Bending sensor, bending detection device, and bending detection method

Abstract

To provide a flexure sensor, a flexure detection device and a flexure detection method, allowing a user to grasp a flexure state in detail.SOLUTION: A flexure sensor for detecting flexure, includes a substrate having flexibility, a thin film transistor array including a plurality of thin film transistors placed on the substrate, a plurality of pixel electrodes placed on the thin film transistor array, a piezoelectric layer placed on the plurality of pixel electrodes, and a common electrode placed on the piezoelectric layer. The piezoelectric layer has a surface electrically connected to the common electrode and a rear face electrically connected to the pixel electrodes. The pixel electrodes are arranged spaced from each other in a plane view of the substrate, and includes a first pixel electrode and a second pixel electrode electrically isolated from each other. The thin film transistor array includes a first thin film transistor electrically connected with the first pixel electrode, and a second thin film transistor electrically connected with the second pixel electrode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bending sensor, a bending detection device, and a bending detection method. [Background technology]

[0002] Known technologies relating to bending sensors include those described in Patent Documents 1 and 2, for example. Patent Document 1 discloses a bending sensor worn on each finger of a glove-type wearing device. The bending sensor disclosed in Patent Document 1 has a configuration in which a metal resistor (strain sensor) is provided inside an elastic body. This bending sensor detects the bending state based on changes in the electrical resistance value of the metal resistor that occur in response to bending movements of the fingers wearing the wearing device. Patent Document 2 discloses a bending sensor provided in an organic electroluminescence (EL) display device. The bending sensor disclosed in Patent Document 2 has a configuration in which a first electrode layer, a piezoelectric layer, and a second electrode layer are stacked in this order on a substrate. This bending sensor detects the bending state based on changes in voltage between the first electrode layer and the second electrode layer in response to bending deformation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-233442 [Patent Document 2] Japanese Patent Application Publication No. 2017-207886 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the bending sensor disclosed in Patent Document 1 is attached to each finger of a wearing device, and therefore can detect bending for each finger, but cannot detect which part of the finger (for example, the fingertip or the base of the finger) the bending has occurred in. Furthermore, the bending sensor disclosed in Patent Document 2 can only detect the bending state of the entire board. Thus, with the bending sensors described above, the information obtained on the bending state is insufficient, making it difficult to grasp the bending state in detail. This limits the scope of application of such bending sensors.

[0005] The present invention provides a bending sensor, a bending detection device, and a bending detection method that are capable of grasping the bending state in detail. [Means for solving the problem]

[0006] A bending sensor according to one aspect of the present invention is a bending sensor for detecting bending, and comprises: a flexible substrate; a thin-film transistor array consisting of a plurality of thin-film transistors arranged on the substrate; a plurality of pixel electrodes arranged on the thin-film transistor array; a piezoelectric layer arranged on the plurality of pixel electrodes; and a common electrode arranged on the piezoelectric layer, wherein the piezoelectric layer has a front surface electrically connected to the common electrode and a back surface electrically connected to the plurality of pixel electrodes, the plurality of pixel electrodes being arranged spaced apart from each other in a planar view of the substrate and having first and second pixel electrodes that are electrically insulated from each other, and the thin-film transistor array has a first thin-film transistor electrically connected to the first pixel electrode and a second thin-film transistor electrically connected to the second pixel electrode.

[0007] When bending is applied to this bending sensor, tensile or compressive stress is applied to the piezoelectric layer, causing changes in the electrical characteristics between the multiple pixel electrodes and the common electrode. The multiple pixel electrodes include first and second pixel electrodes that are spaced apart from each other in a planar view and electrically insulated from each other. Therefore, changes in the electrical characteristics between the first pixel electrode and the common electrode and changes in the electrical characteristics between the second pixel electrode and the common electrode occur independently of each other. Therefore, by separately detecting signals indicating changes in the electrical characteristics between the first pixel electrode and the common electrode and signals indicating changes in the electrical characteristics between the second pixel electrode and the common electrode using first and second thin film transistors, information indicating the bending state at the position of the first pixel electrode and information indicating the bending state at the position of the second pixel electrode can be separately obtained. This allows the local bending state at each of the first and second pixel electrodes to be grasped. Therefore, the bending sensor described above enables detailed grasping of the bending state.

[0008] The plurality of pixel electrodes may be arranged in a matrix. In this case, information indicating the bending state can be obtained for each pixel electrode, thereby enabling a more localized bending state to be grasped. This makes it possible to grasp the bending state of the bending sensor in more detail.

[0009] The first pixel electrode may have a shape extending in a first direction along the substrate, and the second pixel electrode may have a shape extending in a second direction along the substrate and intersecting the first direction. In this case, the first pixel electrode is strongly affected by bending in the first direction, and the second pixel electrode is strongly affected by bending in the second direction. Therefore, by detecting a signal indicating a change in the electrical characteristics between the first pixel electrode and the common electrode as information indicating the bending state in the first direction, and detecting a signal indicating a change in the electrical characteristics between the second pixel electrode and the common electrode as information indicating the bending state in the second direction, the bending state in the first direction and the bending state in the second direction can be distinguished and grasped. This makes it possible to grasp the bending state of the bending sensor in more detail.

[0010] Each of the first pixel electrode and the second pixel electrode may have a Young's modulus higher than that of the inter-electrode region between the first pixel electrode and the second pixel electrode. In this case, it is possible to more reliably realize a state in which the first pixel electrode is strongly affected by bending in the first direction and the second pixel electrode is strongly affected by bending in the second direction. This makes it possible to more reliably distinguish and grasp the state of bending in the first direction and the state of bending in the second direction.

[0011] The inter-electrode region may be formed of an electrically insulating adhesive. In this case, a configuration in which the Young's modulus of each of the first pixel electrode and the second pixel electrode is higher than that of the inter-electrode region can be easily realized. Furthermore, by providing an electrically insulating adhesive between the first pixel electrode and the second pixel electrode, the positional relationship between the first pixel electrode and the second pixel electrode can be fixed while ensuring electrical insulation between the first pixel electrode and the second pixel electrode.

[0012] The neutral plane, where no tensile or compressive stress acts when the bending sensor is bent, may be located at a different height from the piezoelectric layer, and at least a portion of each of the first pixel electrode and the second pixel electrode may be disposed on the same side of the neutral plane as the piezoelectric layer. In this case, by utilizing the magnitude relationship between the Young's modulus of each of the first pixel electrode and the second pixel electrode and the Young's modulus of the inter-electrode region between the first pixel electrode and the second pixel electrode, it is possible to more reliably realize a state in which the first pixel electrode is strongly affected by bending in the first direction and the second pixel electrode is strongly affected by bending in the second direction. This makes it possible to more reliably distinguish and grasp the state of bending in the first direction and the state of bending in the second direction.

[0013] The plurality of pixel electrodes may include a plurality of first pixel electrodes and a plurality of second pixel electrodes, and the first pixel electrodes and the second pixel electrodes may be arranged in a matrix such that they alternate with each other. In this case, by acquiring information indicating the bending state for each pixel electrode, it is possible to grasp the bending state more locally. Furthermore, by arranging the first pixel electrodes and the second pixel electrodes alternately, the first pixel electrodes and the second electrodes can be distributed, which prevents bias in the obtained bending state information.

[0014] The common electrode may have a first extension portion extending in a first direction to encompass the first pixel electrode in a plan view, and a second extension portion extending in a second direction to encompass the second pixel electrode in a plan view and connected to the first extension portion. In this case, by arranging the common electrode to encompass both the first pixel electrode and the second pixel electrode, the first pixel electrode is more strongly affected by bending in the first direction, and the second pixel electrode is more strongly affected by bending in the second direction. This makes it possible to more reliably distinguish and acquire information indicating the state of bending in the first direction from information indicating the state of bending in the second direction.

[0015] The plurality of pixel electrodes may include a plurality of first pixel electrodes and a plurality of second pixel electrodes, each of which is arranged in a matrix, and the common electrode may include a plurality of first extension portions arranged to encompass each of the plurality of first pixel electrodes in a planar view and a plurality of second extension portions arranged to encompass each of the plurality of second pixel electrodes in a planar view, the plurality of first extension portions and the plurality of second extension portions being arranged in a grid pattern in a planar view. In this case, by acquiring information indicating the bending state for each pixel electrode, it is possible to grasp the bending state of a more localized portion. This makes it possible to grasp the bending state of the bending sensor in more detail.

[0016] The plurality of pixel electrodes may further include a third pixel electrode, which is spaced apart from the first pixel electrode and the second pixel electrode in a planar view and electrically insulated from the first pixel electrode and the second pixel electrode. The third pixel electrode may have a shape extending along the substrate in a third direction intersecting the first and second directions. In this case, the third pixel electrode is strongly affected by bending in the third direction. Therefore, by detecting a signal indicating a change in the electrical characteristics between the third pixel electrode and the common electrode as information indicating the bending state in the third direction, the information indicating the bending state in the third direction can be obtained separately from information indicating the bending state in the first direction and information indicating the bending state in the second direction. In other words, the above-described configuration allows the bending state in the third direction to be determined in addition to the bending state in the first direction and the bending state in the second direction. Therefore, the above-described configuration allows the bending state of the bending sensor to be determined in more detail.

[0017] The common electrode may have a first extension portion extending in a first direction to encompass the first pixel electrode in a planar view, a second extension portion extending in a second direction to encompass the second pixel electrode in a planar view and connected to the first extension portion, and a third extension portion extending in a third direction to encompass the third pixel electrode in a planar view and connected to the first and second extension portions. In this case, by arranging the common electrode to encompass the third pixel electrode, the third pixel electrode is more strongly affected by bending in the third direction. This makes it possible to more reliably distinguish and acquire information indicating the state of bending in the third direction.

[0018] A bending detection device according to another aspect of the present invention includes any one of the bending sensors described above and a detection unit that detects bending of the bending sensor, wherein when a bend is applied to the bending sensor, the first thin film transistor outputs to the detection unit a first signal that indicates a change in electrical characteristics between the first pixel electrode and the common electrode in response to the bending, and the second thin film transistor outputs to the detection unit a second signal that indicates a change in electrical characteristics between the second pixel electrode and the common electrode in response to the bending, and the detection unit detects the first signal as information that indicates the state of bending at the position of the first pixel electrode and detects the second signal as information that indicates the state of bending at the position of the second pixel electrode.

[0019] The above-described bending detection device includes any one of the bending sensors described above. As described above, the change in the electrical characteristics between the first pixel electrode and the common electrode and the change in the electrical characteristics between the second pixel electrode and the common electrode occur independently of each other. Therefore, by separately detecting a first signal indicating the change in the electrical characteristics between the first pixel electrode and the common electrode and a second signal indicating the change in the electrical characteristics between the second pixel electrode and the common electrode using the first thin film transistor and the second thin film transistor, it is possible to separately obtain information indicating the bending state at the position of the first pixel electrode and information indicating the bending state at the position of the second pixel electrode. This allows the local bending state at each of the positions of the first pixel electrode and the second pixel electrode to be grasped. Therefore, the above-described bending detection device makes it possible to grasp the bending state in detail.

[0020] The first pixel electrode may extend in a first direction along the substrate, and the second pixel electrode may extend in a second direction along the substrate and intersect with the first direction. The detector may detect a first signal as information indicating the bending state in the first direction at the position of the first pixel electrode and a second signal as information indicating the bending state in the second direction at the position of the second pixel electrode. In this case, the first pixel electrode is strongly affected by bending in the first direction, and the second pixel electrode is strongly affected by bending in the second direction. Therefore, by detecting a first signal indicating a change in the electrical characteristics between the first pixel electrode and the common electrode as information indicating the bending state in the first direction and a second signal indicating a change in the electrical characteristics between the second pixel electrode and the common electrode as information indicating the bending state in the second direction, the bending state in the first direction and the bending state in the second direction can be distinguished and recognized. This allows the bending state of the bending sensor to be recognized in more detail.

[0021] A bending detection method according to yet another aspect of the present invention is a bending detection method implemented using any of the bending sensors described above, and includes the steps of: when a bending is applied to the bending sensor, outputting from a first thin film transistor a first signal indicating a change in electrical characteristics between a first pixel electrode and a common electrode in response to the bending; and outputting from a second thin film transistor a second signal indicating a change in electrical characteristics between a second pixel electrode and a common electrode in response to the bending; and detecting the first signal as information indicating the bending state at the position of the first pixel electrode; and detecting the second signal as information indicating the bending state at the position of the second pixel electrode.

[0022] The above-described bending detection method uses one of the bending sensors described above. As described above, the change in the electrical characteristics between the first pixel electrode and the common electrode and the change in the electrical characteristics between the second pixel electrode and the common electrode occur independently of each other. Therefore, by separately detecting a first signal indicating the change in the electrical characteristics between the first pixel electrode and the common electrode and a second signal indicating the change in the electrical characteristics between the second pixel electrode and the common electrode using a first thin film transistor and a second thin film transistor, it is possible to separately obtain information indicating the bending state at the position of the first pixel electrode and information indicating the bending state at the position of the second pixel electrode. This allows the local bending state at each of the positions of the first pixel electrode and the second pixel electrode to be grasped. Therefore, the above-described bending detection method makes it possible to grasp the bending state in detail.

[0023] The step of outputting the first signal and the second signal may include outputting the first signal using a first pixel electrode having a shape extending in a first direction along the substrate, and outputting the second signal using a second pixel electrode having a shape extending in a second direction along the substrate and intersecting the first direction. The step of detecting the first signal and the second signal may include detecting the first signal as information indicating the bending state in the first direction at the position of the first pixel electrode, and detecting the second signal as information indicating the bending state in the second direction at the position of the second pixel electrode. In this case, the first pixel electrode is strongly affected by the bending in the first direction, and the second pixel electrode is strongly affected by the bending in the second direction. Therefore, by detecting the first signal indicating a change in the electrical characteristics between the first pixel electrode and the common electrode as information indicating the bending state in the first direction, and detecting the second signal indicating a change in the electrical characteristics between the second pixel electrode and the common electrode as information indicating the bending state in the second direction, the bending state in the first direction and the bending state in the second direction can be distinguished and grasped. This makes it possible to grasp the bending state of the bending sensor in more detail. [Effects of the Invention]

[0024] According to the present invention, it is possible to grasp the bending state in more detail. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a plan view showing an example of a bending sensor according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the bending sensor taken along line A1-A1 in FIG. [Figure 3] Fig. 3(a) is a cross-sectional view showing the bending sensor of Fig. 2 bent into a convex shape, and Fig. 3(b) is a cross-sectional view showing the bending sensor of Fig. 2 bent into a concave shape. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the configuration of a group of thin film transistors in one pixel. [Figure 5] FIG. 5 is a plan view showing the configuration of the thin film transistor group shown in FIG. [Figure 6]FIG. 6 is a diagram showing an example of a circuit configuration of a thin film transistor array. [Figure 7] FIG. 7 is a cross-sectional view showing another example of the configuration of a group of thin film transistors in one pixel. [Figure 8] FIG. 8 is a plan view showing the configuration of the thin film transistor group shown in FIG. [Figure 9] FIG. 9 is a diagram showing another example of the circuit configuration of a thin film transistor array. [Figure 10] Fig. 10(a) is a diagram showing an example of the configuration of a current limiting circuit, and Fig. 10(b) is a diagram showing another example of the configuration of a current limiting circuit. [Figure 11] Figure 11(a) is a diagram showing another example of the configuration of the current limiting circuit, and Figure 11(b) is a diagram showing another example of the configuration of the current limiting circuit. [Figure 12] FIG. 12 is a diagram illustrating an example of the configuration of the detection unit according to the first embodiment. [Figure 13] FIG. 13 is a diagram showing another example of the configuration of the detection unit. [Figure 14] FIG. 14 is a diagram showing another example of the configuration of the detection unit. [Figure 15] FIG. 15 is a flowchart showing an example of the operation of the bending detection device. [Figure 16] 16(a) to 16(e) are diagrams for explaining the operation of the bending detection device shown in FIG. [Figure 17] FIG. 17 is a plan view showing an example of the bending sensor according to the second embodiment. [Figure 18] Fig. 18(a) is a cross-sectional view of the bending sensor taken along the line A2-A2 in Fig. 17. Fig. 18(b) is a cross-sectional view of the bending sensor taken along the line A3-A3 in Fig. 17. [Figure 19] Fig. 19(a) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 18(a). Fig. 19(b) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 18(b). [Figure 20]Fig. 20(a) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 18(a). Fig. 20(b) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 18(b). [Figure 21] 21(a) to 21(c) are plan views showing other examples of the bending sensor according to the second embodiment. [Figure 22] 22(a) and 22(b) are plan views showing other examples of the bending sensor according to the second embodiment. [Figure 23] FIG. 23 is a plan view showing an example of a bending sensor according to the third embodiment. [Figure 24] Fig. 24(a) is a cross-sectional view of the bending sensor taken along the line A4-A4 in Fig. 23. Fig. 24(b) is a cross-sectional view of the bending sensor taken along the line A5-A5 in Fig. 23. [Figure 25] Fig. 25(a) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 24(a). Fig. 25(b) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 24(b). [Figure 26] Fig. 26(a) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 24(a). Fig. 26(b) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 24(b). [Figure 27] 27(a) to 27(c) are plan views showing other examples of the bending sensor according to the third embodiment. [Figure 28] 28(a) and 28(b) are plan views showing other examples of the bending sensor according to the third embodiment. [Figure 29] FIG. 29 is a plan view showing another example of the bending sensor according to the third embodiment. [Figure 30] Fig. 30(a) is a cross-sectional view of the bending sensor taken along the line A6-A6 in Fig. 29. Fig. 30(b) is a cross-sectional view of the bending sensor taken along the line A7-A7 in Fig. 29. [Figure 31]Fig. 31(a) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 30(a). Fig. 31(b) is a cross-sectional view showing the bending sensor bent into a convex shape in the cross section shown in Fig. 30(b). [Figure 32] Fig. 32(a) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 30(a). Fig. 32(b) is a cross-sectional view showing the bending sensor bent into a concave shape in the cross section shown in Fig. 30(b). [Figure 33] FIG. 33 is a plan view showing another example of the bending sensor according to the third embodiment. [Figure 34] FIG. 34 is a plan view showing another example of the bending sensor according to the third embodiment. [Figure 35] FIG. 35 is a block diagram showing an example of a care data collection and determination system to which a bending detection device is applied. [Figure 36] 36(a) to 36(f) are perspective views showing examples of the care sensor device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] A bending sensor, a bending detection device, and a bending detection method according to embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and duplicated explanations will be omitted as appropriate. The dimensions and dimensional ratios in the drawings do not necessarily correspond to the actual dimensions and dimensional ratios.

