force is applied as the third pressure applying unit 40C in response to the maximum amplitude value of the detection signal being equal to or greater than the reference value ST3.

[0041] Alternatively, two values ​​indicating a range of voltage values ​​may be set as the reference value of the detection signal for one pressure application unit 40. For example, the reference value of the detection signal corresponding to the first pressure application unit 40A is a value ST1m (V1ave-ΔV) obtained by subtracting the allowable error value from the average value, and a value ST1p (V1ave+ΔV) obtained by adding the allowable error value to the average value.

[0042] In this case, the identifying unit 170 identifies the pressure application unit 40 to which the external force has been applied as the first pressure application unit 40A, for example, in response to the maximum amplitude value of the detection signal being smaller than the reference value ST1p and being equal to or larger than the reference value ST1m. By using the reference value determined by a statistical method or the reference value determined from the design value or the like in this manner, the identifying unit 170 can more accurately identify the pressure application unit 40 to which the external force has been applied.

[0043] The identification unit 170, for example, supplies information on the identified position where the external force is applied to an external circuit, device, etc. Furthermore, the identification unit 170 may display the information on the identified position where the external force is applied on a display unit, etc. The identification unit 170 may store the information on the identified position where the external force is applied in the storage unit 180. Such an identification unit 170 is, for example, a CPU, etc.

[0044] The storage unit 180 stores pressure application unit data in which the positions of the multiple pressure application units 40 are associated with reference values ​​of detection signals. The storage unit 180 may store setting values, thresholds, parameters, and the like used by the identification unit 170 for operation. When the CPU or the like operates as at least a part of the identification unit 170, the storage unit 180 may store information of a program executed by the CPU or the like. The storage unit 180 may also store various information including a database referenced when the program is executed.

[0045] The storage unit 180 includes, for example, a ROM (Read Only Memory) that stores a BIOS (Basic Input Output System) and the like, and a RAM (Random Access Memory) that serves as a working area. Thereby, the CPU and the like function as the identification unit 170 by executing the programs stored in the storage unit 180.

[0046] As described above, in the pressure sensor 110 according to this embodiment, the volume per unit area of ​​the piezoelectric material in the piezoelectric layer 140 differs depending on the position of the pressure application unit 40, and therefore the maximum amplitude value of the detection signal generated when an external force is applied differs depending on the position of the pressure application unit 40. Therefore, the position detection device 100 can identify the position of the pressure application unit 40 corresponding to the region of the piezoelectric layer 140 where the detection signal is generated by comparing the maximum amplitude value of the detection signal of the pressure sensor 110 with a plurality of reference values.

[0047] The pressure sensor 110 having such a piezoelectric layer 140 can be simply configured using a common lower electrode 120 and upper electrode 130 sandwiching the piezoelectric layer 140, without providing a plurality of sensor elements 60. The position detection device 100 can reduce the number of wirings 90 by using the pressure sensor 110 having such a simple configuration. Furthermore, the position detection device 100 can easily identify the position of the pressure application unit 40 to which an external force has actually been applied, among the plurality of pressure application units 40, by simply converting the detection signals output from the common lower electrode 120 and upper electrode 130 into digital signals and performing digital processing.

[0048] In the above pressure sensor 110 according to the present embodiment, an example has been described in which the thickness of the piezoelectric layer 140 varies depending on the position of the pressure application section 40, but the present invention is not limited to this. In the pressure sensor 110, it is sufficient that the volume per unit area of ​​the piezoelectric of the piezoelectric layer 140 varies depending on the position of the pressure application section 40, and the piezoelectric layer 140 may be formed such that the area within a region corresponding to the pressure application section 40 in a plane parallel to the substrate 50 varies depending on the position of the pressure application section 40.

[0049] For example, in a plan view on a plane parallel to the substrate 50, the area of ​​the first piezoelectric region 141 corresponding to the first pressure application section 40A may be formed to be smaller than the area of ​​the second piezoelectric region 142 corresponding to the second pressure application section 40B. Similarly, in a plan view, the area of ​​the second piezoelectric region 142 corresponding to the second pressure application section 40B may be formed to be smaller than the area of ​​the third piezoelectric region 143 corresponding to the third pressure application section 40C.

[0050] This allows the volume per unit area of ​​the piezoelectric of the piezoelectric layer 140 to be varied depending on the position of the pressure application section 40. The thickness of the piezoelectric layer 140 in the vertical direction of the substrate 50 may be formed to be approximately constant. In this case, the upper electrode 130 and the lower electrode 120 are formed approximately parallel to each other, sandwiching the piezoelectric layer 140 of approximately constant thickness. Such upper electrode 130 and lower electrode 120 do not have any portions formed in a stepped shape, so they are easy to manufacture and are less likely to suffer from defects such as step discontinuities that adversely affect electrical characteristics.

[0051] The piezoelectric regions of the piezoelectric layer 140 may be separated by gaps or the like. The piezoelectric regions of the piezoelectric layer 140 may be formed to have different volumes due to voids or the like. A position detection device 100 having such a pressure sensor 110a will now be described.

[0052] <Second Configuration Example of Position Detection Device 100> 3 shows a second configuration example of the position detection device 100 according to this embodiment. The piezoelectric layer 140 of the pressure sensor 110a of the second configuration example has a plurality of piezoelectric regions corresponding to a plurality of pressure application units 40, and a gap region 144 where no piezoelectric is formed is provided between each of the plurality of piezoelectric regions and the other piezoelectric regions. By separating the plurality of piezoelectric regions in this way, when pressure is applied to one piezoelectric region, it is possible to prevent pressure from also being applied to adjacent piezoelectric regions, and it is possible to reduce noise components in the detection signal.

[0053] Furthermore, a plurality of voids 146 in which no piezoelectric body is formed are further formed in the piezoelectric layer 140. The piezoelectric layer 140 is formed such that the volume of the voids 146 in the first piezoelectric region 141 of the piezoelectric layer 140 corresponding to the first pressure application section 40A is different from the volume of the voids 146 in the second piezoelectric region 142 of the piezoelectric layer 140 corresponding to the second pressure application section 40B different from the first pressure application section 40A.

[0054] This allows the piezoelectric layer 140 to be formed so that the volume per unit area of ​​the piezoelectric body varies depending on the position of the pressure application section 40. In addition, the thickness of the piezoelectric body can be made substantially constant, and the upper electrode 130 and the lower electrode 120 can be formed in parallel with the piezoelectric layer 140 of a constant thickness sandwiched therebetween. Such gap regions 144, voids 146, etc. can be easily formed, for example, by etching. Therefore, the position detection device 100 of the second configuration example can also be easily manufactured, and the position to which an external force is actually applied can be identified from among the positions to which multiple pressures are applied, without arranging multiple sensor elements.

