Measurement device

Abstract

To provide a measurement device capable of detecting an expansion / contraction in an in-plane direction and an expansion / contraction in a film thickness direction.SOLUTION: A measurement device includes a piezoelectric element array, a control section, a storage section, and a power source. The piezoelectric element array comprises: a first piezoelectric element 20 and second piezoelectric element 21 constituting a unit piezoelectric element; and a piezoelectric layer 40 commonly provided in the first piezoelectric element 20 and the second piezoelectric element 21 and including a first partial piezoelectric layer 40A and a second partial piezoelectric layer 40B. The first piezoelectric element 20 includes: a first lower electrode 31; the first partial piezoelectric layer 40A provided on the first lower electrode 31; a first upper electrode 33 provided on the first partial piezoelectric layer 40A; and an expansion / contraction suppression layer 34 provided on the first partial piezoelectric layer 40A so as to cover the first upper electrode 33. The second piezoelectric element 21 includes: a second lower electrode 35; the second partial piezoelectric layer 40B provided on the second lower electrode 35; and a second upper electrode 37 provided on the second partial piezoelectric layer 40B. The expansion / contraction suppression layer 34 has an elastic modulus higher than that of the piezoelectric layer 40.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a measuring device equipped with a piezoelectric element. [Background technology]

[0002] Piezoelectric sensors use organic piezoelectric materials such as P(VDF / TrFE). Organic piezoelectric materials can be applied by coating, can be produced in low-temperature processes, and can be easily made into films, so attempts are being made to apply them to flexible sensors for wearable devices and large-area sensors. They are also attracting attention for a variety of possible applications, including biosensors for measuring pulse waves and myoelectric signals, tactile sensors, and pyroelectric sensors.

[0003] In addition, piezoelectric sensors are attached to the body to measure the displacement of the body surface at various parts such as the wrist and foot. Patent Document 1 proposes a technology in which a band equipped with multiple piezoelectric sensors is attached to the wrist to measure the protuberance of the wrist tendons and use the measured data to estimate finger movements. Patent Document 2 proposes a technology in which a flexible organic piezoelectric sensor is used to measure the displacement of the body surface at the wrist, and the finger movements are similarly estimated by learning the information. Furthermore, Patent Document 3 proposes precise measurement of muscle activity by attaching flexible organic piezoelectric sensors to various parts such as the ankles and arms.

[0004] However, when measuring displacement of the body surface using a flexible organic piezoelectric sensor, it is difficult to distinguish between signals resulting from changes in the pressure (contact pressure) on the sensor due to muscle expansion and contraction and tendon bulging, and signals resulting from the bending and expansion of the sensor due to joint bending and the accompanying expansion and contraction of the skin, which leads to increased signal noise and reduced reproducibility.

[0005] Of these, Patent Document 4 proposes a technology in which two types of piezoelectric elements are formed on a flexible substrate, one piezoelectric element is configured so that the center line in the thickness direction coincides with the neutral axis of the sensor, and the other piezoelectric element is configured so that the center line in the thickness direction is offset from the neutral axis of the sensor, thereby using one piezoelectric element as a pressure sensor that does not react to bending and the other as a sensor that detects bending.

[0006] However, in order to configure one sensor to coincide with the neutral axis as in Patent Document 4, the thicknesses of the electrodes, the substrate, and the protective film must be consistent above and below the film thickness direction of the piezoelectric layer, which places great constraints on the design, and the thinner the sensor itself is, the more difficult it is to control it. Also, when a stretchable substrate is used, even if one sensor is configured to coincide with the neutral axis, the output signal when it expands and contracts in the in-plane direction cannot be suppressed, making it difficult to separate pressure from expansion and contraction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-352739 A [Patent Document 2] International Publication No. 2022 / 130684 [Patent Document 3] JP 2020-175280 A [Patent Document 4] JP 2012-7911 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a measurement device capable of detecting expansion and contraction in the in-plane direction and in the film thickness direction. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a measuring device comprising a first piezoelectric element, a second piezoelectric element, and a piezoelectric layer provided in common to the first piezoelectric element and the second piezoelectric element, the piezoelectric layer including a first partial piezoelectric layer and a second partial piezoelectric layer, the first piezoelectric element including a first lower electrode, the first partial piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first partial piezoelectric layer, and an expansion suppression layer provided on the first partial piezoelectric layer so as to cover the first upper electrode, the second piezoelectric element including a second lower electrode, the second partial piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second partial piezoelectric layer, the expansion suppression layer having a higher elastic modulus than the piezoelectric layer.

[0010] According to a second aspect of the present invention, there is provided a measuring device according to the second aspect, further comprising a first protective layer provided on the piezoelectric layer so as to cover the expansion / contraction layer and the second upper electrode.

[0011] According to a third aspect of the present invention, there is provided a measuring device comprising a first piezoelectric element, a second piezoelectric element, and a piezoelectric layer provided in common to the first piezoelectric element and the second piezoelectric element, the piezoelectric layer including a first partial piezoelectric layer and a second partial piezoelectric layer, the first piezoelectric element including a first lower electrode, the first partial piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first partial piezoelectric layer, a first protective layer provided on the first partial piezoelectric layer so as to cover the first upper electrode, and an expansion suppression layer provided on the first protective layer, the second piezoelectric element including a second lower electrode, the second partial piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second partial piezoelectric layer, the first protective layer is configured to further cover the second upper electrode, and the expansion suppression layer has a higher elastic modulus than the piezoelectric layer.

[0012] According to a fourth aspect of the present invention, there is provided the measuring device according to the first or third aspect, wherein the piezoelectric layer is flexible or stretchable.

[0013] According to a fifth aspect of the present invention, there is provided the measuring device according to the first or third aspect, wherein the piezoelectric layer is made of an organic piezoelectric material having elasticity.

[0014] According to a sixth aspect of the present invention, there is provided a measuring device according to the first or third aspect, further comprising a second protective layer provided on a bottom surface of the piezoelectric layer so as to cover the first lower electrode and the second lower electrode.