[0027] [First embodiment] FIG. 1 is a plan view showing a bending sensor 10 according to a first embodiment. FIG. 2 is a cross-sectional view showing the bending sensor 10 taken along line A1-A1 in FIG. 1. The bending sensor 10 detects bending applied to the bending sensor 10. The bending sensor 10, together with a detection unit 5 described below, constitutes a bending detection device 1 (see FIG. 12). The bending sensor 10 is a sensor array in which a plurality of sensors 11 are arranged in a matrix (two-dimensionally). The plurality of sensors 11 that constitute the bending sensor 10 are arranged one for each pixel.

[0028] In this specification, the term "pixel" refers to a detection point corresponding to the intersection of scanning wiring 61 and signal wiring 62 (see FIG. 6), which will be described later. In this case, in the plan view of FIG. 1, a plurality of pixels are arranged in a matrix at a fixed pitch. In this embodiment, a case where a plurality of pixels are arranged in N rows and M columns (M and N are integers of 2 or more) will be described. The plurality of pixels can be divided into a plurality of pixel regions RP arranged in N rows and M columns. FIG. 1 shows the boundary line BL between adjacent pixels (i.e., the boundary line of each pixel region RP). However, the boundary line BL is a virtual line indicating the boundary between each pixel, and is not a line indicating the boundary of an actually existing component.

[0029] As shown in FIGS. 1 and 2, the bending sensor 10 includes a flexible substrate 15, a thin-film transistor layer 20 including a plurality of thin-film transistors, a plurality of pixel electrodes 25, a piezoelectric layer 30, and a counter electrode 35. The flexible substrate 15 is a flexible substrate made of an insulating material. Examples of materials for the flexible substrate 15 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyimide (PI), and acrylic. As shown in FIG. 2, the flexible substrate 15 has a front surface 15a and a back surface 15b facing opposite each other in the thickness direction. On the front surface 15a of the flexible substrate 15, the thin-film transistor layer 20 including a plurality of thin-film transistors, a plurality of pixel electrodes 25, the piezoelectric layer 30, and the counter electrode 35 are stacked in this order.

[0030] In the following description, one direction along the surface 15a of the flexible substrate 15 is referred to as the X direction (first direction), a direction along the surface 15a and perpendicular to the one direction is referred to as the Y direction (second direction), and a direction perpendicular to the surface 15a (i.e., the thickness direction of the flexible substrate 15) is referred to as the Z direction. In this embodiment, a view from the Z direction is sometimes referred to as a "plan view," and the flexible substrate 15 side in the Z direction may be referred to as the "bottom," and the opposite side (i.e., the counter electrode 35 side) may be referred to as the "top." When describing the height of a certain configuration, the height of the back surface 15b of the flexible substrate 15 in the Z direction may be used as a reference.

[0031] In the thin film transistor (TFT) layer 20, a plurality of thin film transistors are arranged in a matrix along the X and Y directions, with one for each pixel or one group for each pixel. That is, each thin film transistor or group of thin film transistors is arranged in N rows and M columns corresponding to each pixel. For example, the circuits shown in FIGS. 4 to 6 (described later) have two thin film transistors, a pixel thin film transistor 21 and a selection thin film transistor 22, per pixel, and the pixel electrode 25 is connected to the gate electrode G1 of the pixel thin film transistor 21. Alternatively, the circuits shown in FIGS. 7 to 9 (described later) have three thin film transistors, a pixel thin film transistor 21, a selection thin film transistor 22, and a reset thin film transistor 23, per pixel, and the pixel electrode 25 is connected to the gate electrode G1 of the pixel thin film transistor 21. As shown in Figures 4 and 5 or 7 and 8, these thin film transistors are formed by arranging thin film transistors having a similar layered structure (e.g., gate electrode, gate insulating film, semiconductor layer, (source / drain electrode), and interlayer insulating film) in a plane and connecting them with wiring. The entire layered structure is referred to as a thin film transistor layer 20. Among the components of the thin film transistor layer 20, the interlayer insulating film 51 and the gate insulating film 50 account for the majority of the volume. Therefore, the Young's modulus of the thin film transistor layer 20 may be that of the laminate of the interlayer insulating film 51 and the gate insulating film 50. In particular, if the interlayer insulating film 51 and the gate insulating film 50 are made of the same material, the Young's modulus of the laminate may be used. Because the plurality of thin film transistors are arranged in an array, the plurality of thin film transistors may be referred to as a "thin film transistor array 20" below. Each thin film transistor may be, for example, an organic thin film transistor (organic semiconductor) or an oxide thin film transistor (oxide semiconductor). Organic thin film transistors and oxide thin film transistors, when primarily composed of an organic insulating film, have the advantage of being flexible and durable.

[0032] Although the thin-film transistor layer 20 is depicted as a single layer in FIG. 2, it actually includes a plurality of thin-film transistors, and as shown in FIG. 4 or 7, the pixel electrode 25 is connected to the gate electrode G1 of the pixel thin-film transistor 21. The plurality of thin-film transistors includes at least two: a first pixel thin-film transistor 21A and a second pixel thin-film transistor 21B (see FIG. 6). The first pixel thin-film transistor 21A and the second pixel thin-film transistor 21B are arranged at positions spaced apart in the X direction on the surface 15a of the flexible substrate 15. The first pixel thin-film transistor 21A is electrically connected to a first pixel electrode 25A, which will be described later, and the second pixel thin-film transistor 21B is electrically connected to a second pixel electrode 25B, which will be described later.

[0033] The pixel electrodes 25 are arranged in a matrix along the X and Y directions, and typically one for each pixel. That is, like the thin-film transistor groups, the pixel electrodes 25 are arranged in N rows and M columns corresponding to the respective pixels. Each pixel electrode 25 is arranged at a position overlapping with or near a pixel thin-film transistor 21 in a plan view. The pixel electrodes 25 are arranged at a constant pitch along the X and Y directions, and are spaced apart from each other in both the X and Y directions.

[0034] The pixel electrodes 25 are spaced apart from one another in the X and Y directions. The pixel electrodes 25 being spaced apart from one another means that the pixel electrodes 25 are physically spaced apart from one another. A solid substance may be present in the region between the pixel electrodes 25 (hereinafter referred to as an "inter-pixel electrode region 26"), or the inter-pixel electrode region 26 may not be present. If a solid substance is present in the inter-pixel electrode region 26, the solid substance is made of an electrically insulating material. In this case, electrical insulation between the pixel electrodes 25 is ensured.

[0035] In this embodiment, an electrically insulating adhesive is provided in the inter-pixel electrode region 26. In this case, it can be said that the inter-pixel electrode region 26 is made of an electrically insulating adhesive. The adhesive is capable of adhering to the pixel electrodes 25 and includes, for example, a pressure-sensitive adhesive. Therefore, the inter-pixel electrode region 26 between each pixel electrode 25 fixes (or maintains) the position of each pixel electrode 25 by being adhered to each pixel electrode 25. If no solid material is present in the inter-pixel electrode region 26, the inter-pixel electrode region 26 is made of air. In this case, too, the air layer present in the inter-pixel electrode region 26 ensures electrical insulation between each pixel electrode 25.

[0036] Each pixel electrode 25 has, for example, a square shape with the same length in the X direction and the same length in the Y direction. Each pixel electrode 25 is made of, for example, a metal film for molybdenum (Mo) or aluminum (Al), a metal paste such as silver (Ag) paste, or a carbon paste.

[0037] Each pixel electrode 25 has a front surface 25a facing the piezoelectric layer 30 and a back surface 25b facing the thin film transistor layer 20. The front surface 25a of each pixel electrode 25 is electrically connected to the piezoelectric layer 30. The back surface 25b of each pixel electrode 25 is in contact with and electrically connected to a corresponding pixel thin film transistor 21. The plurality of pixel electrodes 25 includes at least two: a first pixel electrode 25A (first electrode) and a second pixel electrode 25B (second electrode). In the example shown in FIG. 1, the first pixel electrode 25A and the second pixel electrode 25B are adjacent to each other in the X direction via an inter-pixel electrode region 26. The first pixel electrode 25A is disposed at a position corresponding to the first pixel thin film transistor 21A. The back surface 25b of the first pixel electrode 25A is electrically connected to the first pixel thin film transistor 21A (first thin film transistor). The second pixel electrode 25B is disposed at a position corresponding to the second pixel thin film transistor 21B. The rear surface 25b of the second pixel electrode 25B is electrically connected to the second pixel thin film transistor 21B (second thin film transistor).

[0038] The counter electrode 35 is disposed in a position facing the plurality of pixel electrodes 25 in the Z direction via the piezoelectric layer 30. The counter electrode 35 is, for example, a single common electrode disposed so as to overlap all of the pixel electrodes 25 in a planar view. The counter electrode 35 has a rectangular shape that encompasses all of the pixel electrodes 25 in a planar view. The counter electrode 35 is, for example, a metal thin film made of a metal material such as aluminum (Al), gold (Au), or molybdenum (Mo). The counter electrode 35 is electrically connected to, for example, ground (GND). In this case, a ground potential is applied to the counter electrode 35. The ground potential does not have to be applied to the counter electrode 35, and any constant voltage may be applied thereto.

[0039] The piezoelectric layer 30 is disposed between the plurality of pixel electrodes 25 and the counter electrode 35 in the Z direction. The piezoelectric layer 30 is a layer containing a piezoelectric material. Examples of piezoelectric materials include polyvinylidene difluoride (PVDF), polytrifluoroethylene (PTrFE), and poly(vinylidene difluoride-trifluoroethylene) copolymer (P(VDF-TrFE)). These materials can be imparted with strong piezoelectricity to the piezoelectric layer 30 by a poling process. The piezoelectric layer 30 has a front surface 30a facing the counter electrode 35 and a back surface 30b facing the plurality of pixel electrodes 25. The front surface 30a is in contact with and electrically connected to the counter electrode 35. The back surface 30b is in contact with and electrically connected to all of the pixel electrodes 25.

[0040] When the bending sensor 10 is bent and tensile or compressive stress is applied to the piezoelectric layer 30, a voltage corresponding to the stress is generated in the piezoelectric layer 30 due to the piezoelectric effect, which causes polarization in the piezoelectric material. This changes the electrical characteristics between the counter electrode 35 and the pixel electrode 25. Specifically, a potential difference is generated between the counter electrode 35 and the pixel electrode 25.

[0041] When a constant voltage is applied to the counter electrode 35, the voltage of the pixel electrode 25 is a value obtained by adding the voltage of the counter electrode 35 to the voltage of the piezoelectric layer 30. The voltage of the pixel electrode 25 is output as a voltage signal from the thin-film transistor array 20 and then detected by the detection unit 5 as information indicating the state of bending (bending information). Because the voltage indicated by this signal is proportional to the magnitude of bending, the magnitude of bending can be determined from this signal. The magnitude of bending can provide information such as whether or not there is bending, the amount of bending, and the direction of bending (i.e., whether the bending is upwardly convex or downwardly concave). Therefore, the bending information may include the presence or absence of bending, the amount of bending, and the direction of bending.

[0042] In this embodiment, as described above, multiple pixel electrodes 25 are arranged in a matrix with a space between them relative to one counter electrode 35, and the pixel electrodes 25 are electrically insulated from one another. In this case, the voltage generated in each pixel electrode 25 varies independently for each pixel electrode 25. Therefore, when stress is applied to the piezoelectric layer 30 by bending the bending sensor 10, a voltage corresponding to the stress is generated in each pixel electrode 25 at the position of the pixel electrode 25. That is, of the bending applied to the entire piezoelectric layer 30, a voltage corresponding to the bending at the position of the first pixel electrode 25A is generated in the first pixel electrode 25A, and a voltage corresponding to the bending at the position of the second pixel electrode 25B is generated in the second pixel electrode 25B. Therefore, in the bending sensor 10 according to this embodiment, bending information is acquired for each pixel electrode 25 by separately detecting the voltage generated in each pixel electrode 25. This allows the bending state of the bending sensor 10 to be determined for each pixel electrode 25.

[0043] 2, the piezoelectric layer 30 is positioned at a position different from the neutral plane NP so that stress is applied when the bending sensor 10 is bent. The neutral plane NP is a plane to which no tensile or compressive stress is applied even when the bending sensor 10 is bent. In this embodiment, the neutral plane NP can be shown as an imaginary plane along the XY plane, and is located on any of the layers constituting the bending sensor 10 (i.e., the flexible substrate 15, the thin-film transistor layer 20, the pixel electrode 25, the piezoelectric layer 30, and the counter electrode 35).

[0044] The position of the neutral plane NP in the Z direction can be expressed by the height λ from the rear surface 15b of the flexible substrate 15. The height λ of the neutral plane NP depends on the Young's modulus and thickness of each layer constituting the bending sensor 10 (i.e., the flexible substrate 15, the thin-film transistor layer 20, the pixel electrode 25, the piezoelectric layer 30, and the counter electrode 35). When the bending sensor 10 is composed of N layers (N is a natural number), with the bottom layer being the first layer, the Young's modulus of the ith layer (i is a natural number less than or equal to N) is Ei, the thickness of the ith layer is Ti, and the height of the center of the ith layer from the bottom layer is Yi, the height λ of the neutral plane NP is generally expressed by the following formula (1):

number

number

[0045] As described above, the height λ of the neutral plane NP varies depending on the Young's modulus and thickness of each layer, and can be adjusted by adjusting the Young's modulus and thickness of each layer. The height λ of the neutral plane NP is, for example, located lower than the rear surface 30b of the piezoelectric layer 30. The example shown in FIG. 2 illustrates a case in which the height λ of the neutral plane NP is located at the height of the rear surface 25b of the pixel electrode 25. In this case, the entire pixel electrodes 25, the entire inter-pixel electrode regions 26, and the entire piezoelectric layer 30 are located higher than the height λ of the neutral plane NP. However, the height λ of the neutral plane NP is not necessarily the height of the rear surface 25b of the pixel electrode 25; it may be higher or lower than the rear surface 25b. For example, the height λ of the neutral plane NP may be the internal height of the pixel electrode 25.

[0046] FIG. 3A is a cross-sectional view showing the bending sensor 10 bent in a convex shape. In FIG. 3A, the bending sensor 10 is bent in the X-direction, causing the bending sensor 10 to bend convexly upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is positioned above the neutral plane NP, bending the bending sensor 10 in a convex shape as shown in FIG. 3A applies tensile stress in the X-direction to the piezoelectric layer 30. When the curvature at the position of the first pixel electrode 25A and the curvature at the position of the second pixel electrode 25B are equal, a tensile stress SS1 in the X-direction is applied to the piezoelectric layer 30 at the positions of the first pixel electrode 25A and the second pixel electrode 25B. Therefore, a voltage corresponding to the tensile stress SS1 is generated in the first pixel electrode 25A and the second pixel electrode 25B. When the curvature at the position of the first pixel electrode 25A differs from the curvature at the position of the second pixel electrode 25B, tensile stresses of different magnitudes in the X direction are applied to the piezoelectric layer 30 at the positions of the first pixel electrode 25A and the second pixel electrode 25B. In this case, voltages according to the respective tensile stresses are generated in the first pixel electrode 25A and the second pixel electrode 25B.

[0047] FIG. 3B is a cross-sectional view showing the bending sensor 10 bent in a concave shape. In FIG. 3B, the bending sensor 10 is bent in the X-direction, resulting in the bending sensor 10 being bent in a concave shape upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is positioned above the neutral plane NP, compressive stress in the X-direction is applied to the piezoelectric layer 30 when the bending sensor 10 is bent in a concave shape as shown in FIG. 3B. When the curvature at the position of the first pixel electrode 25A and the curvature at the position of the second pixel electrode 25B are equal, compressive stress SS2 in the X-direction is applied to the piezoelectric layer 30 at the positions of the first pixel electrode 25A and the second pixel electrode 25B. Therefore, a voltage corresponding to the compressive stress SS2 is generated in the first pixel electrode 25A and the second pixel electrode 25B. When the curvature at the position of the first pixel electrode 25A differs from the curvature at the position of the second pixel electrode 25B, compressive stresses of different magnitudes in the X direction are applied to the piezoelectric layer 30 at the positions of the first pixel electrode 25A and the second pixel electrode 25B. In this case, voltages corresponding to the respective compressive stresses are generated in the first pixel electrode 25A and the second pixel electrode 25B. The voltages generated in the first pixel electrode 25A and the second pixel electrode 25B are opposite in direction to the voltages generated in the first pixel electrode 25A and the second pixel electrode 25B in the case shown in FIG. 3(a).

[0048] Here, the voltage generated in the pixel electrode 25 (i.e., the voltage generated in the piezoelectric layer 30) will be described in more detail. If the voltage generated in the pixel electrode 25 is V, the capacitance of the capacitor formed by the counter electrode 35, the piezoelectric layer 30, and the pixel electrode 25 is C, and the charge stored in the capacitor is Q, then the relationship shown in the following equation (3) holds among the voltage V, the capacitance C, and the charge Q. Furthermore, if the electric flux density generated between the counter electrode 35 and the pixel electrode 25 is De, and the electrode area (i.e., the area of the pixel electrode 25 in a plan view) is A, then the charge Q is expressed by the following equation (4). If the Z direction is 3, the X direction is 1, and the Y direction is 2, and the piezoelectric strain constants of the piezoelectric layer 30 are d31, d32, and d33, and the tensile stress in the X direction, Y direction, and Z direction applied to the piezoelectric layer 30 are σ1, σ2, and σ3, respectively, the electric flux density De is expressed by the following equation (5). If the piezoelectric layer 30 is a uniaxially stretched film, and the stretching direction is the X direction, then the relationship d31 >> d32 holds. On the other hand, if the piezoelectric layer 30 is a biaxially stretched or unstretched film, then the relationship d31 = d32 holds.

number

number

number

[0049] Therefore, the voltage V generated in the pixel electrode 25 can be found by using equations (3) to (5). Note that the stress applied to the piezoelectric layer 30 is proportional to the strain, and the strain is proportional to the curvature of the bending of the piezoelectric layer 30, so the stress is proportional to the curvature. Furthermore, the stress is proportional to the charge Q and the voltage V, so the charge Q and the voltage V are proportional to the curvature. Therefore, the voltage V generated in the pixel electrode 25 increases as the curvature of the bending applied to the bending sensor 10 increases.

[0050] FIG. 4 is a cross-sectional view showing the configuration of the thin film transistor group of one pixel. FIG. 5 is a plan view showing the configuration of the thin film transistor group of one pixel. The voltage generated in the pixel electrode 25 is input as a voltage signal to the pixel thin film transistor 21. As shown in FIGS. 4 and 5, the thin film transistor group includes, for example, the pixel thin film transistor 21 and the selection thin film transistor 22. The pixel thin film transistor 21 includes a gate electrode G1, a gate insulating film 50, a source electrode S1, a semiconductor layer SC1, a drain electrode D1, and an interlayer insulating film 51. The selection thin film transistor 22 includes a gate electrode G2, a gate insulating film 50, a source electrode S2, a semiconductor layer SC2, a drain electrode D2, and an interlayer insulating film 51.