[0055] In the position detection device 100 according to the present embodiment described above, an example has been described in which the pressure application sections 40 are arranged in a first direction (X direction) parallel to the substrate 50, and the volume per unit area of ​​the piezoelectric body of the piezoelectric layer 140 varies depending on the position of the pressure application section 40, but the present invention is not limited to this. The pressure application sections 40 may be arranged in a second direction different from the first direction in addition to the first direction on a plane parallel to the substrate 50. The second direction is, for example, a direction substantially parallel to the Y direction.

[0056] The pressure application sections 40 may simply be arranged two-dimensionally on a plane parallel to the substrate 50, and the size and spacing of the pressure application sections 40 do not need to be constant. In response to the two-dimensional arrangement of the pressure application sections 40, it is desirable that the piezoelectric body of the piezoelectric layer 140 is formed so that the volume per unit area varies depending on the position of the pressure application section 40. Alternatively, the pressure sensor 110 may have a plurality of piezoelectric layers and be configured to correspond to the positions of the two-dimensionally arranged pressure application sections 40. A position detection device 10 including such a pressure sensor 110 will be described below.

[0057] <Third Configuration Example of Position Detection Device 100> Fig. 4 shows a third configuration example of the position detection device 100 according to this embodiment. In the position detection device 100 of the third configuration example, parts that operate substantially the same as those of the position detection device 100 of the first configuration example shown in Fig. 2 are given the same reference numerals, and duplicated explanations will be omitted. In the position detection device 100 of the third configuration example, the pressure sensor 110 includes a first piezoelectric layer 210, a common electrode 220, and a second piezoelectric layer 230.

[0058] The first piezoelectric layer 210 is a portion where a piezoelectric body is formed on the lower electrode 120. The first piezoelectric layer 210 is desirably formed on the upper surface of the lower electrode 120. The piezoelectric body is made of the same material as the piezoelectric layer 140 described in FIG.

[0059] The common electrode 220 is formed on the first piezoelectric layer 210. The common electrode 220 is preferably formed on the upper surface of the first piezoelectric layer 210. The common electrode 220 is preferably formed integrally with the first piezoelectric layer 210. The common electrode 220 is formed of, for example, the same material as the lower electrode 120 and the upper electrode 130.

[0060] The second piezoelectric layer 230 is a portion where a piezoelectric body is formed on the common electrode 220. The second piezoelectric layer 230 is desirably formed on the upper surface of the common electrode 220. The piezoelectric body is made of the same material as the piezoelectric layer 140 described in FIG.

[0061] The upper electrode 130 is formed on the second piezoelectric layer 230. The upper electrode 130 is desirably formed on the upper surface of the second piezoelectric layer 230. The signal receiving unit 160 receives the first detection signal output from the lower electrode 120 and the common electrode 220, and the second detection signal output from the common electrode 220 and the upper electrode 130. The identifying unit 170 identifies the position of the pressure application unit 40 to which the external force is applied, based on the first detection signal and the second detection signal received by the signal receiving unit 160 and the pressure application unit data.

[0062] As described above, the pressure sensor 110 of the third configuration example includes the first piezoelectric layer 210 and the second piezoelectric layer 230, and is formed so that the volume of the piezoelectric material per unit area varies depending on the position of the pressure application section 40 in correspondence with the two-dimensionally arranged pressure application sections 40. A more detailed configuration of such a pressure sensor 110 will be described next.

[0063] <Schematic configuration of pressure sensor 110> Fig. 5 shows a schematic configuration of the pressure sensor 110 of the position detection device 100 of the third configuration example shown in Fig. 4. Fig. 5 shows a schematic configuration of the lower electrode 120, the first piezoelectric layer 210, the common electrode 220, the second piezoelectric layer 230, the upper electrode 130, and the pressure application section 40 of the pressure sensor 110.

[0064] The pressure application units 40 are formed on the upper electrode 130 and are arranged in a first direction parallel to the substrate 50 and a second direction different from the first direction. FIG. 5 shows an example in which the first direction is the X direction and the second direction is the Y direction, and nine pressure application units 40 having substantially the same shape are arranged in threes in the first direction and threes in the second direction. In other words, if the first direction is the row direction and the second direction is the column direction, the pressure application units 40 are arranged in three rows and three columns. Here, the positions of the pressure application units 40 are represented in a matrix as (m, n) (m=1, 2, 3, n=1, 2, 3).

[0065] 2, the first piezoelectric layer 210 has piezoelectric bodies formed therein such that the volume of the piezoelectric bodies per unit area varies depending on the position of the pressure application section 40 arranged in the first direction in a plane substantially parallel to the substrate 50. Alternatively, the first piezoelectric layer 210 may be formed in the same manner as the piezoelectric layer 140 described in FIG.

[0066] 5 shows an example in which the thickness of the first piezoelectric layer 210 varies depending on the position of the pressure application section 40 arranged in the first direction. For example, when an external force is applied to the pressure application section 40(m,1) in the first row, a part of the first piezoelectric layer 210 to which pressure is applied corresponding to the pressure application section 40(m,1) directly below the pressure application section 40(m,1) is defined as a first piezoelectric region 211.

[0067] Furthermore, when an external force is applied to the pressure application section 40(m,2) in the second row, a portion of the first piezoelectric layer 210 to which pressure is applied in correspondence with the pressure application section 40(m,2) directly below the pressure application section 40(m,2) is defined as the second piezoelectric region 212. Similarly, when an external force is applied to the pressure application section 40(m,3) in the third row, a portion of the first piezoelectric layer 210 to which pressure is applied in correspondence with the pressure application section 40(m,3) directly below the pressure application section 40(m,3) is defined as the third piezoelectric region 213.

[0068] 5, the thickness of the first piezoelectric region 211 in the direction perpendicular to the substrate 50 (Z-axis direction) is formed to be thicker than the thickness of the second piezoelectric region 212, so the volume of the first piezoelectric region 211 is larger than the volume of the second piezoelectric region 212. Similarly, the thickness of the second piezoelectric region 212 is formed to be thicker than the thickness of the third piezoelectric region 213, so the volume of the second piezoelectric region 212 is larger than the volume of the third piezoelectric region 213.

[0069] Since the pressure sensor 110 has the above-described first piezoelectric layer 210, the identification unit 170 can identify the row of the pressure application unit 40 to which the external force has been applied, based on the first detection signal output from the lower electrode 120 and the common electrode 220. Note that in the first piezoelectric layer 210 of Fig. 5, the positions corresponding to the arrangement (m, n) of the nine pressure application units 40 are similarly indicated as (m, n) (m = 1, 2, 3, n = 1, 2, 3).