[0015] According to a seventh aspect of the present invention, there is provided a measuring device comprising a substrate, a first piezoelectric element and a second piezoelectric element provided on the substrate, and a protective layer covering the first piezoelectric element and the second piezoelectric element, wherein the first piezoelectric element includes a first lower electrode provided on the substrate, a first piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first piezoelectric layer, and an expansion suppression layer provided on the substrate so as to cover the first upper electrode, the first piezoelectric layer, and the first upper electrode, and the second piezoelectric element includes a second lower electrode provided on the substrate, a second piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second piezoelectric layer, and the expansion suppression layer has a higher elastic modulus than the first piezoelectric layer and the protective layer.

[0016] According to an eighth aspect of the present invention, there is provided the measuring device according to the seventh aspect, wherein the substrate is flexible or stretchable.

[0017] According to a ninth aspect of the present invention, there is provided the measuring device according to the seventh aspect, wherein the first piezoelectric layer and the second piezoelectric layer are made of an organic piezoelectric material having elasticity.

[0018] According to a tenth aspect of the present invention, there is provided the measuring device according to the first, third or seventh aspect, wherein a plurality of the first piezoelectric elements and a plurality of the second piezoelectric elements are arranged in an array.

[0019] According to an eleventh aspect of the present invention, there is provided a measuring device according to the first, third or seventh aspect, further comprising a control unit that calculates an output voltage ratio between the first piezoelectric element and the second piezoelectric element, and determines a degree of influence indicating whether the expansion and contraction is in an in-plane direction or in a film thickness direction based on the output voltage ratio.

[0020] According to a twelfth aspect of the present invention, there is provided a measuring device according to the first, third or seventh aspect, further comprising a control unit that calculates an output voltage ratio between the first piezoelectric element and the second piezoelectric element, and determines whether the expansion and contraction is in an in-plane direction or in a film thickness direction based on a comparison result between the output voltage ratio and a threshold value. Effect of the Invention

[0021] According to the present invention, it is possible to provide a measuring device capable of detecting expansion and contraction in the in-plane direction and in the film thickness direction. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a block diagram of a measurement device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the piezoelectric element array. [Diagram 3] FIG. 3 is a cross-sectional view of a first piezoelectric element and a second piezoelectric element which constitute one unit piezoelectric element. [Figure 4] FIG. 4 is a diagram for explaining the definition of the polarization direction of the piezoelectric layer. [Diagram 5] FIG. 5 is a diagram illustrating the compression operation in the film thickness direction of the piezoelectric layer. [Figure 6] FIG. 6 is a diagram illustrating the in-plane expansion operation of the piezoelectric layer. [Figure 7] FIG. 7 is a diagram illustrating a state in which the piezoelectric element array is stretched in the in-plane direction. [Figure 8] FIG. 8 is a diagram illustrating the output voltages of the first and second piezoelectric elements when they expand and contract in the in-plane direction. [Figure 9]FIG. 9 is a diagram illustrating the output voltages of the first and second piezoelectric elements when the piezoelectric element expands and contracts in the film thickness direction. [Figure 10] FIG. 10 is a diagram illustrating the output voltage ratio between the first piezoelectric element and the second piezoelectric element. [Figure 11] FIG. 11 is a flowchart illustrating the measurement operation of the measurement device. [Figure 12] FIG. 12 is a diagram for explaining the operation of determining the degree of influence of expansion / contraction. [Figure 13] FIG. 13 is a flowchart illustrating the measurement operation of the measurement apparatus according to the second embodiment of the present invention. [Figure 14] FIG. 14 is a cross-sectional view of a first piezoelectric element and a second piezoelectric element which constitute one unit piezoelectric element according to a third embodiment of the present invention. [Figure 15] FIG. 15 is a cross-sectional view of a first piezoelectric element and a second piezoelectric element according to a modified example. [Figure 16] FIG. 16 is a plan view of a piezoelectric element array according to a fourth embodiment of the present invention. [Figure 17] FIG. 17 is a cross-sectional view of a first piezoelectric element and a second piezoelectric element which constitute one unit piezoelectric element. [Figure 18] FIG. 18 is a diagram for explaining a state in which the piezoelectric element array is stretched in the in-plane direction. [Figure 19] FIG. 19 is a plan view of a piezoelectric element array according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not necessarily the same as those in reality. In addition, even when the same parts are shown between the drawings, the dimensional relationships and ratios of each may be different. In particular, the following embodiments are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not specified by the shape, structure, arrangement, etc. of the components. In the following description, elements having the same function and configuration are given the same reference numerals, and duplicated descriptions are omitted.

[0024] [1] First embodiment [1-1] Configuration of measurement device 1 1 is a block diagram of a measurement device 1 according to a first embodiment of the present invention. The measurement device 1 is a sensor device that utilizes the piezoelectric effect and is capable of outputting an electrical signal in response to pressure applied to a piezoelectric body. The measurement device 1 includes a piezoelectric element array 10, a control unit 11, a storage unit 12, and a power source 13.

[0025] The piezoelectric element array 10 includes a plurality of piezoelectric elements. The piezoelectric element array 10 is a measurement unit that detects and measures pressure applied to a piezoelectric body. The piezoelectric element array 10 is also a measurement unit that can detect and measure expansion and contraction in the in-plane direction and in the film thickness direction.

[0026] The control unit 11 is composed of one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 11 realizes various functions by executing programs stored in the storage unit 12. The control unit 11 receives an output voltage from the piezoelectric element, and executes arithmetic processing based on this output voltage. Furthermore, the control unit 11 executes processing to determine the degree of influence of the expansion and contraction of the piezoelectric element array 10.

[0027] The storage unit 12 includes a non-volatile storage device such as a Read Only Memory (ROM) and a volatile storage device such as a Random Access Memory (RAM) and a register. The storage unit 12 stores a program executed by the control unit 11. The storage unit 12 stores various data necessary for the control of the control unit 11.

[0028] The power supply 13 generates various voltages necessary for the operation of each circuit in the measurement device 1 based on the control of the control unit 11, and supplies these voltages to the corresponding circuits. The power supply 13 also supplies various voltages to the piezoelectric element array 10.

[0029] Fig. 2 is a plan view of the piezoelectric element array 10. In Fig. 2, the X direction is a direction along one side of the piezoelectric element array 10, and the Y direction is a direction perpendicular to the X direction.

[0030] The piezoelectric element array 10 includes a plurality of first piezoelectric elements 20 and a plurality of second piezoelectric elements 21. The plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21 are arranged in a matrix as a whole. Adjacent first piezoelectric elements 20 and second piezoelectric elements 21 constitute a unit piezoelectric element 22.