[0051] The gate electrode G1 and the gate electrode G2 are disposed on the surface 15a of the flexible substrate 15 and are spaced apart from each other in the X direction. A gate insulating film 50 is disposed on the flexible substrate 15 so as to cover the gate electrode G1 and the gate electrode G2. The gate insulating film 50 electrically insulates the gate electrode G1, the gate electrode G2 from other electrodes. The source electrode S1, the drain electrode D1, the semiconductor layer SC1, the source electrode S2, the drain electrode D2, and the semiconductor layer SC2 are disposed on the gate insulating film 50. The source electrode S1, the drain electrode D1, and the semiconductor layer SC1 are disposed on the gate electrode G1 with the gate insulating film 50 interposed therebetween.

[0052] The source electrode S2, the drain electrode D2, and the semiconductor layer SC2 are disposed on the gate electrode G2 via a gate insulating film 50. An interlayer insulating film 51 is disposed on the gate insulating film 50 so as to cover the source electrode S1, the drain electrode D1, the semiconductor layer SC1, the source electrode S2, the drain electrode D2, and the semiconductor layer SC2. A pixel electrode 25 is laminated on the interlayer insulating film 51. The interlayer insulating film 51 electrically insulates the source electrode S1, the drain electrode D1, the source electrode S2, the drain electrode D2, and the pixel electrode 25 from each other.

[0053] The gate electrode G1 is electrically connected to the pixel electrode 25 via a first via wiring 53 formed in the gate insulating film 50 and a second via wiring 54 formed in the interlayer insulating film 51. The source electrode S1 is electrically connected to the drain electrode D2 via a connection wiring 55. As shown in FIG. 5 , the thin-film transistor array 20 is provided with a drain wiring 60, a scanning wiring 61, and a signal wiring 62. The drain wiring 60 is connected to the drain electrode D1 and extends along the Y direction. The drain electrode D1 is electrically connected to the drain wiring 60, which is electrically connected to a power supply. The scanning wiring 61 is connected to the gate electrode G2 and extends along the Y direction. The gate electrode G2 is electrically connected to the scanning wiring 61. The signal wiring 62 extends along the Y direction and is spaced apart from the drain wiring 60 in the X direction. The source electrode S2 is electrically connected to the signal wiring 62.

[0054] 6 is a diagram showing the circuit configuration of the thin-film transistor array 20. A plurality of signal wirings 62 are arranged at intervals in the X direction, with one wiring provided for each column. A plurality of scanning wirings 61 are arranged at intervals in the Y direction, with one wiring provided for each row. In this embodiment, N scanning wirings 61 and M signal wirings 62 are provided. As shown in FIG. 6, the gate electrodes G2 of a plurality of thin-film transistor groups arranged in a row in the X direction are connected to one scanning wiring 61, and the source electrodes S2 of a plurality of thin-film transistor groups arranged in a row in the Y direction are connected to one signal wiring 62.

[0055] When stress is applied to the piezoelectric layer 30, a voltage is generated in the pixel electrode 25, and the generated voltage is input to the pixel thin film transistor 21 connected to the pixel electrode 25. For simplicity's sake, focusing on one pair of thin film transistors, the voltage of the pixel electrode 25 is input to the gate electrode G1 of the pixel thin film transistor 21. Then, based on the voltage of the power supply connected to the drain wiring 60, the pixel thin film transistor 21 outputs a signal corresponding to the voltage input to the gate electrode G1 from the drain electrode D1 to the source electrode S1. The signal output to the source electrode S1 is input to the drain electrode D2 of the selection thin film transistor 22. Note that the pixel thin film transistor 21, including the load resistance of the signal detection circuit described below, forms a common-drain (source follower) circuit. Furthermore, when an arbitrary constant voltage is applied to the counter electrode 35, a voltage obtained by adding the voltage of the counter electrode 35 and the voltage of the piezoelectric layer 30 is applied to the gate electrode G1. Therefore, the operating point of the pixel thin film transistor 21 can be adjusted by adjusting the voltage of the counter electrode 35.

[0056] The selection thin film transistor 22 controls whether or not a signal input to the drain electrode D2 is output to the signal wiring 62. A gate voltage that switches the selection thin film transistor 22 on / off is applied from the scanning wiring 61 to the gate electrode G2 of the selection thin film transistor 22. The selection thin film transistor 22 functions as a switch that switches on / off between the drain electrode D2 and the source electrode S2 based on the gate voltage applied to the gate electrode G2. When a gate voltage (off voltage) that turns the selection thin film transistor 22 off is applied from the scanning wiring 61 to the gate electrode G2, the signal input to the drain electrode D2 is not output to the signal wiring 62. On the other hand, when a gate voltage (on voltage) that turns the selection thin film transistor 22 on is applied from the scanning wiring 61 to the gate electrode G2, the signal input to the drain electrode D2 is output from the source electrode S2 to the signal wiring 62.

[0057] The signal output to the signal wiring 62 is detected by the detection unit 5 (see FIG. 12 ), which will be described later. In this embodiment, the signal provides the sum of the magnitude of bending in the X direction and the magnitude of bending in the Y direction. Bending in the X direction refers to bending when stress is applied in the X direction. More specifically, bending in the X direction refers to bending in a direction in which the bending sensor 10 becomes convex or concave in the Z direction on an XZ cross section. Bending in the Y direction refers to bending when stress is applied in the Y direction. More specifically, bending in the Y direction refers to bending in a direction in which the bending sensor 10 becomes convex or concave in the Z direction on a YZ cross section. Hereinafter, bending in the X direction may be abbreviated as X bending, and bending in the Y direction may be abbreviated as Y bending.

[0058] However, when a uniaxially stretched film (for example, uniaxially stretched PVDF) is used as the piezoelectric layer 30, it is possible to detect the magnitude of bending in the X direction and the magnitude of bending in the Y direction independently. For example, a configuration can be considered in which two bending sensors 10 using a uniaxially stretched film as the piezoelectric layer 30 are prepared, and the two bending sensors 10 are stacked in the Z direction so that the stretching directions of the piezoelectric layers 30 are shifted by 90°. In this configuration, the stretching direction of the piezoelectric layer 30 of one bending sensor 10 is the X direction, and the stretching direction of the piezoelectric layer 30 of the other bending sensor 10 is the Y direction. In this case, the voltage output from the bending sensor 10 in the stretching direction X is referred to as voltage V X and the voltage obtained from the bending sensor 10 in the extension direction Y is the voltage V Y Let the magnitude of X bending be B X The magnitude of the Y bending is B Y Then, the voltage V X and voltage V Y can be formulated as the following equations (6) and (7), respectively: where k1 and k2 are constants that satisfy k1>k2.

number

number

[0059] Therefore, if k1 and k2 are experimentally determined, the magnitude of X bending B X , and the magnitude of Y bending B Y The following equations (8) and (9) can be derived from equations (6) and (7). In this way, even when the bending sensor 10 according to this embodiment is used, the magnitude of bending in the X direction B X and the magnitude of bending in the Y direction B Y It is possible to detect the and independently.

number

number

[0060] In this way, bending information can be obtained based on the signals output to the signal wiring 62. However, to obtain bending information for each pixel electrode 25, it is necessary to distinguish and detect each signal output from each pixel thin film transistor 21. For this reason, the detection unit 5 (see FIG. 12), which will be described later, is configured to distinguish and detect each signal. As shown in FIG. 12, which will be described later, each signal wiring 62 is connected to a load resistor 76 located in a detection circuit external to the thin film transistor array 20. In this case, current flows through each signal wiring 62, reducing impedance and making it less likely for noise to be mixed into the signal. Furthermore, because the pixel thin film transistor 21 forms a common-drain (source follower) circuit, only the current is amplified, and the potential of the source electrode S1 is close to the potential of the gate electrode G1. Therefore, the signal is less susceptible to the influence of mobility variations in the pixel thin film transistor 21.

[0061] On the other hand, if a load resistor is located inside the thin-film transistor array 20, the current flowing through each signal wiring 62 will be small, and if each signal wiring 62 is long, noise will be more likely to be mixed into the signal. Also, if the impedance of the detection unit 5 is reduced to prevent noise from being mixed into the signal, the current of the detection unit 5 will also flow through the load resistor in addition to the current flowing through the pixel thin-film transistor 21. In this case, the voltage drop across the load resistor due to the current of the detection unit 5 will become an error. Also, if the pixel thin-film transistor 21 forms a common-source circuit, both the voltage and current are amplified, increasing sensitivity, but the signal will be more susceptible to variations in the mobility and threshold of the pixel thin-film transistor 21.

[0062] In the circuit shown in FIG. 6, immediately before bending detection by the bending sensor 10, the voltage of the drain wiring 60 is changed from zero to V dd When the capacitance between the gate electrode G1 and the drain electrode D1 of the pixel thin film transistor 21 (including the pixel electrode 25 connected to the gate electrode G1 and the drain wiring 60 connected to the drain electrode D1) is set to C gd1 and the capacitance between the pixel electrode 25 and the counter electrode 35 is C p Then, the voltage deviation ΔV of the pixel electrode 25 p is expressed by the following equation (10).

number

[0063] Here, the voltage deviation ΔVp of the pixel electrode 25 is the maximum potential change amount ΔV MAX For example, the voltage deviation ΔVp of the pixel electrode 25 is smaller than the maximum potential change ΔV MAX It is desirable to keep the maximum potential change ΔV within 10% of the value of the maximum potential change ΔV. MAX is the amount of change in the potential of the piezoelectric layer 30 when the bending sensor 10 is subjected to a maximum bending (i.e., a bending at which the detection range set for the bending sensor 10 reaches its maximum value) from a state in which no bending is applied to the bending sensor 10. For example, the maximum amount of potential change ΔVMAX When the voltage difference ΔVp of the pixel electrode 25 is 4 [V], it is sufficient if it is 0.4 [V] or less.

number

[0064] FIG. 7 is a cross-sectional view showing the configuration of another example of the thin-film transistor array 20. FIG. 8 is a plan view showing the thin-film transistor array 201 shown in FIG. 7. As shown in FIGS. 7 and 8, the thin-film transistor array 201 has a reset thin-film transistor 23 in addition to the pixel thin-film transistor 21 and the selection thin-film transistor 22. The reset thin-film transistor 23 includes a gate electrode G3, a gate insulating film 50, a source electrode S3, a semiconductor layer SC3, a drain electrode D3, and an interlayer insulating film 51. The reset thin-film transistor 23 shares the gate insulating film 50 and the interlayer insulating film 51 with the pixel thin-film transistor 21 and the selection thin-film transistor 22.

[0065] The gate electrode G3, together with the gate electrodes G1 and G2, is covered with a gate insulating film 50. The source electrode S3, the semiconductor layer SC3, and the drain electrode D3 are disposed on the gate insulating film 50. The source electrode S3, the drain electrode D3, and the semiconductor layer SC3 are disposed on the gate electrode G3 with the gate insulating film 50 interposed therebetween. The source electrode S3, the drain electrode D3, and the semiconductor layer SC3 are covered with an interlayer insulating film 51.

[0066] The drain electrode D3 is connected to the first via wiring 53 and the second via wiring 54, and is electrically connected to the gate electrode G1 of the pixel thin film transistor 21 via the first via wiring 53 and the second via wiring 54. As shown in FIG. 8, the reset thin film transistor 23 is provided with a common wiring 63 and a reset wiring 64. The common wiring 63 is connected to the source electrode S3 and extends along the Y direction. The source electrode S3 is electrically connected to the common wiring 63. The common wiring 63 is set to the same potential as the counter electrode 35. The reset wiring 64 extends along the X direction so as to intersect with the common wiring 63 and the signal wiring 62. The gate electrode G3 is electrically connected to the reset wiring 64. A gate voltage that switches the reset thin film transistor 23 on / off is applied to the reset wiring 64.

[0067] 9 is a diagram showing the circuit configuration of the thin film transistor array 201 shown in FIGS. 7 and 8. The reset thin film transistor 23 has the role of resetting the voltage of the piezoelectric layer 30 to zero by shorting the pixel electrode 25 to the common wiring 63 (i.e., setting the pixel electrode 25 to the same potential as the counter electrode 35) before bending detection by the bending sensor 10. This enables the circuit shown in FIG. 9 to perform more precise detection than the circuit shown in FIG. 6. Note that the circuits shown in FIGS. 6 and 9 are merely examples of circuit configurations of thin film transistor arrays, and other circuits may be used.

[0068] 9, before bending detection by the bending sensor 10 is performed, a gate voltage (on voltage) that turns on the reset thin film transistor 23 is applied to the reset wiring 64 in a state where no stress is applied to the piezoelectric layer 30. At this time, the pixel electrode 25 is electrically connected to the common wiring 63 via the reset thin film transistor 23, so that the charge accumulated in the pixel electrode 25 can be made zero. After that, a gate voltage (off voltage) that turns off the reset thin film transistor 23 is applied to the reset wiring 64, and a voltage V dd is applied.

[0069] Normally, when no stress is applied to the piezoelectric layer 30, the voltage of the piezoelectric layer 30 is zero. However, depending on the past history, for example, if stress has been applied to the piezoelectric layer 30 until immediately before the bending sensor 10 is used, the voltage of the piezoelectric layer 30 may not be zero. In this case, an error may occur due to residual charge in the piezoelectric layer 30. In contrast, according to the circuit shown in FIG. 9, the charge in the pixel electrode 25 can be reset by turning on the reset thin film transistor 23 before detection by the bending sensor 10, thereby suppressing the occurrence of an error due to residual charge in the piezoelectric layer 30.

[0070] In the circuit shown in FIG. 9, the capacitance between the gate electrode G1 and the drain electrode D1 of the pixel thin film transistor 21 (including the capacitance of the pixel electrode 25 connected to the gate electrode G1 and the capacitance of the drain wiring 60 connected to the drain electrode D1) is defined as C gd1 The capacitance between the gate electrode G3 and the drain electrode D3 of the reset thin film transistor 23 (including the capacitance of the reset wiring 64 connected to the gate electrode G3 and the capacitance of the pixel electrode 25 connected to the drain electrode D3) is C gd3 and the capacitance between the pixel electrode 25 and the counter electrode 35 is C p In this case, when the reset thin film transistor 23 is turned off by applying an off voltage to the reset wiring 64, the voltage deviation ΔV of the pixel electrode 25 is p1 is expressed by the following equation (12): reset(on) indicates the on-voltage applied to the reset line 64, and V reset(off ) indicates the off voltage applied to the reset line 64.

number

[0071] Change the voltage of the drain wire 60 from zero to V dd When the voltage of the pixel electrode 25 is set to 0V, the voltage difference ΔV p2 is expressed by the following equation (13).

number

number

[0072] In the circuit shown in FIG. 6 or FIG. 9, a current limiting circuit (protection circuit) may be provided in the drain wiring 60. FIGS. 10(a), 10(b), 11(a), and 11(b) are diagrams showing examples of the configuration of a current limiting circuit. The current limiting circuit is provided to prevent excessive current from flowing through the drain wiring 60 and other wirings (e.g., the scanning wiring 61, the signal wiring 62, and the common wiring 63) in the event of a short circuit between these wirings in the thin-film transistor array 20. In the example shown in FIG. 10(a), a power supply 70 and multiple drain wirings 60 are connected by a connection portion 72. The connection portion 72 includes one connection line 73 connected to the power supply 70 and multiple branch lines 74 branching from the connection line 73 and connected to the multiple drain wirings 60, respectively. One current limiting circuit 71 is provided in each connection line 73.

[0073] In the example shown in FIG. 10( a), if an abnormality occurs in one current limiting circuit 71, the voltage of all drain wirings 60 will drop, and it is assumed that the entire bending sensor 10 will become abnormal. Therefore, as in the example shown in FIG. 10( b), a configuration in which multiple current limiting circuits 71A are provided for multiple branch lines 74, respectively, is conceivable. In this example, each branch line 74 passes through a current limiting circuit 71A and is then connected to a corresponding drain wiring 60. Typically, the drain wirings 60 are provided for each column or row, so it is preferable to provide one current limiting circuit 71A for each drain wiring 60. In this case, if an abnormality occurs in one current limiting circuit 71A, the voltage of one drain wiring 60 connected to that current limiting circuit 71A will drop, which may cause one column or one row of pixels to become abnormal. However, the abnormality in the pixel in one column or one row can be corrected by interpolation.

[0074] As shown in FIG. 11(a), each branch line 74 may be further branched into multiple branches, resulting in a first branch portion 74a and a second branch portion 74b. In this example, the first branch portion 74a and the second branch portion 74b are arranged adjacent to each other. Alternatively, as shown in FIG. 11(b), the first branch portion 74a and the second branch portion 74b may be arranged not adjacent to each other. In this example, the first branch portions 74a of each branch line 74 are arranged adjacent to each other, and the second branch portions 74b of each branch line 74 are arranged adjacent to each other. In the example shown in FIG. 11(b), if an abnormality occurs in one current limiting circuit 71A, the abnormal drain wirings 60 can be dispersed rather than clustered, making it possible to correct the abnormality by complementation. Note that the current limiting circuit is not limited to the above example and may be a current circuit of another type.

[0075] [Bending detection device] Next, a description will be given of the bending detection device 1 equipped with the above-mentioned bending sensor 10. The bending detection device 1 includes the bending sensor 10 and a detection unit 5 for detecting a signal from the bending sensor 10.

[0076] FIG. 12 is a diagram showing the configuration of the detection unit 5 according to this embodiment. As shown in FIG. 12, the detection unit 5 has a signal detection circuit 75, a control circuit 80, and a drive circuit 85. In the example shown in FIG. 12, M signal wirings 62 are divided into M2 blocks B (areas surrounded by dashed lines in FIG. 12) with M1 wirings in between. That is, M1 signal wirings 62 are provided in each of the M2 blocks B. M1 and M2 are each an integer greater than or equal to 2 that satisfies the relationship M=M1×M2.

[0077] The signal detection circuit 75 is electrically connected to the M signal wirings 62 and detects signals output from the M signal wirings 62. The signal detection circuit 75 is configured to sequentially read out each signal row by row in order to distinguish and detect each signal output from each signal wiring 62. The signal detection circuit 75 includes, for example, M2 first switching circuits 81, M2 load resistors 76, M2 amplifiers 77, one second switching circuit 78, and one AD converter 79. The M2 first switching circuits 81, the M2 load resistors 76, and the M2 amplifiers 77 are each divided into M2 blocks B. That is, each block B includes, in addition to M1 signal wirings 62, one first switching circuit 81, one load resistor 76, and one amplifier 77.

[0078] The first switching circuit 81 is, for example, an analog multiplexer including M1 input terminals and one output terminal. An analog multiplexer can perform high-speed switching without losing analog signal information. However, when it is difficult to use an analog multiplexer, such as when the signal voltage range is wide, a relay may be used instead of the analog multiplexer. The M1 input terminals of the first switching circuit 81 are electrically connected to the M1 signal wirings 62 in the block B. The first switching circuit 81 switches the connection destination of the output terminal to one of the M1 input terminals in response to a control signal S81 from the control circuit 80. In other words, the first switching circuit 81 selects one of the M1 signal wirings 62 as the connection destination of the output terminal.