[0070] In the second piezoelectric layer 230, the piezoelectric body is formed so that the volume of the piezoelectric body per unit area varies depending on the position of the pressure application section 40 arranged in the second direction on a surface parallel to the substrate 50. The second piezoelectric layer 230 has, for example, the same configuration as the first piezoelectric layer 210, and is formed so as to be rotated by the angle formed by the first direction and the second direction. Alternatively, the second piezoelectric layer 230 may be formed in the same manner as the piezoelectric layer 140 described in FIG. 3. FIG. 5 shows an example in which the second piezoelectric layer 230 having approximately the same shape as the first piezoelectric layer 210 is rotated approximately 90 degrees around an axis in the direction perpendicular to the substrate 50 (Z direction).

[0071] In this case, for example, when an external force is applied to the pressure application section 40(1,n) in the first row, a portion of the second piezoelectric layer 230 to which pressure is applied corresponding to the pressure application section 40(1,n) directly below the pressure application section 40(1,n) is defined as a fourth piezoelectric region 231. Similarly, a portion of the second piezoelectric layer 230 corresponding to the pressure application section 40(2,n) in the second row is defined as a fifth piezoelectric region 232, and a portion of the second piezoelectric layer 230 corresponding to the pressure application section 40(3,n) in the third row is defined as a sixth piezoelectric region 233.

[0072] The fourth piezoelectric region 231 is thinner than the fifth piezoelectric region 232, and the fifth piezoelectric region 232 is thinner than the sixth piezoelectric region 233. Therefore, the volume of the fourth piezoelectric region 231 is smaller than the volume of the fifth piezoelectric region 232, and the volume of the fifth piezoelectric region 232 is smaller than the volume of the sixth piezoelectric region 233.

[0073] Since the pressure sensor 110 has the above-described second piezoelectric layer 230, the identification unit 170 can identify the row of the pressure application unit 40 to which the external force has been applied, based on the second detection signal output from the common electrode 220 and the upper electrode 130. Note that in the second piezoelectric layer 230 of Fig. 5, the positions corresponding to the arrangement (m, n) of the nine pressure application units 40 are similarly indicated as (m, n) (m = 1, 2, 3, n = 1, 2, 3).

[0074] As described above, the position detection device 100 of the third configuration example identifies the position of the pressure application unit 40 in the first direction from the first detection signal based on the piezoelectric effect of the first piezoelectric layer 210, and identifies the position of the pressure application unit 40 in the second direction from the second detection signal based on the piezoelectric effect of the second piezoelectric layer 230. The position detection device 100 of the third configuration example can identify the position of the pressure application unit 40 to which an external force has been applied, among the many pressure application units 40 arranged two-dimensionally, without providing multiple sensor elements 60, because the pressure sensor 110 has two piezoelectric layers and three electrode layers.

[0075] The configuration of the position detection device 100 of the third configuration example described in FIG. 4 and FIG. 5 is an example, and is not limited thereto. More pressure application sections 40 may be arranged on a surface approximately parallel to the substrate 50. The shapes of the pressure application sections 40 may be different from each other, and the arrangement interval of the pressure application sections 40 does not have to be a constant value. The first piezoelectric layer 210 and the second piezoelectric layer 230 may be provided corresponding to the shapes, intervals, arrangement, etc. of the pressure application sections 40. For example, the first direction and the second direction do not have to be orthogonal to each other. Furthermore, the first piezoelectric layer 210 and the second piezoelectric layer 230 may have different shapes.

[0076] For example, six piezoelectric regions, namely, the first piezoelectric region 211, the second piezoelectric region 212, and the third piezoelectric region 213 of the first piezoelectric layer 210, and the fourth piezoelectric region 231, the fifth piezoelectric region 232, and the sixth piezoelectric region 233 of the second piezoelectric layer 230, may be formed to have different thicknesses (volumes). In addition, it is preferable that the sum of the thickness (volume) of the first piezoelectric layer 210 and the thickness (volume) of the second piezoelectric layer 230 is formed to be different depending on the position of the pressure application unit 40. In other words, the thickness (volume) of the first piezoelectric layer 210 and the second piezoelectric layer 230 is formed to be different depending on the position of the pressure application unit 40.

[0077] 5, for example, the sum of the thickness at the position (m, n) of the first piezoelectric layer 210 corresponding to the nine positions (m, n) of the pressure application unit 40 and the thickness at the position (m, n) of the second piezoelectric layer 230 is nine different thicknesses. The sum of the amplitude values ​​of the first detection signal and the second detection signal output by such a pressure sensor 110 is a different value according to the position (m, n) of the pressure application unit 40. Therefore, the position detection device 100 of the third configuration example can identify the position of the pressure application unit 40 by comparing the sum of the amplitude values ​​of the first detection signal and the second detection signal with a reference value, threshold value, etc. that is preset for each position of the pressure application unit 40.

[0078] The sum of the amplitude values ​​of the first and second detection signals is equal to the potential difference between the lower electrode 120 and the upper electrode 130. Therefore, the signal receiving unit 160 may receive a signal between the lower electrode 120 and the upper electrode 130 instead of the first and second detection signals, and supply the signal to the identifying unit 170. When the signal processing unit 150 operates in this manner, the common electrode 220 may not be required.

[0079] When the magnitude of the applied external force changes, the pressure sensor 110 outputs a detection signal whose maximum amplitude value differs according to the magnitude of the external force. Therefore, the pressure sensor 110 is a sensor that can accurately identify the pressure application unit 40 to which the external force is applied, if the magnitude of the applied external force is within a predetermined range.

[0080] For example, consider a case where an external force larger than normal is applied to one pressure application unit 40. The pressure sensor 110 may output a detection signal with a maximum amplitude value similar to the maximum amplitude value of a detection signal output when an external force of a normal magnitude is applied to another pressure application unit 40 different from the one pressure application unit 40 to which the external force is applied. In this case, it becomes difficult for the identification unit 170 to accurately identify the pressure application unit 40 to which the external force is applied. It is desirable for the position detection device 10 to be able to prevent a decrease in detection accuracy even if the magnitude of the external force varies.

[0081] Therefore, the determination unit 170 may reduce such fluctuations in detection accuracy by calculating the ratio of the amplitude values ​​of the first detection signal and the second detection signal. When the magnitude of the external force applied to the pressure application unit 40 fluctuates, the amplitude values ​​of the first detection signal and the second detection signal fluctuate according to the magnitude of the external force. Therefore, the ratio of the amplitude values ​​of the first detection signal and the second detection signal cancels out the fluctuation in the magnitude of the external force, and becomes a value that reflects the ratio of the thickness (volume) of the first piezoelectric layer 210 to the thickness (volume) of the second piezoelectric layer 230.