[0031] The multiple first piezoelectric elements 20 and the multiple second piezoelectric elements 21 aligned in the X direction are arranged alternately. The multiple first piezoelectric elements 20 and the multiple second piezoelectric elements 21 aligned in the Y direction are arranged alternately. In other words, the multiple first piezoelectric elements 20 are arranged every other one in the X direction and the Y direction. The multiple second piezoelectric elements 21 are arranged every other one in the X direction and the Y direction. The multiple first piezoelectric elements 20 are arranged adjacent to each other in the diagonal direction. The multiple second piezoelectric elements 21 are arranged adjacent to each other in the diagonal direction.

[0032] Fig. 3 is a cross-sectional view of a first piezoelectric element 20 and a second piezoelectric element 21 which constitute one unit piezoelectric element 22. Fig. 3 is a cross-sectional view of the unit piezoelectric element 22 of Fig. 2 cut in the X direction.

[0033] The piezoelectric element array 10 includes a piezoelectric layer 40. The piezoelectric layer 40 is provided in common to the plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21. The piezoelectric layer 40 is provided over the entire piezoelectric element array 10. The piezoelectric layer 40 also functions as a substrate for the piezoelectric element array 10. The piezoelectric layer 40 has flexibility and / or stretchability.

[0034] The piezoelectric layer 40 is made of, for example, an organic piezoelectric material. The piezoelectric layer 40 is made of, for example, a polymer piezoelectric material such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene copolymer (P(VDF / TrFE)), or vinylidene cyanide / vinyl acetate copolymer (P(VDCN / VAc)). In order to give elasticity to P(VDF / TrFE), acrylic resin (PMMA: polymethyl methacrylate) may be added to P(VDF / TrFE). The thickness of the piezoelectric layer 40 is, for example, about 40 μm.

[0035] The first piezoelectric element 20 includes a first lower electrode 31, a partial piezoelectric layer 40A, a first upper electrode 33, and an expansion suppression layer 34. The partial piezoelectric layer 40A is included in the piezoelectric layer 40, and corresponds to a region of the piezoelectric layer 40 that functions as one first piezoelectric element 20.

[0036] A first lower electrode 31 is provided on the bottom surface of the partial piezoelectric layer 40A. The first lower electrode 31 has, for example, a rectangular shape. The first lower electrode 31 is made of a metal material or an organic conductive material. Examples of the metal material include silver (Ag), silver paste, molybdenum (Mo), aluminum (Al), and chromium (Cr). Examples of the organic conductive material include PEDOT / PSS and carbon paste. PEDOT / PSS is a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate (PSS). The thickness of the first lower electrode 31 is, for example, about 10 μm.

[0037] A first upper electrode 33 is provided on the upper surface of the partial piezoelectric layer 40A. The first upper electrode 33 has, for example, a rectangular shape. Like the first lower electrode 31, the first upper electrode 33 is made of a metal material or an organic conductive material. For example, the area of ​​the first upper electrode 33 is smaller than the area of ​​the first lower electrode 31. The area of ​​the first upper electrode 33 may be approximately the same as or larger than the area of ​​the first lower electrode 31. The thickness of the first upper electrode 33 is, for example, about 10 μm.

[0038] An expansion suppressing layer 34 is provided on the upper surface of the partial piezoelectric layer 40A so as to cover the first upper electrode 33. The expansion suppressing layer 34 is made of a material having a higher elastic modulus than the piezoelectric layer 40. The expansion suppressing layer 34 is also made of a material having a higher elastic modulus than a protective layer 38, which will be described later. The elastic modulus is the ratio of stress to strain (stress / strain) in elastic deformation when force is applied to an elastic body.

[0039] The expansion suppressing layer 34 has a function of suppressing the expansion and contraction of the piezoelectric layer 40 due to stress, and in particular has a function of suppressing the expansion and contraction of the piezoelectric layer 40 in the in-plane direction. The expansion suppressing layer 34 is preferably made of an insulating material, but a conductive material may also be used. For example, a cyanoacrylate resin is used as the expansion suppressing layer 34. The thickness of the expansion suppressing layer 34 is, for example, about 600 μm. The expansion suppressing layer 34 is formed by coating on the piezoelectric layer 40 and the first upper electrode 33. The expansion suppressing layer 34 may be formed by bonding to the piezoelectric layer 40 and the first upper electrode 33 using an adhesive.

[0040] The second piezoelectric element 21 includes a second lower electrode 35, a partial piezoelectric layer 40B, and a second upper electrode 37. The partial piezoelectric layer 40B is included in the piezoelectric layer 40, and corresponds to a region of the piezoelectric layer 40 that functions as one second piezoelectric element 21.

[0041] A second lower electrode 35 is provided on the bottom surface of the partial piezoelectric layer 40B. A second upper electrode 37 is provided on the top surface of the partial piezoelectric layer 40B. The second lower electrode 35 and the second upper electrode 37 have the same configurations as the first lower electrode 31 and the first upper electrode 33. The area and thickness of the second lower electrode 35 and the second upper electrode 37 are also the same as the first lower electrode 31 and the first upper electrode 33. The material, area and thickness of the second lower electrode 35 and the second upper electrode 37 may be different from those of the first lower electrode 31 and the first upper electrode 33.

[0042] A protective layer 38 is provided on the piezoelectric layer 40 so as to cover the expansion suppression layer 34 and the second upper electrode 37. The protective layer 38 is provided over the entire piezoelectric element array 10. The protective layer 38 is made of an insulating material and is made of a resin having flexibility and / or expansion properties. The protective layer 38 is preferably made of a resin having high moisture permeability. The protective layer 38 is made of, for example, a polyurethane resin, a polyolefin resin, a polystyrene resin, or a polyester resin. The thickness of the protective layer 38 is, for example, about 50 μm. The protective layer 38 is formed by coating or is attached using an adhesive.

[0043] A protective layer 39 is provided on the bottom surface of the piezoelectric layer 40 so as to cover the first lower electrode 31 and the second lower electrode 35. The protective layer 39 is provided over the entire piezoelectric element array 10. The material of the protective layer 39 is the same as that of the protective layer 38. The thickness of the protective layer 39 is, for example, about 50 μm. The protective layer 39 is formed by coating or attached using an adhesive.