[0079] The amplifier 77 is, for example, a voltage detection amplifier. The amplifier 77 is, for example, a voltage follower circuit. The output terminal of the first switching circuit 81 is connected to the positive input terminal of the amplifier 77. The negative input terminal of the amplifier 77 is connected to the output terminal. The amplifier 77 current-amplifies a signal input from the signal wiring 62 via the first switching circuit 81. The load resistor 76 is disposed between the first switching circuit 81 and the amplifier 77. One terminal of the load resistor 76 is connected to a connection line that connects the output terminal of the first switching circuit 81 and one input terminal of the amplifier 77, and the other terminal of the load resistor 76 is connected to ground (GND).

[0080] The second switching circuit 78 is, for example, an analog multiplexer including M1 input terminals and one output terminal. The M1 input terminals are respectively connected to the output terminals of the amplifiers 77 of the M1 blocks B. The second switching circuit 78 switches the connection destination of the output terminal to one of the M1 input terminals in response to the drive signal S61 from the drive circuit 85. In other words, the second switching circuit 78 selects one of the M1 blocks B as the connection destination of the output terminal. The AD converter 79 is electrically connected to the output terminal of the second switching circuit 78. Therefore, the AD converter 79 is electrically connected to one of the signal wirings 62 selected by the first switching circuit 81 and the second switching circuit 78. The AD converter 79 converts a signal output from one of the signal wirings 62 into a digital value and outputs the digital value to the control circuit 80.

[0081] The drive circuit 85 is electrically connected to the N scanning wirings 61. The drive circuit 85 receives a control signal S85 from the control circuit 80 and outputs a drive signal S61 to the scanning wirings 61, thereby applying an ON voltage to one of the N scanning wirings 61 and applying an OFF voltage to all the other scanning wirings 61. The control circuit 80 is electrically connected to the signal detection circuit 75 and the drive circuit 85, and controls the signal detection circuit 75 and the drive circuit 85. The control circuit 80 is configured by, for example, a computer (for example, a microcomputer) including a processor such as a CPU and a storage device such as a memory.

[0082] The control circuit 80 outputs a control signal S81 to the signal detection circuit 75, which switches the connection destination of the first switching circuit 81 to one of the signal lines 62. The control circuit 80 also outputs a control signal S78 to the second switching circuit 78, which switches the connection destination of the second switching circuit 78 to one of the blocks B. Then, the control circuit 80 outputs a control signal S85 to the drive circuit 85, which applies an ON voltage to one of the scanning lines 61 and an OFF voltage to all the other scanning lines 61.

[0083] As a result, an on-voltage is applied only to the scanning wiring 61 of one row, and signals are output to the signal wiring 62 connected to each of the M thin film transistor groups arranged in that row. The signal output from the pixel thin film transistor 21 of one pixel is input to the AD converter 79 via the first switching circuit 81, the second switching circuit 78, etc., and read out to the control circuit 80. In this way, bending information for one pixel is obtained. Next, with the on-voltage applied only to the scanning wiring 61 of one row, the control circuit 80 switches the connection destination of the first switching circuit 81 and the connection destination of the second switching circuit 78 so that signals are sequentially read out from each signal wiring 62 of one row. In this way, bending information for one row is obtained. The operation of switching the connection destination of the first switching circuit 81 and the connection destination of the second switching circuit 78 will be described in detail later.

[0084] Next, the control circuit 80 outputs a control signal S85 to the drive circuit 85, causing it to apply an ON voltage to the scan lines 61 in the next row and an OFF voltage to all other scan lines 61. In this state, the control circuit 80 sequentially reads out signals from each signal line 62 by switching the connection destination of the first switching circuit 81 and the connection destination of the second switching circuit 78, as described above. This allows bending information for the next row to be obtained. The control circuit 80 repeats the above operation, sequentially switching the scan lines 61 to which the ON voltage is applied, and sequentially reads out signals from each row. This allows bending information to be sequentially obtained for each row. When the signals for all rows have been read out, bending information for all pixels, i.e., bending information for each pixel for one screen, is obtained. Furthermore, by repeating the above operation, bending information for each pixel for multiple screens, i.e., time-dependent bending information for all pixels, is obtained.

[0085] 12 includes a first switching circuit 81, so the required number of load resistors 76 and the required number of amplifiers 77 are M2, which can be reduced compared to the number (M) of signal wirings 62. Furthermore, the signal detection circuit 75 includes a second switching circuit 78, so when the number of input terminals of one second switching circuit 78 is L, the required number of AD converters 79 is M2 / L, which can be reduced compared to the number (M) of amplifiers 77. When the number of input terminals of the second switching circuit 78, L, is equal to M2, the required number of AD converters 79 is one. In this way, the signal detection circuit 75 includes the first switching circuit 81 and the second switching circuit 78, so the required number of load resistors 76 and the required number of amplifiers 77 can be reduced compared to the number of signal wirings 62, and the required number of AD converters 79 can be reduced compared to the number of amplifiers 77. This allows the circuit scale of the signal detection circuit 75 to be reduced, and the installation area and manufacturing costs of the signal detection circuit 75 to be reduced.

[0086] Furthermore, in the signal detection circuit 75, a load resistor 76 is provided on the output side (specifically, on the connection line between the output terminal of the first switching circuit 81 and the input terminal of the amplifier 77) rather than on the input side of the first switching circuit 81. This allows current to flow more easily through the first switching circuit 81, lowering impedance and reducing the influence of noise. Furthermore, in the signal detection circuit 75, current flows only through one signal wiring 62 selected by the first switching circuit 81 out of the M1 signal wirings 62 connected to the first switching circuit 81, thereby reducing power consumption.

[0087] The amplifier 77 is not limited to a voltage follower circuit, but may be a circuit with an amplification factor other than 1, or an inverting amplifier circuit. The amplifier 77 may include a known oscillation prevention circuit, a phase compensation circuit, a capacitance correction circuit, and a protection circuit. A FET (Field Effect Transistor) or the like may be used instead of the amplifier 77. In FIG. 12, the load resistor 76 is provided on the connection line connecting the signal wiring 62 and GND. However, for example, if the amplifier 77 is an inverting amplifier circuit, the load resistor 76 may be provided on the connection line connecting the signal wiring 62 and the output terminal of the amplifier 77. The detector 5 is not limited to the example shown in FIG. 12, and may have another configuration.

[0088] FIG. 13 is a diagram illustrating another example of the detection unit 5. In the detection unit 5A illustrated in FIG. 13, a signal detection circuit 75A has a plurality of counters 82. The plurality of counters 82 are provided for each block B. That is, one counter 82 is provided for each block B. In each block B, the counter 82 is electrically connected to a first switching circuit 81 and a control circuit 80. The counter 82 receives a control signal S82 from the control circuit 80 and outputs a control signal S81 to the first switching circuit 81 to control switching of the connection destination of the first switching circuit 81.

[0089] In the detection unit 5 shown in FIG. 12, in order for the control circuit 80 to control the first switching circuit 81, the number of bits n (where n is 2) that can switch M1 input terminals is set. n-1 <M1≦2 n13 ) is required. For example, the number of digital wires required in each block B is two when M1=4, three when M1=8, and four when M1=16. In contrast, when a counter 82 is used for each block B as in the detection unit 5A shown in FIG. 13 , it is sufficient to provide one digital wire for each block B. This configuration is particularly effective when the number of digital outputs of the control circuit 80 is small.

[0090] FIG. 14 is a diagram showing another example of the detection unit 5. In the detection unit 5B shown in FIG. 14, the signal detection circuit 75B does not have a first switching circuit 81. In this case, the M signal wirings 62 are not divided into blocks B, and therefore M load resistors 76 and M amplifiers 77 are required corresponding to the M signal wirings 62. An analog switch, for example, is used as the second switching circuit 78. Even with the configurations of the detection unit 5A shown in FIG. 13 and the detection unit 5B shown in FIG. 14, signals can be read out sequentially for each row, as with the detection unit 5 shown in FIG. 12, and therefore bending information can be obtained for each pixel.

[0091] [Bending detection method] Next, the operation of the bending detection device 1 will be described, along with a bending detection method according to this embodiment, with further reference to Figures 15 and 16. Figure 15 is a flowchart showing the operation of the bending detection device 1. Figures 16(a) to 16(e) are diagrams for explaining the operation of the bending detection device 1.

[0092] Hereinafter, as shown in FIG. 12, M2 blocks B are respectively designated as blocks B1 to B M2 and each block B1 to B M2 The signal wiring 62 is divided into signal wirings W1 to W M1 In this case, the signal wirings 62 in the 1st to M1th columns correspond to the signal wirings W1 to W2 of the block B1. M1 The signal wirings 62 in the (M1+1)th to 2M1th columns are the signal wirings W1 to W2 in the block B2. M1 The signal wiring 62 in the (M1(M2-1)+1)th to Mth columns is in block B. M2Signal wiring W1~W M1 In addition, the signals output from the pixels arranged in N rows and M columns are respectively represented as signals D 11 ~D NM It is expressed as:

[0093] 16(a) shows the gate voltage (drive signal S61) applied to the scanning wiring of the first row. FIG. 16(b) shows the relationship between the connection (selection) of the first switching circuit 81 and the output voltage of the amplifier 77 of block B1 when the signal is applied to the scanning wiring of the first row. FIG. 16(c) shows the relationship between the connection (selection) of the first switching circuit 81 and the output voltage of the amplifier 77 of block B2 when the signal is applied to the scanning wiring of the first row. FIG. 16(d) shows the relationship between the connection (selection) of the first switching circuit 81 and the output voltage of the amplifier 77 of block B2 when the signal is applied to the scanning wiring of the first row. M2 16(e) shows the connection (selection) of the second switching circuit 78.

[0094] First, the control circuit 80 controls each of the blocks B1 to B M2 The control circuit 80 then sets the connection destination of the first switching circuit 81 to the signal wiring W1. Then, the control circuit 80 applies an ON voltage to the scanning wiring 61 in the first row and an OFF voltage to the scanning wiring 61 in all other rows (step S11). Next, after waiting for a certain period of time, the control circuit 80 sets the connection destination of the second switching circuit 78 to block B1.

[0095] Next, the control circuit 80 sequentially reads out signals from the signal wirings 62 connected to the pixels in the first row (step S12). First, in a state where an on-voltage is applied to the scanning wirings 61 in the first row, a signal D is output from the signal wiring W1 in the block B1 (i.e., the signal wiring 62 in the first column). 11 The control circuit 80 outputs the signal D 11 is detected (read out) as bending information for the pixel in the first row and first column. 11 may be a signal (first signal) output from the first pixel thin film transistor 21A. Next, the control circuit 80 switches the connection destination of the first switching circuit 81 in the block B1 to the signal wiring W2 (i.e., the signal wiring 62 in the second column). Here, the control circuit 80 switches the connection destination of the first switching circuit 81 in the block B1 to the signal wiring W2 (i.e., the signal wiring 62 in the second column).12 Then, the signal D is transmitted from the signal wiring W1 of the block B2. 1(M1+1) The control circuit 80 outputs the signal D 1(M1+1) is detected as bending information in the 1st row and (M1+1)th column.

[0096] Next, the control circuit 80 switches the connection destination of the first switching circuit 81 in the block B2 to the signal wiring W2 (i.e., the signal wiring 62 in the (M1+2)th column). 1(M1+2) The control circuit 80 switches the connection destination of the second switching circuit 78 to block B3 without reading out the data. The control circuit 80 performs the above operation for blocks B3 and onward in the same manner. Then, the control circuit 80 switches the connection destination of the second switching circuit 78 to block B M2 Switch to Block B M2 Signal wiring W1 to signal D 1(M1(M2-1)+1) Read block B M2 The connection destination of the first switching circuit 81 is switched to the signal wiring W2 (i.e., the signal wiring 62 in the (M1(M2-1)+2)th column). M2 A first process is performed in which the signal of the signal wiring W1 is read out and the connection destination of the first switching circuit 81 to the signal wiring W2 is switched repeatedly for each of the first and second switching circuits.

[0097] Next, the control circuit 80 switches the connection destination of the second switching circuit 78 back to the block B1. Then, the signal D 12 At this point, the control circuit 80 finally outputs the signal D 12 is detected as bending information in the first row and second column. 12 may be a signal (second signal) output from the second pixel thin film transistor 21B. Next, the control circuit 80 switches the connection destination of the first switching circuit 81 in the block B1 to the signal wiring W3 (i.e., the signal wiring 62 in the third column). Here, the control circuit 80 switches the connection destination of the first switching circuit 81 in the block B1 to the signal wiring W3 (i.e., the signal wiring 62 in the third column). 13The control circuit 80 switches the connection destination of the second switching circuit 78 to block B3 without reading out the data. The control circuit 80 performs the above operation for blocks B3 and onward in the same manner. Then, the control circuit 80 switches the connection destination of the second switching circuit 78 to block B M2 Switch to Block B M2 Signal wiring W2 to signal D 1(M1(M2-1)+2) Read block B M2 The connection destination of the first switching circuit 81 is switched to the signal wiring W3 (i.e., the signal wiring 62 in the (M1(M2-1)+3)th column). M2 A second process is performed in which the reading (detection) of the signal on the signal wiring W2 and the connection destination of the first switching circuit 81 to the signal wiring W3 are repeated every time the second process is performed.

[0098] The control circuit 80 controls the blocks B1 to B2 in the same manner as the first and second processes. M2 For each block B1 to B5, the control circuit 80 performs a third process of repeatedly reading out the signal from the signal wiring W3 and switching the connection of the first switching circuit 81 to the signal wiring W4. Similarly, the control circuit 80 performs a fourth process of repeatedly reading out the signal from the signal wiring W4 and switching the connection of the first switching circuit 81 to the signal wiring W5. The control circuit 80 then performs the same process to perform the fourth process of repeatedly reading out the signal from the signal wiring W4 and switching the connection of the first switching circuit 81 to the signal wiring W5. M2 For each signal wiring W M1 The M1 process is repeated to read out the signal D and to switch the connection destination of the first switching circuit 81 to the signal wiring W1. 11 ~D 1M are read out in sequence to obtain bending information for each pixel in one row (step S13).

[0099] Next, the control circuit 80 applies an ON voltage to the scanning wiring 61 in the second row, and an OFF voltage to the scanning wiring 61 in all other rows (step S11). Next, the control circuit 80 waits for a certain period of time, and then switches the connection destination of the second switching circuit 78 to block B1. Next, the control circuit 80 performs the first process to the M2nd process in the same way as when the ON voltage is applied only to the scanning wiring 61 in the first row (steps S12 and S13). In this way, the control circuit 80 obtains bending information for the second row. The control circuit 80 performs the above operations up to the Nth row, thereby obtaining the signals D 21 ~D NM In this way, the control circuit 80 sequentially reads out the signal D 11 ~D NM is detected for each pixel, and bending information for each pixel of one screen (i.e., the overall bending distribution) is obtained. Furthermore, the control circuit 80 repeats the above operation to obtain bending information for multiple screens, i.e., time-dependent bending information for all pixels.

[0100] In this way, the control circuit 80 reads out a signal from the signal wiring 62 to which the first switching circuit 81 is connected, switches the connection of the first switching circuit 81 to the next signal wiring 62, and then, before reading out a signal from the next signal wiring 62, switches the connection of the second switching circuit 78 to another block B and reads out a signal from the first switching circuit 81 in the other block B. The control circuit 80 repeats this operation for each block B, thereby acquiring bending information for n rows. The control circuit 80 then performs the same operation for all rows to acquire bending information for one screen.

[0101] However, the control circuit 80 may reverse the procedure of switching the connection destination of the first switching circuit 81 to the next signal wiring 62 and the procedure of switching the connection destination of the second switching circuit 78 to the next block B. In this case, the control circuit 80 applies an on-voltage to the scan wiring 61 in the nth row, reads out a signal from the signal wiring 62 connected to the first switching circuit 81, and then switches the connection destination of the second switching circuit 78 to the next block B. Thereafter, the control circuit 80 switches the connection destination of the first switching circuit 81 to the next signal wiring 62, and reads out a signal from the signal wiring 62 connected to the first switching circuit 81 in the next block B before reading out a signal from the next signal wiring 62. The control circuit 80 may acquire bending information for n rows by repeating this operation for each block B.

[0102] In the above-described operation, it takes a certain amount of time for the read signal to stabilize after the first switching circuit 81 switches the connection destination to the signal wiring 62. Therefore, as described above, the control circuit 80 applies the ON voltage to the scanning wiring 61 of the first row, and then after a certain time has elapsed, the control circuit 80 applies the signal D 11 (See FIG. 16(b)). This "certain time" may be, for example, at least (M2-1) times the measurement time of the AD converter. In this case, a time of at least (M2-1) times the measurement time of the AD converter can be inserted between the time when the connection destination of the first switching circuit 81 is switched to the signal wiring 62 and the time when the signal is measured, thereby ensuring time for the signal to stabilize. This can improve the accuracy of signal detection.

[0103] As described above, in the above-described operation, before reading a signal from the signal wiring 62 immediately after switching in a certain block B, the control circuit 80 reads a signal from the switched signal wiring 62 in another block B at least once (M2-1 times in this embodiment) (see FIGS. 16(b) to 16(d)). While it takes some time for the signal from the signal wiring 62 immediately after switching to stabilize, the signal from the switched signal wiring 62 (i.e., the signal wiring 62 a certain amount of time has passed since switching) is in a stable state. Therefore, after switching the signal wiring 62 in a certain block B, the control circuit 80 does not wait until the signal from the switched signal wiring 62 stabilizes, but reads a signal from the switched signal wiring 62 in another block B while the signal from the switched signal wiring 62 stabilizes. This allows for efficient reading of signals from each signal wiring 62. Furthermore, reading signals in a stable state can improve signal detection accuracy.

[0104] [Effects of the first embodiment] The effects achieved by the bending sensor 10 and bending detection device 1 according to the present embodiment described above will now be described. When bending is applied to the bending sensor 10, stress is applied to the piezoelectric layer 30, generating a voltage in the piezoelectric layer 30, which in turn generates a potential difference between the counter electrode 35 and the pixel electrode 25 (i.e., a voltage is generated in the pixel electrode 25). The pixel electrodes 25 are spaced apart from each other in a planar view and are electrically insulated from each other. Therefore, the voltage of the first pixel electrode 25A and the voltage of the second pixel electrode 25B change independently of each other. Therefore, by separately detecting a signal indicating the voltage of the first pixel electrode 25A and a signal indicating the voltage of the second pixel electrode 25B using the first pixel thin film transistor 21A and the second pixel thin film transistor 21B, bending information at the position of the first pixel electrode 25A and bending information at the position of the second pixel electrode 25B can be separately obtained. This allows the local bending state at the position of each pixel electrode 25 to be grasped. Therefore, the bending sensor 10 according to this embodiment makes it possible to grasp the bending state in detail.