[0082] <First calculation example of detection signal> Fig. 6 shows a first calculation example of the maximum amplitude value of the first detection signal and the second detection signal. In Fig. 6, the positions of the first piezoelectric layer 210 and the second piezoelectric layer 230 corresponding to the position of the pressure application unit 40 to which the external force is applied are shown as "pressed positions". Furthermore, the thickness of each piezoelectric region of the first piezoelectric layer 210 and the second piezoelectric layer 230 is normalized by setting the thickness of the first piezoelectric region 211 to 1 and shown as "film thickness". The gain of the amplifier circuit of the signal receiving unit 160 is shown as "amplifier gain", and the voltage value output by the signal receiving unit 160 after converting the detection signal into a digital signal is shown as "output voltage".

[0083] For example, when an external force is applied to the position (m, 1) of the first piezoelectric region 211 of the first piezoelectric layer 210, the output voltage is 10. The maximum amplitude value, effective value, etc. of the first detection signal are output voltages of this kind. When an external force is applied to the position (2, n) of the fifth piezoelectric region 232 of the second piezoelectric layer 230, the output voltage is 40. The maximum amplitude value, effective value, etc. of the second detection signal are output voltages of this kind. Note that the output voltage in FIG. 6 is a relative value. The actual output voltage can be calculated using the applied pressure, the piezoelectric constant, the sensitivity coefficient, etc., but this will be omitted here. In other words, the output voltage in FIG. 6 is a value that varies depending on the magnitude of the external force applied to the pressure application unit 40.

[0084] FIG. 7 shows a first calculation example of the ratio of the maximum amplitude value of the first detection signal and the second detection signal. In FIG. 7, the positions of the first piezoelectric layer 210 and the second piezoelectric layer 230 corresponding to the position of the pressure application unit 40 to which the external force is applied are shown as "pressed coordinates". In addition, the output voltages of the first piezoelectric layer 210 and the second piezoelectric layer 230 corresponding to the "pressed coordinates" are extracted from FIG. 6 and shown as "output voltages". The ratio of the output voltages of the first piezoelectric layer 210 and the second piezoelectric layer 230 is defined as "output voltage ratio". For reference, the ratio of the "film thicknesses" of the first piezoelectric layer 210 and the second piezoelectric layer 230 corresponding to the "pressed coordinates" is shown as "film thickness ratio".

[0085] 7, the "output voltage ratio" is equal to the "film thickness ratio" of the first piezoelectric layer 210 and the second piezoelectric layer 230, and is an approximately constant value even if the magnitude of the external force varies. In addition, the "output voltage ratio" can be set to nine different values ​​corresponding to the nine positions of the pressure application unit 40 by adjusting the thicknesses of the piezoelectric regions of the first piezoelectric layer 210 and the second piezoelectric layer 230. Therefore, the determination unit 170 can more accurately determine the position of the pressure application unit 40 by, for example, calculating the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal and comparing it with a reference value, threshold value, or the like that is preset for each position of the pressure application unit 40.

[0086] 6 and 7 are merely examples, and the present invention is not limited thereto. For example, the magnitude of the "amplifier gain" may be changed in order to adjust the range of the "output voltage". In addition, the magnitude of the "amplifier gain" of the first piezoelectric layer 210 and the magnitude of the "amplifier gain" of the second piezoelectric layer 230 may be made different.

[0087] <Second calculation example of detection signal> Fig. 8 shows a second calculation example of the maximum amplitude value of the first detection signal and the second detection signal. Fig. 9 shows a second calculation example of the ratio of the maximum amplitude value of the first detection signal and the second detection signal. The second calculation example shown in Figs. 8 and 9 shows the result of changing the magnitude of the "amplifier gain" of the second piezoelectric layer 230 in the first calculation example shown in Figs. 6 and 7 from 10 to 30. By adjusting the magnitude of the "amplifier gain" in this way, the degree of freedom of design can be improved, and it is therefore possible to easily adjust the range of the "output voltage" value, the value of the "output voltage ratio", the range of the "output voltage ratio" value, the difference between different "output voltage ratio" values, and the like.

[0088] When using the pressure sensor 110 of the third configuration example as described above, the position of the pressure application unit 40 to which the external force is applied is identified based on the amplitude values ​​of the first detection signal and the second detection signal, so it is preferable that the voltage range of the amplitude values ​​of the first detection signal and the second detection signal is large. For example, when there are a large number of pressure application units 40, it is preferable that the voltage range of the amplitude values ​​of the first detection signal and the second detection signal is large. In addition, since there is a range in the magnitude of the external force applied to the pressure application unit 40, the voltage range of the amplitude values ​​of the first detection signal and the second detection signal may be further expanded.

[0089] Therefore, the signal receiving unit 160 amplifies the first and second detection signals having a wide voltage range and converts them into digital signals. In other words, the signal receiving unit 160 may be required to have an amplifier circuit with a wide dynamic range. An example of the signal receiving unit 160 capable of processing such detection signals will be described below.

[0090] <Configuration example of piezoelectric sensor 300> 10 shows a configuration example of a piezoelectric sensor 300 according to this embodiment. In this example, a combination of the pressure sensor 110 according to this embodiment and the signal receiving unit 160 is referred to as the piezoelectric sensor 300. The pressure sensor 110 may be the pressure sensor 110 of the third configuration example described in FIGS. 4 to 9, and a description thereof will be omitted here. The signal receiving unit 160 has a signal amplifying unit 310 and an AD converting unit 320.

[0091] The signal amplifier 310 receives the first detection signal output from the lower electrode 120 and the common electrode 220 and the second detection signal output from the common electrode 220 and the upper electrode 130, and outputs an amplified signal obtained by amplifying the first detection signal and the second detection signal. The signal amplifier 310 includes a first amplifier circuit 311, a second amplifier circuit 312, a third amplifier circuit 313, a fourth amplifier circuit 314, a fifth amplifier circuit 315, and a sixth amplifier circuit 316.

[0092] The first amplifier circuit 311 amplifies the first detection signal output from the lower electrode 120 and the common electrode 220 by a first amplification factor. The first amplification factor is an amplification factor of 1 or more. The first amplifier circuit 311 supplies the amplified signal to the second amplifier circuit 312 and the third amplifier circuit 313.

[0093] The second amplifier circuit 312 amplifies the signal amplified by the first amplifier circuit 311 by a second amplification factor. The third amplifier circuit 313 amplifies the signal amplified by the first amplifier circuit 311 by a third amplification factor that is smaller than the second amplification factor. The second amplification factor and the third amplification factor are amplification factors of 1 or more. For example, the second amplifier circuit 312 functions as an amplifier circuit for small signals, and the third amplifier circuit 313 functions as an amplifier circuit for large signals. The second amplifier circuit 312 and the third amplifier circuit 313 supply the amplified signals to the AD conversion unit 320.