[0044] The lower electrodes and upper electrodes of the first piezoelectric element 20 and the second piezoelectric element 21 are respectively led out to the outside of the piezoelectric element array 10 using lead wires (not shown) and wired to the control unit 11 and the power source 13.

[0045] [1-2] Operation Next, the operation of the measuring device 1 configured as above will be described.

[0046] First, the characteristics of the piezoelectric layer will be described. The piezoelectric layer is composed of P(VDF / TrFE). Figure 4 is a diagram for explaining the definition of the polarization direction of the piezoelectric layer. Any direction in the plane of the piezoelectric layer is defined as direction "1". A direction perpendicular to direction "1" in the plane of the piezoelectric layer is defined as direction "2". Both directions "1" and "2" are in-plane directions. A direction perpendicular to the plane of the piezoelectric layer is defined as direction "3". Direction "3" is the film thickness direction.

[0047] Fig. 5 is a diagram for explaining the compression operation in the thickness direction of the piezoelectric layer. Fig. 5 shows how a force is applied to the piezoelectric layer in the thickness direction, causing the piezoelectric layer to be compressed in the thickness direction. The dashed square in Fig. 5 shows the piezoelectric layer before deformation, and the solid square shows the piezoelectric layer after deformation.

[0048] When the piezoelectric layer is compressed in the thickness direction, the polarization direction of the piezoelectric layer becomes the upward direction (direction "3") in the drawing. A positive charge is generated on the upper side of the piezoelectric layer. When the piezoelectric layer is compressed in the thickness direction, the piezoelectric strain constant is d 33 The number on the left of the piezoelectric strain constant indicates the polarization direction, and the number on the right indicates the deformation direction. The compression in the film thickness direction is called d 33 Also called mode.

[0049] Fig. 6 is a diagram explaining the in-plane expansion of the piezoelectric layer. Fig. 6 shows the state in which the piezoelectric layer is pulled in the in-plane direction and the piezoelectric layer expands in the in-plane direction. The dashed square in Fig. 6 shows the piezoelectric layer before deformation, and the solid square shows the piezoelectric layer after deformation.

[0050] When the piezoelectric layer is stretched in the in-plane direction, the polarization direction of the piezoelectric layer becomes the upward direction (direction "3") in the drawing. A positive charge is generated on the upper side of the piezoelectric layer. When the piezoelectric layer is stretched in the in-plane direction, the piezoelectric strain constant is d 31 Or d 32 The in-plane stretching motion is d 31 Mode or d 32 Also called mode.

[0051] 5 and 6, the piezoelectric layer generates charges of the same polarity when it compresses in the film thickness direction and expands in the in-plane direction. That is, the first piezoelectric element 20 and the second piezoelectric element 21 generate output voltages of the same polarity when it compresses in the film thickness direction and expands in the in-plane direction, respectively.

[0052] Fig. 7 is a diagram illustrating the state in which the piezoelectric element array 10 is stretched in an in-plane direction. Fig. 7 shows one unit piezoelectric element 22 (the first piezoelectric element 20 and the second piezoelectric element 21) extracted. For example, when bending occurs in the piezoelectric element array 10, the piezoelectric element array 10 is stretched in the in-plane direction.

[0053] The piezoelectric layer 40, the protective layer 38, and the protective layer 39 are flexible and / or stretchable. When bending occurs in the piezoelectric element array 10, the partial piezoelectric layer 40B of the second piezoelectric element 21 expands in the in-plane direction, and stress is applied in the expanding direction.

[0054] On the other hand, the first piezoelectric element 20 is provided with an expansion / contraction suppressing layer 34 having a high elastic modulus. Therefore, since the partial piezoelectric layer 40A of the first piezoelectric element 20 has a higher elastic modulus of the expansion / contraction suppressing layer 34 than the partial piezoelectric layer 40B of the second piezoelectric element 21, a large stress is applied to the partial piezoelectric layer 40A from the expansion / contraction suppressing layer 34 during expansion / contraction in the in-plane direction. As a result, the first piezoelectric element 20 has a larger output voltage than the second piezoelectric element 21.

[0055] The method of detecting the output voltage of the first piezoelectric element 20 and the second piezoelectric element 21 is to detect the difference between the potential of one of the lower and upper electrodes of the piezoelectric element as a reference (e.g., ground voltage (0V)) and the potential of the other electrode.

[0056] FIG. 8 is a diagram for explaining the output voltage of the first piezoelectric element 20 and the second piezoelectric element 21 when they are stretched in the in-plane direction. The vertical axis of FIG. 8 represents the output voltage (V), and the horizontal axis represents time (sec). The solid line in FIG. 8 represents the first piezoelectric element 20 (with suppression layer), and the dashed line represents the second piezoelectric element 21 (without suppression layer). The suppression layer means a stretch suppression layer. In the experiment of FIG. 8, wiring is connected to the piezoelectric element so that the output voltage becomes negative voltage when stretched (pulled). In the experiment of FIG. 8, the thickness of the stretch suppression layer 34 is about 670 μm. The stretch in FIG. 8 is a case where the piezoelectric element is stretched in the in-plane direction, and the compression in FIG. 8 is a case where the piezoelectric element is compressed in the in-plane direction.

[0057] As can be seen from Fig. 8, when the piezoelectric element is stretched in the in-plane direction, the first piezoelectric element 20 (with suppression layer) has a higher output voltage than the second piezoelectric element 21 (without suppression layer). Here, "higher output voltage" means that the absolute value of the voltage is higher. Also, when the piezoelectric element is compressed in the in-plane direction, the first piezoelectric element 20 has a higher output voltage than the second piezoelectric element 21.

[0058] FIG. 9 is a diagram illustrating the output voltage of the first piezoelectric element 20 and the second piezoelectric element 21 during expansion and contraction in the film thickness direction. The vertical axis of FIG. 9 represents the output voltage (arbitrary unit), and the horizontal axis represents the time change in force ΔF (N / s). In the experiment of FIG. 9, wiring is connected to the piezoelectric elements so that the output voltage becomes negative during compression. In the experiment of FIG. 9, the thickness of the expansion suppression layer 34 is about 670 μm. In FIG. 9, the region where the output voltage is negative corresponds to the case where the piezoelectric element is compressed in the film thickness direction, and the region where the output voltage is positive corresponds to the case where the piezoelectric element is expanded in the film thickness direction.