[0105] In this embodiment, the plurality of pixel electrodes 25 are arranged in a matrix. This allows for more localized bending conditions to be grasped by acquiring bending information for each pixel electrode 25. As a result, it becomes possible to grasp the bending condition of the bending sensor 10 in more detail.

[0106] [Second embodiment] Next, a bending sensor according to a second embodiment will be described. In the second embodiment, the shape of the pixel electrode is different from that of the first embodiment. In the following second embodiment, the description of the same parts as in the first embodiment will be omitted as appropriate, and the differences from the first embodiment will be mainly described.

[0107] FIG. 17 is a plan view of a bending sensor 10A according to a second embodiment. FIG. 18(a) is a cross-sectional view of the bending sensor 10A taken along line A2-A2 in FIG. 17. FIG. 18(b) is a cross-sectional view of the bending sensor 10A taken along line A3-A3 in FIG. 17. In the bending sensor 10A, the multiple pixel electrodes 25 include multiple first pixel electrodes 25A (first electrodes) having a shape extending in the Y direction and multiple second pixel electrodes 25B (second electrodes) having a shape extending in the X direction. "A shape extending in the Y direction" means a shape whose longitudinal direction is the Y direction. "A shape extending in the X direction" means a shape whose longitudinal direction is the X direction.

[0108] The first pixel electrode 25A has, for example, a rectangular shape with the Y direction as its longitudinal direction and the X direction as its transverse direction (i.e., a rectangular shape that is long in the Y direction and short in the X direction). Therefore, the length of the first pixel electrode 25A in the Y direction is longer than its width in the X direction. The width of the first pixel electrode 25A in the X direction may be constant, for example, at each position of the first pixel electrode 25A along the Y direction. The second pixel electrode 25B has, for example, a rectangular shape with the X direction as its longitudinal direction and the Y direction as its transverse direction (i.e., a rectangular shape that is long in the X direction and short in the Y direction). Therefore, the length of the second pixel electrode 25B in the X direction is longer than its width in the Y direction. The width of the second pixel electrode 25B in the Y direction may be constant, for example, at each position of the second pixel electrode 25B along the X direction.

[0109] When the second pixel electrode 25B is rotated by 90° in a plan view, the shape of the second pixel electrode 25B becomes the same as that of the first pixel electrode 25A. Therefore, the length of the first pixel electrode 25A in the Y direction is longer than the width of the second pixel electrode 25B in the Y direction, and the length of the second pixel electrode 25B in the X direction is longer than the width of the first pixel electrode 25A in the X direction. Also, similar to the first embodiment, each pixel electrode 25 has a higher Young's modulus than the inter-pixel region 26. As shown in FIG. 17, each first pixel electrode 25A and each second pixel electrode 25B are alternately arranged, for example, along the X direction and the Y direction.

[0110] In the examples shown in FIGS. 18(a) and 18(b), the neutral plane NP is located on the back surface 25b of each pixel electrode 25. Above the neutral plane NP, a layer including each pixel electrode 25, the piezoelectric layer 30, and the counter electrode 35 are located. Therefore, the entire pixel electrode 25 and the entire inter-pixel region 26 are located on the same side as the piezoelectric layer 30 with respect to the neutral plane NP. Note that at least a part of the pixel electrode 25 and at least a part of the inter-pixel region 26 may be located on the same side as the piezoelectric layer 30 with respect to the neutral plane NP.

[0111] For simplicity of understanding, when the neutral plane NP coincides with the back surface 25b of the pixel electrode 25, only the portion above the neutral plane NP where stress in the same direction as the piezoelectric layer 30 is applied is considered. Here, let the pitch between adjacent pixels be P, the length of the long side of the pixel electrode 25 be U, the length of the short side of the pixel electrode 25 be V, the thickness of each of the pixel electrode 25 and the inter-pixel region 26 be T1, the Young's modulus of the pixel electrode 25 be E11, the Young's modulus of the inter-pixel region 26 be E12, the thickness of the piezoelectric layer 30 be T2, the Young's modulus of the piezoelectric layer 30 be E2, the thickness of the counter electrode 35 be T3, and the Young's modulus of the counter electrode 35 be E3. In this case, as shown in FIGS. 18(a) and 18(b), the width of the first pixel electrode 25A in the X direction is represented by V. And the length of the second pixel electrode 25B in the X direction is represented by U (V << U), which is longer than V. The length U may be set to be equal to the pixel pitch P or shorter than the pitch P.

[0112] When the parameters are set as described above, if the composite Young's modulus of the pixel electrode 25, the piezoelectric layer 30, and the counter electrode 35 is EC1, and the composite Young's modulus of the region 26 between the pixel electrodes, the piezoelectric layer 30, and the counter electrode 35 is EC2, the composite Young's modulus EC1 and the composite Young's modulus EC2 are expressed by the following formulas (15) and (16), respectively.

Equation

Equation

Equation

[0113] On the other hand, when a stress S in the X direction is applied above the neutral plane NP in the cross section shown in FIG. 18(b), if the displacement in the X direction generated in the bending sensor 10A is ΔL2, the displacement ΔL2 is expressed by the following formula (18).

Equation

[0114] 17, the region RA where the pixel electrodes 25 exist in the cross section shown in FIG. 18(a) is indicated by diagonal hatching, and the region RB where the pixel electrodes 25 exist in the cross section shown in FIG. 18(b) is indicated by dotted hatching. In the region RA, (U+V) / 2P (i.e., the ratio of the total length of the pixel electrodes 25 in the X direction to the pitch P of two pixels) is large, so a large voltage is generated when the bending sensor 10A is bent in the X direction. On the other hand, in the region RB, V / 2P is smaller than (U+V) / 2P, so a smaller voltage is generated when the bending sensor 10A is bent in the X direction than in the region RA. Thus, when the bending sensor 10A is bent in the X direction, the second pixel electrode 25B, which is entirely occupied by the region RA, generates more charge, while the first pixel electrode 25A, which is mostly occupied by the region RB, generates less charge. Therefore, the voltage generated in the first pixel electrode 25A is smaller than the voltage generated in the second pixel electrode 25B. In other words, the second pixel electrode 25B has a higher sensitivity to X-bending than the first pixel electrode 25A. Even when the neutral plane NP does not coincide with the rear surface 25b of the pixel electrode 25, the same effect can be obtained.

[0115] Similarly, when the bending sensor 10A is bent in the Y direction, the first pixel electrode 25A generates a large amount of charge, while the second pixel electrode 25B generates a small amount of charge, so the first pixel electrode 25A generates a larger voltage than the second pixel electrode 25B. In other words, it can be said that the first pixel electrode 25A has a higher sensitivity to Y bending than the second pixel electrode 25B. When the voltage of the second pixel electrode 25B is V X and the voltage of the first pixel electrode 25A is V YThen, it can be formulated in the same way as the above-mentioned equations (6) and (7), and the magnitude of X bending B X and the magnitude of Y bending B Y is required.

[0116] In this embodiment, it is also possible to assume that two first pixel electrodes 25A and two second pixel electrodes 25B are arranged in one pixel, that is, four sub-pixels are arranged in one pixel. In this case, the voltage V X is the average value of the voltages obtained from the two second pixel electrodes 25B, and the voltage V Y may be the average value of the voltages obtained from the two first pixel electrodes 25A. The number of pixels (sub-pixels) arranged in one pixel does not have to be four, and may be any number such as two, three, six, or eight.

[0117] Note that equations (17) and (18) are based on the assumption that the Young's modulus E11 of the pixel electrode 25 is greater than the Young's modulus E12 of the inter-pixel electrode region 26. Therefore, the voltage relationship between the region RA and the region RB described above is derived by utilizing the difference between the Young's modulus E11 of the pixel electrode 25 and the Young's modulus E12 of the inter-pixel electrode region 26. To utilize this difference in Young's modulus, it is preferable that most of the pixel electrode 25 and most of the inter-pixel electrode region 26 are located on the same side of the neutral plane NP as the piezoelectric layer 30. Furthermore, when the composite Young's modulus EC1 and the composite Young's modulus EC2 are considered when the bending sensor 10A is bent, the equations become more complicated. However, the pixel electrode 25 is displaced more than the inter-pixel electrode region 26, and the larger (U + V) is, the larger the voltage becomes.

[0118] 19(a) is a cross-sectional view showing the bending sensor 10A bent in a convex shape in the cross section shown in FIG. 18(a). FIG. 19(b) is a cross-sectional view showing the bending sensor 10A bent in a convex shape in the cross section shown in FIG. 18(b). In FIGS. 19(a) and 19(b), the bending sensor 10A is bent in the X-direction, causing the bending sensor 10A to bend so as to be convex upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is located above the neutral plane NP, bending the bending sensor 10A in a convex shape as shown in FIGS. 19(a) and 19(b) applies a tensile stress in the X-direction to the piezoelectric layer 30.

[0119] As shown in FIG. 19(a), a tensile stress SS1A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the first pixel electrode 25A, and a tensile stress SS1A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the second pixel electrode 25B. A tensile stress SS1B in the X direction is applied to the piezoelectric layer 30 at the position of the region RB of the first pixel electrode 25A, where |SS1A|>>|SS1B|. In this case, as can be seen from FIG. 17, a voltage corresponding mainly to the tensile stress SS1B is generated in the first pixel electrode 25A, and a voltage corresponding to the tensile stress SS1A is generated in the second pixel electrode 25B. In this embodiment, the tensile stress SS1B is smaller than the tensile stress SS1A, and therefore the absolute value of the voltage generated in the first pixel electrode 25A is smaller than the absolute value of the voltage generated in the second pixel electrode 25B.

[0120] 20(a) is a cross-sectional view showing the bending sensor 10A bent into a concave shape in the cross section shown in FIG. 18(a). FIG. 20(b) is a cross-sectional view showing the bending sensor 10A bent into a concave shape in the cross section shown in FIG. 18(b). In FIGS. 20(a) and 20(b), the bending sensor 10A is bent in the X-direction, causing the bending sensor 10A to bend so as to be concave upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is located above the neutral plane NP, bending the bending sensor 10A into a concave shape as shown in FIGS. 20(a) and 20(b) applies compressive stress in the X-direction to the piezoelectric layer 30.

[0121] As shown in FIG. 20(a), a compressive stress SS2A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the first pixel electrode 25A, and a compressive stress SS2A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the second pixel electrode 25B. A compressive stress SS2B in the X direction is applied to the piezoelectric layer 30 at the position of the region RB of the first pixel electrode 25A, where |SS2A|>>|SS2B|. In this case, a voltage corresponding mainly to the compressive stress SS2B is generated in the first pixel electrode 25A, and a voltage corresponding to the compressive stress SS2A is generated in the second pixel electrode 25B. In this embodiment, the compressive stress SS2B is smaller than the compressive stress SS2A, and therefore the absolute value of the voltage generated in the first pixel electrode 25A is smaller than the absolute value of the voltage generated in the second pixel electrode 25B. Note that the voltage generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in Figures 20(a) and 20(b) is opposite to the voltage generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in Figures 19(a) and 19(b).

[0122] By configuring the element in this way, it is possible to detect the magnitude of bending in the X direction and the magnitude of bending in the Y direction independently, even when a non-stretched film or a biaxially stretched film (for example, non-stretched PVDF) is used as the piezoelectric layer 30. To further improve accuracy, the voltage output from the thin film transistor connected to the second pixel electrode 25B that is longer in the X direction can be set to V X and the voltage V output from the thin film transistor connected to the first pixel electrode 25A that is long in the Y direction is Y Let the magnitude of X bending be B X The magnitude of the Y bending is B Y Then, the voltage V X and voltage V Y can be formulated as the above-mentioned equations (6) and (7), respectively, where k1 and k2 are constants that satisfy k1>>k2.

[0123] Therefore, if k1 and k2 are experimentally determined, the magnitude of X bending B X , and the magnitude of Y bending B YEquations (8) and (9) can be derived from equations (6) and (7). In this way, even when the bending sensor 10A according to this embodiment is used, the magnitude of bending in the X direction B X and the magnitude of bending in the Y direction B Y It is possible to detect the and independently.

[0124] [Effects of the second embodiment] The effects obtained by the bending sensor 10A according to the present embodiment described above will now be described. In this embodiment, the first pixel electrode 25A has a shape extending in the Y direction, and the second pixel electrode 25B has a shape extending in the X direction. Therefore, the first pixel electrode 25A is strongly affected by Y bending, and the second pixel electrode 25B is strongly affected by X bending. Therefore, by detecting a signal indicating the voltage of the first pixel electrode 25A as bending information in the Y direction and a signal indicating the voltage of the second pixel electrode 25B as bending information in the X direction, it is possible to distinguish between the Y bending state and the X bending state. This makes it possible to grasp the bending state of the bending sensor 10A in more detail.

[0125] In this embodiment, the pixel electrode 25 has a higher Young's modulus than the inter-pixel electrode region 26. Therefore, the inter-pixel electrode region 26 is more easily stretched than the pixel electrode 25. Therefore, the stress applied to the piezoelectric layer 30 at the pixel electrode 25 is greater than the stress applied to the piezoelectric layer 30 at the inter-pixel electrode region 26. In this case, the stress at the positions of the first pixel electrodes 25A, which are more numerous in the Y direction, is greater during Y bending, while the stress at the positions of the second pixel electrodes 25B, which are more numerous in the X direction, is greater during X bending. That is, the voltage of the first pixel electrode 25A is greater during Y bending, and the voltage of the second pixel electrode 25B is greater during X bending. Therefore, the above-described configuration can more reliably realize a situation in which the first pixel electrode 25A is more strongly affected by Y bending and the second pixel electrode 25B is more strongly affected by X bending. This makes it possible to more reliably distinguish and grasp the Y bending state and the X bending state.

[0126] In this embodiment, the inter-pixel electrode region 26 is made of an electrically insulating adhesive. In this case, it is possible to easily achieve a configuration in which the Young's modulus of the pixel electrodes 25 is higher than that of the inter-pixel electrode region 26. Furthermore, by providing an electrically insulating adhesive between the pixel electrodes 25, it is possible to fix the positional relationship between the pixel electrodes 25 while ensuring electrical insulation between the pixel electrodes 25.

[0127] In this embodiment, all of the pixel electrodes 25 and all of the inter-pixel electrode regions 26 are disposed on the same side of the neutral plane NP as the piezoelectric layer 30. In this case, by utilizing the magnitude relationship between the Young's modulus of the pixel electrodes 25 and the Young's modulus of the inter-pixel electrode regions 26, it is possible to more reliably realize an aspect in which the first pixel electrode 25A is strongly influenced by Y bending and the second pixel electrode 25B is strongly influenced by X bending. This makes it possible to more reliably distinguish and grasp the Y bending state and the X bending state.

[0128] In this embodiment, the first pixel electrodes 25A and the second pixel electrodes 25B are arranged alternately in a matrix. In this case, by acquiring bending information for each pixel electrode 25, it is possible to grasp the bending state more locally. Furthermore, by arranging the first pixel electrodes 25A and the second pixel electrodes 25B alternately, it is possible to disperse the first pixel electrodes 25A for acquiring bending information in the Y direction and the second pixel electrodes 25B for acquiring bending information in the X direction, thereby preventing bias in the acquired bending state information.

[0129] In the bending sensor 10 according to the first embodiment, in order to independently detect bending information in the X direction and bending information in the Y direction, two bending sensors 10 each having a uniaxially stretched piezoelectric layer 30 had to be prepared and the two bending sensors 10 had to be stacked so that the stretching directions of the piezoelectric layers 30 were perpendicular to each other. However, in the second embodiment, bending information in the X direction and bending information in the Y direction can be independently detected using a single bending sensor 10A having a biaxially stretched or non-stretched piezoelectric layer 30. Furthermore, in the second embodiment, instead of the thin-film transistor array 20, a thin-film transistor array 201 may be used, or a thin-film transistor array having another circuit configuration may be used.

[0130] [Modification of the second embodiment] The shapes of the first pixel electrode 25A and the second pixel electrode 25B are not limited to the example of the second embodiment described above. FIGS. 21(a) to 21(c), 22(a), and 22(b) are plan views showing other examples of the bending sensor 10A according to the second embodiment. As in the bending sensor 101A shown in FIG. 21(a), the first pixel electrode 251A and the second pixel electrode 251B may each have a cross shape. In this case, the first pixel electrode 251A has a portion 251b extending in the X direction in addition to a portion 251a extending in the Y direction. The portion 251b is disposed so as to intersect with the center of the portion 251a, for example. The length of the portion 251b in the X direction is set shorter than the length of the portion 251a in the Y direction. Similarly, the second pixel electrode 251B has a portion 251d extending in the Y direction in addition to a portion 251c extending in the X direction. The portion 251d is disposed, for example, so as to intersect with the center of the portion 251c. The length of the portion 251d in the Y direction is set to be shorter than the length of the portion 251c in the X direction.

[0131] As in the bending sensor 102A shown in FIG. 21(b), the first pixel electrode 252A may have an elliptical (oval) shape extending in the Y direction. Similarly, the second pixel electrode 252B may have an elliptical (oval) shape extending in the X direction. Alternatively, as in the bending sensor 103A shown in FIG. 21(c), the first pixel electrode 253A may have an isosceles triangular shape extending in the Y direction. In this case, the first pixel electrode 253A may be arranged so that the apex of the isosceles triangle faces one side in the Y direction, or so that the apex of the isosceles triangle faces the other side in the Y direction. Similarly, the second pixel electrode 253B may have an isosceles triangular shape extending in the X direction. In this case, the second pixel electrode 253B may be arranged so that the apex of the isosceles triangle faces one side in the X direction, or so that the apex of the isosceles triangle faces the other side in the X direction.

[0132] As in the bending sensor 104A shown in FIG. 22(a), the width of the first pixel electrode 254A in the X direction may vary at each position on the first pixel electrode 254A along the Y direction. Specifically, the width of the first pixel electrode 254A in the X direction may be smallest at the center of the first pixel electrode 254A in the Y direction, and gradually increase as the distance from the center increases in the Y direction. The width of the second pixel electrode 254B in the Y direction may vary at each position on the second pixel electrode 254B along the X direction. Specifically, the width of the second pixel electrode 254B in the Y direction may be smallest at the center of the second pixel electrode 254B in the X direction, and gradually increase as the distance from the center increases in the X direction.

[0133] As in the bending sensor 105A shown in FIG. 22(b), the first pixel electrode 255A and the second pixel electrode 255B do not have to be arranged so as to fit within one pixel, but may extend outside the pixel. In this case, the first pixel electrode 255A extends in the Y direction beyond the boundary line BL to a position where it does not contact the second pixel electrode 255B adjacent in the Y direction. Similarly, the second pixel electrode 255B extends in the X direction beyond the boundary line BL to a position where it does not contact the first pixel electrode 255A adjacent in the X direction. Furthermore, the multiple pixel electrodes 25 may include a third pixel electrode other than the first pixel electrode 25A and the second pixel electrode 25B. In this case, the third pixel electrode may extend in a direction inclined with respect to both the X direction and the Y direction. The bending sensor 105A described above can also achieve the same effects as the bending sensor 10A according to the second embodiment.