[0094] The fourth amplifier circuit 314 amplifies the second detection signal output from the upper electrode 130 and the common electrode 220 by a fourth amplification factor. The fourth amplification factor is an amplification factor of 1 or more. The fourth amplification factor may be the same as the first amplification factor, or may be an amplification factor different from the first amplification factor. The fourth amplifier circuit 314 supplies the amplified signal to a fifth amplifier circuit 315 and a sixth amplifier circuit 316.

[0095] The fifth amplifier circuit 315 amplifies the signal amplified by the fourth amplifier circuit 314 by a fifth amplification factor. The sixth amplifier circuit 316 amplifies the signal amplified by the fourth amplifier circuit 314 by a sixth amplification factor that is smaller than the fifth amplification factor. The fifth amplification factor and the sixth amplification factor are amplification factors of 1 or more. For example, the fifth amplifier circuit 315 functions as an amplifier circuit for small signals, and the sixth amplifier circuit 316 functions as an amplifier circuit for large signals. The fifth amplifier circuit 315 and the sixth amplifier circuit 316 supply the amplified signals to the AD conversion unit 320.

[0096] The AD conversion unit 320 converts the four amplified signals received from the second amplifier circuit 312, the third amplifier circuit 313, the fifth amplifier circuit 315, and the sixth amplifier circuit 316 into digital signals. The AD conversion unit 320 outputs the converted digital signals as reception results of the signal receiving unit 160. The identification unit 170 receives such reception results of the signal receiving unit 160. The signal receiving unit 160 may further include a comparator or the like that compares a predetermined voltage value with the output of the signal amplifying unit 310. The predetermined voltage value is, for example, a threshold value, a reference value, or the like.

[0097] As described above, the signal amplifying section 310 of the piezoelectric sensor 300 according to this embodiment includes a first path that amplifies the first detection signal by a first amplification factor and a second amplification factor, and a second path that amplifies the first detection signal by a first amplification factor and a third amplification factor and has a smaller amplification factor than the first path. Since the signal amplifying section 310 has a plurality of paths with different amplification factors, for example, the identifying section 170 at the rear stage of the piezoelectric sensor 300 can select an amplified signal of a more appropriate path based on the magnitude of the maximum amplitude value of the first detection signal.

[0098] For example, the identifying unit 170 adopts the amplified signal of the first path if the maximum amplitude value of the signal obtained by amplifying the first detection signal by the first amplifier circuit 311 is within the dynamic range that can be processed by the second amplifier circuit 312. In addition, the identifying unit 170 adopts the amplified signal of the second path if the maximum amplitude value of the signal obtained by amplifying the first detection signal by the first amplifier circuit 311 exceeds the dynamic range of the second amplifier circuit 312.

[0099] Similarly, the signal amplifier 310 includes a third path that amplifies the second detection signal by a fourth amplification factor and a fifth amplification factor, and a fourth path that amplifies the second detection signal by a fourth amplification factor and a sixth amplification factor and has a smaller amplification factor than the third path. This allows the identifying unit 170 at the rear of the piezoelectric sensor 300 to select an amplified signal of a more appropriate path based on the magnitude of the maximum amplitude value of the second detection signal.

[0100] For example, the identifying unit 170 adopts the amplified signal of the third path if the maximum amplitude value of the signal obtained by amplifying the second detection signal by the fourth amplifier circuit 314 is within the dynamic range that can be processed by the fifth amplifier circuit 315. Furthermore, the identifying unit 170 adopts the amplified signal of the fourth path if the maximum amplitude value of the signal obtained by amplifying the second detection signal by the fourth amplifier circuit 314 exceeds the dynamic range of the fifth amplifier circuit 315. As described above, the identifying unit 170 can accurately identify the position of the pressure application unit 40 by using the signals obtained by amplifying the first detection signal and the second detection signal by an appropriate amplifier circuit.

[0101] The determination unit 170 may multiply the reception result of the signal receiving unit 160 by a predetermined constant so as to make the reception result of the signal receiving unit 160 correspond to the amplification characteristic of a predetermined path. For example, when the amplified signal of the second path is adopted, the determination unit 170 multiplies the reception result of the signal receiving unit 160 by a first constant to convert it into a reception result that would be received if the amplified signal of the first path was adopted. As an example, the first constant is the second amplification factor / the third amplification factor.

[0102] As a result, the determination unit 170 can acquire a reception result of an amplified signal that has passed through a predetermined one of the first and second paths, regardless of which of the two paths, the first and second paths, the amplified signal has passed through. Similarly, when the determination unit 170 employs an amplified signal of the fourth path, for example, the determination unit 170 may multiply the reception result of the signal receiving unit 160 by a second constant to convert it into a reception result that would be received if an amplified signal of the third path was employed. As an example, the second constant is the fifth amplification factor / sixth amplification factor.

[0103] The identifying unit 170 may compare the amplified signals that have passed through the two paths and then determine which amplified signal to adopt. For example, if the maximum amplitude value of the signal obtained by amplifying the first detection signal by the first amplifier circuit 311 exceeds the dynamic range of the second amplifier circuit 312, distortion occurs in the amplified signal output by the second amplifier circuit 312, and the maximum amplitude value becomes smaller than the value amplified by the second amplification factor. Therefore, the identifying unit 170 compares the maximum amplitude value of the amplified signal of the first path with the maximum amplitude value of the signal obtained by converting the amplified signal of the second path into the amplified signal of the first path.

[0104] For example, when the comparison results of the two amplified signals are substantially the same, the identifying unit 170 can determine that the amplified signal output by the second amplifier circuit 312 is not distorted, and therefore adopts the amplified signal of the first path. In addition, when the comparison result shows that the maximum amplitude value of the amplified signal of the first path is smaller than that of the two signals, the identifying unit 170 can determine that the amplified signal output by the second amplifier circuit 312 is distorted, and adopts the amplified signal of the second path. Similarly, the identifying unit 170 may compare the maximum amplitude value of the amplified signal of the third path with the maximum amplitude value of the signal obtained by converting the amplified signal of the fourth path into the amplified signal of the third path, and then determine which of the amplified signals of the third path and the fourth path to adopt.

[0105] 6 to 9, the determining unit 170 may determine the position of the pressure application unit 40 by calculating the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal. In this case, for example, it is desirable that the first amplifier circuit 311 and the second amplifier circuit 312 are designed so that the multiplication result of the first amplification factor and the second amplification factor is approximately equal to the value of the "amplifier gain" of the first piezoelectric layer 210 in Fig. 6 or 8. Alternatively, the determining unit 170 may convert the amplification factor of the amplified signal that has passed through the first path and the second path so that it is approximately equal to the value of the "amplifier gain".

[0106] Similarly, it is desirable that the fourth amplifier circuit 314 and the fifth amplifier circuit 315 are designed so that the multiplication result of the fourth amplification factor and the fifth amplification factor is approximately equal to the value of the "amplifier gain" of the second piezoelectric layer 230 in Fig. 6 or 8. Alternatively, the determination unit 170 may convert the amplification factor of the amplified signal that has passed through the third path and the fourth path so that it is approximately equal to the value of the "amplifier gain".