[0059] In the graph of the first piezoelectric element 20 (with the suppression layer), the regression line is expressed as "y = -0.7253x" and the coefficient of determination is "R 2 In the graph of the second piezoelectric element 21 (without the suppression layer), the regression line is represented by "y=-0.7829x" and the coefficient of determination is "R 29, when the piezoelectric element is compressed and expanded in the film thickness direction, there is almost no difference in output voltage between the first piezoelectric element 20 and the second piezoelectric element 21.

[0060] Fig. 10 is a diagram illustrating the output voltage ratio between the first piezoelectric element 20 and the second piezoelectric element 21. Fig. 10 shows a graph of the expansion and contraction in the in-plane direction of the piezoelectric element and a graph of the expansion and contraction in the film thickness direction of the piezoelectric element. The vertical axis of Fig. 10 is the output voltage ratio (with suppression layer / without suppression layer), that is, the ratio of the output voltage of the first piezoelectric element 20 (with suppression layer) to the output voltage of the second piezoelectric element 21 (without suppression layer).

[0061] The output voltage ratio is obtained by detecting the first output voltage of the first piezoelectric element 20 and the second output voltage of the second piezoelectric element 21 and calculating "first output voltage / second output voltage".

[0062] As can be seen from FIG. 10, the output voltage ratio in the in-plane direction is relatively large, and the output voltage ratio in the film thickness direction is relatively small. Specifically, the output voltage ratio in the in-plane direction is about 1.4, and the output voltage ratio in the film thickness direction is about 1.0. Therefore, the closer the output voltage ratio is to 1.4, the stronger the influence of the in-plane direction is, and it can be determined that bending or tension has occurred in the piezoelectric element array 10. The closer the output voltage ratio is to 1.0, the stronger the influence of the film thickness direction is, and it can be determined that the piezoelectric element array 10 is being pressed. In this specification, pressing means that the piezoelectric element is compressed in the film thickness direction. The minimum unit of resolution for pressing is determined by the size of a pair of the first piezoelectric element 20 and the second piezoelectric element 21.

[0063] Next, an operation for determining expansion / contraction in the in-plane direction and the film thickness direction will be described with reference to FIG.

[0064] The control unit 11 receives an output voltage from the piezoelectric element array 10 (step S100). That is, the control unit 11 receives an output voltage from the plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21.

[0065] Next, the control unit 11 calculates the output voltage ratio for each unit piezoelectric element 22 (the first piezoelectric element 20 and the second piezoelectric element 21) (step S101). That is, the control unit 11 calculates "(the first output voltage of the first piezoelectric element 20) / (the second output voltage of the second piezoelectric element 21)" for each unit piezoelectric element 22.

[0066] Next, the control unit 11 calculates the average value of the output voltage ratios of the plurality of unit piezoelectric elements 22 (step S102).

[0067] Next, the control unit 11 determines the degree of influence of expansion / contraction based on the average value of the output voltage ratio calculated in step S102 (step S103).

[0068] Fig. 12 is a diagram for explaining the operation of determining the degree of influence of expansion / contraction. The horizontal axis of Fig. 12 represents the average value of the output voltage ratio, and the vertical axis represents the degree of influence of expansion / contraction (%). The degree of influence of expansion / contraction is expressed as the degree of influence of expansion / contraction in the in-plane direction and the degree of influence of expansion / contraction in the film thickness direction. Specifically, the degree of influence of expansion / contraction in the in-plane direction is the degree of influence of bending or pulling, and the degree of influence of expansion / contraction in the film thickness direction is the degree of influence of pressing.

[0069] In this embodiment, as an example, the average value of the output voltage ratio is set in the range of 1.0 to 1.4 based on the experimental results of Fig. 10. The degree of influence of expansion and contraction in the in-plane direction varies from 0% to 100%. The degree of influence of expansion and contraction in the in-plane direction and the average value of the output voltage ratio are in a proportional relationship. The degree of influence of expansion and contraction in the film thickness direction varies from 100% to 0%. The degree of influence of expansion and contraction in the film thickness direction and the average value of the output voltage ratio are inversely proportional to each other.

[0070] Specifically, when the average value of the output voltage ratio is 1.0, the control unit 11 determines that the influence of expansion / contraction in the in-plane direction is 0% and that of expansion / contraction in the film thickness direction is 100%. When the average value of the output voltage ratio is 1.1, the control unit 11 determines that the influence of expansion / contraction in the in-plane direction is 25% and that of expansion / contraction in the film thickness direction is 75%. When the average value of the output voltage ratio is 1.2, the control unit 11 determines that the influence of expansion / contraction in the in-plane direction is 50% and that of expansion / contraction in the film thickness direction is 50%. When the average value of the output voltage ratio is 1.3, the control unit 11 determines that the influence of expansion / contraction in the in-plane direction is 75% and that of expansion / contraction in the film thickness direction is 25%. When the average value of the output voltage ratio is 1.4, the control unit 11 determines that the influence of expansion / contraction in the in-plane direction is 100% and that of expansion / contraction in the film thickness direction is 0%.

[0071] The piezoelectric element array 10 may be divided into a plurality of regions, and the degree of influence may be determined for each divided region. Also, the degree of influence may be determined for each unit piezoelectric element 22. The determination process may be performed by the control unit 11 disposed inside the measurement device 1, or may be performed by the control unit 11 disposed outside the measurement device 1 and connected by wire or wirelessly.

[0072] Next, the control unit 11 outputs information relating to the degree of influence determined in step S103 to the outside (step S104).

[0073] The measuring device 1 can be applied to a wearable device that is attached to the wrist, arm, etc. By wearing the measuring device 1 on the body, it is possible to measure the displacement of the body surface.

[0074] [1-3] Effects of the first embodiment According to the first embodiment, when a force is applied to the piezoelectric element array 10 in response to a displacement of the body surface on which the measuring device 1 is attached, for example, it is possible to distinguish and determine expansion and contraction in the in-plane direction (including expansion and contraction due to bending or pulling) and expansion and contraction in the film thickness direction (including expansion and contraction due to pressure). This makes it possible to realize the measuring device 1 that can detect expansion and contraction in the in-plane direction and expansion and contraction in the film thickness direction.