[0134] [Third embodiment] Next, a bending sensor according to a third embodiment will be described. In the third embodiment, the shape of the pixel electrode and the shape of the counter electrode are different from those of the first embodiment. In the following third embodiment, the description of the same points as in the first embodiment will be omitted as appropriate, and the points different from the first embodiment will be mainly described.

[0135] FIG. 23 is a plan view of a bending sensor 10B according to a third embodiment. FIG. 24(a) is a cross-sectional view of the bending sensor 10B taken along line A4-A4 in FIG. 23. FIG. 24(b) is a cross-sectional view of the bending sensor 10B taken along line A5-A5 in FIG. 23. In the bending sensor 10B, the pixel electrodes 25 include a plurality of first pixel electrodes 25A (first electrodes) extending in the Y direction and a plurality of second pixel electrodes 25B (second electrodes) extending in the X direction. The "shape extending in the Y direction" refers to a shape whose longitudinal direction is the Y direction. The "shape extending in the X direction" refers to a shape whose longitudinal direction is the X direction. As shown in FIG. 23, the first pixel electrodes 25A and the second pixel electrodes 25B are alternately arranged along the X direction and the Y direction.

[0136] The first pixel electrode 25A has, for example, a rectangular shape with the Y direction as its longitudinal direction and the X direction as its transverse direction (i.e., a rectangular shape that is long in the Y direction and short in the X direction). Therefore, the length of the first pixel electrode 25A in the Y direction is longer than its width in the X direction. The width of the first pixel electrode 25A in the X direction may be constant, for example, at each position of the first pixel electrode 25A along the Y direction. The second pixel electrode 25B has, for example, a rectangular shape with the X direction as its longitudinal direction and the Y direction as its transverse direction (i.e., a rectangular shape that is long in the X direction and short in the Y direction). Therefore, the length of the second pixel electrode 25B in the X direction is longer than its width in the Y direction. The width of the second pixel electrode 25B in the Y direction may be constant, for example, at each position of the second pixel electrode 25B along the X direction.

[0137] When the second pixel electrode 25B is rotated 90° in a plan view, the shape of the second pixel electrode 25B becomes the same as that of the first pixel electrode 25A. Therefore, the length in the Y direction of the first pixel electrode 25A is longer than the width in the Y direction of the second pixel electrode 25B, and the length in the X direction of the second pixel electrode 25B is longer than the width in the X direction of the first pixel electrode 25A. Furthermore, similar to the first embodiment, each pixel electrode 25 may have a higher Young's modulus than each inter-pixel electrode region 26.

[0138] Furthermore, in the third embodiment, the counter electrode 35 has a lattice shape in plan view. The counter electrode 35 has a plurality of first extension portions 35A extending in the Y direction and a plurality of second extension portions 35B extending in the X direction. In plan view, each first extension portion 35A extends linearly along the Y direction so as to encompass each first pixel electrode 25A, and is spaced apart at regular intervals along the X direction. The state in which the first extension portion 35A encompasses the first pixel electrode 25A refers to a state in which the first pixel electrode 25A is contained within the first extension portion 35A in plan view.

[0139] Therefore, the width of the first extension portion 35A in the X direction is equal to or greater than the width of the first pixel electrode 25A in the X direction. The length of the first extension portion 35A in the Y direction is greater than the length of the first pixel electrode 25A in the Y direction. The first extension portion 35A extends continuously in the Y direction from one end to the other end of the flexible substrate 15. Note that the first extension portion 35A does not necessarily have to encompass the first pixel electrode 25A; the first extension portion 35A may overlap the first pixel electrode 25A in a planar view. Therefore, the first pixel electrode 25A may be disposed so as to extend beyond the first extension portion 35A in a planar view, or the width of the first extension portion 35A in the X direction may be smaller than the width of the first pixel electrode 25A in the X direction.

[0140] In a plan view, each second extension portion 35B extends linearly along the X direction so as to encompass each second pixel electrode 25B, and is spaced apart at regular intervals along the Y direction. Each second extension portion 35B is connected to each first extension portion 35A so as to be perpendicular to the first extension portion 35A. Therefore, each first extension portion 35A and each second extension portion 35B are arranged in a grid pattern in the X direction and the Y direction. The state in which the second extension portion 35B encompasses the second pixel electrode 25B refers to the state in which the second pixel electrode 25B is contained within the second extension portion 35B in a plan view.

[0141] Therefore, the Y-direction width of the second extension portion 35B is equal to or greater than the Y-direction width of the second pixel electrode 25B. The X-direction length of the second extension portion 35B is greater than the X-direction length of the second pixel electrode 25B. The second extension portion 35B extends continuously in the X-direction from one end to the other end of the flexible substrate 15. Note that the second extension portion 35B does not necessarily have to encompass the second pixel electrode 25B; the second extension portion 35B may overlap the second pixel electrode 25B in a planar view. Therefore, the second pixel electrode 25B may be disposed so as to extend beyond the second extension portion 35B in a planar view, or the Y-direction width of the second extension portion 35B may be smaller than the Y-direction width of the second pixel electrode 25B.

[0142] As shown in FIGS. 24(a) and 24(b), the neutral plane NP is located on the back surface 25b of each pixel electrode 25. Above the neutral plane NP, a layer including each pixel electrode 25, a piezoelectric layer 30, and a counter electrode 35 are located. Therefore, the entire pixel electrode 25 and the entire inter-pixel electrode region 26 are located on the same side of the piezoelectric layer 30 with respect to the neutral plane NP. Note that at least a part of the pixel electrode 25 and at least a part of the inter-pixel electrode region 26 may be located on the same side of the piezoelectric layer 30 with respect to the neutral plane NP.

[0143] For easy understanding, when the neutral plane NP coincides with the back surface 25b of the pixel electrode 25, only the portion above the neutral plane NP where stress in the same direction as the piezoelectric layer 30 is applied is considered. Here, let the pitch between adjacent pixels be P, the length of the long side of the pixel electrode 25 be U, the length of the short side of the pixel electrode 25 be V, the thicknesses of the pixel electrode 25 and the inter-pixel electrode region 26 be T1, the Young's modulus of the pixel electrode 25 be E11, the Young's modulus of the inter-pixel electrode region 26 be E12, the thickness of the piezoelectric layer 30 be T2, the Young's modulus of the piezoelectric layer 30 be E2, the thickness of the counter electrode 35 be T3, and the Young's modulus of the counter electrode 35 be E3. In this case, as shown in FIGS. 24(a) and 24(b), the length of the first pixel electrode 25A in the X direction is represented by V, and the length of the second pixel electrode 25B in the X direction is represented by U (V << U) which is longer than V. The length U may be equal to the pixel pitch P or set shorter than the pitch P.

[0144] When the above parameters are set as described above, let the composite Young's modulus of the pixel electrode 25, the piezoelectric layer 30, and the counter electrode 35 be EC1, the composite Young's modulus of the inter-pixel electrode region 26, the piezoelectric layer 30, and the counter electrode 35 be EC2, and the composite Young's modulus of the inter-pixel electrode region 26 and the piezoelectric layer 30 be EC3. Then, the composite Young's modulus EC1 and the composite Young's modulus EC2 are represented by the above-described formulas (15) and (16), respectively. Also, the composite Young's modulus EC3 is represented by the following formula (19).

Equation

[0145] 24(a) above the neutral plane NP, if stress S (tensile stress or compressive stress) is applied in the X direction, and if the displacement in the X direction generated in the bending sensor 10B is ΔL1, then the displacement ΔL1 is expressed by the above-mentioned formula (17). On the other hand, if stress S is applied in the X direction above the neutral plane NP in the cross section shown in FIG. 24(b) above the neutral plane NP, and if the displacement in the X direction generated in the bending sensor 10B is ΔL2, then the displacement ΔL2 is expressed by the following formula (20).

number

[0146] 23, the region RA where the counter electrode 35 exists in the cross section shown in Fig. 24(a) is indicated by diagonal hatching, and the region RB where the counter electrode 35 exists in the cross section shown in Fig. 24(b) is indicated by dotted hatching. In the region RA, the counter electrode 35 is located over the entire region. Therefore, in the region RA, a large voltage is generated when the bending sensor 10B is bent in the X direction.

[0147] On the other hand, in the region RB, the counter electrode 35 is present only in a small portion. Therefore, in the region RB, the voltage generated when the bending sensor 10B is bent in the X direction is smaller than that generated in the region RA. Thus, when the bending sensor 10B is bent in the X direction, a large amount of charge is generated in the second pixel electrode 25B, which occupies the entire region RA, while a small amount of charge is generated in the first pixel electrode 25A, which occupies most of the region RB. Therefore, the voltage generated in the first pixel electrode 25A is smaller than the voltage generated in the second pixel electrode 25B. In other words, the second pixel electrode 25B extending in the X direction is more sensitive to X bending than the first pixel electrode 25A extending in the Y direction. The same effect can be achieved even when the neutral plane NP does not coincide with the rear surface 25b of the pixel electrode 25.

[0148] Similarly, when bending sensor 10B in the Y direction, the first pixel electrode 25A extending in the Y direction generates a large amount of charge, while the second pixel electrode 25B extending in the X direction generates a small amount of charge. Therefore, the voltage generated by first pixel electrode 25A is larger than that generated by second pixel electrode 25B. In other words, it can be said that first pixel electrode 25A is more sensitive to Y bending than second pixel electrode 25B. When the voltage of second pixel electrode 25B is V X and the voltage of the first pixel electrode 25A is V Y Then, it can be formulated in the same way as the above-mentioned equations (6) and (7), and the magnitude of X bending B X and the magnitude of Y bending B Y is required.

[0149] In this embodiment, it is also possible to assume that two first pixel electrodes 25A and two second pixel electrodes 25B are arranged in one pixel, that is, four sub-pixels are arranged in one pixel. In this case, the voltage V X is the average value of the voltages obtained from the two second pixel electrodes 25B, and the voltage V Y may be the average value of the voltages obtained from the two first pixel electrodes 25A. The number of pixels (sub-pixels) arranged in one pixel does not have to be four, and may be any number such as two, three, six, or eight.

[0150] FIG. 25(a) is a cross-sectional view showing the bending sensor 10B bent in a convex shape in the cross section shown in FIG. 24(a). FIG. 25(b) is a cross-sectional view showing the bending sensor 10B bent in a convex shape in the cross section shown in FIG. 24(b). In FIGS. 25(a) and 25(b), bending the bending sensor 10B in the X direction causes the bending sensor 10B to bend so that it is convex upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is located above the neutral plane NP, bending the bending sensor 10B in a convex shape as shown in FIGS. 25(a) and 25(b) applies a tensile stress in the X direction to the piezoelectric layer 30.

[0151] As shown in FIG. 25(a), a tensile stress SS1A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the first pixel electrode 25A, and a tensile stress SS1A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the second pixel electrode 25B. A tensile stress SS1B in the X direction is applied to the piezoelectric layer 30 at the position of the region RB of the first pixel electrode 25A, where |SS1A|>>|SS1B|. In this case, a voltage corresponding mainly to the tensile stress SS1B is generated in the first pixel electrode 25A, and a voltage corresponding to the tensile stress SS1A is generated in the second pixel electrode 25B. In this embodiment, the tensile stress SS1B is smaller than the tensile stress SS1A, and therefore the absolute value of the voltage generated in the first pixel electrode 25A is smaller than the absolute value of the voltage generated in the second pixel electrode 25B.

[0152] 26(a) is a cross-sectional view showing the bending sensor 10B bent concavely in the cross section shown in FIG. 24(a). FIG. 26(b) is a cross-sectional view showing the bending sensor 10B bent concavely in the cross section shown in FIG. 24(b). In FIGS. 26(a) and 26(b), the bending sensor 10B is bent in the X-direction, causing the bending sensor 10B to bend concavely upward in the XZ cross section. In the present embodiment, when the piezoelectric layer 30 is located above the neutral plane NP, bending the bending sensor 10B concavely as shown in FIGS. 26(a) and 26(b) applies compressive stress in the X-direction to the piezoelectric layer 30.

[0153] As shown in FIG. 26(a), a compressive stress SS2A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the first pixel electrode 25A, and a compressive stress SS2A in the X direction is applied to the piezoelectric layer 30 at the position of the region RA of the second pixel electrode 25B. A compressive stress SS2B in the X direction is applied to the piezoelectric layer 30 at the position of the region RB of the first pixel electrode 25A, where |SS2A|>>|SS2B|. In this case, a voltage corresponding mainly to the compressive stress SS2B is generated in the first pixel electrode 25A, and a voltage corresponding to the compressive stress SS2A is generated in the second pixel electrode 25B. In this embodiment, the compressive stress SS2B is smaller than the compressive stress SS2A. Therefore, the absolute value of the voltage generated in the first pixel electrode 25A is smaller than the absolute value of the voltage generated in the second pixel electrode 25B. In addition, the voltage generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in Figures 26(a) and 26(b) is opposite in direction to the voltage generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in Figures 25(a) and 25(b).

[0154] By configuring the element in this way, it is possible to detect the magnitude of bending in the X direction and the magnitude of bending in the Y direction independently, even when a non-stretched film or a biaxially stretched film (for example, non-stretched PVDF) is used as the piezoelectric layer 30. To further improve accuracy, the voltage output from the thin film transistor connected to the second pixel electrode 25B that is longer in the X direction can be set to V Xand the voltage V output from the thin film transistor connected to the first pixel electrode 25A that is long in the Y direction is Y Let the magnitude of X bending be B X The magnitude of the Y bending is B Y Then, the voltage V X and voltage V Y can be formulated as the above-mentioned equations (6) and (7), respectively. Therefore, if k1 and k2 are experimentally determined, the magnitude of X bending B X , and the magnitude of Y bending B Y The above-mentioned formulas (8) and (9) can be derived from formulas (6) and (7). In this way, even when the bending sensor 10B according to this embodiment is used, the magnitude of bending in the X direction B X and the magnitude of bending in the Y direction B Y It is possible to detect the and independently.

[0155] [Effects of the third embodiment] The effects achieved by the bending sensor 10B according to the present embodiment described above will now be described. In this embodiment, the first pixel electrode 25A has a shape extending in the Y direction, and the second pixel electrode 25B has a shape extending in the X direction. Therefore, as described above, the first pixel electrode 25A is strongly affected by the Y bending, and the second pixel electrode 25B is strongly affected by the X bending. Furthermore, in this embodiment, the counter electrode 35 has a first extension portion 35A extending in the Y direction so as to encompass the first pixel electrode 25A, and a second extension portion 35B extending in the X direction so as to encompass the second pixel electrode 25B. The portion where the counter electrode 35 is not located is more likely to stretch than the portion where the counter electrode 35 is located. Therefore, the stress in the portion where the counter electrode 35 is located is greater than the stress in the portion where the counter electrode 35 is not located.

[0156] In this case, the stress at the position of the first pixel electrode 25A where the first extension portion 35A of the counter electrode 35 is located increases during Y bending, and the stress at the position of the second pixel electrode 25B where the second extension portion 35B of the counter electrode 35 is located increases during X bending. In other words, the voltage of the first pixel electrode 25A exhibits a large value during Y bending because the counter electrode 35 is located on the first pixel electrode 25A. The voltage of the second pixel electrode 25B exhibits a large value during X bending because the counter electrode 35 is located on the second pixel electrode 25B. Therefore, in this embodiment, the first pixel electrode 25A is more strongly affected by Y bending, and the second pixel electrode 25B is more strongly affected by X bending.

[0157] Therefore, the first pixel electrode 25A is more strongly affected by the Y-direction bending, and the second pixel electrode 25B is more strongly affected by the X-direction bending. Therefore, by detecting a signal indicating the voltage of the first pixel electrode 25A as bending information in the Y direction and detecting a signal indicating the voltage of the second pixel electrode 25B as bending information in the X direction, it is possible to distinguish between the Y-direction bending state and the X-direction bending state. This makes it possible to grasp the bending state of the bending sensor 10B in more detail.

[0158] In this embodiment, the first pixel electrodes 25A and the plurality of second pixel electrodes 25B are arranged in a matrix so as to alternate along the Y and X directions. In this case, by acquiring bending information for each pixel electrode 25, it is possible to grasp a more local bending state. Furthermore, by arranging the first pixel electrodes 25A and the second pixel electrodes 25B alternately, it is possible to disperse the first pixel electrodes 25A for acquiring bending information in the Y direction and the second pixel electrodes 25B for acquiring bending information in the X direction, thereby preventing bias in the acquired bending state information.

[0159] In the bending sensor 10 according to the first embodiment, in order to independently detect bending information in the X direction and bending information in the Y direction, two bending sensors 10 each having a uniaxially stretched piezoelectric layer 30 had to be prepared and the two bending sensors 10 had to be stacked so that the stretching directions of the piezoelectric layers 30 were perpendicular to each other. However, in the third embodiment, bending information in the X direction and bending information in the Y direction can be independently detected using a single bending sensor 10B having a biaxially stretched or non-stretched piezoelectric layer 30. Also, in the third embodiment, instead of the thin-film transistor array 20, a thin-film transistor array 201 may be used, or a thin-film transistor array having another circuit configuration may be used.

[0160] [Modification of the third embodiment] The shapes of the first pixel electrode 25A and the second pixel electrode 25B are not limited to the example of the third embodiment described above. FIGS. 27(a) to 27(c), 28(a), and 28(b) are plan views showing other examples of a bending sensor 10B according to the third embodiment. As in the bending sensor 101B shown in FIG. 27(a), the first pixel electrode 251A and the second pixel electrode 251B may each have a cross shape. In this case, the first pixel electrode 251A has a portion 251b extending in the X direction in addition to a portion 251a extending in the Y direction. The portion 251b is disposed so as to intersect with the center of the portion 251a, for example. The length of the portion 251b in the X direction is set shorter than the length of the portion 251a in the Y direction. Similarly, the second pixel electrode 251B has a portion 251d extending in the Y direction in addition to a portion 251c extending in the X direction. The portion 251d is disposed, for example, so as to intersect with the center of the portion 251c. The length of the portion 251d in the Y direction is set to be shorter than the length of the portion 251c in the X direction.

[0161] As in the bending sensor 102B shown in FIG. 27(b), the first pixel electrode 252A may have an elliptical (oval) shape extending in the Y direction. Similarly, the second pixel electrode 252B may have an elliptical (oval) shape extending in the X direction. Alternatively, as in the bending sensor 103B shown in FIG. 27(c), the first pixel electrode 253A may have an isosceles triangular shape extending in the Y direction. In this case, the first pixel electrode 253A may be arranged so that the apex of the isosceles triangle faces one side in the Y direction, or so that the apex of the isosceles triangle faces the other side in the Y direction. Similarly, the second pixel electrode 253B may have an isosceles triangular shape extending in the X direction. In this case, the second pixel electrode 253B may be arranged so that the apex of the isosceles triangle faces one side in the X direction, or so that the apex of the isosceles triangle faces the other side in the X direction.