[0107] 6, when the value of "amplifier gain" corresponding to all positions of the pressure application unit 40 is a constant value, the amplification factor of the amplifier circuit does not have to be set to the value of "amplifier gain". Since the determination unit 170 calculates the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal, it is sufficient that the amplification factors of the first detection signal and the second detection signal are the same. Alternatively, the amplification factors of the first detection signal and the second detection signal may be converted to be the same.

[0108] For example, the first amplifier circuit 311, the second amplifier circuit 312, the fourth amplifier circuit 314, and the fifth amplifier circuit 315 may be designed so that the multiplication result of the first amplification factor and the second amplification factor coincides with the multiplication result of the fourth amplification factor and the fifth amplification factor. Also, it is preferable that the first amplifier circuit 311, the third amplifier circuit 313, the fourth amplifier circuit 314, and the sixth amplifier circuit 316 are designed so that the multiplication result of the first amplification factor and the third amplification factor coincides with the multiplication result of the fourth amplification factor and the sixth amplification factor.

[0109] In this case, when the identifying unit 170 employs the amplified signal of the first path, it employs the amplified signal of the third path to calculate the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal. When the identifying unit 170 employs the amplified signal of the second path, it employs the amplified signal of the fourth path to calculate the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal. This allows the identifying unit 170 to calculate the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal by simple control using the amplified signal of an amplifier circuit with an appropriate dynamic range.

[0110] In this case, the determination unit 170 may compare the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal using the amplified signals of the first and third paths with the ratio of the maximum amplitude values ​​of the first detection signal and the second detection signal using the amplified signals of the second and fourth paths to determine which calculation result to adopt. For example, when the calculation result using the amplified signals of the first and third paths is substantially equal to the calculation result using the amplified signals of the second and fourth paths, the determination unit 170 can determine that almost no distortion occurs in the amplified signals of all the amplifier circuits, and therefore adopts the calculation result using the amplified signals of the first and third paths.

[0111] Furthermore, when the calculation result using the amplified signals of the first and third paths differs from the calculation result using the amplified signals of the second and fourth paths, the determination unit 170 can determine that distortion has occurred in the amplified signal of the large signal amplifier circuit, and therefore adopts the calculation result using the amplified signals of the second and fourth paths. As described above, the piezoelectric sensor 300 according to this embodiment has a plurality of amplifier circuits with different amplification factors, thereby making it possible to easily amplify the output voltage based on the piezoelectric effect output from the pressure sensor 110.

[0112] As described above, even when an excessively large external force is applied to the pressure application unit 40, or when a relatively weak external force is applied, the identification unit 170 can accurately identify the pressure application unit 40 to which the external force is applied by selecting a path that appropriately amplifies the detection signal from among the multiple paths of the signal amplification unit 310. Note that the method by which the identification unit 170 selects an appropriate path is not limited to the above example. For example, the signal receiving unit 160 may have a detection circuit that detects the maximum amplitude value of the input signal or output signal of the first amplification circuit 311 and the fourth amplification circuit 314, and the identification unit 170 may select an appropriate path depending on the detection result of the detection circuit.

[0113] In the above description of the piezoelectric sensor 300 according to the present embodiment, an example has been described in which the pressure sensor 110 of the third configuration example is provided, but the present invention is not limited to this. The piezoelectric sensor 300 has a signal receiving unit 160 capable of processing detection signals with a wide voltage range of amplitude values, and therefore various pressure sensors can be used. For example, the piezoelectric sensor 300 may include the pressure sensor 110 of the first configuration example, the pressure sensor 110 of the second configuration example, etc.

[0114] 4 and 5, the piezoelectric sensor 300 may detect the magnitude of the external force applied to the pressure application unit 40. For example, the identification unit 170 can identify the magnitude of the external force applied to the pressure application unit 40 by comparing the first detection signal and / or the second detection signal with a reference value or the like corresponding to a certain external force. It is desirable that a plurality of reference values ​​are set in advance corresponding to different magnitudes of the external force.

[0115] In this case, it is desirable that the thickness of the first piezoelectric layer 210 is different from the thickness of the second piezoelectric layer 230. For example, when an external force is applied to the pressure application unit 40, the voltage generated in the thin piezoelectric layer is smaller than the voltage generated in the thick piezoelectric layer. Here, the voltage generated in the thin piezoelectric layer is less likely to be distorted even when a large external force is applied, and the thick piezoelectric layer has high detection sensitivity for small external forces.

[0116] Therefore, by using a thin piezoelectric layer as a sensor for detecting a strong external force and a thick piezoelectric layer as a sensor for detecting a weak external force, the pressure sensor 110 can also function as an external force sensor that can detect a wide range of forces. In this case, when the first piezoelectric layer 210 is formed to be thicker than the second piezoelectric layer 230, it is desirable to design the first amplification factor of the first amplifier circuit 311 to be smaller than the fourth amplification factor of the fourth amplifier circuit 314. In addition, when the first piezoelectric layer 210 is formed to be thinner than the second piezoelectric layer 230, it is desirable to design the first amplification factor of the first amplifier circuit 311 to be larger than the fourth amplification factor of the fourth amplifier circuit 314.

[0117] This allows the piezoelectric sensor 300 to amplify a signal output from an external force sensor that can detect a wide range of force magnitudes using the signal amplifier 310 with a wide dynamic range. Therefore, the identifying unit 170 can identify the position of the pressure application unit 40 to which the external force is applied, while also identifying the magnitude of the applied external force. Note that the piezoelectric sensor 300 may identify only the magnitude of the external force, in which case the thicknesses of the first piezoelectric layer 210 and the second piezoelectric layer 230 may be constant, and the number of pressure application units 40 may be only one.

[0118] In the above embodiment of the piezoelectric sensor 300, an example has been described in which the pressure sensor 110 is provided to identify the position where an external force is applied and / or the magnitude of the external force, but the present invention is not limited to this. The pressure sensor 110 may also function as a vibration sensor that further detects vibrations such as sound waves. In this case, the identifying unit 170 identifies, for example, a signal component in the voice band included in the detection signal as a voice signal. This allows the position detection device 100 to have, for example, a function of a touch panel and a function of a microphone for voice.

[0119] When the piezoelectric sensor 300 functions as a vibration sensor, the multiple amplifier circuits provided in the signal amplifier 310 may be divided into an amplifier circuit that amplifies a detection signal for identifying the magnitude of an external force and an amplifier circuit that amplifies a detection signal for detecting vibration. An example of such a piezoelectric sensor 300 will be described below.