[0075] Specifically, it is possible to distinguish and detect the pressure (contact pressure) of the piezoelectric element array 10 caused by muscle expansion and contraction and tendon bulging, and the bending and pulling of the piezoelectric element array 10 caused by joint bending and the accompanying expansion and contraction of the skin, etc. This enables highly accurate measurement of body surface displacement.

[0076] Furthermore, since the piezoelectric element array 10 is made of a flexible and / or stretchable material, it is easy to deform the piezoelectric element array 10. This allows highly accurate measurement of the displacement of the body surface.

[0077] [2] Second embodiment The second embodiment is another example of the determination operation regarding expansion and contraction. In the second embodiment, it is determined whether the force applied to the piezoelectric element array 10 is expansion or contraction due to bending or pulling, or expansion or contraction due to pressing.

[0078] 13 is a flowchart illustrating the measurement operation of the measurement device 1 according to the second embodiment of the present invention. The operations in steps S200 to S202 in FIG.

[0079] Next, the control unit 11 determines whether the average value of the output voltage ratio is equal to or greater than a threshold value (step S203). The threshold value is set to, for example, 1.2.

[0080] If the average value of the output voltage ratio is equal to or greater than the threshold value (S203=Yes), the control unit 11 determines that the expansion / contraction is in the in-plane direction (step S204). Specifically, the control unit 11 determines that bending or tension has occurred.

[0081] If the average value of the output voltage ratio is less than the threshold value (S203=No), the control unit 11 determines that the expansion / contraction is in the film thickness direction (step S205). Specifically, the control unit 11 determines that a pressure has been applied.

[0082] Next, the control unit 11 outputs the results of the determinations made in steps S204 and S205 to the outside (step S206).

[0083] According to the second embodiment, it is possible to obtain a determination result indicating whether bending, pulling, or pressing has occurred according to the displacement of the body surface to which the measuring device 1 is attached. Other effects are the same as those of the first embodiment.

[0084] [3] Third embodiment The third embodiment is another example of the configuration of the piezoelectric element. In the third embodiment, in the first piezoelectric element 20, the expansion / contraction suppressing layer is disposed on the protective layer .

[0085] The plan view of the piezoelectric element array 10 according to the third embodiment of the present invention is the same as Fig. 2. Fig. 14 is a cross-sectional view of a first piezoelectric element 20 and a second piezoelectric element 21 constituting one unit piezoelectric element 22. Fig. 14 is a cross-sectional view of the unit piezoelectric element 22 of Fig. 2 cut in the X direction.

[0086] The piezoelectric element array 10 includes a plurality of first piezoelectric elements 20 and a plurality of second piezoelectric elements 21. Adjacent first piezoelectric elements 20 and second piezoelectric elements 21 constitute a unit piezoelectric element 22.

[0087] The piezoelectric layer 40 is provided in common to the plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21. The piezoelectric layer 40 is provided over the entire piezoelectric element array 10. The configuration of the piezoelectric layer 40 is the same as in the first embodiment.

[0088] The first piezoelectric element 20 includes a first lower electrode 31, a partial piezoelectric layer 40A, a first upper electrode 33, and an expansion suppression layer 34. The first lower electrode 31 is provided on a bottom surface of the partial piezoelectric layer 40A. The first upper electrode 33 is provided on an upper surface of the partial piezoelectric layer 40A.

[0089] A protective layer 38 is provided on the upper surface of the partial piezoelectric layer 40A so as to cover the first upper electrode 33. The protective layer 38 is attached using an adhesive.

[0090] The expansion suppressing layer 34 is provided on the protective layer 38. The expansion suppressing layer 34 is provided so as to cover the first upper electrode 33 in a plan view. The area of ​​the expansion suppressing layer 34 is larger than that of the first upper electrode 33. The expansion suppressing layer 34 is made of a material having a higher elastic modulus than the piezoelectric layer 40 and the protective layer 38. The expansion suppressing layer 34 is formed by coating on the protective layer 38. The expansion suppressing layer 34 may be attached to the protective layer 38 using an adhesive.

[0091] The configuration of the second piezoelectric element 21 is the same as that of the first embodiment.

[0092] 15 is a cross-sectional view of a modified first piezoelectric element 20 and a second piezoelectric element 21. The upper surface of the piezoelectric element array 10 may be further covered with a protective layer.

[0093] A protective layer 41 is provided on the protective layer 38 so as to cover the expansion suppression layer 34. The protective layer 41 is provided over the entire piezoelectric element array 10. The thickness of the protective layer 41 is, for example, about 50 μm. The protective layer 41 is attached using an adhesive. The material of the protective layer 41 is the same as the material of the protective layer 38.

[0094] The other configurations are the same as those in the first embodiment. The measurement device 1 according to the third embodiment can also perform the same operations as those in the first embodiment.

[0095] [4] Fourth embodiment The fourth embodiment is another example of the configuration of the piezoelectric element. The fourth embodiment includes a substrate that supports the entire piezoelectric element array 10, and further includes a piezoelectric layer provided for each piezoelectric element.

[0096] [4-1] Configuration of piezoelectric element array 10 16 is a plan view of a piezoelectric element array 10 according to a fourth embodiment of the present invention. The piezoelectric element array 10 includes a plurality of first piezoelectric elements 20 and a plurality of second piezoelectric elements 21. Adjacent first piezoelectric elements 20 and second piezoelectric elements 21 constitute a unit piezoelectric element 22. An example of the arrangement of the plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21 is the same as in the first embodiment.

[0097] Fig. 17 is a cross-sectional view of a first piezoelectric element 20 and a second piezoelectric element 21 which constitute one unit piezoelectric element 22. Fig. 17 is a cross-sectional view of the unit piezoelectric element 22 of Fig. 16 taken in the X direction.

[0098] The piezoelectric element array 10 includes a substrate 30. The substrate 30 is provided in common to the plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21. The substrate 30 is provided over the entire piezoelectric element array 10. The substrate 30 is made of an insulating material and is made of a resin having flexibility and / or stretchability. The substrate 30 is preferably made of a resin having high moisture permeability. The substrate 30 is made of, for example, polyurethane resin, polyolefin resin, polystyrene resin, or polyester resin. The thickness of the substrate 30 is, for example, about 100 μm.