[0162] As in the bending sensor 104B shown in FIG. 28(a), the width of the first pixel electrode 254A in the X direction may vary at each position on the first pixel electrode 254A along the Y direction. Specifically, the width of the first pixel electrode 254A in the X direction may be smallest at the center of the first pixel electrode 254A in the Y direction, and gradually increase as the distance from the center increases in the Y direction. The width of the second pixel electrode 254B in the Y direction may vary at each position on the second pixel electrode 254B along the X direction. Specifically, the width of the second pixel electrode 254B in the Y direction may be smallest at the center of the second pixel electrode 254B in the X direction, and gradually increase as the distance from the center increases in the X direction.

[0163] 28(b), the first pixel electrode 255A and the second pixel electrode 255B do not have to be arranged to fit within one pixel, and may extend outside the pixel. In this case, the first pixel electrode 255A extends in the Y direction beyond the boundary line BL to a position where it does not contact the second pixel electrode 255B adjacent to it in the Y direction. Similarly, the second pixel electrode 255B extends in the X direction beyond the boundary line BL to a position where it does not contact the first pixel electrode 255A adjacent to it in the X direction. Even with the bending sensor 105B as described above, the same effects as those of the bending sensor 10B according to the third embodiment can be obtained.

[0164] Various other modifications are possible for the first pixel electrode 25A and the second pixel electrode 25B according to this embodiment. Fig. 29 is a plan view showing another example of a bending sensor 106B according to the third embodiment. Fig. 30(a) is a cross-sectional view of the bending sensor 106B taken along line A6-A6 in Fig. 29. Fig. 30(b) is a cross-sectional view of the bending sensor 106B taken along line A7-A7 in Fig. 29. In the bending sensor 106B shown in Fig. 29, each of the first pixel electrodes 25A and each of the second pixel electrodes 25B extends in a direction inclined with respect to the pixel arrangement direction.

[0165] In the bending sensor 106B, the directions in which the first pixel electrodes 25A and the second pixel electrodes 25B extend are defined as the Y and X directions, respectively. The first pixel electrodes 25A are arranged adjacent to each other at a distance in the Y direction, and the second pixel electrodes 25B are arranged adjacent to each other at a distance in the X direction. The first extension portions 35A of the counter electrode 35 extend along the Y direction to encompass the first pixel electrodes 25A, and the second extension portions 35B extend along the X direction to encompass the second pixel electrodes 25B. Meanwhile, the matrix is arranged in the vertical and horizontal directions of FIG. 29. That is, as shown in FIG. 29, the arrangement direction of the matrix does not have to coincide with the X and Y directions. Note that the first pixel electrodes 25A and the second pixel electrodes 25B are arranged alternately in adjacent pixels in the vertical and horizontal directions of FIG. 29.

[0166] FIG. 31(a) is a cross-sectional view showing the bending sensor 106B bent convexly in the cross section shown in FIG. 30(a). FIG. 31(b) is a cross-sectional view showing the bending sensor 106B bent convexly in the cross section shown in FIG. 30(b). Since the piezoelectric layer 30 is located above the neutral plane NP, when the bending sensor 106B is bent convexly as shown in FIGS. 31(a) and 31(b), a tensile stress in the X direction is applied to the piezoelectric layer 30. At the position of the second pixel electrode 25B, a tensile stress SS1B in the X direction is applied to the piezoelectric layer 30. In this case, a voltage corresponding to the tensile stress SS1B is generated in the second pixel electrode 25B. Meanwhile, at the position of the first pixel electrode 25A, a tensile stress SS1A in the X direction is applied to the piezoelectric layer 30. In this case, a voltage corresponding to the tensile stress SS1A is generated in the first pixel electrode 25A. The tensile stress SS1B is greater than the tensile stress SS1A because the opposing electrode 35 is present over the entire area and the second pixel electrode 25B is long, and the voltage generated in the second pixel electrode 25B is greater than the voltage generated in the first pixel electrode 25A.

[0167] FIG. 32(a) is a cross-sectional view showing the bending sensor 106B bent concavely in the cross section shown in FIG. 30(a). FIG. 32(b) is a cross-sectional view showing the bending sensor 106B bent concavely in the cross section shown in FIG. 30(b). Because the piezoelectric layer 30 is located above the neutral plane NP, a compressive stress in the X direction is applied to the piezoelectric layer 30. When the bending sensor 106B is bent concavely as shown in FIGS. 32(a) and 32(b), a compressive stress in the X direction is applied to the piezoelectric layer 30. At the position of the second pixel electrode 25B, a compressive stress SS2B in the X direction is applied to the piezoelectric layer 30. In this case, a voltage corresponding to the compressive stress SS2B is generated in the second pixel electrode 25B.

[0168] On the other hand, a compressive stress SS2A in the X direction is applied to the piezoelectric layer 30 at the position of the first pixel electrode 25A. In this case, a voltage corresponding to the compressive stress SS2A is generated in the first pixel electrode 25A. The compressive stress SS2B is greater than the compressive stress SS2A because the counter electrode 35 covers the entire area and the second pixel electrode 25B is long. As a result, the voltage generated in the second pixel electrode 25B is greater than the voltage generated in the first pixel electrode 25A. Note that the voltages generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in FIGS. 32(a) and 32(b) are opposite in direction to the voltages generated in the first pixel electrode 25A and the second pixel electrode 25B in the cases shown in FIGS. 31(a) and 31(b). This bending sensor 106B also achieves the same effect as the bending sensor 10B.

[0169] FIG. 33 is a plan view showing another example of a bending sensor 10B according to the third embodiment. The bending sensor 107B shown in FIG. 33 includes a plurality of third pixel electrodes 25C (third electrodes) and a plurality of fourth pixel electrodes 25D in addition to a plurality of first pixel electrodes 25A and a plurality of second pixel electrodes 25B. Each third pixel electrode 25C has a shape extending along a direction DD1 (third direction) inclined with respect to the X and Y directions. The direction DD1 is, for example, the (X, Y) = (1, -1) direction. That is, the direction DD1 is inclined 45 degrees to one side (negative side) of the Y direction with respect to the X direction. Each fourth pixel electrode 25D has a shape extending along a direction DD2 inclined with respect to the X and Y directions and orthogonal to the direction DD1. The direction DD2 is, for example, the (X, Y) = (1, 1) direction. That is, the direction DD2 is inclined 45 degrees to the other side (positive side) of the Y direction with respect to the X direction. Therefore, the direction DD1 and the direction DD2 are inclined with respect to the X direction and the Y direction and are perpendicular to each other.

[0170] The third pixel electrode 25C and the fourth pixel electrode 25D are arranged on both sides of the first pixel electrode 25A in the Y direction. Therefore, the third pixel electrode 25C, the first pixel electrode 25A, and the fourth pixel electrode 25D are arranged alternately in this order in the Y direction. The third pixel electrode 25C and the fourth pixel electrode 25D are arranged on both sides of the second pixel electrode 25B in the X direction. Therefore, the third pixel electrode 25C, the second pixel electrode 25B, and the fourth pixel electrode 25D are arranged alternately in this order in the X direction.

[0171] The counter electrode 351 has a plurality of first extension portions 35A and a plurality of second extension portions 35B, as well as a plurality of third extension portions 35C and a plurality of fourth extension portions 35D. Each third extension portion 35C extends along the direction DD1 so as to encompass each third pixel electrode 25C in a plan view. One end of each third extension portion 35C in the direction DD1 is connected to the second extension portion 35B adjacent to it in the X direction and the first extension portion 35A adjacent to it in the Y direction. Similarly, the other end of each third extension portion 35C in the direction DD1 is connected to the second extension portion 35B adjacent to it in the X direction and the first extension portion 35A adjacent to it in the Y direction.

[0172] Each fourth extension portion 35D extends in the direction DD2 so as to encompass each fourth pixel electrode 25D in a plan view. One end of each fourth extension portion 35D in the direction DD2 is connected to the second extension portion 35B adjacent to it in the X direction and the first extension portion 35A adjacent to it in the Y direction. Similarly, the other end of each fourth extension portion 35D in the direction DD2 is connected to the second extension portion 35B adjacent to it in the X direction and the first extension portion 35A adjacent to it in the Y direction. The counter electrode 351 forms a lattice pattern in a plan view due to the connections between each first extension portion 35A, each second extension portion 35B, each third extension portion 35C, and each fourth extension portion 35D.

[0173] In the bending sensor 107B shown in FIG. 33, similar to the bending sensor 10B, the first pixel electrode 25A is strongly affected by the Y-direction bending, and the second pixel electrode 25B is strongly affected by the X-direction bending. Furthermore, the third pixel electrode 25C is strongly affected by the bending in the direction DD1, and the fourth pixel electrode 25D is strongly affected by the bending in the direction DD2. Therefore, by detecting a signal indicating the voltage of the third pixel electrode 25C as bending information in the direction DD1 and detecting a signal indicating the voltage of the fourth pixel electrode 25D as bending information in the direction DD2, it is possible to distinguish and grasp the bending state in the direction DD1 and the bending state in the direction DD2, in addition to the bending state in the Y-direction and the X-direction bending. Therefore, the bending sensor 107B shown in FIG. 33 allows for more detailed grasping of the bending state.

[0174] Furthermore, by arranging each of the third extension portions 35C so as to encompass each of the third pixel electrodes 25C, and each of the fourth extension portions 35D so as to encompass each of the fourth pixel electrodes 25D, the third pixel electrodes 25C are more strongly affected by the bending in the direction DD1, and the fourth pixel electrodes 25D are more strongly affected by the bending in the direction DD2, which makes it possible to more reliably distinguish and acquire bending information in the direction DD1 and bending information in the direction DD2.

[0175] 33, there are pixels in which the pixel electrode 25 and the counter electrode 351 are not present. In this case, the thin film transistors located in those pixels may be used as a reference circuit. That is, the voltage indicated by the signal from a pixel in which the pixel electrode 25 and the counter electrode 351 are not present may be subtracted from the voltage indicated by the signal from each pixel in which the first pixel electrode 25A, the second pixel electrode 25B, the third pixel electrode 25C, and the fourth pixel electrode 25D are located. This makes it possible to suppress characteristic variations due to the in-plane distribution of the thin film transistor array 20.

[0176] FIG. 34 is a plan view showing another example of a bending sensor 10B according to the third embodiment. The bending sensor 108B shown in FIG. 34 includes a plurality of first pixel electrodes 25A, a plurality of second pixel electrodes 25B, and a plurality of fifth pixel electrodes 25E. Each fifth pixel electrode 25E has a cross shape extending in both the X and Y directions. The fifth pixel electrode 25E includes a first portion 251E extending in the Y direction and a second portion 252E extending in the X direction. The first portion 251E has a rectangular shape with the Y direction as its longitudinal direction, and the second portion 252E has a rectangular shape with the X direction as its longitudinal direction. The length of the first portion 251E in the Y direction and the length of the second portion 252E in the X direction are set to be the same, for example. The first portion 251E and the second portion 252E are arranged, for example, so as to be perpendicular to each other at their centers.

[0177] In plan view, each fifth pixel electrode 25E is disposed at a position overlapping with each intersection (connection point) between each first extension portion 35A and each second extension portion 35B of the counter electrode 352. In plan view, the first portion 251E of each fifth pixel electrode 25E is disposed so as to be encompassed by each first extension portion 35A of the counter electrode 352, and the second portion 252E of each fifth pixel electrode 25E is disposed so as to be encompassed by each second extension portion 35B of the counter electrode 352.

[0178] Between two fifth pixel electrodes 25E adjacent to each other in the X direction, one first pixel electrode 25A is arranged so as to be encompassed by the first extension portion 35A in plan view. Therefore, the first pixel electrodes 25A and the fifth pixel electrodes 25E are arranged alternately along the X direction. Between two fifth pixel electrodes 25E adjacent to each other in the Y direction, one second pixel electrode 25B is arranged so as to be encompassed by the second extension portion 35B in plan view. Therefore, the second pixel electrodes 25B and the fifth pixel electrodes 25E are arranged alternately along the Y direction.

[0179] 34, similar to bending sensor 10B, the first pixel electrode 25A is strongly affected by Y bending, and the second pixel electrode 25B is strongly affected by X bending. On the other hand, the fifth pixel electrode 25E extends evenly in the X and Y directions, and is therefore equally affected by X bending and Y bending. Even with this bending sensor 108B, by detecting a signal indicating the voltage of the first pixel electrode 25A as bending information in the Y direction and detecting a signal indicating the voltage of the second pixel electrode 25B as bending information in the X direction, it is possible to distinguish between Y bending and X bending, thereby achieving the same effect as bending sensor 10B.

[0180] 34, there is a pixel (for example, the pixel in the center of FIG. 34) where a pixel electrode 25 and a counter electrode 352 are not present. In this case, the thin-film transistor located in that pixel may be used as a reference circuit. That is, the voltage indicated by the signal from a pixel where a pixel electrode 25 and a counter electrode 352 are not present may be subtracted from the voltage indicated by the signal from each pixel where the first pixel electrode 25A, the second pixel electrode 25B, and the third pixel electrode 25C are located. This makes it possible to suppress characteristic variations due to in-plane distribution of the thin-film transistor array 20.

[0181] [Care data collection and assessment system] Next, a care data collection and determination system (health condition estimation system) will be described as an example to which a bending detection device according to one embodiment of the present invention is applied. FIG. 35 is a block diagram showing an example of a care data collection and determination system to which a bending detection device is applied. The care data collection and determination system 300 shown in FIG. 35 is used to estimate the health condition of a care recipient. The care data collection and determination system 300 includes a plurality of care sensor devices 200 and a data collection and determination device 210. Each care sensor device 200 includes a bending sensor 110, a signal detection circuit 175, a drive circuit 185, a control circuit 180 (e.g., a microcomputer), and a communication circuit 202.

[0182] The bending sensor 110 has the same configuration as, for example, the bending sensors according to any one of the first to third embodiments described above. The signal detection circuit 175 has the same configuration as, for example, any one of the signal detection circuits 75, 75A, and 75B described above. The drive circuit 185 has the same configuration as the drive circuit 85 described above. The control circuit 180 has the same configuration as the control circuit 80 described above. The bending sensor 110, the signal detection circuit 175, the drive circuit 185, and the control circuit 180 constitute a bending detection device.

[0183] The communication circuit 202 performs wired or wireless communication between the control circuit 180 and an external circuit. Examples of wireless communication include Wi-Fi (registered trademark) and Bluetooth (registered trademark). The communication circuit 202 may be connected to the Internet. The communication circuit 202 transmits bending data indicating bending information for each pixel from the control circuit 180 to the data collection and determination device 210.

[0184] The data collection and determination device 210 includes a control circuit 211 (e.g., a computer), a communication circuit 212, and a database 213. The communication circuit 212 performs wired or wireless communication between the control circuit 211 and the communication circuit 202 of the care sensor device 200. The communication circuit 202 receives bending data from the communication circuit 202 of each care sensor device 200 and sends the received bending data to the control circuit 211. The control circuit 211 processes the bending data. The control circuit 211 sends the bending data to the database 213 either directly or after processing. The database 213 stores the bending data sent from the control circuit 211. The database 213 may store data indicating the medical condition of the care recipient. The control circuit 211 may use artificial intelligence to analyze the big data in the database 213 through machine learning or the like. This makes it possible to clarify the relationship between the posture of the care recipient and the medical condition. The control circuit 211 may also compare the bending data sent from the care sensor device 200 with the data in the database 213 to determine the condition of the care recipient.

[0185] In this way, the care data collection and determination system 300 can perform the following operations: storing the bending data sent from the care sensor device 200 in the database 213 either as is or after processing it; analyzing the big data in the database 213 using artificial intelligence through machine learning, etc.; and comparing the bending data from the care sensor device 200 with the data in the database 213 to determine the medical condition of the person being cared for.

[0186] In the above-described care data collection and determination system 300, one data collection and determination device 210 may be communicably connected to a plurality of care sensor devices 200, or one data collection and determination device 210 may be communicably connected to only one care sensor device 200. When one data collection and determination device 210 is communicably connected to only one care sensor device 200, the exchange of bending data between the data collection and determination device 210 and the care sensor device 200 becomes easy, but the care sensor device 200 is required to have a fast response speed.

[0187] On the other hand, the response speed of the data collection and determination device 210 does not need to be very fast. When one data collection and determination device 210 is communicably connected to a plurality of care sensor devices 200, the data exchange between the data collection and determination device 210 and each care sensor device 200 becomes complicated, but the response speed of each care sensor device 200 may be slow. On the other hand, the response speed of the data collection and determination device 210 is required to be fast. In addition, the control circuit 211 and the database 213 may be communicably connected via a communication circuit (not shown).

[0188] 36(a) to 36(f) are perspective views showing examples of a care sensor device. As shown in Fig. 36(a) to 36(f), a large sheet-like care sensor device is placed on a rectangular parallelepiped bed. In Fig. 36(a) to 36(f), the care sensor device on the bed is shown in a visible state, but in reality, a sheet is placed over the care sensor device and a care recipient is placed on the sheet. In Fig. 36(a) to 36(f), a circuit including a control circuit 180 and a communication circuit 202 will be described as a control / communication circuit 203.

[0189] 36(a), a large sheet-like bending sensor 110 is placed in the center of the bed, a signal detection circuit 175 is placed at the end of the long side of the bed, and a drive circuit 185 is placed at the end of the short side of the bed. Each scanning wiring 61 of the bending sensor 110 extends in the longitudinal direction of the bed and is connected to the drive circuit 185, and each signal wiring 62 of the bending sensor 110 extends in the lateral direction of the bed and is connected to the signal detection circuit 175. A control and communication circuit 203 is placed at the corner between the long and short sides of the bed, and is connected to the signal detection circuit 175 and the drive circuit 185.

[0190] In the care sensor device 200A shown in FIG. 36(b), the positions of the signal detection circuit 175 and the drive circuit 185 are reversed compared to the care sensor device 200. That is, in the care sensor device 200A, the drive circuit 185 is disposed at the end of the long side of the bed, and the signal detection circuit 175 is disposed at the end of the short side of the bed. The care sensor device 200B shown in FIG. 36(c) and the care sensor device 200D shown in FIG. 36(e) are provided with a plurality of strip-shaped bending sensors 110A instead of the large sheet-shaped bending sensor 110. The bending sensors 110A are arranged in the longitudinal direction of the bed at a distance from each other and extend in the lateral direction of the bed. In the care sensor device 200B shown in FIG. 36(c), a connecting part 205 is provided between adjacent bending sensors 110A in the longitudinal direction. The connecting part 205 connects the scanning wirings 61 of the bending sensors 110A in the longitudinal direction.