[0120] <Modifications of the Piezoelectric Sensor 300> Fig. 11 shows a modified example of the piezoelectric sensor 300 according to this embodiment. In the piezoelectric sensor 300 of this modification, parts that operate substantially the same as those in the piezoelectric sensor 300 according to this embodiment shown in Fig. 10 are given the same reference numerals, and the description thereof will be omitted. The signal amplifying section 310 of the piezoelectric sensor 300 further includes a first high frequency filter 331, a first low frequency filter 332, a second high frequency filter 333, and a second low frequency filter 334.

[0121] In this modification, the first amplification factor of the first amplifier circuit 311 is different from the fourth amplification factor of the fourth amplifier circuit 314. As an example, the first amplification factor is larger than the fourth amplification factor, and the first amplifier circuit 311 functions as an amplifier circuit for small signals, and the fourth amplifier circuit 314 functions as an amplifier circuit for large signals.

[0122] The second amplifier circuit 312 amplifies frequency components exceeding a predetermined frequency among the signals amplified by the first amplifier circuit 311. The predetermined frequency is, for example, a frequency of about 10 Hz. In other words, the second amplifier circuit 312 amplifies frequency components in the audible band and functions as an amplifier circuit for a small signal for a microphone. The second amplifier circuit 312 is, for example, an amplifier circuit having an amplification characteristic in the audible band. Alternatively, the second amplifier circuit 312 may function as an amplifier circuit that amplifies frequency components in the audible band by being combined with the first high frequency filter 331.

[0123] The first high frequency filter 331 is provided between the first amplifier circuit 311 and the second amplifier circuit 312, and passes frequency components exceeding a predetermined frequency among the signals amplified by the first amplifier circuit 311. The first high frequency filter 331 passes frequency components in the audible band. The first high frequency filter 331 is, for example, a high pass filter, a band pass filter, or the like.

[0124] The third amplifier circuit 313 amplifies frequency components below a predetermined frequency among the signals amplified by the first amplifier circuit 311. A signal with a frequency lower than the audible band is sufficient as a signal for detecting the magnitude of the external force applied to the pressure application unit 40. Therefore, the third amplifier circuit 313 amplifies frequency components below the audible band and functions as an amplifier circuit for small signals for identifying the magnitude of the external force. The third amplifier circuit 313 is, for example, an amplifier circuit having an amplification characteristic in a frequency range below the audible band. Alternatively, the third amplifier circuit 313 may function as an amplifier circuit that amplifies frequency components below the audible band by being combined with the first low-frequency filter 332.

[0125] The first low-frequency filter 332 is provided between the first amplifier circuit 311 and the third amplifier circuit 313, and passes frequency components below a predetermined frequency in the signal amplified by the first amplifier circuit 311. The first low-frequency filter 332 passes frequency components below the audible range. The first low-frequency filter 332 is, for example, a low-pass filter.

[0126] The fifth amplifier circuit 315 amplifies frequency components exceeding a predetermined frequency among the signals amplified by the fourth amplifier circuit 314. The fifth amplifier circuit 315 amplifies frequency components in the audible band and functions as an amplifier circuit for large signals for a microphone. In other words, the fifth amplifier circuit 315 is an amplifier circuit that uses the second amplifier circuit 312 for large signals.

[0127] The second high frequency filter 333 is provided between the fourth amplifier circuit 314 and the fifth amplifier circuit 315, and passes frequency components exceeding a predetermined frequency among the signals amplified by the fourth amplifier circuit 314. The second high frequency filter 333 may be a filter similar to the first high frequency filter 331.

[0128] The sixth amplifier circuit 316 amplifies frequency components below a predetermined frequency of the signal amplified by the fourth amplifier circuit 314. The sixth amplifier circuit 316 amplifies frequency components below the audible range and functions as a small signal amplifier circuit for identifying the magnitude of an external force. In other words, the sixth amplifier circuit 316 is an amplifier circuit that uses the third amplifier circuit 313 for large signals.

[0129] The second low frequency filter 334 is provided between the fourth amplifier circuit 314 and the sixth amplifier circuit 316, and passes frequency components below a predetermined frequency of the signal amplified by the fourth amplifier circuit 314. The second low frequency filter 334 may be a filter similar to the first low frequency filter 332.

[0130] In the piezoelectric sensor 300 of the above modified example, the first piezoelectric layer 210 of the pressure sensor 110 functions as a small signal sensor for detecting the magnitude of an external force and sound. The second piezoelectric layer 230 of the pressure sensor 110 functions as a large signal sensor for detecting the magnitude of an external force and sound. Therefore, it is desirable that the thickness of the first piezoelectric layer 210 of this example is formed to be thicker than the thickness of the second piezoelectric layer 230. This allows the piezoelectric sensor 300 to detect a wider range of force magnitudes and sound volumes.

[0131] Here, either the first piezoelectric layer 210 or the second piezoelectric layer 230 of the pressure sensor 110 may be formed similarly to the piezoelectric layer 140 of the pressure sensor 110 of the first configuration example or the pressure sensor 110 of the second configuration example described above. This allows the piezoelectric sensor 300 to detect the position where an external force is applied, the magnitude of the external force, and sound.

[0132] In addition, both the first piezoelectric layer 210 and the second piezoelectric layer 230 of the pressure sensor 110 may be formed in the same manner as the piezoelectric layer 140 of the pressure sensor 110 of the first configuration example or the pressure sensor 110 of the second configuration example. In this case, it is desirable that the thickness of each piezoelectric region of the first piezoelectric layer 210 is formed to be thinner than the thickness of each piezoelectric region of the second piezoelectric layer 230. This allows the first piezoelectric layer 210 to function as a large signal sensor for detecting the position where an external force is applied, the magnitude of the external force, and sound, and the second piezoelectric layer 230 to function as a small signal sensor for detecting the position where an external force is applied, the magnitude of the external force, and sound.