[0099] The first piezoelectric element 20 includes a first lower electrode 31, a first piezoelectric layer 32, a first upper electrode 33, and an expansion / contraction suppressing layer .

[0100] A first lower electrode 31 is provided on a substrate 30. The material and shape of the first lower electrode 31 are the same as those in the first embodiment. The thickness of the first lower electrode 31 is, for example, about 200 nm.

[0101] The first piezoelectric layer 32 is provided on the first lower electrode 31. The first piezoelectric layer 32 has, for example, a rectangular shape. The first piezoelectric layer 32 has an area larger than the area of ​​the first lower electrode 31 and covers the entire first lower electrode 31. The material of the first piezoelectric layer 32 is the same as that of the piezoelectric layer 40 described in the first embodiment. More preferably, the first piezoelectric layer 32 is made of P(VDF / TrFE) that can be formed by a printing method, or a material containing P(VDF / TrFE). It is desirable that the first piezoelectric layer 32 has elasticity. The thickness of the first piezoelectric layer 32 is, for example, about 2 μm.

[0102] A first upper electrode 33 is provided on the first piezoelectric layer 32. The material and shape of the first upper electrode 33 are the same as those in the first embodiment. The thickness of the first upper electrode 33 is, for example, about 10 μm.

[0103] An expansion suppressing layer 34 is provided on the first upper electrode 33, the first piezoelectric layer 32, and the substrate 30. The expansion suppressing layer 34 has, for example, a rectangular shape. The expansion suppressing layer 34 has an area larger than that of the first piezoelectric layer 32. The expansion suppressing layer 34 is configured to cover the first lower electrode 31, the first piezoelectric layer 32, and the first upper electrode 33, and is in contact with the substrate 30 at its peripheral portion.

[0104] The expansion suppressing layer 34 is made of a material having a higher elastic modulus than the first piezoelectric layer 32. The expansion suppressing layer 34 is also made of a material having a higher elastic modulus than the protective layer 38 described below. The expansion suppressing layer 34 is formed by coating on the substrate 30, the first piezoelectric layer 32, and the first upper electrode 33. The expansion suppressing layer 34 may be attached to the substrate 30, the first piezoelectric layer 32, and the first upper electrode 33 using an adhesive.

[0105] The second piezoelectric element 21 comprises a second bottom electrode 35 , a second piezoelectric layer 36 , and a second top electrode 37 .

[0106] A second lower electrode 35 is provided on the substrate 30. A second piezoelectric layer 36 is provided on the second lower electrode 35. A second upper electrode 37 is provided on the second piezoelectric layer 36. The configurations of the second lower electrode 35, the second piezoelectric layer 36, and the second upper electrode 37 are the same as those of the first lower electrode 31, the first piezoelectric layer 32, and the first upper electrode 33. The areas and thicknesses of the second lower electrode 35, the second piezoelectric layer 36, and the second upper electrode 37 are also the same as those of the first lower electrode 31, the first piezoelectric layer 32, and the first upper electrode 33. The materials, areas, and thicknesses of the second lower electrode 35, the second piezoelectric layer 36, and the second upper electrode 37 may be different from those of the first lower electrode 31, the first piezoelectric layer 32, and the first upper electrode 33.

[0107] A protective layer 38 is provided on the first piezoelectric element 20 and the second piezoelectric element 21. The protective layer 38 is configured to cover the first piezoelectric element 20 and the second piezoelectric element 21. The protective layer 38 is provided on the entire piezoelectric element array 10. The material of the protective layer 38 is the same as that in the first embodiment. The protective layer 38 is attached using an adhesive.

[0108] A protective layer 39 is provided on the bottom surface of the substrate 30. The protective layer 39 is provided on the entire surface of the substrate 30. The material of the protective layer 39 is the same as that of the protective layer 38. The thickness of the protective layer 39 is, for example, about 50 μm. The protective layer 39 is attached using an adhesive.

[0109] [4-2] Operation Fig. 18 is a diagram illustrating a state in which the piezoelectric element array 10 is stretched in an in-plane direction. Fig. 18 shows one unit piezoelectric element 22 (the first piezoelectric element 20 and the second piezoelectric element 21) extracted from the piezoelectric element array 10. For example, when bending occurs in the piezoelectric element array 10, the piezoelectric element array 10 is stretched in the in-plane direction.

[0110] The substrate 30, the protective layer 38, and the protective layer 39 are flexible and / or stretchable. When bending occurs in the piezoelectric element array 10, the substrate 30 is stretched in an in-plane direction. As the substrate 30 stretches, the second piezoelectric element 21 (specifically, the second piezoelectric layer 36) is stretched in the in-plane direction. As a result, the second piezoelectric layer 36 stretches in the in-plane direction, and the output voltage of the second piezoelectric element 21 increases.

[0111] On the other hand, the first piezoelectric element 20 is provided with an expansion / contraction suppressing layer 34 having a high elastic modulus. Therefore, the expansion of the first piezoelectric element 20 (specifically, the first piezoelectric layer 32) is suppressed compared to the second piezoelectric element 21. When the expansion / contraction suppressing layer 34 is provided, since the elastic modulus of the expansion / contraction suppressing layer 34 is high, most of the stress due to the expansion in the in-plane direction is applied to an area other than the area where the expansion / contraction suppressing layer 34 is formed. As a result, the output voltage of the first piezoelectric element 20 is smaller than that of the second piezoelectric element 21. That is, in this embodiment, the output voltage ratio during expansion / contraction is less than 1.

[0112] Even when the output voltage ratio during expansion / contraction is less than 1, the determination method based on the output voltage ratio is the same as when the output voltage ratio during expansion / contraction is greater than 1. When determining based on the degree of influence, the smaller the output voltage ratio, the greater the influence of expansion / contraction. Also, when a reference value (threshold value) is set, it is determined that anything above the reference value is due to pressure, and anything below the reference value is due to expansion / contraction.

[0113] In the fourth embodiment, the same effects as in the first embodiment can be obtained.

[0114] [5] Fifth embodiment The fifth embodiment is an example relating to the arrangement of a plurality of first piezoelectric elements 20 and a plurality of second piezoelectric elements 21.