[0191] A care sensor device 200D shown in Fig. 36(e) includes a plurality of drive circuits 185A and a plurality of control and communication circuits 203A instead of the drive circuit 185 and the control and communication circuit 203. The plurality of drive circuits 185A are arranged to correspond to the plurality of bending sensors 110A. That is, each drive circuit 185A is arranged between adjacent bending sensors 110A in the longitudinal direction. Each drive circuit 185A is connected to the scanning wiring 61 of each bending sensor 110A. Each control and communication circuit 203A is arranged at a position opposite to each drive circuit 185A in the lateral direction.

[0192] The care sensor device 200C shown in FIG. 36(d) and the care sensor device 200E shown in FIG. 36(f) include a plurality of small sheet-like bending sensors 110B instead of the large sheet-like bending sensor 110. The bending sensors 110B are arranged in a matrix so as to be spaced apart from each other in the longitudinal and lateral directions. In the care sensor device 200C shown in FIG. 36(d), a connecting part 206 is provided between adjacent bending sensors 110B in the longitudinal direction. The connecting part 206 connects the scanning wiring 61 of each bending sensor 110A in the longitudinal direction. A connecting part 207 is provided between adjacent bending sensors 110B in the lateral direction. The connecting part 207 connects the signal wiring 62 of the bending sensors 110A in the lateral direction. In the care sensor devices 200B and 200C, the positions of the drive circuit 185 and the signal detection circuit 175 may be interchanged, as in the care sensor device 200A.

[0193] A care sensor device 200E shown in Fig. 36(f) includes a plurality of drive circuits 185A and a plurality of control and communication circuits 203A instead of the drive circuit 185 and the control and communication circuit 203. Each drive circuit 185A is arranged to extend in the short-side direction between adjacent bending sensors 110A in the longitudinal direction. In addition, in the care sensor device 200E, a connection part 207 is provided between adjacent bending sensors 110B in the short-side direction. The connection part 207 connects the signal wiring 62 of each bending sensor 110A in the short-side direction.

[0194] When determining the posture of a care recipient using any of the above-described care sensor devices, it is not necessary to accurately detect the bending (stimulus value) of all pixels. Even if a defect occurs in one pixel, resulting in abnormal bending data, the bending data can be interpolated using bending data obtained from pixels surrounding the defect. Even if a defect occurs in multiple pixels, resulting in abnormal bending data, the bending data can be interpolated using bending data from pixels surrounding the defect. In this case, if the defective pixels are dispersed, it is easier to interpolate the bending data than if the defective pixels are densely packed. However, even if the defective pixels are densely packed, it is possible to interpolate the bending data. Therefore, even if a defect occurs in one or multiple pixels, the posture of the care recipient can be determined by interpolating using bending data from surrounding pixels. [Example]

[0195] Hereinafter, first to fourth embodiments of the bending sensor 10 according to the present invention will be described. However, the present invention is not limited to the first to fourth embodiments.

[0196] Example 1 The bending sensor 10 shown in Figure 1 was fabricated. A thin-film transistor array 20 was fabricated using a PEN film on a glass substrate as the flexible substrate 15. The circuit of the thin-film transistor array 20 is shown in Figure 6. Next, Ag paste was printed as pixel electrodes 25, and a separately prepared PVDF film with Al was placed on top of it, baked, and peeled off from the glass substrate to fabricate the bending sensor 10. The region 26 between the pixel electrodes was air.

[0197] The flexible substrate 15 is 100 μm thick, the thin-film transistor layer 20 is 4 μm thick, the pixel electrode 25 is 10 μm thick, the piezoelectric layer 30 is 20 μm thick, the counter electrode 35 is 0.1 μm thick, the Young's modulus of the flexible substrate 15 is 5 GPa, the Young's modulus of the pixel electrode 25 is 6 GPa, the Young's modulus of the piezoelectric layer 30 is 3 GPa, and the Young's modulus of the counter electrode 35 is 70 GPa. In this case, the neutral plane NP is located inside the flexible substrate 15, and the pixel electrode 25 and the piezoelectric layer 30 are located above the neutral plane NP. The pixel pitch is 5 mm, and the pixel electrode 25 is a square with a side length of 3.6 mm.

[0198] 14 was used to detect the signal output from the bending sensor 10. By detecting the signal, bending information including the presence or absence of bending, the bending direction, and the bending amount was obtained for each pixel.

[0199] Example 2 The bending sensor 10A shown in Figure 17 was fabricated. A thin-film transistor array 201 was fabricated using a PI film on a glass substrate as the flexible substrate 15. The circuit of the thin-film transistor array 201 is the circuit shown in Figure 9. Next, Ag paste was printed as pixel electrodes 25, and a separately prepared PVDF film with Al was placed on top of it, baked, and peeled off from the glass substrate to fabricate the bending sensor 10A. There was air between the pixel electrodes 25.

[0200] The flexible substrate 15 is 25 μm thick, the thin-film transistor layer 201 is 4 μm thick, the pixel electrode 25 is 10 μm thick, the piezoelectric layer 30 is 20 μm thick, and the counter electrode 35 is 0.1 μm thick. The Young's modulus of the flexible substrate 15 is 5 GPa, the Young's modulus of the pixel electrode 25 is 6 GPa, the Young's modulus of the piezoelectric layer 30 is 3 GPa, and the Young's modulus of the counter electrode 35 is 70 GPa. Since the region 26 between the pixel electrodes is air, the Young's modulus of the region 26 between the pixel electrodes can be considered to be 0. In this case, the neutral plane NP is located inside the thin-film transistor layer 201, and the pixel electrode 25 and the piezoelectric layer 30 are located above the neutral plane NP. The pixel pitch is 5 mm, and the pixel electrode 25 is rectangular with long sides of 4 mm and short sides of 0.6 mm.

[0201] Using the detection unit 5B shown in FIG. 14, the signal (voltage V X and voltage V Y In equations (8) and (9), by experimentally determining k1 and k2, the detected voltage V X and voltage V Y Using X, the bending size B X and the magnitude of Y bending B Y and could be calculated independently.

[0202] Example 3 The bending sensor 10B shown in Figure 23 was fabricated. A thin-film transistor array 201 was fabricated using a PI film on a glass substrate as the flexible substrate 15. The circuit of the thin-film transistor array 201 is the circuit shown in Figure 9. Next, Ag paste was printed and baked as pixel electrodes 25, and an adhesive was placed on the backside of a separately prepared PVDF film with an Al pattern. The films were then bonded together using a laminator, and the adhesive was inserted between the pixel electrodes 25. Therefore, the inter-pixel electrode regions 26 were adhesive. By appropriately selecting the pressure and temperature, electrical connection between the pixel electrodes 25 and the piezoelectric layer 30 was ensured. The bending sensor 10B was then fabricated by peeling it off from the glass substrate.

[0203] The flexible substrate 15 is 25 μm thick, the thin-film transistor layer 201 is 4 μm thick, the pixel electrode 25 is 10 μm thick, the piezoelectric layer 30 is 20 μm thick, and the counter electrode 35 is 0.1 μm thick. The Young's modulus of the flexible substrate 15 is 5 GPa, the Young's modulus of the pixel electrode 25 is 6 GPa, the Young's modulus of the inter-pixel electrode region 26 is 1 MPa, the Young's modulus of the piezoelectric layer 30 is 3 GPa, and the Young's modulus of the counter electrode 35 is 70 GPa. The neutral plane NP is located inside the thin-film transistor layer 201, and the pixel electrode 25 and the piezoelectric layer 30 are located above the neutral plane NP. The pixel electrode 25 is rectangular with long sides of 4 mm and short sides of 0.6 mm. The pixel pitch is 5 mm, and the width of the counter electrode 35 is 0.7 mm.

[0204] Using the detection unit 5B shown in FIG. 14, the signal (voltage VX and voltage V Y In equations (8) and (9), by experimentally determining k1 and k2, the detected voltage V X and voltage V Y The bending size B is used to X and the magnitude of Y bending B Y and could be calculated independently.

[0205] Example 4 The bending sensor 10B shown in Figure 23 was fabricated. A thin-film transistor array 201 was fabricated using a PI film on a glass substrate as the flexible substrate 15. The circuit of the thin-film transistor array 201 is the circuit shown in Figure 9. Next, Al was sputter-deposited as pixel electrodes 25 and processed using photolithography. An adhesive was then placed on the backside of the PVDF film, and the two films were bonded together using a laminator, with the adhesive filling the gaps between the pixel electrodes 25. Therefore, the inter-pixel electrode region 26 was adhesive. By appropriately selecting the pressure and temperature, electrical connection between the pixel electrodes 25 and the piezoelectric layer 30 was ensured. Next, Ag paste was printed and baked as the counter electrode 35, and the film was peeled off from the glass substrate to fabricate the bending sensor 10B.

[0206] The flexible substrate 15 is 10 μm thick, the thin-film transistor layer 201 is 4 μm thick, the pixel electrode 25 is 0.1 μm thick, the piezoelectric layer 30 is 20 μm thick, and the counter electrode 35 is 10 μm thick. The Young's modulus of the flexible substrate 15 is 5 GPa, the Young's modulus of the pixel electrode 25 is 70 GPa, the Young's modulus of the inter-pixel electrode region 26 is 1 MPa, the Young's modulus of the piezoelectric layer 30 is 3 GPa, and the Young's modulus of the counter electrode 35 is 6 GPa. The neutral plane NP is located near the back surface 30b of the piezoelectric layer 30. The pixel electrode 25 is below the neutral plane NP, but most of the piezoelectric layer 30 is above the neutral plane NP. The pixel pitch is 5 mm, and the pixel electrode 25 is rectangular with long sides of 4 mm and short sides of 0.6 mm. The width of the counter electrode 35 is 0.7 mm.

[0207] Using the detection unit 5B shown in FIG. 14, the signal (voltage V X and voltage V YIn equations (8) and (9), by experimentally determining k1 and k2, the detected voltage V X and voltage V Y The bending size B is used to X and the magnitude of Y bending B Y and could be calculated independently.

[0208] The bending sensor, bending detection device, and bending detection method according to the present invention are not limited to the above-described embodiments and can be modified as appropriate. The bending sensor according to any of the first to third embodiments may include components other than the flexible substrate, thin-film transistor array, pixel electrode, piezoelectric layer, counter electrode, and inter-pixel electrode region. For example, the bending sensor may include an insulating cover layer on the counter electrode. In this case, the cover layer may be thin and have a small Young's modulus. The cover layer has little effect on the composite Young's modulus of the laminate. For example, a rubber material with a small Young's modulus may be selected as the material for the cover layer. Furthermore, even if the bending sensor includes another component between the layers, the effect on the composite Young's modulus is small if the component is thin or has a small Young's modulus.

[0209] In each of the above-described embodiments, the potential difference between the counter electrode and the pixel electrode is detected as the "change in electrical characteristics." However, a change in current between the counter electrode and the pixel electrode may also be detected as the "change in electrical characteristics." In this case, the signal output from the bending sensor may indicate a current. Alternatively, a change in resistance value between the counter electrode and the pixel electrode may be detected as the "change in electrical characteristics." Furthermore, in each of the above-described embodiments, a constant voltage may be applied to the counter electrode. [Explanation of symbols]

[0210] 1... bending detection device, 5, 5A, 5B... detection unit, 10, 10A, 10B, 101A, 101B, 102A, 102B, 103A, 103B, 104A, 104B, 105A, 105B, 106B, 107B, 108B, 110, 110A, 110B... bending sensor, 15... flexible substrate (substrate), 30a... front surface, 30b... rear surface, 20, 201... thin film transistor layer (thin film transistor array), 21A... first pixel thin film transistor (first thin film transistor 21B...first pixel thin film transistor (second thin film transistor), 25...pixel electrode, 25A, 251A, 252A, 253A, 254A, 255A...first pixel electrode, 25B, 251B, 252B, 253B, 254B, 255B...second pixel electrode, 25C...third pixel electrode, 26...region between pixel electrodes (interelectrode region), 30...piezoelectric layer, 35, 351, 352...opposing electrode (common electrode), 35A...first extension portion, 35B...second extension portion, 35C...third extension portion, D 11 ~D NM …signal, NP…neutral plane.

Claims

1. A bending sensor for detecting bending, comprising: a flexible substrate; a thin film transistor array consisting of a plurality of thin film transistors arranged on the substrate; a plurality of pixel electrodes disposed on the thin film transistor array; a piezoelectric layer disposed on the plurality of pixel electrodes; a common electrode disposed on the piezoelectric layer, the piezoelectric layer has a front surface electrically connected to the common electrode and a back surface electrically connected to the plurality of pixel electrodes, the plurality of pixel electrodes include a first pixel electrode and a second pixel electrode that are arranged spaced apart from each other in a plan view of the substrate and are electrically insulated from each other; the thin film transistor array includes a first thin film transistor electrically connected to the first pixel electrode and a second thin film transistor electrically connected to the second pixel electrode; When a bending force is applied in a first direction along the substrate, a voltage generated in the first pixel electrode is greater than a voltage generated in the second pixel electrode; A bending sensor, wherein when bending is applied in a second direction along the substrate and intersecting the first direction, a voltage generated in the second pixel electrode is greater than a voltage generated in the first pixel electrode.

2. The bending sensor according to claim 1 , wherein the plurality of pixel electrodes are arranged in a matrix.

3. the first pixel electrode has a shape extending in a first direction along the substrate, The bending sensor according to claim 1 , wherein the second pixel electrode has a shape extending along the substrate and in a second direction intersecting the first direction.

4. The bending sensor according to claim 3 , wherein each of the first pixel electrode and the second pixel electrode has a Young's modulus higher than a Young's modulus of an inter-electrode region between the first pixel electrode and the second pixel electrode.

5. The bending sensor according to claim 4 , wherein the inter-electrode region is made of an adhesive having electrical insulating properties.

6. a neutral plane on which no tensile stress or compressive stress acts when bending occurs in the bending sensor is located at a height different from that of the piezoelectric layer; The bending sensor according to any one of claims 3 to 5, wherein at least a portion of each of the first pixel electrode and the second pixel electrode is arranged on the same side as the piezoelectric layer with respect to the neutral plane.

7. the plurality of pixel electrodes include a plurality of the first pixel electrodes and a plurality of the second pixel electrodes; 7. The bending sensor according to claim 3, wherein the first pixel electrodes and the second pixel electrodes are arranged in a matrix so as to alternate with each other.

8. The common electrode is a first extension portion extending in the first direction so as to encompass the first pixel electrode in the plan view; The bending sensor according to any one of claims 3 to 7, further comprising: a second extension portion connected to the first extension portion and extending in the second direction so as to encompass the second pixel electrode in the planar view.

9. the plurality of pixel electrodes include a plurality of the first pixel electrodes and a plurality of the second pixel electrodes; the plurality of first pixel electrodes and the plurality of second pixel electrodes are arranged in a matrix, The common electrode is a plurality of first extension portions arranged so as to respectively include the plurality of first pixel electrodes in the plan view; a plurality of second extension portions arranged so as to respectively include the plurality of second pixel electrodes in the plan view; The bending sensor according to claim 8 , wherein the plurality of first extending portions and the plurality of second extending portions are arranged in a lattice pattern in a plan view.

10. the plurality of pixel electrodes further include a third pixel electrode that is disposed apart from the first pixel electrode and the second pixel electrode in the plan view and is electrically insulated from the first pixel electrode and the second pixel electrode; The bending sensor according to any one of claims 3 to 9, wherein the third pixel electrode has a shape extending along the substrate and in a third direction intersecting the first direction and the second direction.

11. The common electrode is a first extension portion extending in the first direction so as to encompass the first pixel electrode in the plan view; a second extension portion that extends in the second direction so as to encompass the second pixel electrode in the plan view and is connected to the first extension portion; The bending sensor according to claim 10 , further comprising: a third extension portion that extends in the third direction so as to encompass the third pixel electrode in the plan view and is connected to the first extension portion and the second extension portion.

12. A bending sensor according to any one of claims 1 to 11; a detection unit that detects bending of the bending sensor, when a bend is applied to the bending sensor, the first thin film transistor outputs a first signal to the detection unit, the first signal indicating a change in an electrical characteristic between the first pixel electrode and the common electrode in response to the bend, and the second thin film transistor outputs a second signal to the detection unit, the second signal indicating a change in an electrical characteristic between the second pixel electrode and the common electrode in response to the bend; a bending detection device, wherein the detection unit detects the first signal as information indicating the bending state at the position of the first pixel electrode, and detects the second signal as information indicating the bending state at the position of the second pixel electrode.

13. the first pixel electrode has a shape extending in a first direction along the substrate, the second pixel electrode has a shape extending along the substrate and in a second direction intersecting the first direction; 13. The bending detection device according to claim 12, wherein the detection unit detects the first signal as information indicating the bending state in the first direction at the position of the first pixel electrode, and detects the second signal as information indicating the bending state in the second direction at the position of the second pixel electrode.

14. A bending detection method carried out using the bending sensor according to any one of claims 1 to 11, comprising: When a bend is applied to the bending sensor, outputting from the first thin film transistor a first signal indicating a change in an electrical characteristic between the first pixel electrode and the common electrode in response to the bend, and outputting from the second thin film transistor a second signal indicating a change in an electrical characteristic between the second pixel electrode and the common electrode in response to the bend; detecting the first signal as information indicating the state of the bending at the position of the first pixel electrode, and detecting the second signal as information indicating the state of the bending at the position of the second pixel electrode.

15. In the step of outputting the first signal and the second signal, outputting the first signal using the first pixel electrode having a shape extending in a first direction along the substrate, and outputting the second signal using the second pixel electrode having a shape extending in a second direction along the substrate and intersecting the first direction; In the step of detecting the first signal and the second signal, 15. The bending detection method according to claim 14, wherein the first signal is detected as information indicating the state of bending in the first direction at the position of the first pixel electrode, and the second signal is detected as information indicating the state of bending in the second direction at the position of the second pixel electrode.

16. A bending sensor for detecting bending, comprising: a flexible substrate; a thin film transistor array consisting of a plurality of thin film transistors arranged on the substrate; a plurality of pixel electrodes disposed on the thin film transistor array; a piezoelectric layer disposed on the plurality of pixel electrodes; a common electrode disposed on the piezoelectric layer, the piezoelectric layer has a front surface electrically connected to the common electrode and a back surface electrically connected to the plurality of pixel electrodes, the plurality of pixel electrodes include a first pixel electrode and a second pixel electrode that are arranged spaced apart from each other in a plan view of the substrate and are electrically insulated from each other; the thin film transistor array includes a first thin film transistor electrically connected to the first pixel electrode and a second thin film transistor electrically connected to the second pixel electrode; the first pixel electrode has a shape extending in a first direction along the substrate, The second pixel electrode has a shape extending along the substrate and in a second direction intersecting the first direction.

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