[0133] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0134] 10 Position detection device 20 Pressure Sensor 30 Signal Processing Section 40 Pressure application section 50 Substrates 60 Sensor element 62 Lower electrode 64 Upper electrode 66 Piezoelectric layer 70 Base layer 80 Protective film 90 Wiring 100 Position detection device 110 Pressure Sensor 120 Lower electrode 130 Upper electrode 140 Piezoelectric layer 141 First Piezoelectric Region 142 Second Piezoelectric Region 143 Third Piezoelectric Region 144 Gap Area 146 Cavity 150 Signal Processing Section 160 Signal receiving unit 170 Specific section 180 Storage section 210 First piezoelectric layer 220 Common electrode 230 Second piezoelectric layer 300 Piezoelectric Sensor 310 Signal Amplification Unit 311 First Amplifier Circuit 312 Second Amplifier Circuit 313 Third Amplifier Circuit 314 4th Amplifier Circuit 315 5th Amplifier Circuit 316 6th Amplifier Circuit 320 AD conversion section 331 1st High Frequency Filter 332 First low frequency filter 333 Second High Frequency Filter 334 Second Low Frequency Filter

Claims

1. A substrate; a lower electrode formed on a substrate; a first piezoelectric layer having a piezoelectric body formed on the lower electrode; a common electrode formed on the first piezoelectric layer; a second piezoelectric layer having a piezoelectric body formed on the common electrode; an upper electrode formed on the second piezoelectric layer; a plurality of pressure application units formed on the upper electrode and arranged in a first direction parallel to the substrate, the pressure application units being externally applied to the pressure application units; a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal by amplifying the first detection signal and the second detection signal; Equipped with The signal amplifier unit includes: a first amplifier circuit that amplifies the first detection signal by a first amplification factor; a second amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a second amplification factor; a third amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a third amplification factor that is smaller than the second amplification factor; a fourth amplifier circuit amplifying the second detection signal by a fourth amplification factor; a fifth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a fifth amplification factor; a sixth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a sixth amplification factor that is smaller than the fifth amplification factor; having At least one of the first piezoelectric layer and the second piezoelectric layer is formed such that the volume of the piezoelectric material per unit area varies depending on the position of the pressure application portion arranged in the first direction in a plane parallel to the substrate. Piezoelectric sensor.

2. A substrate; a lower electrode formed on a substrate; a first piezoelectric layer having a piezoelectric body formed on the lower electrode; a common electrode formed on the first piezoelectric layer; a second piezoelectric layer having a piezoelectric body formed on the common electrode; an upper electrode formed on the second piezoelectric layer; a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal by amplifying the first detection signal and the second detection signal; Equipped with The signal amplifier unit includes: a first amplifier circuit that amplifies the first detection signal by a first amplification factor; a second amplifier circuit that amplifies a frequency component exceeding a predetermined frequency of the signal amplified by the first amplifier circuit; a third amplifier circuit that amplifies a frequency component of the signal amplified by the first amplifier circuit that is equal to or lower than a predetermined frequency; a fourth amplifier circuit that amplifies the second detection signal by a fourth amplification factor that is different from the first amplification factor of the first amplifier circuit; a fifth amplifier circuit that amplifies a frequency component exceeding a predetermined frequency of the signal amplified by the fourth amplifier circuit; a sixth amplifier circuit that amplifies a frequency component of the signal amplified by the fourth amplifier circuit that is equal to or lower than a predetermined frequency; A piezoelectric sensor having a

3. A substrate, a lower electrode formed on a substrate; a first piezoelectric layer having a piezoelectric body formed on the lower electrode; a common electrode formed on the first piezoelectric layer; a second piezoelectric layer having a piezoelectric body formed on the common electrode; an upper electrode formed on the second piezoelectric layer; a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal by amplifying the first detection signal and the second detection signal; Equipped with The signal amplifier unit includes: a first amplifier circuit that amplifies the first detection signal by a first amplification factor; a second amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a second amplification factor; a third amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a third amplification factor that is smaller than the second amplification factor; a fourth amplifier circuit amplifying the second detection signal by a fourth amplification factor; a fifth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a fifth amplification factor; a sixth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a sixth amplification factor that is smaller than the fifth amplification factor; having a first high frequency filter provided between the first amplifier circuit and the second amplifier circuit, the first high frequency filter passing a frequency component exceeding a predetermined frequency of the signal amplified by the first amplifier circuit; a first low-frequency filter provided between the first amplifier circuit and the third amplifier circuit, the first low-frequency filter passing a frequency component of the signal amplified by the first amplifier circuit that is equal to or lower than a predetermined frequency; a second high frequency filter provided between the fourth amplifier circuit and the fifth amplifier circuit, the second high frequency filter passing a frequency component exceeding a predetermined frequency of the signal amplified by the fourth amplifier circuit; a second low-frequency filter provided between the fourth amplifier circuit and the sixth amplifier circuit, for passing frequency components of the signal amplified by the fourth amplifier circuit that are equal to or lower than a predetermined frequency; The piezoelectric sensor further comprises:

4. A substrate, a lower electrode formed on a substrate; a first piezoelectric layer having a piezoelectric body formed on the lower electrode; a common electrode formed on the first piezoelectric layer; a second piezoelectric layer having a piezoelectric body formed on the common electrode; an upper electrode formed on the second piezoelectric layer; a signal amplifier that receives a first detection signal output from the lower electrode and the common electrode and a second detection signal output from the common electrode and the upper electrode, and outputs an amplified signal by amplifying the first detection signal and the second detection signal; Equipped with The signal amplifier unit includes: a first amplifier circuit that amplifies the first detection signal by a first amplification factor; a second amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a second amplification factor; a third amplifier circuit that amplifies the signal amplified by the first amplifier circuit by a third amplification factor that is smaller than the second amplification factor; a fourth amplifier circuit amplifying the second detection signal by a fourth amplification factor; a fifth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a fifth amplification factor; a sixth amplifier circuit that amplifies the signal amplified by the fourth amplifier circuit by a sixth amplification factor that is smaller than the fifth amplification factor; having When the thickness of the first piezoelectric layer is greater than the thickness of the second piezoelectric layer, the first amplification factor of the first amplifier circuit is smaller than the fourth amplification factor of the fourth amplifier circuit, When the thickness of the first piezoelectric layer is smaller than the thickness of the second piezoelectric layer, the first amplification factor of the first amplifier circuit is larger than the fourth amplification factor of the fourth amplifier circuit. Piezoelectric sensor.

5. a plurality of pressure application units formed on the upper electrode, arranged in a first direction parallel to the substrate and a second direction different from the first direction, and to which a pressure is applied from an outside; the first piezoelectric layer is formed such that a volume of the piezoelectric body per unit area varies depending on a position of the pressure application portion arranged in the first direction in a plane parallel to the substrate, the second piezoelectric layer is formed such that the volume of the piezoelectric material per unit area varies depending on the position of the pressure application portion arranged in the second direction in a plane parallel to the substrate; The piezoelectric sensor according to claim 2 .

6. The piezoelectric sensor according to claim 5 , wherein thicknesses of the first piezoelectric layer and the second piezoelectric layer vary depending on a position of the pressure application portion.

7. The piezoelectric sensor according to claim 1 , a plurality of pressure application units formed on the upper electrode and to which pressure is applied from an outside; a signal receiving unit that receives the amplified signal output from the signal amplifying unit; a storage unit configured to store pressure application unit data in which the positions of the pressure application units in a plane parallel to the substrate are associated with reference values ​​of the amplified signals when pressure is applied to each of the pressure application units; an identifying unit that identifies a position of the pressure application unit to which an external force is applied based on the amplified signal received by the signal receiving unit and the pressure application unit data; Equipped with Position detection device.

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