[0115] 19 is a plan view of a piezoelectric element array 10 according to a fifth embodiment of the present invention. The piezoelectric element array 10 includes a plurality of first piezoelectric elements 20 and a plurality of second piezoelectric elements 21. The plurality of first piezoelectric elements 20 and the plurality of second piezoelectric elements 21 are arranged in a matrix as a whole. The configurations of the first piezoelectric elements 20 and the second piezoelectric elements 21 are the same as those of the fourth embodiment.

[0116] The number of second piezoelectric elements 21 is set to be greater than the number of first piezoelectric elements 20. Specifically, eight second piezoelectric elements 21 are arranged around (up, down, left, right and diagonally) one first piezoelectric element 20. The multiple first piezoelectric elements 20 are arranged every other one in the X direction and Y direction.

[0117] One first piezoelectric element 20 and the eight surrounding second piezoelectric elements 21 constitute a unit piezoelectric element 22. Unit piezoelectric elements 22 adjacent to each other in the X direction share three second piezoelectric elements 21 in their overlapping portions. Similarly, unit piezoelectric elements 22 adjacent to each other in the Y direction share three second piezoelectric elements 21 in their overlapping portions.

[0118] The output voltage ratio of the unit piezoelectric element 22 is calculated using the first output voltage of one first piezoelectric element 20 and the average value of the second output voltages of the eight surrounding second piezoelectric elements 21 as "(first output voltage of first piezoelectric element 20) / (average value of the second output voltages of eight second piezoelectric elements 21)".

[0119] Note that the multiple first piezoelectric elements 20 and the multiple second piezoelectric elements 21 may be arranged so that adjacent unit piezoelectric elements 22 do not share a second piezoelectric element 21 in the X and Y directions. In this modification, the multiple first piezoelectric elements 20 are arranged every two in the X and Y directions.

[0120] According to the fifth embodiment, the area occupied by the stretch suppressing layer 34 having a high elastic modulus is reduced, so that the substrate 30 can easily stretch. Therefore, it is possible to configure a piezoelectric element array 10 having greater flexibility and stretchability. The other effects are the same as those of the first embodiment. The first to third embodiments can also be applied to the fifth embodiment.

[0121] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made in the implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combination, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0122] 1...measuring device, 10...piezoelectric element array, 11...control unit, 12...memory unit, 13...power supply, 20...first piezoelectric element, 21...second piezoelectric element, 22...unit piezoelectric element, 30...substrate, 31...first lower electrode, 32...first piezoelectric layer, 33...first upper electrode, 34...expansion suppression layer, 35...second lower electrode, 36...second piezoelectric layer, 37...second upper electrode, 38...protective layer, 39...protective layer, 40...piezoelectric layer, 40A, 40B...partial piezoelectric layer, 41...protective layer.

Claims

1. A first piezoelectric element and a second piezoelectric element; a piezoelectric layer provided in common to the first piezoelectric element and the second piezoelectric element, the piezoelectric layer including a first partial piezoelectric layer and a second partial piezoelectric layer; Equipped with the first piezoelectric element includes a first lower electrode, the first partial piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first partial piezoelectric layer, and an expansion / contraction suppression layer provided on the first partial piezoelectric layer so as to cover the first upper electrode; the second piezoelectric element includes a second lower electrode, the second partial piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second partial piezoelectric layer; The elastic modulus of the expansion / contraction suppression layer is higher than that of the piezoelectric layer. Measuring equipment.

2. The piezoelectric device further includes a first protective layer provided on the piezoelectric layer so as to cover the expansion / contraction restricting layer and the second upper electrode. The measurement device according to claim 1 .

3. A first piezoelectric element and a second piezoelectric element; a piezoelectric layer provided in common to the first piezoelectric element and the second piezoelectric element, the piezoelectric layer including a first partial piezoelectric layer and a second partial piezoelectric layer; Equipped with the first piezoelectric element includes a first lower electrode, the first partial piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first partial piezoelectric layer, a first protective layer provided on the first partial piezoelectric layer so as to cover the first upper electrode, and an expansion / contraction suppression layer provided on the first protective layer; the second piezoelectric element includes a second lower electrode, the second partial piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second partial piezoelectric layer; the first protective layer is configured to further cover the second upper electrode; The elastic modulus of the expansion / contraction suppression layer is higher than that of the piezoelectric layer. Measuring equipment.

4. The piezoelectric layer is flexible or stretchable. The measuring device according to claim 1 or 3.

5. The piezoelectric layer is made of an organic piezoelectric material having elasticity. The measuring device according to claim 1 or 3.

6. The piezoelectric device further includes a second protective layer provided on a bottom surface of the piezoelectric layer so as to cover the first lower electrode and the second lower electrode. The measuring device according to claim 1 or 3.

7. A substrate; a first piezoelectric element and a second piezoelectric element provided on the substrate; a protective layer covering the first piezoelectric element and the second piezoelectric element; Equipped with the first piezoelectric element includes a first lower electrode provided on the substrate, a first piezoelectric layer provided on the first lower electrode, a first upper electrode provided on the first piezoelectric layer, and an expansion / contraction suppression layer provided on the substrate so as to cover the first upper electrode, the first piezoelectric layer, and the first upper electrode; the second piezoelectric element includes a second lower electrode provided on the substrate, a second piezoelectric layer provided on the second lower electrode, and a second upper electrode provided on the second piezoelectric layer; The elastic modulus of the expansion suppression layer is higher than that of the first piezoelectric layer and the protective layer. Measuring equipment.

8. The substrate is flexible or stretchable. The measurement device according to claim 7.

9. The first piezoelectric layer and the second piezoelectric layer are made of an organic piezoelectric material having elasticity. The measurement device according to claim 7.

10. The first piezoelectric element and the second piezoelectric element are arranged in a plurality of arrays.

8. The measuring device according to claim 1, 3 or 7.

11. The control unit further includes a controller that calculates an output voltage ratio between the first piezoelectric element and the second piezoelectric element, and determines an influence level indicating whether the expansion and contraction is in an in-plane direction or in a film thickness direction based on the output voltage ratio.

8. The measuring device according to claim 1, 3 or 7.

12. and a control unit that calculates an output voltage ratio between the first piezoelectric element and the second piezoelectric element, and determines whether the expansion and contraction is in an in-plane direction or in a film thickness direction based on a result of comparing the output voltage ratio with a threshold value.

8. The measuring device according to claim 1, 3 or 7.

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